Scrubber Operation Research Articles

Pressure loss and droplet entrainment under spray absorber conditions

The interaction of spray with counter-flowing flue gas causes pressure loss (ΔP) and influences droplet entrainment and sorbent loss in gas–liquid scrubbers. As these phenomena were usually investigated separately and not linked with atomizer characteristics, it is difficult to obtain insight into the scrubber operation and select an atomization device proper to particular process. Atomizers typically used in a spray column, together with pressure-swirl and twin fluid effervescent types, were tested in column-like conditions. All the atomizers were tested at the same liquid flow rate of 140 kg/h, with inlet pressure (pin) from 0.025 to 0.2 MPa under the counter–flow velocity (ucf) ranging from 0to1 m/s. A small-scale low-speed wind tunnel was specially designed to simulate spray column flow conditions. The ΔP and droplet entrainment were correlated with atomizer operating regimes. Empirical and analytical models of ΔP were compared with experimental results for different atomizers. Limitations of both models are discussed. The ΔP is influenced by the spray velocity at the discharge orifice (uL) and correlates well with the liquid kinetic energy (Ek) and Reynolds number at the discharge orifice. The atomizers working on higher pin, provide a larger interfacial area, but yield higher Ek at the discharge orifice, causing larger ΔP and a greater risk of sorbent loss due to presence of smaller droplets.

In-depth characterization of exhaust particles performed on-board a modern cruise ship applying a scrubber

To comply with environmental regulations, ship operators may adopt exhaust after-treatment devices such as scrubbers or selective catalytic reduction (SCR). Beyond gaseous emission control, these technologies impact the exhaust particles emitted from marine engines to the atmosphere. This study characterizes comprehensively the chemical composition and physical properties of exhaust aerosol particles upstream and downstream a hybrid scrubber operating in open loop mode on-board a modern cruise ship. The study considers two engines, one equipped with SCR and both with scrubber, during engine load conditions of 75 % and 40 %, and the influence of marine gas oil (MGO) use in addition to heavy fuel oil (HFO). At least 4 different particle types were observed in the exhaust based on transmission electron microscopy (TEM) studies both upstream and downstream scrubber, and both scrubber and SCR affected the particle number size distribution (PSD). The geometric mean diameter (GMD) of the particles increased over scrubber both due to removal of nucleation mode particles and particle growth in the scrubber. The scrubber effectively decreased particle number (PN) and, also, non-volatile particles, but the effect depended on particle size and no significant decrease was observed in number of particles above 50 nm, typically comprising black carbon (BC) and in the case of HFO combustion, also asymmetrical metal containing particles. In addition to PN, concentrations of PAH compounds were reduced in the scrubber. The results may be further utilized when including the exhaust aerosol characteristics from ships applying scrubbers to emission inventories, as well as climate and air quality models.

Strong economic incentives of ship scrubbers promoting pollution

In response to stricter regulations on ship air emissions, many shipowners have installed exhaust gas cleaning systems, known as scrubbers, allowing for use of cheap residual heavy fuel oil. Scrubbers produce large volumes of acidic and polluted water that is discharged to the sea. Due to environmental concerns, the use of scrubbers is being discussed within the International Maritime Organization. Real-world simulations of global scrubber-vessel activity, applying actual fuel costs and expenses related to scrubber operations, show that 51% of the global scrubber-fitted fleet reached economic break even by the end of 2022, with a surplus of €4.7 billion in 2019 euros. Within five years after installation, more than 95% of the ships with the most common scrubber systems reach break even. However, the marine ecotoxicity damage cost, from scrubber water discharge in the Baltic Sea Area 2014–2022, amounts to >€680 million in 2019 euros, showing that private economic interests come at the expense of marine environmental damage.

