Techno-economic analysis of H2 production processes using fluidized bed heat exchangers with steam reforming – Part 1: Oxygen carrier aided combustion

This work presents the techno-economic assessment for a new process where a fluidized bed heat exchanger (FBHE) is used as heat source for steam reforming in a hydrogen production plant. This suggested process configuration is compared with a reference case representing a conventional steam methane reforming (SMR) large-scale hydrogen production plant. The use of a FBHE as a heat source for the endothermic reforming is an advantage because of the high heat transfer coefficient to the reformer tubes. The suggested process configuration utilizes oxygen carrier particles as bed material and a bubbling fluidized bed reactor with immersed reformer tubes to ensure sufficient heat production for the reforming and improved heat transfer to the reformer tubes compared a conventional plant. The results include a comparison of hydrogen production efficiency and levelized production costs (LCOH) of the two plants where the production efficiency is more than 11% higher and the LCOH is more than 7% lower for the suggested process configuration.     

Cryosorption storage of gaseous hydrogen for vehicular application – a conceptual design

A conceptual design for the cryosorption storage of gaseous hydrogen in activated carbon for vehicular application has been presented. In this work, a novel concept for the storage/discharge of hydrogen has been proposed. This system ensures faster filling and gradual release of hydrogen on demand. These two features are important for making onboard hydrogen storage effective for small cars. Numerical models for adsorption and desorption half cycles are presented. Assuming that the pressurisation and depressurisation are occurring adiabatically, transient analysis has been done to critically study the effective hydrogen storage capacity of activated carbon. The amount of activated carbon required to store hydrogen for travelling a specific distance has been computed.     

Preliminary process analysis for the closed cycle operation of the iodine–sulfur thermochemical hydrogen production process

In the iodine–sulfur thermochemical hydrogen production process, a separation characteristic of 2-liquid phase (H₂SO₄ phase and HI_x phase) in the separator at 0°C was measured. Two-phase separation began to occur at about 0.32 of I₂ molar fraction and over. The separation characteristic became better with the increase in iodine concentration in the solution. The effect of flow rate variations of HI solution and I₂ solution from the HI_x distillation column on the process was evaluated. The flow rate increase in HI solution from the distillation column did not have a large effect on the flow rate of HI solution fed to the distillation column from the separator. The decreasing flow rate of I₂ solution from the distillation column decreased the flow rate of I₂ solution fed to the distillation column from the separator. The variation of I₂ molar fraction in the H₂SO₄ phase in the separator was sensitive to the variation in flow rate of both solutions from the distillation column. The tolerance level of the variation was investigated by considering I₂ solubility, 2-liquid phase disappearance and SO₂ reaction amount.     

Exergoeconomic analysis and determination of power cost in MCFC – steam turbine combined cycle

A novel combined molten carbonate fuel cell – steam turbine based system is proposed herein. In this cycle, steam is produced through the recovery of useful heat of an internal reforming MCFC and operates as work fluid in a Rankine cycle. Exergoeconomic analysis was performed, in order to verify the technical feasibility, including which components could be improved for greater efficiencies, as well as the cost of the power generated by the plant. A 10 MW MCFC was initially proposed, when the system reached 54.1% of thermal efficiency, 8.3% higher than MCFC alone, 11.9 MW of net power, 19% higher than MCFC alone, and an energy cost of 0.352 $/kWh. A sensitivity analysis was carried out and the parameters that most influenced on the cost were pointed out. The analysis pointed to the MCFC generation as the most impactful factor. By manipulating these values, it could be noted a significant power cost decrease, reaching satisfactory values to become economically feasible. The concept of economy of scale could be noticed in the proposed system, proving that a large-scale plant could be the focus of investment and public policies.     

