Conventional Steam Reforming Research Articles

Green hydrogen production from biomass – A thermodynamic assessment of the potential of conventional and advanced bio-oil steam reforming processes

Steam reforming of bio-oil derived from biomass pyrolysis is one of the most promising methods for the production of green hydrogen with minimal carbon footprint. In this context, this work investigates the thermodynamic potential of hydrogen production from bio-oil steam reforming. Four routes – conventional steam reforming (CSR) and three advanced reforming processes – sorption-enhanced steam reforming (SESR), chemical looping steam reforming (CLSR) and sorption-enhanced chemical looping steam reforming (SE-CLSR) - were modeled for this purpose. Bio-oil was modeled as a complex mixture of model compounds belonging to all major oxygenate families in order to have a closer resemblance with raw bio-oil. CaO was selected as the sorbent, while NiO was selected as oxygen carrier. Furthermore, the effect of process parameters such as steam to carbon, sorbent to carbon, oxygen carrier to carbon ratios, and reforming temperature was explored. H2 purity and yield along with energy demand, served as the parameters for comparing the performance of the four processes. SESR provided the highest H2 yield (0.216 kgH2 kgBio-oil−1) among all the processes under optimum conditions along with a purity greater than 99 %. CLSR, meanwhile, had the lowest H2 yield and purity (0.178 kgH2 kgBio-oil−1 and 64.6 %, respectively). The combined SE-CLSR process had H2 yield greater than both CSR and CLSR (0.197 kgH2 kgBio-oil−1) and a H2 purity greater than 99 %. High in-situ heat generation was noted in the reforming reactor for both SESR and SE-CLSR, pointing towards a good potential for auto-thermal operation. Overall, SE-CLSR process is a highly intensified process with substantially lower energy requirements than all the other processes. The results highlight that by combining CO2-sorption and chemical looping with traditional reforming, H2 can be obtained in higher yields and purity and lower energy consumption.

Environmental performance of nonthermal plasma dry and conventional steam reforming of methane for hydrogen production: Application of life cycle assessment methodology

The environmental performance of nonthermal plasma assisted dry reforming of methane (NTP-DRM) for hydrogen production from methane rich natural gas is investigated and compared with the current state of the art steam reforming technology through a cradle-to-gate life cycle assessment (LCA). The NTP-DRM technologies studied in this analysis include dielectric barrier, microwave, and pulsed plasma discharges. Due to the level of technology the study is considered as the prospective LCA of selected types of NTP-DRMs for hydrogen production. Of these, the NTP-DRM using microwave and pulsed plasma presented better environmental performance. The impact categories include midpoints levels applying TRACI 2.1 and AWARE for the water scarcity, using ecoinvent 3.8 and US NETL databases. The scenario analysis regarding carbon dioxide, electricity, and natural gas sources, revealed the highly dependency of NTP-DRMs technologies environmental performance to the energy efficiency of the processes. In terms of steam reforming of methane (SRM) despite the main contribution of steam use in the technology environmental performance, the uncertainty analysis showed higher sensitivity to natural gas input. Investigation showed that using renewable energy sources can have significant improvement regarding NTP-DRMs environmental performance and specifically global warming potential. Accordingly, at their current reactant conversion and product selectivity reaching the energy use of eV per molecule of reactant equal or less than 2, can be a proper target for the studied best case NTP-DRM to make their environmental behavior competitive with the state-of-the-art SRM technologies.

Emerging Copper-Based Semiconducting Materials for Photocathodic Applications in Solar Driven Water Splitting

Hydrogen production through solar-driven water splitting is a promising approach and an alternative to the conventional steam reforming of natural gas and coal gasification. The growing energy demand and environmental degradation through carbon-emitting fossil fuels urge a transition in the usage of non-renewable to renewable sources of energy. The photocathodes in a photoelectrochemical (PEC) water-splitting cell are essential for the direct evolution of hydrogen. Among the known photocathodes, Cu-based p-type semiconducting materials are the most promising photo-absorber materials owing to their low-cost, low toxicity, natural abundance, suitable bandgaps, and favorable band edges for reduction. Moreover, the chemical stability and the rate of recombination significantly limit the longevity, the PEC performance, and practical applicability of Cu-based photocathodes. To overcome these problems, it is critical to have a thorough understanding of the constraints, improvement strategies, and an assessment of current developments in order to construct and design highly stable and efficient photocathodes. Here, in this review we have summarized the development of Cu-based metal oxide and sulfide photocathodes with the significant operational challenges and strategies that have successfully been employed to enhance the PEC performance. Furthermore, the emphasis is placed on recent reports and future perspectives regarding emerging challenges.

