GB2116158A - A process and apparatus for preparation of ammonium phosphates - Google Patents

Abstract

A process of continuous preparation of a melt of condensed ammonium phosphates by the reaction of phosphoric acid or a solution of ammonium phosphates in phosphoric acid with gaseous ammonia which is dosed into the reaction medium in excess and comprising neutralizing-dehydrating reaction between liquid phase and gaseous ammonia, takes place by continuous contact of phases in a film layer which is formed in the reaction medium by gradual pouring of the liquid phase under gravity and also by its dispersion with gaseous phase formed by a mixture of gradually warmed-up gaseous ammonia and gradually warmed-up steam. The apparatus comprises a standup through-flow film reactor (1) having one supporting bottom (2) with organized and/or non-organized filling (3), a supply of liquid phase containing phosphoric acid (4) and a supply of gaseous ammonia (5). The film reactor can also contain distribution partitions (6), directing the flow of reaction mixture in the filling, building-in (7) and/or static mixer (8). <IMAGE>

Description

SPECIFICATION A process and apparatus for preparation of ammonium phosphates The invention relates to a process for continuously preparing a melt of condensed ammonium phoshates and to apparatus operating this process.

A melt of condensed ammonium phosphates containing a mixture of ammonium dihydrogen phosphate and condensed ammonium phosphates, characterized by following chemical formula: (NH4)m H(n+2) - m Pn 03n + 1 wherein 82 and mn + 2 is a starting compound-immediate of producing clear or suspended multi-component liquid fertilizers. At present processes are known for preparing such melts.The most elaborate, and it can be said that at present also the most frequently, used are processes based on atmospheric or pressure neutralization of phosphoric acids having various concentrations and degrees of purity with ammonia.

Various types of reactors are employed for producing the melt of condensated ammonium phosphates, mainly the reactors of tubular type, the most frequently used of which being the socalled T-reactors. Constructional solutions of these reactors are protected by a nurmber of patents and author's certificates such as for example following: US Patents No. 2985513, 3382059, 3420624, 3464808, 3723086, 3502441, 3503706, 3649175, 3650727, 3788817, 3733191, 3949058, 3734708, 3775534, 3939255, 3947261, 3950495, 3988140, 4250147, French Patent No. 1493803, South Africa Patent No. 67/5 806, DOS NO.

1909438, 2114055, 2308716, Swedish Patent No. 366012 and Czechoslovak Author's Certificate No. 180802.

Speical literature presents also various modified pipe reactors in connection with producing condensed ammonium phosphates, from which reactors the so-called Swift reactor is the most well known one. From the literature following can be cited: Chem. Eng. 21(8), 60 (1972); Agric. Chem. 28, (2), 12(1973); Fert. Solns. 1 7, (2), 44 (1 973); ISMA Prague 1 97SMeline R.S: 'Production of High polyphosphate Liquid Fertilizer by the Pipe Reactor Process'; Chim. Prom. No. 10, 752-755 (1975); Phosp. and Potass. 90, 25 (1977) and Chem. Prum. 28, 53, (5), 229 (1978).

Although the employment of pipe reactors represented a substantial progress in the development of the device for producing the melt of condensed ammonium phosphates, these reactors have certain drawbacks. They require treatment of pre-heated and to a various stage concentrated phosphoric acid which inevitably imposes increased requirements for consumption of energy. The assembly of the device is usually quite complicated and thus also relatively demanding for service; complexity of technological units enhances the possibility of crashes, makes the total power blanace of the process worse and the device is also demanding for the occupied space.Prevailing number of the employed pipe reactors requires dosing of phosphoric acid under pressure whereby requirements for corrosion resistance of the device employed for dosing of hot treated acid are enhanced. The processes usually do not allow treatment of extracting phosphoric acids containing higher fractions of contaminating admixtures (mainly Mg, Al, Fe, F and also organic compounds), foaming of the reaction mixture takes place and incrusts are formed at the reaction walls which negatively affects hydrodynamics of the process.They do not allow rational employment of the heat released at neutralization reaction, constructional solution of pipe reactors presupposes in most cases employment of metallic construction materials which with respect to extraordinary high corrosivity of the reaction mixture belong to the group of expensive and frequently also less accessible materials (silver, tantalurm stainless steels with relatively high content of Mo and Cr). The employment of pipe reactors presupposes high accuracy and namely ratio stability of dosing of both basic reacting components, it usually taxes the service and requirements for keeping operational discipline and, therefore, not always it is the guarantee for reaching the necessary standard of safety of operation of the producing device as a whole.

