Urea water producing system and urea water producing method

Abstract

To provide a producing system of urea water and a producing method of urea water capable of mass-producing by preventing clouding of urea water.SOLUTION: A urea water production system for producing urea water that prevents cloudiness, comprising: mixing means for mixing raw water and urea and dissolving the urea in the raw water to produce urea water; raw water supply means that includes a heating device for heating the raw water and supplies the raw water heated by the heating device to the mixing means; urea supply means for supplying the urea to the mixing means; and control means for controlling one or more of the raw water supply means and the urea supply means.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a urea water production system and a urea water production method that prevent the generation of cloudiness. [Background technology]

[0002] Urea solution is used in technology to purify nitrogen oxides (NOx) and is used to purify exhaust gas from internal combustion engines such as diesel engines. When urea water is used to purify exhaust gas, the urea water is sprayed into the exhaust gas. When urea water is introduced into the exhaust gas, ammonia is produced from the urea contained in the urea water, and the ammonia acts as a reducing agent to react with NOx in the exhaust gas. NOx is reduced to nitrogen and water, reducing the amount of NOx in the exhaust gas and purifying the exhaust gas. The exhaust gas purification method using urea solution has attracted attention as an effective clean technology.

[0003] Urea water is used as an important reducing agent in purifying exhaust gas, and various efforts are being made to develop technologies for producing urea water. For example, Patent Document 1 discloses an apparatus for producing an aqueous urea solution, which automatically measures and supplies urea and pure water (raw water) to a stirring vessel, stirs them, and easily produces an aqueous urea solution (urea water) of a desired concentration and volume on a small scale. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4514431 Summary of the Invention [Problem to be solved by the invention]

[0005] On the other hand, urea water is known to become cloudy. When cloudy urea water is used for exhaust gas purification, the cloudy components can clog the piping and equipment of the facility, causing blockages. To avoid problems such as blockages, it is necessary to prevent the urea water from becoming cloudy.

[0006] The solubility of urea in water is one of the causes of cloudiness of urea water. That is, when urea is added to water in an amount exceeding the saturated solubility of urea in water at a given temperature, the urea water becomes cloudy. Another cause of cloudiness in the urea solution is impurities contained in the urea solution, which act as nuclei to form solids, causing the urea solution to become cloudy.

[0007] The device disclosed in the above-mentioned Patent Document 1 is capable of easily producing urea water of a desired concentration and volume on a small scale, but does not take into consideration the clouding of the urea water, and therefore measures to prevent the clouding of the urea water are required. In particular, unlike the small-scale apparatus disclosed in Patent Document 1, when urea water is mass-produced industrially, preventing the urea water from becoming cloudy is a very important issue.

[0008] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a system and method for producing urea water that can prevent urea water from becoming cloudy and that can be mass-produced. [Means for solving the problem]

[0009] The present inventors have conducted extensive research to solve the above problems, and as a result have found that the following invention meets the above object, thereby completing the present invention.

[0010] That is, the present invention relates to the following inventions. <1> A urea water production system for producing urea water that is prevented from becoming cloudy, comprising: a mixing means for mixing raw water and urea and dissolving the urea in the raw water to produce the urea water; a raw water supply means having a heating device for heating the raw water and supplying the raw water heated by the heating device to the mixing means; a urea supply means for supplying the urea to the mixing means; and a control means for controlling at least one of the raw water supply means and the urea supply means. <2> In the control means, two or more production condition set values ​​selected from the group consisting of the following set values ​​(a) to (d) are set, and the control means calculates a control value based on the production condition set values, and controls one or more of the raw water supply means and the urea supply means based on the production condition set values ​​and / or the control value so as to prevent the urea water produced in the mixing means from becoming cloudy. <1> The urea water production system according to claim 1. Set value (a): the amount of raw water supplied to the mixing means Set value (b): Amount of urea supplied to the mixing means Set value (c): concentration of the urea water produced by the mixing means Set value (d): the amount of urea water produced by the mixing means <3> The manufacturing condition set values ​​set in the control means are set values ​​(b) and (c). <2> The urea water production system according to claim 1. <4> The set value (c) is limited to a predetermined range, and the control means calculates a target heating control temperature of the raw water supplied to the mixing means as a control value (e) based on the set value (c) limited to the predetermined range and the heat of dissolution of urea in water so that the urea water produced in the mixing means does not become cloudy, and controls the raw water supply means so that the temperature of the raw water supplied to the mixing means becomes the calculated control value (e). <3> The urea water production system according to claim 1. <5> The set value (c) is 20% by weight or more and 50% by weight or less. <2> from <4> 2. The urea water producing system according to claim 1, wherein <6> The temperature of the raw water supplied to the mixing means is 50°C or higher and 80°C or lower. <1> from <5> 2. The urea water producing system according to claim 1, wherein <7> The temperature of the urea water produced in the mixing means is 20°C or higher and 80°C or lower. <1> from <6> 2. The urea water producing system according to claim 1, wherein <8> The mixing means is a non-heating type. <1> from <7> 2. The urea water producing system according to claim 1, wherein <9> The raw water supply means further includes a raw water purification device that purifies the raw water, and a raw water storage device that stores the raw water purified in the raw water purification device and is connected upstream of the heating device. <1> from <8> 2. The urea water producing system according to claim 1, wherein <10> The raw water supplying means supplies the raw water to the mixing means after the amount of the raw water stored in the raw water storage device exceeds a predetermined amount. <9> The urea water production system according to claim 1. <11> The raw water purification device has a continuous electrodeionization treatment device (EDI device). <9> or <10> The urea water production system according to claim 1.

