Ceramic filter element and method for production thereof

Abstract

The reduction of nitrogen oxides in gas is carried out, by means of selective reaction of the nitrogen oxide with the reducing agent in the in the solid catalyst. In order to achieve high catalytic activity, the above is carried out at high gas temperatures. As a rule, ceramic filter elements, coated with catalytic material are used. This does, however, give rise to the risk the catalytically active components are stripped from the filter during the hot gas filtration. A ceramic filter element with support material in the form of particles, with binder material and catalytic material is thus disclosed, whereby the binder material comprises catalytic material, or the binder material is partly replaced by the catalyst material and the support material particles ( 1 ) are connected to each other by means of the catalyst and/or binder material.

1 . A ceramic filter element, in particular a filter candle or tube, for hot-gas filtration, with a first layer in the flow direction for particle separation and a second layer forming the support body, which exhibits a support material in the form of particles, a bonding material, and a catalyst material, characterised in that: 
 The bonding material exhibits catalyst material or is at least in part replaced by the catalyst material, and that the support material particles ( 1 ) are bonded to one another by the catalyst and/or bonding material.    
     
     
         2 . The filter element according to  claim 1 , characterised in that the catalyst and bonding materials are present as bonding particles ( 2 ).  
     
     
         3 . The filter element according to  claim 1 , characterised in that the bonding particles ( 2 ) consist of 90-99% by weight of catalyst material and the remainder of bonding material.  
     
     
         4 . The filter element according to one of  claims 1  to  3 , characterised in that the catalyst material consists of one or more oxides of the rare earths and/or one or more aluminates and/or one or more silicates.  
     
     
         5 . The filter element according to one of  claims 1  to  3 , characterised in that, with the complete replacement of the bonding material, the catalyst material consists of one or more aluminates, one or more titanates, or titanium dioxide.  
     
     
         6 . The filter element according to claims  4  or  5 , characterised in that the catalyst material consists of at least calcium aluminate.  
     
     
         7 . The filter element according to one of  claims 1  to  6 , characterised in that an adherence enhancer is added to the catalyst material.  
     
     
         8 . The filter element according to one of  claims 1  to  7 , characterised in that the catalyst material is modified with promoters.  
     
     
         9 . The filter element according to one of  claims 1  to  8 , characterised in that the support material consists of SiC, mullite, or aluminium oxide.  
     
     
         10 . The filter element according to one of  claims 1  to  9 , characterised in that the proportion of the support material amounts to 60-90% by weight and that of the catalyst-bonding agent materials  10 - 40 % by weight.  
     
     
         11 . A method for the manufacture of a ceramic filter element, in particular of a filter candle, for hot-gas filtration, with a first layer in the direction of flow for the particle separation, and a second layer forming the support body, which exhibits a support material, a bonding material, and a catalyst material, in which the support body is first manufactured, and thereafter the layer for the particle separation is applied onto the support body, characterised in that: 
 The bonding material is fine-grained and mixed homogenously with the catalytic material;    That this mixture is then mixed with the support material, and;    That the resultant mixture is introduced into a mould and sintered for the manufacture of the support body.    
     
     
         12 . The method for the manufacture of a ceramic filter element, in particular of a filter candle, for hot-gas filtration, with a first layer in the direction of flow for the particle separation, and a second layer forming the support body, which exhibits a support material, a bonding material, and a catalyst material, in which the support body is first manufactured, and thereafter the layer for the particle separation is applied onto the support body, characterised in that: 
 Compound particles ( 2 ) are manufactured from the bonding material and the catalyst material; and    That these compound particles ( 2 ) are then mixed with the support material; and    That the resultant mixture is introduced into a mould and sintered for the manufacture of the support body.    
     
     
         13 . The method for the manufacture of a ceramic filter element, in particular of a filter candle, for hot-gas filtration, with a first layer in the direction of flow for the particle separation, and a second layer forming the support body, which exhibits a support material, a bonding material, and a catalyst material, in which the support body is first manufactured, and thereafter the layer for the particle separation is applied onto the support body, characterised in that: 
 At least one powder-form source material or at least one source material present in a solution, which under the effect of heat form catalytic and/or bonding properties, are mixed with the support material, and;    That the resultant mixture is introduced into a mould and sintered for the manufacture of the support body.    
     
