An analysis of pollution prevention opportunities and impediments in the pulp and paper manufacturing sector in Georgia

An Analysis of Pollution Prevention , Opportunities and Impedimentsin the Pulp and Paper Manufacturing Sector in Georgia

An Analysis of Pollution Prevention . Opportunities and Impedimentsin the Pulp and Paper Manufacturing Sector in Georgia
April 1, 1996 Revised 7/28/97
Prepared by Paul Crumpler Pollution Prevention Engineer

P D ~~ J1

Pollution Prevention Assistance Division
Georgia Department ofNatural Resources

TABLE OF CONTENTS Introduction Methodology Summary Profile of the Pulp and Paper Manufacturing Sector in Georgia Pulp and Paper Industrial Processes Waste Stream and Generation Characteristics of Georgia Pulp and Paper Manufacturers Pollution Prevention Barriers Sources of Pollution Prevention Assistance to Pulp and Paper Mills Key Pollution Prevention Issues Lack of Facility Pollution Prevention Programs Water Use Minimization and Reuse Alternatives to Chlorine Bleaching Reducing Log Yard Waste Lime Mud Waste Reduction Energy Conservation and Recovery Pollution Prevention Assistance Needs of the Georgia Pulp and Paper Manufacturing Sector Approaches to Meeting Assistance Needs of Georgia Pulp and Paper Manufacturers Summary and Conclusion An Approach to Solid Waste Minimization in the Paper Industry NICE3 -- Recovering Lime from Pulp and Paper Operations

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2 4 8 12 15 16 17 18 22 25 28 29 31

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Appendix I

Appendix II

An Analysis of Pollution Prevention Opportunities and Impediments in the Pulp and Paper Manufacturing Sector in Georgia

Introduction

The purpose of this report is to identify the specific causes of waste generation, and cost-effective solutions that will reduce waste in the pulp and paper industry in Georgia. The benefits of reducing waste are reduced pollution and decreased operating cost to the business. Releases of high-priority toxic chemicals are the primary focus ofthis report but other significant solid and liquid wastes will be included. Barriers exist that limit the implementation of pollution prevention projects and technologies. Barriers and strategies to overcome them will also be discussed in this report.

Methodology

Review of trade and environmental publications indicated that the processes responsible for Toxic Release Inventory (TRI) releases in this sector are primarily Kraft pulping and bleaching of pulp. Businesses that use these processes were identified by reviewing 1993 TRI reports and the Georgia Manufacturing Directory. There are relatively few pulp and paper mills in Georgia. Telephone interviews were conducted of Kraft pulp mills and paper mills in the state. Visits were made to six mills; various processes related to Kraft pulping, bleaching, and recycling were reviewed. The interviews and plant visits were conducted to collect information on the various types of equipment and chemistries used in the mills. Water usage, pulp production, and information on various other wastes were collected. Mill environmental and production staffs were also questioned about programs at their facilities to reduce waste and evaluate new technologies available to the pulp and paper industry. The results of this study are presented in this document.

Summary

The following key issues were identified as a result of this study through contacts with Georgia pulp mill personnel, mill tours, interviews with paper industry experts, and review of various trade and environmental publications.



Lack of Facility Pollution Prevention

Programs



Water Use Reduction and Reuse Lime Mud Waste Reduction



Energy Conservation and Recovery Alternatives to Chlorine Bleaching Log Yard Waste Reduction

The Georgia Pollution Prevention Assistance Division (P2AD) will assist Georgia pulp and paper manufacturers in addressing these key issues by developing various programs. P2AD will work with existing technical and business organizations to provide training, publication of fact sheets and case studies, and conduct applied research demonstration projects in order to address critical pollution prevention issues.

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Profile of the Pulp and Paper Manufacturing Sector in Georgia

Georgia pulp manufacturers produce pulp, bleached pulp, or specialty pulp for the food and pharmaceutical industry. Many of these companies also produce finished paper, paperboard, or linerboard. Twenty-four companies are listed in the Georgia Manufacturers Directory within SIC code 26 that are predominately involved in cellulose pulp manufacturing. Approximately 13,000 people work for these manufacturers. A list of these businesses is provided below in Table 1 with a description of the primary products and number of employees.

TABLE 1 -GEORGIA PULP AND PAPER MANUFACTURERS

SIC Company Name

-,

Code

CITY

Primary Product

Employees

2611 Associated Rubber Co. (Recy.)

Calhoun

Treated Fiber Products

6

2611 Georgia Pacific (Pulp)

Brunswick

Bleached Sulphate Pulp 850

2611 Gilman Paper Co.(Pulp)

St. Marys

Pulp_& Paper

1,080

2611 Ponderosa Georgia Div.(Recy.)

Augusta

Reclaimed Pulp Fibers

44

2611 Weyerhaeuser Co.(Pulp)

Oglethorpe

Cellulose Pu!P_

525

2611 Rayonier

Jesup

Bleached Speciality_pulp. 1,076

2621 Augusta Newsprint Co.(Pulp)

Augusta

Newsprint

312

2621 Deerfield Specialty Papers inc.(Paper)

Augusta

Grease Proof Paper

101

2621 Hollingsworth & Vose Co. (Paper)

Hawkinsville Filter Paper

54

2621 Paper Pak Products, Inc.

Washington Tissue Paper, Absorbent 121

2621 Southeast Paper Manufacturing Co.(Recy.) Dublin

Newsprint

420

2631 2631 2631 2631 2631 2631 2631 2631 2631 2631 2631

Caraustar Industries, Inc. (Recy)

Austell

Federal Paper Board Co., Inc.(Pulp)

Augusta

Georgia Pacific Corp.(Pulp)

Cedar Springs

Inland Container Corp.(Pu1p)

Rome

Interstate Paper Corp.(Pulp)

Riceboro

Jefferson Smurfit C~rp. (Recy.)

Cedartown

Tenneco Packaging (Pulp)

Valdosta

Riverwood International Georgia, Inc.(Pulp) Macon

Stone Savannah River Pulp (Pulp)

Savannah

Sweetwater P3.2_er Board Co., Inc. (Recy.) Austell

Union Camp Corp. (Pulp)

