1. By Dr. Estee Yong Siek Ting
Pyrolysis of Palm Waste for Power Generation via Direct Carbon Fuel Cell
By Dr. Estee Yong Siek Ting

2. Content of Presentation
1. Introduction
2. Objective
3. Experimental Work
4. Results & Discussions
5. Conclusion
6. Acknowledgement

3. 1. Introduction What is a DCFC ? Cathode half-cell reaction:
𝑂 2 𝐴𝑖𝑟 + 4𝑒 − → 2𝑂 2−
Anode half-cell reaction:
𝐶+2 𝑂 2− → 𝐶𝑂 𝑒 −
Overall oxidation reaction:
𝐶+ 𝑂 2 → 𝐶𝑂 2
DCFC, like every other types of fuel cell, operates through REDOX reaction to produce electrical output.
Unlike other fuel cell, who mainly rely on fuel such as methane, hydrogen etc., DCFC operates using solid carbon fuel.
The solid carbon fuels are loaded into anode compartment, and the cathode compartment is exposed to air.
The reaction proceeds, when oxygen molecules from the air being reduced to oxide ions, followed by transferring across the electrolyte layer. These oxide ions eventually oxidize carbon particles, forming CO2 in the process while releasing electrons. These electrons are then conducted externally for electrical output. In short, this is how a DCFC operates.

4. 1. Introduction Low emission in CO2 cycle No reforming
Why use DCFC ?
Low emission in CO2 cycle
No reforming
High theoretical efficiency
Simple system
Wide range of fuel choices
Carbon, high energy density
High efficiency- direct conversion of chemical energy into electricity
High efficiency= due to positive entropy of carbon oxidation, which yield high Gibbs energy compared to enthalpy change
DCFC is a fairly new fuel cell technology compared to other common fuel cell such as hydrogen fuel cell.
DCFC offers range of advantages, for instance:
It is a very simple system without any mechanical parts, hence making it high in mobility and could be build on site.
High fuel utilization and theoretical efficiencies.
Low in emission, produces less than half of the emission produced by conventional coal firing plant.
Emission mainly consists of CO and CO2, which could be easily captured without major separation process, for the purpose of further processing.
Moreover, carbon itself is an energy dense fuel compared to fuel such as hydrogen, methanol, methane etc.
Using carbon as a fuel indicates, that coal, biomass, or any carbon source have the potential of being used as a fuel

5. 1. Introduction High DCFC Performance High percentage carbon
How do fuel’s characteristics affect DCFC performance ?
Carbon is important to ensure constant supply of carbon particles for oxidation reaction.
High percentage carbon
Acting as active sites to facilitate oxidation of carbon oxidation.
High oxygen functional groups
Enhance interaction between carbon particles and anode.
High surface area
High DCFC Performance
Before going further, it is important to understand the relationship between the fuel characteristics and the performance of DCFC.
To produce high performance in DCFC, it is important that the fuel posses high carbon content, high amount of surface oxygen functional group and surface area.
High carbon percentage ensure continuously generation of electricity even when large amount of electrons flowing.
As for O functional groups, they aid in oxidation of carbon by acting as active sites.
Lastly, high surface area ensure constant and frequent contact between anode and carbon particles.
Ahn et al. (2013)
Li et al. (2010)
Li et al. (2009)

6. 1. Introduction Biomass in DCFC, a greener technology.
Successful employed in DCFC
By utilizing biomass in DCFC, it could helps in reducing waste in the environment, hence a green technology.
Till date, coconut carbon and wood biomass were reported in DCFC. This also leads to a thinking that other biomass also share a similar potential to be used as a fuel in DCFC.
Malaysia, as a second largest palm oil exporter in the world, produces considerable amount of palm waste.
These waste could be used in DCFC, to reduce the effect of waste posted on the environment, as well as cost saving in waste disposal.
Second largest palm oil exporter
Using palm waste in DCFC benefits economy, social, and environment.

7. 1. Introduction Lignin Cellulose Hemicellulose Biomass However…
Pyrolysis
Lignin
Cellulose
Hemicellulose
Char
Biomass
Condensable vapour
However, biomass could not be used readily in DCFC.
Biomass mainly consists of lignin, cellulose and hemicellulose, hence pyrolysis reaction is needed as a pre-treatment to convert useful biomass into char form.
During pyrolysis, different constituent of biomass convert differently, for instance, lignin mainly form char, cellulose and hemicellulose form condensable and non-condensable vapor respectively.
Non- Condensable vapour
Basu (2010)

8. 2. Objective
To study the suitability of Palm shell as the possible carbon fuel source in Direct Carbon Fuel Cell
Carry out PRELIMINARY study
Study was performed by comparing to CB, a common Carbon fuel source in DCFC
Vulcan XC-72

9. 3. Experimental Work
Methodology
Phase 1: Preparation of palm shell for pretreatment.
Phase 2: Preparation of palm shell biochar by pyrolysis.
Phase 3: Characterizations of biochar samples.
Phase 4: Activity testing in DCFC

