Ammonia separation apparatus and ammonia separation method

Abstract

To provide related technology for a process capable of reducing energy loss in an ammonia separation process compared to Patent Document 2.SOLUTION: An ammonia separation apparatus and related technology for separating ammonia from water to be treated containing ammonia are provided, the apparatus comprising a water-to-be-treated storage part for storing water to be treated, vacuum means for depressurizing the inside of the water-to-be-treated storage part, and stirring blades inserted into the water-to-be-treated storage part.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an ammonia separation device and an ammonia separation method.

Background Art

[0002] Paragraph 0002 of Patent Document 1 has the following description. As a method for separating and removing ammonia-containing wastewater, the steam stripping method is known. In a general ammonia recovery apparatus using this steam stripping method, a distillation column for performing steam stripping is provided, the ammonia-containing vapor discharged from the top of the distillation column is partially condensed by a condenser, the condensed water is returned to the top of the distillation column as reflux liquid, and the remaining concentrated ammonia-containing vapor is supplied to an absorption column and absorbed by water to be taken out as recovered ammonia water.

[0003] On the other hand, the low-boiling point substance recovery apparatus described in claim 1 of Patent Document 1 contacts a stock solution containing a low-boiling point substance with heating steam, separates and gasifies the low-boiling point substance from the stock solution, discharges the steam containing the low-boiling point substance from the top of the column, and stores the treated water from which the low-boiling point substance has been removed from the stock solution at the bottom of the column, a distillation column, by heat-exchanging the steam containing the low-boiling point substance discharged from the top of the distillation column with water, partially condensing the steam containing the low-boiling point substance to concentrate the steam containing the low-boiling point substance, and evaporating the water to discharge it as steam, an evaporator, compresses and raises the temperature of the steam discharged from the evaporator, guides the compressed and heated steam to the distillation column, and uses it as heating steam used in the distillation column, a compression device, takes in the steam containing the low-boiling point substance after partial condensation in the evaporator, cools the steam to remove moisture, and further concentrates the steam containing the low-boiling point substance, a concentration column, is provided.

[0004] Claim 1 of Patent Document 2 describes a method for removing the release of amines and their alkaline decomposition products from combustion gas of a CO2 capture device into the atmosphere. In paragraph 0052 of Patent Document 2, it is described that an ammonia-containing liquid is introduced into reactor 47 for vacuum stripping, and at that time, air is introduced using sparger 49 (a dispersion tube for blowing gas) to separate the ammonia-containing vapor. From the description in paragraph 0049 of Patent Document 2, it can be seen that the ammonia-containing liquid contains various particulate substances (hereinafter also referred to as SS or suspended substances).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] In Patent Document 1, since the moisture in the ammonia-containing vapor returns to the distillation column as condensed water, there is an energy loss. Energy is also required to evaporate water. From the perspective of reducing energy loss and thus reducing costs, stripping equipment with a low evaporation rate is required. The matters related to reducing energy loss and costs may also be paraphrased as "improving energy efficiency".

[0007] Further, in the low-boiling point substance recovery device described in claim 1 of Patent Document 1, there is a risk that the packing inside the distillation column becomes blocked, so it is difficult to treat the waste liquid containing SS. Equipment capable of treating the waste liquid containing SS is required.

[0008] The above problems can be solved by the technology described in Patent Document 2. However, this technology has the following problems.

[0009] When performing treatment with a sparger, the liquid temperature decreases due to the gas. As a result, it is considered that the amount of steam used for heating during the treatment increases. Consequently, energy loss occurs. Also, since gas is introduced into the location where vacuum stripping is being performed, the efficiency of stripping may decrease.

[0010] Therefore, an object of the present invention is to provide a process capable of reducing energy loss more than that in Patent Document 2 in an ammonia separation process (ammonia stripping treatment).

Means for Solving the Problems

[0011] The present invention is as follows. [1] An apparatus for separating ammonia from water to be treated containing ammonia, a water to be treated containing section for containing the water to be treated, a decompression means for decompressing the inside of the water to be treated containing section, and stirring blades inserted into the water to be treated containing section comprising an ammonia separation apparatus.

[0012] [2] The ammonia separation apparatus according to [1], further comprising heating means for heating the inside of the water to be treated containing section.

[0013] [3] further comprising a water collection section connected to the water to be treated containing section for collecting the water evaporated from the water to be treated, and an alkaline water exposure section connected to the water collection section, wherein the alkaline water exposure section is configured to expose alkaline water having a pH of 12 or more to the ammonia and water vapor that have moved from the water collection section, the ammonia separation apparatus according to [1] or [2].

