Flare stack

Abstract

A Coanda flare is described that provides improved operation of a flare stack. A Coanda flare comprises a gas flue having a flare end, a Coanda body disposed adjacent the flare end to form an annular gap between the Coanda body and the flare end of the gas flue, such that gas emitted from the flare end passes through the annular gap and around the Coanda body, and a gas flow adjustor for adjusting pressure on gas flowing through the annular gap. The gas flow adjustor may be provided by a dual acting piston, which may for example be sensitive on one side to waste gas pressure, and on the other side to a control pressure.

1 . A gas flare, comprising:
 a gas flue having a flare end;   the gas flue being connected to a source of waste gas;   a body disposed adjacent the flare end to form a gap between the body and the flare end of the gas flue, such that gas emitted from the flare end passes through the gap and around the body; and   a gas flow adjustor connected to the gas flue and to the body to adjust the gap and control gas flow through the gap.   
   
   
       2 . The gas flare of  claim 1  in which the gap is annular. 
   
   
       3 . The gas flare of  claim 2  in which the gas flow adjustor is responsive to waste gas pressure and to a control pressure from a pressure source. 
   
   
       4 . The gas flare of  claim 3  in which the gas flow adjustor comprises:
 a dual acting piston connected to the body for adjusting the annular gap, the dual acting piston being responsive on a first side of the dual acting piston to waste gas pressure and on a second side of the dual acting piston to the control pressure.   
   
   
       5 . The gas flare of  claim 1  in which the pressure source has an operating pressure range that includes 2 psig and 15 psig. 
   
   
       6 . The gas flare of  claim 3  in which the pressure source is a source of LPG. 
   
   
       7 . The gas flare of  claim 6  further comprising a gas pilot connected to the pressure source. 
   
   
       8 . The gas flare of  claim 2  in which the annular gap has an adjustment range that includes gaps of about 0.05 inches and about 0.5 inches. 
   
   
       9 . The gas flare of  claim 2  in which the body is a Coanda body. 
   
   
       10 . The gas flare of  claim 3  in which the body is a Coanda body. 
   
   
       11 . The gas flare of  claim 4  in which the body is a Coanda body. 
   
   
       12 . A method of controlling a gas flare connected to a waste gas source, comprising:
 providing a gas flare with an adjustable gap between a body and a flare end of a gas flue;   supplying the gas flue with waste gas from the waste gas source; and   controlling the pressure of gas flowing through the adjustable gap by controlling the gap size.   
   
   
       13 . The method of  claim 12  in which the body is an adjustable Coanda body. 
   
   
       14 . The method of  claim 13  in which controlling the pressure of the gas flow comprises providing a control pressure from a gas source to a first side of a pressure responsive control device. 
   
   
       15 . The method of  claim 14  in which the pressure responsive control device is a piston or diaphragm linked to the adjustable Coanda body. 
   
   
       16 . The method of  claim 15  in which:
 the pressure responsive control device has a second side; and   waste gas pressure is provided to the second side of the pressure responsive control device.   
   
   
       17 . The method of  claim 16  in which the gap is adjusted to provide a desired flame characteristic. 
   
   
       18 . The method of  claim 17  in which the desired flare characteristic is selected from a group consisting of flame speed, flame pattern, flame length, Coanda body stability, and noise level. 
   
   
       19 . The method of  claim 12  in which the gap is adjusted to provide a desired flame characteristic. 
   
   
       20 . The method of  claim 19  in which the desired flare characteristic is selected from a group consisting of flame speed, flame pattern, flame length, adjustable body stability, and noise level.