Fodder radish seed cake pyrolysis for bio-oil production in a rotary kiln reactor

Chemical Engineering & Processing: Process Intensification xxx (xxxx) xxx–xxx

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Fodder radish seed cake pyrolysis for bio-oil production in a rotary kiln reactor ⁎

W.P. Silvestrea,b, G.F. Paulettib, M. Godinhoa, , C. Baldassoa a b

Postgraduate Program in Engineering Processes and Technologies, University of Caxias do Sul (UCS), Caxias do Sul, Brazil Course of Agronomy, University of Caxias do Sul (UCS), Caxias do Sul, Brazil

A R T I C L E I N F O

A B S T R A C T

Keywords: Fodder radish Pyrolysis Rotary kiln Bio-oil

Fodder radish seed cake (FRSC) was pyrolyzed in a rotary kiln reactor at different rotation speeds (0, 3 and 6 rpm) and inert gas flow rates (0.25, 0.75 and 1.25 L/min). Pyrolysis of the bran (oil-free FRSC) were also carried out to investigate the effect of residual oil present in the FRSC. The experiments showed that the optimal rotation speed for bio-oil production is 3 rpm, with a bio-oil yield of 60.99 wt.%. The experiments carried out at different inert gas flow rates showed an increase of bio-oil yield at 1.25 L/min (63.22 wt.%). The residual oil in the FRSC increased bio-oil yield, since FRSC bran (oil-free) pyrolysis presented a bio-oil yield of 49.34 wt.%. The bio-oils obtained from FRSC pyrolysis, as well as its bran, presented distinct chemical composition. FRSC bio-oil presented, besides aromatics, amines, amides, and nitriles (nitrogen containing functional groups). The bio-oil obtained from FRSC bran pyrolysis presented higher aromatics content than the bio-oil from FRSC, with lesser amines content and absence of nitriles. The bio-oil obtained from FRSC pyrolysis at 3 rpm was the one that presented the more adequate physicochemical properties for use in industry and for energy production. Due to the composition, the bio-oils can be used as fuel, to obtain chemicals and as a feedstock for gasification.

1. Introduction Fodder radish (Raphanus sativus L.) is an angiosperm belonging to the Brassicaceae family. The high oil content in its seed (from 30 to 50 wt.%) permit to use it as feedstock to produce biofuels (biodiesel). Its applications range from forage and crop rotation to a source of vegetable oil and biomass for many uses, being its most prominent use in biodiesel production, from the seed oil [1,2]. Fodder radish has an average productivity of 3000 kg/ha of dry mass (in relation to aerial part). Seed production is around 800 to 1200 kg/ha, depending on the climate and cultivation nutritional state. The oil is industrially obtained by pressing of the seed in a roller extractor, the oil is obtained and separated and occurs generation of a waste, the bagasse of kneaded seed (cake) [3]. Seed oil is composed by a mixture of saturated and unsaturated fatty acids, whose composition depends on plant genetics, nutritional conditions, climate, soil type and presence of diseases, but the major components are oleic and erucic acids [4]. Fodder radish seed cake (FRSC) is the waste (cake) of the fodder radish seed after the pressing process to extract its oil. In the view of the fact that the extraction process is inefficient, FRSC still has a substantial quantity of residual oil. FRSC can be used as a feedstock in thermochemical processes (pyrolysis) in order to obtain a bio-oil with distinct

⁎

characteristics from lignocellulosic biomasses, composed basically by cellulose, hemicellulose and lignin [1,5]. FRSC has high protein content, being attractive to use this biomass in animal feeding, though the presence of oil is a problem to use the material this way. Literature present studies characterizing FRSC and its bran (cake with the residual oil removed) in order to verify its use in cattle and fish feeding [6,7]. Literature cites works using rapeseed seed cake (Brassica napus), which belongs to fodder radish botanical family. Ucar and Ozkan [8], pyrolyzing rapeseed seed cake in a fixed bed reactor at temperatures between 400 and 900 °C, obtained maximum bio-oil yield at 500 °C, whose fraction bio-oil plus water corresponded to 58.59 wt.% and the main organic constituents of the obtained bio-oil were oleic acid, 1Hindole and 2,3,5-trimethoxy-toluene. Smets et al. [9], working with rapeseed seed cake in an auger reactor at temperatures between 350 and 550 °C, obtained higher bio-oil yield at 550 °C, with value of 42.1 wt.%, being oleic acid the main organic constituent of the organic phase, followed by erucic acid. Smets et al. [10], performing slow pyrolysis of rapeseed seed cake at 550 °C using diverse catalysts, obtained higher biooil yield without use of catalyst (47.1 wt.%). The main constituents of liquid organic fraction were oleic, linoleic and palmitic acids. Bubbling fluidized bed (BFB) and circulating fluidized bed (CFB) are the most used reactors in fast pyrolysis [5,11,12,13]. Literature cites the

Corresponding author. E-mail address: [email protected] (M. Godinho).

https://doi.org/10.1016/j.cep.2017.12.020 Received 13 November 2017; Received in revised form 28 December 2017; Accepted 29 December 2017 0255-2701/ © 2017 Elsevier B.V. All rights reserved.

Please cite this article as: Silvestre, W.P., Chemical Engineering & Processing: Process Intensification (2017), https://doi.org/10.1016/j.cep.2017.12.020

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Fig. 1. Scheme of the pyrolysis system used in the experiments.

Kern et al. [19] carried out pyrolysis experiments of wheat straw in a rotary kiln. At final temperature of 500 °C bio-oil yield was 15 wt.%, while at 550 and 600 °C the yield was lesser than 10 wt.%. Sanginés et al. [20] performed pyrolysis of olive stone using a rotary kiln. The system operated with a rotation speed of 3 rpm, inert gas flow rate of 200 mL/min, heating rate of 10 °C/min and final temperature of 900 °C. The maximum bio-oil yield was observed at 500 °C (37 wt.%), while the yields at 400 and 700 °C were 28 and 35 wt.%, respectively. De Conto et al. [21], conducting pyrolysis experiments with elephant grass (Pennisetum purpureum S.) in a rotary kiln, obtained maximum bio-oil yield at 700 °C and 4 rpm (52.99 wt.%). The yield decreased to 44.52 wt.% at 2 rpm and decreased further at 0 rpm (37.25 wt.%). Literature states that rotary kiln reactor tends to present higher bio-oil yield when compared to other reactor types [14,15]. No study was found in literature about fodder radish pyrolysis, neither its cake (FRSC). Given the potential of fodder radish to produce biofuels (biodiesel), and consequently the generation of a waste (FRSC), the contribution of this study is to evaluate performance of a rotary kiln reactor for bio-oil production through FRSC pyrolysis. Different operational parameters (reactor rotation speed/inert gas flow rate/presence of residual oil in the biomass) were investigated and the obtained bio-oils were characterized under these conditions.

