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 sur- face. It is feasible to capture alkali vapors with some additives such as silica,alumina,graphite,alumina,calcined lime- stone and so on. The bed material was chosen as the adsorbent,and the influences of reaction temperature,alkali con- centration 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 ad- sorption 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 cap- ture the sodium vapor in high-temperature flue gas.