Two continuously regenerating diesel particulate filter(CRDPF) with different configurations and one particles oxidation catalyst(POC) were employed to perform experiments in a controlled laboratory setting to evaluate their effects on NO 2,smoke and particle number emissions.The results showed that the application of the after-treatments increased the emission ratios of NO 2 /NOx significantly.The results of smoke emissions and particle number(PN) emissions indicated that both CRDPFs had sufficient capacity to remove more than 90% of total particulate matter(PM) and more than 97% of solid particles.However,the POC was able to remove the organic components of total PM,and only partially to remove the carbonaceous particles with size less than 30 nm.The negligible effects of POC on larger particles were observed due to its honeycomb structure leads to an inadequate residence time to oxidize the solid particles or trap them.The particles removal efficiencies of CRDPFs had high degree of correlations with the emission ratio of NO 2 /NOx.The PN emission results from two CRDPFs indicated that more NO 2 generating in diesel oxidation catalyst section could obtain the higher removal efficiency of solid particles.However this also increased the risk of NO 2 exposure in atmosphere.
Regulated and unregulated emissions from four passenger cars fueled with methanol/gasoline blends at different mixing ratios (M15,M20,M30,M50,M85 and M100) were tested over the New European Driving Cycle (NEDC).Volatile organic compounds (VOCs) were sampled by Tenax TA and analyzed by thermal desorption-gas chromatograph/mass spectrometer (TD-GC/MS).Carbonyls were trapped on dinitrophenylhydrazine (DNPH) cartridges and analyzed by high performance liquid chromatography (HPLC).The results showed that total emissions of VOCs and BTEX (benzene,toluene,ethylbenzene,p,m,o-xylene) from all vehicles fueled with methanol/gasoline blends were lower than those from vehicles fueled with only gasoline.Compared to the baseline,the use of M85 decreased BTEX emissions by 97.4%,while the use of M15 decreased it by 19.7%.At low-to-middle mixing ratios (M15,M20,M30 and M50),formaldehyde emissions showed a slight increase while those of high mixing ratios (M85 and M100) were three times compared with the baseline gasoline only.When the vehicles were retrofitted with new three-way catalytic converters (TWC),emissions of carbon monoxide (CO),total hydrocarbon (THC),and nitrogen oxides (NOx) were decreased by 24%-50%,10%-35%,and 24%-58% respectively,compared with the cars using the original equipment manufacture (OEM) TWC.Using the new TWC,emissions of formaldehyde and BTEX were decreased,while those of other carbonyl increased.It is necessary that vehicles fueled with methanol/gasoline blends be retrofitted with a new TWC.In addition,the specific reactivity of emissions of vehicles fueled with M15 and retrofitted with the new TWC was reduced from 4.51 to 4.08 compared to the baseline vehicle.This indicates that the use of methanol/gasoline blend at a low mixing ratio may have lower effect on environment than gasoline.
Hong ZhaoYunshan GeJianwei TanHang YinJiadong GuoWei ZhaoPeipei Dai
Two after treatment units,selective catalytic reduction(SCR) and continuously regenerating trap(CRT),were independently retrofitted to a diesel engine,with the objective to investigate their impact on the conversion/reduction(CR) of polycyclic aromatic hydrocarbons(PAHs).The experiments were conducted under the European steady state cycle(ESC) first without any retrofits to get baseline emissions,and then with SCR and CRT respectively,on the same engine.The particulate matter(PM)-phase PAHs were trapped in fiberglass filters,whereas gas-phase PAHs were collected in cartridges,and then analyzed using a gas chromatograph-mass spectrometer(GC-MS).Both PM-phase and gas-phase PAHs were greatly reduced with CRT showing respective CR of 90.7% and above 80%,whereas only gas-phase PAHs were abated in the case of SCR,with CR of above 75%.Lower molecular weight(LMW) PAHs were in abundance,while naphthalene exhibited a maximum relative contribution(RC) to LMW-PAHs for all three cases.Further,the CR of naphthalene and anthracene were increased with increasing catalyst temperature of SCR,most likely due to their conversion to solid particles.Moreover,the Benzo[a]Pyrene equivalent(BaP eq) of PAHs was greatly reduced with CRT,owing to substantial reduction of total PAHs.
