GB2154571A

GB2154571A - Fertiliser from phosphonic acid and ammonia

Info

Publication number: GB2154571A
Application number: GB08403558A
Authority: GB
Inventors: Mikhail Vasilievich Lykov; Vladimir Mikhailovic Lembrikov; Svetlana Ivanovna Golovkina; Nadezhda Nikolaevna Malakhova; Vladimir Naumovich Sterlin; Viktor Nikolaevich Kochetkov; Gennady Mikhailovich Markovin
Original assignee: Individual
Current assignee: Individual
Priority date: 1984-02-10
Filing date: 1984-02-10
Publication date: 1985-09-11
Also published as: GB2154571B; GB8403558D0

Abstract

Liquid compound fertilisers are produced by a process which comprises neutralizing extraction phosphoric acid with an excess of gaseous ammonia which is used in an amount corresponding to 1 to 1.2 times its weight in the final product and at a temperature of from 60 to 250 DEG C, mixing the products of neutralization with a liquid phase consisting of a portion of the final product recycled to the process and water or ammonia water, the mixing being effected under a pressure of 0.05 to 0.7 atm and with an excess of water in the liquid phase of 1.05 to 2.0 parts by weight relative to its content in the final product, the process being carried out at a circulation ratio of the final product of 2 to 40 and at a pressure differential at the neutralization and mixing stages of from 0.1 to 6 atm.

Description

SPECIFICATION Production of liquid compound fertilisers The present invention is concerned with a process for producing liquid compound fertilisers (LCF) which contain N and P and which are widely used in agriculture.

It is an object of the invention to provide a process for the production of liquid compound fertilizers in which both high concentration (with respect to P205) and low concentration extraction phosphoric acids can be used as the starting material.

According to the present invention, there is provided a process for producing a liquid compound fertiliser, which comprises neutralizing extraction phosphoric acid with an excess of gaseous ammonia which is used in an amount corresponding to 1 to 1.2 times its weight in the final product and at a temperature of from 60 to 250"C, mixing the products of neutralization with a liquid phase consisting of a portion of the final product recycled to the process and water or ammonia water, the mixing being effected under a pressure of 0.05 to 0.7 atm and with an excess of water in the liquid phase of 1.05 to 2.0 parts by weight relative to its content in the final product, the process being carried out at a circulation ratio of the final product of 2 to 40 and at a pressure differential at the neutralization and mixing stages of from 0.1 to 6 atm.

High concentration extraction phosphoric acids may be characterised as acids having a concentration of 60 to 64% by weight, calculated as P205, and a content of polymeric forms of up to 10% of the total P205 content of the acid.

Low concentration extraction phosphoric acids may be characterised as acids having a concentration of less than 60% by weight, calculated as P205. Such acids are treated, before neutralization, with gaseous ammonia at a molar ratio of NH3: P205 of from 0.1 to 1.7 at a temperature of from 160 to 200do with the removal of water vapour.

A preferred manner of carrying out the process according to the invention will now be described, all parts and percentages being by weight unless otherwise stated.

Extraction phosphoric acid having a concentration of 56 to 72%, calculated as P205, and a content of polymeric forms of up to 40% is supplied at a temperature of 60 to 250"C together with gaseous ammonia at a temperature of 60 to 1 50"C into a jet-type reactor which is a component of the main apparatus and which is immersed in a liquid phase consisting of a portion of the final product and water or ammonia water.

Neutralization is carried out with an excess of gaseous ammonia equal to 1 to 1.2 parts relative to its content in the final product. The reactor is operated under a pressure which is 0.1 to 6 atm higher than that used for mixing the resulting products of the reaction of neutralization with the liquid phase. This causes a considerable intensification of the processes of dispersing and intermixing of the reagents. Increased concentration of ammonia in a jet reactor enables the neutralization depth of the extraction phosphoric acid to be increased so that a greater amount of heat is evolved which, in turn, contributes to the obtention of products with a higher content of polymeric forms than was present in the starting extraction phosphoric acid.

