JP2004050077A - Wood-derived fuel and production of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing wood-derived fuel usable as fuel for a cement kiln by utilizing wood waste. <P>SOLUTION: The wood-derived fuel production method comprises steps of (A) crushing wood by a crusher into crushed wood chips with 100 mm or shorter length, 10 mm or shorter width, and 5 mm or thinner thickness; (B) heating the wood chips for partial thermal decomposition at 200-300°C in a heating furnace so as to achieve 5-25 wt.% of weight decrease ratio; and (C) obtaining, as wood-derived fuel, a fragments of the partially thermally decomposed wood having a grain size of 1.5 mm or smaller by pulverizing the crushed wood after the heating treatment. As the heat source for the heating treatment in the step (B), waste heat of a cement production facility can be utilized. <P>COPYRIGHT: (C)2004,JPO

Description

【００２６】
［応用例１，２］
実験例と同様の手順により、家屋解体時に発生した廃木材を破砕し、１５ｍｍφの篩（トロンメル）を最終的に使用して、９５重量％以上が幅５ｍｍ以下で厚さ５ｍｍ以下の木材の破砕物（平均含水率：約１３重量％）を得た。
この木材の破砕物に対し、当該木材の破砕物と加熱ガスが反対方向に移動する向流方式の内熱式ロータリーキルン（内径５７ｃｍφ×長さ１０ｍ）を用いて、２２０〜２６０℃の温度領域の通過時間が２０〜３０分となる条件下で、かつ、木材の破砕物の乾燥重量に対する重量減少率が９〜１５重量％の範囲内となるように加熱処理を行なった。
なお、上述の実験例において、木材の破砕物に対し、予め乾燥状態にしてから加熱処理を行なった理由は、本発明の木材由来燃料を得るための好適な乾燥重量基準の重量減少率を求めるためであって、本発明の木材由来燃料の実際の製造方法を説明するためではない。すなわち、本発明の木材由来燃料を得る際には、必ずしも上述の実験例のように木材の破砕物を乾燥させる必要はなく、含水率をある程度把握した上で、乾燥重量基準の重量減少率が目標の値となるように、加熱条件を設定すればよい。
加熱処理後の木材の破砕物を縦型ローラミルによって粉砕した後、１．５ｍｍを超え３ｍｍ以下の粒度を有する木材由来燃料と、１．５ｍｍ以下の粒度を有する木材由来燃料を得た。これら木材由来燃料の高位発熱量は、４，６００ｋｃａｌ／ｇ以上であった。
【００２７】
次に、これら２種の木材由来燃料の各々について、図１に示す設備を用いて、セメントクリンカーの焼成実験を行なった。実験の内容は、次のとおりである。
まず、ロータリーキルンとしては、５，３００トン／日のセメントクリンカー製造能力を有する径５．５ｍで全長８３ｍのプレヒータ付きキルンを用いた。
セメントクリンカーの焼成に際し、まず、微粉炭（微粉砕された主燃料の石炭粉）５を、燃料供給管７を介して、ロータリーキルン１０の下流端に設置したバーナ８に８．５トン／時間（ｈｒ）の割合で供給した。なお、セメントクリンカーの製造量は、３，０００〜３，１００トン／時間にて実験した。一方、本発明の木材由来燃料４を、微粉炭５の供給と同時に、燃料供給管７を介してバーナ８に０．５〜１．０トン／時間の割合で供給した。
【００２８】
その結果、１．５ｍｍ以下の粒度を有する木材由来燃料は、ロータリーキルン１０の内部空間において、クリンカー原料と接触する前に気中燃焼を完結した。また、木材由来燃料を用いることによって、微粉炭の使用量を５〜１０％削減することができた。得られたクリンカーの品質も問題ないものであった。
一方、１．５ｍｍを超え３ｍｍ以下の粒度を有する木材由来燃料は、ロータリーキルン１０内の焼成帯を通過するクリンカー表面に落下して、継続的に燃焼した。そのため、クリンカー表面あるいはクリンカーが覆い被さった状態で燃焼したと考えられる部分は、明らかに木材由来燃料によりクリンカーが還元作用による褐色を呈していた。
したがって、気中燃焼が完結しない大きさの粒度を有する木材由来燃料を、セメントキルンの加熱用燃料として使用した場合、セメントの品質に悪影響を及ぼすという問題があることがわかった。
【００２９】
【発明の効果】
本発明の木材由来燃料によれば、高温雰囲気中でごく短い時間内に気中燃焼が完結するので、例えば、セメントキルンのバーナの燃料として用いた場合に、被焼成物（セメントクリンカーの原料）の表面に木材由来燃料が付着して、セメントクリンカーの品質を低下させるような不具合を生じることがない。
また、本発明の木材由来燃料は、家屋の解体等によって発生する廃木材を利用して製造することができるので、省資源及び省エネルギーを実現することができる。
【図面の簡単な説明】
【図１】本発明の木材由来燃料を用いたセメントクリンカー製造装置の一例を概念的に示す図である。
【符号の説明】
１　破砕装置
２　加熱装置
３　粉砕装置
４　木材由来燃料
５　微粉炭
６　ブロア
７　燃料供給管（一次燃焼空気供給管）
８　バーナ
９　クリンカー原料収容槽
１０　ロータリーキルン
１１　クリンカークーラ
１２，１３　管路[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fuel for cement kilns, a fuel for boilers, etc., obtained by treating various waste woods such as building materials, thinning materials, and recovered branch materials after pruning street trees, which are generated by demolition of houses. The present invention relates to a wood-derived fuel that can be used and a method for producing the fuel.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a technique has been proposed in which waste such as combustible waste is used together with pulverized coal as a fuel for use in a cement kiln or the like for firing cement clinker.
