Solid Oxygen Research Articles

Fast response solid electrolyte oxygen sensors with porous thin film electrodes.

A novel solid electrolyte sensor with considerably improved response times is presented. The new so-called eFIPEX [etched flux (Φ) probe experiment] is based on the FIPEX [flux (Φ) probe experiment] sensor applied for the measurement of molecular and atomic oxygen concentrations. A main application is the measurement of atmospheric atomic oxygen aboard sounding rockets up to altitudes of 250 km. eFIPEX employs a new manufacturing technique for its electrodes combining two manufacturing steps-the deposition of platinum films with a polyol process and electrochemical etching to carve out the electrode geometry. Selectivity toward atomic oxygen is achieved through gold plating. All work steps can be completed in ambient air. Electrodes with thicknesses of 200nm to 1.5μm are manufactured and characterized with optical and electron microscopy as well as with energy dispersive x-ray spectroscopy. It is shown that the significantly faster response times are related to pores in the platinum film reaching down to the substrate. The new eFIPEX were flown in comparison with conventional FIPEX sensors on the PMWE-2 sounding rocket flight showing significantly improved performance. Due to the easier fabrication and the superior transient behavior, this new sensor system will be preferentially used in future missions.

Comparison of composite metal oxides as oxygen carrier for methane chemical looping reforming

Abstract The amount of greenhouse gases has increased considerably in recent years. Additionally, the energy required by humanity for daily activities is also on the rise. The planet is facing one of its worst crises, characterized by the overexploitation of fossil fuels due to population growth. It is estimated that by 2050, the global population will exceed 9 billion inhabitants. Chemical looping combustion (CLC), offers a potential solution. This process involves usually two interconnected reactors, usually with a fluidized bed, where combustion takes place in an alternate way. In this process, the oxygen required for combustion is provided by a solid oxygen carrier, the capacity of this depends on the nature of the material and is crucial to define the most effective one by a comparative study. Moreover, methane emissions are a significant concern, as methane is a potent greenhouse gas with a 25 times greater impact on the atmosphere compared to carbon dioxide as greenhouse gases. To address this, methane reforming in chemical cycles, such as Steam Reforming Chemical Looping Combustion (SR-CLC) or chemical looping reforming (CLR), is proposed. Using a Gibbs reactor and oxygen carrier data reported in the literature, the analysis of NiWO4, FeMoO4, Fe2MnO4 and FeZnO4, their operation, energy yield when exposed to a methane stream and the comparison between different forms of reforming schemes, as well as the estimation of the carrier needed for the process, are presented. Results indicate that after calculations, the g-carrier/g-fuel ratio for NiWO4 is almost 100 % higher than the other carriers studied in this work. Water vapor reforming generates 30.0930 kW and a stream of pure hydrogen that can be separated while carbon dioxide reforming is a general endothermic process that requires 12.22 kW of energy for this process scheme. Once the ideal carrier has been analyzed, the proposed future work should focus on the optimal design of a reaction system that will allow it to operate efficiently under the conditions encountered. In addition, it will be necessary to find the replacement rate for the carrier that will allow us to operate our system continuously.

Evaluating the Impact of Phosphorus and Solid Oxygen Fertilization on Snap Bean (Phaseolus vulgaris L.): A Two-Year Field Study.

