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Hydrogen production from rice husk was carried out via a two-stage system combining CLG (calcium looping gasification) using Ca(OH) 2 adsorbent in a bubbling fluidized bed and catalytic reforming with Ce–Ni/γAl 2 O 3 catalyst in a connected fixed bed. The results show that the maximum H 2 concentration (69.16 vol%) and H 2 yield (11.86 mmol g−1 rice husk) are achieved at Ca/C (Ca(OH) 2 to carbon molar ratio) = 1.5, H 2 O/C (H 2 O to carbon molar ratio) = 1.5, T g (gasification temperature) = 500 °C, T c (catalytic temperature) = 800 °C. The supplementation of fresh Ca(OH) 2 at Ca/C of 0.5 during calcination helps to activate the regenerated CaO by hydration, maintaining its carbonation activity and CO 2 adsorption. Ce–Ni/γAl 2 O 3 catalyst promotes water gas shift (WGS), steam methane reforming (SMR), and C 2 –C 3 hydrocarbons reforming, also exhibits excellent activity stability to maintain H 2 concentration and H 2 yield above 67.21 vol% and 11.67 mmol g−1 rice husk , respectively, during 5 lifetime tests. • Staged catalytic gasification of rice husk in a fluidized bed for H 2 -rich gas. • Ca(OH) 2 adsorbent promotes WGS and hydrocarbons reforming at a moderate temperature. • Fresh Ca(OH) 2 supplement during calcination activates regenerated CaO by hydration. • Ce–Ni/γAl 2 O 3 catalyst promotes WGS, SMR, and C 2 –C 3 hydrocarbons reforming reactions. • Ce–Ni/γAl 2 O 3 catalyst shows excellent activity stability with low carbon deposition. [Display omitted] [ABSTRACT FROM AUTHOR]

Geopolymer concrete offers superior mechanical properties and microstructure, yet micro-level compressive properties and structural evolutions remain insufficiently understood. This study employed molecular dynamics to simulate the uniaxial compressions of the sodium aluminosilicate hydrate (N-A-S-H) under UCZ, BCZ, and TCZ (z-axial compressions with zero, one, and two dimensions restrictions, respectively) conditions at 263 K, 300 K, and 800 K. The results provided valuable insights linking mechanical behavior with structural properties. Stress fluctuations in the yield stage were attributed to the continuous formation and fracture of Al-O-H bonds during micro-molecule processes. In the later compression stages, the rapid increase in Si-O-H groups suggested that water molecules equally attacked Al and Si tetrahedra due to limited voids. Under UCZ and BCZ conditions, slight bond contraction occurred, with the main structural resistance arising from bond angle bending within the skeleton. In contrast, TCZ experienced notable changes in both bond lengths and bond angles due to bilateral displacement constraints. The evolutionary molecular processes exhibited insensitive response to the temperature, especially under TCZ conditions. Additionally, varying trends were observed in different bond-angle styles (e.g., within or inside tetrahedra), providing a crucial insight for the design of N-A-S-H to determine optimal components. • Reactive molecular dynamics was used to simulate uniaxial compressions of sodium aluminosilicate hydrate gels. • Different lateral displacement constraints and temperatures effects was considered in the simulations. • The evolutions of the gel's molecular structure under uniaxial compression were characterized. [ABSTRACT FROM AUTHOR]

A two-stage system involving alkaline thermal gasification of cellulose with Ca(OH) 2 sorbent and catalytic reforming with Ni/Fe dual-functional CaO based catalysts is proposed and applied to enhance H 2 production and in-situ CO 2 capture. The results show that the H 2 concentration is maximized at a considerably lower temperature (500 °C) than commercialized biomass gasification processes, reducing energy consumption. Sol-gel method is deemed better than impregnation method for its lower cost and higher-concentration H 2 production. Among the prepared catalysts, sol-NiCa catalyst exhibits the best performance in CO 2 absorption, resistance to carbon deposition, and cyclic stability, creating maximum H 2 concentration (79.22 vol%), H 2 yield (27.36 mmol g−1 cellulose), and H 2 conversion (57.61%). Introduction of Ni rather than Fe on the CaO based catalyst promotes steam methane reforming at moderate temperature range of 400–600 °C, generating low contents of CH 4 (5.38 vol%), CO 2 (4.82 vol%), and CO (10.58 vol%). [Display omitted] • A two-stage system involving alkaline thermal gasification and catalytic reforming. • Sol-gel shows higher-concentration H 2 production and lower cost than impregnation. • Introduction of Ni rather than Fe on CaO catalysts promotes SMR at 400–600 °C. • Sol-NiCa catalyst exhibits good carbon deposition resistance and cyclic stability. • Maximum H 2 concentration (79.22 vol%) is achieved at moderate temperature of 500 °C. [ABSTRACT FROM AUTHOR]

• A modified ESP model suitable for high temperature gas was established. • The effect of temperature on ESP performance was investigated numerically. • An optimized ESP with assistant electrodes was developed and compared with the conventional ESP. High-temperature electrostatic precipitators (ESPs) are a potentially effective technology for purifying high-temperature gases. In this study, a comprehensive numerical model was developed to investigate the electric field and particle migration characteristics of an ESP at temperatures ranging from 400 to 600 °C. Moreover, an optimized ESP with assistant electrodes for improved high-temperature particle capture was proposed. The electric field, flow field and particle capture characteristics of the two types of ESPs were compared to demonstrate the superiority of the optimized ESP. Results indicated that high temperatures had a negative impact on ESP performance. As the temperature increased, the operating voltage of the ESP decreased, leading to decreases in both the electric field strength and space charge density. The effective migration velocity of the particles also decreased with increasing temperature, and the inhibitory effect of high temperature on particle capture increased with increasing particle size. The optimized ESP with assistant electrodes exhibited more favorable electric field and flow field characteristics for particle capture compared to those of the conventional ESP. The optimized ESP exhibited higher electric field strength, which increased the electric field force on the particles and promoted particle capture. Meanwhile, the space charge density of the optimized ESP was lower, effectively inhibiting the occurrence of back corona. Moreover, the optimized ESP enhanced the ionic wind downstream of the discharge electrode, thereby promoting particle migration towards the collection electrode. Consequently, the ESP with assistant electrodes effectively improved the collection efficiency. [ABSTRACT FROM AUTHOR]

An experimental-scale electrostatic precipitator (ESP) was built to investigate the influence of temperature and gas media on collection efficiency and energy consumption. High temperature was harmful to the performance of the ESP and had a considerable influence on large particles. The maximum collection efficiency was lower and energy consumption was higher under coal pyrolysis gas media than under air. Two improvement methods, namely, gas media conditioning and positive polarity power supply, were studied in this work. Both methods can improve the performance of high-temperature ESP under coal pyrolysis gas media. The improvement in collection efficiency under the effect of gas conditioning decreased and that under the effect of a positive power supply increased with the increase in temperature. Gas conditioning and positive power supply increased the maximum collection efficiencies of the ESP at 600 °C under coal pyrolysis gas media by 3.0% and 11.8%, respectively. Unlabelled Image • High temperature was harmful to the performance of the ESP. • The performance of ESP in coal pyrolysis gas is inferior to that in air. • Gas conditioning and positive power supply can improve the performance of ESP. [ABSTRACT FROM AUTHOR]

Abstract To study the characteristics of positive and negative DC discharge under coal pyrolysis gas media at 20 °C–600 °C, the I V characteristics and the current composition are analyzed under different conditions. Due to the difference of ionization mechanism, the corona onset voltage of negative corona is lower than that of positive corona under air gas medium. Under non-electronegative gas media, no corona occurs during negative discharge. However, during positive discharge, with the increase of output voltage, three types of discharge are successively observed, namely corona, glow and arc. Under N 2 gas media and at 400 °C, the maximum collection efficiency of positive electrostatic precipitator is 98%, while that of negative electrostatic precipitator is 82%. When the collection efficiency is 70%, the energy consumption index of negative electrostatic precipitator is about 200 times higher than that of positive electrostatic precipitator. A linear relationship between I/V and V is observed and the ionic mobility can be calculated through the slope. At 350 °C, the ionic mobility under H 2 gas medium is 5.25 cm2/(V*s) while the ionic mobility under N 2 gas medium is 0.1 cm2/(V*s). The ionic mobility is proportional to the absolute temperature according to the discharge experimental data at 350 °C–600 °C. The factor β i , which is only related to gas media, is 0.0001653 cm2/(V*s*T) for N 2 and 0.0087308 cm2/(V*s*T) for H 2. These results assist in understanding the property of ESP at high temperatures. Graphical abstract Unlabelled Image Highlights • Under coal pyrolysis gas medium, corona only occurs in positive discharge. • Under N 2 gas medium, the positive ESP is better than negative ESP. • The ionic mobility under H 2 is about 52 times higher than that of N 2. [ABSTRACT FROM AUTHOR]

