Chemical Looping Hydrogen Production Research Articles

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.

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.

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

Technoeconomics and carbon footprint of hydrogen production

Decarbonization of the global economy needs not only carbon-free electricity but also a fuel that is free of greenhouse gas emissions. Hydrogen is a prime candidate, with colors such as gray, blue and green production methods receiving attention. Generally missing from this discourse, however, is a quantitative comparison on the cost, scale, carbon footprint and infrastructure requirements for each of these technologies. Here we present a detailed technoeconomic comparison of five hydrogen production technologies: thermochemical water splitting, methane pyrolysis, water electrolysis, steam methane reforming, and chemical looping hydrogen production. Steam or autothermal methane reforming with carbon capture (SMR + CC) at large scale sets the benchmark for costs, but at small scales, electrochemical technologies appear more suitable. Potentially competitive with and sometimes more affordable than SMR + CC are chemical looping hydrogen production and methane pyrolysis. The impacts of the CO2 footprint of the electricity grid and a price on CO2 are also quantitatively evaluated. A qualitative consideration of the ability to leverage existing infrastructure is also offered with a view towards rapid scalability. Finally, the key research needs are identified for each technology.

Experimental and theoretical studies of natural mineral attapulgite supported iron-based oxygen carriers in chemical looping hydrogen production

The low-priced and efficient oxygen carrier is the key to the successful operation of chemical looping hydrogen production (CLH) technology, and also the premise and foundation of its large-scale application. In this study, a novel iron-based oxygen carrier based on natural mineral attapulgite (ATP) was first applied to CLH. The effects of support on the performance of iron-based oxygen carrier and its mechanism in the CLH process were investigated. The results showed the Fe2O3 with ATP as support had more superior activity and stability than those supported by expanded perlite, kaolin or Al2O3. In particular, Fe6ATP4 exhibited a high hydrogen yield at 850 °C which was twice as high as that of Fe2O3/Al2O3. The excellent reaction performance of Fe2O3/ATP was validated by both experimental and theoretical methods. Density functional theory (DFT) calculations revealed that the electrons in Fe2O3/ATP system have stronger delocalization than those of Fe2O3/Al2O3. Moreover, XPS showed there were more defect oxides or hydroxyl groups on the surface of ATP-supported Fe2O3, which further facilitated the reduction reaction.

Performance of red mud oxygen carriers in chemical-looping hydrogen production using different components of plastic waste pyrolytic gas

This study proposed plastic waste-fueled Chemical-looping Hydrogen Production (CLHP) based on the concept of three-reactor chemical-looping process for the purposes of sustainable treatment of plastic wastes while producing high purity H2 and separating CO2. Oxygen carrier prepared from red mud wastes (Bauxite residues) was suggested to be circulating materials to improve combustion efficiency and H2 yield. The feasibility of using pelletized oxygen carrier prepared from red mud wastes was experimentally investigated with major components (H2, CH4 and C2H4) of plastics pyrolysis gases as fuels. The red mud oxygen carrier composed of around 38 wt% Fe2O3 and 50 wt% inert materials, and CuO-promoted oxygen carriers composed of 8.0 wt% CuO and 92 wt% red mud wastes were used. The two oxygen carriers were examined by parallel experiments, focusing on the aspects of oxygen transport, stability, hydrogen productivity and carbon deposition. Temperature and different components of plastic pyrolysis gases had significant impacts on oxygen transport behaviors; reduction tests using CH4 or C2H4 fuels suggested that the operation temperature of Fuel Reactor should be higher than 800 °C for deep reduction and high H2 productivity. CuO addition significantly promoted oxygen carrier's reactivity and oxygen transport capacity with various fuel components. The cyclic CLHP experiments, performed over 10 redox cycles with C2H4 as fuels, showed that there was only a limited degradation in oxygen carriers caused by carbon deposition and element migration. The developed oxygen carriers can meet the requirements of long-term operation for CLHP process. Carbon deposition on the oxygen carriers derived from hydrocarbon fuel cracking seemed to be inevitable, which experimentally determined in the range of 0.01–0.043 g g−1 oxygen carriers as C2H4 was used as fuels. However, the reactivity of these carbon deposits was extremely low; their initial steam-gasification temperatures were around 750 °C, much higher than the temperature used for water splitting reaction. This provides the potential opportunities for an industrial CLHP process to produce high purity H2 (>97%) despite of carbon deposits presents in Fuel Reactor.

