Thermal Decomposition Of Carbonates Research Articles

Direct reduction of calcium carbonate by coupling with methane dry reforming using NiO/S-1 as catalyst

Thermal decomposition of carbonate is an important process in the production of cement, refractory materials, and steel. Nevertheless, this process requires high temperature and is always accompanied with large amounts of CO2 emission. To reduce the decomposition temperature and simultaneously mitigate CO2 emissions, direct reduction of carbonate under a reducing atmosphere has been proposed as a novel strategy. This work mainly investigated the feasibility of direct reduction of CaCO3 by CH4 in the presence of a highly dispersed NiO/S-1 catalyst. It was found that the introduction of a CH4 atmosphere without a catalyst had little promotion effect on CaCO3 decomposition (as compared to air atmosphere), and no notable conversion of CO2 was observed. However, the presence of a highly dispersed NiO/S-1 catalyst significantly decreased the decomposition temperature of CaCO3 in a CH4 atmosphere, and most of the carbon species in CaCO3 can be converted to CO. To gain a comprehensive understanding of CaCO3 reduction in CH4, the effects of reaction temperature, CH4 concentration, and NiO loading in the NiO/S-1 catalyst were systematically explored. With the best-performing catalyst, i.e., 7NiO/S-1, complete CaCO3 decomposition and approximate 90 % CH4/CO2 conversion can be achieved under the condition of 750 °C and 25 vol% CH4. Characterization results indicated that the CaO particles obtained in the CH4 reducing atmosphere exhibited a more porous structure compared to that attained in air, due to the more intensive CaCO3 decomposition in CH4. Further data analysis revealed that reverse water-gas shift reaction also contributed to CO2 conversion during the reduction of CaCO3 in CH4. The findings obtained in this research can provide new perspectives for CO2 emission control and energy saving in traditional heavy-emission and high energy consumption industries.

Internal heat exchange effect on the thermal decomposition of carbonates in the phosphorus-containing raw materials

Internal heat exchange effect on the thermal decomposition of carbonates in the phosphorus-containing raw materials

Evidence of overpressure at the base of huge landslide

Overpressuring from generation of CO2 gas caused by thermal decomposition of basal carbonates can raise pore-fluid pressure and reduce friction during landsliding. We used thermogravimetry and dilatometry to determine the evidence of raised pore-fluid pressure from carbonate thermal decomposition at the base of the 2009 Jiweishan landslide. Results from thermal expansion experiments showed that the rock undergoes expansion and thermal fracture. At a heating rate of 20°C/min, the coefficient of linear thermal expansion increased sharply at 807.3 °C and reached a maximum of 36.6×10−6 °C −1 at 827.3 °C. DTG data show that the temperature of the maximum thermal decomposition rate of calcite is 852.5°C. The evidence showed that CO2 gas can produce great pressure during the rapid sliding process of Jiweishan landslide, and it is conducive to reduce the effective normal load. In addition, thermal fracture may be a explanation for the ultra-low friction during the rapid sliding by reducing the strength of the rock at the sliding surface and making it more easily entrained.

The analysis of gas evolved from casting powder during heating in the mold

In this paper, the thermal stability of two commercial casting powders was assessed with respect to registered mass changes and evolved gas analysis using a combination of TG/DTA/EGA simultaneous thermal analysis methods. The experiments were conducted in a temperature range of 50 ÷ 1300 °C, in an oxidation atmosphere, with a heating rate of 10 K min−1. The results presented in the article perfectly fit into the research trend related to the emission of gases from powders, using for this purpose coupled TG/EGA techniques of thermal analysis. Thermogravimetric measurements together with simultaneous EGA analysis of gases released from the samples enable the identification of the main reactions responsible for mass disturbance. The main registered mass losses were associated with carbon oxidation and thermal decomposition of carbonates presented in investigated powders. Based on the DTA results, melting temperature, as well as other endo/exothermal effects of reactions taking place in the system, was elaborated. The possibility of FactSage usage, to elucidate the influence of selected components on the viscosity of investigated casting powders, is also presented. On the basis of the conducted research, it was found that recorded mass disturbance was not associated with the evaporation of components affecting the viscosity of casting powder.

