Indirect Dryers for Biomass Drying—Comparison of Experimental Characteristics for Drum and Rotary Configurations

Abstract

This paper focuses on indirect biomass drying. It compares the operating characteristics of a laboratory-scale drum dryer and a pilot-scale rotary dryer. Before the design of an industrial dryer for a specific material, it is important to experimentally prove the process and to determine the drying characteristics of the material. To verify the portability of experimental results for indirect dryers, a drum dryer with indirect electric heating in a laboratory scale was designed and built to test and study the process of indirect drying. Based on the results obtained on a small-scale device, a prototype of a pilot steam-heated rotary dryer was designed and manufactured. A broad range of experiments with green wood chips and wet bark from open-air storage with moisture contents of 50 to 65 wt % were carried out on both dryers. The drying curves indicating the process, the square and volumetric evaporation capacities, and the drying energy consumption were obtained and compared, and the feasibility of indirect drying for these tested types of biomass was confirmed.