Production and characterization of bio oil and bio char from flax seed residue obtained from supercritical fluid extraction industry

Journal of the Energy Institute xxx (2016) 1e11

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Production and characterization of bio oil and bio char from flax seed residue obtained from supercritical fluid extraction industry Narayan Gouda a, R.K. Singh b, S.N. Meher c, Achyut K. Panda d, * a

Department of Chemistry, Centurion University of Technology and Management, Parlakhemundi, Odisha, India Department of Chemical Engg, National Institute of Technology, Rourkela, Odisha, India c NALCO, Damonjodi, Odisha, India d Department of Chemistry, Veer Surendra Sai University of Technology Burla, Odisha, India b

a r t i c l e i n f o

a b s t r a c t

Article history: Received 20 November 2015 Received in revised form 19 January 2016 Accepted 25 January 2016 Available online xxx

Fast pyrolysis of the flax seed residue was carried out in a semi-batch reactor with an aim to study the product distribution and to identify optimum temperature condition for maximizing the bio-oil yield. The effect of temperature on product distribution, elemental composition, and physical properties of major products of pyrolysis such as bio oil and bio char was investigated. The maximum condensable fraction yield was found to be 50.66 wt% at a pyrolysis temperature of 500
C, out of which the amount of bio-oil excluding the aqueous layer was 31 wt.%. The chemical composition of bio-oil obtained at optimum condition is analyzed using CHNS analyzer, FTIR and GC-MS. Fuel properties are also determined using IS methods. The bio oil was found to have higher calorific value than the feedstock. Again, it was found slightly basic in nature owing to the presence of higher concentration of basic components than acidic components. The char was characterized for elemental composition, heating value and surface area. © 2016 Energy Institute. Published by Elsevier Ltd. All rights reserved.

Keywords: Flax seed residue Pyrolysis Bio-oil Char Fuel

1. Introduction Fossil fuel has been of great importance for the rapid growth in world economy over the past several decades. Due to rapid depletion of fossil fuel, the fluctuation of oil prices and the environmental issues led to an intensive search for an alternate energy source. Again, in recent years, there is a steady increase in the amount of solid waste due to the increasing human population and urbanization. One of the best methods to manage the solid wastes and get the alternative fuels is the conversion of waste substances in to energy. There are various biomass solid wastes available in different corners of the world including India. Most of the scenarios for future energy supply suggest that renewable biomass energy will play significant role in the 21st century [1]. Biomass accounts for one-seventh of the world-wide energy consumption and for as much as 43% of the energy consumption in some developing countries [2]. Biomass has very high potentials of being a promising green energy source with negligible sulphur and nitrogen content. The reason for its popularity is its abundant supply and ease in farming culture. It has the potential to supply 10e14% of world's total energy if utilized properly [3]. There are five thermal approaches that are commonly used to convert biomass into an alternative fuel such as direct combustion, gasification, liquefaction, pyrolysis, and partial oxidation. Pyrolysis has received special attention since it produces solid, liquid and gas products, yields of each depending on the conditions [4,5]. The products formed, gases, liquid (tar), and solids (char), can be used as fuel to generate energy due to their high calorific value [6]. The solid product (char) can be used as a fuel either directly as briquettes or as chareoil or charewater slurries or for other applications such as metallurgical and leisure industries, soil amender and the production of activated carbon and bio-carbon electrodes [6]. Many researchers have studied on the potential recovery of fuels and chemicals from edible and non-edible de-oiled seed cake biomass via pyrolysis and these are cited below.

* Corresponding author. E-mail address: [email protected] (A.K. Panda). http://dx.doi.org/10.1016/j.joei.2016.01.003 1743-9671/© 2016 Energy Institute. Published by Elsevier Ltd. All rights reserved.

