Biomass recycling system

Abstract

To provide a method for producing biomass fuel, that can improve energy efficiency.SOLUTION: A method for producing a biomass fuel comprises: a step of producing a solid fuel 12, a gaseous product 11 comprising a gaseous fuel, and a liquid product 12 by hydrothermal carbonization using corn stover as raw material; and a step of recovering the solid fuel, the gaseous product, and the liquid product, wherein a process temperature range is 250 to 350°C and a residence time is 0.75 to 1.5 hours in the step of producing.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for producing biomass fuel and a biomass circulation system.

Background Art

[0002] Conventionally, there has been a technology for producing biomass fuel. Patent Document 1 discloses a method for producing biomass fuel, including a step of subjecting biomass to hydrothermal carbonization treatment or steam carbonization treatment, and at least one of a step of washing the obtained treated product and a step of dehydrating it.

[0003] Patent Document 2 discloses a method for producing biomass fuel, including a two-stage carbonization step of carbonizing lignocellulosic biomass in an inert atmosphere at a temperature range of 200 to 240°C for 5 to 90 minutes and then at a temperature range of 240 to 300°C for 5 to 90 minutes, and a molding step of cooling to a temperature range of 120 to 200°C and then performing molding.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] There is still room for improvement in improving the energy efficiency in the production of biomass fuel. For example, if multiple types of fuels including solid fuel can be recovered, the maximization of energy efficiency can be achieved.

[0006] An object of the present invention is to provide a method for producing biomass fuel and a biomass circulation system that can improve energy efficiency.

Means for Solving the Problems

[0007] The method for producing biomass fuel of the present invention includes a step of producing a solid fuel, a gaseous product including a gas fuel, and a liquid product by hydrothermal carbonization using corn stover as a raw material, and a step of recovering the solid fuel, the gaseous product, and the liquid product. In the step of production, the process temperature ranges from 250 to 350 °C, and the residence time is from 0.75 to 1.5 hours.

Advantages of the Invention

[0008] The method for producing biomass fuel according to the present invention includes a step of producing a solid fuel, a gaseous product including a gas fuel, and a liquid product by hydrothermal carbonization using corn stover as a raw material, and a step of recovering the solid fuel, the gaseous product, and the liquid product. In the step of production, the process temperature ranges from 250 to 350 °C, and the residence time is from 0.75 to 1.5 hours. According to the method for producing biomass fuel according to the present invention, not only the solid fuel but also the gas fuel can be recovered, and the energy efficiency can be improved.

Brief Description of the Drawings

[0009]

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DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, a method for producing a biomass fuel and a biomass circulation system according to an embodiment of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited by this embodiment. In addition, the components in the following embodiments include those that can be easily assumed by those skilled in the art or those that are substantially the same.

[0011] [Embodiment] An embodiment will be described with reference to FIGS. 1 to 7. This embodiment relates to a method for producing a biomass fuel and a biomass circulation system. FIG. 1 is a diagram of a biomass circulation system according to the embodiment, FIGS. 2 to 4 are diagrams showing the experimental results of the embodiment, FIG. 5 is a diagram showing the relationship between the residence time and the higher heating value for each process temperature, FIG. 6 is a diagram showing the relationship between the process temperature and the higher heating value for each residence time, and FIG. 7 is a diagram showing the relationship between the process temperature and the higher heating value for each ratio.

[0012] As shown in FIG. 1, the biomass circulation system 1 according to this embodiment includes a raw material generation unit 2, a hydrothermal carbonization device 3, a separation unit 4, an anaerobic digestion unit 5, and a farm 7. The raw material generation unit 2 is a device that generates a raw material to be input into the hydrothermal carbonization device 3. The raw material input into the hydrothermal carbonization device 3 includes a biomass raw material 21 and water 22. The raw material generation unit 2 includes, for example, a crusher that crushes materials such as plant stems and leaves, a device that generates distilled water, an ion removal device, and the like. The raw material generation unit 2 executes a third generation step P3 for generating the biomass raw material 21.

[0013] The biomass raw material 21 of this embodiment is the stems and leaves of corn. The biomass raw material 21 is generated by crushing corn stems and leaves to a predetermined particle size with a crusher and drying them. The particle size of the biomass raw material 21 is, for example, 500 to 800 [μm].

