Thermochemical Behavior Research Articles

Delving into textile fast pyrolysis: A holistic study on the effects of feedstock and temperature variability

Perpetual fast fashion wave, dismal global recycling rate, and poor circularity of textiles urged sustainable textile waste disposal solution in lieu of incineration and landfilling. Herein, textile fast pyrolysis was mooted as a promising solution by dint of its fast disposal rate, mild pollutant emission, and multiple value-added products formation. Following ill-defined thermochemical behaviour of individual textiles, in-depth experimental exploration on textile fast pyrolysis was supplemented by feedstock characterization, product distribution, and product characterization to unravel the effects of feedstock (natural/synthetic) and temperature (500–900oC) variability on pyrolysis products. Textile fast pyrolysis harnessed pyrogas with two variable products, viz. retrievable chars and oils [natural textiles: cotton (C), denim (D), & cashmere/plant fibre (CP)] or non-retrievable chars and waxes [synthetic textiles: polyester (P), P/acrylic (PA), & P/cotton (PC)]. Melting and high aromaticity of polyethylene terephthalate (PET) rendered the synthesis of non-retrievable chars and waxes, separately. Given monotonic char yields (7.31–24.19 wt%) reduction with temperature, the oil/wax (53.19–75.19/60.46–70.52 wt%) and gas (13.44–33.67 wt%) yields were negatively correlated to each other. Twill-woven network of D contributed to exclusively high BET surface area of D chars (132.64–217.10 m2/g). All natural textile chars (28.56–32.88 MJ) exhibited comparable higher heating value (HHV) to commercial coals/coke (14.77–34.39 MJ/kg) and biochars (7.26–33.37 MJ/kg). Compared to the commercial fuels, raw textile oils (incombustible-10.14 MJ/kg) and textile waxes (15.88–23.18 MJ/kg) were inferior fuels with low HHV. Nonetheless, cotton (C & D) oils, CP oils, and P-based textile waxes had respective enriched content of levoglucosan (6.85–34.38 area%), triacetoneamine (6.22–21.09 area%), and benzoic acid (16.37–46.55 area%). Considering noteworthy H2 formation data sets (700–900oC; C700 only), natural textile pyrogas (62.75–79.02%) had greater syngas (H2 & CO) composition than synthetic textile pyrogas (62.48–68.23%). At optimal temperature of 900oC, textile fast pyrolysis generated pyrogas with H2:CO ratios (1.30–3.49 ≈ 2) that nearly ideal for Fischer-Tropsch synthesis. Conversely, textile fast pyrolysis also emitted pollutant gases that differ between natural (NH3, N2O, NO, & SO2) and synthetic [NH3 (excluding P), N2O, & NO2] textiles.

Dissociation Without Detonation: A DFT Analysis of the Thermally Induced Fragmentation of Binary Sulfur-Nitrogen Rings and Cages.

Potential thermal dissociation pathways available to binary sulfur nitrides have been explored by density functional theory methods, and the results interpreted in terms of their known thermochemical behavior. The cyclic cation/anion pair S3N3± both undergo concerted (4 + 2) cycloreversions to afford the 3-membered thiadiazirine ring c-NSN and, respectively, the SNS± cation/anions. A similar pathway has been identified for S4N2, leading to S3 and c-NSN. More complex multistep routes for the elimination of c-NSN have been identified for the bicyclic cation/anion pair S4N5±, as well as for the neutral cage structures S4N4 and S5N6. For the S4N5+ cation a transition state for competing skeletal scrambling via a 1,3-nitrogen σ-bond shift has been located. For the multiply charged cations S3N22+ and S4N42+, dissociation mechanisms are driven by charge repulsion effects, affording SNS+/SN+ and S3N3+/SN+ respectively. Channels leading to loss of NS+ from the cyclic cation species S4N3+ and S5N5+ have also been examined, and the possible role of open-chain and cyclic S3N2-based intermediates in the formation of S2N2 during the thermal cracking of S4N4 over silver wool is explored.

