In the mining industry, the mining and subsequent processing and handling of material generally results in a large amount of fine material being wasted and being left in slurry ponds as unusable. The reason for the fine material being considered unusable is that it is very difficult to work with. The properties displayed by the fine material result in it not being suitable for processing by conventional handling apparatus and methods.

According to a first aspect of the invention there is provided an apparatus for the recovery and utilisation of wet fine material, which includes a drying means and a feed means for feeding fairly dry fine material into a material feed line.

It will be understood that the term"fine material"is to be construed as meaning material of a particle size below a typical usable size and which makes the handling of the material by conventional methods and apparatus difficult and unsuitable. The wet fine material may comprise particles mixed with water. It will further be understood that the fine material mixed with the water may have a water content of at least 14% and, more particularly, between 14% and 22% and is in

a partially dried slurry form.

The drying means may include a pneumatic conveyor. This may preferably be done in two stages. In a first conveying stage, a first very lean phase pneumatic conveyor may be used for drying the wet fine material to provide fairly dry particles and, in a second conveying stage, a second denser phase pneumatic conveyor may be used for transporting the fairly dry particles.

A particle separator may be provided between the very lean and denser phase conveyors. A closed surge hopper may be connected to an output end of the denser phase conveyor. Fairly dry fine material may be supplie from the denser phase conveying stage to the closed surge hopper.

Those skilled in the art will understand that the outflow from an outlet of the particle separator will comprise evaporated water, air and a certain amount of the particles. A filter for filtering and collecting water and outflow particles from an outflow of air from the particle separator may thus be included. A conduit means for returning water and outflow particles to a supply of the fine material may also be provided.

The filter may have an air outlet and the apparatus may further include a fan connected to the air outlet which discharges the air to the atmosphere.

The material may, in particular, be coal. In the coal industry the fine material which is found in suspension in a liquid in coal slurry ponds has a particle size

which is typically less than 100 micron, although this size may vary.

According to a second aspect of the invention there is provided a coal processing plant, which includes an apparatus as described above; milling machinery for milling coal feedstock; a feed line for feeding the coal feedstock to the milling machinery; and a feed means for feeding the fairly dry fine coal particles from the apparatus into the material feed line.

The plant may be a power generating plant.

The feed means may be a screw feeder.

According to a third aspect of the invention there is provided a method of recovering and utilising wet fine material which includes the steps of drying the fine material and feeding fairly dry fine material into a material feed line.

Conveniently, the method further includes feeding the fairly dry coal particles into a material feed line that feeds coal feedstock into milling machinery of a coal processing plant, in particular a power generating plant.

The invention is now described, by way of an example, with reference to the accompanying drawings, in which:

Figure 1 shows a schematic representation of a first embodiment of an apparatus for the recovery and utilisation of wet fine material according to the invention, which forms part of a coal fired power generating plant; and Figure 2 shows a schematic representation of a second embodiment of an apparatus for the recovery and utilisation of wet fine material according to the invention, which also forms part of a coal fired power generating plant.

With reference to Figure 1, a first embodiment of an apparatus for the recovery and utilisation of wet fine material is generally referred to by reference numeral 10. The fine material is comprised of fine coal particles, which is initially in the form of a slurry in a slurry pond. The apparatus 10 forms part of a coal fired power station and is integrated with existing equipment supplying coal feedstock to a mill, as will be explained below. The coal particles are typically of a size of less than 100 micron in suspension in water. The fine material found in the slurry pond is a result of mining and subsequent handling of the coal, which has been discarded.

The apparatus 10 includes a belt conveyor 12 which is used to feed slurry from the slurry pond (not shown) into an open hopper 14 which is attached to a first screw feeder 16. The first screw feeder 16 is used to feed the slurry into a first pneumatic conveyor 18. This first pneumatic conveyor 18 is of the very lean phase type, having an air blower 20 attached to it. The slurry is dried to a large extent as it passes through the conveyor 18.

The first pneumatic conveyor 18 delivers fairly dry coal particles to a cyclone

separator 22. The air outlet of the cyclone separator 22 is connected to a filter 26 via a conduit 24. This filter 26 may be a bag filter or a scrubber. Outflow from the cyclone separator 22 is fed through the filter 26 so as to remove any particles which may still be present therein and provide fairly clean air. The wet removed fine material is fed as a slurry back to the slurry pond.

