ES2310963B1 - "PROCEDURE FOR THE INCORPORATION OF AT LEAST ONE SALT IN A LIQUID AMMONY POLYPHOSPHATE". - Google Patents

Abstract

Procedure for incorporating at least a salt in a liquid ammonium polyphosphate, from acid phosphoric and anhydrous ammonia, consisting of the stages:

1) Heating of phosphoric acid and anhydrous ammonia up to 60 ° C - 100 ° C;

2) Phosphoric acid and anhydrous ammonia are mixed in a common reactor at 180ºC - 250ºC with a pressure between 2 - 3 kg / cm2, obtaining an ammonium phosphate;

3) The ammonium phosphate obtained is brought to a dissolution tank;

4) The tank ammonium phosphate is cooled in one or several cooling towers to room temperature, obtaining an ammonium phosphate rich in polyphosphates;

5) A part of the phosphate tower cooling is taken to the dissolution tank where it meets hot ammonium phosphate at a temperature between 180ºC - 250ºC, and it incorporate at least one salt in aqueous solution, rehydrating slightly polymerized molecules leaving the salts included  intramolecularly in ammonium polyphosphate.

Description

Procedure for incorporating at least a salt in a liquid ammonium polyphosphate.

Technical sector of the invention

The present invention relates to a procedure for incorporating at least one salt in a liquid ammonium polyphosphate.

The process starts from phosphoric acid and anhydrous ammonia as raw materials of ammonium polyphosphate and comprises among other essential stages a first stage of heating of raw materials, a second stage where mix the heated raw materials in a common reactor producing a controlled exothermic reaction and obtaining a ammonium phosphate, a third stage in which ammonium phosphate resulting is taken to a dissolution tank and a fourth stage in which the ammonium phosphate in the tank cools in one or more cooling towers up to a temperature around the room temperature, obtaining an ammonium phosphate rich in polyphosphates

Background of the invention

The use of ammonium polyphosphates in the firefighting sector forestry for the manufacture of flame retardant products. In addition to viscosity modifiers and pigments, retarders Flame contain corrosion inhibitors given the action corrosive of liquid polyphosphates on the components or aluminum or galvanized iron tanks of which they are made container deposits of flame retardants.

Aluminum corrosion inhibitors used in flame retardant compositions are salts as per example potassium dichromate, ferric ferrocyanide or pyrophosphates, oxalates and citrates of the iron ion.

Regarding corrosion inhibition of galvanized iron, the utility has recently been discovered of anhydrous or hydrated zinc sulfate as an inhibitor of said corrosion in flame retardant compositions. In addition to sulfate of zinc mentioned, if the flame retardant composition comprises calcium phosphate, a synergistic action is achieved with a considerable decrease in iron corrosion galvanized.

The incorporation of salts in the polyphosphates of Liquid ammonium is not only necessary in the manufacture of flame retardants for fire prevention but also in sectors such as the paper and cellulose industry, where it is convenient to use ammonium polyphosphate with an additive or a anticorrosive that improves the flame retardant capacity or that inhibits the corrosivity of polyphosphate, respectively; and those of the industry of fertilizers and agricultural nutrition, in which additives to liquid ammonium polyphosphate, such as magnesium salts, iron, zinc or molybdenum, improve the nutritional capacity of ammonium polyphosphate

The procedure of incorporation of salts mentioned above for the manufacture of products as per example flame retardants, fertilizers or nutritional agricultural is the addition of these salts to polyphosphate liquid ammonium, which unfortunately causes risks of Product instability, depolymerization and formation of precipitates when the polymer balance is disturbed.

Thus, the need for a procedure for incorporating at least one salt in a liquid ammonium polyphosphate that avoids the risks above mentioned.

Explanation of the invention.

In order to provide a solution to the problems raised, a new procedure is released to the incorporation of at least one salt in an ammonium polyphosphate liquid.

The process object of the invention starts from phosphoric acid and anhydrous ammonia as raw materials of ammonium polyphosphate, and includes the essential stages following:

- a first stage of acid heating phosphoric and anhydrous ammonia to a temperature included between 60ºC and 100ºC, by means of respective exchangers hot;

- a second stage where phosphoric acid and the anhydrous ammonia are mixed in a common reactor where it has place a controlled exothermic reaction at a temperature between 180ºC and 250ºC with a pressure between 2 and 3 kg / cm2, obtaining an ammonium phosphate;

- a third and fourth stages in which first The ammonium phosphate obtained is taken to a dissolution tank (2) and then to one or several cooling towers (3), up to one temperature around room temperature, obtaining a polyphosphate rich ammonium phosphate.