Utilization of papermaking black liquor as liquid phase for hydrothermal carbonization of corn stalks: The unique role of alkali for production of hydrochar

Papermaking black liquor (BL) contains a large amount of organic matter, alkali, and salt, which has high value in industrial and agricultural production. In the present paper, hydrothermal carbonization (HTC) technology has been employed to deal with BL and corn stalk (CS) under various conditions. A variety of analytical technologies, including Fourier Transform Infrared Spectrometer, X-Ray Diffraction, element analyzer, comprehensive thermal analyzer, scanning electron microscope, chromatography/mass spectrometry, TOC analyzer, and density functional theory (DFT), were used to characterize the physicochemical properties of hydrochar and aqueous phase product. The effects of experimental parameters (temperature, solid-liquid ratio, and time) on the HTC of BL and CS were systematically investigated. The higher energy yield and densification of hydrochar prepared by our HTC technology were obtained at 260 ℃ in 30 min with a solid-liquid ratio of 1:3. Mechanism study indicates that NaOH, which comes from the original BL, could effectively facilitate the cleavage of β–O–4 bond in lignin and β–1–4 glycosidic bond in cellulose and hemicellulose molecules. Hemicellulose and cellulose are more susceptible to degradation relevant to the lignin in the presence of NaOH. Elementary analysis shows that the dosage of BL is important for improving energy densification of hydrochar. The combustion characteristics show that hydrochar presents a thermochemical behavior, which is close to bituminous coal. Owing to hydroxyl ion in NaOH ion pair was consumed in the series of dehydrogenation reactions, pH of HTC aqueous phase product significantly decreases from 11 to 13 in original BL to 4.8–5. Such results indicate that a completely change for the components of BL could be obtained by our HTC technology, which provide a novel idea for the treatment of Papermaking BL without concentration.

CFD-DEM study on the raceway transport phenomena and thermo-chemical behaviors in a three-dimensional blast furnace: Effects of process parameters

An in-depth exploration of the kinetic behaviors of the raceway can provide practical insights for optimizing blast furnace (BF) operations. In this study, the transport phenomena and thermo-chemical behaviors in the raceway of a three-dimensional BF were simulated from particulate scale by using the discrete element method-computational fluid dynamics (DEM-CFD) approach. The effects of process parameters (blast velocity, oxygen concentration, blast temperature, coke size and distribution, tuyere insertion depth, and tuyere inclination) on coke combustion characteristics (mass fraction distributions of gas species and reaction kinetics rate) and thermo-chemical behaviors (particle volume fraction, raceway size, mass loss, and coke temperature) were investigated. Meanwhile, microstructures of coke bed were analyzed, and correlations were established for raceway size prediction. The results indicate that the mass fraction distributions of O2 and CO are similar, both showing balloon-like shapes. The distributions of both the CO2 mass fraction and the kinetic rates of reactions exhibit annular shapes. The raceway size increases or even overlaps with increasing blast velocity/oxygen concentration/PSD standard deviation of coke and decreasing blast temperature/coke size. Too large or too small tuyere insertion depth or tuyere inclination is not conducive to the formation of the raceway. Besides, the mass loss, temperature, and microstructures also vary with the process parameters. RSM model can well predict the raceway depth, width, and height. This study extends the particle-scale model by considering transport phenomena towards the global perspective of a real BF, and the obtained new findings on the complex reacting behaviors in the raceway will provide better insights into the optimization of the BF process.

Characteristics of Gasless Combustion of Core-Shell Al@NiO Microparticles with Boosted Exothermic Performance.

The microstructures and thermochemical behavior of the energetic composites composed of core-shell structured μAl@NiO microparticles were characterized. These core-shell microparticles were synthesized using a wet-chemistry-based one-pot process, where the assembly was proposed to be driven by the electrostatic force between negatively charged Al and positively charged Ni-NH3 ions. Electron microscopic images demonstrated the formation of NiO nanoparticles adhering to the surface of microsized Al particles with different equivalence ratios. Thermal analysis revealed two consecutive exothermic peaks resulting from the initial thermite reaction between 890 and 960 °C and subsequently the intermetallic/alloy formation reactions between 1000 and 1040 °C. The latter was further confirmed by the endothermic peaks of Al-Ni alloy melting at higher temperatures. The formation of alloy was substantiated by the melting of AlNi3, AlNi, and Al3Ni. The onset temperature of the first exothermic peak decreased with increasing nominal equivalence ratio of the core-shell. Compared to the physically mixed (PM) composite, the core-shell structures decreased the activation energy of the thermite reaction by a mere 9.24 kJ/mol; however, it increased the combustibility by the manifold. The PM composite was not able to be ignited at all by a 5 W laser, while the core-shell counterpart ignited at 2.55 ms and was completely combusted within 6.50 ms accompanying a violent impulse.

