Wastewater treatment system

Abstract

Provided is a wastewater treatment system that makes it possible to treat, without increasing treatment capacity of a wastewater treatment facility, ammonia-containing wastewater discharged from an ammonia power generation facility.　The present invention provides a wastewater treatment system comprising an ammonia power generation facility, a flue gas desulfurization facility, and a wastewater treatment facility, wherein: the ammonia power generation facility uses ammonia as fuel to generate power and is configured to discharge ammonia-containing wastewater which contains ammonia; the flue gas desulfurization facility is configured to be capable of removing a sulfur oxide contained in exhaust gas and utilizes the ammonia-containing wastewater as at least part of water which is used in operation of the flue gas desulfurization facility; and the wastewater treatment facility is configured to treat the wastewater from the flue gas desulfurization facility.

Description

Wastewater Treatment System

[0001] The present invention relates to a wastewater treatment system that can treat ammonia-containing wastewater discharged from an ammonia power generation facility without increasing the treatment capacity of the wastewater treatment facility.

[0002] Exhaust gases produced by burning fossil fuels for thermal power generation contain nitrogen oxides. Such exhaust gases are detoxified by reacting the nitrogen oxides with ammonia in a denitration device such as that shown in Patent Document 1, and then released into the atmosphere during standby. In this way, ammonia is used for denitration in thermal power generation facilities.

[0003] Furthermore, in recent years, as disclosed in Patent Document 2, ammonia power generation, which uses ammonia as fuel to generate electricity, has been under consideration.

[0004] JP 2010-271014 A WO2020 / 115822 JP 2010-164150 A JP 2011-200848 A JP 2023-25270 A

[0005] Ammonia has a boiling point of −33.3° C. and is usually stored in a liquefied state in a low-temperature tank, and after being removed from the tank, is vaporized in a vaporizer for use. As described in Patent Document 3, ammonia is usually transported in a liquefied state near the tank by a transport vehicle such as a tank ship or a tank truck, and then transferred into the tank from there using a loading arm.

[0006] The loading arm and vaporizer need to be washed periodically with water. However, since ammonia is water-soluble, the wastewater generated during the washing process contains ammonia. If the ammonia concentration exceeds the wastewater standard, the wastewater cannot be discharged as is, and it is necessary to remove the ammonia using wastewater treatment equipment such as that described in Patent Document 4.

[0007] The amount of ammonia used in an ammonia power generation facility can be 100 times or more the amount used in a denitrification facility, and as the amount of ammonia used increases, the tank, loading arm, and vaporizer all become larger, which increases the amount of wastewater generated during cleaning.If the existing wastewater treatment facility cannot accommodate the increased amount of wastewater, it is necessary to increase the treatment capacity of the wastewater treatment facility by expanding or installing new facilities, but this is not always easy to achieve.

[0008] The present invention has been made in view of the above circumstances, and provides a wastewater treatment system that can treat ammonia-containing wastewater discharged from an ammonia power generation facility without increasing the treatment capacity of the wastewater treatment facility.

[0009] According to the present invention, the following inventions are provided. [1] A wastewater treatment system comprising an ammonia power generation facility, a flue gas desulfurization facility, and a wastewater treatment facility, wherein the ammonia power generation facility generates electricity using ammonia as fuel and is configured to discharge ammonia-containing wastewater containing ammonia, the flue gas desulfurization facility is configured to be able to remove sulfur oxides contained in exhaust gas, and uses the ammonia-containing wastewater as at least a portion of the water used in operation of the flue gas desulfurization facility, and the wastewater treatment facility is configured to treat the wastewater from the flue gas desulfurization facility. [2] The wastewater treatment system according to [1], further comprising a fossil fuel power generation facility, wherein the fossil fuel power generation facility generates electricity using fossil fuel as fuel, and the exhaust gas is gas emitted from the fossil fuel power generation facility. [3] The wastewater treatment system according to [1] or [2], wherein the wastewater treatment facility is configured to be able to reduce the ammonia concentration in the wastewater. [4] The wastewater treatment system according to any one of [1] to [3], wherein the ammonia-containing wastewater is used to cool the exhaust gas in the flue gas desulfurization system.

