JOURNAL OF APPLIED SCIENCE AND AGRICULTURE

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1 AENSI Journals JOURNAL OF APPLIED SCIENCE AND AGRICULTURE ISSN Journal hoe page: The Effect of Carbon Fuel Properties and Pyrolysis Conditions on the Electrocheical Perforance of Direct Carbon Fuel Cell - A Review 1 Shu-Hong Li, 1 Siek-Ting Yong, 1 Chien-Wei Ooi, 2 Veena Doshi, 3 Wan Rali Wan Daud 1 Multidisciplinary Platfor of Advanced Engineering, Cheical Engineering Discipline, School of Engineering, Monash University Malaysia, Jalan Lagoon Selatan, Bandar Sunway, Selangor Darul Ehsan, Malaysia. 2 Discipline of Cheical Engineering, School of Engineering, Taylor s University Malaysia, No.1 Jalan Taylors, 47500, Subang Jaya, Selangor Darul Ehsan, Malaysia. 3 Fuel Cell Institute, University Kebangsaan Malaysia, UKM Bangi, Selangor, Malaysia. A R T I C L E I N F O Article history: Received 31 Deceber 2014 Received in revised for 26 January 2015 Accepted 28 January 2015 Available online 11 February 2015 Keywords: Direct carbon fuel cell, bioass, pyrolysis. A B S T R A C T Direct carbon fuel cell offers an efficient alternative to conventional cobustion syste for electricity generation. The ost attractive feature is its rearkably high overall syste efficiency. However, the ipleentation of this technique is restricted by the liited solid-solid contact between the carbon fuel and electrode. This reviews discusses a sets of cheical and physical properties of the carbon fuel that contribute to the electrocheical perforance of the fuel cell. These properties include cheical coposition, surface functional groups, graphitic structure and textural properties. Meanwhile, bioass can be eployed as a sustainable carbon fuel source after undergoing pyrolysis, a theral pretreatent process. It is essential to control the pyrolysis operating conditions such as the teperature, heating rate and residence tie as these conditions would affect the cheical and physical properties of the carbon fuel, ultiately contributing to the electrocheical perforance of the fuel cell AENSI Publisher All rights reserved. To Cite This Article: Shu-Hong Li, Siek-Ting Yong, Chien-Wei Ooi, Veena Doshi, Wan Rali Wan Daud., The Effect of Carbon Fuel Properties and Pyrolysis Conditions on the Electrocheical Perforance of Direct Carbon Fuel Cell - A Review. J. Appl. Sci. & Agric., 10(5): , 2015 INTRODUCTION Depletion of world s energy reserves, particularly fossil fuel resources, has ade energy sustainability a subject of worldwide debate. The energy shortage crisis acted as a stiulant in intensive developent of alternatives for electricity generation process, that is, the fuel cell technologies. In the field of fuel cell, there are nuerous types and fors of fuel cells which oxidize fuels such as hydrogen, ethanol and ethane to generate 2 O ( air) 4e 2O 2 2 C 2O CO 4e 2 C O ( air) CO 2 2 electricity. Direct carbon fuel cell (DCFC) is a type of fuel cell which produces electricity through electrocheical oxidation of solid carbon into carbon dioxide, without involving cobustion reaction. The first eergence of DCFC could be traced way back to id of 19 th century, where in the year of 1839, Sir Willia Grooves first discovered the existence of direct carbon fuel. Eq. (1) and (2) show the half-cell reactions associated electrons while Eq. (3) depicts the overall oxidation reaction. (1) (2) (3) The ost proising advantage of DCFC is its rearkably high theoretical efficiency for Eq. 3 in converting cheical energy into electricity which is close to 100% (Muthuvel et al. 2009, Chien et al. 2013). Its overall syste efficiency taking into account of auxiliary losses is in the range of 60-70% (Giddey et al. 2012), as copared to less than 40% for a Carnot Cycle. *Corresponding Author: Shu-Hong Li, Multidisciplinary Platfor of Advanced Engineering, Cheical Engineering Discipline, School of Engineering, Monash University Malaysia, Jalan Lagoon Selatan, Bandar Sunway, Selangor Darul Ehsan, Malaysia. Tel: ; fax: ; E-ail: estee.yong@onash.edu

