Urea treatment device and urea treatment method

Abstract

The present invention comprises: a temperature information acquisition unit (120) that acquires first temperature information indicating the temperature of water being treated that is supplied to a reaction tank (180) in which urea in water being treated is treated; a temperature information acquisition unit (130) that acquires second temperature information indicating the temperature of the water being treated that is within the reaction tank (180) or is discharged from the reaction tank (180); and an addition amount adjustment unit (150) that, on the basis of the result of comparing the temperature indicated by the first temperature information and the temperature indicated by the second temperature information, adjusts at least one of the amount of bromide salt added to the water being treated and the amount of hypochlorite added to the water being treated.

Description

Urea treatment device and urea treatment method

[0001] The present invention relates to a urea treatment device and a urea treatment method.

[0002] In a water treatment system, a water treatment device is disclosed in which hypochlorite and bromide salt are added to the water to be treated in order to remove urea contained in the water (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2023-125145

[0004] The reaction to remove urea takes time. Therefore, the water to be treated must be retained in the tank for a long time. If there is a difference in the temperature of the water in the tank and the water flowing into the tank, the flow state of the water to be treated in the tank may change, resulting in a short-path phenomenon. Short-path is a phenomenon in which the water to be treated that flows into the tank moves (passes) along the top or bottom of the water stored in the tank before being discharged. If such a short-path occurs, the water to be treated will not be retained in the tank long enough for the reaction to occur. As a result, there is a risk that sufficient urea removal performance will not be achieved.

[0005] An object of the present invention is to provide a urea treatment apparatus and a urea treatment method that can obtain sufficient urea removal performance.

[0006] The urea treatment device of the present invention has: a first temperature information acquisition unit that acquires first temperature information indicating the temperature of the water to be treated that is supplied to a reaction tank where urea in the water to be treated is treated; a second temperature information acquisition unit that acquires second temperature information indicating the temperature of the water to be treated that is inside the reaction tank or discharged from the reaction tank; and an addition amount adjustment unit that compares the temperature indicated by the first temperature information with the temperature indicated by the second temperature information and adjusts at least one of the amount of bromide salt added to the water to be treated and the amount of hypochlorite added to the water to be treated based on the result of the comparison.

[0007] Furthermore, the urea treatment method of the present invention includes the steps of: acquiring first temperature information indicating the temperature of the water to be treated that is supplied to a reaction tank where the urea in the water to be treated is treated; acquiring second temperature information indicating the temperature of the water to be treated that is in the reaction tank or discharged from the reaction tank; comparing the temperature indicated by the first temperature information with the temperature indicated by the second temperature information; and adjusting at least one of the amount of bromide salt and the amount of hypochlorite to be added to the water to be treated based on the result of the comparison.

[0008] In the present invention, sufficient urea removal performance can be obtained.

[0009] Fig. 1 is a diagram showing an embodiment of a urea treatment device of the present invention. Fig. 2 is a diagram showing an example of a water treatment system to which the urea treatment device shown in Fig. 1 is applied. Fig. 3 is a graph showing the residence time of the water to be treated for each of the magnitude relationships between the temperature of the water to be treated at the inlet of the reaction tank and the temperature of the water to be treated at the reaction tank or outlet shown in Fig. 1. Fig. 4 is a diagram showing the conditions used in the test. Fig. 5 is a diagram showing the residual urea concentration in the water to be treated when adding chemicals in amounts set under each of the above-mentioned conditions 1 to 3 for each of the magnitude relationships between temperature T1 and temperature T2. Fig. 6 is a flowchart for explaining an example of a control method in the control device shown in Fig. 1.

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0011] Fig. 1 is a diagram showing one embodiment of a urea treatment apparatus according to the present invention. As shown in Fig. 1, the urea treatment apparatus 100 according to this embodiment includes temperature information acquisition units 120, 130, a comparison unit 140, an addition amount adjustment unit 150, a bromide salt addition unit 160, a hypochlorite addition unit 170, and a reaction tank 180. The temperature information acquisition units 120, 130, the comparison unit 140, and the addition amount adjustment unit 150 form a control device 110. Fig. 1 shows the main elements of this embodiment among the components included in the urea treatment apparatus 100 according to the present invention.

