Simultaneous Removal Of Particulate Matter Research Articles

Microalgal biochar assisted simultaneous removal of particulate matter, formaldehyde, and total volatile organic compounds (TVOC's) from indoor air

Biochar-based materials for air treatment have gained significant attention for removing health-detrimental volatile organic compounds (VOCs) and particulate matter (PM) in indoor air settings. However, high turnaround time, multiple pretreatment processes involved, and high pore size and low surface area (>10 μm, <100 m2 g−1) of lignocellulosic feedstocks demand alternative biochar feedstock material. Considering this, we designed a simple first-of-its-kind indoor air scrubbing material using diatoms-enriched microalgae biochar. In the present study, the microalgae were cultivated on waste anaerobic digestate (biogas slurry) and were pyrolyzed at three different temperatures: 300 °C (BC300), 500 °C (BC500), and 700 °C (BC700). The BC500 and BC700 showed the highest removal efficiencies (99 %) for total volatile organic carbons (TVOCs) and formaldehyde (HCHO) at concentrations of 1.22 mg m−3 HCHO and 8.57 mg m−3 TVOC compared to 50% efficiency obtained with commercially available surgical, cloth, and N95 masks. The biochar obtained showed a high Brunauer–Emmett–Teller (BET) surface area of 238 m2 g−1 (BC500) and 480 m2 g−1 (BC700) and an average pore size of 9–11 nm due to the mesoporous characteristic of diatom frustules. The comparatively poor performance of BC300 was due to lower surface area (150 m2 g−1) arising from incomplete organic removal, as evidenced by FESEM-EDX and FTIR. The high removal efficiencies in BC500 and BC700 were also attributed to the presence of reactive functional groups such as –OH and R–NH2. Concurrently, the average particulate matter (PM10, PM2.5, and PM1) removal efficiency for BC500 and BC 700 ranged between 66 and 82.69 %. The PM removal performance of BC500 and BC700 was lower (15–20%) than commercially available masks. Overall, the present study highlights the importance of diatoms (reactive Si) present inside the pores of microalgal biochar for enhanced removal of PM, TVOCs, and HCHO at temperatures above 500 °C. This complete approach signifies a step towards establishing a self-sustainable and circular process characterized by minimal waste generation for indoor air treatment.

Numerical simulation of the simultaneous removal of particulate matter in a wet flue gas desulfurization system.

The particulate matter (PM) could be simultaneously removed during the wet flue gas desulfurization (WFGD) process. To analyze the underlying mechanism and removal efficiency, the PM removal process in a desulfurization system was numerically simulated based on the population balance model and general dynamics equation in this study. The equation was solved using the fixed-step Monte Carlo method to determine the PM removal characteristics under different working conditions (such as spray intensity, velocity of the flue gas, and layers of slurry spray). When the flue gas velocity decreased from 7 to 3 m/s, the removal efficiency increased from 90.93 to 93.52%, and when the mean geometric droplet size decreased from 3 to 1 mm, the removal efficiency increased from 67.18 to 99.14%. Besides, large diameter PM was more easily removed by the desulfurization system. Thus, the numerical simulation method was proven to be feasible by comparing these results with field measurements of a WFGD system in a coal-fired power plant.

Simultaneous Reduction of Diesel Particulate and NOx Using a Catalysis-Combined Nonthermal Plasma Reactor

