Techno-economic assessment of solar steam reforming of methane in a membrane reactor using molten salts as heat transfer fluid

This paper reports the results obtained in a techno-economic analysis of the Steam Methane Reforming (SMR) technology aided with solar heat, developed and demonstrated in the European FCH JU project CoMETHy: a compact membrane reformer heated with molten salt up to 550 °C allowed to simultaneously carry out methane steam reforming, water-gas-shift reaction and hydrogen separation. This reactor can be integrated with new generation Concentrating Solar Thermal (CST) systems to supply the process heat. Experimental validation of the technology has been successfully achieved in a pilot scale plant and the results recently published. In this paper, we introduce a fully-integrated scheme and operation strategies of a plant on the 1500 Nm³/h hydrogen production scale. Then, techno-economic analysis of this new solar-driven process is presented to evaluate its competitiveness. Considering a plant capacity of 1500 Nm³/h (pure hydrogen production) and today's costs for the methane feed and the CST technology, obtained Hydrogen Production Cost (HPC) are in the range of 2.8–3.3 €/kg for a “solar-hybrid” system with high capacity factor (8000 h/year operation) and 4.7 €/kg for a “solar-only” case, while HPC≅1.7 €/kg can be obtained with the conventional route under equivalent assumptions. However, a sensitivity analysis shows that the expected drop of the cost of the CST technology will bring the HPC around 2.4 €/kg for the “solar-hybrid” case and close to 3.4 €/kg for the “solar-only” case, thus making the cost of solar reforming closer to conventional SMR with CO₂ capture and with wind/solar electrolysis in the future. In the “solar-hybrid” case total CO₂ production can be reduced by 13–29% with 58–70% of produced CO₂ recovered as pure stream (at 1.3 bar); in the “solar-only” case total CO₂ production can be reduced by 52% and 100% of produced CO₂ recovered as pure stream (at 1.3 bar). However, compared to the conventional route, CO₂ avoidance costs are still relatively high (≥137 €/ton_CO2) and process optimization measures required. Therefore, optimization measures have been outlined to increase the overall process efficiency and further reduce the HPC.     

Efficient H2 production via membrane-assisted ethanol steam reforming over Ir/CeO2 catalyst

Ethanol steam reforming in membrane reactors is a promising route for decentralized H₂ production from biomass because H₂ yield can be greatly enhanced due to the equilibrium shift triggered by instantaneous H₂ extraction. Here a highly active Ir/CeO₂ catalyst has been combined with ca. 4 μm thin Pd membranes employing a 6:1 steam/ethanol feed between 673 K and 873 K at reforming pressures up to 1.8 MPa. The H₂ yield reached 94.5% at 873 K and 1300 kPa due to the separation of 91.8% H₂ whereas H₂ yield was limited to 28.9% without membrane. At lower temperatures and pressures sweep gas was needed at the membranes' permeate side for efficient H₂ generation since the H₂ partial pressure remains equilibrium-limited on the reaction side. Furthermore, the H₂ yield improved from 63.0% to 84.7% at 773 K, 1500 kPa and sweep-to-feed flow ratio 0.5 when the distance between membrane and reactor wall was shortened by ca. 30%. Thus, external H₂ diffusion towards the membrane has a large impact on membrane reactor performance pointing towards microstructured membrane reactors as optimum devices for sustainable H₂ production from biomass.     

Ultra-compact microstructured methane steam reformer with integrated Palladium membrane for on-site production of pure hydrogen: Experimental demonstration

A novel metal-based modular microstructured reactor with integrated Pd membrane for hydrogen production by methane steam reforming is presented. Thin Pd foils with a thickness of 12.5 μm were leak-tight integrated with laser welding between microstructured plates. The laser-welded membrane modules showed ideal H₂/N₂ permselectivities between 16,000 and 1000 at 773 K and 6 bar retentate pressure. An additional metal microsieve support coated with an YSZ diffusion barrier layer (DBL) facilitated the operation at temperatures up to 873 K and pressures up to 20 bar pressure difference. The membrane permeability in this configuration is expressed with Q = 1.58E-07*exp(−1460.2/T) mol/(msPa^0.5).     

