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Potential value added applications of black liquor generated at paper manufacturing industry using recycled fibers
Accepted Manuscript Potential Value Added Applications of Black Liquor Generated at Paper Manufacturing Industry Using Recycled Fiber Zainab Al-Kaabi, Ranjan R. Pradhan, Naresh Thevathasan, Yi Wai Chiang, Andrew Gordon, Animesh Dutta PII:
S0959-6526(17)30288-3
DOI:
10.1016/j.jclepro.2017.02.074
Reference:
JCLP 9000
To appear in:
Journal of Cleaner Production
Please cite this article as: Zainab Al-Kaabi, Ranjan R. Pradhan, Naresh Thevathasan, Yi Wai Chiang, Andrew Gordon, Animesh Dutta, Potential Value Added Applications of Black Liquor Generated at Paper Manufacturing Industry Using Recycled Fiber, (2017), doi: 10.1016/j.jclepro.2017.02.074 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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Highlights: Black liquor generated using recycled fiber as feedstock are different Non plant origin component hexanedioic acid derivatives were identified This material can be processed for extractions and source of bioenergy Potential for enhancement as fuel by removal of mainly sodium component
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Total Word Count of the Manuscript including Tables and Figure = 5,561 words
Potential Value Added Applications of Black Liquor Generated at Paper Manufacturing
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Industry Using Recycled Fiber Zainab Al-Kaabia , Ranjan R. Pradhanb, Naresh Thevathasanb, Yi Wai Chiangb, Andrew Gordona, Animesh Duttab*
School of Environmental Science, bSchool of Engineering, University of Guelph, Ontario,
N1G 2W1, CANADA,
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*Correspondence author: [email protected]
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a
Abstract
Characterization of neutral sulphite semi-chemical black liquor (NSSCBL), sampled from paper manufacturing process that uses recycled fibers as primary feedstock, was carried out for potential bioenergy and biomaterial applications. Physico-chemical characteristics including inorganic elements content, thermogravimetric analysis, GC/MS, and FT-IR are
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presented. The black liquor of the recycled fiber in the manufacturing process revealed unique characteristics in terms of chemical composition profile compared to the black liquor originating from regular pulp and paper industries. The major findings include the presence of chemical compounds, from a non-plant origin, such as derivatives of hexanedioic acid in
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significant quantities. The favorable biofuel characteristics of this black liquor are: neutral pH, a higher volatile content, and HHV. The recycled paper NSSCBL can be a good candidate for
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biomaterial and biofuel applications.
Keywords: Black liquor, Recycled paper, Pulp, Biopolymer 1. Introduction:
Pulp and paper production uses plant cellulose from biomass and generates black liquor as a byproduct which contains 65-85% solids (Ramesh et al., 2013) having 10-50% lignin by weight (Ksibi et al., 2003). The characteristics and compositions of black liquor obtained from various pulping processes depends on the type of raw materials, pulping conditions and source of fibers used in production (Smook, 1992). Raw materials being used are wood,
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agricultural residues, or recycled papers (Bajpai, 2012). The pulp and paper making process applies various pulping processes that includes sulphite pulp to produce fine and printing papers, Kraft sulphate pulp to produce bleached-printing and writing papers, paperboard, unbleached-heavy packaging papers, paperboard, and dissolving pulp to produce viscose
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rayon, cellophane, acetate fibers, and films (Andelin et al., 1989). Neutral Sulphite SemiChemical (NSSC) Pulping uses mix of wood chips from virgin pulp with 20–35 % recovered fiber or re-pulped secondary fibers (Bajpai, 2014). In the neutral sulphite process reaction
temperatures range from 160-180 °C and pH ranges from 5-7, but alkaline sulphite reaction temperatures range from 160-180 °C and its pH 9 - 13.5 (Patt et al., 2005). About 50% of the
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lignocellulosic biomass matter dissolves into the black liquor during the pulping process. The major part of the dissolved matter contains lignin, degraded carbohydrates including cellulose
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and hemicellulose; the minor part contains protein, extractives, (Sjostrom, 1993) and inorganic materials (Wallberg et al., 2006). Many monomers of biopolymers such as 2-methoxyphenol, 2, 6-dimethoxyphenol, 4-hydroxy-3-methoxybenzaldehyde, 4-hydroxy-3, 5dimethoxybenzaldehyde, 1-(4-hydroxy-3-methoxyphenyl) ethanone, 1-(4-hydroxy-3, 5dimethoxyphenyl) ethanone, etc. have been extracted from the process waste which is called black liquor, and were identified using the GC/MS analysis (Radoykova et al., 2013). Very limited data is available on composition of the recycled paper neutral sulphite semi-chemical
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(RPNSSC) process, and related emission factors of their manufacturing facilities that recycles waste paper. Pulp and paper mills that are increasingly using recycled paper would offer a perfect opportunity to keep the environment clean by using a huge quantity of paper waste; on the other hand, this saves a significant number of trees, and reduces the cost of wood pre-
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treatment that should be done prior the pulping process, such as chemical, physical, and biological pre-treatment. Mills that use a certain recycled paper fractionation process could
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serve the economy aspect by reducing the energy consumption, virgin fiber consumption, improve the efficiency of ink detachment, and improve pulp quality (Kong et al., 2016). Many pulp and paper mills are no longer producing only their regular products, but also use biorefinery procedures on their byproducts such as the black liquor, to enhance their profitability and the energy efficiency (JÖnsson et al., 2011). The environmental sustainability
of using different black liquors to produce biofuel and biochemical has been investigated, such as preparing porous polymers from Kraft black liquor (Foulet et al., 2015), producing hydrochar using hydrothermal carbonization of black liquor (Kang et al., 2012), and hydrochar production using hydrothermal conversion of Neutral Sulfite Semi-Chemical red liquor (Gamgoum et al.,2016). However, the black liquor from the RPNSSC pulping process
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is unique and likely to carry forward different components that are inherent components of recycled paper as contributions to the process waste. The general applications adopted for regular black liquors may not be universally applicable for this category of industrial waste and need detailed investigation for efficient utilization and
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further disposal needs must be identified. With absence of any published literature, we are attempting for the first time to investigate the potential value added applications based on its physico-chemical characteristics.
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2. Materials and Methods: 2.1 Raw material
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Neutral sulphite semi-chemical (NSSC) black liquor at the concentrator stage (with approximately 45-50% solids) was procured from Cascades Inc., 404, Marie-Victoria Blvd. Kingsey Falls, Quebec, J0A1B0, and Canada. The samples from concentrator stage which represents a bulk processing stage where huge quantities of the liquid process wastes are collected and concentrated to produce the NSSC products. This NSSC product is stable and physically consistent within different production batches.
The sample representing this
process was collected from Cascade Inc. and is named as RPNSSC for this study. Table 1
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shows the characteristics of RPNSSC sample as received. The manufacturing process at Cascade Inc. uses 42.5% wood fiber with 57.5% recycled paper consisting of corrugated packaging materials that comes from industrial, commercial, institutional, and municipal sources as a feedstock.. The bulk density of the received samples were immediately measured
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according to ASTM D891 – 09 (American Society for Testing and Materials) and is presented in Table 2. The sample was kept in air tight containers in dark and at refrigerated condition till
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further use.
Table 1: Characteristics of RPNSSC black liquor sample 2.1.1 Sample preparation to determine physico-chemical characteristics The recycled Paper NSSC Black liquor sample (RPNSSC) was dried at 105 ºC for 24 hrs using a Thermolyne muffle furnace. Sample were then reduced in size to a particle size of approximately 425 µm using a planetary ball mill PM 100, (make- Retsch, Haan, Germany) to characterize for proximate analysis , ultimate analysis and heating values. Proximate analysis of the sample was carried out for its inherent moisture contents, ash (mineral) contents at 950
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ºC, volatile matter (when heated to 950 °C), and fixed carbon according to ASTM D7582, ASTM D 3174, ASTM D3175, and ASTM D7582 respectively. Ultimate analysis were carried out in the same sample to understand the composition of the biomass as weight percentage of components such as carbon (C), hydrogen (H), nitrogen (N), oxygen (O) and sulfur (S). The
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C, H, N, S, and O contents was determined by combustion using Elemental Analyzer make Thermo Scientific, model Flash 2000 (Lakewood, NJ, USA) according to ASTM D5373. Oxygen content was calculated as the percentage difference from the total. Targeted inorganic elemental analysis of dried RPNSSC black liquor was done by inductively coupled plasma optical emission spectroscopy using Varian Vista Pro Axial viewed plasma ICP- OES
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technology. Calibration standards were made from 1,000 µg/L ICP MS standards. Prior to elemental analysis, in order to eliminate all the organic materials in the samples, the dried
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RPNSSC samples were digested with metal grade concentrated nitric acid and then with trace metal grade concentrated hydrochloric acid so as to measure only the targeted inorganic elements in the sample.
Heating values were experimentally determined using an IKA C200 bomb calorimeter (Wilmington, NC, USA) according to ASTM E 711 and further validated by calculations using a PLS formula as shown in equation (1) for the same dried samples (Friedl et al., 2005).
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PLS Formula:
Q(MJ/kg) = 5.22C2 − 319C − 1647H + 38.6C×H + 133N + 21028
(1)
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Where C = carbon; H = hydrogen; N = nitrogen contents by dry weight basis.
