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.

Degradation of o-dichlorobenzene by DBD-NTP co-modified titanium gel catalyst

In order to study the degradation process of dioxins in industrial flue gas,the decomposition of o-dichlorobenzene(o-DCB)in a DBD plasma catalytic reactor was investigated.The results showed that an NTP-catalyzed system,especially using the Cu Mn Ti Oxcatalyst,had better o-DCB degradation performance compared to plasma alone.The combination of the Cu Mn Ti Oxcatalyst with NTP can achieve a degradation efficiency of up to 97.2%for o-DCB;the selectivity of CO and CO_(2)and the carbon balance were 40%,45%,and 85%,respectively.The dielectric constant and electrical property results indicated that the surface discharge capacity of the catalysts played a major role in the degradation of o-DCB,and a higher dielectric constant could suppress the plasma expansion and enhance the duration of the plasma discharge per discharge cycle.According to the O1s XPS and O_(2)-TPD results,the conversion of CO to CO_(2)follows the M-v-K mechanism;thus,the active species on the catalyst surface play an important role.Moreover,the Cu Mn Ti Oxand NTP mixed system exhibited excellent stability,which is probably because Cu doping improved the lifetime of the catalyst.This work can provide an experimental and theoretical basis for research in the degradation of o-DCB by plasma catalyst systems.

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.