Solid fuel manufacturing method

Abstract

Provided is a method for producing a high-calorific-value solid fuel from biomass at a high yield. SOLUTION: A method for producing solid fuel from biomass, comprising a dissolving step of reacting biomass with a dissolving reaction liquid containing vanadium ions.

Description

[Technical Field]

[0001] The present invention relates to a method for obtaining a suitable solid fuel from biomass, a method for effectively utilizing resources discharged in the process of obtaining the solid fuel, and a system used therefor. [Background technology]

[0002] JP 2013-14737 A describes a method for producing high-heat-value fuel from biomass. This method requires a high-temperature reaction to obtain fuel, and the fuel yield is low. For this reason, a more efficient method for producing solid fuel has been desired. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-14737 Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention aims to provide a method for producing solid fuel by dissolving biomass, a method for effectively utilizing resources generated in the process of producing solid fuel, and a system for use in the method. [Means for solving the problem]

[0005] The present invention achieves one of the above-mentioned objects and is based on the finding from examples that a high calorific value solid fuel can be produced in high yield by adding vanadium ions to a solution for dissolving biomass.

[0006] The above-mentioned problems can be solved by the method of the present invention, which includes a dissolution step of reacting biomass with a dissolution reaction solution containing vanadium ions. [Effects of the Invention]

[0007] As demonstrated in the examples, dissolving biomass in a vanadium ion solution allows for the production of high-calorific-value solid fuel in high yields. Furthermore, the resulting solid fuel contains high-purity lignin. Furthermore, the process for producing such solid fuel can also be used to generate electricity effectively. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a block diagram illustrating an example of an apparatus for producing solid fuel. [Figure 2] FIG. 2 is a block diagram showing another example of the apparatus for producing solid fuel, different from that shown in FIG. [Figure 3] FIG. 3 is a block diagram illustrating an example of the configuration of a power generation system. [Figure 4] FIG. 4 shows a conceptual diagram of a solid fuel production device. [Figure 5] FIG. 5 shows a conceptual diagram of a power generation system using a solid fuel production device. [Figure 6] FIG. 6 is a photograph, in place of a drawing, showing the biomass before the test. [Figure 7] FIG. 7 is a graph, instead of a drawing, showing a temperature profile in an example. [Figure 8] FIG. 8 is a photograph, in place of a drawing, showing the biomass after the test. [Figure 9] FIG. 9 is a graph, instead of a drawing, showing the results of composition analysis of the residue and fuel liquid obtained after the test. [Figure 10] FIG. 10 is a graph, instead of a drawing, showing the results of IR analysis of the residue obtained after the test. DETAILED DESCRIPTION OF THE INVENTION

[0009] A method for producing solid fuel from biomass will be described below, which includes a dissolving step of reacting biomass with a dissolving reaction solution containing vanadium ions.

[0010] This method includes a dissolution step and a solid residue recovery step. FIG. 1 is a block diagram showing an example of an apparatus for producing solid fuel. As shown in FIG. 1, this solid fuel production apparatus 1 has a dissolution reactor 5, a fuel surge tank 7, and a water separator 9. The water separator 9 is an optional element. As shown in FIG. 1, the solid fuel production apparatus 1 may have either or both of a raw material input section 13 and a dissolution reaction liquid input section 19. In the example shown in FIG. 1, a filter 11 is present in the dissolution reactor 5. In addition, in the example shown in FIG. 1, the dissolution reactor 5 and the fuel surge tank 7 are connected via a connection section 15 so as to transport the liquid.

[0011] Pretreatment process The pretreatment step is an optional step for processing biomass into a state suitable for the reaction in the dissolution step. In the pretreatment step, the biomass may be washed or crushed to an appropriate size so that the biomass can be suitably dissolved in the dissolution step. The pretreatment step may be omitted, or the dissolution step may be performed immediately after the pretreatment step. Biomass is typically a naturally occurring organic resource, has renewable resource properties, and may be an animal or plant-derived resource that serves as a carbon source. Examples of animal and plant-derived biomass include wood, wood chips, agricultural residues, livestock manure, food waste (e.g., tea leaves, beer pomace), seaweed, waste oil (e.g., used cooking oil), waste paper, and cardboard. Plant-derived biomass is preferred. Plant-derived biomass includes, for example, cellulose, hemicellulose, and lignin. If the biomass is solid, it is preferable to perform a dissolution step before sending it to the fuel converter 25.

