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Woody Biomass Characterization for 100 Megawatt-hours (MW) Power Generation
Available online at www.sciencedirect.com
ScienceDirect Energy Procedia 105 (2017) 413 – 418
The 8th International Conference on Applied Energy – ICAE2016
Woody biomass characterization for 100 megawatt-hours (MW) power generation Norfadhilah Hamzaha,*, Mohammad Zandia, Koji Tokimatsub, Kunio Yoshikawab a Department of Chemical and Biological Engineering, University of Sheffield, Sheffield S10 2TN, United Kingdom Depatment of Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, Yokohama 226-8502, Japan
b
Abstract
This paper characterized the wood pellet and torrefied wood pellet fuel as compared to coal for 100 MW co-firing power generation plant. There were five experiments to characterise the chemical and physical properties of coal, wood pellet and torrefied wood pellet namely moisture analysis, Thermo gravimetric Analyser (TGA), Bomb Calorimeter, Organic Elemental Analyser and Scanning Electron Microscope (SEM). The moisture analysis result from moisture analyser and TGA shows that the moisture content of torrefied wood pellet is lower than wood pellet at 6.760% and 3.629%. Moreover, the volatile matter, hydrogen and nitrogen content of torrefied wood pellet is lower than wood pellet at 65.20%, 5.993% and 0.4078% correspondingly. The calorific value, fixed carbon content, ash and sulphur also increase in torrefied wood pellet at 20.68 MJ/kg, 28.85%, 2.321% and 0.1656% respectively. In general, torrefaction improve the fuel properties of wood pellet similar to coal. The 100 MW direct co-firing power plant provides less capital investment, operation and maintenance cost for low rate co-firing ratio. However, there is economic challenges for high rate co-firing substation of torrefied wood pellets.
© 2017 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license © 2016 The Authors. Published by Elsevier Ltd. (http://creativecommons.org/licenses/by-nc-nd/4.0/). responsibility of ICAE Selection and/or peer-reviewofunder Peer-review under responsibility the scientific committee of the 8th International Conference on Applied Energy.
Keywords: wood pellet; torrefied wood pellet; co-firing, coal; power generation; woody biomass
* Corresponding author. Tel.: +60139836433; fax: +603-88905679. E-mail address: [email protected].
1876-6102 © 2017 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the scientific committee of the 8th International Conference on Applied Energy. doi:10.1016/j.egypro.2017.03.334
414
Norfadhilah Hamzah et al. / Energy Procedia 105 (2017) 413 – 418
1. Introduction Biomass or bio renewable sources are defined as any biological origin that available on a renewable basis that are categorized into waste such as agriculture and forestry waste, by-products from agriculture process and animal manure and energy crops [1][2]. On the other hand, the municipal solid waste is mix of discarded materials thrown into garbage including plastic, glass and metals hence do not qualify as biomass [1]. The similarity of biomass fuel characteristics with fossil fuels make it unique to be used for power, heat and fuel generation [3]. Biomass particularly torrefied wood pellet can be used to meet the power load requirements as similar to coal due to improved fuel characteristics similar to coal. The main advantage of biomass as compared to coal is the availability to produce less CO 2, reduce emission of SOX and NOX. However, the technical and economic challenges of biomass are low bulk and energy density and low calorific value that cause the high feedstock cost [4]. Besides, the high moisture content resulted in decrease plant efficiency, storage and handling problem. In long term, good forests management will significantly improve the supply of torrefied wood pellet. Hence, the biomass renewable energy will provide energy security, alternatives fuel sources, environmental friendly and improved social living by creation of job. In this study, the wood pellet and torrefied wood pellet were characterized for 100 Megawatt-hours (MW) direct co-firing power generation plant with coal that contribute to high efficiency, economically and environmentally development in the region and thereby provides a better alternative of fuel source than coal for electricity generation.
