Method for lubricating screw expanders and system for controlling lubrication

Abstract

A method for lubricating a screw expander includes condensing a mixture of working fluid and lubricant fed from the screw expander, through a condenser. At least a portion of the mixture of working fluid and lubricant fed from the condenser is pressurized from a first pressure to a second pressure through a pump. The method also includes separating the lubricant from the condensed working fluid of the at least portion of the mixture via a separator and feeding the lubricant to the screw expander; or separating the lubricant from the working fluid of the at least portion of the mixture via an evaporator and feeding the lubricant to the screw expander; or feeding the at least portion of the mixture of condensed working fluid and lubricant to the screw expander; or combinations thereof.

1 . A method for lubricating a screw expander using a mixture of working fluid and lubricant in an organic rankine cycle system, the method comprising:
 condensing the mixture of working fluid and lubricant fed from the screw expander, through a condenser;   pressurizing at least a portion of the mixture of working fluid and lubricant fed from the condenser from a first pressure to a second pressure through a pump;   separating the lubricant from the condensed working fluid of the at least portion of the mixture via a separator and feeding the lubricant to the screw expander; or separating the lubricant from the working fluid of the at least portion of the mixture via an evaporator and feeding the lubricant to the screw expander; or feeding the at least portion of the mixture of condensed working fluid and lubricant to the screw expander; or combinations thereof.   
   
   
       2 . The method of  claim 1 , wherein the lubricant comprises oil. 
   
   
       3 . The method of  claim 1 , wherein the pump comprises a fluid feed pump configured to circulate at least a portion of the mixture of working fluid and lubricant through the organic rankine cycle system. 
   
   
       4 . The method of  claim 3 , comprising separating the lubricant from the condensed working fluid of the at least portion of the mixture through the separator disposed between the fluid feed pump and the evaporator. 
   
   
       5 . The method of  claim 4 , further comprising feeding the separated lubricant to a feed tank configured for temporarily storing the lubricant. 
   
   
       6 . The method of  claim 5 , further comprising feeding the lubricant from the feed tank to the screw expander. 
   
   
       7 . The method of  claim 6 , further comprising controlling the flow of lubricant from the feed tank to the screw expander via a flow control device. 
   
   
       8 . The method of  claim 3 , wherein the pump comprises a lubrication pump configured to feed the at least portion of the mixture of condensed working fluid and lubricant from a predefined location between the condenser and the fluid feed pump to the screw expander. 
   
   
       9 . The method of  claim 1 , comprising feeding the separated lubricant, or the at least portion of the mixture of condensed working fluid and lubricant, or combinations thereof to the screw expander for lubricating one or more rotors, bearings disposed in the screw expander. 
   
   
       10 . The method of  claim 1 , further comprising measuring one or more parameters related to the screw expanders comprising casing temperature, expander speed, expander inlet pressure, expander outlet pressure, bearing temperature, bearing vibration, or combinations thereof. 
   
   
       11 . The method of  claim 1 , further comprising controlling the feed of the lubricant, the at least portion of the mixture of condensed working fluid and lubricant, or combinations thereof to the screw expander based on one or more parameters related to the screw expander. 
   
   
       12 . A method for lubricating a screw expander using a mixture of working fluid and lubricant in an organic rankine cycle system, the method comprising:
 sensing one or more parameters related to the screw expander;   condensing the mixture of working fluid and oil fed from the screw expander, through a condenser;   pressurizing at least a portion of the mixture of condensed working fluid and oil fed from the condenser from a first pressure to a second pressure through a pump;   separating the lubricant from the condensed working fluid of the at least portion of the mixture via a separator and feeding the lubricant to the screw expander;   or separating the lubricant from the working fluid of the at least portion of the mixture via an evaporator and feeding the lubricant to the screw expander; or feeding the at least portion of the mixture of condensed working fluid and lubricant to the screw expander; or combinations thereof,   controlling the feed of the lubricant, the at least portion of the mixture of condensed working fluid and lubricant, or combinations thereof to the screw expander based on one or more parameters related to the screw expander.   
   
   
       13 . The method of  claim 12 , wherein one or more parameters related to the screw expanders comprises casing temperature, expander speed, expander inlet pressure, expander outlet pressure, bearing temperature, bearing vibration, or combinations thereof. 
   
   
       14 . The method of  claim 12 , comprising separating the lubricant from the condensed working fluid of the at least portion of the mixture through a separator disposed between a fluid feed pump and the evaporator. 
   
   
       15 . The method of  claim 14 , further comprising feeding the separated lubricant to a feed tank configured for temporarily storing the lubricant. 
   
   
       16 . The method of  claim 15 , further comprising controlling the flow of lubricant from the feed tank to the screw expander via a flow control device. 
   
   
       17 . The method of  claim 12 , further comprising controlling the flow of the at least portion of the mixture of condensed working fluid and lubricant to the screw expander via a flow control device. 
   
   
       18 . A control system for controlling lubrication of a screw expander using a mixture of working fluid and lubricant circulated in an organic rankine cycle system, the control system comprising:
 a plurality of sensors configured for sensing one or more parameters related to the screw expander;   a separator disposed between an evaporator and a fluid feed pump; wherein the separator is configured to receive at least a portion of a mixture of condensed working fluid and lubricant fed from the fluid feed pump and separate the lubricant from the working fluid;   a flow control device disposed between the separator and the screw expander and configured to control the flow of the lubricant from the separator to the screw expander;   a controller coupled to the plurality of sensors and the flow control device; wherein the controller is configured to receive output signals indicative of one or more parameters related to the screw expander from the plurality of sensors and control the flow control device based on the sensor output signals.   
   
   
       19 . The control system of  claim 18 , further comprising a feed tank configured for receiving lubricant from the separator and for temporarily storing the lubricant. 
   
   
       20 . The control system of  claim 18 , wherein the flow control device comprises one or more flow control valves, a lubrication pump, or combinations thereof. 
   
   
       21 . The control system of  claim 18 , wherein one or more parameters related to the screw expander comprises casing temperature, expander speed, expander inlet pressure, expander outlet pressure, bearing temperature, bearing vibration, or combinations thereof. 
   
   
       22 . A control system for controlling lubrication of a screw expander using a mixture of working fluid and lubricant circulated in an organic rankine cycle system, the control system comprising:
 a plurality of sensors configured for sensing one or parameters related to the screw expander;   a flow control device configured to receive a portion of a mixture of condensed working fluid and oil from a condenser and feed the portion of the mixture of working fluid and oil to the screw expander; wherein the flow control device is configured to control the flow of the portion of the mixture of working fluid and oil from the condenser to the screw expander; and   a controller coupled to the plurality of sensors and the flow control device; wherein the controller is configured to receive output signals indicative of one or more parameters related to the screw expander from the plurality of sensors and control the flow control device based on the output signals.   
   
   
       23 . The control system of  claim 22 , wherein the flow control device comprises one or more flow control valves, a lubrication pump, or combinations thereof. 
   
   
       24 . The control system of  claim 22 , wherein one or more parameters related to the screw expander comprises casing temperature, expander speed, expander inlet pressure, expander outlet pressure, bearing temperature, bearing vibration, or combinations thereof.