It was succeeded to eliminate most of the presented drawbacks by employment of continu ously operating dispersive neutralization-dehydration reactors, the function of which is based on bubbling of gaseous phase through liquid reaction mixture (Czechoslovak Author's Certificate No. 210335, 205849).

The fact that the device operates with hold-up of liquid phase is a certain drawback for the employment of bubbling reactors of column type which fact mainly in the system where liquid phase of the reaction mixture is formed by a melt requires keeping the determined process at maintaining the device in operation and mainly when putting it out of operation.

All the previously mentioned drawbacks are in a substantial measure eliminated by a process for continuous preparation of the melt of condensated ammonium phosphates by the reaction of phosphoric acid containing 50 to 80% of P205 and having temperature 15 6 to 300"C or by the reaction of a solution of ammonium phosphates in phosphoric acid with gaseous ammonia which is dosed into the reaction medium in excess as related to the amout of ammonia bound in the melt in the form of ammonium phosphates, the subject matter of which process consists in that a neutralizing-dehydrating reaction between liquid phase containing phosphorus and gaseous ammonia takes place by continuous contact of phases in a film layer.The film layer is formed in the reaction medium by gradual pouring out the liquid phase as an effect of force of gravity and also by its dispersion with gaseous phase formed by a mixture of gradually warmedup gaseous ammonia and gradually warmed-up steam, which layer pours out along the surface of the reaction medium having the surface of contact 7.10 to 1'8.103 m2.m-3, preferably 4.3.101 to 9.8.102 m2.m-3.

The extra layer flow rate of gaseous phase X is 1.10-2 to 1.101, preferably 2.10-i to 2.100 m.s.-1, gaseous phase flowing in parallel-flow way with the flow of liquid phase.

The extra layer flow rate of fluid is characterized as the ratio of volume flow of fluid (for example gaseous phase of the reaction mixture) and section area of the empty device (without filling).

The melt of condensed ammonium phosphates can be prepared using the apparatus according to the invention, which consists in that, it is composed of a film reactor with at least one supporting bottom whereon organized and/or non-organized filling is placed, for the ratio of equivalent diameter of filling particles de, which ratio is defined as the sphere diameter, the volume of which is equal to the volume of diameter, the volume of which is equal to the volume of filling particles, and of internal diameter of the film reactor body or length of its longest side D the following relations being held 5.10-3 %d,/D%4.5. 10-', for the specific interspace volume of the filling, the so-called porosity e the relation 28foe% 96 percent being held, preferably 60 < e < 80 percent and for the ratio of the total height of filling H and of the internal diameter of the reactor body or the length of its longest side D the relation 1.1~H/D~14.8, the device having further a supply of liquid phase containing phosphoric acid, which supply is led over the layer of filling, having a supply of gaseous ammonia and distribution partitions regulating the flow of reaction mixture in the filling, if need be, and building-in and/or static mixer.

The specific interspace volume, the so-called porosity, is a characteristic of the layer, the porosity being defined as the ratio of volume of free spaces in the layer to the volume of the whole layer L0 s= 1--, L where Leo = the height of the so-called compact layer, that is the height of the layer of particles without spaces and L = the height of the layer.

The specific interspace volume of the layer affects the value of pressure losses quite significantly. When particles of regular shapes are concerned the specific interspace volume of the layer depends mainly on their shape and size, or on the ratio of particles diameter and device diameter wherein the layer is placed. The porosity of layers of particles having regular shapes depends also on the process of layer formation.

