WO2006003354A1

WO2006003354A1 - Fuel product and process

Info

Publication number: WO2006003354A1
Application number: PCT/GB2004/002936
Authority: WO
Inventors: John Kenneth Gilbert; John Samuel Webster
Original assignee: Applied Silicate Technologies Limited
Priority date: 2004-07-07
Filing date: 2004-07-07
Publication date: 2006-01-12
Also published as: EA200602216A1; JP2008506000A; GB0513780D0; GB2416542A; AU2005258956A2; EA010323B1; CA2570522A1; EP1784479A1; WO2006003444A1; AU2005258956A1; CN1997726A; ZA200610697B; UA91981C2; GB2416542B; AU2005258956B2

Abstract

A process for producing fuel pellets is described. The pellets are obtainable from a particulate carbon-based material and a binder, and the process comprises the following steps: admixing the material and binder, and agglomerating the so-formed mixture by tumbling. The tumbling action, such as in a rotary drum, serves to agglomerate the particles and bind the mixture into the pellets, usually with a variable size distribution. No mechanical compression force is required, and the process can be carried out at ambient or near-ambient temperature. The process provides a simple but efficient process for using waste carbon-based materials, and forming a useable fuel product, which is easily transportable and efficiently combustible. Rotating drum or pan agglomerators are relatively low cost to build, and are capable of very high tonnage throughputs. Customised products can be produced and the process enhances the economics of ash and sulphur removal in coal upgrade plants.

Description

Fuel Product and Process

The present invention relates to a fuel product and a process for making same.

A continuing problem in many solid-based fuel extraction processes is dealing with waste ^xfine' materials. As much as 10% of run-of-mine coal can end up as fine (<3mm) or ultra fine (<0.1mm) coal dust. One solution has been to form briquettes. These are formed by compressing the fines at very high pressures to physically form a secondary fuel material. However, the high capital and operating costs of briquetting plants have prevented their use beyond some high cost countries. In many places, coal fines are currently simply Mumped' near the coal mine.

Another industry using the briquetting process is the peat industry. To form a suitably crushable material, the peat must be significantly dried, often two or three times, as well as shredded and crushed, adding to the overall cost of forming the briquettes.

It is an object of the present invention to provide a more efficient fuel product and process by lowering costs of operations and capital requirements

Thus, according to one aspect of the present invention, there is provided a process for producing fuel pellets from a particulate carbon-based material and a binder, comprising of the following steps:

admixing the material and binder, and agglomerating the so-formed mixture by tumbling.

The tumbling action, such as in a rotary drum, serves to agglomerate the particles and bind the mixture into the pellets, usually with a variable size distribution. No mechanical compression force is required, (with its attendant low production rate and high cost) , and the process of the present invention can be carried out at ambient or near- ambient temperature.

Preferably, the process provides pellets having a hardened outer portion, skin, casing or shell. More preferably, the interior of the pellets is dry, and wholly or substantially in an internal dust-like, particulate and/or powderous form. One way of achieving this is to allow the formed pellets to dry at ambient temperatures.

In one embodiment of the present invention, water is part of the material and binder mixture, either by being part of the material, part of the binder, added separately, or a combination of any of these.

The amount of water needed or desired for the process of the present invention may depend upon the nature of the particulate material and the binder. In some circumstances, it is preferred to have a dry particulate material. In other circumstances, the material may be derived from a wet fuel source, such as peat and coal tailings dams, and any reduction in the amount of drying needed (compared with for example the briquetting process) reduces the overall energy input required to form the fuel product.

It is a particular advantage of the present invention that it can use any type of ^Λwet' or ^Λdry' particulate carbon-based material, generally without significant further processing of the material prior to its suitability for use in the process of the present invention.

The ability of the present invention to work on- ^Λwet' and ^Λdry' particulate materials provides yet another advantage. At some power stations, there is currently H million tonnes a year of ^unusable coal' product in stockpiles, as it is too wet, i.e. its moisture content is too high, for efficient burning. Freshly mined coal can have a moisture content of 12-15%, but some mined coal can end up with a moisture content of up to 30%. To drive off this level of moisture (by turning it into steam) prior to any combustion of the actual coal requires so much energy to start with, that this coal is simply not used, as it is not efficient. Grinding such coal to be more ^λburnable' is also inefficient as the moisture-rich coal generally clogs up the grinder.

