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Co-pyrolysis of Low-grade Indian Coal and waste plastics: Future Prospects of Waste Plastic as Source of Fuel Gitika Rani Saha, Tonkeswar Das, Pranjal Handique, Dipankar Kalita, and Binoy K Saikia Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.7b03298 • Publication Date (Web): 05 Jan 2018 Downloaded from http://pubs.acs.org on January 7, 2018

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Co-pyrolysis of Low-grade Indian Coal and Waste Plastics: Future Prospects of Waste Plastic as Source of Fuel Gitika Rani Saha 1, 2, Tonkeswar Das 2, Pranjal Handique2, Dipankar Kalita 3, Binoy K Saikia *2 1 2

Department of Chemical Engineering, Indian Institute of Technology (ISM), Dhanbad, India

Polymer Petroleum and Coal Chemistry Group, Materials Science and Technology Division, CSIR-North East Institute of Science & Technology, Jorhat-785006, India

3

Department of Food Engineering and Technology, Tezpur University, Tezpur-784008, India *Corresponding author: [email protected]; [email protected]

Abstract Co-pyrolysis of waste plastics with different materials, viz. coal, biomass is an eco-friendly and industrially acceptable waste management technique. In the present study, an attempt has been made to produce value-added products by utilizing waste plastics and low-grade North Eastern (NER) Indian coal through co-pyrolysis process. Three thermoplastics commonly found in municipal wastes [Polyethylene terephthalate (PET), Low Density Polyethylene (LDPE), Polypropylene (PP)] and a simulated waste plastic mixture (MP) were selected and blended with NER coal at a mass ratio of 3:2 (coal: plastics). The experiments were performed at 500°C, 600°C, and 700°C in nitrogen atmosphere at a heating rate of 10 °C/min. After analysis it was found that coal/ PP and coal/LDPE produced good quantity of tar whereas coal/MP improved the quality of the char products. Significant interaction between coal and different types of plastics were observed in Thermogravimetric analysis (TGA-DTG). Proximate, solid FT-IR and FE-SEM analyses were done for characterization of the char products. Furthermore, liquid FT-IR, NMR, and GC-MS analysis of the tar samples ensured that higher alkanes, alkenes, and aromatics which are comparable to that of the petrol-derived fuels are present in the tar samples; thus, it can be used as an alternative fuel for the industrial heating purpose.

Keywords: Waste plastics, Low grade coal, Co-pyrolysis, Thermal Analysis, Tar as fuel, Char.


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1. Introduction In today’s world, disposal problem of various ‘End-of-life' plastics which end up in landfill releasing hazardous chemicals, pose a serious threat to the environment. Various waste management techniques have been adapted for proper disposal of the waste plastics. Recycling methods like re-pelletization, remolding, and use of waste plastics as feedstock for liquid fuel production 1-5 are successful for utilization of homogeneous plastic wastes; however, they are not suitable enough for heterogeneous wastes. This emphasizes the use of heterogeneous waste plastics in other alternative techniques such as waste plastics as an additive in pyrolysis of other materials such as coal

6-11

, biomass

12-13

etc. Currently this study has drawn much attention

because it not only partially reduces of the use of non-renewable energy sources but also protects the nature by utilizing the harmful plastic wastes converting to value-added products. Several feed stocks are investigated for co-pyrolysis with plastics, but, among all, an environment friendly and industrially acceptable alternative is co-carbonization of coal with waste plastics 1415

. Coal is the most widely available fossil fuel and, in India a good deposit of low-grade

coal is found in the North Eastern Region (NER); this is a vital energy source and makes important contribution to the economic growth of the country. Low-ash, high-volatile, highsulfur contents make the NER coal unsuitable for combustion, gasification, liquefaction, carbonization and metallurgical purposes16-21. The lumpy coals are infused with shale or carbonaceous materials, which makes it non-caking in nature

17

. Therefore, effective utilization

of low-grade NER coals has become a challenging issue. Various studies have been conducted on co-pyrolysis of coal and plastics showing that small addition of plastics to coal has the ability to enhance the coke quality and liquid yield 22-24; more generally, the overall conversion of coal gets influenced by addition of plastics


