Effect of CaO on catalytic combustion of semi-coke

Abstract Generally, adding a certain amount of an additive to pulverized coal can promote its combustion performance. In this paper, the effect of CaO on the combustion characteristics and kinetic behavior of semi-coke was studied by thermogravimetric (TG) analysis. The results show that adding proper amount of CaO can reduce the ignition temperature of semi-coke and increase the combustion rate of semi-coke; with the increase in CaO content, the combustion rate of semi-coke increases first and then decreases, and the results of TG analysis showed that optimal addition amount of CaO is 2 wt%. The apparent activation energy of CaO with different addition amounts of CaO was calculated by Coats–Redfern integration method. The apparent activation energy of semi-coke in the combustion reaction increases first and then decreases with the increase in CaO addition. The apparent activation energies of different samples at different conversion rates were calculated by Flynn–Wall–Ozawa integral method. It was found that the apparent activation energies of semi-coke during combustion reaction decreased with the increase in conversion.

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Effect of KMnO4 on catalytic combustion performance of semi-coke

Green Processing and Synthesis ◽

10.1515/gps-2020-0057 ◽

2020 ◽

Vol 9 (1) ◽

pp. 559-566

Author(s):

Luyao Kou ◽

Junjing Tang ◽

Tu Hu ◽

Baocheng Zhou ◽

Li Yang

Keyword(s):

Activation Energy ◽

Thermogravimetric Analysis ◽

Apparent Activation Energy ◽

Ignition Temperature ◽

Catalytic Combustion ◽

Integration Method ◽

Kinetic Behavior ◽

Conversion Rates ◽

Coke Combustion ◽

Addition Amount

AbstractThe effect of KMnO4 on the combustion characteristics and kinetic behavior of semi-coke was studied by thermogravimetric analysis. When 6 wt% KMnO4 was added, the ignition temperature of semi-coke was the lowest. The apparent activation energy of semi-coke with different addition amount of KMnO4 was calculated by Coats–Redfern integration method, the apparent activation energy of semi-coke during combustion reaction first decreased and then increased with increase in KMnO4. When 6 wt% KMnO4 is added, the apparent activation energy is minimal. The apparent activation energy of semi-coke with 2 wt% KMnO4 added at different conversion rates was calculated using Flynn–Wall–Ozawa integration method. The results show that the apparent activation energy of semi-coke combustion decreases with the increase of conversion.

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Glass transformation in vitreous As2Se3 studied by conventional and temperature-modulated differential scanning calorimetry

Journal of Materials Research ◽

10.1557/jmr.2001.0329 ◽

2001 ◽

Vol 16 (8) ◽

pp. 2399-2407 ◽

Cited By ~ 12

Author(s):

S. O. Kasap ◽

D. Tonchev

Keyword(s):

Activation Energy ◽

Differential Scanning Calorimetry ◽

Relaxation Time ◽

Glass Transition ◽

Activation Energies ◽

Temperature Modulation ◽

Glass Transition Region ◽

Scanning Calorimetry ◽

Modulated Differential Scanning Calorimetry ◽

Apparent Activation Energies

We have studied the glass transition behavior of vitreous As2Se3 by carrying out temperature-modulated differential scanning calorimetry (TMDSC) and conventional differential scanning calorimetry (DSC) experiments to measure the glass transition temperature Tg. In TMDSC experiments we have examined the reversing heat flow (RHF), that is the complex heat capacity CP in the glass transition region as the glass is cooled from a temperature above the glass transition temperature (from a liquidlike state) and also as the glass is heated starting from room temperature (from a solidlike state). The RHF, or CP versus T, in TMDSC changes sigmoidally through the glass transition region without evincing an enthalpic peak which is one of its distinct advantages for studying the glass transformations. The Tg measurements by TMDSC were unaffected by the amplitude of the temperature modulation. We have determined apparent activation energies by using Tg-shift methods based on the Tg-shift with the frequency (ω) of temperature modulation in the TMDSC mode and Tg-shift with heating and cooling rates, r and q, respectively, in the DSC mode. It is shown that the apparent activation energies ∆h* obtained from ln ω versus 1/Tg and ln q versus 1/Tg plots are not the same, but nonetheless, they are approximately the same as the apparent activation energy ∆hn of the viscosity over the same temperature range where the empirical Vogel expression of Henderson and Ast, η = 12.9 exp[2940/(T - 335)], was used for the viscosity. The latter observation is in agreement with the assertion that the structural relaxation time Ʈ is proportional to the viscosity h. The apparent activation energy ∆hr obtained from the ln r versus 1/Tg plot during heating DSC scans is lower than ∆h* observed during cooling scans. The results are discussed in terms of a phenomenological Narayanaswamy type relaxation time. It was observed that Tg obtained from TMDSC cooling experiments did not depend on the underlying cooling rate for q ≤ 1 °C min-1; and for temperature amplitudes 0.5–5 °C. The transition due to the temperature modulation was well separated from the transition due to the underlying cooling rate. Further, the apparent activation energies obtained from ln ω versus 1/Tg during cooling and heating scans for q and r ≤ 1 °C min−1 are approximately the same as expected from Hutchison's calculations using a single relaxation time model of TMDSC experiments.

