Water treatment method and water treatment system

Abstract

We provide a water treatment method that effectively utilizes hydrogen energy. [Solution] A water treatment method comprising: (1) a step of obtaining sodium hypochlorite and hydrogen from an aqueous sodium chloride solution by electrolysis; (2) a step of disinfecting the water to be treated with the sodium hypochlorite obtained in step (1); (3) a step of obtaining electricity from an internal combustion engine using the hydrogen obtained in step (1) as fuel; and (4) a step of converting the waste heat in step (3) into electricity, wherein at least a portion of the electricity obtained in step (3) and at least a portion of the electricity obtained in step (4) are supplied as electricity to be used in step (1).

Description

Technical Field

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[0001] The present invention relates to a water treatment method and a water treatment system.

Background Art

[0002] Conventionally, a water treatment method and a water treatment system for disinfecting water with sodium hypochlorite have been known. Further, as a technique for producing sodium hypochlorite, a method of obtaining sodium hypochlorite and hydrogen from an aqueous sodium chloride solution by electrolysis is known (for example, see Patent Document 1).

Prior Art Documents

Patent Documents

[0007] Step (4) may include converting waste heat into light and converting the light energy into electricity. The wavelength of the light may be 300 nm to 1 mm.

[0008] A water treatment system according to one aspect of the present invention comprises an electrolysis tank that obtains sodium hypochlorite and hydrogen from an aqueous sodium chloride solution by electrolysis, a disinfection tank that disinfects the water to be treated with the sodium hypochlorite obtained in the electrolysis tank, an internal combustion generator that obtains electricity from an internal combustion engine using the hydrogen obtained in the electrolysis tank as fuel, and a converter that converts the waste heat from the internal combustion generator into electricity, wherein at least a portion of the electricity obtained from the internal combustion generator and at least a portion of the electricity obtained from the converter are supplied as electricity to be used in the electrolysis tank. With such a water treatment system, the energy of hydrogen can be used effectively.

[0009] The above converter may include a first conversion unit that converts waste heat into light, and a second conversion unit that converts the energy of the light into electricity. The wavelength of the light may be 300 nm to 1 mm. [Effects of the Invention]

[0010] According to the present invention, a water treatment method and a water treatment system are provided that can effectively utilize the energy of hydrogen. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic flow diagram of a water treatment system according to one embodiment of the present invention. [Figure 2] This is a schematic flow diagram of a water treatment system according to another embodiment of the present invention. [Modes for carrying out the invention]

[0012] A preferred embodiment of the present invention will be described with reference to the drawings. Figure 1 is a schematic flow diagram of a water treatment system according to one embodiment of the present invention.

[0013] The water treatment system 100 according to this embodiment mainly comprises a dissolution tank 10, an electrolysis tank 20, a sodium hypochlorite storage tank 30, a disinfection tank 40, a hydrogen tank 50, an internal combustion generator 60, a first conversion unit 70, and a second conversion unit 80. The first conversion unit 70 and the second conversion unit 80 constitute a converter 5.

[0014] The dissolution tank 10 dissolves sodium chloride in water to obtain an aqueous sodium chloride solution. The dissolution tank 10 is equipped with a line L1 for receiving sodium chloride from the outside, a line L2 for receiving water from the outside, and a line L10 for discharging the aqueous sodium chloride solution. The dissolution tank 10 is connected to the electrolysis tank 20 via line L10.

[0015] The electrolysis tank 20 obtains sodium hypochlorite and hydrogen from an aqueous sodium chloride solution by electrolysis. The electrolysis tank 20 is connected to the sodium hypochlorite storage tank 30 and the hydrogen tank 50 via lines L20 and L21, respectively.

[0016] The sodium hypochlorite storage tank 30 stores the sodium hypochlorite produced in the electrolysis tank 20. The sodium hypochlorite storage tank 30 is connected to the disinfection tank 40 via line L30.

