Decomposition Of Calcium Carbonate Research Articles

Influence of the Crystal Forms of Calcium Carbonate on the Preparation and Characteristics of Indigo Carmine-Calcium Carbonate Lake

In this study, indigo carmine (IC)-calcium carbonate lakes with different crystalline forms of calcium carbonate were prepared through co-precipitation methods, and the properties of these lakes and their formation mechanisms were investigated. The results showed that amorphous calcium carbonate (ACC) exhibited the smallest particle size and the largest specific surface area, resulting in the highest adsorption efficiency. Vaterite, calcite, and aragonite followed after ACC in decreasing order of adsorption efficiency. Kinetic analysis and isothermal analysis revealed the occurrence of chemisorption and multilayer adsorption during formation of the lakes. The FTIR and Raman spectra suggested participation of sulfonic acid groups in chemisorption. Appearance of IC significantly altered TGA curves by changing weight loss rate before decomposition of calcium carbonate. EDS analysis revealed the adsorption of IC predominantly happened on the surface of calcium carbonate particles rather than the interior.

Insight into mechanisms behind complex reactions by high-dimensional vectorized dynamic analysis

Insight into the mechanisms governing complex reactions requires a thorough and reliable analysis integrating various detected signals. This paper presents a vectorized method for describing chemical reactions and comprehensively discusses the theory and framework of high-dimensional vectorized dynamic analysis for complex reactions. Experimental studies of typical reaction processes such as thermal decomposition of calcium carbonate, thermal oxidation of copper(II) sulfide (CuS), and thermal treatment of industrial waste of aluminum (Al) dross were conducted and analyzed within the high-dimensional vectorized framework. The study identified five sub-reactions of thermal oxidation of CuS, six sub-reactions of Al dross, particularly cross-reactions, competitive reactions, and consecutive reactions that emphasize the mechanisms governing complex reactions. Besides, the study discusses the feasibility, functionality, and application of high-dimensional vectorized dynamic analysis for complex reaction processes including dimension selection, sub-reaction identification, and determination of sub-reaction kinetic parameters. Overall, the high-dimensional vectorized dynamic analysis is confirmed as a scientifically sound method for gaining insight into the mechanisms behind complex reactions. A combination of artificial intelligence (AI) and the high-dimensional vectorized dynamic analysis will further improve significantly the capabilities of identification and analysis of the complex reaction processes.

A Review on durability and microstructure of Fly-Ash based geopolymer concrete (FA-GPC)

Concrete, being the fundamental material in the construction industry, relies largely on cement for its structural integrity and performance. However, new researches have emphasized a significant concern—the considerable increase in global greenhouse gas emissions linked to cement manufacturing. This rise in emissions derives mostly from the thermal decomposition of calcium carbonate during the clinkering process, establishing cement as a key contributor to the rising CO2 footprint. This alarming trend demands prompt attention and inventive remedies. This study intends to solve this important environmental issue by studying the transformational potential of Geopolymer Concrete (GPC) as a sustainable alternative. By adding FA, an abundant industrial waste by-product, as a supplementary cementitious material (SCM) in GPC, we have the possibility to dramatically cut carbon emissions by up to 80%.This transition towards sustainable materials not only decreases the load on traditional cement resources but also illustrates how waste materials may be utilized for the sake of the environment. Our analysis comprises factors such as consistency, curing temperature, chloride corrosion resistance, XRD (X-ray Diffraction) and SEM (Scanning Electron Microscopy) investigations. Through these findings, we hope to underline the considerable potential of GPC, particularly when strengthened with FA, as a strong tool for decreasing the carbon footprint within the building sector.

