Boiler and Method for Operating a Boiler

Abstract

The invention relates to a boiler and to a method for operating a boiler. To effectively prevent damage to the boiler wall, in particular by corrosion, the flow speed characteristic of a furnace floor flow running horizontally to the furnace floor is determined, a source region of the horizontal furnace wall flow on at least one furnace wall is determined and an insulating gas is supplied to the source region of the horizontal furnace wall flow, in such a way that an insulating gas layer, which insulates the respective boiler wall from the flue gas, is created by the horizontal extension of the insulating gas with the aid of the furnace wall flow.

1 . Method for operating a steam generating boiler in which a combustion chamber ( 100 ) defined by boiler walls ( 101 - 104 ) is fired by combustion of fuel causing the formation of a flue gas flow ( 107 ) by means of a plurality of burners ( 105 ,  106 ), including the following steps:
 determining the flow velocity characteristics of a basic combustion chamber flow which in relation to the bottom of the combustion chamber is horizontal;   identifying a source region of the horizontal combustion chamber wall flow on at least one boiler wall ( 103 - 104 ); and   feeding an insulating gas into the source region of the horizontal combustion chamber wall flow, such that by horizontal expansion of the insulating gas by means of the combustion chamber basic flow an insulating gas layer is formed which insulates the respective boiler wall ( 103 - 104 ) from the flue gas flow ( 107 ).   
   
   
       2 . Method according to  claim 1 , wherein the feeding of the insulating gas proceeds by way of a gas feed nozzle arrangement provided in at least one combustion chamber wall which in each of a plurality of mutually adjoining planes, horizontal in respect of the bottom of the combustion chamber, includes exactly one gas feed zone which is arranged in the source region of the horizontal component of the combustion chamber wall flow associated with this plane. 
   
   
       3 . Method according to  claim 2 , wherein the gas feed nozzles are arranged in a line vertical in relation to the respective combustion chamber wall and extending along the vertical center line of the respective combustion chamber wall. 
   
   
       4 . Method according to  claim 2 , wherein the gas feed nozzle arrangement extends essentially along the burner string level of the combustion chamber. 
   
   
       5 . Method according to  claim 2 , wherein the combustion chamber is divided by an intermediate wall, and wherein the gas feed nozzles provided in the source region of the combustion chamber flow are provided in the intermediate wall. 
   
   
       6 . Method according to  claim 1 , wherein the feeding of the insulating gas proceeds by way of a gas feed slot, vertical in relation to the combustion chamber bottom provided on at least one combustion chamber wall and extending more or less continuously essentially along the level of the burner string. 
   
   
       7 . Method according to  claim 1 , wherein air is used as the insulating gas which is fed from the combustion gas supply of the combustion chamber. 
   
   
       8 . Method according to  claim 7 , wherein the content by volume of the air used as the insulating gas amounts to maximally 10%, preferably maximally 5% of the total amount of air required for the conversion of the fuel. 
   
   
       9 . Method according to  claim 1 , wherein an oxidizing gas is used as the insulation gas. 
   
   
       10 . Method according to  claim 1 , wherein an inert gas is used as the insulating gas. 
   
   
       11 . Method according to  claim 1 , wherein the insulating gas flow is generated independently in individual sections of the boiler wall. 
   
   
       12 . Method according to  claim 1  including the further steps of:
 determining volume proportions of flue gas components in the gas atmosphere present adjoining at least one boiler wall; and   regulating the insulating gas flow as a function of the determined proportions of flue gas components.   
   
   
       13 . Method according to  claim 12 , wherein the determination of proportions by volume of the flue gas components and/or regulating the insulating gas flow is performed independently from one another in individual sectors of the boiler wall. 
   
   
       14 . Method according to  claim 13 , wherein the determination of the volume proportions of the flue gas components and/or the regulating of the insulating gas flow is performed repeatedly in a plurality of measuring cycles. 
   
   
       15 . Method according to  claim 12 , wherein the flue gas components include oxygen (O 2 ) and carbon monoxide (CO). 
   
   
       16 . Method according to  claim 12 , wherein the flue gas components include also HCl and/or H 2 S. 
   
   
       17 . Steam generating boiler, including
 a combustion chamber ( 100 ) defined by boiler walls ( 101 - 104 );   a plurality of burners ( 105 ,  106 ) for firing the combustion chamber ( 100 ) by means of fuel combustion with the formation of a flow of flue gas ( 107 ); and   a gas feed device for feeding an insulating gas; wherein the gas feed device is so arranged in the source region of a horizontal combustion chamber flow on at least one boiler wall, that by horizontal expansion of the introduced insulating gas due to the combustion chamber basic flow an insulating gas layer insulating the respective boiler wall ( 103 - 104 ) from the flue gas flow ( 107 ) can be generated.   
   
   
       18 . Steam generating boiler according to  claim 17 , wherein the gas feed means comprises a gas feed nozzle arrangement provided in at least one combustion chamber wall which in a plurality of mutually adjoining planes horizontal in respect of the bottom of the combustion chamber includes exactly one gas feed zone which is arranged in the source region of the horizontal component of the combustion chamber wall flow associated with this plane. 
   
   
       19 . Steam generating boiler according to  claim 18 , wherein the gas feed nozzles are arranged in a line vertical in relation to the respective combustion chamber wall and extending along the vertical center line of the respective combustion chamber wall. 
   
   
       20 . Steam generating boiler according to  claim 18 , wherein the gas feed nozzle arrangement extends at least along the burner string level of the combustion chamber. 
   
   
       21 . Steam generating boiler according to  claim 18 , wherein the combustion chamber is divided by an intermediate wall and wherein the gas feed nozzles provided in the source region of the combustion chamber flow are provided in the intermediate wall. 
   
   
       22 . Steam generating boiler according to  claim 17 , wherein the gas feed means comprises a gas feed slot, vertical in relation to the combustion chamber bottom provided on at least one combustion chamber wall and extending more or less continuously essentially along the level of the burner string. 
   
   
       23 . Steam generating boiler according to  claim 17 , wherein the gas feed means in each boiler wall sector includes a gas feed unit ( 109 - 114 ) for the feeding of insulating gas to the surface of the boiler wall into the combustion chamber ( 100 ). 
   
   
       24 . Steam generating boiler according to  claim 23 , wherein the gas feed units ( 109 - 111 ;  112 - 114 ) associated with the boiler wall ( 103 ; 104 ) are each connected to a main line ( 121 ;  122 ) coupled separately to the combustion gas supply ( 123 ). 
   
   
       25 . Steam generating boiler according to  claim 24 , wherein each main line ( 121 ;  122 ) includes a regulating element ( 125 ) for regulating the gas flow there through. 
   
   
       26 . Steam generating boiler according to  claim 24 , wherein each gas feed unit ( 109 - 114 ) is adapted to be selectively coupled by way of a closure element ( 124 ) to the associated main line ( 121 ;  122 ). 
   
   
       27 . Steam generating boiler according to  claim 25 , wherein the regulating element ( 125 ) and/or the closure element ( 124 ) is operated as a function of the volume ratios of flue gas components determined in the gas atmosphere adjoining the boiler wall. 
   
   
       28 . Steam generating boiler according to  claim 17 , wherein the burners ( 105 ,  106 ) are arranged for linear firing of the combustion chamber ( 100 ). 
   
   
       29 . Steam generating boiler according to  claim 17 , wherein the burners ( 105 ,  106 ) are arranged for tangential firing of the combustion chamber.