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Title:
FUEL COMPOSITION AND A BINDER SYSTEM THEREFOR
Document Type and Number:
WIPO Patent Application WO/2013/030311
Kind Code:
A1
Abstract:
The present invention accordingly provides a fuel composition in the form of a briquette or a wood pellet or such like comprising a hardwood and/or a softwood; and an additive which comprises a binder system resulting in formation of a fuel composition having low dust fines and high calorific value. The binder system preferably comprises a naturally occurring binder. By developing a hardwood/softwood combination fuel composition having very low dust fines, the present invention has the significant advantage of providing a fuel composition with resultant improvement in calorific performance and longer burn time.

Inventors:
MCERLAIN SEAMUS (GB)
Application Number:
PCT/EP2012/066921
Publication Date:
March 07, 2013
Filing Date:
August 30, 2012
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
MCERLAIN SEAMUS (GB)
International Classes:
C10L5/14; C10L9/12; C10L5/36; C10L5/44; C10L10/00
Domestic Patent References:
WO2012126856A12012-09-27
WO2011062488A12011-05-26
WO2011041880A12011-04-14
WO2011041881A12011-04-14
WO2005076770A22005-08-25
Foreign References:
DE202007004725U12007-05-31
US20050005508A12005-01-13
Other References:
None
Attorney, Agent or Firm:
WALSH, Marie Goretti et al. (47 Merrion Square, Dublin 2, IE)
Download PDF:
Claims:
CLAIMS:

1 . A fuel composition comprising a hardwood and/or a softwood and an additive providing a hardwood and/or softwood fuel composition having low dust fines, the fuel composition providing improved calorific performance and longer burn time.

2. A fuel composition as claimed in Claim 1 wherein the additive comprises a binder system. 3. A fuel composition as claimed in any preceding claim wherein the binder system comprises a resin.

4. A fuel composition as claimed in Claim 3 wherein the resin is a naturally occurring resin, preferably a resin found in the heartwood of trees.

5. A fuel composition as claimed in Claim 1 wherein densities for the softwood included in the fuel composition are as follows:

the average density for the softwood is in the range of 350 Kg/m3 to 600 Kg/m3 and most preferably approximately 440kg/m3 ± 60 Kg/m3.

6. A fuel composition as claimed in Claim 1 wherein the average density range for the hardwood species are 600kg/m3 to 1200kg/m3 and most preferably in the range of approximately 800kg/m3 ± 150 Kg/m3. 7. A fuel composition as claimed in any preceding claim wherein the fuel composition has a moisture content of between 6 to 10% w/w.

8. A fuel composition as claimed in Claim 7 wherein the fuel composition has a moisture content of about 6% w/w.

9. A fuel composition as claimed in any preceding claim wherein the fuel composition comprises a hardwood or softwood sawdust having 0.0 to 1.0% moisture content.

10. A fuel composition as claimed in any preceding claim wherein the wood in the fuel composition is combined with the binder in the ratio of 90% hardwood or softwood to 10% binder. 1 1 . The fuel composition of the present invention is of the form of any one or more selected from the following group: pellets, briquettes and similar fuel forms.

12. The fuel composition of the present invention includes wood from hardwood species selected from one or more of the following group:

Acacia erioloba;

Dichorstachys cinera;

Colophospermum mopane;

Acacia cyclops;

Acacia nilotica;

Artocaipus integer;

Aucomea klaineana;

Senna atomaria;

Dalbergia melanoxylon;

Acacia aulacocarpa;

Dalbergia sissoo;

Ash;

Beech; and

Vine stumps.

13. A fuel composition as claimed in any preceding claim wherein wood included in the fuel composition comprises wood from any one or more of the following softwood species:

European Silver Fir (Abies alba);

Grand Fir (Albies grandis);

Noble Fir (Albies rioblis);

Monterey Cypress (Cypresses macrocarpa);

Douglas Fir (Pseudotsuga taxifolia);

European Larch (Larix decidua);

Hybrid Larch (Larix eurolepis); Japanese Larch (Larix leptolepis);

Lawson Cypress (Charaecyparis lawsaniana);

Norway Spruce (Picea abies);

Sitka Spruce (Picea abies);

Western Red Cedar (Thuja plicota);

Western Hemlock (Tsuga heterophylia);

White Spruce (Picea glauca);

Caucasian Fir (Abies nordmanniana);

Fraser Fir (Abies frasen); and

Willow.

14. A fuel composition as claimed in Claim 1 wherein the additive comprises any one or more of the following group: tallow oil, palm oil and vegetable oil. 15. A fuel composition as claimed in Claim 14 wherein the additive comprising tallow oil, palm oil and/or vegetable oil is added to the wood for lubrication and raised calorific heat value in a ratio of natural tallow oil to be added to the wood chip is between 1 litre of tallow oil to 1 kg of wood (1 :1 ) and 1 litre of tallow oil to 100 kg of wood (1 :100). 16. A fuel composition as claimed in any preceding claim wherein the additive comprises the binder system and an oil selected from the following group: tallow oil, palm oil and vegetable oil.

