Patent ID: 8313555

Claim:
In a circulating fluidized bed (CFB) scrubber for removing sulfur oxides from a flue gas produced during the combustion of a sulfur-bearing fuel in a reactor vessel, the CFB further comprising a flue gas inlet duct leading to said reactor vessel, a dry circulating fluidized bed of dry lime sorbent, fuel ash and by-products in said reactor vessel, a water spray infeed for spraying cooling water into said reactor vessel, and an exhaust outlet duct leading from said reactor vessel to a downstream particulate collector, an improvement comprising: a probe mounted in the exhaust outlet duct proximate said reactor vessel or downstream particulate collector for sensing moisture characteristics of the flue gas leaving the CFB scrubber, said moisture characteristics including humidity of the flue gas; a temperature monitor for monitoring approach to adiabatic saturation temperature at said probe based on said sensed moisture characteristics; a programmable controller for automatically periodically comparing said sensed approach to adiabatic saturation temperature at said probe to at least one predetermined setpoint and for selectively outputting a cooling water adjustment signal in response thereto; an actuator coupled to said water spray infeed for adjusting an amount of cooling water sprayed into said reactor vessel, said actuator being electrically connected to said programmable controller; whereby whenever said sensed approach to adiabatic saturation temperature level differs from the predetermined setpoint said programmable controller outputs a cooling water adjustment signal to said actuator to adjust the amount of cooling water sprayed into said reactor vessel.