Particulate Matter Filtration Research Articles

Carbon nanotubes / activated carbon fiber based air filter media for simultaneous removal of particulate matter and ozone

Indoor environment is faced with complex pollution by particulate matter (PM) and ozone. In this study, we proposed to use carbon nanotubes/activated carbon fiber (CNTs/ACF) to remove both PM and ozone with high removal efficiencies, high quality factor and low pressure resistance. The CNTs/ACF filter media were fabricated through growth of CNTs upon pristine ACF using chemical vapor deposition method. The PM filtration efficiencies of the CNTs/ACF and pristine ACF were measured for different particle sizes. The quality factors of these two media were calculated and compared. The ozone removal efficiency of the CNTs/ACF and ACF were tested as well. Results indicate that growth of CNTs on ACF elevated the media for PM filtration, and increased the quality factor by 48%. The CNTs/ACF presented >99% ozone removal, as high as the ACF. Compared with other CNTs-based filter media that have been proposed in previous studies, the CNTs/ACF exhibited higher quality factor, much lower pressure resistance, higher ozone removal efficiency, and upper-middle PM filtration efficiency.

Applying modern automotive technology on small scale gasification systems for CHP production: A compact hot gas filtration system

Cost-effective and durable producer gas cleaning is a necessary step towards the promotion of sustainable gasification systems for electricity production. The automotive industry has vast technological experience on gas filtration both at experimental and theoretical level. In this study hot producer gas cleaning was attempted with the use of ceramic Diesel Particulate Filters (DPF) initially designed to operate in automotive applications. Different types of DPFs were used as downstream hot gas filters in two atmospheric air blown bubbling fluidized bed gasifiers. The experiments included short and long duration tests conducted with olive kernels under various gasification temperatures and air ratios. Being the first attempt on the application of “narrowly structured” ceramic DPF in a gas heavily loaded with particulate matter (PM), main objective was to investigate the operation performance in terms of overall collection efficiency, loading and pressure drop profile, as well as regeneration performance and structural robustness. The results showed high PM filtration efficiency, and highlighted fields for further research. Poor operation performance was experienced due to inlet surface plugging and in some cases limited structural robustness under uncontrolled regeneration conditions. Insight into the overall behavior of the DPF's was gained via axial tomography and imaging analysis. Further research is needed in order to adapt different geometrical structures and obtain better control of loading and regeneration processes.

The treatment of waste gas from fertilizer production - An industrial case study of long term removing particulate matter with a pilot unit

This manuscript covers an on site industrial case study focused on the dry filtration of particulate matter (PM) from the waste stream of fertilizer production. In the industrial plant producing fertilizers, it was necessary to exchange the old wet scrubber with new cleaning equipment for PM disposal. A filter unit with bag filters and pulse-jet cleaning was chosen as the new waste-free technology. Unfortunately, one step in the production involves granulation with steam and water, therefore the waste gas stream was quite humid. Filter bags captured 10g and 40g of H2O/kg of dry gas for GR-SA and NPK fertilizers respectively. Due to dry filtration feasibility concerns, a long term pilot unit test was conducted. The impact of operating conditions, especially the inlet stream temperature and humidity was evaluated. A inlet temperature 100°C for GR-SA and 110°C for NPK fertilizers was necessary to prevent clogging of the filter bags. We found that different cleaning pulses periods and pulse pressures have a minimum impact on the filter pressure difference (ΔP). Based on the results of the pilot test, recommendations for usable technological conditions were given, in order to avoid problematic deposits on filter material associated with increased ΔP. In addition to this, a straightforward comparison method was proposed in this paper for filter clogging according to ΔP between cleaning pulses.

Examination of Pervious Pavement Pore Parameters with X-Ray Tomography

AbstractPervious pavement (PP) is an infrastructure material that can alter rainfall-runoff relationships, filter particulate matter (PM), and sequester runoff constituents. Beyond a measure of total porosity (ϕt), less-commonly measured pore parameters and relationships thereof influence these phenomena. In this study, cementitious PP (CPP), used as a permeable surface for an exfiltration system loaded by runoff, was examined. X-ray tomography (XRT) was utilized to examine pore size and frequency, generate a total-to-effective porosity (ϕt−ϕe) relationship, quantify pore tortuosity (Le/L), and relationships for specific surface area (SSA), pore-size distributions (PSD)pore, and ϕt. Gravimetric analyses were used for SSA based on mass (SSA)s as well as validation of XRT porosity. Results indicate that ϕt ranged from 10 to 30% while ϕe ranged from 4 to 27%. Relationships for (ϕt−ϕe), SSA, ϕt, and median pore diameter (d50n) were represented with a power law model (PLM). Using ϕt the (SSA)pt of pores ranged...