[0011] <1a> A method for producing urea water that prevents clouding, the method comprising: a step (1) of setting two or more production condition set values ​​selected from the group consisting of the following set values ​​(a) to (d) and calculating a control value based on the production condition set values; a step (2) of heating the raw material water based on the production condition set values ​​and / or the control value and supplying the heated raw material water to a mixing means; a step (3) of supplying the urea to the mixing means based on the production condition set values ​​and / or the control value; and a step (4) of mixing the raw material water supplied in step (2) and the urea supplied in step (3) in the mixing means to dissolve the urea in the raw material water and produce the urea water. Set value (a): the amount of raw water supplied to the mixing means Set value (b): Amount of urea supplied to the mixing means Set value (c): concentration of the urea water produced by the mixing means Set value (d): the amount of urea water produced by the mixing means <2a> The method for producing urea water according to <1a>, wherein the production condition set values ​​set in step (1) are set values ​​(b) and (c). <3a> The method for producing urea water according to <1a> or <2a>, wherein the set value (c) is limited to a predetermined range, the temperature of the raw water supplied to the mixing means is calculated as a control value (e) based on the set value (c) limited to the predetermined range and the heat of dissolution of urea in water so that the urea water produced in the mixing means does not become cloudy, and the raw water supply means is controlled in step (2) so that the temperature of the raw water supplied to the mixing means becomes the calculated control value (e). <4a> The method for producing urea water according to any one of <1a> to <3a>, wherein the set value (c) is 20% by weight or more and 50% by weight or less. <5a> The method for producing urea water according to any one of <1a> to <4a>, wherein the temperature of the raw water supplied to the mixing means is 50°C or higher and 80°C or lower. <6a> The method for producing urea water according to any one of <1a> to <5a>, wherein the temperature of the urea water produced in the mixing means is 20°C or higher and 80°C or lower. <7a> The method for producing urea water according to any one of <1a> to <6a>, wherein the mixing means is of a non-heating type. <8a> The method for producing urea water according to any one of <1a> to <7a>, further comprising, in step (2), a process of purifying the raw water before heating the raw water and supplying it to the mixing means, and a process of storing the purified raw water. <9a> The method for producing urea water according to <8a>, wherein in step (2), the raw water is supplied to the mixing means after the amount of the stored raw water exceeds a predetermined amount. <10a> The method for producing urea water according to <8a> or <9a>, wherein in step (2), the raw water is purified using a continuous electrodeionization treatment device (EDI device). [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a system and a method for producing urea water that are capable of preventing urea water from becoming cloudy and that are capable of mass production. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a schematic diagram showing a urea water production system according to an embodiment of the present invention. [Figure 2] 1 is a schematic diagram of a control means (first aspect) according to an embodiment of the present invention. [Figure 3] FIG. 3 is a schematic diagram of a control means (second embodiment) according to an embodiment of the present invention. [Figure 4] 1 is a main flow diagram of a urea water production method according to an embodiment of the present invention. [Figure 5] FIG. 2 is a flowchart showing a production condition setting process of the urea water production method according to the embodiment of the present invention. [Figure 6] FIG. 2 is a flow chart of a raw water supply process of the urea water production method according to the embodiment of the present invention. [Figure 7] FIG. 2 is a flow diagram of a urea supply process of the urea water production method according to the embodiment of the present invention. [Figure 8] FIG. 2 is a flow chart of a mixing process of the urea water production method according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] <1. Urea water production system> The urea water production system of the present invention is a urea water production system that produces urea water that is prevented from becoming cloudy, and includes: a mixing means that mixes raw water and urea and dissolves the urea in the raw water to produce the urea water; a raw water supply means that has a heating device that heats the raw water and supplies the raw water heated by the heating device to the mixing means; a urea supply means that supplies the urea to the mixing means; and a control means that controls one or more of the raw water supply means and the urea supply means.

[0015] With this configuration, the urea water production system of the present invention can mix urea and raw water to produce urea water that is prevented from becoming cloudy.

[0016] Furthermore, in the urea water production system of the present invention, two or more production condition set values ​​selected from the group consisting of the following set values ​​(a) to (d) are set in the control means, and the control means calculates a control value based on the production condition set values, and can control one or more of the raw water supply means and the urea supply means based on the production condition set values ​​and / or the control value so as to prevent the urea water produced in the mixing means from becoming cloudy. Set value (a): the amount of raw water supplied to the mixing means Set value (b): Amount of urea supplied to the mixing means Set value (c): concentration of the urea water produced by the mixing means Set value (d): the amount of urea water produced by the mixing means

[0017] By adopting such a configuration, the urea water production system of the present invention can set production conditions and calculate control values ​​that can prevent the urea water from becoming cloudy, and can automatically produce urea water that is prevented from becoming cloudy.

[0018] In the present invention, the production condition set value is a set value that specifies the conditions necessary for producing urea water. The production condition set value is composed of two or more selected from the group consisting of set values ​​(a) to (d) and is set as a numerical value. The supply amounts related to set values ​​(a) and (b) may be expressed in weight units (e.g., kg) or volume units (e.g., L). The concentration related to set value (c) may be expressed in weight units (e.g., wt%) or molar units (e.g., mol%). The production amount related to set value (d) may be expressed in weight units (e.g., kg) or volume units (e.g., L). In the present invention, the control value is a control variable used for controlling the production of urea water, and is a control variable that defines the conditions necessary for producing urea water. The manufacturing condition setting values ​​and control values ​​according to the present invention will be described in detail later.

[0019] Preferred embodiments of the present invention will now be described with reference to the drawings. The present invention is not limited to the following embodiments, and can be implemented with any modifications within the scope of the present invention. The dimensions, materials, and other specific numerical values ​​shown in the embodiments are merely examples to facilitate understanding of the invention, and do not limit the present invention unless otherwise specified. Furthermore, in all drawings, similar components are given similar reference numerals, and descriptions thereof will be omitted as appropriate.

[0020] FIG. 1 is a schematic diagram showing a urea water production system according to an embodiment of the present invention. The urea water production system 1 is a system that mixes urea with raw water to produce urea water that is prevented from becoming cloudy. The urea water production system includes raw water supply means 10, urea supply means 20, mixing means 30, and control means 90.

[0021] [1-1. Raw water supply means] The raw water supply means 10 heats raw water (water that is a raw material for urea water) and supplies the heated raw water to the mixing means 30. By supplying heated raw water to the mixing means 30 in this manner, it is possible to suppress a decrease in the temperature of the urea water due to the dissolution of urea in water, which is an endothermic reaction, and to produce urea water that is free from cloudiness due to precipitation of urea due to a decrease in saturated solubility.

[0022] The raw water supply means 10 includes a raw water purification device 11 , a raw water storage device 13 , a liquid delivery device 16 , a heating device 12 , and a flow meter 17 .

[0023] As shown in FIG. 1, raw water supplied from a raw water supply source W is purified in a raw water purification device 11 that purifies the raw water. In raw water purification apparatus 11, foreign matter in the raw water is removed by purifying the raw water, so that precipitation of urea due to the foreign matter can be avoided and clouding of the urea water can be prevented.

[0024] In this embodiment, the raw water supplied from the raw water supply source W to the raw water purification device 11 is tap water. In the present invention, the raw water supplied to the raw water purification apparatus can be purified in the raw water purification apparatus, and any type of raw water can be used as long as the urea water produced using the purified raw water does not become cloudy.

