What are the problems faced in Overhead of CDU Condenser, and why do such problems occur?
Answers
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09/07/2018
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Amish Ajmeri, Bahrain Petrolium company, amish_ajmeri@yahoo.com
1-Poor desalting leading carryover salt with crude and formation of HCL due to hydrolysis of salt in heater which is corrosion in overhead system.
2-Napthanic Acid in crude also make weak acid in high temperature which is also indirect support to overhead system corrosion.
3-To prevent corrosion use corrosion inhibitor ( amine filmer ) but CI work on optimum PH if PH goes high or low amine filmer layer break and start overhead system corrosion.
4-To maintain PH use Ammonia, Higher concentration of ammonia start precipitation of NH4Cl which is also plug finfan tubes and deposit corrosion. so use correct rate of wash water to wash out NH4CL in overhead condenser.
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05/12/2008
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Berthold Otzisk, Kurita Europe GmbH, Berthold.Otzisk@kurita-water.com
Crude oils contain salts, which have to be removed at the electrical desalter. This is an important step to avoid corrosion in the overhead system. Most of the salts are washed out with the desalter effluent at the desalter. A small portion of NaCl, CaCl2 and MgCl2 will leave the desalter with the crude oil.
NaCl will not hydrolyse and CaCl2 has a very low tendency. The MgCl2 can hydrolyse at around 150°C and these chlorides will pass the distillation column to end-up in the overhead system. There these chlorides will attack the metal surface, resulting in corrosion.
It is a common practise to inject caustic (NaOH) into the crude oil after desalting. This will force the chlorides to form NaCl salts, which will not hydrolyse like MgCl2. The caustic injection has some disadvantages and can not be used at all crude distillation units.
Kurita´s ACF technology does not have the disadvantages of caustic. ACF products are very strong organic bases. Depending, where ACF products are injected the ACF will directly react with the chlorides to form a volatile non-corrosive gas or liquid ACF salt. The formed liquid ACF salts have a neutral pH and a very low corrosion tendency.
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07/10/2008
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Samuel Sinanan, IPSL, Samuel.Sinanan@ipsl.co.tt
These problems are caused by poor desalting leading to carryover of salt to the charge heater where there is hydrolysis of the salts which results in the formation of HCl which goes overhead and attacks your condenser and piping.
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