Fluidized bed reactors regenerator

The principal advance ia technology for SASOL I relative to the German Fischer-Tropsch plants was the development of a fluidized-bed reactor/regenerator system designed by M. W. Kellogg for the synthesis reaction. The reactor consists of an entrained-flow reactor ia series with a fluidized-bed regenerator (Fig. 14). Each fluidized-bed reactor processes 80,000 m /h of feed at a temperature of 320 to 330°C and 2.2 MPa (22 atm), and produces approximately 300 m (2000 barrels) per day of Hquid hydrocarbon product with a catalyst circulation rate of over 6000 t/h (49). 

Esso-type stable fixed fluidized-bed reactor/regenerator is used for cracking petroleum oils (Fig. 19-23h). 

FIG. 19-23 Reactors with moving catalysts, (a) Transport fluidized type for the Sasol Fischer-Tropsch process, nonregenerating, (b) Esso type of stable fluidized-bed reactor/regenerator for cracking petroleum oils, (c) UOP reformer with moving bed of platinum catalyst and continuous regeneration of a controlled quantity of catalyst, (d) Flow distribution in a fluidized bed the catalyst rains through the bubbles. 

Werther J, Hartge E-U (2004) A population balance model of the particle inventory in a fluidized-bed reactor/regenerator system. Powder Technology 148 113-122... 

Fig. 13-19 Flow diagram for a fluid hydroformer, a fluidized-bed reactor-regenerator combination by permission from Esso Standard Oil Company, Baton Rouge, La.)...

UOP and Norsk Hydro have jointly developed and piloted a fluid bed process for the conversion of methanol to olefins (Fig. 16.) The process uses Union Carbide s (now part of UOP) SAPO-34 catalyst. A two fluidized bed reactor/regenerator system is used. 

Three fluidized bed processes are available for license from Mobil Badger (now ExxonMobil-Badger). These are MBR (Mobil benzene reduction), MOG (Mobil olefins to gasoline), and MOI (Mobil olefin interconversion). All three use zeolite catalyst and a dual dense fluidized bed reactor-regenerator system. The MOI process is shown in Fig. 17. The other two processes are conceptually very similar. 

Figure 2.8 A fluidized-bed reactor allows the catalyst to be continuously withdrawn and regenerated as with the refinery catalytic cracker.

The use of a fluidized-bed reactor is possible only when the reactants are essentiaUy in the gaseous phase. Eluidized-beds are not suitable for middle distiUate synthesis, where a heavy wax is formed. Eor gasoline synthesis processes like the MobU MTG process and the Synthol process, such reactors are especiaUy suitable when frequent or continuous regeneration of the catalyst is required. Slurry reactors and ebuUiating-bed reactors comprising a three-phase system with very fine catalyst are, in principle, suitable for middle distiUate and wax synthesis, but have not been appHed on a commercial scale. 

A salient feature of the fluidized bed reactor is that it operates at nearly constant temperature and is, therefore, easy to control. Also, there is no opportunity for hot spots (a condition where a small increase in the wall temperature causes the temperature in a certain region of the reactor to increase rapidly, resulting in uncontrollable reactions) to develop as in the case of the fixed bed reactor. However, the fluidized bed is not as flexible as the fixed bed in adding or removing heat. The loss of catalyst due to carryover with the gas stream from the reactor and regenerator may cause problems. In this case, particle attrition reduces their size to such an extent where they are no longer fluidized, but instead flow with the gas stream. If this occurs, cyclone separators placed in the effluent lines from the reactor and the regenerator can recover the fine particles. These cyclones remove the majority of the entrained equilibrium size catalyst particles and smaller fines. The catalyst fines are attrition products caused by... 

If deactivation of the catalyst is very short, then moving-or fluidized-bed reactors are required so that the catalyst can be withdrawn continuously, regenerated and returned to... 

The primary advantage of fluidized bed reactors, however, is that they permit continuous, automatically controlled operations using reactant-catalyst systems that require catalyst regeneration at very frequent intervals. Fluidized bed operation permits one to easily add or remove the catalyst from the reactor or the regenerator. Regeneration can be accomplished by any convenient procedure, but the... 

Co/ Fe mixed oxide, while in the second one, a fluidized-bed reactor, the catalyst that in the first step has been reduced by the olefin is reoxidized with air. The catalyst is continuously transported from the first reactor to the regenerator, by means of a C FB R. 

The second reaction vessel in a catalytic cracker is called the regenerator. The solid catalyst from the reactor is combined with a compressed air stream from an air blower, and the solid and gas phases flow upward into a bed of fluidized solid catalyst. The early designs used a bubbling bed reactor in which the velocity in the bed is slightly above the minimum fluidization velocity. More recent designs use a transport fluidized-bed reactor. A typical air-to-oil weight ratio is 0.54. 

The oxidation of butane (or butylene or mixtures thereof) to maleic anhydride is a successful example of the replacement of a feedstock (in this case benzene) by a more economical one (Table 1, entry 5). Process conditions are similar to the conventional process starting from aromatics or butylene. Catalysts are based on vanadium and phosphorus oxides [11]. The reaction can be performed in multitubular fixed bed or in fluidized bed reactors. To achieve high selectivity the conversion is limited to <20 % in the fixed bed reactor and the concentration of C4 is limited to values below the explosion limit of approx. 2 mol% in the feed of fixed bed reactors. The fluidized-bed reactor can be operated above the explosion limits but the selectivity is lower than for a fixed bed process. The synthesis of maleic anhydride is also an example of the intensive process development that has occurred in recent decades. In the 1990s DuPont developed and introduced a so called cataloreactant concept on a technical scale. In this process hydrocarbons are oxidized by a catalyst in a high oxidation state and the catalyst is reduced in this first reaction step. In a second reaction step the catalyst is reoxidized separately. DuPont s circulating reactor-regenerator principle thus limits total oxidation of feed and products by the absence of gas phase oxygen in the reaction step of hydrocarbon oxidation [12]. 

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