The snap bean (Phaseolus vulgaris L.) is highly sensitive to both phosphorus (P) deficiency and hypoxic stress, which together can significantly hinder plant growth, nutrient uptake, and yield; however, limited information exists on the effect of P and oxygen (O2) fertilization to alleviate these stresses and enhance yield. A two-year field experiment assessed the effects of P and O2 fertilization on plant growth, pod yield, and P uptake in acidic sandy soil. Using a randomized complete block design with four replications, we tested five P rates (0, 45, 90, 135, and 179 kg ha-1 of phosphorus pentoxide, P2O5) in the form of triple superphosphate (TSP) along with two rates (0 and 45 kg ha-1) of solid O2 fertilizer as calcium peroxide (CaO2). Phosphorus and O2 fertilizers improved plant growth and pod yield, with the highest yield from the combination of 135 kg ha-1 P2O5 and 45 kg ha-1 CaO2. Pearson correlation analysis indicated strong associations between plant growth, pod yield, and nutrient accumulation. Principal component analysis (PCA) highlighted notable seasonal differences in snap bean and soil characteristics. This study provides essential insights into the use of O2 fertilizers as a cost-effective approach to mitigate hypoxia, enhance P use efficiency, and improve yield in snap bean. Our findings may inspire the development of sustainable nutrient protocols for high-quality snap bean production and serve as a foundation for similar applications in other crops.

Solid State YSZ Electrolyte Oxygen Partial Pressure Under Dynamic Operation

Idaho National Lab has developed a time dependent model of oxygen partial pressure in the electrolyte of a solid oxide cell. This model is of a standard cell used commonly throughout literature and is the reference cell of the H2New consortium. The cell is composed of a generic material set for solid oxide electrolysis. The electrolyte is a 7 micron thick layer of YSZ, 5 micron thick barrier layer of GDC, and an electrode layer of LSCF. During cell operation, there is a slow increase of oxygen partial pressure in the electrolyte. This can be observed to reach a critical threshold which induces micro-cracking. This is one of the underlying degradation mechanisms of solid oxide cells. At high current, the time to reach the threshold changes. By switching between a safe threshold and an unsafe threshold, a meta-stable relaxation and redistribution of oxygen partial pressure avoids reaching the critical threshold. The time scale of the threshold can be between seconds and hours depending on the current and voltage applied. Models have been developed to reduce the impact of oxygen partial pressure using different cycling timescales, as well as identifying safe short-term overproduction rates.

P-Orbital Ferromagnetism Arising from Unconventional O- Ionic State in a New Semiconductor Sr2AlO4 with Insufficiently Bonded Oxygen.

Oxygen in solids usually exists in an O2- ionic state. As a result, it loses its magnetic nature of a single atom, wherein two unpaired electrons exist in its outer 2p orbitals. Here, it is shown that an unconventional stable ionic state of O- is realized in a new semiconductor material Sr2AlO4, leading to an intrinsic p-orbital ferromagnetism stable until ≈900K. Experimental and theoretical investigations have clarified that one-fourth of the oxygen atoms in Sr2AlO4 are insufficiently bonded in the crystal structure, resulting in a unique O--state and p-orbital ferromagnetism. To date, the O- state is reported to exist only in non-equilibrium conditions, and p-orbital magnetism is only suggested in impurity bands with small ferromagnetic moments. The present work provides a new route for creating ferromagnetism in semiconductors and exploring new p-orbital physics and chemistry. In addition, the material shows elastic-mechanoluminescence that may enable unprecedented mechano-photonic-spintronics.

Numerical study of a chemical looping combustion system: Effects of fuel type and particle size distributions on the operating performance

Chemical looping combustion (CLC) using biomass offers a promising pathway for achieving negative carbon emissions. However, the different properties of coal and biomass affect reaction performance, which has not been fully explored in the CLC system. Additionally, the effects of particle size distributions (PSDs) of solid fuels and oxygen carriers (OCs) are inadequately addressed. In this study, a 3D reactive model using the computational particle fluid dynamics (CPFD) method is developed to investigate the effects of PSDs of both solid fuels and oxygen carriers on operating performance with coal and biomass as fuels. Results indicate that the average residence time in FR of coal and biomass particles is 0.86 s and 0.68 s, respectively, but biomass outperforms coal in reaction efficiency. For coal-fueled CLC, the average residence time is 0.46 s for coal particles with diameters of 100–200 μm, whereas it reaches 0.86 s for coal diameters of 300–700 μm. However, the reaction performance is better with smaller coal sizes due to char gasification being the rate-limiting step. In comparison, for biomass-fueled CLC, the reaction efficiency remains consistent across various particle sizes under the specified conditions due to the rapid release of volatile components and the low content of char. Additionally, it is found that the OC conversion ratio is mainly determined by their residence time in the zones with relatively higher concentrations of the combustible gas in FR. Employing OCs with overly wide PSDs such as 300–800 μm can compromise the material seal above the AR, increase the risk of gas leakage and decrease the separation efficiency of the inertial separator.

