High Inorganic Chloride salt n LVGO

Question

High Inorganic Chloride salt n LVGO

DDSpetro (Petroleum)

(OP)

16 Jan 10 05:24

Hello...Experts !! Happy New Year to all of you !!

LVGO –Light Vaccum gas oil is one of the product from Vacuum crude distillation column , high Total chloride especially inorganic chloride is reported , while checking at overhead receiver boot water chloride it remains only 1 or 2 ppm , while LVGO chloride data shows total chloride 15 ppm ,20 ppm some times 23 ppm , it varies from 5 ppm to 25 ppm ; out of which organic chloride is very less say , e.g. out of 20 ppm , 16 ppm is inorganic and rest is organic , desalter efficiency remains ~ 98 % ,LVGO draw temperature is 130 to 140 C; LVGO Return temp. is ~ 40 C ; NH4Cl Desublimation temp. delta online monitoring is there but it shows more than 20 C delta difference, lab analysis shows no presence of Fe,Zn,Al metals & absence of amine,ammonia chloride or not even Na,Ca ; It sounds to be HCl.Caustic dosing in upstream crude unit is ~ 200 to 300 lph.One thing which was observed that , whenever NH3 demands goes up in VDU Column ovhd (Dosing as per Overhead reciver boot water pH), chloride in LVGO goes down ;

What are the potential cause of this chloride ? It is very critical point of concern because this LVGO goes to VGO hydrotreater and it can cause sever corrosion in the downstream.

Thanks in advance to all of you.

25362 (Chemical) · Answer 1 · 2010-01-16 07:19:42

Please consider that iron ^(III) chloride, formed as a result of corrosion, is a salt that boils (!) at around 315^oC.

whammett (Industrial) · Answer 2 · 2010-01-16 14:16:16

I agree with 25362. How old is the system and how long has this been a problem? Is there anyway to check CS piping(if this is in fact the source of the problem) upstream for corrosion while the system is still in operation?

Will Chevron Corp.

DDSpetro (Petroleum) · Answer 3 · 2010-01-17 08:24:35

Thanks 25362 & whammett for your prompt reply.

The Unit is recently commissoned ~ 1 year of operation.

During Lab analysis No traces of Fe is found.If FeCl3 is formed ,I suppose it could have found as "Fe presence" during lab analysis of LVGO sample , but it is not the case ,however let me dig out one more time for sample.

Certain crudes type which is processed in the blend e.g. Merry 16 etc. Some prsence of Arsenic (As) is there as per Crude Assay data in VGO cut i.e. 0.5 ppm ,Is there any chance of AsCl3 at column overhead ?

25362 (Chemical) · Answer 4 · 2010-01-17 09:17:43

I'm not acquainted with that particular crude oil, but AsCl₃ boils at about 130^oC. Therefore, depending on its partial pressure, if present, it may appear with distillates.

whammett (Industrial) · Answer 5 · 2010-01-17 18:02:18

Has this been a problem since the unit started? If not, have you changed types of crude?

The reason I am asking is because if it is a recent development, and has not been present since the start, it could be stemming from corroded piping upstream of the vaccum distillation column.

Will Chevron Corp.

DDSpetro (Petroleum) · Answer 6 · 2010-01-18 01:28:27

Yes, this is the problem since allmost after unit start up.data is attached for reference.Crude blend diet keeps on changing;Merry is suspected crude where good correlation was found but again not all the time.

http://files.engineering.com/getfile.aspx?folder=417a3b94-8443-40e8-9ab1-e90af8eb8500&file=LVGO_Chloride.xls

http://files.engineering.com/getfile.aspx?folder=cb858c4e-a600-4069-a1cf-291fa45ffb29&file=LVGO_Chloride_analysis.ppt

whammett (Industrial) · Answer 7 · 2010-01-18 19:37:24

Is there any way you could use a crude blend that does not require/include "merry", and then test those results?

