Description

APPARATUS AND METHOD FOR MAKING FUEL USING

FOREST RESIDUE

Technical Field

[1] The present invention relates to the use of forest residue as fuel, and more particularly to an apparatus and method for producing fuel from forest residue (biomass), which makes it convenient to transport, store and burn the biomass and can increase the heating value of combustion of the biomass, such that the biomass can provide an economic energy source. Background Art

[2] Biomass is organic material that used as an energy source, like plants or microorganisms, and the importance thereof as an environmental-friendly alternative energy source has been emphasized. Also, methods of obtaining fuels, such as methane, ethanol and hydrogen, through the pyrolysis or fermentation of biomass, have been studied. Specifically, with respect to the utilization of biomass energy, it is generally known to generate heat and electric power by the direct combustion of sawdust, wood chips, pellets and the like, gasify or liquefy them by thermochemical conversion, produce fertilizers or liquid fuels from them by biochemical conversion, or produce biodisel fuel from them by esterification.

[3] Among forest biomass, wood is particularly preferable, because it is infinitely produced and has a high energy content. It is known to make so-called wood pellets in order to use trees in the form of cut trees, trash or similar shapes, and produce energy from the wood pellets. The wood pellets are easy to transport, store and burn, such that they can stand comparison with coal or charcoal. Also, in view of various kinds of biomass and an increase in the demand for alternative energy-containing materials, there is a continued need to provide fuel, which is easy to transport, store and burn and has a high heating value, from biomass other than trees.

[4] However, plants other than trees have shortcomings in that, because have low heating values per unit weight or volume, the weight and volume thereof are increased to provide the same amount of fuel as when trees are used, so that the cost for transporting and storing them is incurred, and in that they are difficult to obtain with good quality. For this reason, plants other than trees are not suitable for the production of a large amount of energy.

[5] To overcome these problems, a novel method of carrying out a carbonization process for optimizing energy density was recently suggested to provide a new opportunity to activate the use of biomass as fuel in boilers (particularly middle-sized and

middle-sized boilers). Disclosure of Invention

Technical Problem

[6] Accordingly, the present invention has been made in view of the above-described problem occurring in the art, and it is an object of the present invention to an apparatus and method for producing fuel from forest residue (biomass), which makes it convenient to transport, store and burn the biomass and can increase the heating value of combustion of the biomass, such that the biomass can provide an economic energy source. Technical Solution

[7] To achieve the above object, according to one aspect of the present invention, there is provided an apparatus for producing fuel from forest residues, in which a variety of forest residues are sent from a first feeder to a crusher, in which the forest residues are crushed, and the crushed material is subjected to intermediate processes and produced as standardized fuel in a pelletizer, the apparatus comprising: a second feeder connected with both the downstream of the first feeder and a mixer and adapted to receive a second raw material for mixing with the first crushed raw material; a carbonizer disposed downstream of the mixer so as to receive an intermediate raw material and adapted to carbonize the intermediate raw material at high temperature and high speed; a crusher disposed downstream of the carbonizer so as to receive the carbonized intermediate material and adapted to crush the intermediate raw material, cooled in a cooler, into fine particles; and a third feeder connected with both the downstream of the crusher and a mixer and adapted to receive a third raw material for mixing with the finely crushed intermediate raw material.

[8] In the apparatus of the present invention, the carbonizer is preferably maintained at a temperature of 400-700 ⁰ C by controlling an air supply unit and a gas supply unit.

[9] According to another aspect of the present invention, there is provided a method for producing fuel from forest residues, in which a first raw material obtained by crushing a variety of forest residues is introduced and produced as standardized fuel through intermediate processes, the method comprising the steps of: (1) mixing the first raw material with a second raw material based on the rubber tree family, to obtain an intermediate raw material; (2) carbonizing the intermediate material to produce a carbide comprising 70-90 wt% of carbon and 8-10 %wt of volatile material; (3) crushing the carbide into fine particles having a size of more than 200 mesh; and (4) mixing the finely crushed intermediate material with a third raw material based on raw sawdust.

