Gas Generation Rate Research Articles

Experimental and modeling analysis of jet flow and fire dynamics of 18650-type lithium-ion battery

The lithium-ion battery (LIB) is widely used in modern society, while the fire accidents caused by battery thermal runaway (TR) also happen frequently. However, the gas generation, jet flow, and fire dynamics of LIB TR are still unclear. In this paper, a lumped model for the characteristics of the 18650-type LIB jet flow and fire dynamics is set up and validated by experiments. The gas generation rate is described by the Arrhenius equation, and the peak generation rate is 2.724 g s−1. The isentropic flow equations are used to simulate the gas venting process. The gas flow is choked when the safety valve opens, then returns to subsonic levels until the onset of TR. When the cell falls into TR, the peak speed of the gas flow at the orifice is 162.0 m s−1, and the corresponding peak mass flow rate is 2.6 g s−1. The trend and peak value of the simulated flame height agree with the experimental results. This feasible model describes the LIB fire dynamics, and the knowledge gap over the gas generation rate and jet flow speed during TR is filled. The reveal of the fire dynamics of LIB provides guidance for the design of safety precaution measures on LIB packs in electric vehicle and energy storage system. Furthermore, the cause of error is analyzed, and some future modifications on the model of LIB fire are proposed.

ДОСЛІДЖЕННЯ ЗМІНИ МАСИ РОСЛИННОЇ БІОМАСИ В ПРОЦЕСІЇ ЇЇ ГАЗИФІКАЦІЇ

The article suggests that the rate of plant biomass gas generation is proportional to the amount of plant biomass, which can still be gasified. To analyse the change in fuel mass during the operation of the gasifier for a certain period of time, three models can be used with the following assumptions: the change in fuel mass is inversely proportional to the fuel mass and time, the change in fuel mass is inversely proportional to the fuel mass, the change in fuel mass is inversely proportional to time. The coefficients of the fuel gasification rate are experimentally found.

Enhancement of landfill gas generation from aged waste by a combination of moisture adjustment and application of biochar and neutral red additives: A field-scale study

Many landfills suffer from a sharp drop in landfill gas generation after an initial period of gas generation. A field-scale study was conducted to investigate the effects of moisture adjustment using stormwater and compost leachate, and additives (neutral red and biochar) on landfill gas quality and quantity. Five different gas wells and five vertical leachate-infiltration wells were drilled to implement moisture addition treatments. During 20 weeks of field study, addition of compost leachate resulted in a significant landfill settlement (24 cm). Mixture of leachate and biochar increased the rate of landfill gas generation at the start of the experiment and increased the total gas flow rate by more than 2.8 times. Neutral red diluted with compost leachate decreased the rate of landfill gas generation compared to pure leachate, but it resulted in more stable landfill gas generation at the end of the experiment. Application of neutral red and biochar additives maximised the methane content to 60.2% and 59.3% of the total landfill gas volume, respectively. However, O2 reached zero for all the liquid-added wells and then increased at the end of the experiment. Temperature and CO content increased for all the liquid-added experiments due to the higher degradation rate compared to the control experiment. Moisture adjustment significantly increased the gas wells’ radius of influence. The maximum radius of influence was 36 m for neutral red application. Biochar mixed with leachate showed the least impact on the radius of influence because of the insolubility of biochar in leachate.

Thermogravimetric study of the kinetics and characteristics of the pyrolysis of pulverized coal

Simultaneous thermogravimetric-mass spectrometric (TG-MS) analyzer was used to investigate the pyrolysis characteristics and gas generation rule of three coal samples. Results indicated that Jing-mei (JM), Xinjiang-mei (XM), and Yan-mei (YM) coals had similar pyrolysis characteristics and gas generation law. Their pyrolysis process could be roughly divided into three stages. YM had the highest weight loss and gas generation rates among all the samples. CO and CO2 components in the escaping gas continued to increase when the temperature reached 800 °C. Coats–Redfern method was employed to calculate the activation energy of three kinds of coal at four temperature stages with different mode functions. The activation energy of the four stages of JM pyrolysis was 33.3 kJ mol−1, 2.66kJ mol−1, 88.51kJ mol−1, and 33.26 kJ mol−1. The result of XM pyrolysis was 51.29 kJ mol−1, 6.84 kJ mol−1, 47.38 kJ mol−1, and 15.65 kJ mol−1. Calculations of XM pyrolysis were 51.35 kJ mol−1, 5.11 kJ mol−1, and 117.49 kJ mol−1, 31.15 kJ mol−1 respectively.

