Q1: Milk is dried usually in a __________ dryer.

ANS:B - spray

Milk is usually dried in a spray dryer. Here's why:

• Spray drying is a common method used for drying milk and other dairy products.
• In a spray dryer, the liquid milk is atomized into small droplets and sprayed into a hot air chamber.
• The hot air rapidly evaporates the moisture from the droplets, leaving behind dried milk particles.
• Spray drying offers advantages such as high efficiency, rapid drying, and the ability to produce a fine powder with good solubility and shelf stability.

Therefore, milk is typically dried in a spray dryer. A spray dryer is a type of industrial drying equipment used to convert liquid or slurry feedstock into dried powder or granules. It operates on the principle of atomizing the liquid feed into small droplets and exposing these droplets to hot air in a drying chamber. As the droplets travel through the drying chamber, the water or solvent evaporates, leaving behind dried particles. Here's how a spray dryer works:

1. Atomization: The liquid feedstock, such as milk or a solution, is pumped into the top of the spray dryer. Inside the spray dryer, the liquid is atomized into small droplets. Atomization can be achieved using various methods, including rotary atomizers, pressure nozzles, or centrifugal atomizers.
2. Drying Chamber: The droplets are then introduced into a drying chamber, which is typically a tall cylindrical vessel. Hot air is simultaneously introduced into the drying chamber from the bottom or side. The hot air is heated to a temperature above the boiling point of the liquid in the droplets.
3. Evaporation: As the droplets travel through the drying chamber, the hot air quickly evaporates the moisture from the droplets. The water or solvent vaporizes into the air, leaving behind dried particles. The residence time of the droplets in the drying chamber is carefully controlled to ensure complete evaporation of moisture and prevent overheating or burning of the dried particles.
4. Separation: Once the droplets have dried, the dried particles are separated from the air stream. This can be achieved using cyclones, bag filters, or electrostatic precipitators, depending on the specific requirements of the application.
5. Collection: The dried particles are collected at the bottom of the drying chamber or in a separate collection chamber. The collected powder or granules are then discharged from the spray dryer for further processing or packaging.

Spray dryers are widely used in various industries, including food and beverage, pharmaceuticals, chemicals, and ceramics, to produce dried products with specific properties such as fine particle size, high solubility, and extended shelf life. They offer advantages such as high drying efficiency, rapid drying rates, and the ability to handle heat-sensitive materials. However, they also require careful control of operating parameters such as inlet temperature, feed rate, and air flow rate to achieve optimal drying performance.