Theoretical modelling and experimental investigation of the convective drying kinetics of biomass in an improved solar tunnel dryer

ABSTRACT

There is rapid depletion of fossil fuel worldwide due to the increase in population and usage of resources, hence alternate sources of fuels are needed. Bio oil production using pyrolysis is of interest. For the pyrolysis method, the moisture content in the biomass should be minimized and the solar tunnel dryer is affordable. The drying rate in the solar tunnel is dependent on global radiation, absorptivity of biomass and surface, dryer temperature, humidity and velocity of air. Analysis of theoretical and experimentation studies of the solar tunnel dryer with different coloured soils having different heat absorption values for switch grass, rice straw and sugarcane trash is the main objective of this paper. Dry air temperature of 78°C and 63°C for theoretical and experimentation studies, respectively, is obtained for the rice straw with soil absorptivity of 0.65 corresponding to yellow coloured soil and maximum moisture removal rate of 380 g/h theoretically and 346 g/h experimentally is obtained. This proposed design and analysis can be used for choosing the soil colour and absorptivity for the respective biomass material with air inlet velocity and global radiation.

KEYWORDS:

• biomass
• drying kinetics
• solar tunnel dryer
• absorptivity
• moisture removal rate
• parallel flow
• cross flow