Computational analysis of geometrical factors affecting experimental data extracted from hydrogen permeation tests: III – Comparison with experimental results from the literature

The membrane thickness is one of the major parameters affecting hydrogen diffusion during electrochemical permeation tests. In this work, we study the effects of membrane thickness by comparing experimental results from the literature with a numerical analysis by finite element method (FEM). We consider the effects of a palladium coating or an oxide layer on the diffusion through α-iron, and we also studied the effects of an oxide layer on the diffusion through martensitic steels. Our model allows us to match the experimental data and determine the initial subsurface hydrogen concentration, trap densities, and the diffusivity of the layer. However, we had to consider the effects of the mechanical polishing on hydrogen trap densities and concentrations to ensure a reasonable correlation. The balance between the effects of trapping and the oxide layer are finally discussed; while hydrogen trapping increases the effective subsurface concentration, the oxide layer decreases its value.     

Ni–Co bimetallic MgO-based catalysts for hydrogen production via steam reforming of acetic acid from bio-oil

Acetic acid (AC) is a representative compound of bio-oil via fast pyrolysis of biomass, and can be processed for hydrogen production via steam reforming (SR). In the current work, the Ni_xCo_1−xMg₆O_7±δ (x = 0–1) bimetallic catalysts were prepared via co-precipitation and impregnation, and tested in SR of AC. The reaction results indicate that the monometallic catalysts were deactivated obviously in SR, while the Ni_0.2Co_0.8Mg₆O_7±δ bimetallic catalyst performed better in both activity and stability: not only the conversion of AC remained stable near 100%, but also the H₂ yield maintained stable near 3.1 mol-H₂/mol-AC. The results of XRD, BET, XPS, TG and TEM indicate that the high catalytic performance of the Ni_0.2Co_0.8Mg₆O_7±δ catalyst can be attributed to 1) resistance to oxidation of active metals, 2) resistance to coking, and 3) stability of structure and electronic properties.     

Effects of hydrogen and steam addition on laminar burning velocity of methane–air premixed flame: Experimental and numerical analysis

Effects of hydrogen enrichment and steam addition on laminar burning velocity of methane–air premixed flame were studied both experimentally and numerically. Measurements were carried out using the slot burner method at 1 bar for fresh gases temperatures of 27 °C and 57 °C and for variable equivalence ratios going from 0.8 to 1.2. The hydrogen content in the fuel was varied from 0% to 30% in volume and the steam content in the air was varied from 0 to 112 g/kg (0–100% of relative humidity). Numerical calculations were performed using the COSILAB code with the GRI-Mech 3.0 mechanism for one-dimensional premixed flames. The calculations were implemented first at room temperature and pressure and then extended to higher temperatures (up to 917 K) and pressures (up to 50 bar). Measurements of laminar burning velocities of methane–hydrogen–air and methane–air–steam agree with the GRI-Mech calculations and previous measurements from literature obtained by different methods. Results show that enrichment by hydrogen increases of the laminar burning velocity and the adiabatic flame temperature. The addition of steam to a methane–air mixture noticeably decreases the burning velocity and the adiabatic flame temperature. Modeling shows that isentropic compression of fresh gases leads to the increase of laminar burning velocity.     

Thermodynamic development and design of a concentrating solar thermochemical water-splitting process for co-production of hydrogen and electricity

A concentrating solar plant is proposed for a thermochemical water-splitting process with excess heat used for electricity generation in an organic Rankine cycle. The quasi-steady state thermodynamic model consisting of 23 components and 45 states uses adjustable design parameters to optimize hydrogen production and system efficiency. The plant design and associated thermodynamic model demonstrate that cerium oxide is suitable for thermochemical water-splitting cycles involving the co-production of hydrogen and electricity. Design point analyses at 900 W/m² DNI indicate that a single tower with solar radiation input of 27.74 MW and an aperture area of 9.424 m² yields 10.96 MW total output comprised of 5.55 MW hydrogen (Gibbs free energy) and 5.41 MW net electricity after subtracting off 22.0% of total power generation for auxiliary loads. Pure hydrogen output amounts to 522 tonne/year at 20.73 GWh/year (HHV) or 17.20 GWh/year (Gibbs free energy) with net electricity generation at 14.52 GWh/year using TMY3 data from Daggett, California, USA. Annual average system efficiency is 38.2% with the constituent hydrogen fraction and electrical fraction being 54.2% and 45.8%, respectively. Sensitivity analyses illustrate that increases in particle loop recuperator effectiveness create an increase in hydrogen production and a decrease in electricity generation. Further, recuperator effectiveness has a measurable effect on hydrogen production, but has limited impact on total system efficiency given that 81.1% of excess heat is recuperated within the system for electricity generation.     