Investigation on thermochemical heat charging and discharging behavior of Ca(OH)2/CaO in a fixed bed reactor

Thermochemical heat storage (TCHS) technology plays a crucial role in the energy system, essential for maintaining the balance between energy supply and demand. The Ca(OH)2/CaO system holds significant promise for TCHS thanks to its high energy storage density, cost-effectiveness, and minimal heat loss. However, further research is required to elucidate the coupling mechanisms of the various physicochemical processes involved and to optimize the overall system performance. This paper focuses on assessing and elucidating the multi-physics coupled transport rules during both the charging and discharging stages in a fixed-bed reactor based on the developed numerical model. Results manifest the bed temperature rapidly increases to around 950 K, then slows down as the endothermic reaction predominates, completing dehydration in 1,900 s. During discharging, hydration conversion advances in a “U”-shaped pattern from the vapor inlet and side wall to the outlet, driven by the high vapor content near the inlet and the lower temperature near the wall. Furthermore, a thorough sensitivity analysis of the main parameters such as thermal conductivity and porosity is conducted to determine how different operating conditions affect the charging and discharging processes. Finally, a new reactor structure is proposed, in which a gas-guide duct is added at the central axis of the reactor to improve mass transport and uniformly distributed finned heating tube bundles to enhance heat transfer. These two functions can shorten the charging period by 9 % and 16 % respectively. The results can aid in predicting thermochemical conversion behaviors and multi-physic coupling transport processes, while also providing a foundational reference for the design of TCHS systems.

Disodium terephthalate as a multifunctional additive for simultaneous enhancing the energy release performance and weakening the water reactivity of aluminum

In this study, disodium terephthalate (Na2TP) has been successfully introduced as a novel multifunctional additive for simultaneous enhancing the energy release performance and weakening the water reactivity of micro-aluminum (μ-Al). Seven μ-Al/Na2TP composites with different contents of Na2TP (R-100 to R-700) and four comparison samples have been prepared to investigate the thermochemical behaviors, combustion performances and water reactivity. Importantly, structure characterizations as well as kinetic parameters (e.g., Ea, ΔS‡) have been performed to reveal the impacts of Na2TP on μ-Al oxidation. Moreover, incorporating Na2TP into μ-Al shows the enhancement of energy release, with R-400 exhibiting the highest heat release (4970 J/g) in the main oxidation stage, compared to μ-Al (1696 J/g). Interestingly, μ-Al shows an increased Ea while R-400 exhibits a decreased Ea as the oxidation proceeds. The decomposition of Na2TP generates both heat and CO2 gases, which are beneficial for destroying alumina shell and increasing oxidation kinetics, in consistent with higher positive ΔS‡ value, rougher surface, and higher surface O content for oxidation of R-400 compared to μ-Al. As a result, the enhanced combustion performances of higher peak pressure, pressurization rate and characteristic shock velocity as well as brighter/larger flame images have been achieved by μ-Al/Na2TP composites. On the other hand, water reactivity of μ-Al has been significantly suppressed by introducing Na2TP in terms of the 85.4 % decrease in heat release, elevated Ea, and alteration of reaction mechanism. Consequently, taking organic Na2TP as a multifunctional additive, two birds of enhancing the energy release and weakening the water reactivity is harvested, showing great potentials in improving the performances of metal-based energy systems.

