Mechanochemical Coupling Of Modified Fly Ash On High Sodium Coal Slag Fouling Characteristics Of The Improvement Mechanism

As an important part of China’s coal resources with abundant reserves,high quality and multiple uses,Zhundong coal is an important support for national energy security and economic development,but its high sodium content causes it to have strong adhesion,which easily leads to slagging and staining problems,causing damage to combustion equipment and reducing power generation efficiency.High alkali coal ash is rich in elements such as Si and Al,which can inhibit the generation of sodium-containing gaseous compounds to a certain extent.Mechanical chemical reaction refers to the phenomenon that when a material is subjected to high intensity mechanical force,it can cause changes in the internal organization of the material and its own physical and chemical properties.Generally under the action of mechanical force can increase the activity and specific surface area of the substance,through the mechanical force modification of high alkali coal ash by ball mill,the ball mill fly ash becomes a highly active and silica-aluminum-rich additive.In addition,P element helps to improve ash fusibility,and in view of this,high alkali coal ash was used as the base material to modify high alkali coal ash with mechanical force coupled with phosphorus-rich reagent NH4H2PO4 to solve the slag staining problem of Zhundong coal.In this paper,the effects of different ratios of ball mill ash,NH4H2PO4 and mechanochemically coupled modified fly ash on the staining slagging and combustion characteristics of quasi-east coal were studied,and the mechanisms of different ratios of additives affecting the staining slagging and combustion characteristics of coal blends were analyzed by the solid sodium rate Z,characteristic temperature of coal ash,and thermogravimetric curves.The main research results are as follows:（1）To investigate the effect and mechanism of different ratios of additives on the staining characteristics of coal blends.The research objects are ball mill ash,NH4H2PO4 and mechanochemically coupled modified fly ash.The results show that:with the increase of the proportion of ball mill ash,the effect of reducing staining on the heat exchange surface becomes better and better;with the increase of the proportion of NH4H2PO4,the effect of reducing staining increases and then decreases;for the mechanochemically coupled modified fly ash,from the proportion of NH4H2PO4,the solid sodium rate decreases with the increase of the mixing proportion;from the ball mill ash,the effect of reducing staining increases and then decreases with the increase of the proportion.In the experiment,the best ratio to reduce staining was 5%of ash（ash to coal mass ratio）and PO43-/Na=0.5.（2）Investigate the effect and mechanism of different ratios of additives on the slagging characteristics of coal blends.It was found that:the increase of the proportion of ball mill ash would lead to the trend of the sample ash melting point curve decreasing first and then increasing;with the increase of NH4H2PO4 mixing ratio,the curve of the sample ash melting point also decreased first and then increased;for the mechanochemical coupling modified fly ash,with the increase of NH4H2PO4 mixing ratio at all ash addition ratios,the ash melting point temperature of the mixed burned produced ash basically showed an increasing trend The best ratio to slow down the slagging is 5%of ash and PO43/Na=4 according to the rule of determination of（FT-DT）.（3）To investigate the effect and mechanism of different ratios of additives on the combustion characteristics of coal blends.The results found that:with the increase of the proportion of ball mill ash added,the ignition difficulty of the coal blend increased,the burning index also decreased,and the overall combustion index had a small increase;with the increase of the NH4H2PO4 mixture proportion,the maximum burning rate,the average burning rate and the overall combustion index all had a significant decrease,which implied a decrease of the combustion performance;for the mechanochemically coupled modified fly ash,the ignition difficulty of the coal blend For the mechanochemically coupled modified fly ash,the ignition difficulty of the blended coal decreases,but the combustion performance of the coal species becomes worse with the increase of the NH4H2PO4 blending ratio.On the whole,the best combustion characteristic ratio is 5%of ash and PO₄^3-/Na=1.