Diesel Particulate Matter Removal Research Articles

Efficient simultaneous removal of diesel particulate matter and hydrocarbons from diesel exhaust gas at low temperatures over Cu–CeO2/Al2O3 coupling with dielectric barrier discharge plasma

Diesel particulate matter (DPM) and hydrocarbons (HCs) emitted from diesel engines have a negative affect on air quality and human health. Catalysts for oxidative removal of DPM and HCs are currently used universally but their low removal efficiency at low temperatures is a problem. In this study, Cu-doped CeO2 loaded on Al2O3 coupled with plasma was used to enhance low-temperature oxidation of DPM and HCs. Removals of DPM and HCs at 200 °C using the catalyst were as high as 90% with plasma but below 30% without plasma. Operando plasma diffuse reflectance infrared Fourier transform spectroscopy coupled with mass spectrometry was conducted to reveal the functional mechanism of the oxygen species in the DPM oxidation process. It was found that Cu–CeO2 can promote the formation of adsorbed oxygen ( – ) and terminal oxygen (M=O), which can react with DPM to form carbonates that are easily converted to gaseous CO2. Our results provide a practical plasma catalysis technology to obtain simultaneous removals of DPM and HCs at low temperatures.

A Fog-and-Tube Scrubber for the Removal of Diesel Particulate Matter from Engine Exhaust

ABSTRACT Diesel particulate matter (DPM), the solid portion of diesel exhaust, has been linked to a range of deleterious health impacts. While a number of control strategies have been effective at reducing DPM in some environments, exposure risks are still high in others such as underground mines. In prior work, a novel scrubber treatment that used fog to remove DPM from engine exhaust was successfully prototyped in bench-scale laboratory experiments. Here, for the first time, the treatment concept was scaled up and field tested in a stone mine. An exhaust blower was used to pull fog, diesel exhaust, and mine air through a 30.5-meter long tube, enabling coagulation of DPM and fog drops resulting in their subsequent removal. Excluding one of the eleven tests, which appeared to be an outlier, the results showed that this fog-and-tube scrubber removed an average of 63% of particles (11.5–154 nm) as compared to 18% in the control case (without fog), yielding an average improvement of 45%. Computer simulations suggest that the observed particle removal is predominantly due to rapid thermal coagulation between the DPM and fog drops, followed by removal of the DPM-laden drops via inertial impaction with the tube walls.

Atmospheric Pressure Plasma for Diesel Particulate Matter Treatment: A Review

The purification of diesel exhaust gas is of great importance to prevent the atmospheric emission of major pollutants such as diesel particulate matter and nitrogen oxides and meet the environmental regulations. The atmospheric-pressure plasma is attracting increasing interest and is a promising after-treatment technology for purifying diesel emission at low temperatures. However, when compared with the numerous publications on nitrogen oxides reduction by non-thermal plasma, using non-thermal plasma to particulate matter treatment have relatively limited. This work provides a comprehensive review of the plasma applications for diesel particulate matter treatment, including self-regenerating diesel particulate filter, diesel particulate matter removal, and simultaneous removal of diesel particulate matter and nitrogen oxides. The treatment of particulate matter from both simulated particulate matter sources and actual diesel engines also discussed in this comprehensive review. The challenge to this technology is limited energy consumption for plasma, which should be less than 5% (~30 J/L) of the overall fuel consumption. Until now, the atmospheric-pressure plasma has been no commercial implementation in diesel exhaust gas treatment, so more research is needed to be done in this field.

Effect of the Reaction Temperature on the Removal of Diesel Particulate Matter by Ozone Injection

This study seeks to investigate the removal efficiency of particulate matter (PM) from the actual diesel exhaust at various reaction temperatures by using non-thermal plasma (NTP). The effect of the reaction temperature on removal efficiency was reflected by the change in the concentration of particles in different modes and the weight fraction of volatile organics in PM. The Arrhenius equation was used to determine the apparent activation energies Ea of the soot in PM. In addition, the difference in the oxidation reaction at various reaction temperatures and the effect of NTP on the properties of PM were discussed. After considering the decreasing ranges of the total concentration and the weight of the PM, it was determined that 120 °C is the optimal temperature choice for PM removal. The decreasing range of the total concentration reached 57.13% and 66.79% of PM was removed when the PM is measured by weight. NTP has better effect on the removal of smaller particles. The weight fraction of the volatile fraction markedly decreases after the reaction and the apparent activation energy of soot noticeably decreased. The oxidizability of the excited species in NTP was enhanced with the increase of the reaction temperature. However, the excited species concentration declined concurrently, resulting in the occurrence of the optimized range of reaction temperature. The particles were removed by the oxidation that occurred on the surface of the primary particle and the disintegration of the structure of the particles.