25

. During

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the co-conversion process the composition of the polymer plays a significant role which affects the coal thermoplastic behavior. The plastics break down to smaller intermediate species which are further degraded to smaller hydrocarbons 7. Formation of such hydrocarbon molecules has the capability to improve the thermal behavior of the coal at the vital stage of metallurgical coke formation at high temperature 7. The polymer plays a role of hydrogen donor while coal promotes radical formation; together it enhances the co-pyrolysis product 27. Industrial utilization of plastic waste in coke ovens first started at the “Nagoya and Kimutsu coke ovens” (capacity 80,000 tons/year) by Nippon Steel Corporation in 2000

41

. A synergistic effect is also observed

during co-pyrolysis at high temperature region, resulting in higher yields compared to that of the pyrolysis of coal alone

23, 28-29

. However, very few investigations have been done on the

interaction between low-grade coals with waste plastics during co-pyrolysis process

29

. The

possibility of upgrading the product quality of low-grade coal, using waste plastics as hydrogen donor is yet to be explored. Addition of waste plastics as a hydrogen source for co-liquefaction of coal is a wellstudied approach. Different grades of plastics (like: PET, PE, PP) have been studied for copyrolysis with coal which resulted in good quality coke and oil product

22-24

. Some researchers

also studied the effect of different types of coals, like: Taghiei et al. obtained high yield of oil through co-liquefaction of bituminous, subbituminous and lignite coals 11, Sakurovs et al. studied the interaction between Australian coking coal and plastics

14

. However, very few works has

been done on the effect of addition of plastics on low-grade coal. Since, the low-grade coals are unsuitable for commercial use; it is important to investigate whether the product quality can be enhanced using plastics as a source of hydrogen or not, which helps in coal liquefaction process 11

. Sharma et al. reported the kinetic study of the co-pyrolysis reaction of low-rank NER coal and

waste LDPE, but a detailed research on the co-pyrolysis behavior and product composition has


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not been done yet and this was the actual motivation as well as the novelty of the current study. The study is important as it focuses on gainful utilization of hazardous waste plastics as well as high-sulfur low-rank coal to value-added products. In the present investigation, the low-grade coal from the North Eastern Region of India was used for co-pyrolysis with waste plastics. The study aims to understand the co-pyrolysis behavior as well as to evaluate the pyrolysed product composition for gainful utilization of hazardous waste plastics as well as high-sulfur low-grade coal to value-added products like industrial coke and oil. The co-pyrolysis of five different samples viz. Raw coal, coal-Mixed waste plastic (MP), coal-Low Density Polyethylene (LDPE), coal-Polypropylene (PP), and coalPolyethylene Terephthalate (PET) were studied at three different temperatures viz. 500°C, 600°C, and 700°C. Thermal behavior during the co-pyrolysis process was also identified through Thermogravimetric Analysis under an inert atmosphere. A primary investigation of the pyrolysis products was carried out through advanced-level characterization techniques.

2. Experimental Sections 2.1 Materials The low-grade coal sample used in this study was obtained from the pilot plant of Coal Chemistry Division, CSIR-NEIST, Jorhat (India), which was collected from NER coalfield (Cenozoic age), India. The raw coal sample was air and sun dried and crushed to below 3.180 mm and ground to about 0.211 mm by adopting standard methods (ASTM D2013/D2013M-12). The simulated mixed waste plastic sample used in this study was collected from the residential area of CSIR-NEIST, Jorhat campus. These were washed properly and air and sun dried. In addition to that, virgin Low Density Polyethylene (LDPE), Polypropylene (PP) and Polyethylene Terephthalate (PET) (Figure S-1) samples were also commercially purchased and used as


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received. The plastics were shredded manually to an average size of 3-5 mm and used for the experimental purpose. 2.2 Preparation of blend samples The finely ground coal sample was blended with PET, LDPE, PP, and MP with an appropriate mass ratio of 3:2 on the basis of the optimized blending ratio as supported by other literatures 29, 42

. The blended samples were denoted as Raw Coal, Coal/PET, Coal/LDPE, Coal/PP, and

