Reaction Mechanism Function Research Articles

A Service Life Prediction Method of Stranded Carbon Fiber Composite Core Conductor for Overhead Transmission Lines.

The effect of temperature on the service life of stranded carbon fiber composite core conductors was studied based on the kinetic theory of material pyrolysis. The thermal decomposition activation energy calculation for stranded carbon fiber composite cores was carried out by thermogravimetric analysis (TGA). The activation energy E of stranded carbon fiber composites was calculated according to the Flynn–Wall–Ozawa, Kissinger, and Coast–Redfern methods, which were 168.76 kJ/mol, 166.79 kJ/mol, and 160.35 kJ/mol, respectively. The results from these different treatments were within 10% or less, and thus the thermochemical reactions of stranded carbon fiber composite cores were considered to be effective. The life prediction model of the carbon fiber composite core was developed based on the kinetic equation of thermal decomposition. The service life is related to the reaction mechanism function G(α) and the reaction rate parameter k(t). The reaction mechanism function G(α) = ((1 − α)−3.3 − 1)/3.3 and the reaction rate parameter k(t) = 2.14 × 1012exp(E/RT) were obtained by fitting the thermal weight loss data of stranded carbon fiber composite cores. Based on the 5% mass loss criterion for the end of life of stranded carbon fiber composites, the service life of the carbon fiber composite core is given at various operating temperatures.

Pyrolysis Kinetics and Combustion Behaviors of a High-Nitrogen Compound, 4,4'-Azobis(1,2,4-triazole).

To study the thermal decomposition behavior of 4,4′-azobis(1,2,4-triazole) (ATRZ), the non-isothermal thermal decomposition kinetics of ATRZ were studied using the thermogravimetric–differential scanning calorimetry (TG–DSC) method. The TG–DSC of ATRZ was analyzed at heating rates of 5, 10, 15, and 20 K·min−1 in an argon atmosphere. The thermal decomposition kinetic parameters at peak temperature (Tp), such as apparent activation energy (Ea) and pre-exponential factor (lgA) of ATRZ, were calculated using the Kissinger, Ozawa, and Satava–Sestak methods. Ea and lgA calculated using the Kissinger, Ozawa, and Satava–Sestak methods are very close, at 780.2 kJ·mol−1/70.5 s−1, 751.1 kJ·mol−1/71.8 s−1, and 762.1 kJ·mol−1/71.8 s−1, respectively. Using a combination of three methods, the reaction mechanism function g(α) of ATRZ was obtained. The results show that the decomposition temperature of ATRZ is about 310 °C, and the decomposition is rapidly exothermic. The pyrolysis path of ATRZ was investigated through a pyrolysis-gas chromatography mass spectrometry (PY-GC/MS) experiment. ATRZ has three different decomposition paths and finally generates N2, HC-N-CH, N≡C-N, and HC=N-C≡N. The laser ignition combustion duration of ATRZ was 0.5033 s and the peak temperature was 1913 °C. The laser ignition combustion duration of ATRZ+CL-20 was 1.0277 s and the peak temperature was 2105 °C. The rapid energy release rate of ATRZ promotes the combustion energy release of CL-20.

Detailed kinetic analysis and modelling of the dry gasification reaction of olive kernel and lignite coal chars

The dry gasification process of solid fuels is a promising pathway to mitigate and utilize captured CO2 emissions toward syngas generation with tailored composition for several downstream energy conversion and chemical production processes. In the present work, comprehensive kinetic analysis and reaction modelling studies were carried out for olive kernel and lignite coal chars gasification reaction using pure CO2 as gasifying agent. Chars reactivity and kinetics of the gasification reactions were thoroughly examined by thermogravimetric analysis at three different heating rates and correlated with their physicochemical properties. The reactivity of olive kernel char, as determined by the mean gasification reactivity and the comprehensive gasification characteristic index, S, was almost three times higher compared to that of the lignite coal char. It was disclosed that the fixed carbon content and alkali index (AI) have a major impact on the reactivity of chars. The activation energy, Ea, estimated by three different model-free kinetic methods was ranged between 140 and 170 kJ/mol and 250–350 kJ/mol for the olive kernel and lignite coal chars, respectively. The activation energy values for the lignite coal char significantly varied with carbon conversion degree, whereas this was not the case for olive kernel char, where the activation energy remained essentially unmodified throughout the whole carbon conversion range. Finally, the combined Malek and Coats-Rendfrem method was applied to unravel the mechanism of chars-CO2 gasification reaction. It was found that the olive kernel char-CO2 gasification can be described with a 2D-diffusion mechanism function (D2) whereas the lignite coal char-CO2 gasification follows a second order chemical reaction mechanism function (F2).

