Enhancement of Gasification Performance for Palm Oil Byproduct by


May 7, 2019 - different washing times to try to resolve this problem. The washing process decreased the ash content from 5.9 wt % to 1.5 wt % when all...
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Biofuels and Biomass

Enhancement of Gasification Performances for Palm Oil By-Product by Removal of Alkali and Alkaline Earth Metallic Compounds and Ash Heung-Min Yoo, Se-Won Park, yean-Ouk Jeong, Gun-Ho Han, Hang Seok Choi, and Yong-Chil Seo Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.9b00158 • Publication Date (Web): 07 May 2019 Downloaded from http://pubs.acs.org on May 8, 2019

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Energy & Fuels

Enhancement of Gasification Performance for Palm Oil By-Product by Removal of Alkali and Alkaline Earth Metallic Compounds and Ash

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Abstract: One of the problems commonly encountered during the gasification process for biomass is the

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agglomeration of residue associated with low efficiency, which occurs due to the use of low-quality fuels

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containing ash and alkali and alkaline earth metallic (AAEM) compounds. In this study, the empty fruit bunch

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(EFB), which is a by-product of the palm oil industry that could potentially be used as fuel, was pre-treated by

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washing with both tap water and a nitric acid solution (0.1 wt. %) for different washing times to try to resolve this

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problem. The washing process decreased the ash content from 5.9 wt. % to 1.5 wt. % when all the washing pre-

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treatments were employed, and over 80 wt. % of the AAEM compounds, such as potassium (K), magnesium (Mg),

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calcium (Ca), and sodium (Na), were removed. Additionally, scanning electron microscopy (SEM) with X-ray

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diffraction (XRD) was used to identify the composition and surface characteristics of the agglomerations produced

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during gasification. The proportion of agglomeration measured in washed EFB decreased by over half compared

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to the agglomeration produced by unwashed EFB, regardless of the type of washing solution used. Previous

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research has shown that, syngas yields of approximately 70 % can be achieved at a temperature range of 900 to

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1,000oC. Thus, washed EFBs were applied to a bubbling fluidized bed reactor (BFB), and the optimum

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experimental conditions (temperature and equivalence ratio, ER) were chosen as 900oC, ER = 0.6. The syngas

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yield of the washed EFB gasification was higher than that of the unwashed EFB. Additionally, agglomeration was

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reduced from 8.7 wt. % to 1.3 wt. %.

Heung-Min Yooa, Se-Won Parka, Yean-Ouk Jeonga, Gun-Ho Hana, Hang Seok Choia, Yong-Chil Seoa* a

Department of Environmental Engineering, Yonsei University, Wonju, Republic of Korea, 220-710

*

Corresponding Author. Tel.: +82-33-760-2438; Fax: +82-33-760-2846; E-mail: [email protected]

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Keywords: Alkali and Alkaline Earth Metallic Compounds, Biomass Gasification, Bubbling Fluidized Bed, Empty Fruit Bunch, Agglomeration, Washing Pre-treatment

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1. INTRODUCTION

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Waste and biomass energy production constitutes approximately 80% of whole renewable energy production in

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Korea. However, surplus amount of domestic biomass is limited in Korea. Therefore, a stable supply of biomass

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and the technology development for energy conversion are required to satisfy the bioenergy supply plan

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established by the government [1-3]. By-products, such as empty fruit bunch (EFB), palm kernel shell (PKS) and

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fiber from the palm oil industry have been generated from countries in South-East Asia as demand for palm oil

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has increased. One of the by-products is EFB, a palm-fiber-waste product, which constitutes approximately 20 %

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of the fresh fruit bunch (FFB) [4]. If EFB could be utilized as a biomass fuel in biomass-to-energy technologies,

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it could realistically become an alternative resource for generating sustainable energy [5, 6].

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Many studies on EFB have been already performed, and one candidate technology is syngas production via the

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EFB gasification. Lahijani et al. (2011) conducted a study of gasification in a bubbling fluidized bed (BFB) with

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agglomeration, and Maastellone et al. (2010) conducted a study on co-gasification with wood, coal, and plastics

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[7, 8]. In the present study, EFB gasification was performed using a thermo-chemical technology in a BFB.