For example, Japanese Patent Publication No. 57-17867 discloses that a raw material for Portland cement is supplied to one end of a rotary kiln, and a fuel for calcination is supplied from the other end of the kiln to a calcination zone together with sufficient combustion air under appropriate conditions. In the method of producing Portland cement clinker, the firing fuel includes crushed municipal waste at a predetermined ratio, the crushed municipal waste is sent to the combustion zone by air, and the raw material is the burned waste. A method for the production of Portland cement clinker, characterized in that it is formulated to accept ash from lime, is described.
[0003]
[Problems to be solved by the invention]
The inventor of the present invention has found that there is the following problem when using wood crushed to an appropriate size as crushed municipal waste in the technology described in the above publication.
In other words, when a crushed piece of wood having a large particle size is used as the fuel for the rotary kiln, the crushed piece of wood put into the kiln does not complete the aerial combustion in the space inside the kiln, and the inside of the kiln does not complete. It burned continuously while falling on the object to be fired. For this reason, there is a problem that a reducing atmosphere is generated around the object to be baked to which the crushed wood adheres while burning, and this reducing atmosphere adversely affects the quality of the cement clinker.
[0004]
On the other hand, in order to complete the aerial combustion of the crushed wood in the space inside the kiln, if the wood is finely crushed in advance so that the particle size of the crushed wood is not more than a predetermined size, a large amount of In addition to requiring energy, the efficiency of treatment is reduced, the cost is increased, and practical application is difficult in terms of economy.
Further, even if the wood can be finely pulverized, the obtained pulverized wood has a problem that the calorific value as a fuel is small. That is, the calorific value of wood is about 2,000 kcal / kg in the case of normal waste wood, and at most about 4,500 kcal / kg in the case of dry wood. As described above, wood has a small calorific value per unit weight, so that it is difficult to use wood as a fuel for kilns requiring high-temperature combustion. In this regard, it would be advantageous if wood could be used as a raw material and a fuel with a large calorific value could be obtained.
Accordingly, an object of the present invention is to provide a wood-derived fuel using waste wood or the like, which can be used as a fuel for a cement kiln or the like, and a method for producing the fuel.
