Q & A > Question Details
We have a problem in the hydrotreated filters when feeding HCGO. In these filters, we usually feed VGO and we haven´t any problems, but when we try feed HCGO from coker unit, the filters are plugged at the few minutes.
The ratio between HCGO and VGO is 30/70% aprox. and the temperature of these filters is 170ºC.
The filter element are wedge wire with 75 microns.
When the filter is plugged, although the filters are backwashed, the AP don´t go down, and It´s necessary to shut down the unit to clean up the filters mechanically.
We are doing some studies to identify the origin of the problem.
- Filtration studies to cuantify the solids of both of feeds: HCGO has 150-500 ppm of solids, which are mayoritary coke. VGO has 300 ppm of solids, which are mayoritary inorganics particles.
- Asphaltene determination (IFP method): HCGO has 200-500 ppm and VGO has 100-300 ppm.
- Compatibility studies: We have done a compatibility study in laboratory, which consists of adding gradually HCGO to VGO, then the mix is viewed in the optical microscope to identify the asphaltene precipitation. In this study we have seen that the feeds are unstable above 15-30% in function of temperature. The higher temperature the higher unstable is the mix, and the asphaltene precipitate at lower HCGO percentage.
Therefore, we think the plugging problems are due to the precipitation of asphaltene forming an impermeable layer on the filter, which doesn´t disappear even when the filters are backwashed.
My first question is if somebody has experience of this sort of event? We think the solution is not to increase the filter area, but eliminate the problem at its source, to reach a HCGO cleaner wiht less asphaltene content.
My second question is related to the effect the asphaltene precipitation with the temperature. I thought that the higher temperature the lower precipitation but we have seen the oppsoite effect.
23/10/2012 A: NS Murthy, Reliance Industries, ns.murthy@ril.com
Pl check the following to solve this issue.
1. Amount of cold feed processing in VGO HT from storage tanks.
2. Wash flow rate adequacy in Coker fractionator below HCGO draw off.
22/10/2012 A: NS Murthy, Reliance Industries, ns.murthy@ril.com
Couple of directions we can think wrt this issue.
1. Extent of wash oil effectiveness in Coker below HCGO draw off. Better wash removes Coke particles from being carried in to VGO HTs.
2. Avoiding / minimizing cold feed processing in VGO HT. There are conjugated diolefins in Coker streams which tend to olegomerize on prolonged storage leading to filtration issue in d/s HT.
11/10/2012 A: Virendra Kapoor, Petroleum Refining Consultants, vkkapoor9@yahoo.com
Such phenomenon are common to occur and can be handled easily without major efforts
04/10/2012 A: David Engel, Nexo Solutions, david.engel@nexosolutions.com
This is somewhat a common problem. You can solve it with filtration in combination with other methods. However, we need to understand a bit more the situation. Filtration alone is likely to be not the most cost effective answer as it is if you use a combination solution. We specialize in these type of difficult separation & filtration problems. Quite often we focus on the root-cause of the problem and not to offer a possible solution to the symptom. if you need technical assistance, please don't hesitate con contact us.
02/10/2012 A: Marcello Ferrara, ITW SrL, mferrara@itw.it
We are expert in asphaltene stabilization and, moreover, have developed an Online Cleaning technology.
01/10/2012 A: Niels van der Horst, Royal Dahlman BV, n.vanderhorst@dahlman.nl
All you say is right and you are not the only one who is experiencing this. Nevertheless it is possible to solve your problem. An on-site pilot filtration test can be done. We have noticed similar problems with filtration and have developed a solution for you.
01/10/2012 A: keith bowers, B and B Consulting, kebowers47@gmail.com
It may be possible to add a 'co-solvent' rich in aromatics such as FCC cycle oil to prevent the asphaltene precipitation
01/10/2012 A: Keng Chung, Well Resources Inc., kengchung@hotmail.com
Yes, I have seen it and published the findings. All the descriptions and questions you posted are consistent. You can look at our previous work in open literature.