17. A method of forming a fuel composition in the form of a pellet, the method comprising the following steps:

(a) providing hardwood and/or softwood;

optionally baking the hardwood and/or softwood at a sufficiently high temperature, for example, approximately 55°C for a predetermined time to reduce moisture content;

(b) combining an additive with the hardwood and/or softwood and mixing the additive together with the hardwood and/or soft wood; and

pressing the mixed hardwood and/or softwood and additive into a desired shape to form the fuel composition, for example, a pellet or a briquette shape.

18. A method as claimed in Claim 17 wherein the method includes the following additional steps: the fuel composition is passed through a mill to convert the sawdust to powder form; and

optionally conveying the powder mix through a feed hopper into the mill which heats the mix up to 90°C, the resin/lignin in the sawdust melts and rises to the outer surface of the pellet as it is extruded through the die at very high friction thus bonding the pellet.

19. A method for manufacturing a fuel composition using wood fragments and oil, preferably tallow oil, vegetable oil or palm oil, most preferably tallow oil, the method comprising the following steps:

(a) Feeding softwood or willow through a wood chipping apparatus and forming wood chips of the desired size; and

(b) drying the wood chips to the desired moisture content of 20% or below. 20. A method for manufacturing a fuel composition as claimed in Claim 19 wherein at step (b) the drying is carried out by kiln dried or natural air drying.

21 . A method as claimed in Claim 19 or 20 wherein the method further comprises the following steps:

after the wood chips has been dried to the desired moisture content, the wood chips are submerged in a tank full of oil comprising tallow oil, vegetable oil or palm oil for a time period of from 1 to 8 hours and up to 24 hours until the wood chips have absorbed the oil; and

and removing the wood chips from the tank and allowing to dry naturally.

22. A method as claimed in Claim 21 wherein the tallow oil is heated to the standard safe level (tallow melting point 50° to 60°C), so that the tallow oil thins out for better absorption into the wood chip. 23. A fuel composition substantially in accordance with any of the embodiments herein described in the Examples.

24. A method for producing a fuel composition substantially in accordance with any of the examples herein described in the Examples.

Description:
FUEL COMPOSITION AND A BINDER SYSTEM THEREFOR

The present invention relates to an improved fuel composition and particularly to an improved fuel composition in the form of wood pellets and briquettes. In another aspect, the present invention also relates to a binder system for the improved fuel composition.

Wood burning pellets are freely available. However, known pine wood pellets have a relatively high moisture content, in some instances, the moisture content is known to be between 6% and 8% w/w. A moisture content of up to 10% w/w in the final fuel form is permitted in such fuels. The disadvantage of the known wood pellets having relatively high moisture content is that this level of moisture content reduces calorific value and burn time thereby affecting efficiency. Furthermore, known pellets also have relatively high dust fines. Relatively high dust fines tend to cause poor combustion and also cause clogging in the auger which is in the delivery system from the silo to the boiler. The dust fines tend to clump together and this gives rise to clinkering which reduces boiler efficiency due to incomplete combustion.

The present invention seeks to alleviate these disadvantages of known wood pellets, briquettes and other fuel forms.

The present invention provides a fuel composition comprising a hardwood and/or a softwood wood and an additive thereby providing a hardwood or softwood fuel composition having low dust fines. The fuel composition of the present invention provides an improvement in calorific performance and longer burn time over known fuel compositions. The hardwood and/or softwood wood is in the form of small fragments comprising wood chips or sawdust or such like. The additive preferably comprises a binder system which functions to bind the wood fragments together so as to achieve low dust fines in the fuel composition. Preferably, the additive comprises a binder system and conveniently the binder system comprises a resin.

Advantageously, the resin comprises a naturally occurring resin, preferably a resin found in the heartwood of trees. Alternatively, the resin may comprise a biodegradable synthetic resin. The resin included in the fuel composition of the present invention binds the wood fragments effectively so there are very low dust fines in the formed fuel composition. Furthermore, the resin improves the calorific value of the fuel composition over and above the calorific value provided by the wood fragments themselves. Meaning of the terms "hardwood" and "softwood"

Hardwood is wood from angiosperm trees (more strictly speaking, non-monocot angiosperm trees). These are usually broad-leaved trees grown in temperate and boreal latitudes; they are mostly deciduous, but in tropics and subtropics mostly evergreen.

Hardwood contrasts with softwood (which comes from gymnosperm trees). Hardwoods are not necessarily actually harder than softwoods. In both groups of hardwood and softwood species, there is an enormous variation in actual wood hardness, with the range in density in hardwoods completely including that of softwoods; some hardwoods (e.g. balsa) are softer than most softwoods, while yew is an example of a hard softwood.

