Reforming system for co-generation of hydrogen and mechanical work

The paper describes a new design for a reforming system for converting hydrocarbon fuels into pure hydrogen. The system is based on an autothermal reforming (ATR) reactor operating at elevated pressures followed by membrane-based hydrogen separation. The high-pressure membrane discharge stream is combusted and expanded through a turbine generating additional power. Process simulation modeling illustrates the effect of pressure and other operating parameters on system performance and demonstrates a system reforming efficiency approaching 80%. When coupled with a PEM fuel cell and an electrical generator, fuel to electricity efficiency is above 40%. Other anticipated benefits of the system include compact size, simplicity in control and fast start up.     

Evaluation of a wind energy based system for co-generation of hydrogen and methanol production

A novel idea of wind energy based methanol and hydrogen production is proposed in this study. The proposed system utilizes the industrial carbon emissions to produce a useful output of methanol. There are several pros of manufacturing the methanol as it has the capability to be employed as conventional automotive fuel as it carries the advantages of efficient performance, low emissions and low flammability risk. The designed system comprises of the major subsystems of wind turbines, proton exchange membrane fuel cell (PEMFC), methanol production system and distillation unit. The Engineering Equation Solver (EES) and Aspen Plus are utilized for system modeling and comprehensive analysis. The proposed system is also investigated to operate under different wind speeds and different wind turbine efficiencies. The proposed integration covers all the electric power required by the system. The industrial flue gas including CO₂ reacts with hydrogen to produce methanol. The designed system produces both methanol and hydrogen simultaneously. For the performance indicator, efficiencies of the overall system are calculated. The exergetic efficiency is found to be 38.2% while energetic efficiency is determined to be 39.8%. Furthermore, some parametric studies are conducted to investigate the distillation column performance, methanol and hydrogen capacities and exergy destruction rates.     

Microwave-activated methanol steam reforming for hydrogen production

Methanol steam reforming (MSR) was carried out in a catalytic packed bed reactor under electrical and microwave heating using the two most common catalysts for this process-CuZnO/Al₂O₃ and PdZnO/Al₂O₃. Significant two-dimensional temperature gradients were found, especially in the latter case. Our results show that for the same average bed temperature, methanol conversion is higher under microwave heating (>10%). On the other hand, the product distribution is not affected by the heating mode. We demonstrate that even in cases where the maximum temperature along the entire height of the bed is significantly higher under electrical heating, conversion is either higher in the microwave case or approximately the same between the two heating modes. Finally, our experimental data indicate that a given methanol conversion can be achieved with lower net heat input to the reactor under microwave heating. This does not mean lower total energy consumption in the microwave process due to the limitations in the magnetron efficiency and the reflected power. However, it may be an implicit indication of higher temperature at metal sites than in bulk phase (microscale hot spot formation) due to the selective heating principle.     

Underwater vehicle hydrogen production from methanol steam reforming using hydrogen peroxide

Methanol steam reforming (MSR) can supply hydrogen (H₂) to underwater vehicles equipped with a fuel cell. Low reaction temperatures ensure the composition of the reformed gas suitable for the H₂ purification unit and increase the design freedom of a reforming plant. However, such temperatures decrease the catalyst activity and thereby the methanol (MeOH) conversion and H₂ production. Herein, hydrogen peroxide (H₂O₂) was supplied with MeOH and water (H₂O) to ensure sufficient MeOH conversion and H₂ production at low temperatures. A tube reactor loaded with a commercial Cu/Zn catalyst was installed in an electric furnace maintained at 200–250 °C, and MeOH and 0 wt%, 11.88 wt%, 22.51 wt%, and 32.07 wt% H₂O₂ were supplied. When the furnace temperature was 200 °C, the MeOH conversion was 49.3% at 0 wt% H₂O₂ but 93.5% at 32.07 wt% H₂O₂. The effect of adding H₂O₂ was greater under the temperature conditions where the MeOH conversion was 100% or less. To analyze the effect of H₂O₂ addition on catalyst durability, the furnace was maintained at 200 °C, and the reactor was continuously operated for 110 h with 0 wt% and 32.07 wt% H₂O₂. The addition of H₂O₂ did not significantly decrease the Cu/Zn catalyst durability.     