The process of the present invention is directly usable with moisture-rich coal fines and similar products, as any water content of the binder can be reduced in line with the level of moisture in the coal without affecting the process. Once the pellets have been formed, their hardened shell stops or significantly reduces water ingress, especially if waterproofing additives are used. Once fully ^λdry' , the pellets can have a moisture content of at least half that of the particulate starting material, and possibly less than 5%, and thus be sufficiently dry for easy grinding to form a suitable fuel product for a power station.

-Thus, the present invention also provides significant moisture reduction in a fuel product, converting an inefficient fuel product into an efficient fuel product.

In a preferred embodiment of the present invention, the amount of water for the process is adjusted in the binder component prior to its admixing with the particulate material. The calculation of this binder to water adjustment is dependent on the moisture content of the particulate material.

According to another embodiment of the present invention, the particulate material is generally of a maximum size or grade of 3mm or lower. Coal Must' or ''fines' can often be of a sub-micron size. Peat is a fuel material which is generally dried/shredded/dried/crushed prior to briquetting. Some shredding of the peat material may still be required to provide a particulate material suitable for the present invention, but to a much lesser extent than that required for briquetting.

More preferably, the particulate material has a range of sizes or grades; preferably biased towards fine or finer particle sizes.

Carbon-based particulate material suitable for the present invention can be accepted wet or dry, and could be provided by any type of maceral fuel, including peat and lignite through to sub-bituminous coals, anthracite fines, petroleum coke fines and the like, as well as sewerage wastes, biomass, animal wastes and other hydrocarbon materials that could be considered a fuel source. The particulate material may also be a combination of two or more starting materials or ^λingredients' , not necessarily premixed, and such as those hereinbefore mentioned, so as to provide ^Λhybrid' fuel pellets. Suitable materials also include low grade or processed fuels, as well as hitherto ^λwaste' products, whose clean combustion would help lower overall pollution levels.

The present invention is not affected by high ash content or sulphur content in the particulate material.

Any suitable binder can be used for the present invention, which binder may be a homogeneous or heterogeneous material, such as cements and raw silicates like calcium, sodium or potassium.

The process may include the addition of one or more further ingredients into the mixing, either separately or integrally with the binder. Such further ingredients include lime, organic binders, silicates, cements, and waterproofing additives. Lime or cement helps to inhibit sulphur emission upon burning of the so-formed pellets. A cementitious material can assist in the green- strength of the pellets, and possibly in forming the hardened outer surface or shell for the pellets as described hereinafter.

According to another embodiment of the present invention, the binder may include one or more surfactants. One or more other mineral additives such as zeolites or vermiculite could also be used as a further ingredient to help bind any metallic contaminants in the ash of the pellets, and so prevent any soluble metals being released from the ash.

The particulate material and binder, and any other separate reagents or ingredients to be added, can be admixed using any known process or arrangement, including simple mixing. Because the next step of the process is a tumbling action, absolute homogenous mixing of the reagents or ingredients prior to the process is not essential, as the tumbling action will generally further the mixing action if necessary or desired. In some circumstances, the admixing may at least partly occur during the tumbling action, such that the steps of the invention may not be wholly distinct.

In one embodiment of the present invention, the binder is coated on to the particulate material. One method of coating is to spray the binder on to the material.

In another embodiment of the present invention, the particulate material is moving prior to and/or during mixing with the binder, and/or the material is in a dispersed arrangement. One particular suitable form of this is a falling curtain of particulate material, such as at conveyor transfers, inside pelletising drums or pans, and from stockpile load outs, etc. In another embodiment of the present invention, the particulate material and binder are directly and/or immediately undergo tumbling after their contact with each other.

The tumbling action serves to agglomerate the particulate material and binder mixture to form particles of greater and greater size, generally having a spherical or ovoid shape. The size of the so-formed pellets can be adjusted based on the process conditions for tumbling, such as rotation speed, moisture content, impact force and duration. The pellets could also be screened and/or recycled during or after pelletising to produce a desired, e.g. narrower, size distribution.

One suitable apparatus for providing tumbling action is a rotary drum. Rotary drums are well known in the art. Their output can be dependent upon the length, diameter, speed of rotation and angle of mounting of the drum, and the output can vary from single figure tonnes per hour, to hundreds of tonnes per hour per drum.