[0012] The reaction tank 180 is a water tank in which water to be treated containing urea is stored (retained). The urea in the water to be treated stored (retained) in the reaction tank 180 is treated. Water containing urea can be used as the water to be treated. For example, raw water for producing ultrapure water, such as industrial water, city water, or well water, can be used as the water to be treated. Bromide salt and hypochlorite are added to the water to be treated that is supplied to the reaction tank 180, and the water to be treated reacts with the bromide salt and hypochlorite to decompose the urea, resulting in treated water being discharged from the reaction tank 180.

[0013] The bromide salt adding unit 160 adds bromide salt to the water to be treated. For example, the bromide salt adding unit 160 adds bromide salt to the water to be treated stored in the reaction tank 180 via a valve 161. Examples of the bromide salt added by the bromide salt adding unit 160 include sodium bromide (NaBr) and potassium bromide (KBr).

[0014] The hypochlorite addition unit 170 adds hypochlorite to the water to be treated. For example, the hypochlorite addition unit 170 adds hypochlorite to the water to be treated stored in the reaction tank 180 via a valve 171. Examples of hypochlorite added by the hypochlorite addition unit 170 include sodium hypochlorite (NaClO), sodium perchlorate (NaClO), and calcium hypochlorite (Ca(ClO)).

[0015] The temperature information acquisition unit 120 is a first temperature information acquisition unit that acquires first temperature information indicating the temperature of the water to be treated supplied to the reaction tank 180. The temperature information acquisition unit 120 may acquire the first temperature information from a thermometer installed at the inlet of the reaction tank 180 that measures the temperature of the water to be treated. When multiple different types of water to be treated flow into the reaction tank 180, the temperature information acquisition unit 120 may acquire the first temperature information when the type of water to be treated flowing into the reaction tank 180 changes. Depending on the type of water to be treated flowing into the reaction tank 180, the water temperatures may differ from one another. Therefore, if the temperature information acquisition unit 120 acquires the first temperature information when the type of water to be treated flowing into the reaction tank 180 changes, treatment appropriate for the water to be treated can be performed. The temperature information acquisition unit 120 may also acquire temperature information by calculating the temperature taking into account the aperture of a valve installed in a supply pipe that supplies the water to be treated to the reaction tank 180 and the flow rate of the water to be treated in the supply pipe. For example, when water to be treated flows into the reaction tank 180 from series A, which has a high temperature, and series B, which has a low temperature, the temperature information acquisition unit 120 may calculate the estimated water temperature of the water to be treated flowing into the reaction tank 180 by taking into account the flow rate of the water to be treated flowing through series A and the flow rate of the water to be treated flowing through series B, or by taking into account the aperture of a valve installed in the supply pipe of series A and the aperture of a valve installed in the supply pipe of series B. In this case, a thermometer is installed in each supply pipe of each series, and the thermometer measures the temperature of each series, and the temperature information acquisition unit 120 acquires temperature information indicating the temperature. The temperature information acquisition unit 120 notifies the comparison unit 140 of the acquired first temperature information.