Modelling of H2 production via sorption enhanced steam methane reforming at reduced pressures for small scale applications

The production of H₂ via sorption enhanced steam reforming (SE-SMR) of CH₄ using 18 wt % Ni/Al₂O₃ catalyst and CaO as a CO₂-sorbent was simulated for an adiabatic packed bed reactor at the reduced pressures typical of small and medium scale gas producers and H₂ end users. To investigate the behaviour of reactor model along the axial direction, the mass, energy and momentum balance equations were incorporated in the gPROMS modelbuilder^®. The effect of operating conditions such as temperature, pressure, steam to carbon ration (S/C) and gas mass flow velocity (G_s) was studied under the low-pressure conditions (2–7 bar). Independent equilibrium based software, chemical equilibrium with application (CEA), was used to compare the simulation results with the equilibrium data. A good agreement was obtained in terms of CH₄ conversion, H₂ yield (wt. % of CH₄ feed), purity of H₂ and CO₂ capture for the lowest (G_s) representing conditions close to equilibrium under a range of operating temperatures pressures, feed steam to carbon ratio. At G_s of 3.5 kg m⁻²s⁻¹, 3 bar, 923 K and S/C of 3, CH₄ conversion and H₂ purity were up to 89% and 86% respectively compared to 44% and 63% in the conventional reforming process.     

H2 production by low pressure methanol steam reforming in a dense Pd–Ag membrane reactor in co-current flow configuration: Experimental and modeling analysis

The aim of this work is to generate a pure or CO_x-free hydrogen stream by using a dense Pd-based packed bed membrane reactor (PBMR) during methanol steam reforming (MSR) reaction and developing a valid model that can provide a tool for deeper analyses of the reaction parameters in the PBMR. Therefore, in this study, a dense Pd–Ag membrane reactor (MR) is used to carry out MSR at different gas hourly space velocity (GHSV), feed molar ratio and sweep gas factor (SF) and for low reaction pressures (1.5–2.5 bar). For a better analysis, a traditional packed bed reactor (PBR) is operated at the same PBMR conditions. In the PBMR setup, a dense Pd–Ag membrane with a thickness of 50 μm is used and also a commercial Cu/ZnO/Al₂O₃ catalyst is packed in both kinds of reactors. Methanol conversion equal to 100% is experimentally achieved in the PBMR at 280 °C, H₂O/CH₃OH = 3/1 and 2.5 bar, while at the same conditions the PBR reaches 91% methanol conversion. Moreover, 46% CO_x-free hydrogen on total hydrogen produced is collected by using sweep gas in the PBMR permeate side. Furthermore, a 1-dimensional and isothermal model is developed for theoretically analyzing MSR performance in both PBMR and PBR, validated by the combined experimental campaign.     

Techno-economic and environmental assessment of methanol steam reforming for H2 production at various scales

According to global trend of transition to a hydrogen society, needs for alternative hydrogen (H₂) production methods have been on the rise. Among them, methanol steam reforming (MSR) in a membrane reactor (MR) has received a great attention due to its improved H₂ yield and compact design. In this study, 3 types of economic analysis – itemized cost estimation, sensitivity analysis, and uncertainty analysis – and integrative carbon footprint analysis (iCFA) were carried out to investigate economic and environmental feasibility. Unit H₂ production costs of MSR in a packed-bed reactor (PBR) and an MR for various H₂ production capacities of 30, 100, 300, and 700 m³ h⁻¹ and CO₂ emission rates for both a PBR and an MR in H₂ production capacity of 30 m³ h⁻¹ were estimated. Through itemized cost estimation, unit H₂ production costs of a PBR and an MR were obtained and scenario analysis was carried out to find a minimum H₂ production cost. Sensitivity analysis was employed to identify key economic factors. In addition, comprehensive uncertainty analysis reflecting unpredictable fluctuation of key economic factors of reactant, labor, and natural gas obtained from sensitivity analysis was also performed for a PBR and an MR by varying them both simultaneously and individually. Through iCFA, lowered CO₂ emission rates were obtained showing environmental benefit of MSR in an MR.     

