Flotation offers a very satisfactory low cost method for recovering a fine low ash clean coal product at a profit Often this fine coal when combined with the cleaned coarser fractions results in an over all superior product low in ash and sulphur giving maximum profit returns per unit mined.
It is highly desirable to extend the range of coal flotation to include the coarser Sizes Not only will this simplify general washery practice but will result in a superior product having desirable marketing characteristics for metallurgical and steam power plant uses It is now possible to efficiently recover coal by flotation through the entire size range beginning at about 4 mesh down to fines minus 200 mesh.
The 8220Sub A Lasseter Type Flotation Machine has proved successful for treating coarse coal with the flowsheet as indicated A frother of the alcohol type is generally added to the flotation feed after conditioning with kerosene Floated coal will collect in a heavy dense matte at the cell surface and as raked off will contain up to 60 solids Mechanical dewatering is usually not necessary Natural drainage dewatering on porous bottom screw conveyors and vibrating screen dewatering are all being used successfully in coarse coal recovery circuits.
A coal flotation machine must not only be able to handle a coarse as well as a fine feed but it must also be simple to operate Gravity circulation permits the treatment of difficult unclassified feeds.
High cost of mining makes it very important from a profit standpoint to recover all of the low ash coal both coarse and fines With the present trend toward mechanization more fines are produced in mining In many operations it is no longer economical to discard these fines to waste even though ash contiminants render the fines unmarketable without additional cleaning.
Water conservation stream pollution and refuse storage are also factors which must be taken into consideration along with marketing requirements for the clean coal product Flotation offers an efficient and low cost method for recovering coal fines at a profit In many cases floated coal fines can be blended with the coarser fractions without affecting ash moisture or size limitations This is being done successfully in coking coal operations Fine coal is also being used extensively in steam plants for electric power generation.
The above flowsheets are based on existing small coal flotation plants They illustrate clearly the simplicity and feasibility of adding 8220Sub A Coal Flotation as an additional process to small washing plants.
This is a typical flowsheet for a small coal mine operationwhere low ash fines are contaminated with high ash materials due to mechanized mining.
Because of its limited output treatment must be very simple and operating costs kept to a minimum At the washery illustrated by flowsheet 8220A the entire mine output is sold for coking coal Mining the relatively narrow seam produces a product with 15 to 20 ash although the coal when cleaned will carry only 3 to 3 ash This low ash coal brings a premiumprice so it is an economic necessity to remove the impurities.
Coal isnt technically a mineral its a black burnable rock and is considered a fossil fuel The coal deposits in the Powder River Basin are among the largest in the world A pound of coal supplies enough electricity to light ten 100 watt light bulbs for one hour By The Numbers 40 Amount of Americas coal that comes from Wyoming.
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