CLEAN BURNING WOOD FIBER FUEL PELLETS AND ITS METHOD OF MANUFACTURE

Abstract

Clean burning wood fuel pellets. The clean burning wood fuel pellet includes a mixture containing wood chips and calcium carbonate.

Description

BACKGROUND OF THE INVENTION

The present invention generally relates to wood fiber fuel pellets. More particularly, the present invention relates to clean burning wood fiber fuel pellets and its method of manufacture.

Due to diminishing quantities of coal, petroleum, and natural gas products, attention is being directed to found renewable fuel sources of energy. With the growing interest in renewable energy, the use of wood fuel pellets has increased considerably. Unfortunately, the smoke produced by the burning of wood fuel pellets contains numerous chemicals that are harmful to the environment.

As can be seen, there is a need for a wood pellet fuel product that may be burned without producing harmful smoke to the environment.

SUMMARY OF THE INVENTION

In one aspect of the present invention, a clean burning wood fuel pellet includes a mixture containing wood chips and calcium carbonate.

In another aspect of the present invention, a method for producing clean burning wood fuel pellets, the method including the steps of: mixing calcium carbonate and wood chips to form a mixture and forming pellets with the mixture.

These and other features, aspects and advantages of the present invention will become better understood with reference to the following drawings, description and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a flow diagram for producing clean burning wood fuel pellets according to an exemplary embodiment of the present invention; and

FIG. 2 illustrates a block diagram of a system for producing clean burning wood fuel pellets 10 according to the exemplary embodiment of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

The following detailed description is of the best currently contemplated modes of carrying out exemplary embodiments of the invention. The description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the invention, since the scope of the invention is best defined by the appended claims.

Various inventive features are described below that can each be used independently of one another or in combination with other features.

Broadly, embodiments of the present invention generally provide wood fuel pellets containing calcium carbonate. In addition, the present invention provides a method of producing the wood fuel pellets.

FIG. 1 illustrates a flow diagram for producing clean burning wood fuel pellets 10 according to an exemplary embodiment of the present invention.

These clean burning wood fuel pellets 10 may be manufactured by using any conventional methods of producing wood fuel pellets as long as CaCo₃ may be added during the manufacturing process. To better understand the present invention, the present invention may be explained by using one of the several conventional methods of producing wood pellets.

The tree (not shown) may be cut into logs 12 of desired size. The logs 12 may be transported by a conveyor belt 14 to a debarker 18. The debarker 18 may remove the bark (not shown) from the log 12. The debarker 18 may be a ring debarker, a drum debarker, or a Rosserhead debarker. Next, the log 12 may be transported by a conveyor belt 14 to a log chipper 20. The log 12 may be fragmented into chips inside the log chipper 20. The size of the chips may depend on the specification of the hammer mill for continuous material flow. The chips (not shown) may be fed into a chip bin 22, which feeds a conveyor belt 14 powered by a motor 40 controlled by a variable speed drive 42. The conveyor belt 14 transports the chips (not shown) to a screen fee bin 34 prior to entering a shaker screen 32. Inside the shaker screen 34, the chips may be separate depending on their size. In some embodiments, the predetermined size may be ¼ of an inch. Chips (not shown) having a size greater than the predetermined size, may be fed to a hopper 36 connected to a screw conveyor 16. The screw conveyor 16 may be powered by a motor 40 controlled by a variable speed drive 42. The screw conveyor 16 may transport the chips (not shown) having a size greater than the predetermined size to a hammer mill 30 to further reduces the size of the chips (not shown). The output of the hammer mill 36 may be fed into a conveyor 14 operatively connected to a bin 28 containing the chips (not shown) having the predetermined size. Chips (not shown) having a size of less than the predetermined size, may be fed to a hopper 38 connected to a screw conveyor 16. The screw conveyor 16 may be powered by a motor 40 controlled by a variable speed drive 42. The screw conveyor 16 may transport the chips (not shown) having a size of less than the predetermined size to the bin 28 containing the chips (not shown) having the predetermined size.

