Production of Bio-Oil from Oil Palm s Empty Fruit Bunch via Pyrolysis

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1 Production of Bio-Oil from Oil Palm s Empty Fruit Bunch via Pyrolysis M. T. AZIZAN*, S. YUSUP, F. D. MOHD LAZIZ, M. M. AHMAD * Chemical Engineering Department, Universiti Teknologi PETRONAS, Seri Iskandar 317 Tronoh, MALAYSIA tazliazizan@petronas.com.my Abstract: -Due to the increase in crude oil prices and environmental concerns, a search for sustainable alternative fuel has gained significant attention. This involves the conversion of biomass to produce multiple types of fuels and products via pyrolysis or gasification. This work focused on synthesizing bio-oil from a type of oil palm waste, i.e. empty fruit bunch. The influences of variables such as temperature, sample size and on the amount of bio-oil produced as well as its composition were investigated. The pyrolysis process was carried out using Fixed Bed Activation Unit under nitrogen gas flow rate of approximately.1 ml/min after the sample has undergone a pretreatment process. The optimum condition for pyrolysis of empty fruit bunch was found to be at o C with particle size of 2μm and 3 hours of. Characterization of pyrolysis liquid produced in terms of density, ph, calorific value and the solid content was determined and reported Key-Words: - Bio-oil, empty fruit bunch, slow pyrolysis 1 Introduction The prospect of producing clean, sustainable power in substantial quantities from biomass in the form of agricultural residues is now arousing interest worldwide, stimulated by increasing concern over the environmental consequences of conventional fossil and nuclear fuel use [1]. In Malaysia, the feasibility to convert the abundant renewable agricultural-based materials such as palm oil solid waste into fuels is widely investigated. Here, the organic or natural wastes were available almost free-of-charge and contributes towards the environmentally clean disposal of organic or natural waste. Malaysian s government plans to tap into biomass energy production to significantly increase the contribution of renewable energy in the country over the next years. Malaysia aims to produce about MW of renewable energy from biomass in the proposed renewable energy policy measures in the Eight Malaysia Plan (21-2) [2]. High yields liquid fuels can be achieved by flash pyrolysis of biomass feedstock such as palm oil solid wastes. Rather than leaving empty fruit bunches being disposed by the land filling method which is very costly or burnt it in the furnaces and further creates air pollution, the solid waste from palm oil mill is taken as the sample under study. Oil palm solid waste will undergo pyrolysis process which is defined as a chemical degradation reaction that is caused by thermal energy alone [3]. The term chemical degradation refers to the decomposition and eliminations that occur in pyrolysis with formation of molecules smaller than the starting material. Oil palm solid wastes are low-priced and abandoned materials formed in palm oil milling process. Every ton of oil palm fruit bunch fed to the palm oil refining process will produce approximately.7 tons of palm shell,.3 tons of palm fibre and.12 tons of kernels as the solid wastes. About 8% of solid wastes are used as boiler fuel in industry while the remaining 2% are abandoned [4]. It is also estimated that approximately 1.18 x 6 tons of organic waste was released from the palm oil mills. The stringent environmental measures implemented at present and those that will be introduced in the future will inevitably affect the waste disposal practice of the mills. Empty fruit bunches from oil palm plantation (EFB) is composed of 4-% cellulose and about equal amounts (2-3%) of hemicellulose and lignin []. Although its approximate chemical constituents have been reported before [6,7,8], the physical and chemical nature of the fibrous strands prepared from oil palm empty fruit bunch has not been investigated in detail. Knowledge on this biomass is of great importance relative to its industrial processing and potential utilization in value-added products, ISSN: ISBN:

