Objective  Although the current domestic helium extraction from natural gas can reduce energy consumption, it still faces problems such as low purity of helium products, numerous equipment and complex processes. To solve these problems, an efficient and low-consumption co-production process is developed to improve product purity and simplify the process.

Method A co-production process with a single tower and a two-stage separator combined with mixed refrigerant refrigeration was proposed. Helium was enriched step by step by cryogenic tower and separator. Support vector machine (SVM) and improved seagull optimization algorithm (ISOA) were used to optimize the key parameters of the process and the product indexes.

Result There were only helium and LNG products in the process, and the whole process formed a closed-loop control. The purity of helium products could exceed 80 mol%, which was better than other literature reports. The total energy consumption was related to all key parameters, the LNG liquefaction rate was related to the parameter setting of the cryogenic tower, and the helium yield and helium product purity were related to the parameter setting of the cryogenic tower and the two-stage separator. The relative errors of the ISOA-SVM model in the prediction results of total energy consumption, LNG liquefaction rate, helium yield and helium product purity are 0.54 mol%, 0.98 mol%, 0.63 mol% and 0.69 mol%, respectively, which was superior to other comparison models, and had strong generalization ability and robustness. After optimization, the total energy consumption could be reduced by 16.21%, the helium yield could reach 97.06%, and the purity of helium products could reach 85.09%.

Conclusion Helium with high yield and purity can be obtained by low temperature rectification, and the comprehensive performance of the process has obvious advantages.