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Wet scrubbers are traditionally used as dedusting systems in waste incineration plants for wet flue gas treatment. Although these devices are not particularly performant at capturing submicron particles, which are associated with health and environmental hazards, their collection efficiency can be improved by optimizing operating conditions. This study presents the design methodology of a downscaled wet scrubber, constructed and implemented at a municipal waste incineration plant to be fed with real fumes, and to study its efficiency towards the removal of submicronic particles. The downscaled scrubber was designed to operate with flue gas at 200 °C, high humidity (1% RH), and an average total particle concentration of 200 mg/Nm3. A criterion of geometric, aerodynamic, and residence time similarities to an existing industrial scrubber was targeted. The height of the device was selected by matching the theoretical fractional particle collection efficiencies of the industrial and downscaled scrubbers. Featuring a cylindrical shape, the downscaled scrubber has a diameter of 0.3 m and a height of 2.5 m. It operates in co-current with water injected through four spray levels. Computational fluid dynamics simulations were conducted to analyze the gas flow structure within the device, and the results were validated by hot wire anemometer velocity measurements. [ABSTRACT FROM AUTHOR]

Odor emissions are a crucial component of atmospheric pollution. As odor is a sensory pollutant, its management and treatment are recalcitrant. A wet scrubber (WS) is an efficient technique for odor removal, but disposal of waste liquid discharge leads to secondary pollution and CO2 emissions during transportation. In this study, a system consisting of WS and electrooxidation (EO) was developed and installed in a swine manure fermentation facility. The absorption and EO characteristics were estimated through the practical implementation of a bench-scale WS (BSW). For EO, a dimensionally stable anode and Cl− were applied. When the BSW was operated without EO, an L/G ratio of 8.88 was essential for securing the simultaneous removal rate of the four odorants (hydrogen sulfide, methyl mercaptan, ammonia, and total volatile compound). With the operation of the EO, the period to change the liquid based on equilibrium was postponed due to the continuous oxidation of the odorants absorbed in the liquid. As the applied current increased, the change period was further prolonged. However, the oxidation and absorption rates differed depending on the odor substances, due to differences in their physicochemical characteristics. Hydrogen sulfide and methyl mercaptan exhibited similar absorption and oxidation rates. Ammonia had a high absorption rate and a low oxidation rate. The acetaldehyde oxidation rate was the most sluggish among the substances. These findings demonstrate that simultaneous consideration of Henry's constant and the reactivity of the target pollutant with HOCl renders the design of BSW appropriate for treating odor gases containing various odorants. This study contributes to efforts to address environmental problems concerning odors and also to global climate threats. [ABSTRACT FROM AUTHOR]

The removal efficiency of particulate matter of less than 2.5 microns (PM2.5) using an innovative wet scrubber tower with an IoT system for PM2.5 real-time monitoring was investigated. The PM2.5 used in this experiment was obtained from vehicle exhaust, specifically from running the diesel engine of a pickup truck with a range of PM2.5 with a concentration ranging from 50 µg/m3 to 500 µg/m3. Focused parameters related to PM2.5 were analyzed, such as the liquid-to-air ratio (it uses air because this device purifies PM2.5 for the airflow from the polluted ambient air), turbulence techniques enabled by the installation of a deflector and a baffle at the airflow inlet, water level fluctuation above the nozzle, spray nozzle size, and the type of packing material. The average PM2.5 removal efficiency was determined for each parameter relevant to the experiment. The results showed that increasing the liquid-to-air ratio increased the average PM2.5 removal efficiency, while the smaller droplet spraying water resulted in higher efficiency. The spray section achieved its highest efficiency at 58.63%, with a liquid-to-air ratio of 13.21 L/m3 and droplet size of 270 µm. The turbulence technique showed a higher potential for the removal of PM2.5, with an efficiency level of 71.56% at a water level of 150 mm. Moreover, the operation incorporates water spraying and turbulence induction, promoting higher removal efficiency, from 71.56% to 87.59%, at a water level of 150 mm and a liquid-to-air ratio of 9.03 L/m3. This condition resulted in an output concentration of PM2.5 less than 15 µg/m3, which meets the WHO's guidelines for PM2.5 intensity. This cleverly designed wet scrubber tower can clean up to 13,320 m3 of air daily or remove up to 2,464 g of PM2.5 per day. No enhancement of PM2.5 removal efficiency was observed when two types of packing materials were used due to the formation of bigger droplets as the packing materials were passed through. [ABSTRACT FROM AUTHOR]

In this work, an experimental study has been conducted in a newly designed and developed dual-flow scrubber with three sieve plates for simultaneous removal of hydrogen sulphide and particulate matter (fly-ash) from syngas produced in a gasifier as these impurities of syngas destroy and decrease the efficiency of the downstream processing equipment. The performance of the scrubber at different gas and liquid flow rates in the range of 16.59 × 10−4- 27.65 × 10−4 Nm3/s 20.649 × 10−6-48.183 × 10−6 m3/s has been observed for both the particulate matter and hydrogen sulphide removal along with the effect of inlet particulate loading (15 × 10−3- 25 × 10−3 kg/Nm3) and 100–300 ppm inlet H2S loading. The H2S removal efficiency in the dual-flow wet scrubber increased from 78.88% to 87.45% when the particulate matter loading was increased from zero to 25 × 10−3 kg/Nm3 at 300 ppm inlet H2S concentration for 48.183 × 10−6 m3/s liquid flow rate and 27.65 × 10−4 Nm3/s gas flow rate. The efficiency of the particulate matter is similar to that of the particulate scrubbing in absence of the H2S.

