JP2005118705A - Apparatus for producing aqueous urea solution - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To produce an aqueous urea solution having a desired concentration and volume easily in a small scale. <P>SOLUTION: A stirring container 2, a pure water apparatus 3 for producing pure water from tap water, a urea supply apparatus 4, and a stirrer 5 are mounted on a movable frame 1. Pure water and urea corresponding to the set concentration and volume are supplied to the stirring container 2 by the pure water apparatus 3 and the urea supply apparatus 4 and stirred by the stirrer 5. Consequently, an aqueous urea solution with a desired concentration and volume can easily be produced. Further, since the apparatus is made to be a single unit, it can easily be transported and produce an aqueous urea solution at any site in a small scale. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a technique for producing an aqueous urea solution easily and on a small scale.

In an exhaust gas purification device that purifies NOx (nitrogen oxide) in exhaust gas, ammonia is used as a reducing agent that causes a NOx reduction catalyst to cause a catalytic reduction reaction with NOx. Ammonia is obtained by hydrolyzing an aqueous urea solution. This aqueous urea solution is produced by measuring and stirring pure water and powdered urea.
On the other hand, in Japanese Patent Application Laid-Open No. 9-283135 (Patent Document 1), two kinds of materials are continuously supplied into a stirring vessel, and the materials are stirred by a stirrer provided in the stirring vessel. An apparatus for manufacturing is disclosed.
JP-A-9-283135

However, when the urea aqueous solution is manufactured by an apparatus as described in Patent Document 1, it is not possible to manufacture only a desired volume of the urea aqueous solution, and there is a possibility that the urea aqueous solution is manufactured more than necessary. In addition, it is difficult for an apparatus as described in Patent Document 1 to be manufactured on a small scale by being installed in a service station or the like.
Therefore, in view of the conventional problems as described above, the present invention supplies urea and pure water to a stirring container while automatically weighing them and stirs, thereby easily and small-scale urea aqueous solution having a desired concentration and volume. An object of the present invention is to provide a urea aqueous solution manufacturing apparatus to be manufactured.

  In the invention according to claim 1, a stirring vessel, a pure water supply device that manufactures pure water from tap water and supplies the pure water to the stirring vessel, a urea supply device that supplies urea to the stirring vessel, and the stirring vessel The stirrer that stirs the pure water and urea supplied to the aqueous solution to form a urea aqueous solution, setting means for setting the concentration and volume of the urea aqueous solution, and pure water and urea corresponding to the concentration and volume set by the setting means A supply control means for controlling the operation of the pure water supply device and the urea supply device so as to supply to the stirring vessel, and after the pure water and urea are supplied to the stirring vessel by the supply control means, the stirrer is operated for a predetermined time. Agitator control means to be operated, and a stirring frame, a pure water supply device, a urea supply device, a stirrer, a setting means, a supply control means, a movable frame carrying the agitator control means, and urea water Characterized in that the liquid preparation device is configured.

  In a second aspect of the present invention, the concentration sensor for detecting the concentration of the urea aqueous solution in the stirring vessel, and the operation of the pure water supply device or the urea supply device are controlled to replenish the stirring vessel with pure water or urea. And a concentration correction control means for repeating the control for operating the stirrer for a predetermined time until the concentration of the urea aqueous solution detected by the concentration sensor substantially coincides with the concentration set by the setting means, To do.

According to a third aspect of the present invention, there is provided a discharge permission means for permitting the discharge of the urea aqueous solution from the stirring vessel when the concentration detected by the concentration sensor substantially matches the concentration set by the setting means. It is characterized by that.
According to a fourth aspect of the present invention, a weight sensor for detecting the total weight of pure water and urea in the stirring vessel, and a weight calculation means for calculating the weight of the aqueous urea solution from the concentration and volume set by the setting means. And the total weight of pure water and urea detected by the weight sensor between the time when the pure water and urea are supplied to the stirring vessel by the supply control means and the time when the stirrer is operated by the stirrer control means. Capacity correction control means for controlling the operation of the pure water supply device and the urea supply device and replenishing the stirring vessel with pure water and urea until the weight of the urea aqueous solution calculated by the weight calculation means is greater than or equal to It is characterized by having.