[0014] The water 22 is deionized water, for example, distilled water. In the raw materials input into the hydrothermal carbonization device 3, the ratio BW of the biomass raw material 21 to the water 22 is adjusted. The ratio BW is, for example, the ratio of the mass of the biomass raw material 21 to the mass of the water 22. In this embodiment, the ratio BW was varied in the range of 0.073 to 0.157 to confirm the appropriate value of the ratio BW in hydrothermal carbonization.

[0015] The hydrothermal carbonization device 3 executes the first production process P1. The first production process P1 is a process of producing the solid fuel 12, the gaseous product 11 containing gaseous fuel, and the liquid product 13 by hydrothermal carbonization of the biomass raw material 21. The hydrothermal carbonization device 3 is a batch reactor with a capacity of 160 [mL] to 190 [mL], and produces biomass fuel 10 from the biomass raw material 21 by hydrothermal carbonization. The hydrothermal carbonization device 3 used in this embodiment is as follows. The biomass raw material 21 and the water 22 are charged in an oxygen-free state by pressurizing nitrogen gas in the headspace of the hydrothermal carbonization device 3. The specifications of the hydrothermal carbonization device 3 used in this embodiment are, for example, as follows. (First device example) Design pressure: 25 [MPa], design temperature: 380 [°C], capacity: 160 [mL], material: SUS316 (Second device example) Design pressure: 10 [MPa], design temperature: 260 [°C], capacity: 190 [mL], material: SUS316

[0016] The hydrothermal carbonization device 3 executes the hydrothermal carbonization process based on the set operating parameters. The operating parameters include the process temperature Tp [°C] and the residence time RT [h].

[0017] The biomass fuel 10 produced by the hydrothermal carbonization process in the hydrothermal carbonization device 3 includes the gaseous product 11, the solid fuel 12, and the liquid product 13. The gaseous product 11 is, for example, hydrogen H 2 , methane CH 4 , carbon monoxide CO, or carbon dioxide CO 2It includes at least one of them. That is, the gaseous product 11 includes gaseous fuels such as hydrogen, methane, and carbon monoxide. The solid fuel 12 is, for example, hydrochar. The liquid product 13 includes at least one of, for example, acetic acid, glycolic acid, or ethanol.

[0018] As shown in FIG. 1, the products generated in the hydrothermal carbonization apparatus 3 are recovered in the recovery step C1. For example, the gaseous product 11 generated in the hydrothermal carbonization apparatus 3 is recovered in a sealed container or the like in the recovery step C1. The gaseous product 11 is recovered as needed in the hydrothermal carbonization process, for example. The separation unit 4 is a device or system that performs gas-liquid separation. The separation unit 4 of the present embodiment is a vacuum filter, which separates the products from the hydrothermal carbonization apparatus 3 into the solid fuel 12 and the liquid product 13. That is, the separation unit 4 recovers the solid fuel 12 and the liquid product 13 from the products in the hydrothermal carbonization apparatus 3 in the recovery step C1.

[0019] The gaseous product 11 and the liquid product 13 are introduced into the anaerobic digestion unit 5. The anaerobic digestion unit 5 performs a second generation step P2 of generating the digestion liquid 51 and the digestion gas 52 by anaerobic digestion. The digestion liquid 51 is stored in a tank or the like and used as a bio-fertilizer on the farm 7. The digestion liquid 51 is used for fertilization in corn cultivation, for example. The stalks and leaves of the corn cultivated on the farm 7 are used as the biomass raw material 21.

[0020] The digestion gas 52 and the solid fuel 12 are introduced into the power generation unit 8 and used as fuel for power generation. The solid fuel 12 is a carbon-neutral fuel having a calorie potential comparable to that of coal. The electric power generated by the power generation unit 8 may be supplied to the hydrothermal carbonization apparatus 3, may be supplied to the anaerobic digestion unit 5, or may be supplied to other processes.

[0021] As described above, the biomass circulation system 1 according to the present embodiment recovers not only the solid fuel 12 from the corn stover but also the gaseous product 11 containing the gas fuel and the liquid product 13. The digestive juice 51 is generated from the gaseous product 11 and the liquid product 13. The liquid product 13 serves as a raw material for the anaerobic digestion treatment. The gaseous product 11 can be used as a heating fuel for the anaerobic digestion treatment.

[0022] According to the biomass circulation system 1 of the present embodiment, biomass resources can be effectively utilized by reproducing corn using the digestive juice 51 as a fertilizer. Further, according to the biomass circulation system 1 of the present embodiment, a regional circulation type energy generation system using liquid fuel (liquid chemicals), gas fuel, and solid fuel as raw materials for anaerobic digestion treatment can be realized.