A methanol autothermal reforming system for the enhanced hydrogen production: Process simulation and thermodynamic optimization

Methanol autothermal reforming is a potential way to produce hydrogen that can be used for vehicle power batteries like PEMFC. Combining a reformer with a combustor to produce substantial hydrogen is promising, but the challenge of heat transfer efficiency between the reformer and combustor must be considered. Furthermore, the complexity of the system structure is not conducive to its large-scale operation level. In this paper, a novel methanol autothermal reforming hydrogen production system without catalytic combustion was built and developed, aiming to produce hydrogen-rich gas with low CO concentration. Process simulation and thermodynamic optimization on the target system were detailedly performed using Aspen Plus software and parameter sensitivity analysis methods. In addition, a methanol autothermal reforming hydrogen production system using catalytic combustion was taken as the reference system. The results indicated that the novel system could achieve a self-sustaining operation by the coupled methanol partial oxidation and steam reforming. And the product gas contained very low CO concentration (<10 ppm) due to the combined effects of water-gas shifting and CO preferential oxidation reactions. It was verified that under the maximal exergy efficiency condition, the exergy efficiency of the novel system is not significantly improved compared with the reference system, but the hydrogen yield is increased by about 27.65%, the thermal efficiency is increased by about 17.51%, and the exergy loss when generating unit molar H₂ is reduced by 20.53 kJ/mol; Under the condition of maximum hydrogen yield, the indicators of the novel system also perform better. Notably, the reformer is the main exergy loss source in the novel system, which provides a theoretical basis for further optimization of parameter configuration. This work will be beneficial to researchers who study the miniaturization design of the integrated system of methanol hydrogen production coupled vehicle power battery.     

On-board methanol catalytic reforming for hydrogen Production-A review

Hydrogen has become a versatile and clean alternative to meet increasingly urgent energy demands since its high heating value and renewability. However, considering the hazards of hydrogen storage and transport, in-situ production processes are drawing more attention. Among all the hydrogen carriers, methanol has become one of the research focuses due to its high H/C ratio, flexibility and sustainability. Regarded as the core of hydrogen supply system, catalysts with higher activity, selectivity and stability are continuously developed for improved efficiency. In this review, two groups of catalysts were investigated namely copper-based and group VIII metal-based catalysts. Not only macro indicators such as feedstock conversion and product selectivity, but also micro interaction and reaction mechanism were elaborated, with respect to the effects of promoters, supports, synthesis methods and binary metal components. Notably, several reaction pathways and catalysts deactivation mechanisms were suggested based on this series of inspection of the structure-reactivity relationship, along with a general perception that large surface area, well dispersed metals, small particle size and synergy effects significantly improve the catalytic performance. Accordingly, a novel concept of single-atom catalysts (SACs) was introduced aimed at efficient hydrogen production under more moderate conditions, by combining the advantages of heterogeneous and homogeneous catalysis. Additionally, an efficient reforming process is required by properly regulating the feed flow and heat flow through a coupled system. Conclusively, a thorough supply and demand network of hydrogen based on methanol was presented, giving an overview for on-board applications of hydrogen energy.     

Thermodynamic evaluation of methanol steam reforming for hydrogen production

Thermodynamic equilibrium of methanol steam reforming (MeOH SR) was studied by Gibbs free minimization for hydrogen production as a function of steam-to-carbon ratio (S/C = 0–10), reforming temperature (25–1000 °C), pressure (0.5–3 atm), and product species. The chemical species considered were methanol, water, hydrogen, carbon dioxide, carbon monoxide, carbon (graphite), methane, ethane, propane, i-butane, n-butane, ethanol, propanol, i-butanol, n-butanol, and dimethyl ether (DME). Coke-formed and coke-free regions were also determined as a function of S/C ratio.Based upon a compound basis set MeOH, CO₂, CO, H₂ and H₂O, complete conversion of MeOH was attained at S/C = 1 when the temperature was higher than 200 °C at atmospheric pressure. The concentration and yield of hydrogen could be achieved at almost 75% on a dry basis and 100%, respectively. From the reforming efficiency, the operating condition was optimized for the temperature range of 100–225 °C, S/C range of 1.5–3, and pressure at 1 atm. The calculation indicated that the reforming condition required from sufficient CO concentration (<10 ppm) for polymer electrolyte fuel cell application is too severe for the existing catalysts (T_r = 50 °C and S/C = 4–5). Only methane and coke thermodynamically coexist with H₂O, H₂, CO, and CO₂, while C₂H₆, C₃H₈, i-C₄H₁₀, n-C₄H₁₀, CH₃OH, C₂H₅OH, C₃H₇OH, i-C₄H₉OH, n-C₄H₉OH, and C₂H₆O were suppressed at essentially zero. The temperatures for coke-free region decreased with increase in S/C ratios. The impact of pressure was negligible upon the complete conversion of MeOH.     

