Characteristic Properties of Lignite To Be Converted to High-Strength

Nov 15, 2017 - A sequence of hot briquetting and carbonization (HBC) is a promising technology for the production of coke with a high mechanical stren...
1 downloads 10 Views 477KB Size
Subscriber access provided by READING UNIV

Article

Characteristic Properties of Lignite to be Converted to High-Strength Coke by Hot-Briquetting and Carbonization Shinji Kudo, Aska Mori, Gentaro Hayashi, Takuya Yoshida, Noriyuki Okuyama, Koyo Norinaga, and Jun-ichiro Hayashi Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.7b03155 • Publication Date (Web): 15 Nov 2017 Downloaded from http://pubs.acs.org on November 20, 2017

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

Energy & Fuels is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 31

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

Characteristic Properties of Lignite to be Converted to High-Strength Coke by Hot-Briquetting and Carbonization

Shinji Kudo†,*, Aska Mori†, Gentaro Hayashi†, Takuya Yoshida‡, Noriyuki Okuyama‡, Koyo Norinaga§, Jun-ichiro Hayashi†,ǁ



Institute for Materials Chemistry and Engineering, Kyushu University, 6-1 Kasuga Koen, Kasuga,

816-8580, Japan ‡

KOBE STEEL, Ltd. 2-3-1, Shinhama, Arima-cho, Takasago, Hyogo, 676-8670, Japan

§

Department of Chemical Systems Engineering, Graduate School of Engineering, Nagoya University,

Furo-cho, Chikusa-ku, Nagoya, 464-8603, Japan ǁ

Research and Education Center of Carbon Resources, Kyushu University, 6-1 Kasuga Koen,

Kasuga, 816-8580, Japan

* Corresponding author. E-mail: [email protected]; Tel/Fax: +81 92 583 7793

ABSTRACT A sequence of hot-briquetting and carbonization (HBC) is a promising technology for the production of coke with a high mechanical strength from lignite, but factors affecting the coke strength have not yet been fully understood. The HBC cokes prepared from twelve lignites in this study showed diverse tensile strength (e.g., from 0.2 to 31.2 MPa in the preparation at 200 °C and 112 MPa for hot-briquetting and 1000 °C for carbonization), and the coke strengths could not be explained by differences in commonly used structural properties of the parent lignites, such as

1 ACS Paragon Plus Environment

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

elemental composition and contents of volatile matter/fixed carbon and ash. In this study, two methods were proposed for correlating the coke strength with the lignite properties, which employed the chemical structure analyzed by solid-state

13

C NMR or the volumetric shrinkage during

carbonization. A stronger coke was obtained from lignite that contained more aliphatic carbons (less aromatic carbons) or shrank more considerably. These characteristics contributed to intensified compaction of lignite in the briquetting and suppression of the formation of large pores, which are a cause of coke fracture. Two empirical equations, predicting the coke strength from the parameters of lignite properties, were established to be criteria for selection of lignite as HBC coke feedstock, although further investigation with more experimental data would be necessary for the validation.

1. INTRODUCTION Lignite, a typical low-rank coal, is a potential feedstock for coke used in metallurgical industries and, especially, in the blast furnace. One of the most important properties required for the coke is mechanical strength. However, the absence of caking property in lignite renders it unsuitable as the coke feedstock, in spite of the huge reserves (proven global reserves are estimated at 280 gigatonnes1). Formed coke technology2 is an option for the use of lignite. Briquetting of coal with or without binders, followed by carbonization, can produce coke having a high mechanical strength, even from low-rank coals.3–11 Among the related studies, we have recently demonstrated binderless preparation of high-strength coke from low-rank carbonaceous materials, including lignite.5–8 A feature of the preparation method is briquetting at temperatures around 200 °C, where lignite hardly undergoes pyrolytic degradation, while its macromolecular structure is relaxed, resulting in the formation of a high-density briquette. The sequence of hot-briquetting and carbonization (HBC) produced a coke having a high tensile strength of over 30 MPa (obtained from a single Victorian lignite), which was far higher than that of conventional coke used in the iron-making industry (13 MPa), medium (13–5 MPa) or low (