| Fresh camellia oleifera has high moisture content,so it needs to be dried in time after harvest,otherwise it is prone to mildew,and the squeezed camellia oil is likely to cause cancer after consumption.At present,it is difficult to distinguish between genuine and fake camellia oil,and the price disparity of camellia oil is extremely detrimental to the healthy development of the camellia industry.Such a severe situation puts forward high-quality requirements for tea oil.Through experiments and analysis,this paper explores the law of moisture and heat transfer during the hot-air drying of camellia seeds,establishes a drying mathematical model,reveals the heat and mass transfer mechanism of camellia seeds,and proposes a new drying process for camellia seeds,which is the development of actual production and related equipment.Provide theoretical support.The work content of this article mainly includes the following 4 aspects:(1)The experiment studied the influence of hot air temperature and loading density on the hot air drying process of camellia seeds at a constant temperature and constant wind speed.It was found that the hot air drying process of camellia seeds was mainly controlled by the diffusion of moisture inside the material.The hot air temperature was the main factor affecting the drying process.The influence of density on the drying characteristics of Camellia oleifera seeds is much smaller than that of temperature.The drying process is mainly composed of an acceleration phase and a deceleration phase,and there is no obvious constant speed phase.According to Fick’s second law,the effective diffusion coefficient of water in the hot air drying process of camellia seed was calculated and the activation energy of camellia seed drying was calculated.Under these conditions,the Logarithmic model can well describe the hot-air drying process of Camellia oleifera seeds at constant temperature and wind speed.(2)Simulating the actual production of camellia seed hot pressing process,researching the influence of hot air temperature and hot air speed on the drying process of camellia seed after the tailing,found that the hot air temperature can still significantly affect the drying process,and the hot air speed also affects the hot air drying process of camellia seeds major factor.Under this condition,the model of Wang et al.can well describe and predict the hot-air drying process of camellia seed under this working condition.(3)Taking hot air temperature and hot air speed as factors,acid value,peroxide value,and drying time as response values,using Central Composite Design(Central Composite Design)design experiment to find the best process for constant temperature hot air drying of camellia seeds:hot air The wind speed is 2.1m/s,the hot air temperature is 60.5℃,and the drying time is 607min.At this time,the acid value of tea oil is 1.72 and the peroxide value is 0.12%.The verification test verifies the theoretical value well.(4)The three-stage variable temperature hot air drying process is optimized with the weight of drying time:acid value:peroxide value=2:1:1,The mathematical model of variable temperature drying was constructed,and the optimal process of stepwise variable temperature hot air drying of camellia seeds was obtained:the hot air speed was set to 2m/s,and the hot air temperature was set to 55℃ for 67 minutes,and then the hot air temperature was adjusted to 60℃ for 213 minutes.,And finally adjust the temperature of the hot air to 65℃ and dry for 297 minutes.The results of verification experiments and optimization design solutions are well verified.Compared with the best process of constant temperature drying,the optimal process of segmented variable temperature drying is improved by 16.7%under the setting of optimized design target and weight ratio(drying time:acid value:peroxide value=2:1:1).Provide scientific basis and theoretical guidance for the development and industrialization of related equipment for the new hot-air drying method of camellia seed. |
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