• Energy Research

Thermal analysis is increasingly being used to obtain kinetic data relating to sample decomposition. In this research differential scanning calorimeter (DSC) was used to determine the combustion kinetics of three (Can, Himmetoglu and Mengen) oil shale samples by ASTM and Roger & Morris methods. On DSC curves two reaction regions were observed on oil shale sample studied except Can oil shale. In DSC experiments higher heating rates resulted in higher reaction temperatures and higher heat of reactions. Distinguishing peaks shifted to higher temperatures with an increase in heating rate. Three different kinetic models (ASTM I-II and Rogers & Morris) were used to determine the kinetic parameters of the oil shale samples studied. Activation energies were in the range of 131.8-185.3 kJ mol-1 for ASTM methods and 18.5-48.8 kJ mol-1 for Rogers & Morris method.

In situ combustion is a thermal recovery technique where energy is generated by a combustion front that is propagated along the reservoir by air injection. Most of the previously conducted studies report thermal and fluid dynamics aspects of the process. Modeling in situ combustion process requires extensive knowledge of reservoir data as well as reaction kinetics data. Unfortunately, limited kinetic data are available on the rates and the nature of partial oxidation reactions and the high-temperature combustion reactions of crude oils and their saturate, aromatic, resin, and asphaltene (SARA) fractions. Moreover, the impact of such data on the modeling of the in situ combustion process has not been investigated thoroughly. Thus, we modeled in situ combustion experiments conducted on a three-dimensional semiscaled physical model that represents one-fourth of a repeated five spot pattern. In all experiments a vertical injector is employed whereas, both vertical and horizontal producers have been installed to recover two different crude oils (heavy and medium). Several locations for the producers have been tried while keeping the length of the wells constant: vertical injector-vertical producer, vertical injector-horizontal side producer, and vertical injector-horizontal diagonal producer. In these experiments horizontal side producers performed better than the others. We first simulated the experiments by incorporating a kinetic model that is based on grouping the products of cracking into six pseudo components as heavy oil, medium oil, light oil, two noncondensable gases, and coke using a commercial thermal simulator (CMG's STARS). Five chemical reactions were considered: cracking of heavy oil to light oil and coke, heavy oil burning, light oil burning, and coke burning. Most of the experiments were history matched successfully with the exception of ones where a diagonal horizontal producer was used. We then repeated the simulations using SARA kinetic parameters and observed that all matches were somewhat improved.

Abstract This research aimed at understanding the effects of particle size and heating rate on combustion characteristics and kinetics of Saray-Thrace region coal by performing thermogravimetry (TG-DTG) analysis. The TG-DTG curves revealed two main reaction regions for each heating rate studied (5, 10, and 15 °C/min, particularly the evaporation of moisture and carbonization stages. The reaction intervals extended while the corresponding peak and burn-out temperatures increased as the heating rate was increased. Furthermore, a slight delay occurred in burn-out temperatures while the peak temperatures mostly increased with increased particle size, which is correlated with the decrease in surface area. On the other hand, the average mass loss percentages in carbonization stages mostly increased with increased particle size. Similarly, the combustion performance and reactivity of coal samples, which were evaluated through the values of combustion performance index (S), maximum reactivity (Rmax), and ignition index (D), suggested that the larger the particle size and the higher the heating rate, the better the combustion activity. The kinetic analysis of coal samples was also performed using model-free (iso-conversional) methods, particularly the Ozawa - Flynn - Wall (OFW) and Kissinger - Akahira – Sunose (KAS). The corresponding average activation energy (Ea) range of different size coal samples varied within the range of 62.1–191.8 kJ/mol, and the lowest Ea found for the largest particle size coal sample, supported the ignition performance and reactivity results.

ABSTRACTIn this study, combustion and pyrolysis behavior of diesel and canola oil is investigated using thermal analysis techniques known as thermogravimetry (TG–DTG) and differential scanning calorimetry (DSC) at different heating rates. Reaction regions, peak temperatures, mass loss, heat flow rates, ignition temperatures, and specific heat of diesel and canola oil samples are determined using TG–DTG and DSC data. It was observed that as the heating rate of the reactions increased, peak temperatures of the reactions shift higher; implying that as the heating rate of the reactions increases the reactions lose their sensitivity. Five different kinetic methods were applied to determine combustion reaction parameters of the reactions. It was observed that averages of the activation energies of the samples are in the order of canola oil and diesel for different heating rates.