If not, can you post the makeup of this merry?

Will Chevron Corp.

DDSpetro (Petroleum) · Answer 8 · 2010-01-18 22:36:54

The attached box plot analysis in ppt shows that when Merry crude was not there at that time, LVGO Chloride mean remains 12 ppm and when Merry was there in the blend at that time mean LVGO chloride remains ~ 20 ppm. Merry in the blend typically remains 10 to 30 % in the blend when it is processed.

The mystry here is that VDU Column overhead reciever boot water only 1 or 2 ppm while LVGO chloride , suspecting is it possible that HCL gets condensed and report along with LVGO instead of overhead

DDSpetro (Petroleum) · Answer 9 · 2010-01-19 02:14:11

LVGO Pump around return temp. remains 46 C in the unit, where LVGO High chloride observed; LVGO Draw temp. is ~ 120 C; VDU Column top temp remains ~ 40 C;

During Day time & night time difference of LVGO chloride is found 1.2 ppm to 3 ppm to see that whether HCl is getting condensed or what , because in other units where LVGO High chloride is not observed – LVGO Pump around return temp. remains 57 C ; is it possible for HCl condensation phenomena ?

Other problem since unit commissioning is that HRCO (Slop wax ) section is facing high corrosion rate as per corrosion coupon installed ( ~ 0.20 mpy/year – Metal Loss) the MOC is P5 material, 5% Cr,1/-Mo,rest Fe & this HRCO goes to Crude main fractionator for quenching media ~ 70 m3/hr , whether is it possible that CrCl3 / MoCl3 or similar compounds gets reported at LVGO through corrosion reaction at VDU Furnace at higher temperature ?

http://files.engineering.com/getfile.aspx?folder=b51d8f9d-d2da-416f-b08b-4e90b6db5715&file=Chloride_LVGO.doc

25362 (Chemical) · Answer 10 · 2010-01-19 04:58:06

Has external contamination by ingress (in-leakage) of cooling (salt-containing) water been considered ?

DDSpetro (Petroleum) · Answer 11 · 2010-01-19 05:56:30

There is no as such cooling water exchangers in between or no any leaky exchangers so, doubt can be ruled out.

DDSpetro (Petroleum) · Answer 12 · 2010-01-19 06:48:44

After LVGO/Crude PA exchanger, one Fine fan cooler followed by C.W.HE is there but cooling tower performance in terms of ORP , monitoring parameters no any tale tale indication found of HE leakage.

whammett (Industrial) · Answer 13 · 2010-01-19 06:51:29

Well it looks like the levels were still high before merry was introduced. However, merry made it worse. This is a tough problem because it's hard to tell if the problem stemmed from the crude blend having merry or not.

The feedstock comes straight from atmospheric distillation before it gets to the VDU?

Is there any way to slow the feed through the furnace to change the incoming feedstock temperture and see if that has an affect on the HCL without significant changes to your product cuts?

Will Chevron Corp.

DDSpetro (Petroleum) · Answer 14 · 2010-01-19 07:10:11

Yes, Before Merry,problem was there but with Merry problem has become worst , as may be it has got higher Ni,V metals any impact ?

Yes, RCO feed goes directly to VDU with ~ 365 C, slow down the feed through VDU furnace is cutting down the throughput may be difficult option ,

One another thing was observed that VDU Furnace transfer line Corrosion rate is high i.e. more than 0.35 mpy in both the units which is having MOC P-5 ,Cr,Mo.

What is the opinion about HCl condensation at vaccum condition i.e. 20 -24 mmhg pressure of VDU column at PA return temp. of 46 C against 57 C ; because boot water reciver is having only constant daily 1 or 2 ppm max.

25362 (Chemical) · Answer 15 · 2010-01-19 08:58:13

Corrosion on transfer lines may also be due to naphthenic acidity.

whammett (Industrial) · Answer 16 · 2010-01-19 09:22:23

I agree with 25362. What is the TAN of the crude blend? Or do you have a TAN of the feedstock going into the VDU?

