Method and apparatus for an on-stream particle replacement system for countercurrent contact of a gas and liquid feed stream with a packed bed

A method of periodically or semi-continuously transferring catalyst or other particles into and out of a substantially packed bed of catalyst in a reactor vessel during continuous operation at elevated pressures and temperatures for contact with a feed stream having a gas component and a liquid component flowing upwardly therethrough which comprises,

• entraining fresh catalyst particles in a liquid stream flowing from a pressurizable catalyst supply hopper into a reactor vessel to inject catalyst into the top of a catalyst bed in said reactor vessel and similarly entraining deactivated catalyst particles at the bottom of said catalyst bed for flow in a stream comprising a portion of said liquid component of said feed stream to a pressurizable catalyst recovery hopper,
• flowing each of said streams between said reactor and its respective hopper through a primary flow path having a substantially uniform cross-sectional area throughout its length and a diameter at least five times the average diameter of the catalyst particles entrained therein, each of said primary flow paths further including at least one full-bore, in-line ball valve having a fully open bore of substantially the same diameter as said flow path,
• selectively controlling the pressurization of each of said catalyst hoppers to a value only sufficiently different from the pressure in said reactor vessel to limit the flow rate of said stream flowing through its said primary flow path to maintain laminar flow while carrying entrained catalyst from said supply hopper into the upper end of said catalyst bed and while removing catalyst from the bottom of said catalyst bed to said recovery hopper, and the inlet for said stream including said entrained catalyst being from an intake zone adjacent to the bottom of said catalyst bed said intake zone being out of the upflow path of said feed stream into said catalyst bed to avoid entrainment of significant amounts of said gas component into said intake zone and to avoid local levitation or ebullition of said catalyst bed above said intake zone during transfer of catalyst out of said reactor vessel, and
• at least one auxiliary fluid flow path opening into each of said primary flow paths between its said ball valve and said reactor vessel for selectively introducing auxiliary fluid into said primary flow path to flush catalyst particles out of said path including said open bore of said ball valve during operation thereof and to block selectively catalyst particles from entering said primary flow path after each transfer of catalyst.

A method of periodically or semi-continuously transferring particles into and out of a reactor vessel during continuous upward flow of a feed stream through a gravitationally descending, substantially packed bed of catalyst which comprises,

• laminarly flowing a liquid stream carrying fresh catalyst into the upper end of said reactor vessel through a primary flow path from a pressurizable catalyst supply hopper to install or replace catalyst forming an axially elongated catalyst bed in said reactor vessel,
• at least periodically withdrawing catalyst from the lower portion of said catalyst bed by laminarly flowing a portion of said feed stream from the lower end of said reactor vessel to carry used catalyst through another primary flow path into a pressurizable recovery hopper,
• each of said primary flow paths for said streams having a substantially constant cross-sectional area throughout its length and a diameter at least five times greater than the average diameter of the catalyst particles flowing therethrough,
• each of said primary flow paths including a downwardly opening inlet portion for upflow of the respective stream and catalyst entrained therein through at least one section for up flow of said entrained catalyst over a distance that is substantially shorter than the balance of said primary flow path,
• said primary flow path additionally including at least one in-line control valve having a full flow through-bore of the same diameter as the balance of said primary flow path to maintain said laminar flow of said liquid stream throughout in said primary flow path, and
• at least one auxiliary flow path for selectively injecting another fluid under pressure into said primary flow path at a point between said reactor vessel and its respective pressurizable hopper for selectively clearing catalyst from said inlet portion and said through-bore of said valve in said flow path after transfer of said entrained catalyst between said reactor vessel and the respective hoppers.

