GB2213829A - Production of solid fuels - Google Patents

Abstract

Solid fuel materials are prepared by the steps: (a) forming a mixture of: (i) a solid particulate combustible material, and (ii) a solid wax; and (b) compressing the mixture to convert it into a solid self-supporting body.

Description

Production of Solid Fuels This invention is concerned with improvements in and relating to the production of solid fuel materials.

Basically, in accordance with the present invention, a solid fuel material is prepared by the steps of: (a) forming a mixture of: (i) a solid particulate combustible material, and (ii) a solid wax; and (b) compressing the mixture to convert it into a solid self-supporting body.

As noted above, the fuel materials of the invention are produced from two principal ingredients, namely a first solid particulate combustible material (other than a solid wax) and a particulate solid wax which, in effect, lubricates the process and serves as binder in the final product of the invention. The first ingredient which may for convenience be termed a 8"combustible filler, may be any of a wide variety of particulate combustible materials and, in particular, two classes of combustible fillers are contemplated, namely cellulosic fibrous combustible fillers and non-fibrous, non-cellulosic combustible fillers.

Examples of the cellulosic fibrous fillers include sawdust, chopped straw, wood shavings, granulated or comminuted peat, shredded paper and like materials.

Non-fibrous, non cellulosic combustible fillers include, for example, anthracite/coal dust and powdered or comminuted solid plastics materials, e.g. ground waste plastics materials such as waste thermoset resinous materials or waste thermoplastic materials.

The particle size of the combustible filler may vary within wide limits and will, to some extent, depend upon the nature of the combustible filler. Thus, in general, the cellulosic fibrous combustible fillers are more conveniently used in larger particle sizes than the non-fibrous, non-cellulosic combustible fillers such as coal/anthracite dust. As a general guide, the cellulosic, fibrous materials such as chopped straw or wood shavings, may have a maximum dimension of up to about 3 inches (7.5 cm) in length but are preferably such that the greater percentage by weight of the material has a maximum length less than 1 inch (2.8 cm). Particulate fibrous cellulosic materials such as comminuted peat or sawdust or preferably of a particle size such that the material can pass through a 2.8 mm mesh sieve, preferably a 1 mm mesh sieve.

In the case of the non-fibrous, non-cellulosic combustible fillers, these suitably have particle sizes such that the material passes through a 1 mm mesh sieve, preferably a 0.25 mesh sieve.

The second- basic ingredient of the fuel material of the invention is a wax, preferably a particulate solid wax and this suitably has a particle size of 0.1 to 2 mm, preferably 0.5 to 1 mm. The wax is preferably a "hard" wax, that is suitably has a congealing point of at least 450C, preferably at least 55 0C. An example of a suitable wax is that sold under the trade name "Kerapress Zorb" by Kerax Ltd of Chorley, Lancashire.

The ratio of combustible filler to wax should be such that there is sufficient wax present to form a cohesive binder matrix and, to this end, the wax is suitably present in an amount such that it forms at least 25%, preferably from 30 to 70%, of the total volume of the finished product.

Other components may be present in minor amounts in the fuels produced in accordance with the invention such as perfumes or other odoriferous agents (e.g. to impart a "pine" smell to the product) or colouring agents.

In accordance with the process of the invention, the mixture of combustible filler and wax is compressed to form a solid self-supporting body. The compression step may be carried out either intermittently, for example in briquetting apparatus such as disclosed in our WO-A1-86/07307, or as a continuous operation, e.g. as a ~continuous extrusion process. In any event, the pressure applied to the mixture should, of course. be sufficient to produce a solid self-supporting material and is preferably at least Stne/in2, more preferably 10 to 35 tonnes/in2.

In the compression step, the solid fuel material may be formed in pieces of the desired size or may be formed into larger pieces which are subsequently cut into pieces of the desired size (as in an extrusion operation). In general it is preferred that the final product of the invention be supplied in pieces having a weight of from 10 to 2000 gm, preferably 200 to 750 gm.

The fuel material produced in accordance with the invention is readily ignitable, for example by the application of a simple flame from a piece of paper, and to this end it is convenient to supply the fuel pieces produced in accordance with the invention wrapped in a combustible wrapper (especially of paper) so that all that is required for ignition of the fuel material is the lighting of the paper wrapper.

In order that the invention may be well understood the following Examples are given by way of illustration only.

Examples Mixtures of the components listed in the table below were compressed in a hydraulic ram press under a presence of about 10 tonne/in to give cylindrical fuel tablets about 5 cm in diameter and 3 cm long. The fuel blocks could be readily ignited using paper.

Table Example Wax Solid partculate combustion (% by wt.) material (% by wt.) 1 Kerapress 2086 Chopped barley straw (50) (50) 2 Kerapress 2086 Wood dust (45) (55) 3 Kerapress 2086 Coal dust (10) (90)

Claims (4)

1. CLAIM: 1. A method for the production of a solid fuel material which comprises the steps of: (a) forming a mixture of: (i) a solid particulate combustible material, and (ii) a solid wax; and (b) compressing the mixture to convert it into a solid self-supporting body.
2. 2. A method as claimed in claim 1 in which the wax i a solid particulate wax.
3. 3. A method as claimed in claim 2 in which the wax has a congealing point of 450C or higher.
4. 4. A method as claimed in claim 1 substantially as hereinbefore described with reference to the Examples.