Fluidized catalytic reactors

The performance of a fluidized bed combustor is strongly influenced by the fluid mechanics and heat transfer in the bed, consideration of which must be part of any attempt to realistically model bed performance. The fluid mechanics and heat transfer in an AFBC must, however, be distinguished from those in fluidized catalytic reactors such as fluidized catalytic crackers (FCCs) because the particle size in an AFBC, typically about 1 mm in diameter, is more than an order of magnitude larger than that utilized in FCC s, typically about 50 ym. The consequences of this difference in particle size is illustrated in Table 1. Particle Reynolds number in an FCC is much smaller than unity so that viscous forces dominate whereas for an AFBC the particle Reynolds number is of order unity and the effect of inertial forces become noticeable. Minimum velocity of fluidization (u ) in an FCC is so low that the bubble-rise velocity exceeds the gas velocity in the dense phase (umf/cmf) over a bed s depth the FCC s operate in the so-called fast bubble regime to be elaborated on later. By contrast- the bubble-rise velocity in an AFBC may be slower or faster than the gas-phase velocity in the emulsion... 

Description The SUPERFLEX process is a proprietary technology patented by ARCO Chemical Tech nology, Inc. (now Lyondell Chemical Co.), and is exclusively offered for license by Kellogg Brown Root. It uses a fluidized catalytic reactor system with a proprietary catalyst to convert low-value feedstocks to desirable propylene and ethylene products. The catalyst is very robust thus, no feed pretreatment is required for typical contaminants such as sulfur, water, oxygenates or nitrogen. Attractive feedstocks include C4 and CB... 

Distributions in Fluidized Catalytic Reactors", Chem. Eng. Progr. Symp. Ser., 1962, 1. 

Catalyst/metal recovery e g., catalysts from fluidized catalytic reactors, nickel, platinum, pharmaceutical products, silicon several hundred plants are currently operating worldwide for such purposes. 

The design equation for a perfectly mixed "fluidized" catalytic reactor can be replaced by that of a CSTR. 

Kellogg Brown Root LLC Propylene Light (C to CJ hydrocarbon olefins-containing streams The SUPERFLEX process uses a fluidized catalytic reactor system with a proprietary catalyst to convert low-value feedstocks to predominately propylene and ethylene products 3 2006... 

Orcutt JC, Davidson JF, Pigford RL. Reaction time distributions in fluidized catalytic reactors. Chem Eng Prog S5m Series 58(38) 1-15, 1962. 

Orcutt, J. C., J. F. Davidson and R. L. Pigford. Reaction Time Distributions in Fluidized Catalytic Reactors. Chem. Engr. Progress Symp. Series No. 38, Vol. 58 (1962) 1. 

Fluidized-bed catalytic reactors. In fluidized-bed reactors, solid material in the form of fine particles is held in suspension by the upward flow of the reacting fluid. The effect of the rapid motion of the particles is good heat transfer and temperature uniformity. This prevents the formation of the hot spots that can occur with fixed-bed reactors. 

Figure 2.8 A fluidized-bed reactor allows the catalyst to be continuously withdrawn and regenerated as with the refinery catalytic cracker.

Fluidized-bed catalytic reactors tend to generate loss of catalyst through attrition of the solid particles, causing fines to be generated. 

Table 7. Fluidized-Bed Catalytic Reactors for Chemical Synthesis...

Fluidized bed catalytic reactors seem to have so many advantageous features that they were considered for many processes. One of the advantages is their excellent heat transfer characteristics, due to the large catalyst surface to volume ratio, so very little temperature difference is needed for heat transfer. This would make temperature control problem-free. The second is the uniformity of reaction conditions in the bed. 

For the manufacturing of sulfosuccinic acid esters, which belong to a special class of surfactants, maleic acid anhydride is needed. Maleic acid anhydride is an important intermediate chemical of the chemical industry. Its worldwide output amounts to about 800,000 tons (1990) [64]. Maleic acid is produced by catalytic vapor phase oxidation process of benzene or n-C4 hydrocarbons in fixed bed or fluidized bed reactors according the following reaction equations. The heat of reaction of the exothermic oxidation processes is very high. 

Marmo, L., Rovero, G., and Baldi, G., Modeling of catalytic gas-solid fluidized bed reactors, Catal. Today, 52, 235-247 (1999). 

Fuel industry is of increasing importance because of the rapidly growing energy needs worldwide. Many processes in fuel industry, e.g. fluidized catalytic cracking (FCC) [1], pyrolysis and hydrogenation of heavy oils [2], Fischer-Tropsch (FT) synthesis [3,4], methanol and dimethyl ether (DME) synthesis [5,6], are all carried out in multiphase reactors. The reactors for these processes are very large in scale. Unfortunately, they are complicated in design and their scale-up is very difflcult. Therefore, more and more attention has been paid to this field. The above mentioned chemical reactors, in which we are especially involved like deep catalytic pyrolysis and one-step synthesis of dimethyl ether, are focused on in this paper. 

Recent research development of hydrodynamics and heat and mass transfer in inverse and circulating three-phase fluidized beds for waste water treatment is summarized. The three-phase (gas-liquid-solid) fluidized bed can be utilized for catalytic and photo-catalytic gas-liquid reactions such as chemical, biochemical, biofilm and electrode reactions. For the more effective treatment of wastewater, recently, new processing modes such as the inverse and circulation fluidization have been developed and adopted to circumvent the conventional three-phase fluidized bed reactors [1-6]. 

Catalytic upgrading of bio-oil was carried out over Ga modified ZSM-5 for the pyrolysis of sawdust in a bubbling fluidized bed reactor. Effect of gas velocity (Uo/U ,f) on the yield of pyrolysis products was investigated. The maximum yield of oil products was found to be about 60% at the Uo/Umf of 4.0. The yield of gas was increased as catalyst added. HZSM-5 shows the larger gas yield than Ga/HZSM-5. When bio-oil was upgraded with HZSM-5 or Ga/HZSM-5, the amount of aromatics in product increased. Product yields over Ga/HZSM-5 shows higher amount of aromatic components such as benzene, toluene, xylene (BTX) than HZSM-5. 

Fluidized-bed noncatalytic reactors. Fluidized beds are also suited to gas-solid noncatalytic reactions. All the advantages described earlier for gas-solid catalytic reactions apply here. As an example, limestone (principally, calcium carbonate) can be heated to produce calcium oxide in a fluidized-bed reactor according to the reaction... 

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