In an on-stream catalyst replacement system for periodically or continuously delivering fresh catalyst to a reactor vessel having an upwardly flowing feed stream including a gas component and a liquid component rising through a descending substantially packed bed of said catalyst extending axially through said reactor vessel, the improvement comprising

• selecting the size, shape and density of said catalyst particles forming the packed catalyst bed in accordance with rate of flow and viscosity of said feed stream during contact with said catalyst to avoid substantial ebullition and/or levitation over a substantial portion of the axial length of said packed bed at a selected flow rate of said feed stream,
• uniformly distributing the gas component of said feed stream into the base of said catalyst bed and across the transverse cross-sectional area thereof so as to avoid localized ebullition of said bed along its axial length, including recirculation of catalyst particles therein as said catalyst moves downwardly in plug flow through said vessel,
• said feed stream being introduced into said base of said bed through a plurality of concentric annular zones under a pervious conical or pyramidal surface extending radially outwardly from a truncated impervious central area supporting said catalyst bed, said concentric annular zones forming uniformly concentric alternate upward feed paths of said liquid and said gas components over said pervious transverse cross-sectional area,
• additionally maintaining said plug flow of said catalyst bed downwardly through said vessel while injecting quench gas and intercepting gas components flowing upwardly in said bed across at least one level intermediate the length of said bed to cool and laterally divert gas flow through a plurality of transversely extending flow paths, each of said transverse flow paths being under an inverted V-shaped shed positioned to deflect downwardly flowing catalyst particles outwardly over the upper transversed surface of said sheds, and each of said sheds includes a plurality of elongated slots forming longitudinally spaced apart flow paths along the outer edges of said transverse surfaces to distribute gas upwardly therethrough,
• periodically removing catalyst particles from a central portion of said base of said bed to a catalyst recovery hopper by flowing a portion of the liquid component of said feed stream from said vessel to said recovery hopper, said liquid flow being at a rate not in excess of laminar flow from directly above said impervious truncated portion of said conical support, and maintaining said laminar flow through a uniform, cross-sectional area flow path between said vessel and said recovery hopper including at least one in-line full bore ball valve for transport of entrained catalyst particles in said liquid flow stream, selectively blocking catalyst particles from entering said flow path by flowing fluid from an auxiliary source back into said primary flow path to prevent blocking of said inlet between withdrawals of catalyst from said bed, and
• periodically replacing catalyst particles in said bed by entraining catalyst particles in a liquid stream pressurized to create laminar flow of said stream into the upper end of said reactor vessel from a pressurizable catalyst hopper, said liquid stream flowing through a flow path having a substantially uniform cross-sectional area throughout its length and a diameter of at least five times the average diameter of the catalyst particles flowing therein, said laminar flow path further including at least one in-line full-bore ball valve of substantially the same diameter as said flow path, to maintain said laminar flow passing therethrough and
• at least one auxiliary fluid flow path for selectively introducing auxiliary fluid into said flow path intermediate to said catalyst hopper and the inlet to said reactor vessel for flushing catalyst particles from said path including said full bore of said in-line control valve.

A method of maximizing the useful volume and reactivity of a bed of catalyst in a reactor vessel during counterflow of an upwardly flowing hydro-carbon feed stream comprising a mixture of liquid and gaseous components through a downwardly moving bed of catalyst while maintaining optimum fluid flow rates of said components in said feed stream undergoing catalytic reaction which comprises

• packing said vessel with at least one bed of catalyst particles having substantially the same size, shape, and density over the axial length of said reactor vessel, said particles being selected in accordance with the average optimum velocity of the feed stream, including said gas components, flowing through said bed,
• controlling the rate of flow of said feed stream in an amount and to an extent sufficient to maintain ebullition or levitation of said catalyst bed to less than 10% over substantially the full axial length of said bed, introducing the gas component and the liquid component of said feed stream at a rate not substantially greater than said optimum rate of flow by simultaneously flowing said components upwardly into the base of said packed bed through a plurality of alternate concentric annular rings of said gas component and said liquid component across substantially the full cross-sectional area of said base,
• periodically adding replacement catalyst to the top of said downwardly moving bed at a rate to replace catalyst withdrawn from the bottom of said bed, and
• transferring catalyst out of said bed from a central portion of said packed bed below the entry point of said annular rings of gas and liquid components by flowing a portion of said liquid component at a rate sufficient only to entrap catalyst particles therein under laminar flow condition of said liquid.