Reactor Steam Research Articles

Reaction kinetics and product evolution of hydrolysis in copper-chlorine thermochemical cycle for hydrogen production

By-products of the hydrolysis reaction in the copper-chlorine thermochemical cycle for hydrogen production are key to the final thermal and hydrogen efficiency. The current study focuses on the influences of reaction time, temperature, and steam partial pressure on the hydrolysis reaction and by-product formation mechanism via experimental and multiple analytical methods. The result demonstrates that the hydrolysis reaction of CuCl2 and steam converts to CuCl and Cu2OCl2, with a high conversion of 97%, while the Cu2OCl2 and CuCl2-CuO product mixtures exhibit interconversion capabilities. The increase of temperature increases the CuCl product content, while the decrease of steam partial pressure increases the by-product CuCl2. Particle morphology and reaction thermodynamics are analyzed for main and by-products formation. Finally, the homogeneous reaction model and shrinking core model are used and compared for the activation energy of the formation of Cu2OCl2 for the hydrolysis reaction and the effect of by-products.

Selective catalytic conversion of model olefin and diolefin compounds of waste plastic pyrolysis oil: Insights for light olefin production and coke minimization

The primary challenges in ex-situ catalytic pyrolysis of plastic waste to produce light olefins lie in the selective conversion of larger olefins and diolefins downstream of the pyrolyzer. Hence, the catalytic cracking mechanism of plastic pyrolysis oil was explored using an α-olefin (1-decene) and a diolefin (1,9-decadiene) model compounds over an HZSM-5 zeolite-based catalyst in a fixed-bed reactor. Key objectives were to elucidate the reaction pathways for light olefin production, aromatization, and coke formation in catalytic cracking of larger olefins and diolefins. The investigation explored the impact of HZSM-5 steam treatment severity, contact time (∼58–226 ms), and reaction temperature (250–450 °C) on product yields. The severity of steam treatment was found to increase the 1-decene isomerization rate while decreasing the cracking rate and conversion of 1-decene to C3-4 light olefins. In the catalytic cracking of 1-decene, major product types included olefins (linear and nonlinear) and a few naphthenes, while in the case of 1,9-decadiene catalytic cracking, non-linear olefins were absent, with abundant naphthenes followed by lighter diolefins and C3-5 linear olefins. Temperature and contact time variations revealed that the catalytic cracking of 1-decene initiated with double bond rearrangement isomerization, progressing to skeletal isomerization, and intensified cracking reactions producing light C3-4 olefins. Conversely, in the catalytic cracking of 1,9-decadiene, cyclization was the primary reaction pathway, followed by β-scission, resulting in lighter conjugated dienes and light linear olefins. Thermal gravimetric analysis (TGA) of spent catalysts confirmed a higher coke amount generated during 1,9-decadiene cracking compared to 1-decene cracking, indicating that diene compounds serve as precursors for significant coke formation in plastic pyrolysis oil. These insights provide valuable understanding for catalytic upgrading of pyrolysis oil from polyolefin pyrolysis.

Introducing K to Regulate the Electronic Structure of Perovskite-Type Oxide for the Efficient Reaction of Coke and Steam

Introducing K to Regulate the Electronic Structure of Perovskite-Type Oxide for the Efficient Reaction of Coke and Steam

Understanding Environmental Barrier Coating Lifetimes and Performance for Industrial Gas Turbines