Model of back pressure pulses generated by coupled pressure pulse (CPP) technology

Filtration of particulate matter from biomass derived product gas is an important part of creating successful biomass conversion processes. A detailed understanding of the filtration system is needed to scope with high dust loads and sticky ash. A physical model describing pressure evolvement in different filter sectors during back pressure pulses generated by coupled pressure pulse (CPP) technology was developed. The CPP recleaning model was developed based on mass conservation, steady state assumptions and ideal gas conditions. Knowing the volumes of the filter sectors, pressures can be determined according to the calculated gas flows and gas accumulations. Model and experimental results were compared showing an average model accuracy of 93% for pressure maxima measured in the recleaning sector. Experiments were conducted with grain ceramic filter elements at ambient temperature and at 450 °C. Flush tank pressures varied between 250 hPa and 1000 hPa. The model was kept as generic as possible allowing the modeling of different CPP filter set-ups and calculations for scale-up considerations. The model capabilities to reproduce pressure evolvements of different filter materials and filter end configurations were tested. Comparing model results of new filters with operational data of used filter elements allows recognizing filter failures such as leakages, permeability reduction and blockages.

Model of Flow Regimes in Porous Pavement and Porous Friction Courses

Porous pavements (PPs) and porous friction courses (PFCs) are increasingly recognized as viable alternatives to traditional impervious pavements. PPs and PFCs passively provide safety, hydrologic, and rainfall-runoff treatment benefits. These benefits are a result of such permeable systems providing hydraulic conveyance and filtration of particulate matter (PM) transported by runoff. With respect to hydrology, these systems reintroduce infiltration, evaporation, and storage phenomena; with respect to traffic and road safety, the systems increase skid resistance in wet conditions, reduce hydroplaning, and reduce splash-and-spray phenomena; with respect to runoff treatment, the systems function as a filter for PM and PM-bound constituents. These phenomena and the models therefore are a function of the hydrodynamics (which are not necessarily laminar) in the porous medium and commonly are characterized by the hydraulic conductivity of the porous medium. The measured hydraulic conductivity (permeability) was examined in 12 common porous asphalt mixes. A Darcian model for hydraulic conductivity in the laminar flow regime was examined, as commonly done for PPs and PFCs. However, hydrodynamic regimes in porous asphalt that extended beyond laminar flow during testing were identified for these porous mixes. Therefore, the variability of the hydraulic conductivity as a function of applied hydraulic head in a hydrodynamic regime (based on the Reynolds number) was measured and modeled. From these results, a saturated seepage model was developed; it is valid for laminar and transitional regimes. Implications for the application of standardized permeameter testing of such porous mix designs are reported.

Phosphorus Speciation and Treatment Using Enhanced Phosphorus Removal Bioretention

This field research investigated the water quality performance of a traditional bioretention cell retrofitted with 5% (by mass) water treatment residual (WTR) for enhanced phosphorus removal. Results indicate that WTR incorporation into the bioretention media does not negatively influence the infiltration mechanism of the bioretention system. Total suspended solids (TSS), total phosphorus (TP), and particulate phosphorus (PP) concentrations in runoff inflow were significantly reduced compared to outflow due to filtration of particulate matter. TP concentrations were significantly reduced by the bioretention cell; before WTR retrofit TP export occurred. Although net removal of soluble reactive phosphorus (SRP) and dissolved organic phosphorus (DOP) from incoming runoff was not found, leaching of dissolved phosphorus (DP) was prevented not only from incoming runoff, but also from the media and captured PP. Near constant outflow SRP and DOP concentrations suggest an equilibrium adsorption treatment mechanism. Both event mean concentrations and mass loads were reduced for TSS and all P species. Pollutant mass removals were higher than the event mean concentration removals due to the attenuation of volume by the bioretention media.

