The Parameter Optimization And Energy Conservation Study Of Mold Pulp Drying Process

Mold pulp is a kind of green packaging product which has broad market prospects. While drying technology is the most energy-intensive process in mold pulp production, so reducing the energy consumption of drying process is an effective way to conserve the total energy in mold pulp manufacturing. In this paper, the drying process of molded pulp and the condensation process of overheating drying exhaust which contains a large amount of noncondensable gas were studied, then a dry- exhaust condensation dehumidifying closed cycle system was proposed and evaluated.Experiments were performed for drying characteristics and the process dynamic model of mold pulp. The factors affecting the drying rate were analyzed; the drying model fit for the falling rate of drying stage was established, and the effective diffusion coefficient of mold pulp was also calculated to optimize the operation parameters of drying technology of mold pulp manufacturing process. With the increase of flow temperature and velocity, critical moisture content of mold pulp rises, which means the falling-rate drying period arrived in advance, however the total drying time decreases as the increase of flow temperature and velocity. The products appear a certain degree of fold and deformation under the influence of overheating air flow. The most suitable theoretical model for mold pulp’s falling rate of drying stage is the Logarithmic model, whose fitting efficiency is more than 0.985. The effective diffusion coefficient of mold pulp will increase from1.944 10 m /s to4.0667 10 m /s as the increase of flow temperature and velocity.The reliability of experiment device was verified by hot air cooling experiments. The condensation process of overheating drying exhaust which contain a large amount of noncondensable gas was studied in a horizontal pipe. The condensation efficiency of wet flue gas was analyzed, the changing of condensation heat transfer driving force and the sensible heat of wet flue gas along the cube were also studied. From the point of improving the dehumidification efficiency of wet flue gas, we should increase the inlet temperature, decrease the flow velocity and reduce the temperature of cooling water under certain conditions. From the point of improving the sensible heat recycling efficiency of wet flue gas, we should reduce the inlet temperature and the flow velocity of wet flue gas under certain conditions. But lower velocity means less dehumidification capacity for the particular condenser.A dry- exhaust condensation dehumidifying closed cycle system was proposed and evaluated. Energy conservation property of traditional open drying system, semi- closed cycle drying system and drying- exhaust dehumidification closed cycle system were compared from the aspects of energy consumption, energy utilization rate and dry area with the same processing capacity of mold pulp. For the energy utilization rate, drying- exhaust dehumidification closed cycle system shows the outstanding performance. While for the dry area, the semi- closed cycle drying system and drying- exhaust dehumidification closed cycle system were both larger than the traditional open drying system, but the increase is small, only about 8~9%. Therefore, drying- exhaust dehumidification closed cycle system is considered to be the best choice.