Bubbling Fluidized-Bed Reactor

A fluidized bed consists of a bed of particles that is kept fluidized by the continuous upward flow of a gas. Typically, the system consists of a vertical cylindrical tube with a perforated distributor plate at the bottom. Some material in particulate form (usually sand) is placed inside the tube, and gas flows from the distributor plate 

---

SASOL has pursued the development of alternative reactors to overcome specific operational difficulties encountered with the fixed-bed and entrained-bed reactors. After several years of attempts to overcome the high catalyst circulation rates and consequent abrasion in the Synthol reactors, a bubbling fluidized-bed reactor 1 m (3.3 ft) in diameter was constructed in 1983. Following successflil testing, SASOL designed and construc ted a full-scale commercial reac tor 5 m (16.4 ft) in diameter. The reactor was successfully commissioned in 1989 and remains in operation. 

Bio-oil upgrading over Ga modified zeolites in a bubbling fluidized bed reactor... 

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. 

The procedure used in the previous section to develop a mathematical model for a catalytic bubbling fluidized bed reactor with a simple reaction A —> B can be extended to develop a model for the practically important consecutive reaction A —U B C, where B is the desired product. 

In spite of the major effort in this field in the last 30 years, the development at industrial scale of post-consumer plastic pyrolysis has considerable uncertainties concerning the selection of the more suitable technology. The more developed technology in the literature is the bubbling fluidized bed reactor [1-5] where the fused plastic coats the inert particles (sand). Nevertheless, the operation at large scale in this reactor presents problems of defluidization, due to particle agglomeration provoked by fusion of particles coated with plastic [4]. 

Baerns, Mleczko, L., Tjitjopoulos, G. J., and Vasalos, I. A. Comparative Study of the Oxidative Coupling of Methane in Circulating and Bubbling Fluidized Bed Reactors, in Circulating Fluidized Bed Technology IV" (Amos A. Avidan, ed.), pp. 509-524. Somerset, Pennsylvania (1993). 

Utikar, R.P. and Ranade, V.V. (1997), MoBB Model for bubbling fluidized bed reactors, CHEMCON. 

Raw biomass and all the pretreated samples except those receiving the water wash (for reasons explained in the Results and Discussions section) were thermally processed in the fast pyrolysis pilot plant at RTI, Ltd. This bubbling, fluidized bed reactor operates between 360 C and 490 C with gas residence times on the order of 2 s. Details on this system can be found in Reference 14. Operating conditions for pyrolysis of the switchgrass and comstover samples are detailed in Tables II and III, respectively. 

Detailed analysis of literature data showed that products of high quality and economic advantage may be obtained under dynamic conditions using bubbling fluidized bed reactor for burning or pyrolysis of RRHs [11, 17, 73, 77-89]. The fluidized bed technology is selected as preferable for the production of amorphous silica from rice husks. 

A circulating fluidized-bed (CFB) reactor is very similar to a bubbling fluidized-bed reactor. The major difference is the gas velocity. If the gas velocity of a bubbling fluidized bed increases, at some point the force exerted mi the particle will be enough to move it upwards, carrying it outside of the bed. This situation is called elutriation. 

Muralidhar R., Gustafson, S., and D. Ramkrishna, Population Balance Modeling of Bubbling Fluidized Bed Reactors-II. Axially Dispersed Dense Phase, Sadhana, 10, 69-86 (1987). 

Lungu M, WangJ, Yang Y Numerical simulations of a bubbling fluidized bed reactor with an energy minimization multiscale bubble based model efiect of the mesoscale, Ind Eng Chem Res 53 16204-16221, 2014. 

Riidisuli M, Schildhauer TJ, BioUaz SMA, van Ommen JR Scale-up of bubbling fluidized bed reactors—a review, Powder Technol 217 21—38, 2012. 

---