Natural gas liquid fractionation plant waste heat conversion to power using dual turbines organic rankine cycle

Abstract

Certain aspects of a natural gas liquid fractionation plant waste heat conversion to power using dual turbines Organic Rankine Cycle can be implemented as a first heating fluid circuit thermally coupled to first multiple heat sources of a natural gas liquid (NGL) fractionation plant, a second heating fluid circuit thermally coupled to second multiple heat sources of the NGL fractionation plant, and two power generation systems, each including an organic Rankine cycle (ORC). A control system actuates a first set of control valves to selectively thermally couple the first heating fluid circuit to at least a portion of the first multiple heat sources of the NGL fractionation plant, and to actuate a second set of control valves to selectively thermally couple the second heating fluid circuit to at least a portion of the second multiple heat sources of the NGL fractionation plant.

1 . (canceled) 
     
     
         2 . A system, comprising:
 a first heating fluid circuit configured to thermally couple a first heating fluid to a first plurality of heat sources of a natural gas liquid (NGL) fractionation plant, the first heating fluid circuit comprising a first plurality of heat exchangers fluidly coupled in parallel;   a second heating fluid circuit configured to thermally couple a second heating fluid to a second plurality of heat sources of the NGL fractionation plant, the second heating fluid circuit comprising a second plurality of heat exchangers fluidly coupled in parallel;   a first evaporator that thermally couples the first heating fluid circuit to a first working fluid to heat the first working fluid with the first heating fluid;   a first expander configured to generate electrical power from the heated first working fluid;   a second evaporator that thermally couples the first and second heating fluid circuits to a second working fluid to heat the second working fluid with the first heating fluid and the second heating fluid;   a second expander configured to generate electrical power from the heated second working fluid;   a condenser that thermally couples the first and second working fluids to a condenser supply liquid to cool the first and second working fluids;   a heating fluid tank that fluidly couples the first and second heat fluid circuits; and   a flow control system that comprises a first set of control valves to selectively thermally couple the first heating fluid to the first plurality of heat sources of the NGL fractionation plant, the control system further comprising a second set of control valves to selectively thermally couple the second heating fluid to the second plurality of heat sources of the NGL fractionation plant.   
     
     
         3 . The system of  claim 2 , wherein the heating fluid tank fluidly couples the first and second evaporators. 
     
     
         4 . The system of  claim 2 , wherein at least one of the first or second working fluids is isobutane. 
     
     
         5 . The system of  claim 2 , wherein at least one of the first or second heating fluids is water or oil. 
     
     
         6 . The system of  claim 2 , further comprising:
 a heating fluid pump fluidly coupled to the first and second heating fluid circuits and the heating fluid tank;   a first evaporator pump fluidly coupled to the first evaporator to circulate the first working fluid through the first evaporator; and   a second evaporator pump fluidly coupled to the second evaporator to circulate the second working fluid through the second evaporator.   
     
     
         7 . The system of  claim 6 , wherein the first and second working fluids are combined in the condenser. 
     
     
         8 . The system of  claim 7 , wherein each of the first and second evaporator pumps are positioned downstream of the condenser. 
     
     
         9 . The system of  claim 6 , wherein the heating fluid pump is positioned downstream of the heating fluid tank. 
     
     
         10 . The system of  claim 2 , wherein the first and second heating fluids are combined between the first and second evaporators, and the first and second heating fluids are separated downstream of the heating fluid tank. 
     
     
         11 . The system of  claim 2 , wherein the first plurality of heat sources comprise a first portion of first sub-units of the NGL fractionation plant that comprises an ethane system, a second plurality of first sub-units of the NGL fractionation plant that comprises a propane system, a third portion of first sub-units of the NGL fractionation plant that comprises a butane system, a fourth portion of first sub-units of the NGL fractionation plant that comprises a natural gasoline system, and a fifth portion of first sub-units of the NGL fractionation plant that comprises a solvent regeneration system; and the second plurality of heat sources comprise a first portion of second sub-units of the NGL fractionation plant that comprises the ethane system, a second plurality of second sub-units of the NGL fractionation plant that comprises the propane system, a third portion of second sub-units of the NGL fractionation plant that comprises the butane system, a fourth portion of second sub-units of the NGL fractionation plant that comprises a pentane system, and a fifth portion of second sub-units of the NGL fractionation plant that comprises the natural gasoline system. 
     