10. Fuel Cell reactor

11. Button Fuel Cell

12. 3. Experimental Work Phase 1 Phase 2
Output gas
Gasket
Solid carbonaceous fuel
Sample holder
Furnace
Purge gas
3. Experimental Work
Phase 1
Dried for 48hrs at 100oC to remove moisture.
Grinded and sieved to size range of 0.5-1mm.
Phase 2
Pyrolysis are carried out at
Temperature of 400, 600, 800 and 1000oC.
Heating rate of 10oC/min.
Residence time of 1hr.
N2 flow of 2L/min.
Figure 1

13. 3. Experimental Work Phase 3 Phase 4
Proximate and Ultimate analyses, XRD, CO2 adsorption
Phase 4
Selection of potential fuel sample is based on similarity of chemical composition with carbon black.
Selected samples are characterized in terms of surface functional group (FTIR) and surface area (N2 adsorption).
10 oC /min
N2 – 110oC for 20 min
-950 for 30min
-Air for 20 min

14. 4. Results & Discussions Percentage Yield
Upon increasing pyrolysis temperature from 400 to 600oC, percentage weight yield drops significantly.
Percentage weight yield remains almost constant despite increasing pyrolysis temperature beyond 600oC.
S400 still contains contains large amount of low molecular weight volatiles.
, release of volatiles is completed.
the volatilization of high molecular weight volatiles occur at temperature range of 650 – 850oC, meaning not much high molecular weight volatiles?
𝑃𝑒𝑟𝑐𝑒𝑛𝑡𝑎𝑔𝑒n weight 𝑦𝑖𝑒𝑙𝑑= 𝑚 𝑝𝑟𝑜𝑑𝑢𝑐𝑡 𝑚 𝑏𝑖𝑜𝑚𝑎𝑠𝑠 𝑥 100%

15. 4. Results & Discussions Proximate analysis
Upon increasing pyrolysis temperature from 400 to 600oC, percentage weight of Carbon increases while Volatiles reduces drastically.
Ash and moisture contents stay almost constant throughout entire range of pyrolysis temperature.
NO NEED: As palm shell was heated at different temperatures during proximate analysis, different products were released in gaseous form, and these gases lead to weight loss. Hence by monitoring the weight lost at different temperature ranges, the chemical compositions of palm shell biochar was simplified into moisture, volatile matters, fixed carbon and ash by percentage weights.
Carbon if primary reactant in the redox reaction. Minimum amount is required.
May imply that S400 is not good enough for DCFC as Carbon is needed as the fuel.
Explain volatiles trend only in General, not specific at 1000 oC as percentage increases about 3 % only.
Slight increase in Volatiles at 1000oC,v MAYBE due to EXPERIMENTAL ERROR
NO NEED: As for volatile component, the decrement is non-linear too. At below 600oC, large amount of low molecular weight volatiles are being released; after exceeding 600oC, only small amount of high molecular weight volatiles are released, resulting in lower drop in percentage weight. Apart from being released to the atmosphere, part of these volatiles could participate in secondary cracking, contributing to C% (HOW IF ALREADY RELEASED INTO ATMOSPHERE???).

16. 4. Results & Discussions Ultimate Analysis
%C trend is consistent with proximate analysis
Lower %O for high pyrolysis temperature
Fuel %C %H %N %S %O
O/C
S400
76.87
1.98
1.40
0.03
19.72
0.26
S600
80.26
1.62
1.28
0.28
16.56
0.21
S800
81.32
1.87
1.89
0.15
14.77
0.18
S1000
80.89
2.89
0.01
0.29
15.92
0.20
The reported %C from ultimate analysis was consistent with the trend obtained for percentage weight fixed carbon in proximate analysis. This in turn justifies The thermal reaction involving chemical structural changes is almost completes upon pyrolysis at 600 oC.
AMOUNT OF CARBON IS CRUCIAL AS IT IS THE PRIMARY REACTANT
Maybe sample of S800 and S1000 was swapped? Not really, as those difference are in term of 1% only! Not big enough to be significant.
Pyrolysis at 600 and higher, lead to more breakdown of oxygen functional groups. These oxygen functional groups recombine and loss as volatiles.
Presence of H,N,S are insignificant.

