The Experimental Research Of Drying Characteristics Of Biomass At Low Temperature

In China, biomass energy is an important supplement to traditional fossil energy. Drying is an important part in the processing of biomass material. For many thermosensitive biomass materials, such as fruits and vegetables, temperature of drying medium (e.g., hot air) should not be too high, so drying at low temperature becomes an appropriate selection, for example from room temperature to 60℃. In addition, low-quality energy can be used for drying at low temperature, which has advantages in energy conservation.In this paper, the main work is researching drying characteristics at low temperature of biomass through experiments. Firstly, the author designed and built an experimental setup for drying biomass particles at low temperature. The drying medium (i.e., hot air) temperature, humidity ratio and velocity can be adjusted in specified range and the mass of biomass particles can be measured instantaneously. Based on the instantaneous mass, the drying characteristics curve can be deduced.Secondly, the author measured the drying characteristics of eight biomass particles (fruits and vegetables), and analyzed the effects of drying medium parameters (temperature, humidity ratio and velocity), the size of biomass particles on drying characteristics. Experimental results show that the side length of cubic biomass particles in the range 5 mm～10 mm and drying at low temperature can fulfill the requirements of storage and long-distance transport. Smaller size of biomass particles and higher temperature of drying medium help increase the drying time significantly. In real applications, the environment determines the humidity ratio which does not need to be controlled artificially. The hot air velocity in the range 0.2m/s-0.4m/s has unimportant effect on the need drying time. The experimental results provide the guidelines for designing drying devices.The author further did the drying experiment for a fix bed at low temperature with sweet potato, and analyzed the distribution characteristics of the moisture content along the hot air flow direction.Finally, the author designed and built a moving bed low-temperature drying setup and analyzed its basic performance. The work provides the foundation for subsequent research.