Date: October 6, 2008 (Finalized: December, 8, 2008)

Subject: Site Visit – Kohler Co mpany, Spartanburg, South Carolina Clay Ceramics Manufacturing NESHAP EPA Contract No. EP-D-06-118; EPA Work Assignment No. 2-09 RTI Project No. 0210426.002.009

From: Gabrielle Raymond Tom Holloway

To: Jeff Telander EPA/SPPD/MMG (D243-02) U. S. Environmental Protection Agency Research Triangle Park, N.C. 27711

I. Purpose

The purpose of this visit was to observe the clay ceramics manufacturing process at the Kohler Company (Kohler) facility in Spartanburg, South Carolina, and to collect information on sources of hazardous air pollutant (HAP) emissi ons and emission controls in support of the redevelopment of national emi ssion standards for hazardous ai r pollutants (NESHAP) for the clay ceramics manufacturing industry.

II. Place and Date

Kohler Company.
Post Office Box 1987 Spartanburg, South Carolina 29304

August 5, 2008

III. Attendees

Kohler Company

Mike Cassidy, Environment, H ealth, and Safety Specialist Telephone: (920) 457-4441, ext. 77263

U. S. Environmental Protection Agency

Jeff Telander Telephone: (919) 541-54272 RTI International

Tom Holloway Telephone: (919) 316-3733

Gabrielle Raymond Telephone: (919) 541-7015

IV. Discussion

A. Background

The Kohler facility in Sparta nburg, South Carolina, manufact ures ceramic sanitaryware. Kohler also operates sanitaryware manufacturin g plants in Kohler, Wisconsin, and Brownwood, Texas. The Spartanburg facility, which was cons tructed in 1958, consists of two plants: the Plastics Plant and the Ceramics Plant. The Plastics Plant produces fiberglass bathtubs and shower stalls. The Ceramics Plant produces se veral vitreous sanitary ware products, including sinks, toilet bowls, toilet tanks, and other sanita ryware products. The Spartanburg facility has been determined to be a majo r source of HAP emissions due to styrene emissions from the Plastics Plant. Because the scope of this project is limited to clay ceramics, only limited
information on the Plastics Plant was obtained du ring the visit, and the Plastics Plant is not discussed further in this repor t. The Spartanburg facility ope rates 24 hours per day, 7 days per
week.

The Spartanburg and Brownwood facilities manufacture high-volume sanitaryware products, while the Wisconsin facility produces low-volume specialty sanitaryware products. The Spartanburg plant has a total of six tunnel kilns and three shu ttle kilns, all of which are gasfired. Four of the tunnel kilns (Kilns 1 through 4) were constructed in 1959, one tunnel kiln (Kiln 8) was built in 1994, and the last tunnel k iln (Kiln 10) was built in 2005. Two of the tunnel kilns (Kilns 3 and 4) are curren tly off-line due to market conditi ons. Of the four operating tunnel kilns, three are used for first fi re (Kilns 2, 8, and 10), and the othe r (Kiln 1) is used for refire. Refire kilns are used to fire pr oducts that had previously been fi red but had minor defects, which were subsequently repaired. A ll three shuttle kilns (Kilns 6, 7, and 9) are in operation and are also being used for refire.

B. Process

The basic process steps used at the South Caro lina facility include raw material storage, glaze preparation, slip preparation, ware fo rming, drying/finishing, glazing, firing, and inspection. The following paragraphs describe the manufacturing process in more detail.

1. Raw Material Storage

The primary raw materials used at the plant include ball clay, kaolin, sand, feldspar, and flint. In addition, the facility uses several other material s, including stains, binders, antifoaming3 agents, fungicides, algaecides, and plaster-of-par is. Clay comprises at least 90 percent of raw
materials used in ceramic sanita ryware manufactured by Kohler at the Spartanburg plant. All materials are received by truck. Kaolin and ball clay are received in tanker trucks as slurries because slurries allow for better uniformity and blending of raw materials and eliminate the need for milling the materials onsite. The other materials are received dry.

2. Glaze Preparation

Glaze making is a batch operation, which is speci fic to the color of the glazed product. Glaze materials are received as dry materials and are metered out into a weigh hopper. After the dry materials are batched in the weigh hopper, th e materials are placed in a ball mill, where water is added to make the glaze, which is 70 per cent solids. The mixed glaze is then discharged into totes, which are transfe rred by forklift to the glaze sprayi ng area of the plant and hooked up to specific glaze spray booths.

3. Slip Preparation

In the slip-making proc ess, clay slurry is pumped from storage tanks to a blunger, where dry materials and additives such as deflocculants and fungicides, are added and mixed. From the blunger, the slip is pumped into an underground mi xer for aging (24 to 96 hours). Waste slip is screened and recycled back to the process.

4. Ware Forming

The plaster production molds are manufactured on-site in the mold shop. To make the plaster production molds, dry plaste r and water are processed in a mi xer to form a plaster slurry. The slurry is then poured into a case mold. The plaster sets up in 15 to 30 minutes. Next, the plaster production mold is removed from the case mo ld and dried in one of two natural gas-fired dryers. After drying, the plaster mold is ready for the sanitaryware casting step.