[Display omitted] Chlorinated volatile organic compounds (CVOCs) are a recalcitrant class of air pollutants, and the strongly oxidizing reactive oxygen species (ROS) generated in advanced oxidation processes (AOPs) are promising to degrade them. In this study, a FeOCl-loaded biomass-derived activated carbon (BAC) has been used as an adsorbent for accumulating CVOCs and catalyst for activating H 2 O 2 to construct a wet scrubber for the removal of airborne CVOCs. In addition to well-developed micropores, the BAC has macropores mimicking those of biostructures, which allows CVOCs to diffuse easily to its adsorption sites and catalytic sites. Probe experiments have revealed HO• to be the dominant ROS in the FeOCl/BAC + H 2 O 2 system. The wet scrubber performs well at pH 3 and H 2 O 2 concentrations as low as a few mM. It is capable of removing over 90% of dichloroethane, trichloroethylene, dichloromethane and chlorobenzene from air. By applying pulsed dosing or continuous dosing to replenish H 2 O 2 to maintain its appropriate concentration, the system achieves good long-term efficiency. A dichloroethane degradation pathway is proposed based on the analysis of intermediates. This work may provide inspiration for the design of catalyst exploiting the inherent structure of biomass for catalytic wet oxidation of CVOCs or other contaminants. [ABSTRACT FROM AUTHOR]

Sulfur and nitrogen oxides (SOX/NOX) are the primary air toxic gas pollutants emitted during fuel combustion, causing health and environmental concerns. Therefore, their emission in flue gases is strictly regulated. The existing technologies used to decrease SOX/NOX content are flue gas desulfurization, which necessitates high capital and operating costs, and selective catalytic reduction, which, in addition to these costs, requires expensive catalysts and high operating temperatures (350–400 °C). New wet scrubbing processes use O3 or H2O2 oxidants to produce (NH4)2SO4 and NH4NO3 fertilizers upon ammonia injection. However, these oxidants are expensive, corrosive, and hazardous. SiO2/Co(OH)2 nanocomposites are presented here as potential catalysts for SOX/NOX oxidation in wet scrubber reactors to scrub these toxic gases using atmospheric oxygen as the oxidant at relatively low temperatures of 60–90 °C. Several silica-cobalt-oxide-based nanocomposites were synthesized as potential catalysts at different concentrations and temperatures. The nanocomposite catalysts were characterized and exhibited excellent catalytic properties for SOX/NOX oxidation using atmospheric oxygen as the oxidant, replacing the problematic H2O2/O3. We thus propose SiO2-supported Co(OH)2 nanoparticles (NPs) as excellent catalysts for the simultaneous scrubbing of polluting SOX/NOX gases in flue gases using atmospheric O2 as the oxidation reagent at a relatively low-temperature range. [ABSTRACT FROM AUTHOR]

• A fast real-time method for measurement of gas holdup characteristics with image information entropy. • The global and local profiles of gas holdup could be collected simultaneously. • Sieve plate resistance and bubbling state were analyzed with the use of image information entropy. Wet scrubbers are often used in various types of industrial workshops to separate dust particles from the air. Non-uniform gas–liquid flow patterns above the sieve plate can result in significant losses in purification efficiency for particles. To improve the flow pattern via sieve plate design and to more accurately predict purification efficiency, a better understanding of the gas holdup is required. Various methods have been developed to measure and analyze the gas holdup from local and global perspectives. However, for guiding the operation and design of reactors, it is obviously insufficient to obtain the phase holdup characteristics under a steady state. The spatial and temporal characteristics of gas holdup in a wet scrubber are rather difficult to measure in real time with the current techniques. In this study, a fast real-time method for measurement of gas holdup characteristics was proposed, based on image information entropy analysis. The axial and radial profiles of gas holdup under different bubble washing operation statuses were obtained and are discussed here. More detailed information about the gas holdup above the sieve plate under various operation conditions has been attained. Sieve plate resistance and bubbling state were analyzed with the use of image information entropy. [ABSTRACT FROM AUTHOR]

The removal of organic pollutants from ship emission was studied using two processes namely electron beam (EB) and hybrid EB with wet scrubbing process. A mobile accelerator unit was used to treat 4915 Nm3/h of flue gas emitted from a tugboat in Riga Shipyard. A volume of 3 m3 seawater containing 36.8 mM of NaClO2 oxidant was used as a wet scrubber solution. Organic pollutants, mainly volatile organic pollutants (VOCs), were collected at three different sampling points, before and after irradiation vessels, and after wet-scrubber unit, respectively. They were collected with glass sampling bottles, tedlar bags, Coconut Shell Charcoal (CSC) sorbents and XAD-2 sorbents. CH3OH and CH3OH/CH2Cl2 (1:1) were used to extract VOCs from CSC and XAD-2 sorbents, respectively. Syringe filters were used to obtain the solid-free extraction solutions. They were concentrated using a micro-extractor under continuously blowing high-purity Ar. A gas chromatography–mass spectrometry (GC-MS) was used for analysis. The identified organic compounds were: aliphatic hydrocarbons (dodecane C12H26 to eicosane C20H42), aromatic hydrocarbon (toluene), esters (C3H7COOCH3, (C4H9OCO)2C6H4), nitro compounds (C3H5NO3, C4H7NO2) and acid (C7H15COOH). After 4.2 kGy EB irradiation, around 50–100% aliphatic hydrocarbons, 83% toluene and 7.5% (C4H9OCO)2C6H4 were removed from the off-gases, and after EB hybrid wet-scrubber process, most organic compounds including nitro compounds were removed. Only trace amount of toluene, hexadecane, octadecane and dibutyl phthalate were found to be present in the gas phase.

