Apparatus and method for controlling the flow of a fluid

Abstract

An apparatus for controlling the flow of a fluid includes a LP fluid inlet ( 18 ) and a LP fluid outlet ( 9 ) connected to a flare/vent system. A LP flow line ( 20 ) connects the LP fluid inlet ( 18 ) to the LP inlet 6 a of a jet pump ( 6 ). A supply of HP fluid is connected to jet pump inlet ( 6 b ), and a MP line ( 8 ) is connected to jet pump outlet ( 6 c ). A control unit ( 28 ) is configured to control operation of first and second LP flow control valves ( 4, 3 ) according to signals received from a flow meter ( 12 ), so that LP gas is diverted from the flare system to the LP inlet ( 6 a ) of the jet pump for pressurisation.

1 . An apparatus for controlling the flow of a fluid, the apparatus including:
 a LP fluid inlet connected to a supply of LP fluid,   a LP fluid outlet connected to a flare system for flaring LP fluid,   a first LP flow line connecting the LP fluid inlet to the LP fluid outlet,   a jet pump having a LP jet pump inlet, a HP jet pump inlet and a MP jet pump outlet,   a second LP flow line having a first end connected to the first LP flow line at a first connection point between the LP fluid inlet and the LP fluid outlet and a second end connected to the LP jet pump inlet,   a HP fluid inlet connected to a supply of HP fluid,   a HP flow line having a first end connected to the HP fluid inlet and a second end connected to the HP jet pump inlet,   a jet pump discharge line having a first end connected to the MP jet pump outlet and a second end connected to a MP fluid outlet;   a first LP flow control valve in the first LP flow line between the first connection point and the LP fluid outlet,   a second LP flow control valve in the second LP flow line between the first connection point and the LP jet pump inlet,   a flow meter configured to detect the flow of LP fluid in the first LP flow line between the LP fluid inlet and the first connection point, and   a control system connected to the flow meter and to the first and second LP flow control valves, wherein the control system is configured to control operation of the first and second LP flow control valves according to signals received from the flow meter.   
     
     
         2 . An apparatus according to  claim 1 , wherein the control system is configured such hat when the flow meter detects a flow of LP fluid, the control system closes the first LP flow control valve and opens the second LP flow control valve so that the LP fluid is directed into the LP jet pump inlet. 
     
     
         3 . An apparatus according to  claim 2 , including a first HP flow control valve in the HP flow line, said first HP flow control valve being connected to the control system, wherein the control system is configured such that when the flow meter detects a flow of LP fluid the control system opens the first HP flow control valve allowing HP fluid to flow from the HP fluid inlet into the HP jet pump inlet. 
     
     
         4 . An apparatus according to  claim 3 , including a pressure detector for detecting the pressure of fluid in the second LP flow line, said pressure detector being connected to the control system. 
     
     
         5 . An apparatus according to  claim 4 , wherein the control system is configured to adjust the first HP flow control valve according to the detected pressure of fluid in the second LP flow line, so as to control the flow rate of HP fluid into the HP jet pump inlet. 
     
     
         6 . An apparatus according to  claim 4 , wherein the control system is configured such that when the pressure detector detects a pressure in the second LP flow line that is higher than a predetermined value, the control system opens the first LP control valve so that at least some LP fluid is directed from the LP gas inlet towards the LP gas outlet. 
     
     
         7 . An apparatus according to  claim 4 , including:
 a return flow line having a first end connected to the jet pump discharge line and a second end connected to the second LP flow line between the second LP flow control valve and the LP jet pump inlet, and   a return flow control valve in the return flow line, said control system being connected to the return flow control valve,   wherein the control system is configured to control operation of the return flow control valve according to signals received from the pressure detector indicating the pressure of fluid in the second LP flow line.   
     
     
         8 . An apparatus according to  claim 1 , wherein the control system is switchable to an alternative operational mode, wherein the control system opens the first LP flow control valve and closes the second LP flow control valve so that the LP fluid is directed towards the flare system. 
     
     
         9 . An apparatus according to  claim 1 , including a knock-out pot in the first LP flow line between the LP fluid inlet and the first connection point. 
     
     
         10 . An apparatus according to  claim 1 , including a by-pass line connected around the first LP flow control valve and a pressure release device provided within the by-pass line. 
     
     
         11 . An apparatus according to  claim 1 , including an oxygen detector in the first LP flow line, wherein the control system is configured to close the second LP flow control valve if oxygen is detected in the first LP flow line. 
     
     
         12 . An apparatus according to  claim 1 , including a plurality of jet pumps connected in parallel. 
     
     
         13 . A method for controlling the flow of a fluid in an apparatus including a LP fluid inlet connected to a supply of LP fluid, a LP fluid outlet connected to a flare system for flaring LP fluid, a first LP flow line connecting the LP fluid inlet to the LP fluid outlet, a jet pump having a LP jet pump inlet, a HP jet pump inlet and a MP jet pump outlet, a second LP flow line having a first end connected to the first LP flow line at a first connection point between the LP fluid inlet and the LP fluid outlet and a second end connected to the LP jet pump inlet, a HP fluid inlet connected to a supply of HP fluid, a HP flow line having a first end connected to the HP fluid inlet and a second end connected to the HP jet pump inlet, a jet pump discharge line having a first end connected to the MP jet pump outlet and a second end connected to a MP fluid outlet;
 a first LP flow control valve in the first LP flow line between the first connection point and the LP fluid outlet, a second LP flow control valve in the second LP flow line between the first connection point and the LP jet pump inlet, a flow meter configured to detect the flow of LP fluid in the first LP flow line between the LP fluid inlet and the first connection point, and a control system connected to the flow meter and to the first and second LP flow control valves, wherein the control system is configured to control operation of the first and second LP flow control valves according to signals received from the flow meter, the method comprising:   supplying LP fluid to the LP fluid inlet,   supplying HP fluid to the HP fluid inlet,   detecting the flow of LP fluid in the first LP flow line between the LP fluid inlet and the first connection point, and   controlling operation of the first and second LP flow control valves according to signals received from the flow meter.   
     
     
         14 . A method according to  claim 13 , comprising closing the first LP flow control valve and opening the second LP flow control valve when the flow meter detects a flow of LP fluid, to direct LP fluid into the LP jet pump inlet. 
     
     
         15 . A method according to  claim 13 , comprising opening the first HP flow control valve when the flow meter detects a flow of LP fluid, to allow HP fluid to flow from the HP fluid inlet into the HP jet pump inlet. 
     
     
         16 . A method according to  claim 13 , comprising detecting the pressure of fluid in the second LP flow line. 
     
     
         17 . A method to  claim 14 , including controlling the flow rate of HP fluid according to the detected pressure of fluid in the second LP flow line. 
     
     
         18 . A method according to  claim 14 , including opening the first LP control valve to direct at least some LP fluid from the LP gas inlet towards the LP gas outlet when the pressure detector detects a pressure in the second LP flow line that is higher than a predetermined value. 
     
     
         19 . A method according to  claim 14 , including controlling operation of the return flow control valve according to signals received from the pressure detector. 
     
     
         20 . A method according to  claim 14 , wherein the jet pump is operated continuously. 
     
     
         21 . A method according to  claim 14 , including selecting an alternative operational mode comprising opening the first LP flow control valve and closing the second LP flow control valve to direct LP fluid towards the LP fluid outlet.