电容层析成像测量甲醇制烯烃催化剂床层温度

Measuring temperature of methanol-to-olefins catalyst bed by use ofelectrical capacitance tomography

甲醇制烯烃作为煤制烯烃的关键一环,对实现煤炭的综合利用有重要意义。这一过程是典型的放热反应,为提高甲醇转化率与产物选择性,需对床层温度进行在线监测。基于高温电容层析成像,提出一种在线测量催化剂床层温度(DMTO工业催化剂,ZSM-5分子筛)的方法。通过与介电常数变化极小的石英砂、氧化铝等床层材料的测量结果对比,发现不同催化剂的介电常数随温度变化规律不同,催化剂床层的测量电容值随温度变化敏感且重复性较好。因此可通过高温电容层析成像装置测量温度分布均匀的床层归一化电容平均值实现对床层温度的测量。通过采用薄壁石英管的固定反应器,对甲醇制烯烃催化剂、ZSM-5分子床层进行在线测温验证了该方法的有效性,发现通过线性反投影算法重构的ECTt图像,可获得床层温度分布。由此,可以通过高温电容层析成像装置实现对固定床床层床层测温。

As a key step in the production of olefins from coal,the methanol-to-olefins(MTO)process is of significant importance in coal chemical industry.Since MTO is an exothermic reaction,it is necessary to monitor the temperature distribution in the bed to improve the conversion of methanol and selectivity of products.In this study,a method was proposed for online monitoring of the catalyst bed temperature(DMTO industrial catalyst,ZSM-5 zeolites)using high-temperature electrical capacitance tomography(ECT)imaging.By comparing the measurement results with different bed materials such as quartz sand and alumina,which have a minimal change in relative permittivity with temperature,It is found that the relative permittivities of catalyst and zeolites vary with temperature,and thus the measured capacitance between electrodes are sensitive to temperature in the catalyst bed.Therefore,the temperature of the bed can be measured by averaging the normalized capacitance of the bed with uniform temperature distribution through the high—temperature ECT.This method was veritied by an online temperature measurement for DMTO catalyst and ZSM-5 zeolites in a thin-walled quartz fixed bed reactor,and further showed that the ECT images reconstructed using the linear back projection algorithm might be used to obtain the temperature distribution in the bed.Therefore,the fixed bed bed tempe rature can be measured by high-temperatur ECT.