Study on the Kinetics and Pyrolysis Behavior of Waste Containing Urea-Formaldehyde Resins

In this work, we studied the kinetics and behavior of wood panel wastes containing ureaformaldehyde resins. For this purpose, we used a TG-FTIR coupled system to analyze the gaseous products of the pyrolysis. With the results, we obtained the models that provide theoretical evidence and data support for the studied reactions. According to our findings, the pyrolysis of the ureaformaldehyde components displayed two stages, and the second stage presented a higher intensity. At a temperature of 900 °C, the gas generation rate for hard UF (UF1) was 32.6% higher than that for soft UF (UF2). When temperature increased from 600 °C to 900 °C, the increase of the gas generation rate was relatively small. In addition, the reaction order was obtained using the CoatsRedfern method, which provided a value for the reaction order of 1.4. The activation energy of UF1 was slightly higher than that of UF2. The FTIR analysis indicated that the main gaseous products of the pyrolysis of the urea-formaldehyde resin samples were CO2, H2O, and other compounds containing the C–H and the N–H bond as well as carbonyl groups. In addition, it was determined that Nitrogen was mainly present in the form of hydronitrogen compounds but not as nitrogen oxides. These last may represent a higher degree of pollution.

Investigation of gas hydrate production with salinity via depressurization and thermal stimulation methods

Natural gas resources trapped in hydrate reserves worldwide are a new substitute for conventional energy. To safely and efficiently extract natural gas from hydrates, fields test and laboratory investigations were systematically conducted. Salinity is a significant factor impacting the exploitation of the marine hydrates. In this study, a two-dimensional cylindrical model was developed to determine the influences of salinity on gas recovery induced by depressurization and thermal stimulation. The results indicated that, with the same exploitation method, higher salinity accelerated the pressure-drop propagation rate and temperature increment spread, thereby promoting the hydrate dissociation rate and shortening the gas production process. Furthermore, thermal stimulation improved the average gas generation rate by almost five times that with depressurization at the same salinity.

Transport model for shale gas well leakage through the surrounding fractured zones of a longwall mine

The environmental risks associated with casing deformation in unconventional (shale) gas wells positioned in abutment pillars of longwall mines is a concern to many in the mining and gas well industry. With the recent interest in shale exploration and the proximity to longwall mining in Southwestern Pennsylvania, the risk to mine workers could be catastrophic as fractures in surrounding strata create pathways for transport of leaked gases. Hence, this research by the National Institute for Occupational Safety and Health (NIOSH) presents an analytical model of the gas transport through fractures in a low permeable stratum. The derived equations are used to conduct parametric studies of specific transport conditions to understand the influence of stratum geology, fracture lengths, and the leaked gas properties on subsurface transport. The results indicated that the prediction that the subsurface gas flux decreases with an increase in fracture length is specifically for a non-gassy stratum. The sub-transport trend could be significantly impacted by the stratum gas generation rate within specific fracture lengths, which emphasized the importance of the stratum geology. These findings provide new insights for improved understanding of subsurface gas transport to ensure mine safety.

Quantification of landfill gas generation and energy recovery estimation from the municipal solid waste landfill sites of Delhi, India

ABSTRACT In this study, estimation of landfill gas (LFG) emission from three existing landfill sites of Delhi such as Ghazipur, Bhalswa, and Okhla was carried out using three LFG generation models, namely, IPCC Default model, First order decay model, and LandGEM. The total estimated methane emissions from all the three landfills was observed till 2030 as 2443.66, 1114.61, and 1642.51 Gg using Default, First order decay, and LandGEM respectively. The average rates of emission from these landfills were found as 20.35, 24.10, and 17.51 Gg/year by IPCC Default method; 18.69, 13.67, 7.59 Gg/year by First order decay model and 9.91, 9.81, 8.40 Gg/year by LandGEM for Ghazipur, Bhalswa, and Okhla sites respectively. The results showed that the Default method overestimated the methane emission due to variable input parameters such as fraction of landfilled waste and methane proportion in LFG. First order decay model provided best possible emission rates with comparatively lesser uncertainty and could relate actual waste deposition practices. LandGEM also provided moderate results of methane emission with significant uncertainties caused by variation in municipal solid waste deposition data, gas generation rate and methane generating potential of waste. Furthermore, Yedla method was employed to quantify energy recovery potential using landfill gas recovery system, which showed 5783.62 TJ energy can be recovered from landfilled municipal solid waste with an efficient recovery system.