2. Experimental methods
The coal sample was collected in Kellingley colliery located in Knottingley in West Yorkshire. Kellingley is deep mined from the oldest geological formations, and therefore has spent the longest time underground and been subjected to the most pressure and heat, making it the most compressed and hardest coal [5]. The wood pellets source from virgin timber in United Kingdom (UK) forest and supplied by Logs2U, a part of CPL Distribution Ltd with the ash content was less than less than 0.7%, moisture content of less than 10%, energy content calorific value of 4800 kWh/1000 kg and mechanical durability of more than 97.5%. The torrefied wood pellets are supplied by New Biomass Holding LLC located in United States and manufactured from torrefied wood that has been ground and extruded using a nonhazardous organic binder with energy content between 20 to 23 GJ/MT [6]. Standard practice for preparation of coal and biomass samples for compositional analysis, the particle size of less than or equal to 250 µm must be use [7][8]. The raw materials were finely ground using Planetary Ball Mill PM100 using high centrifugal forces and very high pulverization energy to give short grinding times. The fine particles were separated using Analytical Sieve Shaker AS200 Basic to get fine particle size of less than or equal to 250 µm [9]. The physical and chemical properties of coals and biomass varies; hence it is important to be able to determine the chemical composition as this often affect the combustion characteristics. The proximate, elemental, calorific values, scanning electron microscope fiber analyses were done to compare fuel properties on dry basis of wood pellet, torrefied wood pellet and coal. All of the analysis were done in
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Norfadhilah Hamzah et al. / Energy Procedia 105 (2017) 413 – 418
accordance with the procedure of American Society for Testing and Materials Standard Test Method for Chemical Analysis of Wood Charcoal [10] and Standard Test Methods for Analysis of Wood Fuels [11]. 3. Results and discussion 3.1. Calorific value, proximate and ultimate analysis The chemical and physical characteristics of biomass is significant to determine the combustion characteristics in power plant. The calorific value, proximate and ultimate analysis of coal, wood pellet and torrefied wood pellet are provided in Table 1. From the result, there are difference in value of moisture content analysed using moisture analyzer and TGA. The standard deviation errors are smaller in moisture analyzer hence, the result is more reliable and accurate. This is due to the determination of moisture content taking into consideration of atmospheric pressure and temperature as compared to loss of moisture weight from TGA. In comparison with wood pellet, it can be seen that the moisture content and volatile matter of torrefied wood decreased due to devolatilization of wood during torrefaction. In addition, torrefaction resulted in higher carbon content, calorific value, ash content and sulphur. Additionally, the hydrogen and nitrogen content of torrefied wood decreased resulting in decreased H/C ratio. Nevertheless, the woody biomass has greater volatile compound than sub-bituminous coal. The fuel ratio or ratio of fixed carbon content to volatile matter is 1/10 of coal. Nonetheless, the moisture content and ash content for Kellingley coal was 1.233% and 2.593% correspondingly. The volatile matter, fixed carbon content, calorific values was 33.55%, 62.62% and 32.00 MJ/kg respectively. Hence, from [12] to classify coals from the calorific value, in increasing coalition order Killingley coal was classified Bituminous High Volatile B. A high rank coal composed mainly of fixed carbon with little volatile content and ash, no or less moisture and high calorific value. Therefore, the highest coal rank is more carbon neutral, high energy density, more brittle, hydrophobic in nature, low sulphur and ash than wood pellet. Table 1: Summary of calorific value, proximate and ultimate analysis of coal, wood pellet and torrefied wood pellet Samples
Moisture Content (wt. %)
CV (MJ/kg)
Coal
2.388
32.00
Wood Pellet
7.060
18.78
Torrefied Wood Pellet
6.760
20.68
Proximate Analysis (wt. %) Moisture
Ultimate Analysis (wt. %)
VM
FC
Ash
C
H
N
S
1.233
33.55
62.62
4.634
74.30
20.80
2.593
76.33
4.801
1.446
1.825
0.2611
49.06
6.311
2.079
0.0000
3.629
65.20
28.85
2.321
59.45
5.993
0.4078
0.1656
3.2. Microstructure Woody biomass is composed of cellulose, hemicellulose and lignin. Drying wood for palletization at temperature below 250°C softens lignin, devolatilised and carbonized hemicellulose. In contrast, during torrefaction drying at temperature above 250°C decomposed hemicellulose into volatiles and char. From the cross section of SEM photo of coal, the morphology of wood pellet and torrefied wood pellets as in
416
Norfadhilah Hamzah et al. / Energy Procedia 105 (2017) 413 – 418
Figure 1 , it can be seen clearly the micro fibrils structure of wood pellet that indicate hydrophilic in structure which easily susceptible to biological degradation. Torrefied wood pellet and coal is more brittle in structure and higher grind ability than fibrous wood. Hence more hydrophobic and stable in storage while wood pellets will deteriorate to gets mouldy.