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Determination of the Apparent Activation Energy of Concrete by Adiabatic Test

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.477.411 ◽

2011 ◽

Vol 477 ◽

pp. 411-417

Author(s):

Jia Chun Wang

Keyword(s):

Activation Energy ◽

Apparent Activation Energy ◽

Temperature Rise ◽

Adiabatic Temperature Rise ◽

Study Results ◽

Stage Development ◽

Concrete Hydration ◽

Apparent Activation Energies ◽

Influence Of Hydration

It is known that apparent activation energy of the binders in concrete characterizes the sensitivity of concrete hydration processes to temperature. In this paper the apparent activation energies of concretes containing different complex binders have been determined through adiabatic temperature rise test. The influence of hydration emission heat on the apparent activation energy of concrete is studied. The study results show that the apparent activation energy is decreasing with the hydration of binder stage development.

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Oxygen exchange at gas/oxide interfaces: how the apparent activation energy of the surface exchange coefficient depends on the kinetic regime

Physical Chemistry Chemical Physics ◽

10.1039/c6cp02131j ◽

2016 ◽

Vol 18 (32) ◽

pp. 22031-22038 ◽

Cited By ~ 5

Author(s):

Peter Fielitz ◽

Günter Borchardt

Keyword(s):

Activation Energy ◽

Apparent Activation Energy ◽

Oxygen Exchange ◽

Oxide Surfaces ◽

Kinetic Regime ◽

Exchange Coefficient ◽

Surface Exchange ◽

Oxide Interfaces ◽

Surface Exchange Coefficient ◽

Apparent Activation Energies

The model explains the range of apparent activation energies measured in different kinetic regimes of oxygen exchange at oxide surfaces.

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Calculations of activation energy and frequency factors for corn leafs pyrolysis using excel solver: new concept

International Journal of Chemical Reactor Engineering ◽

10.1515/ijcre-2020-0140 ◽

2021 ◽

Vol 0 (0) ◽

Author(s):

Omar Salim Al-Ayed ◽

Mohammad Waleed Amer ◽

Sura Al-Harahshah ◽

Birgit Maaten ◽

Muhammad Sajjad Ahmed

Keyword(s):

Activation Energy ◽

Apparent Activation Energy ◽

Frequency Factor ◽

Heating Rates ◽

First Order ◽

First Order Kinetics ◽

Calculated Activation Energy ◽

Apparent Activation Energies ◽

Excel Solver ◽

Calculated Activation

Abstract Thermal degradations of biomass corn leaves were studied for kinetic modeling. Thermogravimetric-differential analyzer runs at 5, 10, 20, and 30 °C min−1 heating rates were employed. Apparent activation energy and frequency factor values were calculated for first-order kinetics using several procedures. The procedure of Coats and Redfern showed 28.89 to 31.78 kJ mol−1 apparent activation energy and 15.5 to 157.12 min−1 frequency factor, respectively. Calculation of the apparent activation energy and frequency factor using Kissinger–Akahira–Sunose procedure gave 229.9–364.2 kJ/mol and 8.567 × 1023 and 1.13 × 1031 (min−1), respectively as the conversion increased from 0.1 to 0.9. The newly introduced excel solver procedure indicates a distribution activation energy over the entire range of conversion. For first-order reaction kinetics, the calculated apparent activation energy magnitudes ranged between 5.0 kJ mol−1 with frequency factor equals to 0.239 and 196.2 kJ mol−1 with frequency factor 2.89 × 1012 in the studied range. The low or high magnitudes of the calculated activation energy are not associated with a particular value of the conversion. The calculated apparent activation energies are related to the direct solution of the simultaneous equations that constitute the basis of the excel solver.

