OBSERVATION OF AN ISOKINETIC TEMPERATURE AND COMPENSATION EFFECT FOR HIGH TEMPERATURE CRUDE OIL FOULING

摘要

The initial fouling rates of four crude oils were determined at a nominal bulk temperature of 315 °C, an initial heated wall shear stress of 13 Pa, and initial surface temperatures between 375 and 445 °C. These initial fouling rates ranged from 1.3(10~(-6)) to 7.8(10~(-5)) m~2 KM. Corresponding Arrhenius plots were linear with the initial fouling rates passing through an isokinetic temperature of 407.5 °C. A plot of the natural logarithm of the pre-exponential factors (7.6(10~4) - 5.2(10~(15)) m~2 K/kJ) versus the apparent activation energies (128 - 269 kJ/mol) was also linear, confirming the validity of the isokinetic temperature and the presence of the compensation effect. Below the isokinetic temperature, the relative fouling rates were Crude Oil C > Crude Oil A > Crude Oil D > Crude Oil B; above the isokinetic temperature, the relative fouling rates were reversed (Crude Oil B > Crude Oil D > Crude Oil A > Crude Oil C). Chemical characterization of a fouling deposit suggested that the dominant fouling mechanism at these conditions was coking with significant contributions from sedimentation (iron sulfide) and corrosion (～340 μm/yr) of the 304 stainless steel test material.