(a)
(b)
(c)
Figure 1: SEM photo for (a) coal (b) wood pellet (c) torrefied wood pellet
3.3. Plant Design Outline for Wood Co-firing with Coal
Figure 2: Direct Co-Firing Biomass-Coal Power Plant Outline
The direct biomass co-firing with coal will improve the efficiency of overall plant performance. The energy efficiency of biomass co-firing will be increase with the implementation of combined heat and power (CHP). Direct co-firing in existing coal power plant requires less capital investment than dedicated biomass power plant. 3.4. Economic From the design outline, the direct co-firing plant provides the cheapest and simplest options of low investment costs because it utilizes the pre-existing boiler and other equipment in coal fired plant. Economies of scale for biomass co-firing plants related with investment, operation, maintenance and fuel
Norfadhilah Hamzah et al. / Energy Procedia 105 (2017) 413 – 418
cost. The investment cost is depending on the plant capacity, service, type of biomass fuel, and existing boiler quality. The estimated cost of retrofitting torrefied biomass in coal power plant is around £200/kW based on 2012 market condition [13]. In this project, the torrefied wood pellet will be co-fired with coal at coexisting power generation plant with output capacity of 100 MW. Nonetheless, torrefaction plants would significantly incurred high capital costs and requires large feedstock availability to compensate for the investment but are expected to have lower operation costs than palletization plants. Co-firing of torrefied wood pellet with coal will increase the fuel handling costs but it will reduce the flue gas treatment and ash disposal cost as the sulphur, nitrogen and ash content are small as compared to conventional coal treatment plant. Therefore, the operation and maintenance cost almost similar to conventional coal fired plant within the range of £3.0/MWh to £6.03/MWh [13]. Moreover, the normal average O&M costs is approximately 2.5% to 3.5% of capital costs and the cost increase with the increase of quality torrefied wood pellet used and higher substitution ratio with coal. Torrefied wood pellet has low ash content than coal with properties almost similar to coal that could significantly contribute to fouling and corrosion problem boilers. The torrefied wood pellet fuel feedstock depends on the biomass origin and cost of transportation, preparation and handling. As torrefied wood pellets are imported from United States, the transportation costs depend on the energy density, calorific value of the fuel. Hence, torrified wood pellet increase the calorific value per volume of biomass fuel as compared to wood pellet. Besides, the torrefied wood pellet produce a more uniform size, hydrophobic and brittle that make the transportation, storage and handling easier. In addition, the torrefied wood pellet can be shipped in large amount as compared to wood pellet due to higher energy density and hydrophobicity, hence reduce the logistic cost. 3.5. Environmental Impact Direct co-firing torrefied wood pellet with coal offers the cheapest option in reducing GHG emission. Woody biomass is a carbon neutral fuel as the CO 2 releases to the atmosphere during combustion will be used during photosynthesis. Therefore, substitution of coal with biomass release less net GHG emission than conventional coal power plant. Replacement of 1% to 10% biomass per year with coal could significantly reduce 45 to 450 million tons of CO2 emissions in 2035 [13]. 4. Conclusion Co-firing offers potential for emerging developing countries to increase the economic value as it using the waste from forestry and agriculture for fuel. Besides, palletization and torrefaction improves the biomass suitability in co-firing and provides the cost effective option co-firing with coal in pre-existing coal fired power plants without significant investment cost. However, there is a need to study the boiler efficiency when co-firing of higher ratio of biomass. Torrefaction process increases the energy density of biomass close to coal in addition to improve the storability and grind ability of biomass. The significant improve in feedstock properties will improve plant reliability, combustion efficiency, reduce collection and transportation cost, minimize fouling and slagging. Therefore, high rate co-firing of torrefied wood pellets with can be achieved. .
