Date: September 17, 2008 

 (Finalized: January 13, 2009) 

Subject: Site Visit – Triangle Brick Company, Moncure, North Carolina 

Brick and Structural Clay Products 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 

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 brick manufacturing process at the 

Triangle Brick 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 (NESHAP) for the brick and structural clay products industry. 

 II. Place and Date 

Triangle Brick Company (Triangle Brick) 

Merry Oaks Plant 

 294 King Road 

 Moncure, North Carolina 27559 

 July 29, 2008 

 III. Attendees 

 

 Triangle Brick 

 

 Howard Brown, Vice President of Production and Engineering 

Telephone: (919) 624-9196 
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Ricky Merritt, Director of Manufacturing 

Telephone: (919) 387-9258 

The Brick Industry Association (BIA) 

Joe Casper, Vice President, Environmental 

Telephone: (703) 674-1545 

Terry Schimmel, Boral Bricks, BIA MACT Task Force Lead 

 Telephone: (334) 480-2488 

 U. S. Environmental Protection Agency 

 Jeff Telander 

 Telephone: (919) 541-5427 

 Tom Walton 

Telephone: (919) 541-5311 

 RTI International 

 Tom Holloway 

 Telephone: (919) 316-3733 

 

 Richard Marinshaw 

 Telephone: (919) 316-3735 

 Gabrielle Raymond 

 Telephone: (919) 541-7015 

 IV. Discussion 

 A. Background 

 The Triangle Brick Company (Triangle Brick) Merry Oaks facility located in 

Moncure, North Carolina, manufactures structural bricks. The plant includes raw material 

mining, crushing, grinding, and screening operations, brick forming operations, and three natural 

gas-fired tunnel kilns (Kilns 1, 2, and 3). Kilns 1 and 2 each have a production capacity of 11.85 

tons of fired brick per hour (ton/hr). Kiln 3 has a production capacity of 24.7 ton/hr of fired 

brick. The facility has been operating since the early 1990’s. When the plant originally went on 

line, it operated a single natural gas-fired tunnel kiln. A second natural gas-fired kiln was 

brought on line in 1992. A third natural gas-fired kiln was brought on line in 1999. The plant 

uses fuel oil as the back-up fuel for all three kilns. 

 

 The facility operates 24 hours per day, 7 days per week: firing operations operate 

continuously, while the raw material mining, brick forming, and packaging operations operate 5 

days per week, or as needed depending on the production schedule. Triangle Brick, which is 
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classified as a small business, has less than 300 employees; approximately 100 employees work 

at the Merry Oaks plant. Before the kiln emission controls were installed in 2006, the facility 

was classified as a major source of HAP emissions. However, Triangle Brick plans to evaluate 

whether the facility can be reclassified as a synthetic minor source. 

 B. Process 

 The Merry Oaks plant manufactures facing brick, which is largely used for residential 

construction. The process steps include raw material mining, crushing, grinding, screening, 

storage, mixing, forming, drying, and firing. Practically all of the handling and transfer 

operations at the plant are automated. The following paragraphs describe structural brick 

production in more detail. Attached is the non-confidential handout provided by the BIA at the 

start of the site visit.

 The raw material used by Triangle Brick is a Triassic shale. Triassic shale is 

relatively low in chlorides and produces a red body brick without the need for blending with 

other materials. The shale is mined by ripping down and around making a bowl shape that is up 

to 20 feet deep. The layers and strata of the raw material are mixed as the raw material is mined. 

Trucks then bring the raw material to a jaw crusher, where it is reduced to between 3.5 and 4 

inches in diameter. The material is then conveyed to a covered storage building where it is 

transferred using a shuttle conveyor to a storage building that can hold a total of 4 weeks of 

material depending on production. A front end loader transports the material to one of the two 

hoppers where it is conveyed to a scalping screen. Oversize material is transferred to the 

hammer mill, which can process approximately 120 ton/hr. Undersize material is transferred 

from the scalping screen to a finishing screen, where the undersize material (less than 8 mesh) is 

transferred to one of five storage bins. At this point, the material has a “flour” consistency and a 

moisture content of 6 to 8 percent. 

