贝壳与石灰石的微孔结构及其脱硫性能

Micro-Pore Structure and Desulphurization Characteristic of Ca-Based Absorbents

采用压汞仪对4种贝壳和2种石灰石的微观结构及孔径分布进行了测量,采用热重分析方法对各种脱硫剂的脱硫性能进行了测试.比较发现,贝壳煅烧后生成的氧化钙主要孔径范围在0.1～5 μm之间 ,比孔容较大.而石灰石煅烧后的主要孔径范围为0.005～0.1 μm,比表面积很大,但比孔容较小.由于贝壳中气孔直径大于0.1 μm,允许气体扩散至颗粒内部,气孔表面同时参加脱硫反应,且反应过程中不易被反应产物堵塞,脱硫反应进行较彻底,钙转化率比石灰石高.另外,在满足气体扩散的前提下,减小孔径尺寸,增加反应比表面积,将使该转化率提高.试验发现,内孔直径较大的贝壳,钙转化率较高,且贝壳中比表面积最大、当量直径最小的扇贝壳钙转化率最高.

The microstructure and the pore size distribution of 4 kinds of shells (scallop shell, trumpet shell, clam shell and ark shell) and 2 kinds of limestones were measured with pore master mercury porosimeter, and the desulphurization characteristics of above absorbents were tested with thermal-gravimetric analyzer. As a result, the calcium oxide from shells have higher pore volume with pore diameter above 0.1 μm, while the particles from limestones have lower pore volume with pore diameter between 0.005 to 0.1 μm, but the surface area are very high. The bigger pore which diameter is above 0.1 μm in shell has many advantages, such as fewer air-blocked pores, lower gas diffusing resistance, and almost simultaneous and completed reaction. So, the calcium conversion rates of the shells are greater than that of limestones. Under the condition of gas diffusion, it is effective for desulphurization to reduce the pore size and to increase the surface area. The test shows that the shells having bigger pore size get higher calcium conversion rate, and among the shells, the scallop shell has the highest calcium conversion rate as its bigger specific surface area.