METHOD OF CLOSED WATER CIRCULATION OF GALVANIC PRODUCTION Russian patent published in 2020 - IPC C02F9/02 C02F9/04 C02F9/08 C02F1/28 C02F1/42 

FIELD: technological processes.

SUBSTANCE: invention relates to closed-cycle water circulation of galvanic production, which envisages separate collection of concentrated process wastes in accumulators in form of spent acidic, alkaline, chromium-containing and cyanide-containing solutions with total concentration of not more than 400 g/l and diluted process wastes from washing of parts in form of spent acid-alkali, chromium-containing and cyanide-containing flushing water with salt content of each of said components of not more than 500 mg/l in terms of NaCl with content of hexavalent chromium Cr⁶⁺ of not more than 200 mg/l and cyanides of not more than 150 mg/l, and their further continuous purification. At that, purification of diluted process wastes is performed to water quality of the second category with total salt content in terms of NaCl of not more than 100 mg/l at pH 6.0–8.5 and absence of hexavalent chromium Cr⁶⁺ and cyanides, for this purpose, acid-alkali flushing water is first subjected to preliminary purification by mechanical filtration to remove contamination particles with size of up to 20 mcm, and then by sorption filtration to remove organic impurities to chemical oxygen demand (COD) value of not more than 50 mg/l, then, pre-cleaned acid-alkaline flushing water by means of pump is supplied to ion exchange plant for their further purification by means of ion exchange to obtain water quality of second category, where the pre-purified acid-alkaline flushing waters pass successively cation-exchange treatment using an ion-exchange resin in the form of a macroporous strong-acid cationite based on a copolymer of styrene-divinylbenzene with high degree of monodispersity and anion-exchange treatment using an ion-exchange resin in form of a macroporous weakly basic anionite based on a copolymer of styrene-divinylbenzene with monodisperse distribution of granules, after which water of the second category is fed into a single water reservoir of the second category, wherein the rate of passage of acid-alkali flush water through mechanical and sorption filtration and purification by ion exchange is 7,500–10,000 l/h, and the volume ratio of cationite and anionite is 0.8–1.0. Chromium-containing flushing water is first subjected to preliminary purification by sorption (coal) filtration to remove mechanical and organic impurities to chemical oxygen demand (COD) value of not more than 50 mg/l, then, pre-purified chromium-containing flushing water is fed by pump to ion exchange plant for further purification by ion exchange to obtain water quality of second category, where the pre-purified chromium-containing flushing waters pass successively cation-exchange treatment by an ion-exchange resin in the form of a macroporous strong-acid cationite based on a styrene-divinylbenzene copolymer with high degree of monodispersity and anion-exchange treatment using an ion-exchange resin in form of a macroporous weakly basic anionite based on a copolymer of styrene-divinylbenzene with monodisperse distribution of granules, after which water of the second category is fed into a single water reservoir of the second category, wherein the rate of passage of chromium-containing flushing water through mechanical and sorption filtration and purification by ion exchange is 4,000–5,000 l/h, and the volume ratio of cationite and anionite is 0.5–0.7. Cyanic flushing water is first subjected to preliminary purification by sorption filtration for purification from mechanical and organic impurities to chemical oxygen demand (COD) of not more than 50 mg/l, then, pre-cleaned cyanide-containing washing water by means of pump is supplied to ion exchange plant for their further purification by means of ion exchange to obtain water quality of second category, where the pre-purified cyanide-containing washing water is successively passed through cation-exchange treatment using an ion-exchange resin in the form of a macroporous strong-acid cationite based on a copolymer of styrene-divinylbenzene with high degree of monodispersity and anion-exchange treatment using an ion-exchange resin in form of a macroporous weakly basic anionite based on a copolymer of styrene-divinylbenzene with monodisperse distribution of granules, after which water of the second category is fed into a single water reservoir of the second category, wherein rate of passage of cyanide-containing washing water through mechanical and sorption filtration and purification by ion exchange is 1,000–1,200 l/h, and volume ratio of cationite and anionite is 0.6–0.8. Then, water of the second category is returned to the galvanochemical production using a pump; and purification of concentrated process wastes is carried out to water quality of third category with total salt content in terms of NaCl of not more than 40 mg/l, dry residue of not more than 35 mg/l, pH 6.0–8.5 and absence of hexavalent chromium Cr⁶⁺ and cyanides, for which concentrated process effluents are first supplied to averaging concentrated effluents, and then into treatment reactor for their neutralization and sedimentation in series and/or simultaneously solutions of sulfuric acid with concentration of 20–30 %, sodium sulphite with concentration of 10–12 %, sodium hydroxide with concentration of 20–30 %, flocculant concentration of 0.02–0.1 % and ferric chloride with concentration of 0.5–5 %, and then – into settler, where settling averaged concentrated process wastewater for at least 2 hours to obtain clarified concentrated process wastes and solid concentrated process sludge. Further, the clarified concentrated effluent is fed into a vacuum evaporator for evaporation at a temperature of not more than 35–45 °C and value of 0.93–0.97 bar vacuum until a concentrated solution of salts density not exceeding 1.25 g/cm³ and the condensate water of the third category, which is returned to the galvanochemical production using the pump, and concentrated solution of salts and solid concentrated process sludge after preliminary dehydration till moisture content is no more than 70 %, is directed for recycling.

EFFECT: elimination of discharge of effluents of galvanic production due to treatment of wastes to water quality of the second and third categories and its repeated use in galvanic production.

7 cl, 5 tbl, 3 ex