| 摘要 |
The invention provides an improved pan granulation process for the production of low-water or substantially anhydrous nitrogenous compounds. Hot nitrogenous melt and cooled particulate solids are fed to a rotating pan to form a cresent-shaped bed of rolling or tumbling particles, the thickness or depth of the bed increasing in the direction towards the periphery of the pan and its overflow sector, i.e. position 2 o'clock to position 6 o'clock when the pan surface is regarded as a clock face and the rotation of the pan is counter-clockwise. The cooled solid particles are fed to the pan at a point where the depth of existing material is small, desirably substantially zero, preferably in position 7 to 8 o'clock, if need be by feeding the particles through a tube or the like which extends into the tumbling material on the pan to the proximity of the surface of the pan itself. Subsequently, the cooled particles will then be covered by and with warmer particles tumbling over them. Further, the temperature of the product material as discharged from the pan is controlled to and maintained at about 4 DEG to 25 DEG C below the melting point of the material, and the main part of the melt is sprayed on to the surface of the bed within a zone in the quadrant 12 to 3 o'clock where the coarser particles appear, whereby the highest temperature of the bed will be restricted to a surface layer within this zone. |