A high-performance PdZn alloy catalyst obtained from metal-organic framework for methanol steam reforming hydrogen production

Methanol steam reforming (MSR) is deemed to be an effective way for hydrogen production and Pd/ZnO catalyst were found to exhibit high activity in this reaction. However, their activities are strongly related to the preparations methods. In most cases, these catalysts are synthesized by impregnation or co-precipitation methods, aiming to change the dispersion and stability of Pd nanoparticle to get better performance. Here we report an efficient Pd/ZnO catalyst that was synthesized with zeolitic imidazolate framework-8 (ZIF-8) as the precursor, on which Pd ions was supported after NaHB₄ reduction. Typically, when the catalyst reduced at 300 °C for 2 h, the methanol conversion could reach 97–98% and the CO₂ selectivity is around 86.3% under the reaction condition of 0.1 MPa, water/CH₃OH = 1.2:1 (mol ratio), WHSV_methanol = 43152ml/g_cat*h, catalyst = 0.1 g, our catalyst was found to show much better performance than other Pd@ZnO catalysts prepared by other methods, especially in terms of selectivity which is particularly important for hydrogen fuel cell application considering that Pt electrode could be poisoned by even trace amount of CO. It turned out that the large surface area, enough holes, evenly distributed PdZn alloy activity sites and abundant oxygen vacancies lead to the overall excellent performance of our catalyst.     

Prediction of selling price of hydrogen produced from methanol steam reforming

Hydrogen is a clean energy carrier. However, it is not naturally available and should be supplied from other organic materials such as biomass or other chemicals such as dimethyl ether. In this article, we estimated the selling price of hydrogen produced by methanol steam reforming and evaluated the effect of some influential factors on selling price using Aspen Plus. Validation process showed that the model and experimental results well agree with each other, especially in high temperatures where reaching equilibrium is followed more rapidly. Similar to temperature, pressure can directly affect the economics of methanol synthesis. As pressure increases from 5 atm to 20 atm, selling price decreases.     

A 75-kW methanol reforming fuel cell system

A 75-kW methanol reforming fuel cell system, which consists of a fuel cell system and a methanol auto-thermal reforming fuel processor has been developed at Dalian Institute of Chemical Physics, Chinese Academy of Sciences (CAS). The core of the fuel cell system is a group of CO tolerant PEMFC stacks with a double layer composite structured anode. The fuel cell stacks show good CO tolerance even though 140 ppm CO was present in the reformate stream during transients. The auto-thermal reforming (ATR) fuel cell processor could adiabatically produce a suitable reformate without external energy consumption. The output of hydrogen-rich reformate was approximately 120 N m³ h⁻¹ with a H₂ content near 53% and the CO concentrations generally were under 30 ppm. The fuel cell system was integrated with the methanol reforming fuel processor and the peak power output of the fuel cell system exceeded 75 kW in testing. The hydrogen utilization approached 70% in the fuel cell system.     

Effect of microwave double absorption on hydrogen generation from methanol steam reforming

Hydrogen generation from steam reforming of methanol (SRM) with a CuO/ZnO/Al₂O₃ catalyst was investigated in the study; particular emphasis was placed on the reactions of SRM exposed to an environment with microwave irradiation. By virtue of the double absorption of microwaves by both the reagents and the catalyst, the experiments suggested that the SRM could be heated and triggered rapidly within a short time, and the methanol conversion from SRM with microwave heating was high compared to that with conventional heating. The obtained results also indicated that, when the reaction temperature was as high as 250 °C, thermodynamic equilibrium governed the SRM, whereas the reaction was kinetically controlled for the temperature lower than 250 °C. Contrary to Le Châtelier's principle, it was noted that an increase in S/C ratio decreased methanol conversion. This can be explained by the fact that water absorbs microwave irradiation stronger than methanol. The performance of the SRM was evaluated based on the carbon conservation method and the nitrogen tracer method. It was found that the latter was also capable of providing an accurate prediction on methanol conversion, even though the flow rate of the product gas was not measured.     