Research on the regulatory mechanism of pore structure in soil matrix prepared by fluidized bed calcination of coal gangue

As a bulk industrial solid waste, coal gangue has caused serious pollution to the environment, and its application in the field of soil amendments has been widely studied, but the mechanism of pore structure regulation of coal gangue as soil substrate has not been reported in the literature. In this paper, the physical and chemical properties of coal gangue are analyzed, and its particle size, element content, and occurrence state are defined. The regulation mechanism of pores and pores in preparing matrix soil with coal gangue is revealed, and an efficient and energy-saving fluidizing activation technology is proposed to prepare active matrix soil. The results show that matrix soil with optimal pore structure can be obtained by fluidized bed calcination at 700 °C for 15 min, with a porosity of 55.0 %, volumetric water content of 28.7 %, and gas phase rate of 24.8 %. The technology also removes carbon, which is prone to natural fires, and fixes sulfur, which is good for plant growth. The formation and regulation mechanism of pores structure of soil matrix prepared by fluidized calcination of coal gangue is as follows: The oxidation reaction of carbon and the decomposition of minerals in coal gangue will form pore structures. Adjusting the reaction temperature and time, controlling the rate of carbon oxidation reaction, and the rate of mineral decomposition can achieve the goal of regulating the pore structure. Large pores with a pore size greater than 0.03 mm are formed by the oxidation of carbon and the decomposition of kaolinite. The pores with a diameter of 0.0001–0.03 mm are formed by the overflow of carbon dioxide gas, which is generated by the oxidation reaction of carbon embedded in coal gangue particles and the decomposition of calcium carbonate. The results of this study will provide technical and theoretical support for promoting the comprehensive utilization of coal gangue and improving environmental protection.

Experimental investigation on the deterioration of the physical and mechanical properties of autoclaved aerated concrete at elevated temperatures

Abstract Autoclaved aerated concrete (AAC) has been extensively studied and applied in the past decades because of its excellent thermal insulation and acoustic performance, energy efficiency, and outstanding structural performance. To investigate the deterioration characteristics of AAC under high temperatures, the physico-mechanical properties of AAC at different temperatures were tested by mass loss, wave velocity, and compressive tests, and the deterioration mechanism was discussed by X-ray diffraction (XRD), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) tests. The results showed that after exposure to elevated temperatures, the parameters of apparent form, mass loss, wave velocity, and compressive strength underwent remarkable conversions. It was observed that the ultrasonic behavior of AAC was affected at high temperatures as it increased at 100°C and decreased beyond 100°C. In addition, the compressive strength exhibited a two-stage transformation, slightly increased from ambient temperature to 300°C, and exhibited a rapid reduction beyond 300°C. At 900°C, the specimen lost its strength. By XRD, TGA, and SEM, it was confirmed that a series of physicochemical changes in AAC, such as the water escape and evaporation, decomposition of calcium silicate hydrate and calcium carbonate, and structural damage, were the primary reasons for the deterioration of the physical and mechanical properties at elevated temperatures.

A thermodynamic view on the in-situ carbon dioxide reduction by biomass-derived hydrogen during calcium carbonate decomposition

In the carbonate industry, deep decarbonization strategies are necessary to effectively remediate CO2. These strategies mainly include both sustainable energy supplies and the conversion of CO2 in downstream processes. This study developed a coupled process of biomass chemical looping H2 production and reductive calcination of CaCO3. Firstly, a mass and energy balance of the coupled process was established in Aspen Plus. Following this, process optimization and energy integration were implemented to provide optimized operation conditions. Lastly, a life cycle assessment was carried out to assess the carbon footprint of the coupled process. Results reveal that the decomposition temperature of CaCO3 in an H2 atmosphere can be reduced to 780 oC (generally around 900 oC), and the conversion of CO2 from CaCO3 decomposition reached 81.33% with an H2:CO ratio of 2.49 in gaseous products. By optimizing systemic energy through heat integration, an energy efficiency of 86.30% was achieved. Additionally, the carbon footprint analysis revealed that the process with energy integration had a low GWP of -2.624 kgCO2-eq·kg-CaO-1. Conclusively, this work performed a systematic analysis of introducing biomass-derived H2 into CaCO3 calcination and demonstrated the positive role of reductive calcination using green H2 in mitigating CO2 emissions within the carbonate industry.