Membrane reactors for green hydrogen production from biogas and biomethane: A techno-economic assessment

This work investigates the performance of a fluidized-bed membrane reactor for pure hydrogen production. A techno-economic assessment of a plant with the production capacity of 100 kg_H2/day was carried out, evaluating the optimum design of the system in terms of reactor size (diameter and number of membranes) and operating pressures. Starting from a biomass source, hydrogen production through autothermal reforming of two different feedstock, biogas and biomethane, is compared.Results in terms of efficiency indicates that biomethane outperforms biogas as feedstock for the system, both from the reactor (97.4% vs 97.0%) and the overall system efficiency (63.7% vs 62.7%) point of views. Nevertheless, looking at the final LCOH, the additional cost of biomethane leads to a higher cost of the hydrogen produced (4.62 €/kg_H2@20 bar vs 4.39 €/kg_H2@20 bar), indicating that at the current price biogas is the more convenient choice.     

Steam reforming of methanol for ultra-pure H2 production in a membrane reactor: Techno-economic analysis

Process simulation and design as well as economic analysis were carried out to evaluate technical and economic feasibility of steam reforming of methanol in a membrane reactor (MR) for ultra-pure H₂ production. Using a commercial process simulator, Aspen HYSYS®, comparative studies were conducted to investigate the effect of operating conditions including the H₂ permeance (1 × 10⁻⁵ - 6 × 10⁻⁵ mol m⁻² s⁻¹ Pa⁻¹), a H₂O sweep gas flow rate (1–20 kmol h⁻¹), and a reaction temperature (448–493 K) in a conventional packed-bed reactor (PBR) and the MR using a previously reported reaction kinetics. Improved performances such as methanol conversions and H₂ yields were observed in the MR compared to the PBR and several design guidelines for the MR were obtained to develop H₂ separation membranes with optimal H₂ permeance and to select a suitable H₂O sweep gas flow rate. In addition, economic analysis based on itemized cost estimations was conducted for a small-sized H₂ fueling station by calculating a unit H₂ production cost for both the PBR and the MR reflecting a current economic status in Korea. As a result, a cost saving of about 23% was obtained in the MR (7.24 $ kgH₂⁻¹) compared to the PBR (9.37 $ kgH₂⁻¹) confirming the benefit of employing the MR for ultra-pure H₂ production.     

Production of H2 via sorption enhanced auto-thermal reforming for small scale Applications-A process modeling and machine learning study

Small scale production of H₂ via sorption enhanced auto-thermal reforming (SEATR) of methane is simulated using Ni based catalyst and CaO sorbent for the capturing of CO₂. One dimensional heterogeneous reactor model was developed using gPROMS model builder to study the performance of SEATR reactor. At low pressure mode, the process was evaluated for varying temperature, pressure, gas flux and steam to carbon ratio. Chemical equilibrium with application (CEA), an equilibrium based software was employed so as to compare both equilibrium and simulation results. Under a range of temperature (500–1000 K), pressure (1–10 bar), S/C ratio (1–6), and O/C ratio (0.2–0.6) close to equilibrium conditions, model outputs satisfactory results with regard to CH₄ conversion, CO₂ capturing, H₂ yield and purity. At 750 K, 2.9 bar, G_s of 0.4 kg/m² s, S/C of 3 and O/C of 0.45, H₂ purity and CH₄ conversion achieved was 97% and 94% respectively in comparison with 66% and 77% from conventional auto-thermal reforming. In Bayesian Regularization (BR), Mean square error(MSE) and R value is minimum for neural network algorithm comparison. It accounts for 1.2e⁻¹⁰ and 0.999 respectively. BR produces minimum error with increase in Epochs and gradients values highlighting maximum performance with optimize computation time for process modeling data-integration studies and generalization.     

Thermodynamic equilibrium analysis of combined carbon dioxide reforming with steam reforming of methane to synthesis gas

Thermodynamics equilibrium analysis of carbon dioxide reforming of methane combined with steam reforming to synthesis gas was studied by Gibbs free energy minimization method to understand the effects of process variables such as temperature, pressure and inlet CH₄/H₂O/CO₂ ratios on product distributions. For this purpose, the calculations were carried out at total pressures of 1 and 20 bar, and at ranges of temperature and steam-to-carbon ratios of 200–1200 °C and 0–0.50, respectively. The results revealed that carbon dioxide reforming of methane combined with steam reforming process was controlled by different reactions with regard to the operating temperature, pressure and varying feed compositions. The H₂/CO product ratio could be modified by changing the relative concentration of steam and CO₂ in the feed, temperature and pressure, depending on the downstream application.     

