Fluidized Bed Reactors

Fluidized Bed Reactors

A fluidized bed reactor is a type of chemical reactor where a bed of solid particles is suspended and fluidized by a gas or liquid stream flowing upward through the bed. This creates a fluid-like behaviour of the solid particles, with characteristics similar to those of a boiling liquid. Fluidized bed reactors are widely used in various industries, including petrochemical, chemical, and pharmaceutical, for processes such as catalytic reactions, combustion, and drying.

The below image (excerpted from Levenspiel) shows various regimes of fluidization.

Fluidized beds may be used in both catalytic and non-catalytic modes. For example, some commercial industrial catalytic processes using Fluidized beds include the following: Catalytic cracking of heavy petroleum fractions (FCC), Phthalic anhydride, Acrylonitrile, Aniline (hydrogenation of nitrobenzene), Synthesis of polyethylene and polypropylene, Fischer-Tropsch synthesis, Oxidation of SO2 to SO3, Chlorination or bromination of methane, ethylene, etc Maleic anhydride (from butane) and Pyridine. Some of our past projects at Amar have been in some of these areas. Below is a P&ID of a fluidized bed reactor fabricated at Amar on a past project.

Perhaps the most well-known use for fluidized beds is the FCC Reactor. Fluidized Catalytic Cracking is a crucial operation in most contemporary refineries and many of our readers may be familiar with the schematic below (courtesy of Kirk Othmer Handbook):

Among non-catalytic processes, the applications we see a push for Fluidized bed reactions include coal gasification, combustion, roasting of various ores, incineration, reduction of catalysts, and catalyst regeneration. Many of our customers are now exploring Fluidized beds for their most challenging reaction needs which may have been performed sub-optimally in other reactors in the past.

Very often Fluidized beds are associated with reactors but we often get customers from the pharma and specialty chemicals industries using fluidized beds for drying, granulation, or coating applications. Ultimately the fluidized bed is a very versatile reactor. We feel it has a lot of potential for adoption but many customers hesitate due to the complexity of the equipment as well as the models associated with it. We admit fluidization is not a simple technology, however, with the right assistance many of our customers adopt it successfully and are delighted with the results. Especially for demanding applications fluidization can be the perfect choice. Some of the technical advantages of a fluidized bed include:

• Excellent heat transfer for highly demanding exothermic reactions
• Allows the use of very active catalysts. These not only generate extremely high heat flux but also the particle size must be very small to prevent mass transfer limitations. This means particles will get easily suspended
• Relatively uniform temperature distribution compared to other reactor choices
• Ability to handle coking and regeneration of catalysts in relatively continuous modes

We do not intend to convey that Fluidized beds are easy to design or operate. Not at all. But if used correctly they can be the perfect solution to a difficult problem!

But more on this in Part 2 of this article. Stay tuned! Meanwhile do contact our experts at Amar for any particular project needs in the Fluidized Bed area. [email protected]