characteristics of bio-oil obtained from pyrolysis of corn...

Characteristics of bio-oil obtained from pyrolysis of corn stalk

Yue Liua ,Renping Liub*,Binbin Dongc,Liangxia Zhao d, Shanhui Wange

Environmental Science and Engineering, Hebei University of Science and Technology, shijiazhuang,China

[email protected] b*[email protected] [email protected] [email protected] [email protected]

Abstract: In this study, corn stalks are selected as the experimental raw material, and Van soest fiber assay is

employed to determine the component of this raw material, what`s more, its proximate analysis was examined.

Purged with nitrogen to ensure that the inert gas atmosphere, using a heating rate of 10 / min to a final ℃

temperature of 500 , with a fixed bed reactor to pyrolysis oil, and pyrolysis oil ’s water, acidity, viscosity, heat ℃

value and other characteristics were determined. Then pyrolysis oil is separated by distillation, using GC-MS to

analysis qualitative analysis of pyrolysis oil. The results show that under the experimental conditions the

pyrolysis liquid yield is 40 percent, its water content was 70.34%, ph was 3.51, viscosity was 1.80cp, calorific

value was 16393J / g. GC-MS analysis showed that the main pyrolysis oil contains large amounts of long-chain

alkane, benzene derivatives, ester derivatives, phenol derivatives, cyclopentene derivative and furan derivatives.

Keywords: biomass; bio-oil; pyrolysis; properties of bio-oil.

1. Introduction

With the development of the global industry, coal, oil and other non-renewable fossil fuels are in a lot of

consumption, therefore, we are facing a dual crisis of energy shortage and environmental pollution, and an

urgent need to find new alternative energy sources [1] is imperative. Bio-oil is a clean fuel prepared by rapid

thermal pyrolysis raw materials, after the improvement of separation and purification, it can replace fossil energy

as a fuel, which is of great significance for optimizing China's energy structure and environmental protection [2].

Since the 1980s, the Massachusetts Institute of Technology Battelle and other internationally renowned

universities of Finland, Italy, the United States and more than ten countries are organized by the IEA to do

laboratories of biomass pyrolysis oil technology research, which have developed transport stream cracking and

other six kinds of fast heating processes [3]. Shenyang Agricultural University who first began the study of

biomass pyrolysis oil technology introduced a liquefaction test device pyrolysis from the University of Twente in

the Netherlands, pyrolysis liquefaction tests are carried out and was successful [6]. Biodiesel in Europe, the

United States and other developed countries have also begun a large-scale industrial production[5]; Curing

biomass fuel technology in Europe, America, Japan and other places have also been gradually commercialized[6],

Brazil through the development of means of standards, policies and legislation and other subsidies, promote

sugar cane biomass industry [7].

At this stage in the study of bio-oil pyrolysis experiment, there are many problems, such as how to control the

best heating rate and final pyrolysis temperature to obtain the most useful components, and how to choose a

suitable scavenging to meet carry gas, but also to ensure the purpose that biomass has enough pyrolysis time in

the reactor to achieve complete decomposition [8].

The experiments selected corn stalks as the main object of this study, and the component of raw materials has

The Second International Conference on Civil Engineering, Energy and Environment

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also been analyzed for determining its calorific value. Familiar with the principles and methods of rapid

pyrolysis biomass for the preparation of bio-oil. Using methods of distillation to separate bio-oil group,

analyzing properties of bio-oil, and using GC-MS qualitative analysis to analyze component.

The purpose of this project is intended to analyze the fuel properties of biomass pyrolysis oil. In order to

identify the optimal pyrolysis bio-oil program and to explore the expectations components of bio-oil, and take

advantage of bio-pyrolysis oil to maximize its effectiveness, in order to achieve the desired purpose of bio-oil

ultimate industrial application.

2. Experiment 2.1 Raw materials

The experiments selected corn stalks as raw material, the Van soest fiber assay [9] was used to determine the

composition of corn stalks; according to GB GB / T212-2008 the proximate analysis of raw material were

analyzed; according to GB GB / T213 with XRY-1B oxygen bomb calorimeter calorific value of corn stover

were analyzed; using DTH-60 TGA to analysis TG of corn stover. The results are shown in Table 1 and Table 2.

Table 1 component analysis of corn stover

Cellulose[%] Hemicellulose[%] Lignin[%] Ash[%] Other[%]

40.31 29.12 17.30 6.09 7.18

Table 2 proximate analysis of corn stover

Water[%] Volatile[%] Ash[%] Fixed carbon[%] Calorific value[J/g]

10.25 77.39 3.96 8.40 13624

2.2 Preparation of pyrolysis oil Take 50g corn stalks into the tubular pyrolysis furnace, a nitrogen blanket at 500 , heating rate of 10 / ℃ ℃

min, nitrogen sweep gas flow rate of 60ml / min, and pyrolysis corn stover, instrumentation diagrams is below:

400.00 600.00 800.00 1000.00 1200.00

Temp [K]

-0.00

1.00

2.00

3.00

4.00

5.00

mgTGA

-0.40

-0.20

0.00

mg/minDrTGA

-0.00

50.00

uVDTA

Fig.1 biomass pyrolysis process diagram Fig.2 TG analysis of corn stalks (15 / min heating rate)℃

2.3 Properties of pyrolysis oil This experiment used the ZSD-2J automatic moisture titrator to titrate water. Using PHS-2F pH meter to

measure pH value of bio-oil. Using DV3T type viscometer to measure viscosity of bio-oil. Using XRY-1B

Microcomputer Oxygen Bomb Calorimeter with oxygen warhead to measure calorific value of bio-oil.