[0010] After extensive research, the present inventors have found that, as described in Patent Document 5, power generation facilities using fossil fuels are typically equipped with flue gas desulfurization equipment for removing sulfur oxides contained in exhaust gases, and that this flue gas desulfurization equipment uses a large amount of water for cooling the exhaust gases and generates a large amount of wastewater, which is treated in a wastewater treatment facility. Furthermore, the present inventors have also found that even if water containing ammonia is used in the flue gas desulfurization equipment, this does not particularly hinder the operation of the flue gas desulfurization equipment or the wastewater treatment facility. Based on this finding, the present inventors have found that ammonia-containing wastewater discharged from an ammonia power generation facility can be treated without increasing the amount of wastewater flowing into the wastewater treatment facility by using the ammonia-containing wastewater discharged from the ammonia power generation facility to cool and humidify the exhaust gas in the flue gas desulfurization equipment, and have completed the present invention.

[0011] 1 is a block diagram showing the configuration of a wastewater treatment system 1 according to one embodiment of the present invention.

[0012] The following describes embodiments of the present invention. The various features shown in the following embodiments can be combined with each other. Furthermore, each feature can be an independent invention.

[0013] A wastewater treatment system 1 according to one embodiment of the present invention will be described with reference to Figure 1. The wastewater treatment system 1 of this embodiment includes an ammonia power generation facility 2, a flue gas desulfurization facility 3, and a wastewater treatment facility 4. It is also preferable that the system includes a fossil fuel power generation facility 5 that generates exhaust gas to be supplied to the flue gas desulfurization facility 3. These facilities are preferably located side by side on the premises of the same power plant, but may be located apart from each other as long as the materials required for treatment can be exchanged. Each component will be described below.

[0014] <Ammonia power generation facility 2> The ammonia power generation facility 2 is a facility that generates power using ammonia as fuel and is configured to discharge ammonia-containing wastewater that contains ammonia. In one example, the ammonia power generation facility 2 includes a loading arm 2a, a tank 2b, a vaporizer 2c, and a generator 2d. The loading arm 2a is used to transfer liquefied ammonia from a transporter 6 such as a tank ship or a tank truck into the tank 2b. The loading arm 2a has an on-off valve and piping (not shown). In one example, one end of the piping is constantly connected to the tank 2b, and the other end of the piping is detachably connected to the transporter 6. The on-off valve is configured to be able to control the flow of liquefied ammonia through the piping. In one example, the on-off valve is closed when the other end of the piping is not connected to the transporter 6, and the on-off valve is opened with the other end of the piping connected to the transporter, thereby allowing the liquefied ammonia to be transferred from the transporter 6 to the tank 2b.

[0015] Vaporizer 2c is configured to be able to supply the ammonia gas generated by vaporizing the liquefied ammonia discharged from tank 2b to generator 2d. Generator 2d is configured to generate electricity by burning the ammonia gas. In one example, generator 2d includes a burner for burning the ammonia gas, a boiler for generating steam using heat generated by the combustion, a turbine that can be rotated by the generated steam, and a power generation unit that generates electricity as the turbine rotates. It is also preferable that generator 2d include a condenser that converts the steam back into water.

[0016] The loading arm 2a and the vaporizer 2c need to be periodically washed with water, and because ammonia is water-soluble, the wastewater generated during washing contains ammonia. Ammonia is also contained in wastewater from a deaeration system that treats small amounts of ammonia gas that leak or cannot be burned by absorbing it into water. Hereinafter, this wastewater will be referred to as "ammonia-containing wastewater." The ammonia concentration of the ammonia-containing wastewater is, for example, 0.01 to 2 mass%, preferably 0.05 to 1.5 mass%, and more preferably 0.1 to 1.0 mass%. Specifically, this concentration is, for example, 0.01, 0.02, 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, or 2.0% by mass, and may be between any two of the values ​​exemplified here or below any of the values. If this concentration is too low, the ammonia-containing wastewater may be discharged directly to the external environment, which makes the application of the present invention meaningless. If this concentration is too high, the heat generation due to the reaction of ammonia and sulfur oxides in the flue gas desulfurization equipment 3 is likely to be significant.

