Abstract: The inventive procedure more accurately maintains an inventory of a catalyst in an ebullated bed of a reactor in an oil refinery, especially a resid hydrotreating unit. The ebullated catalyst bed has therein three phases (catalyst, oil, gas). A first density measurement is made of the two-phase mixture in a freeboard zone i.e. in a catalyst free area above the ebullated catalyst. A second density measurement is made in the catalyst bed where all three phases are present. Density measurements are used, along with values for vapor, liquid, and soaked particle densities and corrections for gamma-ray absorption coefficients, to calculate the catalyst particle holdup in the vessel. From this, the amount of catalyst actually in the reactor can be calculated. Once this amount is known, fresh catalyst may be added to or spent catalyst may be removed from the reactor in order to maintain a fixed catalyst inventory within the catalyst bed.

Abstract: Resid hydrotreating conversion of resid can be substantially increased by blending the resid with high-temperature flash drum oil before being hydrotreated in a train of ebullated bed reactors. The high-temperature flash drum oil also improves the overall thermal efficiency of the process.

Abstract: A special feed distributor is provided to radially, annularly, and uniformly feed and distribute oil and gas in a hydroprocessing unit, such as an ebullated bed reactor. In the preferred form, the feed distributor comprises an octagonal manifold with tangential outlet openings, a circumferential set of downward outlets, and a slotted skirt with radial discharge openings.

Abstract: Resid hydrotreating conversion of resid can be substantially increased by decreasing the feed gas rate and simultaneously increasing the concentration of hydrogen in the feed gases. Hydrogen purity can be increased by increasing the flow rate of lean sponge oil into the sponge oil absorbers, bleeding some of the recycled reactor tail gases, and increasing the makeup gas rate.