The fairly dry particles are fed from the separator 22 into a closed surge hopper 28 which is attached to a second screw feeder 30. The second screw feeder 30 is used to feed the fairly dry particles into a second pneumatic conveyor 32. The second pneumatic conveyor 32 is of the denser phase type, but may still be classified as a lean phase type. The water content of the fairly dry particles which are fed into the second pneumatic conveyor 32 is typically 5%, with a maximum water content of 8%. The fairly dry particles are supplie to a second closed surge hopper 34. The hopper 28 has an outlet with a bag filter 36, so that substantially clean air exits therefrom.

The hopper 34 supplies a third screw feeder 38. The third screw feeder 38 is connected to a pipe 40 which feeds coal feedstock into a mill 42. The third screw feeder 38 joins the pipe 40 in close proximity to where the pipe 40 feeds into the mill 42 and it is used to feed the fairly dry, separated particles into the pipe 40.

The pipe 40 is used to feed coal feedstock from a coal feeder 44 and a fourth screw feeder 46, into the mill 42, by means of gravity.

As the coal is fed from the fourth screw feeder 46, it falls down the pipe 40 and the particles which are fed into the pipe 40 via the third screw feeder 38 are dragged along with the falling coal. The possibility of the particles adhering to the sides of the pipe 40 and thus causing a build-up of material in the pipe 40 which would ultimately lead to a blockage, is minimised. The fairly dry particles, which would otherwise have been discarded, are thus fed into the mill 42 together with the coal feedstock and are then subsequently burnt.

With reference to Figure 2, a second embodiment of an apparatus for the recovery and utilisation of wet fine material is also generally referred to by reference numeral 10. In Figure 2 like parts are designated by like numerals as shown in Figure 1. The fine material is also comprised of wet fine coal particles, which is initially in the form of a slurry in a slurry pond. The apparatus 10 also forms part of a coal fired power generating plant and is integrated with existing equipment supplying coal feedstock to a mill, as will be explained below. The coal particles are typically of a size of less than 100 micron in suspension in water. The fine material found in the slurry pond is a result of mining and subsequent handling of the coal, which has been discarded.

The apparatus 10 includes a feeder (not shown) which is used to feed slurry from the slurry pond (not shown) into a rotary dryer 46 linked to a first pneumatic conveyor 18 at position A, as shown in Figure 2. This first pneumatic conveyor 18 is of the very lean phase type. The slurry is dried to a large extent as it passes through the dryer 46 and the conveyor 18. In a typical power generating plant or other industrial application, flue gas is available and it is used as the conveying

medium. The flue gas generally has waste heat associated with it and is inert, which makes it an inherently safe transport medium. The flue gas is conveyed via flue gas ducting 48 from a common flue gas duct 50 of the power generating plant to a control valve 52. The control valve 52 then controls flow of the flue gas via a first conduit 54 which feeds into the dryer 46 and a second conduit 56 which feeds into the conveyor 18.

The first pneumatic conveyor 18 delivers fairly dry coal particles to a cyclone separator 22. The air outlet of the cyclone separator 22 is connected to a filter 26 via a conduit 24. This filter 26 may be a bag filter or a wet scrubber. Outflow from the cyclone separator 22 is fed through the filter 26 so as to remove any particles which may still be present therein and provide fairly clean flue gas to vent to the atmosphere. The removed fine material is fed as a slurry back to the slurry pond. The fairly clean air is then fed through a fan 58 and out through a chimney 60. The fan 58 is preferably of the induced draft fan type. A forced draft fan type could also be used or a combination of the two types could be used, but the force draft fan would in this case be situated between the common flue gas duct 50 and the flue gas ducting 48. The result of having air fed through the induced draft fan 58 is that a slight vacuum is created in the dryer 46, conveyor 18 and cyclone 26.

This results in a lower saturation pressure existing in these components and therefore better evaporation occurs.

The fairly dry particles are fed from the separator 22 into a second pneumatic conveyor 32. The second pneumatic conveyor 32 is of the denser phase type, but may still be classified as a lean phase type. The water content of the fairly dry

particles which are fed into the second pneumatic conveyor 32 is typically 5%, with a maximum water content of 8%. This pneumatic conveyor 32 is used to convey the particles to a closed surge hopper 34. The hopper 34 has an outlet with a bag filter (not shown), so that substantially clean air exits therefrom.

The hopper 34 supplies a screw feeder 62 via a rotary valve (not shown) which serves as an airlock. The screw feeder 62 is connected to a pipe 40 which feeds coal feedstock into a mill 42. The screw feeder 62 joins the pipe 40 in close proximity to where the pipe 40 feeds into the mill 42 and it is used to feed the fairly dry, separated particles into the pipe 40, as with the embodiment of Figure 1.

Again, the fairly dry particles, which would otherwise have been discarded, are fed into the mill 42 together with the coal feedstock and are then subsequently burnt.