Design and fabrication of steam roaster for shea nut

Abstract

Sheanut (Butyrospernum paradoxum) is an oil rich tropical tree crop, which is indigenous to the West African savannah zone. In Nigeria, most of the shea nut roasters are made of light mild steel materials with openings. The source of heat for the roasting is open fire. This takes time and the mild steel can easily get rusted and contaminate the product. In addition, open fire roasting has the disadvantage of producing burnt crushed kernels which in turn lead to black shea oil formation, loss of vital and essential nutrients. A shea nut roaster which makes use of steam as source of heat energy was designed and fabricated to be used in roasting shea nut prior to extracting oil from them. It was developed to address the aforementioned problems. The equipment consists of heating unit, roasting unit, power transmission unit and the supporting frame. A gear motor of 0.25kW was selected to supply power to the shaft whose end was welded to the stirrer. The roasting unit consists of three compartments: roasting chamber, steam chamber and insulator chamber. The heating unit has two pipes: water inlet pipe and steam delivery pipe. Also, charcoal burner was attached to the heating unit to help boil the water for steam to form; this steam will then be transported by the steam delivery pipe to the steam chamber which in turn heats up the outer surface of the roasting chamber and thus the crushed nuts inside are roasted through the heat being supplied. The machine was fabricated with about 90% local materials. Test results of the roaster using shea nuts indicate successful heating/roasting, the nuts were not scorched or burnt, rather they were looking dry but fresh, this indicates that the design of the machine suits its purpose for roasting shea nuts prior to oil expelling . Also, roasting capacity of 45kg/hr was achieved. The successful development of this machine will reduce drudgery and time taken associated with the traditional method of roasting shea nuts and therefore will increase productivity and utilization.