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However, it is difficult to operate stably, because a lot of agglomeration can form during the thermo-chemical

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process. This agglomeration is caused by ash and alkali and alkaline earth metallic (AAEM) compounds from the

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biomass and can impede continuous operation or de-fluidization.

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To solve this problem, EFB was washed using water and a nitric acid solution (0.1 wt. %). Then, proximate

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analysis and scanning electron microscopy (SEM) with X-ray diffraction (XRD) were used to evaluate the effects

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of this washing on the reduction of ash and AAEM compounds. The EFB gasification was carried out to find out

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the effects of the washing treatment at optimum conditions that were determined during previous research;

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temperature and equivalence ratio (ER) were chosen as 900oC, ER = 0.6 (Yoo et al. 2018) [20].

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2. MATERIALS AND EXPERIMENTAL METHODS

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2.1 Characterization of Unwashed EFB

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The EFB used in this study was obtained from Waris Selesa Sdn. Bhd. in Malaysia. The initial moisture content

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of the EFB was over 60 wt. %. Thus, the EFB was dried for 48 h at 105oC, before being milled to 500㎛in size.

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Subsequently, the physicochemical characteristics were examined using thermos-gravimetric (TG) analysis,

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proximate analysis, element analysis and higher heating value (HHV) measurement.

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Proximate analysis and TG analysis were performed using a thermos-gravimetric instrument (Leco, TGA-701).

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TG analysis was used to monitor weight reduction with increasing temperature. This was achieved by increasing

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the temperature from room temperature (approximately 25oC) to 950oC, and the process was performed under

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reduction conditions. The HHV was analyzed using a calorimeter (Leco, AC-600). The elemental analyzer

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(Thermo Fischer Scientific analyzer, EA 1112) was used to measure five elements: carbon, hydrogen, oxygen,

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nitrogen, and sulfur. All analyzing numbers were triplicated and average values were used in this study. In addition,

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all analytic methods are as follows; ‘proximate analysis – ASTM D 3172’, ‘TG – ASTM E 1131’,’ HHV – ASTM

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D 4809’, and ‘EA – ASTM D 5373’.

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2.2 Treatment and Preparation of Washed EFBs

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The unwashed EFB contained a lot of ash, as a result of the production process in Malaysia. The results of the

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proximate analysis show that the EFB used in this study had a higher ash content (5.9 wt. %) than that of other

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biomass sources [9-13]. The soil attached to the initial EFB is a main component of ash content. To remove it,

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Rafigul et al. (2012) have reported that the EFB must to be washed with distilled water [14, 15]. In the present

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study, however, tap water was used as washing water instead of distilled water; if tap water can be shown to be

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equally as effective as distilled water, then this could reduce the costs of the operation. Nitric acid solution (0.1

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wt. %) was chosen as a second washing solution, because it can remove both AAEM compounds and ash from

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biomass [16, 17]. Consequently, EFBs were prepared in three different ways; unwashed EFB, the EFB washed

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using tap water (WE), and the EFB washed using nitric acid solution (NWE). The EFBs were washed with each

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solution two times (V/V) for periods of 24, 48, and 72 h. The ash content of each EFB was measured using

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proximate analysis before and after washing. Inductively coupled plasma (ICP) analysis was used to measure

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changes in the content of AAEM compounds in the same fashion. According to the results of the previous study,

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the best samples of unwashed and washed EFBs (both of WE and NWE) were chosen based on their washing time

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and the level of ash and AAEM removal (Yoo et al. 2018). These samples were inspected for agglomeration

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reduction using TG analysis (see equation 1 and Table 5), and the composition of the agglomerated particles were

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analyzed using SEM with XRD.

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∑S

88

Agglomeration =

89 90

here, Ti is total weight of fed feedstock (g), To is the total weight of reacted feedstock (g), and ∑S is the weight

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of agglomerated particles (g).

