An innovative integrated process for helium and NGL recovery and nitrogen removal


Raw natural gas is composed of several hydrocarbons, incombustible gases, such as nitrogen and helium, and impurities. While all the impurities are typically rejected at the beginning of the process, the removals of the two inert gases are postponed to last steps, where almost all the hydrocarbons except methane are already produced in an NGL recovery unit. Hence, NGL recovery, nitrogen removal and helium extraction steps are counted the most downstream units of the entire gas processing plant. This study investigates an integrated design and optimization of the three processes. In this paper, a novel process configuration, for co-production of sales gas, NGL and crude helium, is introduced. For this purpose, first we investigate and propose an efficient design to embed the helium extraction unit into a single-column nitrogen removal process. The proposed configuration is extended to an integrated process structure which combines nitrogen removal, NGL recovery and helium extraction units. The design reduces significantly the quantity of equipment as eliminating the need for the open refrigeration cycle and propane pre-cooling systems in NGL plants. High ethane and helium recovery, high nitrogen removal rate for different ranges of nitrogen, as well as the crude helium with high purity, are the outstanding potentials of the novel process. We finally optimize the key process parameters using the particle swarm optimization method to guarantee the minimum required work and present the economic evaluation of the new developed process.
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