Methods and systems for superheating dilution steam and generating electricity

Abstract

Methods and system for superheating dilution steam for use in a steam cracking furnace and generating electricity are provided. Methods can include combusting fuel in the presence of compressed air to produce a flue gas, wherein the flue gas drives a turbine to produce electricity. Methods can further include superheating the dilution steam with the flue gas, combining the dilution steam with a feed stream including hydrocarbons to produce a mixed feed stream, and steam cracking the mixed feed stream to produce a product stream.

1 . A method for superheating dilution steam for use in a steam cracking furnace using compressed air, the method comprising the steps of:
 (a) combusting fuel in the presence of the compressed air to produce a flue gas, wherein the flue gas drives a turbine to produce electricity;   (b) superheating the dilution steam with the flue gas;   (c) combining the dilution steam with a feed stream comprising hydrocarbons to produce a mixed feed stream; and   (d) steam cracking the mixed feed stream to produce a product stream.   
     
     
         2 . The method of  claim 1 , wherein the dilution steam is superheated to a temperature from about 400° C. to about 600° C. 
     
     
         3 . The method of  claim 1 , further comprising heating the feed stream prior to the combining. 
     
     
         4 . The method of  claim 1 , further comprising flash vaporizing the mixed feed stream such that greater than about 70% of the hydrocarbons are vaporized prior to the steam cracking. 
     
     
         5 . The method of  claim 1 , further comprising heating the mixed feed stream prior to the steam cracking. 
     
     
         6 . The method of  claim 1 , wherein the product stream comprises ethylene. 
     
     
         7 . The method of  claim 1 , further comprising quenching the product stream. 
     
     
         8 . The method of  claim 1 , further comprising combusting fuel in the presence of an oxidation agent to heat the steam cracking furnace. 
     
     
         9 . The method of  claim 8 , wherein the oxidation agent is heated with the flue gas prior to the combusting. 
     
     
         10 . The method of  claim 9 , wherein the oxidation agent is heated with the flue gas in a heat exchanger. 
     
     
         11 . The method of  claim 10 , wherein the oxidation agent is ambient air. 
     
     
         12 . The method of  claim 10 , wherein the oxidation agent is the flue gas. 
     
     
         13 . A system for superheating dilution steam for use in a steam cracking furnace, the system comprising:
 (a) a gas turbine generator for combusting air and fuel to produce electrical power and a flue gas stream;   (b) a superheater, coupled to the gas turbine generator, for transferring heat from the flue gas stream to a dilution steam line;   (c) a radiant coil for placement within the steam cracking furnace; and   (d) a feed line, wherein the dilution steam line is combined with the feed line upstream from the radiant coil to form a mixed feed line, and wherein the mixed feed line is coupled to the radiant coil.   
     
     
         14 . The system of  claim 13 , wherein the gas turbine generator comprises a compressor for compressing the air. 
     
     
         15 . The system of  claim 13 , wherein the steam cracking furnace comprises a radiant section and a convection section, and wherein the radiant coil is within the radiant section, further comprising:
 (a) a feed preheater within the convection section for heating the feed line; and   (b) a mixed preheater within the convection section for heating the mixed feed line.   
     
     
         16 . The system of  claim 15 , further comprising a second mixed preheater for heating the mixed feed line. 
     
     
         17 . The system of  claim 15 , further comprising:
 (a) a product line, coupled to the radiant coil, comprising steam cracking products; and   (b) a transfer line exchanger, coupled to the product line, for quenching the steam cracking products by transferring heat to a water feed line to produce a steam line.   
     
     
         18 . The system of  claim 17 , wherein the water feed line is coupled to an economizer within the convection section. 
     
     
         19 . The system of  claim 18 , wherein the steam line is coupled to a superheater within the convection section. 
     
     
         20 . The system of  claim 17 , wherein:
 (a) the water feed line is coupled to an economizer within the convection section and a steam drum;   (b) the steam line is coupled to the steam drum for separating steam from the steam line to generate a second steam line; and   (c) the second steam line is coupled to a superheater within the convection section.