JP6328901B2 - Method for producing solid fuel and solid fuel - Google Patents

Description

  The present invention relates to a solid fuel having a low chlorine content obtained by torrefaction of woody biomass and a method for producing the solid fuel.

In recent years, as a countermeasure against global warming due to depletion of fossil fuels and CO ₂ emissions, the use of fuels made from biomass has been studied. In general, biomass refers to a living organism that can be used as an energy source or an industrial raw material, and representative examples are wood, building waste, agricultural waste, and the like. Various methods for effectively utilizing biomass have been proposed. Among them, as a useful method capable of converting biomass into a high value-added product at a low cost, there is a method for producing a solid fuel by carbonizing biomass. In this method, biomass is put into a carbonization furnace and heated for a predetermined time in an oxygen-deficient atmosphere to be carbonized to produce a solid fuel.

  The solid fuel thus produced is used as a fuel for combustion facilities such as power generation facilities and incineration facilities. In this case, the solid fuel may be finely pulverized and used as a finely divided fuel in order to improve combustion efficiency. is there. Solid fuel is pulverized alone or mixed with coal, but most of wood biomass is fibrous, so the pulverization is poor, the combustion efficiency decreases, the operability of the pulverizer decreases, etc. There was a problem.

  Patent Document 1 discloses a method of pulverizing woody biomass such as wood waste, thinned wood, garden wood, building waste, etc., at a temperature of 240 ° C. or higher and 300 ° C. or lower for 15 minutes or longer and 90 minutes or shorter. Has been. If the heating temperature is lower than 240 ° C, crushability and pulverization will not be improved. If the heating temperature is higher than 300 ° C, the amount of fine powder on the order of submicron will increase during crushing and pulverization, and powder troubles will easily occur. Therefore, it is not preferable.

  Patent Document 2 discloses that biomass containing cereals, berries and seeds is carbonized by heating for 30 to 90 minutes at an oxygen concentration of 1 to 5% and a treatment temperature of 350 to 400 ° C. A method for producing a solid fuel having the same is disclosed.

  Solid fuels obtained from biomass containing chlorine compounds have a high chlorine content, and such solid fuels require measures against corrosion of combustion facilities and exhaust gas treatment facilities. Therefore, it is required to reduce the chlorine content of the solid fuel. Patent Document 3 discloses a method of washing a solid fuel with water in order to reduce the chlorine content of the solid fuel produced by roasting from a raw material containing biomass.

JP 2006-26474 A JP 2009-191085 Special Publication 2009-540097

  However, solid fuels obtained from biomass containing chlorine compounds have a high chlorine content and are difficult to use as boiler fuel. Therefore, post-treatment for reducing the chlorine content, countermeasures against corrosion of combustion equipment, and exhaust gas treatment equipment are required, but the cost increases.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have chlorinated woody biomass under the conditions of an oxygen concentration of 10% or less and a furnace temperature of 250 to 500 ° C., thereby producing chlorine. It has been found that a solid fuel having a content of 0.002% or less can be produced efficiently.

  According to the present invention, a solid fuel having a low chlorine content can be efficiently produced without roasting woody biomass in a specific temperature range without performing special treatment such as washing. In addition, the solid fuel obtained by the production method of the present invention has a high substance yield and a calorie yield, and has a pulverization property equivalent to that of coal and a high density. As a fuel for pulverized coal boilers, it can be used by mixing at a high ratio.

  In the present invention, woody biomass is used as a raw material. Woody biomass includes wood chips, bark, sawdust, sawdust and the like. At present, these woody biomass is not often used and is often discarded. The tree species can be either hardwood or softwood.

  In the present invention, the woody biomass is preferably a pulverized product pulverized to a size of 0.1 to 100 mm, more preferably 0.1 to 50 mm. In the present invention, the size of the pulverized woody biomass is obtained by sieving according to the size of the circular hole of the sieving device. As an apparatus for pulverizing the woody biomass, it is preferable to pulverize with a knife cutting type biomass fuel chipper.