Abstract Hydrogen or hydrogen blend fuels are expected to replace natural gas in land-based industrial gas turbines (IGTs) to support a greener power economy. Silicon carbide (SiC) base ceramic matrix composites (CMCs) are considered for replacement of Ni-based superalloys to facilitate future efficiency improvements. SiC CMCs require environmental barrier coatings (EBCs) to mitigate volatilization from high-temperature steam, thus making the EBC lifetime critical information for identifying CMC component lifetimes. The goal of this project is to determine the maximum bond coating temperature underneath the EBC for achieving an IGT component lifetime goal of 25,000 h, which is far greater than current CMC component lifetime requirements for aeroturbine applications. To provide data for the lifetime model, laboratory testing used atmospheric plasma-sprayed rare-earth silicate EBCs on monolithic SiC substrates with an intermediate Si bond coating. Specimens exposed to 1-h thermal cycles in flowing air–steam environments and reaction kinetics were assessed from 700 °C to 1350 °C by measuring the thickness of the thermally grown silica scales. The silica growth and phase transformation appear critical in predicting EBC lifetime and several strategies have been explored to reduce the oxide growth rate and improve EBC durability at elevated temperatures. Advanced characterization using Raman spectroscopy has helped clarify this system.

Thermal hydraulic analysis of a high-temperature gas reactor steam generator after loss of feed water accidents

The helical coil steam generator is widely employed in the energy conversion process of high-temperature gas-cooled reactors for its high thermal efficiency in producing superheated steam within the helical tubes. These tubes necessitate materials specifically designed to endure high temperatures, prevent ruptures, and ensure durability under various operational conditions. This study aims to identify the maximum temperatures arising from potential transients in the secondary system and to propose immediate safety measures for minimizing associated risks. The RELAP5/MOD3.4 code was used to simulate the behavior of the next generation nuclear plant steam generator's conceptual design using steady-state conditions. Following the validation of the model, the established steady-state conditions were utilized to simulate accident scenarios, including the feed water line break and the loss of feed water flow to the steam generator. The transient scenarios assumptions include closed flap valves and retained hot helium in the shell side. The simulation tasks were conducted both with and without activating the depressurization system, in order to assess its effect on the temperature of tubes on the wall side. The analysis results indicate that tube wall temperatures can reach 720 °C at the steam generator outlet region and 620 °C at the weld region. The immediate activation of the depressurization system with a controlled relief valve can effectively reduce these temperatures by 239 °C in the steam generator outlet and by 133 °C in the weld region. This also lowers the steam generator's secondary side pressure. As a result, an upgrade and enhancement of operational procedures is straightforward.

Frictional pressure drop correlation of steam-water two-phase flow in helically coiled tubes

Helically coiled tubes are utilized as the heat transfer tubes for High-Temperature Gas-cooled Reactor (HTGR) steam generators due to their compactness, thermal expansion accommodation and high heat transfer coefficient. A clear understanding of the pressure drop characteristics is important for the design and operation of steam generators. In this study, experiments were conducted to investigate the frictional pressure drop characteristics in helically coiled tube with a very large curvature ratio of 0.109. The experiments were carried out in a steam quality range of 0.1–0.9, system pressure range of 3.5–7 MPa, mass flux range of 320–1100 kg/m2s. The results indicate that the frictional pressure drop increased with the increase of mass flux, decreased with the increase of system pressure. It first increased with the increase of steam quality, and reached a maximum value at a steam quality of approximately 0.8, then decreased until steam quality reached unity. Based on the present work and existing experimental database, 25 existing correlations are evaluated and none of them could satisfactorily fit all the data. Therefore, a new correlation based on the Martinelli and Nelson correlation was proposed. Compared with existing correlations, it has a broader range of applicability (operating pressure from 0.75 to 8 MPa, mass flux from 200 to 1100 kg/(m2·s), steam quality from 0.03 to 0.99, and curvature ratio from 0 to 0.109.), and higher accuracy (weighted mean MAPE of 8.92 % and arithmetic mean MAPE of 8.81 %). It also has better compatibility with straight tubes.

Elucidating the interaction mechanisms between polyacrylic acid and Alloy 800 oxide films under pressurized water reactor steam generator conditions

The interaction mechanisms between polyacrylic acid (PAA) and Alloy 800 were investigated. Alloy 800 formed a bilayer oxide structure in all conditions, with an outer layer of Fe-rich spinel and α-Ni(OH)2 and a Cr-rich inner layer. The chelating effect of PAA on Fe ions reduced the presence of Fe-rich spinel in the outer layer and increased the Cr content in the inner layer. However, thermal degradation of PAA (≥ 500 ppb) promoted dissolution of Cr in the initial inner layer, increasing the initial corrosion rate. The optimal PAA dosage in steam generators is determined to be approximately 250 ppb.

