Investigation Of The Mechanism Of Inhibiting Slagging On Biomass With Coal Gangue

As the fourth largest energy source in the world,biomass has the advantages of abundant production,wide range of sources,green and low-carbon,and can serve as an alternative to fossil energy with high pollution and high carbon emissions.It is an important force to realize the transformation of global energy structures.With the development of the economy and society and the increasing shortage of energy,biomass energy has re-entered people’s vision and attracted their attention.The large-scale utilization of biomass fuel can effectively alleviate human dependence on fossil energy and can effectively mitigate a series of pollutant emission problems.Coal gangue is the solid waste produced in the process of coal mining and coal washing,and it is one of the largest solid wastes in current production.In addition to a certain amount of carbon,coal gangue also contains SiO₂,Al₂O₃,Ca O,Mg O,Fe₂O₃ and other chemical substances,of which SiO₂ and Al₂O₃ account for the largest proportion.The burning of coal gangue is not only low in efficiency,but also easy to produce a lot of pollutants.Biomass fuels have serious slagging and corrosion problems in practical applications,which are not conducive to the safe operation of boilers.Therefore,coal gangue was selected as an additive and its effect on biomass fuel slagging and its reasonable ratio with biomass fuel combustion were studied.Firstly,the basic physical properties of biomass and coal gangue were determined.The results showed that wheat straw and salix branches contain elemental chloride and alkali metal elements of potassium and sodium,and salix branches contain some alkaline earth metal elements of calcium and magnesium.The coal gangue contained more silicon,aluminum elements,but also contained a very small amount of alkaline metal and alkaline earth metal elements.Wheat straw and salix branches surface were loose and porous,coal gangue particles surface was scale-like structure,dense structure.Secondly,thermogravimetric analysis was performed on the biomass/coal gangue blended fuel.The results showed that blending with biomass can improve the combustibility index and comprehensive combustion performance index of coal gangue.The most obvious effect of improving combustion was when the mixing ratio of biomass to coal gangue was8:2.With the increase of biomass content,the comprehensive combustion index of the specimens increased.After the biomass content increased from 70%to 90%,the integrated combustion index of the mixed specimen of wheat straw and coal gangue increased by1.09×10-8(mg²·min^-2·C^-3),and the integrated combustion index of the mixed specimen of salix branches and coal gangue increased by 0.67×10-8(mg²·min^-2·C^-3).Then,combustion ash production tests were performed in a tube furnace reactor to analyze the morphology and physical composition of ash samples.The results showed that the ash formation rate of both biomass fuels decreased continuously with increasing temperature,and the ash formation rate of wheat straw was for the ash formation rate of salix branches.At 800°C,wheat straw showed serious slagging and salix branches showed slight slagging.Low melting point silicates were present in both biomass ashes at this temperature.The slagging of the biomass fuel was significantly improved by blending with coal gangue,and the presence of non-volatile high melting point minerals in the biomass ash mixture.Slagging was more pronounced in the O₂/CO₂ atmosphere than in the air atmosphere.Finally,calculations were used in FactSage thermodynamic calculation software to analyze the physical phases in the ash samples in a specific temperature interval.The results showed that the composition of the biomass mixed ash was more complex after blending with coal gangue,with an increase in the physical phases and an increase in the content of non-volatile high melting point minerals,which led to a reduction in the tendency of slagging.In terms of the physical phase categories in the whole temperature range,there is no big difference between the phases in the O₂/CO₂ atmosphere compared with those in the air atmosphere,but they are different from each other in terms of phase content.