The advantages of the process for prearing and the apparatus according to the invention are that they enable reational utilization of the heat which is liberated at the reaction of hot liquid phase containing phosphoric acid with gaseous ammonia, they form the optimum conditions for the course of heterogeneous reactions in a system formed by liquid and gaseous phase, and they impose the minimum requirements of power consumption at dosing the liquid reaction component containing phosphoric acid.The device further enables compact constructional solution of the reactor junction at smaller number of single technologic parts/dehydrate, separator of reaction mixture and simiiar/ and at minimized requirements for space at placing technologic part of manufacturing plant, the apparatus is simpe and it does not contain any rotary parts, the apparatus operates with high standard of safety of operation and its function imposes minimum requirements to the service.

One of many modifications of the apparatus according to the invention is schematically represented on the attached drawing.

Treated phosphoric acid or solution of NH4H2PO4 in phosphoric acid continuously flows through the supply 4 of liquid phase placed in the upper part of the reactor body 1 into the vertically located reactor. Acidic liquid reaction component containing phosphorus runs down along organized and/or non-organized filling 3 placed on at least one supporting bottom 2. For the ratio of equivlent diameter of particles of filling de defined as the diameter of a sphere volume of which is equal to the volume of a particle of filling (for spherical particles de is equal to particle diameter) and of the internal diameter of the reactor body D it holds de/D is 0.005 to 0.45.

Some of suitable natural materials can be used as non-organized filling. Suitable synthetically produced fillings are made in various shapes such as for example Raschig, Lessing, Pall rings, Beri saddles Cannon filling and similar and they are supplied also in various sizes. From the point of view of separation of liquid phase it was shown as advantageous when the upper part of filling 3 is formed by particles for which the value of the above discussed ratio de/D is smaller or equal to 1.1 O- 1 it is advantageous as well when the upper layer of filling is closed by a conical layer of filling particles, the supply of liquid phase being led immediately over the vertex of this cone.

Gaseous ammonia is led into the neutralization-dehydration reactor by the supply 5 which is led either above the upper layer of fillig 3 as well. Liquid phase containing phosphorus pours out along the filling surface under the effect of force of gravity, exothermic neutralization reaction between dosed components taking place as a result of presence of gaseous ammonia in the system. Entrainment of liquid phase by gaseous phase also contributes in a substantial measure to the formation of film layer and to intensive equalization of concentration differences at interfacial boundary, gaseous phase being composed of gaseous ammonia and reaction mixture of liberated overheated steam.

Because the contact of reacting phases takes place in a film layer, favourable conditions are provided both for the neutalization and the dehydrating reaction.

It was found to be suitable to build into the interior of the reactor body 1 also distributive partitions 6, which partitions direct the flow of reaction mixture along the filling surface whereby uniform wetting and also further intensification of contact of the reacting phases are reached.

Under certain circumstances if required it is possible to deepen the course of neutralizingdehydrating reaction also by building in suitable baffles 7 and/or static mixer into the interior of the reactor body 1.

Liquid phase of the reaction mixture gradually changes its character as a result of continuously increasing neutralizing and dehydrating reaction at the flow of phase along the surface of filling 3 heated by heat of reaction and in the case when mainly phosphorous raw materials containing organis compounds are treated the liquid phase also intensively foams. By this formation of a certain 'closure' is reached which encumbers free transfer of gaseous ammonia through the apparatus and motion of reaction mixture through the apparatus obtains the character of piston flow.

By the passage of the reaction mixture, both liquid and gaseous phase, through the last perforated supporting bottom 2 foamy melt of condensed ammonium phosphates flows out of the reactor and it is possible to treat it further by direct disolving, reaction with some of the components which are the source of basic, secondary or trace plant nutriments, by granulation or by another form of treatment into its application form. Unreacted gaseous ammonia being contained in gaseous phase of the reaction mixture can be especially advantageously used in some of the further phases of the process (for example to bond it in weakly acidic aqueous solution of the melt under simultaneous adjustment acidity of the final product and similarly).

Example 1 The process for producing condensed ammonium phosphates according to the invention was verified employing models of the apparatus in accordance with the invention in the form of a continuously operating apparatus.