Advanced Steam Reforming of Bio-Oil with Carbon Capture: A Techno-Economic and CO2 Emissions Analysis

A techno-economic analysis has been used to evaluate three processes for hydrogen production from advanced steam reforming (SR) of bio-oil, as an alternative route to hydrogen with BECCS: conventional steam reforming (C-SR), C-SR with CO2 capture (C-SR-CCS), and sorption-enhanced chemical looping (SE-CLSR). The impacts of feed molar steam to carbon ratio (S/C), temperature, pressure, the use of hydrodesulphurisation pretreatment, and plant production capacity were examined in an economic evaluation and direct CO2 emissions analysis. Bio-oil C-SR-CC or SE-CLSR may be feasible routes to hydrogen production, with potential to provide negative emissions. SE-CLSR can improve process thermal efficiency compared to C-SR-CCS. At the feed molar steam to carbon ratio (S/C) of 2, the levelised cost of hydrogen (USD 3.8 to 4.6 per kg) and cost of carbon avoided are less than those of a C-SR process with amine-based CCS. However, at higher S/C ratios, SE-CLSR does not have a strong economic advantage, and there is a need to better understand the viability of operating SE-CLSR of bio-oil at high temperatures (>850 °C) with a low S/C ratio (e.g., 2), and whether the SE-CLSR cycle can sustain low carbon deposition levels over a long operating period.

Blends of bio-oil/biogas model compounds for high-purity H2 production by sorption enhanced steam reforming (SESR): Experimental study and energy analysis

• SESR of bio-oil/biogas blends leads to renewable high-purity H 2 production. • H 2 yield of 87.1% is experimentally obtained at 625 °C and 2.5 bar. • H 2 purity of 98.6 vol% is achieved at 625 °C and 2.5 bar. • Higher temperature and steam/C molar ratio, but lower pressure, favor H 2 production. • Biogas addition increases the energy efficiency of the bio-oil SESR process by 1.34%. H 2 production by sorption enhanced steam reforming (SESR) of bio-oil/biogas blends was demonstrated in a fluidized bed reactor. It combines steam reforming (SR) with simultaneous CO 2 capture by a solid sorbent. SESR was performed on a Pd/Ni-Co catalyst derived from a hydrotalcite-like material (HT) using dolomite as CO 2 sorbent. Bio-oil from fast pyrolysis of biomass is a carbon–neutral and renewable energy source with great potential for clean H 2 production by steam reforming processes. Biogas is also a promising renewable bio-based resource for hydrogen generation that can be used to increase the H 2 production of a biomass-based plant. In turn, it could improve the energy efficiency of the process due to the exothermic reaction of the CO 2 contained in biogas with the sorbent. Bio-oil composed of acetic acid and acetone (1/1 mol/mol) and biogas composed of CH 4 and CO 2 (60/40 vol%) were used as fuels. They were blended (50 wt% bio-oil + 50 wt% CH 4 ) to study the SESR process. Effects of temperature, steam/C molar ratio, and pressure on the process performance were evaluated. SESR results showed an effective reforming of bio-oil/biogas blends and an enhancement in the H 2 production and fuel conversion compared to conventional SR. Higher temperature and steam/C ratio, but lower pressure, favored H 2 yield and purity. High H 2 yield (87.1%) and H 2 purity (98.6 vol%) were obtained at 625 °C and 2.5 bar (steam/C molar ratio three times higher than the stoichiometric value). The thermodynamic energy analysis of the SESR of bio-oil/biogas blends rendered 1.34% higher cold gas efficiency (CGE) than bio-oil SESR.

