Mineral matter extracting from coal

One of the more important considerations in determining the end use of synthetic graphite is its contamination with metallic components Metals such as iron, vanadium, and especially in nuclear applications, boron are deleterious to the performance of graphite Table 3 presented the extraction yields of NMP-soluble material for three bituminous coals. For these coals, mineral matter and insoluble coal residue were separated from the extract by simple filtration through 1-2 pm filter paper fable 13 lists the high-temperature ash content in the dry coal, and in their corresponding NMP-insoluble and NMP-soluble products. The reduced ash content of the extract is typically between 0.1 to 0.3 wt% using traditional filtration techniques for the small-scaled extraction experiments... 

Board, Coal Rank Code 802), and the extract was prepared by digestion at 673°K and 8 bar in anthracene oil, filtration to remove mineral matter and dissolved coal, followed by distillation under reduced pressure until the extract contained about 70% coal. The two coal extract hydrogenates were prepared by catalytically reducing a dilute extract from Annesley (NCB,... 

Albertsson (Paiiition of Cell Paiiicle.s and Macromolecules, 3d ed., Wiley, New York, 1986) has extensively used particle distribution to fractionate mixtures of biological products. In order to demonstrate the versatility of particle distribution, he has cited the example shown in Table 22-14. The feed mixture consisted of polystyrene particles, red blood cells, starch, and cellulose. Liquid-liquid particle distribution has also been studied by using mineral-matter particles (average diameter = 5.5 Im) extracted from a coal liquid as the solid in a xylene-water system [Prudich and Heniy, Am. Inst. Chem. Eng. J., 24(5), 788 (1978)]. By using surface-active agents in order to enhance the water wettability of the solid particles, recoveries of better than 95 percent of the particles to the water phase were obsei ved. All particles remained in the xylene when no surfactant was added. 

Several options have been outlined for the reduction of mineral matter to low levels in filtered extract solution. These are mainly applicable to the British Coal process, but have implications for other 2-stage processes. By running the digestion at a pressure above about 30 bar and reducing the filtration temperature as required, low levels of trace elements have been obtained with a series of different coals and HAO solvents. Discarding the fine fraction of the coal from the feed to the digestor will also result in lower levels of trace elements in the extract solution, as will increasing the saturates content of the HAO. However, in the latter case this may also lead to reduced overall conversion. 

The elemental analyses of the products from the extraction of Bruceton coal are shown in Table III. The mineral matter was separated from the extract quite efficiently as shown by the ash content of the extracts and the insoluble residue. The elemental composition of all fractions was quite similar to that of the original coal. Only the hydrogen content varied to some extent, increasing with increased solubility. The elemental analysis of the products from the extraction of Ireland Mine coal was incomplete. 

A two-step process for extracting mineral matter and sulfur from coal was demonstrated with three different coals under a variety of treatment conditions. The first step Involves treatment with a hot alkaline solution which extracts part of the sulfur and generally converts much of the mineral matter to an acid-soluble form. The second step Involves leaching with an acid to extract the converted mineral matter. Although H2S0k would likely be used in the second step of a commercial process, HNO, was chosen for the present study in order to shed some light on the disposition of organic sulfur. 

These metal analyses indicate a marked reduction of both titanium and iron in the dialytic extract relative to both the coal and the soxhlet extract. The question remaining is, how much of this metal is background It should be noted here that attainment of good trace element analyses in the low ppm range requires very careful experimental precautions and replicate analyses. This particular experiment is, by its nature, difficult to conduct in a scrupulous "trace element clean" manner. However, if it is assumed that contamination from any source (solvents, glassware, utensils, etc.) will usually add to the concentration of metal, we can use the metal content determined in the dialyzate as an upper limit for soluble metals content. The higher iron and titanium concentrations in the soxhlet extract indicate that these metals may be associated with material which is not truly soluble, such as microparticulate mineral matter. 