[0016] The temperature information acquisition unit 130 is a second temperature information acquisition unit that acquires second temperature information indicating the temperature of the water to be treated in the reaction tank 180 or the treated water discharged from the reaction tank 180. The temperature information acquisition unit 130 may acquire the second temperature information from a thermometer that is provided in the reaction tank 180 or at the outlet of the reaction tank 180 and that measures the temperature of the water to be treated or the treated water. In this case, the temperature information acquisition unit 130 may acquire multiple pieces of temperature information from multiple thermometers that are provided in the reaction tank 180 or at the outlet of the reaction tank 180 and that measure the temperature of the water to be treated or the treated water, and may use the average value of the acquired multiple pieces of temperature information as the second temperature information. Alternatively, the temperature information acquisition unit 130 may acquire the second temperature information from temperature information measured by a thermograph that is provided in the reaction tank 180 and that can measure the temperature distribution of the water to be treated in the reaction tank 180. The temperature information acquisition unit 130 may also estimate the temperature of the water to be treated in the reaction tank 180 or the temperature of the treated water at the outlet of the reaction tank 180 based on environmental information indicating the external environment (around the reaction tank 180), and acquire second temperature information from the estimated temperature. This environmental information includes information indicating the weather and outside temperature of the reaction tank 180, or information indicating the time period or period (season, etc.) at which the temperature information acquisition unit 130 acquires the second temperature information. For example, the relationship between the outside temperature and the temperature inside the reaction tank 180 may be associated in advance, and the temperature information acquisition unit 130 may acquire the outside temperature and acquire temperature information indicating the temperature associated with the acquired outside temperature as the second temperature information. For example, the relationship between the time period or season and the temperature inside the reaction tank 180 may be associated in advance, and the temperature information acquisition unit 130 may acquire information indicating the time period or season and acquire temperature information indicating the temperature associated with the acquired information indicating the time period or season as the second temperature information. In this way, the temperature information acquisition unit 130 acquires the second temperature information based on environmental information. This allows the temperature information acquisition unit 130 to acquire the second temperature information even when it is difficult to measure the temperature of the water to be treated inside the reaction tank 180 or the temperature of the water to be treated at the outlet of the reaction tank 180 due to the shape or arrangement of the reaction tank 180. It is preferable that the temperature information acquisition unit 130 acquires the second temperature information at a timing before the target water to be treated is supplied to the reaction tank 180.When a plurality of different types of water to be treated flows into the reaction tank 180, the temperature information acquisition unit 130 may acquire the second temperature information at the timing when the type of water to be treated flowing into the reaction tank 180 is switched. The reason for this is the same as that described above for the temperature information acquisition unit 120. The temperature information acquisition unit 130 notifies the comparison unit 140 of the acquired second temperature information.

[0017] It is also possible for only one of the temperature information acquisition unit 120 and the temperature information acquisition unit 130 to be provided. That is, the temperature information acquisition unit 120 may also serve as the above-described temperature information acquisition unit 130, and the temperature information acquisition unit 130 may not be provided. Alternatively, the temperature information acquisition unit 130 may also serve as the above-described temperature information acquisition unit 120, and the temperature information acquisition unit 120 may not be provided. Alternatively, a configuration may be adopted in which each of the temperature information acquisition units 120 and 130 can also perform part of the function of the other.

[0018] The comparison unit 140 compares the temperature indicated by the first temperature information notified by the temperature information acquisition unit 120 with the temperature indicated by the second temperature information notified by the temperature information acquisition unit 130. For example, the comparison unit 140 may calculate the difference between the temperature indicated by the first temperature information notified by the temperature information acquisition unit 120 and the temperature indicated by the second temperature information notified by the temperature information acquisition unit 130. Alternatively, the comparison unit 140 may calculate the ratio of the temperature indicated by the second temperature information to the temperature indicated by the first temperature information. In the following description, a process in which the comparison unit 140 calculates the difference between the temperature indicated by the first temperature information and the temperature indicated by the second temperature information will be described as an example. The comparison unit 140 compares the calculated difference with a preset threshold value. This threshold value may be "0" or a value preset based on conditions measured during actual operation. The comparison unit 140 notifies the addition amount adjustment unit 150 of the comparison result.

