Staged steam waste gas flare

Abstract

A steam flare is provided that injects steam, unmixed with air into a waste gas stream at locations where the resulting accelerated steam and waste gas mixture upon exposure to the surrounding air induces a mixture of steam, waste gas and air with improved combustion and effectively complete destruction of the waste gas, and where under low-flow conditions, reduced steam and/or assist gas are required to maintain smokeless operation. The steam is injected via multiple tubes each controlled independently so that steam can normally be flowed via a first tube, and then, when operation loads require, flowed via a second tube. The first and second tubes may be concentric and may be in communication with steam supplies that have different pressures of steam.

1 . A steam flare comprising:
 a flare gas conduit configured to receive waste gas and provide the waste gas to a combustion zone, and   a steam tube located in said flare gas conduit, wherein said steam tube comprises an outer tube and an inner tube inside of said outer tube, both of said outer tube and said inner tube having at least one orifice configured to provide steam into the flare gas conduit.   
     
     
         2 . The steam flare of  claim 1 , wherein the outer tube is in communication with a supply of steam having a first steam flow rate and a first pressure. 
     
     
         3 . The steam flare of  claim 2 , wherein the inner tube is in communication with a supply of steam having a second steam flow rate and a second pressure, the second steam flow rate, the second pressure, or both being different, respectively, from the first steam flow rate and the first pressure. 
     
     
         4 . The steam flare of  claim 3 , wherein the second pressure is lower than the first pressure for a given rate of steam flow to either the outer tube or the inner tube. 
     
     
         5 . The steam flare of  claim 3 , wherein the second pressure is higher than the first pressure for a given rate of steam flow to either the outer tube or the inner tube. 
     
     
         6 . The steam flare of  claim 1 , wherein a steam supply through the inner tube is independent of a steam supply of the outer tube. 
     
     
         7 . The steam flare of  claim 1  further comprising:
 a sensor; 
 a flow regulating device configured to regulate a steam flow, a pressure, or both associated with steam provided by one of the inner tube and the outer tube; 
 a controller in communication with the sensor and the flow regulation device and being configured to increase or decrease the steam flow, the pressure, or both based on a signal from the sensor. 
 
     
     
         8 . A steam flare comprising:
 a flare gas conduit in communication with a source of flare gas; and,   a steam tube located proximate said flare gas conduit so that steam from said steam tube is directed into a flame from combustion of said flare gas,   wherein said steam tube comprises a plurality of tubes each having at least one orifice and a first tube from said plurality being configured to provide steam independent of steam provided from a second tube.   
     
     
         9 . The steam flare of  claim 8 , wherein the first tube is concentric with the second tube. 
     
     
         10 . The steam flare of  claim 8 , wherein the steam tube is disposed within the flare gas conduit. 
     
     
         11 . The steam flare of  claim 8 , wherein the first tube is in communication with steam having a first steam flow rate and a first pressure. 
     
     
         12 . The steam flare of  claim 11 , wherein the second tube is in communication with steam having a second steam flow rate and a second pressure, the second steam flow rate, the second pressure, or both being different, respectively, from the first pressure and the first steam flow rate. 
     
     
         13 . The steam flare of  claim 8  further comprising:
 a sensor; 
 a flow regulating device configured to regulate a steam flow, a pressure, or both associated with steam provided by one of the first tube and the second tube; 
 a controller in communication with the sensor and the flow regulation device and being configured to increase or decrease the steam flow, the pressure, or both based on a signal from the sensor. 
 
     
     
         14 . A process of operating a steam flare comprising:
 sending a waste gas stream through a flare gas conduit at a first flare gas flow rate while providing a steam through a first steam tube in communication with a supply of steam having a first steam flow rate and a first pressure, wherein said first steam tube is proximate said flare gas conduit so that steam from the first steam tube mixes with waste gas from said waste gas stream;   causing a flame to burn as a resulting mixture of said waste gas stream, said steam, and oxygen in outside ambient air; and,   sending a second stream of steam through a second steam tube, wherein said second steam tube is in communication with a supply of stream having a second steam flow rate and a second pressure, and wherein said second pressure is greater than said first pressure for a given steam flow rate.   
     
     
         15 . The process of  claim 14  further comprising:
 monitoring said first flare gas flow rate of said waste gas stream; and 
 when, said first flare gas flow rate exceeds a predetermined level, adjusting a flow rate of the second stream of steam. 
 
     
     
         16 . The process of  claim 14 , wherein said first steam tube is concentric with said second steam gas tube. 
     
     
         17 . The process of  claim 14 , wherein said first steam tube and said second steam tube are located within said flare gas conduit.