Semi-dry scrubbers

Element Fresh bottom ash Ivsimeter extracted pore water and leachates (Chandler el al. 1997 Cranncll et al. 2000) Aged boiiuiit ash extracted pore waters (Mciina 1997) Dry and semi-dry scrubber residues low LS (0.0-0.2) column leachates (Chandler et al. 1997) Wet scrubber residue low LS 10.0-0.2) column leachates (Chandler et al. 1997)... 

Any fabric filters used after wet or semi-dry scrubbers should not generally have galvanized support cages, because the chlorine compounds in the flue gas will react with the zinc with a detrimental effect on the filter medium. Black streaks are produced where the filter touches the support cage, thus causing a weakening of the material. 

Semi-dry scrubbers involve a chemical reaction with a wet slurry, and a dry scrubbing of the gases with dry collection of co-products. Typically the process is used to treat acid gases in a spray dryer, coupled with a pulse-jet fabric filter. In the scheme shown in Figure 7.16, with a vertical downflow spray dryer, an alkahne slurry is injected to neutralize the adds present in the flue gas. The gas temperature is controlled by the flow rate of the dilution water. 

There are hundreds of desulfurization processes proposed in the literature. These processes may be classified as wet and dry (Patkar, 1981). Spray drier absorption is a semi-wet system in which an alkali slurry is fed to the unit and the reaction product is collected dry. This process is generally applied to power stations. It is reported by Felsvang et al (1988) that spray drier scrubbers are in operation in power plants of over 10,000 MWe in different parts of Ae world. These absorbers are generally coupled with fabric filters or electrostatic precipitators to collect particulates. Spray drier absorption is experienced as a wet-dry system with different reagents such as lime, limestone, trona (natural soda) and ammonia. 

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