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Apricot and peach pulps were pyrolysed in a fixed-bed reactor to determine the effect of temperature, sweeping gas flow rate and steam velocity on the product yields and liquid product composition. The highest liquid product yield was found to be 27.2% and 27.7% at 550
C for Apricot and peach pulps respectively. A significant increase of Liquid product yield was observed under nitrogen and steam atmospheres [7]. Fluidized bed flash pyrolysis of Jatropha seed cake was carried out to determine the effects of particle size, temperature and nitrogen gas flow rate on the pyrolysis yields. The maximum oil yield of 64.25 wt% was obtained at a nitrogen gas flow rate of 1.75 m3/h, particle size of 0.7-1.0 mm and pyrolysis temperature of 500
C. The calorific value of pyrolysis oil was found to be 19.66 MJ/kg [8]. Olive residues were pyrolysed in a fixed bed reactor to determine the role of temperature, sweeping gas flow rate and steam velocity on the product yields and liquid product composition with a heating rate of 7
C/min. The maximum liquid product yield of 27.26% was obtained at 500
C and increased to 46.39 wt% and 42.12% when inert gas N2 with flow rate 100 cm3/min. and steam with velocity 1.3 cm/s was used to sweep the product from the hot zone respectively [9]. Fast pyrolysis of palm kernel cake was carried out in a closed-tubular reactor over a temperature range of 550-750
C with various retention times. Gas products consisted largely of carbon monoxide mixed with a smaller fraction of carbon dioxide and light hydrocarbon gases. The yields of gas, tar and char after fast pyrolysis were in the range of 32e80.8, 0.1e33, and 8.4e10.7 wt%, respectively [10]. Fast pyrolysis of soybean cake was investigated in a well-swept fixed-bed reactor at temperatures ranging from 400 to 700
C, for various nitrogen flow rates, heating rates and particle sizes. The maximum liquid yield was 42.83% at a pyrolysis temperature of 550
C with a sweeping gas rate of 200 cm3 min1 and heating rate of 700
C min1 for a soybean cake sample having 0.425 < Dp < 0.85 mm particle size. Bio-oil yields from the soybean cake were found to be largely independent of particle size (<2 mm) [11]. Pyrolysis of sesame (Sesamum indicum), mustard (Brassica napus) and neem (Azadirachta indica) de-oiled cakes were performed in a semi-batch reactor at the temperatures between 350
C and 700
C and a heating rate of 25
C min1 to determine the characteristics and yields of liquid and solid products. The maximum liquid product yield of 58.5%, 53.2% (by weight) was obtained at a temperature of 550
C and 40.2% (by weight) was obtained at a temperature of 400
C and has the calorific values 25.5, 25.1 and 30 MJ/kg for sesame, mustard and neem de-oiled cake respectively [12]. Pyrolysis of mahua de-oiled cake (Madhuca indica) was carried in a semi-batch reactor at the temperatures of 350, 400, 450, 500, 550, and 600
C. The optimum temperature at which maximum yield of 41.36% (by weight) liquid product obtained was 550
C [13]. Pyrolysis of rape seed cake was performed under static and nitrogen atmospheric conditions in a Heinze retort 316 stainless steel fixed bed reactor to study the various characteristics of bio-char and bio-oil. The highest bio-oil yield of 59.7% was obtained at a temperature of 500
C and at a heating rate of 7
C/min [14]. Pyrolysis of groundnut de-oiled cake was performed in a semi-batch reactor at a temperature range of 200e500
C and at a heating rate of 20
C/min to determine the physical and chemical characteristics of the bio-fuel and to determine the feasibility as a commercial fuel. The maximum yield of 50% was obtained at the temperature of 450
C [15]. Safflower (Charthamus tinctorius L.) seed press cake was pyrolysed in a fixed-bed reactor to investigate the effect of temperature, heating rate and sweeping gas flow rates on the yields of the product. The highest liquid yield of 36.1% was obtained at 500
C pyrolysis temperature with a heating rate of 50
C min1 under the sweep gas of N2 with a flow rate of 100 cm3 min1 [16]. Fixed-bed pyrolysis of cottonseed cake was carried out in two different reactors namely a tubular and a Heinze retort to determine the possibility of being a potential source of renewable fuels and chemicals feed stocks and to study the effect of temperature and atmosphere on the pyrolysis product yields and the composition. The oil yields of the experiments conducted in the tubular reactor were higher than the oil of the fixed bed Heinze retort. The maximum oil yield of 29.68% was obtained in N2 atmosphere at a pyrolysis temperature of 550
C with a heating rate of 7
C min1 in a tubular reactor [17]. Slow pyrolysis of polanga seed cake was carried out in a semi batch stainless steel reactor to observe the effect of temperature on the yield of the liquid product. The maximum yield of oil about 46% (volume/weight basis) was obtained at a temperature of 550
C and at heating rate of 20
C/min [18]. Flax seed residue obtained from supercritical fluid extraction industry would be one of the similar biomass feedstock for production of bio oil and bio char. Flax seed (Linum usitatissimum L.) is annual herbaceous plant that belongs to the Linacae family, with more than 200 recognised species [19]. Flax, L. usitatissimum, is an upright annual plant growing to 1.2 m (3 ft 11 in) tall, with slender stems. The leaves are glaucous green, slender lanceolate, 20e40 mm long and 3 mm broad. The flowers are pure pale blue, 15e25 mm diameter, with five petals; they can also be bright red. The fruit is a round, dry capsule 5e9 mm diameter, containing several glossy brown seeds shaped like an apple pip, 4e7 mm long. Generally linseed contains 40% oil, 30% diet fibre, 20% protein, 4% ash and 6% moisture [20]. It is high in dietary fibre, one of the richest sources of the short-chain u-3 fatty acid a-linolenic acid (ALA), and it also contains lignans, which are potent antioxidants [21]. In recent years flax seed has become known as a functional food due to its nutritional composition, which has positive effects on disease prevention providing health-beneficial components such as alpha-linolenic acid, lignans and polysaccharides (other than starch). Due to their anti-hypercolesterolemic, anti-carcinogenic and glucose metabolism controlling effects, these components may prevent or reduce the risk of various important diseases such as diabetes, lupus nephritis, arteriosclerosis and hormone dependent types of cancer. Likewise, antibacterial and fungi static activity has been reported in oligosaccharides extracted from this seed, which can control the growth of pathogens affecting the agricultural sector, such as Alternia solani and Alternia alternata, as well as the human pathogen Candia albicans; it can also control the deterioration of foodstuffs by the fungi Penicillium chrysogenum, Fusarium graminearum and Aspergillus flavus. Similarly, the pressed cake is found use in cosmetics in peelings, additive in baking products and face masks and cattle feed and also for aquaculture [22]. In addition, pressed flax seed cakes carries an immense usable, proteins, soluble fibre, lignans. Mucilage and polysaccharides could be extracted and reported to have lot of health benefits [23]. Pag et al. reported the extraction of polyphenols and lignans from flax seed cake using different solvents and as a source of antioxidant and antibacterial properties [24]. Present work includes pyrolysis of flax seed residue to obtain bio oil and bio char. Effect of temperature on the product distribution, composition and physical properties of the bio oil and char is the major aspect of the study. Please cite this article in press as: N. Gouda, et al., Production and characterization of bio oil and bio char from flax seed residue obtained from supercritical fluid extraction industry, Journal of the Energy Institute (2016), http://dx.doi.org/10.1016/j.joei.2016.01.003