A Particulate Matter Sensor with Groove Electrode for Real-Time Diesel Engine On-Board Diagnostics

A particulate matter sensor fabricated by MEMS process is proposed. It is developed to accommodate Euro6 on-board diagnostics regulation for diesel automobile. In the regulation, emission of diesel particulate matter is restricted to 9 mg/km. Particulate matter sensor is designed to use induced charges by charged particulate matter. To increase sensitivity of the sensor, groove is formed on sensor surface because wider surface area generates more induced charges. Sensitivity of the sensor is measured 10.6 mV/(mg/km) and the sensor shows good linearity up to 15.7 mg/km. Also its minimum detectable range is about 0.25 mg/km. It is suitable to detect failure of a diesel particulate filter which should filter particulate matter more than 9 mg/km. For removing accumulated particulate matter on the sensor which can disturb normal operation, platinum heater is designed on the backside of the sensor. The developed sensor can sense very low amount of particulate matter from exhaust gas in real-time with good linearity.

Collection performance of an electrostatic filtration system combined with a metallic flow-through filter for ultrafine diesel particulate matters

An electrostatic diesel particulate matter filtration system (EDPS) has been tested using 3000 cc diesel engines operating at steady state and standard (European Stationary Cycle (ESC) 13 mode) conditions. The system consisted of a flowthrough filter (FTF) and a charging device with a round perforated plate imposing an electrostatic field onto the FTF. An insulating device for the high-voltage electrode was protected from pollutant deposition by using an air slit at velocity of 7 m/s to maintain a stable corona discharge under an exhaust temperature exceeding 300°C. Under steady-state engine conditions, the performance test of the EDPS showed high collection performance (based on the particulate matter (PM) number) of nearly 80–99%, while the efficiency of the FTF remained at 15–50%. Comparing the performance of the EDPS with a commercialised diesel particulate filter (DPF) and an FTF under the ESC 13 mode, the EDPS was almost 40% more efficient than the FTF and 10% less efficient than the DPF, while achieving 73% lower pressure drop than the DPF. Thus, the novel filtration system can achieve collection performance similar to the DPF with significantly less pressure drop.

Influence of Filtration Velocity on Cake Formation in Fibrous Filters

The filtration operation is one of the most widely used procedures in gas-solid separation due to its high removal efficiency, low cost and low sensitivity to variations in operating conditions. Therefore, the objective of this work is to study the effects of operating variables (pressure drop, filtration velocities and cleaning velocity) on the formation of filter cakes using gas-solid polypropylene filter media and particulate matter as for instance phosphate rock. The filtration velocities evaluated were 5, 7.5 and 10 cm/s with maximum pressure drops of 100, 200, 300 and 400mm H2O and filter cleaning velocities of 15 cm/s by the reverse air flow method. The cake filtration porosity was estimated using the classical Ergun equation (1952) in the literature. The results led to important correlations for the use of fibrous filters in the removal of particles suspended in in micrometer aerosols.

Development of electrostatic diesel particulate matter filtration systems combined with a metallic Flow-Through Filter and electrostatic methods

A 3000 cc diesel engine attached to an engine dynamo was used to test three newly developed electrostatic Diesel Particulate matter filtration Systems (DPS 1, 2, and 3) under four steady-state engine operating conditions: idle, 2000 rpm with no load, and 2000 rpm under 25% and 50% loads. Of the two developed alternatives, DPS 1 and DPS 2, DPS 2 comprises an ionization section, electrostatic field additional section and Flow-Through Filter (FTF), which achieved almost 90% removal of particulate matter (PM) under the engine’s operating conditions, and the efficiency of the FTF was maintained between 20% and 50%. Comparing the long-term performance of DPS 2 and DPS 3 (effectively a serial combination of two DPS 2s) with a commercially-available Diesel Particulate Filter (DPF), the DPS 2 and DPS 3 achieved almost the same efficiency for removing PM as the DPF but had significantly improved (75%∼90% lower) differential pressure drops.