[0025] The raw water purification apparatus according to the present invention is an apparatus that purifies raw water by removing foreign matter contained in the raw water. The raw water purification apparatus can use any device or component as long as it can purify raw water in a manner that prevents the urea water from becoming cloudy. Examples of devices and components that can be used in the raw water purification apparatus include reverse osmosis membranes (RO membranes), decarbonation membranes, continuous deionization treatment devices (EDI devices), ion exchange resins, and filter media. Among these, it is preferable that the raw water purification apparatus have a continuous electrodeionization treatment device. By using a continuous electrodeionization treatment device, the raw water purification apparatus can purify raw water without using chemicals, etc., thereby simplifying maintenance and enabling continuous purification of raw water. The raw water purification apparatus can use any combination of the above devices and components depending on the purpose.

[0026] The raw water purified by raw water purification apparatus 11 is stored in raw water storage apparatus 13, which is installed downstream of the raw water purification apparatus. Raw water storage apparatus 13 stores the raw water purified by raw water purification apparatus 11. Raw water storage apparatus 13 is a cylindrical tank with a height of 6.2 m, a diameter of 3.3 m, and a capacity of 50,000 L. The raw water storage device 13 has a water level meter (not shown) that measures the level of the stored raw water. The raw water stored in the raw water storage device 13 is managed to a predetermined amount according to the measurement value of the water level meter.

[0027] The raw water stored in the raw water storage device 13 is sent to the heating device 12 by a liquid sending device (water pump) 16 arranged downstream of the raw water storage device 13.

[0028] The raw water sent to the heating device 12 by the liquid sending device 16 is heated by the heating device (boiler) 12. The heated raw water is supplied from the heating device 12 to the mixing means 30. In other words, the raw water supplying means 10 has the heating device 12 that heats the raw water, and can supply the raw water heated by the heating device 12 to the mixing means 30. In this way, by supplying heated raw water to the mixing means 30, the urea water in the mixing means 30 can be maintained at a predetermined temperature or higher, thereby avoiding precipitation of urea in the produced urea water and preventing the urea water from becoming cloudy.

[0029] The heating device 12 has a thermometer (not shown) that measures the temperature of the heated raw water. While measuring the temperature of the heated raw water using the thermometer, the heating device 12 is controlled by a control means described later, and heats the raw water to a predetermined temperature (control value (e)). Details of the control will be described later.

[0030] A flow meter 17 for measuring the flow rate of the heated raw water is installed downstream of the heating device 12. By integrating the flow rate measured by the flow meter 17, the amount of urea water required to be produced by the mixing means 30 can be determined.

[0031] [1-2. Urea supply means] The urea supplying means 20 supplies urea to the mixing means 30 . In the present invention, the urea supply means may be any means as long as it can supply urea to the mixing means. For example, the urea supply means may be configured to include a urea supply path so that urea can be manually supplied to the mixing means, or may be configured to supply urea to the mixing means using a flexible container bag (FIBC), or may be configured to include a urea storage container and an on-off valve so that urea can be automatically supplied to the mixing means. When urea is manually supplied to the mixing means, the amount of urea to be supplied can be set to a set value (a), and the control means described below does not need to control the urea supply means.

[0032] In this embodiment, the urea supplied from the urea source U to the urea supply means 20 (and the urea supplied from the urea supply means 20 to the mixing means 30) is in a powder form. Note that in the present invention, the form of urea supplied by the urea supply means can be any form of urea as long as it is possible to mix raw water and urea in the mixing means and dissolve urea in the raw water to produce urea water, and the form may be other than a powder, for example, granular.

[0033] [1-3. Mixing means) The mixing means 30 mixes the raw water supplied from the raw water supply means 10 with the urea supplied from the urea supply means, and dissolves the urea in the raw water to produce urea water. The mixing means 30 is a cylindrical tank having a height of 2.0 m, a diameter of 2.7 m, and a capacity of 10,000 L.

[0034] The mixing means 30 includes an agitator (not shown). The raw water and urea supplied to the mixing means 30 are agitated and mixed by the agitator. By mixing the raw water and urea in the agitator, the urea is dissolved in the raw water, and urea water is produced. Note that the mixing means 30 does not need to include an agitator as long as urea is dissolved in the raw water and urea water is produced in the mixing means 30.

[0035] The mixing means 30 is of a non-heated type. As described above, because heated raw water is supplied by the raw water supply means 10, even if the mixing means 30 is a non-heating type, the temperature of the raw water (or urea water) can be increased (the saturated solubility of urea) to prevent urea precipitation, and urea water that does not become cloudy can be produced. Furthermore, by using a non-heating type mixing means 30, it is possible to avoid an increase in energy consumption due to extra capital investment and additional heat. This is particularly advantageous when producing urea water on an industrial scale. The mixing means according to the present invention may be of a heating type as long as it does not impair the object of the present invention.

[0036] In the present invention, the mixing means may be provided with a thermometer that measures the temperature of the urea water (or raw water). By providing the mixing means with the thermometer, the control means controls the raw water supply means to supply heated raw water based on the measurement value of the thermometer, and by increasing the temperature of the urea water in the mixing means and decreasing the urea concentration, it is possible to avoid precipitation of urea and prevent the urea water from becoming cloudy. In the present invention, the mixing means may be provided with a water level meter that measures the level of the urea water (or raw water). By providing the mixing means with the water level meter, the control means can control the raw water supply means to supply (add) raw water to the mixing means based on the measurement value of the water level meter. Furthermore, the control means may control the urea supply means to supply (add) urea to the mixing means as necessary.

[0037] The urea water produced in the mixing means 30 is sent to a urea water storage means (not shown) installed downstream of the mixing means 30 and stored therein.

[0038] [1-4. Control means] As described above, the urea water production system 1 mixes raw water supplied from the raw water supply means 10 with urea supplied from the urea supply means 20 in the mixing means 30, and dissolves the urea in the raw water to produce urea water. In order to produce urea water that is prevented from becoming cloudy by dissolving urea in raw water, the urea water production system 1 has a control means 90 that controls one or more of the raw water supply means and the urea supply means. The control means 90 has a first mode (control means 90A) and a second mode (control means 90B), which will be described with reference to the drawings. FIG. 2 shows a schematic diagram of a control means (first embodiment) according to an embodiment of the present invention, and FIG. 3 shows a schematic diagram of a control means (second embodiment) according to an embodiment of the present invention.

