Coal treatment

Solvents Coal Treatment Time min. Yields Pyridine sols. THF sols. Hydrogen consumptIon (H daf coal)... 

Other Organic Processes. Solvent extraclion has found application in the coal-tar industry for many years, as for example in the recovery of phenols from coal-tar distillates by washing with caustic soda solution. Solvent extraction of I any and resimic acitl from tall oil has been reported. Dissociation extraclion is used in separate ffr-cresol from p-crcsol and 2,4-xylenol from 2.5-xylenol, Solvent extraclion can play a role in the direct manufacture of chemicals from coal, treatment of industrial effluents, biopolymer extraction, and difficult separations. 

Gaseous fuels Principally natural gas (80% to 95% methane, the balance ethane, propane, and small quantities of other gases) also light hydrocarbons obtained from petroleum or coal treatment, acetylene, and hydrogen (the latter two are relatively expensive to produce). 

Besides its direct use in the final product, water is used in breweries as a utility, for purposes such as cleaning, steam generation, etc. Another common utility in breweries are gases, such as air and carbon dioxide, which sometimes might contain impurities that need to be removed in order to ensure the quality and uniformity of the hnal product. Besides traditional methods, i.e., activated coal treatment, purification of utihties can also be successfully done by membrane filtration. Some membrane manufacturers (i.e., Pall Corporation, Donaldson Ultrafilter Inc., Sartorius, Millipore, CPM, etc.) offer commercial membrane separation equipment that is specihcaUy designed for the purification of water, steam, air, or carbon dioxide. This enables breweries to produce sterile and particle-free utihties for the brewing processes. 

It is therefore beneficial to pretreat the coal to remove as much sulfur as is practical before combustion, so that the expense of postcombustion desulfurization can be reduced. Combined with the other benefits of coal cleaning, it is evident that precombustion coal treatment is valuable even when it is not sufficient to completely desulfurize the coal by itself. 

Products of coal conversion Bituminous coal, treatment 30 min, without Ar Bituminous coal, treatment 30 min, with Ar (1300 Pa) Lignite coal, treatment 10 min, without Ar Lignite coal, treatment 20 min, with Ar (1300 Pa)... 

Depending on the prior coal treatment, the sulfur value from the ultimate analysis may include all three of them. Various methods are available for ultimate sulfur determination (e.g., ASTM D-4239 [38], ISO 334 [39]). All are based on the combustion of the sulfur to produce a sulfete, which is measured gravi-metrically or volumetrically. Even x-ray fluorescence can be used to determine the total sulfur. To differentiate between the types of sulfur (ASTM D-2492 [40], ISO 157 [41]), the coal sample is treated with dilute HCl solution in which only sulfete sulfur is soluble. The pyrite sulfur is determined by subtracting the amount of soluble iron in dilute HCl from the amount of iron soluble in HNO3. From this difference, the quantity of FeS2 can be calculated. Together with the total sulfur, the organic sulfur can be determined by difference. Also x-ray spectroscopy can proof the chemical state of the sulfur in the coal. 

Applications. Chromate convrasion coaling treatments are used on five principal types of aluminum parts aircraft and aerospace structural conqxnients, coil (for construction applications such as guttering and siding), extrusions (for window and door fiames), heat exchan parts, and containeis (mainly beverage cans). A considoable amount of aluminum is also used in the automotive industry, but most receives a crystalline phosphate treatment because the aluminum is treated at the same time as the steel fiame. 

The Fischer-Tropsch reaction is essentially that of Eq. XVIII-54 and is of great importance partly by itself and also as part of a coupled set of processes whereby steam or oxygen plus coal or coke is transformed into methane, olefins, alcohols, and gasolines. The first step is to produce a mixture of CO and H2 (called water-gas or synthesis gas ) by the high-temperature treatment of coal or coke with steam. The water-gas shift reaction CO + H2O = CO2 + H2 is then used to adjust the CO/H2 ratio for the feed to the Fischer-Tropsch or synthesis reactor. This last process was disclosed in 1913 and was extensively developed around 1925 by Fischer and Tropsch [268]. 

The ammonia gas is used again and the only by-product, calcium chloride, is used to melt snow, prevent freezing of coal in transit and as an antidust treatment since it is hygroscopic and forms a solution of low freezing point. 

Stone conservations Stonegroundwood Stone treatment Stoneware Stone-washing Stony coal Stop-flow ftir techniques Stopped-flow mixing Stop Scald Storage... 

The KDF Filter. The KDP filter (Pig. 23) (Amafilter, Holland) is based on the same principle as disk filters. It was developed for the treatment of mineral raw materials, like coal flotation concentrates or cement slurries, and can produce a filter cake of low moisture content at very high capacities, up... 

Originally designed for the continuous filtration of conditioned sewage sludges, as were most of the filter belt presses available, the Manor Tower press is increa singly used for the treatment of paper mill sludge, coal, or flocculated clay slurries. 

