PM Removal Research Articles

Renewable Lanthanide Ionic Liquid/Polymer Composites for High‐Efficient Adsorption of Particulate Matter

AbstractParticulate matter (PM) in air pollution is becoming a serious environmental threat to public health globally. The removal of PM, particularly the most harmful PM2.5, is a great challenge for industrialized countries. Hybrid polymer materials have extensive applications in many areas. Herein, types of hybrid polymers obtained from lanthanide ionic liquids and polyvinyl pyrrolidone have excellent PM adsorption capacity especially for PM2.5. The highest adsorption efficiency can exceed 99% for both PM2.5 and PM10. The removal efficiency of PM can be maintained above 90% for 15 h, which can be recycled more than five times without the decline of adsorption efficiency. An introduced luminescent lanthanide can be used to survey the adsorption process by the change of fluorescence intensity. After simple treatment, the PM adsorption capacity of the hybrid polymer can be recovered to be similar with the new one. Besides, the hybrid polymers have favorable thermal stability to adapt to different working conditions. Therefore, the hybrid polymers have potential applications in a high‐efficiency and environmental friendly PM removal filter.

A new 3DOM Ce-Fe-Ti material for simultaneously catalytic removal of PM and NOx from diesel engines

A new 3DOM material was designed and synthesized for the simultaneous removal of PM (soot particulates) and NOx from diesel engine exhausts. The catalytic purification taking place over the material with double efficacy is cost-efficient. The contact between solid PM and catalyst active site has been process intensified by 3DOM unique structure. 3DOM Ce0.7Fe0.2Ti0.1O2 catalyst possess a high SCR activity and an excellent selectivity to N2, giving a maximum concentration of CO2 at 385°C for PM combustion and 100% NO conversion in the temperature range of 281–425°C. The dual redox cycles (Fe3++Ce3+↔Fe2++Ce4+,Fe3++Ti3+↔Fe2++Ti4+) and the excellent reducibility and sufficient acid sites of catalysts play key roles for the highly catalytic performance.

A numerical investigation of the effect of flue gas recirculation on the evolution of ultra-fine ash particles during pulverized coal char combustion

Flue gas recirculation (FGR) has been widely employed for NOx reduction. However, because PM removal in flue gas is never 100% efficient, a gradually accumulated particle concentration (particularly the ultra-fine particles, smaller than 1.0μm in aerodynamic diameter) may occur in the furnace, affecting PM emission and power plant operation. Experimental measurements cannot provide detailed information on the evolution of ultra-fine particle (including formation, and time-dependent growth and number size distribution). In this work, an improvement over our previous effort to model ultrafine particle formation during coal char combustion is developed and applied to elucidate the effects of various FGR parameters on ultrafine particle formation, including FGR ratio, dust removal efficiency, and particle size distribution in FGR. Model results show that FGR without recirculated particles results in the nucleation of fewer but larger particles. However, the presence of diluting FGR gases results in a low particle collision frequency and consequently yields small particle size and high number density after coalescence. The recirculated particles not only provide available surface area for condensable mineral vapors but also take part in coalescence via collision; consequently, larger particles are formed at a lower overall number density. The ultra-fine particle size first increases slowly with an increase in dust removal efficiency, but then drops rapidly after reaching a peak; An increase in recirculated particle size and a decrease in FGR results in increased particle size. For all cases, the particle number density shows opposite trends to particle size. Overall, the results derived here provide meaningful guidelines for practical application.

Numerical Simulation of Simultaneous Electrostatic Precipitation and Trace Gas Adsorption: Electrohydrodynamic Effects

Quasi-1-D analytical expressions for predicting the performance of electrostatic precipitators (ESPs) were developed from first principles decades ago and still find use in the present day, although significant simplifying assumptions are employed and manufacturers and operators still incorporate adjustable parameters to match field data. ESPs tasked with simultaneous particulate removal and trace gas-phase pollutant removal, however, represent a significant departure from their original operational mission. The present study extends our previous study of such ESP operations and uses the same computational platform to examine details of the multi-phase flow phenomena within ESPs as a function of the strength of the electro-hydrodynamic (EHD) fluid flow phenomena that can occur under high current density operating conditions or low fluid velocities. In particular, the results show good agreement between numerical simulation and classical ESP performance prediction equations at low current densities, and increasing divergence in predicted performance at higher current densities. Under the influence of EHD phenomena, the acceleration of the fluid by electric body forces effectively increases average fluid velocities through the ESP channel with the expected reduction in PM removal efficiency. The impact on trace pollutant is mixed, with both promotion and inhibition mechanisms associated with EHD phenomena identified.