The neutralization-dehydrating reactor was composed of a metallic reactor body having the shape of a vertical cylinder, total height 1 200 mm. and internal diameter 1 55 mm. Approximately 2û mm. from bottom edge a perforated supporting bottom containing 37 circular openings was stepped into the reactor body, each of whcih openings had diameter 1 2 mm.On the supporting bottom non-organized filling was placed up to the height 900 mm. which filling was formed by stoneare Raschig rings of the size 25.4 > c z 25.4 mm. with wall thickness 3.6 mm. which corresponded to 16.97. 10-3m3 of filling forming 3.225 m2 of contact area, the average interspace volume, the so-called porosity of which area being equal to 71% and the ratio of equivalent of the particles of filling de to the internal diameter of the reactor body D was equal to de/D = 22.87/155 = 1.47 . 10'. Further 100 mm. layer of non-organized filling consisting of ceramic Raschig rings characterized by dimensions 1 2.7 x 1 2.7 mm. and wall thickness 1.8 mm. was placed on the above specified filling. 0.692 m2 of contact surface corresponded to thus formed layer of filling, the average interspace volume of which, the socalled porosity, was equal approximately to 70%. The ratio of equivalent diameter of particles of filling in this layer to the internal diameter of the reactor body was de/D = 11.44/155 = 7.38 10-2. The last third layer of filling placed on the preceding filling was 75 mm. thick and it was composed of ceramic Raschig rings having size 6.35 X 6.35 mm, height 0.76 mm.

The ratio of equivalent diameter of filling particles de, defined as diameter of a sphere volume of which is equal to the volume of a particle of filling, to the internal diameter of reactor body D was equal to d0/D = 5.45/155 = 3.52. 10-2. A contact surface shaving area 1.12 m2 was formed by the last upper layer of non-organized filling, the average interspace volume of which, the so-called porosity e is 72%. All the layers of filling employed represented the total area of contact surface 5.037 m2. Feed pipings of phosphoric acid and gaseous ammonia were a part of flanged cover closing the reactor body from the upper part and they were led approximately 50 mm. above the last layer of filling, acid supply being located in the vertical axis of reactor body.

The reactor body was insulated along the whole height using approximately 80 mm. thick layer of basalt wool. In the lower third of the body height thermometer pocket filled up with silicone oil with thermometer was built-in.

We have been operating with partially concentrated commercial extraction acid of the socalled black type, which acid was before concentration specified by this chemical composition: content of total P205 (determined photometrically) : 54.91% content of P2O5 determined by acidity calculation : 56.27% -iron content 0.49% -aluminium content : 0.387% -magnesium content . 0.132% calcium content 0.064% 4urine content 0.456% Acid of given quality, after concentrating to 64% P205 (according to photometric results) at continuously operating film evaporator, flowed through a hydraulic closure and centrically located supply of liquid phase into already specified reactor in the amount 1250 g.min-1. The average temperature of the acid dosed into neutralization-dehydrating reactor was 135.5 C.

286.1 g. of gaseous ammonia on the average was dosed each minute into the verified device using the ammonia supply. Temperature in the lower third of reactor height was stabilized at 276 C after approximately 30 minutes of function of the device.

Under these conditions we have been obtaining 1 274g of strongly foamed melt each minute on the average, which melt was specifed by this average content of basic components: 11.7-62.8-0 (%N-%P205-%K20), the product containing on the average 13.9% P205 bound in the form of orthophosphates and 48.9% of P2O5 in the form of condensed ammonium phosphates (the average degree of conversionvonversion to condensed phosphates = 77.9%).

Prepared melt of condensated ammonium phosphates was in the next stage using in continuous process directly treated to a liquid NP-fertilizer of the 10-34-0 type, 104.9 g of NH3 from gaseous reaction phase being on the average each minute bound into weakly acidic melt solution. The obtained liquid NP4ertilizer has slightly acidic reaction (pH = 6.0) and its average density value was 1390 kg.m-3. From the point of view of phase stability the final product did not exhibit any variations even at long-lasting storage at temperature - I 6 C.