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2. Experimental setup and methodology 2.1. Feedstock Fig. 1 shows dry/matured flax seeds, pulverized seed meal for supercritical fluid extraction, seed residue. The flax seed residue/remain chosen for this study was collected from the supercritical CO2 fluid extraction industry Gram-Tarang Foods, a social entrepreneurial outreach of Centurion University Technology and Management located at Parlakhemundi, Odisha, India. The flax seeds were procured from Nimach, Madhya Pradesh, India. The dried seeds were pulverised and subjected to extraction at 300 bar and 50-70
C for 4 h, yielding 26 wt.% oil. The seed residue was then used as feedstock directly in pyrolysis experiments. 2.2. Feedstock characterization Proximate analysis of the Flax seed residue sample such as the percentage of moisture, volatile matter, fixed carbon and ash content has been carried out using prescribed standard methods ASTM D 4442, ASTM D 3172, ASTM D 3177 and ASTM D 3175 respectively. Protein content was determined by combustion method (AOAC 990.03). Lipid content was measured gravimetrically after ether solvent extraction (AOAC 945.16). The fibre content was determined as crude residue remaining after extracting with acid and alkali (AOAC 962.09). Ultimate analysis of the raw material and the liquid fraction, which is used to determine the elemental composition (C, H, N, S, O) of the sample was carried out using a CHNS elemental analyzer (Variael CUBE Germany). Thermo-gravimetric analysis (TGA) of the flax seed residue was done using a DTG60 instrument. Around 10 mg of flax seed residue was taken and heated to 600
C for 1 min. TGA was performed in nitrogen atmosphere with flow rate 35 ml/min, at a heating rate of 20
C/min. 2.3. Experimental conditions for pyrolysis The pyrolysis experiments were carried out in a semi batch reactor of 300 ml capacity shown in Fig. 2. It consists of a reactor made of stainless steel tube sealed at one end and an outlet tube at other end. The tube was heated externally by an electric furnace, with the temperature being controlled by external PID controller with a Cr-Al: K type thermocouple fixed inside the reactor to maintain a pre-defined temperature with a heating rate of 20
C per minutes. The reactor was first stirred with the help of a vacuum pump. Nitrogen gas was used as the carrier gas with flow rate of 5 ml/min for all the experiments. The heating rate of the reactor is 20
C per minutes. 30 g of the seed residue was placed into the 300 ml stainless tube and it was inserted inside the heating chamber after attaining the desired temperature ranging from 400
C to 650
C. Vapours were condensed in a glass condenser by using ice cooled water as cooling media at the outlet of the reactor and the condensed liquid was collected in a jar. The temperature of glass condenser was around 10
C. The liquid fraction collected through the condenser was weighed for its yield. The residue remained in the reactor after pyrolysis was measured as char. Yield of non-condensable gas was calculated by material balance. The percentage yield of condensable fraction, char and non-

Fig. 1. Dry/matured flax seeds, pulverised seed meal and seed residue.

