Cryogenic Distillation System Research Articles

Radon removal commissioning of the PandaX-4T cryogenic distillation system

The PandaX-4T distillation system, designed for the removal of krypton and radon from xenon, is evaluated for its radon removal efficiency using a 222Rn source during the online distillation process. The PandaX-4T dark matter detector is employed to monitor the temporal evolution of radon activity. To determine the radon reduction factor, the experimental data of radon atoms introduced into and bypassed the distillation system is compared. The results indicate that the PandaX-4T distillation system achieves a radon reduction factor exceeding 190 at the flow rate of 10 slpm and the reflux ratio of 1.44. Gas-only online distillation process of a flow rate of 20 slpm is also conducted without observing significant reduction of radon levels in the detector. This observation suggests that the migration flow of radon atoms from the liquid phase to the gas phase is limited, and the flow rate of gas circulation and duration of the process are insignificant compared to the total xenon mass of 5.6 tons in the detector. This study provides the experimental data to support the efficient removal of radon at ∼Bq level using the PandaX-4T distillation system, which is the prerequisite of the radon background control in the detector. The further operation with higher flow rate will be applied for the upcoming science run in PandaX-4T.

Uncorrected soil water isotopes through cryogenic vacuum distillation may lead to a false estimation on plant water sources

Abstract Successful use of stable isotopes (δ2H and δ18O) in ecohydrological studies relies on the accurate extraction of unfractionated water from different types of soil samples. Cryogenic vacuum distillation (CVD) is a common laboratory‐based technique used for soil water extraction; however, the reliability of this technique in reflecting soil water δ2H and δ18O is still of concern. This study examines the reliability of a newly developed automatic cryogenic vacuum distillation (ACVD) system. We further assessed the impacts of extraction parameters (i.e. extraction time, temperature and vacuum) and soil properties on the recovery of soil water δ2H and δ18O for the ACVD and traditional cryogenic vacuum distillation (TCVD) systems. Finally, we investigated the potential influence of CVD (ACVD and TCVD) technique on the prediction of plant water uptake through a sensitivity analysis. Both ACVD and TCVD similarly extracted water from the rewetted soils, but none of the CVD systems successfully recovered the isotopic signatures of doped water from soil materials. Mean δ2H offsets of extracted soil water were −2.6 ± 1.3‰ and −2.4 ± 1.7‰ for ACVD and TCVD, respectively, while mean δ18O offsets were −0.16 ± 0.14‰ and −0.39 ± 0.37‰. The isotopic offsets of CVD systems were positively correlated with soil clay content, and negatively correlated with soil water content. Using corrected soil data (with CVD offsets) could improve the prediction of plant water uptake based on its high correlation with the environmental factors. This study identifies the isotopic offsets of CVD systems (i.e. ACVD and TCVD) and provides possible solutions for better predicting plant water sources. Even though, the wide use of CVD techniques probably induce noticeable uncertainties in the prediction of plants water uptake depths. The dataset of soil water extraction in this study will have implications for the technological development of CVD techniques.

Startup methods analysis of a cryogenic distillation system with two interlinked columns for hydrogen isotope separation

Effective startup methods are crucial for the successful operation of a distillation facility. In order to design a viable startup method for a cryogenic distillation demonstration system with two interlinked columns for hydrogen isotope separation, which is under construction at Institute of Materials, China Academy of Engineering Physics, Aspen Plus and Aspen Dynamics were employed in combination to generate a dynamic numerical model for the startup analysis. Total four conventional startup methods were analysed. The most time-effective method was identified and the other of the four startup methods were found to be able to lead to successful startup results but with varied operation complexity and length of time to reach the steady state. The effective startup method that involved in charging the two distillation columns with equilibrated hydrogen isotope mixtures respectively, took only 50.36 h to reach the target steady state. And the identified method would be employed into the cryogenic distillation demonstration system to check its startup efficient.

