Removal Of Particulate Matters Research Articles

Functionalization of cellulose acetate nanofibrous membranes for removal of particulate matters and dyes

Particulates and organic toxins, such as microplastics and dye molecules, are contaminants in industrial wastewater that must be purified due to environmental and sustainability concerns. Carboxylated cellulose acetate (CTA-COOH) nanofibrous membranes were fabricated using electrospinning followed by an innovative one-step surface hydrolysis/oxidation replacing the conventional two-step reactions. This approach offers a new pathway for the modification strategy of cellulose-based membranes. The CTA-COOH membrane was utilized for the removal of particulates and cationic dyes through filtration and adsorption, respectively. The filtration performance of the CTA-COOH nanofibrous membrane was carried out; high separation efficiency and low pressure drop were achieved, in addition to the high filtration selectivity against 0.6-μm and 0.8-μm nanoparticles. A cationic Bismarck Brown Y, was employed to challenge the adsorption capability of the CTA-COOH nanofibrous membrane, where the maximum adsorption capacity of the membrane for BBY was 158.73 mg/g. The self-standing CTA-COOH membrane could be used to conduct adsorption-desorption for 17 cycles with the regeneration rate as high as 97.0 %. The CTA-COOH nanofibrous membrane has excellent mechanical properties and was employed to manufacture a spiral wound adsorption cartridge, which exhibited remarkable separation efficiency in terms of treated water volume, which was 5.96 L, and retention rate, which was 100 %.

Nano carbon-modified air purification filters for removal and detection of particulate matters from ambient air

Particulate matters (PMs) pose significant risks to human health and the environment, necessitating research to enhance air purification filters and reduce harmful emissions. This study focuses on the preparation of carbon nanomaterials, including graphitic carbon nitride nanosheets (g-C3N4 NSs), reduced graphene oxide (r-GO), and carbon nanotubes (CNT), for modifying filters in air particle monitoring devices. The objective is to investigate the impact of these nanomaterials on enhancing PM adsorption efficiency. Quantitative and qualitative analyses of the modified filters’ adsorption efficiency towards PMs are performed using spectroscopic techniques such as Energy-Dispersive X-ray Spectroscopy (EDX), Inductively Coupled Plasma (ICP), and Laser-Induced Breakdown Spectroscopy (LIBS). The results reveal that CNT-modified filters exhibit superior adsorption efficiency compared to the control, g-C3N4, and r-GO-modified filters. The exceptional performance of CNTs is attributed to their large specific surface area and pore volume. Additionally, LIBS demonstrates its capability to detect heavy metals like Cd, which remain undetected by EDX and ICP. The technique proves sensitive for heavy metal monitoring. This novel approach is expected to garner significant attention and contribute to the development of improved air purification technologies.

Dual-functional membranes of CQDs/TiO2 @PI/PES nanofibers for the high filter efficiency of ultrafine particles and photocatalytic activity

The carbon quantum dot/titanium dioxide (CQDs/TiO2), fabricated on highly porous polyimide (PI)/polyether sulfone (PES) nanofiber via electrospinning process, called the dual-functional CQD/TiO2 @PI/PES membrane, was developed and evaluated for its performance, including both removal of volatile organic compounds (VOCs) and ultrafine particulate matters (PM0.1). The photocatalytic activity of synthesized CQD/TiO2 @PI/PES membranes with 5% CQD loading on the decomposition of acetone was significantly enhanced compared with that of TiO2(P25)@PI/PES. The comprehensive results of photoluminescence emission, X-ray photoelectron spectroscopy, and photocatalytic experiments suggest that up-conversion properties of CQD can enhance the absorption of visible light on TiO2 and reduce the reorganization of electron-hole pairs. Further, the optimized CQD/TiO2 @PI/PES membrane could effectively photodegrade of acetone (>94.5%) and also maintained a good PM0.1 filtration efficiency (> 99%) and a differential pressure of 0.34 Pa for creating level 3 medical face masks as per the standards of ASTM F2299 and EN 14683. Therefore, the dual-functional CQD/TiO2 @PI/PES membrane could be applied as a promising photocatalytic filter for air purification that simultaneously and remarkably filters PM0.1 and decompose VOCs.

