Maximum Combustion Temperature Research Articles

Preparation and study on combustion performance of AP@ZrH2 core-shell composite energetic materials with high volume energy density

The development of composite energetic material with high volume energy density could increase the range and loading capacity of solid propellants. In this study, a series of core-shell composite energetic materials AP@ZrH2 were fabricated by decorating ZrH2 on the ammonium perchlorate (AP) through a solvent-nonsolvent method. A substantial increase in combustion heat (13373.67 J/g) and maximum burning temperature (1415.33 °C) are detected in composites in contrast to physically mixed sample (10660.46 J/g and 837.22 °C). This is due to the enhancement of the decomposition performance of AP, which provides sufficient oxidation gas atmosphere for combustion of ZrH2. In addition, the delay time (524 ms) and burning time (114 ms) of composites are significantly decreased compared to the physical mixed sample (2145 and 256 ms). The remarkable combustion performance and burning rate could be attributed to reduced mass and heat transfer distances. Finally, the improvement of combustion efficiency in the composites makes the size of the residual particles smaller.

Numerical simulation of the effect of multiple factors on the ignition process of a solid rocket motor

AbstractWith the continuous development of manned space technology, higher requirements have been proposed for solid rocket motors. The ignition process of solid rocket motors affects the reliability, stability and safety of their operation. The ignition powder, cover opening pressure and grain length‐diameter ratio are the main factors affecting the ignition process. Therefore, the influence of different factors on the ignition process of solid rocket motors is studied with numerical simulations. Based on the finite volume method, the ignition process of a solid rocket motor is modelled and experimentally verified. Then, the pressure and temperature distribution characteristics during the ignition delay, flame propagation and gas filling times are analysed. Finally, the effects of different ignition powders, cover opening pressures and length‐diameter ratios on the ignition process are compared and analysed. The results show that the model has high prediction accuracy. When the ignition powder is 6 g, the maximum combustion temperature of solid rocket motor increases from 2590 K to 2620 K between 0.1 ms and 0.44 ms. Between 0.44 ms and 3.18 ms, intermittent flame propagation and pressure oscillations occur. In the gas filling time, the flow field gradually stabilizes. Increasing the ignition powder mass is beneficial to the ignition process, but the disadvantages of pressure oscillations should be considered. Increasing the cover opening pressure enhances the ignition process, while increasing the length‐diameter ratio increases the ignition pressure building time. The study results provide technical support for the structural design of solid rocket motors.

Ignition and combustion characteristics of micro/nano-Al and Al@Ni alloy powders at elevated pressures

Nanosizing and alloying of aluminum (Al) promisingly improve ignition and combustion performance of Al-based propellants. To aim this, lased-induced ignition and combustion characteristics of micro/nano-Al and aluminum@nickel (Al@Ni) alloy powders at elevated pressures (0.1–3.0 MPa) were investigated and the pressure effect on these characteristics was correspondingly evaluated. Comparative results demonstrate that nanosizing and alloying significantly shorten ignition delay and total burn time at elevated pressures, with ignition delay reduction of 98.04% and 52.28% at 1.0 MPa for nano-Al and Al@Ni alloy compared to micro-Al counterpart. Nanosizing and alloying can decrease crucial pressure values (‘mid-pressure extinction domains’) influencing ignition delay, and promote the transfer from the surface to gaseous combustion mode. Maximum combustion temperatures of nano-Al are higher than micro-Al and Al@Ni alloy. During combustion, the combustion of Al@Ni alloy is further intensified due to the microexplosion, while possibly inhibited at higher pressures.