Sustainable removal of particulate matter from diesel engine exhaust at low temperature using a plasma-catalytic method

There is a great need for a sustainable diesel particulate matter (DPM) removal approach to effectively control the emission of DPM over long term and to improve the efficiency of diesel engine. However, methods that are currently available either require a high operation temperature or an external device. Here, we report an optimized plasma-catalytic method for the sustainable removal of DPM at low temperature. Au catalyst, which was the most effective in the enhancement of DPM oxidation among the tested noble-metal catalysts, was introduced into the plasma reactor for the diesel engine test. We found that after 1.1h plasma processing, the performance of DPM removal in the condition of sole plasma (without a catalyst) was reduced due to the accumulation of precipitated DPM within the plasma reactor. As a result of an enhanced DPM oxidation efficiency due to the use of Au catalyst, the accumulation of precipitated DPM was inhibited and the performance of DPM removal was maintained until plasma was switched off (8h processing). Importantly, the maintained DPM removal caused an enriched CaSO4 deposition on the plasma-catalytic reactor, which further enhanced DPM oxidation efficiency. Thus, a sustained DPM removal performance over long term could be ensured.

Removal of DPM from an Air Stream Using Micron-Scale Droplets

ABSTRACTRespiratory exposures to diesel particulate matter (DPM) present health risks, particularly in confined environments with a relatively high number of emission sources. Despite a variety of existing control technologies, exposures in some occupational environments remain unacceptably high (e.g., underground mine environments), and new technologies and abatement strategies are needed. The physics of droplet-particle interactions suggests that micron-scale water drops can effectively scavenge DPM from an air stream. Here, experimental results are presented on DPM removal from a diesel exhaust stream using a fog of water droplets. Measured scavenging coefficients, based on both number density and mass, show that significant DPM removal is possible. The potential scavenging mechanisms at play are discussed, and insights are offered on future work necessary for scale-up of a fog-based exhaust treatment technology.

Measurements of Heat Release of Diesel PM for Advanced Thermal Management Strategies for DPF Regeneration

Diesel engines typically require diesel particulate filter (DPF) systems to reduce particulate matter (PM) emissions in order to meet increasingly stringent emission regulations. While there have been noticeable advances in DPF technology, significant efforts are still needed to develop optimum DPF regeneration strategies and achieve efficient removal of diesel PM. In particular, the development of an effective thermal management system is essential to prevent the potential failure of the DPF system by the thermal runaway during soot oxidation in DPF regeneration. In an effort to develop optimum thermal management strategies, this experimental investigation is concerned primarily with measuring the instantaneous rate of heat generation as well as the total amount of heat released during the oxidation of diesel PM containing different concentrations of soluble organic fraction (SOF). The experimental approach was to measure directly, by means of a differential scanning calorimeter (DSC), the amount of heat release during the thermal reactions of diesel PM with air and to elucidate differences in the heat release characteristics of diesel PM and surrogate (model) soot. The diesel samples were collected from a cordierite particulate filter, where PM emissions bypassing the exhaust pipe of a light-duty diesel engine were deposited. Furthermore, a thermogravimetric analyzer (TGA) was used to obtain dry diesel soot samples with no volatile components present. The DSC experiments revealed that the amounts of heat released from the oxidation of SOF-containing diesel PM sample, dry diesel soot, and surrogate soot were approximately 14.67 kJ/g, 17.3 kJ/g, and 14.02 kJ/g, respectively, indicating that the largest heat release was obtained from the dry diesel soot sample. Results also indicated significant differences in the temporal rates of heat release in the oxidation of SOF-containing diesel PM, dry diesel soot, and surrogate soot. In particular, significant differences were found on the results for dry diesel soot samples with respect to the oxidation temperatures of 550°C and below 550°C in air. The heat release rate profile for the 550°C case exhibited a continuous sharp decrease after the peak value, while those for the 535°C and 525°C cases indicated first a sharp decrease, followed by slow and then sharp decrease again. The present experimental data are expected to lead to better predictive tools for thermal energy distribution during DPF regeneration, and thus the development an optimum thermal management system for DPF systems.

