The Advantages and Limitations of Vacuum Drying

The majority of industrial industries, including those that deal with chemicals, pharmaceuticals, food, polymers, and metal powders, can benefit from the use of vacuum drying equipment.

Vacuum drying has a lot of benefits, but as with most things in life, comprehension of the constraints and practical application of each design are equally crucial for implementation success.

As vacuum drying equipment removes water or removes and recovers solvents from a moist material, it is often employed for batch operations. In specialized procedures like as chemical reactions and polymer solid stating, the equipment is also occasionally used to alter a material's molecular and physical chemistry (referred to as a phase transition).

Typically, a volatile liquid is separated from a powder, cake, slurry, or other moist material using a vacuum dryer. Unlike filtration or centrifugation, which entail mechanically separating the liquid from the material, this procedure is inherently thermal in nature.

A vacuum dryer is an example of an indirect-heat dryer, as opposed to a direct-heat dryer, in which the material is submerged directly into the heating media (often a hot gas stream) and dried by convection. In other words, the material is dried by conduction when it comes into touch with the hot surface of the drier.

Understanding this difference is crucial for comprehending the benefits and constraints of vacuum drying as well as for choosing a vacuum dryer that effectively and affordably fulfills your process objectives.

Advantages

The closed-system design that is necessary to create and preserve the low-pressure environment inside the dryer has benefits for handling hazardous materials as well. Examples include explosive substances and poisonous chemicals or solvents. The dangerous vapours from such compounds are properly contained and condensed by the vacuum dryer without endangering your workplace's environment or the surrounding atmosphere. By limiting the amount of oxygen in the vacuum dryer with inert gas, you can further protect some hazardous items.

Limitations

Keep a few restrictions in mind when contrasting a vacuum drier with a direct-heat dryer, such as a direct-heat rotary dryer or fluid bed dryer. Due to the vacuum dryer's sealing requirements, batch mode operation almost always occurs. The procedures in your industry, however, may not make this a problem. For instance, batch operation is definitely preferable if you need to identify and trace individual quantities of your products. Additionally, batch drying offers more process flexibility and is simpler to adjust to evolving manufacturing techniques. However, you'll need to install surge hoppers and other material handling equipment before the dryer if your vacuum dryer is a part of a continuous process in order to set up a hybrid batch-continuous operation.

Regarding the equipment's heat transfer mode, there is yet another restriction for vacuum dryers. The maximum temperature of a vacuum drier is typically less than that of a direct-heat dryer, at roughly 315 deg C (600° F). In a vacuum drier, the pace at which the material temperature can be raised is likewise constrained. This is because, unlike a direct-heat dryer, which is only constrained by the volume of hot gas in the drying chamber, an in direct heat vacuum drier is only as large as the surface area available for heat transmission.