Partial oxycombustion-calcium looping hybridisation for CO2 capture in waste-to-energy power plants

Integrating bioenergy and carbon capture and storage (BECCS) presents a great opportunity for power production with negative global CO2 emissions. This work explores a novel synergetic system that integrates membranes, partial biomass oxycombustion and the calcium looping (CaL) process. Polymeric membranes generate oxygen-enriched air (OEA) with an O2 concentration of 39%v/v, which is used for partial oxycombustion of biomass waste. The CO2-enriched flue gas evolves from the waste-to-energy plant to the CaL unit, where CO2 concentration is increased up to 90–95%v/v, ready for purification and sequestration. Compared to only oxycombustion systems, the proposed concept presents fewer technological challenges in retrofitting boilers to waste-to-energy plants. Moreover, this new approach is highly efficient as integrating membranes to produce OEA instead of cryogenic distillation systems significantly reduces energy consumption. A novel integration concept is modelled to evaluate the whole process efficiency and the effect of key parameters on the system performance, such as the temperature of the reactors, the membrane surface area, and the partial oxy-combustion degree. The results show that the so-called mOxy-CaL system has an energy consumption associated with CO2 capture below 4 MJ/kg CO2 (a 31% lower than that for a conventional CaL process), with a higher CO2 capture efficiency than oxycombustion and the CaL process separately. On the other hand, the economic analysis shows a higher CO2 capture cost for the novel configuration than for the typical CaL configuration due to the additional investment cost of the membrane system. Improvements in membrane performance by increasing its permeance and diminishing the required surface area would significantly reduce the economic cost of this novel integration. Using membranes with permeance over 400 GPU would boost the system's competitiveness.

Experimental evaluation of the performance of a cryogenic distillation system under offshore conditions

Cryogenic distillation is the most widely-used industrial method to produce liquid oxygen with high-purity. However, the distillation process in the sieve tray column is very sensitive to tilting and swing, which limits the application of cryogenic air-separation in marine and offshore infrastructures. In this paper, a small air-separation plant with dual-column distillation process was proposed to improve the distillation performance under the offshore conditions, and experiments were carried out under standard (no-tilting and stationary), tilting and swing conditions. A reduction factor of overall section efficiency is proposed to evaluate the influence of offshore conditions on the system performance. The results indicate that sieve tray column can maintain the distillation purity to a certain extent under offshore conditions within the range of 6° tilting and ±10° swing amplitude. Under severe tilting (6°) and swing (±10°-amplitude&11 s-period) conditions, the reduction factors were reduced to 0.592 and 0.590, respectively. Based on the experimental results, two correlations are presented to predict the reduction factor of section efficiency under different tilting angle and swing parameters, respectively, which provide engineering guidance for the design of cryogenic distillation column for offshore applications.

Modeling, simulation, and techno-economic optimization of argon separation processes

High-purity argon is conventionally recovered from air by cryogenic distillation, which is a mature, efficient but high-cost technology. In recent years, membrane gas separation technology is starting to emerge illustrating the potential to achieve lower production costs compared to distillation, without compromising the final product quality. In this work, a flowsheet of a conventional cryogenic distillation system for the separation of an oxygen-argon mixture was built and simulated in the gPROMS™ modeling environment. Then, a detailed mathematic modeling framework of a hollow fiber membrane system for the same separation was developed. The predictive power of the model is in a good agreement with theoretically expected results for a wide range of operating conditions. The results indicate that commercially available polymeric membranes are not capable of achieving a high-purity argon product while innovative materials, such as carbon membranes, turn out to be more efficient. Finally, the performance of the membrane process was compared with the cryogenic distillation process using an optimization-based techno-economic analysis. The comparison revealed that the distillation process has a lower operational cost compared to a membrane process for a final product purity of 99.9 mol%.

Experiment and optimization of a large scale xenon/krypton cryogenic distillation system

A highly efficient cryogenic distillation system has been designed, developed and assessed to remove radioactive krypton-85 (85Kr) from xenon (Xe), which is commonly used as a valuable medium for dark matter detectors. By using the self-designed distillation system, the concentration of krypton (Kr) in a commercial xenon product can be reduced from 10−9 to 10−12 mol/mol with 99% xenon collection efficiency at maximum flow rate of 5 kg/h. Over 1000 kg of xenon has been purified and employed as the detection medium in project Panda X, the first dark matter detector developed in China. In this present paper, detailed process simulation was conducted to refine the working parameters and to define the optimum operating conditions for the cryogenic distillation system. The predicted results were compared with those of experimental data obtained from the distillation system. The influence of comprehensive factors was investigated. Simultaneously, a dynamic model for the cryogenic distillation system was established to provide an in depth analysis of the dynamic characteristics of the system.