[0012] Melting process In the dissolution step, the biomass is reacted in a dissolution reaction solution containing a mediator (vanadium ions), which preferably contains an acid. Vanadium ions refer to ions of vanadium, e.g., V 2+ ,V 3+ ,VO 2+ , and VO2+ Any cation containing vanadium such as the above may be used. The vanadium ions contained in the dissolution reaction solution are preferably oxidized vanadium ions, and may be divalent to pentavalent vanadium ions, preferably trivalent to pentavalent vanadium ions, or may be tetravalent vanadium ions. In other words, the vanadium ions preferably function as an oxidizing agent. The vanadium ions added to the dissolution reaction solution may be obtained by dissolving vanadium pentoxide (VO) in dilute sulfuric acid or dilute nitric acid, by dissolving vanadium(III) chloride in hydrochloric acid or nitric acid, or by dissolving vanadium(IV) oxide in an acid. A preferred example of vanadium ions in the dissolution reaction solution is vanadyl ions (VO 2+ ) Vanadyl ion (VO 2+ ) is a vanadium oxide ion containing tetravalent vanadium. The vanadyl ion may be derived from, for example, a VOSO4 aqueous solution or may be obtained by dissolving vanadium (IV) oxide in an acid. A commercially available dissolution reaction solution may be used as appropriate. The dissolution reaction solution preferably further contains an acid, which can promote the hydrolysis reaction of polysaccharides in the biomass during the dissolution step. Examples of acids include phosphoric acid, sulfuric acid, nitric acid, and hydrochloric acid. The vanadium ions may be added to the dissolution reaction solution after the dissolution step, or the anode effluent obtained in the electrochemical conversion step described below may be added to the dissolution reaction solution.

[0013] The dissolution reactor 5 is a vessel portion for containing a dissolution reaction solution and reacting the raw materials with the dissolution reaction solution. The dissolution reactor 5 preferably has a stirrer. The dissolution reactor 5 also preferably has elements for solid-liquid separation, such as a filter 11 or a filtering section. The dissolution reactor 5 has, for example, a raw material input section 13 and a connection section 15 with the fuel surge tank 7. In the example shown in Figure 1, the dissolution reactor 5 has a water separator 9 and a dissolution reaction liquid input section 19 upstream thereof. The raw material input section 13 is an element for inputting raw materials into the dissolution reactor 5. The raw material input section 13 may have a rotary valve so that the biomass can be input into the dissolution reactor 5 continuously or batchwise. The biomass may be made into a slurry and input using a slurry pump. When the biomass is made into a slurry, the biomass may be mixed with a dissolution reaction liquid. Alternatively, the dissolution reaction liquid may be input through the raw material input port 13. The connection 15 to the fuel surge tank 7 is an element for guiding the fuel liquid obtained in the dissolving process to the fuel surge tank 7. An example of the connection 15 is a conduit. Various elements may be present along the connection 15. Examples of elements present along the connection 15 are a valve, a sensor, and a pipe for injecting another liquid into the liquid moving through the connection. The water separator 9 is an optional element for cooling gases such as water vapor generated in the dissolution reactor 5 and releasing a portion of the water outside the system. The water separator 9 may also return a portion of the water obtained by cooling the gas to the dissolution reactor 5. The dissolution reaction liquid input unit 19 is an optional element for inputting the dissolution reaction liquid into the dissolution reactor 5. The dissolution reaction liquid may be the anode discharge liquid described below. The dissolution reaction liquid input unit 19 may be used to input the dissolution reaction liquid, an acid, or a liquid containing a mediator into the dissolution reactor 5.