The general sizes and dimensions of agglomerator drums, such as pan, rotary and conical drums, are known in the art, as are their process variations to provide variation in the products formed. See for example UK Patent No 787993. Rotary drums have low capital and low operating costs, especially in comparison with briquetting plants. They can even be provided in mobile form, such that the process of the present invention can be provided where desired or necessary, e.g. moved and located to where a particulate material is currently stored or Mumped' , rather than requiring significant movement (and therefore cost) for transporting the material to a fixed processing site.

The agglomeration action may be carried out in one or more stages, either connected, such as the tumbling conditions changing in the same drum or the material being fed directly into another agglomerator, or separate. In one arrangement for multi-stage agglomeration, the tumbling conditions are variable or varied for each stage. The conditions may be altered either in a continuous manner or action, or discretely.

Where the process of the present invention involves tumbling the mixture in a rotary drum, one or more rotary drums may be used for the agglomeration.

The surfactant action serves to draw the binder towards the surface of the forming pellets, such that once cured, the pellets have a harder outer portion, skin, shell or surface, compared to their interior. Thus the pellets have a variable density towards the core; the density being greater at the surface. Indeed, the ^Λshell' will generally have a high density in comparison with the lower density of the 'interior' .

More preferably, the pellets have sufficient hardness once cured to allow handling, stacking and/or transportation without any significant breakage.

The curing of the pellets may start during or be part of the agglomeration action. Alternatively, the curing may wholly or substantially be a separate step of the process of the present invention, either occurring as a continuous part of the agglomeration tumbling, or as a separate step or steps thereafter.

Preferably, the agglomerated pellets formed by the present invention are rested or tumbled more gently for a short period, generally a number of minutes, prior to undergoing a curing and/or polishing step. This curing and/or polishing step could be provided by further tumbling action, for instance in the same or another rotary drum. If necessary or desired, a cementitious material could be added to the pellets at this stage. This should decrease the curing process time, and/or provide a stronger initial green strength to the pellets to aid handling, etc.

The method of the present invention may include one or more sizing steps. That is, to grade the size of the so-formed pellets to that desired or necessary. This could include extracting those pellets which are damaged or undersized, which pellet material could be recycled back into the process of the present invention.

Following initial curing, the formed pellets are preferably allowed to be rested for some time, possibly a number of days such as 3-7 days, to provide or allow for any final curing. Like other curing products, the pellets continue to cure to gain strength over time, such as a further number of days or weeks.

According to another aspect of the present invention, there is provided a process for encapsulating a particulate material, comprising the steps of:

admixing the material with a binder, and allowing the mixed material to cure.

The particulate material may be any material that has a fine distribution, generally dust-like materials such as uranium tailings dust and waste, coal dust and fly ash waste, asbestos, metal ores, metals such as gold, copper or iron, whether elemental or in compound form such as ores, and vehicle-surface materials such as road-surfacing materials. Indeed any fine material, whose agglomeration, solidification or encapsulation would be beneficial.

The method of admixture may be any form of mixing, including coating, spraying, injecting, etc. Generally, the process can be carried out at ambient or near-ambient temperature, so allowing the process to occur in situ.

The process conditions and parameters and the form of the binder and possible other ingredients as described hereinbefore are applicable to this process also.

According to another aspect of the present invention, there is provided a fuel pellet product formable by agglomeration of a particulate carbon- based material and a binder, preferably at or near ambient temperature.

According to another aspect of the present invention, there is provided a fuel pellet product comprising an agglomerated composition of a particulate carbon-based material and a binder.

According to another aspect of the present invention, there is provided a fuel pellet product whenever formed by a process as herein described.

The fuel pellet product of the present invention is a material which is easily storable. It is also easily transportable due to its variable diameter distribution. This enhances stacking concentration, which also reduces abrasion and consequential breakage of the pellets. The product of the present invention is ready for use as a fuel in many situations, e.g. domestically such as in a home fire, industrially, such as in a power plant, etc.

The product is formed from currently 'waste' materials, thereby increasing the efficiency of current solid-fuel extraction and production.

The product preferably allows a very high percentage of combustion (possibly 100% combustion) , so as to leave little or no combustable fuel in the ash.

Embodiments of the present invention will now be described by way of example only, and with reference to the accompanying drawings in which:

Figure 1 is a flow diagram of a process according to one embodiment of the present invention;

Figure 2 is a front view of tumbling action of agglomerating pellets according to the present invention; and

Figure 3 is a view of a number of pellets according to another embodiment of the present invention.

