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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]

Mitigating air pollutants such as SOx and PM emitted from ships is an important task for marine environmental protection and improving air quality. To address this, exhaust gas after-treatment devices have been introduced, but treating pollutants like SOx and PM individually poses challenges due to spatial constraints on ships. Consequently, a Total Gas Cleaning System (TGCS) capable of simultaneously reducing sulfur oxides and particulate matter has been developed. The TGCS combines a cyclone dust collector and a wet scrubber system. The cyclone dust collector is designed to maintain a certain distance from the bottom of the wet scrubber, allowing exhaust gases entering from the bottom to rise as sulfur oxides are adsorbed. Additionally, the exhaust gases descending through the space between the cyclone dust collector and the wet scrubber collide with the scrubbing solution before entering the bottom of the wet scrubber, facilitating the absorption of SOx. In this study, the efficiency of the developed TGCS was evaluated, and the reduction effects based on design parameters were investigated. Furthermore, the impact of this device on ship engines was analyzed to assess its practical applicability. Experimental results showed that increasing the volume flow rate of the cleaning solution enhanced the PM reduction effect. Particularly, when the height of the Pall ring was 1000 mm and the volume flow rate was 35 L/min, the sulfur oxide reduction effect met the standards for Sulfur Emission Control Areas (SECA). Based on these findings, suggestions for effectively controlling atmospheric pollutants from ships were made, with the expectation of contributing to the development of systems combining various after-treatment devices. [ABSTRACT FROM AUTHOR]

Marine regulations aim to reduce sulfur and nitrogen exhaust emissions from maritime shipping. Here, two compliance pathways for reducing sulfur dioxide emissions, fuel sulfur content reduction and exhaust wet scrubbing, are studied for their effects on physicochemical properties and cloud forming abilities of engine exhaust particles. A test‐bed diesel engine was utilized to study fresh exhaust emissions from combustion of non‐compliant, high sulfur content fuel with (WS) and without (HiS) the usage of a wet scrubber as well as a regulatory compliant, low sulfur content fuel (LoS). Particle number emissions are decreased by ≈99% when switching to LoS due to absence of 20–30 nm sulfate rich particles. While number emissions for WS are also decreased, a shift in the sulfate mode toward larger sizes was found to increase particle mass emission factors by at least 31%. Changes in the mixing state induced by the compliance measures are reflected in the hygroscopicity of the exhaust particles. Fuel sulfur reduction decreased cloud condensation nuclei emissions by at least 97% due to emissions of primarily hydrophobic soot particles. Wet scrubbing increased those emissions, mainly driven by changes in particle size distributions. Our results indicate that both compliance alternatives have no obvious impact on the ice forming abilities of 200 nm exhaust particles. These detailed results are relevant for atmospheric processes and might be useful input parameters for cloud‐resolving models to investigate ship aerosol‐cloud interactions and to quantify the impact of shipping on radiative budgets from local to global scales. Plain Language Summary: We investigate how two pathways to comply with international regulations, aiming to reduce emissions of atmospheric pollutants from ships, alter properties of exhaust particles. Both investigated compliance measures (i.e., combustion of cleaner, low sulfur content fuels and aftertreatment of exhaust from a high sulfur content fuel via wet scrubbing) have substantial impacts on the chemical and physical properties of these particles. We find that, while both alternatives reduce the total number of emitted particles substantially, the effect on emissions of cloud forming particles is path dependent. While fuel sulfur content reduction decreased the number of cloud forming particles by about 97%, wet scrubbing led to a strong increase in emissions, suggesting that the measures can have substantial and opposing impacts on local cloud formation and evolution. Key Points: Low sulfur content fuels can reduce emissions of ultrafine particulate matter significantlyExhaust wet scrubbing can lead to shifts in particle size distributions and reduce soot emissionsUsage of low sulfur content fuels or exhaust wet scrubbing have opposing effects on CCN activity of ship exhaust particles [ABSTRACT FROM AUTHOR]

Small scale gasification combined heat and power (CHP) systems offer an alternative to diesel fuelled generators for power generation in remote communities and industrial sites. Tar and particulates in the producer‐gas can damage the internal combustion engine generator and increase operation and maintenance costs. In this work, we present a novel trickle‐bed scrubber using filtered waste cooking oil as a cost effective and easy‐to‐operate gas clean‐up method for a small CHP system. The performance of the trickle‐bed scrubber was compared against a packed‐bed filter utilizing woodchips in a 20 kWth downdraft gasifier. Used‐cooking oil was selected as the solvent and woodchips as the bed‐material as these are readily available, inexpensive, and can be recycled in the gasifier as fuel. A woodchip packed‐bed filter reduced the tar and particulate matter (PM) in the producer gas from gasification of spruce chips (11% moisture) from 1.6 to 1.4 g/Nm3 and from 0.16 to 0.087 g/Nm3 respectively. The trickle‐bed scrubber was able to reduce the tar and PM in the producer gas from gasification of pinewood (8% moisture) from 1.38 to 0.28 g/Nm3, and 0.209 to 0.082 g/Nm3, respectively. Tar and PM removal efficiency improved by 60% and 29% respectively. Components such as benzene, toluene, naphthalene, and biphenylene were the major tar components. After passing the trickle‐bed, most tar was removed, with a preference for removal of multi‐ringed aromatics and gravimetric tars. Parameters such as the tar and particulate concentration, feedstock moisture content, and feedstock source affect the performance of the gas clean‐up system. [ABSTRACT FROM AUTHOR]