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In essence, the procedure for incorporation of at least one salt in a liquid ammonium polyphosphate It is characterized because it comprises:

- a fifth stage in which at least one part of polyphosphate rich ammonium phosphate from the tower or cooling towers is taken to the dissolution tank where it gasket with hot ammonium phosphate at a temperature included between 180 ° C and 250 ° C, and at least one salt in solution is incorporated aqueous, all in a way that slightly rehydrates the polymerized molecules leaving the salts included intramolecularly in ammonium polyphosphate.

According to another feature of the invention, the Salt is an inorganic salt.

According to another feature of the invention, the salt is chosen independently from a zinc salt, magnesium, iron, molybdenum and / or a mixture of them.

According to another feature of the invention, the salt is an anhydrous or hydrated zinc sulfate.

The procedure for the incorporation of al minus one salt in a liquid ammonium polyphosphate according to the invention, is also characterized in that the salt is a salt organic

Brief description of the drawings

The attached Fig. 1 illustrates, by way of non-limiting example and schematically, a block diagram concerning the procedure for incorporating at least one salt in an ammonium polyphosphate object of the invention.

Detailed description of the drawings

The procedure for the incorporation of al less a salt in a liquid ammonium polyphosphate according to the invention, Its purpose is the incorporation of said salt intramolecularly in liquid ammonium polyphosphate during the manufacturing process of the ammonium polyphosphate itself, thus avoiding the risks of product instability, depolymerization and formation of precipitates that occur when added, in one stage later, simply salt or salts to ammonium polyphosphate finished liquid

The liquid ammonium polyphosphate that incorporates intramolecularly at least one salt is obtained by a process thermally self-powered continuous manufacturing, starting from phosphoric acid and a base formed by anhydrous ammonia as raw Materials.

In a first stage, phosphoric acid, initially at a temperature between 15 ° C and 25 ° C drive through the entrance 6 to the heat exchanger 8 where it reaches a temperature between 60 ° C and 100 ° C; and the ammonia Anhydrous is conducted through the inlet 7 to the heat exchanger 9 also reaching a temperature between 60 ° C and 100 ° C, preferably between 70 ° C and 80 ° C.

In a second stage, phosphoric acid and anhydrous ammonia from their respective exchangers heat 8 and 9, are conducted to a common reactor 1 where it takes place a controlled exothermic reaction at a temperature between 180 ° C and 250 ° C with a pressure between 2 and 3 kg / cm 2, obtaining an ammonium phosphate. The entry of phosphoric acid and Anhydrous ammonia is an entry regulated by respective flow meters, not shown in Fig. 1.

After the reaction, in a third stage the ammonium phosphate is taken to a dissolution tank 2 in which the temperature stabilizes approximately between 90 ° C and 95 ° C. He dissolution tank 2 comprises a peachmeter to regulate the acid and base input ratio and a stirrer, no represented in Fig. 1.

In a fourth stage, much of the phosphate ammonium at the outlet of the dissolution tank 2 is led to one or several cooling towers 3 until leaving the ammonium polyphosphate soluble at a temperature close to room temperature, preferably between 30 ° C and 35 ° C. The tower or towers of cooling 3 can comprise a densimeter and a meter of temperature to obtain information of the product cooled in each moment. If the product is removed at this point in the procedure resulting at the exit of the tower or cooling towers 3 is would obtain liquid ammonium polyphosphate rich in polyphosphates.

In fact, polymerization takes place mostly in dissolution tank 2, where due to sudden drop in temperature, the reaction product from the common reactor 1 is dehydrated, which favors binding of ammonium phosphate molecules.

In a fifth stage, a part of the polyphosphate rich ammonium phosphate from the cooling tower or towers 3 is taken to the dissolution tank 2 (see arrow 5), where it is mixed with hot ammonium phosphate (between 180 ° C and 250 ° C) from the reactor 1. In this fifth stage of the process is when the salt or salts are incorporated in aqueous solution 4, all in such a way that the polymerized molecules are slightly rehydrated, thus leaving the salt or salts included intramolecularly in the ammonium polyphosphate. In addition, it should be borne in mind that the addition of polyphosphate from the cooling tower or towers 3 contributes to regulate the ideal temperature inside the dissolution tank 2, this process being adjustable by means of a regulating valve not represented in the
Fig. 1.