417
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Norfadhilah Hamzah et al. / Energy Procedia 105 (2017) 413 – 418
References [1] Brown, R. C., 2007. Biomass Conversion Processes for Energy Recovery: Power Generation. In: F. Kreith & D. Y. Goswami, eds. Handbook of Energy Conservation and Renewable Energy. Boca Raton: CRC Press Taylor & Francis Group, p. 25.37-25.50 [2] Abbasi, T. & Abbasi, S., 2010. Biomass energy and the environmental impacts associated with its production and utilization. Renewables and Sustainable Energy Reviews, p. 919-937 [3] Sharifi, V. N., 2014. Lecture 3 Handout: Energy from Biomass and Waste, Sheffield: The University of Sheffield. [4] International Energy Agency, 2012. Technology Road Map: Bioenergy for Heat and Power. [Online] Available at: http://www.iea.org/publications/freepublications/publication/bioenergy.pdf [Accessed 14 February 2014]. [5] Zandi, M., 2013. Applied Energy Engineering: Proximate Analysis of Coal, Sheffield: University of Sheffield. [6] New Biomass, 2014. New Biomass. [Online] Available at: http://newbiomass.com/ [Accessed 19 August 2014]. [7] ASTM D5865, 2013. Standard Test Method for Gross Calorific Value of Coal and Coke. [Online] Available at: www.astm.org [Accessed 21 August 2014]. [8] ASTM E1757, 2007. Standard Practice for Preparation of Biomass for Compositional Analysis. [Online] Available at: www.astm.org [Accessed 20 August 2014] [9] Retsch, 2014. Vibratory Sieve Shaker AS 200 basic. [Online] Available at: http://www.retsch.com/products/sieving/sieveshakers/as-200-basic/function-features/ [Accessed 20 August 2014]. [10] ASTM D1762, 2013. Standard Test Method for Chemical Analysis of Wood Charcoal. [Online] Available at: www.astm.org [Accessed 20 August 2014] [11] ASTM E871, 2013. Standard Test Method for Moisture Analysis of Particulate Wood Fuels. [Online] Available at: www.astm.org [Accessed 20 August 2014]. [12] ASTM D388, 2012. Standard Classification of Coals by Rank. [Online] Available at: www.astm.org [Accessed 20 August 2014]. [13] IRENA, 2013. Biomass Co-Firing. [Online] Available at: www.irena.org [Accessed 20 August 2014].
Biography Norfadhilah Hamzah was born in Malaysia in 1983. She received MSc (Eng.) in Environmental and Energy in 2014 at the University of Sheffield. She completed BEng in Biochemical-Biotechnology at the International Islamic University Malaysia in 2007. She is a PhD student at Department of Transdisciplinary Science and Engineering, Tokyo Institute of Technology since 2016 under supervisory of Assoc. Prof Koji Tokimatsu and Prof Kunio Yoshikawa. Her research interests include biomass renewable energy for power generation.
ScienceDirect Energy Procedia 105 (2017) 413 – 418
The 8th International Conference on Applied Energy – ICAE2016
Woody biomass characterization for 100 megawatt-hours (MW) power generation Norfadhilah Hamzaha,*, Mohammad Zandia, Koji Tokimatsub, Kunio Yoshikawab a Department of Chemical and Biological Engineering, University of Sheffield, Sheffield S10 2TN, United Kingdom Depatment of Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, Yokohama 226-8502, Japan
b
Abstract
This paper characterized the wood pellet and torrefied wood pellet fuel as compared to coal for 100 MW co-firing power generation plant. There were five experiments to characterise the chemical and physical properties of coal, wood pellet and torrefied wood pellet namely moisture analysis, Thermo gravimetric Analyser (TGA), Bomb Calorimeter, Organic Elemental Analyser and Scanning Electron Microscope (SEM). The moisture analysis result from moisture analyser and TGA shows that the moisture content of torrefied wood pellet is lower than wood pellet at 6.760% and 3.629%. Moreover, the volatile matter, hydrogen and nitrogen content of torrefied wood pellet is lower than wood pellet at 65.20%, 5.993% and 0.4078% correspondingly. The calorific value, fixed carbon content, ash and sulphur also increase in torrefied wood pellet at 20.68 MJ/kg, 28.85%, 2.321% and 0.1656% respectively. In general, torrefaction improve the fuel properties of wood pellet similar to coal. The 100 MW direct co-firing power plant provides less capital investment, operation and maintenance cost for low rate co-firing ratio. However, there is economic challenges for high rate co-firing substation of torrefied wood pellets.
© 2017 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license © 2016 The Authors. Published by Elsevier Ltd. (http://creativecommons.org/licenses/by-nc-nd/4.0/). responsibility of ICAE Selection and/or peer-reviewofunder Peer-review under responsibility the scientific committee of the 8th International Conference on Applied Energy.
Keywords: wood pellet; torrefied wood pellet; co-firing, coal; power generation; woody biomass
* Corresponding author. Tel.: +60139836433; fax: +603-88905679. E-mail address: [email protected].