Fig. 2. Reactor assembly.

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condensable volatiles were calculated as per the equations (1)e(3). The pyrolysis experiments were repeated for three times to ensure the reproducibility of the results.

%condensable fraction ¼

%char fraction ¼

weight of condensable fraction  100 weight of feedstock

(1)

weight of char fraction  100 weight of feedstock

(2)

%Non­condensable fraction ¼ 100  ½%condensable fraction þ %char fraction

(3)

2.4. Products characterization The FTIR spectrum of the bio-oil was taken in the range of 400-4000 cm1 region with 8 cm1 resolution in a PerkineElmer infrared spectrometer using nujol mull as reference to know the functional group composition. GC-MS of the liquid product was performed using a GC-MS OP 2010 [SHIMADZU] analyzer to determine the Chemical compounds present in the oil. The sample is directly injected without any dilution. A capillary column coated with a 0.25 mm film of DB-5 with length of 30 m and diameter 0.25 mm was used. The GS was equipped with a split injector at 200
C with a split ratio of 1:10. Helium gas of 99.995% purity was used as carrier gas at flow rate of 1.51 ml/min. The oven initial temperature was set to 70
C for 2 min and then increased to 300
C at a rate of 100
C/min and maintained for 7 min. All the compounds can be identified by means of the NIST library. Mass spectrometer was generally operated at an interface temperature of 240
C with ion source temperature of 200
C of range 40-1000 m/z. Indian Standard (IS) methods were adopted to determine the different properties of the bio oil such as PH (IS 3025), specific gravity (IS 1448-32), viscosity (IS 1448-25), flash point (IS 1448-21), pour point (IS 1448-10), calorific value (IS 1448-6), distillation boiling range (IS 1448-18). The pyrolysis char obtained at the optimum condition was analyzed for CHNS analysis using Vario EL CUBE Germany Elemental Analyzer. The surface area was studied using an autosorb BET apparatus from Quanta chrome Corporation. 3. Results and discussion 3.1. Compositional analysis of flax seed residue The proximate analysis (moisture, volatile matter, ash and fixed carbon) and ultimate analysis (elemental composition) of the flax seed residue is summarized in Table 1. The result shows that the Flax seed residue has less moisture (<7%) and ash content, and rich in volatile matter content (77.016%). As the seed residue sample hold less moisture, ash, fixed carbon content and high volatile matter, it should yield more of pyrolysis oil and gas upon pyrolysis and thus suitable for pyrolysis. The major components of the sample are protein, lipids and fibres (consisting of cellulose and hemi-cellulose). The major elements include Carbon and Oxygen, with less percentage of nitrogen and hydrogen. The Gross calorific value (GCV) of the sample calculated based on the elemental composition is too low to be used as a direct fuel. 3.2. TGA results flax seed residue According to the thermo-gravimetric plot which is depicted in Fig. 2, three key regions can be identified. The region “A” which shows an 8.5% drop in weight up to a temperature of 112.6
C is attributed to the evaporation of adsorbed water and few volatiles. When the sample

Table 1 Characterization of flax seed residue. (wt%) Proximate analysis % Moisture % Volatile matter % Ash content % Fixed carbon % Protein % Lipid % Fibre

6.75 77.016 5.3 10.33 41.02 9.5 7.2

Ultimate analysis %C %H %N %S %O Empirical formula H/C molar ratio O/C molar ratio GCV (MJ/kg) Net calorific value (MJ/kg)