I have heard of Ni and V causing problems during FCC, but at the tempertures you mentioned, I do not think that they would pose a problem. However, antimony is a widely used heavy metal passivation additive if you were up for trying that.

If I were to have to try and guess where the chloride problems were coming from, I would suspect that it was from the transfer line corrosion. What is the piping material? CS? There is no quick fix to that problem except changing out the piping.

Will Chevron Corp.

DDSpetro (Petroleum) · Answer 17 · 2010-01-19 12:28:39

THE MOC Of transfer line is P5 MATERIAL.cromium 5%,1/2% moly rest FE, TO cater napthenic acid corrosivity,in VDU COL Feedstock pump circuit,phosphate based inhibitor is in place of well know vendor.

25362 (Chemical) · Answer 18 · 2010-01-20 00:31:56

It has been shown that stainless steels with up to 12% Cr have no advantage over carbon steel vis a vis naphthenic acid corrosion. In addition, naphthenic acids appear to accelerate high-temp sulfidic corrosion in heaters.
See, for example, thread124-214862: High TAN Crudes and thread338-177729: Naphthenic acid resistance of chromized 316.

DDSpetro (Petroleum) · Answer 19 · 2010-01-20 01:59:54

on an avg. crude blend TAN Value remains 0.6 Mg KOH/G OF oil sometime it goes up to 1.0 in the crude blend.

DDSpetro (Petroleum) · Answer 20 · 2010-01-20 04:09:00

There is good amount of correlation has been seen with LVGO chloride vz. LVGO PA Flow as compare to return temp. which remains with in 2 C variation.BY looking at graph, is it possible to prove HCl condensation theory, mean while LVGO sample is again given for Cr,FeCl3,Ni,V metal analysis along with moisture analysis in the sample because HCl only can be present if moisture is present.

give your expert comment pl.

http://files.engineering.com/getfile.aspx?folder=06122da8-21b9-4d0a-9f0a-fc24c45a8d4a&file=HCl_Condensation_theory.ppt

25362 (Chemical) · Answer 21 · 2010-01-20 05:26:59

The presence of chlorides in LVGO, and transfer line corrosion, might indeed be independent/unrelated events.

Magnesium chloride, for example, if not removed by the crude unit's desalter, releases HCl by thermal decomposition mainly in the atmospheric topping column; one of the results may be the formation of ferric chloride.

I don't have the vapor pressures of anhydrous HCl, but since its critical temperature is 51.5^oC, it is reasonable to assume that, if formed by salt decomposition, it stays as a vapor at the temperatures encountered in the distillation columns of a crude unit.

In regard to possible naphthenic acid corrosion, one ROT would be to keep the crude oil blend at an acid number ≤ 0.5 mg KOH/g; therefore, crude oil blends with greater values might result in corrosion.

DDSpetro (Petroleum) · Answer 22 · 2010-01-20 07:31:35

Desalter outlet salt ptb Vz. LVGO Chloride - No correlation found.

http://files.engineering.com/getfile.aspx?folder=d09e03df-fad8-4ff5-a7c6-198dd7c4e8e6&file=LVGO_Chloride_Vz._Desalter_Outlet_salt.ppt

DDSpetro (Petroleum) · Answer 23 · 2010-01-20 12:39:02

mgcl2 is separately not monitored in desalter outlet ,0.6 to 0.8 PTB DESALTED SALT reported as NACL,hardly we can assume 30% mgcl2 again correlation is poor with desalted crude.

25362 (Chemical) · Answer 24 · 2010-01-20 13:59:48

Curiously the left half of the plotted points seem to correlate quite well.

DDSpetro (Petroleum) · Answer 25 · 2010-01-20 22:52:13

Yes, 25362, it was correct ...how do we technically justify ?

