Upcycling municipal solid waste to sustainable hydrogen via two-stage gasification-reforming

As global municipal solid waste(MSW)quantities continue to escalate,serious socio-environmental challenges arise,necessitating innovative solutions.Waste-to-hydrogen(WTH)via two-stage gasification-reforming(TSGR)presents an emergent technology for MSW upcycling,offering to ease waste management burdens and bolster the burgeoning hydrogen economy.Despite early initiatives to advance TSGR technology,a cohesive and critical analysis of cutting-edge knowledge and strategies to enhance hydrogen production remains lacking.This review aggregates literature on MSW upcycling to hydrogen via TSGR,with a focus on optimizing process control and catalytic efficiency.It underscores technological avenues to augment hydrogen output,curtail catalyst costs,and refine system performance.Particularly,the review illuminates the potential for integrating chemical and calcium looping into TSGR processes,identifying opportunities,and pinpointing challenges.The review concludes with a summary of the current state of techno-economic analysis for this technology,presenting outstanding challenges and future research directions,with the ultimate goal of transitioning WTH from theoretical to practical application.

Coal-gas interaction： implications of changes in texture and porosity

Transient sorption and desorption of helium and carbon dioxide in Upper Freeport coal powder and lumps were analyzed. Differences in texture and porosity between the powder and lumps may affect the transport and interaction of the penetrant and coal. In this work, we address macroscopic and mesoscopic structural differences between powdered and non-powdered coals that influence the rates of the gas transport kinetics and changes in coal texture （swelling, shrinkage, and changes in the pore structure and interconnectivity） and the reciprocal free-phase pressure decay （relaxation）. Com- parison of the multi-exponential relaxation time constants as a function of pressure, for CO2 and inert gas （helium）, allows us to postulate several mechanisms responsible for observed pressure decay patterns.

Beneficiation of coal using supercritical water and carbon dioxide extraction:sulfur removal

This work explores the use of carbon dioxide,water,and their mixtures as solvent for the precombustion beneficiation of raw coal without using any toxic mineral acids in the temperature range of 200-400℃.The fluid polarity,ionic constant,and supercritical point can be adjusted by H_(2)O/CO_(2)ratio and temperature.Adding carbon dioxide to hydrothermal fluid also increases the ionization by forming carbonic acid.Extractions with supercritical fluids have several benefits including enhanced mass transport,ease of separation and recycle,wide range of extractive capability and tunability,better inherent safety,and in the case of carbon dioxide and water-low cost.A semi-continuous extraction system was designed and built in which pressure,temperature and the relative flow rates of CO_(2)and H_(2)O can be controlled.Coal powder is kept in a packed bed and the extraction is carried out at 143 bar pressure.Using sulfur as a model heteroatom,extractive efficiency is examined as a function of the temperature,fluid composition,fluid flow,and extraction time.The results indicate that carbon dioxide,water,and supercritical water-carbon dioxide(ScWC)all can effectively extract about 50%of total sulfur from bituminous coal in 1 h.Extraction above 350℃decreased effectiveness,and extraction above the supercritical point of pure water caused hydrothermal carbonization.ScWC extraction may provide necessary control to prevent organic dissolution while removing sulfur.

Geomechanical response of overburden caused by CO_2 injection into a depleted oil reservoir

This study investigates the hydro-mechanical aspects of carbon dioxide(CO2) injection into a depleted oil reservoir through the use of coupled multiphase fluid flow and geomechanical modeling.Both singlephase and multiphase fluid flow analyses coupled with geomechanics were carried out at the West Pearl Queen depleted oil reservoir site,and modeling results were compared with available measured data.The site geology and the material properties determined on the basis of available geophysical data were used in the analyses.Modeling results from the coupled multiphase fluid flow and geomechanical analyses show that computed fluid pressures match well with available measured data.The hydromechanical properties of the reservoir have a significant influence on computed fluid pressures and surface deformations.Hence,an accurate geologic characterization of the sequestration site and determination of engineering properties are important issues for the reliability of model predictions.The computed fluid pressure response is also significantly influenced by the relative permeability curves used in multiphase fluid flow models.While the multiphase fluid flow models provide more accurate fluid pressure response,single-phase fluid flow models can be used to obtain approximate solutions.The ground surface deformations obtained from single-phase fluid flow models coupled with geomechanics are slightly lower than those predicted by multiphase fluid flow models coupled with geomechanics.However,the advantage of a single-phase model is the simplicity.Limited field monitoring of subsurface fluid pressure and ground surface deformations during fluid injection can be used in calibrating coupled fluid flow and geomechanical models.The calibrated models can be used for investigating the performance of large-scale CO2storage in depleted oil reservoirs.