After leaving the jet reactor, the resulting neutralization products in the form of a melt of ammonium polyphosphate, water vapour and non-reacted ammonia are dissolved in the liquid phase. The liquid phase consists of water or ammonia water and a portion of the final product recycled into the process. The excess of water in the liquid phase is 1.05 to 2.0 parts with respect to its content in the final product. The process is carried out with a circulation ratio of the final product of from 2 to 40.

The temperature of interaction of the neutralization products with the liquid phase is adjusted by varying the residual pressure. The heat of neutralization is removed by evaporation of water under a reduced pressure (0.05 to 0.7 atm), this ensuring a stable temperature of the solution within the range of from 35 to 90"C depending on the pressure in the apparatus. The vapour-liquid dispersion formed is moved upwardly and separation of vapours and the solution takes place in a separator. Due to the difference in the specific gravities, intensive circulation of the solution within the apparatus circuit occurs.The formation of the gas phase and the occurrence of shock waves at a particular state of subdivision of the liquid product results in an increased interface surface which ensures active hydrodynamic conditions and, accordingly, very rapid heat- and mass-transfer processes. The ascending flow of a gas-liquid dispersion consisting of 2 to 40 parts of the liquid phase per part by weight of the neutralization products ensures a high circulation ratio in the apparatus during which post-neutralization proceeds under iso-concentration and isothermal conditions.

The condensation of the resulting liquor vapour occurs at high heat emission coefficient values which makes it possible to reduce the surface area of the heat-exchanger used and to increase the temperature drop of the coolant (water) with a corresponding reduction in its supply rate. The vapour condensate with the absorbed ammonia is recycled to the process (for dissolution of the fusion cake). Upon condensation of the vapour, the ammonia is fully absorbed so that the condenser simultaneously serves as an absorption apparatus.

When the acid concentration is less than 60%, calculated as P2O5, the acid contains a signficant amount of waterwhich upon evaporation increases the partial vapour pressure atthe neutralization stage, delaysthe dehydration process, and reduces the polymeric form content in the reaction product. In this case, it is necessary to pretreat the acid with ammonia at a molar ratio of NH:P205 of 0.1 to 1.7 and at a temperature of from 160 to 200 C with separation of water vapour. This enables substantial dehydration to be obtained at the main neutralization stage (with an excess of ammonia) with a degree of conversion in the final product of up to 50%.

Upon dissolution of the fusion cake with LCF and water, particularly for LCF grades with a high nitrogen content, ammonia is partly entrained with the water vapour formed. Upon condensation of the vapour, a weak ammonia water is formed. In this case it is advisable to use the condensate for dissolution of the fusion cake. With a substantial excess of ammonia, the condensation of the liquor vapour is preferably carried out at reflux temperature which enables the excess amount of ammonia to be recycled to the process.

The effectiveness of the selected process parameters within the above-specified ranges is illustrated in the following Tables.

TABLE 1 Amount of ammonia supplied to the phosphoric acid neutralization stage with respect to ammonia content ofthe final product No. Amount of ammonia, kglkg: 0.7 ro 1. 1 1.2 1.5 1 Concentration of EPAX) calc.

as P2O5, wt.% 64 64 64 64 64 2 Nitrogen content of LCF,wt.% 10 10 11 12 12 3 P205 content of LCF, wt.% 34 34 37 40 40 4 Conversion degree in LCD 50 60 60 62 62 5 Entrainment of ammonia, - - 0.1 0.5 2 X > EPA- extraction phosphoric acid As will be seen from Table 1, the most effective amount of ammonia for neutralization is equal to 1.0 - 1.2 parts by weight with respect to its content in the final product; smaller amounts of ammonia lead to a reduced degree of conversion and reduced ammonia contents in the final product, while larger amounts of ammonia do not increase its content of the product and result in an increased amount of entrained ammonia.

TABLE 2 Pressure in the stage of mixing of the reaction products and the liquid phase No. Pressure, atm 0.03 0. t2 0.3 0.5 0.6 1 Concentration of EPA calc. as P2O5, wt.% 64 64 64 64 64 2 Temperature of LCF, 0C 25 52 73.7 85.9 90.5 3 Degree of hydrolysis in the mixing stage,% 0.05 0.1 0.2 0.5 3.0 4 Surface area of heat exchangers, m2/t LCF 18.3 9.6 4.0 2.66 2.4 As will be seen from Table 2, the use of pressures in the range of from 0.12 to 0.5 atm is most preferred since if a lower pressure is used, the heat exchanger surface requirement is increased due to the increased amount of the resulting vapour condensate and the temperature difference between the cooling water and vapour is decreased, while if a higher pressure is used the degree of hydrolysis at the mixing stage is sharply increased with a corresponding reduction in the degree of converstion in the final product.

