Accelerating Rate Calorimetry Tests Research Articles

Chemically Assisted Ignition Technologies for a Light Oil Air Injection Process

Abstract A light oil (API 30 º) reservoir is an excellent candidate for high pressure air injection, but the oil is not believed to be capable of self-ignition at the reservoir temperature. Several chemical additives and catalysts are studied to evaluate their effectiveness of ignition improvement for this light oil sample. Pressurized Differential Scanning Calorimetry (PDSC) and Accelerating Rate Calorimetry (ARC) experiments are examined in this study. The oil sample, which is mixed with certain catalysts and chemical additives, is subjected to a controlled heating schedule under a constant flow rate of air at 4.14 MPa (600 psig) and 13.8 MPa (2,000 psig) pressure for the PDSC and ARC tests, respectively. The amount and rate of heat released by the oxidation reactions is analyzed for those tests. In the presence of a metallic catalyst and chemical initiators, oxidation behaviour of the oil tested is dramatically improved. Also observed are a significant reduction in the onset temperature of significant exotherm and an increased rate for the release of heat. Introduction Air injection has been proven as a viable process in improving oil recovery from light oil reservoirs, and as a result, it has received much interest in recent years(1, 2). The concept of recovery increment is when air is injected into a light oil reservoir and exothermic chemical reactions occur. The desired reactions result in heat generation and the production of carbon dioxide. Downstream of the reaction zone, the combustion produced gas sweeps oil toward the production wells, combining with light hydrocarbon fractions vapourized by heat released from oxidation reactions. Therefore, incremental oil production is achieved. However, air injection for a light oil reservoir is a complex process involving simultaneous heat and mass transfer in a multiphase environment coupled with oxidation chemical reactions. Ignition is the first phase of this process and a satisfactory ignition is of prime importance in initiating a successful air injection process(2). In high temperature reservoirs, the air injection process is initiated by injecting air, which may spontaneously ignite the oil-in-place(1). However, in some cases, spontaneous ignition of the reservoir oil is not likely to occur so that several artificial means have been implemented(3), including down hole electrical heaters, a gas burner or injection of steam, but it is highly desirable to avoid having to run heaters or burners when air injection is to be applied in deep, high pressure reservoirs. As a result, chemical ignition is proposed(2). The concept of chemical ignition is where a slug of chemicals with reactive oxidation characteristics is injected into an oil bearing zone prior to the injection of air from an injector. If heat released from an oxidation reaction is continually generated at a rate greater than it is dissipated, starting at the native reservoir temperature, oil can be spontaneously ignited without the application of artificial means. The reactive nature of the base oil present in the ignition zone can be enhanced or stimulated. A spontaneous ignition may occur within the formation. Bednarski(4) reported on a chemical ignition improvement experiment.

Role of the cathode and anode in heat generation of Li-ion cells as a function of state of charge

Thermal stability of Li-ion cells (from two different manufacturers, A and B) and their cathodes and anodes were evaluated as a function of state of charge (SOC) using accelerating rate calorimetry (ARC). Cell A was rated at 750 mAh and consisted of Sn-doped LiCoO2 cathode and meso-carbon micro-fiber (MCMF) anode. Cell B was rated at 790 mAh and was comprised of a cathode and an anode made of LiCoO2 and graphite. The electrolytes in cells A and B were mixtures of EC:EMC + 1MLiPF6 and EC:EMC:DMC + 1MLiPF6, respectively. ARC results indicated that between 50 and 125% SOC, the total heat generated by cell A is mostly dominated by self-heating of the cathode, while between 125 and 200% SOC the total heat generated by the cell was dominated by the anode. The total heat generated in cell B, however, was dominated by self-heating of the graphite anode, over the entire 50–200% SOC range. Also, the self-heating in cell B was higher than that for cell A. Heat generation of the LiCoO2 increases with increasing SOC, and the Sn-LiCoO2 heat generation reaches a maximum near 125% SOC. At low SOC, the temperature of the onset of chemical reaction (TOSCR) for cell A was higher than that for the cell B. For both cells, at higher SOC, TOSCR decreased with a sharp drop between 100 and 150% SOC. Overall results show that cell A offers a higher thermal stability than cell B. Also, the ARC test is more suitable than differential scanning calorimetry for correlation of cathode and anode heat generations to the thermal performance of full Li-ion cells.

