The assignee for this patent, patent number 8651282, is
Reporters obtained the following quote from the background information supplied by the inventors: "About 63% of the world's electric power and 70% of the electric power produced in
"Eighty-nine percent of the coal mined in
"Lower rank coals like subbituminous and lignite coals have gained increasing attention as heat sources for power plants because of their low sulfur content. However, they still produce sufficient levels of SO.sub.2, NO.sub.x, and fly ash when burned such that treatment of the flue gas is required to comply with federal and state pollution standards. Additionally, ash and sulfur are the chief impurities appearing in coal. The ash consists principally of mineral compounds of aluminum, calcium, iron, and silicon. Some of the sulfur in coal is also in the form of minerals--particularly pyrite, which is a compound of iron and sulfur. The remainder of the sulfur in coal is in the form of organic sulfur, which is closely combined with the carbon in the coal.
"Coal mining companies typically clean their coal products to remove impurities before supplying them to end users like electric power plants and coking production plants. After sorting the pieces of coal by means of a screening device to form coarse, medium, and fine streams, these three coal streams are delivered to washing devices in which the coal particles are mixed with water. Using the principle of specific gravity, the heaviest pieces containing the largest amounts of impurities settle to the bottom of the washer, whereupon they drop into a refuse bin for subsequent disposal. The cleaned coal particles from the three streams are then combined together again and dried by means of vibrators, jigs, or hot-air blowers to produce the final coal product ready for shipment to the end user.
"While the cleaning process employed by coal mining operations removes much of the ash from the coal, it has little effect on sulfur, since the organic sulfur is closely bound to the carbon within the coal. Thus, other methods can be used to further purify the coal prior to its combustion. For example, the coal particles may be fed into a large machine, wherein they are subjected to vibration and pulsated air currents. U.S. Pat. No. 3,852,168 issued to Oetiker discloses such a method and apparatus for separating corn kernels from husk parts. U.S. Pat. No. 5,244,099 issued to Zaltzman et al. on the other hand teaches the delivery of granular materials through an upwardly inclined trough through which a fluidizing gas is forced from the bottom of the trough to create a fluidized material bed. A vertical oscillatory motion is also imparted to the trough to assist in the separation of the various components contained in the material mixture. Less dense components of the mixture rise to the surface of the fluidized bed, while the denser components settle to the bottom. At the output end of the trough, a stream splitter can be used to recover different layers of materials. This apparatus is good for separating agricultural products and sand.
"It is known in the prior art that under some circumstances a fluidized bed may be used without the addition of mechanical vibration or vertical oscillation to achieve particle separation. For example, U.S. Pat. No. 4,449,483 issued to Strohmeyer uses a heated fluidized bed dryer to treat municipal trash and remove heavier particles like glass from the trash before its combustion to produce heat. Meanwhile, U.S. Pat. No. 3,539,001 issued to Binnix et al. classifies materials from an admixture by means of intermediate selective removal of materials of predetermined sizes and specific gravities. The material mixture travels along a downwardly sloped screen support and is suspended by upwardly directed pneumatic pulses. U.S. Pat. No. 2,512,422 issued to Fletcher et al. again uses a downwardly inclined fluidized bed with upwardly directed pulses of air, wherein small particles of coal can be separated and purified from a coal mixture by providing holes in the top of the fluidized bed unit of a sufficient cross sectional area relative to the total cross sectional area of the bed to control the static pressure level within the fluidized bed to prevent the small particles of higher specific gravity from rising within the coal bed.
"The process and devices disclosed in these Strohmeyer, Binnix, and Fletcher patents, however, all seem to be directed to the separation of different constituents within an admixture having a relatively large difference in specific gravity. Such processes may work readily to separate nuts, bolts, rocks, etc. from coal, however, they would not be expected to separate coal particles containing organic sulfur from coal particles largely free of sulfur since the specific gravities of these two coal fractions can be relatively close.
"Another air pollutant of great concern is mercury, which occurs naturally in coal. Regulations promulgated by the
"However, this pre-combustion thermal pretreatment process is still capital intensive in that it requires a dual zone reactor to effectuate the drying and mercury volatilization steps. Moreover, an energy source is required to produce the 550.degree. F. bed temperature. Furthermore, 20-30% of the mercury cannot be removed from the coal by this process, because it is tightly bound to the carbon contained in the coal. Thus, the expensive scrubber technology will still be required to treat flue gas resulting from combustion of coal pretreated by this method because of the appreciable levels of mercury remaining in the coal after completion of this thermal pre-treatment process.
"Therefore, the ability to pre-treat particulate material like coal with fluidized bed operated at very low temperature without mechanical or chemical additives in order to separate and remove most of the pollutant constituents within the coal (e.g., mercury and sulfur) would be desirable. Such a process could be applied to all ranks of coal, and would alleviate the need for expensive scrubber technology for treatment flue gases after combustion of the coal."
In addition to obtaining background information on this patent, VerticalNews editors also obtained the inventors' summary information for this patent: "The present invention includes an apparatus for segregating particulate by density and/or size. The apparatus includes a fluidizing bed having a particulate receiving inlet for receiving the particulate to be fluidized. The fluidized bed also includes an opening for receiving a first fluidizing stream, which can be a primary heat stream, a secondary heat stream, at least one waste stream, or any combination thereof. At least one exit from the fluidized bed is provided for the fluidized particulate as well as at least one exit for the non-fluidized particulate. A conveyor is operatively disposed in the fluidized bed for conveying the non-fluidized particulate to the non-fluidized particulate exit. A collector box is in operative communication with the fluidized bed to receive the non-fluidized particulate. There is also a means for directing a second fluidizing stream through the non-fluidized particulate while it is in the collector box to in order to further separate fluidizable particulate there from.
"One advantage of the present invention is that it permits generally continuous processing of the particulate. As the non-fluidized particulate is conveyed from the fluidized bed to the collector box more particulate can be added for processing.
"Another advantage of the present invention is a generally horizontal conveyance of the non-particulate. The generally horizontal conveyance of the non-fluidized particulate ensures that all of the particulate is processed evenly and quickly by mixing or churning the material while it is being conveyed.
"Still yet another advantage of the present invention is that it includes a second fluidizing step or apparatus to capture more non-contaminated fluidizable particulates that are still trapped, or have become trapped, in the non-fluidized particulate. Capturing more of the fluidized particulate increases the amount of usable non-contaminated particulates, while reducing the amount of contaminated particulates that will be subject to further processing or disposal. By capturing more of the usable non-contaminated particulates and reducing the amount of contaminated particulate a company is able to increase its efficiency while reducing its costs."
For more information, see this patent:
Keywords for this news article include: Oil & Gas, Treatment, Natural Gas, Power Plant, Legal Issues,
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