Extraction of hydrogen from a lean mixture with methane by metal hydride

Hydrogen/methane mixtures draw attention due to the idea of the injection of hydrogen into natural gas networks and biological production of biohythane by one- and two-step anaerobic fermentation/digestion methods. It is hard to extract hydrogen from dilute mixtures with methane by traditional separation processes, since hydrogen is the minor component with low partial pressure. Metal hydrides selectively absorb hydrogen and offer an opportunity to overcome the limitations of traditional separation methods. In the present paper, we present experimental results on the separation of a dilute mixture of hydrogen (10%) with methane in a flow-through metal hydride reactor with inlet mixture pressure of 0.95 MPa by the LaNi_4.8Mn_0.3Fe_0.1 intermetallic compound. Hydrogen was separated in one step with roundtrip (absorption/desorption) recovery of 74%. An exergetic analysis of the metal hydride separation of a binary mixture containing hydrogen was implemented and equations for hydrogen recovery and exergy efficiency of separation are obtained. Thermodynamic analysis shows that the exergy efficiency of the metal hydride purification has a clear maximum at hydrogen concentrations around 5–20%. The advantage of metal hydride purification is the absorption of the minor fraction from the feed, thus it is preferable for dilute mixtures and could be feasible for practical applications. With the use of low potential or waste heat to drive the reaction, it is possible to increase the efficiency of hydrogen purification by metal hydrides. The maximum exergy efficiency is 61% for 0.8 MPa outlet pressure, taking into account the quality of involved heat flows.     

Hydrogen separation from blended natural gas and hydrogen by Pd-based membranes

Hydrogen separation membranes based on a heated metal foil of a palladium alloy, offer excellent permeability for hydrogen as a result of the solution-diffusion mechanism. Here, the possibility to separate hydrogen from the mixture of Natural Gas (NG) and hydrogen (NG+H₂) with various NG concentrations using Pd, PdCu₅₃ and PdAg₂₄ hydrogen purification membranes is demonstrated. Hydrogen concentrations above ∼25% (for Pd and PdCu₅₃) and ∼15% (for PdAg₂₄) were required for the hydrogen separation to proceed at 400 °C and 5 bar pressure differential. Hydrogen permeability of the studied alloys could be almost fully recovered after switching the feed gas to pure hydrogen, indicating no significant interaction between the natural gas components and the membranes surface at the current experimental condition. Hydrogen flux of the membranes at various pressure differential was measured and no changes in the hydrogen permeation mechanism could be noticed under (NG 50%+H₂) mixture. The hydrogen separation capability of the membranes is suggested to be mainly controlled by the operating temperature and the hydrogen partial pressure.     

Modeling and optimal design of cyclic processes for hydrogen purification using hydride-forming metals

Hydrogen at high purity degrees can be obtained by using the well-known Pressure Swing Adsorption (PSA) process. In this paper, a Pressure Swing Absorption (PSAb) alternative operating batch wise is analyzed. An optimal design of cyclic processes for hydrogen purification using hydride-forming metals as absorption material is addressed. The selected case study is a thermo-chemical treatment process that consumes high purity hydrogen to reduce oxides and generates a waste stream that contains residual H₂. PSAb process is fed with this hydrogen-poor stream; and high purity hydrogen recovery levels are obtained. A mathematical model based on an energy integrated scheme is presented to develop the optimal process design and to obtain optimal operating conditions. Various optimized solutions are compared by modifying key parameters or restriction equations. Thus, an interesting trade-off between H₂ recovery and system size is analyzed. Large systems operate at large cycle times, obtaining up to 98% of H₂ recovery in the order of hours, whereas small systems can recover up to 60% of H₂ in short cycles of a few seconds.     

The exploitation of hydrogen sulfide for hydrogen production in geothermal areas

Hydrogen is a valuable energy resource and it is widespread in nature. As a matter of fact, researches on hydrogen production are currently experiencing an increasing interest from scientists around the world since this resource is clean and renewable. Several methods of producing hydrogen have been developed in industrialized countries such as the United States of America and Germany.This paper is interested in the process by which hydrogen sulfide of geothermal areas is exploited for hydrogen production. In fact, research advances in this field have concluded that hydrogen sulfide of geothermal resources can contribute significantly and economically in the process of hydrogen generation.The present paper was principally conducted from a literature study and a synthesis of works achieved in recent years in order to highlight the various aspects of hydrogen production from hydrogen sulfide and particularly to study the possibility of the exploitation of Algeria’s thermal resources in this field.     

