Exhaust Gas Oxygen Concentration Research Articles

Dynamic behavior of Pd/Ca2AlMnO5+δ for purifying automotive exhaust gases under fluctuating oxygen concentration

Automotive exhaust gases containing harmful gases, such as hydrocarbons, CO, and NOx, are purified on a Pd-loaded catalyst. Since the purification efficiency depends on the oxygen concentration in the automotive exhaust gas, a material with a high oxygen storage performance is also essential for effectively purifying automotive exhaust gases. The present study demonstrates that the purification of the exhaust gases under fluctuating oxygen concentration proceeds efficiently on Pd/Ca2AlMnO5+δ which exhibits high oxygen release and storage capacities. Pd/Ca2AlMnO5+δ maintained reduction of NO to N2 for a longer time compared to conventional Pd/CeO2-ZrO2, under oxidative conditions. From the results obtained by combining operando and static X-ray absorption fine structure (XAFS) spectra, the valence state of the Mn species in the catalyst support was readily changed in response to the oxygen concentration in the exhaust gas, rather than that of the Pd species. In other words, the redox properties of the Mn species in Pd/Ca2AlMnO5+δ concern the NO reduction behavior under fluctuating oxygen concentration.

Circulating jet for enhancing the mass transfer in a gas–liquid stirred tank reactor

AbstractThere are some problems in gas–liquid stirred tank reactor (STR), such as low mass transfer efficiency, high exhaust gas oxygen concentration, and low product conversion rate, due to limitations of stirring speed and input power. This article summarizes the effect of adding circulating jet internals on bubble size distribution, overall gas holdup, gas–liquid volumetric mass transfer coefficient, and power per unit volume of the STR. When circulating jet is added, the average bubble Sauter mean diameter in the STR is reduced to 1.26 mm, and the overall gas holdup is increased to 8.23%, which is an increase of 3.62 times of the original STR. The gas–liquid volumetric mass transfer coefficient is increased to 0.05556 s−1, which is 4.84 times of the original STR. The power per unit volume is increased by only 1.4 times. These data provide references for the design and scale‐up of new jet STRs.

Analysis of meat and bone meal clean combustion conditions

The combustion process of meat and bone meal (hereinafter referred to as MBM) must comply with a series of conditions and restrictions, which stem from environmental law and engineering, energy, and constructional requirements. To this end, a multi-dimensional analysis model was developed to determine the working area that provides optimal combustion process conditions. The input parameters consisted of the waste stream, exhaust gas oxygen concentration, and heat flux recovered as saturated steam. The limiting parameters of the MBM combustion process, such as the temperature of the exhaust gas after the post-combustion chamber, the temperature of the exhaust gas before the bag filter, and the exhaust gas residence time in the post-combustion chamber, constituted the output parameters. The results of the multi-dimensional analysis were visualized in terms of the distribution of the output parameter values obtained from the input parameter function. Based on a comparison of every output parameter to its corresponding limit value, optimal working areas of the thermal waste treatment system were defined. The research reveals that it is possible to determine the MBM combustion optimal working area that complies with all of the conditions and restrictions. It is worth understanding this working area during the design and construction of thermal waste treatment systems. The multi-dimensional analysis model has been verified under industrial conditions at a real MBM combustion facility.

물 10%가 혼합된 유화연료유를 적용한 Bunker-C유 보일러버너의 황산화물(SO2)저감 실험적 연구

Recently air pollution is becoming a global environment issue. Especially, the smoke from engines and boiler systems, which burn fossil fuels directly, is an extremely serious issue. For this reason, IMO is tightening regulations for the control of NOSUBx/SUB and SOSUBx/SUB. Therefore, in this study, the SO₂ reduction effect of emulsified oil mixed with 10% of water was tested after applying the emulsified oil to an industrial boiler burner using Bunker-C oil. The study showed that the exhaust gas oxygen concentration of emulsified oil was nearly 1.3% high and this was identified by the effect of dissolved oxygen contained in water. Also, based on the standard oxygen concentration(4%), the average SO₂ reduction rates were 28.54%, which means the reduction efficiency was high.

Bunker-C유를 사용하는 보일러버너에 적용한 유화연료유의 질소산화물(NOx) 저감 효과에 관한 실험적 연구

Recently air pollution is becoming a global environment issue. Especially, the smoke from engines and boiler systems, which burn fossil fuels directly, is an extremely serious issue. For this reason, IMO is tightening regulations for the control of NOx and SOx. Therefore, in this study, the NOx reduction effect of emulsified oil mixed with 10% of water was tested after applying the emulsified oil to an industrial boiler burner using Bunker-C oil. The study showed that the exhaust gas oxygen concentration of emulsified oil was nearly 1.3% high and this was identified by the effect of dissolved oxygen contained in water. Also, based on the standard oxygen concentration(4%), the average and maximum NOx reduction rates were 28.53% and 30.23% respectively, which means the reduction efficiency was very high.

