Wet Scrubber System Research Articles

COMPARATIVE PARAMETRIC ANALYSIS OF GAS FLOW IN THREE DIFFERENT DESIGNS OF IN-LINE SCRUBBER BOTTOM INLET

In this study, gas flow fields were simulated using ANSYS 2020R2, Fluid Flow Fluent computational fluids dynamic (CFD) software based on the continuity, velocity, temperature, energy and k - e turbulence. The overall objective of the study is to compare the velocity maps inside the wet scrubber system for three different In-Line scrubber bottom inlet designs. Also, the behavior of the temperature of the mixture inside the scrubber is studied according to the number of nozzles provided by each system from those proposed for study. The numerical simulation using CFD is an effective method to study the flow characteristics of a counter-flow wet scrubber system and the most efficient wet scrubber model is the one with several. The results show that the residuals have a very good job of converging at minimum flow contours and vectors at the inlet across the scrubbing chamber and outlet shows a distributed flow. The speed of water droplets sprayed by the nozzles during mixing with waste gas in the scrubber chamber is double at model with 52 nozzles compared to the first model, equipped with only 13 nozzles. The velocity of clean gases discharged to the ship’s hull shows increases of over 100% of the values, with the increase of the number of nozzles. Spray nozzles improve mixing between the scrubbing liquid and waste gas, by injecting liquid through nozzles to create a fine droplet spray pattern. In this study it can be seen how the number of nozzles influences the quality of the mixture between the scrubbing liquid and waste gas.

Dielectric barrier discharge coupled with Fe2+, Mn2+ and Cu2+ scrubbing for toluene removal

By-product ozone emission is one of the challenges for applying dielectric barrier discharge (DBD) technology for volatile organic compounds (VOCs) removal. In this study, a DBD reactor followed by a wet scrubber (WS) containing a solution of metal ions (Fe2+/Mn2+/Cu2+) was used to reuse ozone for further oxidation of typical VOC toluene. Compared with the degradation effect of the DBD reactor alone, DBD coupled WS/iron system not only improved the toluene removal efficiency but also significantly reduced the ozone emission. The ozone removal efficiency reached as high as 98% in the DBD coupled WS/Fe2+ system. Electron paramagnetic resonance (EPR) tests showed that ozone was converted into radicals such as hydroxyl radicals in Fe2+ and Cu2+ solution, which further oxidized toluene in WS/iron. Quenching experiments showed that the contribution for toluene degradation by radicals was up to 75% and 62% in Fe2+ and Mn2+ reactor, respectively. This study demonstrates that the DBD coupled WS system has the potential to be an environmentally friendly technology for gaseous VOCs removal.

Experimental Study on Simultaneous Desulfurization and Denitrification by DBD Combined with Wet Scrubbing

A dielectric barrier discharge (DBD) reactor combined with a wet scrubbing tower was used to carry out an experimental study on desulfurization and denitrification. The effects of the packing type, packing height, spray density, mass fraction of the NaOH solution, discharge power in the DBD reactor, and simulated flue gas flow rate on the desulfurization and denitrification efficiency were analyzed, along with the influence weight of each factor, using orthogonal testing. The experimental results showed that SO2 was easily absorbed by the scrubbing solution, while the desulfurization efficiency remained at a high level (97–100%) during the experiment. The denitration efficiency was between 12 and 96% under various operating conditions. Denitration is the key problem in this system. The influence weights of the DBD power, simulated flue gas flow rate, mass fraction of the NaOH solution, spray density, packing type, and packing height on the denitration efficiency were 56.96%, 18.02%, 11.52%, 5.02%, 4.33%, and 4.16%, respectively. This paper can provide guidance to optimize the desulfurization and denitrification efficiency of this DBD reactor combined with a wet scrubbing system.

