Chemical Looping Hydrogen Production Research Articles

Design and Optimization of a Chemical Looping Hydrogen Production System Using Steam Reforming for Petrochemical Plants.

Industrial pollution is a significant environmental concern, and researchers are seeking solutions to minimize its impact. Chemical looping combustion is an efficient technique to decrease CO2 emissions. This study delves into its application within petrochemical plants for hydrogen production. In addition to its high efficiency in hydrogen production, this method yields pure CO2 and nitrogen. The design features four reactors utilizing iron and nickel metals as oxygen carriers. A model in Aspen Plus was developed to simulate this design and evaluate its performance. Aspen Plus uses RGIBBS submodel which works based on minimization of the Gibbs free energy. The research findings indicate that this design significantly boosted the hydrogen production rate from 3380 kmol/h in conventional steam reforming reactors and 4258 kmol/h in the three-reactor chemical looping combustion setup to 4408 kmol/h. Lowering the temperatures of the iron and nickel fuel reactors, as well as the iron steam reactor, reducing the airflow rate, and increasing the pressure of the iron steam reactor all led to increased hydrogen production. Conversely, changing the pressure of the nickel fuel reactor had minimal impact. The inlet steam flow rate exhibited a nonlinear effect, initially increasing and then decreasing the hydrogen production rate.

Improved morphological stability of NiFe2O4 via Sr doping for chemical looping hydrogen production

As a new hydrogen production technology, chemical looping hydrogen production has the advantage of internal CO2 separation. NiFe2O4 is considered as promising oxygen carrier material for chemical looping hydrogen production due to the high oxygen carrying capacity and low cost. However, rapid redox performance fading caused by structure degradation and interface instability in successive redox reactions that led fto poor stability, and seriously limited the practical application of NiFe2O4 in chemical looping hydrogen production. Herein, we reported a method for improving the morphological stability of NiFe2O4 through Sr doping. NiFe2O4 samples containing different SrO contents (2 wt%, 5 wt% and 8 wt%) were prepared by a simple mechanical mixing method. A series of characterization analysis results showed that adding an appropriate amount of Sr could significantly improve the microstructure, increase the oxygen vacancy concentration and inhibit the phase segregation of NiFe2O4. The NiFe-5Sr presented the largest BET surface area (24.63 m2/g) and highest concentration of oxygen vacancies (77.49 %). NiFe-0Sr and NiFe-2Sr experienced severe phase segregation during continuous cyclic reactions, resulting in significant surface sintering and deactivation. During 20 redox cycles, NiFe-5Sr presented the highest hydrogen yield (around 10 mmol/g) and stable surface morphology. The research results indicated that the optimal doping amount for SrO was 5 %.

Reaction Behavior of a Fixed Bed Reactor for Chemical Looping Hydrogen Production with Iron-Based Oxygen Carriers

Reaction Behavior of a Fixed Bed Reactor for Chemical Looping Hydrogen Production with Iron-Based Oxygen Carriers

Reaction kinetics of Ni-Fe oxygen carriers with high performance for chemical looping hydrogen production

The chemical looping hydrogen production (CLHP) process utilizing iron-based oxygen carriers holds promise for practical hydrogen generation applications. However, challenges persist in developing iron-based carriers that are easy to prepare and demonstrate effective reactivity. Our research focuses on evaluating the CLHP reaction performance using bimetallic Ni-Fe oxygen carrier particles, synthesized by a scalable mechanical mixing method. This study unravels the role of Ni in bimetallic Ni-Fe oxygen carriers and investigates the influence of varying nickel-doping ratios on enhancing the reduction reactivity of iron-based oxygen carriers. Compared to the undoped sample, the 20 wt% nickel-doped Fe2O3/Al2O3 (20NiFe) particles enabled a reduction in the reaction temperature by at least 50 K. With the dopant, the methane conversion rate at 923 K is 500% higher than that of carriers without the dopant. Heterogeneous kinetic analysis demonstrates that the global reduction reaction data for the Ni-Fe oxygen carriers fit with the nucleation-nuclei growth model. Through redox reactivity tests and reduction kinetic analysis, 20NiFe shows the lowest apparent activation energy at 53.93 kJ/mol. Furthermore, the kinetic study and quasi in-situ XRD analysis aid in proposing the evolution process of methane reduction reaction for nickel-doped iron-based oxygen carriers, clarifying the role of doping in improving chemical looping reactivity from a kinetic perspective. This work provides valuable guidance for the design and optimization of oxygen carriers, thus accelerating the readiness for industrial deployment of hydrogen production via chemical looping process.

