Plant Preservation Issues and Remedies

Plant Preservation Issues and Remedies

Muhammad Azhar Malik Engro Fertilizers Ltd., Pakistan

Nitrogen+Syngas 2014, Paris

Feb 27th, 2014

• Engro – demonstrate best practices for HSE

Engro’s Ammonia Unit

2 Plant Preservation – Issues & Remedies

2 Ammonia, 3 Urea and 3

Utilities Units

Engro Fertilizer

subsidary of Engro Corp

2-3 M T Urea Capacity

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Engro’s Daharki Combined Site view

Plant Preservation – Issues & Remedies

Background

• Natural Gas Availability Issue for 7 months in 2012

• Gas Situation was not clear, it was asked to be ready to start the plant on 3-4 days notice

• Complete moth balling was not possible so Preservation guidelines developed


Issues faced

• Heavy corrosion in Ammonia plant Process Air Compressor piping

• Heavy corrosion in CO2 Absorber Bottom bed supporting plate

• Thinning of Cooling Water Header

• High Iron Pickup from Utility Boilers


Issue # 1

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Heavy Corrosion in Process Air Compressor


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KGT-2501 Parameters

Load 12.92 MW Normal Speed 5100 RPM

Axial Air Compressor Stages 16 Air Inlet Temperature 115 °F

Air Inlet Pressure 14.4 psi Turbine Exhaust Temperature 1000 °F

Turbine Exhaust Pressure 14.7 psi Air Flow 598,000 lbs/hr

Issue # 1 Heavy Corrosion in Process Air Compressor


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Heavy Corrosion in Process Air Compressor Issue # 1


• On April 11, 2013 Ammonia-2 Plant Startup activities initiated

• KGT-2501 (air Machine gas turbine) coupling was removed for slow-rolling; however the compressor did not rotate.

• Gas turbine was rotating freely.

• LP & HP casing of compressor were dis-coupled but these did not rotate.

• LP & HP casings were removed along with suction & discharge piping and thorough cleaning of all machine parts/rotor were performed.

• The rotor jamming issue was resolved and machine was put on slow roll.

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Heavy Corrosion in Process Air Compressor Root Cause & Lesson Learnt

Issue # 1


• Discharge piping were corroded and turned into flakes, these flakes fell into compressor casing

• Operating discharge piping (>100°C) for more than 45 years has set-in a phenomenon known as microstructural degradation

• Erosion marks on the impellers and IGVs found and it was due to water ingress from 3rd stage KO drum

• LP & HP casings were removed along with piping and thorough cleaning of all machine parts/rotor were performed.

• Piping and compressor will be kept under N2 pressure in long outage

• Piping / Compressor casing will be kept under N2 pressure and Knock out drum will be replaced

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Obs

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Heavy Corrosion in CO2 Absorber Issue # 2



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Observations

• Bottom packing bed supporting plate and its Vapor distributors were found heavily corroded and rings were fell down at bottom of absorber

• Heavy deposition of CATACARB near M-2.




• Damaged Vapor distributor and support plate

• Vapor distributor

• Replaced with inhouse improvised material


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Root Cause & Lesson Learnt

• At Sp. Gravity above 1.32 catacarb system becomes corrosive

• Low S/G ratio project in the year 08-09 & DEA had to increase

• Inadequate wash water line size for absorber flushing and improper flushing prior to long outage


Year Specific gravity 2003 1.3 2004 1.31 2005 1.31 2006 1.31 2007 1.31 2008 1.325 2009 1.33 2010 1.34 2011 1.34 2012 1.33

Thinning of Cooling Water Header Issue # 3

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• Water leakage from cooling water return header at Utility-1 Unit.

• Pipe severely corroded from inside and outside.


Thinning of Cooling Water Header Issue # 3

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Root Cause and Lesson Leant

• Wet passivation and dried depressurization was not carried out. Delay in cooling water draining

• Limitation of time for coming back to plant operation.

• Hot box-up was installed on 150 ft long CWR header


High Iron Pickup from Utilities Boiler Issue # 4

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• Wet lay-up methodology was adopted, 1500-2000 ppm concentration of eliminox water dosed into Utility-1 boilers

• Preservation Chemical’s concentration monitored


High Iron Pickup from Utilities Boiler Issue # 4

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Root Cause & Lesson Learnt

• The wet lay-up methodology did not work for proper preservation.

• Dry layup methodology should be adopted


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ENGRO FERTILIZERS LIMITED GUIDELINES FOR PLANT

PRESERVATIONS


Sr. No. Service Preservation

Media Frequency Criterion

1 Steam Circuits Nitrogen Throughout shutdown

period

All steam circuits to be depressurized and dried with plant air. Remove condensate from low point drains

and ensure that no water content is left in steam circuit piping. Keep it under positive nitrogen

pressure.

2 Natural Gas Circuits Nitrogen Throughout shutdown

period

Natural gas circuit which is not in service is to be purged with Nitrogen and to be kept under Nitrogen

pressure of 2-5 psig.

3 Synthesis Gas, Process Gas Circuits Nitrogen

Throughout shutdown

period

Synthesis gas & Process gas circuit is to be purged with Nitrogen and to be kept under Nitrogen pressure

of 2-5 psig.