Treatment of Flue Gas from an Infectious Waste Incinerator using the Ozone System

Recently, levels of air pollution caused by exhaust gases from infectious waste combustion have been rising at a startling rate. Pollutant gases such as carbon monoxide (CO) and nitrogen dioxide (NO2) have numerous health implications when unsafe amounts are released into the atmosphere. Thus, Pollution Control Systems (PCS) and Gas Cleaner Systems (GCS) play an important role in industries and the monitoring of incinerators. This research evaluated the GCS of rotary kilns in medical facilities located in the Northeast of Thailand. Data was collected from various sites, analyzed, and examined. Furthermore, Ozone (O3) technology was applied to the rotary kiln allowing for the collection of new information on the pollution treatment systems. O3 technology was installed along with the Wet Scrubber System (WSS) catalyzing the oxidation of O3 and pollutant gases. In addition, a chiller was added to control and stabilize the temperature of the water. After the water temperature was controlled, the concentration of O3 increased resulting in an efficient pollution treatment system. Levels of pollutant gas emission were found to be beneath control standards of both Thailand and those of the U.S. EPA. TSP content was reduced significantly from 22.0 mg/m³ to 3.4 mg/m³ (97%), CO content from 13.6 mg/m³ to 1.7 mg/m³ (96%), and NO₂ content fell from 16.3 (mg/m³) to 2.0 mg/m³ (99%). It is clear that the rotary kiln and Ozone technology should be used together in order to create a new and far more effective method of pollution treatment in small and mid-sized cities of Thailand.

Controlling emissions from an ocean-going container vessel with a wet scrubber system

This study assessed the real-world gaseous and particulate emissions for a wet scrubber retrofit to an existing container ocean-going vessel as it cruised from Tacoma Washington to Anchorage Alaska. The vessel was operated with a high sulfur heavy fuel oil and testing was performed following the ISI 8178 E2 steady test cycle. The scrubber unit provided more than a 95% removal efficiency of sulfur dioxide (SO2) emissions across all engine loads. In contrast to the higher removal efficiencies for SO2 emissions, the scrubber only removed approximately 10% (ISO weighted reduction) of particulate matter (PM2.5) emissions. PM2.5 composition was primarily composed of sulfate, followed by organic carbon (OC) and elemental carbon (EC). Pre- and post-scrubber sulfate levels were similar, indicating why the PM2.5 removal efficiencies were low. This phenomenon was likely due to the formation of small sulfuric acid particles in the scrubber fluid that were not efficiently removed by impaction, influencing PM2.5 mass emission measurements.

Wastewater Management of Wet Scrubbers in Waste-to-energy Facilities: a Life Cycle Analysis

Nowadays, increasing attention is focused on the indirect impacts of emission control technologies and the potential burden shifting. A clear example is the generation of wastewater when wet scrubbing systems are used for flue gas cleaning. The present study takes into consideration a typical wet scrubber for waste-to-energy plants and the available options for wastewater management: physicochemical treatment, evaporation or valorisation. A comparative assessment of the environmental footprint of the alternatives is performed by taking into account the burdens related to the supply of reactants, energy and the disposal of process residues (solid and liquid waste streams). It is thus shown that the recovery of a marketable product from the effluent produces a net environmental benefit, while the choice between wastewater discharge or evaporation represents only a shift of burden between the water and the soil compartments.

Simultaneous removal of NOx and SO2 from simulated marine ship flue gas in a novel wet scrubbing system based on divided diaphragm seawater electrolysis technology: efficiency optimization and economic assessment.

This work constructed a divided diaphragm seawater electrolysis system with two tandem packed towers for the synergistic removal of NOx and SO2. The first tower was mainly used to oxidize NO and SO2 by AC (active chlorine), and the second tower was used to further absorb NOx. The factors affecting on NO removal, including ACC (active chlorine concentration), pH value, initial NO concentration and temperature in the oxidation tower were investigated. Moreover, the effect of different inlet gas concentrations and current values were explored. The results showed that with the increase of ACC, the NO and NOx removal efficiency increased rapidly, but when the ACC was higher than 500 mg/L [Cl2], the removal efficiency did not increase further in the oxidation tower. Low pH values in the oxidation tower were favorable for NO removal. NO removal efficiency reached a maximum at 40 °C. Higher NO and SO2 concentrations were favorable for NO removal. The decline of pH in the anode cell was not conducive to the storage of AC in the continuous electrolysis removal process. NOx and SO2 were almost completely removed after being scrubbed in the oxidation and absorption towers. The relationship between current and removal efficiency of NO and SO2 in the oxidation tower was also analyzed. Finally, the removal mechanism and the application prospects were discussed.

