JP4431482B2 - Urea water storage device - Google Patents

Description

  The present invention relates to a method for storing urea water to be added as a reducing agent to a selective catalytic reduction catalyst for reducing and purifying NOx.

  Conventionally, diesel engines are equipped with a selective reduction catalyst (selective reduction catalyst) that has the property of selectively reacting NOx with a reducing agent even in the presence of oxygen in the middle of an exhaust pipe through which exhaust gas flows. The required amount of reducing agent is added to the upstream side of the selective catalytic reduction catalyst, and the reducing agent is subjected to a reduction reaction with NOx (nitrogen oxide) in the exhaust gas on the selective catalytic reduction catalyst, whereby NOx emission concentration There is one that can reduce the above.

On the other hand, in the field of industrial flue gas denitration treatment in plants and the like, the effectiveness of a method for reducing and purifying NOx using ammonia (NH ₃ ) as a reducing agent is already widely known. Since it is difficult to ensure safety with respect to traveling with ammonia itself, in recent years, the use of non-toxic urea water as a reducing agent has been studied.

  That is, if urea water is added to the exhaust gas upstream of the selective catalytic reduction catalyst, the urea water is decomposed into ammonia and carbon dioxide under a temperature condition of about 170 ° C. or higher, and the exhaust gas is exhausted on the selective catalytic reduction catalyst. The NOx contained therein is reduced and purified well by ammonia.

  When urea water is used as a reducing agent in this way, as shown in FIG. 6, the urea water 1 is stored in a tank 2 mounted on a vehicle, and a water supply means inserted into the tank 2 from above is provided. The urea water 1 is sent out through the water pipe 3.

As prior art document information related to measures against freezing of an apparatus for adding a reducing agent to this type of selective reduction catalyst, for example, the following Patent Document 1 has already been proposed.
JP 2000-27627 A

  However, in the case where the urea water 1 is used as the reducing agent in this way, the urea water 1 freezes at -13.5 ° C. or lower, so that the urea water 1 freezes in the tank 2 when used in a cold region. In FIG. 6, there is a case where all of the urea water 1 is frozen. When the frozen urea water 1 is in the middle of thawing, as shown in FIG. Since the melting starts from a position along the inner wall of the tank 2 and the thawing state has advanced to some extent, as shown in FIG. The ice mass of the urea water 1 moves irregularly in the tank 2, and the ice mass of the urea water 1 may collide with the water supply pipe 3, the inner wall of the tank 2, and the like to damage them.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a urea water storage device capable of protecting the water supply means and the inner wall of the tank from collisions caused by ice blocks during thawing of urea water.

  The present invention relates to a urea water storage device to be added as a reducing agent to a selective catalytic reduction catalyst for reducing and purifying NOx, wherein a tank for storing urea water and a storage space in the tank are vertically divided. A separator having a water flow structure to be divided, a flexible water supply hose with an electric heater constituting a water supply means inserted downward from above into a section of the storage space divided by the separator, and the flexible water supply A flexible guide hose is provided that encloses the periphery of the hose and extends downward from the ceiling of the tank.

  Thus, since the storage space in the tank is divided vertically by the separator in this way, when the ice mass of urea water starts to melt, the ice mass is separated at the vertical section of the separator, thereby The size of the ice mass is reduced and the impact force is greatly reduced.

  Furthermore, since the flexible water supply hose is encapsulated and protected by the flexible guide hose, direct impact of the urea water ice mass on the flexible water supply hose is avoided, and the flexible water supply hose is electrically heated. When the heater is heated, the inside of the flexible guide hose is immediately thawed, so that direct transmission of the collision force from the flexible guide hose to the flexible water supply hose is also avoided.

  In addition, since the flexible water supply hose and the flexible guide hose have the property of being able to bend freely, the impact force of the ice block is absorbed by the overall deflection and local stress concentration does not occur, In addition, the movement of the ice block is restricted by the thickness of the flexible guide hose, and the collision force is greatly reduced.

  Furthermore, in the present invention, the urea water concentration sensor should be accommodated in the flexible guide hose, and in this way, the urea water concentration sensor can be protected from collision by the ice block of urea water. Become.

  According to the urea water storage device of the present invention described above, various excellent effects as described below can be obtained.

  (I) According to the invention described in claim 1 of the present invention, the collision force caused by the ice block during the thawing of urea water is greatly reduced as compared with the prior art, and the impact of the ice block on the flexible water supply hose is reduced. Since direct transmission can be avoided, the water supply means and the inner wall of the tank can be reliably protected from collisions caused by ice blocks during the thawing of urea water.

  (II) According to the invention described in claim 2 of the present invention, the urea water concentration sensor can be protected from the collision caused by the ice block of urea water by being housed in the flexible guide hose.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows an example of an embodiment for carrying out the present invention. In this embodiment, the storage space 4 in the tank 2 for storing the urea water 1 has a water flow structure having a plurality of water flow holes 5. A flexible water supply hose 7 with an electric heater 7a that constitutes a water supply means is inserted downward from above into a section of the storage space 4 divided by the separator 6. ing.

  Here, the electric heater 7a of the flexible water supply hose 7 is embedded in the tubular portion of the flexible water supply hose 7, and generates heat by energization from a battery (not shown) to make the flexible water supply hose 7 full length. It is possible to thaw the urea water 1 that has been frozen by heating over its own internal flow path and surroundings.

