Heat recovery from a high pressure stream

Abstract

A process for recovering heat from a high pressure stream during hydroprocessing, where one embodiment of the process includes serially introducing a high pressure stream from a hot separator into a first steam generator and a second steam generator; using the first steam generator to generate a medium pressure stream of steam, and then using the medium pressure stream as stripping steam. The process also includes using the second steam generator to generate a low pressure stream of steam, and then using the low pressure stream as stripping steam.

What is claimed is: 
     
         1 . A process for recovering heat from a high pressure stream during hydroprocessing, the process comprising:
 serially introducing a high pressure stream from a hot separator into a first steam generator and a second steam generator;   using the first steam generator to generate a medium pressure stream of steam, and then using the medium pressure stream as stripping steam; and   using the second steam generator to generate a low pressure stream of steam, and then using the low pressure stream as stripping steam.   
     
     
         2 . The process according to  claim 1 , further comprising:
 routing the medium pressure stream to a stripper; and   routing the low pressure stream to at least one of a product fractionator and a diesel side stripper.   
     
     
         3 . The process according to  claim 2 , wherein a portion of the low pressure stream is routed to the product fractionator and a portion of the low pressure stream is routed to the diesel side stripper. 
     
     
         4 . A process for recovering heat from a high pressure stream during hydroprocessing, the process comprising:
 using a hot separator to create a high pressure vapor stream;   generating both a medium pressure stream of steam and a low pressure stream of steam from the high pressure vapor stream by extracting heat from the high pressure vapor stream;   routing the medium pressure stream to a stripper, where the medium pressure stream is used as stripping steam; and   routing the low pressure stream to at least one of a product fractionator and a diesel side stripper, where the low pressure stream is used as stripping steam.   
     
     
         5 . The process according to  claim 4 , wherein a portion of the low pressure stream is routed to the product fractionator and a portion of the low pressure stream is routed to the diesel side stripper. 
     
     
         6 . The process according to  claim 4 , further comprising:
 routing the high pressure vapor stream from the hot separator to a first steam generator, and extracting heat from the high pressure stream to form the medium pressure steam stream;   routing the high pressure vapor stream, from which heat has been extracted in the first steam generator, to a second steam generator; and   using the second steam generator to extract additional heat from the high pressure stream, thereby forming the low pressure steam stream.   
     
     
         7 . The process according to  claim 6 , further comprising:
 providing at least one first heat exchanger between the hot separator and the first steam generator, and extracting heat from the high pressure stream with the at least one first heat exchanger; and   providing at least one second heat exchanger after the second steam generator and extracting additional heat from the high pressure stream with the at least one second heat exchanger.   
     
     
         8 . The process according to  claim 6 , further comprising:
 providing a medium pressure steam superheater between the first steam generator and the stripper column, and routing the medium pressure stream from the first steam generator through the medium pressure steam superheater; and   providing a low pressure steam superheater after the second steam generator, and routing the low pressure stream from the second steam generator through the low pressure steam superheater.   
     
     
         9 . The process according to  claim 10 , further comprising:
 providing a pressure alarm system that is configured and arranged to activate a valve associated with a boiler feed water line at a predetermined high pressure value, wherein the boiler feed water line provides boiler feed water to both the first steam generator and the second steam generator; and   activating the valve associated with the boiler feed water line, when the pressure alarm system detects that the pressure has reached the predetermined high pressure value, to stop flow of the boiler feed water to both the first steam generator and the second steam generator.   
     
     
         10 . The process according to  claim 4 , further comprising:
 controlling, using a computer processor configured and arranged to control at least one valve, the pressure of the medium pressure stream entering the stripper to be at a first predetermined pressure of approximately 130 psig (9 barg); and   controlling, using the computer processor configured and arranged to control at least one valve, the pressure of the low pressure stream entering at least one of the product fractionator and the diesel stripper to be at a second predetermined pressure of between approximately 15 psig (1 barg) and approximately 20 psig 1.4 barg).   
     
