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From Powder and Bulk Dot Com Air Quality
Located 20 miles south of Fairbanks, in central Alaska, Eielson Air Force Base was established during World War II as a cold air flight testing site. As the Air Force’s northernmost base, it still serves as a testing facility for cold air capabilities. During the last half century, though, the base has been greatly expanded for its strategic location, especially during the 1980s and the cold war period. Hosted by the Air Force’s 354th Fighter Wing, today Eielson Air Force Base spans more than 63,000 miles and houses more than 5,000 active duty personnel and their families. The power and steam heat needs of this population are being handled by a coal-fired utility plant owned and operated by the Air Force, called the Central Heat and Power Plant. Coal is delivered to the power plant by rail car. The power plant burns about 600 to 800 tons of coal per day, depending on weather conditions. Eielson's Coal Dust Issues With temperatures that can easily reach -40F to -50F during the cold winter months, coal handling and ongoing maintenance issues can be just as extreme. In fact, for years the Central Heat and Power Plant had been plagued by frustrating coal dust issues, issues that eventually led plant workers to wear respirators when in the facility. Furthermore, workers conducted manual clean-up with wheelbarrow loads of coal dust being scooped up and removed from around the conveyors daily. During its history, many fixes by different engineering and construction firms to mitigate coal dust had been attempted, but few made headway. Some of the issues stem from the coal processed at the plant, a fine coal derived from the Usibelli Coal Mine in Healy, just east of Alaska’s Denali National Park. With a 26% moisture level, this sub-bituminous coal becomes dustier during transport. This fine dust would escape the coal handling system, creating dust build up that led to additional maintenance, premature plant degradation, and most importantly, potential worker safety concerns. In Spring of 2002, OSHA cited Eielson Air Force Base’s plant for workspace coal dust levels in the tripper deck, basement (feeder area under the unloading hoppers) and rail unloading areas. As a result of the citation and a desire to find a long-term solution, the US Army Corps of Engineers, working as the design and construction agent for Eielson Air Force Base sought outside expertise. After an extensive market survey, the government narrowed their focus to Air Control Science®, Inc. (ACS), a Colorado-based engineering and construction firm that specializes in coal handling, especially Powder River Basin coal, known for its fine particulate and combustible properties. The Solution As a result of an intense, three-day onsite meeting with all stakeholders involved in the project, ACS developed a plan of action that targeted an overhaul of the entire coal handling system. The parties that met included engineers from the Army Corp of Engineers, engineers from Eielson Air Force Base, the plant and crew supervisors, and engineers from ACS. Everything was on the table during these three days, including budget, the engineering costs, resources available, details of the problem and solution sought. Based on input from the group process and onsite analysis, ACS engineers determined coal dust at the plant was being generated through: • Spillage from leaks and sealing on conveyors, crushers and elevators • Carryback dust on belt conveyors from poor belt cleaning • Induced air flow at transfer points • Displaced air in the train discharge zone • Poor sealing of the tripper deck bunkers and conveyor enclosures. To address these issues, the scope of the project was determined to include: repair and replacement of belts, chutes and feeders at transfer points; material containment in the form of metal skirting at transfer points; and proper configuration of chutes. Work on the coal handling system upgrades began in June 2003 and ended in October 2003. Because the work had been so thoroughly discussed in the three-day process leading up to the development of a plan, no change orders were generated throughout the project. As a result, the project finished ahead of schedule. The Results After more than six months, the results have been dramatic and appear to be lasting. “There has been an 800% reduction in dust levels throughout the plant. In addition, morale among plant workers has gone up significantly with the improved work environment,” said Dave Holt, coal handling supervisor with the Eielson Central Heat and Power Plant. The Air Force Bioenvironmental Engineering department documented the dramatic changes through air sampling in the three areas where major upgrades were made - in the plant basement, first floor, and bunker. Samples were collected in two phases, during coal unloading and during the end-of-day clean up. Samples were gathered from sampling pumps worn by workers, who also wore protective respirators and safety gear. Coal dust readings in the three areas before the work was initiated were recorded at 33.75 mg/m3, 3.16 mg/m3, and 32.0 mg/m3 for the basement, first floor, and bunker regions of the Central Heat and Power Plant. In January 2004, four months after modifications were completed, coal dust levels had dropped dramatically to 1.1 mg/m3, .89 mg/m3, and .28 mg/m3, respectively. Today, the wheelbarrows full of coal spillage have been completely eliminated. In fact, the wheelbarrows are now relegated to moving snow. Steven Bradbury is Director of Alliances and Contracts for Air Control Science. Dean Homleid is the Eielson Program Manager for the US Army Corps of Engineers based in Anchorge, AK, and is responsible for all COE military construction projects on Eielson Air Force Base. Copyright 2004 Air Control Science, Inc. Source: http://www.aircontrolscience.com/ © Copyright 1998 - 2008 Powder and Bulk Dot Com |