2 113 Shu-Hong Li et al, Critical carbon fuel properties and its effect on fuel cell perforance: One of the advantages of DCFC is its fuel flexibility; however this does not eans that all fuels perfor equally in DCFC due to the difference in cheical and physical properties. The cheical properties include cheical coposition and surface functional group, while the physical properties include graphitic structure and textural property. 1.1 Cheical coposition: Two ajor analyses are often eployed for the analysis of cheical coposition, naely proxiate and ultiate analyses. Proxiate analysis gives result in the for of percentage weight of fixed carbon, volatile, oisture and ash. As for ultiate analysis, the result generated is in the for of percentage weight of eleents such as C, H, N, S, and O (Cho et al. 2012). Using four coal saples fro four different places in Australia, Li et al. (2010) perfored proxiate analysis on coal saples and tested the in a olten carbonate DCFC. The result suggests that coal saple with highest percentage weight fixed carbon produced the highest reactivity. The iportance of carbon is also reported by Ahn et al. (2013a&b), which states that the lack of percentage weight fixed carbon in bioass will leads to linear decreent of voltage at higher current density region, where voltage could not be aintained due to restricted consuption of carbon when large nuber of electrons are flowing through the syste. There is no report regarding the effect of oisture on the perforance of DCFC. The report of the effect of volatile on DCFC perforance is scarce; it is only found that high percentage weight of volatile causing solid carbonaceous fuel to exist in a liquid-like phase at elevated operating teperature. Such state of atter could aid in reducing polarization activation at the anode, which could lead to increent in DCFC perforance (Ki et al. 2012). As for ash, it is reported that it produces both detriental and beneficial effects on the perforance of DCFC, depending on the inorganic atter present (Li et al. 2010). Percentage weight ash is an indication of inorganic atters that present in solid carbonaceous fuel, where they are output as ash due to cobustion of solid carbonaceous fuel during proxiate analysis. The inorganic atters in solid carbonaceous fuel could be deterined through inductive coupled plasa optical eission spectroetry (ICPOES), where ajor and inor eleents present in the saple will be output as percentage weight of etal oxides. Using such technique, Li etl al. (2010) reported that ajor inorganic atters of four coal saples fro Australia coprised of SiO 2 and Al 2 O 3. As for inor inorganic atters, they differ with different solid carbonaceous fuels. It was also found that the inorganic atters such as Al 2 O 3 and SiO 2 have detriental effects on DCFC perforance. On contrary, inor inorganic atters such as Fe 2 O 3, Na 2 O, K 2 O, MgO and CaO were found to possess catalytic effect, where they increase current and power densities of DCFC at high anode potential region. 1.2 Surface functional group: Carbon and oxygen functional groups at the surface of solid carbonaceous fuel play roles in prooting the electrocheical reactions in DCFC, especially at low current density region as reported by Ahn et al. (2013a&b). Several literature sources have reported the beneficial effects of carbon and oxygen functional groups on DCFC electrocheical perforance (Li et al. 2010&2008, Ahn et al. 2013a). For oxygen functional group, they were reported to be able to provide reactive sites for electrocheical oxidation of solid carbonaceous fuel, therefore, iproving its discharge rate (Li etl al 2010). As for carbon functional groups, it is iportant that they are distributed widely on the solid carbonaceous fuel surface, as electrocheical reaction takes place on fuel's surface. High aount of carbon functional group will also ease the activation. However, this ay leads to preature electrocheical reactions (Ahn et al. 2013a&b). It should be noted that high percentage weight fixed carbon does not indicates high surface carbon functional group. Reuse fuel was reported to possess lower percentage weight fixed carbon but higher carbon functional group (Ahn et al. 2013a&b). Teperature-prograed desorption (TPD) could be used in extracting inforation regarding oxygen function groups, whereby solid carbonaceous fuel's surface releases CO and CO 2 at different teperatures. Evolution of CO 2 ainly originated fro carboxylic acid and lactones at low and high teperature respectively. As for CO, it originates fro phenols and carbonyls at elevated teperature. Such ethod is difficult to provide exact inforation regarding the functional group on the surface, whereby only quantitative inforation could be derived (Li et al. 2008). 