Gas Generation Rate Research Articles

Application of Tetraethylsulfamide (TES) As a Cathode Additive in Cylindrical Cells

Recently, sulfonamides have been shown to be promising electrolyte components due to their high chemical and electrochemical stability in lithium batteries [1, 2]. The electrolyte stability becomes critical when applying high voltage and/or utilizing Ni-rich layered oxides in high energy density lithium-ion batteries. Another approach to successful Ni-rich cathode performance is to develop a stable and effective cathode electrolyte interphase (CEI). Given the success of sultones and sulfates in this regard [3, 4], it is hypothesized that nitrogen analogs, like sulfonamides, could be tailored to provide a similar benefit. Indeed, Yim et al. [5, 6] have shown that N,N,N’,N’-tetraethylsulfamide (TES) forms a CEI on NMC811 that imparts high voltage cycling stability and less cathode corrosion. Our earlier studies of TES with Ni-rich NCA also formed a favorable CEI and these results are the topic of this presentation.Herein, we examine the performance of 0 - 4 wt.% TES in our commercially available, high power INR18650-P28A. These cells contain a composite SiO/graphite anode in addition to a Ni-rich cathode. As shown in Fig 1, TES significantly decreased the impedance of the cathode interface after conditioning compared to the control electrolyte. Thereafter, cells containing up to 2%TES show improved capacity retention during long-term high-rate cycling (+1C/-80W). Part of this success was due to a suppression of resistance growth during cycling by TES. Fast charge cycling (+3C/-2C), however, was moderately impaired with increased TES. Considering the largely reduced impedance of the cathode, fast-charge performance may have suffered due to anode rate limitations. These results will be discussed as well as gas generation, storage performance, and additional rate and cycling tests.[1] Shuting Feng, Mingjun Huang, Jessica R. Lamb, Wenxu Zhang, Ryoichi Tatara, Yirui Zhang, Yun Guang Zhu, Collin F. Perkinson, Jeremiah A. Johnson, Yang Shao-Horn. Chem, 5, 2630-2641 (2019)[2] Weijiang Xue, Mingjun Huang, Yutao Li, Yun Guang Zhu, Rui Gao, Xianghui Xiao, Wenxu Zhang, Sipei Li, Guiyin Xu, Yang Yu, Peng Li, Jeffrey Lopez, Daiwei Yu, Yanhao Dong, Weiwei Fan, Zhe Shi, Rui Xiong, Cheng-Jun Sun, Inhui Hwang, Wah-Keat Lee, Yang Shao-Horn, Jeremiah A. Johnson, Ju Li. Nature Energy, 6, 495-505 (2021)[3] Koji Abe, Manuel Colera, Kei Shimamoto, Masahide Kondo, Kazuhiro Miyoshi. Journal of Electrochemical Society, 161 (6) A863-A870 (2014)[4] Jian Xia, N. N. Sinha, L. P. Chen, J. R. Dahn. Journal of Electrochemical Society, 161 (3) A264-A274 (2014)[5] Kwangeun Jung, Taeeun Yim. Journal of Alloys and Compounds, 834,155155 (2020)[6] Ji Won Kim, Kwangeun Jung, Taeeun Yim. Journal of Mater. Sci & Tech. 86, 70-76 (2021) Figure 1

Field investigation and numerical modelling of gas extraction in a heterogeneous landfill with high leachate level.

A field gas extraction experiment is carried out at a high-kitchen food large-scale landfill site with high leachate level. The leachate level was decreased to improve the pumping efficiency. Considering the heterogeneity of the municipal solid waste (MSW), the pores in the unsaturated MSW are divided into matrix pores and fractures. A transient dual-porosity model was then developed to analyze the pumping test results. The first and second boundary conditions considering the effect of cover layers of landfills was involved. The results show that the gas flow rate can be increased by 14-37% due to the drawdown of the leachate level. Compared with the single pore model, the dual-porosity model can better predict the field results, indicating that the preferential flow in the landfill caused by the heterogeneity of MSWs is very important. As the pumping pressure increases by a factor of 5, the ratio of fractures to pores wf can be decreased by a factor of 4.4. This may be due to the fact that the fractures will be compressed when the effective stress was increased as the negative pumping pressure was applied. The pumping pressure and the anisotropy value of the MSWs have the greater influence on the well radius of influence. The proposed model can be used for effective design of the field gas pumping experiments. The obtained gas generation rate, gas permeability of the dual porosity MSWs can be useful for gas transport analysis and gas pumping well design for the high-kitchen food content landfills.