Geochemical characteristics of natural gases related to Late Paleozoic coal measures in China

By 2013, more than 20 gas fields related to Late Paleozoic coal measures have been discovered in China, primarily distributed in the Bohai Bay, Ordos, Sichuan, and Junggar Basins. The total proven reserve in these gas fields is more than 3200 × 109 m3, accounting for 30.1% of the proven gas reserves in China. After analyzing the molecular compositions, stable carbon isotopes, and helium isotopes of 375 gas samples, genetic types and origins of the natural gas, as well as the secondary alterations it experienced, are discussed in this study. Most of the natural gas related to the Late Paleozoic coal measures are coal-type gas, with some of the gases from the Sichuan Basin and the Jingbian gas field in the Ordos Basin being oil-type gases generated from marine mudstones in the Permian Longtan Formation and marine carbonates in the Ordovician Majiagou Formation, respectively. The equivalent vitrinite reflectance values based on stable carbon isotopes of natural gases vary from 0.8% to 2.5%, indicating the mature to over mature stage. Positive carbon isotope series (δ13C-CH4 < δ13C-C2H6 < δ13C-C3H8) are observed in most gas samples, and carbon isotope reversals occur in the forms of δ13C-CH4 > δ13C-C2H6 and δ13C-CH4 < δ13C-C2H6 > δ13C-C3H8. The form of δ13C-CH4 > δ13C-C2H6 is primarily resulted from the mixing of oil-type gases of different maturities, while the form of δ13C-CH4 < δ13C-C2H6 > δ13C-C3H8 is primarily resulted from the mixing of coal-type gases of different maturities. High concentrations of hydrogen sulfide in natural gas from the Sichuan Basin and the Chenghai gas field in the Bohai Bay Basin are resulted from thermochemical sulfate reduction (TSR), which causes, to some extent, the fractionation of carbon isotopes. By contrast, the fractionation of methane carbon isotopes resulting from the TSR effect is not clear. Carbon dioxide from the Bohai Bay and Junggar Basins is primarily biogenic, generated via the thermal decomposition of organic matter, while that from the Ordos Basin, Sichuan Basin, and Chenghai gas field is generated via the thermal decomposition of carbonates. Carbon dioxide related to the TSR effect has also contributed to the Sichuan Basin and Chenghai gas field.

Geochemical characteristics of He and CO2 from the Ordos (cratonic) and Bohaibay (rift) basins in China

According to the compositional and isotopic analyses of He, CO2 and CH4 of 95 gas samples from the Ordos Basin and 76 gas samples from the Bohaibay Basin in China, this study carried out a detailed investigation on the geochemical characteristics of helium and CO2 from the cratonic and rift basins, especially the cratonic Ordos Basin and rift Bohaibai Basin in China. Compared to the rift Bohaibay Basin, the cratonic Ordos Basin has lower level of helium and CO2, lower R/Ra ratio and lower δ13CCO2 maximum value. When the content of CO2 is <10%, both cratonic and rift basins have organic CO2 associated with the hydrocarbon generation process and inorganic CO2 from the thermal decomposition of carbonates or dissolution of organic acid. Rift basin can also have CO2>20% and δ13CCO2 of −6±2‰ or −4‰–−9‰, which is of volcanic-magmatic or mantle-derived origin, while cratonic basin has no such type of CO2. The cratonic basins (Ordos, Sichuan) have CO2<5% and relatively smaller variation range of δ13CCO2, i.e., 25.6‰ (−0.8‰–−26.4‰). The rift basins have higher level of CO2, R/Ra ratios and δ13CCO2 values. The content of CO2 can reach 100%, the R/Ra ratio can be up to 6.45 and the variation range of δ13CCO2 is 34‰ (7‰–−27‰). Bigger variation range of δ13CCO2 implies stronger tectonic activities, which is not favorable for the gas accumulation. While smaller variation range means more stable structure, which is favorable for the discovery of large gas fields. Sample in the cratonic basin in China generally has CH4/3He of 109–1012 and R/Ra<0.1 and in the rift basin it has CH4/3He of 105–1013 and R/Ra of 0.1–6.45. It is concluded that methane with CH4/3He≤108 is of inorganic origin and methane with CH4/3He≥1011 is of organic origin. The regression equation for the CH4/3He-R/Ra in the cratonic basin is: y=3E+11e−46.28x and it is: y=4E+10e−1.791x in the rift basin. Both Ordos and Bohaibay basins found gas wells with He>0.05%, which has significant commercial values and provides a clue for the exploration of helium-rich gas fields. Traps with R/Ra>2 is a favorable clue for the discovery of CO2 gas fields. Seven CO2 gas fields have been found in the Bohaibay Basin, but no systematic development has been carried out and only some liquid CO2 has been injected for tight oil from the Huagou CO2 gas field.