Effect of Cu doping on morphology and properties of calcium ferrite and its application as oxygen carrier in chemical looping hydrogen production

Chemical looping hydrogen production with inherent CO2 capture has been widely recognized as a clean and efficient approach to high-purity hydrogen production because of the ultra-pure H2 product without any purification facilities. It is crucial to develop oxygen carriers with better performance to improve fuel conversion and hydrogen production efficiency. The potential of Ca2Fe2O5 in steam converting has been confirmed. However, its lower oxygen transfer capacity, that is, it tends to produce lower fuel conversion in fuel reactors, which will limit its practical application. Here, we report the development of Cu-doped Ca2Fe2O5-based oxygen carriers using sol-gel technology. The effects of B-site substitution of Cu element on the morphological properties and redox properties of Ca2Fe2-xCuxO5 (x = 0, 0.1, 0.25, 0.5, 1) oxygen carriers were evaluated based on experiments and density functional theory calculations. The results show that Cu doping not only elevated the surface oxygen content and enhanced the oxygen activity of the oxygen carriers, but also increased the Fe3+ at the B-site, thus enhanced their binding ability with oxygen molecules. Vacancy formation was a rate-determining step in the chemical looping hydrogen production (CLH), and Cu-doped Ca2Fe2O5 reduced the energy of oxygen vacancy formation. In the CLH process, the doping of Cu significantly improved the hydrogen productivity and fuel conversion rate. The fuel conversion rate was positively correlated with the doping amount of Cu. When x = 1, Ca2Fe2-xCuxO5 had the maximum fuel conversion rate, and its average conversion was 54.2% more than that of undoped Ca2Fe2O5. Ca2Fe2-xCuxO5 with x = 0.25 was the most suitable for CLH with the highest H2 yield, which was 20.3% more than that of Ca2Fe2O5. Moreover, its properties remained stable over multiple redox cycles with high activity and stability for CO-CLH.

(La1−xCax)MnO3−δ (x = 0, 0.2, 0.3, 0.4) Perovskites as Redox Catalysts in Chemical Looping Hydrogen Production Process: The Relation between Defect Chemistry and Redox Performance

The interaction between point defects in (La1−xCax)MnO3−δ (x = 0, 0.2, 0.3, 0.4) perovskites and their redox catalytic properties in a three-reactor chemical looping hydrogen production process is investigated. During the reduction step with CH4, the behavior of the materials is extrinsically determined and strongly depends on the Ca content. At small oxygen deficiencies, CH4 becomes oxidized to CO2. As the deficiency increases, partial oxidation to CO and H2 at a molar ratio of approximately 2 is favored. During the water-splitting step, the dependency on the Ca content is much weaker since it is intrinsically determined by the Mn2+→Mn3+ oxidation with simultaneous annihilation of oxygen vacancies that are not required to compensate for the extra negative charge of the Ca dopant. Hydrogen productivities in the order of 13 cm3 (STP) H2/g solid could be achieved during the water-splitting step at 1000 °C. The materials exhibited reproducible catalytic behavior during 10 cycles of the complete three-step process and were found to retain their perovskite structure.