[10] In the method of the present invention, the third raw material in the step (4) is preferably mixed in a ratio of 20-30 wt%.

Advantageous Effects

[11] According to the present invention, it is possible to make it convenient to transport, store and burn biomass, and it is possible to increase the heating value of combustion of the biomass, such that the biomass can provide an economic energy source. Brief Description of the Drawings

[12] FIG. 1 is a front view schematically showing the general construction of an apparatus according to the present invention.

[13] <Description of important reference numbers in the figure>

[14] 10: first feeder; 12: crusher; 15: mixer; 20: second feeder; 22: carbonizer; 24: cooler; 26: crusher; 30: third feeder; 32: mixer; 35: pelletizer; 36: hopper; and 38: packaging machine. Best Mode for Carrying Out the Invention

[15] Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to FIG. 1, which is a front view schematically showing the general construction of an apparatus according to the present invention.

[16] One aspect of the present invention relates to an apparatus, in which a variety of forest residues are sent from a first feeder 10 to a crusher 12, in which they are crushed, and the crushed material is subjected to intermediate processes and produced as standardized fuel in a pelletizer 35. The forest residues include trees, twigs, stickers, sawdust, palm oil waste, woody materials, grasses, weeds, chaff, sugar canes and the like. However, wood timbers, or wood materials containing chemicals such as adhesives are not used in the present invention. As used herein, the term "intermediate processes" refers to processes between the initial processes, including the first feeder 10 and the crusher 12, and final processes, including the pelletizer 35, the hopper 36 and the packaging machine 38.

[17] The first feeder 10 adopts gravity dropping as in a conventional hopper. In the crusher 12, forest residues are cut to the size for optimal carbide integration and energy integration. In the pelletizer 35, the final material subjected to the intermediate processes is formed into pellets, and the hopper 36 is used to determine the packaging quantity of the pellets. Also, the packaging machine 38 is used to package the pellets in set units.

[18] According to the present invention, a second feeder 20, which receives a second raw material for mixing with the first crushed raw material, is connected with both the downstream of the first feeder 10 and the mixer 15. As used herein, the term "first raw material" refers to a raw material, passed through the first feeder 10 and cut to a suitable size in the crusher 12. The second feeder 20 has a hopper structure as in the first feeder 10, but the capacity thereof may be slightly smaller than. The downstream

of the crusher 12 and the downstream of the second feeder 20 are connected with the mixer 15. In the second feeder 20, residue based on the rubber tree family is fed as described below in order to increase the heating value of fuel.

[19] According to the present invention, the carbonizer 22 that carbonizes the intermediate raw material at high temperature and high speed is disposed downstream of the mixer 15, such that it receives the intermediate raw material. The carbonizer 22 is preferably maintained at a temperature of 400-700 ⁰ C by controlling an air supply unit 16 and a gas supply unit 18. As fuel for igniting the carbonizer 22, air from the air supply unit 16 and LPG gas from the gas supply unit 18 are used. The furnace temperature of the carbonizer 22 is maintained at 400-700 ⁰ C and varies depending on the kind of raw material (forest residue) as described below. If the carbonizer 22 is a high-speed carbonizer, it operates for about 40-60 minutes.

[20] According to the present invention, a crusher 26, which crushes the intermediate raw material, cooled through a cooler 24, into fine particles, is disposed downstream of the carbonizer 22, such that it receives the carbonized intermediate raw material. The crusher 26 crushes the intermediate raw material, obtained by carbonizing and cooling the first and second raw materials, into fine particles having size of more than 200 mesh. This is advantageous for maintaining the standard of the product at a constant level in the subsequent pelletizing process.

