Q & A > Question Details
In VGO hydrotreater unit, cracked feed processed from coker unit which is mainly HCGO and HHCGO (Heavy Heavy coker gas oil). If HHCGO end point increased from 570 deg C to 600 degC, then how severe its impact on VGOHT operation and its catalyst performance?
08/06/2017 A: Ralph Ragsdale, Ragsdale Refining Courses, ralph.ragsdale@att.net
Sorry. I missed the reference to the hydrotreater. The catalyst cycle length will certainly suffer. Metal traps are effective only until they are saturated with metals, then breakthrough to the remaining catalyst will occur. The extent of such effects depend on the amount of increase in metals.
28/05/2017 A: Ganesh Maturu, Self, maturu.ganesh@gmail.com
Increasing end point increases CCR, metals and sulphur. We need to make sure that sufficient grading catalyst available to handle extra metals. Another important factor is CCR as it increases coking tendency. Higher sulphur in feed requires higher activation energy and it increases it deactivation rate as well. Other limiting parameters are it requires higher hydrogen consumption and also higher recycle gas requirement.
26/05/2017 A: NS Murthy, Suez, murthy.ns.ext@suez.com
First of all, it is good to know someone is processing HHCGO with an EP as high as 570 deg C in VGO HTs and is keen to increase the EP further to 600 deg C. In the refinery that I worked, does not have any provision to draw HHCGO and typical HCGO EP is of the order of 540 deg C. As such higher EP brings in contaminants like Coke particles, good amount of PNA and other high boiling nitrogen and sulphur species which are tough to treat in conventional trickle bed VGO HTs. Also, higher EP of Coker gasoil imply higher ingress of metals and entrained asphaltenes. One an expect the following implications in VGO HTs.
1. Increased feed filter fouling;
2. Higher requirement of HDM catalyst in guard beds.
3. higher exotherm from increased rise in temp across HT bed owing to olefins / di-olefins increase in combined feed.
4. Higher total nitrogen and sulphur level in VGO HT run down product.
5. Poorer saturation of aromatics / ring opening which shall impact conversion in d/s FCC.
6. Shorter run length of VGO HTs catalyst.
26/05/2017 A: Sridhar Balakrishnan, Bharat Oman Refineries Limited , laksrid@yahoo.com
There is always a restriction on cracked feed stock to be processed in hydrotreater unit.
Catalyst poisons such as asphaltenes, metals, nitrogen and carbon residue , poly cyclic aromatics increases exponentially with boiling point. All these factors contribute for catalyst activity loss. Also poly cyclic aromatics cause fouling rate of heat exchangers.
26/05/2017 A: utkarsh mishra, Ingenero Technologies, utkarsh1612mishra@gmail.com
Increasing endpoint of HCGO will increase amount of metals , more difficult species of sulphur and nitrogen (refractory species etc), more aromatics etc. in incoming feed.
All this will call for increase in reactor inlet temperature, increase in reactor pressure, more H2/oil ratio and ultimately will reduce catalyst cycle length drastically.
25/05/2017 A: Ralph Ragsdale, Ragsdale Refining Courses, ralph.ragsdale@att.net
You should have a target con carbon max which relates to the metals content. At the FCCU, watch the conversion and product distribution to monitor the catalyst activity indirectly. Increased catalyst addition rate will result, and you can determine if you can live with it and the effect on economics.
25/05/2017 A: Morgan Rodwell, Fluor Canada Limited, morgan.rodwell@fluor.com
The end point itself is not the concern. The issue will be how the contaminant level in the oil in the 570-600C range looks like compared to the <570C material. It is likely that the CCR/microcarbon and metals levels rise quite dramatically and you should get an analysis of the oil in narrow cuts to determine this - if is almost impossible to predict this from bulk data.
If the CCR/metals contents do rise dramatically, the impact on the catalyst can be severe and can shorten the life / reduce activity quite dramatically.