바이오매스 순환유동층 연소에서 CaSO4 환원반응에 의한 파울링 발생 방지 연구
A Study on Prevention of Fouling Formation by Reduction Reaction of CaSO4 in a Biomass Circulating Fluidized Bed Combustion
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A large amount of carbon monoxide (CO) is generated in circulating fluidized bed combustion, the process whereby ahot cyclone separates unburned fuel. However, calcium sulfate (CaSO4), when combined with a high CO content, can cause fouling onthe surface of the steam tube installed inside the integrated recycle heat exchangers (INTREX). In this study, CaSO4 decompositionwas investigated using 0.2-3.2 vol.% CO and 1-3 vol.% oxygen (O2) at 850°C for 20 min in a lab-scale fluidized bed reactor. Theresults show that CaSO4 decomposes into CaS and CaO when CO gas is supplied, and SO2 emissions increase from 135 ppm to 1021ppm with increasing CO concentration. However, the O2 supply delayed SO2 emissions because the reaction between CO and O2 isfaster than that of CaSO4; nevertheless, when supplied with CaCO3, the intermediate product, SO2 was significantly released,regardless of the CO and O2 supply. In addition, agglomerated solids and yellow sulfur power were observed after solid recovery, andthe reactor distributor was corroded. Consequently, a sufficient O2 supply is important and can prevent fouling formation on theINTREX surface by suppressing CaSO4 degradation.
Abstract
A large amount of carbon monoxide (CO) is generated in circulating fluidized bed combustion, the process whereby ahot cyclone separates unburned fuel. However, calcium sulfate (CaSO4), when combined with a high CO content, can cause fouling onthe surface of the steam tube installed inside the integrated recycle heat exchangers (INTREX). In this study, CaSO4 decompositionwas investigated using 0.2-3.2 vol.% CO and 1-3 vol.% oxygen (O2) at 850°C for 20 min in a lab-scale fluidized bed reactor. Theresults show that CaSO4 decomposes into CaS and CaO when CO gas is supplied, and SO2 emissions increase from 135 ppm to 1021ppm with increasing CO concentration. However, the O2 supply delayed SO2 emissions because the reaction between CO and O2 isfaster than that of CaSO4; nevertheless, when supplied with CaCO3, the intermediate product, SO2 was significantly released,regardless of the CO and O2 supply. In addition, agglomerated solids and yellow sulfur power were observed after solid recovery, andthe reactor distributor was corroded. Consequently, a sufficient O2 supply is important and can prevent fouling formation on theINTREX surface by suppressing CaSO4 degradation.
참고문헌 (21)
- 이승록, "재생에너지로서 산림바이오매스 활용 촉진을 위한 주요국의 정책분석을 통한 한국의 접근전략", 신재생에너지, 18(3), pp.10~22 (2022), 한국신·재생에너지학회[DOI]
- Hoteit, A., "Sulfate decomposition from circulating fluidized bed combustion bottom ash", Chem. Eng. Sci, 62(23), pp.6827~6835 (2007)
- Zhang, X., "Density functional theory study on the mechanism of calcium sulfate reductive decomposition by carbon monoxide", Ind. Eng. Chem. Res, 51(18), pp.6563~6570 (2012)
- 배달희, "고정층과 순환유동층에서 CaSO4의 환원반응에 대한 온도와 CO농도의 영향", Korean Chemical Engineering Research(HWAHAK KONGHAK), 41(1), pp.99~105 (2003), 한국화학공학회
- Diaz-BOssio, L. M., "Reductive decomposition of calcium sulfate utilizing carbon monoxide and hydrogen", Chem. Eng. Sci, 40(3), pp.319~324 (1985)
- Xia, X., "Recovery of CaO from CaSO4 via CO reduction decomposition under different atmospheres", J. Environ. Manage, 301, pp.113855~ (2022)
- Allen, D., "Reaction between gaseous sulfur dioxide and solid calcium oxide mechanism and kinetics", J. Chem. Soc., Faraday Trans, 92, pp.1227~1238 (1996)
- Zheng, M., "Kinetic model for parallel reactions of CaSO4 with CO in chemical-looping combustion", Ind. Eng. Chem. Res, 50(9), pp.5414~5427 (2011)
- 백승기, "순환유동층보일러의 과열기 튜브 부식에 알칼리 금속과 염소가 미치는 영향", 공업화학, 28(1), pp.29~34 (2017), 한국공업화학회[DOI]
- Okumura, S., "Recovery of CaO by reductive decomposition of spent gypsum in a CO-CO2-N2atmosphere", Ind. Eng. Chem. Res, 42(24), pp.6046~6052 (2003)
- Wang, B. W., "Study on the performance of the purified CaSO4 oxygen carrier derived from wet flue gas desulphurization slag in coal chemical looping combustion", J. Fuel Chem. Technol, 48(8), pp.908~919 (2020)
- Ragland, K. W., "Combustion Engineering" (2011), CRC Press
- Kuusik, R., "Thermal decomposition of calcium sulfate in carbon monoxide", J. Therm. Anal, 30, pp.187~193 (1985)
- "Gas adsorption and ploymorphism in the reductive decomposition of calcium sulfate" (1966)[URL]
- Schwitzegebel, K., "Thermodynamic basis for existing experimental data in magnesium-sulfur dioxide-oxygen and calcium-sulfur dioxide-oxygen systems", Environ. Sci. Technol, 7(13), pp.1147~1151 (1973)
- Shen, L., "A mechanistic investigation of a calcium based oxygen carrier for chemical looping combustion", Combust. Flame, 154(3), pp.489~506 (2008)
- Song, Q., "Multicycle study on chemical-looping combustion of simulated coal gas with a CaSO4 oxygen carrier in a fluidized bed reactor", Energy Fuels, 22(6), pp.3661~3672 (2008)
- Li, C., "Reaction process and mechanism analysis for CaS generation in the process of reductive decomposition of CaSO3 with coal", J. Taiwan Inst. Chem. Eng, 50, pp.173~181 (2015)
- Lyngfelt, A., "Sulphur capture in fluidized bed boilers : The effect of reductive decomposition of CaSO4", Chem. Eng. J, 40(2), pp.59~69 (1989)
- Hansen, P. F. B., "High-temperature reaction between sulfur dioxide and limestone-V. The effect of periodically changing oxidizing and reduction conditions", Chem. Eng. Sci, 48(7), pp.1325~1341
- Mattisson, T., "Reaction between sulfur dioxide and limestone under periodically changing oxidizing and reducing conditions-Effect of cycle time", Energy Fuels, 12(5), pp.905~912 (1998)