use of many other types of reactors, both for slow and fast pyrolysis [5,12,14]. The rotary kiln is widely employed in industry, with varied dimensions and a wide range of applications, being much employed in combustion and calcination (cement industry). In pyrolysis, this reactor shows advantages comparatively to other reactors in biomass processing. The rotary kiln allows the use of solid biomass of several shapes and sizes and the system can operate both in batch and in continuous mode, besides being of more simple construction and operational control, instead of BFB and CFB reactors, which demand a strict control [15,16,17]. As well as in fluidized bed reactors, the pyrolytic vapors are removed from the rotary kilns by the inert gas flow rate (in general, nitrogen gas is used). The residence time of the pyrolytic vapors is associated to the volumetric flow rate of inert gas. To obtain higher bio-oil yields, is recommended a residence time smaller than 2 s in BFB and CFB reactors [5]. Studies has been conducted with rotary kilns for the pyrolysis of different materials. Zhengzhao et al. [18] carried out pyrolysis experiments of mud of oil fields in a rotary kiln at 5 rpm. The results showed bio-oil yields of 10 wt.% at 480 °C, 13 wt.% at 520 °C, 24 wt.% at 550 °C and 19 wt.% at 580 °C. Cha et al. [15] conducted experiments in a rotary kiln coupled to a screw feeder to pyrolyze sand impregnated with bitumen. Authors evaluated the following operational conditions: final temperature of 500 °C, inclination of 2.5°, rotation speed of 3 rpm, feed rate of 10 kg/h and inert gas flow rate of 2.2 m3/h. The authors reported bio-oil yield of 52.8 wt.% at 500 °C. Rotary kilns are also being used in biomass pyrolysis. Li et al. [17] conducted pyrolysis experiments of various materials, among then wood chips, in a rotary kiln at temperatures from 550 to 850 °C. At final temperature of 550 °C, bio-oil yield for wood chips was near 50 wt.%. With increase in final pyrolysis temperature there was a reduction of bio-oil yield.

2. Materials and methods 2.1. Biomass obtainment University of Caxias do Sul Agronomy Course provided the FRSC. Fodder radish was cultivated in a rural unit (geographical coordinates: 2

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2.3. Statistical analysis

28°81′44.13–51°42′55.94). The seeds were processed in the university to extract the oil by pressing and to separate the fractions (cake and oil). FRSC was dried in a kiln for 24 h at 45 °C, being posteriorly milled in a hammer mill. To obtain the bran, the residual oil present in the FRSC was removed using a soxhlet apparatus and hexane as solvent, during 6 h. The biomass granulometry used in pyrolysis experiments and characterization (both FRSC and Bran) was Mesh/Tyler 10 (2 mm).

To evaluate the effect of the rotation speed on product yield it was used a factorial design in three levels, with triplicates. To evaluate the effect of the inert gas flow rate (superficial velocity of the inert gas) on product yield, the experiments were carried out with duplicates, in three levels. The same kind of design (duplicates of FRSC and its bran at optimal speed rotation and inert gas flow rate) was used to determine the influence of the biomass in product yield. The analysis used in both evaluations was ANOVA one-way, with a confidence interval of 95% (α = 0.05). The means between groups were compared by Duncan multiple range test.

2.2. Pyrolysis process Pyrolysis experiments were carried out in a rotary kiln reactor (Sanchis – Brazil). The reactor had a quartz tube internally coupled, with the following dimensions: 981 mm in length, 49 mm of external diameter and 43 mm of internal diameter. The useful length of the tube was 516 mm, with a total useful volume of 749 cm3. The reactor was heated electrically by two resistances, each one with a power of 1900 W. Two ‘K’ type thermocouples were positioned inside the reactor (zones 1 and 2), according to Fig. 1. Maximum working temperature of the reactor was 1200 °C. Control of inert gas (nitrogen) flow rate was performed by a rotameter (0.1 to 2.0 L/min), calibrated at 25 °C. It was used 150 g of dry biomass (FRSC or bran) in each experiment, occupying about 30% of reactor useful volume. The CEN BT/TF 143 [22] standard was adapted to perform bio-oil condensation, in order to ensure all of the generated bio-oil was condensed in the impingers. The condensing system consisted of ten impingers, connected in series, with the addition of 100 mL of isopropanol to each impinger, with exception of first and last impingers, which were empty. The impingers were kept in a cooling bath (near 0 °C) throughout pyrolysis process and reactor cooling. (Fig. 1) Initially the reactor was fed with the biomass and inertized for 30 min by the flow of inert gas (nitrogen). Then, the reactor heating was started (50 °C/min) until final temperature (500 °C). Such final temperature was used since it is well known from literature that this temperature maximizes bio-oil production. Once final pyrolysis temperature was reached, the reactor was kept at this temperature for more 30 min. Pyrolysis experiments of FRSC were performed with the reactor in steady state (0 rpm), at 3 and 6 rpm. In experiments with reactor movement, the rotation was started along with inertization, being turned off when the system started to cool. In these assays, the inert gas flow rate was of 0.75 L/min, kept constant since inertization until cooling of the system until room temperature. In the experiments to evaluate the influence of inert gas, inert gas flow rate was varied to verify the influence of superficial speed of the inert gas on product yield. The experiments were carried out at optimal rotation speed (Table 1). After the reactor temperature reached 40 °C (to avoid spontaneous combustion of the biochar), the inert gas flux was turned off, and the biochar collected and weighted to determine biochar yield. Bio-oil yield was determined by weighting of impingers system (with isopropanol) before and after of pyrolysis process. The mass gain of the system was considered condensed bio-oil. Non-condensable gases yield was obtained from mass balance.