Filtration properties of carbon woven fabric filters supplied with high voltage for removal of PM 1.0 particles

Abstract Electrostatic precipitation is combined with a carbon fabric filter to develop a novel filtration system with high collection efficiency for submicron particles while maintaining a pressure drop as low as 6–56 Pa. The effects of high voltages on the filtration properties of carbon woven fabric filters are investigated by varying the fabric areal density, face velocity, number of fabric layers, and environmental relative humidity (RH). The filtration performance tests show that the corona initiation voltage applied to carbon woven fabric should be higher than 20 kV in ambient condition, and filtration efficiency increases with the increasing of fabric areal density and supplied voltage. As the face velocity increases from 2 m/min to 4 m/min, the filtration efficiency at 30 and 40 kV decreases 13%. As the face velocity increases from 4 to 8 m/min, the filtration efficiency decreases much less. The filtration efficiency is not significantly influenced by the number of fabric layers but can be increased dramatically with the increasing of RH. The maximum filtration efficiency reaches 99.8% for PM 1.0 at high RH. Meanwhile, the corona inception voltage decreases to 10 kV as the RH increased from 40% to 95%.

Field Measurements on the Emission and Removal of PM2.5 from Coal-Fired Power Stations: 4. PM Removal Performance of Wet Electrostatic Precipitators

This study reports the impacts of two commercial wet electrostatic precipitators (WESPs) on the emission of fine particulate matter (PM2.5) and SO3. Field measurements were carried out at two 300 MW coal-fired power station units equipped with WESPs between limestone-gypsum wet flue gas desulfurization (WFGD) unit and the stack. PM samples were collected at the inlet and outlet of the WESPs as well as the inlet and outlet of the dry ESP, and SO3 was collected at the inlet and outlet of the WESP. The results show that 99.21% of the PM2.5 emitted from the boiler is removed in the dry ESP. The WFGD has a removal efficiency of 24.19% for PM2.5 but produces new gypsum particles and then increases the emission of PM1 (by ∼24%). PM at the WESP inlet is centered at 1 μm, and after passing through the WESP, concentrations of PM0.3, PM1, and PM2.5 are reduced by 73.72–93.75%, 83.33–94.41%, and 79.91–90.23%, respectively. SO3 emission is also reduced by the WESP due to the capture of H2SO4 via electrostatic force an...

Comparison of mathematical methods for the evaluation of wastewater settleability by settling column tests

ABSTRACTParticulate matter (PM), which may serve as a vector of pollutants in both natural and human-impacted waters, is of primary interest in water quality studies, particularly for those conducted in urban areas. Separating solids from the liquid phase is one of the main goals of water treatment practices. Above all, the settling process is the most commonly used for this purpose. Generally, settling column tests are used in the laboratory to assess the total PM removal. Besides the traditional graphical method used for the interpretation of the laboratory results, other mathematical methods were developed – with the goal of simplifying the settling efficiency evaluation procedure and making it less subjective. To make a contribution in that direction, a study based on the comparison of four different mathematical methods for estimating PM removal efficiencies was conducted. The analysis was carried out on 15 samples of wastewater and showed that only two methods gave satisfactory results, and only one of them was physically based. Consequently, it is recommended to assess the overall PM removal, Etot, by a monoparametric exponential function, depending on the settling time (t) and on the first-order decay coefficient (k).

In situ TG-MS study of NOx and soot removal over LNT model catalysts

The application of coupled thermogravimetric techniques allowed obtaining interesting information regarding NSR thermodynamic and kinetic for Pt-Ba/γ-Al2O3, Pt-K/γ-Al2O3 and Pt-Ba-K/γ-Al2O3 catalysts. The materials have been tested for simultaneous NOx and soot removal according to standard TRM protocol and soot combustion runs. The catalysts presented high performance in the individualized reaction of NOx reduction, soot oxidation and the simultaneous NOx and PM removal. The apparent activation energy calculated follows the order: Pt-Ba>Pt-Ba-K>Pt-K for O2 and NOx assisted soot combustion, being strongly influenced by the alkali element incorporation that shifts the maximum exothermal process to low temperature, improving the soot removal process.