Hardwood should not be confused with the term 'heartwood' which is used in this specification in the context of the binder system. Advantageously, densities for the softwood included in the fuel composition are as follows: the average density for the softwood is in the range of 350 Kg/m 3 to 600 Kg/m 3 and most preferably approximately 440kg/m 3 ± 60 Kg/m 3 .

Advantageously, the average density range for the hardwood species are 600kg/m 3 to 1200kg/m 3 and most preferably in the range of approximately 800kg/m 3 ± 150 Kg/m 3 .

Advantageously, the fuel composition has a moisture content of between 6 to 10% w/w; and preferably the fuel composition has a moisture content of about 6% w/w. Advantageously, the fuel composition may comprise a hardwood or softwood sawdust having 0.0 to 1 .0% moisture content.

Advantageously, the wood in the fuel composition may be combined with the binder in the ratio of 90% hardwood or softwood to 10% binder. Advantageously, the fuel composition of the present invention is of the form of any one or more selected from the following group: pellets, briquettes and similar fuel forms.

Advantageously, the fuel composition of the present invention may include wood, for example wood fragments comprising wood chips or sawdust, from hardwood species selected from one or more of the following group:

Acacia erioloba;

Dichorstachys cinera;

Colophospermum mopane;

Acacia cyclops;

Acacia nilotica;

Artocaipus integer;

Aucomea klaineana;

Senna atomaria;

Dalbergia melanoxylon;

Acacia aulacocarpa;

Dalbergia sissoo;

Ash;

Beech; and

Vine stumps.

Advantageously, the fuel composition may comprise wood from a softwood species, for example wood fragments comprising wood chips or sawdust from any one or more of the following softwood species:

European Silver Fir (Abies alba);

Grand Fir (Albies grandis);

Noble Fir (Albies rioblis);

Monterey Cypress (Cypresses macrocarpa);

Douglas Fir (Pseudotsuga taxifolia);

European Larch (Larix decidua);

Hybrid Larch (Larix eurolepis);

Japanese Larch (Larix leptolepis);

Lawson Cypress (Charaecyparis lawsaniana); Norway Spruce (Picea abies);

Sitka Spruce (Picea abies);

Western Red Cedar (Thuja plicota);

Western Hemlock (Tsuga heterophylia);

White Spruce (Picea glauca);

Caucasian Fir (Abies nordmanniana);

Fraser Fir (Abies frasen); and

Willow. Advantageously, the additive comprises any one or more of the following group: tallow oil, palm oil and vegetable oil. In a preferred embodiment, the additive comprises the binder system and an oil selected from the above group of oils, most preferably tallow oil.

Advantageously, the additive comprising tallow oil, palm oil and/or vegetable oil is added to the wood for lubrication and preferably also for further raised calorific heat value.

Advantageously, the ratio of natural tallow oil to be added to the wood (e.g. in the form of wood chips) is between 1 litre of tallow oil to 1 kg of wood chip (i.e. a ratio of 1 :1 ) and 1 litre of tallow oil to 100 kg of wood chip (i.e. a ratio of 1 :100).

Advantageously, a method of forming a fuel composition in the form of a pellet, the method comprising the following steps:

(a) providing hardwood and/or softwood;

optionally baking the hardwood and/or softwood at a sufficiently high temperature, for example, approximately 55 ° C for a predetermined time to reduce moisture content;

(b) combining an additive with the hardwood and/or softwood and mixing the additive together with the hardwood and/or soft wood; and

pressing the mixed hardwood and/or softwood and additive into a desired shape to form the fuel composition, for example, a pellet or a briquette shape.

Optionally, the method may also comprise the following steps:

the fuel composition is passed through a mill to convert the sawdust to powder form; and

optionally conveying the powder mix through a feed hopper into the mill which heats the mix up to 90 ° C, the resin/lignin in the sawdust melts and rises to the outer surface of the pellet as it is extruded through the die at very high friction thus bonding the pellet.

Advantageously, the wood pellets are then conveyed to a cooling bin where they solidify and harden. The wood pellets are encapsuled by the binder resulting in formation of a shiny outer surface layer or coating on the wood pellets which makes the pellets of the present invention more durable and moisture resistant than known pellets. The outer surface layer has the added advantage of minimising the quantity of dust fines released into the atmosphere.

Advantageously, a method for manufacturing a fuel composition using wood fragments and oil, preferably tallow oil, vegetable oil or palm oil, most preferably tallow oil, the method comprising the following steps:

(a) Feeding softwood or willow through a wood chipping apparatus and forming wood chips of the desired size; and

(b) drying the wood chips to the desired moisture content of 20% or below.