Cleaning the Air We Breathe – Controlling Diesel Particulate Emissions from Passenger Cars

The mechanism of formation of particulate matter (PM) in the diesel engine combustion process is outlined, and the increasingly stringent PM emissions limits in current and projected environmental legislation are noted in the context of the increasing use of fuel-efficient high-performance diesel engines in passenger cars. The types of filter systems for abating diesel particulates are described, as are the principles of filter regeneration – the controlled oxidation of PM retained in the filter, to prevent an accumulation which would ultimately block the filter and degrade engine performance. PM is characterised in terms of both particle size (coarse, accumulation mode, and nucleation mode nanoparticles) and chemical composition, and the filtration issues specific to the various PM types are outlined. Likely future trends in filter design are projected, including multifunctional systems combining PM filtration with NOx control catalysts to meet yet more stringent legislative requirements, including European Stage 5 and 6, and the so called ‘Bin 5’ levels in the U.S.A.

Evaluation of various activated carbons for air cleaning – Towards design of immune and sustainable buildings

There are increased demands for security, sustainability and indoor air quality in today's building design, construction, operation and maintenance. Installation of air cleaning systems can improve the indoor air quality by reducing the air pollution levels, and enhance the building security against sudden release of chemical and/or biological agents. At the same time, air cleaning techniques may reduce the building energy consumption by reducing the outdoor air supply rate, hence lowering the needs for conditioning of outdoor air. While the air filtration of particulate matter is well standardized, the standards against which the performance of air cleaning for gaseous contaminants is measured or classified are still under development. This study examined the performance of various granular activated carbons (GACs) for the removal of volatile organic compounds (VOCs) from mechanically ventilated buildings. Eight different GACs (three virgin and five impregnated) were tested against toluene using a dynamic test system. The virgin GACs showed better performance than impregnated ones, the percentage and the type of impregnation affected the removal efficiencies. Tests were also conducted with selected GACs against toluene, cyclohexane and ethyl acetate at relative humidity (RH) values of 30%, 50% and 70%. The effect of humidity was dependant on the VOC used. Both for toluene and cyclohexane, the removal efficiency decreased as RH increased. However, higher humidity showed a positive impact on the removal of ethyl acetate.

Health Effects of Subchronic Inhalation Exposure to Gasoline Engine Exhaust

Gasoline engine emissions are a ubiquitous source of exposure to complex mixtures of particulate matter (PM) and non-PM pollutants; yet their health hazards have received little study in comparison with those of diesel emissions. As a component of the National Environmental Respiratory Center (NERC) multipollutant research program, F344 and SHR rats and A/J, C57BL/6, and BALBc mice were exposed 6 h/day, 7 days/week for 1 week to 6 months to exhaust from 1996 General Motors 4.3-L engines burning national average fuel on a simulated urban operating cycle. Exposure groups included whole exhaust diluted 1:10, 1:15, or 1:90, filtered exhaust at the 1:10 dilution, or clean air controls. Evaluations included organ weight, histopathology, hematology, serum chemistry, bronchoalveolar lavage, cardiac electrophysiology, micronuclei in circulating cells, DNA methylation and oxidative injury, clearance of Pseudomonas aeruginosa from the lung, and development of respiratory allergic responses to ovalbumin. Among the 120 outcome variables, only 20 demonstrated significant exposure effects. Several statistically significant effects appeared isolated and were not supported by related variables. The most coherent and consistent effects were those related to increased red blood cells, interpreted as likely to have resulted from exposure to 13–107 ppm carbon monoxide. Other effects supported by multiple variables included mild lung irritation and depression of oxidant production by alveolar macrophages. The lowest exposure level caused no significant effects. Because only 6 of the 20 significant effects appeared to be substantially reversed by PM filtration, the majority of effects were apparently caused by non-PM components of exhaust.

A Study on Fluidized Bed-Type Particulate Filter for Diesel Engines

A fluidized bed-type diesel particulate filter (DPF) was applied to filter particulate matter (PM) in diesel engine exhaust gas. The effects of the fluidized bed design parameters, such as gas velocity, bed particle size, and height, on PM and smoke filtration efficiencies, and pressure drop were experimentally investigated using a single-cylinder direct injection (DI) diesel engine. High PM filtration efficiency and low pressure drop were achieved with the DPF, especially at a lower gas velocity. The PM filtration efficiency was higher with a smaller bed particle size at the lower gas velocity; however, it drastically decreased with an increase in gas velocity due to excessive fluidization of the bed particles. Increase in bed height led to higher PM filtration efficiency while causing an increase in pressure drop. The theoretical work was also conducted for further investigation of the effects of the above-mentioned parameters on PM filtration. These results indicated that diffusion filtration was the dominant mechanism for PM filtration under the conditions of this study and that the decrease in PM filtration efficiency at high gas velocity was caused by a deterioration in the diffusion filtration. The bed particle diameter and the bed height should be optimized in order to obtain a high filtration efficiency without increasing the DPF size.