⋯⋯⋯⋯⋯⋯⋯⋯⋯⋯⋯⋯⋯⋯⋯⋯⋯⋯⋯⋯⋯⋯⋯⋯⋯ < 𝐸𝑞𝑢𝑎𝑡𝑖𝑜𝑛 1 > Ti ― To

92 93

2.3 Washing solution analysis for effluence and treatment

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Recently, to identify the behavior of pollutants or materials, the best available technique (BAT), which can

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involve either life cycle assessment (LCA) or mass-balance, has been introduced in Korea. As the EFB may be

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applied to commercial plants, the effluent emitted from the washing process was analyzed for four regulated

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parameters: chemical oxygen demand (COD), biochemical oxygen demand (BOD), total nitrogen (TN), and total

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phosphorus (TP). In this study, suspended solids (SS) were not analyzed, because a lot of soils were washed and

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discharged during processing. The other four parameters were analyzed following standard test methods for water

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quality in Korea (TN - ES 04908.1c, TP - ES04907.1e, COD – ES 04315.1b, BOD – ES 04305.1c). In the case of

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the TN and TP, this was done using continuous flow injection. All analyzing numbers were triplicated and average

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values were used in this study.

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2.4 Process and Experimental Conditions for Gasification

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Figure 1 shows the BFB gasification process used. The process has four zones, namely the pre-heating zone,

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reaction zone, purification zone, and analyzing zone. A pre-heater was installed between the gas inlet and wind

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box. In the reaction zone, the wind box, with an inner diameter of 134 mm and height of 100 mm, was used as a

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distributor with 37 holes of bubble cap type. The purification zone was composed of a cyclone, scrubber, and filter.

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Finally, the analyzing zone consisted of the temperature monitoring device, to monitor temperature changes, and

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the micro gas chromatograph (micro-GC), to analyze the gas composition. The micro-GC takes samples and

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analyzes them automatically every 5 minutes for an hour in each gasification experiment. Average values were

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used in this study. A dry gas meter (DGM) was installed to check the produced gas flow. The experimental

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conditions of a bubbling fluidized bed (BFB) gasification process are summarized in Table 1.

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115 116 117 118 119 120

1. Pre-heater, 2. Mass Flow Controller (MFC), 3. Screw Feeder, 4. Reactor, 5. Windbox, 6. Furnace, 7. Cyclone, 8. Scrubber, 9. Pump, 10. Dry Gas Meter, 11. Filter, 12. Micro-GC, 13. Vent Fig 1. Schematic Diagram of BFB Gasification Process

Table 1. Operational Conditions for EFB Gasification Parameters Setting Temperature of Pre-heater Feeding Rate of EFBs Experimental Temperatures Flow Rate of Gas

Oxygen Nitrogen

Residence Time (RT) ER Weight of Fluidization Media (Sand)

Unit

Value

˚C

900

g/min

13

˚C

700 / 800 / 900 / 1,000

L/min

1 – 2.2 15 – 19

sec

Over 5

-

0.3, 0.6

kg

7

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3. RESULTS AND DISCUSSION

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3.1Properties of Unwashed and Washed EFBs (WE and NWE)

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Element analysis of the EFB revealed that its carbon, hydrogen, oxygen, and nitrogen contents amounted to

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approximately 41 wt. %, 5 wt. %, 36 wt. %, and 0.8 wt. %, respectively. Sulfur, which can be converted into H2S,

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was not detected. The HHV was 3,930 kcal/kg (see. Table 2).