4 Ammonia& Refrigeration Circuits Nitrogen

Throughout shutdown

period

Ammonia & Refrigeration circuits to be purged with Nitrogen and to be kept under Nitrogen pressure of 2-

5 psig.

5 Catacarb & aMDEA Circuits Nitrogen Throughout shutdown

period

Catacarb & MDEA circuit to be purged with steam in order to remove gases (H2 etc). It should then be

flushed thoroughly with treated water and drain the flushing water. After draining keep the circuit under

positive nitrogen pressure.

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6 Carbamate and Urea Circuits - - Carbamate & Urea circuits to be flushed thoroughly with treated water and drain the flushing water.

7 Carbon dioxide Circuits Nitrogen Throughout shutdown

period

Carbon dioxide circuit is to be purged with Nitrogen and to be kept under positive Nitrogen pressure.

8 Cooling Water Circuits - - Cooling water system circulation with passivation

chemicals is to be carried out for 72 hours and water to be drained after completion of this passivation activity.

9 Catalyst Containing Vessels Nitrogen Throughout shutdown

period

All catalyst vessels (De-sulphurizers, Pre-reformer, Primary reformer, HTS, LTS, Methanator and Ammonia

convertor) are to be kept under Nitrogen pressure of 2-5 psig.

10 Cooling Tower's Red Wood Plant Water Alternate Days

In order to avoid drying & subsequent hazard of fire, red wood of cooling towers to be made wet on alternate

days.

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11 Reverse Osmosis Modules preservation

30% solution of Biocide

Throughout shutdown

period

RO membranes are to be preserved in 30% solution of Biocide. For this purpose, prepare a 30% solution of

biocide and circulate this solution thru RO membrane module for 15 minutes and then shut down the pump,

isolate module valves and keep RO membrane flooded with this solution.

12 De-aerator, Boiler drums & BFW circuits Nitrogen

Throughout shutdown

period

Dry lay up to be carried out at De-aerator, Boiler and BFW circuits. For this purpose, these circuits are to be dried completely with the help of instrument air. After

drying, purge the circuits with nitrogen and keep under positive nitrogen pressure.

13 Turbo Trains (Air Machine) - 15 Days Air machine complete train will be rotated 180

degrees on the frequency of 15 days. During this activity lube oil will kept online.

14 Air, Syn & Refrig Compressor Casing Nitrogen

Throughout shutdown

period

Air, Syn & Refrig Machine casing is to be kept under positive nitrogen pressure.

15 Turbo Trains (Syn. & Refrig. Machine) - 15 Days

Syn. Machine & Refrig. Machine train will be rotated 180 degrees on the frequency of 15 days. During this

activity both lube oil & seal oil will be kept online.

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16 Turbo Trains (Gas Turbines) - 15 Days Long duration idle Gas turbines (GTs) to be rotated

180 degrees on the frequency of 15 days. During this activity lube oil will be kept online.

17 Small & Medium size Machine's Lubrication Lube Oil Once per

Month

For all small & medium size machines having forced feed lubrication, lube oil will be started for 5-10

minutes once a month (ensuring oil flowing from their respective outlets / drains).

18 Small & Medium size Machine's Gear Box - 15 Days Gear boxes having no forced feed lubrication should

be rotated 180 degrees on the 15 days frequency.

19 Semi lean solution reverse pumps - Monthly

For semi lean solution reverse pumps’ turbine trains (excluding Pump & PHT), CW pumps & BFW pumps, 180 degrees rotation is suggested on monthly basis.

During this activity lube oil should be kept online.

20 Cooling Water Pumps Amine Carboxylate Once

CW pumps and other water pumps should be flushed with a volatile corrosion inhibitor (amine carboxylate)

to prevent corrosion.

21 Reciprocating Machines - Once per Month

For reciprocating machines, lube oil system to be energized once a month for a few hours

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Checklist for Monitoring Critical Parameters

Reforming

Parameter Guidelines

Steam bleeders are crack opened at low points Yes

Pigtail Nitrogen Pressure 5-10 psig

Desulfurizer Vessel Nitrogen Pressure 2-5 psig

Pre-reformer Nitrogen Pressure 2-5 psig

60 Hz SGR visit (Check for any abnormality) -

Nitrogen Pressure in Air Machine 2-5 psig

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Purification Parameter Guidelines

Steam bleeders are crack opened at low points Yes

Nitrogen Pressure in HTSC 2-5 psig

Nitrogen Pressure in LTSC 2-5 psig

Nitrogen Pressure in Methanator 2-5 psig

Nitrogen Pressure in Absorber 2-5 psig

Nitrogen Pressure in Stripper 2-5 psig

Back-end Parameter Guidelines

Nitrogen Pressure in Convertor 2-5 psig

Nitrogen Pressure in Syn Loop 2-5 psig

Nitrogen Pressure in Refrig. Loop 2-5 psig

Steam bleeders are crack opened at low point. Yes


Thanks

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Engro’s Fertilizer Division, Daharki


Documents

Plant Preservation Issues and Remedies