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

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.