Thermochemical behavior of several common salts blended with cement raw material

Experiments have been conducted to study the thermochemical behavior of common chlorides, sulfates, and alkali salts (CaCl2, CaSO4, K2CO3, Na2CO3, KCl, NaCl, K2SO4, Na2SO4) when blended with cement raw materials at high temperatures, as well as the phenomena of element migration and transformation of Cl, S, K, and Na in the process. The results indicate that little effect was observed on the formation of clinker with the addition of 20% KCl&NaCl and 10% CaSO4. KCl&NaCl were observed to melt at 800°C but completely volatilize at 1100°C, while CaSO4 was not completely decomposed until 1450°C. The addition of 10% CaCl2, 20% K2CO3&Na2CO3, and 20% K2SO4&Na2SO4 resulted in the appearance of the liquid phase of raw materials at 800°C. K2CO3&Na2CO3 predominantly formed complex and stable potassium salts and sodium salts through reactions with raw materials, significantly affecting the formation of C2S and C3S. CaCl2 and K2SO4&Na2SO4 mainly produced liquid phases through melting. CaCl2 completely volatilized after reaching 1250°C, and the molten CaCl2 inhibited the decomposition of CaCO3, thereby inhibiting the formation of C2S and C3S. Although K2SO4&Na2SO4 melted, they only formed stable sulfate salts, without affecting the formation of C2S and C3S.

Injection Pultrusion of Glass-Reinforced Epoxy: Cure Kinetics, Rheology, and Force Analysis.

Pultrusion is a highly efficient continuous process to manufacture advanced fiber-reinforced composites. The injection pultrusion variant permits a higher control of the resin flow, enabling the manufacturing of a high reinforcement volume fraction. Moreover, it reduces the emission of volatile compounds that are dangerous for the operators and for the working environment. The present study proposes an experimental analysis of injection pultrusion in three different operative conditions. In particular, the activity focused on the effects of the temperature setup on the thermochemical and rheological behaviors of the resin system and on the interaction between the processed materials and the pultrusion die wall. The setup of the parameters was selected to evidence the behavior of the viscous interaction during the thermoset transition to the solid state, which is particularly challenging due to the localization of high adhesive forces related to the sharp increase in resin viscosity. Microscope observations of the cross-sections were performed to discuss the effects of the process parameters.

Microscopic Chemical Reaction Mechanism and Kinetic Model of Al/PTFE.

In order to study the microscopic reaction mechanism and kinetic model of Al/PTFE, a reactive force field (ReaxFF) was used to simulate the interface model of the Al/PTFE system with different oxide layer thicknesses (0 Å, 5 Å, 10 Å), and the thermochemical behavior of Al/PTFE at different heating rates was analyzed by simultaneous thermal analysis (TG-DSC). The results show that the thickness of the oxide layer has a significant effect on the reaction process of Al/PTFE. In the system with an oxide layer thickness of 5 Å, the compactness of the oxide layer changes due to thermal rearrangement, resulting in the diffusion of reactants (fluorine-containing substances) through the oxide layer into the Al core. The reaction mainly occurs between the oxide layer and the Al core. For the 10 Å oxide layer, the reaction only exists outside the interface of the oxide layer. With the movement of the oxygen ions in the oxide layer and the Al atoms in the Al core, the oxide layer moves to the Al core, which makes the reaction continue. By analyzing the reaction process of Al/PTFE, the mechanism function of Al/PTFE was obtained by combining the shrinkage volume model (R3 model) and the three-dimensional diffusion (D3 model). In addition, the activation energy of Al/PTFE was 258.8 kJ/mol and the pre-exponential factor was 2.495 × 1015 min-1. The research results have important theoretical significance and reference value for the in-depth understanding of the microscopic chemical reaction mechanism and the quantitative study of macroscopic energy release of Al/PTFE reactive materials.

Thermodynamic modeling of CsF with LiF-NaF-KF for molten fluoride-fueled reactors

