Incorrect Steam Drum

Level Measurement Can

Result In Multiple

Issues At Ammonia

Plant Muhammad Azhar Malik

Feb 26, 2015

Presentation Synopsis

Purpose of Paper

Process Description

Problems Encountered

Root Cause Analysis

Conclusion

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Purpose of Paper

Sharing Engro's experience on issues faced on HTSC catalyst early

deactivation, waste heat boiler fouling, turbines fouling post new

fertilizer plant successful startup mainly due to incorrect Steam drum

level measurement.

Root cause analysis of problems encountered

Remedial measures taken to overcome problems.

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Worlds Largest single-train Ammonia-Urea complex at the time of

commissioning.

Successfully Commissioned in Dec 2010.

Steam Header Network Configuration

KS Steam 110 kg/cm2

HS Steam 44 kg/cm2

LHS Steam 41 kg/cm2

LS Steam 3.5 kg/cm2

Plant Introduction:

5

Steam Network Configuration:

110 kg/cm2 Steam Drum

42 kg/cm2 Aux

Boiler

Process Steam to Furnace

Heat recovery from WHB Sec Ref / HTS / Amm Convertor

KS Super heater

Syntheses Turbine

Refrig Turbine

CO2 Comp Turbine

PA Comp Turbine

CW Turbine

BFW Turbine

PW Turbine

ID fan Turbine

Lube oil Turbine

KS Network

HS Network 44 kg/cm2

LHS Network 41 kg/cm2

LS Network 3.5 kg/cm2

Problems Encountered

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HTS Catalyst Failure

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HTS Catalyst bed undergoes replacement just after two

effective years of operation.

Plant load got limited due to high delta pressure across HTS

bed - 1.8 kg/cm2

The temperature profile across catalyst bed showed signs of

channeling.

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HTS Bed Radial Temperature profiling

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TI-2091

TI-2092

Window - 1

Window - 2

Window - 3

Window - 4

Window - 5

Window - 6

ACTIVE PORTION (~42% of circumference)

DEAD PORTION (~58% of circumference)

380C

378C

441C

430C

426C

412C

377C

378C

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2ft catalyst bed shrinkage Channelling Signs in

HTS bed

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Dust at Al balls at HTS Top Analysis showed

7% Sodium & 1% Silica contents

HTS Failure - Root cause Analysis

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Inspection revealed Presence of

Shrinkage of 2% catalyst bed with clear signs of channeling

High contents of foreign particles especially Sodium & Aluminium

Crushed catalyst due to increased delta pressure operation

Presence of Sodium questioned steam quality

Presence of Aluminium showed slippage from alumina lumps

from Secondary reformer

WHB Fouling

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Temperature at WHB outlet increased by 25 C.

Inspection showed fouling of WHB tubes

Analysis of dust revealed presence of Sodium and Aluminum.

A lot of dust was also collected at WHB cold end showing

slippage from secondary reformer

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WHB Tube Fouling Dust Analysis Showed

Sodium 8% and Aluminum 18%

BFW Turbine Fouling /Internal seals Failure

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BFW turbine TP-1301 A efficiency dropped significantly.

BFW header pressure reduced by 4 kg/cm2.

Upon inspection, interstage seals of the turbine was found

damaged

Rotor was found covered with heavy deposits.

Analysis showed presence of 40% Sodium contents.

Table 4: Deposit Analysis at TP-1301 A

Componenet Analysis result

Sodium 39.47%

Silica 0.31%

Potassium 1.63%

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Deposits of Sodium on Turbine Interstage seal

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Deposits of Sodium on interstage seals

ID fan Turbine Fouling

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ID fan Turbine vibrations increased till the danger level till 0.34

um.

Efficiency of turbine also dropped significantly

Inspection showed presence of deposits sodium on the rotor

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Fouling of ID fan Turbine Rotor

Root Cause Analysis

Prime reason of above mentioned problems was High quantity of

sodium in Steam.

Sources of Steam

Steam Drum 110 kg/cm2 Heat recovery from WHB at ammonia

Auxiliary Boiler 42 kg/cm2

The reason for poor steam quality was incorrect steam drum

level measurement and its control.

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Steam Drum Level

Level remained higher then normal causing poor steam quality.

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Marks of High

level operation

Normal Level

Remedial Measures

Correction of Level Measurement

Algorithm for level correction was corrected for correct level

transmitter type.

Steam Drum equipped with 02 new DP type transmitters in addition of

03 float type meters

Steam Drum equipped with Conductivity Meter

Isolation Valves at Steam drum rectified.

Maintenance regime for floats of level transmitter at every 6 month

implemented.

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Remedial Measure

Wet Washing regime for Turbines was implemented.

Make up water Quality improved

RO unit and DMW beds were lined up in series

Conductivity dropped to 0.2 us.

DMW is then passed through Polisher to fed to Steam drum.

Steam header Wet Washing

Entire steam headers wet washing carried out

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Conclusion

By taking above mentioned steps, Steam quality improved

significantly.

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Thank You !!!