Abstract: In an upflow, ebullated bed reactor using a heterogeneous catalyst, a transport liquid compatible with the catalyst and the reactor feedstock is used. During the addition of fresh catalyst, a heated slurry of catalyst and transport liquid is pumped into the reactor under conditions to minimize (a) the temperature difference between the slurry and the reactor and (b) exposure of the fresh catalyst to a deactivating elevated temperature. During catalyst withdrawal, the temperature of the reactor effluent stream is controlled by mixing with a transport liquid. Measurement and flowability of the resultant mixture is thus assured.

Abstract: In starting up an upflow, ebullated bed hydroprocessing reactor, a light oil is used, to establish an ebullating bed. As heavy residual feedstock is incrementally substituted, the ebullating pump speed and gas flow rate need to be monitored and adjusted for smooth operation. By knowing and controlling the viscosity and density of the feedstock, flow variations inside the reactor can be minimized, resulting in a constant pump speed and gas flow rate.