Highlights • Novel type of biphasic solvent with low costs and high cyclic capacity is proposed. • DEEA-AEEA solvent shows regeneration energy as low as 2.58 GJ/tCO 2. • Phase split time as short as minutes enables fast phase separation. • Driving and resistance forces dominating the phase split dynamics are analyzed. • CO 2 reactions and phase split mechanism are revealed by NMR analysis. Abstract Using biphasic solvents for carbon dioxide (CO 2) capture is regarded as a promising technology to drastically reduce the regeneration energy. However, this technology hasn't been put into commercial application due to lack of the biphasic solvents with high stabilities and low costs. To overcome this challenge, we developed a novel type of biphasic solvent based on alkanolamine-alkanolamine blends, i.e., aqueous blends of 2-(diethylamino)-ethanol (DEEA, 50 wt%) and monoethanolamine (MEA, 25 wt%) or 2-((2-aminoethyl) amino) ethanol (AEEA, 25 wt%). The aqueous DEEA-AEEA solvent demonstrated a cyclic capacity as high as 0.64 mol CO 2 /mol which is significantly higher than those of 30 wt% MEA and other reported biphasic solvents. In addition, a phase split time as short as a few minutes is obtained. The phase split dynamics were analyzed to investigate the effects of CO 2 loading, temperature, gas flow rate and height-to-diameter ratio. Quantitative 13C NMR analysis was then performed to reveal the reaction and phase split mechanism of CO 2 absorption in the DEEA-AEEA solvent. It indicated that the reaction of AEEA with CO 2 dominated at the beginning of CO 2 absorption and the products are formed as carbamates. Then, DEEA began reacting with CO 2 to yield bicarbonate and carbonate. The phase split mechanism indicated that the reaction products of carbamates and HCO 3 −/CO 3 2− migrated to the lower phase while DEEA and unreacted AEEA migrated to the upper phase. Finally, the cyclic tests were repeated and the energy consumption was evaluated. The regeneration energy of the biphasic solvent, without process optimizations, is 2.58 GJ/tCO 2 , which is 32% lower than that of the traditional 30 wt% MEA solvent. [ABSTRACT FROM AUTHOR]

• Reactive molecular dynamics is utilized to simulate shock compression in sodium aluminosilicate hydrate gels. • Distinctive shock-wave induced mechanical response stages are determined. • The relationships between shock-induced wave speed and impact velocity are demonstrated. • Structural deformation mechanisms are proposed in disparate mechanical response stages. Sodium aluminosilicate hydrate (N-A-S-H) gels have gained attention due to their potential use as components of geopolymers to improve structural and mechanical properties. In this study, we investigated the propagation of shock waves in N-A-S-H gels subjected to impact velocities (U p) ranging from 0.1 to 3.0 km/s, as well as the resulting mechanical responses and structural deformations. Our results showed that when U p <0.4 km/s, only one elastic wave existed, and the Hugoniot elastic limit was estimated to be 4.1 GPa. Above this limit, a two-wave structure formed. The elastic and elastoplastic deformation mechanisms involved initial compaction and densification of the N-A-S-H gel structure, followed by bond angle bending. The Hugoniot U s - U p relationship was found to be linear in the elastoplastic region, with a linear parameter λ of approximately 2.75. These new atomistic insights into the shock compression of N-A-S-H gels will provide valuable guidance for future studies. [ABSTRACT FROM AUTHOR]

An experimental system composed of microscopic visualization and high-speed photography was developed to observe the relative motion and agglomeration characteristics between fine particles and a large glass particle directly. The large glass particle was fixed in the middle of a rectangular flow channel, fine particles were generated by burning sandalwoods in a buffer tank. The observations showed that fine particles flowed over the large glass particle when they were uncharged. When the large particle and fine particles carried charge of different polarities, an obvious attraction between them was observed. When the large particle and fine particles carried charge of the same polarity, the fine particles showed two kinds of motion characteristics, depending on the charge number they carried. When fine particles carried a small number of charge, they still attracted each other. In contrast, fine particles carrying a large number of charge led to repelling. The induced dipole force was taken into consideration to explain the observed phenomenon. A simulation of the movements of the fine particles considering the combined effects of the induced dipole force, the Coulomb force, the drag force and the electric field force was carried out. The simulation results matched the experimental results well. [ABSTRACT FROM AUTHOR]

• Novel alkanolamine-based biphasic solvent with low regeneration energy and viscosity is proposed for CO 2 capture. • Tertiary amine 3-(dimethylamino)propan-1-ol(3DMA1P) is firstly introduced to decrease regeneration energy. • Phase separation mechanism is revealed by NMR and LogP analysis. • Molecular dynamics simulation is applied to study liquid structure and monitor the phase separation process. Biphasic solvents for CO 2 capture have received significant attention due to their potential for energy conservation. However, traditional biphasic solvents result in highly viscous CO 2 rich-phases and high amine losses. To overcome these drawbacks, we have developed a novel alkanolamine-based biphasic solvent by blending 2-(methylamino) ethanol (MAE), 3-(dimethylamino)propan-1-ol (3DMA1P), diethylene glycol dimethyl ether (DGM), and water. The aqueous MAE/3DMA1P/DGM solvent showed a cyclic capacity of 0.45 mol CO 2 /mol amine, which is 1.8 times that of monoethanolamine (MEA), and a desorption rate and regeneration efficiency twice those of MEA. The viscosity of the biphasic solvents can be reduced to 13.12 mPa⋅s at 313 K, which is lower than that of reported biphasic solvents. The evaluated regeneration energy was 2.33 GJ/ton CO 2. Cation chromatography measurements revealed the tendency of MAE to accumulate in the CO 2 -rich phase with increasing CO 2 absorption loading. Quantitative 13C NMR analyses were performed to investigate the species distribution in both phases, and DGM was found to be the major component of the CO 2 -lean phase. Different solubilities of the MAE molecules and MAE carbamate in DGM resulted in phase separation. Molecular dynamics (MD) simulations on the CO 2 -unloaded and CO 2 -loaded solutions verified the phase separation mechanism. MAE molecules tended to cluster, and the interactions between MAE and DGM dropped significantly, with increasing DGM concentration. [ABSTRACT FROM AUTHOR]

In this study, a numerical model of an electrostatic precipitator (ESP) suitable for high-temperature flue gas was established using COMSOL Multiphysics, and the effects of temperature and H 2 O concentration on the high-temperature ESP performance were studied. The results showed that, at the same voltage, increasing the temperature increased the negative ion density, thereby improving the particle charge and collection efficiency. However, increasing the temperature led to a decrease in the maximum operating voltage of the ESP, which reduced the negative ion density and electric field intensity at the maximum operating voltage and weakened the diffusion and field charges of the particles, leading to a further decrease in the maximum collection efficiency. Increasing the H 2 O concentration in the flue gas increased the negative ion density and, thus, enhanced the diffusion charge of the particles, which helped improve the collection efficiency. [Display omitted] • A modified ESP model suitable for high temperature gas was established. • The plasma model was used to simulate corona discharges in the ESP. • The effect of temperature on ESP performance was studied numerically. • The effect of H 2 O concentration in flue gas on ESP performance was studied. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two-stage steam gasification and catalytic reforming of rice husk for H 2 -rich gas. • Ce 0.7 Ni 1 Ca 5 catalyst achieves 85.81 vol% H 2 with H 2 yield of 35.82 mmol g-1 biomass. • Ce 0.7 Ni 1 Ca 5 exhibits excellent cyclic stability and inhibition of carbon deposition. • High oxygen transport capacity of CeO 2 helps to promote WGS and SMR reactions. • CeO 2 prevents the sintering of NiO and CaO particles, stabilizing CO 2 sorption. Hydrogen-rich gas production from rice husk via steam gasification and catalytic reforming using CeO 2 -modified Ni-CaO sorption bifunctional catalysts synthesized by sol–gel method in a two-stage system was investigated. The results show that the Ce 0.7 Ni 1 Ca 5 catalyst achieves maximum H 2 concentration (85.81(±0.39) vol.%) and H 2 yield (35.82(±0.28) mmol g-1 biomass) under a condition of 500 °C, S/C (steam/carbon in biomass) molar ratio of 5, catalyst/biomass mass ratio of 2.5, producing the lowest content of CO 2 (3.62(±0.16) vol.%), CO (4.27(±0.11) vol.%), CH 4 (4.49(±0.18) vol.%), and C 2 -C 3 (1.81(±0.09) vol.%), correspondingly. Ce 0.7 Ni 1 Ca 5 also exhibits excellent cyclic stability in H 2 production, CO 2 sorption, and inhibition of carbon deposition. The H 2 concentration and H 2 yield remain above 81.88 vol% and 32.11 mmol g-1 biomass , respectively, and CO 2 emission keeps below 4.85 vol% during 10 cyclic tests. The carbon deposition of Ce 0.7 Ni 1 Ca 5 is only about 30% of that of Ni 1 Ca 5 after 10 cycles and hardly increased after 5 cycles. It is found that well-dispersed CeO 2 can effectively prevent the sintering of NiO and delay agglomeration of CaO species, stabilizing CaO carbonation and CO 2 sorption, and the strong Ni-O-Ce interaction induces the creation of oxygen vacancies that facilitate the fracture of O–H bonds of water for the formation of H 2. Furthermore, the high oxygen transport capacity of CeO 2 not only forms abundant mesopores structure to promote WGS and SMR reactions for enhancing H 2 production, but also contributes to reforming the carbon deposited on the catalyst surface by lowering the oxidation temperature of amorphous carbon containing low-molecular aromatic or aliphatic compounds with lower degree of graphitization. [ABSTRACT FROM AUTHOR]