In order to separate major soluble fractions of RPNSSC black liquor for characterizing the
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contents of the sample were processed for extraction in polar and non polar solvents like water, methanol, and hexane. Initially extraction was carried out by mixing 100 gm of wet black liquor sample with 100 gm of water as extraction solvent in 1:1 ratio. The mixture was centrifuged for 20 minutes at 4,000 rpm using centrifuge. The residue of water extract portion was then extracted individually with methanol and hexane in 1:1 ratio. All the extracts were dried using a Thermolyne muffle furnace at 105 ºC for 24 hrs for evaluating further by FT-IR and GC/MS studies. 2.2 Thermogravimetric Analysis
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The thermogravimetric analyzes were performed using micro-TGA SDT Q 600 (TA Instruments, New Castle, USA). A pair of platinum weight pans/crucible was used for holding the samples that were ground to pass through 500 microns in a powder form. All the raw and ground biomass was dried and kept in desiccators to be used for thermal treatment in micro-
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TGA. The Micro-TGA was heated up at the rate of 20 °C /min to the desired temperature. The sample weight of about 10-12 mg was placed in a crucible. Nitrogen was supplied inside the reactor at the rate of 50 ml/minutes. The weight loss and heat flow characteristics were monitored and analyzed with Thermal Analysis Universal software (TA Instruments, New
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Castle) to generate DSC-TGA plots.
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2.3 Fourier Transform Infrared Spectroscopy (FT-IR) Study
Oven dried and ball milled samples were analyzed out with a FT-IR spectrometer in the wave number range 400–4,000 cm-1. The IR instrument Varian 660-IR equipped with liquid nitrogen cooled the MCTA detector. The ATR was a Pike MIRacle single reflection ATR with a ZnSe/Diamond crystal. The spectra were collected at a resolution of 4 cm-1.
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2.4 Gas Chromatography Mass Spectrometry (GC-MS) Study GC/MS analysis of the extractable components of RPNSSC black liquor sample was performed for the three solvents extracts. Water extract of RPSSC black liquor was suspended in dimethylformamide for analysis. Methanol and hexane extracts of water extract residue
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were injected directly in to the Agilent 7890A gas chromatograph coupled to Agilent 5975 MSD single quadrupole mass analyzer. The analytes were separated using a BR-SWax
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capillary column (Bruker, 30 m × 0.25 mm i.d., film thickness 0.25 mm), operating at 7 psi of column head pressure, resulting in a flow of 1.0 ml /min at a starting temperature 40 °C. One ml sample volume was introduced into the injection port at 250 °C in a split less mode. The temperature program was isothermal for 2 min at 40 °C, raised to 100 °C at a rate of 20 °C per minute, and then raised to 220 °C at a rate of 10 °C per minute, and finally raised to 250 °C at a rate of 40 °C per minute and held for 4 minute. The transfer line to the mass spectrometer was maintained at 260 °C. The ionization source temperature was 230 °C and the ions were obtained by electron impact ionization in a positive ion mode at 70 eV, collecting data at a rate of 1 scan per 200ms over the m / z range of 50 to 550. Compounds were tentatively identified
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by comparing their mass spectra with those contained in the NIST/EPA/NIH and Wiley libraries.
3. Results and Discussions:
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3.1Physico-chemical characteristics
The bulk density of this test material as presented in Table 2, is comparatively better than the other similar energy feedstock such as coal as the test resulting in 840 kg/m3 for dry RPNSSC black liquor while at 700 kg/m3 for Coal. The total solid and ash contents of the RPNSSC
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black liquor are as presented in Table 4, showing higher ash content and may need to be processed for removal of ash for higher efficiency. The energy density of RPNSSC black
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liquor as shown in Table 3 which is 15.71 MJ/Kg could be suggested as a potential for fuel applications.
Table 2: Comparative bulk density of RPNSSC black liquor as fuel materials
Table 3: Total solids, ash contents and HHV of RPNSSC black liquor and its water extracted
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components
The results of proximate and ultimate analyzes of RPNSSC and other black liquors reported in literature are presented in Table 4. The observed high volatile content of 66.19 % can help ignition in an early stage of combustion. RPNSSC black liquor contains only 0.39% nitrogen
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which is a relatively low amount of fuel-bound nitrogen compared to many biomasses (Sommersacher et al., 2012). This characteristic is beneficial as nitrogen content along with
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other parameters such as oxygen ratio and particle size that can significantly influence NOx formation. The sulfur content of this black liquor is below detection limits and is a preferable criterion for fuel application. The high ash content of 23.27% lowers the energy density and may cause fouling problems and corrosion of the boilers or similar industrial application. The higher heating values (HHV) of 15.71 MJ/kg is higher than the other black liquors resulted from using different feedstock and different pulping processes. Because RPNSSC poses highest carbon and hydrogen content among the other black liquors, it may be considered the ideal sample to use as fuel directly or after a further purification process, to be suitable for particular industrial applications (Kambo and Dutta, 2014).
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Table 4: Proximate and ultimate analysis of RPNSSC black liquor and other industrial black liquors studied and reported in literature
The inorganic elemental content which usually contributes to higher ash content was evaluated
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and is presented in Table 4 as an individual percentage of each tested element present. The source of inorganic compounds in RPNSSC black liquor is due to added chemicals during the pulping process; and the elements were identified with the major component of this being sodium at 12.71% of the total sample.
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The solvent extractable profile of the RPNSSC black liquor is presented in Figure 1. As shown in the Figure, 98.95 % of the contents in the sample were water extractable. The residues after the water extraction were further extracted by a polar solvent methanol, a nonpolar solvent
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hexane and the results as are presented in Figure 1. The solubility of RPNSSC black liquor in hexane was very low at about 7.7% of water extracted residue part. Therefore, 92.3 % of RPNSSC black liquor was insoluble in the nonpolar solvent hexane indicating a presence of about only 7.7 % nonpolar fraction in RPNSSC. As shown in Figure 1, about 33.15 % of the polar compounds were extracted with methanol with a residual insoluble portion of 66.85 % in
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RPNSSC black liquor.
Figure 1: The soluble and insoluble components of RPNSSC black liquor extracted in water in solvents
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3.2 Thermogravimetric study during pyrolysis The thermal degradation trend of the RPNSSC black liquor samples processed for pyrolysis is
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presented in the TGA curve Figure 2 for weight loss at different temperatures. As shown in Figure 2, there are three major peaks of weight loss identified with the TG – DTG curve with the 1st degradation peak (Tmax 1) at 277 ᵒC, the 2nd degradation peak (Tmax 2) at 482 ᵒC peak, and the 3rd degradation peak (Tmax 3) at 880 ᵒC. During pyrolysis, the moisture is removed
initially at a temperature below 150 ᵒC. The further loss of weight with temperature is
identified herewith as Tmax 1-3 and the initial temperature Ti and final temperature Tf is indicated in Figure 2. The temperature at which maximum degradation is observed is recorded as Tmax for each peak. During the first degradation peak, the weight loss was 26.7 % which can be attributed to the decomposition of chemical bonds of low molecular weight organic acids and macromolecules to release of volatile compounds (Gu et al. 1992) followed by the 2nd
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peak with the weight loss of 18.5 %, which was mainly due to the decomposition of lignin and other long chain lipid molecules (Alén et al. 1995). The 3rd peak demonstrates the weight loss of about 43.67 %, due to the release all the organic and fixed carbon existing in the material (Wäg 1996) and decomposition of inorganic sodium salt; in addition there are resulting
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reactions among salts indicating impact on the residual ash in a pyrolysis process (Song et al., 2015).
Figure 2: TG and DGT Curve of RPNSSC black liquor with three thermal degradation stages
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during the pyrolysis process
3.3 FT-IR Study
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The FT-IR spectra of the RPNSSC black liquor, water extract, water extract residue, methanol extract, and methanol extract residue are as presented in the Figure 3. The bands are assigned according to Lin and Dence (1992) for peaks specific to lignin, and Yuan et al. (2011) and for hemicellulose and other functional group as listed in Table 5. As shown in the Figure 3, the FT-IR spectra of black liquor clearly indicated the presence of major functional groups in the
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macro molecules in biomass.
Table 5: The major functional groups in the macro molecules in biomass The FT-IR spectra of RPNSSC black liquor are different and lacked any significant presence of lignin from that of milled wood lignin, for example; the peak at 1,660 cm-1 attributed to the
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coumaryl ether groups or aldehyde groups is missing. The absence of these conjugated carbonyls in the spectra of the black-liquor lignin is possibly due to the oxidation during
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pulping (Froass et. al., 1996). Ester C=O is noticeable at 1,730 – 1,750 cm-1, alkyne C≡C is identified at 2,100 – 2,250 cm-1, and aldehyde C-H is observed at 2,700 – 2,900 cm-1; this is
observed in all the samples suggesting a presence of numerous organic molecules with the identified functional groups. There are distinct differences observed in the spectra of the extractive samples studied. The residues from the extraction distinctly show characteristic peaks that are not noticeable in the extracted portion indicating removal of the related molecules. A typical peak at 1,520–1,510 cm-1 attributed to aromatic skeletal vibrations is observed in the residues.The C–O stretch in guaiacyl rings can be observed for residues at 1,270 cm-1. The C–O stretch assigned to
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syringyl rings is presented at 1,220 cm-1 in the residue. The examination of the 900-1,200 cm-1 revealed significant increase in CO and COH content for water insoluble black liquor, methanol insoluble black liquor, dried black liquor, and water soluble black liquor; however, methanol soluble black liquor showed a significant decrease regarding to CO and COH
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content. 1,030 cm-1 corresponded to C–O deformation in secondary and primary alcohols or aliphatic ethers. The bands of these groups can be assigned to polysaccharides like compounds whose peak absorbance decreased, indicating removal of the polysaccharides during
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extractions.
