Reaseach Of Heat Exchange Between Solid Heat Carrier And Biomass Powder And Biomass Chars

Biomass pyrolysis is one of the most promising technologies in utilization of biomass, and research on mechanism of biomass pyrolysis plays an important influence on designation and development of pyrolytic reactor, distribution of pyrolysis products and quality of bio-oil, so it's particularly important to study the mechanism of biomass pyrolysis. Using temperature difference between heat carrier and biomass to realize biomass fast pyrolysis is a new technology, which has higher heat transfer efficiency and liquid conversion rate.Based on analysis of physical,chemical characteristics and thermal characteristic of biomass material, the heat exchange device was designed and made, heat exchange characteristics between heat carrier (ceramic ball) and biomass was studied in this paper. The study mainly including the following inspects:the proximate analysis, elemental composition and heating value determination of wheat straw, corn straw,peanut shells and pine; design and make heat exchange device which is a multi-function device including feeding, mixing, heat exchanging and separating; experimental study on heat exchang between heat carrier and biomass and temperature inside device were measured at different heat carrier temperature and different feed ratio; then the heat convective coefficient between heat carrier and gas inside the device and the heat of carrier, biomass powder and biomass chars was calculated. The experimental results of biomass powder and biomass chars at the same conditon were compared, so heat exchang characteristics between heat carrier and biomass can be concluded.Through experimental studies,some conclusions are obtained:1.The volatile content has little difference from each other among similar biomass, but it has slightly different between species; the highest ash content is presented in wheat straw and corn straw, then is peanut shell, and ash content of pine is the smallest; moisture content of different biomass has slightly difference; fixed carbon content of different biomass are greatly different, the highest fixed carbon content is presented in peanut shell, which is11.9%,the lowest is appeared in pine which is3.9%.2.Experiments on heat exchang between heat carrier and biomass(powder and chars)shows:temperature inside the device decreased after feeding biomass; temperature inside the device keep unchanged, temperature at the cone rising rapidly after separation of heat carrier and biomass.3.Experiments on heat exchang between heat carrier and biomass powder at different heat carrier temperature(80℃,90℃,100℃,110℃)and different feed ratio(10:1,14:1,18:1,22:1)shows:the higher temperature of the heat carrier, the higher temperature of the biomass powder after heat exchang; the bigger the feed ratio, the higher temperature of the biomass powder after heat exchang.4.Experiments on heat exchang between heat carrier and biomass chars at different heat carrier temperature(80℃,90℃,100℃,110℃)and different feed ratio(10:1,14:1,18:1,22:1)shows:the higher temperature of the heat carrier, the higher temperature of the biomass chars after heat exchang;temperature of the biomass chars after heat exchang increased with the feed ratio increase, when the temperature of heat carrier is110℃, the highest temperature occurs at feed ratio18:1.5. Experiments on heat exchang between heat carrier and biomass powder, the heat convective coefficient between heat carrier and gas inside the device is1.48W/(m2·s). The heat exchange of heat carrier, biomass powder and gas is caculated, the proportion of heat conduction and heat convective of biomass powder is compared:proportion of heat conduction is higher than heat convective.6. Experiments on heat exchang between heat carrier and biomass chars, the heat convective coefficient between heat carrier and gas inside the device is1.95W/(m2·s). The heat exchange of heat carrier, biomass chars and gas is caculated, the proportion of heat conduction and heat convective of biomass chars is compared:proportion of heat conduction is higher than heat convective.7.Expetimental results of biomass powder and biomass chars are compared: the biomass chars temperature rising much higher than the biomass powder under the same condition, this trend amplituded with temperature increased; heat absorption of biomass powder is higher than biomass chars at low temperature, but it's changed with temperature increased, heat absorption of biomass powder is gradually lower than biomass chars when temperature of the heat carrier increased.