The effects of the transesterification parameters on the yield and quality of the methyl esters (MEs) produced from waste frying oil (WFO) were investigated. A two-step alkali transesterification reaction followed by silica gel purification step was applied. The investigated reaction parameters were the methanol/oil molar ratio (6:1 and 9:1), the catalyst/oil weight ratio (1.0 and 1.5 mass %) and the type of catalyst (NaOH and KOH). The physical and chemical properties of the employed feedstock and the obtained biodiesel were determined in order to investigate the effects of both the properties of the WFO and the reaction parameters on the characteristics and yields of the product. It was found that the properties of the feedstock had a determinant effect on the physical and chemical properties of the MEs, as the majority of them did not differ significantly under the studied reaction parameters. However, the reaction parameters influenced the yields of the product. Higher yields were obtained with a 1.0 than with a 1.5 mass % catalyst to oil ratio. The increasing yield with decreasing catalyst/oil ratio was more pronounced with NaOH (9.15-14.35 %) than with KOH (2.84-6.45 %). When KOH was used as the catalyst, the yields were always higher (the mean yield was 94.86 %) in comparison to those obtained with NaOH (the mean was 84.28 %). Furthermore, the efficiency of KOH in conversion of WFO to purified MEs in comparison to NaOH was even more pronounced in the case of the higher methanol/oil ratio, i.e., for the 9:1 methanol/oil ratio, the yield increase with KOH was about 2 times higher than the yield with NaOH, regardless of the applied catalyst/oil ratio.
Fundamentally based model for pressure drop in gas-flowing solids-fixed bed contactors is presented, together with a phenomenological semiempirical model for prediction of dynamic holdup. These simple models do not require any parameters that need to be determined by measurements in the actual system of interest. The predictions are compared with all available data and give good agreement for a wide range of experimental conditions, different constructions, types, and dimensions of packing and for a variety of flowing solids properties.Countercurrent flow of gas and fine solids through packed beds was patented as an idea in 1948, 1 and the first recorded industrial use occurred in 1965 (Compagnie de Saint Gobain) 2 in heat-transfer applications. The fluid dynamics of such systems received considerable attention over the years, 3-14 and this included heat-and mass-transfer studies. 8,[15][16][17] The interest in exploiting the unique features of the countercurrent gas-fine solids systems was enhanced by the studies of Westerterp and colleagues, 18,19 who proposed the use of fine solids as a regenerative adsorbent flowing through the bed of catalyst for methanol synthesis. Additional reactor-oriented studies included catalytic oxidation of hydrogensulfide 20 and regenerative desulfurization of flue gases. 17,21 The application of this type of gas-flowing solidsfixed bed contactors would be enhanced if the fluid dynamics in these systems could be fully quantified, at least in the macroscopic engineering sense. Reliable prediction of pressure drop, flowing solids holdup, residence time distribution, back mixing, and so forth, are some of the quantities needed when assessing the applicability of the "flowing" or "trickling solids" systems in a variety of processes.Previous studies resulted in a semiquantitative description of the fluid dynamics of the system and empirical correlations for determination of some quantities of interest. Three flow regimes were observed, similar to gas-liquid systems: preloading, loading, and flooding. Gas-flowing solids interaction increases with the increase in gas superficial velocity. When the terminal velocity of gas relative to flowing particles is approached, a sudden increase in pressure drop and fine solids holdup occurs, together with accumulation of solids at the top of the bed and unstable operation, which is characteristic for flooding.The complexity of the fluid dynamics of these systems did not permit, so far, a unique pressure drop equation to emerge without empirical constants. The problem is further complicated by the lack of consensus in accounting for the effects of particle shape, size, roughness, bed porosity distribution, and so forth. The models presented were often developed by fitting the data of a few studies and were not extensively tested, thus lacking in predicting ability. Moreover, the approach used was such that data on the system of interest were always needed to complete the correlation (i.e., one had to have data to predict them!). 6,10 In our earlier s...
The purpose of this work is to characterize biodiesel (i.e. methyl esters, MEs) produced from linoleic and oleic sunflower oils (LSO and OSO, respectively) by alkali transesterification with methanol and CaO as a heterogeneous catalyst under different reaction parameters. The parameters investigated were the methanol/oil molar ratio (4.5:1, 6:1, 7.5:1, 9:1 and 12:1) and the mass ratio of CaO to oil (2% and 3%). The physical and chemical properties of the feedstocks and MEs, like density at 15oC, kinematic viscosity at 40oC, acid value, iodine value, saponification value, cetane index, fatty acid (methyl ester) composition, were determined in order to investigate the effects of LSO and OSO properties and reaction parameters on the product characteristics, yields and purity. The properties of feedstock had decisive effect on the physical and chemical properties of MEs as majority of them did not differ significantly under studied reaction conditions. The MEs produced generally met the criteria required for commercial biodiesel; in fact, the only exception was in the case of iodine value of ME produced from LSO. The product yields only slightly changed with the applied conditions; the highest yield (99.22%) was obtained for ME-LSO produced at 6 mol% methanol to oil ratio, while the lowest one (93.20%) was for ME-OSO produced under the lowest methanol/oil molar ratio (4.5:1). The applied catalyst amounts had similar influence on the oil conversion to biodiesel. The yields of ME-LSOs were in general somewhat higher than those obtained for ME-OSOs under the same conditions, which was attributed to the influence of the respective feedstocks' acid value and viscosity
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