유해대기오염물질인 중금속의 배출은 그 위해성으로 인해 엄격한 법적 규제를 하는 등 지대한 관심이 기우려지고 있다. 무연탄을 사용하는 상용 화력발전시설로부터 배출되는 중금속의 농도 및 배출특성에 대한 연구를 실시하였다. 대상 발전시설은 순환 유동층 연소로, 싸이클론, 보일러, 전기집진기 설비로 구성되었고 가스상 수은을 포함한 주요 중금속의 농도를 측정하기 위해 분진과 가스상 시료를 전기집진기(ESP) 전단과 연돌에서 측정하였다. 총 먼지량(TPM), PM-10, PM-2.5와 같은 입자상 물질의 배출량은 ESP 전단에서 각각 23,274, 9,555, 7,790 mg/Sm3로 매우 높았으며, 이는 예측했던 바와 같이 미분탄 화력발전소보다 높은 수치였다. 그러나 ESP에 의한 먼지의 제거효율이 높기 때문에 연돌에서의 총 먼지량은 0.16 mg/Sm3 정도였다. 마찬가지로 중금속 배출량 또한 ESP에서 높은 제거효율을 보였다. 입도분포와 입경 범위 별 중금속 농축 정도에 대한 데이터를 살펴볼 때 일부 금속의 농도는 작은 입경 범위에서 더 농축된 것을 보여 입자의 크기와 상관관계를 지어 볼 수 있었다. 수은의 경우 다른 금속들과 다르게 높은 휘발성 때문에 대부분이 가스 상태로 배출되며 그로 인하여 수은의 제거효율은 68% 정도로 다른 중금속들에 대한 제거효율보다 낮았다. ESP를 지나면서 수은 화학종이 원소수은에서 산화수은으로 변하는 것이 확인되었으며, 그로 인하여 습식세정탑이 설비된 다른 석탄 화력발전소에서는 원소 수은이 지배적인 데 반해 본 시설의 경우 연돌에서 총 수은의 절반 정도만 원소수은이었다.

Emission of heavy metals as hazardous air pollutants has been focused with tightening regulatory limits due to their hazardousness. Measurements and characteristic investigations of heavy metals emitted from a commercial power plant burning anthracite coal have been carried out. The plant consists of a circulating fluidized bed combustor, a cyclone, a boiler and an electrostatic precipitator(ESP) in series. Dust and gaseous samples were collected to measure_x000D_ main heavy metals including gaseous mercury before ESP and at stack. Dust emissions as total particulate matter (TPM), PM-10 and PM-2.5 at inlet of ESP were very high with 23,274, 9,555 and 7,790 mg/Sm3, respectively, as expected, which is much higher than those from pulverized coal power plants. However TPM at stack was less than 0.16 mg/Sm3, due to high dust removal efficiency by ESP. Similarly heavy metals emission showed high collection efficiency across ESP. From particle size distribution and metal enrichment in sizes, several metal concentrations could be correlated with particle size showing more enrichment in smaller particles. Mercury unlike other solid metals behaved differently by emitting as gaseous state due to high volatility. Removal of mercury was quite less than other metals due to it's volatility, which was 68% only. Across ESP, speciation change of mercury from elemental to oxidized was clearly shown so that elemental mercury was half of total mercury at stack unlike other coal power plants which equipped wet a scrubber.

Circulating Fluidized Combustor Heavy Metals Mercury Dust Emissions

Linak WP, Miller CA, Wendt JOL, Proc. Combust. Inst., 2651 (2000)
Linak WP, Miller CA, Wendt JOL, J Air Waste Manage Assoc., 50, 1532 (2000)
Chang MB, Huang CK, Wu HT, Lin JJ, Chang SH, J. Hazard. Mater., 79(3), 229 (2000)
U.S. Environmental Protection Agency, Control of Mercury Emissions from Coal-Fired Electric Utility Boilers, EPA-600/R-01-109 (2002)
US EPA Method 5-Determination of Particulate Matter Emissions from Stationary Sources (1977)
US EPA Method 3050 B, Test method for Evaluating Solid Waste, SW-846-3050B, Acid Digestion of Sediments, Sludges, and Soils, 3rd Edition US EPA, Office of Solid Waste and Emergency Response, US Government Printing Office, Washington DC.
US EPA Method 201A-Determination of PM-10 Emissions(Constant Sampling Rate Procedure)
ASTM D6784-02, Standard Test Method for Elemental, Oxidized, Particle-Bound and Total Mercury in Flue Gas Generated from Coal-Fired Stationary Sources(Ontario Hydro Method)
US EPA Method 101A-Determination of Particulate and Gaseous Mercury Emission from Sewage Sludge Incinerators (2000)
Yoo JI, Seo YC, Environ. Eng. Sci., 22, 272 (2005)
Meij R, Kema Sci. Technol. Rep., Special Issue, 7, 269 (1989)
LINAK WP, WENDT JOL, Fuel Process. Technol., 39(1-3), 173 (1994)
Kim JH, Pudasainee D, Lee SH, Seo YC, “Emission Characteristics of Toxic Metals and VOCs from Fossil Fuel Power Plants”, 1st Asian Conference on Innovative Energy and Environmental Chemical Engineering(ASCON-IEEChE), August, Japan (2008)
Park KS, Seo YC, Lee SJ, Lee JH, Powder Technol., 180(1-2), 151 (2008)
HELBLE JJ, Fuel Process. Technol., 39(1-3), 159 (1994)
Lee SJ, Seo YC, Jang HN, Park KS, Baek JI, An HS, Song KC, Atmos. Environ., 40, 2215 (2006)
Pudasainee D, Lee SJ, Lee SH, Kim JH, Jang HN, Cho SH, Seo YC, “Effect of Selective Catalytic Reactor on Oxidation and Enhanced Removal of Mercury in Coal-Fired Power Plants,” FUEL. DOI: 10.1016/j.fuel., 2009. 06. 022.
Pavlish JH, Sondreal EA, Mann MD, Olson ES, Galbreath KC, Laudal DL, Benson SA, Fuel Process. Technol., 82(2-3), 89 (2003)