[0017] The disinfection tank 40 disinfects the water to be treated with sodium hypochlorite obtained in the electrolysis tank 20. The disinfection tank 40 is provided with a line L30 for receiving sodium hypochlorite from the sodium hypochlorite storage tank 30, a line L3 for receiving the water to be treated from the outside, and a line L41 for discharging the treated water to the outside.

[0018] The hydrogen tank 50 stores the hydrogen generated in the electrolysis tank 20. The hydrogen tank 50 is connected to the internal combustion generator 60 via a line L50.

[0019] The internal combustion generator 60 obtains electric power by an internal combustion engine using the hydrogen obtained in the electrolysis tank 20 as fuel.

[0020] The converter 5 converts the exhaust heat in the internal combustion generator 60 into electric power. In the present embodiment, the converter 5 includes a first conversion unit 70 and a second conversion unit 80. The first conversion unit 70 converts the exhaust heat into light. The wavelength of the light can be, for example, 300 nm to 1 mm. The wavelength of the light may be, for example, 700 nm to 1 mm, 300 nm to 1100 nm, or 800 nm to 1300 nm.

[0021] The first conversion unit 70 can be, for example, a heat radiator. Examples of the heat radiator include a metal with a high melting point, carbon nanotubes (CNT), and metamaterials. The first conversion unit 70 can be appropriately selected according to the temperature of the exhaust heat and the like.

[0022] The second conversion unit 80 converts the energy of light into electric power.

[0023] The second conversion unit 80 can be, for example, a photoelectric conversion element such as a thermophotovoltaic element (TPV) or a solar cell (PV cell). The second conversion unit 80 can be appropriately selected according to the wavelength of the light and the like. Also, a combination of a thermophotovoltaic element that generates electricity with infrared light and a PV cell that generates electricity with visible light transmitted through it may be used.

[0024] At least a portion of the power obtained by the internal combustion generator 60 and at least a portion of the power obtained by the converter 5 are supplied as power for use in the electrolysis tank 20. Power may also be supplied from an external source (external power) for use in the electrolysis tank 20.

[0025] Next, we will explain the water treatment method using the water treatment system 100.

[0026] Sodium chloride and water are supplied to the dissolution tank 10 via lines L1 and L2, respectively. In the dissolution tank 10, sodium chloride is dissolved in water to obtain an aqueous sodium chloride solution (dissolution step).

[0027] The sodium chloride aqueous solution obtained in the dissolution process is supplied to the electrolysis tank 20 via line L10. In the electrolysis tank 20, sodium hypochlorite and hydrogen are obtained from the sodium chloride aqueous solution by electrolysis (electrolysis process).

[0028] The sodium hypochlorite obtained in the electrolysis process is supplied to the sodium hypochlorite storage tank 30 via line L20 and stored in the sodium hypochlorite storage tank 30.

[0029] Sodium hypochlorite from the sodium hypochlorite storage tank 30 is supplied to the disinfection tank 40 via line L30. The water to be treated is supplied to the disinfection tank 40 via line L3. In the disinfection tank 40, the water to be treated is disinfected with sodium hypochlorite to obtain treated water (disinfection step). The obtained treated water is discharged from the system via line L41.

[0030] The hydrogen obtained in the electrolysis process is supplied to the hydrogen tank 50 via line L21 and stored in the hydrogen tank 50.

[0031] The hydrogen in the hydrogen tank 50 is supplied to the internal combustion generator 60 via line L50. The internal combustion generator 60 uses hydrogen as fuel to generate electricity through an internal combustion engine (power generation process). When obtaining electrical energy using a fuel cell, the required purity of hydrogen is usually 99.97% or higher. In contrast, in the power generation process according to this embodiment, since electricity is obtained through an internal combustion engine using hydrogen as fuel, the purity of the hydrogen may be lower. The purity of the hydrogen supplied to the internal combustion generator 60 may be, for example, 70-80%.

[0032] The temperature of the waste heat in the internal combustion generator 60 (power generation process) can be, for example, 200 to 1000°C.