1.3 Graphitic structure: Carbon has the capability of foring any allotropes due to its valency, and one of the coon fors is graphite. Graphite possesses an orderly layered and planar structure, and such crystalline structure ade graphite an electrical conductor (Li et al. 2008). Graphitic structure is a easureent of the degree of graphitization a solid carbonaceous fuel has in its structure, and coonly, such analysis could be carried out using X-ray diffraction (XRD). Analysis of diffraction peaks caused by solid carbonaceous fuel in the XRD would give an indication of the degree of graphitization. Such diffraction peaks occur at (002) and (100) planes, where they are attributed to turbostratic crystalline structure of carbon (Li et al. 2008). The ore distinct

3 114 Shu-Hong Li et al, 2015 peaks observed at these entioned planes indicate high degree of graphitization, which eans ore order structure in solid carbonaceous fuel. On top of that, the quantitative crystalline paraeters such as inter-planar distance, stacking height and average diaeter obtained are also iportant. For instance, Li et al. (2008) reported that highest degree of graphitization associates with sallest inter-planar distance and largest stacking height and average diaeter. The degree of graphitization closely associates with electrical conductivity, which contributes to DCFC perforance. Apart fro that, disordered structure of carbon also contributed to DCFC perforance where such structure consists of ore surface defects and edges sites which served as reactive sites (Li et al. 2008). Solid carbonaceous fuel in DCFC does not only act as a reactant for the electrocheical reaction, but also act as a carrier for the transfer of electrons. The transfer of electrons to external circuit would first require the to be transferred through the solid carbonaceous fuel particles that were in contact with current collectors, before being transferred to external circuit (Li et al. 2008). Li et al. (2008) reported that high conductivity of solid carbonaceous fuel increases the effective surface area of anode by extending the electrode into electrolyte. However it is interesting to note that lowest reactivity was reported for solid carbonaceous fuel with the highest conductivity. Siilar case was reported by Chen et al. (2010) who stated that high conductivity and low resistance graphite alone would not perfor well in DCFC due to lacking of lattice defects. 1.4 Textural property: Textural property was reported to be critical in deterining the reaction of solid carbonaceous fuel in electrocheistry. Pores are classified according to range of sizes they fit in, for instance, icropore, diaeter < 2n; esopore, 2n < diaeter < 50n; and acropore, diaeter > 50n. Cherepy et al. (2005) reported that surface area does affect the perforance of DCFC strongly. On the other hand, Li et al. (2009) reported that electrocheical process involving carbon was often highly dependent on carbon's surface characteristic, and fro the experient, it was observed that reactivity of solid carbonaceous fuel in DCFC increases with surface area and pore volue. It was found that these textural properties help in iproving contact between solid carbonaceous fuel and electrolyte, as well as wetting ability of solid carbonaceous fuel, particularly in the case of olten-based DCFC (Ahn et al. 2013b). There is also a report regarding effects of different pore sizes on power density produced by DCFC, whereby Li et al. (2008) states that the pores were only able to contribute to DCFC perforance if they were accessible by electrolyte. Coon exaination of textural property of solid carbonaceous fuel is carried out using gas adsorption, where specific surface area, total pore volue, average pore diaeters could be deterined. 