WO2009038241A1

WO2009038241A1 - Method for preparing solid carbonizing fuels using wood biomass

Info

Publication number: WO2009038241A1
Application number: PCT/KR2007/004472
Authority: WO
Inventors: Bok Yim Chung
Original assignee: Kenertec
Priority date: 2007-09-17
Filing date: 2007-09-17
Publication date: 2009-03-26

Abstract

The present invention relates to a method for preparing a solid carbonized fuel using wood biomass, and more particularly, to a method for preparing an environmentally friendly, solid carbonized fuel by mixing wood biomass which is abundantly available in nature, cassava starch showing ignition, bonding and adhesion properties, and potassium nitrate as an oxidant, and then molding them. According to the present invention, it is possible to prepare an environmentally friendly, solid carbonized fuel which is economical due to the use of wood biomass abundantly available in nature, can be easily prepared due to simple raw material compositions and has high combustion efficiency, as well as, high heating value per unit weight, and thus the solid carbonized fuel can be used as fuel for a large boiler which can produce electricity and steam.

Description

METHOD FOR PREPARING SOLID CARBONIZING FUELS

USING WOOD BIOMASS

Technical Field

[1] The present invention relates to a method for preparing a solid carbonized fuel using wood biomass, and more particularly, to a method for preparing an environmentally friendly, solid carbonized fuel by mixing wood biomass which is abundantly available in nature, cassava starch showing ignition, bonding and adhesion properties, and potassium nitrate as an oxidant, and then molding them.

[2]

Background Art

[3] Recently, the plan 'the twenty-first century wood fire', which aims to utilize wood fuel as an alternative energy source, has been progressing at government level. Specifically, the plan is to prepare a support system so that waste wood spontaneously generated from forest, or waste wood generated from households and industry, can be used as fuel for cogeneration process, and particularly, 'a plan for stimulating wood biomass supply' is suggested as one of plans for promoting renewable energy utilization. Biomass refers to living organisms, including plants receiving sunlight, plant- fungi symbiosis, and animals and plants feeding on the plant fungi.

[4]

[5] Every year, 3,180,000 tons of wood, that can be used as fuel, are generated, which include wood waste generated from natural disaster, such as floods etc., woodland development, household furniture or industrial by-products, and it is estimated that, from which energy corresponding to 1,430,000 tons of petroleum can be obtained. However, at present, 90% of wood byproducts, and more than 60% of waste wood generated from household, construction industry and wood industry are discarded. Thus, there is an urgent need to develop a technique to utilize the discarded wood waste as an alternative energy source.

[6]

[7] At present, in an attempt to use wood biomass as an energy source, a study for bioethanol production using wood has been conducted, but it has not been commercialized yet, and, in other fields, the study results that can be used for practical application of wood biomass as an energy source, is insufficient.

[8]

[9] Meanwhile, in prior art, in a process for preparing carbonized fuel, as an adhesive for molding carbonized charcoal powder, kneaded grain starch was added or chemical adhesives such as silicon was added. However, the grain starch dough has a problem in that it is impossible to mass-produce it and thus it is not economical for the production of carbonized fuel, and the chemical adhesives have a problem in that they generate harmful gases upon combustion of the carbonized fuel.

[10]

[11] In addition, in order to improve combustion efficiency of the carbonized fuel, the fuel is prepared by adding volatile organic compounds such as benzene, and in this case, they produce carcinogens, harmful gases and thus cause environmental problems as well as are extremely harmful to the human body.

[12]

[13] Recently, solid fuel prepared by pulverizing wood biomass and compressing it at

180~230°C, was developed, but its strength is weak and its heating value is merely 4800~5500kcal, so that its effectiveness as fuel is limited (WO 06/077652A1). In addition, solid fuel prepared by pulverizing wood waste to adjust the water content of wood waste, and then compressing it at 50~200°C under a pressure of 100~1000kgf/cm without using a binder, was recently developed, but since binders are not used, relatively high-intensity pressure is required in the compression process, the prepared fuel has a disadvantage in that it is apt to be broken (JP 2006-31531A2).

[14]

[15] As a representative example of solid fuel preparation technologies using carbonized wood charcoal, a solid fuel unit having a unit packaged burning material and a unit packaged ignition material was disclosed (Korean Patent Registration 10-0478876). In the solid fuel unit, the burning material is bamboo charcoal made from natural bamboo by a carbonization process, and the ignition material is prepared by molding a mixture of bamboo charcoal powder, activated charcoal, fine sugar, potassium nitrate, barium and starch in a mold, to cut into regular size of pieces, and the solid fuel is characterized in that the burning material combustion is performed by the heating power of ignition material. However, it has disadvantages in that a lot of raw materials are required to prepare the solid fuel, and fuel composition is complicated and production cost thereof is high, which cause limited supply of fuel, thus it is not suitable to be used as fuel for large boilers.