[0014] [4] The ammonia separation device according to [3], further comprising a cooler connected to the alkaline water exposure section, the cooler cooling the water vapor and ammonia that have passed through the alkaline water exposure section to condense water.

[0015] [5] The water to be treated storage section, water collection section, alkaline water exposure section, cooler, and decompression means are connected in series in this order. The ammonia separation device according to [4], wherein the water to be treated storage section, water collection section, alkaline water exposure section, and cooler are decompressed by the decompression means.

[0016] [6] The ammonia separation device according to [2], wherein the heating means is configured to heat the water to be treated to 35 to 60°C.

[0017] [7] The ammonia separation device according to [2], wherein the heating means is configured to heat the water to be treated to 35 to 55°C.

[0018] [8] The ammonia separation device according to any one of [1] to [7], wherein the decompression means is configured to decompress the pressure in the water to be treated storage section to 0.4 atm or less.

[0019] [9] The ammonia separation device according to any one of [1] to [8], wherein the water to be treated contains copper sulfide.

[0020]

[10] An ammonia separation method for separating ammonia from water to be treated containing ammonia by stirring under reduced pressure.

[0021]

[11] The ammonia separation method according to

[10] , wherein the stirring is performed in an atmosphere of 0.4 atm or less.

[0022]

[12] The ammonia separation method according to

[10] or

[11] , wherein the stirring is carried out while heating the water to be treated to 35 to 60 °C for separation.

[0023]

[13] The ammonia separation method according to any one of

[10] to

[12] , wherein the stirring is carried out while heating the water to be treated to 35 to 55 °C. [Advantages of the Invention]

[0024] According to the present invention, in the ammonia separation process, a process capable of reducing energy loss more than that in Patent Document 2 is provided. [Brief Description of the Drawings]

[0025]

Figure 1

Figure 2

Figure 3

[0026] Hereinafter, embodiments of the present invention will be described.

[0027] [Water to be Treated R] The water to be treated R is not limited as long as it is water in which ammonia can be generated as a gas. Further, the present invention can also be applied to liquids containing volatile substances other than ammonia. Hereinafter, as an example of the water to be treated R, wastewater generated in the manufacturing process of printed circuit boards will be exemplified. The wastewater contains copper sulfide (CuS).

[0028] The content of copper sulfide in the water R to be treated is not particularly limited. For example, it is an amount such that the sludge sedimentation rate of the water R to be treated is 2 to 8%. In addition to ammonia and the copper sulfide, components that may be contained in the water to be treated include sulfate ions, sodium ions, chloride ions, nitrate ions, fluoride ions, lithium ions, calcium ions, zinc ions, aluminum ions, cobalt ions, copper ions, and magnesium ions. The above components can exist in the water R to be treated in the form of ionized ions, simple substances, or compounds with counter ions. However, according to the measurement method adopted in the present invention, all of them are quantified as ions. Furthermore, the water R to be treated may contain various carbon compounds.

[0029] In the water R to be treated, the content of each component is, for example, as follows. Ammonium ions: 500 to 20,000 ppm Sulfate ions: 50 to 50,000 ppm Sodium ions: 500 to 40,000 ppm Chloride ions: 10 to 5000 ppm Nitrate ions: 10 to 1000 ppm Fluoride ions: 5 to 150 ppm Lithium ions: 200 to 8000 ppm Calcium ions: 30 to 1000 ppm Zinc ions: 1 to 100 ppm Aluminum ions: 1 to 100 ppm Cobalt ions: 1 to 100 ppm Copper ions: 1 to 100 ppm Magnesium ions: 1 to 100 ppm TOC (total organic carbon): 1000 to 25,000 ppm

[0030] The pH of the water R to be treated is not particularly limited. However, since ammonia is easily removed, it is preferably 9 to 14.

[0031] [Ammonia separation device 1] FIG. 1 is a schematic side cross-sectional view of the ammonia separation device 1 according to the present embodiment and the present example. The ammonia separation device 1 according to this embodiment is a device for separating ammonia from the water to be treated R containing ammonia.

[0032] The ammonia separation device 1 according to this embodiment includes a water-to-be-treated storage unit 2 that stores the water to be treated R, a decompression means 3 that decompresses the inside of the water-to-be-treated storage unit 2, and a stirring means 4 inserted into the water-to-be-treated storage unit 2. Then, the inside of the water-to-be-treated storage unit 2 is decompressed to separate the ammonia evaporated from the water to be treated R from the water to be treated R.

