Ethylene Cracked Gas Compressor
Transcript of Ethylene Cracked Gas Compressor
Ethylene Unit Cracked Gas CompressorCase Studies on Fouling
Visagaran 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 Diagram
Cracked Gas
Caustic& Dryers
Stage 1 Stage 2 Stage 3 Stage 4
Stage 5
ToRecoverySection
HP DeC3
Acetylene Converters
Wash Oils
Diffusers
BalanceLine
Wheels
Inlet Vanes
Compressor Overview
Fouling Phenomenon - What,Why and How
• Organic : Free radicalmechanism catalyzed byperoxides, transition metals andheat
• Inorganic : Quench watercarryover
• Organic or inorganic depositsdehydrogenate over timeleaving behind
InitiateInitiate
PropagatePropagate
TerminateTerminate
R-H
• R • H
• ROO
heat
O2
ROOH + •R
R-H
•R•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 Efficiency
50
55
60
65
70
75
80
85
90
23/4/9628/6/9625/11/9630/4/9729/9/97
23/12/9721/5/9816/9/9805/12/9823/3/9916/07/9907/10/9925/12/9902/01/0006/03/0003/05/0010/07/0007/09/0004/11/0012/12/0005/01/01
Eff
icie
ncy
(%)
2nd stg Polly. Eff 3rd stg Polly. Eff 4th stg Polly. Eff 5th stg Polly. Eff
AFTER TURNAROUND
96
AFTER TURNAROUND
99
TURNAROUND 2001
Compressor Delta T
30
35
40
45
50
55
60
65
70
23/4
/96
28/6
/96
25/1
1/96
30/4
/97
29/9
/97
23/1
2/97
21/5
/98
16/9
/98
05/1
2/98
23/3
/99
16/0
7/99
07/1
0/99
25/1
2/99
02/0
1/00
06/0
3/00
03/0
5/00
10/0
7/00
07/0
9/00
04/1
1/00
Stage 1 delta T Stage 2 delta T Stage 3 delta T Stage 4 delta T
AFTER TURNAROUND
96
AFTER TURNAROUND
99TURNAROUND
2001
Identification of Turbine Fouling
? Unable to maintain speed at max steam flow
? HP and LP valve fully open
? Backpressure from LP turbine
HPValve
SHP
LPValve
P1 P2
HP SteamExtraction
ExhaustSteam
HP Casing LP Casing
Causes of Turbine Fouling
• BFW quality upset
– High Sodium / Silica due to capacity overrun orimproper regeneration of demin train
• Water Carry-over
– Steam drum level control high
• Steam contamination
– Attemporating water
high in sodium or silica
Water level
Impacts of Compressor-TurbineFouling
£ Throughput limited due to maximum driver governorvalve 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 & TA2001
Summary of the Inspection Findings
Suct/Dischpiping
Impeller/Diffuser
Volute
1st stage
2nd stage
3rd stage
4th stage
5th stage
Turbine
1st Discharge1st Discharge 2nd Discharge2nd Discharge 4th Discharge4th Discharge3rd Discharge3rd Discharge
1st to 4th Stage Discharge Condition during Turnaround 2000/011st to 4th Stage Discharge Condition during Turnaround 2000/01
RotorRotor CasingCasing
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 - HPG + C5
? 4th stage - HPG
? Specific gravity - 0.77-0.80
? Aromatic content - 65 %
? Existent gums - < 5mg/100ml
? Distillation D-86
– IBP - 70 oC
– End point - 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 Run
Cracked Gas
Caustic& Dryers
Stage 1 Stage 2 Stage 3 Stage 4
Stage 5To
RecoverySection
HP DeC3
Acetylene Converters
Wash Oils
Antifoulant : 2-5ppm wt based on the4th stage charge rate
• Polytropic efficiency improved - 4-5%
• Comp discharge temperature reduced - 3-4oC
• Delta T reduced
• Pressure drop across inter-cooler maintained
• Vibration normal
Antifoulant Trial Run Findings
4th Stage Polytropic Efficiency and Delta T
65
66
67
68
69
70
71
72
73
74
75
76
05-0
1-02
15-0
1-02
25-0
1-02
04-0
2-02
14-0
2-02
24-0
2-02
06-0
3-02
16-0
3-02
26-0
3-02
05-0
4-02
15-0
4-02
25-0
4-02
05-0
5-02
15-0
5-02
25-0
5-02
04-0
6-02
14-0
6-02
4th
Sta
ge P
olyt
ropi
c E
ffici
ency
, %
51
52
53
54
55
56
57
58
59
60
61
Com
pres
sor D
elta
T, d
egC
Efficiency (%) DT
Dosage 2ppm Dosage 3-4 ppm
4th Stage Polytropic Efficiency and Delta T
C-300 Efficiency
60
62
64
66
68
70
72
74
76
78
80
31-Mar-02
05-Apr-02
10-Apr-02
15-Apr-02
20-Apr-02
25-Apr-02
30-Apr-02
05-May-02
10-May-02
15-May-02
20-May-02
25-May-02
30-May-02
04-Jun-02
09-Jun-02
14-Jun-02
19-Jun-02
24-Jun-02
Eff
, %
2nd stage
4th stage
Ave eff = 1st to 3rd stage
Future Improvements� Wash 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 areessential to each producer
? Part of this review should include turbine andcompressor fouling
? Adequate wash oil selection and antifoulant injectionenables cracker extension of cracked gas compressorrun lengths by reducing the amount of polymerfouling.
? Any review should also include future optimizations
Thank You
Q & A