Understanding the Co-Pyrolysis Behavior of Indonesian Oil Sands and

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Understanding the co-pyrolysis behavior of Indonesian oil sands and corn straw Zisheng Zhang, Hongfei Bei, Hong Li, Xingang Li, and Xin Gao Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.6b02863 • Publication Date (Web): 27 Jan 2017 Downloaded from http://pubs.acs.org on January 30, 2017

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Energy & Fuels

1

Understanding the co-pyrolysis behavior of Indonesian

2

oil sands and corn straw

3

Zisheng Zhanga,b, Hongfei Beia, Hong Lia,c, Xingang Lia,c,d, Xin Gaoa,c*

4

a

5

P.R. China.

6

b

7

K1N 6N5, Canada

8

c

9

China.

School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072,

Department of Chemical and Biological Engineering, University of Ottawa, Ottawa

National Engineering Research Center of Distillation Technology, Tianjin, 300072, P.R.

10

d

11

Tianjin 300072, P.R. China.

Collaborative Innovation Center of Chemical Science and Engineering (Tianjin),

12 13

Abstract

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In this work, co-pyrolysis of Indonesian oil sands and corn straw was investigated to

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evaluate the potential synergetic effect. Thermogravimetric analysis (TGA) was

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conducted to study the thermal decomposition behaviors of individual and blend

17

feedstocks. Improved pyrolysis characteristics and higher conversion were observed,

18

indicating a remarkable synergetic effect. Moreover, co-pyrolysis experiments were

19

carried out using a fixed bed reactor. The results showed that the co-pyrolysis liquid

20

product yield was increased, while the formation of solid residue was reduced, suggesting

*

Corresponding author. Tel.: +86-022-27404701; Fax: +86-022-27404705. E-mail

address: [email protected] (X. Gao). 1

ACS Paragon Plus Environment

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a higher conversion. The liquid product characterization by GC-MS also indicated the

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significant synergetic effect on the liquid chemical composition. Valuable phenols and

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alcohols were increased, while unstable aldehydes were decreased, suggesting the

24

chemical interactions between two feedstocks during co-pyrolysis process. The yield

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improvement and compositional variations of the co-pyrolysis liquid product were

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beneficial for its use as fuel and chemicals feedstock.

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1. Introduction

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Oil sands, also known as tar sands, are unconsolidated deposits comprising sand,

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clays, water and bitumen, a highly viscous petroleum. The largest sources of oil sands are

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found in Canada and Venezuela.1 The total recoverable oil sands deposit in Canada is

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even larger than Saudi Arabia’s established oil reserve.2 The commonly used processes to

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separate bitumen from sand grains include hot water extraction, solvent extraction and

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pyrolysis. The large-scale commercially applied hot water extraction process showed

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great success in the last century in Canada. However, both the large consumption of water

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and the treatment of toxic tailing ponds have limited its further utilization.1 Solvent

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extraction process achieves relatively high bitumen recovery efficiency and reduces

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water and energy consumption, but it’s not recommended because of the involvement of

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expensive, volatile, flammable and toxic organic solvents. Pyrolysis is an alternative

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method to recover bitumen from oil sands. Pyrolysis can be defined as a thermal

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decomposition process, where the material is heated and kept at a high temperature

41

(normally 400 ℃ -600 ℃ ) in the absence of oxygen. The volatiles in the material

42

decomposes

into

lighter

compounds,

generating

tar

2


(after

condensation),

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non-condensable gas and residue char. During oil sands pyrolysis, bitumen cracks into

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smaller hydrocarbons, forming tar, gas and solid residue product, which are both valuable

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fuel and chemicals source. Pyrolysis process of oil sands requires no water or solvent

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consumption and produces no pollution. However, the formation of chars during the

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pyrolysis process reduces the conversion of bitumen. The pyrolysis oil contains

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significant amounts of heavy hydrocarbons and further upgrading process is needed.

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Another disadvantage is that the sand grains absorb a large amount of heat during

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pyrolysis. Though the high temperature sands can be used as heat carrying agent to

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preheat the feedstock or the carrier gas, the heat loss is not neglectable.

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Biomass is the world’s largest sustainable energy resource attracting ever-growing

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attentions of researchers. Approximately 220 billion tons of dry biomass is produce

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worldwide annually,3 providing the world with an alternative to fossil fuels. The

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utilization methods of the valuable biomass have been investigated intensively in recent

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years. Pyrolysis process shows some advantages both environmentally and technically

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compared to other biomass processes such as direct combustion and gasification.4 One of

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the most important advantages is that the main product liquid fuel, also called bio-oil, can

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be easily stored and transported. Additionally, the pyrolysis products bio-oil, char and

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gases are not only fuels but also source of valuable chemicals. Bio-oil has some

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environmental advantages since it’s renewable and carbon-neutral. However, it also

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shows several disadvantages for its application as fuel directly, such as high viscosity,

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high water content, corrosiveness, high oxygen content and chemical instability.5 The

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upgrading of bio-oil is necessary and an increasing number of methods have been 3


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investigated including hydrotreating, esterification and reactive distillation.6

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Recent studies have shown that the co-pyrolysis of biomass and fossil fuels or

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fossil-based wastes was beneficial for upgrading of the pyrolysis oil. Biomass and fossil

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fuels or fossil-based wastes, as carbonaceous materials, have different chemical

69

compositions and physical properties, such as atomic H/C ratio, volatiles composition,

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ash composition, porosity, density, etc. Those variations could result in distinct thermal

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decomposition behaviors and potential chemical interactions during co-pyrolysis of

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different feedstocks. As the hydrogen-donor, biomass can release much more H and OH

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radicals during co-pyrolysis process, which may promote chemical interactions between

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both feedstocks, resulting in variations in product distributions and compositions.7-11

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Meanwhile, the existence of different alkali and alkaline earth metals (AAEMs) in

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biomass and fossil fuels or fossil-based wastes may have a catalytic effect, facilitating the

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chemical interactions in further.12,

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fossil-based wastes may improve the quality of pyrolysis oil, such as lower oxygen

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content, lower water content and increased valuable chemicals content.14-16 Yang et al. 7

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investigated the co-pyrolysis of lignite and biomass (rice husk) in a vacuum fixed bed

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reactor with high temperature (900℃), low heating rate (10℃/min) and long contact time

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(more than 2 h). Distinct variations were observed in the respect of product yields, char

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structure and tar composition, which indicated a remarkable synergetic effects during the

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co-pyrolysis of lignite and biomass. Meng et al.

85

platanus wood and lignite in a drop tube fixed bed reactor under nitrogen atmosphere.

86

There was evident change in the product yields, gas components and char surface

13

Co-pyrolysis of biomass and fossil fuels or

17

studied the co-pyrolytic behavior of

4


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morphology, which was attributed to the secondary reactions and tar cracking during

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co-pyrolysis. The co-pyrolysis of biomass and waste tires was also investigated and

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evident synergetic effect was found.18, 19 The results showed that the addition of waste

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tires on biomass in the co-pyrolysis process had significant effects on product

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distributions, bio-oil compositions and physico-chemical properties when compared with

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the pyrolysis of biomass.

93

However, the findings were controversial since some studies indicated no evident

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synergetic effect in the co-pyrolysis of biomass and fossil fuels or fossil-fuel based wastes.

95

Masnadi et al.

