Gasification and liquefaction of solid fuels by hydrothermal conversion methods

Accepted Manuscript Title: Gasification and liquefaction of solid fuels by hydrothermal conversion methods Author: Kristjan Kruusement Hans Luik Maurice Waldner Fr´ed´eric Vogel Lea Luik PII: DOI: Reference:

S0165-2370(14)00082-5 http://dx.doi.org/doi:10.1016/j.jaap.2014.04.006 JAAP 3182

To appear in:

J. Anal. Appl. Pyrolysis

Received date: Revised date: Accepted date:

6-9-2013 9-4-2014 18-4-2014

Please cite this article as: K. Kruusement, H. Luik, M. Waldner, F. Vogel, L. Luik, Gasification and liquefaction of solid fuels by hydrothermal conversion methods, Journal of Analytical and Applied Pyrolysis (2014), http://dx.doi.org/10.1016/j.jaap.2014.04.006 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 Spruce needles, reed, peat and oil shale samples were submitted to the hydrothermal conversion. Non-catalytic liquefaction and Ni-catalyzed gasification were the methods of hydrothermal conversion used. It was demonstrated that using these methods, solid fuels can be upgraded to gaseous and liquid products with a higher energy density than the original feedstock.

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Gasification and liquefaction of solid fuels by hydrothermal conversion methods Kristjan Kruusementa, Hans Luika, Maurice Waldnerb*, Frédéric Vogelb and Lea Luika a

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Tallinn University of Technology, Department of Polymeric Materials, Laboratory of Oil Shale and Renewables Research, 5 Ehitajate Road, Tallinn 19086, Estonia b Paul Scherrer Institut, General Energy Department, Laboratory for Bioenergy and Catalysis, 5232 Villigen PSI, Switzerland * Current address: Hitachi Zosen Inova AG, Hardturmstrasse 127, Postfach 680, 8037 Zürich, Switzerland

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Abstract. Spruce needles, reed, peat and oil shale samples, representing available natural resource of solid organic feedstock, were submitted to the hydrothermal conversion. Noncatalytic liquefaction (NL – 380 °C, 4 h, feed-to-water ratio 1:3) and Ni-catalyzed gasification (CG – 400 °C, 0.5 h, feed-to-catalyst-to-water ratio 1:2:10, initial pressure with argon to 20 bar) were the conditions of the conversion used. Both processes were performed using supercritical water in 30 and 500 cm3 autoclaves, and resulted in redistribution of the organic matter (OM) of the solid fuel feedstocks between gaseous, liquid, and solid conversion products. NL of Kukersite oil shale resulted in almost total conversion of oil shale kerogeneous OM to the benzene soluble oil (63%) and gas (31%). Biomass samples and peat known as specially rich in oxygen content (33-49%), the latter being mostly transferred to carbon dioxide and water, whereas the oils obtained from biomass and peat were characterized by oxygen contents 16–18%. Content of hydrocarbons was higher in the shale oil and peat oil compared to bio-oils. In CG, all organic carbon in the initial solid matter of the biomass samples, and up to 75% of that in peat, was transferred to gas with CH4 concentrations in the range of 36-40 vol.%. The main gaseous compound produced from oil shale was H2 and its concentration as high as 61 vol.% was measured. It was demonstrated that using NL and CG hydrothermal conversion methods, solid fuels can be upgraded to gaseous and liquid products with a higher energy density than the original feedstock.

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Keywords: Biomass; Peat; Oil shale; Supercritical water conversion; Skeletal Nickel catalyst; Liquid and gaseous products. 1. Introduction

The demand for energy as well as the dependence on exhaustive supplies of natural gas and petroleum increase in all over the world. Growing biomass, peat and oil shale represent a vast resource for liquid and gaseous fuels. Biomass is a term for all organic material that stems from plants. The biomass resource is also considered to be a combustible natural high molecular matter of lignocellulosic origin, in which the energy of sunlight is stored in chemical bonds. Biomass in its varieties is renewable and, thus, a practically inexhaustible resource of feedstock for energy. Most often biomass refers to trees, plants and purposely grown crops. The whole plant or its ingredients can be used [1]. Oil shales and coals can be considered as fossilized biomass, since they are sedimented and fossilized remains of terrestrial flora and marine fauna that grew and lived millions, or even, hundreds of millions of years ago. Oil shale deposits are found on all continents and the reserves of oil shale are more evenly distributed compared to petroleum. A specific feature of

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oil shales is their high mineral matter content. Both the content and chemical composition of the organic matter (OM) in different oil shales vary significantly [2]. Peat is a regular natural organic resource in the world stratifying in wetlands. Peat includes decayed and decaying residues of higher plants and is the youngest and least altered member of fossils, with time turning into brown coal. Besides humic substances formed as a result of humification, peat contains mainly lignin, celluloses and bitumen as typical constituents of lignocellulosics not maintained in the fossilized OM. Thus, peat has somewhat an intermediate position between fossil and renewable fuels [3]. In fact, the OM of solid fuels originates from bioproduction and, depending on the fuel type, is characterised by different degree of metamorphism. The energy enclosed in biomass, oil shale and peat can be released either by direct combustion or converted and concentrated by thermochemical upgrading into liquid or gaseous fuels. The latter processes are preferred because different types of OM can be readily processed into liquid and gaseous energy carriers similar to natural petroleum and gas by using thermochemical conversion methods. Synthetically produced petroleum and gas represent emerging alternatives to the natural ones enabling to realize the energy potential of different types of organic solid feedstocks everywhere in the world. Liquids or gases produced from those feedstocks by thermochemical processing usually show higher energy density compared to the original solid fuel. The OM of biomass, its ingredients, and peat is characterized by a high oxygen content. Thermochemical processing can lead to the significant deoxygenation of the initial OM via carbon dioxide and water formation, and finally to the production of hydrocarbonaceous oil and gas with elevated calorific value. A huge oil shale resource is still practically unused, with the exception of Estonia. There is extensive know-how and long-term practice on both liquefaction and gasification of oil shale in Estonia. Shale oil has been produced permanently since 1924 by local Kukersite oil shale liquefaction in retorts of different configuration. Retorting technology bases on oil shale slow pyrolysis and, depending on retort type and OM content 11-17% of shale oil per shale has been obtained. Kukersite retort oil differs from natural petroleum by an elevated content of oxygen compounds (mostly phenols) and alkenes. Dephenolation and hydrogenation methods have been developed with the aim of shale oil upgrading to syncrude [4, 5]. The latter can be submitted to the separation schemes known in petrochemistry to get straight-run motor fuels of high quality. Industrial gasification of Kukersite oil shale, basing on chamber furnace technology, was practised in 1950-60s of short duration. The thermal treatment of oil shale in chamber furnaces yielded on an average 300 m3 of coke oven gas (with the higher heating value - HHV of about 50 MJ/m3), 55 kg of shale oil, 28 kg of gasoline and up to 200 kg of pyrolytic water per 1 t of oil shale [6]. As one can see, the industrial gasification of oil shale was accompanied with production of significant fractions of shale oil and gasoline. In both liquefaction and gasification of oil shale, the pyrolysis as common method has been used at different temperatures, 450-500 °C and higher than 800-900 °C. Firewood and peat briquettes are still widely used for heating though their liquefaction and gasification would be preferred to direct combustion. Besides having higher energy density, conveying and transporting of liquid or gaseous fuels is much easier. Also, liquid and gaseous fuels burn more cleanly than solids. Much attention has been paid to the thermal transformations of the lignocellulosic biomass types since early 1980s in Europe and in America [7, 8]. It is evident that pyrolysis varieties used for oil shale and biomass liquefaction and gasification are making way for more advanced and novel thermochemical methods such as conversions with supercritical water. Hot compressed water has been extensively used in the decomposition of oil shales and biomass varieties with and without catalysts [9-51]. In subcritical water conversion of the Chinese oil shale (330 °C, 2.5 h) the oil yield much lower than in Fischer assay pyrolysis,

