Method for preparing monoammonium phosphate

FIELD: fertilizers, chemical technology.

SUBSTANCE: invention relates to a method for preparing monoammonium phosphate used broadly as a mineral fertilizer. Method involves decomposition of phosphate with a mixture of phosphoric and sulfuric acid, separation of reaction mass with isolation of the production acid, its purifying from impurities, concentrating, ammoniation to obtain phosphate pulp and the following procedures of granulation and drying. The separated production acid is concentrated and then subjected for purification from impurities and ammoniated maintaining the content of P2O5 in the concentrated acid at these stages in the range 52-56%, the content of SO3 at the range 1.5-3.2%, the residual content of solid impurities in the cleared concentrated acid 0.2-0.6% by mass, and the mole ratio NH3 : H3PO4 in the range 1.01-1.16. Regulation of the yield for required sort of monoammonium phosphate by the content of main nutrient substances and the ratio is carried out by change of the SO3 content in dilute phosphoric acid and by change of the mole ratio NH3 : H3PO4 in the ammoniation process. Invention provides enhancing content of total sum of nutrient substances in the fertilizer and enhancing strength index of granules and their homogeneity.

EFFECT: improved preparing method.

2 cl, 4 ex

 

The invention relates to a method of producing monoammonium phosphate, widely used as a mineral fertilizer based on the decomposition of phosphate rock with a mixture of phosphoric and sulphuric acids to produce phosphoric acid and its further processing to monoammonium phosphate.

Known methods for producing monoammonium phosphate from phosphate rock by the decay of his obtaining phosphoric acid, neutralizing it with ammonia in one or two stages to molar relationships NH3:H3PO4equal to 1.03-1,2, granulation and drying of the finished product (the Technology of phosphate and compound fertilizers./ Edited Sudionika and Ads. M.: Chemistry, 1987, s-194. Phosphate fertilizers in Russia. M: Margus, 1995, s-231, Brodsky A., Grinevich V. A., Grinevich V. current state of production of monoammonium phosphate from Apatite EPA and its optimization. The chemical industry today, No. 8, 2003, p.29-35). According to methods for the production of monoammonium phosphate is used as one stripped off phosphoric acid, and a mixture of one stripped off and neoprenes phosphoric acids, as well as neuverenna phosphoric acid. From Apatite EPA depending on the method of production of weak EPA (digitally or polyhedrally) and a stage of concentration is the following range of monoammonium phosphate with the apprehension of nutrients from 11:52 to 13:52 (nitrogen content,%: the phosphorus content in terms of P 2O5,%). The principal standard brand of phosphate is mark 12:52. The manufacturing process can be done without additional purification of phosphoric acid from impurities. To obtain a product with a content of P2O552% use enter in the technological process of production of ammophos sulfuric acid, which is a method of regulating the content of P2O5in the product. Input standard sulphuric acid in some cases, achieved 100 kg MNG/t R2O5.

The disadvantage of these methods is to obtain products with the total content of major nutrients (P2O5and (N) not more than 62-64% R2O5on the basis of Apatite concentrate - one of the cleanest types of industrial phosphate rock in the world.

The closest to describing the technical essence and the achieved result is known a method of producing ammonium phosphates, in particular of mono-ammonium phosphate, including the decomposition of the phosphate mixture of phosphoric and sulfuric acids, separation of the reaction mass with selection of acid production, purification from impurities, concentration, ammonization obtaining phosphate slurry and subsequent granulation and drying of the product (RF Patent No. 2230026, 01 25/28, 05, 7/00, 2003).

In this way the decomposition of the Khibiny Apatite concentration the and carry out a mixture of sulfuric (93% H 2SO4and phosphoric acids.

The resulting reaction mass is divided emitting production of phosphoric acid containing 28.5-37% P2O5and 0.5-2% solids. The content of P2O5in a weak phosphoric acid depends on the mode of its reception (digitally or polyhedrally), weak phosphoric acid cleaned (lighten). In the result, get productive, the clarified phosphoric acid with a content of 0.2-0.5% by weight of solids and condensed slurry containing 20% solids. The thickened portion completely return to the stage of decomposition.

Perhaps after cleaning the weak phosphoric acid to concentrate and continue to ammoniate to molar relationships NH3:H3PO4=1,05-1,10 (in case of receipt of monoammonium phosphate).