Shipping is a large industry responsible for atmospheric emissions of hazardous substances including SOX, NOX, and particulate matter. Many ships have installed exhaust gas cleaning systems (scrubbers) to remove primarily SOX from the exhaust, but the hazardous substances are instead transferred to the water used in the scrubbing process. Ships with closed-loop scrubbers recirculate the water but can still discharge around 126-150 m³ directly to the surrounding marine environment every day. The discharged water contains metals and organic substances, such as polycyclic aromatic hydrocarbons, that are known to be toxic to marine zooplankton. Here we show that closed-loop scrubber washwater is toxic to communities of marine mesozooplankton at our lowest tested dilution, 1.5% (v/v), and affects survival, reproduction, diversity, and ability to predate on microzooplankton. The cumulative toxic unit of the undiluted closed-loop scrubber washwater was estimated to 17, which indicates that the water could be toxic at levels below what was tested in this study. Among all detected substances, vanadium, copper, benzo[ghi]perylene, nickel, and zinc were identified as toxicity-driving substances in the order listed. Closed-loop scrubber washwater has been shown to affect development and survival in single species of copepods, but here we find evidence of toxicity at the community level, irrespective of seasonal community structure, and that the exposure has potential to disrupt the interactions between trophic levels in the pelagic food web. We show that the closed-loop scrubber washwater cause both lethal and sublethal effects in marine zooplankton, due to contaminants, some of which are persistent in the marine environment. [ABSTRACT FROM AUTHOR]

This paper introduces a numerical model dedicated to simulating SO2 adsorption during the dynamic interplay between combustion gases and water droplets. The research delves into essential chemical–physical parameters governing mass transfer in these interphase interactions. The proposed simplified model provides preliminary results regarding the granulometric curve of sprays, particularly focusing on the minimal droplet size crucial for effective wet scrubber operation. Our findings underscore a critical diameter below which the spray loses its efficacy under varied boundary conditions. Notably, a single droplet with a maximum diameter of 2 mm absorbs more SO2 than smaller counterparts, peaking at 4.36 × 10−5 g of SO2 within the simulation timeframe. Furthermore, the study explores a specific water mass, revealing that smaller droplets, such as 1 mm, significantly optimize the absorption process. These droplets achieve a SO2 absorption quantity over 5.77 times greater than that of a 2 mm droplet. This research serves as an initial tool for optimizing droplet distribution in sprays, thereby enhancing capture efficiency. The insights presented here offer valuable guidance for designing efficient wet scrubber systems, crucial for pollution control in industrial and environmental applications. [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]

Wet scrubber systems (WSSs) are commonly used for effective flue gas cleaning by removing acid gases and dust. To determine the influence of a WSS on polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) and flue gas particles, a field study was carried out in a full-scale municipal solid waste (MSW) incinerator (850 t/d). Phase-separated samples at four flue gas sampling points and two scrubbing solution sampling points were collected for PCDD/F analysis. Two particle samples at the WSS inlet and outlet were simultaneously obtained for TEM-EDS analysis. The memory effect inside the WSS apparently elevated the PCDD/F I-TEQ concentration from 0.0056 to 0.0088 ng I-TEQ Nm−3 by increasing the mass concentrations of 17 congeners. A PCDD/F flux chart was established to interpret the adsorption/desorption mechanism of PCDD/Fs inside the WSS that showed apparent desorption from scrubbing solution. The potential interaction relationship between PCDD/F and flue gas particles were also observed, that was, the desorbed PCDD/Fs from scrubbing solution might be adsorbed by flue gas particles again and therefore enhanced the concentration of solid-phase PCDD/Fs from 0.0236 to 0.0411 ng Nm−3. Furthermore, TEM-EDS analysis indicated that the WSS could evidently remove some soluble particles and reduce the particle size. And the variation in morphology, elemental composition, and distribution of flue gas particles were observed during the scrubbing process. This study systematically analyzed the memory effect of PCDD/Fs and firstly investigated the specific impact of WSS on flue gas particles, thereby improving the comprehensive understanding of WSS applications. [Display omitted] [ABSTRACT FROM AUTHOR]

Understanding and managing the generation of odour nuisances throughout the raw rubber processing industry are vital to reduce the impact on the community. This paper aims to review literature on odour studies and management in the raw rubber processing industry. The generation of odour is typically associated with microbial reactions occurring in non-rubber components. The most offensive compound groups commonly discussed in the literature are sulfur derivatives and volatile fatty acids due to their unpleasant characteristics and low-odour threshold. Major sources of these odorants are from effluent treatment of the latex processing plant and exhaust gas from the drying process at the block rubber processing plant, respectively. However, studies performed on the composition of rubber emissions also reported the presence of other compound groups such as aldehyde, ester, amine and aromatic, which could potentially contribute to the odour emissions. Single or multiple odour assessment methods can be applied based on the objective of the odour assessment. Olfactory and chemical testings were generally applied to evaluate the odour concentration, offensiveness and identification of potential odorants, while odour wheel and dispersion modelling were employed to assess the impact on the community. Odour legislations mainly used olfactory techniques and dispersion modelling to control the odour emissions by limiting the odour release at a tolerable limit. Numerous mitigation measures have been studied and performed upstream and downstream of rubber processing, such as utilising biological methods and aerated effluent treatment that produces less odour, chemical substitution and installation of wet scrubber to reduce the odour emissions from drying process. Nevertheless, the literature is lacking studies conducted at the industrial scale on odour generation and mitigation where knowledge can be applied to develop an appropriate odour management strategy in the current industrial scenario to mitigate the odour effectively. [ABSTRACT FROM AUTHOR]

