Management of working fluid during heat engine system shutdown

Abstract

Provided herein are a heat engine system and a method for managing a working fluid in the heat engine system during an emergency shutdown. The heat engine system utilizes a working fluid (e.g., sc-CO2) contained within a working fluid circuit to absorb and transport heat. An inventory system is coupled to the working fluid circuit and configured to receive and store at least a portion of the working fluid in the working fluid circuit during an emergency shutdown process. An attemperation line is coupled to the working fluid circuit upstream one or more heat exchangers and configured to direct a portion of the working fluid flow around at least one or more heat exchangers, thereby managing the temperature of the working fluid in the working fluid circuit.

We claim: 
     
         1 . A heat engine system, comprising:
 a working fluid contained in a working fluid circuit having a high pressure side and a low pressure side, wherein a portion of the working fluid is in a supercritical state in the high pressure side of the working fluid circuit;   at least one heat exchanger in the working fluid circuit, in thermal communication with a heat source stream coupled to the working fluid circuit, and configured to provide thermal energy from the heat source stream to the working fluid in the working fluid circuit;   a power turbine disposed between the high pressure side and the low pressure side of the working fluid circuit, and operative to convert a pressure drop in the working fluid to mechanical energy;   a recuperator in the working fluid circuit operative to transfer thermal energy between the high pressure side and the low pressure side of the working fluid circuit;   a cooler in thermal communication with a cooling medium and the low pressure side of the working fluid circuit, and operative to control a temperature of the working fluid in the low pressure side of the working fluid circuit;   a turbo pump disposed in the working fluid circuit, coupled to the low pressure side and to the high pressure side of the working fluid circuit, and operative to flow the working fluid through the working fluid circuit;   an attemperation line including an attemperation valve disposed therein, the attemperation line fluidly coupled to the working fluid circuit upstream of at least one or more heat exchangers and downstream of at least one heat exchanger, and configured to circumvent the working fluid around at least one or more heat exchangers;   a power turbine bypass line including a power turbine bypass valve disposed therein, the power turbine bypass line fluidly coupled to the working fluid circuit upstream of the power turbine and downstream of the power turbine, and configured to circumvent the working fluid around the power turbine; and   an inventory system operatively coupled to the working fluid circuit by an inventory system line, the inventory system comprising an inventory tank and at least two refrigeration systems.   
     
     
         2 . The heat engine system of  claim 1 , wherein the volume of the inventory tank is greater than the volume of the working fluid circuit. 
     
     
         3 . The heat engine system of  claim 1 , wherein the inventory tank is a low-pressure storage tank, and wherein the inventory tank has a maximum allowable working pressure rating of about 2.4 MPa or less. 
     
     
         4 . The heat engine system of  claim 3 , wherein the inventory system is configured to maintain the working fluid in the inventory tank within a temperature range from about −31° C. to about −13° C. and a pressure within a range from about 1.4 MPa to about 2.4 MPa. 
     
     
         5 . The heat engine system of  claim 1 , wherein the inventory system further comprises one or more heat sinks disposed therein. 
     
     
         6 . The heat engine system of  claim 5 , wherein the one or more heat sinks disposed therein comprise a volume of working fluid configured to absorb at least a portion of thermal energy from the working fluid discharged from the working fluid circuit. 
     
     
         7 . The heat engine system of  claim 1 , wherein a first refrigeration system of the inventory system has a greater cooling capacity than a second refrigeration system, wherein the first refrigeration system is configured to maintain the temperature of the inventory tank, and the second refrigeration system is configured to reduce thermal absorption by the inventory tank. 
     
     
         8 . The heat engine system of  claim 1 , further comprising a mass management system connected to the working fluid circuit and the inventory system, the mass management system having a working fluid vessel connected to the low pressure side of the working fluid circuit. 
     
     
         9 . The heat engine system of  claim 1 , further comprising a fluid fill system connected to the working fluid circuit and the inventory system, and configured to receive at least a portion of the working fluid from the inventory system. 
     
     
         10 . A method for managing a working fluid in a heat engine system during an emergency shutdown, comprising:
 circulating the working fluid within a working fluid circuit having a high pressure side and a low pressure side, wherein at least a portion of the working fluid is in a supercritical state;   preventing the venting of the working fluid through one or more pressure relief valves by flowing the working fluid through a power turbine bypass line, thereby circumventing the working fluid around a power turbine;   cooling the working fluid in the heat engine system by:
 flowing a first portion of the working fluid through an attemperation line, thereby avoiding the flow of the first portion of the working fluid through one or more heat exchangers; and 
 combining the first portion of the working fluid with a second portion of the working fluid downstream of one or more heat exchangers, wherein the attemperation line is fluidly coupled to the working fluid circuit upstream of at least one heat exchanger through an attemperation valve, and fluidly coupled to the working fluid circuit downstream of at least one heat exchanger; 
   discharging at least a third portion of the working fluid from the working fluid circuit to an inventory tank;   regulating the temperature of the inventory tank during the emergency shutdown within a predetermined temperature range; and   regulating the pressure of the inventory tank during the emergency shutdown within a predetermined pressure range.   
     
     
         11 . The method of  claim 10 , wherein the first portion of working fluid flowing through the attemperation line is at a lower temperature than the second portion of the working fluid downstream of one or more heat exchangers. 
     
     
         12 . The method of  claim 10 , wherein the predetermined temperature range is within a range from about −31° C. to about −13° C. 
     
     
         13 . The method of  claim 10 , wherein the predetermined pressure range is within a range from about 1.4 MPa to about 2.4 MPa. 
     
     
         14 . The method of  claim 10 , further comprising restoring the temperature of the working fluid within the inventory tank to a nominal operating condition. 
     
     
         15 . The method of  claim 10 , further comprising restoring the pressure of the working fluid within the inventory tank to a nominal operating condition. 
     
     
         16 . The method of  claim 10 , wherein the third portion of the working fluid includes a portion of the working fluid in the high pressure side of the working fluid circuit. 
     
     
         17 . The method of  claim 16 , wherein the third portion of the working fluid further includes the first portion of the working fluid flowing through the attemperation line and the second portion of working fluid downstream of the one or more heat exchangers. 
     
     
         18 . The method of  claim 14 , further comprises storing the working fluid within the inventory tank. 
     
     
         19 . The method of  claim 18 , further comprises recycling the working fluid within the inventory tank back to the heat engine system.