Gas compression

Abstract

An industrial system for compressing a waste gas product, such as CO 2 , including a compressor train having an upstream rotor portion and a downstream rotor portion arranged in flow series with said upstream portion. Each rotor portion includes one or more compressor stages and said downstream portion is arranged to rotate at a variable relative speed to that of the upstream rotor portion. Sensing equipment for the compressor train is arranged to determine one or more flow conditions and a controller is arranged to receive data indicative of said one or more sensed flow conditions. The controller is arranged to set the rotational speed of the upstream rotor portion based upon the pressure or flow rate of gas upstream of said compressor train and to set operational parameters for said downstream portion so as to maintain a desired surge margin for said upstream rotor portion.

1 . An industrial system for compressing a waste gas product comprising:
 a compressor train having an upstream rotor portion and a downstream rotor portion arranged in flow series with said upstream portion, each rotor portion comprising one or more compressor stages and said downstream portion being arranged to rotate at a variable relative speed to that of the upstream rotor portion;   sensing equipment arranged to determine one or more flow conditions for the compressor train; and,   a controller arranged to receive data indicative of said one or more sensed flow conditions, wherein the controller is arranged to set the rotational speed of the upstream rotor portion based upon the pressure or flow rate of gas upstream of said compressor train and to set operational parameters for said downstream potion so as to maintain a desired surge margin for said upstream rotor portion.   
     
     
         2 . A system according to  claim 1 , wherein the rotational speed of the upstream and downstream rotor portions is independently controllable. 
     
     
         3 . A system according to  claim 1 , further comprising intercooling apparatus arranged to cool the gas flow between one or more stages of the compressor train. 
     
     
         4 . A system according to  claim 3 , wherein an intercooler is located between each adjacent compressor stage of at least the downstream rotor portion. 
     
     
         5 . A system according to  claim 1 , wherein the compressor train comprises a gas recirculation conduit arranged to selectively bleed gas from the downstream rotor portion. 
     
     
         6 . A system according to  claim 5 , wherein the gas recirculation conduit provides a selectively operable gas path between the exit and the inlet of the downstream rotor portion. 
     
     
         7 . A system according to  claim 5 , wherein the gas recirculation conduit comprises a valve arrangement which is selectively operable under the control of the controller. 
     
     
         8 . A system according to  claim 1 , wherein the controller comprises machine readable instructions to process the received sensor data indicative of said one or more sensed flow conditions and to compare said sensed flow conditions against a predetermined schedule of desired flow conditions for said compressor train. 
     
     
         9 . A system according to  claim 8 , wherein the controller determines by way of said comparison whether a predetermined surge flow margin threshold criterion for the upstream and/or downstream rotor portion has been met by said sensed flow conditions. 
     
     
         10 . A system according to  claim 1 , wherein the controller sets operational parameters comprising any or any combination of rotational speed, intercooler temperature and/or gas recirculation conduit operation so as to maintain a desired surge margin for said compressor train. 
     
     
         11 . A system according to  claim 1 , wherein the controller comprises machine readable instructions to apply an iterative control scheme to converge towards determination of desired operational parameters for said compressor train. 
     
     
         12 . A system according to  claim 11 , wherein the controller iterates steps of receiving data indicative of said one or more sensed flow conditions; comparing said sensed flow conditions against a predetermined schedule of desired flow conditions; and, outputting control signals to said compressor train to achieve said desired surge margin for at least said upstream rotor portion. 
     
     
         13 . A system according to  claim 1  for use in a gas sequestration process. 
     
     
         14 . A carbon dioxide capture system according to  claim 1 . 
     
     
         15 . A method of compressing a waste gas product for storage using a compressor train having a plurality of discrete portions and comprising an upstream portion, and a downstream portion arranged successively in flow series, the method comprising:
 (i) performing a first compression step by directing a flow of said gas into the upstream compressor portion and driving the upstream compressor portion to compress the gas based upon the pressure or flow rate of gas upstream of said compressor train;   (ii) performing a second compression step by directing the compressed flow from the upstream compressor portion into the downstream compressor portion and operating the downstream compressor portion to further compress the gas under operational parameters which are determined so as to achieve a desired surge margin for said upstream rotor portion.   
     
     
         16 . A method according to  claim 15  wherein the waste gas is carbon dioxide from an electrical power plant and the electrical output of the power plant is used to determine the amount of required compression.