[0033] Preferably, the ammonia separation device 1 according to this embodiment further includes a heating means 5 that heats the inside of the water-to-be-treated storage unit 2. Also preferably, the ammonia separation device 1 according to this embodiment further includes a first water collection unit 61 connected to the water-to-be-treated storage unit 2 for collecting the water evaporated from the water to be treated. Also preferably, the ammonia separation device 1 according to this embodiment further includes an alkaline water exposure unit 8 connected to the first water collection unit 61. Also preferably, it further includes a cooling means 7 that cools the water vapor and ammonia that have passed through the alkaline water exposure unit 8 to condense the water. In this embodiment, the case of having the above-described preferred configurations is exemplified.

[0034] Hereinafter, the details of each configuration will be described.

[0035] The water-to-be-treated storage unit 2 is not limited in terms of material and shape as long as it can store the water to be treated R and can perform vacuum distillation of ammonia.

[0036] The stirring means 4 is not limited in form as long as it can stir the water to be treated R. For example, it may include stirring blades 41 that are rotated by a motor M. The stirring blades 41 are not limited in terms of material and shape as long as they can stir the water to be treated R. Also, the number and shape of the blades are not limited. As an example, a configuration including a disk (wing part) having a diameter that can be accommodated in the water-to-be-treated storage unit 2 and a rotating shaft arranged vertically at the center of the disk can be mentioned.

[0037] The water to be treated storage unit 2 is connected to the pressure reducing means 3. The pressure reducing means 3 is not particularly limited as long as it is configured to be able to reduce the pressure inside the water to be treated storage unit 2 (and optionally the first water collection unit 61, the alkaline water exposure unit 8, the second water collection unit 62, and the cooler 71 in the cooling means 7 described later). In this specification, a vacuum pump 31 is exemplified as the pressure reducing means 3. The vacuum pump 31 is controlled by a controller 32 according to the indication of a pressure indicating regulator PIC.

[0038] There is no limitation on the connection mode between the water to be treated storage unit 2 and the pressure reducing means 3. For example, the water to be treated storage unit 2 and the pressure reducing means 3 may be directly or indirectly connected. "Directly connected" refers to a state in which the water to be treated storage unit 2 and the pressure reducing means 3 are connected by piping without passing through other storage units. "Indirectly connected" refers to a state in which the water to be treated storage unit 2 and the pressure reducing means 3 are connected by piping with other storage units interposed therebetween. FIG. 1 shows an example of indirectly connecting the water to be treated storage unit 2 and the pressure reducing means 3 (details will be described later).

[0039] The specific configuration of the heating means 5 is not particularly limited. For example, the heating means 5 may be a heater disposed around the bottom or outer periphery of the water to be treated storage unit 2. The heater is controlled according to the indication of a temperature indicating regulator TIC. The water to be treated R may be heated by the heating means 5 to, for example, 30 to 90°C, preferably 35 to 60°C, and more preferably 35 to 55°C from the viewpoints of the treatment efficiency of ammonia separation and energy efficiency.

[0040] By connecting the water to be treated storage unit 2 and the pressure reducing means 3, ammonia can be selectively evaporated to some extent under negative pressure from among water and ammonia which is a volatile substance. As a result, the evaporation amount of water can be reduced.

[0041] By providing the above-described water to be treated storage unit 2, pressure reducing means 3, and stirring means 4, the separation efficiency of ammonia is improved. Moreover, since only the above-described respective configurations are required, large-scale equipment is not necessary, and the ammonia separation apparatus 1 as a whole can be miniaturized.

[0042] Also, although some conventional distillation columns use packing materials, it is not even necessary to provide such packing materials. To illustrate an extreme case, only the stirring blades 41 may be provided as the device configuration inside the water to be treated storage unit 2. With this configuration, the SS in the water to be treated R will not block the inside of the water to be treated storage unit 2. The SS only adheres to the inner wall or the inner bottom of the water to be treated storage unit 2. In that case, it is only necessary to remove the stirring blades 41 and clean the inside of the storage unit 2. That is, even when the water to be treated R contains SS, the ammonia separation device 1 according to the present embodiment can treat the water to be treated R.

