Mass transfer resistance of CuCl₂ hydrolysis in a fixed bed reactor

The hydrolysis reaction of the Copper-Chlorine (Cu-Cl) cycle is examined in this research to investigate corresponding reaction kinetics with respect to mass transfer resistance through an experimental approach. The experiment was operated at a temperature of 390 °C at atmospheric pressure. The reaction is heterogeneous in which solid reactant CuCl₂ and gaseous reactant H₂O produce Cu₂OCl₂ and HCl. The heterogeneous behaviour of the reaction causes resistance to mass transfer of gaseous reactant H₂O. The resistance in internal diffusion and a surface reaction with mass transfer were analyzed with respect to the initial solid reactant particle size using a shrinking core model (SCM). The results present the thermophysical property of the reaction rate coefficient 0.201 65 s⁻¹ for a particle size of 620 μm and sphericity of 0.68. The experimentally determined reaction and conversion rates of hydrolysis with respect to time are presented, which are experimentally calculated parameters. Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD) analysis were used for more accurate results. An uncertainty analysis for the sensors and transducers of the experiment shows that the experimental results have an uncertainty of ±30.1%

Integrated heat pump options for heat upgrading in Cu-Cl cycle for hydrogen production

The Copper Chlorine (Cu-Cl) hydrogen production cycle is a promising green method to meet the future demand for hydrogen. The Cu-Cl cycle has a number of endothermic reactions that take place at high temperature level. One of the highest temperature demanding components in the Cu-Cl cycle is the copper oxychloride decomposition reactor. This thesis proposes two potential methods to address this demand by using a cuprous chloride (CuCl) vapor compression heat pump cascaded with a mercury heat pump as a first option, and cascaded with a biphenyl heat pump as a second option. These cascaded heat pumps are meant to upgrade heat from nuclear power plants with a heat input of approximately 300???C or industrial waste heat to meet the copper oxychloride decomposition reactor demand. A comprehensive energetic, exergetic, and exergoeconomic assessment is made to understand the heat pump performance and costs. The CuCl-mercury heat pump had an overall energetic coefficient of performance of 1.93 and an exergetic performance of 1.25. Its total estimated cost is US$1,446,554 which is 62$/hour. The CuCl-biphenyl heat pump, on the other hand, also shows high coefficient of performance for certain operating conditions of compressors isentropic efficiencies, and excess CuCl feed temperature. Its base energetic and exergetic coefficient of performances are 1.76 and 1.15, respectively. Its estimated cost of $892,440 is lower than its CuCl-mercury counterpart. However, its overall exergy destruction cost flow rate was two times higher, 4,903$/hour

Plantwide Control and Simulation of Sulfur-Iodine Thermochemical Cycle Process for Hydrogen Production

A PWC structure has developed for an industrial scale SITC plant. Based on the performance evaluation, it has been shown that the SITC plant developed via the proposed modified SOC structure can produce satisfactory performance – smooth and reliable operation. The SITC plant is capable of achieving a thermal efficiency of 69%, which is the highest attainable value so far. It is worth noting that the proposed SITC design is viable on the grounds of economic and controllability

Combined Coal Gasification and Alkaline Water Electrolyzer for Hydrogen Production

There have been many studies in the energy field to achieve different goals such as energy security, energy independence and production of cheap energy. The consensus of the general population is that renewable energy sources can be used on a short-term basis to compensate for the energy requirement of the world. However, the prediction is that fossil fuels will be used to provide the majority of energy requirements in the world at least on a short-term basis. Coal is one of the major fossil fuels and will be used for a long time because there are large coal reservoirs in the world and many products such as hydrogen, ammonia, and diesel can be produced using coal. In the present study, the performance of a clean energy system that combines the coal gasification and alkaline water electrolyzer concepts to produce hydrogen is evaluated through thermodynamic modeling and simulations. A parametric study is conducted to determine the effect of water ratio in coal slurry, gasifier temperature, effectiveness of carbon dioxide removal, and hydrogen recovery efficiency of the pressure swing adsorption unit on the system hydrogen production. In addition, the effects of different types of coals on the hydrogen production are estimated. The exergy efficiency and exergy destruction in each system component are also evaluated. Although this system produces hydrogen from coal, the greenhouse gases emitted from this system are fairly low

Numerical study of high temperature heat exchanger and decomposer for hydrogen production