Correction to:Beneficiation of coal using supercritical water and carbon dioxide extraction:sulfur removal

In the original publication,there were few amendments to be made in Section 3.2 Extractive reactions involved.The updated version of the section is provided in this correction.The original article has been corrected.

Calibrated dilatometer exercise to probe thermoplastic properties of coal in pressurized CO2

This research was aimed at testing a hypothesis, that at elevated CO2 pressure coal can soften at temperatures well below those obtained in the presence of other gases. That could have serious negative implications for injection of CO2 into deep coal seams. We have examined the experimental design issues and procedures used in the previously published studies, and experimentally investigated the physical behavior of a similar coal in the presence of COa as a function of pressure and temperature, using the same high-pressure micro-dilatometer refurbished and carefully calibrated for this purpose. No notable reduction in coal softening temperature was observed in this study.

CeFe_(2-x)In_x合金磁性研究与CeFe_(1.95)In_(0.05)合金磁相变临界参数分析

通过等温磁化曲线和等磁场变温曲线测量与标度理论,系统研究了CeFe_(2-x)In_x合金的磁性和CeFe_(1.95)In_(0.05)合金的磁相变临界参数.结果表明:用2.5 at.%的铟替代CeFe_2合金中的铁并不能使合金中的反铁磁态在低温下完全稳定,低场下在2—80 K均能观察到反铁磁相振荡; CeFe_2与CeFe_(1.95)In_(0.05)合金的顺磁-铁磁二级相变居里温度均在230 K附近;在0—5 T磁场范围内, CeFe_(1.95)In_(0.05)合金居里温度处的最大磁熵变为3.13 J/(kg·K),相对制冷量为151.3 J/kg.通过不同方法得到的具有高度自洽性的磁相变标度临界参数均表明CeFe_(1.95)In_(0.05)合金的磁相互作用可以用基于短程相互作用的3D-Ising模型来描述.

Bayesian optimization with active learning of design constraints using an entropy-based approach

The design of alloys for use in gas turbine engine blades is a complex task that involves balancing multiple objectives and constraints.Candidate alloys must be ductile at room temperature and retain their yield strength at high temperatures,as well as possess low density,high thermal conductivity,narrow solidification range,high solidus temperature,and a small linear thermal expansion coefficient.Traditional Integrated Computational Materials Engineering(ICME)methods are not sufficient for exploring combinatorially-vast alloy design spaces,optimizing for multiple objectives,nor ensuring that multiple constraints are met.In this work,we propose an approach for solving a constrained multi-objective materials design problem over a large composition space,specifically focusing on the Mo-Nb-Ti-V-W system as a representative Multi-Principal Element Alloy(MPEA)for potential use in next-generation gas turbine blades.Our approach is able to learn and adapt to unknown constraints in the design space,making decisions about the best course of action at each stage of the process.As a result,we identify 21 Pareto-optimal alloys that satisfy all constraints.Our proposed framework is significantly more efficient and faster than a brute force approach.

