Heavy crude processing

[Petro0707]

Dear All experts,

Currently we are operating our CDU/VDU units with 27 API crude mix.We are carrying out desktop study for processing of 24 API Crudemix with simulation that what will be impact ?

I have following issues to be discussed :

1.As,VR yield will increase but how to minimize VGO drop in VR ? what cutpoint (D1160 95 % ) of HVGO should we go ? still it is decided to go min. 570 C to minimize VGO drop in VR but my ASPEN simulation model predicts higher Ni+V ppmwt fraction along with HVGO i.e.3+14 ppm.~17 ppm,while advisable limit is 1.8 ppmwtmax.(NI+V).Can you pl. throw some light about this type of experience while going to heavy crudemix processing.Still I am having around 2.5 % VGO dropping in VR-burning issue.Our constraint is VDU heater.

2.Currently we are operating damp vaccum condition,Dry vaccum tower operation without stripping steam is also thought about and I already simulated that case but in that case C-factor in Slop wax bed is higher i.e. 0.5 ft/sec.Has anybody experience for dry vaccum tower operation ?How to resolve such issues.Is it worth to operate under dry tower condition ?

3.Crude mix slat is blend of diffrent types of crudes including Dobablend2,Maya,Merry,RG etc.As far as reliability is concerned,what will be the impact on metalurgy ?TAN-Napthenic acid will be issue but we have taken care as far as metalurgy is concerned.

4.What will be the impact on desalters ?

Yes,I agree that indepth study is required and we are doing this,but can anybody throw some highlights about these issues to be focused upon or can anybody share their experience while going from 27 to 24 API crudemix or similar experience what will be focus points.

Sorry for such long description.Thanks in advance to one and all of you.....!!!

 

[Milutin]

Hi Petro,

I have no experience on heavy crude processing but there is good article on

http://www.revamp.com,

so if you didn't read it:

http://www.revamps.com/Revamps/documents/173.pdf

Regards,

Milutin

 

[Petro0707]

Dear Milutin,

Thanks for your effort but I have already gone through this before it.Looking for some more critical inputs from experts like you.

Thanks & Regards,

 

[Milutin]

Dear Petro,

I am curios how you modeled metal content in HVGO?

Regards,

Milutin

 

[Petro0707]

From the available datas in Shell COED or similar materials , you can mannually enter it while defining petroproperties in ASPEN -cutpoint wise metal content and then u can simulate.

 

[Jason5000]

The heavier your slate gets the more you're going to struggle with emulsion problems and the like in your desalters. Be careful not to overwhelm your WWTP; although I'm not much of a desalter guy and can't comment too much on if the change your talking about will have a big impact or not. The folks with Nalco or Baker Petrolite could probably offer some useful advice in this area.

Also, you're definitely right to keep an eye on TAN as you heavy up. A "bulletproof" crude unit is great, but don't lose sight of how the compositions will shift and propagate throughout all the units in the refinery.

 

[0707]

Maya crude is very difficult to dessalificate because of is high density. To minimize the impact of Maya desalinisation it has to be blended to lower the density of the mix to improve dessalters efficiency.

Above a tan of 0.5mg KOH/g and with a 0.2% low sulphur mix if your lines material are not SS317 you have to be careful with naphtenic corrosion on heavy cuts of CDU or VDU units at temperatures between 200ºC and 400ºC.

Most of these acids are believed to have the chemical formula R (CH2) nCOOH where R is a cyclopentane ring and n is typically greater than 12. Naphtenic crude corrosivity is not only dependent of TAN number. Some height TAN number crude are some times less corrosive than low TAN. Carboxyl molecule arrangement within the hydrocarbon ring determines naphtenic crude corrosivity. If the carboxyl is arranged inside the hydrocarbon ring even with a high TAN, such naphtenic crude will be less corrosive than a low TAN with the carboxyl arranged on the extremity of the hydrocarbon ring.

Luis Marques