| Calcium carbide is an important chemical raw material that connects the organic and inorganic worlds.The energy structure of China’s "rich in coal and poor in oil" determines that coal based calcium carbide is the mainstream process for calcium carbide production in China.However,during the process of producing acetylene from calcium carbide,a large amount of solid waste calcium carbide residue is generated,and its stacking has caused severe environmental pollution and ecological damage.The resource utilization of calcium carbide residue is of great significance to the sustainable development of the coal chemical industry.At present,China’s traditional calcium carbide production process has the characteristics of "high energy consumption" and "high carbon emissions".Recycling calcium carbide residue as a calcium source to produce calcium carbide not only can reduce the carbon dioxide emissions brought by limestone in traditional calcium carbide production,but also can improve the comprehensive utilization rate of solid waste calcium carbide residue,which has important practical significance for resource efficiency and carbon reduction in the calcium carbide production industry.However,there is still a lack of systematic research on the performance of calcium-containing carbon pellets based on calcium carbide residue used in calcium carbide production,which is crucial for the industrial application of circulating low carbon calcium carbide residue from solid waste.Based on experimental research and Fact Sage calculations,this paper has studied the strength and reactivity of calcium-containing carbon pellets prepared from calcium carbide residue and different carbon sources(coke powder,low rank coal,biomass)for calcium carbide production at a macro scale.Combined with analysis of mineral phase composition,micro morphology,and functional group evolution,the strength evolution and high-temperature reaction rules of calcium-containing carbon pellets with temperature have been explored from a micro perspective.The initial conditions for the reaction of calcium carbide residue with different carbon containing raw materials to generate calcium carbide and the impact of impurities on the reaction of calcium carbide were clarified,and a preliminary process for the production of calcium carbide using calcium carbide residue combined with multiple carbon sources was formed to provide an efficient,low consumption,and energy saving path selection for the low carbon production of calcium carbide using calcium carbide residue recycling.The environmental impact of using calcium carbide residue molding to produce calcium carbide was evaluated and compared through the e Footprint system,and the energy consumption during the production of calcium carbide using the electrothermal method was estimated,which provide theoretical guidance for energy conservation and consumption reduction in calcium carbide production process.The preparation of calcium-containing carbon pellets for calcium carbide using calcium carbide residue and coke powder had been studied.The results showed that the strength of the pellets decreases with the increase of temperature,and had a high strength at 600°C and 700°C,with a strength of over 1000 N.The addition of inorganic binder sodium based bentonite had a positive effect on improving the strength of the pellets.As the addition of sodium based bentonite gradually increases,the strength of the pellets gradually increases.The strength of calcium-containing carbon pellets prepared by adding 5% sodium based bentonite as binder was better.The main mineral phase in calcium-containing carbon pellets at high temperatures was calcium oxide,but there were also small amounts of calcium aluminum melilite and calcium silicate formed,indicating that the reaction of calcium components and impurities in the pellets results in a small amount of calcium source loss.With the increase of temperature,the calcium containing components in the pellets undergo softening deformation,resulting in a porous microstructure of the pellets,indicating that the deformation of calcium containing materials at high temperatures was an important factor causing the strength change of the pellets.The preparation of calcium-containing carbon pellets for calcium carbide using calcium carbide residue and low rank coal carbon sources had been studied.The results showed that at 600°C and 700°C,the strength of pellets using sub bituminous coal coke and sub bituminous coal as carbon sources was above 300 N,and the strength of pellets using lean coal coke and lean coal as carbon sources was above 1200 N.The strength of pellets using lean coal coke and lean coal as carbon sources was generally higher than that using sub bituminous coal coke and sub bituminous coal as carbon sources,and the strength of pellets decreases as temperature increases.This might be due to the fact that the volatile content in sub bituminous coal char and sub bituminous coal was higher than that in lean coal char and lean coal,and the volatilization of organic components in coal quality caused the formation of pore structures in the pellets,reducing the strength of the pellets.The presence of impurities could cause a small amount of calcium component loss,and the softening deformation of calcium source materials was the main factor that reduces the strength of the pellets.Through the preparation of calcium-containing carbon pellets for calcium carbide using calcium carbide residue and biomass carbon sources,the research showed that the strength of pellets prepared using corn stalk coke as a carbon source was generally higher than that using corn stalk as a carbon source.With higher strength at 600°C and 700°C,the strength of pellets using corn stalk coke as a carbon source could reach over 900 N,while the strength of pellets using corn stalk as a carbon source was only 250～600 N,which might be due to the fact that corn stalk was used as a high volatile carbon source.The pore size formed by gaseous substances generated at high temperatures greatly reduced the strength of the pellets.The presence of impurities could cause a small amount of calcium source material loss,and the softening and deformation of calcium source material was the main reason for reducing the pellet.Through the study of the reactivity of carbon and the influence of impurities on the reaction of calcium carbide,it was concluded that different cokes had different initial reaction temperatures for the formation of calcium carbide at different carbon calcium ratios.Compared to coke powder,sub bituminous coal coke,and lean coal coke,the initial temperature for the reaction of calcium carbide from calcium carbide residue and corn straw coke was the lowest,indicating that biomass coke had the potential to reduce the initial temperature for the formation of calcium carbide and reduce energy consumption.According to the theoretical analysis and calculation of Fact Sage thermodynamic software,the presence of impurities could cause the formation of some by-products in the production process of calcium carbide,but it would not affect the theoretical starting temperature for the formation of calcium carbide.Through the e Footprint system evaluation of the environmental impact of using calcium carbide residue molding to produce calcium carbide,it could be seen that the impact of calcium carbide residue and coke powder molding to produce carbide on the environment was lower than that of traditional bulk raw materials to produce calcium carbide,indicating that using powdered solid waste to produce calcium-containing carbon pellets to produce calcium carbide had a positive effect on the environment and energy consumption. |
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