Experimental Study on Pyrolysis Characteristics of Oil Sludge with a

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Experimental Study on Pyrolysis Characteristics of Oil Sludge with a Tube Furnace Reactor Zhiqiang Gong, Aixun Du, Zhenbo Wang, Peiwen Fang, and Xiaoyu Li Energy Fuels, Just Accepted Manuscript • Publication Date (Web): 12 Jul 2017 Downloaded from http://pubs.acs.org on July 12, 2017

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Experimental Study on Pyrolysis Characteristics of Oil Sludge with a Tube Furnace Reactor Zhiqiang Gong 1, Aixun Du 1, Zhenbo Wang 1,*, Peiwen Fang 1, Xiaoyu Li 1 1 State Key Laboratory of Heavy Oil, China University of Petroleum (East China), 266580, Qingdao, China *

Corresponding author: Tel: +86 +0532 86981865 E-mail address: [email protected]

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Abstract: Oil sludge (OS) pyrolysis was conducted with a tube furnace reactor. Production distributions and compositions were investigated under different conditions of pyrolysis temperature, heating mode, and atmosphere (N2/CO2). Little change was detected with the products yields of char, oil, and gas when the final temperature exceeded 600 °C. Compared with slow pyrolysis, oil and char yields decreased and gas yield increased in fast pyrolysis. CO2 could promote OS pyrolysis, resulting in a reduction of char yield. SEM images showed that the surface of OS was smooth with a dense texture while the surface of OS char was rough with well-developed pore structure that formed after pyrolysis. Simulated distillation results showed that light fractions from OS pyrolysis were more than 30% higher than those of oil from OS extraction. With the increase of pyrolysis temperature, light fractions (gasoline, diesel and jet fuel) in pyrolysis oil decreased. During fast pyrolysis, the heavy fractions produced can be cracked into light fractions. The content of light fractions was 46% compared with 34% for oil from slow pyrolysis. It did not differ much with the oil products distributions from pyrolysis in inert (N2) and CO2 atmosphere. The yields of C4-6 and C6 were higher than those of CH4 in slow pyrolysis between 500 °C and 700 °C. Fast pyrolysis and CO2 atmosphere favored the conversion of stable macromolecules to short chain methyl compounds, resulting in a higher CH4 yield.

Key Words: Oil sludge, Pyrolysis, Tube furnace reactor.


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1. Introduction Oily sludge (OS), an oil-containing solid waste, is produced during oil extraction, transportation, refining and oily wastewater treatment.1, 2 The average oil content in the OS is 10~50% and the moisture content is 40~90%. In the petroleum chemical industry in China, over three million tons of OS are produced per year. OS contains heavy metals, benzene, phenols, anthracene, and other toxic substances, if not treated properly, it can pollute the environment and endanger people’s lives. And also it is a waste of resources as OS has a high oil content.3-5 OS treatment has been a major problem plaguing researchers in the field of oil field for years. Various OS treatment methods have been developed these years, such as solidification,6-8 ultrasonic,2,

9, 10

solvent extraction,11-13 bioremediation1,

14-16

,

incineration,17-20 and pyrolysis.21-26 These technologies can help reduce and even eliminate certain hazardous constituents in OS. Among these methods, pyrolysis attracts much attention as it can realize energy cascade use of OS better. OS pyrolysis process produces hydrocarbons with lower molecular weight in condensation (i.e. liquid) and/or non-condensable gases. It also generates a solid product, OS char.5 OS char can be used as adsorbents or fuels for power plants. The products may have a more elevated heating value than the raw oily sludge.27 Overall, the quality of products is better in OS pyrolysis compared with other techniques. A lot work has been done on products from pyrolysis of OS. Chang et al.28 studied the major products obtained from pyrolysis of OS. They observed that the major