[0039] (1-4-1. Control Means - First Aspect) As shown in FIG. 2, a control means 90A according to the embodiment of the present invention includes a setting unit 91, a calculation unit 92, a receiving unit 93, and a control unit 94.

[0040] The setting unit 91 has a display and can set the production condition setting values ​​required for producing urea water. The production condition setting values ​​that can be set by the setting unit 91 are the following setting values ​​(a) to (d). Note that the units for setting the production condition setting values ​​are also indicated. Set value (a): Amount of raw water supplied to the mixing means 30 (unit: kg) Set value (b): Amount of urea supplied to the mixing means 30 (unit: kg) Set value (c): concentration of urea water produced in the mixing means 30 (unit: weight %) Set value (d): Amount of urea water produced by the mixing means 30 (unit: kg)

[0041] The setting unit 91 can set two or more production condition set values ​​selected from the group consisting of the set values ​​(a) to (d). As will be described later, the calculation unit 92 calculates control values ​​necessary for producing urea water from two or more production condition set values ​​selected from the group consisting of the set values ​​(a) to (d). The control unit 94 controls one or more of the raw water supply means 10 and the urea supply means 20 based on the production condition set values ​​and / or control values. That is, the control means 90 sets two or more production condition set values ​​selected from the group consisting of the set values ​​(a) to (d), and the control means 90 calculates a control value based on the production condition set values ​​and controls one or more of the raw water supply means 10 and the urea supply means 20 based on the production condition set values ​​and / or control value so as to prevent the urea water produced in the mixing means 30 from becoming cloudy.

[0042] The setting unit 91 can arbitrarily set two or more production condition set values ​​selected from the group consisting of the above set values ​​(a) to (d), but the production condition set values ​​set in the control means may be set values ​​(b) and (c). By setting the production condition set values ​​to set values ​​(b) and (c), the control for producing urea water can be simplified. By setting the supply amount of urea supplied to the mixing means by manual labor or the like as set value (b) and setting the concentration of urea water to be produced as set value (c), the control means 90 controls only the raw water supply means 10 to produce urea water that is prevented from becoming cloudy.

[0043] The calculation unit 92 receives the production condition setting values ​​from the setting unit 91 and calculates control values ​​necessary for control to produce urea water that is prevented from becoming cloudy. The control values ​​can include the following control values ​​(a) to (e). Control value (a): Control target value of the supply amount of raw water supplied to the mixing means 30 Control value (b): Control target value of the amount of urea supplied to the mixing means 30 Control value (c): Control target value of the concentration of urea water produced in the mixing means 30 Control value (d): Control target value of the amount of urea water produced in the mixing means 30 Control value (e): Control target value of the heating temperature of the raw water supplied to the mixing means 30 (target heating control temperature of the raw water)

[0044] The control values ​​to be calculated are control values ​​other than the manufacturing conditions set as the manufacturing condition set values. For example, if set values ​​(a) and (b) are set as the manufacturing condition set values, the control values ​​to be calculated are control values ​​(c) to (e). Also, if set values ​​(b) and (c) are set as the manufacturing condition set values, the control values ​​to be calculated are control values ​​(a), (d), and (e). The details of the calculations in the calculation unit 92 will be described later.

[0045] The calculation unit according to the present invention does not need to calculate all of the control values ​​(a) to (e) as long as the control unit can control each means so as to produce urea water that is prevented from becoming cloudy. For example, when set values ​​(a) and (b) are set as the production condition set values, the calculated control value can be only control value (e). The control unit can control the raw water supply means based on set value (a) and control value (e), and can control the urea supply means based on set value (b). Furthermore, when set values ​​(b) and (c) are set as the production condition set values, the calculated control values ​​can be control values ​​(a) and (e). The control unit can control the raw water supply means based on the control values ​​(a) and (e), and can control the urea supply means based on the set value (b). Furthermore, when set values ​​(c) and (d) are set as the production condition set values, the calculated control values ​​can be control values ​​(a), (b), and (e). The control unit can control the raw water supply means based on the control values ​​(a) and (e), and can control the urea supply means based on the set value (b).

[0046] The calculation unit 92 transmits the manufacturing condition setting values ​​and the control values ​​to the control unit 94 .

[0047] The calculation unit 92 can calculate the control value from the manufacturing condition setting value, but the control means according to the present invention may display the control value calculated in the calculation unit on a display unit (not shown), reset the displayed control value in the setting unit, and the calculation unit may transmit the newly set value as the manufacturing condition setting value to the control unit. For example, the setting unit may set the setting values ​​(b) and (c) as manufacturing condition setting values, the calculation unit may calculate the control values ​​(a) and (e), the control value (a) may be displayed on the display unit, the control value (a) displayed on the display unit may be set as the manufacturing condition setting value (setting value (a)) in the setting unit, and the setting value (a) may be transmitted from the calculation unit to the control unit. Alternatively, the control value (a) displayed on the display unit may be set as the manufacturing condition setting value (setting value (a)) in the setting unit, and the setting value (a) may be transmitted from the setting unit to the control unit (without passing through the calculation unit).

[0048] The receiving unit 93 receives signals transmitted from the devices provided in the raw water supply means 10, the urea supply means 20, and the mixing means 30, respectively. Signals are transmitted from the raw water supply means 10 regarding the operating status of the raw water purification device 11, the water level of the water level gauge of the raw water storage device 13, the operating output of the liquid delivery device 16, the operating status of the heating device 12, the raw water temperature after heating, and the raw water flow rate of the flow rate measuring device 17. The urea supplying means 20 sends a signal to the mixing means 30 regarding the amount of urea to be supplied. The mixing means 30 sends a signal regarding the operating status of the agitator. The receiving unit 93 receives these signals and transmits them to the control unit 94 .

[0049] The receiving unit according to the present invention may receive signals other than those described above, as long as it can produce urea water that is free from cloudiness. For example, the receiving unit may receive signals related to the operating time of the raw water purification apparatus and the amount of raw water processed from the raw water supplying means. Furthermore, if the mixing means is equipped with a thermometer and / or a water level gauge, the receiving unit may receive signals related to the temperature and / or water level of the urea water (raw water) from the mixing means. Furthermore, the receiving unit according to the present invention may not receive some of the above-mentioned signals as long as it can produce urea water that is prevented from becoming cloudy. For example, when the setting unit sets the set value (b) (the amount of urea supplied to the mixing means), the receiving unit may not receive a signal regarding the amount of urea supplied from the urea supply means.