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5.75-6.95 versus 12.1% was demonstrated [19]. Biomass contains cellulose, hemicellulose and lignine as the main constituents those characterized by different termal stabilities [43]. The advantages of supercritical water over other solvents can be highlighted as follows:  Water is cheap, easily available and chemically safe.

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 Hot compressed water also dissolves polar hydrophilic oxygeneous compounds such as certain phenols, alcohols, carboxylic acids, aldehydes and sugars. These compounds can be separated from the shale oil or bio-oil composition in aqueous solution as chemicals whereby improving oil quality.

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 Wet feedstocks, containing varied moisture and water contents can be used [15, 3034].

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Water conversion of oil shale can give higher oil yield at lower temperatures, compared to retorting technology [35]. Biomass water conversion though often giving no higher oil yields than semicoking [25, 26, 35], yields the higher content of the benzene soluble fraction as the most valuable one. The oils obtained are moderately deoxygenated [26, 35]. Gasification of feedstocks in supercritical water has also advantages over classical (atmospheric pressure) gas-phase gasification, and there is no necessity for drying of the feedstocks [5, 6, 29-34, 36-39]:  Supercritical water, acting as homogeneous medium, allows lowering the impact of transport resistance phenomena in a heterogeneous reaction system.

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 High solid conversion, i.e. a low level of organic compounds and low level of solid residue, has crucial importance when considering the effect of the residual chars and tars on continuous reactors.  The product gas is produced at higher pressure directly, which means a smaller reactor volume and a lower energy to pressurize the gas in a storage tank. Water can act as an oxidant, and oxygen in water can be transferred to the carbon atoms of the feedstock resulting carbon monoxide in the watergas shift reaction [40].

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The effect of catalysts in water conversion processes on oil yield and composition have been studied. For example raw iron ore has been used as a catalyst in direct liquefaction of peat into syncrude by supercritical water treatment at 350-500 °C under residence time from 10 min to 4 h, resulting in 19-40 wt.% yield of heavy oil with a higher heating value of 30-37 MJ/kg [15]. The yields in catalytical and non-catalytical liquefaction of peat did not differ significantly, the heavy oil obtained was characterized as rich in oxygen. In practice, all of the feedstock does not react with supercritical water, although its reactivity is higher in this specific medium than in atmospheric pressure steam [40]. Significant amounts of tars and chars can be formed during the reaction. This shift from thermodynamic expectations can be reduced by the use of a catalyst. The most targeted products of biomass gasification in supercritical water are hydrogen, carbon monoxide, and methane. Large amounts of hydrogen are used in chemical and petrochemical industries. Hydrogen is used in developments of fuel cells and with carbon monoxide as syngas. Methane and carbon monoxide have been determined in the product gas in lower concentrations [41]. Many studies on hydrogen production by gasification of biomass species and its main constituents, cellulose and lignin, have been published [30-34, 42-46].

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The gas product from biomass gasification in supercritical water obtained in these works contained as maximum 55 vol.% of hydrogen. Obtaining synthetic natural gas via biomass methanation in supercritical water has also been investigated [29, 36-39, 47-51]. Depending on the method used, the yield and composition of the gas can vary in a large range. Estonian experience on pyrolytical gasification is described in [6]. The coke gas has the highest calorific value of about 50 MJ/m3 followed by the coke oven gas (16.7 MJ/m3). The coke gas contains 73.1% alkanes while coke oven gas is rich in H2 (28.6%). It has been shown that the gas from coking the oil shale semicoke at 1000 °C comprises mainly CO (56.7%). Depending on the parameters of technological process, the yield of products varied significantly. The goal of the current study is to demonstrate the potential of supercritical water conversion methods for producing liquid and gaseous fuels of higher energy density from various solid fuels compared to the original feedstock.

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2. Experimental 2.1. Samples

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Finely powdered (less than 0.1 mm), then homogenized and air dried samples of wildly grown spruce (Picea abies) needles and reed (Phragmites communis) biomass, peat, and mineable Kukersite oil shale, characterized in Table 1, were used as initial material subjected to the hydrothermal processing. All the samples prepared for the analysis were of Estonian origin.

