Kajian Pengering Rotari Tipe Co-Current untuk Pengeringan Sawut Ubijalar

Abstract

Rotary drying is a very complicated process that implies not only thermal drying but also movement of wet material within the dryer. The objective of this research were to evaluate performance of rotary dryer, to identify amount of energy consumption which are used during the drying process, to develop model of rotary drying and to identify drying cost per kg of sweet potato grates. Drying characterisctics of product need to be established because of important information for the design, prediction, and modelling. The model of rotary drying was constructed based on energy and mass balance. The differential equations were solved by simultaneous-numerically. This model applied to predict temperature dryer chamber, temperature product, moisture content and RH. The result showed that the performance of rotary dryer depends on feed rate sweet potato grates into drying chamber. High feed rate could decrease temperature in drying chamber. The residence time of all experiments were 18 minutes. Hold-up of all experiments in this study were relatively low that ranges 9-36 kg. The specific energy consumption in all of the experiments was between 5.51-14.26 MJ/kg H2O. The high feed rate (3 kg/1 min) had the lowest specific energy consumption. Conversely, the lowest feed rate (3 kg/4 min) had the highest specific energy consumption for all experiments. The high total efficiency could be found from high feed rate, the feed rate (3 kg/1 min) is highest total efficiency for all experiments. The model can be used to obtain temperature profiles of air and the product in dryer chamber. Using the model, change of air temperature and product during drying were successfully predicted. Coefficient of determination (COD) between measured and calculated ranges 0.819-0.992, respectively. However, the model could not predict moisture content and RH accurately. The drying cost of grates is Rp 1 494 per kg wet grates. It is relatively expensive for drying.