Savannah

Paperboard for Industry 632

Bleached Paperboard

925

Kraft Linerboards

843

Container Board

718

Kraft Linerboard

287

Paperboard

49

Linerboard

450

Container Board

530

Kraft Linerboard

498

Gypsum Linerboard

90

Unbleached Kraft Products 2,997

2676 Fort Howard (Recy.) ACR Industries (Recy.)

Rincon Cornelia

Recycled Pa.r>_er Products 998

Cellulose Insulation

12

Total Employees 13,618

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Ofthe 24 manufacturers in Georgia, thirteen are large manufacturers of pulp only, pulp and paper, or pulp and linerboard. These manufacturers produce virgin pulp and form a finished paper product. The pulp may be either bleached or unbleached. Four Georgia mills produce bleached virgin pulp. Pulp is also sold to paper manufacturers that make paper, filter paper, or other speciality paper from pulp. There are approximately 100 companies in Georgia that are primarily paper, paperboard, or paper products manufacturers that do not manufacture pulp. These companies are not the focus of this study. Another manufacturing group repulps old corrugated cardboard, linerboard, newsprint, and other recycled paper. There are at least nine mills producing recycled pulp in Georgia. Recycling mills manufacture pulp for sale to other industries or manufacture a finished paper product. Some recycling mills deink printed stock using floatation or continuous deinking. Bleaching is done primarily with peroxide and less with sodium hypochlorite by recyclers. At least one company recycles newsprint and other paper in a dry repulping process to make insulation, animal bedding, and reseeding material used on highway right of ways. Paper mills need a source of water and a receiving body to dispose of wastewater. Paper mills are generally located near a river to provide a means of disposal for the often tremendous wastewater stream generated by the mill. A secondary reason is to provide water for mill usage since a number of mills use wells as the primary source of mill supply water. Cooling water is also needed and is usually supplied from surface water. All Georgia mills have wastewater treatment plants except some of the small specialty product mills, and dispose of wastewater directly to a river after treatment. At least one mill disposes of wastewater to a municipal treatment system. Several mills also purchase water from a city or other source of treated water.
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Pulp and Paper Industrial Processes
In order to understand the pulp and paper industry, a general description of the pulping and paper making process is needed. Each of the companies uses some or all of these processes.
Wood Yard Operations
Wood is delivered to a pulp mill either as logs or chips. Logs are delivered with the bark attached to prevent loss of moisture and other degradation. Logs are handled in the yard by cranes or log trucks. They are loaded onto a conveyor or log flume where they are carried to a debarker and chipper. Chips are screened to remove over and undersized chips, and then stored in the yard awaiting digestion. The majority of the Georgia virgin pulp mills have wood yards. A growing trend is to eliminate wood yards and receive chipped wood only. Several mills receive only wood chips or are planning wood yard closure in the near future.
Water Treatment
Pulp mills generally require a large amount of water in processing to remove lignin and bleaching byproducts. Water is generally obtained from rivers or wells. From 5,000 to 40,000 gallons of water is required to produce one ton of dry pulp in Georgia's virgin pulp mills. This water is treated prior to use to remove suspended solids and other contaminants.
Digestion
Chips are heated by steam and white liquor is added. The liquor impregnated chips then enter the digester where they are heated to cooking temperature. Spent cooking liquor or black liquor is removed from the brownstock after cooking. In batch digesters, the brownstock is blown from the bottom ofthe digester vessel prior to washing. In a continuous digester, washing takes place inside the digester to remove liquor and cool the pulp. In either case, brownstock is washed to remove the majority of spent liquor. It is also screened to remove undigested knots. The majority of the 13 pulp mills use the Kraft process. One mill uses the thermo-mechanical pulping process.
Washing
Pulp washing takes place after each major process. The purpose ofwashing is to remove undesirable elements from the pulp stream. Black liquor, fines, lignin, and bleach byproducts are removed after each processing step. Washer efficiency can be measured by the cleanliness of the pulp and the amount of water used to achieve that level of cleanliness. There are a number of different types of washers available. Vacuum drum brownstock washers (six-stage or three-stage) were the industry standards up to the 1970s. At least six Georgia mills currently use vacuum drum washers. Pressure brownstock washers represent a later washing technology with at least one mill using this
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technology. Diffusion brownstock washers are currently the industry standards, but diffusion washers are also being improved upon. Diffusion washers are used by at least three mills. At least two pulp mills in Georgia use Chemi washers, which are the most efficient washers available currently. Each improvement represents cleaner pulp with a water usage reduction.
Refining
Pulp passes through slots in rotating plates to separate the cellulose clumps into fibers and condition the fibers for paper making. Essentially, the fibers are cut to a uniform length during refining which reduces strength. The fibers are also conditioned by refining which improves bonding and strength of the finished paper product.
Oxygen Delignification
Some mills have installed an oxygen stage to further remove lignin from the brownstock as a prebleaching step. Reduced lignin content produces a whiter pulp. Oxygen and white liquor are added to the brownstock in a heated reactor where additional delignification takes place. Lignin compounds freed as a result of oxygen delignification are removed in washing and extraction stages. At least two Georgia mills use oxygen delignification. Oxygen delignification reduces the amount of chlorine or other bleaching chemicals required to whiten the pulp in the bleach stage.
Extended Delignification
Various extended delignification techniques are used to remove more lignin prior to bleaching. Sodium hydroxide (NaOH) and heat act to break complex bonds in the lignin to make them soluble in water or volatile. NaOH and heat also break bonds in the cellulose reducing strength and yield. Extended delignification techniques cook the wood chips at lower temperature for longer periods of time to remove lignin with reduced damage to the cellulose. Several techniques are in use to control temperature and liquor chemistry in the digester. At least four mills in Georgia use extended delingnification. Extended delignification reduces the amount of bleaching chemicals required in the bleaching stage to produce the same pulp whiteness.
Bleaching
Bleaching usually takes place in a multistage process. The purpose of bleaching is to remove lignin without damaging the cellulose. One process is the DED process; D represents chlorine dioxide
(Cl02) and E represents extraction. In this process, brownstock is mixed with qo in the Dl
reactor which further reacts with lignin in the pulp. Washing follows to remove the chlorinated lignin compounds from the pulp. NaOH is added to the pulp stream in theE tower and is followed by washing in a press. Extraction neutralizes the pulp and improves subsequent washing. The D2 tower is the last stage ofbleaching where Cl02 provides the final whitening of the pulp. If preceded
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by oxygen delignification, the process is abbreviated ODED. Chlorine (C), peroxide (P), oxygen (0), sodium hypochlorite (H), and ozone (Z) are other chemicals that can be used in various configurations. For example, ODEoD would consist of:
oxygen reactor> Cl02 reactor> extraction with oxygen added (EJ > Cl02 reactor
The fmal stage ofbleaching is often used to whiten or lighten remaining lignin. Eight Georgia mills bleach pulp in some manner, four of which are virgin pulp mills.
Paper Making
The pulp is then transported to the paper machine where a pulp mat is formed on a screen. Water is removed from the sheet by a combination of vacuum, heat, and pressure applied through rollers. The finished paper can be made in a variety of weights and is rolled onto large rollers for shipment to other processing plants. Paper is sometimes coated on the paper machine with kaolin to provide a white surface or has a binder added to increase wet strength. Some binders contain formaldehyde; many companies have replaced these with nonformaldehyde binders. Other coatings and binders contain ammonia or polyvinyl alcohol (PVA). Approximately 17 mills in Georgia produce paper, paperboard, or similar products.
Power Boiler
Energy in the form ofheat and steam is generated by burning waste wood from the log yard or fossil fuels. In addition to steam, electricity is also often generated on-site at pulp mills. Pulp and paper mills require a large amount of energy to operate.
Liquor Recovery Cycle
NaOH and sodium sulfide (Na2S) are the primary pulping chemicals. NaOH reacts with lignin in the wood to release the cellulose fiber. Na2S buffers the reaction to keep the solution caustic, and aids in the removal of digested lignin by increasing its solubility. Spent cooking liquor, or black liquor contains various organic and sulfur compounds in addition to the reactive pulping components of NaOH and Na2S. The black liquor is removed from the pulp at various locations after the delignification process and concentrated in an evaporator. The concentrated liquor, or strong black liquor is combusted in a furnace along with sodium sulfate (Na2S04) to recover Na2S, and sodium carbonate (Na2C03) in the form of ash. This ash is mixed with water and lime (CaO). The resultant reaction forms green liquor and replenishes the original pulping chemicals NaOH and Na2S; calcium carbonate (CaC03). CaC03 is precipitated from the green liquor in a clarifier and converted back to CaO in a lime kiln. After removal of CaC03, the green liquor becomes white liquor. The recovery cycle consists of a liquor evaporator, recovery boiler, clarifier, and lime kiln.
6

Wastewater Treatment Wastewater gathered from various mill processes is treated prior to discharge to reduce biological oxygen demand (BOD), chemical oxygen demand (COD), and total suspended solids (TSS). Wastewater typically passes through a primary clarifier to remove the bulk ofthe cellulose fibers lost during processing and other solids. Wastewater then passes through aeration ponds to further reduce BOD and COD. Nutrients in the form of ammonium nitrate or ammonia are often added to encourage microbe activity. Wastewater is then discharged directly to a river or tidal river. Wastewater volumes are very large ranging up to 40,000,000 gallons per day with relatively low contaminant concentrations. In addition to BOD, COD, and TSS, color and chlorinated compounds such as dioxin have been of great concern to pulp mills. Aeration and clarification do not significantly reduce color or chlorinated compounds.
Paper Recycling Another segment ofthe industry repulps cardboard or newsprint into recycled paper or paperboard. Recycled material is repulped by adding water, sodium hydroxide, and heat. The pulp is then made into a finished paper product on a paper machine in the same manner as a virgin paper mill. Deinking and bleaching are also done at some recycle mills. Floatation is one common method of deinking. Peroxide is commonly used in the bleaching process. Approximately nine Georgia mills are involved in repulping recycled paper products.
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Waste Stream and Generation Characteristics of Georgia Pulp and Paper Manufacturers

Wastes are generated by the industrial processes used by Georgia pulp and paper manufacturers. Almost all ofthe wastes generated are derived from unusable portions of the tree such as bark and lignin. Additional wastes are generated from power generation or from the chemicals used in pulping, bleaching, and chemical recovery. Energy is also a waste stream. Water entering the mill is heated for process use. Thermal energy is emitted to the environment from numerous sources.

The usable portion of a tree is cellulose from which paper is made. Other materials such as

. ,

turpentine are byproducts which have a market value. Most other components are released to the environment as solid waste, liquids, gasses, or energy derived from combustion.

Toxic Wastes
Toxic wastes reported on the 1993 TRJ totaled more than 18.8 million pounds of which 16.4 million pounds were released to the air. TRJ releases for 1993 are shown in Figure 2. Of the 26 chemicals reported, methanol was released in the largest quantity at approximately 9.3 million pounds. Methanol is generated :from pulping at the rate of 12 to 20 pounds per ton ofproduction in the Kraft process. Bleaching can increase that amount up to 25 pounds. Thermo-mechanical pulping also releases methanol, but in much lower quantities at about 0.5 pounds per ton ofpulp. Methanol and other organics (MEK, acetone, etc.) are released primarily :from process vents, but are also found in wastewater and the recovery furnace stack. Wastewater leaving the mill can contain large amounts ofthe methanal; biological destruction ofmethanol is estimated to be in excess of99% in wastewater treatment plants. Non-contact recovery boilers available since the 1970s reduce methanol stack releases to near zero. Newer and modernized facilities collect and combust process vent gasses in the recovery boiler, lime kiln, or power boiler furnaces reducing methanol and sulfur releases. Older facilities still have uncontrolled process vents releasing significant amounts of methanol.
Noncondensable gasses are usually burned in the lime kiln or recovery boiler. Mills have traditionally avoided burning noncondensable gasses in the recovery boiler due to an increased risk of an explosion. Some mills have lime kilns which cannot meet the capacity required to burn all noncondensable gasses, or have significant downtime due to mechanical failures. The result is increased emissions of sulfur and organics when the kilns are used to combust noncondensable gasses. Burning noncondensable gasses in the kiln also decreases the lime recovery capacity, thus increasing solid waste in the form of disposed lime mud. A few mills have begun to burn noncondensable gasses in recovery furnaces to take advantage of their greater capacity.
Sulfuric and hydrochloric acids are also released by pulp mills. These materials are combustion byproducts from coal-fired boiler operations. Sulfuric acid is also used in paper making and other mill processes to adjust pH. Zinc is another material reported that is nonpulp related. Zinc is contained in ash from burning tires as a boiler fuel. Tire burning for energy recovery is a popular tire recycling or disposal method.
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Figure 2 1993 Georgia TRI Releases by Pulp and Paper Manufacturers in Pounds

10,000,000

8,000,000

6,000,000

4,000,000

2,000,000

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Chlorinated compounds such as chloroform are emitted from wastewater and bleach plant process vents. Chloroform is primarily associated with the use of sodium hypochlorite and chlorine bleaching. Mills generally have replaced both of these materials to some degree. Hypochlorite use is discontinuing. Chlorine is being replaced either partially or fully by chlorine dioxide. Ozone is also used in place of chlorine on a limited basis in other states. For these reasons, chloroform emissions have decreased. Dioxin is another chlorine related pollutant. Dioxin levels in effluent from mills that have switched to 100% chlorine dioxide are usually below detectable levels. Chlorine dioxide has replaced chlorine completely, 100% substitution, in three Georgia mills. Several other mills have replaced 20% to 30% of the chlorine used for bleaching with chlorine dioxide.