The fifth stage is carried out when the Liquid ammonium polyphosphate manufacturing process is stabilizes, the temperatures being controlled and presenting the product coming from the tower or cooling towers 3 a level Optimum polyphosphate formation. Preferably, the incorporation of the salt or salts in aqueous solution 4 is brought to out when the density of ammonium polyphosphate rich in Polyphosphates is between 1.3 and 1.5 g / cm3. For it, the tower or cooling towers 3 include inside product process analysis devices, such as meters of temperature, densimeters, etc.

The addition of salt or salts in aqueous solution 4 in this fifth stage is done by dosing in the tank of solution 2, under stirring, by means of an injection pump (no represented), the determined amount of salt on the product resulting at the exit of the common reactor 1. In this way it is achieved A correct reaction and incorporation.

It should be noted that in a conventional process of manufacturing liquid ammonium polyphosphate, polymerization of said polyphosphate is achieved by the loss of intramolecular water during the exothermic reaction between phosphoric acid and the hot anhydrous ammonia, and for a later stage of hydration in very strict conditions of pressure and temperature. Well well, according to the method object of the invention, it is precisely at the time of hydration at controlled temperature and pressure when the salt or salts are incorporated in aqueous solution 4, rehydrating the polymerized molecules with said aqueous solution instead of rehydrating only with water. In this way, the salts are incorporated intramolecularly to ammonium polyphosphate liquid.

In the procedure for the incorporation of al minus one salt in a liquid ammonium polyphosphate, the salt in aqueous solution will not be incorporated into dissolution tank 2 until that in the latter the part of the polyphosphate has not been received ammonium rich in polyphosphates from the exit of the tower or cooling towers 3 (according to arrow 5), since when mixed ammonium polyphosphate rich in polyphosphates at different temperatures the unstable equilibrium necessary to get the inorganic salts in aqueous solution are those that rehydrate slightly polymerized molecules.

Obviously, the greater the number of Recirculations of ammonium polyphosphate from the towers cooling 3 occur in dissolution tank 2 and higher be the number of incorporations of the salt or salts in solution aqueous 4, ammonium polyphosphate will increase its percentage rich in polyphosphates and salt or salts incorporated. To this In this regard, it should be mentioned that the procedure described in incorporation of at least one salt in a liquid ammonium polyphosphate it is a controlled procedure, in which the percentages of rich in polyphosphates and salts can be controlled at will of the operator according to the requirements of the ammonium polyphosphate with desired incorporated salts. To do this, the temperatures, frequencies and recirculation volumes e incorporation of polyphosphate and salt, respectively.

The percentage of organic salts or inorganic (zinc sulfate, magnesium sulfate, salts with molybdate, oxalate, citrate, etc.) is a function of its compatibility with polyphosphate formation and destination You will have the final product.

Thus, for example, in the manufacture of a liquid ammonium polyphosphate indicated for the manufacture of a Optimal flame retardant composition has been proven that the anhydrous or hydrated zinc sulfate concentration is between 0.1% and 0.5% by weight with respect to the total ammonium polyphosphate plus zinc sulfate, being the index of polymerization of 25% liquid ammonium polyphosphate or even higher.

The above described procedure of incorporation of at least one salt is applicable to both the incorporation of an organic salt as inorganic. Among the salts inorganic to incorporate in the liquid ammonium polyphosphate stand out those of zinc, magnesium, iron, molybdenum and / or a mixture of them, depending on the sector to which the polyphosphate is destined liquid ammonia, such as flame retardants, the of agricultural fertilizers and nutritional or that of industries bins and cellulosic.

The incorporation of an anhydrous zinc sulfate or hydrated to a liquid ammonium polyphosphate according to the procedure object of the invention becomes especially relevant in manufacturing of a flame retardant composition in which zinc salt acts as a polyphosphate corrosion inhibitor ammonium

It should be noted that according to another embodiment, the procedure for incorporating at least one salt in a Liquid ammonium polyphosphate is a continuous manufacturing process thermally powered, since a part of the polyphosphate ammonium with the built-in salt produced with a temperature between 80ºC and 100ºC it is sent to the exchangers of heat to heat raw materials, at temperatures included between 60ºC and 100ºC for phosphoric acid and at temperatures between 60 ° C and 90 ° C for anhydrous ammonia, placing them at the reaction temperature, as indicated by the arrows eleven.

\ sqbullet Example

By way of non-limiting example, a then the manufacturing process of a batch of liquid ammonium polyphosphate with zinc sulfate.

