The present invention relates to a device for producing an aqueous solution of urea from solid urea and demineralised water, of the type comprising:

- at least one solid urea dissolution apparatus in deionized water, wherein the solid urea is dissolved in deionized water to form an aqueous urea solution, said device comprising dissolving a receiving tank of solid and deionized water urea and an outlet for recovering the urea aqueous solution,

- a storage station of solid urea,

- a routing device of the solid urea from the storage station to the dissolution device, said conveying device being arranged for discharge of solid urea in the tank of the dissolver.

The present invention also relates to a process for producing an aqueous solution of urea by means of such a production device.

Known manner, such an aqueous solution of urea is used in the process of selective catalytic reduction and to convert most of the nitrogen oxides (NOx) contained in the nitrogen exhaust gas and vapor water.

Such an aqueous urea solution can also be used in the NOx reduction process by direct injection into the combustion fumes industrial facilities.

The aqueous urea solution is obtained by diluting concentrated liquid urea or solid urea solution in deionized water.

In the case of a liquid urea diluting the mixture with deionized water is carried out on the site of production of urea in order to avoid concentrated liquid urea transport. Such a production method is binding because it must be performed on the site of production of urea.

When the solid urea is dissolved in demineralized water, the production of the aqueous solution may be carried out at another site than the production of urea as the solid urea transport is less cumbersome and less expensive than transport of liquid urea. In this case, the solid urea is poured into a blender containing demineralised hot water and the mixer was operated to mix urea and water to dissolve the solid urea in deionized water. Such a process is however not satisfactory. Indeed, manual operations during the introduction of urea into the mixer are required. In addition, to ensure the production of a satisfactory amount of aqueous urea solution, the mixer has a significant bulk to ensure a good mix of products in the blender. The dimensions

of the mixing member, formed by mobile mixing blades rotated, must in fact be sufficient to ensure the mixing and the mixture of all the volume of liquid and solids introduced into the mixer. In addition, the actuating means of the mixing member further increase the bulk of the production device.

Such generating devices are not satisfactory because they are too bulky and have low productivity.

One aim of the invention is to overcome the above drawbacks by providing a device for producing an aqueous solution of urea safe, compact and with improved productivity.

To this end, the invention concerns a device for producing an aqueous urea solution of the aforementioned type, wherein the dissolving device comprises at least one injection nozzle of deionized water in the tank in urea solid discharged into the tank, said deionized water injection nozzle being arranged in the vicinity of the bottom of the tank to create turbulence in the water surface of the solid urea discharged into the tank and dissolve the solid urea in deionized water so as to form the urea aqueous solution.

The production device of the invention allows to avoid manual handling operations of the solid urea during filling of the tank through the routing device capable of discharging the content of a solid urea in the tank containing . In addition, the size of the device can be reduced because it is the injection water which is arranged to ensure the dissolution of the solid urea in deionized water, which allows to dispense with a member of cumbersome mixing and means for actuating the mixing element. In addition, the positioning of the nozzle near the bottom of the tank under the pile of urea released into the tank prevents any vapor release or splash out of the tank at the injection

According to other features of the production device of the invention, taken individually or in any technically possible combination:

- the output device comprises at least two dissolving devices, the routing device being arranged to consecutively discharge of solid urea in the vessel of a dissolution device and into the tank on the other dissolver ;

- the output device comprises three dissolving devices, the routing device being arranged to consecutively discharge of solid urea in the tanks of said dissolving devices;

- the dissolving device comprises at least one liquid recirculation nozzle into the vessel, said recirculating nozzle being arranged to homogenize the aqueous urea solution in the tank;

- the storage station is arranged to store containers urea agglomerates, the routing device comprising a gripping member of a container and at least one rail on which moves the gripping member for moving the container up to the vessel of a dissolution device, said device comprising dissolving a container opening unit;

- the containers urea agglomerates are formed by bags, the gripping member and the rail being arranged to cause a container above the tank of the dissolver, the aperture unit comprising at least one diamond tip provided with cutting knives extending at right of the tank and being arranged to tear the bottom of the container so that the urea agglomerates flow into the tank under the effect of gravity when the container bottom was torn up ;

- the output device comprises a container retrieval station after they have been emptied, the gripping member and the rail being arranged to cause the container to said recovery station once the solid urea was poured said containing in a vessel;

- a solid urea-receiving tray is partially immersed in the tank, at least the immersed portion of said tray forming a basket in fluid communication with the interior volume of the tank so that the urea contained in the tray immersed in deionized water in the tank; and

- the tank comprises a filter element through which the solid urea is poured into the tank, said filtering element being arranged to retain solid urea agglomerates having an average diameter greater than a predetermined average diameter.