[0019] The addition amount adjustment unit 150 adjusts (controls) at least one of the amount of bromide salt added by the bromide salt addition unit 160 and the amount of hypochlorite added by the hypochlorite addition unit 170 based on the comparison result notified from the comparison unit 140. Specifically, when the difference between the comparison results notified from the comparison unit 140 exceeds a threshold, the addition amount adjustment unit 150 increases or decreases at least one of the amount of bromide salt added by the bromide salt addition unit 160 and the amount of hypochlorite added by the hypochlorite addition unit 170 from the current addition amount. When adjusting the amount of bromide salt added by the bromide salt addition unit 160, the addition amount adjustment unit 150 adjusts the opening / closing or opening degree of the valve 161. When adjusting the amount of hypochlorite added by the hypochlorite addition unit 170, the addition amount adjustment unit 150 adjusts the opening / closing or opening degree of the valve 171. More specifically, if the difference in the comparison result notified by the comparison unit 140 exceeds a threshold, the addition amount adjustment unit 150 estimates the residence time of the water to be treated in the reaction tank 180. If the estimated residence time is below a predetermined specified time, the addition amount adjustment unit 150 determines that the above-mentioned short-pass phenomenon has occurred. In this case, the addition amount adjustment unit 150 increases at least one of the amount of bromide salt added by the bromide salt addition unit 160 and the amount of hypochlorite added by the hypochlorite addition unit 170 from the current addition amount. On the other hand, if the measured residence time exceeds the predetermined specified time, the addition amount adjustment unit 150 decreases at least one of the amount of bromide salt added by the bromide salt addition unit 160 and the amount of hypochlorite added by the hypochlorite addition unit 170 from the current addition amount. This is because, depending on the shape of the reaction tank 180 (rectangular tank, vertical bypass tank, horizontal bypass tank, etc.), there may be a temperature difference between the temperature indicated by the first temperature information notified from the temperature information acquisition unit 120 and the temperature indicated by the second temperature information notified from the temperature information acquisition unit 130, which may create an area where the liquid is likely to stagnate, resulting in a longer residence time. The amount by which the addition amount adjustment unit 150 increases or decreases the addition amount is set in advance based on, for example, the shape and structure of the reaction tank 180, the timing of the adjustment, the magnitude of the temperature difference, etc.This setting may be based on the relationship between the residence time and the temperature difference (the difference between the temperature indicated by the first temperature information and the temperature indicated by the second temperature information) when a tracer substance is flowed in the reaction tank 180 that is actually used, or when the amount of bromide salt and hypochlorite added is temporarily changed and the response at the outlet of the reaction tank 180 is measured. Note that by setting the threshold value used by the comparison unit 140 to "0," the addition amount adjustment unit 150 adjusts at least one of the amount of bromide salt added by the bromide salt addition unit 160 and the amount of hypochlorite added by the hypochlorite addition unit 170 based on the difference between the temperature indicated by the first temperature information notified by the temperature information acquisition unit 120 and the temperature indicated by the second temperature information notified by the temperature information acquisition unit 130. Specifically, when the temperature indicated by the first temperature information notified from the temperature information acquisition unit 120 is not equivalent to the temperature indicated by the second temperature information notified from the temperature information acquisition unit 130, the addition amount adjustment unit 150 adjusts at least one of the amount of bromide salt added by the bromide salt addition unit 160 and the amount of hypochlorite added by the hypochlorite addition unit 170.

[0020] If the reaction tank 180 is provided with a heat exchanger for adjusting the temperature of the water to be treated in the reaction tank 180, the set temperature of the heat exchanger may be set to the temperature of the water to be treated in the reaction tank 180. In this case, the set temperature of the heat exchanger may be adjusted (controlled) so that the difference between the temperature of the water to be treated at the inlet of the reaction tank 180 and the temperature of the water to be treated in the reaction tank 180 is small (for example, so that it is less than a preset threshold value). If the heat exchanger used in this way is provided outside the reaction tank 180, the water to be treated may be sucked out of the reaction tank 180, passed through the heat exchanger, and then returned to the reaction tank 180. Alternatively, the heat exchanger may be installed inside the reaction tank 180.

