燃煤污染物对钾基吸收剂脱碳影响机制研究

Using dry potassium-based sorbents for post-combustion CO2 capture technology is thought to be one of the interesting methods due to the high CO2 sorption performance, the low cost, low energy consumption and so on. However, the CO2 capture performances of potassium-based sorbents will be affected by the various compositions of flue gas from coal fired power plant. As a result, this is identified as the most important problem in this project, and several key issues will be solved. First, the effects of acid gases such as SOx, NOx and HCl in flue gas, and fly ash particles on the CO2 capture performances of potassium-based sorbents should be studied with the tests using TGA, a bench-scale reactor and various analysis apparatuses. Then, the gas-solid reaction dynamics performances of potassium-based sorbents with CO2 under the complex conditions of coal-fired flue gas will be studied. At last, the new method for preventing the deactivation of the sorbents will be obtained by changing the compositions and the prepared methods of the sorbents. The mechanisms and the reaction dynamics performances for the deactivation of the sorbents in the complex conditions of flue gases will be confirmed, and a new method for improving the performances of the sorbents will be obtained. The work of this project can be used as basic data for the development of the technology for China's coal-fired power plants ultra-low emissions of greenhouse gases.

钾基吸收剂干法脱碳技术具有脱碳能力强、造价低廉、工艺能耗低的优势值得关注。由于燃煤烟气中的酸性气体和飞灰颗粒将会影响钾基吸收剂的脱碳性能，但其影响机制并不明确。本项目将围绕这一核心问题，采用热重、小试反应床实验结合各种理化性质分析仪器研究燃煤烟气中SOx、NOx和HCl等酸性气体对钾基吸收剂碳酸化反应的影响机制，研究飞灰颗粒及所含各元素对吸收剂晶相结构和脱碳性能的影响机制，通过添加掺杂剂和改变吸收剂制备方法的途径探索抑制吸收剂失效的新方法。通过研究揭示钾基吸收剂在燃煤烟气复杂环境下的失效机制，探明其化学反应动力学机理，通过改性最终研制出高寿命高活性的新型钾基CO2吸收剂。本研究可为我国燃煤电厂温室气体超低排放技术发展提供相关基础理论储备。

负载型钾基吸收剂在燃烧后烟气CO2捕集中具有潜在应用，但烟气中酸性气体和飞灰颗粒会直接影响其脱碳性能。有鉴于此，本项目重点关注燃煤烟气中复杂组分对负载型钾基吸收剂脱碳性能的影响机制。揭示了负载型钾基吸收剂在含杂质气氛下脱碳失活反应机理：活性组分K2CO3和中间产物K4H2(CO3)3·1.5H2O易与H2O/SO2/NO2发生反应形成K2SO3和KNO3。所形成的副产物不可再生，在吸收剂表面和孔内累积，覆盖表面活性位并堵塞孔隙结构，降低K2CO3利用效率。提出了H2O预处理、KOH添加和PEI掺杂等改性方法抑制吸收剂在杂质气氛下失活，并揭示了其抑制失活的反应机理。实际应用中，对原样进行水预处理或对碳酸化后样品蒸汽再生，使活性组分K2CO3或碳酸化产物KHCO3转变为稳定物相K2CO3 1.5H2O，可有效提高吸收剂在杂质气氛下脱碳活性与稳定性。以乙醇为溶剂，以TEOS为前驱体，采用溶胶-凝胶/浸渍法合成了高活性的新型硅胶负载型钾基吸收剂。相比于传统以水为溶剂，采用简单浸渍法合成的吸收剂，其脱碳容量由0.15 mmol CO2/g显著提高至1.32 mmol CO2/g。揭示了溶胶-凝胶改性提高吸收剂脱碳性能的机理：溶胶-凝胶法可保证吸收剂较好的微观结构和较高的K2CO3负载量，而乙醇为溶剂可保证K2CO3均匀分布，提高活性组分利用效率。基于多种动力学模型考察了新型硅胶负载型钾基吸收剂的脱碳动力学特性，并揭示了操作条件对其脱碳动力学性能的影响机制。本项目的研究结果为负载型钾基吸收剂应用于燃煤烟气CO2捕集奠定了理论基础并提供了技术支撑。