Integration of water electrolysis for fossil-free steel production

This study investigates the integration of water electrolysis technologies in fossil-free steelmaking via the direct reduction of iron ore followed by processing in an electric arc furnace (EAF). Hydrogen (H₂) production via low or high temperature electrolysis (LTE and HTE) is considered for the production of carbon-free direct reduced iron (DRI). The introduction of carbon into the DRI reduces the electricity demand of the EAF. Such carburization can be achieved by introducing carbon monoxide (CO) into the direct reduction process. Therefore, the production of mixtures of H₂ and CO using either a combination of LTE coupled with a reverse water-gas shift reactor (rWGS-LTE) or high-temperature co-electrolysis (HTCE) was also investigated. The results show that HTE has the potential to reduce the specific electricity consumption (SEC) of liquid steel (LS) production by 21% compared to the LTE case. Nevertheless, due to the high investment cost of HTE units, both routes reach similar LS production costs of approximately 400 €/tonne LS. However, if future investment cost targets for HTE units are reached, a production cost of 301 €/tonne LS is attainable under the conditions given in this study. For the production of DRI containing carbon, a higher SEC is calculated for the LTE-rWGS system compared to HTCE (4.80 vs. 3.07 MWh/tonne LS). Although the use of HTCE or LTE-rWGS leads to similar LS production costs, future cost reduction of HTCE could result in a 10% reduction in LS production cost (418 vs. 375 €/tonne LS). We show that the use of HTE, either for the production of pure H₂ or H₂ and CO mixtures, may be advantageous compared to the use of LTE in H₂-based steelmaking, although results are sensitive to electrolyzer investment costs, efficiencies, and electricity prices.     

H2 production by low pressure methane steam reforming in a Pd–Ag membrane reactor over a Ni-based catalyst: Experimental and modeling

Nowadays, there is a growing interest towards pure hydrogen production for proton exchange membrane fuel cell applications. Methane steam reforming reaction is one of the most important industrial chemical processes for hydrogen production. This reaction is usually carried out in fixed bed reactors at 30–40 bar and at temperatures above 850 °C. In this work, a dense Pd–Ag membrane reactor packed with a Ni-based catalyst was used to carry out the methane steam reforming reaction between 400 and 500 °C and at relatively low pressure (1.0–3.0 bar) with the aim of obtaining higher methane conversion and hydrogen yield than a fixed bed reactor, operated at the same conditions. Furthermore, the Pd–Ag membrane reactor is able to produce a pure, or at least, a CO and CO₂ free hydrogen stream. A 50% methane conversion was experimentally achieved in the membrane reactor at 450 °C and 3.0 bar whereas, at the same conditions, the fixed bed reactor reached a 6% methane conversion. Moreover, 70% of high-purity hydrogen on total hydrogen produced was collected with the sweep-gas in the permeate stream of the membrane reactor. From a modeling point of view, the mathematical model realized for the simulation of both the membrane and fixed bed reactors was satisfactorily validated with the experimental results obtained in this work.     

Methanol steam reforming in an Al2O3 supported thin Pd-layer membrane reactor over Cu/ZnO/Al2O3 catalyst

In this experimental study, a membrane reactor housing a composite membrane constituted by a thin Pd-layer supported onto Al₂O₃ is utilized to perform methanol steam reforming reaction to produce high-grade hydrogen for PEM fuel cell applications. The influence of various parameters such as temperature, from 280 to 330 °C, and pressure, from 1.5 to 2.5 bar, is analyzed. A commercial Cu/Zn-based catalyst is packed in the annulus of the membrane reactor and the experimental tests are performed at space velocity equal to 18,500 h⁻¹ and H₂O:CH₃OH feed molar ratio equal to 2.5:1. Results in terms of methanol conversion, hydrogen recovery, hydrogen yield and products selectivities are given. As a best result of this work, 85% of methanol conversion and a highly pure hydrogen stream permeated through the membrane with a CO content lower than 10 ppm were reached at 330 °C and 2.5 bar. Furthermore, a comparison between the experimental results obtained in this work and literature data is proposed and discussed.     