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Table 2. Summary of Elemental Analysis for Various Biomass

Biomass

HHV

H

O

N

41.8

5.7

37.4

0.8

(41.7-41.9)

(5.7-5.8)

(37.1-37.8)

(0.8-0.9)

EFB[9]

48.79

7.33

ND

40.18

0.68

4,514

EFB[10]

49.07

6.48

0.7

38.29

< 0.1

4,209

EFB[11]

51.78

7.04

0.72

40.31

0.16

4,036

[Present Study]

S

[kcal/kg]

C

EFB

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Elemental Analysis [wt. %]

ND*

3,930 (3,881-4,010)

*ND: Not Detected

129 130

The element analysis revealed that the properties of the EFB are similar with to those of other general biomass

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sources, indicating that it may be adequate to use as a fuel [9-11]. To confirm this conclusion, the analysis of the

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EFB was compared with the analysis of other biomass sources that have been published in the literature. The

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elemental components and HHV of the EFB showed results similar with that of other biomass [12, 13]. Palm

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kernel shell (PKS) was higher than those of woody biomass. In particular, the carbon content (approx. 50 wt. %)

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and HHV (4,952 kcal/kg) of jatropha seed cake (JSC) were higher than those of other biomass. The published

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elemental contents of sawdust were higher than that of the EFB for the following elements: carbon (45.93 wt. %

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in sawdust), hydrogen (6.65 wt. %) and oxygen (46.00 wt. %; approx. 10 wt. % higher than the EFB). The sawdust

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also has the highest sulfur content. The HHV of sawdust (4,196 kcal/kg) is higher than that of the EFB.

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Proximate analysis of the sample EFB revealed 9.63 wt. % of moisture, 64.95 wt. % of volatility, 19.48 wt. % of

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fixed-carbon and 5.94 wt. % of ash. In particular, the volatility and fixed-carbon are the most important

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components in the thermo-chemical process, because the yields of biocrude oil and synthesis gas increases with

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increasing values of these two variables [18]. However, the wt. % of fixed-carbon and volatility of the sample EFB

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are lower than that of other biomass sources (Yoo et al. 2018) [19, 20].

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Table 3. Results of Proximate Analysis for EFBs AAEM Content [mg/kg] (Removal Efficiency)

Proximate Analysis [wt. %]* Moisture

Volatile

Fixedcarbon

Ash

Calcium

EFBs (unwashed)**

9.6 (9.0-10.0)

65.0 (64.0-66.0)

19.5 (18.9-19.9)

5.9 (5.1-6.4)

1,868

9,489

1,108

59

Washed EFBs (by tap water)

3.8 (3.4-4.2)

78.4 (75.4-80.4)

16.1 (15.2-17.2)

1.7 (1.3-2.3)

1,432 (23.34%)

2,576 (72.85%)

1,159 (-)

61 (-)

Washed EFBs (by nitric acid)

0.2 (0.1-0.2)

81.1 (81.0-81.3)

16.7 (16.5-17.0)

2.0 (1.8-2.3)

314 (83.19%)

415 (95.63%)

56 (94.95%)

10 (83.05%)

Potassium Magnesium

Sodium

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* wt. %: Weight Percentage, ** Unwashed EFBs have crushed and dried before used.

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Furthermore, the moisture and ash contents of the EFB are higher (9.63 wt. % and 5.94 wt. % respectively) than

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that of sawdust (6.27 wt. % and 0.58 wt. %, respectively), which is considered a typical biomass in Korea (Yoo et

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al. 2018) [19, 20]. When the sample EFB was obtained from the palm oil company, it had a high moisture content,

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and was dumped outside, possibly into a field. Thus, moisture and ash need to be removed before it could be used

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as a biomass fuel, similar to the way that sawdust is treated today in Korea. It was anticipated that a higher yield

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of synthesis gas could be obtained by using the washed sample EFB.

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As detailed above, different washing processes were trialed to remove ash and AAEM compounds from the

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sample EFB. As shown in Table 3, all the washing methods showed a clear trend - ash content was reduced from

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5.94 wt. % to 1.68 wt. %, (before and after the process, respectively); a 24 h period was enough to achieve the

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desired results. The results also show that tap water can be used for the washing process in place of distilled water,

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which increases the economic viability of using the EFB, as a biofuel. In addition, in the case of NWE, the process

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of dehydration also showed a positive effect; it was concluded that the sample EFB was affected by the acidic

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solution, which led to the decomposition of bound water [9, 21]. The TG graphs for all the washed EFBs also

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showed clear reduction trends. In particular, the graph for the sample NWE shows that the weight began to reduce

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at a lower temperature than the other EFBs; this suggests an increase in the thermal reaction rate (Figure 2). Finally,

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it was determined that the WE would be washed for 24 h, and the NWE for 48 h, because these conditions produced

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the greatest reductions in AAEM compounds (> 80 %). Previous studies have established that washing biomass

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with a nitric acid solution can decompose organic compounds [22].

