Method for recycling silica and polyaluminum ferric chloride in coal ash by using iron and steel pickling waste water

Abstract

The invention discloses a method for recycling silica and polyaluminum ferric chloride in coal ash by using iron and steel pickling waste water, comprising the following steps of: firstly, soaking, centrifuging and separating the coal ash by using water to acquire an alkaline aqueous solution and residues; then adding the iron and steel pickling waste water into the residues and stirring for full reaction at a temperature of 85 DEG C; standing for 5 hours and then centrifuging and separating to recycle the silica; and acquiring the polyaluminum ferric (PAFC) by drying and crystallizing the supernate, wherein the weight ratio of the coal ash to the water is 2:1(g / ml), and the weight ratio of the residues to the pickling waste water is 1:10(g / ml). The alkaline aqueous solution with a pH value of 12.2 which is recycled through the method disclosed by the invention can be directly used for wet flue gas desulfurization, and a mixture of sodium hydroxide and potassium hydroxide is acquired after the alkaline aqueous solution is dried and crystallized; and the polyaluminum ferric chloride (aluminium chlorohydrate and polymerization ferric chloride) can be used as a coagulant for treating industrial water. By adopting the method, the purposes of reducing water environment pollutions and recycling and comprehensively utilizing resources are achieved.

Description

[0001] This application is supported by the Tianjin Applied Basic and Frontier Technology Research Project (10JCZDJC24500) and the Tianjin Higher Education Science and Technology Development Fund Project (20080514). technical field [0002] The invention belongs to the technical field of environmental protection, and relates to a method for comprehensive utilization of solid waste and industrial waste water and treatment of polluted waste water, in particular to a method for recovering silica and polyaluminum ferric chloride in coal ash from steel pickling waste water. Background technique [0003] With the rapid development of my country's economy, the market demand for steel is increasing, and cold-rolled steel plates, cold-rolled steel strips and cold-rolled steel pipes are widely used in industrial and agricultural production. During steel processing, it is usually necessary to pickle steel plates, steel strips and steel pipes to remove scale on their surfaces. By pickli...

AI Technical Summary

Problems solved by technology

All in all, the treatment methods of general iron and steel pickling wastewater mainly include: ① Iron and steel pickling wastewater is directly discharged into natural water bodies, which not only pollutes the water body, but also wastes a lot of FeSO4 or FeCl2 Resources

In order to reduce the pollution to the environment, the traditional treatment method is to use Ca(OH)2, the product of calcium carbide slag or lime digestion reaction, to neutralize the pickling wastewater to produce solid precipitation, and use a filter to separate the solid-liquid Separated, the waste water is directly discharged, and the sludge is transported to landfill; ② The raw material for the production of inorganic coagulants under normal temperature and pressure from steel pickling wastewater - high-concentration polyferric solution, such as the preparation of polyferric chloride, polyferric sulfate, etc. Oxidation method is commonly used in industrial production abroad, and when polyferric sulfate is prepared by catalytic oxidation method, there will be secondary pollution caused by nitrogen oxides, etc., and the process is very complicated and the cost is high. At the same time, polyferrous sulfate and polyferric chloride have Certain corrosiveness, the maintenance cost of the pipeline is relatively high; ③Diffusion dialysis is used to treat acidic wastewater. 5%, the recovered acid contains more than 10 g / L of iron, which affects the reuse of acid and does not have the possibility of industrial application

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