Apr 17, 2018 - To achieve the energy security with the minimum greenhouse emission, efforts have been directed toward the efficient conversion of raw ...
May 10, 2010 - Department of Chemical Engineering, University of Michigan, Ann Arbor, ...... liquefaction of cornelian cherry stones for bio-oil production.
May 10, 2010 - Tylisha M. Brown, Peigao Duan, and Phillip E. Savage*. Department of Chemical Engineering, University of Michigan, Ann Arbor, Michigan ...
Mar 30, 2011 - ABSTRACT: The char of three typical biomasses, rice straw char (RS char), chinar leaves char (CL char), and pine sawdust char. (PS char) ...
Apr 16, 2015 - Table 5 shows tentative identities for several of the major individual molecular components in the portion of the biocrude from HTL over Ru/C that is amenable to GC analysis. These identities are tentative because they are based solely
Apr 16, 2015 - The procedure for gas-phase products, except C3âC5 alkanes, was ..... 5. Brown , T. M.; Duan , P.; Savage , P. E. Hydrothermal liquefaction and ...
Apr 16, 2015 - Catalytic upgrading of bio-oil in hydrothermal liquefaction of algae major model components over liquid acids. Wenchao Yang , Xianguo Li , Dahai Zhang , Lijuan Feng. Energy Conversion and Management 2017 154, 336-343 ...
been studied. RDF and sodium hydroxide corresponding to NaOH/C mass ratios of 0.2 to 1.2 were reacted at. 375 °C using initial water densities of 0.04, 0.10, ...
May 19, 2011 - Douglas C. Elliott , Andrew J. Schmidt , Todd R. Hart , Justin M. Billing. Biomass Conversion and Biorefinery 2017 7 (4), 455-465 ...
In the present work, a systematic study has been conducted to explore the .... Green Processing and Synthesis 2015, 4 DOI: 10.1515/gps-2015-0037. Po-Chih ...
Gasification of Char Derived from Catalytic Hydrothermal Liquefaction of Pine Sawdust under CO2 Atmosphere Flabianus Hardi, Akihisa Imai, Sarut Theppitak, Kawnish Kirtania, Erik Furusjö, Kentaro Umeki, and Kunio Yoshikawa Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.8b00589 • Publication Date (Web): 17 Apr 2018 Downloaded from http://pubs.acs.org on April 18, 2018
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The integration between K2CO3-catalytic hydrothermal liquefaction (HTL) and gasification is explored to improve the gasification process. In this study, the CO2 gasification characteristics and the activation energies of the chars derived from four kinds of HTL products, black liquor (BL) and virgin pine sawdust (PS) are investigated non-isothermally using a thermogravimetric analyzer. The complete conversion of BL char and HTL product chars was achieved at lower temperatures (1150 K) than that of PS char (1300 K). BL char showed the highest DTG peak, an indicator of high reactivity, followed by HTL product chars and PS char. HTL liquid product chars exhibited the lowest DTG peak temperature (1023–1058 K) which is advantageous for the low temperature gasification. The activation energies were calculated iso-conversionally using the Kissinger-Akahira-Sunose (KAS), the Flynn-Wall-Ozawa (FWO) and the Starink approximations. Based on KAS method, the range of the activation energy for the HTL aqueous product char sample was 127–259 kJ/mol which was wider than that for BL char (171–190 kJ/mol). The HTL process can improve the gasification feedstock reactivity and the use of HTL liquid product allows the gasification at low temperature.
Lignocellulosic biomass is a green fuel and a chemical source which is available worldwide and its use does not pose a threat to human food security. In order to achieve the energy security with the minimum greenhouse emission, efforts have been directed towards the efficient conversion of raw biomass into chemicals, fuel and energy, thus reducing dependency on fossil fuels.