47.20 3.21 2.91 0.11 46.57 CH0.816N0.016S0.0008O0.771 0.816 0.771 11.92 11.04

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was heated beyond 112
C up to 600
C there are two regions that can be distinguished. The significant difference in the change in the gradient indicates that they belong to two different reaction regimes. According to the information given in Fig. 3, the 57.25% weight loss up to the temperature 404.24
C in region “B” can be attributed predominantly to the loss of oxygenated, nitrogen, and sulphide compounds. Maximum degradation of biomass occurs in this stage. This observation can be related mainly to the thermal degradation of pectin, cellulose, hemicelluloses, glycolipid and glycoprotein at the temperature range of 100-500
C. The third region “C” with remaining biomass of 34.25% up to a temperature of 544.24
C was significantly different that from region “B” and is due to degradation of more aromatic complex compounds, lignins and char as the process was carried out in presence of air. The different peaks in the DTG curve are shown in Fig. 3. It can be observed that DTG curves have a large number of peaks, infers that the pyrolysis of these biomass materials is rather complex indicate three main decomposition steps. The first step (<120
C) corresponding to dehydration, 120e420
C corresponding to de-volatilisation and a region 420-550
C involves the decomposition. The de-volatilisation includes the stepwise decomposition of the different bio-polymer fractions such as pectin, cellulose, hemicelluloses protein and lipid. 3.3. Distribution of pyrolysis products with temperature The fast pyrolysis of flax seed residue was carried out at different temperature. The effect of temperature on product distribution and reaction time is summarized in Fig. 4. It can be seen that yield of condensable product is low at lower temperature i.e. 37.67 wt.% at 400
C, increases gradually with increase in temperature until it reaches a maximum value of 50.67 wt.% at 500
C, and then decreases with further increase of temperature. The decrease of liquid product above 500
C is due to the formation of more amounts of non-condensable gases due to extensive cracking. The higher pyrolysis temperature is associated with secondary cracking reactions of the pyrolysis vapours to produce increased gas yields and reduced bio-oil yield [9]. The condensable fraction was found to contain considerable amount of aqueous fraction and its concentration is 19.6% by wt.% at optimum condition. So, the amount of bio-oil is 31 wt.% at 500
C. The char yield decreases with increase in temperature. It is 41.33 wt% at 400
C and decreased to 23.67 wt% as the temperature increased to 600
C. At low temperature, high char yield is due to more reaction time and more carbonization. As the temperature increases the char yield decreased because of greater primary decomposition or de-polymerization of cake to primary volatiles at higher temperatures or may be due to secondary decomposition of the char residue [25]. The fraction of non-condensable product was 21 wt% at 400
C, increased to 40.6 wt% as the temperature increased to 500
C, At lower temperature due to high reaction time, secondary cracking of pyrolysis vapour occurs leading to high gases whereas at high temperature vigorous cracking of raw material as well as secondary cracking of char yield more non-condensable gaseous fraction [26]. The reaction water yields were found to marginally decrease with increasing temperature, indicating that the dehydration reactions taking place during fast pyrolysis were enhanced at lower temperature. This is consistence with the literature. 3.4. Functional group analysis of bio-oil Fig. 5 shows the infrared spectra of the bio oil obtained at optimum temperature, representing functional group analysis of the sample. The OeH stretching and CeN stretching vibrations corresponding to 3426 cm1 of the bio-oils indicate the presence of phenols, alcohols, water and amines; CeH stretching vibrations appear at 2854, 2925 and 2956 cm1 and CeH deformation vibrations appear at 1442 cm1, which indicate the presence of alkane groups in pyrolysis oil derived from biomass. The CeO stretching vibrations between 1652 cm1 are compatible with the presence of amide, ketone, aldehyde groups, etc. The absorbance peaks between at 1442 and 1577 cm1 represent CeC stretching vibrations indicative of alkenes and aromatics. Furthermore, mono and polycyclic and substituted aromatic groups are indicated by the absorption peak at 698 cm1. 3.5. Detailed composition of bio-oil The composition of the pyrolytic oil obtained at 500
C is identified by comparing the GCeMS chromatogram of the oil (Fig. 6) with standard chromatographic data available from the NIST library and summarized in Table 2. It was determined that the pyrolysis oil contained

Fig. 3. TGA at 20
C/min.

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Fig. 4. Effect of temperature on product distribution and reaction time.

Fig. 5. FTIR of bio-oil.

various groups of compounds such as alkanes, alkenes, aromatics, esters, amides and nitriles of carbon content C6eC24. In general, the formation of hydrocarbons, esters and acids in the pyrolysis oil may be attributed to the spent lipid content of seed. The amide and nitrile content in the pyrolysis oil is mainly derived from the protein content of seed. The areas of major compounds in bio-oils are given in Table 2. They were classified with increasing the retention times. Taking into account of area percentage, the highest peak areas of total ion chromatogram (TIC) of compounds were Oleanitrile (9.39%), Hexadecanenitrile (8.08%), Pentadecanenitrile(8.08%), Pentadecane (6.53%), Tridecane (6.53%), 8-Heptadecene (6.41%), Heptadecane(6.33%), Octadecanenitrile (5.67%), 2-Pyridinamine, 4,6-dimethyl- (9.39%), 1,4Benzenediamine, 2-methyl- (9.39%). In addition, 49 other compounds comprising of hydrocarbons, esters, ketones, hydroxyl, amides, carboxylic acids etc. are present in the bio oil. Oleanitrile, hexadecanenitrile and octadecanenitrile are used as suitable softeners for synthetic rubber. N-pentadecane is used as a solvent for inks and degreasing; used as an intermediate for chemical synthesis. N-Pentadecane can be used as a reference substance for gas chromatography. Heptadecane can be used as an internal standard in the reaction to study the first direct comparison of kava lactone residue ion efficiencies. It is also used as the appropriate suspended solvent for the residue ion and concentration of essential oil. 3.6. Elemental composition and physical properties of bio oil and bio char The basic elemental compositions of bio oil and bio char are listed in Tables 3 and 5 respectively. The percentages of carbon, hydrogen and oxygen of bio-oil and bio-char were completely different from that of original biomass. Bio-oil has higher carbon, nitrogen and hydrogen contents and lower oxygen contents, whereas bio-char has slightly higher carbon and nitrogen content than the original biomass. The presence of nitrogen compounds can be a drawback when burning bio-oils because of the high potential for NOx emissions. On elemental composition basis, the bio-oils differ significantly from petroleum oils, which contain mainly of hydrogen and carbon with very small quantity of oxygen. The oxygen in bio-oils exists in a variety of functional groups such as hydroxyl, carboxyl, and carbonyl groups. It is the presence of oxygen that is responsible for certain unfavourable properties of bio-oils such as low heating value and instability. Therefore, bio-oils should be upgraded by catalytic de-oxygenation in order to improve their heating values and stability. The lower sulphur content of the oil also makes it suitable from pollution aspect. The various physical properties of the oil product obtained at the optimum conditions of pyrolysis process i.e. at 500
C have been investigated and compared with literature data for bio-oils produced from similar sources, is summarized in Table 4. The fuel properties Please cite this article in press as: N. Gouda, et al., Production and characterization of bio oil and bio char from flax seed residue obtained from supercritical fluid extraction industry, Journal of the Energy Institute (2016), http://dx.doi.org/10.1016/j.joei.2016.01.003