Examples 2-17 The neutralizating-dehydating reactor employed in the course of this series of experiments was connected into an assembly of model continuously operating apparatus for preparing nitrogenphosphate liquid fertilizers of polyphosphate type and it consisted of: -cylindrical reactor body made of impregnated graphite GRAFODUR, having height 1 000 mm.

dia. 1 55 X 1 7.5 mm. in its bottom having thickness 20 mm. 37 circular openings with diameter 12 mrm. being drilled, whereby perforated carrying bottom for deposition of filler was made; -non-organized filling mostly composed of filed rings from graphite pipes 38/24 and 30/10 mm; -supplies of phosphoric acid and gaseous ammonia, being led above the layer of filling.

For the particles of employed non-organized filling their characteristics were obtained by determination and calculation, which characteristics are summarily presented in the Table No. 1.

First experiments with this type of grafodur filling reactor were made with extraction H3P34 which was continuously dosed through film evaporator into the reactor. In the course of the first experiment it was dosed on the average 6.65 . 10-3 kg of non-concentrated H3PO4. s-1 (23.94 kg . tq H3PO4 . h-l), in next experiments the average weight rate of acid dosing being gradually enhanced by 64.4, 1 24.7 and 160.9% so that in the last experiment of this series it was dosed already 17.35 . 10-3 kg of H3PO4 . s-' on the average. The degree of conversion of monophosphates to condensed phosphates in liquid phase of the reaction mixture gradually decreased in single experiments of the series in relation to gradual decrease of concentration of trihydrogen phosphoric acid flowing from evaporator into the reactor (as an effect of enhanced dosing of the acid into evaporator). The highest average value of the degree of conversion in the samples of melt taken in the course of the experiment was 71.2%. The lowest fraction of condensed phosphates (61.4%) was found in the samples of melts from the experiment 1 65 when the highest tested weight rate of dosing the acid (17.35 . 10-3 kg.s-1) was used within the scope of evaluated series of the experiments. In the course of all the experiments continuous free feed of the treated acid into reactor was kept.Reaction mixture flowed uniformly through the reactor, no non-uniformities in the appearance of reaction mixture or drawbacks in the function of verified reactor were observed. The function of reactor was evaluated particularly advantageously in the course of the last two experiments of the series (1 64 and 165) when the flow of reaction mixture through reactor reached unambiguously piston character.In the course of the experiments 1 66A to D extraction acid of the same quality and origin was employed with the difference the acid was concentrated in advance and in single experiments of the discussed series the acid was already only heated to temperature 110 to 11 5 C by flowing through evaporator without its further evaporating/evaporator walls were tempered toi lower temperature than corresponded to boiling temperature of the dosed acid 140 to 1 55"C. By this method it was largely succeeded to eliminate the effect of variation of H3PO4 concentration at the experimental determination the capacity of the tested reactor.In the single experiments of this series following average weight rates of H3PO4 dosing were employed: (11.84; 16.22; 19.52 and 22.56) . 10-3 kg of H3PO4 . s-1 that corresponded to (7.39; 10.12; 12.18 and 14.08) .

10-3 kg of P2O5 . s~ 1 By calculation on the basis of determined values of volume weights of the reaction mixture at the output from the reactor (305 to 563 kg.nn-3) it was found the average contact time of the reaction mixture decreases in relation to enhanced dosing of H3PO4 and NH3(g) from the value 245 to 273 second to 81 to 90 second. The degree of conversion of monophosphates to condensated phosphates varied from 61.1 to 67.5%.

In the two further experiments (1 67Q,B) function of filling reactor with parallel flow of reacting components in the case of employment thermal trihydrogen phosphoric acid was tested.

The results of the experiments confirmed the possibility of employment the filling reactor of described construction also for preparation of the melt KFA from thermal H3PO4. It was nevertheless shown that reaching the optimum function of the filling reactor at treatment of thermal acid would at given filling reactor require keeping relatively narrow limits of weight rates of dosing i H3PO4 and ammonia. At the treatment of thermal trihydrogen phosphoric acid reaction mixture does not form continuous foam as when extraction H3PO4 is employed, wherein this foam fills up the whole free space in the layer of filling and it is the cause of origin of space flow of reaction mixture.