Comprehensive study on the pyrolysis process of chestnut processing waste (chestnut shells): Kinetic triplet, thermodynamic, in-situ monitoring of evolved gasses and analysis biochar

Chestnut shell (CS) is a potential renewable energy source as a typical agricultural waste. CS obtained two kinds of samples of chestnut outer pericarp (COP) and chestnut inner pericarp (CIP) with widely different physicochemical properties by crushing and separation. The kinetic triplet (apparent activation energy (Eα), pre-exponential factor (A), reaction mechanism function (f(α)), thermodynamic and products of COP and CIP are investigated by TGA, FTIR and SEM. Moreover, the Eα and the A are estimated using three isoconversional methods. The value of Eα for COP ranges from 155.63 to 392.95 kJ/mol and the CIP ranges from 185.24 to 337.03 kJ/mol. The Eα and A of CIP are found to be much smaller than COP at high conversion α, indicating that CIP is more susceptible to pyrolysis than COP. The 18 commonly theoretical models can only confirm that the reaction mechanism of COP at low α satisfies the A3, F1, R3 and D3 models, and the CIP satisfies the F1.5, R3, Pn and D1 models. Therefore, the empirical model (Šesták-Berggren) is used to determine f(α) for the whole pyrolysis process of COP and CIP. Through thermodynamic calculations, both CIP and COP were found to have a high potential to generate products as bioenergy through pyrolysis. The analysis of pyrolysis products shows that CIP can release more gaseous products (e.g., CH4, CO and CO2) during pyrolysis due to different physicochemical properties. COP-char and CIP-char exhibited two completely different microscopic morphologies of dense masses and loose bands. The results obtained can contribute to understand the thermal behavior of the CS pyrolysis process and the properties of the pyrolysis products, and give a reference for the high-value utilization of CS.

Study of Gases and Thermal Behavior of Oxidized Coal during Spontaneous Combustion Process

Coal spontaneous combustion is one of the most severe and constant hazards in the coal industry. Understanding the mechanisms is the basis for effective hazard control in the coal-producing process. This paper investigated two types of oxidized coal samples from the re-mining faces of an underground coal mine. Proximate analysis, elemental analysis, surface analysis, temperature-programmed experiments, and differential scanning calorimetry analysis were conducted to study the spontaneous combustion characteristics. Various reaction mechanism functions were adopted to calculate the kinetic parameters, and multiple linear regression was performed to simulate the reaction behavior. The results show that the thermal decomposition of the oxidized coal followed a two-stage reaction model. The first stage reaction occupied smaller apparent activation energy and promoted the second stage reaction, dominating the heat production. Therefore, significant prevention measures for coal spontaneous combustion should be conducted and emphasized appropriately in the first stage to break the continuous reaction. The findings of this study can serve as a reference for predicting and preventing spontaneous combustion of oxidated coal.

Structural Characterization, Thermal Stability and Non-Isothermal Kinetic Analysis of Decomposition of Poly(methylmethacrylate) and Titanium Dioxide Nanocomposites