[0043] Also, when the atmosphere inside the water to be treated storage unit 2 is heated by the heating means 5, the stirring blades 41 increase the gas-liquid contact area, and ammonia gas is more likely to volatilize. Also, since aeration by a sparger or the like from the outside is not performed at that time, the liquid temperature of the water to be treated R hardly decreases. If the liquid temperature of the water to be treated R decreases, heat quantity (energy) is required to compensate for the decrease. This leads to energy loss associated with heating to compensate for the decrease in the liquid temperature of the water to be treated R. On the other hand, with the configuration according to the present embodiment, since the liquid temperature of the water to be treated R hardly decreases, the energy loss related to the decrease in the liquid temperature of the water to be treated R is almost eliminated.

[0044] The ammonia gas generated by vacuum distillation inside the water to be treated storage unit 2 is discharged from the discharge port provided above the location where the liquid of the water to be treated storage unit 2 exists (ammonia stripping step in the present embodiment).

[0045] Then, the ammonia gas moves through a pipe to the next storage unit connected to the water to be treated storage unit 2 (the first water collection unit 61 in the present embodiment, the alkaline water exposure unit 8 connected to the first water collection unit 61). Not only ammonia gas but also some water vapor is generated by vacuum distillation. Although the amount of water vapor generated is less compared to the case where vacuum distillation is not used, some water vapor is still generated.

[0046] By connecting the water to be treated storage unit 2 to the first water collection unit 61 through a pipe, the water vapor and ammonia gas discharged from the water to be treated storage unit 2 may be guided to the first water collection unit 61. Here, at least a part of the water vapor may be condensed to obtain condensed water W1. The ammonia gas and the uncondensed water vapor are discharged from the discharge port provided in the first water collection unit 61 and move through a pipe to the next storage unit (typically the alkaline water exposure unit 8) connected to the first water collection unit 61 (the alkaline water exposure step in this embodiment).

[0047] The first water collection unit 61 may or may not be cooled. When the cooler 71 described later is not provided in the ammonia separation device 1 according to this embodiment, it is preferable to cool the first water collection unit 61 to condense substantially all of the water vapor here to obtain condensed water W1.

[0048] A valve 9 may be provided in the pipe between the water to be treated storage unit 2 and the first water collection unit 61. The valve 9 is provided to prevent the backflow of the alkaline water A due to the backflow of air from the vacuum pump 31 when the ammonia separation device 1 is stopped. That is, the backflow can be prevented by opening the valve 9 when the ammonia separation device 1 is stopped.

[0049] The water vapor and ammonia gas discharged from the water to be treated storage unit 2, or the water vapor and ammonia gas discharged from the first water collection unit 61 can be guided to the alkaline water exposure unit 8 through a pipe. The alkaline water exposure unit 8 is configured to expose the ammonia and water vapor to alkaline water A with a pH of 12 or more. The ammonia separation device 1 according to this embodiment preferably further includes this alkaline water exposure unit 8.

[0050] There is no limitation on the specific configuration of the alkaline water exposure unit 8. As an example of the configuration, the alkaline water exposure unit 8 stores alkaline water A, and the opening on the alkaline water exposure unit 8 side of the openings of the pipes connecting the water to be treated storage unit 2 or the first water collection unit 61 to the alkaline water exposure unit 8 is arranged in the alkaline water A in the alkaline water exposure unit 8.

[0051] As another configuration, the alkaline water exposure unit 8 is a spray tower, and a configuration in which alkaline water A is sprayed onto ammonia and water vapor introduced into the spray tower may be mentioned.

[0052] The composition of the alkaline water A with a pH of 12 or more is not limited, and it may be an aqueous solution of an alkali metal hydroxide or other alkaline water A. In this embodiment, an aqueous NaOH solution is exemplified. Also, there is no limit to the upper limit of the pH of the alkaline water A, but for example, 14 may be mentioned.

[0053] By exposing ammonia and water vapor to alkaline water A in the alkaline water exposure unit 8, impurities (e.g., carbonic acid) in these gases remain in the alkaline water A, while highly pure molecular ammonia gas moves upward from the alkaline water A and is discharged from the discharge port, and can be sucked and recovered by the decompression means 3 (vacuum pump 31) connected to the alkaline water exposure unit 8.

[0054] When the ammonia gas discharged from the discharge port of the alkaline water exposure unit 8 contains a certain amount of water vapor, it is desirable to cool the gas with the cooling means 7 (cooler 71 in this case) to condense the water vapor and increase the purity of the ammonia gas (cooling process after exposure in this embodiment). The ammonia separation device 1 according to this embodiment preferably further includes this cooler 71.

[0055] There is no limitation on the specific configuration of the cooling means 7. It is sufficient if it can accommodate volatile substances (ammonia gas) and water vapor and has a cooling function to condense the water vapor. A known cooler may be used.

