姚宗路, 李 敏, 赵立欣, 孟海波, 丛宏斌, 侯书林. 生物炭二级循环折流式冷却中试系统的设计与试验[J]. 农业工程学报, 2015, 31(13): 222-228. DOI: 10.11975/j.issn.1002-6819.2015.13.031
    引用本文: 姚宗路, 李 敏, 赵立欣, 孟海波, 丛宏斌, 侯书林. 生物炭二级循环折流式冷却中试系统的设计与试验[J]. 农业工程学报, 2015, 31(13): 222-228. DOI: 10.11975/j.issn.1002-6819.2015.13.031
    Yao Zonglu, Li Min, Zhao Lixin, Meng Haibo, Cong Hongbin, Hou Shulin. Design and experiment on biochar second-stage cooling system with spiral-flow[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2015, 31(13): 222-228. DOI: 10.11975/j.issn.1002-6819.2015.13.031
    Citation: Yao Zonglu, Li Min, Zhao Lixin, Meng Haibo, Cong Hongbin, Hou Shulin. Design and experiment on biochar second-stage cooling system with spiral-flow[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2015, 31(13): 222-228. DOI: 10.11975/j.issn.1002-6819.2015.13.031

    生物炭二级循环折流式冷却中试系统的设计与试验

    Design and experiment on biochar second-stage cooling system with spiral-flow

    • 摘要: 针对热解炭化后生物炭温度高、冷却慢、余热难以回收等导致热解生产周期长、生物炭热能利用率低的问题,该文采用固-液间接换热原理,设计了循环水二级折流式冷却换热装置并开发了生物炭二级循环冷却中试系统,并对不同生物炭在不同水流量、转速条件下开展试验,试验结果表明,采用该系统后出口生物炭平均温度为30℃,能够满足冷却要求。进出口生物炭温差随水流量的增大而增大,当螺旋轴转速为5 r/min,水流量分别为8、6.5、4 m3/h时,进出口生物炭温差分别为272、242、222℃。水流量固定为6.5 m3/h,螺旋轴转速为25 r/min时,生物炭出炭温度为40℃,而转速降低为5 r/min时,出炭温度降低到25℃;不同生物炭综合传热系数不同,玉米秸秆生物炭冷却时达到最大为100.6 W/(m2·K)。该研究中冷却系统能够与热解炭化设备相匹配,并且满足生物炭连续冷却的需求,可以开展不同生物质炭的冷却试验。

       

      Abstract: Abstract: Biomass pyrolysis is an energy converting technology, but during the pyrolysis process, the outlet temperature of biochar is high due to high final pyrolysis temperature. As such biochar continue burning when exposed in air. So only after cooling, biochar can be transported and used. Currently, common practice is that biochar are natural cooled in a sealed container or by sprinkling water directly to biochar after pyrolysis. Both of the methods need a long time, besides, a great deal of residual heat of biochar is wasted during cooling. This leads to the long production cycle, lowly utilization rate of biochar heat in pyrolysis process. So a sealed cooling device is needed to solve the problem. Through this device, the outlet temperature of biochar should be <40-50℃. Because biomass heat transfer coefficient is low, the cooling process needs more time than other materials, and the new device should be long enough to allow sufficient cooling. As such, a two-stage heat exchange device is needed, using the principle of solid-liquid indirect heat exchange. Such design can ensure that the cooled biochar can be used directly for package, transportation or experiment. In this study, we first examined the details about device structure and size design. Based on analysis and comparison of different structure and biochar sizes, we selected water cooled screw type as the main structure. Biochar was delivered by screw blade in the inner tube with circulating water in out surface of the tube. For such device, the most important part was baffles, it was added between the inner tube and external tube, making circulating water flow in the form of spiral-flow around the inner tube, thus increasing heat transfer time between circulating water and wall surface of inner tube. Based on this, a second-stage biochar cooling system was designed with temperature acquisition terminal and control device, the temperature acquisition terminal was used to monitor the temperature of circulating water and biochar, including two temperature sensors and temperature patrol instrument. The control device regulated water flow and rotation speed of screw axis. We then conducted different cold water flow test,different rotation speeds of screw axis test and different biochar test by use of the system. The application results showed that, the average outlet temperature of biochar was 30℃, it reached the design requirement. Besides, the application results showed that the temperature difference increased with the rise of cold water flow. The temperature difference of peanut biochar was 272, 242, 222℃ when rotation speeds of screw axis was 5 r/min, cold water flow was 8, 6.5, 4 m3/h. Meanwhile the outlet temperature of peanut biochar was 40℃, while rotation speed of screw axis was 25 r/min, and cold water flow was 6.5 m3/h. In contrast, when rotation speed of screw axis was 5 r/min, the outlet temperature of peanut biochar was 25℃. In all heat transfer coefficient was different with different biochar. The experiments showed that corn stalk biochar, peanut biochar, corncob biochar overall heat transfer coefficient was 100.6, 85.3, 57.6 W/(m2·K), respectively. The cooling process completed smoothly with the cooperation of cooling system and pyrolysis equipment, this system could meet the need of continuous cooling process for various kinds of biochar.

       

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