JP5796550B2 - Method for producing solid fuel from lignocellulosic material - Google Patents

Description

  The present invention relates to a method for producing a fuel using a lignocellulosic material as a raw material. More specifically, the present invention relates to a method for producing a fuel having a high energy density by hydrothermally treating a lignocellulosic material to remove most of hemicellulose by acid hydrolysis and then drying it.

Renewable biomass-derived energy has attracted attention against the background of global warming prevention measures. Biomass is mainly composed of lignocellulosic substances and is used as a solid fuel as it is, or after being separated into cellulose, hemicellulose, and lignin, and then converted into ethanol, butanol, etc. and used as a liquid fuel around the world. Yes. In recent years, a technique of semi-carbonizing a lignocellulosic material into a solid fuel having a high energy density is called trefaction and has attracted particular attention (Patent Documents 1 and 2). Usually, the lignocellulosic material that is in a water-containing state is once dried and then subjected to heat treatment to thermally decompose and remove hemicellulose having a relatively low calorific value in the lignocellulosic material. By increasing the energy density physically and physically, the value as a solid fuel is increased. In the treatment, the weight of the fuel is reduced and the hydrophobicity is achieved, and the value as a solid fuel excellent in transportability and storage is also increased. However, the utilization method of thermally decomposed hemicellulose is not sufficient, and it is only used as an auxiliary fuel in the production process.

It is known that hemicellulose in a lignocellulosic material can be decomposed and removed not only by thermal decomposition but also by acid hydrolysis. When hemicellulose such as xylan is hydrolyzed, it has the advantage that it is reduced in molecular weight while leaving the sugar form, and can be separated and utilized as xylooligosaccharide, xylose and the like. Further, by further proceeding with the reaction, it can be converted into furfural and utilized as furfural. Therefore, if the lignocellulosic material is used as a solid fuel as in the above-described trephination, and the hemicellulose decomposition product is also effectively used, it can be said that the hemicellulose decomposition method is not thermal decomposition but acid hydrolysis. In addition, since the lignocellulosic substance is usually in a water-containing state, it is considered that the acid hydrolysis is efficient because it does not need to be dried as in the case of thermal decomposition.

It is known that if water-containing lignocellulosic material is heated as it is or after further addition of water, the acetyl group in hemicellulose is eliminated and acetic acid is generated, which automatically becomes acidic and acid hydrolysis proceeds. (Patent Document 3). Hydrothermal treatment has advantages over pyrolysis as described above, but lignocellulosic material after hydrothermal treatment has a high moisture content and has a drawback of high drying load when converted to solid fuel.

JP 2003-206490 A Special table 2009-522097 gazette JP 2002-59118 A

In the present invention, when producing a solid fuel having a high energy density by removing hemicellulose from a lignocellulosic material, the decomposition method of hemicellulose is acid hydrolysis by hydrothermal treatment, thereby realizing effective utilization of the hemicellulose decomposition product, It solves the conventional problem.

  The present inventors hydrolyzed the lignocellulosic material to hydrolyze hemicellulose, and then subjected to dehydration and compression treatment, followed by drying treatment to produce a solid fuel with a high energy density at the same dry load as in the refracting process. It has been found that valuable materials such as xylooligosaccharides, xylose and furfural can be simultaneously produced as hemicellulose degradation products, and the present invention has been completed.

The present invention includes the following inventions.
(1) In a method for producing a solid fuel by hydrothermally treating a lignocellulosic material, followed by dehydration and compression treatment, and further drying treatment, furfural is removed from the gas generated during the hydrothermal treatment and / or dehydration and compression treatment. A method for producing a solid fuel using a lignocellulosic material to be produced as a raw material.
(2) A method for producing a solid fuel using a lignocellulosic material as a raw material according to (1), wherein the liquid ratio during the hydrothermal treatment is 0.5 to 8.0.
( 3 ) The lignocellulose according to (1) or (2) , wherein at least one compound of various oligosaccharides and monosaccharides is produced from the liquid generated during the hydrothermal treatment and / or dehydration and compression treatment. A method for producing a solid fuel using a substance as a raw material.

  According to the present inventor, if the lignocellulosic material is hydrothermally treated to acid-hydrolyze hemicellulose, and then dehydrated and compressed, and further dried, a solid fuel having a high energy density can be obtained as in the case of the torsion. In addition, valuable materials such as xylooligosaccharides, xylose and furfural can be simultaneously produced as hemicellulose degradation products.

The lignocellulosic material used in the present invention may be either wood or non-wood, but hardwood is preferred because of the high utility value of hemicellulose degradation products. Examples of broad-leaved trees include eucalyptus globulas, eucalyptus grandis, eucalyptus eurograndis, eucalyptus perita, eucalyptus brushana, acacia melanci, acacia mangum, and acacia auricular formis. From the standpoint of sex, afforestation trees are preferred, and these materials suitable for afforestation are particularly preferred, but are not limited. Needless to say, broad-leaved trees, coniferous trees, and non-woods can be used alone or in combination, and the combination is not limited. Moreover, it can be used as a raw material at any site such as a bark or a bast portion.