Chromium and dichloromethane are two chemicals reported from Georgia mills on the 1993 TRI. These are nonpulp related and are due to specific situations that occurred at particular mills.

Solid Waste
Solid waste generation by pulp and paper manufacturers varies between 0.01 and 0.26 tons of waste per ton of product (TPT). The wide diversity is due to several factors. Lime mud and wood yard debris can be large solid waste streams. The sources of these wastes are log handling and insufficient capacity lime kilns. Some mills have sufficient lime kiln capacity and thus produce small amounts of waste. Other mills have reduced wood yard waste by purchasing wood chips and eliminating log storage. Other solid wastes typical in pulp mills are wastewater treatment sludge and digester knots. Sludge and knots are reused in some mills and disposed of in others.
Solid waste is usually disposed of in on-site landfills; some mills use municipal or private landfills. Disposal costs are often very high, exceeding $2 million annually in some mills whether on-site or off-site. Some municipal landfills used by pulp mills have closed. As on-site landfills reach capacity, several mills are considering building new landfills. New landfills can cost $10 to $20 million to open and are not an attractive option to most pulp mills.
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Wood Yard Waste

Wood yard waste generation by Georgia pulp and paper manufacturers varies between 0.02 and 0.06

TPT. Oversized logs, wood debris, decayed wood, sand, soil, and bark are typical wastes. Wood

waste can be burned in power boilers if soil and sand are removed. Much of this material is

landfilled, or used in the landfill as cover material. Wood chips that are burned for energy are still

considered waste by most mills if originally intended for pulping. Several mills indicated that wood

yard waste was the largest solid waste stream from their facilities.

Chip making also generates some wood waste. Knots and undersized chips are removed from the chip screen. These materials, along with bark, are usually used as fuel. Clean, palm-sized bark chunks have a high market value as a landscaping material. Some mills sell bark for landscaping. Sawmills and other bark sources that traditionally sold this material to pulp mills for fuel have diverted the landscaping suitable bark to other markets. The smaller, dirtier bark is sold to mills for fuel use. Soil and other debris in this bark must be removed prior to burning or after as increased ash volume, thus creating additional waste.



Sludge

Various mill sludges are also disposed of as solid waste but are derived from wastewater treatment

systems. Primary and secondary clarifier sludges consist of dirt, debris, and cellulose. This material

is intentionally rejected due to being out of specification or accidentally due to inherent

inefficiencies in the pulp washing systems. At each washing or refining stage, some usable pulp is

lost even after passing though save-ails. Deinking sludges are generated from recycling plants and

consist of inks, clays, soils, and some cellulose fiber. Mills sometimes dry and bum the sludges for

energy recovery and volume reduction. Deinking sludge will have approximately 50% ofthe energy

value of bark. Sludges are sometimes applied to forest or farm land partially as a disposal method

and partially to recover nutrients. Sludge generation is reported to be 0.02 to 0.06 TPT. Some pulp

mills indicated that improvements have been made in reducing the amount of cellulose inadvertently

sent to wastewater treatment. As the cellulose content in sludge is reduced, sludge volume

decreases. The sludge generated is then less useful for traditional recycling options such as reuse

in ceiling tile manufacture or as fuel.

Ash Ash is generated due to combustion. Coal, bark, wood, tires, and sludge are burned producing varying amounts of ash due in part to the amount of noncombustibles in the materials. Ash is disposed of in landfills or has some limited reuse. Wood and bark ash are sometimes used agriculturally for their liming potential. Ash generation rates are approximately 0.04 TPT from Georgia pulp mills. Ashes from different fuels will have varying metal content. Ash from burning tires will contain zinc. Some pulp mills in Georgia bum only wood and bark; other mills primarily burn some mixture of coal, wood, fuel oil, or natural gas.



Limemud

Lime mud is also disposed of as a solid waste. Pulp mills have lime kilns for regenerating lime mud

from the liquor recovery process. Often lime kiln capacity does not meet mill requirement, thus

requiring disposal of lime mud and purchase of fresh lime. Waste lime mud generation is only

related to kiln capacity, not production. Waste lime mud generation of up to 200 tons per day is

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reported. Other lime related wastes are green liquor dregs and slaker grits in relatively low volumes. Burning of noncondensable gasses in lime kilns can also increase the volume of grits and dregs generated.



Undigested knots

Knots generated in the digester and are resin-loaded pieces of wood that are not fully digestible due

to poor impregnation with cooking liquor and high lignin content. This material is separated from

digested pulp in various screening operations. Some mills mechanically break the knots down and

reintroduce them to the digester or pulp stream. Other mills dispose ofknots as a solid waste or burn

for energy recovery. Undigested knots also contain black liquor and are a source of air emissions.

Wastewater



Process Wastewater

Water is the largest raw material input in the pulp and paper industry. Georgia integrated

brownstock mills will use 5,000 to 12,000 gallons per ton of production. Bleached pulp mills in

Georgia have water usages ranging from 13,000 to 25,000 gallons per ton; approximately 50% is

used in the bleaching process. Specialty pulp mills can approach 40,000 gallons per ton. Recycle

mills also use a considerable amount of water. The lowest water usage noted during this study was

810 gallons per ton at Sweetwater Paper Board, a corrugated recycling mill located in Austell,

Georgia. The highest usage was over 17,000 gallons per ton in a recycling mill with deinking

processes and bleaching.

Wastewater as previously discussed can contain methanol, chlorinated compounds, cellulose, and other materials. Wastewater removes undesirable material from the process and carries them to a treatment system to partially concentrate and remove, stabilize, or destroy those materials that could damage the environment prior to releasing the water. Wastewater is generated in every washing stage, as well as in the woodyard and chemical generation.



Storm Water

Storm water may be affected by chipping dust that escapes as fugitive releases from the chipper or

chip piles. Bark, debarking dust, and other woody debris are lost around the edges of woodyards.

This material was obviously present on the ground around some manufacturing plants visited. Storm

water contamination with wood dust is not likely to cause long term problems such as ground water

contamination, but can prompt complaints from neighbors, block storm drains, and foul standing

water. Storm water runoff is often captured and treated. Wood yard areas and areas where pulp or

pulping chemicals are spilled do contribute to storm water pollution and increased treatment costs.

Mills typically collect and treat storm water from outside production and storage areas. Increased

BOD is the primary storm water pollutant.

Hazardous Waste

Hazardous waste is generated by pulp mills but not in large quantities. Maintenance wastes from degreasing and painting are typical waste sources.

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Pollution Prevention Barriers

Economic Barriers

The greatest barrier to pollution prevention in the pulp and paper industry is economic. A pulp mill is a large scale, mostly in-line production process composed oflarge and expensive devices. In-line production means that all ofthe product passes through each process component. If one piece fails, then the entire mill ceases to function. There are exceptions. Older mills tend to have many batch digesters while newer and upgraded mills use one or two continuous digesters. Process change becomes riskier as mills move more to in-line production.

A large integrated pulp mill producing 2,000 tons per day of product will cost almost $1 billion to construct if built today. Recovery boilers can cost up to $1 00 million for new installations. In addition to expensive equipment, the product is very expensive. Virgin bleached pulp prices have been in excess of $1,000 per ton. Upgrades to a pulp mill could require many weeks of construction. A single week of downtime could cost $14 million in lost sales. For these reasons, changes in technology are not implemented until the risk of failure is very low and economic payback high.

Newer pulping technologies are definitely more efficient that older technologies. Due to the cost of equipment and upgrades, it is difficult to justify major changes or replacement of entire systems until the working life of existing equipment has been reached.

Technological Barriers



Kraft Pulping

The Kraft process is the leading pulping technology in Georgia. Mechanical pulping is used at one

mill. Kraft pulping in many ways has remained unchanged; wood, water, energy, NaOH, and Na2S are the traditional process inputs. Wastes generated are methanol and other various organic

chemicals, solid waste, wastewater, sulfur compounds, and waste heat. Reduction in pollution has

resulted primarily from pollution control measures such as combustion of vented gasses and

scrubbing combustion stack gasses. Equipment modification to improve boiler combustion

efficiency has also reduced emissions. Pollution prevention techniques have resulted in improved

recovery ofNaOH and Na2S, reduced water usage, and reduced energy usage. Even with these improvements, the Kraft pulping process will continue to produce organic waste. Environmental

pollution reduction from the Kraft process will continue to be primarily capture and control since

there are few if any methods available for eliminating pollution at the source. Use of catalysts and

enzymes in pulping represents the first new technology changes in many years. Catalysts are

discussed later in the report under Alternatives to Chlorine Bleaching.



Bleaching and Pulp Washing

On the other hand, pulp washing and bleaching are continuing to change to reduce waste. Economic

barriers and some technical barriers still exist in implementing pollution prevention technologies in

bleaching and pulp washing, but there appears to be a steady evolution of these processes to reduce

waste and cost.

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Technological evolution in bleaching is evident by reviewing the existing bleaching technologies in 1995 compared to 1970. Bleaching began almost exclusively using chlorine and sodium hypochlorite. Due initially to dioxin concerns in the 1980s, alternatives to chlorine were researched and implemented. Chlorine dioxide has now either totally or partially replaced elemental chlorine and sodium hypochlorite. Oxygen and peroxide are also now used in bleaching and prebleaching stages. In addition, various methods to improve delignification in the pulping stage have been developed which reduce the dependance upon chlorine in bleaching.
Organizational Barriers
Lack of Pollution Prevention Programs The typical pulp or paper mill in Georgia does not have a program in place to evaluate wastes and develop methods of reducing. The primary focus of pulp mill personnel is to keep the mill in production by meeting quality, production, and environmental regulatory mandates. Mill personnel are extremely busy; tasks beyond the normal scope of work are commonly handled by using consultants. Pulp and paper mills use external consultants for environmental and design services. Through organizations such as the Technical Association ofthe Pulp and Paper Industry (TAPPI), the National Council of the Paper Industry for Air and Stream Improvement (NCASI), the Environmental Protection Agency (EPA), and other pulp and paper trade associations, technologies that improve environmental performance are well known to both mill personnel and consultants. For this reason, new mills are constructed with leading edge technologies; many older mills have also upgraded. Several pulp and paper manufacturers have corporate programs to reduce waste. In general, these programs are designed to identify and evaluate those leading edge technologies.



