Method of combusting sulfur-containing fuel

Abstract

A method of combusting sulfur-containing fuel in a circulating fluidized bed boiler includes the steps of (a) feeding sulfur-containing fuel into a furnace of the circulating fluidized bed boiler, (b) combusting the fuel with oxidant gas consisting essentially of pure oxygen and circulated exhaust gas, so as to form exhaust gas having carbon dioxide and water as its main components, and (c) feeding calcium carbonate containing material into the furnace so as to capture sulfur dioxide into calcium sulfate in the furnace. The temperature in the furnace is maintained above 870° C.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to a method of efficiently combusting sulfur-containing fuel in a circulating fluidized bed boiler by using oxyfuel combustion, i.e., the fuel is combusted by using pure oxygen or a mixture of a substantially pure oxidant and circulated fluidizing gas as the oxidant gas. The invention especially relates to oxyfuel combustion, in which the fuel is combusted with an oxidant gas having an oxygen content of about the same as that or higher than that of air.[0003]2. Description of the Related Art[0004]Combustion of sulfur-containing fuels, such as coal, generates sulfur dioxide, SO2, which is an acid rain creating pollutant, if released to the atmosphere. In order to minimize pollution of the environment, today's combustion systems often comprise special equipment, such as an exhaust gas scrubber, arranged in the exhaust gas channel to remove sulfur dioxide from the exhaust gas. Such special equ...

AI Technical Summary

Benefits of technology

[0010]An object of the present invention is to provide a method of efficiently combusting sulfur-containing fuel in a circulating fluidized bed boiler.

[0018]The use of combustion temperatures higher than those used in conventional air-firing fluidized bed combustion allows a circulating fluidized bed boiler to generate steam at higher temperatures, while still achieving a high level of in-furnace sulfur dioxide capture. Thus, the present invention helps to facilitate improved steam cycle efficiency in supercritical and ultra-supercritical circulating fluidized bed boiler applications. The boiler is then preferably used to generate steam at a temperature of at least about 650° C., even more preferably, at least about 700° C.

Problems solved by technology

Such special equipment is usually expensive to build and to operate.

Thus, a combustion process using a circulating fluidized bed boiler does not need additional sulfur capturing equipment in the exhaust gas channel, or the efficiency of such equipment can be relatively low.

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