Effect of AP coating or blending on the ignition and combustion of Al particles under a high-pressure water vapour–Ar environment

Overcoming the difficulty of ignition and combustion of aluminium in water vapour is the key to being applied in underwater propellant applications. The effect of coating or blending 20 mass% ammonium perchlorate (namely, AP@Al or AP–Al samples) on the ignition and combustion of Al particles in a 1.0 MPa water vapour–Ar environment was investigated using a constant temperature pressurized combustion chamber and a CO2 laser. The results show that the combustion of Al particles in a water vapour–Ar environment is a non-homogeneous reaction and that agglomeration processes of Al droplets are observed. The ignition and combustion properties of the AP@Al and AP–Al samples under water vapour were greatly improved due to the decomposition of AP for heat/oxygen (particularly, O2 provided a new pathway for AlO(g) generation) supply and the effect of dispersed particles. The maximum pressure change and combustion temperature (Tmax) were increased significantly for the AP@Al and AP–Al samples combustion, while their ignition delay time (ti) and combustion time (tc) decreased remarkably. In addition, the coating form is more effective in the combustion-promoting effect of AP than the blending form. Interestingly, the increase in water vapour concentration is not conducive to the ignition and combustion of samples in this work. It is probably because the reaction system is lean-fuel where the excess water vapour absorbs some of the heat and prevents effective collisions among the radicals. In addition, the chemical equilibrium largely influences the combustion temperature, resulting in a conspicuous effect of changes in water vapour concentration on the Tmax values. The reaction interface largely influences the combustion reaction rate of Al, so changes in particle size have a significant effect on the ti and tc values.

Charcoal analysis for temperature reconstruction with infrared spectroscopy

The duration and maximum combustion temperature of vegetation fires are important fire properties with implications for ecology, hydrology, hazard potential, and many other processes. Directly measuring maximum combustion temperature during vegetation fires is difficult. However, chemical transformations associated with temperature are reflected in the chemical properties of charcoals (a by-product of fire). Therefore, charcoal could be used indirectly to determine the maximum combustion temperature of vegetation fires with application to palaeoecological charcoal records. To evaluate the reliability of charcoal chemistry as an indicator of maximum combustion temperature, we studied the chemical properties of charcoal formed through two laboratory methods at measured temperatures. Using a muffle furnace, we generated charcoal from the woody material of ten different tree and shrub species at seven distinct peak temperatures (from 200°C to 800°C in 100°C increments). Additionally, we simulated more natural combustion conditions by burning woody material and leaves of four tree species in a combustion facility instrumented with thermocouples, including thermocouples inside and outside of tree branches. Charcoal samples generated in these controlled settings were analyzed using Fourier Transform Infrared (FTIR) spectroscopy to characterize their chemical properties. The Modern Analogue Technique (MAT) was employed on FTIR spectra of muffle furnace charcoal to assess the accuracy of inferring maximum pyrolysis temperature. The MAT model temperature matching accuracy improved from 46% for all analogues to 81% when including ±100°C. Furthermore, we used MAT to compare charcoal created in the combustion facility with muffle furnace charcoal. Our findings indicate that the spectra of charcoals generated in a combustion facility can be accurately matched with muffle furnace-created charcoals of similar temperatures using MAT, and the accuracy improved when comparing the maximum pyrolysis temperature from muffle furnace charcoal with the maximum inner temperature of the combustion facility charcoal. This suggests that charcoal produced in a muffle furnace may be representative of the inner maximum temperatures for vegetation fire-produced charcoals.

A comprehensive fluid–solid coupling dynamic simulation for spatiotemporal distribution of regression rate in hybrid rocket motors

The spatiotemporal distribution characteristics of the regression rate are crucial aspects of the research on Hybrid Rocket Motor (HRM). This study presents a pioneering effort in achieving a comprehensive numerical simulation of fluid dynamics and heat transfer in both the fluid and solid regions throughout the entire operation of an HRM. To accomplish this, a dynamic grid technique that incorporates fluid–solid coupling is utilized. To validate the precision of the numerical simulations, a firing test is conducted, with embedded thermocouple probes being used to measure the inner temperature of the fuel grain. The temperature variations in the solid fuel obtained from both experiment and simulations show good agreement. The maximum combustion temperature and average thrust obtained from the simulations are found to deviate from the experimental results by only 3.3% and 2.4%, respectively. Thus, it can be demonstrated that transient numerical simulations accurately capture the fluid–solid coupling characteristics and transient regression rate. The dynamic simulation results of inner flow field and solid region throughout the entire working stage reveal that the presence of vortices enhances the blending of combustion gases and improves the regression rate at both the front and rear ends of the fuel grain. In addition, oscillations of the regression rate obtained in the simulation can also be well corresponded with the corrugated surface observed in the experiment. Furthermore, the zero-dimension regression rate formula and the formula describing the axial location dependence of the regression rate are fitted from the simulation results, with the corresponding coefficients of determination (R2) of 0.9765 and 0.9298, respectively. This research serves as a reference for predicting the performance of HRM with gas oxygen and polyethylene, and presents a credible way for investigating the spatiotemporal distribution of the regression rate.