[0056] For example, the cooling means 7 may include a cooler 71 capable of accommodating and passing ammonia gas and water vapor, and a refrigerant supply unit 72 that allows a refrigerant to pass through the piping in the cooler 71 to cool the inside of the cooler 71.

[0057] In the configuration of FIG. 1, cold water flows through the coiled flow path in the cooler 71, and the ammonia gas and water vapor passing through here are cooled and water condenses. By condensing the water, the cold water in the coil is heated, moves toward the refrigerant supply section 72 in the upper left, is cooled, and is returned to the coiled flow path again.

[0058] In the cooler 71, water vapor is condensed into water, and the condensed water W2 is stored. Alternatively, a second water collection section 62 may be provided at the lower part of the cooler 71, and the condensed water W2 may be dropped onto this section and collected here. Thereby, the ammonia gas is separated from the state in which the ammonia gas and water vapor are mixed. Another cooling member may be provided around the cooler 71 in order to quickly condense the water vapor into water.

[0059] The water to be treated storage section 2, the first water collection section 61, the alkaline water exposure section 8, the cooler 71 (and the second water collection section 62 connected thereto), and the decompression means 3 described above are connected in series in this order, and by this decompression means 3, it is preferable for the efficiency of the apparatus to decompress all of the water to be treated storage section 2, the first water collection section 61, the alkaline water exposure section 8, the second water collection section 62, and the cooler 71. This is because only the energy for operating only one decompression means 3 needs to be consumed.

[0060] By operating only one decompression means 3, the configuration shown in FIG. 1 can also be realized. Specifically, the following connection modes are possible. · The water to be treated storage section 2 and the first water collection section 61 are directly connected · The first water collection section 61 and the alkaline water exposure section 8 are directly connected · The alkaline water exposure section 8 and the cooler 71 are directly connected · The cooler 71 and the decompression means 3 are directly connected

[0061] That is, when the decompression means 3 is operated, the inside of the cooler 71 is decompressed, and as a result, the inside of the alkaline water exposure section 8 is decompressed. At this time, in FIG. 1, in the pipe connecting the alkaline water exposure section 8 and the cooler 71, the opening on the cooler 71 side is above the water surface of the condensed water, while the opening on the alkaline water exposure section 8 side is below the water surface of the alkaline water A. Even in this state, by decompressing the inside of the alkaline water exposure section 8, the inside of the first water collection section 61 is also decompressed. As a result, the inside of the water to be treated storage section 2 connected to the first water collection section 61 is also decompressed. In the embodiment shown in FIG. 1, except for the opening on the alkaline water exposure section 8 side of the pipe connecting the first water collection section 61 and the alkaline water exposure section 8, the openings of each pipe connecting from the cooler 71 to the water to be treated storage section 2 are all arranged above the water surface.

[0062] In the above configuration, the decompression means 3 is directly connected to the cooler 71, while it is not directly connected to the alkaline water exposure section 8, the first water collection section 61, and the water to be treated storage section 2. Even with this configuration, as shown in the items of the examples described later, the evaporation rate of water in the process of ammonia separation can be reduced, and the energy efficiency during ammonia separation can be improved.

[0063] According to the ammonia separation apparatus 1 according to the present embodiment, an ammonia removal rate of 95% or more can be achieved. Further, when the apparatus is operated until the ammonia removal rate reaches the above level, the evaporation rate of water in the water to be treated R (the method of obtaining it will be described in the examples below) can be set to 45% or less, preferably 35% or less, more preferably 20% or less. Note that the evaporation rate of water is usually 2% or more.

[0064] From the perspective of reducing the evaporation rate of water and enhancing the energy efficiency of ammonia removal, it is preferable that the pressure reducing means 3 is configured to reduce the pressure in the water to be treated containing section 2 (as well as in the cooler 71, the alkaline water exposure section 8, and the first water collection section 61) to 0.4 atm or less (= 1013.25 × 0.4 = 405.3 hPa). As shown in the examples described later, by performing pressure reduction at this level and preferably setting an appropriate heating temperature, the evaporation rate of water can be reduced to 30% or less. Also, it is not necessary to set the temperature in the heating means 5 to an excessively high temperature, which also contributes to the improvement of energy efficiency. There is no limitation on the lower limit value of the pressure, and for example, it may be 0.01 atm or 0.1 atm. Also, the upper limit may be 0.7 atm, 0.6 atm, 0.5 atm, 0.3 atm, or 0.2 atm.