17. 4. Results & Discussions CO2 adsorption analysis
Micropore surface area and volume increase from oC
Micropore surface area and volume reduce from oC, with increasing pore size.
Fuel
Smicro (m2/g)
VMicro (cm3/g)
Average pore size (Å)
S400
394.16
0.12
11.85
S600
582.68
0.16
11.06
S800
734.34
0.20
S1000
642.92
0.19
11.32
Clearance of blocked micropores through vaporization of volatiles
This happens as the wall structures between micropores could not withstand the high pyrolysis temperature, thus, they are sintered and melted, which leads to destruction of the walls [48].
The destruction of walls between micropores were further validated by comparing the pore sizes of S800 and S1000, whereby the pore size was slightly increased, due to merging of micropores after wall’s destruction.
HIGH SURFACE AREA IS NOT DESIRABLE, as it LIMIT ELECTRON TRANSFER ACROSS FUEL
Indicate almost all increases with temp, while D similar
Interesting to point out that S 900 iseven greater than CB
Hopefully, this is able to help in compensating slightly lower in percentage carbon of palm shell biochar.
The trend obtained in surface area is different compared to literature source suggesting that above 700oC, destruction of wall occurs which depletes surface area. Such condition could be explained by different in other pyrolysis parameters as well as constituent biomass.
Apart from that, the surface areas of biochar sample is seen to be higher compared carbon black, this in turn, is believed to be able to help in compensating slightly lower in percentage carbon of palm shell biochar.
Type I isotherm suggesting adsorption occurs on microporous solids, this result is in conjunction with the micropore area of biochar, which contributes most of the total surface area. However, according to the figure, with the increase in relative pressure, a slight decrease in quantity of N2 adsorbed was observed. This situation could be due to insufficient energy possessed by N2 for adsorption. Moreover, micropores are not readily accessible by N2.
As for type III isotherm, which suggests the structure is non-porous. Furthermore, the average pore diameter of carbon black of if found to be 7.90nm and this further confirmed the lack of micropores in carbon black (where micropores characterized by size less than 2nm).

18. 4. Results & Discussions XRD analysis
Presence of graphitic structure is associated with a distinct peak at ~ 25o
S400 and S600 are amorphous
CB show the ideal graphite.
It is widely known that palm shell is amorphous in nature where the atoms arrange in random order.
Through pyrolysis, physicochemical properties of palm shell are modified, forming palm shell biochar.
However, palm shell biochar may inherits complex structural property from palm shell to some extent.
Such statement was clearly depicted in XRD curves of S400 and S600.
Further increase in pyrolysis temperature, increasing the degree of graphitivity in palm shell biochar.
BASICALLY, MORE SURFACE DEFECT AT LOW TEMP.
The peaks of palm shell biochars in the XRD curves were broader compared to ideal graphite peaks. This is associated with the existence of gamma (γ) band, where a large and broad diffraction peak was made from combination of another smaller peak.
Gamma (γ) band indicates the presence of saturated carbon structure such as aliphatic side chain attached on the edge of parent carbon structure.
For XRD curve of S800, there were others smaller constituent’s peaks apart from γ band.
These small peaks are associated with small crystallite dimension perpendicular to aromatic layers of parent carbon structure.

19. 4. Results & Discussions DCFC Reactivity analysis
Steep linear decline of V-I curve due to fuel starvation
Consistent trends in OCV and Peak Power density for all samples:
S600S400S800S1000
-Fuel starvation at anode leading to high cell impedence/resistance
-Peak Power density then decreases: any carbon that is in contact with anode surface would rapidly be consumed, leaving only ashes only in contact with anode. This rapidly degrade the fuel cell performance as seen by the drop in power density, as ashes would form an insulating layer between fuel cell and current collector, blocking the charged transfer.
-The consistent trend is quite common. Usually low OCV is related to low activity (i.e. low power density) whereby there is limited gases species to facilitate surface exchange between fuel and the electrode. The gases include CO2 (primary product from reaction between carbon fuel and oxygen), CO (formed due to reaction between carbon fuel and decomposed oxygen-containing ash eg Fe2O3) and also CO from reaction between carbon fuel and CO2.

20. 4. Results & Discussions DCFC Reactivity analysis
Optimum pyrolysis temperature is 600oC 
Below this temp, carbon content is too low
Above this temp, microporous surface area too big
Above this temp, surface defect is limiting
Optimum pyrolysis temperature is 600oC 
Below this temp, carbon content is too low
carbon important as primary fuel reactant.
Above this temp, microporous surface area too big
limiting the electron transfer across the fuel
Above this temp, surface defect is limiting
restricting active site for the electrochemical reaction involving transfer of O. 

21. 5. Conclusion Optimum pyrolysis temperature is 600oC
Determining factor:
Minimum carbon content
Optimum microporous surface area
Adequate surface defect
-possible to operate solid state direct carbon fuel cell using palm shell.
-still not as good if compared to Carbon black. Generally from ??? See weng report.
-few ways to improve: higher temp, 850, power density can be doubled, however need to strike a balance from providing the heat in the beginning and power output.
-Significant improvement in fuel cell design may lead to a practical device.
-continuous feeder for palm shell fuel, hence it is anticipated that the continuous gas species produced can enhance the surface exchange between fuel and electrode, ultimately increasing the power density.
-Another way is to make it a hybrid fuel cell, combining palm with molten carbonate, facilitating charge transfer in liquid state.
Currently, we are testing these sample in DCF , for 30 mg , recorded about 5 mA of current.
We would also like to study the characterizations more in depth, including XRD- tells the degree of graphitization.
From Literatures, a highly disordered structure aids in electron transfer hence the Carbon oxidation process.

22. 6. Acknowledgement I would like to express my greatest gratitude to:
Ministry of Science, Technology and Innovation (MOSTI) for eScience Fund SF0186.
Mr. Lim Shu Hong PhD student for performing experiment and analyzing data.