[0033] The waste heat generated during the power generation process is converted into light by the first conversion unit 70. The wavelength of the light can be, for example, 300 nm to 1 mm. The wavelength of the light may also be, for example, 700 nm to 1 mm, 300 nm to 1100 nm, or 800 nm to 1300 nm. The energy of the light output from the first conversion unit 70 is converted into electricity by the second conversion unit 80. In this way, the waste heat generated during the power generation process is converted into electricity (thermoelectric conversion process).

[0034] At least a portion of the electricity obtained in the power generation process and at least a portion of the electricity obtained in the thermoelectric conversion process are supplied as electricity for use in the electrolysis process. External power may be further supplied as electricity for use in the electrolysis process.

[0035] Figure 2 is a schematic flow diagram of a water treatment system according to another embodiment of the present invention. Here, only the differences from water treatment system 100 will be explained, and redundant explanations will be omitted.

[0036] The water treatment system 200 shown in Figure 2 replaces the converter, which consists of a first conversion unit 70 and a second conversion unit 80, with a converter consisting of a thermoelectric converter 90. The thermoelectric converter 90 converts heat into electricity.

[0037] As the thermoelectric conversion device 90, for example, a device including a thermoelectric conversion element such as a Peltier element, and a binary power generation device can be used. These devices can efficiently convert thermal energy into electricity. In a binary power generation device, for example, the thermal energy of waste heat is used to evaporate a medium with a boiling point lower than water (ammonia water, pentane, etc.), and the resulting steam is supplied to a turbine to obtain electricity.

[0038] In the water treatment method using the water treatment system 200, waste heat from the power generation process is converted into electricity by the thermoelectric converter 90.

[0039] The thermal energy from the waste heat may be supplied to the thermoelectric converter 90, for example, via a heat conductor (not shown), or via a heat exchanger (not shown). This allows for more effective utilization of the waste heat.

[0040] The water treatment method according to the above embodiment comprises: (1) a step of obtaining sodium hypochlorite and hydrogen from an aqueous sodium chloride solution by electrolysis; (2) a step of disinfecting the water to be treated with the sodium hypochlorite obtained in step (1); (3) a step of obtaining electricity from an internal combustion engine using the hydrogen obtained in step (1) as fuel; and (4) a step of converting the waste heat in step (3) into electricity, wherein at least a portion of the electricity obtained in step (3) and at least a portion of the electricity obtained in step (4) are supplied as electricity used in step (1). This makes it possible to effectively utilize the energy of hydrogen (by-product hydrogen) generated when producing sodium hypochlorite.

[0041] In this method, step (4) preferably includes converting waste heat into light and converting the energy of the light into electricity. This allows for more efficient conversion of waste heat into electricity. The wavelength of the light can be, for example, 300 nm to 1 mm.

[0042] The water treatment system according to the above embodiment includes an electrolysis tank that obtains sodium hypochlorite and hydrogen from an aqueous sodium chloride solution by electrolysis, a disinfection tank that disinfects the water to be treated with sodium hypochlorite obtained from the electrolysis tank, an internal combustion generator that obtains electricity from an internal combustion engine using hydrogen obtained from the electrolysis tank as fuel, and a converter that converts waste heat from the internal combustion generator into electricity. At least a portion of the electricity obtained from the internal combustion generator and at least a portion of the electricity obtained from the converter are supplied as electricity to be used in the electrolysis tank. This makes effective use of the energy of hydrogen.

[0043] In this system, the converter preferably includes a first conversion unit that converts waste heat into light, and a second conversion unit that converts the energy of the light into electricity. This allows for more efficient conversion of waste heat into electricity. The wavelength of the light can be, for example, 300 nm to 1 mm.

[0044] The present invention is not limited to the above embodiments, and various modifications are possible.