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(sub-bituminous coal or fluid coke) pyrolyzed almost independently in their blended

97

mixtures through co-pyrolysis thermogravimetric analysis. Idris et al.

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co-pyrolysis of sub-bituminous coal and oil palm biomass using thermogravimetric

99

analysis. The results showed that the thermal profiles of coal and oil palm biomass blends

100

appeared to correlate with the percentage of biomass added in the blends, thus, suggesting

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lack of interaction between coal and oil palm biomass. Meesri et al.

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co-pyrolytic behaviors of coal and woody biomass (pine sawdust) under both low and

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high heating rate conditions. Results showed that the yields of pyrolysis products and

104

compositions of the gaseous products from blended samples were linearly proportional to

105

those of their parent feedstocks, indicating that the two feedstocks underwent

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independent thermal conversion without any chemical interactions. Researchers also

107

found that the differences of pyrolysis conditions (temperature, heating rate, pressure,

108

contact time, etc.), reactor types and feedstock types employed in those studies might

20

found that biomass (switchgrass or pine sawdust) and fossil fuel

5


22

21

studied the

investigated the

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determine whether the synergetic effects were observed.23

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Although co-pyrolysis of biomass and coal or waste tires has been studied

111

extensively, few researches about the co-pyrolysis of oil sands and biomass were reported.

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In this study, co-pyrolysis of oil sands from Indonesia and biomass (corn straw) was

113

studied to evaluate the synergetic effect on product yield and quality improvement. In the

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first place, the thermogravimetric analysis (TGA) was carried out to investigate the

115

thermal decomposition behavior and determine the potential temperature interval where

116

simultaneous devolatilisations of both feedstocks take place. Secondly, a laboratory-scale

117

fixed bed reactor was applied to carry out the co-pyrolysis process using four different

118

pyrolysis methods and the operating conditions were then optimized. Finally, the yield

119

distributions and the compositions of co-pyrolysis products were determined to

120

demonstrate the existence of the synergetic effect during co-pyrolysis of oil sands and

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corn straw.

122

2. Experimental section

123

2.1 Raw materials

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Oil sands from Buton, Indonesia and corn straw from rural area of Tianjin, China

125

were used in this study. Both materials were crushed into fine powders less than 0.8 mm

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and dried at 105℃ for 6 h prior to experiments. The ultimate analysis of both materials

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was carried out in an Elementar Vario MICRO Cube for carbon, hydrogen, nitrogen and

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sulphur (CHNS) contents. The proximate analysis of both materials was conducted

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according to National Standard of China (GB/T 212-2008) for the moisture, ash, volatile

130

matter and fixed carbon contents. The lignocellulosic compositions (i.e., extractives, 6


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lignin, hemicelluloses and cellulose) of corn straw were determined according to Li’s

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method.24 Inorganic elemental compositions of both materials were determined by X-ray

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fluorescence (XRF), which was performed using a wavelength dispersive spectrometer

134

S4 Pioneer (Bruker AXS). The raw materials characterization results were listed in Table

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1.

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2.2 Thermogravimetric analysis (TGA)

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To study the thermal decomposition behavior of each feedstock and their blends on

138

different heating rates (5℃/min,10℃/min and 20℃/min) and different blending ratios

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(25 wt.%, 50 wt.% and 75 wt.% of corn straw), the pyrolysis was firstly carried out in a

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thermogravimetric analyzer (Thermal Analysis Q500) under a N2 flow rate of 50 mL/min.

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The sand of Indonesian oil sands is mainly composed of CaCO3, which starts to

142

decompose at 600℃.25 Therefore the final temperature was set at 550℃. In a typical

143

experiment, the sample (20mg) was distributed evenly in an alumina crucible and placed

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in the thermogravimetric analyzer. Each sample was heated from ambient temperature to

145

550℃ under the heating rate of 5℃/min,10℃/min or 20℃/min. The solid weight loss

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and the temperature at which the sample started to decompose were determined.

147

2.3 Pyrolysis in a fixed bed reactor

148

The pyrolysis experiments were conducted in a laboratory-scale fixed bed reactor.

149

The schematic diagram of the experimental system was shown in Figure 1. The horizontal

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sealed fixed bed cylindrical reactor tube had an internal diameter of 50 mm and a length

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of 500 mm. The fixed bed reactor tube contained a hollow half cylindrical drawer with a

152

length of 450 mm, allowing the samples to be spread flat when the drawer was charged 7


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into the reactor tube. The reactor tube was heated externally by an electric heating

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element of a temperature programmed furnace and the temperature was measured by a

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thermocouple inside the reactor tube. The inlet and the outlet of the reactor tube were

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connected to a carrier gas preheater and a cooling unit respectively. Gas and volatiles

157

formed during pyrolysis flowed out from the outlet, then crossed through the cooling unit

158

which was comprised of a round-bottomed flask and two glass condensers cooled with

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the circulation of water glycol using a cryostat at approximately -4℃. The liquid product

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was then condensed and collected in the flask. There were also tars condensed on the

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cooling unit since the tar had a relatively high viscosity. Therefore, dichloromethane

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(weighed and recorded as Mdcm) was used as solvent to wash the tars on the cooling unit.

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The liquid we finally collected (weighed and recorded as Mt) from the flask contained tar

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(liquid product) and dichloromethane. The weight of the liquid product (Mliquid) could be

165

calculated by Eq (1).

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M liquid = M t − M dcm

(1)

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where Mliquid is the weight of the liquid product, Mt is the total weight of the liquid product

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and dichloromethane we collected from the flask, and Mdcm is the weight of

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dichloromethane we used to wash the cooling unit.

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The non-condensable gas was collected in a gas bag connected to the end of the condenser.

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When the reactor tube reached ambient temperature inside after each pyrolysis run, the

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solid residue product (char) was collected, weighed and recorded as Msolid. The weight of

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gaseous product was obtained by difference using Eq (2).

174

M gas = M F − M liquid − M solid 8


(2)

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where Mgas is the weight of the gaseous product, MF is the initial weight of the feedstock,

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Mliquid is the weight of the liquid product, and Msolid is the weight of the solid residue

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product.

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In order to achieve a relatively high conversion of the feedstocks, the pyrolysis

179

experiments were first conducted using four different pyrolysis methods, i.e., retorting,

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pyrolysis under N2, vacuum pyrolysis and closed vacuum pyrolysis. For each pyrolysis

181

method, three pyrolysis experiments, i.e., individual corn straw and oil sands pyrolysis

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and co-pyrolysis of the mixture (50 wt.% of corn straw), were investigated. The samples

183

were heated from room temperature to the final temperature of 550℃ at 10 ℃/min and

184

then kept at 550℃ for 30 min.

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During the retorting process, the valve between the preheater and the reactor tube

186

was closed and the produced vapors flowed out spontaneously under no carrier gas.

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During the pyrolysis under N2, the valve between the preheater and the reactor tube was

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opened and N2 was introduced into the reactor tube as inert gas at a flow rate of 0.1 L/min

189

constantly. The vapors produced during pyrolysis were swept out of the reactor tube by

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N2. During vacuum pyrolysis process, the valve between the preheater and the reactor

191

tube was closed and a vacuum pump was connected to the end of the cooling unit. The

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absolute pressure inside the reactor tube was kept 0.005 MPa as the vacuum pump

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working constantly. During closed vacuum pyrolysis process, N2 was firstly used to purge

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air in the reactor tube providing an oxygen-free atmosphere and N2 was then removed by

195

the vacuum pump. The initial absolute pressure inside the reactor tube was kept 0.005

196

MPa. Then the valve between the reactor tube and the cooling unit was closed to keep the 9


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197

reactor tube closed during the whole pyrolysis process and it was opened after pyrolysis

198

to pump the volatile products out for 30 min. The liquid product yield using each

199

co-pyrolysis method was then calculated and compared with each other.