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Fig. 6. GCeMS of bio-oil.

determined the feasibility of the pyrolysis oil as an alternate fuel. The properties studied include water and solids contents, pH value, basic elemental composition; heating value, molecular weight distribution and stability. Understanding the basic properties of bio-oils would be beneficial for identifying their appropriate applications and for upgrading them. The calorific value of pyrolysis oil was found to be about 70% of that of diesel which is quite appreciable for pyrolysis oils although it may result in less performance if combusted as it is. Water content in bio-oil is available as aqueous layer and is presented in the plot 3. Certainly the higher the reaction water yields, the higher the water content in the bio-oils. Water in bio-oils also comes from original moisture in the biomass feedstock. Water content of biooils is one of the factors affecting their quality and use. The presence of water in bio-oils can be disadvantageous and advantageous. It reduces the heating value, especially the LHV and flame temperature. On the other hand, it improves bio-oil flow characteristics by reducing

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Table 2 GCeMS composition of bio-oil. Peak value

Area percentage

Name of the compound

Formula

1 2 3

Retention time 3.708 3.848 5.464

0.37 0.61 0.46

1-Nonene Nonane 1-Decene

C9H18 C9H20 C10H20

4

5.623

0.58

Decane Octane, 4-ethylUndecane

C10H22 C10H22 C11H24

5

7.258

0.69

5-Tetradecene, (E)2-Dodecene, (Z)3-Tetradecene, (Z)-

C14H28 C12H24 C14H28

6

7.410

0.52

Undecane

C11H24

7

7.487

0.77

5-Undecene 2-Undecene, (Z)4-Undecene, (E)-

C11H22 C11H22 C11H22

8

7.633

0.41

5-Undecene 5-Undecene, (E)2-Nonene, (E)-

C11H22 C11H22 C9H18

9

8.422

0.45

Spiro[4.5]decan-1-one 8,10-Dodecadien-1-ol, (E,E)-

C10H16O C12H22O

10

8.925

0.72

1-Dodecene

C12H24

11

9.058

0.67

Dodecane Tetradecane

C12H26 C14H30

12 13 14 15 16 17 18 19

9.459 10.445 10.566 11.851 11.959 12.640 12.882 13.085

0.24 0.69 0.94 1.47 1.42 0.35 0.31 0.48

1,10-Undecadiene 1-Tridecene Tridecane 2-Tetradecene, (E)Tetradecane 7-Tetradecene, (E)1-Heptylcyclohexene n-Pentadecanol