Advantageously, a method for manufacturing a fuel composition using wood chips wherein at step (b) the drying is carried out by kiln dried or natural air drying.

Advantageously, the method further comprises the following steps:

after the wood chips has been dried to the desired moisture content, the wood chips are submerged in a tank full of oil comprising tallow oil, vegetable oil or palm oil for a time period of from 1 to 8 hours and up to 24 hours until the wood chips have absorbed the oil; and

and removing the wood chips from the tank and allowing to dry naturally.

Advantageously, in a preferred embodiment of the method, the tallow oil may be heated to the standard safe level (tallow oil melting point 50 ° to 60 ° C). At this point, the tallow oil thins out for better absorption into the wood chip. The tallow oil should not be heated to the flash point/combustion point which is in the range of from 288 ° to 316 ° C. Due to the zero percentage sulphur in tallow oil, tallow oil is ideal as an additive to biomass fuel. Therefore the problem of corrosive acids in the wood boiler do not exist. The tallow oil is non-hazardous to human exposure in its natural form. The tallow is also the natural lubricant in the production of the range of wood pellets in accordance with the present invention. The main objectives of the tallow oil is to add higher calorific heat value and act as a lubricant in the production of the range of biomass wood fuels of the present invention. The natural tallow oil is drip fed to the sawdust species during pellet production by means of an online oil reservoir attached to the pellet mill which will help to lubricate and extrude the pellet through the pellet die. The natural tallow oil is drip fed to the sawdust species by means of a peristaltic pump which can increase or decrease the rate of drip. The pump is connected to the online reservoir attached to the pellet mill.

Thus, the present invention accordingly provides a biomass fuel composition. The biomass fuel composition of the present invention may be in the form of a briquette or a wood pellet or such like. The fuel composition can be made from wood fragments in the form of wood chips or saw dust for instance, the wood fragments comprising a hardwood species or a coniferous softwood species having moisture content of below 15% w/w; and a binder system comprising a binder for binding the wood fragments, for example, wood chips or saw dust, together. The binder functions to bind the softwood or hardwood in the fuel composition for the purpose of combustion or providing heat. In accordance with the present invention, the binder is preferably a resin and most preferably the resin comprises a naturally occurring resin found in the heart (i.e. the core) of certain trees grown in tropical regions. However, the binder may alternatively comprise a biodegradable synthetic binder. When the pellet forms inside the pellet mill, the binder resin mixes with the wood chips. The resin moves from the centre casing to the outer layer of the pellet. The resin also repels water from the outside of the pellet.

The resin is very flammable so when the resin rises to the surface of the briquettes or the pellet, it will help ignite the pellet. By developing the fuel composition of the present invention having moisture repelling properties, the present invention has the significant advantage of providing a fuel composition which has resultant improvement in calorific performance and longer burn time. The most preferred optimal densities for the hardwood and the softwood included in the fuel composition of the present invention are as follows:

The average density for the softwood is in the range of 350 Kg/m 3 to 600 Kg/m 3 and most preferably approximately 440kg/m 3 ± 60 Kg/m 3 . The average density range for the different hardwood species are 600kg/m 3 to 1200kg/m 3 and most preferably approximately 800kg/m 3 ± 150 Kg/m 3 .

In accordance with the present invention, it is preferable to provide a fuel composition in one embodiment in the form of a wood pellet having a moisture content of between 6.0% and 10% w/w and preferably about 6.0% w/w in a preferred embodiment of the wood pellet of the invention. This is achieved by combining wood fragments or sawdust having 0.0 to 1 .0% moisture content with a binder system thereby providing an improved, longer lasting fuel composition (in the form of wood pellet or a briquette, for example) with superior calorific values in accordance with the present invention.

If the wood pellets of the present invention are made through torrefaction (i.e. no oxygen present, giving rise to charring) then the moisture content can be below 6% w/w in the final wood pellet. However, most mills do not use the torrefaction process and instead, most mills work with traditional processes for producing wood pellets.

In accordance with one embodiment of the present invention, to form a hardwood briquette or a hardwood pellet, the hardwood is baked at a sufficiently high temperature, for example, approximately 55 ° C for a predetermined time to reduce moisture content to about 1 % w/w moisture. A binder system is combined with the hardwood, and these are then mixed together and pressed into the desired shape or form, for example, a pellet or a briquette shape. The binder system preferably comprises a resin, most preferably, a naturally occurring resin found in the heart (i.e. the core) of trees. No other additives are necessary for the mix to form the resultant product. However, an additive such as tallow oil can be added in a preferred embodiment of the present invention. In the preferred embodiment of the invention, the fuel composition ratio of hardwood or softwood to the binder system is preferably 90% hardwood or softwood to 10% binder system.