2.4. Biomass and bio-oil characterization The bio-oil obtained from FRSC pyrolysis, due to the operational conditions of the condensing system, was diluted in isopropanol. To carry out some characterization tests (pH, EC, ash, viscosity, specific mass, elemental analysis), the mixture (bio-oil + isopropanol) was separated in a rotary evaporator. Vacuum was applied to the system (system absolute pressure of 21 kPa), operating at 50 ± 5 °C. During the separation, rotary evaporator rotation was 30 rpm. To perform the ultimate analysis of the organic fraction of the biooil, the water in the bio-oil was extracted using ethanol 95% v/v, mixed in equal proportions. The mixture (bio-oil + ethanol) was separated by rotary evaporation at 75 ± 5 °C and 21 kPa. Ultimate analysis (CHNS) of the biomass was carried out in accordance to the ASTM D5373-02 standard for carbon, nitrogen and hydrogen analysis and the ASTM D4239-14e2 standard for sulfur determination. Oxygen content was determined by mass balance. It was used a Vario Macro Cube elemental analyzer. Bio oil ultimate analysis followed the same methodology applied to the biomass, with isopropanol and water removed from the liquid fraction by rotary evaporation. Bio-oil chemical characterization was performed by gas chromatography coupled to mass spectrometry (GC/MS) and ultimate analysis. The samples analyzed by GC/MS were not separated in the rotary evaporator, to avoid loss of volatile compounds. GC/MS analysis was performed using a HP (Hewlett-Packard) gas chromatograph, model 6890, coupled to a selective mass detector HP 6890/MSD5973, equipped with HP Chemstation software and Wiley 275 library. It was used a HP-5 column (30 m x 250 μm), with 0.25 μm of film thickness (HP, Palo Alto, USA). Temperature program was 40 °C for 10 min, 40 to 250 °C at 5 °C/min, 250 °C for 20 min, injector temperature of 220 °C and interface temperature of 250 °C, split ratio of 1:5, helium was used as carrier gas at 56 kPa, flow rate of 1.0 mL/min, ionization energy of 70 eV. The following bio-oil physicochemical parameters were determined: viscosity, specific mass, pH, ash content and heating values. Such parameters were determined after isopropanol separation by rotary evaporation. Water content was determined with the bio-oil diluted in isopropanol, being the latter discounted in the calculation. Specific mass determination was performed by taking an aliquot of 5 mL of the bio-oil using a calibrated volumetric instrument and subsequent weighting of this volume in an analytical balance, in a temperature controlled environment (20 °C). Specific mass was obtained by division of the mass by aliquot volume. The pH determination was carried out in accordance to the ASTM D4980-03 standard. The bio-oil was diluted with distilled deionized water in the ratio of 1:10 (10 vol.%). The pH meter was calibrated before the readings with standard buffer solutions (4.00 and 7.00). Electrical conductivity (EC) was determined from the same mixture used in pH determination, using a conductivity meter with cell constant of 1.0 cm−1. Dynamic viscosity was determined using a Brookfield viscometer with a S18 spindle at 30 rpm and 20 °C. Kinematic viscosity was calculated by the ratio between dynamic viscosity and specific mass of the

Table 1 Operational parameters for the assays with variation of inert gas flow rate. Assay

Inert gas flow rate (L/min)

Superficial speeda(cm/s)

Residence time in the reactora(s)

A B C

0.25 0.75 1.25

0.53 1.60 2.66

97 32 19

a Values obtained considering the mean between room temperature (25 °C) and final pyrolysis temperature (500 °C).

3

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fluid. Ash content was determined in accordance to the ASTM D317412 standard. Water content was determined by Karl Fisher volumetric method, in accordance to the ASTM E203-08 standard, using an automatic titrator. The higher heating values (HHV) and lower heating values (LHV) were estimated from the Eqs. (1) and (2) [23,24].

HHV(MJ/kg) = −1.3675 + 0.3137 × C+ 0.7009 × H+ 0.3318 × O*

(1)

LHV(MJ/kg) = HHV − 0. 218217 × H

(2)

Table 3 Average yield1 (wt.%) of pyrolysis products for each inert gas flow rate.

2.5. Energy balance

Wp × HHVp

Energy conversion efficiency =

× 100%

∑

Wp × HHVp

Wb × HHVb

× 100% (4)

3. Results and discussion 3.1. Effect of rotation speed on product yield Reactor speed rotation was evaluated in three levels (0, 3 and 6 rpm), keeping inert gas flow rate constant at 0.75 L/min. Product yields of FRSC pyrolysis are presented in Table 2. From reactor rotation (0 to 3 rpm) was observed a decrease in biochar yield and an increase in bio-oil yield. The rotation of the reactor facilitates the releasing of primary pyrolysis vapors, decreasing secondary gas-phase reactions (cracking/partial oxidation/(re)polymerization/condensation). The mixing effect on the biomass also provides a better heat exchange [14,15]. In a circulating bed at near uniform particle size, the speed fields resulting from bed rotation and by self-diffusion improved the effective thermal conductivity of the bed, decreasing temperature gradients [21,25]. The lower temperature gradient within the bed and the easier releasing of pyrolysis vapors due to the rotation disfavored the secondary gas-phase reactions. The increase of rotation speed (from 3 to 6 rpm) does not cause significant changes in bio-oil yield. Industrial kilns operate at rotation speeds near 2 to 3 rpm, indicating that the use of low rotations did not

Non-condensable gases

25.79 ± 0.15a 24.83 ± 0.40a 25.74 ± 0.21a

13.83 ± 0.06a 14.41 ± 1.38a 11.05 ± 0.37a

60.39 ± 0.21b 61.27 ± 0.28b 63.22 ± 0.57a

3.3. Effect of residual oil of the biomass on product yield The residual oil present in the biomass (in a content of near 20 wt. %) is an important component of FRSC, whose presence is one of the possible causes of the high bio-oil yield of the biomass [28]. To evaluate the impact in product yield caused by the presence of residual oil in the biomass, pyrolysis experiments were carried out at 3 rpm and 0.75 L/ min of FRSC and its bran (oil-free FRSC). (Table 4) According to Smets et al. [9], part of the remaining bio-oil present in the biomass (FRSC) vaporized at temperatures above 350 °C, being recondensed in the heavy liquid fraction. Unlike the primary pyrolysis

Table 2 Average yield1 (wt.%) of pyrolysis products for each rotation speed. Biochar

0.25 0.75 1.25

Once determined the optimal rotation speed of the reactor (3 rpm), pyrolysis experiments were performed in duplicates for the three inert gas flow rates. The following inert gas flow rates (at 25 °C) were evaluated: 0.25, 0.75 and 1.25 L/min. (Table 3) It was observed that the increase in inert gas flow rate caused an increase in bio-oil yield when inert gas flow rate increased from 0.75 to 1.25 L/min. The bio-oil increase would be associated to the smaller residence time of the pyrolytic vapors inside the reactor. The residence time of the vapors in the reactor is an important factor to the kinetics of the secondary reactions (cracking of the primary vapors and formation of the secondary char). In accordance to Table 3, an increase of only 2.0 wt.% in bio-oil yield to an increase of more than 50% in inert gas flow rate would not justify adopt 1.25 L/min as the optimal inert gas flow rate. Thus, it was considered 0.75 L/min the optimal inert gas flow rate for the process. Montoya et al. [26], working with the pyrolysis of sugarcane bagasse at 500 °C and 50 °C/min, obtained bio-oil yield of 70 wt.% with inert gas (nitrogen) flow rate of 20 L/min; the bio-oil yield increased to 78 wt.% with inert gas flow rate of 40 L/min. Hsu et al. [27], pyrolyzing rice husk at 600 °C with feeding rate of 20 g/min, obtained bio-oil yield of 19.83 wt.% at inert gas (nitrogen) flow rate of 30 L/min; the bio-oil yield increased to 27.14 wt.% at the inert gas flow rate of 40 L/min. Therefore, the increase of bio-oil yield with the increase of inert gas flow rate (lower residence time) was associated to the fostering of secondary cracking and char forming reactions – recharring. However, it was observed the alteration in inert gas flow rate did not cause statistical significant changes in biochar yield.

