Spray drier scrubbers

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. 

One of the important stages for a successfiil operation of a spray drier scrubber is slurry preparation in lime processes. As lime cannot be simply dissolved in water it must be ground. Particle size and slaking temperature are important parameters. Sahar and Kehat (1991) give 1.46/im as recommended average particle size for the lime slurry to be fed to the system. Unless the slurry is in a homogeneous form, the extensive surface area required for a complete gas-solid contact cannot be achieved by atomization. Plugging problems may occur in pipes in which lime slurry flows. 

The gas contains solid particles and hydrogen sulfide the former are removed and recycled to the combustor by means of a spray drier, cyclone separators, and Venturi scrubbers and the hydrogen sulfide is removed and elemental sulfur produced by the Stretford process. 

---