Date: October 6, 2008 (Finalized December 12, 2008)

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

From: Richard Marinshaw

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 and to collect information on sources of hazardous air pollutant (HAP) emissions and emission controls in support of the redevelopment of national emission standards for hazardous air pollutants (N ESHAP) for the clay ceramics manufacturing industry.

II. Place and Date

Kohler Company. 444 Highland Drive Kohler, Wisconsin 53044-1515

August 11, 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

Richard Marinshaw Telephone: (919) 316-3735

IV. Discussion

A. Background

The Kohler Company (Kohler) facility in Kohler, Wisconsin, manufactures ceramic sanitaryware, such as toilets and sinks. Kohler also operates sanitaryware manufacturing plants in Brownwood, Texas, and Spartanburg, South Caro lina. The Wisconsin facility includes six plants: the Vitreous Plant, Brass Plant, Foundr y Complex, Enamel Shop, Engine Plant, and Die Cast Plant. The facility is classified as a major source of HAP emissions due to metal and organic HAP emissions from the Foundry Comple x. Because the focus of the visit was the Vitreous Plant, where the ceramic sanitaryware is manufactured, the other plants are not discussed further in this report.

The Vitreous Plant was constructed in the 1920’s. Whereas the Spartanburg and Brownwood facilities manufacture high-volume sani taryware products, the Wisconsin facility produces low-volume specialty sanitaryware products . The plant has a total of five tunnel kilns
and six shuttle kilns. The tunnel kilns were cons tructed with the original plant, one of the six shuttle kilns was constructed in 1960, while the othe r five shuttle kilns have been installed since 2002. Three of the tunnel kilns are currently o ff-line due to market conditions. Of the two operating tunnel kilns, one is used for first fire, a nd the other is used for refire; refire kilns are used for firing products that had already been fired but had minor defects, which were subsequently repaired. All six shuttle kilns are in operation. One is used exclusively for refire, and the other five are used for first fire, or refire , as needed. Kohler sta ff noted that it is more
efficient to use shuttle kilns than tunnel kilns when business is slow.

B. Process

The basic process steps used at the Wisconsin facility include raw material storage, mold production, glaze preparation, slip preparation, wa re forming, drying/finishing, glazing, firing, and inspection. The following paragraphs descri be 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. Kaolin and ball clay are received in th e form of slurries and are stored in tanks until needed; the other raw materials are received dry. The Vitreous Plant uses several other materials in the process of manufacturing sanitaryware, incl uding plaster of paris for mold making; various glaze materials, such as clays and stains; and other materials to facilitate the handling and transfer of slurries, such as, binders, anti -foaming agents, fungici des, and algaecides.3 2. Mold Production The Vitreous Plant includes a mold-making shop, which produces the plaster production molds used to form the sanitaryware products. Mold-making is a multi-step process that begins by making a model of the sanitarywa re product. Next, a block mold is cast from the model. The block mold then is used to make a case mold, wh ich is used to make the plaster production molds used to cast sanitaryware. To make the plas ter production molds, dry plaster and water are processed in a mixer to form a plaster slurry. Th e 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 mold and dried in a natural gas-fired dryer fo r about 24 hours. The dryers operate at about 120°F. After drying, the plaster of paris molds ar e ready for the sanitarywa re casting step. Each case mold can be used to make between 50 and 100 castings of sanitaryware.

3. Glaze Preparation Glaze making is a batch operation, which is speci fic to the color of the glazed product. Glaze materials are metered out into a weigh hopper, then dry mixed. After mixing, the material is milled in ball mills, where water is also added. The mixed glaze is then discharged into totes, which are transferred by forklift to the glaze spraying area of the plant.

4. 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 mixer for aging. Waste slip is screened and recycled back to the process.

5. Ware Forming Kohler uses two types of casti ng processes: pressure casting and slip casting. Pressure casting can be used for simple shapes, such as pedestals and toilet tanks. For more complex shapes, such as toilet bowls, slip casting is us ed. For either type of casting, the aged slip is pumped from the mixer to the casting shop. For s lip casting, the slip is deposited into a plaster of paris mold. Capillary action draws the liquid out of the slip while building up a layer of solids over the inside surface of the mold, forming th e body of the ware. After approximately 1 hour, excess slip is emptied out to a llow the cast form to set up. Then, the mold is disassembled, and the ware is removed for air dryi ng. At this point, the ware co ntains approximately 30 percent moisture. Pressure casting is a similar process except that, instead of re lying on capillary action, hydrostatic pressure is applied to fo rce 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 recycled back into the process.

6. Drying/Finishing After casting, the unfired ware, called “greenware”, is placed on racks for drying, or on carriers, which are racks attached to an overhead rail/trolley system for transport. Some ware is air-dried at room temperature for 3 to 4 days; so me ware is air-dried a nd placed in a tunnel dryer4 for further drying; and some ware is placed di rectly into tunnel dryers. Dryer operating temperatures are approximately 200°F. After dryi ng, the ware, now called “dryware,” is finished to remove seams and burrs. Finishing is perf ormed manually using a wet sponge and a palette (scraper).

7. Glazing After drying, the green ware is transporte d to the glaze shop. The Wisconsin facility operates a total of 10 glaze spra y booths. Two of the spray bo oths are exhausted to a wet scrubber; the other spray booths are all equipped w ith water curtains and baffles to remove large particulate matter (PM) from the over spray. The wet scrubber had been used to control emissions from an automated bowl-spraying mach ine and booth, which wa s recently converted to two spray booths. The water curtains drain into basins below the booths and then to a clarifier for pretreatment (solids removal). The baffles ar e manually scraped to recl aim some of the glaze material. Note that there are no defined proce ss lines and a piece of ware can be glazed in any booth and fired in any kiln.

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

After glazing, the ware is loaded onto kiln cars for firing.

8. Firing
As noted above, Kohler uses bot h tunnel kilns and shuttle kilns to fire 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 of about 2200° to 2300°F in the firing zone. From that point, the temperature decreases as the kiln cars continue to be pushed th rough, and the ware is gradually
cooled.

Shuttle kilns are batch process units, which are used to fire a single kiln load of green ware. The kiln car is pushed into the kiln, whic h 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 20 to 22 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).

9. 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 a tunnel kiln or shuttl e kiln at a temperature of approximately
2100°F. If the defect cannot be repaired, the ware is discarded.5 C. Emissions and Controls

The Wisconsin facility uses a combination of wet scrubbers, fabric filters, and water
curtains to control emissions fr om the process. Emissions from dry glaze batching operations are controlled with fabric filters, which are vented ba ck into the building. A wet scrubber is used to control emissions from glaze mixing and milling. As noted above, emissions from glaze spraying booths are controlled w ith either water curtains or we t scrubber. Emissions from the ware grinder are controlled with a fabric filt er. Emissions from the dryers and kilns are
uncontrolled.