200

The pyrolysis operating conditions were further optimized in order to achieve higher

201

liquid product yield and evident synergetic effect. The pyrolysis operating conditions

202

studied were heating rate (5, 10 and 20 ℃/min), absolute pressure (0.005, 0.02, 0.04,

203

0.06, 0.08 and 0.1 MPa) and nitrogen flow rate (0.1, 0.2, 0.4, 0.6, 0.8 and 1 L/min). The

204

investigation was also focused on the feedstock mixing ratios (corn straw mass fraction of

205

25%, 50% and 75%, named acronym C25, C50 and C75).

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Each pyrolysis experiment was conducted in triplicates in order to confirm

207

reproducibility and the value reported for each yield was the average of three equivalent

208

runs with its absolute error. In order to find whether the synergetic effect existed, the

209

experimental values were compared with the calculated values.

210

2.4 Characterization of pyrolysis products

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2.4.1 Liquid product characterization

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Fractionation. The liquid products obtained from individual pyrolysis and

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co-pyrolysis contained two phases: an oil phase and an aqueous phase. In a typical

214

experiment, the liquid product collected in the flask was firstly washed using

215

dichloromethane, then the oil phase was separated from the aqueous phase using a

216

separating funnel. After distillation of dichloromethane at 65℃, the oil phase was

217

obtained and weighed. Dichloromethane had medium polarity (3.4) and its low boiling

218

point (39.8℃) made it easier to remove with lower loss of light compounds. It should be 10


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mentioned that there were not only dichloromethane-soluble organic compounds (DCM)

220

in the oil phase, but also some entrained high molecular weight compounds (HM). To

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understand the distribution of water and HM, the liquid product was fractionated into

222

several groups using a simplified method based on Oasmma’s method.26 The oil phase

223

was firstly extracted by Soxhlet extraction using dichloromethane as solvent for 8 h to

224

separate DCM from entrained HM. After evaporation of dichloromethane, the extracted

225

fraction DCM was weighed and the weight difference of dried filter paper thimble was

226

regarded as the weight of HM. The total weight of HM and DCM was lower than that of

227

the initial oil phase, which was caused by the evaporation of low boiling point

228

compounds (LB) and the difference was regarded as the weight of LB. The aqueous phase

229

consisted of mainly water and a small number of water-soluble organic compounds. The

230

aqueous phase was weighed and its water content was measured by Karl-Fischer titration,

231

then the weights of water and water-soluble organics could be calculated separately. The

232

liquid product was therefore fractionated into five groups, i.e., water, water-solubles, LB,

233

DCM and HM. The fractionation method was shown in Figure 2.

234 235

CHNO Analysis. Elemental analysis of the oil phases was performed with an Elementar Vario MICRO Cube to obtain CHNO contents.

236

GC-MS Analysis. The chemical compositions of the oil phase samples were

237

determined using the gas chromatography mass spectrometry (GC-MS). The oil phase

238

samples were diluted with dichloromethane to a ratio of 1:100, then dried with anhydrous

239

sodium sulphate and filtered by 0.45 µm PTFE filter. GC-MS analysis was carried out on

240

an Agilent 7890A GC System equipped with an Agilent 5975C Mass Selective Detector 11


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and an Agilent 7683B autosampler. The column used was HP-5MS capillary column

242

(30m×0.25mm×0.25µm). Helium was employed as the carrier gas at a constant flow rate

243

of 1.0 mL/min at a split ratio of 100:1. A sample of 0.2 µL was injected. The initial oven

244

temperature was maintained at 50℃ for 3 min and programmed to increase at 15℃/min

245

to 280℃ (held for 5 min). The temperatures of the injector, the ion source and the MS

246

transfer line were kept constant at 300℃, 230℃ and 260℃ respectively. The solvent

247

delay was set at 2 min. The ionization mode of MS was EI and the ionization voltage was

248

70 eV. The voltage applied to the multiplier detector was 2059 V and an m/z from 30 to

249

550 was scanned. The identification of main compounds in oil phases was based on

250

computer matching of the mass spectra with the NIST library database.

251

HHV Determination. The higher heating values (HHV) of co-pyrolysis and

252

individual pyrolysis oil phase samples were measured using an automated oxygen bomb

253

calorimeter (Shicheng SCLR-5000A, China).

254

2.4.2 Gaseous product characterization

255

The major constituents of gaseous products (H2, CO, CH4 and CO2) obtained from

256

individual pyrolysis and co-pyrolysis were determined using a Perkin-Elmer AutoSystem

257

XL gas chromatograph (GC) equipped with a carbon molecular sieve packed column

258

(TDX-01) and a thermal conductivity detector (TCD). Helium was used as the carrier gas

259

to analyze the content of CO, CH4 and CO2. The oven temperature was kept 90℃ for 14

260

minutes. The injector and detector temperatures were set at 120 ℃ and 150 ℃

261

respectively. Nitrogen was used as the carrier gas to analyze the content of H2 in which

262

the oven, injector and detector temperatures were 170℃ (7 minutes), 80℃ and 170℃ 12


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respectively.

264

2.4.2 Solid residue product characterization

265

The elemental analysis of the solid residue products from individual pyrolysis and

266

co-pyrolysis was conducted by an Elementar Vario MICRO Cube for CHNS contents.

267

The proximate analysis of the solid residue products was carried out according to

268

National Standard of China (GB/T 212-2008) for the moisture, ash, volatile matter and

269

fixed carbon contents. HHV determination of the solid residue products was conducted

270

using an automated oxygen bomb calorimeter (Shicheng SCLR-5000A, China).

271

2.5 Calculation method

272

The weights of liquid, gaseous and solid residue products in the fixed bed reactor

273

pyrolysis were recorded as M liquid , M gas and M solid respectively. The yields of liquid,

274

gaseous and solid residue products in all pyrolysis experiments were calculated by Eq (3).

275

Yi =

Mi ×100% MF

(3)

276

where Yi is the yield of i (liquid, gas and solid) in pyrolysis, Mi is the weight of i

277

(liquid, gas and solid), and MF is the initial weight of the feedstock.

278

In thermogravimetric analysis, calculated thermogravimetric (TG) curve of mixed

279

sample was obtained by Eq (4). Differential thermogravimetric (DTG) curves of all

280

samples were obtained by taking the derivative of corresponding TG data.

281

Wcalc = WOS (1 − α ) + WCSα

(4)

282

where Wcalc is the calculated sample weight at each temperature point, WOS is the

283

sample weight at each temperature point in individual oil sands TG analysis, WCS is the

284

sample weight at each temperature point in individual corn straw TG analysis, and α is 13


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the mass fraction of corn straw in the initial sample.

286

Calculated product yields and calculated product properties or component

287

percentages in co-pyrolysis were used to evaluate the synergetic effect, which were

288

calculated by Eqs (5-6).