Optimization of two bio-oil steam reforming processes for hydrogen production based on thermodynamic analysis

Thermodynamics of hydrogen production from conventional steam reforming (C-SR) and sorption-enhanced steam reforming (SE-SR) of bio-oil was performed under different conditions including reforming temperature, S/C ratio (the mole ratio of steam to carbon in the bio-oil), operating pressure and CaO/C ratio (the mole ratio of CaO to carbon in the bio-oil). Increasing temperature and S/C ratio, and decreasing the operating pressure were favorable to improve the hydrogen yield. Compared to C-SR, SE-SR had the significant advantage of higher hydrogen yield at lower desirable temperature, and showed a significant suppression for carbon formation. However excess CaO (CaO/C > 1) almost had no additional contribution to hydrogen production. Aimed to achieve the maximum utilization of bio-oil with as little energy consumption as possible, the influences of temperature and S/C ratio on the reforming performance (energy requirements and bio-oil consumption per unit volume of hydrogen produced, QD/H2 (kJ/Nm3) and YBio-oil/H2 (kg/Nm3)) were comprehensively evaluated using matrix analysis while ensuring the highest hydrogen yield as possible. The optimal operating parameters were confirmed at 650 °C, S/C = 2 for C-SR; and 550 °C, S/C = 2 for SE-SR. Under their respective optimal conditions, the YBio-oil/H2 of SE-SR is significant decreased, by 18.50% compared to that of C-SR, although the QD/H2 was slightly increased, just by 7.55%.

Hydrogen production via chemical looping dry reforming of methane: Process modeling and systems analysis

AbstractThe present study presents and analyses a family of “chemical looping dry reforming” (CLDR) processes that produce inherently separated syngas (H2 and CO) streams via a combination of methane cracking in a “cracker reactor” and the Boudouard reaction (i.e., conversion of the formed carbon with CO2 to CO) in a “CO2 reactor,” and then further maximize the H2 yield via conversion of the produced CO via water‐gas‐shift. Remaining CO2 emissions are minimized via CO2 capture and sequestration. Four different configurations are evaluated which differ in how the heat required for the highly endothermic dry reforming reaction is supplied: (i) combustion of additional CH4 feed (CLDR‐CH4); (ii) combustion of some of the CO produced in the CO2 reactor (CLDR‐CO); and combustion of some of the carbon produced in the cracker reactor with (iii) pure oxygen (CLDR‐C‐oxy); or (iv) with air (CLDR‐C‐air). Process models are developed to comparatively analyze the mass and energy balances of these configurations, and benchmark them against H2‐production via conventional dry reforming and steam reforming of methane. Our results show that CLDR‐C‐oxy is the most promising H2‐production pathway among the chemical looping and conventional technologies both in terms of chemical energy efficiency and in terms CO2 emissions. Thus, the unique flexibility offered by the production of inherently separated syngas streams in CLDR enables overcoming the disadvantage of the strongly endothermic dry reforming reaction by combusting carbon internally in the reactor and thus achieving highly effective heat integration. Overall, the results support the technical viability and demonstrate the promise for strong process intensification of CLDR compared to conventional dry reforming and even steam reforming, the most widely used H2‐production pathway to‐date.

Optimisation of syngas production from a novel two-step chemical looping reforming process using Fe-dolomite as oxygen carriers

The production of syngas from hydrogen carbon feedstocks such as natural gas and biomass is of high importance to the chemical industry. In conventional chemical looping steam reforming(CLSR), the composition of the syngas produced is limited by the chemical equilibrium of the water-gas-shift reaction. In this study, we demonstrate that a two-step chemical looping reforming (TS-CLR) process is capable of alleviating the equilibrium limit to produce syngas of higher CO and H2 contents. For example, the total mole fraction of H2 and CO in the syngas produced from the conventional CLSR of toluene at 900 °C is limited to below 89.4 vol% (dry basis), whereas TS-CLR could produce syngas with >94 vol% of CO and H2 under the same condintions. The TS-CLR process is best carried out in a bed of Fe-dolomite oxygen carriers with a Ca:Fe ratio of 1:1 (denoted as C1F1). Compared to the pure Ca2Fe2O5 and Fe2O3/Al2O3 oxygen carriers, the C1F1 affords improvements in syngas yield, carbon conversion and syngas purity. The superior performance of C1F1 is attributed to the promotion of the lattice oxygen activities of Ca2Fe2O5 by MgO, as well as its excellent phase reversibility over redox cycles.

