Method and apparatus of controlling oxygen supply in oxyfuel combustion boiler

摘要

Provided are a method and an apparatus of controlling an oxygen supply in an oxyfuel combustion boiler capable of attaining stable oxyfuel combustion even when properties of coal are changed. A boiler-brought-in oxygen density is obtained when coal with a fuel ratio measured by fuel measuring means 39 is burned stably with oxygen in a boiler 4 so that a relationship between the fuel ratio and/or carbon content of the coal and the boiler-brought-in oxygen density is obtained and inputted in advance into the controller. When the coal is changed to the new kind of coal, a total amount of gases recirculated is regulated such that a boiler-brought-in oxygen density becomes accordance with a fuel ratio and/or a carbon content which is measured in advance for the new kind of coal.

主权项

1. A method of controlling oxygen supply in an oxyfuel combustion boiler wherein a portion of an exhaust gas recirculated is introduced into a mill as primary recirculated exhaust gas; pulverized coal pulverized by said mill is supplied to a burner of the boiler by the primary recirculated exhaust gas; another portion of the exhaust gas recirculated is supplied to a wind box of the boiler as secondary recirculated exhaust gas; the rest of the exhaust gas recirculated is supplied to an OAP as OAP recirculation exhaust gas; a portion of oxygen produced by an air separation unit is supplied to the primary recirculated exhaust gas as primary oxygen; another portion of the oxygen is supplied to the secondary recirculated exhaust gas as secondary oxygen; yet another portion of the oxygen is supplied to the OAP recirculation exhaust gas as OAP supplied oxygen; and the rest of the oxygen is supplied directly to the burner as directly supplied oxygen,
said method comprising: inputting predetermined relationships into a controller, the relationships being determined by
measuring at least one of a fuel ratio and a carbon content of coal;obtaining by calculation, upon stable combustion of the coal in the boiler, a point P1 representing a relationship between at least one of the fuel ratio and a boiler-brought-in oxygen density or the carbon content of coal and the boiler-brought-in oxygen density;executing the same operation as the operation to obtain the point P1 for each of one or more kinds of coal to obtain one or more points P2, and obtaining from a line connecting the points P1 and P2 a first relationship between at least one of the fuel ratio and the boiler-brought-in oxygen density or the carbon content of coal and the boiler-brought-in oxygen density;obtaining by calculation, upon stable combustion of the coal with at least one of the fuel ratio and the carbon content of coal having been measured in the boiler, a further point P1 representing a relationship between at least one of the fuel ratio and a rate of the directly supplied oxygen to the burner to a total oxygen amount from the air separation unit or the carbon content of coal and the rate of the directly supplied oxygen to the burner to the total oxygen amount from the air separation unit; andexecuting the same operation as the operation to obtain the further point P1 for each of one or more kinds of coal to obtain one or more further points P2, and obtaining from a line connecting the further points P1 and P2 a second relationship between at least one of the fuel ratio and the rate of the directly supplied oxygen to the total oxygen amount or the carbon content of coal and the rate of the directly supplied oxygen to the total oxygen amount; and controlling, using the controller inputted with the predetermined relationships, the oxygen supply in the oxyfuel combustion boiler based on at least one of the fuel ratio and the carbon content of the coal, wherein a total amount of gases recirculated is reduced to increase the boiler-brought-in oxygen density, or the rate of the directly supplied oxygen to the total oxygen amount is increased in case that at least one of the fuel ratio and the carbon content of coal is higher than a predetermined value, using the controller, and wherein the total amount of gases recirculated is increased to reduce the boiler-brought-in oxygen density, or the rate of the directly supplied oxygen to the total oxygen amount is reduced in case that at least one of the fuel ratio and the carbon content of coal is lower than the predetermined value, using the controller.