Advanced separation technology for flue gas cleanup. Topical report

The objective of this work is to develop a novel system for regenerable SO{sub 2} and NO{sub x} scrubbing of flue gas that focuses on (1) a novel method for regenerating spent SO{sub 2} scrubbing liquor and (2) novel chemistry for reversible absorption of NO{sub x}. In addition, high efficiency hollow fiber contactors (HFC) are proposed as the devices for scrubbing the SO{sub 2} and NO{sub x} from the flue gas. The system will be designed to remove more than 95% of the SO{sub 2} and more than 75% of the NO{sub x} from flue gases typical of pulverized coal-fired power plants at a cost that is at least 20% less than combined wet limestone scrubbing of SO{sub x} and selective catalytic reduction of NO{sub x}. The process will generate only marketable by-products. Our approach is to reduce the capital cost by using high-efficiency hollow fiber devices for absorbing and desorbing the SO{sub 2} and NO{sub x}. We will also introduce new process chemistry to minimize traditionally well-known problems with SO{sub 2} and NO{sub x} absorption and desorption. Our novel chemistry for scrubbing NO{sub x} will consist of water-soluble phthalocyanine compounds invented by SRI as well as polymeric forms of Fe{sup ++} complexes similar to traditional NO{sub x} scrubbing media. The final novelty of our approach is the arrangement of the absorbers in cassette (stackable) form so that the NO{sub x} absorber can be on top of the SO{sub x} absorber. This arrangement is possible only because of the high efficiency of the hollow fiber scrubbing devices, as indicated by our preliminary laboratory data. This arrangement makes it possible for the SO{sub 2} and NO{sub x} scrubbing chambers to be separate without incurring the large ducting and gas pressure drop costs necessary if a second conventional absorber vessel were used. Because we have separate scrubbers, we will have separate liquor loops and simplify the chemical complexity of simultaneous SO{sub 2}/NO{sub x} scrubbing