1876-6102 © 2017 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the scientific committee of the 8th International Conference on Applied Energy. doi:10.1016/j.egypro.2017.03.334
414
Norfadhilah Hamzah et al. / Energy Procedia 105 (2017) 413 – 418
1. Introduction Biomass or bio renewable sources are defined as any biological origin that available on a renewable basis that are categorized into waste such as agriculture and forestry waste, by-products from agriculture process and animal manure and energy crops [1][2]. On the other hand, the municipal solid waste is mix of discarded materials thrown into garbage including plastic, glass and metals hence do not qualify as biomass [1]. The similarity of biomass fuel characteristics with fossil fuels make it unique to be used for power, heat and fuel generation [3]. Biomass particularly torrefied wood pellet can be used to meet the power load requirements as similar to coal due to improved fuel characteristics similar to coal. The main advantage of biomass as compared to coal is the availability to produce less CO 2, reduce emission of SOX and NOX. However, the technical and economic challenges of biomass are low bulk and energy density and low calorific value that cause the high feedstock cost [4]. Besides, the high moisture content resulted in decrease plant efficiency, storage and handling problem. In long term, good forests management will significantly improve the supply of torrefied wood pellet. Hence, the biomass renewable energy will provide energy security, alternatives fuel sources, environmental friendly and improved social living by creation of job. In this study, the wood pellet and torrefied wood pellet were characterized for 100 Megawatt-hours (MW) direct co-firing power generation plant with coal that contribute to high efficiency, economically and environmentally development in the region and thereby provides a better alternative of fuel source than coal for electricity generation.
2. Experimental methods
The coal sample was collected in Kellingley colliery located in Knottingley in West Yorkshire. Kellingley is deep mined from the oldest geological formations, and therefore has spent the longest time underground and been subjected to the most pressure and heat, making it the most compressed and hardest coal [5]. The wood pellets source from virgin timber in United Kingdom (UK) forest and supplied by Logs2U, a part of CPL Distribution Ltd with the ash content was less than less than 0.7%, moisture content of less than 10%, energy content calorific value of 4800 kWh/1000 kg and mechanical durability of more than 97.5%. The torrefied wood pellets are supplied by New Biomass Holding LLC located in United States and manufactured from torrefied wood that has been ground and extruded using a nonhazardous organic binder with energy content between 20 to 23 GJ/MT [6]. Standard practice for preparation of coal and biomass samples for compositional analysis, the particle size of less than or equal to 250 µm must be use [7][8]. The raw materials were finely ground using Planetary Ball Mill PM100 using high centrifugal forces and very high pulverization energy to give short grinding times. The fine particles were separated using Analytical Sieve Shaker AS200 Basic to get fine particle size of less than or equal to 250 µm [9]. The physical and chemical properties of coals and biomass varies; hence it is important to be able to determine the chemical composition as this often affect the combustion characteristics. The proximate, elemental, calorific values, scanning electron microscope fiber analyses were done to compare fuel properties on dry basis of wood pellet, torrefied wood pellet and coal. All of the analysis were done in
415
Norfadhilah Hamzah et al. / Energy Procedia 105 (2017) 413 – 418
accordance with the procedure of American Society for Testing and Materials Standard Test Method for Chemical Analysis of Wood Charcoal [10] and Standard Test Methods for Analysis of Wood Fuels [11]. 3. Results and discussion 3.1. Calorific value, proximate and ultimate analysis The chemical and physical characteristics of biomass is significant to determine the combustion characteristics in power plant. The calorific value, proximate and ultimate analysis of coal, wood pellet and torrefied wood pellet are provided in Table 1. From the result, there are difference in value of moisture content analysed using moisture analyzer and TGA. The standard deviation errors are smaller in moisture analyzer hence, the result is more reliable and accurate. This is due to the determination of moisture content taking into consideration of atmospheric pressure and temperature as compared to loss of moisture weight from TGA. In comparison with wood pellet, it can be