循环流化床O2/CO2燃烧S迁移规律研究

Oxy-fuel circulating fluidized bed combustion is one of the most promising carbon capture technologies for coal-fired power plant. Due to the enrichment of CO2/SO2/H2O in the flue gas, the sulfur transformation behaviors （such as limestone desulfurization mechanism,SO3 formation, etc.）during oxy-CFB combustion will deviate substantially from air-fired CFB. However,the related study especially the quantitative investigation on sulfur fate in the gas and solid phase during oxy-fuel CFB combustion has rarely been involved at present. In this project, limestone desulfurization experiment under O2/CO2/H2O atmosphere will be carried out in a bench scale fluidized bed combustor to obtain the influence of vapor on the limestone desulfurization behavior. The SO3 formation experiment by homogenous and heterogeneous reactions will be carried out on a drop tube furnace and the effects of atmosphere, fly ash physical and chemical property, etc. on the SO3 formation during oxy-fuel CFB combustion will be revealed.Based on the mechanism obtained from the bench experiments, an oxygen/flue gas recycle CFB combustion experiment burning varied fuels will be accomplished to study the sulfur transformation behavior in gas and solid phase quantitatively,also the sulfur balance data will be achieved through the accurate measurement of the gas-solid flow and composition. It is of great theoretical value and practical significance to investigate the sulfur transformation mechanism for controlling sulfur oxides emission during oxy-fuel CFB combustion process.

循环流化床O2/CO2燃烧技术是最具前景的燃煤电站CO2捕集方法之一。与常规循环流化床相比，烟气再循环带来炉内CO2、SO2和H2O等组分的富集，使煤燃烧过程S迁移规律（如石灰石的脱硫机理、SO3的生成等）变化很大，而目前尚缺少相关研究，尤其S的气固两相迁移定量化研究。采用小型流化床进行石灰石在O2/CO2/H2O气氛下的脱硫试验，获得水蒸气对石灰石脱硫途径的影响机理；采用滴管炉模拟O2/CO2燃烧烟气中SO3生成的气相和气固异相反应实验，探明气氛、飞灰物理化学性质等参数对SO3生成的影响机理。在探明机理的基础上，进行多种燃料的循环流化床O2/CO2循环燃烧试验，通过气固流量和S组分的准确测量，获得S的气固两相迁移定量数据，建立S平衡方程。本项目对于掌握循环流化床O2/CO2燃烧过程中S的迁移机理及抑制硫氧化物的排放具有重要的理论价值和现实意义。

循环流化床O2/CO2燃烧技术是最具前景的燃煤电站CO2捕集方法之一。在O2/CO2燃烧湿烟气循环中，烟气再循环带来炉内CO2、SO2和H2O等组分的富集，使煤燃烧过程S迁移规律变化很大。深入理解S的气固两相迁移规律，对循环流化床O2/CO2燃烧技术的发展具有重要意义。本项目以富氧气氛下石灰石的脱硫机理和SO3的生成规律为主要研究对象，经过项目组3年研究得到了以下成果：探明水蒸气对石灰石脱硫途径的影响机理。O2/CO2气氛下水蒸气的存在对石灰石直接硫化及煅烧后硫化特性均有一定的影响。硫化反应初期水蒸气对石灰石直接硫化及煅烧后硫化几乎无影响，而在反应后期对硫化反应有显著的促进作用。水蒸气的存在促进了产物层内固态离子扩散，促进了反应的进行；开发研制了新型SO¬3控制冷凝法取样系统；研究气氛、飞灰物理化学性质等参数对 SO3 生成的影响机理。水蒸气的存在增加了-OH浓度，促进了SO3的生成反应。飞灰对SO3生成的影响规律主要取决于飞灰的组分；进行多种燃料的循环流化床O2/CO2循环燃烧试验，获得S的气固两相迁移定量数据。湿烟气循环可以提高石灰石的脱硫效率。循环流化床富氧燃烧过程中，SO3的生成主要来自于SO2的二次反应，较高的SO2、H2O浓度及飞灰较低的固硫能力有助于SO3的生成。本项目研究成果对于掌握循环流化床O2/CO2燃烧过程中S的迁移机理及抑制SO2/SO3的排放具有重要的理论和现实价值。