Elevated-temperature bio-ethanol-assisted water electrolysis for efficient hydrogen production

Steam electrolysis over solid oxide electrolysis cells (SOECs) is a promising technique to store renewable power (such as solar and wind power) into hydrogen, and bio-ethanol-assisted steam electrolysis not only increases energy conversion efficiency but also store bio-mass energy into valuable fuels. This study developed SOEC-type reactors for conducting ethanol-assisted water electrolysis for the first time. Conventional catalytic steam reforming of ethanol for hydrogen production consumes a lot of heat and includes a complicated process, while the ethanol-assisted water electrolysis can achieve thermoneutral operation at the electrolysis potential of 0.36 V and generate heat at the electrolysis potentials of above 0.36 V, simultaneously obtaining pure hydrogen from cathode chamber by one step. Micro-reformer constructed by loading fibrous catalysts within channeled anode supports performed efficient ethanol reforming to facilitate fuel oxidation on anode and hence promote steam electrolysis on cathode. Employing Ni-based materials for both anode and cathode enables the co-sintering of three layers of SOEC components, resulting in low cell resistances and stable electrolysis at a record high current density of 3.0 A cm−2 under a low overall cell voltage of less than 1.3 V. Therefore, this study has demonstrated an efficient way to generate green hydrogen energy from renewables.

How to give a renewed chance to natural gas as feed for the production of hydrogen: Electric MSR coupled with CO2 mineralization

Recent years have seen a growing interest in water electrolysis as a way to store renewable electric energy into chemical energy, through hydrogen production. However today the share of renewable energy is still limited and there is the need to have a continuous use of H2 for industrial chemicals applications. Firstly the paper discusses the use of electrolysis - connected to a conventional grid - for a continuous H2 production in terms of associated CO2 emissions and compares such emissions with conventional methane steam reforming (MSR). Therefore, it explores the possibility to use electrical methane steam reforming (eMSR) as a way to reduce the CO2 emissions. As a way to have zero emissions, carbon mineralization of CO2 is coupled - instead of in-situ carbon capture and storage technology (CCS) - to eMSR; associated relevant cost of production is evaluated for different scenarios. It appears that to minimize such production cost, carbonate minerals must be reused in the making of other industrial products, since the amount of carbonates generated by the process is quite significant.

Optimal design of large-scale solar-aided hydrogen production process via machine learning based optimisation framework

Hydrogen is an important energy carrier in the transportation sector and an essential industrial feedstock for petroleum refineries, methanol, and ammonia production. Renewable energy sources, especially solar energy have been investigated for large-scale hydrogen production in thermochemical, electrochemical, or photochemical manners due to considerable greenhouse gas emissions from the conventional steam reforming of natural gas and oil-based feedstock. The solar steam methane reforming using molten salt (SSMR-MS) is superior due to its unlimited operation hours and lower total annualized cost (TAC). In this work, we extend the existing optimisation framework for optimal design of SSMR-MS in which machine learning techniques are employed to describe the relationship between solar-related cost and molten salt heat duty and establish relationships of TAC, hydrogen production rate and molten salt heat duty with independent input variables in the whole flowsheet based on 18,619 sample points generated using the Latin hypercube sampling technique. A hybrid global optimisation algorithm is adopted to optimise the developed model and generate the optimal design, which is validated in SAM and Aspen Plus V8.8. The computational results demonstrate that a significant reduction in TAC by 14.9 % ~ 15.1 %, and CO2 emissions by 4.4 % ~ 5.2 % can be achieved compared to the existing SSMR-MS. The lowest Levelized cost of Hydrogen Production is 2.4 $ kg−1 which is reduced by around 17.2 % compared to the existing process with levelized cost of 2.9 $ kg−1.