Conversion of biodiesel synthesis waste to hydrogen in membrane reactor: Theoretical study of glycerol steam reforming

Hydrogen production from waste glycerol, mainly producible as a by-product of biodiesel synthesis, is investigated as an attractive opportunity for exploiting renewable energy sources for further applications. Glycerol steam reforming using membrane technology was modeled by taking into accounts the maim transport phenomena, thermodynamic criteria and chemical process kinetics. A sensitivity analysis of operating conditions was made for key performance metrics such as glycerol conversion, hydrogen yield and hydrogen recovery. Glycerol conversion intensifies with enhancement of operating pressure and temperature, whereas high feed molar ratio and sweep ratio have limiting effect. Hydrogen permeation and subsequently, hydrogen recovery facilitates with increasing sweep gas ratio and sweep gas temperature. Hydrogen recovery enhances from 70% to 99% with increasing temperature from 350 to 500 °C at feed molar ratio of 3. Also, hydrogen recovery improves from 50% to 71% with increasing sweep ratio from 0 to 20 at 350 °C and 1 bar.     

Hydrogen recovery,cleaning, compression,storage, dispensing,distribution system and End-Uses on the university campus from combined heat,hydrogen and power system

To address the problem of fossil fuel usage at the Missouri University of Science and Technology campus, using of alternative fuels and renewable energy sources can lower energy consumption and hydrogen use. Biogas, produced by anaerobic digestion of wastewater, organic waste, agricultural waste, industrial waste, and animal by-products is a potential source of renewable energy. In this work, we have discussed the design of combined heat, hydrogen and power (CHHP) system for the campus using local resources. An energy flow and resource availability study is hydrogen recovery, cleaning and energy End-Uses on the university campus from CHHP system. Following the resource assessment study, our team selects Fuel Cell Energy direct fuel cell (DFC) 1500TM unit as a molten carbonate fuel cell. The CHHP system provides the hydrogen for transportation, back-up power and other needs. The research presented in this paper was performed as part of the 2012 Hydrogen Student Design Contest. In conclusion, the CHHP system will be able to reduce fossil fuel usage, greenhouse gas (GHG) emissions and hydrogen generated is used to power different applications on the university campus.     

An iterative method for designing hydrogen networks with regeneration unit

In order to release resource shortage constraints, hydrogen effective use is of great importance for refineries nowadays. Hydrogen utility consumption in a hydrogen network involving regeneration can be reduced further compared to that of the network involving reuse only. In this article, an iterative method is presented for design of hydrogen networks involving regeneration reuse. The following new insight obtained in water networks is adopted: the hydrogen network involving regeneration can be formed by adding the regenerated stream into the original hydrogen network. This will simplify the design and targeting of the networks with regeneration unit(s). The iterative method proposed can be used to design and target the networks with both fixed regenerated concentration and that with fixed hydrogen recovery ratio. An estimation method is proposed to calculate the regenerated concentration and flow rate for the regeneration unit with fixed hydrogen recovery ratio. A few literature examples are investigated with the proposed method. The results obtained in this work are comparable to that obtained in the literature. It is shown that the method proposed is simple and effective.     

Green hydrogen production potential for developing a hydrogen economy in Pakistan

Pakistan's energy crisis can be diminished through the use of Renewable and alternative sources of energy. Hydrogen as an energy vector is likely to replace the fossil fuels in the future owing to the political, financial and environmental factors associated with the latter. In this regard it is imperative that conscious effort is directed towards the production of hydrogen from Renewable resources. Renewable energy resources are abundantly available in Pakistan. The need to produce Hydrogen from Renewable resources in Pakistan (or any developing economy) is investigated because it is possible to store vast amount of intermittent renewable energy for later use. Thus the introduction of Hydrogen in the energy supply chain implies the start of a Pakistan Hydrogen Economy. Many nations have developed the Hydrogen Energy Roadmap, and if Pakistan has to follow suite it is only possible through the employment of Renewable energy resources. This study estimates the potential of different Renewable resources available in Pakistan i.e. Solar, Wind, Geothermal, Biomass and Municipal Solid waste. An estimate is then made for the potential of producing hydrogen from various established technologies from each of these Renewable resources. A number of reviews have been published stating the availability and usage of Renewable energy in Pakistan; however no specific study has been focused on the use of Renewable resources for developing a Hydrogen economy or a power-to-gas system in Pakistan. This study concludes that that Biomass is the most feasible feedstock for developing a Hydrogen supply chain in Pakistan with a potential to generate 6.6 million tons of Hydrogen annually, followed by Solar PV that has a generation potential of 2.8 million tons and then Municipal solid waste with a capacity of 1 million ton per annum.     