A series of Ni-rich bimetallic phosphides incorporating different metals were successfully prepared by initial wetness impregnation, followed by temperature-programmed reduction. Catalyst characterization indicates that the bulk structure and physical properties maintained after adding 2.5 mol% another metal on Ni 2 P. Electron transfer from the second metal to Ni was found on Mo 0.05 Ni 1.95 P, Co 0.05 Ni 1.95 P, and Fe 0.05 Ni 1.95 P, except on W 0.05 Ni 1.95 P. Simultaneous hydrodenitrogenation (HDN) of quinoline and hydrodesulfurization (HDS) of dibenzothiophene (DBT) over phosphides and a commercial metal sulfide were studied at 320–380 °C, 3 MPa, weight hourly space velocity of 6 h − 1 , and H 2 /feed ratio of 500:1. Metal phosphides show higher HDN of quinoline and the same HDS of dibenzothiophene activities than that of a commercial catalyst at 380 °C. Mo 0.05 Ni 1.95 P shows the best performance and lowest N and S content adsorbed on the catalyst, due to the active M(2) sites. HDS conversion and product selectivities are seriously impacted by the adsorption of N-containing compounds on active sites of catalysts. Increasing temperature to 360 °C or/and decreasing N content to less than 1000 ppm quinoline in the feed are suggested to obtain simultaneous efficient removal of N and S. [ABSTRACT FROM AUTHOR]

Highenergy consumption is a crucial issue for the regenerationof solvent for postcombustion CO2capture by chemical absorption.Primary modeling results show the potential to reduce the energy consumptionthrough a novel solvent regeneration process by direct steam stripping.This work is an extension of our previous exploration and aims tovalidate the direct steam stripping process by experimental studieson a lab-scale stripping platform. We investigated the direct steamstripping and the conventional stripping mode in terms of energy consumptionand steam condensation. The results showed, for the direct steam strippingmode, the optimum energy consumption at 1 atm was 2.98 MJ/kg CO2, 23.2% lower than that of the conventional stripping mode.Higher solvent feeding temperature and carrier steam superheatingtemperature were beneficial to reduce steam condensation in the column.We found 96–99.5 °C feeding solvent temperature was suitableconsidering both the energy consumption and steam condensation. Besides,we proposed an improved direct steam stripping process using carriergases such as hydrocarbon, which could further reduce the latent heatrequired. [ABSTRACT FROM AUTHOR]

In order to investigate the mechanism of membrane wetting in the membrane absorption process at elevated temperature, the commercial polypropylene (PP) hollow fiber membrane was used to simulate the absorption exposure conditions by immersing the membrane into different absorbents at 60°C up to 40 days. Three absorbents which are 30wt% of aqueous monoethanolamine (MEA), 2-amino-2-hydroxymethyl-1,3-propanediol (THAM) and potassium sarcosinate (KSar) were selected to investigate the interaction between absorbents and membrane. Several characterization methods including X ray photoelectron spectroscopy (XPS), field emission scanning electron microscope (FE-SEM), atomic force microscope (AFM), mercury intrusion porosimetry (MIP) and contact angle measurement were used to study the changes of membrane properties. The results showed that the pore size, porosity and surface roughness of membrane increased after immersion. XPS demonstrated that absorbent molecules diffuse into the polymer matrix resulting in the swelling of membrane. Membrane deformation is dependent on the surface tension of the absorbent. KSar with a high surface tension caused less deformation of membrane than other absorbents. The change of membrane resistances as a function of operating time was also examined by continuous testing of membrane modules for a prolonged period under membrane absorption conditions at 60°C. It is found that transmembrane pressure has significantly increased the membrane resistance. KSar has a less tendency of increasing membrane resistance than MEA and THAM, but this advantage is not as significant as that at lower temperature. [ABSTRACT FROM AUTHOR]

Highlights: [•] Product composition is seriously influenced by thermodynamics equilibrium shift. [•] Cycloalkanes and phenyl cycloalkanes are the primary hydrogenated product. [•] Biaromatics are rarely transfomed into monoaromatics unless at low LHSV. [•] The incomplete hydrogenation is related to the methyl substituted on aromatic ring. [•] A reaction scheme of aromatics is proposed based on the composition of product. [Copyright &y& Elsevier]

Trace carbon dioxide (CO2) removal from an enclosedspace was studied experimentally and theoretically in a hollow-fibermembrane contactor using monoethanolamine (MEA) solution. Changesin trace CO2removal performance with liquid flow rate,gas flow rate, absorption temperature, and CO2loadingwere investigated individually in an apparatus under well-definedand controlled experimental conditions. We developed a two-dimensional(2-D) mathematical model to predict and further analyze the experimentalresults. The modeling results agreed well with the experimental work.Liquid flow rate positively influences trace CO2removal,but is not recommended for operation at a very high level. Increasingthe gas flow rate improves CO2absorption flux at the costof reducing CO2removal efficiency; the optimal gas flowrate for the trade-off between CO2removal efficiency andabsorption flux is presented. The optimal absorption temperatureschange with liquid CO2loading for trace CO2removal. CO2removal efficiency is a decreasing functionof CO2loading; the recommended CO2loadingof MEA solution is below 0.35 mol CO2/mol MEA. To predictthe influence of membrane wetting on trace CO2removal,we also propose a model that incorporates membrane wetting. The minimumbreakthrough pressure are 0.38 and 0.0581 MPa for fresh membrane andold membrane, respectively. Membrane wetting significantly deterioratestrace CO2membrane absorption performance, with CO2removal efficiency decreasing suddenly once the membraneis wetted. [ABSTRACT FROM AUTHOR]

To understand and optimize CO2absorption in binaryamine systems, we experimentally and theoretically investigated CO2absorption using typical amines and blended amines in a polypropylenehollow-fiber membrane contactor. The amines studied were monoethanolamine(MEA), diethanolamine (DEA), and N-methyldiethanolamine(MDEA), and their aqueous blends of MEA/MDEA, DEA/2-amino-2-methyl-1-propanol(AMP), and MDEA/piperazine (PZ). The predicted results, includingoverall mass transfer coefficients and CO2removal ratio,agreed very well with those determined experimentally. For singleamines, the optimal concentration was around 30 wt % for MEA and 20wt % for DEA. MDEA concentration had little effect on the overallmass transfer coefficient. We optimized the formulation of blendedamines using theoretical analysis. The optimal compositions in MEA/MDEA,DEA/AMP, and MDEA/PZ systems were respectively 30 wt % MEA, with MDEAin proportions from 0.1 to 0.3; 15 wt % DEA, with AMP in proportionsfrom 0.5 to 0.8; and 20 wt % MDEA, with PZ in a proportion of 0.3.To further understand the CO2membrane absorption process,we also analyzed individual mass transfer resistances as a functionof additive concentration in blended amines and the effects of liquidvelocity on the overall mass transfer coefficient. This shows thatCO2absorption is controlled by the liquid side for DEA/AMPblends and by combined liquid–gas phases for MEA/MDEA blends.For MDEA/PZ blends, control of CO2absorption is characterizedby a gradual transition from liquid side controlled to liquid–gascombined controlled as the concentration of PZ increases. [ABSTRACT FROM AUTHOR]