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Table 1 Growing biomass and peat are known as materials of lignocellulosic origin. Oil shale OM (kerogen) is formed as a result of biomass fossilization and sedimentation. The age of Kukersite oil shale is about 460 millions of years when that of biomass samples and peat from years to tens of years only. Peat from the Estonian peatland belongs to well-humified (over 25% of its lignocellulosic OM decayed). Species of the lignocellulosic biomass are rich in oxygen (usually 35–50%) that decreasing in biomass further decaying to peat. Oil shale kerogen is characterised by much lower contents of oxygen compared with biomass or peat, that belonging to the oxygeneous structures survived after natural deoxygenation processes. The samples of biomass, peat and oil shale represent types of OM largely differing by their age of formation, OM content and its chemical composition. As a common feature, all these feedstocks are characterized by a significant content of oxygen amounting from 9.7% in oil shale kerogen to as high as 49.2% in reed biomass. In fact, the feedstocks used represent specific varieties of fossilized, humified and growing biomass differing significantly by the chemical composition and degree of metamorphism.

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2.2. Methods of liquefaction, gasification and analysis The non-catalytic liquefaction (NL) was carried out in a 500 cm3 rocking batch stainless steel autoclave equipped with a manometer and a valve for gases inlet-outlet (manufactured by Special Construction Bureau Estonia), filled with feed and water (feed 60 g : water 180 g). The autoclave was heated to 380 °C with stirring and then maintained at this temperature for 4 h. The maximum pressure amounted to 400 bar. At the end of the heating period the autoclave was cooled down to room temperature. On the next day the residual pressure in the autoclave was registered (6-23 bar). After that, the pressure valve was opened to release the gases, which were captured in a gas receiver, measured and analysed by gas chromatography

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(Chrom-4 apparatus) in packed columns (molecular sieves, sepharon) under isothermal conditions at room temperature. The reaction mixture remaining in the autoclave was separated into liquid and solid products. The separation scheme was suited to all kinds of fossil and renewable fuels. First, the autoclave content was diluted with extra portions of water and the water phase was poured on a filter. The water solubles were extracted from the aqueous solution by diethyl ether. The rest was removed from the autoclave with benzene and then extracted exhaustively on the filter. Oil fractions were recovered by evaporation of the solvents from the filtrates in a rotary evaporator. The yield of oil obtained was determined as the total weight of solvent solubles, summarizing the weights of solubles in water and benzene. The insoluble solid residue remaining after filtration and extraction contained the mineral and charred organic input material. It was dried in a thermostat at 105 °C for 2 hours to a constant weight. The benzene soluble oil portion was separated into groups of compounds by preparative thin layer chromatography (PTLC). Plates, 24×24 mm, coated with a 2 mm layer of silica gel were used and samples of 500 mg were analysed. n-Hexane was used as the eluent. Five different compound groups were separated: 1) non-aromatic hydrocarbons, 2) monoaromatic hydrocarbons, 3) polyaromatic hydrocarbons, 4) neutral heteroaromatic hydrocarbons, 5) high polar heteroaromatic compounds, including asphaltenes. The individual composition of hydrocarbons was determined in gas chromatograph Chrom-5. Capillary column (50 m, stationary phase OV-101) with temperature programming to 320 °C was used for hydrocarbon analysis. Ultimate anlysis of the initial feedstocks and of the total oils was performed by using an Elementar Vario EL analyzer. The catalytic gasification (CG) experiments were carried out in an unstirred 30 cm3 batch autoclave (SITEC, Switzerland) made of stainless steel, which was filled with feed, a skeletal nickel catalyst suspension (Raney® nickel 2800 from Sigma Aldrich) and water (feed 0.5 g, catalyst-suspension 1 g, water 5 g). The autoclave was connected to a pressure gauge via a small diameter stainless steel capillary. Argon was used for initial pressurization. Static gasification conditions were as follows: temperature 400 °C, holding time 30 min, and initial pressure 20 bar. Heating up lasted 20 min. At the end of the heating the autoclave was cooled down to room temperature in a water bath, and the gas samples were taken with a syringe for gas chromatographic analysis. Depending on the sample, the pressure in the autoclave rose up to 404 bar, the residual pressure after cooling was 30-41 bar. Solid and liquid products were washed from the autoclave and the capillary as follows: the water solution was filtered, the solid residue remaining in the autoclave was rinsed with methanol and filtered; the capillary was also rinsed with methanol. From the methanol solutions the water content was determined by Karl-Fischer titration. The chemical composition of the water and methanol solutions was determined by high pressure liquid chromatography (HPLC). The content of total organic carbon (TOC) in the water solution was measured by a TOC analyser (Dohrmann DC-190) as difference between total carbon (TC) and total inorganic carbon (TIC). From the methanol soluble oil, TC was determined after evaporation of methanol. After rinsing the solid residue it was dried, weighted, and the carbon content was determined also by the TOC analyzer using a boat module for solid samples.

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3. Results and discussion 3.1. Non-catalytic liquefaction 3.1.1. Yield of liquid fractions

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Highly compressed water above its critical temperature and critical pressure as the reaction medium or reactant, has attracted increased attention for various biomass conversion processes, including gasification and liquefaction. At the same time, an increase in the operating temperature generally increases gas yield and decreases oil yield, and that is why in liquefaction the temperatures only slightly surpassing the critical value are often used [15]. As is known, a three-dimensional steric structure of oil shale kerogen is especially resistant to external influence of temperature and solvents. The kerogen can be decomposed as a result of pyrolysis at high temperature (up to 525 °C in Fischer assay) or at lower temperatures by using supercritical solvents, e.g. water at 380 °C. In this work the experiments of NL with supercritical water were performed at 380 °C, slightly surpassing the respective critical value (374 °C). The working pressure amounted to 40 MPa that being significantly higher than the critical pressure of water (22 MPa). It was demonstrated that the oil yields obtained from hydrothermal treatment of biomass at low temperature and short resistance time (280 °C, 15 min) were low, less than 10% [18]. The balance of the products is shown in Table 2. Yields of total oil and solid residue were determined directly. As the yield of reaction water can not be determined, in hydrothermal conversion the yield of pyrogenetic water and gas (%) was calculated as 100% – total oil (%) – solid residue (%). One can see that almost all of the OM in oil shale was transferred to oil and gas (62.7 and 30.8%, respectively). Only 6.5% of the OM remained as solid residue. The oil yield from lignocellulosics varied in the range 14.6-26.3%, the latter value being close to that obtained from peat (23.6%). 42.6-52.9% of biomass was transferred to the gas and pyrogenetic water. Table 2

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In the paper [26] one can find that the oil yields obtained from lignocellulosics as a result of slow and flash pyrolysis were 16-26 and 50-80%, respectively. The higher the oil yield, the higher its oxygen content. It can be seen in Table 2 that similar oil yields in water conversion and slow pyrolysis can be obtained from spruce needles, reed and peat. The oils have typically water contents of 15-35% whereas flash pyrolysis oils are characterized by higher and slow pyrolysis oils by lower water contents. Being mostly emulsions, the flash pyrolysis oils obtained in high yield do not form separate layers of water and oil, and the water is a constitutional part of the single-phase chemical solution. So, the water cannot be removed from flash pyrolysis oil by conventional methods like distillation. Quite the contrary, both slow pyrolysis and water conversion oils do not contain organically integrated water and form separate layers of water and oil. The most of total oil is benzene soluble (Fig. 1) making up 87% of shale oil and 56-67% of bio-oils.

