Coal iron content

Saniter A modification of the Basic Open Hearth process for reducing the sulfur content of the steel product by adding relatively large quantities of limestone and calcium chloride. Invented by E. H. Saniter at the Wigan Coal Iron Company in England in 1892, and used there and in Germany for approximately 20 years until superseded by the use of calcium fluoride as a flux. 

The Illinois H-Coal syncrude contains the greatest amount of iron. This iron could be from corrosion during processing or storage, rather than from the coal itself. We have observed high iron contents in California gas oils which contain acidic and corrosive oxygen. In California gas oils, the iron is soluble in the oil as iron naphthenates (iron salts of organic acids) ... 

The reactivity of each hydrocarbon was also studied on a variety of model adsorbents. All hydrocarbons are observed to be less photoreactive on coal ash surfaces than when adsorbed on alumina, silica, or glass surfaces. Different coal ashes stabilize polycyclic aromatic hydrocarbons to phototransformation with differing efficiencies. The role of the chemical composition of coal ashes (especially carbon and iron content) and physical properties of the ashes (especially color) is discussed. 

It is conceivable that the relationship of carbon and iron content of coal ashes with their ability to suppress PAH phototransformation may be due in part to the fact that the ashes high in carbon and/or iron are relatively dark in color, whereas the TX and AR ashes (upon which all PAHs undergo photodecomposition) are much lighter in color. If the adsorbent is highly colored and relatively porous, it is possible for an adsorbate (PAH) molecule to become sequestered in the pore structure and be "shielded" from the incident light by the absorbing substrate. Such "inner-filter" effects are well known in photochemistry (16), and they have previously been presumed to play a role in the photochemistry of PAHs adsorbed on particulate solids ( 1). 

Although the authors in this sand study reported the iron content of the sand, there remains a possibility that noniron species were acting as catalysts. In fact, a study of coal (anthracite) oxidation by hydrogen peroxide indicates that formation of hydroxyl radical occurs even after the removal of iron from the coal [47], This study suggested that surface sites on the coal may have acted as catalytic centers for hydroxyl radical formation. Whereas coal is... 

While the pyrrhotite composition has been established for a very small fraction of the many coal liquefaction experiments, it does seem apparent that all of the iron forms added are converted to pyrrhotites rather quickly and that the pyrrhotites interconvert, responding to the total iron content of the system and the composition of the fluid phase. 

The iron content in the filtrates was converted similarly to the coal basis. 

The iron content of acid-extracted residues was generally 0.10% or less. The one notable exception, Lovilia/ROM coal... 

Table IV. Nitrogen and Iron Content in Raw and in Treated Coals Before and After Extraction with Nitric Acid.

The usual method utilized to identify the clay minerals in coal is X-ray diffraction of the low-temperature ash (LTA), but because of the poor crystallinity of the clays in the coal, the technique cannot be used for quantitative measurements. The Mossbauer effect does not provide much improvement owing to the small iron content of the clays. A coal rich in clays is shown in Figure 7 (about 10% mineral matter). The two peaks at higher... 

Recent work has shown that pulverized coal, if separated by gravity fractionation, can yield important information relative to slagging potential due to the iron content. (6,7). Results of this work have shown that the percentage of iron in the heavy fractions correlates very well to the slagging behavior in commercial boilers. (See Figure 3). This technique appears to identify the proportion of relatively pure pyrites particles that are generated in the pulverized coal feed and that are capable of melting at relatively low temperatures and that would account for enrichment of iron in lower furnace waterwall deposits. 

It might be expected that coals high in pyrite (e.g., bituminous) would be more reactive than coals that have lower pyrite contents (e.g., subbituminous and lignites). Twenty coals of various ranks were tested by Gulf under SRC-II process conditions 30 wt. percent coal, 440-465°C, 1800-2250 psia H2, one-hr residence time. Coals which processed well had pyritic sulfur or iron contents greater than 1.5%, and were generally Eastern and Interior Province bituminous coals ( 0 ). C5 oil yields (875°F") ranged from 30-35% for coals with pyritic sulfur contents of 1.0 to 1.5% to 40-45% for coals with pyritic sulfur contents of 2.0 to 3.0%. 

