Thermal Kinetic Analysis Research Articles

Investigation of CO2 desorption kinetics in MDEA and MDEA+DEA rich amine solutions with thermo-gravimetric analysis method

In this paper, by means of thermo-gravimetric analysis(TGA), the desorption kinetics of CO2 absorbed in two kinds of rich amine solutions, MDEA (3.25mol/L) and MDEA+DEA(3.25mol/L-0.3mol/L), were investigated under different heating rates(2.5℃/min, 5℃/min, 10℃/min and 20℃/min). The thermal analysis kinetics was applied to analyze the TG-DTG curves of two rich amine solutions so as to research CO2 desorption kinetics. In addition, the CO2 desorption kinetics parameters have been calculated with model-free method Flynn-Wall-Ozawa (FWO) and model-fitting method Coats-Redfern (CR). The results indicated that CO2 desorption process could be divided into two stages. The CO2 and H2O were released with non-uniform speed in the first stage and MDEA or DEA with higher boiling points were evaporated in the second stage. For MDEA solution the average activation energy E was 50.36kJ/mol, the pre-exponential factor A was 1.68×107, and the most probable integral mechanism function was Gα=α3/2. For MDEA+DEA solution the average activation energy E was 59.68kJ/mol, the pre-exponential factor A was 2.22×107, and the most probable integral mechanism function was Gα=[(1+α)1/3−1]2. The technical feasibility of CO2 desorption performance in rich amine solutions with thermo-gravimetric analysis method was demonstrated.

Kinetic Analysis of Thermal Decomposition of Inorganic Solids and Polymer by Sample Controlled Thermal Analysis and Kinetic Deconvolution Analysis

Kinetic Analysis of Thermal Decomposition of Inorganic Solids and Polymer by Sample Controlled Thermal Analysis and Kinetic Deconvolution Analysis

Kinetic studies of isothermal decomposition of (NH4)4UO2(CO3)3 to uranium oxide

The ammonium uranyl carbonate, (NH4)4UO2(CO3)3, is an important material used in UO2 and U3O8 ceramics production for the nuclear fuel fabrication. Thermal study and kinetic analysis of ammonium uranyl carbonate conversion under isothermal conditions has been studied in air atmosphere to obtain the tri-uranium octoxide (U3O8), using muffle furnace equipment, UV–visible spectrophotometer, gas adsorption, Hg porosimetry, laser granulometry, and optic spectroscopy. The textural properties (specific surface area, morphology, pore size, grain size, inter-particular porosity, and intra-particular porosity) and characteristics (uranium content and stoichiometry) of the prepared samples were estimated from the physical–chemical characterization. The kinetic parameters were estimated by a fitting of the experimental data. The activation energy Ea, frequency factor A, and reaction rate constants k were calculated from the conventional and iso-conversion kinetic models and were within the range of literature values. The activation energy average values are 36.69 and 30.36 kJ mol−1 by conventional and iso-conversion models, respectively.

Thermal decomposition characteristics and kinetic analysis of C4F7N/CO2 gas mixture

In recent years, the C4F7N/CO2 gas mixture has been considered one of the most promising candidates to replace the strong greenhouse gas SF6 in high-voltage power equipment. However, there are few studies on the thermal stability of the C4F7N/CO2 gas mixture. In this paper, the characteristics and mechanism of the thermal decomposition of C4F7N/CO2 gas mixture are analyzed by both experiment and calculation. Gas chromatography-mass spectrometry (GC-MS) is applied to detect the decomposition products at different temperatures and pressures. The measurements show that the C4F7N/CO2 mixture undergoes significant decomposition above about 700°C and the main products are CO, C2F6, C3F6, C3F8, C2F3N, C3F5N and C2N2. Previous studies have explored the possible decomposition pathways of C4F7N and predicted the free radicals produced after the decomposition. However, the subsequent processes in which the free radicals recombine and form stable products have not been considered. In this study, both the decomposition and recombination pathways are considered and the corresponding reaction rate constants are calculated. Based on this, precise chemical kinetic composition results at steady state during the thermal decomposition of C4F7N/CO2 mixture are obtained. Further, the influences of pressure and temperature on the decomposition products are theoretically investigated. It is also found that C4F7N/CO2 gas mixtures are more stable under higher pressures. The results provide an important reference for the engineering application of C4F7N/CO2 gas mixtures.

