Sulfation of limestone under O2/H2O combustion conditions in circulating fluidized bed
Sulfation of limestone under O2/H2O combustion conditions in circulating fluidized bed
复制标题
DOI：
10.1016/j.ijggc.2020.102979
复制
发表时间：
2020-04-01
影响因子：
3.9
通讯作者：
Anthony, Edward J.
中科院分区：
文献类型：
--
作者：
Chen, Liang;Wang, Zhongrui;Anthony, Edward J.
O-2/H2O燃烧是新一代的富氧CO2捕集技术，具有比O-2/CO2燃烧更好的热力学性能和经济性。O-2/H2O燃烧的主要特点是使用O-2-蒸汽混合物作为氧化剂，因此，炉内H2O可高达80%。为了确定在循环流化床（CFB）锅炉中是否仍能使用石灰石原位捕集SO2，对其硫酸化行为进行了研究。利用恒温热重分析仪，研究了高H2O浓度、SO2浓度、温度和粒度对O-2/H2O燃烧条件下石灰石硫酸化反应的影响。在0- 80%的范围内，H_2O对快速硫酸化阶段的影响很小，但随着H_2O浓度的增加，缓慢硫酸化阶段的硫酸化速率提高。因此，尽管炉内H2O浓度很高，石灰石仍然可以用于在CFB锅炉的O-2/H2O燃烧中捕获SO2。H2O更可能促进CaSO 4产物层中的固态离子扩散，而不是促进SO2气体在颗粒孔隙中的扩散。在80%H_2O条件下，当烟气中SO_2浓度从0.15%增加到0.45%时，快速硫酸化阶段的硫酸化速率显著增加，而慢速硫酸化阶段的硫酸化速率变化不大。随着石灰石粒径从0.45 mm减小到0.075 mm，快速和慢速硫酸化阶段的硫酸化速率均显著增加。在840 ℃ ~ 930 ℃的试验范围内，O-2/H2O燃烧条件下SO2捕集的最佳温度约为900 ℃。
O-2/H2O combustion is a new generation of oxy-fuel technology for CO2 capture, offering better thermodynamic and economic performance than O-2/CO2 combustion. The main feature of O-2/H2O combustion is that an O-2-steam mixture is used as the oxidant and, as a result, H2O in the furnace can be as high as 80 %. To determine whether limestone can still be used to capture SO2 in-situ in circulating fluidized bed (CFB) boilers with such a high H2O concentration, its sulfation behavior was studied. Using a constant-temperature thermogravimetric analyzer, the influences of high H2O concentration, SO2 concentration, temperature and particle size on sulfation of limestone under O-2/H2O combustion were examined. The fast sulfation stage was hardly influenced by H2O over the entire range of 0-80 %, but the sulfation rate in the slow sulfation stage improved with the increase of H2O concentration. Therefore, limestone can still be used to capture SO2 in O-2/H2O combustion in CFB boilers, in spite of the high in-furnace H2O concentration. H2O is more likely to enhance the solid-state ion diffusion in the CaSO4 product layer, rather than the SO2 gas diffusion in the pores of the particles. Under conditions with 80 % H2O, when the SO2 concentration in the flue gas increased from 0.15 % to 0.45 %, the sulfation rate in the fast sulfation stage increased remarkably, while in the slow sulfation stage it barely changed. The sulfation rates in both the fast and slow sulfation stages were significantly increased with the decrease of limestone particle size from 0.45 mm to 0.075 mm. In the tested range of 840 degrees C-930 degrees C, the optimum temperature for SO2 capture under O-2/H2O combustion is about 900 degrees C.