DCU FURNACE TROUBLESHOOTING: “HIGH TUBE METAL...
Transcript of DCU FURNACE TROUBLESHOOTING: “HIGH TUBE METAL...
DCU FURNACE
TROUBLESHOOTING: “HIGH TUBE
METAL TEMPERATURE”
C K SINHASenior Manager Technical Services,
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TO COKE DRUM
1
2
7
25
28
1
2
7
25
28
� 2 - Pass Bottom FiredNatural draft Furnace
� Design Fired duty- 8.16Gcal/hr
� Low Nox flat flameburner
� Total 36 no of tubes inradiation section
� Tube metal T t’coupleon tube no 1,2,7,25,28 &shock zone (SZ) tube
HC
BFW BFW
HC
S Z
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FURNACE
OVERVIEW
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� Rise in tube metal temperature(TMT) in short time
� No on-line spalling facility
� Frequent SAD
� Frequent DCU outage
� Reduction in Refinery Profit
PROBLEM
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Problem Analysis
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FIELD CHECKS
� CROSS CHECKING OF TMT BY THERMOGRAPHY
� FEED PROPERTY , FG PROPERTY
� CONTAMINATION OF FEED WITH RESIDUE
� FURNACE FEED PUMP SUCTION STRAINER
� START-UP CIRCULATION PUMP SUCTION STRAINER
� TRAMP AIR
� FIRED DUTY
520
540
560
580
600
620
640 1-N
1-M
1-S
2-N
2-M
2-S
7-N
7-M
7-S
25-N
25-M
25-S
28-M
SZ-1
SZ-2
TMT TREND OF PAST RUN-1
25TH TUBE
7TH TUBE & BELOW
SHOCK ZONE
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TMT TREND OF PAST RUN-2
520
540
560
580
600
620
640 1-N
1-M
1-S
2-N
2-M
2-S
7-N
7-M
7-S
25-N
25-M
25-S
28-M
SZ-N
SZ-S
SHOCK ZONE
25TH TUBE
7TH TUBE & BELOW
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520
540
560
580
600
620
640
660
1-N
1-M
1-S
2-N
2-M
2-S
7-N
7-M
7-S
25-N
25-M
25-S
28-M
SZ-N
SZ-S
TMT TREND OF PAST RUN-3
SHOCK ZONE25TH & 28TH
TUBE
7TH TUBE & BELOW*One additional t’couple installed on 25th in Middle position and on
28th in Middle position 8
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0.00
1.00
2.00
3.00
4.00
5.00
6.00
7.00
8.00
9.00
Series1
Series2
-1.00
0.00
1.00
2.00
3.00
4.00
5.00
6.00
7.00
8.00
9.00
Series1
Series2
0.00
2.00
4.00
6.00
8.00
10.00
12.00
ConvDelP-1
ConvDelP-2
CONVECTION COIL PRESSURE DROP
� HC flow 29 m3/hr� BFW to convection coil flow rate 0.32 m3/hr� CIT- 325⁰C , COT- 492.5⁰C� Furnace draft- 7 mmWC� O2 analyzer reading- 8 vol%� Convection O/L T- 433⁰C� Stack T- 230⁰C� Flue gas T at arch- 740⁰C� Flue gas T at floor-620⁰C� Fuel Gas flow- 560 kg/hr
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OPERATING CONDITIONS
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1
2
3
4
5
6
7
8
9
10
300
350
400
450
500
550
600
650
700
CrOvT-1
COT-1
CrOvPr-1
O/L Pr-1
PROCESS TEMPERATURE DURING SAD WITH SAME DRAFT AND O2 IN FLUE GAS
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� HIGH DRAFT, HIGH EXCESS AIR, HIGH TMT IN SHOCK ZONE &
RADIANT TOP ZONE
� HIGH HEAT TRANSFER IN CONVECTION TUBES
� HIGH RADIATION INLET TEMP
� CONVECTION COIL FOULING
� HIGH AMOUNT OF HEAT AVAILABLE IN RADIATION TOP ZONE
� COKE FORMATION IN RADIATION TOP ZONE AT FAST RATE
� COKE LAYER IN 25TH & 28TH TUBE
� TUBE 1 & 2 VERY CLEAN
OBSERVATIONS
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• Reduce the draft inthe furnace box toshift the heat transferto radiation bottom
• Increase the HCvelocity at theradiation inlet toslow down coke layerformation in radiationtop tubes
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NEW OPERATING CONDITION
� HC flow 29 m3/hr/pass� BFW to convection coil flow rate 0.32 m3/hr/pass� BFW to radiation I/L coil flow rate 0.2 m3/hr/pass� CIT- 325⁰C , COT- 495⁰C� Convection O/L T- 420⁰C� Furnace draft- 2.3 mmWC� O2 analyzer reading- 3.2 vol%� Stack T- 210⁰C � Flue gas T at arch- 730⁰C� Flue gas T at floor-620⁰C� Fuel Gas flow- 530 kg/hr
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RESULTS
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0.00
1.00
2.00
3.00
4.00
5.00
6.00
7.00
8.00
Series1
Series2
0.00
1.00
2.00
3.00
4.00
5.00
6.00
7.00
Series1
Series2
CONVECTION COIL PRESSURE DROP
500
520
540
560
580
600
620
1-N
1-M
1-S
2-N
2-M
2-S
7-N
7-M
7-S
25-N
25-M
25-S
28-M
SZ-N
SZ-S
NEW TMT TREND RUN-1
SHOCK ZONE
25TH & 28TH TUBE
7TH TUBE & BELOW
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500
520
540
560
580
600 1-N
1-M
1-S
2-N
2-M
2-S
7-N
7-M
7-S
25-N
25-M
25-S
28-M
SZ-N
SZ-S
25TH & 28TH TUBE7TH TUBE & BELOW
SHOCK ZONE
NEW TMT TREND RUN-2
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BEFORE
AFTER
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