Cryogenic bath-type heat exchangers for ultra-pure noble gas applications

Two cryogenic bath-type heat exchangers for ultra-pure noble gas applications were developed with particular emphasis on noble gas liquefaction in cryogenic distillation systems. The main objective was to construct heat exchangers for xenon from materials that do not emanate radon and that fulfill ultra-high vacuum standards. Therefore, only high-quality copper and stainless steel materials were used. Especially, large-area oxygen-free copper fins with high conductivity in a new design ensure efficient heat transfer. One bath-type Xe-Xe heat exchanger was designed with a diameter of 50 cm to achieve a xenon condensing capacity of at least 100 kg/h. In order to guarantee the necessary heat transfer between the two xenon reservoirs, this heat exchanger features a specially manufactured stainless steel flange with a copper plate welded inside. We first tested our concept on a dedicated bath-type heat exchanger with a reduced diameter of 30 cm using liquid nitrogen to liquefy the xenon. A model based on conservative assumptions such as film boiling on the nitrogen side and film condensation on the xenon side was developed and applied to caluclate the expected heat transfer for our design. We were able to demonstrate an adjustable xenon liquefaction rate of up to 113 kg/h limited only by our measurement procedure at a cooling efficiency of (0.98 ± 0.03) for the LN2-Xe heat exchanger.

PandaX-4T cryogenic distillation system for removing krypton from xenon.

An efficient cryogenic distillation system was designed and constructed for the PandaX-4T dark matter detector based on the McCabe-Thiele method and the conservation of mass and energy. This distillation system is designed to reduce the concentration of krypton in commercial xenon from 5 × 10-7 to ∼10-14 mol/molwith 99% xenon collection efficiency at a maximum flow rate of 10 kg/h. The offline distillation operation has been completed and 5.75 tons of ultra-high purity xenon was produced, which is used as the detection medium in the PandaX-4T detector. The krypton concentration of the product xenon is measured with an upper limit of 8.0 ppt. The construction, operation, and stable purification performance of the cryogenic distillation system are studied with the experimental data, which is important for theoretical research and distillation operation optimization.

Membranes for olefin–paraffin separation: An industrial perspective

In the next decade, separation science will be an important research topic in addressing complex challenges like reducing carbon footprint, lowering energy cost, and making industrial processes simpler. In industrial chemical processes, particularly in petrochemical operations, separation and product refining steps are responsible for up to 30% of energy use and 30% of the capital cost. Membranes and adsorption technologies are being actively studied as alternative and partial replacement opportunities for the state-of-the-art cryogenic distillation systems. This paper provides an industrial perspective on the application of membranes in industrial petrochemical cracker operations. A gas separation performance figure of merit for propylene/propane separation for different classes of materials ranging from inorganic, carbon, polymeric, and facilitated transport membranes is also reported. An in-house–developed model provided insights into the importance of operational parameters on the overall membrane design.

Simulation and Optimization of Ultra-High Purity Krypton/Xenon Cryogenic Distillation System Based on HYSYS

Simulation and Optimization of Ultra-High Purity Krypton/Xenon Cryogenic Distillation System Based on HYSYS

Operation Analysis of PandaX-4T Ultra-High Purity Xenon Cryogenic Distillation System for Removal of Krypton

Operation Analysis of PandaX-4T Ultra-High Purity Xenon Cryogenic Distillation System for Removal of Krypton

Design and commissioning of the PandaX-4T cryogenic distillation system for krypton and radon removal

An online cryogenic distillation system for the removal of krypton and radon from xenon was designed and constructed for PandaX-4T, a highly sensitive dark matter detection experiment. The krypton content in a commercial xenon product is expected to be reduced by 7 orders of magnitude with 99% xenon collection efficiency at a flow rate of 10 kg/h by design. The same system can reduce radon content in xenon by reversed operation, with an expected radon reduction factor of about 1.8 in PandaX-4T under a flow rate of 56.5 kg/h. The commissioning of this system was completed, with krypton and radon operations tested under respective working conditions. The krypton concentration of the product xenon was measured with an upper limit of 8.0 ppt.

