FLUIDIZED BED GRANULATION

Abstract

Method and fluidized bed reactor for the production of granules, such as granules of urea or ammonium nitrate. The fluidized bed reactor comprises at least one granulation compartment with air inlets, and an air moving device downstream of the granulation compartment, e.g., downstream of at least one scrubbers. The air moving device is configured to draw air through said at least one air inlet into at least one granulation compartment.

Claims

1. A fluidized bed reactor comprising at least one granulation compartment with one or more air inlets, and at least one air moving device downstream the granulation compartment configured to draw air through said one or more air inlets into the granulation compartment.

2. The fluidized bed reactor according to claim 1, comprising a scrubber downstream the granulation compartment, wherein the at least one air moving device is downstream the scrubber.

3. The fluidized bed reactor according to claim 1 comprising at least one after-cooler and the at least one an air moving device downstream the after-cooler.

4. The fluidized bed reactor according to claim 3, comprising a scrubber downstream the after-cooler, the at least one air moving device being positioned downstream the scrubber.

5. The fluidized bed reactor according to claim 1, wherein the air moving device comprises one or more exhaust fans for discharging air.

6. A method for producing granules using a fluidized bed reactor comprising at least one granulation compartment having one or more air inlets and a bed of granules, and at least one air moving device downstream the granulation compartment, the method comprising: drawing air in the at least one granulation compartment through the one or more air inlets using the at least one air moving device; and fluidizing the bed of granules with the drawn in air.

7. The method of claim 6, wherein drawing air in the at least one granulation compartment includes creating a pressure drop between the one or more air inlets and an air exhaust below 800 mm water column.

8. The method of claim 7, wherein the pressure drop is below 750 mm water column.

9. The method according to claim 6, wherein the pressure drop over the granulation compartment is at most 500 mm water column.

10. The method according to claim 6, wherein the bed of granules include urea granules.

11. The method according to claim 6, wherein the bed of granules include ammonium nitrate granules.

12. A fluidized bed reactor comprising at least one granulation compartment with at least one air inlets and at least one air moving device, configured to move air through said at least one air inlet into said at least one granulation compartment, characterized in that said air is moved essentially by the action of said at least one air moving device downstream of said granulation compartment.

13. The fluidized bed reactor according to claim 12, devoid of any air moving device which is configured to move air through said at least one air inlet into said granulation compartment and which is positioned upstream of the granulation compartment.

14. The fluidized bed reactor according to claim 12, comprising at least one after-cooler wherein the at least one air moving device is positioned downstream of the at least one after-cooler.

15. The fluidized bed reactor according to claim 14, wherein the at least one after-cooler is integrated in the fluidized bed reactor as a set of at least two compartments subsequent to the granulation compartments.

16. The fluidized bed reactor according to claim 12, comprising at least one scrubber downstream of the at least one granulation compartment, wherein the at least one air moving device is positioned downstream of the at least one scrubber.

17. The fluidized bed reactor according to claim 14, further comprising at least one scrubber downstream of the at least one after-cooler, wherein the at least one air moving device is positioned downstream of the at least one scrubber.

18. The fluidized bed reactor according to claim 12, wherein the at least one air moving device comprises at least one exhaust fan for discharging air.

19. A method for the production of granules using a fluidized bed reactor comprising at least one granulation compartment with at least one air inlets and at least one air moving device, configured to move air through said at least one air inlet into said at least one granulation compartment, wherein said air is moved essentially by the action of said at least one air moving device downstream of said granulation compartment, the method comprising: drawing air in the at least one granulation compartment through the at least one air inlet using the at least one air moving device; and fluidizing the bed of granules with said drawn in air.

20. The method according to claim 19, devoid of any air moving step by an air moving device which is configured to move air through said at least one air inlet into said granulation compartment and which is positioned upstream of the granulation compartment.

21. The method according to claim 19, wherein drawing air in the at least one granulation compartment includes creating a pressure drop between the at least one air inlet and an air exhaust of between 10 and 100 mbar.

22. The method according to claim 21, wherein the pressure drop is between 10 and 80 mbar.

23. The method according to claim 19, wherein drawing air in the at least one granulation compartment includes creating a pressure drop over the granulation compartment of between 10 and 60 mbar.

24. The method according to claim 19, wherein the air drawn into the at least one granulation compartment is not preheated, either deliberately using pre-heating equipment, or as a side effect of the action of upstream equipment.

25. The method according to claim 19, wherein the bed of granules include urea-based granules.

26. The method according to claim 19, wherein the bed of granules include ammonium nitrate-based granules.

27. The method according to claim 25, wherein the urea based granules are urea, urea ammonium nitrate, urea ammonium sulphate or urea doped with elemental sulphur.

28. The method according to claim 26, wherein the ammonium nitrate-based granules are ammonium nitrate granules or calcium nitrate granules.