[0014] An aqueous acid solution may initially be present in the dissolution reactor 5. After the raw materials are added, the aqueous acid solution may be stirred to dissolve the raw materials, and then vanadium ions may be added. However, a dissolution reaction solution containing vanadium ions may be present in the dissolution reactor 5 from the beginning. An acid may be added to this dissolution reaction solution in advance. Below, each step will be described based on an example using vanadyl ions and sulfuric acid. However, each step may use other vanadium ions or other acids. Furthermore, the dissolution reaction solution may contain various catalysts or other elements.

[0015] The concentration of vanadium sulfate (VOSO4) (ion component) added to the dissolution reaction solution may be, for example, 0.01 mol / L or more and 100 mol / L or less, 0.1 mol / L or more and 10 mol / L or less, 0.1 mol / L or more and 5 mol / L or less, or 0.5 mol / L or more and 1.8 mol / L or less. The concentration of sulfuric acid (acid) in the dissolution reaction solution may be, for example, 0.01 mol / L or more and 100 mol / L or less, 0.1 mol / L or more and 10 mol / L or less, 1 mol / L or more and 10 mol / L or less, or 1.8 mol / L or more and 3 mol / L or less. The dissolution reactor 5 preferably has a heating unit (not shown). The temperature of the dissolution reaction liquid in the reaction chamber is, for example, 50°C or higher and 1000°C or lower, or may be 50°C or higher and 500°C or lower, 100°C or higher and 300°C or lower, or 150°C or higher and 250°C or lower. The pressure inside the dissolution reactor 5 is preferably adjusted to be equal to or higher than the vapor pressure of the dissolution reaction liquid. On the other hand, it is preferable to prevent the pressure inside the dissolution reactor 5 from becoming higher than the endurable pressure of the dissolution reactor 5.

[0016] The vapor in the dissolution reactor 5 may be led through a conduit to the water separator 9. The conduit may have a cooling section, and the vapor may be introduced into the water separator 9 as a liquid. For example, the biomass is reacted with the dissolution reaction solution under stirring for 1 minute to 1 day (it may be 10 minutes to half a day, 20 minutes to 5 hours, or 0.5 hours to 4 hours). This causes a reaction in which the cellulose and hemicellulose contained in the biomass are dissolved in the liquid phase. The dissolved cellulose and hemicellulose become sugars and dissolve in the liquid phase. On the other hand, lignin remains almost undissolved in the dissolution reaction solution. In addition, the tetravalent vanadyl ion (VO 2+ ) is partly composed of trivalent vanadium ions (V 3+ The reaction mixture is reduced to vanadyl ions (VO 2+As shown in the examples below, the presence of vanadyl ions (VO ) increases the solubility of cellulose and hemicellulose and also increases the purity of lignin in the residue. For this reason, for example, when biomass is continuously fed into the dissolution reactor 5 or when new biomass is fed into the dissolution reactor 5 by batch processing, it is recommended to use vanadyl ions (VO 2+ It is preferable to introduce a vanadyl ion source into the dissolution reactor 5. An example of such a vanadyl ion source is the anode effluent, which will be described later.

[0017] The filter 11 installed in the dissolution reactor 5 is an element for preventing biomass residue (solid fuel) from flowing into the connecting part 15. The filter 11 may have an appropriate mesh size to match the size of the material that passes through the filter 11. A hole for connecting to the connecting part 15 is formed in the bottom surface of the dissolution reactor 5, and the filter 11 may be installed to cover the hole. Although not shown, the bottom surface of the dissolution reactor 5 may be flat like a normal chamber, or may have a shape in which the area where the filter 11 is installed (e.g., the central area of ​​the bottom surface) is raised (elevated) compared to the surrounding area. The height of the raised area may be adjusted appropriately depending on the size of the dissolution reactor 5 and the amount of biomass to be introduced. Such a shape can prevent biomass residue (solid fuel) from accumulating around the filter 11 and on the filter 11.

[0018] Solid residue recovery process The solid residue recovery step is a step for recovering the solid residue of the biomass after the dissolution step. The dissolution reactor 5 may have a solid-liquid separator such as a filter 11 or a filtering section inside the dissolution reactor 5. The dissolution reactor 5 may have a lid, and opening the lid may open the dissolution reactor 5 so that the solid residue of the biomass can be recovered.

