| In order to solved the problem of easily corroded 418 type heat-exchange equipment and optimized its heating performance,the text used a excellent conductivity non-metallic refractory heat-exchanger, which was designed for including sixheat-exchange tubes with a diameter of 270 mm, three layers configuration, each layer of the two, three in the same vertical planing s-shaped connected. The heat-exchanger supporting a tunnel type stove with disposable feeding coal. Used the 418 type metal fin heat-exchange equipment for reference, we comparatively studied the heating performances of two kinds of bulk curing-barn. The results are as follows:1. This research designed a non-metallic refractory heat-exchanger installed in b ulk curing-burn with a tunnel type stove with disposable feeding coal(The furnace co ver is cast-iron). The furnace's length is 2700 mm,wide is 500 mm,hight is 650 mm and the volume is 0.88m3 which is 1.1 times bigger than the theoretical value.The cast-iro n furnace cover's section is half-circle and its length is 2980 mm, inside diameter is 530 mm. The heat-exchange equipment includes six heat-exchange tubes and some high-te mperature brackets is made by high-aluminium fireclay which have excellent conductiv ity. Each heat-exchange tube's lentgh is 2200 mm, diameter is 270 mm, thickness is 10 mm. The tubes forms a structure which is transversely vertical and it have double r ow and three layers. Three tubes in the same vertical plan s-shaped connected. The h eat-exchange equipment total heat dissipation area is 1.2 times bigger than the theore tical value and it can meet the needs of the tobacco curing. As the equipment is re movable structure, it is easy to transport and install. It is also equiped end caps wich can be opened in both side which is easy to clean up the dust and dirt in heat-ex change tubes. The non-metallic refractory heat-exchange equipment has good corrosio n resistance and solves the defect that the metal heat-exchange tube is easily rusty and corrodible.2.From the point of heating and temperature performance, relative to metal heat-exchange equipment, non-metallic materials heating equipment has a slower rate of warming and cooling.This is more in line with the current bulk-curing process of slow warming and the delopment of stable temperature field.In different stage of tobacco curing, the experimental treatment which installed non-metallic heat-exchanger had lower level and vertical temperature difference and more stable internal temperature distribution.The level and vertical temperature difference presented the basically consistent inverted "V" type changing trend.3.The change of heat-exchanger's material and structure had reduced energy consumption of curing.Compared with the metall heat-exchanger which commonly used at present,non-metallic heat-exchanger was more economical. The thermal efficiency of middle and upper leaf was 54.24% and 54.43% respectively. Compared with the contrast, the cured tobacco leaves of the non-metallic heat-exchanger had higher proportion of me-dium-high grade and lower energy consumption that the coal consumption reduced by 22.5% and 22.5% respectively. The analysis of the conventional chemical content showed that using the non-metallic heat-exchanger to cure the tobacco can promote the transformation of starch degradation of upper leaves and improve the total sugar and reducing sugar content.4. During the curing process, the tobacco leaf filtration process is relatively stabl e in the barn which installed the non-metallic heat-exchanger. Filtration process can be basic consistent in different locations inside the barn. Compared themetall heat-e xchanger, non-metallic heat-exchanger can promote degradation of chlorophyll, caroten oid and starch.It also can improve the amylase activity and improve the total sugar and reducing sugar content to a certain extent. In addition, the curves of each index is relatively consistent of different shed tobacco in the the barn during the curing p rocess and its had a good consistency of tobacco leaves turning yellow and lossing water during the process.5. In different stage of tobacco curing, the non-metallic heat-exchanger tobacco's PPO activity was lower than the constrast and the difference was especially obvious when the curing process turned into the stage of fixing color. This meaned the non-metallic heat-exchanger can lower the change of non enzymatic browning reacton of tobacco curing. During the stage of fixing color, the tobacco of the non-matallic heat-exchanger's MDA content was low which meaned the cell membrane lipid peroxidation level and the probability of brown reaction is low. |
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