2 replies to this topic

[Wong]

Dear all,

 

       The operation engineer has requested us to study the effect of changing the temperature setpoint on column reboiler TC controller which measures the inlet temperature of hot process water(Shellside). This hot process water is used to heat up and partially vapourise the feed containing 89 wt% H20 & 11% EO prior to being introduced into the column.

 

       The distillation column is used to make pure refined Ethylene Oxide and contains 86 trays. On normal operation, almost all trays consist mostly of liquid ethylene oxide. We are interested in studying the effect on reducing the temperature setpoint on column performance. Our main concern is by reducing the temperature, we might stall the column and cause weeping/dumping due to insufficient vapour flowrate.

 

      By reducing the temperature setpoint, less of the hot process water is bypassed from heat exchanger E6774 which is upstream of the column reboiler. 

 

      Appreciate if anyone can advice and point me to the right direction on how I can accomplish this. I was thinking of running simulation on the column since design data is available

[Bobby Strain]

I believe that you already answered your question.

 

Bobby

[pavanayi]

Wong,

Why has the operation engineer requested the study? What does the operation engineer want to achieve? Changing the reboiler set point is a means to achieve what? There is no point in making a simulation and playing with it unless you know what you are trying to achieve. 

 

If you have a tuned process simulation and do a hydraulic analysis on the column, yes you would be able to have an idea about where your present operation is and where it might move, once the change is made. The way the column is spec'ed to converge will be key to understand the effect as you mentioned. 

 

Also, please post a PFD of the process as it is easy to visualize your question with a picture. You mention altering the column reboiler temperature set point, while also mentioning that the heat is used to pre-heat the feed into the column. It is confusing for a person who is not familiar with your plant.