In the case when thermal H3PO4 is dosed, this flows down along the filling surface in the form of film layer, reaction of the acid with gaseous ammonia taking place by a contact of reacting phases at phase boundary. Due to presented reasons it is therefore important to operate in the case of thermal acid at optimum wetting of the filling with liquid phase, to employ finer filling with larger surface and thus prevent from formation of the so-called chimney flow of gaseous ammonia in the layer of filling.Different character of the reaction mixture in the course of experiments with thermal acid probably negatively effected the size of interspace surface what manifested itself in suppressing the degree of conversion of monophosphates to condensated phosphates absolutely by 1 0 to 20% as compared to samples of melts prepared under comparable conditions from extraction acid. It can be supposed that also in the case of filling reactor of the tested type a mixture of additives suppressing surface tension of the reaction mixture and improving its foaming (for example some of derivatives of iignosulphonic acid and similar) would advantageously affect the degree of molecular dehydration of phosphates at treatment of thermal trihydrogen phosphoric acid.

In the course of experiments 168 (A,B) it was again operated with already specified extraction H3PO4 of the so-called black type. These experiments were directed to experimental testing the possibilities of employing filling reactor with vertical flow of reaction mixture for hightemperature neutralization of commercial extraction trihydrogen phosphoric acids containing 52 to 54% of P205 without its further concentrating with gaseous ammonia. Achieved results of the experiments confirrned fundamental suitability of the filling reactor of given construction for the examined process.

Average results of the experiments as well as summary of some determined and calculated parameters for tests with grafodur neutralizating-dehydrating filling reactors are presented in the Tables 2 and 3.

TABLE NO. 1 Lower layer Upper layer (placed at (supply of Location of paticles of filling in the body perforated reacting of neutralizing-dehydrating reactor bottom). Middle layer components).