     
         12 . A method, comprising:
 circulating a first heating fluid through a first heating fluid circuit to thermally couple the first heating fluid to a first plurality of heat sources of a natural gas liquid (NGL) fractionation plant, the first heating fluid circuit comprising a first plurality of heat exchangers fluidly coupled in parallel;   circulating a second heating fluid through a second heating fluid circuit to thermally couple the second heating fluid to a second plurality of heat sources of the NGL fractionation plant, the second heating fluid circuit comprising a second plurality of heat exchangers fluidly coupled in parallel;   heating, with the first heating fluid, a first working fluid in a first evaporator that thermally couples the first heating fluid circuit to the first working fluid;   generating electrical power with a first expander from the heated first working fluid;   heating, with the first and second heating fluids, a second working fluid in a second evaporator that thermally couples the first and second heating fluid circuits to the second working fluid;   generating electrical power with a second expander from the heated second working fluid;   cooling the first and second working fluids in a condenser that thermally couples the first and second working fluids to a condenser liquid supply fluid;   circulating the first and second heating fluids to combine in a heating fluid tank;   actuating, with a flow control system, a first set of control valves to selectively thermally couple the first heating fluid to the first plurality of heat sources of the NGL fractionation plant; and   actuating, with the flow control system, a second set of control valves to selectively thermally couple the second heating fluid to the second plurality of heat sources of the NGL fractionation plant.   
     
     
         13 . The method of  claim 12 , further comprising fluidly coupling the heating fluid tank to the first and second evaporators. 
     
     
         14 . The method of  claim 12 , wherein at least one of the first or second working fluids is isobutane. 
     
     
         15 . The method of  claim 12 , wherein at least one of the first or second heating fluids is water or oil. 
     
     
         16 . The method of  claim 12 , further comprising:
 circulating the first and second heating fluids through the respective first and second heating fluid circuits with a heating fluid pump fluidly coupled to the heating fluid tank;   circulating the first working fluid through the first evaporator with a first evaporator pump; and   circulating the second working fluid through the second evaporator with a second evaporator pump.   
     
     
         17 . The method of  claim 16 , further comprising fluidly combining the first and second working fluids in the condenser. 
     
     
         18 . The method of  claim 17 , further comprising fluidly separating the first and second working fluids at or upstream of the first and second evaporator pumps. 
     
     
         19 . The method of  claim 16 , wherein the heating fluid pump is positioned downstream of the heating fluid tank. 
     
     
         20 . The method of  claim 12 , further comprising:
 fluidly combining the first and second heating fluids between the first and second evaporators; and   fluidly separating the first and second heating fluids downstream of the heating fluid tank.   
     
     
         21 . The method of  claim 12 , wherein the first plurality of heat sources comprise a first portion of first sub-units of the NGL fractionation plant that comprises an ethane system, a second plurality of first sub-units of the NGL fractionation plant that comprises a propane system, a third portion of first sub-units of the NGL fractionation plant that comprises a butane system, a fourth portion of first sub-units of the NGL fractionation plant that comprises a natural gasoline system, and a fifth portion of first sub-units of the NGL fractionation plant that comprises a solvent regeneration system; and the second plurality of heat sources comprise a first portion of second sub-units of the NGL fractionation plant that comprises the ethane system, a second plurality of second sub-units of the NGL fractionation plant that comprises the propane system, a third portion of second sub-units of the NGL fractionation plant that comprises the butane system, a fourth portion of second sub-units of the NGL fractionation plant that comprises a pentane system, and a fifth portion of second sub-units of the NGL fractionation plant that comprises the natural gasoline system.