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SPM Refrigeration Series
SPM-8010 Single-Stage Refrigeration System

Process Description

The purpose of the Simtronics Single-stage Refrigeration System is to cool a process stream to a temperature significantly below ambient temperature. This is accomplished in a closed system which circulates a compound that will chill to low temperatures when it is depressured in the liquid phase and whose vapor will condense at temperatures above ambient when compressed. Such compounds are called refrigerants. In this system, propane is the compound of choice.

The Single-stage Refrigeration System consists of:

Suction Drum V-601 removes any liquid that may be contained in the refrigerant vapor from the Process Chiller E-521 prior to entry into the Refrigeration Compressor. The vapor proceeds into the Refrigeration Compress K-601 which is a centrifugal compressor. K-601 compresses the vapor to a pressure high enough that the refrigerant will condense in the Air-Cooled Condenser E-601. The Refrigeration Compressor K-601 is driven by Compressor Turbine KT-601 using high pressure steam as the motive fluid. The speed of the compressor is regulated by SIC-601 whose setpoint is adjusted by suction pressure controller PIC-601.

Hot, high pressure vapor from K-601 discharges into Air-Cooled Condenser E-601 which uses ambient air to cool the vapor from K-601. E-601 uses an electric-motor driven fan to move the air through the exchanger. Condensed refrigerant near ambient temperature leaves E-601 and is collected in Accumulator V-604. The Accumulator serves as a reserve vessel that dynamically absorbs fluctuations of pressure and level in other parts of the refrigeration system. Liquid refrigerant in the V-604 is essentially at the discharge pressure of K-601 and is sent to the Process Gas Chiller E-521. As the liquid passes through the level control valve for E-521, it depressures to essentially the suction pressure of the Refrigeration Compressor. As the liquid depressures, it will flash off vapor which, in turn, will decrease the temperature of the mixed phase refrigerant entering E-521.

The chilled, mixed-phase refrigerant enters Process Gas Chiller E-521 on the shell side of the heat exchanger. A liquid level is maintained in E-521 to submerge all of its tubes in the liquid holdup. As heat is absorbed into liquid the from process gas, some of the liquid refrigerant vaporizes. The vaporized refrigerant combines with the vapor entering with the mixed-phase refrigerant from the level control valve for E-521. The combined vapor is returned to the Suction Drum V-601 to complete the refrigeration cycle. An interlock system stops operation of the Refrigerant Compressor and Turbine in the event of high discharge pressure, high discharge temperature, high suction drum level or high compressor speed.