Influence of Cs Promoter on Ethanol Steam-Reforming Selectivity of Pt/m-ZrO2 Catalysts at Low Temperature

The decarboxylation pathway in ethanol steam reforming ultimately favors higher selectivity to hydrogen over the decarbonylation mechanism. The addition of an optimized amount of Cs to Pt/m-ZrO2 catalysts increases the basicity and promotes the decarboxylation route, converting ethanol to mainly H2, CO2, and CH4 at low temperature with virtually no decarbonylation being detected. This offers the potential to feed the product stream into a conventional methane steam reformer for the production of hydrogen with higher selectivity. DRIFTS and the temperature-programmed reaction of ethanol steam reforming, as well as fixed bed catalyst testing, revealed that the addition of just 2.9% Cs was able to stave off decarbonylation almost completely by attenuating the metallic function. This occurs with a decrease in ethanol conversion of just 16% relative to the undoped catalyst. In comparison with our previous work with Na, this amount is—on an equivalent atomic basis—just 28% of the amount of Na that is required to achieve the same effect. Thus, Cs is a much more efficient promoter than Na in facilitating decarboxylation.

Nickel supported ZIF-8.PEG modified catalyst: A designed active catalyst with high H2 productivity in steam reforming of ethanol at moderate temperature

Steam reforming of renewable ethanol at moderate temperatures is an attractive alternative for hydrogen production than conventional steam reforming of natural gas which is only feasible at very high temperatures (>650 ℃). Formulating a catalyst for this reaction with ideally dispersed metallic active phase can reduce the activation energy and enhance the activity at moderate temperatures. With this purpose in mind, ZIF-8 with high specific surface area has been nominated as catalytic support in this survey for the dispersion of nickel nanoparticles. The support compositional and interfacial properties were further modified by polyethylene glycol (PEG) to prepare an ideal support with high activity at moderate temperatures. Pristine and modified samples were comparatively characterized by XRD, TGA, BET, FTIR, TEM, FESEM, EDS, AAS, H2-TPR and NH3-TPD analyses and catalytically evaluated at 400–450 ℃. TPR profiles of catalysts have demonstrated notable differences in the reduction temperature and quantity of metallic centers which have directly affected the catalytic activity. Lower reduction temperature and higher number of metallic centers were observed for Ni/ZIF-8. PEG which has originated from the tuned interface i.e. high accessibility of nickel centers with highly exposed flower-like structure and lower strength of support/active phase interaction. Thus, Ni/ZIF-8. PEG has revealed considerable improvement in terms of ethanol conversion and H2 yield. At 450 °C, the average H2 yield employing Ni/ZIF-8. PEG catalyst reached 52.6% which was about 16% and 46% higher than those observed by Ni/ZIF-8 and conventional Ni/Al2O3, respectively. Moderate acidity of the ZIF-8. PEG, higher reducibility of active phase and suitable interfacial interactions have resulted in better performance of this catalyst.

High-purity hydrogen production by sorption-enhanced methanol steam reforming over a combination of Cu–Zn–CeO2–ZrO2/MCM-41 catalyst and (Li–Na–K) NO3·MgO adsorbent

In this study, sorption-enhanced methanol steam reforming (SEMSR) was applied to generate high-purity hydrogen. The mesoporous MCM-41 as support and CuO, ZnO, CeO2, ZrO2 as active agents and promoters were employed for the catalyst preparation. In addition, (Li–Na–K) NO3·MgO as a CO2 adsorbent was prepared by the wet mixing method. The fresh and used catalysts were characterized by XRD, BET, FTIR, FESEM, TEM, H2-TPR and TGA analyses. Also, the CO2 sorbent was studied by XRD, BET, FESEM, TEM and TGA analyses before and after the reaction. The SEMSR performances of the synthesized catalyst and adsorbent were evaluated experimentally in a fixed-bed reactor. The effect of various conditions such as temperature, WHSV, feed molar ratio and sorbent/catalyst ratio were investigated. The best results were obtained at 300 °C, a feed molar ratio (water/methanol) of 2:1, a WHSV of 1.62 h−1, and the sorbent/catalyst ratio of 8:1, which produced 99.8% hydrogen, 25% more than the hydrogen production during conventional methanol steam reforming. Moreover, the cyclic stability of the catalyst and the sorbent was studied for 10 cycles.