289

Ycalc,i = YOS ,i (1 − α ) + YCS ,iα

290

Pcalc,i =

(5)

POS ,iYOS ,i (1 − α ) + PCS ,iYCS ,iα YOS ,i (1 − α ) + YCS ,iα

(6)

291

where Ycalc,i is the calculated yield of i (liquid, liquid fractions, gas and solid) in

292

co-pyrolysis, YOS ,i is the yield of i (liquid, liquid fractions, gas and solid) in oil sands

293

pyrolysis, YCS ,i is the yield of i (liquid, liquid fractions, gas and solid) in corn straw

294

pyrolysis, Pcalc ,i is the calculated product property or component percentage of i (liquid

295

or gas component) in co-pyrolysis, POS ,i is the product property or component

296

percentage of i (liquid or gas component) in oil sands pyrolysis, PCS ,i is the product

297

property or component percentage of i (liquid or gas component) in corn straw pyrolysis,

298

and α is the mass fraction of corn straw in the feedstock.

299

3. Results and discussion

300

3.1 Thermogravimetric analysis

301

The TG and DTG curves of Indonesian oil sands, corn straw and their blends with

302

different blending ratios (25 wt.%, 50 wt.% and 75 wt.% of corn straw) at 10℃/min were

303

shown in Figure 3 and Figure 4 respectively. Two steps can be distinguished for

304

individual Indonesian oil sands pyrolysis based on the TG and DTG curves. The first step

305

was a small weight loss due to the evaporation of moisture and light hydrocarbons at

306

about 150℃. The second step of weight loss between 300℃ and 500℃ was caused by 14


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the main thermal decomposition of bitumen,27 during which the weight loss was about

308

21wt.% from TG curve and the maximum rate of weight loss occurred at about 460℃

309

from DTG curve. On the other hand, the thermal decomposition of corn straw mainly

310

took place in two steps: first step of moisture evaporation at about 100℃ and second step

311

of organic compounds decomposition between 200℃ and 500℃. The second step of

312

decomposition was a combination of degradation of three major chemical constituents of

313

biomass. Hemicellulose decomposition occurred firstly between 200 ℃ and 260 ℃ ,

314

followed by cellulose decomposition between 240℃ and 350℃. The lignin decomposed

315

from 260℃ and lasted for a wide temperature range until 500℃.28

316

The temperature ranges for the thermal decomposition of individual corn straw and

317

oil sands overlapped at 300-500℃, during which the released radicals could coexist and

318

possibly interact. To evaluate the synergetic effect of co-pyrolysis, the experimental DTG

319

curve of blends was compared with the calculated DTG curve. The experimental and

320

calculated DTG curves of co-pyrolysis with 50 wt.% of corn straw at different heating

321

rates (5 ℃ /min,10 ℃ /min and 20 ℃ /min) were also shown in Figure 5. Both the

322

experimental and the calculated DTG curves had similar trends and showed two peaks

323

around the temperature ranges of 250-380℃ and 400-500℃ which were attributed to

324

the decomposition of bitumen of oil sands and organic compositions of corn straw

325

respectively. As seen from Figure 4 and Figure 5, the experimental peak temperatures

326

corresponding to the maximum weight loss rates of two peaks were decreased about 5℃

327

-10℃ compared to the calculated data, indicating improved pyrolysis characteristics at

328

different heating rates and blending ratios. Moreover, the experimental DTG curves of 15


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329

co-pyrolysis showed higher rates of weight loss than the calculated values between 250℃

330

and 450℃, which was consistent with the yield increase of volatile matters from the

331

experimental TG curve of co-pyrolysis. The differences between the experimental and

332

calculated DTG curves at different heating rates and blending ratios could be explained

333

by the catalytic effect caused by the radicals and AAEMs in biomass. The results of TGA

334

showed the existence of remarkable synergetic effect in co-pyrolysis of oil sands and corn

335

straw.

336

3.2 Co-pyrolysis product yields in a fixed bed reactor

337

3.2.1 Product yields using different co-pyrolysis methods

338

The co-pyrolysis product distributions using four different pyrolysis methods were

339

shown in Figure 6. Vacuum pyrolysis and pyrolysis under N2 showed higher liquid

340

product yields which were 33.9 wt.% and 32.6 wt.% respectively, while their gaseous

341

product yields were lower which were 14.9 wt.% and 15.0 wt.% respectively. Retorting

342

and closed vacuum pyrolysis showed lower liquid product yields of 26.4 wt.% and 18.4

343

wt.% respectively, while they showed higher gaseous product yields which were 19.0 wt.%

344

and 24.8 wt.% respectively. It should be noted that since the high value and the

345

convenience in storage and transportation, liquid product was preferred over gaseous

346

product. Vacuum pyrolysis and pyrolysis under N2 also showed relatively lower solid

347

residue product yields (51.3% and 52.3% respectively) than retorting and closed vacuum

348

pyrolysis (54.6% and 56.9% respectively), indicating higher volatile matters conversions.

349

The large differences in product distributions using different pyrolysis methods were

350

mainly attributed to their different vapor residence times which were the critical factor. 16


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Short vapor residence time could reduce secondary cracking reactions and avoid the

352

cracking of volatile matters into non-condensable gases. The vapor residence time in

353

vacuum pyrolysis was the shortest among the four cases and the vacuum pressure also

354

created a favorable condition for the organics to evaporate, leading to the highest liquid

355

product yield. The N2 sweeping could also reduce the vapor residence time and avoid

356

secondary cracking reactions effectively. However, the vapor residence time was long in

357

atmospheric retorting and even much longer in the closed vacuum pyrolysis, resulting in

358

secondary cracking of volatile matters and producing more gases and chars. It was also

359

worth mentioning that the experimental liquid product yields were mostly higher than the

360

calculated values, especially in the cases of vacuum pyrolysis and pyrolysis under N2,

361

suggesting the synergetic effect in co-pyrolysis.

362

In summary, vacuum pyrolysis and pyrolysis under N2 showed significant

363

advantages over other methods. Since the use of vacuum pump at the end of the cooling

364

system in vacuum pyrolysis limited the collection of non-condensable gases for further

365

compositional analysis, the pyrolysis under N2 was selected as the co-pyrolysis method

366

for product distribution analysis and product chemical characterization.

367

3.2.2 Optimization of co-pyrolysis operating conditions

368

To obtain higher liquid product yield and more remarkable synergetic effect, the

369

pyrolysis operating conditions in vacuum pyrolysis and pyrolysis under N2 were further

370

optimized and the results were shown in Figure 7. In the case of pyrolysis under N2, the

371

optimized conditions were a heating rate of 10℃/min, a corn straw mass fraction of 50%

372

and a N2 flow rate of 0.1 L/min. For vacuum pyrolysis, the optimized conditions were a 17


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373

heating rate of 10℃/min, a corn straw mass fraction of 50% and an absolute pressure of

374

0.005 MPa.

375

As known high heating rates and short vapor residence times were favorable for

376

improving the liquid yield, since secondary cracking reactions of volatiles into gas

377

product fraction could be minimized in that case. However, from Figure 7 (a) and (d), the

378

highest liquid product yields occurred at the intermediate heating rate of 10℃/min. This

379

was because that in a batch pyrolysis process, higher heating rates shortened the time to

380

reach the desired temperature (550℃) and the total reaction time was reduced, thus fewer

381

liquid products could yield. Therefore the highest liquid yields occurred at the

382

intermediate heating rate of 10℃/min. From Figure 7 (b) and (e), the co-pyrolysis with