It has not been possible to date to produce a low moisture wood pellet using conventional wood pelletising mills. The draft standard CEN/TS 14961 gives a maximum moisture content of 10% w/w. The fuel composition of the present invention has a moisture content of between 6.0 and 10.0% w/w and preferably approximately 6.0% w/w. Indeed, if the torrefaction process is used to produce wood pellets or briquettes, then the moisture content would be even lower than 6.0% w/w moisture content. The fuel composition of the present invention is of the form of any one or more selected from the following group: pellets, briquettes and similar fuel forms.

The fuel composition of the present invention in an embodiment in which the final composition is in the form of briquettes, includes wood (most preferably wood as sawdust) from hardwood species selected from one or more of the following group:

Acacia erioloba;

Dichorstachys cinera;

Colophospermum mopane;

Acacia cyclops;

Acacia nilotica;

Artocaipus integer;

Aucomea klaineana;

Senna atomaria;

Dalbergia melanoxylon;

Acacia aulacocarpa;

Dalbergia sissoo;

Ash;

Beech; and

Vine stumps.

It is to be understood that the term "vine" means any climbing or trailing plant. Aucomea klaineana and vine stumps can also be used to produce wood pellets in accordance with the present invention.

Dalbergia melanoxylon has a calorific value of 205 MJ/KJ and would provide an excellent substitute for coal in industrial coal fire boilers.

The following coniferous softwood species can be used to produce wood pellets or wood chip fuel compositions in the present invention include all softwood tree species; particularly all softwood coniferous species but especially the following preferred coniferous softwood species: European Silver Fir (Abies alba);

Grand Fir (Albies grandis);

Noble Fir (Albies rioblis);

Monterey Cypress (Cypresses macrocarpa);

Douglas Fir (Pseudotsuga taxifolia);

European Larch (Larix decidua);

Hybrid Larch (Larix eurolepis);

Japanese Larch (Larix leptolepis);

Lawson Cypress (Charaecyparis lawsaniana);

Norway Spruce (Picea abies);

Sitka Spruce (Picea abies);

Western Red Cedar (Thuja plicota);

Western Hemlock (Tsuga heterophylia);

White Spruce (Picea glauca);

Caucasian Fir (Abies nordmanniana);

Fraser Fir (Abies frasen); and

Willow.

A significant advantage of the fuel form of the present invention is that it gives rise to superior calorific values. Preferably, the calorific values of the fuel composition of the invention are in the range of 19 MJ/Kg to 205 MJ/Kg. Test results have shown that the following hardwoods (as set out in the table below) when formed into wood pellets in accordance with the method of the present invention produce a wood pellet having the calorific values set out in the table below.

The extremely high calorific value provided by the fuel compositions of the invention comprising the species Dalbergia melanoxylon is significant for use in industrial facilities where high temperatures are required. An advantage of the present invention is that the heat provided by the fuel composition is steadier than that of prior art fuel compositions due to the reduced dust fines in the fuel composition because the binder system of the present invention provides a tighter bond between the wood and the dust fines because there is a high resin content - the lignin (i.e. resin) concentrates into the centre of the stump because of the heat in tropical countries such as South America causes the resin to concentrate in the heart of the tree. . It is to be understood that the moisture content in a fuel composition affects the calorific value of the pellet or briquette. Consequently, by minimising the dust fines in each of the wood pellets and/or briquettes, a constant combustion level can be maintained by the fuel composition of the present invention. This is very desirable for all users of the fuel composition of the present invention and in particular industrial users where constant heat levels are often required for operation of various processes. A significant problem with many current boiler systems is clogging of the auger due to dust fines. There are usually two points of blockage in such systems. Transferring wood pellets from a delivery container to the storage hopper and then from the storage hopper to the boiler for burning. The wood pellets of the present invention have greater durability with less dust fines and longer shelf life, as the natural binders in the binder system of the present invention act as a moisture repellant. Consequently, the wood pellets and briquettes in accordance with the present invention help the auger system to transport the wood pellets to the pellet boiler more freely and efficiently.

Accordingly, the present invention also provides a binder system for use in the fuel composition of the present invention. The preferred binder system of the present invention is a naturally occurring binder which is provided by softwood species growing in tropical regions, especially in Central America.

Under EN Plus wood pellet standards, wood glues that have been chemically processed and contain chemicals are not allowed in the production of biomass wood pellet fuel, as they are harmful to humans and the environment. Synthetic man-made resin glues are also not allowed in the production of wood pellet fuels. However, synthetic biodegradable resins which would comply with the regulation requirements may be permissible. Synthetic resin which is produced through a chemical process known as polymerization will contain traces of chemicals in the synthetic resin known as ethylene. Ethylene is a compound refined from petroleum which is a fossil fuel and therefore is not allowed in the production of wood pellets.

