Use of high-temperature, high-torque rheometry to study the viscoelastic properties of coal during carbonization

被引:12
作者
Diaz, M. Castro [1 ]
Duffy, John J. [1 ]
Snape, Colin E. [1 ]
Steel, Karen M. [1 ]
机构
[1] Univ Nottingham, Nothingham Fuel & Energy Ctr, Sch Chem Environm & Mining Engn, Nottingham NG7 2RD, England
关键词
D O I
10.1122/1.2754317
中图分类号
O3 [力学];
学科分类号
08 ; 0801 ;
摘要
When coal is heated in the absence of oxygen it softens at approximately 400 degrees C, becomes viscoelastic, and volatiles are driven off. With further heating, the viscous mass reaches a minimum viscosity in the range of 10(3)-10(5) Pa s and then begins to resolidify. A high-torque, high-temperature, controlled-strain rheometer with parallel plates has been used to study the theology during this process. Under shear, the viscosity of the softening mass decreases with increasing shear rate. During resolidification, the viscosity increases as C-C bond formation and physical interactions gives rise to an aromatic network, but, under shear, the network breaks apart and flows. This is viewed as a yielding of the structure. The higher the shear rate, the earlier the yielding occurs, such that if the shear rate is low enough, the structure is able to build. Also, further into resolidification lower shear rates are able to break the structure. It is proposed that resolidification occurs through the formation of aromatic clusters that grow and become crosslinked by non-covalent interactions. As the clusters grow, the amount of liquid surrounding them decreases and it is thought that the non-covalent interactions between clusters and liquid could decrease and the ability of growing clusters to move past each other increases, which would explain the weakening of the structure under shear. This work is part of a program of work aimed at attaining a greater understanding of microstructural changes taking place during carbonization for different coals, in order to understand the mechanisms that give rise to good quality cokes and coke oven problems such as excessive wall pressure. (c) 2007 The Society of Rheology.
引用
收藏
页码:895 / 913
页数:19
相关论文
共 30 条
[1]   The viscosity of solutions. [J].
Arrhenius, S .
BIOCHEMICAL JOURNAL, 1917, 11 (02) :112-133
[2]   THE CHARACTERIZATION OF INTERFACES BETWEEN TEXTURAL COMPONENTS IN METALLURGICAL COKES [J].
BARRIOCANAL, C ;
HANSON, S ;
PATRICK, JW ;
WALKER, A .
FUEL, 1994, 73 (12) :1842-1847
[3]   The laboratory identification of dangerously coking coals [J].
Barriocanal, C ;
Patrick, JW ;
Walker, A .
FUEL, 1998, 77 (08) :881-884
[4]   Contribution of the isotropic phase to the rheology of partially anisotropic coal-tar pitches [J].
Blanco, C ;
Fleurot, O ;
Menéndez, R ;
Santamaría, R ;
Bermejo, J ;
Edie, D .
CARBON, 1999, 37 (07) :1059-1064
[5]   Determination of the effect of different additives in coking blends using a combination of in situ high-temperature 1H NMR and rheometry [J].
Díaz, MC ;
Steel, KM ;
Drage, TC ;
Patrick, JW ;
Snape, CE .
ENERGY & FUELS, 2005, 19 (06) :2423-2431
[6]  
ELLIOT MA, 1981, CHEM UTILIZATION
[7]   Change in viscosity of softening coal upon heating with its liquid content. Part II: Examination of rheological property and phase structure of softening coal [J].
Hayashi, JI ;
Morita, M ;
Chiba, T .
FUEL, 2003, 82 (14) :1743-1750
[8]   Change in viscosity of softening coal upon heating with its liquid content. Part I: linear relationship between logarithm of viscosity and liquid fraction [J].
Hayashi, JI ;
Morita, M ;
Moriyama, R ;
Chiba, T .
FUEL, 2003, 82 (14) :1735-1741
[9]   Network structure of coals and association behavior of coal-derived materials [J].
Iino, M .
FUEL PROCESSING TECHNOLOGY, 2000, 62 (2-3) :89-101
[10]   Changes in the rheology and microstructure of processed cheese during cooking [J].
Lee, SK ;
Buwalda, RJ ;
Euston, SR ;
Foegeding, EA ;
McKenna, AB .
LEBENSMITTEL-WISSENSCHAFT UND-TECHNOLOGIE-FOOD SCIENCE AND TECHNOLOGY, 2003, 36 (03) :339-345