383

corn straw mass fraction of 50% showed the most remarkable synergetic effect. When the

384

corn straw mass fraction was 25%, the number of radicals in corn straw was relatively

385

inadequate. While when the corn straw mass fraction was 75% and the radicals were

386

sufficient, the low content of bitumen limited the increasing space of liquid product yield

387

and it was also highly possible that those unstable radicals reacted with each other.29

388

Hence the co-pyrolysis with corn straw mass fraction of 50% showed the most

389

remarkable liquid product yield growth. For pyrolysis under N2, Figure 7 (c) showed that

390

the sweeping effect of N2 shortened the vapor residence time and improved the liquid

391

yield remarkably compared with retorting (N2 flow rate of 0). However, as the increase of

392

the flow rate, the liquid yield decreased because high flow rates lowered the partial

393

pressure of volatiles, making their condensation more difficult. Thus, a relatively low

394

flow rate (0.1 L/min) showed the highest liquid product yield. For vacuum pyrolysis, 18


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Energy & Fuels

395

Figure 7 (f) showed that low absolute pressure could shorten the vapor residence time and

396

lower the boiling point of organics. Hence, the highest liquid yield was observed at the

397

lowest absolute pressure of 0.005 MPa.

398

3.3 Product distribution and characterization

399

3.3.1 Product distribution

400

For pyrolysis under N2, the product distribution and compositional analysis were

401

investigated. Figure 8 illustrated the product yield distribution of the individual pyrolysis

402

and co-pyrolysis (C25, C50 and C75). The results were the average values of three

403

repetitions with relative errors. The co-pyrolysis liquid product yields of C25, C50 and

404

C75 were 24.7±1.3 wt.%, 32.6±1.2 wt.% and 37.5±0.9 wt.% respectively, which were

405

3.4%, 8.2% and 2.7% higher than the calculated values relatively. The remarkable

406

increase of liquid product yield indicated the existence of synergetic effect during

407

co-pyrolysis. The gaseous product yields in three co-pyrolysis cases were 11.1±1.3 wt.%,

408

15.0±0.8 wt.% and 20.0±1.1 wt.% respectively, which were slightly lower than the

409

calculated values. The solid residue product yields of C25, C50 and C75 were 64.2±1.2

410

wt.%, 52.3±1.8 wt.% and 42.5±0.9 wt.% respectively. They were all decreased compared

411

to the calculated values, implying that higher conversion was achieved by blending the

412

feedstocks. Corn straw was a great hydrogen source due to its high hydrogen content and

413

a large number of H and OH radicals were generated during the co-pyrolysis process.

414

Radicals and AAEMs in corn straw facilitated the cracking of bitumen and reduced the

415

formation of char, leading to a higher liquid product yield.

416

3.3.2 Liquid product characterization 19


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417

Fractionation. The yields of liquid fractions on a feedstock basis were obtained. In

418

the individual oil sands and corn straw pyrolysis, water yields were 1.35% and 13.15%

419

respectively. While the moisture contents in the oil sands and corn straw feedstocks were

420

1.22% and 4.41% respectively. The water content of bio-oil increased largely compared

421

to the feedstock, indicating that the water in corn straw pyrolysis liquid was mostly

422

generated in the pyrolysis reactions. Water was immiscible with oil sands pyrolysis liquid

423

since the latter was mainly hydrocarbons. Bio-oil contained many polar hydrophilic

424

compounds and it could dissolve some water. In the C25, C50 and C75 co-pyrolysis,

425

water yields were 4.35%, 6.88% and 9.67% respectively, all lower than the calculated

426

values which were 4.50%, 7.38% and 10.27% respectively. The reduction of water

427

content was preferred since the existence of water lowered the heating value of oil. The

428

yields of water-solubles in co-pyrolysis stayed approximately the same as the calculated

429

values. The total yields of DCM and LB were 18.35%, 23.04% and 24.00% in C25, C50

430

and C75 respectively, much higher than the calculated values which were 17.32%, 19.92%

431

and 22.53% respectively. Moreover, the HM yields in co-pyrolysis were lower than the

432

calculated values, meaning that fewer heavy compounds and more light compounds were

433

obtained in the co-pyrolysis liquids. This could be explained by the catalytic effect of

434

AAEMs on the cracking of heavy compounds. The results showed that as fuel, the

435

pyrolysis oil achieved higher quality since the generation of more light compounds.

436

CHNO Analysis. The elemental (CHNO) analysis result of oil phase samples was

437

given in Table 2. The co-pyrolysis oil showed a decrease of oxygen content compared to

438

individual pyrolysis oil, suggesting an oxygen removal due to the synergetic effect. The 20


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439

atomic H/C ratio of co-pyrolysis oil phase increased obviously compared with the

440

individual pyrolysis oil, indicating a remarkable improvement of oil quality after

441

co-pyrolysis process. The reduction of oxygen content and the increase of atomic H/C

442

ratio might be caused by some decarbonylation reactions and catalytic hydrogenation

443

reactions which needed to be further studied.

444

GC-MS Analysis. Chemical compositions of oil phase samples from individual

445

pyrolysis and co-pyrolysis were analyzed by means of GC-MS and more than 120

446

compounds were identified. Table S1 in the Supporting Information showed the main

447

identified compounds with their relative peak areas in each oil phase sample. It can be

448

observed that the pyrolysis oil from oil sands was composed mainly of aliphatic, alicyclic

449

and aromatic hydrocarbons. The most abundant compounds in the pyrolysis oil from oil

450

sands

451

1,2,3-trimethylbenzene and 2-methylnaphthalene. However, only a very small number of

452

hydrocarbons were detected in bio-oil, which was dominated by oxygenated compounds

453

like phenols, furans, ketones and aldehydes. The main compounds present in bio-oil

454

included phenol, 4-ethylphenol, 2,3-dihydrobenzofuran, 2,6-dimethoxyphenol and

455

2-methoxy-4-vinylphenol. In the cases of co-pyrolysis (C25, C50 and C75), considerable

456

hydrocarbons and oxygenated organic compounds could be both identified depending on

457

the blend ratio.

were

o-xylene,

1-methyl-1-phenyl-2-cyclopropene,

1-methylnaphthalene,

458

To better understand the pyrolysis oil compositions, the detected compounds were

459

classified into several groups, i.e., aliphatic hydrocarbons, alicyclic hydrocarbons,

460

aromatic hydrocarbons, carboxylic acids, ketones, aldehydes, alcohols, furans, phenols, 21


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461

esters, ethers, amines, amides, S-heterocyclic compounds and others. The percentage

462

contents of component types were shown in Figure 9. In order to evaluate the synergetic

463

effect, calculated values were given. Aliphatic, alicyclic and aromatic hydrocarbons

464

comprised over 93% of oil sands pyrolysis oil, while less than 2% of hydrocarbons were

465

identified in bio-oil. Most of the identified compounds in bio-oil were phenols (about

466

50%), which were mostly formed from the decomposition of lignin. This result was in a

467

good agreement with previous studies.30-32 Bio-oil also contained 19.3% of ketones and

468

aldehydes, 10.3% of furans, 6.2% of esters and 4.1% of alcohols. The composition of

469

co-pyrolysis oil was similar with those from their parents in chemical family, but the

470

concentration was different due to the synergetic effect. More phenols were produced in

471

co-pyrolysis (C25, C50 and C75) compared with the calculated values. This phenomenon

472

could also be found in Table S1 in the Supporting Information. The relative areas of main

473

phenolic compounds (phenol, 4-ethylphenol, 2-methoxyphenol, 4-methylphenol, etc.)