The effects of in situ-produced hydrogen on catalytic upgrading of lignite pyrolysis volatiles over ZSM-5 zeolites to produce light aromatics

The introduction of in situ hydrogen donors to obtain a high H/Ceff ratio is an effective way to upgrade coal pyrolysis volatiles to light aromatics. In this study, the influence of different in-situ hydrogen suppliers in catalytic reforming of coal pyrolysis vapors was explored. The abilities of active hydrogen donation were greatly corresponded to structures of hydrogen donors. Isopropanol showed the best catalytic performance due to the release of a large amount of active α-H as a result of negative inductive effect of hydroxyl. Whereas tertbutanol showed the poorest catalytic performance owing to the lack of α-H. Meanwhile, the effect of in-situ hydrogen production via steam reforming with different alcohols on light aromatic yields was investigated. The highest BTEXN yield was obtained under in-situ hydrogen production from isopropanol steam reforming. Two circumstances of hydrogen supply were further compared. Relatively higher BTEXN yield was presented in the reaction of methanol steam reforming than that of using methanol solely. However, higher BTEXN yield was contrarily obtained from sole isopropanol as a hydrogen donor despite lower H2 production was gained compared to the case of isopropanol steam reforming. The fact was probably ascribed that high electron-withdrawing effect of hydroxyl for isopropanol promoted the cleavage of α-C-H bond and favored the transfer of active hydrogen to reactants over acid sites.

Modeling and thermodynamic optimization of distributed combined heat and power system based on biomass chemical looping hydrogen generation process

Distributed biomass combined heat and power (CHP) system is becoming an important way to use local biomass for ensuring regional energy supply and reducing CO2 emissions. In this work, a high-efficient CHP system based on a new separated-type biomass gasification process is proposed. The gasification system includes a chemical looping hydrogen generation (CLHG) process combined and a tar catalytic steam reforming (TCSR) unit, in which the general CLHG process includes a fuel reactor (FR), a steam reactor (SR) and an air oxidation reactor (AR), but in this study, the AR is removed and instead, the FR is decoupled into two reaction stages, namely, pyrolysis and gasification. In addition, the biomass pyrolysis-gasification-hydrogen generation (BPGH) combined cycle system is established by using oxygen carrier to couple pyrolysis, gasification and hydrogen generation stages. The TCSR process is used to convert volatiles generated by pyrolysis into syngas. To maximize thermodynamic efficiency of the system, the influences of temperature for the catalytic steam reforming (TCSR) and the ratio of steam to carbon (S/C) on the overall energy and exergy efficiency are mainly studied. The results show that the overall energy and exergy efficiencies reach the highest values of 75.93% (LHV) and 32.61%, respectively, when TSCR=800 °C and S/C = 3 while the net power generation energy and exergy efficiencies are 27.43% (LHV) and 27.54%, respectively.

The several hydrotalcites investigated as precursors of catalysts by Angelo Vaccari

Hydrotalcite-derived catalysts are applied in a very broad range of processes. In this paper, the contribution of Angelo Vaccari’s work to the development of these catalysts is reported. His work spanned from the preparation of novel hydrotalcites in powder and in structured forms, which after thermal treatments are applied in gas phase catalytic processes for reactions of hydrogenation, steam and dry reforming, partial oxidation, condensation and environmental applications. Moreover, he reviewed several aspects of hydrotalcite-derived catalysts. In this work, we summarize the main results that Angelo Vaccari together with his numerous co-workers has achieved.