Phase transition kinetics of superionic H2O ice phases revealed by Megahertz X-ray free-electron laser-heating experiments

H2O transforms to two forms of superionic (SI) ice at high pressures and temperatures, which contain highly mobile protons within a solid oxygen sublattice. Yet the stability field of both phases remains debated. Here, we present the results of an ultrafast X-ray heating study utilizing MHz pulse trains produced by the European X-ray Free Electron Laser to create high temperature states of H2O, which were probed using X-ray diffraction during dynamic cooling. We confirm an isostructural transition during heating in the 26-69 GPa range, consistent with the formation of SI-bcc. In contrast to prior work, SI-fcc was observed exclusively above ~50 GPa, despite evidence of melting at lower pressures. The absence of SI-fcc in lower pressure runs is attributed to short heating timescales and the pressure-temperature path induced by the pump-probe heating scheme in which H2O was heated above its melting temperature before the observation of quenched crystalline states, based on the earlier theoretical prediction that SI-bcc nucleates more readily from the fluid than SI-fcc. Our results may have implications for the stability of SI phases in ice-rich planets, for example during dynamic freezing, where the preferential crystallization of SI-bcc may result in distinct physical properties across mantle ice layers.

Advancing the performance characteristics of rubber asphalt mixtures through the integration of Basic Oxygen Furnace (BOF) slag: A focus on static and dynamic mechanical enhancements.

To investigate the advantageous effects of incorporating industrial solid waste basic oxygen furnace (BOF) slag on the mechanical characteristics of warm-mixed rubber asphalt (WMRA) and hot-mixed rubber asphalt (HMRA) mixture, varying proportions of BOF slag were substituted for limestone coarse aggregates (0%, 25%, 50%, and 75%). Additionally, a 1.5% dosage of Sasobit warm-mixed modifier was introduced to prepare the rubber asphalt. Subsequent to preparation, both static mechanical tests (including Marshall and indirect tensile tests) and dynamic mechanical tests (including dynamic creep and elastic modulus tests) were conducted to evaluate the influence of BOF slag on the mechanical behavior of WMRA and HMRA mixtures across different substitution levels. Following testing, a two-way analysis of variance (ANOVA) was employed to dissect the impact of BOF slag content and Sasobit warm-mixed modifier on the static and dynamic mechanical properties of the rubber asphalt mixtures. The findings reveal that BOF slag exhibits commendable engineering aggregate properties, enabling substantial substitution of coarse aggregates in both HMRA and WMRA mixtures. As the proportion of BOF slag increases, it enhances the resistance of asphalt mixtures to permanent deformation and cracking under static and dynamic loading conditions, while broadening the range of elastic deformation for both WMRA and HMRA mixtures subjected to repeated loading. Moreover, a synergistic enhancement in the resistance of rubber asphalt mixtures to dynamic load-induced deformation is observed when employing both BOF slag and Sasobit warm-mixed modifier. The findings offer valuable insights for enhancing the performance of WMRA and HMRA mixtures, as well as broadening the utilization of BOF slag and waste rubber.