Particulate matter (PM) and NO x emitted from diesel engines is simultaneously reduced by a barrier-type catalyst-packed nonthermal plasma (NTP) application, driven by a pulse high-voltage power supply under oxygen-lean conditions. Catalyst particles of γAl2O3 and Ag/γAl2O3 with a diameter of 2–4 mm are used as packed pellets and carbon PM is loaded among the pellets. The reduction results are compared with those in a previous study using a noncatalytic BaTiO2 pellet packed bed reactor. NO x is reduced by N radicals, and PM is incinerated by oxygen radicals induced either by NO x or ozone (O3) reduction at elevated local temperatures among the pellets. Since CO and CO2 are generated, the carbon PM is actually combusted under oxygen-lean conditions, resulting in the simultaneous removal of PM and NO x with NTP-assisted catalysts. It is found that in the presence of the catalysts, PM removal calculated from CO and CO2 generation increases with an increase in the oxygen concentration. The maximum PM removal energy efficiency of 0.92 g(C) /kWh is observed for O2 = 2%. Furthermore, NO x removal decreases with an increase in the oxygen concentration. The maximum NO x removal energy efficiency of 14.2 g(NO2 ) /kWh is observed for O2 = 0%. Compared with the experimental results obtained without the catalyst pellets, the NO x removal energy efficiency increases by a maximum of 47% for O2 = 2%. When comparing the present results with those in the previous study using BaTiO3 pellets, NO x removal energy efficiency is larger, but the PM removal is lower in the case of catalyst packed-bed reactor.

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.

Simultaneous removal of PM and NOx over highly efficient 3DOM W/Ce0.8Zr0.2O2 catalysts

Herein, three-dimensional ordered macropore (3DOM) x% W/Ce0.8Zr0.2O2 (x = 0.5, 0.8, 1, 3) catalysts were prepared and employed for the simultaneous removal of PM (particulate matter) and NOx from diesel engine exhaust.

Removal of NOx and soot over Ce/Zr/K/Me (Me = Fe, Pt, Ru, Au) oxide catalysts

The potentiality of ceria/zirconia based catalysts in the simultaneous removal of particulate matter (soot) and NOx is investigated in this work, and compared with that of a model LNT Pt-K/Al2O3 sample. Ceria-zirconia (molar ratio 75/25) catalysts doped with Pt, Au, Ru or Fe (2% by weight) and containing K (7% by weight) were prepared by a modified citrate method and characterized by X-ray diffraction, surface area and pore volume measurements. The behavior of the catalysts in the soot combustion and NOx removal was separately analyzed by means of temperature programmed oxidation (TPO), isothermal combustion and isothermal NOx adsorption experiments. The results showed that all the ceria/zirconia based catalysts are more active than Pt-K/Al2O3 in soot combustion; the Ru-containing system also showed NOx storage performances comparable to Pt-K/Al2O3. Accordingly the capability of the Ru-based catalyst to accomplish the removal of NOx in the absence and in the presence of soot was further investigated by reactivity experiments and FT-IR spectroscopy to analyze both the gas phase and the catalyst surface species. The data indicate that the Ru-based system is able to simultaneously remove soot and adsorb NOx pointing out higher performances in the soot combustion as compared to the Pt-K/Al2O3 catalyst, and similar behavior in the NOx storage capacity. However the NOx reduction activity results lower than the traditional LNT Pt-based catalyst. Conversely, when the Ru-based catalyst is mixed with the LNT sample (physical mixture) a NOx reduction efficiency similar to Pt-K/Al2O3 is found.

Simultaneous Removal of Soot and NOx Over Silver and Ruthenium-Based Catalysts

Silver- and ruthenium-based materials are herein investigated for the simultaneous removal of particulate matter (soot) and NOx and their behaviour is compared with that of a model Pt–Ba/Al2O3 catalyst. The catalytic activity for diesel soot combustion, in loose contact conditions, is studied by means of TPO (temperature programmed oxidation) while NOx removal is investigated through NOx Storage-Reduction cycles (SRC), performed both in the presence and in the absence of soot. Both the Ag- and Ru-based formulations result active in the soot oxidation, more than the traditional Pt-containing DPNR catalyst. Also, the Ru-based sample shows remarkable performances in the DeNOx-DeSoot activity, although its activity in the reduction step of the stored NOx still needs further improvements.