© 2018 Elsevier B.V. In this research, kinetics of four crude oils from different origins are determined by iso-conversional methods using thermogravimetry data (TGA-DTG). The experiments were performed at three different heating rates (5-10-15 K/min) between 300 and 1200 K. Thermal characteristics of the crude oil samples such as, reaction intervals and corresponding peak and burn-out temperatures are also determined. Three different iso-conversional methods, known as Starink, Kissinger and Friedman are used in order to determine the activation energy values of the crude oil samples studied that represents the novelty of the research. Activation energy values of the crude oil samples are varied between 50 and 102 kJ/mol and 69–132 kJ/mol in low temperature oxidation region and high temperature oxidation region, respectively.

In the first part of this research, kinetic software was developed for the evaluation of kinetic parameters using nonisothermal thermogravimetry data. Different computational methods were used and applied to a set of experimental and simulated data distributed in the ICTAC (International Confederation for Thermal Analysis and Calorimetry) kinetics project. The reliability of the software was verified by comparing the kinetic results and it was observed that the results were in good agreement. In the second part, developed software was applied to determine the kinetics of a tar sand sample. Therefore, experiments were performed at three different heating rates, in the temperature range of 20–900°C. Different stages of mass loss regions were observed in TG-DTG curves. Ozawa-Flynn-Wall (OFW), Kissinger, and Augis-Bennett kinetic models were used to determine the activation energy of tar sand sample and the results are discussed.

This research comprises the coal pyrolysis by thermogravimetry (TG/DTG). During the pyrolysis of the coal samples studied, gradual and continuous weight loss over the entire temperature range was observed. The weight loss below 210°C is related to the removal of moisture. The subsequent pyrolysis process as revealed by the corresponding DTG peak that is related to primary devolatilization, during which carbon, hydrogen, and oxygen compounds are released. Arrhenius-type kinetic model was used to determine the kinetic parameters and the results are discussed.

© 2016 Taylor & Francis Group, LLC.In this research, thermal characteristics and model free kinetics of five different °American Petroleum Institute gravity crude oil samples from different locations were studied using combustion calorimetry and thermogravimetry (TGA) techniques. Higher heating values of crude oils were determined from the combustion calorimetry experiments. It was shown that these values increase with an increase in saturate fraction and °API gravity of studied samples and decrease with an increase in viscosity, aromatics fraction, and resin fraction of crude oils. In thermogravimetry, experiments were performed at 10, 20, and 30°C/min heating rates under an air atmosphere. Thermal characteristics of the samples such as reaction intervals and corresponding peak temperatures, mass loss, and residue of the crude oil samples were also determined. Two different model free kinetic methods, known as Ozawa-Flynn-Wall (OFW) and Kissinger-Akahira-Sunose (KAS), were used in order to determine the activation energy values of the crude oil samples studied.

Abstract In this research, non-isothermal kinetics and thermal analysis of Gercus tar sand sample is studied by DSC (differential scanning calorimeter) and TG/DTG (thermogravimetry). Experiments were performed using three different mesh size (20–35, 35–50 and >50) of sample. Differential scanning calorimeter (DSC) curves revealed three reaction regions in the temperature range of 20–600 °C. On the other hand, thermogravimetry (TG/DTG) curves of tar sand samples at different particle sizes demonstrated three stages of weight loss. Two different kinetic models (Coats & Redfern and Arrhenius) were used to determine the kinetic parameters of the samples and it was observed that the average activation energy values were between 17.5 and 26.6 kJ/mol, for reaction region-II and 126.2–160.1 kJ/mol for reaction region-III, respectively. In order to see the contribution of each region to the overall reactivity of the tar sand sample, weighted mean apparent activation energy of the samples are also determined.