Currently, there is no easy-to-use method for determination of catalytic active phase volume (APV). Therefore, the current study designed a calculation method by defining APV (α → β nm) as the difference in pore volume (α → β nm) between the catalyst support and the catalyst (without taking fine structure of the catalyst into account for simplicity). This new method was successfully validated through regression analysis of 15 catalysts (R2 > 0.97). Moreover, the couplings of pore structures and metal loadings on catalytic hydrogenation of reactants were quantitatively assessed based on the calculation of APV. The promotion or inhibition effect of one compound on hydrogenation of other compounds may also vary with the couplings of metal loading and pore structure, but it wasn't taken into account in this study. The key segmented APVs (SAPVs) in various pore sections for hydroconversion of reactants were determined using a stepwise linear regression model at the 95% confidence level. The findings showed that the SAPVs in the pores with a pore size of 5–10 nm and 10–20 nm were responsible for hydroconversion of quinoline and most of the aromatic compounds, respectively. The predicted key SAPVs were consistent with the experimental observations, which demonstrated availability of the proposed APV. [Display omitted] • The QM-based calculation methods for kinetic diameters of molecules were provided. • Coupling effects of metal loading and pore structure were quantitatively assessed. • The catalytic active phase volume (APV) was firstly proposed and validated. • The stepwise linear regression model was used to find the key segmented APVs. • The found segmented APVs accorded well with the experimental observations. [ABSTRACT FROM AUTHOR]

Promoted aqueous ammonia is a potentialsolvent for CO2separation processes. In this work, weinvestigated the effect of temperature, sarcosinate concentration,and CO2loading on the mass transfer coefficients of CO2absorption in a sarcosinate-promoted aqueous ammonia solutionon a wetted-wall column. We further investigated the kinetics of thereaction between CO2and a blended NH3/sarcosinateabsorbent using stopped-flow spectrophotometric techniques, followingthe pH changes via coupling to pH indicators. Our study revealed thatthe mass transfer coefficient for CO2absorption in a 3M ammonia + 1.5 M sarcosinate blended solution at 288 K is close tothat in 5 M monoethanolamine absorbent at 313 K. We did not observeany synergistic or catalytic effects between NH3and sarcosinatein the blended solution; the mechanism of the reaction of CO2with the NH3/sarcosinate mixture is the simple combinationof the individual reactions of NH3and sarcosinate withCO2. [ABSTRACT FROM AUTHOR]

Abstract: A novel membrane vacuum regeneration (MVR) technology was developed to achieve lower regeneration energy demand for CO2 absorption process. Sixteen different amine-based absorbents including primary, secondary, tertiary amines, polyamines, diamines, and sterically hindered amines were analyzed by combined absorption–desorption screening experiments for selecting the most effective absorbents for CO2 membrane vacuum regeneration (MVR) technology. The CO2 absorption experiments were conducted in a hollow fiber membrane contactor (HFMC) at 25°C and 12.5kPa CO2 partial pressure. The CO2 rich solvent was regenerated at 75°C and 20kPa regeneration pressure by using the MVR technology. The chain length, number of functional groups, side chain, and number of hydroxyl groups of amines were investigated to get a better understanding on the effects of the structure in the MVR process. The results show that the tertiary amines have greater regeneration performances than the primary amines, but the CO2 absorption rates of the tertiary amines are worse than the primary amines. For the polyamines, the absorption performance of polyamines can be improved by increasing the number of amine groups while the MVR performance of the polyamines can be reduced. Steric hindered amines exhibited greater MVR performances. In addition, amines with steric hindrance effect caused by the substitution of hydroxyl group or methyl group to amine group in structure has also shown good performance in the MVR process for CO2 desorption. The overall performance of amine-based absorbents was also investigated by an absorption–desorption characters analysis. It shows triethylenetetramine (TETA) and N-methyldiethanolamine (MDEA) have great average CO2 absorption rates and relatively high cyclic capacities per mole absorbent, and ethylenediamine (EDA) is considered to be the promising absorbent as cyclic capacity in mol CO2/kg absorbent. Diethanolamine (DEA) and 2-Amino-2-methyl-1-propanol (AMP) are found to have the best overall performances in terms of CO2 absorption rate at lean loading and cyclic capacity in mol CO2/mol absorbent. In terms of overall performance, MDEA is mostly recommended for using in MVR process. Sweeping steam can significantly improve MVR performance in most selected absorbents except AMP and 2-amino-2-hydroxymethyl-1,3- propanediol (THAM) absorbents which present the potential to reduce the regeneration energy demand by operating without sweeping steam. The study also finds that MVR shows better regeneration performance as compared to traditional thermal regeneration process at the same regeneration temperature. [Copyright &y& Elsevier]

Aqueous sarcosine salts are fast carbon dioxide (CO2) absorbents suitable for use in postcombustion CO2capturein coal-fired power plants. We have developed a detailed reactionscheme including all the reactions in the sarcosine–CO2–water system. All unknown rate and equilibrium constantswere obtained by global data fitting. We investigated the temperature-dependentrate and equilibrium constants of the reaction between aqueous CO2and sarcosine using stopped-flow spectrophotometry, by followingthe pH changes over the wavelength range 400–700 nm via couplingto pH indicators. The corresponding rate and equilibrium constantsranged from 15.0 to 45.0 °C and were analyzed in terms of Arrhenius,Eyring, and van’t Hoff relationships. The rate constant forthe reaction between CO2and sarcosine to form the carbamateat 25.0 °C is 18.6(6) × 103M–1s–1, which is very high for an acyclic amine;its activation enthalpy is 59(1) kJ mol–1and theentropy is 33(4) J mol–1K–1.In addition, we investigated the slow reaction between bicarbonateand sarcosine using 1H nuclear magnetic resonance spectroscopyand report the corresponding rate and equilibrium constants at 25.0°C. This rate constant is 5.9 × 10–3M–1s–1. [ABSTRACT FROM AUTHOR]

Abstract: In order to give a better understanding for the selection of suitable absorbents for the novel membrane vacuum regeneration technology (MVR) which has the potential to reduce CO2 energy requirement by utilizing the waste heat or low-grade energy, an experimental study to determine the relationships between chemical structure and vacuum regeneration behavior of CO2 absorbents at 70°C and 10kPa was performed. Eleven typical absorbents with different functional groups in their chemical structures were investigated in terms of vacuum regeneration efficiencies. Results showed that the regeneration efficiency decreased with an increase of number of activated hydrogen atom in amine group and decreased with the number of hydroxyl group. Especially, more attention should be paid to these alkanolamines with one hydrogen atom in amine group and two or more hydroxyl groups in the structures due to their better comprehensive performance in regeneration, absorbent loss and CO2 absorption aspects. Increasing the carbon chain length and amine groups in the absorbent structure contributed to the improvement of regeneration performance and reduction of absorbent volatile loss. These absorbents with a four carbon chain length bonded at amine group might be more attractive to MVR. Furthermore, polyamines were superior to monoamines in terms of higher regeneration efficiencies and lower absorbent losses. Additionally, the individual effects of the potassium carboxylate group and hydroxymethylene group were also compared in this study. Results showed that amino acid salts were more appropriate for MVR due to their advanced regeneration performance, negligible absorbent losses and higher surface tensions. In this study, the regeneration performance of the same absorbents was also investigated by using the conventional heating regeneration method at 75°C and ambient pressure (HRM). It could be found that although longer regeneration time and relatively higher regeneration temperature were given for HRM, it was still inferior to MVR in terms of its lower regeneration efficiency. [Copyright &y& Elsevier]

Abstract: The novel regeneration concept by using reduced thickness and vacuum technology was put forward in this paper to solve the higher regeneration energy consumption in the chemical absorption process for CO2 separation from flue gas. A 120-mm I.D. vessel was precisely designed to regenerate the CO2-rich solution, and the change of the thickness of thin-layer solutions was simulated by controlling the volume of rich solution added into the vessel. The experimental results show that vacuum regeneration may be viable if the CO2-rich solution can be easily partitioned into the continuous single thin-layer solutions with an appropriate thickness. The great decrease of thin-layer solution thickness and regeneration pressure, and the increase of liquid temperature can improve the regeneration performance considerably. In addition, it is worthy to determine the optimum initial CO2 loading of rich solution, regeneration time and absorbent concentration due to the contradiction between the CO2 loading of lean solution and regeneration energy consumption per kg of CO2. Finally, the simple comparison between vacuum and heating regeneration methods shows that the novel regeneration method may have the potential to reduce the regeneration energy requirement. [Copyright &y& Elsevier]

This paper firstly evaluated the CO2 absorption performance of a membrane gas absorption system (MAS) and chemical absorption system (CAS) using the overall mass transfer coefficient (K G a V) as a basis for comparison. MAS selected microporous polypropylene (PP) hollow fiber membrane contactors to capture CO2 from the simulated flue gas while CAS used a randomly packed column containing stainless Pall packing. Aqueous monoethanolamine (MEA) solution was adopted in both absorbers. Experimental results show that if the fresh membranes were tested, MAS has the higher K G a V values than that of CAS. However, when all the membrane pores were completely wetted or 50% pores were plugged, CAS inversely performs better than MAS in terms of K G a V values. In addition, the economic performance of MAS and CAS was also estimated. Results indicate that if the real operational time of membrane module is reduced to less than the critical value affected by the membrane price, the CO2 captured cost of MAS is inversely higher than that of CAS. Therefore, the current well-accepted statement that MAS is superior to CAS in any case may be somewhat arbitrary unless membrane pore-wetting and pore-plugging problems, how to reduce the membrane price and how to prolong the membrane lifetime can be solved perfectly in the future. [Copyright &y& Elsevier]

