Co-production Of Hydrogen Research Articles

Chemical looping dry reforming of methane with hydrogen generation on Fe2O3/Al2O3 oxygen carrier

A chemical looping dry reforming process for co-production of hydrogen and syngas was proposed. This process contains four different stages, i.e. reduction, dry reforming, steam oxidation and air oxidation. The partial oxidation of CH4 with lattice oxygen occurred along with dry reforming reaction on the reduced iron oxide in the dry reforming stage, which helps to obtain the flexibility syngas ratio and increase hydrogen yield in the next steam oxidation stages. In this study, Fe2O3/Al2O3 oxygen carrier was used to verify the feasibility of this process in a fluidized-bed reactor at 900 °C and 1.01 bar. Carbon deposition and physical properties of the carrier were studied by using O2-TPO, XRD and BET methods. It was found that the efficient conversion of CO2 and CH4 to syngas can be achieved on the reduced iron oxygen carrier. When the feed ratio of CH4/CO2 was 1 and the reduction extent of iron was 33%, the CH4 conversion and syngas yield (the output of syngas/the input of CH4) reached 98.32% and 3.84 during the dry reforming stage, respectively. Moreover, increasing the feed ratio of CH4/CO2 raised the H2/CO ratio of syngas, but the deposited carbon would form with the available lattice oxygen depleted. Finally, superior redox activity and stability were obtained during the 15 cycles, although slight sintering was observed on the reacted oxygen carrier.

Techno-economic analysis of polygeneration systems based on catalytic hydropyrolysis for the production of bio-oil and fuels

The present paper presents an assessment of the techno-economic performance of novel polygeneration concepts for bio-oil production. They are based on catalytic hydropyrolysis and hydrodeoxygenation, and can be integrated with other processes for co-production of synthetic natural gas, molecular hydrogen and methanol. Thirteen system layouts were evaluated considering different technological alternatives and process pathways. Firstly, detailed thermodynamic and economic models were developed to calculate and compare the energy demands, capital and production costs of all plants, given a biomass input of 2000 dry metric tonnes per day. Sensitivity analyses using local approaches, Morris screening and multi-variable linear regression tools were then conducted to identify the essential parameters. Finally, uncertainty analyses were performed to estimate the minimum selling price of bio-oil for each case. The results show that the total capital costs range between $180 and $620 million, for a production cost between $17 and $24 per GJ of fuel. The feedstock and electricity costs represent the greatest share (up to 60% together) followed by the annualised investment costs (up to 18%). The sensitivity analyses suggest that the plant profitability is mostly impacted by the bio-oil yield, by-product characteristics, electrolysis costs, wood and power prices. The uncertainty analysis, through Monte-Carlo simulations, demonstrates that the minimum fuel selling prices may vary from $-3 to $240 per GJ. The most promising layouts are those with SNG and H2 production, whilst the riskiest ones are those with electrolysis.

Co-production of hydrogen and power from palm mill wastes

An integrated system to harvest efficiently the energy from palm mill wastes, which are empty fruit bunch (EFB) and palm oil mill effluent (POME), is proposed and evaluated. The proposed system adopts the supercritical water gasification (SCWG) of mixed EFB and POME, which is integrated with also with chemical looping and power generation. To minimize the exergy loss throughout the system, and therefore, optimize the energy efficiency, process design and integration is conducted by employing the principles of exergy recovery and process integration technologies. Hydrogen is set as the main output, while power is produced by utilizing the heat generated throughout the process. Process simulation is conducted using a steady state process simulator Aspen Plus V8.8. Energy efficiency is defined into three categories: hydrogen production efficiency, power generation efficiency, and total energy efficiency. From process simulation, the integrated systems show high total energy efficiency. Further study should be performed to investigate the effect of EFB/POME ratio, gasification temperature, SCL pressure condition on the system performance including total energy efficiency.