Enhancing redox stability through metal substitution in nickel ferrite for chemical looping hydrogen production via water splitting

NiFe2O4 oxygen carrier has tremendous potential for application in chemical looping hydrogen production via water splitting. However, it exhibits poor high-temperature cycling stability. The current study investigates the impact of substituting other elements (Cu, Ce, La or K) for Fe in NiFe2O4 on the hydrogen production performance during the chemical looping water splitting process. No crystalline phase of oxides for Fe, La or Ni has been detected in the XRD patterns, indicating that substituting element has been successfully doped into the spinel structure of NiFe2O4. After the substitution with the other elements such as K, La, and Ce, the hydrogen yield of the oxygen carrier has been improved, with the highest hydrogen yield observed for the NiLa0.02Fe1.98O4 oxygen carrier. Through optimized experiments, the optimum substitution amount of La is 10%, resulting in the formation of NiLa0.2Fe1.8O4. With the substitution of 10% Fe by La, the hydrogen production performance of the fresh oxygen carrier is increased from 170 mL/kg to 297 mL/kg, which can be explained by various characterization results. Lattice distortion and an obvious increase in oxygen vacancy content are observed in NiLa0.2Fe1.8O4, with the reduction peak shifting to the low-temperature region. In addition, compared to NiFe2O4, NiLa0.2Fe1.8O4 exhibits better cycling stability in 30 cycles. Finally, the changes of structure and morphology for NiFe2O4, NiLa0.2Fe1.8O4 before and after 30 cycles have been comparatively analyzed using XRD, XPS, SEM, BET, and H2-TPR.

Co-feeding biomass and municipal solid waste for enhanced hydrogen and synthetic natural gas yields employing chemical looping process

Synthetic natural gas (SNG) is a promising alternative to conventional fossil natural gas. This study proposes a chemical looping hydrogen production (CLHP)-based route for SNG synthesis and elucidates the insights and necessities of appropriately co-feeding different types of feedstocks to maximize the yields of hydrogen and subsequent SNG. A study employing microalgae (MA) and refuse-derived fuel (RDF) as biomass and municipal solid waste representatives demonstrates that blending MA with RDF in a proportion of 40 %:60 % (0.4MA-0.6RDF) eradicates oxygen carrier splitting. This boosts fuel-to-hydrogen efficiency from 74.1 % to 77.8 %, as well as subsequent thermal and exergy efficiencies of SNG production from 59.07 % and 55.8 % to 61.3 % and 57.92 %, respectively, compared to the use of MA alone. Nonetheless, blending fuels does not yield substantial economic advantages, as evidenced by the levelized cost of SNG production using pure MA and the 0.4MA-0.6RDF blend remaining at approximately 0.63 USD/Nm3.

Co, Ni and Cu-doped Ca2Fe2O5-based oxygen carriers for enhanced chemical looping hydrogen production

Oxygen carrier determines the output characteristics of the chemical looping cycle reaction and is a key factor affecting the chemical looping hydrogen production (CLH) process. In this work, the effect of different dopants (Co, Ni and Cu) on Ca2Fe2O5 brownmillerite-type oxygen carriers and the feasibility of low doping were investigated in an attempt to improve CO conversion and hydrogen yield in the CLH reaction. The redox activity of the transition metal doped oxygen carriers was significantly enhanced. The fuel conversion of CaFeNi was increased to 1.29 times. The average hydrogen yield of CaFeCo was as high as 102.20 mL/g, which was 1.58 times that of CaFe. In addition, density functional theory calculations show that metal-doped Ca2Fe2O5 reduced the energy of oxygen vacancy formation, but they bore a significant energy barrier in the formation of hydrogen molecules. These findings may provide ideas for the modification of oxygen carriers for the CLH process.

