The initial rate of chemical reaction fouling of the surface of a furnace tube by polymerisation of styrene in an otherwise non-fouling kerosene feedstock was studied as a function of mass flow rate over the range 336 to 1620 1b/hr and wall temperature between 556 and 909 °R. The investigation was carried out by conducting experiments at constant heat flux with continuous circulation of the liquid in a single horizontal tube. The change in fouling resistance with time was measured over the initial twelve hours of operation. In all runs the fouling resistance increased steadily with time. At the highest temperatures, the fouling resistance increased almost linearly with time, and for a given surface temperature the initial fouling rate increased with increasing mass flow rate indicating that mass transfer effects were important. At the lowest temperatures studied, the initial fouling rate decreased with increasing mass flow rate indicating again that mass transfer effects were important. At intermediate temperatures, the initial fouling rate passed through a maximum with respect to mass flow rate showing that mass transfer and kinetic effects could be both effective and competitive simultaneously. The initial fouling rates were compared with the experimental results of the kinetics of polymerisation of 1% styrene in kerosene in a batch vessel. At low temperatures the initial fouling rate was slightly higher than the initial rate of poly-merisation of 1% styrene indicating that the fouling rate may be kinetically controlled. At higher temperatures, the initial fouling rate became progressively lower than the initial rate of polymerisation of 1% styrene indicating the additional resistance of mass transfer to the fouling process. A mathematical model based on a chemical reaction and mass transfer mechanism is applied to describe the deposition process and incorporates physical properties of the system, geometry, chemical reaction kinetics and mass transfer. The model predicts the mass flow rate and temperature dependence of the initial fouling rate in agreement with the experimental results. It is believed that it can also be applied more generally to other chemical reaction fouling systems.
|Date of Award||1983|