Gibbs energy models were developed to describe the thermochemical behavior of CsF in molten FLiNaK (46.5LiF-11.5NaF-42KF mol%), a proposed molten salt reactor (MSR) fuel solvent and coolant, as cesium is of concern due to its high radiotoxicity and volatility. Initially, it was necessary to obtain a more accurate Gibbs energy function for CsF which required fitting parameters to reported vapor pressures over condensed phase CsF. The pseudo-binary systems CsF-LiF, CsF-NaF and CsF-KF were then evaluated utilizing phase equilibria and enthalpy of mixing (ΔmixH) values, together with original differential scanning calorimetry (DSC) measurements performed for the CsF-LiF and CsF-KF systems. The CsF-LiF-NaF, CsF-LiF-KF and CsF-NaF-KF pseudo-ternary system representations were obtained by interpolation of the constituent pseudo-binary systems, with DSC measurements performed for the CsF-LiF-NaF system to corroborate the calculated liquidus temperature. Ultimately, the pseudo-ternary systems were interpolated to obtain Gibbs energy models for the pseudo-quaternary CsF-LiF-NaF-KF system, supported by DSC measurements at low CsF compositions (1–10 mol%), yielding computed equilibria and cesium-containing vapor pressures that compare favorably with reported values. The Molten Salt Thermal Properties Database – Thermochemical (MSTDB-TC) was subsequently expanded to include these Gibbs energy models allowing description of the thermochemical behavior of the CsF-LiF-NaF-KF system.

Parametric Study of Transpiration Cooling Using Oxides for Sharp Hypersonic Leading Edges

Recent escalating interest in the development of highly maneuverable hypersonic vehicles demands sharp leading edges. However, sharp leading edges induce severe aerothermal conditions where conventional passive or ablative thermal protection systems fail to protect the leading edge. Here, we numerically demonstrate transpiration cooling employing oxide coolants as a new alternative system to thermally protect sharp leading edges. We parametrically characterize the performance of transpiration cooling for various coolant properties, flight conditions, and leading edge radii using a semi-analytic boundary-layer model validated with third-order direct numerical simulations. We further utilize direct numerical simulation to examine the impact of the thermochemical behavior of oxide vapors with the external hypersonic flow on transpiration cooling. Our findings do not readily align with an optimal set of material properties for transpiration cooling. Instead, certain coolant properties are more appropriate for various flight conditions and leading edge sizes. Our results also demonstrate that the thermochemical interactions between the oxide vapors and the external hypersonic flow have a negligible impact on the performance of transpiration cooling. Our study provides numerical frameworks to evaluate the performance of transpiration cooling and optimize the coolant properties for various flight conditions to protect sharp leading edges, which are paramount across hypersonic applications.

Effect of Deashing Treatment on Ash Fusion Characteristics of Biochar from Bamboo Shoot Shells.

To investigate the influence of deashing on fusion characteristics, a combined method of water and acid washing with different sequences (water washing followed by acid washing, and acid washing followed by water washing) was used to treat the biochar of bamboo shoot shells (BBSSs). The results show that deashing decreased the K content of the biochar from 50.3% to 1.08% but increased the Si content from 33.48% to 89.15%. The formation of silicates and aluminosilicates from alkali metal oxides with silicon was an inevitable result of ash phase transformation at the high temperatures used to improve the fusion temperature (>1450 °C). The thermochemical behavior of ash mainly occurs at 1000 °C. The deashing treatment significantly reduced the reaction intensity during the high-temperature process. This significantly increased the thermal stability of the ash. The adjustment of the washing sequence had a slight impact on the chemical compositions, but the differences in ash micromorphology were obvious. Deashing treatments with different washing sequences can significantly improve ash fusion properties effectively and reduce the risk of scaling, slagging, and corrosion. This study provides a new and reasonable strategy for the deashing of biochar to commercially utilize bamboo shoot shell resources.

A novel CFD-DEM-DPM modelling of fluid-particles-fines reacting flows

The complex fluid-particle-fine (FPf) reacting flows have been widely practised in many energy-intensive engineering processes, yet numerical methods capable of comprehensively describing the particle-scale thermochemical behaviours related to the FPf reacting flows were still lacking. In this work, a novel CFD-DEM-DPM model is developed, for the first time, to describe the fluid, particles and fines reacting flows and their interactions. Then, to demonstrate its effectiveness, it is employed to simulate the co-combustion of coke and pulverized coal in a dynamic raceway in ironmaking blast furnaces (BFs). After model validation, the complex in-furnace phenomena related to the co-combustion of coarse coke particles and fine coal particles are comprehensively captured. Particularly, instead of the pre-set raceway treatment in the previous raceway simulations, a dynamic raceway cavity is predicted explicitly driven by the fluid-particle-fine interactions and further, inside the dynamic raceway, the combustion of coal fines including moisture evaporation, devolatilization and char reactions are presented in detail. Subsequently, the impact of operations with and without coal injections are quantitatively compared, showing that both the reducing gas and reaction heat from the coal combustion contribute to an expansion of the raceway cavity. Further, the effects of pulverized coal rate on the in-furnace phenomena are studied. The present work represents a significant breakthrough in the explicit modelling of FPf reacting flows, and provides a cost-effective tool for understanding FPf-related processes and developing new technologies including carbon–neutral ironmaking technologies.