[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]

One of the most important environmental worries related to poultry production is ammonia gas emission which is affected by poultry manure moisture. This research was aimed at investigating poultry manure drying in a hot air dryer and its influence on ammonium nitrogen losses to provide an overview of ammonia gas emissions and absorption of emitted ammonia by a spray scrubber. The effect of air temperature (60–80 °C), air relative humidity (8–18 %), manure depth (2–4 cm), and air velocity (2–3 m s−1) were analyzed to optimize the drying process. The optimization of ammonia absorption involved analyzing the effects of absorbent solution temperature (30–50 °C), solution pH (2−4), and nozzle operating pressure (0.2–0.6 Mpa). The Box–Behnken design was applied to optimize these processes. Manure depth was the factor that had the most significant effect on both drying duration and ammonia emission (ammonium nitrogen losses). during the drying process, the ammonium nitrogen losses increased with increasing the manure depth and decreasing the air velocity and air temperature. The optimum ammonium nitrogen was 570,330 mg h lit−1 at an air temperature of 60 °C, air relative humidity of 8.11 %, manure depth of 3.95 cm, and air velocity of 2 m s−1. Both the temperature of the absorbent solution and the solution pH had opposite effects on the ammonia absorption. Increasing nozzle operating pressure increased ammonia absorption. The maximum ammonia absorption was obtained at a solution temperature of 49.2 °C, solution pH of 2, and nozzle operating pressure of 0.58 Mpa. At these conditions, the amount of ammonium sulfate in the absorbent solution was 9.09 g lit−1 and the efficiency of the spray scrubber was 66.79 %. So, we can be sure that ammonia emission from poultry manure and the absorption of emitted ammonia can be controlled by varying the investigated variables. [ABSTRACT FROM AUTHOR]

Modernisation of marine power plants in the transport vessel fleet to satisfy the requirements of the International Maritime Organization is an urgent scientific and technical problem. Currently, the use of catalytic selective filters, dry and wet scrubber systems and exhaust gas recirculation for marine diesel engines is widely used for this purpose. An analysis of the use of ejection gas-air coolers is presented as an additional method of emission reduction. However, the use of such device does not neutralise the harmful emissions of power plant engines, but only increases the volume concentration of their exhaust gases. But this will help to increase the efficiency of dispersion of harmful emissions, by reducing the concentration of harmful emissions to values not exceeding the maximum permissible concentrations. Its efficiency depends on the load mode of the diesel engine. It is found that the initial concentration of harmful substances in combustion products due to their dilution with fresh air at 100% engine load is reduced by about 50%. The values of the reduction of the concentration and temperature of exhaust gases with the reduction of the engine load to 75% and 50% depending on the louvre angle are obtained. It is proved that ejection gas-air coolers can be an effective additional means for compliance with modern environmental parameters, especially when vessels are in special areas of the world's oceans. [ABSTRACT FROM AUTHOR]

The generation of the cooking gas in from the natural resources are available in the market from quiet a long time. But the major problem with these are it chambers are get damaged easily due to low quality material and to construction of which usually requires skilled labor intense and high-quality materials. To address these problems in the present work a balloon type biogas has been designed and developed which is cheap, weather resistance, and thermophilic (i.e it can operate in temperature as high as (50°-55°), which helps in digest the bacteria mesophilic bacteria range (40°-50°), it generates the gas. The main objective is to improve the biogas efficiency by using scrubber to remove H2S, CO2, and H2O and it used for household. [ABSTRACT FROM AUTHOR]

The application of the chemical precipitation method to produce struvite at processing the ammonia-saturated liquid phase of wet acid scrubbers is challenging task, since this phase is an acidic solution of an ammonium salt, and the precipitation of struvite requires a simultaneous introducing salts containing magnesium and phosphate ions into the solution and neutralizing it, which usually leads to the appearance of an admixture of competing phases of newberite (MgHPO4·3H2O) and boberite (Mg3(PO4)2·8H2O) in the struvite sediment. The pure struvite phase was obtained by fast neutralizing an acidic solution with the full set of phase-forming ions necessary to form the struvite crystal lattice. Based on the results of the study, conditions were determined that make it possible to achieve a high practical yield of struvite (98% and above) without the admixture of foreign phases at a Mg : N : P molar ratio in the reaction medium of 1.2 : 1 : 1, close to its stoichiometric composition. The conditions for achieving this result consist in limiting the pH to no higher than 3.8 at preparing the reaction medium, maintaining the neutralization stage time from 10 to 45 s, and precipitating struvite at a pH in the range of 8.5–9.5. [ABSTRACT FROM AUTHOR]