Negative net global warming potential hydrogen production through biomass gasification combined with chemical looping: Environmental and economic assessments

The integration of biomass gasification (BG) with chemical looping hydrogen production (CLHP) offers one prospective approach for green hydrogen production. The environmental and economic assessments are conducted to evaluated the sustainable performance of the BG-CLHP system during the hydrogen production cycle (HPC). The results showed that the environmental impacts of BG-CLHP are concentrated in freshwater aquatic ecotoxicity (FAETP), human toxicity (HTP), and acidification (AP). The BG-CLHP system can provide a more cost-competitive hydrogen supply solution for hydrogen refueling stations compared the offshore wind or photovoltaic (PV) powered electrolysis, given the same hydrogen production target. For global warming potential (GWP) and cost, the BG-CLHP demonstrates excellent integrated performance with GWP values of −15.13 and −17.00 kg CO2, eq/kg H2, for the Air case and Oxygen case, and the costs of 3.05 and 2.82 $/kg H2, respectively, and sensitivity analysis reveals that the CLHP stage is the primary contributor to GWP. Compared with existing hydrogen production routes, BG-CLHP can still be improved in terms of costs and the technical maturity, however, the excellent negative GWP properties of BG-CLHP make it will play a more important role in future large-scale hydrogen production.

Deposition and release behavior of H2S during chemical looping hydrogen production process

Chemical looping hydrogen production process is a promising technology for producing low-carbon hydrogen from various fossil and biogenic energy sources. However, the typical contaminant in feedstock, hydrogen sulfide, has a potential influence on the process. Herein, this study investigated the influence of hydrogen sulfide on the chemical looping hydrogen production process. Results show that the presence of hydrogen sulfide in the fuel reduces the reaction performance of the oxygen carrier because sulfur is deposited in the oxygen carrier during the reduction stage to produce iron sulfide species (FeS2, Fe7S8 and FeS). Then the iron sulfide is converted to hydrogen sulfide and sulfur dioxide during the hydrogen production and air oxidation stage, respectively. H2 production temperature is an important factor in controlling the production of hydrogen sulfide, which will not be produced at temperature below 710 °C. In addition, the air oxidation regeneration step ensures that sulfur does not accumulate in the oxygen carrier, thus improving the cycle stability of the oxygen carrier.

Dicalcium ferrite: A chemical heat pump in integrated carbon capture and chemical looping combustion for the steel industry

An integrated calcium and chemical looping combustion using dicalcium ferrite (Ca2Fe2O5, C2F), a mixed phase from iron and calcium oxides, is proposed here to remove carbon (CO + CO2) contained in the blast furnace gas from the steel industry. C2F is particularly attractive in chemical looping hydrogen production due to its lower PO2, therefore C2F can split steam into H2. Here, the low PO2 property allows C2F to have endothermic combustions in CO and H2 combustion (Stage 1 in the carbonator). The heat of combustion is chemically stored as reduced-carbonated C2F to be utilised for sorbent regeneration (Stage 2 in the calciner), essentially pumping the heat from the carbonator to the calciner. Combustion that occurred at PCO/PCO2 of the typical BFG in which the C2F should have not been able to combust CO, suggesting an enhanced combustion phenomenon. Experiments demonstrated in a fluidised bed and a thermogravimetric analyser led to indications that rather than following reaction pathways in an order of (i) C2F is reduced into CaO and metallic Fe and (ii) the CaO is absorbed CO2 in Stage 1, C2F might directly form Fe + CaCO3 under a mixture of CO and CO2, allowing the C2F to react with BFG. Reincorporation of the reduced-carbonated oxides into C2F drives lower decarbonation temperatures compared to CaO alone, suggesting a promising route to improve energy efficiency in capturing carbon in the hard-to-decarbonise steel industry.

