Technical report on the assessment of improved drying systems for high quality cassava products

Abstract

Typically, the square type batch bin dryers with product heating through the perforated plated at the base of the bin is used in Ghana. Bin dryers from five High Quality Cassava Flour (HQCF) processing companies in Ghana were assessed. Detail technical evaluations were performed on two of the bin dryers. The Ahlborn Gmbh ALMEMO 2890-9 advanced measurement and data logging device was used to measure temperature, moisture, air flow rate, electrical energy consumption and heat transfer in the bin dryers. Additionally, a point and measure infrared thermometer was used to measure the surface temperatures of the bin dryer. During drying, random samples were taken every 30 minutes from the bin and the moisture content analyzed in the laboratory using the oven drying technique. Based on the technical evaluation of the bin dryers in Ghana, technical modifications to the existing dryers have been identified. A new design for bin dryer has been proposed. The present heat exchangers are about 50% inefficient. Extra piping in the exchangers have been proposed. To improve efficiencies, the assessed bin dryers need at least 50 mm thickness lagging of the walls and floors to improve the temperature reaching the products by 20 °C. Additionally inclusion of a control system for reduction of the blower fan speed especially the drying moisture between 25 and 12 % for the cassava products has been proposed to reduce the drying time by at least 1 to 2 hours making energy saving costs