seen that the moisture content and volatile matter of torrefied wood decreased due to devolatilization of wood during torrefaction. In addition, torrefaction resulted in higher carbon content, calorific value, ash content and sulphur. Additionally, the hydrogen and nitrogen content of torrefied wood decreased resulting in decreased H/C ratio. Nevertheless, the woody biomass has greater volatile compound than sub-bituminous coal. The fuel ratio or ratio of fixed carbon content to volatile matter is 1/10 of coal. Nonetheless, the moisture content and ash content for Kellingley coal was 1.233% and 2.593% correspondingly. The volatile matter, fixed carbon content, calorific values was 33.55%, 62.62% and 32.00 MJ/kg respectively. Hence, from [12] to classify coals from the calorific value, in increasing coalition order Killingley coal was classified Bituminous High Volatile B. A high rank coal composed mainly of fixed carbon with little volatile content and ash, no or less moisture and high calorific value. Therefore, the highest coal rank is more carbon neutral, high energy density, more brittle, hydrophobic in nature, low sulphur and ash than wood pellet. Table 1: Summary of calorific value, proximate and ultimate analysis of coal, wood pellet and torrefied wood pellet Samples
Moisture Content (wt. %)
CV (MJ/kg)
Coal
2.388
32.00
Wood Pellet
7.060
18.78
Torrefied Wood Pellet
6.760
20.68
Proximate Analysis (wt. %) Moisture
Ultimate Analysis (wt. %)
VM
FC
Ash
C
H
N
S
1.233
33.55
62.62
4.634
74.30
20.80
2.593
76.33
4.801
1.446
1.825
0.2611
49.06
6.311
2.079
0.0000
3.629
65.20
28.85
2.321
59.45
5.993
0.4078
0.1656
3.2. Microstructure Woody biomass is composed of cellulose, hemicellulose and lignin. Drying wood for palletization at temperature below 250°C softens lignin, devolatilised and carbonized hemicellulose. In contrast, during torrefaction drying at temperature above 250°C decomposed hemicellulose into volatiles and char. From the cross section of SEM photo of coal, the morphology of wood pellet and torrefied wood pellets as in
416
Norfadhilah Hamzah et al. / Energy Procedia 105 (2017) 413 – 418
Figure 1 , it can be seen clearly the micro fibrils structure of wood pellet that indicate hydrophilic in structure which easily susceptible to biological degradation. Torrefied wood pellet and coal is more brittle in structure and higher grind ability than fibrous wood. Hence more hydrophobic and stable in storage while wood pellets will deteriorate to gets mouldy.
(a)
(b)
(c)
Figure 1: SEM photo for (a) coal (b) wood pellet (c) torrefied wood pellet
3.3. Plant Design Outline for Wood Co-firing with Coal
Figure 2: Direct Co-Firing Biomass-Coal Power Plant Outline
The direct biomass co-firing with coal will improve the efficiency of overall plant performance. The energy efficiency of biomass co-firing will be increase with the implementation of combined heat and power (CHP). Direct co-firing in existing coal power plant requires less capital investment than dedicated biomass power plant. 3.4. Economic From the design outline, the direct co-firing plant provides the cheapest and simplest options of low investment costs because it utilizes the pre-existing boiler and other equipment in coal fired plant. Economies of scale for biomass co-firing plants related with investment, operation, maintenance and fuel
Norfadhilah Hamzah et al. / Energy Procedia 105 (2017) 413 – 418
cost. The investment cost is depending on the plant capacity, service, type of biomass fuel, and existing boiler quality. The estimated cost of retrofitting torrefied biomass in coal power plant is around £200/kW based on 2012 market condition [13]. In this project, the torrefied wood pellet will be co-fired with coal at coexisting power generation plant with output capacity of 100 MW. Nonetheless, torrefaction plants would significantly incurred high capital costs and requires large feedstock availability to compensate for the investment but are expected to have lower operation costs than palletization plants. Co-firing of torrefied wood pellet with coal will increase the fuel handling costs but it will reduce the flue gas treatment and ash disposal cost as the sulphur, nitrogen and ash content are small as compared to conventional coal treatment plant. Therefore, the operation and maintenance cost almost similar to conventional coal fired plant within the range of £3.0/MWh to £6.03/MWh [13]. Moreover, the normal average O&M costs is approximately 2.5% to 3.5% of capital costs and the cost increase with the increase of quality torrefied wood pellet used and higher substitution ratio with coal. Torrefied wood pellet has low ash content than coal with properties almost similar to coal that could significantly contribute to fouling and corrosion