On the effect of biogas composition on the H2 production by sorption enhanced steam reforming (SESR)

Abstract Biogas is a valuable source of renewable energy produced from biodegradable organic materials via anaerobic digestion. The production of H2 by sorption enhanced steam reforming (SESR) of biogas has been studied thermodynamic and experimentally. A Pd/Ni–Co catalyst and dolomite as CO2 sorbent were used. The effect of biogas composition (CH4/CO2 vol%) on the process was evaluated at 600 and 650 °C in a fluidized bed reactor using biogas CO2 concentrations of 5–50 vol%. During conventional biogas steam reforming (SR), high CH4 partial pressures in the feed favor the process, producing high H2 concentrations. During biogas SESR, CO2 was effectively removed from the gas phase by the sorbent for all the biogas compositions, and it did not alter the process compared to pure methane. Steam methane reforming (SMR) and water-gas shift (WGS), together with carbonation, were the main reactions occurring during biogas SESR. Dry (or CO2) methane reforming did not occur under the conditions studied due to the relatively low temperature and the presence of steam. High H2 purity (98.4 vol%) and H2 yield (91%) were experimentally obtained, pointing out the biogas SESR as a promising technology for the efficient production of high-purity high-yield hydrogen from a renewable source.

Syngas production plus reducing carbon dioxide emission using dry reforming of methane: utilizing low-cost Ni-based catalysts

Applicability of using Dry Reforming of Methane (DRM) using low-cost Ni-based catalysts instead of Conventional Steam Reformers (CSR) to producing syngas simultaneously with reducing the emission of carbon dioxide was studied. In order to achieving this goal, a multi-tubular recuperative thermally coupled reactor which consists of two-concentric-tubes has been designed (Thermally Coupled Tri- and Dry Reformer [TCTDR]). By employing parameters of an industrial scale CSR, two proposed configuration (DRM with fired-furnace and Tri-Reforming of Methane (TRM) instead of fired-furnace (TCTDR)) was simulated. A mathematical heterogeneous model was used to simulate proposed reactors and analyses were carried out based on methane conversion, hydrogen yield and molar flow rate of syngas for each reactor. The results displayed methane conversion of DRM with fired-furnace was 35.29% and 31.44% for Ni–K/CeO2–Al2O3 and Ni/La2O3 catalysts, respectively, in comparison to 26.5% in CSR. Methane conversion in TCTDR reached to 16.98% by Ni/La2O3 catalyst and 88.05% by NiO–Mg/Ce–ZrO2/Al2O3 catalyst in TRM side. Also, it was 15.88% using Ni–K/CeO2–Al2O3 catalyst in the DRM side and 88.36% using NiO–Mg/Ce–ZrO2/Al2O3 catalyst in TRM side of TCTDR. Finally, the effect of different amounts of supplying energy on the performance of DRM with fired-furnace was studied, and positive results in reducing the energy consumption were observed.

Sorption-enhanced ethanol steam reforming on Ce-Ni/MCM-41 with simultaneous CO2 adsorption over Na- and Zr- promoted CaO based sorbent

In this study, sorption-enhanced ethanol steam reforming (SEESR) is investigated using a Ce-Ni/MCM-41 as a catalyst in the presence of Na or/and Zr promoted CaO-based adsorbents. Ce-Ni/MCM-41 and promoted sorbents were synthesized by wet impregnation method. The catalyst was characterized by XRD, FTIR, TGA, EFSEM, TEM, H2-TPR and N2 adsorption/desorption and promoted sorbents were studied by XRD, EFSEM, BET, TEM and TGA analysis. Sorption experiments were performed to verify sorbent activity for CO2 removing. The results indicated that with doping different promoter on CaO sorbent and also with increasing Na loading, there was an increase in BET surface area, the reduction in particle size and thereupon an enhancement in CO2 sorption capacity. Higher BET surface area, smaller particle size, and superior CO2 sorption capacity were obtained on Na-Zr-CaO sorbent. Sorption-enhanced steam reforming process of ethanol on synthesized catalyst and sorbents were performed at 600 °C and water to ethanol molar ratio of 6. The effect of sorbent to catalyst ratio and the arrangement of sorbent and catalyst (like two separated layers and the mixture of sorbent and catalyst in a single layer) were also studied. The best results were demonstrated on Na-Zr-CaO sorbent and with the separated array. Hydrogen production via a SEESR process with Na-Zr-CaO as sorbent was ∼94% that is 24% more than that of conventional ethanol steam reforming (ESR) reaction.