CuFeO2–CeO2 nanopowder catalyst prepared by self-combustion glycine nitrate process and applied for hydrogen production from methanol steam reforming

Hydrogen (H₂) is being considered as an alternate renewable energy carrier due to the energy crisis, climate change and global warming. In the chemical industry, hydrogen production is mainly accomplished by the steam reforming of natural gas. In the present study, CuFeO₂–CeO₂ nanopowder catalyst with a heterogeneous delafossite structure was prepared by the self-combustion glycine nitrate process and used for steam reforming of methanol (SRM). The precursor solution was fabricated from Cu–Fe–Ce metal-nitrate mixed with glycine and an aqueous solution. The prepared CuFeO₂–CeO₂ nanopowder catalyst was studied by different physical and chemical characterization techniques. The prepared CuFeO₂–CeO₂ nanopowder catalyst was immensely porous with a coral-like structure. The BET surface area measurement revealed that the specific surface area of as-combusted CuFeO₂–CeO₂ nanopowder varied from 5.6248 m²/g to 19.5441 m²/g. In addition, the production rate of CuFeO₂–CeO₂ was improved by adding CeO₂ and adjusting the feeding rate of the methanol. The highest H₂ generation rate of the CuFeO₂–CeO₂ catalyst was 2582.25 (mL STP min⁻¹ g-cat⁻¹) at a flow rate of 30 sccm at 400 °C. Hence, the high specific surface area of the 70CuFeO₂–30CeO₂ nanopowder catalyst and the steam reforming process could have a very important industrial and economic impact.     

Hydrogen microscopy – Distribution of hydrogen in buckled niobium hydrogen thin films

Hydrogen absorption in thin metal films clamped to rigid substrates results in mechanical stress that changes the hydrogen's chemical potential by Δμ_H(σ) = −1.124σ kJ/mol_H for σ measured in [GPa]. In this paper we show that local stress relaxation by the detachment of niobium hydrogen thin films from the substrate affects the chemical potential on the local scale: using coincident proton–proton scattering at a proton microprobe, the hydrogen concentration is determined with μm resolution, revealing that hydrogen is not homogenously distributed in the film. The local hydrogen solubility of the film changes with its local stress state, mapping the buckled film fraction. In niobium hydrogen thin films loaded up to nominal concentrations in the two-phase coexistence region, the clamped film fraction remains in the solid solution phase, while the buckles represent the hydride phase. These results are compared to a simple model taking the stress impact on the chemical potential into account.     

Numerical analysis of the electrochemical Bunsen reaction for hydrogen production from sulfur–iodine cycle

The sulfur–iodine (S-I) water-splitting cycle is one of the most promising hydrogen production methods. The Bunsen reaction in the cycle affects the flowsheet complexity and thermal efficiency, but an electrochemical technique has recently been applied to make the S-I cycle more simplified and energy efficient. However, the performance of the electrochemical Bunsen reaction, especially the electrode reactions inside the electrolytic cell (EC) are not clear at present. In this work, a two-dimensional numerical model of EC was developed. The detailed reaction process was numerically calculated with considering the coupling of mass transfer and electrochemical reactions, and was verified using experimental data. The effects of various operating parameters on the reactions were investigated. The results showed that the increase of current density significantly improves the conversion rates of reactants. A higher temperature is unfavorable for concentrating H₂SO₄ and HI. Increase in the inlet flow rate reduces the conversion rates of reactants, but the impact declines with further rising flow rate. An optimal operating condition is also proposed. The theoretical simulation study will provide guidance for the improvement of experimental work.     

