Hydrogen production system and hydrogen production method

Abstract

To decompose hydrogen sulfide produced in a process of wastewater treatment and produce hydrogen to be usable as an energy source.SOLUTION: A hydrogen production system includes: a solid-liquid separation tank for separating matter to be separated from liquid containing at least a sulfate ion, organic matter, and the matter to be separated; and a reaction tank which stores a photocatalyst which promotes reaction for producing hydrogen from hydrogen sulfide contained in the liquid undergoing solid-liquid separation. The solid-liquid separation tank stores a carrier for carrying a sulfate-reducing bacterium. In the solid-liquid separation tank, the hydrogen sulfide is produced from the sulfate ion by the sulfate-reducing bacterium.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a hydrogen generation system and a method for generating hydrogen. [Background technology]

[0002] Various systems for treating wastewater (hereinafter also referred to as wastewater treatment systems) have been proposed. For example, an organic matter recovery device that uses solid-liquid separation using a filter medium has been proposed (see Patent Document 1). It should be noted that wastewater treatment systems are also called effluent treatment systems. It is known that hydrogen sulfide can be generated depending on the properties of the wastewater. Hydrogen sulfide is harmful to the human body and corrodes concrete and ducts, so a wastewater treatment system equipped with a decomposition treatment tank that decomposes hydrogen sulfide has been proposed (see Patent Document 2).

[0003] Meanwhile, hydrogen is attracting attention as a next-generation energy source that can replace carbon in order to realize a decarbonized society, and a method that uses a photocatalyst has been proposed as an alternative to the Claus process as a method for recovering hydrogen by decomposing hydrogen sulfide absorbed in an alkaline aqueous solution (aqueous amine solution) (see Patent Document 3). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-239941 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-212622 [Patent Document 3] Japanese Patent Application Laid-Open No. 2006-307333 Summary of the Invention [Problem to be solved by the invention]

[0005] It is desirable to decompose hydrogen sulfide produced during wastewater treatment and produce hydrogen that can be used as an energy source. [Means for solving the problem]

[0006] One aspect of the present disclosure is a hydrogen generation system comprising: a solid-liquid separation tank that separates a separation target from a liquid containing at least sulfate ions, organic matter, and the separation target; and a reaction tank that contains a photocatalyst that promotes a reaction that produces hydrogen from hydrogen sulfide contained in the liquid after solid-liquid separation, wherein the solid-liquid separation tank contains a carrier that supports sulfate-reducing bacteria, and hydrogen sulfide is produced from the sulfate ions by the sulfate-reducing bacteria in the solid-liquid separation tank. [Effects of the Invention]

[0007] According to the present invention, hydrogen sulfide produced in the process of wastewater treatment can be decomposed and hydrogen that can be used as an energy source can be produced. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram illustrating a wastewater treatment system 100 to which a hydrogen generation system 1 according to the first embodiment of the present disclosure is applied. [Figure 2] FIG. 2 is a diagram illustrating a schematic diagram of the hydrogen generation system 1. As shown in FIG. [Figure 3] FIG. 3 is a diagram illustrating a wastewater treatment system 100 to which the hydrogen generation system 1 of the present disclosure is applied in the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] (First embodiment) 1 is a diagram illustrating a wastewater treatment system 100 to which a hydrogen generation system 1 according to the present disclosure is applied in a first embodiment. The wastewater treatment system 100 includes the hydrogen generation system 1, a hydrogen utilization facility 2, and a downstream facility 3. The hydrogen utilization facility 2 and the downstream facility 3 may be located outside the wastewater treatment system 100.

[0010] The hydrogen generation system 1 includes a solid-liquid separation tank that separates solid matter (hereinafter also referred to as suspended matter) from a liquid (hereinafter simply referred to as liquid) containing at least sulfate ions, organic matter, and the separation target. The reaction tank contains a photocatalyst that promotes a reaction to generate hydrogen from hydrogen sulfide contained in the liquid (a liquid mainly composed of soluble components after solid-liquid separation) flowing out of the solid-liquid separation tank. The liquid containing at least sulfate ions, organic matter, and the separation target is so-called wastewater, such as, but not limited to, influent sewage, industrial wastewater, or mining wastewater. While the following description illustrates a case in which the wastewater is influent sewage, the wastewater may also be return water from sludge treatment or dehydrated separated liquid generated in a sewage treatment facility. The hydrogen generation system 1 can perform water treatment to separate (filter) suspended matter contained in the wastewater and generate hydrogen from hydrogen sulfide. Therefore, hydrogen sulfide generated during the wastewater treatment process can be decomposed and hydrogen can be generated as an energy source.

[0011] The hydrogen utilization facility 2 is a facility that utilizes the hydrogen generated in the hydrogen generation system 1. For example, the hydrogen utilization facility 2 is a facility that utilizes hydrogen for power generation or stores hydrogen. The stored hydrogen may be sold.