Synergistic solar energy integration for enhanced biomass chemical looping hydrogen production: Thermodynamics and techno-economic analyses

The concept of solar-assisted biomass chemical looping hydrogen (H2) production (BCLHP), wherein solar energy is directly integrated into the thermochemical H2 production process, was proposed. The mechanism behind the increased H2 production due to solar assistance was elucidated. Subsequently, a system design was proposed based on this principle, accompanied by strategies for managing solar energy fluctuations during system operation. Thermodynamics and techno-economic analyses were then conducted. The results indicate that the key principle behind the increased H2 production in solar-assisted BCLHP lies in substituting solar energy for the direct oxidation of the oxygen carrier, enabling full utilization of the oxygen carrier for H2 production without the need to maintain thermal balance. The integrated system based on this principle achieves a high solar-to-H2 exergy efficiency, with a theoretical maximum exceeding 30%, outperforming the exergy efficiencies of photovoltaic (PV) and solar thermal H2 production methods, while increasing the molar ratio of H2 to CO2 from 1.31 to 1.74. The economic viability of solar-assisted BCLHP systems and systems combining PV-based H2 production with BCLHP depends on a comprehensive assessment of local PV panel costs, heliostat costs, H2 selling prices, and solar conditions. This research presents a novel approach to enhance solar-to-H2 efficiency.

Hydrodynamic study on the riser of chemical looping hydrogen production system with multiple fluidized bed reactors

Chemical looping technology is an available way for hydrogen production with low penalty energy for improving gas purity and CO2 is captured simultaneously. Understanding the operation and flow behavior is crucial for development of chemical looping hydrogen production. Experimental investigations of the system with dual interconnected fluidized bed reactors were carried out and presented in this work. The results indicated the system reached stable operation with current design. Influence of superficial gas velocity on the pressure distribution was examined and the corresponding mass inventory in the reactor was also analyzed. It showed that the relative pressure decreases with the increase of riser fluidization velocity and more particles will be transported to the fuel reactor from riser. The pressure curve fluctuated in sinusoidal shape as expected. It was better to make a large fuel reactor which holds most of solids and contributed to the stability. A tanks-in-sires model was utilized for analyzing the pressure evolution in the riser, which was less time consumed compared with computational fluid dynamic method. It showed the obvious phase shift of pressure drop along height. Also, the force balance of a particles was analyzed for predicting the mass inventory of riser and this method overcame the insufficient of measurement technology. The influences of solid circulating rate and gas velocity were obtained and be investigated further. This is a feasible way for quick prediction of flow behavior in the riser for both the design and operation under a certain operating condition.

A comparative study of the reaction mechanism for deep reduction hydrogen production using two special steel solid wastes and a chemical looping hydrogen production scheme

Pickling sludge (PS) and presintered waste (PW) are two special steel solid wastes that have potential as oxygen carriers due to their Fe content. Using these raw materials to produce hydrogen allows for the resource utilization of solid waste, which has good environmental effects. Here, we studied the deep reduction-hydrogen production characteristics. Specifically, the effects of temperature, papermaking sludge (PMS) blended ratio, and reaction time on the deep reduction characteristics of Fe in pickling sludge and presintered waste were studied. On this basis, the study also aimed to investigate the effects of temperature and PMS blended ratio on hydrogen production. The results indicated that when exposed to high temperature, PMS shows the ability to effectively reduce pickling sludge and presintered waste. The maximum Fe recovery rate can reach 65.63 and 96.94 % in a fixed bed reactor operating at 700 °C and a blended ratio of approximately 10 %. Under the conditions of 900 °C and 15 %/50 % papermaking sludge addition, the Fe content within pickling sludge and presintered waste was reduced to FeCr2O4 and FeO, respectively. Subsequently, during the reaction with steam, Fe2O3 and Fe3O4 were generated in PS and PW, respectively. The hydrogen production per unit mass of Fe2O3 in pickling sludge is higher due to the existence of the FeCr2O4 spinel structure in the reduction product of pickling sludge. According to the above results, two hydrogen production strategies of PS and PW through different deep reduction paths are proposed.