It was observed in laboratery that in LVGO sample, chloride gets reduced by 60 % by water wash at room temperature.Static mixture followed by coalscer will be good option ?

25362- can you pl. elaborate about HCl will remain in vapor phase as you mentioned in previous post ..so, Low LVGO PA flow or High LVGO Return temp. will not be the solution is it like that ?

earlier first time chloride analysis in LVGO no, presence of Fe found , however,second sample is given for it.

25362 (Chemical) · Answer 26 · 2010-01-21 01:10:52

A water wash is what actually an electrical crude oil desalter does. However, efficient mass transfer, and addition of demulsifiers, do not manage to reduce the salt content by 100%; that's the reason why refineries install two desalters in series.

See thread124-136505: Chloride Removal Alternatives for tips.

It is apparent that HCl formed by hydrolysis and by thermal decomposition of salts at the (P,T) conditions prevailing in the topping and vacuum towers should be in the vapor state.

DDSpetro (Petroleum) · Answer 27 · 2010-01-21 02:09:49

So, Chance of corrosive product FeCl3 will be higher rather than HCl,it looks like but why again i am wondering why PA flow should correlate with LVGO chloride salts as attached in the slide.

In fact one datapoint/outlier was removed from Desalter outlet salt vz. LVGO Chloride & very good positive corrleation has seen between one of desalter train outlet salt & LVGO chloride as attached in the slide ; while other train outlet salt was not correlating with LVGO chloride ,other parameters are studied and attached for your expert comments if any one contributing like HVGO CCR,95 %,Caustic injection,VDU Column flash zone temp. in crude unit as some good correlation has been seen with chloride salt as attached.

http://files.engineering.com/getfile.aspx?folder=2ce72d93-6bbb-43c2-aaf0-95e09a485a02&file=LVGO_Chloride_analysis.ppt

Once again thanks 25362 for expert tips.

25362 (Chemical) · Answer 28 · 2010-01-21 08:59:00

Thanks for the undeserved star. One could venture a logic hypothesis to go this way: the PA flow rate affects the condensation of volatile salts in the main tower. More PA more salts condensed.

DDSpetro (Petroleum) · Answer 29 · 2010-01-27 08:49:05

Hello,25362

Lab analysis received in terms of Moisture / Metal presence in LVGO ; Moisture to the tune of 1821 ppm @ 90 C is found . But Fe metals is <1 ppm while Na is 1 to 1.4 ppm observed as attached in the file.

It is really struggle to check the effectivness of Caustic injection ( 6.6 % solution) in desalter downstream

Pl. for your expert comments.

DDSpetro (Petroleum) · Answer 30 · 2010-01-27 08:49:54

http://files.engineering.com/getfile.aspx?folder=1d437729-15dd-4a6b-aefe-f36f50a7f05a&file=Metals_&_Moisture_in_chlorides.xls

25362 (Chemical) · Answer 31 · 2010-01-27 09:03:15

Water content seems to be dissolved water from stripping steam. Are U using a stripper for the LVGO? Please note that Na may also come with stripping steam.

DDSpetro (Petroleum) · Answer 32 · 2010-01-27 10:42:31

lvgo section does not have stripper,vaccum column is using around 13 tph lp superheated steam 190 c and in vdu furnace in each pass 750 kg/hr turbulizing steam.generally chloride and Na is not monitored ,however i wil look for lab analysis.

DDSpetro (Petroleum) · Answer 33 · 2010-01-28 02:35:47

One intresting observation is that LVGO chloride is very well correlating with upstream crude column overhead boot water chloride as attached.

http://files.engineering.com/getfile.aspx?folder=4201bdb3-cfca-4d1d-837e-3593a95546ab&file=LVGO_Chloride_vz._Crude_Col._boot_water_chloride.ppt

25362 (Chemical) · Answer 34 · 2010-01-28 03:33:09

Although one should beware of falling prey to the common logical fallacy "post hoc ergo propter hoc", these results seem to support the hypothesis that both have the same source.

