Abstract Nitrogen is a component that often needs to be removed from natural gas. A dual-reflux pressure swing adsorption (DR PSA) technology with activated carbon as the adsorbent was explored for N2 rejection from a binary mixture of 75 mol% CH4 and 25 mol% N2 via non-isothermal numerical modelling. The performance of the four DR PSA configurations (PL-A, PH-A, PL-B and PH-B) was studied by varying the following process parameters: heavy product/feed flow rate ratio (H/F), light reflux/feed flowrate ratio (RL/F), and feed step time duration. The simulation results showed that A-cycles were generally better than B-cycles with respect to the achievable heavy product methane purity and recovery. The underlying reasons for the different performances of A-cylces and B-cylces for this methane-rich feed were investigated via the comparison of the methane profiles in the pressure reversal step. The best performing cycle was the PL-A configuration which obtained a methane product purity and recovery of 93%, satisfying regional pipeline gas specifications and recovery target. The impact of the feed location on the process performance was also studied and the results showed that for A-cycles the feed location as a fraction of the bed length should be maintained at a value lower than the feed methane mole fraction to achieve optimal heavy product purity and recovery. For the PH-B cycle, the feed location should be as close as possible to the heavy product end to maximise product purity and recovery. For PL-B cycles, the effect of feed location is negligible.

中文翻译：

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活性炭双回流变压吸附去除天然气中的N2

摘要 氮气是天然气中经常需要去除的成分。使用活性炭作为吸附剂的双回流变压吸附 (DR PSA) 技术通过非等温数值模拟从 75 mol% CH4 和 25 mol% N2 的二元混合物中去除 N2。通过改变以下工艺参数来研究四种 DR PSA 配置（PL-A、PH-A、PL-B 和 PH-B）的性能：重质产品/进料流速比 (H/F)、轻质回流/进料流量比 (RL/F) 和进料步骤持续时间。模拟结果表明，就可实现的重产物甲烷纯度和回收率而言，A 循环通常优于 B 循环。通过比较压力反转步骤中的甲烷分布，研究了这种富含甲烷的进料的 A-cylces 和 B-cylces 性能不同的根本原因。性能最好的循环是 PL-A 配置，获得了 93% 的甲烷产品纯度和回收率，满足区域管道气体规格和回收率目标。还研究了进料位置对工艺性能的影响，结果表明，对于 A 循环，进料位置作为床长度的一部分应保持在低于进料甲烷摩尔分数的值，以实现最佳重质产品纯度和回收率。对于 PH-B 循环，进料位置应尽可能靠近重质产品端，以最大限度地提高产品纯度和回收率。对于 PL-B 循环，