Study On Thermal Decomposition Of Flue Gas Desulfurization Intermediate CaSO₃

With the rapid development of China's economy and the constant abundance of material life,environmental problems are becoming more and more serious.The increasingly severe haze has seriously affected People's Daily production and health..Coal emissions of SO₂ in flue gas is one of the main factors of fog.With the increasingly strict environmental laws and regulations,the desulphurization control of coal-fired flue gas is an inevitable choice for the environmental protection departments to strictly supervise and the enterprises to meet the standard of emission.At present,the common problem of all kinds of desulfurization technologies is how to deal with desulfurization by-products efficiently.The current mainstream process of flue gas desulfurization is limestone/lime-gypsum wet desulfurization technology,which accounts for about 90%of flue gas desulfurization technology.A large amount of lime or lime slurry is needed as a desulfurizer in the desulfurization process,and the product is desulfurized to form CaSO₄·2H₂O,also known as desulfurized gypsum,At present,most of them are disposed of in landfills.takes up a lot of land resources,pollute the environment,and waste of the calcium sulfur resources at the same time.To this end,the main solution proposed by the researchers is to reduce and decompose the desulfurized gypsum and reducing agent into SO₂ and CaO,and use the recovered SO₂ to prepare sulfite and sulfuric acid to realize the resource utilization of low concentration sulfur in the flue gas.Therefore,it is necessary to simplify the desulfurization process and reduce the operating cost of desulfurization.Therefore,it is urgent to develop new technologies for recycling and recycling flue gas desulfurization products.We propose to simplify the existing desulfurization by limiting the limestone/lime-gypsum wet flue gas desulfurization process to the SO₂ absorption stage,ie,the stage of CaSO₃ formation,and then treating and thermally decomposing CaSO₃ to obtain SO₂ and CaO.The process reduces the cost of desulfurization operation,and at the same time realizes the recovery of sulfur resources in low-concentration flue gas and the use of CaO for cyclic desulfurization.In this paper,the CaO content of thermal decomposition products is taken as the index.Firstly,the effects of thermal decomposition conditions on CaO content of CaSO₃ thermal decomposition products are studied,including thermal decomposition atmosphere,thermal decomposition temperature,thermal decomposition time,thermal decomposition heating rate,gas flow rate.Experiment with the experiment to optimize.The results show that CaSO₃ needs to be thermally decomposed under anaerobic conditions to prevent CaSO₃ from being oxidized to CaSO₄.The thermal decomposition is better under N₂ protection;the order of influence of thermal decomposition on CaO content is:thermal decomposition temperature>thermal decomposition time>thermal decomposition heating rate>N₂ flow rate;the orthogonal optimization conditions for thermal decomposition of CaSO₃ are:thermal decomposition temperature 1150?,thermal decomposition time 2h,thermal decomposition heating rate 6?/min,N₂ flow rate 80 mL/min,thermal decomposition oxygen CaO is 98.85%.On the basis of anaerobic thermal decomposition,the thermodynamics and kinetics of CaSO₃ were studied.Thermal analysis experiments show that the initial thermal decomposition temperature of CaSO₃ is about 650?under N₂ atmosphere;when different O₂ content is present in the atmosphere,CaSO₃ will be oxidized,affecting the thermal decomposition products CaO and SO₂.generate.Under these conditions,the theoretical parameters of thermodynamic equilibrium and kinetic rate in the decomposition reaction of CaSO₃ are calculated,and the mechanism of thermal decomposition is explained.The reaction mechanism functions are:G???=[-ln?1-??]^1/2,apparent activation energy E=200.668 kJ/mol,pre-exponential factor ln(A/s^-1)=11.193.Therefore,its dynamic equation is:d?/dt=d?/dt=2.68×10¹¹×exp?-2.35×10⁴/T?×?1-??[1-ln?1-??]^1/2,The thermal decomposition process is controlled by nucleation and growth.In order to further reduce the thermal decomposition temperature of CaSO3 and increase the CaO content in thermal decomposition products,the effect of the external admixture on CaO content was studied.Through the study of the components of desulfurization ash,we screened five components that have a greater influence on the content of thermal decomposition products of CaSO₃.By adding and mixing,we simulated the influence of five influencing factors on the content of thermal decomposition products of CaSO₃,CaCO₃ content>Ca?OH?₂ content>C content>FA?abbreviation of fly ash,hereinafter referred to as the abbreviation?content>Fe₂O₃ content.At the same thermal decomposition temperature,the content of thermal decomposition products of mixed sample CaSO₃ is higher than that of pure CaSO₃,but the thermal decomposition temperature of mixed sample CaSO₃ is lower than that of pure CaSO₃,and the additive is obtained.The orthogonal optimization conditions for the thermal decomposition of CaSO₃ are:Ca?OH?2 content 15%,CaCO₃ content 15%,C content 1%,FA content 0.5%,Fe₂O₃ content 0.5%.