Optimization of Pelleting and Infrared-Convection Drying Processes of Food and Agricultural Waste Using Response Surface Methodology (RSM)

The use of agricultural wastes as livestock feed is an appropriate method to convert these materials into high value-added materials. These wastes have low nutritional value per unit volume and high transportation, storage and labor costs when they are used in original form. Compaction of wastes in the form of pellet is a proper solution to solve these problems. The pellet drying stage is one of the most important pellet production processes that affect the quality of the pellets. In the present study, the impacts of moisture content, particle size, inlet air temperature of dryer and infrared power of dryer were investigated on properties of physical (unit and bulk density and shrinkage) and thermal (effective moisture diffusivity and specific energy consumption) properties of pellets produced from food and agriculture wastes. The results indicated that all independent variables had a significant negative effect on unit and bulk densities. The effective moisture diffusivity increased with the increase in particle size, infrared power and air temperature dryer. Also specific energy consumption in infrared-convection drying of pellets increased with finer grinding of raw materials.