循环灰作为固体吸附剂脱除高温烟气中碱金属蒸汽研究

准东煤等高钠煤在使用过程中为避免由于碱金属(主要为钠钾盐)引起的锅炉沾污、结渣及腐蚀等问题。选择具有丰富空隙结构的循环灰作为高钠煤添加剂,并与碱金属盐(NaCl)进行掺混,分别采用热重分析仪(TGA)和马弗炉进行掺烧实验,研究了不同温度(800,850,900℃)、不同掺混比例(1%,2%,3%,5%,8%)下循环灰对碱金属盐的吸附特性。实验结果表明:在800,850,900℃下,分别以NaCl∶循环灰=8∶100的比例进行掺烧,分别在约125,65,30 min后质量达到稳定。马弗炉实验结果表明,在800,850,900℃及8%掺烧比例下,循环灰最终吸附NaCl的增重量可达5.56%,3.61%,2.96%,且随着温度升高,循环灰增重量呈下降趋势。相同温度下,循环灰增重量随着掺烧比例的增长几乎呈线性增加。随着温度的升高,相同掺烧比例下循环灰的增重量降低。实验证明,循环灰可有效吸附外部加入的NaCl,可以用作燃用高钠煤时吸收高温烟气中钠的添加剂。

Experimental study of adsorption of alkali in high temperature flue gas with bed material

Alkali in high-sodium coal causes a variety of problems including fouling，and the corrosion of heating surface.It is feasible to capture alkali vapors with some additives such as silica，alumina，graphite，alumina，calcined limestone and so on.The bed material was chosen as the adsorbent，and the influences of reaction temperature，alkali concentration on the adsorption of alkali with bed material were studied through experiments.The mixture of NaCl and bed material was heated in thermogravimetric analysis (TGA) and muffle furnace.The TG curves (8%NaCl+cycling ash) show that the alkali adsorption will reach the steady state in less than 125，68 and 25 minutes at 800，850 and 900 ℃ respectively.As temperature increases，the mixture weight reaches a steady state in a shorter time.In the capturing time of 125，65 and 30 minutes，the results of muffle furnace indicate a decreasing tendency of alkali adsorption with the increasing temperature at a range of 800-900 ℃.At the temperature of 800，850 and 900 ℃，bed materials can adsorb NaCl up to 5.56%，3.61% and 2.96% respectively of its own weight at the blending ratio of 8%.The alkali adsorption amount increases nearly linear while the blending ratio increases at the range of 1%-8%.The alkali adsorption amount decreases while the temperature increases at the same blending ratio.Experimental results show that the bed materials can effectively absorb the external addition of NaCl and it is feasible to be used as adsorbent to capture the sodium vapor in high-temperature flue gas.