The role of petrography on the thermal decomposition and burnability of limestones used in industrial cement clinker

The present research examines the influence of the petrographic features on the thermal decomposition and burnability of three limestones, the main raw materials for Portland cement-making. A detailed characterisation of the limestones has been performed by means of optical microscopy and X-Ray Powder Diffraction. The carbonate thermal decomposition was conducted under isothermal conditions by means of in situ High Temperature X-Ray Powder Diffraction and the heated samples were further investigated by Scanning Electron Microscopy. Three kiln feeds were then prepared and submitted to burning trials and the temperature of occurrence of the main clinker phases was investigated as well as the content of the uncombined CaO in the heated samples was determined by using the Franke method. The results attest that the microfabric, a combination of depositional and diagenetic features, drives the kinetics of the thermal decomposition of the selected limestones as well as it appears to influence the temperature of crystallisation of the main clinker phases and the uncombined CaO content in the final clinker. In particular, the limestone with the lowest micrite to sparite ratio (1) exhibits the lowest Apparent Activation Energy (E a ) value and the highest rate of calcination and (2) requires a lower temperature for observing the clinker phases crystallisation and has the lowest content of uncombined CaO in the final clinker, thus reflecting a high burnability of the limestone.

Synthesis of Cobalt Oxide Nanostructures on Carbon Paper Using Intense Pulsed Light (IPL) and Supercapacitor Electrode Applications

Transition metal oxides have received tremendous interests in supercapacitor materials over the last decade because they can provide higher energy density than conventional carbon materials and better electrochemical stability than polymer materials. They not only store energy like electrostatic carbon materials but also exhibit electrochemical faradaic reactions between electrode materials and ions within appropriate potential windows. Several methods have been used to synthesize metal oxide nanostructures including chemical bath deposition, hydroxide decomposition, thermal decomposition of carbonates, nanocasting, electrodeposition, combustion, coprecipitation, and the sol-gel method. Many of these have drawbacks in that they are energy consuming, lengthy and involve multiple steps. Especially, all methods require calcinations/heat treatment at 200-600oC for 1-24hrs. Therefore, faster, more facile and energy efficient methods for metal oxide nanostructure production are of interest. Here we report an agile and facile method for the preparation of high-performance supercapacitive cobalt oxide nanoflakes by using an intense pulsed light (IPL) technology. By this method, the cobalt oxide formation can be accomplished within milliseconds by irradiating the broad wavelength light with high energy density on cobalt oxide precursor, which is exceptionally faster than other metal oxide formation methods. We have fabricated cobalt oxide nanoflakes on flexible carbon-paper substrate by using the IPL technique. The as-prepared substrates are further utilized as a supercapacitor electrode, and their supercapacitive performance will be discussed in the presentation.

Volatile and Organic Compositions of Sedimentary Rocks in Yellowknife Bay, Gale Crater, Mars

H2O, CO2, SO2, O2, H2, H2S, HCl, chlorinated hydrocarbons, NO, and other trace gases were evolved during pyrolysis of two mudstone samples acquired by the Curiosity rover at Yellowknife Bay within Gale crater, Mars. H2O/OH-bearing phases included 2:1 phyllosilicate(s), bassanite, akaganeite, and amorphous materials. Thermal decomposition of carbonates and combustion of organic materials are candidate sources for the CO2. Concurrent evolution of O2 and chlorinated hydrocarbons suggests the presence of oxychlorine phase(s). Sulfides are likely sources for sulfur-bearing species. Higher abundances of chlorinated hydrocarbons in the mudstone compared with Rocknest windblown materials previously analyzed by Curiosity suggest that indigenous martian or meteoritic organic carbon sources may be preserved in the mudstone; however, the carbon source for the chlorinated hydrocarbons is not definitively of martian origin.