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Fig. 1

Comparing the yields of total oil (Table 2) and its fractions obtained (Fig. 1) one can see that the renewable feedstocks yield in supercritical water conversion less total oil with higher content of water soluble compounds. 3.1.2. Group composition of the benzene soluble oil: hydrocarbons and heteroatomic compounds As is known, Kukersite slow pyrolysis oil is almost entirely soluble in benzene [26]. NL of Kukersite oil shale yields both, benzene soluble (87%) and water soluble (13%) oil fractions

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referring to the role of supercritical water as reactant (see Fig. 1). The shale oil was chemically modified and hydrophilic compounds were formed. Peat oil and bio-oils contain lots of compounds soluble in water, 32-44% of total oil. Several times higher yield of water solubles from lignocellulosics, than from shale oil was an expected result, considering the oxygeneous character of those ones. However, the benzene solubles are dominating in all oils obtained. As it can be seen in Fig. 2, all the benzene soluble oil fractions are characterised by the elevated concentration of high polar heteroatomic compounds (52.9-58.3%, in shale oil even amounting to 71.1%). Similarly in supercritical extraction of Moroccan oil shale [22] and Kukersite extraction with various supercritical solvents [17], polars and asphaltenes in concentrations 50-75% were registered. Another dominating fraction is neutral heteroatomic compounds. Their content is considerably lower than that of high polar heteroatomic compounds but still higher than that of any hydrocarbonaceous fraction obtained. The total content of hydrocarbons, including alkanes, monoaromatic arenes and polyaromatic arenes, makes 13.8-26.7%. The polyaromatic arenes are prevailing over monoaromatic arenes and alkanes. The latters form only 5.4–8.8% of the benzene soluble fraction. Thus, judging by the group composition, the benzene soluble fractions originating from Kukersite oil shale, peat, spruce needles and reed, are rather similar than different. Fig. 2 3.1.3. Composition of alkanes: homologous rows

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Hydrocarbons are common compounds found in the composition of oils and bitumens from natural combustible feedstocks. Depending on the type of parent matter the content and composition of converted hydrocarbons is varying. Investigation their composition gives some information on the oil quality, characterises composition of initial feedstock, its maturation, etc. One can see in Fig. 3 that the non-aromatic hydrocarbons separated from the benzene soluble oil fraction by PTLC are represented by homologous n-alkanes containing up to 33 carbon atoms in alkyl chain. The n-alkanes are typical compounds in oil shale water conversion oils [17, 22, 27]. Kukersite shale oil is characterized by n-alkanes up to C22 being shorter than n-alkanes originating from lignocellulosics: C12-C28 from spruce needles, and C14-C33 from reed and peat. From Kukersite oil shale, tetra- and pentadecane and from spruce needles tetradecane in outstandingly high concentrations were formed. In the benzene soluble oil produced from peat and reed homologous n-alkanes are more evenly distributed. The OM of oil shales can consist in both marine and terrestrial biomass. It is known to the oil shale specialists that the most ancient oil shales were formed as a result of fossilization and sedimentation of marine biomass while the younger ones include remnants of higher plants. Ordovician Kukersite oil shale belongs to the oldest ones in the world and consists mainly of marine biomass, yielding shorter n-alkanes than those formed from terrestrial material. In Ordovician, only algae thrived everywhere in water basin, as at that time there were no higher plants. The presence of n-alkanes up to C33 from terrestrial plants in bio-oils and peat oil refers to the stability of long-chain hydrocarbons in supercritical water those being survived. No secondary cracking of primary formed products occurred.

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Fig. 3 3.1.4. Elemental composition of total oils

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Represented in Table 3 the elemental composition of initial feedstocks and oils obtained allows to describe regularities of distribution the elements between products. Particularly interesting in this context are transformations of oxygen. Table 3

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These data demonstrate that the total oils obtained from peat and biomass species contain more oxygen than shale oil. The content of oxygen in the oil seems to be dependent on the oxygen content in the initial feed subjected to the NL. Looking at Fig.4 it can be seen that the oils are grouped as originated from lignocellulosics, and shale oil. Fig. 4

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3.1.5. Gas composition

Fig. 5

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The NL was accompanied with significant gas formation. The gas quantity cannot be precisely calculated as that of pyrogenetic water is not known. Indirectly estimating, pyrolysis water makes only 1.9% of Kukersite dry pyrolysis products and the gas yield calculated from Kukersite water conversion can roughly indicate that from other feedstocks. The gas content presumed would be not more than ~15%. One can see in Fig. 5 that the main gaseous compound formed from all feedstocks was CO2 amounting from 56.6 vol.% in the case of spruce needles to 79 vol.% in the case of reed and peat. The main gaseous hydrocarbons formed were methane, ethane and propane. According to [19], the main gases at 330 °C, 2 h obtained from Chinese oil shale were methane, ethylene, propane, propylene, butane, butylenes, pentane and hexane. Compared with other feedstocks the yield of methane from oil shale was lower but that of ethane and propane higher. The highest amount of methane (23.3 vol.%) and CO (4.9 vol.%) was formed from spruce needles. The yield of hydrogen was the highest (7.3 vol.%) from peat.