Thermal chemistry and decomposition behaviors of energetic materials with trimerizing furoxan skeleton

AbstractTrimerizing furoxans are ideal molecular skeletons for the construction of high energetic substances due to their compact structures and high enthalpy of formations. To explore and compare the thermal behaviors of energetic materials with tandem trimerizing furoxan molecular skeleton, we reported the first systematic research on the thermochemical behaviors and decomposition mechanism of 3,4‐bis(3‐fluorodinitromethylfuroxan‐4‐yl)furoxan (BFTF), 3,4‐bis(3‐cyanofurazan)furazan oxide (BCTFO) and benzotrifuroxan (BTF). According to the research results of the DSC‐TG experiments, both the substituted furoxan based energetic compounds (BCTFO and BFTF) exhibited low melting points and complicated thermal decomposition behaviors around 240 °C, while the melting point of unsubstituted furoxan (BTF) was much higher. Their detailed decomposition mechanisms were proposed based on the experimental results through tandem techniques including in‐situ FTIR spectroscopy method and DSC‐TG‐FTIR‐MS quadruple technology, which indicated that the cleavage of substituent would trigger the decompositions of BFTF and the decomposition of trimerizing furoxan skeletons almost synchronous occurrence with substituents in BCTFO. The self‐oxidation‐reduction of the linear and annular trimerizing furoxans lead to similar decomposition fragmented small molecule products.

Insights into pyrolysis of ginger via TG-FTIR and Py-GC/MS analyses: Thermochemical behaviors, kinetics, evolved gas, and products

One of the key leverages for lessening the heavy reliance on fossil fuels is the conversion of non-food biomass into bioenergy and high value-added products. This study aimed to quantify the bioenergetic, emission, and biochar performances of ginger (Zb) pyrolysis. The main pyrolysis stage of Zb occurred in the range of 127–540 °C, releasing gaseous products, primarily CO2, in significant quantities between 200–600 °C. The dominant pyrolysis products were CO functional groups, accounting for 52.18–62.68% of the total. As the temperature rose, the primary pyrolysis products transitioned from ketones to benzene and its derivatives. Through the application of three model-free and three model-fitting methods, the most suitable mechanism identified for the main pyrolysis stage (0.2 < conversion degree < 0.7) was the three-dimensional diffusion (spherically symmetric) function, serving as an internal diffusion mechanism. Results of this study provide impactful and actionable insights into control over the generation of bioenergy potential, gas emissions, and value-added products via the Zb pyrolysis.

Thermo-chemical behaviour of Dunaliella salina biomass and valorising their biochar for naphthalene removal from aqueous rural environment

Thermo-chemical behavior of a microalgal biomass; Dunaliella salina was investigated through thermo-gravimetric analyses. Fully-grown D. salina biomass were subjected for biochar conversion using pyrolytic treatment at three distinct heating rates such as 2.5, 5, and 15 °C min−1. The kinetic appraisals were explained by using model-free kinetics viz., Kissinger-Akahira-Sanose, Flynn-Waal-Ozawa and Starink iso-conversional correlations with concomitant evaluation of activation energies (Ea). The Ea value is 194.2 kJ mol−1 at 90% conversion in FWO model, which is higher as compared to other two models. Moisture, volatile substances, and other biochemical components of the biomass were volatilized between 400 and 1000 K in two separate thermo-chemical breakdown regimes. Microscopic and surface characterization analyses were carried out to elucidate the elemental and morphological characteristics of the biomass and biochar. Further, the proficiency of the prepared biochar was tested for removing naphthalene from the watery media. The novelty of the present study lies in extending the applicability of biochar prepared from D. salina for the removal of a model polyaromatic hydrocarbon, naphthalene.

