CN1552639A

CN1552639A - Method for comprehensive treating waste emulsion liquid and chromium containing waste water by metallurgy chemical industry technology

Info

Publication number: CN1552639A
Application number: CNA031288030A
Authority: CN
Inventors: 李峻泰
Original assignee: Individual
Current assignee: Individual
Priority date: 2003-05-26
Filing date: 2003-05-26
Publication date: 2004-12-08
Anticipated expiration: 2023-05-26
Also published as: CN1254444C

Abstract

A process for treating the used emulsified liquid and Cr-contained sewage includes such steps as removing oil from the used emulsified liquid, chemically reducing the 6-valence Cr in said sewage, mixing them with high-temp metallurgical slags to obtain water and slag mixture, supplying the water to the closed-loop circulation of slag-treating water, and using the slag mixture as raw material to produce cement.

Description

Method for comprehensively treating waste emulsion and chromium-containing wastewater by using metallurgical and chemical technology

The technical field is as follows: the invention belongs to the technical field of environmental pollution treatment. Mainly solves the secondary pollution caused by the discharge of high COD value waste water, chromium-containing waste water and chromium-containing sludge after deoiling waste emulsion to the environment.

Background art: the emulsion is prepared by mixing mineral oil, vegetable oil and animal oil in certain proportion, adding dispersant stabilizer, and emulsifying with water. The emulsion is used as lubricant and coolant in the processes of metallurgical steel rolling, automobile manufacture, equipment processing and maintenance and the like, and the components and the state of the emulsion are changed and discarded after being repeated for many times, namely the waste emulsion, which contains oil and has high COD value (chemical oxygen demand). Environmental protection requirements are carefully treated, and the wastewater can be discharged into a water environment after reaching the discharge standard. In order to meet the requirement of environmental protection, advanced enterprises use an ultrafiltration deoiling method and a biological method to remove COD, and the two processes are used in series. The COD value is still higher, some other waste water except COD is adsorbed by activated carbon, and because of huge equipment investment, complex operation and high operating cost, a plurality of enterprises adopt outsourcing treatment, while the waste emulsion is subjected to standing aeration and deoiling in rural private enterprises in suburbs, and the waste water with high COD value is simply treated by lime water and then discharged to the environment, thereby causing secondary environmental pollution.

The electroplating industry, the repairing industry, the metallurgy enterprise products, the plate and tube processing and the like use a large amount of chromic acid, chromic anhydride, stainless steel smelting process and the like to generate a large amount of chromium-containing wastewater. Chromium is a substance which is most strictly controlled in the environmental protection discharge standard, some enterprises reduce hexavalent chromium in the hexavalent chromium into trivalent chromium through chemical treatment, then adjust the pH value to precipitate the trivalent chromium, water is discharged to the environment, the treatment of the precipitate is adifficult problem, many enterprises treat the chromium-containing wastewater outsourcing suburb private enterprises, the civilian small plants reduce the hexavalent chromium into the trivalent chromium, then adjust the pH value to precipitate the trivalent chromium, water is discharged to the surrounding water body, and the precipitate is sent to brick factories to be baked or filled into deep pits.

Both COD (chemical oxygen demand) and chromium are pollution factors that are strictly controlled in environmental protection drainage standards. After deoiling, the COD value of the waste emulsion is up to 20000 mg/L-30000 mg/L (chromium method) or even higher, and far exceeds the national emission standard of 100mg/L (chromium method). After the chromium-containing wastewater is chemically reduced, a certain amount of chromium is always contained in the wastewater, and the precipitate of trivalent chromium is sent to a brick factory for brick baking or filled into a pit, which is not always a proper disposal method.

In the industrial production of metallurgy (blast furnaces, converters, electric furnaces, ferroalloy smelting furnaces and the like), a large amount of liquid slag (1400-1500 ℃) is generated while precious metals are obtained. At present, there are two kinds of slag treatment methods, one is to carry out water quenching granulation by using a large amount of high pressure water in front of or near the furnace, the other is to inject the slag into a slag tank for slight cooling (natural cooling or water spraying) to reach about 600 ℃, then send the slag blocks into the slag tank of the slag treatment hot disintegrating process, cover and spray water, and pulverize by using the characteristics of the slag (the process is mainly used for slag treatment). Because the slag temperature is very high, a large amount of water is needed for operation in the processes of water quenching and hot sealing in front of the furnace, a large amount ofwater is evaporated, and part of water is taken away. Although the slag treatment process employs a closed cycle of water, large quantities of industrial water are required to be replenished each day.

