Development of a Mix-kneader for Bar Soap Production

Abstract

Drying neat soap is one of the key steps in the process of manufacturing bar soap. Currently, small and medium-scale local processors in Uganda rely entirely on tarpaulins and buckets to dry neat soap. These methods are labour intensive and take a lot of time (about 24 hours) to dry neat soap from 29-35% (w.b.) to the required moisture content of 15% - 21% (w.b.). Therefore, the aim of this research was to the development of a Mix-kneader for bar soap production in order to facilitate local production of bar soap. First, the different parts of the machine were designed and simulated in order to achieve optimal dimensions. For simulation, Finite element analysis (FEA) of the shaft assembly and computational fluid dynamic (CFD) analysis of the kneading process were done. This was accomplished by using SolidWorks and ASNYS Workbench software. Fabrication and assembling of the component parts was done and finally, performance and economic evaluation of the machine was carried out. Performance evaluation results of the machine at the ‘No’ load test showed that the machine can run freely without too much noise and there were no visual breakdowns. At ‘Full’ load test, the Mix-kneader was able to dry 180 kg of neat soap in an average time of 15.5 minutes. The average machine capacity was approximately 560 kg/h with a drying efficiency of 83.4%. The drying rate of the machine was calculated as 2.13 kg of water per minute. Soap was able to cool from an average initial temperature of 64.9 oC to an average temperature of 33.3 oC. The machine was able to discharge most of the dry soap from the kneading trough with a discharge efficiency of 77.1%. The material wastage was calculated as 1.31% which can be attributed to the fabrication errors. Economic analysis results revealed that the prototype can be a viable venture for small and medium soap processors since the machine Benefit-Cost ratio was 1.68. This shows that the processor can easily meet his/her daily expenses when using the Mix-kneader. The machine is affordable to processors and can be fabricated from any workshop since it is made up of readily available and locally sourced materials. After the performance evaluation, it was recommended to change the discharge mechanism to a mechanism that will ensure that fine soap particles (noodles) are got to ease the next production steps. Also, a continuous cooling system must be designed to increase the machine drying rate and efficiency.