DDSpetro (Petroleum) · Answer 35 · 2010-01-28 11:57:25

crude unit return condensate conductivity remains 2.8 MICRO OHM,So, possibility of chloride,Na can be eliminated.further it has been seen that incoming 45 % Caustic has only 50 ppm NaCl,further it gets diluted up to 6.6% with condensate and further in plant with non phenolic striped water but 20 to 25 ppm in lvgo is higher , desalter wash water doesnt hv mg & ca hardness but outlet brine is hving mg ,ca hardness ,so,desalter removes ca & mg salt. how to prove to increase lvgo pa return temp as it involves entire column upset.

786392 (Petroleum) · Answer 36 · 2010-01-29 07:35:15

Dear kindly Pardon me is the Conductivity measure micro mho's & was it a typo? or not!

Best Regards
Qalander(Chem)

25362 (Chemical) · Answer 37 · 2010-01-29 10:00:08

DDSpetro, your assumption of condensing HCl is not to be discarded prima facie.

The azeotrope HCl-water (normal BP: 108.6^oC, 20.2% w/w acid) due to the acid differing "activities" at low concentrations and varying T,P conditions may explain the difference of Cl- contents between LVGO and the overhead boot-water.

I suggest you look for more published information on the HCl-water azeotrope at reduced pressures.

DDSpetro (Petroleum) · Answer 38 · 2010-01-29 10:54:48

u r right 786392, 25362- ok ,meanwhile,i hv seen caustic injection quill is of alloy steel in the direction of crude flow,270 to 350 liter/hr diluted caustic ~ 3 % from 6.6 % ,no choking in nozzle ,(location in d/s of desalter ) & stoichiometry wise ok to nulify it as cause; high acid treatment chemical has chloride but 50 ppm in 8kg/kt of crude ,very negligible in terms of 25 ppm chloride in 100 mt/hr lvgo draw,it seems that crude is definately playing a role but i wil see HCL/WATER AZEO as suggested and to check caustic injection effectiveness. thanks 25362 for ur prompt , expert & memorable help.i wil revert soon.

25362 (Chemical) · Answer 39 · 2010-01-30 04:18:14

It is not necessarily an azeo composition, but info about the vapor/liquid composition at low pressures on the water- rich side of the HCl/water mixture may be of help.

Try to find the expected liquid concentration of the HCl-water mixture at T,P conditions, taking into account that the Cl concentration (if it is indeed all HCl) in the LVGO, is about 1-1.3% of the water content.

Perry VI gives a partial pressure for HCl at 40 ^oC of 0,00047 mm Hg for a 2% solution. Regretfully it doesn't show values for lower concentrations. The water-HCl mix is dissolved in the LVGO, thereby, IMO, its mol fraction in the liquid should be taken into account.

DDSpetro (Petroleum) · Answer 40 · 2010-01-30 07:19:36

OK,

On internet, I have found out some Pxy,Txy graph as well as Azeo at low pressure @ Vaccum colum pressure i.e.24 mmHg top pressure as attached.

http://www.me.gatech.edu/energy/andy_phd/two.htm#f210

Can you pl. guide if it will helpful to control chloride in LVGO.

http://files.engineering.com/getfile.aspx?folder=57bc4c0d-9687-42fd-a832-cc93bfcfc841&file=IMG00104.gif

http://files.engineering.com/getfile.aspx?folder=d261bccc-652c-43d5-aad9-28947ae74598&file=IMG00110.gif

http://files.engineering.com/getfile.aspx?folder=ff2a7006-03d4-408c-b05c-cf53f5979f27&file=Abb15_e.gif

DDSpetro (Petroleum) · Answer 41 · 2010-01-30 07:34:02

25362,

Chloride was analysed in 6.6 % caustic but it was 8 ppm only; if we consider 350 liter/hr dilute caustic of 3 % concentration then based on 1090 kg/m3 density;pure Caustic flow will be ~ 11 kg/hr & desalter outlet salt which remains 0.6 to 0.8 ptb max. ( 1 ptb = 3 wtppm salt) ; assuming 1.8 to 1.98 Kiloton/hr of crude flow ; stochiometric wise caustic injection seems to be allright , i.e. ~5.94 kg/hr of pure salt, 11 kg/hr caustic is available.