     
         14 . The method according to  claim 12 , characterised in that calcium oxide and aluminium oxide or calcium nitrate and aluminium nitrate are used as source materials.  
     
     
         15 . A ceramic filter element, filter candle or tube in particular, for hot-gas filtration, with a first layer in the direction of flow for the particle separation, and a second layer forming the support body, which exhibits a support material in the form of particles, a bonding material, and a catalyst material, characterised in that; 
 The support material is replaced at least in part by the catalyst material.    
     
     
         16 . The filter element according to  claim 15 , characterised in that the catalyst material consists of one or more aluminates, one or more titanates, or titanium dioxide.  
     
     
         17 . The filter element according to  claim 15 , characterised in that the catalyst material consists of oxides or mixed oxides of the rare earths, with which the support materials are coated.  
     
     
         18 . The filter element according to  claim 15 , characterised in that the catalyst material consists of a mixture of at least one oxide or mixed oxide of the rare earths and at least one aluminate, one titanate, or titanium dioxide.  
     
     
         19 . A method for the manufacture of a ceramic filter element, in particular of a filter candle, for hot-gas filtration, with a first layer in the direction of flow for the particle separation in a second layer forming the support body, which exhibits a support material, a bonding material, and a catalyst material, in which the support body is first manufactured, and thereafter the layer for the particle separation is applied onto the support body, characterised in that: 
 For the manufacture of the support body 
 a) Support material and catalyst material are used which are present in fine-grain form and mixed, or;  
 b) Only support material is used which is present in fine-grain form, and these support material grains are coated with one or more oxides or mixed oxides of the rare earths and/or with one or more aluminates, one or more titanates, or titanium dioxide, or;  
 c) Only catalyst material is used which is present in fine-grain form,  
   and that these materials prepared in this manner are thereafter sintered.    
     
     
         20 . The method according to  claim 19 , characterised in that in method step b) the coating is carried out by means of the sol-gel method.  
     
     
         21 . The method according to  claim 20 , characterised in that the support material grains are sprayed with the sol in a mixer.  
     
     
         22 . The method according to  claim 19 , characterised in that in method step b) the coating is carried out by means of coating by spraying on a ceramic mud.  
     
     
         23 . The method according to  claim 22 , characterised in that the support material grains are sprayed with the ceramic mud in a mixer.  
     
     
         24 . The method according to  claim 19 , characterised in that in method step c) two grain fractions are manufactured, which are mixed with one another, and that a fine-grain sintering is carried out at reduced burn temperature.  
     
     
         25 . The method according to  claim 19 , characterised in that in method steps a) or b) the support material grains are doped with catalytically-active noble or non-noble metals.  
     
     
         26 . The method according to  claim 19 , characterised in that the catalyst and/or support material grains are doped with catalytically active noble or non-noble metals after the burning.  
     
     
         27 . The method according to  claim 25  or  26 , characterised in that the doping is carried out with platinum, palladium, rhodium, gold, silver, nickel, copper, manganese, or cobalt.  
     
     
         28 . A filter candle for hot-gas separation, which exhibits a cylindrical mould body, closed on one side, characterised in that the interior space of the mould body is filled with a bulk deposit of catalyst material and that a closure is arranged on the open side of the mould body.  
     
     
         29 . The filter candle according to  claim 28 , characterised in that the closure is formed as a porous ceramic layer.  
     
     
         30 . The filter candle according to  claim 28  or  29 , characterised in that the catalyst material consists of one or more oxides or mixed oxides of the rare earths, and/or of one or more aluminates, and/or of one or more silicates, and/or of one or more titanates or titanium dioxide.  
     
     
         31 . The filter candle according to  claim 30 , characterised in that the catalyst material consists of at least calcium aluminate.  
     
     
         32 . The filter candle according to one of  claims 28  to  31 , characterised in that the catalyst material is modified with promoters.  
     
     
         33 . The filter candle according to  claim 32 , characterised in that the catalyst material is doped with catalytically-active noble or non-noble metals.  
     
     
         34 . The filter candle according to  claim 33 , characterised in that the catalyst material is doped with platinum, palladium, rhodium, gold, silver, nickel, copper, manganese, or cobalt.