Study on Temperature Field in Common-rail Diesel Engine Combustion Chamber at Different Altitudes

The plateau covers 26% of China’s land area, the higher altitude, the lower atmospheric pressure, the smaller air density, the lower average temperature. Therefore diesel engine power decreases significantly, fuel consumption increases, starting performance deteriorates, and soot emissions increase. In this paper, virtual simulation and simulation test methods are used to study the temperature field change in the combustion chamber of CA6DL2-35E3R common-rail diesel engine at different altitudes and atmospheric pressures. The results show that the altitude has a great influence on the temperature field in the combustion chamber. The maximum combustion temperature gradually increases with increase of altitude, post-combustion is serious and the exhaust temperature increases.

Complex TiC-Ni-based composites joined to steel support by thermal explosion under load: synthesis, microstructure and tribological behavior

ABSTRACT The combustion in thermal explosion mode of reactive mixtures of Ti–Ni–graphite(carbides, borides, oxides), under load, was used to produce complex composite materials, densified and joined to a C55 carbon steel support. The ignition of the exothermic reaction, carried out thanks to the rapid high-frequency heating of a green compact up to 1573 K, was followed by an isothermal holding at 1373 K for 360 s. This procedure ensured a perfect mechanical assembly between the composite material and the steel substrate. SEM analysis and concentration profiles carried out at the interface testified to the interdiffusion of iron and titanium atoms between the two materials. The maximum combustion temperature (Tmax.) exceeding 2200 K induced the appearance of a liquid phase that assisted densification and joining, and in which a part of the additions was dissolved before cooling. The starting chemical composition of reactive mixtures largely determined the microstructure, hardness and tribological behavior of the composites after the process. Thereby, the maximum hardness (1235 HV0.15) and the lowest wear rate (1.824 × 10−6 mm3.N−1.m−1) were obtained in the sample containing TiC, Al2O3 and TiB2 hard phases. The manufactured samples exhibit no deterioration of the composite by spalling, regardless of the starting composition.

Investigation of Lips-Guided-Flow Combustion Chamber and Miller Cycle to Improve the Thermal Efficiency of a Highly Intensified Diesel Engine

An investigation into the lips-guided-flow combustion chamber (LGFC) and Miller cycle was conducted on a highly intensified diesel engine under rated power conditions to improve thermal efficiency. The radius and depth of the chamber bowl and lips were optimized to intensify the guided flow and fuel/air mixing. The experimental and simulated results show that the LGFC had a higher fuel/air mixture quality and quicker combustion rate, leading to a higher indicated power and higher thermal efficiency. A late intake valve closing (LIVC) Miller cycle with a higher expansion ratio of 11 and a lower compression ratio of 8.2 was used to control the energy distribution of the thermodynamic cycle and reduce the mechanical and thermal loads. The results show that the maximum combustion temperature was decreased by about 45 K and the thermal efficiency was improved by 2.1%. The research results are useful to guide the improvement in thermal efficiency through combustion chamber design and Miller cycle application for highly intensified diesel engines.