Kohler uses two types of cas ting processes: pressure cas ting and manual slip casting. Pressure casting can be used for simple shapes, such as pedestals and to ilet tanks. For more complex shapes, such as toilet bowls, manual slip casting is used. For either type of casting, the aged slip is pumped from the mixer to the ca sting shop. For manual slip casting, the slip is deposited into a plaster of paris mold. Capilla ry action draws the liquid out of the slip while building up a layer of solids over the inside surf ace of the mold, forming the body of the ware. After approximately 1 hour, excess slip is emptied out to allow the cast form to set up. Then, the mold is disassembled, and the ware is removed for air drying. At this po int, the ware contains approximately 30 percent moisture. Pressure casting is a similar pr ocess except that, instead of relying on capillary action, hydrostatic pressure is applied to drive the liquid out of the slip.

After casting by either process, the waste slip basins are transporte d to open storage bins in the raw materials mixing area, where the waste slip is screened to remove large pieces and contaminants before it is recycl ed back into the process.4 5. Drying/Finishing

After casting, the unfired ware, called “greenware,” is placed on racks for drying. Some ware is air-dried at room temperature for 3 to 4 days; some ware is air-dried and placed in a tunnel dryer for further drying; and some ware is placed directly into tunnel dryers. Before the ware is dried, it is green-finishe d to remove seams and burrs. Finishing is performed manually using a wet sponge and a palatte (scraper). Th e racks of greenware ar e then transported by forklift to one of several dryers , two of which are gas-fired an d the others steam-heated. The steam-heated dryers are heated by a boiler that is supplemented with waste heat from some of the kilns. Dryer operating temperatures are approximately 60oC (140oF).

6. Glazing

After drying, the greenware is transported to the glaze shop. The same basic process steps and raw materials are used for producing clay slip and glazes to ensure that the glazes expand and contract at the same rate as the body of the ware; otherwise, cracking and other defects would occur. The primary difference be tween the raw material mix used for the ware body and for glaze is that antifoaming agents, binder s, and stains are added to glazes. Stains contain small quantities of zinc , cobalt, chromium, and nickel.

The glaze materials are loaded into a we igh hopper and proportioned. The hopper feeds the materials and water into a ball mill, which serves primarily as a mixer. From the ball mill, the glaze is applied either manua lly or mechanically in one of the three types of spray booths operating at the Spartanburg f acility--robot, automated, and manua l. The booths are equipped with water curtains and baffles to remove large particulate matter (PM) fr om the over spray. The
water curtains drain into basins below the booths and then to a cl arifier for pre-tr eatment (solids removal). The baffles are manually scraped to re claim some of the glaze material. Note that there are no defined process lines, and a piece of ware can be glazed in any booth and fired in any kiln.

The plant also has spot spray booths and one respray booth used for touching up or reglazing ware. The spot spray booths are exhausted to fabric f ilters, and the re spray booth has a water curtain for controlling emissions.

After glazing, the ware is manually placed on racks for short-term storage prior to loading onto kiln cars for firing. There are no product lines; ware can go from any spray booth to any kiln. All defective pieces that have not been fired are re cycled. The recycled pieces are sent from a storage area on th e floor, where they are emptied into a blunger by forklift.

7. Firing

As noted above, Kohler uses tunnel kilns to fi re green sanitaryware. For the tunnel kilns, which operate continuously, the ware is loaded onto kiln cars that are pushed into the kiln one car at a time according to a set schedule. As the kiln cars are pushed through the kiln, they pass through various zones characterized by increasing temperature, up to the peak temperature of5 about 2200° to 2300°F in the firing zone. From that point, the temperature decreases as the kiln cars continue to be pushed through, a nd the ware is gradually cooled.

Shuttle kilns are batch process units, which are used to fire a single kiln load of ware. The kiln car is pushed into the kiln, which is then closed. The burners are ignited, and the temperatures are gradually ramped up to a peak firing temperature, then ramped down to complete the cycle. The typical kiln cycle for the shuttle kilns at Kohl er is 24 to 42 hours from
the time when the kiln is loaded and the burners are ignited, to the time when the fired ware has cooled enough to be removed (cold to cold).

8. Inspection

After firing, the product is unloaded from th e kilns cars, inspected, finished with a grinder, water-tested, and packaged for shipment. If the fired ware has minor defects, the ware is machined, reglazed, and refired in one of three s huttle kilns or in the re fire tunnel kiln at a temperature of approximately 2100°F. If the def ect cannot be repaired, th e ware is discarded.

C. Emissions and Controls

The South Carolina facility uses a combinati on of wet scrubbers, fabric filters, and water curtains to control emissions from the proce ss. Emissions from dry glaze batching and milling are controlled with a baghouse that exhausts outsi de. As noted above, emissions from glaze spraying booths are controlled with water curtains. Emissions from the ware grinder are
controlled with a fabric filter. Emissions from the dryers and kilns are uncontrolled, except for a caustic scrubber installed on Kiln 10 to comply with the original Clay Ceramics NESHAP. However, Kohler is in negotiations with the Stat e of South Carolina to have the scrubber shut down in light of the vacature of the original Clay Ceramics NESHAP. The South Carolina Department of Health and Envi ronmental Control (SCDHEC) publis hed a proposal to repeal the state-only Clay MACT rule in the September 25, 2008 State Register. K ohler Co. expects the state-only rule to be repealed in early 2009, after wh ich time the wet scrubber on tunnel kiln 10
will be shut down.