Initial phase

Thus, in an initial phase of the procedure, the phosphoric acid and anhydrous ammonia are taken to reactor 1 where the exothermic reaction takes place acid-base, forming ammonium phosphate, which at be redirected to dissolution tank 2, it stabilizes at a temperature from 90 to 95 ° C. At this precise moment, approximately 80% of the product of dissolution tank 2 is sent to the cooling tower or towers 3, finally obtaining a product consisting of ammonium phosphate with a high percentage of ammonium polyphosphate molecules.

In order to get the subjects raw, phosphoric acid and anhydrous ammonia, are at the temperature suitable for the reaction, approximately 20% of the product that it is removed from the dissolution tank 2 is redirected by pipes 11 in a closed circuit that transmits heat to them and that finally it enters the dissolution tank 2 again.

Similarly, a part of polyphosphate ammonium towers or cooling towers 3 is redirected to dissolution tank 2 contributing to the latter's cooling At the same time it is enriched in ammonium polyphosphate.

Stabilization phase

Once the procedure is stabilized, that is, once the desired product density has been achieved in the cooling tower or towers 3 and the optimum level of formation of polyphosphates, the aqueous solution 4 of zinc sulfate in the dissolution tank 2.

For this, a part of the ammonium phosphate rich in polyphosphates from the tower or cooling towers 3 is taken to the dissolution tank 2 and mixed at its entrance with the reaction product from reactor 1, that is with Ammonium phosphate at a temperature between 180ºC and 250ºC. It is also in the entrance to the dissolution tank 2 where it is added, for example by means of an injection pump not shown, the aqueous solution 4 with zinc sulfate.

The amount of zinc sulfate is calculated to which is between 0.1% and 0.5% by weight with respect to Total ammonium polyphosphate plus zinc sulfate.

Next, about 80% of the product resulting from dissolution tank 2 is taken to the tower or towers of cooling 3 where the polymer continues to form polyphosphate but now with zinc sulfate incorporated intramolecularly In the same way as in the initial phase, 20% of the product from tank 2 is carried by pipes 11 to Heat the raw materials.

Finally, once the desired characteristics in ammonium polyphosphate with sulfate zinc, the finished product is sent to a tank 10.

Described sufficiently the procedure according to the invention, it should be understood that the equipment used corresponds to those commonly used in this type of industry.

The procedure for incorporation intramolecular of at least one salt in an ammonium polyphosphate liquid may be subject to changes in shape and timing of execution of the different stages that integrate it without it get out of the object of the invention. Thus, the times are foreseen and flows of raw materials and suitable intermediate products in function of what are the requirements of the final product to obtain.

Claims (5)

1. Procedure for the incorporation of al minus one salt in a liquid ammonium polyphosphate, starting with acid phosphoric and anhydrous ammonia as polyphosphate raw materials ammonium, which comprises the following essential stages: - a first stage of acid heating phosphoric and anhydrous ammonia to a temperature included between 60ºC and 100ºC, by means of respective heat exchangers (8, 9); - a second stage where phosphoric acid and the anhydrous ammonia are mixed in a common reactor (1) where a controlled exothermic reaction takes place at a temperature between 180ºC and 250ºC with a pressure between 2 and 3 kg / cm2, obtaining an ammonium phosphate; - a third and fourth stages in which first The ammonium phosphate obtained is taken to a dissolution tank (2) and then to one or several cooling towers (3), up to one temperature around room temperature, obtaining a polyphosphate rich ammonium phosphate; characterized in that it comprises: - a fifth stage in which at least one part of polyphosphate rich ammonium phosphate from the tower or cooling towers is taken to the dissolution tank where it gasket with hot ammonium phosphate at a temperature included between 180 ° C and 250 ° C, and at least one salt in solution is incorporated aqueous (4), all in a way that slightly rehydrates the polymerized molecules leaving the salts included intramolecularly in ammonium polyphosphate. 2. Method for incorporating at least one salt in a liquid ammonium polyphosphate according to claim 1, characterized in that the salt is an inorganic salt. 3. Method for incorporating at least one salt in a liquid ammonium polyphosphate according to claim 1 or 2, characterized in that the salt is independently selected from a salt of zinc, magnesium, iron, molybdenum and / or a mixture thereof. 4. Method for incorporating at least one salt in a liquid ammonium polyphosphate according to one of the preceding claims, characterized in that the salt is an anhydrous or hydrated zinc sulfate. 5. Method for incorporating at least one salt in a liquid ammonium polyphosphate according to claim 1, characterized in that the salt is an organic salt.