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gaseous products were CO2, HCs (hydrocarbons), H2O, and CO. And the liquid product was close to diesel oil after distillation analysis. Shen et al.29 pointed out that the oil yield was initially increased with increasing pyrolysis temperature increasing, reaching a maximum of 30% wt% of the OS feed at 525 °C, but it decreased when temperature was above 525 °C as a result of secondary cracking reactions. Schmidt and Kaminsky30 investigated the distribution of the oil products from OS at pyrolysis temperature between 460 °C and 650 °C and found that up to 84% of the oil could be separated from the sludge in fluidized bed reactors. OS pyrolysis is influenced by many factors, such as pyrolysis temperature, heating rate, atmosphere, additives, characteristic of OS, etc. Chen et al.31 observed that CaO and NiO catalysts promoted the deep transformation of the products effectively. Shie et al.23-25, 32 studied effects of sodium and potassium additives on OS pyrolysis and pointed out that the additives improved the liquid yields in the order of KCl>Na2CO3>NaCl>no additives>NaOH>K2CO3>KOH. Wang et al.26 indicated that the pyrolysis conversion of OS could be effectively promoted with a higher temperature, an interval holding stage, and catalyst adding. Simulated distillation has been widely used for the analysis of pyrolysis oil.28 By simulated distillation, valuable information about pyrolysis oil from OS pyrolysis can be obtained, such as the composition of pyrolysis oil. In this study, OS pyrolysis was firstly conducted with a thermogravimetric analyzer (TGA), receiving basic information about the thermal process. Then the pyrolysis


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characteristics of OS were investigated in a tube furnace reactor system, with pyrolysis temperature between 500 °C and 700 °C, both slow and fast heating modes, and different atmospheres (N2/CO2). Characteristics of both gaseous and liquid products were investigated and presented. This study can help realize cascade utilization of OS and determine an optimized operation range for OS pyrolysis. 2. Experimental 2.1 Oil sludge The crude OS was collected from Shengli oilfield in Dongying, Shandong Province. To determine the sludge composition, soxhlet extraction with methylbenzene and n-heptane as an analytical standard (AS) was performed for 3 h three times. Figure 1 shows the schematic diagram of soxhlet extraction system. Based on the reflux and siphon principle of the extracting agent, OS samples can be extracted by pure agent with a high extraction efficiency. Before extraction, OS was ground fine to increase the area of liquid leaching. Then OS was placed in an absorbent cotton, which was put into the extraction chamber. When the agent was heated and boiled, the steam rised through the connecting tube and was condensed into liquids, dropping into the extraction chamber. When the liquid level exceeded the highest point of the siphon tube, the siphon phenomenon occurred and the solution was refluxed into the flask. The agent-soluble material could be extracted and the oil content in the OS can be determined in this way. The amount of residue retained in the cartridge was determined indirectly by drying and the water content in OS can be


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calculated. The oil content in OS was 47.91%, moisture content was 26.55%, and the residue content was 25.54%.

cooling-water outlet

1 cooling-water inlet 2 3 4 5

10

6

7 8 9

1-condensing tube, 2-extraction chamber, 3-connecting tube, 4-absorbent cotton, 5-OS samples, 6- siphon tube, 7-extraction flask, 8-extracting agent, 9-electric heater, 10-holder Figure 1. Schematic diagram of soxhlet extraction system Proximate and ultimate analyses of OS are shown in Table 1. Table 1. Proximate and ultimate analyses of OS Items

Oil sludge

Proximate analysis (wt%) Moisturea

26.55

Volatile matterb

51.19

Fixed carbona

2.17


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Asha

42.27

Ultimate analysisa (wt%) Carbon

16.38

Hydrogen

4.25

Oxygen

8.91

Nitrogen

0.32

Sulfur

2.34

Low heating valuea (kJ/kg) a

As received.

b

Dry basis.

8536.15

2.2 Analysis methods Thermogravimetric analysis of OS was performed in a Linseis STA PT1600 thermogravimetric analyzer (TGA). Before analysis, a thermogravimetry baseline needs to be created to reduce measurement errors. To start the experiment, a sample of about 10 mg with a particle size of 0.5-1.0 mm was tiled at the bottom of an Al2O3 crucible, and the internal atmosphere was filled with nitrogen, with a flowrate of 100 mL/min. The sample was heated from 25°C to 1000°C with a heating rate of 10°C/min. Pyrolysis oil was collected and analyzed by a Varian-CP-3800 gas chromatograph with application of ASTM D86, a standard test method for distillation of petroleum products. Pyrolysis gas was collected by air bag and analyzed by a gas chromatograph (Agilen7890A). The morphology of residues after pyrolysis (OS char) were studied via scanning electron microscope (SEM).