The invention described in claim 5 is characterized in that the agitator control means controls the operation time of the agitator based on the concentration and capacity set by the setting means.
In the invention described in claim 6, the urea supply device has a storage container for discharging urea from an opening provided in the bottom plate, and the bottom plate is inclined toward the opening. And

According to the first aspect of the present invention, after pure water and urea corresponding to the concentration and volume set by the setting means are supplied to the stirring vessel, the pure water and urea are stirred by the stirrer. An aqueous urea solution having a set concentration and volume can be easily produced.
Also, since the stirring vessel, pure water supply device, urea supply device, stirrer, setting means, supply control means, and stirrer control means are mounted on a movable frame and made into one unit, it can be easily used with a forklift or crane Can be conveyed. For example, it can be installed in a service station and the urea aqueous solution can be manufactured on a small scale.

According to the second aspect of the present invention, it is repeated that pure water or urea is replenished and stirred until the concentration of the urea aqueous solution substantially matches the set concentration. Can be improved.
According to the invention described in claim 3, since the urea aqueous solution discharge from the stirring vessel is not permitted until the concentration of the urea aqueous solution in the stirring vessel substantially matches the concentration set by the setting means, The concentration of the aqueous solution can be guaranteed.

  According to the fourth aspect of the present invention, the pure water and urea in the stirring container are supplied after the supply control means supplies pure water and urea to the stirring container until the stirrer is operated by the stirrer control means. Since the pure water and urea are replenished until the total weight becomes equal to or greater than the weight of the urea aqueous solution calculated from the concentration and volume set by the setting means, the accuracy of the volume of the urea aqueous solution can be improved.

  According to the invention described in claim 5, since the operation time of the stirrer is controlled based on the concentration and capacity set by the setting means, for example, when the concentration is low and the capacity is small, the operation of the stirrer If the time is set short, the time for producing the urea aqueous solution can be shortened. According to the invention described in claim 6, since the bottom plate of the storage container of the urea supply device is inclined toward the opening, urea can be smoothly discharged from the opening and the remaining amount of urea is reduced. Even if it decreases, it can be discharged from the opening without remaining in the storage container.

As shown in FIG. 1, the urea aqueous solution manufacturing apparatus of the present invention includes a stirring container 2, a pure water device 3, a urea supply device 4, a stirrer 5, and a control panel 6 mounted on a movable frame 1. It is a unit.
Tap water is supplied to the pure water device 3 from the outside, and pure water is produced by ion exchange. Pure water produced by the deionizer 3 is supplied into the stirring vessel 2 through the supply pipe 7. A flow rate sensor 8 is interposed in the supply pipe 7. The flow sensor 8 detects the flow rate of pure water passing through the supply pipe 7 to detect the flow rate of pure water supplied into the stirring vessel 2. A normally closed electromagnetic on-off valve 9 is interposed in the supply pipe 7 on the downstream side of the flow rate sensor 8 to open or shut off the supply pipe 7. The deionizer 3, the supply pipe 7, the flow sensor 8, and the electromagnetic on-off valve 9 correspond to the deionized water supply device.

