Date: September 17, 2008 (Finalized: January 13, 2009)

Subject: Site Visit – Triangle Bric k 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 informa tion on sources of hazardous air pollutant (HAP) emissions and emission controls in support of th e redevelopment of national emission standards for hazardous air pollutants (NESHAP) for the br ick 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 Presiden t of Production and Engineering Telephone: (919) 624-91962

Ricky Merritt, Direct or 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 Br ick) Merry Oaks facility located in Moncure, North Carolina, manufactures structur al 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). K ilns 1 and 2 each have a production capacity of 11.85 tons of fired brick per hour (t on/hr). Kiln 3 has a production ca pacity of 24.7 ton/hr of fired brick. The facility has been ope rating since the early 1990’s. When the plant originally went on line, it operated a single natural gas-fired tunnel kiln. A s econd natural gas-fired kiln was brought on line in 1992. A third natural gas-fire d 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 da ys per week: firing operations operate continuously, while the raw material mining, bric k forming, and packaging operations operate 5 days per week, or as needed depending on the production schedule. Triangle Brick, which is3

classified as a small business, has less than 300 employees; approximately 100 employees work at the Merry Oaks plant. Before the kiln emi ssion controls were inst alled in 2006, the facility was classified as a major source of HAP emissions . However, Triangle Brick plans to evaluate whether the facility can be reclassi fied 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 ra w material mining, crushing, grinding, screening, storage, mixing, forming, drying, and firing. Pr actically all of the handling and transfer operations at the plant are automated. The fo llowing paragraphs descri be 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 rippi ng 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 materi al to a jaw crusher, where it is reduced to between 3.5 and 4

inches in diameter. The material is then c onveyed to a covered stor age building where it is transferred using a shuttle conveyor to a storag e 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 scre en. 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, wh ere 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 cont ent 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 tran sferred to a vacuum ch amber, 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 applie d 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 th rough 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 th e bricks. At this point, the green bricks are ready for final drying and firing in the tunnel kiln.4

Kilns 1 and 2 are each 6 90 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 pe riodically pushed through the kiln, with each push being one-third of a car. The dryer zones are h eated with waste heat (c ontaining 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 h eat them up uniformly. The bricks then are pushed through the remaining porti on 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 z one of the kiln. After c ooling, the cars exit the k iln and are rolled to an unloading area. There, the br icks are unloaded from the kiln cars by robots, packaged, and transported to an open storage area. The enti re kiln cycle takes approximately 3.5 days to complete (depending on kiln schedule).

Kiln 3 operates in a similar fashion as K ilns 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). Em issions from Kiln 3 are exhausted to a second

DLA. Both DLAs were installed in 2006 to comply with the origin al NESHAP, which was subsequently vacated. According to Triangle Br ick, the DLA is a relatively simple but reliable technology for controlling emissions of hydr ogen fluoride (HF). Although the capital and operating costs for a DLA are significantly less th an for a dry injection fabric filter (DIFF), DLAs can achieve comparable levels of HF contro l. 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 exhaus t gases from the kiln, which flow across the

reaction chamber. When the limestone reaches th e bottom of the chamber, it is transferred by augur to a peeling drum, which removes the reac ted material on the surface of the limestone. The processed limestone is then conveyed pneumatic ally 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 la nd application.

Under the now-vacated MACT, Triangle Brick was originally required to monitor the pressure drop across the DLA. However, mainta ining pressure drop with in a range established during a performance test is not a reasonable indicator of effec tive operation of the DLA. By regulatory requirements, initial performance test s 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. Tr iangle Brick obtained an alternate monitoring parameter from the North Ca rolina Department of Environment and Natural5

Resources after having demonstrated this fact . The alternative monitoring requires the DLA bypass to be locked out, these by ensuring that ex haust from the kilns is routed through the

control devices.