Design of gas collection systems: Issues and challenges.

The design of a gas collection system (GCS) for a landfill involves estimating several critical parameters, such as the radius of influence (ROI), suction pressures, number of wells and their spacing. One of the biggest challenges lies in the estimation of ROI for a particular landfill. In this study, the ROI for a Bagalur landfill is estimated for various possible gas generation rates. ROI for active and passive GCS is estimated with numerical modelling (two-dimensional) for all definitions of ROI at different suction pressures. An inverse correlation was observed between the values of various definitions of ROI at different gas generation rates. Justification for this behaviour is brought out by addressing the conceptual difference between these definitions. The number of wells along with their spacing was then calculated, and the efficiency of the design was assessed with three-dimensional modelling. Passive and active systems had average methane recovery rates of 84% and 88%, respectively, with an atmospheric methane flux ranging from 10-9 to 10-10 kg m-2 s-1. The high recovery rate and low methane flux indicate the effectiveness of the design. The values of the methane flow rate from the extraction well were validated with a theoretical method, suggesting the usability of the model for future investigations.

Investigations of Middle-Caliber Anti-Aircraft Cannon Interior Ballistics including Heat Transfer Problem in Estimation of Critical Burst Length

Numerical and experimental investigations of armament systems are an important part of modern design processes. The presented paper reports problems that were encountered on the theoretical analysis of the performance of 35 mm anti-aircraft cannon and the way in which they were solved. The first problem concerns the application of results of closed vessel tests of used propellant in interior ballistics simulations. The use of a nonstandard form of the gas generation rate equation solved this problem. The second problem concerned the assessment of projectile–barrel interaction. The barrel resistance was estimated making use of finite element analysis. The third problem arose from the need to determine the heat transfer from propellant gases to the barrel. The employed formula for the heat exchange coefficient and 2D modelling of the heat conduction in the barrel provided the solution. Selected elements of the theoretical model were validated by shooting range experiments and data provided by the ammunition producer. Using the considered approach, crucial ballistic parameters (maximum propellant gas pressure and muzzle velocity) were estimated with an error of less than 6.0%, without application of additional fitting coefficients. The numerical estimation of the barrel external surface temperature provided a relative discrepancy with the experimental data lower than 6% and enabled the estimation of the critical burst length, equal to 14 shots.

Accelerating gas production of the depressurization-induced natural gas hydrate by electrical heating

Natural gas hydrate (NGH) will be one of the major future energy sources due to its properties of clean energy and large reserves. Depressurization is proposed as an effective method to extract natural gas from hydrate, however, the gas production from hydrate dissociation may be interrupted by ice generation and hydrate re-formation due to insufficient heat supply in the single depressurization process. To solve this issue, this work conducted simulation on accelerating gas production from the depressurization-induced methane hydrate by electrical heating. The continuous heating and intermittent heating modes were employed and then the electrical heating scheme was optimized for the comprehensive effect of high energy efficiency and high gas production rate. The results show that electrical heating is conducive to gas production from hydrate dissociation at a rapid rate. In the continuous heating, a high initial hydration saturation, low initial water saturation, low specific heat capacity, and high thermal conductivity result in the high gas generation rate and efficient electrical energy utilization (a large energy efficiency ratio). The intermittent heating has a higher efficient utilization of electrical energy than continuous heating. The optimal scheme is determined as the first-half heating type with the optimized electrical heating power of 25.6 W and the heating time of 12.5 min by the gradient descent method of AdaGrad. Compared to the baseline continuous heating case, the energy efficiency ratio (10.70) of the optimal scheme is enhanced by 24.7% with the average gas production rate (2.55 SmL/s) enhanced by 18.2%. It's hoped that the findings of this work can provide some insights into extracting natural gas from gas hydrate deposits. Electrical heating is employed to provide heat for the endothermic dissociation of methane hydrate induced by depressurization for accelerating natural gas production in this work. The electrical heating scheme is optimized to achieve high-efficient utilization of electrical energy for the fast extraction of natural gas from hydrate dissociation. • Electrical heating accelerates the depressurization induced dissociation of hydrate. • The effects of phase components and porous media properties are analyzed. • Intermittent heating has higher efficiency of energy utilization than continuous heating. • The electrical heating power is optimized by the gradient descent method of AdaGrad. • The optimal scheme is first-half heating with the optimized electrical heating power.

