Modeling of a double pass belt conveyer dryer of yerba mate

Abstract

Yerba mate is an herbal tea produced in the central part of South America. One of the main steps of the process is drying. Among the different types of dryers which are used at present, the double pass belt conveyer dryer is the most energy efficient. The increase in wood prizes used as fuel, has generated a demand from industrial producers to improve the thermal efficiency of the process. In order to do this, a numerical model of a double deck dryer of yerba mate has been developed to study the way of improving the energy efficiency and propose modifications to the present working conditions in industry. The good of fitness of the model was determined using experimental data from two industrial dryers. The results of the model were that using hot air at 100 °C and a solid mass flow rate of 4,000 kg/h, the energy efficiency was of 40.60%. Simulating the process at different drying conditions, it was found that the energy efficiency of the dryer could be improved by recirculating 15% of the exhaust air (63.70%), or drying at 120 °C and using a higher solids mass flow rate of 6,200 kg/h with an energy efficiency of 46.21%.