In this study poly(methylmethacrylate) (PMMA) and the corresponding nanocomposites loaded with titanium dioxide (TiO2) films were prepared by a solution casting method. All materials were characterized by Fourier transform infrared spectroscopy, UV-visible spectroscopy, X-ray diffraction and scanning electron microscopy. The thermal properties were investigated by differential scanning calorimetry and thermogravimetric analysis. The results showed that the incorporation of TiO2 nanoparticles in PMMA decreased the thermal stability of the polymer. Moreover, the kinetic study of the thermal degradation showed that the apparent activation energies of the nanocomposites PMMA/TiO2 were lower compared to the pure PMMA, confirming the catalytic effect of TiO2 nanoparticles on the PMMA thermal decomposition. Furthermore, g(α), which is the integral form of the reaction mechanism function, showed that the degradation mechanism of the PMMA nanocomposites was strongly dependent on the TiO2 amount introduced into their matrices. Finally, the degradation mechanism of the pure PMMA obeyed the R3 model corresponding to a phase boundary reaction (n = 3), whereas in the case of the PMMA/TiO2 nanocomposites, they obeyed the R2 model, corresponding to a phase boundary reaction (n = 2), for PMMA/TiO2 (3%) and an A1.5 model, corresponding to an Avrami-Erofeev correlation (m = 1.5), was obtained for the remaining nanocomposites PMMA/TiO2 (5, 7 and 10%).

Mechanochemical effect of spontaneous combustion of sulfide ore

Spontaneous combustion of sulfide ore is a typical disaster in mining, which can cause a series of environmental and safety problems. In order to reveal the mechanical activation’s influence on the spontaneous combustion of sulfide ore during the mining process, the changes in the microstructure of sulfide minerals and their spontaneous combustion kinetics before and after activation were studied in this paper. The most probable mechanism function, apparent activation energy, and pre-exponential factor were derived using the Malek and Friedman methods, respectively. The results showed that mechanical activation leads to aggregation of mineral particles, defect generation in crystals, reduction in crystallize size, and increase in lattice distortion rate, which result in samples more actively. In the process of oxidation and spontaneous combustion, the main products were Fe2O3 and SO2 gas. And the mechanochemical effect will cause the reaction rate to become faster and lead the reaction to move toward low temperature. The mechanochemical effect will also lead to chemical reactions at low temperatures, causing some ore samples to be oxidized without changing the samples’ reaction mechanism functions. After mechanical force, the average apparent activation energy decreased by 26.27 kJ/mol, 32.73 kJ/mol, 27.01 kJ/mol, and 35.30 kJ/mol, respectively, and the sample’s spontaneous combustion tendency increased. In addition, ore samples’ active surface and grain boundary area increased under the mechanical forces, the lattice was distorted and dislocated, and a sub-stable amorphous phase was formed. In this process, the mechanical energy was partially converted into energy storage in the solid material, significantly increasing reactivity.

Effect of bastnaesite as reductant on hematite reduction during in-situ suspension magnetization roasting of refractory iron ore under neutral atmosphere

The iron tailings of Bayan Obo mines are solid waste, which occupies land area and also causes environmental pollution; however, this waste can be recycled. In this study, based on the characteristics of iron minerals and fluorocarbonate contained in Bayan Obo iron tailings, clean magnetization roasting of iron minerals by bastnaesite from iron tailings during in-situ suspension magnetization roasting in a neutral atmosphere was explored. The results show that for iron tailings with a mass of 12 g, a N 2 gas flow rate of 600 mL/min, and roasting for 5 min at 800 °C, iron concentrate with a 60.44% iron grade at an iron recovery of 76.04% could be obtained. X-ray diffraction analysis showed that the weak magnetic hematite was reduced to strong magnetic magnetite in the neutral atmosphere, without additional reductant. The kinetics of the magnetization roasting of mineral mixtures (bastnaesite and hematite) in a neutral atmosphere showed that the optimal reaction mechanism function was the three-dimensional diffusion model with activation energy of 161.8838 kJ·mol −1 ; this indicates that the reaction was a heterogeneous, diffusion-controlled solid-state reaction.

