Research On The Synergistic Control Process Of Calcium Carbide Slag Wet Desulfurization And Gypsum Crystallization Process

The annual discharge of calcium carbide slag in my country is large,and the comprehensive utilization rate is less than 40%.A large amount of storage has caused serious environmental pollution.Calcium carbide slag is rich in calcium resources and is a good raw material for replacing limestone as a desulfurizing agent.This article focuses on the difference in the dissolution characteristics of the two in the process of wet desulfurization with calcium carbide slag instead of limestone,and the problem of incomplete oxidation and crystallization of gypsum and high water content in the calcium carbide slag desulfurizer,The comparative study on the composition,dissolution activity and desulfurization and oxidation characteristics of calcium carbide slag and limestone has been systematically carried out,The double-membrane theory is used to study the desulfurization efficiency of calcium carbide slag-based desulfurizer under different process conditions,Compare the desulfurization performance of calcium carbide slag and limestone,The mechanism of action of impurities in calcium carbide slag in the process of calcium sulphate dissolution and calcium sulfate dihydrate oxidation and crystallization is clarified,The optimal process conditions for the desulphurization and gypsum oxidation process of calcium carbide slag were optimized and determined.The relevant conclusions provide a good reference for the removal and utilization of calcium carbide slag,and provide a good foundation for the utilization of calcium carbide slag-based desulfurizer and the optimization of the desulfurization process.The contents and conclusions to be studied are as follows:(1)The research on the dissolution characteristics of the calcium carbide slag desulfurizer under different processes and impurity content conditions has been systematically carried out.The results show that calcium component in calcium carbide slag is 5.07%higher than limestone,and the specific surface area is large,the solubility is high,and it is easy to form a strong alkaline slurry;reducing the p H value and the particle size of calcium carbide slag,increasing the reaction temperature and stirring speed are all beneficial to calcium carbide For the dissolution of slag,the dissolution rate of calcium carbide slag under optimized conditions is 29.26%higher than that of limestone.Analyzing the liquid phase composition of the calcium carbide slag dissolving process,it is found that sodium,silicon,aluminum,magnesium,iron and other impurities are leached during the calcium carbide slag dissolving process.Among them,silicon has basically no effect on the dissolution;sodium and magnesium can promote the dissolution of calcium carbide slag;Al and Fe hinder its dissolution.(2)The double-membrane theory is used to analyze the desulfurization and mass transfer process,and the response surface analysis method is used to study the influence of process conditions on the desulfurization performance of two desulfurizers.The results show that:different desulfurizers dissolve to different control points for desulfurization:When the SO₂ concentration is lower than 1000mg/m³,the dissolution of limestone is the rate-controlling step for desulfurization;when the SO₂ concentration is higher than 1000 mg/m³,the dissolution of calcium hydroxide in the calcium carbide slag is the rate-controlling step for desulfurization,and the mass transfer efficiency is higher than that of limestone,Suitable for processing flue gas with higher SO₂ concentration;Under the optimized conditions,the desulfurization rates of the two desulfurizing agents of calcium carbide slag and limestone are respectively 98.15%and 95.53%,and the consumption of calcium carbide slag slurry in the desulfurization process is only half of that of limestone.(3)The effect of calcium carbide slag-CaSO₃ on the oxidation crystallization of desulfurized gypsum under different process conditions was investigated.The results show that when the concentration of calcium sulfite and the initial p H value are low,and when the temperature and aeration rate are relatively high,the desulfurized gypsum has large particle size,low water content,high purity and uniform morphology.The influence of impurities on the oxidation process of calcium sulfite was investigated by simulated addition of impurities.Among them,Mg,Si,Fe can promote the oxidation of gypsum,while Na and Al show inhibition.The product analysis by SEM shows that Si,Fe,and Na have an effect on oxidation.The morphology of the product has little effect,while Al and Mg have a significant effect on the microscopic morphology of the oxidation product.Comprehensive analysis shows that the presence of Fe and Si can make the oxidation reaction more thorough.