| Coal/biomass oxygen-enriched co-combustion not only promotes renewable energy utilization,but also reduces CO2 and pollutant emissions,which has become one of the research hotspots in the field of low-carbon energy.The synergistic effect in combustion and the effect of oxygen-enriched atmosphere make the combustion characteristics differ significantly compared to conventional combustion.Existing studies are not yet universally conclusive about the pollutant release characteristics of coal/biomass oxygen-enriched co-combustion.Therefore,the elucidation of combustion heat reaction process and pollutant release mechanism is of great significance to the development and application of this technology.In this paper,the following studies were conducted for coal/biomass oxygen-rich co-combustion:Firstly,in this paper,two samples of Huaneng Huating coal and rice husk were proximate and ultimate analyzed to theoretically analyze the complementarity of coal and rice husk mixture combustion.The heat value of coal was predicted by existing formulas;the heat value prediction formula for a single material of rice husk was established by using the proximate analysis data of rice husk and HHV,and it was found that the prediction formula proposed in this paper had the smallest error after its analysis and verification compared with the existing formulas.Then,oxygen-enriched co-combustion thermogravimetric experiments were conducted on rice husk/coal.The results showed that with the increase of rice husk blending ratio to 70%,the combustion temperature decreased from 730℃to 650℃,the degree of combustion increased,and the synthetic combustion index increased from 2.153×10-8 to 1.183×10-7.With the increase of the heating rate,the combustion temperature and the synthetic combustion index of the samples increase.As the air changes to an oxygen-enriched atmosphere,the ignition temperature and the combustion temperature of the samples decrease and the synthetic combustion index increases.As the oxygen concentration increases to 100%,the combustion temperature decreases from 530℃to 442℃and synthetic combustion index increases from1.9×10-7 to 2.52×10-7.The synergistic effect occurs between components during co-combustion,and the synergistic effect parameter gradually increases with the increase of blending ratio,while the increase of oxygen concentration has more and more significant effect on the synergistic effect.After analyzing the activation energy of the samples,it was found that the activation energy showed a trend of increasing and then decreasing with the increase of rice husk blending ratio during the combustion process,and the average activation energy of the fuel mixture also showed a decreasing trend as the air changed to an oxygen-enriched atmosphere and the oxygen concentration increased.Lastly,experiments on the pollutant release characteristics of coal/rice husk oxygen-enriched co-combustion were conducted.The results show that with the increase of blending ratio,the SO2 release in the mixture of fuel flue gas tends to decrease,the release curve of NO changes from single peak to double peak trend,and the peak release decreases from 316 mg/m3to 149.8 mg/m3.Oxygen-enriched combustion,where the peak SO2 and NO emissions and the total emissions are lower in the oxygen-enriched atmosphere than in the air atmosphere.With the increase of oxygen concentration,the peak SO2 release and total release decreased sequentially,while the peak NO release and total release increased.With the increase of combustion temperature,the SO2 release decreases and then increases,and the total NO release increases from 842.7 mg/m3 to 2690 mg/m3.Therefore,it is important to choose the right oxygen concentration and combustion temperature during oxygen-enriched combustion to improve the combustion characteristics of the fuel and thus reduce the amount of pollutants released. |
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