Effect of long reaction distance on gas composition from organic-rich shale pyrolysis under high-temperature steam environment

When high-temperature steam is used as a medium to pyrolyze organic-rich shale, water steam not only acts as heat transfer but also participates in the chemical reaction of organic matter pyrolysis, thus affecting the generation law and release characteristics of gas products. In this study, based on a long-distance reaction system of organic-rich shale pyrolysis via steam injection, the effects of steam temperature and reaction distance on gas product composition are analyzed in depth and compared with other pyrolysis processes. The advantages of organic-rich shale pyrolysis via steam injection are then evaluated. The volume concentration of hydrogen in the gas product obtained via the steam injection pyrolysis of organic-rich shale is the highest, which is more than 60%. The hydrogen content increases as the reaction distance is extended; however, the rate of increase changes gradually. Increasing the reaction distance from 800 to 4000 mm increases the hydrogen content from 34.91% to 69.68% and from 63.13% to 78.61% when the steam temperature is 500 °C and 555 °C, respectively. However, the higher the heat injection temperature, the smaller the reaction distance required to form a high concentration hydrogen pyrolysis environment (hydrogen concentration > 60%). When the steam pyrolysis temperature is increased from 500 °C to 555 °C, the reaction distance required to form a high concentration of hydrogen is reduced from 3800 to 800 mm. Compared with the direct retorting process, the volume concentration of hydrogen obtained from high-temperature steam pyrolysis of organic-rich shale is 8.82 and 10.72 times that of the commonly used Fushun and Kivite furnaces, respectively. The pyrolysis of organic-rich shale via steam injection is a pyrolysis process in a hydrogen-rich environment.

Sol-gel auto-combustion synthesis of bimetallic Pt-Co/Al2O3 catalysts for hydrogen production via acetic acid steam reforming

Green hydrogen production from renewable biomass via bio-oil catalytic steam reforming was a prospective technology. In order to accelerate the development of high-performance and long-term catalyst, we selected acetic acid as a typical bio-oil model compound to carry out the studies of steam reforming. Excellent bimetallic Pt-Co/Al2O3 catalysts were prepared using a sol-gel auto-combustion method. The effects of the molar ratio of ethylene glycol: citric acid: metal ions (EG/CA/M) on the catalyst structure and subsequent reforming performance were systematically investigated. It was found that the catalyst’s textural properties, reducibility, basic sites, and the dispersion of active metal could be carefully tuned by the EG/CA/M ratio. The catalyst prepared under EG/CA/M ratio of 6:3:1 performed the best reactivity in acetic acid steam reforming, showing a 97.6% acetic acid conversion and a 96.6% H2 yield at the reaction conditions of 650 °C, steam to carbon molar ratio of 5, and space velocity of 6957 h–1. Furthermore, a bifunctional reaction mechanism of acetic acid catalytic steam reforming was proposed by in-situ diffuse reflective infrared Fourier transform spectroscopy analysis coupled with density functional theory calculations.

Global Vision of the Reaction and Deactivation Routes in the Ethanol Steam Reforming on a Catalyst Derived from a Ni-Al Spinel.

Ethanol steam reforming (ESR) over a Ni/Al2O3 catalyst prepared by reduction of a NiAl2O4 spinel is a promising alternative route to produce H2 from biomass. This work deepens into the effect of reaction conditions (450-650 °C, a steam/ethanol (S/E) ratio of 3-9, and a weight space time up to 1.3 h) and evaluates the time on stream evolution of the yields of H2, gaseous byproducts (CO, CO2, CH4, C2H4, C2H4O), and formed carbon/coke. The results are explained taking into consideration the thermodynamics, the extent of each individual reaction, and the catalyst deactivation. Up to 600 °C, the predominant intermediate in the H2 formation is C2H4 (formed by ethanol dehydration) with the preferential formation of nanostructured carbon (nanotubes/filaments) by C2H4 decomposition. The deposition of this type of carbon partially deactivates the catalyst, mainly affecting the extent of the C2H4 decomposition causing a sharp decrease in the H2 and carbon yields. Nevertheless, the catalyst reaches a pseudosteady state with an apparent constant activity for other reactions in the kinetic scheme. At 650 °C, C2H4O (formed by the ethanol dehydrogenation) is the main intermediate in the H2 formation, which is the precursor of an amorphous/turbostratic carbon (coke) formation that initially causes a rapid deactivation of the catalyst, affecting the ethanol dehydration and, to a lower extent, the reforming and water gas shift reactions. The increase in the S/E ratio favors the H2 formation, attenuates the catalyst deactivation due to the suppression of the ethanol dehydration to C2H4, and promotes the reforming, water gas shift, and carbon/coke gasification reactions. A H2 yield of 85% stable for 48 h on stream is achieved at 600 °C, with a space time of 0.1 h and an S/E ratio of 9.

