CS200402B1 - Process for preparing condensed vitreous alkali metal phosphates - Google Patents

Description

(54) A method for producing fused glass ^{* 1} metal phosphates alkaliokýeh

The invention relates to a process for the production of condensed vitreous alkali metal phosphates, in particular a high-melting mixture of water-soluble polyphosphates of the Grahams salt type, by heating the corresponding monophosphates and by rapidly cooling the resulting melts.

By heating the acidic sodium monophosphate up to a melting point of 800-850 ° C and cooling the melt, depending on the cooling conditions, mainly polyphosphates / chains form condensed phosphates / with average chain lengths of 10 to 60 with rapid cooling or metaphosphates / phosphates form rings - trimetaphosphate and tetrametaphosphate / with slow cooling.

The large-scale industrial Grahams salt produced is a glassy condensed sodium phosphate which contains, in addition to the predominant polyphosphates, small amounts of astaphosphates.

For the softening of water and for use in detergents and cleaning agents, a high degree of complexity to alkaline earth metals and heavy metals, which only have phosphates, is essential. · Larger proportions of metaphosphates are not desirable in industrial Grahams salts because they have no complexing and they are worthless for the most common uses.

The use of acidic sodium monophosphate NaHgPO4, to which is added medium sodium phosphate HagHKt, results in a rapid cooling of the melt with a mixture of polyphosphates with

200 402 proportions of sodium pyrophosphate, while slowly polishing the polyphosphates in admixture with seventh triphosphate and motaphosphate.

Thus, for the production of condensed glassy phosphates of alkali metal with good properties for thermosetting applications, i.e. and with a good ability to form complexes, my method of cooling the melt is of particular importance.

Are there known processes for the production of condensed alkali metal phosphates which are outlined by this _? forming o mixtures (msnsphosphates) in crystalline form or as ammonium salts / oo are heated in bathtubs or in melt rotary tube furnaces o cool down by serie on solid metal atolls *

The continuous preooo cooling was converted so that the melt had poured a water-cooled metal conveyor belt.

Another form of continuous cooling was carried out by leaving the melt on two rotating and smoothed rolls, and thin film was rolled and solidified.

Melting of the melt using a casting machine has also been described. From the melting point the melting was discharged continuously into flat rectangular metal pans with overlapping edges, which in the shape of endless chains moved constant ryohloot, while the pans on the lower bottom were immersed in running water.

The above-described glazing processes essentially use equally in the production of condensed phosphates by reacting alkali metal chlorides with phosphoric acid, by melting or reacting alkali metal noboic metal halides with phosphoric acid nobo phosphate in the reaction tower.

The batch-like discontinuous cooling of the condensates of condensed alkali metal phosphates has the disadvantage that the product solidified in the blocks requires a lot of manual preaction to be released. The uniform composition and quality of the final product is difficult to ensure! · Compliance with even layer thicknesses during glazing requires special care by operators operating the equipment ·

Even in continuous processes, it is necessary to take into account the high thermal stresses of the apparatuses and in part a considerable corrosion of the material with a strongly corrosive melt at> 650 · C · Very rapid cooling is only conditionally possible. If the glasses are in the form of blocks as with the use of metal pans, an increased mechanical expense for breaking and grinding is necessary, so that the condensed phosphates can additionally contaminate the metals.

A very effective cooling of the phosphate melts can be achieved by pouring into liquid halohydrocarbons, with possibly addition of carbonic acid snow to improve the cooling effect. This process has no industrial significance because of the considerable cost of cooling and recovering solvents / G.Brauer, Handbuch der Priparativen Anorg. Chemie, Ferdinand Enke-Verlag, Stuttgart 1954, 8.425 / ·

The condensed glassy phosphates produced by known methods are highly hygroscopic in lumps when stored. When introduced into water, syrup-like masses are formed, which only dissolve in intensive mixing.

To improve shelf life and water solubility and / or dissolution rate, the powdered condensed phosphates are granulated with the aid of granulating agents such as sodium bicarbonate, sodium sulfate, sodium silicate, sodium monophosphate, amino acid salts, etc. Because of the condensation granulation. Alkali metal phosphates represent an additional costly work step to improve the application properties, in particular solubility and storage, the need for savings in this operation and the application properties of condensed glass phosphates · / Henkel and Clo, GmbH, and Pat. 649.757, cl. 12 i (1937).

The invention achieves a considerable simplification of the technology, in particular the intensification of the quench prooose, and since the starting products are obtained immediately as granules, grinding and granulation are eliminated in order to improve the dissolution and storage properties.

SUMMARY OF THE INVENTION It is an object of the present invention to produce condensed glassy alkali metal phosphates by special arrangement of the cooling process in order to produce well-soluble and easily storable products with a high phosphate content.