Self-Charging, Breathable, and Antibacterial Poly(lactic acid) Nanofibrous Air Filters by Surface Engineering of Ultrasmall Electroactive Nanohybrids.

Despite the great promise in the development of biodegradable and ecofriendly air filters by electrospinning of poly(lactic acid) (PLA) nanofibrous membranes (NFMs), the as-electrospun PLA nanofibers are generally characterized by poor electroactivity and smooth surface, challenging the exploitation of electrostatic adsorption and physical interception that are in need for efficient removal of pathogens and particulate matters (PMs). Herein, a combined "electrospinning-electrospray" strategy was disclosed to functionalize the PLA nanofibers by direct anchoring of highly dielectric BaTiO3@ZIF-8 nanohybrids (BTO@ZIF-8), conferring simultaneous promotion of surface roughness, electret properties (surface potential as high as 7.5 kV), and self-charging capability (∼190% increase in tribo-output voltage compared to that of pure PLA). Benefiting from the well-tailored morphology and increased electroactivity, the electrospun-electrosprayed PLA/BTO@ZIF-8 exhibited excellent PM-capturing performance (up to 96.54% for PM0.3 and 99.49% for PM2.5) while providing desirable air resistance (only 87 Pa at 32 L/min) due primarily to the slip flow of air molecules over the nanohybrid protrusions. This was accompanied by excellent antibacterial properties (99.9% inhibition against both Staphylococcus aureus and Escherichia coli), arising presumably from the synergistic effects of enhanced reactive oxygen species (ROS) generation, plentiful ion release, and surface charges. Our proposed strategy opens up pathways to afford exceptional combination of high-efficiency and low-resistance filtration, excellent antibacterial performance, and mechanical robustness without sacrificing the biodegradation profiles of PLA NFMs, holding potential implications for efficient and long-term healthcare.

Spraying coupled with turbulence mechanisms enhanced the removal of fine particles in wet flue gas

Agglomeration pretreatment has been proved as the most effective method to enhance the removal of fine particulate matters (PM2.5). However, the common technologies were not suitable for the high-humidity conditions, such as the wet flue gas after desulphurization. Herein, we proposed a method for enhancing the agglomeration of fine particles by applying the combination mechanisms of spraying and turbulence effects. Through the experiments and simulation studies, we found that the number concentration proportions of fine particles can decrease by 19.9% in the size range of 0–0.5 μm, and increased by 15.2% in the range of 0.5–3.0 μm with the spray volume of 15 L/min. The turbulence effects can make the movement states of fine particles more disordered, and increase the collision and agglomeration opportunities among particles and droplets. The average particle size can be increased by 35% with the integrated turbulence structures and spraying. Combined with the agglomeration system, the graded removal efficiency of fine particles with the size of below 1.0 μm in WESP can be improved by 15%. This study contributes to comprehend the mechanism of turbulence on the particle agglomeration, and provides a reference for the upgradation and transformation of the existing dust removal equipment.

Quantifying the potential contribution of urban trees to particulate matters removal: A study in Chattogram city, Bangladesh

Urban trees have capacity to reduce atmospheric particulate matters (PM) concentration through deposition on leaves. However, we have very limited studies on the contribution of urban trees toward removal of PM in Bangladesh. In this study, conducted in Chattogram City Corporation (CCC), Bangladesh, we aimed to i) quantify the ambient atmospheric PM (PM2.5 and PM0.50), ii) quantify deposition of PM by urban trees, and iii) find out variation of PM with respect to common tree species, height of trees (low: 2.0–3.5 m and mid: 3.5–4.5 m), leaf traits (shape, surface), and seasons. Monthly air PM concentrations were measured from September 2020 to April 2021 in six sites (viz. roadside, residential, industrial, commercial, medical, and park area) in CCC. For measuring PM deposition, we collected 128 sample leaves from eight randomly selected trees of eight tree species in every month from study sites. At roadside, where relative greenspace was lowest, the atmospheric PM concentration was the highest. Conversely, where relative greenspace was higher (e. g. residence and park), the PM concentration was the lowest. In winter season (December–February), both ambient PM concentrations and deposition on leaves were the highest. Psidium guajava had significantly (p < 0.05) higher PM deposition than other tree species at both height levels. Deposition of PM was highest in trees with oblong and ovate-shaped, and rough-surfaced leaves at lower height, and therefore, recommendation is made to plant trees with these attributes in urban areas.