[0005]
[Means for Solving the Problems]
The present inventors have conducted intensive studies to solve the above problems, and as a result, after crushing wood to an appropriate size, the crushed wood was heated at a predetermined temperature so as to be partially thermally decomposed. Further, it has been found that if the crushed wood material after heating is further crushed to obtain a crushed wood material having a predetermined particle size, the crushed wood material can be suitably used as a fuel for a cement kiln, a boiler, or the like. completed.
[0006]
That is, the method for producing a wood-derived fuel according to the present invention (Claim 1) comprises: (A) a crushing step of crushing wood to obtain a crushed wood; and (B) partially crushing the wood. A heating step of performing a heat treatment at a temperature at which thermal decomposition can occur, and (C) a wood-derived material that is obtained by crushing the crushed wood after the heat treatment and partially crushing the wood. And a pulverizing step of obtaining fuel.
The wood-derived fuel of the present invention obtained in this way, in a high-temperature atmosphere, emits a large amount of heat and completes aerial combustion in a very short time, for example, the fuel of a burner of an internally heated cement kiln When used as a material, the inside of the kiln can be maintained at a high temperature, and wood-derived fuel can adhere to the surface of the material to be fired (raw material for cement clinker), causing inconvenience such as degrading the quality of cement clinker. Absent. Further, the wood-derived fuel of the present invention can be manufactured by using waste wood generated by dismantling a house or the like, so that resource saving and energy saving can be realized.
[0007]
In the crushing step (A), the particle size of the crushed wood is preferably adjusted to a length of 100 mm or less, a width of 10 mm or less, and a thickness of 5 mm or less (claim 2).
By adjusting the particle size to this size, uniform heating of each piece of wood constituting the crushed material can be performed, and a fuel of stable quality can be obtained after the crushing step (C), and the heating step (B) The heating time can be reduced, and the processing efficiency can be increased.
The heat treatment in the heating step (B) is preferably performed such that the weight reduction ratio of the crushed wood after the heat treatment to the dry weight of the crushed wood before the heat treatment is 5 to 25% by weight. (Claim 3).
By adjusting the weight loss rate within this numerical range, good pulverizability in the pulverization step (C) and a sufficient yield of the finally obtained fuel can be secured.
[0008]
The heating temperature in the heating step (B) is preferably adjusted to 200 to 300 ° C (Claim 4).
By adjusting the heating temperature within this numerical range, the degree of thermal decomposition of wood and the heating time can be made appropriate, and as a result, a wood-derived fuel having excellent quality and sufficient yield can be obtained. Can be obtained efficiently.
The pulverization treatment in the pulverization step (C) is preferably performed so that the particle size of the partially thermally decomposed wood pulverized material is 1.5 mm or less (claim 5).
As described above, by adjusting the particle size of the pulverized wood material to a predetermined particle size or less, air combustion of the fuel can be completed in a shorter time when the fuel of the present invention is used.
[0009]
As a heat source for the heat treatment in the heating step (B), for example, waste heat of cement production equipment can be used (claim 6).
With this configuration, in producing the fuel of the present invention, the amount of energy (for example, due to the combustion of fossil fuel such as coal) to be introduced from outside the system in the heating step (B) can be reduced. , Resources can be saved.
The wood-derived fuel of the present invention (claim 7) is characterized in that it is partially pyrolyzed and consists of a crushed wood product having a particle size of 1.5 mm or less.
The wood-derived fuel can be suitably used as a fuel for heating a cement kiln (claim 8). For example, the wood-derived fuel is suitably used as a fuel for a burner of an internally heated rotary kiln for firing clinker, lightweight aggregate, and the like.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail.
The method for producing a wood-derived fuel of the present invention comprises: (A) a crushing step of crushing wood to obtain a crushed wood; and (B) a crushing process of the wood at a temperature at which partial thermal decomposition can occur. A heating step of performing a heat treatment; and (C) a pulverizing step of pulverizing a crushed piece of wood after the heat treatment to obtain a wood-derived fuel composed of a partially pulverized piece of wood. is there.
[0011]
[A. Crushing process]
This step is a step of crushing wood to obtain a crushed wood having a predetermined particle size.
