Synergistic Catalytic Decomposition Characteristics And Experimental Study Of Semi-dry Sintering Flue Gas Desulfurization Ash

With the improvement of environmental protection requirements,metallurgical industry sintering production process in large-scale application of flue gas desulphurization process,resulting in a large number of flue gas desulphurization byproducts.At present,how to make efficient use of flue gas desulfurization by-products has become a common problem faced by steel enterprises.In this paper,we propose to add sintered flue gas desulphurization ash containing ferrosulphate powder and ferrous sulphate to the boiling furnace chamber for sulphuric acid preparation,and use its high temperature waste heat and oxygen depleted atmosphere to collaboratively prepare sulphuric acid,which can not only reduce the environmental problems caused by the disposal of desulphurization by-products in open piles,but also realise the recycling of sulphur resources.In the paper,the thermodynamics of the decomposition of desulfurization ash by the composite catalyst was firstly calculated using Fact Sage 8.1 software to determine the likelihood of the reaction occurring.Thermogravimetric experiments were used to investigate the thermal weight loss curves of desulfurization ash at different heating rates,and then the kinetic parameters were calculated using the conversion rate methods of Kissinger,FWO and Starink to derive the kinetic equations for the thermal decomposition of desulfurization ash.In the experimental part,a five-factor,four-level orthogonal experiment was set up using a high-temperature vertical tube furnace to simulate a boiling furnace,and the effects of temperature,holding time and gas flow rate on the desulfurization rate were investigated;a six-factor,five-level orthogonal experiment was set up using desulfurization ash as the main reactant,and the effects of temperature and holding time on the roasted product were investigated.（1）Thermodynamic calculations show that the composite catalytic preparation of sulphur dioxide gas using ferrous sulphide and ferrous sulphate for desulfurization ash is feasible.The calcium sulphite with the addition of the composite catalyst starts to decompose at around 873 K and the higher the temperature the more fully the reaction takes place.The ash melting point of the system is higher when presenting a weak reducing atmosphere compared to an oxidising atmosphere.The high temperature and low oxygen ambient conditions are more favourable for the reaction to proceed smoothly.（2）Thermogravimetric experiments showed that the thermal decomposition curves of the desulfurization ash at the same heating rate followed more or less the same trend,but as the heating rate increased,both the TG curve and DTG curve moved towards the high temperature region,which was mainly due to the fact that too fast a heating rate would lead to a lag in the chemical reaction temperature and the reaction moved towards the high temperature region.The mean activation energy was calculated to be 217.54 k J/mol,which corresponds to a mean finger front factor of 11.81.（3）The optimal combination of the following factors was obtained from the boiling furnace doping of desulfurization ash:temperature 900°C,Fe S addition of 2%,Fe SO₄addition of 2%,carrier gas flow（Ar）of 2000 m L/min,holding time of 30 min and heating rate of 2°C/min.The results of the fluidized-bed furnace experiments show that with the increase in temperature,the desulfurization ash with the addition of ferrous sulphide and ferrous sulphate is more The results of the boiling furnace experiments show that with the increase of temperature,the desulfurization ash with the addition of ferrous sulphide and ferrous sulphate is more likely to decompose and produce SO₂ gas,which increases the desulfurization rate of the reactants.The results show that it is feasible to use ferrous sulphide and ferrous sulphate as composite catalysts for the catalytic decomposition of desulfurization ash in a fluidized-bed furnace.