Method and device for purifying gaseous effluents

Gas separation: processes – Electric or electrostatic field – And nonelectrical separation of fluid mixture

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55228, 95 71, 96 53, B03C 3014

Patent

active

056244762

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION



MODES OF PRODUCTION OF A LIQUID MIST BETWEEN ELECTRODES

A gas can be purified highly efficiently by dispersing a liquid reactant between the electrodes of an electrostatic filter. Several methods have been employed, proposed or patented in order to produce a liquid mist in this type of contactor between three media, respectively gaseous, liquid and solid: electrodes, of a liquid coming from a reservoir with pressure head and electric charge (French Patent No. 1,406,086 of May 06, 1964) potential, of a liquid supplied through pipelines at the top of these electrodes pressurized atomizers at earth potential (U.S. Pat. No. 2,874,802 of Feb. 24, 1959 and French Patent No. 73,18584 of 22, May 1973) electrodes, of the liquid runoff supplied by primary spraying using atomizers at the earth potential (French Patent No. 74,17094 of 16, May 1974) families of electrodes, respectively at high voltage and at earth potential (U.S. Pat. No. 3,785,118 of Jan. 15, 1974. This arrangement, called "bi-ionized field" promotes the agglomeration of the particles in suspension, to the detriment of their electrical sedimentation. It is not in general desirable because it promotes the return of sludge into suspension in the gas.


ADVANTAGES OF THE DISPERSION OF A LIQUID IN AN ELECTROSTATIC FILTER

The advantages expected from the dispersion of a solution, of an aqueous suspension or of an emulsion between the electrodes of an electrostatic filter are the following: removed by mechanical means; reduction of their volume flowrate through the electrostatic filter; impact or by mutual electrostatic attraction; participating in the electrochemical corrosion of the metal structures; electrostatic filter are not electronically conducting. This is the case, for example, when the casing is made of masonry internally lined with a coating and when the electrodes are plates of tubes or polymer materials in order to avoid electrochemical corrosion of the apparatus; NO.sub.x, odours, etc., the wet electrostatic filter then acting as a bi- or triphase reactor.


DRAWBACKS

Wet electrostatic filters have, however, encountered only moderate success up until now, for the following reasons: effluent to a liquid effluent, and therefore solve a problem only by creating another; a weak constraint and monitoring of the industrial plant unstrict; often incompatible with the local supply possibilities; the specificity of certain reactants used in spraying, for the requirement for depolluting the liquid effluent.


THE NEW SITUATION

The ending of prejudice against electrostatic filters/washers is due to the following new facts: with much more restrictive European standards, and consequently to invest in higher-performance apparatuses; research with a view to improving the techniques which are currently most promising, without being held back by financial constraints as severe as in the past; of water, which contribute to minimizing the drawbacks linked with the transfer of pollution; between a gas and a liquid mist", exploited in the present patent in the form of an electrostatic reactor between three states, respectively liquid, solid and gaseous, constitutes a suitable technological solution to the problem of physico-chemical treatment of gaseous and liquid media within one and the same method.


SUMMARY OF THE INVENTION

An electrostatic reactor according to the invention has two functional features: liquids in a contact method with multiple stages and gas/liquid counterflow (liquid back-flow). Since the pollutant transfers take place within aerosols, the back-flow is necessarily produced from the liquid contained in the accumulation tanks which collect, via funnels, the run-off of the planar or tubular electrodes of the electrostatic filter/washer and partly recycles it into the corresponding spraying fields; liquids withdrawn at the particular accumulation tanks called "extraction tanks", with a view, on the one hand, to completely or partially remove the undesirable constituents by suitable separation techniques and,

REFERENCES:
patent: 2050797 (1936-08-01), Kerschbaum et al.
patent: 2874802 (1959-02-01), Gustafsson et al.
patent: 3404513 (1968-10-01), Roberts
patent: 3509695 (1970-05-01), Egan et al.
patent: 3785118 (1974-01-01), Robertson
patent: 3958960 (1976-05-01), Bakke
patent: 4247307 (1981-01-01), Chang
patent: 4305909 (1981-12-01), Willett et al.

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