Heat and mass transfer in a copper oxy-chloride spray reactor for thermochemical hydrogen production

A new predictive model is developed in this paper to analyze the height of the reactor for continuous production of copper oxy-chloride in the thermochemical Cu–Cl cycle for hydrogen production. The volumetric phase fraction is used to develop an energy balance and integrated spatially to determine the inlet temperature of nitrogen and steam mixtures for continuous production of copper oxy-chloride. The effects of the ratio of mixing power to mass of the suspended particle, the ratio of interfacial surface area of the gas film to the volume of liquid, and diameter of the steam/nitrogen bubble in the reactor, on the height of the reactor are reported for a production capacity of 3 kg of hydrogen per day. Results indicate that a smaller ratio of interfacial surface area to volume of liquid significantly reduces the height of the reactor

Two-phase bubble flow and convective mass transfer in water splitting processes

When hydrogen or oxygen is produced from water splitting by electrolysis, thermochemical cycles or solar-based photocatalytic methods, bubble flow and vapor transfer into the gas phase occur during phase transition. This undesirable vapor transfer requires the use of more energy input to compensate for the evaporation heat requirement as well as for subsequent gas purification in the downstream unit. In this paper, both experimental and modeling studies are performed to examine the dynamics of bubble flows and kinetics of water vapor transfer, particularly related to processes of hydrogen production. Experimental data are obtained using an advanced laser-based shadow imaging system and on-line vapor monitoring system. The bubble dynamics and water vapor transfer kinetics are modeled with non-dimensional parameters involving the bubble diameter, velocity and trajectories so that the water vapor transfer rate can be quantified under different operating conditions for various hydrogen production methods. Also, a predictive model is developed to simulate the physical processes of bubble transport in a vertical liquid column, as it occurs in water splitting processes such as oxygen generation in the thermochemical copper–chlorine cycle, as well as hydrogen generation in electrolytic and photocatalytic processes

Indirect contact heat recovery with solidification in thermochemical hydrogen production

An analysis is presented for the heat transfer from molten salt in the copper–chlorine thermochemical cycle for hydrogen production. For this cycle to become economical relative to other existing or developing technologies, effective heat recovery is very important. Heat recovery processes are investigated from molten CuCl (a product of the copper oxychloride decomposition process in the Cu–Cl cycle). Recovering heat from molten CuCl at 500 °C is challenging due to its phase change from liquid to solid. Based on a previous examination of different options for this heat recovery (including atomization with steam generation, casting/extrusion, drum flaker and a rotary spinning atomizer), the casting/extrusion method was deemed advantageous. Hence that process is considered here, with a counter-current air flow as a coolant. Predicted results for axial growth of the solid layer and variations of the coolant and wall temperatures are presented and discussed. The effects of the inner tube diameter and air mass flow rate are also investigated

Analysis of the hazards for the molten cuprous chloride pouring operation in an industrial hydrogen production facility

An analysis is reported of a design for a local exhaust ventilation system for the molten cuprous chloride pouring station inan industrial plant. Heat recovery from molten cuprous chloride is a key process within the copper–chlorine (Cu–Cl) cycle of thermochemical water splitting for hydrogen production. Because of particulate matter, dust, and vapors emitted by the molten salt, an effective and safe design is crucial. The design process involves calculating duct diameters to provide the desired duct air velocity through the system. The static pressure is evaluated so that the fan size can be determined. An ad-equate supply of makeup air must be provided to replace the air exhausted through the ventilation system. The economics of the ventilation system and ways to protect employee health, as well as minimize the costs associated with exhaust ventilation, are also describe

Experimental investigation of molten salt droplet quenching and solidification processes of heat recovery in thermochemical hydrogen production

This paper investigates the heat transfer and X-ray diffraction patterns of solidified molten salt droplets in heat recovery processes of a thermochemical Cu–Cl cycle of hydrogen production. It is essential to recover the heat of the molten salt to enhance the overall thermal efficiency of the copper–chlorine cycle. A major portion of heat recovery within the cycle can be achieved by cooling and solidifying the molten salt exiting an oxygen reactor. Heat recovery from the molten salt is achieved by dispersing the molten stream into droplets. In this paper, an analytical study and experimental investigation of the thermal phenomena of a falling droplet quenched into water is presented, involving the droplet surface temperature during descent and resulting composition change in the quench process. The results show that it is feasible to quench the molten salt droplets for an efficient heat recovery process without introducing any material imbalance for the overall cycle integration

X-ray diffraction of crystallization of copper (II) chloride for improved energy utilization in hydrogen production