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166 167 168 169

Fig. 2 TG Graphs of the EFB Samples

3.2 Washing solution analysis of effluent treatment

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For viable use of the EFB as biomass, the discharged effluent from the washing process needs to be treated so

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that it meets the effluent standards of Korea. Above all, the effluents analyzed in this study exceeded the standard

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values for COD and BOD by over 20 times, because it contains a high concentration of organic compounds.

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Settling method (with flocculant) of sewage treatment plant used to reduce the COD and BOD contents to below

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the standard values would simultaneously decrease the TN content. In the case of the NWE, the effluent should be

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neutralized to pH 6.0 (Table 4).

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Table 4. Results of Water Quality Analysis of Effluents Analysis Item [Water Quality Analysis Standard Method in Korea]

Unit

Total Nitrogen [ES 04908.1c] Total Phosphorus [ES 04907.1e] Chemical Oxygen Demand (COD) [ES 04315.1b]

mg/L

Biochemical Oxygen Demand (BOD) [ES 04305.1c] pH [ES 04904.1d] 177 178

-

Solutions

BATAEL*

Tap water

Nitric acid

60

30.3(30.0-30.4)

175.4(175.3-175.8)

2

11.7(11.2-11.9)

16.4(16.0-16.7)

40

718(715-721)

668(665-672)

-

440(437-445)

340(333-345)

-

6.8(6.7-6.9)

4.2(4.0-4.2)

* BAT-AEL: Emission Level Associated with the Best Available Techniques 3.3 Agglomeration Analysis of EFB ash

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The composition of the agglomeration produced during gasification was investigated by sampling the recovered

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ash and analyzing the samples using SEM with XRD. SEM analysis clearly showed agglomerated particles in ash

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(Figure 3). Figure 4 shows SEM with XRD analysis focused on the agglomeration that formed on the EFB samples’

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surfaces. The SEM analysis clearly shows that the unwashed EFB produced a lot of agglomeration in ash. The ash

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was discharged from a mixture of the sample EFB and sand. Additionally, it showed that when the unwashed EFB

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sample was mixed with fluidization media (sand), the produced agglomeration was adsorbed onto the surfaces of

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the sand grains [23]. From this experimental result, even though the sample EFB adsorbed to the surface of the

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sand, when applied to a fluidized bed it is predicted that there would be reduced agglomeration (Table 5).

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188 189

Fig 3. SEM Images of Agglomerated Particles in EFB Ash

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Fig 4. SEM Image and XRD Spectrum on Surface of Agglomerated Particles in Ash

Table 5. Production Rate of Agglomeration Wt. %

Samples

700 ℃

800 ℃

900 ℃

N2

Air

N2

Air

N2

Air

EFB

-

-

-

100

100

100

WE / NWE / Sand

-

-

-

-

-

-

EFB with Sand

-

-

98.2

100

100

100

WE with Sand

-

21.6

4.7

23.2

54.5

-

39.9

3.3

44.1

32.7

62.9

-

NWE with Sand 194 195

The agglomeration observed using SEM was analyzed by XRD, revealing that its main components were of

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oxygen, silica, and AAEM compounds (Figure 4). Additionally, the composition of agglomerations was the same

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across all the sample EFBs, such as unwashed EFB, washed EFB and a mixed sample of EFB and sand. Thus, it

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was concluded that agglomerations containing trace AAEM compounds formed in all the EFBs. This phenomenon

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might also be a result of the heterogeneous EFB samples.