Contact electrification characteristics of solid oxygen particle-laden flows in liquid hydrogen transportation

The issue of electrostatic safety in liquid hydrogen systems has garnered increasing attention, especially concerning the potential threat of electrostatic explosions due to the collision-electrification phenomenon of solid oxygen particles formed after air leakage in liquid hydrogen pipelines. To delve into the contact electrification characteristics of solid oxygen particle-laden flows in liquid hydrogen transportation, a mathematical model based on the computational fluid dynamics-discrete element method (CFD-DEM) two-phase flow dynamics has been developed. This model integrates the Hertz contact theory for describing particle collision processes and the condenser model for describing particle collision-electrification. The reliability of this model has been validated in existing literature through its ability to capture the flow characteristics of two-phase flow and the electrification characteristics of particle groups. Using density functional theory to compute the solid oxygen work function and considering the low-temperature properties of liquid hydrogen, a series of numerical studies on the flow sedimentation and electrification characteristics of solid oxygen particle-laden flows in liquid hydrogen pipelines have been conducted. The results indicate that particles carry negative charges after colliding with stainless steel pipe walls, with single charge exchange magnitudes of approximately 10−12C for particle-wall continuous collision processes and 10−14C for particle-particle collision processes, resulting in particle charge-to-mass ratios on the order of tens of μC/kg at the outlet interface. The impact of electrostatic forces on particle motion is significant and cannot be overlooked. Furthermore, the effects of velocity, particle diameter, and pipe diameter on particle charge characteristics have been thoroughly analyzed. At low flow velocities, severe particle settlement occurs, leading to increased collision frequency between particles and walls and significant charge accumulation. Increasing flow velocity can mitigate particle settlement and reduce charge levels. Changes in particle and pipe diameters have a minor impact on particle settlement but can increase single charge amounts with larger particle diameters and intensify particle charging with reduced pipe diameters due to shortened radial travel distances, leading to increased collision frequency. Our study meticulously illustrates the charge characteristics of individual particles and particle groups, providing a theoretical basis for assessing the electrostatic safety of liquid hydrogen transportation systems under extreme conditions.

Structural changes and grading mechanism of lignin during solid alkali-active oxygen extraction and grading

Cooking with active oxygen and solid alkali (CAOSA) is an efficient pretreatment method for biomass. For better grading of the lignin yellow liquor, the different lignin fractions and the recovered solid alkali were obtained using a simultaneous acid-alkali graded separation method. The results indicated that the recovery rate of solid alkali was 67.25 %, and the grading of lignin components was characterized by smaller dispersion coefficients, and more stable properties and structure. Lignin fractions with low dispersion coefficients possess more key structures, including the Phenol hydroxyl group (ArOH), Methoxy (OMe), and β-aryl ether (β-O-4), and have better thermal properties. The low molecular weight L4 has the highest ArOH content (2.1 mmol/g), which provides better antioxidant properties. The CAOSA process destroyed the S-unit and prevented lignin from condensation. Furthermore, the CAOSA process protected carbohydrates, which could effectively prevent them from dehydrating and re-polymerizing into pseudo-lignin. This allowed the pulp to remain natural, which was beneficial for subsequent transformation and utilization. Overall, the efficient separation of biomass components and lignin grading method proposed by combining the CAOSA process with the acid-alkali grading separation method has a strong application prospect and provides a theoretical basis for the high-value utilization of biomass and lignin.

Evaluation of the Mineral Manganese OXMN009 and OXMN009P in the Chemical Looping Combustion (CLC) Process Using Thermogravimetry