Comparison of the renewable transportation fuels,hydrogen and methanol formed from hydrogen,with gasoline – Engine efficiency study

The use of hydrogen derived methanol in spark-ignition engines forms a promising approach to decarbonizing transport and securing domestic energy supply. Methanol can be renewably produced from hydrogen in combination with biomass or CO₂ from the atmosphere and flue gases. From well to tank studies it appears that hydrogen derived methanol compares favourably with liquid or compressed hydrogen both in terms of production cost and energy efficiency. Since existing well to wheel studies are based on outdated technology, this paper tries to provide efficiency figures for state-of-the-art hydrogen and methanol engines using published data and measurements on our own flex-fuel engine.     

Dynamic behavior of metal–hydrogen reactor during hydriding process

The present study involves numerical simulation of transient transport of hydrogen and heat within a metal–hydrogen reactor connected to a hydrogen tank during the hydriding process. This problem is of particular interest in the design of many installations in the field of energy technology (compressor, heat pumps, thermal or hydrogen storage systems). The reactor presents an expansion volume for hydrogen. The hydrogen flow is described by general momentum conservation equations instead of Darcy's law. The evolutions of the temperature, of the hydrogen concentration and of the hydrogen flow velocity are presented. The effects of the reactor dimensions, the inlet diameter, the volume of the expansion part, the tank volume, the initial pressure and the amount of hydrogen in the tank, on the heat and hydrogen transfer are determined.     

Research on the design of hydrogen supply system of 70 MPa hydrogen storage cylinder for vehicles

A hydrogen supply system of 70 MPa hydrogen storage cylinder on vehicles is designed, in which a compressor is proposed to use the new type of ion compressor. The system is simulated statically by Aspen Plus. Meanwhile, during the process of hydrogen charged from the third-stage high-pressure hydrogen storage tank to the hydrogen storage cylinder on vehicles, the dynamic variety of the third-stage high-pressure hydrogen storage tank is simulated dynamically by Aspen HYSYS Through the simulation, obtaining the results that there are difference between theoretical calculation and simulation for the volume of third-stage high-pressure hydrogen storage tank and the average volume flow of hydrogen in a third-stage high-pressure hydrogen storage tank varies with its pressure and volume. By comparing the results of Aspen Plus simulation and Aspen HYSYS simulation, there are some differences. The designed system can be applied to hydrogen stations and any operating conditions involving the supply hydrogen.     

Preparation of Ni–Cu/Mg/Al catalysts from hydrotalcite-like compounds for hydrogen production by steam reforming of biomass tar

Ni–Cu/Mg/Al bimetallic catalysts were prepared by the calcination and reduction of hydrotalcite-like compounds containing Ni²⁺, Cu²⁺, Mg²⁺, and Al³⁺, and tested for the steam reforming of tar derived from the pyrolysis of biomass at low temperature. The characterizations with XRD, STEM-EDX, and H₂ chemisorption confirmed the formation of Ni–Cu alloy particles. The Ni–Cu/Mg/Al bimetallic catalyst with the optimum composition of Cu/Ni = 0.25 exhibited much higher catalytic performance than the corresponding monometallic Ni/Mg/Al and Cu/Mg/Al catalysts in the steam reforming of tar in terms of activity and coke resistance. The catalyst gave almost total conversion of tar even at temperature as low as 823 K. This high performance was related to the higher metal dispersion, larger amount of surface active sites, higher oxygen affinity, and surface modification caused by the formation of small Ni–Cu alloy particles. In addition, the Ni–Cu/Mg/Al catalyst showed better long-term stability than the Ni/Mg/Al catalyst. No obvious aggregation and structural change of the Ni–Cu alloy particles were observed. The coke deposition on the Ni–Cu/Mg/Al catalyst was approximately ten times smaller than that on the Ni/Mg/Al catalyst, indicating good coke-resistance of the Ni–Cu alloy particles.     