Crystallization is an effective method to recover solids from solution, due to its relatively low energy utilization, low material requirements and lower cost compared to other alternatives. Hence, crystallization is of particular interest in the thermochemical copper-chlorine cycle for hydrogen production as an energy-saving means to extract solid CuCl2 from its aqueous solution. It has been determined from experiments that there is a range of concentrations that will demonstrate crystallization. If the initial concentration exceeds the upper bound of this range, the solution will be saturated and instantly become paste-like without forming crystals. Conversely, if the initial concentrations fall below the lower bound of a specified range, the solution will remain liquid upon cooling. As a result, it has been observed that crystallization does not occur for HCl concentrations below 3 M and above 9 M. Also, it has been found that anhydrous CuCl2 does not crystallize under any of the conditions tested. To analyze the composition of the recovered solids, X-ray diffraction (XRD) was employed. The samples were also analyzed using thermogravimetric analysis (TGA) in order to determine their thermochemical properties such as melting and decomposition temperatures. The stationary point on the TGA curve was found to be around 462 °C which is below the normal melting temperature of CuCl2. Also, the vaporization of the samples was found to be approximately 600 °C

Progress in thermochemical hydrogen production with the copper–chlorine cycle

Recent advances are reported by an international team on research and development of the copper chlorine (Cu–Cl) cycle for thermochemical hydrogen production. New experimental and numerical results are given for several processes of the cycle. Experimental results for CuCl/HCl electrolysis and integration of unit operations in the Cu–Cl cycle are presented. A new solubility model for the CuCl–CuCl2–HCl–H2O quaternary system is presented, which optimizes the cupric chloride selective precipitation prior to the hydrolysis reactor. Also, recent progress on photo-electrochemical cell development for enhancement of the electrolysis process is reported along with its integration with a concentrated solar radiation system

Progress of international program on hydrogen production with the copper–chlorine cycle

This paper highlights and discusses the recent advances in thermochemical hydrogen production with the copper–chlorine (Cu–Cl) cycle. Extended operation of HCl/CuCl electrolysis is achieved, and its performance assessment is conducted. Advances in the development of improved electrodes are presented for various electrode materials. Experimental studies for a 300 cm2 electrolytic cell show a stable current density and production at 98% of the theoretical hydrogen production rate. Long term testing of the electrolyzer for over 1600 h also shows a stable cell voltage. Different systems to address integration challenges are also examined for the integration of electrolysis/hydrolysis and thermolysis/electrolysis processes. New results from experiments for CuCl–HCl–H2O and CuCl2–HCl–H2O ternary systems are presented along with solubility data for CuCl in HCl–H2O mixtures between 298 and 363 K. A parametric study of multi-generation energy systems incorporating the Cu–Cl cycle is presented with an overall energy efficiency as high as 57% and exergy efficiency of hydrogen production up to 90%

The Coronavirus Anxiety Scale: Cross-National Measurement Invariance and Convergent Validity Evidence

Coronavirus Anxiety Scale (CAS)is a widely used measure that captures somatic symptoms of coronavirus- related anxiety. In a large-scale collaboration spanning 60 countries (Ntotal = 21,513), we examined the CAS’s measurement invariance and assessed the convergent validity of CAS scores in relation to the fear of COVID-19(FCV-19S) and the satisfaction with life (SWLS-3) scales. We utilized both conventional exact invariance tests and alignmentprocedures,with results revealing that the single-factor model fit the data well in almost all countries. Partial scalar invariance was supported in a subset of 56 countries. To ensure the robustness of results, given the unbalanced samples, we employed resampling techniques both with and without replacement and found the results were more stable in larger samples. The alignment procedure demonstrated a high degree of measurement invariance with 9% of the parameters exhibiting non-invariance. Wealso conducted simulations of alignment using the parameters estimated in the current model. Findings demonstrated reliability of the means but indicated challenges in estimating the latent variances. Strong positive correlations between CAS and FCV-19S estimated with all three different approaches were found in most countries. Correlations of CAS and SWLS-3were weakandnegativebutsignificantly differed from zero in several countries. Overall, the study provided support for the measurement invariance of the CAS and offered evidence of its convergent validity while also highlighting issues with variance estimation

Progress of international hydrogen production network for the thermochemical Cu–Cl cycle

This paper presents recent advances by an international team which is developing the thermochemical copper–chlorine (Cu–Cl) cycle for hydrogen production. Development of the Cu–Cl cycle has been pursued by several countries within the framework of the Generation IV International Forum (GIF) for hydrogen production with the next generation of nuclear reactors. Due to its lower temperature requirements in comparison with other thermochemical cycles, the Cu–Cl cycle is particularly well matched with Canada's Generation IV reactor, SCWR (Super-Critical Water Reactor), as well as other heat sources such as solar energy or industrial waste heat. In this paper, recent developments of the Cu–Cl cycle are presented, specifically involving unit operation experiments, corrosion resistant materials and system integration