[16]

[17] Accordingly, the present inventors have made extensive efforts to solve the above- described problems occurring in the prior art, and, as a result, prepared a solid carbonized fuel, only using carbonized charcoal powder derived from brigalow biomass, cassava starch, and potassium nitrate as raw materials, and confirmed that the solid carbonized fuel prepared with simple raw material composition shows a high combustion efficiency without producing harmful gases, thereby completing the present invention. [18] [19] SUMMARY OF THE INVENTION

[20] It is a main object of the present invention to provide a solid carbonized fuel using wood biomass, and a method for preparing the same. [21] [22] It is another object of the present invention to provide a solid carbonized fuel containing charcoal derived from wood biomass, cassava starch and potassium nitrate. [23] To achieve the above object, the present invention provides a method for preparing a solid carbonized fuel using wood biomass, which comprises the steps of: (a) preparing charcoal powder by carbonizing wood biomass; (b) preparing a mold by mixing 8-17 parts by weight of cassava starch and 1-3 parts by weight of potassium nitrate to 100 parts by weight of the charcoal powder and molding them; and (c) drying the mold to obtain a solid carbonized fuel. [24] The present invention also provides a solid carbonized fuel containing charcoal derived from wood biomass, cassava starch and potassium nitrate, which is prepared by the above method. [25] The above and other objects, features and embodiments of the present invention will be more clearly understood from the following detailed description and accompanying claims. [26]

[27] BRIEF DESCRIPTION OF THE DRAWINGS

[28] FIG. 1 is a flow chart showing the preparation process for the solid carbonized fuel using wood biomass according to the present invention. [29] [30] FIG. 2 shows a solid carbonized fuel using wood biomass, which is prepared according to the present invention. [31] [32] DETAILED DESCRIPTION OF THE INVENTION. AND PREF ERRED EM-

BODIMENTS [33] In one aspect, the present invention relates to a method for preparing a solid carbonized fuel using wood biomass, which comprises the steps of: (a) preparing charcoal powder by carbonizing wood biomass; (b) preparing a mold by mixing 8-17 parts by weight of cassava starch and 1-3 parts by weight of potassium nitrate to 100 parts by weight of the charcoal powder and molding them; and (c) drying the mold to obtain a solid carbonized fuel (FIG.l). [34] [35] In the present invention, wood biomass means trees and herbaceous plants containing lignin and cellulose, and products, waste wood, paper etc. derived therefrom. Thus, it is different from wood which is not processed into products such as paper etc., and is limitlessly available in nature.

[36]

[37] In the present invention, the wood biomass is preferably selected from the group consisting of brigalow, oak, bamboo, rubber tree, maple, coconut tree, and palm tree. In the present invention, heating value of the charcoal powder in the step (a) is preferably 6,500-7,800 kcal/kg.

[38]

[39] Specifically, when wood biomass is carbonized by heating in a carbonizing furnace with no air flow thereinto, water and some volatile components are eliminated and the amount of fixed carbon is increased, so that it is possible to obtain charcoal whose heating value is increased by more than two folds per unit weight, and the thus obtained charcoal is pulverized to prepare charcoal powder, thus using the charcoal powder for the preparation of the inventive solid carbonized fuel.

[40]

[41] The charcoal powder prepared by carbonizing the wood biomass allows the solid fuel to emit heat corresponding to heating value of the charcoal powder by oxidation during combustion, and function as fuel. The charcoal powder is a main component of solid carbonized fuel prepared according to the present invention, and it emits heat corresponding to heating value of the charcoal powder, i.e., 6,500-7,800 kcal by oxidation during combustion, thus functioning as fuel.

[42]

[43] According to an embodiment of the present invention, as wood biomass, brigalow can be used. The brigalow is used for railroad ties, furniture, firewood, etc., and particularly, it emits little smoke and has superior heating power, thus it is highly useful as fuel. Moreover, charcoal prepared using the brigalow contains more volatile components than that of charcoal prepared using other woods, and thus, has fast burning velocity and allows a long-lasting combustion.

[44]

[45] In the present invention, cassava starch functions as a natural binder available in nature, unlike the conventional chemical binders.