Abstract A laboratory scale, 1.0 CMM (m3 min− 1) wet scrubber packed with water-absorbing honeycomb material (HWS) with a very large geometric surface area of 480 m2 m− 3 and a low pressure drop developed in our previous study was shown to achieve a very high removal efficiency for acidic gases but there were no long-term test data. In this study, the HWS scaled up to operate at a 100 CMM flow rate was tested for removing mixed acidic gases at a semiconductor fab for a very long period of 3.5 yr. Results showed that the removal efficiency for the mixed gases emitted from the fab always maintained as high as > 95% for HF, CH3COOH, HCl, HNO3, HNO2, and H2SO4 with the inlet concentrations ranging from supper-ppmv to sub-ppmv, during a 3.5-yr period. With water jet cleaning of the honeycomb modules once per year, the pressure drop of the HWS remained to be low at 0.5–0.8 cm H2O, indicating minimal scaling in the HWS. Additionally, the predicted height and removal efficiencies of the HWS were very close to the experimental data. The excellent long-term performance of the HWS warrants its potential applications in many areas in which liquid absorption is the preferred treatment method and the theoretical equations can facilitate the design of the HWS.

Tobacco dust represents a critical threat to the operators' respiratory health. Even when wet scrubbers display high purification efficiencies and strong adaptability to dust, their potential applications in the tobacco industry have not been studied. In the present research, removal efficiency of wet scrubber for tobacco dust and fine dust were examined at laboratory and industrial level. Results showed that the dust removal efficiency of the wet scrubber under laboratory conditions reached a maximum value of 99.17%. In addition, the dust discharge concentration was reduced to a minimum value of 1.1 mg/m3. Our data indicated that after using the wet scrubber, large dust particles (≥10 μm) were more effectively removed than fine dust particles (≤5 μm). After the use of the wet scrubber at the industrial facility, the overall dust removal efficiency reached a value of 98.9%, and dust concentration at the discharge point was as low as 1 mg/m3. This value complies with the ultra-low discharge standard and industrial production requirements. Our study demonstrated the feasibility of using wet scrubbers in the removal of tobacco dust and provides new insights for dust suppression in the tobacco processing industry. [ABSTRACT FROM AUTHOR]

In contrast to conventional dry separators, new types of wet scrubbers with innovative nozzle geometries are capable of separating submicron particles with comparatively low pressure drop. As those geometries can easily be adapted using 3D‐printing manufacturing, an applied geometry optimization can lead to a fast and cost‐efficient product development cycle. In this study, the lattice Boltzmann method is used to optimize the pressure drop associated with a novel nozzle design. Simulated pressure drop data are validated with experimentally determined ones. By replacing originally installed ellipsoid‐shaped bluff bodies with foil‐shaped structures according to the 4‐digit NACA‐series, an optimization approach regarding the resulting pressure drop is described. [ABSTRACT FROM AUTHOR]

Kebutuhan yang semakin meningkat sejalan dengan tingginya permintaan pasar terhadap suatu produk. Salah satu produk yang banyak digunakan yaitu kertas. Salah satu industri kertas daur ulang adalah PT. Pura Nusapersada Unit Paper Mill 7/8 dimana proses produksinya menggunakan uap air dari boiler yang berbahan bakar batubara. Proses tersebut berpotensi menghasilkan ash yang dapat mencemari udara sehingga diperlukan alat pengendali pencemar udara seperti cyclone dan wet scrubber. Diperlukan evaluasi terhadap efisiensi cyclone dan wet scrubber dengan mengetahui spesifikasi dan prinsip kerja alat, emisi yang dihasilkan, efisiensi alat, faktor yang mempengaruhi, permasalahan, operasi, dan pemeliharaannya. Metode yang digunakan yaitu pengamatan secara langsung, wawancara, data berupa dokumen, referensi, dan laporan rutin. Cyclone yang digunakan berjenis multicyclone dan wet scrubber berjenis venturi scrubber. Dari perhitungan yang telah dilakukan, didapatkan efisiensi Boiler Hitachi 94,195% dan Boiler Hamada II 96,844%. Boiler tersebut menghasilkan emisi yang telah memenuhi baku mutu Peraturan Menteri Lingkungan Hidup Nomor 07 Tahun 2007. Perhitungan efisiensi sebaiknya setahun sekali agar kualitas alat terpantau dan tidak mencemari kualitas udara di sekitarnya.