Figure 3: Fourier Transform Infrared (FT-IR) spectra of solvent extracts and residue of
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RPNSSC black liquor
3.4 GC/MS analysis
Tables 6, 7 and 8 present the list of major compounds in the ascending order of their retention time as identified in GC/MS for the water extract, methanol extract and hexane extract
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respectively.
As listed in Table 6, the following major compounds have been identified to be present in the water extracts:
A significant content of octadecanoic acid (2,3-dihydroxypropyl ester),
phenolic compounds (Phenol, 2,4-bis(1,1-dimethylethyl), hexadecanoic acid - 2-hydroxy-1-
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(hydroxyl) are present with a GC/MS area percent of 28.57, 19.16 and14.36 respectively. Phenol, 2, 6-dimethoxy that represents syringol, is one of the three fundamental monomers of
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lignin is detected in small amount, due to their low solubility in water. Table 6: List of major compounds identified by GC/MS in the water extraction sample As presented in Table 7, the prominent compounds that were identified in methanol extraction are hexanedioic acid, bis (2-ethylhexyl) ester with a significantly higher area percentage of 41.04 % of the total sample. Apart from this another major component present in the methanol fraction is 9, 12-Octadecadienoic acid (Z, Z)-, methyl ester formed about 22.17%. Presence of Squalene is detected as 7.1% in this fraction. The solubility of both these compounds is very low and is therefore not extracted and detected in the water extract fraction earlier.
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Table 7: List of major compounds identified by GC/MS in the methanol extraction sample
Table 8 presents the list of compounds detected in a hexane extract of the water extracted
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residue. This is a minor fraction unlike regular black liquor representing 7.7 % of RPNSSC black liquor that are the nonpolar extracts present in hexane. A significant area percent of 18.9 was observed for phenol, 2, 6-dimethoxy which is also called syringol is a naturally occurring aromatic organic compound and a component of lignin. Other major components are benzene, 1,2,4,5-tetrakis(1-methylethyl)- at 6.3 %, n-Pentadecanol at 5.7%, and Phenol, 2,4-bis(1,1-
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dimethylethyl)- at 5.3% that are indicative of the presence of lignin fractions in the RPNSSC black liquor (Radoykova, 2013).
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Table 8: List of compounds (>1%) identified by GC/MS in the hexane extraction sample The compound like hexanedioic acid, bis (2-ethylhexyl) ester is not reported to be present in the black liquors of pulp and paper industries and is assumed to be of non-plant origin. Hexanedioic acid is a synthetic chemical commonly known as adipic acid (Davis and Kemp, 1991). Adipic acid produced currently from cyclohexane, which may be converted to cyclohexanol or a mixture of cyclohexanol and cyclohexanone. (Reimer et al., 1994). These
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chemical derivatives of non-plant origin molecules are inherited from the recycled paper products that are unique to this production system. Di (2-ethylhexyl) adipate is used primarily as a plasticizer in the flexible vinyl industry and is widely used in flexible poly (vinyl chloride) (PVC) food packaging - Cling Wrap. These derivatives are of importance as they
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have many commercial applications such as flooring, wall coverings, cladding and roofing, film and sheet, automotive, tubes and hoses, coated fabrics, inks and waxes and toys. It is
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commonly blended with di (2-ethylhexyl) phthalate and di (isooctyl) phthalate in PVC and other polymers. It is used as a solvent and as a component of aircraft lubricants. It is important in the processing of nitrocellulose and synthetic rubber, in plasticizing polyvinyl butyral, cellulose acetate butyrate, polystyrene and dammar wax and in cosmetics (cellulose-based liquid lipsticks) (Cadogan and Howick, 1992, 1996). 4. Conclusion The comparative evaluation of the values demonstrates that RPNSSC black liquor is a potential superior candidate for biofuel application. The favourable characteristics are neutral pH, with a higher heating value and suitable carbon content as a renewable fuel resource. The
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major findings include the presence of non-plant origin chemical compounds such as hexanedioic acid in significant quantities.
This chemical is of interest to various
environmental and industrial applications. Black liquor exhibiting a high-energy content is slated for combustion in modern biorefineries due to its inherent heterogeneity and
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recalcitrance, whereas RPNSSC black liquor containing significant level of industrially important components may be processed further for recovery of renewable chemicals. However, it is critical for the viability of third-generation biorefianeries to valorize this black liquor alongside below par extractive industrial chemicals. Future potential exists for extraction of industrially important chemicals with separations of a hexanedioic acid
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derivative and squalene from this black liquor prior to use it as a fuel.
Acknowledgements
This research work was supported by Ministry of Higher Education and Scientific Research, Baghdad, Iraq. The authors, also would like to thank Cascade Inc., Canada, Tembec pulp and paper, Canada, and Alberta-Pacific Forest industries Inc., Canada for supplying the black
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Sjöström, E., 1993. Wood Chemistry: Fundamentals and Applications, Second ed. Academic Press, An imprint of Elsevier, San Diego, California, USA. Smook G.A., 1992. Handbook for pulp and paper technologists, 2nd edn. Angus Wilde Publications, Vancouver, British Columbia, Canada, p 419
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Sommersacher, P., Brunner, T., Obernberger, I., 2012. Fuel indexes: A novel method for the evaluation of relevant combustion properties of new biomass fuels. Energy and Fuels 26, 380–390. doi:10.1021/ef201282y Song, X., Bie, R., Ji, X., Chen, P., Zhang, Y., Fan, J., 2015. Kinetics of reed black liquor (RBL) pyrolysis from thermogravimetric data. BioResources 10, 137–144.
Wag, K., 1996. Characterization and Modelling of Black Liquors Char Combustion Processes. Doctoral thesis, Oregon State University, USA. Wallberg, O., Linde, M., Jönsson, A.S., 2006. Extraction of lignin and hemicelluloses from kraft black liquor. Desalination 199, 413–414. doi:10.1016/j.desal.2006.03.094 Yuan, T.Q., Sun, S., Xu, F., Sun, R.C., 2011. Isolation and physico-chemical characterization of lignins from ultrasound irradiated fast-growing poplar wood. BioResources 6, 414– 433. doi:10.15376/biores.6.1.414-433
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Zhao, Y., Bie, R., Lu, J., Xiu, T., 2010. Kinetic study of NSSC black liquor combustion using different kinetic models. Energy Sources, Part A: Recovery, Utilization and Environmental Effects 32, 962–969. doi:10.1080/15567030802578815
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Black liquor
Color
dark brown
pH
7.1±0.5
Moisture (%)
46.88±1.3
Solid content (%)
53.12±1.5
Viscosity at 25ºC (cps)
<1000
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Characteristics
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Table 1: Characteristics of RPNSSC black liquor sample
Table 2: Comparative bulk density of RPNSSC black liquor as fuel materials kg/m3
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Bulk density RPNSSC black liquor (dry)
840
Pucks
480-640*
Coal
700*
*Clarke S; Fact sheet, Biomass Densification for energy production, OMAFRA (2015)
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http://www.biomassinnovation.ca/pdf/Factsheet_OMAFRA_BiomassDensification.pdf
Table 3: Total solids, ash contents, and the HHV for samples of RPNSSC black liquor and its
Total solid
Ash content
Energy density
(wet basis)%
(dry basis)%
HHV (MJ/Kg)
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Materials
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water extracted components
RPNSSC black liquor
53.12±1.5
23.27±0.8
15.71
Water extract
1.05±0.01
7.34±1.5
n.d.
Water extract residue
98.95±0.5
15.93±0.5
16.76
n.d. = not determined
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Table 4: Proximate and ultimate analysis of RPNSSC black liquor and other industrial black liquors studied and reported in literature RPNSSC
Kraft1
process source Feedstock
Pine &
paper
spruce
7.1±0.5
11.8±0.5
Alkaline
kraft2
pulping3 pulping4
Wood
Reed
Soda
Wheat
NSSC5
Broadleaf
straw
wood
n.d.
11.3
n.d.
Volatile 66.19±0.3 56.92±0.3 Matter
45.15±0.3
50.00
49.32
50.62
Fixed carbon
7.15±0.4
17.81±0.7
25.61
20.10
25.21
23.27±0.8 35.93±0.5
37.04±0.5
Ash
10.54±0.7
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13.77.1±0.5
24.39
27.38
24.17
33.76
33.43
36.32
38.30
30.67
30.34
H
4.74
3.74
3.69
4.15
2.77
3.43
N
0.39
0.67
0.22
0.38
0.23
0.04
S
0.00
0.00
4.95
0.95
0.13
5.45
Na
12.71
n.d.
n.d.
