Catalyst fluidized

Catalytic methanation processes include (/) fixed or fluidized catalyst-bed reactors where temperature rise is controlled by heat exchange or by direct cooling using product gas recycle (2) through wall-cooled reactor where temperature is controlled by heat removal through the walls of catalyst-filled tubes (J) tube-wall reactors where a nickel—aluminum alloy is flame-sprayed and treated to form a Raney-nickel catalyst bonded to the reactor tube heat-exchange surface and (4) slurry or Hquid-phase (oil) methanation. 

Fluidized-bed catalytic cracking units (FCCUs) are the most common catalytic cracking units. In the fluidized-bed process, oil and oil vapor preheated to 500 to SOOT is contacted with hot catalyst at about 1,300°F either in the reactor itself or in the feed line (called the riser) to the reactor. The catalyst is in a fine, granular form which, when mixed with the vapor, has many of the properties of a fluid. The fluidized catalyst and the reacted hydrocarbon vapor separate mechanically in the reactor and any oil remaining on the catalyst is removed by steam stripping. 

A fluidized catalyst behaves like a liquid. Catalyst flow occurs in the direction of a lower pressure. The difference in pressure between any two points in a bed is equal to the static head of the bed between these points, multiplied by the fluidized catalyst density, but only if the catalyst is fluidized. 

Dense Phase is the region where the bulk of the fluidized catalyst is maintained. 

Fluidized Catalyst Reactor. Two systems have been proposed, based on large scale operation of the Fischer-Tropsch process (to produce liquid hydrocarbons) at SASOL and at Carthage Hydrocol. The SASOL system was designed by M. W. Kellogg and has been operating for about 20 years (57, 58, 59, 60). 

The catalyst losses in either system are moderate and not excessively costly when inexpensive iron catalyst is used (as for production of liquid hydrocarbons). It is questionable, however, whether comparable losses of expensive nickel catalysts (for methanation) could be tolerated. For this reason, it is quite likely that the fluidized catalyst system will be used for methanation only after a cheap methanation catalyst is developed. 

Fluidized catalytic cracking (FCC) Heavy oils, Cig- - Fluidized catalyst particles None... 

Figure 11.10(b) can be modeled as a piston flow reactor with recycle. The fluid mechanics of spouting have been examined in detail so that model variables such as pressure drop, gas recycle rate, and solids circulation rate can be estimated. Spouted-bed reactors use relatively large particles. Particles of 1 mm (1000 pm) are typical, compared with 40-100 pm for most fluidizable catalysts. 

Fluidization quality of fluidized catalyst beds involving a decrease in gas volume... 

The fluidization quality significantly decreased when the reaction involving a decrease in the gas volume was carried out in a fluidized catalyst bed. In the present study, we carried out the hydrogenation of CO2 and used relatively large particles as the catalysts. Since the emulsion phase of the fluidized bed with these particles does not expand, we expected that the bed was not affected by the gas-volume decrease. However, we found that the fluidization quality decreased and the defluidization occurred. We studied the effects of the reduction rate of the gas volume and the maximum gas contraction ratio on the fluidization behavior. 

It is reported [1] that the fluidization quality was drastically decreased when the hydrogenation of CO2 was carried out in a fluidized catalyst bed (FCB). Recently, the phenomena occurring in the bed were directly observed [2] and it was found that the upper part of the emulsion phase was defluidized and this packed particles was lifted up through the column like a moving piston. 

Gaseous monomers can polymerize in the gas phase in the presence of a fluidized catalyst bed. As polymer forms, hot gas forces the newly made material out of the reactor to a collector. Figure 2.15 shows a simplified schematic diagram of a generic polymerization reactor. 

Terukatsu Miyauchi, Shintaro Furusaki, Shigeharu Morooka, and Yoneichi Ikeda, Transport Phenomena and Reaction in Fluidized Catalyst Beds... 

Catalytic cracking is a process that is currently performed exclusively over fluidized catalyst beds. The fluid catalytic cracking (FCC) process was introduced in 1942 and at that time replaced the conventional moving bed processes. These early processes were based on acid-treated clays as acidic catalysts. The replacement of the amorphous aluminosilicate catalysts by Faujasite-type zeolites in the early-1960s is regarded as a major improvement in FCC performance. The new acidic catalysts had a remarkable activity and produced substantially higher yields than the old ones. 

Transport Phenomena and Reaction in Fluidized Catalyst Beds... 

A simplified diagram of a typical FCC unit is shown in Figure 16.9. The reaction chemistry described above is carried out in this process at temperatures in the range of 500-540 °C by contachng the fluidized catalyst in the form of particles in the range of 30-120 xm in diameter with the hot feed injected near the top of a riser reactor followed by rapid disengagement after a short contact time (on the... 

Miyauchi, T., Furwsaki, S., Mooroka, S. and ikdea, Y., Transport phenomena and reaction in fluidized catalyst beds, Adv. Chem. Eng., 11 (1981) 276-448. 

In the United States, approximately one-third of all processed crude oil, amounting to about 5 x 10° bbl/day, is catalytically converted over fluidized catalysts. Over 500 tons of catalyst are required daily, yielding sales that in 1987 were estimated at -250 million dollars (1). Thus, in terms of catalyst usage and product value, catalytic cracking is still the most important unit operation of the petroleumrefining industry. This year, the worldwide sales of catalysts to the petroleum, petrochemical, and chemical industry are expected to exceed 2.4 billion dollars, and catalyst producers are preparing themselves for the turn of the century when catalysts are projected to become a 5 billion dollars per year global business (2). 

As the fluidized catalyst descends the standpipe, the increasing pressure compresses the fluidizing gas resulting in a decrease in the gas volume. If allowed to continue without adding aeration, the flowing catalyst will defluidize leading to unstable flow and potential loss of catalyst circulation. This is particularly true... 

Fluidize. In general to convert to a liquid state but in recent technology the term refers to processes in which a finely divided solid is caused to behave like a fluid by bringing it into suspension in s moving or liquid. The solids so treated are frequently catalysts and hence the term "fluid catalysts . In such a case the fluidized catalyst is brought into intimate contact and causes a desired reaction in the suspending liquid or gas mixture. Local over-... 

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