Q & A > Question Details
Our naphtha sample from crude distillation unit went off on chloride content with result showing 1.3 ppm.So we checked organic chloride in our crude tank. The result showed presence of organic chloride in that particular crude tank. So that tank is kept blocked and we resumed to our normal operation.
We did many brain-stroming and looked for solution.
Can the experts in this forum please suggest how to process this crude having high organic chloride. Is there any chemical treatment available. How can this problem be solved?
 
Answers
05/10/2018 A: Muhammad Faisal, Oman Oil Refineries & Petroleum Industry (Orpic)-Oman, engr.faisalfraz@gmail.com
1. crude column OVHD SW to be test for detail analysis i.e. to identify types of chlorides (Ca, Mg, crystalline salts, organic salts). organic salts usually not treated in desalters. sometimes, using caustic injection (downstream of desalter helps, but it is to be injected carefully (FCC/RFCC catalyst is poison if Na > 3wtppm or more).
2. crude tank reported 1.3wtppm org.cl2 is very negligible. normally org cl2 sources can be FCC slops, or upstream feed quality. you can partially mix the tank material with other crude tanks and re-process to CDU.
3. For NHT, feed, ensure water injection d/s of HDT R'x to avoid salt formation. monitor Temp d/s of R'x effluent AFC to knock down all chlorides.
04/10/2018 A: Eric Vetters, ProCorr Consulting Services, ewvetters@yahoo.com
While it's possible for some organic chlorides to hydrolyze to form HCl in the crude unit, it will normally go out with naphtha to the NHT. Some methods for measuring organic chlorides, infer the presence or organic chlorides rather than actually measuring them. If you have chlorides in the naphtha though, the chances are good that it is organic (you can confirm by washing the naphtha sample with water. Any chlorides still there after washing should be organic.). In the NHT, the Cl in organic chlorides gets converted to HCl.
When processing this crude, you should increase the frequency of chloride measurement in the crude tower overhead system and be prepared to increase neutralizer addition if it hydrolyzes or if it turns out some of what you thought was organic chloride actually wasn't). In the NHT you want a water wash, and may need a neutralizer. There is some ammonia formed in the NHT. If there is more ammonia than HCl, you may be able to control pH without adding neutralizer. If the N content of the naphtha is low, there may not be NH3 formed to neutralize all the HCl formed in the NHT reactor. If you can control the crude rate from the contaminated tank relative to other tanks, that gives you an additional way to control the amount of organic chloride in the NHT at any time.
04/10/2018 A: Berthold Otzisk, Kurita Europe GmbH, Berthold.Otzisk@kurita.eu
Organic chlorides in crude oils are not unusual and sometimes analysed in the range between 1 and 5 ppm. Organic chlorides are coming from artificial sources like pipeline or ship cleaning with organic solvents. The problem with the analysis of crude oils is, that the inorganic chloride concentration is analysed, but in most cases the organic chloride concentration is not measured. Organic chlorides pass the electrical desalter. In the furnace the bounded organic chlorides are removed from the hydrocarbon chain and enter the distillation column as volatile chlorides. At the end very corrosive HCl is formed and high chloride concentrations are measured, if no treatment occurs before.
Methyl chloride (CH3Cl) is not corrosive and has a thermal stability of about 450°C. It will not decompose in the furnace and will end up in the gas phase of the overhead system. The addition of caustic after desalting can help to reduce some of the overhead chlorides in the sour water phase, but the sodium is a catalyst poison and cannot be used at all refineries.
Chloride guard traps can be a solution to reduce the amount of chlorides if that is a severe problem. Another alternative could be Kurita´s ACF technology. A very strong organic base is injected after the desalter system before the furnace. Chlorides will immediately react with the ACF product to form an ACF salt. Under that high temperature conditions the ACF salt will thermally decompose into volatile CH3Cl gas and a neutralizing amine. Both products will go overhead, where the neutralizing amine will shift the pH of the sour water to a higher level and also will bound overhead chlorides. The volatile CH3Cl will leave the overhead system with the gas phase. It needs to be checked first, if CH3Cl in the LPG is accepted, when no organic chloride specification is implemented. Otherwise a combination of caustic plus ACF injection could be used, adjusted to defined operating conditions. By using ACF after desalting no chlorides should be analysed in the naphtha product.
04/10/2018 A: Mohamed Banjar, SA &PRC, banjarms@yahoo.com
a. The crude oil with high content chlorine should be
blended with crude oil with zero or low content chlorine. The
total chlorine content of the mixed crude oil is controlled below
30mg/kg
b. Remove organic chlorides from crude oil by using chlorine
transfer agent
04/10/2018 A: Sridhar Balakrishnan, Bharat Oman Refineries Limited , laksrid@yahoo.com
Can you tell us by which technique organic chloride has been estimated?
03/10/2018 A: NS Murthy, GE, murthy.ns@ge.com
Typically Org Chlorides are handled thru chloride guard beds u/s of reforming process. As such, 1.3ppm as Cl is not an alarming level for naphtha. Further, if the unit has depentanizer before reforming unit, there is chance the Org Cl will go into C5 stream which then can be added to gasoline pool post correction for mercaptans in C5 stream. The refiner concerned may take up with licensor of reforming unit to install chloride guard bed.
As regards the second query, the Org Chloride containing crude needs to be liquidated thru blending with remaining crudes in the diet. Normally we specify org Cl content of 1ppm max on crude.