Apparatus and method for quenching in hydroprocessing of a hydrocarbon feed stream

A method for maximally occupying a reactor volume with a substantially packed bed of hydroprocessing catalyst during hydroprocessing by contacting the substantially packed bed of hydroprocessing catalyst with an upflowing hydrocarbon feed stream having a liquid component and a hydrogen-containing gas component comprising the steps of:

• (a) disposing a substantially packed bed of hydroprocessing catalyst in a reactor zone contained within a reactor volume such that said substantially packed bed of hydroprocessing catalyst occupies at least about 50% by volume of said reactor volume;
• (b) upflowing into said substantially packed bed of hydroprocessing catalyst a hydroprocessing feedstream including a liquid component and a hydrogen-containing gas component and having a rate of flow such that said substantially packed bed of hydroprocessing catalyst expands to less than 10% by length beyond a substantially full axial length of said substantially packed bed of hydroprocessing catalyst in a packed bed state;
• (c) injecting a liquid hydrocarbon quench into said substantially packed bed of hydroprocessing catalyst;
• (d) withdrawing a volume of said hydroprocessing catalyst from said reactor zone to commence essentially plug-flowing downwardly of said substantially packed bed of hydroprocessing catalyst within said reactor zone;
• and
• (e) adding hydroprocessing replacement catalyst to said essentially plug-flowing downwardly, substantially packed bed of hydroprocessing catalyst of step (d) at a rate to substantially replace said volume of said hydroprocessing catalyst of step (d).