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Ethylene Unit Cracked Gas Compressor Case Studies on Fouling Visagaran Visvalingam - Presenter Cyron Anthony Soyza Sew Nyit Tong Karl Kolmetz

Cracked Gas Compressor

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Ethylene Unit Cracked Gas Compressor Case Studies on FoulingVisagaran Visvalingam - Presenter Cyron Anthony Soyza Sew Nyit Tong Karl Kolmetz

Outlines?? ? ? ? ? ? ? Overview of Equipment and Setup CGC Fouling Experiences Identification of Turbine Fouling Impacts of Compressor-Turbine fouling Turnaround Inspections Countermeasures for Fouling Control Future Improvements Conclusions

Overview of Equipment & Setup CGC is a five stages centrifugal compressor Caustic wash and drying are facilitated between 4th and 5th stage 5th stage is a heat pump for DeC3 system where C4 and heavier are removed CGC is driven by a SHP steam turbine Turbine extracts HP steam while condensing is controlled by CGC power demand

Compressor System Flow DiagramWash Oils

Stage 1

Stage 2

Stage 3

Stage 4

Cracked Gas

Acetylene Converters Caustic & Dryers To Recovery Section

Stage 5

HP DeC3

Compressor OverviewDiffusers Inlet Vanes

Wheels

Balance Line

Fouling Phenomenon - What,Why and How Organic : Free radical mechanism catalyzed by peroxides, transition metals and heat Inorganic : Quench water carryover Organic or inorganic deposits dehydrogenate over time leaving behindR-H

InitiateR

heat

HO2

Propagate

ROOR-H

ROOH + R

TerminateR + R

CGC Fouling Experiences Polytropic efficiencies dropped Discharge temperatures increased Inter-cooler pressure drops increased Governor valve opening maximum Turbine steam rate increased Max continuos speed not sustainable

CGC Polytropic Efficiency90 85

AFTER TURNAROUND 96

AFTER TURNAROUND 99

TURNAROUND 2001

80

Efficiency (%)

75

70

65

60

55

50

01 1/ /0 05 00 2/ /1 12 00 1/ /1 04 00 9/ /0 07 00 7/ /0 10 00 5/ /0 03 00 3/ /0 06 00 1/ /0 02 99 2/ /1 25 99 0/ /1 07 99 7/ /0 16

9 /9 /3 23 98 2/ /1 05 8 /9 /9 16

8 /9 /5 21 97 2/ /1 23 7 /9 /9 29

7 /9 /4 30 96 1/ /1 25 6 /9 /6 28 6 /9 /4 23

2nd stg Polly. Eff

3rd stg Polly. Eff

4th stg Polly. Eff

5th stg Polly. Eff

23 /4

30

35

40

45

50

55

60

65

70

/9 6 /9 6

28 /6 25 /1 1/ 96

30 /4 /9 7 /9 7 /9 29 23 /1 2/ 97

AFTER TURNAROUND 96

21 /5 /9 8 /9 8 /9 16 05 /1 2/ 98

Compressor Delta T

Stage 1 delta T23 /3 /9 9 16 /0 7/ 99 99 99 00 /0 03 10 07 04 /0 /0 /0 /1 3/ 5/ 7/ 9/ 1/ 00 00 00 00 00 0/ 2/ 1/ /1 /1 /0 07 25 02 06

AFTER TURNAROUND 99

Stage 2 delta T Stage 3 delta T Stage 4 delta T

TURNAROUND 2001

Identification of Turbine Fouling?? ?SHP HP Valve

Unable to maintain speed at max steam flow HP and LP valve fully open Backpressure from LP turbine

P1 LP Valve

P2

HP Casing

LP CasingHP Steam Extraction Exhaust Steam

Causes of Turbine Fouling BFW quality upset High Sodium / Silica due to capacity overrun or improper regeneration of demin train

Water Carry-over Steam drum level control high

Water level

Steam contamination Attemporating water high in sodium or silica

Impacts of Compressor-Turbine Fouling Throughput limited due to maximum driver governor valve opening Increased suction pressure Energy inefficient due to higher steam rate Short run length, 3 years down for cleaning