Influence of woodgrain orientation on the upward flame spread over discrete wood chips

To have a deep understanding of influence of woodgrain orientation on the upward flame spread performance, a series of tests were conducted to obtain the profile of mass loss rate (MLR), flame spread rate (FSR), total burning duration (TBD), and the maximum flame characteristic length (MFL) by using a traditional flame spreading measurement facility. The woodgrain orientation of samples tested in the current work are horizontal (H), vertical (V), and slanting (S). During the tests, a series of six 2 cm-long 10 cm-wide wood chips were uniformly installed on a vertical sample holder. The distance of air-gap differed from 1.0 cm to 3.0 cm and the thickness of wood chips varied from 1 mm to 4 mm. It is found that flame spread over discrete solid fuels depends on the generation rate of pyrolysis gas and direction of gas-flow, which is highly differed by the woodgrain orientation with respect to the wooden chips. The charring rate of samples imposed a strong effect on the flame spread performance. The a-MLR of three kinds of woodgrain are ranked as V > S > H. The FSR are ranked in general as H > V > S. The thickness of the samples imposed a larger effect on the TBD comparing with wood grains orientation. The TBD are ranked as S > V > H. The results of MFL indicate that as the thickness of the sample increases, MFL of samples performed with the H woodgrain is reduced greatly. However, both S and V woodgrain show a small effect on the MFL. It hopes to provide a deep understanding of flame spreading performance over wooden structures.

Factors Affecting Substrate Heating with Printed Thermites

AbstractVarious nano‐aluminum thermites were printed and burned on substrates. The reactions were recorded using high‐speed and infra‐red videography in order to investigate the factors affecting the resulting substrate heating. A large number of factors are found to affect the achieved substrate temperature. The thermite's exothermic energy release, gas generation, and burn rate are significant factors, as are the substrate's mass and thermal conductivity. Full‐thickness heating to 360 °C is demonstrated for a standard glass microscope slide. This work will hopefully inspire new applications in actuators or on‐chip thermal processing utilizing the high energy density of printed thermites.

Measurement of gas pressure in packaged electric double layer capacitors

Electric double layer capacitors (EDLCs) are popular energy storage devices in part because they have very long life with a highly predictable failure time. EDLCs generate gas during operation, particularly when operated at their maximum rated temperature and voltage, which leads to pressure rise in a sealed package with the possibility of package rupture. However, EDLC package rupture is seldom observed because it can be prevented with proper application engineering, which requires knowledge of the gas generation rate. We demonstrate two approaches for the measurement of gas pressure in packaged EDLCs. The first is indirect and relies on package deformation to infer the internal gas pressure. This is easy to implement and has low cost but it lacks high precision. The second approach measures gas pressure directly using an electronic transducer. It is more cumbersome and costly (a special apparatus is needed) but does provide continuous measurement with high precision. Details of both gas pressure measurement approaches are reported and demonstrated using packaged 100-F-size EDLCs. • Gas pressure was measured in packaged electric double layer capacitors two ways. • Gas generation began when voltage was first applied to the capacitor. • The indirect measurement approach was fast and low cost but it lacked precision. • The direct measurement approach had high precision but was more cumbersome.

Study on Splashing Mechanism in Basic Oxygen Furnace Based on Slag Foaming Modeling

Inappropriate slag foaming is the main cause of splashing in basic oxygen furnace (BOF). Through the physical modeling, the effects of slag–metal reaction rate, viscosity of slag, slag–metal interface tension, and lance height on the slag foaming are investigated, and further analyzed the relation between the extent of BOF slag foaming and splashing. Consequently, two patterns of overflowing splashing and eruptive splashing and their critical conditions are summarized. The experimental results indicate that gas released by slag–metal reaction is primarily responsible for slag foaming in BOF, and the maximum height of foamed slag increases with increasing reaction rate of slag–metal. Moreover, an increase in dynamic viscosity of slag prevents the foam structure transforming from spherical foam to polyhedral foam, and thus improves the maximum foaming ability of slag and the stability of foam structure. With decreasing slag–metal interface tension, the slag–metal emulsification and the stability of foam structure are promoted. Finally, it is concluded that overflowing splashing occurs under the conditions of the higher dynamic viscosity of slag and the larger gas generation amount; whereas, eruptive splashing occurs under the conditions of the lower dynamic viscosity of slag and the higher gas generation rate.