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In this study, recovered ash was sampled at different temperature conditions and then analyzed to determine

201

changes in the agglomeration production ratio. Equation (1) was then used to quantify the agglomeration. The

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unwashed EFB showed an agglomeration production ratio of 100 %; agglomeration was produced only at 900oC

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under reducing conditions but began to be produced from 800oC under oxidizing conditions. In addition, when the

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sand was heated to 900oC under oxidizing conditions, agglomeration did not occur. Agglomeration did occur,

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however, in the sample of unwashed EFB mixed with sand (100 %). In contrast to the unwashed EFB, the washed

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EFBs (both WE and NWE) were not agglomerated, and the production ratio decreased by approximately half of

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that when the washed EFBs were mixed with sand. Considering the sample EFBs, the soil attached to EFB has

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high AAEM content, and the AAEM leads to agglomeration of particles. Thus, the agglomeration of particles

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could be appeared at any temperatures, since the removal efficiency for AAEM was not 100%. However, the EFB

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was combusted perfectly at 900 oC with oxidation condition in TG analysis. All experimental results may have

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exception since the EFB does not have high level of homogeneity. However, the production rate of agglomeration

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could be decreased at over 900 oC. Thus, in order to prevent agglomeration, washed EFB would need to be

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processed at temperatures over 900oC (Table 5) [22, 24].

214 215

3.4 Gasification of Unwashed EFB

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The optimum temperatures for the pyrolysis and gasification were concluded to be 400oC and 900oC, respectively.

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During the pyrolysis of biomass, volatility compounds can easily be converted into gas at low temperatures. This

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must be monitored, because the main purpose is to condense the pyrolytic vapor produced, and when the biomass

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fuel is fed into the combustor or reactor, it is easy to cause cracking by heating at too high a temperature or for too

220

long of a residence time [25]. The gasification process uses all the combustible gas to produce hydrogen and carbon

221

monoxide, and the process requires a high temperature (> 900oC) [26].

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The experimental results in EFB gasification showed that the hydrogen and carbon monoxide yields increased

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with increasing ER and temperature (Yoo et al. 2018) [19, 20]. These results suggest that thermal cracking

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increased with increasing temperature, because the endothermic reactions were dominated by a water gas shift

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(WGS) reaction [6], which increased the steam gasification reaction by using the moisture of the EFB. However,

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as oxygen increased, exothermic reactions began, and carbon monoxide levels were increased via the heat of the

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reaction. According to the result of previous research, the optimum temperature range for producing syngas was

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900 to 1,000oC, which yielded the highest syngas yield and the lowest solid residue yield (Yoo et al. 2018) [19,

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20]. During the gasification process in power plants, the volumes of syngas and solid residue produced are both

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important factors that affect the efficiency and sustainability of power generation. The HHV of syngas was also

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estimated, and HHV trend was similar to those of carbon monoxide and methane. Based on the results, syngas

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produced could be used directly as a fuel in commercial production (see Figure 5).

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234 235

Fig 5. Gas Composition at Different ER and Temperatures

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Figure 6 shows the yields of dry gas, solid residue, and tar formation from the EFB gasification performed at

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different temperatures. It was concluded via results of previous research that the conversion ratio increased with a

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change in temperature because thermal cracking was more evident at higher temperatures (Yoo et al. 2018) [19,

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20]. In addition, comparing the experimental results with the proximate analysis results, the EFB reacted well; the

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volume of solid residues (char and ash) were kept within 20 wt. %. However, there was a high amount of tar in

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the EFB gasified at 700oC because the organic compounds in the EFB were volatized, then condensed during the

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oil phase in a scrubber. As shown in Figure 6, dry gas yields were affected by changing ER and temperature.

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During EFB gasification, the dry gas yield was optimized at 900oC and ER = 0.6 (Yoo et al. 2018) [19, 20]. In

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accordance with the experimental results, the optimal conditions for continuous operation were therefore 900oC

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and ER = 0.6 [27, 28].

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Fig 6. Yields of Solid Residue and Dry Gas at Different ER and Temperatures

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Carbon conversion and cold gas efficiency (CGE) are important factors for evaluating gasification efficiency [27,

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28]. The carbon conversion rate can be calculated by measuring the hydrocarbon gases produced, which originated

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from the total carbon content of the EFB. Table 6 shows the relevant equations.

