SYSTEM AND METHOD FOR PRODUCING A LIQUEFIED HYDROCARBON STREAM AND METHOD OF OPERATING A COMPRESSOR

• US 20140311183A1
• Filed: 12/13/2012
• Published: 10/23/2014
• Est. Priority Date: 12/15/2011
• Status: Abandoned Application

• Current Assignee: Shell Oil Company (Shell Plc)
• Original Assignee: Shell Internationale Research Maatschappij BV (Shell Plc), Shell Oil Company (Shell Plc)
• Inventors: Van Aken, Michiel Gijsbert
• Application Number:
  US14/365,171
• Publication Number:
  US 20140311183A1
• Time in Patent Office: Days
• US Class Current: 62/611
• CPC Class Codes: F04D 27/002 by varying geometry within the pumps, e.g. by adjusting vanes
• CPC Class Codes: F04D 27/0246 by varying geometry within the pumps, e.g. by adjusting vanes
• CPC Class Codes: F25J 1/0022 Hydrocarbons, e.g. natural gas
• CPC Class Codes: F25J 1/0284 Electrical motor as the prime mechanical driver
• CPC Class Codes: F25J 1/0298 Safety aspects and control of the refrigerant compression system, e.g. anti-surge control
• CPC Class Codes: F25J 2280/20 Control for stopping, deriming or defrosting after an emergency shut-down of the installation or for back up system

Abstract

At least part of a fluid is compressed in a compressor driven by an electric motor. The compressor has variable inlet guide vanes of which an angle can be adjusted. The electric motor is powered using a power supply network, and a signal representative of a condition of the power supply network is monitored. From the signal, it is automatically determined whether additional load shedding is needed, by comparing the signal to a predetermined criterion. The variable inlet guide vanes angle is automatically adjusted when the criterion is satisfied and additional load shedding is needed. This automatically reduces the loading of the compressor. The compressor and the method of operating it may be employed as part of a system for producing a liquefied hydrocarbon stream and/or in the course of producing a liquefied hydrocarbon stream, in which case the compressor can be a refrigerant compressor and the fluid a refrigerant fluid.

Claims

1. A method of producing a liquefied hydrocarbon stream, comprising:

circulating a refrigerant fluid through a refrigerant circuit, comprising compressing at least part of the refrigerant fluid in a refrigerant compressor driven by an electric motor wherein the refrigerant compressor comprises variable inlet guide vanes of which an angle compared to a reference position can be adjusted;

removing heat from an initially vaporous hydrocarbon stream thereby condensing at least part of the initially vaporous hydrocarbon stream to form the liquefied hydrocarbon stream, said removing heat comprising heat exchanging at least said part of the initially vaporous hydrocarbon stream against at least part of the refrigerant fluid circulating through the refrigerant circuit;

powering the electric motor using a power supply network;

monitoring a signal representative of a condition of the power supply network;

automatically determining from the signal whether additional load shedding is needed by comparing the signal to a predetermined criterion; and

,

automatically adjusting the variable inlet guide vanes angle thereby reducing the loading of the refrigerant compressor when the criterion is satisfied and additional load shedding is needed.

2. The method of claim 1, further comprising maintaining the variable inlet guide vanes at an optimized target angle to optimize one or both of efficiency and operating envelope of the refrigerant compressor when the criterion is not satisfied.

3. The method of claim 2, wherein said adjusting the variable inlet guide vanes angle comprises deliberately changing the variable inlet guide vanes angle away from the optimized target angle.

4. The method of claim 1, wherein said condition of the power supply network represents power available on the power supply network relative to power being consumed, and wherein the predetermined criterion is satisfied when the available power, according to the monitored signal, drops below a predetermined value.

5. The method of claim 1, wherein the power supply network operates at a network frequency and wherein the signal representative of the condition of the power supply network represents the network frequency at which the power supply network operates.

6. The method of claim 1, wherein the initially vaporous hydrocarbon stream comprises natural gas and wherein the liquefied hydrocarbon stream is a liquefied natural gas stream.

7. System for producing a liquefied hydrocarbon stream, comprising:

a refrigerant circuit arranged to circulate a refrigerant fluid, comprising a refrigerant compressor for compressing at least part of the refrigerant fluid and an electric motor engaged to the refrigerant compressor to drive the refrigerant compressor wherein the refrigerant compressor comprises variable inlet guide vanes having an adjustable angle compared to a reference position;

a heat exchanger train comprising at least one heat exchanger, said heat exchanger train arranged to remove heat from an initially vaporous hydrocarbon stream thereby condensing at least part of the initially vaporous hydrocarbon stream to form the liquefied hydrocarbon stream, said least one heat exchanger arranged to accommodate at least said part of the initially vaporous hydrocarbon stream and at least part of the refrigerant fluid circulating through the refrigerant circuit in a mutual heat exchanging relationship;

a power supply network connected to the electric motor for powering the electric motor; and

,

a load shedding controller arranged to monitor a signal representative of a condition of the power supply network, to automatically determine from the signal whether additional load shedding is needed by comparing the signal to a predetermined criterion, and, when the criterion is satisfied and additional load shedding is needed, to adjust the variable inlet guide vanes angle to a position wherein the refrigerant compressor is unloaded relative to the loading in a previous condition whereby the variable inlet guide vanes angle was in a previous position when the criterion was not satisfied.

8. The system of claim 7, further comprising a process controller arranged to maintain the variable inlet guide vanes at an optimized target angle to optimize one or both of efficiency and operating envelope of the refrigerant compressor when the criterion is not satisfied.

9. The system of claim 7, wherein said condition of the power supply network represents power available on the power supply network relative to power being consumed, and wherein the predetermined criterion is satisfied when the available power, according to the monitored signal, drops below a predetermined value.

10. The system of claim 7, wherein the power supply network operates at a network frequency and wherein the signal representative of the condition of the power supply network represents the network frequency at which the power supply network operates and wherein the predetermined criterion is satisfied when the network frequency drops below a pre-determined nominal network frequency.

11. Method of operating a compressor, comprising:

compressing at least part of a fluid in a compressor driven by an electric motor, wherein the compressor comprises variable inlet guide vanes of which an angle can be adjusted;

powering the electric motor using a power supply network;

monitoring a signal representative of a condition of the power supply network;

automatically determining from the signal if additional load shedding is needed by comparing the signal to a predetermined criterion; and

,

automatically adjusting the variable inlet guide vanes angle thereby reducing the loading of the compressor when the criterion is satisfied and additional load shedding is needed.

12. The method of claim 11, further comprising maintaining the variable inlet guide vanes at an optimized target angle to optimize one or both of efficiency and operating envelope of the compressor when the criterion is not satisfied.

13. The method of claim 12, wherein said adjusting of the variable inlet guide vanes angle comprises deliberately changing the variable inlet guide vanes angle away from the optimized target angle.

14. The method of claim 11, wherein said condition of the power supply network represents power available on the power supply network relative to power being consumed, and wherein the predetermined criterion is satisfied when the available power, according to the monitored signal, drops below a predetermined value.

15. The method of claim 11, wherein the power supply network operates at a network frequency and wherein the signal representative of the condition of the power supply network represents the network frequency at which the power supply network operates and wherein the predetermined criterion is satisfied when the network frequency drops below a pre-determined nominal network frequency.

16. The method of claim 11, wherein the compressor is a refrigerant compressor, whereby the fluid is a refrigerant fluid.