Heat Recovery System and Method

Abstract

The present techniques are directed to a heat recovery system, such as a waste heat recovery system (WHRU) that receives and passes a vapor across a heat exchanger to transfer heat from the vapor to a heating medium in the heat exchanger. The vapor may be an exhaust gas from a source outside of the heat recovery system. The heat recovery system includes a collection system to deinventory the heating medium from the heat exchanger during abnormal operation of the heat recovery system.

What is claimed is: 
     
         1 . A heat recovery system comprising:
 a tube bundle having multiple tubes;   an enclosure housing at least a portion of the tube bundle, wherein the enclosure is configured to receive a vapor and pass the vapor over the tube bundle;   a pump configured to flow a heating medium through the tube bundle to one or more users;   a control system configured to detect an abnormal operation of the heat recovery system, wherein the abnormal operation comprises a reduction of flow of the heating medium below a predetermined range of flow values; and   a collection system configured to reduce thermal degradation of the heating medium during the abnormal operation by evacuating the heating medium from the tube bundle during the abnormal operation.   
     
     
         2 . The heat recovery system of  claim 1 , wherein the enclosure comprises ductwork. 
     
     
         3 . The heat recovery system of  claim 1 , wherein the vapor comprises exhaust gas from a source outside of the heat recovery system. 
     
     
         4 . The heat recovery system of  claim 1 , wherein the abnormal operation comprises a shutdown of the pump. 
     
     
         5 . The heat recovery system of  claim 1 , wherein the abnormal operation comprises continued flow of the vapor across the tube bundle in the enclosure. 
     
     
         6 . The heat recovery system of  claim 1 , wherein the collection system comprises a collection vessel configured to accumulate the heating medium removed from the multiple tubes during the abnormal operation. 
     
     
         7 . The heat recovery system of  claim 1 , wherein the collection system is configured to evacuate the heating medium from the tube bundle without back-flushing the multiple tubes. 
     
     
         8 . The heat recovery system of  claim 1 , wherein the collection system is configured to receive and vent heating medium vaporized in the tube bundle during the abnormal operation. 
     
     
         9 . The heat recovery system of  claim 1 , wherein the collection system comprises a purge gas inlet configured to pass purge gas through the tube bundle during the abnormal operation, wherein the purge gas is inert. 
     
     
         10 . The heat recovery system of  claim 1 , comprising an ambient air inlet on the enclosure configured to introduce ambient air into the enclosure to dilute and reduce temperature of the vapor. 
     
     
         11 . The heat recovery system of  claim 1 , wherein the tube bundle comprises multiple tubes comprising coils. 
     
     
         12 . A waste heat recovery unit comprising:
 a heat exchanger;   a ductwork enclosing at least a portion of the coils, wherein the ductwork is configured to receive and pass an exhaust gas over the heat exchanger;   a pump configured to circulate a heating medium through an internal flow path of the heat exchanger to absorb heat from the exhaust gas, and wherein the pump is configured to circulate the heating medium from the waste heat recovery unit to users of the heating medium;   a collection system configured to remove the heating medium from the heat exchanger during an abnormal operation to reduce thermal degradation of the heating medium in the heat exchanger, wherein the collection system comprises a collection vessel configured to receive heating medium removed from the heat exchanger during the abnormal operation, and wherein the abnormal operation comprises a cessation of flow or substantial reduction in a flow rate of the heating medium through the heat exchanger.   
     
     
         13 . The waste heat recovery unit of  claim 12 , wherein the abnormal operation comprises a shutdown of the pump. 
     
     
         14 . The waste heat recovery unit of  claim 12 , wherein the abnormal operation comprises continued flow of the exhaust gas across the heat exchanger. 
     
     
         15 . The waste heat recovery unit of  claim 12 , wherein the collection system comprises a conduit configured to drain the heating medium from the heat exchanger to the collection vessel. 
     
     
         16 . The waste heat recovery unit of  claim 12 , comprising a control system configured to detect the abnormal operation, and configured to automatically implement removal of the heating medium from the coils during the abnormal operation. 
     
     
         17 . A method of operating a waste heat recovery unit, the method comprising:
 circulating a heating medium through multiple tubes of a tube bundle in the waste heat recovery unit and to users of the heating medium outside of the waste heat recovery unit;   passing a vapor over the tube bundle to transfer heat from the vapor to the heating medium;   detecting via a control system an abnormal operation of the waste heat recovery unit, the abnormal operation comprising loss of circulation of the heating medium through the multiple tubes; and   removing the heating medium from the multiple tubes to a collection vessel in the waste heat recovery unit during the abnormal operation to reduce or avoid thermal degradation of the heating medium.   
     
     
         18 . The method of  claim 17 , wherein the vapor comprises exhaust gas. 
     
     
         19 . The method of  claim 17 , comprising diluting the vapor with air to reduce a temperature of the vapor during the abnormal operation. 
     
     
         20 . The method of  claim 17 , wherein removing comprises draining the heating medium from the multiple tubes to the collection vessel when the heating medium is a liquid and venting the heating medium from the multiple tubes to the collection vessel when the heating medium is a vapor. 
     
     
         21 . The method of  claim 17 , comprising purging the multiple tubes with an inert gas during the abnormal operation. 
     
     
         22 . A method of constructing or retrofitting a waste heat recovery unit (WHRU) to prevent or reduce thermal degradation of heating medium during abnormal operation of the WHRU, the method comprising:
 adding a conduit downstream of a tube bundle configured to transfer heat from an exhaust gas to the heating medium, wherein the conduit is configured to divert flow of the heating medium in the WHRU during the off-specification operation of the WHRU, the abnormal operation comprising cessation of normal flow of heating medium through the tube bundle;   installing a collection vessel coupled to the conduit and configured to receive heating medium drained from the tube bundle via the conduit during the abnormal operation; and   installing a valve on the conduit, wherein the valve is configured to isolate the collection vessel during normal operation of the WHRU and to place the collection vessel in service during the abnormal operation.   
     
     
         23 . The method of  claim 22 , comprising installing an inert-gas purge inlet configured to provide an inert gas purge through tubes of the tube bundle during the abnormal operation. 
     
     
         24 . The method of  claim 22 , comprising installing another conduit configured to receive vaporized heating medium from the tube bundle during the abnormal operation. 
     
     
         25 . The method of  claim 22 , comprising installing an ambient-air inlet on ductwork receiving the exhaust gas and housing the tube bundle.