2. Pretreatent for bioass: 2.1 Iportance of pretreatent and different pretreatent processes: As entioned in section 2, high percentage weight fixed carbon, large nubers of surface oxygen and carbon functional groups, high surface area, extensive pores, and optiu degree of graphitization are beneficial to DCFC perforance. Unlike fossil fuel such as coal, which possesses high percentage weight fixed carbon that could operate DCFC without uch odification; bioass on the other hand, is difficult to be used in DCFC at its raw state. The ain reason is such that bioass ainly coprised of lignin, cellulose and heicellulose. Furtherore, it has low energy density, low grindability and high oisture content which are unsuitable to be used in DCFC, thus, a proper pretreatent process is required (Abdullah and Wu 2009). There are various pre-treatent processes available such as theral pre-treatent, acid pretreatent and alkali pre-treatent. Theral or heat pre-treatent includes liquefaction, gasification and pyrolysis. Liquefaction produces liquid as the ain product; while gasification reaction ainly generates H 2, CO, CO 2 and H 2 O (Mohan et al. 2006). As for pyrolysis, it is defined as therocheical decoposition of organic atter in the absence of liited or total supply of oxidizing agents and such condition converts organic atter to solid, liquid and gas (Mohan et al. 2006). In ost cases, it ais to induce carbonization reaction through therolysis process. Pyrolysis process is capable of producing biochar fro bioass, which is an organic copound with high percentage weight fixed carbon, aking it an iportant pre-treatent process in converting bioass into usable solid carbonaceous fuel in DCFC. Other than that, odification in other properties such as textural property, surface functional groups, and degree of graphitization will occur as well. 2.2 Pyrolysis: Pyrolysis works under the absence of oxidizing agent at elevated teperature, and such requireent is achieved by purging oxidant gas using inert gas for an interval before heating the reactor, creating an inert gas atosphere. Following that, heating coences with specified heating rate until highest teperature known as pyrolysis teperature is achieved, and subsequently, the subject will be held at such condition for an extended interval known as residence tie (Basu 2010). Pyrolysis teperature, heating rate and residence tie are iportant in deterining the biochar properties (Czernik and Bridgwater 2004). Literature sources have classified various cobinations of these physical conditions into three types of pyrolysis,

4 115 Shu-Hong Li et al, 2015 naely, slow, fast and flash pyrolysis (Maggi and Delon 1994, Apaydin-Varol et al. 2007, Onay and Kockar 2003, Bridgwater 1999). Slow pyrolysis is characterized by slow heating rate and extensive residence tie; fast pyrolysis operates at high heating rate; finally flash pyrolysis is reported to be working at high heating rates up to 10 4 Ks -1 followed by rapid quenching (Mohan et al. 2006, Onay and Kockar 2003). With different types of pyrolysis, different products will be yield. For exaple, flash pyrolysis operates at <650 o C favours foration of liquid products; on contrary, operation at >650 o C favours foration of gaseous products. Slow pyrolysis prootes production of char (Apaydin-Varol et al. 2007, Onay and Kockar 2003, Bridgwater 1999). It is reported that pyrolysis teperature has the greatest effect on biochar produced, as fundaental physical changes such as foration and volatilization of interediate elts are all teperature dependant [60]. As for heating rate, it is regarded as having second greatest effect on biochar physical properties (Basu 2010). Apart fro that, residence tie is iportant as well. Lengthy residence tie prootes secondary cracking (Bridgwater 1999). Individual pyrolysis paraeter does not contribute directly to biochar properties; but instead, it is the cobination of these pyrolysis paraeters that shape the biochar. For exaple, long residence tie at pyrolysis teperature > 500 o C, priary vapour are cracked, yielding specific products along with organic liquids; when pyrolysis teperature < 400 o C, condensation occurs, foring low olecular weight liquids; slow heating rate accopanied by long residence tie enable volatiles to be gradually reoved and perits secondary reaction between priary char and volatiles, foring secondary char (Basu 2010, Bridgwater 1999) Conversion of bioass to biochar: Through pyrolysis pre-treatent, the bioass is converted into biochar according to Eq. 4: Cn H O p heat ( bioass) liquid C x H y O z gas C a H b O c H 2 O C( biochar) (4) Under identical pyrolysis condition, not all bioasses react equally and for biochar with identical properties. In reference to the general forula of bioass in Eq. (1), it could clearly observed that different bioasses