The process for producing condensed glass alkali metal phosphates by heating a mixture of menophosphates and cooling the resulting phosphate melts according to the invention is to cool the melt by introducing it into water or aqueous solutions of alkali metal phosphates, carbonates, sulphates or silicates in less than 15 seconds. are granulated.

In a preferred embodiment of the process according to the invention, the cooling is carried out within 3 seconds and the granulates are cooled to 100-250 ° C.

According to a further embodiment of the invention, the alkali metal phosphate melts are rolled onto the strip in the form of a thin beam, cooled by direct treatment with a cooling liquid and simultaneously granulated, either directly introduced into or sprayed with the cooling liquid.

The effect of the invention is to find that when an alkali metal phosphate melt of Ιίβ ₂ 0 0 P2O5 »<1.5: 1 to 0.9» 1 does not flow into water or aqueous solutions of inorganic salts, effective cooling and condensed alkali metal phosphates occur are obtained in the form of granules. In this way, it is possible to cool the melt from -> 550 ° C in a maximum of 15 seconds, usually in less than 3 seconds to 100 to $ 2 ° C. When the resulting granulates are introduced continuously from the cooling liquid at temperatures of> 100 ^° C, dry granulate. In order to obtain granules with uniform grain size, it is necessary to adhere to certain conditions, ie melt temperature, coolant temperature, coolant composition.

The melt phosphates should be very thin and it is heated to at least 50 'D above the melting point of the respective liquid produktu.Teplota chladíoí my be between 20 to 80 ⁰ 0, preferably about 45 ⁰ 0th The content of salts of the coolant, i.e. the content of alkali metal phosphates, carbonates, sulphates or silicates, should be between 0 and 80% by weight or a saturated solution concentration, preferably about 10% by weight. Preference is given to using medium sodium monophosphate solutions, since this results in a small proportion of the monosodium phosphate being deposited on the granule surface and thus provides an additional improvement in shelf life. By using alkali metal carbonates, alkali metal sulphates or alkali metal silicates in the cooling liquid, it is possible to enrich the porosity of the phosphate granules with these salts, thereby ee. may improve solubility.

The process according to the invention is carried out by allowing the melt of phosphates to flow from the melting furnace of the cooling liquid tank, whereby the resulting granule is discharged through a metal fabric conveyor belt immersed in the liquid cooler for a maximum of 15 s through a drying path to which the liquid continues to evaporate through the pellet's own heat and is conveyed to the storage tank. The temperature of the smoothing liquid is maintained at a prescribed value by indirect cooling. * Optionally, it is also possible to add leads to the liquid to maintain temperature. A particular embodiment of the process according to the invention is that the melt is fed to a metal disk rotating in a coolant or a cylinder, thereby achieving the desired melt shape and thus a uniform granulate.

Another embodiment of the process according to the invention is that the melt is rolled between two rotating DC cylinders under gentle cooling onto a plastic belt which falls perpendicularly into the liquid fluid and disintegrates there into a granulate which is conveyed by the conveyor belt. smooth plastic tape by spraying liquid with granules *

Recognizing that condensed glassy phosphates can be obtained by rapid direct cooling of phosphate melts lead through salified saline solutions without substantial hydrolysis, the miners must find it somewhat surprising * From the knowledge of the reaction behavior of condensed phosphates with water or aqueous solutions, Extreme conditions of contact of the hot melt with aqueous solutions resulted in considerable dissolution and hydrolysis of the polyphosphates and formation of significant proportions of monophosphates Z When heated in an aqueous solution of Srahams salt and at 90 ° C for 60 minutes, more than 50% hydrolyzed to non-phosphate. product degradation. It was therefore surprising to find that the process according to the invention yielded products with a monophosphate content of 0.05 to 1.0%, predominantly 0.1% * The loss of products on ignition ranged between 0.1 and 0.8%. below 3, 0%

Compared to ground condensed glassy phosphates, the granulates produced by the process of the invention are more rapidly soluble. Thus, the ryohloot dissolution of the drahano donkeys containing 68.0% phosphorus pentoxide, produced according to the invention, is improved by a factor of about twice as much as the product cooled in the conventional manner through the grinding and grinding.

Although the foregoing embodiments all relate to condensed phosphate and sodium phosphate, it has been shown that the process can also be used in the production of potassium phosphate and mixed potassium phosphate.

By heating medium potassium pyrophosphate according to Example 6, or the corresponding mixtures of potassium chloride and phosphoric acid, and by rapidly cooling the melt, a perfectly water-soluble potassium polyphosphate can be obtained. for the production of phosphate-potassium fertilizers. The process according to the invention represents a convenient start-up possibility for the production of perfectly water-soluble potassium phosphate fertilizers.

The method according to the invention will be further explained by way of examples.