[0050] The control unit 94 receives manufacturing condition setting values ​​and control values ​​from the calculation unit 92 and receives various signals from the receiving unit 93 . The control unit 94 controls the raw water supply means 10, the urea supply means 20, and the mixing means 30 based on the production condition set values ​​and control values ​​received from the calculation unit 92. Based on the various signals from the receiving unit 93 obtained by controlling each means, the control unit 94 controls (adjusts) each means so that the various signals become the production condition set values ​​and / or control values. Specifically, the control unit 94 controls the raw water supply means 10 based on the set value (a) or control value (a) and the set value (e) or control value (e). The control unit 94 also controls the urea supply means 20 based on the set value (b) or control value (b). In this way, the control means 90 controls the raw water supply means 10, the urea supply means 20, and the mixing means 30, so that the urea water production system 1 can produce urea water that is prevented from becoming cloudy.

[0051] Although the control unit 94 according to the embodiment of the present invention controls the raw water supply means 10, the urea supply means 20, and the mixing means 30, the control unit according to the present invention controls one or more of the raw water supply means and the urea supply means. For example, if urea is supplied manually via the urea supply means, the control unit according to the present invention does not need to control the urea supply means. Furthermore, if the mixing means according to the present invention does not have a stirring device or a measuring instrument, the control unit according to the present invention does not need to control the mixing means.

[0052] The calculation unit 92 can calculate control values ​​for the concentration of urea water, the amount of urea water produced, the amount of raw water supplied, and the amount of urea supplied by using two or more production condition setting values ​​selected from the group consisting of setting values ​​(a) to (d) set in the setting unit 91. Specifically, by using simultaneous equations including variables Xa to Xd corresponding to four set values ​​(a) to (d), the following control values, which are unset manufacturing conditions, can be calculated appropriately from two or more set manufacturing condition set values. Control value (a): Control target value of the supply amount of raw water supplied to the mixing means 30 Control value (b): Control target value of the amount of urea supplied to the mixing means 30 Control value (c): Control target value of the concentration of urea water produced in the mixing means 30 Control value (d): Control target value of the amount of urea water produced in the mixing means 30

[0053] As will be described later, it is also possible to determine the target temperature at which the raw water is heated in order to produce urea water that is prevented from becoming cloudy. Control value (e): Control target value of the heating temperature of the raw water supplied to the mixing means 30 (target heating control temperature of the raw water)

[0054]

number

[0055]

number

[0056] For example, when a set value (a) (amount of raw water supplied) and a set value (b) (amount of urea supplied) are set in the setting unit 91, the amount of urea water produced (control value (d)) can be calculated by adding the set value (a) and the set value (b) using equation (1), and the concentration of urea water (control value (c)) can be calculated by dividing the set value (b) by the calculated amount of urea water produced using equation (2). Similarly, it is possible to calculate the control value of an unset manufacturing condition from two or more set manufacturing condition values ​​other than the above (set value (a) and set value (b)). Therefore, by using two or more production condition setting values ​​selected from the group consisting of setting values ​​(a) to (d) set in the setting unit 91, the calculation unit 92 can set the conditions for producing urea water that is prevented from becoming cloudy (the supply amount of raw water, the supply amount of urea, the concentration of urea water, and the production amount of urea water) as production condition setting values ​​and control values.

[0057] The calculation unit 92 calculates the temperature of the raw water heated by the raw water supply means 10 based on the set or calculated supply amount of raw water and the set or calculated supply amount of urea so as to prevent the urea water produced in the mixing means 30 from becoming cloudy. The dissolution of urea in water is an endothermic reaction, and heating the raw water to a predetermined temperature or higher can prevent urea from precipitating (the urea content exceeding the saturated solubility) and prevent clouding.

[0058] The calculation unit 92 can calculate the temperature change (decrease) when urea dissolves in water from the set or calculated supply amount of raw water and the set or calculated supply amount of urea using the dissolution enthalpy of urea in water and the specific heat of water.

[0059]

number

[0060] The molecular weight of urea (M) is 60, and the enthalpy of dissolution of urea in water (H UW ) is 15.4 kJ / mol, and the specific heat of water (C W ) is 4.2kJ / kg K, so equation 3 can be transformed as follows:

[0061]

number

[0062] As shown in equations (3) and (4), the supply amount of raw water is included as a variable in the denominator, and the supply amount of urea is included as a variable in the numerator. If the relative supply amounts (supply ratio) of raw water and urea can be determined, the temperature change (decrease) when urea is dissolved in water can be calculated. The relative supply amounts (supply ratio) of raw water and urea can be calculated from the concentration of the urea water, and therefore, by setting a set value (c) or control value (c), which is the concentration of the urea water, the temperature change (decrease) when urea is dissolved in water can be calculated.

[0063] In order to prevent the urea water from becoming cloudy, it is necessary to maintain the temperature of the urea water produced in the mixing means 30 at a predetermined temperature or higher, and a control value (e) (target temperature to which raw water is heated) is calculated taking into account the temperature drop when urea is dissolved in water. That is, the control value (e) can be calculated by adding the temperature change (ΔT) of urea when it is dissolved in water to the temperature of the urea water to be maintained.

[0064] By performing the above calculation in the calculation unit 92, it is possible to calculate the control values ​​(a) to (e) from two or more manufacturing condition setting values ​​selected from the group consisting of the setting values ​​(a) to (d).

[0065] From the viewpoint of producing high-quality urea water, when the setting unit 91 selects the set value (c) which is the concentration of the urea water, it is preferable that the set value (c) be limited to a predetermined range. If the concentration of the urea water of the set value (c) is too low, the amount of urea contained in the urea water will be small, and it may become difficult to obtain sufficient effects when using the urea water. Also, if the concentration of the urea water of the set value (c) is too high, urea will precipitate, causing the urea water to become cloudy.

[0066] The range of the set value (c) (the concentration of the urea water produced in the mixing means) is, for example, 20% by weight to 50% by weight, 25% by weight to 45% by weight, or 30% by weight to 40% by weight.

[0067] The set value (c) may be set by selecting a concentration of urea water from among options in the setting unit 91. As the options for the concentration of urea water, for example, two or more options selected from the group consisting of 20 wt %, 22.5 wt %, 25 wt %, 27.5 wt %, 30 wt %, 32.5 wt %, 35 wt %, 37.5 wt %, and 40 wt % may be set. By allowing the concentration of urea water to be set by selecting from among the options in this way, the setting can be simplified.