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Table 6. Equations of Carbon Conversion and CGE Cold-gas Efficiency (%)

HHV of Produced Gas (kcal/kg) ÷ HHV of Fuel (kcal/kg) × 100

Dry Gas (D.G)

Flow Rate of Produced Gas (Nm3/hr) ÷ Mass of Fed Feedstock (kg/hr)

Carbon Conversion (%)

12 × D.G × (CO + CO2 + CH4 + 2 × C2H6 + 3 × C3H8) ÷ (22.4 × C)

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In this study, nitrogen was not considered via “N2 free basis” theory [29]. Figure 7 shows the carbon conversion

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and the CGE at different temperatures. The highest carbon conversion and dry gas yield were obtained at a

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temperature of 1,000oC and ER = 0.6 (see Figure 7). The CGE is correlated with the volumes of hydrogen and

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carbon monoxide produced. As the hydrocarbon levels increased, the CGE was also increased and both hydrogen

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and carbon monoxide increased with increasing ER. Therefore, the CGE was the highest at a temperature range of

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900-1,000oC and ER = 0.6.

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The HHV trend was irregular; the highest value occurred at a temperature of 800oC and ER = 0.6. This implies

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that the HHV value depends on gas composition, and the CGE depends on the amount of syngas produced.

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Additionally, it was concluded that the results were affected by ash content in the EFB, because the EFB sample

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was heterogeneous [8]. In other words, the ash led to an unstable reaction, resulting in a lower yield of gas.

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Fig 7. Results of Carbon Conversion and CGE

3.5 Comparison of Syngas Yields

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This study showed that the optimal temperature and ER for gasification were 900oC and 0.6 respectively, when

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considering both the optimal syngas yield and the smooth operation of EFB gasification in a commercial plant.

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Thus, in this study, these experimental conditions were chosen, when processing the washed EFBs and when using

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the fluidized bed. Figures 8 shows the decreases in agglomeration achieved by each washing treatment; the sample

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of NWE showed the highest agglomeration reduction rate (from 8.72 wt. % to 1.39 wt. %). Reducing

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agglomeration is critical to allowing the continuous operation of a commercial plant, so this result is promising.

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Furthermore, the hydrogen yield was increased by approximately 5% when using washed EFBs (compared to

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unwashed EFBs), and the carbon monoxide yield was also increased by 1- 2%. It was concluded that the main

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effect is that molecular bonding forces became weak through washing by tap water or nitric acid solution. In

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addition, as the ash was removed during washing, only the pure EFBs were fed into the fluidized bed. Furthermore,

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carbon dioxide, which is one of the main sources of greenhouse gases decreased from 17.98 % to 11.73 %;

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minimizing carbon dioxide emissions is critical for the development of clean energy technologies. Consequently,

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the yields of hydrogen and carbon monoxide in the syngas were considered to evaluate the gasification efficiency

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(Figure 8).

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Fig 8. Changing Gas Composition with Agglomeration production

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The washing pre-treatment also affected carbon conversion, CGE, and HHV. Washed EFBs showed outstanding

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values for carbon conversion and CGE: carbon conversion increased by over 20 % (from 45 % to 68 %) and CGE

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increased by approximately 20 % (from 32 % to 52 %).

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Finally, the HHVs of syngas for unwashed EFB, WE, and NWE were 2839 kcal/m3, 2836 kcal/m3 and 3019

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kcal/m3, respectively. Since, carbon dioxide emissions decreased, when washed EFBs were used, it was concluded

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that the highest calorific value was shown in the gasification experiment that used the pre-treated EFB washed

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with nitric acid solution (Figure 9).

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294 295

Fig 9. Carbon Conversion, CGE, and HHV

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In general, higher ER values and lower operational temperatures yield identical volumes of syngas. Therefore, the washing pre-treatment methods could be a positive way to not only improve gasification efficiency, but also to reduce agglomeration, which is one of critical factors for the continuous operation of commercial plants.

