METHOD FOR PRODUCING ANHYDROUS CALCIUM NITRATE POWDER

Abstract

The invention relates to a method for producing an anhydrous powder having a calcium nitrate content of between 92 and 99.9 weight %, a water content of between 0.1 and 8 weight %; and a particle size of between 0.05 and 1.5 mm, wherein the method comprises the step of subjecting a calcium nitrate solution having a water content of between 70 and 15 weight % and a calcium nitrate content of between 30 and 85 weight % to a drying step in an industrial turbo-dryer, resulting in the anhydrous calcium nitrate powder. The invention furthermore relates to such an anhydrous calcium nitrate powder and the use of an industrial turbo-dryer to produce such anhydrous calcium nitrate powder.

Claims

1-14. (canceled)

15. A method for producing an anhydrous powder, wherein the method comprises the step of subjecting a calcium nitrate solution having a water content of between 70 and 15 weight % of water and a calcium nitrate content of between 30 and 85 weight % to a drying step, CHARACTERISED IN THAT the calcium nitrate solution is subjected to a drying step performed at a temperature of between 200 and 300 C. in an industrial turbo-dryer, wherein the industrial turbo-dryer comprises a drum having a horizontal axis and being closed at opposite ends that are provided with openings for the introduction of the solution and a stream of dry air travelling in the same direction, and further comprises a heating jacket for heating the internal wall of the tubular body to a predetermined temperature, and a bladed rotor rotatable supported in the drum, and wherein the drying step produces the anhydrous calcium nitrate powder having a calcium nitrate content of between 92 and 99.9 weight %; a water content of between 0.1 and 8 weight %; and a particle size of between 0.05 and 1.5 mm.

16. The method according to claim 15, characterized in that the drying step is performed a temperature of between 240 and 280 C.

17. The method according to claim 15, characterized in that the calcium nitrate solution has a water content of between 45 and 50 weight % and a calcium nitrate content of between 55 and 50 weight %.

18. The method according to claim 15, wherein the drying step produces anhydrous calcium nitrate powder having a content of calcium nitrate between 95 and 99.9 weight % and a water content of between 0.1 and 5 weight %.

19. The method according to claim 18, wherein the produced anhydrous calcium nitrate powder has a content of calcium nitrate between 96 and 99.9 weight % and a water content of between 0.1 and 4 weight %.

20. The method according to claim 15, wherein the drying step produces anhydrous calcium nitrate powder having a particle size between 0.1 and 1 mm.

21. The method according to claim 15, wherein the drying step produces anhydrous calcium nitrate powder having a particle size of between 0.08 and 1 mm.

22. The method according to claim 15, wherein the calcium nitrate solution is purified before being subjected to the drying step.

23. The method according to claim 15, wherein the anhydrous calcium nitrate produced in the drying step has a calcium nitrate content and a water content adding up to 100 weight %.

24. Anhydrous calcium nitrate CHARACTERISED IN THAT it is produced by a method according to claim 15, wherein the calcium nitrate content and the water content add up to 100 weight %.

25. Use of an industrial turbo-dryer comprising a drum having a horizontal axis and being closed at opposite ends that are provided with openings for the introduction of the solution and a stream of dry air travelling in the same direction, and further comprises a heating jacket for heating the internal wall of the tubular body to a predetermined temperature, and a bladed rotor rotatable supported in the drum, to produce anhydrous calcium nitrate powder having a calcium nitrate content of between 92 weight % and 99.9 weight %; a water content of between 0.1 weight % and 8 weight %; and a particle size of between 0.05 and 1.5 mm; starting from a calcium nitrate solution having a water content of between 70 and 15 weight % and a calcium nitrate content of between 30 and 85 weight % that is subjected to a drying step in the industrial turbo-dryer at a temperature of between 200 and 300 C.

26. Use according to claim 25 implementing a method for producing an anhydrous powder, wherein the method comprises the step of subjecting a calcium nitrate solution having a water content of between 70 and 15 weight % of water and a calcium nitrate content of between 30 and 85 weight % to a drying step, CHARACTERISED IN THAT the calcium nitrate solution is subjected to a drying step performed at a temperature of between 200 and 300 C. in an industrial turbo-dryer, wherein the industrial turbo-dryer comprises a drum having a horizontal axis and being closed at opposite ends that are provided with openings for the introduction of the solution and a stream of dry air travelling in the same direction, and further comprises a heating jacket for heating the internal wall of the tubular body to a predetermined temperature, and a bladed rotor rotatable supported in the drum, and wherein the drying step produces the anhydrous calcium nitrate powder having a calcium nitrate content of between 92 and 99.9 weight %; a water content of between 0.1 and 8 weight %; and a particle size of between 0.05 and 1.5 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0036] The present invention relates to a method to produce anhydrous calcium nitrate powder by subjecting a calcium nitrate solution to a drying step which is performed in an industrial turbo-dryer which is a continuous operating process. In order to obtain a pure end product, the calcium nitrate solution preferably is purified by filtering it.