474

showed an increase in co-pyrolysis. This suggested that the synergetic effect promoted

475

the decomposition of lignin and more phenols were generated. Besides of the promotion

476

of lignin decomposition, the synergetic effect might selectively promote the degradation

477

of cellulose and hemicellulose, which was also a pathway for phenols generation.33

478

Phenols were excellent feedstock for resin production and phenolic derivatives could be

479

used as flavors in the food industry.34 A significant enhancement in alcohols was also

480

observed in Figure 9. Alcohols were widely used in the production of medicine, detergent

481

and wine. The higher yields of valuable phenols and alcohols in co-pyrolysis oil revealed

482

the quality improvement of oil caused by the synergetic effect. Moreover, the relative 22


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Energy & Fuels

483

areas of ketones and aldehydes in C25, C50 and C75 were decreased about 1.7%, 2.1%

484

and 3.3% respectively, compared to the calculated values. Ketones and aldehydes were

485

known to be primary decomposition products of cellulose and hemicellulose. The

486

co-existence of P, Cl, and Ni from corn straw and oil sands acted as catalyst and aided

487

more decarbonylation reactions of ketones and aldehydes,35, 36 producing CO at the same

488

time.37 It should be noted that the highly reactive aldehydes could lead to secondary

489

degradation reactions of oil compositions and they were undesired for the stability of oil.

490

The addition of oil sands in co-pyrolysis decreased the content of aldehydes, indicating

491

that the synergetic effect was beneficial for improving the stability of oil. The total

492

amount of oxygenated compounds was also lower, which was consistent with the oxygen

493

reduction shown by the elemental analysis result.

494

HHV Determination. The HHV determination results of co-pyrolysis and individual

495

pyrolysis oil phase samples were listed in Table 2. The HHVs of commercial heavy fuel

496

oil and bio-oil were also given in Table 2. As shown the individual corn straw pyrolysis

497

oil had a low HHV due to the high oxygen content, which limited its use as fuel directly.

498

The co-pyrolysis oils (C25, C50 and C75) showed higher HHVs than expected, which

499

was mainly because of the decrease of oxygen content and the increase of hydrocarbons

500

in co-pyrolysis oils. This result indicated that the synergetic effect of co-pyrolysis was

501

beneficial for the co-pyrolysis oil to be used as fuel.

502

3.3.3 Gaseous product characterization

503

The volume percentages of H2, CO, CH4 and CO2 of gaseous products determined

504

using GC were given in Figure 10. The total amount of CO and CO2 was 75.04% in gas 23


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

505

obtained from corn straw pyrolysis. The carbon oxides were dominant in gas because

506

lignocellulosic biomass was rich in oxygen content, showing a good agreement with

507

previous study.38 However, the gas produced from oil sands pyrolysis was mainly

508

composed of H2 and CH4. After co-pyrolysis, CO and CO2 contents increased whereas H2

509

and CH4 contents decreased. The increase of CO and CO2 was due to the promoted

510

decarbonylation and decarboxylation reactions respectively, which were caused by the

511

catalytic effect of AAEMs. The increase of oxygen in co-pyrolysis gases was in

512

accordance with the reduction of oxygen content of co-pyrolysis oil samples. However,

513

H2 and CH4 components were the main contributors to heating value and their reduction

514

resulted in a lower heating value of the co-pyrolysis gas.

515

3.3.4 Solid residue product characterization

516

The pyrolysis solid residues had a wide range of applications, such as fuel, absorbent

517

and feedstock for value-added chemicals production.39 For application as solid fuels, it

518

was necessary to the evaluate the quality of the solid residue by determining its proximate

519

analysis, elemental analysis and HHV. Table 3 showed the proximate analysis, elemental

520

analysis and HHV determination results of the solid residue products. The data of some

521

other commercial solid fuels40-43 were also given for comparison. No major differences

522

were found of the synergetic effect on the CHNS contents of solid residues. From the

523

proximate analysis results, it showed that the ash content of solid residue from the

524

individual oil sands pyrolysis was high since the large concentration of sands (calcium)

525

within oil sands. The high content of ash decreased the energy density of solid fuels,

526

which explained the low HHV of oil sands solid residue. The experimental proximate 24


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Energy & Fuels

527

analysis of co-pyrolysis (C25, C50 and C75) solid residues were close to the calculated

528

values, only relatively lower ash contents, higher fixed carbon contents and higher HHVs

529

were found, suggesting that the synergetic effect on solid residues was not significant. In

530

addition, the HHVs of co-pyrolysis solid residues were much lower than the commercial

531

solid fuels like lignite and charcoal because of the high ash content of oil sands solid

532

residue. However, they had higher HHVs than some other biomass chars, such as rice

533

husk char and rose apple char.

534

4. Conclusions

535

Co-pyrolysis of Indonesian oil sands and corn straw was investigated in this study.

536

From thermogravimetric analysis, improved pyrolysis characteristics and higher volatile

537

matters conversion were observed based on the TG and DTG curves, revealing the

538

existence of a remarkable synergetic effect. In the fixed bed reactor, four different

539

pyrolysis methods were first studied. Vacuum pyrolysis and pyrolysis under N2 were the

540

preferred methods to acquire liquid products and optimized operating conditions of both

541

methods were also obtained. In the co-pyrolysis experiments under N2, higher liquid

542

product yield was obtained. Chemical interactions were suggested to happen between

543

two feedstocks during co-pyrolysis process based on the GC-MS results of co-pyrolysis

544

oil. The contents of valuable phenols and alcohols were increased, while unstable

545

aldehydes were reduced, indicating a higher quality of the co-pyrolysis oil used as fuel or

546

chemicals feedstock.

547

Acknowledgements

548

The authors are grateful for the financial support from the International S&T 25


Energy & Fuels

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549

Cooperation Program of China, ISTCP (No. 2015DFR40910) and Major Science and

550

Technology

551

2015ZX07202-013).

552

Supporting Information

553

Program

for

Water

Pollution

Control

and

Treatment

(No.

Main chemical compounds identified by GC-MS in co-pyrolysis and individual

554

pyrolysis oil supplied as Supporting Information.