Indirect combustion with the chemical looping combustion (CLC) of solid oxygen carriers is one of the most promising technologies for capturing carbon dioxide (CO2) in energy production from fossil fuels since the separation of the generated CO2 is inherent to the process itself. Therefore, the cost associated with capturing this gas will be significantly reduced. This technology transfers oxygen from air to fuel through a metal oxide that acts as an oxygen carrier, avoiding direct contact between air and fuel. This oxygen carrier circulates in a fluidized bed reactor called a reduction reactor and an oxidation reactor. (1) This research work has focused on evaluating the behavior of oxygen carriers based on the original and improved manganese mineral (copper-impregnated mineral) named for this study, OXMN009 and OXMN009P, respectively. (2) Equilibrium experiments were carried out on a thermogravimetric balance (TGA) to evaluate the kinetic behavior of these oxygen transporters OXMN009 and OXMN009P, using the gases methane (CH4), carbon monoxide (CO), and hydrogen (H2). (3) The enhanced solid oxygen carrier OXMN009P exhibited good performance for the CLC process with gaseous fuels in terms of reactivity and combustion efficiency, having high reactivity and oxygen transfer properties due to copper impregnation. (4) The results show that OXMN009P has comparable reactivity to other manganese-based materials reported in the literature. It may be an effective option for carbon dioxide capture, as it uses metal oxides as the oxygen transporters (TO). (5) These oxygen transporters, OXMN009 and OXMN009P, are used in a cyclic process that prevents the formation of nitrogen oxides by keeping the air and fuel separate. (6) Thermogravimetric balance (TGA) experiments were conducted to evaluate the kinetic behavior of these copper-modified oxygen transporters. (7) It was found that OXMN009P improved the reactivity and oxygen transfer properties due to copper impregnation. The kinetic parameters obtained in the TGA indicate that the reaction is non-thermal and requires less energy to initiate. (8) The results show that OXMN009P has reactivity comparable to other manganese-based materials reported in the literature and can be an effective option for carbon dioxide capture.

Revealing the mechanism of hydration on the CO2 kinetic adsorption of CaO surface via ReaxFF MD simulations with experiments

Hydration has been regarded as an effective method to improve the cyclic activity of CaO during the Calcium looping CO2 capture process, but its mechanism remains unclear. In this work, the hydration reaction of CaO surface and its underlying mechanism was studied by ReaxFF molecular dynamics simulation combing with TGA experiments. The effect of hydration on the initial CO2 adsorption rate showed a trend of promoting at low H2O degree and inhibiting at high H2O concentration. The CaO surface was easily passivated, and it can maintain its crystal structure and begin to distort at about 1.0 H2O monolayer contents. Hydration failed to promote the CO2 adsorption rate, inversely the CO2 adsorption process accelerated the diffusion of H ions inward the CaO lattice·H2O dissociation produced two hydroxyl groups: direct OwH and indirect OsH. Atomic density profiles showed that the direct hydroxyl pairs were always, and indirect OsH groups can consume surface oxygen active sites, reducing the initial rapid CO2 adsorption activity. On the pre-hydrated CaO surface, CO2 molecules were more likely to bind to solid oxygen active sites than OH groups. The H free radical diffused inside the lattice in the form of transition HO2 state, promoting the slow CO2 adsorption amount.

Numerical mass transfer simulations of Venturi-type solid phase oxygen control with mass exchanger in UPBEAT loop

The Venturi-type solid-phase oxygen control system with a bypass mass exchanger is widely regarded as an effective approach to keep the oxygen concentration in the LBE under reasonable ranges to reduce the corrosion. In this work, numerical simulations of the particle–fluid mass transfer of the oxygen concentration in LBE are performed for the 1:1 scale 3D UPBEAT loop under various conditions. The discrete element method is applied to generate the geometry of the packing of the PbO spheres. The velocity profile and oxygen concentration governing equations are solved by using the SST turbulence model. At the same temperature, the oxygen mass transfer coefficient increases monotonically with the flow rate. At the same mass flow rate, the mass transfer coefficient increases with the temperature, reaching a maximum at about 475 °C. It provides guidance for future research in the design and optimization of oxygen control systems under high temperature in lead–bismuth nuclear reactors.

