Performance and mechanism of CO_(2) absorption during the simultaneous removal of SO_(2) and NO_(x) by wet scrubbing process

The co-removal of CO_(2)while removing SO_(2)and NOxfrom industrial flue gas has great potential of carbon emission reduction but related research is lacking.In this study,a wet scrubbing process with various urea solutions for desulfurization and denitrification was explored for the possibility of CO_(2)absorption.The results showed that the urea-additive solutions were efficient for NOxand SO_(2)abatement,but delivered<10%CO_(2)absorption efficiency.The addition of Ca(OH)_(2)dramatically enhanced the CO_(2)absorption,remained the desulfurization efficiency,unfortunately restricted the denitrification efficiency.Among various operating parameters,pH of solution played a determining role during the absorption.The contradictory pH demands of CO_(2)absorption and denitrification were observed and discussed in detail.A higher pH of solution than 10 was favorable for CO_(2)absorption,while the oxidizing of NO to NO_(2),NO_(2)^(-)or NO_(3)^(-)by NaClO_(2)was inhibited in this condition.When7<pH<10,it was favorable for the conversion and absorption of NO and NOx.However,the conversion of HCO_(3)^(-)to CO_(3)^(2-)was significantly inhibited,hence preventing the absorption of CO_(2).Large part of Ca(OH)_(2)became CaCO_(3)with a finer particle size,which covered the unreacted Ca(OH)_(2)surface after the reaction.Kinetic analysis showed that the CO_(2)absorption in urea-NaClO_(2)-Ca(OH)_(2)absorbent was controlled by chemical reaction in early stage,then by ash layer diffusion in later stage.

Activity enhancement of acetate precursor prepared on MnO_(x)-CeO_(2) catalyst for low-temperature NH_(3)-SCR: Effect of gaseous acetone addition

MnO_(x)-CeO_(2) catalysts are developed by hydrolysis driving redox method using acetate precursor(3 Mn1 Ce-Ac) and nitrate precursor(3 Mn1 Ce-N) for the selective catalytic reduction(SCR) of NO_(x) by NH_(3).A counterpart sample(Cop-3 Mn1 Ce) was prepared by the NH_(3)·H_(2) O co-precipitation method for comparison purpose.Combining the results of physicochemical properties characterization and performance test,we find that the 3 Mn1 Ce-Ac catalyst with some nanorod structures is highly active for the deNOx process.The SCR activity of the 3 Mn1 Ce-Ac catalyst is more admirable than the 3 Mn1 Ce-N and the Cop-3 Mn1 Ce catalysts due to plentiful Lewis acid sites,excellent low-temperature reducibility,and superior surface area resulted from O_(2) generation during the pre paration procedure.The 3 Mn1 Ce-Ac still exhibits the greatest performance for the deNO_(x )process when gaseous acetone is in the SCR feed gas.The NOx conversion and N2 selectivity over the 3 Mn1 Ce-Ac are both improved by gaseous acetone above150℃ due to the inhibition of SCR undesired side reactions(NSCR & C-O reactions) and "slow-SCR" process.