Prognostic model and failure mechanisms of steam generators in Sodium-Cooled fast reactors

This paper presents a prognostic model for sodium-cooled fast reactor (SFR) steam generators (SGs). The purpose of the model is to estimate the remaining useful life of SFR SGs and thus to support the decision-making of autonomous control. SFR SGs are of great interest for plant integrity due to their harsh operation environment. They operate at higher temperatures and higher coolant-to-steam pressure differences than those of current light water reactors (LWR). The severity of the SFR SG failure consequences, which include water-sodium contact, is another reason. Understanding its failure mechanisms is important for the development of its prognostic model. Based on our literature review and physics-based analysis, we concluded that creep would be a dominant degradation mode of SFR SGs due to SFR’s high-temperature and high-pressure environment. Thus, creep is the focus of the prognostic model. Various other failure modes were also investigated in this study. The mechanical fatigue due to flow-induced vibration is usually observed in early developmental phases and would not be an important issue during normal operation. The thermal fatigue due to thermal stripping is occasionally observed in other components in SFRs but does not affect SG integrity. Pure water stress corrosive crack, fretting, and so on are commonly observed in LWR SGs but are significantly less important in SFR SGs because of the high temperatures, high pressure differences, and chemical properties of liquid sodium. Based on these investigations, a prognostic model focusing on creep failures was developed. It estimates the failure probability profile by sampling the Larson-Miller parameter (LMP) and temperature and associated uncertainties through Monte Carlo methods. Two case studies were presented. The first one demonstrated the model’s capability to calculate the failure probability for a new specimen within a given time. If the tube is working under temperatures of 500C ± 3 and pressures of 15.2 MPa, which leads to LMP of 20,100 ± 50, the failure probabilities within 50, 70, and 90 years are approximately 0.1 %, 3.2 %, and 17.5 %. The second demonstrated how adjusting the workload can help to protect the integrity of the component. For an old tube reaching 99 % of its lifespan, continuing to run at temperatures of 500C ± 3 and LMP of 20,100 ± 50 leads to a failure probability of about 29.0 % within a year. If the temperature is reduced by 5C, the failure probability can be reduced to 2.5 %, and, if the pressure is also reduced such that the LMP is increased by 100, the failure probability can further be reduced to 0.12 %.

Process intensification of tar chemical looping reforming based on ReaxFF reaction kinetics investigation

Traditional chemical processes currently produce tar as a by-product with low efficiency. This paper proposes a novel tar chemical looping reforming (t-CLR) process based on reactive force field (ReaxFF) reaction kinetics investigation to enhance its utilization efficiency. Firstly, the t-CLR process is initially established to determine the optimum operating conditions. Through ReaxFF molecular dynamics (ReaxFF-MD) simulations conducted under above conditions, the activation energies of the fuel reactor, steam reactor, and air reactor are determined to be 63.25 kJ/kmol, 107.85 kJ/kmol, and 159.53 kJ/kmol respectively. By implementing micro-dynamic parameters filling, oxygen carrier recovery, and heat integration, the optimal t-CLR process achieves a 97.60 % recovery rate of the oxygen carrier and reduces external utility consumption by 71.39 %. The comprehensive framework with macro and micro dimensions is established based on the above studies to promote the cleaner production of traditional processes. Finally, the utilization efficiency of tar is efficiently improved through t-CLR technology, which allows for an adjustable C/H ratio in syngas. The t-CLR technology can be applied to the chemical and energy industries by adding value to by-products and optimizing energy utilization. Overall, this work provides important guidance for process intensification, energy conservation, environmental protection, and waste utilization. The study further promotes the development of industrial production in a cleaner and more efficient direction.