Synthesis of Spinel MnCo2O4 by Thermal Decomposition of Carbonates and Kinetics of Thermal Decomposition of Precursor

The cubic MnCo2O4 was prepared by calcining MnCO3-2CoCO3⋅1.5H2O above 600 ∘C in air. The precursor and its calcined products were characterized by thermogravimetry and differential scanning calorimetry, Fourier transform infrared spectroscopy, X-ray powder diffraction, scanning electron microscopy, and vibrating sample magnetometer. The result showed that high-crystallized MnCo2O4 with cubic structure [space group Fd-3m(227)] was obtained when the precursor was calcined above 600 ∘C in air for 6 h. Magnetic characterization indicated that cubic MnCo2O4 behaved weak magnetic behavior at room temperature. The thermal process of the precursor in air experienced three steps, which are: first, the dehydration of 1.5 water molecules, then the decomposition of MnCO3-2CoCO3 into cubic MnO2 and cubic Co3O4, and at last the reaction of MnO2 with Co3O4 into cubic MnCo2O4. Based on the KAS equation, the values of the activation energies associated with the thermal process of MnCO3-2CoCO3⋅1.5H2O were determined.

QUANTUM CHEMICAL STUDY ON THERMAL DECOMPOSITION MECHANISM OF CALCIUM CARBONATE

A detailed quantum chemical calculation is performed at the MP2(full)/6-311G* level to explore the mechanism of calcium carbonate thermal decomposition. Four microscopic pathways are identified. The rate constants of rate-determining steps in four pathways are calculated over a temperature range 298–1200 K. The calculating results show that only path A (R( CaCO 3) → IM 1 → P( CaO + CO 2)) and path B (R( CaCO 3) → IM B1 → IM B2 → P( CaO + CO 2) have contributions to the CaCO 3 thermal decomposition, and path A may be more favorable than path B. The present theoretical studies may provide useful information in understanding reaction mechanism of metal carbonates at the molecular level.

Isotopic and geochemical investigation of two distinct Mars analog environments using evolved gas techniques in Svalbard, Norway

The 2010 Arctic Mars Analog Svalbard Expedition (AMASE) investigated two distinct geologic settings on Svalbard, using methodologies and techniques to be deployed on Mars Science Laboratory (MSL). AMASE-related research comprises both analyses conducted during the expedition and further analyses of collected samples using laboratory facilities at a variety of institutions. The Sample Analysis at Mars (SAM) instrument suite on MSL includes pyrolysis ovens, a gas-processing manifold, a quadrupole mass spectrometer (QMS), several gas chromatography columns, and a Tunable Laser Spectrometer (TLS). An integral part of SAM development is the deployment of SAM-like instrumentation in the field. During AMASE 2010, two parts of SAM participated as stand-alone instruments. A Hiden Evolved Gas Analysis-Mass Spectrometer (EGA-QMS) system represented the EGA-QMS component of SAM, and a Picarro Cavity Ring Down Spectrometer (EGA-CRDS), represented the EGA-TLS component of SAM. A field analog of CheMin, the XRD/XRF on MSL, was also deployed as part of this field campaign. Carbon isotopic measurements of CO2 evolved during thermal decomposition of carbonates were used together with EGA-QMS geochemical data, mineral composition information and contextual observations made during sample collection to distinguish carbonates formation associated with chemosynthetic activity at a fossil methane seep from abiotic processes forming carbonates associated with subglacial basaltic eruptions. Carbon and oxygen isotopes of the basalt-hosted carbonates suggest cryogenic carbonate formation, though more research is necessary to clarify the history of these rocks.