Small‐scale biomass boilers contribute to the emission of particulate matter (PM) to the environment. In this study, the performance of a wet‐scrubber purification system for flue gas was experimentally investigated. The experimental setup consisted of a boiler, a wet scrubber, a generator, and heat exchangers. The results showed an average PM collection efficiency of ca. 42 % for a PM size range of 0.08–10 µm over a testing period of five months. Furthermore, the results showed an improvement in the heat recovery of about 18 %. Focusing only on the heat losses through exhaust flue gases, the losses were shown to have decreased by 72 %. During the total testing period of 8.5 months, no decrease could be noticed in the absorption solution ability. [ABSTRACT FROM AUTHOR]

For decades, wet scrubbers have been used to control particulate matter (PM) emitted by bagasse-fired boilers in the sugarcane industry. This choice was justified by their acceptable performance in meeting environmental standards, the abundance of water resources, and the fact that their operation was simpler and less expensive than other dry cleaning operations. However, the progressive tightening of PM emission limits, as well as the need for more rational water and wastewater management in these applications, has changed this aspect of the industry. Despite the extensive technical literature on wet scrubbers, the lack of up-to-date indicators of their performance in sugarcane industries has prevented the optimization of wet scrubbing processes. This paper clearly shows that the use of wet scrubbers can result in significant water and heat losses, as well as high operating costs for wastewater treatment stations (WTSs). Mass and energy balances were determined for a typical ethanol-sugar plant operating in Brazil, which is the world's largest sugarcane producer. The key boiler and scrubber performance indicators were evaluated experimentally over the course of a crop season and were compared to the legal particulate emission and water quality requirements in Brazil. The boiler processed an average of 114.8 t/h of bagasse containing 46.8% moisture and generated 4.75 t of gas and 28.2 kg of PM for each ton of dry burned bagasse. Of the total PM (ash and soot), 68% was collected as dry material in the grate, heat exchangers, and multicyclone; 25% was collected in the wet scrubber; and 7% was emitted to the atmosphere, in compliance with the Brazilian standards. The operation of the WTS linked to the gas cleaning system was inefficient, using 70% of the water to convey the dry PM retained in the boiler, heat exchangers, and multicyclone and only 30% to operate the wet scrubber. Evaporation caused the loss of 10.5% of the scrubbing water to the atmosphere. The transportation of moist cake (7.9 t/h, 78% wb) for disposal in fields resulted in significant fuel costs and water losses. The operation of the WTS accounted for 62% of the total capital expenditure of the cleaning system, while the wet scrubber accounted for only 38%. This work provides updated performance indicators and alternatives for optimizing a gas cleaning system to promote more rational water and wastewater management and savings for the sugarcane sector. Required collection efficiency for bagasse boilers based on the inlet PM concentration and emission limits imposed in Brazil, China, and most countries [ABSTRACT FROM AUTHOR]

[Display omitted] • The porous graphitized carbon (PGC) loaded with CoS was successfully prepared. • Wet scrubber containing CoS/PGC and PMS was effective in chlorobenzene removal. • Intermittent or continuous PMS supplementation allowed long-term CVOCs removal. • SO 4 •- and HO• play a dominant role for CVOCs degradation. Chlorobenzene (CB) is a typical example of chlorinated volatile organic compounds (CVOCs) that require pollution control. Using wet scrubbers coupled with advanced oxidation processes (AOPs) has become a promising technique to degrade gaseous CVOCs. Here, a CoS-loaded porous graphitized carbon (PGC) served as an adsorbent for CVOCs and a catalyst to activate peroxymonosulfate (PMS) to construct a wet scrubber for CB degradation. CoS/PGC exhibited excellent catalytic performance at pH 9.0; a 0.1 g/L CoS/PGC dosage and a 10 mM initial PMS concentration achieved 90% CB (25 ppmv) removal within 500 min. Electron spin resonance and quenching experiments identified hydroxyl radicals and sulfate radicals as the main reactive oxygen species that removed CB. In addition, we proposed possible CB degradation pathways by intermediates identified using liquid chromatography-mass spectrometry and density functional theory calculations. Electrochemical experimental results such as cyclic voltammetry and Nyquist proved that CoS/PGC has superior electron transport capacity compared to CoS. A possible catalytic mechanism for CB removal in CoS/PGC + PMS system was proposed by ESR and XPS spectra. By using continuous dosing or pulsed dosing to replenish PMS to maintain its suitable concentration, the system achieves a commendable long-term efficiency. Moreover, this catalyst displayed excellent recyclability and universal applicability to treat various gaseous CVOCs as well as the scrubbing solution replacement with tap water for efficient CB removal. This study may provide new fundamental insights into the PGC-supported catalysts for wet oxidation of CVOCs or other contaminants. [ABSTRACT FROM AUTHOR]

