Date: January 16, 1998

(Finalized: May 22, 1998)

Subject: Site Visit--Lenzing Fibers Corporation, Lowland, Tennessee

Miscellaneous Cellulose Manufacturing Industry NESHAP

EPA Contract No. 68-D6-0012; Task Order No. 0011; EPA Project No. 97/06

MRI Project No. 4800-11

From: Karen Schmidtke

Rebecca Nicholson

To: William Schrock (MD-13)

OAQPS/ESD/OCG

U. S. Environmental Protection Agency

Research Triangle Park, NC 27711

I. Purpose

The purpose of the visit to the Lenzing Fibers Corporation (Lenzing) facility in Lowland,

Tennessee, was to develop an understanding of Lenzing’s rayon manufacturing process and the

facility’s emission points and emission controls. 

II. Place and Date 

Lenzing Fibers Corporation

Post Office Box 2000, Highway 160

Lowland, Tennessee 37778-2000

November 13, 1997

III. Attendees

Lenzing Fibers Corporation

Dan Blair, Production Manager

Calvin Bonawitz, Vice President, Human Resources and Site Services

B.B. Bradley, Jr., Project Engineer

David Cooper, Environmental Engineer

Gunther Krohn, Vice President, Operations

William South, Environmental/Auxiliary Service Manager
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U. S. Environmental Protection Agency (EPA)

Bill Schrock, ESD/ OCG, Environmental Engineer

Midwest Research Institute (MRI)

Rebecca Nicholson, Senior Environmental Engineer

Karen Schmidtke, Staff Environmental Engineer

IV. Discussion

The site visit included a plant overview discussion, a process overview discussion, a

discussion of the emission controls studied, and a tour of the facility.

A. Plant Overview

The site visit began with a general overview of the facility, led by Calvin Bonawitz. Three

plants are co-located at the site: (1) Lenzing Fibers (rayon staple production), (2) BASF (idle),

and (3) Intercontinental Polymers (polyester production). Lenzing Fibers Corporation is a

subsidiary of Lenzing USA Corporation (parent company), which is owned by Austria-based

Lenzing AG. Lenzing purchased the rayon plant from BASF in 1992. The entire facility covers

347 acres and contains a power plant, wastewater treatment facility, and a landfill. There are

approximately 410 employees at the plant (Lenzing employees for rayon staple production). The

facility operates 3 shifts per day, 7 days per week. The maximum production rate for the plant,

actual production rates for 1997, and the selling price for rayon product are contained in the

Confidential Addendum, item 1. Production rate trends are provided in Attachment 1. 

Attachment 1 is contained in the Confidential Addendum. Facility personnel estimate that the

cost to produce rayon staple consists of raw materials (approximately 50 percent), labor, energy,

and maintenance services (approximately 50 percent). A breakdown of the cost to produce rayon

staple is contained in the Confidential Addendum, item 2. Rayon staple produced at the facility

is used in apparel, drapery, nonwovens, and feminine hygiene products.

Rayon processes include filament (one continuous strand) and staple (cut into short

lengths). The Lenzing facility uses the rayon staple process. There are two rayon staple

producers in the U.S. Domestic rayon production is in tough competition with foreign facilities;

therefore, rayon production in the U.S. has been declining.

B. Process Overview and Facility Tour

Mr. Dan Blair provided a process overview and discussion. A general process flow

diagram is provided in Attachment 2 and a detailed diagram is provided in Attachment 3. 

Attachment 3 is contained in the Confidential Addendum. The rayon staple process can be

divided into two distinct processes: the chemical plant for production of viscose solution and the

fiber plant for production of the rayon fiber. The number of process lines is contained in the

Confidential Addendum, item 3. The storage facilities, chemical plant processes, fiber plant
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processes, wastewater facilities, currently-used emission controls, other emission controls

researched by plant personnel, and modernization projects completed at the facility are discussed

below.

1. Raw Material Storage. Raw material for rayon staple production includes purified,

highly reactive wood pulp, sodium hydroxide (NaOH) solution, carbon disulfide (CS2), sulfuric

acid (H2SO4), and zinc sulfate (ZnSO4). Most raw materials, including pulp and CS2, are shipped

onsite by railroad. Fresh water for process usage is taken from the Nolichucky River.

