Ebullating Pumps

The ebullating pump circulates oil from the recycle cup through the downcomer and the grid. The circulation has to be snfflcient enough to lift and expand the catalyst bed from its initial settled level to its steady-state expanded and ebullating level. The recycle pump can be enclosed within the reactor shell (internal pnmp) so that high temperature and pressure of a full-scale reactor may be maintained without requiring to enter into the reactor shell to operate the pump (Lyzinski et al., 1993). 

The ebullating pumps are canned motor pumps (Kressmann et al., 1998), which are a combination of a centrifngal pnmp and a squirrel cage induction motor built together into a single hermetically sealed unit. 

These kinds of pumps offer advantages such as absence of dynamic seals, minimized maintenance, increased reliability, elimination of seal flush systems, minimized number of parts, maximized safety, and more compact design (Chacchia etal.,2004). 

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The extrudate catalyst requires higher liquid velocities than the flne catalyst to maintain the desired bed expansion. The liquid velocity is provided by recycling a portion of the eflBuent back to the inlet. The recycle or ebullating pump can be located internal or external to the reactor. 

Modeling of Processes and Reactors for Upgrading of Heavy Petroleum 10.2.1.5 Ebullating Pumps... 

In the reactor of Figure 8.3, a stable fluidized bed is maintained by recirculation of the mixed fluid through the bed and a draft tube. An external pump sometimes is used instead of the built-in impeller shown. Such units were developed for the liquefaction of coal and are called ebullating beds.. 

Ebullated bed a process in which the catalyst bed is in a suspended state in the reactor by means of a feedstock recirculation pump which pumps the feedstock upwards at sufficient speed to expand the catalyst bed at approximately 35% above the settled level. 

The H-Oil reactor (Fig. 21) is rather unique and is called an ebullated bed catalytic reactor. A recycle pump, located either internally or externally, circulates the reactor fluids down through a central downcomer and then upward through a distributor plate and into the ebullated catalyst bed. The reactor is usually well insulated and operated adiabatically. Frequently, the reactor-mixing pattern is defined as backmixed, but this is not strictly true. A better description of the flow pattern is dispersed plug flow with recycle. Thus, the reactor equations for the axial dispersion model are modified appropriately to account for recycle conditions. 

The H-Coal process (Stotler and Schuller, 1979) (Figure 19.14) is an extension of the ebullated-bed technology that is used to convert heavy oils and residua into lighter liquid products. Crushed (-60 mesh) coal is slurried with recycle oil and pumped to a pressure of up to 3000 psi after which the mixture is preheated and introduced into the bottom of the ebullated-bed reactor. The overhead products are fractionated into gases, light distillate, and heavy distillate. 

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