Among thermochemical conversion alternatives, gasification is a proven process to convert biomass or coal into syngas (CO, H2, CO2 and CH4). Established gas-to-liquid (GtL) conversion technologies transform syngas into methanol, dimethyl ether (DME), ammonia and liquid hydrocarbons
1,2
. Biomass gasification, together with GtL, is a promising technology for
realizing conversion of lignocellulosic biomass to liquid fuels or chemicals 1,3.
Black liquor (BL) gasification is an established technology for converting biomass waste generated from a Kraft pulp mill into syngas. The key success of this process is the catalytic effect of alkali salt. Thus, the positive effect of the alkali catalyst from this technology can be also adopted to pre-treat virgin biomass by means of alkali-catalyzed hydrothermal liquefaction (HTL) before it is fed into the gasifier. Since the main product of HTL is in liquid form, it does not require a complex feeding system when using a pressurized gasifier. In the industrial application, combined HTL and gasification process is expected to reduce dependency of BL supply, to improve the gasifier feedstock, increase the gasifier performance and to be independent from a pulp mill to maximize the biofuel production.
The catalytic activity, recyclability and availability of the catalyst are also crucial. K2CO3 is the most active catalyst in HTL and gasification processes
4–7
, it can be recycled, it is similar to
Na2CO3 present in BL 8 and the potassium itself is abundantly available in the ash of terrestrial plant
9,10
. Although K2CO3 can be utilized in a consecutive HTL and gasification process, the
gasification research is still limited to the impregnation on wood or coal with K2CO3 8,11,12.
At present, BL is the most well-studied gasification feedstock derived from biomass. A 3 MW BL gasifier built by Chemrec in Piteå, Sweden, has been demonstrated for more than 25,000 h operation and the research on various aspects of BL gasification has been intensely conducted 13. Recently, the performance of the pilot scale BL gasifier, the kinetic of BL gasification, the flexibility to do co-gasification with various kind of biomass and the techno-economic assessment of its commercial scale have been reported 13–17. Hence, it is necessary to include BL as a reference sample, as well as virgin pine sawdust which represents a raw lignocellulosic biomass.
Among the reactions occurring inside gasifiers, CO2 char gasification represents the rate determination step. Therefore, it is important to study the CO2 char gasification (Boudouard reaction)
18
. The type of the gasifying agent, the distribution between char particles and the
gasifying agent, the temperature, the sample geometry and the active site affect the reaction rate and the char conversion
19
. Increasing the reactivity of the char means improving the gasifier
performance. Knowledge on char gasification is the key for the optimal gasifier design.
The CO2 char gasification characteristics and kinetics from virgin biomass, coal, or their mixture 4 ACS Paragon Plus Environment
the catalytic HTL and gasification is developed, as proposed in our previous study 23. This study, for the first time, evaluates the characteristics of CO2 gasification of the chars derived from K2CO3-catalytic HTL products, including char activation energy by non-isothermal thermogravimetry.
2. Materials and methods
2.1 Materials
Char samples were made by pyrolyzing six parent samples. The details of the parent samples are shown in Table 1.
APc, AP, SR and APSR samples were produced from the K2CO3-catalytic HTL of pine sawdust. According to our previous K2CO3-catalytic HTL study, it was predicted that a moderate reaction temperature (543 K), pine sawdust to solvent mass ratio 1:10 and a short reaction time (0 min) gave high AP yield; therefore, AP, SR and APSR were produced based on this HTL conditions 23. Black liquor (BL) was received from Smurfit Kappa pulp mill, while pine sawdust was collected from Norrbotten, Sweden. The elemental compositions of BL and pine sawdust have been reported in the previous studies 17,24. The summary of the elemental and proximate compositions for all parent samples is shown in Table 2.
< Table 2. Ultimate and proximate analysis of the parent samples.>
The ultimate analysis was performed using an elemental micro analyzer (Micro Corder JM10) in analytical center of Tokyo Institute of Technology. The proximate analysis was done using using thermogravimetric analyzer (Shimadzu DTG-60H with thermal analyzer TA-60WS). The temperature program was adopted from Warne 25. Approximately 6.5 mg sample was loaded into the TG pan. Initially, N2 was continuously supplied (150 ml/min) while the sample was heated up to 383 K with 20 K/min heating rate, held for 15 min; then temperature was increased to 1148 K with 20 K/min heating rate and held for 5 min. Lastly, the gas was switched into air (150 ml/min) at the same temperature and this condition was kept for 10 min. Air, high purity N2, high purity CO2 and high purity argon were purchased from Tomoe Shokai and used as they were received.