17.64
12.18
18.35
K
0.61
n.d.
n.d.
1.92
2.04
1.03
(Mg, Ca, Al, P, Mn, Fe, Ba)
(0.10, 0.76, 0.07, 0.03, 0.01, 0.01, 0.01)
n.d.
n.d.
n.d.
n.d.
n.d.
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(dry wt. basis)
Analysis basis) %
Si
0.01
n.d.
n.d.
1.78
3.10
n.d.
Cl
n.d.
n.d.
n.d.
1.57
n.d.
0.21
O
42.25
64.92
60.8
36.37
32.86
35.17
O/C
1.11
1.62
1.50
0.81
0.73
0.73
H/C
1.48
1.50
1.46
1.48
0.99
1.13
HHV (MJ/Kg)
15.71
14.51
14.43
13.35
n.d.
14.98
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Ultimate Analysis and the inorganic elements (dry wt.
Proximate
pH
Recycled
Spent
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Black liquor
n.d. = not done 1
Sample was procured from Tembec pulp and paper, Montréal, Québec, Canada.
2
Sample was procured from Alberta-Pacific Forest industries Inc. Boyle, Alberta, Canada
3
Song et al., 2015, 4Cao, 2010, 5Zhao et al., 2010
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Table 5: The major functional groups identified by FTIR for the macro molecules in biomass Wave number cm-1
Functional group & assigned species
4,000-3,500 O-H Stretching, H2O
3,000-2,800 C-H aliphatic stretching, CH4 2,400-2,310 C=O, CO2 2,182- 2,114 C-O, CO
1,680-1,600 C=C stretching (alkenes) 1,600-1,500 C=C stretching (aromatics) 1,600-1,450 C-C stretching (aromatics)
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1,790-1,650 C=O Stretching, Acids, aldehydes, ketones
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3,016 C-H aromatic or olefin stretching
1,450-1,350 ethers lipids
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C-H bending or scissor (CH2), Alkanes, alcohols, phenols,
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1,260-1,180 C-O stretching, alkanes, alcohols, phenols, ethers lipids
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Table 6: List of major compounds identified by GC/MS in the water extraction of RPNSSC black liquor Mol. weight (amu) gm/mol
Benzaldehyde, 2,5-dimethyl-
0.56
134.18
Disulfide, di-tert-dodecyl
0.88
11-Methyldodecanol
0.72
Cyclopentane, 1-butyl-2-propyl-
2.18
Phenol, 2,6-dimethoxy-
0.94
Heptadecane, 2,6,10,15-tetramethyl-
2.03
Phenol, 2,4-bis(1,1-dimethylethyl)-
402.78
200.36
168.32
154.16
296.57
19.16
206.32
0.81
200.36
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11-Methyldodecanol
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Area (%)
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Compounds
Benzenemethanol, .alpha.-ethyl-4-methoxy
2.15
166.21
Nonadecane
1.63
268.52
0.72
242.44
Benzaldehyde, 4-hydroxy-3,5-dimethoxy-
0.55
182.17
Heptadecane, 2,6,10,15-tetramethyl-
1.46
296.57
Hexacosyl acetate
1.17
284.47
4.59
605.15
1.94
242.44
Tetratriacontyl heptafluorobutyrate
1.11
690.94
n-Hexadecanoic acid
2.86
256.42
Hentriacontane
1.40
436.83
Octadecanoic acid
3.35
284.47
Tetracontane, 3,5,24-trimethyl-
2.35
605.15
Pentadecanoic acid, 2-hydroxy-1-(hydroxy
3.45
330.50
Hexadecanoic acid, 2-hydroxy-1-(hydroxym
14.36
330.50
2-(4-Hydroxy-4-methyl-tetrahydro-pyran-3
0.94
130.14
Octadecanoic acid, 2,3-dihydroxypropyl e
28.57
358.55
Tritetracontane
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1-Decanol, 2-hexyl-
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1-Decanol, 2-hexyl-
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Table 7: List of major compounds identified by GC/MS in the methanol extraction of RPNSSC black liquor Mol. weight (amu) gm/mol
Cyclopropyl carbinol
0.88
72.10
2-Deoxy-D-galactose
1.89
164.15
Pentanal
0.94
86.13
1,3-Dioxane-4,6-dione, 2,2-dimethyl-
1.05
144.12
1,2-Cyclopentanediol, trans-
5.33
116.16
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Area (%)
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Compound
Phenol
0.80
94.11
0.58
124.13
1.63
154.16
Stearic acid, 3-(octadecyloxy)propyl ester
0.48
595.03
1,2-Benzenedicarboxylic acid, butyl octyl ester
0.81
334.44
Oxacycloheptadec-8-en-2-one, (8Z)
1.12
252.39
12-Hydroxydodecanoic acid
1.29
216.31
Hexanedioic acid, bis(2-ethylhexyl) ester
41.04
370.56
9-Octadecynoic acid, methyl ester
0.400
296.48
Fumaric acid, dec-4-enyl heptadecyl ester
0.91
492.77
9,12-Octadecadienoic acid (Z,Z)-, methyl ester
22.17
294.47
9,12,15-Octadecatrienoic acid, (Z,Z,Z)-
3.54
278.42
Arachidonic acid
1.72
304.46
0.59
224.38
0.47
356.53
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2,4-Dimethoxyphenol
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Phenol, 4-methoxy-
Cyclopentadecanone
9,12,15-Octadecatrienoic acid, 2,3
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dihydroxypropyl ester, (Z,Z,Z)trans-Traumatic acid
3.12
228.28
Cyclopentadecanone
0.38
224.38
Squalene
7.15
410.71
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Table 8: List of compounds (>1%) identified by GC/MS in the hexane extraction RPNSSC black liquor Mol. weight Area (%)
(amu) (gm/mol)
2-Hexanone
7.88
100.08
3-Hexanol
1.89
2-Hexanol
1.73
Cyclopentanol, 1-methyl-
4.02
Cyclohexasiloxane, dodecamethyl-
3.26
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Compounds
Cyclopentanol, 3-methyl-
102.10 102.10
100.15
444.11
1.22
100.15
1.20
190.17
1.78
145.07
1.97
88.05
3.26
284.19
2-Cyclopenten-1-one, 2-hydroxy-3,4-dimethyl-
1.66
126.06
Hexanoic acid
1.99
116.08
4.13
124.05
4.15
140.15
1.17
135.01
3.26
94.04
1.73
144.11
5.66
228.24
Cyclohexanol, 2-[2-pyridyl]-
1.36
177.11
Phenol, 2,6-dimethoxy-
18.93
154.06
Phenol, 2,4-bis(1,1-dimethylethyl)-
5.27
206.16
n-Nonadecanol-1
4.016
284.30
Tetracosane
1.40
338.39
4,4-Dimethylcyclohexadienone
2.46
122.07
Benzene, 1,2,4,5-tetrakis(1-methylethyl)-
6.32
246.23
Benzoic acid
1.80
122.03
Pentacosane
1.03
352.40
2-Aminoethanol, N,O-diacetylButanoic acid Oxalic acid, cyclohexyl octyl ester
Phenol, 2-methoxy-
Benzothiazole Phenol Octanoic acid
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n-Pentadecanol
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1-Decene
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Benzene, 1,3-bis(1,1-dimethylethyl)-
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100 soluble (%) 98.95
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Percentage (%)
10
insoluble (%)
0.08
0.33 1 1.05
0.92
0.67
0.1 Methanol extraction of residue in water
Hexane extraction of residue in water
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water extraction
120
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Figure 1: The soluble and insoluble components of RPNSSC black liquor extracted in water in solvents
Wt. Loss %
0.7
DTG(%/C)
Tmax 3 (880 °C)
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0.5
60
0.4
Tmax 1 (277 °C)
0.3
Tmax 2 (482 °C)
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Wt. Loss (%)
80
0.6
40
0.2
Tf 1(364) Ti 2(364)
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20
Ti 1(170)
0.1
Tf 2(521) Ti 3(675) Tf 3(960)
0
0
200
DTG (%/ °C)
100
400
600
800
0 1000
Temperature (°C)
Figure 2: TG and DGT Curve of RPNSSC black liquor with three thermal degradation stages during the pyrolysis process
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RPNSSC Black liquor Methanol extract residue Water extract residue
180
Methanol extract Water extract
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140 120 100 80 60 4000
3600
3200
2800
2400
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Transmitance (a.u.)
