Energy & Fuels 2001, 15, 659-665
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Classification of Volatile Products Evolved from the Temperature-Programmed Co-Pyrolysis of Turkish Oil Shales with Atactic Polypropylene (APP) Levent Ballice* University of Ege, Faculty of Engineering, Department of Chemical Engineering, 35100 Bornova, Izmir, Turkey Received September 18, 2000. Revised Manuscript Received January 19, 2001
Temperature-programmed co-pyrolysis of Turkish oil shales with atactic polypropylene (APP) was investigated. The aim of this research was to determine the volatile product distribution and product evolution rate of co-processing of oil shale with APP. A series co-pyrolysis operation was performed with oil shale and APP using a 1:3, 1:1, 3:1 total carbon ratio of oil shale to plastic. A fixed bed reactor was used to pyrolyze a small sample of an oil shale and APP mixture under an inert gas flow (argon). A special sampling technique was used for collecting organic products eluted from the reactor at different temperature and time intervals. The co-pyrolysis products were analyzed by capillary gas chromatography and the total product evolution rate was investigated as a function of temperature and time. n-Paraffins and 1-olefins in aliphatic fractions of pyrolysis products were classified as a carbon number. In addition, the recovery of total organic carbon as an organic volatile product was determined. The assessments were based on incorporating the results on temperature-programmed pyrolysis of oil shale1,2 and APP. The effect of co-processing of oil shale with APP was determined by calculating the difference between the experimental and the hypothetical mean value of conversion of total organic carbon into volatile products. The effect of kerogen type of oil shale on co-pyrolysis operation was also investigated. Conversion into volatile hydrocarbons was found higher with an increasing APP ratio in the oil shale-APP systems while C16+ hydrocarbons and the amount of coke deposit were lower in the presence of APP.
Introduction Synthetic gaseous or liquid fuels are obtained by converting a carbonaceous material to another form. The most abundant naturally occurring materials suitable for this purpose are coal, oil shale, and tar sand. It has estimated that the worldwide deposits of oil shale are equivalent to 400 billion tonnes of shale oil, 30 billion tonnes of which are recoverable under existing technological conditions.1-3 Over 5 billion tonnes of oil shale reserves in seven areas in Turkey have been characterized by Mineral Research and Exploration Institute. Some of the largest deposits are Go¨ynu¨k-Bolu (2.5 billion tonnes) and Beypazari-Ankara (1 billion tonnes).1-3 Like these conventional natural energy resources, most organic waste materials such as municipal solid waste (MSW), lignocellulosic waste, and plastics are also potential energy resources. The majority of MSW is landfilled, and recovery of energy from these sources, especially transportation fuels, can have an economic importance.3 The level of plastic recycling is expected to increase during the next 10 years from * E-mail:
[email protected]. (1) Ballice, L.; Yu¨ksel, M.; Sagˇlam, M.; Schulz, H. Fuel 1996, 75, 453. (2) Ballice, L.; Yu¨ksel, M.; Sagˇlam, M.; Schulz, H. Fuel 1997, 76, 375. (3) Ballice, L.; Yu¨ksel, M.; Sagˇlam, M.; Schulz, H.; Reimert, R. Fuel 1998, 77, 1431.
the present level of about 10% to about 15-25% of all the plastic waste. Recycling of plastic waste by other techniques such as hydrogenation, feedstock recycling, or energy recovery will also increase during this period, while the amount of plastic waste that is disposed as landfill will drastically decrease.4 The dominant components of MSW-type waste plastics (mainly polyethylene, polystyrene, polyethylene teraphthalate, and polypropylene) are rich in carbon and hydrogen so that the possibility of converting waste plastic into liquid fuels would appear to be a logical alternative to plastic recycling.3,4 The conversion, oil yield, and its composition depend on the type of plastic.5 Thermogravimetric analysis showed that the propensity of the different polymers to decompose decreased according to the series polyisobutadiene > low-density polyethylene (LDPE) > polypropylene (PP) > highdensity polyethylene (HDPE). In addition, relative to liquefaction source materials such as oil shales, these waste plastics are hydrogen-rich so that co-processing of oil shale with plastics could be another way to recycle waste plastics into useful products.3 There is considerable interest in the efficient conversion of waste plastics and waste plastic mixed with coal into clean hydrocar(4) Herbst, H.; Hoffmann, K.; Pfaendner, R.; Zweifel, H. NATO ASI Series, 1997; Vol. 351, p 73. (5) Ades, H. F.; Subbaswamy, K. Fuel Process. Technol. 1996, 46, 207.