Coal/MP for the subsequent analysis 2.3 Co-pyrolysis of the coal/plastic mixtures Pyrolysis of the raw coal sample along with co-pyrolysis of four different blends of coal/plastics were carried out in a quartz fixed-bed reactor (19-mm internal diameter) connected with a temperature programming system in an inert atmosphere (Figure 1). Approximately 10 g of the air dried samples were taken into a quartz retort. At the end of the coal bed, the remaining space of the retort was filled with quartz wool and ceramic granules to keep the coal bed intact. In order to collect the tar, a condensation assembly was used whose one end was connected to the retort and the other end was dipped into a water bath to impede the emission of the hazardous gases to the environment. During pyrolysis, the retort was flushed with nitrogen to create an inert atmosphere and then sealed using an asbestos plug. Then it was inserted into the furnace and heated up to 500°C, 600°C, and 700°C in different batches with a heating rate of 10 °C/min and was kept constant at the corresponding terminal temperatures for 1 h. Then, the retort was removed and cooled to room temperature. The char and tar products (as denoted in Table 2) were collected for further studies. 2.4 Characterizations Techniques The proximate analysis (Moisture, Ash content, Volatile Matter, and Fixed carbon) of the raw coal sample was carried out in a Thermogravimetric Analyzer (Leco TGA701) (ASTM D758215). The sulfur content was determined by means of a Dual Range Sulfur Analyzer (Leco SACS Paragon Plus Environment

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144DR Dual Range Sulfur Analyzer) (ASTM D5016-08e1). The crucible swelling number (CSN) of the raw coal and coal/plastics blends were obtained by adopting the standard BIS/ ASTM method (IS 1353:1993). Fourier transform infrared (FT-IR) spectra of both char and tar products were recorded in transmittance mode with 4 cm-1 spectral resolution using a FT-IR spectrophotometer (IR Affinity-1, Shimadzu, Japan) and IR solution software. The solid samples were tested by making solid KBr pellets using hydraulic pellet press whereas a NaCl pellet was used for FT-IR analysis of the tar products. For Field Emission-Scanning Electron Microscopic (FE-SEM) analysis, the char samples were critical-point dried, and fixed to metal stubs with carbon-conducting doublesided adhesive tape. The samples were coated with gold with the aid of an Auto Fine Coater (QI5ORS) with a spot size of 36 mm and examined under a scanning electron microscope (ΣIGMA-Field Emission Scanning Microscope, Carl Zeiss Microscopy). Observations on the SEM images were made at 20 kV with a working distance of 11 mm and spot size of 36 mm. The SEM micrographs were further developed by using the “Image J” program (software version 1.47). The calorific value of the tar samples was determined with the aid of a Leco AC-350 Automatic Bomb Calorimeter (ASTM D5865-13).

13

C nuclear magnetic resonance (NMR)

analyses of the tar samples were obtained with an Ascend-500 MHz, FT-NMR instrument. For NMR analysis, tar samples were dissolved in CDCl3 which was used as internal standard. Chromatographic analysis of the tar samples were carried out using an Agilent 7890A gas chromatograph equipped with 240 Ion Trap MS. The separation was done with 19091J-413 capillary column of dimensions 30m x 320µm x 0.25µm. First, the tar samples were dissolved in acetone and then 1 µl of each sample was injected into a split less mode with an injection temperature of 250°C. The oven temperature was increased from 50°C to 250°C with a rate of


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7°C/minute with a total runtime of 34.5 minutes. Helium was used as carrier gas with a constant flow rate of 1.4 ml/min linear velocity. For MS, a mass range of 50 to 500 m/z was used with trap temperature of 200°C, manifold temperature of 50°C, and a transfer line temperature of 250°C was maintained. The components present in the sample were identified by comparing retention time with their reference protocol and reconfirmed by mass spectral library of standard compounds (NIST-MS Search 2.0 software, National Institute for Standard Technology). 2.5 Thermogravimetric analysis The non-isothermal analyses (TGA-DTG) of the samples were performed in a Thermal Analyzer (model Leco TGA701 Thermogravimetric Analyzer) in nitrogen atmosphere. The experiments were carried out with a heating rate of 10ºC min-1 from room temperature to 900ºC using an Al2O3 crucible. Approximately 500 mg of the sample was used for each experimental run for each of the samples. The experiments were repeated for three times for a single heating rate to confirm the authenticity of the data generated and their average was taken as the final value.