The invention also relates to a process for producing an aqueous solution of urea from solid urea and deionized water using a production apparatus as described above, comprising the steps of:

- feeding solid urea from the storage station to the vessel of a dissolution device and discharge solid urea in said tank by means of the conveying device so as to form a solid urea heap in said vessel ,

- injecting deionized water in the tank under the pile of solid urea so as to dissolve urea in deionized water to form the aqueous urea solution in the tank,

- recover the aqueous urea tank.

According to other features of the production process:

- demineralized water is injected at a temperature substantially between 30 ° C and 50 ° C in the vessel; and

- the conveying device conveys and discharges solid urea in the vessel of one of the dissolving devices then in the vessel of another dissolution device, the injection of demineralized water into said tanks commencing as soon as a lot of solid urea is formed in said tanks so that the start of the dissolution in a dissolution apparatus is shifted in time relative to the start of the dissolution in another dissolver.

Other aspects and advantages of the invention will become apparent from reading the following description given by way of example and with reference to the accompanying drawings, wherein:

- Fig. 1 is a schematic representation of a device for producing an aqueous urea solution according to the invention,

- Fig. 2 is a diagrammatic side view of part of Fig producing device. 1

- Fig. 3 is a schematic perspective representation of a dissolution device of FIG production device. 1

- Fig. 4 is a schematic sectional view along line IV-IV of Fig.

3, and

- Fig. 5 is a graph showing the production cycles of the aqueous urea solution from the production device according to the invention.

Referring to Fig. 1 describes a device for producing an aqueous solution of urea from solid urea and deionized water. Such an aqueous solution of urea form a Diesel exhaust fluid (EDF) for converting the bulk of the nitrogen oxides contained in the nitrogen exhaust gas and water vapor. The concentration of urea in aqueous solution is substantially equal to 32.5% and corresponds to the standard IS022241.

Solid urea is for example provided in the form of solid urea agglomerates.

The agglomerates are, for example in the form of ball. The agglomerates are eg transported in containers 1. The containers are, for example bags of the type "big bag" (large bag) of substantially equal capacity to 1 .5 m 3 , corresponding to a solid urea tonne. Such bags are sealed manner so that the solid urea is not in contact with the environment and the operators manipulating the bags do not affect the solid urea contained in the bags. The marbles

for example have an average diameter between 1 mm and 3 mm Alternatively, solid urea may be provided in powder form.

The production device comprises a storage station 2 of the containers 1. The storage station 2 extends between an inlet 4 to which the containers 1 are introduced into the storage station 2 and an outlet 6 to which the containers are removed from the storage station 2 to be emptied, as will be described later . Between the inlet 4 and the outlet 6, the example comprises two storage station an inclined ramp 8 allowing containers to slide towards the outlet under the effect of gravity. At the output, the two storage station comprises a transfer table 10 for receiving the container 1 about to be removed from the storage station 2. The containers 1 are transported for example on pallets 12 arranged to move on the inclined ramp 8. In this case,

According to one embodiment, the two storage station may include several parallel ramps.

The output of the storage station 2, a container 1 is placed on the transfer table 10 and is positioned on the table of the depalletizer 13, to be collected by a conveying device 14 for transporting a container 1. The routing device 14 comprises at least one rail 16 on which a gripping element 18 is mobile in translation.

The rail 16 extends in an upstream-downstream direction between an upstream end 20 extending above the outlet 6 of the storage station 2 and a downstream end 22 extending above a recovery station 24 of containers 1 empty, described later. Between the upstream end 20 and downstream end 22, the rail 16 extends over one or more output devices 26 of the urea aqueous solution, as will be described later. According to the embodiment shown in Fig. 2, the conveying device 14 includes two rails 16 parallel to each other and supporting each other the gripping member 18.