  The urea supply device 4 is provided vertically above the stirring container 2 and supplies urea by dropping it into the stirring container 2. As shown in FIG. 2, the urea supply device 4 includes a storage container 20, a vibration generator 21, normally closed electromagnetic on-off valves 22 and 23, a cylinder 24, and a weight sensor 25. ing. The storage container 20 stores urea powder. An opening 20b is provided in the bottom plate 20a of the storage container 20, and urea stored from the opening 20b can be dropped downward and discharged. The electromagnetic on-off valve 22 opens and closes the opening 20b. The cylindrical body 24 is open at both ends in the vertical vertical direction, and is fixed to the bottom plate 20a so that the opening 24a at the upper end and the opening 20b of the storage container 20 communicate with each other. The electromagnetic opening / closing valve 23 opens and closes the opening 24 a at the lower end of the cylindrical body 24. The weight sensor 25 is provided in the cylinder body 24 and detects the weight of urea contained in the cylinder body 24. The vibration generator 21 is provided in the storage container 20, and causes the urea stored in the storage container 20 to be smoothly discharged from the opening 20 b to the cylinder body 24 by vibrating the storage container 20.

The stirrer 5 stirs pure water and urea in the stirring vessel 2 to make a urea aqueous solution.
The stirring container 2 is provided with a weight sensor 30 that detects the total weight of pure water and urea in the stirring container 2. On the side wall in the vicinity of the lower end of the stirring vessel 2, a discharge port 2a for discharging the urea aqueous solution from the stirring vessel 2 and an electromagnetic on-off valve 31 (discharge permission means) for opening and closing the discharge port 2a are provided. . The electromagnetic on-off valve 31 is provided with a concentration sensor 32 for detecting the concentration of the urea aqueous solution in the stirring vessel 2 near the discharge port 2a. A manual opening / closing valve 33 is provided at the discharge port 2 a, and the urea aqueous solution in the stirring vessel 2 passes through the electromagnetic opening / closing valve 31 and the manual opening / closing valve 33 and is discharged to the outside.

  The control panel 6 is provided with a start switch 6a for instructing the start of production of the urea aqueous solution, a capacity setting device 6b for setting the volume of the urea aqueous solution, and a concentration setting device 6c for setting the concentration of the urea aqueous solution. The capacity setting device 6b and the density setting device 6c correspond to setting means. The control panel 6 has a built-in computer, and inputs signals from the start switch 6a, the capacity setting device 6b, the concentration setting device 6c, the flow rate sensor 8, the weight sensors 25 and 30, and the concentration sensor 32, and the stirrer 5 The operation of the electromagnetic on-off valves 9, 22, 23, 31 and the vibration generator 21 is controlled.

Here, the control procedure in the control panel 6 will be described in detail with reference to FIG.
After setting the volume and concentration of the urea aqueous solution by the volume setting device 6b and the concentration setting device 6c, the control is started by turning on the start switch 6a. In the following description, the set capacity and density are referred to as set capacity and set density, respectively.
First, in step 1 (denoted as S1 in the figure, the same applies hereinafter), the electromagnetic on-off valve 31 is closed.

In step 2, the target supply amounts of urea and pure water necessary for producing a urea solution having a set concentration and a set capacity are calculated, and a target weight that is the weight of the urea solution is calculated. Note that the calculation of the target weight in step 2 corresponds to the weight calculation means.
In step 3, the electromagnetic opening / closing valve 9 is opened to supply pure water from the pure water device 3 to the stirring vessel 2. Then, the flow rate of pure water detected by the flow rate sensor 8 is integrated, and when this integrated value reaches the target supply amount of pure water, the electromagnetic on-off valve 9 is closed. Thus, the target supply amount of pure water is supplied from the pure water device 3 to the stirring vessel 2.

  In step 4, first, the electromagnetic on-off valve 22 is opened and the vibration generator 21 is operated. Thereby, urea falls smoothly from the storage container 20 to the cylinder 24. Next, the electromagnetic on-off valve 22 is closed and the weight of urea in the cylinder 24 is read from the weight sensor 25. Thereafter, the electromagnetic on-off valve 23 is opened, and urea in the cylinder 24 is dropped into the stirring vessel 2. Then, after a predetermined time has elapsed, the electromagnetic opening / closing valve 23 is closed. This series of control is repeated until the integrated value obtained by integrating the weight of urea read from the weight sensor 25 reaches the target supply amount of urea. As a result, the target supply amount of urea is supplied to the stirring vessel 2. Note that the series of control in steps 2 to 4 corresponds to supply control means.