10.1021/ef0002041 CCC: $20.00 © 2001 American Chemical Society Published on Web 03/31/2001
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bon fuel or other valuable products such as lubricants.6,7,8 It has been suggested that the addition of plastic into the coal during liquefaction may result in an enhanced coal conversion and oil production compared to the yields obtained when coal alone is reacted.6,8 The argument for this synergistic effect is that waste materials such as plastics and rubber tires possess a high hydrogen content, and may therefore serve as an inexpensive hydrogen source aiding the dissolution of coal during the liquefaction.3,6 Atactic polypropylene (APP) is the side product of polypropylene production and because the structure of the polymer chain is not regular, APP is not resistant to chemical attack and not stronger than other type of PP such as isotactic PP and syndiotactic PP. Thus, APP is an undesired and unemployed product in the petrochemical industry. In this study, the temperature-programmed co-pyrolysis of Turkish oil shales with APP was investigated by using a new, highly efficient sampling technique. Pyrolysis products were swept out from the reactor and mixed with a reference gas (20 mL min-1 of 0.507 vol % neopentane in N2) before passing them through the sampling system. Fractions were collected in preevacuated glass ampules sealed with a gas burner, and samples were analyzed later by capillary gas chromatography using a special design sample introducing system.9 This sampling technique for gas-vapor multicomponent mixture was developed by Schulz et al.9 This technique offers a number of advantages: simplification of sampling as compared with conventional procedures of fractionation for product recovery, safe handling and storage of samples, decoupling of sampling from analysis, and sampling in small time intervals, which allows nonstationary systems to be studied.9 The purpose of this study was to determine the temperatures at which the product evolution rate is a maximum, to classify the n-paraffins and 1-olefins in the co-pyrolysis product by carbon number at each desired temperature. The recovery of total organic carbon of co-pyrolysis sample mixtures as aliphatic hydrocarbons was determined and compared with the recovery in the pyrolysis operation of oil shale and APP samples, individually. The effect of APP ratios on the co-processing of oil shale with APP was determined by calculating the difference between the experimental and the hypothetical mean value of conversion of total organic carbon into volatile products. The effect of kerogen types of oil shale on co-pyrolysis operation were also investigated. For that purposes, Go¨ynu¨k oil shale (kerogen type-1)10 and Beypazari oil shale (kerogen type-2)10 were used. Experimental Section Samples. The model plastic used in this research was APP in gummy form which was obtained from Petkim Petrochemi(6) Ochoa, R.; Woert, H. V.; Lee, W. H.; Subramanian, R.; Kugler, E.; Eklund, P. C. Fuel Process. Technol. 1996, 49, 119. (7) Feng, Z.; Zhao, J.; Rockwell, J.; Baily, D.; Huffmann, G. Fuel Process. Technol. 1996, 49, 17. (8) Ding, W. B.; Tuntawiroon, W.; Liang, J.; Anderson, L. L. Fuel Process. Technol. 1996, 49, 17. (9) Schulz, H.; Bo¨hringer, W.; Kohl, P.; Rahman, N. M.; Will, A. Deutsche Gesellschaft fu¨r Mineralo¨lwisssenschaft und Kohle E. V., DGMK-Projekt 320, 1984. (10) Ballice, L.; Yu¨ksel, M.; Sagˇlam, M.; Schulz, H.; Hanogˇlu, C. Fuel 1995, 74, 1618.
Ballice Table 1. Elemental Analysis and Fisher Assay of Go1 ynu 1k and Beypazari Oil Shale (wt %)1,2,3,9 Go¨ynu¨k-Bolu
Beypazari-Ankara
Ultimate Analysis of Oil Shales moisture 3.8 C (total) 47.2 C (organic) 46.3 C (inorganic) 0.9 CO2 3.3 H 5.8 N 1.3 S (total) 2.2
0.6 12.9 7.7 5.2 19.0 1.3 0.3 1.5
Fisher Assay 31.8 9.6 3.6 51.2
6.4 1.1 0.7 91.2
Composition of Gas Product 1.5 10.0 39.1 15.3 34.1
2.7 5.4 52.7 4.0 35.2
C H N S
Elemental Analysis of Shale Oil 76.1 11.3 1.1 1.5
79.6 11.4 1.3 1.3
C H N S
Elemental Analysis of Residue 37.9 1.7 1.5 0.8
shale oil gas decomposition water residue H2 CO CO2 CH4 C2-C7
8.5 0.3 0.03 0.3
Table 2. Go1 ynu 1 k Oil Shale and APP Amount and Ratios Used in Temperature-Programmed Co-Pyrolysis Go¨ynu¨k oil shale (g)
APP (g)
total carbon ratio
0.13 0.27 0.39
0.22 0.15 0.07
1:3 1:1 3:1
Table 3. Beypazari Oil Shale and APP Amount and Ratios Used in Temperature-programmed Co-pyrolysis Beypazari oil shale (g)
APP (g)
total carbon ratio
0.48 0.96 1.45
0.22 0.15 0.07
1:3 1:1 3:1
cal Company in Turkey. The plastic samples were ground in a liquid nitrogen-cooled jaw mill until the desired particle size was obtained. The sample was sieved to obtain
