Conventional and emerging processes that require the application of multiphase reactors are reviewed with an emphasis on catalytic processes. In the past, catalyst discovery and development preceded and drove the selection and development of an appropriate multiphase reactor type. This sequential approach is increasingly being replaced by a parallel approach to catalyst and reactor selection. Either approach requires quantitative models for the flow patterns, phase contacting, and transport in various multiphase reactor types. This review focuses on these physical parameters for various multiphase reactors. First, fixed-bed reactors are reviewed for gas-phase catalyzed processes with an emphasis on unsteady state operation. Fixed-bed reactors with two-phase flow are treated next. The similarities and differences are outlined between trickle beds with cocurrent gas–liquid downflow, trickle-beds with countercurrent gas–liquid flow, and packed-bubble columns where gas and liquid are contacted in coc...

Multiphase catalytic reactors: a perspective on current knowledge and future trends

Flow regime identification in gas-liquid flow and three-phase fluidized beds

http://www.nt.ntnu.no/users/skoge/prost/proceedings/aiche-2008/data/papers/P137638.pdf

Catalytic deoxygenation of liquid biomass for hydrocarbon fuels

Hydrodynamics of three-phase fluidized bed systems examined by statistical, fractal, chaos and wavelet analysis methods

The operation of a hydrocarbon synthesis reactor (2) and catalyst distributed in the reaction slurry (3) therein are improved by the presence in said reactor of one or more vertical downcomers (6) open at both ends with gas disengaging areas located at their top end (7). The downcomer (6) which circulates catalyst from the top of the reaction slurry to the bottom of said slurry is fully immersed in the reaction slurry (3) and preferably extends from just above the bottom of the reaction zone of the reaction vessel to just below the top surface of the reaction slurry. The bottom end of said downcomer is shielded from intrusion of rising synthesis gas by the placement of a baffle (9) which blocks rising gas entry but facilitates the exit of catalyst and liquid from the bottom of said downcomer and distributes them radially throughout the adjacent reactor slurry.

Hydrocarbon synthesis reactor employing vertical downcomer with gas disengaging means.

Experiments were performed to study the hydrodynamic characteristics of a cocurrent, gas-liquid-solid fluidized bed containing cylindrical hydrotreating catalysts under conditions of high gas holdup. These conditions were established using an aqueous t-pentanol (0.5 wt. %) solution as the liquid phase in an attempt to simulate reaction conditions for hydrotreating of residual oils and coal liquefaction. Separate three-phase experiments were performed with air and water to investigate the effect of surface tension on hydrodynamic behavior.

A mathematical model was developed to describe the minimum fluidization velocity behavior. Bed voidage, gas holdup and terminal velocity of the particles were analyzed and correlated empirically to investigate the effect of particle shape and liquid surface tension. A bubble-wakes interaction coefficient defined by Jean and Fan (1987) was determined for cylindrical particles.

Hydrodynamics of three‐phase fluidized bed containing cylindrical hydrotreating catalysts

An effective hydrotreating process is provided to minimize precipitation of asphaltenic solids in the product oil. In the preferred process, an aromatic diluent, preferably comprising decanted oil, is injected into one or more of the fractionators downstream of the reactor.

Process for reducing resid hydrotreating solids in a fractionator

A resid refining reactor has an ebullated catalyst bed. Hydrogen gas is released into the catalyst bed at a point which is far enough above a distributor plate at the bottom of the catalyst bed to form a gas updraft in a committed zone through the bed. This committed updraft causes a reduction in gas holdup which increases the residence time of a liquid phase in the catalyst bed.

Reduced gas holdup in an ebullated bed reactor

A reactor for refining resid includes an elongated vertical vessel containing a bed of catalyst which is expanded or ebullated by a liquid/gas mixture. The mixture rises in an updraft through the bed and then is recirculated with an increased velocity by an ebullating pump. To reduce gas holdup of the ebullated bed and to promote a more uniform flow, the gas is entrapped by two cascaded stages of baffles which have an internal conical shape to guide, direct, and entrap the gas. One of these two stages has a shape which creates a countercurrent in the flowing liquid to deflect any catalyst particles which might otherwise be elutriated by the increased velocity.

Reduced gas holdup in catalytic reactor

A vapor collector and process utilizes a skirted pan to collect vapor in an ebullated bed reactor and substantially minimize gas entrainment so as to enhance the efficiency and yield of resid hydrotreating.

Robert D. Buttke

Papers

Hydrodynamics of three‐phase fluidized bed containing cylindrical hydrotreating catalysts

Process for reducing resid hydrotreating solids in a fractionator

Reduced gas holdup in an ebullated bed reactor

Reduced gas holdup in catalytic reactor

Process for collecting vapor in ebullated bed reactors