3. Results and Discussions 3.1 Physico-chemical Characterization The fundamental difference in composition of various coal/plastic blends were examined by proximate analysis, as summarized in Table 1. Volatile matter and ash content are the two important factors that influence the char and tar yield in the pyrolysis process. High volatile matter content favors the liquid oil production while high ash content results in more gas and char product 30. High volatile matter content and low ash content of both coal/LDPE & coal/PP ensures a good quantity of liquid tar, as evident from Table 1. The coal/PET blend, on the other hand, showed some ability to produce improved quality char owing to its significant content of fixed carbon. However, the mixture of coal/MP showed an intermediate behavior.


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Proximate analysis of the char samples revealed that temperature plays a significant role in the char composition. After co-pyrolysis, the fixed carbon content of most of the char products was found to increase with increasing temperatures (except coal/ PP blend which showed an opposite trend) (Table 1). This confirmed that the char quality was improved through the copyrolysis process with increasing temperature. The sulfur content of the char samples was also found to reduce after the pyrolysis process. The swelling index was measured for the raw coal and coal/plastics blends to evaluate their coking property and the CSN of the raw coal sample was found to be 1. For other coal/ plastic blends the CSN ranged between 0-2.5. 3.2 Analysis of Co-Pyrolysis Efficiency The mass balance of the co-pyrolysis process at three different temperatures viz. 500℃, 600℃ and 700℃ are listed under Table 2. The efficiency of the co-pyrolysis process was calculated according to Eq. (2) 12:

=

× % ()

Where, ‘Ej’ is the pyrolysis process efficiency for any ‘j’ fraction (solid, liquid, gas), Mj is the weight of the ‘j’ fraction (solid, liquid, gas), and ‘M’ is weight of the feed used in the process (pyrolysis, co-pyrolysis). The amount of the gas released or the loss that took place during the process was calculated using difference method. The results show that the addition of PP and LDPE had the highest impact on the liquid fraction 31 whereas PET addition enhanced the solid and gaseous fraction. An intermediate behavior was obtained for coal/MP which implies the interaction between different grades of plastics with coal. Figure 2 shows the effect of temperature on the pyrolysis products. From the physico-chemical analysis and yield of co-pyrolysis it was observed that comparatively better quality char and tar products are obtained at the pyrolysis temperature of ACS Paragon Plus Environment

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700°C. Hence, 700°C can be considered as the optimum temperature for the co-pyrolysis process and some of the analyses were done based on this temperature. 3.3 Thermal analysis (TGA-DTG) of raw coal and coal/plastic mixtures Figure 3 shows the thermal analysis (TGA-DTG curve) behaviour of raw coal and coal/plastic blends. Thermal analysis revealed that coal and coal/plastic blends degrade in a different fashion. The raw coal started degrading at a comparatively low temperature (300ºC) and weight loss occurred over a vast temperature range (650ºC), whereas all coal/plastic blends had a narrow degradation range ( coal/PP> raw coal> coal/MP>coal/PET, which shows that the thermal stability of the blends depends on the type of polymer blended with the coal. Moreover, it is also important to observe that the final residue (57.28 %) of the coal sample was very high compared to that of coal/plastic blends (Table 3). This can be explained from their proximate analysis (Table 1) showing high ash content and fixed carbon in coal which was not degraded completely at 900°C. On the contrary, coal/LDPE yielded a very small amount of residue (25.01 wt. %) due to its lower ash and fixed carbon content

25

. Finally, beyond 650°C the weight loss

can be predicted to be conducive due to the re-solidification of coal which finally converted to semi-coke 33, 29. At around 750°C the degradation rate of coal/plastics mixtures become relatively constant which corresponded to the presence of unreactive solid residue. 3.4 Analysis of the Char products 3.4.1 Solid FT-IR spectroscopic analysis