In the present invention, the woody biomass is preferably densified. Densification in the present invention means a process of forming a pulverized woody biomass into briquettes or pellets. By performing the molding process, the bulk density can be significantly increased. Although the bulk density before woody pulverized biomass densifying is about ^{0.01g / cm 3 ~0.3g / cm 3} , the bulk density after densification is 0.55 g / ^cm 3 to 1 0.0 g / cm ³ .

The bulk density of the pulverized woody biomass after the densification treatment is preferably 0.55 g / cm ³ or more, and more preferably 0.6 g / cm ³ or more. When the bulk density is less than 0.55 g / cm ³ , the volume in the grinding chamber of the pulverized coal mill increases when the solid fuel is burned with the fuel as fuel and spills out of the grinding chamber. Since the ratio cannot be increased too much, the effect of the present invention cannot be obtained to the maximum.

  Before densification in the present invention, it is desirable that the water content of the bark pulverized product is 10 to 50%. If the water content is less than 10%, clogging occurs inside the briquetter or pelletizer, and a stable molded product cannot be produced. If the water content exceeds 50%, it cannot be molded and is discharged in the form of powder or paste.

  In this invention, you may add 0-50 mass parts of binders with respect to 100 mass parts of woody biomass. The binder is not particularly limited, but an organic polymer (such as lignin), an inorganic polymer (such as acrylic amide), an agricultural residue (such as bran (residue generated during the production of wheat flour)) and the like are desirable. From the viewpoint of efficiently using woody biomass efficiently, it is desirable that the number of added parts of the binder is small, and 0 to 50 parts by weight, more preferably 0 to 20 parts by weight with respect to 100 parts by weight of woody biomass. desirable. However, even if 50 parts by mass or more is added, it is not impossible to increase the density.

  In the present invention, the apparatus for performing the densification treatment is not particularly limited, but a briquetter (made by Kitagawa Iron Works Co., Ltd.), a ring die type pelletizer (made by CPM Co., Ltd., made by Miike Iron Works Co., Ltd.) A flat die type pelletizer (manufactured by Dalton Co., Ltd.) is desirable.

  The torrefaction in the present invention is a process of heating in a low oxygen atmosphere at a temperature lower than a so-called carbonization process. The normal carbonization temperature of wood is 400-1200 ° C., but roasting is performed at a lower temperature. By performing the roasting, a solid fuel having an energy density higher than that of the starting material can be obtained.

  The treatment conditions for roasting in the present invention are an oxygen concentration of 10% or less and a furnace temperature of 250 to 500 ° C. When the oxygen concentration exceeds 10%, the substance yield and the calorie yield are lowered. Moreover, when the furnace temperature is less than 250 ° C., it is insufficient to reduce the chlorine content, and the grindability described later is insufficient. When the furnace temperature exceeds 500 ° C., the reduction of the chlorine content reaches its peak. Moreover, when temperature exceeds 350 degreeC, the fall of a substance yield and a calorific value yield will become remarkable. Therefore, considering the substance yield and the heat yield, the furnace temperature is preferably 250 to 400 ° C, more preferably 260 to 350 ° C. Hemicellulose is prone to thermal decomposition at around 270 ° C, whereas cellulose is prone to thermal decomposition at around 355 ° C, and lignin is prominent at around 365 ° C. Thus, it is speculated that hemicellulose can be preferentially pyrolyzed to produce a solid fuel that can achieve both material yield and pulverization.

  In the present invention, the apparatus for performing the roasting treatment is not particularly limited, but a rotary kiln and a vertical furnace are preferable. In order to adjust the oxygen concentration to 10% or less, the inside of the apparatus is preferably replaced with an inert gas such as nitrogen. The treatment time is preferably 1 to 180 minutes, more preferably 1 to 60 minutes. Moreover, you may use an external heating type rotary kiln as an apparatus for performing a roasting process. An externally heated rotary kiln has a structure in which part or all of the kiln inner cylinder is covered with the kiln outer cylinder. The wood biomass is roasted in the inner cylinder, and fuel is burned in the outer cylinder. The woody biomass inside the cylinder is indirectly heated.