Highly Selective Photoreduction of CO2 with Suppressing H2 Evolution by Plasmonic Au/CdSe-Cu2 O Hierarchical Nanostructures under Visible Light.

Here, the photocatalytic CO2 reduction reaction (CO2 RR) with the selectivity of carbon products up to 100% is realized by completely suppressing the H2 evolution reaction under visible light (λ > 420 nm) irradiation. To target this, plasmonic Au/CdSe dumbbell nanorods enhance light harvesting and produce a plasmon-enhanced charge-rich environment; peripheral Cu2 O provides rich active sites for CO2 reduction and suppresses the hydrogen generation to improve the selectivity of carbon products. The middle CdSe serves as a bridge to transfer the photocharges. Based on synthesizing these Au/CdSe-Cu2 O hierarchical nanostructures (HNSs), efficient photoinduced electron/hole (e- /h+ ) separation and 100% of CO selectivity can be realized. Also, the 2e- /2H+ products of CO can be further enhanced and hydrogenated to effectively complete 8e- /8H+ reduction of CO2 to methane (CH4 ), where a sufficient CO concentration and the proton provided by H2 O reduction are indispensable. Under the optimum condition, the Au/CdSe-Cu2 O HNSs display high photocatalytic activity and stability, where the stable gas generation rates are 254 and 123 µmol g-1 h-1 for CO and CH4 over a 60 h period.

Great Depths in the Crust - Peculiarities of Hydrocarbon Generation

The purpose of research is to identify the features of hydrocarbon generation at great depths of the Earth. It is shown that all the conditions necessary for generation of oil and gas are kept at great depths in the crust in the zones of high pressures and temperatures. However, generation of hydrocarbons in such settings significantly differs from the processes of oil and gas formation at shallow depths. A complex system of mutual thermobaric factors and distribution of the oil and gas potential at great depths was revealed: the start of generation and the phase distribution of hydrocarbons in the section are largely affected by settling of abnormally high pore pressure, as well as by paleotemperatures that could differ considerably from the present-day ones depending on the age of deposits. It is shown that different thicknesses of catagenetic zones are related to the kinetic rate of oil and gas generation, which depends on the type of kerogen, the gradient of temperature change, pressure, lithology, and hydrogeological conditions of the host rocks, the sedimentation rate, and other factors.

Numerical simulation and experiment verification of the static boil-off rate and temperature field for a new independent type B liquefied natural gas ship mock up tank

In this paper, a new independent type B liquefied natural gas (LNG) ship mock up tank with the net capacity of 40 m3 and an insulation thickness of 400 mm was taken as the research target. After reasonable simplification, two-phase flow and phase change heat transfer of cryogenic fluid in the mock up tank was simulated by using unsteady three-dimensional CFD method. Volume of fluid (VOF) model was selected to track the vapour-liquid interface, Lee model was used as the phase change model, and the influence of the static pressure on the phase change model was considered. The temperature distribution and the static boil-off gas (BOG) generation rate of the mock up tank was calculated, and working conditions of the simulated tank under different liquid levels and partial insulation system damage were discussed. The pressurization characteristics of the mock up tank under closed conditions was also studied. Comparing the simulation with the experimental results, it showed that this model could effectively simulate the evaporation process of cryogenic liquids in the mock up tank under stationary conditions, which provides an important reference for the design and improvement of the new independent type B LNG ship.

Study on the solid propellant burning rate enhanced by plasma in the closed bomb

A closed bomb experimental system is employed to discuss the ignition and combustion characteristics of the solid propellant with the capillary plasma generator (CPG). 4/7 high-nitrogen solid propellant, 5/7 high-graphite solid propellant and 5/7 low temperature sensitivity coated propellant are ignited in the closed bomb. Compared with the experimental results with the conventional ignition, the ignition delay time with the CPG is reduced and the burning process of the propellant is enhanced. The pressure changing rate is used to analyse the enhanced gas generation rate (EGGR) of the propellant with the plasma. Compared with the pressure changing rate with different igniters, the enhanced gas generation rate during electrical discharge (EGGRDED) is proved. When 4/7 high-nitrogen solid propellant and 5/7 low temperature sensitivity coated propellant are ignited in the closed bomb, the enhanced gas generation rate post electrical discharge (EGGRPED) appears. The EGGRPED is mainly influenced by the composition of the propellant. The influence of the electrical parameters of the CPG and the distance between the CPG and the solid propellant is studied by the closed bomb experiments. The ignition delay time and the burning time of the propellant reduce with the increasing of the electric power or the decreasing of the distance between the CPG and the propellant. Depending on the pressure changing rate in the closed bomb experiments, the EGGRDED increases with the increasing of the electric power or the decreasing of the distance between the CPG and the propellant, while the EGGRPED is not influenced by the electric power or the distance between the CPG and the propellant.

