Method for recycling waste cathode carbon blocks of aluminum electrolysis cell

Abstract

The invention discloses a method for recycling waste cathode carbon blocks of an aluminum electrolysis cell. The method comprises the following steps: 1, grinding the waste cathode carbon blocks into powder of 100-200 meshes through superfine grinding, and then winnowing the powder to separate the carbon powder from aluminum and aluminum carbide; 2, adding the fine carbon powder into water, stirring the fine carbon powder, then filtering the obtained solution, and preparing filtrate and filter residues for later use; 3, adding the filter residues in the step 2 into an aluminum sulfate solution, leaving the mixed solution to stand at normal temperature for 20-30 hours, then filtering the mixed solution, washing obtained filter residues to obtain the carbon powder with the carbon content higher than 90% and preparing filtrate for later use; 4, mixing the filtrate obtained in the step 2 and the filtrate obtained in the step 3, adjusting the pH value to be 5.5, increasing the temperature to 90 DEG C, then carrying out reaction for 3 hours to obtain flocculent hydroxyl aluminum fluoride, and carrying out filtering to obtain filter residues; and 5, calcining the filter residues obtained in the step 3 at 485 DEG C to obtain AlF3 and Na5Al3F14 and using AlF3 and Na5Al3F14 as raw materials of aluminum electrolysis. Through the method, the waste cathode carbon blocks of the aluminum electrolysis cell can be efficiently recycled.

Description

Technical field [0001] The invention belongs to the technical field of aluminum electrolysis, and specifically relates to a method for recycling waste cathode carbon blocks of an aluminum electrolysis cell. Background technique [0002] The waste cathode carbon block produced by aluminum electrolysis contains 30-50wt% electrolyte, and its main components are fluoride, cryolite, alumina, calcium fluoride, sodium carbonate, aluminum carbide and cyanide. After the cathode block is exposed to water, the fluorine content of the leaching solution is as high as 6000mg / L, and the cyanide content is 10-40mg / L, which is much higher than the F required in the "Identification Standard for Hazardous Waste-Identification of Extraction Toxicity" - <50mg / L, CN - <1mg / L, belongs to industrial hazardous solid waste. [0003] In the existing waste cathode carbon block treatment method, the graphite is separated from the electrolyte mainly by crushing and various flotation methods, the separate...

AI Technical Summary

Problems solved by technology

CN105401169 A discloses a recycling and environmental protection utilization method of waste cathode carbon blocks of aluminum electrolytic cells. The disadvantages are: 1) The method can theoretically incorporate waste cathodes into electrolytic aluminum carbon anode raw materials for utilization, but since the added amount only accounts for 1 %, and the actual output of spent cathode blocks is 10% of the consumption of carbon anodes, so the application of this method cannot completely process spent cathode blocks