The air separation system can include: a process control unit 201 for controlling components constituting the air separation system; an oxygen concentration estimating unit 202 for estimating, by calculation, the oxygen concentration of oxygen-enriched liquid that accumulates in a column bottom portion of the higher-pressure column; a flow rate estimating unit for estimating, by calculation, the flow rate of oxygen-enriched liquid that has been discharged from the column bottom portion of the higher-pressure column and that is to be introduced into a distillation portion of the lower-pressure column; and a target temperature calculating unit for calculating a target temperature of an argon extraction portion on the basis of the flow rate of feed air that has passed through at least a portion of the main heat exchanger 1 and that is to be sent to an expansion turbine, the oxygen concentration of the oxygen-enriched liquid, and the flow rate of the oxygen-enriched liquid.

A process for the separation of nitrogen from a feed stream containing at least methane and nitrogen, with a methane content between 4 and 12% mol. consists of at least the following steps: separation of the feed stream by means of a rubbery-type membrane to produce a permeate enriched in methane at a pressure greater than 2 bara and a non-permeate which is a nitrogen-enriched residue gas at a pressure greater than 2 bara and processing of the high-pressure residue gas in a cryogenic separation unit to produce a methane rich liquid and a nitrogen-enriched gas wherein the pressure of the membrane permeate is controlled as a function of the nitrogen concentration in the nitrogen-enriched gas.

Systems and methods for operating a natural gas liquids (NGL) plant can include obtaining upstream flow volumes, input flows, and operating conditions of a refinery complex including the NGL plant for a first time period and a second time period. One or more features can be extracted from the upstream flow volumes, input flows, and operating conditions for multiple first time periods and used to form multiple feature vectors. A machine learning model trained with labeled data (e.g., labeled data associating upstream flow volumes, input flows, and operating conditions with incoming feed gas volumes) representing incoming feed gas of the NGL can be used to process the feature vectors to determine predicted incoming feed gas volumes.

A method for operating a main cryogenic heat exchanger for use in a natural gas liquefaction process, involves monitoring or predicting variations in the flow rate of a feed gas stream provided to the main cryogenic heat exchanger. When a variation of the flow rate exceeding a predetermined threshold value is monitored or predicted, a control scheme is started to control one or more compressor recycle valves in response to the monitored or predicted variation of the flow rate to recycle part of a compressed mixed refrigerant stream in a refrigerant loop.

A split mixed refrigerant (MR) natural gas liquefication system, where low-pressure (LP) and medium pressure (MP) MR compressors are driven by a first gas turbine and a propane compressor and a high-pressure (HP) MR compressor is driven by a second gas turbine, is disclosed. The split MR liquefication system is configured to adjust the characteristics of the HP MR compressor to require less power when less power is available and more power when more power is available compared to the system's design point. Such adjustments allow for shifting the balance of power between the propane compressor and the HP MR compressor to improve LNG production efficiency.

Process and apparatus for producing helium, neon, or argon product gas using an adsorption separation unit having minimal dead end volumes. A second separation unit receives a stream enriched in helium, neon, or argon, and a stream is recycled from the second separation unit back to the adsorption separation unit in a controlled manner to maintain the concentration of the helium, neon, or argon in the feed to the separation unit within a targeted range.

Process and apparatus for producing helium, neon, or argon product gas using an adsorption separation unit having minimal dead end volumes. A second separation unit receives a stream enriched in helium, neon, or argon, and a stream is recycled from the second separation unit back to the adsorption separation unit in a controlled manner to maintain the concentration of the helium, neon, or argon in the feed to the separation unit within a targeted range.

A method for operating a main cryogenic heat exchanger for use in a natural gas liquefaction process, involves monitoring or predicting variations in the flow rate of a feed gas stream provided to the main cryogenic heat exchanger. When a variation of the flow rate exceeding a predetermined threshold value is monitored or predicted, a control scheme is started to control one or more compressor recycle valves in response to the monitored or predicted variation of the flow rate to recycle part of a compressed mixed refrigerant stream in a refrigerant loop.

Systems and methods for controlling a natural gas production system in an upset scenario, and/or during startup of turbo-expander system are disclosed. In one embodiment, a method of operating a Joule-Thomson valve of a natural gas production system includes determining an upset event within the natural gas production system, obtaining a flow rate through at least one expander prior to the upset event, and calculating, based on the flow rate, a percent opening of the Joule-Thomson valve. The method further includes opening the Joule-Thomson valve to the percent opening, controlling the Joule-Thomson valve by a PID controller in a set point tracking mode for a period of time, and controlling the Joule-Thomson valve by the PID controller in an automatic mode.

A method for controlling flow in a Natural Gas Liquids (NGL) extraction system includes determining an operational characteristic of one or more residue gas compressors operating within the NGL extraction system and calculating a rate of closure for one or more throttle valves associated with the one or more residue gas compressors based on the operational characteristic determined. When a process upset in the NGL extraction system is detected, the one or more throttle valves are closed at the calculated rate of closure in response to detecting the process upset.