[0065] In the present invention, by performing the pressure reduction as described above, the evaporation of ammonia is promoted. This evaporation can be further promoted by heating, and conversely, when the temperature is lowered, the evaporation rate tends to decrease. In the present invention, the sparger in Patent Document 2 is not used, so the temperature drop of the water to be treated R in the water to be treated containing section 2 is suppressed, and ammonia is likely to evaporate. Ammonia is considered to exist as a gas and ions (ammonium ions) in water. The evaporation of ammonia as a gas disrupts the balance (equilibrium) between the gas and ions of ammonia in water, and a part of the ions becomes a gas and is supplied, which is considered to evaporate more easily (due to the pressure reduction).

[0066] [Ammonia separation method] Figure 2 is a flowchart of the ammonia separation method according to the present embodiment and the present example. Contents not described below can refer to the description of the above [Ammonia separation device 1].

[0067] In the ammonia separation method according to this embodiment, the water to be treated R containing ammonia is stirred under reduced pressure to separate ammonia from the water to be treated R. As a specific example, the above ammonia stripping step, the above alkali water exposure step, and the above post-exposure cooling step are performed in order. The rotation speed during stirring in the ammonia stripping step may be 150 to 1500 rpm. In FIG. 1, the water surface of the water to be treated R in the water to be treated water storage unit 2 is described horizontally, but it is preferable to perform strong stirring to form a vortex around the rotation axis. At that time, a large number of bubbles are generated in the water to be treated R.

[0068] In order to increase the removal efficiency of ammonia, it is preferable to perform the stirring in an atmosphere of 0.4 atm or less. Further, in order to reduce the evaporation rate of water, it is preferable to perform the stirring while heating the water to be treated R to 35 to 60°C, and more preferably to perform the stirring while heating to 35 to 55°C.

[0069] The present invention is not limited to the above-described embodiments in any way, and can be modified into various different forms without departing from the gist of the present invention.

Examples

[0070] Hereinafter, the present invention will be described in more detail using examples and comparative examples, but the present invention is not limited thereto.

[0071] [Device configuration used in this test] In this test, the ammonia separation device 1 shown in FIG. 1 was used. This ammonia separation device 1 is the ammonia separation device 1 described as this embodiment. In Comparative Example 1, the vacuum pump 31 was not operated.

[0072] The treated water storage section 2 is a cylindrical reaction tank with a capacity of 1 L. It is configured to be heated by placing it on a heater (manufactured by TOSHIBA, HP-103K). A TIC (Thermal Indicatior Controller) was inserted into the reaction tank to monitor the temperature of the treated water R, and the temperature was adjusted to a constant temperature shown in Table 1 below. A stirring blade 41 connected to a motor M was inserted into the reaction tank.

[0073] The treated water storage section 2 (reaction tank) was connected to a drain pod (first water collection section 61) with a capacity of 250 mL through a pipe. Cooling was not performed on the drain pod. This drain pod was connected to a NaOH scrubber (alkaline water exposure section 8) through a pipe. The scrubber is a container with a capacity of 125 mL containing 50 mL of a 5 mass% sodium hydroxide aqueous solution. The pH of the aqueous solution is approximately 13, and the pipe connecting the drain pod to the scrubber was opened in the sodium hydroxide aqueous solution in the scrubber.

[0074] The NaOH scrubber was connected to a cooler 71 through a pipe. In the cooler 71, cold water was passed through a coiled flow path so that the gas passing through the cooler 71 could be cooled. The cold water was configured to be recooled by an external cooler (refrigerant supply section 72). A drain pod (second water collection section 62) with a capacity of 1 L was provided at the lower part of the cooler 71 and connected by a pipe so that the condensed water W2 would accumulate here.

[0075] As the pressure reducing means 3, a diaphragm type vacuum pump (manufactured by DIVAC, model 1.2L) was used. A PIC (Pressure Indicator Controller) was installed between the cooler 71 and the vacuum pump 31 to monitor the pressure, and the vacuum pump 31 was controlled by a vacuum controller 32 (manufactured by EYELA, NVC-2000).

[0076] The vacuum pump 31 reduced the pressure of the water to be treated storage section 2, the drain pod (first water collection section 61), the NaOH scrubber, the drain pod (second water collection section 62), and the cooler 71, which were connected in series as described above, to a predetermined pressure. Although not shown in FIG. 1, the ammonia gas that passed through the vacuum pump 31 was led into and recovered in an aqueous sodium hydroxide solution contained in another scrubber having the same structure as the above NaOH scrubber.

