DE2437748A1 - PROCESS FOR THE PRODUCTION OF POTASSIUM PHOSPHATE OR - POLYPHOSPHATE - Google Patents

Description

Process for the production of potassium phosphate or

polyphosphate The present invention relates to the manufacture of Fertilizers. In particular, it relates to the production of potassium dihydrogen phosphate and / or soluble polymerized derivatives of this salt. These products are of great value as a source of both potassium and phosphorus and can be direct or used together with other products as fertilizers.

Potassium dihydrogen phosphate can be made by reacting phosphoric acid with potassium chloride according to the known reaction of the following equation: The quantitative removal of the hydrogen chloride from the reaction mixture is extremely difficult in practice unless high temperatures or a large excess of phosphoric acid is used.

In the first case, water-insoluble potassium metaphosphate is formed preferentially and in the latter case the separation of the salt from the acid is difficult in practice and expensive.

The inventive method for the production of potassium phosphate and polyphosphate is characterized in that one has potassium chloride and phosphoric acid or a polyphosphoric acid in a molar ratio of phosphorus to potassium im Range of 1: 1 to 1.25: 1, with the aid of facilitating the removal of the hydrochloric acid is blown through the reaction mixture Lut.

The preferred molar ratio of phosphorus to potassium is about 1.1: 1.

The resulting reaction product is valuable as such Fertilizer and can be used without further treatment. On the other hand, can however, the reaction product can also be hydrolyzed by treating it with water is heated to a temperature in the vicinity of 100 OC, whereby the hydrolysis product afterwards is won. The reaction product still provides cooling a glass-like solid that dissolves in water to form highly pure solutions dissolves, which are used for the production of liquid fertilizers k ## n. That Hydrolysis product can and can also be obtained as a crystalline solid be dissolved in water to make liquid fertilizers.

Although temperatures in the range of 100 to 120 ° C, preferably 110 ° C give satisfactory results, even larger deviations from these temperatures, in which the reaction product is heated with water, can be used.

Similarly, different temperatures can be used to carry out the reaction between phosphoric acid and potassium chloride. In general temperatures of at least 150 ° C and preferably temperatures of above 180 ° C applied.

Temperatures in the range from 180 to 300 ° C. are particularly preferred and especially in the range from 220 to 250 ° C.

The phosphoric acid used in the process according to the invention is generally commercially available phosphoric acid containing 50 to 54% P2O5. as However, phosphoric acid can also be dehydrated commercially available Phosphoric acids are used, which contain more than 54% and less than 75% P2O5.

In general, phosphoric acid is used with a P2O5 content in the range used from 30 to 75%.

Liquid fertilizers with a very low chloride content can be used be prepared in that the product hydrolyzed as mentioned above is dissolved in water or in an ammonia solution or a solution of the reaction product formed from hydrolysis in water and then gaseous ammonia by the Solution is directed.

The process according to the invention comprises the preparation of potassium dihydrogen phosphate and polymers of this salt by reacting phosphoric acid with potassium chloride according to the known reaction of the following formula: The dehydration of the orthophosphate takes place at elevated temperatures with the formation of pyrophosphate and higher polymer phosphates. However, the reaction temperature must be low enough to avoid the formation of insoluble metaphosphate.

The temperature is preferably below 300 ° C.

According to the invention it was found that the removal of the chloride from the reaction mixture easily and effectively when using stoichiometric or almost stoichiometric amounts of the reaction components and with a P: K molar ratio in the range from 1.0: 1 to 1.25: 1 without the use of very high and large temperatures Excesses of acid can be achieved if the reaction mixture is mixed with air ventilated.

The inventive method has the advantage that the preferred Formation of the water-insoluble metaphosphate as well as the difficult and expensive separation of the desired potassium dihydrogen phosphate from a large excess of present Acid is avoided.

The phosphoric acid used can be that obtained from the wet process Commercial phosphoric acid with a P205 content in the range from 30 to 54% or a dehydrated phosphoric acid with a P205 content of essentially 75% or Commercial super phosphoric acid or one of the various other concentrated products Be phosphoric acids such as are commercially available.

