Wet Scrubber System Research Articles

Development and Performance Evaluation Experiment of a Device for Simultaneous Reduction of SOx and PM

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.

Density functional theory study the mechanism of oxygen-functionalized graphene to activate peroxymonosulfate for VOCs removal in aqueous solution

Utilization of carbon materials for persulfate activation has revolutionized advanced oxidation processes in effluent treatment. However, its potential volatile organic compounds (VOCs) removal in gas phase remains an intriguing research area. In this research, the peroxymonosulfate (PMS) activated by graphene functionalized with diverse oxygen groups was investigated, and the corresponding performances for VOCs treatment were examined. Furthermore, the feasibility of employing various functionalized graphene/PMS systems for VOCs treatment by simulating a wet scrubber system was explored. Density functional theory (DFT) calculations were served as a useful tool to comprehensively analyze the intricate chemical processes involved: the adsorption and the activation of PMS, as well as the adsorption and degradation of VOCs. The favorable activity of graphene materials incorporating ketone group was showcased in our findings, as evidenced by charge distribution trends, charge transfer during persulfate adsorption, and the lower energy barrier. The mechanism of employing functionalized graphene/PMS systems for effective VOCs treatment was shed light by this research, thereby contributing to the advancement of exhaust gas treatment methods.

Modelling and Simulation of a Wet Scrubber System

Shipping is a relatively clean transport method with low emissions per ton-mile compared with road transport. However, harmful emissions emitted in coastal areas are a concern, as these affect local air quality and health. To reduce sulphur oxide (SOX ) emissions, the International Maritime Organization (IMO) implemented a global sulphur cap of 0.5 wt% and the 0.1 wt% limit in emission control areas (ECAs). Ship owners can opt for either low sulphur fuels or wet scrubber systems. Wet scrubber systems are a reliable method for reducing SOX emissions with capture rates of up to 98%. These systems may use seawater alkalinity or caustic soda (e.g. closed-loop systems) to neutralise the SOX emissions. However, the dynamic loading of engines can cause large fluctuations in the exhaust flow conditions, and it is unknown how these affect the effectiveness of the scrubber. This study explores the impact of dynamic loads on the SOX removal efficiency of closed-loop wet scrubbers. A dynamic model of a closed-loop wet scrubber utilising fresh water and caustic soda is developed and verified using publicly available data. The model applies the two-film theory to model the gas-liquid interface. Billet and Schultes liquid hold-up theory is used to model the liquid film thickness in the packed bed. Maintaining scrubber efficiency with large load fluctuations or high-frequency fluctuations requires an increased liquid flow. The scrubber control system used a set-point of 75% of the equivalent compliance limit to ensure compliance with the 0.1% ECA limit during load fluctuations. The model and results can be used to develop a more advanced control system for improved scrubber operation and integration with a selective catalytic reduction (SCR) system to demonstrate compliance with the IMO NOX Tier III limit when using high-sulphur heavy fuel oil (HFO).

Numerical Analysis of SO2 Absorption inside a Single Water Drop

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.

Deep mineralization of VOCs in an embedded hybrid structure CoFe2O4/MoS2/PMS wet scrubber system

Peroxymonosulfate (PMS)-based advanced oxidation processes in liquid phase systems can actively degrade toluene. In this work, the catechol structural surfactant was introduced to synthesize the dispersed and homogeneous CoFe2O4 nanospheres and embedded into MoS2 nanoflowers to form magnetically separable heterojunction catalysts. The innovative approach effectively mitigated the traditionally low reduction efficiency of transition metal ions during the heterogeneous activation process. In CoFe2O4/MoS2/PMS system, the toluene removal efficiency remained 95% within 2 h. The contribution of SO4⋅-, ·O2-, ·OH, and 1O2 was revealed by radical quenching experiment and electron paramagnetic resonance spectroscopy. The results illustrated that MoS2 offers ample reduction sites for facilitating PMS activation via Fe3+/Fe2+ redox interactions. Furthermore, an investigation into the toluene degradation pathway within the CoFe2O4/MoS2/PMS system revealed its capability to suppress the formation of toxic byproducts. This ambient-temperature liquid-phase method presented promising route for the removal of industrial volatile organic pollutants.

Field study on variation characteristics of PCDD/Fs and flue gas particles along MSW incinerator

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.