[0045] For example, in the water treatment system 100 shown in Figure 1, the converter 5 may include a wavelength adjustment unit between the first conversion unit 70 and the second conversion unit 80 to adjust the wavelength of light. If a wavelength adjustment unit is included between the first conversion unit 70 and the second conversion unit 80 to adjust the wavelength of light, for example, the wavelength of light output from the first conversion unit 70 can be adjusted by the wavelength adjustment unit, and then the energy of the light output from the wavelength adjustment unit can be converted into electricity by the second conversion unit 80.

[0046] This disclosure relates to the following matters. [1] A water treatment method comprising: (1) obtaining sodium hypochlorite and hydrogen from an aqueous sodium chloride solution by electrolysis; (2) disinfecting the water to be treated with the sodium hypochlorite obtained in step (1); (3) obtaining electricity from an internal combustion engine using the hydrogen obtained in step (1) as fuel; and (4) converting the waste heat in step (3) into electricity, wherein at least a portion of the electricity obtained in step (3) and at least a portion of the electricity obtained in step (4) are supplied as electricity to be used in step (1). [2] The water treatment method according to [1], wherein step (4) is to convert waste heat into light and to convert the energy of the light into electricity. [3] The water treatment method according to [2], wherein the wavelength of the light is 300 nm to 1 mm. [4] A water treatment system comprising: an electrolysis tank for obtaining sodium hypochlorite and hydrogen from an aqueous sodium chloride solution by electrolysis; a disinfection tank for disinfecting water to be treated with sodium hypochlorite obtained in the electrolysis tank; an internal combustion generator for obtaining electricity from an internal combustion engine using hydrogen obtained in the electrolysis tank as fuel; and a converter for converting waste heat from the internal combustion generator into electricity, wherein at least a portion of the electricity obtained in the internal combustion generator and at least a portion of the electricity obtained in the converter are supplied as electricity to be used in the electrolysis tank. [5] The water treatment system according to [4], wherein the converter includes a first conversion unit that converts waste heat into light and a second conversion unit that converts the light energy into electricity. [6] The water treatment system according to [5], wherein the wavelength of the light is 300 nm to 1 mm. [Explanation of symbols]

[0047] 5...Converter, 10...Dissolution tank, 20...Electrolysis tank, 30...Sodium hypochlorite storage tank, 40...Disinfection tank, 50...Hydrogen tank, 60...Internal combustion generator, 70...First conversion unit, 80...Second conversion unit, 90...Thermoelectric converter, 100, 200...Water treatment system.

Claims

1. (1) A step of obtaining sodium hypochlorite and hydrogen from an aqueous sodium chloride solution by electrolysis, (2) A step of disinfecting the water to be treated with sodium hypochlorite obtained in step (1), (3) A process to obtain electricity using an internal combustion engine with hydrogen obtained in process (1) as fuel, (4) A step of converting the waste heat in step (3) into electricity, A water treatment method comprising supplying at least a portion of the electricity obtained in process (3) and at least a portion of the electricity obtained in process (4) as electricity used in process (1).

2. The water treatment method according to claim 1, wherein step (4) includes converting waste heat into light and converting the energy of the light into electricity.

3. The water treatment method according to claim 2, wherein the wavelength of the light is 300 nm to 1 mm.

4. An electrolysis tank for obtaining sodium hypochlorite and hydrogen from an aqueous sodium chloride solution by electrolysis, A disinfection tank for disinfecting the water to be treated with sodium hypochlorite obtained in the electrolysis tank, An internal combustion generator that uses hydrogen obtained in the electrolysis tank as fuel to generate electricity using an internal combustion engine, The system comprises a converter that converts waste heat from the internal combustion generator into electricity, A water treatment system that supplies at least a portion of the electricity obtained by the internal combustion generator and at least a portion of the electricity obtained by the converter as electricity used in the electrolysis tank.

5. The water treatment system according to claim 4, wherein the converter includes a first conversion unit that converts waste heat into light, and a second conversion unit that converts the light energy into electricity.

6. The water treatment system according to claim 5, wherein the wavelength of the light is 300 nm to 1 mm.

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