On the Scale-Up of Uneven DBD Reactor on Removal of Diesel Particulate Matter

The scale-up of an uneven type of dielectric barrier discharge (DBD) reactor driven by a positive–negative pulse power supply for the removal of particulate matter (PM) from a diesel engine has been carried out. The scale of the uneven DBD reactor was changed by using three kinds of reactors consisting of 20, 30, or 50 pairs of uneven alumina and stainless steel plates. In this study, relations of energy injection into the above DBD reactors, PM removals, PM removal efficiencies with pair numbers have been investigated. The parameters in the kinetic model used to describe the PM removal are given.

Characterization of an uneven DBD reactor for diesel PM removal

AbstractAn uneven dielectric barrier discharge (DBD) reactor of 21 electrode pairs that can improve the energy efficiency for the removal of particulate matter (PM) from a diesel engine is characterized. Ninety percent of PM (about 0.48 g/h) is removed by plasma discharges at an energy injection of 90 W into an exhaust gas (40 Nm3/h with PM emission rate 0.53 g/h). The discharge properties and relations of PM removal and energy efficiency with energy injection are given. The fuel penalty due to the use of the uneven DBD reactor is estimated. Comparison with other types of DBD reactors is carried out. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd.

Simultaneous removal of NOx and fine diesel particulate matter (DPM) by electrostatic water spraying scrubber

In this study, experiments were performed with an electrostatic water spraying scrubber to evaluate its effectiveness for simultaneous removal of NOx and Diesel Particulate Matter (DPM) emissions in marine exhaust gas. The effects of several parameters, such corona power, gas flow rate and engine load, on the contaminant removals have been investigated intensively. The present study shows that for a given gas flow rate, the removal of DPM is enhanced with the increase of applied voltage. Total DPM removal efficiency was higher than 97% by electrostatic attraction, DPM with a range smaller than 1Όm is removed for higher efficiency. NO, NOx were removed with values higher than 20%, depending on Cl- concentration in the seawater and engine loads. As a result, the electrostatic water spraying scrubber would appear to be a promising alternative method for control of mass-based, as well as number-based DPM emissions.

Control of Diesel Gaseous and Particulate Emissions with a Tube-Type Wet Electrostatic Precipitator

Abstract In this study, experiments were performed with a bench-scale tube-type wet electrostatic precipitator (wESPs) to investigate its effectiveness for the removal of mass- and number-based diesel particulate matter (DPM), hydrocarbons (HCs), carbon monoxide (CO), and oxides of nitrogen (NOx) from diesel exhaust emissions. The concentration of ozone (O3) present in the exhaust that underwent a nonthermal plasma treatment process inside the wESP was also measured. A nonroad diesel generator operating at varying load conditions was used as a stationary diesel emission source. The DPM mass analysis was conducted by means of isokinetic sampling and the DPM mass concentration was determined by a gravimetric method. An electrical low-pressure impactor (ELPI) was used to quantify the DPM number concentration. The HC compounds, n-alkanes, and polycyclic aromatic hydrocarbons (PAHs) were collected on a moisture-free quartz filter together with a PUF/XAD/PUF cartridge and extracted in dichloromethane with sonication. Gas chromatography (GC)/mass spectroscopy (MS) was used to determine HC concentrations in the extracted solution. A calibrated gas combustion analyzer (Testo 350) and an O3 analyzer were used for quantifying the inlet and outlet concentrations of CO and NOx (nitric oxide [NO] + nitrogen dioxide [NO2]), and O3 in the diesel exhaust stream. The wESP was capable of removing approximately 67–86% of mass- and number-based DPM at a 100% exhaust volumetric flow rate generated from 0- to 75-kW engine loads. At 75-kW engine load, increasing gas residence time from approximately 0.1 to 0.4 sec led to a significant increase of DPM removal efficiency from approximately 67 to more than 90%. The removal of n-alkanes, 16 PAHs, and CO in the wESP ranged from 31 to 57% and 5 to 38%, respectively. The use of the wESP did not significantly affect NOx concentration in diesel exhaust. The O3 concentration in diesel exhaust was measured to be less than 1 ppm. The main mechanisms responsible for the removal of these pollutants from diesel exhaust are discussed.