[0068] When the set value (c) is limited to a predetermined range, the control unit 94 (control means 90A) calculates a control value (e), which is the target heating control temperature of the raw water supplied to the mixing means 30, based on the set value (c) limited to the predetermined range and the heat of dissolution of urea in water so that the urea water produced in the mixing means 30 does not become cloudy, and can control the raw water supply means 10 so that the temperature of the raw water supplied to the mixing means 30 becomes the control value (e).

[0069] If the temperature of the raw water is low, urea is difficult to dissolve in the raw water, and even if urea dissolves, there is a possibility that it will precipitate. Furthermore, if the temperature of the raw water (or urea water) is high, ammonia is generated from the dissolved urea, which may result in a decrease in the quality of the urea water, such as the generation of an unpleasant odor. In order to prevent the produced urea water from becoming cloudy and to maintain its quality, it is preferable that the temperature of the raw water in the mixing means 30, i.e., the temperature of the urea water produced in the mixing means 30, is within a predetermined temperature range. The temperature of the urea water produced in the mixing means 30 is, for example, 20°C or higher and 80°C or lower, 30°C or higher and 75°C or lower, or 40°C or higher and 70°C or lower.

[0070] In order to maintain the urea water at a predetermined temperature or higher, the raw water is heated taking into consideration the temperature drop that occurs when urea dissolves in water. If the temperature of the urea water is maintained at 20°C or higher and the temperature drop that occurs when urea dissolves in water is 30°C, the temperature of the raw water supplied to the mixing means 30 will be 50°C or higher.

[0071] On the other hand, if the temperature of the raw water supplied to the mixing means 30 is too high, the energy required for heating will be wasted, and if the temperature of the urea water is too high, the urea will decompose into ammonia (and the unpleasant odor of ammonia will occur). Therefore, it is preferable that the temperature of the raw water supplied to the mixing means 30 be controlled within a predetermined temperature range. The temperature of the raw water supplied to the mixing means 30 is, for example, 50°C or higher and 80°C or lower, 55°C or higher and 75°C or lower, or 60°C or higher and 70°C or lower.

[0072] (1-4-2. Control Means - Second Aspect) As shown in FIG. 3, the control means according to the embodiment of the present invention (second aspect, hereinafter referred to as control means 90B) includes a setting unit 91, a calculation unit 92, a receiving unit 93, a control unit 94, and a storage unit 95.

[0073] The details of the setting unit 91 and the receiving unit 93 are as described above, and therefore will not be described again. In addition, the details of the calculation unit 92 and the control unit 94 may be omitted where appropriate for portions that overlap with the above content. The storage unit 95 is a component newly added in the control means 90B (second aspect), and will be described in detail below.

[0074] The memory unit 95 stores control values ​​required for the control unit 94 to control each means. One of the control values ​​stored in the memory unit 95 is a control value (e) (a control target value for the heating temperature of the raw water supplied to the mixing means 30 (target heating control temperature of the raw water)). The memory unit 95 transmits the control value (e) to the control unit 94. The storage unit according to the present invention can store any control value and transmit it to the control unit so that the urea water production system can produce urea that is prevented from becoming cloudy.

[0075] As described above, the calculation unit 92 can calculate the control values ​​(a) to (d) by using two or more set values ​​selected from the group consisting of the set values ​​(a) to (d) set in the setting unit 91. Note that since the memory unit 95 stores the control value (e) (target heating control temperature of the raw water) and transmits it to the control unit 94, the calculation unit 92 does not need to calculate the heating temperature.

[0076] The control value (e) stored in the memory unit 95 is arbitrary as long as it can prevent the urea water produced in the mixing means 30 from becoming cloudy. The control value (e) stored in the memory unit 95 can be, for example, 50°C or higher and 80°C or lower, 55°C or higher and 75°C or lower, or 60°C or higher and 70°C or lower.

[0077] The control unit 94 receives manufacturing condition setting values ​​and control values ​​from the calculation unit 92 and the storage unit 95 , and receives various signals from the receiving unit 93 . The control unit 94 controls the raw water supply means 10, the urea supply means 20, and the mixing means 30 based on the production condition set values ​​and control values ​​received from the calculation unit 92 and the memory unit 95. The control unit 94 controls (adjusts) each means based on various signals from the receiving unit 93 obtained by controlling each means so that the various signals become the production condition set values ​​and control values. In this way, the control unit 90 controls the raw water supply means 10, the urea supply means 20, and the mixing means 30, so that the urea water production system 1 can produce urea water that is prevented from becoming cloudy.

[0078] The urea water production system of the present invention has been described above. Hereinafter, the urea water production method of the present invention will be described with reference to the drawings. FIG. 4 shows a main flow diagram of the urea water production method according to an embodiment of the present invention, FIG. 5 shows a flow diagram of the raw material water supply process of the urea water production method according to an embodiment of the present invention, FIG. 6 shows a flow diagram of the urea supply process of the urea water production method according to an embodiment of the present invention, FIG. 7 shows a flow diagram of the urea supply process of the urea water production method according to an embodiment of the present invention, and FIG. 8 shows a flow diagram of the mixing process of the urea water production method according to an embodiment of the present invention. In addition, explanations that overlap with the above content may be omitted as appropriate.

[0079] <2. Urea water production method> The method for producing urea water of the present invention is a method for producing urea water that is prevented from becoming cloudy, and includes the steps of: a step (1) of setting two or more production condition set values ​​selected from the group consisting of the following set values ​​(a) to (d) and calculating a control value based on the production condition set values; a step (2) of heating the raw water based on the production condition set values ​​and / or the control value and supplying the heated raw water to a mixing means; a step (3) of supplying the urea to the mixing means based on the production condition set values ​​and / or the control value; and a step (4) of mixing the raw water supplied in step (2) and the urea supplied in step (3) in the mixing means and dissolving the urea in the raw water to produce the urea water. Set value (a): the amount of raw water supplied to the mixing means Set value (b): Amount of urea supplied to the mixing means Set value (c): concentration of the urea water produced by the mixing means Set value (d): the amount of urea water produced by the mixing means

[0080] By adopting such a configuration, the urea water producing method of the present invention can produce urea water that is prevented from becoming cloudy by mixing urea and raw water.

[0081] FIG. 4 shows a main flow diagram of the urea water production method according to the embodiment of the present invention. The urea water producing method according to the embodiment of the present invention includes a setting step (S100), a raw material water supply step (S200), a urea supply step (S300), and a mixing step (S400).