The role of various functional groups in the co-pyrolysis process was analyzed using FT-IR analysis as shown in Figure 4. The FTIR assignment was assessed from various studies 17, 26, 34-35 and summarized in Table S-1. A sharp absorption peak, observed at 1455.9 cm-1 for coal/MP, corresponds to strong aliphatic CH2 and CH3 groups. This implies its ability to produce hydrocarbon derivatives through co-pyrolysis process. The FTIR of coal/LDPE and coal/PP blends were found to be very similar to each other; this supports their similar degradation behavior as evident from DTG curve (Figure 3). The peak at around 1568.9 cm-1 observed for coal/LDPE and coal/PP showed CH2 asymmetric vibration and CH3 symmetric vibration related to aromatic groups. ACS Paragon Plus Environment

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Furthermore, FT-IR spectra of the char products displayed a drastic change with varying temperatures. Addition of MP to coal displayed strong absorbance peaks at 1686.8cm-1 at 500°C, 3431.5 cm-1 and 1383.5 cm-1 at 600°C and finally 2844.8 cm-1 and 1033.3 cm-1 at 700°C. These peaks confirmed the aromatic C=C stretching, O-H, N-H stretching vibration, and presence of aliphatic CH2 and CH3 groups. However, huge variation was obtained in coal and PET mixture before and after the co-pyrolysis process. The broad peak intensity at around 1600 cm-1 of the sample is increased after the co-pyrolysis process, and showed a sharp peak due to the formation of C=C double bonds during the process. 3.4.2 Observation from FE-SEM

The surface morphology of the crushed and dried forms of the char products, obtained from copyrolysis of raw coal and coal/MP at 700°C, was observed with a Field Emission Scanning Electron Microscope. The FE-SEM images at low and high magnifications are shown in Figure 5. The SEM images of the raw coal sample show a flake-like structure and devolatilization holes on the surface of the carbonized char. A mesoporous structure ( coal/PP> coal/ MP> coal/PET> raw coal. Coal/ LDPE and coal/PP tar were found to have very high calorific values (almost double of the coal tar). But, the presence of oxygenated compounds in coal/PET and coal/MP tar made the liquid fraction corrosive in nature with lower heating value (29.27 MJ/kg). However, several hydrocarbons detected in GC-MS were comparable with that of the petrol-derived fuels and, thus, it can be used as a source of alternative fuel for the industrial heating purpose.

Acknowledgements The authors are thankful to the Director, CSIR-North East Institute of Science and Technology (NEIST), Jorhat, Assam for providing facilities to complete this work. The authors express special thanks to Dr Jim Hower for editing the paper and Mr Nipu Dutta for providing the plastic


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samples. Financial assistance from CSIR (OLP-2003) is thankfully acknowledged. The constructive comments received from esteemed reviewers are thankfully acknowledged.


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Figure 1: Schematic diagram of the pyrolysis unit


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(a)

(b)

(c) Figure 2: Effect of temperature on percentage yields of (a) Char, (b) Tar and (c) Gas + Loss


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Figure3: TGA-DTG curves at heating rate 10 ºC min-1

(a)

(b)


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(c)

(d)

(e) Figure 4: FT-IR analysis of (a) Raw Coal, (b) Coal/PET, (c) Coal /LDPE, (d) Coal/PP and (e) Coal /MP


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A (×6000)

B (×45000)

Thermal Cracks

C (×200000)

Carbon nanotubes

D (×45000)

E (×200000)


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Carbon nano-balls

F (×261170) Figure 5: FE-SEM images of the char products obtained after pyrolysis of Raw Coal (A-C), Coal/ MP (D-F)

Figure 6: FT-IR analysis of the pyrolytic tar samples obtained from raw coal sample and coal/plastics blends at 700°C


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Table 1: Physico-chemical properties of raw materials and char samples obtained during co-pyrolysis at 500°C, 600°C and 700°C

Sl. No.

Proximate Analysis (%) Identification No.

M

Ash

VM

FC

S

1.

Raw Coal

3.2

1.2

40.5

55.1

2.31

2.

Coal/PET

2.10

0.84

33.96

63.10

1.10

3.

