Design and Fabrication of an Automated Organic Matter Slurry Mixer for Bio Digester

Abstract

Biodigesters are designed to optimize biogas production using organic wastes, thereby attaining clean, low-cost renewable energy. In thisstudy, an automated mixer with electronically controlledstirring system was designed, fabricated and tested using local available materials for a biogas production small digester. Cow dung obtained from an abattoir in Effurun-Sapele road was used as the feedstock. The mixer is designed to mix a calculated amount of cow dung in a tank using anaerobic digestion application, resulting ina homogeneous mixture. The mixer comprises of fourmain parts:The conicalsewage tank,stirrer, hopper and electric motor. The tank (about 250L) wasmade of Mild steel (ASTM A36) of 830mm high and 600 diameters wide. The length of the stirrerof galvanizedsteel (ASTM A653) wassame asthe height of the tank.While the hopper and electricmotor were 220mm high and 2Hp (approximately 2800rpm). Experimental conditions results revealed relationship between vital parameters wherein a direct proportionate relationship was established for the operation time, feed content mass rate, volume of mixing requirements and output slurry. From the experimental results obtained, mixing 50kg of biowaste (cow dung) with 50litres of water, produced 74litres of slurry matter while increasing the mixture to 150kg of organic matter with a corresponding volume of 150litres of water, produced 221litres of slurry matter. The total cost for the design and fabrication of the automated mixer was estimated at ₦281,000. The results also showed that the designed mixer was environmentally sustainable. Finally in order to improve on the quality and performance of this design, additional features andcomponents like: flushing system, tires for easy mobility and a mechanical pump for transferringthe slurry to a biodigester should be incorporated.