Experimental analysis of lengthwise/transversal thermal characteristics and jet flow of large-format prismatic lithium-ion battery

• Thermal runaway characteristics of prismatic batteries with lengthwise and transversal placements are investigated. • The jet flow behavior of the battery during thermal runaway is analyzed in detail. • A method is proposed to estimate the jet velocity based on mass loss rate. Lithium-ion batteries (LIBs) are among the most promising technologies for electric vehicles and electric energy storage systems, while the safety accidents associated with thermal runaway happen frequently. Thermal characteristics and the jet behavior of prismatic LIBs under overheating conditions are still unclear. In this study, the thermal runaway characteristics of LIBs under lengthwise and transversal placements, such as battery surface temperature, voltage and mass loss are investigated through the overheating experiments. Results show that the center and bottom of the LIB surface of lengthwise placement have higher temperatures during thermal runaway. Compared with lengthwise placement, transversal placement accelerates the occurrence of thermal runaway under overheating conditions. The onset temperature of the safety valve opening is 129 °C, which is not affected by electrical energy stored inside the battery and placements. To comprehensively understand the prismatic LIB jet flow, a method is proposed to determine the jet velocity at the safety valve based on mass loss using mathematical deductions. The jet behavior, internal pressure and gas generation rate are also quantitatively characterized by experiments. The maximum jet velocity occurs with a value of 42.05 m/s occurs at the moment when the safety valve opens. This work further reveals thermal abuse characteristics and jet behavior of prismatic LIBs, the research outcomes of which provide guidance for the safe design and thermal hazard prevention in battery storage systems.

Assembling Hybrid Energetic Materials with Controllable Interfacial Microstructures by Electrospray.

Constructing hybrid energetic materials (HEMs) consisting of nanothermites and organic high explosives is an efficient strategy to regulate the reactivity of energetic composites. To investigate the role of interfacial microstructures in determining the reactivity of HEMs, we employ electrospray, one ramification of electrohydrodynamic atomization, to assemble Al/CuO and hexanitrohexaazaisowurtzitane (CL-20) into composites with various morphologies from different solvent systems. The morphology and compositional information of the assembled clay-like or granular HEMs, which are obtained from ketone, ester, or mixtures of alcohol and ether, are confirmed by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). The phase transition of CL-20 due to the fast evaporation of charged droplets and insufficient time for recrystallization is studied by Fourier transform infrared spectroscopy (FTIR). Thermogravimetric-differential scanning calorimetry (TG-DSC) is applied to investigate the thermodynamic behaviors and synergistic effect of the nanothermite and high explosive. Enhancements in combustion performance and pressurization characteristics of the as-sprayed HEMs have been observed through open burn tests and pressure cell tests. Granular HEMs show high gas generation and high pressurization rate, while nitrocellulose (NC) fibers existing in the clay-like HEMs would weaken the reactivity to a certain extent. HEMs obtained from the mixture of n-propanol and diethyl ether, in which nano-CL-20 exists as independent particles rather than a matrix, exhibit high gas generation but low pressurization rate. The results indicate that the energy releasing performance of the prepared HEMs can be readily regulated by constructing various interfacial microstructures to satisfy the broad requirements of energy sources.