An Experimental Investigation on the NO and CO Emission Characteristics of a Swirl Convergent-Divergent Nozzle at Elevated Pressure

The behavior of the pollutants NO and CO at elevated combustor pressure are of special importance due to the continuing trend toward developing engines operating at higher pressure ratios to yield higher thermal efficiency. An experiment was performed to examine the NO and CO emissions for a swirl convergent-divergent nozzle at elevated pressure. The NO and CO correlations were obtained. Meanwhile, the flame length, exhaust gas oxygen concentration, exit temperature and global flame residence time were also determined to analyze the NO and CO emission characteristics. The results showed that, with the increase in combustor pressure P, flame length decreased proportionally to P−0.49; exit O2 volume fraction increased and exit temperature was reduced. The global flame residence time decreased proportionally to P−0.43. As pressure increased, The NO and Emission Index of NO (EINO) levels decreased proportionally to P−0.53 and P−0.6 respectively, which is mainly attributed to the influence of global flame residence time; the NO and EINO increased almost proportionally with the increase in global flame residence time. The EINO scaling EINO (ρue/d) was proportional to Fr0.42, which indicated that compared with pure fuel, the fuel diluted with primary air can cause a decrease in the exponent of the Fr power function. At higher pressure, the CO and Emission Index of CO (EICO) decreased proportionally to P−0.35 and P−0.4, respectively, due to the increased unburned methane and high pressure which accelerated chemical reaction kinetics to promote the conversion of CO to CO2.

Impact of Process Parameters on Oxygen-Bearing Low Concentration Coal Mine Methane Enrichment by Proportion Pressure Swing Adsorption

Conventional PSA methods with a single adsorbent can result in an explosive CH4 concentration of 5 to 15%, making low concentration coal mine methane (LCCMM) or risky in terms of safety at a concentration of 30%. Proportion Pressure Swing Adsorption (PPSA) is a new and safer enrichment method suggested for LCCMM enrichment that uses a mixture of active carbon (AC) and carbon molecular sieves (CMS) as adsorbents. The effect of adsorption Pressure, adsorption time and bed length on the PPSA process were investigated to verify the feasibility of this method. The experiment results show that the methane concentration in desorption gas and the oxygen concentration in exhaust gas increased and decreased, respectively, with an increase in adsorption pressure or bed length. And the methane concentration in desorption gas is increased with the adsorption time expanding, but the recovery of methane is reduced. So the methane concentration in desorption gas can be increased to more than 30% and the oxygen concentration in exhaust gas be decrease to less than 12% by increasing the adsorption pressure or lengthening the bed.

Oxygen Concentration Dynamic Model and Observer-Based Estimation Through a Diesel Engine Aftertreatment System

Due to the chemical reactions occurring inside the diesel oxidation catalysts (DOCs) and diesel particulate filters (DPFs) that are commonly equipped on diesel engines, the exhaust gas oxygen concentrations considerably vary through the aftertreatment systems. Oxygen concentration in exhaust gas is important for the performance of catalysts such as the NOx conversion efficiencies of the selective catalytic reduction systems and lean NOx traps. Moreover, in the presence of a low-pressure loop exhaust gas recirculation, the exhaust gas oxygen concentration after DPF also influences the in-cylinder combustion. From system control, estimation, and analysis viewpoints, it is thus imperative to have a control-oriented model to describe the oxygen concentration dynamics across the DOC and DPF. In this paper, a physics-based, lumped-parameter, control-oriented DOC–DPF oxygen concentration dynamic model was developed with a multi-objective optimization method and validated with the experimental data obtained on a medium-duty diesel engine equipped with a full suite of aftertreatment systems. Experimental results show that the model can well capture the oxygen dynamics across the diesel engine aftertreatment systems. As an application of the experimentally validated model, an observer was designed to estimate the DOC-out and DPF-out oxygen concentrations in real time. Experimental results show that the estimated states from the proposed observer can converge to the measured signals fastly and accurately.

Performance and emissions of motorcycle engines using water-fuel emulsions

This article studied water?gasoline emulsions for reducing the NOx emissions of a motorcycle engine. Emulsified gasoline fuels of 0, 5, 10 and 15% water by volume were used in a four-stroke, 125 cc, port injection, spark-ignition engine. Both full throttle speed ranging from 2,000 to 7,000 rpm and low load were tested. The engine torque, fuel consumption, exhaust emissions and combustion characteristics were investigated. The experimental results show that the engine torque and fuel consumption are improved for 5 and 10% water emulsions. However, at 15%, the engine torque and fuel consumption deteriorate and the exhaust temperature is increased owing to slow burn rate. The exhaust emissions of NOx and CO decrease as the water percentage in the emulsion increases. A higher oxygen concentration in exhaust gas of emulsified fuel was found, which results in lower CO emission. The HC emission is increased with increasing water content, which might be caused by the thicker quench layer of emulsified fuel combustion. An appropriate concentration of water in the emulsified gasoline fuel for a 125 cc motorcycle engine is found to be 10%.