[0077] [Various Measurements] In the following Examples and Comparative Examples, various measurements were carried out as follows. · Content of metal ions other than Na ions: Measured using an ICP emission spectroscopic analyzer SPS-5100 manufactured by Hitachi High-Tech Sciences and an ICP mass spectrometer Agilent 7900 ICP-MS manufactured by Agilent Technologies. · Content of Na ions: Measured using a polarized Zeeman atomic absorption photometer ZA3300 manufactured by Hitachi High-Tech Sciences. · Nitrate ion concentration: Measured using an ion chromatograph Tosoh IC-8100EX. · Ammonium ion concentration: Measured using an ion chromatograph Tosoh IC-8100EX. · Fluoride ion concentration: Measured using an ion chromatograph Tosoh IC-8100EX. · Chloride ion concentration: Measured using an ion chromatograph Tosoh IC-8100EX. · Sulfate ion concentration: Measured using an ion chromatograph Tosoh IC-8100EX. · pH: Measured at 25°C using a pH meter and electrode HORIBA D-73. · TOC (total organic carbon): Measured using a TOC-LCSN.J / 100V standard model manufactured by Shimadzu Corporation.

[0078] [Comparative Example 1 and Examples 1 to 4] Using the above apparatus, ammonia separation (ammonia stripping) was carried out on the water to be treated R having the following composition (also referred to as the raw water for treatment R in this test). The main component of the raw water R in this test (the compound with the largest mass percentage among the constituent compounds excluding water) is a precipitate of copper sulfide (CuS). The SV (sludge sedimentation rate) of the raw water R for treatment was 4.1%. This SV was determined from the amount of sludge when 780 mL of the raw water R for treatment was poured into a graduated cylinder and allowed to stand for 30 minutes. The other compositions are as follows. Ammonium ion: 18,970 - 19,721 ppm SO4 2- : 33,000 ppm TOC: 7,800 ppm Na + : 24,000 ppm Cl - : 24 ppm

[0079] The treatment conditions and test results of each test example are described in Table 1 below.

Table 1

[0080] Regarding the treatment conditions, in each of Comparative Example 1 and Examples 1 - 4, the degree of vacuum by the vacuum pump 31 was adjusted (no vacuum in Comparative Example 1), and the liquid temperature was as shown in Table 1 respectively. The stirring speed by the stirring blade 41 in the water to be treated storage section 2 (reaction tank) was 300 rpm, and the treatment time was 30 minutes, 45 minutes, or 60 minutes. The liquid volume in the reaction tank before and after treatment and the NH3 concentration in the liquid were determined, and the NH3 removal rate and the evaporation rate of water in the reaction tank were determined. The evaporation rate of water in the reaction tank was determined as the percentage of the difference in the liquid volume in the reaction tank before and after stripping to the liquid volume in the reaction tank before stripping. The NH3 removal rate was determined as the percentage of the difference in the NH3 concentration in the liquid in the reaction tank before and after stripping to the NH3 concentration before stripping.

[0081] In each test example, the NH3 removal rate was high, but there was a difference in the evaporation rate of water in the apparatus between Comparative Example 1 and Examples 1 to 4. In Examples 1 to 4, the evaporation rate of water could be reduced compared to Comparative Example 1. Reducing the evaporation rate of water means reducing the amount of water evaporated, which implies that the energy consumed for the evaporation of that water can be saved. This means that the configurations of Examples 1 to 4 contribute to the improvement of energy efficiency. In particular, in Examples 2 to 4, the evaporation rate of water could be made 30% or less. Also, when comparing Comparative Example 1 and Example 4, just the fact that the temperature in the treated water storage part 2 decreased from 100 °C (Comparative Example 1) to 40 °C (Example 4) results in energy savings. Moreover, the treatment time was also halved (from 60 minutes in Comparative Example 1 to 30 minutes in Example 4), achieving significant energy savings and an increase in treatment efficiency.

[0082] [Example 5] In this example, the correlation between the treatment time of ammonia stripping, the transition of the pH of the raw water R to be treated, and the transition of the ammonia (ammonium ion) concentration in the raw water R to be treated was obtained.

