LT5342B - Method for production of nitrate-containing products from undercooling melts - Google Patents

Abstract

The invention concerns a method for the production of nitrate containing products (fertilizers, technical products) from undercooling melts, wherein a XN - water solution is evaporated up to a content of 50-99,8 weight percent XN, where X is one or more selected from Ca, Mg, NH4, Na and K, and N means nitrate. The preferred range of XN is 70-99,5 weight percent. The melt is cooled down to and kept at a temperature at or below the crystallisation point and finely divided solid XN powder consisting of the equilibrium phases is added to the melt. Melt drops are then formed and allowed to cool and solidifay during up to 70 seconds. It is preferred to use a cooling belt for solidification of the particles. The belt is cooled by air, oil or another medium.

Description

The present invention relates to the production of nitrate-containing products (fertilizers, technical products) from frozen melts.

Pure Ca (NO ₃ ) 2 (CN) melts at 560 ° C and this very high temperature is inconvenient to give shape. In order to use equipment such as a centrifugal or spray grinder or a plate / drum granulator, the CN melt must have a composition containing 5-8% by weight of ammonium nitrate (AN). Today, all prilled or granulated CNs contain this amount of AN with an additional up to 14-16% by weight of water (crystallization water). If this amount of ammonium nitrate is removed from the melt, the composition will freeze so that caking / granulation is no longer possible.

Therefore, there is still a need for calcium nitrate (CN) without ammonium nitrate (AN) and to find ways to easily produce large amounts of solid water in the CN system.

From British patent no. No. 392531 discloses a known method for producing distributed and non-agglomerating fertilizers containing calcium nitrate. According to this patent, the calcium nitrate / water solution is evaporated to a sand viscosity consistency of about 90-95% by weight of calcium nitrate (calculated as anhydrous calcium nitrate). The concentrated product is then converted, without any other substantial concentration, into granular form by mechanical disaggregation at 50-100 ° C. In this method, salt precipitates on the unit and the product in the form of flakes and dust. In addition, this process is not considered to be suitable for the production of large amounts of calcium nitrate.

The CN * 4H ₂ O crystals may be obtained by crystallization from a CN-water solution as is well described in the literature. Such crystals are commercially available. These crystals contain 69-70% by weight of CN, but usually have a high tendency to sinter and become solid over time and thus become difficult to use. Therefore, producing crystalline material is undesirable.

By constructing a CN-AN-water phase diagram (from Gmelin), one can find a narrower melting range of the composition that can be granulated by conventional industrial equipment and today granulated or prilled CN has 77-80% by weight CN, 5-8% by weight AN and 15-17% by weight of water.

Studying the phase diagram of CN-water (Fig. 1), it can be seen that the following solid compounds may be included in the system:

Ca (NO ₃ ) * 4H ₂ O

Ca (NO ₃ ) * 3H ₂ O

Ca (NO ₃ ) * 2H ₂ O

Ca (NO ₃ ) ₂ .

Further, it may be realized that, under the CN-water system, all concentrations greater than 70% by weight of CN can be solidified, with the assumption that all liquid must disappear at equilibrium if the temperature is below 40-43 ° C. Further, it can be seen that upon freezing the CN-water solution, when CN is less than 70% by weight, crystals of CN * 4H ₂ O will be formed.

The present invention relates to a process for the easy production of high-quality CN-water solid particles in large quantities. Another object of the invention is a process for the preparation which can be applied to the common nitrate salts which tend to form extremely cooled melts.

These and other objects of the invention are achieved in the manner described below, and the invention is characterized and defined by the following claims.

Therefore, the present invention relates to the production of nitrate-containing products (fertilizers, technical products) from frozen melts in which the XN-water solution is evaporated to 50-99.8% by weight of XN, where X is one or more selected from Ca, Mg, NH ₄ , Well and K, while N represents nitrate. Preferred is when the XN is in the range of 70-99.5 wt%. The melt is cooled and stored at or below the crystallization point temperature and the finely divided solid XN powder consisting of equilibrium phases is added to the melt. The melt droplets are then formed and left to cool and solidify within 70 seconds, preferably within 20-70 seconds. Preferably, a cooling belt is used to solidify the particles. The belt is cooled by air, oil or other environment.