An air recirculated ventilation system (ARVS) for a pig house was developed to improve the rearing environment, prevent livestock disease, reduce odour emission, and save energy. The validation experiments for winter were completed in our previous research (Kim et al.., 2023), but additional experiments were carried out in spring and crucially in summer when the cooling of pig house is important. Since directly using cooling devices may use excessive energy, more efficient cooling methods were required. In this study, ARVS, cooling methods that can lower the windchill temperature of piglets were evaluated. When the recirculating water temperature of the wet scrubber module was maintained at about 20 °C, the air temperature can be lowered by about 4 °C. From calculating the calorific value based on the heat production of piglets and ventilation rate, thus the capacity of the cooling device of the recirculating water was expected to be very large. The ventilation rates in the ARVS piglet room during spring and summer therefore remained consistently high. In particular, the humidity inside the ARVS piglet room was maintained appropriately despite the significant rainfall that occurred in the summer. The ammonia concentration was found to be below 5 ppm in ARVS piglet room, but as high as 57 ppm in the conventional piglet room. The odour concentration emitted from the ARVS piglet room was generally <100 OU. As a result, the body mass gain was improved by 2.8 kg and 1.0 kg, respectively, during the spring and summer. • Air recirculated ventilation system (ARVS) was developed and applied to solve the typical problems of the pig farm. • The ARVS was developed with optimally designed modules and the operating algorithm. • The validation experiments in real pig farm were conducted in spring and summer season using ARVS. • The cooling effect was evaluated using effective temperature for decreasing the heat stress of piglets. [ABSTRACT FROM AUTHOR]

Flue-gas desulphurization (FGDs) systems were developed primarily to remove sulphur dioxide (SO2) from industrial gas streams. The main techniques adopted involve wet scrubbing, particularly lime/limestone scrubbing. These techniques are relatively simple, cost less, and have thus, become applicable to other types of plants that emit SO2 such as refineries and smelters. In lime and limestone scrubbing, calcium compounds are added as slurry to the scrubber liquid, and this can result in the formation of solid calcium salts. As a result, the efficiency of such wet calcium-containing scrubbing systems is limited by the solubility of calcium salts in the slurry. As the concentrations of calcium ions build up in the water, the solubility limit of calcium sulphate (CaSO4) and many other compounds is often exceeded. In such systems, the formation of supersaturated CaSO4 causes scaling or deposition in the scrubber. The scaling problem further results in numerous plant downtimes due to the need to open lines and descale. The current review looks into existing and potential methods that have and can be developed to prevent or remove the formation of scaling in FGD systems such as scrubbers. A particular focus of this review is given to approaches such as chemical "softening" of hard waters using ion-exchange and precipitation using lime and soda ash. This review also looks into a contentious physical water treatment – magnetic water treatment (MWT) - as a potential alternative and environmentally conscious solution for the prevention of scale in scrubbers and hard waters in general. [ABSTRACT FROM AUTHOR]

This paper presents the wet scrubber performance on acid gas absorption based on pH and conductivity measurements. The waste combustion system comprised of a CFB combustor in which mainly plastics waste was loaded into the riser (15 cm ID x 1.5 m long). The scrubbing experiments were conducted using a two-stage wet scrubber used as air pollution control device. The performance of the wet scrubber system was assessed by studying the changes in the pH and conductivity. The scrubbing solution was prepared using lime. The optimum lime concentration was obtained from bench experiments, giving an initial pH of up to 13. The scrubbing solution samples were collected from the solution tanks after every 2 minutes for 40 minutes. The scrubbing solution flow rate ranged from 0.53 to 0.95 L/s while the gas flow rate from the blower was kept constant at 16 m/s. It was observed that the pH of the scrubbing solution for both stages decreased to neutral range with increasing operation time. The decrease in pH and conductivity was initially faster before increasing slightly due to deposition of fly ash. It was concluded that the multistage wet scrubber is capable of removing toxic acid gas and particulate matter. [ABSTRACT FROM AUTHOR]

According to the findings of this study, nations should adopt uniform regulations regarding the discharge of washwater from exhaust gas cleaning systems into their ports, territories, and Exclusive Economic Zones. Scrubbers are used by ships to reduce their emissions of greenhouse gases so they can adhere to the International Maritime Organization's limit on the sulfur content of ship fuel. The global upper limit was 0.5% in January 2020. Scrubber washwater is discharged into the ocean by ships. Toxic substances are present in the washwater for the scrubbers. The level of washwater for the scrubbers is governed by the 2008 and 2015 Guidelines for the Exhaust Gas Cleaning Systems. Regarding the washwater from the scrubbers' effects on the marine environment and people's health, there still is some uncertainty. The national level is also affected by this uncertainty. Currently, there are three main ways that nations implement policies for the use of scrubbers in their jurisdiction. First are nations like Egypt and Qatar, that have enacted outright bans on using scrubbers in their territorial waters. The second category consists of nations that only partially permit the use of scrubbers. Two different variations exist for this partial prohibition of scrubbers. First, nations restrict the use of scrubbers in specific internal water areas (Germany), or ports (Sweden and Finland). The second option for a partial prohibition (Argentina, China, and France) is to outlaw certain discharge and disposal methods involving open loops. The third and final category consists of countries that do not regulate the discharge of scrubbers. These nations either rely on the general legal regulations concerning ship pollution (Article 192-237 of the UNCLOS), or they adopt a complete permission standard for the discharge of scrubbers in their water. There are three Parts to this research paper. In particular, the transboundary harm of the washwater from the scrubbers is discussed in the first Part of the essay, along with who is responsible for conducting the investigation. Three key players in the marine environment are recognized by the UNCLOS. These actors are the flag state, the port state, and the coastal state, and this Part includes a discussion of each of their functions. In light of the growing number of nations regulating scrubbers' washwater, it also discusses ways to harmonize their actions. The second Part covers the legal frameworks that the national regulatory body has adopted in relation to the washwater used by scrubbers. These four models contrast limited and unlimited bans, specific and general regulations, and binding and non-binding regulations. The answer to the problem of uncertainty is covered in the third Part. Two answers to the impending scientific uncertainty and the adoption of uniform regulations are put forth in the research. [ABSTRACT FROM AUTHOR]