Lack of Waste Accounting

Some of the more murtdane aspects of waste minimization and pollution prevention are overlooked.

Mills have various means of accounting for waste generation, but these methods mostly focus on

major waste steams. Ash generation, sludge generation, solid waste generation, and overall water

usage are known. Specific sources of waste and water usage are unknown. Georgia pulp mills

generally account for waste generation and cost as overhead. Most mills have not attempted to trace

waste generation back to individual processes. In some of the mills, water usage was only known

as a total volume. Flows to individual processes, and waste materials contributed to the wastewater

stream by individual processes are unknown. Approximately 50% of the Georgia pulp mills have

<. ..

formal pollution prevent plans to evaluate waste and implement waste minimization methods. Even

the mills with formal pollution prevention programs tend to look toward the technological solutions

and not the simpler methods such as materials management. The simpler methods often require a

significant investment of time to develop and implement, but can have very large financial returns.

Air emissions by pulp and paper mills are calculated using emission factors or they are measured. Emissions factors provide an estimate of the amount of a chemical emitted per ton of pulp production. Emission factors are based on the type of equipment used to produce pulp. For example, the emissions factor for estimating methanol emissions from a batch digester and blow tank will be greater than the emissions factor for a continuous digester on a per ton basis. NCASI, EPA, and other organizations publish emissions factors. Emissions calculated by using emissions factors

13

may be higher or lower than measured values depending upon a number of factors. The general state of repair of equipment can also affect emissions; additional emissions due to failures may not be calculated when using emissions factors according to some mill personnel. In one facility, the pulp washer appeared to have some seal damage in an access door emitting steam, liquid, and odor. Other mills had darkly colored liquid streams escaping from pulp washers and storage areas. In every case, the liquid was collected in sewers for treatment at the mill's treatment plant. Air emissions from these failures may not be estimated by using emission factors according to some pulp mill personnel. The use of emission factors does not seem to provide an incentive for repair of relatively minor system leaks such as these. Measurement of emissions may not provide an incentive either since emissions from leaks or failures would be only measured if sensors were located in close proximity or were intentionally measured. Leaks from equipment in disrepair do increase operating cost and actual emissions. Preventive maintenance and leak repair should be included in all pulp mill procedures. Mills that have few leaks, few spills, and maintain a high level of housekeeping may release fewer air emissions than mills that do not maintain equipment or housekeeping as well. However, reported emissions for the two situations may be the same based on stack measurements or emissions factors.
14

Sources of Pollution Prevention Assistance to Pulp and Paper Mills
Most Georgia mills have received assistance in reducing waste. Some of the sources of assistance are listed below.

Trade Organizations and Technical Assistance Organization

Most Georgia pulp mills are involved in various trade and technical assistance organizations. A listing of some of the trade and technical assistance organizations are provided below. For this reason, pulp and paper mills are well informed of major technical and environmental trends.

TAPPI NCASI IPST
p2AD EDI GTRI UGA

Technical Association of the Pulp and Paper Industry

(770) 446-1400

National Council of the Paper Industry for Air and Stream Improvement (352) 377-4708

Institute ofPaper Science and Technology

(404) 894-5700

Herty Foundation

(912) 963-2600

Georgia Pollution Prevention Assistance Division

(404) 651-5120

Georgia Tech Economic Development Institute

(404) 894-5240

Georgia Tech Research Institute

(404) 894-3806

University of Georgia- Driftmier Engineering Center

(706) 542-8382

The Herty Foundation is an authority of the State of Georgia that offers contractual research and development to the pulp, paper, and nonwoven industries. The University of Georgia also offers the use of a 20 ton per day pulp mill for research of ozone, chlorine free, enzyme assisted, and other bleaching and deinking technologies.

Corporate and Facility Pollution Prevention Programs

Several of the Georgia mills use their corporate engineering and technical resources to reduce waste.

Other plants have mill personnel who measure and characterize waste streams with the goal of

reducing waste. Whether using corporate or plant personnel, some mills actively track waste

generation to the source and seek ways to reduce. A case study is attached in Appendix I describing

Weyerhaeuser's approach to waste minimization. Tenneco, Weyerhaeuser, Georgia-Pacific, Fort

Howard, Southeast, Federal, Gilman, and Rayoneer are some of the major pulp and paper

"- ..

manufacturers in Georgia with waste minimization programs. In each case, the specific goals and

methods may be very different depending upon the organization.

15

Key Pollution Prevention Issues

The following key issues were identified through contacts with Georgia pulp mill personnel, mill tours, interviews with paper industry experts, and review of various trade and environmental publications.



Lack of Facility Pollution Prevention Programs



Water Use Reduction and Reuse



Alternatives to Chlorine Bleaching



Log Yard Waste Reduction



Lime Mud Waste Reduction



Energy Conservation and Recovery

16

Lack of Facility Pollution Prevention Programs
A number ofmills do have formal pollution prevention plans while others do not. Some ofthe mills are part of wider corporate pollution prevention plans. The goals and methods used are different for each program. Regardless of goals and methods used, the plans should all include waste audits that track waste streams back to the source and estimate total costs associated with the waste streams. Once costs are known, specific projects can be identified that can be justified for their cost reduction potential. Discussions with plant and corporate personnel indicated that many of the plans do not include this basic requirement. Some of the plans were directed toward long-term technology goals such as zero discharge of wastewater or total chlorine free bleaching. These goals are necessary, but may be realized in 10 or more years. All current paper making technologies will not be replaced with long-term technology changes.
17

Water Use Reduction and Reuse
Water is used by all pulp, paper, and recycling mills in significant quantity. There are a number of processes which use water and generate waste water, but the primary uses are pulp washing following digestion and bleaching, and deinking and washing in recycling mills. Since most water used by a pulp mill is heated prior to use, reducing water usage can very significantly reduce energy usage. Energy costs and savings are often the most significant aspects of water usage reduction programs.

Brownstock Washing

Pulp washing is usually done in either of four washing systems, vacuum drum, pressure, diffusion, or Chemi. A brief description of each is provided below. Washing is done to remove cooking chemicals and to remove lignin breakdown byproducts as a prerequisite to pulp drying, bleaching, and paper making.



Vacuum Drum Washing

Vacuum drum washers usually consist ofthree to six counter-flow stages. Each stage consists of

a rotating screen drum which has a partial vacuum applied to the interior. The drum sits in a tank

where pulp is diluted with wash water. The vacuum draws a pulp mat against the surface and wash

water through the mat. The drum rotation advances the washed pulp mat to the next dilution tank.

Wash water discharged from this wash stage is sent to the previous washing stage. At least six

Georgia mills use vacuum drum washers.



Pressure Washing

Pressure washing is similar to vacuum drum, but differs by spraying water under pressure through

the pulp mat as the drum rotates. At least one mill in Georgia uses pressure washing.



Diffusion Washing

Diffusion washing is a counterflow process that takes place in one or more stages. Pulp flow is

upward and is carried on a perforated plate; water flow is downward through a series ofbaffles. This

method offers a high degree of cleaning with low water use. At least three mills use diffusion

washers in Georgia.



Chemi or Belt Washing

A Chemi or belt washer is perhaps the simplest washing system design and offers reduced water

usage with excellent cleaning. Belt washing is a counter flow process where pulp enters the washer

area on a wire belt. Washing takes place under a series of showers. Clean water enters on the

opposite end from the pulp and is sprayed vertically through the pulp. The used wash water is then

collected and reapplied to the dirtier pulp by the next washing head countercurrent to the direction

that the pulp moves. This process is continued through at least seven stages until the wash water is

18

saturated with liquor after washing immediately incoming pulp. The wash water is then sent to the recovery process. Two mills in Georgia are known to use Chemi washers. Reduced dilution of the liquor recovered from washing will result in reduced energy usage in the recovery process.
The effluent from brownstock washing contains black liquor that must be recovered in addition to varying amounts of water. Diffusion washing and belt washing can reduce the amount of water used per ton of pulp in brownstock washing by 50% or more according to published data. However, the mills in Georgia do not show order of magnitude reductions when using the newer washing technologies. Comparison between mills is difficult due to product mixes of virgin and recycled pulp; mills that have replaced vacuum drum washing with diffusion or belt washing report that improved cleanliness or water reductions were achieved with the new technology, but exact figures were not available. Improved cleanliness is important in reducing bleaching load.

Costs of Pulp Washing With a Chemi Washer

Although several mills in Georgia have upgraded pulp washing, specific information on cost and water usage was not available. In the EPA's document, Pollution Prevention Technologies for the Bleached Kraft Segment of the U.S. Pulp and Paper Industry, the following estimate was provided.



Capital Equipment Costs



including Chemi washer and all support facilities

$10.2 to $12.3 MM



Operating Cost Reduction Compared to Vacuum Drum Washing $4.67 per Ton of Pulp



including water and energy reductions



Annual Cost Reduction in a 1,500 tons per day mill

$2.4 MM



Payback Period

4.25 to 4.9 years

Due to the long payback period, replacement of vacuum drum washers with a Chemi washer is more feasible in a new installation or when a new washer is required to replace a vacuum drum washer that has reached the end of its service life. The installation cost does include all support facilities such as a building to house the unit and piping. The actual replacement cost would be less if support facilities were already existing. Also, the operating cost reduction does not include savings in the bleaching stage. Improved washing will result in less lignin in the pulp thus reducing bleaching requirements.