Silver-based catalytic materials for the simultaneous removal of soot and NOx

The potential of silver-based catalysts in the simultaneous removal of particulate matter (soot) and NOx is investigated in this work and compared with that of a model Pt–Ba/Al2O3 catalyst. The Ag (5wt%) – Ba (10wt%)/MO (MO=CeO2, ZrO2, Al2O3) and Ag (5wt%) – Sr (10wt%)/CeO2 catalysts have been prepared by incipient wetness impregnation and characterized by BET, XRD, HRTEM, XPS and temperature-programmed reduction (TPR) experiments. The behavior of the catalyst in the soot combustion (under loose conditions) and NOx removal has been separately analyzed by means of temperature programmed oxidation (TPO) and isothermal concentration step change (ICSC) experiments, respectively. The results show that all the catalysts are active in soot combustion with a significant decrease of oxidation onset temperature compared to uncatalyzed soot oxidation. The removal of NOx in the absence and in the presence of soot was investigated under cycling conditions, i.e. alternating lean–rich phases according to the LNT strategy. It has been found that the Ag-based samples are able to simultaneously remove soot and NOx. In particular, comparing the behavior of the prepared catalysts, the Ba-containing systems showed higher NOx storage capacity than Sr-catalyst; also, the nitrogen selectivity increased even if resulted lower than the traditional LNT Pt-based catalyst. A detrimental effect of soot on the NOx storage activity has been also observed.

Simultaneous Removal of Particulate Matter and Gas-Phase Pollutants within Electrostatic Precipitators: Coupled In-Flight and Wall-Bounded Adsorption

Older combustion facilities are favored to comply with imposed regulations limiting emissions of trace toxic metals by modifying the operation of existing emissions control devices to concurrently capture the regulated toxic metal compound; a prominent example of this is adsorption of mercury by added activated carbon within electrostatic precipitators (ESPs). Our previous quasi-1-D analyses employed simplifying assumptions, some of which were initially proposed decades ago. The present study leverages a modern computational platform to remove restrictive, simplifying assumptions and capture details of multi-phase flows and electric and electro-hydrodynamic phenomena that were previously out of computational reach. The results reveal the conflicting interdependent trends in particulate matter (PM) collection and adsorption of a trace gas-phase pollutant, assumed here to be mercury. In particular, we show the power of the inverse correlation between PM removal efficiency and trace pollutant adsorption efficiency, for two representative particle size distributions for increasing treatment times and under constant electrical conditions (applied voltage and current density). Also noteworthy is the finding that the two mechanisms of trace pollutant adsorption within an ESP, in-flight adsorption by suspended sorbent particles and wall-bounded adsorption by sorbent-covered walls, cannot be treated as additive. Wall-bounded adsorption depletes trace pollutant concentrations in the concentration boundary layer near the walls, reducing the driving potential for in-flight adsorption in these regions. For the conditions simulated, the additional rate of pollutant removal by the former is almost entirely counter-balanced by diminished rates of pollutant removal by the latter. Such findings highlight the need to optimize emissions control processes originally designed for a single pollutant but operated for the purpose of dual-pollutant control.

Simultaneous Removal of Particulate Matter and Gas-Phase Pollutants within Electrostatic Precipitators: Coupled In-Flight and Wall-Bounded Adsorption

Older combustion facilities are favored to comply with imposed regulations limiting emissions of trace toxic metals by modifying the operation of existing emissions control devices to concurrently capture the regulated toxic metal compound; a prominent example of this is adsorption of mercury by added activated carbon within electrostatic precipitators (ESPs). Our previous quasi-1-D analyses employed simplifying assumptions, some of which were initially proposed decades ago. The present study leverages a modern computational platform to remove restrictive, simplifying assumptions and capture details of multi-phase flows and electric and electro-hydrodynamic phenomena that were previously out of computational reach. The results reveal the conflicting interdependent trends in particulate matter (PM) collection and adsorption of a trace gas-phase pollutant, assumed here to be mercury. In particular, we show the power of the inverse correlation between PM removal efficiency and trace pollutant adsorption efficiency, for two representative particle size distributions for increasing treatment times and under constant electrical conditions (applied voltage and current density). Also noteworthy is the finding that the two mechanisms of trace pollutant adsorption within an ESP, in-flight adsorption by suspended sorbent particles and wall-bounded adsorption by sorbent-covered walls, cannot be treated as additive. Wall-bounded adsorption depletes trace pollutant concentrations in the concentration boundary layer near the walls, reducing the driving potential for in-flight adsorption in these regions. For the conditions simulated, the additional rate of pollutant removal by the former is almost entirely counter-balanced by diminished rates of pollutant removal by the latter. Such findings highlight the need to optimize emissions control processes originally designed for a single pollutant but operated for the purpose of dual-pollutant control.