Preferably, the melting point is maintained at 0-10 ° C below the crystallization point of the melt. For the production of calcium nitrate particles, CN * 2H ₂ O and CN * 3H ₂ O particles are used as crystallizers. The resulting particle size is between 0.2 and 0.8 mm, preferably between 0.4 and 0.6 mm. The particles may be made of a melt consisting of 74% by weight of calcium nitrate, 14% by weight of potassium nitrate and 12% by weight of water. Particulates may also be prepared from a homogeneous mixture of nitrates, chlorides and water of crystallization. Examples include particles made of a melt consisting essentially of 50% by weight of calcium nitrate, 4% by weight of ammonium nitrate, 26.5% by weight of calcium chloride and 8-20% by weight of water.

A series of experiments have been carried out to try to produce melt particles.

An example is pellets

The CN-water solutions were evaporated to more than 70, 75 and 78% by weight of calcium nitrate (CN).

at various ratios and temperatures, various melts were sprayed onto a rotating laboratory plate granulator containing solid NH-CN (calcium nitrate from Norsk Hydro ASA).

None of the tests were successful because the fluid / melt did not solidify. The entire matrix (CN + solid melt) was transformed into a solid suspension which could no longer form a liquid / solid ratio within acceptable limits.

Example - prilled fertilizers

The alloys containing the CN concentrations mentioned above were stored at temperatures close to the crystallization point reported in the literature. The finely ground NH-CN is mixed into the melt and then, under high pressure, into the pumped melt into a droplet nozzle and left to cool below 20 ° C for 5-10 seconds. Oil and air were tested as cooling environments. Freezing did not cause particulate matter to form.

example- production of lozenges test:

Micro-droplets of CN-melts at 70, 75 and 78 wt% pure CN were left to cool for several minutes on a refrigerated metal plate below 10 ° C. The melt droplets turned into a viscous, viscous liquid, and no solid particles formed.

test:

The same steps were performed as before, but now the finely divided solid CN powder was added to the melt before the microparticles were placed on the plate. Solid NH-CN crystals and crushed CN * 4H ₂ O crystals were used.

The melt-microparticles turned into suspension and were not particle-strength when frozen.

test:

CN melt containing 23 wt% water and 77 wt% CN was allowed to cool on a plate at 20 ° C for 48 hours. During this time a white solid formed.

Now, during these hours, the melt has clearly turned into a strong solid and X-ray analysis has shown that the material consists of CN * 2H ₂ O and CN * 3H ₂ O.

However, for the normal particle production time, the cure time was too long.

Test 4a:

The same steps as in Test 1 were performed, but now the CN melt consisting of 23 wt% water and 77 wt% GN was cooled to 50-55 ° C and 2 wt% of the crushed material was thoroughly mixed into the melt.

As the drops cool, crystals formed and solid lozenges with a particle strength of about 1 kg were formed within 30-70 seconds. Over time, the particle strength became substantially higher.

Particles were not formed due to this procedure and the decisive part of this procedure was obvious as fine solids consisting of the equilibrium phases of the system (CN * 2H ₂ O and CN * 3H ₂ O) were added at room temperature.

Test 4b:

Following the same procedure as in Test 4a, the melt composition was now 25% w / w / 75% and 21.5% w / w / 78.5% w / w H ₂ O / CaN.

test:

Follow the same procedure as in Test 4, after reducing the temperature of the melt (23% w / w H ₂ O / 77% w / w CN) to about 45 ° C, the finely divided solid was admixed as crystalline particles. When crystals began to form in the beaker, the drops were allowed to fall onto the refrigerated dish while simultaneously adding pure melt (23 wt% / 77 wt%) below 50 ° C to the beaker during mixing.

In this way, the drops of the required composition of solid crystals were formed consistently and solidified on the metal plate immediately with the addition of one part of the solid to form a crystallization nucleus.

However, a period of 40-70 seconds is too long for the granulation or grinder technique with an acceptable circulation ratio.

Large particle yields using Test Method 5 to obtain a crystallization time of 40-70 seconds were expected.

an example is the industrial production of CN pastilles

The experiment was performed on a moving steel cooling belt (as described in U.S. Patent No. 5326541), which was conducted at low temperature using water as a cooling agent. A rotating drum with sprays on this belt produces drops that can harden on the belt. Growth assay was performed on CN melt (23 wt% / 77 wt%).

Using the method described in Test 5, several hundred kg of CN particles (lozenges) were produced on the cooling belt.

