Liquid Phase Catalytic Exchange Column Research Articles

Liquid phase catalytic exchange column of water detritiation system: Steady-state modeling, simulation, and optimization

This paper presents a steady-state modeling, simulations, and optimization for an LPCE column of water detritiation system. It introduces a three-fluid model that integrates isotopic exchange, equilibrium-stage, and hydrodynamic models, considering energy balance and multiple feeds with adaptable feed location. The models were implemented in Pyomo, an equation-oriented, Python-based optimization modeling framework. Parametric studies are presented to analyze the effects on the detritiation factor and deuterium concentration resulting from changes in the gas to liquid feed mole ratio, gas feed composition, heat duty distribution, and gas feed location. Using the three most commonly employed catalysts, a design study investigates the minimal number of hypothetical stages required to meet the defined annual tritium discharge levels.

MICRO-CHANNEL REACTOR FOR LOW LEVEL H2 OXIDATION WITHIN AN O2 STREAM: PRELIMINARY TESTS IN VIEW OF INTEGRATION IN A H2 GENERATOR WITHIN CECE PROCESS

CECE (Combined Electrolysis Catalytic Exchange) process is the candidate for low level tritiated water detritiation within any application. The process consists mainly of a H2 generator, a LPCE (Liquid Phase Catalytic Exchange) column and an O2 striping column. During operation, tritium is being accumulated within the H2 generator in the form of tritiated water and the effluent streams (hydrogen and oxygen) show in time an increase concentration in tritium in the form of both tritiated water vapors and gas, which needs to be recovered. The tritium in the H2 stream is recovered in a LPCE column, while the tritium in the O2 stream is recovered in a striping column. In view of lowering the load onto the striping column and to recover the tritium in gas form, a micro-channel reactor is proposed to be included for H2 oxidation followed by vapor recovery. The design of the equipment together with the preliminary results of the tests done with H2 and air will be shown, prior to integration in the CECE process.

Commissioning of the LPCE and purification systems as front-end of the experimental pilot plant for D-T separation

Abstract Liquid Phase Catalytic Exchange (LPCE) as front-end process and Cryogenic Distillation (CD) as back-end process are key processes in detritiation of heavy water used in Cernavoda CANDU-type Nuclear Power Plant (NPP) from Romania as neutron moderator and in the primary heat transfer system. Same technology is used in the Water Detritiation System (WDS) of International Thermonuclear Experimental Reactor (ITER) from Cadarache, France, in order to recover tritium from moderately tritiated water. The purpose of this paper is to give a detailed overview of the current status for the front-end of the ICSI pilot plant, LPCE and purification systems, including all process components. Additionally, the paper will present the results of the non-radiological commissioning of the actual LPCE. The tests were made using protium and deuterium in order to have the confirmation of fully availability for all systems, to verify the operability in manual and automate mode for all sequences involved by start-up, normal operation and safe shut-down of the installation. The principal results consist in the safety and operability design confirmation. Secondly we present the mass transfer data of LPCE column equipped with catalytic package COMPACK C–P 001 consisting of the structured B7 stainless steel packing manufactured and patented by ICSI and a Pt/C/PTFE hydrophobic catalyst at the commissioning low concentration heavy water tests.

Experimental Results and Experience with the LPCE Process

This paper presents further investigation of the liquid phase catalytic exchange (LPCE) process on the LPCE-3 column (50-mm inner diameter and 2-m height) of the EVIO pilot plant. The characteristics of the column filled with alternating layers of RCTU-3SM hydrophobic catalyst and stainless steel spiral-prismatic packing have been studied at a catalyst/packing volume ratio of 2:1 and compared to a ratio of 4:1. The EVIO-5 computer model is used for the column performance evaluation (as before) but this time the mass transfer coefficient for phase exchange Bx is not fixed. Due to the unequivocal separation of the catalytic and phase exchange with the help of the EVIO-5 code, the comparison of catalyst activity given by mass transfer coefficient Kc has been made for the experiments at two different catalyst/packing volume ratios. The column performance has also been expressed by the value of the height-equivalent-to-theoretical-plate average along the column. Some experience concerning the control of an LPCE column operating at the mode “with independent flows” is discussed.

Hydrodynamic characteristics of mixed catalytic packing for heavy water detritiation

The majority of technologies for tritium removal from heavy water, released within International Thermonuclear Experimental Reactor (ITER) or used in CANDU reactors are based on Liquid Phase Catalytic Exchange (LPCE) between deuterium and tritiated water. In LPCE process, the key role is played by a mixture between the hydrophobic catalyst and the hydrophilic packing in so – called “catalytic mixed packing”.A new improved and more compact mixed catalytic packing, has been developed at National Institute for Cryogenics and Isotopic Technology, characterized and proposed to be used in the future Industrial Tritium Removal Facility for detritiation of heavy water from Cernavoda Nuclear Power Plant. The paper, presents the main hydrodynamic characteristics of mixed catalytic packing, as: static and dynamic hold-up, voids fractions, pressure drop, water flowing aspects. All hydrodynamic characteristics are presented and discussed in close relation with operation parameters of LPCE column. Other important characteristics of the hydrophilic packing as wettability and textural properties of the hydrophobic catalyst are also showed. The knowledge of these characteristics, will facilitates the prediction of the fluids dynamic inside of LPCE columns for any Water Detritiation System. All these characteristics will be taken in consideration in designing process of the LPCE columns for the future Industrial Tritium Removal Facility.