Direct deposition of air pollutants in the wake of container vessels: The missing term in the environmental impact of shipping

Understanding the deposition of pollutants produced by the operation of vessels is necessary to quantify air-water pollution interactions. This work develops and presents a novel model for calculating the amount of pollutants deposited on the sea water at the wake of vessels. Deposition depends on meteorological conditions, and vessel operation and design. The work was repeated for several subcategories of vessels included within the broader category of container ships and considered the impact of scrubber operation if such a system were installed on the vessel. Computational fluid dynamics (CFD) modelling was utilized, employing the open-source code OpenFOAM, to calculate the concentration of pollutants in the wake of the vessel. The sensitivity of deposition to different parameters was studied. The key parameters, including the wind relative speed and angle, the main engine power as a proxy for vehicle size, and the exhaust gas velocity, were combined to a single equation that can be used to predict deposition from sea-going container vessels. Direct deposition of pollutants (e.g., SO2) in the wake of vessels was found to be as much as 24 % of the total pollutant quantity produced, under favourable conditions. Direct deposition is so far neglected by air quality models that only report regional level deposition, starting from background ambient levels of pollution. This creates a bias to the predicted air and water pollution impacts. The use of the model proposed to whole vessel fleets, taking stock of the local weather conditions, will enable understanding the global impacts of direct deposition.

Modeling and improving the scrubbing efficiency of an intensified ammonia process for coke oven gas purification

Coke oven gas (COG) is a valuable byproduct of coke production in the steel industry. Conventionally, undesired H2S and NH3 in COG are removed in separate columns in an ammonia process. In this work, an intensified ammonia process which removes both H2S and NH3 in a single column with multiple sections is studied. The intensified process occupies less space and is less expensive. A process model is built and validated using plant operating data. The underlying principal of scrubber operation is explained through the simulated concentration profile. The influences of important operating variables such as inlet COG flowrate, strong ammonia liquid flowrate, low ammonia liquid flowrate and concentrated NaOH solution flowrate are studied. It is shown that the H2S removal efficiency is sensitive to inlet COG flowrate, and that the flowrate of low ammonia liquid should be used as manipulate variable to control the outlet COG composition. Furthermore, it is found that to improve the H2S removal efficiency, the flowrate of concentrated NaOH solution should exceed a certain threshold. Otherwise the scrubbing liquid will be neutralized by CO2 in the COG, which will decrease the pH and alkalinity of the scrubbing liquid significantly.

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.

Optical multi-context scrubbing operation on a redundant system.

This paper presents a proposal of the world-first optical multi-context scrubbing operation on a redundant system that can maintain the state of a sequential circuit and the operation continuously without any interruption on a radiation-hardened optically reconfigurable gate array even after a permanent failure suddenly happens on the sequential circuit or a flip-flop by radiation. Up to now, a high-speed optical scrubbing operation has been demonstrated on a radiation-hardened optically reconfigurable gate array. In addition, a multi-context scrubbing operation based on the high-speed optical scrubbing operation has already been demonstrated. Although the multi-context scrubbing operation presents the benefit that it can treat both soft-errors and permanent failures caused by radiation simultaneously, the conventional contributions have never presented how to maintain the state of a sequential circuit after a permanent failure occurs on flip-flops. Therefore, in the conventional multi-context scrubbing operation, all the operations must be restarted from the initial condition each time a permanent failure occurs on a programmable gate array. As a result, conventional multi-context scrubbing operations could not be applied for real-time systems. The proposed optical multi-context scrubbing method that can solve the issue has been experimentally evaluated on a radiation-hardened optically reconfigurable gate array.

