This paper describes membrane processes to capture the CO₂ produced by combustion gas turbines in natural gas combined cycle power plants. Because combustion turbines typically use a large excess of air, the resulting turbine exhaust gas is relatively dilute (only 3–4% CO₂), making subsequent CO₂ capture difficult and costly. Previously, we’ve shown that a membrane process can be used to selectively recycle CO₂ to the combustion step, which significantly increases the CO₂ content in the exhaust gas. In this way, selective exhaust gas recycle (S-EGR) makes CO₂ capture energetically easier. Here, various membrane design concepts incorporating S-EGR are described and compared. A combination of S-EGR with non-selective exhaust gas recycle (EGR) is shown to offer advantages in reduced capital, while retaining most of the energy benefits of S-EGR alone. For all of the membrane designs analyzed, the energy and cost of capture vary with the capture rate. Generally, if flue gas compression is not used, the lowest capture cost ($/tonne CO₂) for membranes occurs at partial capture rates of 60–70%. Of the process designs studied, the lowest cost of capture (∼$44/t) is achieved by an integrated turbine/membrane design that would require changes to existing turbines.

本文介绍了膜工艺来捕获天然气联合循环发电厂中燃气轮机产生的CO ₂。由于燃气轮机通常使用大量过量的空气，因此，涡轮机产生的废气相对稀薄（仅3–4％CO ₂），从而使后续的CO ₂捕集困难且成本高昂。以前，我们已经表明，膜工艺可用于选择性地将CO ₂再循环至燃烧步骤，从而显着提高废气中的CO ₂含量。这样，选择性废气再循环（S-EGR）使CO ₂精力上的捕获更容易。在此，描述并比较了结合S-EGR的各种膜设计概念。显示S-EGR与非选择性废气再循环（EGR）的组合可提供降低资本的优势，同时仅保留S-EGR的大部分能源优势。对于所有分析的膜设计，捕集的能量和成本随捕集速率而变化。通常，如果不使用烟道气压缩，则膜的最低捕获成本（美元/吨CO ₂）发生在60-70％的部分捕获率下。在所研究的工艺设计中，采用集成涡轮机/膜设计可实现最低的捕集成本（约$ 44 / t），而这需要对现有涡轮机进行更换。