Recycling method for waste cathode carbon blocks of electrolytic aluminum electrolysis cell

Abstract

The invention discloses a recycling method of waste cathode carbon blocks of an aluminum electrolysis cell. The method comprises the following steps: breaking, crushing and ball milling the waste cathode carbon block raw material of the aluminum electrolysis cell to form powder, and then adding hydrogen peroxide to remove cyanide; adding concentrated sulfuric acid to react to generate hydrogen fluoride gas, introducing the hydrogen fluoride gas into a condensation absorption tower, and circularly absorbing the hydrogen fluoride gas with deionized water or a low-concentration hydrofluoric acidsolution to obtain a 25-40% hydrofluoric acid product; neutralizing carbon powder by adding NaOH, filtering and drying the carbon powder to use as a raw material for processing a new cathode for recycling; finally, concentrating a large amount of sodium sulfate contained in filtrate to obtain sodium sulfate crystals. The recycling method has the advantages of advanced technology and obvious advantages, and realizes zero emission of environmental pollutants in the recycling process. The treated waste cathode carbon blocks can be reused to process new cathode carbon blocks, and the main harmfulcomponent fluorine in the original waste cathode carbon blocks is converted into high side addition hydrogen fluoride to realize the recycling of fluorine.

Description

technical field [0001] The invention belongs to the technical field of solid waste comprehensive treatment in the electrolytic aluminum industry. Specifically, the invention relates to a method for harmless treatment of waste cathode carbon blocks of an electrolytic aluminum electrolytic cell and effective recovery of carbon and fluorine resources therein. Background technique [0002] By 2017, my country has built an aluminum electrolytic production capacity of about 45 million tons, with an actual output of more than 36 million tons, accounting for more than 50% of the global electrolytic aluminum production capacity. During the production process of aluminum electrolysis, the carbon cathode expands due to the penetration of fluorine-containing salts, which further causes damage to the electrolytic cell and scraps it. Aluminum electrolytic cells generally need to be shut down for overhaul after about 4 to 6 years of use, and all waste tank lining materials (referred to as...

AI Technical Summary

Problems solved by technology

[0005] Judging from the existing technical achievements, the following problems still exist in the wet treatment and high-temperature treatment of spent cathode carbon blocks in aluminum electrolytic cells. Secondary pollution; produced H 2 、CH 4 , NH 3 The gas is not controlled and utilized, and the generated HF causes serious pollution; the recovered electrolyte and carbon materials have too high impurity content and cannot be directly used; the difference in the capacity and age of the electrolytic aluminum tank, the fluctuation of the composition, the particle size of the powder, etc. Due to the influence of various factors, it is difficult to control the process; a large amount of tail gas entrained with HF and dust will be generated during high-temperature treatment; the electrolyte recovery is not complete, and part of it remains in carbon materials or slag; the electrolyte with a low melting point melts and agglomerates in the furnace, resulting in The incomplete oxidative combustion of carbon materials has a large residual amount, and the electrolyte is melted and agglomerated in the furnace, which leads to deterioration of production conditions and poor production stability

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