Optimization of Fleet Scrubber Installation and Utilization Considering Sulfur Emission Control Areas and Marine Fuel Switching

With the rising environmental consciousness, emission pollution has become one of the major concerns of the maritime industry, which is the artery of international trade. To handle the significant cost increase resulting from stringent emission regulations, ship operators have adopted multiple methods, including operational and technical methods. Scrubbers are a mature and effective technology that can reduce sulfur dioxide and particulate matter emissions by cleaning the exhaust gases before emitting them. However, the existing literature regarding the operation of scrubbers does not consider the prohibition of open scrubber usage in the vicinity of certain ports or the variable costs of using scrubbers. Therefore, this study explores the fleet scrubber installation and utilization problem, considering sulfur emission control areas, marine fuel switching, and open-scrubber-prohibited areas. A mixed-integer nonlinear model was developed to formulate and address the problem. Numerical experiments and sensitive analyses based on practical data were conducted to validate the originally proposed model and show the effectiveness of this technology under various scenarios. The results indicated that the operational cost was effectively reduced by using scrubbers, compared to not using them. Additionally, the disparity between total costs with and without scrubbers was significant, regardless of the sailing speed and proportion of the regulation areas. It was also proven that spreading the scrubber installation work over several years will relieve financial pressures due to scrubber investment and thus obtain a better installation plan.

Analysis of a marine scrubber operation with a combined analytical/AI-based method

This paper describes the performances of a marine SO2 absorption scrubber installed onboard a large Ro-Ro cargo ship. The study is based on the reconstruction of an extensive dataset from one-year continuous monitoring of the scrubber’s performances and operating conditions. The dataset has been interpreted with a conventional analytical, physical-mathematical, model for absorbers' rating and its combination with an Artificial Intelligence (AI) one. First, the analytical model has been used to provide a deterministic mathematical framework for the interpretation and the prediction of the scrubber’s performances in terms of absorbed SO2 molar flow and SO2 concentration at the scrubber exit. Then, data mining and AI techniques have been applied to develop an Artificial Neural Network able to predict the error between the actual SO2 concentration at the scrubber exit and the corresponding analytical model predictions. The final result is a combined model providing superior robustness and accuracy in the prediction of the scrubber performance while preserving a rationale for process design and operation. This interesting outcome suggests that the development of combined, or hybrid, Analytical/AI models can be a reliable and cost-effective way to improve chemical engineers' ability to design and control marine scrubbers, as well as other chemical equipment.

A risk assessment of scrubber use for marine transport by rule-based fuzzy FMEA

To comply with the International Maritime Organization’s sulfur regulations, shipping companies have mainly favored scrubber systems. Even though the ship’s operations might be continued provided regulatory constraints are followed, the installation presents system-based risks depending on the scrubber type. This study’s primary aim is to inform the shipping industry about the risks associated with various scrubber applications on ships and to propose guidelines to ensure safer scrubber operation on marine vessels. Consequently, a risk evaluation is conducted on all kinds of scrubber systems. Experts in the marine industry identify the main subsystems and components and evaluate their failure modes and consequences. Using the fuzzy failure modes and effects analysis method, the acquired judgments are analyzed. The risk value of each failure scenario is computed using the Mamdani fuzzy inference technique and the evaluation of expert ratings. The riskiest failure modes identified by the investigation include the sensing element, injection nozzles, packed peds, and seawater system valves.

Metal and PAH loads from ships and boats, relative other sources, in the Baltic Sea

The Baltic Sea is a sensitive environment that is affected by chemical pollution derived from multiple natural and anthropogenic sources. The overall aim of this study was to estimate the load of metals and polycyclic aromatic hydrocarbons (PAHs) from shipping and leisure boating, relative other sources, to the Baltic Sea and to identify possible measures that could lead to major reductions in the loads of hazardous substances from maritime shipping and leisure boating. The use of copper-based antifouling paints, and operation of scrubbers in open loop mode, were the two most dominant identified sources of hazardous substances to the Baltic Sea. Open loop scrubbers accounted for 8.5 % of the total input of anthracene to the sea. More than a third of the total load of copper can be reduced if copper-free antifouling paints or other biocide-free antifouling strategies are used on ships and leisure boats.

