Controlling Liquefaction of Natural Gas

a technology of natural gas and control system, which is applied in the direction of refrigeration and liquifaction, lighting and heating apparatus, solidification, etc., can solve the problems of adverse effects on the standard day to day operation, and achieve the effect of avoiding the need to manipulate the mr compressor and stress on the heat exchange means

Inactive Publication Date: 2009-01-29
AIR PROD & CHEM INC
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Benefits of technology

[0008]A control system for typical NG liquefaction processes has been devised in which the thermal stress on the heat exchange means is limited and the need to manipulate the MR compressor can be avoided by controlling the refrigeration so that variation to reduce any difference between actual and required LNG temperature is initiated before variation of the LNG product flow rate to reduce any difference between actual and required LNG flow rate. Accordingly, refrigeration leads LG production. The

Problems solved by technology

However, if regulatory control is not adequate, even

Method used

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  • Controlling Liquefaction of Natural Gas
  • Controlling Liquefaction of Natural Gas
  • Controlling Liquefaction of Natural Gas

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[0245]Each of the embodiments of FIGS. 2 to 5 and the comparative process of FIG. 7 was subject to the following disturbances:[0246]Increase LNG rundown temperature from −247° F. (−155° C.) to −245° F. (−153.9° C.) in 24 minutes;[0247]Decrease production by 5% while simultaneously decreasing turbine speed by 1% in 24 minutes; and[0248]Increase production by 2.8% in 24 minutes.

[0249]The process of FIG. 7 differs from that of FIG. 1 in that the LNG product flow rate is directly adjusted to the required value and FIC 126 is controlled by the difference between actual and desired LNG product temperature difference

Response to Increase LNG Rundown Temperature

[0250]The process of FIG. 1 had some oscillations in its response to the increased rundown temperature with both the LNG flow rate and the LNG temperature oscillating somewhat as they reached the new steady state. It is believed that this was more a result of conflict between the two controllers rather than a tuning issue. The process...

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Abstract

A gas liquefaction process, especially for producing LNG, maintains product flow rate and temperature by controlling the refrigeration so that variation to reduce any difference between actual and required product temperatures is initiated before variation of the product flow rate to reduce any difference between actual and required flow rates.

Description

BACKGROUND OF THE INVENTION[0001]This invention relates to the field of control systems for production of liquefied gas (LG), and more specifically, to a process and system which controls LG production and LG temperature. It has particular but not exclusive application to liquefying natural gas (NG) to produce liquefied natural gas (LNG).[0002]Systems for the liquefaction of natural gas (NG) by refrigeration in heat exchange means, especially using a multicomponent refrigerant, are in use throughout the world. Control of the LNG production process is important to operate a plant efficiently, especially when attempting to meet demands for incremental production for downstream processing or when attempting to adjust to external process disturbances. Essentially simultaneous and independent control of both the LNG production flow rate and temperature is important for LNG plant operation. By fixing and maintaining the LNG production rate, plant operators can adequately plan and achieve ...

Claims

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Application Information

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IPC IPC(8): F25J1/00
CPCF25J1/0022F25J1/0055F25J1/0249F25J1/0292F25J1/0244
Inventor SICINSKI, MICHAEL ANDREWJOHNSTON, BRIAN KEITHTRAUTMANN, SCOTT ROBERTROBERTS, MARK JULIAN
Owner AIR PROD & CHEM INC
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