A laboratory scale, 1.0 CMM (m3 min− 1) wet scrubber packed with water-absorbing honeycomb material (HWS) with a very large geometric surface area of 480 m2 m− 3 and a low pressure drop developed in our previous study was shown to achieve a very high removal efficiency for acidic gases but there were no long-term test data. In this study, the HWS scaled up to operate at a 100 CMM flow rate was tested for removing mixed acidic gases at a semiconductor fab for a very long period of 3.5 yr. Results showed that the removal efficiency for the mixed gases emitted from the fab always maintained as high as > 95% for HF, CH3COOH, HCl, HNO3, HNO2, and H2SO4 with the inlet concentrations ranging from supper-ppmv to sub-ppmv, during a 3.5-yr period. With water jet cleaning of the honeycomb modules once per year, the pressure drop of the HWS remained to be low at 0.5–0.8 cm H2O, indicating minimal scaling in the HWS. Additionally, the predicted height and removal efficiencies of the HWS were very close to the experimental data. The excellent long-term performance of the HWS warrants its potential applications in many areas in which liquid absorption is the preferred treatment method and the theoretical equations can facilitate the design of the HWS. [ABSTRACT FROM AUTHOR]

The current research is aimed at experimentally finding out characteristic parameters of the operation of the fog unit and their effect on the efficiency of particulate matter capture. To conduct the experiment, a laboratory equipment—fog unit—was designed and prepared. The fog unit is suitable for 10, 20 and 30 kW pellet boilers. The impact of the parameters on essential changes of indicators important for PM capture is described: sprayed water and gas contact surface; droplets and gas contact time in the unit; droplets holdup in the unit. In the process, a regression equation for predicting the effectiveness of PM capture in a direct contact fog unit is obtained. A good experimental and calculated data correlation is observed (adjusted R squared statistics is 85.32%). [ABSTRACT FROM AUTHOR]

[Display omitted] A pilot-scale packed-bed wet scrubber with plastic packing materials was made and experimented to control hydrogen sulfide.TiO 2 nanoparticles were coated on the surface of packing to improve the hydrophilicity of scrubbing liquid to form a homogeneous liquid layer on the packing surface. Air flow rate, H 2 S concentration, and liquid pH were selected to evaluate their effect on scrubber removal efficiency. To evaluate and model the effects of selected variables, two separate sets of experiments were designed and conducted using response surface methodology, central composite design. The former was to model the effects of air flow rate and H 2 S inlet concentration on removal efficiency at natural liquid pH, and the latter was aimed at total optimization, where all three variables were evaluated. Results showed that TiO 2 nanoparticles substantially increased surface hydrophilicity and hydrogen sulfide removal efficiency in natural pH and total optimization by 3.12 % and 3.63 %, respectively. Moreover, air flow rate and H 2 S concentration had an adverse effect on H 2 S removal efficiency, while liquid pH positively influenced the efficiency. The optimum removal efficiency for natural pH and total optimizations were 98.83 % and 99.93 %, respectively. The results showed that hydrophilicity of packing materials has a strong effect on hydrogen sulfide removal. [ABSTRACT FROM AUTHOR]

Tobacco dust represents a critical threat to the operators’ respiratory health. Even when wet scrubbers display high purification efficiencies and strong adaptability to dust, their potential applications in the tobacco industry have not been studied. In the present research, removal efficiency of wet scrubber for tobacco dust and fine dust were examined at laboratory and industrial level. Results showed that the dust removal efficiency of the wet scrubber under laboratory conditions reached a maximum value of 99.17%. In addition, the dust discharge concentration was reduced to a minimum value of 1.1 mg/m3. Our data indicated that after using the wet scrubber, large dust particles (≥10 μm) were more effectively removed than fine dust particles (≤5 μm). After the use of the wet scrubber at the industrial facility, the overall dust removal efficiency reached a value of 98.9%, and dust concentration at the discharge point was as low as 1 mg/m3. This value complies with the ultra-low discharge standard and industrial production requirements. Our study demonstrated the feasibility of using wet scrubbers in the removal of tobacco dust and provides new insights for dust suppression in the tobacco processing industry.

There have been studies recently on bubble-column scrubbers with low cost and high efficiency for the absorption and treatment of hazardous gases in the event of a chemical spill. Bubble columns are vulnerable to freezing at temperatures below zero because the absorbents generally do not circulate. To address this issue, this study focused on the applicability, absorbed amount, and performance of brine as an absorbent. Under three different temperatures, i.e., −5 °C, −8 °C and −10 °C we examined brine (NaCl, CaCl2, and MgCl2) by varying the concentration required at each temperature. Following the experiments, CaCl2 brine was determined as the optimal brine for its absorption performance and affordability. Based on the experimental results, the absorption performance for ammonia, ethylene oxide, and methylamine, which are hazardous and water-soluble gases among accident preparedness substances (APS), was tested by using ASEPN PLUS. Our results suggested although the efficiency dropped by about 5% to 25% when brine was used as an absorbent, it can be used at the low temperatures because the gas solubility increased with decreasing temperature. Therefore, if brine, as an alternative, is used at temperatures about 15 °C, it can operate efficiently and stably without deterioration in the absorption performance. Given our experimental results and design data on the absorbed amount and absorbent replacement period for major hazardous gases are utilized to prevent bubble columns from freezing, it can be commercially used for small and medium-sized enterprises because it can help reduce installation and operation costs.