  The solid fuel obtained by the present invention has a material yield of 60 to 95% and a calorific yield of 70 to 95% with respect to the raw woody biomass. The hard glove grindability index (HGI) defined in JIS M 8801: 2004, which is an index of grindability, is preferably 30 or more, and more preferably 40 or more. It shows that it becomes easy to grind, so that HGI becomes high. If HGI is in the range of 30 to 70, it can be mixed with coal and pulverized. Since the HGI of coal is usually 40 to 70, the solid fuel obtained in the present invention has the same pulverizability as coal.

  EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

[Example 1]
Eucalyptus chips were pulverized with a knife cutting type biomass fuel chipper (Wood Hacker MEGA360DL, manufactured by Green Products Co., Ltd.). After pulverization, the bark pulverized material that passed through a 70 mm screen was used as a raw material, and a drying treatment was performed at 120 ° C. for 10 minutes using a dryer. The water content of the obtained product was adjusted to 12%, and the die hole diameter was 6 mm and the die thickness was 36 mm using a ring die pelletizer (MIIKE Multipurpose Granulator Pellet Mill SPM-500, manufactured by Miike Iron Works Co., Ltd.). Density treatment was performed using a ring die to obtain pellets with a bulk density of 0.60 g / cm ³ . Subsequently, using this pellet as a raw material, using a small kiln type carbonization furnace, nitrogen purge (oxygen concentration of less than 1%), and roasting was performed at a furnace temperature of 260 ° C. and a residence time of 30 minutes to obtain a solid fuel.

[Example 2]
A solid fuel was obtained in the same manner as in Example 1 except that the furnace temperature was 280 ° C.

[Example 3]
A solid fuel was obtained in the same manner as in Example 1 except that the furnace temperature was 300 ° C.

[Example 4]
A solid fuel was obtained in the same manner as in Example 1 except that the furnace temperature was 500 ° C.

[Comparative Example 1]
The pellet prepared in Example 1 was used as a solid fuel without being roasted.

[Comparative Example 2]
A solid fuel was obtained in the same manner as in Example 1 except that the furnace temperature was 200 ° C.

[Comparative Example 3]
A solid fuel was obtained in the same manner as in Example 1 except that the furnace temperature was 240 ° C.

[Comparative Example 4]
A solid fuel was obtained in the same manner as in Example 1 except that the furnace temperature was 600 ° C.

The following items were evaluated for the products obtained in Examples 1 to 4 and Comparative Examples 1 to 4, and the results are shown in Table 1.
Chlorine content: Chlorine concentration was measured by ion chromatography according to JIS Z 7302-6 and calculated based on this.
Material yield: calculated from the weight of the sample before and after roasting.

  As shown in Table 1, the solid fuels of Examples 1 to 4 had a chlorine content of 0.002% or less. In particular, Examples 1 and 2 also had a high substance yield. On the other hand, in Comparative Examples 1 to 4, the chlorine content exceeded 0.002%.

Claims (2)

The pulverized size eucalyptus 0.1~100mm treated densified such that the bulk density ^{0.55g / cm 3 ~1,0g / cm 3} , an oxygen concentration of 10% or less, and the furnace temperature 250 A solid fuel having a chlorine content of 0.002% or less, measured according to JIS Z 7302-6, obtained by roasting at 350 ° C. The pulverized size eucalyptus 0.1~100mm treated densified such that the bulk density ^{0.55g / cm 3 ~1,0g / cm 3} , an oxygen concentration of 10% or less, and the furnace temperature 250 A method for producing a solid fuel having a chlorine content measured according to JIS Z 7302-6 of 0.002% or less, characterized by roasting under conditions of 350 ° C.