Effectiveness of Three Reactor Chemical Looping for ammonia production using Aspen Plus simulation

This study uses Aspen Plus simulations to explore the performance of a new flowsheet for ammonia production using Three Reactor Chemical Looping (TRCL) technology. In TRCL, the solid Oxygen Carrier continuously circulates between a Fuel Reactor, a Steam Reactor and an Air Reactor. The Oxygen Carrier is reduced in the Fuel Reactor and oxidised in the Steam and Air Reactors. Hydrogen generated in the Steam Reactor and nitrogen produced from the Air Reactor form a synthesis gas that is converted to ammonia. This study compares the TRCL process with the conventional ammonia process and a pseudo-continuous Chemical Looping Reforming (CLR) process that uses packed beds. Energy and environmental indicators are evaluated for the three processes. It was found that the energy consumed in the TRCL process is higher than the other two processes because of higher steam consumption in the Steam Reactor for generating hydrogen. However, if conversion in the Steam Reactor of greater than 67.5% can be achieved, the energy performance indicators are comparable with the conventional and CLR processes. At 67.5% conversion, the specific energy consumption becomes 21.5 GJ/tNH3. It is also noted that the Specific Energy Consumption for Carbon dioxide Avoidance (SPECCA) is much better than the conventional ammonia process at a steam conversion higher than 67.5%. Although further development is needed, this study shows that TRCL holds promise for lower energy consumption and better environmental performance than other commercial ammonia production technologies.

Single-phase heat transfer prediction in helical coiled tubes in turbulent regime

The accurate estimation of thermal–hydraulic parameters is crucial for the design of Small Modular Reactor steam generators, particularly in the case of complex geometries such as helical coiled tubes (HCTs). Reliable design tools are therefore essential for successful design. In this study, we compiled a database of 706 experiments to evaluate the predictive performance of commonly used correlations for heat transfer estimation in turbulent regime HCTs. Despite ranking the correlations according to their predictive performance, none of the existing correlations were able to accurately predict the broad range of experimental data. Therefore, a new correlation called FAMA was derived, which is simple to use, robust and significantly more accurate than any other correlation. Based on the Colburn Analogy, the FAMA correlation achieved a mean absolute difference of 6.21% compared to the experimental database, which represents a 25.7% improvement over the best existing correlation. Furthermore, the FAMA correlation exhibits good asymptotic behavior in straight tubes and is recommended for single-phase flow in HCTs for turbulent Reynolds numbers up to 135,000, curvatures from 0.00963 to 0.2035, and torsions up to 0.81. The Schmidt́s criterion is adopted for determining the critical Reynolds number. Due to its superior performance and wide range of applicability, the FAMA correlation is recommended for modeling and studying helically coiled steam generators as found in novel integral reactors.

Optimization effect of propylene oxide (PO) on evaporation, combustion, and pollutant emissions of high-energy–density JP-10 fuel

JP-10 is a high-energy–density fuel that is widely used in aerospace propulsion systems due to its wide range of synthetic raw materials and low production costs. However, it faces challenges related to difficult ignition, low combustion efficiency and high pollutant emissions. To address this, blending JP-10 with propylene oxide (PO), a highly volatile substance, provides a practical solution. This study investigates the propagation and evolution characteristics of JP-10/PO binary fuel in large horizontal pipelines. The results demonstrate a synergistic enhancement effect achieved by the JP-10/PO hybrid fuel. PO, with its lower boiling point, quickly evaporates from the mixed droplets, creating a continuous primary flame. As the droplet temperature increases, JP-10, known for its high combustion heat, starts to evaporate, actively participating in the explosion process and forming a secondary flame that spreads in two directions. The combustion of the JP-10/PO mixed droplets involves both physical and chemical processes, including droplet evaporation and gaseous combustion. A binary droplet evaporation model is developed to quantitatively assess the impact of PO fuel ratio on spray evaporation. Additionally, the study examines steam explosion parameters and reaction product characteristics under different PO fuel ratios. It is observed that the evaporation of JP-10/PO mixed droplets occurs in three stages: transient heating, binary equilibrium evaporation, and single component equilibrium evaporation. Increasing the PO fuel ratio leads to a higher temperature rise rate of the droplets and an increased evaporation reaction rate constant. Moreover, the ignition delay time of JP-10/PO gas-phase mixture fuel decreases, while the adiabatic flame temperature gradually reduces. Furthermore, higher PO fuel ratios help reduce the emissions of unstable products in both mixed fuels due to the inherent oxygen content of PO molecules. The current research results can provide scientific references for the improvement of high-energy density fuels and the development of new propellants.

