Substrate Coating System

Abstract

The current invention reveals equipment and the method to utilize it to produce coated honeycomb catalyst monoliths as for catalytic converters. This invention utilizes two chambers, the first to contact the substrate with a washcoat, the second to ensure removal of coating solution from the interior of the substrate. The first coating chamber uses a precisely controlled volumetric application from below ensuring complete internal contact with no overflow from the top of the substrate. Removal of excess washcoat is volumetric, providing a relatively high pressure differential across the substrate to effectively remove all of the excess washcoat from the substrate. The second chamber provides a higher differential pressure through a similar mechanism, preferentially with the substrate inverted. Washcoat removed from the substrate in chamber two impinges on water, and is re-introduced to chamber 1 through the seal cleaning mechanism. Fresh make up water is supplied to chamber 2 to replenish water removed to the seal cleaning system. After each washcoat contact with substrate in chamber 1, a precise replenishment of the washcoat in the retained washcoat solution is made, this quantity providing precisely the desired concentration of washcoat on the substrate. Any lost volume in chamber 1 coating solution is adjusted with water from chamber 2 as required. The unique nature of the invention minimizes and in some cases avoids issues common to existing technologies. These include consistent washcoat mean loading, even washcoat distribution regardless of selective adsorption due to particle size, even distribution of washcoat throughout the substrate interior, uncoated exterior, and greatly reduced waste water production.

1 . In a manufacturing process where it is desired to introduce materials in solution or suspension onto the interior surfaces of a substrate, the improvement consists of a coating system which is comprised of: 
 a. a cylindrical coating chamber having a chamber wall with an interior facing surface defining an interior space, at least one interior seal positioned within the wall having a seal face arranged to face the interior space within the chamber, the seal capable of securing the bottom lateral face of a substrate, and an impermeable moveable bottom interior wall, with an interior facing surface, such that the interior volume defined by the chamber wall, interior seal and bottom interior wall can be varied;    b. a cylindrical coating pulse chamber having a chamber wall with an interior facing surface defining an interior space, an impermeable interior facing moveable top interior wall, the exterior of said moveable wall being the moveable bottom interior wall in a coating chamber, and a bottom surface provided by a volumetric pump, where the interior volume described by the pulse chamber is confined in volume with an incompressible fluid, such that action by the volumetric pump moves the moveable top interior wall to vary the volume described by the coating chamber;    c. a metering system supplying coating solution to the coating chamber; and    d. a level indicator measuring the solution level within the coating chamber.    
   
   
       2 . The device in  claim 1 , wherein the interior surface described by the cylindrical walls of the coating chamber is formed by two truncated cones, the upper cone inverted, joined at the minimum radius.  
   
   
       3 . The device in  claim 1 , wherein the moveable interior wall of the coating chamber is a flexible diaphragm secured at the cylinder wall.  
   
   
       4 . The device in  claim 1 , wherein the non-compressible fluid in the coating pulse chamber is isothermal degasified water.  
   
   
       5 . The device in  claim 1 , wherein the seal is an inflatable flexible seal.  
   
   
       6 . The device in  claim 2 , wherein the level indicator is positioned such that the level is measured at the minimum radius of the joined truncated cones.  
   
   
       7 . The device in  claim 1 , wherein the base of a catalyst substrate is secured by the seal and the coating chamber moveable surface is displaced into the coating chamber interior space by action of the volumetric pump through the coating pulse chamber, thereby reducing the coating chamber interior space and forcing solution into the substrate.  
   
   
       8 . The device in  claim 7 , wherein the volume of solution forced into the substrate is controlled by the operation of the volumetric pump to regulate the volume and rate of solution introduced into and removed from the substrate.  
   
   
       9 . In a manufacturing process where the interior surfaces of a substrate have been coated with an excess of materials in solution or suspension, and it is desired to remove that excess solution or suspension, the improvement consists of a suction system which is comprised of: 
 a. a cylindrical suction chamber having a chamber wall with an interior facing surface defining an interior space, at least one interior seal positioned within the wall having a seal face arranged to face the interior space within the chamber, the seal capable of securing the bottom lateral face of a substrate, and an impermeable moveable bottom interior wall, with an interior facing surface, such that the interior volume defined by the chamber wall, interior seal and bottom interior wall can be varied; and    b. a cylindrical suction pulse chamber having a chamber wall with an interior facing surface defining an interior space, an impermeable interior facing moveable top interior wall, the exterior of said moveable wall being the moveable bottom interior wall in a coating chamber, and a bottom surface provided by a volumetric pump, where the interior volume described by the pulse chamber is confined in volume with an incompressible fluid, such that action by the volumetric pump moves the moveable top interior wall to vary the volume described by the coating chamber.    
   
   
       10 . The device in  claim 9 , wherein the interior surface described by the cylindrical walls of the suction chamber is formed by two truncated cones, the upper cone inverted, joined at the minimum radius.  
   
   
       11 . The device in  claim 9 , wherein the moveable interior wall of the suction chamber is a flexible diaphragm.  
   
   
       12 . The device in  claim 9 , wherein the non-compressible fluid in the suction pulse chamber is isothermal degasified water.  
   
   
       13 . The device in  claim 9 , wherein the seal is an inflatable flexible seal.  
   
   
       14 . The device in  claim 9 , wherein the level indicator is positioned such that the level is measured at the minimum radius of the joined truncated cones.  
   
   
       15 . The device in  claim 9 , wherein the coating chamber moveable surface is displaced from the coating chamber interior space, by reversing the volumetric pump through the coating pulse chamber, thereby increasing the coating chamber interior space and creating a vacuum in the suction chamber, pulling solution from the substrate into the coating chamber at a rate capable of removing entrained solution from the interior surfaces of the substrate, the removed entrained solution impinging onto the solution in the suction chamber.  
   
   
       16 . The device in  claim 1  and the device in  claim 9 , wherein the two are connected in series with a solution transfer system to recycle the recovered entrained from the suction chamber device in  claim 9  to the coating chamber device in  claim 1.