COMPARATIVE CFD BASED PARAMETRIC ANALYSIS OF GAS FLOW IN TWO CONTER-FLOW WET SCRUBBER SYSTEMS

" In this study, gas flow field were simulated using ANSYS 2020R2, Fluid Flow Fluent computational fluids dynamic (CFD) software based on the continuity, velocity, temperature, energy and k -  turbulence. The overall objective of the study is to compare the pressure and velocity maps inside the wet scrubber system for two different scrubber designs. I have choose to analyse an In-Line scrubber bottom inlet, type I, and In-Line scrubber side inlet, type L. Bottom entry or side entry designs to allow a direct up-flow configuration and simplify engine exhaust gas duct routing for any type of vessel. The flow in a wet scrubber is very complex due to the interaction between dust particles, water droplets, and bulk water and flue gas. The flue gas flow is turbulent and there are multiple phases (gas, liquid and solid). CFD codes that predict gas flow patterns are based on conservation equations for mass, momentum and energy. The results show that the residuals have a very good job of converging at minimum flow contours and vectors at the inlet across the scrubbing chamber and outlet shows a distributed flow. The velocity profiles have fully conformed to the recommended profile for turbulent flow in pipes. As can be seen in the figures above, the velocity flow contour inside the scrubber is higher in the scrubber side inlet. Even though I choose to study the simplified scrubber model without taking into account that spray nozzle improve mixing between the scrubbing liquid and waste gas; from the results obtained, it can be deduced that the numerical simulation using CFD is an effective method to study the flow characteristics of a counter-flow wet scrubber system. "

Air Pollution Control for a Hot Mix Asphalt Plant

The report explores how to reduce pollution by improving the emission control system in Hot Mix Asphalt (HMA) plants. The majority of emissions come from the combustion of fuel and particulate matter (PM) diffusion. The key finding is that combining a wet scrubber system and baghouse system will reduce the major pollutants significantly. Thousands of HMA plants across the country are in operation every day in rural, suburban, and urban areas, affecting all neighbors in their local communities. How an asphalt plant impacts the neighborhood and the environment mainly depends on their sustainable operation. Asphalt plant emissions are very low and getting lower due to innovative control systems and manufacturing technology. The objective of this report is to exppore the emission control system of a Hot Mix Asphalt plant. The main point is how to improve the scrubber system and baghouse filter for controlling criteria pollutants in the Hot Mix Asphalt plant during production to reduce the emissions.

Life Cycle and Cost Assessment of a Marine Scrubber Installation

ABSTRACT This paper is to provide a guidance as to which scrubber system is applied for marine vessels in both environmental and economic perspectives. It performs a comparative analysis for two different types of wet scrubber systems: they are generally referred as“open loop” and “closed loop” systems. Those systems are evaluated via life cycle assessment technique, which is further used for evaluating the global warming, acidification and eutrophication potentials. The economic aspect of the scrubber installation will be estimated by establishing the payback time of the installation costs. Sensitivity analysis is performed to determine the effect of various economic scenarios on payback times. Research results reveal that the environmental impacts are higher for the closed loop scrubber than open loop scrubber. The open loop scrubber has a marginally shorter payback time under different scenarios; for No EGCS (MGO) case, it was revealed 3.2 years (with open loop) and 3.6 years (with closed loop), and for No EGCS (VLSFO + MGO) case, 5.4 years (with open loop) and 5.9 years (with closed loop).

Development of an Integrated Electrostatic Precipitator and Wet Scrubber System for Controlling Nox and Particulate Matter Emissions From a Semiconductor Manufacturing Process

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

Oxidation absorption of hydrogen sulfide from gas stream using vacuum ultraviolet/H2O2/urea wet scrubbing system

Hydrogen sulfide has serious harm to human body and equipment. Advanced oxidation technology shows excellent development prospect for hydrogen sulfide (H2S) removal due to strong oxidation ability and green process. This article proposed a novel separation process for H2S from gas stream using vacuum ultraviolet (VUV)/H2O2/urea wet scrubbing system in a VUV-spraying scrubber, and studied the effectiveness of H2S removal and removal pathways using VUV/H2O2/urea wet scrubbing system. Results indicated that the highest H2S removal efficiency was up to 98.2 % under optimal experimental conditions. Increasing UV-light intensity and solution pH improved the H2S removal efficiency. Increasing flue gas flow rate and H2S concentration decreased the H2S removal efficiency. The increase of H2O2 concentration, reaction temperature, liquid-gas ratio or urea concentration first increased and then reduced the H2S removal efficiency. H2S was removed by five pathways such as ionization, urea absorption, H2O2 oxidation, photolysis and ·OH oxidation. Photolysis and ·OH oxidation were the two major pathways for the H2S removal.

