Study On Oxy-fuel Combustion Characteristics Of Biomass And Coal Blending In Circulating Fluidized Bed

Climate change sets an enormous challenge for human survival environment. The energy utilization technology featuring negative emission is an important approach to tackle and slow climate change. Renewable biomass utilization has been considered to be zero emission energy utilization technology. If the technology of biomass utilization and carbon capture and storage (CCS) can be combined, it will become biomass carbon capture and storage technology which can help reduce the content of carbon dioxide in the atmosphere. Oxygen-enriched combustion of biomass and coal blending in circulating fluidized bed (CFB) belongs to Bio-CCS technology, which has become new research focus in the field of low-carbon energy due to its CO2capture during combustion and negative emission characteristics.This thesis is focused on oxygen-enriched combustion of biomass and coal blending in circulating fluidized bed. Experiments and analysis were conducted by using thermal analyzer on the oxygen-enriched combustion of blended biomass and coal which cover three kinds of typical biomass and four types of typical coal in china. The research aims to demonstrate the influence of oxygen concentration, biomass proportion, heating rate, type of biomass and coal on the combustion process and combustion characteristics. Dynamics parameters of combustion process of cotton stalk and Datong coal blending were calculated and analyzed with iso-conversional method and Coat-Redfern integral method, through which the influence of oxygen concentration and heating rate on the activation energy was obtained. To verify the feasibility of technology of oxygen-enriched combustion of biomass and coal blending, experiments of cotton stalk and Datong coal blending under different oxygen concentration and combustion temperature were carried out in the50kW CFB experimental platform. The detailed research contents are as as follows.The oxygen-enriched combustion characteristics of biomass and coal blending were studied through thermo-gravimetric analysis. The results show that comprehensive combustion characteristic of blending fuel for biomass and coal was improved with the increase of oxygen concentration and heating rate. The higher volatile content and lower ash content in the coal, the greater the degree of interaction between biomass and coal will be. The promotion effect to coal combustion increased with the increase of proportion of biomass with high volatile content and low ash content. But for the biomass with high ash content, when its proportion exceeds a certain value, the comprehensive combustion performance will degrade gradually.Dynamics parameters of combustion process of cotton stalk and Datong coal blending were calculated and analyzed with iso-conversional method and Coat-Redfern integral method. The results reveal that reaction activation energy increases with the increase of oxygen concentration, the reaction activation energy in O2/N2atmosphere is greater than in O2/CO2atmosphere. When the heating rate increases, there is unobvious change in activation energy at the early stage, which decreases at late stage. The experiment verifies that F1mechanism model fits with the oxygen-enriched combustion dynamics mechanism of cotton stalk and Datong coal blending.Experiments of cotton stalk and Datong coal blending under different oxygen concentration and combustion temperature were carried out in the50kW circulating fluidized bed experiment table. The experimental results show that cotton stalk and Datong blending fuel can combust stably in50kW CFB experimental platform with temperature being uniformly distributed in the experimental process. Concentration of CO and N2O decreases as combustion temperature increases, while SO2and NO concentration increases; the concentration of CO, SO2, NO and N2O reduce with the increase of inlet oxygen concentration.