Bleach Mill Effluent Reduction
Washing of brownstock prior to bleaching allows the recovery of wash effluent in the recovery boiler. Once the pulp has gone through a chlorination stage, recovery is not practical due to corrosiveness. Improved washing and increased delignification prior to bleaching decreases bleaching load and reduces the load placed on wastewater treatment. Bleach mill effluent reductions
19

can then best be achieved prior to any chlorination stage. Improved delignification can allow bleached pulp mills to eliminate certain bleaching and extraction stages while achieving the same level of brightness. Elimination of a bleaching stage can reduce water usage by 2,500 gallons per ton ofpulp production.

Bleach Mill Effluent Recycling Several mills and corporate organizations are exploring reuse or are reusing bleach mill effluent in previous bleaching stages. Bleach mill effluent accounts for approximately 50% of a bleached Kraft mill's water usage with effluent streams from each stage of bleaching. Recycling water to previous stages could reduce water usage by 60% depending upon the bleaching configuration. Wastewater from bleaching and pulping will contain methanol, other organics, and chlorinated compounds. Reuse in uncontrolled areas could increase air emissions. Typically, a mill will recycle white water from the paper machine back through the various bleaching stages in a counter-current process.

Other Water Use Reduction Opportunities



Process Pump Seals

Seal water used in various pumps has been eliminated by replacing with mechanical face and lip

seals in several facilities around the state. Seal water flows are typically not very high, but are

continuous and can add up to large volumes over time. Replacing water seals with mechanical seals

usually increases energy consumption due to friction. Seal water can also be collected and reused

for other processes but may contain contaminants from the chemical passing through the pump.

Seals are also a source of air emissions, water pollution, and raw material loss due to leakage of the material being pumped through the seal. Chemical pump seals are being investigated by some mills for replacement with sealless and magnetically coupled pumps. An example of a sealless pump is a diastolic tube pump. Magnetically coupled pumps transmit power from the motor to the pump with a magnetic field. Traditionally, both designs are better suited for low torque applications. In either case, sealless pumps are not new technology and should work well in the pulp industry.

Union Camp in Savannah has replaced water lubricated seals with mechanical seals. According to an article published in the November 1995 issue of "Pulp and Paper," replacement of braided packing seals with a self-lubricating compound has reduced water usage and equipment failure. The compound used is a "colloidal mixture of lubricants amalgamated with Aragraphe fibers" manufactured by Tom-Pac of Montreal, Canada. The sealing compound also allows leaks to be repaired by injecting more compound into the seal. Replacement of water lubricated seals also reduces the potential ofbearing and gearbox contamination with water, and seal water contamination with oil or other materials. Union Camp points out that 95% of the seal replacement projects have been successful. The benefits of this waterless sealing compound to Union Camp have been:



reduced water usage. reduced equipment damage.



reduced water contamination.



reduced maintenance time.

20

Vacuum pumps are used to supply vacuum to vacuum drum pulp washers and other mill equipment. Vacuum pumps are typically liquid ring pumps which use water for sealing and cooling. Water usage is continuous and can be high depending upon the size of the pump. Liquid ring vacuum pumps represent the common technology used in hospitals and other facilities needing large vacuum volumes. In resent years, oil-free and oil-flooded rotary screw pumps have been used in some cases to replace liquid ring pumps to reduce water usage in hospitals. This technology may be useful in the paper industry to replace liquid ring vacuum pumps. Water discharged from liquid ring pumps should be suitable for reuse in any number of mill applications, but may contain some process contaminants.



White Water Recycling

Paper machines can generate significant amounts of wastewater. One mill generated 3,000 gallons

per ton of paper. White water is typically clean, but may contain some contaminants such as fiber,

lignin compounds, and various organics. Some of Georgia's pulp mills are recycling paper machine

water back to bleaching or pulping operations. Where bleaching does not exist, white water from

the paper machine can be reused or partially reused directly in pulp washing or in the wet end of the

paper machine. One Georgia mill recycling corrugated material reuses all white water after

clarification. The sludge that settles during clarification is also reintroduced into the process. The

company, Sweetwater Paper discharges approximately 810 gallons per ton of pulp produced.

21

Alternatives to Chlorine Bleaching

Waste Generation
Wastes of greatest concern from bleaching are chloroform and dioxins. Elemental chlorine and sodium hypochlorite are the two bleaching chemicals most associated with chloroform and dioxin formation. For this reason, most mills have eliminated sodium hypochlorite and replaced chlorine to some degree. Of the six virgin bleached Kraft pulp mills in Georgia, three have replaced elemental chlorine with chlorine dioxide. The other three have substituted varying amounts of chlorine dioxide.
Bleaching, as previously discussed, is a multistage process. Historically, bleaching was considered . a separate process from digestion and began with a chlorine stage. Currently, with elemental
chlorine use in decline, it is more difficult to define where digestion or delignification ends and bleaching begins. Some of the pollution prevention options discussed below perhaps are closer to delignification than bleaching in historical terms. In either case, the basic purpose of bleaching is to further selectively delignify pulp.

Pollution Prevention Options



Chlorine Dioxide Substitution

Georgia pulp mills have proven that 100% chlorine dioxide replacement for elemental chlorine is

technically and economically feasible. Mills nationally have reported pulp quality improvements

by switching to chlorine dioxide. Some mills using less than 100% chlorine dioxide report that

increases in substitution rate are not economically feasible. The lack of economic feasibility seems

to be related to equipment costs as opposed to chlorine dioxide cost. Replacement or upgrade of

washers, bleach tower materials, and chlorine dioxide generators were all mentioned as needed prior

to increasing substitution rates at these mills. Full substitution can also cause reduced pulp yield and

reduced brightness according to some published data.

Chlorine dioxide costs more than elemental chlorine. Even with chlorine dioxides greater reactivity, chlorine dioxide can cost more than eight times as much as elemental chlorine according to EPA documents. It is estimated by the EPA that the total cost of generating one pound ofchlorine dioxide is approximately $0.50. The cost of an equivalent amount of chlorine is $0.06. In a 1,000 ton per day mill operating at 11% substitution, an increase to 50% substitution would cost $5 million initially with an increase in operating costs of $1.9 million annually or $5.40 per ton. Increasing to 100% substitution would cost $15.9 million initially with an increase in operating cost of $7.1 million annually or $20.30 per ton. Considering that pulp prices can approach $1,000 per ton, 100% substitution represents an increase in operating cost of about 2%. These estimates are based on general averages and not one particular mill.

22

Reducing dependance on chlorine bleach can best be achieved prior to bleaching. Bleaching is basically an extended chemical delignification process. Chlorine is used to selectively delignify pulp without causing the damage to cellulose that traditional pulp digestion causes. The key to reducing chlorine use is to find methods which delignify further prior to the bleaching stage.



Improved Chip Uniformity

Uniform, thin chips achieve a greater degree of delignification in standard or modified cooking

processes by allowing the chip charge to reach a predictable amount of digestion using a specific

chemical and thermal mix. Various methods are available and include improved screening and

rechipping of oversized chips. This is a lower cost option for improved delignification with or

without bleaching.



Extended Delignification

A number ofmethods exist for improving delignification without extensive cellulose degradation.

At least four mills in Georgia use extended delignification techniques. These techniques are

primarily applicable to continuous digesters. New digesters can cost upwards of $15 million. Some

Kamyr digesters, which are the most common type, can be refitted at costs reported in the $1 million

range. Batch digesters can also be refitted in some cases. Reduced operating cost by refitting results

in payback periods of approximately 18 months according to EPA documents. The cost savings are

reported to be in steam and reduction in bleach chemical usage.



Oxygen Delignification

Oxygen delignification requires the addition of a reaction tower between the brownstock washers

and bleach plant. Oxygen and sodium hydroxide is added to brownstock. Reduction of bleaching

chemistry by 50% can be achieved in the bleaching process if preceded by oxygen delignification.

Washing follows oxygen delignification; effluent can be recovered or discharged. At least two

Georgia mills use oxygen delignification. Cost of building a new oxygen delignification tower can

be in the $10 to $30 million range, but may be offset by reducing bleaching needs. Operating costs

have been estimated to decrease by up to $3.70 per ton for softwood and to increase by up to $6.65

per ton for hardwood based on studies conducted in Sweden and published by the EPA.



Ozone Delignification and Bleaching

Ozone delignification is not used by any Georgia mills; only one full-scale mill operates within the

U.S. Ozone delignification is similar to oxygen delignification. The Union Camp mill in Franklin,

Virginia, began operation in 1992 with an OZEoD extended delignification and bleaching process

at 1,000 tons per day of bleached kraft production. The overall installation cost was $113 million.

Operating costs of the OZEoD delignification and bleaching process are reported to be about 50%

less when compared to the more conventional CEDED or DEDED process. D represents chlorine

dioxide, E represents extraction, 0 represents oxygen, and Z represents ozone. There is one pilot

mill in Georgia capable of ozone delignification and bleaching. The mill is operated by the

University of Georgia for the use of the school and industrial customers for research.

23



Alternative Chemicals Used in Bleaching

Chlorine and chlorine dioxide are the only bleaching chemicals used in Georgia by virgin Kraft pulp mills. Oxygen and peroxide are used to augment sodium hydroxide extraction. Oxygen and peroxide act to delignify in the extraction stage essentially replacing chlorine in later stages. Sodium hydrosulfite is used by one mill in a bleaching operation producing newsprint. No Georgia mills use ozone in bleaching, although ozone bleaching is used in a pilot mill in South Carolina and a fullscale mill in Virginia.



Enzyme Bleaching

Enzymes are used by wood eating insects and bacteria to break lignin bonds or to delignify pulp.

Xylanase is an enzyme family related to the chemicals secreted by such bacteria; it appears to be

useful in pulp bleaching, extended delignification, and deinking. Mills nationally have used this

chemical in trial runs; results indicate that up to 50% reductions in chlorine requirements can be

achieved without damage to the cellulose. Application ofxylanase appears to be simple. Following

brownstock washing, xylanase is applied to the pulp as it enters the high density storage tank.

