Replacement of wash water with hydrocarbon at Upstream of Coker fractionator overhead condenser 1

[PetroDDP]

Normally wash water is used to wash ammonium and cynaide salts in overhead vapour line (upstream of condenser) in Delayed coker fractionator.Is it technically feasible /viable to replace this stream with hydrocarbon instead of water.

 

[EmmanuelTop]

No. These salts are insoluble in hydrocarbons.

Dejan IVANOVIC
Process Engineer, MSChE

 

[PetroDDP]

Thanks for your prompt feedback. If the fractionator overhead has sufficient water in form of steam along with hydrocarbon then is there any feasibility as partial pressure of H2O will remain same after mixing that means 10 % water vapour already will remain in the overhead stream? (as velocity steam is already being put in coker furnace).
Thanks in advanced.

 

[EmmanuelTop]

To force condensation of water, you need to either increase condenser duty (more cooler banks) or inject liquid water, that will in turn decrease the overhead stream temperature upstream of the condenser and ensure liquid water droplets at the condenser inlet.

By injecting liquid hydrocarbon that is supposed to evaporate upon injection, you are effectively reducing partial pressure of water which further reduces condensation temperature of water, meaning that you would need to cool the entire stream much below the temperature that is sufficient for water condensation in the case when liquid water is injected. The main problem (or drawback) of wash water injection in general is that LMTD of the overhead condenser is reduced, resulting in reduced condenserperformance. Injecting hydrocarbons would make things worse, and would not solve your problem.

Dejan IVANOVIC
Process Engineer, MSChE

 

[PetroDDP]

Got the point.Thanks.!!