The wood is not particularly limited as long as it is flammable. Specific examples of timber include, for example, waste building materials generated in the demolition of wooden houses, discarded wooden furniture products, thinned timber obtained by cutting down forests, drift wood flowing into dams, etc. Branch materials and the like obtained at the time of pruning of street trees and the like are included.
Wood is preferably 100 mm or less in length, 10 mm or less in width, and 5 mm or less in thickness, more preferably 50 mm or less, 5 mm or less in width, and 5 mm or less in thickness, particularly preferably by means of a crushing device. Crushed to a particle size of 30 mm or less in length, 3 mm or less in width, and 3 mm or less in thickness.
[0012]
Here, the "granularity" of the crushed wood refers to the largest dimension of the piece of wood constituting the crushed material, "length", and any piece cut perpendicular to the "length" direction. Of the faces, the one having the largest area, the largest dimension is "width", and the dimension in the direction perpendicular to the "width" direction is "thickness", "length", "width", " Thickness refers to the size of a piece of wood.
If the particle size exceeds any of the dimensions of length 100 mm, width 10 mm, and thickness 5 mm, each heat treatment in the heating step (B) in the next step involves cutting each piece of wood (rod-like) constituting the crushed wood. Objects, lumps or granules) are not preferred because the following problems occur. That is, when the length of the wood piece exceeds 100 mm, especially when heat treatment is performed by a rotary kiln type dryer, the wood crushed material becomes bulky, and the treatment efficiency is reduced. Further, if the width of the wood piece exceeds 10 mm or the thickness exceeds 5 mm, the heat capacity of the crushed wood becomes too large, so that it is difficult to uniformly heat the inside, and the degree of decomposition as a whole becomes uneven. Become.
[0013]
In the present invention, the maximum particle size of the crushed wood is desirably not more than a predetermined size. Specifically, the maximum particle size of the crushed wood is preferably 10 mm or less and 5 mm or less in thickness, more preferably 5 mm or less in thickness and 5 mm or less, particularly preferably 3 mm or less in width and 3 mm or less in thickness. It is.
Here, the "maximum grain size" of the crushed wood refers to the largest area when all the pieces of wood constituting the crushed wood are cut arbitrarily so as to intersect perpendicularly to the length direction. Is shown by the width and thickness dimensions of the surface having the following, and does not mean the maximum length dimension of the piece of wood. For example, a crushed piece of wood containing a bar-shaped piece of wood having a length of 50 mm, a width of 10 mm, and a thickness of 5 mm, and among the pieces of wood other than the piece of wood, the maximum area of the piece of wood (width 10 mm) X area with a thickness of 5 mm), the maximum particle size of the crushed wood is 10 mm in width, even if a piece of wood having a length of more than 50 mm is included. , Thickness 5 mm ".
[0014]
In the present invention, the smaller the particle size and the maximum particle size of the crushed wood, the shorter the heat treatment time in the heating step (B) and the lower the set heating temperature.
On the other hand, the lower limit of the maximum particle size of the crushed wood in the crushing step (A) is not particularly limited. However, if it is excessively small, the energy required for crushing and the processing time increase, and the economic efficiency and the processing efficiency decrease. In consideration of the overall efficiency in all the steps including the heating step (B) and the pulverizing step (C), it is desirable to set the size to an appropriate size (for example, a width of 5 mm or less and a thickness of 3 mm or less).
[0015]
[B. Heating step]
This step is a step of heat-treating the crushed wood obtained in the crushing step (A) at a temperature at which partial thermal decomposition can occur.
When the wood crushed material is subjected to the heat treatment, a part of the wood constituent components is decomposed and fragile, and the crushability is improved.
The heating temperature is preferably from 200 to 300C, more preferably from 220 to 280C, particularly preferably from 235 to 265C. When the heating temperature is lower than 200 ° C., a long time is required for the heat treatment, the treatment efficiency is reduced, and it is difficult to efficiently obtain a heat-treated wood crushed material having excellent crushability. . When the heating temperature exceeds 300 ° C., not only does the energy cost increase, but also the degree of thermal decomposition of the wood becomes too large and carbonizes, or the wood burns in an atmosphere having a high oxygen concentration. As a result, the yield of wood-derived fuel decreases, and the amount of harmful gases such as CO gas and dioxin increases, which is not preferable.