have different cheical constituents, which ultiately defines the final biochar produced. In fact, biochar was observed to be an iprint structure of the original bioass, for exaple, the C skeleton and ineral foration retained in the biochar structure after pyrolysis. This further suggests that pyrolysis acts in odifying the original structure but not copletely changes it (Aonette and Joseph, 2009). To siplify, ajor part of bioass is ainly ade up of cellulose, heicellulose, and lignin (Mohan et al. 2006, Bridgwater 1999). Each of these contents degrade at different rates, echaniss, pathways and different teperature ranges, for instance, cellulose degrades at o C, while heicellulose and lignin degrade at teperature range of o C and o C, respectively (Aonette and Joseph, 2009). Different types of pyrolysis ai to produce different products. Different organic coponents are also favourable in producing different end-products, for instance, cellulose is ore likely to yield condensable vapour; heicellulose yields non-condensable gasses; as for lignin, it degrades slower and contributes to foration of char (Basu 2010). Different organic copounds coprise of different proportion cellulose, heicellulose and lignin. Hence, this leads to different reactivity degrees, which influence the extent of odification on physical and cheical properties of bioass. Other than organic copounds, inorganic copounds are also crucial in shaping the final biochar structure. Unlike organic copounds, they do not react cheically during pyrolysis, but through ash fusion or sintering. The aount of inorganic copounds often reains the sae after pyrolysis. Report states that high percentage weight ash causes swell and fusion effect during pyrolysis, which leads to structural loss (Aonette and Joseph, 2009). On contrary, bioass with low percentage weight ash can still exhibits inor theroplastic property (Basu 2010) Percentage weight yield and percentage weight conversion: Percentage weight yield is defined as the ratio of ass of pyrolysis product to ass of original bioass as shown in Eq. 5: Percentage weight yield biochar x100% bioass (5) Percentage weight yield is reported to decrease as pyrolysis teperature increases (Jia and Lua 2008). Such result is associated with ore volatiles being released resulting in larger ass loss (Lua et al. 2006). On top of that, it is also reported that decrease of yield is also associated with rearrangeent of carbon structure, which causes release of hetero-atos (Daud et al. 2001). Percentage weight conversion bioass biochar x100% bioass (6) Percentage weight conversion indicates the theral degradation that occurs in pyrolysis as given in Eq. 6 (Jia and Lua 2008). It is reported that percentage weight conversion increases abruptly in teperature range of 400 o C 650 o C. Follow by 650 o C 850 o C, the percentage weight conversion only increases slightly (Jia and Lua 2008). Jia and Lua (2008) explained that at lower teperature range, volatiles released are ainly coprise of low olecular weight volatiles; as for high teperature range, high olecular weight volatiles will be

5 116 Shu-Hong Li et al, 2015 released. Although high olecular weight volatiles are released at high teperature range, only sall decreent of weight was reported. 3. Effect of pyrolysis on biochar properties: As discussed in previous section, pyrolysis teperature, heating rate and residence tie are crucial factors in shaping biochar s structure. This section discussed the effects of pyrolysis paraeters on the various properties of biochar, such as cheical copositions, textural property, surface functional groups and graphitic structure. These properties directly affect DCFC perforance, and as such, the linkage between DCFC perforance and pyrolysis paraeters could be established. 