蒸汽活化生物质焦吸附模拟烟气中SO2和NO的研究

以麦秆和稻壳生物质为研究对象,在不同的热解温度、热解速率以及蒸汽活化温度条件下制备了生物质焦,采用比表面积与孔隙度分析仪测定生物质焦的比表面积和孔隙结构参数。利用固定床吸附装置,研究了热解温度、热解速率、活化温度和模拟烟气中SO₂和NO浓度等因素对生物质焦吸附SO₂和NO性能的影响。结果表明,蒸汽活化可以显著提高生物质焦的BET比表面积、D-R比表面积、D-R微孔容积和总孔容,降低其平均孔径,并显著增加蒸汽活化生物质焦对SO₂与NO吸附的起始穿透时间和吸附量。快速热解下制得的蒸汽活化焦对SO₂和NO的吸附效果优于慢速热解,热解温度为873 K的蒸汽活化焦的吸附性能明显好于热解温度为673与1 073 K的蒸汽活化焦。在973~1 173 K下,随着蒸汽活化温度的提高,蒸汽活化生物质焦对SO₂和NO的吸附量呈现先上升后下降的趋势。随着模拟烟气中SO₂与NO浓度的降低,蒸汽活化生物质焦对SO₂与NO吸附的起始穿透时间延长,但相应的SO₂和NO吸附量下降。在873 K、快速热解和1 073 K条件下制得的蒸汽活化麦秆焦对SO₂和NO吸附量最大,其值分别为109.02和21.77 mg/g。

Adsorption characteristics of SO2 and NO in a simulated flue gas over the steam activated biomass chars

Biomass chars were prepared under different pyrolysis temperatures, pyrolysis rates (rapid and slow pyrolysis) and steam activation temperatures from wheat straw and rice husk; their surface area and pore structure parameters were measured by nitrogen sorption at 77 K. The effects of pyrolysis temperature, pyrolysis rate, steam activation temperature as well as the concentration of SO₂ and NO in a simulated flue gas on the adsorption characteristics of SO₂ and NO over the biomass chars were carried out in a fixed-bed adsorber. The results indicated that the steam activation can significantly increase the surface area, micropore volume and total pore volume of biomass chars, while decrease their average pore sizes; as a result, the breakthrough time and adsorption capacities of SO₂ and NO over the activated biomass chars are increased. Moreover, rapid pyrolysis gives the biomass chars better adsorption characteristics than slow pyrolysis. A pyrolysis temperature of 873 K is superior to 673 and 1 073 K to get biomass chars of high adsorption performance for SO₂ and NO. Similarly, there also exists an optimum steam activation temperature between 973 and 1 173 K to prepare activated biomass chars of high adsorption performance. The breakthrough time increases but the adsorption capacities of SO₂ and NO decrease with the decrease of the concentration of SO₂ and NO in the simulated flue gas. The wheat straw char prepared under the conditions of rapid pyrolysis, pyrolysis temperature of 873 K, and steam activation temperature of 1 073 K performs best for the adsorption of SO₂ and NO; over it, the adsorption capacities of SO₂ and NO reach 109.02 and 21.77 mg/g, respectively.