[0016]
The heating time varies depending on the particle size of the crushed wood, the heating temperature and the like, but is usually about 5 to 60 minutes.
The weight reduction rate of the crushed wood by heating (however, the weight is based on the total dry weight) is preferably 5 to 25% by weight, more preferably 8 to 20% by weight, particularly preferably 10 to 10% by weight. 15% by weight. If the weight reduction rate is less than 5% by weight, a large amount of energy is required in the pulverizing step (C), and a special pulverizing device is required as a pulverizing means, which is not preferable. When the weight loss rate exceeds 25% by weight, not only the yield of wood-derived fuel finally obtained by the pulverization step (C) decreases, but also the exhaust gas generated by the thermal decomposition of wood during heat treatment (specifically, Is not preferable because the amount of gas containing hydrocarbons and COs) increases and the burden of exhaust gas treatment increases.
The atmosphere around the object to be heated during the heat treatment may be ordinary air, but the oxygen concentration should be kept low to prevent the heating temperature from rising due to the self-heating of the wood chips due to oxidation and to prevent combustion. Is desirable.
[0017]
The heating means may be a heating device capable of raising the temperature to about 400 ° C., and examples thereof include a fixed box-type drying oven and a rotary drying oven. Among them, a multi-stage tunnel drying furnace configured to continuously pass crushed wood through a movable conveyor or the like and heat it, or have a crushed wood input port at one end and heated wood at the other end The rotary kiln-type drying device having the crushed material discharge port is preferably used because it can be continuously processed and has good operability.
As a heat source for the heat treatment, for example, waste heat (excess heat of exhaust gas or the like) of a cement manufacturing facility can be used. Specifically, waste heat of exhaust gas generated by baking of clinker in a cement kiln, sensible heat of air discharged after cooling of clinker in a clinker cooler, and the like can be used. Furthermore, sensible heat of a raw material extracted in the manufacturing process (for example, a cement raw material extracted from a preheated cyclone or the like) can also be used.
[0018]
[C. Grinding process]
In this step, a wood-derived fuel composed of a partially pyrolyzed wood pulverized material is obtained by pulverizing the wood pulverized material that has been partially pyrolyzed and reduced in weight in the heating step (B). It is a process.
The pulverization treatment is carried out in such a small size that the pulverized wood (ie, the wood-derived fuel of the present invention) after the treatment can complete in-air combustion within a very short time in a high-temperature atmosphere such as the internal space of a cement kiln. It is performed so as to have a granularity.
Specifically, the particle size of the pulverized wood (wood-derived fuel) after the pulverization treatment is preferably 1.5 mm or less, more preferably 1.0 mm or less, further preferably 0.5 mm or less, and particularly preferably 0.1 mm or less. It is 25 mm or less.
Here, the “grain size” relating to the ground wood refers to the minimum value of the mesh size when the ground wood can pass through a sieve having a specific mesh size of 90% by weight or more.
When the particle size exceeds 1.5 mm, it becomes difficult to completely burn the wood-derived fuel in the air when using the wood-derived fuel in a cement kiln or the like, and for example, the quality of the cement clinker deteriorates. May occur.
The maximum particle size of the ground wood is preferably 1.5 mm or less, more preferably 1.0 mm or less, further preferably 0.5 mm or less, and particularly preferably 0.25 mm or less.
Here, the “maximum particle size” of the ground wood refers to the size of the particles having the largest size among the particles constituting the ground wood.
When the maximum particle size is 1.5 mm or less, the wood-based fuel can be completely and completely burned in the air when the wood-based fuel is used in a cement kiln or the like.
[0019]
As the pulverizing means, for example, a pulverizing device such as a roller mill, a ball mill, a vibration mill or the like is used.