Coal/LDPE

2.35

0.96

61.85

34.84

1.11

4.

Coal/PP

2.43

1.09

61.52

34.96

1.06

5.

Coal/MP

2.11

0.91

43.32

53.66

1.09

6.

500Craw coal

4.13

2.39

19.31

74.17

1.80

7.

500Ccoal/PET

3.31

1.71

36.01

58.97

1.65

8.

500Ccoal/LDPE

3.06

2.20

28.97

65.77

1.53

9.

500Ccoal/PP

6.01

2.58

8.76

82.65

1.57

10.

500Ccoal/MP

3.70

2.36

24.11

69.83

1.63

11.

600Craw coal

4.68

2.42

16.15

76.75

1.80

12.

600Ccoal/PET

4.70

1.91

20.14

73.25

1.59

13.

600Ccoal/LDPE

4.34

2.64

13.93

79.09

1.56

14.

600Ccoal/PP

4.28

2.59

13.09

80.04

1.73

15.

600Ccoal/MP

3.75

2.18

28.98

65.09

1.63

16.

700Craw coal

6.12

2.65

9.30

81.93

1.58

17.

700Ccoal/PET

6.22

2.10

12.65

79.03

1.43

18.

700Ccoal/LDPE

5.34

2.66

10.98

81.02

1.46

19.

700Ccoal/PP

3.64

2.50

18.79

75.07

1.80

20.

700Ccoal/MP

7.83

2.43

12.19

77.55

1.33

M: Moisture; Ash: Ash content; VM: Volatile matter; FC: Fixed carbon; S: Total sulfur


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23 Table 2: Yield of Pyrolysis

Pyrolysis Temperature (°C)

Sl. No.

500 Sample

1.

Solid Fraction

2.

Liquid Fraction

3.

Gas Fraction + Loss

500Craw coal 500Ccoal/PET 500Ccoal/LDPE 500Ccoal/PP 500Ccoal/MP 500Traw coal 500Tcoal/PET 500Tcoal/LDPE 500Tcoal/PP 500Tcoal/MP 500Graw coal 500Gcoal/PET 500Gcoal/LDPE 500Gcoal/PP 500Gcoal/MP

600 Yield (wt. %) 69.96 52.06 31.57 36.80 52.63 14.81 13.27 15.7 31.97 17.17 15.23 34.67 52.74 31.23 30.20

Sample 600Craw coal 600Ccoal/PET 600Ccoal/LDPE 600Ccoal/PP 600Ccoal/MP 600Traw coal 600Tcoal/PET 600Tcoal/LDPE 600Tcoal/PP 600Tcoal/MP 600Graw coal 600Gcoal/PET 600Gcoal/LDPE 600Gcoal/PP 600Gcoal/MP

700 Yield (wt. %) 66.85 51.74 39.67 35.62 50.10 14.47 9.78 24.36 27.43 14.85 18.68 38.48 35.97 36.95 35.05

Sample 700Craw coal 700Ccoal/PET 700Ccoal/LDPE 700Ccoal/PP 700Ccoal/MP 700Traw coal 700Tcoal/PET 700Tcoal/LDPE 700Tcoal/PP 700Tcoal/MP 700Graw coal 700Gcoal/PET 700Gcoal/LDPE 700Gcoal/PP 700Gcoal/MP

Table 3: Percentage weight loss and maximum temperature obtained from TGA-DTG curves

Sl. No.

Sample

∆W1

∆W2

Tmax

Final Residue

(%)

(%)

(ºC)

(Wt. %)

1.

Raw Coal

4.69

15.38

473

57.28

2.

Coal/PET

3.26

67.35

437

36.92

3.

Coal/LDPE

4.02

77.67

482

25.01

4.

Coal/PP

4.23

75.54

480

26.18

5.

Coal/MP

3.04

64.07

439

38.14


Yield (wt. %) 63.12 46.79 35.88 35.52 44.91 14.47 9.78 24.36 27.43 14.85 16.94 39.46 39.16 29.67 40.99

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Energy & Fuels

24 Table 4: Elemental composition of coke/char products obtained after pyrolysis of Raw Coal (C1), Coal/MP (C15) and Carbon nano-balls at 700°C

Sl. No.