Insights into the thermal decomposition of organometallic compound ferrocene carboxaldehyde as precursor for hematite nanoparticles synthesis

Abstract The paper deals with the thermal decomposition of organometallic compound ferrocene carboxaldehyde [(C5H4CHO)Fe(C5H5)] in oxidative atmosphere, which leads to pure hematite nanoparticles, studied with non-isothermal thermogravimetry (TG) protocol. Deconvolution method with Fraser-Suzuki fit function is adopted to resolve the complex multistep TG profiles into six different reaction steps. Step-wise reaction kinetic parameters (activation energy, reaction mechanism function, reaction rate) are estimated based on the mathematical analysis of the multi-heating rate TG data primarily following model-free (integral isoconversional) approach and using master-plot method. The estimated kinetic parameters are utilised to reconstruct the conversion plots which successfully resemble the experimentally observed ones. A plausible reaction process leading to hematite on thermal decomposition of ferrocene carboxaldehyde as the end product is discussed. A comparative discussion on the thermal decomposition of two ferrocene derivatives have been made. The novelty of the present work lies in successful deconvolution of complex TG profiles and hence obtaining the step-wise reaction kinetic parameters demonstrating different reaction mechanisms involved in the thermal synthesis of hematite nanoparticles starting from ferrocene carboxaldehyde which have no prior reporting. Further, a satisfactory agreement between the reconstructed and experimental decomposition profiles establishes the correctness of the applied modelling approach as well as the methodology adopted.

Cholesterylation of Smoothened is a calcium-accelerated autoreaction involving an intramolecular ester intermediate.

Hedgehog (Hh) is a morphogen that binds to its receptor Patched 1 and activates Smoothened (SMO), thereby governing embryonic development and postnatal tissue homeostasis. Cholesterol can bind and covalently conjugate to the luminal cysteine-rich domain (CRD) of human SMO at the D95 residue (D99 in mouse). The reaction mechanism and biological function of SMO cholesterylation have not been elucidated. Here, we show that the SMO-CRD undergoes auto-cholesterylation which is boosted by calcium and involves an intramolecular ester intermediate. In cells, Hh stimulation elevates local calcium concentration in the SMO-localized endosomes through store-operated calcium entry. In addition, we identify the signaling-incompetent SMO D95E mutation, and the D95E mutant SMO can bind cholesterol but cannot be modified or activated by cholesterol. The homozygous SmoD99E/D99E knockin mice are embryonic lethal with severe developmental delay, demonstrating that cholesterylation of CRD is required for full-length SMO activation. Our work reveals the unique autocatalytic mechanism of SMO cholesterylation and an unprecedented role of calcium in Hh signaling.

Inhibition on de novo synthesis of PCDD/Fs by an N–P-containing compound: Carbon gasification and kinetics

In this study, an N–P-containing compound (ammonium dihydrogen phosphate (ADP)) and an auxiliary material (CaO) were used to inhibit the formation of polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs). ADP significantly inhibited the formation of PCDD/Fs by the inhibition efficiencies of 98.45% for total concentration and 96.55% for toxic concentration. ADP was the best single inhibitor on toxic PCDFs (96.55%), and the inhibition on toxic PCDDs improved after ADP (90.91%) coupled with CaO (95.69%). In the temperature range of 300–350 °C, ADP inhibited the carbon gasification by reducing CO2 and CO (400%–500% (20 K/min)), which could attributed to the formation of Cu2P2O7 and copper nitrides from the Cu deactivation by P and N, respectively. However, the synergy of ADP and CaO decreased CO and CO2 by 200%–300% (20 K/min), because CaO could promote carbon gasification. In addition, the apparent activation energy (Ea) increased from 78.50 kJ/mol to 102.04 kJ/mol with the addition of ADP but decreased to 73.92 kJ/mol after adding ADP and CaO. These results revealed that one inhibition route of de novo synthesis was the inhibition of carbon gasification by ADP, while CaO mainly inhibited de novo synthesis via the consumption of HCl and Cl2. Furthermore, a reaction mechanism function in model fly ash was built as f(α)=2α−1/2/3, which included carbon gasification and de novo synthesis. The results pave the way for further research on the inhibition kinetics of PCDD/F and development of other inhibitors.

