Ebullated bed

Laboratory reactor for studying three-phase processes can be divided in reactors with mobile and immobile catalyst particles. Bubble (suspension) column reactors, mechanically stirred tank reactors, ebullated-bed reactors and gas-lift reactors belong the class of reactors with mobile catalyst particles. Fixed-bed reactors with cocurrent (trickle-bed reactor and bubble columns, see Figs. 5.4-7 and 5.4-8 in Section 5.4.1) or countercurrent (packed column, see Fig. 5.4-8) flow of phases are reactors with immobile catalyst particles. A mobile catalyst is usually of the form of finely powdered particles, while coarser catalysts are studied when placing them in a fixed place (possibly moving as in mechanically agitated basket-type reactors). 

Reported residue conversion is significantly high for the five types of included reactors and largest for the slurry type of reactor. Besides, the slurry reactor together with the ebullated bed reactor can handle heaviest feedstocks and highest metal contents. Resid conversion requires higher temperatures, and pressure drop is essentially zero in these two reactors. However, product quality is better for the fixed and moving bed processes. 

Product yields and qualities obtained from HCK of heavy Safaniya VR are compared in Table 12 [142], As can be seen, higher yields on slurry and ebullated beds are associated with poorer product quality, besides the asphaltene concentration in the hydrocracked VR makes almost impossible any further improvement by further processing. 

The T-STAR ebullated bed is shown schematically in Fig. 6. The figure demonstrates that a uniform catalyst distribution is maintained throughout the reaction chamber via the upward flow of the hydrogen, feed oil, and recycle oil. The internal recycle allows for increased conversion and assists in maintaining a uniform temperature throughout the reactor. Careful monitoring of the temperature in an ebullated bed... 

Figure 6. T-STAR three-phase ebullated bed for hydrotreating petroleum intermediates. (From Clausen et al, 1992.)...

In normal operation of ebullated bed reactors, the reactor feed temperature is the control variable. The desired reactor feed temperature depends on both the feed rate and feed composition. The feed temperature is chosen such that the overall heat generation in the reactor is used to elevate the low temperature feed material to the bed temperature during... 

Johns, W. F., Clausen, G., Nongbri, G., and Kaufman, H., Texaco T-STAR Process for Ebullated Bed Hydrotreating/Hydrocracking, paper presented at the 1993 National Petroleum Refiners Association Annual Meeting, San Antonio, TX (1993)... 

H-Coal A coal gasification process. Crushed coal is mixed with process-derived oil and catalytically hydrogenated in an ebullated bed under pressure at 455°C. The catalyst is a mixture of cobalt and molybdenum oxides on alumina. Developed by Hydrocarbon Research from the 1960s and piloted in Catlettsburg, KY, from 1980 to 1982. See also CSF, H-Oil, CSF, Synthoil. 

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.. 

The H-Cocd Process, based on H-Oil technology, was developed by Hydrocarbon Research, Inc. (HRI). The heart of the process was a three-phase, ebullated-bed reactor in which catalyst pellets were fluidized by the upward flow of slurry and gas through the reactor. The reactor contained an internal tube for recirculating the reaction mixture to the bottom of the catalyst bed. Catalyst activity in the reactor was maintained by the withdrawal of small quantities of spent catalyst and the addition of fresh catalyst. The addition of a catalyst to the reactor is the main feature which distinguishes the H-Coal Process from the typical process. 

Reactors with moving solid phase Three-phase fluidized-bed (ebullated-bed) reactor Catalyst particles are fluidized by an upward liquid flow, whereas the gas phase rises in a dispersed bubble regime. A typical application of this reactor is the hydrogenation of residues. 

Catalysts in coal liquefaction are used in moving-bed, ebulating-bed, and fixed-bed processes. Disposable iron catalysts must be used in moving beds. More expensive Co-Mo and Ni-Mo catalysts are used in either ebulating or fixed beds, and catalyst deactivation rates and ultimate lifetime are of concern (80, 81). In ebulating beds, a small portion of fresh catalyst is continuously fed to balance the catalyst being purged. 

In ebullating bed reactor, such as the H-coal process, Ni-Mo or Co-Mo alumina catalysts have been used (96). The catalyst definitely improves the oil yields by accentuating aromatic hydrocracking, achieving conversions around 95% at catalyst make-up rates of 1 3%. 

A liquid/solid separation step is usually required before the catalytic reaction with nondisposable catalysts. This is an expensive step. To remove it, the catalyst must be compatible with the contaminating solids. Ebulating beds can partially satisfy this condition, but the rate of catalyst replacement becomes large if the deactivation is severe. 

The ebullated, expanded, and slurry-bed reactors utilize a fluent catalyst zone unlike the stationary catalyst design of fixed-bed reactors. This design overcomes several of the problems encountered when processing residua in fixed-bed catalytic reactors. The commercial H-Oil process (Eccles et al., 1982 Nongbri and Tasker, 1985) employs the ebullated-bed, whereas the... 

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