Numerical simulation of altering the raw meal inlet position in a novel swirl precalciner

Conducted a numerical simulation to model a novel swirl precalciner, investigating how altering in the position of the raw meal inlet affects the internal gas flow, temperature field, and component concentration field within the precalciner. Applied the Realizable k-? two-equation turbulent model to the continuous phase. For the particle phase (pulverized coal), employed the Discrete Particle Model and the discrete random walk model. Simulated the combustion of pulverized coal and the decomposition of calcium carbonate by using the Species Transport model combined with the Finite-Rate/Eddy-Dissipation model. Modeled the generation of NOx using a NOx model. The results show that, in comparison to the condition with four raw meal inlets, the six raw meal inlets condition has a better coupling of pulverized coal combustion and raw meal decomposition. The decomposition rate of raw meal has seen a slight improvement, and there is a significant improvement in the occurrence of localized high temperatures within the precalciner, resulting in a reduction of the outlet NOx concentration from 1251 ppm to 225 ppm.

Effects of nano-Al2O3 dosage on pyrolysis kinetics and formation of hydration products in tailings wet shotcrete

The use of tailings as aggregate for the preparation of wet shotcrete is one of the most important technical approaches to the sustainable development of mines. In this study, the pyrolysis kinetics of tailings wet shotcrete with different Nano-Al2O3(NA) dosage and the formation mechanism of hydration products are carried out based on the theory of pyrolysis kinetics and various micro characterization methods. The findings show that 1% NA dosage(NA1) specimen significantly improves uniaxial compressive strength by 48.72% and 34.69% compared to NA0 and NA2, respectively. Pyrolysis of concrete has 3 stages: dehydration of ettringite(AFt) and calcium silicate hydrate(C-S-H), dehydroxylation of calcium hydroxide(CH), and CO2 release from calcium carbonate decomposition. These stages conform to the S-B model. The average apparent activation energy for NA1 specimen during the first pyrolysis stage is 114.01 kJ/mol, indicating an increased energy barrier for the pyrolysis of hydration product, which diminishes when NA dosage exceeds 1%. Furthermore, NA1 specimen exhibits enhanced kinetic parameters, including a notable increase in the preexponential factor during the first pyrolysis stage. This suggests higher activation and effective collision of molecules, leading to optimal AFt and C-S-H formation at 1% NA dosage. Microscopic and thermal analyses reveal that NA aids TWSC hydration through gap filling, nucleation, bond-breaking recombination on tailings surfaces, and calcium (alumino) silicate hydrate(C-(A)-S-H) formation. This process augments hydration product generation, decreases microstructural porosity, and enhances macroscopic strength. However, exceeding 1% NA dosage inversely affects these properties, highlighting an optimal NA concentration for maximizing TWSC performance.

Screening of Acetic Acid Bacteria Isolated from Various Sources for Use in Kombucha Production

The objective of this study was to isolate and identify strains of Acetobacter suitable for use in the development of a complex microbial culture for producing Kombucha and to examine the fermentation characteristics for selection of suitable strains. A medium supplemented with calcium carbonate was used for isolation of acetic acid bacteria from 22 various sources. Colonies observed in the clear zone resulting from decomposition of calcium carbonate by acid produced by microorganisms were collected. Identification of the collected strains was based on biological and morphological characteristics, and the results of base sequence analysis. A total of 37 strains were identified, including six species in the Acetobacter genus: Acetobacter pasteurianus, Acetobacter orientalis, Acetobacter cibinongensis, Acetobacter pomorum, Acetobacter ascendens, and Acetobacter malorum, as well as one species in the Gluconobacter genus, Gluconobacter oxydans. Among thirty-seven strains, seven strains of acetic acid bacteria with exceptional acid and alcohol tolerance were selected, and an evaluation of their fermentation characteristics according to fermentation temperature and period was performed. The results showed a titratable acidity of 1.68% for the Acetobacter pasteurianus SFT-18 strain, and an acetic acid bacteria count of 9.52 log CFU/mL at a fermentation temperature of 35 °C. The glucuronic acid and gluconate contents for the Gluconobacter oxydans SFT-27 strain were 10.32 mg/mL and 25.49 mg/mL, respectively.