Example 5 - Production of MgN Pastilles Example 5 test was repeated by replacing the CN melt with 1: MgN water melt containing 67 wt% MgN and 33 wt% H ₂ O (boiling point 180 ° C) and 2: MgN-water melt 58 wt% MgN and 42 wt% H ₂ O (boiling point 155 ° C). Both melts 1 and 2 were cooled to 30 ° C according to the method described in Test 5 (Example 3). Formulations 1 and 2 were allowed to solidify for 3 days in a desiccator and then the solid was crushed and converted into a finely divided powder to give crystalline material.

According to the procedure described, from melt 1 and 2 we obtained MgN * 4H ₂ O and MgN * 6H ₂ O respectively. MgN * 6H ₂ O was also obtained without crystallizer as the MgN * 6H ₂ O melt hardens very easily.

example is the production of MgN-AN and CN pastilles

A melt consisting of 67 wt% CN, 4.0 wt% AN, 10 wt% MgN and 20 wt% water was stored at 110 ° C. The melt was cooled to 65 ° C and the crystallizer was thoroughly mixed when the drops were allowed to fall on a cold metal plate.

Within 60 seconds, solid lozenges formed on the plate. The melt composition was allowed to crystallize in a desiccator for 2-3 days and then ground to a finely divided powder to form a crystallizer.

an example is a mixture of CN, AN and CaCl ₂

A melt consisting of 50 wt% CN, 4 wt% AN, 26.5 wt% CaCl ₂ and 18-20 wt% water was prepared by melting a mixture of NH-CN and CaCl ₂ * 2H ₂ O (130-140 ° C). .

Using the method described in Test 4b (crystallizer added at 120 ° C), fine particles formed on the cooled steel belt within 30 seconds. The particles consisted of homogeneous solidified CaN-AN CaCI ₂ particles.

an example is a mixture of CN and CN

A melt consisting of 74 wt% CN, 14 wt% KN, and 12 wt% water was prepared by evaporation of the water from the CN-KN-H ₂ O solution. The melt temperature was lowered to 86 ° C, about 5-6 ° C below the crystallization temperature. 3% by weight of finely ground crystalline was thoroughly mixed and the droplets were allowed to fall on a cold metal belt (23 ° C).

Within 50-60 seconds, solid lozenges / particles formed on the plate.

A good crystallizer is made by allowing the melt composition to crystallize in a desiccator for 2-3 days, and then the solid formed is powdered.

Thus, using:

- suitable melt or CN-water composition,

- suitable melting temperature (at or below crystallization point),

- suitable crystalline material (consisting of the solid phase equilibrium phases),

- A cooling belt or similar system that allows crystallization for 20-70 seconds or more can find a way to obtain solid CN particles (CN + crystallization water) without AN. The process can be adapted to obtain solid nitrate systems containing Ca, Mg, K, Na, NH ₄ , or mixtures of these nitrates, or mixtures of nitrates and chlorides.

Claims (11)

DEFINITION OF INVENTION 1. A process for the production of nitrate-containing products (fertilizers, technical products) from frozen melts, wherein the XN-water solution is evaporated to 5099.8% by weight of XN, wherein X is one or more selected from Ca, Mg, NH ₄ , Na and K, when N is nitrate, cool the melt to the crystallization point and time at or below that temperature, then add to the melt a finely divided solid XN powder consisting of equilibrium phases, after which the droplets have been allowed to cool and solidify to seconds. 2. A process according to claim 1, wherein the amount of XN is 7099.5% by weight. 3. A method according to claim 1, wherein the cooling belt is used to solidify the particles. 4. The method of claim 3, wherein the belt is cooled by air, water, oil or another environment. 5. The method of claim 1, wherein the melt drops are cooled and solidified within 20-70 seconds. 6. A process according to claim 1, wherein the temperature is preferably maintained at 0-10 ° C below the initial crystallization point of the melt. 7. A process as claimed in claim 1, which comprises producing calcium nitrate and using CN * 2H ₂ O and CN * 3H ₂ O as crystallizers. 8. A process according to claim 1, wherein the particles have a particle size between 0.2 and 0.8 mm, preferably between 0.4 and 0.6 mm. 9. The method of claim 1, wherein the particles are comprised of a melt consisting of 74% by weight of calcium nitrate, 14% by weight of potassium nitrate and 12% by weight of water. 10. A process according to claim 1, wherein the solid particles consist of a homogeneous chemical mixture of nitrates, chlorides and water of crystallization. 11. A process according to claim 10 wherein the particulate is made from a melt consisting essentially of 50% by weight of calcium nitrate, 4% by weight of ammonium nitrate, 26.5% by weight of calcium chloride and 18-20% by weight of water.