[46]

[47] Cassava is a South American dicotyledonous deciduous shrub belonging to the

Spurge family, Euphorbiaceae, which is characterized in that it is a tuberous root spreading widely. It is a tuberous root spreading widely, produces thick root tubers like sweet potato, and contains 20-25% starch. Starch extracted from cassava tubers is called tapioca, and has glutinous property, so that it can be used as an ingredient for snacks, alcohol, paste and foods.

[48]

[49] In the present invention, cassava starch is prepared by cutting cassava tubers into pieces, drying them, and grinding into a fine powder using a pulverizer, and the cassava starch is mixed with water, and then heated to prepare a cassava starch mixture, thus using the cassava starch mixture as a binder.

[50]

[51] As described above, in addition to the function as a binder allowing a material to congeal by providing viscosity, cassava starch shows a function as an igniting agent for rapid ignition and a function as an adhesive capable of adhering to other materials to help attach them together. Therefore, the cassava starch used in the present invention has the effects of simplifying the constitution of the solid carbonized fuel according to the present invention, as well as enhancing the effectiveness thereof, compared to the conventional solid fuel in which a binder, an igniting agent, an adhesive etc. are separately added upon preparation of solid carbonized fuel.

[52]

[53] Meanwhile, the ignition property of cassava starch is due to high amylose level. The cassava starch has a high amylose concentration and low gelatinization temperature compared to natural starches such as cornstarch, thus reducing heating time in gelatinization process of cassava starch, so that it is possible to increase production due to reduced processing time, and less fuel is consumed for heating.

[54]

[55] In the present invention, if the cassava starch is used in a ratio of less than 8 parts by weight, its viscosity weakens when mixed with charcoal powder, so that the resulting solid carbonized fuel is likely to be broken and its ignition velocity decreases, and if the cassava starch is used in a ratio of more than 17 parts by weight, the added amount of charcoal powder is relatively reduced, so that heating value of solid carbonized fuel is decreased and the solid carbonized fuel ignites suddenly to reduce its stability, resulting in low fuel effectiveness, thus the cassava starch is preferably used in a ratio of 8-17 parts by weight based on 100 parts by weight of charcoal powder.

[56]

[57] Niter is one of nitrate minerals containing KN03 that is used as an oxidant, and in the present invention, it functions as an oxidant upon combustion of solid carbonized fuel, so that it has the effect of allowing the solid carbonized fuel to be easily ignited, and to continuously burn.

[58]

[59] Specifically, the potassium nitrate is one of gunpowder components that has a function of reducing combustion time since it produces oxygen upon combustion to rapidly react with carbon, resulting in an oxidation reaction, thus causing rapid combustion. That is, potassium nitrate improves the combustion efficiency of fuel to enable complete fuel combustion.

[60]

[61] In the present invention, if the potassium nitrate is used in a ratio of less than 1 part by weight, its function as an oxidant is impaired, and if the potassium nitrate is used in a ratio of more than 3 parts by weight, its function as an oxidant remains the same, thus the potassium nitrate is preferably used in a ratio of 1-3 parts by weight based on 100 parts by weight of charcoal powder.

[62]

[63] Meanwhile, in the present invention, water soluble nitrate in the form of a powder is preferably used such that it is uniformly mixed with the charcoal powder and the cassava starch.

[64]

[65] In the present invention, the molding in the step (b) is preferably compression molding. In the present invention, solid carbonized fuel having a regular shape and homogeneous composition can be prepared by the compression molding.

[66]

[67] In another aspect, the present invention relates to solid carbonized fuel containing charcoal derived from wood biomass, cassava starch and potassium nitrate, which is prepared by the above method (FIG.2).

[68]

[69] In the present invention, heating value of the solid carbonized fuel prepared by using the wood biomass is preferably 6,000~7,300 kcal/kg, and the solid carbonized fuel is preferably used as fuel for a large boiler.

[70]

[71] The solid carbonized fuel prepared according to the present invention has a regular shape and homogeneous composition to show a uniform heating value per unit weight, so that when they are used as fuel for a boiler which can produce electricity and steam, combustion control is easy and an output of the boiler is stabilized, which can reduce operator's burden during boiler operation and facility control efficiency can be improved.