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3.2.Skeletal-Ni-catalyzed gasification Gasification needs usually higher temperature compared with liquefaction of solid fuels. Gasification technologies provide the opportunity to convert renewable biomass feedstocks into clean fuel gases or synthetic gases. The duration of pyrolytical gasification process depends essentially on temperature, and, as a rule, when no special catalyzers are used, it is higher than 800-900 °C [6]. Hydrothermal gasification has the advantage of high efficiency to produce hydrogen, methane and other hydrocarbon gases at relatively low temperatures, at around 400 °C, and even below 374 °C when the catalyst used. It is known [31, 38, 48] that Ni-based catalysts show an excellent activity on the gasification. When biomass was gasified in supercritical water the gas consisted of H2, CO2, CO, CH4, and a small amount of C2H4 and C2H6 [47]. It was noticed that in hydrothermal gasification of biomass skeletal Ni-catalyst sintered rapidly but Ru/C was stable during 220 h of testing. That is why a carbon supported Ru catalysts at 400 °C for the methanation reaction was used [49]. Product gas contained CO2 21.9, H2 18.2, CH4 59.8 and CO 0.15 vol.%.

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Hydrogen is a cleaner source of energy. The production of hydrogen from fossil fuels causes the co-production of carbon dioxide, which is assumed to be the main responsible for the so-called greenhouse effect. The carbon balance of the products obtained in CG in Table 4 indicates that the carbon input to the reactor remarkably exceeds the carbon output from the reactor for the oil shale and peat (ratio of carbon in products to that in feed, 57.4 and 91.9%, respectively). As a matter of fact, peat and, particularly, Kukersite oil shale are feedstocks characterized by high mineral matter content, 6.8 and 49.5%. The share of inorganic carbon in TOC of the initial feedstock and char was not determined. The quantity of OM in oil shale sample submitted to CG was roughly twice lower and that of peat by ~10% lower compared with biomass samples. The content of carbon in the gas resulting from oil shale gasification was 3-4 times lower compared to that in the gas formed from biomass species or peat. At the same time, all water solutions contained mostly organic carbon. The content of carbon fixed to shale oil is about 3 times higher in shale oil compared with other samples. The char formed from peat and oil shale contains their mineral matter and 4-5 times more organic carbon than the char formed from reed and the spruce needles. As for carbon balances in Table 4, in case of biomass samples (spruce needles, reed), carbon input and output are well balanced. Concerning oil shale, one can see that carbon output exceeds its input. The reason is that under the condition of CG tested the carbonates in mineral matter of oil shale were partially decomposed forming additional amounts of CO2 influencing carbon output. Table 4

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3.2.1. Gas yield and composition

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The data on CG in Table 5 indicate that the volumetric yield of gas per air-dry feedstock from Kukersite was more than two times lower compared to the other samples. Comparing these yields on the basis of the OM shows smaller differences. Comparing mass yields, the difference between Kukersite and biomass species, both per air-dry feedstock and per OM, is bigger than in volumetric yields. Over-100% yield in mass yields is related to water reacting and the incorporation of the hydrogen and oxygen atoms into molecules of gaseous compounds in the presence of the skeletal Nickel catalyst. The methane mass yield per air-dry feedstock from Kukersite was about one order of magnitude lower than that from other samples, and per OM 5-6 times lower.

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402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451

Table 5

Composition of gases formed in the gasification experiments is presented in Fig. 6. One can see that the concentration of methane formed from oil shale (8.4 vol.%) is 4-5 times smaller than that formed from other species (36–40 vol.%). The concentration of hydrogen formed from oil shale (60.5 vol.%) is 2–4 times higher than that formed from other species (16–25 vol.%). This is in accordance with [49] where the hydrogen content in the gas formed from woody biomass by using skeletal-Ni-catalyzed gasification was 3-24 vol.%. The concentration of CO2 varies between 30.6 (oil shale) and 39.4 (spruce needles). The concentration of CO is below 1 vol.% (zero content in case of peat). Fig. 6 3.3. Comparison of the gas yields and composition in NL and CG

Page 10 of 23

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In NLthe yield of gas was lower than in CG (Tables 2 and 5). Comparing the OM based yields, one can see that the difference between the yields in the case of spruce needles and peat is bigger than in the case of Kukersite and reed. In NL the dominating gas (56.6-79 vol.%) was CO2 (Fig. 5). In CG of the biomass species the concentration of CO2 was only slightly higher than the concentration of methane (Fig. 6). At the same time, in the CG of Kukersite the concentration of CO2 and methane was remarkably lower than the concentration of hydrogen. This phenomenon may be related to the composition of the mineral matter of Kukersite, which may have influenced the skeletal Nickel catalyst, e.g. by partial poisoning of the active sites for methanation. Also, as the yield of methane was only ca. 4 mass% OM, a relatively high share of hydrogen would be expected. The concentration of hydrogen in the NL was always lower: less than 10 vol.% versus 16-60 vol.% in CG. As expected, the yield of methane was higher in CG due to the use of skeletal Nickel catalyst in this process (Figs. 5 and 6). In the case of Kukersite, the difference of the methane concentration was the smallest: by 1.5 vol.%. In the case of the biomass species the difference was between 16 and 26 vol.%. Comparing the methane mass yields (Tables 5 and 6), one can see that in CG methane was formed up to one order of magnitude more than in NL. In both processes the highest yield of methane was obtained from spruce needles and the smallest one from Kukersite.

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Table 6 3.4. HHV of samples and products

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Table 7

d

The HHV values of the initial samples and those of liquid and gaseous products are calculated in Table 7.

One can see in Table 7 that hydrothermal conversion in supercritical water results in obtaining products of higher energy density than the initial solid fuels.

Ac ce p

452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501

4. Conclusions

The potential of hydrothermal liquefaction and gasification of varied natural solid fuels was investigated by using non-catalytic liquefaction (NL) and skeletal Nickel-catalyzed gasification in supercritical water (CG). The experiments were carried out in two research laboratories (Estonia and Switzerland) using the same samples of spruce needles biomass, reed biomass, peat and kukersite oil shale as feedstocks for both liquefaction and gasification. As a common feature, all these feedstocks are characterized by a significant content of oxygen amounting from 9.7% in oil shale kerogen to as high as 49.2% in reed biomass. In fact, the feedstocks used represent specific varieties of fossilized, humified and growing biomass differing significantly by the chemical composition and degree of metamorphism. The latter choice has been used as a basis to obtaining the conclusive regularities on conversion processing of solid fuels of different origin as follows. 1. In NL, the conversion of the OM of oil shale was the highest (93.5%) among the solid fuels tested giving the highest yield of oil (62.7%), and also, the highest content of hydrocarbons in the oil composition (26.5%). The order of conversion of the initial feedstocks decreases in the row: oil shale OM > spruce needles biomass > reed biomass ≈ peat.