[0021] FIG. 2 is a diagram showing an example of a water treatment system to which the urea treatment device 100 shown in FIG. 1 is applied. The water treatment system shown in FIG. 2 is composed of a pretreatment system, a primary pure water system, and a subsystem (secondary pure water system). Treated water treated in the subsystem (secondary pure water system) is supplied to a point of use. In the example shown in FIG. 2, the urea treatment device 100 is provided in the pretreatment system. The urea treatment device 100 is disposed between a pump that pumps raw water (i.e., water to be treated) from a raw water tank in the pretreatment system and a coagulation / filtration device that removes fine particles from the supplied water to be treated. In the example shown in FIG. 2, raw water is supplied to the pretreatment system. Specifically, the raw water is treated in the urea treatment device 100 and then the coagulation / filtration device. The treated water treated in the pretreatment system is supplied to the primary pure water system as the treated water. Specifically, the treated water treated in the pretreatment system is stored in a filtration tank of the primary pure water system, treated in an activated carbon device and an ion exchange device in that order, and then stored in a desalination tank. The treated water stored in the desalinated water tank is treated in a reverse osmosis membrane (RO membrane) device and stored in the RO water tank. The treated water stored in the RO water tank is treated in an ion exchange device and a membrane degassing device, in that order. The treated water treated in the primary pure water system is supplied to the subsystem as water to be treated. Specifically, the treated water treated in the primary pure water system is stored in the primary pure water tank of the subsystem and treated in a heat exchanger, an ultraviolet (UV) oxidation device, an ion exchange device (CP), a membrane degassing device, and an ultrafiltration membrane (UF membrane) device, in that order. The temperature information acquisition unit 120 shown in FIG. 1 may also acquire temperature information indicating the temperature measured by a thermometer installed upstream of the raw water tank shown in FIG. 2.

[0022] Figure 3 is a graph showing the residence time of the water being treated when the temperature of the water being treated at the inlet of the reaction tank 180 shown in Figure 1 is higher or lower than the temperature of the water being treated inside or at the outlet of the reaction tank 180. The vertical axis of the graph shown in Figure 3 represents the ratio of the measured residence time to a predetermined ideal residence time. The data shown in Figure 3 are the results of tests conducted under the following conditions: The shape of the reaction tank 180 was rectangular, and a flat-to-circuit model was used. The temperature difference between the temperature of the water being treated supplied to the reaction tank 180 and the temperature of the water inside the reaction tank 180 was set to 1 degree. Methylene blue was added to the reaction tank 180, and the ratio to the residence time under ideal conditions (residence time ratio) was measured. The residence time under ideal conditions was calculated using a flow analysis. ANSYS Fluent R18.1 (manufactured by ANSYS, Inc.) and modeling software Gambit 2.4.6 (manufactured by ANSYS, Inc.) were used for the flow analysis.

[0023] When temperature T2 (the water temperature in the reaction tank 180; the same applies in the following explanation) is lower than temperature T1 (the water temperature of the water to be treated supplied to the reaction tank 180; the same applies in the following explanation) (Case 1), the water to be treated is likely to short-pass through the upper part of the reaction tank 180. Therefore, as shown in Figure 3, the retention time ratio is low. Furthermore, when temperature T2 is higher than temperature T1 (Case 2), the water to be treated is likely to short-pass through the lower part of the reaction tank 180. Therefore, as shown in Figure 3, the retention time ratio is low. When temperatures T1 and T2 are equal (Case 3), the water to be treated flows more evenly within the reaction tank 180, resulting in a higher retention time ratio compared to Cases 1 and 2, and a better reaction. Thus, it was confirmed that a temperature difference between temperatures T1 and T2 has a significant effect on shortening the retention time relative to the ideal state.

[0024] If the residence time of the water to be treated in the reaction tank 180 is short, the reaction time with the added chemicals will be short, resulting in a high residual urea concentration in the water to be treated supplied from the reaction tank 180. If water to be treated with a high residual urea concentration is supplied to a subsequent stage, it will be impossible to supply water that meets the required conditions. Therefore, by increasing the amount of chemicals added to the water to be treated in the reaction tank 180, the residual urea concentration can be reduced in a short reaction time, making it possible to supply water that meets the required conditions.

