This sequence allows the C5 / C6 feed introduction in the system through the Feed
Dryers, to the Stabilizer, the Deisohexaniser and the LPG recovery section by utilizing the start-up line by-passing the Feed dryers and the reactors and the other one only by- passing the reactors.
The dryers regeneration circuit is also flushed with oil and the oil is finally routed to storage through the product lines. This performs a thorough flushing of foreign material from the equipment and liquid lines.
- Check the C5/C6 feed availability and quality. It must be on-spec with regard to
contaminant content.
- Check that the Feed Dryers are blocked off from the reaction section.
- Check that the C5/C6 feed is by-passing the Feed Dryers. Line call “start-up line”
Before establishing the complete loop it is necessary to draw off the C5/C6 to off-spec
storage to remove the equipment oil coating and not to contaminate the dryers molecular sieves. A period of 8 hours is necessary before closing the loop. During this step, the chloride guard bed will be by passed.
- Establish a level in the stabilizer bottoms 73-C-01.
- When the level in the stabilizer reaches 40%, route the bottoms to the Deisohexaniser 73-C-02. The chloride guard bed 73-V-06 is still by-passed.
- Commission the Deisohexaniser air condenser 73-A-03A-H and then the reboiler 73-
E-10. Remove in a first step, route the isomerate product to off-spec storage (side- draw control valve LV-2101 closed). In a second step, after all the equipment are cleaned, commission the side-draw, and begin recycling the side-draw and keep removing the isomerate to the off-spec storage. Set the pressure controller at the deisohexaniser overhead.
After the 8 hour period, the complete loop including dryers can be established.
- Slowly fill each Feed Dryers separately using the globe valves and venting the nitrogen to flare through the pressure safety valves bypass. Dryers filling and nitrogen displacement is to be monitored through the level glasses on the PSV bypasses.
- Once both dryers are full, the start-up line by passing the dryers is closed and the oil
circulation is continued to the stabilizer through the reactor bypass line.
- Commission the stabilizer overheads air condenser.
- As the level appears in the stabilizer, commission the reboiler.
- Slowly bring the stabilizer up to operating temperature. As the level appears in the
reflux drum 73-V-05 start the reflux pumps 73-P-05A/B and reflux back to the column.
- Adjust the flow on the reactors by-pass line to reach a circulation rate of 60% of
design throughput.
- Crack open the flow controller on the regeneration loop and flush the loop free of foreign material, back to rundown to storage.
- Adjust the flow to design rate, hold for 4 hours and then stop the circulation through
the regeneration loop. Close the by-pass line and re-establish the flow through the dryers.
- Calibrate the moisture analyzers on the feed and hydrogen dryers. Commission them
to monitor dryer performance.
- During the circulation, switch the flow pattern around the dryers and ensure all
possible dead legs are adequately purged.
Oil Circulation and stabilizer / Deisohexaniser start-up
Treated Naphtha from 73-V-01 73-P-01 A/B NHDT 6”-P-73-1105 Start-up line 4”-P-73-1321 Chloride Guard 73-C-01 Bed bypass (4”-P-73-1902) 8”-P-73-1908
73-A-03
(LV-2101 close)
1st step: - 73-P-08/B Start-up line 3”-P-73-2212
Off-spec isomerate 73-E-11
to storage for min. 8 hrs.
Note: - Feed dryers blocked off from the reaction section:
NOTE: Enclosed start up circuits will be detailed by process licensor during Pre- commissioning/Commissioning and shall be submitted accordingly by the licensor. 2nd Step:-
73-C-02 8”-P-73-2206 73-V-07
4”-P-73-1615) 73-E-08 A/B 73-E-02 73-P-07A/B
4”-P-73-2101
73-V-01
After 8 hours: (Feed Dryers taken on line) 6”-P-73-1105
From 73-V-01 73-DR-01 A/B
6”-P-73-1303 73-C-01 (through reactor bypass line 4”-P-73-1513 Reflux
Commission 73-E-05 & A02 reboiler & condenser
after level appears
73-P-05 A/B 73-V-05 through
73-C-01 overhead
73-C-02 73-E-07 73-V-06
Similar to previous circulation
Note: Enclosed start up circuits will be detailed by process licensor during Pre- commissioning/Commissioning and shall be submitted accordingly by the licensor. LPG recovery section Start-up
Section status
- Leak test has been performed
- Raschig rings are installed on top of the scrubber and pall rings in the LPG separator
drum.
- Absorbent is loaded in the scrubber off-gas dryer.
- All utilities are available including chilling package
- Section is isolated as follows
Off gas from caustic scrubber : UV 2501 + block valves closed
Lean gas from LPG separator drum to fuel gas : PV 2801 + block valves closed
LPG : FV 3301 + block valves closed
Heavy product outlet : PV 2802 + block valves closed
LPG stripper bottom : FV 2803 close
LPG stripper reflux drum : PV 3001
Procedure
- Line-up the internal circuit between 73-V-11 (LPG separator drum) and 73-C-04
(LPG stripper).
- Slowly introduce heavy product from DIH bottom through FV-2202 at 73-P-08 discharge to 73-V–11 upto 100 % at LG-2802 (LPG separator drum).
- Start the pump 73-P-04 and through FV 2801 introduce liquid to 73-C-04 (LPG
stripper)
- Commission VHP steam to 73-E-17 (LPG stripper reboiler) and bring 73-C-04 at
total reflux conditions. Make-up heavy product to 73-V-11 and restart 73-P-14 as necessary to maintain LPG stripper levels.
- Commission the PIC-2801 at the LPG separator drum overhead. When PIC has
reached normal operating pressure set point, open UV 2501. - Most of the rich off gas is still routed to fuel gas.
- Very slowly start to romp down PV 2501 (valve to close in approximately 20 mins)
- When PV 2501 is fully closed, then close UV 2503
- Commission chilling medium to 73-E-13 A/B
- Start recycling heavy product through FV 2804 , then restart 73-P-14 A/B
- PV 3001 (LPG stripper reflux drum), in auto mode, will start to open , to maintain
73-C-04 pressure, recycling the lean off gas to separator.
- When level reaches 50% at draw off tray level gauge (LG 2907), start 73-P-16 A/B
on minimum flow line, and then open FV 3301. The LPG product is ent to the off spec storage during 8 hours.
6.8 REACTION CIRCUIT OIL-IN