The rayon staple process is capable of handling a variety of fiber sources. The facility

mixes the type of fiber sources for product optimization. Large rolls of pulp are stored in a

warehouse room adjacent to the rayon process (beginning of the chemical process). The rolls of

pulp allow continuous feed to the process. Information on the types of wood fiber, size of the

pulp rolls, and the plant’s suppliers is contained in the Confidential Addendum, item 4.

Storage of CS2 and unloading of CS2 railcars takes place away from the production area

because of the high flammability of CS2. Carbon disulfide is stored in six storage tanks; four

tanks contain raw CS2 and two tanks contain recovered CS2 from the process. The volume of the

CS2 storage tanks is contained in the Confidential Addendum, item 5. All six tanks are

submerged under water in an above-ground water-covered containment pool. This system

prevents fire or explosion hazards. If a leak in a storage tank occurs, the CS2 will settle to the

bottom (CS2 has a higher specific gravity than water) and be covered by the “water blanket” in

the containment pool. Carbon disulfide is slightly soluble in water, at approximately 2,000 ppm. 

Additional precautions to eliminate exposure to air or sparks during the transfer of CS2 have

been implemented as follows: pipelines from the storage tanks to the process are submerged in

water trenches, pipelines for recovered CS2 from the process to the storage tanks are

underground, transfer of CS2 is achieved either by gravity or magnetically sealed pumps, and use

of flanges has been reduced where possible. Unloading of CS2 railcars is performed by

displacing the CS2 in the car with water (CS2 has higher specific gravity). The CS2 supplier

handles the CS2 and N2 gas remaining in the railcar. In addition to submersion under water in the

containment pool, the CS2 within the individual storage tanks is blanketed with water. As the

storage tanks are filled (loaded from the railcars) and emptied (CS2 piped to the process), water

from the containment pool is added to or displaced from the individual storage tanks. Additional

information on the current unloading system for the CS2 storage tanks, a new unloading system

to be implemented at the plant, and the total CS2 usage at the plant is contained in the

Confidential Addendum, item 6.

Sodium hydroxide is received as a 50 percent NaOH solution and is stored in three large

storage tanks. This solution is diluted for use in the process. The volume of the NaOH storage

tanks is contained in the Confidential Addendum, item 7. 

There are two H2SO4 storage tanks used onsite. The volume of the H2SO4 storage tanks is

contained in the Confidential Addendum, item 8.
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2. Viscose Solution (Chemical Plant). The steeping, shredding, and aging steps of the

viscose solution process are continuous. The steeping step of the viscose solution process

generates alkali cellulose. A Foxboro digital control system (DCS) and an intelligent automation

system (IAS) are used for process control of the steeping step. Cellulose pulp is unrolled and

shredded into a tank of weak NaOH solution where a liquid solution of the pulp, or slurry, is

made. The concentration of the NaOH solution is contained in the Confidential Addendum,

item 9. This slurry is fed to the mercerization tank, where a sodium atom from NaOH is added to

the cellulose chain. The reaction temperature is contained in the Confidential Addendum,

item 10. (The pulp slurry looks like and has the consistency of applesauce.) From here, the

slurry of pulp is pressed or forced between perforated rollers to remove excess water and NaOH. 

The NaOH solution is recycled. After dewatering, the pulp is shredded and looks like “white

crumbs.” The “white crumbs,” or alkali cellulose, is conveyed on an aging belt where autooxidation, or natural de-polymerization occurs. The temperature for the aging process is

contained in the Confidential Addendum, item 11. The de-polymerization step decreases the

viscosity of the alkali cellulose pulp. The length of time necessary for the aging step varies

depending on the rayon product or customer specifications. The aged alkali cellulose is the first

intermediate generated in the rayon staple process.

