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Gas purification techniques

Gas scrubber

Gas scrubber are cleanings installations in which the gas flow is brought in intensive contact with a fluid which as aim to remove gaseous components from the gas to the fluid. Gas scrubber can be applied as emission control technique at various gaseous emissions. Gas scrubbing is also called absorption.
At gas scrubbers there therefore talk of a transition of components of the gas phase to the Liquid phase. The degree in which is possible to convert gaseous components to the fluid phase depends on solubility on these components in the fluid. The balance concentration at the mist stage which belongs to a certain concentration at the fluid stage depends on the temperature, a higher temperature of the fluid phase results in a higher balance concentration at the mist stage. Lowering of the temperature has therefore also a favorable impact on the output. By adding chemicals to the carrier fluid in which absorbed components are converted, the load can increase. Adding of chemicals that can react with the absorbed gases has a favorable impact on the absorption output has.

Beside water (wet scrubbers) also organic fluids are used as an absorption means. In many cases chemicals or micro-organism are added to the carrier fluid to put or neutralize the gases which are solved in the fluid (conditioned scrubber). By this conversion the concentration in water becomes lower and more of the gasses can solve (according to the law of Henry). In practice gas scrubber exist from three components: an absorption section for substance exchange, demister and a recirculation tank with pump.

The liquid gas ratio L/G of the gas scrubber is the proportion between the flow of the carrier fluid
and the flow of the gas flow. Concerning the dimensioning and for the appraisal of the functioning
of the gas scrubber it is important know how much fluid by m³ gas is necessary to reach the desired remaining emission. L/G proportion is not only stipulated by required the remaining emission, but also in the concentration of the removable components in the gas flow and in - and outgoing liquid flows. L/G proportion in a concrete situation depends therefore on the chosen carrier system, the properties of the to purify gas, the carrier fluid and the removable component and the demands which are made to the remaining emission. Gas scrubber can be classified to the flow direction of the gas regarding to the fluid. Thereby it is distinguished in counter-, crossflowscrubbers or flowscrubber.
Gas scrubber can be also classified to the implementation of the transmission section, as it happens with or without deduction. The built-in can be a dumped or a structured packing is or a construction with plates or a
rotating disk.
Applicability of the different types of scrubbers is especially stipulated by properties of the gas to purify.
The advantages of gas scrubbing are:

  • Broad application range

  • Very high disposal output

  • Compact installation and simply in maintenance

  • Relatively simple technology

  • Can serve also as refrigeration for warm gas flows (quencher)

The disadvantages of the gas scrubbing are:

  • Effluent must be treated

  • Water - and reactant consumption

  • When dust becomes simultaneous catched from, is demoisterizing is needed

  • Frost sensitive

  • Dependent on the place construction can be necessary

  • Packing material are for constipation by substance (> possibly
    sensitive 10 mg/m3) and

  • For fragrance problems frequently pilot tests have been required
    value the feasibility in.

Gas scrubbers are mainly applied in the chemical - and pharmaceutical
industry, detritus combustion installation, on - and transshipment of chemicals and surface treatment

Click here for overview about gas purification technology and for the solubility's of different substances.

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