The naturally occurring fat wood binder used in the preferred embodiment of the present invention is allowed under EN Plus wood pellet standards, as it does not contain any harmful chemicals or has not been chemically treated. Thus, the preferred binder system used in the fuel composition of the present invention is a fat wood binder found in the heart of trees grown in tropical regions. This provides an improvement in the composition of existing wood pellets due to lower dust fines and better combustion. The fat wood is in the form of a natural fine powder form and not a chemically treated wood glue or synthetic resin which are in liquid form. In its natural form, this preferred binder includes some of the softwood of the trees from which the binder is harvested (approximately 20% softwood:80% resin in the naturally occurring binder).

The physical from of the preferred natural fatwood/heartwood binder used in the present invention is a natural dry powder form. There is no chemical extraction process to extract the resin from the heartwood. The binder is mixed directly with the natural hardwood or softwood sawdusts which are ground into powder form before pelletizing.

The list of softwood species that can provide the binder system of the present invention are selected from one or more of the following non exhaustive list of wood species:

Fatwood (pino de octo);

Pinus ayacahuite;

Pinus caribaea;

Pinus oocarpa; and

Pinus Palustris range.

In a further embodiment of the invention, one or more further natural binding agents are added to the binder system of the invention selected from the group of Tallow oil, vegetable oil, palm oil, starch, cornstarch and cornflower. Tallow oil is the preferred additive to the binder system. The further natural binding agent included in the binder system of the present invention is added in appropriate quantities to provide enhanced binding and calorific properties to the fuel composition of the invention. Slack wax, which is a petroleum based binder may also be used but preferably is not used as it is derived from a fossil fuel.

In a further example of the invention, the wood species Pinus ayacahuite; Pinus caribaea; and Pinus oocarpa are formed into wood pellets in a process using trace quantities of Tallow oil or vegetable oil.

Vegetable oil can be used as a lubricant but the vegetable oil will not provide any calorific value. Tallow oil will provide both lubricant properties as well as added calorific value; therefore tallow oil is the preferred oil for use in the fuel composition and method for manufacturing a fuel composition in accordance with the present invention.

In a further example of the invention, the softwood species are formed into briquettes in a process using the Tallow oil, palm oil or vegetable oil as an additional binding agent. The resin of the binder system is preferably in the range of 1 to 40% w/w, more preferably in the range of 5 to 35% w/w and most preferably in the range of 5 to 20% of the fuel composition.

The most preferred optimal densities for the hardwood and the softwood included in the fuel composition of the present invention are as follows:

The average density for the softwood is in the range of 350 Kg/m 3 to 600 Kg/m 3 and most preferably approximately 440kg/m 3 ± 60 Kg/m 3 . The average density range for the different hardwood species are 600kg/m 3 to 1200kg/m 3 and most preferably approximately 800kg/m 3 ± 150 Kg/m 3 .

The density and low dust content of the fuel composition of the present invention and the use of the binder system of the invention give rise to the superior calorific properties of the finished fuel form (e.g. pellet or briquette). If tallow oil or palm oil is added, the addition of the oil may give rise to higher calorific value but such addition of tallow oil or palm oil is merely optional in accordance with the present invention.

The present invention also provides briquettes with the same ratios of sawdust and binder mixes as the wood pellets provided by the present invention.

In further embodiments of the invention, the wood pellets and briquettes are formed with the following ratios;

95% Hardwood or Softwood Sawdust and 5% binder system; or

80% Hardwood or Softwood Sawdust and 20% binder system; or

65% Hardwood or Softwood Sawdust and 35% binder system. In a further embodiment of the invention, the binder of the binder system comprises approximately 2% to 5% and up to 35% of the total fuel composition.

Further additives and species which may be included: 1 . Tallow oil for wood pellets, wood chip, willow and briquettes grade 1 , 2 and 3 oils.

2. Softwood wood chip/willow normative specification length 5 to 10mm

Particle sizes P16mm/P31 .5/P45/P63/P100

Moisture content (M20/M25/M30/M40/M55/M65)

Ash content (A0.07) A1 .5/A3.0/A6.0/A10.0)

The target moisture content for Tallow oil saturation absorption = 20%

The wood chip/hog fuel will be dried to 20% than the wood chip/hog fuel will be dipped in Tallow oil grade 1 , 2 or 3 and left for saturation from 1 to 8 and up to 24 hours. The wood fuels will then be lifted out and left to dry before use.

3. Hog fuel particle size of the chips making up the hog fuel:

P16mm/P45/P63/P100/P125/P200/P300mm

Briquettes are manufactured by means of a briquetting machine using the same process as for manufacturing wood pellets as described below. The preferred briquette sizes in block form are as follows:

Dimensions, 260mm x 100mm, 240mm x 70mm, 150mm x 70mm, 150mm x 60mm. The preferred briquette sizes in cylinder form are as follows:

Diameters: 40mm, 50mm, 60mm, 70mm, 80mm.