An integrated electrostatic precipitator (ESP) and wet scrubber system were developed to control nitrogen oxides (NOx) and particulate matter (PM) emissions from a semiconductor manufacturing process. The integrated system consisted of a NO oxidizer, wet scrubber, and ESP. In the NO oxidizer, NO gas was fully oxidized to NO2 by O3 before the flow gas entered the wet scrubber. To control NO2, Na2S was used as a reducing agent, and NaOH was added to suppress H2S in the wet scrubber. The NO2 removal efficiency could be controlled by maintaining an oxidation-reduction potential higher than −330 mV, and H2S was suppressed by keeping the pH higher than 11. To ensure there was no PM peak during the cleaning cycle, dual-type cylindrical collection plates containing a water film were designed. A negative voltage of 15 kV was applied to the collection plate, and the PM removal efficiency was higher than 95%. The experimental particle-removal efficiency was higher than the theoretical value because the ion loading by plasma in the point of use scrubber was greater than the theoretically calculated value. In addition, the PM removal efficiency was maintained at 95% for 60 min through the water film. The integrated ESP and scrubber system were able to control NOx and PM for long periods at a removal efficiency of over 95%. [ABSTRACT FROM AUTHOR]

The reduction of high concentrations of NOX and SO2 has been studied for the simulation of NOX and SO2 removal from off-gases generated by diesel engines in which heavy fuel oil is usually used. The combination of electron beam (EB) and a wet scrubber method proved to be very promising for this purpose. In this work, we investigated NOX reduction under EB with the application of NaClO, NaClO2, or NaClO3 as an oxidant in two different scrubber solutions, phosphate buffer (Na2HPO4–KH2PO4)–simulated sea water solution and NaOH–simulated sea water solution. The concentration of buffer in the scrubber solution was 5 mM. The concentration of NaOH in the scrubber solution was 7 mM. Compared with the removal performance of NO for the three different oxidants, the application of NaClO2 gave the best removal efficiency. For the inlet concentration of NO gas set at 1000 ppm and the EB dose set at 10.9 kGy, the application of NaClO2 reaches a maximum of 95.03% NO removal efficiency, while the NaClO oxidant reached a maximum of 49.84% removal efficiency and the NaClO3 oxidant reached a maximum of 54.25% removal efficiency. The results show that the chosen series of oxidants have the potential to be applied in the removal of NOX and SO2 from the off-gases of a diesel engine. For example, they could be used on cargo ships, which generate large amounts of NOX and SO2 from the combustion of heavy oil which contains sulphur and nitrogen. [ABSTRACT FROM AUTHOR]

[Display omitted] • VOCs from soil thermal desorption were treated via wet scrubbing coupled with AOPs. • MnCoO x /Kaolin were synthesized via cation-exchange based impregnation-calcination. • Continuous dosing of oxidant was designed and compared in wet-scrubber system. • The stability of VOCs removal rate and mineralization rate was enhanced. • SO 4 · - was proposed to be reactive species responsible for benzene degradation. The heterogeneous advanced oxidation processes coupling with wet scrubber is a promising method for the treatment of VOCs produced by soil thermal desorption. Mn-Co bimetallic oxides/Kaolin (MnCoO x /Kaolin) were successfully synthesized via cation-exchange based impregnation-calcination. The abundant SiO-OH and AlO-OH groups on the Kaolin carrier can inhibit metal aggregation, and the synergistic effect between Kaolin and metal oxide can improve the catalytic performance. The removal rate of benzene via wet scrubber with MnCoO x /Kaolin as catalyst remained above 98 %, which was better than that of single metal oxide. Moreover, the system exhibited significant application effects on the single component (toluene, ethylbenzene, xylene) and BTEX mixture, with the removal rates maintaining at higher than 90 %. The dosing method of PMS was optimized, and the method of continuous dosing of oxidant was proposed instead of one-time dosing. The main active oxygen in the MnCoO x /Kaolin system was sulfate radical, as shown by the results of characterization analysis and quenching experiments. Based on the intermediates identified by GC–MS, a possible degradation pathway of benzene in MnCoO x /Kaolin + PMS system was proposed. [ABSTRACT FROM AUTHOR]

Influence of inhibition and memory effect on PCDD/Fs are carried out in a full-scale (23 t h−1) municipal solid waste (MSW) incinerator under three conditions. Ammonium dihydrogen phosphate (ADP) is injected into the post combustion zone of incinerator. The results show that the inhibition efficiency of PCDD/Fs in flue gas was 53.34% (71% for TEQ), and ADP possibly also didn't have effect on the chlorination reaction of PCDD/F formation. The memory effect phenomenon, PCDD/F adsorption/desorption, is clearly discovered in the wet scrubber system (WSS), resulting in PCDD/F concentration increased by 6.2–19.9 times. Memory effect also changes the distribution of PCDD/Fs by increasing the proportions of low-chlorinated PCDD/Fs, which is easily to be desorbed because of their higher vapor pressure comparing with the high-chlorinated PCDD/Fs. After renewing the scrubbing solution and cleaning the bottom sludge in WSS, the PCDD/F TEQ concentrations decreases from 0.51 to 0.24 ng I-TEQ Nm−3, further mitigating but still not enough to eliminate the memory effect because the PCDD/F desorption of wall and scrubber fillings in the WSS. The results are paving the way for further industrial optimized design of WSS and assist in controlling the PCDD/F emissions from MSWI. • Inhibition efficiency of P-N-inhibitor for PCDD/F from a full-scale MSWI is identified to be 53.34% (71% for TEQ). • Memory effect from wet scrubber system increases emission concentration of PCDD/Fs by 6.2–19.9 times. • Memory effect increases the proportions of low-chlorinated PCDD/Fs in outlet flue gas. [ABSTRACT FROM AUTHOR]

