Enhancement of Gasification Performance for Palm Oil Byproduct by

Subscriber access provided by UNIV OF LOUISIANA

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

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 20 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

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

1 2 3 4 5 6 7 8 9 10 11 12 13 14

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

15

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

16

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

17

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

18

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

19

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

20

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

21

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

22

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

23

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

24

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

25

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

26

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

27

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

28

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

29

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]

30 31 32

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

33

ACS Paragon Plus Environment

1

Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

34

Page 2 of 20

1. INTRODUCTION

35

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

36

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

37

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

38

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

39

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

40

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

41

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

42

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

43

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

44

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

45

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

46

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

47

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

48

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

49

biomass and can impede continuous operation or de-fluidization.

50

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

51

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

52

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

53

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

54

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


2

Page 3 of 20 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

55

2. MATERIALS AND EXPERIMENTAL METHODS

56

2.1 Characterization of Unwashed EFB

57

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

58

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

59

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

60

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

61

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

62

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

63

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

64

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

65

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

66

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

67

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

68

D 4809’, and ‘EA – ASTM D 5373’.

69 70

2.2 Treatment and Preparation of Washed EFBs

71

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

72

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

73

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

74

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

75

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

76

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

77

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

78

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

79

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

80

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


3

Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 4 of 20

81

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

82

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

83

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

84

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

85

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

86

analyzed using SEM with XRD.

87

∑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

91

of agglomerated particles (g).

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

92 93

2.3 Washing solution analysis for effluence and treatment

94

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

95

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

96

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

97

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

98

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

99

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

100

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

101

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

102

values were used in this study.

103 104

2.4 Process and Experimental Conditions for Gasification

105

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

106

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


4

Page 5 of 20 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

107

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

108

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

109

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

110

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

111

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

112

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

113

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

114

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


5

Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

121

3. RESULTS AND DISCUSSION

122

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

Page 6 of 20

123

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

124

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

125

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

126 127

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

128

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

131

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

132

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

133

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

134

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

135

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

136

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

137

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

138

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

139

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


6

Page 7 of 20 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

140

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

141

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

142

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

143

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

144 145

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

146

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

147

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

148

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

149

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

150

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

151

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

152

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

153

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

154

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

155

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

156

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

157

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


7

Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 8 of 20

158

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

159

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

160

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

161

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

162

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

163

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

164

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

165

166 167 168 169

Fig. 2 TG Graphs of the EFB Samples

3.2 Washing solution analysis of effluent treatment

170

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

171

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

172

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

173

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

174

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

175

neutralized to pH 6.0 (Table 4).


8

Page 9 of 20 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

176

Energy & Fuels

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

179

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

180

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

181

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

182

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

183

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

184

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

185

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

186

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

187

188 189

Fig 3. SEM Images of Agglomerated Particles in EFB Ash


9

Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 10 of 20

190 191 192 193

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

196

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

197

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

198

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

199

might also be a result of the heterogeneous EFB samples.

200

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

202

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

203

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


10

Page 11 of 20 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

204

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

205

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

206

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

207

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

208

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

209

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

210

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

211

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

212

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

213

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

214 215

3.4 Gasification of Unwashed EFB

216

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

217

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

218

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

219

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].

222

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

223

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

224

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

225

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

226

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

227

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

228

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

229

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


11

Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 12 of 20

230

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

231

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

232

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

233

234 235

Fig 5. Gas Composition at Different ER and Temperatures

236

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

237

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

238

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

239

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

240

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

241

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

242

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

243

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

244

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

245

and ER = 0.6 [27, 28].

246


12

Page 13 of 20 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

247 248

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

249

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

250

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

251

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

252 253

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)

254 255

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

256

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

257

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

258

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

259

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

260

900-1,000oC and ER = 0.6.

261

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

262

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

263

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


13

Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

264

Page 14 of 20

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

265

266 267

Fig 7. Results of Carbon Conversion and CGE

3.5 Comparison of Syngas Yields

268

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

269

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

270

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

271

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

272

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

273

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

274

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

275

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

276

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

277

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

278

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

279

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

280

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

281

(Figure 8).

282


14

Page 15 of 20 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

283 284 285

Fig 8. Changing Gas Composition with Agglomeration production

286

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

287

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

288

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

289

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

290

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

291

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

292

with nitric acid solution (Figure 9).

293

294 295

Fig 9. Carbon Conversion, CGE, and HHV


15

Energy & Fuels 1 2 3 296 4 5 297 6 7 298 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 16 of 20

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.


