# + . ASSOCIATION

MACTTask Force 

# Memorandum To: From: 

### Date: JeffTelander, EPA Dr. Garth Tayler: AcmeBrickCompany July 1, 2010 

### Re: Follow Up Questions to June 23, 2010 "Discussion ofwhy there are no HF and HCl emissions for brickplant dryers" memorandum BACKGROUND On June 23, 2010, the MACT TF submitted a technical discussion ofwhy there would be no HF and HCl emissions from brick dryers. A separate diagram detailing the airflow in a kiln was also submitted. TheEPAhas asked for additional information in two areas: • Explanation for how tests ofbrick dryers conducted in the 1990s included some dryers withHF and HCl emissions. • Explanation ofthe types ofworkpractices orotherrequirements that could be included in theupcomingBrickMACTthat would precludeHF andHCl emissions from dryers. PREVIOUS BRICK DRYER TESTS Tunnel kilns: During the earlier stack tests the kilns were back drafting. Back drafting was not as big a concern inthe 90'sas it istoday. Furthermore, the kiln control technology available then was not as effective as it is today. Since the availability ofthe new kiln technologies such as pulse firing, variable frequency drives and modem PLC control systems, the brick maker now hasthe abilitytocontrol back drafting. Back drafting is avoided today for three main reasons: 

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### o It causes scumming and acid attack on the brick, hence impairing the product quality. o Products ofcombustion in the dryer causes destructive acid attack on the structure ofthe dryer. o It 

### has a negative impact the energy efficiency ofthe dryer/kiln system. Over the past 10 to 15 years, brick manufacturers have greatly increased energy efficiency by the use ofthe modern control technologies that have become available. Periodic kilns: The presence ofproducts ofcombustion in the old Fort Smith periodic plant dryer during the stack test in 1992 was due to leakage in the underground waste heat recovery flue. The flue system was situated adjacent to the row ofkilns and was under suction. Products ofcombustion were drawn into the flue through cracks in the structure. The Fort Smith kilns and the waste heat recovery flue system have since been replaced and improved in design since the 1992 stacktest. The underground flue system is now isolated from the kiln such that no leakage offlue gasses into the duct is possible. The hot air recovery duct is only connected to the kiln during the cooling cycle, hence eliminating the possibility ofproducts ofcombustion entering the dryer from thekiln. PRECLUDINGHF

## AND HCLEMISSIONS FROMBRICKDRYERS Back drafting is no longer an accepted practice even on an occasional basis. In addition, there are economic and product quality issues, as described above, that would be a deterrent to allowing back drafting. However, ifEPAwould need to include some language in the upcoming brick MACT that would ensure that no back drafting occurs, there would be two primary approaches: 1. Semi-annual or quarterly monitoring of the presence of a small pressure differential between the rapid cooling zone and the furnace zone. By demonstrating that there is a higher pressure in the rapid cooling zone than there is in the furnace zone, EPA can be assured that no products ofcombustion enter the waste heat recovery area through the 2 1PageASSOCIATION MACTTask Force neutral zone into the cooling zone. This pressure differential could be measured in the following ways, including but not limited to: a. Magnehelic pressure gauge b. Electronicpressure measuring instrument. 2. Semi-annual or quarterly visual inspection using a flame in the neutral zone to indicate flow. This has been done for decades on brick kilns. In some kilns, there is a flame in the neutral zone that can be checked through a flame tube site glass. In other kilns, a flame would be introduced into the neutral zone through a port (e.g., on a long stick). The observation is then made ofthe flame movement within the neutral zone. The flame should indicatethat the gas flow is in the direction ofthe kiln exhaust. TheEPAcould leave it tothe individual facility toidentify which approach would workfor each oftheirkilns. Again, the available approaches may belimited bykiln age and kiln design. Brick manufacturers may also provide additional options that could be approved by the permitting authority. Records ofeach inspection would be maintained by the facility, either automatically or in a log book, available for inspection.

Acme Brick Company

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