活化改性半焦用于烟气脱硫催化剂制备工艺优化

A new approach to optimizing the process of making desulfurized catalyst via the activated modified semi-coke

为研究不同制备工艺条件下的烟气脱硫催化剂吸附去除烟气中硫化物的性能,采用硝酸活化的半焦脱硫剂,通过穿透时间和硫容评价所制备催化剂的脱硫性能。采用固定床反应器考察了催化剂表面基团酸碱性、催化剂成型的制备顺序、黏结剂和催化剂尺寸及负载金属氧化物等制备工艺条件对催化剂脱硫性能的影响。结果表明:原料半焦表面呈碱性,半焦经硝酸氧化改性后,表面呈酸性,高温煅烧可以使半焦表面酸性官能团分解成碱性官能团,催化剂表面净碱量越大,脱硫性能越好;采取先将半焦成型再进行高温煅烧、水气活化的工艺,脱硫活性更高;最适合的黏结剂为煤焦油;最佳的催化剂粒径为3mm;烟气中通入O2能显著提高半焦吸附催化剂的脱硫性能,O2体积分数以5%为宜,烟气中适量H2O是脱硫必不可少的条件,水汽体积分数以8%最佳;在催化剂制备过程中添加质量分数为1%的V2O5,可以明显改善催化剂的脱硫性能。

This paper is aimed at introducing its exploration of the new approach to optimizing the process of making desulfurized catalyst via the activated modified semi-coke. To achieve the said purpose,we have first of all studied how the sulfide adsorption is affected by the different preparation conditions of the flue gas desulfurization catalyst. And,then,we have managed to activate the semi-coke desulfurizer through calculating the penetration time and the sulfur capacity by using the nitric acid and its desulfurization behavior. In addition,we have also analyzed all the parameters involved,such as the desulfurization performance of the catalyst; the acidity of the catalyst surface groups,the resulting sequence of the catalyst under study,the different binders,the catalyst size and supported metal oxides,etc.,with the fixed-bed reactor employed for evaluation. The results of our study show that the surface of the raw semi-coke is alkaline,whereas the modified semi-coke surface by nitric oxide should be acidic. The preparation process indicates that it is possible to break the acidic surface functional groups of the semi-coke into alkaline functional groups through high-temperature calcination. Thus,the net amount of alkali on the catalyst surface has been found favorable for the adsorptive removal of sulfide from the flue gas. As to the activated modified semi-coke catalyst, it can be prepared by molding and calcinating the semi-coke at the presence of water and oxygen at 700 ℃. Our experience also shows that the desulfurization activity of catalyst can be greatly improved via calcinating. The other involving factors are to be illustrated as follows：（ 1） While the most suitable binder can be said the coal tar,the optimal size of the catalyst to be used should be 3 mm.（ 2） Aerating the flue gas with oxygen can significantly improve the performance of semi-coke adsorption desulfurization catalyst,whereas the oxygen volume fraction should be 5%.（ 3） According to the testing results,we have found that the optimal water vapor volume rate is 8% with the flue desulfurized gas taken as an indispensable parameter. Moreover,we have also confirmed that adding a mass fraction of V2O5 at the rate 1% can significantly promote the performance of the desulfurized catalyst in its preparation process.