Fine coal recovery systems are now a common part of modern coal process operations, but there has been a requirement for a cost effective high tonnage solution for utilising the wet coal fines generated by the various benef iciation (benefaction) processes .

High capital and operating costs of briquetting plants have prevented numerous operations from maximising their coal reserves. Briquetting is a process where some type of material is compressed under high pressure. Compression of the material causes the temperature to rise, which makes the raw material liberate various adhesives.

There are low-priced hydraulic briquetting presses which are designed to operate for only a number of hours a day. Bigger mechanical presses are used for large-scale installations making hundreds of kilograms per hour, but these require approximately 20OkWh energy input (for drying and processing) per tonne of briquetting material. The cost of this is prohibitive in countries where the cost of coal is already low, such that coal fines are currently simply dumped on nearby ground in many countries around the world.

Similarly, the current method of forming peat briquettes requires initial drying of the dug peat to about 55% moisture, shredding, further drying to a lower moisture content, followed by crushing, followed by high pressure briquetting. Each mechanical step requires significant energy input.

Other waste materials include petroleum coke, a by- product from cracking oil, which currently has no beneficial use and is therefore also currently stockpiled or sold off at a very low cost.

The process of the present invention allows for use of all these materials in a cost-efficient process, to provide a beneficial fuel product.

Figure 1 shows a flow diagram for the process of the present invention.

In Stage 1 - Preparation

The raw fuel feed is prepared for agglomeration. Depending on its raw state it may need grinding, screening or drying. The finer the raw feed is, the more effective the process.

Depending on the moisture content and chemical characteristics of the raw fuel feed, the liquid feed is adjusted to suit. This will involve balancing the quantity of water relative to the binder and surfactants used.

The above parameters can be established during pre- testing of the process and apparatus. For coal fines agglomeration, it has been found that between 20-25% of liquid binder (to weight of raw feed) is generally needed for efficient agglomeration. Generally, the wetter the raw feed, the less water is required to be added at this stage.

Stage 2 - Agglomeration The fuel feed is carried along and any dry reagents are added to the feed. It then falls from the end of a conveyor belt. The liquid binder is sprayed onto the falling curtain of fines, which together fall into a rotating drum, generally l-5m (such as 3m) in diameter. As the mixture tumbles while being sprayed with the binder and water mixture, it forms small pellets which agglomerate and grow, forming pellets of desired shape and size as shown in Figure 2.

The drum can be lined with loosely fitting heavy duty rubber sheet to avoid material sticking to the sides of the drum. The drum is set at an incline (e.g. 3-5%) to aid progression of the pellets therealong, and to control the residence time in the drum. The completed pellets exit at the opposite end of the drum onto another conveyor.

Pellets can be varied in size with only operational drum adjustments (speed of rotation, moisture content and longitudinal drum angle which directly affects residence time in the drum) . Expensive mould changes, such as in present briquetting operations, are not required to vary the product dimensions.

Stage 3 - Initial Curing/Polishing

At this stage, the pellets are green and must be handled carefully until the initial cure, which will take from 30-60 minutes, has taken place. After such time the green strength will have increased dramatically allowing stacking to take place.

This initial curing/polishing step, if necessary, may take place in another rotating drum, similar to but with larger diameter than the agglomerating drum. It may be of greater diameter and longer than the agglomeration drum. Here the pellets progress slowly through the drum, allowing sufficient time for the pellets to initially cure or receive surface treatment, and thereby allow handling and stacking. The residence time within this drum is dependent on the fuel characteristics, and its use can be determined in pre-production tests.

Selected surface treatment additives can be added at this stage to increase the surface area of the pellet skin, to prevent sticking, and/or to prevent leaking fluid into bags, etc.

Should the green strength of the pellets be poor, certain additional binders or cementitious chemicals can be added at stage 2 to rapidly speed-up the curing process, and thereby give quicker and stronger initial green strength to aid handling, etc. Broken and undersized pellets can be removed at this stage using for instance a slotted section of drum or a vibrating screen at the drum exit. The damaged and undersized pellets can then be returned to the agglomerating drum for reprocessing. Stage 4 - Stock Piling and Final Curing

Following the initial cure/polishing stage the pellets are then stockpiled for final curing. During this time, generally between 3-7 days for coal fine pellets, and depending on ambient temperature, the pellets reach such strength as to allow more rigorous handling. No heating or force draught drying is required. An example of formed pellets is shown in Figure 3.