The process of the present invention gives LCF of the grades (N: P205) :10 :34,11 11:37, 12:40 with a polymeric form content of from 50 to 80% of the total amount of P2O. Quality control of the final product is based on the amount of ammonia supplied to neutralization; the pH of the final product is kept at 6-6.5.

The use of the process according to the present invention enables standard grades of LCF (N:P205) - 10:34, 11:37, 12:40 to be obtained from orthophosphoric acid having a concentration of less than 60%, calculated as P205, with a conversion degree of up to 50%.

The process of the present invention also enables LCF to be obtained with the total content of nutrient agents of up to 52% by weight, instead of 44% by weight, and this reduces the production cost as there is a reduced consumption of water, the capacity of the plant is increased and the power consumption is reduced; the increase in the nutrient content also makes the transportation, storage and use of the LCF more economic.

Furthermore, the process flow sheet is considerably simplified due to the preparation of the product in one apparatus, the use of mechanical stirring means, powerful pumping devices and an absorption system is obviated and the surface area of heat exchange apparatus can be reduced by a factor of 3 to 4. The reliability of operation of the equipment is also increased.

In order that the invention may be more fully understood, the following examples, in which all parts and percentages are by weight unless otherwise stated, are given by way of illustration: Example 1 1000 kg of extraction phosphoric acid containing P205 - 64.0%; S03 - 3.5%; CaO - 0.3%; sesquioxides 2.0%; F - 0.2%, polymeric forms - 4% of the overall P205 at the temperature of 80"C, were neutralized with 229 kg of gaseous ammonia at the temperature of 100 C (amount of ammonia with respect to its content in the final product was equal to 1.0). The fusion cake was formed at the temperatu re of 320"C under the pressure of 0.32 atm.

The neutralization products were reacted wth a liquid phase consisting of 20000 kg of the final product and 1155 kg of water (the excess of water with respect to its content in the final product was 1.45 part) under the residual pressure of 0.12 atm. The evaporation of 502 kg of water was carried out at a constant temperature of 52"C, which corresponded to the residual pressure in the apparatus. The resulting vapour liquid dispersion was separated, in a separator, into 1882 kg of final product which was discharged, a liquid phase of the same composition and temperature as the final product for recycling, and water vapour containing a trace of ammonia. The condensed water vapour, at a temperature below the boiling point, was recycled to the process.

The final product contained: nitrogen - 9.5-10.5%; P2O5- 33.5-34.5% including as polymeric forms - 60% of the total P205 content.

Example 2 1000 kg of extraction phosphoric acid containing P205 - 64.0%; S03 - 3.5%; CaO - 0.3%; sesquioxides 3.0%; F - 0.2%; polymeric forms - 4% of the overall P205, at the temperature of 80"C, were neutralized with 229 kg of gaseous ammonia at a temperature of 100 C (the amount of ammonia with respect to the content thereof in the final product was equal to 1.0).

The neutralization products were reacted with a liquid phase consisting of 72000 kg of the final product and 1,069 kg of water (the excess of water with respect to the content thereof in the final product was equal to 1.34 part), under a residual pressure of 0.5 atm. 416 kg of water was evaporated at a constant temperature of 86"C which corresponded to the residual pressure in the apparatus.

The resulting vapour-liquid dispersion was separated, in a separator, into 1882 kg of final product which was discharged from the apparatus, a liquid phase of the same composition and temperature as the final product which was recycled, and water vapour containing a trace of ammonia. The latter was condensed and recycled, at a temperature below the boiling point, to the process.

The final product contained: nitrogen - 9.5-10.5%, P205 - 33.5-34.5%, including polymeric forms amounting to 58% of the total P205 content.

