Pressure distillation column startup and tuning
Start the model Continuous pressure distillation column with default parameters (benzene-toluene mixture, benzene mass fraction 35%, non condensable 2%, 10 trays+boiler, feed tray n°5)
Operating conditions are: feed 2000 kg.h-1, reflux ratio 4, pressure 1.4 to 1.6 bar a, steam to reboiler ~600 kg.h-1, distillate specification 95% of benzene, residue specification 5% of benzene
- Column bottom is already filled, fill it up to 100% level, then open degazing valve at 80% and dispose cooling water on condenser
- Start heating bottom with heating steam flow controller at 600 kg.h-1
- Follow temperature profile in thermosiphon reboiler, and at boiling, vapor rising up in the column
- When vapor reach condenser, purge non condensable gas and close the degazing valve to keep pressure around 1.5 bar a
- When reflux drum level reach 30%, start reflux pump and put cascade reflux drum level -> reflux flow control in operation
- When you think it's time, set feed flow control up to 1000 kg.h-1, feed pre-heater at boiling temperature, cascade bottom level -> residue flow rate control, cascade reflux ratio -> distillate flow rate, and overhead pressure control on degazing at 1.5 bar a
- When column is on specification, start increase the feed up to 2000 kg.h-1
- When you succeded in controlling the column, try to find the feed limit of the column
- If the limit is on degazing flow rate, let the pressure increase, and/or change degazing valve cv
- If the limit is on reboiler, decrease the operating pressure, or increase steam network pressure and/or reboiler heating area
Remarks:
- This column is also able to treat feed without non condensable, operating though with the condenser flooding pressure controller
- You can see with this model what happen in case of heat excess (pressure relief valve), or heat default (vaccuum breaker)
Page précédente : Continuous distillation at total reflux
Page suivante : Evaporation-Crystallization