Diesel Exhaust Gas Research Articles

Synergetic effects of plasma and metal oxide catalysts on diesel soot oxidation

The synergetic effects of a pin-to-plate corona plasma and Mn, Co and Fe oxide catalysts on soot oxidation were investigated under diesel exhaust gas conditions of 10% oxygen and 180–350°C. The catalysts were synthesized by a precipitation method and characterized by XRD, BET surface area, SEM, EDX mapping, and temperature programmed methods of H2-reduction, O2-desorption and oxidation. The effects of energy injection, gas temperature, NOx, and water vapor were investigated on the soot removal efficiency in the absence and presence of catalysts. Both tight and in-situ catalyst–soot contacts were examined. NOx as the most hazardous pollutant in the diesel exhaust gas is completely removed in plasma. In the presence of the catalyst, the soot removal efficiency and selectivity to CO2 enhance by up to 77 and 29%, respectively, as compared to those in the plasma alone. The highest removal efficiency and CO2 selectivity are obtained on manganese and iron oxides at high and low temperatures, respectively. 49.3 and 17.4% enhancements of energy efficiency are observed, when 3.5% H2O vapor or 450ppm NOx is added to the plasma–MnOx catalysis system at 5.7W and 300°C, respectively. High energy efficiencies at very low energy injections are the advantages of this study.

Use of a µ-Scale Synthetic Gas Bench for Direct Comparison of Urea-SCR and NH3-SCR Reactions over an Oxide Based Powdered Catalyst

The selective catalytic reduction (SCR) of NOx by NH3 has been extensively studied in the literature, mainly because of its high potential to remediate the pollution of diesel exhaust gases. The implementation of the NH3-SCR process into passenger cars requires the use of an ammonia precursor, provided by a urea aqueous solution in the conventional process. Although the thermal decomposition and hydrolysis mechanisms of urea are well documented in the literature, the influence of the direct use of urea on the NOx reduction over SCR catalysts may be problematic. With the aim to evaluate prototype powdered catalysts, a specific synthetic gas bench adjusted to powdered material was developed, allowing the use of NH3 or urea as reductant for direct comparison. The design of the experimental setup allows vaporization of liquid urea at 200 °C under 10 bar using an HPLC pump and a micro injector of 50 μm diameter. This work presents the experimental setup of the catalytic test and some remarkable catalytic results towards further development of new catalytic formulations specifically dedicated to urea-SCR. Indeed, a possible divergence in terms of DeNOx efficiency is evidenced depending on the nature of the reductant, NH3 or urea solution. Particularly, the evaluated catalyst may not allow an optimal NOx conversion because of a lack in ammonia availability when the urea residence time is shortened. This is attributed to insufficient activity of isocyanic acid (HNCO) hydrolysis, which can be improved by addition upstream of an active solid for the hydrolysis reaction such as ZrO2. Thus, this µ-scale synthetic gas bench adjusted to powdered materials enables the specific behaviour of urea use for NOx reduction to be demonstrated.

Reduction of NOx and PM in marine diesel engine exhaust gas using microwave plasma

Abatement of NOx and particulate matters (PM) of marine diesel exhaust gas using microwave (MW) non-thermal plasma is presented in this paper. NOx mainly consist of NO and less concentration of NO2 in a typical two stoke marine diesel engine and microwave plasma generation can completely remove NO. MW was generated using two 2kW microwave sources and a saw tooth passive electrode. Passive electrode was used to generate high electric field region within microwave environment where high energetic electrons (1-3eV) are produced for the generation of non-thermal plasma (NTP). 2kW gen-set diesel exhaust gas was used to test our pilot-scale MW plasma reactor. The experimental results show that almost 100% removal of NO is possible for the exhaust gas flow rate of 60l/s. It was also shown that MW can significantly remove soot particles (PM, 10nm to 365nm) entrained in the exhaust gas of 200kW marine diesel engine with 40% engine load and gas flow rate of 130l/s. MW without generating plasma showed reduction up to 50% reduction of PM and with the plasma up to 90% reduction. The major challenge in these experiments was that igniting the desired plasma and sustaining it with passive electrodes for longer period (10s of minutes) as it required fine tuning of electrode position, which was influenced by many factors such as gas flow rate, geometry of reactor and MW power.

