Biodiesel is a renewable, biodegradable, environmentally benign fuel for use in the diesel engines. It can be produced from renewable sources such as vegetable oils or animal fats. Although this fuel has gained worldwide recognition for many years, it is not being widely commercialized mainly because it is more expensive than petroleum diesel. A cheaper feedstock, such as fryer grease, may be used to improve the economics of biodiesel. <p>Methanol is the most common alcohol used in the transesterification process due to its low cost. However, recently, ethanol has been promoted as an alcohol for use in transesterification since it can be produced from renewable resources such as switchgrass, corn and wood, thereby reducing the dependency on petroleum sources (Pimentel and Patzek, 2005). A mixture of methanol and ethanol is hypothesized to take the advantages of both methanol and ethanol. The present work is focused on the production of biodiesel from fryer grease via transesterification with various mixtures of methanol and ethanol. Also, the kinetics of transesterification from fryer grease was studied. <p> Since fryer grease contains a high concentration of free fatty acids (FFA) (5.6 wt. %) and water (7.3 wt. %), a two-step acid/alkaline transesterification process was used to produce the esters. Sulfuric acid and potassium hydroxide were used as acid and alkaline catalysts, respectively. The methanol to ethanol molar ratio was varied from 3:3 to 5:1, whereas alcohol to oil molar ratio was maintained at 6:1. After the fryer grease was transesterified, all esters met ASTM standard D-6751. The viscosity of these esters ranged from 4.7 to 5.9 mm2/s. The heating value of the esters was approximately 10% less than that of petroleum diesel. The cloud point and pour point were in the range of 1 to -1 oC and -3 to -6 oC, respectively. When the mixed alcohol was used ethyl esters were also formed at a lower concentration along with methyl esters. The dominant fatty acid in fryer grease esters was found to be oleic acid. The lubricity of kerosene fuel was improved by as much as 33 % through the addition of these esters at rates as low as 1 %. <p>For the kinetic study of alkali-catalyzed transesterification of fryer grease, the alcohol to oil molar ratio, the reaction temperature, and the catalyst loading were varied as 6:1, 9:1, 12:1; 30, 40, 50 oC; and 0.5, 1.0, 1.5 %, respectively. The ester concentration was found to rise with an increase in the catalyst loading or the reaction temperature and with a decrease in the alcohol to oil molar ratio. The overall forward and backward reaction orders were assumed to follow first and second order kinetics, respectively. The kinetic parameters were calculated using MATLAB. The conversion of triglyceride to diglyceride was found to be the rate determining step (RDS) of the overall reaction, with an activation energy of 36.9 kJ/mol.

Biodiesel is a renewable, biodegradable, environmentally benign fuel for use in the diesel engines. It can be produced from renewable sources such as vegetable oils or animal fats. Although this fuel has gained worldwide recognition for many years, it is not being widely commercialized mainly because it is more expensive than petroleum diesel. A cheaper feedstock, such as fryer grease, may be used to improve the economics of biodiesel. <p>Methanol is the most common alcohol used in the transesterification process due to its low cost. However, recently, ethanol has been promoted as an alcohol for use in transesterification since it can be produced from renewable resources such as switchgrass, corn and wood, thereby reducing the dependency on petroleum sources (Pimentel and Patzek, 2005). A mixture of methanol and ethanol is hypothesized to take the advantages of both methanol and ethanol. The present work is focused on the production of biodiesel from fryer grease via transesterification with various mixtures of methanol and ethanol. Also, the kinetics of transesterification from fryer grease was studied. <p> Since fryer grease contains a high concentration of free fatty acids (FFA) (5.6 wt. %) and water (7.3 wt. %), a two-step acid/alkaline transesterification process was used to produce the esters. Sulfuric acid and potassium hydroxide were used as acid and alkaline catalysts, respectively. The methanol to ethanol molar ratio was varied from 3:3 to 5:1, whereas alcohol to oil molar ratio was maintained at 6:1. After the fryer grease was transesterified, all esters met ASTM standard D-6751. The viscosity of these esters ranged from 4.7 to 5.9 mm2/s. The heating value of the esters was approximately 10% less than that of petroleum diesel. The cloud point and pour point were in the range of 1 to -1 oC and -3 to -6 oC, respectively. When the mixed alcohol was used ethyl esters were also formed at a lower concentration along with methyl esters. The dominant fatty acid in fryer grease esters was found to be oleic acid. The lubricity of kerosene fuel was improved by as much as 33 % through the addition of these esters at rates as low as 1 %. <p>For the kinetic study of alkali-catalyzed transesterification of fryer grease, the alcohol to oil molar ratio, the reaction temperature, and the catalyst loading were varied as 6:1, 9:1, 12:1; 30, 40, 50 oC; and 0.5, 1.0, 1.5 %, respectively. The ester concentration was found to rise with an increase in the catalyst loading or the reaction temperature and with a decrease in the alcohol to oil molar ratio. The overall forward and backward reaction orders were assumed to follow first and second order kinetics, respectively. The kinetic parameters were calculated using MATLAB. The conversion of triglyceride to diglyceride was found to be the rate determining step (RDS) of the overall reaction, with an activation energy of 36.9 kJ/mol.

A batch vacuum frying system, which processes fruits and vegetables, includes a frying pan, a surface-condenser, and a vacuum pump. With health and safety issues in mind, this research focused on developing a modified surface-condenser to prevent cavitation of the vacuum pump. The final oil-content was reduced by centrifugal de- oiling of the product under vacuum, which make the product healthier than what is currently available. The de-oiling mechanism consists of a centrifuge with a motor attached to the basket shaft, rotating up to 750 rpm (63 g units). The condenser consists of a (counter- flow) spiral-coil heat exchanger (SHE) connected to a refrigeration system that uses R404a refrigerant. De-oiling for 40 s at 300 and 750 RPM removed up to 67% and 72% of the chip’s surface oil, respectively. At 750 RPM for 10 s, 40 s, and 60 s the oil-content was reduced by 38%, 44%, and 51%, respectively. The convective heat transfer coefficient (h) of the frying oil was determined at 120°C and 140°C using the lumped capacitance method. The h-values were 217±13 W/m2K (120°C) and 258±37 W/m2K (140°C) using a copper-ball thermocouple. The h- values increased to 3.6 times during the boiling period. COMSOLTM Multiphysics was used to model the heat transfer in the vacuum fryer pan. Based on the simulation results, a 1.5 cm thick insulation material was installed in the fryer to reduce the energy losses. The refrigeration system operates at Tevap = -26°C and Tcond = 50°C with 26°C sub-cooling. Sensitivity analysis showed that the system Coefficient of Performance (COP) was about 3.87 at these conditions and compressor power requirement (CPR) was 74 W (85% efficiency) when frying 30 g of potatoes slices. The best results were obtained at Tevap = -10°C and Tcond = 40°C with 26°C sub-cooling and superheat of 5°C. The predicted COP was 4 and the CPR 70 W. The ice-formation on coils reduced the condensation rate. Reducing the refrigerant temperature to -10°C (from -26°C) reduced the condensation rate by 30%. These results show a more effective vacuum frying system for high-quality fruits and vegetables than the system previously used.