| A number of industrially important hydroprocessing reactions are three phase and are highly exothermic. Experimental data on the thermal behavior of such reactors are scarce. An adiabatic, computer-controlled, slurry reactor has been designed and operated to evaluate the thermal behavior of a prototype commercial reactor. The Fischer-Tropsch (FT) reaction has been used as a case study using two different catalysts, supported ruthenium and fused iron. High conversion of carbon monoxide (>90%) and high rate of heat generation were obtained with the ruthenium catalyst, in contrast to fused iron where a maximum of 10% conversion of carbon monoxide was achieved. A fundamental study of the effects of temperature, pressure, stirrer speed and gas space velocity and feed composition, on the thermal behavior of an FT slurry reactor has been done. A jump in rate of heat generation and product distribution was observed at around 560K for both catalysts. Further study with supported ruthenium catalyst indicated the existence of multiple steady states in a three phase FT reactor. Depending upon start-up procedures and reactor operating conditions, the reactor can operate in three possible modes, 'FT mode', 'Methanation mode' or 'Deactivation mode'. Effects of the process variables on the existence and region of multiplicity have been studied. Based on these results, some important control problems of a commercial FT slurry reactor are discussed. |