Prediction of Van Hove singularity systems in ternary borides

A computational search for stable structures among bothαandβphases of ternary ATB4 borides(A=Mg,Ca,Sr,Ba,Al,Ga,and Zn,T is 3d or 4d transition elements)has been performed.We found thatα-ATB4 compounds with A=Mg,Ca,Al,and T=V,Cr,Mn,Fe,Ni,and Co form a family of structurally stable or almost stable materials.These systems are metallic in non-magnetic states and characterized by the formation of the localized molecular-like state of 3d transition metal atom dimers,which leads to the appearance of numerous Van Hove singularities in the electronic spectrum.The closeness of such singularities to the Fermi level can be easily tuned by electron doping.For the atoms in the middle of the 3d row(Cr,Mn,and Fe),these singularities led to magnetic instabilities and magnetic ground states with a weakly metallic or semiconducting nature.Such states appear as non-trivial coexistence of the different spin ladders formed by magnetic dimers of 3d elements.These magnetic states can be characterized as an analog of the spin glass state.Experimental attempts to produce MgFeB4 and associated challenges are discussed,and promising directions for further synthetic studies are formulated.

Conversion of confined metal@ZIF-8 structures to intermetallic nanoparticles supported on nitrogen-doped carbon for electrocatalysis

We report a facile strategy to synthesize intermetallic nanoparticle （iNP） electrocatalysts via one-pot pyrolysis of a zeolitic imidazolate framework, ZIF-8, encapsulating precious metal nanoparticles （NPs）. ZIF-8 serves not only as precursor for N-doped carbon （NC）, but also as Zn source for the formation of intermetallic or alloy NPs with the encapsulated metals. The resulting sub-4 nm PtZn iNPs embedded in NC exhibit high sintering resistance up to 1,000℃. Importantly, the present methodology allows fine-tuning of both composition （e.g., PdZn and RhZn iNPs, as well as AuZn and RuZn alloy NPs） and size （2.4, 3.7, and 5.4 nm PtZn） of the as-formed bimetallic NPs. To the best of our knowledge, this is the first report of a metal-organic framework （MOF） with multiple functionalities, such as secondary metal source, carbon precursor, and size-regulating reagent, which promote the formation of iNPs. This work opens a new avenue for the synthesis of highly uniform and stable iNPs.

Minimum spouting velocity of flat-base spouted fluid bed

Experiments were performed on spout characteristics of a cylindrical spout-fluidized bed （I.D. = 10 cm） with different static heights and two materials （A1203 and high density polyethylene）. Results of minimum spouting velocity obtained in this study were compared with reported correlations for both spouted and spout-fluidized beds. Considerable discrepancies were found between the values obtained using different model equations as well as with respect to experimental results. Based on the Mathur-Gishler correlation, a new correlation is proposed for calculating the minimum spouting velocity that introduces the ratio U/Umf. It was found that the minimum spouting velocity decreases with increasing fluidizing gas velocity （U/Umf）. The pressure drop at the point of minimum spouting velocity is also correlated using this dimensionless group and is presented in this work. This investigation demonstrates that the use of correlations reported in the literature that focus primarily on conical bottom spouted beds are not applicable to fiat-bottom spouted and spout-fluidized beds.

Evolving carbon dioxide emission rate intensities of coal-fired power plant on U.S. electricity operating systems

For many years, coal-fired power plant generation comprised the largest share of electricity in the U.S.power sector. While natural gas plants now constitute a greater portion of the total, coal is projected to remain a shrinking but significant component of U.S. electricity production. Natural gas-fired technologies are dispatchable and versatile generation sources, but the recent and anticipated growth of wind and solar technologies will add nondispatchable, intermittent power generation sources to U.S.electricity grids. Numerous emissions-related benefits arise from the deployment of these technologies, but they must coexist with coal plants, many of which run most efficiently under baseload operating procedures. Historical monthly emissions data has been analyzed on a sample of coal plants to show how modified coal operations have affected plant emission rates, as measured by carbon dioxide emitted per unit of electricity output. Statistically significant correlations between plant capacity factors and emission rate intensity have been observed by the majority of the sample, showing a worsening under more sporadic operations. Since nearly all of the coal plants in the sample are generating less electricity, determining the emission impact of operational decisions will assist policymakers as they seek to minimize total system emissions without severe disruptions to electricity cost and service reliability.

