Fine coal

Very finely divided minerals may be difficult to purify by flotation since the particles may a ere to larger, undesired minerals—or vice versa, the fines may be an impurity to be removed. The latter is the case with Ii02 (anatase) impurity in kaolin clay [87]. In carrier flotation, a coarser, separable mineral is added that will selectively pick up the fines [88,89]. The added mineral may be in the form of a floe (ferric hydroxide), and the process is called adsorbing colloid flotation [90]. The fines may be aggregated to reduce their loss, as in the addition of oil to agglomerate coal fines [91]. 

Several utility-scale demonstration facilities having power outputs in the 300-MW class have been constmcted in the United States and Europe. These started accumulating operating experience in 1995 and 1996. Other IGCC plants have been constmcted, including units fueled by petroleum coke and refinery bottoms. Advanced 500-MW class IGCC plants based around the latest heavy-duty combustion turbines are expected to be priced competitively with new pulverized-coal-fined plants utilising scmbbers. 

Additions of new flocculants after conventional thickening produce further dewatering of mineral slimes. A clay flocculated with polyacrylamides and rotated in a dmm can produce a growth of compact kaolin pellets (84), which can easily be wet-screened and dewatered. A device called a Dehydmm, which flocculates and pelletizes thickened sludges into round, 3-mm pellets, was developed for this purpose. Several units reported in commercial operation in Japan thicken fine refuse from coal-preparation plants. The product contains 50% moisture, compared with 3% soflds fed into the Dehydmm from the thickener underflow (85). In Poland, commercial use of the process to treat coal fines has been reported (86), and is said to compare favorably both economically and technically to thickening and vacuum filtration. 

Immiscible wetting in mixers Sol-gel processes Pellet flocculation <0.3 Low Up to 10 ton/hr Wet processing based on flocculation properties of particulate feed Coal fines, soot and oil removal from water Metal dicarhide, silica hydrogels Waste sludges and slurries... 

The ash content of the coal is significant, not only in its mass but also with respect to the constituents of the ash, the fusion temperature, the range of fusion temperature between initial deformation and actual fusion and the amount of coal fines present. 

Davison, J., The lambda process - for desulfurization of slurry coal fines prior to combustion, in Eighth Annual Surface Mine Drainage Task Force Symposium. 1987. Morgantown, West Virginia, April 7-8. 

HIsmelt A direct iron smelting process in which noncoking coal, fine iron ore, and fluxes and gases, are injected into a molten iron bath the carbon monoxide produced is used to prereduce the ore in a fluidized bed. Under development by CRA, Australia, since the early 1980s, joined by Midrex Corporation in 1988. Their joint venture company, Hismelt Corporation, commissioned a pilot plant at Kwinana, near Perth, Australia, in 1993. 

BAC has been formulated to minimize the cost of adsorbent by using waste as its starter material. BAC is made from a mixture of approximately 85% waste coal fines and 15% municipal sewage sludge on a dry basis. Both materials have very low or no cost and have attributes that contribute to good pore development. 

Cutting oils and aqueous metal working fluids Industrial wastewater Agricultural waste and runoff Cyanide contamination Desulfurization of coal fines Chlorinated aliphatics Pesticides... 

The absorber pump constantly recycled the fluid through the oxygen absorber so that the fluid was always essentially saturated with oxygen. A small side stream was removed from the gas absorber recycle by the reactor pump. The side stream could either flow through the reactor or bypass the reactor. The reactor bypass was used when it was desired to study the decomposition in solution of the humic acids. Down stream from the reactor was a filter to remove any coal fines produced, a sight glass to observe the fluid, a flow colorimeter to measure the rate of production of humic acids, and a flow rate indicator. 

Power Coal Fines, Fly Ash, FGD Sludge, Boiler Ash, Wood Ash... 

Froth flotation process for cleaning coal fines in which separation from mineral matter is achieved by attachment of the coal to air bubbles in a water medium, allowing the coal to gather in the froth while the mineral matter sinks (ASTM D-5114). 

Experiments were carried out to determine the reduction of lump coal degradation due to the presence of coal fines (-16.0 mm) with the lumps at the different impact surfaces. Cushioning effects of fines consists of five different types of tests are as follows. 

Coal fines Ash-producing shales and rocks, and S02 emission-producing metal sulfides Electric power... 

Similarly, in floe flotation the small-sized particles become aggregated into floes that can attach to the air bubbles. Here, polymers may be used to induce the required level of flocculation. Examples include the floc-flotation of coal fines [631] or galena [632],... 

A novel technique for separating ultrafine pyrite particles (minus 1 0 micrometers) from coal fines has been conceptually developed and tested. The technique involves the use of a selective polymeric dispersant for pyrite, while flocculating coal particles with a polymeric flocculant. The suspended pyrite can then be removed from the flocculated coal fines which settle preferentially by gravity. 

Attia, Y. A., and Fuerstenau, D. W., "Feasibility of Cleaning High Sulfur Coal Fines by Selective Flocculation", Fourteenth Intern. Miner. Process Congr., Toronto, Canada, 1982. 

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