Drainage processing system

Abstract

To provide a drainage processing system capable of processing ammonia-containing wastewater discharged from ammonia power generation facilities without enhancing the processing capacity of drain processing facilities.SOLUTION: The present invention relates to a drainage processing system that comprises ammonia power generation facilities, flue-gas desulfurization facilities and wastewater processing facilities. The ammonia power generation facilities use ammonia as fuel to generate electric power and are configured to discharge ammonia-containing wastewater including the ammonia, the flue-gas desulfurization facilities are configured to remove sulfur oxide included in the exhaust gas and utilize the ammonia-containing wastewater as at least part of water used to operate the flue-gas desulfurization facilities, and the wastewater processing facilities are configured to process the wastewater from the flue-gas desulfurization facilities.SELECTED DRAWING: Figure 1

Description

[Technical field]

[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. [Background technology]

[0002] Nitrogen oxides are contained in exhaust gases generated by burning fossil fuels for thermal power generation. Such exhaust gases are detoxified by reacting the nitrogen oxides with ammonia in a denitration device as shown in Patent Document 1, and then released during standby. Thus, ammonia is used for denitration in thermal power generation facilities.

[0003] Furthermore, in recent years, as shown in Patent Document 2, ammonia power generation, which uses ammonia as fuel to generate electricity, has been considered. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2010-271014 A [Patent Document 2] WO2020 / 115822 [Patent Document 3] JP 2010-164150 A [Patent Document 4] JP 2011-200848 A [Patent Document 5] Patent Publication No. 2023-25270 Summary of the Invention [Problem to be solved by the invention]

[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, it is vaporized in a vaporizer before 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 using a loading arm.

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

[0007] The amount of ammonia used in an ammonia power plant can be 100 times or more that used in a denitrification plant, and as the amount of ammonia used increases, the tank, loading arm, and vaporizer all become larger, so the amount of wastewater generated during cleaning also increases. If the existing wastewater treatment facility cannot accept the increased amount of wastewater, it is necessary to increase the treatment capacity of the wastewater treatment facility by expanding or constructing a new facility, 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. [Means for solving the problem]

[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 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] The wastewater treatment system according to [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] The wastewater treatment system according to [1] or [2], wherein the wastewater treatment equipment is configured 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. Effect of the Invention

[0010] The present inventors have conducted extensive research and found that, as described in Patent Document 5, power generation facilities using fossil fuels are usually equipped with flue gas desulfurization equipment for removing sulfur oxides contained in exhaust gas, and that this flue gas desulfurization equipment uses a large amount of water for cooling exhaust gas, etc., and generates a large amount of wastewater, which is treated in a wastewater treatment facility. The inventors have also found that even if water containing ammonia is used as the water used in the flue gas desulfurization equipment, there is no particular problem with the operation of the flue gas desulfurization equipment or the wastewater treatment facility. Based on this knowledge, the inventors have found that it is possible to treat ammonia-containing wastewater discharged from an ammonia power generation facility without increasing the amount of wastewater flowing into the wastewater treatment facility by using the ammonia-containing wastewater discharged from an ammonia power generation facility for cooling or desulfurizing exhaust gas in the flue gas desulfurization facility, and have completed the present invention. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a block diagram showing a configuration of a wastewater treatment system 1 according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, embodiments of the present invention will be described. Various features shown in the following embodiments can be combined with each other. Also, each feature can be an invention independently.

[0013] A wastewater treatment system 1 according to one embodiment of the present invention will be described with reference to Fig. 1. The wastewater treatment system 1 according to 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 to include 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 installed together 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 transport 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), and in one example, one end of the piping is always connected to the tank 2b, and the other end of the piping is connected to the transport 6 in a detachable manner. The on-off valve is configured to be capable of controlling 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 transport 6, and the on-off valve is opened with the other end of the piping connected to the transport, thereby allowing the liquefied ammonia to be transferred from the transport 6 to the tank 2b.

[0015] The vaporizer 2c is configured to be able to supply the ammonia gas generated by vaporizing the liquefied ammonia discharged from the tank 2b to the generator 2d. The generator 2d is configured to generate power by burning the ammonia gas. In one example, the 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 power with the rotation of the turbine. It is also preferable to include a condenser that returns the steam to water.

[0016] The loading arm 2a and the vaporizer 2c need to be periodically washed with water, but since ammonia is water-soluble, the wastewater generated during washing contains ammonia. Ammonia is also contained in wastewater from a degassing facility that treats small amounts of ammonia gas that leaks or cannot be burned by absorbing it into water. Such wastewater is hereinafter 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, the 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, 2.0% by mass, and may be in the range between any two of the numerical values ​​exemplified here or less than any one of them. If the concentration is too low, the ammonia-containing wastewater can be discharged directly to the external environment, which is meaningless for applying the present invention. If the concentration is too high, the heat generated by the reaction of ammonia and sulfur oxides in the flue gas desulfurization equipment 3 tends to be significant.

