Drying characteristics of Chinese wolfberry under different drying methods and pressure drop characteristics of airflow thick-layer drying

The drying experiments of Chinese wolfberry were performed at natural drying, oven thin-layer drying and airflow thick-layer drying conditions. The influences of drying temperature and spraying alkali water on Chinese wolfberry were studied, the drying rate curves and drying characteristics were obtained.At the same time, the pressure drop in the airflow bed was simulated to investigate the influence of different factors on the pressure drop during drying process. The results showed that, the fresh Chinese wolfberry were dried to moisture content below 13% under 26 ℃ natural drying conditions, it needed103 h and 350 h for the wolfberry with spraying alkali water and without alkali water, respectively. When the fresh Chinese wolfberry were dried under oven thin-layer drying conditions, it needed 14, 10.5, 6.5 h for the wolfberry with spraying alkali water at 50, 60, 70 ℃, respectively.The temperature played a decisive role in drying rate of Chinese wolfberry.The drying rate increased significantly after spraying alkali water, and the surface of wolfberry was bright. The results of airflow thick-layer drying showed that the air velocity and porosity had significant influence on the pressure, air temperature on the pressure drop was not significant.In Re small, the Ergun equation predicted pressure drop values agreed well with experimental values. This simulation method could accurately predicted the pressure drop of airflow thick-layer drying conditions.