Design, Construction and Performance Evaluation of a Combined Coffee Dehulling and Polishing Machine

Abstract

In spite of the facts that coffee is highly economical and can boost the country’s revenue, coffee production is fast declining in Nigeria and the participation of farmers has become very low. This may be attributed to inadequate processing technology as result of the high level of drudgery involve in the shelling of the coffee bean by manual method. Therefore, there is need to develop a dehulling and polishing machine that will help increase both the quality and production of coffee seed. This work was aimed at the design, construction and performance evaluation of a combined coffee bean dehulling and polishing machine. The two unitsdehulling and polishing units were incorporated in a single machine in order to prevent drudgery associated with the traditional method of dehulling and separation of the hull from the dehulled coffee bean seed. The first unit of the machine consist of a hopper; through which the coffee was fed into the the machine, and dehulling cylinder; which houses the dehulling shaft that dehulls the bean. The second unit of the machine consists of the polishing drum and brushes, attached to the dehulling shaft. The performance of the machine was evaluated following optimum operating condition of the length of dehulling shaft, speed of rotation of the dehulling shaft and the rotating brushes attached to the rotating shaft in polishing unit of the machine. Based on this conditions, the worked optimally at the rate of 180kg/hr. the result showed that the performance of the machine were 56.67% and 64.66% respectively for dehulling and polishing unit. This was obtained at a dehulling head of 500rpm as the speed of the dehulling shaft.