2 mitigating the environmental concerns mentioned earlier. The conversion of biomass into useful products and fuels using pyrolysis technologies to produce char, bio-oils and gaseous products is one of the most promising alternatives under study nowadays [9]. However, the chemical composition of bio-oils is very complex []. Bio-oils are mainly composed of water, organics and a small amount of ash. It can be globally represented as approximately 2 wt% water, 4 wt% GC-detectable compounds, 1 wt% non-volatile HPLC detectable compounds and around 1 wt% high molar mass non-detectable compounds. A comprehensive analysis of bio-oils involves the combined use of more than one analytical technique [9]. The pyrolysis reaction is relatively complex and results in non-equilibrium products, making their properties hard to predict. The properties of the products are heavily dependent on the pyrolysis conditions such as process temperature, the period of heating, ambient conditions, the presence of oxygen, water and other gases, and the nature of feedstock. It is a renewable liquid fuel and can also be used for production of chemicals. Slow pyrolysis, which employs lower process temperatures and longer s, favors charcoal production [11,12,13]. Currently, most research is focusing on maximizing the yield of liquid product as opposed to char. The liquid pyrolytic product can be easily stored and transported, readily upgraded and refined to produce high quality fuels and may contain chemicals in economically recoverable amounts [12]. It can be maximized by using short residence times (generally less than a few seconds) and high heating rates [14,13] that characterize the fast pyrolysis method with temperatures of approximately C [11]. Fast pyrolysis yields up to 8 wt% liquid on dry feed [1] and has now achieved a commercial success for production of chemicals and is being actively developed for producing liquid fuels. Gaseous products consisting of aerosols, true vapors, non-condensable gases, and solid char make up the balance. The compositions of each fraction are based on the reaction condition and feedstock storage. The crude pyrolysis liquid or bio-oil is dark brown in color, approximates to biomass in elemental composition and is a complex mixture of oxygenated hydrocarbon and an appreciable amount of water [11]. Oxygenated hydrocarbons are hydrocarbons combined with oxygenated functional groups hydrocarbons such as aldehydes, ketones, alcohols, acids and nitrates. The liquid has a distinctive odour - an acrid smoky smell, which can irritate the eyes if exposed for a prolonged period to the liquids. The cause of this smell is due to the low molecular weight aldehydes and acids. Biomass pyrolysis liquids differ significantly from petroleum-based fuels in both physical properties and chemical composition. The liquids are usually high in water and solids, acidic, have heating value of about half of mineral oils and are unstable when heated, especially in air [16]. The collection of liquids has long been a major difficulty in the operation of fast pyrolysis processes due to the nature of the liquid product that is mostly in the form of aerosols rather than a true vapor. Quenching, that is the contact with a cooled liquid is effective with a careful design and temperature control to avoid blockage from differential condensation. Our work mainly focused on investigating the effect of pyrolysis temperature, and sample size on the yield of the liquid products of the bio-oil produced. This paper highlighted the physical and chemical characteristics of these bio-oils and to determine the suitability of upgrading this bio-oil into useful products and fuels. 2 Experimental Study 2.1 Apparatus Fixed Bed Activation Unit The main equipment used for this study is the lab scale sized Fixed Bed Activation Unit (FBAU), which consists of a fixed bed reactor that can operate at a maximum temperature of o C at atmospheric pressure. The manufacturer for this equipment is Mahkota Technologies Sdn Bhd, Malaysia. Nitrogen gas at ml/min was used throughout the experimental run to provide inert condition inside the fixed bed. Industrial grade molecular sieve with the diameter of approximately 1 mm was used as an adsorbent to adsorb the moisture into the system. The equipment capacity for empty fruit bunch fiber is approximately 6g due to the physical characteristics of the sample. This amount makes up to 9% of the FBAU capacity. Sufficient sample amount is crucial to avoid the damaged of the rod sensor inside the instrument. ISSN: ISBN:

3 2.2 Experimental procedure Sample Pre-treatment The empty fruit bunches were washed to separate the sample from physical impurities and volatile component. The samples were heated at 1 C to remove the water content inside the sample and weighted regularly to determine the moisture content of the sample. The samples were weighed until they reached constant weight to ensure all the moisture content was dried out. The samples were ground and sieved in the range of 12µm to 1mm and further screened into different size fractions (12 µm, 2 µm and µm respectively). The treated samples of the empty fruit bunches were stored in the desiccators to maintain the low moisture content of the samples Experimental Parameters using FBAU Three main parameters were tested in the experiment i.e. the effect of temperature, particle size and contact time in FBAU. Two main analyses were tested onto the samples i.e. the proximate analysis test (the moisture content post-reaction, ash content and volatile matter) using weight analysis calculation and pyrolysis liquid characterisation (density using densitometer, ph using ph paper and calorific value using bomb calorimeter). 3 Results and Discussions 3.1 Heating and drying of samples Moisture content (% M oisture content vs heating time 1 2 Time (hr) Fig. 1: Moisture content versus heating time The sample was dried for a period of 24 hours at the oven temperature of 1 C. The weight of the biomass sample was taken periodically until the weight remained constant and Figure 1 is plotted. The results in Figure 1 shows that the moisture content (on wet basis) of empty fruit bunch is 8.3 wt% in the beginning of the drying ( hour). After further drying, a gradual decrease in moisture content was observed untill the end of the period. A rapid moisture loss during the initial stage of drying was observed for the first 7 hours for the samples. The empty fruit bunch moisture content reduced to 4 wt% in the first hour of drying but after to 6 hours, the rate of moisture loss became slower. When heat is applied into wood particles, the particles begin to dry more intensely at the outer boundary as the temperature is higher [17]. Whereas the bound and free water tend to move outwards by convection and diffusion although some may migrate towards the inner, colder parts of the solid, where condensation occurs. However, as the drying process continued, the penetration of heat into the deeper part of the wood particle and moisture movement to the surface became harder due to material resistance. This results in a slower rate of drying and this explains the occurence mentioned above. 3.2 Effect of temperature on product yield Relation between % liquid yield and temperature for 1.hr Temperature (degc) 12um 2um um Fig. 2: Percentage of liquid yield versus temperature at different particle size with 1. hours Relation between %liquid yield and temperature for 3hr Temperature (degc) 12um 2um um Fig. 3: Percentage of liquid yield versus temperature at different particle size with 3 hours ISSN: ISBN:

4 Relation between % liquid yield and temperature for 4hr Temperature (degc) 12um 2um um Fig. 4: Percentage of liquid yield versus temperature at different particle size with 4 hours The influence of temperature on the liquid products obtained from biomass samples via pyrolysis were examined in relation to the yield of the product liquids and the results was plotted in Figure 2. As the temperature increases from 4 o C to 6 o C, the conversion of empty fruit bunch to liquid is increased to maximum of 26 wt% while char yield decrease. It can be shown that liquid yield increases as the temperature increased but decreased at much higher temperature. This is because, more oil cracking occurs at higher temperature resulting in higher gas yield and lower oil yield [18]. High temperatures continue to crack the vapors and the longer the vapors are at high temperature, the extent of cracking were greater. Although secondary reactions become slower of approximately below 3 o C, some secondary reaction continues down to room temperature in the liquids, which contributes to the instability of the pyrolysis liquid. Figures 3 and 4 demonstrate the effect of temperature at 3 and 4 hours of reaction and for the sample size of 12μm and μm. It is observed that the liquid yield continue to increase as the temperature increased. However, the maximum liquid yield still occurs at o C with a particle size of 2μm since the particle size of 2 μm has a larger surface area compared to the sample of size μm. For the particle size of 12 