Abstract: Aiming at the engineering problem of helium extraction from low-grade helium-containing natural gas in China, based on the analysis of the development status and improvement direction of the existing deep-cooling process, to solve the problem of low helium purity and high energy consumption,a low-temperature helium extraction process by coupling multi-stage flash evaporation and multi-column distillation was proposed and simulated with ASPEN HYSYS. The results showed that the helium product with purity of 99% could be obtained by the proposed process from helium-poor natural gas with helium content of 0.05%. At the same time, 99.96% of methane and 99% of nitrogen, LNG and fuel gas were obtained, respectively, which enhanced the flexibility of the product scheme. The cooling capacity of the separation system was provided by throttling expansion refrigeration, and the reasonable matching heat transfer between the cold and hot materials in the process was realized. The unit compression power consumption of the multi-stage flash distillation + multi column distillation was 0.058 kW.h/kmol, which was much lower than that of the improved ExxonMobil helium extraction process (1.29 kW.h/kmol). It showed that the design of helium extraction process had a certain application potential.

Key words: helium extraction, low-grade helium-containing natural gas, cryogenic method, flash evaporation, distillation, process coupling