[0017] The height of tank 2b (i.e., the height of the highest part of tank 2b) is, for example, 15 m or more, preferably 30 m or more, and preferably 40 m or more. This height is, for example, 15 to 100 m, specifically, for example, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 70, 80, 90, or 100 m, and may be in a range between any two of the values ​​exemplified here or greater than any two of them. The outer diameter of tank 2b is, for example, 20 m or more, preferably 40 m or more, and preferably 60 m or more. This outer diameter is, for example, 20 to 150 m, specifically, for example, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, or 150 m, and may be in a range between any two of the values ​​exemplified here.

[0018] Tanks containing ammonia used for denitrification typically have a height of less than 15 m and an outer diameter of less than 20 m. These tanks are smaller than tanks containing ammonia used as fuel, and therefore generate less ammonia-containing wastewater during cleaning. In contrast, when ammonia is used as fuel, a significantly larger amount is required, resulting in larger loading arms 2 a, tanks 2 b, and vaporizers 2 c, and the generation of large amounts of ammonia-containing wastewater. The wastewater treatment facility 4 has an upper limit on its wastewater treatment rate. If the facility receives ammonia-containing wastewater from the ammonia power generation facility 2 in addition to the wastewater already being received, the inflow rate of the wastewater may exceed the treatment rate. In this case, the wastewater treatment rate must be increased by expanding or constructing a new facility for the wastewater treatment facility 4. However, increasing the wastewater treatment rate may not be easy to achieve from economic and other perspectives. Therefore, in this embodiment, in order to prevent an increase in the inflow rate of the wastewater into the wastewater treatment facility 4, the ammonia-containing wastewater is transferred to the flue gas desulfurization facility 3 rather than to the wastewater treatment facility 4.

[0019] A large amount of ammonia-containing wastewater is generated during cleaning or when the desulfurization equipment is used, but little or no ammonia-containing wastewater is generated at other times. Therefore, it is preferable to store the ammonia-containing wastewater in a tank for storing this wastewater and supply it to the flue gas desulfurization equipment 3 at a rate that can be accepted by the flue gas desulfurization equipment 3. The rate at which the ammonia-containing wastewater is supplied to the flue gas desulfurization equipment 3 is, for example, 0.1 to 20 t / h, preferably 0.5 to 10 t / h, and more preferably 1 to 5 t / h. Specific examples of this discharge rate are 0.1, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, and 20 t / h, and may be within a range between any two of the numerical values ​​exemplified here.

[0020] <Flue Gas Desulfurization Equipment 3> The flue gas desulfurization equipment 3 is equipment configured to be able to remove sulfur oxides (e.g., sulfur dioxide gas) contained in exhaust gas. The exhaust gas is usually gas emitted from a fossil fuel power generation equipment 5. The fossil fuel power generation equipment 5 is equipment that generates electricity using fossil fuels such as coal, oil, and natural gas as fuel. Since fossil fuels usually contain sulfur, sulfur oxides are almost inevitably produced by burning fossil fuels. Because these sulfur oxides are contained in the exhaust gas, the exhaust gas cannot be released directly into the atmosphere, and so the exhaust gas is transferred to the flue gas desulfurization equipment 3 to remove the sulfur oxides.

[0021] Methods by which the flue gas desulfurization equipment 3 removes sulfur oxides include the limestone-gypsum method and the ammonia-ammonium sulfate method. The limestone-gypsum method is a method in which an absorption liquid in which limestone or the like is dissolved and / or suspended in water is brought into gas-liquid contact, and sulfur oxides in the exhaust gas are immobilized as gypsum and recovered. The ammonia-ammonium sulfate method is a method in which an aqueous ammonia solution is brought into gas-liquid contact with the exhaust gas, and sulfur oxides in the exhaust gas are recovered as ammonium sulfate. In either method, a large amount of water is used for cooling and humidifying the exhaust gas, and a large amount of wastewater is generated, which is treated in the wastewater treatment equipment 4.