29. A fluidized bed reactor comprising at least one granulation compartment with one or more air inlets; at least one scrubber downstream from the at least one granulation compartment; at least one air duct between the at least one granulation compartment and the at least one scrubber; and at least one air moving device downstream from the at least one granulation compartment, wherein when a fluid bed is present in the at least one granulation compartment, the at least one air moving device has or devices have sufficient capacity to create a vacuum exceeding the total pressure drop between the one or more air inlets and the at least one air moving device.

30. The fluidized bed reactor according to claim 29, wherein the at least one air moving device is downstream from the scrubber.

31. The fluidized bed reactor according to claim 29, further comprising at least one after-cooler downstream from the at least one granulation compartment.

32. The fluidized bed reactor according to claim 31, wherein the after-cooler is upstream from a scrubber and the at least one air moving device is positioned downstream from the scrubber.

33. The fluidized bed reactor according to claim 31, wherein the air moving device comprises one or more exhaust fans for discharging air.

34. A method for producing granules using a fluidized bed reactor comprising at least one granulation compartment having one or more air inlets and a bed of granules, at least one scrubber downstream from the at least one granulation compartment, at least one air duct between the at least one granulation compartment and the at least one scrubber, and at least one air moving device downstream from the at least one granulation compartment, the method comprising fluidizing the bed of granules by drawing air into the at least one granulation compartment through the one or more air inlets using the at least one air moving device, wherein the air drawn into the at least one granulation compartment is not heated by a blower upstream from the one or more air inlets.

35. The method of claim 34, wherein drawing air in the at least one granulation compartment includes creating a pressure drop between the one or more air inlets and an air exhaust below 800 mm water column.

36. The method of claim 35, wherein the pressure drop is below 750 mm water column.

37. The method according to claim 34, wherein the pressure drop over the granulation compartment is at most 500 mm water column.

38. The method according to claim 34, wherein the bed of granules include urea granules.

39. The method according to claim 34, wherein the bed of granules include ammonium nitrate granules.

40. A method for producing fertilizer granules by crystallization of urea and/or ammonium nitrate, using a fluidized bed reactor comprising at least one granulation compartment with one or more air inlets and a bed of granules, at least one scrubber downstream from the at least one granulation compartment, at least one air duct between the at least one granulation compartment and the at least one scrubber, and at least one air moving device downstream from the at least one granulation compartment, the method comprising fluidizing the bed of granules by drawing air into the at least one granulation compartment through the one or more air inlets using the at least one air moving device, wherein the air drawn into the at least one granulation compartment is not heated by a blower upstream from the one or more air inlets.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0060] FIG. 1: shows an exemplary fluidized bed reactor setup according to the invention. This system has being realized by Yara International ASA in a semi-industrial pilot plant (SIPP) in Sluiskil, The Netherlands.

[0061] FIG. 2: shows a pressure graphs of the pressure in a fluidized bed reactor setup with two ventilators in different operational modes.

DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENT

[0062] FIG. 1 shows an exemplary embodiment of a fluidized bed reactor 1 for the production of urea granules, or ammonium nitrate granules. The fluidized bed reactor 1 as shown in the figure comprises three granulation compartments 2, 3, 4 for granulation and two after-cooler compartments 5, 6 for subsequent cooling and drying the granules.

[0063] The first granulation compartment 2 of the fluidized bed reactor 1 comprises an inlet 7 for the supply of nuclei. Opposite to the inlet 7 is a first passage 8, leading to the second compartment 3. The second compartment 3 comprises a second passage 9 opposite to the first passage 8 and leading to the third compartment 4. The third compartment 4 comprises an outlet 10 opposite to the second passage 9. As a result, the nuclei can flow from the inlet 7 to the outlet 10 in a straight flow path.

[0064] The fluidized bed reactor 1 comprises a floor 12 made of a grid which supports a bed 13 of nuclei and which permits the passage of ambient fluidization air, supplied from a space 14 below the grid floor 12. Air inlets can for example be located at a side wall of the space 14 below the grid 12 and/or in the bottom of that space 14. In case the ambient air is relatively cold, for example during winter, the air can be preheated by heaters 15 in or upstream the space 14. The heated air fluidizes the bed 13 of nuclei.

[0065] The space 14 below the grid floor 12 is divided into compartments 17, 18, 19 in line with the compartments 2, 3, 4 above the grid floor 12. In each of the compartments 2, 3, 4 the grid floor 12 of the fluidized bed reactor 1 is provided with clusters of air-assisted sprayers 21 projecting above grid floor 12. The sprayers 22 are fed with a flow of liquid product (e.g. urea or ammonium nitrate) (F1) and a flow of pressurized air (F2), and spray an aqueous solution of urea or ammonium nitrate into the fluidized bed 13. In the granulator compartments 2, 3, 4, the water of the sprayed urea or ammonium nitrate solution evaporates and urea crystallizes on the nuclei, which grow to form granules.

[0066] The after-cooler is integrated into the fluidized bed reactor and comprises a fluidized bed cooler with a grid floor 12 supporting a bed 13 of freshly produced granules and a space 20, 21 below the grid floor in line with the compartments 5 and 6 above the grid floor 12, also supplied with a heater 23 for the supply of air fluidizing and drying the bed 13.