Mass Transfer Model Liquid Phase Catalytic Exchange Column Simulation Applicable to any Column Composition Profile

Liquid Phase Catalytic Exchange (LPCE) is a key technology used in water detritiation systems. Rigorous simulation of LPCE is complicated when a column may have both hydrogen and deuterium present in significant concentrations in different sections of the column. This paper presents a general mass transfer model for a homogenous packed bed LPCE column as a set of differential equations describing composition change, and equilibrium equations to define the mass transfer driving force within the column. The model is used to analyze Combined Electrolysis and Catalytic Exchange (CECE) sensitivity to deuterium accumulation in the electrolyser.

Modification of a solid polymer electrolyte (SPE) electrolyser to ensure tritium compatibility

A Water Detritiation System (WDS) is required for the ITER Tritium Plant in order to process tritiated water which is accumulated in various subsystems (e.g. the hall ventilation systems). For the ITER-WDS, the Combined Electrolysis Catalytic Exchange (CECE) process with an electrolyser unit as one of the major components is envisaged. An experimental WDS was built and commissioned at the Tritium Laboratory Karlsruhe (TLK) for the investigation of various subsystems of the CECE process in tritium environment. The TLK-WDS consists of an 8 m Liquid Phase Catalytic Exchange column and two Solid Polymer Electrolyte electrolysers, each with a maximum hydrogen output of 1 m 3/h. The commercially available Hogen40 electrolyser units from Proton Energy Systems are not tritium compatible concerning materials, joints and quality documentation (e.g. necessary certificates). In order to process tritiated water with tritium concentrations up to 370 GBq/kg, tritium compatibility had to be ensured by appropriate modifications. Up to now, the modified system has been operated with tritiated water for 3500 h, the maximum tritium concentration in the electrolysers being 190 GBq/kg. This contribution reports on the necessary modifications of the electrolyser units and the experiences gained thereby. The results are equally important for the ITER-WDS, where the maximum tritium concentration in the feed water of the electrolyser units will be even higher with 11 TBq/kg.

Simulation of CECE Facility for Water Detritiation

This paper presents a program to simulate performance of a liquid phase catalytic exchange (LPCE) column of a water detritiation facility based on combined electrolysis and catalytic exchange (CECE) technology over a wide range of deuterium contents in a feed stream. The program uses rate constants of the chemical isotopic exchange reactions between gaseous hydrogen and water vapor occurring on a hydrophobic catalyst and the mass transfer rate between water vapor and the film of liquid water on packing material in the LPCE column, which have been measured experimentally using a specially developed method and at a low concentration of deuterium in a three-isotope mixture. The effect of the deuterium presence on the kinetics of isotopic exchange reactions and the performance of the LPCE column are taken into account considering several possible mechanisms that can control the overall rate of reaction. Selection of the most suitable mechanism was carried out by comparing the simulations with the results of an experimental test with a large deuterium content.The simulation program allows calculation of isotope profiles in streams of liquid water, water vapor, and gaseous hydrogen along the LPCE column over a very wide range of isotopic compositions and for CECE facilities of several different layouts.

Modification, enhancement and operation of a water detritiation facility at the Tritium Laboratory Karlsruhe

For the design and development proposal of the European procurement package of the Water Detritiation System (WDS) for ITER, an experimental WDS was installed at the Tritium Laboratory Karlsruhe (TLK) to investigate the process and various components of the system. The WDS facility at TLK uses the Combined Electrolysis Catalytic Exchange (CECE) process and consists of two Solid Polymer Electrolyte (SPE) electrolysis cells and a stainless steel Liquid Phase Catalytic Exchange (LPCE) column with an effective length of 8 m. After installation and commissioning, the first experimental runs were performed with a tritium concentration up to 0.6 GBq kg −1 in the feed water to test the operation modes of the facility, all the safety installations and procedures and the performance of the LPCE column during a runtime of up to 130 h. Regarding the final design of the WDS for ITER, the first experiments indicated several aspects which had to be modified in order to enhance the procedural and operating performance of the facility.

