Stuart 1991 International Conference on Coal Science Proceedings

Proceedings of the International Conference on Coal Science, 16-20 September 1991, University of Newcastle-Upon-Tyne, United Kingdom
1. Auflage 2013
ISBN: 978-1-4831-4214-2
Verlag: Elsevier Science & Techn.
Format: EPUB
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E-Book, Englisch, 1056 Seiten

1991 International Conference on Coal Science Proceedings

Dr. Sam Stuart is a physiotherapist and a research Fellow within the Balance Disorders Laboratory, OHSU. His work focuses on vision, cognition and gait in neurological disorders, examining how technology-based interventions influence these factors. He has published extensively in world leading clinical and engineering journals focusing on a broad range of activities such as real-world data analytics, algorithm development for wearable technology and provided expert opinion on technology for concussion assessment for robust player management. He is currently a guest editor for special issues (sports medicine and transcranial direct current stimulation for motor rehabilitation) within Physiological Measurement and Journal of NeuroEngineering and Rehabilitation, respectively.

Autoren/Hrsg.

Stuart, Sam

Leseproben

EXAMINATION OF MACROMOLECULAR NETWORK OF COAL BY DIFFERENTIAL SCANNING CALORIMETRY

Kouichi Miura, Kazuhiro Mae, Shoji Takebe and Kenji Hashimoto*,     Research Laboratory of Carbonaceous Resources Conversion Technology,

Publisher Summary

This chapter explores the macromolecular network of coal by differential scanning calorimetry. It describes the properties of five coals used in a study described in the chapter. These coals were ground into the particles of less than 74 µm in diameter and were then dried in vacuo at 110°C for 24 h before use. Four solvents, namely, tetralin (Tet.), 1-buthanol (1-BuOH), ethanol (EtOH), and quinoline (Q) were used for the swelling. Tetralin was mainly used because of its nonpolarity. The swelling of coal was performed by simply mixing coal and solvent by the ratio of 1 to 0.6 by weight in a closed tube. It was performed at 30°C for 24 h for the polar solvent and was performed at 100 to 220°C for 1 h under 1 MPa of N2 for the nonpolar solvent. The chapter presents the swelling ratio of Taiheiyo (TC) coal treated with tetralin and that of the vacuum-dried coal against the swelling temperature. It was found that TC began to swell at around 70°C and seemed to reach an equilibrium swelling ratio of ca. 1.35 over 150°C.

1 INTRODUCTION

Several attempts[1–4] have been made to estimate the non-covalent bond in coal from calorimetric measurements during the solvent swelling, in which the heat of wettability of the strong polar solvent was mainly measured using the micro calorimeter. However, the information on the non-covalent bond could not be successfully extracted from these studies because of the strong interaction between the polar solvent and the coal. Non-polar or weak polar solvents should be used to study carefully the macromolecular structure of coal through the solvent swelling.

From this viewpoint we used the non-polar solvent for the swelling, but the swelling was performed at the temperatures as high as 220 °C. Then we tried to estimate the heat required to break the non-covalent bonds in coal by measuring the DSC and TG profiles of this swollen coal.

2 EXPERIMENTAL

The properties of five coals used are given in Table 1. These coals were ground into the particles of less than 74 µm in diameter, then dried in vacuo at 110 °C for 24 h before use. Four solvents, tetralin (Tet.), 1-buthanol (1-BuOH), ethanol (EtOH) and quinoline (Q) were used for the swelling. Tetralin was mainly used because of its non-polarity. The swelling of coal was performed by simply mixing coal and solvent by the ratio of 1 to 0.6 by weight in a closed tube. It was performed at 30 °C for 24 h for the polar solvent, and was performed at 100 to 220 °C for 1 h under IMPa of N2 for the non-polar solvent. The swollen coal (STC) was evacuated at 70 °C for 24 h to completely remove the solvent from the STC. The swelling ratio of the STC and thus prepared vacuum-dried coal (VDC) was measured by the volumetric technique [5].

