Method and system for energy generation in a chemical plant by utilizing flare gas

Abstract

The present techniques provide systems and methods for recovering energy from flare gases in chemical plants and refineries. The systems use an engine to burn a portion of gas diverted from the flare system. The engine may be a reciprocating engine, or a burner in a boiler system, among others. The power generated by burning the flare gas is then used to power an energy recovery device. The energy recovery device may be an electrical generator, a compressor, or a steam boiler, among others.

1 .- 24 . (canceled) 
     
     
         25 . A method for recovering energy, comprising:
 diverting at least a portion of a flare gas from a flare header and into a divergent path to form a diverted flare gas, wherein the flare header fluidly couples a process vessel and a flare in a chemical plant, a refinery, or a combined plant, and wherein the divergent path fluidly couples the flare header with a power generation system;   combusting the diverted flare gas in the power generation system up to a maximum capacity of the power generation system; and   storing a remaining amount of the diverted flare gas in the power generation system, combusting the remaining amount of the diverted flare gas in the flare, or both.   
     
     
         26 . The method of  claim 25 , wherein the power generation system comprises a reciprocating engine, a burner, or a combination thereof. 
     
     
         27 . The method of  claim 25 , wherein the chemical plant comprises a polyolefin production facility. 
     
     
         28 . The method of  claim 25 , comprising adding fuel gas to the diverted flare gas along the divergent path. 
     
     
         29 . The method of  claim 28 , comprising adding the fuel gas to the diverted flare gas during startup of the power generation system. 
     
     
         30 . The method of  claim 25 , wherein the power generation system comprises an electrical generator, an air compressor, or a combination thereof. 
     
     
         31 . The method of  claim 25 , comprising diverting substantially all of the flare gas from the flare header and into the divergent path. 
     
     
         32 . The method of  claim 25 , wherein the flare gas is placed into an active condition and any flare gas not consumed in the power generation system is burned in the flare in response to a process change in the power generation system, or the process vessel. 
     
     
         33 . The method of  claim 25 , comprising storing power produced from combustion of the flare gas by the power generation system during a first time frame, and releasing the power during a second time frame. 
     
     
         34 . A system for recovering energy from a flare gas, comprising:
 a flare system comprising a flare and a flare header, wherein the flare header fluidly couples the flare to a process vessel in a chemical plant, a refinery, or a combination thereof, and the process vessel is configured to discharge a process gas into the flare header, wherein the process gas is a component of the flare gas;   a power generation system configured to burn the flare gas, and to produce power;   a conduit diverging from the flare header at a point between the process vessel and the flare, the conduit coupling the flare header with the power generation system to enable at least a portion of the flare gas to flow from the flare header to the power generation system; and   a water weir isolating the flare from the flare header, wherein the water weir is configured to divert substantially all of the flare gas to the power generation system, and wherein water in the water weir is configured to be displaced by a high-pressure gas discharge to open a path to the flare when the high-pressure gas discharge reaches a threshold pressure.   
     
     
         35 . The system of  claim 34 , wherein the water weir comprises a vessel fluidly coupled between a flare knockout pot and the flare. 
     
     
         36 . The system of  claim 35 , comprising a level controller configured to adjust a level of water in the vessel by controlling a water line valve configured to cause water to flow into the vessel and a drain valve configured to cause water to drain from the vessel, and wherein the level of water in the vessel determines the threshold pressure. 
     
     
         37 . The system of  claim 36 , comprising a bypass line enabling the flare gas to bypass the water weir before startup of the power generation system. 
     
     
         38 . The system of  claim 34 , wherein the water weir is incorporated into the flare knockout pot. 
     
     
         39 . The system of  claim 34 , wherein the water weir is configured to block entrained liquid in the flare gas from reaching the flare. 
     
     
         40 . The system of  claim 34 , wherein the power generation system comprises a machine that includes a reciprocating engine, a burner, a boiler, or a compressor, or any combination thereof. 
     
     
         41 . The system of  claim 40 , comprising a blower with an inlet coupled to the flare header via the conduit and an outlet coupled to an inlet of the machine, wherein the blower is configured to increase a pressure of the flare gas provided to the machine. 
     
     
         42 . The system of  claim 40 , comprising a fuel gas conduit configured to add fuel gas to the inlet of the machine. 
     
     
         43 . The system of  claim 42 , comprising a mixing conduit configured to form a mixture of the fuel gas with the flare gas, wherein the mixing conduit is configured to add the mixture to the inlet of the machine. 
     
     
         44 . A power generation system, comprising:
 a reciprocating engine or a burner configured to burn a low-BTU gas, wherein the low-BTU gas comprises a flare gas having an energy content greater than about 30% methane by volume;   a chemical production plant comprising a flare system comprising the flare gas, a flare, and a flare header fluidly coupling the flare to a process vessel in the chemical production plant;   a conduit diverging from the flare header at a point between the flare and the process vessel and fluidly coupling the flare header and the reciprocating engine or the burner, wherein the conduit is configured to divert at least a portion of the flare gas from the flare header to power the reciprocating engine or the burner;   an energy recovery device powered by the engine or the burner; and   a water weir coupled between the flare header and the flare, wherein the water weir is configured to divert substantially all of the flare gas to the reciprocating engine.