Meanwhile,attached are various parameters analysis including brine Mg & ca.In Vaccum residue chloride was analysed and found 9 to 13 wtppm.RCO sample is also given for Chloride analysis for chloride balance.

http://files.engineering.com/getfile.aspx?folder=0f44a2e2-a318-457c-b259-f7c0525ae300&file=Chloride1.xls

25362 (Chemical) · Answer 42 · 2010-01-30 11:00:42

It appears to me that liberated HCl is the culprit.

BTW, a 3% mass soda solution would have a density of 1031.8 kg/m³ at 20^oC; it still gives about 11 kg/h, which is above stoichiometric.

Therefore, the following things come to mind in line with your posting dd Jan 27th.:

• Check personally the caustic dosing pumps for true mechanical performance.
• Try to increase the caustic dosage to improve mass transfer and see whether chlorides in LVGO drops.
• Verify the chloride content of the HVGO, it should be similar to the contents found in the VR and the LVGO.
• Find what are the operating conditions that result in a low pH in the boot water that requires automatic injection of ammonia, since as you tell us under these conditions the chloride content of LVGO drops.

786392 (Petroleum) · Answer 43 · 2010-01-31 05:55:07

Dear DDSpetro
I feel that 25362 estimation seems pertinent to have a try and give feedback,but do not ignore the word of caution 'physically'

as occassionally the flow does not finds its way for which it is destined and

either recycles back or

unknowingly goes to some other area.

That must carefully checked,ensured for the caustic flow here.
Good luck for successful way forward.

Best Regards
Qalander(Chem)

DDSpetro (Petroleum) · Answer 44 · 2010-01-31 11:04:47

i wil post physical observation soon on caustic injection,meanwhile today it was observed surprisingly,unit 1 where lvgo PA return temp was 48 c,col top temp 41 c,lvgo total chloride was observed 2.7 wtppm ,unit 2 lvgo PA return temp 39 c,top temp 33 c,lvgo total chloride 3.4 wtppm,unit 2,boot water chloride 3.5 ppm which was usually 1 ppm,even mery crude was present in the blend 20 %,caustic flow 270 lph,5.7 M3 dosing tank capacity,thrugh screw pump caustic is injected.

786392 (Petroleum) · Answer 45 · 2010-01-31 13:36:12

Dear Somehow I feel as if you indicated mercury in crude is this correct? or what

Best Regards
Qalander(Chem)

25362 (Chemical) · Answer 46 · 2010-01-31 14:18:45

• Modern "dry" vacuum distillation units handling topped crudes operate at 3-5 mm Hg at the top of the vacuum tower and about 25-30 mm Hg in the flash zone.

• Please note that of both salts, MgCl₂ hydrolyzes easily (although not completely, say 90%) at topping temperatures, while CaCl₂ is more resistant (less than about 15% decomposes). H₂S also helps in liberating HCl. This is seen in the submitted (vacuum) brine analyses. BTW, calcium chloride is used in oil well drilling and completion operation.

• This fact implies that NaOH might not neutralize all the "potential" HCl from the 0.6-0.8 PTB of salts in the desalted crude oil at the topper. The remaining Mg and Ca chlorides apparently decompose/hydrolyze at the vacuum unit where steam catches and brings the HCl to the column top and eventually to boot water, as well as to the LVGO drawoff section.

25362 (Chemical) · Answer 47 · 2010-01-31 15:02:59

Besides, Ca and Mg chlorides readily absorb water. The hydrates decompose at the operating temperatures releasing HCl.

