OPTIMIZATION OF PRODUCTION PROCESS, CHARACTERIZATION AND ENGINE TESTING OF WASTE COOKING OIL BIODIESEL

This paper analyzes the suitability of mixed waste cooking oil (WCO)biodiesel as a viable fuel for diesel engines. WCO feedstock was purchased from a Enfields Chemicals a waste cooking oil buying firm based in Durban, boiled and cleaned to remove food particles and water. The oil was then evaluated for free fatty acid (FFA) composition and acid value and other physiochemical properties. The WCO acid value was found to be higher than the stipulated value for a single-step process hence a two-step production method of esterification and transesterification was instituted. Esterification was performed using sulphuric acid and methanol at a molar ratio of 9:1, 1 wt% H2SO4, 60 °C for 90 minutes until it became 0.688 mg of KOH down from an initial value 8.67 mg of KOH. Thereafter homogenous alkali transesterification was performed with a methanol molar ratio of 6:1, 1 wt% NaOH and temperature 60 °C for 60 minutes. Four factors selected for optimization were: molar ratio, catalysts concentration, reaction time and reaction temperature. The process parameters were optimized using a combination of Taguchi method using the MINI TAB-16 programming tool and ANOVA test. A total of27 experiments were performed by varying the process parameters and manipulation of the S/N ratio. The best conditions found were molar ratio of 7:1, temperature of 65°C, catalyst concentration of 1.5wt% and reaction time of 80 minutes. In terms of influence on yield the ranking was: reaction temperature, catalysts concentration, molar ratio and reaction time. The optimal parameters resulted in an increase in yield from 93% to 96 %. The biodiesel was property evaluated and compared with fossil diesel (FD) using ASTM D6751 standards. Four fuel samples namely,FD fuel, WCO100, WCO20 and WCO40 were formulated and tested in a single cylinder Kirloskar engine for performance and emissions behavior. The results showed a maximum reduction of BTE of 17.8 % with WCO100 and a BSFC increase of 23.7 % compared with FD fuel. Emission parameters revealed a reduction in CO of 62.5 %, UBHC of 27.2 % and smoke opacity of 34.45 %. However, an increase in CO2 of 28.43 % and NOX of 27.2 % were determined when compared with FD fuel. The researchers concluded that WCO biodiesel can be utilized as an alternative fuel for diesel engines as its properties conform to ASTM D6751 and EN14214 and its combustion and emission behavior showed similar trends to those of FD fuel.