[0083] The pH of the raw water R used in this example was 12.91. The concentrations of each component in the raw water R were as follows. (Anion) SO4 2- : 160 ppm NO3 ― : 245 ppm F - : 12 ppm (Cation) Ammonium ion: 2815 ppm Li ion: 1811 ppm Na ion: 1409 ppm Ca ion: 196 ppm Zn ion: 10 ppm Al ion: 6 ppm Co ion: 5 ppm Cu ion: 5 ppm Mg ion: 1 ppm

[0084] Ammonia stripping according to the present invention was carried out under the conditions of a liquid temperature of 48 to 49 °C, a stirring speed of 200 rpm, and a treatment pressure of 70 hPa. The pH and ammonia (ammonium ion) concentration of the raw water R to be treated in the apparatus were measured at each treatment time.

[0085] The measurement results are shown in Table 2 below. Figure 3 shows these results graphically.

Table 2

[0086] During the stripping treatment, discoloration of the raw water R to be treated in the reaction tank was observed. This discoloration is due to the separation of ammonia from the raw water R to be treated in the reaction tank. Specifically, it is presumed that the separation of ammonia from the raw water R causes the pH of the raw water R to decrease, resulting in changes in the existing forms of various metals contained in the raw water R in the liquid, leading to discoloration. Even if the raw water R remaining after the treatment changes color or precipitation occurs in this way, in this example, since there are no multiple trays or packing materials installed as in a conventional distillation column, there is no particular hindrance to the ammonia separation operation.

[0087] [Examples 6 to 8] In this example, the stirring speed in the reaction tank was changed to evaluate the effects on the ammonia removal rate and the evaporation rate of water in the reaction tank. Specifically, for the water R to be treated with the ammonia concentration and pH shown in Table 3 below, the rotation speed of the stirring blade 41 was changed to 200 rpm, 300 rpm, and 700 rpm, and ammonia stripping according to the present invention was carried out at a temperature of 50 °C, a pressure of 60 hPa, and a treatment time of 30 minutes. The results are also shown in Table 3.

[0088]

Table 3

Explanation of Reference Numerals

[0089] 1... Ammonia separation device 2... Raw water storage section 3... Pressure reduction means 31…Vacuum pump 32…Controller 4…Stirring means 41…Stirring blade 5…Heating means 61…First water collection section 62…Second water collection section 7…Cooling means 71…Cooler 72…Refrigerant supply section 8…Alkaline water exposure section 9…Valve R…Water to be treated (raw water for treatment) W1, W2…Condensed water A…Alkaline water M…Motor TIC…Temperature indicating controller PIC…Pressure indicating controller

Claims

1. An apparatus for separating ammonia from water to be treated containing ammonia, comprising: a water to be treated containing section for containing the water to be treated; a decompression means for decompressing the inside of the water to be treated containing section; and stirring blades inserted into the water to be treated containing section. The ammonia separation apparatus.

2. The ammonia separation apparatus according to claim 1, further comprising a heating means for heating the inside of the water to be treated containing section.

3. The ammonia separation apparatus according to claim 2, further comprising: a water collection section connected to the water to be treated containing section for collecting water evaporated from the water to be treated; and an alkaline water exposure section connected to the water collection section, wherein the alkaline water exposure section is configured to expose alkaline water having a pH of 12 or more to ammonia and water vapor that have moved from the water collection section.

4. The ammonia separation apparatus according to claim 3, further comprising a cooler connected to the alkaline water exposure section for cooling water vapor and ammonia that have passed through the alkaline water exposure section to condense water.

5. The water to be treated containing section, the water collection section, the alkaline water exposure section, the cooler, and the decompression means are connected in series in this order, and the decompression means decompresses the water to be treated containing section, the water collection section, the alkaline water exposure section, and the cooler.

6. The ammonia separation apparatus according to claim 2, wherein the heating means is configured to heat the water to be treated to 35 to 60°C.

7. The ammonia separation apparatus according to claim 2, wherein the heating means is configured to heat the water to be treated to 35 to 55°C.

8. The ammonia separation apparatus according to any one of claims 1 to 7, wherein the decompression means is configured to decompress the pressure inside the water to be treated containing section to 0.4 atm or less.

9. The ammonia separation apparatus according to claim 8, wherein the water to be treated contains copper sulfide.

10. An ammonia separation method for separating ammonia from water to be treated containing ammonia by stirring the water to be treated under reduced pressure.

11. The ammonia separation method according to claim 10, wherein the stirring is performed in an atmosphere of 0.4 atm or less.

12. The ammonia separation method according to claim 10 or 11, wherein the stirring is performed while heating the water to be treated to 35 to 60°C.

13. The ammonia separation method according to claim 10 or 11, wherein the stirring is carried out while heating the water to be treated to 35 to 55°C.

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