Electron beam treatment of simulated marine diesel exhaust gases

Abstract The exhaust gases from marine diesel engines contain high SO2 and NOx concentration. The applicability of the electron beam flue gas treatment technology for purification of marine diesel exhaust gases containing high SO2 and NOx concentration gases was the main goal of this paper. The study was performed in the laboratory plant with NOx concentration up to 1700 ppmv and SO2 concentration up to 1000 ppmv. Such high NOx and SO2 concentrations were observed in the exhaust gases from marine high-power diesel engines fuelled with different heavy fuel oils. In the first part of study the simulated exhaust gases were irradiated by the electron beam from accelerator. The simultaneous removal of SO2 and NOx were obtained and their removal efficiencies strongly depend on irradiation dose and inlet NOx concentration. For NOx concentrations above 800 ppmv low removal efficiencies were obtained even if applied high doses. In the second part of study the irradiated gases were directed to the seawater scrubber for further purification. The scrubbing process enhances removal efficiencies of both pollutants. The SO2 removal efficiencies above 98.5% were obtained with irradiation dose greater than 5.3 kGy. For inlet NOx concentrations of 1700 ppmv the NOx removal efficiency about 51% was obtained with dose greater than 8.8 kGy. Methods for further increase of NOx removal efficiency are presented in the paper.

The effect of iron loading and hydrothermal aging on one-pot synthesized Fe/SAPO-34 for ammonia SCR

The current commercially-available technique for NOx reduction for diesel engines is the selective catalytic reduction (SCR) of NOx with NH3 over Cu zeolites. One of the problems of this technique is their limited ability to convert NOx at diesel particulate filter (DPF) regeneration temperatures. In addition, during regeneration of the DPF there is a risk of thermally deactivating the SCR catalyst. Thus, the aim of the current work was the development of a catalytic system that can reduce NOx both at low as well as high temperature and in addition is stable at high temperature. In order to reach this goal, a Fe/SAPO-34 with chabazite (CHA) structure was combined in a system with a commercial Cu/CHA catalyst. Earlier studies have shown that it is difficult to ion-exchange Fe into CHA structures due to steric hindrance, and we have therefore used a novel synthesis procedure which incorporated iron directly into the zeolite structure. Fe/SAPO-34 with three different Fe-loadings (0.27; 0.47 and 1.03wt.% Fe) were synthesized and the catalysts were characterized using inductively coupled plasma atomic spectroscopy (ICP-AES), N2 adsorption–desorption isotherms, BET area measurements and X-ray diffraction (XRD). The chemical composition, porous and crystalline structure of the parent SAPO-34 sample were found to be only slightly affected by addition of small amounts of Fe in the framework zeolite structure. However, more visible changes in the crystallinity were observed in the Fe/SAPO-34 catalysts with higher Fe content, which were attributed to the unit cell size expansion provoked by integration of higher amounts of Fe into the zeolite SAPO-34 framework. The Fe/SAPO-34 with the lowest Fe-loading (0.27wt.%) was found to be the best catalyst when considering activity as well as high temperature stability. The synthesized Fe/SAPO-34 catalyst demonstrated a significantly improved NOx reduction performance at high temperatures (600–750°C) when compared to a commercial Cu/CHA SCR system, and the combined system (Fe/SAPO-34+Cu/CHA) exhibited a very good performance in a large temperature interval (200–800°C) that encompasses most diesel exhaust gas conditions.

