Enhanced Turbocompressor Startup

Abstract

A control method and apparatus for startup of turbocompressors to avoid overpowering a driver of the turbocompressor. In a first embodiment, the control system monitors input signals from transmitters of various control inputs. When the input signals exceed threshold values, the control system begins to close the antisurge valve. In a second embodiment, the antisurge valve begins to close after a predetermined time measured from the time startup is initiated. In both embodiments, the antisurge valve continues to ramp closed until the compressor has reached its operating zone, or until the compressor's operating point reaches a surge control line, at which point the antisurge valve is manipulated to keep the compressor from surging.

1 . A method of minimizing an energy required to start a turbocompressor having an antisurge valve and a control system, the method comprising:
 (a) opening the antisurge valve fully;   (b) initiating a startup of the turbocompressor;   (c) increasing a rotational speed of the turbocompressor from a zero rotational speed; and   (d) actuating the antisurge valve toward its closed position before said turbocompressor reaches a minimum operating rotational speed.   
   
   
       2 . The method of  claim 1  wherein an initiation of a closing of the antisurge valve comprises:
 (a) sensing at least one signal by the control system;   (b) comparing a magnitude of the at least one signal with a minimum threshold value; and   (c) initiating the closing of the antisurge valve when the magnitude of the at least one signal exceeds the minimum threshold value.   
   
   
       3 . The method of  claim 1  wherein an initiation of a closing of the antisurge valve comprises:
 (a) initializing a timer to an initial value at a time of initiating the startup of the turbocompressor;   (b) measuring time elapsed from the initial value;   (c) comparing the measured time with a threshold value; and   (d) initiating the closing of the antisurge valve when the elapsed time exceeds the threshold value.   
   
   
       4 . The method of  claim 3  wherein the minimum operating rotational speed comprises a constant operating rotational speed of the turbocompressor, the method additionally comprising:
 (a) permitting a driver of the turbocompressor to reach the constant operating rotational speed; and   (b) operating the turbocompressor at the constant operating speed.   
   
   
       5 . The method of  claim 1  wherein increasing a rotational speed of the turbocompressor from a zero rotational speed comprises:
 (a) increasing a turbocompressor rotational speed set point within the control system; and   (b) controlling the turbocompressor rotational speed based on said turbocompressor rotational speed set point.   
   
   
       6 . The method of  claim 3  wherein the threshold value is equal to the initial value. 
   
   
       7 . The method of  claim 1  wherein an initiation of a closing of the antisurge valve comprises:
 (a) sensing a plurality of signals input to the control system;   (b) comparing magnitudes of each of said plurality of signals with a respective minimum threshold value; and   (c) initiating the closing of the antisurge valve when the magnitudes of the plurality of signals exceed the respective minimum threshold values.   
   
   
       8 . The method of  claim 1  wherein actuating the antisurge valve towards its closed position before said turbocompressor reaches a minimum operating rotational speed comprises:
 (a) detecting a signal indicating a turbocompressor operating point;   (b) comparing said signal to a value representing a surge control line; and   (c) manipulating the antisurge valve to keep the turbocompressor operating point from residing nearer a surge region than the surge control line.   
   
   
       9 . An apparatus for minimizing an energy required to start a turbocompressor, the apparatus comprising:
 (a) an antisurge valve;   (b) a control system;   (c) a first control system function to generate a first signal to open the antisurge valve fully;   (d) a second control system function to initiate a startup of the turbocompressor and increase a rotational speed set point of the turbocompressor from a zero rotational speed set point;   (e) a third control system function to discern that conditions are appropriate to initiate a closing of the antisurge valve before said turbocompressor reaches a minimum operating rotational speed; and   (f) a fourth control system function to generate a second signal to actuate the antisurge valve towards its closed position after the third control system function has discerned conditions are appropriate to initiate the closing of the antisurge valve.   
   
   
       10 . The apparatus of  claim 9  additionally comprising:
 (a) at least one signal generated by a measurement system and sensed by the control system;   (b) a comparator in the control system to compare a magnitude of the at least one signal with a minimum threshold value; and   (c) an antisurge actuation signal generating function within the control system to initiate a closing of the antisurge valve when the magnitude of the at least one signal exceeds the minimum threshold value.   
   
   
       11 . The apparatus of  claim 9  additionally comprising:
 (a) a timer, used to measure a time elapsed from an initiation of the startup of the turbocompressor;   (b) a comparator in the control system to compare the elapsed time with a threshold value; and   (c) an antisurge actuation signal generating function within the control system to initiate a closing of the antisurge valve when the elapsed time exceeds the threshold value.   
   
   
       12 . The apparatus of  claim 9  wherein the second control system function additionally comprises:
 (a) a rotational speed set point generating function within the control system; and   (b) a feedback control system to control the turbocompressor rotational speed based on said turbocompressor rotational speed set point.   
   
   
       13 . The apparatus of  claim 9  additionally comprising:
 (a) a plurality of signals generated by a measurement system and sensed by the control system;   (b) a comparator in the control system to compare a magnitude of each of the plurality of signals with a respective minimum threshold value; and   (c) an antisurge actuation signal generating function within the control system to initiate a closing of the antisurge valve when the magnitude of all the plurality of signals exceed the respective minimum threshold values.   
   
   
       14 . The apparatus of  claim 9  wherein the fourth control system function additionally comprises:
 (a) a signal indicating a turbocompressor operating point;   (b) a comparator function to compare said signal to a value representing a surge control line; and   (c) a closed-loop control system to manipulate the antisurge valve to keep the turbocompressor operating point from residing nearer a surge region than the surge control line.   
   
   
       15 . An apparatus for minimizing an energy required to start a turbocompressor, the apparatus comprising:
 (a) an antisurge valve;   (b) a constant speed turbocompressor driver having a constant operating rotational speed;   (c) a control system;   (d) a first control system function to generate a first signal to open the antisurge valve fully;   (e) a second control system function to initiate a startup of the turbocompressor to increase a rotational speed of the turbocompressor from a zero rotational speed;   (f) a third control system function to discern that conditions are appropriate to initiate a closing of the antisurge valve before said turbocompressor reaches the constant operating rotational speed; and   (g) a fourth control system function to generate a second signal to actuate the antisurge valve towards its closed position after the third control system function has discerned conditions are appropriate to initiate the closing of the antisurge valve.