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Abstract  

In this study, combustion curves of twenty-five Turkish lignites were obtained through use of a differential thermal analyser. 20 mg lignite samples were heated at a constant rate of 10 deg·min−1 in a 40 cc/min flow of air up to 1073 K and held for 10 minutes at this constant temperature. The combustion curves of the samples are compared and discussed.

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Combustion characteristics of crude oil-limestone mixtures

High pressure thermogravimetric analysis and their relevance to in-situ combustion

Journal of Thermal Analysis and Calorimetry
Authors: M. Kök, R. Hughes, and D. Price

Abstract  

High pressure thermogravimetric analysis (HPTG) was used in order to study the oxidation of crude oil in a porous medium under pressurised conditions for simulation of in-situ combustion during oil recovery. Three distinct reaction regions were observed from the HPTG curves in an oxidising environment subjected to a constant heating rate. These were low temperature oxidation, fuel deposition and high temperature oxidation. The method of Coats and Redfern was used to obtain kinetic parameters and the results are discussed.

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In this study, thermal characteristics and kinetic parameters of cleaned Tunçbilek lignite were determined by using a Setaram Labsys DTA/TG/DSC thermal analysis system both for combustion and pyrolysis reactions. Experiments were performed at a heating rate of 10°C min–1 under reactive (air) and inert (nitrogen) gases up to 1000°C. Non-isothermal heating conditions were applied and reaction intervals were determined for combustion and pyrolysis reactions from obtained curves. The combustion properties were evaluation by considering the burning profile of the lignite sample. Burning temperatures and rate of combustion were determined from TG/DTG curves. Calorific value of the lignite sample was measured by DSC curve and compared with the adiabatic bomb calorimeter result.

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Journal of Thermal Analysis and Calorimetry
Authors: M. Stenseng, A. Zolin, R. Cenni, F. Frandsen, A. Jensen, and K. Dam-Johansen

Abstract  

Thermal analysis is widely used in combustion research for both fundamental and practical investigations. Efficient combustion of solid fuels in power plants requires understanding of properties and behavior of fuel and ash under a wide range of conditions. At the Department of Chemical Engineering, Technical University of Denmark, thermogravimetric analysis and differential scanning calorimetry are applied in order to investigate various aspects of combustion and gasification processes: pyrolysis, char reactivity and ash melting behavior. This paper shows examples of the application of simultaneous thermal analysis in these three research areas, and it demonstrates the flexibility of this technique in combustion research.

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Abstract  

Combustion and pyrolysis experiments of Huadian oil shale have been conducted using a STA409 thermogravimetric analyzer. The effect of various factors on combustion of oil shale is studied. Particle size has little effect on combustion process of oil shale; starting temperature of combustion mass loss and ignition temperature of oil shale decrease with increasing O2 concentration of ambient gas; increase of heating rate can result in ignition temperature, burn-out temperature and maximum rate of combustion mass loss increasing. Homogeneous ignition mechanism of oil shale is ascertained using a hot state microscope. Activation energy was determined using Arrhenius model that is solved by Freeman–Carroll method. Calculation results show activation energy will increase with heating rate.

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Abstract  

The pyrolysis and combustion kinetics of Gynk oil shale were investigated by thermogravimetric analysis in the present study. All experiments were conducted at non-isothermal conditions with a heating rate of 10–60 K min–1 in the 298–1173 K temperature interval under argon and air atmospheres for pyrolysis and combustion, respectively. Differential thermogravimetric data were analyzed by a reaction rate model assuming first order kinetics.

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Abstract  

The combustion kinetics of Göynük oil shale, polystyrene and several polystyrene-oil shale blends were investigated by thermogravimetric analysis in the present study. Experiments were conducted at non-isothermal conditions with a heating rate of 5, 10 and 20 K min−1 in the 298–1173 K temperature interval under an air atmosphere. Differential thermogravimetric data were analyzed by two different models. Effects of blending ratio of oil shale and polystyrene and heating rate on the combustion kinetics were investigated. Kinetic parameters were determined and the results were discussed.

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Abstract  

Simultaneous thermogravimetry (TG) and differential thermal analysis (DTA) were applied to light crude oil combustion in the presence and absence of metal oxide. In crude oil-limestone mixture, three main transitional stages are detected. These are distillation, low-temperature oxidation (HTO) and high temperature oxidation (HTO) regions respectively. In the case of experiments with Fe(III)-chloride at different amounts, the shape of TG-DTA curve is changed considerably. Kinetic parameters of the samples are determined using ASTM method. Reduction in activation energy is considered to be an indication of the catalytic activity of the additive.

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Abstract  

Combustion profiles of coal-limestone-paper blends were studied using thermogravimetric/ Fourier transform infrared spectroscopy (TG/FTIR). The role of limestone in promoting the initial combustion of coal-paper blends and its ability to absorb sulphur oxides were examined.

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Abstract  

Combustion of brick-shaped carbonaceous materials (carbon deposits from coke oven, coke and electrographite) was carried out in thermobalance in static air. Analysis of kinetics of the process was carried out using both classical (Arrhenius law) and newer (three-parametric equation) methods. In classical approach two types of kinetic equations were used in calculations: differential and integral. The results obtained show that, independently on kinetic variables (α – conversion degree or m – mass of sample) used in differential equations, kinetics of combustion of brick-shaped carbonaceous materials is characterized by only one pair of Arrhenius coefficients: activation energy (E) and pre-exponential constant (A). At the same time the integral equation demonstrates distinction in relation to methods based on differential equations, generating higher activation energies and separate isokinetic effect (IE). Parallel IE shows that kinetic analysis has to encompass activation energy in connection to second coefficient, pre-exponential constant A, depending on assumptions made for kinetic equations. On the other hand three-parametric equation allows describing kinetic of combustion in alternative way using only one experimental value – initial temperature in form of point of initial oxidation (PIO) – and also offers new methods of interpretation of the process.

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