Method for treating fluorine-containing waste electrolyte

Abstract

The invention discloses a method for efficiently treating fluorine-containing waste electrolyte, which comprises the following steps: adding an additive and a reaction aid into the waste electrolyte, uniformly mixing, grinding to below 0.355 mm, roasting, cooling at a specific rate, crushing and washing to obtain an aluminum fluoride product, and concentrating filtrate to further extract other byproducts. According to the invention, the reaction aid is added to reduce the primary crystal temperature of the system, so that the reaction is carried out in a molten state, the mass transfer efficiency is high, the reaction conversion rate is high, and the content of effective aluminum fluoride in the product is high; meanwhile, the heat preservation time and the cooling rate are further controlled, so that aluminum fluoride grains generated by the reaction grow up, the obtained aluminum fluoride is good in flowability and can be well compatible with automatic discharging equipment of the current industrial aluminum electrolysis cell, and green and sustainable development of the electrolytic aluminum industry is achieved.

Description

technical field [0001] The invention relates to a method for treating fluorine-containing waste electrolyte, which belongs to the field of metallurgical solid waste recovery and treatment. Background technique [0002] Fluorine-containing waste electrolyte is one of the main solid wastes produced in the aluminum electrolysis process, which mainly comes from three aspects: one is the electrolyte taken out during the operation of the electrolytic cell to stabilize the molecular ratio; the other is the waste electrolyte mixed in the residual anode ; The third is the electrolyte mixed in the waste cathode when the tank is overhauled. It is understood that the production of 1 ton of aluminum often requires 20-30kg of various waste electrolytes. At present, in the industry, fluorine-containing waste electrolytes are generally disposed of in the form of stockpiling, which not only occupies the effective space of electrolytic aluminum enterprises, but also soluble fluorine may seep...

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Problems solved by technology

It can be seen that the composition of spent electrolytes is complex, which brings great challenges to the separation and extraction of valuable components.

Chinese patent application specification CN108677020A, CN110668483A, CN111517349A, CN109759423A and CN110194478A etc. provide a series of wet treatment process of waste electrolyte, all adopt acid or (and) aluminum salt to process waste electrolyte, use cryolite, aluminum fluoride or hydroxyl fluoride Recovering aluminum and fluorine elements in the electrolyte in the form of aluminum, etc., the process is long, the recovery rate is low, the acidic leachate has high requirements for equipment, and the further treatment of the wastewater generated in the process is still a problem

Recently, the Chinese patent application specification CN111485252A provides a dry processing process similar to the above-mentioned RU2462418C1 patent. Its hydrate polymer, etc.; in fact, the boiling point of aluminum chloride is 181 ° C, which is not conducive to the reaction at too low a temperature, and aluminum chloride is gaseous at a high temperature, and it is difficult to contact with fluorine-containing materials. Pollution; aluminum nitrate begins to decompose at about 135°C to produce highly toxic nitrogen oxides

[0005] In general, the cores of the above-mentioned RU2462418C1 and CN111485252A are to use aluminum sulfate and fluorine-containing waste electrolyte to carry out solid phase reaction at high temperature, and to recover valuable aluminum fluorine in the form of aluminum fluoride, which requires high processing temperature; however, The efficiency of solid-phase reaction is low and the conversion rate is not high, which leads to low utilization rate of raw materials and low content of effective aluminum fluoride in the product. At the same time, solid-phase reaction is not conducive to mass transfer and crystallization, and the particle size of aluminum fluoride produced is too fine and has poor fluidity. Not good for AlF 3 Automatic unloading

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