Pyrite coal with added

Coal and Coal with Added Pyrite. In Figure 11 are again presented values for Blacksville coal with additional points representing the pyrrhotites resulting when pyrite has been added to the coal in an autoclave at 400 C and in a miniautoclave at 450°C. The pyrites used are obtained from the Robena Mine, from the Vesta... 

Barton equilibrium line, or fall on the pyrite-pyrrhotite line of the phase diagrams. The coals with higher intrinsic pyrite content or those to which pyrite or iron-containing materials were added have pyrrhotites which fall nearer the reactor zone. 

In the determination of sulfate, 2 to 5 g of the analysis sample is mixed with HC1 (2 volumes concentrated HC1 + 3 volumes of water), and the mixture is gently boiled for 30 minutes. After filtering and washing, the undissolved coal may be retained for the determination of pyrite sulfur, or it may be discarded and a fresh sample used for pyrite sulfur. Saturated bromine water is added to the filtrate to oxidize all sulfur forms to sulfate ions and ferrous ions to ferric ions. After boiling to remove excess bromine, the iron is precipitated with excess ammonia and filtered. This precipitate must be retained for the determination of nonpyrite iron if a fresh sample of coal was used for the determination of the pyrite iron. The sulfate is then precipitated with ISaCE, and the BaSC>4 is determined gravimetrically. 

For the last experiment reported here, we added 5% pyrite to the IL6 coal, the sample was well mixed and solvent was added (2 1) and mixed with the coal the runs were carried out in the presence of H2 (250 psi). We observed in this case that full conversion to pyrrhotite takes place in five minutes at 420° C. Similar effects as before were observed in the IS and linewidth. The atomic % Fe in the pyrrhotite formed in this experiment was 46.8, indicating a strong change in the stoichiometry of the pyrrhotite. In Figure 7 the Moessbauer spectrum of this residue is shown. It is clear to the eye that the spectra in Figures 7 and 8 are significantly different. 

The effect of added hydrochloric acid concentration was studied in order to determine whether or not the acid had any effect on pyrite and ash removal, sulfate-to-sulfur ratio, final heat content, and possible chlorination of the coal. Coal has many basic ash constituents, so increased ash removal was expected, as well as some suppression of the sulfate-to-sulfur ratio because the reaction that results in sulfate formation also yields eight moles of hydrogen ion per mole of sulfate (common ion effect). Added acid was studied in the range of 0.0 to 1.2M (0.0, 0.1, 0.3, and 1.2M) hydrochloric acid in 0.9M ferric chloride. Duplicate runs were made at each concentration with all four coals for a total of 32 runs. The results showed no definite trends (except one-uide infra) even when the data were smoothed via computer regression analysis. Apparently the concentration range was not broad enough to have any substantial effect on the production of sulfate or to cause the removal of additional ash over that which is removed at the pH of IM ferric chloride ( pH 2). 

A few years ago, an ad hoc group of workers interested in coal minerals. The Mineral Matter in Coal Group, prepared and distributed a round-robin low temperature ash to ten laboratories. Each laboratory was to prepare, mount and quantify the mineral components in the ash by their respective XRD techniques. The data were then compared. Even though a wide variety of techniques was used for each phase of the analysis, with the exception of the clay mineral estimates made by one laboratory (significantly lower than the others) and the pyrite estimate made by another (too high), the data compared reasonably well. The averages of all the submitted estimates are summarized in Table III. 

In every case in which pyrite was added to a coal that was deficient in pyrite, the yield of oil under SRC-II conditions increased substantially. 0 The fact that pyrite actually is a catalyst was confirmed when similar results were obtained with catalysts that contained neither iron nor sulfur. 

---