Page 11 of 23

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2. The yield of benzene soluble oil was: kukersite – 54.5%, spruce needles – 17.6%, peat – 15.8%, reed – 8.2% (on OM basis), and the main compounds in oil were the high polar oxygen compounds. 3. In CG the order of conversion of the initial feedstocks to gas and oil was arranged in the row: spruce needles biomass ≈ reed > peat > oil shale. The main gaseous compound of lignocellulosic gas was CH4 (4.4-28.6%), and from oil shale H2 (61%). 4. In NL the oil formation was accompanied with marked gas formation (mainly CO2) while in CG very low oil yields were observed. 5. Liquid and gaseous fuels of higher calorific value compared with parent feedstocks were obtained.

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Acknowledgements

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The authors thank the Estonian Ministry of Education and Research for financing the project SF0140028s09 and the Swiss Academy of Sciences (SANW) for financing the exchange programme of researchers between Estonia and Switzerland. The authors are deeply grateful to Vilja Palu, Natalia Vink and Thanh-Binh Truong for their assistance in products analysis.

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References [1] P. McKendry, Energy production from biomass (part 1: overview of biomass, Biores. Technol. 83 (2002) 37-46. [2] K. Urov, A. Sumberg, Characteristics of oil shales and shale-like rocks of known deposits and outcrops, MONOGRAPH, Oil Shale, 16 (1999) 13-19. [3] H. Luik, V. Palu, L. Luik, J. Sokolova, J. Koefoed, Peat semicoking and hydrocracking, J. Anal. Appl. Pyrolys. 85 (2009) 497-501. [4] H. Luik, N. Vink, E. Lindaru, Upgrading of Estonian shale oil. 1. Effects of hydrogenation on the chemical composition of kukersite retort oil, Oil Shale 13 (1996) 13-20. [5] H. Luik, Hydrogenation of Estonian oil shale and shale oil, Oil Shale 11 (1994) 151-160. [6] J. Kann, A. Raukas, A. Siirde, About the gasification of kukersite oil shale, Oil Shale 30 (2013) 283-293. [7] D. C. Elliott, D. Beckman, A.V. Bridgewater, J.P. Diebold, S.B. Gevert, Y. Solantausta, Developments in direct thermochemical liquefaction of biomass: 1983-1990, Energ. Fuel. 5 (1991) 399-410. [8] D. L. Klass, Energy from biomass and wastes: 1985 update and review, Reours. Conserv.15 (1987), 7-84. [9] W. Feng, H.J. van der Kooi, J. de Swaan Arons, Phase equilibria for biomass conversion processes in subcritical and supercritical water, Chem. Eng. J. 98 (2004) 105-113. [10] W. Feng, H.J. van der Kooi, J. de Swaan Arons, Biomass conversions in subcritical and supercritical water: driving force, phase equilibria, and thermodynamic analysis, Chem. Eng. Process. 43 (2004) 1459-1467. [11] F. Akdeniz, M. Gündoğu, Direct and alkali medium liquefaction of Laurocerasus officinalis Roem., Energ. Convers. Manage. 48 (2007) 189-192. [12] Y. Qian, C. Zuo, J. Tan, J. He, Structural analysis of bio-oils from sub- and supercritical water liquefaction of woody biomass, Energy 32 (2007) 196-202. [13] S. S. Toor, L. Rosendahl, A. Rudolf, Hydrothermal liquefaction of biomass: A review of subcritical water technologies, Energy 36 (2011) 2328-2342. [14] R. Hashaikeh, Z. Fang, I.S. Butler, J. Hawari, J.A. Kozinski, Hydrothermal dissolution of willow in hot compressed water as a model for biomass conversion, Fuel 86 (2007) 1614-1622.

