Coal reactivity

The slopes of the regression lines for conversion yield against reactive macerals for the hot-rod and for the rotating autoclave modes of hydrogenation are shown by statistical analysis to be similar (compare Figures 9 and 10). This suggests that the relationship between total reactive macerals and coal reactivity as measured by conversion is not dependent on the conversion technique. 

However, coal reactivity as measured by total conversion to liquids and gases becomes less dependent on coal parameters as processing severity increases. The effect of process temperature in the hot-rod reactor was studied using three coals of varying properties. These were Waterberg, Sigma and Landau. At 650°C the conversion yields of these coals were 89, 90 and 88 per cent of the coal (dmmf) respectively. Within experimental error the conversion yields had converged to the same value, whereas at 500°C the conversion yields were 85, 75 and 65 per cent respectively. 

It is well known that the characteristics of coal differ widely according to the age of the coal formation as well as to the location of coal, etc. And the reactivity during hydroliquefaction depends on the characteristics of coals. This relationship will he a guidance to select and develop coal mines. Many parameters to indicate the reactivity of coal have heen proposed (l, 2, 2). Among these parameters, carhon content, volatile matter content, value of H/C atomic ratio, reactive macerals content, etc. are reported to he relatively closely related parameters to coal reactivity. However, these relations are usually found only in limited reaction conditions. Therefore, attempts to find better parameters still continue. 

In this study, we have tried to find a more comprehensive parameter related to coal reactivity, as represented hy conversion, hy liquefying several ranks of coals. These cover a wide range from lignite to bituminous coal. Also we have studied the difference of coal reactivity caused hy the mining sites in Australian brown coal mines. Selected coals from a wide range of rank are located in the coal hand shown in Fig.2. The resulting parameters are compared with other parameters reported hy other researchers (2, 3.) ... 

The relations between coal reactivity and several parameters are shown in Figs. 3 to 8. In these figures the reactivity of coal is measured by conversion. In the results, volatile carbon % is selected as a more closely related parameter than the common parameters, such as C%9 H, 0, H/C atomic ratio, volatile matter, etc. 

It is well known that coal reactivity depends on the solvent, the conditions of hydroliquefaction, and the composition of the coal. Different extracting solvent results in different conversion, but it can be considered that the different conversion shows a similar tendency to coal reactivity. Thus, it is desirable that the parameter representing coal reactivity shows essentially the same tendency, despite the conditions of hydroliquefaction. Accordingly comparison of parameters was carried out, using some previously reported results (2, 3). 

Since the earliest days of coal liquefaction processing and research, the need for correlations of coal properties with coal reactivity under direct hydroliquefaction conditions has been recognized by coal scientists. This article traces the history of reactivity correlations from the earliest work of Bergius through the classic work at the Bruceton Bureau of Mines during the 1940 s to the most recent advances in this subject. Particular emphasis in this review is placed on an examination of the contributions of Professor Peter Given and his co-workers. Reactivity methodologies and techniques for correlation are presented and critically evaluated for utility and applicability as predictive tools. 

During the 1970 s. Professor Peter Given and his coworkers at Penn State University began a very extensive study of the effect of coal composition on coal reactivity utilizing 104 coals from the U.S. To date, a series of ten papers have been published concerning the coal reactivity studies of Given et al., of which two pertain directly to the subject of reactivity... 

There are numerous other cases in the literature that could be used as examples of reagent access limitations. This review is not exhaustive, and those cases cited here serve to establish the point that the limited accessibility of reagents is an important factor in coal chemistry. Clearly it is worthwhile to attempt to improve the accessibility of coals to reagents. Perhaps in this way significant increases in coal reactivity can be obtained. 

Pyrolysis results are very important for coal characterization, as all conversion processes of coal such as combustion, liquefaction, and gasification start with a pyrolytic step. For this reason, pyrolysis was frequently used for the analysis of coals [17,18). Pyrolysis data were correlated with coal composition, coal characterization and ranking [18a], prediction of coal reactivity as well as of other properties related to coal utilization. Techniques such as Py-MS, Py-GC/MS with different ionization modes, Py-FTIR, or evolved gas analysis (EGA) [19] were described for coal analysis. Programmed temperature pyrolysis is another technique that has been proposed [17] for a complete evaluation of the two types of molecules present in coal. 

CAS 1189-08-8 EINECS/ELINCS 214-711-0 Uses Crosslinking monomer for preparation of inks, photoresists for printed circuit boards, photopolymer printing plates, wire and cable coalings reactive diluent for PVC plastisols, rubber crosslinking, glass reinforc plastics, adhesives, sealants, impregnated wood composites, and other surf, coatings... 

Coal reactivity, which is the second factor with a significant influence on kinetics, depends on... 

The relationship between coal composition and hydrogenation reactivity has been studied extensively and coal with less than 85% w/w carbon (daf) made poor liquefaction feedstocks. It has been suggested that coal reactivity is related to rank (Francis, 1961). Coal is, in actual fact, a hydrogen-deficient organic natural product having an atomic hydrogen/carbon ratio of approximately 0.8 compared with an atomic hydrogen/carbon atomic ratio of 1.4 1.8 for various crude oils, heavy oil, and bitumen (Table 12.1). 

Van Dyk et al. [63] report reactivities between 2 and 5 h for South African coals, whereas the overall measured range was between 0.5 and 9 h . In the case of catalytic active ash elements and low-rank coal, reactivity can exceed 9 h [62]. 

Coal reactivity (the lower the rank the higher the reactivity)... 

The coal or carbon conversion in a gasification process is governed by complex mechanisms that are dependent on the quahty of the coal used (coal structure or rank, particle size, evolving pore structure, catalytic effects of char minerals content, changes in surfece area, char fi acturing, and coal moisture) and the physical and chemical conditions around the particle (temperature, pressure, concentration of reactants such as O2, H2O, CO2, H2 and their diffusion properties). Because of these numerous influences, a theoretical prediction of coal reactivity is nearly impossible without laboratory data [4]. One important aspect of heterogeneous reactions is whether rate is controlled by diffusion limitations in the boundary layer around the particle, so-called bulk surface diffusion, or by diffusion inside the pores of the particle. 

---