Analysis of the Combustion Characteristics and Performance of Lemon and Orange Peel Biomass Composite Fuel Diesel

Background: Orange and lemon peels are a type of biomass waste, as the demand for the production of these citrus species and their use in various food industries leads to their significant accumulation in the form of waste. This study was designed so that this waste is recycled to be added to diesel fuel and to verify its suitability as a composite fuel. Method: This study aimed to investigate the thermal combustion behavior of lemon peel powder, LPP, and orange peel powder, OPP biomass composite fuel diesel. The citrus peel was dried and ground to a powder material of 450-750 µm in size, then mixed in different percentages with diesel fuel. Different parameters were controlled to improve the composite fuel characteristic. The pyrolysis experiments of the diesel/citrus composite fuel were conducted in an internal combustion engine. Results: The results showed that the citrus/diesel composite fuel sustains its combustion properties at 30% of the added citrus peel powder, with a reduction of harmful emissions. The results showed that calorific values of diesel containing 30% LPP or 15% LPP + 15% OPP were very close to that of pure diesel. The maximum calorific values were obtained at α = 0.85, 0.80, and 0.90 for 30% OPP, 30% LPP, and 15% OPP + 15% LPP composite fuels respectively. It was found that the addition of homogenization material and combustion activator to the composite fuel raised the maximum temperature of combustion by 230 °C, 200 °C, and 330 °C for 30% OPP, 30% LPP, and 15% OPP + 15% LPP respectively. The TGA analysis of lemon and orange showed that the weight loss has proceeded in three stages, the first at 150°C – 200 °C due to water evaporation, the second at 400 °C due to hydrolysis of cellulose and hemicellulose, and the third at 600 °C due to combustion of fuel material forming carbon residue. Conclusion: The composite fuel without additives showed the highest combustion temperature at about 600 °C, while the maximum combustion temperature for the composite fuel with additives was achieved at 800 °C at a shorter time.

Hybrid porous media gasification of urban solid waste pre-treated by hydrothermal carbonization.

Global population growth and rising consumption levels have significantly increased resource use and energy demand, leading to higher greenhouse gas concentrations and increased waste output. As a result, alternative waste treatment methods for sustainable municipal solid waste (MSW) management are crucial. This research evaluates the efficiency of integrating hydrothermal carbonization (HTC) and gasification for an optimized MSW biomass blend. HTC was conducted for one hour at 220°C in a 5 L reactor, followed by gasification in a hybrid porous medium gasifier. The study investigated the effects of different filtration speeds on combustion temperature and hydrogen concentrations. The results showed that a filtration speed of 35 cm/s resulted in a maximum combustion temperature of 1035.7°C. The temperature remained consistent across filter speeds, while higher velocities yielded higher hydrogen concentrations. Additionally, increasing the filtration velocity raised temperatures in the hybrid bed while increasing the volumetric fraction of biomass decreased maximum temperatures. This research contributes to the understanding of merging HTC and gasification for MSW biomass blend treatment, aiming to reduce environmental impacts and costs while promoting renewable resources for long-term energy production.

Thermal coupling of methanol steam reforming and hydrogen combustion to produce fuel cell hydrogen: A comparative theoretical study between membrane and hydrogen-recycled shell-and-tube reactors

Methanol steam reforming (MSR) is one the most interesting routes for production of fuel cell grade hydrogen. As this reaction is endothermic, its energy supply is one of the most important problems. In this line, recycling and burning the unconverted hydrogen exits from the exhaust of the fuel cells on the shell side of a shell-and-tube reactor (HR) has been suggested in the literature as one the energy supply solutions. In this work, the performance of a membrane-assisted shell-and-tube reactor (MR-HCO), in which part of the hydrogen produced by the MSR is continuously transferred to the shell side through the membrane layer and burned to supply energy, is investigated and compared with HR reactor. To this end, a set of heterogeneous 1D and 2D models are employed to model the shell and the tube sides of the reactors, respectively. The influence of air and steam-methanol feed hourly space velocities on maximum combustion temperature and methanol conversion are examined. It is observed that the MR-HCO has higher methanol conversion, hydrogen flow, and thermal efficiency, while lower CO concentration compared with the HR reactor. Furthermore, the MR-HCO showed a good potential to control the shell temperature rise and prevent hot spots.