The remaining steps for the viscose solution process are batch. The aged alkali cellulose is

cooled and is conveyed by air to be weighed and manually charged by dropping through a chute

to one of several reactors. Carbon disulfide and a catalyst are added to the reactor and

xanthation reaction occurs under vacuum to generate sodium cellulose xanthate. The

temperature the cellulose is cooled to, the number and type of reactors, and other process details

are contained in the Confidential Addendum, item 12. The reactors are purged with N2 and

vented to remove excess CS2 before opening and emptying following the reaction. Plant

personnel indicated that venting of the reactor is an emission point that might also be controlled,

given the lower flow and higher concentration of this stream. The xanthation room is ventilated

to reduce operator exposure to CS2. Carbon disulfide losses from the reactor include conversion

to reaction products which later yield H2S in the spin bath, volatilization losses sent to the

exhaust stack, and the amount remaining in any waste viscose. The sodium cellulose xanthate

(looks like orange/yellow crumbs) is the second intermediate for the rayon staple process. 

Sodium cellulose xanthate is not a stable intermediate and must be processed immediately to

prevent conversion back to alkali cellulose. Operation of the reactors is staggered to create a

continuous process following the reactor room through the rest of the rayon staple process.

The sodium cellulose xanthate is dissolved in a weak NaOH solution in a dissolving vessel

and then is sent to a blending vessel with a high shear mixer to generate viscose solution. The

concentration of the NaOH solution is contained in the Confidential Addendum, item 13. The

NaOH solution charged to this step is a recycled stream (that has been diluted) from the steeping

process above. (Depending on customer specifications, titanium dioxide may be added to the

viscose solution as a delustering agent.) From the dissolving/mixing vessel, the viscose solution

is ripened (i.e., aged) and filtered to produce a uniform solution. Air bubbles and undissolved

cellulose that will interfere with the spinning, or extrusion, of the viscose solution must be

removed prior to the spinning machine. Filtering and de-aerating are critical steps in the process. 

The viscose solution is sent to a series of filters before being sent to the spinning machine. The
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filter series is described in the Confidential Addendum, item 14. In the filters, the viscose

solution is forced through a metallic mesh. The reject filtrate is composed of undissolved

cellulose fiber and is recycled to the dissolving vessels.

A concrete containment area is used as an elementary neutralization tank for wastewater

and waste viscose from the aging and filtering operations. Wash water from cleaning of the

aging room area is sent to the containment area; these wash waters contain cellulose that must be

removed to minimize solids in the wastewater treatment system. Problem batches of viscose,

which contain large amounts of cellulose, are also sent to the containment area. The wastewater

and viscose streams are neutralized and the cellulose is separated from the wastewater. The

separated wastewater is sent to the wastewater treatment system and the cellulose is left in the

containment area for later disposal. Disposal of the cellulose sludge is contained in the

Confidential Addendum, item 15.

3. Rayon Spinning (Fiber Plant). Viscose solution is pumped to the spinning machine in

the fiber department. The viscose solution is fed to an individual jet and forced through the

spinnerette into a bath of H2SO4 solution and ZnSO4. A description of the spinnerettes is

contained in the Confidential Addendum, item 16. The cellulose precipitates out of the H2SO4

solution and the sodium atom on the cellulose polymer reacts with the H2SO4 to generate Na2SO4

byproduct (sold). (Some spin bath solution is removed from the spinning machine to recover the

Na2SO4. The spin bath solution is evaporated to increase the concentration of Na2SO4 and the

Na2SO4 is crystallized and removed from the solution.) The ZnSO4 is added to the spin solution

to control regeneration of the cellulose in the spin bath. Exhaust from the spinning machine is

vented to one of the main stacks. Carbon disulfide is emitted from the spinning steps, including

the CS2 exhausted from the spinning bath, stretching, hot dip, and cutting steps and CS2 lost to

the spin bath (and later emitted from the bath solution). The area around the spinning machine is

well-ventilated to decrease the concentration of CS2 to which operators are exposed. The

spinning machines are partially enclosed for emission control. Information on total enclosure of

the spinning machines is contained in the Confidential Addendum, item 17.

The precipitated filaments from the spinning machine are threaded through take-up wheels

and onto the first set of rollers. The precipitated filaments are sent through a hot dip bath. 

