Combustion Characteristics Of Different Brewing Raw Materials Lees And Emission Characteristics Of NO_x And CO During Combustio

Distiller’s grains are the residue of brewing raw materials produced by microbial fermentation in the production process of brewing industry.Distiller’s grains direct combustion technology has high combustion efficiency and is suitable for large-scale resource utilization of distiller’s grains.In view of the problem that the combustion characteristics of distiller grains produced by different brewing materials and the emission characteristics of NO_x and CO in flue gas produced by combustion are not clear,this paper carries out the following research:Firstly,the thermal weight loss kinetics of sorghum distillers’grains,corn distillers’grains,wheat distillers’grains and barley distillers’grains were studied by thermogravimetric differential scanning calorimeter（TG-DSC）,and the combustion dynamic behavior of distillers’grains was analyzed by using the combustion characteristic index and combustion thermal kinetic parameters.The results showed that the weight loss process of different brewing materials underwent four stages in sequence:water precipitation,complete pyrolysis of hemicellulose and cellulose,partial pyrolysis of lignin,combustion and burnout of lignin.The comprehensive combustion index SN was 24.50×10^-7%²/（min²·K³）,the flammability index Cr was2.29×10^-4%/（min·K²）,and the ignition index D_i was 11.59×10^-3%/（min³）.Compared with other three kinds of distillers’grains,sorghum distillers’grains have better combustion performance.The ash melting temperature of the four kinds of distilling grains was determined,and it was found that the deformation temperature of corn distilling grains was lower than 900℃,which was more prone to slagging,while the deformation temperature of other kinds of distilling grains was higher than 1500℃.The slag and ash accumulation tendency of distiller’s grains of different brewing materials during boiler combustion was predicted by using a variety of slag and ash accumulation discriminant indexes based on ash composition analysis,and it was found that distiller’s grains had a high slag accumulation tendency during combustion.Secondly,in order to obtain the NO_x and CO emission characteristics of distillers’grains during the combustion process of different brewing materials,the distillers’grains combustion experiment was carried out with the help of one-dimensional tube furnace,and the effects of furnace temperature and water content of distillers’grains on the concentration and emission of NO_x and CO during the combustion process of distillers’grains were studied.It is found that with the increase of furnace temperature,the peak time of NO_x emission is gradually advanced,and the peak concentration and average concentration value of NO_x emission increase.At 900℃,the peak NOx emission mass concentration of barley distillage,sorghum distillage,corn distillage and wheat distillage were 0.556 mg/L,0.631 mg/L,0.68 mg/L and 0.624 mg/L,respectively.The average discharge mass concentrations were 0.112 mg/L,0.11 mg/L,0.099 mg/L and 0.10 mg/L,respectively.Nitrogen conversion rate and NO_x emission mass increased first and then decreased,and reached the maximum value when the furnace temperature was 700℃,NO_x emission mass was 1.35 mg,1.32 mg,1.89 mg and 1.64mg,nitrogen conversion rate was 17%,12.4%,21.1%and 15.57%,respectively.With the increase of furnace temperature,the average emission concentration and peak emission concentration of CO in flue gas show a trend of first increasing and then decreasing,and reach the maximum value at 600℃.The CO emission mass of sorghum and corn distill grains reached a maximum at 600°C,while that of barley and wheat distill grains reached a maximum at 500°C.When the furnace temperature is 700℃,the combustion reaction time is gradually delayed with the increase of the moisture content of distiller grains,while the peak NO_x emission concentration increases and the average NO_x emission concentration increases.The peak emission concentration,emission mass and average emission concentration of CO increased,with the most obvious change in corn distillers’grains.Finally,sorghum distillers’grains and barley distillers’grains were selected to study the NO_x and CO emission characteristics of distillers’grains during fluidized bed combustion with the help of the bubbling fluidized bed thermal experiment device.The effects of excess air coefficient,furnace temperature and grain size of distiller grains on NO_x and CO emission concentration during combustion were studied.The results show that CO emission concentration decreases with the increase of furnace temperature,while NO_x emission concentration increases first and then decreases.As the excess air factor increases,the CO emission concentration shows a decreasing trend,while the NO_x emission concentration shows an increasing trend.When the furnace temperature was 800℃,NO_x and CO emission concentrations increased to varying degrees with the increase of grain size of distiller grains.