The length of briquettes depends on the setting to which the briquetting machine is set to and this can vary as desired.

Density range of woods/sawdust to be used

The density range of the wood species to be used in making the pellets is from 350Kg/m 3 to 1200Kg/m 3 . One of the wood species to be used namely, kameeldoring [scientific name: Acacia erioloba], is only harvested when a branch falls from the tree as it is a protected species. The wood bakes in temperatures of up to 55 ° C in its natural habitat. Optionally the moisture content of the wood is removed using other techniques known to a person skilled in the art. This wood has a moisture content of from zero to 1 % which gives the wood/sawdust a very high calorific heat value. During transportation of the wood species prior to formation of the fuel composition the wood species is stored in sealed containers to ensure that the moisture content remains between zero to 1 %. Prior to forming the fuel composition the moisture content of the wood species is tested by means of a moisture metre and further dried if necessary.

Other wood species which can be used provide a calorific range from 19 MJ/Kg to 205 MJ/Kg.

In a further embodiment of the invention, a fuel composition is formed in which

The optimal specific ratios are as follows:

5 to 35% heartwood/fatwood binder dried to below 6% moisture and

80 to 95% hardwood/sawdust mix having up to 1 % moisture content.

It is to be understood that the lower the moisture in the fuel composition, the higher the calorific value of the pellet or briquette. The preferred binder in the binder system of the present invention is a resinous binder system comprising a heartwood binder. Composition of the binder system (heartwood binder)

The composition of the heartwood binder is 80% resin and 20% pinewood. The natural resin in this heartwood binder serves as a moisture repellent. Since 20% of the heartwood binder comprises pinewood, the heartwood binder can also be referred to as a "resinous softwood binder system".

The hardwood sawdust cannot be pelletised through a pellet mill on its own as the mill cannot produce quality pellets with zero to 1 % moisture content. Quality pellets will only form when the hardwood sawdust is combined with the softwood binder system. The natural heartwood/fatwood binder system is processed after the pine trees have been harvested leaving the stump of the tree to rot after which the resin gathers in the centre of the tree stump and solidifies.

It is only after the resin has solidified that the resinous softwood binder system is ready to be harvested by peeling away the outer layer of the stump thereby revealing the heartwood of the softwood binder system.

The briquettes and wood pellets of the present invention will now be described more particularly with reference to the examples in which are described, by way of example only, a number of embodiments of the present invention.

Example 1 : Forming Pellets

The pelletising process for forming the fuel composition of the present invention in the form of wood pellets:

The sawdust of softwood or hardwood trees are passed through a hammer mill to bring the sawdust to powder form. The powder mix is then conveyed through a feed hopper into the mill which heats the mix up to 90 ° C. The resin/lignin in the sawdust melts and rises to the outer surface of the pellet as it is extruded through the die at very high friction thus bonding the pellet. Preferably, a further natural binding agent is added, if necessary, to ensure quality pellets are formed. The natural binding agent is preferably the heartwood binder described hereinabove. The pellets are then conveyed to a cooling bin where they solidify and harden. The pellet is encapsuled by the binder with a shiny outer coat which makes the pellets of the present invention more durable and moisture resistant. The shiny surface has the added advantage of minimising the quantity of dust fines released into the atmosphere.

Example 1a: Softwood Pellet Composition

Preferred Composition:

80KG of sawdust

20KG of binder system providing a combined 100KG of sawdust and binder system; and 1 L of tallow oil per 100KG of sawdust

Example 2: Forming Briquettes

Briquettes: Briquettes are manufactured by means of briquetting machine using the same process as for the formation of wood pellets.

Composition of Briquettes

95% Sawdust - 5% binders.

80% Sawdust - 20% binders.

2% to 5% and up to 20% optimal specific ratios.

Forms

Briquette sizes in block form:

Dimensions, 260mm x 100mm, 240mm x 70mm, 150mm x 70mm, 150mm x 60mm.

Cylinder form:

Diameters: 40mm, 50mm, 60mm, 70mm, 80mm. The length of the briquettes depends on what setting the briquetting machine is set to. Example 3: Wood Pellets

It is also possible to produce wood pellets using the known torrefaction process which further reduces the moisture content in the final fuel composition to between approximately 2% and 3%. Wood pellets

The tallow oil ratio to be added to the range of pellets for lubrication and raised calorific heat value is preferably

1 litre of tallow oil to 100kg sawdust (i.e. ratio of 1 :100)

The natural tallow oil is drip fed to the sawdust species during pellet production by means of an online oil reservoir attached to the pellet mill which will help to lubricate and extrude the pellet through the pellet die. The natural tallow oil will be drip fed to the sawdust species by means of a peristaltic pump which can increase or decrease the rate of the drip feed to the sawdust. The pump is connected to the online reservoir attached to the pellet mill.

