Liquid purification or separation – Processes – Making an insoluble substance or accreting suspended...
Reexamination Certificate
2001-02-16
2003-04-08
Hruskoci, Peter A. (Department: 1724)
Liquid purification or separation
Processes
Making an insoluble substance or accreting suspended...
C209S005000, C210S728000, C210S732000, C210S770000, C210S787000, C210S803000, C210S806000, C044S626000
Reexamination Certificate
active
06544425
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to methods and apparatus for separating solids from liquids and other solids and, in particular, to dewatering and decontaminating coal tailings, clean coal products, and mineral slurries. The present invention also relates to methods and apparatus for liquid purification and, in particular, to methods and apparatus for recovering decontaminated process water from coal tailings, clean coal products and mineral slurries.
2. Background Information
In the cleaning or washing of coal for commercial use as a fuel and the like, the uncombustible ash content of coal is usually removed to enhance the heat content of the coal. Reduction in the ash content results in savings in transportation and ash disposal costs. Other materials frequently occurring with coals that may be removed in washing operations include various clays and sulfides. Such clays commonly include aericite (KAl
2
(AlSi
3
O)(OH)
12
, smectite (Al
2
Si
4
O
10
(OH
12
)H
2
O, and kaolinite clays (Al
2
Si
4
O
5
(OH)
4
. Sulfides are usually pyrite (FeS
4
(isometrical)).
During the processing of coal to effect such washing, a coal refuse slurry is generated. This slurry comprises coal fines known as tailings, and contaminants such as clay and mud suspended in plant process water. Due to the high volume of water used in the processing of coal, it is necessary to reclaim the wash water for recirculation in the plant. The concentrated solids are sent to an impoundment pond for disposal. In some cases in which coal washing plants have been operating for years, such slurry ponds may occupy hundreds of acres and may contain millions of tons of coal fines. These slurry ponds may also contain coal slurry to a depth of 70-150 feet. Such slurry ponds not only occupy a great deal of valuable land, but they also contain a considerable amount of energy and water resources.
Clean coal slurries are also used as, for example, an effective and cost effective means for transporting coal over distances from the place of production to the place of use.
The prior art discloses various methods and apparatuses for dewatering and decontaminating refuse pond coal slurries and for dewatering clean coal slurries.
U.S. Pat. No. 4,128,474 to Ennis discloses a wet mechanical process for cleaning, upgrading and dewatering fine coal. The process provides for forming an aqueous feed slurry of fine coal and its associated contaminant particles wherein all particles have a particle portion size of less than about 6 mm. ranging to zero. The feed slurry is separated into coal slurry and refuse slurry portions in a spiral gravity concentrator by removing contaminants having a particle size greater than about 0.15 mm. The concentrated coal slurry is then fed to a hydrocyclone separator where all the. ultra-fine silt material having a particle size of less than 0.15 mm. is removed and the coal particle fraction 6 mm. to 0.15 mm. is accumulated and thoroughly dewatered.
U.S. Pat. No. 4,257,879 to Bogenschneider, et al. discloses a coal slurry dewatering process in which the fine grain content is regulated to keep the filter cake at a constant level. A separation of the slurry into a predominantly relatively fine grain fraction and a relatively coarse grain fraction, with the division point being between about 0.03 and 0.15 mm. is carried out with a formation. if a coal agglomerate from the fine grain fraction is accomplished.
U.S. Pat. No. 4,526,121 to Shudo, et al. discloses a ship for treating a coal slurry comprising a pair of opposed trays disposed in the vicinity of the upper deck for causing the coal slurry supplied thereto to flow forward and delivering the slurry, a slanting dewatering screen disposed below each of the trays for dewatering the coal slurry delivered from the tray to separate a particulate coal fraction having relatively large particle sizes and conveyors for transporting to a specified position on the upper deck the particulate coal fraction dewatered and falling off the screen.
U.S. Pat. No. 4,620,672 to Liebson, et al. discloses a system for converting a coal slurry flowable through a pipeline to a coal water mixture capable of being rendered suitable for direct combustion in a boiler. The system includes a pipeline extending from a region adjacent to a mine or source of a coal to a region adjacent to a boiler or furnace at which combustion is to take place. In the furnace region, the slurry from the pipeline is directed into a holding space, such as a pond, from which it is directed to a grinding apparatus. On the way to the grinding apparatus from the pond, a side stream of the slurry is directed through a dewatering apparatus where the concentration of the side stream is increased form 50-55 weight percent of solids to about 70-80 weight percent of solids. The outlet of the dewatering apparatus is directed back to the main flow of slurry from the pond, and the main flow enters the grinding apparatus where the slurry is ground to a particle size suitable for combustion, such as 70-80% weight percent of solids at 200 mesh. The ground slurry can then be directed into a small agitated. tank and from this tank it can be directed into the boiler or furnace for combustion.
U.S. Pat. No. 4,810,371 to Fonseca discloses a process for automating fine coal cleaning including monitoring the operation of a flotation cell for separating coal from ash impurities by automatically detecting the coal content of the tailings from the cell and controlling the supply of additives to the cell to optimize slurry coal recovery and automatically monitoring the fluid level of the coal slurry in a dewatering filter tub to control the supply of additives to the filter tub and functioning of a dewatering filter.
U.S. Pat. No. 5,236,596 to Greenwald, Sr. discloses a method and apparatus for dewatering an aqueous coal slurry which includes imparting high shear forces to the aqueous coal slurry in the presence of a peptizing agent to render coal particles hydrophobic by stripping clay from the coal particles and peptizing the clay in the aqueous medium of the slurry. The slurry is separated to recover coal particles and the aqueous medium is drained from the coal particles.
U.S. Pat. No. 5,256,169 to Roe discloses a process for dewatering and agglomerating fine coal. The process consists of treating an aqueous fine coal slurry with a chemical binding agent prior to filtration or drying. The preferred chemical binding agent is an emulsifiable process oil. Efficiencies in dewatering and in low dustiness of the treated coal are disclosed.
U.S. Pat. No. 5,346,630 to Kenney discloses a process for the vacuum filtering of coal slurries. Dewatering of a filter cake is achieved by contacting the coal with a C
8
-C
20
aliphatic carboxylic acid or a derivative thereof, especially sodium oleate.
U.S. Pat. No. 5,476,522 to Kerr, et al. discloses a method for concentrating coal tailings and for dewatering coal products employing a copolymer of diallyldimethlylammonium halide and a vinyl alkoxysilane, preferably a copolymer of diallyldimethlylammonium chloride and vinyltrimethoxysilane as a coagulant. The method for concentrating coal tailings comprises steps of feeding the coal tailings to a thickener; treating the coal tailings with the coagulant, discharging substantially concentrated tailing; and withdrawing substantially clarified liquid from the thickener. A method for dewatering coal products containing water comprising the steps of feeding the clean coal containing water to a twin belt filter press; treating said coal with an effective amount of a copolymer coagulant of diallyldimethlylammonium halide and vinyl alkoxysilane, preferably diallyldimethlylammonium chloride and vinyl trimethoxysilane is also disclosed. The method encompasses removing water from the coal product through the addition of the subject polymer coagulant; removing the dewatered clean coal product from the filter; and withdrawing the recycled water through the filter.
U.S. Pat. No. 5,622,647 to Kerr, et al. discloses a metho
Hruskoci Peter A.
Sand + Sebolt
Slurry Cleanup Environmental, Inc.
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