According to the embodiment shown in Fig. 2, the gripping member 18 is formed by a main gripper 28 and a second clamp 30. The main clamp 28 is arranged to provide a filled container 1 with its side walls 32 while transporting the container 1 along the rail . The secondary clamp 30 is arranged to provide a container 1 with its upper end portion 34 which forms for example a node when the container 1 is closed. Thus, the main clamp 28 can transport the container when it is filled while the secondary gripper 30 can transport the container when it is emptied, as will be described later. The main gripper 28 and secondary 30 each include two jaws 36 movable with respect to the another between an approximated position and a spaced position for adjusting the spacing of the clamps. Actuation of the clamps for example is performed by actuators 38 provided at one end of the jaws 36, as shown in Fig. 2.

The gripping element 18, in addition to moving in translation along the rail or rails 16, is also mobile in translation relative to the (x) rail (s) 16 in an elevation direction substantially perpendicular to the upstream direction -downstream. This movement allows to vary the distance between the gripping element 18 and the stations and devices above which the gripping member 18 moves. To do this, the gripping element comprises for example a carriage 40 mobile in translation along the upstream-downstream direction on the rails 1 or 6, the main gripper 28 and secondary 30 is movably mounted in translation along the elevation direction the carriage 40.

We will now describe a dissolving device 26 of the solid urea in deionized water.

The dissolver 26 comprises a vessel 42 adapted to receive the solid urea in a container 1. More particularly, the solid urea is received in a tray 46 partially immersed in the tank 42. The tank 42 has a liquid holding capacity for example between 3.0 m 3 and 3.4 m 3 , allowing vessel 42 contain all of the aqueous urea solution produced from solid urea contained in a container 1 as described above.

An aperture unit 48 of the container 1 extends substantially the center of the upper tray 46 to allow opening of the bag when inserted into the upper part of the tray 46. The opening unit 48 comprises for example a diamond 50 equipped advanced cutting knives arranged to tear the bottom of the container 1 and thus release the urea contained in the container 1 can flow into the bottom of the tank 46 by gravity.

Under the aperture unit 48, filter member 47 is provided across the tray 46 in order to filter solid urea flowing into the tank 46. More particularly, the filter element 47, for example a grating or a gate, possible to prevent urea agglomerates are too large to fall into the tray 46, which may damage the deionized water injection nozzles to be described later. To this end, the filter element 47 comprises suitable openings for passing the urea agglomerates having an average diameter less than a predetermined average particle diameter and for preventing the passage of agglomerates having an average diameter greater than the predetermined average diameter . The predetermined mean diameter by

example substantially equal to 3 mm. The filter element 47 also prevents the passage of pieces of container 1, these pieces can break off the container 1 when the opening unit 48 has broken the bottom of the container 1.

At least the immersed portion of the tray 46 is formed by a basket 52, such as perforated plates, that is to say provided with a plurality of openings permitting fluid communication between the Contents and the internal volume of the tank 42. the volume occupied by the basket 52 into the internal volume of the tank 42 is for example between 1 .5 m 3 and 2 m 3 , for example equal to 1 .7 m 3 . According to one embodiment, the tray 46 is formed of an upper portion projecting from the tank 42 and the walls of which are closed to prevent exhaust of solid urea from the tank and a lower part s extending into the internal volume of the vessel 42 and formed by a basket 52 as described above.

The dissolving device 26 further comprises at least one water injection nozzle 54 into the internal volume of the basket 52. The injection nozzle 54 is used to inject water into the internal volume of the basket 52 in order to dissolving the heap of solid urea formed during the opening of the container 1. The injection nozzle 54 is connected through an inlet 56 to a source of water and water heating means. Water is demineralized water, e.g., reverse osmosis water heated to a temperature between 30 ° C and 50 ° C, generally around 45 ° C.

According to the embodiment shown in Figs. 2 and 4, the injection nozzle 54 is located at the bottom of the basket 52 near the bottom of the vessel 42. Such an arrangement wherein the injection nozzle 54 injects water into the urea pile arranged in the tray 46 creates a turbulence of water beneath the surface of the solid urea to dissolve the solid urea in deionized water.