Thermal characteristics and kinetic analysis of coal-oxygen reaction under the condition of inert gas

ABSTRACT To ascertain fire prevention and extinguishing mechanism of inert gas in coal mine goaf, TG-DTG-DSC experiments of coal-oxygen reaction at 30–850℃ under N2 and CO2 conditions were carried out, and the thermal characteristics and kinetic factors were analyzed. The process of coal-oxygen reaction was divided into five stages by the four characteristic temperatures of T1 (temperature at which water evaporates completely), T2 (temperature at which coal begins to decompose intensely), T3 (ignition temperature) and T4 (burnout temperature). With the decrease of O2 concentration, T2, T3, and T4 increased, the total mass loss and heat release decreased, and the decomposition degree increased. The injection of N2 and CO2 reduced the apparent activation energy and pre-exponential factor of T1–T2, T2–T3 and T3–T4 stages, and there was dynamic compensation effect between activation energy and pre-exponential factor. Under the same O2 concentration conditions, the effect of CO2 was more significant than that of N2. Reducing oxygen concentration by injecting N2 and CO2 could rapidly reduce the degree of coal-oxygen reaction rate. This study is of great significance for the prediction of coal spontaneous combustion and the using of N2 and CO2 coal fire prevention and extinguishing technology.

Flame retardancy and thermal degradation of rigid polyurethane foams composites based on aluminum hypophosphite

Rigid polyurethane foam/aluminum hypophosphite (RUPF/AHP) composites were fabricated by one-step water-blown method. Furthermore, thermal conductivity test and scanning electron microscope (SEM) confirmed RPUF/AHP composites presented well cell structure with thermal conductivity of 0.0434–0.0466 k W/m · k and density of 59.0–60.3 kg m−3. Thermogravimetric analysis test showed significantly enhanced Tmax value of RPUF/AHP in second stage, indicating enhanced thermal stability of the composites, which was as also confirmed by thermal degradation kinetics analysis. Flame retardant test revealed that AHP presented high flame retardancy efficiency to RPUF, only 5 php AHP incorporation can make RPUF/AHP5 reach V-1 rating in UL-94 test. Microscale combustion calorimetry (MCC) test showed that AHP could effectively decrease peak of heat release rate (PHRR) of RPUF/AHP composites. RPUF with 30 php AHP loading presented PHRR value of 164 W g−1, which was 20.3% decreased compared with that of virgin RPUF. Thermogravimetric analysis-Fourier transform infrared spectroscopy (TG-FTIR) was introduced to investigate gaseous products in degradation process of RPUF/AHP composites. It can be found that AHP enhanced the release of CO2, isocyanate compound while inhibit the release of hydrocarbons, aromatic compounds and esters. Furthermore, scanning electron microscope (SEM) and x-ray photoelectron spectroscopy (XPS) were applied to research char residue of the RPUF/AHP composites. It was confirmed that AHP could promote C and N elements in RPUF matrix to form aromatic and aromatic heterocyclic structure, which combined with aluminum phosphate to form compact char residue, thus significantly inhibit mass and heat transmission in combustion. Consequently, a possible gas-solid flame-retardant mechanism of RPUF/AHP composites was proposed.