The invention content is as follows: the invention utilizes the waste water after being treated to adjust the PH value of the waste water containing chromium and the alkalization of the waste water with high COD value, and returns the generated slurry turbid matter to the water treatment system of the closed circulation water for treating the slag, thereby ensuring that the waste emulsion and the waste water containing chromium are not discharged to the natural environment, comprehensively utilizing the water, saving the water resource and the energy, and thoroughly solving the problems of the discharge pollution of the waste water with high COD value and the waste water containing chromium and the treatment problem of the sludge after the waste water containing chromium is treated.

The specific implementation mode is as follows: 1. and (3) treating the waste liquid after the waste emulsion is kept stand, carrying out microporous aeration for degreasing, and then treating the steel slag by using a hot sealing process, wherein the pH value of the water (pH value is 11-12) carrying fine slag is adjusted to be about 9. Then the water is returned to a slag treatment closed-loop circulating water treatment system to be used as make-up water of slag treatment closed-loop circulating water, and the organic matters in the high-COD value wastewater are burnt and boiled by boiling water for complete digestion through contact with high-temperature metallurgical slag, so that zero emission to the environment is achieved.

2. Using Fe in acidic medium for chromium-containing waste water and waste liquid²⁺，SO₃ ^2-，S₂O₃ ^2-Or reducing hexavalent chromium to trivalent chromium by a reducing agent such as sodium metabisulfite. For example: reducing hexavalent chromium to trivalent chromium with sodium pyrosulfite at pH less than or equal to 4

Measurement of [ Cr]⁶⁺Is [ Cr]guaranteed⁶⁺0.5mg/L (national standard). Treating the steel slag by a hot smoldering process and adding water (pH is 11-12) with fine slag to adjust the pH to 8-9 so as to precipitate trivalent chromium

Precipitate and powdered steel slag (phi less than 5)^m/_m) The water is returned to the slag treatment closed-loop circulating water treatment system and used as make-up water of the slag treatment closed-loop circulating water, so that zero emission to the environment is achieved.

Claims

A method for comprehensively treating waste emulsion and chromium-containing wastewater by utilizing metallurgical and chemical technologies is characterized by comprising the following steps:

1. a large amount of high-temperature liquid slag (1400-1500 ℃) is generated in the smelting process of metallurgical enterprises (blast furnaces, converters, electric furnaces, ferroalloy smelting furnaces and the like), the slag is granulated and treated by a large amount of closed-loop circulating water in front of the furnaces and near the furnaces or massive steel slag at the temperature of about 600 ℃ is sent into a hot closed tank to be covered and sprayed with closed-loop circulating water for pulverization, a high COD value factor of deoiled waste emulsion is a mixture of multiple organic matters, the deoiled high COD value wastewater is added into the closed-loop circulating water, and the high-temperature granulation or high-temperature closed decomposition function of the metallurgical slag treatment is used for thorough digestion. The water is used as partial make-up water of the closed-loop circulating water, so that the problem of black and odorous water body caused by the discharge of the high-COD value waste water to the environment is perfectly solved.
2. Adjusting the pH value of the chromium-containing wastewater to be acidic, and using Fe²⁺，SO₃ ^2-，S₂O₃ ^2-Or reducing agent such as sodium pyrosulfite to remove hexavalent chromium (Cr)⁶⁺) Reduction to trivalent chromium (Cr)³⁺) Then the water (carrying fine slag) of the steel slag is treated by a hot disintegration process (phi is less than 5)^m/_m) The pH value of the waste water is 11-12, the waste water reduced into trivalent chromium is adjusted to 8-9, the purpose of treating waste with waste is achieved, and the precipitate of trivalent chromium ((Cr (OH))₃↓)) is precipitated together with the powder steel slag. At present, phi<5^m/_mThe steel powder slag is a raw material for producing cement or is widely used as a sintering raw material of a metallurgical enterprise, so that the trivalent chromium sludge is well finally treated.
3. The two kinds of waste water are treated and then used as make-up water of closed circulation water for metallurgical slag treatment, so that the purpose of saving water resources and energy sources is achieved.