The thermal decomposition kinetics of carbonaceous and ferruginous manganese ores in atmospheric conditions

The thermal decomposition of carbonate minerals as pre-treatment before smelting reduces the energy requirement for smelting. It can also make the combustion of fossil fuels for heating unnecassary. Thermal decomposition may become important in reducing greenhouse gas emissions when producing ferromanganese alloys while simultaneously reducing electrical energy demand during smelting. A kinetic reaction rate model for the thermal decomposition of manganese ores is presented, based on published reaction rate kinetics for the decomposition of manganese oxides and calcium carbonate. The model was validated against thermogravimetric data for two carbonaceous manganese ore samples and one ferruginous manganese ore sample. The reaction rate model shows that carbonate minerals in the manganese ores are decomposed at temperatures above 900 °C while pyrolusite is decomposed at temperatures from 450 °C to 500 °C. Mn2O3 decomposes rapidly at 550 °C. Braunite decomposition at temperatures below 1000 °C was negligible. The presence of organic carbon in the samples led to further reduction of the samples during thermal treatment.

Simulation on coal combustion and calcium carbonate decomposition in a 5500 t/d full scale cement calciner

With the continuous growth of global cement production, the increasing coal consumption in the cement industry has been drawing great attention, thus adopting advanced technologies to reduce energy consumption has become an important issue. To address this problem, this study carried out 3D Eulerian-Lagrangian simulations of the coupling process of pulverized coal combustion and CaCO3 decomposition in a 5500 t/d full-scale cement calciner. On the basis of the multiphase particle-in-cell (MP-PIC) approach, reaction models including devolatilization, combustion of char and volatiles, and CaCO3 decomposition are incorporated into the scheme. Detailed combustion characteristics including temperature distribution, carbon exhaust rate, and gas emission characteristics, as well as decomposition characteristics are comprehensively analyzed. Besides, effects of different operating performances including O2 content in bottom flue gas on carbon exhaust rate, CaCO3 decomposition rate, and NOx emission are also investigated. Results show that under the typical working condition with O2 concentration in the flue gas of 1.7 %, the CaCO3 decomposition rate can reach around 96.42 %, the carbon conversion rate is up to 98.65 %, and the NOx can be controlled at around 105 ppm. The increase of O2 content promotes higher carbon conversion rates with excessive O2 leading to higher NOx emission. Appropriately increasing the proportion of raw material flow rate in upper tubes can facilitate a more complete CaCO3 decomposition.

Hydrogenation of calcium carbonate to carbon monoxide and methane

The current cement, steel, refractory and calcium carbide industries rely on thermal decomposition of calcium carbonate (CaCO3) that forms calcium oxide (CaO) and carbon dioxide (CO2). Hydrogenation of CaCO3 may reduce or eliminate CO2 in CaO generation and simultaneously generate carbon monoxide (CO) and/or methane (CH4). This work mainly investigates CaCO3 hydrogenation conditions for CO and CH4 and establishes the kinetics for these reactions. It is found that CH4 forms at temperatures lower than that of CO2 but higher than that of CO. The rates of CO and CH4 formation increase with increasing hydrogen pressure (PH2) but that of CO peaks at PH2 of 0.05–0.10 MPa. The CO2, CO and CH4 yields are 17.7%, 81.4% and 0.9% at the PH2 of 0.10 MPa while 1.2%, 20.0% and 78.8% at the PH2 of 6.00 MPa. The kinetics of CaCO3 conversion and CO and CH4 formation can be better modeled by the shrinking core model (SCM) than the volume reaction model (VRM) and the gas reaction model (GRM). The activation energy (Ea) for CaCO3 conversion and CO and CH4 formation by SCM is 165.8, 156.4 and 211.9 kJ·mol−1, respectively, with the order of PH2 of 0.108, 0.005 and 0.673, respectively.