A state of the art review on biomass processing and conversion technologies to produce hydrogen and its recovery via membrane separation

Hydrogen is a zero-emission green fuel containing sufficient energy potentially suitable for electricity generation. Currently, large quantities of hydrogen are produced using classical fossil fuels. Nevertheless, the finite quantities of these resources have compelled the global community to look into using more sustainable and environmentally friendly resources such as bio-based waste. There are several approaches, to convert biomass to hydrogen, among which the thermochemical and biological processes are considered as the most important ones. The aim of this review paper is twofold, namely, (a) to evaluate hydrogen production and biomass processing methods to give a better insight into their potential merits and identify gaps for sustainable hydrogen generation, and (b) to evaluate current and future opportunities in membrane technology for hydrogen separation and purification from biomass processing. By fulfilling these gaps, the objectives of economical, sustainable, and environmentally-friendly resources for hydrogen production and separation can be recommended.     

Parametric study of pressure swing adsorption cycle for hydrogen purification using Cu-BTC

Metal organic framework (MOF), for example Cu-BTC, has the characteristics of structure adversity, high pore volume, large surface area and strong selectivity. It is being considered as a new adsorbent in the field of pressure swing adsorption (PSA). A model describing hydrogen mixture flow, heat and mass transfer with multi-component adsorption is developed for predicting breakthrough curves and performance of PSA cycles in the hydrogen purification system using Cu-BTC as adsorbent. The model is implemented on Aspen platform and validated by experiments. Hydrogen purification performances (purity, recovery, productivity) were evaluated, and parametric study on the performance of hydrogen purification has been performed. The results show that the simulated mole fractions, temperature and pressure in the PSA cycles agree with the experiments very well. In general, the variation trend of hydrogen purity is opposite to that of recovery and productivity. As the parametric study shows, within a certain range, higher adsorption pressure, shorter feeding time and lower feeding flow rate lead to higher hydrogen purity, then lower recovery and productivity. Parametric studies help to effectively improve hydrogen purification performance in the Cu-BTC adsorption bed. Furthermore, a multi-objective algorithm is needed to optimize the PSA process.     

Monitoring,analysis, and quantification of hydrogen from biomass and biowaste: A review

Hydrogen is called to play a crucial role in decarbonizing different sectors by meaningfully reducing their emissions. Hydrogen production from biomass and biowaste has recently gained momentum due to the high availability of the resource and maturity of thermochemical conversion technologies. However, hydrogen monitoring and purification is required to optimize the process and to meet end-point-applications specifications. This paper provides a comprehensive state-of-the-art on the hydrogen monitoring, analysis, and quantification techniques, with a focus on gas mixtures containing hydrogen. Precision, response time, stability, selectivity of the methods together with other key parameters namely poisoning, interaction with other gases, hydrogen concentration, operating conditions, are confronted. The need for fast and precise hydrogen quantification, especially in the case of complex gaseous mixtures and for high-grade hydrogen applications, together with the need of reliable standards and materials able to provide fast hydrogen adsorption-desorption cycles are the main challenges that arise from our analysis.     

Review of Polybed pressure swing adsorption for hydrogen purification

Hydrogen (H₂) will play a key role in the future low-carbon energy society. The industrial production of hydrogen involves chemical reactions and purification steps. Pressure Swing Adsorption (PSA) is a versatile process able to produce ultrapure hydrogen (99.99+%) from various gas mixtures, resulting in the most widespread purification technology worldwide. In particular, the Polybed PSA system, having more than six beds and a complex cycle configuration, has proven to maximize H₂ recovery and H₂ throughput, exceeding 90% and 240 MMSCFD (265,000 Nm³ h^?1) per single train, respectively.This paper systematically reviews the Polybed H₂ PSA process for the first time, highlighting the latest technical advances and discussing its optimal integration in industrial clusters. A bespoke Polybed PSA process designed for simultaneous production of high-purity hydrogen and carbon dioxide (CO₂) is also reviewed in light of the recent international directives aimed to reduce CO₂ emissions and produce blue hydrogen.     

