RU2752381C1 - Method for synthesising ammonium sulphate from ammonia and concentrated sulphuric acid - Google Patents

Abstract

FIELD: chemical industry.

SUBSTANCE: invention relates to chemical industry, namely to a method for synthesising ammonium sulphate by a dry method. The method includes feeding sprayed sulphuric acid and gaseous ammonia into a reactor in a stoichiometric ratio, as well as ammonia water as a sprayed cooler. The method is characterised by the fact that sulphuric acid at a concentration of 91 to 92 wt.%, gaseous ammonia and ammonia water are sprayed with a nozzle from top to bottom, wherein the formed particles of ammonium sulphate fall into a fluidised bed liquefied by a circulating flow of a vapour-ammonia mixture, in the upper part whereof the temperature is maintained at 140 to 160°C.

EFFECT: proposed method allows to produce a dry normal salt of ammonium sulphate and to minimise use of expensive corrosion-resistant materials.

2 cl, 1 dwg, 3 ex

Description

The present invention relates to the chemical industry, in particular, to the production of mineral fertilizers, in particular to the production of ammonium sulfate by a dry method, i.e. without obtaining salt solutions.

Known dry method for producing ammonium salts (patent US 1971563 C1, W. Hirschkind, N. Bender, published on 28.08.1934), according to which they are obtained from ammonia and the corresponding acid. In this case, the acid is sprayed in an atmosphere of ammonia supplied to the reactor and circulating in the loop from the reactor and apparatus for cleaning off-gases from water vapor and product dust. Salt crystals settling on the bottom of the reactor are removed from the apparatus by an unloading device. As a way to maintain the required temperature of the process, it is proposed to use an acid solution of the required concentration (temperature reduction due to complete evaporation of water) and heating / cooling of the reagents. The main disadvantage of the proposed method in the production of ammonium sulfate (a process with a high heat of neutralization reaction) is the need to use dilute sulfuric acid (68-71% of the mass), and, therefore, expensive corrosion-resistant materials, which leads to a significant increase in the cost of industrial production.

There is a known method for producing ammonium sulfate (US patent 2524341 C1, H. D. Chapman, W. I. Denton, R. B. Bishop, published 03.10.1950), in which it is proposed to use concentrated sulfuric acid (80-100 wt.%). In the reactor, into the lower part of which gaseous ammonia is injected, concentrated sulfuric acid is sprayed upwards. A coolant, in particular water, is sprayed towards the acid torch from top to bottom. This scheme eliminates the need for particularly corrosion resistant materials, but does not provide a dry medium ammonium sulfate salt. A mixture of ammonium sulfate and hydrogen sulfate is obtained.

The closest in technical essence and the achieved result when using is the scheme of the process for obtaining ammonium sulfate by the dry method, described in the book of I.D. Fotyinich "Production of nitrogen fertilizers" (Moscow, State Scientific and Technical Institute of Chemical Literature, 1956, pp. 149-153). According to this scheme, sulfuric acid is sprayed into the reactor from above towards the ammonia flow fed from below. Ammonium sulphate particles falling to the bottom are removed by a discharge device. The disadvantage of this process is the use of dilute acid, as well as the short residence time of partially ammoniated particles in the ammonia stream, which does not guarantee the absence of a significant content of ammonium hydrogen sulfate in the resulting product.

The technical result of the proposed invention is the guaranteed production of dry average salt of ammonium sulfate while minimizing the use of expensive highly corrosion-resistant materials.

The technical result in the proposed dry method for producing ammonium sulfate is achieved due to the fact (see drawing) that the primary product (1), obtained by neutralizing concentrated sulfuric acid (2) with gaseous ammonia (3), undergoes preammonization in a fluidized bed (4), liquefied the reverse flow of the vapor-ammonia mixture (5). In this case, the primary product is formed by spraying concentrated sulfuric acid, gaseous ammonia and ammonia water (8) into the vertical reactor (6) from top to bottom by the nozzle / nozzles (7). The consumption of sulfuric acid and ammonia is maintained in a stoichiometric ratio (2 mol of ammonia per mol of sulfuric acid), and the consumption of ammonia water is maintained at a level that provides the required thermal regime.