Impact of sulfation and desulfation on NOx reduction using Cu-chabazite SCR catalysts

This bench reactor study investigates the impact of gaseous sulfur on the NOx reduction activity of Cu-chabazite SCR (Cu-CHA) catalysts at SO2 concentrations representative of marine diesel engine exhaust. After 2h of 500ppm SO2 exposure at 250 and 400°C in the simulated diesel exhaust gases, the NOx reduction activity of the sulfated Cu-CHA SCR catalysts is severely degraded at evaluation temperatures below 250°C; however, above 250°C the impact of sulfur exposure is minimal. EPMA shows that sulfur is located throughout the washcoat and along the entire length of the sulfated samples. Interestingly, BET measurements reveal that the sulfated samples have a 20% decrease in surface area. Furthermore, the sulfated samples show a decrease in NOx/nitrate absorption during NO exposure in a DRIFTS reactor which suggests that Cu sites in the catalyst are blocked by the presence of sulfur. SO2 exposure also results in an increase in NH3 storage capacity, possibly due to the formation of ammonium sulfate species in the sulfated samples. In all cases, lean thermal treatments as low as 500°C reverse the effects of sulfur exposure and restore the NOx reduction activity of the Cu-CHA catalyst to that of the fresh condition.

Air Contaminants Associated with Potential Respiratory Effects from Unconventional Resource Development Activities

Unconventional natural gas development uses horizontal drilling in conjunction with hydraulic fracturing to gain access to natural gas deposits which may be tightly held in shale deposits and unavailable to conventional vertical drilling operations. The intensive work required to extract this source of energy results in higher than usual numbers of vehicles involved, potential release of emissions from those vehicles in congested zones surrounding the drill site, and release of other contaminants from materials drawn back out of the borehole after fracturing of the shale. Typical contaminants would be diesel exhaust particulate and gases, volatile organic compounds and other hydrocarbons both from diesels and the drilling process, crystalline silica, used as part of the hydraulic fracturing process in kiloton quantities, and methane escaping from the borehole and piping. A rise in respiratory disease with proximity to the process has been reported in nearby communities and both silica and diesel exposures at the worksite are recognized respiratory hazards. Because of the relatively short time this process has been used to the extent it is currently being used, it is not possible to draw detailed conclusions about the respiratory hazards that may be posed. However, based on the traffic volume associated with each drill site and the number of drill sites in any locale, it is possible at least to compare the effects to that of large traffic volume highways which are known to produce some respiratory effects in surrounding areas.

Numerical Study of Combustion and Emission Characteristics of a Diesel/Methanol Dual Fuel (DMDF) Engine

In comparison to the extensive experimental studies, numerical studies of a diesel/methanol dual fuel (DMDF) engine are very limited. In this work, an improved KIVA-3V code was coupled with the CHEMKIN solver to model combustion and emission of a DMDF engine. First, a chemical reaction mechanism including 65 reactions and 43 species was developed and validated with premixed flame species profiles. Second, new engine experiments at varied loads in both diesel and DMDF modes were performed to further validate the present model. Results show that the model predicts the engine combustion and emission in two modes well. At last, parameter studies on diesel injection timings and exhaust gas recirculation (EGR) rates were performed. Results show that the ignition delay time in DMDF mode is longer than that in diesel mode. Methanol supplied through the intake port significantly reduces soot emissions and slightly increases NOx emissions at different injection timings. In two modes, soot emissions are both formed ...

Theoretical research of ozonation influence on the soot content in the exhaust gases of diesel

In this paper we examine the effect of ozonation on the process of burning petroleum diesel fuel and diesel fuel of biological origin. The analysis of existing research in the field of ozonation of hydrocarbon fuels is conducted.The mechanism of formation of solid particles in the combustion chamber of a diesel engine is developed. A mathematical model describing the formation and soot burning in the combustion chamber of diesel engine is developed.The technique is developed and results of calculation of temperature, solids content and the rate of their formation in the combustion chamber of diesel engine are presented.As a result of work it is established that oxygen that included in the diesel fuel composition of biological origin intensifies the soot burning in the later stages of the combustion mixture, resulting in lower levels of particulate matter in diesel exhaust gases.