Complementary use of thermogravimetric analysis and oven to assess the composition and bound CO2 content of recycled concrete aggregates

The carbonation of recycled concrete aggregates (RCA) has emerged as a possible significant carbon sink to mitigate the increase of CO2 concentration in atmosphere and global warming. A reliable determination of bound CO2 content is thus needed to optimize carbonation processes but there is no real consensus on the existing quantification methods, mainly based on thermal decomposition of calcium carbonate. With the aim of developing a relevant quantification method of bound CO2 during the carbonation of RCA, an experimental study based on the combination of two main techniques – thermogravimetric analysis (TGA) and high-temperature oven – was performed at different scales: paste, mortar, and concrete. XRD analyses allowed highlighting the overlaps between the decomposition of portlandite and calcium carbonate polymorphs during linearly increasing temperatures. Oven and TGA with isothermal steps were found to provide consistent and complementary data on RCA composition and their bound CO2 content from initially dried specimens.

Carbon fiber to improve the resistance of high strength PVA-ECC to elevated temperatures

Engineered cementitious composite (ECC) with polyvinyl alcohol (PVA) fiber shows great potential in buildings and infrastructure constructions due to its characteristics of strain-hardening and multiple-cracking. However, its fire resistance shall be paid with great attention since the fibers would melt and components are prone to spall under elevated temperatures, especially for cement-based materials with high strength. Present study focuses on the fire resistance improvement of high strength ECC (HSECC) by adopting carbon fiber with higher thermal performance. Behaviors were qualitatively compared in the aspects of visual observation, surface cracking and spalling in HSECC with and without carbon fiber. Mass loss, residual strength and brittleness of all groups are quantitatively analyzed. Results show that carbon fiber enhances high temperature-exposed residual strength of HSECC and shows hysteresis effect on the decomposition of calcium hydroxide (CH) and calcium carbonate. The bridging and take-over effect of carbon fiber contributes to microcrack inhibition at elevated temperatures observed from surface cracking and micro-morphologies. HSECC with higher carbon fiber content shows greater resistance to high temperatures.

Activation of sawdust with eggshells

Eggshell is a kitchen waste containing abundance of calcium carbonate. The CO2 from decomposition of calcium carbonate can be used to activate biomass to produce activated carbon (AC) to realize full utilization of eggshells. In this study, the activation of poplar sawdust with non-contact eggshells and no carrier gas in a crucible at 900ºC was performed. The results indicated that the sawdust could be activated with only a given amount of CO2 from eggshells, developing mainly micropores (92.0 %, 612.2 m2/g) and rendering the AC of the superior capability to adsorb phenol in the aqueous phase. The CO2 mainly facilitated dehydrogenation, dehydration, deoxygenation of the CO in esters/lactones intermediates, gasification, carbonization reactions, etc, reducing the yields of AC but enhancing C/O and C/H ratios and thermal stability of the AC. In addition, the eggshells facilitated cracking reactions at the temperatures for the pyrolysis of sawdust, producing more light aliphatic organics, heavier phenolics, and gaseous products. The non-contact activation without carrier gas eliminates the issue of post-treatment such as separation of AC and activating agent, which also features low operating cost and produces simultaneously CaO-rich material as a solid base catalyst.

