Effects of liquid viscosity and surface tension on atomization in two-phase, gas/liquid fluid coker nozzles

Abstract

This is an experimental study of the effects of liquid viscosity ( μ L ) and surface tension ( γ) on the size of droplets produced by an atomizer fed with a two-phase gas/liquid (TPGL) mixture. The nozzle is a one-quarter scale model of an industrial fluid coker nozzle used for bitumen upgrading. The primary objective of this study was to compare the Sauter mean diameter SMD or D 32 or D qp q - p = ∫ D min D max D q dn dD dD ∫ D min D max D p dn dD dD of the TPGL sprays for different μ L and γ. Compressed air was used as the gas phase; the liquid phases were water, canola oil and a glycerine–water solution. The μ L was varied from 1 mPa s to 67 mPa s, and γ was varied from 25 mN/m to 61 mN/m. The liquid flow rates were varied from 0.095 L/s to 0.105 L/s, and the gas-to-liquid ratio GLR or β = m ˙ g / m ˙ l , by mass, was fixed at 2%, similar to the ratio used in commercial fluid coker nozzles. Fluid mixing pressures in the test were between 400 kPa and 700 kPa. The D 32 within the spray was measured using a Dantec 2D-Fibre mode Phase-Doppler-Particle-Anemometer (PDPA). With measurements performed at axial distances of 100 and 202 mm from the nozzle orifice and within a spray radius of 40 mm. The results showed that the 67-fold increase in μ L results in 46 μm increase in D 32 which roughly extrapolates to a power law relationship exponent of 0.11 (based on two points). In contrast, the 2.4-fold increase in γ indicates roughly 42 μm increase in D 32, giving an exponent of −0.24. For both parameters the exponent is small, indicating weak dependence. The γ effects appear stronger, but the modest increase is barely exceeds the margin of error.