3.1 Cheical coposition: Biochar cheical copositions such as percentage weights oisture, volatiles, ash, and fixed carbon are greatly dependent on the pyrolysis teperature. Increase in pyrolysis teperature increases the percentage weight fixed carbon as reported by Lua et al. (2006). This increent corresponds to decrease in percentage weight volatiles, where ore volatiles are released at higher pyrolysis teperature (Basu 2010). As for percentage weight oisture, there is no specific trend observed. Slight difference in percentage weight oisture after pyrolysis could be due to the differences in the original percentage weight oistures of various bioasses (Lua et al. 2006). As for percentage weight ash, it is fairly stable as it originates fro bioass initially as reported by Lua et al. (2006). Apart fro pyrolysis teperature, residence tie and heating rate play iportant roles in deterining biochar cheical properties as well. Lengthy residence tie enables ore volatiles to be released fro bioass structure, decreasing percentage weight volatiles. Moreover, lengthy residence tie also provides sufficient tie for secondary cracking, contributing to percentage weight fixed carbon (Mohan et al.2006). High heating rate contributes to extensive reaction rate, which also leads to ore volatiles being release, causes low percentage weight volatiles. On contrary, low heating rate such as the case of slow pyrolysis enables reaction to achieve equilibriu (Onay and Kockar 2003). 3.2 Graphitic structure: Surface functional groups on biochar are teperature dependent as reported by Xiao et al. (2010), where increase in pyrolysis teperature will lead to loss of functional groups, particularly oxygen functional groups. Such condition is associated with breakdown of functional groups, and soe of the could recobine, foring volatiles and escape to the abient environent. Siilar report by Jia and Lua (2008) was found after analysing the IR transittance of functional groups at 900 o C, which found that IR transittance peak shrank, iplying possible theral cracking of organics foring light gas species, leading to loss of functional groups. 3.3 Surface functional group: As entioned in previous section, increase in pyrolysis teperature causes ore carbon layer rearrangeent, leading to orderly arranged lattice. Such observation could be associated with increasing degree of graphitization. The increase in degree of graphitization also indicates the loss of surface defects, which act as active sites during electrocheical oxidation. 3.4 Textural property: Textural properties such as porosity and surface area are interrelated properties. Lua et al. (2006) shows that in the range of o C, increase in pyrolysis teperature leads to release of low olecular weight volatiles fro the bioass atrix structure, rearrangeent of carbon layers occur, which leads to creation of pores. Eergence of ore pores indicates increase in nuber of pores, which also associates with increase in pore volue (Daud et al. 2001). Further increase in pyrolysis teperature to the range of 700 o C 900 o C, produces detriental effects on textural properties, where volatiles of high olecular weight sinter and soften, causing destruction of wall between pores (Aonette et al. 2009). This leads to depolyerisation of elt and total volue shrinking (Lua et al. 2006). Destruction of wall between the pores also leads to pore-fusion, foring larger pores such as esopores (Daud et al. 2001). Heating rate also plays an iportant role in deterining biochar surface area. According to Lua et al. (2006), increase in heating rate favours foration of icropores, hence surface area. However, such condition persists until heating rate is greater than 10 o C/in. High heating rates causes cell structure elts down and destroyed, leading to plastic transforations. Additionally, residence tie also affects surface area, where, saple is held longer at pyrolysis teperature, degree of pore foration is ore extensive due to larger aount of volatiles being released fro the bioass atrix structure (Lua et al. 2006). However, increasing residence tie at teperature >600 o C leads to decreasing surface area due to foration of interediate elts through softening and sintering by low olecular weight volatiles. These elts are capable of sealing off the pores, decreases pores nuber (Lua et al. 2006). Flow rate of purge gas affects textural property of biochar as well, whereby low flow rate produces less effective purging effect, leading to a possibility that volatiles could be entrained in nitrogen gas strea. These deposits could re-deposited on the biochar surface, such condition will lead to blockage of pore structure, leading to restriction of further foration of pores, which in turn, reducing the