A review of hydrogen production via biomass gasification and its prospect in Bangladesh

Hydrogen has been using as one of the green fuel along with conventional fossil fuels which has enormous prospect. A new dimension of hydrogen energy technology can reduce the dependency on non-renewable energy sources due to the rapid depletion of fossil fuels. Hydrogen production via Biomass (Municipal solid waste, Agricultural waste and forest residue) gasification is one of the promising and economic technologies. The study highlights the hydrogen production potential from biomass through gasification technology and review the parameters effect of hydrogen production such as temperature, pressure, biomass and agent ratio, equivalence ratios, bed material, gasifying agents and catalysts effect. The study also covers the all associated steps of hydrogen separation and purification, WGS reaction, cleaning and drying, membrane separation and pressure swing adsorption (PSA). To meet the huge and rising energy demand, many countries made a multidimensional power development plan by adding different renewable, nuclear and fossil fuel sources. A large amount of biomass (total biomass production in Bangladesh is 47.71 million ton coal equivalent where 37.16, 3.49 and 7.04 MTCE are agricultural, MSW and forest residue based biomass respectively by 2016) is produced from daily uses by a big number of populations in a country. It also includes total feature of biomass gasification plant in Bangladesh.     

Hydrogen production and End-Uses from combined heat,hydrogen and power system by using local resources

To address the problem of fossil fuel usage at the Missouri University of Science and Technology campus, using of alternative fuels and renewable energy sources can lower energy consumption and hydrogen use. Biogas, produced by anaerobic digestion of wastewater, organic waste, agricultural waste, industrial waste, and animal by-products is a potential source of renewable energy. In this work, we have discussed Hydrogen production and End-Uses from CHHP system for the campus using local resources. Following the resource assessment study, the team selects FuelCell Energy DFC1500™ unit as a molten carbonate fuel cell to study of combined heat, hydrogen and power (CHHP) system based on a molten carbonate fuel cell fed by biogas produced by anaerobic digestion. The CHHP system provides approximately 650 kg/day. The total hydrogen usage 123 kg/day on the university campus including personal transportation applications, backup power applications, portable power applications, and other mobility applications are 56, 16, 29, 17, and 5 respectively. The excess hydrogen could be sold to a gas retailer. In conclusion, the CHHP system will be able to reduce fossil fuel usage, greenhouse gas emissions and hydrogen generated is used to power different applications on the university campus.     

Electrochemical hydrogen compressor: Recent progress and challenges

Hydrogen has higher specific energy than conventional fuels but compared per unit volume under normal conditions, its energy density is lower. This difference is compensated with compression. Theoretically, compression is possible with a proton exchange membrane electrolyzer (PEME), in the process of hydrogen production, but the hydrogen permeation to the oxygen side forms a potentially explosive mixture. An electrochemical hydrogen compressor (EHC) with an analogous working principle presents the most promising solution due to its noiseless and vibration-free operation, modularity, absence of moving parts, and higher efficiency compared to mechanical compressors. Hydrogen purification and its extraction from gaseous mixtures are additional benefits that give electrochemical compression further advantage. This paper discusses the working principle of electrochemical hydrogen compression technology and its design development. The focus is on research trends, recent advances, and transpired challenges. In addition, reviewed literature aspects not studied sufficiently are highlighted, and future research directions are proposed.     

Plasma reforming for hydrogen production: Pathways,reactors and storage

Hydrogen is an energy carrier with a very high energy density (>119 MJ/kg). Pure hydrogen is barely available; thus, it requires extraction from its compounds. Steam reforming and water electrolysis are commercially viable technologies for hydrogen production from water, alcohols, methane, and other hydrocarbons; however, both processes are energy-intensive. Current study aims at understanding the methane and ethanol-water mixture pathway to generate hydrogen molecules. The various intermediate species (like CH_X, CH₂O, CH₃CHO) are generated before decomposing methane/ethanol into hydrogen radicals, which later combine to form hydrogen molecules. The study further discusses the various operating parameters involved in plasma reforming reactors. All the reactors work on the same principle, generating plasma to excite electrons for collision. The dielectric barrier discharge reactor can be operated with or without a catalyst; however, feed flow rate and discharge power are the most influencing parameters. In a pulsed plasma reactor, feed flow rate, electrode velocity, and gap are the main factors that can raise methane conversion (40–60%). While the gliding arc plasma reactor can generate up to 50% hydrogen yield at optimized values of oxygen/carbon ratio and residence time, the hydrogen yield in the microwave plasma reactor is affected by flow rate and feed concentration. Therefore, all the reactors have the potential to generate hydrogen at lower energy demand.     

