Effects Of Adding Biomass Ash On Formation Characteristics And Fouling Behavior Of Xinjiang Coal Ash

Coal is one of the important energy sources in Xinjiang.The development and utilization of Xinjiang coal has been promoted to the national energy strategy.The unique coal-forming environment in this region leads to most Xinjiang coals possessing high alkali/alkaline earth metal characteristics,which leads to serious ash deposition-related problems faced by Xinjiang coals during combustion.Therefore,it is important to conduct prevention and control studies for the deposition problems of coal in Xinjiang.The existing research shows that additives and co-firing can effectively alleviate the problems of contamination and slagging in the process of coal combustion.The biggest problem of mineral additives such as kaolin is its high cost,so it is difficult to realize industrial application.Rice husk and other biomass are usually used as biomass power plant fuel.The ash after combustion contains a lot of silicon,which is a potential excellent silicon-based raw material.In order to explore the influence of biomass ash on the formation characteristics and fouling behavior of coal in Xinjiang,the fly ash from four different biomass power plants was selected as the research object,and compared with kaolin and high-silicon-aluminum coal in this paper.The main research work and conclusions are as follows:Firstly,the bulk ash collection experiment was carried out in the drop tube furnace(DTF),and the particle size distribution,element distribution and mineral distribution of the samples were tested.The results show that EK coal has a high content of Ca,Na and Fe,and the organically bound Ca in coal is easy to interact with other mineral elements to form fine spherical particles rich in Ca,Na and Fe,which leads to serious ash deposition.Silicon-rich biomass ash can react with alkali / alkaline earth metal elements in coal,and change ash particle size and element particle size distribution.The silica-rich biomass ash(A4)and kaolin greatly reduce the proportion of complex aluminosilicate in the ash,while the proportion of high melting point minerals increases significantly.When the proportion of SF coal is low,the dilution effect of high-silicon-aluminum coal ash will be covered by the interaction reaction,and promote the formation of low-melting complex aluminosilicates.Subsequently,the melting characteristics of minerals in the bulk ash was quantitated by the combination of CCSEM technology and thermodynamic equilibrium calculation.Silica-rich biomass ash can significantly improve ash melting point,and the effect is equivalent to that of kaolin.Four kinds of biomass ash and kaolin can reduce the sintering strength of the ash,and the effect of A4 and kaolin are the best.The silica particles in rice husk ash are very inert,and there is no obvious melting sintering phenomenon even at high temperature.The unique empty shell structure can significantly reduce the sintering strength of EK ash.In addition,silica-rich biomass ash and kaolin can effectively reduce the liquid phase ratio of bulk ash.However,mixed firing of SF coal leads to the increase of liquid phase ratio of bulk ash.Therefore,low proportion of SF coal may worsen ash deposition.Although silica-rich biomass ash and kaolin can reduce the melting proportion of bulk ash,it also leads to the increase of the proportion of calcium containing complex aluminosilicate in the ash,which eventually leads to the increase of the liquid phase proportion of Ca O.Although co-firing promoted the formation of complex aluminosilicate,it did not promote the migration of liquid Ca O to large particle size ash,which may reduce the probability of deposition of large molten particles.Finally,the deposition experiments of different samples were carried out on the ash deposition test bench.The results show that different kinds of biomass ash have different effects on preventing and controlling coal contamination in Xinjiang.Silica-rich biomass ash(A2,A4)has a good effect on pollution alleviation.Although co-firing results in a significant increase in the proportion of bulk ash fusion,it can still reduce the quality of contaminated inner layer.Aiming at the prevention and control of coal ash deposits in Xinjiang,the following guiding principles are put forward: The alkali-acid ratio of biomass ash can significantly affect the bulk ash alkali-acid ratio.It is suggested that biomass ash with alkali-acid ratio less than 0.6 should be selected as additive.When the alkali-acid ratio is greater than 0.6,the application of addictive and high-silicon-aluminum coal to prevent coal contamination in Xinjiang has a good effect;when the alkali-acid ratio is lower than 0.6,the control effect is poor,which may reduce the economy of the technology.The alkali-acid ratio of the mixed ash can be assumed to be 0.6,and the addition amount of biomass ash can be estimated by linear superposition method.Based on this guiding principle,this paper makes a brief economic comparison of the use of silicon-rich biomass ash,kaolin and high-silica-aluminum SF coal to suppress Xinjiang EK coal contamination.