Given the opportunity to obtain emission credits by reducing the amount of NOXand CO exhausted from its process, one manufacturer retrofit its dryer with direct-fired air -heating burners. Now, the plant is well on the way to being 'Super Compliant.'

A 400' long, three-zone oven dries wet perlite board by circulating hot air at approximately at 400 and 600oF.
As a manufacturer of products designed to help users reduce fuel consumption and conserve heating energy, BMCA Insulation Products Inc., a subsidiary of GAF Materials Corp., always is looking for ways to conserve energy. Yet its manufacturing process consumed a significant amount of thermal energy. To reduce energy consumption and minimize harmful emissions, BMCA decided that a retrofit was in order.

BMCA manufactures Permalite brand perlite roof insulation products at its plant in Ontario, CA. Permalite roof insulation is a homogenous board composed of expanded perlite particles, selected binders and cellulose fibers that impart its integral insulating properties.

Perlite is a volcanic rock that expands when heated. The ore initially looks like finely ground sand, but when exposed to high heat, it pops like popcorn to 10 to 15 times its original volume and forms small, white insulating beads. The expanded volcanic material will not burn and, when combined with repulped newsprint and certain chemical additives in a water slurry, constitutes the basic material for manufacturing perlite insulation board.

Produced in thicknesses from 0.5 to 1.25", the insulation is manufactured in a process similar to making paper, except the perlite board is much thicker. The 95% water slurry is passed from a blending tank onto an 8' wide wire screen board-forming machine that terminates in a press section. As the slurry approaches the press, water is drained off over a series of vacuum boxes to form a mat. Next, the mat, which is composed of 75% water at this stage, is cut into specific lengths by a guillotine-type cutter prior to entering a gas-fired three-zone, eight-level dryer.

In the 400' long oven, 8.5' lengths of wet perlite board are dried by circulating hot air at approximately 400 to 600oF (204 to 316oC) to evaporate the remaining moisture. Depending on thickness, it takes 1 to 2 hr for a board to pass through the dryer. Finally, it is trimmed, sized and packed.

Although a lot of thermal energy is expended during the manufacturing process, perlite insulation board repays these energy costs many times over in fuel savings for the owners of buildings it insulates. NOX and CO emissions emanating from the drying operation, however, are another matter, and one the company takes seriously.

The Problem

BCMA's Ontario, CA, plant is located within the South Coast Air Quality Management District (SCAQMD), the smog control agency for Los Angeles, Orange, Riverside and San Bernardino counties in California. The second most populous urban area in the country, this region is home to 14 million people -- about half the state's population -- who breathe the dirtiest air in the United States.

Many of the factors that make living in Southern California so desirable contribute to the smog problem. Gentle ocean breezes carry pollutants into the inland valleys, where they are trapped by surrounding mountains, and thermal inversions act like a lid over the basin. Bright sunshine and warm temperatures cause some pollutants to react with each other, forming even more pollution. These natural conditions -- along with the pollution from more than 9 million motor vehicles, thousands of businesses, and countless consumer products -- create an ideal smog factory.

Different types and levels of air pollution can cause problems ranging from watery eyes and fatigue to respiratory disease, lung damage and even cancer. Because this area's smog problem is so severe, AQMD often finds itself at the forefront of the nation's efforts to reduce air pollution.

AQMD is responsible for controlling emissions from stationary sources of air pollution (not mobile sources such as airplanes, cars, trucks, buses, etc.). These include anything from large power plants and refineries to the local gas station. They also include industry such as BMCA's insulation plant.

Six Minnox direct-fired air-heating burners were retrofitted in the drying oven to reduce NOx and CO emissions.

Meeting the Challenge

"At BMCA, we take the AQMD compliance requirements seriously," said plant engineer Paul Davila. "Our business has always been environmentally friendly, within the limits of existing technology. We also repulp waste newsprint, a main ingredient in our board composition, and we were doing so long before recycling became ecologically fashionable.

"So, when SCAQMD contacted us about lowering the emissions from our drying oven, we were eager to participate in the program," Davila noted. "In fact, we made 'Super Compliance' our ultimate goal. The question, of course, was how to go about it."