[0012] The downstream equipment 3 is equipment that performs predetermined treatment on the treated water from the hydrogen generation system 1. Hereinafter, the hydrogen generation system 1 will be described in detail with reference to FIG.

[0013] FIG. 2 is a diagram illustrating a schematic diagram of the hydrogen generation system 1. As shown in FIG.

[0014] The hydrogen generation system 1 includes a solid-liquid separation tank 10, a reaction tank 20, and a connecting pipe 30. The solid-liquid separation tank 10 separates suspended solids from a liquid (wastewater) containing at least sulfate ions, organic matter, and suspended solids. The solid-liquid separation tank 10 includes an inlet pipe 11 and a filtration unit 12. The inlet pipe 11 is a pipe that communicates with the primary side of the solid-liquid separation tank 10, and wastewater flows into the solid-liquid separation tank 10 through the inlet pipe 11. The filtration unit 12 houses a carrier 12a that supports sulfate-reducing bacteria. The carrier 12a may be made of any material or have any shape as long as it has the function of separating the material to be separated from the wastewater (i.e., solid-liquid separation function) and the function of supporting various bacteria such as sulfate-reducing bacteria. Specifically, for example, the material to be separated is separated on the surface of the carrier 12a.

[0015] The internal space of solid-liquid separation tank 10 is divided into upper space 10a and lower space 10b by filtration section 12. Lower space 10b communicates with communication pipe 30 via communication port 10c.

[0016] In the solid-liquid separation tank 10, hydrogen sulfide is produced from sulfate ions contained in the wastewater by sulfate-reducing bacteria supported on the carriers 12a. The produced hydrogen sulfide is contained in the wastewater, i.e., dissolved in the wastewater.

[0017] The cross section of the solid-liquid separation tank 10 in the horizontal direction may be cylindrical, such as circular or elliptical, or may be box-like with a rectangular cross section.

[0018] The reaction vessel 20 communicates with the solid-liquid separation vessel 10 via the flow port 20a and the communication pipe 30, and is provided with a photocatalyst 21 that promotes a reaction to produce hydrogen from hydrogen sulfide contained in the liquid (hereinafter also referred to as filtrate) after solid-liquid separation. The photocatalyst 21 is structured so that the filtrate flows from the bottom to the top of the reaction vessel 20, and the photocatalyst 21 in the form of solid particles is applied to a support (not shown) arranged (installed) in the reaction vessel 20 so as to come into contact with the filtrate.

[0019] The photocatalyst 21 is a catalyst that is activated by light. By irradiating the photocatalyst 21 with light using a light irradiation device (not shown) placed inside or outside the reaction vessel 20, hydrogen is produced with high efficiency from the hydrogen sulfide contained in the filtered water due to the action of the photocatalyst that is activated by the light.

[0020] The light irradiation device may be one that introduces natural sunlight, or may use an LED (Light Emitting Diode), a lamp, or the like.

[0021] The reaction tank 20 further includes a discharge pipe 25 for discharging the generated hydrogen to the hydrogen utilization equipment 2, and a discharge pipe 26 for discharging the treated water in the reaction tank 20 (hereinafter also simply referred to as treated water) to the downstream equipment 3. The wastewater discharged from the solid-liquid separation tank 10 (the wastewater after solid-liquid separation in the solid-liquid separation tank 10) passes through the photocatalyst 21 and is discharged to the downstream equipment 3 via the discharge pipe 26.

[0022] Next, the flow of wastewater treatment and hydrogen generation will be described with reference to Fig. 2. Note that, before wastewater treatment is carried out, various bacteria such as sulfate-reducing bacteria are grown in the carrier 12a of the filtration section 12.

[0023] First, wastewater flows into solid-liquid separation tank 10 (see arrow F1 in FIG. 2) and accumulates in upper space 10a. The accumulated wastewater then flows into filtration section 12 and moves downward (see arrow F2). That is, the wastewater passes through filtration section 12 in a downward flow. Here, sulfate ions contained in the wastewater are reduced by sulfate-reducing bacteria supported on carrier 12a of filtration section 12, thereby decomposing organic matter such as acetic acid. This reduction of sulfate ions and decomposition of organic matter produces hydrogen sulfide, water, carbon dioxide, and the like.

[0024] The carrier 12a supports various bacteria in addition to sulfate-reducing bacteria, and biologically treats organic matter contained in the wastewater.

[0025] Furthermore, suspended matter (substances to be separated) contained in the wastewater is filtered by the carrier 12a. In this way, organic matter in the wastewater is decomposed, and furthermore, the suspended matter is filtered out, thereby reducing the turbidity.

[0026] The wastewater that has passed through the filtration unit 12 is filtrate. The filtrate contains dissolved hydrogen sulfide generated in the filtration unit 12. The filtrate is discharged into the reaction tank 20 via the lower space 10b and the communication pipe 30 (see arrow F3). The filtrate then passes upward through the photocatalyst 21 (see FIG. 2) in the reaction tank 20 (see arrow F4).

[0027] Next, the flow of hydrogen generation in the reaction vessel 20 will be described.