Efficient removal of high-temperature particulate matters via a heat resistant and flame retardant thermally-oxidized PAN/PVP/SnO2 nanofiber membrane

Particulate matters (PMs) emissions from energy consumption contribute the vast majority of PM pollution, which are typically associated with high temperatures (>300 °C) and are difficult to remove directly at high temperatures. Electrospinning nanofiber membranes have irreplaceable advantages of high removal efficiency and low pressure drop for PMs filtration, however, the efficient filtration of PMs at high temperature is challenging for polymer-based nanofiber membranes because of the poor heat resistance and inflammability. Herein, we design a thermally-oxidized polyacrylonitrile/polyvinylpyrrolidone/SnO2 (OPAN/PVP/SnO2) nanofiber membrane by performing the thermally induced cyclization and oxidation reaction of PAN/PVP/SnCl2 nanofiber membrane at 350 °C in air. During the thermal oxidization process, Sn2+ acted as a catalyst and activation, preventing the melting and fusion of PAN nanofibers. The addition of PVP greatly increased the mechanical properties of OPAN/SnO2 nanofiber membrane. The prepared OPAN/PVP/SnO2 nanofiber membrane possesses superior PMs filtration performance at room temperature, with the PM0.3 and PM2.5 filtration efficiency of 99.53% and 99.98%, respectively. The OPAN/PVP/SnO2 nanofiber membrane exhibits high temperature tolerance up to 350 °C and wide pH tolerance of 1–14, it remains a high PMs removal efficiency of 98.51% at 350 °C and 98.67% at 300 °C. Moreover, the OPAN/PVP/SnO2 nanofiber membrane shows excellent fire retarding and self-extinguishing property not shown in pristine PAN nanofiber membrane. This work provides a novel approach for clean use of energy via a cost-effective, heat-resistant, and flame-retardant nanofiber membrane.

Polyelectrolyte aerogels with regeneration capacity for efficient removal of particulate matters

HypothesisWith the rapid development of economy and global industrialization, the problem of air pollution has become a worldwide topic. The efficient filtration of airborne particulate matters (PMs) is critical for human health and environmental sustainability. ExperimentsHerein, self-supporting bio-based polyelectrolyte aerogels were prepared and acted as the advanced filters for efficient removal of PMs. The natural choline cation (Ch+) or the organic cation, 1-butyl-3-methylimidazolium (Bmim+), are introduced into alginate (Alg-) to form the polyelectrolytes of ChAlg or BmimAlg due to the electrostatic interaction. By the directional freeze-drying in liquid N2, hierarchically porous aerogels with mechanical robustness, flexibility and thermo-stability were prepared. This specific structure may permit the polluted air to pass adequately through the aerogel channels, which are conducive to intercept various PMs with different diameters. FindingsAs an example, the removal efficiency of ChAlg aerogels for PM10, PM2.5 and PM0.3 are respectively up to (99.24 ± 0.03)%, (99.22 ± 0.02)%, and (93.41 ± 0.22)% within 15 h durability test. One outstanding character lies in ensuring high removal efficiency, while achieving a good balance with the low pressure drop (10 Pa), which is driven by synergistic effect of passive trapping and electrostatic capture. Moreover, the polyelectrolyte aerogels exhibit excellent antimicrobial activity and regenerated capacity. These properties endow the aerogels of polyelectrolyte ChAlg or BmimAlg with remarkable potential as new advanced filters for masks and other personal protective equipment.