The detection of carbonate in the martian soil at the Phoenix Landing site: A laboratory investigation and comparison with the Thermal and Evolved Gas Analyzer (TEGA) data

Data collected by Phoenix Lander’s Thermal and Evolved Gas Analyzer (Phoenix-TEGA) indicate carbonate thermal decomposition at both low and high temperatures. The high-temperature thermal decomposition is consistent with calcite, dolomite, or ankerite, (3–6wt.%) or any combination of these phase or, presumably, solid solutions of these phases having intermediate composition. The low-temperature thermal decomposition is consistent with the presence of magnesite or siderite, their solid solutions, or any combination of magnesite and siderite, and possibly other carbon-bearing phases (e.g., organics). The carbonate concentration for the low temperature release, assuming magnesite–siderite, is ∼1.0wt.%. This revised interpretation of the Phoenix-TEGA data resulted from new laboratory measurements of carbonate decomposition at a Phoenix-like 12mbar atmospheric pressure. Phoenix carbonate was inherited in ejecta from the Vastitas Borealis and Scandia regions, inherited from material deposited by aeolian processes, and/or formed in situ at the Phoenix Landing site (pedogenesis). Inherited carbonate implies multiple formation pathways may be represented by carbonates at the Phoenix Landing site. Soil carbonates and associated moderate alkalinity indicate that the soil pH is favorable for microbial activity at the Phoenix Landing site and presumably throughout the martian northern plains.

Calcium carbonate thermal decomposition in white-body wall tile during firing. II. Influence of body thickness and calcite content

The thermal decomposition process of the calcium carbonate (calcite powder) contained in porous ceramic pieces, with the same composition as that used industrially to manufacture white-firing wall tile bodies, was studied using test disks with different thicknesses and calcite concentrations.The experiments were conducted in a CO2-free air atmosphere, and the results confirmed the validity of the kinetic model and the equation proposed in a previous paper to reproduce the experimental results in the studied range of operating conditions.

Effect of Mn Doping on the Dielectric and Electrical Conductivity of CaBi4Ti4O15 Ceramics

Ca1-xMnxBi4Ti4O15 (CMBT) ceramics were prepared using solid state reaction method with x = 0 to 0.3. X-ray diffraction confirms the orthorhombic structure of CMBT ceramics. FTIR and Raman spectroscopy study indicates the formation of single phase layered perovskite material. Thermo-gravimetric studies shows that the thermal decomposition of carbonates was completed at 700°C for Mn doped samples whereas was 950°C for CaBi4Ti4O15 ceramic. DC conductivity exhibits non-Arrhenius behaviour and the activation energy decrease from 1.35 to 1.0eV with increase in x from 0 to 0.3. The room temperature dielectric constant decreases from 160 to 140 at 1MHz with the increase in Mn concentration (x = 0–0.3). Curie's temperature (790°C) was found to be independent of Mn incorporation at Ca site.

The long runout of the Heart Mountain landslide: Heating, pressurization, and carbonate decomposition

The Heart Mountain landslide of northwestern Wyoming is the largest subaerial landslide known. This Eocene age slide slid ∼50 km along a shallow 2° slope, posing a long‐standing enigma regarding its emplacement mechanism. We suggest here a mechanism for the catastrophic emplacement of the Heart Mountain landslide that is independent of slide triggering. The mechanism is a feedback between shear heating, thermal pressurization, and thermal decomposition of carbonates at the slide shear zone. Such a feedback arises when a porous, fluid‐filled shear zone heats up because of frictional sliding. If the shear zone is confined, the generated heat leads to pore pressure rise, which in turn reduces frictional resistance to sliding, leading to acceleration. Temperatures at the shear zone quickly reach the decomposition temperature of carbonates. Since the shear zone of the Heart Mountain slide is located within a dolomite layer, it is expected that thermal decomposition of dolomite occurred within the Heart Mountain shear zone. This prediction is supported by ample field evidence for carbonate decomposition during the emplacement. Simulation of the sliding dynamics of the Heart Mountain block, accounting for feedback between shear heating, thermal pressurization, and thermal decomposition of carbonates, successfully reproduce the travel distance of the Heart Mountain block. The simulation results also predict that the maximum sliding velocity ranged between tens of meters per second to more than 100 m s−1 (depending on model assumptions) and that the duration of sliding was of the order of a few tens of minutes, in agreement with previous assessments.