[0028] Light is irradiated onto the photocatalyst 21 from a light irradiation device disposed inside or outside the reaction tank 20. When the photocatalyst 21, which has been activated by exposure to light, comes into contact with the filtered water, the hydrogen sulfide contained in the filtered water is decomposed into hydrogen and sulfur by the light energy conversion of the photocatalyst 21.

[0029] The hydrogen is discharged as a gas from the filtered water through the discharge pipe 25 to the downstream hydrogen utilization equipment 2 (see arrow F5 in FIG. 2). The treated water containing sulfur is discharged through the discharge pipe 26 to the downstream equipment 3 (see arrow F6 in FIG. 2). The sulfur is S2 2- This sulfur cluster exists stably in the treated water. By recovering this sulfur and using it for fertilizer, sulfur resources can be utilized.

[0030] As described above, water treatment is performed by solid-liquid separation in the solid-liquid separation tank 10, and hydrogen sulfide produced during this water treatment process can be decomposed into sulfur and hydrogen. Decomposing hydrogen sulfide in this manner eliminates the need for a decomposition facility, or allows the scale of deodorization facilities to be reduced. This means that the cost of treating hydrogen sulfide can be reduced. Furthermore, since hydrogen sulfide produced during wastewater treatment is used as a hydrogen source, the cost of hydrogen production can be reduced.

[0031] (Second embodiment) 3 is a diagram illustrating a wastewater treatment system 100 to which the hydrogen generation system 1 of the present disclosure is applied according to the second embodiment. The wastewater treatment system 100 includes the hydrogen generation system 1, a hydrogen utilization facility 2, a downstream facility 3, a sulfur utilization facility 4, and a dissolving device 5. The hydrogen utilization facility 2, the downstream facility 3, the sulfur utilization facility 4, and the dissolving device 5 may be located outside the wastewater treatment system 100.

[0032] The downstream facility 3 recovers sulfur from the treated water containing sulfur, and discharges the recovered sulfur to the sulfur utilization facility 4.

[0033] The sulfur utilization facility 4 burns the discharged sulfur and uses the generated thermal energy to generate electricity. The sulfur utilization facility 4 discharges sulfur dioxide gas generated during the sulfur combustion process to the dissolving device 5. The sulfur utilization facility 4 may also recover the thermal energy generated during the combustion process and supply it to other facilities.

[0034] The dissolving device 5 dissolves the sulfur dioxide gas emitted from the sulfur utilization facility 4 into wastewater such as inflow sewage. By dissolving the sulfur dioxide gas into the wastewater, the concentration of sulfate ions in the wastewater can be increased. As a result, the concentration of hydrogen sulfide in the hydrogen generation system 1 can be increased, and the amount of hydrogen generated can be increased.

[0035] As described above, according to the wastewater treatment system 100 of the second embodiment, the sulfur dioxide gas generated in the process of sulfur combustion can be effectively used as a hydrogen source in the hydrogen generation system 1.

[0036] Although the wastewater passed through the filtration section 12 in a downward flow direction, it may also pass through in the opposite direction, i.e., in an upward flow direction. Furthermore, although the filtrate passed through the reaction tank 20 in an upward flow direction, it may also pass through in the opposite direction, i.e., in a downward flow direction. [Explanation of symbols]

[0037] 1: hydrogen generation system, 2: hydrogen utilization equipment, 3: downstream equipment, 10: solid-liquid separation tank, 10a: upper space, 10b: lower space, 10c: communication port, 11: inlet pipe, 12: filtration section, 12a: carrier, 20: reaction tank, 20a: flow port, 21: photocatalyst, 25: discharge pipe, 26: discharge pipe, 30: communication pipe, 100: wastewater treatment system

Claims

1. a solid-liquid separation tank for separating the separation target from a liquid containing at least sulfate ions, organic matter, and the separation target; a reaction vessel containing a photocatalyst that promotes a reaction for producing hydrogen from hydrogen sulfide contained in the liquid after solid-liquid separation, The solid-liquid separation tank accommodates a carrier supporting sulfate-reducing bacteria, a hydrogen generation system, characterized in that hydrogen sulfide is generated from the sulfate ions by the sulfate-reducing bacteria in the solid-liquid separation tank.

2. A solid-liquid separation tank for separating a separation target from a liquid containing at least sulfate ions, organic matter, and the separation target using a carrier, growing sulfate-reducing bacteria on the carrier; the liquid is passed through the solid-liquid separation tank in an upward or downward direction, and solids are removed from the surface layer. Then, hydrogen sulfide is generated from the liquid, which is mainly composed of soluble components, by the sulfate-reducing bacteria from the sulfate ions and the organic matter; activating a photocatalyst by irradiating the photocatalyst with light, the photocatalyst promoting a reaction for generating hydrogen from hydrogen sulfide contained in the liquid after solid-liquid separation; A hydrogen generation method comprising contacting the activated photocatalyst with hydrogen sulfide contained in the liquid to generate hydrogen.

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