Pyrolysis of Radioactive Spent Resins in the PRIME Installation

Montair and Belgoprocess developed the pilot PRIME (Pyrolysis Resins In Mobile Electric) Installation for treatment of spent resins in one single reactor without pre-treatment and without intermixing of other waste, allowing for easy traceability and isotopic characterization of the end product. Both low level waste (LLW, < 2 mSv/h) and medium level waste (MLW, > 2 mSv/h) can be treated in the installation. The PRIME pilot installation is designed to treat 2 batches of 100 litre of saturated ion exchange resins over a period of 24 hours. The pyrolysis reactor contains a special design mechanical stirrer and can operate at a temperature of up to 600°C under inert conditions. As a result, the organic molecules will decompose at an accelerated rate until only carbon-rich and mineralised product free of hydrocarbons remains. Gases that are released during drying and pyrolysis are treated in a thermal oxidizer, which uses an innovative, electrically heated design instead of a traditional natural gas- or fuel oil secondary combustion chamber design. After passing through the thermal oxidizer, the gases are cooled down to saturation temperature and treated in the wet scrubbing system. An induced draft fan keeps the system under negative pressure to prevent the possibility of any off-gas leakage out of the system. The pyrolysing reactor and oxidiser are fully electrically powered which creates also a higher safety level. A series of tests were performed successfully with wet cationic resins, anionic resins and a mixture of both. The results of these tests are described in the presentation. For intellectual property protection, the system and process of pyrolysis of organic waste and the system of thermal oxidation of pyrolysis gases described in this paper are patent pending.

Research of Emission Decrease using Venturi Vacuum in Three-Stage Filter Wet Scrubber Systems

Control of gas emissions from incinerator combustion needs to be done to prevent air pollution. One of the tools to reduce gas emissions is by using a venturi vacuum in a wet scrubber three-stage filter system. This research was conducted to determine whether there is an influence of the filter media size and filter media height. The filter media that used are PVC pipes with filter media sizes varying 2 cm, 4 cm and 6 cm. The height of the filter media varies 5 cm, 10 cm and 15 cm. The parameters studied were NO, CO, and SO2 gas emissions. Result data from the study was carried out statistical tests using One-way Anova to determine the relationship of the influence of variables and parameters on the efficiency of the wet scrubber three-stage filter reactor. The results of the study using a venturi vacuum reactor obtained the highest efficiency values of 66,67% (NO), 29,69% (CO), and 66,87% (SO2). This is contrary to SO2 which has the highest solubility value in water compared to the solubility values of NO and CO.

Computer simulation of NOx removal from diesel engine off-gases under electron beam and wet scrubber system

NOx emission from diesel engine off-gases in marine transportation sector is still an environmental issue to be solved in present day. Electron beam (EB) followed by a seawater wet scrubber method to removal NOx has been experimentally studied (Chmielewski et al., 2018). In this work numerical simulation of NOx reduction using EB followed by a water scrubber system has been carried out. The first stage was to calculate NOx removal versus dose under EB irradiation. Computer code “KINETIC” and Gear method were used, the model has been improved based our previous work (Zwolinska E. et al., 2015) and verified by the experimental results. The calculation results of NOx removal efficiency was 4.9% at 10.9 kGy dose under EB irradiation, which was a little higher than experimental value (3.5%). Computer program MATLAB was used to study NOx absorption in water. The NOx removal efficiency was increased by 17.5% at 10.9 kGy dose for inlet concentration of NOx being 1333 ppm after EB-water absorption process. At the end, NOx reduction in the simulated marine off-gas using microwave plasma was simulated using computer program Chemical Workbench. Less than 20% NOx was removed from the off-gases in microwave plasma reactor even at 9000 kGy dose for the inlet concentration of NOx being 1500 ppm. EB is more energy efficient than microwave plasma for NOx removal.