Co-production of hydrogen and power from black liquor via supercritical water gasification, chemical looping and power generation

Abstract An integrated system to harvest efficiently the energy from the waste of pulp mill industry, which is black liquor (BL), is proposed and evaluated. The proposed system consists of the supercritical water gasification (SCWG) of BL, syngas chemical looping, and power generation. To minimize the exergy loss throughout the system and to optimize the energy efficiency, process design and integration is conducted by employing the principles of exergy recovery and process integration methods. Hydrogen is set as the main output, while power is produced by utilizing the heat generated throughout the process. Process simulation is conducted using a steady state process simulator, Aspen Plus. Energy efficiency is defined into three categories: hydrogen production efficiency, power generation efficiency, and total energy efficiency. From process simulation, both of the integrated systems show very high total energy efficiency of about 73%.

Study of the co-production of butanol and hydrogen by immobilizing Clostridium acetobutylicum CICC8012

Three kinds of carrier materials, activated carbon, bagasse and brick were used as immobilizing carriers during fermentation by Clostridium acetobutylicum CICC8012. Compared with cell suspended fermentation, enhanced fermentation performance was achieved during immobilizing cell fermentation, with shorter fermentation time required. During the experiments, hydrogen and butanol appear to be competitive events. The best fermentation performance of butanol was obtained in the case of bagasse as immobilizing carrier (5.804g/L of butanol production, 0.22g/g of yield and 0.44g/L/h of productivity), while the hydrogen yield was just 1.41 mol/mol. The highest hydrogen productivity (402mL/L/h) and yield (1.808mol/mol glucose) could be obtained in the case of brick as immobilizing carrier, while the butanol yield was 0.18 g/g. The highest hydrogen concentration of 66.76 % was obtained in the case of activated carbon as immobilizing carrier.

Performance analysis and carbon reduction assessment of an integrated syngas purification process for the co-production of hydrogen and power in an integrated gasification combined cycle plant

The integrated gasification combined cycle (IGCC) is prominent in coal-based power plants because of its high efficiency and environmental benefit. Because of global warming, the integration of a carbon capture process (CCP) into the IGCC is exigent. In this study, performance analysis of an integrated syngas purification process was performed for a 500 MW-class IGCC. First, various carbon capture efficiencies were investigated to elucidate the most economical carbon capture efficiency, and a carbon capture efficiency of 90% was recommended. This value includes sour gas (H2S) removal cost, and it is essential for coal-power plants regardless of carbon capture. Thus, the net carbon capture cost was calculated from the difference in the operating costs of the integrated syngas purification process with/without a CCP. The net carbon capture cost per ton of CO2 was determined as approximately 21 USD. In addition, the exergy analysis and H2 co-production from the integrated syngas purification process with pressure swing adsorption (PSA) were presented to suggest the direction of the potential process improvement and carbon reduction assessment. The study can contribute towards decision-making related to investment in near-future candidate technologies for increasing efficiency and carbon emissions.

Coproduction of hydrogen and methane in a CSTR-IC two-stage anaerobic digestion system from molasses wastewater.

A continuous hydrogen and methane production system in a two-stage process has been investigated to increase energy recovery rate from molasses wastewater in this study. This system consisted of a continuous stirred-tank reactor for hydrogen production and an internal circulation (IC) reactor for methane production, and was studied under the influent organic loading rate (OLR) of 18, 24, 30 and 36kg COD/(m3·d) (COD: chemical oxygen demand). The maximum volumetric hydrogen production rate of 2.41 L/(L·d) was obtained at the OLR of 30kg COD/(m3·d) with a hydrogen content of 42%, and the maximum volumetric methane production rate of 2.4 L/(L·d) with a methane content of 74.45% was obtained at the OLR of 36kg COD/(m3·d) using the effluents of hydrogen fermentation as substrate. The maximum of 71.06% of the molasses wastewater energy was converted to biogas (hydrogen and methane) at the OLR of 30kg COD/(m3·d).