Sample

Element

Weight%

Atomic%

1.

700Traw coal

Carbon

88.22

90.89

Oxygen

11.78

9.11

Carbon

91.63

93.58

Oxygen

8.37

6.42

Carbon

96.73

97.53

Oxygen

3.27

2.47

2.

700Tcoal/MP

3.

Nano-balls

Table 5: Gross calorific value of tar products

Sl. No.

1.

2.

3.

Samples 500Traw coal 500Tcoal/PET 500Tcoal/LDPE 500Tcoal/PP 500Tcoal/MP 600Traw coal 600Tcoal/PET 600Tcoal/LDPE 600Tcoal/PP 600Tcoal/MP 700Traw coal 700Tcoal/PET 700Tcoal/LDPE 700Tcoal/PP 700Tcoal/MP


GCV of Tar (MJ/kg) 20.18 28.51 39.38 42.75 21.94 22.27 29.06 43.27 41.70 28.53 21.90 29.10 43.58 38.67 29.27

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Page 26 of 35

25

Table 6: FT-IR Assignments of the co-pyrolized tar samples obtained from raw coal sample and coal/plastics blends at 700°C 24, 26, 42, 59

Samples

700Traw coal

Wave number (cm−1) (w: weak; m: medium; s: strong; b: broad) 2929.42 (s), 2857.83 (m) 1609.09 (m)

700Tcoal/PET

700Tcoal/LDPE

700Tcoal/PP

700Tcoal/MP

1368.89 (w), 1368.89 (w), 1457.17 (m) 1216.97 (m) 761.22 (s), 816.89 (w) 1689. 42 (s) 1417.41(m) 1297.30 (s) 1185.15 (w) 704.75 (s), 936.99 (m) 3401.88(b) 2913.51(s),2849.88(s) 1649.66 (b) 1449.22(m) 761.22(w), 712.70(w) 2953.03 (s), 2907.71(s) 1455.85 (m) 1372. 01 (m) 1695.88(s) 1424.62(m) 1281.06(m) 713.95(w)

Assignments

CH2 asymmetric vibration and CH3 symmetric vibration bonded to aromatic groups Aromatic C=C stretching vibrations, C=C vinyl or other containing functional group Aliphatic CH2, COO- and CH3 group For C-O stretching of COOH Aromatic ring structures Aromatic C=C stretching vibrations, C=C vinyl or other containing functional group Aliphatic CH2, COO- and CH3 group For C-O stretching of COOH Condensation of benzene rings Aromatic ring structures O-H and N-H stretching vibration CH2 asymmetric vibration and CH3 symmetric vibration bonded to aromatic groups Aromatic C=O stretching COO- and CH3 group Aromatic ring structures CH2 asymmetric vibration and CH3 symmetric vibration bonded to aromatic groups COO- and CH3 group Aliphatic CH2 and CH3 group Aromatic C=C stretching COO- and CH3 group For C-O stretching of COOH Aromatic structures


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

Energy & Fuels

26 Table 7: 13C-NMR Assignments of the pyrolytic tar samples obtained from raw coal sample and coal/plastics blends at 700°C 37

Identification

Chemical Shift (ppm)

Type of Carbon

29.25-31.82

Short, long, and branched aliphatics

76.65-77.15

Alcohols, esters, phenolic-methoxys

14.01-32.11


76.66,77.17


126.45, 130.10, 133.94,144.57

Aromatic and olefins

14.27-39.16


76.88


111.17, 144.86


21.66-31.76

Short, long and branched aliphatics

61.39, 76.91, 77.16


128.32-133.71, 144.55


171.83

Esters and carboxylic acids

14.00, 22.58, 29.25-33.76


76.64, 76.89, 77.15


113.91


No. 700Traw coal

700Tcoal/PET

700Tcoal/LDPE

700Tcoal/PP

700Tcoal/MP


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

Page 28 of 35

27 Table 8: 1H-NMR Assignments of the pyrolytic tar samples obtained from raw coal sample and coal/plastics blends at 700°C 37