AQMD's emissions-trading program allows facilities to choose the most cost-effective way of achieving annual reductions in air pollution.

"Under the district's RECLAIM program, companies that are able to reduce emission levels more than required -- in other words, are 'super compliant' -- can obtain emission credits they can sell on the open market to other RECLAIM facilities," explained Sam Atwood of the AQMD News Bureau. NOX emissions requirements are established annually and will be lowered incrementally each year until they are fixed at a permanent level in 2003, according to Atwood.

AQMD staff conducts periodic inspections to ensure continued compliance with requirements. When necessary, strict enforcement action is taken -- including fines up to $50,000 per day and/or a day in jail for each day of violation -- to bring balking businesses into compliance with the rules.

According to Davila, the AQMD challenge came at a time when the drying oven's existing burners were scheduled for replacement. "The vintage burners with long uncontrolled flames didn't come close to meeting today's emissions requirements," Davila noted. "The search for replacement burners was on."

Davila contacted BMCA's corporate office in New Jersey for advice. They referred him to Eclipse Combustion Inc. in Rockford, IL, which in turn suggested he contact Wirth Gas Equipment Inc. in Glendale, CA. Wirth Gas represents Eclipse in southern California, southern Nevada and, more recently, Arizona.

Although BMCA had no prior experience with Eclipse equipment, the company's products were being used in infrared paper drying and other applications at GAF Corp. plants.

"We were contacted late in the procurement process," said Wirth Gas sales associate Jeff Dorfner. "BMCA had already received bids from two competitors, and we were the 'required third bid,' if you will. But we were ready to meet the challenge. I knew that the Eclipse Minnox burner was made for this low temperature, emissions-sensitive application."

BMCA agreed following an after-installation guarantee of 9 ppm NOX at 3% O2 from Eclpise. The company ordered six direct-fired air-heating burners (two each of 16, 20 and 12 million BTU/hr) to be retrofitted in the drying oven after a new firewall was installed.

Dorfner felt confident about the ppm guarantee. "We wouldn't have made it if we weren't confident about Minnox's capability based on previous in-stallations."

The burner's design utilizes a premixed gas/air mixture with excess air, which results in a cooler flame temperature (2,000oF [1,200oC]) and produces low NOX discharge from the burner head. In addition, the burner's configuration creates a recirculating flame geometry that reduces CO emissions without affecting performance.

In the past, achieving acceptable product quality often required the use of less efficient indirect heating. And, with conventional direct-fired systems, care had to be taken with many products to avoid discoloration or taste contamination. By minimizing the amount of emissions emanating from the heat source, this direct-fired design effectively controls product discoloration, one of BMCA's major concerns. And, there is no performance penalty: The direct-fired burner design uses less energy than indirect-fired burners.

BMCA has found that to be so. "The burners perform well in our three-zone drying oven, which operates at a fixed rate depending on board thickness," BMCA's Davila noted. "We're experiencing a fuel savings and production increase, and we've also achieved more uniform heating -- resulting in less downtime -- and better dryer control. Morale has even improved. But, for us, the really excellent outcome is in the area of emissions, which is what drove the project in the first place."

Cut-to-length wet perlite boards are loaded onto an eight-level conveyor prior to passing through the dryer.

The Result

To demonstrate compliance with SCAQMD Rule 2012, the Super Compliance guidelines, the agency hired Pacific Environmental Services (PES) Inc., Baldwin Park, CA, to conduct a source test. According to the independent firm's report, the oven was tested at three different operating conditions while producing 0.5, 0.75 and 1" insulation board.

Each source test was conducted using continuous analyzers to monitor the combustion gases, by SCAQMD methods, in the three oven zones, simultaneously. Eclipse's guarantee of 9 ppm NOX was achieved and even bettered at BMCA: In all three tests, NOX concentration levels never exceeded 3.8 ppm (0.75" board) at 3% O2 and ranged as low as 0.42 (1" board). As a result, BMCA expects to achieve AQMD Super Compliance status as well as Year 2003 fixed emissions levels.