Investigation of non-isothermal pyrolysis kinetics of waste industrial hemp stem by three-parallel-reaction model

The evaluation of pyrolysis kinetics for waste industrial hemp stem (IHS) is essential to achieve the high-value utilization of agricultural waste. In present study, firstly, non-isothermal pyrolysis experiments of IHS were performed at different heating rates using a thermogravimetric analyzer. Then, the kinetic triplets (apparent activation energy, pre-exponential factor, and reaction mechanism) of the three pseudo components for IHS (hemicellulose, cellulose, and lignin) were determined by a three-parallel-reaction model. Moreover, the pyrolysis products were also characterized via FTIR and SEM. The results showed that the apparent activation energies of hemicellulose, cellulose and lignin were 86.523, 113.257 and 197.961 kJ/mol, respectively; the pre-exponential factors were 6.887 × 107, 8.179 × 109 and 1.801 × 1015 s−1, respectively; and the reaction mechanism functions were f(α) = α1.35629(1-α)0.34832[-ln(1-α)]−1.20128, f(α) = α3.42900(1-α)0.01288[-ln(1-α)]-2.84445, f(α) = α0.68738(1-α)3.09313[-ln(1-α)]-1.58522, respectively. The release temperature for volatile products of IHS pyrolysis was mainly between 440 and 840 K. IHS as an agricultural waste is a suitable feedstock to produce renewable energy.

In-situ measurement of mineral phase transition and kinetics in roasting process of Bayan Obo mixed rare earth concentrate by sodium carbonate

In this study, the Bayan Obo rare earth concentrates mixed with Na2CO3 were used for roasting research. The phase change process of each firing stage was analyzed. The kinetic mechanism model of the continuous heating process was calculated. This study aims to recover valuable elements and optimize the production process to provide a certain theoretical basis. Using X-ray diffraction (XRD), Fourier infrared spectroscopy, scanning electron microscopy with energy dispersive spectrometry, the reaction process and the existence of mineral phases were analyzed. The variable temperature XRD and thermogravimetric method were used to calculate the roasting kinetics. The phase transition results show that carbonate-like substances first decompose into fine mineral particles, and CaO, MgO, and SiO2 react to form silicates, causing hardening. Further, REPO4 and NaF can directly generate CeF3 and CeF4 at high temperatures, and a part of CeF4 and NaF forms a solid solution substance Na3CeF7. Rare earth oxides calcined at a high temperature of 750 °C were separated to produce Ce0.6Nd0.4O1.8, Ce4O7, and LaPrO3+x. Then, BaSO4, Na2CO3, and Fe2O3 react to form barium ferrite BaFe12O19; the kinetic calculation results show that during the continuous heating process, the apparent activation energy E reaches the minimum in the entire reaction stage in the temperature range of 440–524 °C, and the reaction order n reaches the maximum, which indicates that the decomposition product REFO significantly impacts the reaction system and reduces the activation energy. The mechanism function is F(α) = [−ln (1−α)]1/3. The reaction order n reaches the minimum in the temperature range of 680–757 °C, and the apparent activation energy E is large. The difficulty of the reaction increases during the final stage. The reaction mechanism function is F(α) = [1−(1−α)1/3]2. Observing the entire reaction stage, the step of controlling the reaction rate changes from random nucleation to three-dimensional diffusion (spherical symmetry).

Model-free kinetic determination of pre-exponential factor and reaction mechanism in accelerating rate calorimetry

Accelerating rate calorimetry (ARC) is an essential tool in thermal hazard assessment of self-reactive chemicals. Compared to the thermal analysis, the kinetic approaches for ARC are relatively less. To enrich the kinetic approaches for ARC, the feasibility of a model-free based pre-exponential factor and reaction model determining method in ARC data process is investigated in this article. By using the compensation effect in association with Friedman's isoconversional method, the Eα, lnAα and f(α) dependency with α are obtained from several experiments under different thermal inertia. Then, the apparent reaction mechanism function is determined based on non-linear regression method. For effective verification, the numerical simulations are carried out based on a Sestak-Berggren decomposition model. In addition, the applicability of this kinetic approach is investigated by studying the effect of NaOH on the thermal decomposition of cumene hydroperoxide/cumene solutions. Both the simulative and experimental results show the value of this kinetic approach.