The kind of filling grafodur grafodur ceramic rings rings Raschig rings The avrage dimensions of-external diameter 38.395 # 0.189 29.985 # 0.167 14.925 # 0.322 particles of filling -internal diameter 24.495 # 0.220 9.950 # 0.053 9.475 # 0.475 .10-3/m/ -height 29.930 # 1.93 9.820 # 0.596 14.045 # 1.153 The average weight of particle, Gpi(kg).10-3 36.546 # 1.93 9.955 # 0.459 3.623 The surface of a particle of filling determined from its average dimensions, Api(m) 7.283.10-3 2.362.10-3 1.346.10-3 The volume of a particle-determined by calvculation 20.539 5.540 1.550 of filling Vpi.10-6(m )-determined by measureme & t 20.0 6.25 1.40 (in a graduated cylinder) Specific weight. 103(kg.m-3) 1.763 1.914 2.374 Volume weight of non-organized filling.10(kg.m-3) 6.01 8.01 6.94 The number of particles in unit volume of non-organized filling 1.645.104 8.047.104 1.916.104 The specific interspace volume of the layer of non-organized filling -porisity,(%)-determined by measurement in a glass cylinder d = 0.1 m 69.9 57.5 70.8 -determined by calculation 66.3 54.3 70.7 average 68.1 55.9 70.75 TABLE NO. 2 Example number: 2 3 4 5 6 7 8 9 Experiment designation 161/A 161/B 162 163/A 163/B 163/C 164 165 Concentration of dosed 1 H3PO4/%P2O5/-photometry 54.91 54.91 54.91 54.91 54.91 54.91 54.91 54.91 2 - alkalimetry 56.27 56.27 56.27 56.27 56.27 56.27 56.27 56.27 3 Dosing of raw -H3PO4 tq 7.09 6.37 6.65 10.93 10.51 10.76 14.94 17.35 4 Materials -P2O5 3.89 3.50 3.65 6.00 25.77 5.91 8.20 9.53 5 10-3/kg.s-1 -NH3 1.06 1.79 1.25 4.17 2.33 2.59 2.78 4.02 6 Weight ratio NH3/P2O5 0.272 0.511 0.342 0.695 0.404 0.438 0.339 0.422 H3PO4 concentration at its flow into reactor 7 -photometry 62.24 61.97 63.26 61.25 61.79 61.42 - 8 -alkalimetry 64.40 62.63 64.65 63.34 64.23 63.75 - The average temperature C heatcarrying material evaporator 9 -inlet 210.5 210.5 210 210.5 209.7 211 211 211 10 -outlet 204 204 203.6 202.5 202.5 203.7 203 202.7 11 Acid(at reactor inlet) 110.8 120.5 115.6 126 131.7 130.5 133.3 135 12 Reactor (reaction mixture) 258.3 265 293.3 275 280 281 276.7 265.3 13 Pressure in reactor (determined from acid column height) (kPa) 104.8 106.7 102.0 101.6 - 103.1 104.0 104.8 14 Amonia pressure in the inlet piping (kPa) 106.4 109.7 102.3 113.5 109.4 108.7 110.2 117.2 15 Specification of the melt: nitrogen content (% N) 7.18 11.52 11.03 11.92 11.28 11.14 10.89 11.37 16 Total phosphorus content (% P2O5) 63.77 63.36 62.85 63.13 62.51 62.34 63.64 62.30 17 Phosphorus content in the form of monophosphates (% P2O5) 48.92 23.31 18.69 18.17 19.23 19.56 23.48 24.06 18 Weight ratio NH3/total P2O5 in the melt 0.137 0.221 0.213 0.229 0.219 0.217 0.208 0.221 19 Degree of conversion (%) 23.3 63.2 70.3 71.2 69.2 68.6 63.1 61.4 20 Duration of the experiment (min) 47 34 179 30 72 90 90 85 TABLE NO. 2-Cont'd: Example number: 10 11 12 13 14 15 16 17 Experimental designation 166/A 166/B 166/C 167/A 168/A 168/B Characteristics No. (see page 1 of the Table) 1 62.40 62.40 62.40 62.40 52.35 52.35 54.91 54.91 2 63.94 63.94 63.94 63.94 53.51 53.51 56.27 56.27 3 11.84 16.22 19.52 22.56 16.20 19.90 16.08 20.69 4 7.39 10.12 12.18 14.08 8.48 10.42 8.83 11.36 5 2.62 3.65 4.85 6.67 2.50 3.61 3.11 4.00 6 0.354 0.361 0.398 0.474 0.295 0.346 0.352 0.352 7 61.99 61.55 61.45 60.97 61.11 61.07 54.08 53.77 8 64.19 63.09 63.79 64.32 62.16 61.58 55.98 56.57 9 145.5 154 155.5 211 216.5 109.5 99.3 10 141.5 148.5 149 149.5 199.5 205.5 105.0 95 11 109.5 111.3 115.5 118 132.5 131.5 100.0 85.3 12 261.3 269 265 258 266 241.5 216.4 211.7 13 103.5 104.3 105.3 105.5 101.5 101.7 105.9 104.9 14 110.4 114.5 118.5 135.8 106.4 113.5 114.8 118.2 15 11.13 11.14 10.82 11.46 11.55 11.70 11.67 11.63 16 62.14 62.10 62.91 60.55 62.34 62.36 56.64 57.39 17 24.15 22.79 22.88 19.67 29.62 37.25 49.71 51.79 18 0.218 0.233 0.209 0.230 0.225 0.228 0.250 0.246 19 61.1 63.3 63.6 67.5 52.5 40.3 12.2 9.8 20 89 114 55 35 110 75 115 75 The total volume of reactor body VR (m3) : 10.91 . 10-3 Volume of filling Vv (m3) : 10.12 . 10 3 The average interspace volume in the layer of filling, layer porisity (%) : 67.9 Free volume in the layer of filling V = Vv (m ) : 6.87 . 10-3 Free volume of neutralizing-dehydrating reactor V2 (m ) : 7.66 . 10 -3