This dissertation deals with three-dimensional computational modeling of a high temperature heat exchanger and decomposer for hydrogen production based on sulfur-iodine thermochemical water splitting cycle, a candidate cycle in the U.S. Department of Energy Nuclear Hydrogen Initiative. The conceptual design of the shell and plate decomposer is developed by Ceramatec, Inc. The hot helium from a nuclear reactor (T=975°C) is used to heat the SI (sulfuric acid) feed components (H2O, H2SO4 , SO3) to get appropriate conditions for the SI decomposition reaction (T\u3e850°C). The inner wall of the SI decomposition part of the decomposer is coated by a catalyst for chemical decomposition of sulfur trioxide into sulfur dioxide and oxygen. The proposed material of the heat exchanger and decomposer is silicon carbide (SiC); According to the literature review, there is no detailed information in available publications concerning the use of this type of decomposer in the sulfur-iodine thermochemical water splitting cycle. There is an urgent need for developing models to provide this information for industry. In the present study, the detailed three-dimensional analysis on fluid flow, heat transfer and chemical reaction of the decomposer have been completed. The computational model was validated by comparisons with experimental and calculation results from other researchers; Several new designs of the decomposer plates have been proposed and evaluated to improve the uniformity of fluid flow distribution in the decomposer. To enhance the thermal efficiency of the decomposer, several alternative geometries of the internal channels such as ribbed ground channels, hexagonal channels, and diamond-shaped channels are proposed and examined. It was found that it is possible to increase the thermal efficiency of the decomposer from 89.5% (baseline design) up to 95.9% (diamond-shaped channel design); The calculated molar sulfur trioxide decomposition percentage for the baseline design is 64%. The percentage can be increased significantly by reducing reactants mass flow rate and with increasing channel length and operation pressure. The highest decomposition percentage (∼80%) for the alternative designs was obtained in the diamond-shaped channels case; The sulfur dioxide production (throughput) increases as the total mass flow rate of reacting flow increases, regardless of the fact that the decomposition percentage of sulfuric trioxide decreases as total mass flow rate of reacting flow increases

A comparative analysis of different hydrogen production methods and their environmental impact

This study emphasises the growing relevance of hydrogen as a green energy source in meeting the growing need for sustainable energy solutions. It foregrounds the importance of assessing the environmental consequences of hydrogen-generating processes for their long-term viability. The article compares several hydrogen production processes in terms of scalability, cost-effectiveness, and technical improvements. It also investigates the environmental effects of each approach, considering crucial elements such as greenhouse gas emissions, water use, land needs, and waste creation. Different industrial techniques have distinct environmental consequences. While steam methane reforming is cost-effective and has a high production capacity, it is coupled with large carbon emissions. Electrolysis, a technology that uses renewable resources, is appealing but requires a lot of energy. Thermochemical and biomass gasification processes show promise for long-term hydrogen generation, but further technological advancement is required. The research investigates techniques for improving the environmental friendliness of hydrogen generation through the use of renewable energy sources. Its ultimate purpose is to offer readers a thorough awareness of the environmental effects of various hydrogen generation strategies, allowing them to make educated judgements about ecologically friendly ways. It can ease the transition to a cleaner hydrogen-powered economy by considering both technological feasibility and environmental issues, enabling a more ecologically conscious and climate-friendly energy landscape

Thermal management of the copper-chlorine cycle for hydrogen production: analytical and experimental investigation of heat recovery from molten salt

Hydrogen is known as a clean energy carrier which has the potential to play a major role in addressing the climate change and global warming, and thermochemical water splitting via the copper-chlorine cycle is a promising method of hydrogen production. In this research, thermal management of the copper-chlorine cycle for hydrogen production is investigated by performing analytical and experimental analyses of selected heat recovery options. First, the heat requirement of the copper-chlorine cycle is estimated. The pinch analysis is used to determine the maximum recoverable heat within the cycle, and where in the cycle the recovered heat can be used efficiently. It is shown that a major part of the potential heat recovery can be achieved by cooling and solidifying molten copper(I) chloride exiting one step in the cycle: the oxygen reactor. Heat transfer from molten CuCl can be carried out through direct contact or indirect contact methods. Predictive analytical models are developed to analyze a direct contact heat recovery process (i.e. a spray column) and an indirect contact heat recovery process (i.e. a double-pipe heat exchanger). Characteristics of a spray column, in which recovered heat from molten CuCl is used to produce superheated steam, are presented. Decreasing the droplet size may increase the heat transfer rate from the droplet, and hence decreases the required height of the heat exchanger. For a droplet of 1 mm, the height of the heat exchanger is predicted to be about 7 m. The effect of hydrogen production on the heat exchanger diameter was also shown. For a hydrogen production rate of 1000 kg/day, the diameter of the heat exchanger is about 3 m for a droplet size of 1 mm and 2.2 m for a droplet size of 2 mm. The results for axial growth of the solid layer and variations of the coolant temperature and wall temperature of a double-pipe heat exchanger are also presented. It is shown that reducing the inner tube diameter will increase the heat exchanger length and increase the outlet temperature of air significantly. It is shown that the air temperature increases to 190oC in a heat exchanger with a length of 15 cm and inner tube radius of 10 cm. The length of a heat exchanger with the inner tube radius of 12 cm is predicted to be about 53 cm. The outlet temperature of air is about 380oC in this case. The length of a heat exchanger with an inner tube diameter of 24 cm is predicted to be about 53 cm and 91 cm for coolant flow rates of 3 g/s and 4 g/s, respectively. Increasing the mass flow rate of air will increase the total heat flux from the molten salt by increasing the length of the heat exchanger. Experimental studies are performed to validate the proposed methods and to further investigate their feasibility. The hazards involving copper(I) chloride are also investigated, as well as corresponding hazard reduction options. Using the reactant Cu2OCl2 in the oxygen production step to absorb CuCl vapor is the most preferable option compared to the alternatives, which include absorbing CuCl vapor with water or CuCl2 and building additional structures inside the oxygen production reactor

