Study On Co-combustion Of Rice Straw And Coal And Chlorine Migration Characteristics

In view of the problems of low energy density,high chlorine content and low comprehensive utilization efficiency of biomass energy,the co-combustion of rice straw and coal could not only improve fuel utilization efficiency,but also reduce CO,NO and gaseous chloride emissions in pollutants and control environmental pollution.The synergistic interaction and kinetics of rice straw?RS?,pulverized coal?PC?and their blends in the combustion process were investigated in this study.The experiments were carried out at different heating rates?10,20 and 40?/min?under air atmosphere and the temperature ranged from room temperature to 1000?.Meanwhile their activation energy during combustion was studied by Kissinger-Akahira-Sunose?KAS?and Flynn–Wall–Ozawa?FWO?methods.The results indicated that the RS showed one more weight loss peak than the PC in the derivative thermogravimetric?DTG?curves and the residual mass of RS was lower than PC.The different mass of PC in the samples had no obvious effect on the co-combustion weight loss characteristics at the low temperature stage,but there was significant effect in the high temperature zone.As the heating rate increasing,the DTG curves of all samples were shifted to the high temperature side,resulting in thermal hysteresis.When content of PC was 50wt%,the activation energy reached the lower level,76.0 kJ/mol by KAS and 83.2 kJ/mol by FWO,which indicated that the chemical reaction was easy to complete.The experiments at tube furnace platform were tested to study the CO and NO emission characteristics of RS and PC on different conditions:blending ratios and combustion temperature.Results indicated that the total CO emission of RS was highest at 800?,and the total CO emission was lowest when the proportion of PC was 50wt%,which was only 1.70 mg.The amount of NO emission raised with the increase of PC ratio.When the blending ratio of RS and PC was 5:5,the amount of CO emission was highest under 700?,and the amount of NO emission raised first and decreased with the increase of combustion temperature.The effects of combustion temperature,combustion time,O₂ content and blending ratio on the chlorine migration characteristics in the combustion process of RS,and the influences of combustion temperature and combustion time on the chlorine retention effect in the mixture were studied.The chlorine migration characteristics during the combustion process were simulated by FactSage software.The results showed that the precipitation of chlorine in the RS were promoted with the increase of combustion temperature,combustion time and O₂ content.And the doping of coal powder could reduce the precipitation of chlorine in the mixture.The simulation results of FactSage were basically consistent with the experimental results.Chlorine is mainly precipitated into the gas phase in the form of potassium chloride at high temperature.