Ethanol steam reforming on Ni/CaO catalysts for coproduction of hydrogen and carbon nanotubes

Catalytic steam reforming of ethanol is considered as a promising technology for producing H2 in the modern world. In this study, using a fixed-bed reactor, steam reforming of ethanol was performed for production of carbon nanotubes (CNTs) and H2 simultaneously at 600°C on Ni/CaO catalysts. Commercial CaO and a synthetic CaO prepared using sol-gel were scrutinized for ethanol's catalytic steam reforming. Analysis results of N2 isothermal adsorption indicate that the CaO synthesized by sol-gel has more pore volume and surface area in comparison with the commercial CaO. When Ni was loaded, the Ni/CaO catalyst shows an encouraging catalytic property for H2 production, and an increase in Ni loading could improve H2 production. The Ni/CaO catalyst with sol-gel CaO support has presented a higher hydrogen production and better catalytic stability than the catalysts with the commercial CaO support at low Ni loading. The highest hydrogen yield is 76.8% at Ni loading content of 10% for the Ni/sol-gel CaO catalyst with WHSV of 3.32/h and S/C ratio of 3. The carbon formed after steam reforming primarily consists of filamentous carbons and amorphous carbons, and CNTs are the predominant type of carbon deposition. The deposited extent of carbon on the used Ni/CaO catalyst lessen upon more Ni loading, and the elongated CNTs are desired to be formed at the surface of the Ni/sol-gel CaO catalyst. Thus, an efficient process and improved economic value is associated with prompt hydrogen production and CNTs from ethanol steam reforming.

A computational study on ligand assisted vs. ligand participation mechanisms for CO2 hydrogenation: importance of bifunctional ligand based catalysts.

CO2 hydrogenation products are not only useful chemical sources but also promising hydrogen storage materials. A DFT study has been carried out on the CO2 hydrogenation reaction catalyzed by a series of bifunctional aminomethyl based Mn(i) complexes. We find that the N-H functionality in the aminomethyl ligand shows a metal-ligand cooperation (MLC) mechanism for the CO2 hydrogenation reaction. Here, the N-H functionality assists the MLC mechanism by stabilizing the formate anion via N-HO hydrogen bonding interactions. This is opposite to the MLC mechanism proposed by Noyori for ketone hydrogenation, where the N-H functionality actively participates in the reaction mechanism via cleavage/formation of N-H/M-H bonds. Furthermore, the stabilized formate anion initiates heterolytic H2 cleavage, which requires a very low barrier compared to external base/ligand participation heterolytic H2 cleavage. Therefore, the bifunctional aminomethyl based Mn(i) complexes are promising for the CO2 hydrogenation reaction and our study may be very helpful for experimentalists for the development of efficient bifunctional ligand-based catalysts for the CO2 hydrogenation reaction.

In situ generation of nickel/carbon catalysts by partial gasification of coal char and application for methane decomposition

Catalytic methane decomposition (CMD) has a good potential to develop environmentally friendly hydrogen economy, and the catalyst plays a vital role on its applications. In this work, a novel strategy was proposed to fabricate efficient and effective nickel/carbon catalysts for CMD by introducing some additional nickel and K2CO3 into partial steam gasification of coal char. The gasification process is conducive to in situ synthesize nickel crystallites with high reduction degree (the value of Ni0/(Ni0+Ni2+) up to 76%–81%) on the catalyst surface, and it is competent for co-generation of hydrogen-rich gas and nickel/carbon hybrids with large surface areas (around 86–149 m2/g after washing off the residual potassium salts). The nickel/carbon hybrid as the gasification residue could serve as the catalyst for CMD, showing high and stable methane conversion (up to 80%–87%) at 850 °C. It is observed that co-production of hydrogen and filamentous carbons can be achieved in the 600-min process of CMD, thanks to the positive effect of K2CO3 on formation and activity improvement of the nickel/carbon catalyst.