The resulting glassy product is a polymerized one mixture of phosphates with a small amount of free acid ranging from 5 to 15 % P2O5 depending on the relative amount of acid and potassium chloride used The product can be ground to produce a high P2O5 and fertilizer K2O degree of purity. The product can also be dissolved in water and results in this a liquid high purity fertilizer with a low chloride content.

The reaction product is hydrolyzed by treating it with water heated to a temperature substantially near the boiling point of water. In this way the solid potassium dihydrogen phosphate is obtained. This product can be dried and a crumbly powder is obtained. On the other hand, can However, it also forms a highly pure liquid containing potassium and phosphate Fertilizers with a very low chloride content can be dissolved in water.

According to one embodiment of the method according to the invention, the Reaction product in the form of a vitreous fast substance with a chloride content of less than 1.5% and a free acid content of less than 15% P2O5.

The factors that adversely affect the chloride content of the product, are the reaction temperature and the ratio of phosphoric acid to the potassium compound.

Other reaction conditions that have an influence on the chloride content are the reaction time and that passed through the reaction mixture Air as illustrated in Examples 3 and 2 below. So could according to the following Example 1 obtained a product with a chloride content below 1.5% if the molar ratio of P: M is increased to above 1.1 or if the temperature is increased to above 250 OC or if the dwell time is increased became.

The solution of both the reaction product and the hydrolysis product can be treated with ammonia, creating a stable solution with analytical values for N, P and K is obtained, which are much higher than it has been with commercially available Products was possible.

It was found that despite the fact that the solutions with high Analysis values obtained with the hydrolyzed product, which is an orthophosphate solutions with even higher analysis values can be produced in this way can that the polymeric reaction product is dissolved in water. Hence the Reaction product, a product that is valuable in the manufacture of liquid fertilizers is. The hydrolysis product is therefore preferably used if the product still has to be stored and transported or if a solid product should be preserved.

A device that is used to carry out the method according to the invention can be used is described in conjunction with the drawing. In the drawings Figure 1 is a diagrammatic representation of a method in accordance with the present invention Invention for the production of potassium phosphate from potassium chloride (muriate of potash) and FIG. 2 shows a modification of FIG. 1.

The device shown in Figure 1 comprises a reactor 3, with phosphoric acid from a storage container 1 and with potassium chloride from one Reservoir 2 is fed. Air is introduced at 12. Hydrochloric acid goes off together with some water vapor at 4. The product of the reactor 3 can be one Hydrolysis device 5 are supplied, where it is supplied with through line 6 Water is mixed. The hydrolyzed product from the hydrolysis device 5 is directed to a dryer 7 and from here to storage location 8.

On the other hand, the product obtained from the reactor 3 can also be one Cooling device 9 and from there a shredding device 10, from where it is given to storage location 11.

Figure 2 shows a modification in which the product of the first Reactor 3A is transferred to a second reactor 3B, where it is treated again with air that is killed by 123 bubelei.tot.

Example 1 Potassium chloride (muriate of potash) with a K2O content of 60% and a degree of purity for fertilizers is carried out at a constant rate (1800 g / h) together with phosphoric acid in an air-split reactor given, which is kept at 250 ° C.

The ratio of phosphoric acid to potassium chloride in the starting mixture was such that a reactor product containing 1.1 moles of P per mole of K was obtained. Air was passed through the reaction mixture at a rate of 15 liters per Minute passed. The reaction product is continuously poured into a second Reactor flow, where the temperature was also 250 oC and air again with it a rate of 15 liters per minute was initiated. The resulting Product was analyzed at appropriate time intervals. It had an average Free acid content expressed as P205, amounting to 7.7% and an average Chloride content of 1.5. The average analysis was as follows: 54.5 % Total - P2O5 32.6% Total - K2O 48.5% Soluble P2O5 29.4% Soluble K2O Das Reaction product was divided into two portions.

One portion was cooled, crushed and filled into sacks. The other portion was used to hydrolyze the phosphates with water for two hours 110 ° C heated and the hydrolysis product was cooled, dried in vacuo and deposited. The hydrolysis product showed an analysis of 49.2% total - P2O5 and 29.4% total - K2O.