Description of the hot dip bath is contained in the Confidential Addendum, item 18. The

filament is then taken up on a second set of rollers; the filament is stretched across the hot dip

bath between the two sets of rollers. The stretch is described in the Confidential Addendum,

item 19. Stretching aligns the cellulose molecules in the fiber. Both CS2 and H2S gas are

released during the hot dip and stretching steps (the high temperature volatilizes these

compounds). Carbon disulfide is emitted from the hot dip step; CS2 is volatilized and recovered

from the bath by a condenser, some CS2 is lost to the hot dip bath (and later emitted from the

bath solution), and a small amount is exhausted to the stack. The recovered CS2 stream is

condensed and returned to the CS2 storage tanks for reuse in the xanthation step (discussed

above).

Following the second stretch, the continuous tow filament is cut into various fiber lengths

called “chips” (length depends on individual customer requirements) and the cut fiber is
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conveyed by hot sluice water to the wash track and onto a stainless steel mesh belt conveyor. 

Carbon disulfide is emitted from the belt conveyor and the cutter. The cut fiber is referred to as

“dirty cellulose” or “acid chips,” which must be washed and bleached to purify the fiber and

generate white rayon staple. Emissions of CS2 from the sluice box are condensed and returned

to the CS2 storage tanks. The fibers are sent through several washing steps. The washing steps

are described in the Confidential Addendum, item 20. The washes used to purify the fiber

depend on the rayon product and the customer’s specifications. A finishing spray may also be

applied as a lubricant that aids the customer in handling and processing the rayon fiber; these

lubricant sprays include oleic acid, mineral oil, or coconut oils. The rayon fibers are pressed

through a squeeze roller and sent to the dryer. Moisture content of the rayon fiber is contained

in the Confidential Addendum, item 21. The rayon fiber is conveyed through one dryer with

three heating zones and a second dryer with one heating zone, a cooling zone, and a conditioning

zone. The moisture content for the final rayon fiber is approximately 11 percent. Several

physical tests are performed on the fiber, including tensile strength, the elongation, the cut length

of the fiber, etc. The dry rayon fiber is packed as 500 pound bales for shipment off site.

There are two cooling towers in use at the plant. The cooling towers are a small source of

CS2 emissions. The large cooling tower handles water streams from the evaporation step for

Na2SO4 recovered from the spin bath. The small cooling tower is used for water streams from

the crystallization steps associated with the Na2SO4 recovery.

4. Wastewater Treatment System. The wastewater treatment system handles

approximately 7 to 8 million gallons of water per day; the maximum water that can be processed

is 12 million gallons per day. A Foxboro DCS is used to control the wastewater process. 

Wastewater collected from the rayon staple process contains approximately 20 ppm CS2. 

Wastewater from all sources (including the International Polymers plant and leachate from the

onsite landfill) is sent to the equalization basin where mixing of the various influent streams

occurs. The wastewater is then sent to the aeration basin (where pH is adjusted with lime), two

clarifiers, a digester, and a press where sludge is removed. Sludge from the wastewater is sent to

the onsite landfill. Water from the wastewater treatment plant is mixed with clear-water lagoon

effluent before it is returned to the Nolichucky River through water outfall 001. Storm waters

are also collected on the plant site and returned to the river through outfalls 002, S03, S04, or

S05.

5. Emission Controls and Modernization Projects. Carbon disulfide and H2S are emitted

from the rayon staple process at Lenzing Fibers. Carbon disulfide is emitted from the reactors,

spinning machines, stretch rollers and hot dip step, the conveyor and cutters, and the sluice box. 