Ac ce p

502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551

Page 12 of 23

te

d

M

an

us

cr

ip t

[15] H. Li, S. Hurley, C. Xu, Liquefactions of peat in supercritical water with a novel iron catalyst, Fuel 90 (2011) 412-420. [16] C. Xu, J. Donald, Upgrading peat to gas and liquid fuels in supercritical water with catalysts, Fuel 102 (2012) 16-25. [17] H. Luik, I. Klesment, Liquefaction of kukersite concentrate at 330–370 °C in supercritical solvents, Oil Shale 14 (1997) 419-432. [18] S. Karagoz, T. Bhaskar, A. Muto, Y. Sakata, Comparative studies of oil compositions produced from sawdust, rice husk, lignin and cellulose by hydrothermal treatment, Fuel 84 (2005) 875-884. [19] S. Deng, Z. Wang, Q. Gu, F. Meng, J. Li, H. Wang, Extracting hydrocarbons from Huadian oil shale by sub-critical water, Fuel Process. Tehcnol. 92 (2011), 1062-1067. [20] M. Canel, P. Missal, Extraction of solid fuels with sub- and supercritical water, Fuel 73 (1994) 1776-1780. [21] O. M. Ogunsola, N. Berkowitz, Extraction of oil shales with sub- and near-critical water, Fuel Process. Technol., 45 (1995) 95-107. [22] K. El harfi, C. Bennouna, A. Mokhlisse, M. Ben chanaa, L. Lemee, J. Joffre, A. Ambles, Supercritical fluid extraction of Moroccan (Timahdit) oil shale with water, J. Anal. Appl. Pyrol. 50 (1999) 163-174. [23] N. Olukcu, J. Yanik, M. Saglam, M. Yuksel, M. Karadumen, Solvent effect on the extraction of Beypazari oil shale, Energ. Fuel 13 (1999) 895-902. [24] H. Luik, V. Palu, M. Bityukov, L. Luik, K. Kruusement, H. Tamvelius, N. Pryadka, Liquefaction of Estonian kukersite oil shale kerogen with selected superheated solvents in static conditions, Oil Shale 22 (2005) 25-36. [25] R. Veski, V. Palu, H. Luik, K. Kruusement, Thermochemical liquefaction of reed, Proc. Est. Acad. Sci. Chem. 54 (2005) 45-56. [26] H. Luik, V. Palu, L. Luik, K. Kruusement, H. Tamvelius, R. Veski, N. Vetkov, M. Bityukov, Trends in biomass thermochemical liquefaction: global experience and recent studies in Estonia, Proc. Est. Acad. Sci. Chem. 54 (2005) 194-229. [27] L. Luik, H. Luik, N. Vink, K. Kruusement, R. Veski, Thermochemical co-liquefaction of woody biomass and fossil fuel in supercritical water, Proc. Int. Conf. Berlin, Germany, 7-11 May 2007 [DVD], 2007, 1955-1959. [28] R. Veski, V. Palu, K. Kruusement, Co-liquefaction of kukersite oil shale and pine wood in supercritical water, Oil Shale 23 (2006) 236-248. [29] A. Peterson, F. Vogel, R. P. Lachance, M. Fröling, M. J. Antal, J. W. Tester, Thermochemical biofuel production in hydrothermal media: A review of sub- and supercritical water technologies, Energy Environ. Sci. 1 (2008) 32-65. [30] Q. Yan, L. Guo, Y. Lu, Thermodynamic analysis of hydrogen production from biomass gasification in supercritical water, Energ. Convers. Manage. 47 (2006), 15151528. [31] J. A. Onwudili, A. R. Lea-Langton, A. B. Ross, P. T. Williams, Catalytic hydrothermal gasification of algae for hydrogen production: Composition of reaction products and potential for nutrient recycling, Bioresource Technol., 127 (2013) 72-80. [32] N. Ding, R. Azargohar, A. K. Dalai, J. A. Kozinski, Catalytic gasification of cellulose and pinewood to H2 in supercritical water, Fuel, 118 (2014) 416-425. [33] P. D’Jesùs, N. Boukis, B. Kraushaar-Czarnetzki, E. Dinjus, Gasification of corn clover grass in supercritical water, Fuel 85 (2006) 1032-1038. [34] E. Kirtay, Recent advances in production of hydrogen from biomass, Energ. Convers. Manage. 52 (2011) 1778-1789. [35] K. Kruusement, Water Conversion of Oil Shales and Biomass. Dissertation, 2007, Tallinn University of Technology Press.

Ac ce p

552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601

Page 13 of 23

te

d

M

an

us

cr

ip t

[36] F. Vogel, Catalytic conversion of high-moisture biomass to synthetic natural gas in supercritical water. In: Handbook of Green Chemistry, Paul Anastas (Series Editor), Volume 2 Heterogeneous Catalysis, Robert Crabtree (Volume Editor), Wiley-VCH: Weinheim, 2009, chapter 12, 281-324, ISBN 978-3-527-32497-2. [37] A. Kruse, Supercritical water gasification, Biofuels. Bioprod. Bior. 2 (2008) 415–437. [38] A. Kruse, Hydrothermal biomass gasification, J. Supercrit. Fluids 47 (2009) 391–399. [39] G. Brunner, Near critical and supercritical water. Part I. Hydrolytic and hydrothermal processes, J. Supercrit. Fluids 47 (2009) 373–381. [40] Y. Calzavara, C. Joussot-Dubien, G. Boissonnet, S. Sarrade, Evaluation of biomass gasification in supercritical water process for hydrogen production, Energ. Convers. Manage. 46 (2005) 615-631. [41] P. Ji, W. Feng, B. Chen, Q. Yuan, Finding appropriate operating conditions for hydrogen purification and recovery in supercritical water gasification of biomass, Chem. Eng. J. 124 (2006) 7-13. [42] A. Sharma, I. Saito, H. Nakagawa, K. Miura, Effect of carbonization temperature on the nickel crystallite size of a Ni/C catalyst for catalytic hydrothermal gasification of organic compounds, Fuel 86 (2007) 915-920. [43] P. J. de Wild, H. den Uil, J. H. Reith, J. H. A. Kiel, H. J. Heeres, Biomass valorisation by staged degasification. A new pyrolysis-based thermochemical conversion option to produce value-added chemicals from lignocellulosic biomass, J. Anal. Appl. Pyrolysis 85 (2009) 124-133. [44] T. Yoshida, Y. Oshima, Y. Matsumura, Gasification of biomass model compounds and real biomass in supercritical water, Biomass Bioenerg. 26 (2004) 71-78. [45] Y. Matsumura, T. Minowa, B. Potic, S.R.A. Kersten, W. Prins, W.P.M. van waaij, B. van de Beld, D.C. Elliott, G.G. Neuenschwander, A. Kruse, M.J. Antal Jr., Biomass gasification in near- and super-critical water: Status and prospects, Biomass Bioenerg. 29 (2005) 269-292. [46] Y. Guo, S. Z. Wang, D. H. Xu, Y. M. Gong, H. H. Ma, X. Y. Tang, Review of catalytic supercritical water gasification for hydrogen production from biomass, Renew. Sust. Energ. Rev. 14 (2010) 334-343. [47] M. H. Waldner, F. Krumeich, F. Vogel, Synthetic natural gas by hydrothermal gasification of biomass: Selection procedure towards a stable catalyst and its sodium sulfate tolerance, J. Supercrit. Fluid. 43 (2007) 91-105. [48] F. Vogel, M. H. Waldner, A. A. Rouff, S. Rabe, Synthetic natural gas from biomass by catalytic conversion in supercritical water, Green Chem. 9 (2007) 619-619. [49] M. Dreher, B. Johnson, A. A. Peterson, M. Nachtegaal, J. Wambach, F. Vogel, Catalysis in supercritical water: Pathway of the methanation reaction and sulphur poisoning over a Ru/C catalyst during the reforming of biomolecules, J. Catal., 301(2013) 38-45. [50] J. S. Luterbacher, M. Fröling, F. Vogel, F. Maréchal, J. W. Tester, Hydrothermal gasification of waste biomass: Process design and life cycle assessment, Environ. Sci. Technol. 43 (2009) 1578-1583. [51] D. C. Elliott, Catalytic hydrothermal gasification of biomass, Biofuels. Bioprod. Bior. 2 (2008) 254–265. [52] S. A. Channiwala, P.P. Parikh. Correlation for estimating HHV of solid, liquid and gaseous fuels, Fuel 81 (2002) 1051-1063. [53] L. Waldheim, T. Nilsson, Heating value of gases from biomass gasification. Report prepared for: IEA Bioenergy Agreement, Task 20 – Thermal Gasification of Biomass TPS-01/16. 2001. Available: http://www.media.godashboard.com/gti/IEA/HeatingValue.pdf.