[0025] Note that a decrease in the temperature of the water to be treated supplied to the reaction tank 180 reduces the reactivity of the added chemicals. To prevent a decrease in the temperature of the water to be treated, the water to be treated may be heated using the heat exchanger described above. The addition amount adjustment unit 150 may calculate a base amount of chemical to be added (a reference amount to be added before adjustment) based on the temperature of the water to be treated supplied to the reaction tank 180. Furthermore, the addition amount adjustment unit 150 may measure values ​​such as the urea concentration, pH, water temperature, and residual chlorine concentration of the water to be treated, and acquire relationship data indicating the relationship between reaction time and the concentration of the treated water based on these values ​​in a reference state such as an ideal state of a completely mixed system (e.g., a state in which the temperature of the water to be treated supplied to the reaction tank 180 is within a predetermined temperature range). The addition amount adjustment unit 150 may then calculate the base amount of chemical to be added based on the acquired relationship data. Furthermore, if the water to be treated contains ammonia, hypochlorite is consumed. Therefore, the amount of hypochlorite required to be added to the water to be treated increases. Therefore, the addition amount adjustment unit 150 may calculate the base addition amount taking into account the presence of ammonia in the water to be treated. The addition amount adjustment unit 150 may also correct the calculated base addition amount by taking into account fluctuations in residence time due to the temperature difference between temperature T1 and temperature T2. Furthermore, the relationship between the urea residual rate y in the water to be treated and the reaction time x is known to proceed as a first-order reaction of y = exp(-kx). Therefore, by calculating the reaction rate constant k for each chemical addition condition, it is possible to estimate the chemical addition conditions required to achieve the required removal rate for the residence time shortened by the short path. Furthermore, the addition amount adjustment unit 150 may compare the actual urea removal rate with the urea removal rate under ideal conditions. This may allow for an estimation of the extent to which the residence time has been shortened. The increase or decrease in the amount of chemical addition may be estimated based on the estimated change in residence time.

[0026] The addition amount adjusting unit 150 may set a plurality of values ​​of the chemical addition amount according to the temperature difference between the temperature T1 and the temperature T2, and may increase or decrease the chemical addition amount in stages. Specifically, for example, the addition amount adjusting unit 150 may increase or decrease the chemical addition amount in stages as the temperature difference between the temperature T1 and the temperature T2 increases.

[0027] Below, we will explain the results of a test conducted by passing water to be treated with a urea concentration of 25 ppb through a water tank corresponding to the reaction tank 180 shown in FIG. 1 and adding a fixed amount of sodium bromide and varying amounts of sodium hypochlorite to the water to be treated. FIG. 4 shows the conditions used in the test. Three conditions were set in this test. Condition 1 was a condition in which the amount of sodium bromide added was 3 mg / L and the amount of sodium hypochlorite added was 2.8 mg / L. Condition 2 was a condition in which the amount of sodium bromide added was 3 mg / L and the amount of sodium hypochlorite added was 3.4 mg / L. Condition 3 was a condition in which the amount of sodium bromide added was 3 mg / L and the amount of sodium hypochlorite added was 6.4 mg / L. When sodium bromide and sodium hypochlorite were added in the amounts specified in Condition 1, the amount of residual chlorine in the water to be treated was 0.4 mg / L. When sodium bromide and sodium hypochlorite were added in the amounts specified in Condition 2, the amount of residual chlorine in the water to be treated became 1.0 mg / L. When sodium bromide and sodium hypochlorite were added in the amounts specified in Condition 3, the amount of residual chlorine in the water to be treated became 4.0 mg / L.

