Electrolysis: processes – compositions used therein – and methods – Electrolytic material treatment – Organic
Patent
1994-11-17
1996-10-15
Hruskoci, Peter A.
Electrolysis: processes, compositions used therein, and methods
Electrolytic material treatment
Organic
210757, 210760, 210748, 205753, 205754, 205756, 205760, C02F 146
Patent
active
055651070
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process for purifying streams which contain organic and/or inorganic impurities, the stream to be treated being introduced into a water-containing reaction zone, and to an apparatus which can be used for this process.
International Patent Application PCT/NL90/00075 (publication number WO 90/14312) discloses a process for the treatment of water which is contaminated with unwanted constituents such as (aromatic) hydrocarbons and pesticides, by treating the contaminated water or the gaseous and/or liquid components present therein or originating therefrom with ozone and a catalyst such as activated carbon, the catalyst being regenerated continuously with ozone. This process, however, has the drawback that the ozone consumption for the purpose of decomposition of the impurities (expressed as COD=chemical oxygen demand), in spite of the relatively low values, is still too high for many applications and the residence time in the reactor is rather long.
Dutch Patent Application 9000118 discloses a method for purifying streams which contain organic and/or inorganic impurities, in which the stream to be treated is introduced into a water-containing reaction zone to which current is supplied via one or more electrodes while a substance is supplied at the same time which, under the influence of the electric current supplied, produces radicals which react with the impurities. The examples given of substances of this type comprise methane, carbon monoxide, hydrogen, ammonia, oxygen, ozone and hydrogen peroxide. The substance producing electrochemical radicals in the process is preferably fed to the reaction zone via a porous electrode. The residence time in the reaction zone can be shortened by employing elevated temperatures, preferably in the range from 10.degree. to 95.degree. C. The degree of conversion and the electric energy consumption in this known method still leaves something to be desired.
A process and apparatus for electrochemical reactions to be used for pollution control are known from U.S. Pat. No. 3,915,822. An electrochemical cell is used wherein an electrolyte--which contains impurities or undesirable components--is treated in a reaction zone containing electrically conductive particles, e.g. carbon pellets, as well as a plurality of electrodes. The conductive particles may consist of activated carbon in granular, spherical or other form. The voltage is normally a DC potential gradient in the order of 0.1 to 10 Volts/cm. During the process of this U.S. patent a gas reactant such as O.sub.3 or Cl.sub.2 may be used. It is indicated that a mixture of O.sub.3 in a diluent gas can be introduced to the liquid filled bed of electrically conductive particles as fine bubbles containing ozone in an amount of 2-20 vol. %. The use of a sub-stoichiometric amount of ozone or any other reactant is not suggested.
The object of the present invention is to overcome the above-mentioned drawbacks regarding energy consumption and expensive starting materials.
To this end, the invention provides a process for purifying streams which contain undesirable organic and/or inorganic impurities which impurities may be converted into harmless compounds by reduction or oxidation, the stream to be treated being introduced into a water-containing reaction zone which comprises a packed bed of activated carbon to which an electrochemical potential is applied and to which ozone or hydrogen is fed at the same time.
The degree of polution for oxidisable impurities can be quantified as Cemical Oxygen Demand (COD). This relates to the standard USEPA method of analysis which determines the amount of oxygen that would be needed for a near complete oxidation of the micro pollutants. Evidently, in ozonation processes the resulting reaction products are also formed by introduction of oxygen into the molecules of the micro pollutants. Obeying the law of mass conservation one would expect to find an equal mass of ozone consumed as the mass of COD reduced if all oxygen atoms of the ozone molecule would have been effectiv
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Campen Jan P.
Jaspers Blandikus C.
Kaptijn Joannes P.
Casey Donald C.
ECO Purification Systems, B.V.
Green Theodore M.
Hruskoci Peter A.
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