Xylanase works in the high density storage tank and requires between 30 and 180 minutes of reaction

time. A washing stage follows the xylanase treatment. No Georgia mills report using xylanase, but

it appears to be a low cost method of achieving significant results. Other enzymes such as

mannanase are being investigated.



Catalyst Improved Delignification

Anthraquinone - Anthraquinone is a pulping reaction catalyst which was found to increase the

speed of pulping, increase yield, and reduce pulping chemical usage by up to 10%. Anthraquinone

is one of the few new technological discoveries in the Kraft pulping field. Due to cost,

anthraquinone has not been used extensively in the U.S. except in testing. Approximately 100 mills

worldwide use anthraquinone. Although developed as a pulping pollution prevention technology,

it may have greater use and be more cost effective if used as an aid to extended delignification. The

cost of anthraquinone is expected to drop in the near future due to patent expiration. Renewed

interest may develop as a result. Anthraquinone has been estimated to increase pulping costs by

approximately $5.00 per ton, but with increased yields of 0.75% and reduced recovery boiler loading.

An increase yield of0.75% represents an increase in production of7.5 tons per day in a 1,000 tons

per day mill.

Polysulfide - Polysulfide is another catalyst mentioned in trade magazines applicable in pulping. Yield increase of 1.5% are possible with improvements in strength. It is possible to use both anthraquinone and polysulfide together. TAPPI publications report that yield increases of approximately 2.5% are possible.

24

Log Yard Waste Reduction
Waste Generation
Log yard waste is for some mills the largest solid waste stream. Mills with on-site landfills will often use some ofthis material as landfill cover, but there is often more waste than needed for this purpose. Log yard wastes are typically bark and woodchips mixed with soil, oversized logs and undersized limbs, metal-containing logs, and mold damaged chips. Energy usage in the form of fuel for log handling trucks is another raw material input. In addition to pulp mills, saw mills, plywood plants, and similar facilities will have log or wood yards and use some of the processes described below.

Characteristics of Log Yard Operations
The purpose.of a log yard is to receive incoming logs and chips, debark logs, chip logs, and store bark and chips. Logs, chips, and bark are delivered by truck and rail. These materials are stored in stacks or piles. Logs are handled either by rail-mounted cranes or large wheeled log trucks. Logs and chips are stored by using some inventory management program to reduce weathering and spoiling.

Specific Causes of Waste Generation



Bark and Chip Contamination

Bark and wood chips that become mixed with soil cannot be used for fuel or pulping. Both materials

fall from the margins of piles and become soiled. Additional bark falls from logs prior to debarking

as a result ofhandling. All log yards are outside facilities. Some are partially or completely paved.

Others are completely unpaved. Soil that becomes mixed with chips and bark comes from exposed

soil in the log yard.



Over-sized Logs

Oversized logs are logs that are too large to be debarked or chipped by mill equipment. The material

is delivered to mill log yards by truck and rail. Delivery of oversized logs is caused by a lack of

incoming material inspection.



Metal-containing Logs

Metal-containing logs have nails or wire imbedded in the logs. The metal may not be visible, but

is detected electronically on the chipper or debarking decks.



Woody Debris and Soil

Undersized limbs and other debris such as soil and sand are delivered attached to logs or trapped

25

between logs. Soil and sand is also delivered with bark and wood chips that are manufactured offsite.



Decay

Various molds damage logs and chips. The length of time stored as well as weather conditions

contribute to mold growth.



Poor Log Yard Layout

Fuel usage can be significant. In one logyard that was handled entirely by log trucks, an estimate of

the miles traveled annually by log trucks totaled 17,000 miles. The distance driven contributes to

''"),

fuel usage and maintenance costs.

Pollution Prevention Options



Log Yard Delivery Specifications

Oversized and undersized log disposal in landfills can be reduced to near zero. Publishing of log

size standards and rigidly enforcing delivery standards will prevent delivery of oversized logs.

Incoming inspection of logs can prevent delivery and disposal. Oversized logs that are delivered can

be cut to smaller size so as to fit in existing equipment or sold to specialty lumber companies and

mills that can accept larger logs.



Purchase ofAdditional Chipping Equipment

Undersized logs can be debarked and chipped. Debarkers are advertised in trade magazines that can

handle small and irregular shapes. Once debarked, undersized logs can be chipped. Several mills

have purchased mobile chippers to handle this material.

Metal-containing logs were traditionally landfilled. Some mills cut the metal-containing area from logs. The metal-containing portion is landfilled; the metal-free portion is debarked and chipped. There are chippers that can chip metal-containing logs without damage. Metal, which is most often steel, is magnetically separated. This material can then be used a boiler fuel or chips for particleboard manufacture.



Paving and Improving Log Yards

Paving log yards seem to be the best practice for reducing soil contamination. Bark and chips that

do fall onto the ground will be less likely to become contaminated. Paved areas also allow bark and

chips to be collected for use. Maintenance costs will probably decline for log yard trucks, debarkers,

and chipping equipment by preventing soil contamination. Log flumes will also have reduced soil

loading.



Chip and Bark Cleaning

Wood chips and bark that has become contaminated with soil can be cleaned in vibratory screening

26

systems. Several mills are considering screening systems. The bark and chips would be used as fuel after screening. Soil and fines can be used as landfill cover or other soil use.



Improved Log Yard Layout

Fuel and truck maintenance costs can be reduced by designing log yards to reduced distance driven.

Time and material flow studies are commonly conducted in manufacturing plants to reduce fork

truck travel and travel time. The sam~ techniques and benefits could be realized in log yards.

27

Lime Mud Waste Reduction

Waste Generation
Lime mud waste is directly related to lack of lime kiln capacity. Some mills dispose of up to 200 tons per day. Lime mud disposed of must be replaced by purchasing calcium oxide. Disposal and purchase increase operating cost and fill landfills. There is some offsite reuse of lime mud, but the majority is disposed in landfills or storage lagoons.
. ,
Characteristics of Lime Kilns
Lime kilns are typically long rotating tubes where combustion gasses and calcium carbonate pass through changing calcium carbonate to calcium oxide and carbon dioxide. Heat loss is great since insulation is difficult to apply to the rotating housing. Downtime is one reported additional problem. For various reasons such as mechanical failure, kilns are often offline. Since pulp mills operate continuously, lime mud produced during kiln downtime is often landfilled.

Pollution Prevention Options



Install Second or Larger Lime Kiln

Some mills have increase kiln capacity by adding second kilns. In some cases, Georgia mills have

reclaimed tons of lime mud stored in treatment lagoons after adding kiln capacity. Kilns are high

cost devices. The economics of installing a new kiln are not known.



Vertical Kilns

Vertical lime kilns can offer reduced down-time, improved energy efficiency, and larger kiln

capacity in a smaller footprint area. Vertical kilns have not traditionally been used due to some

manufacturing limitations. A NICE3 grant was awarded to Altex Incorporated to develop a vertical

lime kiln; the pilot plant tests are targeted to Weyerhaeuser's Flint River Plant in Oglethorpe,

Georgia. More information is contained in Appendix II.

28

Energy Conservation and Recovery
Waste Generation
Energy is heavily used by the pulp and paper industry. Most mills generate steam and electricity by burning black liquor, coal, wood, and natural gas. Coal combustion is responsible for much of the sulphuric acid and sulphur dioxide emissions reported on the TRI. Additional expense to pulp mills in treating exhaust stack emissions is also incurred. Ash is also a significant solid waste stream and disposal problem when burning coal or wood waste.

Characteristics of Energy Generation in Georgia Mills
Mills typically burn wood both as an energy source and disposal method to reduce volume. Mills that cannot meet their energy needs from wood waste and black liquor combustion purchase additional fuel in the form of wood, coal, bark, fuel oil, and natural gas. Some mills have chosen to only burn wood since it is a low sulphur fuel source. Many mills generate excess electricity to sell back to utility companies or participate in the utilities' power grid load management program. This can be a good source of revenue for some mills. The majority of energy is used to generate steam to heat water, processes, or generate electricity.

Pollution Prevention Options
Sulphur emissions and ash generation can be reduced by burning less fuel. Less fuel will be burned if the energy demand of the mill is reduced, and energy value of the fuel is maximized.



Water Usage Reduction

Since water is generally heated prior to use in mill operations, water usage reduction will reduce

energy costs. If a heated water flow at 180 op is reduced 100 gallons per minute, the annual water

reduction is 50,400,000 gallons. The energy reduction assuming 65 op ambient is 46,368,000,000

BTU. Assuming that water costs $2 per 1,000 gallons, water costs will reduce $100,800. Energy

costs will reduce $289,336 assuming an energy cost of $6.24 per million BTU.

Thermal Energy Recovery Energy demand can be lowered in pulp and paper mills by capturing and reusing waste heat. Energy lost through cooling towers, exhaust stacks, wastewater, and product can all be recovered for reuse. Heat recovery and utilization opportunities vary at each mill depending upon the mill age and layout. One mill in Georgia has identified several recovery opportunities. In this one mill specific example, recovery of heat from wastewater by installing liquid-to-liquid heat exchangers to heat incoming process water was estimated. to cost approximately $1 million for installation with a payback of less than two years.

29



Improved Efficiency

Energy requirements can be lowered by using more efficient equipment such as high efficiency

electric motors or by redesigning processes. For example, energy required for drying can be reduced

by decreasing water content of pulp before drying.

Pollution Prevention Recommendations for Reducing Energy Usage



Conduct Energy Audits

A complete energy assessment should be conducted at each facility to identify opportunities.