Assessing environmental pollutionfrom shrimp farming activities in Soc Trang province

The study aimed to evaluate the level of environmental pollution from shrimp farming in coastal areas of Soc Trang province. A total of 10 shrimp farming households and 50 neighbouring households were interviewed about emissions and environmental sanitation conditions. At the end of the shrimp season, pond water samples were collected from 5 semi-intensive ponds and 5 intensive ponds, bottom sediment samples were collected from 5 semi-intensive ponds to evaluate the level of pollution. Interview results indicated that wastewater and bottom sediment from shrimp farming are the main causes of declining surface water quality and reducing the number of wild fish; pollution levels are likely to increase in the future. The pH, total suspended solid (TSS), BOD5, and chemical oxygen demand (COD) values of pond water samples are suitable for shrimp farming (except TSS of water samples in Cu Lao Dung and Long Phu); total Kjeldahl nitrogen (TKN) and total phosphorus (TP) contents fluctuate widely between sampling ponds. The metal content in the bottom sediment is lower than the allowable discharge threshold of sediment quality standards. Solid waste generated in farming areas has not been properly collected and treated. To sustainably develop the shrimp industry, local authorities need to encourage shrimp farmers to apply proper waste treatment technologies in addition to state management solutions.

Effect of Biomass Torrefaction on the Syngas Quality Produced by Chemical Looping Gasification at 20 kWth Scale.

The innovative Biomass Chemical Looping Gasification (BCLG) process uses two reactors (fuel and air reactors) to generate nitrogen-free syngas with low tar content under autothermal conditions. A solid oxygen carrier supplies the oxygen for partial oxidation of the fuel. This study investigated the BCLG process, conducted over 25 h of continuous operation at 20 kWth scale, using ilmenite as the oxygen carrier and wheat straw pellets as fuel (WSP). The effect of using torrefied wheat straw pellets (T-WSP) on the syngas quality was assessed. In addition, the impact of several operational variables on the overall process performance and syngas yield was analyzed. The primary factors influencing the syngas yield were the char conversion through gasification and the oxygen-to-fuel ratio. Higher temperatures, extended residence times of solids in the fuel reactor, and using a secondary gasifier led to increased char conversion, enhancing H2 and CO production. Optimizing the air reactor design could enhance the CO2 capture potential by inhibiting the combustion of bypassed char. While char conversion and syngas yield with T-WSP were lower than those with WSP at temperatures below 900 °C, T-WSP achieved a higher syngas yield under conditions favoring high char conversion. The presence of CH4 and light hydrocarbons showed minimal sensitivity to operating conditions variation, limiting the theoretical syngas yield. Overall, the CLG unit operated smoothly without any agglomeration issues.

Thermodynamic analysis on the fate of ash elements in chemical looping combustion of solid fuels – Manganese-Based oxygen carriers

Chemical looping combustion (CLC) is an innovative technology suitable for converting waste-derived fuels into heat and power. The process inherently produces pure CO2, which is highly favorable for carbon capture and storage and could be instrumental for achieving negative emissions. CLC operates by utilizing solid oxygen carriers (OCs) to transfer heat and oxygen between two reactors. The OC play a crucial role in achieving an efficient combustion. Manganese-based OCs are particularly interesting, due to their ability to release gaseous oxygen. However, ash components from solid fuels could alter their oxygen transfer capacity, and cause problems related to corrosion and agglomeration. The objective of this work is to obtain in-depth insights about Mn-based OCs for CLC of waste-derived fuels. This is achieved by investigating phase transitions during CLC of solid fuels when utilizing two manganese-based OCs: manganese oxide and a representative manganese ore. For this purpose, thermodynamic modeling is employed, and a specific focus is given to K, Na, Cu, Zn, and Pb, due to their important role in corrosion and/or agglomeration. Thermodynamic databases are expanded by calculating properties from first-principles. It is shown that Mn-based OCs are suitable for effectively converting waste-derived fuels while limiting corrosion. Furthermore, the iron in manganese ores is found to have positive implications for oxygen-transfer reactions. In terms of alkali release to the gas phase, manganese ore seems to be a more promising material compared to manganese oxide. The pathways for the heavy metals Zn, Cu, and Pb were, meanwhile, independent of the OC type.