Table 1

Properties of Coal

Morwell (MW)

48. 2

50. 3

1. 5

67. 1

4. 9

0. 6

0. 3

27. 1

1. 34

1. 00

Jacobsranch(JR)

48. 8

39. 4

11. 8

68. 3

5. 5

0. 9

0. 5

24. 8

1. 32

1. 24

Taiheiyo (TC)

43. 2

45. 8

11.0

74. 5

6. 0

1. 3

0. 2

18. 0

1. 33

1. 28

Illinois #6 (IL)

57. 8

34. 8

7. 4

77. 1

5. 6

1. 5

3. 9

11. 9

1. 22

1. 01

Liddel (LD)

57. 4

34. 5

8. 1

83. 4

5. 5

2. 2

0. 6

8. 3

1. 20

1. 04

To examine the change of non-covalent bond of the coal during the swelling by calorimetrically, the DSC profile and the TG curve of the raw coal, the STC, and the solvent were measured under a constant heating rate of 5 °C/min by use of a differential scanning calorimeter (Shimadzu Co., DSC 50) and a thermobalance (Shimadzu Co., TGA 50), respectively.

3 RESULTS AND DISCUSSION

The swelling ratio of TC treated with tetralin and that of the VDC are shown against the swelling temperature. TC began to swell at around 70 °C, and seemed to reach an equilibrium swelling ratio of ca.1.35 over 150 °C. The swelling ratio of the VDC, ?VDC, is shown by the closed key in Fig. 1. At the swelling temperatures lower than 100 °C the ?VDC value is exactly unity. This means the swollen then vacuum dried coal returned to the raw coal as far as the volume is concerned at these temperatures. On the other hand, the ?VDC value does not return to unity at the swelling temperatures of 150 and 220 °C, and interestingly ?VDC is very close to ?STC at 220 °C. This indicates that the swelling at 220 °C is almost irreversible. This is also the case for JR as shown in Table 1. The irreversibly swollen VDC is utilized later to estimate solvent-coal interaction solely.

Fig. 1 Changes of the swelling ratios of the STC and its VDC

We have clarified that the swelling by tetralin affects solely to the non-covalent bonding of coal as far as the swelling is performed at a temperature lower than a critical temperature, Tc. The critical temperature, Tc, which varied with coal type was estimated to be around 230 °C for TC, for example. In the solvent swollen coal some non-covalent bonding are broken, and the macromolecular network is expected to be altered from the raw coal. In this work we have tried to estimate the energy required to break the non-covalent bonding through the TG and DSC measurements during the heat up of raw coal, solvent, and the STC from 25 to 220 °C.

Figure 2 shows schematically the enthalpy levels of the raw coal heated to 220 °C (state A), the STC at 25 °C (state B), and the STC heated to 220 °C (state C) on the basis of the raw coal and the solvent at 25 °C. The enthalpy at state A, HC', is easily measured. In the STC at state B some non-covalent bonding are broken, and the solvent-coal interaction exists. Therefore, the enthalpy at state B, Hi, is the sum of the energy to break the non-covalent bonding, HNC, and that deriving from the solvent-coal interaction, HS-C. The value of HNC is expected to be positive, whereas that of HS-C is negative. The enthalpy at state C, Hf, consists of the enthalpy of the solvent, HS, and the coal, HC. HS is easily obtained from the DSC measurement of the solvent. The enthalpy difference ?H (=Hf – Hi) can be obtained from the DSC and TG measurements of the STC. Then we can extract the value of Hi from the measurable quantities if we assume that the coal at state C is the same as that at state A, namely Hc=Hc', by

Fig. 2 Schematic enthalpy level of various state of coal and STC

i=Hf-?H = HC’+HS-?H (1)

(1)

If we could further estimate the value of HS-C, we can determine the enthalpy required to break the non-covalent bonding by

NC=Hi- HS-C (2)

(2)

It was possible to determine the value of HS-C for the coal swollen by tetralin by measuring the DSC and TG profiles during the desorption of the tetralin from the irreversibly swollen VDC which adsorbed tetralin. Figure 3 shows the TG and DSC curves for tetralin and the TC swollen at 100 °C and 220 °C. The endothermic heats integrated over 25 to 220 °C correspond to HS for tetralin, HC for the coal and ?H for the STC, respectively.

Fig. 3 TG and DSC profiles of STCs and tetralin

Figure 4 shows the values of Hi of TC estimated using several solvents. Hi decreased with the increase in the polarity of solvent, and it was large negative value in the case of the swelling by quinoline as mentioned in other earlier works [1–4]. This is because the polar solvent interacts with the functional groups in the coal and the strong coal-solvent hydrogen bonding is formed in place of the coal-coal hydrogen bonding during the swelling, leading to |HS-C|>HNC.

Fig. 4 Effect of solvent type on Hi

Figure 5 shows the changes of the values of HS-C and HNC against the swelling ratio. All the values were estimated by utilizing tetralin as the solvent. HS-C decreased with the increase of the swelling ratio. This means that the solvent interacts strongly with the stronger non-covalent site...