Degradation Diagnostics in Graphite-NMC Cells Under Fast SEI Formation

The formation process is the last step in the lithium ion battery manufacturing process but plays an outsize role in determining cell costs [1], [2]. A typical formation protocol consists of multiple low-rate charge-discharge cycles which can take many days to complete. During formation, the solid-electrolyte interface (SEI) is created through irreversible lithium reduction reactions with the electrolyte at the negative electrode surface. Formation protocols are difficult to optimize in part because their impact to long term cell lifetime and safety remain under debate. For example, while some authors have reported that the voltage window and charging rate during formation could impact cycle life[3], [4], others have found that formation protocols as fast as 14 hours[5] or ones causing lithium plating[6] have little to no impact on cycle life. The current evidence suggests that there remain opportunities to optimize the formation protocol for a given cell chemistry and design. However, finding an optimal formation protocol will require a more detailed understanding of the long-term impact on cell degradation and with consideration for cell safety.In this study, we design a test sequence and identify diagnostic signals to elucidate the impact of a fast formation protocol[5] on the long-term cycle life behavior of NMC/graphite cells. The study consists of 40 identical pouch cells built in-house at the University of Michigan Battery Lab. Half of the cells were subjected to the fast formation protocol and the remaining cells used a baseline formation protocol. Each set of cells were further split into two groups to be cycled at room temperature and inside a temperature-controlled oven at 45°C. The aging test consists of 1C charge-discharge cycles between 3.0V and 4.2V. Periodic reference performance tests were inserted as part of the aging test to provide additional diagnostic signals, including cell internal resistances as a function of state of charge and low-rate voltage curves for differential capacity analysis. Cells were stopped after discharge capacities were measured to be below 50%. At the end of the test, the degree of cell swelling was measured.The results showed that the cells with fast formation had a longer cycle life compared to control, but the same cells also showed higher cell-to-cell variability towards the end of life. Nearly all cells with fast formation showed moderate to severe swelling when cycled at 45°C, in contrast to the cells with baseline formation which showed little to no volume change. Taken together, these results suggest that it is possible for a fast formation protocol to yield similar or better cycle life but still potentially compromise the safety of the cell through increased gas generation rates. We also monitored the cycle life of several cells that showed a non-monotonic current behavior during formation attributable to a reversible lithium plating process. The cycle life and resistance growth of these cells fell within the expected range of values after considering cell-to-cell variation, suggesting that the presence of transient lithium plating during formation does not have a long-term impact to cell lifetime. Finally, in exploring the diagnostic signals, we identify two beginning-of-life signals that showed positive correlation with the maximum cycle count and cell resistance measured at the end-of-life: (1) the cell resistance measured at low states of charge, and (2) the voltage decay during a rest step inserted at the end of the last formation charge cycle. This last finding revitalizes the possibility of designing cell lifetime predictors using simple metrics measured at the beginning of life.[1] D. L. Wood, J. Li, and C. Daniel, J. Power Sources, vol. 275, pp. 234–242, 2015[2] K. Kuhlmann, S. Wolf, C. Pieper, G. Xu, and J. Ahmad, Bost. Consult. Gr., pp. 1–22, 2018[3] T. S. Pathan, M. Rashid, M. Walker, W. D. Widanage, and E. Kendrick, J. Phys. Energy, vol. 1, no. 4, p. 044003, 2019[4] C. Mao et al., J. Power Sources, vol. 402, no. July, pp. 107–115, 2018[5] D. L. Wood, J. Li, and S. J. An, Joule, vol. 3, no. 12, pp. 2884–2888, 2019[6] M. Ryan et al., J. Power Sources, vol. 484, pp. 0–7, 2021 Figure 1

Coupling hydrothermal carbonization of digestate and supercritical water gasification of liquid products

This work investigates the coupling of hydrothermal carbonization (HTC) and supercritical water gasification (SCWG) as a combined process to fully valorise digestate from anaerobic digestion. Firstly, HTC was performed at three different temperatures (180, 220 and 250 °C) to convert digestate to hydrochar (HC) and aqueous HTC liquids (AHLs) and then, SCWG was performed on AHLs to produce a H2-rich gas. Different SCWG temperatures (500, 550 and 600 °C), residence times (15, 30, 60 and 90 s) and AHLs concentrations (6.7, 13.6 and 20.0%) were tested. Increasing SCWG temperature resulted in an increase of the carbon yield and H2 content in the gas phase, for increasing residence time the carbon yield in the gas phase decreased, while increasing the feedstock concentration led to a higher gas generation rate without affecting the carbon yield of the gas. The maximum carbon yield in the gas phase (51%) was reached for tests run at 600 °C, 15 s, and 6.7% of AHLs, the maximum hydrogen content in the gas phase (79%) was reached at 600 °C, 30 s, 6.7% of AHLs, the maximum gas generation rate (9.33 mL min−1) was reached at 600 °C, 30 s, 20.0% of AHLs.