Determination of Rational Design Values for Gas-Air Coolers Components of Exhaust Gases of Marine Power Plants

Abstract 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.

A feasibility Study on the exhaust-gas treatment efficiency of a wet-scrubber system equipped in a diesel engine: A focus on smoke emission

A feasibility examination was conducted on a wet-scrubber system designed in this study to investigate the exhaust gas treatment efficiency of a wet-scrubber system equipped with a diesel engine. This preliminary investigation limits to evaluate the feasibility of the wet scrubber system in decreasing smoke. The influence of multiphase flow configuration in wet-scrubbing aftertreatment systems on emission formation is an interesting topic in the field of exhaust gas aftertreatment. It is our initial attempt to investigate the influence of multiphase flow configuration in a wet-scrubbing hybrid aftertreatment system on key pollutants emitted from Diesel engines in the future. This wet scrubber works by spraying water into the exhaust gas stream. The engine was tested at three-speed conditions (1,500 rpm, 1,800 rpm, and 2,000 rpm, respectively) while varying its torque from 15 to 30 N.m. The results show that under these operating conditions, the smoke level after the scrubber decreases by up to 50%. Please note that only fresh water was used in this study, and the impact of catalysts that could further decrease exhaust gas pollution will be investigated in future studies. The water droplets serve as a medium for capturing and collecting the soot particles present in the exhaust gas. Through collisions, the water droplets cause the soot particles to adhere to their surfaces, a process known as impaction. Additionally, the larger water droplets can facilitate coagulation or agglomeration of the particles, resulting in their enlargement and enhanced capture efficiency.

Non-thermal plasma coupled with a wet scrubber for removing odorous VOC

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.

Assessment of a Multi-Stage Wet Scrubber Performance Based on Characteristics of Scrubbing Solution

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 multi- stage wet scrubber is capable of removing toxic acid gas and particulate matter

Porous graphitized carbon-supported FeOCl as a bifunctional adsorbent-catalyst for the wet peroxide oxidation of chlorinated volatile organic compounds: Effect of mesopores and mechanistic study

Wet scrubbing coupled with adsorption-enhanced heterogeneous advanced oxidation processes (AOPs) are promising approaches to the treatment of chlorinated volatile organic compounds (CVOCs). However, microporous activated carbon-based adsorbents and catalyst supports have the disadvantage of difficult molecule diffusion. Herein, we have demonstrated that porous graphitized carbon (PGC) allowed faster intra-particle diffusion of organic molecules due to its well-developed mesoporous structure. Therefore, a wet scrubbing system containing H2O2 and a PGC-supported FeOCl catalyst has been developed to effectively remove gaseous dichloroethane, trichloroethylene, dichloromethane and chlorobenzene. The scrubber performed well at pH 3.0 using a FeOCl/PGC dosage of 0.2 g/L and initial H2O2 concentration of 40 mM. Its good long-term performance was achieved by replenishing H2O2 to maintain a suitable concentration. The degradation pathways of dichloroethane have been proposed using a combination of intermediate analysis and density functional theory calculations. PGC-supported catalysts may be desirable bifunctional adsorbent-catalyst materials for wet scrubbing of CVOCs.

Evaluating the Application of Bubble Wet Scrubber Systems for Gas Cleaning in Gasification

Evaluating the Application of Bubble Wet Scrubber Systems for Gas Cleaning in Gasification

High-efficiency destruction of aromatic VOC mixtures in a MoS2 cocatalytic Fe3+/PMS reaction

Advanced oxidation processes (AOPs) has been intensively applied for the treatment of single VOCs but rarely for that of mixture in a wet scrubber system. However, a multitude of VOCs are present simultaneously in industries. This work first studied the degradation of a typical toxic aromatic VOC (AVOC, chlorobenzene, styrene, toluene) mixture in a MoS2 cocatalytic Fe3+/PMS (peroxymonosulfate) reaction. Extensive HO, SO4- and O2- from the efficient activation of PMS and molecular O2 cooperated well in the simultaneous removal of multiple AVOCs. The degradation of AVOCs in the mixture was significantly affected by the existence of different pollutants. For example, the toluene removal efficiency was 91 % and 74 % in the presence of styrene and chlorobenzene, respectively. Compared with that in the single-pollutant system, chlorobenzene degradation in the presence of toluene was more complex due to the generation of dichlorobenzene and toluene via an e-aq-mediated reaction. The diverse molecular structure, adsorption behavior and ring-opening process of AVOCs on the MoS2 (001) surface accounted for their different degradation performances. Molecular O2 was involved in AVOC mixture degradation and significantly shortened their degradation pathways due to the generation of more reactive benzaldehyde and benzoquinone. The total hazard index (HI) of the purified waste gas was 5.06 × 10-1 and within the safe range for human health. This study is expected to drive great advances in the simultaneous degradation of VOCs mixture by AOPs.

