A method for regenerating carbonaceous waste from aluminum electrolysis cell into alternative coal-fired

Abstract

A method for regenerating aluminum electrolysis bath carbon waste into alternative fire coal comprises the following steps that (1) conducting pelletization and detoxication, wherein the aluminum electrolysis bath carbon waste is crushed, a detoxicating agent solution is atomized and sprayed, and then pelletized detoxicated materials are obtained; (2) conducting activation, wherein a catalytic oxidant is added, homogenizing and modifying are conducted, and then the alternative fire coal is obtained; or, the catalytic oxidant and lime are added, water is added, stirring is conducted or rolling mixing is conducted, oxidation alkaline removal are conducted, filtering or filtering and washing are conducted, drying is conducted, and then the alternative fire coal is obtained; or, the catalytic oxidant, lime and sodium hydroxide are added, water is added, stirring is conducted or rolling mixing is conducted, oxidation aluminum removal and alkaline removal are conducted, filtering or filtering and washing are conducted, drying is conducted, and then the alternative fire coal is obtained; or, supercritical or liquid-state carbon dioxide is adopted for leaching processing, the catalytic oxidant is added to carbon dry powder for homogenizing and modifying, and then the alternative fire coal is obtained. The calorific value of the regenerated alternative fire coal is equal to that of semibituminous coal and anthracite and is about 5000 kcal / kg on average, and the regenerated alternative fire coal can be used as alternative fire coal; and the method is simple in technology, low in energy consumption and cost and suitable for industrialized production.

Description

technical field [0001] The invention relates to a method for regenerating waste into alternative coal, in particular to a method for regenerating carbon waste from an aluminum electrolytic cell into alternative coal. Background technique [0002] At present, the output of electrolytic aluminum in my country and the world is developing rapidly. According to statistics, by the end of December 2016, the aluminum smelting enterprises of electrolytic aluminum in my country had built a production capacity of 43.698 million tons, and the operating production capacity had reached 36.739 million tons. With the increase of electrolytic aluminum production, the solid waste produced in the electrolysis process, such as waste cathode carbon, waste anode carbon particles, waste refractory bricks, waste insulation bricks, and waste insulation slag, has also increased rapidly, of which only my country's electrolytic aluminum The annual waste cathode produced by the industry has reached 250,...

AI Technical Summary

Problems solved by technology

However, this method obviously has the following problems: first, toxic dust and gas containing cyanide are produced during the crushing and screening process of electrolytic aluminum waste cathode carbon; The power consumption of vacuum suction is higher, and the requirements and cost of equipment are also very high; the third is that the fluoride gas volatilized at 2600-2800 ° C is absorbed by water mist, which has too high requirements on equipment, because the water vapor at 1200 ° C is enough to fluorine Calcium chloride and other fluorides are directly converted into highly toxic and highly corrosive hydrogen fluoride; fourth, serious secondary pollution is likely to occur, and the recovered carbon materials still contain 3% or more fluorides, and recycling will shorten the overhaul Deadline is not cost-effective

However, this method obviously has the following problems: first, toxic dust and gas containing cyanide are produced during the crushing and screening process of electrolytic aluminum waste cathode carbon; The power consumption of vacuum suction is higher, and the requirements and cost of equipment are also high; the third is that the flue gas purification investment after secondary combustion is high, and it is easy to produce serious secondary pollution; Carbon still contains a large amount of fluoride, because the boiling point of calcium fluoride is as high as 2497 ° C, the recycling of fluorine-containing carbon materials will shorten the overhaul period and is not cost-effective

[0010] (3) Combustion separation method: professional incinerator and fluidized bed furnace technology are used. Because electrolytic aluminum waste cathode charcoal is different from coal combustion, although the calorific value is generally as high as 4000-5500kcal / kg, the activation energy required for oxidation reaction is high. , needs to reach a high temperature of 1500°C to effectively oxidize and burn, so the combustion method has the problems of cumbersome separation process, long heating time required for burnout, high energy consumption, and difficulty in effectively recovering fluoride in it, and the problem of secondary pollution is also difficult to deal with

[0011] (4) Fuel method: Because the main component of electrolytic aluminum waste cathode carbon block is charcoal, and the theoretical calorific value of complete combustion is generally above 4000kcal / kg, and the highest is 5500kcal / kg, which is equivalent to the calorific value of commonly used anthracite. Therefore, A large number of technical workers at home and abroad have made unremitting efforts, but the results have been extremely unsatisfactory so far

However, there are still safety issues, the amount of addition, and the impact on production. After all, waste cathode carbon is not coal-fired, and the carbon in waste cathode carbon blocks is extremely difficult to burn

However, the real defect is not the erosion of refractory materials caused by fluoride and the excessive fluorine in the flue gas, because the production of calcium fluoroaluminate cement can also ensure the safety of refractory materials and the fluorine in the flue gas does not exceed the standard. After all, normal cement The kiln preheater system objectively has a preheater that realizes five-stage exchange and capture of alkaline high-concentration powder; it is not a problem of extremely high alkali content, because the coal consumption per ton of clinker is generally only 0.15-0.18t, and a small amount The electrolyte in the cathode carbon block is mainly aluminum fluoride, calcium fluoride, sodium fluoroaluminate, magnesium fluoroaluminate, sodium fluoride only accounts for a small amount, and the total alkali in sodium fluoroaluminate and sodium fluoride when the dosage is small The amount is limited, and generally has limited influence on the later strength of cement

Therefore, the real reason why Shandong Aluminum Plant has not been able to use cathode carbon normally as an alternative coal combustion is: firstly, it affects the grinding efficiency of coal mills, and secondly, the low-activity graphite carbon seriously reduces the overall combustion performance of coal powder , seriously affects the normal combustion efficiency of pulverized coal, and the carbon that cannot be burned effectively in time and releases heat falls into the clinker or is wrapped in the powder to produce strong reduction, which affects the working conditions of the kiln system and the quality of the clinker

Apparently, the prior art still cannot use electrolytic aluminum waste cathode carbon block as an effective alternative fuel

[0012] (5) Safe landfill method: Due to the problems of high energy consumption, high cost and secondary pollution in the existing treatment methods, the environmental pollution problem of electrolytic aluminum waste cathode carbon blocks has not been effectively solved, resulting in the vast majority of aluminum The spent cathode carbon block of the electrolyzer is still discarded, and the high-cost safe landfill method is still mainly used at present

However, the process is complicated, the secondary pollution is large, the energy consumption is high, and the recovered graphite fine powder has high impurity content.