Flotation or froth flotation is a physicochemical property-based separation process. It is widely utilised in the area of mineral processing also known as ore dressing and mineral beneftciation for mineral concentration. In addition to the mining and metallurgical industries, flotation also finds appHcations in sewage treatment, water purification, bitumen recovery from tar sands, and coal desulfurization. Nearly one biUion tons of ore are treated by this process aimuaHy in the world. Phosphate rock, precious metals, lead, zinc, copper, molybdenum, and tin-containing ores as well as coal are treated routinely by this process some flotation plants treat 200,000 tons of ore per day (see Mineral recovery and processing). Various aspects of flotation theory and practice have been treated in books and reviews (1 9). 

A significant issue in combustors in the mid-1990s is the performance of the process in an environmentally acceptable manner through the use of either low sulfur coal or post-combustion clean-up of the flue gases. Thus there is a marked trend to more efficient methods of coal combustion and, in fact, a combustion system that is able to accept coal without the necessity of a post-combustion treatment or without emitting objectionable amounts of sulfur oxides, nitrogen oxides, and particulates is very desirable (51,52). 

Medicated Dandruff Shampoos. Dandmff is a scalp condition characterized by the production of excessive cellular material (18). A number of shampoos have been marketed which are designed to control and alleviate this condition, and many additives have been included in shampoo compositions to classify them as treatment products for dandmff. These additives include antimicrobial additives, eg, quaternary ammonium salts keratolytic agents, eg, saUcychc acid and sulfur heavy metals, eg, cadmium sulfide coal tar resorcinol and many others. More recent (ca 1993) systems use selenium sulfide [7488-56-4] or zinc pyrithione [13463-41 -7] as active antidandmff shampoo additives. Both of these additives are classified as dmgs, but can be found in over-the-counter products. A stronger version, incorporating the use of higher levels of selenium sulfide in a shampoo, is available but requires a prescription for purchase. 

Cationic polymerization of coal-tar fractions has been commercially achieved through the use of strong protic acids, as well as various Lewis acids. Sulfuric acid was the first polymerization catalyst (11). More recent technology has focused on the Friedel-Crafts polymerization of coal fractions to yield resins with higher softening points and better color. Typical Lewis acid catalysts used in these processes are aluminum chloride, boron trifluoride, and various boron trifluoride complexes (12). Cmde feedstocks typically contain 25—75% reactive components and may be refined prior to polymerization (eg, acid or alkali treatment) to remove sulfur and other undesired components. Table 1 illustrates the typical components found in coal-tar fractions and their corresponding properties. 

Partial oxidation of heavy Hquid hydrocarbons requires somewhat simpler environmental controls. The principal source of particulates is carbon, or soot, formed by the high temperature of the oxidation step. The soot is scmbbed from the raw synthesis gas and either recycled back to the gasifier, or recovered as soHd peUetized fuel. Sulfur and condensate treatment is similar in principle to that required for coal gasification, although the amounts of potential poUutants generated are usually less. 

Flocculation. The interaction of the cationic PEIs with anionic substrates leads to substrate flocculation. AppHcations of this property include the coagulation of latex (434), commercial appHcation in effluent treatments (435—437), and stabiHzation of highly loaded coal—water mixtures in mining (438). 

Step 4 of the thermal treatment process (see Fig. 2) involves desorption, pyrolysis, and char formation. Much Hterature exists on the pyrolysis of coal (qv) and on different pyrolysis models for coal. These models are useful starting points for describing pyrolysis in kilns. For example, the devolatilization of coal is frequently modeled as competing chemical reactions (24). Another approach for modeling devolatilization uses a set of independent, first-order parallel reactions represented by a Gaussian distribution of activation energies (25). 

Humic acids are alkaH-extractable materials and total humic acid content is a term that refers to the humic acid content of coal that has had its carboxylate cations removed with sodium pyrophosphate. Values for some typical AustraHan brown coals range from 24—92% (13). Treatment of lignitic coals with mineral acid to release the alkaH and alkaline cations may dissolve up to 20% of the coal. The naturally moist coals are slightly acidic and have a pH of 3.5—6.5. 

Pyrolysis. Heating in the absence of oxygen releases moisture at low temperatures, carbon dioxide at temperatures >200° C, and a variety of gaseous products at very high temperatures. Acid washing of the raw coal is used to remove extractable cations, followed by treatment with selected cations. Yields of CO2, CO, CH, H2, and H2O depend on the amounts of inorganic species in the coal (42). 

British Coal Corp. is developing a gasoline-from-coal process at a faciUty at Point of Ayr (Scotiand). This process involves treatment with Hquid recycle solvents, digestion at 450—500°C, filtration to separate unconverted residues, and separation into two fractions. The lighter fraction is mildly hydrotreated, and the heavier one is hydrocracked (56). 

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