GB2181449A - Fuel briquettes - Google Patents

Abstract

Briquettes are bonded together with molasses containing a minor amount of a basic oxide or hydroxide of an alkali metal or alkaline earth metal (e.g. calcium oxide). The latter reacts exothermically with the molasses to cause it to cure to produce a hard briquette of low friability.

Description

SPECIFICATION Fuel briquettes The present invention is concerned with fuel briquettes and, in particular, briquettes made from carbonaceous fuel particles, such as powdered coal.

Coal briquettes are conventionally formed by bonding together coal particles using a binder such as bitumen or pitch. With such binders, the bonding process is carried out at elevated temperatures, resulting in the emission of substantial quantities of smoke and other polluting byproducts from the briquetting plant.

Several other binders (both organic and inorganic) are known; see in this connection to discussion of the prior art in European Patent Specifications 135784 and 135785.

Molasses has been suggested as an organic binder, but it is unsatisfactory for use in modern briquetting plants because of its water solubility, its low weathering resistance, and its prolonged hardening time. It is known to improve the weathering resistance by the addition of sulphuric acid (or precursors thereof), but this has the disadvantage that the briquette combustion products contain sulphur dioxide.

The above-mentioned European specification 135784 is concerned with the improvement of a molasses-containing binder by the incorporation of certain polyvinyl alcohols; such binders can be used in a low-temperature process. Polyvinyl alcohol is highly water-absorbent, and although the briquettes have satisfactory thermal stability, they may suffer from undesirable water absorption.

The present invention seeks to provide a binder for fuel briquettes in which the use of such synthetic polymer binders can be avoided, and which can be used in a low temperature briquetting process.

According to the present invention, there is provided a fuel briquette comprising carbonaceous fuel particles bonded together with a binder comprising molasses in an amount of at least 2%, based on the weight of the briquette, and a minor amount of a basis oxide or hydroxide of an alkali metal or alkaiine earth metal.

Molasses as used in the briquettes according to the invention is a natural-derived viscid resin, which is sticky, adhesive and semi-fluid in consistency; it may be derived from any suitable sugar source, such as sugar beet, sugar cane, or even holly bark. Sugar beet molasses comprises 85 to 89% by weight of dry matter, including carbohydrates (predominantly sugars), amino acids, other organic acids and inorganic salts (primarily potassium, sodium and calcium salts). Sugar cane molasses is similar, except that it has a slightly higher water content.

It is particularly preferred that molasses is substantially the only organic binder present in the briquettes; that is, the binder is substantially free of synthetic polymer binders.

The basic oxide or hydroxide reacts exothermically with the molasses to cause curing (setting) thereof, which can result in very hard briquettes with low friability. The resulting briquettes can be burnt very satisfactorily, without causing significant quantities of hazardous polluting byproducts.

The basic oxide or hydroxide may be of sodium, potassium, magnesium, calcium or barium; calcium is preferred and calcium oxide (lime) is most preferred. (Lime may be used in smaller amounts than calcium hydroxide to achieve the same effect.) The latter may be added in substantially pure form or, in one embodiment, at least in part, in the form of cement. In the latter case, the briquettes preferably contain up to 10% (based on the weight of the briquettes) of cement. The latter serves to enhance the resistance of the briquettes to water (for example, during storage in the open).

It is preferred that the briquettes according to the invention comprise 30 to 97% fuel particles, 2 to 50% of molasses and 1 to 10% of the basic oxide or hydroxide, all the above percentages being by weight.

The ingredients are preferably present in the proportions by weight of 75% to 95% carbonaceous fuel particles, 4 to 20% molasses, with a balance of 1 to 10% comprising calcium hydroxide or oxide and cement together. More particularly the ingredients may be present in the proportion by weight of 77 to 80% fuel particles, about 15% molasses, 2 to 5% calcium hydroxide or oxide, and about 3% cement.

The binder preferably further includes a minor amount of an alcohol; methanol (optionally with ethanol) is preferred. The use of an alcohol is believed to catalyse the reaction between the basic oxide or hydroxide and the molasses.

It is further preferred to include in the binder an inhibitor against fungal attack; it is preferred to employ a fungicidal amount of formaldehyde.

The binder may further contain calcium carbonate (for example, in an amount of up to 2% by weight, based on the weight of the briquettes) which may further improve the heat resistance of the briquettes.

The carbonaceous fuel used in the briquettes according to the invention may be charcoal, coke, or one of various grades of coal, of which anthracite is preferred in view of its clean combustion characteristics.

The present invention further comprises a method of forming briquettes, which comprises mixing the carbonaceous fuel particles with the binder comprising molasses and the basic oxide or hydroxide, forming the mix into briquettes and allowing them to dry and harden. The briquettes may subsequently be dried in a dehumidifier cabinet and/or by means of gentle heating.

The carbonaceous fuel particles may be substantially dry when mixed with the binder; it is, however, an advantageous feature of the present invention that the particles can be wet when mixed with the binder without deleterious effect on the resulting briquettes.

In order that the present invention may be more fully understood, the following Exampie is given by way of illustration only.

EXAMPLE A dry mixture was formed from 77% anthracite coal dust and 15% of molasses, 5% lime and 3% cement, all these proportions being given by weight. A small quantity of methylated spirit was also stirred into the mixture.

The mixture so formed was pressed into individual briquettes which were left to dry and set in a dehumidifier cabinet.

The briquettes so formed were substantially non-friable, resistant to water absorption and burnt without producing significant amounts of atmosphere pollutants. Furthermore, they have a good slumber factor (that is they will commence burning again quickly after a period of being starved of air).

Claims (8)

1. Fuel briquette comprising carbonaceous fuel particles bonded together with a binder comprising molasses in an amount of at least 2%, based on the weight of the briquette, and a minor amount of a basic oxide or hydroxide of an alkali metal or alkaline earth metal.

2. Fuel briquette according to claim 1, in which the binder is substantially free of synthetic polymers.

3. Fuel briquette according to claim 1 or 2, in which the basic oxide or hydroxide is of calcium.

4. Fuel briquette comprising 30 to 97% by weight of powdered cabonaceous fuel, 2 to 50% by weight of molasses and 1 to 10% by weight of calcium hydroxide or oxide.

5. Fuel briquette according to any of claims 1 to 4, which further contains up to 10% by weight of cement.

6. Fuel briquette according to any of claims 1 to 5, in which the binder further contains an alcohol.

7. Fuel briquette according to any of claims 1 to 6, in which the carbonaceous fuel is anthracite.

8. A method of forming fuel briquettes according to any of claims 1 to 7, which comprises mixing the fuel particles with the binder, forming the mix into briquettes and allowing them to set.