Method and system for multi-stage flue gas cleaning

Abstract

Flue gas processing is described. A circulating dry flue gas desulfurization (DFGD) scrubber is positioned upstream of a wet flue gas desulfurization (WFGD) scrubber. Flue gas temperature and humidity is controlled. Reagent use is monitored and controlled. The DFGD scrubber is controlled without concern for sulfur dioxide absorption and thus reagent utilization is controlled based on the goal of removing one or more of: sulfur trioxide and/or other acid gases. In some embodiments the circulating DFGD scrubber removes the majority of sulfur trioxide, HCL, and/or HF from the flue gas stream supplied to the DFGD scrubber. The DFGD scrubber is followed by the WFGD scrubber that removes sulfur dioxide and mercury, to achieve a high degree of pollutant removal at a low operating cost as compared to some other systems. WFGD scrubber liquid waste is sent to the circulating DFGD scrubber and used for temperature and/or humidity control purposes.

Dependencies are inferred from the claim text.