Laboratory evaluation of electrostatic spray wet scrubber to control particulate matter emissions from poultry facilities

ABSTRACTParticulate matter (PM) is a major air pollutant from animal production with significant impacts on human health and the environment. Abatement of PM emissions is imperative and effective PM control technologies are strongly needed. In this work, an electrostatic spray wet scrubber (ESWS) technology designed for removal of PM (PM10 and PM2.5) emissions from poultry facilities was evaluated under simulated laboratory conditions. Effects of primary operating parameters – including charging voltage (0–14 kV), air speed (0.5–3.5 ms−1), droplet diameter (100–300 µm), and PM concentration (1–5 mg m−3) on the PM removal performance of the ESWS – were investigated. Predictive empirical models for PM10 and PM2.5 removal efficiencies were also developed. The preliminary results showed that the ESWS technology reduced emissions of PM10 by 85–94% and PM2.5 by 85–88% with a charging voltage of 7 kV, air speed of 0.5–0.75 m s−1, and droplet diameter of 100–150 µm. The water consumption rate was approximately 2.35 L min−1, while the total power consumed was 270 W. This study demonstrates that the ESWS could be a potentially effective and feasible tool in controlling PM emissions for commercial poultry facilities.

Roll-to-Roll Transfer of Electrospun Nanofiber Film for High-Efficiency Transparent Air Filter.

Particulate matter (PM) pollution in air has become a serious environmental issue calling for new type of filter technologies. Recently, we have demonstrated a highly efficient air filter by direct electrospinning of polymer fibers onto supporting mesh although its throughput is limited. Here, we demonstrate a high throughput method based on fast transfer of electrospun nanofiber film from roughed metal foil to a receiving mesh substrate. Compared with the direct electrospinning method, the transfer method is 10 times faster and has better filtration performance at the same transmittance, owing to the uniformity of transferred nanofiber film (>99.97% removal of PM2.5 at ∼73% of transmittance). With these advantages, large area freestanding nanofiber film and roll-to-roll production of air filter are demonstrated.

Synthesis and filtration properties of polyimide nanofiber membrane/carbon woven fabric sandwiched hot gas filters for removal of PM 2.5 particles

In this work, hot gas filters composed of polyimide nanofiber membrane sandwiched between carbon woven fabrics are fabricated to capture fine particles of PM 2.5 level. Polyimide (PI) nanofibers with an average diameter of 190nm are electrospun on supporting carbon fabrics as filtration layers. The filtration performance tests show that the maximum filtration efficiency reaches 99.99% for PM 2.5, while the maximum pressure drop is only 251.86Pa after continuously testing for 25min under a constant flow rate of 20L/min. As the areal density of the PI nanofiber membrane increases, the filtration efficiency increases first and then levels off when the areal density reaches 11.64g/m2. In regeneration performance test with back air flush at a pressure of 500KPa, the composite filter maintains a filtration efficiency of 99.99% and a pressure drop of about 410Pa. After heat treatment at 260 and 300°C, the composite filter shows a relatively high filtration efficiency while the tensile strength of the carbon fabric does not change significantly.

An experimental investigation of the PM adhesion characteristics in a fluidized bed type PM removal device

To remove PM2.5 effectively, we applied a fluidized bed to a PM2.5 removal device to take advantage of the adhesion force. An experimental study has been performed to investigate the effects of the PM diameter, PM inlet concentration and superficial gas velocity on the PM adhesion characteristics in a fluidized bed type PM2.5 removal device. The experimental results indicate that the collection efficiency of PM with a diameter of less than 2.25μm was 100% for a PM inlet concentration of several tens of mg/m3 and more than 90% at a PM inlet concentration of 100mg/m3, which is a high concentration. The collection efficiency of a PM with a diameter less than 2.25μm displays a nearly identical value under a superficial gas velocity of 0.3–0.5m/s. The reason why the collection of PM2.5 displays a higher efficiency is that the behavior of PM2.5 is mainly dominated by the adhesion force in the fluidized bed. The fluidized bed type PM2.5 removal device displays an excellent collection capacity for PM2.5. However, when the PM diameter exceeds 8.95μm, the behavior of the PM is mainly dominated by the gravity in the fluidized bed. The collection efficiency of a PM with a diameter less than 8.95μm shows approximately 60% under a PM inlet concentration of 100mg/m3 and a superficial gas velocity of 0.4m/s after 180min, decreasing with the increasing superficial gas velocity.