TG-FTIR and Py-GC/MS combined with kinetic model to study the pyrolysis characteristics of electrolytic manganese residue

The manuscript used TG-FTIR, Py-GC/MS along with kinetic models to investigate the pyrolysis characteristics of electrolytic manganese residue. The possible reaction mechanism for the pyrolysis process of electrolytic manganese residue and the change rule of volatiles release characteristics during the pyrolysis were analyzed. The result shows that the pyrolysis process of electrolytic manganese residue can be divided into five processes: the dehydration of CaSO4·2H2O, the removal of ammonium salt compounds, the transformation of anhydrous CaSO4 crystal form, the decomposition of carbon-containing organic matter and the solid-phase reaction between the substances to form a new phase. According to the difference of activation energy values, the kinetic process for the pyrolysis of electrolytic manganese residue was divided into four sections. The pyrolysis reaction mechanism functions for different kinetic mechanism were the second-order phase boundary chemical reaction function: g(α) = (1-α)−1, Mampel Power law function g(α) = α1/4, 2/3-order phase boundary chemical reaction function g(α) = (1-α)-1/2 and three-dimensional diffusion function g(α) = [1-(1-α) 1/3] 1/2. The major gases released during the pyrolysis of electrolytic manganese residue were NH3, CO2 and SO2. The intermediate product of CO was unstable and participated in the reaction to promote the formation of CO2 and SO2.

Pyrolysis of predried dyeing sludge: Weight loss characteristics, surface morphology, functional groups and kinetic analysis

AbstractThe weight loss characteristics, surface morphology, functional group, and kinetic parameters of predried dyeing sludge (PDS) pyrolysis was studied for the first time in this paper. The contents of both volatile matter and organic matter in PDS char both decreased with the increase of pyrolysis temperature. The PDS pyrolysis process can be divided into four stages: S1 (30°C‐180°C)—water evaporation, S2 (180°C‐500°C)—decomposition of organic compounds such as aliphatic compounds and biomass fibres, S3 (500°C‐900°C)—decomposition of the former stage residues, and S4 (900°C‐1350°C)—decomposition of carbonaceous material remaining in the char and vaporization of partial ash. With the increase of pyrolysis temperature, the number density of small spherical particles on the PDS particle surface increased. The decomposition of aliphatic hydrocarbon was basically completed at 700°C. The average activation energy of PDS in S2‐S4 stages were 172.93, 445.65, and 301.76 kJ/mol, respectively. The pyrolysis reaction of PDS samples could be described by nth‐order reaction mechanism function.

Effect of CuO on the thermal kinetics and combustion properties of Al/MoO3 thermite prepared by ball milling

To explore the influence of CuO additive on the thermal kinetics and combustion performance of thermite, Al/MoO3 thermite composites with different mass fractions of CuO were prepared by ball milling. Field emission scanning electron microscope (FE-SEM), X-ray diffractometer (XRD), and differential scanning calorimeter (DSC) were used to test the samples. From the DSC results, Al/MoO3 thermite and Al/CuO thermite released 1066 J/g and 849 J/g heat, respectively. The peak temperature of the exothermic reaction was 560.22 °C and 609.43 °C. Interestingly, the Al/MoO3 thermite with 5% CuO released higher heat, about 1747 J/g. The temperature of the exothermic peak was also greatly advanced to 526 °C. Thermodynamic analysis results showed that the activation energy (Ea) of Al/MoO3/5% CuO thermite was merely 184.75 kJ mol−1, which was a decrease of 18.3% and 20.8% of the Al/MoO3 and Al/CuO thermite. The reaction mechanism function of Al/MoO3 thermite, Al/MoO3/5% CuO and Al/CuO thermite can be set as f(α)=1−α. The fast electric heating wire ignition experiment showed that the flame brightness of the Al/MoO3/5% CuO thermite was the brightest and the burning time was the longest. Surprisingly, when the mass fraction of CuO additives in Al/MoO3 thermite reached 10% and 20%, the thermal kinetics and combustion performance of the thermite were completely changed. There was a violent and sharp exothermic peak accompanied by a large amount of heat release of 2042 J/g and 2252 J/g, respectively. The reaction mechanism of Al/MoO3 thermite with 10% and 20% CuO addition can be set as f(α)=3/2∗(1−α)[−ln(1−α)]1/3. The burning speed became faster and the flame was bright with sparks. This work lays the foundation for the further study of the thermite mechanism.