C11H20 C13H26 C13H28 C14H28 C14H30 C14H28 C13H24 C15H32O

20

13.162

0.87

1-Pentadecene 9-Octadecene, (E)-

C15H30 C18H36

21

13.270

6.53

Pentadecane Tridecane

C15H32 C13H28

22 23

13.957 14.173

0.86 0.79

n-Nonylcyclohexane Spiro[5.6]dodecane

C15H30 C12H22

24

14.205

0.50

1,15-Hexadecadiene 1,13-Tetradecadiene

C16H30 C14H26

25

14.230

0.57

7-Hexadecene, (Z)3-Hexadecene, (Z)-

C16H32 C16H32

26

14.294

0.96

2-Tetradecene, (E)3-Hexadecene, (Z)-

C14H28 C16H32

27

14.383

1.31

Cyclotetradecane 9-Octadecene, (E)-

C14H28 C18H36

28 29 30

14.472 15.229 15.293

1.34 0.61 0.64

Hexadecane 3-Heptadecene, (Z)8-Dodecen-1-ol, (Z)-

C16H34 C17H34 C12H24O

31

15.388

6.41

8-Heptadecene 3-Heptadecene, (Z)-

C17H34 C17H34

32 33

15.522 15.547

0.45 0.85

3-Heptadecene, (Z)1-Heptadecene

C17H34 C17H34

34

15.636

6.33

Heptadecane Nonadecane

C17H36 C19H40

35

15.726

0.27

Benzene, (1-methyldecyl)-

C17H28

36

15.904

0.47

8-Dodecen-1-ol, (Z)3,4-Octadiene, 7-methyl-

C12H24O C9H16

37 38 39 40

16.273 16.457 16.527 16.642

0.41 0.41 0.45 0.42

3-Octadecyne 1,9-Tetradecadiene 3-Octadecene, (E)1-Octadecene

C18H34 C14H26 C18H36 C18H36

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N. Gouda et al. / Journal of the Energy Institute xxx (2016) 1e11

9

Table 2 (continued ) Peak value

Retention time

Area percentage

Name of the compound

Formula

41

16.712

0.50

Octadecane Tridecane

C18H38 C13H28

42

17.780

8.08

Hexadecanenitrile Pentadecanenitrile

C16H31N C15H29N

43

17.997

1.13

Hexadecanoic acid, methyl ester

C17H34O2

44

19.479

2.81

Octadecane, 1-(ethenyloxy)1-Hexacosanol

C20H40O C26H54O

45

19.555

9.39

Oleanitrile 2-Pyridinamine, 4,6-dimethyl-

C18H33N C7H10N2

46

19.594

5.27

Oleanitrile cis-Vaccenic acid

C18H33N C18H34O2

47

19.702

1.94

Trans-13-Octadecenoic acid, methyl ester

C19H36O2

48

19.778

5.67

Heptadecanenitrile Octadecanenitrile

C17H33N C18H35N

49

19.931

0.78

Methyl stearate

C19H38O2

50

20.611

2.24

Hexadecanamide Dodecanamide

C16H33NO C12H25NO

51

21.050

2.00

cis-Vaccenic acid 9-Tricosene, (Z)Oleic acid

C18H34O2 C23H46 C18H34O2

52 53

21.108 21.273

0.78 0.89

Z-8-Hexadecene cis-Vaccenic acid

C16H32 C18H34O2

54

21.585

0.85

Heptadecanenitrile Octadecanenitrile

C17H33N C18H35N

55

22.037

2.84

9-Octadecenamide, (Z)-

C18H35NO

56

22.094

1.62

10-Heneicosene (c,t) Cyclotetracosane

C21H42 C24H48

57

22.234

0.87

Octadecanamide 9-Octadecenamide, (Z)Hexadecanamide

C18H37NO C18H35NO C16H33NO

58

22.291

0.46

Oleic Acid

C18H34O2

59

23.506

1.02

9-Octadecen-1-ol, (Z)1,9-Tetradecadiene

C18H36O C14H26

60

23.563

1.02

E-11-Hexadecen-1-ol Z-9-Hexadecen-1-ol acetate

C16H32O C18H34O2

the viscosity. The water also leads to a more uniform temperature profile in the cylinder of a diesel engine as well as to lower NOx emissions [27]. It can be seen from the figure that the temperature had a small influence on bio-oils water contents. The pH values of fractions of bio oil derived at different temperature are displayed in Table 4. It was found that the oils obtained at different temperature were slightly basic and not acidic as reported in the literature for pyrolysis of biomass. The basic pH values of bio-oils may be explained by the presence of majority of neutral compounds, small amount of carboxylic compounds (8.62%) such as cis-Vaccenic acid, Octadec-9-enoic acid, Oleic Acid and basic compounds (29%) such as Pentadecanenitrile, Hexadecanenitrile, Heptadecanenitrile, Octadecanenitrile, Oleanitrile, 2-Pyridinamine, 4,6-dimethyl-1,4-Benzenediamine and 2-methyl-Oleanitrile. Nitriles being very weak bases do not contribute much increase of PH of the bio oil. The effect of pyrolysis temperature on concentration of acids was recently investigated by Thangalazhy-Gopakumar et al. [28]. They found that the acids remained almost constant or slightly increased with the increase in temperature although the pH value of the bio-oil decreased with the increase in temperature. The pH value is one of the important bio-oils properties as it is an indicator of their corrosiveness. The neutral properties of bio-oils wouldn't cause corrosion of vessels and pipe work. The heating values of bio-oils and bio char at different temperature are summarised in Tables 4 and 5 respectively. It was found that the heating values of bio-oil and bio char obtained at optimum condition of temperature are 2.8 times and 1.35 times higher than that of original biomass respectively. This may be explained due to the higher carbon content in them. The other fuel properties such as kinematic viscosity, pour point, flash point and specific gravity of bio oil are suitable enough to be used as a liquid fuel in blend with diesel fuel. H/C and O/C ratios decreased with increase in temperature and char became increasingly more carbonaceous in nature at a high temperature. The surface area of char is important since, like other physic-chemical characteristics, it may strongly affect the reactivity and combustion behaviour of the char. At higher temperature, the de-volatilization is more intensive making the char more porous. The char obtained at different temperatures are mainly macro-porous materials with a low surface area but it could be used for the production of activated carbon and also as a solid fuel in boilers. In addition, it can be used further for the gasification process to obtain hydrogen rich gas by thermal cracking.