Characteristics of Particulate Matter Collection in a Diesel Engine Using a Fluidized-bed DPF

A fluidized bed filter was applied to filtrate particulate matter (PM) in diesel engine exhaust gas. Experiment was carried out using a single-cylinder DI diesel engine to investigate the effects of gas velocity, bed particle diameter and bed height on PM and smoke filtration efficiencies and pressure drops. A theoretical work has been also conducted for further investigation of the effects of the mentioned parameters on PM filtration. The experimental results show that the fluidized-bed DPF provides high PM filtration efficiency and low-pressure drop especially under lower gas flow rates. Smaller diameter bed particles provide higher filtration efficiency under the low gas flow rate ; however, the filtration efficiency drastically decreases with the increase in gas flow rate due to excessive fluidization of the bed particles. The increase in bed height gives higher PM filtration efficiency while it causes an increase in pressure drop. The calculation results indicate that the diffusion collection is a dominant mechanism for PM filtration under the conditions of this study. The lower PM filtration ratios at high exhaust gas flow rates are caused by reduction of the filtration efficiency in diffusion collection.

Particulate matter filtration and seasonal nutrient dynamics in permeable carbonate and silicate sands of the Gulf of Aqaba, Red Sea

This study compares mineralization in permeable silicate and carbonate sands in the shallow shelf of the Gulf of Aqaba. From July 1999 to March 2000, we monitored concentrations of inorganic nutrients in water and pore water at two neighboring sites, one dominated by silicate, the other by carbonate sand. Although the carbonate was coarser than the quartz sand, organic matter, dissolved inorganic nitrogen (DIN), and ortho-phosphate concentrations in the biogenic carbonate sediment always exceeded those in the terrigenic silicate sands (factor 1.5–2.0 for organic matter, 1.7–14.0 for nutrients). Higher nutrient concentrations in the water column during winter months caused increases in pore-water nutrient concentrations in both sediments down to 10 cm depth with no significant delay, emphasizing the effect of advective transport of solutes and particles into permeable sands. An experiment was conducted where sieved clean quartz and carbonate sands of same grain size (250–500 µm) were incubated in-situ. Although exposed to the same water and boundary current conditions, the sieved carbonate sand accumulated more organic matter and developed higher nutrient concentrations than the incubated silicate sediment. We conclude that the mineralogical characteristics of the carbonate sand (higher porosity, sorption capacity and pH buffer capacity) enhance the filtration capacity, and the biocatalytic conversion efficiency relative to the smooth crystalline quartz grains.

Measurement of particulate matter from diesel engine exhaust using a tapered element oscillating microbalance

Acquisition of real-time particulate matter (PM) data is proposed by the use of a Rupprecht and Patashnick Company, Inc. Series 110 diesel particulate monitor tapered element oscillating microbalance (TEOM) mass measuring device. The objectives of using a TEOM diesel particulate analyser were to validate its collection capability and evaluate its real-time transient characteristics. Conventional PM measured using dilute diesel exhaust filtration was used as the base line for evaluating the TEOM collection capability. Real-time mass rate data were separated into positive and negative values, then integrated over the duration of the test. The integrated positive mass was divided by the integrated negative mass to create a ratio that is indicative of real PM collected versus moisture released from the filter. Tests were performed on heavy-duty diesel engines on a stationary dynamometer using the US Heavy Duty Federal Test Procedure speed and load cycle. TEOM sample tube temperatures at 35°C yielded the best TEOM-conventional PM filtration mass ratio. However, as sample path temperatures decreased, a decrease in the positive-negative mass ratio occurred. A compromise between conventional filter agreement and real-time data was made in selecting the temperature set point of 40°C as the most desirable sampling temperature. The sample flowrate was varied from one to four litres per minute. A comparison of the TEOM with a conventional filter decreased as the TEOM flow increased. The 1 l/min set point provided the best TEOM-conventional filtration ratio. The positive-negative mass ratio increased as flow decreased. The flow-rate of 3 l/min was chosen to be a compromise between the TEOM-conventional filtration mass ratio and real-time results. The best TEOM-conventional filtration ratio measured was 0.97. The best set of test results was a three-test averaged TEOM-conventional filtration ratio of 0.92 with a coefficient of variance of 0.15 per cent.