Reaction-Diffusion Model for Gasification of a Shrinking Single Carbon-Anode Particle.

The present work focuses on the gasification of a single carbon-anode particle with CO2, using a detailed reaction-transport model based on the reaction intrinsic kinetics and transport of gaseous species. The model includes the mass conservation equations for the gas components and solid carbon particles, resulting in a set of nonlinear partial differential equations, being solved using numerical techniques. The model may predict the gas generation rate, the gas compositions, and the carbon consumption rate during the gasification of a carbon particle. Five kinetic models were compared to describe the gasification behavior of carbon particles. It was found that the random pore model (RPM) provided the best description of the reactivity of anode particles. The model also predicted the particle shrinkage during the gasification process. The model was validated using experimental results obtained with different particle size ranges, being gasified with CO2 at 1233 K. The experiments were performed in a thermogravimetric analyzer (TGA). Good agreement between the model results and the experimental data showed that this approach could quantify with success the gasification kinetics and the gas distribution within the anode particle. In addition, the Langmuir–Hinshelwood (L–H) model is used in order to capture the inhibition effect of carbon monoxide on the gasification reaction. The effectiveness factor and Thiele modulus simulated for various particle sizes helped assess the evolution of the relative dominance of diffusion and chemical reactions during the gasification process.

Two-phase transport in a cemented waste package considering spatio-temporal evolution of chemical conditions

The long-term evolution of cemented waste packages is governed by (bio)chemical reactions between waste, cement, and barrier materials, and by transport processes inside the waste package and through openings in the waste package hull. Inside a waste package, gases can be generated by pH-dependent anoxic corrosion of metals and the degradation of organic matter. The (bio)chemical reactions consume water and will not proceed under dry conditions. The degradation of cementitious materials lowers the alkaline pH of the pore water. The modeling of such a complex feedback system shows that the internal structure of a waste package and the exchange of mass with the environment (boundary conditions) are major factors that determine the importance of process couplings. The (bio)chemical reactions are controlled by internal re-distribution of water predominantly via vapor transport. Calculated gas generation rates were found to be affected by dry-out processes inside the drum.

Effect of crosslinking points on bubble nucleation in the microcellular foaming of thermosets

Thermoset foams are often produced by chemical foaming with control of both curing degree and foaming gas generation rate in a heating process. In this study, to analyze the effect of the degree of curing on bubble nucleation independently from the effect of the gas generation rate, batch physical foaming was conducted with a thermoset polymer with controlled crosslinking degree using supercritical carbon dioxide. A styrene/divinylbenzene (DVB) mixture was polymerized with various copolymer ratios and used as model thermoset polymer with different crosslinking degrees. The foaming experiments clearly showed that not the viscosity of the polymer but the distance between crosslinking points was the key factor in determining the bubble nucleation in the physical foaming process. When the distance between the crosslinking points was shorter than the critical diameter of a bubble calculated from classical nucleation theory, bubbles could not be nucleated, i.e., the distance between the crosslinking points determined the foamability of the thermoset polymer.

Investigation of the kinetics of spontaneous combustion of the major coal seam in Dahuangshan mining area of the Southern Junggar coalfield, Xinjiang, China

In the present paper, with using diverse methods (including the SEM, the XRD, the TPO, the FTIR, and the TGA) , the authors analysed samples of the major coal seam in Dahuangshan Mining area with different particle sizes and with different heated temperatures (from 50 to 800 °C at regular intervals of 50 °C). The results from SEM and XRD showed that high temperature and high number of pores, fissures, and hierarchical structures in the coal samples could facilitate oxidation reactions and spontaneous combustion. A higher degree of graphitization and much greater number of aromatic microcrystalline structures facilitated spontaneous combustion. The results from TPO showed that the oxygen consumption rate of the coal samples increased exponentially with increasing temperature. The generation rates of different gases indicated that temperatures of 90 °C or 130 °C could accelerate coal oxidation. With increasing temperature, the coal oxidation rate increased, and the release of gaseous products was accelerated. The FTIR results showed that the amount of hydroxide radicals and oxygen-containing functional groups increased with the decline in particle size, indicating that a smaller particle size may facilitate the oxidation reaction and spontaneous combustion of coal. The absorbance and the functional group areas at different particle sizes were consistent with those of the heated coal samples, which decreased as the temperature rose. The results from TGA showed that the characteristic temperature T3 declined with decreasing particle size. After the sample with 0.15–0.18 mm particle size was heated, its carbon content decreased, and its mineral content increased, inhibiting coal oxidation. This result also shows that the activation energy of the heated samples tended to increase at the stage of high-temperature combustion with increasing heating temperature.

