Method for producing a lignite product

Abstract

A method for producing a lignite product comprising the steps of (a) digging lignite from a lignite seam, (b) grinding the lignite, (c) forming a slurry comprising the lignite, (d) transporting the slurry to a locus for drying, and (e) drying the slurry to form a lignite product, wherein steps (a) to (c) are carried out using a mobile device.

Description

FIELD OF THE INVENTION[0001]The invention relates to a novel method of producing a value-added lignite product. In particular, the present invention relates to a process that provides a comparatively low moisture content product that has improved handling and utilisation compared with unprocessed lignite.BACKGROUND OF THE INVENTION[0002]In this specification where a document, act or item of knowledge is referred to or discussed, this reference or discussion is not an admission that the document, act or item of knowledge or any combination thereof was at the priority date, publicly available, known to the public, part of common general knowledge; or known to be relevant to an attempt to solve any problem with which this specification is concerned.[0003]Coal is a fossil fuel formed in swamp environments from the remains of organic matter such as plants that have been preserved (at least in part) by immersion in water and mud. Coal is a non-renewable energy source because it takes mill...

AI Technical Summary

Benefits of technology

[0055]The slurry consistency will depend upon the amount of water added and any admixture. Other additives or admixtures may include, for example, calcium hydroxide, ammonium hydroxide, coal ash, ash water or other alkaline material. Alkaline material is typically added to achieve better grinding performance including lower power consumption, a suitable slurry consistency and desirable final product characteristics.

[0056]Preferably the pH of the slurry is between 5.0 and 8.5 and alkaline material such as Ca(OH)2 or other hydroxides may be added to achieve the desired pH. Control of the slurry pH enables optimisation of the slurry milling, slurry rheology and lignite product. It has been found that at pH values below 5 the coal colloid spontaneously flocculates and the resultant lignite product tends to be soft, and of low density and high porosity.

[0057]Without wishing to be bound by theory it appears that the higher pH has a significant effect on the slurry product by altering the structure of the lignite. Lignite is essentially composed of a bimodal mixture of partia

Problems solved by technology

Coal is a non-renewable energy source because it takes millions of years to create.

Because of its low energy density and therefore energy potential, lignite is inefficient to transport and is not traded extensively on the world market compared with higher coal grades.

Removal of ash is useful in raising the value of the fuel, but acid treatment of lignite coal typically creates a light, fluffy coal product that is unlikely to create a product having desirable hard, dust free and good weathering characteristics.

However the products of these processes typically consist of a dry powder which is potentially hazardous due to the risk of powder explosion, difficult to handle because of the high fines content and raises occupational health issues for workers who may inhale the fines.

Accordingly, the products typically require special handling and costly storage facilities.

None of the aforementioned processes appear to be readily adapted for mobile performance or location at the coal digging face.

Several require expensive fixed plant or steam/heat generation facilities.

Furthermore, typically the dried granular, powder or oily lignite product is unsuitab

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