How do fluid bed dryers provide an effective method of drying?
Question
Leave an answer
kvjinstruments
Register Now
If You're New to this Website - Create an Account for 100% Free !!
Answer ( 1 )
To dry relatively free-flowing particles with a narrow particle size distribution, fluid bed dryers are an excellent choice.
Fluid Bed Dryer
From heavy mining to fine chemicals and pharmaceuticals, fluid bed dryer can be found in a wide range of industries. Particles with a relatively narrow size distribution can be effectively dried using this technique. Powders, granules, crystals, pre-forms, and non-friable agglomerates are all possible forms of feed. No mention will be made of the possibility of processing liquids in fluid bed systems with host media.
From a few pounds to several hundred tones per hour, rapid dryer are capable of processing a wide range of material feed rates. Fluid bed dryers come in three main varieties. Static fluid beds are the most common, due to the dryer’s inability to move while in use. Static fluid bed dryers can be used in continuous or batch mode and can be either round or square. As with the first type, the body of a vibrating fluid bed drying unit vibrates to help move material through the drying chamber. The majority of vibrating fluid bed dryers are rectangular. Utilizing tubes that deflect on a solid pan, this third type of fluid bed dryer fluidizes the material from above. This technology will not be discussed in this article. Direct, indirect, or combination heat sources can be used in fluid bed dryers. VJ’s Instrument is the best Fluid Bed Dryer manufacturer you will find.
A system’s operating principle
In most fluid bed dryers, the gas flows through the product perpendicular to the direction of travel, resulting in a through-the-bed flow pattern. The batch operation involves metering a dose of feed into the dryer bowl and processing it until the desired final moisture content is achieved… Wet feed is metered into the drying section (zone) of a continuous system using a suitable feeder. The dry product exits the same section.
In direct systems, the dryer’s wind-box or plenum is filled with hot gas. To distribute the gas across the distributor or fluidizing plate, a “Pressurized box” known as a plenum is required. Perforated plates with either non-directional or directional holes (nozzles) are known as fluidizing plates. The gas passes through these holes (nozzles) either with or without caps.
The drying chamber is filled with the process gas, which interacts with the feed and lifts it into a fluidized state known as a bed. The bed takes on the characteristics of a liquid, flowing and mixing in much the same way. The fluidization creates an efficient transfer device by allowing each material particle to come into direct contact with the gas stream.
Upon completion of the transfer of energy, the gas enters an expansion chamber, where the velocity is reduced so that entrained particles can return to the bed. A dust collection system such as a cyclone and baghouse, scrubber, or electrostatic precipitator is then used to remove the gas (ESP). A dust control system is required for fluid bed systems because of the interaction between the gas and the product.
The majority of fluid bed dryers are equipped with both forced and induced draught fans for drying purposes. For fluidization, the static pressure required can be high, requiring large motors on the fans – particularly the fluidizing fan. The expansion chamber above the bed is designed to have a zero or null pressure point.
A weir on the product discharge is the most common method of controlling the drying time. The bed depth can be controlled by this weir, which response to various inputs. Alternatively, the same system inputs can be used to modulate the feed rate with a constant weir setting (by using a variable speed drive on a vibrating or screw feeder). Monitored frequently in these systems are the bed temperature, the inlet air temperature, the exhaust air temperature, the wind box pressure, the bed differential pressure and the product temperature.