2.2 Experimental procedure
The experiment consisted of two steps: The 1st step was the fast pyrolysis to produce char and The 2nd step was the CO2 char gasification. The use of metal (e.g. stainless steel) which contains nickel was avoided because, even at 773 K (500 °C), nickel can accelerate the devolatilization and promote the char conversion 26. This intervention was prevented by means of using alumina ceramic or glass apparatus during the fast pyrolysis and gasification. Additionally, the ceramic bowl is favored during the fast pyrolysis to hold the swollen char sample during the pyrolysis 15.
Some authors concluded that the mass loss during the pyrolysis (about 873–973 K) of coal, BL, or lignocellulosic material was not affected by the gas selection (CO2 or N2) 16,27,28. However, the 6 ACS Paragon Plus Environment
char surface morphology is highly affected by the choice of gas (CO2 or N2) 29 and this can affect the char reactivity during the gasification 18. Saddix et al. emphasized the different properties (e.g. the molecular size, the heat capacity) between CO2 and N2 affecting the diffusivity and the heat transfer
30
. The use of N2 should be avoided during gasification because it promotes the
breakdown of carbonate salt and auto-ignition of the sample, thus leading to inaccuracy on the weight measurement 8,31. Therefore, in this study, CO2 was consistently used during the pyrolysis and gasification.
2.2.1 Char preparation (fast pyrolysis)
Before the CO2 gasification was carried out, the char samples were prepared from the parent samples. Each parent sample (listed in Table 1) was pyrolyzed at 873 K (600 °C) for 30 min under 600 ml/min CO2 flow rate in a fixed bed glass reactor (Figure 1). As shown in Figure 1, the reactor consists of an inner glass tube with a porous material in the bottom part, an outer glass tube and an electric heater. The outer glass tube was bound to the heater but the inner glass tube was slidable, which allowed the position adjustment for a cold (room temperature) and a hot region (873 K).
Except for the BL sample, prior to the fast pyrolysis, all parent samples have been dried in a drying oven (378 K, 24 h) to remove moisture and the weight of the sample (including an alumina tube) before and after the fast pyrolysis were measured. About one gram of parent sample was loaded into a pre-weighted alumina ceramic tube and it was placed inside the inner 7 ACS Paragon Plus Environment
glass tube. In order to reach a very high heating rate (approximately 600 K/min), first, the outer tube was heated up to 873 K and then the inner tube containing the sample was inserted. Prior to the insertion, the CO2 and argon were continuously supplied to the inner and outer glass tubes, respectively, to displace air inside the reactor. Argon supply was cut immediately after the insertion; meanwhile CO2 was continuously flowing during the pyrolysis and cooling processes. The temperature was kept at 873 K for 30 min and the reactor was cooled down slowly to prevent a thermal shock in the inner glass tube. Prior to the gasification experiment, the char samples were collected and ground to a size below 90 micron to assure the gasification under chemical control regime 32,33. The visual appearance of the parent and char samples and the SEM images of the chars are provided in Figures S1 and S2 (Supporting Information), respectively.
