SRU OPERATION
CONDITIONS
MFG - DHDS
SRU BLOCK FLOW DIAGRAM
ACIDGAS
MP STEAM
REACTION
FURNACE
AIR
FUEL GAS
ACID GAS
LP STEAM FUEL GAS
AIR
WASTE HEAT
BOILER
BFW
SULPHUR
CONDENSOR I
LINE BURNER
CLAUS
CONVERTOR
BFW
SULPHUR
REHEATER
LP STEAM
CONDENSOR II
MCRC I
MCRC II
BFW
MCRC III
LP STEAM
CONDENSOR III
CONDENSOR IV
CONDENSOR V
AIR
BFW
SULPHUR
INCINERATOR
FUEL GAS
Case 1 - 72 TPD capacity
(Each Train)
Case 2 - Turn down capacity
(30% of design)
Case 3 - 120 TPD capacity
(both Trains)
Case 4 - Below turndown capacity
(0.5 TPH AG)
Case 5 – VGO mode operation,with NH3 gas
in main burner
Case 6 – VGO mode operation,with NH3 gas
in incinerator
Case 7 – Diesel mode operation,with NH3 gas
in incinerator
DESIGN FLOW RATES
Flow
Kg/hr
case case case case case case case
1
2
3
4
5
6
7
AG to MB
3357
1000
2797
475
2930
2930
1671
SG to MB
110
100
100
100
312
312
91
NH3 gas
86*
75*
75*
75*
258
516*
150*
Air to MB
6524
2068
5446
1081
6951
5519
2902
Steam MB
150
AG to LB
158
50
132
25
106
106
61
Air to LB
377
119
314
60
266
266
151
Mass Velocity Calculations
Mass
velocity
Kg/m2 sec
Case case2 case case4 case5 case6 case
1
3
7
WHB o/l
20.11
6.38
16.79
3.63
21.04
17.63
9.39
Cond I o/l
19.89
6.31
16.61
3.59
20.59
16.34
8.75
Reheater o/l 15.71
4.98
13.16
2.84
16.00
12.83
6.89
Cond II o/l
22.19
7.03
18.52
4.01
23.32
18.49
9.93
Cond III o/l
23.89
7.57
19.94
4.32
24.32
19.19
10.32
Cond IV o/l
23.18
7.34
19.35
4.19
23.78
18.74
10.08
Cond V o/l
22.54
7.14
18.82
4.07
23.64
18.62
10.02
SRU CAPACITY CALCULATION
DESIGN CONDITIONS
SRU capacity (72 TPD)
3000
Recovery
99%
Actual Sulphur in the feed
3030.30
H2S Equivalent of AG
3219.70
Average Mole wt of AG(design basis)
33.80
Acid Gas Equivalent(AG+SG)
3622.76
Acid Gas Flow
3512.76
Kg/hr
Kg/hr
Kg/hr
Kg/hr
Kg/hr
AG Composition(89.4% H2S,4.9%H2O,5.5%CO2,0.1%H2,0.1%HC)
Design conditions of Burners
Flow Rate - Kg/hr
Acid gas (max)
Sour gas(max)
Air (max)
Tail gas (max)
Sweep gas (max)
NH3 rich gas(max)
Fuel Gas (max)
Turn down ratio
* for fuel gas operation
MB
LB
3357
110
6524
IB
158
377
10500
15062
700
86
300*
19.2*
405
10% of Design 25% of Design 10% of Tail gas
TURNDOWN
On feed flow
-
On H2S content -
30 % of capacity of
each train(3.6TPH)
1.08 MT/Hr AG feed
50 Mole % of H2S in
feed
Lower Turndown Requirement
• The unit is required to be operated from 0.35 to
0.5 TPH, when DHDS unit is shut down and
crude units are running on low sulphur crude,
ARU is running for existing refinery.