555

References

556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585

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fluidized bed reactor. Fuel 2015, 156, 40-46. (16) Shadangi, K. P.; Mohanty, K., Co-pyrolysis of Karanja and Niger seeds with waste polystyrene to produce liquid fuel. Fuel 2015, 153, 492-498. (17) Meng, H.; Wang, S.; Chen, L.; Wu, Z.; Zhao, J., Study on product distributions and char morphology during rapid co-pyrolysis of platanus wood and lignite in a drop tube fixed-bed reactor. Bioresour. Technol. 2016, 209, 273-81. (18) Martínez, J. D.; Veses, A.; Mastral, A. M.; Murillo, R.; Navarro, M. V.; Puy, N.; Artigues, A.; Bartrolí, J.; García, T., Co-pyrolysis of biomass with waste tyres: Upgrading of liquid bio-fuel. Fuel Process. Technol. 2014, 119, 263-271. (19) Uçar, S.; Karagöz, S., Co-pyrolysis of pine nut shells with scrap tires. Fuel 2014, 137, 85-93. (20) Masnadi, M. S.; Habibi, R.; Kopyscinski, J.; Hill, J. M.; Bi, X.; Lim, C. J.; Ellis, N.; Grace, J. R., Fuel characterization and co-pyrolysis kinetics of biomass and fossil fuels. Fuel 2014, 117, 1204-1214. (21) Idris, S. S.; Abd Rahman, N.; Ismail, K.; Alias, A. B.; Abd Rashid, Z.; Aris, M. J., Investigation on thermochemical behaviour of low rank Malaysian coal, oil palm biomass and their blends during pyrolysis via thermogravimetric analysis (TGA). Bioresour. Technol. 2010, 101 (12), 4584-92. (22) Meesri, C.; Moghtaderi, B., Lack of synergetic effects in the pyrolytic characteristics of woody biomass/coal blends under low and high heating rate regimes. Biomass Bioenergy 2002, 23 (1), 55-66. (23) Jones, J. M.; Kubacki, M.; Kubica, K.; Ross, A. B.; Williams, A., Devolatilisation characteristics of coal and biomass blends. J. Anal. Appl. Pyrolysis 2005, 74 (1-2), 502-511. (24) Li, S.; Xu, S.; Liu, S.; Yang, C.; Lu, Q., Fast pyrolysis of biomass in free-fall reactor for hydrogen-rich gas. Fuel Process. Technol. 2004, 85 (8), 1201-1211. (25) Liu, P.; Zhu, M.; Zhang, Z.; Zhang, D., Pyrolysis of an Indonesian oil sand in a thermogravimetric analyser and a fixed-bed reactor. J. Anal. Appl. Pyrolysis 2016, 117, 191-198. (26) Oasmaa, A.; Kuoppala, E.; Solantausta, Y., Fast pyrolysis of forestry residue. 2. Physicochemical composition of product liquid. Energy Fuels 2003, 17 (2), 433-443. (27) Ma, Y.; Li, S., Study of the characteristics and kinetics of oil sand pyrolysis. Energy Fuels 2010, 24 (3), 1844-1847. (28) Mohan, D.; Pittman, C. U.; Steele, P. H., Pyrolysis of wood/biomass for bio-oil: a critical review. Energy Fuels 2006, 20 (3), 848-889. (29) He, W.; Liu, Q.; Shi, L.; Liu, Z.; Ci, D.; Lievens, C.; Guo, X.; Liu, M., Understanding the stability of pyrolysis tars from biomass in a view point of free radicals. Bioresour. Technol. 2014, 156, 372-5. (30) Qu, T.; Guo, W.; Shen, L.; Xiao, J.; Zhao, K., Experimental Study of Biomass Pyrolysis Based on Three Major Components: Hemicellulose, Cellulose, and Lignin. Ind. Eng. Chem. Res. 2011, 50 (18), 10424-10433. (31) Jiang, H.; Deng, S.; Chen, J.; Zhang, L.; Zhang, M.; Li, J.; Li, S.; Li, J., Preliminary Study on Copyrolysis of Spent Mushroom Substrate as Biomass and Huadian Oil Shale. Energy Fuels 2016, 30 (8), 6342-6349. (32) Yang, H.; Huan, B.; Chen, Y.; Gao, Y.; Li, J.; Chen, H., Biomass-Based Pyrolytic Polygeneration System for Bamboo Industry Waste: Evolution of the Char Structure and the Pyrolysis Mechanism. Energy Fuels 2016, 30 (8), 6430-6439. (33) Xin, S.; Yang, H.; Chen, Y.; Wang, X.; Chen, H., Assessment of pyrolysis polygeneration of biomass based on major components: Product characterization and elucidation of degradation pathways. Fuel 2013, 113, 266-273. (34) Horne, P. A.; Williams, P. T., Influence of temperature on the products from the flash pyrolysis of 27


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biomass. Fuel 1996, 75 (9), 1051-1059. (35) Abu-Hasanayn, F.; Goldman, M. E.; Goldman, A. S., Development and mechanistic study of a new aldehyde decarbonylation catalyst. J. Am. Chem. Soc. 1992, 114 (7), 2520-2524. (36) Santillan-Jimenez, E.; Crocker, M., Catalytic deoxygenation of fatty acids and their derivatives to hydrocarbon fuels via decarboxylation/decarbonylation. J. Chem. Technol. Biotechnol. 2012, 87 (8), 1041-1050. (37) Zhang, H.; Xiao, R.; Nie, J.; Jin, B.; Shao, S.; Xiao, G., Catalytic pyrolysis of black-liquor lignin by co-feeding with different plastics in a fluidized bed reactor. Bioresour. Technol. 2015, 192, 68-74. (38) Duman, G.; Okutucu, C.; Ucar, S.; Stahl, R.; Yanik, J., The slow and fast pyrolysis of cherry seed. Bioresour. Technol. 2011, 102 (2), 1869-78. (39) Azargohar, R.; Jacobson, K. L.; Powell, E. E.; Dalai, A. K., Evaluation of properties of fast pyrolysis products obtained, from Canadian waste biomass. J. Anal. Appl. Pyrolysis 2013, 104, 330-340. (40) Bliek, A., Mathematical modeling of a cocurrent fixed bed coal gasifier. Technische Hogeschool Twente: 1984. (41) Grover, P.; Iyer, P.; Rao, T., Biomass-thermochemical characterization. IIT-Delhi and MNES: 2002. (42) Rose, J.; Cooper, J. In Technical Data on Fuel. 7th edn London: British National Committee, World Energy Conference, 1977. (43) Parikh, J.; Channiwala, S.; Ghosal, G., A correlation for calculating HHV from proximate analysis of solid fuels. Fuel 2005, 84 (5), 487-494.

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Energy & Fuels

650

Figure captions

651

Figure 1. Schematic diagram of the experimental system. (1) Nitrogen; (2) flowmeter; (3)

652

carrier gas preheater; (4) valve; (5) thermocouple; (6) reactor tube; (7) furnace; (8) drawer;

653

(9) raw material; (10) temperature controller; (11) pressure gauge; (12) cooling unit; (13)

654

gas bag; (14) vacuum pump.

655

Figure 2. Fractionation method of liquid product

656

Figure 3. TG curves of oil sands, corn straw and their blends with different blending

657

ratios at the heating rate of 10℃/min

658

Figure 4. DTG curves of oil sands, corn straw and their blends with different blending

659


660

Figure 5. DTG curves of oil sands and corn straw blends with 50wt.% of corn straw at

661

different heating rates

662

Figure 6. Co-pyrolysis product yields using different pyrolysis methods

663

Figure 7. Liquid product yield at different pyrolysis operating conditions: (a) heating

664

rates of pyrolysis under N2, (b) corn straw contents of pyrolysis under N2, (c) N2 flow

665

rates of pyrolysis under N2, (d) heating rates of vacuum pyrolysis, (e) corn straw contents

666

of vacuum pyrolysis, (f) absolute pressure of vacuum pyrolysis.