The spherical shape of the pellets will allow air to move freely through the stockpile to assist the curing process and prevent heat build up and the risk of spontaneous combustion. At this stage, the pellets are also tightly sealed, preventing air ingress into the pellets, and so also slowing the effect or chance of any spontaneous combustion. If spontaneous combustion is still a problem, preventative reagents can be added during agglomeration.

Stage 5 - Final Sizing (if required)

At this stage the pellets can be further graded to the desired cross section if necessary. Any damaged and undersized pellets can then be returned to the agglomerating drum for reprocessing.

Stage 6 - Transportation and Packing Tumble and growth agglomeration can result in a wide variation in the final pellet size - as in natural lump coal. This has the advantage of lowering the bulking factor of the pelletised product, resulting in lower transportation costs.

The pellet sizing could even be designed to be made dependent upon proposed use. The pellet size can be adjusted by means of changes to process conditions, equipment configuration, and even reagent dosage. The formed product could then be bagged or stacked and allowed to cure at ambient temperatures, curing time being dependent upon local humidity. Generally, the higher the moisture content of the feed, the longer the pellets will require to be cured at ambient temperatures and humidity.

Process rates can be selected, but production rates of between 10-500 tonnes per hour of coal material per drum would be a general rate. The production rate can be scaled up using multiple process units, or scaled down with smaller equipment.

Production costs are dependent upon the production rate, particle size distribution of the feed, and characteristics of the particulate materials. However, energy input per tonne of product has been measured at approximately 0.5 to 2kWh, at least a hundred times less than the energy input needed for briquetting. In particular, the process of the present invention can be modified to treat very high ash and/or very high sulphur coals, as the pellets remain stable throughout the combustion process, allowing even for low rank coals to burn efficiently.

The present process is also suitable for fuel products that need to lower ash and sulphur to be sellable. The present process allows fine grinding to release contaminants by gravity or flotation methods, generating a much higher quality fuel source. The process also provides the manner of re- forming the fine pure concentrate into a usable stable and valuable product form.

Sulphur emissions, even from very poor quality coal, can be wholly or substantially eliminated by simple adjustment of pelletising additives, eliminating any sulphur dioxide pollution leading to acid rain. The process of pelletising also simultaneously reduces fly ash by the inherent cementation, silicification and stabilisation of the residual ash instigated by the reagents used. Additionally, higher product combustion temperatures are easier to generate due to high gas transfer rates, not only between the pellets, but also between particles within the pellets, providing more rapid and/or more controllable combustion than normal fuels; the higher temperatures tend to form clinker particulates as opposed to fly ash. A further advantage of the present invention is the very complete combustion of the contained fuel in the pellets due to the high gas transfer rates and the maintenance of the integral structure of the pellets until combustion is complete. The retaining hardened shell, skin, etc, allows for significant heat increase or build-up inside the pellet, causing very high levels of combustion, resulting in the completion of any pre-designed chemical reactions in the interior content of the pellet. As the content is dry, generally of a 'fine' nature still, and is now pre-heated, rapid and so complete combustion of the content occurs. The pellets maintain their form even at white heat, and show very stable combustion characteristics.

In particular, the process of the present invention can involve no forced drying of the pellets because the action of any surfactant (s) used is maximised in ambient temperatures. Moreover, where water is used, the surfactant causes the binder-containing moisture to rapidly migrate to the surface of the pellet by capillary action, giving the ^Λegg shell' effect of a hardened surface and softer interior, due to the final heavy surface concentration of the binder. This results in a significantly enhanced skin strength, giving a very robust and low moisture content pellet (approximately 5%) , which also resists moisture absorption from the air.

One further application of the present process is lowering the feed moisture of pulverised coal fuels in power and heat stations, where the coal fines or coal tailings are pelletised and allowed to thoroughly cure and dry before being pulverised and burnt in the furnace. The general moisture content found in current coal fines dumps is usually in the range 12-35%, making them very difficult to use or blend with other feeds .

As can be recognised from the above, the process of the present invention, overcomes or solves a number of financial and operational problems.

Once the ^λegg shell' effect has been fully developed after curing, the pellet will retain its strength even during white heat combustion. This allows high temperature reactions to take place inside the pellet resulting in much higher levels of combustion of the fuel, giving effective oxidation and sequestration of any contained sulphur, and negligible unburnt carbon levels in the residue ash. The shell effect allows the pellet to retain its structure during combustion, resulting in less particulate emissions in the flue gas.