Turnaround Inspections Inspection done during TA99 and TA 2001 1st and 5th stage - relatively clean 2nd, 3rd & 4th stage - heavily fouled Polymer deposits and most samples were organic component Inter-coolers fouled with polymers and tars Discharge piping layered with polymer

CGC Inspection- TA99 & TA2001Summary of the Inspection FindingsSuct/Disch piping 1st stage 2nd stage 3rd stage 4th stage 5th stage Turbine Impeller/ Diffuser Volute

1st to 4th Stage Discharge Condition during Turnaround 2000/01

1st Discharge

2nd Discharge

3rd Discharge

4th Discharge

Rotor

Casing

2nd stage intercooler bundle

Bundle entrance

Polymer laced inlet pipeline

Inlet to intercooler

Turnaround inspections - CGC Turbine

Countermeasures for Fouling Control Compressor wash oil review Feed points available at the suction piping Injection spray atomizers enhance distribution Increased wash oil injection rate to 3-4% vol. Quality monitoring - existent gums Quantity monitoring - dP

Antifoulant Injection Trial run at the 4th stage - worst case

Improved BFW quality Proper Demin regeneration and lower steam drum level

Compressor Wash Oil Review? 1st to 3rd stage ? 4th stage ? Specific gravity ? Aromatic content ? Existent gums ? Distillation D-86 IBP End point - HPG + C5 - HPG - 0.77-0.80 - 65 % - < 5mg/100ml - 70 oC - 185 oC

Anti-foulant Injection Trail run at 4th stage Start of run - 9 May 02 Co-injection with the existing wash oil Injection rate at 2-5 ppm by weight Monitoring parameters : Polytropic Efficiency Suction / Discharge Temperatures Pressure Drop Across Inter-cooler Steam Consumption Vibrations

Antifoulant Trial RunWash Oils

Antifoulant : 2-5 ppm wt based on the 4th stage charge rateStage 4

Stage 1

Stage 2

Stage 3

Cracked Gas

Acetylene Converters Caustic & Dryers To Recovery Section

Stage 5HP DeC3

Antifoulant Trial Run Findings Polytropic efficiency improved - 4-5% Comp discharge temperature reduced - 3-4oC Delta T reduced Pressure drop across inter-cooler maintained Vibration normal

4th Stage Polytropic Efficiency, % 76 75 74 73 72 71 70 69 68 67 66 6505-01-02 15-01-02 25-01-02 04-02-02 14-02-02 24-02-02 06-03-02 16-03-02 26-03-02 05-04-02 15-04-02 DT 25-04-02 05-05-02 15-05-02 25-05-02 04-06-02 14-06-02 Efficiency (%)

Dosage 2ppm

4th Stage Polytropic Efficiency and Delta T

Dosage 3-4 ppm 61

51

52

Compressor Delta T, degC

53

54

55

56

57

58

59

60

4th Stage Polytropic Efficiency and Delta T

24-Jun-02 19-Jun-02 Ave eff = 1st to 3rd stage 14-Jun-02 09-Jun-02 04-Jun-02 30-May-02 25-May-02

2nd stage

C-300 Efficiency

4th stage

20-May-02 15-May-02 10-May-02 05-May-02 30-Apr-02 25-Apr-02 20-Apr-02 15-Apr-02 10-Apr-02 05-Apr-02 31-Mar-02

80

78

76

74

72

70

68

66

64

62

60

Eff, %

Future ImprovementsWash oil quality C8+ High aromatics, low gums & higher FBP Intermittent or Continuos - 0.5% wg High volume flush - 2% wg

Wash oil and Antifoulant injection to casing Revamp or TA modification

Wash water injection max 1% throughput to minimize rotor erosion

Inter-coolers Antifoulant injection facilities for online cleaning

High efficiency 3D impeller blades (new service) More efficient and larger gas passage

Conclusions? A review of equipment and maintenance records are essential to each producer ? Part of this review should include turbine and compressor fouling ? Adequate wash oil selection and antifoulant injection enables cracker extension of cracked gas compressor run lengths by reducing the amount of polymer fouling. ? Any review should also include future optimizations

Thank You

Q&A