[0082] The urea water production method according to the embodiment of the present invention is carried out in the order of the production condition setting step (S100), the raw water supply step (S200), the urea supply step (S300), and the mixing step (S400). However, as long as the object of the present invention is not impaired, the urea water production method according to the present invention may carry out the urea supply step before the raw water supply step, or may carry out the raw water supply step and the urea supply step in parallel. Furthermore, the urea water production method according to the present invention may carry out the raw water supply step, the urea supply step, and the mixing step in parallel. By carrying out each step in parallel, the production time can be shortened.

[0083] [2-1. Manufacturing condition setting process] The manufacturing condition setting step (S100) is a step (1) of setting two or more manufacturing condition setting values ​​selected from the group consisting of the following setting values ​​(a) to (d) and calculating a control value based on the manufacturing condition setting values. Set value (a): the amount of raw water supplied to the mixing means Set value (b): Amount of urea supplied to the mixing means Set value (c): concentration of the urea water produced by the mixing means Set value (d): the amount of urea water produced by the mixing means FIG. 5 shows a flow chart of the production condition setting process of the urea water production method according to the embodiment of the present invention.

[0084] In the manufacturing condition setting step (S100), two or more set values ​​selected from the group consisting of the following set values ​​(a) to (d) are input (set) as set values ​​to be used in the manufacturing method of urea water prevented from becoming cloudy (S110). From the two or more input set values, control values ​​(a) to (e) are calculated (S120). The calculation of the control values ​​is as described above, and a description thereof will be omitted. When the calculation of the control value is completed, the process proceeds to the raw water supply step (S200).

[0085] The method for producing urea water of the present invention can have the following configurations as long as the object of the present invention is not impaired. For example, instead of calculating the control value, the control value stored in the storage unit can be used. The manufacturing condition set values ​​set in step (1) may be set values ​​(b) and (c). Furthermore, the set value (c) may be limited to a predetermined range, and the temperature of the raw water supplied to the mixing means may be calculated as a control value (e) based on the set value (c) limited to the predetermined range and the heat of dissolution of urea in water so that the urea water produced in the mixing means does not become cloudy, and the raw water supply means may be controlled so that the temperature of the raw water supplied to the mixing means in step (2) becomes the calculated control value (e). The set value (c) may be 20% by weight or more and 50% by weight or less.

[0086] [2-2. Raw water supply process] The raw water supply step (S200) is a step (2) of heating the raw water and supplying it to the mixing means based on the production condition set values ​​and / or the control values. FIG. 6 shows a flow diagram of a raw water supply process in a urea water production method according to an embodiment of the present invention.

[0087] When the process proceeds to the raw water supply step (S200), purification of the raw water is initiated (S210). The raw water is purified by removing foreign matter from the raw water (tap water) using a raw water purification device. Purifying the raw water removes foreign matter from the raw water, preventing the urea water from becoming cloudy due to the foreign matter. The purified raw water is stored in a raw water storage device. A water level meter installed in the raw water storage device measures the level of the stored raw water, and the raw water is purified until it reaches a predetermined level (S210, S220). When the level of raw water stored in the raw water storage device reaches a predetermined level, the raw water is heated by the heating device, and the heated raw water is supplied to the mixing means (S230). That is, the raw water supply means supplies raw water to the mixing means only after the amount of raw water stored in the raw water storage device exceeds a predetermined amount. By performing these processes (S220, 230), subsequent heating and supply of raw water can be performed without interruption, thereby avoiding the wait time for restart due to interruption. Avoiding the wait time for restart prevents a drop in the temperature of the heated raw water already supplied to the mixing means and the clouding of the urea water due to urea precipitation caused by the temperature drop. The heating of the raw water by the heating device is performed based on a set value or a control value calculated from the set value. The calculation and control related to the heating of the raw water are as described above, and therefore a description thereof will be omitted. By supplying the heated raw water to the mixing means, the saturated solubility of urea in the urea water can be increased, urea precipitation can be prevented, and urea water that is free from cloudiness can be produced. A flow meter provided in the raw water supply means measures the cumulative flow rate of raw water supplied to the mixing means. Raw water is heated and supplied to the mixing means until the cumulative flow rate reaches a set value (a) (the supply amount of raw water) or a control value calculated from the set value (S230, S240). After the integrated flow rate reaches a set value (a) (amount of raw water supplied) or a control value calculated from the set value, the process proceeds to the urea supply step (S300).

[0088] The method for producing urea water of the present invention can have the following configurations as long as the object of the present invention is not impaired. For example, the temperature of the raw water supplied to the mixing means may be 50°C or higher and 80°C or lower. Furthermore, as described above, in step (2), before the raw water is heated and supplied to the mixing means (S230), a process for purifying the raw water (S210) and a process for storing the purified raw water (S220) are further included, but the process for purifying the raw water (S210) and the process for storing the purified raw water (S220) do not necessarily have to be included. Furthermore, as described above, in step (2), the raw water is supplied to the mixing means after the stored raw water exceeds a predetermined amount (S220, S230), but the raw water may be supplied to the mixing means before the stored raw water exceeds a predetermined amount. In step (2), the raw water may be purified using a continuous electrodeionization treatment device (EDI device).

[0089] [2-3. Urea supply process] The urea supply step (S300) is a step of supplying the urea to the mixing means based on a set value. FIG. 7 shows a flow diagram of the urea supply process in the urea water production method according to the embodiment of the present invention.

[0090] When the process proceeds to the urea supply step (S300), the supply of urea to the mixing means is started (S310). Urea is manually supplied to the mixing means until the supply amount of urea (set value (b) or control value) is reached (S310). After the urea is supplied to the mixing means, the process proceeds to the mixing step (S400).

[0091] The supply of urea may be performed automatically by providing a urea storage container and an on-off valve to the mixing means.

[0092] [2-4. Mixing process] The mixing step (S400) is a step of mixing the raw water supplied in the raw water supply step and the urea supplied in the urea supply step in a mixing means to dissolve the urea in the raw water and produce urea water. FIG. 8 shows a flow diagram of the mixing process of the urea water production method according to the embodiment of the present invention.

[0093] When the process proceeds to the mixing step (S400), an agitator provided in the mixing device is activated (S410). As the agitator is activated, the raw water and urea supplied to the mixing means are agitated and mixed within the mixing means. As the raw water and urea are mixed within the mixing means, the urea dissolves in the raw water, and urea water is produced. The raw water supplied to the mixing means is purified to remove foreign matter, and the raw water is heated before supply, so that precipitation of urea due to foreign matter and solubility saturation can be avoided, and urea water that is prevented from becoming cloudy can be produced. After the agitator has been running for a predetermined time, the agitator stops when the production of urea water is completed (S420, S430). When the agitator stops, the production of urea water is completed (S900).