Comparative thermodynamic analysis of adsorption,membrane and adsorption-membrane hybrid reactor systems for methanol steam reforming

The thermodynamic analysis of steam reforming of methanol without and with fractional removal of H₂ and CO₂ in adsorption, membrane and adsorption-membrane hybrid reactor systems to produce fuel cell grade H₂ with minimal carbon formation is investigated. The results indicate that the removal of undesired CO₂ by CO₂ adsorbent is most effective process for the production of high purity H₂ than H₂ removal by membrane. However, the membrane is effective only above 30% H₂ removal. It is possible to obtain H₂ yield of 2.6 with negligibly small amount of CO and carbon formation at T = 405 K, P = 1 atm, 80% removal of CO₂ and 100% methanol conversion. Identical results are achieved even at lower temperature of 345 K in adsorption-membrane hybrid reactor system at 80% removal of H₂ and CO₂. Thus high grade H₂ can be produced by single step process and further processing to reduce CO by PROX reactor is not necessary.     

Low-carbon hydrogen production via electron beam plasma methane pyrolysis: Techno-economic analysis and carbon footprint assessment

Electron beam plasma methane pyrolysis is a hydrogen production pathway from natural gas without direct CO₂ emissions. In this work, two concepts for a technical implementation of the electron beam plasma pyrolysis in a large-scale hydrogen production plant are presented and evaluated in regards of efficiency, economics and carbon footprint. The potential of this technology is identified by an assessment of the results with the benchmark technologies steam methane reforming, steam methane reforming with carbon capture and storage as well as water electrolysis. The techno-economic analysis shows levelized costs of hydrogen for the plasma pyrolysis between 2.55 €/kg H₂ and 5.00 €/kg H₂ under the current economic framework. Projections for future price developments reveal a significant reduction potential for the hydrogen production costs, which support the profitability of plasma pyrolysis under certain scenarios. In particular, water electrolysis as direct competitor with renewable electricity as energy supply shows a considerably higher specific energy consumption leading to economic advantages of plasma pyrolysis for cost-intensive energy sources and a high degree of utilization. Finally, the carbon footprint assessment indicates the high potential for a reduction of life cycle emissions by electron beam plasma methane pyrolysis (1.9 kg CO₂ eq./kg H₂ – 6.4 kg CO₂ eq./kg H₂, depending on the electricity source) compared to state-of-the-art hydrogen production technology (10.8 kg CO₂ eq./kg H₂).     

Performance analysis of a membrane‐based reformer‐combustor reactor for hydrogen generation

Hydrogen is mostly produced in conventional steam methane reforming plants. In this work, we proposed a membrane‐based reformer‐combustor reactor (MRCR) for hydrogen generation in order to improve heat recovery and overall thermal efficiency. The proposed configuration will also reduce the complexity in existing steam methane reforming (SMR) plants. The proposed MRCR comprises combustion zone, hydrogen permeate zone, and SMR zone. A computational fluid dynamics model was developed using ANSYS‐Fluent software to simulate and analyze the performance of the proposed MRCR. Results show that high hydrogen yields were observed at high reformer pressures (RPs) and low gas hourly space velocities (GHSVs). Furthermore, by increasing the steam to methane ratio and addition of excess air in the combustion side, the hydrogen yield from the MRCR decreases. This is attributed to the reduction in the effective temperature of the hydrogen membrane. High RP, low GHSV, and low steam to methane ratio that increased the hydrogen yield also decreased carbon monoxide (CO) emissions. For an increased RP from 1 to 10 bar, the CO emission decreased by about 99%. The reduction in CO emission at high RP would be attributed to the effect of water gas shift reaction in the MRCR. Results of the extensive parametric study presented in this work can be used to determine the operating conditions based on tradeoffs between hydrogen yield (mole H₂/mole CH₄), hydrogen production rate (kg of H₂/h), allowable CO emissions, and exhaust gas temperature for other applications such as gas turbine.     