Effect of airflow pattern and distance on removal of particulate matters and volatile organic compounds from cigarette smoke using Sansevieria trifasciata botanical biofilter

Botanical biofilters can effectively remove indoor air pollution. However, to apply botanical biofilters in situ, the distance of botanical biofilter to the pollutants and airflow pattern can be important factors impacting efficiency. This study examined the removal efficiency of particulate matters (PMs) and volatile organic compounds (VOCs) from cigarette smoke, such as formaldehyde and acetone, at various distances (100 cm, 175 cm, 240 cm, and 315 cm) using a Sansevieria trifasciata botanical biofilter. The botanical biofilter was placed inside a testing room (24 m3) and exposed to cigarette smoke. The pollutants removal efficiency was evaluated for six cycles (24 h/cycle) and one cycle as a recovery period where botanical biofilter was placed under normal conditions for 30 days. Results showed that the botanical biofilter could remove 140–250 μg m−3, 147–257 μg m−3, 212–455 μg m−3 for PM1, PM2.5, and PM10, respectively, at 8 h. Total VOCs, formaldehyde, and acetone removal were 40%–65%, 46%–69%, and 31%–61% at 24 h. PMs and VOCs removal efficiency can be affected by both distance and pattern of airflow in the testing room. The highest PM1 and PM2.5 elimination appeared at 240 cm and 315 cm, while VOCs removal was high at 100 cm. Botanical biofilter creates airflow vortices around 100 cm, indicating low removal of PMs. This is the first study that demonstrated the effect of airflow patterns on different pollutants removal efficiency.

Performance evaluation of air pollution control device at traffic intersections in Delhi.

Urban air pollution and exposure-related health impacts are being noticed and discussed very intensely in India. On the other hand, source-specific control is the primary focus for policymakers; however, diverse and complex sources make it difficult to immediately see the action and consequent impacts on better air quality. Many cities across the world have witnessed high air pollution levels at traffic junctions, more so in all Indian cities. Site-specific air pollution reduction can be a promising solution for managing the pollution level at highly polluted locations. CSIR-National Environmental Engineering Research Institute, India, has designed and developed Wind Augmentation and purifYing Unit (WAYU) to remove particulate and gaseous pollutants from urban hot spots such as traffic locations. In the present study, the authors attempted to evaluate the performance of two different designs of WAYU for the removal of particulate matters from polluted air at different traffic locations in Delhi City, the national capital territory of India. The performance analyses show that the current design of WAYU removes PM10 and PM2.5 concentrations in the range of 34–49% and 19–25%, respectively from the inlet air. The total PM collected from all WAYU devices was 34.19 kg from 120,557 operating hours’ at all the sampling sites. The PM removal rate depends on the size-segregated particulate matter pollution load in the ambient air.Supplementary InformationThe online version contains supplementary material available at 10.1007/s13762-021-03641-3.

Simultaneous removal of VOCs and PM2.5 by metal-organic framework coated electret filter media

The electret filter media coated with highly porous metal-organic frameworks (MOFs) particles, named E-MOFilter, is newly developed and evaluated for its capacity for simultaneous removal of fine particulate matters (PM2.5) and volatile organic compounds (VOCs). Three different MOF particles, including MIL-125-NH2, UiO-66-NH2, and ZIF-67, were synthesized and systematically characterized. The produced MOF particles were suspended in ultrapure water and then a liquid filtration apparatus was used to deposit the MOF particles onto two electret media with different minimum efficiency reporting values (MERV 13 and 17) to form the E-MOFilters. Results showed that the MOF particles deposited in MERV 13 media more uniformly than that of MERV 17. In the PM filtration tests, results showed that the E-MOFilter gained only a few more pascals of air resistance compared with clean electret media. Besides, its PM removal efficiency was found to be close to that of clean electret media. This indicates that a uniform MOF particle deposition and negligible charge degradation from the current coating process were obtained. Further, the E-MOFilter with MIL-125-NH2 particle coating not only had a decent toluene removal efficiency (>80%) but also maintained its original PM2.5 holding capacity. This work may shed light on applying the novel E-MOFilter in the residential and commercial HVAC systems and indoor air purifiers to simultaneously and effectively remove PM2.5 and VOCs.