Emissions of marine traffic can be lowered by switching to less polluting fuels or by investing in exhaust aftertreatment. Electrostatic precipitation is a widely used method for particle removal but it is not currently used in combination with marine engines. This study presents the particle filtration characteristics of an emission reduction system designed for marine applications and consisting of a scrubber and a Wet Electrostatic Precipitator (WESP) in series. Partial flow of exhaust from a 1.6 MW marine engine, operated with light and heavy fuel oil, was led to the system. Particle concentrations were measured before the system, after the scrubber and after the WESP. Particle removal characteristics were determined for different engine loads. The scrubber alone removed 15–55% of non-volatile particle number, 30–40% of particle mass and 30–40% of black carbon mass depending on engine load, when HFO fuel was used. By studying particle size distributions, scrubber was found also to generate particles seen as an additional mode in 20–40 nm size range. The system combining the scrubber and WESP removed over 98.5% of particles in number, mass and black carbon metrics when HFO fuel was used. With MDO fuel, 96.5% of PN and 99% of black carbon were removed. [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]

Sulphur Emission Control Areas (SECAs), mandated by the International Maritime Organization (IMO), regulate fuel sulphur content (FSC) to mitigate the environmental and health impact of shipping emissions in coastal areas. Currently, FSC is limited to 0.1% (w/w) within and 0.5% (w/w) outside SECAs, with exceptions for ships employing wet sulphur scrubbers. These scrubbers enable vessels using non-compliant fuels such as high-sulphur heavy fuel oils (HFOs) to enter SECAs. However, while sulphur reduction via scrubbers is effective, their efficiency in capturing other potentially harmful gases remains uncertain. Moreover, emerging compliant fuels like highly aromatic fuels or low-sulphur blends lack characterisation and may pose risks. Over three years, we assessed emissions from an experimental marine engine at 25% and 75% load, representative of manoeuvring and cruising, respectively. First, characterizing emissions from five different compliant and non-compliant fuels (marine gas oil MGO, hydro-treated vegetable oil HVO, high-, low- and ultra-low sulphur HFOs), we calculated emission factors (EF). Then, the wet scrubber gas-phase capture efficiency was measured using compliant and non-compliant HFOs. NO x EF varied among fuels (5200–19700 mg/kWh), with limited scrubber reduction. CO (EF 750–13700 mg/kWh) and hydrocarbons (HC; EF 122–1851 mg/kWh) showed also insufficient abatement. Carcinogenic benzene was notably higher at 25% load and about an order of magnitude higher with HFOs compared to MGO and HVO, with no observed scrubber reduction. In contrast, carbonyls such as carcinogenic formaldehyde and acetaldehyde, acting as ozone precursors, were effectively scrubbed due to their polarity and water solubility. The ozone formation potential (OFP) of all fuels was examined. Significant EF differences between fuels and engine loads were observed, with the wet scrubber providing limited or no reduction of gaseous emissions. We suggest enhanced regulations and emission abatements in the marine sector to mitigate gaseous pollutants harmful to human health and the environment. [Display omitted] • Ship engine gaseous emissions vary widely with fuel type and engine load. • Wet sulphur scrubbers are ineffective in reducing especially water-insoluble gases. • SECA-compliant fuels generally emit less than non-compliant fuels with scrubbers. • Wet scrubbers effectively reduce carbonyls acting as ozone precursors. • Further legislation is required to address non-SO 2 gaseous pollutants. [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 fine particles generated by the foundry industry are present in the atmosphere; they have an impact on the climate because of their influence on atmospheric radioactive phenomena. As a result of this scenario, there is a rising amount of legislation restricting the emission of pollutants from foundry industries and related businesses. In response to this situation, many researchers have concentrated on end-of-pipe technologies, one of which is the wet scrubber, which is a device that is primarily used in foundries to control pollution and is one of the devices that has been incorporated. The disadvantage of using this wet scrubber, on the other hand, is that it contributes to secondary pollution when it is used. In order to combat secondary pollution, a model of an enhanced wet scrubber system that incorporates a multi-sand filtering technology was developed. The performance of this redesigned wet scrubber system was evaluated with the use of computational fluid dynamics (CFD) software. In CFD, the Reynolds stress model was applied for simulation. The pressure magnitudes and velocity magnitudes are obtained by this simulation. The volume fraction of the dust was evaluated through the DPM approach. Because of the introduction of the filtration tank's computation, it was discovered that successful filtration was accomplished using sand filters, meaning that environmental chemicals and particles were totally filtered from 0.17 kg at the entrance to zero kg of particles at the outflow. [ABSTRACT FROM AUTHOR]