Thermal Stability of 18650 Size Li-Ion Cells Containing LiBOB Electrolyte Salt

Lithium bis(oxalato)borate (LiBOB) has been proposed recently as an electrolyte salt for Li-ion batteries, however safety testing of full Li-ion cells incorporating this salt has not been reported. Earlier accelerating rate calorimetry (ARC) work demonstrated that the thermal reactivity between LiBOB ethylene carbonate/diethyl carbonate (EC/DEC) electrolyte and was lower than that between EC/DEC electrolyte and the same negative electrode material, suggesting that LiBOB may be an attractive salt choice for safer Li-ion cells. Here, we report ARC studies of the reactions between LiBOB EC/DEC electrolyte and and compare them to the reactions between EC/DEC and the same positive electrode material. Unfortunately, the reactivity of LiBOB electrolyte with the charged positive electrode initiates at a substantial rate at about 40°C lower in temperature than for electrolyte. Oven exposure tests on charged (4.2 V) 18650 Li-ion cells made using the same electrolytes and electrode materials show that the heat caused by the reaction of the negative electrode with electrolyte is less for LiBOB electrolyte than for electrolyte but that the opposite is true for the heat caused by the reaction of the positive electrode with electrolyte, as expected based on the ARC measurements. Using ARC tests on the individual electrode reactivity and oven exposure testing on 18650 Li-ion cells, the usefulness of electrolytes with mixed salts is also explored. © 2004 The Electrochemical Society. All rights reserved.

Accelerating rate calorimetry study on the thermal stability of interpenetrating network type poly(siloxane- g-ethylene oxide) polymer electrolyte

Safety study regarding an exothermic reaction at elevated temperature of comb-shaped siloxane polymer and its interpenetrating network type solid polymer electrolyte (SPE) are investigated. Accelerating rate calorimetry (ARC) is used to examine exothermic reactions. The thermal stability of the polymer electrolyte in the presence of charged electrodes is also monitored. Resulting data were compared with those of 1.0 M LiPF 6 in ethylene carbonate:ethyl methyl carbonate (3:7 by wt.) electrolyte. The self-heating exothermic reaction of mono comb-shaped siloxane polymer electrolyte starts at approximately 300 °C. Comparison of the heat generation profiles from ARC tests indicates that SPE reduces the intensity of exothermic reactions resulting from charged electrodes and electrolyte.

Thermal Stability Studies of Li‐Ion Cells and Components

Thermal stability of fully charged 550 mAh prismatic Li‐ion cells (Sn‐doped carbon) and their components are investigated. Accelerating rate calorimetry (ARC) is used to determine the onset temperature of exothermic chemical reactions that force the cell into thermal runaway. Differential scanning calorimetry (DSC) and thermogravimetry analysis are used to determine the thermal stability of the cell's positive electrode (PE) and negative electrode (NE) materials from 35 to 400°C. The cell self‐heating exothermic reactions start at 123°C, and thermal runaway occurs near 167°C. The total exothermic heat generation of the NE and PE materials are 697 and 407 J/g, respectively. Heat generations of the NE and PE materials, washed in diethyl carbonate (DEC) and dried at ≈65°C under vacuum, are significantly lower than unwashed samples. Lithium plating increases the heat generation of the NE material at temperatures near the lithium melting point. Comparison of the heat generation profiles from DSC and ARC tests indicates that thermal runaway of this cell is close to the decomposition temperature range of the unwashed PE material. We conclude that the heat generation from the decomposition of PE material and reaction of that with electrolyte initiates thermal runaway in a Li‐ion cell, under thermally or abusive conditions. © 1999 The Electrochemical Society. All rights reserved.