[Display omitted] • Using alkanolamine to regulate the viscosity of biphasic solvents is proposed. • A novel polyamine-based biphasic solvent with low costs is developed. • The phase split mechanism is investigated by NMR analysis. • A molecular-scale understanding of the viscosity regulation mechanism is revealed. Biphasic solvent has attracted widespread attention in CO 2 chemical absorption technology due to its significant potential for reducing capture energy consumption. However, the high viscosity of CO 2 -rich phase after phase split could lead to issues such as high flow resistance, low heat transfer efficiency, and phase separation instability in application. To address these limitations, a strategy of using alkanolamine as a viscosity regulator for biphasic solvents was proposed. Diethanolamine(DEA), an alkanolamine regulator, was introduced to a system of polyamine/amide absorbent, and then a novel biphasic solvent of diethylenetriamine (DETA)/diethanolamine(DEA)/N, N-Dimethylacetamide(DMAC)/water(H 2 O) was developed. The viscosity of the CO 2 -rich phase solvent was reduced to 19.02 mPa⋅s, a significant decrease compared to the solution without DEA regulation. The novel solvent exhibited a high cyclic capacity of 2.08 mol/kg, which was 43.4 % higher than that of the solution without DEA, and a desorption rate twice as high as 30 wt% monoethanolamine(MEA). Quantitative 13C Nuclear Magnetic Resonance (NMR) and Molecular Dynamics (MD) simulations revealed the phase split and viscosity regulation mechanisms. It was proved that DETA species, especially carbamates, tend to self-aggregate with each other due to intermolecular hydrogen bonding with the CO 2 loading increases, which leads to phase split and high viscosity of the saturated solution. Through DEA regulation, the protonation of carbamates and the generation of HCO 3 –/CO 3 2– were promoted, which weakened the self-aggregation of carbamates species, decreasing the viscosity and the regeneration energy of saturated CO 2 -rich phase solution. The regeneration energy reached 2.19 GJ/ton CO 2 , which exhibited a 42.4 % reduction compared with that of 30 wt% MEA. [ABSTRACT FROM AUTHOR]

An integrated model was developed to investigate the effect of temperature on the particle re-entrainment in a high-temperature electrostatic precipitator (ESP). The numerical model considered the electric field, flow field, particle migration, and particle re-suspension due to the rupture of static equilibrium. The electric and flow field distributions at different temperatures were investigated. The minimum critical shear velocity needed to detach high-temperature deposited particles from the plate surface was calculated and discussed. On these basis, five types of ESPs with collection plates of different configurations were compared. The results show that high temperatures will exacerbate particle re-entrainment caused by airflow scouring and electrostatic lifting by enhancing the ionic wind and reducing particle resistivity. The hole-type plate may be a better plate form to reduce re-entrainment in the high-temperature ESPs, as it creates a low velocity, low electric field region in the near-plate region. [Display omitted] • A modified high-temperature ESP model involving particle re-entrainment was developed • The effect of temperature on the electric and flow field was investigated numerically. • The effect of temperature on the particle re-entrainment was evaluated. • The effectiveness of different types of collection electrodes in reducing particle re-entrainment was evaluated. [ABSTRACT FROM AUTHOR]

Dual fluidized bed (DFB) reactor systems are widely used in gas–solid two-phase flow applications, whose gas–solid flow characteristics have a significant effect on the performance of many kinds of technologies. A numerical simulation model was established on the basis of a large-scale DFB reactor with a maximum height of 21.6 m, and numerical simulations focused on gas–solid flow characteristics were carried out. The effects of the superficial gas velocity of both beds and the static bed height and particle size on the distribution of the pressure and solid suspension density and the solid circulation rate were studied. The simulation results were in good agreement with the experimental data. With the strong support of the experimental data, the gas–solid flow characteristics of large-scale DFB reactors were innovatively evaluated in this numerical simulation study, which effectively makes up for the shortcomings of the current research. The results showed that the superficial gas velocity of both beds and the static bed height have different degrees of influence on the gas–solid flow characteristics. Specifically, for 282 μm particles, when the superficial gas velocity of both beds and the static bed height were 4.5 m/s, 2.5 m/s, and 0.65 m, respectively, under typical working conditions, the bottom pressure of the two furnaces was 3412.42 Pa and 2812.86 Pa, respectively, and the solid suspension density was 409.44 kg/m3 and 427.89 kg/m3, respectively. Based on the simulation results, the empirical formulas of the solid circulation rate were fitted according to different particle sizes. Under similar conditions, the solid circulation rates of particles with a particle size of 100 μm, 282 μm, 641 μm, and 1000 μm were 2.84–13.28, 0.73–4.91, 0.024–0.216, and 0.0026–0.0095 kg/(m2s), respectively. It can be found that the influence of the particle size on the solid circulation rate is the most significant among all parameters. [ABSTRACT FROM AUTHOR]

The construction of nuclear power plants necessitates careful consideration of the discharge and fixation of nuclear waste. Geopolymers are new cement-based materials (CBMs) with three-dimensional cage-like structures that enable effective nuclear waste fixation. In this work, the adsorption of radioactive caesium and strontium ions by sodium aluminosilicate hydrate (NASH) gel, the main component of geopolymers, was investigated using molecular dynamics simulations to obtain nanoscale insights into the ions' interactions with the gel. The formation of strong ion–oxygen bonds allowed both ions to be effectively adsorbed on the NASH surface, but the adsorption ratio of strontium ions (17.2%) was slightly lower than that of caesium ions (21.0%). Because strontium ions are divalent, they can form stronger electrostatic interactions with water molecules and chloride ions, which hinders their approach to the interface. For the same reason, the diffusion coefficient of strontium ions in solution is lower than that of caesium ions. These results provide new insights into the nuclear waste fixation capacity of NASH gel and guidance for the design of new CBMs for radioactive waste disposal. [ABSTRACT FROM AUTHOR]

Calcium silicate aluminate hydrate (C-A-S-H) is the main hydration product of cement mixed with industrial wastes. The purpose of this study is to understand the dynamic mechanical behavior and structural transformations of molecular-scale C-A-S-H induced by shock waves. Three C-A-S-H models with Al/Si ratios of 0.0, 0.1, and 0.2 are constructed and reactive molecular dynamics simulations are used to perform shock compressions with different shock velocities from 0.1 km/s to 3.6 km/s. The distributions of particle velocity, pressure, and density along the shock direction are calculated using the binning analysis method, allowing Hugoniot pressure-specific volume curves to be derived. The results reveal that shock waves may induce elastic, elastic-plastic, or shock Hugoniot responses in molecular-scale C-A-S-H, depending on the Al/Si ratio and the shock velocity. Below the Hugoniot elastic limit (HEL), higher Al/Si ratios cause the elastic wave to propagate farther due to the cross-linking effect of aluminate units. Above the HEL, higher Al/Si ratios give rise to a distinct two-wave structure characteristic comprising a plastic front and an elastic precursor. This characteristic becomes less pronounced as the shock velocity increases. Analysis of the molecular structural transformations of C-A-S-H revealed that the main atomic deformation behavior below the HEL involves a reduction of interatomic distances; above the HEL the main response is a densification of water molecules followed by a general collapse of the layered structure as the shock velocity increases. [ABSTRACT FROM AUTHOR]

Steady‐state process simulation and techno‐economic analysis of a pyrolysis‐based coal staged conversion polygeneration (CSCP) plant, integrated with wastewater biochemical treatment after phenol‐ammonia recovery, are studied using Aspen Plus software. Appropriate models for the proposed system are set up in detail. Furthermore, by optimization of a methanation unit, a conventional supercritical circulating fluidized bed (SCCFB) power plant with the same capacity is chosen for comparison. Simulation results reveal that system energy and exergy efficiency of the CSCP system can reach much higher values than those of a conventional SCCFB power plant. In conclusion, a CSCP plant will have practical and economic advantages in the near future. A coal staged conversion polygeneration plant for the coproduction of coal gas, tar, and electricity power, integrated with wastewater biochemical treatment after phenol‐ammonia recovery, is proposed and simulated. Appropriate models for the proposed system are assessed. Such kind of plant exhibits practical and economic advantages, with excellent values of system energy and exergy efficiency. [ABSTRACT FROM AUTHOR]