Overcoming equilibrium constraints in the reverse water gas shift with counter-current gas–solid flow and oxygen transport in La0.75Sr0.25Cr0.5Mn0.5O3-δ

Utilizing carbon dioxide in the reverse water gas shift (RWGS) reaction (CO2+H2→CO+H2O) is a potential pathway for mitigating CO2 emissions, as the resulting CO can be used to produce valuable products, such as chemicals and fuels. Here, we explore the implementation of the RWGS reaction by solid-oxide redox cycling in a two-reactor moving-bed process with counter-current gas–solid flow. We also develop a method for obtaining design diagrams from the thermodynamic data of the solid oxide utilized for redox cycling. Using this tool and screening the previous literature for relevant thermodynamic data, we identify the perovskite La0.75Sr0.25Mn0.5Cr0.5O3-δ as a highly promising candidate material, and we experimentally determine its non-stoichiometry under conditions relevant for the RWGS. The reaction kinetics are also obtained for its reduction in H2 and its reoxidation in CO2. We observe that the inward diffusion of oxygen into the perovskite grains during reoxidation in CO2 is likely to determine the minimum feasible temperature at which this process can be operated, and we estimate an effective diffusion coefficient of D = 7.7−1.4+1.8 *10−14 cm2 s−1 at T = 550 °C, with an activation energy of 122±4.4 kJ mol−1. Implementing the RWGS with this material in counter-current gas–solid flow is expected to significantly improve the RWGS process by decreasing the operating temperature, enabling continuous gas production, and increasing the gas conversion.

Photoabsorption spectra of solid O2 in ultraviolet and far-vacuum ultraviolet region at 9–30 K

Abstract We report ultraviolet and far-vacuum ultraviolet (FUV) absorption spectra of solid molecular oxygen recorded over the wavelength region 110–365 nm for temperatures between 9 and 30 K, in which the light source was dispersed from a synchrotron. The UV/FUV spectra of solids O2 deposited at various temperatures appeared distinctly different profiles due to variation of compositions of α-O2, β-O2, and the imperfect crystal structure at the specific temperature; in addition, the icy sample exhibited its own scattering curve deposited at specific temperature. Resolved from the thermal ramping technique, the absorption spectra of solids α-O2 and β-O2 were established in the wavelength region 110–250 nm at 9 and 30 K, respectively, for the first time.

Impact of high-temperature biomass pyrolysis on biochar formation and composition

The development and utilization of biomass play a vital role in reducing fossil fuel dependency and mitigating greenhouse gas emissions. High-temperature pyrolysis provides a promising route for converting biomass into valuable products without tar formation. Kinetic models are essential for understanding biomass pyrolysis processes, aiding reactor design and optimization. In this study, rice husk (RH) and corn straw (CS) are selected, which exhibit significant differences in ash content but are widely present. Pyrolysis is performed using a thermogravimetric analyzer coupled with a mass spectrometer (TGA-MS). The results show a rapid decrease in solid residue oxygen content at elevated temperatures, which stabilized after reaching 900°C, accounting for about 8–10%. MS quantification indicates increased release of H2O and CO during this stage. Fourier transform infrared spectroscopy (FTIR) analysis on the biochar unveils that this phenomenon is attributed to the stretching vibration of C-O bonds and the conversion of -OH groups. The remaining oxygen primarily exists as carbonyl and carboxyl groups. Subsequently, the CRECK-S-B biomass pyrolysis kinetic model is updated, specifically targeting the transformation mechanism of oxygen-containing solids at high temperatures to improve the prediction of biochar yield and elemental composition. The relative error of oxygen content prediction is less than 10%. The accuracy of the model is validated through experimental data and an extensive literature database, leading to the establishment of a comprehensive database. The updated model demonstrates significantly enhanced prediction accuracy for pyrolysis temperatures above 800°C, expanding its applicability range. Moreover, it achieves an accuracy rate exceeding 80% for char yield and elemental content in the temperature range of 200–1000°C, including torrefaction conditions. It provides a theoretical foundation for the effective utilization of high-temperature biochar, offers a novel insight into biomass thermochemical conversion, and contributes to the sustainable development of biomass energy.

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.