Ethanol-fueled low temperature combustion: A pathway to clean and efficient diesel engine cycles

Low temperature combustion (LTC) in diesel engines offers the benefits of ultra-low NOx and smoke emissions but suffers from lowered energy efficiency due to the high reactivity and low volatility of diesel fuel. Ethanol from renewable biomass provides a viable alternate to the petroleum based transportation fuels. The high resistance to auto-ignition (low reactivity) and its high volatility make ethanol a suitable fuel for low temperature combustion (LTC) in compression-ignition engines.In this work, a Premixed Pilot Assisted Combustion (PPAC) strategy comprising of the port fuel injection of ethanol, ignited with a single diesel pilot injection near the top dead centre has been investigated on a single-cylinder high compression ratio diesel engine. The impact of the diesel pilot injection timing, ethanol to diesel quantity ratio and exhaust gas recirculation on the emissions and efficiency are studied at 10 bar IMEP. With the lessons learnt, successful ethanol–diesel PPAC has been demonstrated up to a load of 18bar IMEP with ultra-low NOx and soot emissions across the full load range. The main challenge of PPAC is the reduced combustion efficiency especially at low loads; therefore, the authors have presented a combustion control strategy to allow high efficiency, clean combustion across the load range. This work entails to provide a detailed framework for the ethanol-fueled PPAC to be successfully implemented.

Dust, Radiation and Diesel Exhaust Exposures in Ontario Uranium Mines and Mills

Aim: The objective of this paper was to summarize a comprehensive survey of airborne dust, radiation, and diesel exhaust in two Ontario uranium mines which was conducted by the Occupational Health Protection Branch of Ontario Ministry of Health in 1974. Materials and Methods: About 1000 dust samples of various types were collected from the mine and mill areas under normal routine working conditions. Dust sampling was conducted using various sampling devices including midget impingers, konimeters, and both area and personal respirable dust samplers. About 400 measurements of radon daughter concentrations were made, usually in the same area where dust samples were taken. Diesel exhaust gases, carbon monoxide, formaldehyde, and oxides of nitrogen, were measured using Drager colorimetric tubes, as an index of diesel exposure. Unburnt carbon from diesel exhaust was determined from some of the dust samples. Results: The results show that dust exposure, including crystalline silica (α‑quartz), was generally higher than the recommended exposure limits of the time. Radon exposure was also in excess of the exposure limits of the time in some work areas. Diesel exhaust gases were mostly below the threshold limit value of the time. Conclusions: The data set described in this paper would be useful in future epidemiological or health studies of the uranium miners group for establishing the work‑relatedness for diseases such as lung cancer from radon exposure and silica, respiratory diseases such as silicosis and chronic obstructive pulmonary disease, and autoimmune diseases. It would also be useful in estimating exposure of individual miners for the assessment of compensation claims.

1420 ディーゼルエンジンから排出されるPMの静電集塵と非熱プラズマ分解による処理

Particulate matter (PM) emitted from diesel engines has harmful influences on human body and the regulations on the emission have become increasingly stringent. It is difficult for conventional electrostatic precipitators to treat the highly conductive PM in diesel exhaust gas. This study aims to achieve the electrostatic collection of PM with the electrode configuration that enables both the control of PM re-entrainment and the incineration of the collected PM with nonthermal plasma. The result of a basic PM collection test with DC corona discharge showed a collection efficiency of 76%.

Microwave Plasma System Design and Modelling for Marine Diesel Exhaust Gas Abatement of NOx and SOx

Microwave Plasma System Design and Modelling for Marine Diesel Exhaust Gas Abatement of NOx and SOx

Design, preparation and catalysis of the catalysts for oxidative elimination of soot particles (PM2.5) emitted from diesel-powered vehicle exhaust

The soot particles (PM2.5) in the exhaust gases emitted from diesel engines have led to serious environmental pollution problems. As one of the most efficient technologies for the treatment of soot particles from diesel engines, the catalytic purification technology has become a research hotspot now. However, development of efficient catalysts is the most active and important factor for catalytic purification technology. In this paper, the latest research progress of catalysts for the combustion of soot particles in diesel exhaust gases was summarized. The research results and progress (especially in our group) about design, preparation and catalysis mechanism of catalysts were mainly introduced, including low eutectic melting point catalysts, nano-catalysts, three-dimensional ordered macroporous (3DOM) catalysts and 3DOM metal oxide-supported noble metal catalysts. And the possible reaction mechanisms of soot combustion were reported. At last, some main problems and potential application prospects for soot combustion were also put forward.