Rates and routes of trace element uptake in zebra mussels

The zebra mussel, Dreissena polymorpha, a nonindigenous invasive species, is now widespread throughout the eastern half of North America. Because zebra mussels are ubiquitous and because they effectively filter particulate matter out of suspension, the cycling and residence times of particle‐reactive metals will likely be affected in waters with zebra mussels. This study describes experiments designed to assess the possibility of using this species as a bioindicator of metals in ambient freshwater environments. Laboratory exposures of zebra mussels to 110mAg, 109Cd, 51Cr, 14C, 203Hg, and 75Se were employed to measure their assimilation efficiencies (percentage of ingested element that crosses gut lining) from eight food types (four algal species and bacteria, seston, and mineral assemblages), absorption efficiencies from water (percentage of element pumped by the mussel that is absorbed by the animal), and rates of depuration of these elements from mussels following long‐term exposures to food and water. Assimilation efficiencies of elements from foods ranged from 4 to 29% for silver (Ag), 19 to 72% for cadmium (Cd), 42 to 85% for carbon (C), 2 to 19% for chromium (Cr), 4 to 40% for mercury (Hg), and 8 to 46% for selenium (Se). Absorption efficiencies from the dissolved phase were 1.87% for Ag, 1.02% for Cd, 0.47% for Cr(III), 0.27% for Cr(VI), 1.17% for Hg, and 0.03% for Se. Efflux rate constants (d 21 ) following long‐term exposure to food and water were 0.067 and 0.084 for Ag, 0.013 and 0.011 for Cd, 0.019 and 0.011 for Cr, 0.050 for Hg (food only), and 0.026 and 0.035 for Se. These loss rates corresponded to biological half‐lives ranging from 8 d for Ag to 76 d for Se. Loss rates of trace elements from zebra mussel feces followed the following sequence: Cr < Ag < Se < Hg ≤ Cd, with average retention half‐times being 59, 43, 11, 6.7, and 5.1 d, respectively, which indicates that geochemical cycling rates from zebra mussel biodeposits are element specific. Egestion patterns of the radioisotopes indicated two digestive phases, extracellular and intracellular digestion. The extent of intracellular digestion ranged from 7 to 40%, depending on the food source, and correlated with assimilation efficiency for Ag, Cd, and Hg. The bioaccumulation parameters measured for D. polymorpha can be used in kinetic models to quantify the relative importance of food and water as sources of metals and to predict on a site‐specific basis the tissue concentrations of metals in these mussels, as shown for Cd. Because D. polymorpha accumulates metals from dissolved and particulate sources in proportion to ambient concentrations, this species can be an effective bioindicator of freshwater metal contamination.

Sorption and filtration of metals using iron-oxide-coated sand

Iron oxides are good adsorbents for uncomplexed metals, some metal-ligand complexes, and many metal oxyanions. However, the adsorbent properties of these oxides are not fully exploited in wastewater treatment operations because of difficulties associated with their separation from the aqueous phase. This paper describes experiments in which iron oxides were coated onto the surface of ordinary filter sand, and this composite media was used in a fixed bed configuration for simultaneous filtration of particulate matter and sorption of dissolved metals. The process was successful in removing uncomplexed and ammonia-complexed cationic metals (Cu, Cd, Pb, Ni, Zn), as well as some oxyanionic metals (SeO 3, AsO 3), from simulated and actual waste streams over a wide range of metal concentrations. The adsorbent was stable during backwashing and regeneration operations, releasing most metals quantitatively; the exception was AsO 3, which was not efficiently recovered by regeneration with either acid or base. The composite media is inexpensive to prepare and could serve as the basis of a useful metal removal and possibly metal recovery process in a variety of settings.