Research On Optimization Of Processing Parameters And Dedusting Technology In The Refining Production Line Of Northern Fujian Oolong Tea

The thesis took the refining production line of northern Fujian Oolong tea as the object,disscussing the design concept,technical requirement and configuration scheme of the clean and automation refining production line of Oolong tea.It focused on the process parameters optimization of colour sorting,baking and blending,whilst it studied on ventilation and dust controlling technology for baking workshop.All of these researches provided scientific basis for the reasonable operation of the refining production line and the refinement control of dust in Oolong tea.The results were as follows:1.Analysis of technical indexs in the clean and automation refining production line of Oolong Tea(1)The process of Oolong tea refining production line:tea classification?colour sorting?static visual sorting?baking?electrostatic impurity?blending?dynamic visual sorting(magnetic impurity)?sieving?rock fragment selection?mental detection?the on-line monitoring of moisture?automatic weighing?packing?finished tea.(2)The Oolong tea refining production line consists of removing impurity,baking,sieving,blending and assistant modules.Removing impurity module includes 6CSX-256 type of CCD intelligent tea color sorter,XF-6CJT-M type of static visual sorting equipment,6CDJ-280 type of electrostatic stalk sorting machine,DSB600-2980-2 type of dynamic visual sorting equipment,the magnetic force sorting tick roller,XD400 type of rock fragment sorting machine,KD8124A type of metal detector and other equipments;Baking module includes 4 sets of 6CH-25 type of electric automatic chain plate dryer;Sieving module includes PS4A type of screen machine;Blending module includes XF6CYD-80 type of transverse-pave vertical-cut of blending machine;Assistant module includes IMS-W8B type of rapid detection device for tea moisture content and XF6CZX-500 type of automatic packing equipment.2.Testing study on the optimization of process parameters of Oolong tea color sorter(1)The single factor test.The results showed that tea flow,gray threshold of No.l and No.2 color selection mirror had a significant effect on picking tick efficiency,sorting net rate and error-sorting rate.(2)Optimal parameters of color sorter combining with response surface methodology.The optimal processing parameters were as follows:tea flow 3.0 × 10-4m3/s?the gray threshold of NO.1 color selection mirror 170 and the gray threshold of NO.2 color selection mirror 180.(3)Verification of the optimization parameters of tea color sorter.The experimental values of sorting net rate and error-sorting rate were in accordance with the predicted values.Sorting net rate increased by 11.59%,whilst error-sorting rate decreased by 5.75%.The results of validation experiments suggested the good application of RSM for optimization of processing parameters on CCD color sorter of northern Fujian Oolong tea.3.Testing study on the optimization of process parameters of chain dryer machine(1)Temperature distribution in the chain dryer.The temperature on left side was higher than right side,the temperature on back side was higher than front side,which had a effect on the uniformity of tea drying quality.(2)Color chemical composition change of Oolong tea in the chain dryer.With the baking time increased,the color chemical constituents of flavonoids,thearubigins and theabrownins showed dynamic changes in Oolong Tea.The soluble sugar content was gradually decomposed,theaflavins increased,the degree of dark,red and blue color for dry tea powder deepened,and color value away from standard whiteboard increased,whilst the color of dry tea was significantly deepened.The different baking time had a significant effect on the L*,b*,de*values of tea infusion color.(3)Optimal parameters of baking process combining with response surface methodology.The model of comprehensive evaluation indexes for Oolong tea color changeswas that:F=0.372F1+0.252 F2+0.157F3+0.083F4+0.058F5.Optimization of the process conditions in the Oolong tea baking under chain dryer were that:the baking temperature was 130.97?,and the baking time was 2.32h.4.Optimizing test of the technology parameters under blending machine(1)It had a significant effect on the bulk density and angle of repose and the tea infusion color in different sieve size of Oolong tea.With the sieve size increased,brightness weakened,the degree of red and blue color for tea infusion deepened,whilst the color of tea infusion was gradually deepened.(2)The significant effect of different blending order on the stability of oolong tea product quality.The best blending order was that:the middle segment of tea as the first layer,the upper segment of tea as the second layer,and the lower segment of tea as the third layer.(3)The significant effect of different blending times on the stability of oolong tea product quality.By different brewing times,it was more ideal that lightness degree value L*in the treatment of single blending time,red and green degree value a*in the treatment of two blending times,and yellow and blue degree value b*in the treatment of B1.The total color difference degree value de*of one,two,three blending times were in accordance with CK.5.Detection and analysis of the environment parameters of natural ventilation in baking workshop(1)Effect of natural ventilation in baking workshop was poor in rainy weather of the spring.In the operation position of dryer,the average temperature was 30.35 ? and the relative humidity was 51.68%,which is over the comfortable working range of human body.(2)Under the condition of natural ventilation in baking workshop,the total tea dust content range of the dryer inlet and outlet was 21.93?49.11mg/m3,which was significantly higher than that of the tea dust allowable concentration(10 mg/m3)by the Japanese Ministry of labor?and the respective concentration range of PM2.5 and PMI0 were 0.14?0.17 mg/m3 and 0.32?0.41 mg/m3.To achieve the effect of ventilation,dust control and working environment improvent,we should take timely dedusting measures like mechanical ventilation,and pay special attention to control the total content of tea dust and prevent PM10 and PM2.5.6.Study on the dedusting technology of mechanical ventilation in baking workshop and test of its CFD simulation(1)Natural ventilation mode(M1),the temperature of dryer region was higher(orange area from 130 to 180?);the tempeture of other regions were lower(light blue area from 30 to 50?);the average temperature of each equipment was 46.44±3.21?;Mechanical ventilation mode(M2),the average temperature of whole workshop changed from 71.70 ±69.40 ? decreased to 66.80 ±68.60?,which means that mechanical ventilation had significant effects on the temperature of baking workshop.(2)The air flow distribution of baking workshop under the mechanical ventilation.The temperature trend of baking workshop was "the higher the temperature is high" and "the norther the tempeture is high";the airflow velocity trend of baking workshop was "large to small to large" in the X-Y direction;the mean-age-air trend of baking workshop was "the higher the age is large" and "the norther the age is large".(3)In case that 6 sets of axial flow fan have been installed at the top of baking workshop,would significantly increase the flow and exchange of air,reducing the temperature of the working region,reducing the mean-age-air of the overall space,significantly improving the speed of vent,changing the particle traces of airflow,forming the reasonable ventilation mode in"air inlet of below and exhaust of above",finally,achieving the remove effect of tea dust.