The egg shell pelletisation could also be used on sulphide concentrates and iron ores to allow the manufacture of pre-fluxed furnace feeds which can lead to ^λsulphur emission free' smelter technology. This could be used in existing operations cost effectively with high industrial tonnage output. The present invention provides significant benefits compared with present technologies, including:

• <3mm coal/lignite fines can be pelletised dry or direct from a filtration plant. • Tonnage throughput can be from 10 tones per hour (community size) up to 300 or 500 tonnes per hour per pelletising line. • High level of automation can be used during pelletising for accurate control and reagent usage. • Pellets just air dry while chemically ^curing' . • Pellets can be handled by bulk handling equipment when cured or alternatively bagged when ^λgreen' . • Pellet size can be customised from 5mm to 150mm if required depending upon coal characteristics and process parameters. • Special heavy duty reagents can be added for high strength, for rapid cure, for high temperature strength, and for enhanced water resistance. • Pyrite removal can be reduced or eliminated due to various binder combinations to eliminate SO₂ due to gas transfer to form CaSO₄ inside the pellet. • Due to excellent combustion characteristics, high ash coal fines will ignite and burn with high efficiency. • Long lasting combustion, with high percentage carbon combustion. • <20mm coal can be crushed and pelletised with fines for high value pellets. • Contaminated coal or waste products such as sawdust, rice husks, sewage, animal wastes, petroleum coke or waste oil can be included into the pellets. • Residual ash has negligible un-burnt fuel (e.g. coal) residue and is excellent for other industrial uses. • Residual ash can also be pelletised with similar binder reagents for concrete feedstock, aggregate blending and high porosity landfill. • Lignite and peat can be treated with identical technology or can be blended with other fuel sources to create hybrid pellet fuels with pre- designed characteristics such as smokeless burning.

Examples

Examples of the starting materials and pellets formed by the present invention are listed hereafter.

Fuel # 1 - Sub-bituminous coal fines • -3mm fraction • 15% moisture • 45% ash « 0.4% sulphur

• 25mm pellets +/-5mm formed 1 Fuel # 2 - Sub-bitummous coal fines

2 • -3mm fraction

3 • 15% moisture

4 • 45% ash

5 • 0.4% sulphur

6

7 • 15mm pellets +/-5mm formed

Q

O

9 Fuel # 3 - Anthracite coal fines 0 • -2mm fraction 1 • 5% moisture 2 • 15% ash 3 • 0.1% sulphur 4 5 • 25mm pellets +/-5mm formed 6 7 8 Fuel # 4 - Lignite fines 9 • -5mm fraction 0 • 20% moisture 1 • 28% ash

• 0.1% sulphur

• 20mm pellets +/-5mm formed

6 Fuel # 5 - Raw Peat

• Shredded to -40mm 8 • 30% moisture 9 • 35% ash

• 0.1% sulphur • 10mm, 25mm and 50mm pellets +/-5mm formed

Fuel # 6 - Sub-bituminous high sulphur coal fines • -3mm fraction • 15% moisture • 35% ash • 2.0% sulphur

• 25mm pellets +/-5mm formed

The present invention provides a simple but efficient process for using waste carbon-based materials, and forming a useable fuel product, which is easily transportable and efficiently combustible. Rotating drum or pan agglomerators are relatively low cost to build, and are capable of very high tonnage throughputs. Customised products can be produced and the present invention enhances the economics of ash and sulphur removal in coal upgrade plants.

Low technology applications in countries where there is little investment for efficient coal process plants can also easily utilise the present invention, therefore allowing the provision of high efficiency, environmentally friendly and cost effective process plants to be manufactured and operated. In such places, any materials not immediately useable are currently treated as waste and simply stockpiled in bigger and bigger piles, increasing the environmental hazard thereof.

Claims

1. A process for producing fuel pellets from a particulate carbon-based material and a binder, comprising of the following steps :

2. A process as claimed in claim 1 for providing pellets of a variable size distribution.

3. A process as claimed in Claim 1 or Claim 2 wherein the process is carried out at ambient or near-ambient temperature.

4. A process as claimed in any one of the preceding claims wherein the pellets have a hardened shell.

5. A process as claimed in any one of the preceding claims wherein the so-formed pellets are allowed to dry at ambient or near-ambient temperature.

6. A process as claimed in Claim 5 wherein the drying is at least partly provided by tumbling.

7. A process as claimed in any one of the preceding claims wherein the particulate material and binder mixture includes water.

