Pilot

Abstract

A pilot ( 10 ) is shown for igniting a combustible fluid stream. The pilot comprises an inlet ( 12 ), for receiving a fuel gas ( 14 ), including a fuel and air/oxygen mixture, into the pilot. Ignition means ( 16 ), for example a spark igniter or an ignition electrode, are provided for igniting the fuel gas ( 14 ). A generally annular conduit ( 18 ) is open along an annular extent forming a circumferential aperture ( 20 ). The conduit ( 18 ) conveys fuel gas from the inlet to the circumferential aperture. When the fuel gas flowing out of the circumferential aperture ( 20 ) is ignited a continuous annular pilot flame is generated radially of the conduit.

1 . A pilot for igniting a combustible fluid stream, the pilot comprising an inlet for receiving a fuel gas into the pilot; means for igniting the fuel gas; and a generally annular conduit open along an annular extent by a circumferential aperture for conveying fuel gas from the inlet and so that when the fuel gas is ignited an annular pilot flame is generated. 
     
     
         2 . A pilot as claimed in  claim 1 , wherein the conduit is open along a radially inner annular extent so that when the fuel gas is ignited an annular pilot flame is generated radially inwardly of the conduit. 
     
     
         3 . A pilot as claimed in  claim 1  or  2 , wherein when ignited said pilot flame is continuous around the annular extent of the pilot. 
     
     
         4 . A pilot as claimed in any preceding claim, the ignition means comprises a spark igniter. 
     
     
         5 . A pilot as claimed in any preceding claim, wherein the ignition means comprises a single igniter and in use ignites the fuel gas to form the continuous annular pilot flame. 
     
     
         6 . A pilot as claimed in any preceding claim, wherein the generally annular conduit comprises a plenum chamber for receiving fuel gas from the inlet and a circumferential channel for channelling fuel gas from the plenum chamber for forming the continuous annular pilot flame. 
     
     
         7 . A pilot as claimed in  claim 6 , wherein in use the plenum chamber distributes the fuel gas at a generally equal pressure around the annular extent of the conduit so that when ignited the continuous annular pilot flame burns generally evenly about the annular extent of the of the conduit. 
     
     
         8 . A burner for removing noxious substances from a fluid stream, the burner comprising:
 a combustion region in which a fuel gas can be burnt for combusting the fluid stream; and   a pilot as claimed in of  claims 1  to  7  for igniting the fuel gas in the combustion chamber.   
     
     
         9 . A burner as claimed in  claim 8 , wherein the combustion region is formed by a chamber having a surrounding generally cylindrical wall for introducing therethrough into the combustion chamber a fuel gas for burning on a surface of said wall when ignited by the pilot so that a fluid stream passing through said chamber can be combusted. 
     
     
         10 . A burner as claimed in  claim 9 , wherein the pilot is located so that when ignited the annular pilot flame and the wall are adjacent along their respective annular extents such that the fuel gas passing through the wall can be efficiently ignited and a flame at the surface maintained. 
     
     
         11 . A burner as claimed in  claim 10 , comprising a weir arrangement positioned downstream of the combustion chamber for receiving the combusted fuel stream, wherein the pilot is located so that when ignited the annular pilot flame thermally insulates the generally cylindrical wall from relatively cold liquid passing over the weir arrangement. 
     
     
         12 . A burner as claimed in any of  claims 8  to  11 , said combustion region comprising an inlet upstream of the combustion chamber for introducing the fluid stream and a fuel gas as a mixture into the combustion region. 
     
     
         13 . A burner as claimed in  claim 12 , wherein said mixture is ignited at said inlet by the flame formed at the surface of the generally cylindrical wall. 
     
     
         14 . A burner as claimed in  claim 13 , wherein said pilot is located between the generally cylindrical wall and the inlet for igniting mixture at the inlet and the fuel gas at the surface of the generally cylindrical wall. 
     
     
         15 . A burner as claimed in  claim 8 , wherein said combustion region comprises an inlet upstream of the combustion chamber for introducing the fluid stream and a fuel gas as a mixture into the combustion region and said pilot is located so that when ignited the annular pilot flame surrounds the mixture to be burned. 
     
     
         16 . A burner as claimed in  claim 14 , wherein comprising a plurality of inlets to the combustion chamber for introducing a plurality of fluid streams and fuel gas as respective mixtures into the combustion chamber and said pilot is located so that when ignited the annular pilot flame surrounds mixtures to be burned so that all of the mixtures can be ignited by said pilot. 
     
     
         17 . A burner as claimed in  claim 11  or  12 , in which a portion of the weir arrangement is integral with the pilot and wherein the pilot comprises a closeable passage which when open water used to clean the pilot flows through the passage and over the weir, and when closed the pilot can form said annular flame.