Short Communication
Journal of Chemical Engineering of Japan, Vol. 40, No. 2, pp. 105–107, 2007
Combustion Properties of Emulsion Fuel Prepared from Heavy Crude Oil in Oman Rashid S. AL-MAAMARI1, Naoya SHIGEMOTO2, Akihiko HIRAYAMA3 and Mark N. SUEYOSHI3 1
Petroleum and Chemical Engineering Department, College of Engineering, Sultan Qaboos University, P.O. Box 33, Al-Khoud, Muscat 123, Sultanate of Oman 2 Chemical Technology Department, Shikoku Research Institute Inc., 8, Yashima-nishimachi 2109, Takamatsu-shi, Kagawa 761-0192, Japan 3 Energy Solutions Department, Shimizu Corp., Seavans South, 1-2-3, Shibaura, Minato-ku, Tokyo 105-8007, Japan
Keywords: Heavy Crude Oil, Emulsion Fuel, Combustion, Flue Gas, Vanadium Corrosion An emulsion of Omani heavy crude oil was prepared to reduce its viscosity, and combusted in a test boiler to investigate its combustibility and to analyze its flue gas composition, e.g., CO, SO 2, NOx, and dust. The emulsion was evaluated to be suitable for use as a combustion fuel due to its lower environmental impact and lower possibility of high-temperature corrosion of boiler materials, in comparison with a commercial emulsion fuel, Orimulsion.
Introduction Although large reserves of heavy crude oil have been identified throughout the world, higher viscosity has restricted their development. For example, over 340 million cubic meters of heavy crude oil reserves have been estimated at Mukhaizna oil field in Oman. However, high viscosity presents difficulties for production, transportation, and utilization. Emulsifying is an excellent method to reduce the viscosity of heavy oil (Pilehvari et al., 1988). Orimulsion, which is an emulsified viscous tar from the Orinoco River area in Venezuela, is a well known emulsion fuel (HernandezCarstens and Rodriguez, 1991; Kennedy, 1991). Emulsified heavy oil is more suitable as a fuel rather than as a raw material for refineries, because of the higher water content of emulsion. Suitability of emulsion fuel for power plants should be evaluated by analyzing combustibility and flue gas composition (Kaneko et al., 1996; Quig and Hernandez-Carstens, 1996). In this study, an emulsion of Omani heavy crude oil was prepared and combusted in a test boiler in order to evaluate combustion characteristics and flue gas composition, e.g., CO, SO2, NOx, and dust. Moreover, the experimental results of the emulsion combustion were compared with those of Orimulsion and a heavy residual oil. Received on October 3, 2006; accepted on October 6, 2006. Correspondence concerning this article should be addressed to R. Al-Maamari (E-mail address:
[email protected]).
Copyright © 2007 The Society of Chemical Engineers, Japan
1.
Experimental
A heavy crude oil sampled from the Mukhaizna oil field in Oman was used in the study. The kinematic viscosity of the crude oil was 7,160 cSt at 303 K and the calorific value was 39,960 kJ/kg. A mixture of the heavy crude oil and water (79/21, weight ratio) including 0.4% of a nonylphenol type surfactant (Liponox 86, Lion Corp.) was agitated by an in-line mixer (TK Homomix Lineflow Mixer, Type 100, Tokushukakoki Co.) at 294–301 K. Table 1 compares the properties of the heavy crude oil, its emulsion, and other reference fuels, Orimulsion and a heavy residual oil. The emulsion showed lower kinematic viscosity (555–602 cSt at 303 K) than that of the crude oil (7,160 cSt at 303 K). The calorific value of the heavy crude oil was reduced from 39,960 to 31,040 kJ/kg for the emulsion, mainly due to dilution by emulsion water. A horizontal, cylindrical boiler (1.3 m in internal diameter, 7.5 m in length) equipped with a steamatomizing burner (Ishikawajima Harima Industry Corp.), was used for combustion of the emulsion and the other fuels. The maximum fuel consumption rate of the test boiler was 150 kg/h. The effects of boiler operational conditions, such as the air (O 2) supply rate and the steam/fuel consumption ratio, on the flue gas composition (CO, SO2, NOx, and dust), were investigated to clarify the combustion properties of the Mukhaizna emulsion. The minimum air (O2) supply rate for complete combustion, was determined by varying the air flow rate to adjust the O2
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Table 1 Item
Properties of Mukhaizna crude oil, its emulsion, and other fuels Mukhaizna crude oil
Mukhaizna emulsion
Orimulsion
Heavy residual oil
Density at 288 K [g/cm ] Calorific value [kJ/kg] Viscosity at 303 K [cSt]
0.957 39,960 7,160
0.966 31,040 555—602
1.012 29,500
