Design and construction of a shea nut oil screw press expeller.

Abstract

Vegetable oils and fats have gained popularity in food, cosmetic, soap, pharmaceutical and medical industries for the production of cooking oil and margarine, pomade, toilet soaps, drugs and medical ointments respectively. Recently, they have found their uses in energy and automotive industries as biodiesel and engineering industry as cooling fluid in machining process and. lubricants for machine components. The objectives of this work are: to design a small scale screw press oil expeller for shea nut oil extraction; to fabricate the components of the expeller based on the design specifications and to test the expeller after fabrication and assembly of the components. While in designing and in material selection, consideration will be given to the techno economic status of the micro and small scale shea oil processors who are the intended. users of the machine. The functional. parts of the machine included barrel, worm shaft, prime mover, oil outlet, cake outlet, hopper, pulley, stove, transmission belts and bearings. The Worm shaft is at an increasing diameter while the screw system is at a decreasing pitch, a combination that is. essential for obtaining maximum pressure for oil extraction and cake extrusion process. In operation, the gradually built-up pressure along. the worm shaft travel conveys, crushes, grinds, presses and squeezes oil out of the seeds into the oil outlet via the oil channel. The residual cake from where the oil is extracted is extruded out of the cake outlet in form of flakes. Heat from the stove helps break the latex content of shea kernels for easy squeezing and flow of oil. Powered by a 4hP motor, the expeller has oil extraction efficiency, Oil yield and extraction loss of 8.439%, 3.785% and 121978% respectively. The expeller can be used by small scale shea oil extraction in rural and urban communities. A cottage shea nut oil processing plant based on this technology can provide employment for at least two persons at the same time providing shea oil/butter at affordable costs for rural dwellers. The expeller has an initial cost of UGX 384500 which includes the cost of material, machinery and hired labor to construct the material. With a monthly depreciation of UGX 32041.679 interest: of UGX. 8010.42, total operating cost of 38450 per month and monthly expected revenue of UGX 308581 from sale of shea oil (butter, the investment in the expeller has a payback period of I .46 months. The investment seems viable since it has a benefit/cost ratio of 6.78.