Effect of AlH3 on the energy performance and combustion agglomeration characteristics of solid propellants

Increasing the performance of an energetic material can be achieved by changing its composition or using additives, such as metal powders. Aluminum hydride (AlH3) exhibits attractive properties, such as high hydrogen/energy storage, relatively good stability, and low dehydrogenation temperature. AlH3 has excellent prospects for use as a component in solid propellants for increasing the specific impulse of rocket engines and effectively reducing the erosion of engine nozzles. In this work, the effect of AlH3 on the energy performance, ignition characteristics, and combustion characteristics of solid propellants, as well as the agglomeration characteristics of metal particles was investigated. It was found that with increasing AlH3 content, the theoretical mass heat of combustion and the theoretical volumetric heat of combustion of the propellants increased, and the combustion efficiency also gradually improved. When the content of AlH3 in the propellant increased from 0.00% to 17.00%, the temperature of the propellant combustion chamber was reduced from 3314.59 to 2957.49 K and the theoretical specific impulse increased from 2584.2 to 2641.7 N‧s/kg. The average molecular mass of the gas was reduced from 25.54 to 21.54 due to the large amount of hydrogen gas released by the combustion of AlH3. The maximum combustion temperature decreased and the burning rate increased with the gradual replacement of aluminum (Al) in the propellant with AlH3. The maximum combustion temperatures of the pure Al propellant and the pure AlH3 propellant were 2510.5 and 2232.5 K, respectively. The linear burning rates were 0.29 and 0.46 cm/s at 1.0 MPa, respectively. The agglomeration process of AlH3 included three main stages, namely accumulation, aggregation, and agglomeration. With the increase in the AlH3 content, the number of agglomerated particles in the propellant gas-phase flame region decreased continuously.

Effects of fuel-hydrogen levels on combustion, operability, and emission parameters of CH4/H2/O2/CO2 stratified flames in a dual-swirl gas turbine burner

Towards the development of emission-free hydrogen gas turbines with wider operability limits, the combined effects of lean premixed combustion, dual combustion (combustion staging), hydrogen enrichment, and oxy-fuel combustion on the combustion and emission characteristics of CH4/H2/O2/CO2 flames are investigated in a dual annular counter-rotating swirl burner. The central stream is of a higher equivalence ratio (∅) of 0.9 for stable flame ignition, whereas the annular stream is of a lower ∅ of 0.65 to maintain the burner’s environmental performance. The stratified flame reactions are modelled using the partially premixed combustion model, which has been validated using the available experimental data. The inner recirculation zone becomes smaller as the hydrogen fraction (HF) becomes higher until it vanishes and there exists only an outer recirculation zone when the secondary hydrogen fraction approaches 100%. For 100% HF in both primary and secondary flow, the maximum combustion temperature within the combustor was observed to be as high as 2350 K. Increasing HF makes the flame more compact and anchored to the burner centre body with faster kinetics, less ignition delay time, and, accordingly, with increased potential for flashback. The product formation rate was found to increase in the inner shear layer at higher HF, implying a higher flame intensity and a more compact flame. The hydrogen fraction of the primary stream (maintained at higher equivalence ratio) is observed to be dominant in regulating CO mole fractions. Stable well-anchored flames are obtained over the considered fuel mixtures, indicating the role of stratified combustion in widening the operability of gas turbine combustors under stratified combustion conditions.

Study on Spontaneous Combustion Law and Prevention Technology of Abandoned Coal in Goaf of Coal Mine

The spontaneous combustion of coal in goaf areas is a significant natural disaster encountered during coal mining operations. To investigate the oxygen consumption characteristics of different coal types, we conducted TG experiments and closed oxygen consumption experiments using seven coal samples exhibiting various degrees of metamorphism. The findings revealed the following key observations: During the oxidation combustion process of coal, the absorbed heat originates from the physical and chemical adsorption of coal and oxygen. The first exothermic peak on the DSC curve represents the maximum combustion temperature of volatile matter and signifies the initiation of coal burning. Coal with higher ignition temperatures is less prone to spontaneous combustion. Analyzing the thermogravimetric curves, we observed that the ignition temperatures of 15# coal and 8+9# coal predominantly extracted from Duanwang Coal Mine are higher compared to the ignition temperature of the 4# coal seam (known for its susceptibility to spontaneous combustion) in Jiudaoling Coal Mine, Liaoning. This observation aligns with their nonspontaneous combustion characteristics. In the closed oxygen consumption experiment, we determined the volume oxygen consumption attenuation coefficients for the main mining areas’ 8+9# and 15# coal seams as 3.9001 × 10 − 4 and 3.83559 × 10 − 4 , respectively. Additionally, the critical oxygen consumption concentrations were measured as 15.71% and 16.78%. The shortest spontaneous combustion periods were determined to be 119.24 days and 121.25 days, respectively, for the aforementioned coal seams. To mitigate spontaneous combustion, the addition of inhibitors is necessary. The selection of an appropriate inhibitor depends on the increase in ignition activation energy. Notably, coal samples treated with a 15% MgCl2 inhibitor exhibited the highest increase in ignition activation energy. Hence, we concluded that a 15% MgCl2 inhibitor is the most suitable ratio for preventing spontaneous combustion.