Coal Liquefaction, Steam is used to produce hydrogen for the liquefaction of coal. In the liquefaction process, coal is crushed, dried, pulverized, and then added to a solvent to produce a slurry. The slurry is heated, usually in the presence of hydrogen to dissolve the coal. The extract is cooled to remove hydrogen, hydrocarbon gases, and hydrogen sulfide. The liquid is then flashed at low pressure to separate condensable vapors from the extract. Mineral matter and organic soHds are separated and used to produce hydrogen for the process. The extract may be desulfurized. The solvent is separated from the products. There are at least six different liquefaction processes (see Coal conversion process, liquefaction Fuels, synthetic-liquid fuels). 

Mineral matter has been known to enhance the conversion of coal to liquid products (1,2,3). Addition of pyrite, pyrrhotite, and liquefaction residues ( ) to coal has been shown to affect the coal conversion yields and the viscosity of the products (5.). Of all the minerals present in coal, pyrite (and marcasite) are the most important for coal utilization, especially in direct coal liquefaction (1,5). However, one has to remember that under coal liquefaction conditions pyrite rapidly transforms to a nonstoichiometric iron sulfide Fe S(0 x 0.125). It is noted that the sulfur formed as a result of the decomposition of pyrite is able to extract hydrogen from poor donor solvents. The stoichiometry of the pyrrhotite formed from FeSp depends strongly on the partial pressure of H S. 

Most of the mineral matter was removed from a representative coal (Illinois No. 6) by first leaching the finely ground material with a hot alkaline solution and then washing the product with a mineral acid and water. The effectiveness of various alkalis for converting or extracting mineral matter decreased in the following order ... 

A series of experiments was assigned to explore the extraction of mineral matter from coal in the size ranges below 0.25 mm. The raw coal samples were obtained from three different sources in the Pittsburgh seam which permitted a degree of comparison over a rather large geographic area. The results are interesting in that they allow a new perspective in the demineralization of coal. 

From a more practical viewpoint, the solvent extraction of bituminous coals has been used as a means of coproducing clean liquid transportation fuels as well as solid fuels for gasification. Coal solvents are created by hydrogenating coal tar distillate fractions to the level of a fraction of a percent, thus enabling bituminous coal to enter the liquid phase under conditions of high temperature (above 400°C [750°F]). The pressure is controlled by the vapor pressure of the solvent and the cracked coal. Once liqnefied, mineral matter can be removed via centrifnga-tion, and the resultant heavy oil prodnct can be processed to make pitches, cokes, as well as lighter products. 

There are also solvent extraction methods for producing low-sulfur and low-mineral matter coal, but hydrotreatment of the coal extract is also required. In these methods, the organic material is extracted from the inorganic material in coal. A study has indicated that solvent-refined coal will probably not penetrate the power generation industry on a large scale for several years to come. 

This paper deals with the subject of solvent extraction and hydrogenation of coal (l.e. direct liquefaction). The main purpose of liquefaction Is to produce clean fuel (both liquid and solid), eliminating the mineral matter and heteroatoms from the parent coal. Most of the processes aim towards high liquid yields. In all processes, crushed coal, mixed with the process solvent Is contacted with hydrogen gas under pressure. The... 

The fly ash was from a burner using pulverized high volatile bituminous coal with a carbon content of —58 wt%. The carbon content was enriched by a float-sink procedure followed by extraction of mineral matter by HCI/HNO3/HF, called DEM-PCCl. This carbon was activated with steam at 850 °C for 60 min in a horizontal furnace, called AC-PCCl. Analytical data for these two carbons and a conunercial carbon, Darco Insul, are in Table 8.3. 

Let s consider some tangible examples of metal extraction/refining, starting with vanadium metal. There are approximately 50 types of minerals that will yield a viable amount of V metal, such as vanadinite, patronite, bauxite, and carbon deposits such as crude oil, coal and butiminous matter. The oxide obtained from these deposits via flotation is first mixed with NaCl or Na2C03 at 900° C to yield sodium orthovanadate, NaV03. This salt is dissolved in water and acidified with sulfuric acid to a pH between 2 and 3 to yield a red solid, which is hydrated V205. ... 

Montan Wax is derived from lignite which is vegetable matter partly mineralized to a product related to bituminous coal. The lignites from which the Montan Waxes are extracted are found chiefly in Central Europe and California. 

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