• A novel idea of scrubbing for simultaneous removal of SO 2 and NOx is proposed. • SO 2 /NOx removal can be increased compared to spray or jet bubble reactor technology. • The field test of pilot-scale spray-and-scattered-bubble facility is presented. • Energy consumption can be decreased by ∼10% by this new technology. A new technology (called here, spray-and-scattered-bubble technology) based on preozonation was designed and tested for simultaneous removal of SO 2 and NOx from power plant flue gas. It combines the advantages of the common spray tower and the jet bubble reactor, in which the flue gas experiences an initial SO 2 /NOx removal in the spray zone and then undergoes further removal in the bubble zone. Factors that affect the simultaneous removal of SO 2 /NOx were investigated through lab-scale experiments, by varying the O 3 /NO molar ratio, liquid/gas ratio and the immersion depth. The results showed the removal of SO 2 and NOx can be significantly improved as compared to a separate spray column or bubble reactor, by as much as 17%, for the spray column and 18% for the bubble reactor for NOx and 11% for the spray column, and 13% for the bubble reactor for SO 2 , for liquid/gas ratio of 4 dm3/m3 or immersion depth of 100 mm. The O 3 /NO molar ratio had little effect on the SO 2 removal, but it strongly affected the removal efficiency of NOx especially when it was less than 1.0. Both the liquid/gas ratio and immersion depth demonstrated a positive correlation with the removal efficiency. However, a balance must be maintained between efficiency and economics, since the liquid/gas ratio directly influences the performance and number of the circulating pumps, and the depth is closely related to the flue gas pressure drop, and both factors affect energy requirements. To further confirm its industrial feasibility, a 30 h test using real coal-fired flue gas was conducted in a pilot-scale experimental facility (flue gas volume of 5000 Nm3/h). Increasing SO 2 concentration in flue gas can promote the removal efficiency of NOx, but the SO 2 removal was almost complete under all conditions tested. Finally, taking a 300 MW unit as an example, the total energy cost of this new technology is estimated as being 10% lower than that of the common spray tower technology, based on an analysis using Aspen Plus™, with the largest difference reflected in the energy requirements of the circulating pumps and the ozonizer. Over all, the new technology offers the collaborative advantages of reducing emissions and saving energy. [ABSTRACT FROM AUTHOR]

Despite the treatment given to the wastes at Cienfuegos oil refinery, there is a high level of contaminant loads released to the environment. The technology used for the H2S removal or recovery is not sufficient to achieve the gaseous emissions to meet the established regulations. This situation is expected to increase with the refinery expansion that includes new process units. Along with that situation, there are other elements that make the issue even more concerning, such as the high investment cost to purchase new sulphur recovery units; the moderate price for the sulphur sales at the international market and the contaminants restrictions. This research proposes the inclusion of a caustic scrubber packaged tower, for the treatment of the residual gases as a proposal for the technological improvement of the sulphur recovery unit, to allow such process sustainability and achieving the emissions standards. A bibliography review on the major technologies for the sulphur recovery and residual gases treatment is made. Then the caustic scrubber is designed with the use of three types of packages, as to analyze the most viable one. Afterwards an economical assessment is developed to determine which makes the sulphur recovery process more sustainable. This proposal allows obtaining an elementary sulphur recovery of 99, 8 %, the atmospheric emissions are reduced up to 100 mg/Nm³ as SO2 and the population exposure to the gaseous emissions, in general is reduced. [ABSTRACT FROM AUTHOR]

The feasibility of the combined air-cleaning method, which consisted of a wet scrubber and the photo-Fenton reaction, in the removal of gaseous acetaldehyde was evaluated. An acetaldehyde-gas removal efficiency of 99% was achieved in the one-pass test (residence time of 17 s) using an inlet acetaldehyde-gas concentration of 1000 ppb at an initial total-iron-ion concentration of 50 mg L−1 and initial hydrogen peroxide concentration of 630 mg L−1. Even at the low initial total-iron-ion concentration of 4 mg L−1, a removal efficiency of 92% was achieved. The acetaldehyde removal efficiency was relatively independent of the initial hydrogen peroxide concentration. UV irradiation further augmented the rate of the photo-Fenton reaction leading to enhanced acetaldehyde-gas removal.

