Low-temperature combustion characteristics of heavy oils by a self-designed porous medium thermo-effect cell

Abstract

The combustion characteristics of two Xinjiang heavy oils were studied by the self-designed porous medium thermo-effect cell (PMTEC) that can monitor the temperature alterations caused by oxidation/combustion reactions occurring within a porous medium under dynamic air flow. The results indicated that the heavy oils encountered obvious low-temperature combustion (LTC) in the temperature range of about 280–360 °C, accompanied by a maximum temperature increase to roughly 600 °C and significant release of CO and CO2. Then, PMTEC was adopted to evaluate the effects of air injection rate and water saturation on crude oil combustion. The increase of the air injection rate was conducive to triggering the LTC reactions and enhancing the intensity of LTC. The highest air injection rate (1 L/min in this work) led to the occurrence of fairly intense LTC reactions, during which large amounts of oxygen and oil sample were consumed. The increase of water saturation produced a minor influence on the occurrence of LTC, but obviously weakened the intensity of LTC. In addition, the influence of four metallic salts on the combustion behavior of heavy oil was examined using PMTEC. Cobalt naphthenate exhibited the good catalytic effect for promoting the occurrence of LTC. The mixed catalyst (cobalt naphthenate + manganese naphthenate) was found to have a better catalytic performance than any used single metallic salt. This mixed catalyst has a good potential for application in in-situ combustion of the Xinjiang heavy oil.