Biodiesel production from waste cooking oil using biodiesel conversion equipment

Abstract: In the last few years, biodiesel has emerged as one of the most potential renewable energy to replace current petrol-derived diesel. It is a renewable, biodegradable and non-toxic fuel. Biodiesel production using waste cooking oil (WCO) is receiving increasing attention. However, the large range of free fatty acids (FFA) content has become the main drawback for the conversion of WCO into biodiesel with single procedure, and the lack of government management of WCO makes it difficult to collect feedstock in large scale, which reduces the economic feasibility of biodiesel. In order to satisfy the requirement for producing biodiesel in miniature, efficient biodiesel conversion from WCO with high FFA was achieved via a home-made biodiesel conversion equipment. There were four sorts of feedstocks for biodiesel production, including fried chicken oil, WCO1, WCO2 and WCO3, whose acid value were 10.2, 30.8, 45.6 and 80.0 mg/g, respectively. The reaction process was involved two procedures called A and B. The procedure A was an esterification reaction to decrease the acid value and moisture of feedstocks. It was carried out with reaction temperature 60℃, methanol 10%, H2SO4 1%, reaction time 5 h, and then some byproducts were separated from the reaction mixture. The conversion rate of FFA of feedstocks was above 90% through procedure A. An orthogonal design was applied to optimize main performance parameters for the transestrification reaction of procedure B. The procedure B started with an acidic catalysis with reaction temperature 60℃, methanol 4%, H2SO4 0.1%, reaction time 5 h, followed by a basic catalysis with methanol 12%, NaOH 0.8%, reaction time 1.5 h, and then some byproducts were separated from the reaction mixture. Final product was obtained through water washing using 70 L of water. The separation of byproducts and water from the mixture reaction was accomplished by electrostatic layered process which decreased the separation time from 12 h to 1 h. The procedure B was adopted for WCO with low acid value and moisture content. With high acid value and moisture content, procedure A was used to reduce acid value, and then procedure B was utilized to complete biodiesel conversion. The equipment with unique reaction procedure can produced biodiesel from WCO with large range of acid values. The output of equipment was about 400 L/d. The yields of biodiesel from fried chicken oil, WCO1, WCO2 and WCO3 were 97.6%, 95.9%, 95.4% and 95.5%, respectively. The quality indexes of biodiesel production from fried chicken oil and WCO2 met GB\T20828-2007 except oxidation stability and total glycerin content. The oxidation stability was lower than the standard value, which could be solved by adding antioxidant. The total glycerin content was slight higher than the standard value, which could be solved by prolonging separation time. The study provided a new approach for producing biodiesel from WCO in small scale.