Abstract:

Post-combustion CO₂ removal from flue gas at power plant via a two-bed CaO-CO₂ loop (CaL) with heat provided by in-situ oxy-fuel combustion has been investigated. Based on the principle of chemical reaction engineering, a simple analytical model with one variable N only (solids circulation ratio) has been built and used for analysis of the CaL process systematically, which includes effects from sorbent reactivity, fuel impurity and the utilization of fuel heat to looping. From the model, the minimum heat duty and the looping penalty are obtained. Both of them are impacted by fuel sulfur and ash significantly. The result also indicates that the optimum solids circulation ratio N will be located between the two minimum points. The furnace factor is important, because it can eventually reduce the fuel firing rate, fuel ash and sulfur effect, oxygen requirement and related auxiliary power, and increase steam cycle efficiency. As found, the heat duty approaches to infinite at a critical solids circulation ratio N_C, which is a constraint to the operable N and the fuel burned. All of the effects are interconnected by the model.

Key words: CO₂ capture, calcium looping, reactivity, modeling

摘要：

采用燃料氧燃烧直接供热的氧化钙-二氧化碳双床循环系统已经被研究开发,用于从电厂尾气中脱碳。本研究基于实验和化学反应工程原理建立了分析模型,用于系统地研究循环特征,氧化钙活性衰减,燃料及其炉内热利用率的影响。基于模型推导获得了重要参数:最小循环热损失和最小热需求量,以及对应的固体循环比。它们都受供热燃料灰分和含硫量的影响,也受脱碳率的影响。显然最佳固体循环比介于二者之间。另一个重要参数是燃料在炉内的热利用率。高的热利用率不仅降低燃料需求量,降低其灰分和含硫的影响,降低氧的需求量及其辅助功,而且提高蒸汽循环的发电效率。一个发现是热需求量在临界固体循环比接近无穷大,这就限制了固体循环比的可操作范围, 以及燃料的灰分和含硫量。建立的分析模型和推导直接提供了这些变量之间的关系和范围。

关键词: CO₂捕集, 钙循环, 反应性, 模型