The following test results are provided to show the calorific value of the pine wood pellets, biomass wood pellets and other test parameters and characteristics of the wood pellets in accordance with the present invention.

Early test results are listed for each of two samples of each type of pellet tested:

Test Result (1 )

SAMPLE ID Pine Wood Pellets Pine Wood Pellets

Sample 1 Sample 2

Bulk Density (kg/m 3 ) 645 638

Moisture (%) 6.74 6.74

Ash (%) 0.30 0.29

Calorific Value (MJ/kg) 19 18

Axial crush load (N) 45.9 (standard deviation

33.9)

Radial crush load (N) 823.8 (standard deviation

229.2)

Dust fines (% w/w) <1000 μηι 0.78

<500 m 0.38

Metals (full scan) mg/kg mg/kg Al 7.45 6.35

As <2 <2

B 2.63 2.02

Ba 12.23 12.94

Ca 501 496

Cd <1 <1

Co <0.15 <0.15

Cr <0.6 <0.6

Cu 8.74 8.88

Fe 30.46 35.33

Hg <1 <1

K 222 237

Mg 150 149

Mn 49.62 50.53

Na 138 138

Ni <0.15 <0.15

Pb <2 <2

S 150 138

Sb <1.5 <1.5

Se <3 <3

Si 1 .47 1 .39

Sn <2 <2

Sr 7.94 7.93

Ti 0.44 0.18

V <0.5 <0.5

Zn 1 1.29 10.60

Test Result (2)

SAMPLE ID New Biomass Wood New Biomass Wood

Pellets Pellets

Sample 1 Sample 2

Bulk Density (kg/m 3 ) 664 677

Moisture (%) 8.18 8.21

Ash (%) 2.51 2.51 Calorific Value (MJ/kg) 19 19

Axial crush load (N) 132.3 (standard deviation

34.5)

Radial crush load (N) 861 .2 (standard deviation

403.3)

Fines (% w/w) <1000 μηΊ 0.31

<500 μηι 0.13

Metals (full scan) mg/kg mg/kg

Al 170 121

As <2 <2

B 5.67 4.95

Ba 17.00 15.79

Ca 3910 3553

Cd <1 <1

Co <0.15 <0.15

Cr <0.6 <0.6

Cu 17.80 7.48

Fe 359 239

Hg <1 <1

K 435 384

Mg 643 571

Mn 12.32 10.75

Na 320 230

Ni <0.15 <0.15

Pb <2 <2

S 589 544

Sb <1.5 <1.5

Se <3 <3

Si 26.13 25.85

Sn <2 <2

Sr 91.97 84.95

Ti 6.72 4.29 V <0.5 <0.5

Zn 8.63 6.91

Burn Tests

Test Result (3)

Test Result (4)

The wood pellets burned easier than the biomass pellets but this may be due to the moisture content in the biomass. This also affected the burn ability of the biomass pellets which extinguished themselves when removed from the heat source.

Further examples: Process for fuel composition manufactured using woodchip fuel and tallow oil or palm oil. The clean, bark-free softwood or willow is put through a wood chipping apparatus and the softwood or willow is formed into chips of the required size. The wood chip is then kiln dried or naturally air dried to the correct moisture content of 20% or below. The following methods are given by way of example to form wood chip fuel ("hog fuel").

Wood chip

The ratio of natural tallow oil to be added to the range of wood chip are:

1 litre of tallow oil to 1 kg of wood chip (i.e. ratio of 1 :1 )

1 litre of tallow oil to 100 kg of wood chip (i.e. ratio of 1 :100)

Method 1 .

When the wood chip has been dried, it is submerged in a tank full of tallow oil for a time period of from 1 to 8 hours and up to 24 hours until the wood chip has absorbed the tallow oil. The wood chip is then removed from the tank and left to dry naturally.

Method 2.

The tallow oil is heated to the standard safe level (tallow melting point 50 ° - 60 ° C). At this point, the tallow oil thins out for better absorption into the wood chip. The tallow oil should not be heated to the flash point/combustion point which is in the range of from 288 ° to 316 ° C. Due to the zero percentage sulphur in tallow oil, tallow oil is ideal as an additive to biomass fuel. Therefore the problem of corrosive acids in the wood boiler do not exist. The tallow oil is non-hazardous to human exposure in its natural form. The tallow is also the natural lubricant in the production of the range of wood pellets in accordance with the present invention. The main objectives of the tallow oil is to add higher calorific heat value and act as a lubricant in the production of the range of biomass wood fuels of the present invention.

It will of course be understood that the invention is not limited to the specific details described herein which are given by way of example only and that various modifications and alterations are possible without departing from the scope of the invention as defined in the appended claims.