In-situ hydrothermal synthesis of Cu-SSZ-13/cordierite for the catalytic removal of NOx from diesel vehicles by NH3

Cu-SSZ-13/cordierite monolithic catalyst was prepared by in situ hydrothermal synthesis method. The physicochemical properties of the as-prepared Cu-SSZ-13/cordierite were investigated by X-ray diffraction analysis, scanning electron microscopy, transmission electron microscopy, N2-adsorption, inductively coupled plasma, X-ray photoelectron spectroscopy, and solid-state NMR techniques. The removal of nitrogen oxides (NOx) from simulated diesel vehicle exhaust gas was performed using fixed-bed reactor. The effects of crystallization time and addition of HF during hydrothermal synthesis, reaction space velocity, and aging treatment of catalyst on the catalytic performances of NOx reduction reactions were investigated. The results indicate that the optimum crystallization time was 72h. Highly crystalline structure of zeolite Cu-SSZ-13 was formed, in a close combination with a carrier, via one step hydrothermal process. Cu-SSZ-13/cordierite showed excellent DeNOx performance for selective catalytic reduction (SCR) and anti-aging properties in a simulated diesel exhaust gas under a high space velocity. At a high space velocity of 72,000h−1, the highest conversion and N2 selectivity of 94% and 90%, respectively, were achieved. After the aging for 50h at 720°C, NOx reduction rate was still >80% in the temperature range of 350–550°C. The larger height to diameter ratio of the same catalysts enhanced the NH3-SCR catalytic activity and broadened the active temperature window. The addition of HF increased the catalytic activity and anti-aging performance of the sample.

커먼레일 디젤엔진의 흡기 매니폴더 클리닝이 배기가스에 미치는 영향에 관한 연구

산업이 고도로 발달함으로 인하여 화석연료의 사용이 많아짐으로 인하여 환경문제가 대두되고 있으며, 이에 자동차의 매연에 대한 연구가 필요하다. 일반적으로 공기는 흡기 매니폴드를 통하여 엔진에 흡입된다. 따라서 본 연구에서는 매연증가와 출력저하의 하나의 원인이 되는 카본 퇴적물을 세척하여 노후 된 자동차의 배출가스의 저감과 출력향상, 배기가스 저감량, 출력변화 그리고 공전속도의 안정성을 분석 검토하는데 그 목적이 있다. 흡기 매니폴드 내의 카본을 클리닝하였을 때의 자동차 매연의 발생정도를 검사장비(KD147)를 통하여 분석하였다. 흡기 매니폴드 클리닝으로 매연의 감소효과가 있음을 확인하였다. 【Owing to highly developed industries and the use of fossil fuels, environmental problems becoming becoming pressing issues globally. Therefore, a study of automobile exhaust is urgently needed. Generally, air is sucked into the engine through the intake manifold. The aims of this study were to reduce the exhaust from used cars and increase the output by removing carbon deposits, which are considered a reason for the increasing exhaust and reduction of output, and the reduction of exhaust, variation of output and stability of idle speed were analyzed. The formation of carbon deposits within the suction manifold was investigated through a test device (KD147). In the intake manifold, the exhaust cleaning effect was confirmed.】

Chemical characterization and in vitro toxicity of diesel exhaust particulate matter generated under varying conditions.