160
2000
1600
1200
800
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Wavenumber (cm-1)
Wave
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Figure 3: Fourier Transform Infrared (FTIR) spectra of solvent extracts and residues of RPNSSC black liquor
400
S0959-6526(17)30288-3
DOI:
10.1016/j.jclepro.2017.02.074
Reference:
JCLP 9000
To appear in:
Journal of Cleaner Production
Please cite this article as: Zainab Al-Kaabi, Ranjan R. Pradhan, Naresh Thevathasan, Yi Wai Chiang, Andrew Gordon, Animesh Dutta, Potential Value Added Applications of Black Liquor Generated at Paper Manufacturing Industry Using Recycled Fiber, (2017), doi: 10.1016/j.jclepro.2017.02.074 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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Highlights: Black liquor generated using recycled fiber as feedstock are different Non plant origin component hexanedioic acid derivatives were identified This material can be processed for extractions and source of bioenergy Potential for enhancement as fuel by removal of mainly sodium component
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• • • •
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Total Word Count of the Manuscript including Tables and Figure = 5,561 words
Potential Value Added Applications of Black Liquor Generated at Paper Manufacturing
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Industry Using Recycled Fiber Zainab Al-Kaabia , Ranjan R. Pradhanb, Naresh Thevathasanb, Yi Wai Chiangb, Andrew Gordona, Animesh Duttab*
School of Environmental Science, bSchool of Engineering, University of Guelph, Ontario,
N1G 2W1, CANADA,
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*Correspondence author: [email protected]
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a
Abstract
Characterization of neutral sulphite semi-chemical black liquor (NSSCBL), sampled from paper manufacturing process that uses recycled fibers as primary feedstock, was carried out for potential bioenergy and biomaterial applications. Physico-chemical characteristics including inorganic elements content, thermogravimetric analysis, GC/MS, and FT-IR are
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presented. The black liquor of the recycled fiber in the manufacturing process revealed unique characteristics in terms of chemical composition profile compared to the black liquor originating from regular pulp and paper industries. The major findings include the presence of chemical compounds, from a non-plant origin, such as derivatives of hexanedioic acid in
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significant quantities. The favorable biofuel characteristics of this black liquor are: neutral pH, a higher volatile content, and HHV. The recycled paper NSSCBL can be a good candidate for
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biomaterial and biofuel applications.
Keywords: Black liquor, Recycled paper, Pulp, Biopolymer 1. Introduction:
Pulp and paper production uses plant cellulose from biomass and generates black liquor as a byproduct which contains 65-85% solids (Ramesh et al., 2013) having 10-50% lignin by weight (Ksibi et al., 2003). The characteristics and compositions of black liquor obtained from various pulping processes depends on the type of raw materials, pulping conditions and source of fibers used in production (Smook, 1992). Raw materials being used are wood,
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agricultural residues, or recycled papers (Bajpai, 2012). The pulp and paper making process applies various pulping processes that includes sulphite pulp to produce fine and printing papers, Kraft sulphate pulp to produce bleached-printing and writing papers, paperboard, unbleached-heavy packaging papers, paperboard, and dissolving pulp to produce viscose
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rayon, cellophane, acetate fibers, and films (Andelin et al., 1989). Neutral Sulphite SemiChemical (NSSC) Pulping uses mix of wood chips from virgin pulp with 20–35 % recovered fiber or re-pulped secondary fibers (Bajpai, 2014). In the neutral sulphite process reaction
temperatures range from 160-180 °C and pH ranges from 5-7, but alkaline sulphite reaction temperatures range from 160-180 °C and its pH 9 - 13.5 (Patt et al., 2005). About 50% of the
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lignocellulosic biomass matter dissolves into the black liquor during the pulping process. The major part of the dissolved matter contains lignin, degraded carbohydrates including cellulose
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and hemicellulose; the minor part contains protein, extractives, (Sjostrom, 1993) and inorganic materials (Wallberg et al., 2006). Many monomers of biopolymers such as 2-methoxyphenol, 2, 6-dimethoxyphenol, 4-hydroxy-3-methoxybenzaldehyde, 4-hydroxy-3, 5dimethoxybenzaldehyde, 1-(4-hydroxy-3-methoxyphenyl) ethanone, 1-(4-hydroxy-3, 5dimethoxyphenyl) ethanone, etc. have been extracted from the process waste which is called black liquor, and were identified using the GC/MS analysis (Radoykova et al., 2013). Very limited data is available on composition of the recycled paper neutral sulphite semi-chemical
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(RPNSSC) process, and related emission factors of their manufacturing facilities that recycles waste paper. Pulp and paper mills that are increasingly using recycled paper would offer a perfect opportunity to keep the environment clean by using a huge quantity of paper waste; on the other hand, this saves a significant number of trees, and reduces the cost of wood pre-
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treatment that should be done prior the pulping process, such as chemical, physical, and biological pre-treatment. Mills that use a certain recycled paper fractionation process could
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serve the economy aspect by reducing the energy consumption, virgin fiber consumption, improve the efficiency of ink detachment, and improve pulp quality (Kong et al., 2016). Many pulp and paper mills are no longer producing only their regular products, but also use biorefinery procedures on their byproducts such as the black liquor, to enhance their profitability and the energy efficiency (JÖnsson et al., 2011). The environmental sustainability
of using different black liquors to produce biofuel and biochemical has been investigated, such as preparing porous polymers from Kraft black liquor (Foulet et al., 2015), producing hydrochar using hydrothermal carbonization of black liquor (Kang et al., 2012), and hydrochar production using hydrothermal conversion of Neutral Sulfite Semi-Chemical red liquor (Gamgoum et al.,2016). However, the black liquor from the RPNSSC pulping process
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is unique and likely to carry forward different components that are inherent components of recycled paper as contributions to the process waste. The general applications adopted for regular black liquors may not be universally applicable for this category of industrial waste and need detailed investigation for efficient utilization and
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further disposal needs must be identified. With absence of any published literature, we are attempting for the first time to investigate the potential value added applications based on its physico-chemical characteristics.
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2. Materials and Methods: 2.1 Raw material
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Neutral sulphite semi-chemical (NSSC) black liquor at the concentrator stage (with approximately 45-50% solids) was procured from Cascades Inc., 404, Marie-Victoria Blvd. Kingsey Falls, Quebec, J0A1B0, and Canada. The samples from concentrator stage which represents a bulk processing stage where huge quantities of the liquid process wastes are collected and concentrated to produce the NSSC products. This NSSC product is stable and physically consistent within different production batches.
The sample representing this
process was collected from Cascade Inc. and is named as RPNSSC for this study. Table 1
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shows the characteristics of RPNSSC sample as received. The manufacturing process at Cascade Inc. uses 42.5% wood fiber with 57.5% recycled paper consisting of corrugated packaging materials that comes from industrial, commercial, institutional, and municipal sources as a feedstock.. The bulk density of the received samples were immediately measured
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according to ASTM D891 – 09 (American Society for Testing and Materials) and is presented in Table 2. The sample was kept in air tight containers in dark and at refrigerated condition till
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further use.
Table 1: Characteristics of RPNSSC black liquor sample 2.1.1 Sample preparation to determine physico-chemical characteristics The recycled Paper NSSC Black liquor sample (RPNSSC) was dried at 105 ºC for 24 hrs using a Thermolyne muffle furnace. Sample were then reduced in size to a particle size of approximately 425 µm using a planetary ball mill PM 100, (make- Retsch, Haan, Germany) to characterize for proximate analysis , ultimate analysis and heating values. Proximate analysis of the sample was carried out for its inherent moisture contents, ash (mineral) contents at 950
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ºC, volatile matter (when heated to 950 °C), and fixed carbon according to ASTM D7582, ASTM D 3174, ASTM D3175, and ASTM D7582 respectively. Ultimate analysis were carried out in the same sample to understand the composition of the biomass as weight percentage of components such as carbon (C), hydrogen (H), nitrogen (N), oxygen (O) and sulfur (S). The
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C, H, N, S, and O contents was determined by combustion using Elemental Analyzer make Thermo Scientific, model Flash 2000 (Lakewood, NJ, USA) according to ASTM D5373. Oxygen content was calculated as the percentage difference from the total. Targeted inorganic elemental analysis of dried RPNSSC black liquor was done by inductively coupled plasma optical emission spectroscopy using Varian Vista Pro Axial viewed plasma ICP- OES
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technology. Calibration standards were made from 1,000 µg/L ICP MS standards. Prior to elemental analysis, in order to eliminate all the organic materials in the samples, the dried
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RPNSSC samples were digested with metal grade concentrated nitric acid and then with trace metal grade concentrated hydrochloric acid so as to measure only the targeted inorganic elements in the sample.
Heating values were experimentally determined using an IKA C200 bomb calorimeter (Wilmington, NC, USA) according to ASTM E 711 and further validated by calculations using a PLS formula as shown in equation (1) for the same dried samples (Friedl et al., 2005).
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PLS Formula:
Q(MJ/kg) = 5.22C2 − 319C − 1647H + 38.6C×H + 133N + 21028
(1)
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Where C = carbon; H = hydrogen; N = nitrogen contents by dry weight basis.
In order to separate major soluble fractions of RPNSSC black liquor for characterizing the
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contents of the sample were processed for extraction in polar and non polar solvents like water, methanol, and hexane. Initially extraction was carried out by mixing 100 gm of wet black liquor sample with 100 gm of water as extraction solvent in 1:1 ratio. The mixture was centrifuged for 20 minutes at 4,000 rpm using centrifuge. The residue of water extract portion was then extracted individually with methanol and hexane in 1:1 ratio. All the extracts were dried using a Thermolyne muffle furnace at 105 ºC for 24 hrs for evaluating further by FT-IR and GC/MS studies. 2.2 Thermogravimetric Analysis
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The thermogravimetric analyzes were performed using micro-TGA SDT Q 600 (TA Instruments, New Castle, USA). A pair of platinum weight pans/crucible was used for holding the samples that were ground to pass through 500 microns in a powder form. All the raw and ground biomass was dried and kept in desiccators to be used for thermal treatment in micro-
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TGA. The Micro-TGA was heated up at the rate of 20 °C /min to the desired temperature. The sample weight of about 10-12 mg was placed in a crucible. Nitrogen was supplied inside the reactor at the rate of 50 ml/minutes. The weight loss and heat flow characteristics were monitored and analyzed with Thermal Analysis Universal software (TA Instruments, New
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Castle) to generate DSC-TGA plots.
