Pretreatment process for oily watewater of cold rolling mill

A pretreatment and wastewater technology, applied in flotation water/sewage treatment, water/sewage multi-stage treatment, water/sludge/sewage treatment, etc. Analyzed and other problems to achieve the effect of promoting energy saving, emission reduction and sustainable development, high waste oil recovery rate and low maintenance cost

Inactive Publication Date: 2009-07-08
WUHAN IRON & STEEL (GROUP) CORP
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Problems solved by technology

The biggest disadvantage of using this method to treat oily wastewater is that the quality of the effluent after treatment is unstable and often does not meet the standard, and the application effect in major domestic iron and steel enterprises is not satisfactory.
The main reason is that the emulsion oily wastewater with high degree of saponification and long molecular chain will block the surface of the ultrafiltration membrane, so that the ultrafiltration cannot continue, so the soluble COD cannot be removed.
At the same time, the method occupies a large area and requires high investment.
(2) The chemical pretreatment process represented by demulsification usually adopts one-time chemical demulsification plus air flotation treatment, and the treatment effect fo

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  • Pretreatment process for oily watewater of cold rolling mill

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Embodiment Construction

[0025] Below in conjunction with accompanying drawing, the present invention will be further explained:

[0026] refer to figure 1 , the pretreatment process of oily wastewater from cold rolling mills is specifically the following steps:

[0027] (1) oil recovery treatment; feed steam into the regulating tank 1, heat the oily waste water temperature to 60°C-70°C, and add concentrated nitric acid (more than 30% by mass) to adjust the pH between 3.0-4.0, and react 3- 5 hours, collect the oil that floats on the surface of the waste water by the floating oil collection device 2 (oil skimmer);

[0028] (2) Demulsification treatment: pump the waste water after oil recovery treatment into the flocculation tank 4, add sodium hydroxide to adjust the pH at 7.0-8.5, add a composite demulsifier of polyferric sulfate and polyaluminum chloride for demulsification treatment , the mass ratio of the two is 8-12:1, the concentration in the wastewater is 400-800mg / L, and the reaction is stirre...

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Abstract

The invention relates to a process for pre-treating wastewater containing oil of a cold rolling mill, which solves the problems of poor demulsification effect, high investment, high energy consumption, low recovery rate of waste oil, mass waste residue generation and substandard treated effluent existing in the prior process for pre-treating wastewater containing oil of the cold rolling mill. Recycling of waste oil can be realized through acidification demulsification, oil reclaiming treatment, re-demulsification treatment, flocculation treatment and air floatation separation by steam introduction and the acidification demulsification, so that reclamation rate of the waste oil is improved, energy consumption and investment are reduced, the amount of the waste residue is small, and each index of the pretreated wastewater can be reduced to meet the requirement of secondary treatment so as to greatly reduce the load of the secondary treatment.

Description

technical field [0001] The invention relates to a wastewater treatment process in the metallurgical industry, in particular to a pretreatment process for oily wastewater in a cold rolling mill. Background technique [0002] The oily wastewater from cold rolling mainly comes from the rolling mill unit, roll room, strip degreasing unit, skin pass unit, and oil depot drainage of each unit. It is one of the most difficult wastewater to treat in the steel industry. According to the shape and separation characteristics of oil, oily wastewater can be divided into floating oil, dispersed oil, emulsified oil, dissolved oil and oil two solids. Among them, the emulsified oil is milky in the sewage, and the particle size of the oil droplet is generally 0.1-25 μm. The surface of the oil droplet is wrapped with a negatively charged hydration film. It remains stable for a long time and is difficult to separate by mechanical means. The main characteristics of oily wastewater from rolling ...

Claims

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Application Information

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IPC IPC(8): C02F9/02C02F1/40C02F1/52C02F1/24
Inventor 舒纯吴高明王增玉何晶刘汉杰吴启兵张大华杨文枝
Owner WUHAN IRON & STEEL (GROUP) CORP
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