The disadvantage of this method is that the resulting phosphate by this method has a relatively low strength pellets (not more than 6 MPa) and the homogeneity of the content of fractions 3-4 mm does not exceed 50%due to the following reasons:

- a relatively small distance ballasting impurities (calcium sulphate and other) from the weak phosphoric acid (27-59 kg/t R2About5) because of their considerable solubility at concentrations of 28-37%;

- the processes of vysalivaniya impurities from the clarified phosphoric acid is ri its concentration, the precipitation of these impurities in the capacitive equipment and, as a consequence, fluctuations in the composition of phosphoric acid input in the production of fertilizers, which destabilizes the quality of the phosphate chemical composition;

- the presence of deposited when the concentration of the impurities of water-insoluble compounds of fluorine, sodium and potassium, have a negative impact on the process of granulation and physico-chemical properties of the final product.

We set ourselves the task of getting monoammonium phosphate with a maximum content of total nutrients while improving the quality of the finished product on the chemical and granulometric composition, its physical and chemical properties.

The problem is solved in the proposed method of producing monoammonium phosphate, including the decomposition of Apatite with a mixture of phosphoric and sulfuric acids, separation of the reaction mass with selection of acid production, purification from impurities, concentration, ammonization obtaining phosphate slurry and subsequent granulation and drying of the product. According to this method, first the separated acid production concentrated, and then purified from impurities and ammonition, while varying at these stages, the content of P2O5in the concentrated acid within 52-56%, the content of SO3- 1,5-3,2%, the residual is the content of solids in the clarified concentrated acid - 0.2 to 0.6% by weight, and the molar ratio of NH3:H3PO4within 1,01-1,16.

Control access to the required grade monoammonium phosphate content of essential nutrients and their value is realized by changing the content of SO3in a weak phosphoric acid and the change in the value of the molar relationship NH3:H3PO4when ammonization.

Depending on the process conditions and available equipment the cleaning process one stripped off of phosphoric acid from suspended impurities conduct: clarification of radial sumps, thin clarifiers type "Lamella" or thin cylindrical tanks with rotating conical plates; filtering using belt vacuum filters; jointing using sedimentation and other types of centrifuges.

The most effective removal of suspended impurities from one stripped off of phosphoric acid derived from Apatite concentrate as digitatum and palpitatin method to a residual content of 0.2-0.6%, is the use of thin-layer tanks. When used as a method to clean the sediment settling condensed part of the acid to return to the stage of decomposition of Apatite directly into the extractor or put a filter on vacuum filters. With the aim of minimizing losses of P About5when using a filtration process, the thickened part of the acid processing of precipitation after vacuum filters extraction is carried out in a reactor system in the production of EPA weak.

Most tech is cleaning palpitates EPA as a result of higher settling velocities and specific releases in the division on vacuum filters.

The method consists in the following. The concentration of weak phosphoric acid leads to the content of P2O5it 52-56%. When the concentration of the impurities dissolved in the weak phosphoric acid (calcium sulfate, cremetoria sodium and potassium, and others), precipitates (process vysalivaniya caused by the change of solubility of salts). Stage removal of sediment from one stripped off EPA can significantly reduce (up to 80-100 kg/t R2O5hit it in production phosphate ballasting impurities. Therefore, the nutrient content in the phosphate increases. The process of cleaning one stripped off of phosphoric acid from the solids is carried out at scheduled the suspended solids in the purified acid at the level of 0.2-0.6% by mass.

The process of ammonization of phosphoric acid with more concentrated brands nonammoniated is carried out without the introduction of additional quantities is and sulfuric acid in the production of fertilizers. Management desired brand of mono-ammonium phosphate sulfate is produced by changing the mode in the production of a weak acid. Sulfate mode in the production of weak phosphoric acid is adjusted according to the content SO3in phosphoric acid after the stage of concentration. The content of SO3in one stripped off phosphoric acid varies from 1.5 to 3.2%.

Possible changes in the content of sulfate mode are determined by the type of production process weak phosphoric acid. Possible brand product by the sum of the nutrient content at the fixed content of the sediment and the concentration of EPA determined the content of SO3in one stripped off of phosphoric acid and a molar ratio of NH3:H3PO4when ammonization.

Introduction to the technological process of production of ammophos stage of removal of sediment from one stripped off of phosphoric acid substantially stabilizes the quality of EPA before ammonization (given the high dispersion of the solid phase after the cleanup phase to suspended matter content of EPA less than 0.6% almost unlikely their deposition of sediment in capacitive equipment)that will stabilize the quality of the finished product on the chemical composition and to create a real possibility of excluding input corrective additives in the production of fertilizers and to improve the process the grain is investing and physico-mechanical properties of the product due to a sharp decrease of water-insoluble compounds of fluorine, potassium and sodium.