Adsorption-enforced Fenton-like process using activated carbon-supported iron oxychloride catalyst for wet scrubbing of airborne dichloroethane

Wet scrubbing is a low-cost process for disposing of air pollutants. Nevertheless, this method is rarely used for the treatment of volatile organic compounds (VOCs) because of their poor water solubility. In this study, we used a unique wet scrubbing system containing H2O2 and activated carbon (AC)-supported iron oxychloride (FeOCl) nanoparticles to remove airborne dichloroethane (DCE). The operating conditions of the wet scrubber were optimized, and the mechanism was explored. The results showed that the adsorption of dissolved DCE onto AC promoted its transfer from air to water, while the accumulation of DCE on AC facilitated its oxidation by •OH generated on FeOCl catalyst. The wet scrubber performed well at pH 3 and low H2O2 concentrations. By pulsed or continuous dosing H2O2, the cooperative adsorption-catalytic oxidation allowed long-term DCE removal from air. Benefiting from satisfactory cost-effectiveness, avoidance of toxic byproduct formation, and less corrosion and catalyst poisoning, wet scrubbers coupled with cooperative adsorption and heterogeneous advanced oxidation processes could have broad application potentials in VOC control.

Integration of wet scrubbing system and SOx additive technologies to reduce the SO2 emissions generated in FCCU

Integration of wet scrubbing system and SOx additive technologies to reduce the SO2 emissions generated in FCCU

Reduction of environmental chemicals, toxicity and particulate matter in wet scrubber device to achieve zero emissions

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.

Role of Sulfite Oxidation in NO2 Absorption in a pH-Neutral Scrubber Solution

Nitrogen dioxide (NO2) absorption in aqueous sulfite solutions has recently gained more attention to reduce NOx emissions. The NO2 removal efficiency is strongly influenced by the competing reactions of NO2 absorption and sulfite oxidation. The present study investigates the role of sulfite oxidation in NO2 absorption at neutral pH. The effects of sulfite concentration, thiosulfate, pH, NO2 inlet concentration, oxygen concentration on NO2 absorption efficiency, and sulfite oxidation rates were investigated under well-controlled conditions at 25 °C in a laboratory-scale wet scrubbing system. NO2 absorption rates showed a strong dependence on the sulfite concentration and increased linearly with increasing NO2 inlet concentrations between 25 and 150 ppm. At the highest investigated sulfite concentration, 20 mM, the NO2 removal efficiency was around 80%. Oxidation rates of sulfite during NO2 absorption in the presence of 5 vol % O2 increased with increasing sulfite concentrations in the scrubbing solution and ranged from 20 mg·L–1·min–1 with 1 mM sulfite to 200 mg·L–1·min–1 with 20 mM sulfite. The oxidation rate decreased significantly when thiosulfate was added, while the oxidation rates were independent of the oxygen concentration between 2–10 vol % O2. The NO2 absorption rate decreased with decreasing pH between pH 6 and 8 proportionally to the sulfite concentration as predicted by the sulfite–bisulfite equilibrium. The implication from these results is that significantly less sulfite feeding is needed in industrial NO2 absorption if the pH can be maintained at neutral pH, instead of lower pH such as in simultaneous SO2 and NO2 scrubbing.