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2.3 Fourier Transform Infrared Spectroscopy (FT-IR) Study
Oven dried and ball milled samples were analyzed out with a FT-IR spectrometer in the wave number range 400–4,000 cm-1. The IR instrument Varian 660-IR equipped with liquid nitrogen cooled the MCTA detector. The ATR was a Pike MIRacle single reflection ATR with a ZnSe/Diamond crystal. The spectra were collected at a resolution of 4 cm-1.
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2.4 Gas Chromatography Mass Spectrometry (GC-MS) Study GC/MS analysis of the extractable components of RPNSSC black liquor sample was performed for the three solvents extracts. Water extract of RPSSC black liquor was suspended in dimethylformamide for analysis. Methanol and hexane extracts of water extract residue
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were injected directly in to the Agilent 7890A gas chromatograph coupled to Agilent 5975 MSD single quadrupole mass analyzer. The analytes were separated using a BR-SWax
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capillary column (Bruker, 30 m × 0.25 mm i.d., film thickness 0.25 mm), operating at 7 psi of column head pressure, resulting in a flow of 1.0 ml /min at a starting temperature 40 °C. One ml sample volume was introduced into the injection port at 250 °C in a split less mode. The temperature program was isothermal for 2 min at 40 °C, raised to 100 °C at a rate of 20 °C per minute, and then raised to 220 °C at a rate of 10 °C per minute, and finally raised to 250 °C at a rate of 40 °C per minute and held for 4 minute. The transfer line to the mass spectrometer was maintained at 260 °C. The ionization source temperature was 230 °C and the ions were obtained by electron impact ionization in a positive ion mode at 70 eV, collecting data at a rate of 1 scan per 200ms over the m / z range of 50 to 550. Compounds were tentatively identified
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by comparing their mass spectra with those contained in the NIST/EPA/NIH and Wiley libraries.
3. Results and Discussions:
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3.1Physico-chemical characteristics
The bulk density of this test material as presented in Table 2, is comparatively better than the other similar energy feedstock such as coal as the test resulting in 840 kg/m3 for dry RPNSSC black liquor while at 700 kg/m3 for Coal. The total solid and ash contents of the RPNSSC
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black liquor are as presented in Table 4, showing higher ash content and may need to be processed for removal of ash for higher efficiency. The energy density of RPNSSC black
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liquor as shown in Table 3 which is 15.71 MJ/Kg could be suggested as a potential for fuel applications.
Table 2: Comparative bulk density of RPNSSC black liquor as fuel materials
Table 3: Total solids, ash contents and HHV of RPNSSC black liquor and its water extracted
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components
The results of proximate and ultimate analyzes of RPNSSC and other black liquors reported in literature are presented in Table 4. The observed high volatile content of 66.19 % can help ignition in an early stage of combustion. RPNSSC black liquor contains only 0.39% nitrogen
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which is a relatively low amount of fuel-bound nitrogen compared to many biomasses (Sommersacher et al., 2012). This characteristic is beneficial as nitrogen content along with
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other parameters such as oxygen ratio and particle size that can significantly influence NOx formation. The sulfur content of this black liquor is below detection limits and is a preferable criterion for fuel application. The high ash content of 23.27% lowers the energy density and may cause fouling problems and corrosion of the boilers or similar industrial application. The higher heating values (HHV) of 15.71 MJ/kg is higher than the other black liquors resulted from using different feedstock and different pulping processes. Because RPNSSC poses highest carbon and hydrogen content among the other black liquors, it may be considered the ideal sample to use as fuel directly or after a further purification process, to be suitable for particular industrial applications (Kambo and Dutta, 2014).
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Table 4: Proximate and ultimate analysis of RPNSSC black liquor and other industrial black liquors studied and reported in literature
The inorganic elemental content which usually contributes to higher ash content was evaluated
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and is presented in Table 4 as an individual percentage of each tested element present. The source of inorganic compounds in RPNSSC black liquor is due to added chemicals during the pulping process; and the elements were identified with the major component of this being sodium at 12.71% of the total sample.
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The solvent extractable profile of the RPNSSC black liquor is presented in Figure 1. As shown in the Figure, 98.95 % of the contents in the sample were water extractable. The residues after the water extraction were further extracted by a polar solvent methanol, a nonpolar solvent
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hexane and the results as are presented in Figure 1. The solubility of RPNSSC black liquor in hexane was very low at about 7.7% of water extracted residue part. Therefore, 92.3 % of RPNSSC black liquor was insoluble in the nonpolar solvent hexane indicating a presence of about only 7.7 % nonpolar fraction in RPNSSC. As shown in Figure 1, about 33.15 % of the polar compounds were extracted with methanol with a residual insoluble portion of 66.85 % in
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RPNSSC black liquor.
Figure 1: The soluble and insoluble components of RPNSSC black liquor extracted in water in solvents
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3.2 Thermogravimetric study during pyrolysis The thermal degradation trend of the RPNSSC black liquor samples processed for pyrolysis is
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presented in the TGA curve Figure 2 for weight loss at different temperatures. As shown in Figure 2, there are three major peaks of weight loss identified with the TG – DTG curve with the 1st degradation peak (Tmax 1) at 277 ᵒC, the 2nd degradation peak (Tmax 2) at 482 ᵒC peak, and the 3rd degradation peak (Tmax 3) at 880 ᵒC. During pyrolysis, the moisture is removed
initially at a temperature below 150 ᵒC. The further loss of weight with temperature is
identified herewith as Tmax 1-3 and the initial temperature Ti and final temperature Tf is indicated in Figure 2. The temperature at which maximum degradation is observed is recorded as Tmax for each peak. During the first degradation peak, the weight loss was 26.7 % which can be attributed to the decomposition of chemical bonds of low molecular weight organic acids and macromolecules to release of volatile compounds (Gu et al. 1992) followed by the 2nd
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peak with the weight loss of 18.5 %, which was mainly due to the decomposition of lignin and other long chain lipid molecules (Alén et al. 1995). The 3rd peak demonstrates the weight loss of about 43.67 %, due to the release all the organic and fixed carbon existing in the material (Wäg 1996) and decomposition of inorganic sodium salt; in addition there are resulting
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reactions among salts indicating impact on the residual ash in a pyrolysis process (Song et al., 2015).
Figure 2: TG and DGT Curve of RPNSSC black liquor with three thermal degradation stages
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during the pyrolysis process
3.3 FT-IR Study
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The FT-IR spectra of the RPNSSC black liquor, water extract, water extract residue, methanol extract, and methanol extract residue are as presented in the Figure 3. The bands are assigned according to Lin and Dence (1992) for peaks specific to lignin, and Yuan et al. (2011) and for hemicellulose and other functional group as listed in Table 5. As shown in the Figure 3, the FT-IR spectra of black liquor clearly indicated the presence of major functional groups in the
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macro molecules in biomass.
Table 5: The major functional groups in the macro molecules in biomass The FT-IR spectra of RPNSSC black liquor are different and lacked any significant presence of lignin from that of milled wood lignin, for example; the peak at 1,660 cm-1 attributed to the
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coumaryl ether groups or aldehyde groups is missing. The absence of these conjugated carbonyls in the spectra of the black-liquor lignin is possibly due to the oxidation during
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pulping (Froass et. al., 1996). Ester C=O is noticeable at 1,730 – 1,750 cm-1, alkyne C≡C is identified at 2,100 – 2,250 cm-1, and aldehyde C-H is observed at 2,700 – 2,900 cm-1; this is
observed in all the samples suggesting a presence of numerous organic molecules with the identified functional groups. There are distinct differences observed in the spectra of the extractive samples studied. The residues from the extraction distinctly show characteristic peaks that are not noticeable in the extracted portion indicating removal of the related molecules. A typical peak at 1,520–1,510 cm-1 attributed to aromatic skeletal vibrations is observed in the residues.The C–O stretch in guaiacyl rings can be observed for residues at 1,270 cm-1. The C–O stretch assigned to
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syringyl rings is presented at 1,220 cm-1 in the residue. The examination of the 900-1,200 cm-1 revealed significant increase in CO and COH content for water insoluble black liquor, methanol insoluble black liquor, dried black liquor, and water soluble black liquor; however, methanol soluble black liquor showed a significant decrease regarding to CO and COH
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content. 1,030 cm-1 corresponded to C–O deformation in secondary and primary alcohols or aliphatic ethers. The bands of these groups can be assigned to polysaccharides like compounds whose peak absorbance decreased, indicating removal of the polysaccharides during
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extractions.
Figure 3: Fourier Transform Infrared (FT-IR) spectra of solvent extracts and residue of
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RPNSSC black liquor
3.4 GC/MS analysis
Tables 6, 7 and 8 present the list of major compounds in the ascending order of their retention time as identified in GC/MS for the water extract, methanol extract and hexane extract
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respectively.