  In the present invention, first, the lignocellulosic material is immersed in water, then dehydrated, and the moisture content of the lignocellulosic material is increased while removing foreign substances adhering to the lignocellulosic material. The dipping apparatus is not particularly limited, but a general chip washer is preferably used. The water for immersion is not particularly limited, such as factory water and water recovered from black liquor evaporator, but is preferably as colorless and transparent as possible and close to distilled water. At this time, agents such as surfactants and chelating agents can be added as necessary. The dehydrator after the immersion is not particularly limited, but a drainer type dehydrator is preferably used. Immersion and dehydration conditions are adjusted so that the lignocellulosic material after immersion and dehydration contains at least 50% of its own weight of water. This is because if the water content in the lignocellulose material is too low, the presence of water in the lignocellulosic material becomes non-uniform, and the acid hydrolysis reaction of hemicellulose during the hydrothermal treatment in the next step is not performed uniformly.

In the present invention, hydrothermal treatment is then performed. The hydrothermal treatment of the present invention is performed by heating the water-containing lignocellulose material as it is or after adding water. Heating is usually performed by directly adding steam, but is not particularly limited, and indirect heating or the like can be performed depending on circumstances. The liquid ratio during hydrothermal treatment is 0.5 to 8.0, preferably 1.0 to 4.0, the temperature is 140 to 200 ° C., preferably 150 to 180 ° C., and the treatment time depends on the treatment temperature, but 10 Min to 8 hours, preferably 30 minutes to 5 hours. If the liquid ratio is lower than 0.5, the acid hydrolysis reaction of hemicellulose becomes non-uniform, which is not suitable. In addition, the concentration of hemicellulose degradation products in the filtrate is lowered, and these are not suitable because they are separated and purified, and a large load is applied when they are used effectively. If the temperature is lower than 140 ° C., acid hydrolysis of hemicellulose is insufficient, and if it is higher than 200 ° C., the frequency of cellulose decomposition is increased, which is not suitable. When the treatment time is less than 10 minutes, acid hydrolysis of hemicellulose is insufficient, and when the treatment time is longer than 8 hours, the reaction vessel for hydrothermal treatment becomes huge, which is not economical and is not suitable. As a means to increase the acid hydrolysis rate of hemicellulose during hydrothermal treatment, it is possible to add acids such as acetic acid, sulfuric acid, and sulfurous acid. However, the quality of the solid fuel may be impaired. It is a preferred embodiment that does not. The apparatus used in the hydrothermal treatment is not particularly limited, but a pressure vessel such as a pressurized chip bin or a digester for producing paper pulp is preferably used. In addition, since the gas generated during hydrothermal treatment contains a large amount of furfural, which is a decomposition product of hemicellulose, it is also a preferable practical form of the present invention that the gas is separated and separately distilled to produce furfural. is there.

In the present invention, after the lignocellulosic material is hydrothermally treated, dehydration and compression are performed. In the present invention, if necessary, it is possible to add a dilution water before the dehydration and compression treatment to give a cleaning effect. The apparatus used in the present invention is not particularly limited, but a combination of a strainer-type dehydrator and a compression-type dehydrator is good, and the latter dehydrator is easy to control the dehydration amount and pressure. A plug screw type is preferably used. The present invention is characterized in that the waste liquid from which the hemicellulose decomposition product is eluted during the dehydration and compression processes can be separated and utilized. The separated waste liquid can be separated into a gas layer and a liquid layer by sending it to a flash tank, and furfural contained in a large amount in the gas layer can be separated, purified and commercialized relatively easily by distillation. On the other hand, monosaccharides such as various oligosaccharides, xylose and mannose, which are hemicellulose degradation products contained in a large amount in the liquid layer, can be easily separated, produced and commercialized by conventional methods.

In the present invention, after the dehydration and compression treatment, the drying treatment is performed. The drying treatment conditions of the present invention are not particularly limited as long as the moisture of the solid fuel after drying is 5% or less, but from the viewpoint of improving the calorific value of the solid fuel, it is preferably carried out in a nitrogen atmosphere. Although the apparatus used for the drying process of this invention is not specifically limited, A rotary kiln type | mold has good drying efficiency, and is used suitably. Depending on the use of the solid fuel, it can be molded like a pellet before the drying treatment.

Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to these examples. Unless otherwise indicated, xylose, xylooligosaccharide, and furfural were quantified by the following methods.

[Quantification of xylose]
The sugar analysis system (ICS5000) made by DIONEX was used for quantification of xylose in the sample solution. The column was Carbo Pac PA-1 (2 × 250 mm), and a 20 mM NaOH solution was used as an eluent, and measurement was performed at a flow rate of 0.25 ml / min. For detection, a pulse amperometry detector was used, a calibration curve was prepared using a xylose sample, and the xylose content in the filtrate was determined.

[Quantification of xylooligosaccharides]
Sulfuric acid was added to the sample solution so as to have a final concentration of 4% by mass, hydrolysis was performed at 120 ° C. for 1 hour, and then xylose was quantified. A value obtained by subtracting the xylose content in the sample before hydrolysis from this value was calculated as the xylooligosaccharide content.