The injection nozzle 54 comprises for example an oriented outlet to the bottom of the tank 42 and through which water is injected and a deflector 55 extending opposite the outlet and oriented at 45 ° to the top of the bin 46 , that is to say towards the top of the tray 46, in order to redirect the injected water to urea pile in the basket 52. such an arrangement helps to protect the nozzle 54 when urea is poured into the tray 46 and to prevent the outlet of the nozzle may be clogged by urea.

According to one embodiment, a plurality of injection nozzles 54 are distributed at the bottom of the basket 52 so as to inject hot water under the entire heap of solid urea and allow to uniformly dissolve the base of the heap of urea located in the bottom of the vis-à-vis the cart 52. According to one embodiment, sixteen injection nozzles 54 forming rows and columns of four nozzles in the bottom of the basket 52 are provided. Each injection nozzle 54 has such a substantially even flow rate between 2 m 3 / hour and 3 m 3 / hr so that 2.1 m 3 of water may be injected into the vessel 42 for 3 minutes. The urea solution formed and deionized water flows through the perforations in the basket 52 into the tank 42.

According to one embodiment, the dissolving device 26 further comprises at least one recirculation nozzle 58 provided in the tank 42 and arranged to mix the liquid in the tank 42. More particularly, as shown in Fig. 4, the dissolving device 26 comprises for example a recirculation circuit 60 formed by a duct provided for recirculation of nozzles 58 and connected to an input 57. The duct is arranged along the bottom of the vessel 42 and creates a flow liquid circulation in the tank so that the liquid in the tank is mixed. The dissolving device 26 finally comprises a 62 liquid outlet arranged at the bottom and at one end of the vessel 42. The outlet 62 is connected to a pump (not shown) which makes it possible either to feed input 57 to effect recirculation ,3/h.

The dissolving device 26 described above makes it possible to produce, from a containing T 1 of solid urea and 2.1 m3 of osmosed water heated to a temperature between 30 ° C and 50 ° C, generally around 45 ° C, 2.85 m3 of concentrated aqueous urea solution urea 32.5%. Indeed, to obtain 1 m3 of concentrated aqueous urea to 32.5% urea solution requires the mixture of 0.736 m3 of water at 45 ° C and 0354 urea T. Between the delivery of the urea containing 1 and drain the aqueous solution obtained, fifteen minutes has elapsed, as will be described later. Such a dissolution device enables to produce an aqueous urea solution having the IS022241 standard using a single deposition step the whole of the solid urea contained in a container. The dimensions of the dissolving device can be reduced since the volume of the tank can be adjusted to the amount of water required to dissolve the entire solid urea contained in a container 1 for producing the aqueous solution of urea at the desired concentration without the need for movable mixing element, the rotary type mixer. Thus, the dissolution device does not require any actuating means of such a movable member mixture outside the vessel. solid urea contained in a container 1 for producing the aqueous solution of urea at the desired concentration without the need for movable mixing element, the rotary type mixer. Thus, the dissolution device does not require any actuating means of such a movable member mixture outside the vessel. solid urea contained in a container 1 for producing the aqueous solution of urea at the desired concentration without the need for movable mixing element, the rotary type mixer. Thus, the dissolution device does not require any actuating means of such a movable member mixture outside the vessel.

Production of an aqueous urea solution can be optimized by providing several dissolving devices 26 as described above. Thus, two dissolving devices 26 may be used. This allows to use the feed device 14 for feeding a container 1 to the second dissolving device 26 while the dissolution of the solid urea Following a first container takes place in the first dissolver. The production process is, however, particularly improved dissolution using three devices 26 as shown in Fig. 1. In this case, the three dissolving devices 26 are arranged next to each other along the upstream-downstream direction by the conveying device 14, as shown in Fig. 1.

A process for producing an aqueous solution of urea by means of a production device comprising three dissolving devices 26 will now be described in more detail.

The storage station is provided with two containers 1, at least is located at the output 6 of the storage station 2 or on the table 10 or on the depalletizer 13. The gripping member 18 of the router 14 is positioned above the outlet 5 and is lowered with the main gripper 28 and secondary 30 in the open position. When the main gripper 28 is brought around the side walls 32 of the container 1, the secondary gripper 30 is located opposite the loop 34 formed at the upper end of the container 1. The main gripper 28 and secondary 30 are then placed in the closed position and the gripping member 18 is raised to lift the container 1.

