Regenerator, fluidized bed

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). 

The Effect of Cohesive Forces on Catalyst Entrainment in Fluidized Bed Regenerators... 

Entrainment rates measured in a laboratory or pilot plant unit can also underpredict entrainment rates in commercial nnits if the solids tend to form clusters. This could be the case if the commercial-scale plant contains baffles and the laboratory or pilot plants do not. This was the case illnstrated in Fignre 11.10. Even the spacing of the baffles can have an effect on the entrainment rate. Adding baffles to a fluidized bed regenerator may actnally increase entrainment rates. As discussed above, particle clusters may need snfficient time in the emnlsion or bnbble region of the bed to form. Thus, a particle cluster may start growing near the bottom of the bed and continue to grow as it travels to the top of the bed. Baffles spaced... 

Fig. 1. A 1 MMTA fluid catalytic cracking unit with fast fluidized bed regenerator (courtesy Gaoqiao Petrochemical Company). 1, regenerator 2, first-stage FFB regenerator 3, second-stage FFB regenerator, 4, main fractionator, 5. FFB catalyst cooler 6, catalyst hoppers 7, cyclone...

Owing to the rapid formation and dissolution of particle clusters which contribute to high slip velocities and solid backmixing but preserve a limited extent of gas backmixing, the fast fluidized bed regenerator exhibits unique axial and radial profiles for voidage, temperature and carbon concentration (see Figs. 9 and 11 and Table VIII). 

Recentlyr Schockaert and Proment [ref. 41] simulated the catalytic cracking of gasoil in both fluidized bed or riser reactors, connected with a fluidized bed regenerator. The kinetic model for the cracking was based upon the lO- lump loodel of Mobil [ ref 42 ]. Only one deactivation function was used for all the coking reactions and it was exponential in the coke content ... 

Fig. 5.4. Bergbauforschung process for de Aenolizatian by activated carbon, (a) Hlter (b) adsorbs (c) sieve (d) fluidized bed regenerator, ( ) quench (f) combustor...

In the UOP/Hydro MTO process unit, the methanol and recycled DME come into contact with the catalyst in the reactor and are converted into light olefins. Residence times are very short and the reactor operates in a stable steady-state in the vapor phase at temperatures between 350 and 600 °C, and pressures between 0.1 and 0.3 MPa. In the process, the catalyst is deactivated by coke accumulation, and a part of catalyst is transferred to the fluidized bed regenerator in order to restore its activity. 

As a result of the cracking reactions, coke is deposited on the catalyst, consequently the catalyst is poisoned and has to be regenerated. This exothermic regeneration process is carried out by circulating it to a fluidized bed regenerator, where under excess oxygen, the coke is burned off the catalyst at a temperature and pressure of about 1272 T (690 °C) and 34 psia (2.3 bara) respectively. The process conditions should ensure that nearly all carbon monoxide produced in the bed is converted to carbon dioxide. The carbon monoxide concentration in the stack gas should meet the following constraint Xco < 10" mol/mol. 

---