6 117 Shu-Hong Li et al, 2015 surface area. On contrary, high flow rate would lead to cooling of surface of the biochar, reducing reaction rate of theral degradation, causes less volatiles being reoved, disrupting pore foration (Lua et al. 2006). 4. Conclusion: DCFC offers any proising advantages in ters of electricity generation and environental aspects, as copared to the conventional cobustion syste. Critical properties of fuels including cheical coposition, surface functional group, degree of graphitization and textural property would strongly affect the DCFC electrocheical perforance. While eploying bioass as the carbon fuel for DCFC, these cheical and physical properties should be carefully-controlled by finetuning the pyrolysis conditions including the heating rate, residence tie and pyrolysis teperature. ACKNOWLEDGEMENT This work was funded by the Ministry of Science, Technology and Innovation (MOSTI) Malaysia under the escience Fund SF0186 and Monash University under Major Grant EM1-11. REFERENCES Ahn, S.Y., S.Y. Eo, Y.H. Rhie, Y.M. Sung, C.E. Moon, G.M. Choi and D.J. Ki, 2013a. Utilization of wood bioass char in a direct carbon fuel cell (DCFC) syste. Applied Energy, 105: Ahn, S.Y., S.Y. Eo, Y.H. Rhie, Y.M. Sung, C.E. Moon, G.M. Choi and D.J. Ki, 2013b. Application of refuse fuels in a direct carbon fuel cell syste. Energy, 51: Aonette, J.E. and S. Joseph, Characteristics of biochar: Microcheical properties. Biochar for Environental Manageent: Science and Technology, Aonette, J.E., S. Joseph, J. Lehann and S. Joseph, Characteristics of biochar: Microcheical properties. Biochar for Environental Manageent: Science and Technology, Apaydin-Varol, E., E. Pütün and A.E. Pütün, Slow pyrolysis of pistachio shell. Fuel, 86(12), Basu, P., Bioass gasification and pyrolysis: practical design and theory: Acadeic press. Bridgwater, A., D. Meier and D. Radlein, An overview of fast pyrolysis of bioass. Organic Geocheistry, 30(12): Chen, M., C. Wang, X. Niu, S. Zhao, J. Tang and B. Zhu, Carbon anode in direct carbon fuel cell. International Journal of Hydrogen Energy, 35(7): Cherepy, N.J., R. Krueger, K.J. Fiet, A.F. Jankowski and J.F. Cooper, Direct conversion of carbon fuels in a olten carbonate fuel cell. Journal of the Electrocheical Society, 152(1): A80- A87. Chien A.C., G. Corre, R. Antunes and J.T.S. Irvine, Scaling up of the hybrid direct carbon fuel cell technology. International J Hydrogen Energy, 38: Cho, W.T., S. Ki, H.K. Choi, Y.J. Rhi, J.H. Li, S.H. Lee and J. Yoo, Characterization of chars ade of solvent extracted coals. Korean Journal of Cheical Engineering, 29(2): Czernik, S. and A. Bridgwater, Overview of applications of bioass fast pyrolysis oil. Energy & Fuels, 18(2): Daud, W.M.A.W., W.S.W. Ali and M.Z. Sulaian, Effect of carbonization teperature on the yield and porosity of char produced fro pal shell. Journal of Cheical Technology and Biotechnology, 76(12): Giddey S., S.P.S. Badwal, A. Kulkarni and C. Munnings, A coprehensive review of direct carbon fuel cell technology. Progress in Energy and Cobustion Science, 38: Jia, Q. and A.C. Lua, Effects of pyrolysis conditions on the physical characteristics of oilpal-shell activated carbons used in aqueous phase phenol adsorption. Journal of Analytical and Applied Pyrolysis, 83(2), Ki, J.P., H.K. Choi, Y.J. Chang and C.H. Jeon, Feasibility of using ash-free coal in a solidoxide-electrolyte direct carbon fuel cell. International Journal of Hydrogen Energy. Li, X., Z.H. Zhu, R.D. Marco, A. Dicks, J. Bradley, S. Liu and G.Q. Lu, Factors that deterine the perforance of carbon fuels in the direct carbon fuel cell. Industrial & engineering cheistry research, 47(23), Li, X., Z. Zhu, J. Chen, R. De Marco, A. Dicks, J. Bradley and G. Lu, Surface odification of carbon fuels for direct carbon fuel cells. Journal of Power Sources, 186(1), 1-9. Li, X., Z. Zhu, R. De Marco, J. Bradley and A. Dicks, Evaluation of raw coals as fuels for direct carbon fuel cells. Journal of Power Sources, 195(13): Lua, A.C., F.Y. Lau and J. Guo, Influence of pyrolysis conditions on pore developent of oilpal-shell activated carbons. Journal of analytical and applied pyrolysis, 76(1): Maggi, R. and B. Delon, Coparison between slow and flash pyrolysis oils fro bioass. Fuel, 73(5): Mohan, D., C.U. Pittan and P.H. Steele, Pyrolysis of wood/bioass for bio-oil: a critical review. Energy & Fuels, 20(3): Muthuvel M., X. Jin and G.G. Botte, Fuel cells exploratory fuel cells direct carbon fuel cells.

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