[0028] FIG. 5 shows the residual urea concentration in the water to be treated when the chemicals added in the amounts set for the above-mentioned conditions 1 to 3 are added for each case of the magnitude relationship between temperatures T1 and T2. As shown in FIG. 5 , in all three cases of the magnitude relationship between temperatures T1 and T2, the residual urea concentration in the water to be treated is lower under condition 2, in which the amount of sodium hypochlorite added is increased compared to condition 1. The residual urea concentration in the water to be treated is even lower under condition 3, in which the amount of sodium hypochlorite added is even greater than under condition 2. In other words, increasing the amount of chemicals added to increase residual chlorine further improves treatment performance. On the other hand, if the target urea concentration in the treated water is 10 ppb, and temperatures T1 and T2 are equal when operating under condition 3, in which the amount of sodium hypochlorite added is the highest, the residual urea concentration will be lower than necessary, resulting in excessive chemical addition. Therefore, by adjusting the amount of chemicals added depending on the temperature difference between temperatures T1 and T2, it can be said that the amount of chemicals used can be reduced while stabilizing the quality of the treated water.

[0029] The reaction rate and the urea removal rate (or the residual urea concentration) may be measured in advance for each of a plurality of conditions, and the conditions (amount of chemical to be added) may be determined based on the decrease in residence time due to the temperature difference between the temperature T1 and the temperature T2 and the urea removal rate (or the residual urea concentration).

[0030] The following describes a control method in the control device 110 shown in Fig. 1. Fig. 6 is a flowchart for explaining an example of a control method in the control device 110 shown in Fig. 1.

[0031] First, the temperature information acquisition unit 120 acquires first temperature information indicating the temperature of the water to be treated at the inlet of the reaction tank 180 (step S1). Then, the temperature information acquisition unit 130 acquires second temperature information indicating the temperature of the water to be treated in the reaction tank 180 or the treated water at the outlet of the reaction tank 180 (step S2). Either the process of step S1 or the process of step S2 can be performed first.

[0032] Next, the comparison unit 140 calculates the difference between the temperature indicated by the first temperature information and the temperature indicated by the second temperature information (step S3). The comparison unit 140 compares the calculated difference with a threshold value (step S4). If the calculated difference exceeds the threshold value, the addition amount adjustment unit 150 changes at least one of the amount of bromide salt added by the bromide salt addition unit 160 and the amount of hypochlorite added by the hypochlorite addition unit 170 from the current amount (step S5).

[0033] As described above, when there is a temperature difference between temperatures T1 and T2, short-path water is likely to occur in the water being treated as it passes through the reaction tank 180. In such cases, stable urea removal performance can be achieved by adding a large amount of chemical to the water being treated. By monitoring the temperature difference between temperatures T1 and T2 and adjusting the amount of chemical added according to the temperature difference, it is possible to achieve good urea removal performance. This ensures sufficient urea removal performance. Furthermore, the temperature difference between temperatures T1 and T2 may result in the residence time of the water being treated in the reaction tank 180 being longer than expected. In such cases, there is a risk of excessive chemical addition. The present invention reduces chemical costs by appropriately adjusting the amount of chemical injection according to the residence time. Furthermore, when the difference between temperatures T1 and T2 exceeds a threshold value, the amount of chemical addition is adjusted. This allows for the amount of chemical addition to be avoided, even if there is a temperature difference between temperatures T1 and T2, if the temperature difference is small and does not require adjustment of the amount of chemical addition. Therefore, excessive chemical addition can be prevented.

[0034] Although the above description has been given by allocating each function (process) to each component, this allocation is not limited to the above. Furthermore, the configuration of the components is also not limited to the above-described form, which is merely an example.

[0035] The processing performed by the control device 110 described above may be performed by a logic circuit that is individually manufactured depending on the purpose. Alternatively, a computer program (hereinafter referred to as a program) that describes the processing content as a procedure may be recorded on a recording medium that can be read by the control device 110, and the program recorded on the recording medium may be read and executed by the control device 110. Recording media readable by the control device 110 include removable recording media such as floppy (registered trademark) disks, magneto-optical disks, DVDs (Digital Versatile Discs), CDs (Compact Discs), Blu-ray (registered trademark) Discs, USB (Universal Serial Bus) memories, and SD cards, as well as memories such as ROMs (Read Only Memory) and RAMs (Random Access Memory) built into the control device 110, and HDDs (Hard Disc Drives). The programs recorded on these recording media are read by a CPU (not shown) provided in the control device 110, and the same processing as described above is performed under the control of the CPU. Here, the CPU operates as a computer that executes the programs read from the recording media on which the programs are recorded.

