+. 

ASSOCIATION 

MACT Task Force 

Memorandum 

To: 

From: 

Date: 

JeffTelander, EPA 

Dr. Garth Tayler: Acme Brick Company 

July 1, 2010 

Re: Follow Up Questions to June 23, 2010 "Discussion of why there are no HF and 

HCl emissions for brick plant dryers" memorandum 

BACKGROUND 

On June 23, 2010, the MACT TF submitted a technical discussion of why there would be no HF 

and HCl emissions from brick dryers. A separate diagram detailing the airflow in a kiln was also 

submitted. The EPA has asked for additional information in two areas: 

• Explanation for how tests of brick dryers conducted in the 1990s included some dryers 

with HF and HCl emissions. 

• Explanation of the types of work practices or other requirements that could be included in 

the upcoming Brick MACT that would preclude HF and HCl 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 in the 90's as it is today. Furthermore, the kiln control technology available then 

was not as effective as it is today. Since the availability of the new kiln technologies such as 

pulse firing, variable frequency drives and modem PLC control systems, the brick maker now 

has the ability to control back drafting. 

Back drafting is avoided today for three main reasons: 

ljPage 
ASSOCIATION 

MACT Task Force 

o It causes scumming and acid attack on the brick, hence impairing the product 

quality. 

o Products of combustion in the dryer causes destructive acid attack on the structure 

of the dryer. 

o It has a negative impact the energy efficiency of the dryer/kiln system. Over the 

past 10 to 15 years, brick manufacturers have greatly increased energy efficiency 

by the use of the modern control technologies that have become available. 

Periodic kilns: The presence of products of combustion 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 of kilns and was under suction. Products 

of combustion 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 stack test. The underground flue system is now isolated from the kiln such that no leakage 

of flue 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 of products of combustion entering the 

dryer from the kiln. 

PRECLUDING HF AND HCL EMISSIONS FROM BRICK DRYERS 

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, ifEPA would 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 of combustion enter the waste heat recovery area through the 

2 1Page 
ASSOCIATION 

MACT Task 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. Electronic pressure 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 of the flame movement within the neutral zone. The flame 

should indicate that the gas flow is in the direction of the kiln exhaust. 

The EPA could leave it to the individual facility to identify which approach would work for each 

of their kilns. Again, the available approaches may be limited by kiln age and kiln design. Brick 

manufacturers may also provide additional options that could be approved by the permitting 

authority. 

Records of each inspection would be maintained by the facility, either automatically or in a log 

book, available for inspection. 

Acme Brick Company 

3jPage