Anion structural effects on interaction of rare earth element ions with Dowex 50W X8 cation exchange resin

The effect of the anion in the original rare earth element（REE） solution on the reversible ion exchange of Ce nitrate and Ce sulfate with the Dowex 50 W X8 was investigated using attenuated total reflection infrared（ATR-IR） spectroscopy, continuous flow reactor studies coupled with inductively coupled plasma mass spectroscopy（ICP-MS）, and density functional theory（DFT）. The simulated IR spectrum at the DFT B3 LYP/6-31 G（d） level was compared to the experimental results to characterize the IR spectrum, molecular interactions, and bonding of the ion exchanged species. The continuous liquid flow reactor studies show a capacity of 0.72 mmol/g sorbent for the Ce nitrateand 0.96 mmol/g sorbent for the Ce sulfate with the Dowex 50 W X8. The flow reactor studies reveal the type of solute anion（SO_4^（（2-）） or NO_3^（（-））） associated with the REE during cation exchange significantly affects the sorption capacity of the Dowex 50 W X8 ion exchange resin. The calculated REE binding energy（BE） and the DFT optimized structures suggest that the differences in sorption capacity is the result of the formation of different types of partially ionexchanged Ce_2^（（3＋））2 SO_4^（（2-）） and Ce^（（3＋）） 3 NO_3^（（-））. These results suggest that the solute anion affects the equilibrium constants of the Dowex resin by the formation of a charged layer capable of retaining the counterion. Modifying the sulfonic acid site（H＋） in the Dowex 50 W X8 with the NH_4~＋ counterion does not affect the sorption capacity and retention times of the Ce nitrate and Ce sulfate species. These results suggest that the counterions and co-ions having a finite size, may limit access to the Dowex sulfonate active site where the type of REE cation as a nitrate or sulfate in solution may significantly modify the sorption capacity of the ion exchange resin. Similar results are obtained during sorption with nitrates and sulfates of Sm and Yb.

Investigation on the 773K isothermal section of Ho-Ni-Si ternary phase diagram by X-ray powder diffraction and magnetic property of Ho3NiSi2 alloy

The isothermal section of the Ho-Ni-Si system at 773 K was constructed by X-ray powder diffraction(XRD)in this work.The system contains sixteen known type structure compounds TiNiSi-type HoNiSi,BaAl4-type HoNi2Si2,CeNiSi2-type HoNiSi2,U1Co3Si5-type Ho2Ni3Si5,SmNiGe3-type HoNiSi3,Ce3 Ni6Si2-type Ho3Ni6Si2,ThMn12-type HoNi10Si2,YPd2Si-type HoNi2Si,YNi5Si3-type HoNi5Si3,YNi4Si-type HoNi4Si,Gd3NiSi2-type Ho3NiSi2,YNi6Si6-type HoNi6Si6.AlB2-type Ho2NiSi3,AlB2-type Ho3Ni2Si4,AlB2-type Ho4NiSi7,Gd3Ru4Al12-type Ho8Ni31Si11,and one unknown type structure compound Ho5Ni2Si3.At the same time,one unknown structure new phase Ho37Ni3Si60 was observed.In ternary compounds,Ho2NiSi3 and Ho4NiSi7 have the solid solution phenomena;the solid solution ranges are about Ho33.3Ni18.7-9.7Si-48.0-57.0 and Ho33.Ni-8.3-2.6Si-58.3-64.1,respectively.At the same time,quasi-binary solid solutions were detected at 773 K for Ho2Ni17,HoNi5,Ho2Ni7,HoNi3,HoNi2,HoNi,HoSi.Other binary compounds of the Ho-Ni-Si system do not show any visible solubility.The magnetic property studies show that Ho3NiSi2 compound has two successive magnetic phase transitions in a low field:a spinreorientation transition at TSR=10 K and a second order ferromagnetic(FM)-paramagnetic(PM)transition at Tc=37 K.

