Rotary double cone vacuum dryers are suitable for drying & mixing multiple raw materials, chemicals, pharmaceutical materials, crystalline materials and food products. The design combines the drying and mixing function in one simple and stable device. The operation and maintenance costs are very low. The drying times are reduced to an acceptable level. This dryer can also be used for temperature sensitive products. This is suitable for the raw materials that need to be concentrated, mixed and dried at low temperature (for example, biochemistry) products in chemical, pharmaceutical food & multiple other process industries. Particularly it is suitable for the raw materials that are easy to be oxidized, volatilized and have heat sensitivity as well as are poisonous in nature which are not allowed to destroy its crystal in drying process.The equipment can also be used as rotary evaporator.