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RECYCLEExterran Office
Jakarta, Dec 1 ST 2012
UNDERSTANDING
HYSYS
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Understanding process with recycle streamUnderstanding process
design
Objectives
Case : Refrigeration System
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Typical refrigeration system
Typical single stage VaporCompression Refrigeration
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Refrigeration System using Economizer
Do you know economizer function? I believe you know the
functionby its name. To get clearer information, lets start the
simulation.
The green box on picture above represents Economizer.
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Problem Solving1. Make equipment arrangement as per
Refrigeration System usingEconomizer process. Do not connect
recycle to main streambefore main stream can be simulate.
2. Set compressor compression ratio to 3. Ensure pressure unit
inpsia.
3. Input pressure drop on each equipment (Cooler, Scrubbers).4.
Put P, Molar Flow and gas composition to suction compressor as
initial trial value. Find Tsuction which is limited by
condenserperformance.Note : outlet temperature of condenser is
limited to 120 F due to
approach temperature of air process gas.
Command : adjust inlet temperature of condenser to 120 F
withsuction temperature as variable. .Please note that the result
is the minimum temperature, raise fewdegrees above the result.
Fluid condition shall be superheated(gas only).
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Result of step 1 - 4:
2-phase, so the governing is fluid phase
Fluid at suctioncompressor shallbe in gas phase(vapour fraction
=1).
For this case, takeout ADJ-1 and setTsuction at 5 F.
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5. To get maximum refrigeration capacity, set pressure drop
VLV-100 to 0(zero) psi. Set vapour fraction at Stream 6 = 1.
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6. Set pressure at recycle with main stream as referenceP6 =
P11; P12 = P11; P13 = P14.
5 MMSCFD at 40 psia/ 5 F Refrigeration -2.28 MMBtu/hr.
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6. Connect recycle stream to main stream.
7. To get refrigeration duty 4 MMBtu/hr, Adjust Molar Flow at
Stream 11with target Q-ref at -4 MMBtu/hr.
The result is 8.743 MMSCFD for refrigeration capacity 4
MMBtu/hr.Compressor duty is 2.554 MMBtu/hr.
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