Where Wb is biomass weight, HHVb is higher heating value (HHV) of biomass, Wp is products weight (biochar/bio-oil/non-condensable gases) and HHVp is higher heating value of products. The HHV values for biomass, liquid and solid fractions were calculated using equations 1 and 2. HHV value of non-condensable gases was obtained from its components mass fractions (N2 free basis) determined at 500 °C; HHV values of H2 (141.80 MJ/kg), CH4 (55.80 MJ/kg) and CO (20 MJ/kg) were provided by NRC [43]. A gas chromatograph Dani Master CG, with a TCD detector was used to analyze the non-condensable gases (H2/CO/CH4/CO2). More details can be obtained elsewhere (De Conto et al., 2016) [21].

Rotation speed

Bio-oil

3.2. Effect of inert gas flow rate on product yield

(3)

energy output = energy input

Non-condensable gases

harm bio-oil yield of FRSC pyrolysis. Thus, it was considered 3 rpm as the optimal rotation speed for bio-oil production.

It was carried out a simplified energy balance for the pyrolysis process at the optimal rotation speed condition (3 rpm) in accordance to Eqs. (3) and (4), provided by Hanif et al. [42].

Wb × HHVb

Biochar

1 The means in column followed by the same letter does not present significant statistical difference when compared by Duncan multiple range test.

C and H contents are on dry basis, while O*=100-C-H-%ash.

Percent energy recovery =

Inert gas flow rate (L/min)

Table 4 Average yield1 (wt.%) of pyrolysis products for FRSC and its bran (oil-free) at 3 rpm and 0.75 L/min. Bio-oil Biomass

0 rpm 3 rpm 6 rpm

26.00 ± 0.16 24.89 ± 0.30 24.90 ± 0.09

a b b

16.20 ± 2.09 14.13 ± 1.09 13.45 ± 0.43

a a a

57.80 ± 1.09 60.99 ± 0.79 61.74 ± 0.65

Biochar

Non-condensable gases

Bio-oil

b a

FRSC FRSC bran

a

1 The means in column followed by the same letter does not present significant statistical difference when compared by Duncan multiple range test.

24.89 ± 0.30 31.17 ± 0.55

b a

14.13 ± 1.09 19.49 ± 0.17

b a

60.99 ± 0.79 49.34 ± 0.72

a b

1 The means in column followed by the same letter does not present significant statistical difference when compared by Duncan’s multiple mean comparison.

4

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The low O/C ratio, which indicates the degree of oxygenation and oxidation of the bio-oil, is typical of lipid biomasses, associated to high H/C ratio, indicates a bio-oil with higher HHV values, what is energetically interesting. The removal of oxygen from liquid organic fraction (low O/C ratio) rendered the bio-oil more suitable for different applications. The N/C ratio may be environmentally important, since nitrogen is released as NOx when the bio-oil is used as a fuel. However, the presence of nitrogen in the biomass is interesting for oxygen removal, due to the nucleophilic characteristics of nitrogen. It was remarkable the sulfur content, being considerably high for a biomass. Literature on rapeseed seed cake report values of S content ranging from 0.8 to 1.4 wt.%, considerably high when compared to lignocellulosic biomasses (< 0.5 wt.%) [8,28,32,33,34]. Other authors reported similar results of ultimate analysis of bio-oil produced from rapeseed seed cake pyrolysis. A study using a fixed bed reactor obtained bio-oil at 500 °C with the following composition (wt. %): 66.80 of C, 8.72 of H, 9.05 of N, 0.59 of S and 14.84 of O, and molar ratios H/C and O/C of 1.56 and 0.16, respectively [8]. In other work using flash pyrolysis at 450 and 550 °C, the bio-oil produced at 450 °C presented the following composition (wt.%): 64.4 of C, 9.4 of H, 4.7 of N, 0.9 of S, and 20.6 of O, with molar ratios H/C and O/C of 1.48 and 0.24, respectively. The bio-oil produced at 550 °C presented the following composition (wt.%): 70.2 of C, 10.0 of H, 5.1 of N, 0.6 of S and 14.1 of O, with molar ratios H/C and O/C of 1.71 and 0.15, respectively [9]. In another work carrying out slow pyrolysis of rapeseed cake without catalyst at 550 °C, the obtained bio-oil had the following composition (wt.%): 61.5 of C, 9.1 of H, 5.1 of N, 0.6 of S and 23.7 of O, with molar ratios H/C and O/C of 1.78 and 0.29, respectively [10]. Variation of inert gas flow rate did not cause important changes in C, H, N and O contents; the same is observed for the molar ratios. Only S content changed in an important degree, decreasing its content with increase in inert gas flow rate. As expected, bran bio-oil ultimate analysis was quite distinct from biomass and FRSC bio-oil. It is remarkable both high N and S contents and smaller C and H contents, probably due to the lack of oil that composes the biomass. High S presence can be explained because the seed, being a storage organ, must provide enough nutrients to the seedling until its root becomes functional. Most enzymes and proteins have sulfur in its composition, and sulfur is a major metabolic element, being necessary in considerable amounts [35]. GC/MS analysis aimed to identify the main organic compounds for each rotation speed (Table 6). The bio-oil produced at 0 rpm presented linear and branched aromatics; the quantity of saturated and unsaturated aliphatics (and especially oleic acid) was high. It was observed the presence of nitriles and amides, probably from the protein fraction of the biomass. The bio-oil contained a high content (24.25% of chromatogram area) of oleic acid, which ended up being not completely decomposed by the primary and secondary reactions, evaporating and being collected in the liquid fraction. Smets et al. [9,10], working with rapeseed pyrolysis (flash and fixed bed reactors) obtained a similar behavior pattern, with substantial amount of oleic acid in the generated bio-oil, regardless of final pyrolysis temperature. The authors also reported the presence of some unsaturated aliphatic compounds, such as 8-heptadecene, 9-octadecenoic acid methyl ester and 9-octadecenamide. The qualitative composition of the bio-oil produced at 3 rpm was similar to the bio-oil produced at 0 rpm. However, it was observed the presence of species not found in the bio-oil produced at 0 rpm. It was identified branched aromatics (4-ethyl-phenol, 2-methyl-phenol), and aliphatic hydrocarbons (9-nonadecene). Chutia et al. [36], pyrolyzing oil-free karanja seed (Pongamia glabra) at 500 °C, also detected similar species, especially aromatics. It is possible to observe the increase in oleic acid content due to rotation (from 24.25% of chromatogram area at 0 rpm to 37.28% at 3 rpm). This trend of increase in oleic acid content was observed in reactors whose residence times are low; this would minimize secondary reactions that cracks fatty acids. As observed by Smets et al. [9,10],