Experimental Study on the Effect of Chemical Composite Additives on Heat Release Characteristics of Coal Oxidation Spontaneous Combustion

ABSTRACT To study the effect of chemical composite additives (CCAs) on the heat release characteristics of coal oxidation spontaneous combustion, this paper develops a CCA comprising multiple chemical reagents that is formulated into different concentrations and used to treat coal samples. Microcalorimetry technology with high precision and high sensitivity was used in this experimental research. The heat release parameters of the oxidation of different treated coal samples were obtained and compared by varying the heating rate. The experimental results show that the general trend for coal is first absorbing heat and then releasing heat with increasing temperature, and there is a “step-like” trend in the heat releasing stage. For the same heating rate, water treatment and CCA treatment delay the temperature increase in the coal in the heat absorbing stage, and in the heat releasing stage, water treatment increases the heat release rate and maximum heat flow. CCA treatment decreases the heat release parameters value of the oxidation of coal, and the effect is increased with the increasing CCA concentration. The thermal analysis kinetics method was used to study the coal oxidation reaction. CCA treatment can increase the activation energy of coal, increase the difficulty of reaction process and reduce the heat release rate, which has an inhibitory effect on the spontaneous combustion of coal. Increasing the heating rate can accelerate the reaction rate of the system, resulting in an increase in the spontaneous combustion tendency of coal.

Energy Recovery of Furnace Slag from Steel Industrial and Thermochemical Conversion of Lignocellulosic Biomass: Thermal Behavior and Kinetic Analysis on Cellulose under Fast Pyrolysis Conditions

The combination of biomass pyrolysis with heat recovery from molten slag is a feasible and economically applicable technology. The thermal behavior and kinetic analysis on cellulose (CE) with furna...

Thermal kinetic analysis of exothermic nature and cupric ion catalysis of electronic-grade etching solutions by using calorimetry

Wet etching is a fundamental process in the electronic industry, particularly in the production of liquid crystal display panels, integrated circuit wafers, and printed circuit boards. Various electronic-grade etchants, such as Cu-etchant, Al-etchant, and sodium persulfate (SPS)-etchant, have been used for etching process. Furthermore, the Cu-etchant, which contains hydrogen peroxide and concentrated acids, are widely used in panel etching nowadays owing to its high etching rate and ease of regeneration. Nonetheless, high-tech industries that use etchants should consider their hazardous properties, such as explosiveness, flammability, and corrodibility. This study evaluated the exothermic nature and incompatibility of the Cu-etchant in the storage tanks and etching tools. Understanding the exothermic and runaway hazards of the Cu-etchant and its reaction with cupric ion catalyst is necessary in case the etching process fails due to mixing, contamination, or lack of temperature control. Data of thermal dynamic scanning on various etchants can ascertain the exothermic onset temperature (T0), peak power, and exothermic enthalpy (ΔH). Reaction kinetic data were evaluated after comparison with various etchants' exothermic behaviors. Moreover, various self-heating models (dT/dt) of thermal decompositions for the Cu-etchant and its cupric-ion catalysis were proposed using thermokinetic analysis methods for improving the safety of operation while conducting etching process.

Curing and Characteristics of N,N,N′,N′-Tetraepoxypropyl-4,4′-Diaminodiphenylmethane Epoxy Resin-Based Buoyancy Material

Buoyancy material is a type of low-density and high-strength composite material which can provide sufficient buoyancy with deep submersibles. A new buoyancy material with N,N,N′,N′-tetraepoxypropyl-4,4′-diaminodiphenylmethane epoxy resin (AG-80) and m-xylylenediamine (m-XDA) curing agent as matrix and hollow glass microsphere (HGM) as the filler is prepared. The temperature and time of the curing process were determined by the calculations of thermal analysis kinetics (TAK) through differential scanning calorimetry (DSC) analysis. The results show that the better mass ratio of AG-80 with m-XDA is 100/26. Combined TAK calculations and experimental results lead to the following curing process: pre-curing at 75 °C for 2 h, curing at 90 °C for 2 h, and post-curing at 100 °C for 2 h. The bulk density, compressive strength, and saturated water absorption of AG-80 epoxy resin-based buoyancy material were 0.729 g/cm3, 108.78 MPa, and 1.23%, respectively. Moreover, this type of buoyancy material can resist the temperature of 250 °C.