Behavior of nitrogen and sulfur compounds in the rice husk pellet bioscrubber and its circulation water

In this study, pellet-type biofilter media was developed with rice husk and applied in a wet scrubber system for odor removal. The lab-scale bioscrubber system was operated for 200 days to evaluate odorous gas removal (i.e., NH3, H2S, methyl mercaptan, and dimethyl sulfide), and the removal mechanism of odor gases was studied by analyzing the behavior of nitrogen and sulfur compounds in circulation water of bioscrubber system. The rice husk pellets supplied the organic carbon source and phosphoric acid necessary for microbial growth, allowing the system to continue successfully for 200 days without any maintenance technology.By analyzing the behavior of the nitrogen and sulfur compounds in the circulation water, we confirmed that the odor gas removal resulted from various mechanisms, including adsorption and biodegradation. Ammonia gas was absorbed by the rice husk pellets and accumulated in the circulation water as nitrite under conditions of sufficient alkalinity and above pH 7. Conversely, when the alkalinity and pH decreased, nitrite was rapidly converted to nitrate. However, H2S gas was oxidized to sulfate and continuously accumulated in the circulation water regardless of the pH and alkalinity. In addition, it was confirmed that the decrease in nitrate in the bioscrubber system was due to heterotrophic denitrification by the organic carbon source supply and autotrophic denitrification by sulfur gas.During the operation of the rice husk pellet bioscrubber for 8 months, under low solubility condition, more than 99% of NH3 and H2S were removed and about 85% of methyl mercaptan (MM) and dimethyl sulfide (DMS) were removed.

Emission levels and phase distributions of PCDD/Fs in a full-scale municipal solid waste incinerator: The impact of wet scrubber system

The emission of polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) from municipal solid waste (MSW) incinerations will pose serious risk to ecological environment and human health. To further understand the memory effect of wet scrubber system (WSS) on PCDD/Fs emission and phase distribution characteristics, a field study was conducted in a full-scale (850 t d−1) MSW incinerator where a WSS was newly adopted. The four exhaust flue gas samples and the two scrubbing solution samples inside WSS were separately collected for PCDD/Fs analyzing. The results indicated that the memory effect of WSS obviously enhanced the I-TEQ concentration of PCDD/Fs from 0.007 to 0.033 ng I-TEQ Nm−3 after flue gas passed through WSS, owing to increasing the total mass concentration of PCDD/Fs and the proportion of low-chlorinated congeners. The gas-phase PCDD/Fs was dominant (62.5%–88.9%) in flue gas, among which the PCDD/Fs enriched in condensed water notably contributed to nonnegligible proportions of 25.0%–67.6%. The adsorption/desorption process of PCDD/Fs was considered as one of the reasonable mechanisms of memory effect, based on the PCDD/Fs phase distribution and the congeners profile inside the WSS. Besides, the I-TEQ concentration of PCDD/Fs determined in scrubbing solution was up to 50.2 pg I-TEQ L−1, which might be a potential source to cause the enhancement of PCDD/Fs emission. This study verified the enhancement impact of WSS on PCDD/Fs emission and inspired the optimal design of WSS, i.e., choosing more suitable filling materials and timely replacing them to reduce the negative impact of memory effect, keeping WSS operated in relatively stable and consistent conditions, and safely disposing the scrubbing solution to mitigate the secondary pollution of PCDD/Fs.

New concept of in/out air quality control in livestock buildings

The object of this research is the new concept of the original universal system for air quality and energy control in laboratory conditions (wet scrubbing system) based on the ?clean air in/out? principle. Namely, the process involves a partial or complete exchange of recirculated treated air. From the aspect of water, as a pure medium, the system is characterized by broad application in the open, semi-open, and closed air treatment systems: primarily in the breeding and accompanying agricultural facilities, industrial, cultural, sports, tourist, medical and other controlled spaces. The analysis showed that the system at its inlet unit and with the block structure and logical phase development, proved energy, environ-mental and qualitative efficiency in the removal of PM10 and PM2.5 particles from the controlled dust doses in laboratory air. The measurements of PM10 and PM2.5 concentrations were performed with two Alphasense OPC-N3 optical counters at the inlet and outlet of the system. Five operating regimes with frequency regulated number of revolutions of the turbo elements that was taken as an independent variable, achieved different degrees of removal of PM10 and PM2.5 from the treated laboratory air: 97.70-98.53% and 62.19-75.75%, respectively. The assessment of system energy use was done by parallel measuring of electric power and comparative deviations of its absolute values in the first decimal. Energy consumption for the treatment of 1m3 of air ranged from 0.00011- 0.00016 kWm?3. Statistical analysis of qualitative indicators revealed significant differences between the operating regimes and the obtained values.