Objective: To optimize spray drying process of Equiseti Hiemalis Herba dispensing granule for preparing qualified intermediates. Method: Taking flour yield and particle size distribution as indicators to screen the auxiliary materials category.This research was studied based on the Plackett-Burman design in Minitab 16 software

taking flour yield as indicator

screening out three major factors (inlet air temperature

solid content ratio and feed rate) influenced the spray drying process

and determining the level of non-main factors.On this basis

with transfer rate of kaempferol

moisture absorption rate of fine powder and flour yield as indexes

Box-Behnken was employed to optimize process parameters. Result: Optimum spray drying process conditions were obtained as follows:adding 3%micro-silica into Equiseti Hiemalis Herba extract with solid content ratio of 20%

temperature of feed liquid 65℃

inlet air temperature at 151℃

intake air volume of 4 m3·min-1

feed rate of 33 mL·min-1.Under these conditions

transfer rate of kaempferol was 94.2%

moisture absorption rate of fine powder was 20.6%and flour yield was 85.0%. Conclusion: This optimized spray drying process is stable and feasible

which can provide basis for mass production of Equiseti Hiemalis Herba dispensing granule.