Effect of copper precursor on simultaneous removal of PM and NOx of a 2-way SCR/CDPF

The purpose of this study is to analyze the effect of Cu-precursors for a Selective Catalytic Reduction (SCR) catalyst on the de-NOx and de-PM performance of a 2-way SCR/DPF. For the SCR catalyst in the Diesel Particulate Filter (DPF) substrate, beta zeolite (BEA) was used as the catalyst support and Cu as the main catalyst. In this case, copper (II) sulfate and copper (II) chloride were used as the Cu-precursors. A model gas reactor was used to evaluate the performance of the catalyst, and Fourier Transform Infrared (FTIR) spectrometry was used to analyze the concentrations of nitrogen oxides (NOx), ammonia NH3, and other gases. The result from one experiment indicated that the NOx conversion of the fresh CuSO4–BEA catalyst was similar to that of the fresh CuCl2–BEA catalyst. However, after hydrothermal aging, the NOx conversion of the CuCl2–BEA catalyst was much higher than that of the CuSO4–BEA catalyst. These findings indicate that the CuCl2–BEA catalyst had outstanding durability, which was analyzed to verify the structure of the catalyst and its chemical changes. Varieties of ion-exchanged copper types were observed in the zeolite catalyst support, implying that the activation of the catalyst was mainly due to copper. The CuCl2–BEA catalyst also showed superior PM oxidation performance compared to the other SCR/DPF catalysts.

A numerical simulation of PM adhesion characteristics in a fluidized bed type PM removal device by a finite volume Eulerian–Eulerian method

Fluidized bed has been used in a PM removal device to remove PM2.5 effectively through the use of adhesion force, experimentally demonstrating the capability for effective PM2.5 removal. In the present work, numerical simulations of this device have been performed using the Eulerian–Eulerian method for the further development of this device. The results obtained by the Gidaspow drag force model and using the EMMS method are compared to the reference data to verify the drag force model, and it is shown that the EMMS method is better than the Gidaspow drag force model. The filtration mechanism of Clift et al. was incorporated in the simulation code to calculate the behavior of PM adhesion in the fluidized bed type PM removal device. However, the predicted results differ substantially from the experimental results. Therefore, a PM adhesion model that considers PM deposition has been incorporated in the simulation code, and numerical simulations have been conducted to analyze the behavior of PM adhesion in the fluidized bed type PM removal device. It was found that these numerical simulations represent the characteristics of PM adhesion in the fluidized bed type PM removal device with a high degree of accuracy. The predicted results show that PM adheres mainly to the surface of the bed particle at the high volume fraction of the bed particle phase and is approximately uniformly collected over the entire bed particle phase.

Evaluation on toxic reduction and fuel economy of a gasoline direct injection- (GDI-) powered passenger car fueled with methanol–gasoline blends with various substitution ratios

Methanol exhibits better capability of lowering engine emissions and fuel cost, but a potential rise in pipe-out NOx and carbonyl emissions has increased health-related risks and stalled its application. This paper examined regulated, unregulated and particulate emissions from a 1.8L GDI-powered passenger car running the New European Driving Cycle (NEDC). Conventional gasoline, together with three gasohol samples with 15%, 25% and 40% methanol substitution (M15, M25 and M40), was used. To evaluate health risk linked with pipe-out formaldehyde and benzene, a human exposure model was established. The results showed that compared with gasoline, burning gasohol significantly reduced pipe-out CO and HC emissions. Evident decrease in NOx emission was noticed with M15 and M25 fueling, but in the case of M40, NOx emissions were similar with gasoline. Carbonyls, about 50% of which were found formaldehyde, surged sharply with increased methanol percentage in the blend, while VOCs showed an opposite propensity. Health risk assessment showed that, even under a severe exposure condition, the levels of exhaust-borne formaldehyde and benzene were not sufficient to cause acute or chronic symptoms. Cancer-related risks induced by gasoline and gasohol engine exhaust were found in the same magnitude. Burning gasohol enabled an over 30% PM removal but resulted in an increase in particulate number due to an increased number of nuclei-mode particles. At last, burning gasohol produced about 0.8–4.1% less pipe-out CO2 emission than gasoline, while saving fuel cost by 5.7–15%.

