Method for removing and recovering sulfate in acrylonitrile wastewater by utilizing freezing crystallization

Abstract

The invention provides a method for removing and recovering sulfate in acrylonitrile wastewater by utilizing freezing crystallization. The method is characterized in that NaOH is added to wastewater; suspended particles and acrylonitrile oligomer of which the molecular weight is more than 30,000 in the wastewater are removed through sand filtration, microfiltration and ultrafiltration; the wastewater is conveyed by a corrosion-resistant pump to enter a tube pass of a hydrophobic hollow fiber membrane; when the wastewater flows in the tube pass, volatile NH3 in the wastewater and H2SO4 absorption solution are subjected to neutralization reaction on an interface of the membrane to form nonvolatile (NH4)2SO4 which is recovered; the wastewater is rapidly frozen to separate out high-concentration sulfate crystals in the wastewater; the crystals are separated by use of a high-speed centrifuge; mother liquor is returned or incinerated; and refined salt is obtained from recovered crude sulfate through washing, drying and other processes. The method has the advantages of simple operation, low energy consumption, no secondary pollution, capability of recovering inorganic salt and the like, and is a novel wastewater treatment technique which is high in efficiency, economic and friendly to environment.

Description

Method for removing and reclaiming sulfate in acrylonitrile waste water by freezing crystallization technical field The invention belongs to the technical field of water pollution control, and in particular relates to a method for removing high-concentration sulfate in acrylonitrile wastewater by using freezing and crystallization. This method can change the current high-cost treatment status of acrylonitrile wastewater to a certain extent. Background technique Acrylonitrile (AN for short), structural formula CH2=CH-CN, is an important organic chemical raw material, widely used in many industrial fields such as synthetic fiber, synthetic chemistry and synthetic rubber. In recent years, with the development of acrylic fiber, ABS / AS, acrylamide and other downstream products of propylene oxide, the demand for acrylonitrile in the world has been increasing. The production process of acrylonitrile is mainly the propylene ammoxidation method (Sohio method), which uses propylene...

AI Technical Summary

Problems solved by technology

If the wastewater is sent to incineration, it will also consume a lot of energy, and the treatment cost will remain high; if conventional biological treatment is carried out, the microorganisms will not be able to metabolize normally due to the high salt content

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