[0067] The after-cooler is provided with an outlet 24 for discharging the dried and cooled granules. Subsequently (not shown), undersized and oversized granules are separated from granules of the desired size, which are discharged for storage. The oversized granules can be crushed to finer particles, which can be recycled together with the undersized particles.

[0068] Air and air borne dust particles are discharged from the granulator compartments 2, 3, 4 and the after-cooler compartments 5 and 6 via one or more air ducts 25 to at least one scrubbers 28. In the schematic drawing of FIG. 1 a single scrubber is shown. Separate scrubbers may be used for treating air from the granulation compartments and air from the cooler, respectively. The scrubber may be a wet scrubber.

[0069] In the scrubber 28 the air is stripped. Separated dust particles can be recycled to the granulator compartments 2, 3, 4 via one or more ducts 27. Clean air leaves the scrubber 28 via a discharge duct 29 comprising an exhaust fan 30.

[0070] The exhaust fan 30 creates a pressure drop of about 10 and 100 mbar, e.g., about 75 mbar over the full flow path from the grid floor 12, 12 to the exhaust fan 30. As a result, fluidization air is sucked into the granulation compartments 2, 3, 4 via the grid floors 12 and 12. No additional blowers are provided. The difference with known systems is shown in FIG. 2. FIG. 2 shows a pressure graphs of the pressure in a system, with either a downstream ventilator active (this application, C), an upstream ventilator active (A), or both an upstream ventilator and a downstream ventilator active (B) active such that a small underpressure (0.1 to 10 mbar) is formed in the fluidized bed reactor, as disclosed in U.S. Pat. No. 5,779,945 (DSM N.V., 1998) and EP 2253374 A1 (Stamicarbon, 2010). It is obvious that in the setup according to this invention, a larger underpressure is formed in the fluidized bed reactor, typically between 10 and 60 mbar.

Example

[0071] A setup of the fluidized bed reactor according to the invention with three granulation compartments and integrated after-cooler was used for the continuous production of ammonium nitrate granules (see FIG. 1). The parameters of the experiment are summarized in the Tables 1 and 2 below. These are typical parameters for the operation of the fluidized bed reactor according to the invention.

TABLE-US-00001 TABLE 1 Average material balance After 7 Units Start hours After 13.5 hours Outflow kg/h 11,775 11,385 11,221 granulator Ready product kg/h 7,660 7,520 7,380 after sieving Fines after kg/h 2,782 2,388 2,784 sieving (returned to granulator) Coarse after kg/h 1,308 1,452 1,032 sieving (to be crushed) Product after kg/h 1,308 1,452 1,032 crushing Dust at exit kg/h n.m. n.m. n.m. granulator Dust after kg/h n.m. n.m. n.m. ventilator Agglomerates kg/h 25 25 25 n.m. not measured

TABLE-US-00002 TABLE 2 Process parameters Ammonium nitrate solution Temperature 178 C. Concentration 97.6 % Flow rate 5.5 m.sup.3/h Pre-pressure 2.0 ato.sup.1 Per nebulizer 1st about m.sup.3/h compartment 0.561 Number of nebulizer: 4 Per nebulizer 2th about m.sup.3/h compartment 0.360 Number of nebulizer: 5 Per nebulizer 3th about m.sup.3/h compartment 0.291 Number of nebulizer: 5 Injection air Temperature 142 C. Pressure 0.52 ato Flow rate about Nm.sup.3/h 1,800 Per nebulizer 1st about 130 Nm.sup.3/h compartment Number of nebulizer: 4 Per nebulizer 2th about 130 Nm.sup.3/h compartment Number of nebulizer: 5 Per nebulizer 3th about 130 Nm.sup.3/h compartment Number of nebulizer: 5 Fluidization air Temperature Flow rate Speed ( C.) (Nm.sup.3/h) Nm/sec 1st compartment 78 2,471 2.02 2d compartment 81 2,359 1.93 3d compartment 79 2,836 2.92 4th compartment 20 2,235 5th compartment 18 2,299 Suction 113 about 14,000 Fluidized bed Height 685 mmwk.sup.2 Temperature 1st compartment 127 C. Temperature 2d compartment 127 C. Temperature 3d compartment 130 C. Temperature 4th compartment n.m. C. Temperature 5th compartment 119 C. Temperature after granulator 119 C. Expansion room (space over the granulator compartments) Temperature 1st compartment 127 C. Temperature 2d compartment 130 C. Temperature 3d compartment 127 C. Temperature 4th + 5th n.m. C. compartment Temperature top granulator 113 C. .sup.1atmospheres of overpressure over the standard atmospheric pressure; n ato = n + 1 atm (absolute) n + 1 bar .sup.2mmwk = mm water column; 1 mmwk = 0.0981 mbar 0.1 mbar

RESERVATIONS

[0072] Although the subject matter has been described in language, specific to structural features and/or methodological acts, it is to be understood that the subject matter as defined in the appended claims is not necessarily limited to the specific features or acts described above as has been held by the courts. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims. The claimed subject matter is not limited to implementations that solve any or all disadvantages noted in the background.