مدل‌سازي رياضي راكتورهاي بستر پرشده جريان شعاعي براي توليد هيدروژن از تجزيه كاتاليستي آمونياك

In this research, mathematical modeling an‎d simulation of the catalytic decomposition of ammonia in radial flow packed bed reactors in adiabatic conditions are discussed, with the aim of comparing the performance of various types of contact patterns in radial flow reactors an‎d comparing them with axial flow packed bed reactors. For this purpose, the behavior of these reactors in different operating conditions such as temperature, pressure an‎d feed flow were investigated using simulation in COMSOL Multiphysics 6.2 software in two dimensions. In addition, the effect of changing parameters such as bed depth an‎d dimensions of catalyst particles on ammonia conversion, pressure dro‎p an‎d flow distribution in different structures of radial flow reactors were investigated. The results showed that in the four models of radial flow packed bed reactors, although there are clear differences in the flow patterns, but in the conditions where the chemical reaction is carried out, the ammonia conversion is almost the same in all models. In the following, it was shown that under the same conditions, radial flow packed bed reactors have a lower conversion (about 2%) compared to axial flow packed bed reactors, but the pressure dro‎p created in these reactors is far less than axial flow packed bed reactors. which provides the possibility of increasing the production ratio by increasing the flow rate of feed. Also, the temperature dro‎p caused by the endothermic reaction of ammonia decomposition inside the catalyst bed is almost the same for both types of reactors. The maximum conversion of ammonia was measured at 66.8% in adiabatic conditions, which decreased by 33.2% compared to constant temperature conditions. In addition, comparing the performance of radial flow reactors in catalysts with a diameter of 2 an‎d 5 mm, although a lower conversion was obtained in 5 mm catalysts than in 2 mm catalysts (8.4%), but the pressure dro‎p created in this diameter was optimal an‎d remains acceptable (0.251 kPa per reactor length). The results obtained in this research can be effective in the optimal design of packed bed reactors for the catalytic decomposition of ammonia.

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