The gripping member 18 then moves along the rail or rails 16 to be located above the inlet housing 46 of the first dissolver 26. The gripping element 18 is then lowered again to penetrate the bottom of the container 1 in the tray 46. the bottom of the container 1 is torn by the opening device 48 so that the solid urea is empty and forms a pile in the basket 52 through the filter element 47 of the tank 42. the upper part of tray 46 prevents solid urea is discharged out of the dissolving device 26. When the container 1 has been emptied, the gripping element 18 is then noted that the container 1 is always maintained by the secondary gripper 30. thegripping member 18 carrying the empty contant 1 is then moved along the rail or rails 16 to be located above the collection station 24. The secondary clamp 30 is then opened and the container 1 is dropped into the vacuum 24 recovery station.

The gripping element 18 is reduced at the output 6 of the storage station 2 where it enters a new container 1 and leads to the second dissolver 26. The operations described above are repeated by the gripping element 18 then the gripper starts the operations for the third dissolution device 26.

The step of routing a container over a dissolver

26, shown hatched in Fig. 5, requires approximately three minutes. The step

lancing the container 1 and solid urea discharged into the tray 46, shown in black in Fig. 5, requires about one minute. The gripping element 18 is then brought to the recovery station 24 and then to the outlet 6 of the storage station 2, where it is again available to perform a new step of routing to another dissolver 26 .

Each dissolution device 26 as soon as it receives a pile of solid urea, the injection of demineralized water heated to a temperature substantially between 30 ° C and 50 ° C, for example a temperature of about 45 ° C, in the tank 42 begins. This step, shown in dots in Fig. 5, lasts about 3 minutes at which time about 2.1 m 3 of water were injected into the vessel 42.

As soon as the first m 3 of water was injected into the vessel 42, the recirculation or nozzles 58 are operated in order to homogenize the mixture of water and urea in the tank. This step, as shown in Fig. 5 begins in one minute after the beginning of the water injection step and takes about 5 minutes.

At the end of this step, the solid urea contained in the container 1 was completely dissolved in water and the tank 42 contains the aqueous solution of desired urea. Drain the tank through the outlet 62 can begin to transfer the aqueous urea solution to the storage tank. As shown in Fig. 5, the emptying of the tank 42 lasts about 4 minutes and 30 seconds. During the transfer of the aqueous urea solution tank 42 of a dissolving device 26 to the storage tank, a mass density meter may be provided to save the characteristics of the urea aqueous solution, such as its urea concentration.

Each dissolving device 26 operates with a 4 minute delay with the dissolving device 26, the previous or next. Thus, the dissolution step in the second dissolution device 26 starts four minutes after that in the first dissolver 26 and four minutes before that in the third dissolving device 26. When the first device 26 receives dissolution urea solid from a container, recirculation step occurs in the second dissolving device 26 and the emptying of the tank 42 of the third dissolution device 26 takes place.

Such device and method for producing it possible to produce an aqueous urea solution satisfying the requirements of the standard IS022241 while optimizing use of available water resources (tank 140 m 3 of cold demineralized water and 6 m 3 d heated water) flows imposed by the drain pump tank 42 (about 40 m 3 / h) and the number of aqueous urea solution storage tanks (for example, three tanks 140 m 3 ) of a production site of the urea aqueous solution. In addition, as indicated above, the footprint of the production device is reduced through the use of the dissolving devices 26.

The volume values, weight, speed, etc. have been given by way of example and may vary depending on production sites. In particular, the volume of the vessel of a dissolution device may vary depending on the amount of solid urea in the containers 1.