• Water-lean EMEA was tested in a pilot with 280 m3/h flue gas for 100 operating hours. • Water-lean EMEA achieved 90% CO 2 removal and regeneration energy of 2.2 GJ/tCO 2. • Measured ΔT for lean/rich exchanger increases with viscosity in a power function relation. • Water-lean EMEA has a volatile amine emission higher than 110 mg/m3. Water-lean solvent for post-combustion CO 2 capture is promising to significantly reduce regeneration energy. It hasn't been put into commercial application due to unsolved challenges including water balance issue, increased viscosity, and high volatility. Even though numerous water-lean solvents were developed in laboratory, rare of them were tested in pilot scale. Water-lean solvent of 2-(ethylamino) ethanol (EMEA) dissolving into 1-methyl-2-pyrrolidinone (NMP) and water was tested in a CO 2 capture pilot with flue gas rate of 280 m3/h. Effects of liquid/gas ratio and reboiler steam rate on CO 2 removal efficiency, regeneration energy, lean/rich heat exchanger performance, and volatile amine emission were investigated. Water-lean EMEA achieved CO 2 removal efficiency greater than 90 % and the lowest regeneration energy of 2.3 GJ/tCO 2 , which is 43 % lower than that of 5 M MEA. Water-lean EMEA showed significantly reduced latent heat, greater CO 2 capacity, and lower reaction heat (secondary amino) than aqueous MEA and amine blends. It was found that water-lean EMEA regeneration in stripper had extremely lower lean loading (0.1–0.5 mol CO 2 /L) than aqueous MEA and amine blends, which enables a faster CO 2 absorption rate in absorber and a greater CO 2 capacity, but also causes larger volatile amine emission. Volatile amine emission after water wash was 110–380 mg/m3. 13C NMR spectrum suggested amine carbamate dominated CO 2 absorption products. Due to that increased viscosity decreases heat transfer coefficient (h), lean/rich heat exchanger temperature difference (Δ T) for water-lean EMEA (6.5–7.5℃) was greater than MEA (3.5-5℃) and amine blends (5-6℃), yet smaller than biphasic solvent (8-9℃). A negative power (-0.614) function relation between h and viscosity was fitted and can be further used to normalize sensible heat. [ABSTRACT FROM AUTHOR]

Inhalable particulate matter, especially PM 2.5 , is a main pollutant in China that is harmful to both human health and the atmosphere. The PM 2.5 removal efficiency of traditional dust removal devices such as ESP is low, and pretreatment must be conducted before dust enters the dust remover. Acoustic agglomeration is a pretreatment technology that uses high-intensity sound waves to agglomerate and develop fine particles; this method improves the PM 2.5 removal efficiency of traditional dust removal devices. In a sound wave field, fine particles are carried by a medium (air in this study) and vibrate at different amplitudes when they vary in size. Thus, relative movement is generated and subsequently, particles increasingly collide and agglomerate. In this study, the movements of differently sized particles in traveling and standing wave sound fields are calculated, including the velocities, displacements, and amplitudes. Re < 1 in this study, and the viscous force in the Stokes region is chosen as the main force. High-speed photography is employed to observe particle movement in different sound wave fields. The vibration speed and amplitude determined by analyzing the tracks in the photos are consistent with the calculated results. The movement of fine particles in a sound field with different conditions must be studied to identify the mechanisms of acoustic agglomeration. [ABSTRACT FROM AUTHOR]

Performing online evolution analysis of tar in actual pyrolysis process is a major challenge. In this work, the effects of heating rate (HR) on evolution curves of in-situ tar for low-rank coals pyrolysis were investigated in a novel laboratory bench. The escape law of volatiles was obtained, the influence of HR on secondary reactions was analyzed, the association between products and molecular structures was constructed, and pyrolysis mechanism was deduced. Aliphatic hydrocarbons (except dienes), phenols, and oxygenated compounds have only one peak, while dienes and aromatics have multiple peaks throughout the pyrolysis process. The first peak is attributed to coal primary pyrolysis. At increased HRs, the second peak for 1∼2ring aromatics is from the cracking of primary volatiles, and that for 3∼4ring aromatics from coal continued cracking. The proportion of phenols and oxygenated compounds decreases, aromatics increases, and aliphatic hydrocarbons varies for different coals. Generally, HR increases the yield of primary volatiles by enhancing coal primary pyrolysis, elevates the proportion of light aromatics by promoting secondary cracking and aromatization of primary volatiles, reduces char yield by inhibiting condensation reactions throughout the pyrolysis process. The similar macromolecular structures of different coals make the evolution curve versus HRs follow a common law. [Display omitted] • Dienes and aromatics have more than one evolution peaks during pyrolysis process. • The first peak of tar components is attributed to the coal primary pyrolysis. • As heating rate rises, the second peak of 1∼2ring aromatics is from the cracking of primary volatiles. • As heating rate rises, the second peak of 3∼4ring aromatics is from the cracking of coal at high temperatures. • The mechanism of heating rate on different low-rank coals remains consistent. [ABSTRACT FROM AUTHOR]

Lignite-based polygeneration systems for coproducing tar and electricity with and without carbon capture and storage (CCS) were proposed and simulated. Predried lignite was pyrolyzed into coal gas, tar, and char. Coal gas was fired in a gas turbine after the cleanup process, while char was combusted in circulating fluidized-bed (CFB) boilers. The polygeneration plant without CCS turned out to be more efficient than the conventional CFB power plant, suggesting that the former is a promising and efficient option to utilize lignite resources. Moreover, the performance and emissions of polygeneration plants with and without CCS were compared. It was shown that the more CO2 is captured, the larger energy penalty it will cost. Therefore, a trade-off should be made between low emissions and high efficiency. [ABSTRACT FROM AUTHOR]

Alkali metal pretreatment in pyrolysis is proposed to address alkali-induced issues in high-alkali coal utilization, on the basis of staged fuel combustion. However, the newfound carbon engulfment remains an intractable problem. This work investigated the effect of pyrolysis conditions on enhancing alkali metal pretreatment during Zhundong coal pyrolysis over 500–1000 °C in a laboratory fixed-bed apparatus, which focused on heating rate, volatile-char interaction, and CH 4 atmosphere. Multiple analytical methods were integrated to relate the facilitation effect of pyrolysis conditions on sodium pretreatment with the suppression of carbon engulfment. The results indicated carbon engulfment primarily blocked mesopores with a size <5 nm to retain large quantities of water-soluble sodium species. It resulted from coal swelling induced by the fusibility of semi-fusinites. Fortunately, volatile-char interaction and CH 4 atmosphere eliminated carbon engulfment through the intra-particle reaction between gasification agents/active radicals and char matrix. They fully eliminated carbon engulfment at 800 °C, which mainly reopened mesopores with a diameter of 4–5 nm. They also promoted the formation of sodium silicates/aluminosilicates. A slow heating rate weakened carbon engulfment by limiting the fusibility of semi-fusinites, but to a lower extent. Volatile-char interaction and CH 4 atmosphere were proposed as universal enhancements for alkali metal pretreatment. [Display omitted] • Pyrolysis pretreatment was proposed to address alkali-induced issues in combustion. • It aimed at promoting alkali release and the formation of stable alkali species. • Carbon coating blocked mesopores with width < 5 nm to impede the pretreatment. • Volatile-char interaction and CH 4 removed carbon coating to promote sodium release. • Volatile-char interaction and CH 4 benefited the formation of sodium minerals. [ABSTRACT FROM AUTHOR]

• Three cases of heating surface layout are proposed in the new 600 MWe coal-fired power plant. • The heat exchange area of three cases increases by around 33.6%, 47.3% and 53.7% as comparing to the benchmark power plant. • The economic analysis of new power plant was investigated. • Case 1 has a slight advantage as comparing to cases 2 and 3. This work provides a practical engineering design on the new 600 MWe coal-fired power plant coupled with CaO-based carbon capture system. Three heating surface layout cases are proposed in order to realize the high temperature heat source of the new power plant to heat the feed water into the superheated steam (24.2 MPa, 566 °C). In addition, pipeline calculation and economic analysis for three cases are carried out. The results show that the heat exchange area of three cases increases, respectively by around 33.5%, 47.3% and 53.7% as comparing to the benchmark 600 MWe coal-fired power plant under the carbon capture efficiency of the coupled system is around 90%. In the pipeline design, the flue gas resistance of case 1 through heat exchange pipeline is about 0.74 MPa. The economic analysis shows that case 1 has a slight advantage as comparing to cases 2 and 3. The research provides a good direction for future research direction of the coal-fired power plant coupled with CaO-based carbon capture system. [Display omitted] [ABSTRACT FROM AUTHOR]

Highlights: [•] A lignite pyrolysis-based polygeneration plant was proposed and modeled. [•] Polygeneration plant has a 9.04% point higher efficiency than CFB power plant. [•] Polygeneration plant increases ca. 14% point of IRR based on CFB power plant. [•] Electricity price rise makes polygeneration plant less competitive. [ABSTRACT FROM AUTHOR]