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

[0018] The tank for storing ammonia used for denitrification is usually less than 15 m in height and less than 20 m in outer diameter, and is smaller in scale than the tank for storing ammonia used as fuel, and accordingly the amount of ammonia-containing wastewater generated during cleaning is smaller. On the other hand, when ammonia is used as fuel, the required amount is significantly larger, so the sizes of the loading arm 2a, the tank 2b, and the vaporizer 2c are all large, and a large amount of ammonia-containing wastewater is generated. Since the wastewater treatment facility 4 has an upper limit on the wastewater treatment speed, if the ammonia-containing wastewater from the ammonia power generation facility 2 is received in addition to the wastewater already received, there is a risk that the inflow rate of the wastewater will exceed the treatment rate. In that case, it is necessary to increase the wastewater treatment speed by expanding or newly installing the wastewater treatment facility 4, etc., but increasing the wastewater treatment speed may not be easy to achieve in terms of economics, etc. In this embodiment, therefore, in order to suppress an increase in the inflow rate of the wastewater to the wastewater treatment facility 4, the ammonia-containing wastewater is not transferred to the wastewater treatment facility 4 but is transferred to the flue gas desulfurization facility 3.

[0019] Incidentally, a large amount of ammonia-containing wastewater is generated during cleaning or when the desulfurization equipment is used, but is hardly or not generated at other times, so 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 the flue gas desulfurization equipment 3 can accept. 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. Specifically, this discharge rate is, for example, 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, or 20 t / h, and may be within a range between any two of the numerical values ​​exemplified here.

[0020] <Exhaust gas desulfurization equipment 3> The flue gas desulfurization equipment 3 is equipment configured to be capable of removing sulfur oxides (e.g., sulfur dioxide gas) contained in exhaust gas. The exhaust gas is usually gas discharged 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 generated by burning fossil fuels. Since 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 to immobilize and recover sulfur oxides in the exhaust gas as gypsum. The ammonia-ammonium sulfate method is a method in which an aqueous ammonia solution is brought into gas-liquid contact with the exhaust gas to recover sulfur oxides in the exhaust gas as ammonium sulfate. In either method, a large amount of water is used for cooling 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 part of the water used in the operation of the flue gas desulfurization equipment 3. In this way, although industrial water is usually used in the flue gas desulfurization equipment 3, the amount of industrial water used can be reduced by using the ammonia-containing wastewater. In addition, even if the ammonia-containing wastewater is used instead of the industrial water, the amount of wastewater from the flue gas desulfurization equipment 3 is hardly or not increased at all, so that it is possible to treat the ammonia-containing wastewater without increasing the load on the wastewater treatment equipment 4. The ratio of the ammonia-containing wastewater in the water used in the operation of the flue gas desulfurization equipment 3 is, for example, 1 to 100 mass%, preferably 10 to 100%, and more preferably 20 to 100 mass%. Specifically, this ratio is, for example, 1, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, and 100 mass%, and may be in the range between any two of the numerical values ​​exemplified here. In addition, in cases where there is no supply of ammonia-containing wastewater, the flue gas desulfurization equipment 3 may be temporarily operated without using the ammonia-containing wastewater.

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

[0024] <Wastewater treatment facility 4> The wastewater treatment facility 4 is configured to treat wastewater from the flue gas desulfurization facility 3. The wastewater treatment facility 4 may be configured to reduce the ammonia concentration contained in the wastewater, but is preferably configured to reduce the concentrations of selenium, fluorine, and boron compounds as disclosed in Patent Document 4. As disclosed in Patent Document 4, examples of methods for reducing the ammonia concentration include a method of adding an alkaline agent such as NaOH or Ca(OH)2 to the wastewater to increase the pH to 10 or more and stripping NH3, biological treatment, and a method of adding hypochlorous acid to convert NH3 to N2.

[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 is 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 is possible to treat ammonia-containing wastewater by simply adding an ammonia removal step to the existing treatment flow, so that it is possible to treat ammonia-containing wastewater without making a major expansion of the facility. [Explanation of symbols]

[0026] 1: Wastewater treatment system 2: Ammonia power generation facility 2a: Loading arm 2b: Tank 2c: Carburetor 2d: Generator 3: Flue gas desulfurization equipment 4: Wastewater treatment equipment 5: Fossil fuel power generation facilities 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, The ammonia power generation facility is a facility that generates power using ammonia as fuel and is configured to discharge ammonia-containing wastewater that contains ammonia, The flue gas desulfurization equipment is configured to be capable of removing sulfur oxides contained in exhaust gas, and the ammonia-containing wastewater is used as at least a part of the water used in the operation of the flue gas desulfurization equipment, A wastewater treatment system, wherein the wastewater treatment facility is configured to treat wastewater from the flue gas desulfurization facility.

2. The wastewater treatment system according to claim 1, It will also have fossil fuel power generation facilities. The fossil fuel power generation facility is a facility that generates electricity using fossil fuels as fuel, The wastewater treatment system, wherein the exhaust gas is gas discharged from the fossil fuel power generation facility.

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

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

Images