If there are solid particles in the crude, such as clay, the added "surface" may increase the extent of reactions between steam and chlorides.

DDSpetro (Petroleum) · Answer 48 · 2010-01-31 23:18:24

786392- It is Merry Crude type ( 20 wt % in the blend) it is venezulen crude - High Metal crude with As is also there in it.

25362,

Caustic dossing vessel is having gear pumps with one standby pump, its discharge goes to booster pump suction / slip stream of desalter downstream section : Two exchanger where quill is located  , pressure remains 25 kg/cm2g with once in a day caustic batch making frequency with 40 % Low alaram & 75 % high alaram, one vessel is stand by; as V-12 chloride gets monitored every 2 hour so, with 300-400 liter/hr caustic injection ,so, mechanical performance wise caustic injection pump seems to be ok and NRV,pressure indication,flow indicator is also there in the line.

Meanwhile Chloride analysis in lab is through ASTM D-4929 ; Culometry ( Silver test) ; Once Desalter downstream salt Ca metal was analyzed and found 0.43 ppm while Na & Mg was < 0.1 ppm ; so, it seems that CaCl2 gets sliped froM Desalter downstream.So, CaCl2 decomposition theory seems intresting because we have seen High Potential H2S crude like Eocene when processed ,it is also  coorelating with LVGO chloride.So, H2S helps in liberating HCl - if you can elaborate pl.

Thanks

PS : Earlier posted Brine analysis is of Desalter Brine water analysis.

DDSpetro (Petroleum) · Answer 49 · 2010-01-31 23:28:41

In previous post V-12 is Crude atmospheric column overhead reciver boot water ; caustic batch is prepared once in a day.

786392 (Petroleum) · Answer 50 · 2010-02-01 01:23:23

Undoubtedly Magnesium Chloride is the worst culprit salt if not handled/got removed and drained at de-salter stage

since this most usually gets decomposed generating HCl(Hydrogen Chloride)which is main source of internal corrosion of overhead systems and certain chlorides generated thereby are found as being experienced in your case as pointed out accurately by "25362".

I believe it is desalting which needs to be focused since caustic is not showing satisfactory due impact its injection point(s) might need review for positioning further upstream.

Additionally each Crude storage feed tank's adequate settling and aqueous salt& sediments layer's thorough/careful draining may prove greatly useful.(Just an out of box idea)

Hope this proves helpful,ensures trouble shooting succes!

Best Regards
Qalander(Chem)

25362 (Chemical) · Answer 51 · 2010-02-01 04:55:31

• A typical salt composition in crude oils would be 75% NaCl, 15% MgCl₂ and 10% CaCl₂.

• It is commonly accepted that the NaOH injection can be increased and tolerated to a maximum of 3 lb/1000 bbl (~10 ppm) of crude oil without causing downstream problems.
Therefore, you could try to increase the soda dosage in cases where heavy and viscous crudes can not be effectively desalted.

• The effect of H₂S is, apparently, via a corrosion intermediate at the top cooler column and condenser sections. The accepted mechanism is: wet HCl forms ferric chloride by corrosion, which in the presence of H₂S deposits gray/black iron sulfide on the metallic surfaces while, at the same time, regenerating HCl.

I hope you succeed in your troubleshooting efforts.

786392 (Petroleum) · Answer 52 · 2010-02-01 05:30:57

Thanks! 25362,
the adequately/appropriately highlighting H2S(Hydrogen Sulfide)issue,I incidentally forgotten.

Best Regards
Qalander(Chem)

25362 (Chemical) · Answer 53 · 2010-02-01 09:14:51

DDSpetro, have you tried to correlate the HCl content of the LVGO with the temperature of the returning PA? It seems that higher temperatures reduce the HCl content. Please comment.