Thermal characterization and kinetic analysis of polyvinyl chloride containing Sn and Zn

Polyvinyl chloride (PVC) films containing the mercaptan methyltin (S), zinc stearate (Z) and dipentaerythritol (D) additives were prepared. The thermal degradation kinetics of the films were investigated by nonisothermal thermogravimetry and TG–FTIR techniques. Using the nonmodel method and the Kissinger, the Friedman, the Kissinger–Akahira–Sunose and the Flynn–Wall–Ozawa methods, the average apparent activation energies of the PVC–SZD films in the first and second thermal decomposition stages obtained were 127.5 and 261.6 kJ mol−1, respectively. Compared with the experimental master plot by the generalized master plot, the experimental and theoretical master plots on the master plot of θ/θ0.5 versus α show that the thermal degradation of PVC-SZD film conforms to the chemical reaction F1.5 mechanism model. TG–FTIR analysis showed that the infrared vibration peaks ordered from strong to weak after adding SZD components were: νCO2 (638 °C) > ν(–COOR) (275 °C) > νHCl (299 °C). The thermal degradation of the film did not show hydroxyl or moisture formation compared to the blank. The removal of carboxyl groups of plasticizer dioctyl terephthalate (DOTP) in PVC was significantly inhibited, and the CO2 gas released by thermal degradation was reduced by 85.2%. This suggests that SZD has a strong interaction with the ester groups in DOTP, and there is the possibility of generating a more stable carboxyl group-containing metal complex, which creates favorable conditions for the recovery of DOTP. When the heating rates were 2.5, 5.0, 10 and 20 °C min−1, the lowest temperatures at which the conversions reached 5 and 10% were 226.1 °C and 239.1 °C, respectively.

Effects of diluents on laminar burning characteristics of bio-syngas at elevated pressure

A study on the effect of diluents (N2/CO2) on laminar flame speed and flame instability of H2/CO/CH4/air premixed flame was conducted using outwardly propagating spherical flame and CHEMKIN package. Experiments and numerical computation were conducted at an initial temperature of 303 ± 3 K, pressures of 0.1–0.5 MPa, equivalence ratios of 0.6–1.5 with N2 or CO2 dilution ratios from 0% to 45%, at an interval of 15%. The measured laminar flame speed was compared with values predicted using the Li mechanism. The thermal and chemical kinetic analyses were also presented. The results show that the Li mechanism can give a good predication on laminar flame speed of H2/CO/CH4/air premixed flames. But with N2/CO2 dilution, the Li mechanism gives slight underestimations at fuel-rich conditions. Laminar flame speed decreases with the increase of N2/CO2 dilution ratios. Results indicate that CO2 dilution has a stronger dilution effect, thermal effect, and chemical effect than those of N2 dilution, and thereby it can substantially decrease the laminar flame speed of H2/CO/CH4/air mixture. On the other hand, flame instability is slightly promoted with N2/CO2 dilution at atmospheric pressure, while at elevated pressure, it is suppressed with N2/CO2 dilution due to the significant decrease of thermal expansion ratio and increase of flame thickness. Compared with N2 dilution, CO2 dilution has a stronger inhibiting effect on hydrodynamic instability.

Co-pyrolysis of lignin and polyethylene with the addition of transition metals - Part I: Thermal behavior and kinetics analysis