 Plant 1 operates two brick forming lines. The raw material is conveyed from storage 

to one of the processing lines. The material is fed into a pug mill, where the raw material is 

mixed with water to increase the moisture content to about 15 percent. A lignosulfonate 

material (Additive A) is also added to the material to provide better green strength to the formed 

bricks. From the pug mill, the material is transferred to a vacuum chamber, where the air 

removed. The material is vacuum-extruded with an auger through a die as a continuous column 

onto an open conveyor belt. Colorants are applied in a very thin layer to the outside of the 

column. The colorants consist of a mixture of materials, including shale, calcium fluoride, and 

manganese dioxide, with sawdust as a carrier. The next step is cutting. One process line 

immediately cuts the column into slugs. The slugs are then pushed through a wire, to form 

individual green bricks. The green bricks travel by conveyor to the stacking area, where the 

bricks are stacked onto kiln cars by automated equipment for drying. 

 

 The kiln cars loaded with green bricks are next rolled down a track into the holding 

room, where the bricks wait to be loaded in the dryer. The lower ceilings control the humidity in 

the room which allows for controlled drying of the bricks. At this point, the green bricks are 

ready for final drying and firing in the tunnel kiln. 

 
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 Kilns 1 and 2 are each 690 ft in length. The first 375 ft are the designated drying 

zones, which operate at a maximum temperature of 300F. This removes any remaining 

moisture from the bricks. The kiln cars are periodically pushed through the kiln, with each push 

being one-third of a car. The dryer zones are heated with waste heat (containing no products of 

combustion) from the cooling zones of the kilns. After drying, the cars continue to be pushed 

through the preheat zone. Here, air flows around the bricks to heat them up uniformly. The 

bricks then are pushed through the remaining portion of the kiln. Flashing, which is an oxygenstarved reduction process, occurs at the hottest point of the kiln where the temperature can reach 

approximately 2100F. Flashing results in a darkening of the bricks. From the firing zone, the 

bricks enter the cooling zone of the kiln. After cooling, the cars exit the kiln and are rolled to an 

unloading area. There, the bricks are unloaded from the kiln cars by robots, packaged, and 

transported to an open storage area. The entire kiln cycle takes approximately 3.5 days to 

complete (depending on kiln schedule). 

 Kiln 3 operates in a similar fashion as Kilns 1 and 2 but is wider and therefore has a 

higher production capacity. 

 C. Emissions and Controls 

 The primary emission units are the kilns. Emissions from Kilns 1 and 2 are exhausted 

to a common dry limestone adsorber (DLA). Emissions from Kiln 3 are exhausted to a second 

DLA. Both DLAs were installed in 2006 to comply with the original NESHAP, which was 

subsequently vacated. According to Triangle Brick, the DLA is a relatively simple but reliable 

technology for controlling emissions of hydrogen fluoride (HF). Although the capital and 

operating costs for a DLA are significantly less than for a dry injection fabric filter (DIFF), 

DLAs can achieve comparable levels of HF control. The operation of the DLAs is described in 

the following paragraph. 

 

 Limestone (3/8 inch size) is fed into a reaction chamber at the top of the DLA at a 

rate of 63 pounds per hour for each DLA. The limestone cascades through multiple baffles 

within the chamber and reacts with the exhaust gases from the kiln, which flow across the 

reaction chamber. When the limestone reaches the bottom of the chamber, it is transferred by 

augur to a peeling drum, which removes the reacted material on the surface of the limestone. 

The processed limestone is then conveyed pneumatically back to the top of the reaction chamber. 

New limestone is periodically added to the system as needed, as reacted limestone is removed. 

Triangle Brick has a permit to ship the waste material from the DLAs off-site to a specified farm 

for agricultural land application. 

 

Under the now-vacated MACT, Triangle Brick was originally required to monitor the 

pressure drop across the DLA. However, maintaining pressure drop within a range established 

during a performance test is not a reasonable indicator of effective operation of the DLA. By 

regulatory requirements, initial performance tests are required to be conducted at the maximum 

capacity of a kiln. If kilns are operated at lower than capacity, the flowrate will also be reduced. 

Flowrate is a primary factor in the pressure drop across a kiln. Triangle Brick obtained an 

alternate monitoring parameter from the North Carolina Department of Environment and Natural 
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Resources after having demonstrated this fact. The alternative monitoring requires the DLA 

bypass to be locked out, these by ensuring that exhaust from the kilns is routed through the 

control devices.