The pulverized wood (pulverized wood-derived fuel) after the pulverization treatment can be used as a fuel for a combustion burner, like ordinary pulverized coal. For example, when a wood-derived fuel is used as a fuel for a clinker firing burner of an internally heated cement kiln, the wood-derived fuel is vaporized in a space inside the kiln before dropping onto a material to be fired (clinker raw material). Since the middle combustion is completed, the periphery of the object to be fired does not have a reducing atmosphere, and the quality of the clinker is not significantly affected.
[0020]
Next, the method of the present invention will be described with reference to the drawings. FIG. 1 is a diagram conceptually showing an example of a cement clinker manufacturing apparatus using a wood-derived fuel according to the present invention.
In FIG. 1, first, wood such as waste building material is crushed by a crushing device 1 to a predetermined particle size (for example, particles having 95% by weight or more and having a size of 5 mm or less and a thickness of 5 mm or less), and then heated. It is sent to the apparatus 2 and heated at a predetermined temperature (for example, about 240 ° C.) for a predetermined time (for example, about 30 minutes). By this heat treatment, the crushed wood is partially thermally decomposed. Next, the wood crushed material after the heat treatment is sent to the crushing device 3 and crushed to a predetermined particle size (for example, 0.5 mm or less). The obtained crushed wood is stored as a wood-derived fuel 4 in the hopper.
[0021]
On the other hand, the raw material for cement clinker stored in the clinker raw material storage tank 9 is supplied into the rotary kiln 10 and fired by the burner 8. At this time, pulverized coal 5 and wood-derived fuel 4 are used as fuel for burner 8. The pulverized coal 5 falls from a pulverized coal hopper into a fuel supply pipe (primary combustion air supply pipe) 7 and is sent to a burner 8 by a blower 6. The wood-derived fuel falls from the wood-derived fuel hopper located downstream of the pulverized coal hopper into the fuel supply pipe 7 and is sent to the burner 8 together with the pulverized coal by the blower (blower) 6. In addition, the usage ratio of the pulverized coal and the wood-derived fuel may be determined as appropriate.
The cement clinker calcined in the rotary kiln 10 is discharged from the rotary kiln 10, quenched in the clinker cooler 11, and then discharged to the outside.
The high-temperature exhaust gas discharged from the rotary kiln 10 and the high-temperature air discharged from the clinker cooler 11 are guided to the heating device 2 via the pipes 12 and 13, respectively, and are used as heat sources for heating the crushed wood. Used as
[0022]
【Example】
Next, a production example of the wood-derived fuel of the present invention will be described.
[Example of experiment]
After passing the waste wood through a hammer crusher and removing iron-containing foreign substances such as nails by a magnetic separator, the length is determined using a twin-screw crusher and a sieve (a trommel; rotary sieve) having an opening of 50 mmφ. The crushed material having a size of 100 mm or less, a width of 20 mm or less, and a thickness of 15 mm or less crushed until 95% by weight or more was occupied.
Next, after the remaining portion of the crushed material is further crushed by a four-shaft cutter crusher, a sieve having a mesh size of 25 mmφ (Trommel), a sieve having a mesh size of 15 mmφ (Trommel), and a sieve having a mesh size of 8 mmφ (Trommel) are arranged in this order. Those which did not pass through a sieve having a mesh size of 25 mmφ were again put into a 4-shaft cutter type crusher and pulverized, and sieved as described above.
[0023]
In this manner, (1) the total amount (100% by weight) is 50 mm or less in length and 95% by weight or more is 10 mm or less in width and 5 mm or less (pass only through a sieve having an aperture of 25 mmφ). (Crushed material C)) (2) The total amount (100% by weight) is 30 mm or less in length, and 95% by weight or more is 5 mm or less in width and 5 mm or less in thickness (mesh size 25 mmφ). (3) The total amount (100% by weight) is 20 mm or less in length, 95% or more is 3 mm or less in width and 3 mm or less in thickness. Samples in three categories of a certain product (a product having passed through a sieve having an aperture of 8 mmφ; “crushed product A”) were obtained.