[0019] FIG. 2 is a block diagram showing another example of an apparatus for producing solid fuel, different from that shown in FIG. 1. In this example, a solid-liquid separator 17 is provided outside the chamber of the dissolution reactor 5. In this way, the apparatus 1 may have the solid-liquid separator 17 separate from the dissolution reactor 5. As shown in FIG. 1, a hole for connecting to the connecting part 15 may be provided at the bottom of the dissolution reactor 5, or as shown in FIG. 2, a hole for connecting to the connecting part 15 may be provided at the side of the dissolution reactor 5. In the case of FIG. 2, the main part of the solid residue may be deposited at the bottom of the dissolution reactor 5, and a portion of the solid residue conveyed to the connecting part 5 may be separated by the solid-liquid separator 17. However, the biomass residue present in the dissolution reactor 5 may also be conveyed to the solid-liquid separator 17 and separated into a solid portion and a solution portion by the solid-liquid separator 17. Alternatively, as shown in FIG. 1, a filter 11 may be provided inside the dissolution reactor 5, and the solid-liquid separator 17 may be provided outside the dissolution reactor 5. The solid-liquid separator 17 may be provided between the fuel surge tank 7 and the dissolution reactor 5, or may be provided downstream of the fuel surge tank 7.

[0020] The biomass reacts with the dissolution reaction solution, and the partially dissolved biomass is separated into a residue component and a component in which the biomass is dissolved in the dissolution reaction solution. These are separated into the residue and the dissolved component in the solution by a solid-liquid separator 17. After the residue is collected, a post-treatment process may be performed. The post-treatment process is the final process for purifying the product and properly disposing of waste. Specifically, after the biomass residue is collected, it can be washed and dried as needed to obtain solid fuel. As shown in the examples below, this residue contains highly purified lignin. Therefore, this apparatus 1 can also function as an apparatus for producing (high-purity) lignin. The produced lignin can be used as solid fuel, and because it has an aromatic polymer skeleton, it can be used as a raw material for phenol derivatives and aromatic chemicals through oxidation, decomposition, catalytic reforming, etc. Thus, this apparatus can also be used to produce lignin as a chemical raw material. The solution separated by the filter 11 or the solid-liquid separator 17 contains a large amount of reducing sugar components and vanadyl ions (VO 2+), as well as vanadium ions (V 3+ ) and sulfate ions. This solution is introduced into the fuel surge tank 7 as appropriate. The vanadium ions are utilized in the power generation system described below, and may be converted into a liquid containing vanadyl ions as the anode discharge liquid.

[0021] Fig. 3 is a block diagram for explaining an example configuration of a power generation system. As shown in Fig. 3, the power generation system 21 includes a dissolution reactor 5, a fuel converter 25, a heat exchanger 27, a carbon dioxide separator 29, and a power generation cell 31. The power generation cell 31 is a site where an electrochemical reaction occurs. The power generation system 21 is an apparatus for obtaining electric power using the above-described solid fuel production apparatus 1. However, since the example shown in Fig. 3 can also function as a battery system, it may be a system that is not intended to produce solid fuel. Solid biomass may be introduced into the dissolution reactor 5 in the power generation system 21 shown in FIG. 3. A liquid containing vanadium ions and sulfate ions is stored in the fuel surge tank 7. The fuel surge tank 7 is an element for holding the dissolution reaction liquid (fuel liquid) after the reaction in the dissolution reactor 5, from which residue has been removed. This fuel liquid contains dissolved biomass, which is a component derived from biomass that has passed through the dissolution reactor and dissolved in the liquid phase. The fuel liquid in the fuel surge tank 7 is used as a reducing agent in the electrochemical reaction described below. However, the power generation system 21 does not necessarily require the fuel surge tank 7 to be present.