In step 5, the total weight of pure water and urea (hereinafter referred to as actual weight) is read from the weight sensor 30.
In step 6, it is determined whether the actual weight is equal to or greater than the target weight. When the actual weight is greater than or equal to the target weight, the process proceeds to step 8. When the actual weight is not equal to or greater than the target weight, the process proceeds to Step 7.

In step 7, the replenishment amount of urea and pure water necessary to bring the actual weight closer to the target weight is calculated as the target supply amount of urea and pure water. Then, the process returns to step 3. Note that the series of control in steps 5 to 7 corresponds to the capacity correction control means.
In step 8, the stirrer 5 is operated to stir the pure water and urea in the stirring vessel 2. Thereby, the pure water and urea in the stirring vessel 2 become urea aqueous solution.

In step 9, it is determined whether or not a predetermined time has elapsed since the agitator 5 was operated. When the predetermined time or more has elapsed, the process proceeds to step 10. If the predetermined time has not elapsed, step 9 is repeated.
In step 10, the stirrer 5 is stopped. In addition, a series of control of step 8-10 corresponds to a stirrer control means.

In step 11, the concentration of the aqueous urea solution (hereinafter referred to as the actual concentration) is read from the concentration sensor 32.
In step 12, it is determined whether or not the actual density substantially matches the set density. This may be determined by determining whether or not the actual density is within a predetermined range having a predetermined width centered on the set density. If they substantially match, the process proceeds to step 15. If not, the process proceeds to step 13.

In step 13, the minimum amount of pure water or urea replenishment amount necessary to bring the actual concentration close to the set concentration is calculated.
In step 14, as in step 3 or step 4, the replenishment amount of pure water or urea calculated in step 13 is replenished to the stirring vessel 2. Then, the process returns to step 8. Note that a series of control in steps 8 to 14 corresponds to density correction control means.

In step 15, the electromagnetic on-off valve 31 is opened and the control is terminated.
As described above, the concentration and the volume are set by the volume setting device 6b and the concentration setting device 6c, and pure water and urea are supplied to the stirring vessel 2 while being automatically measured by simply pressing the start switch 6a. Then, the pure water and urea are agitated to automatically produce an aqueous urea solution having a desired concentration and volume. Furthermore, since pure water and urea are replenished while being automatically measured until the actual weight exceeds the target weight after pure water and urea are supplied to the stirring vessel 2 and stirred, urea is added. The accuracy of the capacity of the aqueous solution can be improved.

Further, since the replenishment and stirring while automatically weighing pure water or urea are repeated until the actual concentration substantially matches the set concentration, the accuracy of the concentration of the aqueous urea solution to be manufactured can be improved.
The electromagnetic opening / closing valve 31 closes the discharge port 2a when the production of the urea aqueous solution is started, but does not open until the actual concentration substantially matches the set concentration. Therefore, even if the manual opening / closing valve 33 is opened during the production of the urea aqueous solution. The urea aqueous solution is not discharged. Thereby, the concentration of the urea aqueous solution can be guaranteed. In addition, what is necessary is just to accommodate the discharged | emitted urea aqueous solution in the container which can be conveyed, for example.

In the urea aqueous solution manufacturing apparatus according to the present embodiment, the constituent devices are mounted on the frame 7 to form a single unit, and therefore can be easily transported by a forklift or a crane. For example, it can be installed in a service station and the urea aqueous solution can be manufactured on a small scale.
It is desirable to incline the bottom plate 20a of the storage container 20 of the urea supply device 4 toward the opening 20b. In this way, the urea stored in the storage container 20 can be smoothly discharged into the cylinder 24, and even if the remaining amount of urea decreases, the urea does not remain in the storage container 20 and remains in the cylinder 24. It can be discharged.