Li-N-H system – Reversible accumulator and store of hydrogen

The statistical theory of phase transformations in the course of chemical reactions on hydrogen absorption–desorption in the lithium nitride with the formation of lithium amide and hydride has been developed. The calculation of free energies of all constituent phases of chemical reactions has been performed on the basis of molecular-kinetic notions, their dependences on temperature, pressure, hydrogen concentration and energetic parameters have been ascertained. The hydrogen solubility in phases has been estimated, it has been ascertained the possibility of manifestation of peculiarities of its temperature dependence. The constitution diagram for the system being investigated has been constructed. The actual conditions of manifestation of hysteresis effect has been justified. The calculation results have been compared with experimental literature data for the examined system.     

Modeling of a catalytic membrane reactor for CO removal from hydrogen streams – A theoretical study

Typical industrial hydrogen streams arising from reforming processes contain about 1% of carbon monoxide (CO). For fuel cell applications hydrogen should contain less than 10 ppm of CO, since it poisons the platinum catalysts in the electrodes. Traditionally, this is carried out through a selective oxidation reactor – PROX reactor. However, the parallel oxidation of hydrogen to water should be avoided. This work proposes the use of a catalytic membrane reactor (MR) whose design is based on a CO permselective membrane containing the selective catalyst loaded in the permeate side. It is considered plug-flow pattern and segregated feed of CO and oxygen. This strategy should improve the selective oxidation, as the permselective membrane enhances the CO/H₂ ratio at the catalyst surface.     

Application of nickel–lanthanum composite oxide on the steam reforming of ethanol to produce hydrogen

Nickel–lanthanum composite oxides, LaNiO_x, were used for steam reforming of ethanol (SRE). The composite oxides (with 3:1, 1:1, 1:3 M ratios, assigned as 3La–1Ni, 1La–1Ni, and 1La–3Ni, respectively) were prepared by co-precipitation-oxidation (PO) and assisted with ultrasonic irradiation (240 W). Meanwhile, the as-prepared 1La–1Ni sample was further calcined at 300 and 700 °C for 2 h (assigned as C300 and C700). All samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and temperature programmed reduction (TPR). Catalytic activities towards the SRE reaction were tested from 300 to 450 °C in a fixed-bed reactor. The study focused on deriving optimized composition of composites and compared the effect on the reduction pretreatment under 200 °C [assigned with (H)]. The results indicated that the ethanol conversion reached completion around 325 °C for the 1La–1Ni(H) sample while it required 400 °C for the 1La–1Ni sample with a minor CO distribution for both samples under an H₂O/EtOH molar ratio of 13 and 22,000 h⁻¹ GHSV. The yield of hydrogen (YH₂$Y_{{\text{H}}_2}$) approached 5.2 around 375 °C for the 1La–1Ni(H) sample.     

High-temperature electrolysis for large-scale hydrogen production from nuclear energy – Experimental investigations

The Idaho National Laboratory (INL) is currently assessing the feasibility of using solid-oxide based electrolysis cell technology for high temperature electrolysis of steam for large-scale hydrogen production. In parallel, the INL is studying the simultaneous electrolysis of steam and carbon dioxide for syngas (hydrogen/carbon monoxide mixture) production. When linked to a nuclear power source, this technology provides a carbon neutral means of producing syngas while consuming CO₂. The scope of experimental investigations at the INL includes single button cell tests, multi-cell stacks, and multi-stack systems. Multi-cell stack testing used 10 cm × 10 cm (8 cm × 8 cm active area) or 20 cm × 20 cm (18 cm × 18 cm active area) planar cells supplied by Ceramatec, Inc (Salt Lake City, Utah, USA). Multi-stack testing encompassed up to 720 10 cm × 10 cm cells and was conducted in a newly developed 15 kW Integrated Laboratory Scale (ILS) test facility. Gas composition, operating voltage, and operating temperature were varied during testing. The tests were heavily instrumented, and outlet gas compositions were monitored with a gas chromatograph. Results to date show the process to be a promising technique for large-scale hydrogen and syngas production.