The Research On Drying Theory And Process Parameters Of Molded Pulp Packaging Products

Pulp mold packaging product (paper mould product for short) is a kind of elaborate paper product, which is made of pulp of waste paper or plant fibred. Using metal mold with lots of very small mesh and bringing proper pumping pressure to make the pulp cling to the metal mold, the pulp mold product is shaped after being dewatered, taken out of mold, drying and formed with hot pressure. Pulp mold packaging product has developing prospect, which is light , dissolvable and accords with the green environment protecting code and the developing needs of packaging industry after connecting with international. But the questions of energy consuming and distortion have limited developing of manufacture in some in a way.There are two main way to drying wet pulp mold product, one is drying inside the mold and the other is using hot wind outside of the mold. Because of larger throughput, most companies use the hot wind drying lines now. The main factors of hot wind drying lines are drying temperature and wind speed. Improper drying parameters will not only increase the expenditure of energy, but also cause stronger distortion.This paper analyses the drying theory foundation of pulp mold packaging product and set a clear shape of drying model equation. The drying process of pulp mold product as wet porous media is researched and the differential coefficient models of heat and mass transfer is inferred in the drying process. Using hot wind drying experimental equipment to test the drying characteristics of the pulp mold, based on the tests data, the drying characteristics is researched on the effects to drying speed and drying efficiency of different wind speed and drying temperature. The shrinkage coefficient at different drying temperature is got by testing the product's shrinkage. Based on thin-lay model and testing data, the thin-lay model of pulp mold product is founded at constant-speed drying moment and down-speed moment. Internal moisture model is found on tests and heat transfer differential coefficient equations to simulate the internal moisture distribution of pulp mold product. The models and theories of this paper react on the parameters of the real production.