Oxy-combustion typically consists of burning coal with a combination of oxygen and a large amount of recycled flue gas (60–70%) to obtain a similar heat flux profile to that of air-fired systems. As the cost of electricity from first-generation oxy-combustion is relatively high, several new oxy-combustion process concepts have been proposed in recent years, and within these, the proposed amount of flue gas recycle (FGR) has varied from near-zero to 80%. To better understand the fundamental impact of FGR on the efficiency of oxy-combustion systems, a thermodynamic approach is used herein. Second-law losses associated with flue gas recycle are found to be significant and highly non-linear with recycle ratio. A difference in efficiency of up to 10 %-points can be realized, with a maximum efficiency occurring at zero FGR. Furthermore, due to the non-linear relation of plant efficiency with recycle ratio, processes with low recycle (< ∼33%) experience only a small efficiency penalty, compared to no recycle. Additionally, fan power requirements also scale non-linearly with recycle ratio, resulting in significantly lower FGR fan power requirements for low recycle processes as well. These results suggest that for systems employing cold recycle, FGR should be kept below 33%.

Due to the recent interest in developing pressurized oxy-combustion (POC) for efficient, low-cost carbon capture, the impact of flue gas recycle on POC systems is also presented, with a discussion on the valorization strategies for the latent heat of flue gas moisture recovery.

含氧燃烧通常是将煤与氧气和大量的循环烟气（60-70％）混合燃烧，以获得与空气燃烧系统相似的热通量曲线。由于第一代氧燃烧产生的电力成本较高，因此近年来提出了几种新的氧燃烧工艺概念，在这些概念中，拟议的烟气再循环量（FGR）已从接近零变化到80％为了更好地理解FGR对氧气燃烧系统的效率的基本影响，本文使用热力学方法。发现与烟气再循环相关的二次律损失显着，并且与再循环比高度非线性。可以实现高达10％点的效率差异，最大效率出现在FGR为零的情况下。此外，由于工厂效率与回收率之间存在非线性关系，与没有回收相比，低回收率（<〜33％）的过程效率损失很小。此外，风扇功率要求也随回收率成非线性关系，因此对于低回收率流程，FGR风扇功率要求也大大降低。这些结果表明，对于采用冷循环的系统，FGR应保持在33％以下。

由于最近对开发用于高效，低成本碳捕集的加压氧燃烧（POC）的兴趣，还介绍了烟气再循环对POC系统的影响，并讨论了烟气潜热的增值策略。水分回收。