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2.3 Tube furnace reactor system A novel tube furnace reactor system for OS pyrolysis was designed. The schematic diagram of the system can be seen in Figure 2. The system consists of a gas supply system, an electric furnace, a tube furnace, a constant temperature controller, a water-cooling system and an auxiliary system. The diameter of the corundum tube reactor is 60 mm, with a height of 1020 mm. N2 and CO2 are used as pyrolysis gas supplied by Qingdao Instrument & Equipment center, with a purity >99.999%. The gas flows is controlled by float flowmeters. There is a K-type thermocouple placed in the heating rods of the eclectic furnace to measure the temperature of the heating zone. To collect the pyrolysis oil from OS, a water-cooling system was designed, which consists of a constant temperature controller, two water-cooling tubes, and a water-cooling flask, ensuring that most of the oil can be cooled and collected in the flask. The pyrolysis gas was collected by gas bag and used for analysis. At the beginning of temperature programmed experiments, OS sample was put into the reactor and then the reactor was heated by electric furnace and the gas was introduced into the reactor. After the temperature of the furnace reached the set value and last for 30 min, the power of electric furnace was shut off while the gas (N2 or CO2) was kept supplying until the temperature in the reactor dropped below 50 °C. As for fast pyrolysis, OS sample was not put into the reactor until the temperature of the furnace reached to the set value and the furnace was filled with the inert gas (N2 or CO2). After 60-min pyrolysis, the power of electric furnace was shut off and the


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remaining steps are the same as above.

1-N2 cylinder, 2-CO2 cylinder, 3-gas flowmeter, 4-electric furnace, 5-temperature controller, 6-tube reactor, 7-oil sludge, 8-distributor, 9-constant temperature controller, 10-water-cooling

flask,

11-water-cooling

tube,

12-cooling

water

inlet,

13-colling-water outlet, 14-pyrolysis gas outlet Figure 2. Schematic diagram of tube furnace reactor system 2.4 Experimental Conditions The experimental conditions are shown in Table 2. Factors of pyrolysis temperature, atmosphere and heating mode that affect characteristics of OS pyrolysis were investigated. Pyrolysis temperature was between 500 and 700 °C. Temperature programmed pyrolysis with a heating rate of 5 °C/min and fast pyrolysis were carried out. As for fast pyrolysis, OS was directly put into the furnace when the temperature


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reaches the set value. To figure out the effect of pyrolysis atmosphere, both N2 and CO2 were used as inert gas in the experiments. The OS sample was 28±0.1 g with a particle size of 0.5-1.5 mm and the flowrate of pyrolysis gas was maintained at 500 mL/min in all cases. Table 2. Experimental conditions

Cases

1

Pyrolysis Pyrolysis temperature atmosphere

1.1

500 °C

1.2

600 °C

1.3

700 °C

600 °C

N2

5 °C/min

600-N2 700-N2

N2

2.2

5 °C/min

600-N2

Fast Pyrolysis

600-N2-F

~102-103 °C/s

3.1 3

Label

500-N2

2.1 2

Heating mode

N2 600 °C

3.2

600-N2 5 °C/min

CO2

600-CO2

3. Results and Discussion 3.1 Thermogravimetric study of OS Pyrolysis characteristics of OS were investigated by a TGA as mentioned above. Figure 3 shows the thermogravimetric (TG) and differential thermogravimetric (DTG) profiles of OS in N2 atmosphere at a heating rate of 10 °C/min. There were mainly three weight loss region, stage 1, 2 and 3, as marked in the graph. The first weight loss was because of water release, between 80 °C and 200 °C. The second weight loss,