[0036] Although the present invention has been described above with reference to the embodiments, the present invention is not limited to the above-described embodiments. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention.

[0037] This application claims priority based on Japanese Patent Application No. 2024-043835, filed March 19, 2024, the disclosure of which is incorporated herein in its entirety by reference.

[0038] REFERENCE SIGNS LIST 100 Urea treatment device 110 Control device 120, 130 Temperature information acquisition unit 140 Comparison unit 150 Addition amount adjustment unit 160 Bromide salt addition unit 161, 171 Valve 170 Hypochlorite addition unit 180 Reaction tank

Claims

1. A urea treatment device having: a first temperature information acquisition unit that acquires first temperature information indicating the temperature of the water to be treated that is supplied to a reaction tank where urea in the water to be treated is treated; a second temperature information acquisition unit that acquires second temperature information indicating the temperature of the water to be treated inside the reaction tank or discharged from the reaction tank; and an addition amount adjustment unit that compares the temperature indicated by the first temperature information with the temperature indicated by the second temperature information and adjusts at least one of the amount of bromide salt added to the water to be treated and the amount of hypochlorite added to the water to be treated based on the result of the comparison.

2. A urea treatment device according to claim 1, further comprising a comparison unit that compares the difference between the temperature indicated by the first temperature information and the temperature indicated by the second temperature information with a threshold value, and the addition amount adjustment unit adjusts at least one of the amount of bromide salt added and the amount of hypochlorite added based on the comparison result in the comparison unit.

3. A urea treatment device according to claim 1 or 2, wherein the addition amount adjustment unit measures at least one of the values ​​of the urea concentration, pH, water temperature, and residual chlorine concentration of the water to be treated in a reference state, obtains relational data showing the relationship between reaction time and the concentration of the treated water based on the measured values, and calculates the reference addition amount before adjustment based on the obtained relational data.

4. A urea treatment device according to claim 1 or 2, wherein the addition amount adjustment unit detects whether the water to be treated contains ammonia, and calculates a reference addition amount before adjustment based on the detection result.

5. A urea treatment device according to claim 1 or 2, wherein the addition amount adjustment unit increases at least one of the addition amount of the bromide salt and the addition amount of the hypochlorite from the current addition amount when the retention time of the water to be treated in the reaction tank is shorter than a predetermined specified time, and decreases at least one of the addition amount of the bromide salt and the addition amount of the hypochlorite from the current addition amount when the retention time exceeds the specified time.

6. A urea treatment device according to claim 1 or claim 2, wherein the second temperature information acquisition unit estimates the temperature of the water to be treated in the reaction tank or discharged from the reaction tank based on environmental information indicating the environment around the reaction tank, and acquires the second temperature information indicating the estimated temperature.

7. A urea treatment device according to claim 6, wherein the environmental information includes information indicating the outside air temperature of the reaction tank or the time period during which the second temperature information acquisition unit acquires the second temperature information.

8. A urea treatment device according to claim 1 or claim 2, wherein the first temperature information acquisition unit and the second temperature information acquisition unit acquire the temperature information when the type of water to be treated flowing into the reaction tank is switched.

9. A urea treatment device according to claim 1 or claim 2, comprising a heat exchanger for adjusting the temperature of the water to be treated in the reaction tank, and adjusting the heat exchanger so that the difference between the temperature indicated by the first temperature information and the temperature indicated by the second temperature information is smaller than a threshold value.

10. A urea treatment method comprising the steps of: acquiring first temperature information indicating the temperature of the water to be treated that is supplied to a reaction tank where urea in the water to be treated is treated; acquiring second temperature information indicating the temperature of the water to be treated that is discharged from the reaction tank or in the reaction tank; comparing the temperature indicated by the first temperature information with the temperature indicated by the second temperature information; and adjusting at least one of the amount of bromide salt and the amount of hypochlorite added to the water to be treated based on the result of the comparison.

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