problem boilers. The torrefied wood pellet fuel feedstock depends on the biomass origin and cost of transportation, preparation and handling. As torrefied wood pellets are imported from United States, the transportation costs depend on the energy density, calorific value of the fuel. Hence, torrified wood pellet increase the calorific value per volume of biomass fuel as compared to wood pellet. Besides, the torrefied wood pellet produce a more uniform size, hydrophobic and brittle that make the transportation, storage and handling easier. In addition, the torrefied wood pellet can be shipped in large amount as compared to wood pellet due to higher energy density and hydrophobicity, hence reduce the logistic cost. 3.5. Environmental Impact Direct co-firing torrefied wood pellet with coal offers the cheapest option in reducing GHG emission. Woody biomass is a carbon neutral fuel as the CO 2 releases to the atmosphere during combustion will be used during photosynthesis. Therefore, substitution of coal with biomass release less net GHG emission than conventional coal power plant. Replacement of 1% to 10% biomass per year with coal could significantly reduce 45 to 450 million tons of CO2 emissions in 2035 [13]. 4. Conclusion Co-firing offers potential for emerging developing countries to increase the economic value as it using the waste from forestry and agriculture for fuel. Besides, palletization and torrefaction improves the biomass suitability in co-firing and provides the cost effective option co-firing with coal in pre-existing coal fired power plants without significant investment cost. However, there is a need to study the boiler efficiency when co-firing of higher ratio of biomass. Torrefaction process increases the energy density of biomass close to coal in addition to improve the storability and grind ability of biomass. The significant improve in feedstock properties will improve plant reliability, combustion efficiency, reduce collection and transportation cost, minimize fouling and slagging. Therefore, high rate co-firing of torrefied wood pellets with can be achieved. .
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Norfadhilah Hamzah et al. / Energy Procedia 105 (2017) 413 – 418
References [1] Brown, R. C., 2007. Biomass Conversion Processes for Energy Recovery: Power Generation. In: F. Kreith & D. Y. Goswami, eds. Handbook of Energy Conservation and Renewable Energy. Boca Raton: CRC Press Taylor & Francis Group, p. 25.37-25.50 [2] Abbasi, T. & Abbasi, S., 2010. Biomass energy and the environmental impacts associated with its production and utilization. Renewables and Sustainable Energy Reviews, p. 919-937 [3] Sharifi, V. N., 2014. Lecture 3 Handout: Energy from Biomass and Waste, Sheffield: The University of Sheffield. [4] International Energy Agency, 2012. Technology Road Map: Bioenergy for Heat and Power. [Online] Available at: http://www.iea.org/publications/freepublications/publication/bioenergy.pdf [Accessed 14 February 2014]. [5] Zandi, M., 2013. Applied Energy Engineering: Proximate Analysis of Coal, Sheffield: University of Sheffield. [6] New Biomass, 2014. New Biomass. [Online] Available at: http://newbiomass.com/ [Accessed 19 August 2014]. [7] ASTM D5865, 2013. Standard Test Method for Gross Calorific Value of Coal and Coke. [Online] Available at: www.astm.org [Accessed 21 August 2014]. [8] ASTM E1757, 2007. Standard Practice for Preparation of Biomass for Compositional Analysis. [Online] Available at: www.astm.org [Accessed 20 August 2014] [9] Retsch, 2014. Vibratory Sieve Shaker AS 200 basic. [Online] Available at: http://www.retsch.com/products/sieving/sieveshakers/as-200-basic/function-features/ [Accessed 20 August 2014]. [10] ASTM D1762, 2013. Standard Test Method for Chemical Analysis of Wood Charcoal. [Online] Available at: www.astm.org [Accessed 20 August 2014] [11] ASTM E871, 2013. Standard Test Method for Moisture Analysis of Particulate Wood Fuels. [Online] Available at: www.astm.org [Accessed 20 August 2014]. [12] ASTM D388, 2012. Standard Classification of Coals by Rank. [Online] Available at: www.astm.org [Accessed 20 August 2014]. [13] IRENA, 2013. Biomass Co-Firing. [Online] Available at: www.irena.org [Accessed 20 August 2014].
Biography Norfadhilah Hamzah was born in Malaysia in 1983. She received MSc (Eng.) in Environmental and Energy in 2014 at the University of Sheffield. She completed BEng in Biochemical-Biotechnology at the International Islamic University Malaysia in 2007. She is a PhD student at Department of Transdisciplinary Science and Engineering, Tokyo Institute of Technology since 2016 under supervisory of Assoc. Prof Koji Tokimatsu and Prof Kunio Yoshikawa. Her research interests include biomass renewable energy for power generation.