The ammonium sulfate powder is discharged through the chute (9), which is a vertical branch pipe above the fluidized bed grate (10) and covered from above by a raised protective cap (11). The height of this branch pipe determines the height of the fluidized bed and, accordingly, the residence time of the particles in the fluidized bed - the zone of preammonization of the product. The flow rate of ammonia water through the nozzle provides the required temperature in the upper part of the fluidized bed at a level of 140-160 ° C, which is lower than the decomposition temperature of ammonium sulfate, but sufficient to obtain a product with a moisture content of no more than 0.1% by weight.

The vapor-gas mixture leaving the upper part of the reactor (12) contains ammonia, water vapor, and fine ammonium sulfate dust entrained by the ascending flow of the ammonia-vapor mixture. The ammonia-vapor mixture is sent to the heat exchanger-cooler (13), in which the water vapor is partially condensed, which ensures the removal of excess water from the cycle, which comes with sulfuric acid. Part of the ammonia and the dust of ammonium sulfate dissolve in the condensate of water vapor to form a weak solution of ammonium sulfate in ammonia water. This solution enters the collector of ammonia water (14), from where it is pumped (15) to the nozzle, and purified, cooled and partially dried ammonia is supplied by a gas blower (16) to liquefy the fluidized bed in the reactor and create a pre-ammonization zone.

An additional feature of the proposed nozzle is that it mixes and interacts with sulfuric acid and ammonia water. As a result of this interaction, a steam-gas mixture (PGM) is formed with a temperature of 115-120 ° C, containing 8-10% of the mass. water vapor and a solution of ammonium hydrogen sulfate in dilute sulfuric acid. This SGM with a liquid phase partially dispersed by steam is supplied to the spray through a central nozzle. In this case, this internal mixing-flow part of the nozzle must be made of highly corrosion-resistant materials. The main atomization of the liquid phase is produced by gaseous ammonia supplied through a coaxial annular nozzle.

A simplified technological scheme of a pilot plant (OPU), on which work was carried out to test the proposed dry method for the production of ammonium sulfate, is shown in the drawing, where:

1. Torch of a nozzle, consisting of ammonia, water vapor, drops of a solution of ammonium hydrogen sulfate in sulfuric acid and particles of ammonium sulfate.

2. Concentrated sulfuric acid supply line to the nozzle.

3. Line for supplying gaseous ammonia to the nozzle.

4. A fluidized bed of ammonium sulfate particles.

5. The flow of the vapor-ammonia mixture supplied under the grate of the fluidized bed.

6. Reactor.

7. Nozzle.

8. Ammonia water supply line to the nozzle.

9. Stream - branch pipe for unloading the product from the fluidized bed.

10. Fluidized bed gas distribution grid.

11. Cap that closes the chute from the nozzle flame.

12. Stream of ammonium vapor mixture and ammonium sulfate dust.

13. Heat exchanger-cooler.

14. Collector of ammonia water with dissolved dust of ammonium sulfate.

15. Pump supplying ammonia water to the nozzle.

16. Gas blower supplying a vapor-ammonia stream for fluidizing the fluidized bed.

Examples of carrying out processes at a pilot plant. The duration of the processes after the establishment of a stationary regime was 1.5-2 hours.

Example. 1. Installed a nozzle for internal mixing of liquid components and external mixing of the products of their reaction with gaseous ammonia (nozzle No. 1).

Example. 2. Installed nozzle No. 1

Example. 3. Installed nozzle # 2 for external mixing of reagent and coolant streams.

Claims (2)

1. A method for producing ammonium sulfate by the dry method, including feeding into the reactor atomized sulfuric acid and gaseous ammonia in a stoichiometric ratio, as well as ammonia water as a atomized cooler, characterized in that in order to ensure the formation of a dry average salt of sulfuric acid with a concentration of 91-92 wt%, gaseous ammonia and ammonia water are sprayed by a nozzle from top to bottom, and the resulting particles of ammonium sulfate fall into a fluidized bed, liquefied by a reverse flow of a vapor-ammonia mixture, in the upper part of which the temperature is maintained at 140-160 ° C. 2. The method according to claim 1, characterized in that in order to improve the dispersion of the liquid phase and reduce the moisture content of the product, sulfuric acid, ammonia water and gaseous ammonia are fed together to the spray nozzle / nozzles, while the liquid interacting streams are mixed in the nozzle / nozzles, forming a vapor-liquid stream that is sprayed with gaseous ammonia with external mixing.

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