The issue of recycling calcium carbide slag.
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Newcomer seeking help: Which companies currently have mature technologies for recycling calcium carbide slag to produce calcium oxide? Is the recycling process one in which calcium carbide slag is used to produce active calcium oxide, which is then used to manufacture calcium carbide?
Is there anyone who can give a brief explanation to newcomers?
Regarding your question about where this technology comes from, it’s not available in China. Theoretically, calcium carbide is produced from calcium oxide, but it has to be in solid form; powdered calcium oxide cannot be used. Is the preparation of calcium oxide from calcium hydroxide done through heating, or by some other technique?
It was proposed by a company from Liaoning during the technical exchange; they aren’t very familiar with the feasibility. But they say there are successful cases. The process generally involves selecting and separating refined calcium carbide slag from crude calcium carbide slag; the refined calcium carbide slag is then used to produce active calcium oxide through calcination, followed by balling ； Coarse calcium carbide slag is dried to produce calcium hydroxide desulfurization agent as a by-product. Is there anyone who can provide a simple analysis of the process feasibility and economic benefits?
It was proposed by a company from Liaoning during the technical exchange; they aren’t very familiar with the feasibility. But they say there are successful cases. The process generally involves selecting and separating refined calcium carbide slag from crude calcium carbide slag; the refined calcium carbide slag is then used to produce active calcium oxide through calcination, followed by balling ； Coarse calcium carbide slag is dried to produce calcium hydroxide desulfurization agent as a by-product. Is there anyone who can provide a simple analysis of the process feasibility and economic benefits?
It is generally used for manufacturing cement; I haven’t heard of it being used to produce calcium hydroxide or calcium oxide. The cost must be high. Could it be used together with mirabilite produced from caustic soda to make gypsum?
They state that the dry calcination system can achieve a production volume of 55,000 T/A of active calcium oxide (with 110,000 T/A of raw materials after purification), and 20,000 T/A of calcium hydroxide desulfurizer (with 30,000 T/A of raw materials before purification).
Theoretically, it is feasible, but today a calcium carbide production facility has a capacity of at least 500,000 tons; the output level you propose is too low. Moreover, the cost of producing calcium oxide by burning limestone is not high – so why go to the extra trouble? It can be used as a desulfurization agent, but it gets blackened by flue gas; its usage in gypsum plants and cement plants is very low. It is still more feasible to use calcium carbide slag directly as a cement raw material.
What was shown to me were demonstration projects; they should be pilot projects. The cost is quite high, over 10 million, but it seems that environmental regulations will pose pressure soon. Aren’t many industries currently cutting back excess production capacity?
It mainly depends on whether there is economic value; otherwise, state-owned enterprises would not undertake projects that would result in losses； The pilot project is meant to determine whether the desired results can be achieved. If this technology can truly be refined and applied on a large scale in production (provided that it has low energy consumption), it holds great potential for widespread adoption, and it could also help solve the problem of piles of calcium carbide slag accumulated at many companies.
There are too many impurities in the calcium carbide slurry – waste alkali, defective sodium hydroxide, and various types of wastewater. I’m not sure if it’s difficult to remove these substances.