Design of an industrial multi-bed (V)PSA unit for argon concentration

Pressure swing adsorption systems have been devised to concentrate argon from a binary gas mixture of oxygen and argon (O2:Ar = 95:5 mol%) that an industrial oxygen generation vacuum swing adsorption (VSA) unit produces from air. The kinetically-driven adsorption processes investigated in this study contain a self-purging step and up to two double-ended pressure equalization steps. Three adsorption cycle configurations, each of which has one, two and three beds, were simulated. The effects of pressure ranges of the adsorption cycle, either pressure swing adsorption (PSA, 1–3 bar) or vacuum swing adsorption (VSA, 0.1–1 bar), as well as adsorption step time were extensively assessed with respect to the following separation key performance indicators (KPIs): argon purity, argon recovery, bed productivity and specific energy consumption. It turned out that argon purity and recovery could be significantly improved in the VSA cycles at the expense of bed productivity and energy consumption. The single VSA unit could not concentrate argon up to a purity of 98+% which is typically required for certain applications such as steel production and inert gas welding. Thus, a second VSA unit was added to increase further the argon purity and it was found that the integrated two-stage VSA system is capable of achieving the following overall performances: argon purity of 98.1%, argon recovery of 20.3%, bed productivity of 0.011 molAr kgads−1h−1 and specific energy consumption of 53.2 MJ kgAr−1. Considering real efficiencies of turbomachinery the energy consumption of the proposed VSA unit resulted 75% higher than that of a conventional stand-alone cryogenic distillation system designed to achieve the same separation. However, the VSA technology is expected to be a more attractive option than the cryogenic process in terms of CAPEX.

Overview about cryogenic distillation control and safety approach for Isotopes Separation Facility (ISF)

Abstract Isotopes separation technologies are used in both Tritium Removal Facilities associated with CANDU reactors (to remove tritium from heavy water) and fusion applications (eq. ITER Isotope Separation System) to recover and enrich tritium for further operation. The expertise gained during design, manufacturing, building, commissioning and operation of the Cryogenic Distillation System (CDS) with proprietary four column design built at ICSI Rm. Valcea, could be applied for various tritium recovery applications, regardless of the type of front-end process used, Liquid Phase Catalytic Exchange or Combined Electrolysis and Catalytic Exchange. Cryogenic Distillation feed is a mixture of hydrogen isotopes which presents hazards in operation (explosion and tritium contamination), therefore the CDS of PESTD was designed to meet industrial and nuclear applicable standards. In this paper we present an overview of the CDS focusing on the process control and safety approach which meet specific conditions of Romanian codes and standards required for operation. However, specific information may be used later as reference for design consideration for other CDS. The cryogenic distillation process from ICSI Rm. Valcea is designed as four columns cascade inside a cold-box which acts as second barrier against hydrogen release and thermal insulation. The CDS process control is based on a Programmable Automation Controller (PACs), a Supervisory Control and Data Acquisition (SCADA) and specific low temperature field equipment and devices. The control room operator supervises the process using a specific designed Human Machine Interface (HMI) which permits to monitor process parameters, alarms acknowledgment and acts to adjust the process or override normal PACs control.

Development of specific software for hydrogen isotopes separation by cryogenic distillation of ICSI Pilot Plant

Abstract ITER Isotope Separation System (ISS) is based on cryogenic distillation process and is one of the main systems within the ITER Fuel Cycle. Similar to ITER ISS, one of the key systems of a detritiation plant for low level tritiated light or heavy water is the cryogenic distillation. Provisions are being made in ICSI to design and build an experimental facility based on CECE (Combined Electrolytic Catalytic Exchange) process coupled to a cryogenic distillation system able to process these kinds of waters. The aim of this work is to present the results of the design and simulation activities in support to the development of a cryogenic distillation system capable to achieve the required decontamination factor and tritium enrichment better than 90 %. This is done by using a software developed “in house”, based on heat and mass transfer model. Based on the input data like, flow rates, composition of the feeding gas, pressure drop, the simulation provides the distribution of all the molecular species involved, temperature profile and also the liquid and vapor enthalpies along the column. The results may provide useful information for the ITER ISS decontamination factor during dynamic operation due to the ISS transient feed flow rate coming from the WDS (Water Detritiation System).