The study presents the results of research on using fixed-bed, activated carbon (AC) adsorbers in the cleaning of heavily tar-laden producer gas from the gasification of biomass. The efficiency of removal of organic compounds as well as the remaining adsorption capacity of the bed were determined using a spectrum of commonly applied diagnostic methods, including qualitative and quantitative analyses of the adsorbed compounds and changes in the pore volume of the bed material (IN, MN). The authors compare these lab quantifications with a simple technique which is based on the analysis of the changes in the position of temperature front in the bed. The main benefit of the latter is the possibility of performing the diagnostics of the bed "online" and using low-cost temperature measurements. The test was performed using a commercially available AC Desotec AIRPEL 10-3 and real producer gas obtained through the gasification of alder chips. For tar, VOC and C2–C5 compounds, the removal efficiencies reached respectively 74.5%-wt., 52.8%-wt., and 85.5%-wt. Obtained results indicate that depending on the final application of the gas, the use of dry adsorption systems is an interesting alternative to the well-established but complicated, cumbersome, and costly wet scrubbers. Moreover, a concept for in situ regeneration of the adsorbent, coupled with direct reforming of the tars, is presented and discussed. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Materials Engineering / Cailiao Gongcheng is the property of Journal of Materials Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Ethanol is a significant source of energy as a biofuel; however, its production using corn involves the generation of harmful emissions from both fermentation tanks and dryers. Scrubbers control the emissions from fermentation tanks, while the emissions from the dryers are controlled by regenerative thermal oxidizers. Potential alternatives to these energy- and water-intensive technologies are biotrickling filters (BTFs). In this study, two BTFs were operated in parallel to treat formaldehyde and methanol emissions in a volumetric ratio of 4:1, one at 25°C (mesophilic), and the other at 60°C (thermophilic). The mesophilic BTF simulated emissions from fermentation tanks, while the thermophilic BTF simulated emissions from dryers. Both beds were operated at an empty bed residence time of ~30 s and influent formaldehyde concentrations of 20, 50, and 100 parts per million per volume (ppmv). Formaldehyde polymerization was reduced in this study by adding NaOH to pH levels of 7.0–7.4 and heating the solution to a temperature of 60°C. BTFs have successfully removed formaldehyde at typical ethanol plants emissions ~21 ppmv. The BTF technology have the potential in replacing the conventional air treatment methods used at ethanol plants. Implications: Currently, ethanol plants remove and treat hazardous air pollutants (HAPs) using wet scrubbers from the fermenter off-gasses and using thermal oxidizers to combust off-gasses. The utilization of biotrickling filters (BTFs) for HAP removal generally and formaldehyde particularly has wide implication in the field of renewable energy. Utilizing BTFs in the 200+ ethanol plants in USA will save cost and reduce water and energy needs significantly. BTFs can reduce an ethanol plant's carbon intensity (CI) by 1 to 3 g CO2/MJ. This can result in roughly $50 million per year in additional revenue in Nebraska for instance. [ABSTRACT FROM AUTHOR]

Animal buildings are an important source of particulate matter (PM) pollution. Particulate matter has been known to have both environmental and health impacts and control measures for PM are essential. This study developed a laboratory-scale electrospray system to generate engineered water nanostructures (EWNS), which are highly-charged nano-sized water droplets, and tested the effectiveness of the EWNS in reducing livestock PM. The efficacy of the generated EWNS in reducing PM was evaluated under various electrospray settings and operating conditions using pig and poultry barn PM. The experiments were conducted using an acrylic chamber to simulate the airspace in an animal confinement area. EWNS generation rates were also determined under various electrospray settings. It was found that negative voltages generated higher numbers of EWNS. The highest reduction efficiency obtained for PM 15.0 was 75% for pig barn PM and 83% for poultry barn PM. These reduction efficiencies are comparable to those obtained by wet electrostatic scrubbers; however, the water consumption of the electrospray developed in this study was relatively low (maximum of 4 μl min−1, equivalent to a liquid–gas flow rate ratio of 6.4 × 10−5 l m−3). The results indicate that the EWNS generated by the electrospray effectively reduced the livestock PM. However, in-barn tests are required before the system can be implemented in commercial animal rearing facilities. • An electrospray was developed to generate engineered water nanostructures (EWNS). • Efficacy of the EWNS to remove particulate matter (PM) was evaluated. • Generated EWNS were effective in reducing concentrations of livestock PM. • Reductions achieved equivalent to wet electrostatic scrubbers but less water use. [ABSTRACT FROM AUTHOR]

[Display omitted] • Euchlorine-based WOS completely removes NO x on top of SO x. • SO 2 plays a synergistic role in NO x absorption. • Acidity promotes a gas–liquid dual oxidation making the de-NO x process more efficient. • WOS under acidic conditions saves 83% chemical and 70% water. • WOS can be a viable alternative to the conventional FGD-SCR plants. This paper reports the performances of a pilot-scale Wet Oxidative Scrubber (WOS) in the treatment of a simulated flue-gas containing 500 ppm v SO 2 and 1030 ppm v NO x and operated at 60 °C and 1 atm. The scrubber is fed with an oxidizing solution containing NaClO 2 at either 0.75 % or 1 % w/w initially at pH > 9 and then acidified to pH down to 3 with HCl, to obtain the additional oxidative contribution given by euchlorine species during the simultaneous absorption. Further experiments of single-component NO x absorption are performed to better understand the role exerted by SO 2 in the simultaneous absorption. These experimental tests are carried out to investigate the effect of the acidity of the chlorite-based scrubbing solution on the simultaneous absorption performance of SO 2 and NO x , highlighting the intensification with respect to the bare de-NO x system. Experiments also allow determining the optimal dosages and solution pH for a complete and optimized removal of NO x and SO x also being less energy-intensive. For a scrubbing solution under acid-induced conditions (pH = 3), the retrieved results show that the NaClO 2 molar dosage needed for a complete simultaneous removal results 3.6 times greater than the total NO x concentration in the flue-gas. This allows an interesting reduction of 83 % in oxidant consumption and a water-saving of 70 % with respect to the same process applied to the simultaneous NO x absorption but without altering the solution pH. Overall, the results confirm the enhancing role exerted by euchlorine deriving from chlorite acidification and sulfur dioxide presence in the flue-gas. [ABSTRACT FROM AUTHOR]