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Effect of Filament Material on the Decomposition of SiH4 in Hot Wire CVD of Si-Based Films

MRS Proceedings ◽

10.1557/proc-715-a15.5 ◽

2002 ◽

Vol 715 ◽

Cited By ~ 8

Author(s):

H. L. Duan ◽

G. A. Zaharias ◽

Stacey F. Bent

Keyword(s):

Activation Energy ◽

Growth Rate ◽

Apparent Activation Energy ◽

Surface Reaction ◽

Film Growth ◽

Activation Energies ◽

Film Deposition ◽

The Other ◽

Hot Wire ◽

Radical Production

AbstractThe choice of filament material has an effect on the decomposition of silane during the hot wire chemical vapor deposition (HW-CVD) of amorphous and microcrystalline silicon films. The Si radicals produced from W, Re, Mo and Ta filament materials have been probed by laserbased single photon ionization (SPI) as a function of hot wire temperature. The Si radical profiles are shown to demonstrate two distinct regimes: a regime below 1600°C-1800°C (depending on filament material) limited by surface reaction at the filament in which Si concentration increases monotonically; and a mass transfer limited regime above 1600°C-1800°C where Si intensity saturates. The apparent activation energy of Si radical production in the surface reaction regime from Ta (140-170 kcal/mol) is found to be close to the corresponding Si thermal desorption energy from a Ta surface, suggesting that the Si production is controlled by the desorption process from the bare metal. On the other hand, the Si activation energies from W and Re (30-60 kcal/mol) are lower than the related desorption energies, suggesting that other rate limiting reactions play a role for these materials. The apparent activation energy for the Mo surface (60-90 kcal/mol) is intermediate between the other metal values. In addition to the Si radical study, corresponding film deposition is detected in situ by multiple internal reflection infrared (MIR-IR) spectroscopy. The IR measurements have been used to estimate the growth rate of a-Si:H deposited on a Ge substrate. The results show similar activation energies for both the growth rate and the Si formation from a W filament, implying that Si radical production and subsequent film growth may be dominated by the same elementary reactions within the decomposition and film growth processes at low pressure.

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Activation energies and frequency factors in the thermal decomposition of paraffin hydrocarbons

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1952.0183 ◽

1952 ◽

Vol 214 (1119) ◽

pp. 471-481 ◽

Cited By ~ 10

Keyword(s):

Activation Energy ◽

Thermal Decomposition ◽

Apparent Activation Energy ◽

Molecular Mechanisms ◽

Activation Energies ◽

Small Surface ◽

Molecular Reaction ◽

Methyl Pentane

Further evidence supports the view that the thermal decomposition of paraffin hydrocarbons occurs by simultaneous chain and non-chain (molecular) mechanisms, the latter being isolated by addition of suitable inhibitors such as nitric oxide. It is concluded that certain small surface effects are secondary disturbances of an essentially homogeneous reaction. With one group of hydrocarbons, type 1, including ethane (propane), iso -butane, iso -pentane, neo -pentane and neo -hexane, this molecular reaction is of the normal unimolecular kind, showing a single transition from the first order towards the second as the pressure drops, and an activation energy which is independent of the initial pressure. In the second group, type 2, including n -butane and higher normal paraffins, 2∙3-dimethyl butane, 2-methyl pentane and 3-methyl pentane, the molecular reaction seems to be a superposition of two unimolecular reactions with different pressure dependences and different activation energies. There is a double order transition, and a marked variation with pressure of the apparent activation energy. This apparent activation energy is influenced by the addition of certain gases (propylene, ethane, propane) in such a way as to be in any given case a unique function of the total pressure of paraffin plus added gas. The frequency factors in the equation k = A e -E/RT have been determined. With the paraffins of type 2, the ‘high- pressure’ components of the reaction give values within the range expected by the theories which relate A to a vibration frequency, and assume the localization of the critical energy in a single bond. With some of the paraffins of type 1 the frequency factors are outside the probable range (10 12 to 10 14 s -1 ), and the values suggest that the transition states may be less sharply defined than the localization condition demands. The apparent values of the frequency factors associated with the ‘low-pressure’ components of the reactions are still higher and appear to demand a special interpretation which must be the subject of further investigation.

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