Experimental analysis on calcination and carbonation process in calcium looping for CO2 capture: study case of cement plants in Indonesia

AbstractCarbon dioxide (CO2) is the main contributor to greenhouse gases that affect global warming. The industrial sector is the third largest producer of CO2 and the cement industry is one of the industries that consistently produces the most significant CO2 emissions. The cement industry produces 5–8% of global CO2 emissions. Several methods for reducing specific CO2 emissions have been reported in the cement industry, including calcium looping, which uses the reversible reaction between calcination [calcium carbonate (CaCO3) decomposition] and carbonation [CO2 capture by calcium oxide (CaO)]. This work investigates calcium looping employing limestone obtained directly from several cement factories in Indonesia to observe the carbon-absorption characteristics of limestone from different mining locations. The experiment was carried out using a tube furnace equipped with a controlled atmospheric condition that functions as a calciner and a carbonator. X-ray diffraction and scanning electron microscopy with energy-dispersive x-ray spectroscopy characterization were conducted to analyse the changes in the experimental samples. The results demonstrated that the reactor configuration was capable of performing the calcination process, which converted CaCO3 to calcium hydroxide [Ca(OH)2], as well as the carbonation process, which captured carbon and converted it back to CaCO3. Parametric analysis was performed on both reactions, including pressure, temperature, duration, particle size and reaction atmosphere. The results show that the limestone obtained from all sites can be used as the sorbents for the calcium-looping process with an average reactivity of 59.01%. Limestone from cement plants in various parts of Indonesia has the potential to be used as carbon sorbents in calcium-looping technology. With a similar CO2 concentration as the flue gas of 16.67%, the experimental results show that Bayah limestone has the maximum reactivity, as shown by the highest carbon-content addition of 12.15 wt% and has the highest CO2-capture capability up to >75% per mole of Ca(OH)2 as a sorbent. Similar levels of the ability to capture CO2 per mole of Ca(OH)2 can be found in other limestones, ranging from 14.85% to 34.07%. The results show a promising performance of raw limestones from different mining sites, allowing further study and observation of the possibility of CO2 emission reduction in the sustainable cement-production process.

Replacing Lime with Rice Husk Ash to Reduce Carbon Footprint of Bituminous Mixtures

There have been several emphasized pathways toward a reduction in carbon footprint in the built environment such as recycling, technologies with lower energy consumption, and alternative materials. Among alternative materials, bio-based materials and nature inspired solutions have been well-received. This study examines the merits of using rice husk ash as a replacement for lime; lime has a high carbon footprint mainly associated with the decomposition of calcium carbonate to calcium oxide to form lime. Lime is commonly used in bituminous composites for roadway construction to mitigate their susceptibility to moisture damage. Replacing lime with a low-carbon alternative could allow a reduction in CO2 equivalent of bituminous composites. This paper studies the merits of using rice husk ash (RHA) as a substitute for conventional hydrated lime (HL) in bituminous composites. It should be noted that rice industries burn rice husks in a boiler as fuel, generating a substantial volume of RHA. The disposal of this ash has major environmental impacts associated with the contamination of air and water. Here, we study physical and chemical characteristics of both HL and RHA for use in bitumen mixtures. This was followed by examining the extent of dispersion of each filler in bitumen via optical microscopy to ensure their uniform dispersion. The properties of the mixtures were further studied using the Marshall mix design method. It was found that a 25.67% increase in Marshall stability and a 5.95% decrease in optimum binder content were achieved when HL was replaced by RHA at 4% filler concentration. In addition, mixtures containing RHA exhibited higher resistance to cracking and permanent deformation compared to mixtures containing HL. Additionally, 4% RHA in the mix showed stripping resistance similar to the conventional mix with HL. The mixture with 4% RHA had a lower carbon footprint with enhanced economic and environmental impacts compared to the conventional mix with HL. The study results provide insights pertaining to the merits of bio-based materials to reduce the carbon footprint of pavements.