μm, the surface area is too large and therefore it easily converted into gaseous products at much lower temperature. This means that the maximum oil yield occured at the temperature of o C which in turn is the optimum temperature for pyrolysis of empty fruit bunch to produce bio-oil. 3.3 Effect of particle size on product yield Figures, 6 and 7 demonstrate the effect of particle size on product yield as particle size is an important parameter than can affect the pyrolysis behaviors Relation between % liquid yield and sample size for 1.hr Sample size (µm) 4degC degc 6degC Fig. : Percentage of liquid yield versus particle size at different temperature with 1. hours Relation between % liquid yield and sample size for 3hr Sample size (µm) 4degC degc 6degC Fig. 6: Percentage of liquid yield versus particle size at different temperature with 3 hours Relation between % liquid yield and sample size for 4hr Sample size (µm) 4degC degc 6degC Fig. 7: Percentage of liquid yield versus particle size at different temperature with 4 hours Although these figures may repeated the results obtained from Figures 2, 3 and 4, it is our interest to highlight clearly the effect of particle size to the product yield. By referring to Figure, 6 & 7, we observed that an increase in particle size could establish the temperature gradient, causing increased heat transfer resistance inside the pyrolized particles, which in turn can cause decrease in liquid yield, an increase in the final solid yield and decrease in volatile matter during the pyrolysis process. On the other hand, sufficient small particle size is uniformly heated throughout the process. From the plotted graphs in Figures, 6 and 7, the particles size of ISSN: ISBN:

5 2μm obtained the maximum liquid yield at o C and various which is 26 wt%, wt% and 28.4 wt% respectively. Therefore, the particle size of 2 μm is taken as the optimum size for pyrolysis process. 3.4 Effect of on product yield Another important effect that we observed in this experimental work is the effect of to the percentage of liquid yield (Figures 2, 3 and 4). In general, lower process temperature (4 o C) and longer heating duration (4 hours) result in the production of charcoal, known as torrefaction process. A high temperature and longer heating duration however increases the biomass conversion to gas. Thus, moderate temperature and short heating periods are the optimum conditions for producing pyrolytic liquids. This theory is further proved from Figure 2 of which lower reaction temperature produced low liquid yield while higher reaction temperature will cause an increased in liquid produced. Liquid yield decreased as the reaction time increased at all reaction temperature. For the particle size of 12μm, the liquid yield decreased from 12.4 wt% to 11.2 wt% at 4 o C, whilst at o C, the liquid yield decreased from 23.6 wt% to 14.4 wt%. At 6 o C, the liquid yield decreased from 22.8 wt% to 2.2 wt%. These are all the results when the reaction prolonged from 1. hours to 4 hours. We observed that the sample size of 2μm and the temperature of o C yielded the maximum pyrolysis liquid. By analyzing Figure 2, 3 and 4, it is confirmed that the of 3 hours is the best optimum condition for the production of bio-oil from FBAU, of which yielded wt% of the bio-oil. 3. Characterization of pyrolysis liquid Once we attained the optimum condition, the samples were characterized using CHNS analyzer to check the carbon, hydrogen, nitrogen and sulphur compound. The optimized samples were also tested in a bomb calorimeter to obtain the calorific value and some other tests were conducted by using solvent methods (solid content), digital density meter (density), and ph paper (ph value). The analytical results are indicated in Table 1. Table 1: Analytical results of pyrolysis liquid characterization Moisture content 6 % Density g/cm 3 ph Solid content.2 2% Viscosity N/A C.36% H 7.83% N 4.4% S.16% O 37.21% Calorific value ±. MJ/ kg The liquid contains varying quantities of water, which forms a stable single-phase mixture, ranging from about 1 wt% to an upper limit of about -wt% water, depending on how it was produced and subsequently collected. In this study, the water content is ranging from to 6% even though the correct method to determine the water content could not be obtained. The (hydrophilic) bio-oils have water contents, which is difficult to be removed by conventional methods like