| Coal is the most used fossil energy in China,which belongs to the unclean category of fossil energy.Briquette is a uniform mixture of pulverized coal with sulfur fixing agent,binder,catalyst and so on,and pressure is applied to mould to make it have a fixed shape.Briquette combustion desulfurization technology system is simple,processing is convenient,operation cost is low,combustion efficiency is high,as a kind of coal fuel which can effectively reduce ash content,it is widely used.China is a big mining country,and the amount of solid waste produced by mining industry is very large every year.At present,tens of billions of tons of tailings have accumulated and become the largest country in tailings discharge.This paper puts forward a new way of thinking on how to realize the reuse of this part of solid waste and further achieve the ultimate goal of treating it with waste.In view of the above problems,this subject puts forward an experimental study on the use of tailings as a new type of sulfur fixing additive.By simulating the combustion process of coal in a tube type resistance furnace,the best effect of sulfur retention is explored,and the proportions of various substances in the compound tailings additive are used to make use of the obtained formula to make the briquette and study the addition.The effect of the agent on the physicochemical properties of briquette is carried out in the briquette combustion system in the briquette combustion system,and the coal ash slag is analyzed.On this basis,the promotion mechanism of sulfur retention is preliminarily explored.In this experiment,a single factor experimental method was used to study the parameters affecting a variety of conditions of sulfur retention,and the optimum conditions for sulfur retention were explored.The experimental conditions of coal combustion were as follows:combustion time was 10min,the combustion temperature was determined to be 900?,consistent with the combustion temperature of civil briquette and air flow rate of 1.2 L/min,which was beneficial to the reaction.It should be carried out that pulverized coal with a particle size of 106?-180?m has the most suitable surface area,which will not lead to excessive diffusion resistance.The sulfur retention effect of calcium based sulfur fixing agent and tailings was separately mixed with coal,and it was found that when the molar ratio of Ca/S=2.0,CaCO3 and Ca(OH)2 was 2:3,the calcium based sulfur fixing agent could reach a sulfur retention rate of 50.8%.The tailings can have a certain sulfur retention effect in different mixing ratios(2%,4%,6%,8%,10%),and the sulfur retention rate is close to 20%.The sulfur retention rate of calcium based sulfur fixing agent can be raised to 54.2%when adding 2%mass fraction of the iron ore tailings.After the optimization of the four main components SiO2,Fe2O3,TiO2 and Al2O3 in the tailings,the optimization experiments of the single,double and three component additives are carried out in turn.The experimental results of the single component additives show that the 1.4%TiO2 sulfur retention rate is the highest under the condition of Ca/S=2.0,which is related to the pore gap structure of CaO,followed by 1.0%Fe2O3 and 1.2%Al2O3 and 0.5%SiO2 were increased by 10.8%,7.8%,7%,4.9%when compared with no additives,and the Fe2O3-Al2O3 system with the best sulfur retention effect was found in the dual component additive system.The sulfur retention rate was up to 64.7%when both were added to 1%.The multi component additive experiment showed that the sulfur retention rate of the three component SiO2-Fe2O3-Al2O3 additive system was 69.3%.Tailings used as additives for coal combustion should be mixed with 30%SiO2,50%Fe2O3 and 60%Al2O3 to make composite tailings additives.The process of making briquette is explored,the influence of compound tailings additives on the physical and chemical indexes of briquette is analyzed,and the combustion experiment of briquette combustion furnace is built.It is proved that the compound tailings additive can improve the mechanical strength,waterproof and thermal strength of briquette.The effect of the compound tailings additive was evaluated from the calorific value.The combustion characteristics were reflected by the thermo gravimetric analysis of the coal combustion process.The coal ash was characterized by XRD,SEM,and a variety of new sulfur retention products were detected in the ash.The microstructure of the slag was also improved,which explained the mechanism of the tailings to promote sulfur retention.It provides a reference for resource recovery of coal mining solid waste and sulfur retention of briquette. |
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