2.4 component Analysis Hexane extraction agent is added in the dewatered bio-oil, then pouring them into a separator funnel, standing

layer. Use method of distillation to separate the pyrolysis oil with an oil bath pot, according to the different


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components with different boiling points.

3. Discussions 3.1 TG analysis

Taking 5mg corn stalks into DTH-60 TGA in nitrogen pyrolysis access. Setting a heating rate of 15 / min, ℃

dwell 20min at 105 to remove water, then heated to 850 . The results ℃ ℃ are shown in Figure 2.

As can be seen from Figure 2, there are three characteristics similar stage of corn stalks on TG and DTA

curves: The first stage, from 30 ~ 110 ℃, TG curve has a weightless step, weight loss of about 10.33%, mainly

as a result of dehydration reaction caused endothermic peak corresponding to a 64 ℃ in the DTA curve; the

second stage is from 250 ~ 380 ℃, a weight loss appears on the TG curve slope, weight loss of about 77.04%,

which is due to the raw material has started to become part of the pyrolysis gas is volatilized, corresponding to

an endothermic peak at 313.14 ℃ on DTA curve; third emergence stage from 415 ~ 527 ℃, the TG curve of

weightlessness ramp, weight loss of about 17.44%, which is due to secondary cracking and caused part of a

cleavage.

3.2 Apparent characteristic of pyrolysis oil In this study, the moisture content, pH, viscosity, calorific value of the pyrolysis bio-oil were measured, the

results are shown in Table 3.

Table 3Apparent characteristic of pyrolysis oil

water[%] pH viscosity[cp] calorific value[J/g]

70.34 3.51 1.86 16393

Results show that the pyrolysis bio-oil has high moisture content, it has a great influence on the late

application of bio-oil, so we need to remove water from the bio-oil. Pyrolysis bio-oil’s acidity is strong, so it put

forward higher request for storage and transport. Water and bio-oil aging effects viscosity, reducing moisture

makes bio-oil viscosity increased, and placing bio-oil a long time makes bio-oil viscosity decreased. Calorific

value of pyrolysis bio-oil still has a certain gap with diesel fuel, but compared to the direct combustion of corn

stalks it is more fully utilizing the heat.

3.3 GC-MS analysis Distilling extraction layered upper pyrolysis oil, and the product chromatogram at 150 has ℃ been shown in

Figure 3.

Fig.3 150 upper pyrolysis oil distillation℃

products chromatogram Fig.4 percentage of bio-oil components

By analyzing the pyrolysis bio-oil chromatogram obtained bio-oil components of the particular compound,

the analysis results are shown in Table 4.


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Table 4 Analysis of the upper components of bio-oil

Number Retention time

[min] Molecular structure Formula

Molecular

weight

Peak area

[%]

1 2.400

H3N 17 2.88

2 4.269

C3H6O 58 4.92

3 4.965

C6H14 86 6.05

4 5.306

C6H14 86 60.86

5 6.032

C6H12 84 12.63

6 6.697 C7H16 100 0.35

7 6.813

C6H12 84 0.44

8 6.914

C7H16 100 0.43

9 7.194

C2H4O2 60 1.43

10 7.428 C7H16 100 0.42

11 8.056 C6H8O 96 0.71

12 8.428

C5H8O2 100 0.74

13 9.370

C3H6O2 74 0.91

14 9.815

C7H8 92 1.74

15 11.270

C5H8O 84 0.42

16 12.291

C8H10 106 0.49

17 12.491

C5H4O2 96 3.08

18 13.033

C5H6O2 98 0.74

19 13.945

C6H8O 96 0.35

20 14.099

C6H6O2 110 0.41


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Summarizing the various substances of pyrolysis bio-oil in Table 4, percentage results of compounds as

shown in Figure 4.

Obtained from Figure 4 corn stalk pyrolysis bio-oil mainly contains long-chain alkanes, benzene derivatives,

ketone derivatives, aldehydes derivatives, furan derivatives, etc.

Long chain alkane does not dissolve in water, dissolve in organic solvents, density is usually smaller than

water, so bio-oil does not dissolve in water easily soluble in hexane, chloroform and other organic solvents, so

the upper component contains a lot of paraffins. Alcohols are chemically active, more polar, so the presence of

an alcohol compound makes bio-oil unstable, and the alcohol chemical structure of carbon atoms with a

hydroxyl group attached to is easily oxidized to aldehyde, ketone or acid, so bio-oil contains aldehydes, ketones,

acids and other substances. Olefins is easily oxidized to aldehydes, ketones and other compounds, which would

increase the viscosity of the bio-oil. Most phenols have pungent odor and acidic, which can affect the smell and

acidity bio-oil. Phenol is easily oxidized discoloration in the air, so the bio-oil also easily oxidized in the air [10].

4. Conclusion

Through this pyrolysis bio-oil experiments, the following conclusions are obtained:

(1) The pyrolysis process of corn stalks has three characteristics phases: the first phase is from 30 ~ 110 , ℃

mainly as a result of dehydration reaction; the second stage is from 250 ~ 380 , since the raw material has ℃

started pyrolysis into volatile gases; the third stage, from 415 ~ 527 , since the first cracking and part of ℃

secondary cracking.

(2)Under 60ml / min airflow rate sweep, with the 10 / min heating rat℃ e to reach 500 ℃ as final pyrolysis

temperature, the pyrolysis liquid yield is about 40%. Water content of pyrolysis bio-oil is 70.34%, pH is 3.51,

and viscosity is 1.80cp, calorific value is 16393J / g.

(3)GC-MS analysis showed that the main component of bio-oil comprises long chain alkane, benzene

derivatives, ester derivatives, phenol derivatives, cyclopentene derivative and furan derivatives.

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