The bark (not shown) may be fed to a bark bin 24 which may be connected to a screw conveyor 16 powered by a motor 40 controlled by a variable speed drive 42. The bark (not shown) and the chips (not shown) present on the bin 28 may be fed into a tumble dryer 26. The tumble dryer 26 may dry the chips and bark to a moisture content between about 11 and 19%. The tumble dryer 26 may be operatively connected to a conveyor belt 14 powered by a motor 40 controlled by a variable speed drive 42. The conveyor belt 14 may feed the dried chips and bark (not shown) to a finished chips hopper 44 which may be connected to a screw conveyor 16 powered by a motor 40 controlled by a variable speed drive 42. The screw conveyor 16 may transport the dried chips (not shown) into a mixing conveyor belt 63. A predetermined amount of CaCO₃ may be fed into the mixing conveyor belt 63 by a dispenser 46. The mixing conveyor 63 may feed the mixture into a mixing bin 48. The mixing bin 48 may be operatively connected to a screw conveyor 16 powered by a motor 40 controlled by a variable speed drive 42. The mixture (not shown) may be fed into a pellet mill 52. No binding agents may be added to the pellet mill 52. The mixture (not shown) may be then pelletized inside the pellet mill 52 forming the clean burning wood fuel pellets 10. The clean burning wood fuel pellets 10 may have a length/diameter ratio of 2:1 to optimize the combustion and emission process. The clean burning wood fuel pellets 10 may be transported by a cooling conveyer 50 into a clean burning wood fuel pellets bin 54. Then, the clean burning wood fuel pellets 10 may be transported by a screw conveyor 16 to a storage bin 55. The user (not shown) may feed the clean burning wood fuel pellets 10 to a boiler or stove 56. The boiler or stove 56 may emit heat 60 to the surrounding areas. Ash 58 coming out of the stove or boiler 56 may have a low pH and may be used as filler for fertilizers and concrete. Gas emission 62 produced by the stove or boiler 56 may contain water and CO₂.

The amount of CaCO₃ added to the dried chips may represent between about 0.2 to 2.0% weight of the dried chips before combustion. After a long period of trial, it has been that the addition of CaCO₃ at a rate of about 0.2% to 2% to the dried chips before combustion may greatly reduce or eliminate many of the pollutants by chemically reacting with their molecular structure. The CaCO3 may react with chemicals having a pH of less than 7 (acids), changing the chemicals into water and carbon dioxide The CaCO₃ may have a particle size between 0.2 mesh and 35 microns. These ranges of particle size may allow the CaCO₃ to better mix with the dried chips. In addition, these range of particle size may help to speed the chemical reaction between the CaCO₃ and the acids.

Both hardwoods and softwoods may primarily contain three components: cellulose at about 40% to 50% by weight, hemicelluloses at about 20% to 30% by weight and lignin at about 20% to 30% by weight. Studies performed by the present inventor have shown that hardwoods and softwoods produce different levels of pollutants, ash and heat. This requires the addition of different levels of CaCO₃ during the manufacturing process to achieve the desired reduction of pollutants in the emissions and the ash.

For example, burning 1 kg of wood may produce approximately 1.8 to 2.4 g of acidic acid. The chemical make-up of the acidic acid is 2CH₃COOH. When acidic acid reacts with calcium carbonate, the reaction creates water (H₂), carbon dioxide (CO₂) and calcium acetate [(CH₃COO)₂]. This basically eliminates the largest occurring acid in the smoke and ash.

FIG. 2 illustrates a block diagram of a system 100 for producing clean burning wood fuel pellets 10 according to the exemplary embodiment of FIG. 1.

It should be understood, of course, that the foregoing relates to exemplary embodiments of the invention and that modifications may be made without departing from the spirit and scope of the invention as set forth in the following claims.

Claims

1. A clean burning wood fuel pellet comprising:

a mixture containing wood chips and calcium carbonate.

2. The clean burning wood fuel pellet according to claim 1, wherein the mixture includes between about 0.2 to 2.0% weight of the calcium carbonate.

3. The clean burning wood fuel pellet according to claim 1, wherein the calcium carbonate has a particle size between 0.2 mesh and 35 microns.

4. The clean burning wood fuel pellet according to claim 1, wherein the clean burning wood fuel pellet emits heat, water, and carbon dioxide during combustion.

5. The clean burning wood fuel pellet according to claim 1, wherein the clean burning wood fuel pellet have a length/diameter ratio of 2:1.

6. A method for producing clean burning wood fuel pellets, the method comprising the steps of:

mixing calcium carbonate and wood chips to form a mixture; and

forming pellets with the mixture.

7. The method of claim 6, further comprising the step of drying the wood chips prior to mixing with calcium carbonate.

8. The method of claim 6, wherein the mixture includes between about 0.2 to 2.0% weight of the calcium carbonate.

9. The method of claim 6, further comprising the step of cutting the wood chips to ¼ of an inch prior to mixing with the calcium carbonate.

10. The method according to claim 6, wherein the calcium carbonate has a particle size between 0.2 mesh and 35 microns.