Development and performance evaluation of a mini horizontal flash dryer

Abstract

Cassava (Manihot esculenta) is a major staple crop in Nigeria, as cassava itself and its products are found in the daily meals of Nigerians. Currently, cassava crop is undergoing a transition from a mere subsistent crop found on the field of peasants to a commercial crop that will be grown in large quantities in plantations. A flash dryer was designed, fabricated, assembled and tested following the standard procedures. The flash dryer is a mechanized way of drying cassava mash for mass production of cassava flour, for flour mills, confectionery and pharmaceutical industries. The traditional method of producing cassava flour, results to low product quality and quantity for industrial usage because the mode of drying is dependent on climatic conditions and susceptible to contamination. The equipment was tested using already prepared cassava mash dewatered to a moisture content of 40%. Twenty five samples of this prepared cassava mash at varied temperatures of 70°C, 80°C, 90°C, 100°C and 110°C were subjected to different air velocities of 5 m/s, 10 m/s, 15 m/s, 20 m/s and 25 m/s. The equipment was fed at the rate of 60 kg/h. Air velocities of 5 m/s and 10 m/s were too low to convey the cassava mash and not all the material fed into the dryer went through. Air velocities of 20 m/s and 25 m/s were too high and do not allow enough drying time instead, the materials formed knots. Thus, these velocities and their corresponding temperatures were not appropriate for use in this dryer. At air velocity of 15 m/s all the materials went through and the combination of this velocity (15 m/s) with the air temperature of 90ºC the first constant moisture content of 12.4% was obtained. The same moisture content was also obtained at a temperature of 100°C and 110°C at air velocity of 15 m/s. The flash dryer is very effective in drying cassava mash; it can be used to dry products to safe storage moisture content level.