Highly Efficient CO2 Capture and Utilization of Coal and Coke-Oven Gas Coupling for Urea Synthesis Process Integrated with Chemical Looping Technology: Modeling, Parameter Optimization, and Performance Analysis

The resource endowment structure of being coal-rich and oil-poor makes China’s production of coal-based ammonia and urea, with a low production cost and a good market, a competitive advantage. However, the process suffers from high CO2 emissions and low energy efficiency and carbon utilization efficiency due to the mismatch of hydrogen-to-carbon ratio between raw coal and chemicals. Based on the coal-to-urea (CTU) process and coal-based chemical looping technology for urea production processes (CTUCLAS&H), a novel urea synthesis process from a coal and coke-oven gas-based co-feed chemical looping system (COG-CTUCLAS&H) is proposed in this paper. By integrating chemical looping air separation and chemical looping hydrogen production technologies and the synergies between coal gasification, low-energy consumption CO2 capture and CO2 utilization are realized; the excess carbon emissions of the CTU process are avoided through coupling the pressure swing adsorption of COG, and the low carbon emissions of the proposed system are obtained. In this work, the novel process is studied from three aspects: key unit modeling, parameter optimization, and technical-economic evaluation. The results show that COG-CTUCLAS&H achieves the highest system energy efficiency (77.10%), which is much higher than that of the CTU and CTUCLAS&H processes by 40.03% and 32.80%, respectively, when the optimized ratio of COG to coal gasified gas is 1.2. The carbon utilization efficiency increases from 35.67% to 78.94%. The product cost of COG-CTUCLAS&H is increased compared to CTU and CTUCLAS&H, mainly because of the introduction of COG, but the technical performance advantages of COG-CTUCLAS&H make its economic benefits obvious, and the internal rate of return of COG-CTUCLAS&H is 26%, which is larger than the 14% and 16% of CTU and CTUCLAS&H, respectively. This analysis will enable a newly promising direction of coal and COG-based co-feed integrated chemical looping technology for urea production.

Chemical Looping Enhanced Oil Shale-to-Liquid Fuels Process: Modeling, Parameter Optimization, and Performance Analysis

The solid heat carrier moving bed with internals is an advanced oil shale retorting technology. However, the retorting gas produced by pyrolysis is generally used as fuel gas. The content of CO, H2, and CH4 in the retorting gas is high, and direct combustion leads to resource waste and environmental pollution. In addition, heteroatomic sulfur and nitrogen, as well as unsaturated hydrocarbons, reduce the quality of shale oil. To solve these problems, this paper proposed a chemical looping enhanced oil shale-to-liquid fuels (CLeSTL) process. The chemical looping hydrogen production technology is applied to convert retorting gas to hydrogen, and the hydrogen produced is used for shale oil hydrogenation to improve the oil quality. In this paper, the new process is modeled and simulated; then technoeconomic analysis is carried out. Technical analysis shows that shale oil yield is increased from 65% to 95.7% and the yield of light fraction is increased from 20% to 64%–83%. Economic analysis shows that the CLeSTL process with ligh fraction hydrogenation has the highest investment profit rate and large profit space. In addition, when the oil price is lower than 50 USD/bbl, the investment profit is 5%, which shows strong anti-risk ability.

The effect of microscopic phenomena on the performance of iron-based oxygen carriers of chemical looping hydrogen production

The scope of this work was to investigate and understand the microscopic effects on the performance of the active catalytic system in the chemical looping process. The inhibiting and accelerating effects of the different materials have been extensively studied. The ZrO2 doped with MgO and Y2O3 showed a chemical inertness and the formation of a porous morphology for an enhanced cyclic stability. Testing in large-scale application indicates that supporting material with higher yttrium content in ZrO2 has an excellent performance for 100 cycles. The HT-XRD and DSC analyzes clearly show microscopic phenomena play a fundamental role in the process and correspond to the phase transition. Stabilization of the cubic/tetragonal crystal structure leads to suppression of the phase transition and exhibits highest activity. The work reveals new fundamental principles for the design of OC in chemical looping hydrogen and understanding the influence of microscopic effects on the stability of oxygen carriers.

Polygeneration of Hydrogen and Power Using Chemical Looping Water Splitting with Dual Loops of Oxygen Carrier

The demand for hydrogen as a fuel, particularly in the transportation and power sectors, has recently been increasing due to its environmental benefit of clean combustion. However, the conventional technologies for hydrogen production involve an energy penalty in purification of hydrogen and the carbon dioxide capture, which reduce the process efficiency, whereas the technique of chemical looping hydrogen production (CLH) has an inherent capacity for CO2 capture and produces pure stream of hydrogen. This paper proposes modifications in the conventional three-reactor CLH setup, leading to elimination of the energy-intensive air separation unit and imparting flexibility in terms of polygeneration (hydrogen and power). The design modification for thermally integrating the air reactor, gasifier, and splitter for an oxygen carrier has facilitated two distinct oxygen carrier loops to meet the polygeneration objectives. The performance metrics based on efficiency have been utilized to assess the performance of the proposed process and demonstrate the flexibility in polygeneration. The effect of varying operational parameters such as split fraction, composition of metal oxide, and temperature of air reactor on the performance of the proposed process has also been evaluated.