活性炭吸附正丁烷过程传热特性研究

Investigation of the heat transfer characteristicsfor n⁃butane adsorption on activated carbon

  • 摘要: 在固定床反应器上研究了活性炭吸附正丁烷的性能,采用实验和数值模拟相结合的方法, 探究吸附过程中的传热规律。 根据吸附实验测得的吸附穿透曲线,活性炭对正丁烷的饱和吸附量 为 19.135 g;结合 Yoon⁃Nelson 模型等 3 种动力学方程拟合结果,活性炭床层吸附穿透时间为 924 min;一级吸附速率常数和二级吸附速率常数分别为0.023 86 min-1和0.000 98 g/(mg∙min)。 基于吸附过程床层温度变化参数,根据两能态模型公式和经典吸附热公式,正丁烷的理论吸附热和 实际吸附热分别为 5.48 kJ / mol 和 5.56 kJ / mol,2 者的偏差率为 1.44%,说明活性炭吸附正丁烷以物 理吸附为主。 借助计算流体力学软件 Fluent 建立活性炭固定床吸附模型,根据实验所获得的参数 结合理论公式推导得出与实验过程相一致的质量源项 Sm 和能量源项 ST 表达式,通过 User Defined Functions(UDF)加载质量源项Sm和能量源项ST,模拟活性炭吸附正丁烷的传热过程。 以穿透时间 和监测点最大升温为评价指标,对比分析实验数据与模拟结果,吸附穿透时间模拟值为 939 min,与 实验值 924 min 的偏差率为 1.62%,6 个监测点最大升温模拟值与实验值偏差率在2.17% ~ 4.29%, 验证了模型的准确性。 并对进口正丁烷体积分数、进气速度进行了敏感性分析,结果表明:固定床 的最大升温与上述2个参数均呈正相关。 在工业Volatileorganiccompounds(VOCs)处理工程中,可 通过优化进口有机物浓度和进气速度,消除装置的安全隐患。

     

    Abstract: The performance of activated carbon(AC) adsorbing n⁃butane was studied on the fixed⁃bed reactor. The ex⁃ periment and numerical simulation were used to investigate the heat transfer law in the adsorption process. By measur⁃ ing adsorption experiment’s the break through curve,the saturated adsorption capacity of AC for n⁃butane was 19.135 g. By fitting calculation with three kinetic equations such as Yoon Nelson model,the breakthrough time of the AC fixed⁃bed was 924 min,and the first⁃order adsorption rate constants and the second⁃order adsorption rate constants were 0.023 86 min-1 and 0.000 98 g/ (mg∙min),respectively. Based on the change parameters of the AC fixed⁃bed’ s temperature in the adsorption process,according to the two⁃energy⁃state model formula and the classical adsorption heat formula,the theoretical and actual adsorption heat of n⁃butane were 5.48 kJ / mol and 5.56 kJ / mol,respec⁃ tively,with a deviation of 1.44%. It shows that the adsorption process of n⁃butane by activated carbon is mainly physi⁃ cal adsorption. The fixed AC bed’s adsorption model was established by computational fluid dynamics(CFD) software Fluent. According to the parameters obtained from the experiment and the theoretical formula,the expressions of mass source term ( Sm ) and energy source term ( ST ) consistent with the experimental process are derived. And the heat transfer process of AC adsorbing n⁃butane was simulated by loading the mass source term(Sm) and the energy source term(ST) with User Defined Functions(UDF). The breakthrough time and the maximum rise of temperature were used as the evaluation indexes. Compared with the experimental data and simulation results,the simulation value of the breakthrough time is 939 min,the deviation rate from the experimental value of 924 min is 1.62%,and the devi⁃ ation rate between the simulation value of maximum temperature rise of six monitoring points and the experimental val⁃ ue is between 2.17% and 4.29%. The accuracy of the model was verified. The sensitivity of the inlet’s n⁃butane con⁃ centration and the gas flow was analyzed. The results showed that the maximum temperature rise of the fixed⁃bed was positively correlated with the above two parameters. In industrial Volatile organic compounds(VOCs) treatment projects,the safety hazards of the device can be eliminated by optimizing the inlet gas concentration and speed.

     

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