Thermal Decomposition Mechanism of GIS Basin Insulator and Kinetic Parameters-Based Lifetime Prediction Methodology.

To reliably detect the latent defects and accurately evaluate the remaining life of gas insulated switchgear (GIS) basin insulators, more effective detection and characterization methods need to be explored. The study of pyrolysis kinetic parameters based on the intrinsic characteristics of materials provides a new way to solve this problem. First, an integral expression model of the reaction mechanism function with four parameters is proposed in this paper, which can represent various existing reaction mechanism functions with better universality and more application fields. Then, on the basis of the temperature transformation equation, an improved method for calculating the activation energy is presented, which shows higher computational accuracy than the existing methods. Further, based on a non-isothermal kinetic equation, the structure of the experimental function is given. It is a method for solving the pyrolysis reaction mechanism function of insulating materials, which can also be used to calculate the pre-exponential factor simultaneously. The thermogravimetric analysis experiment is carried out on a certain basin insulator sample at different heating rates. The pyrolysis kinetic state parameters, including the activation energy, reaction mechanism function and pre-exponential factor of the basin insulator, are calculated. Finally, the life prediction method of basin insulators is established, and the key factors affecting the life of insulators are discussed.

Synergistic effect, kinetic and thermodynamics parameters analyses of co-gasification of municipal solid waste and bituminous coal with CO2

Co-gasification of municipal solid waste (MSW) with bituminous coal (BC) is an attractive alternative to realize the harmless disposal and energy harvesting of MSW. In this work, co-gasification characteristics and synergistic interaction of MSW and BC with CO2 atmosphere are studied by thermogravimetric method, including analyses of thermodynamics, kinetic parameters and reaction mechanism function. Results indicate that MSW gasification process can be divided into four main stages, and that of BC has only three main stages. Gasification temperature of coal char is much higher than that of MSW char, and addition of MSW can significantly improve the gasification reactivity of BC. Besides, a significant synergistic effect is observed for all the blends in char gasification stage. Based on three kinetic methods of Flynn-Wall-Ozawa (Xie et al., 2018), Starink (Zhang et al., 2019a) and Friedman, the minimum average activation energy Ea (184.13 kJ/mol) is obtained when the blend ratio of BC is 40% which might be an optimal option for co-gasification of the blends. The average values of the enthalpy, the Gibbs function and the entropy changes for sample 60MSW40BC are 176.82 kJ/mol, 257.89 kJ/mol and −89.16 J/mol·K, respectively. According to the Malek method, F6, A1 and D7 models are probably more suitable to describe three main stages of sample 60MSW40BC CO2 co-gasification.

Preparation of Sub‐Micron Sized CL‐20 and Its Mechanical and Thermal Properties

AbstractHigh sensitivity limits the broad application of CL‐20 despite that it is considered as the most powerful explosive. Numerous efforts and technologies of fabricating CL‐20 with small particle size have been implemented for solving this problem. In this study, CL‐20 with sub‐micron particle size was prepared by superfine comminution technique. The results of impact and friction sensitivities tests showed that the mechanical sensitivities of CL‐20 were improved after ultra‐fine treatment. DSC results showed that the decomposition of CL‐20 advanced with the particle sizes decreased. The sub‐micron sized CL‐20 showed lower activation energy (Eα) compared to that of raw CL‐20, suggesting that particle size reduction is in favour of decreasing the threshold of decomposition. The reaction models of CL‐20 with different particle sizes could all be categorized as n‐th order reactions with autocatalysis. The function of reaction mechanism could be expressed as f(α)=(1‐α)n(1+kcat•α). On aspect of heat sensitivity, the results of deflagration point tests showed that although particle size had little influence on the deflagration point with 5 s delay time (Tb) of CL‐20, apparent activation energy of explosion (Eb) decreased apparently with the particle sizes decreased, which could impact the thermal sensitivity significantly.