Evolution of methane and hydrogen from ethanol wastewater with maximization of energy yield by three-stage anaerobic sequencing batch reactor system

A new anaerobic sequencing batch reactor (ASBR) unit with three stage concept was proposed and tested for spontaneous generation of hydrogen (H2) and methane (CH4) from ethanol wastewater with maximum energy yield. The system was controlled at 37 °C, a fixed pH of 5.5 in the first bioreactor and a recycle ratio of unity from the third bioreactor to the first bioreactor to lower the amount of sodium hydroxide for pH regulation in the first bioreactor and to increase total alkalinity and process stability. Under the optimum organic loading rate of 15 kg COD/m3d (based on the total liquid holding volume), it exhibited the highest yields and specific generation rates of both gases, resulting in the uppermost overall energy yield which was much higher than those of all other anaerobic systems. The lactic acid was found to be about 4–8 times more toxic than acetic acid to methanogens. The higher the solution pH in any anaerobic system, the greater the reduction of micronutrients.

Development of (γ-Al2O3-Zeolite Y)/α-Al2O3-HPCM Catalyst based on Highly Porous α-Al2O3-HPCM Support for Decreasing Oil Viscosity

Highly porous cellular material (α-Al2O3-HPCM) support was synthesized by the template method. Highly porous support was used for the synthesis of the catalyst. A thin secondary layer with 25–30 μ thick γ-Al2O3 and zeolite Y was applied on the α-Al2O3-HPCM surface ((γ-Al2O3 (85%)-zeolite Y (15%))/α-Al2O3-HPCM). The catalyst based on the highly porous support was tested in a process of decreasing oil viscosity. The catalyst in the form of cylindrical granules and a thermal process of decreasing oil viscosity without the catalyst were used as the basis for comparison. α-Al2O3-HPCM in the catalyst provides low-quantity pores (d < 10 nm) and a quantity of general acid centers compared with the granular catalyst. On the other hand, it shows a more significant oil viscosity decrease (from 2500 to 41 cPs) and a low rate of gas generation (137 mL/h) for the catalyst with highly porous support. A high oil fraction was observed in the presence of the (γ-Al2O3-zeolite Y)/α-Al2O3-HPCM compared to the granular catalyst. The presence of large transport cells (pores) 1500–2000 μ for the catalyst based on highly porous support allowed a work period four times longer than that of experiment only with temperature without catalysts.

Solid-State NaBH4 Composites as Hydrogen Generation Material: Effect of Thermal Treatment of a Catalyst Precursor on the Hydrogen Generation Rate

Solid-state composites based on sodium borohydride (NaBH4) were studied for applications as hydrogen generation materials. Hydrates of cobalt and nickel chlorides subjected to a thermal treatment were added to the composites as catalyst precursors. Using thermal analysis and FTIR spectroscopy, it was shown that the amount of water removed increases with the increasing temperature. Herewith, the water molecules that remained in the samples were strongly bound to the metal and isolated from each other. According to the ultraviolet–visible (UV-vis) spectroscopy data, with the increasing temperature of the thermal pretreatment there took place a substitution of a portion of water molecules by chloride ions in the nearest environment of the metal. It appeared that it was the resulting weakening of the electrostatic field on metal that was mainly responsible for the formation of a more finely dispersed catalytic phase of amorphous cobalt boride in the reaction medium under the action of sodium borohydride. The smaller particles of the active components led to a faster rate of gas generation when water was added to the solid-state NaBH4 composites. This trend remained for both the cobalt and the nickel catalytic systems even when the activity was calculated per gram of the metal. Thus, for the preparation of solid-state NaBH4 composites, hydrates of cobalt and nickel chlorides with a low content of water should be used.