Effect of dilution on the performance of ionic liquids in milliflow solvent extraction applications: Towards integration of extraction, scrubbing and stripping operations with in-line membrane-based phase separation

The combination of ionic liquids (ILs) and millifluidic reactors is often suggested as a form of process intensification. The high viscosity of ILs has, however, raised concerns about hydrodynamics, mass-transfer enhancement and the ability to integrate several millifluidic operations. In the present study the performance of a quaternary ammonium hydrogensulfate IL, [A336][HSO4], in a millifluidic solvent extraction (SX) process was evaluated and compared with various, lower viscosity solutions of the IL in a diluent. Dilution of [A336][HSO4] significantly improved the slug flow hydrodynamics by reducing the film thickness, avoiding the loss of secondary recirculations inside the plugs and improving stability at elevated flow rates. The overall mass-transfer performance of the system was also improved upon dilution by a balancing of mass-transfer and reaction limitations. It was also observed that dilution reduced reagent consumption and improved the extraction selectivity. In addition, the decrease of the viscosity of the IL upon dilution facilitated the use of an in-line membrane-based phase separator. An integrated millifluidic set-up containing an extraction, scrubbing and stripping reactor was built using these in-line phase separators and applied to the SX purification of germanium from a synthetic zinc refinery residue leachate. The integrated reactor system was operated using a 30 vol% [A336][HSO4] dilution in p-cymene and successfully run for 4 h without any loss in separation performance or stability.

Enhanced mar/scratch resistance in automotive clear coatings by modifying crosslinked polyurethane network with branched flexible oligomers

Mar and scratch resistance are a major concern for automotive and other industrial sectors from causing inconvenient aesthetic changes on clear coats. Then, a series of two-component solvent-borne polyurethane coatings were formulated with branched polycaprolactone (PCL) oligomers. The effect of the partial substitution of acrylic polyols by tri- and tetra-functional PCL polyols on adhesion, chemical resistance, thermo-mechanical properties and aesthetic response was analysed. The PCL polyols drove to plasticised networks with lower glass transition temperature (Tg) and promoted rubbery state at room temperature. The associated growth in chain mobility did not appreciably affect the key performance of the coatings, apart from the chemical resistance of formulations with PCL triols. Furthermore, remarkable improvement of wear resistance from promoted recovery response was demonstrated. The clear coats with moderated content of PCL polyols yielded a reduced loss of specular gloss with time after repeated scrubbing operations by an abrasive paper. The proposed approach, thus, is presented as a versatile strategy to tailor the mechanical surface properties of clear coats.

Environmental impact of pig production affected by wet acid scrubber as mitigation technology

Ammonia (NH 3 ) is the most common air pollutant in pig farms, affecting animals and workers’ health, and causing damages to ecosystems. Hence, there is a need to reduce NH 3 emissions. Many mitigation strategies can be applied to limit gaseous emissions, such as the application of air treatment technologies. In this study, the environmental impact of a typical Italian pig farm, adopting a wet acid scrubber to abate NH 3 emissions, was evaluated using the Life Cycle Assessment approach. 1 kg of live weight (LW) was selected as Functional Unit. Two scenarios were considered. The baseline scenario (BS) represents the situation as it is, while the alternative scenario (AS) a wet scrubber prototype (with 70% NH 3 removal efficiency) was adopted. For 8 of the 12 evaluated impact categories, AS shows the highest environmental impact, due to the scrubber construction and maintenance. However, it was the best for those impact categories most affected by NH 3 . Observed reduction ranged from 10% (for acidification, TA, and terrestrial eutrophication, TE) to 0.4% (for marine eutrophication, ME). The climate change impact was 3.55 kg CO 2 eq kg -1 LW and 3.65 kg CO 2 eq kg -1 LW for BS and AS, respectively. For almost all impact categories, the consumable materials for wet scrubber operation represented around 85% of the total impact of the scrubber. The results of the sensitivity analysis showed that variation in NH 3 removal efficiency had the greatest effect on particulate matter formation, TA, and TE. The achieved results provide a first quantitative indication of the environmental benefits that can be achieved using wet acid scrubber in naturally ventilated pig facilities.

