WO2001014504A1

WO2001014504A1 - Coal adhesion material for use at low temperatures

Info

Publication number: WO2001014504A1
Application number: PCT/ZA2000/000144
Authority: WO
Inventors: John Rutherford Moody
Original assignee: Mineral Enhancement South Africa (Proprietary) Limited
Priority date: 1999-08-23
Filing date: 2000-08-23
Publication date: 2001-03-01
Also published as: GB9919866D0; AU6805600A

Abstract

The invention concerns an agglomerating material for coal fines, particularly duff coal fines, and a product of coal fines and the agglomerating material which consists of carboxy cellulose and guar gum each within a range of 1 % to 6 % of the agglomerated product.

Description

COAL ADHESION MATERIAL FOR USE AT LOW TEMPERATURES

FIELD OF THE INVENTION

This invention relates to an adhesion material for coal fines to be used in burning at low temperatures of up to about 1200°C.

BACKGROUND TO THE INVENTION

There are large quantities of discard quality or duff coal fines which are available but generally not commercially usable in that form. For the coal to be useful as a source of domestic heating it needs to be agglomerated into briquettes or similarly sized products. This need to be achieved in a manner which will enable the agglomerated product to withstand normal handling to reach its location for combustion without substantial disintegration back into fines. The agglomeration must also be effected in a manner which will not materially interfere with the normal burning of coal.

Duff coal fines have in the past been agglomerated using binders such as starch or molasses in high dosage rates with consequent expense. Molasses also forms a containment in the combustion environment which is highly undesirable. In the result these binders are not really adequate for their purposes. OBJECT OF THE INVENTION

It is the object of this invention to provide a material which will enable the coal fines to be utilised as agglomerated masses.

In this specification all constituent percentages are percentages by weight.

SUMMARY OF THE INVENTION

In accordance with this invention there is provided a material for agglomerating coal fines for use in combustion at temperatures below 1300° C which material comprises a mixture of carboxy cellulose and guar gum each in a proportion of 0.1% to 6.0% of agglomerated product.

Further features provide for the carboxy cellulose to be carboxy ethyl methyl cellulose and to be of high viscosity, particularly of the order of 20,000 cps.

The invention also provides an agglomerated product of coal fines in a mixture in the range of 5.0 mm to 0.05 mm mixed with a material as defined above.

Still further features of this invention provide for there to be an approximately even mixture of size of coal particles and for there to be a carboxy cellulose quantity of about 1.5% and guar gum quantity of about 0.5% of the final mixture and for the mixture to include a quantity of between 1% and 5% of agglomerating material as mixed.

DETAILED DESCRIPTION OF ONE EMBODIMENT OF THE INVENTION

These and other features of this invention will become apparent from the following description of one embodiment thereof.

Duff coal fines having a particle size range of between 0.05 mm to 5 mm are obtainable and has an analysis as follows:-

Particle distribution 0.05 mm to 0.5 mm 25%

0.5 mm to 1 mm 25%

1 mm to 6 mm 50%

Ash content 2.0% to 45%

Volatile material 1 % to 48% Where the ash content is in excess of 20% it is desirable that this content toe reduced before the fines are agglomerated. This can be effectively done by washing and separating in well known flotation and centrifuging processes. The fines should also be dried to a moisture content of around 2% and this can be effected in a cyclone separator for example. Treatment in this manner renders the fines a good quality coal for general domestic use for heating and cooking.

The fines are then mixed with agglomerating material prepared from:-

Carboxy methyl ether cellulose 1.5%

Guar gum 0.5% Coal fines 96% and

Water content 2%

The cellulose will have a viscosity of the order of 20,000 cps and the coal fines preferably has a fairly even mixture between small and large size range particles.

Mixing can be effected at ambient temperature in standard mixing equipment such as concrete mixers similar to the Eimich type mixer.

After mixing the material is briquetted in any convenient manner for example in a modified brick making machine using low pressures.

Using a mixture of the agglomerating material at a dosage rate from 0.5% to 1.5% set out above it is possible to achieve a green strength after curing at 50° C to

100°C of between 5 mPa to 18 mPa. The agglomerating material forms a strong film around the fine coal particles which adhere to each other in a manner without interference with the high volatiles present in the coal. Because the compounds are non-reactive they do not change the standard properties of the coal.

The resultant dried briquettes sustain and burn evenly up to a temperature of about 1200 °C.

It will be appreciated that the specific example given above can be varied particularly with regard to the kind of coal used. Generally however the coal used will be duff coal which even after reduction of the ash content would not be suitable for use in the smelting industry. The properties of the constituents of the agglomerated material may of course vary dependant on the particular circumstances in which the material is to be used but determination of the most satisfactory properties can readily be made by experiment by a suitably skilled person in the art.

The invention thus provides a satisfactory agglomerated coal product particular suitable for domestic and general heating purposes from a product of basically waste material.

Claims

1. A material for agglomerating coal fines comprising a mixture of carboxy cellulose and guar gum each in a proportion of 0.1% to 6% of agglomerated product.

2. A material as claimed in claim 1 in which the carboxy cellulose is carboxy ethyl methyl cellulose.

3. A material as claimed in claim 2 in which carboxy ethyl methyl has a viscosity of about 20,000 cps.

4. A material as claimed in any one of the preceding claims in which the quantity of carboxy cellulose is 1.5% and guar gum 0.5%.

5. An agglomerated product of coal fines having a particle size ranging between 0.05 mm and 6.0 mm mixed with an agglomerating material as defined in any one of claims 1 to 4.

6. An agglomerated product of coal fines as claimed in claim 5 in which the fines include an even mixture of small and larger size particles and the carboxy cellulose and guar gum are present in quantities of 1.5% and 0.5% respectively.

7. An agglomerated product of coal fines substantially as described in the example in the specification.