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Flotation separation of fine coal particles from ash-forming particles

a technology of ash-forming particles and flotation separation, which is applied in the direction of flotation, liquid carbonaceous fuels, fuels, etc., can solve the problems of increasing the processing cost, no current commercial process to recover and sell particles, and increasing the cost of coal processing. , to achieve the effect of reducing the bubble size, increasing the natural hydrophobicity of the coal particle surface, and reducing the size of the bubbl

Inactive Publication Date: 2016-03-24
EARTH TECH USA
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The patent describes a process for separating ash-forming component particles from coal particles using a high-speed mixing process. This process involves mixing water and coal fines together to form an aqueous slurry. The slurry is then introduced into bubbles in a flotation cell, where the ash-forming component particles are captured and floated to form a coal-froth. The process is carried out with a low height of the coal-froth, which improves the efficiency of the flotation process. A flotation aid, such as a frother or collector, can be added to the slurry to improve the separation of the ash-forming component particles from the coal particles. This process provides a more efficient way to separate ash-forming component particles from coal particles and improve the quality of the coal product.

Problems solved by technology

The current industrial process to recover coal particles less than 1 mm in size is more expensive than other coal processing.
The smaller the particles, the greater the processing cost.
Further, there are no current commercial processes to recover and sell particles less than 100 microns (0.1 mm).
While coal fines are the same chemical composition of the larger-size mined coal product, it is considered waste because the conventional coal recovery process is not designed to handle small particles.
The waste coal fines are left unused because they are typically too wet to burn, too dirty to be worth drying, and too fine to transport.
They are often impounded as environmentally hazardous.
Of particular challenge in the coal industry is the burning of coal with typical ash-forming components.
The components are the major source of most harmful emissions, such as SOx, and reduce energy value and heat transfer efficiency.
While coal fines separation, classification and drying technologies are known, they are too inefficient and expensive with particles less than 150 microns to be commercially feasible.
Further significant money is being wasted in the transportation and handling of the moisture fraction and the ash-forming mineral fraction of the coal.
However, reports in literature and patents have not demonstrated theory, instead they show combustible recovery increased with increasing particle size [Yoon 1995, Vapur 2010, Peng 2013].
Even with recent advances in some coal processes, including attempts to recover coal fines via coal flotation processes, the coal industry does not have an effective process for upgrading and handling coal fines less than 500 microns (0.5 mm), more specifically less than 300 microns (0.3 mm), less than 150 microns (0.15 mm), less than 100 microns (0.1 mm), and certainly less than 50 microns (0.05 mm).
These massive amounts of fine waste are inefficient and are an environmental and disposal problem.

Method used

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  • Flotation separation of fine coal particles from ash-forming particles
  • Flotation separation of fine coal particles from ash-forming particles
  • Flotation separation of fine coal particles from ash-forming particles

Examples

Experimental program
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Effect test

example 1

Measuring Moisture Content and Ash-Forming Component Content of a Coal Sample

[0112]The moisture content and ash-forming component content of any coal sample, in this case the slurry, were obtained by following the procedure outlined in ASTM Standard D7582—Standard Test Methods for Proximate Analysis of Coal and Coke by Macro Thermogravimetric Analysis and ASTM Standard D3173-11—Method for Moisture in the Analysis Sample of Coal and Coke.

[0113]For moisture, the mass of the slurry was measured. The slurry was then dried in an oven at 110° C. under flowing, dry air for one to two hours. The mass of the sample was obtained after complete drying. The mass remaining after drying is the solid content of the sample, and the mass lost is the moisture content of the material. Wt. % solid and wt. % moisture are calculated for the sample. Wt. % solids content=mass wet sample / mass dry sample. Wt. % moisture=100%−wt. % solids sample.

[0114]For quantifying ash-forming component content of the sampl...

example 2

High Shear or High Energy Slurry Preparation and Vibratory Screen Deslime Unit

[0116]Regular un-milled aqueous slurry is made from coal fines by introducing the coal fines into a paddle mixer. The paddle homogenizes the sample and the moisture content is obtained. Water is added to the coal fines to reduce the solids content to between 45 wt. % and 50 wt. % solids. While the paddle mixers are still turning, high energy mixers are also turned on for up to two minutes. The high shear mixers break apart clumps and agglomerations of coal and ash-forming component particles creating a slurry of discrete coal and ash-forming component particles.

[0117]High energy mixing was initially developed using lab-scale equipment by testing shear mixing. First, an aqueous slurry of coal fines was made using a 0.13 m3 Hobart paddle mixer with a 0.42 m diameter paddle. Tip speed is a measure of the velocity of the tip of a blending element and is used to characterize the mixing action of a turning eleme...

example 3

Milling Circuit to Prepare a Milled Slurry

[0131]The retained particles on the 0.7 mm and 1.4 mm screens of the vibratory screen deslime unit were processed through a wet mill to reduce their size to 0.3 mm or below. Particles with an average particle size less than 0.15 mm have been produced. In some embodiments, the average particle size of the milled slurry was less than 0.04 mm. In other embodiments, the average particle size of the milled slurry was 16.5 μm. The milled slurry preferably has no particles greater than about 200 μm. A target average particle size can be produced by varying the exit dimensions of the mill, residence time in the mill, media size in the mill, and media volume in the mill.

[0132]Ash-forming component particles are entrapped in coal particles. The entrapped ash-forming component particles have an average particle size on the range of less than 0.01 mm. In one instance the average particle size of the ash-forming component particles was measured to be of ...

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Abstract

Coal fines are processed by flotation separation to separate coal particles from ash-forming component particles. Coal fines are mixed water under high shear mixing conditions to form an aqueous slurry of coal fines containing between 15 wt. % and 55 wt. % coal fines. The aqueous slurry is introduced into a coal flotation cell to separate coal particles from ash-forming component particles by flotation separation, wherein the coal fines have a particle size less than 500 μm, and more preferably less than 300 μm. Bubbles are generated in the coal flotation cell having a bubble size and bubble quantity selected to float the coal particles and to form a coal-froth containing at least 15 wt. % solid particles. The solid particles include coal particles and ash-forming component particles. The coal-froth is collected for further processing.

Description

BACKGROUND OF THE INVENTION[0001]This disclosure relates to systems and methods for the flotation separation of fine coal particles from ash-forming component particles, thereby enabling the recovery of fine coal particles to be processed into upgraded, commercially valuable coal products.BACKGROUND[0002]Coals are ranked primarily based on the carbon makeup of the material (e.g. macerals and fixed carbon vs. volatile matter) and BTU value as a function of the ash-forming mineral and moisture content:[0003]Anthracite is the highest ranking coal and is used by the steel industry as a coke substitute through processes such as pulverized coal injection in metallurgical coal applications. It is a dense, hard rock with a metallic luster. It contains between 85% and 98% fixed carbon by weight. Anthracite coal contains approximately 14,000+BTU / lb (32+MJ / Kg).[0004]Bituminous is the second highest ranking coal and used for both electric power generation and coke production. It is a relatively...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): B03D1/02C10L1/32C10L5/00
CPCB03D1/025C10L5/00C10L2290/54C10L2250/06C10L1/326C10L5/04C10L5/366C10L9/00B03D1/028B03D1/1456B03D1/24B03D2203/08B03D1/02
Inventor SWENSEN, JAMES, S.HODSON, SIMON, K.HODSON, JONATHAN, K.
Owner EARTH TECH USA
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