In July, the sun shone brightly in Ordos, Inner Mongolia, and in Mengxi Aluminum Company, a subsidiary of Mengxi High-tech Group Co., Ltd. (Hereinafter referred to as Mengxi Group), the sintering rotary kiln for extracting alumina from fly ash made a "rumbling" muffled sound. The temperature of the rotary
kiln is as high as thousands of degrees Celsius. At this moment, dozens of people gathered around the discharge port, they looked anxious, sweat had already soaked through the work clothes.
One man shoveled out a lump of iron alumina clinker . . The crowd immediately came up. As the temperature drops, the lumpy clinker begins to pulverize automatically, making a "snap" crisp sound. Through field inspection, the pulverization diameter is less than 25 microns, and the pulverization rate is more than 98%.
The whole audience cheered loudly! For this moment, the technical team of Mengxi Group has struggled for 25 years.
Project: "The First Step of the Long March"
The alumina clinker in the shovel of He Jun, Assistant Production Director of Mengxi Aluminum Company, comes from the waste of coal industry-fly ash.
For a long time, China's raw materials for alumina and electrolytic aluminium production have been largely dependent on imports. The coal industry in Inner Mongolia is developed. Although most of the huge amount of fly ash is rich in aluminum, it has been buried deep underground as industrial waste.
Industry experts estimate that if the efficient recycling of high-alumina fly ash resources in Inner Mongolia can be realized, the guarantee period of aluminium resources in China will be increased by 65%, and the external dependence will be reduced to less than 60%.
Thirty years ago, Mengxi Group began to explore new ways of high-value utilization of fly ash while using fly ash as an auxiliary material for cement production. "After anchoring the goal of extracting alumina from fly ash, the mechanism study of the project laboratory was officially launched in 1998." Gao Yongfu, general manager of Mengxi Aluminum Company, told Sci-tech Daily.
"At that time, we had nothing but a few technicians." Gao Yongfu recalls. Through consulting information, we know that Poland once industrialized the project of extracting alumina from fly ash, and Liu Ailin, founder of Mengxi Group, immediately led a team to Poland.
It was expected that the technical leader of the project had passed away, and the team took great pains to find several of his important collaborators and students, consulted and recorded, and finally signed a technology transfer agreement with the other party, completing the earliest technical accumulation of the project.
In 2003, the technology went from the laboratory to the pilot production line. However, this is only the first step of the Long March.
Persistence: "Spend 100 million yuan a year"
Wang Yingjie, technical director of Mengxi Group, showed reporters a summary of all previous industrialization experiments. Since 2003, dozens of large-scale test data have been recorded without omission.
This is also the full record of the technical team's 20 years of trial and error, repeated failures and difficult progress. "How to make the sintered clinker automatically pulverize into micron-sized powder, how to make full use of calcium silicate slag and not produce secondary industrial solid waste, these two core problems have plagued us for more than 20 years." Wang Yingjie said.
Among them, clinker self-pulverization is one of the core contents of the technology of extracting alumina from fly ash, which was named "self-pulverization method" in Poland. In order to solve the problem of low self-pulverization rate of clinker, Mengxi Group spares no expense. The requirement of the leading group of the group is simple and firm: "We should concentrate our efforts and eliminate all interference to tackle key problems."
"Over the years, experiments on the production line have basically cost 100 million yuan a year." Speaking of the pressure, Gao Yongfu's tone was heavy.
In 2014, Mengxi Group built an industrial production line with an annual output of 200000 tons of alumina. "The production line is industrialized, but many technical difficulties have not been overcome, resulting in high production costs, low output rate and unprofitable." Wang Yingjie said, "We simply use this huge industrial production line to continue experiments and tackle key problems until one day we can calculate the economic accounts!" Li Jun, production director
of Mengxi Aluminum Company, told reporters: "There was a time when the project was in a dilemma, and the technicians felt confused and once had the idea of giving up." At this time, the technical team heard the most exhortations from the top, that is, "re-teeth, re-persistence, re-struggle".
Finally, the problem of clinker self-pulverization was solved through the technical transformation of the clinker cooling system, the adjustment and control of trace elements in fly ash, and the improvement of the transformation speed and efficiency of dicalcium silicate crystal.
Wang Yingjie introduced that over the past 20 years, the technical team has solved the problem of low self-pulverization rate of clinker while conducting multi-channel research on the application of calcium silicate slag. With the successful conclusion and application of scientific research projects, the compression of industrial production lines and the simplification of process flow step by step, all the waste residues in the process of extracting alumina from fly ash are utilized, and zero emission in the production process is realized.
A few weeks ago, after the last process problem was solved, the 400,000-ton fly ash extraction alumina production line of Mengxi Aluminum Company was completed.
Gao Yongfu is often asked: "Do you produce coal?"? Are you engaged in coal chemical industry? If not, why do you want to do this? He always smiles without saying a word. With the popularity of "ecological priority, green development" and "double carbon", there is no need to answer this question. Liu Pengfei, chairman
of Mengxi Group, said frankly that he had been sharpening his sword for 25 years, but it would take some time to see the return. They calculate not only the economic account, but also a big account-let the strategic resource of alumina change its "origin", which is of great significance for demonstration and guidance.
"The process route of the project of extracting alumina from fly ash is mature and feasible, and the cost of the production line will be greatly reduced after optimization, so the prospect is very broad.". The success of the project has a positive demonstration role for the recycling of large industrial solid wastes such as fly ash, and also has an important strategic significance for ensuring the safety of the national aluminium industry. Chen Dezuo, Deputy Engineer of Guiyang Aluminum and Magnesium Institute of China Aluminum International, said during the expert review.
At present, the technical team of Mengxi Group has started relevant research on the downstream of the production line of extracting alumina from fly ash. "Accelerating the construction of waste recycling system has been written into the report of the 20th National Congress of the Communist Party of China," Wang Yingjie told reporters, "Driving green development with scientific and technological innovation, our mission is far from over!"
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