New incremental isoconversional method for kinetic analysis of solid thermal decomposition

A simple and precise incremental isoconversional integral method based on Li-Tang (LT) method is proposed for kinetic analysis of solid thermal decomposition, in order to evaluate the activation energy as a function of conversion degree. The new method overcomes the limitation of LT method in which the calculated activation energy is influenced by the lower limit of integration. By applying the new method to kinetic analysis of both the simulated nonisothermal case and experimental case of strontium carbonate thermal decomposition, it is shown that the dependence of activation energy on conversion degree evaluated by the new method is consistent with those obtained by Friedman (FR) method and the modified Vyazovkin method. As the new method is free from approximating the temperature integral and not sensitive to the noise of the kinetic data, it is believed to be more convenient in nonisothermal kinetic analysis of solid decompositions.

Calcium carbonate thermal decomposition in white-body wall tile during firing. I. Kinetic study

This study examines the thermal decomposition of calcium carbonate, contained in disk-shaped test pieces formed from a mixture of raw materials of a similar composition and characteristics to those of the mixtures customarily used for the manufacture of white-body wall tile. The experiments were conducted under isothermal conditions at different temperatures in the range 825–950 °C in an air stream free of carbon dioxide. The experimental results have been interpreted using the Shrinking Unreacted Core kinetic model, assuming that, at low conversion degrees, the process is only controlled by the chemical reaction step of CaCO 3 decomposition, while at high conversion degrees the diffusion of the resulting CO 2 through the porous structure of the reacted ceramic layer also affects the process. The derived equations, which relate the conversion degree of calcium carbonate in the ceramic body to residence time, temperature, and initial porosity of the test pieces, allow the experimental results to be satisfactorily reproduced.

Correction to “Thermal decomposition of carbonates in fault zones: Slip‐weakening and temperature‐limiting effects”

[4] The conclusions of the paper are not changed: The endothermic character of the decarbonation reaction limits the co-seismic temperature increase; decarbonation is a source of CO2 that significantly increases the slip-weakening effect of thermal pressurization; the pore fluid pressure exhibits an initial phase of increase due to thermal pressurization, then a sudden acceleration of generated pore pressure when the solid decomposition is activated. The increase of permeability limits the pore pressure that reaches a maximum and then decreases. The numerical results reproduce this pore pressure pulse and the initial fault weakening followed by a restrengthening of the shear stress.

Thermal decomposition of carbonates in fault zones: Slip‐weakening and temperature‐limiting effects

During an earthquake, the heat generated by fault friction may be large enough to activate the devolatilization of minerals forming the fault rocks. In this paper, we model the mechanical effects of calcite thermal decomposition on the slip behavior of a fault zone during an earthquake. To do so, we introduce the coupled effects of calcite volume loss, heat consumption, and CO2 production in the theoretical analysis of shear heating and thermal pressurization of pore fluids. We consider a rapidly deforming shear band consisting of a fluid‐saturated carbonate rock. The equations that govern the evolution of pore pressure and temperature inside the band and the mass of emitted CO2 are deduced from the mass and energy balance of the multiphase‐saturated medium and from the kinetics of the chemical decomposition of calcite. Numerical simulation of seismic slip at depths of 5 to 8 km show that decarbonation has two critical consequences on fault slip. First, the endothermic reaction of calcite decomposition limits the coseismic temperature increase to less than ∼800°C (corresponding to the initiation of the chemical reaction) inside the shear band. Second, the rapid emission of CO2 by decarbonation significantly increases the slip‐weakening effect of thermal pressurization. The pore pressure reaches a maximum and then decreases due to the reduction of solid volume, causing a restrengthening of shear stress. Our theoretical study shows, on the example of decarbonation, that the thermal decomposition of minerals is an important slip‐weakening process and that a large part of the frictional heat of earthquakes may go into endothermic devolatilization reactions.