8. A process as claimed in Claim 7 wherein the binder includes the water prior to admixture with the particulate material .

9. A process as claimed in any one of the preceding claims wherein the particulate material is generally of a maximum size or grade of about 3mm or lower.

10. A process as claimed in any one of the preceding claims wherein the particulate material is coal dust or coal fines.

11. A process as claimed in any one of Claims 1 to 9 wherein the particulate material is partly, substantially or wholly peat.

12. A process as claimed in Claim 11 wherein the peat is in combination with coal fines.

13. A process as claimed in any one of the preceding claims wherein the particulate material is a combination of two or more starting materials.

14. A process as claimed in any one of the preceding claims wherein the binder is partly, wholly or substantially sodium silicate or potassium silicate.

15. A process as claimed in any one of the preceding claims wherein the process includes the addition of one or more further ingredients.

16. A process as claimed in Claim 15 wherein the or each further ingredient is selected from the group comprising: lime, organic binders, silicates, cements and waterproofing additives.

17. A process as claimed in any one of the preceding claims wherein the binder includes one or more surfactants.

18. A process as claimed in any one of the preceding claims wherein the particulate material and binder are at least partly mixed with agitation.

19. A process as claimed in any one of the preceding claims wherein the binder is sprayed on to the particulate material.

20. A process as claimed in any one of the preceding claims wherein the particulate material is moving prior to and/or during mixture with the binder.

21. A process as claimed in any one of the preceding claims wherein the pellets have a spherical or ovoid shape.

22. A process as claimed in any one of the preceding claims wherein the pellets are screened after tumbling.

23. A process as claimed in any one of the preceding claims wherein the tumbling is carried out in a rotary drum.

24. A process as claimed in any one of the preceding claims wherein the agglomeration action is carried out in one or more stages, which stages are either connected or separate.

25. A process as claimed in any one of the preceding claims wherein the pellets are cured either during or separately from the agglomeration step.

26. A process as claimed in any one of the preceding Claims for reducing moisture in the particulate material.

27. A process for encapsulating a particulate material, comprising the steps of:

admixing the particulate material with a binder, and allowing the mixed material to cure.

28. A process as claimed in Claim 27 wherein the particulate material is one or more selected from the group comprising: uranium tailings dust and waste, coal dust and fly ash waste, asbestos, metal ores, gold, copper or iron, whether elemental or in compound form such as ores, and vehicle-surface materials such as road-surfacing materials.

29. A process as claimed in Claim 27 or Claim 28 wherein the process is carried out at ambient or near-ambient temperature.

30. A process as claimed in any one of Claims 27 to 29 wherein the pellets have a hardened shell.

31. A process as claimed in any one of Claims 27 to 30 wherein the binder includes water, is partly, wholly or substantially sodium silicate or potassium silicate, and includes one or more surfactants.

32. A fuel pellet product formable by agglomeration of a particulate carbon-based material and a binder.

33. A fuel pellet product comprising an agglomerated composition of a particulate carbon-based material and a binder.

34. A fuel pellet product whenever formed by a process as claimed in any one of Claim 1 to 26.

35. A product as claimed in any one of Claims 32, 33 or 34 formed at ambient or near-ambient temperature.

36. A fuel pellet as claimed in any one of claims 32 to 35 ready for combustion.

37. A fuel pellet as claimed in any one of Claims 32 to 36 having a hardened shell.

38. A fuel pellet as claims in any one or Claims 32 to 37 having a variable density towards its core.

39. A fuel pellet as claimed in any one of Claims 32 to 38 having a dry interior.

40. A fuel pellet as claimed in any one of Claims 32 to 39 having sufficient hardness once cured to allow handling, stacking and/or transportation without any significant breakage.

41. A fuel pellet as claimed in any one of Claims 32 to 40 being wholly or substantially combustible, so as to leave little or no combustible fuel in the ash.

42. A fuel pellet as claimed in any one of Claims 32 to 41 being formed from a coal dust or coal fines.

43. A fuel pellet as claimed in any one of Claims 32 to 42 having little or no sulphur emission during combustion.

44. A fuel pellet as claimed in any one of Claims 32 to 43 wherein the moisture in the pellet is less than the moisture in the starting particulate material.

45. A fuel pellet as claimed in any one of Claims 32 to 44 wherein the pellet has a moisture content of <5%.