vapors from other components of the biomass (proteins, cellulose, lignin), the vapors from the residual oil would not have sufficient time to react and crack, even when in the hot zone of the reactor. Lappi and Alén [29], working with the pyrolysis of fatty acids with chains from twelve to twenty carbon atoms, also observed this behavior. In accordance to the experiments, there was a significant reduction in bio-oil yield, accompanied by an increase in bio-char and non-condensable gases yield. The absence of residual oil in FRSC bran reduced the mass of vapors during the reaction, increasing the residence time of these vapors inside biomass particles. The greater residence time of the volatiles formed in the primary pyrolysis of FRSC bran fostered the formation of non-condensable gases to the detriment of bio-oil [30,31]. The increase in non-condensable gases yield in the experiments with FRSC bran may be associated to a greater residence time of the volatiles formed in the primary pyrolysis inside the particles, fostering secondary reactions. The increase in bio-char yield may also be associated to the greater residence time of the pyrolytic vapors inside the particles of the biomass, fostering the formation of secondary char (recharring). 3.4. Bio-oil characterization The bio-oils were characterized to determine their chemical and elemental (CHNOS) composition. The physicochemical parameters were also evaluated to identify properties of bio-oils produced at different operational conditions, which could bestow more suitable uses of the material for industry, synthesis of chemicals or in bioenergy. 3.4.1. Chemical characterization of bio-oils obtained at different rotation speeds Bio-oil ultimate analysis determined the composition of the major elements present in the biomass (FRSC) and their distribution in the liquid fraction (bio-oil) in function of different process conditions. (Table 5) The variation of rotation speed did not cause changes in the elemental composition of the bio-oils, whose concentrations were similar to the ones literature reported for bio-oils obtained from rapeseed seed bagasse. FRSC bio-oil had a higher H/C ratio when compared to H/C ratio of bio-oil obtained from lignocellulosic biomasses (in general, H/C is less than 1.5). Higher H/C ratio indicates a lower degree of aromatization of the bio-oil, and may be attributed to the effect of the remaining oil in the biomass, which has a high content of hydrogen, reducing cyclization and aromatization of pyrolytic vapors, providing nascent hydrogen during the secondary reactions [28,32]. Table 5 Results of bio-oils ultimate analysis (organic fraction, dry basis) obtained at different process conditions. Element1 (wt.%)

Carbon (C) Hydrogen (H) Nitrogen (N) Sulfur (S) Oxygen2 (O) H/C3 O/C3 N/C3 1 2 3

Biomass

0.75 L/min

3 rpm

0.75 L/ min; 3 rpm

0 rpm

3 rpm

6 rpm

0.25 L/min

1.25 L/min

Bran

47.97

64.58

65.32

64.54

63.96

65.11

57.57

8.50

9.54

9.56

9.63

9.73

9.62

8.47

6.43

8.00

7.87

7.71

6.62

7.05

10.17

2.09 31.88

0.57 17.31

0.57 16.68

0.66 17.46

2.59 17.00

0.19 15.49

3.56 21.93

2.128 0.499 0.115

1.756 0.201 0.106

1.740 0.192 0.103

1.774 0.203 0.102

1.809 0.199 0.089

1.757 0.178 0.093

2.010 0.286 0.152

Contents disregarding water in bio-oil. Obtained by difference. Molar ratio.

5

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secondary reactions or even may be generated by them [5,28]. The fatty acids presented their maximum releasing rate between 250 and 350 °C, which would explain the high content of oleic and erucic acids (although erucic acid was identified with less than 90% of confidence, its concentration was greater than 3.0% of chromatogram area) in the bio-oils. The presence of long chain hydrocarbons (pentadecane, dodecane, butylbenzene) may be attributed to decarboxylation reactions. Amines and amides are product from the reactions between fatty acids vapors with ammonia or nitrogenous products from protein degradation. The nitrogenous aromatics (pyridine, indoles) may be generated by the degradation of protein chains of the biomass that contain these structures. Benzene and toluene may be product of side chains of some aminoacids, as well as of lignin [34].

Table 6 Concentrations (% chromatogram area) of species detected in the bio-oils (correspondence range was considered as equal or greater than 90% of confidence) produced at inert gas flow rate of 0.75 L/min and different speed rotations. Component name

CAS Number

0 rpm

Oleic acid Erucic acid Hexadecanamide 4-methyl-phenol 9-octadecenamide Phenol Indole 8-heptadecene 2-methyl-phenol Pentadecane 2–6-dimethoxyphenol Butyl benzene 3-methyl-1H-indole 5-methyl-1H-indole 2-methyl-pyridine 9-octadecenoic acid methyl ester Benzyl nitrile 4-ethyl-phenol Dodecane Benzenepropanenitrile 9-nonadecene Pentadecanonitrile Hexadecanonitrile Heptadecanonitrile Pyridine 1,2-benzenedicarboxylic di-isoctyl ester Σ Saturated and unsaturated aliphatics Σ Amides Σ Aromatics Σ Nitrogen aromatics Σ Nitriles

112−80-1 112−86-7 629−54-9 106−44-5 301−02-0 108−95-2 120−72-9 2579−04-6 95−48-7 629−62-9 91−10-1 104−51-8 83−34-1 614−96-0 109−06-8 112−62-9 140−29-4 123−07-9 112−40-3 645−59-0 31035−07-1 18300−91-9 629−79-8 5399−02-0 110−86-1 27554−26-3 – – – – –

24.25 3.15 3.10 5.06 4.89 1.83 1.77 1.65 – 0.32 0.72 0.78 – 0.63 0.68 0.77 0.57 – a

3 rpm

6 rpm

37.28

34.64

a

a

7.50 3.51 4.00 1.72 1.56 1.47 0.80 0.64 0.63 0.57 0.51 – 0.46 0.23 0.46 0.54 0.41