Example 1

Υ gas-fired melting furnace »with melting mw cooling, led by noble eoeli, bullfinch melted * mixture of sodium monophosphate e discount

Bago ^»of 2 ° 5" L "06 ¹¹ · Kezultujíeí melt flowed .s * Temp C 650 ® which vláhh · s 0 10 60 56ního an de Nespek hydregonfesferečnanu solution, maintained at 60 ® C while penetrating the granules which have 0, 5 to 5 &quot; large, were trapped about 5 mm below the surface of the coolant by a metal fabric conveyor belt and removed within 2.5 seconds * from the coolant,

125 [deg.] C crockery granules were obtained

95.1% polyphosphate at 3.0% trimetaphosphate 1.0% monophosphate

0.001% in the science of insoluble fractions.

0.7% annealing losses

Example 2

Analogously to the method described in Example 1, the phosphate melt was cooled by flowing into a 5% sodium sulphate solution and granulated. The granulate had a temperature of 120 ® 0, a grain size ranging from 0.1 to 8.0 and contained

96.3% polyphosphate 2.4% trimetaphosphate 0.1% monophosphate ₍ 0.01% water insoluble fractions)

0.05 56 sodium sulfate

0,5% loss on ignition '

Example 3

In an analogous manner to that described in Example 1, the phosphate melt was cooled by flowing into a 1056 solution of silica and sodaéhe and granulated.

A granulate of β at a temperature of 118 ° C and a maturation of 1.0 to 6.0 Ba containing 95.9% polyphosphate was obtained

2.9% trimetaphosphate

0.2 56 monophosphate

0.09 56 in non-aqueous proportions

0,00 $ silicic acid / SiOg / ',

0,7 56 loss on ignition _in

Example 4

The phosphate melt described in Example 1 was passed through two oppositely rotating water-polished stainless steel cylinders and equilibrated to a 5 m thick. A 450 ^° C plastic strip slid perpendicularly to a smoothing bath with a 10% sodium sulfate solution, which was tempered to 65 ^° C. Forming about 3.0 am large granules were trapped 5 mm below the surface of the smoothing liquid through the conveyor belt. metal fabric and within 2 plinths. taken from the fluid scanner ·

A granulate having a temperature of 110 ^° C following 96% polyphosphate was obtained

2.8% trimetaphosphate

0.3% monophosphate

0.02% water insoluble fractions

0.09% sodium sulfate

0.6% loss on ignition

Example 5

The melt of the phosphate obtained in Example 1 Hýla at 680 ⁹ C Shiloh fibers 6 mm guided on rotujíoí metal disc through a conveyor belt made of metal fabric which is moved in the depth of 60 mA at 95 ⁰ 0 hot water and the granules having plotted during 12 sok from liquid smoothers ·

A 110 ° C hot granulate was obtained

96.5% polyphosphate

2.4% trimetaphosphate

0.1% monophosphate ^f

0.001% water insoluble fractions 0.5% by loss on ignition

The zaltity was between 0.5 and 2.0 mm

Example 6

Acid potassium monophosphate of the following composition was melted in a gas-fired pool with a fire-bricks

KgO * Τ'ζθς · 1 * 1

The resulting melt with a temperature of 960 ⁹ C, the analogous manner as described in Example 1, granulated by having allowed to flow into the sodium sulfate solution which was kept at 80 ⁹ C and a three shock delivered from the coolant · The resulting granules were 1 to 6 mm large and were 250 ⁹ C warm. Analysis provided

97.3% polyphosphate 0.8% monophosphate

0,5% water-insoluble matter 0,9% loss on ignition

Example 7

The dissolution rate of the sodium polyphosphate granulate produced by the process of the invention described in case 5 was compared with the ground sodium polyphosphate granulate under the same melted conditions, which was smoothed by application to a rotating and indirectly cooled metal roll.

Under the same dissolution conditions, the dissolution rate was determined by the funnel dissolution method (according to H. Lux, Aaexganiseh-ehemisohe Exporimentierkunst, Leipzig 1970) with 227 / · 1 g of sodium polyphosphate granules dissolving after 7 minutes and 1 g of powdered and conventional polyphosphorus sodium 13 minutes in 100 ml of water.

Analysis of the product cooled on metal cylinders provided t

79.9% polyphosphoric acid

8.9% trimetaph osf orečnaau

1.8% menophosphate 0.1% water insoluble matter 0.4% loss on ignition

Claims (3)

SUBJECT OF THE INVENTION CLAIMS 1. A process for the production of condensed glass alkali metal phosphates by heating a mixture of monophosphates and by lubricating the resulting phosphate and melt, wherein the melt is cooled by introducing into water or aqueous solutions of phosphates, carbonates, sulphates or alkali metal silicates in less than 15 seconds. granuluji. 2. Process according to claim 1, characterized in that the cooling is preferably carried out within 3 seconds and the granulates are cooled to 100-250 ° C. 3. A process according to claim 1, wherein the alkali metal phosphate melts are rolled or dropped, cooled by direct treatment with a coolant, and granulated while being directly introduced into the coolant or with the coolant. spray liquid.