A rapid solid-state synthesis of electrochemically active Chevrel phases （Mo6T8; T = S, Se） for rechargeable magnesium batteries

High energy mechanical milling （HEMM） of a stoichiometric mixture of molybdenum and metal chalcogenides （CuT and MOT2; T = S, Se） followed by heat treatment at elevated temperatures was successfully applied to synthesize Chevrel phases （Cu2Mo6T8; T = S, Se） as positive electrodes for rechargeable magnesium batteries. Differential scanning calorimetry （DSC）, thermogravimetric analyses （TGA）, X-ray diffraction （XRD）, and scanning electron microscopy （SEM） were used to understand the phase formation following milling and heat treatment. CuS and Mo were observed to react at 714-800 K and formed an intermediate ternary Chevrel phase （Cu1.83Mo3S4）, which further reacted with residual Mo and MoS2 to form the desired Cu2MosSs. Quantitative XRD analysis shows the formation of a -96%-98% Chevrel phase at 30 min following the milling and heat treatment. The electrochemical performance of de-cuprated Mo6S8 and Mo6Ses phases were evaluated by cyclic voltammetry （CV）, galvanostatic cycling, and electrochemical impedance spectroscopy （EIS）. The results of the CV and galvanostatic cycling data showed the expected anodic/cathodic behavior and a stable capacity after the first cycle with the formation of MgxMo6T8 （T = S, Se; 1 ≤ x 〈 2）. EIS at -0.1 V intervals for the Mo6Ss electrode during the first and second cycle shows that partial Mg-ion trapping resulted in an increase in charge transfer resistance Re. In contrast, the interfacial resistance Ri remained constant, and no significant trapping was evident during the galvanostatic cycling of the Mo6,Se8 electrode. Importantly, the ease of preparation, stable capacity, high Coulombic efficient35 and excellent rate capabilities render HEMM a viable route to laboratory-scale production of Chevrel phases for use as positive electrodes for rechargeable magnesium batteries.

Analysis of hourly generation patterns at large coal-fired units and implications of transitioning from baseload to load-following electricity supplier

Several factors have led to the decline of electricity generation from coal over the past decade, and projections forecast high rates of growth for wind and solar technologies in coming years. This analysis uses hourly generation data from large coal-fired power stations to determine how operations have been modified in recent years and describes the implications of these changes for plant equipment and unit reliability. The data shows increasing variability in intraday generation output that affects nearly all of the units in the sample, but the magnitude of increase varies widely among plants. Outage patterns were examined as was the relationship between renewable energy growth in a region and the changes in coal plant operations. Aggregate direct and indirect costs associated with running coal plants as load-following units have not yet been quantified in large-scale studies on a sector-wide basis, largely due to differences in how specific equipment responds to output fluctuations. Due to findings from the hourly generation data analysis and the high degree of potential impact on coal plant equipment, the study suggests the development of a new modeling tool that will represent the costs of running coal-fired power plants at lower capacity factors.

Leaching of lanthanide and yttrium from a Central Appalachian coal and the ashes obtained at 550-950℃

In this work,we investigated leaching of lanthanide and yttrium(REY) from a Central Appalachian coal and its ashes obtained at 550-950℃ with the main purpose of understanding the impact of ashing temperature on REY leachability in water,ammonium sulfate,and hydrochloric acid.It is found that the coal contains a negligible amount of water-soluble REY,less than 1% ion-exchangeable REY,and about 28% of HCl-soluble REY.Ashing leads to dramatic changes in REY leachability in both ammonium sulfate and hydrochloric acid solutions,which is believed to be related to transformation and redistribution of organically-associated REY in coal during the ashing process.Ashing temperature significantly affects REY leaching from coal ashes;higher ashing temperature results in lower REY leachability in both solutions.Clay minerals may play a significant role in changing the leachability of REY after ashing.In addition,the results also suggest that the organic matter in the coal is relatively enriched in heavy REY.