Identification

Chemical Shift (ppm)

Type of Carbon

1.18,1.52

Other aliphatic (bonded to aliphatic only) such as alkanes

2.15,2.18,2.20,2.24

Aliphatic adjacent to aromatic/alkene group

7.19

Aromatics

0.80, 0.82, 1.18, 1.34, 1.36


2.06-2.66


4.35

Aliphatic adjacent to oxygen/hydroxyl group such as alcohols, methylene dibenzene

7.19-8.13

Aromatics

1.18, 1.5-1.73


1.93-1.99, 2.20-2.28


4.57, 4.65


7.18

Aromatics

1.18,1.35


2.23-2.59


No. 700Traw coal

700Tcoal/PET

700Tcoal/LDPE

700Tcoal/PP

700Tcoal/MP

4.35


7.18-7.55, 7.95, 8.05-8.10

Aromatics

0.81, 0.82,1.18,1.52


7.19

Aromatics


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Energy & Fuels

28

Table 9: Compounds detected from GC-MS analysis of tar samples collected at 700°C

Sample Identification Number

Retention Time (min)

Component

% of Total

700Traw coal

3.524

1,3-Dioxolane-2,2-diethanol

2.340

6.384

Phenol

22.280

7.811

Phenol, 3-methyl-

4.122

8.275

p-Cresol

8.071

8.685

2,7-Bis-(4-piperidin-1-yl-butoxy)-fluoren-9-

13.480

one

700Tcoal/PET

700Tcoal/LDPE

9.134

4(1H)-Quinolinone, octahydro-1-methyl-

7.982

11.361, 18.949

Benzene, 1,3-bis(1,1-dimethylethyl)-

2.496

3.342

Ethylbenzene

2.340

3.495

o-Xylene

22.280

5.342

Benzene, (1-methylethyl)-

4.122

7.636

Ethanone, 2-(formyloxy)-1-phenyl-

8.071

9.832

Benzoic acid, ethyl ester

13.480

11.522

2-Chloroethyl benzoate

7.982

13.178

Benzoic acid, 4-methyl-

2.496

13.964

Biphenyl

2.340

14.452

4-Ethylbenzoic acid

22.280

16.032

1,1'-Biphenyl, 4-methyl-

4.122

3.591

(R)-(-)-2,2-Dimethyl-1,3-dioxolane-4-methanol

2.295

11.505


0.312

15.881

1-Hexadecanol

0.389

19.186, 20.624, 22.183 23.581

10-Heneicosene (c,t)

0.995

Dodecane, 1-cyclopentyl-4-(3-

1.239

cyclopentylpropyl)24.738

Cyclopropaneoctanoic acid, 2-[[2-[(2-

1.086

ethylcyclopropyl)methyl]cyclopropyl]methyl]-, methyl ester 26.198, 27.591, 29.792

Erucic acid ACS Paragon Plus Environment

3.061

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Page 30 of 35

29

700Tcoal/PP

3.501

1-Undecanol

6.712

7.914

3-Tetradecene, (Z)-

2.039

12.455, 12.777, 19.865 17.606

11-Methyldodecanol

11.114

Naphthalene, decahydro-1,4a-dimethyl-7-(1-

2.785

methylethyl)-, [1S-(1α,4aα,7α,8aβ)]20.976

Silane, tetra-2-propenyl-

2.647

24.011

Cyclopropanol, 1-(3,7-dimethyl-1-octenyl)-

2.956

26.772

Cyclododecanemethanol

3.657

29.301

Cyclopentane, 1,1'-[3-(2-cyclopentylethyl)-1,5-

3.394

pentanediyl]bis-

700Tcoal/MP

32.181

11,13-Dimethyl-12-tetradecen-1-ol acetate

8.303

4.107

Benzene, 1,3-dimethyl-

2.783

5.838

Benzene, (1-methylethyl)-

5.337

7.587

Cyclohexane, 1,3-butadienylidene-

0.946

11.594


4.214

13.749

Benzoic acid, 4-methyl-

5.654

14.300

Biphenyl

5.292


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Energy & Fuels

30

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