Integrated process for simulation of gasification and chemical looping hydrogen production using Artificial Neural Network and machine learning validation

A significant driver of global warming is fast growth in greenhouse gas (GHG) generated by energy-producing areas. Converting biomass into useful products, chemical looping gasification is an appropriate route. Using integrated steam gasification technology that utilizes a chemical looping method to produce hydrogen. Mn-, Ni-, and Ca-based materials are the three types of oxygen carriers (OC), and they are utilized. This process offers the syngas, in the greatest quality and quantity, which is a key factor. We consider that the optimum gasifier temperature is 1100 °C. The steam-to-biomass ratio is 0.95, if the steam is further increased then the char gasification reaction starts moving in the reverse direction. In this process, 736.629 MW of power is produced when only natural gas and air are used in the combustion chamber and if we add hydrogen, power is increased up to 16 MW. To predict syngas composition and the S/B ratio, machine learning modeling using Artificial Neural Networks (ANN) algorithms are applied and compared, Bayesian Regularization and Scaled Conjugate gradient proves to be the best ANN model for validating and comparing with process model, demonstrating its accuracy and potential for optimizing biomass gasification processes as high as up-to 0.99 R2 value.

Enhanced morphological maintenance and redox stability by dispersing nickel ferrite into silica matrix for chemical looping hydrogen production via water splitting

Chemical looping hydrogen production (CLHP) is widely regarded as a clean and efficient route for high purity hydrogen production. However, a huge barrier is how to avoid serious deactivation caused by sintering and agglomeration of oxygen carriers. A novel fabrication process of highly dispersing NiFe2O4 into silica matrix is proposed. The oxygen carriers of NiFe2O4 completely dispersed over silica matrix (NFSM) are successfully synthesized. The characterizations, hydrogen production capacity and cycle redox performance of oxygen carriers are further investigated. The results illustrate that NiFe2O4 active components are homogeneously dispersed on the silica matrix without any impurities. NFSM demonstrates the highest reactivity with CO as well as the greatest hydrogen production of 296 mL/g due to the strong confinement effect of silica matrix and good particle dispersion. The porous silica matrix offers large amounts of channels for the lattice oxygen transport and effectively prevents Fe and Ni cations outward migration to particle surface, which actually inhibits the larger clusters and sintering. NFSM can keep stable hydrogen production of approximately 290 mL/g during the cyclic experiments. Briefly, the innovation method of embedding active component into well-established silica matrix supports contributes to the enhanced anti-sintering properties and redox stability of oxygen carriers.

Comparative Analysis of Energy and CO2 Emission for the Integration of Biomass Gasification with a Dual-Reactor Chemical Looping Hydrogen Production Process

Comparative Analysis of Energy and CO₂ Emission for the Integration of Biomass Gasification with a Dual-Reactor Chemical Looping Hydrogen Production Process

CoxFe1-xFeAlO4-δ as highly active oxygen carriers for enhanced chemical looping hydrogen production

The oxygen carrier is a key factor to enable efficient and high-quality chemical looping hydrogen production. Here, we prepared several oxygen vacancies engineered CoxFe1-xFeAlO4-δ spinel by tuning Co loading of and investigated the performance for hydrogen production through chemical looping. The results show that Co0.4Fe0.6FeAlO4-δ displays a high hydrogen yield of 10.56 mmol.g−1 with a stable trend for 100 cycles at 600 °C. Mechanism studies demonstrate that doping Co decreases the energy barriers for oxygen vacancy formation, resulting in a high oxygen vacancy concentration on the surface. The high oxygen vacancy concentration accelerates the bulk oxygen diffusion, which is the rate-limiting step of the redox reaction. The enhanced bulk oxygen diffusion improves the oxygen release and redeposition of the lattice oxygen during redox cycles, thus promoting the chemical looping hydrogen production performance. No obvious phase separation can be found for Co0.4Fe0.6FeAlO4-δ during 100 cycles. The observed doping effect can pave way to developing more advanced oxygen carriers with high reactivity and stability for chemical looping applications.

Numerical Study on the Process of Chemical Looping Hydrogen Production with Multiple Circulating Fluidized Bed Reactors

Numerical Study on the Process of Chemical Looping Hydrogen Production with Multiple Circulating Fluidized Bed Reactors