In addition, when supplying urea to the stirring vessel 2, it is desirable to supply a stabilizer together. This stabilizer makes it difficult to precipitate urea in an aqueous urea solution. If it does in this way, it can control that the concentration of urea aqueous solution changes because urea precipitates after manufacture of urea aqueous solution.
Note that a predetermined time for operating the agitator 5 may be set according to the set concentration and the set capacity. For example, when the set concentration is low and the set capacity is small, the time for producing the urea aqueous solution can be shortened by shortening the operation time of the stirrer 5.

  Moreover, although powdery urea was used in the above embodiment, you may use high concentration urea aqueous solution. If it does in this way, the structure of the urea supply apparatus 4 can be simplified similarly to a pure water supply apparatus.

Structural diagram of an embodiment of the urea aqueous solution production apparatus of the present invention Structural diagram of urea supply device The flowchart which shows the control procedure of the control panel same as above

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Frame 2 Stirring container 2a Outlet 3 Pure water device 4 Urea supply device 5 Stirrer 6 Control panel 6b Capacity setting device 6c Concentration setting device 7 Supply pipe 8 Flow rate sensor 9 Electromagnetic switching valve 20 Storage container 20a Bottom plate 20b Opening 30 Weight sensor 31 Electromagnetic on-off valve 32 Concentration sensor

Claims (6)

A stirring vessel;
A pure water supply device for producing pure water from tap water and supplying it to the stirring vessel;
A urea supply device for supplying urea to the stirring vessel;
A stirrer that stirs pure water and urea supplied to the stirring vessel to form an aqueous urea solution;
Setting means for setting the concentration and volume of the urea aqueous solution;
Supply control means for controlling the operation of the pure water supply device and the urea supply device so as to supply pure water and urea corresponding to the concentration and volume set by the setting means to the stirring vessel;
Agitator control means for operating the agitator for a predetermined time after supplying pure water and urea to the agitation vessel by the supply control means;
A movable frame carrying the stirring vessel, pure water supply device, urea supply device, stirrer, setting means, supply control means, stirrer control means;
The urea aqueous solution manufacturing apparatus characterized by including. A concentration sensor for detecting the concentration of the urea aqueous solution in the stirring vessel;
Control of operating the pure water supply device or urea supply device to replenish the stirring vessel with pure water or urea and operating the stirrer for a predetermined time, the concentration of the urea aqueous solution detected by the concentration sensor is Density correction control means that repeats until it substantially matches the density set by the setting means;
The urea aqueous solution manufacturing apparatus according to claim 1, comprising:   3. The apparatus according to claim 2, further comprising a discharge permission unit that permits discharge of the urea aqueous solution from the stirring vessel when the concentration detected by the concentration sensor substantially matches the concentration set by the setting unit. The urea aqueous solution manufacturing apparatus as described. A weight sensor for detecting the total weight of pure water and urea in the stirring vessel;
Weight calculating means for calculating the weight of the urea aqueous solution from the concentration and volume set by the setting means;
The total weight of pure water and urea detected by the weight sensor between the time when the pure water and urea are supplied to the stirring vessel by the supply control means and the time when the stirrer is operated by the stirrer control means is as follows: Capacity correction control means for controlling the operation of the pure water supply device and the urea supply device until the weight of the urea aqueous solution calculated by the weight calculation means is equal to or more, and replenishing the stirring vessel with pure water and urea;
The urea aqueous solution manufacturing apparatus according to any one of claims 1 to 3, wherein:   5. The urea aqueous solution manufacturing apparatus according to claim 1, wherein the stirrer control unit controls an operation time of the stirrer based on the concentration and capacity set by the setting unit. . The urea supply device has a storage container for discharging urea from an opening provided in a bottom plate,
The urea aqueous solution manufacturing apparatus according to claim 1, wherein the bottom plate is inclined toward the opening.

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