Reforming of biogas using a non-thermal, gliding-arc, plasma in reverse vortex flow and fate of hydrogen sulfide contaminants

Biogas is being produced everyday around the world due to land filling of organic wastes. Reforming of biogas to hydrogen rich gas offers a green source of energy. This work demonstrates reforming biogas into hydrogen rich gas via a non-thermal gliding arc plasma stabilized in a reverse vortex flow with very low and competitive specific energy requirement. Parametric tests determined the individual effects of power input (140-300 W), steam to carbon ratio (0.0–3.0), and equivalence ratio (0.1–0.7) on reformer performance. Factorial tests identified optimal operating condition based on minimizing the specific energy requirement, determined to be 184 kJ/mol H2 or 1.91 eV/H2 molecule, significantly below the value for conventional steam reforming of methane, 3.37 eV/H2 molecule produced. The optimum operating conditions were found at an equivalence ratio of 0.11, a steam to carbon ratio of 0.14, and an input plasma power of 160 W, resulting in methane conversion of 48.8%, hydrogen yield of 23.4%, hydrogen selectivity of 47.8%, and an efficiency of 25.3%. Hydrogen sulfide as a common contaminant in landfill gas has detrimental effects on downstream facilities. The reactor was also evaluated on synthetic biogas containing hydrogen sulfide at low concentration (21 ppm). About 5.7% of the sulfur input to the system was partitioned to the dry outlet reformate stream with the remainder captured as sulfate in a downstream impinger or recovered as a solid of unknown molecular structure deposited on tubing surfaces between the reformer and the impinger. This reforming technology offers potential to be deployed as a lightweight compact portable system for on-site applications such as landfills, and depending on available fuels, in mobile applications such as ships.

Performance comparison among different multifunctional reactors operated under energy self-sufficiency for sustainable hydrogen production from ethanol

Four ethanol-derived hydrogen production processes including conventional ethanol steam reforming (ESR), sorption enhanced steam reforming (SESR), chemical looping reforming (CLR) and sorption enhanced chemical looping reforming (SECLR) were simulated on the basis of energy self-sufficiency, i.e. process energy requirement supplied by burning some of the produced hydrogen. The process performances in terms of hydrogen productivity, hydrogen purity, ethanol conversion, CO2 capture ability and thermal efficiency were compared at their maximized net hydrogen. The simulation results showed that the sorption enhanced processes yield better performances than the conventional ESR and CLR because their in situ CO2 sorption increases hydrogen production and provides heat from the sorption reaction. SECLR is the most promising process as it offers the highest net hydrogen with high-purity hydrogen at low energy requirement. Only 12.5% of the produced hydrogen was diverted into combustion to fulfill the process's energy requirement. The thermal efficiency of SECLR was evaluated at 86% at its optimal condition.

Mass Transfer Coefficient in Multi-Stage Reformer/Membrane Modules for Hydrogen Production.

Hydrogen is a promising energy carrier, and is exploitable to extract energy from fossil fuels, biomasses, and intermittent renewable energy sources and its generation from fossil fuels, with CO2 separation at the source being one of the most promising pathways for fossil fuels’ utilization. This work focuses on a particular configuration called the Reformer and Membrane Module (RMM), which alternates between stages of Steam Reforming (SR) reactions with H2 separation stages to overcome the thermodynamic limit of the conventional SR. The configuration has numerous advantages with respect to the more widely studied and tested membrane reactors, and has been tested during a pilot-scale research project. Although numerous modelling works appeared in the literature, the design features of the material exchanger (in the so-called RMM architecture) of different geometrical configurations have not been developed, and the mass transfer correlations, capable of providing design tools useful for such membrane modules, are not available. The purpose of this work is therefore to apply a physical-mathematical model of the mass transfer, in three different geometries, considering both concentration polarization and membrane permeation, in order to: (i) simulate the cited experimental results; (ii) estimate the scaling-up correlations for the “material exchange modules”; and (iii) identify the mass transfer limiting regime in relation to the gas mass flow rate.