Performance evaluation and process simulation for synergetic removal of NOx, CO2 and PM using green alkaline solution in a high-gravity rotating packed bed

The high-gravity rotating packed bed (HiGee RPB) developed here can simultaneously remove multiple air pollutants using alkaline solution, thus achieving the flue gas deep purification. The electric-arc-furnace reduction slag (EAFRS) leachate was then used as the alkaline absorbent in HiGee RPB for assessing the removal efficiencies of nitrogen oxide (NOx), carbon dioxide (CO2) and particulate matters (PM) from flue gas. The results indicated the changes to the CO2 capture was enhanced by increasing the initial PH value of the alkaline solution. In contrast, this value has no significant influence on NOx removal. The suitable NOx removal efficiency ranged from 90.9% to 97.09% at the liquid-to-gas (L/G) ratio of 0.01 and high gravity factor of 58.9 to 368. The precipitated calcium carbonate gained from carbonation via HiGee process exhibited similar physical properties to commercial products. In addition, 95.9% of PM removal efficiency was achieved at the L/G ratio and high gravity factor of 0.03 and 235.4, respectively. This treatment furthermore demonstrated a high efficiency for PM collection of over 90% and balanced the energy consumption. Based on the result, an Aspen simulation and a preliminary cost-benefit analysis were carried out to develop a mass-balance model for this system and determine the favorable operating conditions.

Removal of Particulate Matters with Isostructural Zr-Based Metal-Organic Frameworks Coated on Cotton: Effect of Porosity of Coated MOFs on Removal.

Effective removal of particulate matters (PMs) from air is very important for our safe environment, health, and sustainability. In this study, isostructural (with the same topology of fcu) Zr-metal-organic frameworks (Zr-MOFs) such as UiO-66, UiO-67, and DUT-52 (with different porosity) were coated onto cotton and utilized in PM removal from air to understand the contribution of MOFs in improving the performances of air filters. Moreover, UiO-66s with different porosities were also prepared under different conditions from the same reaction mixture. Experiments to remove PMs such as PM2.5 and PM10 showed a critical role of porosity of coated MOFs in the PM removal. Or, the removal efficiency or quality factor increased linearly with the increasing surface area of all the studied MOFs, irrespective of the applied linkers (for synthesizing different MOFs) and synthesis conditions (for different porosities of UiO-66s). Therefore, this work confirms, for the first time, that the porosity of MOF is one of the most important parameters to improve the performance of air filter (to remove PMs) that is modified with coated MOFs. Moreover, we could suggest why porous materials with small pores were effective in capturing PMs (larger in size than pores of porous materials) from air.

Highly Improved Performance of Cotton Air Filters in Particulate Matter Removal by the Incorporation of Metal-Organic Frameworks with Functional Groups Capable of Large Charge Separation.

Currently, air contamination, especially with particulate matters (PMs), is severe in several countries. To increase the efficiency of air filters in PM removal, metal-organic frameworks (MOFs, here, Zr-MOFs, especially with functional groups (FGs) such as -NO2) were coated, after synthesis, onto cotton using covalent bonding for the first time. The removal efficiencies (REs) and quality factors (QFs) of cottons with or without MOFs were in the order: cotton < Zr-MOF/cotton < Zr-MOF-NH2/cotton < Zr-MOF-NH-SO3H/cotton < Zr-MOF-NH3+Cl-/cotton < Zr-MOF-NO2/cotton. This monotonic increase in the PM removal efficiency or QF could be explained with the order of charge separation or developed charges (total, in absolute value: ∼0 to 2.0) on FGs of MOFs. Importantly, Zr-MOF-NO2 coating on cotton showed a very high increase in the performance of cotton in PM removal. QF and RE of Zr-MOF-NO2/cotton were 4.6 times and 6.2 times of the bare cotton, respectively, for PM2.5 removal, even with a very small increase in pressure drop (3 Pa or less) with MOF coating. Based on the research, it can be suggested that coating MOFs on substrates is a promising way to improve the performances of air filters for PM removal, especially when MOFs have FGs that can have large charge separation such as -NO2. This work may pave a way to utilize a functionalized MOF in the effective removal of PMs from air.