2.2.2 Char gasification
The CO2 char gasification was conducted using a thermogravimetric analyzer (Shimadzu DTG-60H with thermal analyzer TA-60WS). About 6.5 mg of char was placed into the TG alumina pan. Prior to heating, the air inside the TG chamber was replaced with CO2 by means of flushing. Initially, the sample was heated up to 373 K with the heating rate of 20 K/min and held for 5 min. Then, a heating rate of 20, 30, or 40 K/min was applied until it reached the predetermined final temperature (Table 3). All samples were studied to full conversion, however, the maximum temperature used in the experiment was limited by the ash melting temperature of each char. In all TG experiments, the CO2 flow rate was maintained constant at 150 ml/min and the sample was immediately cooled after reaching the target temperature to minimize the alkali loss 31. 8 ACS Paragon Plus Environment
At least two replications of each TGA experiment were done and the average results were reported. The order of experiment was randomized to prevent systematic errors. Before taking the average value, the Gaussian method which is applicable for data with an irregular interval and suitable for non-isothermal TG data, was applied to reduce the noise on each conversion level 34.
The char conversion (X) and its derivative (dX/dT = DTG) against the temperature (T)
34
are
defined according to the following equations:
X =
m − m (1) m − m
dX X − X = (2) dT (T − T )
where m0, mt, mash are the initial mass, the mass at time of t and the mass of ash. DTG is calculated according to the central derivation.
2.3 Kinetic analysis
There are several methods to study the kinetic of the CO2 char gasification. The iso-conversional method is a model-free approach to calculate the activation energy. In this study, the activation energy was calculated using: (a) The Kissinger-Akahira-Sunose (KAS, Eq. (3))
Flynn-Wall-Ozawa (FWO, Eq. (4)) which was derived from the Doyle approximation
Page 10 of 32
37–39
and
(c) The Starink methods (Eq. (5)) 40. Those methods have integral behavior, hence, they are less influenced by the noise and the baseline determination 40,41. The KAS method is known for high accuracy 40 while the FWO method is reliable for practical applications in various research fields, including the pyrolysis and gasification 20,38,41–43. The Starink type B-1.92 method was designed to improve the accuracy of the KAS method 40.
β A . R E ln = ln − (3) T E . g(X) R . T
A . E E ln β = ln − 5.331 − 1.052 (4) R . g(X) R . T
β E ln ." = Constant −1.008 (5) T R . T
where A, β, R, g(X) and E are the frequency factor, the heating rate, the gas constant, the integral reaction model and the activation energy respectively. In the KAS method, the activation energy obtained from a certain conversion level can be calculated after obtaining the slope from plotting *
ln ) , - against ) -. A similar calculation procedure was applied for the FWO and the Starink + + methods.
Careful consideration is taken into account when calculating the activation energy at high conversion level or at high temperature 44,45. At very high conversion, sample would suffer from 10 ACS Paragon Plus Environment
a change between porous surface to ash dominated surface reaction. Meanwhile, at high temperature there is a chance to move into transition or mass transfer limited zone and the activation energy becomes less predictable. For these reasons, the activation energy is calculated up to 0.7 conversion.
3. Results and Discussion
3.1 Fast Pyrolysis and Gasification under CO2 Atmosphere
Figure 2 shows the overall organic and ash content of parent samples. PS has the lowest ash content, less than 1%, while SR contains more, 6.17%. Although washing was done during the separation step in HTL experiment, K2CO3 was chemically bound on SR during HTL. The acquired SR ash is consistent with what was reported during the impregnation of pine sawdust with K2CO3 without washing (2.0–9.5% of ash content) 8.
The ash content in BL constitutes about half of its weight, while that in APc, AP and APSR contribute to about 70%. The reason for this high ash content in APc, AP and APSR is that the largest fraction of K2CO3 used during HTL is present in the aqueous products fraction. The weight of BL char after the pyrolysis could not be measured accurately using our experimental set up because BL swelled greatly, leading to that a small portion of the sample overflowed from the alumina tube. The volume increase during BL pyrolysis in nitrogen at the atmospheric pressure has been reported to be a factor of 30 46. Although the organic and ash contents in BL 11 ACS Paragon Plus Environment
could not be measured directly, Kirtania et al. has reported the inorganic and organic fraction of BL under the similar conditions 16.
The portion of the volatile organic release during the fast pyrolysis and the gasification on dry ash free basis is shown in Table 4.
