Flash pyrolysis of sunflower oil cake for production of liquid fuels
Introduction
The future depletion of fossil fuels and environmental pollution make the investigation of new and renewable energy resources important. Also, substantial increases in oil prices have forced countries to consider other sources for commercial production of synthetic fuels.
Biomass, as an energy source, has both advantages and problems, like all energy sources. However, the facts that (a) it provides cleaner synthetic fuels than do coal, shale and tar sands and (b) that about 14% of the world's energy is derived from biomass in various forms mean that it must play a significant role in both global and national energy planning [1].
Since biomass materials are abundant, inexpensive and renewable resources, their conversion to synthetic fuels and chemical feedstocks has emerged as an attractive alternative during the past decade. There has been a growing interest for upgrading energy in terms of more easily handled fuels, namely gases, liquids and charcoal [2], [3].
Of the available biomass conversion options, flash pyrolysis processes that maximize the liquid product may be used to produce low grade fuel directly or else fuels may be upgraded to higher quality liquid fuels. In addition, the possibility exists that chemicals may be recoverable directly from the liquid product. Moreover, a medium value heating gas and char are generated, both of which are good quality fuels [4].
Each product class can be commercially viable. In this respect, it is very useful to understand how the product distribution depends on process conditions and feedstock properties. From this point of view, there are a number of waste and biomass sources considered as potential sources of fuels and chemical feedstocks [5], [6], [7], [8], [9].
Energy requirements in Turkey are increasing, while energy production is rather stable. The known deposits of petroleum, natural gas and hard coal in Turkey are very limited, but tertiary lignite deposits are found extensively throughout Turkey. The proven reserves of lignites amount to 8×109 metric tons [10]. These lignites with high sulphur content, low calorific value, and high moisture content are the main cause of coal-based pollution. Therefore, Turkish researchers have investigated the alternative use and upgrading of Turkish coals [11], [12]. However, Turkey has extensive biomass resources. From this point of view, there are a number of waste and biomass sources being considered as potential sources for fuels and chemical feedstocks [13], [8]. Biomass resources consisting of forest residue, wood mill residue, agricultural waste and municipal wastes, have an important role to play in the primary energy production of Turkey. Total energy produced from biomass was 348 PJ in 1992 [14].
Turkey's geographic and climatic conditions are suitable for growing energy crops. Based on the total production of cereals (26.9 million tons) and oil-seeds (4.0 million tons) it is estimated that 53–60 million tons of agricultural residues are produced annually in Turkey, 60% of which can be used for energy purposes. Thus, sunflower oil [7], cotton seed oil [15], and rapeseed oil industry wastes [16] and latex-producing plants [17] are being considered as feedstocks for a future thermochemical demonstration unit in Turkey. The Turkish sunflower oil industry generates 800 000 tons of extraction residue (cake) per annum. Sunflower press cake has already been studied as a raw material for synthetic fuels in a fixed bed reactor [7].
Flash pyrolysis experiments were performed on sunflower press cake in a tubular transport reactor. The effects of final temperature, nitrogen flow rate and particle size on the yields of the pyrolysis products were investigated. Then, the chemical composition of the pyrolytic oil was investigated using chromatographic and spectroscopic techniques, 1H NMR, IR, elemental analysis, column chromatography and GC.
Section snippets
Material
The pressed oil cake sample investigated in this study was taken from sunflower oil factories around Eskişehir located in central Anatolia. Sunflower press cake is the biomass remaining as a by-product of industrial processes after removal of the oil by pressing. Prior to use, the sample was air dried, ground in a high-speed rotary cutting mill, and then screened to give fractions Dp<0.224, 0.224–0.425, 0.425–0.850 mm in size. The materials used were found to consist of 16 wt.% oil, 22.3 wt.%
Product yields
Fig. 1 shows the product yields of sunflower press cake in relation to final pyrolysis temperatures at 450, 550 and 700°C for the particles of 0.224–0.425 mm size under a fixed sweep gas velocity of 100 cm3 min−1. The yield of conversion increased from 77 to 87.7%, when the final pyrolysis temperature was increased from 450 to 700°C. As shown in Fig. 1, the yields of product were affected significantly by the pyrolysis temperature. In general, the yields increased to an optimum value with
Conclusion
In this study, flash pyrolysis experiments of sunflower (Helianthus annuus L.) oil cake were performed in a tubular transport reactor under nitrogen atmosphere.
The highest liquid yield of ca. 45% was obtained at a final pyrolysis temperature of 550°C with a particle size of 0.425–0.850 mm, and nitrogen flow rate of 300 cm3 min−1.
The bio-oil is a mixture of aliphatic and aromatic hydrocarbons having an empirical formula of CH1.512O0.175N0.070, H/C molar ratio 1.73 and O/C molar ratio 0.175 at
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