July 1-6, 2007
Gums formed when organic fluids are in contact with air can cause fouling of process equipment. The oxidation and formation of gum in a naphtha stream was studied in a stirred batch reactor as a function of temperature (96 to 130ºC) and at a total pressure of 584 kPa. Mixtures of air and nitrogen in the pressurizing gas gave dissolved oxygen contents in the range 10-270 ppm wt. Peroxide and existent (dissolved) gum contents were measured over periods of up to 80 hours. Rates of reaction were low, with maximum concentrations of peroxide typically below 4 meq/L, and gum formation rates of 4-5 mg/L-h. Fouling experiments were attempted in a re-circulation loop equipped with either steam or electrically heated annular probes. With bulk temperatures of about 90ºC, and test section pressures of 825 kPa, initial surface temperatures from 125oC to 185ºC were investigated. At lower surface temperatures, no significant decline in heat transfer coefficient was measured, and deposits were recovered only from the dead zones at the ends of the annular unit after times up to 450h. At higher surface temperatures of 185ºC, rapid fouling occurred when dissolved gum content had reached ~2300 mg/L. Gum and deposit analyses were similar, showing oxygen contents of about 20% wt., and carbon contents of 71% wt. Further experimentation is needed to link the gum formation step with the fouling rate.
Yonghua Li, Paul Watkinson, Patricio Herrera, Feridoun Fahiminia, and Morgan James, "FORMATION OF GUM AND DEPOSITS IN AN OXYGENATED NAPHTHA STREAM" in "Heat Exchanger Fouling and Cleaning VII", Hans Müller-Steinhagen, Institute of Technical Thermodynamics, German Aerospace Centre (DLR) and Institute for Thermodynamics and Thermal Engineering, University of Stuttgart, Germany; M. Reza Malayeri, University of Stuttgart, Germany; A. Paul Watkinson, The University of British Columbia, Canada Eds, ECI Symposium Series, (2007). http://dc.engconfintl.org/heatexchanger2007/12