Method for purifying waste water from a stainless steel slag treatment process

A technology for stainless steel slag and wastewater, applied in chemical instruments and methods, multi-stage water treatment, water/sewage treatment, etc., can solve the problems of less molybdenum removal, no trivalent chromium removal efficiency, etc., to reduce salt load. Effect

Inactive Publication Date: 2013-10-30
ORBIX SOLUTIONS
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Problems solved by technology

[0008]Therefore, the purification process has the disadvantage of having to add a large amount of ferric iron sludge and remove it again from the wastewater, although there is a large amount of ferric iron in the wastewater , the mo

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  • Method for purifying waste water from a stainless steel slag treatment process
  • Method for purifying waste water from a stainless steel slag treatment process
  • Method for purifying waste water from a stainless steel slag treatment process

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Embodiment Construction

[0037] The present invention generally relates to new methods for purifying wastewater generated during the treatment of stainless steel slag. Stainless steel mainly comprises iron and further at least chromium and optionally other heavy metals such as nickel and molybdenum. During the production of stainless steel, calcium and magnesium oxides / carbonates (i.e., calcined lime, calcite, dolomite, and magnesite) are added to furnaces (especially electric arc furnaces) to produce liquid slag on top of the molten metal . This slag serves the purpose of oxidizing impurities. After the steelmaking process, the slag is poured into the pit and allowed to cool. To speed up the cooling process, water is sprayed onto the hot slag. During cooling, different amorphous and crystalline phases are formed, including calcium silicate.

[0038] The solidified stainless steel clinker is comminuted to produce fine or coarse agglomerates which can be used in particular for the production of con...

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Abstract

The present invention relates to a method for purifying highly alkaline waste water from a stainless steel slag treatment process. This waste water contains between 0.5 and 5 mg/l of trivalent chromium (Cr(III)) and between 0.5 and 10 mg/l of molybdenum. To reduce the chromium and molybdenum content a trivalent iron is added to the waste water in the form of a water soluble ferric salt and the trivalent iron is allowed to co-precipitate with said chromium and molybdenum by lowering the pH of the waste water. It was found that by performing the co-precipitation at a pH of 3.5 to 5.7, both the chromium and the molybdenum content could be effectively reduced to a level of less than 0.5 mg/l, and this without having to provide large amounts of trivalent iron in the waste water, without having to repeat the purification process for several times, without having to add sulphide to the waste water, and without having to lower and raise the pH of the waste water for more than one time.

Description

technical field [0001] The present invention relates to a method for purifying waste water such that its chromium and molybdenum content is reduced, the chromium content is reduced to a concentration below 0.5 g / l, and the molybdenum content is reduced to a concentration below 4 mg / l, said waste water It is waste water from stainless steel slag treatment processes in which stainless steel slag is brought into contact with water, in particular to neutralize the free lime contained therein, thus generating said waste water. The waste water thus obtained has an initial pH greater than 10, in particular higher than 11, and more particularly higher than 11.5. It contains chromium, contains 0.5 to 5 mg / l trivalent chromium (Cr(III)), and also contains 0.5 to 10 mg / l molybdenum. Typically, it also contains 200 to 2500 mg / l of chloride. During the purification process, the chromium and often molybdenum content has to be reduced in order to be able to discharge the purification waste...

Claims

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Application Information

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IPC IPC(8): C02F1/52C02F1/66C02F101/20C02F101/22C02F103/16
CPCC02F2101/22C02F1/5236C02F2101/20C02F1/5245C02F2301/08C02F1/705C02F2103/16C02F1/66C02F1/52
Inventor E·内谷仁D·梵梅彻恩
Owner ORBIX SOLUTIONS
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