Example3 1000 kg of extraction phosphoric acid containing: P205 - 64.0%; S03 - 3.5%; CaO - 0.3%; sesquioxides 2.0%; F - 0.2%; polymeric forms - 4% of the overall P205, at a temperature of 80"C, were neutralized with 232 kg of gaseous ammonia at a temperature of 100"C (the amount of ammonia with respect to the content thereof in the final product was 1.0).

The neutralization products were reacted with a liquid phase consisting of 9000 kg of the final product and 903 kg of water (the excess of water with respect to the content thereof in the final product was 1.4 part) under a residual pressure of 0.3 atm. 400 kg of water was evapourated at a constant temperature of 75"C which corresponded to the residual pressure in the apparatus. The resulting vapour-liquid dispersion was separated, in a separator, into 1735 kg of final product which was discharged, a liquid phase having the same composition and temperature as the final product which was recycled, and water vapour containing a trace of ammonia. This was condensed and recycled to the process at a temperature below the boiling point.

The final product contained: nitrogen - 10.5-11.5%, P205 - 36.5-37.5% including polymmeric forms amounting to 64% of the total P205 content.

Example 4 1000 kg of extraction orthophosphoric acid containing: P2O5 - 58%; 503 - 3.1%; CaO - 0.27%; sesquioxides - 1.8%; F - 0.185, at a temperature of 140 C, was treated with 52 kg of gaseous ammonia at a temperature of 140"C (molar ratio of NH3:P205 = 0.75) and 1.35 kg of water vapour was separated.

813 kg of the fusion cake obtained, at a temperature of 180"C, was neutralized with 207 kg of gaseous ammonia (the excess of ammonia with respect to its content in the final product was 1.20). The neutralization products (ammonium polyphosphates, unreacted ammonia and water vapour) were reacted with a liquid phase consisting of 34000 kg of final product and 952 kg of water (the excess of water with respect to the content thereof in the final product was 1.4 parts) under a residual pressure of 0.2 atm.318 of or water was evaporated at a constant temperature of 65"C which corresponded to the residual pressure in the apparatus.

The vapour-gas mixture obtained was separated into 1706 kg of the final product which was withdrawn, a liquid phase having the same composition and temperature as the final product which was recycled and 318 kg of a liquor vapour and 52 kg of ammonia. The liquor vapour was condensed in a heat-exchanger and the condensate was recycled to the process, while the gaseous ammonia was pressurized and used for the treatment of extracton phosphoric acid and other kinds of fertilizers.

The final product contained: nitrogen - 9.5-10.5%; P205 - 33.5-34.5% including polymeric forms amounting to 50% of the total P205 content.

Example 5 1000 kg of extraction phosphoric acid containing:P205 - 68.0%; SO3 - 2.82%; Fe2O3 - 0.84%; F - 0.1%; sesquioxides - 2.47%; polymeric forms - 30% of the overall P205, at a temperature of 1 OO"C, was neutralized with 243 kg of gaseous ammonia at a temperature of 100 C (the content of ammonia with respect to that in the final product was 1.0). The neutralization products were reacted with a liquid phase consisting of 20000 kg of final product and 1274 kg of water (the excess of water with respect to the content thereof in the final product was 1.61 parts) under a residual pressure of 0.2 atm. 517 kg of water was evaporated at a temperature of 65"C which corresponded to the residual pressure in the apparatus.

The resulting vapour-liquid mixture was separated into 2000 kg of the final product which was withdrawn, a liquid phase having the same composition and temperature as the final product which was recycled, and water vapour containing a trace of ammonia. The latter was condensed and recycled to the process at a temperature below the boiling point.

The final product contained: nitrogen - 9.5-10.5%, P205-33.5-34.5% including polymeric forms amounting to 70-75% of the total P205 content.

Example 6 1000 kg of extraction phosphoric acid containing: P205 - 64.0%; S03 - 3.5%; CaO - 0.3%; sesquioxides 2.47%; F - 0.2%; polymeric forms - 4% of the overall P2O5, at a temperature of 80 C, were neutralized with 233 kg of gaseous ammonia at a temperature of 80"C. The neutralization products were reacted with a liquid phase consisting of 48000 kg of the final product and 846 kg of water (the excess of water with respect to the content thereof in the final product was 1.66 parts) under a residual pressure of 0.2 atm. 479 kg of water was evaporated at a constant temperature of 67"C which corresponded to the residual pressure.

