噴霧乾燥造粒における品質工学の適用に関する研究(2)

生成物重量の動的機能窓法による解析

抄録

In our previous study on a spray drying granulation process to improve yield, the relationship between time and yield was used for SN ratio calculations. The study resulted a significant improvement on the reduction of the product sticking to dryer surface, suggesting the importance of viewing the functionality of the process. In this report, analysis method, dynamic operating window, was used based on suggestions given by Dr. Taguchi. In the previous study, the following function was considered : Y=βM where y is the amount of material fed into the dryer and M is yield. But the water in the feeding material evaporates, and part of the product sticks to dryer surface, therefore, M is not directly to y. Similar to chemical reactions, the amount of material stuck on the dryer surface was considered the side reaction, denoted by M₂. Also the dried powder (the objective product) was considered as the main reaction, denoted by M₁. The purpose for the dynamic operating window it is to maximize the difference between situations M₁ and M₂, i. e., to maximize the main reaction and minimize the side reaction. Comparing the two analysis methods, the new analysis showed a better conformance on the gains of both SN ratio and sensitivity, indicating the superiority of the dynamic operating window approach.