This paper proposes the general design of a Wet Electrostatic Scrubber aimed at mitigating fine and ultrafine particles emissions from domestic heating boilers. The design is based on particle capture modelling supported by specific experiments and technical literature information. Results indicate up to 96.6% removal efficiency, consuming 1.2 kg/h of water and 0.3 W per 1 m3/h of gas treated. Comparative analysis highlights the balanced performance of Wet Electrostatic Scrubber in particle capture, energy and water usage, pressure drop, and space occupancy, with the additional benefit of more efficient absorption of gas pollutants. • Wet electrostatic scrubbing is proposed for biomass boilers. • Removal efficiencies estimated through a robust stochastic model up to 96% in number and 99% in volume can be achieved. • Energy consumption is around 0.3 Wh/m3 for water consumption of 1 kg/kg. • WES performance ranks high among consolidated techniques. • Water losses at the scrubber walls are the main sources of efficiency reduction. [ABSTRACT FROM AUTHOR]

In the present work, the contemporary exhaust gas treatment systems (EGTS) used for SOx, PM, and NOx emission mitigation from shipping are reviewed. Specifically, after-treatment technologies such as wet scrubbers with seawater and freshwater solution with NaOH, hybrid wet scrubbers, wet scrubbers integrated in exhaust gas recirculation (EGR) installations, dry scrubbers, inert gas wet scrubbers and selective catalytic reduction (SCR) systems are analyzed. The operational principles and the construction specifications, the performance characteristics and the investment and operation of the reviewed shipping EGTS are thoroughly elaborated. The SCR technology is comparatively evaluated with alternative techniques such as LNG, internal engine modifications (IEM), direct water injection (DWI) and humid air motor (HAM) to assess the individual NOx emission reduction potential of each technology. Detailed real data for the time several cargo vessels spent in shipyards for seawater scrubber installation, and actual data for the purchase cost and the installation cost of seawater scrubbers in shipyards are demonstrated. From the examination of the constructional, operational, environmental and economic parameters of the examined EGTS, it can be concluded that the most effective SOx emission abatement system is the closed-loop wet scrubbers with NaOH solution which can practically eliminate ship SOx emissions, whereas the most effective NOx emission mitigation system is the SCR which cannot only offer compliance of a vessel with the IMO Tier III limits but can also practically eliminate ship NOx emissions. [ABSTRACT FROM AUTHOR]

Increasing attention on the use of biomass derived syngas as internal combustion engine fuel, impacts on rising the demand of the scrubber for tar removal of the syngas. Wet scrubber is been used widely for this purpose. However, the liquid adsorbent containing tar may harmful when exposes to the environment. Thus to encounter the problem, the present work proposes the use of dry scrubber with zeolite as an adsorbent. The work aims to develop a simple and low cost zeolite scrubber and investigate and effect of zeolite size on performance of the scrubber for tar removal of syngas from biomass gasification. The result shows that zeolite size is proportional to specific area, heat transfer rate, and scrubber's effectiveness. The highest scrubber's effectiveness of 0.25 is obtained for the smallest zeolite size, i.e. 30 mm. [ABSTRACT FROM AUTHOR]

NOx removal performance accompanying with SO2 is investigated in a two-step process containing O3 pre-oxidation of NO and NOx post-absorption in the scrubber of wet flue gas desulfurization (WFGD) unit. Based on Eulerian-Lagrangian framework, a comprehensive CFD model is established to describe the reactions of NO2 and N2O5 with S(IV) in droplets coupled with NOx transfer process and hydrodynamics in the scrubber. Taking the WFGD scrubber of 330 MW coal-fired power unit as case study, the results indicate NOx absorption efficiency in scrubber is increased by increasing O3/NO molar ratio from 1.0 to 2.2 and decreasing reaction temperature from 423 1< to 363 K in O3 pre-oxidation process. The obtained highest removal efficiency is 85.79% for pH of 5.5 or 96.32% for pH of 9.0 in droplets. NO2 absorption is much slower than N2O5 and more sensitive to chemical compositions in droplets or hydrodynamics in scrubber. The overall mass transfer coefficient (KG) for NO2 is mainly determined by pH and S(IV) concentration in droplets, while the specific interfacial area (α) is largely influenced by gas-droplet hydrodynamics in scrubber. Finally, a correlation is proposed to predict the volumetric mass transfer coefficient (KGα) for NO2 absorption accompanying with SO2 in WFGD scrubber. [ABSTRACT FROM AUTHOR]

