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What is the temperature and pressure maintained in the fractionator of a delayed coker unit? Does it not cause premature thermal cracking of the reduced crude oil even before it enters the coke drums?
 
Answers
13/05/2018 A: niranjan puttaraju, reliance industries ltd, niranjanmurthyp@gmail.com
Premature cracking of residue starts @370degC, however providing linger residence time @lower temperature will result in asphaltene precipitation.
Inlet to coke drum is supplid from heater outlet at very high temperature, where thermal cracking is already started in heaters.
Fractionator operating temperature varies between 305 to 370degC. And pressure varies depend on type of coke- 1barg to 5bar
11/05/2018 A: keith bowers, B and B Consulting, kebowers47@gmail.com
Some unit process designs route pre-heated fresh vacuum bottoms to the fractionator bottoms to 'quench' the heavy coker gas oil to keep it from coking up the fractionator boot and demister grid. The combined fresh feed feed/.and heavy coker gas oil then goes through the fired heater, effectively recycling the unconverted heavy coker gas oil. Net HCGO is taken over a baffle into a small boot which is on level control to ensure there is always flow in the recycle circuit.
11/05/2018 A: Ralph Ragsdale, Ragsdale Refining Courses, ralph.ragsdale@att.net
The feed is preheated to 580-700° F and exits the furnace at 900-950° F. The temperature depends on the crude source. The bottom of the column, which serves as a feed surge drum does collect some coke deposits. The internals plus filters are designed to prevent premature shutdowns due to such coke deposits. Column pressure is near atmospheric as in crude distillation designs.