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602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651

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[54] H. Arro, A. Prikk, T. Pihu, Calculation of qualitative and quantitative composition of Estonian oil shale and its combustion products. Part 1. Calculation on the basis of heating value, Fuel 82 (2003) 2179-2195. [55] A. Friedl, E. Padouvas, H. Rotter, K. Varmuza. Prediction of heating values of biomass fuel from elemental composition, Anal. Chim. Acta 544 (2005) 191-198.

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Figure captions Fig. 1. Distribution of total oil between the fractions soluble in water (W) and soluble in benzene (B) in NL experiments.

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Fig. 2. Composition of the benzene soluble oil in NL experiments. 1 – high polar heteroatomic compounds, 2 – neutral heteroatomic compounds, 3 – polyaromatic hydrocarbons, 4 – monoaromatic hydrocarbons, 5 – non-aromatic hydrocarbons. Fig. 3. Composition of n-alkanes separated from the benzene soluble oil by PTLC in NL experiments.

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Fig. 4. Oxygen content in parent matters and derived oils in NL experiments. 1 - Kukersite, 2 peat, 3 - spruce needles, 4 - reed.

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Fig. 5. Gas composition formed as a result of NL from various solid fuels.

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Fig. 6. Gas composition formed in CG experiments.

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Table 1 Characterization of the initial feedstocks (%). Characteristic Spruce needles Analytical moisture, Wa 7.3 Ash (per dry mass), Ad 3.5 CO2 of carbonates (per dry mass), CO2d 96.5 Dry organic matter, OMd Elemental composition of OMd C 50.4 H 9.5 N 0.3 S negligible O (by diff) 39.8 H/C molar ratio 2.26 O/C molar ratio 0.59

Ac ce p

652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679

680 681 682 683 684 685

Reed

Peat

Kukersite

7.5 3.0 -

12.9 6.8 -

0.6 37.2 12.3

97.0

93.2

50.5

43.7 6.5 0.6 negligible 49.2 1.78 0.84

57.1 7.2 2.6 0.1 33.0 1.52 0.43

79.0 9.5 0.3 1.5 9.7 1.44 0.09

Table 2 Yields of liquefaction of feedstocks (%) (1 – from dry feedstock, 2 – from OMd). Product Kukersite Spruce needles Reed Peat

Page 15 of 23

1 25.3 46.8

2 26.3 48.4

1 14.2 51.3

2 14.6 52.9

1 22.0 39.7

2 23.6 42.6

51.9

6.5

27.9

25.3

34.5

32.5

38.3

33.8

N 0.2 0.3 0.5 0.5

4.5 0.9 3.6 2.3

d

0.1 0.4 0.2 1.1

12.7 3.6 3.8

Char 16.8 2.8 2.7 10.4

C balance, % On feed On feed TC bases TOC bases 57.4 113.7 97.2 100.7 97.5 100.5 91.9 98.6

Table 5. Yield of gas and methane obtained in CG (1 – from air-dry feedstock), 2 – from OM). Feedstock Total gas CH4 L/g mass% mass% 1 2 1 2 1 2 Oil shale 0.4 0.79 21.2 41.9 2.3 4.6 Spruce needles 0.9 0.93 113.3 117.4 27.6 28.6 Reed 0.9 0.93 88.6 91.3 23.7 24.4 Peat 0.9 0.97 105.8 113.5 23.1 24.8

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694 695 696 697 698

23.3 93.1 87.4 74.3

O (by diff.) 6.6 18.4 16.0 16.9

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Kukersite Spruce needles Reed Peat

Oil

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690 691 692 Table 4 693 Carbon balance of CG (% from carbon in feed). Feedstock Gas Water Inorganic Organic

S 0.7 0.4 0.4 0.3

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Table 3 Ultimate analysis of total oils (%). Feedstock C H Kukersite 82.5 10.0 Spruce needles 73.9 7.0 Reed 75.9 7.2 Peat 75.1 7.2

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2 62.7 30.8

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686 687 688 689

1 32.1 16.0

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Total oil Gas and pyrogenetic water Solid residue

699 700 701 Table 6 702 Yield of methane (mass %) obtained in the NL. Feedstock From air-dry From OM feedstock Kukersite 0.4 0.8 Spruce needles 5.1 5.3 Reed 1.7 1.8 Peat 1.9 2.0 703

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707 708 709 710 711 712 713

Table 7 HHV of parent matters, derived oils and gases. Feedstock NL CG a b 3 c Feed (MJ/kg) Total oil (MJ/kg) Gas (MJ/Nm ) Gas (MJ/Nm3) c d Kukersite 18.7 40.0 21.7 11.1 20.6e Spruce needles 32.2 19.8 17.8 e f 16.9 33.2 Reed 10.7 17.7 22.6e 33.0 12.4 17.4 Peat a on a dry basis b HHV = 0.3491C+1.1783H+0.1005S-0.1034O-0.0151N-0.0211A [52] c HHV of components [53] d HHV(OM) = 0.3566C+1.0623H-0.1339O+0.0658S+0.0106N-0.0280Cl [54] e HHV = 3.55C2−232C−2230H+51.2C×H+131N+20,600 [55] f Benzene soluble oil: 36.70 MJ/kg

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704 705 706

Page 17 of 23

713 Spruce needles

Reed

Peat

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714 715

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Kukersite

Page 18 of 23

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cr

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715

Ac ce p

te

d

M

716 717 718 719

Page 19 of 23

ip t cr us an Ac ce p

te

d

M

719 720 721

Page 20 of 23

ip t cr us Ac ce p

te

d

M

an

721 722

Page 21 of 23

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te

d

M

722 723 724

Page 22 of 23

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M 724 725 726 727

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CO2

H2

CO

Ac ce p

CH4

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