[0022] Fuel Converter 25 The fuel converter 25 is an element for oxidizing sugar components contained in the fuel liquid into carbon dioxide and water. The fuel liquid containing the dissolved biomass together with the dissolution reaction liquid is sent to the fuel converter 25 from the dissolution reactor 5 via the connection part 15. Vanadyl ions (VO 2+ ), the vanadium ions (V 3+) This process is also called the chemical energy conversion process. In the fuel converter 25, the biomass dissolved in the fuel liquid may be oxidized. The liquid containing the mediator (vanadyl ions) reduced by the fuel converter 25 is transferred to the next heat exchanger 27 or the power generation cell 31 via, for example, a connecting pipe. The mediator refers to a chemical species that mediates the exchange of electrons in an oxidation-reduction reaction.

[0023] The fuel converter 25 may have, for example, a mechanism (catalyst layer) in which a solid catalyst is packed in a tubular container. The solid catalyst may be any catalyst capable of decomposing sugar into carbon dioxide and water. Examples of such solid catalysts include metal catalysts, metal oxide catalysts, mixed oxide catalysts, photocatalysts, peroxides, and radical-generating catalysts. Examples of metal catalysts include platinum (Pt), palladium (Pd), ruthenium (Ru), rhodium (Rh), iridium (Ir), gold (Au), silver (Ag), and catalysts supporting Pt or Pd. Examples of metal oxide catalysts include copper oxide (CuO, Cu2O), manganese oxide (MnO2), iron oxide (Fe2O3, Fe3O4), cobalt oxide (Co3O4), chromium oxide (Cr2O3), nickel oxide (NiO), cerium oxide (CeO2), and vanadium oxide (VO5). Examples of mixed oxide catalysts include perovskite-type oxides (e.g., LaMnO3 and LaCoO3), spinel-type oxides (e.g., MgAl2O4), zeolite-supported metal catalysts (e.g., Pt / ZSM-5), and ceria-zirconia catalysts (CeO2-ZrO2). Examples of photocatalysts include titanium dioxide (TiO2), nitrogen-doped titanium dioxide, ZnO (zinc oxide), CdS (cadmium sulfide), graphitic carbon nitride, and BiVO4 (bismuth vanadate). Examples of peroxide and radical-generating catalysts include Fenton reaction catalysts. These catalysts can be used alone or in combination. These solid catalysts may be supported on a carrier.

[0024] The fuel converter 25 is preferably adjusted to an appropriate temperature depending on the type of catalyst. The temperature inside the fuel converter is between 50°C and 1000°C, and may be between 50°C and 500°C, between 100°C and 300°C, or between 150°C and 250°C. The reaction in the fuel converter may be carried out for between one minute and one day. The reaction time may be between 10 minutes and half a day, between 20 minutes and 5 hours, or between 0.5 hours and 4 hours. The temperature inside the fuel converter is preferably adjusted to a value equal to or greater than the vapor pressure of the solution to prevent the solution from evaporating. Therefore, carbon dioxide generated by the oxidation of sugar may dissolve in the solution and exist as carbonate ions, carbonate salts, or carbon dioxide.

[0025] heat exchanger 27 The heat exchanger 27 is an element for exchanging heat between the high-temperature solution (converted fuel liquid) output from the fuel converter 25 and a low-temperature fluid (for example, a low-temperature anode discharge liquid output from a power generation cell). The heat exchanger 27 is an optional element. The low-temperature liquid may be a fuel liquid, cooling water supplied from outside the system, or cooling air. For example, the solution (dissolved reaction liquid) output from the fuel converter 25 may be subjected to heat exchange in the heat exchanger 27 and further cooled in a cooling section to be cooled to 100°C or below.

[0026] carbon dioxide separator 29 The converted fuel liquid, which is a solution output from the fuel converter 25, contains some dissolved carbon dioxide, while the rest forms bubbles and is sent to the carbon dioxide separator 29 in a gas-liquid mixed phase state. The carbon dioxide separator 29 is an optional element. The carbon dioxide is separated by the carbon dioxide separator 29 and can be recovered as high-purity carbon dioxide. The carbon dioxide separator 29 preferably controls the air pressure in the gas phase section to a predetermined gauge pressure (e.g., 4 MPaG or less) using a control valve provided in the gas phase section of the carbon dioxide separator 29. The converted fuel liquid from which most of the carbon dioxide has been removed by the carbon dioxide separator 29 contains the dissolved reaction liquid and reduced vanadium ions. The carbon dioxide separator 29 may have a condenser and a water separator. The water separated by the water separator may be returned to the dissolution reactor 5.