Further, a product (crushed material D) having a length of 100 mm or less, 95% by weight or more, a width of 20 mm or less, and a thickness of 10 mm or less was obtained.
The obtained crushed material in each section was dried in a dryer at 100 to 105 ° C until no decrease in weight was observed, and then the weight (dry weight before heating) was measured.
[0024]
Next, the crushed material of each section was placed in a hot-air stirring type drier and heated as shown in Table 1 at a heating temperature of 350 to 180 ° C and a heating time of 5 to 720 minutes. After the heat treatment, the crushed material was air-cooled, and the weight (the weight of the partially thermally decomposed product after heating) was measured. From this weight and the above-mentioned dry weight before heating, the weight reduction rate of the crushed wood was calculated.
The crushability of the crushed material after heating was evaluated using a disk mill.
Table 1 shows the above results. From Table 1, the crushed wood having a particle size of not more than 50 mm in length, not more than 10 mm in width, and not more than 5 mm in thickness (that passes through a sieve having an aperture of 25 mmφ) has a weight loss rate of about 5% by weight or more after heat treatment. It can be seen that the crushability is improved by heating so that
Also, from Table 1, it can be seen that the suitable heating temperature decreases as the particle size of the crushed wood decreases. For example, in the case of a crushed material C having a particle size of not more than 10 mm in width and not more than 5 mm in thickness (that passes through a sieve having an opening of 25 mmφ), a good wood-derived fuel is easily obtained by heating at 250 ° C. for about 30 minutes. In addition, in the case of the crushed material A having a particle size of 3 mm or less in width and 3 mm or less in thickness (which has passed through a sieve having an aperture of 8 mmφ), a good wood-derived fuel can be obtained by heating at 235 ° C. for about 30 minutes. It turned out that it was easy to be done.
On the other hand, in the crushed material D having a particle size of 100 mm or less in length, 20 mm or less in width, and 10 mm or less in thickness, the preferable range of the heating temperature is limited to an extremely narrow range of about 280 ° C., and the yield is small. I understood.
[0025]
[Table 1]

[0026]
[Application Examples 1 and 2]
By the same procedure as in the experimental example, waste wood generated at the time of house demolition is crushed, and finally, a 15 mmφ sieve (trommel) is used to crush wood having a width of 95 mm or more and a width of 5 mm or less and a thickness of 5 mm or less. (Average moisture content: about 13% by weight) was obtained.
For the crushed wood, a countercurrent internal heat rotary kiln (inner diameter 57 cmφ × length 10 m) in which the crushed wood and the heating gas move in the opposite direction is used to obtain a temperature in the range of 220 to 260 ° C. The heat treatment was performed under the conditions that the passage time was 20 to 30 minutes, and the weight reduction ratio based on the dry weight of the crushed wood was within the range of 9 to 15% by weight.
In addition, in the above-mentioned experimental example, the reason why the heat treatment was performed after the crushed wood was dried beforehand is to determine the suitable weight loss rate on a dry weight basis to obtain the wood-derived fuel of the present invention. This is for the purpose of explaining the actual method for producing the wood-derived fuel of the present invention. That is, when obtaining the wood-derived fuel of the present invention, it is not always necessary to dry the crushed wood as in the experimental example described above, and after grasping the water content to some extent, the weight loss rate on a dry weight basis is reduced. What is necessary is just to set a heating condition so that it may become a target value.
After the heat-treated wood was pulverized by a vertical roller mill, a wood-derived fuel having a particle size of more than 1.5 mm and 3 mm or less and a wood-derived fuel having a particle size of 1.5 mm or less were obtained. The high calorific value of these wood-derived fuels was 4,600 kcal / g or more.
[0027]
Next, for each of these two wood-derived fuels, a cement clinker firing experiment was performed using the equipment shown in FIG. The contents of the experiment are as follows.
First, as the rotary kiln, a kiln with a preheater having a diameter of 5.5 m and a total length of 83 m having a cement clinker production capacity of 5,300 tons / day was used.