[0037] The industrial turbo-dryer consists of a horizontal drum with heating walls. Preferably, oil is used as the heating medium. In the longitudinal direction of the drum, a rotating shaft with blades has been mounted. The blades are extending only 5 mm from the wall of the drum. During operation, the shaft rotates with a high speed and creates a strong turbulence. By varying the angle of the blades, the retention time of the material in the drum can be varied. The liquid calcium nitrate solution is fed into the drum by warm air, and anhydrous calcium nitrate powder is extracted from the air stream leaving the drum by using a cyclone.

[0038] The temperature applied in the industrial dryer is preferably between 200 and 300 C., and more preferably between 240 and 280 C.

[0039] The starting calcium nitrate solution has a water content of between 15 and 70 weight % and a calcium nitrate content of between 30 and 85 weight %, and more preferably a water content of between 45 and 50 weight % and a calcium nitrate content of between 55 and 50 weight %, and most preferably approximately 50 weight % and a calcium nitrate content of approximately 50 weight %.

[0040] Subjecting this calcium nitrate solution to a turbo-dryer as disclosed above, allows an almost complete removal of the calcium nitrate dissolved in the calcium nitrate solution, resulting in an anhydrous calcium nitrate powder having [0041] a calcium nitrate content of between 92 and 99.9 weight %; [0042] a water content of between 0.1 and 8 weight %; and [0043] a particle size of between 0.05 and 1.5 mm.

[0044] The obtained anhydrous calcium nitrate powder more preferably has a calcium nitrate content of between 96 and 99.9 weight % and a water content of between 0.1 and 4 weight %, and most preferably a calcium nitrate content of between 95 and 99.9 weight % and a water content of between 0.1 and 5 weight %.

[0045] In order to measure the particle size, the sample can be segregated by particle size. In particle segregation, particulate solids tend to segregate by virtue of differences in the size, and also physical properties such as volume, density, shape and other properties of particles of which they are composed. In the present example the particles obtained were segregated in a sieve shaker using a stack of woven wire mesh sieves having mesh sizes of 2 mm, 1.5 mm, 1 mm, 0.5 mm, 0.1 mm and 0.05 mm, respectively. Additional sieves can be used to obtain additional segregation.

[0046] The anhydrous calcium nitrate powder more preferably has a particle size between 0.1 and 1 mm, and most preferably between 0.08 and 1 mm.

Example

[0047] 2000 litres of a purified calcium nitrate solution having a water content and a calcium nitrate content of 50 weight %, for example a purified Nutriox solution, commercialised by Yara, having a density of 1.482 kg at 22 C. and a pH of 6.0, was pumped into a pilot turbo-dryer commercialised by the Italian firm VOMM. The feeding rate of the drum of this turbo-dryer was between 70 and 80 litre per hour. By applying a temperature of approximately 270 in the VOMM turbo-dryer, an anhydrous calcium nitrate powder was obtained at a rate of 35 to 40 kg per hour. The obtained anhydrous calcium nitrate powder was collected and analysed. Results of this analysis can be found in Table 1 below.

TABLE-US-00001 TABLE 1 Results of analysis of calcium nitrate produced by VOMM turbo-dryer Feeding rate of Wall drum of temperature VOMM of the drum pH Appear- turbo-dryer of VOMM Composition of 10% ance Particle (litre/ turbo-dryer obtained solu- obtained size hour) ( C.) product tion product (mm) 70 270 1.7 weight % 9.0 Dry white 0.5-1.5 H.sub.2O powder 98.2 weight % Ca(NO.sub.3).sub.2 80 270 2.5 weight % 9.1 Dry white 0.5-1.5 H.sub.2O powder 97.4 weight % Ca(NO.sub.3).sub.2

[0048] The obtained anhydrous calcium nitrate powder has a calcium content of 23.5-24 weight % of calcium and around 16.5 weight % of nitrogen.

[0049] X-ray diffraction of the obtained calcium nitrate powder shows that the powder mainly consists of pure dry Ca(NO.sub.3).sub.2 with traces of Ca(NO.sub.3).sub.2.2H.sub.2O and Ca(NO.sub.3).sub.2.3H.sub.2O. No CaO and Ca(OH).sub.2 were detected. It is however likely that some ppm of these latter components were formed, being responsible for the pH increase.

[0050] The obtained anhydrous calcium nitrate powder dissolves quickly in water and forms a clear solution up to 10-15 weight % calcium nitrate. On further increasing the calcium nitrate in the solution, the calcium nitrate solution becomes weakly turbid, this probably due to the presence of some ppm CaO and Ca(OH).sub.2.

[0051] In order to store the anhydrous calcium nitrate powder according to the invention for a longer period of at least a year, this anhydrous calcium nitrate powder must be stored in well-sealed, vapour tight bags. The anhydrous calcium nitrate powder according to the invention can also be compacted into granules by using various compaction machines.