– 4.36 4.98 1.86 1.28 1.46 – 0.37

a

a

– 0.49 – – – – 26.99 7.99 8.39 3.08 1.06

0.38 – – a

– 0.47 40.41 11.50 7.67 2.53 0.46

a

3.4.2. Chemical characterization of bio-oils obtained at different inert gas flow rates The bio-oils obtained at optimal speed rotation (3 rpm) and different inert gas flow rates (0.25; 0.75; 1.25 L/min) were also analyzed by GC/MS in order to verify bio-oil chemical composition. According to Table 7, the chemical composition of the bio-oils was influenced by ranging of inert gas flow rate. Also it was possible to observe in the smaller flow rate (0.25 L/min) and, therefore, in the greater residence time of pyrolytic vapor inside the reactor (97 s), that the bio-oil did not present oleic acid in its composition, but a nonaromatic cyclic hydrocarbon (2-metyhl-6-[4-(4-metyhlpentyl)cyclohexyl]heptane). This may be result of condensing reactions of fatty acid chains due to high residence times. In this condition, the number of amines and amides was smaller and nitriles were not observed, with exception of oleanitrile (which is from oleic acid). For the highest inert gas flow rate, oleic acid content was higher (42.81 at 1.25 L/min against 37.28 at 0.75 L/min), because the smaller residence time of the vapor is at this flow rate (near 19.4 s against 32.25 s at 0.75 L/min). This may minimize secondary reactions, rendering the residual oil in the biomass suffer small changes on its structure. The erucic acid content did not change significantly when the inert gas flow rate increased from 0.25 until 1.25 L/min. Authors who worked with pyrolysis of similar biomasses reported the occurrence of many compounds that were found in FRSC bio-oil, at the three inert gas flow rates. The presence of amines, amides, nitriles and various aromatics, as well as phenolics and even saturated and unsaturated hydrocarbons gave a different characteristic to the FRSC in relation to lignocellulosic biomasses, whose aromatics content is very high due to the presence of lignin, which is composed of aromatic monomers that are depolymerized when on thermolysis. The high residual oil content in the composition, along with nitrogen content in the biomass (near 6 wt.%) would be the main cause of the diverse composition, the great presence of nitrogenous compounds in the condensed liquid fraction, and the low O/C molar ratio of the biooil. The higher nitrogen compounds content and smaller aromatics content make the bio-oils obtained both at 0.75 and 1.25 L/min suitable as feedstock to obtain amines and nitriles for the chemical industry [8,9,10,28,36,38].

a

– 0.59 0.49 0.30 0.40 0.54 – 0.24 1.04 – 0.54 0.35 0.68 0.40 37.81 4.98 7.16 3.04 1.53

a Indicates a compound identified by GC/MS, but the correspondence was smaller than 90% of confidence. The trace (−) indicates absence of the compound in the bio-oil.

pyrolyzing rapeseed cake, and Seal et al. [37], pyrolyzing cotton seed at 500 °C, the presence of amines, amides and nitriles may be result of nucleophilic interaction of nitrogen from the biomass, where higher nitrogen contents would tend to produce larger amounts of these species in the products [5,12]. At 6 rpm the qualitative composition of the bio-oil was similar to the one obtained at 3 rpm. However, at 6 rpm was observed the presence of pyridine (aromatic amine), hexadecanonitrile and heptadecanonitrile (aliphatic nitriles) in low concentrations, probably result of nucleophilic interaction of nitrogen with carboxyl groups in the oily fraction of the biomass (oleic acid). The oleic acid content for both rotation speeds (3 and 6 rpm) was similar (37.28% of chromatogram area at 3 rpm and 34.64% at 6 rpm). The smaller residence time of primary pyrolysis vapors minimized secondary cracking reactions, and consequently, at 6 rpm there was the presence of species with relatively long carbon chains (hexadecanonitrile, benzenopropanonitrile, 9-nonadecene), with more than fifteen carbon atoms. Smets et al. [9,10], Chutia et al. [36] and Seal et al. [37] reported species (4-etyhl-phenol, 2-metyhl-phenol, indole) similar to the ones obtained in this work. From Table 6 it was observed the increase in reactor rotation speed from 0 to 3 rpm reduced the concentration (chromatogram area) of many compounds (aliphatics, aromatics and nitriles), although there is no clear trend. It also occurred a trend of increase in oleic acid and linear amides (hexadecanamide) contents. The many species found in the bio-oil were result of the heterogeneous cracking of the macromolecules that form the biomass. In general, the bio-oil had aromatics and branched aromatics in higher concentrations. This is due to hydrogen loss during pyrolysis. The benzenic ring and its conjugates are energetically stable, this decreases their degradation due to resistance to thermolysis, so they participate in

3.4.3. Chemical characterization of bio-oil from FRSC bran pyrolysis The bio-oil obtained by FRSC bran pyrolysis was also analyzed by GC/MS in order to evaluate the effect of the residual oil of the biomass on the composition of the liquid fraction (Table 8). The experiments were conducted at 3 rpm and 0.75 L/min. The pyrolysis of FRSC bran generated a liquid fraction (bio-oil) with fewer detected components than the bio-oil from biomass (FRSC). The bran bio-oil presented aromatics and nitrogen aromatics in greater quantity, but did not presented nitriles and almost did not present amines and amides when compared to the bio-oil from FRSC. Chutia et al. [36], characterizing by GC/MS the bio-oil of karanja bran obtained at 500 °C, also reported the presence of aromatics (toluene, phenol) and unsaturated compounds, in particular heterocyclic 6

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Table 7 Concentrations (% chromatogram area) of species detected in the bio-oils (correspondence range was considered as equal or greater than 90% of confidence) produced at 3 rpm and different inert gas flow rates. Component name

CAS Number

0.25 L/min

0.75 L/min

1.25 L/min

2-methyl-6-[4-(4-methylpentyl)ciclohexyl]heptane Oleic acid Hexadecanamide 9-octadecenamide 4-methyl-phenol Phenol Indole 8-heptadecene 2-methyl-phenol Pentadecane 2–6-dimethoxy-phenol Butyl benzene 4-ethyl-phenol 3-methyl-1H-indole 1,2-benzenedicarboxylic acid di-isoctyl ester 2-methyl-pyridine Benzyl nitrile Dodecane 9-nonadecene 9-octadecenoic acid methyl ester Toluene Hexadecanoic acid Octadecanoic acid Tetradecanamide Hexadecanonitrile Heptadecanonitrile Oleanitrile Hexadecine Octadecanamide 9-octadecenoic acid Erucic acid Cis-11-eicosenamide Z-13-docosenamide Stigmastan-3,5-diene 6-octadecenoic acid methyl ester Z,Z-9,12-octadecadienoic acid Σ Saturated and unsaturated aliphatics Σ Amides Σ Aromatics Σ Nitrogen aromatics Σ Nitriles

56009−20-2 112−80-1 629−54-9 301−02-0 106−44-5 108−95-2 120−72-9 2579−04-6 95−48-7 629−62-9 91−10-1 104−51-8 123−07-9 83−34-1 27554−26-3 109−06-8 140−29-4 112−40-3 31035−07-1 112−62-9 108−88-3 57−10-3 57−11-4 638−58-4 629−79-8 5399−02-0 1000308−88-1 629−74-3 124−26-5 1000190−13-7 112−86-7 10436−08-5 112−84-5 1000214−16-4 2777−58-4 60−33-3 – – – – –

42.49 – – 4.44 – 0.60 0.85 – – – 0.68 – – 0.35 – – – – – 0.67 1.54 7.84 3.45 2.71

– 37.28 7.50 4.00 3.51 1.72 1.56 1.47 0.80 0.64 0.63 0.57 0.54 0.51 0.47 0.46 0.46 0.41 0.38 0.23