[Quantification of furfural]
For the determination of furfural in the sample solution, an HPLC system manufactured by Agilent Technologies was used. Aminex HPX87P (7.8 × 300 mm) manufactured by Bio-Rad was used as the column, and measurement was performed at a flow rate of 1 ml / min using 5 mM sulfuric acid as an eluent. A UV-Vis detector was used for detection. Using a furfural sample, a calibration curve was prepared to determine the content in the sample.

Example 1
Eucalyptus / perita material chips (300 g) were collected in an absolutely dry weight and immersed in 10 liters of tap water overnight. Thereafter, the chips were taken out, emptied through a 400 mesh sieve, and filtered. The dehydrated chip was placed in a 2.5 liter autoclave, 7K steam was injected, the temperature was raised to 165 ° C., and hydrothermal treatment was performed at 165 ° C. for 60 minutes. When water contained in 7K vapor was also added, the liquid ratio during hydrothermal treatment was 2.5. After the hydrothermal treatment, the waste liquid is extracted from a waste liquid cock having an autoclave strainer and sent to a flash tank. S). The dehydrated chip is again placed in a 2.5 liter autoclave, the air in the autoclave is replaced with nitrogen gas, heated to 165 ° C by indirect heating using an electric heater, and heated at 165 ° C for 100 minutes. Processed to solid fuel. The absolute dry weight of this solid fuel was 257 g, and the yield was 85.8% per chip. The amount of heat of the solid fuel was 4722 cal / g as a result of measurement using a calorimeter (trade name: 1013-J, manufactured by Yoshida Seisakusho Co., Ltd.).

The hydrothermal treatment waste liquid sent to the flash tank was separated into a gas layer and a liquid layer. The gas layer was cooled to 60 ° C. and drained, and then the furfural was quantified. The amount of furfural was 0.3% based on the dry weight of the chip. On the other hand, the liquid separated in the slush tank was used as the recovered liquid together with the squeezed liquid discharged by the desktop press. The amount of xylooligosaccharides in the recovered solution was 5.6% per chip dry weight, and the amount of xylose was 1.8%. Table 1 shows the results.

Example 2
In Example 1, the same operation as in Example 1 was performed except that the hydrothermal treatment condition was changed from 60 minutes to 100 minutes. Table 1 shows the results.

Example 3
In Example 1, the same operation as in Example 1 was performed except that the hydrothermal treatment condition was changed from 60 minutes to 180 minutes. Table 1 shows the results.

Example 4
In Example 2, the liquid ratio at the time of hydrothermal treatment was changed from 2.5 to 0.5, and after hydrothermal treatment, the liquid was drained by adding warm water (100 ° C.) corresponding to the liquid ratio 2 before liquid removal. The same operation as in Example 2 was performed. Table 1 shows the results.

Example 5
In Example 2, the same operation as in Example 2 was performed except that the liquid ratio was changed from 2.5 to 8.0 by adding water during hydrothermal treatment. Table 1 shows the results.

Example 6
In Example 2, the same operation as in Example 2 was performed except that the eucalyptus / perita material chip was changed to eucalyptus / globula. Table 1 shows the results.

Comparative Example 1
Extract 300g of Eucalyptus / Perita chips in an absolutely dry mass, dry them at 105 ° C overnight using a blower dryer, place them in a 2.5 liter autoclave, and replace the air in the autoclave with nitrogen gas. did. Then, it heated to 240 degreeC by indirect heating using the electric heater, and heat-processed at 240 degreeC for 100 minutes, and was made into solid fuel. The absolute dry weight of this solid fuel was 243 g, and the yield was 81.0% per chip. Moreover, the calorific value of the solid fuel was 5290 cal / g as a result of measurement using a calorimetric analyzer (trade name: 1013-J, manufactured by Yoshida Seisakusho Co., Ltd.). Table 1 shows the results.

As is clear when comparing Examples 1 to 6 and Comparative Example 1 in Table 1, the lignocellulose material was hydrothermally treated to hydrolyze hemicellulose, and then the hemicellulose degradation product was removed and separated by dehydration and compression treatment. It can be seen that if the drying treatment is performed, a solid fuel that is inferior to a solid fuel produced by a conventional trefflection technique can be produced, and in addition, valuable materials such as xylooligosaccharides, xylose, and furfural can be produced from hemicellulose decomposition products. The present invention is characterized in that a degradation product of hemicellulose, which could not be used in conventional treffection, can be effectively used as a valuable material.

Claims (3)

In the method of producing a solid fuel by hydrothermally treating a lignocellulosic material, then dehydrating and compressing, and further drying , producing furfural from the gas generated during the hydrothermal treatment and / or dehydration and compression treatment A method for producing a solid fuel using a lignocellulosic material as a raw material.   2. The method for producing a solid fuel using a lignocellulosic material as a raw material according to claim 1, wherein the liquid ratio during the hydrothermal treatment is 0.5 to 8.0. The ligno according to claim 1 or 2 , wherein at least one compound of various oligosaccharides and monosaccharides is produced from a liquid generated during the hydrothermal treatment and / or dehydration and compression treatment. A method for producing a solid fuel using a cellulose material as a raw material.