667

Figure 8. Product distribution in co-pyrolysis and individual pyrolysis

668

Figure 9. Percentage contents of component types in co-pyrolysis and individual

669

pyrolysis oil

670

Figure 10. Gaseous component volume percentages in co-pyrolysis and individual

671

pyrolysis 29


Energy & Fuels

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672 673

Figure 1. Schematic diagram of the experimental system. (1) Nitrogen; (2) flowmeter; (3)

674

carrier gas preheater; (4) valve; (5) thermocouple; (6) reactor tube; (7) furnace; (8) drawer;

675

(9) raw material; (10) temperature controller; (11) pressure gauge; (12) cooling unit; (13)

676

gas bag; (14) vacuum pump.

30


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677 678

Figure 2. Fractionation method of liquid product

31


Energy & Fuels

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679 680

Figure 3. TG curves of oil sands, corn straw and their blends with different blending

681


32


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682 683

Figure 4. DTG curves of oil sands, corn straw and their blends with different blending

684


33


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685 686

Figure 5. DTG curves of oil sands and corn straw blends with 50wt.% of corn straw at

687

different heating rates

34


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688 689

Figure 6. Co-pyrolysis product yields using different pyrolysis methods

35


Energy & Fuels

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690 691

Figure 7. Liquid product yield at different pyrolysis operating conditions: (a) heating

692

rates of pyrolysis under N2, (b) corn straw contents of pyrolysis under N2, (c) N2 flow

693

rates of pyrolysis under N2, (d) heating rates of vacuum pyrolysis, (e) corn straw contents

694

of vacuum pyrolysis, (f) absolute pressure of vacuum pyrolysis.

36


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695 696

Figure 8. Product distribution in co-pyrolysis and individual pyrolysis

37


Energy & Fuels

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697 698

Figure 9. Percentage contents of component types in co-pyrolysis and individual

699

pyrolysis oil

38


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700 701

Figure 10. Gaseous component volume percentages in co-pyrolysis and individual

702

pyrolysis

39


Energy & Fuels

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703

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Table 1. Raw Material Characterization Results Oil sands (dry, wt.%)

Corn straw (dry, wt.%)

Ultimate analysis C H N S Oa Atomic H/C

82.43b 9.32b 0.92b 4.39b 2.94b 1.35b

44.07 5.94 0.89 0.27 48.82 1.61

Proximate analysis Moisture Ash Volatiles Fixed carbona

1.22 71.17 26.78 0.83

4.41 6.69 72.69 16.21

Extractivesc

-

5.62

Lignin

-

14.37

Hemicellulose

-

29.87

Cellulose

-

41.63

Component analysis

Inorganic elemental analysis by XRF Ca 24.49 K 0.21 Fe 0.4 Mg 0.08 Al 0.49 P 0.75 S 2.04 Si 1.48 Ti 0.08 Cl 0.02 Ni 0.41 704

a

by difference

705

b

daf (dry ash-free basis)

706

c

toluene/alcohol (2:1 in volume)

2.89 6.42 1.13 1.07 0.05 0.32 0.37 0.95 0.02 2.53 0.03

40


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707

Table 2. Elemental Analysis and HHV of the Oil Phases Sample

C

H

Oil sands C25 C50 C75 Corn straw

81.72 78.65 76.62 69.33 64.71

9.77 9.93 9.88 8.66 7.97

Atomic H/C 0.48 4.06 3.97 1.42 0.66 2.12 8.64 1.50 0.83 1.31 11.36 1.54 0.94 0.77 20.30 1.49 1.20 0.34 25.78 1.47 N

S

Oa

Commercial heavy fuel oil Bio-oil 708

a

HHV (MJ/kg) exp calc 41.68 37.66 34.54 33.18 29.38 27.53 25.49 22.43 40-46 16-20

by difference

41


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Table 3. Characterization Results of Solid Residue Products

Oil sands C25 C50 C75 Corn straw

Elemental analysis (dry, wt.%) C H N exp calc exp calc exp calc 15.51 0.96 1.24 21.05 21.35 1.09 1.16 1.48 1.34 30.60 29.56 1.21 1.43 1.65 1.49 41.90 41.78 1.62 1.84 1.88 1.70 62.20 2.53 2.06

Other solid fuels German 63.89 lignite Charcoal 92.04 Coke 89.13 Block wood 46.90 Rice husk char Rose apple char a

S exp 4.62 3.71 2.45 1.13 0.34

calc 4.08 3.33 2.21

O exp 32.87a

Proximate analysis (dry, wt.%) Moisture Ash exp calc exp calc 1.21 61.72 1.37 1.39 54.84 56.03 1.66 1.63 45.15 48.17 2.13 2.00 33.73 36.31 2.62 16.70

Volatiles exp calc 0.64 2.69 2.18 5.73 4.34 10.31 7.56 12.93

Fixed carbon exp calc 36.43 41.10 40.33 47.46 45.86 53.83 54.02 67.75

HHV (MJ/kg) exp calc. 1.76 4.47 4.09 7.61 7.36 12.63 12.23 20.37

a

4.97

0.57

0.48

24.54

-

4.50

49.47

46.03

25.10

2.45 0.43 6.07

0.53 0.85 0.95

1.00 1.00 0.00

2.96 0.98 43.99

-

1.02 7.61 2.09

9.88 0.92 83.32

89.10 91.47 14.59

34.39 31.12 18.26

-

-

-

-

-

52.90

5.90

41.20

14.94

-

-

-

-

-

65.60

22.20

12.20

7.58

by difference

42


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Energy & Fuels

Figure 1. Schematic diagram of the experimental system. (1) Nitrogen; (2) flowmeter; (3) carrier gas preheater; (4) valve; (5) thermocouple; (6) reactor tube; (7) furnace; (8) drawer; (9) raw material; (10) temperature controller; (11) pressure gauge; (12) cooling unit; (13) gas bag; (14) vacuum pump. 41x21mm (600 x 600 DPI)


Energy & Fuels

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Figure 2. Fractionation method of liquid product 38x18mm (600 x 600 DPI)


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Energy & Fuels

Figure 3. TG curves of oil sands, corn straw and their blends with different blending ratios at the heating rate of 10℃/min 50x32mm (600 x 600 DPI)


Energy & Fuels

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Figure 4. DTG curves of oil sands, corn straw and their blends with different blending ratios at the heating rate of 10℃/min 50x32mm (600 x 600 DPI)


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Energy & Fuels

Figure 5. DTG curves of oil sands and corn straw blends with 50wt.% of corn straw at different heating rates 50x32mm (600 x 600 DPI)


Energy & Fuels

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Figure 6. Co-pyrolysis product yields using different pyrolysis methods 50x32mm (600 x 600 DPI)


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Energy & Fuels

Figure 7. Liquid product yield at different pyrolysis operating conditions: (a) heating rates of pyrolysis under N2, (b) corn straw contents of pyrolysis under N2, (c) N2 flow rates of pyrolysis under N2, (d) heating rates of vacuum pyrolysis, (e) corn straw contents of vacuum pyrolysis, (f) absolute pressure of vacuum pyrolysis. 79x39mm (600 x 600 DPI)


Energy & Fuels

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Figure 8. Product distribution in co-pyrolysis and individual pyrolysis 56x40mm (600 x 600 DPI)


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Energy & Fuels

Figure 9. Percentage contents of component types in co-pyrolysis and individual pyrolysis oil 47x27mm (600 x 600 DPI)


Energy & Fuels

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Figure 10. Gaseous component volume percentages in co-pyrolysis and individual pyrolysis 62x49mm (600 x 600 DPI)


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Understanding the Co-Pyrolysis Behavior of Indonesian Oil Sands and

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