[72]

[73] In addition, an environment-polluting material, nitrogen oxides emitted are mostly thermal NOx, which is highly temperature dependent and thus is formed at the portion of flame close to the burner where high temperature oxidation of atmospheric nitrogen occurs by peak flame temperature, and also produced due to high levels of excess air upon combustion in a boiler facility, the thermal NOx formation increases when the excess air ratio increases upon combustion or local temperature increase occurs in a combustion chamber. When the solid carbonized fuel according to the present invention is used, a boiler can be operated under low air ratio upon fuel combustion due to constant heating value thereof as described above, and homogeneous temperature distribution can be achieved in a combustion chamber of a boiler, thus making it possible to reduce NOx formation, which is highly temperature dependent and excess-air-dependent.

[74]

[75] Meanwhile, the weight and volume of charcoal powder prepared by carbonizing wood biomass are decreased compared to the wood biomass used for preparation thereof, and thus there is an advantage in that costs for transporting the solid carbonized fuel prepared using the charcoal powder can be greatly reduced. Specifically, the weight percentage of carbonized charcoal powder weight is about 15-25% based on the weight of the wood biomass, and its volume percentage thereof is less than 40% based on the volume of the wood biomass.

[76]

[77] Generally, the water content of wood biomass is 40% before drying, and 20% after drying. When fuel has a high water content, there is a disadvantage in that its weight is increased to incur high transport costs, as well as, thermal efficiency is reduced since 600 kcal per unit weight (kg) of water for evaporating water, are released. In other words, the lower the water content of fuel is, the higher the thermal efficiency of fuel becomes and the higher heating value fuel has.

[78]

[79] In the present invention, heating value of the inventive solid carbonized fuel decreases through the steps of mixing charcoal powder prepared by carbonizing wood biomass having 6,500-7,800 kcal/kg of heating value, and cassava starch, then molding them. Thereafter, water content of the solid carbonized fuel is reduced by drying step to increase heating value thereof again, thus obtaining solid carbonized fuel having 6,000-7,300 kcal/kg of heating value.

[80]

[81] Examples

[82] The present invention will hereinafter be described in further detail by examples.

However, it is to be understood that these examples can be modified into other various forms, and the scope of the present invention is not intended to be limited to such examples.

[83]

[84] Example 1: Preparation of solid carbonized fuel using brigalow. cassava starch, and potassium nitrate [86] Brigalow was heated at 400~600°C for 22 hours in a carbonizing furnace with no air flow thereinto to eliminate water and volatile components, thus preparing carbonized brigalow charcoal, and then, the resulting charcoal was finely ground to prepare charcoal powder. At this time, heating value of the prepared charcoal was 6,800 kcal/ kg-

[87]

[88] 100kg of the charcoal powder, 12kg of cassava starch obtained by adding water and heating the mixture, and 2kg of potassium nitrate were mixed and then subjected to compression molding to prepare a mold. The mold was dried at 12O⁰C for 3 hours to prepare cylindrical solid carbonized fuel.

[89]

[90] Comparative Example 1 : Preparation of solid carbonized fuel using brigalow. cornstarch, and potassium nitrate

[91]

[92] Brigalow was heated at 400~600°C for 22 hours in a carbonizing furnace with no air flow thereinto to eliminate water and volatile components, thus preparing carbonized brigalow charcoal, and then, the resulting charcoal was finely ground to prepare charcoal powder. At this time, heating value of the prepared charcoal was 6,800 kcal/ kg-

[93]

[94] 100kg of the charcoal powder, 12kg of cornstarch obtained by adding water and heating the mixture, and 2kg of potassium nitrate were mixed and then subjected to compression molding to prepare a mold. The molded material was dried at 12O⁰C for 3 hours to prepare cylindrical solid carbonized fuel.

[95]

[96] Comparative Example 2: Preparation of solid carbonized fuel using brigalow and potassium nitrate

[97]

[98] Brigalow was heated at 400~600°C for 22 hours in a carbonizing furnace with no air flow thereinto to eliminate water and volatile components, thus preparing carbonized brigalow charcoal, and then, the resulting charcoal was finely ground to prepare charcoal powder. At this time, heating value of the prepared charcoal was 6,800 kcal/ kg-

[99]

[100] 101kg of the charcoal powder and 13kg of cornstarch obtained by adding water and heating the mixture were mixed and then subjected to compression molding to prepare a mold. The mold was dried at 12O⁰C for 3 hours to prepare cylindrical solid carbonized fuel.