Oglethorpe Power and Georgia Power, the primary suppliers of electricity in Georgia, both will

conduct very thorough audits complete with recommendations and cost I benefit estimates. The

Energy Analysis and Diagnostic Center (EADC) of Georgia Tech's Economic Development Institute

also performs advanced energy audits. EADC can be contacted by calling (404) 894-3844. Some

of the common opportunities identified through audits are:



Replacing cooling towers with heat exchanger loops to heat supply water.



Recovery of steam condensate.



Recovery of "low grade" heat from hoods, vents, and waste water.

Specific recommendations will vary at each mill location.



Improved Fuel Storage

The energy value of wood chips can be increased by decreasing moisture content. Moisture content

will increase in chips stored in piles outdoors. Placing a cover over chip and bark fuel piles is one

method of reducing moisture, increasing energy value, and decreasing decay. Mills will sometimes

store pulp chips in silos; this would be a good storage method for fuel as well. Turning chip piles

is another method of decreasing decay and moisture content. Energy values can increase 10% or

more by decreasing moisture content, with a resulting 10% reduction of ash, fuel demand, and some

air emissions.

30

Pollution Prevention Assistance Needs of the Georgia Pulp and Paper Manufacturing Sector

Organizational Needs



Education on the value of pollution prevention programs that provide for audits, waste

cost accounting, and implementation of projects.

This information may allow mills to upgrade existing outdated technologies by proving or disproving

cost effectiveness for specific projects. Opportunities that are not obvious to mill personnel can be

identified by conducting audits.

Technical Needs



Information on leading industry and standard pulp and paper technologies

Mills are generally aware ofthe major technologies used by the pulp industry. Specific information

on the benefits of specific technologies is still needed. Several mills indicated that leading

technologies such as belt washers and pressure washers had been installed, but provided less than

expected performance. Technologies used by other industries for maintenance cleaning and coating,

or water filtration may be of use to pulp and paper mills in replacing processes. Several requests for

this type of information were made by mill staff during research for this paper.

Technology Research Needs



Basic Research

Basic research needs of the pulp and paper industry are being met by various trade and educational

institutions. Research currently focusses on enzyme and catalytic augmentation of current processes.

Additional research involving zero-effluent mill design is ongoing. Some industry experts predict

that the next century will bring totally biologic and enzymic pulping and bleaching which will reduce

energy and chemical use.



Applied Research

Of greater interest to pulp and paper mills is bringing current laboratory technology to the pulp mill.

Enzymes, catalysts, alternative bleaching, water reuse technology, and advances in lime calcining

are areas of applied research interest.

31

Approaches to Meeting Assistance Needs of Georgia Pulp and Paper Manufacturers
The following section discusses how P2AD will meet the pollution prevention needs of Georgia mills.
Meeting Organizational Needs
Provide Pollution Prevention Training Organization needs are primarily education and training of mill management and production staff
').
on the pollution prevention techniques. The ultimate goal is to have each mill conduct pollution prevention assessment, evaluate results, and implement cost-effective solutions. Several Georgia mills and corporate organizations do have working pollution prevention plans in place.
Two roles that Georgia P2AD (in conjunction with Georgia Tech, UGA, IPST, Herty Foundation, etc) can play in pulp and paper mill pollution prevention planning are to improve awareness among mill personnel and to facilitate communication between different pulp mills.
Facilitate Exchange of Information Between Manufacturers Facilitation can occur by identifying successful pollution prevention programs in pulp mills and educating other mills of success and opportunities identified. Publicizing successes through published information and providing public forums for information exchange are the methods that P2AD and its partners can use.
Provide Experienced-based Training to Georgia Mills Teaching and training mill personnel by offering industry wide and mill specific workshops are the suggested approaches for providing general pollution prevention training. Specific training on pollution prevention techniques applicable to a particular mill process is also needed. In order to meet these needs, P2AD and its partners must develop greater expertise in pulp and paper mill processes. P2AD will gain the needed expertise by participating in training offers extended by some of Georgia's paper mills. Additional expertise will be gained by conducting assessments with mill personnel at Georgia facilities. Contacts made during the research for this paper will likely lead to assessment opportunities. Training can take place by attending courses and seminars offered by TAPPI and other pulp and paper organizations.
32

Meeting Technical Needs
Publish Fact Sheets and Case Studies on New and Standard Technologies Technical needs are primarily information on new technologies as well as information on industry standard technologies for reducing waste and cost. Fact sheets providing general information on new technologies can be developed and can include enzyme, catalytic, and ozone processes. Case studies of implementation of mill standard technologies can be developed also and can include continuous digestion, belt washing, diffusion washing, extended delignification, oxygen delignification, and other mill processes. This information can also be presented in public forums at technology conferences. Cost reduction is perhaps the key issue when presenting case studies.

Meeting Research Needs



Use Existing Research Resources

P2AD can aid in meeting applied research needs by encouraging the use of existing state resources

such as IPST, Herty Foundation, and the research pulp mill at the University of Georgia. The NICE3

project with Weyerhaeuser and Altex is one such applied research project. Results of this project

and other paper industry related projects will be provided to Georgia mills through fact sheets and

workshops. P2AD will investigate state and national resources for pilot studies in pulping, bleaching,

and paper making. This information can be distributed through fact sheets and workshops.

Any new or existing basic research needs can be identified though mill and corporate contact. P2AD will attempt to find existing research programs addressing a particular need. If research is not ongoing, contacts can be made at various educational and industry organizations to determine a course of action. This may include finding researchers with appropriate expertise, additional industries interesting in funding research, and other financial assistance sources.

<- ..

33

Summary and Conclusion

The purpose of this study is to identify the pollution prevention needs of the Georgia pulp and paper industry. This information will be used to develop programs within P2AD or through partners to
address industry needs. Some of the needs and methods of meeting needs are listed below.



Significant opportunity does exist within Georgia pulp and paper manufacturers to reduce

waste. Waste reduction has been accomplished at several mills by implementing pollution

prevention programs to identify opportunities and implement cost-effective solutions. P2AD

can provide the greatest assistance by facilitating the development of programs in all mills.



Georgia mills need information to replace existing processes with more efficient technology.

P2AD can assist by developing case studies for various mill standard and cutting edge

technologies. Mills can also benefit by learning oftechnologies used by other manufacturing

sectors to reduce waste from maintenance and other non-process related operations.



Applied research is needed to industrialized new technologies. P2AD can educate mills on

various applied research projects and resources in Georgia and nationally.

New basic research needs probably exist concerning such issues as enzyme use. These issues will be identified through discussions with mill, corporate, trade, and research organizations. P2AD can assist in matching research needs with the appropriate technical and financial resources.



P2AD will continue to seek educational resources for AD and partner organization staff

with the goal of becoming well informed on pulp and paper mill industrial practices. P2AD

cannot provide adequate assistance to Georgia mills without achieving a high level of

expertise in pulp and paper technologies.

34

APPENDIX I
~.

AN APPROACH TO SOLID WASTE MINIMIZATION IN THE PAPER INDUSTRY

Manfred K. Buder, Solid Waste Minimization Project Manager Weyerhaeuser Company - Tacoma, Washington

Since the late 1980s the paper industry has written numerous success stories in the reduction of the solid waste it generates and disposes. According to a survey by NCASI (National Council for Air and Stream Improvement), in 1989, the industry generated over 13 million tons of process wastes, nearly all of which were land filled. Most of this waste consists of effluent treatment solids ("sludge"), boiler ash, lime wastes, and wood debris. In recent years the industry has made inroads in shifting much of these residuals to useful alternative practices, such as energy recovery and land application.

Weyerhaeuser Company ascribes to an integrated approach for managing the solid wastes from its manufacturing facilities. This means the coordination of a "full tool kit" of waste management options and their implementation across all of Weyerhaeuser's facilities. A key part of this strategy is to make progress in reducing the generation of and finding beneficial uses for these solid residual streams. There are five key drivers for the company's waste minimization effort:

0

Environmental protection and tightening regulations

0

Stakeholder expectations

0

Company policy to conserve resources and minimize waste

0

Landfill depletion and high replacement costs

0

Economic benefits: avoided disposal cost and material recovery credits.

Accordingly, Weyerhaeuser's mills in Georgia have made and are continuing endeavors to minimize their solid waste streams. The Flint River pulp mill recycles scrap metal, office paper, and aluminum cans. The mill has also made significant strides to reduce fiber loss, thereby not only conserving raw materials, but also decreasing the quantity of primary effluent treatment sludge that needs to be dewatered and hauled to the landfill. Our composite panels mill at Adel provides another example of solid waste minimization. Instead of land filling its sanderdust waste, the mill sells it to a Florida utility company that uses it for fuel. Per unit of product, our sawmill at Barnesville landfills less of its manufacturing wastes that any other Weyerhaeuser sawmill. This is largely because of the mill's resolve to recycle these residuals as raw materials for particleboard manufacture (at Adel), for use by horticultural and landscaping companies, as a fuel (both internally and at Flint River), and for other beneficial uses. The Barnesville sawmill has also undertaken pollution prevention measures to reduce its generation of log yard waste to a level that is unmatched by similar mills within the company.

In support of this companywide effort, a technical team from the Corporate R&D group has been charged with providing assistance to Weyerhaeuser's pulp, paper, paperboard, and wood products mills to minimize solid waste generation and disposal. This Solid Waste Minimization (SWMin) Team works with the mills and with sister entities at the corporate offices to obtain data, evaluate solid waste reduction opportunities at mills, develop mill SWMin plans, and stay abreast ofpertinent technologies. At the heart of the program for the past several years have been the SWMin studies conducted at Weyerhaeuser manufacturing facilities. The SWMin Team with the help of mill staff, obtains data on recurring, non-hazardous solid waste streams, and assists the mills in identifying and

capturing significant waste reduction and utilization opportunities. Since the onset of the decade, SWMin studies have been completed for nearly all of the company's thirteen pulp, paper, and paperboard manufacturing sites. In the last couple ofyears Weyerhaeuser's SWMin Team has been busy working with various wood products facilities.