CLAIMS

1 .- An apparatus for producing an aqueous solution of urea from solid urea and deionized water, said apparatus comprising:

- at least one dissolution device (26) of the solid urea in deionized water, wherein the solid urea is dissolved in deionized water to form an aqueous urea solution, said dissolution device (26 ) comprising a vessel (42) receiving the solid urea and deionized water and an outlet (62) for recovering the urea aqueous solution,

- a storage station (2) of the solid urea,

- a routing device (14) of the solid urea in the storage station (2) the dissolution device (26), said conveying device (14) being arranged for discharge of solid urea in the tank (42) of the dissolving device (26),

characterized in that the dissolving device (26) comprises at least one injection nozzle (54) deionized water in the tank (42) into solid urea discharged into the vessel (42), said nozzle injection (54) of deionized water being arranged in the vicinity of the bottom of the tank (42) to create a water turbulence in the surface of the solid urea discharged into the vessel (42) and dissolve the solid urea in deionized water so as to form the urea aqueous solution.

2. A producing apparatus according to claim 1, comprising at least two dissolving devices (26), the conveying device (14) being arranged to consecutively discharge of solid urea in the tank (42) of one the dissolving devices (26) then into the vessel (42) of the further dissolution device (26).

3. - Apparatus for producing according to claim 2, comprising three dissolving devices (26), the conveying device (14) being arranged to consecutively discharge of solid urea in the tanks (46) of said dissolving devices (26 ).

4. - A producing apparatus according to any one of claims 1 to 3, wherein the dissolver (26) comprises at least one recirculation nozzle (58) of liquid in the vessel (42), said recirculating nozzle ( 58) being arranged to homogenize the aqueous urea solution in the tank (42).

5. - A producing apparatus according to any one of claims 1 to 4, wherein the storage station (2) is arranged to store containers (1) urea agglomerates, the routing device (14) comprising a gripping member (18) of a container (1) and at least one rail (16) on which moves the gripping element (18) for moving the container (1) to the tank (42) a dissolving device (26), said dissolution unit (26) comprising an aperture unit (48) of the container (1).

6. A production method of claim 5, wherein the containers (1) urea agglomerates are formed by bags, the gripper (18) and the rail (16) being arranged to bring a container (1) above the vessel (42) of the dissolving device (26), the aperture unit (48) comprising at least one diamond tip (50) equipped with cutting blades extending to the right of the tank (42) and being arranged to tear the bottom of the container (1) so that urea agglomerates flow into the tank (42) under the effect of gravity when the bottom of the container (1) has been torn.

7. A device for producing according to Claim 6, comprising a recovery station (24) of the containers (1) after they have been emptied, the gripping element (18) and the rail (16) being arranged to cause the container (1) to said recovery station once the solid urea has been discharged from said container (1) in a tank (42).

8. A producing apparatus according to any one of claims 1 to 7, wherein a tray (46) receiving the solid urea is partly immersed in the tank (42), at least the immersed portion of said tray ( 46) forming a basket (52) in fluid communication with the interior volume of the vessel (42) so that the urea contained in the tray (46) is immersed in deionized water in the tank (42).

9. A device for producing according to any one of claims 1 to 8, wherein the vessel (42) comprises a filter element (47) through which solid urea is discharged into the vessel (42), said element filtering (47) being arranged to retain the solid urea agglomerates having an average diameter greater than a predetermined average diameter.

10. A process for producing an aqueous solution of urea from solid urea and deionized water by means of a generating device according to any one of claims 1 to 9, comprising the steps of:

- feeding solid urea from the storage station (2) to the tub (42) of a dissolution device (26) and discharge the solid urea in said vessel (42) by means of the conveying device ( 14) so ​​as to form a solid urea heap in said vessel (42),

- injecting deionized water in the tank (42) under the pile of solid urea so as to dissolve urea in deionized water [MHI jet form the urea aqueous solution in the tank (42),

- to recover the aqueous urea solution from the tank (42).

January 1. - The production process according to claim 10, wherein demineralized water is injected at a temperature substantially between 30 ° C and 50 ° C in the vessel (42).

12. - A process for producing according to claim 10 or 1 1 by means of a device according to claim 2 or 3, wherein the conveying device (14) conveys and discharges the solid urea in the tank (42) of one of the dissolving devices (26) then into the vessel (42) of another dissolution device (26), deionized water injection through said tanks (42) starting from a heap of solid urea is formed in said tanks (42) so that the start of the dissolution in a dissolving device (26) is shifted in time relative to the start of the dissolution in another dissolution device (26).