Chapter 1

Oxy-Fuel Combustion in Fluidized Beds

Isabel Guedea, Irene Bolea, Carlos Lupiañez, Luis M. Romeo and Luis I. Díez

Abstract

Fluidized beds particular features drive this technology as an appropriate candidate technology to apply oxy-fuel combustion, producing so a highly concentrated CO<sub>2</sub> flue gas stream to be processed and stored. Still, there are several issues differencing the conventional combustion to that with O<sub>2</sub>/CO<sub>2</sub> mixtures. This chapter examines the main issues involved in oxy-fuel combustion in fluidized beds through the experimental results obtained in the CIRCE oxy-fuel bubbling fluidized bed. </p><p> The fluidization velocity during oxy-firing is in general, below the air-firing case. This is caused by the higher O<sub>2</sub> concentration in the oxidant stream, together with the higher gas density when substituting air-N<sub>2</sub> by CO<sub>2</sub>. The lower fluidization velocity affects in opposite ways the combustion and pollutant formation: it increases the residence time of particles in bed, whereas poorer mixing of fuel particles disadvantages reactions. Higher O<sub>2</sub> at inlet obliges to increase the fuel input to maintain proper fluid-dynamics conditions. This is adequate for the combustion efficiency and also, for the in-furnace SO<sub>2</sub> capture. Unlike in conventional combustion, SO<sub>2</sub> capture optimum temperature is higher than 850 ºC, because of the influence of high CO<sub>2</sub> partial pressure. </p><p> NO<sub>x</sub> emissions showed no significant differences with air-firing case, if concentration is expressed per unit of energy. This is due again to the lower flow of flue gases per thermal fuel input. Plant heat balance of large oxy-fuel fluidized bed boilers will change considerably in oxy-fuel case. Boilers will be more compact and thus, additional heat transfer surface will be essential.

Total Pages: 3-39 (37)

Purchase Chapter  Book Details

RELATED BOOKS

.Advances in Dye Degradation (Volume 1).
.Biological and Medical Significance of Chemical Elements.
.Advanced Catalysts Based on Metal-organic Frameworks (Part 2).
.Cerium-Based Materials: Synthesis, Properties and Applications.