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4. CONCLUSIONS

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This analyzed the physico-chemical and thermal characteristics of the gasification of the EFB, a palm oil by-

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product, for application in the commercial biofuel industry. The results of the gasification experiments revealed

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that the syngas production was efficient. Moreover, the results presented in this study showed that syngas

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composition could be improved by removing AAEM compounds, which can otherwise produce agglomeration;

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agglomeration is known to impede the continuous operation of the fluidized bed process. From these investigations

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the following conclusions can be drawn:

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1. The elemental analysis of the EFB revealed 41.81 wt. % of carbon, 5.73 wt. % of hydrogen, 0.84 wt. % of

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nitrogen, and 37.36 wt. % of oxygen. In addition, no sulfur was detected in the EFB, and EFB contained more

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moisture (9.63 wt. %) than sawdust. The composition of EFB is similar to a typical woody biomass. Therefore,

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the EFB could be used as a woody biomass in Korea.

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2. The washing process applied to the EFB in this study was shown to reduce AAEM compounds by over 80%.

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Furthermore, the removal of AAEM compounds led to a reduction in the agglomeration production rate. When

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unwashed EFB was fed into the gasification process an agglomeration production ratio of approximately 8.72 wt.

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% was evident. However, when the sample of washed EFB was fed to gasification process; the production ratio

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was decreased to 1.39 wt. %, showing that it is possible to control agglomeration production through washing.

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3. The EFB washed with nitric acid solution produced ratios of hydrogen and carbon monoxide in syngas of

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approximately 35 %. Additionally, the washing pre-treatment also showed positive effects on carbon conversion,

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CGE, and HHV. Washed EFBs showed outstanding values for carbon conversion, which increased from 45% to

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68% after washing, and CGE was also increased from 32% to 52%.

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5. ACKNOWLEDGMENTS

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This work was financially supported by the Korean Ministry of Knowledge Economy as “Development of bio-

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energy production technology using palm-oil by-product” and by the Korean Ministry of Environment (MOE) as

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“Knowledge-based environmental service (Waste to energy recycling) Human resource development Project”.

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6. REFERENCES

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[2] Roh S A, Kim W H, Keel S I, Yun J H, Min T J, Kwak Y H. Waste Gasification with High Temperature Steam,

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The 2007 Environmental Societies Joint Conference 2007;19(4): 215 – 220. [3] Korea Energy Management Corporation. New & renewable energy RD&D strategy 2030 - waste part; 2007: 1 -14. [4] Global Green Synergy. Palm Oil Biomass Industry, 2010. http://www.ggs.my/index.php/main-services/palmbiomass. [5] Koo B S. A Study on Fast Pyrolysis Characteristics of Jatropha and Palm wastes in a Bubbling Fluidized Bed, Master Dissertation, Sungkyunkwan University, Korea; 2011: 1 – 7. [6] Hwang H. Gasification of Wood Pellet using Multi-stage Reactor System, Master Dissertation, Seoul National University of Science and Technology, Korea; 2011. [7] Lahijani P, Alimuddin Z A. Gasification of palm empty fruit bunch in a bubbling fluidized bed: A performance and agglomeration study. Bioresour Technol 2011;102: 2068 – 2076. [8] Mastellone M L, Zaccariello L, Arena U. Co-gasification of coal, plastic waste and wood in a bubbling fluidized bed reactor, Fuel 2010;89: 2991 – 3000. [9] Kim S W, Koo B S, Ryu J W, Lee S J, Kim C J, Lee D H, Kim G R, Choi S. Bio-oil from the pyrolysis palm and Jatropha wastes in a fluidized bed. Fuel Process Technol 2013;108: 118 –24. [10] Yang H, Yan R, Tee Liang D, Chen H, Zheng C, Pyrolysis of Palm Oil Wastes for Biofuel Production, As. J. Energy Env 2006;7(02): 315 - 323. [11] Sulaiman F, Abdullah N. Optimum conditions for maximizing pyrolysis liquids of oil palm empty fruit

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