Study On Combustion Characteristics Of Pulverized Coal Based On Non-isothermal Thermogravimetry

In recent years,the reserves of anthracite coal have been declined sharply in China,and the types of coal used for BF injection has gradually increased.At the same time as the structural differences of coal property increasingly apparent,which makes the combustion performance of blended coal after mixing is unpredictable,and the various factors impacts on blended coal injection effect differ.Meanwhile,as the injected coal rate rasing,blended coal ash slagging will have a more severe impact on the BF tuyere.Therefore,while studying the combustion performance of the blended coal,the influence of coal ash on the BF injection should also be studied.This thesis firstly analyzed the functional group structure and carbon structure of selected coals.According to the analysis of the functional group structure of coal samples,it is concluded that three coal samples have more characteristics in common the functional group structure,but there are differences in the vibration forms of aliphatic hydrocarbon?CH₂,CH₃?in three coal samples,where YQ and HLL coal samples belong to symmetrical stretching vibration,TSH coal sample for shear vibration.In the analysis of carbon structure of three coal samples,it is found that TSH coal sample has the highest degree of metamorphism,and the defect level of YQ coal sample is larger than others coal samples.Meanwhile,aromatic ring content in YQ and TSH coal samples is higher,aromatic carbon enrichment degree is higher,aromatic layer arrangement is higher,and side chain and heteroatomic content is lower.Exploring the influence of different factors on the combustion performance of blended coal,it is found that the smaller the particle size of TSH coal sample blending,the better the combustion performance of TH,while the YQ coal sample changes with the particle size,and the YH combustion behavior is more uniform.At higher heating rates,YH coal sample coal has better combustion performance,while TH blended coal has a more pronounced burning effect at low heating rates.With the increase of oxygen enrichment,the catalytic effect between bituminous coal and anthracite coal is weakened,and the effect on YH independent combustion performance is more obvious.Meanwhile,comparing the characteristic indexes of coal blended samples under different factors,it is found that the heating rate has a greater influence on the combustion performance of blended coal.The combustion time of TH and YH blended coal is shortened by 36.1 and 67.1 min,and the S values are from 5.49×10^-10,3.73×10^-10 min^-2·?^-3 increased to 36.48×10^-10 min^-2·?^-3,37.12×10^-10 min^-2·?^-3,respectively.In the study of the effects of different heating rates on the combustion kinetics of blended coal,it is found that the correlation coefficients R²?>0.990,0.982?of the HT and HY blended coal samples after fitting through the RPM model were larger,and the standard error RMSE?<0.13%,0.16%?is smaller and more suitable for describing the combustion process of blended coal samples.At the same time,it is obvious that the activation energy E(13.01 kJ·mol^-1)of HY coal blend is much lower than that of HT(18.65k kJ·mol^-1)at a higher heating rate,so the combustion performance of HY blended coal is higher at a higher heating rate.In the study of the characteristics of coal ash slagging,it is found that there are three main weight loss peaks in the coal ash melting process.The first stage is mainly caused by the decomposition of siderite.The second stage is mainly the decomposition of carbonate and ferric sulfate to form CaO and Fe₂O₃.The third stage of coal ash has the largest weight loss,and the mass loss includes:the decomposition of sulfates such as CaSO₄ and Al₂?SO₄?₃ in the ash when the temperature is greater than 1100?;the oxide in the ash reacts with the silicate to form a fayalite?2FeO·SiO₂?when the temperature exceeds 1200?;leucite?K?AlSi₂O₆??and quartz?SiO₂?are formed in the coal ash to form potassium feldspar?K₂O·Al₂O₃·6SiO₂?when the temperature is greater than 1300?.At the same time,from the ash melting point and the deformation curve of the ash melting process,as the temperature increases,the A_YH coal ash reaches the deformation temperature first at 1311?,and reaches the flow temperature at 1377?;however,the ATH coal ash showed slight deformation at 1350?,and the softening speed was slow,and the flow temperature was greater than 1500?.The results show that the ash melting point of ATH is higher than that of A_YH coal ash,which is more conducive to improving the slagging performance before the tuyere.