One of the interesting findings is that the during fast pyrolysis, APc, AP and APSR lost 85.4–90.2% of their organic matter which is significantly higher than that for BL (65.1%). The high losses on APc, AP and APSR are most likely due to the high content of volatile organic produced during HTL.
Table 5 shows the metals and sulfur compositions in the ash of chars which were measured by X-Ray Fluorescence (XRF, Horiba Scientific XGT-7200 X-Ray Analytical Microscope).
< Table 5. Metals and sulfur compositions in the ash of the char samples.>
According to Table 5, potassium is identified as the only major metal element in APc, AP, SR and APSR chars. The added potassium during the catalytic HTL accumulates in the aqueous liquid product (APc, AP and APSR) and some of it is still left in SR. The other metal elements whose salts insoluble in the water such as calcium, iron, nickel and chromium, could not have passed through the filter paper during separation in the catalytic HTL and they were collected together with SR. Sodium, potassium and sulfur are detected as the major elements in the ash of 12 ACS Paragon Plus Environment
3.2 CO2 Char Gasification Characteristics and Reactivity
The solid lines in Figure 3 show the char conversion (X) against the gasification temperature (T) at various heating rates. APc char, AP char, SR char, APSR char and BL char reached almost complete conversion at approximately 1150 K, while PS char required higher temperature, about 1300 K to achieve near complete conversion. Each sample was exposed to three different heating rates, 20 K/min, 30 K/min and 40 K/min. The conversion curve is slightly shifted to higher temperature by the increase of the heating rate but it did not affect the final conversion level.
Derivative of the conversion against the temperature (DTG) of each char is presented in dashed lines (Figure 3). At 40 K/min heating rate, the DTG peaks of APc char, AP char, SR char and APSR char are in the range of 6.9×10-3 to 8.7×10-3 /K which is about half of that of BL char. Another observation from Figure 3 is that across all the chars, PS char has the lowest DTG peak, 6.2×10-3 /K. In short, chars from BL and HTL products have higher DTG peaks than PS char.
SR char, BL char and PS char show single narrow peaks, meanwhile APc char, AP char and APSR char have broad peaks. The possible reason for the broad peaks may be related to ash content in the char. According to Figure 2, the ratio of ash and organic in APc char, AP char and APSR char (organic loss during the gasification) is more than ten times, while that of BL is about 13 ACS Paragon Plus Environment
three times. This may have an implication of more difficulty of converting the small amount of organic left on APc char, AP char and APSR than that of BL char, SR char and PS char during the gasification step. A study on the coal char gasification mentioned that the saturation of K2CO3 catalyst loading was observed at 20% 7. Similarly, Kirtania et al. found that the pine sawdust char containing 23% K2CO3 showed the highest catalytic activity and high alkali deposition on char caused less structural effect on the reaction rate 8.
The shouldering peak on APSR char can be true and reasonable. The APSR parent sample contains approximately 78% of AP and 22% of SR. In such proportion, the APSR char peak characteristic must be the convolution of AP char and SR char peaks, with strong influence from AP char peak. The primary peak at about 1030 K should come from AP, while the secondary peak at 1100 K probably results from SR.
Two important points of the char reactivity are the DTG peak height and the temperature which the DTG peak exists (the peak temperature). They can be conveniently plotted according to Figure 4.
The most reactive char, which has a high conversion rate at low temperatures, must be located in the top-left area on the graph (Figure 4). On the other hand, the least reactive char occupies the bottom-right area of the graph. Accordingly, BL char has the highest reactivity, followed by HTL product chars; and the least reactive is PS char. APc char, AP char and APSR char are found to 14 ACS Paragon Plus Environment
have similar DTG peaks and peak temperatures. The benefit of having a low peak temperature indicates the possibility to operate the gasifier at a lower temperature which allows energy saving, safer operation and lower investment cost.