Evolution of Phosphine from Aluminum Phosphide Pellets

HighlightsThis study developed a mathematical relationship accounting for the production rate of phosphine.The effect of temperature on phosphine sorption into wheat is described mathematically.A computational fluid dynamics (CFD) model was built to predict the phosphine concentration in fumigated grain.Experiments were conducted to validate the CFD model.Abstract. Phosphine gas (PH3) is widely used as a fumigant for stored product insect infestations due to its relatively low price and the near absence of residual chemical on the grain. Understanding the behavior of phosphine gas inside the fumigated space is crucial to maintaining a lethal dosage and protecting stored grain from subsequent insect damage. Phosphine is available either in gas form or is produced from a solid material, as pellets or tablets, that reacts with water in the air. The solid form is the most commonly used; however, limited information is available on the rate of phosphine gas generated from the solid material. In this study, a mathematical equation was formulated, based on previous studies in the literature, to describe the gas generation rate. This equation was incorporated into a computational model using ANSYS Fluent 19.1, a commercial software for computational fluid dynamics (CFD) analysis. The computational model developed here allows prediction of the phosphine concentration within a fumigated grain bulk. The PH3 sorption was included in the model. The effect of temperature on the sorption rate was investigated based on published data, and the rate change due to temperature was characterized. The gas generated by a single pellet was measured in laboratory experiments in a 0.208 m3 sealed barrel. The measurements confirmed the CFD results with an error of 0.3%, 0.9%, and 7.2% for three different configurations. The deviations seen between the experimental replicates increased the error and show the need for further investigation of the effects of temperature, grain age and history, leakage, and other factors. Keywords: CFD, Evolution rate, Phosphine, Sorption.

A new method to explore thermal and venting behavior of lithium-ion battery thermal runaway

Along with the popularization of the lithium-ion battery (LIB), much more attention is attracted to its problem of thermal runaway. This paper proposes a simple but novel method to investigate the gas generation throughout the process of thermal runaway. The novelty from the previous study lies in that the battery cells without the cap are used as the test samples. The naked battery offers a key to decouple the pressure caused by the vapor of electrolyte and that of the gases generated in the chemical reaction. This study makes up the knowledge gap of measuring internal pressure before the venting behavior and provides a more accurate method to describe the gas generation of thermal runaway. Three 100% state of charge LIBs with the cathode of LiNi0·8Co0·1Mn0·1O2 are used as tested samples to illustrate the application of this method. Two important results are withdrawn from the samples’ test: (I) the relationship between temperature increasing rate and gas generation rate is not linear until battery temperature approaches the uncontrollable temperature; (II) the partial pressure of gas generated due to the redox reactions bears the major responsibility for the safety valve opening.

(Invited) Internal Gas Pressure Measurement of Packaged Electric Double Layer Capacitors

One mode of electric double layer capacitor failure is package rupture, which usually leads to rapid deterioration of its electrical performance. This typically is caused by gas generated within a sealed capacitor with a subsequent pressure rise that eventually leads to the package bursting. The rate of gas generation, which ultimately can determine capacitor life, depends on materials purity, capacitor operating voltage, and the capacitor operating temperature. We measured the internal gas pressure and rate of gas pressure rise in spiral-wound, packaged electric double layer capacitors using an indirect and a direct approach. The indirect approach relied on physically measuring capacitor package deformation that had been caused by the internal gas pressure. This was then quantified by comparing the value with deformation caused by a known applied gas pressure. The direct approach relied on the use of an attached and calibrated solid-state pressure transducer. Internal gas pressure measurements using both approaches were made on 100-F-size electric double layer capacitors held at several temperatures with different applied voltages. Experimental details are reported with internal pressure measurements shown for 2000 hours of capacitor aging at 65 oC. Figure 1