RETRACTED ARTICLE: Theory-guided Sn/Cu alloying for efficient CO2 electroreduction at low overpotentials

Electrochemical CO2 reduction to formate provides an avenue to reduce globally accelerating CO2 emissions and produce value-added products. Unfortunately, high selectivity in formate electrosynthesis has thus far only been achieved at highly cathodic potentials. Here we use density functional theory to investigate the effect of alloying Cu and Sn on the activity and selectivity towards formate. A theoretical thermodynamic analysis of the reaction energetics suggests that the incorporation of copper into tin could suppress hydrogen evolution and CO production, thus favouring formate generation. Consistent with theoretical trends, the designed CuSn3 catalysts by co-electrodeposition exhibit a Faradaic efficiency of 95% towards formate generation at −0.5 V versus RHE. Furthermore, the catalysts show no degradation over 50 h of operation. In situ Sn L3-edge and Cu K-edge X-ray absorption spectroscopy indicate electron donation from Sn to Cu, which indicates positive oxidation states of Sn in CuSn3 under operating conditions. The electroreduction of carbon dioxide to formate represents a desirable strategy for the production of fuels and commodity chemicals. Now, guided by density functional theory, Cui and colleagues report CuSn3 alloys that exhibit high activity and selectivity for formate production from CO2 electroreduction at potentials as low as −0.5 V versus RHE.

Co-production of high quality hydrogen and synthesis gas via sorption-enhanced steam reforming of glycerol coupled with methane reforming of carbonates

The sorption enhanced steam reforming (SESR) produces high-purity hydrogen and capture CO2 in the form of carbonates, allowing for controllable CO2 storage or utilization. However, the decarbonation of carbonates at temperatures high up to 800–900 °C makes the SESR process and the subsequent CO2 utilization energy-intensive. Herein, we report the feasibility coupling the SESR of glycerol with CH4 reforming of carbonates, which combines the decarbonation with CO2 utilization to simplify the technology and avoid the energy-consuming temperature swing. A high-efficiency bi-functional Ni-CaO-Ca12Al14O33 catalyst was proposed to this process. The catalyst was derived from a Ni-Ca-Al hydrotalcite-like (HTl) material to achieve homogeneous mixing of Ni, CaO and Ca12Al14O33 which were active metal, sorbent and a spacer to prevent CaO sintering. Thanks to the high activity and stability of Ni-CaO-Ca12Al14O33 catalysts, 98.53% hydrogen-enriched gas could be obtained in SESR of glycerol, and the high CH4 conversion (95.3%) and H2/CO molar ratio (<2) suitable for further Fisher-Tropsch synthesis were achieved during the CH4 reforming reaction. Meanwhile, Ca12Al14O33 as a spacer had provided a stability for ten cycles. Our results highlight the significance of process intensification and high-efficiency bi-functional catalysts for the hydrogen production with low carbon emissions.

High purity syngas and hydrogen coproduction using copper-iron oxygen carriers in chemical looping reforming process

Chemical looping reforming presents an attractive alternative to the conventional processes for chemicals and energy production from carbonaceous fuels with significant reduction in carbon emissions and high exergy efficiency. Production of syngas and hydrogen is important because the former is a critical building block for valuable chemicals and latter is a source of clean energy. The use of copper-iron (Cu-Fe) oxygen carriers for coproducing syngas and hydrogen in a chemical looping reforming process is studied via experiments and process simulations. Three different compositions of Cu and Fe oxides are examined for their properties concerning the reactivity towards fuel and the selectivity towards syngas. The feasibility of using a co-current moving bed reactor configuration for syngas production is probed experimentally in a fixed bed reactor by placing the fully oxidized and reduced oxygen carrier in series. The methane conversion and dry syngas purity as high as 99.5% and 97.5%, respectively, are observed for copper oxide (20 wt%) - iron oxide (60 wt%) - aluminium oxide (20 wt%) oxygen carrier in a simulated co-current moving bed reactor. Key performance parameters including effective thermal efficiency for 5 different configurations of the chemical looping reforming process from ASPEN Plus simulation software are compared against the baseline case of the auto-thermal reforming process. Apart from an improvement in the natural gas conversion and syngas purity in the chemical looping reforming process, the net hydrogen production is increased by 28% and effective thermal efficiency is increased by 10% over that of the auto-thermal reforming process.

