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首页> 外文期刊>Computational thermal sciences >INFLUENCE OF DUST ON THE HEAT TRANSFER IN A FIXED BED REACTOR
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INFLUENCE OF DUST ON THE HEAT TRANSFER IN A FIXED BED REACTOR

机译：灰尘对固定床反应器传热的影响

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摘要

This investigation focuses on the influence of dust on heat transfer in a fixed bed reactor. Industrial application shows that the heat transfer with dust is significantly smaller than without dust. To determine the reason for this effect, a laboratory-scale fixed bed reactor was built and transient temperature profiles measured at different positions in the fixed bed. In the experimental study, a three-phase system (solid, solid, gas) including dust is compared with a two-phase system (solid, gas) for three different bed materials, such as mono- and polydisperse solid iron spheres, direct reduced iron ore, and char particles. The measured data were evaluated by using a modified two-phase model with separate heat balances for a pseudohomogenous solid and a gas phase which were solved by analytical approximation and a numerical method using a commercial program, Aspen Custom Modeler. For determination of the heat-transfer coefficients, parameter estimation was done using the internal program Nelder Mead algorithm. The results were compared with established correlations and data from literature and show significant influence of dust on the heat-transfer rates due to channeling effects caused by local dust accumulation. Due to particle size distribution and different specific surfaces, the reduction of the gas–solid heat-transfer coefficient for char and direct reduced iron ore is less pronounced than for mono- and polydisperse solid iron spheres. The heat-transfer coefficient decreases to 6% in comparison with the results without dust.
机译：这项研究的重点是粉尘对固定床反应器中传热的影响。工业应用表明，有灰尘的传热比没有灰尘的传热小得多。为了确定这种影响的原因，建立了实验室规模的固定床反应器，并在固定床的不同位置测量了瞬态温度曲线。在实验研究中，将包含灰尘的三相系统（固体，固体，气体）与直接还原的三种不同床料（例如单分散和多分散固体铁球）的两相系统（固体，气体）进行了比较铁矿石和炭颗粒。使用改进的两相模型评估测量数据，该模型具有单独的假均质固体和气相热平衡，通过使用商业程序Aspen Custom Modeler进行解析逼近和数值方法来求解。为了确定传热系数，使用内部程序Nelder Mead算法进行参数估计。将结果与文献中已建立的相关性和数据进行了比较，结果表明，粉尘由于局部粉尘堆积引起的窜流效应而对传热速率产生重大影响。由于粒径分布和不同的比表面积，与单分散和多分散的固态铁球相比，炭和直接还原铁矿石的气固传热系数降低的幅度较小。与没有粉尘的结果相比，传热系数降低到6％。

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