[Display omitted] • The ILs biphasic absorbent [TEPAH][CPL]/EG/DGDE was developed for CO 2 capture. • Phase separation was due to polarity change of the absorbent after CO 2 absorption. • The regeneration energy consumption is 51% lower than that of 30 wt% MEA solution. • The absorbent showed obvious low-corrosive advantage since the absence of H+. To achieve low regeneration energy consumption and low corrosion, a novel ILs nonaqueous biphasic absorbents composed of Tetraethylenepentamine (TEPA) Caprolactam (CPL), Ethylene glycol (EG), and Diethylene glycol dimethyl ether (DGDE) have been proposed for CO 2 capture. The maximum CO 2 loading of the optimal absorbent ([TEPAH][CPL]/EG/DGDE) could reach 1.88 mol·mol−1, with 40 % of the saturated phase volume containing 98 % of the mass percentage of CO 2 products. Furthermore, the regeneration energy consumption was only 1.88 GJ·t−1 CO 2 , approximately 51 % lower than that of 30 wt% monoethanolamine (MEA) aqueous solution. 13C NMR analysis has shown that the amino group on the cation [TEPAH]+ reacted with CO 2 to form CO 2 products-carbamate, and the anion [CPL]- assisted the proton transfer during the reaction. Combined with the results from quantum chemical calculation, the phase separation behavior of the absorbent was mainly due to the polarity difference between the CO 2 products and the solvent. Additonally, [TEPAH][CPL]/EG/DGDE was non-corrosive to 20# carbon steel before and after CO 2 absorption, and exhibited superior stability than MEA aqueous solution. [ABSTRACT FROM AUTHOR]

[Display omitted] • The novel in-situ gas sampling provides 2D spatial maps of gas product compositions. • The CO 2 conversion drops significantly in the afterglow due to recombination. • Dissociation dominates in the plasma, while recombination prevails in the afterglow. • Afterglow quenching considerably increases the CO 2 conversion and energy efficiency. Warm plasma offers a promising route for CO 2 splitting into valuable CO, yet recombination reactions of CO with oxygen, forming again CO 2 , have recently emerged as critical limitation. This study combines experiments and fluid dynamics + chemical kinetics modelling to comprehensively analyse the recombination reactions upon CO 2 splitting in an atmospheric plasmatron. We introduce an innovative in-situ gas sampling technique, enabling 2D spatial mapping of gas product compositions and temperatures, experimentally confirming for the first time the substantial limiting effect of CO recombination reactions in the afterglow region. Our results show that the CO mole fraction at a 5 L/min flow rate drops significantly from 11.9 % at a vertical distance of z = 20 mm in the afterglow region to 8.6 % at z = 40 mm. We constructed a comprehensive 2D model that allows for spatial reaction rates analysis incorporating crucial reactions, and we validated it to kinetically elucidate this phenomenon. C O 2 + M ⇌ O + C O + M and C O 2 + O ⇌ C O + O 2 are the dominant reactions, with the forward reactions prevailing in the plasma region and the backward reactions becoming prominent in the afterglow region. These results allow us to propose an afterglow quenching strategy for performance enhancement, which is further demonstrated through a meticulously developed plasmatron reactor with two-stage cooling. Our approach substantially increases the CO 2 conversion (e.g., from 6.6 % to 19.5 % at 3 L/min flow rate) and energy efficiency (from 13.5 % to 28.5 %, again at 3 L/min) and significantly shortens the startup time (from ∼ 150 s to 25 s). Our study underscores the critical role of inhibiting recombination reactions in plasma-based CO 2 conversion and offers new avenues for performance enhancement. [ABSTRACT FROM AUTHOR]

In this paper, the vibration and buckling behavior of a functionally graded piezoelectric porous cylindrical microshell under thermo-electro-mechanical loads are explored on the basis of modified couple stress theory and higher-order shear deformation theory. First, the model of a functionally graded piezoelectric porous cylindrical microshell composed of piezoelectric materials with gradient change in the thickness direction was described. Second, the governing equations of the microshell were derived by Hamilton's principle and Maxwell equation. Third, the modal frequency and buckling equations of the microshell with simply supported ends were obtained on the basis of harmonic trigonometric functions. Finally, the effects of parameters on the modal frequency and buckling behavior were carried out by case studies. The results show that the modal frequency of the microshell can be adjusted by changing the porosity volume fraction, power index, applied voltage, axial load and geometric dimensions. It is also found that the vibration of the microshell is suppressed by positive voltage and axial compression but is strengthened by negative voltage and axial tension, and the material length scale parameter increases stiffness. In addition, the effects of applied voltage and axial load on the buckling behavior are larger than those of temperature. Results can be used to guide the design and application of piezoelectric devices. [ABSTRACT FROM AUTHOR]

An external heat exchanger (EHE) is believed to be a viable way to solve the heat transfer surface arrangement and furnace temperature control to scale-up of circulating fluidized bed (CFB) boilers. A new concept of EHE is developed in this paper. The flow of hot solid particles diverted from the standpipe is controlled by pneumatic (aeration airflows of recycle device or EHE), not the mechanical valve that is in popular use in many CFB boilers. The major feature of this EHE system is that it avoids the use of the mechanical valve that causes heavy erosion and high cost. An in-series connection between the EHE and the recycle device (i.e. the recycle device is on top of the EHE) is proposed. Experiments completed in cold test rigs show that the solid mass flow rate diverted from the standpipe to the EHE or the loop seal may be controlled well by adjusting the fluidizing air of the overflow part of the loop seal, the fluidized air of the fluidized chambers of the EHE and the aeration airflow to the standpipe. In addition, the new EHE has been validated successfully in a 12 MWe CFB boiler. [Copyright &y& Elsevier]

• MnO x /HZ is proposed as an efficient catalytic packing for CO 2 desorption. • Visualization method can quantify the CO 2 desorption rate per unit surface area of packing. • The E a of CO 2 desorption with MnO x /HZ can be reduced by 58.6%. • The catalytic performance of MnO x /HZ declines due to the blockage of micropores by reaction product. The high energy consumption in the CO 2 desorption process is one of the main issues of the chemical absorption method. To address this issue, a MnO x modified HZSM-5 catalyst (MnO x /HZ) was prepared by impregnation method and used as catalytic packing to improve the CO 2 desorption rate in the monoethanolamine (MEA) solution. Since the catalytic effects mainly work around the catalytic packing, a visualization method, which can measure the CO 2 desorption rate per unit surface area (v C O 2 / a r e a ) of a single packing, is proposed to avoid some uncertain effects occurring as the conventional bubbling method is used. The results showed that the v C O 2 / a r e a of the MnO x /HZ catalytic packing is 10.06 μmol·cm−2·s−1 at 80 °C, which is 1.78 times of that of HZSM-5 and 15 to 60 times of that of commercial packings. Actually, the MnO x /HZ has more Brønsted and Lewis acid sites than HZSM-5 according to the pyridine adsorption infrared spectroscopy (Py-IR) characterization. As a result, the apparent activation energy (E a) of the CO 2 desorption reaction with the addition of MnO x /HZ can be reduced by 58.6% and 18% compared with the addition of ceramic saddle ring packing and HZSM-5, respectively. However, the catalytic performance of MnO x /HZ packings degrades gradually due to the blockage of micropores by the reaction product, that needs to be settled in the future. [ABSTRACT FROM AUTHOR]

• We proposed a novel desorption process based on ion exchange for CO 2 sorbents. • The sorbents were demonstrated with high working capacity and improved desorption kinetics. • Key factors of kinetics improvement were discussed among optimization of the OH–/HCO 3 – ratio at inlet, concentration, and external diffusion. • The solution after desorption (ion exchange) could be regenerated through an electrochemical DAC system to utilize renewable energy efficiently. To satisfy the Paris Agreement's 1.5 °C goals, direct air capture (DAC) has become an increasingly crucial technology. However, the ultralow partial pressure of CO 2 in ambient air contributes to a low desorption rate and high regeneration energy consumption. In this study, we proposed a fast regeneration method for CO 2 sorbents based on an ion exchange process. Utilizing an alkaline solution rich in hydroxide (OH–) ions, the quaternary ammonium (QA)-based ion exchange resin can be changed from carbonate (CO 3 2–) to OH– form, which directly captures CO 2 from ambient air. The results showed that the working capacity of the sorbents in the OH– form was 1.85 mmol⋅g−1, which was double that of the CO 3 2– form (0.88 mmol⋅g−1). The kinetics showed that the ratio of OH–/HCO 3 – at inlet, concentration, and external diffusion influence the desorption rate of CO 3 2– because of the ion exchange reaction. With a high ratio of OH–/HCO 3 – at inlet, 1 M alkaline solution, and 3 mL⋅s−1 cyclic flow rate, the desorption time of the sorbents was approximately 20 min. Finally, because the energy consumption of the entire process comprises mainly electric energy required to regenerate the alkaline solution after ion exchange, it is expected to establish an electrochemical DAC system to utilize renewable energy efficiently. [ABSTRACT FROM AUTHOR]