Methane decomposition over Ni/carbon catalysts prepared by selective gasification of coal char

Catalytic methane decomposition (CMD) can pave the route for co-production of COx free hydrogen and valuable carbon materials, and it is considered as a potential promising strategy to develop eco-friendly and low-carbon hydrogen economy. However, there are still some challenges for utilization of traditional metal and/or carbon catalysts. In this work, relatively dispersed and efficient Ni/carbon catalysts were handily prepared for CMD by selective steam gasification of coal char with addition of nickel and/or cerium compositions. Carbothermal reduction during the gasification process could enable in-situ formation of Ni0 crystallites and facilitate the gasification efficiency and thus achieving co-production of hydrogen-rich gas and Ni/carbon hybrids with large surface areas (217–265 m2/g). When the Ni/carbon hybrids as the selective gasification residues were used for CMD, high and stable methane conversion (up to about 90% at 850 °C) can be obtained in the 600-min CMD reaction, thanks to the relatively dispersed and active Ni0 crystallites, large surface area of the porous carbon support and formation and growth of the fibrous carbon deposits.

Handy synthesis of robust Ni/carbon catalysts for methane decomposition by selective gasification of pine sawdust

Hydrogen is a clean fuel and potential alternative for fossil fuels, and many efforts have been devoted to low-carbon hydrogen production. Highly dispersed and robust Ni/carbon catalysts can be handily prepared in situ for catalytic methane decomposition (CMD) by selective steam gasification of pine sawdust. Effect of the gasification conditions (temperature, mass ratio of PS:Ni, steam flow rate and gasification reaction time) was investigated on the nickel species, activity and stability of the Ni/carbon catalyst in CMD. Besides hydrogen-rich gas released from the gasification process, co-production of hydrogen and carbon fibers can be obtained on the optimized catalyst with high and stable methane conversion (up to higher than 90% at 850 °C) in the 600-min CMD reaction. The implementation of such selective biomass gasification and CMD could be one promising approach towards process intensification for highly cost-effective hydrogen production, and enables it possible to yield a high metal efficiency as well.

On improving the hydrogen and methanol production using an auto-thermal double-membrane reactor: Model prediction and optimisation

The concentric configured thermally-coupled double-membrane reactor (TCDMR) was optimised to improve the co-production of hydrogen and methanol. Using a detailed approach, we identified the non-linear differential evolution (DE) algorithm as the most suitable optimisation tool among the most used optimisation algorithms in reactor design (GA, PSO, and DE) due to its ability to converge to the optimal solution with fewer iterations. Considering DE algorithm with the industry benchmark data, we optimised the key operational parameters of TCDMR (as OTCDMR), leading to the improved reactor performance (regarding the overall heat transfer and methanol/hydrogen production) compared to the conventional methanol reactor (CMR) and TCDMR. Simulation results show that the methanol production rate of OTCDMR could reach 315.7 tonnes day−1, representing a 22.6% enhancement than CMR (257 tonnes day−1). For the hydrogen production, OTCDMR is predicted to deliver 19.7 tonnes of hydrogen per day, surpassing the 15.5 tonnes day−1 production rate by TCDMR.