In order to realize a promissing disposal of solid wastes, especially for biomass and plastics, and the recovery of high value-added products, lignin (LG) and polyethylene (PE) were co-pyrolyzed with the addition of transition metals. Thermal behavior and kinetics of the mixtures affected by the type of transition metals (0.5 mmol/g Ni, Co, Fe and Mn), the concentration of Ni (0–1 mmol/g Ni), the ratio of LG to PE (4:1-1:4) and heating rate (10–40 °C/min) were investigated according to thermogravimetric analysis (TGA). It is found that the treatment of LG/PE with 0.5 mmol/g Ni, Co, Fe or Mn results in the decrease of the initial decomposition temperature of LG and PE in the mixture by 10–53 °C and 9–18 °C, respectively. According to the difference of weight loss (ΔW), the introduction of Fe and Mn has slight influences on the interaction between LG and PE while a negative effect of PE on the devolatilization of LG in LG/PE can be largely diminished with the involvement of Ni and Co. Kinetic analysis reveals that the pyrolysis of LG and PE can be well fitted by a single first order model reaction while two consecutive first order model reactions are needed to exactly describe the co-pyrolysis of LG/PE with or without transition metals. The E value of LG and PE in the mixture is reduced by 6.11–21.62 kJ/mol and 7.67–50.11 kJ/mol, respectively, when 0.5 mmol/g Ni, Co, Fe or Mn was involved. Moreover, the concentration of Ni, the ratio of LG to PE and the heating rate play important roles on the thermal behavior and kinetics of the co-pyrolysis of LG/PE.

Thermal characterization and kinetic analysis of nano‐ and micro‐Al/NiO thermites: Combined experimental and molecular dynamics simulation study

In the experimental part of this study, thermal properties of the Al and NiO composites in micro‐ and nano‐sized Al are investigated. Differential scanning calorimetry (DSC) analysis of the onset temperatures of ignition, activation energy (Ea), frequency factor (A), rate constant (k), critical ignition temperature of thermal explosion (Tb), and self‐accelerating decomposition temperature (TSADT), as well as the thermodynamic parameters (ΔS≠, ΔH≠, and ΔG≠) are used to explore the thermal behavior and analyze the kinetics. Thermal analysis suggests that the mechanism is based on solid–solid diffusion and liquid–gas for the nano‐ and micro‐Al/NiO composite, respectively. Our results indicate that the incorporation of nano‐Al particles can significantly reduce the ignition temperature, Ea, A, k, Tb, and TSADT. In the second part of this work, molecular dynamics (MD) simulation is used to investigate the behavior of Al/NiO thermite reaction using the Reaxff force field to evaluate the experimental results. Theoretically, MD results show 1,154 K as the reaction ignition temperature, which is in reasonably good agreement with experimental temperature of 893°C (1,166 K). The radial distribution function (RDF) shows that no reaction occurs at 500 K but it is complete at 1,200 K.

Thermal effect and kinetic analysis on co-pyrolysis of furnace slag with cellulose from biomass

Abstract Metallurgical industry accounts for 20.40% of the total energy consumption in the industry of China. Energy saving from furnace slag of the steel industry is essential for the clean and green development of China. Thus, in this paper, the thermal effect and kinetic analysis of the biomass mixed with furnace slag at different mass ratios (10 wt%, 30 wt.% and 50 wt.%) was investigated via TGA under different heating rate from ambient temperature to 900 oC. Cellulose was selected as the primary organic compound in biomass, and iso-conversional method was applied for calculating activation energy. The maximum decomposition rate and temperature of maximum decomposition rate get higher as the heating rate increases. Furnace slag shows positive synergistic effects under 30% mass ratio with 6% higher volatile yield than that from theory calculation. The average activation energy values of CE, Slag-CE-10, Slag-CE-30, Slag-CE-50 were 187.54 kJ·mol-1, 260.81 kJ·mol-1, 132.79 kJ·mol-1 and 159.45 kJ·mol-1.

Thermal analysis kinetics of dioscorea saponin by mechanical activation

Dioscorea saponin isolated from the rhizome of Dioscorea nipponica Makino was activated by AGO mill. On the basis of TG-DSC analysis, two endothermic peak of dioscorea saponin after mechanical activation both moved back, and it had finished weightlessness in advance due to the accelerated decomposition. According to thermal analysis kinetics, the average thermal decomposition activation energy of dioscorea saponin after mechanical activation increased, and the maximum activation energy at different conversion rates moved back. According to the determining results of kinetic mechanism function, the thermal decomposition kinetics mechanism functions of dioscorea saponin before and after mechanical activation both fitted the Jander formula. After mechanical activation, the thermal decomposition kinetic mechanism of dioscorea saponin transformed from three-dimensional to two-dimensional diffusion.

