Question

In mechanical vapour recompression (MVR), vapour compression is accomplished mechanically using :

• A. Venturi scrubber
• B. Electric motor
• C. Pre-heater
• D. Cyclone unit

Hint:

MVR evaporators use about \(10\) to \(20\text{ times}\) less primary energy than conventional multi-effect thermal evaporators because they use an electric motor to reuse the latent heat of the vapor.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Evaporation is energy-intensive.
Mechanical Vapour Recompression (MVR) is a heat recovery technology used to reuse the latent heat of the evaporated water vapor, reducing the steam requirement of the evaporator.

Step 2: Detailed Explanation:
In an MVR system:
- The low-pressure water vapor leaving the separator of the evaporator is sent to a compressor instead of a condenser.
- This compressor is driven mechanically by a high-efficiency electric motor (or sometimes a steam turbine).
- The compressor raises the pressure and temperature of the vapor.
- The compressed, higher-temperature vapor is then returned to the heating side of the same evaporator stage.
- Here, the vapor condenses, releasing its latent heat of vaporization to boil more milk.
The mechanical energy provided by the electric motor acts as the driving force to upgrade the energy level of the waste vapor.
This makes MVR systems highly energy-efficient, requiring only a small amount of electricity to operate the motor instead of large amounts of fresh boiler steam.
Venturi scrubbers, pre-heaters, and cyclones are not used for mechanical vapor compression.

Step 3: Final Answer:
In MVR systems, vapor compression is accomplished using an Electric motor to drive the compressor.