     
         11 . The process according to  claim 10 , wherein:
 during the controlling of the pressure of the medium pressure stream, a supplemental high pressure stream of high pressure steam is controlled to be combined with the medium pressure stream to arrive at the first predetermined pressure; and   during the controlling of the pressure of the low pressure stream, a supplemental medium pressure stream of medium pressure steam is controlled to be combined with the low pressure stream to arrive at the second predetermined pressure.   
     
     
         12 . The process according to  claim 4 , further comprising:
 combining the medium pressure stream with high pressure header steam to provide the stripper with a stream at a predetermined pressure;   combining the low pressure stream with medium pressure header steam to provide the diesel side stripper with a stream at a predetermined pressure; and   combining the low pressure stream with medium pressure header steam to provide the product fractionator with a stream at a predetermined pressure.   
     
     
         13 . The process according to  claim 6 , wherein:
 the first steam generator comprises a first cooler; and   the second steam generator comprises a second cooler.   
     
     
         14 . A process for recovering heat from a high pressure stream during hydroprocessing, the process comprising:
 routing a high pressure stream to a first process vessel;   routing a first feed water stream to the first process vessel;   extracting heat from the high pressure stream within the first process vessel to create a medium pressure stream of steam from the first feed water stream, routing the high pressure stream from the first process vessel to a second process vessel;   routing a second feed water stream to the second process vessel; and   extracting heat from the high pressure stream within the second process vessel to create a low pressure stream of steam from the second feed water stream.   
     
     
         15 . The process according to  claim 14 , further comprising:
 providing a first pressure alarm system that is triggered by pressure above a first predetermined level, wherein said first pressure alarm system isolates the first process vessel by stopping flow of said first feed water stream into said first process vessel and by stopping flow of said medium pressure stream; and   providing a second pressure alarm system that is triggered by pressure above a second predetermined level, wherein said second pressure alarm system isolates the second process vessel by stopping flow of said second feed water stream into said second process vessel and by stopping flow of said low pressure stream.   
     
     
         16 . The process according to  claim 14 , further comprising:
 routing the medium pressure stream to a first superheater to create a first superheated stream of medium pressure steam;   using the first superheated stream as stripping steam;   routing the low pressure stream to a second superheater to create a second superheated stream; and   using the second superheated stream as stripping steam.   
     
     
         17 . The process according to  claim 16 , further comprising:
 using the first pressure alarm system to stop flow of a first blowdown stream from the first process vessel; and   using the second pressure alarm system to stop flow of a second blowdown stream from the second process vessel.   
     
     
         18 . The process according to  claim 16 , further comprising:
 providing a first pressure alarm system that is triggered by pressure above a first predetermined level, wherein said first pressure alarm system isolates the first process vessel by stopping flow of said first feed water stream into said first process vessel and by stopping flow of said medium pressure stream;   determining a first pressure of said medium pressure stream between the first process vessel and the first superheater, and comparing the first pressure with the first predetermined pressure;   activating the first pressure alarm system if the first pressure exceeds the first predetermined pressure;   providing a second pressure alarm system that is triggered by pressure above a second predetermined level, wherein said second pressure alarm system isolates the second process vessel by stopping flow of said second feed water stream into said second process vessel and by stopping flow of said low pressure stream;   determining a second pressure of said low pressure stream between the second process vessel and the second superheater, and comparing the second pressure with the second predetermined pressure; and   activating the second pressure alarm system if the second pressure exceeds the second predetermined pressure.   
     
     
         19 . The process according to  claim 15 , further comprising:
 providing a line to rout a first effluent stream from the first processing vessel to a relief header;   providing a first safety valve configured and arranged to be normally closed, but to allow flow of said first effluent stream to the relief header when activated;   providing a line to rout a second effluent stream from the second processing vessel to the relief header;   providing a second safety valve configured and arranged to be normally closed, but to allow flow of said second effluent stream to the relief header when activated.   
     
     
         20 . The process according to  claim 19 , wherein:
 said first safety valve is activated to allow flow of said first effluent stream if said first pressure alarm system has been activated and if a first predetermined pressure safety valve pressure has been reached; and   said second safety valve is activated to allow flow of said second effluent stream if said second pressure alarm system has been activated and if a second predetermined pressure safety valve pressure has been reached.