Применение компьютерного моделирования при выборе параметров работы пылеотсоса, встраиваемого в проходческие комбайны

An increase in the rate of mine workings excavation leads to the ingress of large amount of dust into the mine atmosphere. Ensuring the aerological safety of coal mines drifting faces according to the dust factor is an urgent task. To reduce the level of dustiness of a dead mine roadheading during its sinking, the scrubbers built into the roadheader are used. In this case, the joint operation of the ventilation system and the dust extraction system is not considered. This leads to the risk of occurrence of the stagnation zones or air recirculation near the bottom-hole area. At the intensive ventilation with a high air flow, the dust is removed, and the dust extraction system becomes useless. As the analysis showed, currently there are no methods that allow to take into account these two processes simultaneously. The idea of using computer modeling in the Ansys software package is proposed. To correctly solve the problems of optimizing the scrubber operation, a method is given for determining the grid parameters, as well as for setting the initial and boundary conditions. All the data obtained were verified at the coal mines of Russia. To achieve maximum efficiency, it is proposed to use the dust and aerodynamic criteria of the scrubber operation, which will allow to increase the mining operations safety. The dust criterion characterizes the efficiency of the dust extraction systems. The aerodynamic criterion allows to determine the joint operation mode in which there will be no recirculation and not ventilated zones. To take into account the large number of factors that affect the ventilation of a dead mine working and the operation of the dust extraction system, an artificial intelligence was added to computer modeling in system design. It is implemented in the ANSYS DesignXplorer module. In a given range of changing factors during the operation of artificial intelligence, by performing multiple calculations, such a combination of operating parameters of the two systems is obtained, at which the efficiency is maximum.

Improvement of human health and environmental costs in the European Union by air scrubbers in intensive pig farming

Intensive pig farming is responsible for significant air pollutant emissions. This study explores the effect that the large-scale implementation of air cleaning technologies (wet acid scrubbers) for pig housing facilities could have in the European Union. Emissions related to the housing stage of NH3, PM10, NMVOC and indirect N2O from large pig farms (>1000 heads of sows or fattening pigs) are first estimated in the actual situation (current scenario - CS), considering implementation rates and removal efficiencies of the different emission abatement techniques available. Subsequently, alternative scenarios (AS1 and AS2) are simulated with a growing implementation rate of the wet acid scrubber (35% and 65% of the concerned pig farms in all Member States). A comparison between the scenarios was carried out, taking into account emissions reduction, consumables for scrubber operation and environmental credit given by the avoidance of synthetic nitrogen fertilizer production. The annual impact on human health of 21,212 disability-adjusted life years (DALY) in CS was significantly reduced in AS1 (-15%) and in AS2 (-40%), showing that the environmental trade-off given by the consumables is largely overwhelmed by emission abatement. At the same time, the current environmental cost to society of the concerned emissions was estimated at 4154 million € per year (of which 89% due to NH3), which also was reduced in alternative scenarios (−668 and −1765 million € for AS1 and AS2). The abatement of NH3, on which the wet acid scrubber expresses the greatest removal efficiency, was fundamental in both reducing the human health impact and environmental costs, demonstrating the key environmental role of this pollutant and the growing need to find solutions for its containment in the EU.

Comparative Economic Analysis on SOx Scrubber Operation for ECA Sailing Vessel

The IMO (International Maritime Organization) has mandated the restriction of SOx emissions to 0.5 % for all international sailing vessels since January 2020. And, a number of countries have designated emission control areas for stricter environmental regulations. Three representative methods have been suggested to cope with these regulations; using low-sulphur oil, installing a scrubber, or using LNG (Liquefied Natural Gas) as fuel. In this paper, economic analysis was performed by comparing the method of installing a scrubber with the method of using low-sulphur oil without installing additional equipment. We suggested plausible layouts and compared the pros and cons of different scrubber types for retrofitting. We selected an international sailing ship as the target vessel and estimated payback time and benefits based on navigation route, fuel consumption, and installation and operation costs. Two case of oil prices were analyzed considering the uncertainty of fuel oil price fluctuation. We found that the expected payback time of investment varies from 1 year to 3.5 years depending on the operation ratio of emission control areas and the fuel oil price change.