Water draining from abandoned coal mines causes considerable environmental damage because of its iron content and acidity. In an attempt to understand the chemistry of these waters, the following measurements were made in water in the Loree 2 shaft near Wilkes-Barre, PA. (Barnes et al., uses Prof. Paper 473-B, 1964). 

Another environmental problem associated with sulfur is called acid mine drainage. Groundwater in both coal and metal sulfide mines can become contaminated with sulfuric acid. This is particularly a problem in the coal mines of the Appalachian Mountains. Coal deposits often contain pyrites. Metal ores can include toxic salts of zinc, lead, arsenic, copper, and aluminum. In both cases, acid mine drainage can kill fish and other aquatic organisms, as well as corrode boats and piers. Streams sometimes turn red in color because of the iron content from the mine... 

San5>le-preparation procedures for Md ssbauer spectroscopy are relatively sin5>le. Depending on the iron content of the coal, 0.3 to 1.0 g of very finely crushed (-400 mesh) coal is placed in a plexiglass con5>ression holder of 1.3-cm-diameter. The filled holder is then placed in a metallic shield with a... 

A schematic drawing of the sensor system employed in the Sortex Ash Monitor is shown in Figure 4. The x-rays emitted by the Pu source irradiate the coal sample and penetrate up to 38 mm. This radiation is absorbed and scattered the fraction backscattered is counted with a gas proportional counter. The aluminum filter is used to compensate for iron fluorescent x-rays, which are excited by the incident x-rays. The filter preferentially absorbs most of the iron fluorescent x-rays ( 6 KeV), and its thickness is chosen based upon the iron content of the coal samples. The aluminum filter also compensates for sulfur variations in the coal. This occurs because a major fraction of sulfur is present as pyrite and the decrease in x-ray backscatter intensity due to sulfur is partially offset by an increase in iron fluorescence. Organic sulfur is generally constant, and it is corrected for in the calibration of the instrument ( 5). 

The nature of their formation and their porosity means that both oil and coal SCPs are never spherical. However, they do have some degree of sphericity to their morphology and for this reason they are termed spheroidal. IASs are spherical and come in a variety of colours from colourless through yellow, red, brown and black, depending on their elemental, and in particular iron, content. Therefore, the counting of black spheres and terming them SCPs (e.g., Larsen et al., 1996) may lead to further confusion as to the exact nature of the particle types included in the enumeration. Here, spherical fly-ash particles of any colour are deemed IASs and are precluded from being identified as SCPs for that reason. 

Fortunately, unlike the Cu-S system, molten Fe and FeS are completely miscible and the sulfur potential decreases with increasing iron content in the Fe-S matte. Thus, the sulfur potential can be controlled to any desired low value by varying the Fe/S ratio in the Fe-S matte. Basically, the iron required for fixation of the sulfur can be in any form, such as scrap iron, iron ore, steel plant dust and even zinc plant leach residues. When iron oxides are used, reductants such as coal or coke are required to produce reduced iron. The overall reaction of direct zinc smelting is ... 

The fusibility characteristics of coal ash will vary with its chemical constituents. Most low-rank coals produce an ash high in basic metals and low in iron content. Therefore, they have a higher softening temperature, and consequently, are less susceptible to slagging. The behavior of ash is extremely complex, and while some constituent melt below 1040°C (1900°F), as the calcium and sodium content of the ash increases, the rate of deposition increases on tube surfaces. The sodium oxide content, in particular, can have a catalytic effect on the rate of deposition, and investigations have shown that ash with a sodium content above 5% fouls at an accelerated rate. 

Example Pyrite is one of the most abimdant mineral of the sulphide deposits. It may also be present in coal seams or in the shale beds associated to them. Being insoluble in water, it does not increase the iron content of water and degrade water quality. But at the smface of earth it can be naturally oxidised in presence of atmospheric oj gen and water, as shown in the following activating reaction... 

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