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Bridgeman T.G., Jones J.M., Shield I., Williams P.T., 2008. Torrefaction of reed canary grass, wheat straw and willow to enhance solid fuel qualities and ...

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ScienceDirect Procedia Environmental Sciences 35 (2016) 890 – 894

International Conference on Solid Waste Management, 5IconSWM 2015

Torrefaction Reaction Characteristic of various Biomass Waste on Pilot Scale of Torrefaction Reaction System S. B. Nam, Y. S. Park, D. J. Kim, J. H. Gu* Plant Engineering Center, Institute for Advanced Engineering, Yongin-Si, South Korea

Abstract Torrefaction processes of three kinds of waste biomass species, including EFB(Empty Fruit Bunches), wood pellet and rice husks were investigated on the pilot scale of torrefaction reaction system with rotary kiln type of reactor. The yield of torrefied material from EFB(61.0 wt%) and waste pellet(76.7 wt%) was higher than that of gas and liquid, while only 30.8 wt% of torriefied rice husks was obtained. Especially, the energy density of torrefied material with respect to waste biomass species is following order; rice husks § EFB > wood pellet. In addition, O/C and H/C for EFB and Rice husks after torrefaction reaction was similar with that of coal, while wood pellet was affected slightly. It is mainly related to the lignocelluloses components in waste biomass materials. From this result, we concluded that the torrefied EFB is more suitable to coal-firing power plant compared to rice husks and wood pellet. © by Elsevier B.V. This is an open access article under the CC BY-NC-ND license © 2016 2016Published The Authors. Published by Elsevier B.V. (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility ofthe organizing committee of 5IconSWM 2015. Peer-review under responsibility of the organizing committee of 5IconSWM 2015 Keywords:Char, Biomass, Torrefaction, Pyrolysis;

1. Introduction Renewable energy resources from biomass have been globally attention from advantage of steady supply power generation for reducing reliance on fossil fuel and curbing global warming. To produce energy from biomass, a variety of thermochemical conversion techniques is commonly used such as combustion, gasification and pyrolysis. Especially, torrefied biomass can be easily adjusted to coal-fired power plants and entrained-flow gasification plants[Bridgeman T.G., et al, 2008]. The torrefaction, which is a mild pyrolysis process with the temperature in the

* Corresponding author. E-mail address:[email protected]

1878-0296 © 2016 Published by Elsevier B.V. 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 organizing committee of 5IconSWM 2015 doi:10.1016/j.proenv.2016.07.044

S.B. Nam et al. / Procedia Environmental Sciences 35 (2016) 890 – 894

range of 225~230oC at inert atmosphere, substantially reduce organic volatile components and moisture in raw biomass with higher energy density. The characteristic of torrefied material is quite similar with that of coal substitute for co-firing power plants. Recently, the torrefaction of waste biomass has attracted more interest from its potential application in world wide.20 million tons of EFB(Empty Fruit Bunches),which are generated annually in Malaysia, are restrictively treated such as soil mulching and boiler fuel. However, the incineration of biomass is strictly regulated by the Department of Environment(DOE)[ Baharuddin A.S., et al, 2010].Since 2012, Renewable Portfolio Standard(RPS) has been a regulatory mandate to power generation plant to supply electricity from biomass in Korea[http://www.energy.or.kr/knres/index.asp. Accordingly, in the present study, the torrefaction characteristics of three different biomass materials has been explored on the pilot scale of torrefaction system with rotary kiln type of reactor. The characteristic of system has been evaluated using mass yield and calorific value of torriefied materials. These results will contribute to further work involving economic analysis for this torrefaction technique. 2. Materials and Methods EFB provided from palm oil mill in Malaysia after drying process was shredded to 20 cm length to feed into the torrefaction reactor. Two types of biomass including wood pellet and rice husks obtained in Korea were selected as the raw materials to be tested. Proximate, ultimate and calorific value analysis of employed waste biomass were conducted as listed in Table 1. Most of raw materials are including combustible components. This result is quite related to 44.66% of carbon and 45.4 % of oxygen in EFB, while wood pellet and rice husk are including 39.1% and 41.7% for Cl from ultimate analysis.

Fig. 1.Pilot scale of waste biomasstorrefaction system

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S.B. Nam et al. / Procedia Environmental Sciences 35 (2016) 890 – 894

Figure 1 presented pilot scale of torrefaction system is including waste biomass feeding system, torrefaction reactor, char tank, gas purification system, cooling system and gas combustion system. The torrefaction temperature was 265 oC with 30 min of retention and 60 kg/h of feed rate. The concentrations of H2, CH4, C3H6, CO, CO2 and N2 in produced gas were analyzed by gas chromatography (GC) equipped with a TCD (model 3000 micro GC, Inficon Co.). Table 1:Proximate, ultimate and calorific value analysis for raw waste biomass

Proximate analysis (%)

Calorific value (kcal/kg)

Ultimate analysis (%)