The resulting vapour-liquid mixture was separated, in a separator, into 1600 kg of the final product which was withdrawn, a liquid phase having the same composition and temperature as the final product which was recycled, and water vapour containing a trace of ammonia. The latter was condensed and recycled to the process at a temperature below the boiling point.

The final product contained: nitrogen - 12%, P205 - 40%, including polymeric forms amounting to 58% of the total P205 content.

Example 7 1000 kg of extraction phosphoric acid containing P205 - 72.0%; S03 - 2.82%; Fe2O3 - 0.84%; sesquioxides 2.47%; F - 0.1% polymeric forms - 40% of the overall P2O5, at a temperature of 1 200C, were neutralized with 265 kg of gaseous ammonia at a temperature of 120 C. The neutralization products were reacted with a liquid phase consisting of 43600 kg of the final product and 1547 kg of water (the excess of water with respect to the content thereof in the final product was 1.61) under a residual pressure of 0.05 atm. 662 kg of water was evaporated at a constant temperature of 35which corresponded to the residual pressure in the apparatus.

The resulting liquid-vapour mixture was separated, in a separator, into 2180 kg of the final product which was withdrawn, a liquid phase having the same composition and temperature as the final product which was recycled, and water vapour containing a trace of ammonia. The latter was condensed and the condensate, at a temperature below the boiling point, was recycled to the process.

The final product contained: nitrogen - 9.5-10.5%, P205 - 33.5-34.5% including polymeric forms amounting to 75-85% of the total P205 content.

Example 8 1000 kg of extraction phosphoric acid containing: P205 - 60.0 /O; SO3 - 3.5%; CaO - 0.3%; sesquioxides - 2%, F - 0.2%, at a temperature of 1 20"C, were neutralized with 235 kg of gaseous ammonia at a temperature of 1200C (the amount of ammonia with respect to that in the final product was equal to 1.1).

The neutralization products were reacted with a liquid phase consisting of 25000 kg of the final product and 872 kg of water (the excess of water with respect to the content thereof in the final product was 1.24 part by weight) under a residual pressure of 0.7 atm. 321 kg of water was evaporated at a constant temperature of 94"C which corresponded to the residual pressure in the apparatus. The resulting vapour-liquid mixture was separated, in a separator, into 1765 kg of the final product which was discharged, a liquid phase having the same composition and temperature as the final product which was recycled, and water vapour containing a trace of ammonia. The latter was condensed and the condensate, at a temperature below the boiling point, was recycled to the process.

The final product contained: nitrogen - 9.5-10.5%, P205 - 33.5-34.5%, including polymeric forms amounting to 50% of the total P205 content.

Claims

1. A process for producing a liquid compound fertilizer, which comprises neutralizing extraction phosphoric acid with an excess of gaseous ammonia which is used in an amount corresponding to 1 to 1.2 times its weight in the final product and at a temperature of from 60 to 250 C, mixing the products of neutralization with a liquid phase consisting of a portion of the final product recycled to the process and water or ammonia water, the mixing being effected under a pressure of 0.05 to 0.7 atm and with an excess of water in the liquid phase of 1.05 to 2.0 parts by weight relative to its content in the final product, the process being carried out at a circulation ratio of the final product of 2 to 40 and at a pressure differential at the neutralization and mixing stages of from 0.1 to 6 atm.

2. A process according to claim 1, in which the extraction phosphoric acid used as starting material has a concentration of 60 to 64%, calculated as P205, and a content of polymeric forms of up to 10% of the total content of P205 in the acid.

3. A process according to claim 1, in which the extraction phosphoric acid used as starting material has a concentration of less than 60%, by weight, calculated as P205, and the acid is treated, prior to neutralization with gaseous ammonia at a molar ratio of NH3: P205 of 0.1 to 1.7 at a temperature of from 160 to 200"C and water vapour is removed.

4. A process for producing a liquid compound fertilizer substantially as herein described in any of the Examples.

5. Liquid compound fertilizers when produced by the process claimed in any of the preceding claims.