Combustion temperature in a three-dimensional porous stove with a high-fidelity structure

The combustion temperature in a three-dimensional (3-D) porous stove was investigated numerically by using a novel high-fidelity structure of ceramic foam. The surface temperatures of the present stove were compared with those in corresponding experiments to verify the numerical model. Based on the discussion of gas velocity in the combustion state, the internal combustion temperature in the 3-D structure was analyzed by focusing on the solid–gas temperature profiles and the heat transfer characteristics. The results showed that large Venturi effects occurred with formation of jets on the upper surface of the ceramic foam. Numerous discrete flames were clearly formed in the 3-D pores of the ceramic foam and not only showed wrinkling induced by the staggered skeletons, but also differed significantly owing to the difference in pore structures, resulting in different temperature profiles in different axial cross-sections. The temperature for the axial cross-section with the same height was basically same in the circumferential direction, with even the same temperature difference between gas and solid. The driving force of internal heat transfer in porous media combustion (PMC) originates from the gas–solid temperature difference, resulting in the formation of an enclosing steady self-heat circulation process. The surface heat transfer coefficient (SHTC) obtained in this work agreed well with those of corresponding experiments in previous work. Their maximum region emerged near the interface between the distributor and foam ceramic, and not in the region of the maximum combustion temperature. The heat transfer coefficients gradually decreased along the axial direction in spite of undergoing combustion expansion, whereas it increased from the center to the outside edge in the radial direction. The results are conducive to numerical simulation of PMC, and helpful for combustion in domestic gas stoves.

Investigation of Gas Exchange Process on a Highly-Intensified Single Cylinder Diesel Engine with Late Intake Valve Closing Miller Cycle

Late intake valve closing (LIVC) Miller cycle was used on a highly-intensified single cylinder diesel engine to reduce the maximum combustion pressure and temperature. Three intake cams with three LIVC timings were designed and tested on the engine bench. The gas exchange process of the Miller cycle was investigated by a 1-D simulation model which was calibrated by experimental data. The analysis was conducted at a constant speed of 3600 r/min and two IMEP loads of 25 bar and 15 bar respectively. Miller depth is named to reflect the retard degree of the LIVC timing. The analysis results show that as the LIVC Miller depth increases, the intake pressure is considerably increased in order to keep the same load. This causes an increase in intake boost work. In addition, the averaged intake pressure difference during the period of BDC-IVC is negative and increases with the retard of IVC timing, resulting in more backflow with the LIVC timing. The backflow rate quickly increases from nearly zero at the original IVC timing of 70°CA ABDC to 22% at the deepest LIVC timing of 120°CA ABDC. Furthermore, the charging efficiency and pumping loss reduce with the retard of IVC timing. The Miller loss is obviously increased at deeper LIVC Miller cycle. On the other hand, the exhaust energy slightly decreases with the retard of IVC timing in this study case, but the ratio of the boost work over the exhaust energy increase considerably with the retard of IVC timing.