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10

N. Gouda et al. / Journal of the Energy Institute xxx (2016) 1e11

Table 3 Ultimate analysis of bio-oil at different temperatures. Elements (%)

C H N S O GCV (MJ/kg) H/C O/C Empirical formula

Temperature (
C) 400

450

500

550

600

73.21 7.93 1.21 0.45 17.2 31.2 1.3 0.176 CH1.3N0.014S0.002O0.176

73.29 7.89 1.14 0.43 17.25 31.37 1.291 0.176 CH1.291N0.013S0.002O0.176

72.31 7.66 1.04 0.43 18.56 31.769 1.271 0.192 CH1.271N0.012S0.002O0.192

72.49 7.69 1.18 0.47 18.17 31.69 1.273 0.187 CH1.273N0.013S0.002O0.187

73.23 7.89 1.23 0.45 17.2 30.86 1.293 0.176 CH1.293N0.014S0.002O0.176

Table 4 Physical properties and elemental composition of bio oil. Physical properties

Temperature (
C)

Appearance Odour PH Specific gravity @30
C Kinematic viscosity at 30
C (Cst) Pour point (
C) Flash point by Abel method (
C) Fire point by Abel method (
C) GCV (MJ/Kg) IBP (
C) FBP (
C) Miscibility

Dark brown free flowing liquid Burning/smoky 7.6 7.5 0.9578 0.9603 78.9 79.14 12 11 52 52 69 70 31.2 31.37 81 85 358 374 Ethanol, methanol, CCl4

400

450

500

550

600

7.53 0.9674 79.14 11 53 70 31.769 89 387

7.45 0.9678 80.13 10 55 69 31.69 92 392

7.4 0.9686 80.15 10 55 70 30.86 92 387

Table 5 Analysis of bio-char. Elements (%) and properties

C H N S O GCV (MJ/kg) H/C O/C Empirical formula Surface area (m2/g) Total pore volume (cm3/g)

Temperature (
C) 400

450

500

550

600

50.21 3.98 1.06 0.34 44.41 14.786 0.951 0.663 CH0.951N0.017S0.002O0.663 2.6 0.12

50.87 3.63 1.17 0.22 44.11 14.561 0.856 0.650 CH0.856N0.019S0.001O0.650 2.9 0.21

51.34 3.78 1.13 0.28 43.47 15.050 0.883 0.634 CH0.883N0.018S0.001O0.634 3.7 0.24

51.48 3.49 1.04 0.23 43.76 14.631 0.813 0.637 CH0.813N0.017S0.001O0.637 4.2 0.31

51.93 3.37 1.09 0.28 43.33 14.690 0.778 0.625 CH0.778N0.017S0.001O0.625 4.3 0.38

4. Conclusion Fixed-bed fast pyrolysis of flax seed residue was carried out under different temperatures in order to obtain optimized synthetic liquid fuels. The significance outcomes of the work are as follows;  The bio-oil yield was obtained as 31 wt% at a pyrolysis temperature of 500
C.  The heating value of the bio-oil and bio-char is found to be significantly higher than the feedstock, thus can be an economically viable process. The fuel properties of the oil also support its suitability as a fuel.  The pH value of bio-oil at different temperature was found to be in neutral range owing to the composition of the oil conformed from GCeMS study.  The major components of the oil are Oleanitrile, Hexadecanenitrile, Pentadecanenitrile, Pentadecane, Tridecane, 8-Heptadecene, Heptadecane, Octadecanenitrile, 2-Pyridinamine, 4,6-dimethyl-, and 1,4-Benzenediamine, 2-methyl-, which are of importance in different applications.  The char obtained in the process could be used as a solid fuel as well as an adsorbent. Thus fast pyrolysis bio-oil from flax seed residue can be considered as a chemical feedstock for producing valuable chemicals or as liquid fuel. Upgradation of the pyrolysis oil is required to enhance its suitability as a substitute of fossil fuel.

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