Exhaust Gases Cleaning Technology for Vessels

The present investigation aims to propose results of development of an effective system for the purification of exhaust gases that are emitted to the environment by ship power plant from sulfur oxides (SOx) and solid particles. Numerical simulation of a combined scrubber with vortex plate based on the developed theoretical approach was performed. Mathematical model of aerohydrodynamic and heat-mass transfer processes contains five interconnected modeling blocks. There was investigated the influence of the scrubber’s geometric characteristics onto the quality of its work. As a result, for the elements of vortex plate the rational design parameters were determined (the angle of blades installation for the swirls =60-90, the ratio between internal and outer radius of the swirls R1/R2=0,6-0,7). The interaction of gas aerosol with water foam was studied during numerical simulation. It was done with consideration of hydrodynamic regime on the surface of a vortex plate. As a result, for the scrubber rational design and operating parameters were formulated (inlet flow velocity V=18-25 m/s, the height of foam layer H=70-150 mm, inlet dust concentration 40-50 g/cub.m of the gas to be cleaned, cross-sectional area of the purification unit up to 2 sq.m). Computer-based solid-body scrubber model was created during numerical simulation. CFD modeling of the main hydrodynamic processes based on this model was carried out. It was done for all developed structural solutions for scrubber elements. The main results obtained during CFD modeling of the scrubber operation make it possible to analyze the technology of its use and to achieve a reduction in energy costs while maintaining the quality of gas cleaning. The developed theoretical model of a scrubber gives an ability to simulate the flow of a gas-dust stream considering all changes that were done in the geometry of the scrubber. The very model can also be used to optimize the scrubber’s design depending on the type of production and parameters of the gas to be contaminated. During research works there was formulated a conclusion about the necessity to take into consideration the uneven distribution of the field of velocity when modeling the process of gas purification and cooling inside a scrubber. In order to determine the efficiency of heat transfer process inside the scrubber, heat transfer coefficients were found out. They were compared with characteristics of a traditional scrubber’s model based on a perforated plate. Calculation data have shown an excess of the heat transfer coefficient of the vortex plate by 5-7%. It was stated also that the value of the heat transfer coefficient depends on average velocity and moisture content of the gas to be supplied. The rational design and operational parameters of the scrubber obtained on the models made it possible to develop a pilot industrial model of the scrubber and method of engineering calculation. During experimental studies of the scrubber, new scientific results were obtained. They allow one to establish the technological range of irrigation density values, at which the maximum efficiency of trapping solid particles and sulfur oxides (SOx) is ensured. Experiments were carried out that reveal the relationship between the angle of blades installation of the swirl and the height of the installation of the baffle plate onto the efficiency of foaming and total resistance of the vortex plate.

Rigorous Tritium Wet Scrubber Column Modeling and Design

The rigorous steady-state equilibrium stage Tritium Wet Scrubber Column model has been developed. The model includes the six water isotopologues H2O, HDO, HTO, D2O, DTO, and T2O; heat balance; and packing pressure drop. Heat balance is particularly important in wet scrubber calculations due to evaporative cooling of air with less than 100% relative humidity. Evaporative cooling is generally beneficial, but freezing is possible with very cold dry air, making it important to understand operating limits. The pros and cons of precooling and saturation of the airstream are discussed. The Tritium Wet Scrubber Column model has been applied to scrubbing airstreams containing tritiated light water vapor and for tritiated heavy water vapor in CANDU® heavy water applications. Deuterium and tritium are recovered at slightly different efficiencies, and because of differences in the latent heat of vaporization for H2O and D2O, liquid and vapor compositions affect the column heat balance. Case studies are presented for tritiated light water vapor air detritiation and also for tritiated heavy water vapor air detritiation to provide guidance for design. Further, practical aspects of the wet scrubber column construction and operation are discussed.