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where the maximum weight loss peak appeared, was caused by the release of volatile matter and organic compounds, between 200 °C and 580 °C. To be noticed, there were two minor weight loss peaks between 200 °C and 370 °C, which was attributed to the release of light oil components with relatively low boiling points. Between 370 °C and 580 °C in stage 2, there was a large weight loss peak, a maximum one, which was caused by mainly two reasons. The first one was resulted from the release and decomposition of heavy oil components with higher boiling points. And the second one was because of the carbonation reaction. The main groups in OS included proteins, fats and oils,33, 34 which were easy to be broken down during the thermal process. There were mainly two weight loss peaks in stage 3, which was attributed to the decomposition of organic residues and inorganic matters.35, 36 There were some heavy metals salts in OS and these salts had complex reactions at high temperature36. 0.05 100 0.00

TG DTG

-0.10

80 -0.15 70

-0.20

-0.25 60

Stage 1 0

200

Stage 2 400

Stage 3 600

T (°C)


800

-0.30 1000

DTG (%/°C)

-0.05

90

TG (%)

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

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Figure 3. TG and DTG profiles of OS pyrolysis 3.2 Pyrolysis characteristics of OS 3.2.1 Pyrolysis char, oil, and gas yields distribution The distributions of char, oil and gas yields in different cases of OS pyrolysis are shown in Figure 4. With the increase of pyrolysis temperature, oil yield increased while gas and char yields decreased. When pyrolysis temperature exceeded 600 °C, the yields of products showed little change. The yields of oil did not demonstrate an obvious increase when the final temperature exceeded 600 °C, which was consistent with the TG curve of OS pyrolysis as the release of oil components occurred between 200 °C and 580 °C. Some researchers pointed out that fast pyrolysis maximizes the liquid yield.

37, 38

However in this work, compared with slow pyrolysis, oil and char yields decreased and gas yield increased in fast pyrolysis. This was because parts of oil components escaped by the carrier gas before condensed in the flask. Therefore, the overall proportion of pyrolysis oil and gas increased but the proportion of pyrolysis oil decreased. As is shown in Figure 4, oil yield increased and gas yield decreased compared with products yield from OS pyrolysis in N2 atmosphere. The overall yield of oil and gas increased while char yield decreased in CO2 atmosphere. The gasification reaction of CO2 with newborn char promoted the breakage of groups such as hydroxyl, methyl and methylene, and the formation of H radicals, which promoted the process of OS


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pyrolysis and reduces the yield of char, resulting in a more generation of volatiles. 80

Oil Gas Char

70 60 50

Yield (%)

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

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40 30

57.45

54.43

54.06

53.71

50.19

20 32.04 26.61

10

15.94

26.28 19.29

25.58 20.71

24.6525.16 13.9

0

500-N2

600-N2

700-N2

600-N2-F

600-CO2

Figure 4. Distribution of char, oil, and gas yields in OS pyrolysis 3.2.2 Surface morphology of OS char The surface morphology of OS and OS chars from pyrolysis in the tube furnace reactor is shown in Figure 5, analyzed by scanning electron microscopy (SEM). The surface of OS was smooth with a dense texture while the surface of OS char was rough with well-developed pore structure formed during pyrolysis.39 Volatile of OS was released during OS pyrolysis from the inside of the OS particles, causing formation of pores on the surface of particles and the increase of specific surface area. With the increase of pyrolysis temperature, the degree of pore development increased firstly and then decreased. As the pyrolysis temperature increased, the process of volatilization was more intense, and the pores were continuously grown,


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further forming mesoporous and macrospores. However, when temperature continued to rise, the pores would collapse and melting reaction occurred, resulting in a poor pore structure. From Figure 5(b), (c), and (d), it can be seen that the pore structure was well developed between 500 °C and 700 °C. Compared with OS char from temperature programmed pyrolysis (Figure 5(c)), OS char from fast pyrolysis (Figure 5(e)) had smaller particle size and poorer pore structure. The reactions were intense during fast pyrolysis. Large OS particles could be easily broken into small ones, and formed pores disappeared in the process of particle fragmentation. Figure 5(f) shows the SEM images of OS char from pyrolysis in CO2 at temperature of 600 °C. The surface of OS char was rough with well-developed pore structure under CO2 atmosphere, which was categorized to dense-type char with more microspores 40, 41 compared with OS char from pyrolysis in an inert atmosphere (N2). In CO2 atmosphere, due to the large CO2 partial pressure, the pressure gradient inside and outside of the particles was small during the volatile release process. Therefore, the release rate of volatiles was relatively slow and many more microspores were reserved after pyrolysis.