Numerical analysis of microwave stimulation for enhancing energy recovery from depressurized methane hydrate sediments

In addressing the global demand for clean and renewable energy, natural gas hydrate stands out as one of the most suitable alternative energy resources with great potential and has aroused intense research interest. In this study, a two-dimensional axisymmetric model was developed and validated to investigate the effect of microwave stimulation on energy recovery from depressurized methane hydrate sediments. Simulation results indicate that the microwave stimulation can provide timely and sufficient energy to promote the rapid and continuous hydrate dissociation. Discrepant energy absorption and conversion leads to a rapid hydrate dissociation rate in the upper region of the sediments. The increasing microwave radiation density accelerates the average gas production rate but weakens the energy efficiency ratio. For evaluating the effects of selected factors including initial conditions and sediment's physical properties on hydrate dissociation, an optimal value of microwave radiation density was determined by using the Pareto optimality criterion. Compared results of the energy efficiency reveal that the effect of microwave heating on the hydrate dissociation is advantageous in the sediments with the condition of high initial water and hydrate saturation, low specific heat capacity, high thermal conductivity, and low absolute permeability. Moreover, the intensity of thermal stimulation and the range of depressurization should be adjusted to be suitable for the reservoir conditions through considering the balance between the gas generation rate and the gas production rate. Although there are still many uncertainties in the hydrate dissociation behaviors, the findings of this study can provide some insights for evaluating and optimizing the methodology for gas recovery from gas hydrate reservoirs.

Evaluation of Processing Parameters for Densification of Composite Propellants

The present work investigated the effects of varying two parameters of a pilot-scale composite propellant plant: the mechanical vibration and the vacuum level. The application of mechanical vibration to the casted mold after the end of mixing has improved the propellant density. On the other hand, the change of the vacuum level had no significant effect. Static firing tests showed an increase in the gas generation rate with the increase of the number of voids.

A novel scanning electrochemical microscopy strategy for the investigation of anomalous hydrogen evolution from AZ63 magnesium alloy

The evolution of hydrogen gas from corroding magnesium arises not exclusively from the cathodic half-cell reaction due to the consumption of the electrons released by the dissolving metal, but anodized magnesium generates significant amounts of H2 gas as well. In addition, the increase of the anodic overpotential enhances the rate of hydrogen gas generation. Therefore, spatially-resolved detection of the actual sites for hydrogen evolution related to anodically-activated sites is attempted using scanning electrochemical microscopy (SECM). This work describes a new experimental procedure for SECM based on a three-step (off-on-off) anodization operation sequence that was designed to obtain new insights into the behavior of magnesium and magnesium alloys when they are subjected to anodic polarization. Results obtained with scanning electrochemical microscopy (SECM) and scanning vibrating electrode technique (SVET) experiments presented here demonstrate the catalytic properties of the magnesium-oxide film for the hydrogen-evolution reaction.

Agar-based aqueous electrolytes for electrochemical capacitors with reduced self-discharge

This paper reports on the electrochemical performance of symmetric carbon/carbon electrochemical capacitors operating in aqueous electrolyte (0.5 mol L−1 K2SO4 solution) and modified with various amounts of agar (up to 5 wt%). It has been found that a change in electrolyte form (from liquid to gel-like) increases the hydrogen storage efficiency on the negative electrode (confirmed by operando Raman spectroscopy), improves the cycle life at elevated voltages and reduces the self-discharge. Furthermore, it has been found that the gas generation rate during capacitor operation is remarkably diminished (by ca. 4 times), and thus, the detrimental impact of increased internal pressure is noticeably reduced.

Design and development of a small-scale biomass downdraft gasifier

This study focused on the design and testing of a downdraft gasifier. The gasifier design was based on a combination of the Imbert and stratified models with some modifications. Sizing of the gasifier was done using empirical relations and some experimental data relating to specific gas generation rate, biomass flow rate, throat diameter and reduction zone diameter etc. The thermal capacity of the gasifier was set at 5 kW. A cyclone separator, an air-cooling unit and a filter unit (containing wood shavings) were coupled to the gasifier’s reactor to purify the produced syngas. The gasifier system was tested in a forced draught mode using air as the gasifying medium. The feedstock conversion rate of the gasifier was 1.25kg/hr for wood chunks (10-70mm) and 2.1kg/hr for wood shavings (2-5mm). The syngas produced for both types of wood residues burnt with stable blue flames, indicating minimal tar percentage in the syngas. This signifies that the produced syngas can be safely utilized not only for cooking but also in internal combustion engines to generate electricity. http://dx.doi.org/10.4314/njt.v38i4.15