Effect of trichome structure of Tillandsia usneoides on deposition of particulate matter under flow conditions

The removal of particulate matters (PM) has emerged as one of the most significant issues in public health and environment worldwide. Environmentalists have proposed the use of indoor air-purifying plants as an eco-friendly strategy to resolve PM-related problems and effectively remove fine particulate matter (PM2.5). Among air-purifying plants, Tillandsia usneoides (L.) L. (T. usneoides) has been used as a biomonitor for heavy metals and air pollutants. However, the PM removal effect of T. usneoides and its primary mechanism remain unclear. Here, we investigated the PM removal performance of T. usneoides in a closed chamber under flow conditions, the effects of trichomes, and the array density according to the different types of PM. The chamber with bulk T. usneoides under flow conditions exhibited 16.5 % and 9.2 % higher removal efficiency in PM2.5T. usneoides for incense and A1 rigid PM, respectively, than that without T. usneoides. T. usneoides with trichome structure exhibited larger removal efficiencies of 7% and 2% in PM2.5 and PM10, respectively, than without trichome for incense particles. In addition, the increase in total effective surface was effective for the deposition of both PM types. The increase in effective surface area by trichome structure and array density of T. usneoides is a crucial factor for the deposition of PM.

Experimental investigation on flue gas purification and gas‐liquid multiphase flow in a spraying column with perforated plate

AbstractThe synergetic removal of sulphur dioxide and particulate matters (PM) in flue gas was investigated in a spraying column equipped with flow pattern controlling (FPC) internals. The performance of the novel column was compared with that of the traditional open column by monitoring the removal efficiency and system pressure drop. To understand the gas‐liquid multiphase flow field and mass transfer process inside the column with different structures, image processing based on the Otsu method and particle image velocimetry (PIV) technology were used. It was found that the FPC column with a section size of 200 mm × 200 mm, hole diameter of 4 mm, and aperture ratio of 0.65 demonstrated the best performance. As clearly observed from the flow filed, bubble flow was formed in FPC column, while the dispersive and falling‐film flow was developed in the open column. The liquid holdup in FPC unit was much more than in the open spraying column, which enhanced the mass transfer process. According to the PIV results, the reverse flow of the liquid, caused by the gas jet ascribed to the perforated plate and the confined space in the FPC unit, was the primary reason for bubble generation and the gas‐liquid flow pattern in the column.

Effect of Functional Groups of Metal-Organic Frameworks, Coated on Cotton, on Removal of Particulate Matters via Selective Interactions.

Currently, the contamination of air with particulate matters (PMs such as PM2.5 and PM10) is very severe, especially in Asian countries. Metal-organic frameworks (MOFs), with or without extra functional groups such as -NH2 and -NH-SO3H, were coated on conventional cotton to improve the efficiency of filters (composed of cotton fabric) in the removal of PMs from air. More importantly, the effect of the functional group of MOFs on the effective PM removal was analyzed quantitatively for the first time and could be interpreted via selective interactions. The removal efficiency was increased on the order: cotton < UiO-66/cotton < UiO-66-NH2/cotton < UiO-66-NH-SO3H/cotton, and the efficiency of the UiO-66-NH-SO3H-coated cotton was more than three times that of the pristine cotton. Moreover, the quality factor of cotton was more than doubled (or, 2.5-3 times) by UiO-66-NH-SO3H (only 20%) coating. The plausible mechanism for PM removal could be suggested based on the characterization of captured PM and introduced functional groups on MOFs. Based on the removal efficiency, pressure drop, and quality factor, coating of MOFs with functional groups, especially that are effective for charge separations (such as -SO3H), is one of the promising ways to improve the performance of PM filters. Moreover, the suggested strategy might be applied in capturing most of PMs composed of oxides, ammonium species, and carbons with polar outside.