The glassy product obtained from the reactor and the hydrolyzed one Product were dissolved in water and ps saturated solutions were obtained at 20 ° C. Analysis of the saturated solutions showed the following potassium content: Solution of the reactor product (% K2O) 18.5 Solution of the hydrolyzed product (% K2O) 7.9 Example 2 200 g of potassium chloride (muriate of potash) with 60% K20 content and a Degree of purity for fertilizers was stirred at 220 ° C with 452 g of phosphoric acid stirred from the wet process. This phosphoric acid was previously heated to 250 ° and concentrated to a P205 content of 58.85. The quantities used correspond a P: K molar ratio of 1.4: 1.0. After the formation of the Hydrochloric acid stopped, the reaction product was divided into two parts. Every part was heated to 220 ° C for 120 minutes. One part got air through one Glass tube initiated. The other portion was not treated with air. The reaction products were analyzed and the following values result: Treated with air Untreated delt residual chloride content, 1.64 3.21% Cl total - P205,% 55.6 54.5 total - K20, % 26.4 2f, 9 Example 3 200 g of potassium chloride (muriate of potash) with 60% K20 content and a degree of purity for fertilizers, while stirring at 220 ° C, was 356 g Phosphoric acid reacted, which is produced by the wet process and previously on a P205 content of 58.8% had been concentrated. The raw materials used correspond to a molar ratio of P: K of 1.1 to 1.0. After finishing education of the hydrogen chloride gas, resulting in the termination of the foaming of the reaction product shows, the mixture was treated with air while maintaining the temperature at 220 ° C became. Samples were taken at appropriate intervals for analysis for chloride content.

The result of these analyzes is as follows: Time after completion of the Foaming (min.) 120 180 240 300 Residual chloride content,% Cl 6.56 4.96 3.58 2.68 The analysis of the final product was as follows: Total - P205,% 53.1 Total - K20, % 31.9 The glassy reaction product and the hydrolysis product from it can with Ammonia can be treated, whereby products are obtained that have a valuable Contain potassium, nitrogen and phosphorus. E.g. 150 ml of a 20% aqueous ammonia mixed with 203 g of the product obtained from the reactor, the resulting solution contains 4.2% N, 33 O P205 and 17.8% K20 and can be used as valuable fertilizer can be used.

Patent claims:

Claims (9)

PATENT CLAIMS 1 Process for the production of potassium phosphate resp. -polyphosphate H. e t that potassium chloride and Phosphoric acid or a polyphosphoric acid in a molar ratio of phosphorus can be converted to potassium in the range 1: 1 to 1.25: 1, with for relief the removal of the hydrochloric acid, air is blown through the reaction mixture is, and the reaction product obtained, optionally by treatment with water is hydrolyzed and / or aftertreated with ammonia. 2. The method according to claim 1, characterized in that potassium chloride and phosphoric acid or the polyphosphoric acid are used in such amounts that des molar ratio of phosphorus to potassium is about 1.1: 1. 3. The method according to claim 1 or 2, characterized in that the reaction product from the reaction of potassium chloride with the acid in shape a glassy solid with a chloride content of less than 1, 5% and is isolated with a free acid content of less than 15% P205. en 4. The method according to claims / 1 to 3, characterized in that the hydrolysis is effected by the fact that the reaction of potassium chloride product obtained with the acid with water at a temperature of 100 to 120 ° C is treated. 5. The method according to claim 4, characterized in that the hydrolysis is carried out at a temperature of about 110 ° C. 6. Process according to Claims 1 to 5, characterized in that the reaction of potassium chloride with phosphoric acid or polyphosphoric acid is carried out at a temperature in the range from 150 to 250 0C. 7. The method according to claim 6, characterized in that the reaction is carried out at a temperature in the range from 220 to 250 ° C. 8. Process according to Claims 1 to 7, characterized in that assumed a phosphoric acid with a P205 content in the range from 30 to 75% will. 9. The method according to claim 8, characterized in that of one Phosphoric acid with a P205 content of more than 54% and less than 75% was assumed will.