A wet packed-bed scrubber combined with dry oxidation by an indirect dielectric-barrier-discharge plasma for the conversion of NO to NO2 and wet reduction with two reduction agents of Na2S and Na2SO 3 to remove NO2 was developed at room temperature for semiconductor manufacturing industries. The design and operation parameter for the wet scrubber such as gas concentration, liquid-to-gas ratio, reducing agent concentration, residence time, and pressure drop were investigated at 2 m3/min and 200 ppm of pure NO gas. Na2S solution was more suitable than Na2SO3 with less chemical consumption and liquid-to-gas ratio. The removal efficiency of over 80% was achieved with the liquid-to-gas ratio of 10 L/m3, reduction agent solution of 0.1% w/w, which corresponds to oxidation and reduction potential of −310 mV and pH of 12.3, residence time of 2 s, and pressure drop of 25 mmAq/m, respectively. Finally, a demonstration test of the wet scrubber was conducted for 1 month with an exhaust gas from the perfluorinated compounds gas scrubber at the rooftop of a semiconductor manufacturing plant in Korea. In order to suppress H2S as byproducts of the wet scrubber, pH over 12 was carefully controlled with NaOH solution because commonly highly acid gases such as HF and HCl were fed from the manufacturing process. The NO x removal efficiency was 83.8% on an average, which was very similar to those obtained from the lab tests. These results indicate that the combination of the dry oxidation and wet reduction method could be a promising solution to remove NOx from semiconductor manufacturing industries. [ABSTRACT FROM AUTHOR]

Thermal conversion of sewage sludge can be a clean source of renewable energy if the emission of air pollutants from the source is controlled. In 2013, the Minamata Convention on Mercury was adopted, placing greater emphasis on the control of mercury emissions, including mercury emissions from sewage sludge incinerators. To characterise the behaviour of mercury in flue gas, particulate and gaseous mercury concentrations in two incinerators and a melting furnace were measured by manual sampling. In a third facility, continuous emission monitoring was used to characterise temporal trends in gaseous mercury concentrations. Wet scrubbers were determined to be effective air pollution control devices suitable for mercury removal. Stack mercury concentrations were found to be <10 µg/Nm³, which meets the mercury emission standard for existing plants (50 µg/Nm³). [ABSTRACT FROM AUTHOR]

The reduction of high concentrations of NOx and SO 2 from simulated flue gas has been studied. Our aim was to optimise energy consumption for NOx and SO 2 removal from off-gases from a diesel generator using heavy fuel oil. A hybrid process: electron beam (EB) plasma and wet scrubber has been applied. A much higher efficiency of NO x and SO 2 removal was achieved in comparison to dry, ammonia free, electron beam flue gas treatment (EBFGT). A recorded removal from a concentration of 1500 ppm NO x reached 49% at a low dose of 6.5 kGy, while only 2% NO x was removed at the same dose if EB only was applied. For SO 2 , removal efficiency at a dose of 6.5 kGy increased from 15% (EB only) to 84% when sea water was used as a wet scrubber agent for 700 ppm SO 2 . The results of this study indicate that EB combined with wet scrubber is a very promising technology to be applied for removal of high concentrations of NOx and SO 2 emitted from diesel engines operated e.g. on cargo ships, which are the main sources of SO 2 and NO x pollution along their navigation routes. [ABSTRACT FROM AUTHOR]

A wet scrubber technique was studied for the separation of particles < 2.5 μm from exhaust gas by a gas-liquid cross-flow array. The cleaning water of the separator flows vertically down along many regularly configured wires and the generated water film acts as an independent sink for particle collection. Due to the surface-orientated horizontal particle movement caused by diffusio- (DP) and thermophoresis (TP), the particles can be captured by the water films. Since wastewater from the same production process can be used, the necessary cleaning water recycling costs can be saved due to the already available water treatment device. Experiments on a laboratory-scale test rig show the particle grade removal efficiency (PGRE) for different inlet gas-water temperature gradients and for a constant vapor injection. [ABSTRACT FROM AUTHOR]

In order to develop an iodine scrubbing model for nuclear severe accidents, experimental data on filtration efficiency of a wet scrubber for gaseous molecular iodine are collected to improve understanding of the basic mechanisms involved in iodine chemical scrubbing. A bubble column reactor 1.5 m high and 0.2 m in diameter equipped with an injection nozzle and a bubble breaker is used to investigate retention under relevant flow regimes. Scrubber is loaded with a scrubbing solution containing sodium hydroxide and sodium thiosulphate, no irradiation is provided. Retention efficiency is found to be strongly dependent on flow regime and on residence time as models predict. It was found that jet-like injection has a strong effect on filtration efficiency introducing a significant dependence on iodine initial concentration in gas phase believed to be due to nozzle hydrodynamics. [ABSTRACT FROM AUTHOR]

Odorous volatile organic compounds (VOCs) deteriorate the quality of life and affect human health. In this study, a process was developed to remove an odorous VOC using a combined non-thermal plasma (NTP) and wet scrubber (WS) system. The low removal efficiency of WSs and the large amount of ozone generated by NTP were resolved. Compared to the decomposition effects when using a WS and NTP separately, the NTP + WS system improved the removal efficiency of ethyl acrylate (EA) and significantly reduced ozone emissions. The maximum EA removal efficiency was 99.9%. Additionally, an EA removal efficiency of over 53.4% and a 100% ozone removal efficiency were achieved even at discharge voltages lower than 4.5 kV. Ozone catalysis was confirmed to occur in the NTP + WS system. Furthermore, we verified the removal of by-products such as residual ozone and formaldehyde, which is a representative organic intermediate of EA. This study demonstrates that the NTP + WS system is a green technology for removing odorous VOCs. [Display omitted] • The combined NTP + WS system for removing odorous VOC is proposed. • The VOC removal efficiency is considerably increased. • Secondary air pollution associated with ozone and organic intermediate is reduced. • The VOC degradation mechanism in the NTP + WS system was explored. [ABSTRACT FROM AUTHOR]