Characterization of a limestone in a batch fluidized bed reactor for sulfur retention under oxy-fuel operating conditions

Abstract CO 2 and SO 2 are some of the main polluting gases emitted into atmosphere in combustion processes using fossil fuel for energy production. The former is one of the major contributors to build-up the greenhouse effect implicated in global climate change and the latter produces acid rain. Oxy-fuel combustion is a technology, which consists in burning the fuel with a mix of pure O 2 and recirculated CO 2 . With this technology the CO 2 concentration in the flue gas may be enriched up to 95%, becoming possible an easy CO 2 recovery. In addition, oxy-fuel combustion in fluidized beds allows in situ desulfurization of combustion gases by supplying calcium based sorbent. In this work, the effect of the principal operation variables affecting the sulfation reaction rate in fluidized bed reactors (temperature, CO 2 partial pressure, SO 2 concentration and particle size) under typical oxy-fuel combustion conditions have been analyzed in a batch fluidized bed reactor using a limestone as sorbent. It has been observed that sulfur retention can be carried out by direct sulfation of the CaCO 3 or by sulfation of the CaO (indirect sulfation) formed by CaCO 3 calcination. Direct sulfation and indirect sulfation operating conditions depended on the temperature and CO 2 partial pressure. The rate of direct sulfation rose with temperature and the rate of indirect sulfation for long reaction times decreased with temperature. An increase in the CO 2 partial pressure had a negative influence on the sulfation conversion reached by the limestone due to a higher temperature was needed to work in conditions of indirect sulfation. Thus, it is expected that the optimum temperature for sulfur retention in oxy-fuel combustion in fluidized bed reactors be about 925–950 °C. Sulfation reaction rate rose with decreasing sorbent particle size and increasing SO 2 concentration.

[1]  Y. Suyadal,et al.  Deactivation model for dry desulphurization of simulated flue gas with calcined limestone in a fluidized-bed reactor , 2005 .

[2]  Ken Okazaki,et al.  Sulfation behavior of limestone under high CO2 concentration in O2/CO2 coal combustion , 2000 .

[3]  Chunbo Wang,et al.  The effect of water on the sulphation of limestone , 2010 .

[4]  A. Lyngfelt,et al.  Sulphur capture in fluidized-bed combustors: temperature-dependence and lime conversion , 1989 .

[5]  I. Barin.  Thermochemical data of pure substances , 1989 .

[6]  J. C. Abanades,et al.  Progress of sulfation in highly sulfated particles of lime , 2003 .

[7]  D. L. Keairns,et al.  A thermogravimetric study of the sulfation of limestone and dolomite—the effect of calcination conditions , 1976 .

[8]  Antonio B. Fuertes,et al.  Study of the direct sulfation of limestone particles at high CO2 partial pressures , 1994 .

[9]  P. Rowe,et al.  A model for desulphurisation with limestone in a fluidised coal combustor , 1982 .

[10]  A. B. Fuertes,et al.  Analysis of the direct sulfation of calcium carbonate , 1994 .

[11]  Kim Dam-Johansen,et al.  Direct sulfation of limestone , 2007 .

[12]  A. B. Fuertes,et al.  Sulphur retention by limestone particles under PFBC conditions , 1993 .

[13]  Changsui Zhao,et al.  Calcination and sintering characteristics of limestone under O2/CO2 combustion atmosphere , 2007 .

[14]  J. C. Abanades,et al.  Residual activity of sorbent particles with a long residence time in a CFBC , 2000 .

[15]  Adel F. Sarofim,et al.  DIRECT SULFATION OF CALCIUM CARBONATE , 1988 .

[16]  A. Abad,et al.  Selection of Oxygen Carriers for Chemical-Looping Combustion , 2004 .

[17]  Adel F. Sarofim,et al.  Analysis and modeling of the direct sulfation of CaCO3 , 1988 .

[18]  Alberto Abad,et al.  Simultaneous Calcination and Sulfidation of Calcium-Based Sorbents , 2004 .

[19]  J. C. Abanades,et al.  Methods for characterization of sorbents used in fluidized bed boilers , 1994 .

[20]  A. B. Fuertes,et al.  Sulfation of dolomite particles at high CO2 partial pressures , 1995 .

[21]  Edward J. Anthony,et al.  Emissions of SO2 and NOx during Oxy−Fuel CFB Combustion Tests in a Mini-Circulating Fluidized Bed Combustion Reactor , 2010 .

[22]  N. H. Ulerich,et al.  A thermogravimetric study of the sulfation of limestone and dolomite — prediction of pressurized and atmospheric fluidized-bed desulfurization , 1980 .

[23]  F. García-Labiano,et al.  Factors affecting the thermogravimetric technique in the characterization of sorbents for AFBC , 1993 .

[24]  C. Tullin,et al.  Direct sulfation of calcium carbonate: the influence of carbon dioxide partial pressure , 1993 .

[25]  Kim Dam-Johansen,et al.  REVIEW OF THE DIRECT SULFATION REACTION OF LIMESTONE , 2006 .