NO x removal performance accompanying with SO 2 is investigated in a two-step process containing O 3 pre-oxidation of NO and NO x post-absorption in the scrubber of wet flue gas desulfurization (WFGD) unit. Based on Eulerian Lagrangian framework, a comprehensive CFD model is established to describe the reactions of NO 2 and N 2 O 5 with S(IV) in droplets coupled with NO x transfer process and hydrodynamics in the scrubber. Taking the WFGD scrubber of 330 MW coal-fired power unit as case study, the results indicate NO x absorption efficiency in scrubber is increased by increasing O 3 /NO molar ratio from 1.0 to 2.2 and decreasing reaction temperature from 423 K to 363 K in O 3 pre-oxidation process. The obtained highest removal efficiency is 85.79% for pH of 5.5 or 96.32% for pH of 9.0 in droplets. NO 2 absorption is much slower than N 2 O 5 and more sensitive to chemical compositions in droplets or hydrodynamics in scrubber. The overall mass transfer coefficient (K G) for NO 2 is mainly determined by pH and S(IV) concentration in droplets, while the specific interfacial area (a) is largely influenced by gas droplet hydrodynamics in scrubber. Finally, a correlation is proposed to predict the volumetric mass transfer coefficient (K G a) for NO 2 absorption accompanying with SO 2 in WFGD scrubber. [Display omitted] [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. [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]

Seawater, NaOH, NaClO, NaClO2, H2O2, and KMnO4 were used as scrubbing liquids to react with SOx and NOx separately in a customized wet scrubber. The absorption of SO2 in the aqueous phase was influenced by three factors: pH, ionic concentration, and oxidation potential. For NOx removal, the effectiveness of various chemical compounds can be ranked from least to most effective as follows: seawater, NaOH, H2O2 < NaClO < KMnO4 < NaClO2. This effectiveness was influenced by the chemical compound's ability to oxidize NO to NO2, absorb the NO2 that was formed, and retaining the nitrogen in the aqueous phase. High oxidation potential promoted the oxidation of NO to NO2 but hindered the absorption of NO2. NaClO2 was superior compared to NaClO in all three categories of oxidizing, absorption and retention. NaClO could not retain a significant amount of NO2 which it absorbed in the aqueous phase. The pH around 8 provided a good balance between oxidation versus absorption/retention and reactant utilization for the chlorine-based oxidants. KMnO4 had the lowest reactant consumption rate; only half a mole was consumed for every mole of NO removed, compared to around 2–3 mol of chlorite or 3–5 mol of hypochlorite. [ABSTRACT FROM AUTHOR]

Nanomaterials (NMs) are currently treated via recycling, incineration and/or landfilling at their end-of-life. Little is known about the fate of NMs in incineration systems and the efficiency of the available flue-gas cleaning technologies (FGCT) in these systems on the removal of NMs before stack release. In combination with other FGCT such as cyclones, electrostatic precipitator or bag filters, scrubbers participate to limit the release of particulate matter (PM) into the atmosphere. No study has been carried out to investigate wet scrubber collection efficiency regarding nanoparticles under conditions found in a waste incineration plant. In the present study, experimental campaigns were carried out to quantify the performance of a pilot-scale spray scrubber regarding the removal of nanoparticles. The pilot was designed with respect to geometrical, hydrodynamic and residence time scale similitude and operated in gas temperature and humidity conditions representative of full-scale scrubbers in hazardous waste incineration plants. A collection efficiency of 45–62% for a particle size range of 12–90 nm was reported. To evaluate the experimental results, an existing PM collection model based on the 3 main particle collection mechanisms of diffusion, interception and impaction, was adapted for extreme humidity and gas temperature conditions typical of a waste incineration plant. A comparison of the experimental and theoretical results was made indicating that the model results were in good agreement with the experimental results. Contrary to prior studies, the impaction-dominant region occurred at smaller particle sizes (0.1–0.2 µm) corresponding to Stokes number 9 × 10−3 to 4 × 10−2. Numerically, the contribution of the interception mechanism in the collection of nanoparticles (particle sizes 1–100 nm) was found to be negligible (i.e., Interception number 2 × 10−5 to 2 × 10−3). [ABSTRACT FROM AUTHOR]

Biomass gasification is the thermo-chemical conversion of biomass into producer gas. The latter can be then integrated in a combined heat and power unit or chemically converted into biofuels. Tar formation during biomass gasification is the main process disadvantage. Tar leads to fouling and clogging problems in the process, in addition to catalyst deactivation when production of chemicals is envisaged. Eliminating tar from the producer gas forms the trigger point for any further valorization. This work hence evaluates the efficiency of wet scrubbers on tar removal from producer gas, based on simulations conducted using Aspen Plus. Wet scrubbers are highly efficient tar removal methods suitable for small scale gasifiers and having a low cost. Two scrubbers are placed in series to increase the tar removal efficiency. The tar reduction efficiency is assessed function of the scrubbing liquid: rapeseed methyl ester and water. Sensitivity studies handling the variation of the liquid to gas ratio and the scrubbing liquid temperature were conducted to study their impact on the tar removal efficiency. Results showed that increasing the liquid to gas ratio and decreasing the scrubbing liquid temperature leads to higher tar removal efficiencies. However, the conducted economic analysis indicated that the operational cost increases as well. A balance between the non-aqueous scrubbing liquid higher tar removal efficiencies with lower utilities cost and the actual liquid cost makes water an alternative scrubbing liquid choice. Finally, the selection of the optimal conditions depends mainly on the required tar limit set for the producer gas application. [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 FROM AUTHOR]

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]

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]