The catalytic performance of two types of catalysts, an ion-exchange resin, Purolite D5081 and an immobilised enzyme, Novozyme 435, was compared for the esterification pretreatment of used cooking oil (UCO) for the preparation of biodiesel. The reactions were carried out using a jacketed batch reactor with a reflux condenser. The effect of mass transfer limitations was investigated and it was shown that internal and external mass transfer limitations were negligible. An immobilised enzyme, Novozyme 435, was investigated because it has been shown to give high free fatty acids (FFAs) conversion. This catalyst has been compared to an ion-exchange resin, Purolite D5081, which was developed for the esterification of UCO for the production of biodiesel. It was found that a conversion of 94% was achieved using Purolite D5081 compared to 90% conversion with Novozyme 435. However, the optimum methanol to FFA ratio for Purolite D5081 was 98: 1 compared to 6.2:1 for Novozyme 435. In addition, it has been found that with Novozyme 435 there are side reactions which result in the formation of additional fatty acid methyl esters (FAMEs) and FFAs at longer reaction times. (C) 2013 Elsevier Ltd. All rights reserved.

Thermal lens (TL) spectroscopy in a dual-beam configuration was applied in a study on biodiesel and oil-biodiesel blends. The goal of this work was to evaluate the behavior of the thermal and mass diffusivities that arose when oil was added to biodiesel and to verify the capability of the method to identify small concentrations of triacylglycerol in biofuel. When transitioning from pure biodiesel to a blend consisting of 98% biodiesel and 2% soybean oil, the thermal diffusivity decreased 15% and the mass diffusivity increased 59%, which indicated that both parameters can provide significant information about the presence of oil in biodiesel. Therefore, TL spectroscopy can be a useful method for certifying the quality of biodiesel and biodiesel blends. Crown Copyright (C) 2012 Published by Elsevier Ltd. All rights reserved.

On purpose of studying volume expansion of CO2 + oil system at near critical and supercritical conditions of CO2, a pressure-volume-temperature (PVT) cell with visible window was used for measuring the liquid volume of CO2 + kerosene, tetradecane, white oil and mixing oil, and the solubility of CO2 in the oils at 313.15 K with different pressures. The results of the study showed that the dispersion state of CO2 molecules in oil phase under near critical or supercritical condition of CO2 play a dominate role for increasing the volume of CO2 + oil systems, especially for light fraction oil, and as pressure being increased, the solubility of CO2 in oil increases which cause increasing of the distance between oil molecules and decreasing of intermolecular force operating within oil molecule, consequently caused the oil volume expansion. (C) 2013 Elsevier Ltd. All rights reserved.

The objective of this study was to investigate solvent extraction and in situ transesterification in a single step to allow direct production of biodiesel from jatropha seeds. Experiments were conducted using milled jatropha seeds, and n-hexane as extracting solvent. The influence of methanol to seed ratio (2:1-6:1), amount of alkali (KOH) catalyst (0.05-0.1 mol/L in methanol), stirring speed (700-900 rpm), temperature (40-60 degrees C) and reaction time (3-5 h) was examined to define optimum biodiesel yield and biodiesel quality after water washing and drying. When stirring speed, temperature and reaction time were fixed at 700 rpm, 60 degrees C and 4 h respectively, highest biodiesel yield (80% with a fatty acid methyl ester purity of 99.9%) and optimum biodiesel quality were obtained with a methanol to seed ratio of 6:1 and 0.075 mol/L KOH in methanol. Subsequently, the influence of stirring speed, temperature and reaction time on biodiesel yield and biodiesel quality was studied, by applying the randomized factorial experimental design with ANOVA (F-test at p = 0.05), and using the optimum values previously found for methanol to seed ratio and KOH catalyst level. Most experimental runs conducted at 50 degrees C resulted to high biodiesel yields, while stirring speed and reaction time did not give significantly effect. The highest biodiesel yield (87% with a fatty acid methyl ester purity of 99.7%) was obtained with a methanol to seed ratio of 6:1, KOH catalyst of 0.075 mol/L in methanol, a stirring speed of 800 rpm, a temperature of 50 degrees C, and a reaction time of 5 h. The effects of stirring speed, temperature and reaction time on biodiesel quality were not significant. Most of the biodiesel quality obtained in this study conformed to the Indonesian Biodiesel Standard. (C) 2013 Elsevier Ltd. All rights reserved.

This paper compares the laboratory-based fireside corrosion tests on superheater/reheater materials in simulated air-firing combustion conditions with oxy-firing combustion conditions (with hot gas recycling before flue gas de-sulphurisation). The gaseous combustion environment was calculated based on a specific co-firing ratio of CCP with Daw Mill coal. The fireside corrosion tests were carried out using the deposit recoat'' test method to simulate the damage anticipated in specific environments. A synthetic deposit (Na-2 SO4:K2SO4:Fe2O3 = 1.5:1.5:1 mol.) which has commonly been used in fireside corrosion screening trials and is a mix that forms alkali-iron tri-sulphate (identified in many investigations as a cause of fireside corrosion) was used in these tests. The air-fired tests were carried out at temperatures of 600, 650 and 700 degrees C and oxy-fired tests were carried out at temperatures of 600, 650, 700 and 750 degrees C to represent the superheater/reheater metal temperatures anticipated in future power plants with and without synthetic deposits, with four candidate materials: T92, HR3C and 347HFG steels; nickel-based alloy 625 (alloy 625 was only tested with screening deposits). The progress of the samples during their exposures was measured using mass change methods. After the exposures, the samples were examined by SEM/EDX to characterise the damage. To quantify the metal damage, pre-exposure micrometre measurements were compared to the post-exposure image analyser measurements on sample cross-sections. The trends in corrosion damage in both air and oxy-firing conditions showed a bell-shaped'' curve, with the highest metal damage levels (peak) observed at 650 degrees C for air-firing and 700 degrees C for oxy-firing tests. However, at 600 and 650 degrees C similar damage levels were observed in both environments. The shift in peak corrosion damage in oxy-firing condition is believed to be the presence of higher levels of SOx, which stabilised the alkali-iron tri-sulphate compounds. Generally, in both air and oxy-firing conditions the mean metal damage was reduced with increasing the amount of Cr in the alloys. However, at the highest temperatures in both air-firing (700 degrees C) and oxy-firing conditions (750 degrees C) the metal damage of nickel based superalloy 625 was higher than HR3C. (C) 2013 The Authors. Published by Elsevier Ltd. All rights reserved.

The study focuses on the generation and distribution of mineral species in fly and bottom ashes. These were formed during a fluidised co-combustion of a fossil fuel (coal) and a non-fossil fuel (tyre rubber) in a small fluidised bed combustor (7 cm x 70 cm). The pilot plant had continuous fuel feed using varying ratios of coal and rubber. The study also focuses on the lixiviation behaviour of metallic elements with the assessment of zinc recovering. (C) 2012 Elsevier Ltd. All rights reserved.