Pure hydrogen co-production by membrane technology in an IGCC power plant with carbon capture

The CO2 capture in Integrated Gasification Combined Cycle (IGCC) plants causes a significant increase of the cost of electricity (COE) and thus determines high CO2 mitigation cost (cost per ton of avoided CO2 emissions). In this work the economic sustainability of the co-production of pure hydrogen in addition to the electricity production was assessed by detailed process simulations and a techno-economic analysis. To produce pure hydrogen a Water Gas Shift reactor and a Selexol® process was combined with H2 selective palladium membranes. This innovative process section was compared with the more conventional Pressure Swing Adsorption in order to produce amount of pure hydrogen up to 20% of the total hydrogen available in the syngas.Assuming for a base case a hydrogen selling price of 3 €/kg and a palladium membrane cost of 9200 €/m2, a cost of electricity (COE) of 64 €/MWh and a mitigation cost of 20 €/tonCO2 were obtained for 90% captured CO2 and 10% hydrogen recovery. An increase of the hydrogen recovery up to 20% determines a reduction of the COE and of the mitigation cost to 50 €/MWh and 5 €/tonCO2, respectively. A sensitivity analysis showed that even a 50% increase of cost of the membrane per unit surface could determine a COE increase of only about 10% and a maximum increase of the mitigation cost of further 5 €/tonCO2.

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.

Thermodynamic modeling and optimization of a combined biogas steam reforming system and organic Rankine cycle for coproduction of power and hydrogen

Abstract This paper aims to use waste heat of the biogas steam reforming (BSR) system for organic Rankine cycle (ORC) for simultaneous power and hydrogen production. A comprehensive thermodynamic modeling of the proposed combined system is carried out. In addition, optimization of the proposed system is conducted, using genetic algorithm (GA). Four different working fluids of R600, R245fa, R123, and R113 are used in ORC, where among all of them R600 is recommended due to its high performance and environment benefits. Using R600 as working fluid in ORC, results of the optimization demonstrated that the proposed system performs in an optimum state based on the selected objective functions when steam to carbon molar ratio, carbon dioxide to methane molar ratio, reaction pressure, reactor temperature, pump pressure ratio and pinch point temperature difference of the internal heat exchanger (IHE) are set in 2.99, 0.502, 1.004 bar, 998.85 K, 7.21 K, and 5.44 K, respectively. In this case, the optimum net output power, hydrogen production rate, energy efficiency and exergy efficiency are obtained 15.9 kW, 0.02529 kg s−1, 45.63%, and 74.89%, respectively. Moreover, the results of exergy analysis indicated that among all components, recuperator and reactor are accountable for the highest exergy destruction through the system. To better understand the effect of various parameters on performance of the system, a comprehensive parametric study of some key thermodynamic parameters on the main performance criteria is performed. It is concluded that the energy and exergy efficiencies of the combined BSR-ORC system can be increased by increasing steam to carbon molar ratio and pump pressure ratio or decreasing reaction pressure, carbon dioxide to methane molar ratio and pinch point temperature difference of the IHE.

Co-production of Hydrogen and Methane From the Organic Fraction of Municipal Solid Waste in a Pilot Scale Dark Fermenter and Methanogenic Biofilm Reactor

The co-production of biohydrogen and methane from the organic fraction of municipal solid waste was investigated using a two-stage AD system, composed of a pilot scale dark fermenter (DF) and a continuous methanogenic biofilm reactor. From the DF process, a biohydrogen yield of 41.7 (± 2.3) ml H₂/gVSadded was achieved. The liquid DF effluent (DFE) was rich in short chain volatile fatty acids, i.e. mainly acetic and butyric acid. The DFE was valorized by producing methane in the methanogenic biofilm reactor. Two methanogenic biofilm reactors were used to assess the biotic and abiotic role of the DFE on the performance of the reactors. Regardless of the different DFE feeding (i.e. biotic and abiotic), similar and stable operational performance of the two methanogenic biofilm reactors were observed with a respective methane yield and COD removal efficiency of 280-300 ml CH₄/gCODremoved and 80-90 %. Both methanogenic biofilm reactors showed significant resistance towards organic shock loads and recovered faster after reactor disturbance. The total estimated energy recovered in the form of hydrogen and methane gas was, respectively, 28 % and 72 %, of the initial COD.