Effects of the gas–liquid ratio on the optimum catalyst quantity for the CECE process with a homogeneously packed LPCE column

In order to improve the separative performance of a combined electrolysis catalytic exchange (CECE) process, we have carried out experimental studies on hydrogen isotope separation by a CECE process using a liquid phase catalytic exchange (LPCE) column of trickle-type packed beds. Two types of trickle beds were tested in our previous study. One was the layered bed, where layers of Kogel catalysts and Dixon gauze rings were alternately filled in the column. The other was the homogeneous bed, where Kogel catalysts and Dixon gauze rings were homogeneously mixed and filled in the column. We found that (1) the homogeneously packed bed was more efficient than the layered packed bed, and (2) the catalyst quantity was optimal, which resulted in the highest separative performance. In this study, the effect of the gas–liquid ratio ( G/ L) on the optimum catalyst quantity was studied experimentally in a homogeneously packed bed. When the value of G/ L was 1.7, total separation factors were relatively small and the optimum catalyst quantity could not be determined. On the other hand, when the values of G/ L were 0.9 and 0.7, the values of the total separation factors had maximums and the optimal quantities of the catalyst were clearly obtained.

Development of Water Detritiation Facility for JET

This paper presents results from the concept evaluation, experimental trials, and design of a water detritiation facility (WDF) for the JET fusion machine. The design is based on the combined electrolysis and catalytic exchange process and will allow construction of the plant and for its integration into the JET tritium plant in three stages.The first stage includes a liquid phase catalytic exchange column and electrolyzer to concentrate the water into a smaller amount of tritium-enriched water. There would then be three options for dealing with this water: processing off-site, conversion to solid intermediate-level waste for disposal, and further processing on-site for complete tritium recovery. The latter option will require the second stage of implementation to integrate the WDF with the isotope separation system of the tritium plant. The third stage might be desirable to reduce the amount of time that the existing isotope separation system would need to be involved in the recovery of tritium from the WDF.

Commissioning of water detritiation and cryogenic distillation systems at TLK in view of ITER design

The ITER Isotope Separation System (ISS) and Water Detritiation System (WDS) will be integrated in order to reduce potential chronic tritium releases from the ISS by routing the top (protium) product from the ISS into the Liquid Phase Catalytic Exchange (LPCE) column of WDS. This provides an additional barrier against ISS tritium releases and should mitigate the memory effects due to process parameter fluctuations in the ISS. To support the research activities needed to characterize the performances of various components for WDS and ISS processes in various working conditions and configurations as needed for ITER design, an experimental facility called TRENTA and representative of the ITER WDS and ISS protium separation column has been commissioned at Tritium Laboratory Karlsruhe (TLK). The TRENTA facility consists of Combined Electrolysis Catalytic Exchange (CECE) process, with an LPCE column of 8 m, in combination with a cryogenic distillation (CD) process. The processes description and the status of commissioning of TRENTA facility is presented.

Operational analysis of a liquid phase catalytic exchange column for a detritiation of heavy water

An operational analysis for a liquid phase catalytic exchange column was carried out by the model equations, composed of a material balance and equilibrium relationships for a scrubbing and catalyst bed. The solutions were determined by using the Newton–Raphson method and the parametric investigations were simulated for the effect of the operating variables on the detritiation factor. It was observed that the maximum detritiation performance could be obtained at certain temperature conditions by considering the flow ratio of the water vapor to the given hydrogen stream in the catalyst bed and the water vapor–liquid equilibrium in the scrubbing bed. The optimum operating temperature should be chosen at the larger detritiation conditions providing a reasonable processing flow rate.

Deactivation of Hydrophobic Pt/SDBC Catalyst in the WTRF LPCE Column for Tritium Separation

The styrene divinylbenzene copolymer (SDBC) supported platinum catalyst and the liquid phase catalytic exchange (LPCE) column have been developed to be applicable to the Wolsong tritium removal facility (WTRF) in Korea. The catalyst deactivation subject to both reversible uniform poisoning and permanent loss by impurity poisoning was investigated using a time-on-stream theory and a simplified shell progressive poisoning scenario in special case of higher internal diffusion resistance. Experimental data from fixed bed reactors with the Pt/SDBC catalysts have been used to establish the deactivation model and to estimate key parameters to be used in the WTRF LPCE column design. It was found that an impurity control in the streams would be critical to the WTRF LPCE column operation since the impurity poisoning played a very important role in the overall catalytic exchange reaction. Except for the case of the severe impurity poisoning of the whole catalysts, the LPCE column can be in operation over 10 years without any regeneration of the catalysts.