distillation. The density of the liquid is between 1.1 to 1.2 g/cm 3, which is higher than fuel oil at around.8g/cm 3, and significantly higher than of the original biomass which is 1.142g/cm 3. This means that the liquid has approximately 42% of the energy content of fuel oil on a weight basis, but 61% on a volumetric basis. This will give implications on the design and specification of equipment to process and handle the bio-oil such as pumps and atomisers in boilers and engines of which the bio-oil is denser than water. The calorific value of pyrolysis liquid is ±. MJ/ kg compared to MJ/kg for conventional fuel oils. Thus, there is a need to further upgrade the bio-oil in order to substitute the existing fuel oils. 4 Conclusion The work covers the effect of pyrolysis temperature, and sample size on the yield of products and the physical characterization of the biooil produced with sweep gas flow rate of approximately ml/min. Fixed Bed Activation ISSN: ISBN:

6 Unit able to undergo pyrolysis process and convert the biomass to bio-oil. The optimum condition for pyrolysis of empty fruit bunch was attained at o C with particle size of 2μm and 3 hours reaction time. The results of the experiment show significant influence of pyrolysis temperature, particle size and heating rate on the percentage of weight loss, ash and volatile matter. Characteristics of bio-oil offer a few advantages and disadvantages where it is difficult to store and handle. On the other hand, the liquid product can be used as a source of low-grade fuel directly, or it may be upgraded to higher quality liquid fuels.. Acknowledgements The authors wish to thank Universiti Teknologi PETRONAS for the facilities and financial support for the projects. References: [1]A.E Ghaly and A. Ergudenler, Thermal Degradation of Cereal Straws in Air and Nitrogen. Journal of Applied Biochemistry and Biotechnology, Vol.27, No.1,1991, p.p [2]The Sun, 17/1/21 pp.11, Commercialize Biomass Energy-Malaysia aims to Produce MW under 8MP. [3] C.D. Hurd, The Pyrolysis of Carbon Compounds, A.C.S. Monograph Series, The Chemical Catalog Co., New York, 1979 [4]Pensamut, V., Pongrit, Intarangsi C., The Oil Palm, Department of Alternative Energy Development and Efficiency, Ministry of Energy Thailand, 23 []Deraman M., Carbon Pellets Prepared From Fibers Of Oil Palm Empty Fruit Bunches: 1.A Quantitative X-Ray Diffraction Analysis, PORIM Bulletin Palm Oil Res. Inst. Malaysia 26, 1993 [6]Khoo, K. C., Killmann, W., Lim, S. C. and Mansor. Characteristics of the oil palm stem. Research Pamphlet No. 7: Oil Palm Stem Utilization, Kuala Lumpur, Malaysia, FRIM, 1991, p.p [7] Mansor, H. and Ahmad, A.R., Chemical composition of the palm trunk, Proc. Natl. Seminar on Oil Palm Trunk and other Palmwood Utilization, Kuala Lumpur, Malaysia, FRIM,1991, p.p [8] Jalil, A. A., Kasin, J. and Ramli, R., Proc. Natl. Seminar on Oil Palm Trunk and ither Palmwood Utilization, Kuala Lumpur, Malaysia, FRIM, 1991, p.p [9]M. Garcia-Perez, A. Chaala, H. Pakdel, D. Kretschmer, C. Roy, Characterization of bio-oils in chemical families, 26. []Meir D.New Methods for chemical and physical characterization and round robin testing in Bridgwater A, et al., editors.fast pyrolysis of biomass: a handbook.newbury, UK: CPL Press; p.p [11]Bridgwater, A.V., Renewable fuels and chemicals by thermal processing of biomass. Chem. Eng. J., Vol.91 No.2-3, 23, p.p [12]Karaosmanoglu, F., Tetik, E., Gollu, E.,. Biofuel Production Using Slow Pyrolysis Of The Straw And Stalk Of The Rapeseed Plant, Fuel Process. Technol. Vol. 9, No.1, 1999, p.p [13]Yaman, S., Pyrolysis of biomass to produce fuels and chemical feedstocks. Energy Convers. Manage. Vol. 4, No., 24, p.p [14]Onay, O., Kockar, O.M.,. Fixed-bed pyrolysis of rapeseed (Brassicanapus L.). Biomass Bioenergy Vol. 26, No.3, 24, p.p [1]Bridgwater, A.V., Peacocke, G.V.C.,. Fast pyrolysis processes for biomass. Renew. Sust. Energy Rev. Vol.4, No.1, 2, p.p [16]Anja Oasmaa and Cordner Peacocke, A Guide to Physical Property Characterisation of Biomassderived Fast Pyrolysis Liquids, Technical Research Center of Finland, Espoo 21. [17]Alves, S.S. and Figuieredo, A, Model For Pyrolysis For Wet Wood, Chemical Engineering Science, Vol. 44, No.12, 1989, p.p [18]Acikgoz C., Kockar O.M., Flash pyrolysis of linseed (Linum usitatissimum L.) for production of liquid fuels. Journal of Analytical and Applied Pyrolysis, Vol.78 No. 27, 26, p.p ISSN: ISBN: