Scrubbing pilot-scale

In electron beam dry scrubbing (EBDS), flue gases from the combustion of medium- to high-sulfur fuels are injected with water and ammonia vapor, and expo.sed lo high-energy electron beams (Ratafia-Brown el al 1995). The SOt and NOj react to form ammonium sulfate and nitrate, and the aerosol product is collected for sale as a fertilizer. Several existing installations are operated on a large pilot scale, about 1% of plant-scale gas flow rates. 

Experiments in Slurries, In a slurry system, Borgwardt (14,8) studied enhanced oxidation in a pilot-scale scrubbing system (pH 4.5) with a forced oxidation tank. Even with advanced-design gas distributors, he found the overall rate of oxidation was limited by the mass transfer of oxygen to the solution. An air stoichiometry of 2,6 was used in this investigation. Neither gas distributor orifice size nor chloride concentration had an effect on the rate. 

The data obtained from small-scale continuous operations will be required to determine whether the process should be investigated on a larger scale, such as a pilot plant. These data should be sufficient to draw a conceptual flow sheet, which will include a number of stages for extraction, scrubbing [10], and stripping the flow rates, size and type of equipment, and the various parameters considered earlier in this chapter. Another important aspect should also be considered in the continuous test work, and that is chemical analysis of both the aqueous and organic phases for their various components. 

Contaminated feedstock is heated in an indirectly fired rotary dryer. The vapors are then transported to a gas treatment system via an inert gas such as nitrogen where they are scrubbed and cooled to condense the organics. The carrier gas is reheated and recycled to the dryer. The recovered organics can be reclaimed, used on-site or off-site as fuel, or incinerated. The technology is available in laboratory-, pilot-, and full-scale systems. 

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