– 1.14 1.06 0.74 6.51 4.72 0.36 0.52 – – – 66.74 8.77 2.82 1.20 1.14

– –

– 42.81 3.24 5.32 0.91 – 1.07 0.62 – – 0.59 – – 0.48 – – – – – – 1.20 6.94 – – 0.46 0.32 2.05 –

a

a

–

5.37 4.69 1.32 1.45 0.58 0.44 2.35 60.83 11.33 2.70 1.39 2.83

a

a

– – –

a

a

– – – – – 40.41 11.50 7.67 2.53 0.46

Indicates a compound identified by GC/MS, but the correspondence was smaller than 90% of confidence. The trace (−) indicates absence of the compound in the bio-oil.

the reaction of ammonia (generated in the decomposition of protein fraction of the biomass) with the vapors of free fatty acid. These reactions may be more pronounced in the gas phase (secondary reactions), once in primary pyrolysis would occur volatilization of lipids (fatty acids). The presence of indole (nitrogen aromatic) may be attributed to the presence of natural amino acid tryptophan in FRSC, which has an indole ring in its structure. Other nitrogen aromatics and pyrroles possibly would be cyclization products of aliphatic amino acids vaporized during primary pyrolysis that reacted in a posterior stage, and would not be direct products from thermal degradation of proteins [34].

aromatics (indole, pyrrole and derivatives) with nitrogen as the heteroatom. Nayan et al. [39], also characterizing bio-oil from pyrolysis of karanja seed at 500 °C, reported similar composition, however, due to the remaining oil of the biomass, were present also amines and amides with long carbonic chain (> 10C). The absence of residual oil in the bran, whose carboxyl groups could be easily attacked by the nitrogen of the biomass to generate amines, amides, nitriles and heterocyclic aromatics, made it difficult or even precluded the formation of these nitrogenous compounds [28,29]. It was observed the presence of unsaturated hydrocarbons, but in a much smaller content than in FRSC bio-oil (with oil). The great presence of benzene-derivative aromatics (toluene, 2-metyhl-phenol, 4-metyhlphenol, 2–6-dimethoxy-phenol) in bran bio-oil may be attributed to cyclization reactions of primary pyrolytic vapors, as well as of decomposition of the lignin in the bran. The nitrogen in the biomass acted as a nucleophilic center, with consequent increase in nitrogenous aromatics contents [5,11]. The presence of linear and aromatic amines, amides and nitriles in the bio-oil was result of specific reactions of the nitrogenous compounds in the biomass (proteins, enzymes, and amino acids) during depolymerization and releasing of the primary vapors. The bio-oil produced in all experiments (except in the ones with the bran) presented, beyond free and non-degraded fatty acids, amines and amides of long chain. The presence of these compounds may be possibly due to

3.4.4. Physicochemical parameters of bio-oils The physicochemical analysis of bio-oils was performed without the presence of isopropanol (which was removed by rotary evaporation). Only the water content was determined with the bio-oils diluted in isopropanol. (Table 9) It was observed that bio-oil water content decreased with increase in rotation speed. The rotation speed minimized the secondary reactions, as water is a product of these reactions, so that the increase in rotation speed reduced water formation. The moisture present in the biomass (FRSC) also contributed to the water content of the bio-oil. Ucar and Ozkan [8], performing pyrolysis of rapeseed cake in a fixed bed reactor, obtained bio-oil water content of 40 wt.%. Smets 7

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(ionization), increasing EC values. The specific mass of the bio-oils did not present important variations with the changing of rotation speed (from 0.907 to 0.932 g/cm3). Smets et al. [10] reported specific mass values of rapeseed seed cake which varied from 0.96 to 0.98 g/cm3. Ash content was very small, indicating that there was an insignificant drag of inorganic material to the liquid phase. The ashes present in the bio-oil may be from biochar aerosol, which was dragged to the liquid phase (bio-oil) and posteriorly collected in the impingers [40]. Kinematic and dynamic viscosities of the bio-oil obtained at 3 rpm were the smallest found in relation to the rotation speeds evaluated. Higher oleic acid content at this rotation speed may be associated to the smaller viscosity observed. Mortensen et al. [33] reported typical values of dynamic viscosity (measured at 50 °C) from 40 to 100 cP for bio-oil obtained by pyrolysis and immediate catalytic upgrading of the pyrolytic vapor of lignocellulosic biomass. For pumping and fluid transport, smaller viscosities indicate less energetic spends with shaft work and losses from friction [41]. So, the bio-oil obtained at 3 rpm, presenting a dynamic viscosity of 17.53 cP, was the one that had the best viscosity for industrial and energy production applications. HHV of the bio-oils were not affected by reactor rotary speed, remaining around 31.5 MJ/kg. Smets et al. [10] reported HHV values of 29.8 MJ/kg for rapeseed seed cake bio-oil, pyrolyzed at 500 °C without catalyst. In a similar work, Smets et al. [9] presented HHV values of 32.8 MJ/kg for rapeseed seed bagasse bio-oil, produced at 550 °C. Ucar and Ozkan [8], also working with rapeseed seed cake, reported HHV values of 33.17 MJ/kg for bio-oil produced at 500 °C. Inert gas flow rate did not change bio-oil pH. Water content, ash content and EC had increased with the increase in flow rate. This could be result of aerosol drag from the reactor to the condenser system [40]. Specific mass had a slight increase trend with increase in flow rate, while dynamic viscosity had a strong decrease with increase in flow rate, probably due to fatty acids drag and condensation at higher flow rates [29]. HHV and LHV values decreased slightly in relation to the increase in inert gas flow rate as result of CHNOS distribution in the biooils. The bio-oil from bran had smaller water content and pH value and greater specific mass when compared to FRSC, probably due to the removal of fatty acids from the biomass. Dynamic viscosity, EC value and ash content did not present a trend, because these parameters may be more dependent of inert gas flow rate than biomass composition [9,10]. HHV and LHV values were smaller than the ones of FRSC.

Table 8 Comparison of concentrations (% of chromatogram area) for the compounds detected in the bio-oils (the correspondence range was considered as equal or greater than 90% of confidence) produced by pyrolysis of FRSC and its bran at 3 rpm and 0.75 L/min. Component name

CAS Number

FRSC

Bran

Oleic acid Hexadecanamide 9-octadecenamide 4-methyl-phenol Phenol Indole 8-heptadecene 2-methyl-phenol Pentadecane 2–6-dimethoxy-phenol Butyl benzene 4-ethyl-phenol 3-methyl-1H-indole 1,2-benzenedicarboxylic acid di-isoctyl ester 2-methyl-pyridine Benzyl nitrile Dodecane 9-nonadecene 9-octanodecenoic acid methyl ester Toluene 2-methoxy-4-vinylphenol Pyrrole[1,2-a]pyrazine-1,4-diona Hexadecanoic acid E-9-octadecenoic acid Σ Saturated and unsaturated aliphatics Σ Amides Σ Aromatics Σ Nitrogen aromatics Σ Nitriles