• Test run with 0.5 TPH was carried out on
17/10/2001,1635 hrs to 21/10/2001,1730 hrs
• Test run with 0.35 TPH was carried out on
27/10/2001,2040hrs to 29/10/2001,2240hrs
COMPARISON OF LOW TURN DOWN OPERATIONS
Normal
T/D Claus T/D Claus T/D Claus
+
+
+
1MCRC
2 MCRC 1MCRC
Feed
3.5
0.5
0.5
0.35
MB temp
1200-1250
1035-1060
1035-1060
950-960
LB temp
270-280
270-280
270-280
279-290
Claus
280-340
280-340
280-340
290-335
MCRC i/l
280
265-277
265-277
260-265
MCRC reg
270-285
230-255
240-270
220-240
MCRC SD1
135-170
MCRC SD2
135-141
% recovery
99
95
98.5
95
SO2 emmission
1200
4300
1300
3500
Flame stability
yes
less
less
less
Flow variation
no
yes
yes
Yes
130-152
Limitations at Lower turndown
conditions
•Sulphur fog formation in reactor/condenser
•Unstable flame in burners
•Lower reaction furnace temperature
•Fluctuation of acid gas flow at lower flow
rate
•Problems with flame scanner
•Maintaining of temperature profile in reactor
system
Modifications for turndown
operation
•A trim bypass control valve for ARU pressure
control valve
•A trim bypass butterfly valve and lower range
venturi meter for SRU feed control valve
•Superheated LP steam to SRU main burner
•HC2 gas to SRU burners
•Air line modifications with lower range venturi
meters and new trim air control valves
Major Modifications for Lower Turn Down Operations
Flow rate, Kg/hr
Area
ARU- Acid Gas
SRU- Feed line
New facility
PV 2901 C
FE 1201A / FE 5201A
FV 1201A / FV 5201 A
Air line
FE 1301A / FE 5301A
FV 1302 / FV 5302
Steam to MB
PV 3312
PSV 3305
FE 3304
HC2 gas to burners PV 2802 A
Inter connecting line
from LPG kod o/l to
FG line near MB
RO
PSV 2801 A/B
size
3"
4*6
3"
8"
8"
2"
7 kg/cm2g
2"
2"
3"
3"
5.5 kg/cm2g
min
200
200
200
300
300
100
50
normal
max
500
1000
500
1000
500
1000
500
1000
500
1000
150
150
185
300
Trim bypass control valve for
ARU pressure control valve
PV2901C
PV2901A
To SRU
PV2901 B
From
V-31
DD V 32
To Flare
Trim bypass valve for SRU feed
control valves
FE 1201A/5201A
FE 1202/5202
FE 5201
FV 1202/5202
To CC
To LB
FV1201/5201
To MB
FV1201A/5201A
New trim air control valve and
Venturi meter
FE 1302/5302
Ff
FV1302/5302
FE 1301/5301
FV 1301/5301
Air to MB
FE 1301 A/5301A
Air to LB
From Blower Discharge
Superheated LP steam to SRU
main burners
LP Steam from Header
SDV 1502
To MB Tr A
LP Steam from Header
SDV5502
To MB Tr B
FE 3304
FV 3304
PSV 3305
PV 3312
MP steam from DHDS b/l (2")
MP steam from SRU (12")
HC2 gas to SRU burners
To Flare
HC2 gas
PSV 2801 A/B
LPG/FG
FG to LB Tr A
FG to LB Tr B
PC2802
RO
FG to MB Tr A
PC2802A
DS V 6
FG to MB Tr B
Modifications during CEMP phase1
•New Reduction furnace for NH3 reductionassociated facilities such as new blowers.
•New sulphur yard with capacity 9*10*1.5 m3.
•New NH3 analyser at exit of WHB in each Train.
•New O2 analyser at exit of WHB in each Train.
•New NOx analyser for flue gas on stack.
•Vap LPG/ Constant composition fuel gas to MB for
start up / sweeping / hot stand by conditions
Modifications during CEMP phase1
•DS V002 i/l and o/l feed nozzle and line size
modifications to 6” from 2”.
•DS V003 i/l and o/l feed nozzle and line size
modifications to 6” from 2”.
•Inert gas purging to AG bypass line to CC –
SDV 1503/5503 and FG1513/5513 & RO
1503/5503.
•New flow transmitters 1203,1204, 1301/5301,
1601/5601,1602/5602,1701/5701,1702/5702,2601,
2603
Modifications during CEMP phase1
•New control valves FV-1203/5203,FV1204/5204,
FV-1601/5601,TV-2601,PV-2803,TV-2901
•New PV 2603 and d/s line 4*6 to reduction
furnace.
•New safety valves for WHB (19.7) and nozzle
modified.
Flow (new)
DP
new
Flow (Old)
DP
old
Min
Nor
Max
Max
Min
Nor
Max
Max
FV1203
76
312
345
0.4
10
49
99
0.75
FV1204
65
258
284
0.4
8.6
43
86
0.75
FV1301
1738
6951
7646
0.4
1631
5436
6524
0.84
FV1601
2310
7700
8470
1.1
2220
5680
7430
1.1
LV1701
304
1013
1114
14.9
300
840
1000
14.9
PV1701
295
983
1034
1.4
280
772
927
1.4
TV2601
50
478
500
0.9
40
322
405
1.2
PV2603
52
516
568
0.45
86
0.5
FV2601
1162
11627
12600
0.17
PV2803
60
600
600
0.4
TV2901
135
903
993
1.5
1000
7688
10467
105
654
700
1.5
Flow
Transmitter
Flow Rate, Kg/hr
Min Nor
Max
(NEW)
Flow Rate, Kg/hr
Min Nor
Max
(OLD)
FT 1203
624
624
686
29.7
99.0
99.0
FT 1204
516
516
568
25.8
86
86
FT 1301
1631
7217
7936
1631
5436
6524
FT 1601
2310
7700
8470
2116
5397
7056
FT 1602
2240
7469
8216
2055 5241 6850
FT 1701
295
983
1081
278
772
927
FT 1702
304
1013
1114
315
885
1050
FT 2601
1163
11627
12600
1000
7688
10467
FT 2603
47.8
478
525
Sl no
problem
reason
solution
modification
implement
ation status
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