Hydrogen-rich syngas production from acetic acid as bio-oil model compound: Effect of intermediate phases (La2NiO4, La2O3 and Ni) of LaNiO3 catalyst

In biomass gasification, bio-oil is the main component of the condensable by-products. It is considered an attractive source for H2 production via steam reforming. This study conducted acetic acid as a bio-oil model compound with LaNiO3 perovskite catalyst due to its high oxygen vacancies and active sites. However, the perovskite structure of LaNiO3 catalysis can be destroyed by produced H2 gas, forming additional phases, including La2NiO4, La2O3 and Ni. The LaNiO3 and different phases were synthesized via a sol-gel method to probe its contribution and interaction with the H2 gas produced from steam reforming of acetic acid. Through 300 min of reaction in steam to carbon (S/C) ratio of 3, the results showed that reduced-LaNiO3 has stable H2 gas production, while the other phases decrease with time. In particular, CH4 is the main composition with the La2O3 phase. A series of characterization techniques, such as XRD, BET, XPS, SEM, TG, H2-TPR and (CO2 and O2)-TPD, were utilized to investigate fresh and used samples. The results showed that the LaNiO3-reduced phase has high oxygen storage capacity, oxygen mobility, oxygen vacancies and surface area, preventing coke deposition. In contrast, the LaNiO3 and La2NiO4 phases have poor coke deposition resistance.

Solar-driven biomass chemical looping gasification using Fe3O4 for syngas and high-purity hydrogen production

A novel solar-driven biomass chemical looping gasification (SBCLG) system was proposed and experimentally demonstrated for the co-production of pure hydrogen and syngas from biomass wastes using high-flux solar irradiation. In this system, a steam reactor and a solar fuel reactor were adopted to replace the air and fuel reactors in a typical biomass chemical looping gasification (BCLG) system, respectively. The SBCLG exhibits two advantages over BCLG: (1) the syngas yield is raised as the high-temperature process heat is provided by solar radiation rather than biomass combustion, and (2) a pure hydrogen stream is generated in addition to the syngas stream, which allows a flexible adjustment of the carbon-to-hydrogen ratio for downstream chemical processes. This study marked the first demonstration of a complete cycle of SBCLG in a cavity-type packed-bed solar reactor under simulated high-flux solar irradiation. Magnetite (Fe3O4) was circulated between the steam reactor and the solar fuel reactor as the oxygen carrier (OC). The optimal operational parameters, the reaction temperature and solid contact pattern, were first determined in preliminary experiments in an electric furnace. Then, the effect of biomass to oxygen carrier mass ratio (mRH:mOC) on the key performance indicators was also investigated in a solar reactor. When mRH:mOC = 1:2, the highest values of the average carbon-gas yield of 0.69 ± 0.05 and energy upgrade factor of 0.71 ± 0.04 were achieved. The solar fuel reactor produced CH4, CO, CO2 and H2 at 0.63, 11.86, 8.85, and 18.53 mmol/g biomass, respectively, with the steam reactor yielding high-purity H2 at 7.17 mmol/g biomass. The results indicated that the SBCLG is a viable method for co-production of pure hydrogen and syngas in separate streams.