Method of and system for generating power by oxyfuel combustion

Abstract

A method of generating power by oxyfuel combustion. Carbonaceous fuel and oxidant gas are fed into a furnace. In a first operating mode, the oxidant gas includes a stream of substantially pure oxygen conveyed from an oxygen supply for combusting the fuel with the oxygen to produce exhaust gas including mainly carbon dioxide and water. The exhaust gas is discharged from the furnace and is divided into a recycling portion and an end portion. The recycling portion is recycled to the furnace. Heat is transferred from the end portion to the stream of substantially pure oxygen by circulating a liquid heat transfer medium in a passage between an exhaust gas cooler and an oxygen heater.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to a method of and a system for generating power by oxyfuel combustion. The invention especially relates to a flexi-burn or dual-firing combustion system, i.e., a system which can be easily switched between the modes of oxyfuel combustion and combustion with air.[0003]2. Description of the Related Art[0004]Oxyfuel combustion is one of the methods suggested for removing CO2 from the combustion gases of a power generating boiler, such as a pulverized coal (PC) boiler or a circulating fluidized bed (CFB) boiler. Oxyfuel combustion is based on combusting carbonaceous fuel with substantially pure oxygen, typically of about 95% purity, so as to have carbon dioxide and water as the main components of the exhaust gas discharged from the boiler. Thereby, the carbon dioxide can be captured relatively easily, without having to separate it from a gas stream having nitrogen as its main component, such a...

AI Technical Summary

Benefits of technology

[0020]According to a preferred embodiment of the present invention, the gas feeding rate to a boiler retrofitted from air-firing to oxycombustion is adjusted so as to maintain the original gas velocity in the furnace, whereby the oxygen content of the oxidant gas is advantageously adjusted to be near to that of air, typically, from about 18% to about 28%. The furnace temperature or heat flux of the retrofitted boiler shall advantageously also be maintained at about its original level to avoid, e.g., corrosion or material strength problems of the furnace walls.

[0021]Due to the high heat capacity of the exhaust gas ge

Problems solved by technology

Generating power by oxyfuel combustion is more complicated than conventional combustion by air, because of the need of an oxygen su

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