Epidemiologic studies have linked diesel exhaust (DE) to cardiovascular and respiratory morbidity and mortality, as well as lung cancer. DE composition is known to vary with many factors, although it is unclear how this influences toxicity. We generated eight DE atmospheres by applying a 2×2×2 factorial design and altering three parameters in a controlled exposure facility: (1) engine load (27 vs 82 %), (2) particle aging (residence time ~5 s vs ~5 min prior to particle collection), and (3) oxidation (with or without ozonation during dilution). Selected exposure concentrations of both diesel exhaust particles (DEPs) and DE gases, DEP oxidative reactivity via DTT activity, and in vitro DEP toxicity in murine endothelial cells were measured for each DE atmosphere. Cell toxicity was assessed via measurement of cell proliferation (colony formation assay), cell viability (MTT assay), and wound healing (scratch assay). Differences in DE composition were observed as a function of engine load. The mean 1-nitropyrene concentration was 15 times higher and oxidative reactivity was two times higher for low engine load versus high load. There were no substantial differences in measured toxicity among the three DE exposure parameters. These results indicate that alteration of applied engine load shifts the composition and can modify the biological reactivity of DE. While engine conditions did not affect the selected in vitro toxicity measures, the change in oxidative reactivity suggests that toxicological studies with DE need to take into account engine conditions in characterizing biological effects.

Catalytic DPF microwave assisted active regeneration

In the last decades, diesel engines have attracted an increasing interest from vehicles producer and public, due to their higher thermal efficiency, less CO and unburned hydrocarbons emission, and longer lifetime comparing with gasoline engines. However, the high emission of soot particulates and NOx are still their key problems. The combination of filters and oxidation catalysts is one of the most effective after-treatment techniques to eliminate soot particles from the exhaust gases: the deposited catalyst lowers the soot ignition temperature from 550°C (uncatalyzed reaction) to the typical values of diesel exhaust gases (180–400°C).In our previous works we showed that the simultaneous use of a microwave (MW) applicator and a specifically catalyzed Diesel Particulate Filter (DPF), loaded up to 20wt% of Copper Ferrite (CuFe2O4), allows to reduce the temperature, the energy and the time required for the regeneration. Starting by these very promising results, in this work we continued to study in order to further improve the performances of the catalyzed DPF, reducing the temperature and minimizing the MW energy required for the regeneration. Furthermore we verified the feasibility of the MW technology by assessing the energy balance of the regeneration phase, comparing it to the actually employed regeneration technologies.

Effect of ammonia on the decomposition of ammonium formate over Au/TiO2 under oxidizing conditions relevant to SCR: Enhancement of formic acid decomposition rate and CO2 production

Ammonium formate (AmFo) and formic acid decomposition were carried out in the presence of excess O2 and H2O over 0.5wt% Au/TiO2 anatase monolithic catalysts using various contact times and temperatures between 160°C and 300°C, under spray conditions in a dedicated setup. A systematic investigation of ammonia influence on formic acid decomposition revealed a highly beneficial influence on the reaction rate and the CO2 yield in the temperature range 160–300°C. Ammonia oxidation did not occur at any of the studied temperatures and space velocities. Both AmFo and a stoichiometric ammonia–formic acid mixture exhibited identical homogeneous gas phase as well as heterogeneous catalytic decomposition behavior. With the introduction of ammonia at a concentration of only 0.25 molar equivalents, the pseudo-first-order rate constants for formic acid decomposition experienced close to 110% and 15% increase at 160°C and 260°C, respectively and dosing 12 molar equivalents of ammonia in the gas phase, the rate constants underwent nearly 8-fold increase at 160°C, while at 260°C, only two times increase was achieved. Increasing the ammonia to formic acid molar ratio from 0 to 12 lead to a steep increase in the CO2 yield from 18% to 75% at 160°C, while a relatively smaller rise from 60% to 75% was observed at 260°C. Activity testing of bare titania revealed an inhibitory effect of ammonia on formic acid decomposition to CO. Overall, it can be concluded that the presence of gold is critical for the realization of such an ammonia-induced enhancement of rate and CO2 yield. The obtained results are relevant for the application of formate-based ammonia precursor compounds in the selective catalytic reduction of NOx in Diesel exhaust gases.

Nitric Oxide Reduction of Heavy‐Duty Diesel Exhaust Gas by NH3‐SCR Upstream of the Turbocharger (Pre‐Turbo SCR)

Nitric Oxide Reduction of Heavy‐Duty Diesel Exhaust Gas by NH₃‐SCR Upstream of the Turbocharger (Pre‐Turbo SCR)