Development of Nozzle Plate for Granulation Process

In granulation process for plastics and raw materials of those, obtaining particle products with narrow distribution of size is important for quality control and easy handling. While there are a lot of method known to control particle size distribution, one of the most widely used applications is punched nozzle plate through which melted liquid droplets are discharged, cooled, and solidified. The purpose of this study is finding out the optimum nozzle shape to produce particles with narrow distribution of size in granulation process. In our hypothesis, one of the main causes that broaden particle size distribution in the granulation process using nozzle plate is coalescence of droplets. Once unset droplet has contact on other particles, they would coalesce into a bigger particle. We thought that cutting liquid flow line uniformly and avoiding coalescent are the most considerable points when designing the nozzle plate and developed new type of nozzle plate. The successful results with new type nozzle plate was obtained by tapering liquid flow path in the plate. The influence of taper degree and the ratio of liquid path length to bore diameter (L/D) to particle size distribution were also studied by experiment.