Development Of Stevia Rebaudiana Drying-Cleaning Device

As a sweetener and sugar substitute,stevia has the characteristics of pure nature,high sweetness,and low calories.It is a sugar source with great development potential,and has been favored by the international sugar market and consumers.favorite.Aiming at the problems of rising agricultural cost in our country,decreasing annual planting area of sugar crops,transfer of rural labor,and low mechanization level of stevia production in the south,a stevia drying-cleaning device was developed.By comparing the effects of different drying methods(cold air,hot air,infrared,and infrared-hot air drying)on the stevia drying efficiency,an infrared-hot air combined drying method was proposed to clarify the drying characteristics and optimize the drying process.Based on the drying The stem and leaves of the stevia are mixed,and a differential brush cleaning device is designed.Through the kinematic analysis and the simulation of the airflow field of the FLUENT air separation chamber,the air inlet angle and the uniformity of the wind field by the spoiler are clear.And conducted performance test research to obtain better working parameters.Finally,a stevia drying-cleaning device was designed to make the treated stevia reach the industry standard "double ten" index(that is,the moisture content and Impurities are less than 10%).This study can provide a reference and theoretical basis for dry storage,cleaning and impurity removal in mechanized production of stevia rebaudiana in the south.The main research contents and conclusions are as follows:(1)In order to explore the fast and efficient drying method of stevia,the drying time and energy consumption were used as evaluation indicators.The cold,hot air,infrared,and infrared-hot air combined drying technology was used to study the drying characteristics of stevia.Under the same conditions,it was found that infrared-Compared with hot air drying,the time and energy consumption of hot air drying are reduced by 36.8% and 25.2%,90.5% lower than the infrared drying time,and 94.0% lower than the cold air drying time.An infrared-hot-air combined drying process was proposed for stevia storage.Based on the analysis of infrared drying theory,an experimental device for infrared-hot-air combined drying of stevia was developed.(2)The infrared-hot air drying characteristic curve and drying rate curve of stevia were obtained through experiments.The research results show that the stevia drying process includes the preheating accelerated drying stage and the deceleration drying stage.The order of factors affecting drying is: hot air temperature> Radiation distance>Dehumidifying power;Increasing hot air temperature and reducing radiation distance can shorten the drying time.Reasonable dehumidifying power is beneficial to reduce drying power consumption.The best process parameters of stevia infrared-hot air combined drying are hot air temperature 120 ℃,The dehumidification power is 240 W,the radiation distance is 140 mm,the drying time is 6.57 minutes,and the energy consumption is 1.25 k W · h.This conclusion provides a reference for the design of a continuous drying device.(3)Taking Stevia Shoutian 3 in Ganzhou,Jiangxi as a test object,the kinetic theory of the separation of stems and leaves by a differential belt brush was analyzed,and the motion parameters of the differential belt brush were obtained.Based on the stevia leaves and impurities(gravel,Stem,etc.)have a large difference in suspension speed.Using FLUENT software,a simulation of the airflow field of the air separation chamber with the air inlet angle in the range of 20 ～ 40 ° and the spoiler was carried out,and the movement parameters of the cleaning device were clearly obtained.A differential brush cleaning device was developed.Based on the comprehensive evaluation index of loss rate and impurity rate,the optimal working parameters were determined through orthogonal test research.The research results show that the installation of the spoiler can improve the uniformity of the wind speed in the bellows.The best working parameters of the differential belt cleaning device are: the inlet angle is 40 °,the relative belt speed is 50mm/ s,and the fan power is 50 HZ.The impurity rate is 5.12%,the loss rate is 2.07%,and the feed is 30 kg / h dry leaves.In this process,the impurity ratio and loss rate are greatly reduced compared to manual cleaning,and the machine cleaning speed is about 2 times faster than manual cleaning.(4)The infrared-hot air heating system,adjustable conveying system,automatic dehumidification circulation system and air-selection cleaning system of stevia are designed,the key structural parameters are clarified,and a continuous stevia drying-cleaning is developed.The device can quickly mix stevia with stems and leaves with a moisture content of 70% and an impurity content of more than 30%,and then dry and clean them to less than 10%.