As listed in Table 6, the following major compounds have been identified to be present in the water extracts:
A significant content of octadecanoic acid (2,3-dihydroxypropyl ester),
phenolic compounds (Phenol, 2,4-bis(1,1-dimethylethyl), hexadecanoic acid - 2-hydroxy-1-
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(hydroxyl) are present with a GC/MS area percent of 28.57, 19.16 and14.36 respectively. Phenol, 2, 6-dimethoxy that represents syringol, is one of the three fundamental monomers of
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lignin is detected in small amount, due to their low solubility in water. Table 6: List of major compounds identified by GC/MS in the water extraction sample As presented in Table 7, the prominent compounds that were identified in methanol extraction are hexanedioic acid, bis (2-ethylhexyl) ester with a significantly higher area percentage of 41.04 % of the total sample. Apart from this another major component present in the methanol fraction is 9, 12-Octadecadienoic acid (Z, Z)-, methyl ester formed about 22.17%. Presence of Squalene is detected as 7.1% in this fraction. The solubility of both these compounds is very low and is therefore not extracted and detected in the water extract fraction earlier.
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Table 7: List of major compounds identified by GC/MS in the methanol extraction sample
Table 8 presents the list of compounds detected in a hexane extract of the water extracted
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residue. This is a minor fraction unlike regular black liquor representing 7.7 % of RPNSSC black liquor that are the nonpolar extracts present in hexane. A significant area percent of 18.9 was observed for phenol, 2, 6-dimethoxy which is also called syringol is a naturally occurring aromatic organic compound and a component of lignin. Other major components are benzene, 1,2,4,5-tetrakis(1-methylethyl)- at 6.3 %, n-Pentadecanol at 5.7%, and Phenol, 2,4-bis(1,1-
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dimethylethyl)- at 5.3% that are indicative of the presence of lignin fractions in the RPNSSC black liquor (Radoykova, 2013).
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Table 8: List of compounds (>1%) identified by GC/MS in the hexane extraction sample The compound like hexanedioic acid, bis (2-ethylhexyl) ester is not reported to be present in the black liquors of pulp and paper industries and is assumed to be of non-plant origin. Hexanedioic acid is a synthetic chemical commonly known as adipic acid (Davis and Kemp, 1991). Adipic acid produced currently from cyclohexane, which may be converted to cyclohexanol or a mixture of cyclohexanol and cyclohexanone. (Reimer et al., 1994). These
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chemical derivatives of non-plant origin molecules are inherited from the recycled paper products that are unique to this production system. Di (2-ethylhexyl) adipate is used primarily as a plasticizer in the flexible vinyl industry and is widely used in flexible poly (vinyl chloride) (PVC) food packaging - Cling Wrap. These derivatives are of importance as they
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have many commercial applications such as flooring, wall coverings, cladding and roofing, film and sheet, automotive, tubes and hoses, coated fabrics, inks and waxes and toys. It is
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commonly blended with di (2-ethylhexyl) phthalate and di (isooctyl) phthalate in PVC and other polymers. It is used as a solvent and as a component of aircraft lubricants. It is important in the processing of nitrocellulose and synthetic rubber, in plasticizing polyvinyl butyral, cellulose acetate butyrate, polystyrene and dammar wax and in cosmetics (cellulose-based liquid lipsticks) (Cadogan and Howick, 1992, 1996). 4. Conclusion The comparative evaluation of the values demonstrates that RPNSSC black liquor is a potential superior candidate for biofuel application. The favourable characteristics are neutral pH, with a higher heating value and suitable carbon content as a renewable fuel resource. The
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major findings include the presence of non-plant origin chemical compounds such as hexanedioic acid in significant quantities.
This chemical is of interest to various
environmental and industrial applications. Black liquor exhibiting a high-energy content is slated for combustion in modern biorefineries due to its inherent heterogeneity and
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recalcitrance, whereas RPNSSC black liquor containing significant level of industrially important components may be processed further for recovery of renewable chemicals. However, it is critical for the viability of third-generation biorefianeries to valorize this black liquor alongside below par extractive industrial chemicals. Future potential exists for extraction of industrially important chemicals with separations of a hexanedioic acid
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derivative and squalene from this black liquor prior to use it as a fuel.
Acknowledgements
This research work was supported by Ministry of Higher Education and Scientific Research, Baghdad, Iraq. The authors, also would like to thank Cascade Inc., Canada, Tembec pulp and paper, Canada, and Alberta-Pacific Forest industries Inc., Canada for supplying the black
References
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liquor samples
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Jönsson, J., Ruohonen, P., Michel, G., Berntsson, T., 2011. The potential for steam savings and implementation of different biorefinery concepts in Scandinavian integrated TMP and paper mills. Applied Thermal Engineering 31, 2107–2114. doi:10.1016/j.applthermaleng.2011.03.001
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Patt, R., Kordsachia, O., Süttinger, R., Ohtani, Y., Hoesch, J., Ehrler, P., Eichinger, R., Holik, H., Hamm, U., Rohmann, M., Mummenhoff, P., Petermann, E., Miller., R., Frank., D., Wilken, R., Baumgarten, H., Rentrop, G. H., 2005.Paper and Pulp. Ullmann's Encyclopedia of Industrial Chemistry; Wiley-VCH Verlag GmbH and Co. KGaA; doi: 10.1002/14356007.a18_545 Radoykova, T., Nenkova, S., Valchev, I., 2013. Black liquor lignin products, isolation and characterization. Journal of Chemical Technology and Metallurgy 48, 524–529.
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Ramesh, S., Chaurasia, A.S., Mahalingam, H., Rao, N.J., 2013. Kinetics of Devolatilization of Black Liquor Droplets in Chemical Recovery Boilers - Pyrolysis of Dry Black Liquor Solids. International Journal of Chemical Engineering and Applications 4. doi:10.7763/IJCEA.2013.V4.248 Reimer, R.A., Slaten, C.S., Seapan, M., Lower, M.W., Tomlinson, P.E., 1994. Abatement of N2O emissions produced in the adipic acid industry. Environmental Progress 13, 134– 137. doi:10.1002/ep.670130217
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Sommersacher, P., Brunner, T., Obernberger, I., 2012. Fuel indexes: A novel method for the evaluation of relevant combustion properties of new biomass fuels. Energy and Fuels 26, 380–390. doi:10.1021/ef201282y Song, X., Bie, R., Ji, X., Chen, P., Zhang, Y., Fan, J., 2015. Kinetics of reed black liquor (RBL) pyrolysis from thermogravimetric data. BioResources 10, 137–144.
Wag, K., 1996. Characterization and Modelling of Black Liquors Char Combustion Processes. Doctoral thesis, Oregon State University, USA. Wallberg, O., Linde, M., Jönsson, A.S., 2006. Extraction of lignin and hemicelluloses from kraft black liquor. Desalination 199, 413–414. doi:10.1016/j.desal.2006.03.094 Yuan, T.Q., Sun, S., Xu, F., Sun, R.C., 2011. Isolation and physico-chemical characterization of lignins from ultrasound irradiated fast-growing poplar wood. BioResources 6, 414– 433. doi:10.15376/biores.6.1.414-433
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Zhao, Y., Bie, R., Lu, J., Xiu, T., 2010. Kinetic study of NSSC black liquor combustion using different kinetic models. Energy Sources, Part A: Recovery, Utilization and Environmental Effects 32, 962–969. doi:10.1080/15567030802578815
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Black liquor
Color
dark brown
pH
7.1±0.5
Moisture (%)
46.88±1.3
Solid content (%)
53.12±1.5
Viscosity at 25ºC (cps)
<1000
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Characteristics
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Table 1: Characteristics of RPNSSC black liquor sample
Table 2: Comparative bulk density of RPNSSC black liquor as fuel materials kg/m3
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Bulk density RPNSSC black liquor (dry)
840
Pucks
480-640*
Coal
700*
*Clarke S; Fact sheet, Biomass Densification for energy production, OMAFRA (2015)
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http://www.biomassinnovation.ca/pdf/Factsheet_OMAFRA_BiomassDensification.pdf
Table 3: Total solids, ash contents, and the HHV for samples of RPNSSC black liquor and its
Total solid
Ash content
Energy density
(wet basis)%
(dry basis)%
HHV (MJ/Kg)
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Materials
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water extracted components
RPNSSC black liquor
53.12±1.5
23.27±0.8
15.71
Water extract
1.05±0.01
7.34±1.5
n.d.
Water extract residue
98.95±0.5
15.93±0.5
16.76
n.d. = not determined
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Table 4: Proximate and ultimate analysis of RPNSSC black liquor and other industrial black liquors studied and reported in literature RPNSSC
Kraft1
process source Feedstock
Pine &
paper
spruce
7.1±0.5
11.8±0.5
Alkaline
kraft2
pulping3 pulping4
Wood
Reed
Soda
Wheat
NSSC5
Broadleaf
straw
wood
n.d.
11.3
n.d.