Design of high-strength refractory complex solid-solution alloys

Nickel-based superalloys and near-equiatomic high-entropy alloys containing molybdenum are known for higher temperature strength and corrosion resistance.Yet,complex solid-solution alloys offer a huge design space to tune for optimal properties at slightly reduced entropy.For refractory Mo-W-Ta-Ti-Zr,we showcase KKR electronic structure methods via the coherent-potential approximation to identify alloys over five-dimensional design space with improved mechanical properties and necessary global(formation enthalpy)and local(short-range order)stability.Deformation is modeled with classical molecular dynamic simulations,validated from our first-principle data.We predict complex solid-solution alloys of improved stability with greatly enhanced modulus of elasticity(3×at 300 K)over near-equiatomic cases,as validated experimentally,and with higher moduli above 500 K over commercial alloys(2.3×at 2000 K).We also show that optimal complex solid-solution alloys are not described well by classical potentials due to critical electronic effects.

Experimental isothermal section phase diagram of Ho-Fe-In at 773 K and magnetic properties of Ho_(12)Fe_(2.08)In_(2.92) alloy

The isothermal section of the Ho-Fe-In system at 773 K has been constructed by X-ray powder diffraction.One known structure ternary compound Er_(12)Fe_(2) In_(3)-type Ho_(12)Fe_(2) In_(3) has been confirmed.At the same time,solid solutions are not detected in Ho-Fe-In system at 773 K.The magnetic transition and magnetocaloric effect of Ho_(12)Fe_(2.08)In_(2.92) alloy with Er_(12)Fe_(2) In_(3)-type structure were investigated by magnetic susceptibility and isothermal magnetization measurements.One normal antiferromagnetic-paramagnetic transition and another abnormal one are discovered at 18 and 76 K in ground state,respectively.Owing to a first-order field-induced metamagnetic transition(antiferromagnetic-ferromagnetic) at/below the Neel temperature of 18 K),the negative entropy changes are observed at corresponding temperature.There is only a second-order ferromagnetic-paramagnetic transition near Curie temperature(TC),the maximum entropy change(Δ_(Smax)) values are-6.14 J·kg^(-1)·K^(-1) at 3 K and 7.88 J·kg^(-1)·K^(-1) at 28 K in a field range of 0-7 T.The reversible relative cooling power corresponding to negative entropy change can reach about 600 J·kg^(-1) in an wide operating temperature region Δ_(Tcycl)=74 K from 16 to90 K,which suggests that Ho_(12)Fe_(2.08)In_(2.92) could be a potential material for magnetic refrigeration in the corresponding temperature range.

Effect of calcination temperature on steam reforming activity of Ni-based pyrochlore catalysts

This work served as the second part of a study evaluating the effect of calcination temperature(700-1000℃) on Ni-based lanthanum zirconate pyrochlore catalysts for methane steam reforming.A previous study(Haynes et al.Ceram.Int.2017(43) 16744) provided a thorough characterization of the material properties for the catalysts used here,and this study focuses on the evaluation of catalytic activity.The activity was assessed by two different experimental studies:the effect of reaction temperature using a temperature programmed surface reaction(TPSR),and the effect of reaction pressure.The results demonstrate a complex interaction between the Ni particles and surface LaOx species under the methane steam reforming conditions.Specifically,the material calcined at the lowest temperature(700℃) possesses the highest activity and selectivity,which is attributed to smaller and more welldispersed Ni particles on the surface,and,more importantly,a lesser degree La enrichment at the surface.All catalysts were deactivated by steam to NiO under all conditions tested,but at certain low reaction pressure(p=0.23 MPa) conditions the materials calcined at 700-900℃ are able to completely recover equilibrium activity in-situ that is then robust and stable under both low and high reaction pressures(p=1.8 MPa) suggesting the formation of a synergistic relationship between Ni and La for syngas production.However,exposure of a fresh material to high reaction pressures leads to a rapid and irreversible loss in both CH4 conversion and syngas selectivity whether in the fresh(no pretreatment),or pretreated(steam,H2 or Ar only at 800℃) form for any catalyst.The mechanism for deactivation appears to be due to the presence of LaOx species that become mobile,possibly by the formation of La-OH,and covers the active Ni particles and inhibits sites responsible for the CH4 decomposition.