When firing the cement clinker, first, pulverized coal (pulverized coal powder of the main fuel) 5 is supplied to the burner 8 installed at the downstream end of the rotary kiln 10 via the fuel supply pipe 7 at 8.5 tons / hour ( hr). The experiment was performed at a cement clinker production amount of 3,000 to 3,100 tons / hour. On the other hand, the wood-derived fuel 4 of the present invention was supplied to the burner 8 via the fuel supply pipe 7 at a rate of 0.5 to 1.0 ton / hour simultaneously with the supply of the pulverized coal 5.
[0028]
As a result, the wood-derived fuel having a particle size of 1.5 mm or less completed in-air combustion in the internal space of the rotary kiln 10 before coming into contact with the clinker raw material. Also, by using wood-derived fuel, the amount of pulverized coal used could be reduced by 5 to 10%. The quality of the obtained clinker was also satisfactory.
On the other hand, the wood-derived fuel having a particle size of more than 1.5 mm and not more than 3 mm dropped on the surface of the clinker passing through the firing zone in the rotary kiln 10 and was continuously burned. For this reason, the clinker surface or a portion considered to have burned in a state covered with the clinker clearly showed a brown color due to the reduction action of the clinker due to the wood-derived fuel.
Therefore, it has been found that when a wood-derived fuel having a particle size that does not completely complete aerial combustion is used as a fuel for heating a cement kiln, there is a problem that the quality of cement is adversely affected.
[0029]
【The invention's effect】
According to the wood-derived fuel of the present invention, aerial combustion is completed within a very short time in a high-temperature atmosphere. Therefore, when used as a fuel for a burner of a cement kiln, for example, a material to be fired (a raw material of a cement clinker) There is no problem that the fuel derived from wood adheres to the surface of the cement clinker and deteriorates the quality of cement clinker.
Further, the wood-derived fuel of the present invention can be manufactured by using waste wood generated by dismantling a house or the like, so that resource saving and energy saving can be realized.
[Brief description of the drawings]
FIG. 1 is a diagram conceptually illustrating an example of a cement clinker manufacturing apparatus using a wood-derived fuel according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Crushing apparatus 2 Heating apparatus 3 Crushing apparatus 4 Wood-derived fuel 5 Pulverized coal 6 Blower 7 Fuel supply pipe (Primary combustion air supply pipe)
8 Burner 9 Clinker raw material storage tank 10 Rotary kiln 11 Clinker coolers 12, 13 Pipe line

Claims (8)

(A) a crushing step of crushing wood to obtain a crushed product of the wood;
(B) a heating step of heating the crushed wood at a temperature at which partial thermal decomposition can occur;
(C) a pulverizing step of pulverizing the crushed wood obtained after the heat treatment to obtain a wood-derived fuel comprising a partially pyrolyzed crushed wood. Manufacturing method. The method for producing a wood-derived fuel according to claim 1, wherein in the crushing step (A), the particle size of the crushed wood is adjusted to a length of 100 mm or less, a width of 10 mm or less, and a thickness of 5 mm or less. The heat treatment is performed in the heating step (B) such that the weight reduction rate of the crushed wood after heat treatment with respect to the dry weight of the crushed wood before heat treatment is 5 to 25% by weight. Or the method for producing a wood-derived fuel according to 2. The method for producing a wood-derived fuel according to any one of claims 1 to 3, wherein the heating temperature in the heating step (B) is adjusted to 200 to 300 ° C. The wood according to any one of claims 1 to 4, wherein, in the grinding step (C), the partially thermally decomposed wood is pulverized so that a particle size of the pulverized wood is 1.5 mm or less. Production method of derived fuel. The method for producing a wood-derived fuel according to any one of claims 1 to 5, wherein waste heat of a cement production facility is used as a heat source for the heat treatment in the heating step (B). A wood-derived fuel which is partially pyrolyzed and comprises a crushed wood having a particle size of 1.5 mm or less. The wood-derived fuel according to claim 7, wherein the wood-derived fuel is a fuel to be used as a fuel for heating a cement kiln.

Images