  In addition, a flexible guide hose 8 extending downward and enclosing the periphery of the flexible water supply hose 7 is suspended from the ceiling of the tank 2 in which the flexible water supply hose 7 is inserted. The flexible water supply hose 7 is protected by the flexible guide hose 8.

  Thus, when the engine is started and the electric heater 7a of the flexible water supply hose 7 is energized from the state where all of the urea water 1 in the tank 2 is frozen as shown in FIG. The internal flow path of the flexible water supply hose 7 and the inside of the flexible guide hose 8 are immediately thawed to become the urea water 1, and further, urea water is supplied from the inner wall of the tank 2 and the portion along the separator 6 by heat transfer from the engine side. One ice block begins to melt.

  Further, when the ice blocks are defrosted in the tank 2, as shown in FIG. 3, the ice blocks of the urea water 1 are separated at the longitudinal section of the separator 6, thereby reducing the size of each ice block and greatly increasing the impact force. Reduced.

  That is, the collision force is proportional to the square of the collision speed and also to the mass, but when the acceleration α is applied to the entire tank 2, the ice block that receives the acceleration accelerates and the surroundings can be displaced. The speed is increased in proportion to the square of the gap (the gap generated by thawing), and this speed becomes the collision speed of the ice mass, so that the ice mass of the urea water 1 is separated at the longitudinal section of the separator 6 and can move freely. At that time, the size of each ice block is reduced to less than half and the mass is greatly reduced. Therefore, compared with the case of the tank 2 without the separator 6 as in the conventional case, the impact force of the ice block is It will be greatly reduced.

  As shown in FIG. 4, even if the ice mass of the urea water 1 in the middle of thawing is irregularly moved in the tank 2 due to running vibration and inertial force of starting / stopping, the flexible water supply hose 7 is flexible guide hose. Since it is encapsulated and protected by 8, direct impact of the ice mass of urea water 1 on the flexible water supply hose 7 is avoided, and the collision force from the flexible guide hose 8 to the flexible water supply hose 7 is avoided. Is also avoided because the flexible guide hose 8 has already been thawed.

  In addition, since the flexible water supply hose 7 and the flexible guide hose 8 have the property of being able to bend freely, the collision force of the ice block is absorbed by the overall deflection and local stress concentration occurs. In addition, the movement of the ice block is restricted by the thickness of the flexible guide hose 8 and the collision force is greatly reduced.

  Therefore, according to the above-described embodiment, the collision force caused by the ice block during the thawing of the urea water 1 is significantly reduced as compared with the prior art, and the direct hit of the ice block to the flexible water supply hose 7 and the direct transmission of the collision force are avoided. Therefore, the water supply means (flexible water supply hose 7) and the inner wall of the tank 2 can be reliably protected from collisions caused by ice blocks during the thawing of the urea water 1.

  FIG. 5 shows another embodiment of the present invention. In this embodiment, the urea water concentration sensor 9 is held by the upper and lower mounting brackets 10 that are fitted to the lower portion of the flexible guide hose 8. The flexible guide hose 8 accommodates the urea water concentration sensor 9 in the urea water 1 in addition to the functions and effects of the embodiment shown in FIGS. It can protect against collisions caused by ice blocks.

  Here, when the urea water concentration sensor 9 is accommodated in the flexible guide hose 8, the urea water concentration sensor 9 is not only attached to the inside of the flexible guide hose 8 via the fitting 10, The water concentration sensor 9 may be suspended in the flexible guide hose 8 from above by a suspension cable (which may also be used as an electric wire).

  Note that the urea water storage device of the present invention is not limited to the above-described embodiment, and the flexible water supply hose and the flexible guide hose have various flexibility such as rubber and resin. The material can be appropriately adopted, the number of divisions of the storage space by the separator is not limited to two, the separator may be configured in a mesh shape, and other aspects of the present invention Of course, various changes can be made without departing from the scope of the invention.

It is sectional drawing which shows an example of the form which implements this invention. It is sectional drawing which shows the state which the ice block in the tank of FIG. 1 began to melt. FIG. 3 is a cross-sectional view showing a state where thawing has further progressed from the state of FIG. 2. FIG. 4 is a cross-sectional view showing a state at the time of collision of an ice block that has further been thawed from the state of FIG. 3. It is sectional drawing which shows another example of a form of this invention. It is sectional drawing which shows a prior art example. It is sectional drawing which shows the state which the ice block in the tank of FIG. 6 began to melt. It is sectional drawing which shows the state at the time of the collision of the ice block which the thawing | decompression progressed further from the state of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Urea water 2 Tank 4 Storage space 6 Separator 7 Flexible water supply hose 7a Electric heater 8 Flexible guide hose 9 Urea water concentration sensor

Claims (2)

  A urea water storage device to be added as a reducing agent to a selective catalytic reduction catalyst for reducing and purifying NOx, a tank for storing urea water, and a water passage for vertically dividing a storage space in the tank A separator having a structure, a flexible water supply hose with an electric heater that constitutes a water supply means inserted downward from above into a section of the storage space divided by the separator, and the periphery of the flexible water supply hose. A urea water storage device comprising: a flexible guide hose encapsulated and extending downward from the ceiling of the tank.   The urea water storage device according to claim 1, wherein a urea water concentration sensor is accommodated in the flexible guide hose.

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