Thermal debinding behavior of a low-toxic DMAA polymer for gelcast ceramic parts based on TG-FTIR and kinetic modeling.

In this work, the pyrolysis characteristics of a low-toxic N,N-dimethylacrylamide (DMAA) gel polymer was investigated through nonisothermal thermogravimetry (TG) and TG-FTIR analyses. Moreover, the thermal debinding kinetics of gelcast SiAlON ceramic parts was studied through three different kinetic models: the Coats–Redfern (C–R) method, distributed activation energy model (DAEM) and three-Gaussian-DAEM-reaction model (3-DAEM). The rationality and adaptability of the three models to the thermal debinding kinetics study were analyzed by comparison with experimental data. The results showed that three mass loss zones were observed in the temperature ranges of 100–320 °C, 320–520 °C and 520–600 °C, respectively, and the main pyrolysis gas products were CO2, H2O and CH4. The conversion rate (α) curves calculated by 3-DAEM were more consistent with the experimental values than those calculated with the C–R and DAEM methods. The fitting quality parameter (Fit%) was less than 2.63%, and the reaction rate (dα/dT) curves calculated by 3-DAEM were bimodal distribution curves, which were in good agreement with the experimental results. The kinetic parameters (E0,i, k0,i and σi) of the global thermal debinding process calculated by 3-DAEM were 116.00–145.79 kJ mol−1, 1.10 × 109 s−1 and 1.67–43.25 kJ mol−1, respectively. It is anticipated that the study achievements can be used to help predict the thermal debinding behavior and design a reasonable debinding technology for the gelcasting of ceramic parts.

Thermal analysis kinetics of Tartary buckwheat flour

Thermal analysis kinetics of Tartary buckwheat flour

Nucleation of supercooled Co melts under a high magnetic field

Abstract The nucleation behavior of undercooled Co melts under a strong static magnetic field up to 12 T was investigated using a glass fluxing technique in a superconductor magnet. Due to the strong magnetic field effect, our results show that the undercooled Co melt is separated into two sharp needle like parts before solidification, showing two consecutive recalescence peaks. The application of magnetic field leads to the variations of nucleation undercooling. The mean undercooling of the supercooled liquid is shown almost keep constant independent of the magnetic field, whereas, the maximum temperature during recalescence is found to be strongly depressed by the applied magnetic field. The effects of magnetic field on nucleation and subsequent recalescence process are interpreted based on the thermal dynamics and kinetics analysis of undercooled Co melts with response to high magnetic field.

Thermal instability and kinetics analysis on triacetone triperoxide (TATP)

Differential Scanning Calorimetry (DSC), Thermogravimetry(TG) and vent sizing package 2 (VSP2) were performed to understand thermal behavior and decomposition kinetics of triacetone triperoxide (TATP) under non-isothermal and adiabatic conditions, respectively. Then the maximum self-heating rate [(dT/dt)max], maximum pressure rise rate[(dP/dt)max] were acquired. DSC studies revealed a coupling phenomenon of decomposition reaction and phase transition. Based on the DSC data, the thermal decomposition kinetic parameters were worked out and compared through the Friedman and ASTM E698 methods. The results indicated that Heat of decomposition (ΔHd) was extraordinary large even up to 2700 Jg−1 for which recrystallized with methanol merely. The activation energy of which used methanol to recrystallize was 155.5kJ/mol by (ASTM) E-698 methods. By Friedman method Linear regression was able to reach a high enough level when the reaction progress (α) was between 0.1–0.9. The results can be used to calculate the optimal parameters for processing a safer design and establish the database of TATP for loss prevention protocol.