[101]

[102] Comparative Example 3: Preparation of solid carbonized fuel using bamboo charcoal, cassava starch and potassium nitrate

[103]

[104] Bamboo was carbonized in a charcoal kiln to prepare bamboo charcoal, and then, the bamboo charcoal was finely pulverized to prepare bamboo charcoal powder. 100kg of the bamboo charcoal powder, 12kg of cassava starch obtained by adding water and heating the mixture, and 2kg of potassium nitrate were mixed and subjected to compression molding to prepare a mold. The resulting mold was dried at 12O⁰C for 3 hours to prepare cylindrical solid carbonized fuel.

[105]

[106] Experimental example 1 : Comparison between solid carbonized fuels according to the kind of binder

[107]

[108] As a result of comparing efficiencies of solid carbonized fuels prepared in Example 1 and Comparative Example 1, as shown in Table 1, the results showed that heating values of both fuels were similar, but the combustion time of solid carbonized fuel prepared in Example 1 was shorter than that of solid carbonized fuel prepared in Comparative Example 1. The above result was due to the difference between cassava starch and cornstarch which were used as a binder in Example 1 and Comparative Example 1, respectively, suggesting that although both of the cassava starch and the cornstarch are natural binders, in the case of preparing fuel using cassava starch, combustion time is decreased. Specifically, this result is due to difference between the levels of amylose present in the cassava starch and the cornstarch, that is, the cassava starch has high amylose content, so that its gelatinization temperature is low(66°C) and the cornstarch has low amylose content, so that its gelatinization temperature is high(76°C), thus, in a gelatinization process of the cassava starch, heating time is reduced, which results in overall reduction in the combustion time.

[109]

[110] Table 1 [Table 1] [Table ]

[111] [112] Experimental example 2: Comparison between solid carbonized fuels according to whether potassium nitrate is used

[113] As a result of comparing efficiencies of solid carbonized fuels prepared in Example 1 and Comparative Example 2, as shown in Table 1, the results showed that heating values of both fuels were similar, but the combustion time of the solid carbonized fuel prepared in Example 1 was shorter than that of the solid carbonized fuel prepared in Comparative Example 1. This result is due to the absence and presence of potassium nitrate, which suggests that the potassium nitrate functions as an oxidant upon combustion to induce rapid combustion.

[114] [115] Experimental example 3: Comparison between solid carbonized fuels according to the kind of charcoal powder

[116] As a result of comparing efficiencies of solid carbonized fuels prepared in Example 1 and Comparative Example 3, as shown in Table 1, it was observed that they showed similar combustion time, but heating value of solid carbonized fuel prepared in Example 1 was higher than that of solid carbonized fuel prepared in Comparative Example 3. This result is due to difference between the brigalow charcoal powder and bamboo charcoal powder, suggesting that fuel prepared using brigalow charcoal powder has high heating value and thus has high fuel efficiency, and it has high levels of volatile components, and thus has possibility of being used as fuel for equipment like large boiler.

[117]

Industrial Applicability

[118] As described above in detail, according to the present invention, it is possible to prepare an environmentally friendly, solid carbonized fuel which is economical due to the use of wood biomass abundantly available in nature, can be easily prepared due to simple raw material compositions and has high combustion efficiency, as well as, high heating value per unit weight, and thus the solid carbonized fuel can be used as fuel for a large boiler which can produce electricity and steam.

[119]

[120] While the present invention has been described with reference to the particular illustrative embodiment, it is not to be restricted by the embodiment but only by the appended claims. It is to be appreciated that those skilled in the art can change or modify the embodiment without departing from the scope and spirit of the present invention.

[121]

Claims

[1] A method for preparing a solid carbonized fuel using wood biomass, the method comprises the steps of:

(a) preparing charcoal powder by carbonizing wood biomass;

(b) preparing a mold by mixing 8-17 parts by weight of cassava starch and 1-3 parts by weight of potassium nitrate to 100 parts by weight of the charcoal powder and molding them; and

(c) drying the mold to obtain a solid carbonized fuel.

[2] The method according to claim 1, wherein the wood biomass in the step (a) is selected from the group consisting of brigalow, oak, bamboo, rubber tree, maple, coconut tree, and palm tree. [3] The method according to claim 1, wherein heating value of the charcoal powder in the step (a) is 6,500-7,800 kcal/kg. [4] The method according to claim 1, wherein the molding in the step (b) is compression molding. [5] A solid carbonized fuel containing charcoal derived from wood biomass, cassava starch and potassium nitrate, which is prepared by the method of any one claim among claims 1 to 4. [6] The solid carbonized fuel according to claim 5, wherein heating value thereof is

6,000-7,300 kcal/kg. [7] The solid carbonized fuel according to claim 5, which is fuel for a large boiler.