In the proposed method, the achieved effect can be achieved only by varying and maintaining strictly stated within all of the above process parameters.

For example, when the reduction in the content of P2About5in one stripped off the acid less than 52% loss of these compounds decreases, which leads to an increase blascovich impurities in the acid stage after the removal of sediment. Concentrated acid above 56% leads to an increase in the viscosity of the acid, which is difficult to transport acid and reduction of the deposition rate of suspended impurities.

The reduction in the content of solids in the final one stripped off the acid is less than 0.2% is associated with a significant decrease in performance. The increase in suspended matter content higher than 0,6% leads to spontaneous sedimentation of suspended impurities in capacitive devices, which will lead to the destabilization of the quality of the phosphate chemical composition.

The reduction in the content of SO3below 1.5% in one stripped off of phosphoric acid leads to the deterioration of the process of crystallization of calcium sulfate in the production of weak EPA, which dramatically reduces the performance of the filter equipment. The increase in the content of SO3in one stripped off EPA above 3.2 per cent leads to blocking of the particles of phosphate in which otlozhenii phosphate in the production of weak phosphoric acid. The one and the other affects the decomposition of phosphate rock and leads to additional losses of P3O5and , consequently, more expensive products.

The decrease in molar relationships NH3:H2PO4below 1,01 leads to the possibility of neonatally free phosphoric acid and, consequently, a deterioration of physical and mechanical properties of the finished product, increase above values of 1.16 to increased excretion of ammonia from the stage of neutralization, due to the need for reconstruction system cleaning exhaust gases.

Using the proposed method of producing monoammonium phosphate at stated intervals in the aggregate allows comparison with the prototype to increase the total content of nutrients to 68-70%, to increase the strength of the granules to 7-9 MPa and their homogeneity (the content of fractions 2-5 mm to 98 and fractions 3-4 mm to 75%level). The method creates a real possibility of exceptions input corrective additives in the production of fertilizers.

The method is illustrated by the following examples:

Example 1. The decomposition of the Khibiny Apatite concentrate (39% R2O5the contents of fractions +0.16 - 13%) is a mixture of sulfuric (93% H2SO4and phosphoric acids in the mode palpitating process of obtaining production of phosphoric acid containing 37,2% P2O5and 1.2% of the solid is x substances. Weak phosphoric acid is subjected to concentration to 56% R2O5. The content of H2SO4in terms of SO3in one stripped off EPA is 1.5% and is supported by changes sulfate mode when the production of weak phosphoric acid. One stripped off phosphoric acid cleaned from solids to a residual content of 0.2% with the use of centrifuges. Purified from suspensions one stripped off phosphoric acid is subjected to single-stage ammonization in a tubular reactor to a molar relationships NH3:H3PO4=1,14. The resulting slurry simultaneously granularit and dried in the apparatus BGS. Commodity phosphate contains N - 13,1%, P2O5- 57,2% at a moisture content of 1.2%. Granule strength 8 MPa. The contents of fractions 3-4 mm - 74%.

Example 2. The decomposition of the Khibiny Apatite concentrate (39% P2O5the contents of fractions +0.16 - 13%) is a mixture of sulfuric (93% H2SO4and phosphoric acids in the mode digitalneho process of obtaining production of phosphoric acid containing 28.5% R2O5and 2% solids. Weak phosphoric acid is subjected to concentration to 52% P2O5. The content of H2SO4in terms of SO3in one stripped off EPA is 3.2% and is supported by changes sulfate mode when the production of weak phosphoric acid. One stripped off fo fornow acid lighten to a residual content of suspended solids 0.5% in the lamella settlers. The thickened portion containing 10-30% of suspended solids, is fed into the extractor and processed in the weak production of EPA. Clarified one stripped off phosphoric acid is subjected to two-stage ammonization (1-d stage in a tubular reactor, the 2nd step in ammoniator-granulator (AH)) to the molar relationships NH3:H2PO4=1,01, granulation in the office of the AG and drying in a tumble dryer to a residual moisture content of 1.2%. Commodity phosphate contains N - 12,0%, P2O5- 56,0%. The strength of granules of 8.5 MPa. The contents of fractions 2-5 mm - 98%.

