FCC Process: Revamps & Technical Solutions |
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Fluid Catalytic Cracking (FCC) process is playing
a vital role in petroleum refining industry in upgrading heavier hydrocarbons
to valuable transportation fuels. In the competitive scenario, FCC process
has reoriented its position through continuous improvements in the hardware
and catalyst to cater to the need for processing heavy feed i.e., VGO or
mixture of VGO and vacuum residue to improve the profitability. In the
recent past, attempts are being made worldwide to revamp existing FCC units
to enhance lighter products and integrate with petrochemicals to further
improve the economics.
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 Capabilities & Infrastructure |
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FCCMOD is a rigorous kinetic model developed
in-house using micro-reactor and pilot plant FCC data. This simulator can
predict the effect of feed, catalyst, operating conditions and hardware
parameters accurately. This model is validated for various refineries and
extensively utilized in studies namely plant optimization, catalyst
selection, revamp studies, etc.
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FCC cold stand pilot plant for hardware study |
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Automated circulating FCC pilot plants |
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Several Micro Activity Test (MAT) units namely
- ACE MAT (For resid cracking)
- ASTM and Simulated MAT units for VGO Cracking
- Cyclic deactivation unit for metal doping of resid FCC catalyst
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High pressure fluid bed reactor for FCC and high light
ends related studies
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Riser revamp study for one distillate mode FCC unit in India |
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IndianOil R&D Centre had successfully revamped an
Exxon FCC unit with a small riser, using in-house expertise. The main
objective of the revamp was to increase the conversion and LPG yield
while minimizing the dry gas production. Studies revealed that increasing
the riser diameter and length in the FCC unit within the unit constraints
would meet the objective. The plant results vis-a-vis IOC R&D
predictions are summarized below.
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| Yield, wt% |
Incremental Shift |
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Plant |
R & D Prediction |
| Dry Gas |
-0.5 |
-0.7 |
| LPG |
+2.2 |
+2.0 |
| CRN |
+2.78 |
+3.4 |
| HCGO |
+1.9 |
-0.1 |
| CLO |
-5.3 |
-4.8 |
| Coke |
-1.0 |
+0.2 |
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The above
results indicate very close match of R&D prediction with plant data.
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Technical Solutions-Plant Optimization |
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FCCMOD model was used to optimize the operating
conditions in one of the IndianOil's FCCUs. The change in operating
conditions recommended and incremental yield achieved in plant vis-à-vis
R&D prediction is tabulated below :
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| Optimization Case Study
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| Recommended Conditions |
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| Rx Temperature, 0C |
+6 |
| Recycle, m3/hr |
-15 |
| Riser steam, T/hr |
-1.5 |
| Stripper steam, T/hr |
0.85 |
| Yield, wt% |
Incremental Shift |
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Plant |
R & D Prediction |
| Dry Gas |
+0.38 |
+0.33 |
| LPG |
+0.71 |
+0.73 |
| Gasoline |
-0.44 |
-0.65 |
| TCO |
-0.28 |
-0.53 |
| CLO |
+0.38 |
+-.39 |
| Coke |
+0.01 |
-2.70 |
| Regen. air Nm3/hr |
-5.60 |
-8.20 |
| Reg. Dense 0C |
+2.50 |
+3.0 |
| RX temp. 0C |
+2.0 |
+3.0 |
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Trouble-Shooting Study Solution for after-burning problem |
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One of IndianOil refinery's FCCUs had suffered from
a typical afterburning problem in regenerator, resulting in severe
limitation in capacity utilization. Upon detailed study, it was found
that low regenerator temperature coupled with poor air distribution and
catalyst loss was the reason for the same. Accordingly, it was suggested
to use CO promoter and change the air grid holes plugging pattern while
minimizing the catalyst losses. This had led to significant improvement
in higher dense bed temperature and lower CRC resulting in improved
conversion/activity.
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| Yield, wt% |
Incremental Shift |
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Plant |
R & D Prediction |
| Dry Gas |
+0.0 |
+0.12 |
| LPG |
+0.0 |
+1.08 |
| Gasoline |
+3.0 |
+2.3 |
| TCO |
+0.38 |
-0.68 |
| CLO |
-3.0 |
-3.41 |
| Coke |
-0.50 |
-0.46 |
| Process Conditions |
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| Feed T'put, MT/D |
+80 |
0.0 |
| Regen, Temp., 0C |
+18 |
+22.0 |
| Air Rate, Nm3/hr |
-775 |
-775 |
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It may be noted that addition of CO promoter reduced
the afterburning level by about 200C, reduced CRC, which eventually
improved plant product yield pattern. The reduced load on air blower
made room for processing of additional 80 ton/day VGO leading to
significant economic benefits.
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One of IndianOil refinery's FCCU was facing
problem of high CRC and afterburning during Nov'97 to March'98. This
resulted in poor yield pattern, especially, high CLO yield. IOC R&D
Centre, collected the feed/product and catalyst samples and found that
there is no major change in feed and catalyst which could result in the
prevailing problem in FCCU. Then the hardware and the fluidization aspect
were looked into. Average Particle Size (APS) was found to be 103 micron
which is significantly higher than normal value of 80 micron. More
drastic changes were observed in the particles below 80 micron. Based on
the PSRI fluidization software, FCCMOD and commercial plant data, the
relationship between particle size 0-80 micron and plant CRC was
established. Finally, it was predicted that there was some physical
damage in the regenerator cyclone causing higher catalyst loss and bigger
APS and less fines in the range of 0-80 micron. This subsequently
resulted in inadequate burning in regenerator. After shutdown the above
was confirmed and the hardware problems were rectified.
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