Fluidized-bed systems are another commonly used gravity-based powder-feeding system for feedstock delivery. In this system, the powder feedstock is suspended by an upward flow of gas, creating a fluid-like state that allows for consistent and controlled delivery of the powder to the process.
The image shows a fluidized-bed system where the feedstock is gas-suspended within the hopper. The powder feed rate is determined by a venturi effect that is created when the carrier gas passes across an aperture within a powder port that is placed in the hopper. The variables that control the powder feed rate are carrier gas flow rate and orifice size.
Perceived advantages of such equipment are that it does not rely on mechanical systems and their associated instrumentation, and the flow of powder is continuous and uniform.
Image – Powder-feeding system: fluidized-bed feeder.
This information is from ASM Handbooks Online, Vol. 5A: Thermal Spray Technology, Coating Structures, Properties, and Materials. To find this information (subscription required), click on the link below and scroll down to Figure 18.
https://dl.asminternational.org/handbooks/edited-volume/12/chapter/133823/Feedstock-Material-Considerations-for-Thermal