Trapezoidal cavity for high reforming temperature performance of auto-thermal methanol steam reforming micro-reactor for hydrogen production

To realize high reforming temperature performance of auto-thermal methanol steam reforming micro-reactor (ATMSRM) for hydrogen production (HP) and enhance its long-term HP performance, a trapezoidal cavity on methanol steam reforming (MSR) chamber plate is proposed. A numerical simulation model of the ATMSRM for HP is built. The influence of different geometric sizes of the trapezoidal cavity on reforming temperature performance of ATMSRM is investigated by the numerical simulation model. The reforming temperature performance and HP performance of ATMSRMs using the optimal trapezoidal cavity, the combustion reaction support (CRS) with optimal multiple micro-channels and the non-optimization are compared. The reforming temperature performance and HP performance of the size-enlarged ATMSRM with the optimal trapezoidal cavity are also studied. The results show that compared to other trapezoidal cavities, reforming temperature difference per 1 °C (△TA) of the ATMSRM using the F-type trapezoidal cavity with 50 mm length, 76 mm width, 0.4 mm front end depth and 0.2 mm back end depth is smaller, which is 0.01709 °C °C^?1 under 0.9 mL/min combustion methanol injection rate and 4 mL/h reforming methanol-water mixture injection rate. Compared with ATMSRMs using the CRS with optimal multiple micro-channels and the non-optimization, ATMSRM using F-type trapezoidal cavity has a better comprehensive HP performance. Compared with non-enlarged ATMSRM using F-type trapezoidal cavity, size-enlarged ATMSRM using F-type trapezoidal cavity has bigger △TA, larger reforming methanol conversion rate, higher hydrogen yield and more carbon monoxide selectivity. This research work offers a new method for enhancing reforming temperature performance of ATMSRM for HP.     

Robust multi-objective optimization of methanol steam reforming for boosting hydrogen production

Methanol steam reforming (MSR) has been considered as a promising method for producing pure hydrogen in recent decades. A comprehensive two-dimensional steady-state mathematical model was developed to analyze the MSR reactor. To improving high purity hydrogen production, a triple-objective optimization of the MSR reactor is performed. Non-dominated Sorting Genetic Algorithm-II (NSGA-II) is employed as a robust optimization approach to maximize the three objectives, termed as, methanol conversion, CO selectivity, and H₂ selectivity. The Pareto optimal frontier has also been provided and the ultimate solution of the Pareto front has been found by the three decision-making methods (TOPSIS, LINMAP, and Shannon's Entropy). Among the three distinct decision-making approaches, LINMAP presents better results according to the deviation index parameter. It has been shown that a perfect agreement is available between the plant and simulation data. Operating under the optimum values based on the LINMAP method confirms an almost 47.04% enhancement of H₂ mass fraction compared to the conventional industrial MSR reactor. The predicted results advocate that the key superiority of the optimized-industrial reactor is the remarkable higher production rate of hydrogen compared to the conventional MSR reactor which makes optimized-industrial reactor both feasible and beneficial.     

Experiments on hydrogen production from methanol steam reforming in fluidized bed reactor

A novel approach for the hydrogen production which integrated methanol steam reforming and fluidized bed reactor (FBR) was proposed. The reaction was carried out over Cu/ZnO/Al₂O₃ catalysts. The critical fluidized velocities under different catalyst particle sizes and masses were obtained. The influences of the operating parameters, including that of H₂O-to-CH₃OH molar ratio, feed flow rate, reaction temperature, and catalyst mass on the performance of methanol steam reforming were investigated in FBR to obtain the optimum experimental conditions. More uniform temperature distribution, larger surface volume ratio and longer contacting time can be achieved in FBR than that in fixed bed reactor. The results indicate that the methanol conversion rate in FBR can be as high as 91.95% while the reaction temperatures is 330 °C, steam-to-carbon molar ratio is 1.3, and feed flow rate is 540 ml/h under the present experiments, which is much higher than that in the fixed bed.     

Experiments on hydrogen production from methanol steam reforming in the microchannel reactor

The entire experiments were conducted for microchannel methanol steam reforming, by which, the selection of catalyst, the operating parameters and the configuration of microchannels were discussed thoroughly. It was found that the higher the Cu concentration is, the more the corresponding active surface area of Cu will be, thereby improving the catalytic activity. The Cu-to-Zn ratio in Cu/ZnO/Al₂O₃ catalyst should be set at 1:1. The impacts of reaction temperature, feed flow rate, mixture temperature, and H₂O-to-CH₃OH molar ratio on the methanol conversion rate were also revealed and discussed. Characteristics of micro-reactors with various microchannels, including that 20 mm and 50 mm in length, as well as non-parallel microchannels, were investigated. It was found that the increase of microchannel length can improve the methanol conversion rate significantly. Besides, non-parallel microchannels help to maintain flow and temperature distribution uniformity, which can improve the performance of micro-reactor. In the present experiments, the presence of CO was under the condition that the methanol conversion rate was above 70%.     

