Climbing film evaporator (GP B2)

Summary

A rising film evaporator system works by introducing liquor at the bottom of a tube, forming a liquid film that rises as vapor forms due to heat transfer from the tube walls. This system benefits from high film velocity, efficient heat transfer, and rapid vaporization, making it effective for evaporation processes. The vapor rises through the tube, with a mixture of vapor and concentrated liquid entering a cyclone separator for further processing. While it offers advantages like improved heat transfer and minimal temperature differences, it is challenging to maintain and clean due to the need for significant headroom during tube replacement.

Takeaways

• 😀 The rising film evaporator system includes a steam inlet, liquor inlet, chamber containing tubes, and a cyclone separator.
• 😀 The vapor travels faster than the liquid, causing the liquid to rise up the tube in a film.
• 😀 The liquid film is highly turbulent, leading to high heat transfer rates.
• 😀 The liquor to be evaporated is introduced at the bottom of the tube, forming a liquid film on the walls.
• 😀 Heat is transferred to the liquor from the walls, causing boiling to begin and vapor to form.
• 😀 Smaller vapor bubbles unite to form large bubbles, trapping liquid above them and pushing the liquid up the tube.
• 😀 The tube is filled with vapor, while the liquid forms a film over the walls that continues to vaporize.
• 😀 The mixture of vapor and concentrated liquor enters a cyclone separator.
• 😀 The vapor passes on to a condenser, while the concentrate goes to a receiver.
• 😀 The high film velocity reduces boundary layers, improving heat transfer efficiency and minimizing temperature differences.
• 😀 The use of long, narrow tubes provides large areas for heat transfer, contributing to increased efficiency.
• 😀 The main disadvantage of this system is that it is difficult to clean and maintain, especially because tube replacement requires significant headroom clearance.

Q & A

What is the basic principle behind the operation of a Climbing Film Evaporator?

The basic principle behind a Climbing Film Evaporator is that vapor flows faster than liquid, causing the liquid to form a film on the walls of the tube. This film rises as the liquid is heated, allowing for efficient evaporation.

How does the vapor travel in the Climbing Film Evaporator system?

In the Climbing Film Evaporator system, the vapor travels through the center of the tube, moving faster than the liquid, which results in the liquid forming a turbulent film on the walls of the tube.

What role does the cyclone separator play in the Climbing Film Evaporator?

The cyclone separator separates the vapor from the concentrated liquid at the upper end of the tube. The vapor is sent to a condenser, while the concentrated liquid is collected in a receiver.

What is the main advantage of the high film velocity in the system?

The high film velocity reduces the boundary layers between the liquid and the heating surface, which minimizes resistance to heat transfer and improves the system's overall heat transfer efficiency.

How do the long narrow tubes contribute to the efficiency of the Climbing Film Evaporator?

The long, narrow tubes increase the surface area available for heat transfer, which helps improve the efficiency of the evaporation process.

Why is the short contact time between the liquor and heating surface beneficial?

The short contact time reduces the risk of damaging heat-sensitive materials, allowing for safer and more efficient operation of the system.

What challenges are associated with maintaining the Climbing Film Evaporator?

A key challenge of maintaining a Climbing Film Evaporator is the difficulty in cleaning the system, and tube replacement requires significant headroom clearance (approximately 7 meters).

How does the Climbing Film Evaporator minimize the risk of thermally sensitive material damage?

By operating with a smaller temperature difference and a short contact time between the liquid and the heating surface, the system reduces the risk of damaging thermally sensitive materials.

What happens to the liquid and vapor as they move up the tube?

As the liquid moves up the tube, it forms a turbulent film on the walls. As more vapor is formed, it drags the liquid film upward. Eventually, bubbles merge to form large bubbles that trap liquid above them, which is then carried upward by the vapor.

What industries can benefit from using a Climbing Film Evaporator?

Industries such as food processing, chemical production, and wastewater treatment can benefit from using a Climbing Film Evaporator due to its efficient heat transfer and rapid evaporation capabilities.