DDSpetro (Petroleum) · Answer 54 · 2010-02-01 13:37:50

no correlation found as posted earlier,pa return flow has correlation as since last two days without doing lvgo chloride has come down with pa return temp of 39 c ,chloride is 3 ppm in both units.if we put higher caustic then stochiometry,is it possible it can carry foreword and helps cacl2 decomposition.

25362 (Chemical) · Answer 55 · 2010-02-02 01:37:10

Let's summarize:

• The desalter suceeds in bringing the salt content downto 0.6-0.8 ptb which is considered OK.

• Now, apparently, the point is to avoid the further decomposition of the chlorides remaining in the reduced crude.

• The naphthenic acidity of the crude mix can act in the vacuum hot sections by displacing chlorides producing HCl in the process. Apart from its possible action in the evolution of H₂S.

• If this is so, one common procedure is to reduce this acidity by making crude blends with crudes having lower neutralization numbers. Try to correlate HCl in LVGO with the crude total acid numbers.

• Otherwise, contact a chemical company who may help in providing an additive that neutralizers this acidity as encountered in venezuelan crudes, apparently "active" at the vacuum section operating conditions. There are some amines that can do the job.

DDSpetro (Petroleum) · Answer 56 · 2010-02-03 23:43:26

25362 ,Yes,

LVGO Chloride is very well correlating with Crude TAN - 80 % positive correlation as attached.

Further in Lab , one more experiement is done without water wash as such there was 6 ppm chloride with no free water.

With 5 % water wash and centrifuge of LVGO sample further chloride analysis done and it was found 1.6 ppm.so, most of the chloride was water soluble,which was confirmed.

http://files.engineering.com/getfile.aspx?folder=5613116c-2fb0-4246-b4b9-9425461c0337&file=LVGO_Chloride_Vz._Crude_TAN.ppt

DDSpetro (Petroleum) · Answer 57 · 2010-02-04 01:11:53

With 10 % distill of LVGO sample, Out of total 6 ppm of LVGO Chloride sample, 4 ppm has come in to that 10 % recovery.

786392 (Petroleum) · Answer 58 · 2010-02-04 08:06:52

Dear DDSpetro Hello/Good Evening,

All what you indicate in above two posts nothing but Confirms;

good initial upstream handling/treatment needs

And there is a definite need for desalter wash water flow rate and quality reviews to get rid of Chlorides at this stage.

at upstream stage ensuring thorough mixing of NaOH (i.e. caustic stream)with Crude Oil Suction pipeline through some in-line static or other mixer prior to landing into de-salter.

Sometime De-emulcifiers are helpful(if not in use,or might need replacement) or

even desalting electrodes and High potential difference ensuring mechanism may need overhauling etc.

Hope this helps in way forward for your problem resolution soon.

Best Regards
Qalander(Chem)

25362 (Chemical) · Answer 59 · 2010-02-04 10:59:19

The lab distillation seems to confirm the presence of volatile wet HCl.

DDSpetro (Petroleum) · Answer 60 · 2010-02-11 05:57:52

Pl. find here with the attached file of lab analysis.LVGO 5 % SIMDIST remains 301 C while LVGO 10 % SIMDIST remains 321 C ; I was thinking whether based on this lab analysis , increasing 10 % cut point of LVGO will help as minimum cost option ; one is that CaCl2 in desalter downstream can be monitored eventhough Desalted Crude is mostly operates with less than 1 PTB outlet salt.

http://files.engineering.com/getfile.aspx?folder=3b1da289-a813-4399-8c74-86f47c130574&file=Chloride-Revised.xls

DDSpetro (Petroleum) · Answer 61 · 2010-02-11 06:24:50

Any negative implications by increasing 10 % LVGO cut point ?

25362 (Chemical) · Answer 62 · 2010-02-11 23:58:03

It is possible the following link may be of interest:

http://www.revamps.com/Revamps/documents/167.pdf

also

thread483-185668: Properties of VDU fractions.

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