Progress on methanol reforming technologies for highly efficient hydrogen production and applications

With the continuous development of human society, the shortages of fossil resource and environmental pollution are increasingly prominent. Hydrogen is a clean and efficient alternative energy, among various hydrogen production technologies, methanol reforming has been regarded as a promising candidate to produce hydrogen for daily energy supply due to its low cost and safe transportation. In this review, we discuss the sources of methanol and the methods of methanol reforming for hydrogen production. Then, we focus on the catalysts for methanol reforming and their preparation methods. Particular attention is paid to the structural design and manufacturing process to make methanol reforming microreactors. We also summarize recent studies on the practical applications of methanol reforming technologies, as well as the capture and utilization of the generated carbon to reduce its emission. Finally, the prospect challenges of methanol reforming for highly efficient hydrogen production technologies and contribution to the “double carbon” goals and the challenges are discussed. In summary, this review will be conducive to the development of hydrogen-methanol economy for practical and industry applications.     

An investigation of a stratified catalyst bed for small-scale hydrogen production from methanol autothermal reforming

This research project explored a methanol reforming system using a stratified catalyst bed. Commercially available catalysts were used within a single reactor and the system was run autothermally (fuel, steam and oxidizer). The investigation explored the fuel conversion and reactor temperature profile at various O₂/CH₃OH ratios. The experiments showed that the stratified system had fairly high conversions at low O₂/CH₃OH ratios. Additionally, it showed high selectivity towards hydrogen, and low selectivity for carbon monoxide. The experimental results gathered show a promising use of stratified catalyst beds for small-scale reforming systems.     

Thermal behavior and hydrogen production of methanol steam reforming and autothermal reforming with spiral preheating

The present study aims to investigate the thermal behavior and hydrogen production characteristics from methanol steam reforming (MSR) and autothermal reforming (ATR) under the effects of a Cu-Zn-based catalyst and spiral preheating. Two different reaction temperatures of 250 and 300 °C are taken into account. Meanwhile, the O/C ratio (i.e. the molar ratio between O₂ and methanol) and S/C ratio (i.e. the molar ratio between steam and methanol) are controlled in the ranges of 0-0.5 and 1-2, respectively. The condition of O/C = 0 represents the reaction of MSR. By monitoring the supplied power into the reactor with a fixed gas hourly space velocity (GHSV) of 72,000 h⁻¹, the experimental results indicate that an exothermic reaction from ATR can be attained once the O/C ratio is as high as 0.125. Increasing O/C ratio causes more heat released from the reaction, this results in the decrease in the frequency of supplied power, especially at O/C = 0.5. It is noted that the concentration of CO in the product gas is quite low compared to that of CO₂. An increase in O/C ratio abates the concentration of H₂ from the consumption of per mol methanol; however, the H₂ yield in terms of thermodynamic analysis is increased. On account of the utilization of spiral preheating on the reactants, within the investigated operating conditions the methanol conversion and hydrogen yield were always higher than 95 and 90%, respectively. A comparison suggests that the methanol conversion from ATR of methanol with spiral preheating is superior to those of other studies.     

Thermal management of methanol reforming reactors for the portable production of hydrogen

Three-dimensional numerical simulations were performed to address the thermal management issues associated with the design of a methanol reforming microchannel reactor for the portable production of hydrogen. The design of the reactor was fundamentally related to the direct coupling of reforming and combustion reactions by performing them on opposite sides of dividing walls in a parallel flow configuration. Effective autothermal operation was achieved through a combination of microchannel reactor technology with heat exchange in a direction perpendicular to the reacting fluid flow. Computational fluid dynamics simulations and thermodynamic analysis were carried out to investigate the effect of various design parameters on the characteristics of the generation, consumption, and exchange of thermal energy within the system. The results indicated that the ability to control temperature and temperature uniformity is of great importance to the performance of the system. The degree of temperature uniformity favorably affects the autothermal operation of the reactor. Temperature uniformity of the reactor can be improved by controlling the rate of heat transfer through a variety of factors such as wall thermal conductivity, fluid velocities, and dimensions. High wall thermal conductivity would be greatly beneficial to the performance of the system and the temperature uniformity of the reactor.