Patent ID: 6152053
Filing Date: 2000-11-28
Classification: F23G,F23J,F23L,F23N,Y02E

Abstract:
A method for efficiently converting waste water to a gaseous state, the waste water being produced by a system having a combustion assembly, a regenerative air preheater, and a spray dryer reactor, the combustion assembly for burning combustible material in a process which produces flue gas having sulfur oxides therein and the flue gas passing successively through the regenerative air preheater for an exchange of heat from the flue gas to incoming air ultimately introduced into the burning process and thereafter through the spray dryer reactor for contacting the flue gas with a liquid slurry having sulfur oxide absorbent material so as to produce a dry particulate reaction product which can be disentrained from the flue gas after it has exited the spray dryer reactor, the method for efficiently converting waste water to a gaseous state comprising:feeding the slurry to the spray dryer reactor, the slurry having a predetermined ratio of liquid to absorbent;controlling the feed rate of the slurry into the spray dryer reactor as a function of a monitored sulfur oxide level such that the sulfur oxide level is maintained within an acceptable range;sensing the temperature of the flue gas exiting the spray dryer reactor;monitoring the sulfur oxide level of the flue gas downstream of the spray dryer reactor;supplying supplemental liquid into the spray dryer reactor in a non-proportionate manner relative to the feed of absorbent into the spray dryer reactor such that the ratio of liquid to absorbent in the spray dryer reactor changes; andcontrolling both the supply rate of supplemental liquid into the spray dryer reactor and the temperature of the flue gas entering the spray dryer reactor in dependence upon the temperature of the flue gas exiting the spray dryer reactor such that, in the event that the sensed temperature of the flue gas exiting the spray dryer reactor is below a minimum acceptable flue gas exit temperature, the supply rate of supplemental liquid is controlled as follows:(a) the supply rate of supplemental liquid into the spray dryer reactor is decreased by an initial decrease amount,(b) thereafter, the temperature of the flue gas exiting the spray dryer reactor is sensed, and(c) if the sensed temperature of the flue gas exiting the spray dryer reactor is still below the minimum acceptable flue gas exit temperature, implementing at least one of a further decrease in the initially decreased supply rate of supplemental liquid and a further increase in the temperature of the flue gas entering the spray dryer reactor until the sensed temperature of the flue gas exiting the spray dryer reactor is above the minimum acceptable flue gas exit temperature.