Insights into the gas-solid hydrodynamics and thermochemical characteristics in a pilot-scale chemical looping combustion unit using MP-PIC

Chemical looping combustion (CLC) emerges as an efficient pathway for CO2 capture and storage, yet complex in-furnace phenomena are still far from being understood. Accordingly, the multiphase reactive flow during the CLC process in a pilot-scale dual circulation fluidized bed (DCFB) is numerically investigated by the multi-phase particle-in-cell method considering thermochemical sub-models. After model validations, the thermochemical behaviors and the impact of operating parameters on CLC performance are explored, followed by unveiling the underlying mechanisms of heat and mass transfer characteristics. The pressure gradient is explicitly correlated with the solid holdup in two reactors. Gas-solid flow in the fuel reactor (FR) is more heterogeneous than that in the air reactor (AR) due to complex reactions and large amounts of gas/particle exchanges with other parts of the DCFB, and the whole CLC unit shows good circulating and heat transfer performance. Higher temperatures improve fuel conversion and increase CO2 yield. Elevating the air/fuel ratio (ψ) significantly enhances CLC performance at ψ ≤ 1.0 but it insignificantly affects the CLC performance at ψ > 1.0. A higher total inlet flow rate leads to suppressed fuel conversion and a subsequent decline in CO2 yield. The particle heat transfer coefficient (HTC) in the AR is approximately 450 W/(m2·K), significantly higher than that in the FR of about 300 W/(m2·K).

Thermochemical modeling and performance evaluation of freeze desalination systems

Freeze desalination (FD) is a method in which saline water is cooled below its freezing point and freshwater is separated from the brine in the form of ice crystals. FD is relatively insensitive to the salinity of the feed solution, making it suitable for desalination of high concentration brines such as the brine rejected from the seawater desalination plants. The design of the FD system and the thermochemical behavior of the brine upon freezing are critical factors in the energy performance of this method. To date, thermochemical properties of the concentrated seawater during cooling, such as the threshold of formation of ice and salt-hydrates and their corresponding cooling load of formation, are not well known. Likewise, the optimal configuration of the FD system to achieve the maximum energy efficiency has not been investigated. This work provides comprehensive data about the cooling load of freezing of concentrated brine rejected from seawater desalination plants along with the threshold of formation of ice and salt-hydrates backed-up by validation. Furthermore, the optimal configuration of the FD system is identified and the effects of the compressor isentropic efficiency and effectiveness of the system's heat exchangers on the work consumption of the FD system were investigated.

Influence of temperature on the chemical evolution and desorption of pure CO ices irradiated by cosmic-rays analogues

ABSTRACT Carbon monoxide (CO) plays a vital role in interstellar chemistry, existing abundantly in both gaseous and frozen environments. Understanding the radiation-driven chemistry of CO-rich ices is crucial for comprehending the formation and desorption of C-bearing molecules in the interstellar medium (ISM), particularly considering the potential impact of temperature on these processes. We report experimental data on irradiation processing of pure CO ice by cosmic ray analogues (95.2 MeV 136Xe23+ ions) at temperatures of 10, 15, and 20 K, in the IGLIAS set-up coupled to the IRRSUD beamline at GANIL (Caen, France). The evolution of the irradiated frozen samples was monitored by infrared spectroscopy. The computational PROCODA code allows us to quantify the chemical evolution of the samples, determining effective reaction rates coefficients (ERCs), molecular abundances at the chemical equilibrium (CE) phase, and desorption processes. The model integrated 18 chemical species – 8 observed (CO, CO2, C3, O3, C2O, C3O, C3O2, and C5O3) and 10 non-observed but predicted (C, O, C2, O2, CO3, C4O, C5O, C2O2, C2O3, C4O2) – linked via 156 reactions. Our findings reveal temperature-driven influences on molecular abundances at chemical equilibrium, desorption yields and rates, and ERC values. Certain reaction routes exhibit distinct thermochemical behaviours of gas- and ice-phase reactions which may be attributed to the presence of neighbouring molecules within the ice matrix. This study provides pivotal insights into the chemical evolution of CO-enriched ice under irradiation, impacting solid-state astrochemistry, clarifying molecular abundances, and advancing our understanding of ISM chemistry and temperature effects on ionized radiation-processed frozen ices.