[0027] Power generation cell 31 The power generation cell 31 includes a container for containing an electrolyte, an anode, a cathode, and an ion exchange membrane installed in the container. The electrolyte refers to a solution that allows ions to move within the power generation cell and enables oxidation-reduction reactions. An example of an electrolyte is a solution containing 1.8 M VOSO4 (vanadium electrolyte) and 3 M H2SO4 (supporting electrolyte). The structure and mechanism of the power generation cell 31 are publicly known. In the power generation cell, for example, the converted fuel solution obtained in each of the above processes is supplied to the anode side of the power generation cell as an anode feed solution, and the vanadium ions contained in the anode feed solution are oxidized to obtain an anode discharge solution containing oxidized vanadium ions. This process is also called the electrochemical conversion process. The electrochemical conversion process can be performed in the following two patterns, for example.

[0028] (1) The converted fuel liquid (anode supply liquid) from which carbon dioxide has been removed by the carbon dioxide separator 29 is sent to the anode side of the power generation cell using the operating pressure of the carbon dioxide separator 29. A solution containing dissolved vanadium ions or air is supplied to the cathode side of the power generation cell. The vanadium ions on the anode side are then oxidized, and the vanadium ions on the cathode side or the oxygen in the air are reduced. The electromotive force generated by this oxidation-reduction reaction generates electricity. For example, trivalent vanadium is supplied to the anode side and pentavalent vanadium is supplied to the cathode side, and each is oxidized or reduced to tetravalent vanadium, either in whole or in part.

[0029] (2) The converted fuel liquid (anode feed liquid), from which most of the carbon dioxide has been removed by the carbon dioxide separator 29, is sent to the anode side of the hydrogen production cell using the operating pressure of the carbon dioxide separator 29. Water is supplied to the cathode side of the hydrogen production cell and charged. The vanadium ions on the anode side are oxidized, and the water on the cathode side is reduced to hydrogen. For example, if trivalent vanadium is supplied to the anode side and water to the cathode side and charged, the trivalent vanadium is oxidized and reduced to tetravalent vanadium, and the water is oxidized and reduced to hydrogen, respectively.

[0030] In either of the above patterns, the vanadium ions supplied to the anode side are oxidized, e.g., to vanadyl ions (VO 2+ The anode effluent thus obtained may be heated appropriately via a heat exchanger 27 and added to the fuel converter 25. Alternatively, the anode effluent may be added to the dissolution reactor 5.

[0031] The power generation method described herein may include a solid residue recovery step, a chemical energy conversion step, and an electrochemical conversion step. The above-described method for producing a solid fuel may further include a chemical energy conversion step and an electrochemical conversion step after the solid residue recovery step, or may further include a vanadium oxide ion addition step after the electrochemical conversion step. The solid residue recovery step is a step of recovering the solid residue after the dissolving step. The chemical energy conversion process is a process in which biomass-derived components (e.g., reducing sugar components) contained in the fuel liquid after the solid residue recovery process are oxidized to carbon dioxide to obtain a converted fuel liquid. In other words, the chemical energy conversion process is a process for converting chemical energy by using chemical reactions to change raw materials (solution) into target compounds (fuel liquid). The electrochemical conversion process is a process for oxidizing and reducing substances using electrochemical reactions to extract electrical energy. Specifically, the electrochemical conversion process is a process in which the converted fuel liquid (anode feed liquid) obtained after the chemical energy conversion process is supplied to the anode side of the power generation cell, the vanadium ions contained in the anode feed liquid are oxidized, and an anode discharge liquid containing oxidized vanadium ions is obtained. The vanadium oxide ion addition step is a step of adding the anode discharge solution to either or both of the dissolution reaction solution in the dissolution step and the fuel solution in the chemical energy conversion step.