SWMin is a seven-step process (see Figure 1). The first step is the planning and coordination ofthe study with the mill. Second, the SWMin Team, typically two engineers and two technicians, conduct a week-long onsite survey to identify waste steams and their sources/destinations, glean facts and data, take samples, and obtain ideas and other input from mill staff. In the third step, the solid waste streams are screened down to a manageable number of key streams for which various short- and long-term minimization alternatives are identified. Three screening criteria are used: annual disposal cost, annual recovered value ofthe stream, and associated environmental issues. Also, at this point in the process the SWMin Team surveys potential uses and users for selected residual streams as a reality check against some of the utilization alternatives being considered. In Step 4,

Figure 1:

MILL SWMIN Project Flow Diagram

I

Project Planning & Coordination

I I

1

I

lnMill Solid Waste Survey

I

l

I

Alternative Identification

I I

1

I

Opportunity Evaluation

I

l

I Goal Setting and Implementation Planning

I I

1

I

Implementation Project

I

1

I

Documentation of Progress

I
I

Periodic Reanalysis as Required

the most promising combinations of waste streams and minimization alternatives are further developed and evaluated based on roughly estimated life-cycle economics. The "top" economic opportunities are ranked by their net present values and reported to the mill (see Figure 2). These opportunities are reviewed and revised, as appropriate, with mill staff in the fifth step of the SWMin process. The purpose of this step is to select a reduction target, finalize the SWMin project roster, and develop a five-year SWMin plan. Step 6 is the implementation of this plan and Step 7 is the documentation of SWMin progress against the plan. The SWMin Team is available to the mills for

37

Figure 2-
Typical Economic Pareto Diagram
Economic Benefit of the "Top Seven" Waste Minimization Opportunities Pretax Net Present Value of Benefit by Minimization Opportunity

60%

-,.

Pretax

Net

Present

Value of

Benefit

40%

$0

Logyar<l Debris Separator

Fiber Recovery to ReducePri.
Sludge

Boiler Upgrade to
Reduce Flyash

UmeMud Spill
Control

Grits/Dregs Washing and LMtd
Application

Fuel Use of Secondary
Fiber Rejects

General Miill Waste Source Segregation &
Recycling

technical support during the implementation and documentation phases. Of course, since costs, markets, production, and other things do change over time, it will be necessary to loop back and revisit some earlier steps in the process from time to time.

Typically, 50 to 100 solid waste streams, some ofthem very small on a relative scale, are identified at each company pulp and paper mill. Most of these wastes end up being land filled, usually onsite. Others are burned, typically in the power boiler, or land applied. Secondary effluent treatment solids are impounded in lagoons for the most part, since few company mills use activated sludge treatment systems. Small, but growing, quantities of the mills' solid residuals are recycled.

The largest solid waste categories being generated by the mills are various woodwastes, boiler ash, effluent treatment sludges (primary and secondary), recausticizing wastes (dregs, grits, lime, etc.), and general mill trash. Minimization of these types of streams is certainly challenging. As examples, the SWMin team and Weyerhaeuser mills have evaluated, and in many cases implemented, the following SWMin approaches:

0 Woodyard debris: (1) debris separation into hog fuel, rocks, and fines (soil supplement);

and (2) woodyard paving.

0 Boiler ash: (1) boiler upgrade to improve combustion efficiency, (2) flyash screening and

char reinjection, and (3) ash utilization as a soil supplement or construction material.

0 Primary sludge: (1) avoiding mixture of ash, line, and other separable streams flowing into

the primary effluent treatment system, (2) spill and leak control, and (3) recovery of fiber for

internal or external use, or for energy recovery as a fuel.

0

Grits and dregs: (1) purchased lime quality control, and (2) washing and land application.

Although there are similarities among mills, the SWMin Team found the mills to be at different stages of waste management along the hierarchy of alternatives (i.e., from disposal up through recycling and source reduction). However, significant opportunities exist for cost effective improvement at each facility surveyed. One result ofthese studies has been to make the mills more aware ofthe solid wastes they generate, must manage, and can minimize through examination of the projected economic benefit. The risk mitigation "stick" and opportunity "carrot" are significant enough to encourage the mills to place higher priority on tracking their solid wastes and planning for their future reduction. It is interesting to note that those Weyerhaeuser mills that have made the greatest effort to improve and have realized the associated benefits tend to be the strongest advocates for further SWMin progress.

APPENDIX II

NICE3: Recovering Lime from Pulp and Paper Operations

http://es.inel.gov/program/p2dept/energy/nice3/nice3-8.html

E11.vi118$et1$e
NICE3: Recovering Lime from Pulp and Paper Operations

DOE/CHI 0093-345 DE94006946 September 1994
!IIZIW'i!IZIIIIPIZilliliilliliiliiiil&iliiilii illll'll!il'i'lillii&IZIIIEI' liil'b
A joint cost-sharing grant program of:
U.S. Department ofEnergy's Office oflndustrial Technologies and Office ofTechnical and Financial Assistance;
U.S. Environmental Protection Agency's Office of Pollution Prevention
Produced by the National Renewable Energy Laboratory, a laboratory of the U.S. Department of Energy, 1000 Independence Ave., SW, Washington, DC 20585

Regional Utility: Atlanta Gas and Light Company

Partners:

Altex Technologies Corporation, Weyerhauser Corporation, J.S. Steele, Inc., Industrial Gas Technology Commercialization Center, Georgia Department of Natural Resources' Pollution Prevention Assistance Division

SIC Codes:

2611,3554,2679,5032,1422,2062,5149,2812,5169,3589,2899,5093

Cost:

$864,733 (industry Share: $456,700)

Energy Savings:

0.2 trillion Btu (0.21 petajoules)/yr

Environmental Benefits:

NOx emissions reduction of 12,770 tons (11,609 tonnes)/yr; C02 emissions reduction of3.4 million tons (3.1 megatonnes)/yr; Spent-lime waste reduction of 7.6 million tons (6.9 megatonnes)/yr

Economic Savings: $677,000/yr/unit

National Impact (2010):

24.4 trillion Btu (25.7 petajoules)/yr of energy savings

Applications:

Pulp, paper, and paperboard mills; Sugar refining; Caustic soda production;

Water treatment

~ ..

Contact:

State: Greg Andrews

(404) 651-5120

DOE: Bill Ives (303) 275-4755

The pulp and paper industry is the ninth largest industry in the United States, yet it is ranked third in energy consumption among all U.S. industries. Any new technology that is introduced into pulp and paper mills to reduce energy consumption will have a major positive impact on the environment.
A significant portion of the energy consumed by these mills is used to recover chemicals that can be recycled in the wood pulsing process. Altex Technolog~es Corporation has developed a new method for recovering lime used in the process. The Gas Research Institute has supported testing of the process. With the help of a grant from NICE3, sponsored by the U.S. Department ofEnergy (DOE) and the U.S. Environmental Protection Agency, Altex will test and evaluate various lime recovery equipment in preparation for a large-scale commercial demonstration.

9/4/97 1:36 PM

NICE3: Recovering Lime from Pulp and Paper Operations

http://es.inel.gov/program/p2dept/energy/nice3/nice3-8.htm

preparation for a large-scale commercial demonstration.
Challenge:
In pulp and paper manufacturing, lime (calcium carbonate) is used to recover sodium hydroxide used in the wood pulsing process. Every ton of process lime creates 2.5 tons (2.3 tonnes) of spent lime mud. Typically, a high-temperature, rotary kiln heats and calcines the mud to recover the lime, which is then recycled in the process loop. Rotary kilns are inefficient, need a high degree of maintenance, and require valuable plant space. Because rotary kilns are large and expensive, paper processing plants delay their kiln purchases as long as possible. This practice requires that the plants purchase excessive quantities of fresh lime and landfill substantial lime wastes.
Solution:
In the advanced mineral calciner (AMC) developed by Altex, the spent mud is reconstituted into pellets. The pellets are then dried prior to calcining in a bed. The regenerated lime pellets are removed from the bed by vibrating hoppers.
The AMC system has much better heat transfer between the gas and pellets than does a rotary kiln. More of the reactor (porous bed) volume is filled by solids than in the rotary kiln, thus reducing system size. In addition to being smaller than a rotary kiln, the AMC system does not rotate, so it can be heavily insulated to minimize heat loss. This results in a high system efficiency.
An AMC system can be designed for virtually any size plant. The system is more compact, simpler, lower in cost, more energy efficient, and lower in NOx emissions than is a rotary kiln. The vertical AMC system requires an area of only 40ft by 40ft (12m by 12m), compared to 200ft by 40ft (60.1 m by 12 m) required for a rotary kiln.
Energy Savings:
The AMC technology will save an estimated 2.3 million to 7.3 million Btu/ton (2.4 gigajoules to 7.7 gigajoules/0.907 tonne) oflime produced from the recovery process compared to the output of the rotary kiln, depending on the kiln size. The concept is also applicable to the sugar refining, caustic soda, and water treatment industries in which an additional4.8 billion Btu (5.1 terajoules)/yr could be saved.
Environmental Benefits:
The fixed-bed AMC system provides more control of the heating process, thus reducing NOx emissions. The average rotary kiln pro-duces 200 ppm ofNOx while an AMC system produces less than 40 ppm of NOx. In addition, landfilled spent-lime waste would be reduced by 7.6 million tons (6.9 megatonnes)/yr.
Economic Savings:
For incremental capacity units of 80 tons (72 tonnes) oflime/day, the AMC will cost 50% less to operate than will a comparable rotary kiln. Producers can recover the lime, thus saving the cost of buying new lime and disposing of spent lime. Also, the AMC should increase productivity by being on line 98% of the time, compared to 90% for rotary-kiln systems.
Applications:
About 800 pulp, paper, and paperboard mills in the United States could use this technology The AMC system also makes it economical for small producers and secondary markets-such as sugar refining, caustic soda production, and water treatment-to install lime recovery systems in their plants.

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