Principle, Construction, Working, Uses, Merits and Demerits of Fluidized Bed Dryer (FBD)

Fluidized Bed Dryer

Principle

The bottom of the fluidized-bed dryer is perforated, where hot air moves through the granules to be dried. The granules rise from the bottom of the air stream as they are suspended in it. The process is known as fluidization. To dry each granule completely, hot air surrounds it. This results in uniform drying of the materials.

Constructions

• There is a removable bowl on the side of the stainless steel fluidized bed dryer, and the pressure chamber is made of stainless steel.
• Air handling units, product vessels, exhaust filters, exhaust blowers, control panels, air distribution plates, spray nozzles, and solution delivery apparatuses are typical fluidized bed dryer components.
• Fluidization is stable and even when the proper distributor is used during the drying process.
• A suitable pressure drop across the distributor is necessary to ensure proper fluidization.

Working

Fluid bed dryers work according to a basic principle that is explained here. Solid powdered material is allowed to flow through an upward stream of air. This causes all particles to move at a faster rate than their setting rate. The air will blow up solid particles and suspend them in the airstream as it passes over them. Solid beds containing boiling liquids are known as fluidized beds. Hot air can be used to aid in the fluidization of the bed after it has been fluidized.

Hot air accelerates the drying process. Removable perforated bottom machines with stainless steel chambers are often called bowl machines. This bowl must contain all the materials that need to be dried. The air is introduced into the bowl from the bottom and heated to a set temperature by heaters. Filtered air is passed through the bed of the material after it has been filtered. Fans at the top of the equipment are responsible for the constant airflow. Through the use of a control panel, all parameters of the equipment, such as flow rate and temperature, can be adjusted.

A high drying rate is a characteristic of this machine since it quickly dries the material. Throughout the process, all materials remain free-flowing. As a result of the finger-like structure of the bags here, the drying bed has a greater surface area. The fluid bed drying process works well when this type of design is used, as it increases the drying rate and reduces the drying time. When not handled correctly, this machine can cause some serious problems. A few examples are as follows:

• The particles become electrostatically charged.
• Overheating of the fluid bed dryers.
• If the outlet filter is clogged, the pressure inside the vessel could increase, which can lead to an accident.

Uses

The pharmaceutical industry can be an excellent application for several powders; however, these powders lack uniformity, flow and tight packing, making them unsuitable for other purposes. The process of granulation consists of aggregating numerous primary powder materials into larger, more uniform granules with higher density. Fluid bed dryers can serve this purpose. The granulation system can be combined with it so that operations such as drying, mixing, finishing, granulation, and cooling can all be completed at the same time. This fluid bed drying technology is rapidly replacing traditional trays of drying products in the pharmaceutical industry.

Fluid bed drying reduces drying times and keeps drying conditions uniform. Additionally, a fluid bed dryer system allows the inlet air temperature to be controlled to ensure the granules' surface is drained of the correct amount of moisture. Many different purposes can be served by fluid bed dryers. It can be used to dry a wide range of materials, such as granules, fertilizers, powders, tablets, plastics, etc. In addition to the industries listed here, it is useful in other industries as well:

• Metallurgical
• Dyes
• Pharmaceutical
• Chemical
• food

Merits

• Strong heat and mass transfer rates result from excellent gas particle constants, which means high moisture removal rates.
• If part of the heating power is supplied by the internal heat exchanger, a high thermal efficiency will usually be achieved.
• It is also cheaper to operate.
• This reduces the time spent drying.
• Easy control and stability.

Demerits

• The need to suspend the entire bed in gas results in significant pressure drops and high energy costs.
• A high thermal efficiency operation requires increased gas handling due to the substantial recirculation of exhaust gas.
• Whether the feed is too wet, there is insufficient fluidization and flexibility.
• During drying, this equipment is not recommended when organic solvents must be removed.
• Some fluidized bed dryers don't produce uniformly high-quality products.
• Fine particles can aggregate in some situations and attrition is a high risk.
• There is a risk of fire or explosion if flammability limits are exceeded when processing poisonous or flammable substances using traditional hot air fluidized bed dryers.

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