Cyclone furnace for oxygen fired boilers with flue gas recirculation

Abstract

A cyclone furnace and method uses a cyclone burner having a cyclone barrel with a re-entrant throat connected to a main furnace for passing combustion products including flue gas that is rich in carbon dioxide. Crushed coal and oxygen are supplied the cyclone burner and at least some of the flue gas from the main furnace is recirculated to the cyclone barrel.

Description

FIELD AND BACKGROUND OF INVENTION [0001] The present invention relates generally to the field of furnaces, and in particular to a new and useful cyclone furnace which produces reduced emissions of NOx. [0002] Cyclone furnaces have been in use since the early 1950's as an efficient method for combusting coal. They also allow for a smaller boiler because up to 90% of the ash is tapped out of the furnace bottom permitting a smaller convection pass without slagging on the heat transfer surface. However, with the more stringent NOx emissions in today's environment, cyclone furnaces are no longer a desirable method of coal combustion because of their heavy NOx production. [0003] More information about the construction and operation of cyclone furnaces can be found in the publication STEAM—ITS GENERATION AND USE, 40TH EDITION, published by Babock & Wilcox, a McDermott Company, at Chapter 14. SUMMARY OF INVENTION [0004] It is an object of the present invention to provide a cyclone furnace m...

AI Technical Summary

Benefits of technology

[0004] It is an object of the present invention to provide a cyclone furnace method and apparatus which reduces NOx emissions while retaining many of the advantages of cyclone furnaces.

[0006] The present invention uses cyclone burners in a new boiler utilizing oxygen combustion with recirculated flue gas for the purpose of concentrating carbon dioxide. This combination takes advantage of the combustion efficiency of cyclone furnaces to overcome the problems of high moisture inherent in recirculated flue gas and eliminates the high NOx levels produced by air-fired cyclones. Additional benefits are: 1) the lower fly-ash produced allows high convection pass velocities resulting in a closer spaced convection pass design and a smaller boiler and 2) the elimination of pulverizers, since only crushed coal is needed, reduces auxiliary power helping to compensate for the power consumption needed to produce oxygen.

Problems solved by technology

However, along with the high concentration of carbon dioxide in the recirculated flue gas is also a high concentration of moisture.

Because of these two concentrations, complete combustion of the coal becomes problematic with pulverized coal firing methods.

Images