To reveal the effect mechanism of CO atmosphere on coal pyrolysis, a study on raw and demineralized lignite was carried out in a horizontal tube furnace under N2 and CO/N2 atmosphere. CO had a negligible effect on the char yield at low temperatures, whereas it enhances the char yield at temperatures higher than 550 °C. The release of tar was higher in the presence of CO above 450 °C because of more free radicals, which reduced low‐temperature crosslinking, and higher selectivity of hydroxyl groups to phenols in the CO‐containing atmosphere. The yields of CO2 and H2 increased, water and CO yields decreased under CO/N2 atmosphere. Light hydrocarbon gases were not affected by changing the reaction atmosphere. The difference between product yields from raw and demineralized coal confirmed that the catalysis of inherent minerals had a great catalytic effect on the water‐gas shift reaction and Boudouard reaction. [ABSTRACT FROM AUTHOR]

Staged coal combustion is a promising solution to the alkali-induced slagging issue. It innovatively separates coal pyrolysis and char combustion into different reactors. This study investigated migration and transformation of sodium during staged coal combustion of two Zhundong coals in a fixed-bed apparatus. Behavior of sodium during coal pyrolysis and char combustion are integrated. Carbon coating on sodium species was experimentally confirmed for the first time by low-temperature oxygen-plasma ashing and ultrafine grinding. Up to 62 wt% of initial water-soluble Na in ZJ coal and 51 wt% in WCW coal were coated with the carbon matrix during coal pyrolysis. Coated water-soluble Na appeared from 500 °C and its amount reached a peak value at around 700 °C, followed by decrease over 700–1000 °C. Thermoplastic behavior of coal during pyrolysis is expected to play an important role in the formation of coating which hinders pretreatment of sodium. During char combustion, all coated water-soluble sodium species were exposed and participated in the subsequent release. Part of them can also react with minerals to generate insoluble and HCl-soluble sodium species. Char combustion is the main period of the sodium release while coal pyrolysis is the principal period of the generation of HCl-soluble Na. • Carbon coating on sodium species during pyrolysis was experimentally confirmed for the first time. • Sodium behaviors in coal pyrolysis and char combustion are integrated. • Carbon coating is the key point of staged coal combustion in solving the slagging issue. [ABSTRACT FROM AUTHOR]

Circulating fluidized bed (CFB) technology has been continuously developing with an increasing number of large-capacity and supercritical CFB boilers being put into operation. This article reviews the current developments in large capacity CFB boilers in China and presents a note on the most recent development trends. It includes discussions on (1) gas-solid hydrodynamics in large-size CFB furnaces, (2) heat transfer on suspended surfaces, (3) combustion atmosphere and emissions, (4) 3-D CFD numerical simulation for large-scale supercritical CFB boilers, (5) integrated energy saving technologies, (6) optimal operation of an integrated desulfurization system, (7) erosion and protection of heat transfer surfaces, (8) problems in operation and their solutions, (9) combustion of coal with high alkali content. Unlabelled Image • Large-capacity and supercritical CFB boilers operated in China increased. • Current development trends of large capacity CFB boilers are discussed and noted. • Key aspects and issues during CFB development are discussed and noted. [ABSTRACT FROM AUTHOR]

• Water-lean EMEA/NMP was developed for CO 2 capture based on structure–activity. • EMEA/NMP achieved 69% lower regeneration energy than 5 M MEA. • Volatile amine emission of EMEA/NMP at absorber top was 109–1891 mg/m3. Water-lean amine are promising solvent for CO 2 capture to significantly reduce regeneration energy. However, existing water-lean solvent hasn't been put into commercial application due to high reaction heat, slow CO 2 absorption rate, and high amine volatility of amine. In this paper, amines with one secondary amino (—NH), one hydroxyl (—OH), and carbon chain length between 3 and 6 (C 3 -C 6) in structure were preferred for water-lean solvent in the light of amine structure–activity relationship. 2-(ethylamino) ethanol (EMEA) dissolving into 1-methyl-2-pyrrolidinone (NMP) and water were favorable water-lean solvent for CO 2 capture, and EMEA/NMP was tested in a bench-scale platform. EMEA/NMP solvents have equivalent CO 2 removal efficiencies, and 40–69% lower regeneration energy compared to blended amines and MEA solvents. The lower regeneration energy of EMEA/NMP results from lower water vapor ratio, lower reaction heat, and lower heat capacity. Viscosity of EMEA/NMP at rich loading is 6.92–11.11 mPa·s at 40℃. Increased stripper temperature increases CO 2 removal efficiency by decreasing lean loading in EMEA/NMP solvents. CO 2 desorption dominates mass transfer in stripper at low temperature while water evaporation dominates at high temperature. The lowest regeneration energy obtained with 5.0 M EMEA/NMP at liquid/gas ratio of 10.5 L/m3 and stripper temperature of 80℃ was 0.99 kWh/kg CO 2 (equivalent to 3.6 GJ/tCO 2), which is 69% lower than that of 5 M MEA. EMEA/NMP has an increasing amine emission from 109 to 1891 mg/m3 as absorber temperature increases from 34℃ to 54℃. Advanced processes would be employed for volatile amine emission control in future study. [ABSTRACT FROM AUTHOR]

As a low-carbon, environment-friendly and economical resource for nuclear power generation, radionuclide emission and storage has received worldwide attention. Geopolymer concrete is a green and sustainable building material that can be used to immobilize radionuclides. In the present study, molecular dynamics simulations were conducted to investigate the structural and mechanical properties of sodium aluminosilicate hydrate (NASH) gel, the main component of geopolymer concrete, with/without immobilized radioactive Cs and Sr ions. The three-dimensional structure of NASH gel enabled good immobilization of both radioactive Cs and Sr ions owing to the large radius of Cs ions and high charge density of Sr ions. Addition of Cs ions reduced the strength of the gel and increased the fracture strain, whereas addition of Sr ions increased the strength and significantly increased the ductility. Addition of Sr ions increased the number of penta-coordinated Al in the structure. Consequently, breakage of these bonds required more energy to be absorbed from outside. The nanoscale molecular dynamics simulations provided a theoretical support at atomic level for understanding the structural and mechanical characteristics of geopolymers pertinent to the immobilization of nuclear waste. [Display omitted] • The molecular dynamics approach provided a nanoscopic basis for radioactive waste disposal. • NASH gel has a good immobilization effect on Cs and Sr ions at nanoscopic scale. • Addition of radioactive ions alters the structural and mechanical properties of NASH. • Addition of Sr ions improves the ductility of the structure. [ABSTRACT FROM AUTHOR]

• China has implemented a huge CO 2 capture project, the 150,000 tons/year CO 2 capture and purification project of Shaanxi Guohua Jinjie Power Plant, which is the largest flue gas capture project in China. • The energy consumption level of regeneration reaches the leading level of flue gas CO 2 capture demonstration project. New energy-saving process of "interstage cooling + MVR heat pump + desorption heat energy recovery" is applied, and comprehensive regeneration energy consumption is less than 2.4GJ/tCO 2. • The final research results show that the project has technical feasibility and economic feasibility. The results show that the regeneration energy consumption per unit product is 2.32GJ/tCO 2 , and the loss of absorbent is less than or equal to 1.0 kg/tCO 2. There was little research and demonstration experience in large flue gas carbon projects in China. 150 kt/a flue gas CO 2 capture project in the Guohua Jinjie power plant, which is the largest-scale flue gas carbon capture project in China, effectively solved this technical bottleneck. The performance of the used compound amine absorbent, phase change absorbent, and the ionic liquid was described, and the compatibility of performance was considered in the project; new energy-saving processes integrated mechanical vapor recompression heat pump, interstage cooling, and split flow desorption. The plane layout of the project was put forward, and the utility consumption of the capture system was analyzed. The paper explained the health, safety, and environmental protection instructions, presented test category tables, and developed energy consumption and economic analyses. The results showed that the renewable energy consumption per unit product was 2.32 GJ/t CO 2 , the loss of absorbent was less than or equal to 1.0 kg/t CO 2 , and the total investment (excluding tax) of the project was 13.8398 million yuan. When the CO 2 sales price (excluding tax) was 203.43 Yuan/t, the yield was 0 %, and when the CO 2 sales price (excluding tax) was 260.949 Yuan/t, the yield was 8 %. The feasibility study research conclusions indicated that the project was technically and economically feasible. [ABSTRACT FROM AUTHOR]