A study on the combustion performance and NOx emissions characteristics of a novel U-type radiant tube based on MILD combustion theory

Based on the theory of moderate or intense low-oxygen dilution (MILD) combustion, a 3D steady-state CFD model coupling dual flue gas recirculation and dispersion combustion was developed to describe the flow field, combustion temperature field, wall temperature distribution, and NOx concentration field during the operation of a novel U-type radiant tube (N-URT). A user-defined function (UDF) method was implemented to simulate the dilution of O2 concentration in the combustion air due to external flue gas recirculation (E-FGR). The effects of the E-FGR ratio on combustion characteristics and NOx emission were evaluated. The simulated results were consistent with experimental results. The simulated NOx concentration at the outlet was reduced to 105.5 mg/m3 at 8% O2, which was about 35.2% lower than the conventional combustion method. The study found that when the E-FGR ratio was increased from 0 to 25%, the standard deviation of wall temperature decreased from 30.3 °C to 23.3 °C, and the non-uniformity coefficient decreased from 0.2598 to 0.2183, indicating an improvement in temperature uniformity. However, the thermal efficiency decreased from 82.1% to 76.2%. Moreover, at higher E-FGR ratios, the volume of the high-temperature region (above 1500 ℃) gradually decreased, and both the maximum flame temperature and the outlet NOx concentration decreased sharply. Regression equations for the E-FGR ratio (β) on the maximum combustion temperature (Tmax) and the outlet NOx concentration (CNOx) were obtained, and an E-FGR ratio greater than 13.4% was recommended to meet the emission requirements.

Study of bifunctional calcium-based catalysts for PCDD/Fs removal in medical waste pyrolysis-combustion process

In order to achieve energy reuse and rapid harmless treatment of the mixed component medical waste (MCMW), this study adopted an integrated pyrolysis-combustion process by introducing the synthesized bifunctional catalysts Ca12Al14O33@CaO/Cu and Ca12Al14O33@CaO/Ni in the pyrolysis stage. The catalysts's structure and properties were first characterized, and then investigated the pyrolysis gas generated under catalysts engagement conditions. The results indicated that catalysts in pyrolysis stage could remove harmful HCl gas while upgrading the combustible gas content (H2, CO and CH4). pyrolysis gas yield increased with increasing temperature, and the highest combustible gas yield reached 96.91 μmolg−1min−1 and 108.53 μmolg−1min−1 for Ca12Al14O33@CaO/Cu and Ca12Al14O33@CaO/Ni, respectively. Moreover, the maximum HCl removal rate by Catalysts was up to 85∼91%. Elevated combustible gas content promoted higher temperatures in the combustion stage, resulting in a maximum combustion temperature of 918 °C, and the elevated combustion temperature promoted the high-temperature cleavage of the PCDD/Fs. The removal of HCl by catalysts in the pyrolysis stage reduced the chlorine source for PCDD/Fs synthesis in the combustion stage. Finally, the removal of HCl in the pyrolysis stage and the increased temperature in the combustion stage of MCMW with catalysts participation resulted in a PCDD/Fs removal efficiency of up to 85%.

Development of a coupled model of heat generation and jet flow of lithium-ion batteries during thermal runaway

A large amount of heat will be generated during battery thermal runaway. However, the current models for the battery thermal runaway mainly consider the heat generated inside the battery cell and rarely consider the effects of the jet fire. Therefore, it cannot provide an effective way to evaluate the thermal runaway propagation in a battery pack. This study develops a coupled model considering the heat generation inside the battery and the jet fire outside the battery during thermal runaway, which can better evaluate the thermal hazard. Experimental and simulation activities are carried out based on 18,650 cylindrical NCM lithium-ion batteries. First, a test bench is built to trigger and record the thermal runaway. High-speed camera and thermocouples are applied to record the fire shape and temperature. Totally 15 cells with 100 % SOC are abused and six samples experienced intense combustion. The jet fires last for at least 20 s and the maximum combustion temperature was 1075.4 °C, at the location 80 mm above the cell. Then a coupled model consisting of 0D heat generation, gas generation and injection sub-models and 2D CFD sub-model is established based on ANSYS Fluent. The heat and gas generation rates inside the battery are calculated based on chemical reaction mechanisms. The flow, combustion and heat transfer in the open space are solved in a 2D axisymmetric domain. The proposed model can reasonably capture the main characteristic of the jet fire and temperature rise during thermal runaway. The maximum deviation of peak temperature between the experiment and simulation is 8.56 %.