Liquid Scrubbers

Liquid scrubbers remove contaminants quite effectively. They can be made even more effective by breaking up the gas into smaller bubbles with screens or diffusor/air-stones. These devices expose a greater surface area of the gas to the liquid removal agent and thus make the scrubbing more efficient. Use a larger pore diffuser for this - finer pores take more pressure and clog up faster. Better quality glass bonded silica diffusers have better resistance to KOH and do not deteriorate as quickly as other types. 

Liquid scrubbers, or bubblers as they are sometimes called, simply release the gas through a liquid. The liquid absorbs contaminants, refining the gas so that it will not be detrimental to the device being fed, in this case, a fuel cell. We chose distilled water or vinegar, and a combination of both, though there are other liquids that will work. 

The bubbler operates by conducting the gas through the connector, down the tube, and into the liquid scrubber. The screen on the end of the inside tube breaks up the gas into smaller bubbles. The bubbles rise to the surface... 

Problem 13.4 A chemical process produces a waste stream that is mostly air but contains dimethlyamine (DMA) at a mol fraction of 0.01. To satisfy emission standards, the gas stream must be purified to contain no more than 100 ppm of DMA. To achieve this concentration, the gas is passed through a liquid scrubber in which water is sprayed from the top of the tank while the gas rises. During the contact between the drops and the gas, some DMA is transferred to the liquid phase. The inlet water contains no DMA and the exiting streams may be assumed to be in equilibrium with each other. The process is operated at 25 °C, 1 bar. 

Excessive concentrations of silicone or inhibitor Charcoal filter Condensing hydrocarbons Extraneous surfactants Plugged level control taps Liquid-liquid scrubbers... 

Removal of NOx from stack gas presents some formidable problems. Use of liquid scrubbers such as those employed to remove SOj from stack gas is not very effective for NOx removal because of the low solubilities of nitrogen oxides. Sorption onto solids followed by destruction of the sorbed gases has been tried. Catalytic reduction and decomposition of nitrogen oxides are employed in automobile catalytic converters (see Section 8.8) and may be applicable to stack gas, although sulfur gases and particles in stack gas may interfere and poison the catalysts. Another possibility is the use of biofilters in which microorganisms held on support media metabolize NOx Section 8.9). 

Figure 8.1.5. Nine-plate (nine-stage) gas-liquid scrubber with the absorbent liquid in crossflow over each perforated plate, throu which the gas bubbles move up the overall pattern of flow of the gas and liquid phases is countercurrent.

Figure 4.5 Some Effluent Removal Systems (a) Liquid Scrubbers, (b) Thermal Decomposition-Pyrolisis Scrubber, (c) Combustion, Liquid, Catalysis Scrubber System...

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