Combustion apparatus with direct firing system

Abstract

The invention relates to a combustion apparatus, in particular to a burner for the combustion of carbonaceous fuel. The combustion apparatus comprises a burner having a burner inlet for receiving a supply of combustible pulverous fuel and a supply of comburant gas and a burner outlet in the vicinity of which combustion of the fuel is supported during use; at least a primary conduit defining a flow channel for conveying a mixture of fuel and comburant gas from the burner inlet to the burner outlet; a fuel feed line defining a flow channel which conveys a pulverous combustible fuel in a dense phase; and a supply conduit fluidly connecting a comburant gas supply to the primary conduit and defining with the primary conduit a primary flow stream; wherein the fuel feed line is provided with a fuel feed outlet into the supply conduit upstream of the burner inlet to supply pulverous combustible fuel in a dense phase; and wherein the primary flow stream is provided with a mixing device downstream of the fluid supply outlet. A method for combusting pulverous combustible fuel in a burner embodying such principles is also described.

1 . A combustion apparatus comprising:
 a burner having a burner inlet for receiving a supply of combustible pulverous fuel and a supply of comburant gas and a burner outlet in the vicinity of which combustion of the fuel is supported during use;   at least a primary conduit defining a flow channel for conveying a mixture of fuel and comburant gas from the burner inlet to the burner outlet;   a fuel feed line defining a flow channel which conveys a pulverous combustible fuel in a dense phase; and   a supply conduit fluidly connecting a comburant gas supply to the primary conduit and defining with the primary conduit a primary flow stream;   wherein the fuel feed line is provided with a fuel feed outlet into the supply conduit upstream of the burner inlet to supply pulverous combustible fuel in a dense phase;   and wherein the primary flow stream is provided with a mixing device downstream of the fluid supply outlet.   
     
     
         2 . A combustion apparatus in accordance with  claim 1  wherein the primary flow stream is provided with a mixing device at or about the burner inlet. 
     
     
         3 . A combustion apparatus in accordance with  claim 1  further adapted to effect mixing of the dense phase pulverous combustible fuel and the comburant gas upstream of the burner inlet by means of a duct arrangement upstream of the burner, whereby a dense phase stream of solid pulverous fuel is introduced to a primary stream containing the comburant gas. 
     
     
         4 . A combustion apparatus in accordance with  claim 1  wherein the mixing device comprises a static mixing device. 
     
     
         5 . A combustion apparatus in accordance with  claim 4  wherein the static mixing device comprises a static formation located in the primary flow stream and configured to effect at least a partial obstruction of flow of the primary flow stream. 
     
     
         6 . A combustion apparatus in accordance with  claim 4  wherein the static mixing device comprises a static formation located in the primary conduit at or towards a burner inlet end thereof 
     
     
         7 . A combustion apparatus in accordance with  claim 4  wherein the static mixing device comprises a static formation configured to impart a swirling motion to the primary flow stream. 
     
     
         8 . A combustion apparatus in accordance with  claim 4  wherein the static mixing device comprises one or more bladed formations presenting a flow deflection surface at an angle to a primary flow direction of the stream, for example at an angle to an axial flow direction. 
     
     
         9 . A combustion apparatus in accordance with  claim 4  wherein the static mixing device comprises one or more helical bladed formations. 
     
     
         10 . A combustion apparatus in accordance with  claim 4  wherein the static mixing device comprises a scroll plate. 
     
     
         11 . A combustion apparatus in accordance with  claim 1  wherein the fuel feed line is adapted to convey a pulverous combustible fuel in a dense phase with pulverous fuel to transport gas mass ratio of at least 3 at pressures of 0.5 to 5 bar and at flow speeds of at least 10 ms-1. 
     
     
         12 . A combustion apparatus in accordance with  claim 1  wherein the supply conduit is fluidly linked to the primary conduit at an angle thereto, such that there is an angle between an axial flow direction in the supply conduit and an axial flow direction in the primary conduit. 
     
