To minimize entropy production means to reduce the lost work in a process, and to optimize the use of energy resources. Due to the need for re-compression, membrane units for separation of CO₂ from natural gas require large amounts of electrical power. We show that this power requirement can be reduced by controlling the permeation process so that the entropy production is minimum. With the use of optimal control theory, we develop in this work a detailed and robust method to minimize the entropy production of a membrane unit for separation of CO₂ from natural gas, by control of the partial and total pressures on the permeate side. Moreover, we show how the continuous optimal results can serve as ideal limits for the practical design. A three-step permeate pressure that approximates the optimum reduces both the entropy production and the compressor power, when the permeate gas is re-compressed.

最小化熵产生意味着减少过程中的功损失，并优化能源的使用。由于需要重新压缩，用于从天然气中分离CO _2的膜单元需要大量的电能。我们表明，可以通过控制渗透过程来降低此功率需求，从而使熵产生最小。通过使用最佳控制理论，我们在这项工作中开发了一种详细而强大的方法，以最大程度地减少用于分离CO ₂的膜单元的熵产通过控制渗透侧的分压和总压从天然气中提取。此外，我们展示了连续的最佳结果如何可以作为实际设计的理想极限。当渗透气体被重新压缩时，接近最佳值的三级渗透压力会降低熵的产生和压缩机的功率。