A Review of the Research Results into the Technologies of Solid-Fuel Combustion in a Circulating Fluidized Bed Conducted Abroad and in Russia

Abstract

The article provides an analysis of the current status and the development of the circulating fluidized bed (CFB) combustion technology. The main distinguishing features of the CFB combustion technology and the stages of its development worldwide are provided. The advantages and disadvantages of the CFB technology compared with traditional flame combustion are outlined. Examples of the largest power-generating units equipped with CFB boilers are provided. The latest studies of the specific features of the CFB boiler designs have been analyzed to increase the steam parameters and assure the highest efficiency of the power units equipped with material CFB boilers. The basic trends in the research into the hydrodynamics, separation, composition of the bed, etc. are considered. It is shown that the capturing efficiency of solid particles is the decisive factor in increasing their consumption and retention of fine calcinated particles in the circulating material. The high concentration in the disengaging space of the combustor results in an increase in the heat-transfer coefficient and ensures a uniform temperature distribution in the combustor, the required degree of reaction of limestone particles with SO2 for the most efficient binding of sulfur, and more complete combustion of the fuel (the highest possible residence time of the fuel particles in the combustor). Studies of Chinese researchers, their practical developments, and the introduction of energy-saving technology with a low volume of particles in the bed are analyzed. The results of the latest studies on the minimization of emissions of both conventional hazardous substances, such as nitrogen and sulfur oxides and other pollutants, including greenhouse gases, are provided. The problems that arise during the combustion of several kinds of fuel, including biomass, are investigated. Results of studying the processes of bed agglomeration, fouling of the heat-transfer surfaces, and corrosion of CFB boiler superheaters are presented.