Q & A > Question Details
During Crude distillation unit start up activities, water travels from crude storage tank to crude tower when furnace outlet temperature was 172C. It caused crude tower trays to dislodge. What if level of crude tower remains high then flash zone, does level of crude tower have significant effect on tray dislodge? Our system is furnace operated crude tower.
16/11/2015 A: keith bowers, B and B Consulting, kebowers47@gmail.com
First: Be thankful the furnace is still there. Slugs of water entering with the crude have wrecked many furnaces. Water has an expansion ratio over 1000 times at low pressures. Entire furnaces have been blown apart violently and burned down. The lower 5 trays in the distillation tower should be designed to withstand at least 2.0 psi uplift so minor surges will not damage or displace them.
JOB No 1 is to prevent the water slugs
05/02/2015 A: Celso Pajaro, Sulzer Chemtech, celso.pajaro@sulzer.com
The sudden large water vaporization increase the vapor flowrate thru column internals creating an uplift force that dislodge the trays above the flash zone. Trays above flash zone are specified to hold 1 psi of uplift (some designers may prefer 2 psi, or 1/2 psi), this apply only to 3-5 trays located above the flash zone.
If bottom crude level is high (above the flash zone), and water gets into the column, then large water bubbles rising thru the liquid will dislodge the trays