Omar Aboelazayem

An experimental-based energy integrated process for biodiesel production from waste cooking oil using supercritical methanol

Biodiesel has been recognised as one of the effective, green, renewable and sustainable fuels. It is derived from renewable living resources either animal fats or vegetable oils. Biodiesel production in the absence of catalyst using supercritical methanol has recently been receiving significant attention. Non-catalytic transesterification reaction eliminates the difficulties of catalyst preparation and separation processes. Although it has shown high conversion for the reactants with relatively short reaction time in comparison with the conventional catalytic transesterification processes, it has some disadvantages including higher reaction temperature and pressure, large excess of methanol to oil (M:O) molar ratio and higher energy consumption. In an attempt to mitigate these problems, an experimental study followed by process design/integration for biodiesel production from waste cooking oil (WCO) has been performed. A low-quality WCO collected from local restaurants has been selected as a feedstock for the reaction. The experimental phase of the transesterification reaction together with an optimisation procedure resulted in the optimised conditions of M:O molar ratio of 37:1, reaction temperature of 253.5 oC, reaction pressure of 198.5 bar in 14.8 min. The maximum yield was 91%. In addition, kinetics of the reaction has been studied concluding an irreversible pseudo first order reaction with a reaction rate constant of 0.0006 s-1. Moreover, thermodynamics of the reaction has been studied at a temperature range of 240 - 270 oC with resulting frequency factor and activation energy of 4.05 s-1 and 50.5 kJ/mol. A kinetic reactor has been simulated using the experimentally determined kinetic and thermodynamic data. The enthalpy content of the reactor product stream has been used to separate most of the unreacted methanol in an adiabatic flash drum. Finally, a scheme has been developed for an energy integrated process in order to maximise the heat recovery. Energy savings resulted from the developed heat exchanger network (HEN) have been concluded as 32.2 % and 23.8 % for both heating and cooling energies respectively, in comparison with an existing process energy requirements in the literature. The amount of heat exchanged for each unit has been determined in addition to composition, temperature and pressure of the streams. Vacuum distillation column has been designed to separate the unreacted triglycerides from biodiesel in order to fulfil the quality restrictions of the final biodiesel product.

A comparative study on biodiesel production from waste cooking oils obtained from different sources using supercritical methanol

Biodiesel has been considered as a reasonable replacement fuel for petroleum diesel. It has many advantages over petroleum diesel including its biodegradability and non-toxicity. In addition, it provides free aromatics and sulphur combustion and it is a greener fuel with lower carbon monoxide and hydrocarbons emissions. However, biodiesel has lower heating value and it is relatively more expensive than petroleum diesel. In an attempt to reduce the cost of biodiesel, waste cooking oil (WCO) has been considered as a competitive feedstock. It also provides more sustainability for the produced biodiesel as it is a result of transformation of waste to greener source of energy. The main concern for using WCO as a feedstock for biodiesel production is the presence of high concentration of free fatty acids (FFA), which result in saponification reaction while using the conventional alkaline catalysed process. Saponification lowers the biodiesel yield by preventing the separation of biodiesel from the product. In this study, a non-catalytic method for biodiesel production from WCO using supercritical methanol has been investigated. Two different feedstocks with different FFA concentration have been examined. Response surface methodology (RSM) using Box Behnken Design (BBD) and Central Composite Design (CCD) has been employed to analyse the effect of different reaction variables including methanol to oil (M:O) molar ratio, temperature, pressure and time on biodiesel yield. Numerical optimisation has been applied to determine the optimum conditions for maximum production of biodiesel for each feedstock. It has been concluded that the feedstock with higher FFA concentration produce higher biodiesel yield within the same reaction conditions. This result indicates the significance of using supercritical methanol technique for feedstocks with high FFA concentration as it enhances both esterification of FFA and transesterification of triglycerides (TG) to fatty acids methyl esters (FAME).A possible solution is studied to solve the global solid waste, air pollution, and energy crisis issues. Rice straw is an abundant biomass that is often disposed of by open-field burning. The carbohydrates and sugars in rice straw can be acid hydrolysed to produce furans which are the building blocks of a fuel known as ethoxymethyl furfural, which has an energy density similar to gasoline. A model was created to represent the concentration of the different components present in the reactor with respect to residence time.

Optimising biodiesel production from high acid value waste cooking oil using supercritical methanol

In this study, biodiesel production from a typical Egyptian waste cooking oil (WCO) with high acid value content (18 mg KOH/g oil) has been analysed by studying the main factors affecting biodiesel and glycerol yields. Response Surface Methodology (RSM) via Central Composite Design (CCD) has been used to analyse the effect of four independent variables, i.e. methanol to oil (M:O) molar ratio, temperature, pressure and time on the reaction responses. A quadratic model for each response has been concluded representing the interrelationships between reaction variables and reaction responses. In addition, the predicted models’ adequacy has been evaluated through Analysis of Variance (ANOVA) method. Numerical optimisation technique has been applied to conclude the optimum reaction conditions for maximum production of biodiesel resulting in 98% and 2.05% for biodiesel and glycerol yields at M:O molar ratio, temperature, pressure and time of 25:1, 265oC, 110 bar and 20 minutes, respectively. Experimental validation has been analysed for the predicted optimum conditions resulting in 98.82% biodiesel yield with 0.83% relative error.