Abstract: The liquid level in at least one flash economizer associated with a refrigeration process is maintained at a desired level by controlling the flow of the liquid leaving the flash economizer in response to a control signal which is responsive to the difference between the actual liquid level in the flash economizer in the desired liquid level. The liquid level in the chiller associated with a refrigeration process is maintained by controlling the flow of fluid to the flash economizer in response to a control signal which is responsive to the difference between the actual liquid level in the chiller and the desired liquid level.

Abstract: In accordance with the present invention a normally gaseous feed mixture, having a temperature of essentially atmospheric temperature and a pressure substantially above atmospheric pressure, is cooled to a lower temperature sufficient to liquefy a portion of the feed mixture, the cooled feed mixture is separated into a first vapor phase and a first liquid phase, the first vapor phase is further cooled to a temperature sufficiently low to liquefy a portion of the first vapor phase, the cooled first vapor phase is separated into a second vapor phase and a second liquid phase, the pressures of the first liquid phase and the second liquid phase are separately reduced to a pressure sufficiently low to flash portions of the liquid phases, the reduced-pressure, first liquid phase is introduced into the lower portion of a third separation step while the reduced-pressure, second liquid phase is introduced into the upper portion of the third separation step, in which the reduced-pressure, first and second liquid phases

Abstract: A compressor surge control system is provided for a compressor system in which recirculation of gas from the discharge outlet of the compressor to the suction inlet of the compressor is utilized to prevent surging of the compressor. The recirculation of gas from the discharge outlet of the compressor to the suction inlet of the compressor is substantially minimized by using a first controller to provide a floating set point for a second controller. This reduced recirculation substantially increases the efficiency of the compressor system.

Abstract: In the separation of low boiling gases such as ethane or propane and heavier from a gas stream such as natural gas, a first portion of the feed is heat exchanged with an overhead from a downstream stripper column, such as a demethanizer, a second portion is heat exchanged with a stream from a lower portion of said stripper column, and these two portions passed as separate streams to a separator-contactor. The first stream is added at a point above the second. This results in an increase in the recovery of liquid products.

Abstract: In the separation of low boiling gases such as ethane and heavier from natural gas utilizing two expanders in series, liquid condensed before expansion is not passed to the fractionator but is flashed and the resulting vapor combined with the expanded vapor from the first expander. This results in both increased work output from the second expander and simplified design of the downstream fractionator column since it reduces the amount of lighter materials introduced into the lower section thereof.