Rigorous Dynamic Simulation of Cryogenic Distillation of Hydrogen Isotopologues in the Fuel Cycle of a Thermonuclear Reactor Based on UV Flash

Operation of the fuel cycle of a thermonuclear fusion reactor naturally leads to accumulation of surplus protium, but in some cases it can also lead to accumulation of surplus deuterium. Both surplus protium and deuterium have to be separated, detritiated, and discharged to the environment, normally passing a final detritiation stage based on either the liquid phase catalytic exchange or water distillation process. The concept of a multicolumn cryogenic distillation (CD) system capable of discharging a time-varying surplus of deuterium is presented in this paper. A model of a CD column based on a UV (internal energy U – volume V) flash formulation and equation of state (EOS) thermodynamic model for hydrogen isotopologue mixtures is also presented at the principal step to a comprehensive model of the isotope separation system. Although fundamental for constant volume systems, the UV formulation of the thermodynamic state has not been widely used in transient simulations; in particular, for distillation dynamics modeling, other approaches are much more common. At the same time, in helium cryogenics the UV formulation has gained wide usage in large-scale dynamic simulations. It is known from the literature that a UV formulation of the distillation problem is very challenging for a numerically stable implementation. To cope with this situation, we present our findings on the sources of numerical instabilities and approaches.

Applicability of a cryogenic distillation system for D-T isotope rebalancing and protium removal in a DEMO power plant

The tritium plant at the future European DEMOnstration (DEMO) fusion power plant will require isotope separation systems for protium removal and isotopic rebalancing of the torus exhaust stream. Protium removal and isotopic rebalancing can occur within a single separation technology which is based upon the exploitation of isotopic effects; the minimum amount of exhaust gas processing can be calculated using a heuristic developed for this purpose. A model has been developed to quantify the size and separation ability of a cryogenic distillation system to perform the required separation duties. Comparison of a reference scenario and six alternative scenarios shows that the isotope imbalance ratio between deuterium and tritium has the largest effect on the size and separation ability of a cryogenic distillation system; provided that a trace amount of protium is acceptable within the gas introduction system into the torus. A cryogenic distillation system is found to be a suitable technology in terms of energy usage and isotope separation, but a single system size is not suitable to process a range of different compositions. This evaluation of the applicability of cryodistillation to isotope rebalancing and protium removal for a DEMO reactor, form a base case against which other hydrogen isotope separation technologies can be investigated and compared in terms of size, power requirements and safety.

Sub-ambient air separation via Li+ exchanged zeolite

In this study, we extend the concept of adsorptive air separation using zeolites to sub-ambient temperature conditions. Sub-ambient temperature conditions investigated in this study (210–270 K) enable larger swing capacities for solid adsorbents under significantly milder conditions than those required by cryogenic distillation systems. Experimental O2 and N2 isotherms—measured in a wide range of temperatures (150 K–300 K)—were utilized to construct multicomponent isotherms (IAST) and estimate the temperature-dependent separation performances of Li+-exchanged type X zeolite (Si/Al ratio ∼1) under synthetic air mixture (22 mol% O2 and 78 mol% of N2). As temperature decreases from ambient conditions, the IAST selectivity (N2/O2) increases. Sorption breakthrough tests at 240 K with synthetic air mixtures further validated the enhanced swing capacity and selectivity provided by sub-ambient conditions. Dual-bed vacuum pressure swing adsorption (VPSA) experiments at sub-ambient temperatures were compared to standard VPSA experiments at room temperature. The sub-ambient temperature (240 K) application of VPSA process using synthetic air mixture produced O2 with a purity over 99% and recovery over 56%, surpassing the VPSA performance at ambient temperature conditions (298 K). The separation process investigated in this study could potentially be coupled to certain cryogenic air separation units to reduce the overall energy cost of the unit by supplying O2 enriched stream into the distillation system.

Investigation of some critical scenarios due to various failures of ICSI Cryogenic Distillation System

During normal operation of a CANDU reactor, large amounts of tritiated heavy water are being produced as result of neutron absorption by the heavy water used as moderator and cooling agent. Tritium in the heavy water brings a significant contribution to the personal doses and also represents an environmental hazard if water spills occur.The technology employed in the Pilot Plant for T2 and D2 separation from Rm. Valcea (Romania) is based on Liquid Phase Catalytic Exchange and Cryogenic Distillation (CD) processes and the whole system is in preoperational stage. The CD system consists of a cascade of four columns placed inside a vacuum insulated cold box and a refrigeration unit providing the cooling capacity for the columns condensers.This paper analyzes some critical scenarios due to single failure mode or a combination of failures such as loss of cooling capacity, loss of cooling agent into the columns, and loss of electric power, cases seen as conservative for the system in order to investigate the behavior during abnormal operation or accident.The study presented in the paper is concerning the CD system from Rm. Valcea but gives information and some references for the methodology that can be implemented for ITER Isotope Separation Systems.