16

Page 17 of 20 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

299

Energy & Fuels

4. CONCLUSIONS

300

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

301

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

302

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

303

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

304

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

305

the following conclusions can be drawn:

306 307

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

308

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

309

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

310

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

311 312

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

313

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

314

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

315

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

316

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

317 318

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

319

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

320

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

321

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

322


17

Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

323

Page 18 of 20

5. ACKNOWLEDGMENTS

324

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

325

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

326

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

327 328

6. REFERENCES

329

[1] Cho Y H. Bio diesel Korea Institute of Science and Technology Information; 2005: 5 - 7.

330

[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,

331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348

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


18

Page 19 of 20 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

349 350 351 352 353

Energy & Fuels

bunches, Energy 2011;36: 2352 – 2359. [12] Cho S J. Studies on Gasification and Melting Characteristics of Waste and Biomass, Ph. D. Dissertation, Yonsei University, Korea. 2012. [13] Cuiping L, Chuangzhi W, Yanyongjie Haitao H. Chemical elemental characteristics of biomass fuels in China, Biomass Bioenergy 2004;27: 119 – 30.

354

[14] Abdullah N, Gerhauser H. Bio-oil derived from empty fruit bunches, Fuel 2008;89: 2606 – 2613

355

[15] Rafigul I S M, Mimi Sakinah A M. Design of process parameters for the production of xylose from wood

356

sawdust, Chemical Engineering Research and Design 2012;90: 1307 – 1312.

357

[16] Mourant D, Wang Z, He M, Wang X S, Garcia-Perez M, Ling K, Li C Z. Mallee wood fast pyrolysis: Effects

358

of alkali and alkaline earth metallic species on the yield and composition of bio-oil, Fuel 2011;90: 2915 – 22.

359

[17] Iwasa N, Yamane T, Arai M. Influence of alkali metal modification and reaction conditions on the catalytic

360

activity and stability of Ni containing smectite-type material for steam reforming of acetic acid, International

361

Journal of Hydrogen Energy 2011;36: 5904 –5911.

362

[18] Lee J K, Kim J H, Lee S H, Choi Y C, Kim Y K, Yoo K S, Lee S H. Development of fluidized bed reactor

363

for the pyrolysis and gasification of agricultural and forestry wastes. Korea Institute of Energy Research; 2005:

364

19 - 73.

365 366 367 368

[19] Yoo H M. A Study on Gasification Characteristics of EFB and Coal, Master Dissertation, Yonsei University, Korea. 2013. [20] Yoo H M, Lee J S, Yang W S, Choi H S, Jang H N, Seo Y C. Co-gasification characteristics of palm oil byproducts and coals for syngas production. Korean Journal of Chemical Engineering 2018;35.

369

[21] Kim J H, Kim Y H, Shin S M, Yoon J Y, Choi J H. Sitology, Intellectual: 2012, p. 24 – 7.

370

[22] Palamae S, Palachum W, Chisti Y, Choorit W. Retention of hemicellulose during delignification of oil palm

371

empty fruit bunch (EFB) fiber with peracetic acid and alkaline peroxide, Biomass Bioenergy 2014; 66: 240-8.

372

[23] Kim J R, Bae H J, Kim E H. Agglomeration and Defluidization by the Alkali Metal Compounds in a Fluidized

373 374

Bed Incinerator, J. Korea Society of Waste Management 2003;20(2): 154 – 161. [24] Mac an Bhaird S T, Walsh E, Hemmingway P, Maglinao Amado L, Capareda Sergio C, McDonnell Kevin P.


19

Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 20 of 20

375

Analysis of bed agglomeration during gasification of wheat straw in a bubbling fluidized bed gasifier using

376

mullite as bed material, Powder Technology 2014;254: 448 – 459.

377 378 379 380 381 382 383 384 385 386

[25] Bridgwater A V. Principles and practice of biomass fast pyrolysis processes for liquids. J Anal Appl Pyrol 1995;51(1): 3 - 22. [26] Bridgwater A V. Review of fast pyrolysis of biomass and product upgrading, Biomass Bioenergy 2012; 38: 68 – 94. [27] Kaewluan S, Pipatmanomai S. Gasification of high moisture rubber woodchip with rubber waste in a bubbling fluidized bed, Fuel Processing Technology 2011;92: 671 – 7. [28] Kim M J, Ryu H I, Lee W K. Coal Gasification in a Fluidized Bed at Atmospheric Pressure, Journal of the Korean Institute of Chemical Engineers 1983;21(1): 27 – 34. [29] Karatas H, Olgun H, Akgun F. Coal and coal and calcined dolomite gasification experiments in a bubbling fluidized bed gasifier under air atmosphere, Fuel Processing Technology 2013;106: 666 – 672.


20

Enhancement of Gasification Performance for Palm Oil Byproduct by

Recommend Documents