3.3 Activation Energy
Figure 5 shows the activation energies from six char samples during the CO2 gasification at 0.1–0.7 conversion levels which were calculated using the KAS, the FWO and the Starink approximations. All approximations gave consistent trend of the activation energy change for all the char samples. The activation energies calculated by the KAS and the Starink methods gave approximately equal values, while those obtained from the FWO method had higher values.
The activation energy of the chars derived from the liquid product of HTL (APc, AP and APSR) have an ascending trend (Figures 5a, b and d). This indicates that, the greater the extent of the char conversion, the more energy required to initiate and maintain the reaction. In section 3.2, it was discussed that a huge portion of the organic components are released during the fast pyrolysis, thus, it leaves chars (APc char, AP char and APSR char) with high alkali ash content (Figure 2), which exceeded the concentration for the optimal catalytic effect. At high conversion stage, the surface saturation, the pore plugging and the sintering of the alkali catalyst might have contributed to difficulties in the char conversion 47,48.
Unlike chars derived from liquid product of HTL (APc char, AP char and APSR char), SR char and PS char showed a decrease in the activation energy as the char conversion increased (Figures 5c and f). The activation energy of SR char (the KAS method) started from 229 kJ/mol and decreased to 127 kJ/mol. The activation energy of PS char decreased from 223 kJ/mol to 149 kJ/mol which is consistent with what was previously reported
49,50
. PS and SR chars had
relatively higher organic matter (87.2% and 97.8%, respectively) and a low ash content (12.7% and 2.18%, respectively). Therefore, it retained a strong catalytic effect and exhibited a reducing trend in the activation energy until the chars reached approximately 0.5 conversion.
According to the KAS method, the activation energies of APc char, AP char APSR char are 148–232 kJ/mol, 127–259 kJ/mol and 215–253 kJ/mol, respectively. Among all char samples, AP char shows the lowest activation energy at 0.1 conversion. The high activation energy on APSR char implies that mixing AP and SR does not reduce the activation energy.
The activation energy of BL char is substantially affected by the fractional conversion, hence, a narrow range of the activation energy (171–190 kJ/mol) was observed (Figure 5e). Although BL char shows the highest DTG peak (Figure 4), it does not have the lowest activation energy compared to other char samples. The activation energy increased marginally with the char conversion. This ascending trend of the activation energy is similar to those of obtained from liquid product of HTL char (APc char, AP char and APSR char).
A combination of diverse alkali salt composition could result in more complex reactions contributing towards lowering the activation energy and increasing the char reactivity. The 16 ACS Paragon Plus Environment
sodium and potassium contents in the virgin BL is 20.6% and 3.12%, respectively 17. They are bounded with the organics and present in inorganic forms: carbonate and sulfate. Sodium sulfate (Na2SO4), however, only exists in the BL sample and this can be an influential factor for the high reactivity and the narrow range of activation energy of BL char. At 873–1150 K sodium sulfate promotes char conversion via sulfate reduction, as follows 48,51,52:
2C(s) + Na2SO4(s) →
Na2S(s) + 2CO2(g)
(6)
4C(s) + Na2SO4(s) →
Na2S(s) + 4CO(g)
(7)
Na2SO4(s) + 4CO(g) →
Na2S(s) + 4CO2(g)
(8)
The consecutive HTL and gasification process can be the answer to increase the reactivity virgin biomass, reduce the gasification temperature and transform the solid into liquid fuel for a convenient gasifier feeding system. In terms of the activation energy during CO2 gasification, the use of HTL liquid product or solid residue is more favorable than the mixture of them. The form of gasification feedstock can be a concern when using pressurized gasifiers which favor liquid state. Consequently, the liquid product needs to be separated from the solid residue before it is charged into a gasifier.
4. Conclusions
The CO2 gasification of the chars derived from the HTL products (APc, AP, SR and APSR), BL and PS were studied by means of TGA. The char reactivity evaluated from their maximum conversion rate is ranked as follows (high to low): BL char, SR char, APc char, AP char, APSR 17 ACS Paragon Plus Environment
char and PS char. APc char and AP char reached near complete conversion at lower temperature (1150 K) and had the lowest temperature at the DTG peak. This indicates that the use of HTL liquid product can be advantageous for the low temperature gasification. APc char (148–232 kJ/mol) and AP char (127–259 kJ/mol) have wider activation energy range than BL char (171–190 kJ/mol). The use of HTL liquid product as gasification feedstock can be used for increasing the reactivity of virgin biomass and reducing the gasification temperature.