[0094] The method for producing urea water of the present invention can have the following configurations as long as the object of the present invention is not impaired. For example, the temperature of the urea water produced by the mixing means may be 20°C or higher and 80°C or lower. The mixing means may be of a non-heating type.

[0095] Although the embodiments of the present invention have been described above with reference to the drawings, the embodiments disclosed herein are illustrative in all respects and are not limiting. In particular, in the embodiments disclosed herein, matters not expressly disclosed, such as operating conditions, operating conditions, various parameters, dimensions, weights, volumes of components, etc., do not deviate from the scope of ordinary practice by a person skilled in the art, and values ​​that can be easily assumed by a person skilled in the art are used. [Example]

[0096] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[0097] Using the urea water production system and urea water production method of the present invention, urea water of the example was produced as follows. <1. Production of urea solution> 1-1. Example 1 1,560 kg of purified tap water was used as raw water using a water treatment device (Muromachi Chemical Co., Ltd.). The raw water was heated to 53°C, and 750 kg of urea (industrial granular urea, manufactured by Nissan Chemical Co., Ltd.) was added to the raw water. The raw water and urea were mixed (stirred) to dissolve the urea water in the raw water, producing the urea water (concentration 32.5 wt%) of Example 1. [1-2. Example 2] Urea water of Example 2 (concentration 40 wt %) was produced using the same procedure as the urea water production method of Example 1, except for using 1,350 kg of raw water (purified tap water), a raw water heating temperature of 63°C, and adding 900 kg of urea to the raw water. 1-3. Example 3 Urea water of Example 2 (concentration 42.5 wt %) was produced using the same procedure as the urea water production method of Example 1, except for using 1,350 kg of raw material water (purified tap water), a raw material water heating temperature of 63°C, and adding 1,000 g of urea to the raw material water.

[0098] <2. Evaluation of urea solution> The temperature (heating temperature) of the raw water used in each example and the temperature immediately after production of the urea water of each example were measured to measure the temperature change due to the dissolution of urea in water. In addition, the urea water of Examples 1 to 3 was checked for cloudiness. The results are shown in Table 1, along with the temperature change calculated from the concentration of the urea water of each example.

[0099] [Table 1]

[0100] As shown in Table 1, it was confirmed that the measured and calculated values ​​of temperature change due to dissolving urea in water were almost the same. It was also confirmed that urea water that did not become cloudy could be produced. [Industrial Applicability]

[0101] INDUSTRIAL APPLICABILITY The present invention has industrial applicability as a urea water production system and a urea water production method in the field of urea water production, particularly in the field of industrial urea water production. [Explanation of symbols]

[0102] 1. Urea water production system 10 Raw water supply means 11 Raw water purification equipment 12 Heating device 13 Raw water storage device 16 Liquid delivery device 17 Flow Measuring Device 20 Urea supply means 30 Mixing means 90, 90A, 90B Control means 91 Setting section 92 Arithmetic section 93 Receiving unit 94 Control Unit 95 Memory section

Claims

1. A urea water production system for producing urea water that is prevented from becoming cloudy, a mixing means for mixing raw water and urea and dissolving the urea in the raw water to produce the urea water; raw water supply means having a heating device for heating the raw water and supplying the raw water heated by the heating device to the mixing means; a urea supply means for supplying the urea to the mixing means; and a control means for controlling at least one of the raw water supply means and the urea supply means.

2. In the control means, two or more manufacturing condition setting values ​​selected from the group consisting of the following setting values ​​(a) to (d) are set, 2. The urea water production system according to claim 1, wherein the control means calculates a control value based on the production condition set value, and controls one or more of the raw water supply means and the urea supply means based on the production condition set value and / or the control value so as to prevent the urea water produced in the mixing means from becoming cloudy. Set value (a): the amount of raw water supplied to the mixing means Set value (b): Amount of urea supplied to the mixing means Set value (c): concentration of the urea water produced by the mixing means Set value (d): the amount of urea water produced by the mixing means

3. 3. The urea water production system according to claim 2, wherein the production condition set values ​​set by the control means are set values ​​(b) and (c).

4. The set value (c) is limited to a predetermined range, 4. The urea water production system according to claim 3, wherein the control means calculates a control value (e) which is a target heating control temperature of the raw water supplied to the mixing means based on a set value (c) limited to a predetermined range and the heat of dissolution of urea in water so that the urea water produced in the mixing means has a temperature at which it does not become cloudy, and controls the raw water supply means so that the temperature of the raw water supplied to the mixing means becomes the calculated control value (e).

5. 3. The urea water production system according to claim 2, wherein the set value (c) is 20% by weight or more and 50% by weight or less.

6. 2. The urea water production system according to claim 1, wherein the temperature of the raw water supplied to the mixing means is 50°C or higher and 80°C or lower.

7. 2. The urea water producing system according to claim 1, wherein the temperature of the urea water produced by the mixing means is 20°C or higher and 80°C or lower.

8. 2. The urea water production system according to claim 1, wherein the mixing means is of a non-heating type.

9. The raw water supply means a raw water purification device for purifying the raw water; 9. The urea water production system according to claim 1, further comprising a raw water storage device connected upstream of the heating device, for storing the raw water purified in the raw water purification device.

10. 10. The urea water producing system according to claim 9, wherein the raw water supply means supplies the raw water to the mixing means after the amount of the raw water stored in the raw water storage device exceeds a predetermined amount.

11. 10. The urea water production system according to claim 9, wherein the raw water purification device has a continuous electrodeionization treatment device (EDI device).

12. A method for producing urea water that prevents cloudiness, comprising: A step (1) of setting two or more manufacturing condition setting values ​​selected from the group consisting of the following setting values ​​(a) to (d) and calculating a control value based on the manufacturing condition setting values; a step (2) of heating raw water and supplying the heated raw water to a mixing means based on the production condition set values ​​and / or the control values; (3) supplying the urea to the mixing means based on the production condition set value and / or the control value; a step (4) of mixing the raw water supplied in the step (2) and the urea supplied in the step (3) in the mixing means to dissolve the urea in the raw water, thereby producing the urea water; A method for producing urea water comprising the steps of: Set value (a): the amount of raw water supplied to the mixing means Set value (b): Amount of urea supplied to the mixing means Set value (c): concentration of the urea water produced by the mixing means Set value (d): the amount of urea water produced by the mixing means

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