From: "Cassidy Mike" <MICHAEL.CASSIDY@kohler.com>

Sent: 05/28/2009 04:56 PM

To: Jeff Telander/RTP/USEPA/US@EPA

Cc:

Subject: RE: Emission Test Data for Kohler Company 

Jeff,

Some of the follow-up items from our discussion last Friday (May 22) are:

1) Alternatives and options for glaze spray booth emission limitations

2) Options for if and how shuttle kilns (periodic kilns) should be addressed

3) Options for if and how refire (2-fire) kilns should be addressed

This e-mail presents some thoughts I have on item 3) above.

After discussing the refire process with in-house ceramic engineers, I understand that it's a common 

ceramic engineering understanding that most anything the will be emitted during the firing of a clay 

body is given off during the initial vitrification step. Where Kohler Co. will refire a piece of sanitaryware 

to correct surface blemishes so the piece can become an A-1 product and sold in the marketplace, 

surface blemishes are only spot sprayed with little glaze and so there is only a tiny amount of unvitrified 

material on a piece of sanitaryware being refired. This tiny amount results in insignificant material 

emissions, and refire kiln emissions are essentially all products of combustion.

I'm not sure what information EPA had available when the Clay MACT was originally developed, but the 

decision to exclude refire kilns from the rule at that time seems like a very appropriate decision that 

should still be applicable today. The information this decision was based on should still be in EPA's file 

for this MACT. Kohler Co. encourages EPA to revisit this topic so it's familiar with the information 

already provided.

Attached is an excerpt from a research report that investigated HF emissions in clay ceramics 

manufacturing. I received this from an in-house ceramic engineer. The body of this report focused on 

one-fire processes. The excerpt presents what little information the report included for refiring. Note 

that the comparison is for wall tiles, not sanitaryware. Also note that a biscuit kiln refers to a kiln 

processing unglazed tiles, and a glost kiln refers to a kiln processing glazed, and usually already fired, 

tiles. The data in Table 6 show measurable HF emissions from the first-fire kiln (processing unglazed 

tiles), while HF emissions from the second firing (glazed pre-fired tiles) were not detectable.

I also note that AP-42, Section 11.7, includes an HF emission factor for first-fire but not for re-fire, 

though fluoride emission factors for first fire and refire are shown. Based on the fluoride emission 

factors listed, about 97% of fluoride is emitted during first fire. It's possible a similar fraction applies to 

HF emissions.

I'm investigating test options for some sample tiles for fluoride and chloride content after first firing and 

after refiring to get an estimate of fluoride and chloride loss during refiring. If done, would EPA find 

these data helpful in determining whether refire kilns need to be addressed in the redeveloped Clay 

MACT?
I look forward to hearing your thoughts on the ideas expressed above for this topic, and I will send 

additional emails on item 2) above as I give some thought on how to approach it. Thanks, and let me 

know if any questions.

Michael J. Cassidy

EHS Specialist

Kohler Co.

444 Highland Drive

Mail Stop 009

Kohler, WI 53044

p. (920) 457-4441, x 77263

f. (920) 208-4744

mike.cassidy@kohler.com

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