112−80-1 629−54-9 301−02-0 106−44-5 108−95-2 120−72-9 2579−04-6 95−48-7 629−62-9 91−10-1 104−51-8 123−07-9 83−34-1 27554−26-3 109−06-8 140−29-4 112−40-3 31035−07-1 112−62-9 108−88-3 7786−61-0 19179−12-5 57−10-3 112−79-8 – – – – –

37.28 7.50 4.00 3.51 1.72 1.56 1.47 0.80 0.64 0.63 0.57 0.54 0.51 0.47 0.46 0.46 0.41 0.38 0.23

– – 1.01 3.76 2.91 4.46 – – – 3.15 – – 2.03 – – – – – – 9.15 2.33 3.15 3.99 7.79 14.11 1.01 18.97 9.64 –

a

– – – – 40.41 11.50 8.24 2.53 0.46

a Indicates a compound identified by GC/MS, but the correspondence was smaller than 90% of confidence. The trace (−) indicates absence of the compound in the bio-oil.

et al. [9], carrying out flash pyrolysis of the same biomass, reported water content of 6.7 wt.% in organic fraction of the bio-oil produced at 550 °C. The same authors [10], in a 2013 work using slow pyrolysis, reported water content of 14.9 wt.% in the organic fraction and 67.7 wt. % in the aqueous phase of the bio-oil. In this work was not performed the separation between organic and aqueous phases, neither of the isopropanol, to determine bio-oil water content. The pH did not present a trend, being its higher value (6.02) at 3 rpm. Although literature cites that, in general, bio-oil pH is quite acid (from 2 to 3), the high nitrogen content of the biomass contributed to the increase in bio-oil alkalinity [11,33]. Smets et al. [9,10], reported pH values of 6.9 to the bio-oil produced in slow pyrolysis and 7.2 to the bio-oil produced in flash pyrolysis of rapeseed cake. The electrical conductivity presented an inverse behavior to the one observed for pH, i.e., the smaller electrical conductivity was associated to a higher pH (3 rpm). The presence of carboxylic acids may acidify the medium

3.4.5. Energy balance of pyrolysis process Since the optimal rotation of the process was 3 rpm, a simplified energy balance for FRSC pyrolysis at 3 rpm and 0.75 L/min of inert gas flow rate was provided. The results of the energy balance are presented in Table 10. The energy balance for the process presented a global energy

Table 9 Physical-chemical parameters of bio-oils obtained at different process conditions. Parameter

1

Water (wt.%) Ash (wt.%) pH Electrical conductivity (mS/cm) Specific mass (kg/m3) Dynamic viscosity at 20 °C (cP) Kinematic viscosity2 (10−5 m2/s) HHV (MJ/kg) LHV (MJ/kg) 1 2

0.75 L/min

3 rpm

3 rpm; 0.75 L/min

0 rpm

3 rpm

6 rpm

0.25 L/min

1.25 L/min

Bran

41.99 0.72 5.58 1.333 932.78 65.87 7.06 31.31 29.23

38.75 0.48 6.02 1.155 907.42 17.53 1.93 31.34 29.25

36.71 0.56 5.85 1.281 923.08 30.43 3.30 31.41 29.31

54.68 0.10 5.68 0.645 1055.10 102.44 9.71 31.15 29.03

57.56 0.85 5.72 1.131 1102.00 12.15 1.10 30.94 28.84

35.47 0.60 5.38 0.864 1121.05 53.87 4.81 30.79 28.94

Water content was determined in the mixture bio-oil + isopropanol, while the other parameters were determined in the bio-oil separated by rotary evaporation. Kinematic viscosity was calculated by the ratio between dynamic viscosity and the specific mass of the fluid.

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Table 10 Energy balance for FRSC pyrolysis at 3 rpm and inert gas flow rate of 0.75 L/min. Fraction

HHV (MJ/ kg)

Pyrolysis yield (wt. %)

Mass (g)

Energy content (MJ)

Energy recovery (%)

Biomass Biochar Bio-oil Non-condensable gases

30.22 22.98 31.34 9.25

– 24.89 60.98 14.13

150.00 37.34 91.47 21.19

4.533 0.858 2.867 0.196

– 18.93 63.25 4.32

Energy input (MJ) Energy output (MJ) Energy conversion efficiency (%)

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Knudsen, A.D. Jensen, A review

4.533 3.921 86.49

conversion efficiency of 86.49%. Hanif et al. [42], working with several kinds of biomass and performing computational simulations, presented efficiency ranges from 65 to 75%, depending on final pyrolysis temperature. Most of energy was recovered in bio-oil fraction as result of both greater bio-oil yield and HHV value when compared to solid and gas fractions (biochar and non-condensable gases). Rapeseed seed cake bio-oil HHV values reported by Ucar and Ozkan [8] and Smets et al. [9,10] ranged from 29 to 45 MJ/kg. Stedile et al. [28], in a review work on bio-oil properties from lignocellulosic and oily biomasses, reported greater bio-oil HHV values from oily biomasses, ranging from 32 to 42 MJ/kg, when compared to lignocellulosic biomasses, whose bio-oil HHV values are quite smaller, ranging normally between 15 and 25 MJ/ kg. As a result of bio-oil high HHV, the process presented a high-energy conversion efficiency. 4. Conclusion FRSC pyrolysis in a rotary kiln had a bio-oil yield near 60 wt.%. An optimal speed rotation of 3 rpm was observed for bio-oil production. The flow rate of 1.25 L/min increased bio-oil yield, however, this increase was small (around 2%). Therefore, a flow rate of 0.75 L/min can be considered optimal for bio-oil production in FRSC pyrolysis. The smallest S content in bio-oil was observed in FRSC pyrolysis at 3 rpm and 1.25 L/min, while the greatest S content was observed in the bio-oil produced from bran pyrolysis. Bio-oil from FRSC pyrolysis presented high content of oleic acid in its composition, and was observed an increase at the flow rate of 1.25 L/min. The high H/C ratio in the bio-oil from FRSC pyrolysis indicated lesser aromatization degree, suggesting a decreasing in PAH formation. It was also observed a small O/C ratio, which was desirable, because increases bio-oil chemical stability. Bran pyrolysis had the smallest bio-oil yield (near 50 wt.%), with a distinct composition than the one from FRSC pyrolysis. Bran bio-oil had smaller content of saturated and unsaturated aliphatics, amines and amides, higher content of aromatics and absence of nitriles. The high pH (near to 6) indicated a bio-oil less aggressive to process materials. The smaller viscosity of the bio-oil is important for industrial uses. The bio-oil obtained at 3 rpm presented the more suitable composition and characteristics for industrial applications and in bioenergy, although is necessary further upgrading processes for each specific use. Acknowledgments The authors would like to thank Eng. C. Manera (UCS) for providing the reactor scheme and Mr. A. A. Munz (UCS), who kindly helped with fodder radish cultivation and harvesting. References [1] R.N.A. Ávila, J.R. Sodré, Physical–chemical properties and thermal behavior of

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