Industrial fluidized bed reactors

In Section I, we mentioned that the TFM can simulate fluidized beds at engineering scales (height 1-2 m), and that the large-scale industrial fluidized-bed reactors (diameter 1-5m, height 3-20m) are still far beyond its capabilities. Clearly, it would be highly desirable to predict the properties of gas-solid flows at the industrial scale however at present, there is no fully evolved model— based on fundamental principles—which is capable of this. In this section, we outline some new ideas in this direction that have been developed both at the... 

The experiments were carried out on a semi-industrial fluidized bed reactor, illustrated in Figure 9.6, which shows four different sensor positions (A, B, C and D). Screw fittings were used to mount the sensors in order to secure optimal sensor pickup efficiency. Sensor location A is mounted onto an orifice plate on the main supply line of liquid urea to the reactor nozzles, following Esbensen et al. [5]. The sensors B, C and D are located on the wall of reactor chambers 1, 2 and 4, respectively. 

In industrial fluidized bed reactors, the bed height is commonly fixed by an overflow weir. Thus, as the gas velocity, U, increases from Umf, the apparent bed density decreases. An important design principle for the gas distributor is to ensure its sufficient pressure drop for a uniform gas distribution, i.e., without gas channeling, and stable bed operation. Specifically, the total pressure drop across both the distributor and the bed should be in an increasing trend with an increase in the gas velocity. Suppose that the pressure drop across a perforated distributor, Apdistnbuior, with a total orifice area of Ao can be expressed by... 

A number of sources can be identified for catalyst attrition in industrial fluidized-bed reactors ... 

The hydrochlorination of silicon was carried out in a test device consisting of feed supply, reactor, and product analysis. The reactor is made of glass and has an internal diameter of 35 mm. HCl feed is introduced to the silicon powder through a glass frit bottom of the reactor. The reaction temperature was controlled by a furnace with temperature controller and measured by a thermocouple inserted into an indent on the side of the reactor, reaching to the silicon bed. To adapt the conditions to the industrial fluidized bed reactor, the glass reactor was forced to vibrate by a commercial excentric drive. 

It must be noted here that most industrial fluidized bed reactors operate in a turbulent flow regime. Trajectory simulations of individual particles in a turbulent field may become quite complicated and time consuming. Details of models used to account for the influence of turbulence on particle trajectories are discussed in Chapter 4. These complications and constraints on available computational resources may restrict the number of particles considered in DPM simulations. Eulerian-Eulerian approaches based on the kinetic theory of granular flows may be more suitable to model such cases. Application of this approach to simulations of fluidized beds is discussed below. 

Werther J, Hartge E-U (2004) Modeling of Industrial Fluidized-Bed Reactors. Ind Eng Chem Res 43 5593-5604... 

Werther J. Modeling and scale-up of industrial fluidized bed reactors. Chem Eng Science 35 372-379, 1980. 

DESIGN ASPECTS OF INDUSTRIAL FLUIDIZED BED REACTORS, RESEARCH NEEDS. SELECTED SUBJECTS... 

SUGGESTED APPROACH FOR DESIGNING A LARGE-SCALE INDUSTRIAL FLUIDIZED BED REACTOR. 

Because of the particular complexities presented by a new process, industrial fluidized bed reactor design is almost always done as a custom job. A handbook approach is just not possible. If the company does not have extensive experience in the fluidization field (or even if it has), consultants with years of practical design and development experience should be consulted. Management would be foolish, indeed, to embark on a venture which is going to cost possibly hundreds of millions of dollars and require several years of effort without getting its hands on the best information, experience and judgement available. 

Many industrial fluidized bed reactors operate within, or close to, this range. 

---