[0023] FIG. 2 shows the results of the hydrothermal carbonization process executed under various operating conditions. Each column in FIG. 2 is, in order from the left, the experiment number, the process temperature Tp, the residence time RT, the ratio BW, the final pressure [Mpa], the higher heating value HHV [MJ / kg], the energy yield [%], and the mass yield [%].

[0024] H in the gas fraction 2 , CO 2 and CH 4 have higher yields under supercritical conditions than under subcritical conditions. From this, in order to obtain combustible gases such as H 2 and CH 4 at high yields, it is desirable that the process temperature be as high as possible. The higher heating value HHV of hydrochar is higher under subcritical conditions (26.03 MJ / kg) than under supercritical conditions (21.75 MJ / kg). The highest biomass yield and energy yield (29.91% and 42.38% respectively) were obtained with the treatment parameters of a residence time of 45 minutes, a biomass / water ratio of 0.115, a treatment temperature of 215.91 °C, and a pressure of 8.85 MPa. When the process conditions are brought closer from subcritical conditions to supercritical conditions up to around 300 °C, the HHV value and the biomass yield are maintained, but above this temperature, the HHV and the yield parameters decrease.

[0025] Figure 3 is a graph showing the operating conditions and the concentration [g / L] of the liquid product 13 recovered under those operating conditions. Figure 4 is a graph showing the operating conditions and the concentration [%v] of the gas product 11 recovered under those operating conditions.

[0026] As shown in Figure 2, the maximum value of the mass yield of char of 29.91 [%] and the maximum value of the energy yield of 42.38 [%] were recorded in Experiment No. 12. The process temperature Tp at this time was 215.91 [°C], the residence time RT was 0.75 [h], and the ratio BW was 0.115.

[0027] The maximum value of the higher heating value HHV of 26.03 [MJ / kg] was recorded in Experiment No. 16. The process temperature Tp at this time was 300 [°C], the residence time RT was 1.170 [h], and the ratio BW was 0.115.

[0028] The maximum value of the acetic acid concentration of 6.93 [g / L] was recorded in Experiment No. 17. The process temperature Tp at this time was 350 [°C], the residence time RT was 1.00 [h], and the ratio BW was 0.14.

[0029] The maximum value of the gas fraction of hydrogen of 0.25 [%v] was recorded in Experiment No. 7. The process temperature Tp at this time was 384.09 [°C], the residence time RT was 0.75 [h], and the ratio BW was 0.115.

[0030] The central composite design (CCD) module of the response surface method (RSM) was applied to the experimental results shown in Figure 2, and the process was optimized to obtain the maximum higher heating value HHV. As shown in Figure 2, the calculated optimum process had a process temperature Tp of 305 [°C], a residence time RT of 1.00 [h], a ratio BW of 0.14, and a higher heating value HHV of 25.42 [MJ / kg].

[0031] The test results of the optimal process are shown in the bottom row of Figure 2. When the operating conditions of the hydrothermal carbonization apparatus 3 were set to the conditions of the optimal process, a higher heating value HHV of 24.45 [MJ / kg] was obtained.

[0032] Figure 5 shows the relationship between the residence time RT and the higher heating value HHV for each process temperature Tp. Figure 6 shows the relationship between the process temperature Tp and the higher heating value HHV for each residence time RT. Figure 7 shows the relationship between the process temperature Tp and the higher heating value HHV for each ratio BW.

[0033] As can be seen from Figures 5 to 7, for the process temperature Tp, within the range of 250 [°C] to 350 [°C], and for the residence time RT, under the operating conditions of 0.75 [h] or more (hereinafter simply referred to as "the first operating conditions"), a good higher heating value HHV can be obtained. As can be seen from Figure 4, in the range of the process temperature Tp from 250 [°C] to 350 [°C], the recovery amounts of hydrogen and methane are large. That is, according to this temperature range, the total energy efficiency including solid fuel and gaseous fuel can be maximized.

[0034] Regarding the residence time RT, it is preferably not greatly deviated from the time of the optimal process. For example, it may be 1.50 [h] or less. The upper limit value of the residence time RT may be 1.17 [h]. As is clear from Figure 5, it has been confirmed that a good higher heating value HHV can be obtained at a residence time RT of 1.17 [h].