(E.F.) RISE Bioeconomy, Drottning Kristinas väg 61, Stockholm, Sweden.
Acknowledgements
This work was supported by the Japan Society for the Promotion of Science (JSPS) and the Swedish Foundation for International Cooperation in Research and Higher Education (STINT) through Japan–Sweden Research Collaboration Program. Flabianus Hardi and Sarut Theppitak thank the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan for the Japanese government scholarship. The contributions of (1) Alexander Mosqueda and Astryd Viandila from Tokyo Institute of Technology in SEM analysis; (2) analytical center staff from Tokyo Institute of Technology (Suzukakedai campus) in elemental analysis are deeply appreciated.
Supporting Information
Visual appearance of the parent samples and char samples (Figure S1) and SEM images of char 19 ACS Paragon Plus Environment
samples (Figure S2) are provided. The supporting information is available free of charge via the Internet at http://pubs.acs.org.
Glossary
Nomenclature X = char conversion (from 0 to 1) β = heating rate (Kelvin/second) A = frequency factor dX/dT = first differential of char conversion against temperature; conversion rate (/Kelvin) E = activation energy g(X) = integral reaction model R = gas constant (8.314 J/(mol.Kelvin)) t = time (second) T = temperature (Kelvin)
Abbreviations AP = aqueous product obtained from hydrothermal liquefaction (dried) APc = aqueous product obtained from the center of hydrothermal liquefaction design experiment (dried) APSR = a mixture of aqueous and solid residue product obtained from hydrothermal liquefaction (dried) BL = black liquor 20 ACS Paragon Plus Environment
Umeki, K.; Moilanen, A.; Gómez-Barea, A.; Konttinen, J. Chem. Eng. J. 2012, 207–208, 616–624. Ahmed, I. I.; Gupta, A. K. Appl. Energy 2011, 88 (5), 1613–1619. Edreis, E. M. A.; Luo, G.; Yao, H. J. Anal. Appl. Pyrolysis 2014, 107, 107–115. Zhang, J.; Guo, J.; Wang, G.; Xu, T.; Chai, Y.; Zheng, C.; Xu, R. Int. J. Miner. Metall. Mater. 2016, 23 (9), 1001–1010. Lin, Y.; Ma, X.; Peng, X.; Yu, Z.; Fang, S.; Lin, Y.; Fan, Y. Fuel 2016, 181, 905–915. Hardi, F.; Furusjö, E.; Kirtania, K.; Imai, A.; Umeki, K.; Yoshikawa, K. Biofuels Accepted (March 22th, 2018). Hardi, F.; Mäkelä, M.; Yoshikawa, K. Appl. Energy 2017, 204, 1026–1034. Warne, S. S. J. Thermochim. Acta 1996, 272, 1–9. Osaki, T.; Mori, T. React. Kinet. Catal. Lett. 2006, 89 (2), 333–339. Chen, L.; Yong, S. Z.; Ghoniem, A. F. Prog. Energy Combust. Sci. 2012, 38 (2), 156–214. Zhang, J.; Chen, T.; Wu, J.; Wu, J. Bioresour. Technol. 2014, 166, 87–95. Rathnam, R. K.; Elliott, L. K.; Wall, T. F.; Liu, Y.; Moghtaderi, B. Fuel Process. Technol. 