Troubleshooting of WFE - (Wiped Film Evaporator)

  • #1
Rachit
5
0
TL;DR Summary
Continuous boiloff operation in WFE.
Feed Details :
Component X : 80% ( Boiling point : 105 deg.C)
Component Y : 20% ( Boiling point : 256 deg.C)
Feed Rate : 600 kg/hr
Heating medium : Steam @ 145 deg.C
operating condition : 50 Torr, 90 deg.C ( Based on Aspen Flash Simulation).

Desired Outcome :
TO remove 99% of component X from Component Y.

History :
Earlier this operation was performed in batch mode. Where all of component X was boiled off.
During this, Bottom mass temperature was observed to go upto 120 deg.C uder 50 torr of vacuum.
No component Y was observed in the top distillate - throughout the operation.

Current Scenario :
Observations in WFE :
  1. In top distillate component Y is found ~10%.
  2. In bottom residue component Y is found ~80%.
  3. At 50 torr vacuum, operating temperature is only 40 deg.C.
  4. Upon increasing flowrate, component Y is found less in top distillate.

What should be done to minimize loss of component Y in top distillate ?
 
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  • #2
Have you tried to model this operation? Is the solution ideal so that Raoult's Law can be applied.
 
  • #3
Chestermiller said:
Have you tried to model this operation? Is the solution ideal so that Raoult's Law can be applied.
The solution is not ideal, but I have modeled the operation in Aspen plus and component Y in top distillate is ~0.5% w/w.
 
  • #4
The first step is to determine why your model is not matching the observed split. What are your thoughts on this? How do other observational measurements compare with model predictions? How confident are you in the VLE part of the model?
 
  • #5
My friend

Aspen Plus has a set of properties packages that will approach the simulation to the real process. It has a tutorial to select the best ones. However, you have to select PR if your components do not have a polar behavior.

To optimize the process, it could be done with the process data. Of course, anyone needs to know X and Y, to have a view of the distillation equilibrium of the mix. Simulation is a tool, just that; but trained process engineers should do it by analyzing the field process data.

Horacio
 

1. What are the common reasons for low throughput in a Wiped Film Evaporator (WFE)?

Low throughput in a WFE can often be attributed to several factors including feed rate inconsistencies, inadequate vacuum levels, and temperature settings that are not optimal for the material being processed. Additionally, fouling or clogging within the internal components such as the wiper blades or the evaporator column can significantly reduce efficiency.

2. Why is there a product degradation or color change in the output from a WFE?

Product degradation or color change in the output from a WFE can occur due to overheating, prolonged exposure to high temperatures, or improper vacuum levels. These conditions can cause thermal degradation of the product. It is important to optimize the temperature and vacuum settings according to the specific properties of the material being processed to minimize degradation.

3. How can I improve the separation efficiency of my Wiped Film Evaporator?

To improve the separation efficiency of a WFE, ensure that the wiper system is functioning properly to create a uniform film for efficient heat transfer. Additionally, optimizing the feed rate, vacuum levels, and temperatures based on the volatility and thermal sensitivity of the components can enhance the efficiency. Regular maintenance to prevent fouling and ensure clean and clear pathways is also crucial.

4. What should I do if the vacuum level in the WFE is not stable?

Instability in the vacuum level of a WFE can be due to leaks in the system, inadequate vacuum pump performance, or blockages in the vacuum lines. Check for and repair any leaks, ensure the vacuum pump is adequately sized and functioning properly, and clear any blockages in the lines. Regular maintenance and checks are recommended to prevent these issues.

5. How often should maintenance be performed on a Wiped Film Evaporator?

Maintenance frequency for a WFE depends on the usage intensity and the nature of the materials processed. Generally, routine checks should be performed after each batch or operation cycle to clean and inspect the wiper blades and internal surfaces for any deposits or wear. Comprehensive maintenance including checking vacuum pumps, heating systems, and other mechanical parts should be conducted every 3 to 6 months, depending on operational demands.

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