Control of Diesel Gaseous and Particulate Emissions with a Tube-Type Wet Electrostatic Precipitator

In this study, experiments were performed with a bench-scale tube-type wet electrostatic precipitator (wESPs) to investigate its effectiveness for the removal of mass- and number-based diesel particulate matter (DPM), hydrocarbons (HCs), carbon monoxide (CO), and oxides of nitrogen (NOx) from diesel exhaust emissions. The concentration of ozone (O3) present in the exhaust that underwent a nonthermal plasma treatment process inside the wESP was also measured. A nonroad diesel generator operating at varying load conditions was used as a stationary diesel emission source. The DPM mass analysis was conducted by means of isokinetic sampling and the DPM mass concentration was determined by a gravimetric method. An electrical low-pressure impactor (ELPI) was used to quantify the DPM number concentration. The HC compounds, n-alkanes, and polycyclic aromatic hydrocarbons (PAHs) were collected on a moisture-free quartz filter together with a PUF/XAD/PUF cartridge and extracted in dichloromethane with sonication. Gas chromatography (GC)/mass spectroscopy (MS) was used to determine HC concentrations in the extracted solution. A calibrated gas combustion analyzer (Testo 350) and an O3 analyzer were used for quantifying the inlet and outlet concentrations of CO and NOx (nitric oxide [NO] + nitrogen dioxide [NO2]), and O3 in the diesel exhaust stream. The wESP was capable of removing approximately 67–86% of mass- and number-based DPM at a 100% exhaust volumetric flow rate generated from 0- to 75-kW engine loads. At 75-kW engine load, increasing gas residence time from approximately 0.1 to 0.4 sec led to a significant increase of DPM removal efficiency from approximately 67 to more than 90%. The removal of n-alkanes, 16 PAHs, and CO in the wESP ranged from 31 to 57% and 5 to 38%, respectively. The use of the wESP did not significantly affect NOx concentration in diesel exhaust. The O3 concentration in diesel exhaust was measured to be less than 1 ppm. The main mechanisms responsible for the removal of these pollutants from diesel exhaust are discussed.

Experimental investigation on diesel PM removal using uneven DBD reactors

AbstractThe removal of diesel particulate matter (PM) is experimentally carried out using two types of uneven dielectric barrier discharge (DBD) reactors driven by positive–negative pulse voltage power supplies. One uneven DBD reactor is fed with exhaust gases from a diesel engine at the exhaust gas temperature and another uneven DBD reactor is fed with PM dispersed in a gas mixture of oxygen and nitrogen at room temperature, where PM was collected from the exhaust gases of the diesel engine. PM emission rates, PM sizes, and PM oxidation products are measured using a PM emission rate monitor, a particle size spectrometer, and a gas chromatograph at various discharge energy densities. It has been found that most of PM is oxidized completely into gaseous products of CO and CO2 under plasma discharge conditions. © 2007 American Institute of Chemical Engineers AIChE J, 2007

Removal of diesel particulate matter (DPM) in a tubular wet electrostatic precipitator

In this study, experiments were performed with a tubular wet electrostatic precipitator (wESP) to evaluate its effectiveness for the removal of mass- and number-based DPM emissions. A nonroad diesel generator utilizing a low sulfur diesel fuel (500 ppm w) operating under varying load conditions was used as a stationary DPM emission source. The US EPA Method 5 “Sampling Method for Stationary Sources” and Method 1A “Sampling and Velocity Traverses for Stationary Sources with Small Stacks or Ducts” were adopted as reference methods for measurement of DPM mass concentration. An electrical low-pressure impactor (ELPI) was used to quantify the DPM number concentration in the diluted exhaust gas at each tested condition. The wESP was evaluated with respect to varying engine loads and to different operational control parameters, such as corona power and gas residence time, to determine their effect on overall removal efficiency. The results show that the removal efficiency of the wESP increased as the engine loads decreased principally due to an increase in gas residence time and a decrease in DPM concentrations. At a constant wESP voltage and engine load, the increase of gas residence time within the wESP led to a significant increase in total DPM removal efficiency. In addition, total DPM removal efficiency was found to be directly related to the corona power, with increasing removal efficiency measured for increases in corona power. The linear correlation of DPM effective migration velocity and superficial gas velocity was established and an empirical equation is given. The wESP appears to be a promising alternative method for control of mass-based as well as number-based DPM emissions.

Advances in the Development of Filterless Soot Deposition Systems for the Continuous Removal of Diesel Particulate Matter

A model catalytic converter system has been developed to investigate and characterize novel catalyst structures for filterless diesel particulate matter deposition and oxidation in modern heavy duty vehicle diesel engine exhaust systems. The particulate traps are designed for low exhaust gas back pressures and to avoid the clogging effects observed in ceramic filters. In experiments under realistic flow conditions deposition efficiencies of up to 70% have been achieved for submicrometer particles in stacks of corrugated stainless steel foil with microsphere surface coating. The model catalytic converter system is also used to study the reaction kinetics of soot oxidation and volatilization by oxygen and nitrogen oxides under a wide range of reaction conditions, for real diesel engine soot, different model soot substances, and different types of converter surfaces.