Species

EFB Wood Pellet Rice husk

Moisture

Combustible

Ash

C

H

O

N

S

Cl

HHV

6.52

91.19

2.29

44.66

7.12

45.4

0.38

0.00

0.00

4,231

7.99

84.19

7.82

45.07

7.12

0.18

0.00

0.00

39.1

4,272

7.02

78.78

14.20

37.10

5.76

0.14

0.00

0.00

41.7

3,954

3. Results and Discussion The results of gas, liquid and solid yields after torrefaction reaction using waste biomass are shown in Table 2. After torrefaction reaction, the largest value of yield was solid (61.0 wt%) in EFB, and liquid yield and gas yield were 22.8 wt% and 9.3 wt%, respectively. This trend of yield for products was similar with that of wood pellet, while the liquid yield(35.9 wt%) was relatively higher than that of gas(26.4 wt%) and solid yield(30.8 wt%) for torrefied rice husk. It is mainly due to the difference of volatile and lignocellulose components in raw materials. Table 2:Gas, liquid and solid yield after torrefaction reaction for waste biomas Species

EFB

Wood pellet

Rice husk

Gas yield (wt%)

9.3

5.3

26.4

Liquid yield (wt%)

22.8

12.4

35.9

Solid yield (wt%)

61.0

76.7

30.8

Figure 2 and 3 show the characteristics of produce gas during torrefaction reaction with respect to waste biomass species detected by GC analyzer. Major components of the gas were CO and CO2, regardless of biomass species. For example, the sum of composition for CO and CO2 in produced gas from rice husks, wood pellet and EFB were 96.02%, 95.65% and 95.19%, respectively. This result is quite related to the high value of carbon composition in ultimate analysis results.The calorific value of produced gas from rice husks, wood pellet and EFB were 1,297 kcal/Nm3, 890 kcal/Nm3 and 1,223 kcal/Nm3, which is related to the composition of CO in produced gas. Therefore, produced gas during torrefaction reaction from waste biomass can be used for supplement fuel to supply energy resources for torrefaction system or heat generation system.

S.B. Nam et al. / Procedia Environmental Sciences 35 (2016) 890 – 894

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Fig. 2.Composition of produced gas during torrefaction reaction with respect to waste biomass species

Table 3 presents the characteristics of torrefied materials with respect to waste biomass species. After torrefaciton reaction, energy density was increased due to the conversion quantity from raw materials to torrefied materials are higher than gas and liquid. The calorific value ranking of the torrefied materials during torrefaction is the following order; EFB > Rice husks §Woodpellet. Especially, the O/C and H/C for EFB and Rice husks after torrefaction reaction was closer to the values for coal, while there was no substantial effect on torrefaction reaction over wood pellet, as depicted in figure 4. It is might be related to lower composition of hemicellulose, which is the most reactive component in lignocelluloses, in wood biomass compared to the graminaceous crops[Chen W.H., et al, 2010]. However, the torrefied rice husks are not suitable to energy resource due to lower char yield and higher ash components compared to that of EFB and wood pellet. In addition, the wood pellet is required severe torrefaction condition for intensifying its energy density, which is related to high operating cost and high performed system. Therefore, the torrefied EFB is showed high suitability to coal-firing power plant.

Fig. 3.Yield and calorific value for produced gas during torrefaction reaction with respect to waste biomass species

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S.B. Nam et al. / Procedia Environmental Sciences 35 (2016) 890 – 894 Table 3:Characteristics of torrefied material with respect to waste biomass species Species

EFB

Wood pellet

Rice husks

5,456

4,883

4,888

Weight

61.0

76.7

30.8

Energy

78.6

87.7

44.9

1.3

1.1

1.4

Calorific value (HHV, kcal/kg) Yield(%) Energy density

Fig. 4.Van Krevelen Diagram for torrefied materials and raw materials

4. Conclusion In this study, we evaluated characteristics of torrefaction reaction with respect to waste biomass species on the pilot scale of torrefaction system. The most of waste biomass species have combustible components, while the alteration trend of physical properties was different during torrefaction reaction. It is mainly related to the lignocelulose components in raw biomass. From this result, torrefied EFB presented high suitability to coal-fired power plant compared to rice husks and wood pellet. Acknowledgement This work was supported by the International Cooperation of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant funded by the Korea government Ministry of Knowledge Economy (No. 2011T100100333). In addition, this work was supported by the Renewable energy’s technology development of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant funded by the Korea government Ministry of Knowledge Economy (No. 20143010101910). References 1) 2)

3)

4)

Bridgeman T.G., Jones J.M., Shield I., Williams P.T., 2008. Torrefaction of reed canary grass, wheat straw and willow to enhance solid fuel qualities and combustion properties. Fuel 87:844-856, Baharuddin A.S., Hock L.S., Yusof M.Z., Rahman N.A.A., Shah U.M., Hassan M.A., Wakisaka M., Sakai K., Shirai Y., 2010. Effcts of palm oil mill effluent(POME) anaerobic sludge from 500 m3 of closed anaerobic methane digested tank on pressed-shredded empty fruit bunch(EFB) composting process. African Journal of Biotechnology. 9(16): 2427-2436. Chen W.H., Kuo P.C., 2010. A Stduy on torrefaction of various biomass materials and its impact on lignocellulosic structure simulated by a thermogravimetry. Energy 35:2580-2586. http://www.energy.or.kr/knres/index.asp

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