Volatile 66.19±0.3 56.92±0.3 Matter
45.15±0.3
50.00
49.32
50.62
Fixed carbon
7.15±0.4
17.81±0.7
25.61
20.10
25.21
23.27±0.8 35.93±0.5
37.04±0.5
Ash
10.54±0.7
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13.77.1±0.5
24.39
27.38
24.17
33.76
33.43
36.32
38.30
30.67
30.34
H
4.74
3.74
3.69
4.15
2.77
3.43
N
0.39
0.67
0.22
0.38
0.23
0.04
S
0.00
0.00
4.95
0.95
0.13
5.45
Na
12.71
n.d.
n.d.
17.64
12.18
18.35
K
0.61
n.d.
n.d.
1.92
2.04
1.03
(Mg, Ca, Al, P, Mn, Fe, Ba)
(0.10, 0.76, 0.07, 0.03, 0.01, 0.01, 0.01)
n.d.
n.d.
n.d.
n.d.
n.d.
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C
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(dry wt. basis)
Analysis basis) %
Si
0.01
n.d.
n.d.
1.78
3.10
n.d.
Cl
n.d.
n.d.
n.d.
1.57
n.d.
0.21
O
42.25
64.92
60.8
36.37
32.86
35.17
O/C
1.11
1.62
1.50
0.81
0.73
0.73
H/C
1.48
1.50
1.46
1.48
0.99
1.13
HHV (MJ/Kg)
15.71
14.51
14.43
13.35
n.d.
14.98
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Ultimate Analysis and the inorganic elements (dry wt.
Proximate
pH
Recycled
Spent
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Black liquor
n.d. = not done 1
Sample was procured from Tembec pulp and paper, Montréal, Québec, Canada.
2
Sample was procured from Alberta-Pacific Forest industries Inc. Boyle, Alberta, Canada
3
Song et al., 2015, 4Cao, 2010, 5Zhao et al., 2010
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Table 5: The major functional groups identified by FTIR for the macro molecules in biomass Wave number cm-1
Functional group & assigned species
4,000-3,500 O-H Stretching, H2O
3,000-2,800 C-H aliphatic stretching, CH4 2,400-2,310 C=O, CO2 2,182- 2,114 C-O, CO
1,680-1,600 C=C stretching (alkenes) 1,600-1,500 C=C stretching (aromatics) 1,600-1,450 C-C stretching (aromatics)
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1,790-1,650 C=O Stretching, Acids, aldehydes, ketones
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3,016 C-H aromatic or olefin stretching
1,450-1,350 ethers lipids
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C-H bending or scissor (CH2), Alkanes, alcohols, phenols,
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1,260-1,180 C-O stretching, alkanes, alcohols, phenols, ethers lipids
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Table 6: List of major compounds identified by GC/MS in the water extraction of RPNSSC black liquor Mol. weight (amu) gm/mol
Benzaldehyde, 2,5-dimethyl-
0.56
134.18
Disulfide, di-tert-dodecyl
0.88
11-Methyldodecanol
0.72
Cyclopentane, 1-butyl-2-propyl-
2.18
Phenol, 2,6-dimethoxy-
0.94
Heptadecane, 2,6,10,15-tetramethyl-
2.03
Phenol, 2,4-bis(1,1-dimethylethyl)-
402.78
200.36
168.32
154.16
296.57
19.16
206.32
0.81
200.36
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11-Methyldodecanol
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Area (%)
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Compounds
Benzenemethanol, .alpha.-ethyl-4-methoxy
2.15
166.21
Nonadecane
1.63
268.52
0.72
242.44
Benzaldehyde, 4-hydroxy-3,5-dimethoxy-
0.55
182.17
Heptadecane, 2,6,10,15-tetramethyl-
1.46
296.57
Hexacosyl acetate
1.17
284.47
4.59
605.15
1.94
242.44
Tetratriacontyl heptafluorobutyrate
1.11
690.94
n-Hexadecanoic acid
2.86
256.42
Hentriacontane
1.40
436.83
Octadecanoic acid
3.35
284.47
Tetracontane, 3,5,24-trimethyl-
2.35
605.15
Pentadecanoic acid, 2-hydroxy-1-(hydroxy
3.45
330.50
Hexadecanoic acid, 2-hydroxy-1-(hydroxym
14.36
330.50
2-(4-Hydroxy-4-methyl-tetrahydro-pyran-3
0.94
130.14
Octadecanoic acid, 2,3-dihydroxypropyl e
28.57
358.55
Tritetracontane
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1-Decanol, 2-hexyl-
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1-Decanol, 2-hexyl-
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Table 7: List of major compounds identified by GC/MS in the methanol extraction of RPNSSC black liquor Mol. weight (amu) gm/mol
Cyclopropyl carbinol
0.88
72.10
2-Deoxy-D-galactose
1.89
164.15
Pentanal
0.94
86.13
1,3-Dioxane-4,6-dione, 2,2-dimethyl-
1.05
144.12
1,2-Cyclopentanediol, trans-
5.33
116.16
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Area (%)
SC
Compound
Phenol
0.80
94.11
0.58
124.13
1.63
154.16
Stearic acid, 3-(octadecyloxy)propyl ester
0.48
595.03
1,2-Benzenedicarboxylic acid, butyl octyl ester
0.81
334.44
Oxacycloheptadec-8-en-2-one, (8Z)
1.12
252.39
12-Hydroxydodecanoic acid
1.29
216.31
Hexanedioic acid, bis(2-ethylhexyl) ester
41.04
370.56
9-Octadecynoic acid, methyl ester
0.400
296.48
Fumaric acid, dec-4-enyl heptadecyl ester
0.91
492.77
9,12-Octadecadienoic acid (Z,Z)-, methyl ester
22.17
294.47
9,12,15-Octadecatrienoic acid, (Z,Z,Z)-
3.54
278.42
Arachidonic acid
1.72
304.46
0.59
224.38
0.47
356.53
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2,4-Dimethoxyphenol
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Phenol, 4-methoxy-
Cyclopentadecanone
9,12,15-Octadecatrienoic acid, 2,3
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dihydroxypropyl ester, (Z,Z,Z)trans-Traumatic acid
3.12
228.28
Cyclopentadecanone
0.38
224.38
Squalene
7.15
410.71
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Table 8: List of compounds (>1%) identified by GC/MS in the hexane extraction RPNSSC black liquor Mol. weight Area (%)
(amu) (gm/mol)
2-Hexanone
7.88
100.08
3-Hexanol
1.89
2-Hexanol
1.73
Cyclopentanol, 1-methyl-
4.02
Cyclohexasiloxane, dodecamethyl-
3.26
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Compounds
Cyclopentanol, 3-methyl-
102.10 102.10
100.15
444.11
1.22
100.15
1.20
190.17
1.78
145.07
1.97
88.05
3.26
284.19
2-Cyclopenten-1-one, 2-hydroxy-3,4-dimethyl-
1.66
126.06
Hexanoic acid
1.99
116.08
4.13
124.05
4.15
140.15
1.17
135.01
3.26
94.04
1.73
144.11
5.66
228.24
Cyclohexanol, 2-[2-pyridyl]-
1.36
177.11
Phenol, 2,6-dimethoxy-
18.93
154.06
Phenol, 2,4-bis(1,1-dimethylethyl)-
5.27
206.16
n-Nonadecanol-1
4.016
284.30
Tetracosane
1.40
338.39
4,4-Dimethylcyclohexadienone
2.46
122.07
Benzene, 1,2,4,5-tetrakis(1-methylethyl)-
6.32
246.23
Benzoic acid
1.80
122.03
Pentacosane
1.03
352.40
2-Aminoethanol, N,O-diacetylButanoic acid Oxalic acid, cyclohexyl octyl ester
Phenol, 2-methoxy-
Benzothiazole Phenol Octanoic acid
AC C
EP
n-Pentadecanol
TE D
1-Decene
M AN U
Benzene, 1,3-bis(1,1-dimethylethyl)-
ACCEPTED MANUSCRIPT
100 soluble (%) 98.95
RI PT
Percentage (%)
10
insoluble (%)
0.08
0.33 1 1.05
0.92
0.67
0.1 Methanol extraction of residue in water
Hexane extraction of residue in water
SC
water extraction
120
M AN U
Figure 1: The soluble and insoluble components of RPNSSC black liquor extracted in water in solvents
Wt. Loss %
0.7
DTG(%/C)
Tmax 3 (880 °C)
TE D
0.5
60
0.4
Tmax 1 (277 °C)
0.3
Tmax 2 (482 °C)
EP
Wt. Loss (%)
80
0.6
40
0.2
Tf 1(364) Ti 2(364)
AC C
20
Ti 1(170)
0.1
Tf 2(521) Ti 3(675) Tf 3(960)
0
0
200
DTG (%/ °C)
100
400
600
800
0 1000
Temperature (°C)
Figure 2: TG and DGT Curve of RPNSSC black liquor with three thermal degradation stages during the pyrolysis process
ACCEPTED MANUSCRIPT
RPNSSC Black liquor Methanol extract residue Water extract residue
180
Methanol extract Water extract
RI PT
140 120 100 80 60 4000
3600
3200
2800
2400
SC
Transmitance (a.u.)
160
2000
1600
1200
800
M AN U
Wavenumber (cm-1)
Wave
AC C
EP
TE D
Figure 3: Fourier Transform Infrared (FTIR) spectra of solvent extracts and residues of RPNSSC black liquor
400