Evaluation of a new geothermal based multigenerational plant with primary outputs of hydrogen and ammonia

Increasing environmental concerns and decreasing fossil fuel sources compel engineers and scientists to find resilient, clean, and inexpensive alternative energy options Recently, the usage of renewable power resources has risen, while the efficiency improvement studies have continued. To improve the efficiency of the plants, it is of great significance to recover and use the waste heat to generate other useful products. In this paper, a novel integrated energy plant utilizing a geothermal resource to produce hydrogen, ammonia, power, fresh water, hot water, heated air for drying, heating, and cooling is designed. Hydrogen, as an energy carrier, has become an attractive choice for energy systems in recent years due to its features like high energy content, clean, bountiful supply, non-toxic and high efficiency. Furthermore in this study, hydrogen beside electricity is selected to produce and stored in a hydrogen storage tank, and some amount of hydrogen is mixed with nitrogen to compound ammonia. In order to determine the irreversibilities occurring within the system and plant performance, energy and exergy analyses are then performed accordingly. In the design of the plant, each sub-system is integrated in a sensible manner, and the streams connecting sub-systems are enumerated. Then thermodynamic balance equations, in terms of mass, energy, entropy and exergy, are introduced for each unit of the plant. Based on the system inputs and outputs, the energy and exergy efficiencies of the entire integrated plant is found to be 58.68% and 54.73% with the base parameters. The second part of the analysis contains some parametric studies to reveal how some system parameters, which are the reference temperature, geothermal resource temperature and mass flow rate, and separator inlet pressure in the geothermal cycle, affect both energy and exergy efficiencies and hence the useful outputs.     

Electro-stimulated biological production of hydrogen from municipal solid waste

Hydrogen production from municipal solid wastes was investigated by applying a weak current (0.06 A) to a slurry of municipal solid waste in an anaerobic reactor at 55 °C using 4 electrodes (carbon graphite for the cathode and platinum electroplated titanium for the anode). Current application to the organic waste stimulated the hydrogen producing bacteria especially bacteria related to the Thermotogales and Bacillus families. Measured hydrogen production rates were comprised between 16 and 41 mL/h. Comparison of bacterial and archaeal communities in methane-producing (control) and electro-stimulated reactors showed similar species but with different dynamics correlated to hydrogen or methane production. Energy efficiency of the overall bioelectrolysis process using municipal solid waste and an applied voltage of 3V was approximately 12.4%, which is relatively low compared to values reported in the literature for organic wastes and can be explained by the low organic carbon content and availability in the municipal solid waste. Results of this study highlight some important operational constraints with respect to electro-stimulated hydrogen production from organic wastes; related in particular to electrode lifetime expectancies. Results nevertheless illustrate the potential for hydrogen production from municipal solid waste as a possible route for energy recovery.     

Liquid hydrogen production via hydrogen sulfide methane reformation

Hydrogen sulfide (H₂S) methane (CH₄) reformation (H₂SMR) (2H₂S + CH₄ = CS₂ + 4H₂) is a potentially viable process for the removal of H₂S from sour natural gas resources or other methane containing gases. Unlike steam methane reformation that generates carbon dioxide as a by-product, H₂SMR produces carbon disulfide (CS₂), a liquid under ambient temperature and pressure—a commodity chemical that is also a feedstock for the synthesis of sulfuric acid. Pinch point analyses for H₂SMR were conducted to determine the reaction conditions necessary for no carbon lay down to occur. Calculations showed that to prevent solid carbon formation, low inlet CH₄ to H₂S ratios are needed. In this paper, we analyze H₂SMR with either a cryogenic process or a membrane separation operation for production of either liquid or gaseous hydrogen. Of the three H₂SMR hydrogen production flowsheets analyzed, direct liquid hydrogen generation has higher first and second law efficiencies of exceeding 80% and 50%, respectively.     

Simulation-based optimization and design of refinery hydrogen networks with hydrogen sulfide removal

Hydrogen consumption in oil refineries increases sharply because of more and more heavy and sour crude oil processing, which also makes hydrogen sulfide a considerable contaminant in off-gases of hydrotreaters. This work presents a simulation-based optimization model for synthesis of hydrogen networks with H₂S removal. Aspen HYSYS is employed for rigorous process and thermodynamic modeling of the H₂S removal unit. The proposed model is solved using the genetic algorithm combined with the linprog and fmincon solvers in the Matlab platform. The optimal hydrogen sources and the recirculated absorbent fed into the H₂S removal unit as well as the optimal design of the hydrogen network can be determined simultaneously. A case study is performed to illustrate the application and effectiveness of the proposed model. The result shows that the introduction of H₂S removal can decrease the fresh hydrogen consumption by 43% and the total annualized cost by 17%.