Views: 263 Author: Wendy Publish Time: 2023-07-11 Origin: Site
The mass transfer process known as vacuum drying involves creating a vacuum in order to remove the moisture that is present in a substance, usually a wet solid. Drying is a crucial unit activity to remove moisture in chemical process sectors like food processing, pharmacy, agriculture, and textiles. Vacuum drying focuses on the idea of creating a vacuum to lower the chamber pressure below the pressure level of the water, causing it to boil, and is typically used for the drying of substances that are hygroscopic and heat sensitive. The pressure surrounding the material to be dried is decreased with the aid of vacuum pumps. As a result, the product's water has a lower boiling point, which lowers its ability to evaporate quickly. Vacuum drying can be done in batches and at lower relative humidity and pressures than close pressure, which allows for faster drying. Combining microwave power with vacuum drying improves the kinetics and efficiency of vacuum drying for fruits and vegetables.
That piece of equipment known as a vacuum dryer is used to assist in vacuum drying. In the pharmaceutical sector, vacuum dryer is more commonly referred to as a vacuum oven. Although most vacuum dryers are now built of stainless steel rather than their traditional cast iron construction, this allows them to withstand the high vacuum pressure without deforming.To maximize the amount of heat conductivity, the oven is divided into hollow trays.The oven door is securely fastened and coupled to an air pump to lower the pressure.
The vacuum dryer's trays are used to hold the materials to be dried while a pump lowers pressure. The dryer door is tightly closed, and conductivity is used to transmit heat by passing steam through the space between the trays and jacket. After the drying pump is disengaged and the product has dried, water vapours from the feed are distributed into the condenser. The dried product is then collected from the trays.
Drying heat-sensitive, hygroscopic, and poisonous materials in a vacuum drier is sometimes necessary. Since the solvent is frequently recovered by condensation, a vacuum dryer can be used to dry a feed that is a solution. Hybrid drying, which combines osmotic dehydration followed by heat pump drying and microwave-vacuum drying, has been demonstrated successful for improving product quality in areas like fruit preservation.
For heat-sensitive, hygroscopic, and/or poisonous powders and granules, drying is one of the most important industrial drying procedures. It's also important to avoid using too much heat when drying powder for a number of reasons, from safety to product quality:
When heated, the active components in pharmaceutical powders may lose their therapeutic action.
Drying – if exposed to high temperatures, some nutrients may degrade. Under excessive heat, the taste, consistency, and appearance can all deteriorate.
Plastics and chemical processing - When exposed to heat for an extended period of time, synthetic materials can leach poisons. Convection drying techniques may even become dangerous because the hot air stream must finally be released.
For drying massive quantities of heat-sensitive powders or granules at a far lower temperature than would be required in a conventional industrial drier, vacuum drying may be a safe and exceedingly meticulous process. Anywhere ambient pressure is decreased in a vacuum, liquids' flashpoints drastically decrease.
Due to the high latent heat of vaporization of water and the inherent inefficiency of employing hot air as the (most common) drying medium, drying is one of the most energy-intensive unit operations. Different forms of drying technology are required by various business sectors depending on the particular product qualities required. Biological goods, food, and other high-value items that appear to be heat-sensitive require extra care when being dried. These heat-sensitive items are then convection-dried at greater temperatures.