Carbon dioxide reforming of methane in a SrCe0.7Zr0.2Eu0.1O3−δ proton conducting membrane reactor

Utilizing CO₂ for fuel production holds the promise for reduced carbon energy cycles. In this paper we demonstrate a membrane reactor, integrating catalytic CO₂ reforming of methane with in-situ H₂ separation, that results in increased CO₂ and CH₄ conversion and H₂ production compared to a Ni catalyst alone. The tubular proton-conducting SrCe_0.7Zr_0.2Eu_0.1O_3−δ membrane reactor demonstrates that the addition of the membrane improves CO₂ conversion, due to in-situ H₂ removal, by 10% and 30% at 900 °C for CH₄/CO₂ = 1/1 and CH₄/CO₂/H₂O = 2/1/1 feed ratios, respectively. It also improves total H₂ production at 900 °C by 15% and 18% for CH₄/CO₂ = 1/1 and CH₄/CO₂/H₂O = 2/1/1, respectively. Further, the H₂/CO in the reactor side effluent can be adjusted for subsequent desired Fischer-Tropsch products by combining CO₂ reforming and steam reforming of methane.     

Pure hydrogen production via autothermal reforming of ethanol in a fluidized bed membrane reactor: A simulation study

In this paper the production of ultra-pure hydrogen via autothermal reforming of ethanol in a fluidized bed membrane reactor has been studied. The heat needed for the steam reforming of ethanol is obtained by burning part of the hydrogen recovered via the hydrogen perm-selective membrane thereby integrating CO₂ capture. Simulation results based on a phenomenological model show that it is possible to obtain overall autothermal reforming of ethanol while 100% of hydrogen can in principle be recovered at relatively high temperatures and at high reaction pressures. At the same operating conditions, ethanol is completely converted, while the methane produced by the reaction is completely reformed to CO, CO₂ and H₂.     

Thermodynamic analysis of a membrane-assisted chemical looping reforming reactor concept for combined H2 production and CO2 capture

There is great consensus that hydrogen will become an important energy carrier in the future. Currently, hydrogen is mainly produced by steam reforming of natural gas/methane on large industrial scale or by electrolysis of water when high-purity hydrogen is needed for small-scale hydrogen plants. Although the conventional steam reforming process is currently the most economical process for hydrogen production, the global energy and carbon efficiency of this process is still relatively low and an improvement of the process is key for further implementation of hydrogen as a fuel source. Different approaches for more efficient hydrogen production with integrated CO₂ capture have been discussed in literature: Chemical Looping Combustion (CLC) or Chemical Looping Reforming (CLR) and membrane reactors have been proposed as more efficient alternative reactor concepts relative to the conventional steam reforming process. However, these systems still present some drawbacks. In the present work a novel hybrid reactor concept that combines the CLR technology with a membrane reactor system is presented, discussed and compared with several other novel technologies. Thermodynamic studies for the new reactor concept, referred to as Membrane-Assisted Chemical Looping Reforming (MA-CLR), have been carried out to determine the hydrogen recovery, methane conversion as well as global efficiency under different operating conditions, which is shown to compare quite favorably to other novel technologies for H₂ production with CO₂ capture.     

Thermodynamic and experimental study of combined dry and steam reforming of methane on Ru/ ZrO2-La2O3 catalyst at low temperature

Analysis of the effect of adding small amounts of steam to the methane dry reforming feed on activity and products distribution was performed from thermodynamic equilibrium calculations of the system based on the Gibbs free energy minimization method. This analysis is supported by new insights from the direct experimental investigation of the influence of co-feeding with H₂O over a Ru/ZrO₂-La₂O₃ catalyst. Activity measurements were carried out in a fixed-bed reactor but using the operating conditions applicable in a Pd membrane reactor, that is, at maximum reaction temperature below 550 °C. Experimental results were in good agreement with thermodynamics predictions. It was observed that the addition of H₂O into the dry reforming feed strongly affects activity and products distribution. The co-feeding of steam resulted in increasing methane conversion and hydrogen yield but decreasing carbon dioxide conversion and carbon monoxide yield. At a given temperature, syngas composition (H₂/CO ratio) can be tuned by changing the amount of H₂O co-fed. Interestingly the stability of the Ru/ZrO₂-La₂O₃ catalyst was improved by adding steam to the dry reforming reactant mixtures.