[21] According to the present invention, a third feeder 30, which receives a third raw material for mixing with the finely crushed intermediate raw material, is connected with both the downstream of the crusher 26 and a mixer 32. The third feeder also adopts a hopper structure as in the second feeder 20 and has a capacity similar to that of the second feeder 20. In the third feeder 30, general sawdust (raw sawdust) is introduced as described below, and in the mixer 32, the discharged material is mixed with 10-50 wt% of the third raw material.

[22] Another aspect of the present invention relates to a method for producing fuel from forest residues, in which a first raw material, obtained by crushing a variety of forest residues, is introduced and subjected to intermediate processes to produce standardized fuel. As the forest residues in the method of the present invention, fruit shells, coconuts, twig roots, leaves, chaffs, sugar cane husks, weeds, grasses, and in addition, wood wastes, which cannot be used for other applications, can be used. Dried aquatic plants and wet aquatic plants may also be used in the present invention, but it should be avoid to forest waste, which undergoes carbon dioxide assimilation (photosynthesis), and in addition, seaweeds, such as brown seaweed or laver. Also, the water content of the raw material is preferably about 10-50%, and material having a water content of a maximum of 40-50% may also be used in the present invention, but it is preferable to use material having a reduced water content. In the crushing process,

the raw material can be introduced without any processing and crushed with feed screws. Alternatively, the raw material may also be primarily crushed, and then secondarily crushed to a size of about 10 mesh using feed screws.

[23] According to the present invention, a step (1) of mixing the first raw material with a second raw material based on the rubber tree family is carried out. Although it is preferable in terms of heating value to mix the first and second raw materials, introduced in the mixer 15, at the same ratio, it must be considered that the amount of the second raw material is relatively small. Fagaceae plants may be used instead of the rubber tree family, but are slightly inferior in terms of heating value. A few kinds of rubber trees are distributed mainly in the tropics, and the rubber trees that can be used in present invention are not limited to any particular kinds.

[24] According to the present invention, a step (2) of carbonizing the intermediate raw material to produce a carbide, which comprises 70-90 wt% of carbon and 8-10 wt% of volatile material, is carried out. The intermediate raw material is obtained by mixing the first raw material and the second raw material, and produces the carbide, when it is maintained at 400-700 ⁰ C for about 1 hour. In the present invention, hard materials, such as twig roots and fruits, which become black coal, are preferably maintained at 400-450 ⁰ C, and soft materials, such as leaves, chaffs and grasses, which become white coal, are preferably maintained at 550-700 ⁰ C. When the step (2) is carried out as described above, it is expected that the second raw material will clog the pores of charcoal to reduce the loss of heating value. When the carbide contains 80 wt% carbon, 10 wt% volatile material, 4 wt% water, 0.02 wt% sulfur (S), 0.2 wt% nitrogen (N) and 2.8 wt% hydrogen (H), a heating value of about 7200 kcal/kg, which is about two-fold higher than that of pellet fuel prepared in a general process, will be generated.

[25] According to the present invention, a step (3) of crushing the carbide into fine particles having a size of more than 200 mesh is carried out. The finer the carbide particles are, the higher the porosity of the pellet product formed from the particles will be.

[26] According to the present invention, a step (4) of mixing the finely crushed intermediate material with a third raw material based on raw sawdust is carried out. The larger particle size of sawdust provides advantages in terms of formability and heat efficiency. When this step is carried out, the pellet product is prevented from reaching the ash melting point thereof in a boiler combustion process, until it is completely burned in a combustion furnace, thus facilitating the complete combustion of the product. In the step (4), the third raw material is preferably mixed at a ratio of 10-50 wt%, and more preferably 20-30 wt%. The content of the third raw material has a close connection with heating value.

[27] In a final process, the pellets are preferably formed to have a diameter of about 4-8

mm and a length of 10-15 mm in order to facilitate the complete combustion of the pellets. The formed pellets are packaged in different units in consideration of the fact that the capacity of boilers varies depending on users.

[28] Although the preferred embodiment of the present invention has been described for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.