Particle extrusion

Abstract

A die is provided for extruding elongate particles suitable for use in catalysis. The die comprises a plurality of channels extending from an inlet to an outlet. From the inlet to the outlet each channel comprises a first section with a helical bore with a non-circular cross-section, and a second section with a cylindrical bore. The cylindrical bore of the second section which has a diameter equal or greater than that of the first section. The second section is at least twice as long as a diameter of the first section.

1 . A die for extruding elongate particles suitable for use in catalysis, the die comprising a plurality of channels extending from an inlet to an outlet, wherein from the inlet to the outlet each channel comprises a first section with a helical bore with a non-circular cross-section, and a second section with a cylindrical bore which has a diameter equal or greater than that of the first section, wherein the second section is at least twice as long as a diameter of the first section. 
     
     
         2 . The die as claimed in  claim 1 , wherein the first section has a helical trilobal form. 
     
     
         3 . The die as claimed in  claim 1 , wherein a length of the first section is at least equal to a pitch of the helical bore. 
     
     
         4 . The die as claimed in  claim 1 , wherein the second section is substantially circular in cross-section. 
     
     
         5 . The die as claimed in  claim 1  wherein each channel of the die further comprises between the inlet and the first section a tapered inlet section wider at the inlet than at the first section, wherein an angle of taper for the tapered inlet section is between 30 degrees and 60 degrees. 
     
     
         6 . The die as claimed in  claim 1 , wherein each channel is separated from each adjacent channel by a land at both the inlet and the outlet. 
     
     
         7 . The die as claimed in  claim 1 , wherein the diameter of the second sections of the channels is 10 to 50% greater than the diameter of the first section of the channels. 
     
     
         8 . The die as claimed in  claim 1 , wherein the inlet forms an inlet plane, and the outlet forms an outlet plane, and wherein the inlet plane and the outlet plane are not parallel. 
     
     
         9 . The die as claimed in  claim 1 , wherein the die is provided in two or more modules which may engaged with or detached from each other, such that the first section of each channel is provided in one module and the second section of each channel is provided in another module. 
     
     
         10 . A method of making helically formed extrudate particles for use in catalysis, comprising:
 providing an extruder with a die as claimed in  claim 1 ;   preparing a starting mixture for extrusion;   feeding the starting mixture through the die of the extruder; and   separating extruded material from the die of the extruder to provide the helically formed extrudate particles.