2009, 90 (6), 797–802. Shaddix, C.; Hecht, E.; Geier, M.; Molina, A. In 3rd Oxyfuel Combustion Conference, Spain; Ponferrada, 2013. Kopyscinski, J.; Rahman, M.; Gupta, R.; Mims, C. A.; Hill, J. M. Fuel 2014, 117, 1181–1189. Kirtania, K.; Bhattacharya, S. Fuel Process. Technol. 2015, 137, 131–138. Dupont, C.; Boissonnet, G.; Seiler, J. M.; Gauthier, P.; Schweich, D. Fuel 2007, 86 (1–2), 32–40. Chen, H. X.; Liu, N. A.; Shu, L. F.; Zong, R. W. J. Therm. Anal. Calorim. 2004, 78 (3), 1029–1041. Kissinger, H. E. Anal. Chem. 1957, 29 (11), 1702–1706. Akahira, T.; Sunose, T. Res. Rep. Chiba Inst Technol (Sci Technol) 1971, 16, 22–31. Doyle, C. D. J. Appl. Polym. Sci. 1961, 5 (15), 285–292. Ozawa, T. Bull. Chem. Soc. Jpn. 1965, 38 (11), 1881–1886. Flynn, J. H.; Wall, L. A. J. Res. Natl. Bur. Stand. Sect. A Phys. Chem. 1966, 70A (6), 487. Starink, M. J. Thermochim. Acta 2003, 404 (1–2), 163–176. Opfermann, J.; Kaisersberger, E. Thermochim. Acta 1992, 203 (C), 167–175. Edreis, E. M. A.; Luo, G.; Yao, H. J. Anal. Appl. Pyrolysis 2014, 107 (9), 107–115. Dowdy, D. R. J. Therm. Anal. Calorim. 1987, 32, 137–147. Lahijani, P.; Zainal, Z. A.; Mohammadi, M.; Mohamed, A. R. Renew. Sustain. Energy Rev. 2015, 41, 615–632. Qadi, N. M. N.; Hidayat, A.; Takahashi, F.; Yoshikawa, K. Biofuels 2017, 8 (2), 281–289. Whitty, K.; Backman, R.; Hupa, M. Bioresour. Technol. 2008, 99 (3), 663–670. Hamilton, R. T.; Sams, D. A.; Shadman, F. Fuel 1984, 63, 1008–1012. Li, J.; Van Heiningen, A. R. P. Ind. Eng. Chem. Res. 1990, 29 (9), 1776–1785. Butterman, H. C.; Castaldi, M. J. In Synthetic Liquids Production and Refining; 2011; pp 27–73. Khalil, R.; Várhegyi, G.; Jäschke, S.; Grønli, M. G.; Hustad, J. Energy & Fuels 2009, 23 (1), 94–100. Cameron, J. H.; Grace, T. M. Ind. Eng. Chem. Fundam. 1985, 24 (4), 443–449. Sricharoenchaikul, V.; Hicks, A. L.; Frederick, W. J. Bioresour. Technol. 2001, 77 (2), 22 ACS Paragon Plus Environment
Table 1. Parent samples used for char production. No.
Sample Description abbreviation
Origin
Yield of sample produced from HTL (wt%, dry ash-free basis) a
Obtained from K2CO3 catalytic HTL at 543 K, 30 min reaction time and 17.1% pine sawdust mass fraction (pine sawdust and 76.1 1 APc Dried aqueous product solvent mass ratio was 1: 4.9; the solvent was 20 wt% K2CO3 solution) 2 AP Dried aqueous product Obtained from K2CO3 catalytic 72.3 HTL at 543 K, 0 min reaction 19.0 3 SR Dried solid residue Dried mixture of aqueous time and 9.1% pine sawdust mass product and solid residue fraction (pine sawdust and solvent 4 APSR n.m. (no separation during mass ratio was 1: 10; the solvent was 20 wt% K2CO3 solution) HTL) Black liquor (viscous Obtained from Smurfitt Kappa 5 BL N/A liquid) Kraftliner, Piteå Pine sawdust (500–600 Obtained from Norrbotten 6 PS N/A µm) County, Sweden a Yield of specified HTL product = mass of specified HTL product/initial mass of pine sawdust. n.m. = not measured N/A = not available
