Achieve cooling of mixed refrigerant in the main cryogenic heat exchanger by throttling flow and reducing pressure significantly.
The Joule-Thomson (JT) effect is leveraged throughout all of the primary LNG liquefaction processes to achieve cooling of the feed gas or the refrigerant streams. It is used to achieve cooling of liquids, gases, or multi-phase fluids. Traditionally, this effect has been facilitated by a control valve that reduces the pressure of the fluid significantly and induces the desired cooling. Because of the elevated pressure drop, the control valve can experience excessive noise levels if not addressed properly. It also experiences very low process temperatures and must be capable of precise throttling down to full cryogenic temperatures.
•Significant pressure drop
•Excessive noise levels
•Full cryogenic temperatures
When the mixed refrigerant moves up the tubes between the inlet to the main heat exchanger and the warm Joule-Thomson valve, it loses its heat to the colder mixed refrigerant fluids moving countercurrent through the shell. Therefore, when the mixed refrigerant reaches the inlet to the warm Joule-Thomson valve in the lower section of the main heat exchanger, it is typically at cryogenic temperatures, around −200F (−130C). The mixed refrigerant fluid that flows through the valve may turn into a liquid and vapor mix as it exits the valve. The proper trim must be selected. Balanced cryogenic valves are preferred. If a large percentage of refrigerant by volume is converted to a vapor when the valve takes its pressure drop to spray the bundles, then the drilled-hole or slotted trim in a flow up direction is used to eliminate flashing related noise, vibration and erosion.
The inlet temperature of the mixed refrigerant entering the cold Joule-Thomson valve is lower than the temperature of the mixed refrigerant entering the warm Joule-Thomson valve, approximately −240F (−150C). This is due to the longer pass through the heat exchanger. The mixed refrigerant fluid that flows through the valve may turn into a liquid/vapor mix as it exits the valve. The proper trim must be selected. Balanced cryogenic valves are preferred. If a large percentage of refrigerant by volume is converted to a vapor when the valve takes its pressure drop to spray the bundles, then the drilled-hole or slotted trim in a flow up direction is used to eliminate flashing related noise, vibration, and erosion.
The Fisher Joule-Thomson control valve utilizes pressure drop to achieve the cooling of liquids, gases, or multi-phase fluids.
•Withstands full cryogenic temperatures
•Maintains stable flow of refrigerant to chillers and cold boxes under large differential pressures
•High precision assembly with ≤ .25% deadband