Hybridized microfiltration-Fenton system for the treatment of greywater

The purpose of this study is to reuse greywater and prevent it from being released into the environment. In order to reduce the COD to the standard value, the combined method of membrane and advanced oxidation was used. Ten types of membrane samples with different concentrations of kaolin, alumina and calcium carbonate were prepared at a temperature of 1250(°C). The results of TGA, porosity and shrinkage analysis exhibited the decomposition of calcium carbonate at 800 (°C). The porosity and the average pore size of the membrane increased with the increase of calcium carbonate, so that by adding 5%, 10% and 15% of calcium carbonate to the mullite membrane, the porosity was 39%, 48% and 55% respectively, and the average pore size was 0.198, 0.283 and 0.306(µm) respectively. According to the results MAC(50−35−15) membrane, a promising mechanical strength of 17.9 (MPa) demonstrates a 58% porosity and a permeability of 19980(L/m2.h) of distilled water. Besides, the greywater was further treated with the Fenton process at a pH= 3 and a reaction time of 90 (min) to meet the required standards of reusing wastewaters. The optimal hydrogen peroxide (H2O2) and ferrous ion (Fe2+) values were 500 (mg/L) and 750 (mg/L), respectively. In addition, based on the COD results, the mullite membrane with 78.9% and the MAC(50−35−15) with 63.2% showed the highest and lowest rejection values, respectively. Similarly, the best COD removal efficiency of greywater was obtained at a value of 40 (mg/L) after treatment via the Fenton process.

A Physical Basis for Kinetic Compensation.

Kinetic compensation is a strong, positive correlation between the Arrhenius activation energy E and the frequency factor A for a reaction between the same reactants under similar experimental conditions or similar reactants under the same conditions, even though these parameters are supposed to be independent. The kinetic compensation effect (KCE) is demonstrated by a linear relationship between ln[A] and E/R in the eponymous Constable plot and has been the subject of more than 50 000 publications over the past 100 years, with no consensus opinion about the cause of this effect. In this paper, it is suggested that the linear relationship between ln[A] and E is the result of a real or spurious path dependence of the reaction history between the initial state of the pure reactant(s) and the final state of the pure product(s) having standard enthalpy and entropy differences, ΔH° and ΔS°, respectively. The single-step rate law approximation of a reversible reaction leads to T0 = H°/ΔS° as the dynamic thermal (thermodynamic) equilibrium temperature and 1/T0 = (ln[A̅/k0])/(E̅/R) as the slope of a Constable/KCE plot or the crossover temperature of Arrhenius lines in an isokinetic relationship (IKR), where A̅ and E̅ are mean values for the ensemble of compensating {Ei, Ai} pairs and k0 is a constant that accounts for the path dependence of the reaction history and reconciles the KCE with the IKR. This proposed physical basis for the KCE and IKR is supported by qualitative agreement between ΔH° and ΔS° calculated from the statistics of compensating {Ei, Ai} pairs in the literature, and the difference in the standard enthalpies and entropies of formation of the products and reactants for thermal decomposition of organic peroxides, calcium carbonate, and poly(methyl methacrylate).

Pyrolysis behavior and kinetic analysis of waste polypropylene-based complex for cable filler

To better understand the thermochemical conversion for the pyrolysis recycling of cable waste, the pyrolysis kinetics of the typical cable filler was investigated in detail. Thermogravimetric experiments were conducted at different heating rates ranging from 5 °C/min−1 to 40 °C/min−1. Three degradation stages were observed in the process of pyrolysis. The influence of air on the superposition of the first two peaks was also identified. The activation energy at different heating rates was calculated using three commonly used model-free methods. A three-component reaction scheme was proposed to describe the whole degradation process. The first one was associated with the stearic acid decomposition, the second was dominated by the polypropylene decomposition, while the third was attributed to the calcium carbonate decomposition. The created reaction model combined with an optimization algorithm was applied to determine the kinetic parameters. The values of activation energy estimated by this method were in accordance with those by isoconversional methods, which verified the accuracy of the parameter calculation by the optimization algorithm. The predicted results based on the optimized parameters agreed well with the experimental data. Finally, the whole kinetics process was deconstructed into three independent reactions corresponding to all reactants and products.