[0032] Another aspect of the present invention relates to a method for producing lignin from biomass. In this method, the above-mentioned solid fuel can be read as lignin. As will be shown in the examples below, the residue obtained by this method has a high purity of lignin. [Example]

[0033] Identification of vanadium ions Vanadium ions can be analyzed using known methods. For example, the presence of these ions can be analyzed by analyzing the ultraviolet absorption spectrum of the solution. For example, vanadyl ions exhibit absorption around 450 to 600 nm. After confirming the presence of vanadium ions, the valence of the ions contained in the solution can be evaluated by adding an oxidizing or reducing agent and checking the color change.

[0034] [Examples 1 and 2 and Comparative Example] Figure 4 shows a conceptual diagram of a solid fuel production apparatus in accordance with the present embodiment. The system comprises a dissolution reactor where the reaction takes place; a biomass inlet located upstream of the dissolution reactor for introducing biomass into the dissolution reactor; a dissolution reaction liquid inlet for injecting the dissolution reaction liquid into the dissolution reactor, which includes piping, a heater, and a pump for delivering the liquid; and a connection located downstream of the dissolution reactor, which includes a cooler and a back-pressure valve. Furthermore, covers and filters were installed at the connections to the various pipes of the fuel converter to prevent biomass from entering the pipes. Figure 5 shows a conceptual diagram of a power generation system using the solid fuel production apparatus.

[0035] A cylindrical container was packed with 500 mg of biomass (dried cedar) on a dry basis and sandwiched between liquid-permeable filters. The biomass was at room temperature and had a moisture content of 30-60%. This state is shown in Figure 6. Figure 6 is a photograph, replacing a drawing, showing the biomass before the test. The cylindrical container packed with biomass was placed in a dissolution reactor. A room-temperature dissolution reaction solution with the concentration shown in Table 1 was pumped at 1 mL / min and heated to the test temperature using a heater. After that, it was added to the dissolution reactor through the dissolution reaction solution inlet. More specifically, the sulfuric acid concentration of the aqueous vanadium oxide sulfate solution used in the experiment was 1-2 mol / L, and the acidity was pH -0.3 to -0.6. The pump was operated at 1 mL / min at room temperature. The aqueous vanadium oxide sulfate solution flowing through the piping was heated to 150°C in Example 1 and Comparative Example 1, and to 200°C in Example 2, using a heater, and the reaction was carried out for approximately 30 minutes. The piping (or hose) used was resistant to vanadium oxide sulfate. An aqueous solution of vanadium oxide sulfate was injected into the dissolution reactor through the lid. A (first) filter was installed inside the dissolution reactor. This filter was used to prevent the biomass in the dissolution reactor from flowing into the piping. The pressure inside the dissolution reactor was 2 MPa. The material fed into the dissolution reactor was plant biomass. A (second) filter was also installed at the biomass inlet, and a lid was prepared. Piping was installed through the lid. In this example, a cooler was prepared to cool the liquid flowing through the piping.

[0036] In the examples, the temperature of the system was controlled according to the temperature profile shown in Figure 7. After maintaining the temperature for the residence time under each condition shown in Table 1, the temperature of the system was lowered. The biomass after the test is shown in Figure 8. Figure 8 is a photograph, instead of a drawing, showing the biomass after the test. After the test, filtration was carried out to separate the residue and the solution.

[0037] Composition analysis and IR analysis were performed on the residue and solution obtained after the test. Figure 9 is a graph, instead of a drawing, showing the results of the composition analysis of the residue and solution obtained after the test. From left to right, the graph shows the raw material, Example 1 (residue), Example 2 (residue), Comparative Example 1 (residue), lignin (dealkalized), Example 1 (solution), Example 2 (solution), cellulose, hemicellulose, and monosaccharides. Figure 10 is a graph, instead of a drawing, showing the results of IR analysis of the residue obtained after the test. The horizontal axis represents wavenumber, and the vertical axis represents absorption. From bottom to top, the graph shows Example 1, Example 2, Comparative Example 1, and lignin (dealkalized).