Preparation of Composite Filters Based on Porous Coordination Polymers by Using a Vacuum Filtration Method for Highly Efficient Removal of Particulate Matters.

In this study, two novel crystal materials pcp1 and pcp1-L have been synthesized successfully. The different conformations of the two crystals are mainly attributed to the introduction of the Schiff-base ligand L (L=(E)-4-methyl-N-((6-methoxypyridin-2-yl)methylene)aniline). Subsequently, pcp1 and pcp1-L composites have been firstly produced by a vacuum filtration method on various substrates (i.e., melamine foam, plastic mesh, carbon fiber cloth and glass cloth). The obtained robust composites show excellent performance in removing PMs owing to high ζ potential, microporous structure, large conjugation system and electron cloud-exposed metal center (DFT calculations) of pcp1 and pcp1-L. Particularly, pcp1-L@glass cloth with low pressure drop exhibits high thermal stability and high long-term reproducibility. Additionally, the high removal efficiency of pcp1-L@glass cloth towards particulate matters could also be maintained, even achieving >99.9 % in the car exhaust gas field test.

Numerical investigation on urea particle removal in a spray scrubber using particle capture theory

The effective removal of particulate matters from the flue gas emitted from Urea Prilling Tower is very essential to conform to the environmental standards. Based on particle capture theory, the user-defined-function (UDF) codes were written to implement the simulation of particle removal. A novel numerical simulation method is carried out to study the flow field and the effects of gas-phase loading factor, spray density, particle size and droplet size on the particles removal efficiency. The results show that the removal efficiency of particles above 10 μm can reach 97%. But the removal efficiency of particles less than 10 μm deteriorates with decreasing particle diameter due to the randomness of a fine particle movement. In addition, the improved empirical correlations of the removal efficiency were obtained based on numerical simulation, which provides the guidance for optimum design of a spray scrubber in practical engineering applications.

Effects of FGR and Changeable Combustion Parameters and Coal/Char Properties on the Formation of Ultrafine PMs during Pulverized Coal Char Combustion under Various O2/N2 and O2/CO2 Atmospheres

ABSTRACTAiming at the wide adoption of flue gas recirculation (FGR) in coal power plants for NOx removal and CO2 capture, and the imperfect removal of particulate matters (PMs), especially ultrafine PMs which constitute most of the particles discharged into atmosphere, consequently causing atmospheric haze and diseases, the effects of FGR and combustion parameters, and coal/char properties on PMs formation were therefore studied under different O2/N2 and O2/CO2 atmospheres using a self-developed kinetic model. Modeling results showed that the inclusion vaporization rate and ratio had a dominant effect on PMs number density and size respectively. At the same level of oxygen content, smaller ultrafine PMs were generated under O2/CO2 than those generated under O2/N2. Increasing oxygen content facilitated the formation of larger and fewer PMs. The PMs size in 27O2/73N2 shows the biggest, followed by that in 36O2/64CO2, 27O2/73CO2, 21O2/79N2, and 21O2/79CO2 in turn. Compared to without FGR, FGR decreased the size of ultrafine PMs and increased the number, thus hindering PMs removal. With increasing FGR ratio, which had the most significant effect, the ultrafine PMs size decreased due to dilution effect. With increasing dust removal efficiency, the ultrafine PMs size decreased initially and then increased, peaking close to 100% of dust removal efficiency. The effect of recirculated particle size was negligible. Sensitivity analyses revealed that furnace gas temperature, inclusion size, and char density were the most influential factors on inclusion vaporization and PMs formation. The effects of CO/CO2 ratio, char load, coal ash content, and inclusion content were positive, while the effects of char density and ash content, inclusion size, and moisture were negative. High furnace temperature increased vaporization, but significantly decreased the PMs size. The number density of ultrafine PMs followed mass conservation. These results provide meaningful guidelines for practical applications.