Catalytic removal of PM by Li-Co delafossite catalysts

By using solution combustion synthesis method, several Li-Co delafossite catalysts were prepared via a highly exothermic and self-sustaining reaction. The prepared catalysts were characterized by XRD, SEM and the catalytic activities of the catalysts were evaluated by small sample experiment. It is shown that under loose contact conditions this catalyst can catalyze soot combustion at 360 °C, and the best prepared catalyst LiCo0.9O2 can ignite soot combustion below 300 °C. In the incompletely synthesized catalysts the Co cations shift to higher electrovalence, so the number of the surface adsorbed oxygen (O−) of the prepared delafossite catalysts increase and LiCo0.9O2 has the optimum catalytic activity.

Transparent air filter for high-efficiency PM2.5 capture.

Particulate matter (PM) pollution has raised serious concerns for public health. Although outdoor individual protection could be achieved by facial masks, indoor air usually relies on expensive and energy-intensive air-filtering devices. Here, we introduce a transparent air filter for indoor air protection through windows that uses natural passive ventilation to effectively protect the indoor air quality. By controlling the surface chemistry to enable strong PM adhesion and also the microstructure of the air filters to increase the capture possibilities, we achieve transparent, high air flow and highly effective air filters of ~90% transparency with >95.00% removal of PM2.5 under extreme hazardous air-quality conditions (PM2.5 mass concentration >250 μg m(-3)). A field test in Beijing shows that the polyacrylonitrile transparent air filter has the best PM2.5 removal efficiency of 98.69% at high transmittance of ~77% during haze occurrence.

LNT/CDPF catalysts for simultaneous removal of NOx and PM from diesel vehicle exhaust

The objective of the present study is to investigate the simultaneous removal characteristics of NOx and PM over LNT/CDPF which the combination of an lean NOx trap (LNT) catalyst and a diesel particulate filter (DPF). LNT catalysts were prepared by an impregnation method, and then analyzed through TEM, BET surface area, and EDS to investigate their physical characteristics. It was found from experiments with the LNT catalysts that the NOx conversion of 2Pt20Ba/Al2O3 coated with cordierite substrate was 65% at 350°C, which demonstrated the highest de-NOx performance among other LNT catalysts. The NOx conversion of LNT(2Pt20Ba)/CDPF combined with LNT and CDPF was 49% at 370°C. When 5wt% cobalt was added to 2Pt20Ba/Al2O3 catalyst to improve the NOx conversion of the LNT/CDPF, the NOx conversion of the LNT(2Pt20Ba5Co)/CDPF was improved to 55% at 310°C. The initiation temperature for PM oxidation was 250°C, and LOT50 of the PM was 550°C over the LNT/CDPF. In particular, the rate of PM oxidation over the LNT/CDPF was higher than one over the bare DPF, which was not coated with LNT catalyst.

Characteristics of the simultaneous removal of PM and NOx using CuNb-ZSM-5 coated on diesel particulate filter

The purpose of this study is to investigate the characteristics of the simultaneous removal of PM and NOx on the CuNb-ZSM-5 SCR/DPF catalysts coated onto DPF substrate. NOx conversion by the CuNb-ZSM-5 catalyst was higher than those by Cu- or Fe-ZSM-5 catalysts. NOx conversion of the SCR/DPF catalyst with a wall-flow (plugged) was considerably lower under 450°C than that of the SCR/DPF catalyst with a channel-flow (unplugged). The de-NOx performance of the SCR/DPF catalyst coated with CuNb-ZSM-5 was highest among the catalysts examined. SCR/DPF catalyst coated with CuNb-ZSM-5 had superior PM oxidation performance compared to the other SCR/DPF catalysts.

Charged spray generation for gas cleaning applications

The paper presents results of experimental investigation of properties of charged sprays generated by two types of pressure atomizers with charging by induction. Among other possible methods of charged spray generation, the induction charging has been considered due to its most practical importance. The goal of this research is to optimise the charging process with respect to obtain droplets of required size and charge for their application for exhaust gas cleaning from submicron particles in electrostatic scrubber used for the removal of PM from Diesel engine exhausts. Electrostatic scrubbers use electrostatic forces in order to deposit fine charged particles onto oppositely charged droplets.