Deactivation of Hydrophobic Pt/SDBC Catalyst in the WTRF LPCE Column for Tritium Separation

The styrene divinylbenzene copolymer (SDBC) supported platinum catalyst and the liquid phase catalytic exchange (LPCE) column have been developed to be applicable to the Wolsong tritium removal facility (WTRF) in Korea. The catalyst deactivation subject to both reversible uniform poisoning and permanent loss by impurity poisoning was investigated using a time-on-stream theory and a simplified shell progressive poisoning scenario in special case of higher internal diffusion resistance. Experimental data from fixed bed reactors with the Pt/SDBC catalysts have been used to establish the deactivation model and to estimate key parameters to be used in the WTRF LPCE column design. It was found that an impurity control in the streams would be critical to the WTRF LPCE column operation since the impurity poisoning played a very important role in the overall catalytic exchange reaction. Except for the case of the severe impurity poisoning of the whole catalysts, the LPCE column can be in operation over 10 years wi...

Long term performances assessment of a water detritiation system components

Development of a water detritiation system (WDS), i.e. configuration, design and performance testing of critical components is essential for ITER. WDS is one of the key systems to control the tritium content in the effluent streams, to recover as much tritium as possible and consequently to minimize the impact to the environment. The ITER WDS is based on combined electrolysis catalytic exchange (CECE) process employing a liquid phase catalytic exchange (LPCE) column. The separation performances after 6 months exposure to tritiated water of the catalyst–packing mixture to fill the LPCE column developed at Tritium Laboratory Karlsruhe (TLK) are presented. A small stand-alone electrolysis cell has been in operation with tritiated water for 6 months. After 6 months continuously operation, the mechanical properties such as tensile strength and elongation of a solid polymer membrane (SPM) in service with tritiated water have been compared with those of a reference SPM in service with demineralized water.

Influence of deuterium on the design of the JET water detritiation system

The water detritiation system (WDS) for JET is based on the combined electrolysis catalytic exchange (CECE) process employing a liquid phase catalytic exchange (LPCE) column. The final goal of WDS is to convert tritiated water to tritium–deuterium–hydrogen mixture for further enrichment of tritium by cryogenic distillation (CD), followed by recovery of high quality tritium in the gas chromatography (GC) from active gas handling system (AGHS) of JET. A tritium decontamination factor (DF) of 10 4 is required along the striping section of the LPCE column in order to discharge essentially tritium free molecular hydrogen product into the environment. A detailed analysis of the combination CECE–CD processes revealed the necessity to consider also the deuterium content in the water to be processed. Based on deuterium content measured in tritiated water collected at JET, the interface between the CECE and CD was evaluated in detail and the optimum values for deuterium and tritium composition at this interface have been established.

Endurance Test for SCK-CEN Catalytic Mixed Packing, Proposed for Water Detritiation System at JET

JET machine’s operation lead to continuously generation of tritiated water and therefore, it is necessary to consider the development of a Water Detritiation System (WDS) for JET and also for ITER. The key point of WDS is the efficiency and stability of liquid phase catalytic exchange (LPCE) column, that has to achieve a high decontamination of tritiated streams.Two catalytic mixed packing based on hydrophobic Pt-catalyst, and having closed separation performances have been proposed for LPCE column. A complete data base concerning the influence of β-radiation of tritium and the influence of impurities from feed streams on the catalytic mixed packing’ s performances and parameters is absolutely necessary.The results of 3 months endurance test for one of these packing (SCK-CEN packing), are presented in this paper. No significant modifications of performances and physico-structural parameters have been observed.

Development and Improvement of Devices for Hydrogen Generation and Oxidation in Water Detritiation Facility Based on CECE Technology

Water detritiation facility based on CECE (Combined Electrolysis and Catalytic Exchange) technology needs an electrolyser for water conversion to hydrogen. Use of a conventional alkali electrolyser requires a very deep purification of hydrogen stream from alkali prior to injection to LPCE (Liquid Phase Catalytic Exchange) column. In some applications conversion of detritiated hydrogen back into water is required. This is usually performed via hydrogen catalytic oxidation in a recombiner. This paper presents results of study to improve hydrogen and oxygen purification for alkali electrolysers and develop a hydrogen recombiner based on use of hydrophobic catalyst.

Tritium related studies at the JET facilities

The Joint European Torus (JET) fusion machine is the only device capable of operation with tritium and of handling Be and therefore best suited to study tritium and fusion related issues. JET is now managed under the European Fusion Development Agreement (EFDA) and experiments, enhancements and technology issues are organized as Scientific and Technical (S/T) tasks within various Task Forces (TFs). A large variety of different activities is performed within the fusion technology (FT) TF. A brief summary of FT-studies related to tritium is given presenting topics such as tritium inventory in flakes and tiles, tritium depth profiles in plasma facing components (PFCs), development of a facility for full recovery of the tritium in flakes and tiles, erosion and deposition of plasma exposed materials determined by surface sensitive techniques, development of detritiation techniques for different waste categories, characterization of packing/catalyst combinations for liquid phase catalytic exchange column and design studies of a water detritiation plant using either a solid polymer or KOH electrolyser, test of ITER cryo-panels in the JET Active Gas Handling System, etc.