Combustion Characteristics Of Coal And Biomass Mixtures In Oxygen-enriched Atmosphere

Thermogravimetric analyzer was used in combustion experiments for mixtures ofcoal and biomass in three oxygen concentrations. Influences of oxygen concentration,mixing ratio, and particle size on combustion characteristics were obtained. A briefanalysis was done that promotion or inhibition of biomass on coal combustion. Kineticparameters of combustion process were calculated, which were used to analyzeinfluence of oxygen concentration, and mixing ratio on combustion process in terms ofthermal dynamics. Then under the conditions of the three types of oxygen concentration,in the fixed bed combustion system, for mixtures of coal and biomass, experiments ofcombustion were done in a given furnace temperature. Also, it was concluded thatinfluence of oxygen concentration, mixing ratio on the combustion temperature. Carbondioxide concentration in combustion flue gases was measured using gas chromatograph,which help conclude influence of oxygen concentration, mixing ratio, heatingtemperature on time curve and average concentration of carbon dioxide concentration.（1）Oxygen concentration impacts obviously on combustion of coal and biomassmixture. With oxygen concentration increasing, both thermogravimetric (TG) curvesand differential thermogravimetric (DTG) curves move to lower temperature zone, andpeak value on DTG curves increases significantly. Oxygen concentration increasingsignificantly reduces the temperature of burning out but increases synthetic index.（2）With mixing ratio increasing, TG curves move to lower temperature zone andpeak value on DTG curves in volatile components releasing section increases. Also,peak value in fixed carbon combustion section on DTG curves decreases and with itremains of unburned. Coal particle size increasing helps DTG values grow in fixedcarbon combustion segment and increase quality of unburned materials. When mixingratio is less than20%, biomass plays a positive role on latter part of coal combustion.（3）Apparent activation energy of fixed carbon combustion segment increases asthe oxygen concentration increasing, and decreases as the mixing ratio increasing.（4）Role of oxygen concentration on combustion temperature divides intosegments. In initial segment of fixed bed combustion experiment, oxygen concentrationhas basically no impact on temperature curves, and mixtures have basically a linear rateof heating. After ignition of mixtures, temperature curves under different oxygenconcentrations begin to separate. As time goes on, temperature curve’s separation trend is more obvious. After temperature reaches peak value, temperature of mixture reducesrapidly to furnace temperature.In the range of lower oxygen concentrations, combustion peak temperatureincreases with oxygen concentration increasing. But in range of the higher oxygenconcentration, with oxygen concentration increasing, small mixing ratio increases peaktemperature, but medium mixing ratio maintains it, and high mixing ratio decreases itsignificantly. Burning time increases with the oxygen concentration. Combustion peaktemperature decreases with mixing ratio.（5）Average concentration of carbon dioxide emissions increases significantlywith oxygen concentration and furnace temperature.