Emissions from the hot dip step and the sluice box are controlled by condensers. Because of the

toxicity of CS2, many areas of the plant where operator exposure is likely are well-ventilated to

protect the operators. Operators are also required to wear respirators for certain operations. The

OSHA standard for CS2 is 10 ppm, and the Tennessee State limit is 4 ppm CS2. Ventilation air is

vented to and exhausted from the process area surrounding the reactors, spinning machines,

stretch rollers, the hot dip step, and the purifying washes. Because rich streams are necessary to

achieve significant reduction, the exhaust streams from these areas are very dilute, which affects

the recovery efficiency of the condensers.
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Both CS2 and H2S from the hot dip step vent stream are controlled by a condenser (located

in a separate building). In this system, water vapors (steam) are condensed out of the vent

stream with a direct-contact condenser and the condensed water is sent to the wastewater

treatment system. The remaining CS2 and H2S vapors are pulled by vacuum jet to a second

direct-contact condenser. The H2S is scrubbed from the gas stream with a cool, weak lye

solution and the CS2 condenses due to the decrease in temperature. Noncondensibles exit

through one of the main stacks. The lye (NaOH) solution and condensed CS2 are sent to a

settling tank for separation (by gravity) and the condensed CS2 is piped underground to the

submerged CS2 storage tanks in the water containment pool. The separated lye solution is

returned to the condensation system. Another condensation system similar to this system

controls CS2 and H2S emissions from the sluice box. The inlet vent stream temperature and the

condenser lye solution temperature are contained in the Confidential Addendum, item 22. The

emission reduction achieved by each of these condensers is 99 percent for CS2.

Carbon disulfide is emitted through several stacks to the atmosphere (there are four main

stacks and several smaller stacks). Two of the main stacks vent the spinning area (spinning

machine through the cutters); the other two stacks vent the finishing operations for the rayon

fiber. Random sampling has shown concentrations of CS2 in the main stack outlets between 300

to 500 ppm. Information on the main stacks is contained in the Confidential Addendum, item 23.

The facility implemented several modernization projects from 1992 to 1994. The facility

has implemented projects to increase the amount of CS2 recovered from the process. 

Attachment 4 shows the percent recovery from 1991 to 1997. Attachment 4 is contained in the

Confidential Addendum. The plant has also established a goal for the ratio of CS2 used per

metric ton of fiber produced. Attachment 5 shows the trend for this ratio at the plant. 

Attachment 5 is contained in the Confidential Addendum. Additional information on CS2

recovery, CS2 usage, equipment changes, and control costs are contained in the Confidential

Addendum, item 24.

As part of the plant’s improvement process, a material balance for CS2 usage and emissions

has been performed for the entire plant. The plant tracks the total usage of CS2 through its

accounting department. The engineering department has determined air flow rates and

concentrations (ppm) plant-wide. Plant-wide CS2 material balance data is provided in

Attachment 6. Attachment 6 is contained in the Confidential Addendum. 

6. Other CS2 Control Technologies. Plant personnel have researched a number of potential

control technologies for reducing CS2 emissions to the atmosphere. These control technologies

are listed in Attachment 7 and include: (1) condensation, (2) chemical scrubbing, (3) carbon

adsorption, (4) catalytic reaction, (5) biological treatment, (6) oil absorption, and (7)

incineration. Plant personnel indicated that the ventilation air supplied to some areas of the plant

affects the emission reduction achievable for some control devices. The ventilation air that is

vented to these areas dilutes the concentration of CS2. Sending diluted vent streams to an

incinerator would require a device that could handle large volumes of flow while also requiring

significant auxiliary fuel to maintain combustion temperatures. Diluted streams also are a

problem for recovery devices such as condensers where low temperatures are required to get
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significant condensation from the stream. In addition to technical concerns, plant personnel have

concerns about the cost for environmental controls and indicated that their foreign competitors

do not have to make environmental expenditures as U.S. companies do. The technical and

economic difficulties for each of the control technologies researched by the company were

discussed during the site visit.

Use of condensers to control CS2 emissions has limited applicability for the rayon

production plant. A condenser system has been installed for the hot dip step following the

spinning operation and for the sluice box prior to the wash track. These systems each achieve

99 percent reduction in CS2 emissions. Because of the large quantity of ventilation air required

to reduce operator exposure to CS2 and the dilution of vent streams containing CS2 under the

LEL to prevent fire hazards, the majority of vent streams from the process are very dilute. Use

of condensation to treat these streams is not economically feasible given the low temperatures

required to condense the CS2 vapor. Condensers are appropriate for high concentration, low

volume vent streams.