Modeling of a compressor-less thermal compression H2 refueling station: design and optimization

The compressor-less thermal compression hydrogen refueling station concept is being analyzed as a cost-effective alternative to “traditional” fueling stations. A transient thermodynamic model was developed and used in this paper to evaluate the pathways that minimize both operating (venting losses) and capital (size of the cryogenic vessels cascade) costs. Various conditions were simulated, including operating conditions and vessel design. Results were given as a ratio of venting losses per kg H2 dispensed, and as a material balance (liner and overwrap) for the cascade necessary to meet a certain given size. Typical HDSAM assumptions were used for station sizing, including the utilization profile, also known as “Chevron” profile

High Efficiency Generation of Hydrogen Fuels Using Nuclear Power: Final Report

OAK B202 HIGH EFFICIENCY GENERATION OF HYDROGEN FUELS USING NUCLEAR POWER. Combustion of fossil fuels, used to power transportation, generate electricity, heat homes and fuel industry provides 86% of the world's energy. Drawbacks to fossil fuel utilization include limited supply, pollution, and carbon dioxide emissions. Carbon dioxide emissions, thought to be responsible for global warming, are now the subject of international treaties. Together, these drawbacks argue for the replacement of fossil fuels with a less-polluting potentially renewable primary energy such as nuclear energy. Conventional nuclear plants readily generate electric power but fossil fuels are firmly entrenched in the transportation sector. Hydrogen is an environmentally attractive transportation fuel that has the potential to displace fossil fuels. Hydrogen will be particularly advantageous when coupled with fuel cells. Fuel cells have higher efficiency than conventional battery/internal combustion engine combinations and do not produce nitrogen oxides during low-temperature operation. Contemporary hydrogen production is primarily based on fossil fuels and most specifically on natural gas. When hydrogen is produced using energy derived from fossil fuels, there is little or no environmental advantage. There is currently no large scale, cost-effective, environmentally attractive hydrogen production process available for commercialization, nor has such a process been identified. The objective of this work is to find an economically feasible process for the production of hydrogen, by nuclear means, using an advanced high-temperature nuclear reactor as the primary energy source. Hydrogen production by thermochemical water-splitting (Appendix A), a chemical process that accomplishes the decomposition of water into hydrogen and oxygen using only heat or, in the case of a hybrid thermochemical process, by a combination of heat and electrolysis, could meet these goals. Hydrogen produced from fossil fuels has trace contaminants (primarily carbon monoxide) that are detrimental to precious metal catalyzed fuel cells, as is now recognized by many of the world's largest automobile companies. Thermochemical hydrogen will not contain carbon monoxide as an impurity at any level. Electrolysis, the alternative process for producing hydrogen using nuclear energy, suffers from thermodynamic inefficiencies in both the production of electricity and in electrolytic parts of the process. The efficiency of electrolysis (electricity to hydrogen) is currently about 80%. Electric power generation efficiency would have to exceed 65% (thermal to electrical) for the combined efficiency to exceed the 52% (thermal to hydrogen) calculated for one thermochemical cycle. Thermochemical water-splitting cycles have been studied, at various levels of effort, for the past 35 years. They were extensively studied in the late 70s and early 80s but have received little attention in the past 10 years, particularly in the U.S. While there is no question about the technical feasibility and the potential for high efficiency, cycles with proven low cost and high efficiency have yet to be developed commercially. Over 100 cycles have been proposed, but substantial research has been executed on only a few. This report describes work accomplished during a three-year project whose objective is to ''define an economically feasible concept for production of hydrogen, by nuclear means, using an advanced high temperature nuclear reactor as the energy source.'' The emphasis of the first phase was to evaluate thermochemical processes which offer the potential for efficient, cost-effective, large-scale production of hydrogen from water in which the primary energy input is high temperature heat from an advanced nuclear reactor and to select one (or, at most three) for further detailed consideration. During Phase 1, an exhaustive literature search was performed to locate all cycles previously proposed. The cycles located were screened using objective criteria to determine which could benefit, in terms of efficiency and cost, from the high-temperature capabilities of advanced nuclear reactors. The more promising cycles were then analyzed in depth as to their adaptability to advanced high-temperature nuclear reactors. As a result, the Sulfur-Iodine (S-I) cycle was selected for integration into the advanced nuclear reactor system. In Phases 2 and 3, alternative flowsheets were developed and compared. This effort entailed a considerable effort into developing the solution thermodynamics pertinent to the S-I cycle