[0035] As described above, the method for producing biomass fuel according to the present embodiment includes a generation step and a recovery step. In the generation step, solid fuel 12, gaseous product 11 containing gaseous fuel, and liquid product 13 are generated by hydrothermal carbonization using corn stover as a raw material. In the recovery step, solid fuel 12, gaseous product 11, and liquid product 13 are recovered. In the generation step, the range of the process temperature Tp is 250 to 350 °C, and the residence time RT is 0.75 to 1.5 hours. Under these operating conditions, a plurality of types of fuels including solid fuel 12 and gaseous fuel can be recovered. Therefore, the method for producing biomass fuel according to the present embodiment can improve energy efficiency.

[0036] In addition, in the hydrothermal carbonization by the hydrothermal carbonization apparatus 3, the mass ratio of the biomass raw material 21 to be input and water 22 may be 0.073 to 0.157.

[0037] The biomass circulation system 1 according to the present embodiment includes a first generation step P1, a second generation step P2, and a third generation step P3. In the first generation step P1, solid fuel 12, gaseous product 11 containing gaseous fuel, and liquid product 13 are generated by hydrothermal carbonization of the biomass raw material 21. In the second generation step P2, digestion liquid 51 is generated by anaerobic digestion treatment using liquid product 13 as a raw material and gaseous product 11 as a heating fuel. In the third generation step P3, biomass raw material 21 is generated from plants cultivated using digestion liquid 51 as a fertilizer. According to the biomass circulation system 1 according to the present embodiment, in addition to solid fuel 12 in the first generation step P1, gaseous fuel is generated, so that the energy efficiency in the biomass circulation can be improved.

[0038] In this embodiment, corn stover is used as biomass raw material 21. The corn stover is cultivated in abandoned cultivated lands in China, Nigeria, and even within Japan, and is left unharvested. This embodiment provides an appropriate hydrothermal treatment technology for maximizing the recovery of bioenergy from corn stover with a high water content. According to this embodiment, hydrochar, high acetic acid, and hydrogen gas can be produced and integrated with an anaerobic digestion process (biorefinery) to obtain maximum bioenergy and biofertilizer. The biomass circulation system 1 according to this embodiment facilitates the utilization of unharvested corn stover in the applicable area for the production of biofuels and biofertilizers.

[0039] An example of the component composition of corn stover is as follows. Note that the total is 100.06 [%], but the two decimal places are treated as errors. Volatile components: 71.34 [%] Fixed carbon: 17.67 [%] Ash content: 11.05 [%]

[0040] When supplying herbaceous biomass with a high ash content ratio as fuel, the alkali components contained in the combustion ash cause furnace corrosion. As an effect of the manufacturing method according to this embodiment, it is characterized in that herbaceous biomass such as corn stover containing a large amount of ash content can be efficiently utilized. Incidentally, the ash content of the woody biomass supplied as biofuel is often 1% or less.

[0041] [Modification example of the embodiment] The statistical analysis method for obtaining the conditions of the optimal process is not limited to the response surface method. Other statistical methods may be used. The capacity of the hydrothermal carbonization device 3 is not limited to the exemplified capacity. The hydrothermal carbonization device 3 may be any device that can appropriately execute the hydrothermal carbonization process for the biomass raw material 21.

[0042] The contents disclosed in the above embodiments and modification examples can be executed in appropriate combination.

Explanation of symbols

[0043] 1 Biomass circulation system 2 Raw material generation unit 3 Hydrothermal carbonization device 4 Separation unit 5 Anaerobic digestion unit 7 Farm 8 Power generation unit 10 Biomass fuel 11 Gas product 12 Solid fuel 13 Liquid product 21 Biomass raw material 22 Water 51 Digestate 52 Digester gas P1 First generation process P2 Second generation process P3 Third generation process C1 Recovery process

Claims

1. A step of producing solid fuel, gaseous products including gaseous fuel, and liquid products by hydrothermal carbonization of biomass raw materials; A step of recovering the solid fuel, the gaseous products, and the liquid products; A step of producing digested liquid from the liquid products and the gaseous products by anaerobic digestion; A step of producing the biomass raw materials from plants cultivated using the digested liquid as fertilizer; comprising; the plant is corn, and the biomass raw material is corn stover; in the step of producing, the process temperature ranges from 250 to 350°C and the residence time is from 0.75 to 1.5 hours A biomass recycling system.

2. In the anaerobic digestion, the liquid product is used as a raw material and the gaseous product is used as a heating fuel The biomass recycling system according to Claim 1.

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