[0038] The residue yield, calorific value, and amount of heat recovered from biomass are shown in Table 1. The Steuer equation was used to calculate the calorific value. The Steuer formula calculates the calorific value from the elemental composition (carbon C, hydrogen H, sulfur S, oxygen O [%]). It assumes that the oxygen in the combustible matter is CO and the other half is bonded in the form of HO, and calculates the calorific value using the following formula: Hh=339.4(C-(3 / 8)O)+238.8×(3 / 8)O+1435.1(HO / 16)+94.3·S

[0039] [Table 1]

[0040] Consideration FIG. 9 shows that the residues (solid fuels) obtained in Examples 1 and 2 approached the elemental composition of pure lignin, and that the solutions (dissolved biomass) obtained in Examples 1 and 2 approached the elemental composition of monosaccharides. This tendency was stronger in Example 1 than in Example 2. FIG. 9 shows that the amount of cellulose contained in the biomass raw material was reduced in the examples. Furthermore, FIG. 10 shows that the residues (solid fuels) obtained in Examples 1 and 2 exhibited absorption spectra close to that of pure lignin. Therefore, it can be said that this method also functions as a method for producing highly pure lignin. Comparing Example 2 with Comparative Example 1 in Table 1, it can be seen that the inclusion of vanadyl ions in the dissolution reaction solution improves the residue yield by 20% or more and the amount of recovered heat by about 10%. This demonstrates that the inclusion of vanadyl ions in the dissolution reaction solution improves the yield of solid fuel.

[0041] In this example, dried cedar was used as biomass. The effect of this example is believed to be due to the function of vanadyl ions as an oxidizing agent. Therefore, any biomass that can be used as a carbon source is believed to have the same effect as this example. Furthermore, since any oxidizing agent that contributes to biomass may have the same effect as in the examples, it is believed that adding ions that can function as an oxidizing agent, such as vanadium ions, to the reaction solution can improve the yield of solid fuel. Therefore, the concentration of these ions and their ratio to the acid are not limited to those in the examples and can be adjusted appropriately (for example, the concentration of vanadium ions in the dissolved reaction solution may be 0.01 mol / L or more and 100 mol / L or less). While the reaction can be carried out at room temperature, it is preferable to carry out the reaction at a relatively high temperature (e.g., 50°C or more and 400°C or less) and under high pressure (e.g., 1.5 atm or more and 100 atm or less) to improve the yield of solid fuel. Furthermore, although sulfuric acid was used as the acid component in the examples, any acid that can dissolve biomass and form a salt with vanadium can be suitably used in this system. [Industrial Applicability]

[0042] Since the present invention can preferably obtain solid fuel from biomass, it can be used in fields such as solid fuel and fields utilizing biomass-derived chemical raw materials. [Explanation of symbols]

[0043] 1. Solid fuel manufacturing equipment 5. Dissolution reactor 7. Fuel surge tank 9 Water separator 13 Raw material input section 15 Connecting part 19. Dissolution reaction solution input section 21 Power Generation System 25 Fuel Converter 27 Heat exchanger 29 Carbon dioxide separator 31 Power generation cell

Claims

1. A method for producing solid fuel from biomass, comprising: a dissolution step of reacting the biomass with a dissolution reactor containing 0.01 mol / L or more and 100 mol / L or less of vanadium ions and 0.01 mol / L or more and 100 mol / L or less of sulfuric acid to dissolve cellulose and hemicellulose contained in the biomass and obtain a solid residue of the biomass containing lignin contained in the biomass; a recovery step after the dissolving step to recover a solid residue of the biomass.

2. 2. The method of claim 1, wherein the vanadium ions comprise vanadyl ions.

3. 3. The method of claim 2, further comprising, after the recovering step, a drying step for drying the solid residue of the biomass.

4. The method according to any one of claims 1 to 3, further comprising a pretreatment step prior to the dissolving step for processing the biomass into a state suitable for the dissolving step.

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