Efficient Operation of Wet Scrubbing System in Pollution Containment

Wet Scrubbers working depends on the type of gas contaminant whether it is a solid, liquid, odour or recovery a variety of collection mechanisms and scrubbing liquid types are used. For gaseous contaminants, mass transfer is the mechanism that absorbs the gas into a liquid through creation of liquid films or droplets. Large surface area packing media, trays, fluidized beds and hydraulic or shear atomization techniques are mostly used to create the films and droplets necessary for mass transfer to occur. A chemical reagent scrubbing liquid is incorporated in many cases to enhance removal of contaminants by producing a stable salt by-product. The predominant mechanism used for particulate collection is impaction between the particle contained in the gas stream and liquid droplets. The liquid droplet encapsulates the particle into a larger size so both can be removed from the cleaned gas stream either centrifugally or by means of mist eliminator elements. The smaller the size of the particle the smaller the size of the droplet needed to collect the particle. Normally a droplet no larger than 10 times the size of the particle must be used. The smaller the droplet the more energy it takes to create it either hydraulically or through gas shear effects. For hot gases scrubbing system has perfected a method to condense water vapour onto the particle to achieve a larger size agglomerated mass to increase removal efficiency at reduced energy cost. Hydrophobic particles are also hard to scrub wherein it is perfected chemical additions to the scrubbing liquid to overcome the problem. There are various control devices for controlling particulate contaminants however article covers only on the wet scrubbing system in detail.

Legionella in factory water systems – a regulated future

Legionella are pathogenic fresh water bacteria in natural and manmade water systems with a unique water-to-air transmission route. The water temperature is an important factor influencing the colonisation of water systems. Potential critical areas are cooling water, wet scrubbers, sanitary water systems, and aerobic part of wastewater treatment plants. The most recent legislation in Europe, 42nd German Federal Immission Control Act, regulates the technical and organizational requirements for the operators of evaporative cooling, cooling towers, and wet scrubber systems. The regulation specifies two test and one action limit for Legionella and the required measures when exceeding each limit. The reference method, ISO 11731:2017, has disadvantages e.g. analysis time of 7–10d and interfering non-Legionella bacteria that can give false negative results. Alternative methods includes quantitative PCR and fluorescence in situ hybridisation (FISH). Both methods are suitable for in-house evaluation of Legionella. The operation of Legionella positive system is a challenge mainly due to significant resistance to biocides when the bacteria are associated with biofilms. Preventative and corrective actions with focus on cooling water systems are summarised.

Removal of Gaseous Hydrogen Sulfide by a Photo-Fenton Wet Oxidation Scrubbing System

In this article, a photo-Fenton wet oxidation scrubbing system was used to remove and oxidize gaseous hydrogen sulfide in an ultraviolet (UV)-bubbling column scrubber. The technical feasibility of ...

Influence factors and mass balance of memory effect on PCDD/F emissions from the full-scale municipal solid waste incineration in China

Studies are carried out in two wet scrubbing systems (WSSs) subordinated to two similar full-scale (30 t h−1) municipal solid waste (MSW) incinerators to explore the influence factors and mass balance of memory effect on polychlorinated-ρ-dibenzodioxins and dibenzofurans (PCDD/Fs) emissions. The results show that the memory effect on two WSSs notably increases the TEQ concentrations by 13.6 and 3 times, respectively, through increase in the total mass concentration and the proportions of low-chlorinated PCDD/Fs, directly resulting in the PCDD/F emissions of 1# MSW incinerator over the national standard. PCDD/F adsorption/desorption in WSSs is the reasonable acting mechanisms of memory effect. In addition, memory effect mainly influences gaseous PCDD/F emissions by elevating the percentage of PCDFs, while slightly affects PCDD/Fs in residuals. A mass balance of PCDD/Fs is established to further analyze the influence factors of memory effect on WSSs, indicating filling as the largest potential source discharging PCDD/Fs into outlet flue gas. The results pave the way for further industrial optimization of WSSs design, such as the filling materials with less adsorption capacity on PCDD/Fs and more reasonable operation.

Influences of P-N-containing inhibitor and memory effect on PCDD/F emissions during the full-scale municipal solid waste incineration

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