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 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.

An automated control loop for dynamically adjusting a temperature of wet steam is provided. This leads to increased heat transfer and decreased fouling in a reboiler of a distillation column used for distilling a petrochemical. The control loop includes controlling the combining of condensed water with dry steam to produce the wet steam. The produced wet steam is input to the reboiler in order to transfer heat to the petrochemical while being converted to the condensed water. The control loop further includes monitoring a pressure of the produced wet steam, and setting a target temperature for the produced wet steam based on the monitored pressure. In addition, the control loop includes monitoring the temperature of the produced wet steam, and adjusting a proportion of the condensed water in the produced wet steam in response to the monitored temperature deviating from the set target temperature by at least a threshold value.

A method for determining an operating condition of a liquefied natural gas plant (2) includes preparing a training model (88) generated by machine learning using training data in which operating conditions data including a composition of a feed gas, a composition of a mixed refrigerant, and an ambient temperature and operation result data including a production efficiency of a liquefied product containing liquefied natural gas and a heavy component of the feed gas are associated together; and determining, as one new operating condition, a composition of the mixed refrigerant that optimizes a production efficiency of the liquefied natural gas predicted by the training model (88) from a latest composition of the feed gas in the liquefied natural gas plant (2) and a latest ambient temperature.

The present disclosure provides a heat axchanger and heat exchange method for cooling a gaseous process stream. The heat exchanger unit (100, 200, 300) comprises: a heat exchanger vessel (2), the heat exchanger vessel (2) comprising a plurality of process stream conduits (12, 14) arranged to receive the gaseous process stream (10) and discharge a cooled process stream (18), and a plurality of refrigerant conduits (46, 48, 49) to receive at least part of a pre-cooled mixed refrigerant stream (58) and to discharge at least one cooled mixed refrigerant stream (72, 82); at least one expansion device (74, 84) arranged to receive at least part of the cooled mixed refrigerant stream (72, 82) and discharge a further cooled mixed refrigerant stream (76, 86), the further cooled mixed refrigerant stream (76, 86) being connected to at least one of a third refrigerant inlet (77) and a fourth refrigerant inlet (87) of the heat exchanger vessel (2) to provide cooling to the process stream conduits (12, 14) and the refrigerant conduits (46, 48, 49); a refrigerant bleed vessel (110) arranged to receive a first refrigerant split-off stream (112) from the cooled mixed refrigerant stream (72, 82) and to receive a second refrigerant split-off stream (114) from the pre-cooled mixed refrigerant stream; the refrigerant bleed vessel (110) comprising a bleed outlet (116) to discharge a bleed stream (118) and a recycle outlet (120) to discharge a recycle stream (122), the recycle outlet being fluidly connected to at least one of the third refrigerant inlet (77) and the fourth refrigerant inlet (87) of the heat exchanger vessel (2).

A method to continuously monitor for tube leakage in a shell and tube thermosiphon reboiler for heating feedstock in a fractionating column includes: determining the column is in service by continuously monitoring an input flow of the feedstock into the column; determining the reboiler is inactive by continuously monitoring an output valve of tube-side heating fluid from the reboiler; determining the reboiler is losing the heating fluid by continuously monitoring an output flow of the heating fluid from the reboiler; determining the reboiler is heat exchanging by continuously monitoring a temperature difference between input and output flows of shell-side bottoms fluid with the column; and determining the tube leakage in the reboiler is taking place when the column is determined to be in service, the reboiler is determined to be inactive, the reboiler is determined to be losing the heating fluid, and the reboiler is determined to be heat exchanging.

Disclosed are a facility and a method using the facility for treating a feed gas stream comprising at least methane and carbon dioxide by membrane permeation, the facility comprising: —a first membrane separation unit capable of receiving the feed gas stream and providing a first permeate and a first retentate, —a second membrane separation unit capable of receiving the first retentate and providing a second permeate and a second retentate, —a compressor for compressing the first permeate to a pressure of between 17 bar and 25 bar, —a means for cooling the first compressed permeate to a temperature lower than −40° C., —a distillation column for separating the first cooled permeate into a gas stream and a liquid stream, —at least one means for recycling the gas stream exiting the distillation column to the inlet of the first membrane separation unit, —a means for measuring the concentration of methane and/or carbon dioxide in the gas stream exiting the distillation column, —a means for comparing the concentration of methane and/or carbon dioxide measured by the measurement means with a target value, and —a means for adjusting the pressure and/or the temperature of the first permeate depending on the comparison carried out by the comparison means.

A method to continuously monitor for tube leakage in a shell and tube thermosiphon reboiler for heating feedstock in a fractionating column includes: determining the column is in service by continuously monitoring an input flow of the feedstock into the column; determining the reboiler is inactive by continuously monitoring an output valve of tube-side heating fluid from the reboiler; determining the reboiler is losing the heating fluid by continuously monitoring an output flow of the heating fluid from the reboiler; determining the reboiler is heat exchanging by continuously monitoring a temperature difference between input and output flows of shell-side bottoms fluid with the column; and determining the tube leakage in the reboiler is taking place when the column is determined to be in service, the reboiler is determined to be inactive, the reboiler is determined to be losing the heating fluid, and the reboiler is determined to be heat exchanging.

Provided herein are methods, apparatus, and systems for delivering carbon dioxide as a mixture of solid and gaseous carbon dioxide to a destination.

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.