Method for controlling a gas flow between a plurality of gas streams
The present invention relates to a method and apparatus for controlling a gas flow through a conjunction between one or more incoming streams and one or more outgoing streams through a conjunction. The method uses a biased mass flow imbalance value obtained by comparing the aggregate of incoming mass flow measurement value(s) with the aggregate of outgoing mass flow measurement value(s) and adding a bias component to provide the biased mass flow imbalance value. The flow of at least one of the incoming and outgoing streams ( 12, 14, 16, 18, 20 ) is adjusted to move the biased mass flow imbalance value towards zero. In addition, a conjunction pressure measurement (PC) is provided, which is used to adjust the bias component in response to a change in the conjunction pressure measurement (PC) relative to a pressure set point (PSP), to mitigate the change in the conjunction pressure measurement (PC) relative to the pressure set point (PSP).
1. A method for controlling the gas flow between one or more incoming streams and one or more outgoing streams through a conjunction comprising:
(a) determining the mass flow of at least one of the incoming streams to provide one or more respective incoming mass flow measurement value(s);
(b) determining the mass flow of at least one of the outgoing streams to provide one or more respective outgoing mass flow measurement value(s);
(c) providing a biased mass flow imbalance value by comparing the aggregate of all the incoming mass flow measurement value(s) of step (a) with the aggregate of all the outgoing mass flow measurement value(s) of step (b) and adding a bias component to provide the biased mass flow imbalance value;
(d) measuring a quantity indicative of the gas pressure at the conjunction to provide a conjunction pressure measurement (PC);
(e) adjusting the flow of at least one of the incoming and outgoing streams to move the biased mass flow imbalance value towards zero; and
(f) adjusting the bias component of the biased mass flow imbalance value in response to a change in the conjunction pressure measurement (PC) relative to a pressure set point (PSP) to mitigate the change in the conjunction pressure measurement (PC) relative to the pressure set point (PSP).
2. A method as claimed in claim 1 wherein the biased mass flow imbalance value is:
(Total of all incoming mass flow measurement values)−(Total of all outgoing mass flow measurement values)+bias component.
3. A method as claimed in claim 1 , wherein each incoming stream is one or more selected from the group comprising: steam, fuel gas, one or more hydrocarbons, nitrogen and hydrogen.
4. A method as claimed in claim 1 , comprising at least two incoming streams.
5. A method as claimed in claim 1 , comprising at least two outgoing streams.
6. A method as claimed in claim 4 wherein the conjunction is a manifold.
7. A method as claimed in claim 1 , wherein the incoming stream is provided by a respective gaseous stream provider, and the outgoing stream is provided to a gaseous stream user.
8. A method as claimed in claim 7 wherein the incoming stream is provided by a gaseous stream provider being one or more selected from the group consisting of: boilers, heat recovery units, hydrocarbon sources, and hydrocarbon processing units.
9. A method as claimed in claim 7 wherein the outgoing stream is provided to a gaseous stream user comprising one or more selected from the group consisting of: boilers, turbines, export gas and hydrocarbon processing units.
10. A method as claimed in claim 1 wherein determining the mass flow comprises direct measurement of at least one of the incoming streams.
11. A method as claimed in claim 1 , wherein determining the mass flow comprises the indirect measurement of at least one of the incoming streams.
12. A method as claimed in claim 11 wherein determining the mass flow comprises the measurement of the flow of a fluid stream to at least one gaseous stream provider to provide measurement of the flow from the at least one incoming stream from the gaseous stream provider.
13. A method as claimed in claim 1 comprising direct adjustment of the flow of one outgoing stream.
14. A method as claimed in claim 1 comprising indirect adjustment of the flow of at least one incoming stream.
15. A method as claimed in claim 1 wherein an incoming stream is provided by a wellhead, and at least one outgoing stream is provided to a hydrocarbon processing facility.
16. Apparatus for controlling the gas flow between one or more incoming streams and one or more outgoing streams through a conjunction; comprising:
one or more incoming flow measurers each able to provide one or more respective incoming mass flow measurement values representing the flow of the one of the respective incoming streams;
one or more outgoing flow measurers each able to provide one or more respective mass outgoing flow measurement values representing the flow of the one of the respective outgoing stream;
one or more pressure measurers able to measure a quantity indicative of the pressure of gas at the conjunction to provide a conjunction pressure measurement;
one or more flow adjusters to adjust the flow of at least one of the incoming and outgoing streams;
a controller to provide a biased mass flow imbalance value by comparing the aggregate of the incoming mass flow measurement values of the incoming flow measurers with the aggregate of the outgoing mass flow measurement values of the outgoing flow measurers and adding a bias component to provide the biased mass flow imbalance value; receive the conjunction pressure measurement; instruct the one or more flow adjusters to adjust the flow of at least one of the incoming and outgoing streams to move the mass flow imbalance value towards zero; and adjust the bias component of the biased mass flow imbalance value in response to a change in the conjunction pressure measurement relative to a pressure set point to mitigate the change in the conjunction pressure measurement relative to the pressure set point.