High performances of Pt-K/Al2O3 versus Pt-Ba/Al2O3 LNT catalysts in the simultaneous removal of NO x and soot

The potentiality of a Pt-K/Al2O3 catalyst in the simultaneous removal of particulate matter (soot) and NO x is investigated in this work by means of Temperature Programmed Oxidation (TPO) experiments and Transient Response Method (TRM), and compared with Pt-Ba/Al2O3. The results point out the higher performances of K-based sample in the soot combustion as compared to the Ba-based catalyst, and similar behaviour in the NO x -storage.

Simultaneous removal of NOx and soot on Pt–Ba/Al2O3 NSR catalysts

The potentiality of a typical Pt–Ba/Al2O3 NSR catalyst in the simultaneous removal of particulate matter (soot) and NOx is investigated in this work, and compared with that of a Pt/Al2O3 sample. The behaviour of the catalyst in the soot combustion and NOx removal has been separately analyzed by means of temperature programmed oxidation (TPO) experiments, isothermal combustions and transient response method (TRM), respectively. The results show that in presence of only oxygen, soot oxidation occurs slowly even at a temperature as high as 400°C. On the other hand, the presence of NO greatly increases the rate of soot conversion, which becomes significant at 350°C. The capability of the Pt–Ba/Al2O3 and Pt/Al2O3 catalysts to accomplish the removal of NOx in the absence and in the presence of soot was investigated under cycling conditions, i.e. alternating lean-rich phases according to the typical NSR strategy. It has been found that the Pt–Ba/Al2O3 sample is able to simultaneously remove both soot and NOx, as opposite to the Pt/Al2O3 catalyst which effectively performs the soot oxidation but is not able to remove gas phase NOx to a significant extent. The presence of soot does not significantly affect the activity in the NOx reduction of the Pt–Ba/Al2O3 catalyst. The comparable level of activity in the soot combustion which is observed between the Pt/Al2O3 and the Pt–Ba/Al2O3 sample in spite of the fact that the ternary sample accomplishes the removal of NOx in the gas phase has been tentatively ascribed to specific oxidizing properties of the stored nitrate species.

High-temperature fuel gas cleaning and removal of alkalis using molten slag

Fuel gas cleaning is an important step in the development of coal-based combined cycle technologies. By integrating hot gas cleaning facilities in the combined cycle power plant, higher operating temperatures can be achieved. Research is being carried out at the Institute of Ferrous Metallurgy, Technical University of Aachen, to develop a process for gas cleaning at temperatures above 1300°C using a venturi scrubber with molten slags as sorbents. This process offers simultaneous removal of particulate matter and alkali vapours in the gas stream. The present paper deals with the particulate removal tests, with major emphasis on investigations carried out to study the reaction between molten slags of various compositions and alkali vapours. These investigations included thermochemical calculations as well as an experimental reaction study.

Fine particle control using sulfur oxide scrubbers.

Compliance with sulfur oxides standards will in many cases result in the installation of scrubbing devices. If these devices operate on an effluent gas stream containing particulate as well as sulfur oxides, simultaneous removal would be expected. Since effective simultaneous removal of particulate matter and sulfur oxides is economically desirable, it is of considerable import to characterize scrubber designs being considered as sulfur oxide absorbers as particulate control devices; especially, for fine particulate control. Data on the fine particle collection efficiency of sulfur oxides scrubbers at two power generating stations is presented. At the first, a venturi and a turbulent contacting absorber (TCA) both with capacities of 30,000 cfm were tested. At the second, a venturi with 600,000 scfm capacity was tested. Fine particle collection efficiency was determined at three pressure drops for the TCA using a cascade impactor. Results for the TCA show high removal efficiencies. It collected more than 9...