Experiment Weight rate of dosing raw Volume weight The average time o mRZ VRZ designa- materials m NH3 of reaction remaining reaction tion (mH3Po4+ mixture at mixture in reactor 10-5 10-3 (kg.s-1) m P2O5 the reactor (s) +MNH3). outlet (m .s-1) m H3PO4 m P2O5 m NH3 RZ T1 T2 10-3 (kg.s-1) (kg.m-3) 162 6.65 3.65 1.25 0.342 7.90 1652.0 0.478 1437 1682 163/A 10.93 6.00 4.17 0.695 15.10 1600.0 728 811 163/B 10.51 5.77 2.33 0.404 12.84 1271.0 1.010 680 696 163/C 10.76 5.91 2.59 0.438 13.95 1680.0 0.795 864 963 164 14.94 8.20 2.78 0.339 17.72 1166.0 1.520 452 504 165 17.35 9.53 4.02 0.422 11.37 458.0 4.666 147 164 166/A 11.84 7.39 2.62 0.354 14.46 515.0 2.808 245 273 166/B 16.22 10.12 3.65 0.361 19.87 563.0 3.529 195 217 166/C 19.52 12.18 4.85 0.398 24.37 305.0 7.990 86 96 166/D 22.56 14.08 6.67 0.474 29.23 345.0 8.472 81 90 167/A 16.20 8.48 2.50 0.295 18.70 1078.0 - - 168/A 16.08 8.83 3.11 0.353 19.19 350.0 5.360 128 143 168/B 20.69 11.36 4.00 0.352 24.69 415.0 5.949 1165 129 Notes T1 - the average time of remaining reaction mixture in neutralizing-dehydrating reactor in the case only the average interspace volume in the layer is concerned T2 - the average time of remaining reaction mixture in the reactor when we suppose foaned reaction mixture fills up bee ides the volume in the layer also the whole space above the layer

Claims (4)

1. A process for continuous preparation of a melt of condensed ammonium phosphates by the reaction of phosphoric acid containg 50 to 80% of P205 and having temperature 15 to 300"C or by the reaction of a solution of ammonium phosphates in phosphoric acid with gaseous ammonia which is dosed into the reaction medium in excess as related to the amount of ammonia bound in the melt in the form of ammonium phosphates, characterized in that neutralizing-dehydrating reaction between liquid phase containing phosphorus and gaseous ammonia takes place by the form of continuous contact of phases in a film layer which is formed in the reaction medium by gradual pouring out the liquid phase as an effect of force of gravity and also by its dispersion with gaseous phase formed by a mixture of gradually warmedup gaseous ammonia and gradually warmed-up steam, which layer pours out along the surface of the reaction medium having the surface of contact 7 . 10 to 1.8 . 103 m2 . m-3, preferably 4.5 . 10' to 9.8 . 102 m2 . m-3 and extra layer flow rate of gaseous phase (X) is 1 . 10-2 to 1. 10', preferably 2 . 10-' to 2 . 100 m.s. -', gaseous phase flowing in parallel-flow way with the flow of liquid phase.

2. Apparatus for continuous preparation of a melt of condensed ammonium phosphates according to the process of Claim 1, being composed of a stand-up through-flow film reactor, characterized in that the body of a film reactor (1) has at least one supporting bottom (2) whereon organized and/or non-organized filling (3) is placed, for the ratio of equivalent diameter of filling partices d, and of internal diameter of the film reactor body or length of its longest side D the following relations being held 5.10-3~de/D~4.5 . 10-1, for the specific interspace volume of the filling e the relation 28~~96 percent being held, preferably 60 < e < 80 percent and for the ratio of the total height of filling H of the internal diameter of the reactor body or the length of its longest side D the relation holds 1.1#H/D#14.8, the device having further a supply (4) of liquid phase containing phosphoric acid, which supply is led over the layer of fi(3), having a supply (5) of gaseous ammonia and/or distribution partitions (6), building-in (7) and/or static mixer (8), if need be.

3. A process for continous preparation of a melt of condensed ammonium phosphates substantially as described in any of the examples disclosed herein.

4. An apparatus for continuous preparation of a melt of condensed ammonium phosphates substantially as described herein with reference to the accompanying drawings.