Liquefaction characteristics

This article presents results from an experimental study of pre- and post-liquefaction characteristics of non-plastic sand-silt mixes at silt contents from 0% to 100% by weight, and three natural non-plastic silts. Undrained cyclic triaxial tests followed by dissipation of cyclic-induced pore pressures were carried out in order... 

Singh, S. (1994). Liquefaction characteristics of silts. Ground failures under seismic conditions. In S. Prakash P. Dakoulas (Eds.), Proceedings ASCE Convention, GSP 44, ASCE, (pp. 105-116). 

Given, P. H., Cronaucr, D. C., Spackman, W., Lovell, H. L., Davis, A., and Biswas, B., Dependence of coal liquefaction behavior on coal characteristics 1. vitrinite-rich samples. Fuel, 1975, 54, 34 39. 

The different processes and their material requirements are reviewed in References 19 and 20, while annual conferences have been held under the auspices of the U.S. Bureau of Standards and other interested bodies since 1976. The processes involved embrace combustion, gasification and liquefaction, each of which presents characteristically different corrosive environments. 

The reactions of some aromatic metal carboxylates are on the borderline of classification as solid-state processes. While there is no evidence of liquefaction, rates of decomposition in the poorly crystallized or vitreous reactant obey kinetic expressions more characteristic of reactions proceeding in a homogeneous phase. 

A further factor is that in any one continental land mass, at any one point in time, there have been a number of different environments of deposition of peat, which may well have influenced the characteristics of the coals derived from the peats. It is not proposed to review these in any general sense, but some discussion is offered later on the possible relevance of this factor in determining the liquefaction behavior of U.S. coals. In the meantime, we summarize, for future reference, the major coalbearing areas, or provinces, of the United States in Table III. 

Experimental Studies of the Dependence of Liquefaction Behavior of U.S. Coals on Coal Characteristics... 

A statistical study of the conversion with tetralin of 68 coals (60) must now be regarded as superseded by a later, more comprehensive paper (61), but it did show very clearly that bivariate plots are of little value in interrelating liquefaction behavior with coal properties at least two or three coal properties must be taken into account in seeking to explain the variance of liquefaction behavior, and some of these properties are not related to the rank of the coal. The paper implies strongly that any interrelationships of coal characteristics must necessarily be multivariate. Hence in any study of coal a large sample and data base is essential if worthwhile generalizations are to be made. 

Thus our rather small set of samples from a few selected areas of the U.S.A. shows a dispersion of some aspects of liquefaction behavior that is evidently associated with differences in the geology and geochemistry of the sample. Still more would we expect many sets of complex interrelationships between coal characteristics to emerge had we had a sufficiently large world-wide sample base to work with. 

In absolute terms, the quantities of reactor solids found in various processes do vary considerably. The rate of accumulation is related to several factors, such as coal characteristics, recycle solvent quality and reactor design. However, it can be stated in general terms that liquefaction of low rank coals (sub-bituminous C and lignites) does result in higher rates of accumulation of solids than do similar operations with bituminous coals. For example, during normal operations of the SRC-I pilot plant at Wilsonville, Ala., it has been found that the amount of solids retained varies from about 0.2-0.5 wt.% (moisture-free) for bituminous coals to 1.0-1.9 wt.% (moisture free) for a subbituminous C coal (Wyodak) (72). Exxon also reports much larger accumulations for lignites and subbituminous coals than those found for bituminous coals (73). 

Perhaps the most important components of reactor solids are those that are generated during processing rather than those that are derived from inert minerals (quartz, clays) and macerals (fu-sinites, etc.) in the feed coal (74). The retention of these formed materials is more difficult to predict from the characteristics of the feed and, hence, control in liquefaction processes. 

H. L. Coleman, M. Painter, P. C. "The Relation of Coal Characteristics to Liquefaction Behavior", Quart. Tech. Prog. Repts for period Jan.-June 1978 to U.S. Department of Energy under Contract No. EX-76-C-01-2494, Rept. Nos. FE-2494-7/8, 1978. 

The Characteristics of Australian Coals and Their Implications in Coal Liquefaction... 

Coal Characteristics and Their Effects in Liquefaction Process... 

The analytical data for coal samples used by other researchers and their experimental results are shown in Tables 6 and 7. A rough comparison of the liquefaction conditions used in this study to explore the parameter representing coal characteristics is shown in Table 8. 

The characteristics of this relationship are found to differ greatly from one another in the conditions of liquefaction and the coals used. Thus, the volatile matter in coal is not particularly useful as a parameter. 

The effectiveness of these parameters is considered to depend heavily on the liquefaction conditions and the characteristics of the coal which is used. The better parameters can possibly be derived from both the amounts of the petrographic components %9 such as inerts ingredients %9 or reactive macerals % and their quality, such as H/C atomic ratio and so on. Consequently, it must be said that much further study is necessary to finally clarify the more comprehensive parameter. 

Various mechanisms and kinetics of coal liquefaction have been proposed and examined by many investiga tors(l,2,4-8). As a general kinetic model of coal lique-action, scheme 1 was assumed. The reaction rate of every reaction step in the scheme assumed to be first order with respect to reacting species and dissolved hydrogen. A few typical cases of a general kinetic model and the general characteristics for their cases are illustrated on Table 3. When compared these typical figures, the curves are apparently different in shape. 

Tarmy, B. L., Chang, M., Coulaloglou, C. A., and Ponzi, P. R., The Three-Phase Hydrodynamic Characteristics of the EDS Liquefaction Reactors Their Development and use in Reactor Scaleup, Proc. 8th Int. Symp. Chem. Reaction Eng., 30 239 (1984)... 

Pyrolysis and liquefaction processes take an intermediate position in the sense that they maintain some larger molecular characteristics. Pyrolysis is a process in which the biomass material is quickly heated. The thermal cracking process, de-polymerizes waste or dry biomass and produces a liquid of complex composition (Fig. 1.17). 

During secondary liquefaction at 95 C or 90 C, a r id reduction in viscosity was observed. At 90 C, the viscosity reduction was monitored over time with a Nametre viscometer. The results demonstrated there was a r id reduction in viscosity to 400 centipoise x gm/cm by 7 minutes into secondary liquefaction (Figure 6). The action patterns of the liquefied starches following secondary liquefaction demonstrated the characteristic cyclodextrin action pattern at both temperatures. DE values were < 1.0 indicating the absence of reducing end-groups consistent with the mechanism of a CGTase. 

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