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(a) OS

(b) OS char-500-N2

(c) OS char-600-N2

(d) OS char-700-N2


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(e) OS char-600-N2-F

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(f) OS char-600-CO2

Figure 5. SEM structures of OS and OS char 3.2.3 Simulated distillation of pyrolysis oil Pyrolysis oil was collected and analyzed by a Varian-CP-3800 gas chromatograph with application of ASTM D86. Simulated distillation results of the pyrolysis oil and extracted oil from OS are shown in Figure 6. The boiling point curves of the pyrolysis oil from different temperature did not show significant differences above 500 °C, as typical main decomposition reactions occurred below 500~600 °C.42 Compared with the boiling curves of pyrolysis oil, the boiling curves of OS extracted oil did not change much until the temperature exceeded 400 °C, indicating that light fractions were less in extracted oil. With the increase of pyrolysis temperature, mass recovery between 200 °C and 450 °C decreased firstly and then the curves gradually coincided above 450 °C. The boiling point curve of oil from fast pyrolysis was above the curve of oil from slow pyrolysis below 400 °C, indicating that more light fractions produced during fast pyrolysis. Compared with the boiling point curve of pyrolysis oil from pyrolysis in N2 atmosphere, the curve was slightly higher between 100 °C and 400 °C and lower above 400 °C when the pyrolysis atmosphere was CO2.


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100

Extracted oil from OS 500-N2 600-N2

80

Mass Recovery (%)

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

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700-N2 600-N2-F

60

600-CO2 40

20

0 100

200

300

400

500

600

700

800

T (°C) Figure 6. Simulated distillation results of the oil As demonstrated in Table 3, pyrolysis oil products can be divided into different commercial oil products by simulated distillation according to the boiling points range.43 Consistent with analysis of boiling point curves, production distributions of different cases were close, and the productions mainly consisted of diesel and distillates (>83%). While the predominating portions were heavy fractions, including distillates and heavy oil (64% and 30%, respectively) in the extract oil. With the growth of pyrolysis temperature, light fractions (gasoline, diesel and jet fuel) decreased and heavy fractions (distillates and heavy oil) slightly increased. Heavy fractions tended to be converted into lighter fractions at a higher temperature, as some straight-chain bonds, such as the C−C and C−H of aliphatic compounds, were easily broken when temperature was high.31 During fast pyrolysis, the heavy fractions produced could be cracked into light fractions. The content of diesel was 42%


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compared with 30% for oil from slow pyrolysis while the content of distillates and heavy oil was 54% and 66%, respectively, which mean fast pyrolysis helped enhance the yield of light oil. It did not differ much with the oil products distributions from pyrolysis in inert (N2) and CO2 atmosphere at 600 °C with a heating rate of 5 °C/min, as the content of gasoline and diesel was 39% and 34 %, respectively. Light fractions (gasoline and diesel) from OS pyrolysis were more than 30% higher than those of oil from OS extraction.

Table 3. Distribution of gasoline, diesel, distillates, heavy oil, and jet fuel by simulated distillation (wt%) Gasoline

Diesel

Distillates

Heavy oil

Jet fuel

IBP-180 °C

180-350 °C

350-500 °C

>500 °C

140-240 °C

500-N2

7

38

47

8

19

600-N2

4

30

56

10

11

700-N2

5

28

56

11

9

600-N2-F

4

42

46

8

12

600-CO2

7

32

52

9

11

Extracted oil from OS

2

4

64

30

2

Item

Note: IBP is the initial boiling point. 3.2.4 Analysis of pyrolysis gas composition Gas product compositions under different pyrolysis conditions are shown in Figure


