表面强化传热对固定床费-托合成的影响

摘要

The boiling properties of smooth tube,sintered coated porous reactor tube and mechanically fabricated porous surface tube,and the effects of reactor structure parameters on boiling heat transfer were investigated in a pool boiling device.The effects of surface enhanced heat transfer on Fischer-Tropsch synthesis were studied in a fixed-bed reactor with three kinds of tubes,respectively.The results in pool boiling show that the heat transfer properties in enhanced surface tubes are better than the plain tube,resulting in lower incipient boiling superheat and earlier boiling.The heat transfer performance is different for sintered coated porous tube and mechanically fabricated porous surface tube at different heat flux ranges,but both can improve the F-T performance.However,the influence of heat transfer enhancement is not obvious for sintered coated porous reactor tube under lower CO conversion rate.With the increase of heat flux and improvement of heat transfer performance,the distribution of catalyst bed temperature becomes more even and the mechanically fabricated porous surface tube shows more obvious promotion for heat transfer.Under same reaction conditions,higher CO conversion and C5+ selectivity are observed.The mechanically fabricated porous surface tube could get higher wall heat transfer coefficient than that of sintered coated porous reactor tube.%采用小型池沸腾实验装置研究普通光滑管、表面多孔管和T型槽管的沸腾特性,考察反应管的结构参数对沸腾传热的影响规律,并在中型装置上分别采用普通光滑管、多孔表面管和T型槽管3种形式的反应器,研究了强化传热对固定床费-托合成性能的影响.结果表明:在小型池沸腾实验装置上,表面多孔管和T型槽管的强化传热性能明显优于普通光滑管,能降低起始沸腾过热度,使得沸腾现象较普通光滑管提早发生,但在不同的热流密度范围,表面多孔管和T型槽管的强化传热性能不同;表面多孔管和T型槽管反应器均可以改善费-托合成性能,表面多孔管在低转化率时强化传热效果不明显,但随热流密度增加,传热性能得到改善,催化剂床层温度分布趋于均匀,T型槽管对反应的促进效果更明显,在相同反应条件下,CO转化率增加,C5+选择性提高;与多孔表面管相比,T型槽管可以显著提高管外介质对管壁的给热系数,使反应管的传热得到强化.