     
         13 . A combustion apparatus in accordance with  claim 12  wherein a mixing device is located at or about the deviation in flow direction. 
     
     
         14 . A combustion apparatus in accordance with  claim 1  wherein the burner is a pulverized coal burner. 
     
     
         15 . A combustion apparatus in accordance with  claim 1  wherein the burner is a low-NOx burner. 
     
     
         16 . A combustion apparatus in accordance with  claim 1  wherein the burner comprises one or more secondary and/or one or more tertiary or higher order conduits comprising flow channels for the supply of further gases such as further comburant gases to the combustion site at the burner outlet. 
     
     
         17 . A combustion apparatus in accordance with  claim 16  wherein one or more secondary and/or one or more tertiary or higher order conduits are disposed annularly in concentric manner about a primary conduit. 
     
     
         18 . A combustion apparatus in accordance with  claim 1  wherein the burner comprises a core tube about which the primary conduit is annularly disposed. 
     
     
         19 . A combustion apparatus in accordance with  claim 1  adapted for oxyfuel firing. 
     
     
         20 . A combustion apparatus in accordance with  claim 19  wherein the comburant gas supply apparatus includes a source of comburant gas having a reduced nitrogen content relative to air. 
     
     
         21 . A combustion apparatus in accordance with  claim 20  wherein the comburant gas supply apparatus is additionally adapted to supply comburant air. 
     
     
         22 . A combustion apparatus in accordance with  claim 21  wherein the comburant gas supply apparatus is adapted to switchably supply either air or the comburant gas having a reduced nitrogen content relative to air to at least one conduit of the burner. 
     
     
         23 . A combustion apparatus in accordance with  claim 1 , further comprising a flue gas recirculation conduit fluidly connected in series or parallel to the comburant gas supply apparatus such that a comburant gas mixture including recycled flue gas may be supplied to at least one conduit of the burner. 
     
     
         24 . A method for combusting pulverous combustible fuel in a burner having at least a primary conduit defining a flow channel for conveying a mixture of fuel and comburant gas from a burner inlet to a burner outlet comprising the steps of:
 feeding comburant gas to the primary conduit via a supply conduit fluidly continuous therewith;   feeding the fuel to the supply conduit by a dense phase conveyance, via a fuel supply outlet within the supply conduit in particular to a point closely upstream of the burner inlet;   disposing a mixing device downstream of the fluid supply outlet to effect mixing of the pulverous combustible fuel and comburant gas.   
     
     
         25 . A method in accordance with  claim 24  comprising the step of disposing a mixing device at or about the burner inlet. 
     
     
         26 . A method in accordance with  claim 24 , wherein mixing of the pulverous combustible fuel and comburant gas is effected by supplying a dense phase stream of solid pulverous fuel into a stream containing the oxidant and by causing subsequent interaction of the flow of combustible fuel and comburant gas is with a suitable flow stream mixing device. 
     
     
         27 . A method in accordance with  claim 24 , wherein the mixing device is a static mixing device. 
     
     
         28 . A method in accordance with  claim 24 , wherein the mixing device is used to effect at least a partial obstruction of flow of the primary flow stream of pulverous fuel in dense phase and comburant gas to facilitate mixing thereof. 
     
     
         29 . A method in accordance with  claim 24 , wherein the mixing device is used to impart a swirling motion to the primary flow stream of pulverous fuel in dense phase and comburant gas to facilitate mixing thereof. 
     
     
         30 . A method in accordance with  claim 29 , wherein the primary flow stream is caused to deviate in flow direction at the mixing device and/or at the burner inlet to assist in mixing of the dense phase pulverous fuel stream and the primary comburant gas stream. 
     
     
         31 . A method in accordance with  claim 24 , wherein the burner is operated in low-NOx operation. 
     
     
         32 . A method in accordance with  claim 24 , wherein the comburant gas is one or more of: air; oxygen; a comburant gas having a reduced nitrogen content relative to air; recycled flue gas.