Chemical scrubbing has also been examined for scrubbing H2S emissions from the

spinning and hot dip vents. The H2S in the vent stream is removed by contact and reaction with

a lye solution. This technology achieves a high removal of H2S, approximately 95 percent.

Carbon adsorption has been analyzed as an option for reducing and recovering CS2

emissions. In this control technology, the vent stream is passed through an activated carbon bed 

and the CS2 is adsorbed on the bed. The carbon bed is then regenerated, usually with steam, and

the steam and contaminant are condensed and separated. The autoignition temperature of CS2 is

low, and steam desorption can be used, but only when purged in an inert atmosphere such as N2. 

The facility estimates a cost of $44 million to enclose the process equipment, concentrate the

vent streams, and purchase and install the carbon bed system. This technology might achieve a

65 percent reduction in CS2 emissions and has the added benefit of recovering the CS2 for reuse

in the process (i.e., a cost savings). The plant has looked at both fixed bed and fluidized bed

carbon systems. Problems with this technology include bed fires (safety concern), which are

more prevalent given the flammability of CS2; the difficulties in regenerating the carbon beds or

removing/desorbing the CS2 from the bed; and the presence of H2S in the vent stream, which

contaminates the carbon bed (although H2S could be stripped prior to the carbon bed).

Use of catalytic reaction to generate H2SO4 from H2S and CS2 has been considered. In this

system, a two-stage conversion occurs where CS2 and H2S are converted to SO2 in the first bed

and converted to SO3 in the second bed. In a condenser unit, the SO3 is “wetted out” to generate

98 percent H2SO4 solution. The cost to purchase and install a catalytic reaction unit by Haldor

Topsoe is in excess of $30 million and is not attractive given the low cost of H2SO4 compared

with CS2. The Haldor Topsoe unit uses a vanadium pentoxide catalyst to promote the reaction;

the unit operates at high temperature (800° to 900°C) and is subject to the corrosive nature of the

SO3 generated. The plant has also looked at a catalytic reaction unit manufactured by German

company Kanzler Berfahrenstechnik (vendor is Maurer). The plant estimates that an additional

500 to 600 tons per year of SO2 will be generated from oxidation of CS2. Given the plant’s

proximity to Great Smoky Mountain National Park, the National Park Service must approve the
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facility’s SO2 emissions; however, Lenzing has excess SO2 capacity because current SO2

emissions from the onsite power plant are less than permitted levels.

The plant has also considered use of a biological treatment system for CS2. The vent

stream would pass over a bed of peat. The company the plant contacted, Envirogen, indicated

that the vent streams are too large and contain too much sulfur for biological treatment to be

applicable. 

Use of oil absorption has been examined. In this control technology, CS2 is removed from

the vent stream by contact with oil absorption liquid in a counter-current packed bed tower. The

oil absorption liquid containing the absorbed CS2 is then stripped; the recovered CS2 is

condensed and returned to storage and the oil absorption liquid is recycled to the packed bed

tower. This control technology is generally applicable for vent streams with higher concentrations. Lenzing has been discussing this option with PPG Industries, who is the CS2 supplier. 

Analysis of the streams at the Lenzing facility indicate that the most concentrated stream at the

facility could possibly be controlled with this technology; two of the most dilute streams at the

plant were determined not to be candidates for this technology. From a safety and economic

standpoint this is the most practical method evaluated to date.

Incineration of the CS2 and H2S has also been analyzed. The plant considered combusting

the vent streams in the power plant, which is 1,000 feet from the rayon staple process. The plant

would have to pipe the vent stream to the power plant, and there is a fire hazard associated with

venting these streams across the facility. In addition, the power plant can handle only a portion

of the vent streams from the process. This option has the disadvantage of generating SO2

emissions, like the catalytic reaction option discussed above, and there are safety concerns.

2 non-CBI Attachments

F:\USER\NPATE\atw_rules\cellulose\lenzing.wpd
ATTACHMENT 7

CS2 REMOVAL TECHNOLOGIES

• Condensation

• Chemical

Scrubbing

• Carbon

Adsorption

• Catalytic

Reaction

• Biological

• Oil Absorption

• Incineration