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7, 8 and 9. Actually, OS pyrolysis gas products contained CO2, CO, H2, and light hydrocarbons. In this study, the gas product components were focused on hydrocarbons, CH4, C2H6, C2H4, C3H8, C4-6, and C6+, specifically. Figure 7 shows the composition of pyrolysis gas in different pyrolysis temperature. It can be seen that with the increase of pyrolysis temperature between 500 °C and 700 °C, the contents of CH4, C2H4, C4-6 and C6+ increased, while the contents of C2H6, C3H8, and C3H6 decreased. The secondary decomposition of the -CH3 side chain could contribute to the increase of CH4.44 The yields of C4-6 and C6 were higher than those of CH4 in slow pyrolysis between 500 °C and 700 °C, indicating that –CH3 side chain content in OS was less as –CH3 is the key factor in the production of CH4.26 Compared with slow pyrolysis, the overall contents of C2-6 increased obviously while content of CH4 decreased slightly and content of C6+ dropped significantly in fast pyrolysis of OS. The overall yields of micromolecules’ hydrocarbons increased while macromolecules (C6+) yields were small. The results showed that fast pyrolysis was beneficial to the cracking of macromolecules into small molecules, resulting in an increase of the yield of methane. The

CO2 atmosphere can

promote

the selective conversion of stable

macromolecules into short chain methyl compounds. As can be seen in Figure 9, the contents of C1-4 increase and the contents of C4+ decreased significantly compared with the pyrolysis gas composition in N2 atmosphere. The CH4 yield was higher than that of C4-6 or C6+ in CO2 atmosphere. This results suggested that CO2 expedited the


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thermal cracking, which was in agreement with the work from Kim et al.45 25

500-N2 600-N2

Content (%)

20

700-N2

15

10

5

0

CH4

C2H6 C2H4 C3H8 C3H6 C4-6 Composition of pyrolysis gas

C6+

Figure 7. Composition of pyrolysis gas in different pyrolysis temperature 25

600-N2 600-N2-F

20

Content (%)

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

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15

10

5

0

CH4

C2H6

C2H4

C3H8

C3H6

C4-6

C6+

Composition of pyrolysis gas Figure 8. Composition of pyrolysis gas in slow and fast pyrolysis


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25

600-N2 600-N2-CO2

20

Content (%)

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

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15

10

5

0

CH4

C2H6

C2H4 C3H8 C3H6 C4-6 Composition of pyrolysis gas

C6+

Figure 9. Composition of pyrolysis gas in N2 and CO2 atmosphere OS has been classified as a hazardous waste in China. Currently, there is not a mature technique for massive OS treatment in China. Pyrolysis is a promising way to massive utilization of OS with productions of pyrolysis gas and oil. Pyrolysis temperature, heating mode, and pyrolysis atmosphere are the key parameters that affect the OS pyrolysis behaviors. Experimental results of OS pyrolysis in this work can help figure out the behaviors of OS pyrolysis and the optimal operating ranges according to acquirements for specific pyrolysis products, which can help promote the massive utilization of OS in a way of resource recycling. 4. Conclusion In this present work, OS pyrolysis was conducted with a TGA and tube furnace reactor. Factors of pyrolysis temperature, heating mode, and different atmosphere


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(N2/CO2) that affect the pyrolysis behavior of OS were investigated. The surface of OS was smooth with a dense texture while the surface of OS char was rough with well-developed pore structure formed during pyrolysis. The products yields of char, oil, and gas did not demonstrate an obvious increase when the final temperature exceeded 600 °C. Compared with slow pyrolysis, oil and char yields decreased and gas yield increased in fast pyrolysis. CO2 could promote OS pyrolysis, resulting in the reduction of char yield. Light fractions from OS pyrolysis were more than 30% higher than those of oil from OS extraction. With the growth of pyrolysis temperature, light fractions (gasoline, diesel and jet fuel) in pyrolysis oil decreased and heavy fractions (distillates and heavy oil) slightly increased. During fast pyrolysis, the heavy fractions produced can be cracked into light fractions. The oil products distributions from pyrolysis in inert (N2) and CO2 did not display much difference. The contents of CH4, C2H4, C4-6 and C6+ increased, while the contents of C2H6, C3H8, and C3H6 decreased with pyrolysis temperature increasing. Fast pyrolysis and CO2 atmosphere favored the conversion of stable macromolecules into short chain methyl compounds, resulting in a higher CH4 yield.

ACKNOWLEDGMENT The research was supported by the Talent Introduction Project of China University of Petroleum (East China), Grant No. Y1704008.


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Experimental Study on Pyrolysis Characteristics of Oil Sludge with a

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