[0022] In this embodiment, ammonia-containing wastewater is used as at least a portion of the water used in the operation of the flue gas desulfurization equipment 3. Thus, while industrial water is normally used in the flue gas desulfurization equipment 3, the use of ammonia-containing wastewater can reduce the amount of industrial water used. Furthermore, even when ammonia-containing wastewater is used instead of industrial water, the amount of wastewater from the flue gas desulfurization equipment 3 increases little or not at all, making it possible to treat the ammonia-containing wastewater without increasing the load on the wastewater treatment equipment 4. The proportion of ammonia-containing wastewater in the water used in the operation of the flue gas desulfurization equipment 3 is, for example, 1 to 100% by mass, preferably 10 to 100%, and more preferably 20 to 100% by mass. Specific examples of this proportion are 1, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, and 100% by mass, and may be within a range between any two of the values ​​exemplified here. In cases where there is no supply of ammonia-containing wastewater, the flue gas desulfurization equipment 3 may be temporarily operated without using ammonia-containing wastewater.

[0023] In the limestone-gypsum method, calcium ions eluted from limestone react with sulfate ions generated from sulfur oxides to produce gypsum, but an insoluble coating of fluorine or the like may form on the surface of calcium carbonate, making it difficult for the calcium ions to be eluted. It is known that the formation of such an insoluble coating can be suppressed by adding water-soluble cations, and a similar effect is expected for ammonium ions generated from ammonia. Therefore, by using ammonia-containing wastewater as the water for dissolving and / or dispersing limestone, the formation of an insoluble coating can be suppressed without the need for the separate addition of water-soluble cations.

[0024] <Wastewater Treatment Equipment 4> The wastewater treatment equipment 4 is configured to treat the wastewater from the flue gas desulfurization equipment 3. The wastewater treatment equipment 4 may be configured to be able to reduce the ammonia concentration contained in the wastewater, but as disclosed in Patent Document 4, it is preferable that the wastewater treatment equipment 4 is also configured to be able to reduce the concentrations of selenium compounds, fluorine compounds, and boron compounds. As a method for reducing the ammonia concentration, as disclosed in Patent Document 4, for example, adding NaOH, Ca(OH) ２ Add alkaline agents such as NH to raise the pH to 10 or higher. ３ stripping method, biological treatment, and even adding hypochlorous acid to remove NH ３ N ２ There are methods for converting it into

[0025] When the original treatment flow in the wastewater treatment facility 4 includes an ammonia removal step for reducing the ammonia concentration in the wastewater, it becomes possible to treat ammonia-containing wastewater without adding a new step. Even when the original treatment flow in the wastewater treatment facility 4 does not include an ammonia removal step, it becomes possible to treat ammonia-containing wastewater simply by adding an ammonia removal step to the existing treatment flow, so that it becomes possible to treat ammonia-containing wastewater without making a major expansion of the facility.

[0026] 1: Wastewater treatment system, 2: Ammonia power generation equipment, 2a: Loading arm, 2b: Tank, 2c: Vaporizer, 2d: Generator, 3: Flue gas desulfurization equipment, 4: Wastewater treatment equipment, 5: Fossil fuel power generation equipment, 6: Transport aircraft

Claims

1. A wastewater treatment system comprising an ammonia power generation facility, a flue gas desulfurization facility, and a wastewater treatment facility, wherein the ammonia power generation facility is a facility that generates electricity using ammonia as fuel and is configured to discharge ammonia-containing wastewater that contains ammonia, the flue gas desulfurization facility is configured to be able to remove sulfur oxides contained in exhaust gas, and uses the ammonia-containing wastewater as at least a portion of the water used in the operation of the flue gas desulfurization facility, and the wastewater treatment facility is configured to treat wastewater from the flue gas desulfurization facility.

2. A wastewater treatment system as claimed in claim 1, further comprising a fossil fuel power generation facility, the fossil fuel power generation facility being a facility that generates electricity using fossil fuel as fuel, and the exhaust gas being gas discharged from the fossil fuel power generation facility.

3. A wastewater treatment system according to claim 1 or 2, wherein the wastewater treatment equipment is configured to be capable of reducing the ammonia concentration in the wastewater.

4. A wastewater treatment system according to claim 1 or 2, wherein the ammonia-containing wastewater is used to cool the exhaust gas in the flue gas desulfurization facility.

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