2 2 3
The above table shows that the heat duty actual of 25-E-103 and 25-E-203 are operated at 50% to the design. This caused by the flow rate of lean amine to be cooled also only about 50% - 60% from design capacity.
The flow rate of lean amine does not affect to the power required of fan cooler driver, so the power required to motors also higher than calculated value. At this case, the actual fan be operated closed to design (11 fans for 25-E-103 and 12 fans running for 25-E-203). This condition related with performance of cooler, especially with heat transfer rate. The U (overall heat transfer rate) at operating condition give value about 2 BTU/(Hr/Ft2.F) for operated and 3 BTU/(Hr/Ft2.F for the design value. This difference indicated that the performance of cooler lower than the design performance.
Table 4-11 : Performance of Rich-Lean Amine Exchanger:
25-E-104A/B 25-E-204A/B DESIGN
RICH AMINE SIDE
Pressure, psig 108.00 OFF 95.00
Temp inlet, F 155.00 OFF 167.00
Flowrate of Rich Amine, USGPM 2,572.00 OFF 2,496.80 LEAN AMINE SIDE
Temp inlet, F 250.00 OFF 261.00
Temp outlet, F 229.00 OFF 224.00
Delta T LMTD 59.48 OFF 55.99
HEAT DUTY, Btu/hr 53,656,356 OFF 42,413,111 HEAT TRANSFER RATE, BTU/(Hr/Ft2.F) N/A OFF N/A
The above table shows that the heat duty operated of exchanger 25-E-104A/B is higher than design value. The difference is about 25% higher than design.
The different heat load should be caused by :
Design amine is CR302, but the actual operation is AP-16668. The difference of amine causes different specific heat.
Flow rate of rich amine at operation is higher than the design value (3.5% difference)
The difference between operated LMTD and design is 6.5%.
Table 4-12 : Performance of Regenerator Reflux Condenser :
25-E-101 25-E-201 DESIGN
ACID GAS SIDE :
Temp inlet, F 218.47 OFF 217.00
Temp outlet, F 143.15 OFF 120.00
Flow of acid gas removed, MMSCFD 20.60 OFF 23.25
AIR COOLANT SIDE :
Temp inlet, F 92.00 OFF 95.00
Temp outlet, F 132.00 OFF 131.60
Delta T LMTD 67.27 OFF 57.60
HEAT DUTY, Btu/hr 55,701,905 OFF 61,714,112
ELECTRIC CONSUMPTION, KW 23.79 OFF 29.84
ACTUAL FAN OPERATED 11.00 OFF 12.00
CALCULATE FAN OPERATED 10.83 OFF 12.00
HEAT TRANSFER RATE,
BTU/(HR.Ft2.degF) 3.57 OFF 4.19
The above table shows that regen reflux condenser and amine regenerator re-boiler are operated close to design condition. It has difference of heat duty about 11% than the design value. This caused by the flow rate of acid gas to be removed also only
13% less than the design capacity (operated is 20.6 MMSCFD, and the design value is 23.25 MMSCFD).
Power required of motor fan driver also proportional with the exchanger heat duty. At this condition the actual operate 11 fans, and the calculated result is also same fans to be operated.
Caused by the flow rate capacity of cooler load, the overall heat transfer also follow with this condition. The U (overall heat transfer rate) at operating condition give value about 3.57 BTU/(Hr/Ft2.F) and 4.19 BTU/(Hr/Ft2.F for the design value.
Table 4-13 : Performance of Amine Charge Pump
DESCRIPTION UNIT 25-P-102C Design
value value
specific gravity 1.03 1.00
Temperature F 245.00 70.00
suction pressure psia 98.00 25.00
discharge pressure psia 1210.00 1185.00
flow GPM 2862.00 2487.00
Total head ft 2,503.97 2679.60
Electric motor power HP 2240.00 2059.00
Mechanical work HP 1946.39 1719.89
Efficiency % 86.89 83.53
Only one Amine charge pump (Charge pump C) was running very close to design condition. It’s efficiency reached 86.89% with flow rate of 2862 GPM, This pump is designed to running with 83.53% efficiency at 2487 GPM flow rate. The pump was running actually in even higher efficiency than the design condition. Attention should be addressed to this situation since the pump draw consumed electric power of 2240 HP. It just below it's maximum power rating: 2250 HP.
Table 4-14 : Performance of Amine Booster Pump
DESCRIPTION UNIT 25-P-101B 25-P-101C Design
value value value
specific gravity 1.03 1.03 1.00
Temperature F 180.00 180.00 70.00
suction pressure psia 16.70 18.70 N/A
discharge pressure psia 119.70 129.70 N/A
Total head ft 231.93 249.95 188.00
Electric motor power HP 142.00 136.00 170.00
Mechanical work HP 98.02 88.66 139.30
Efficiency % 69.03 65.19 81.94
Two of the Amine booster pumps were running. They were Amine Booster pump B and C. Their efficiencies are 69.03% at 1556 GPM and 65.19% at 1306 GPM respectively. At the other side, we have data from design condition when each pump handles 2871 GPM. At this design condition, we got 81.94% efficiency. These two pumps were running in good condition and within the range of operation.
4.2.3. REFRIGERATION SYSTEM A. DESCRIPTION
Propane refrigerant gas from gas chiller at 75 psig, compress by propane compressor (single stage screw compressor). The compressor discharge at about 252 psig goes to the propane condenser where it is totally condensed at about 122 oF. The propane condenser is an air cooled heat exchanger.
The condensed propane goes to the propane accumulator and then to the gas chiller via the level control valve. The refrigerant chills the sales gas from 57 F to 45 F and then goes to LTS to separate the gas from the condensate.
B. PERFORMANCE
The main equipment at Refrigeration System are Exchanger (Gas chiller 30-E-102), Propane compressor 30-K-101A/B and Gas/Gas Exchanger.
Table 4-15 : Performance of Gas Chiller
UNITS DESIGN EVAPORATOR
TEMPERATURE GAS IN DEG.F 57.00 57.00 TEMPERATUR GAS OUT DEG.F 45.00 45.00 GAS FLOW MMCFD 100.00 39.00 CONDENSATE FLOW BCD 700.00 700.00
HEAT RELEASE BTU/H 2,477,633.80 841,348.85 ACTUAL POWER KW 260.00 110.00 C.O.P 2.79 2.24
The above table shows that the refrigeration system operated at low load and the propane chiller are operated at 40 % load (39 MMSCFD ) at actual power 110 KW compare to design condition. The COP at actual condition is 2.24 compare to design value is 2.79
Table 4-16 : Performance of propane compressor
Only one compressor is operated to handle the refrigeration system. The operating conditions are as follows;
UNITS DESIGN ACTUAL
SUCTION TEMPERATUR ( oF ) 35.00 30.00 CONDENSING TEMPERATUR ( oF ) 127.00 120.00
PROPANE FLOW LBS/H 14,000.00 7,191.72 (Calculated)
TOTAL POWER REQUIRED KW 242.17 101.64 ACTUAL POWER KW 260.00 110.00 COP 3.00 2.87
At the actual condition, the refrigerant flow is 7191 lb/hr at actual power 110 KW and COP = 2.87. Compare to design condition, the refrigerant flow is 14,000 lb/hr at power design 260 KW and COP = 3. It means that the performance of compressor is still in good condition.
Table 4-17 : Performance of Gas/Gas Exchanger
30-E-101 DESIGN