Example 3. The process of obtaining EPA conduct in palpitation mode (see example 1). Weak phosphoric acid is subjected to concentration to 54% P2O5. The content of H2SO4in terms of SO3in one stripped off EPA is 2.0% and is supported by changes sulfate mode when the production of weak phosphoric acid. One stripped off phosphoric acid cleaned from solids to a residual content of 0.5% with the use of vacuum filters. Precipitation after vacuum filter process in the production of weak EPA (extractor). Purified from suspensions one stripped off phosphoric acid is subjected to single-stage ammonization in a tubular reactor to a molar relationships NH3:H2PO4=1,16. The resulting slurry simultaneously granularit and dried in the apparatus BGS. Trademarks the phosphate contains N - 13,2%, P2O5- 56,2% at a moisture content of 1.5%. Granule strength 90 MPa. The contents of fractions of 3-4 mm is 75%.

Example 4. The process of obtaining EPA conduct in palpitation mode (see example 1). The content of H2SO4in terms of SO3in one stripped off EPA (53% P2O5) is 2.0% and is supported by changes sulfate mode when the production of weak phosphoric acid. One stripped off phosphoric acid lighten to a residual content of 0.6% in the radial sumps. The thickened portion containing 10-30% of suspended solids, is fed into the extractor and processed in the weak production of EPA. Clarified one stripped off phosphoric acid is subjected to two-stage ammonization (see example 2) to the molar relationships NH3:H2PO4=1,03, granulation in the office of the AG and drying in a tumble dryer to a residual moisture content of 1.2%. Commodity phosphate contains N - 12,0%, P2O5- 57,1% at a moisture content of 1.5%. The granule strength of 85 MPa. The contents of fractions of 3-4 mm is 73%.

1. The method of producing monoammonium phosphate, including the decomposition of Apatite with a mixture of phosphoric and sulfuric acids, separation of the reaction mass with selection of acid production, purification from impurities, concentration, ammonization obtaining phosphate slurry and subsequent granulation and drying of the product, characterized in that sleep is Ala separated production acid concentrate, and then subjected to purification from impurities and ammonition, with support at these stages, the content of P2O5in the concentrated acid within 52-56%, the content of SO3- 1,5-3,2%, the residual content of solids in the clarified concentrated acid of 0.2-0.6% by weight, and the molar ratio of NH3: H3PO4within 1,01-1,16.

2. The method according to claim 1 characterized in that the control output to the desired grade monoammonium phosphate content of essential nutrients and their ratios carried out by changing the content of SO3in a weak phosphoric acid and the change in the value of the molar relationship NH3: H3PO4when ammonization.



 

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SUBSTANCE: invention relates to production of ammonium phosphates, notably ammophos, widely used as mineral fertilizers. Process involves neutralization of phosphoric acid with ammonia at elevated pressure, stirring of resulting mixture in static mixer, and subsequent granulation and drying of product. According to invention, neutralization is carried out in two steps: in the first step, 80-85% H3PO4 of its total amount is added and process is carried out at gauge pressure 3.5-8 atm and, in the second step, the rest of acid is added and pressure is lowered to pressure 1.5-3.0 atm. Stirring is effected simultaneously with ultrasonic treatment of the mixture with pulse power from 100 to 1000 W and, before granulation, pressure is lowered by 0.5-0.8 atm relative to pressure of the second neutralization step. Ultrasonic treatment can likewise be employed in the first neutralization step.

EFFECT: improved process control to form uniform improved-quality product and reduced ammonia emission.

2 cl, 3 ex

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SUBSTANCE: method of manufacturing complex granulated mineral fertilizer consists in mixing ammonium nitrate and monoammonium phosphate-containing phosphate additive. The latter is granulated mineral double fertilizer simultaneously containing ammonium nitrate, monoammonium phosphate, and calcium phosphates at total content of digestible phosphorus 13÷21% (calculated as P2O5). Additive is introduced by way of melting it followed by admixing resulting melt to molten ammonium nitrate. Phosphate additive utilizes nitroammophosphate at weight ratio N:P2O5 equal to 23:21 or 26:13 and phosphate additive melt is preliminarily completely or partly separated from infusible solid phase, after which phosphate additive is introduced in amount 2-6% (as P2O5) of the weight of final product. Granulated mineral fertilizer contains ammonium nitrate and monoammonium phosphate with total content of digestible P2O5 within a range of 2÷6%, in which case 0.4÷28.6% of P2O5 is present in the form of dicalcium phosphate.

EFFECT: reduced corrosiveness of process medium, increased nutritive value of fertilizer having physicochemical properties competitive with those of known fertilizers, and simplified manufacturing technology.

5 cl, 1 tbl, 5 ex

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FIELD: industrial inorganic synthesis.

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EFFECT: improved process control to form uniform improved-quality product and reduced ammonia emission.

2 cl, 3 ex

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