UA59800C2 - Method for producing granulated lime-ammonium nitrate from limestone - Google Patents

Abstract

A method for producing granulated lime-ammonium nitrate from limestone, which method comprises granulation in drum-granulator-drier by sputtering on the screen of suspension recycle, being obtained before granulation by mixing at first fusion cake of ammonium nitrate with ammonium sulphate and solution, after purification of effluent gases with subsequent addition of reactive limestone and drying.

Description

Description of the invention

The invention relates to the chemical industry, the technology of obtaining fertilizers based on ammonium nitrate, 2 in particular to methods of obtaining granular lime-ammonium nitrate (CA).

Known methods of obtaining granulated lime-ammonium nitrate include mixing liquid ammonium nitrate with a concentration of 98.0 - 99.595 and calcareous raw materials (inert limestone) and granulating the resulting mixture in granulators (1). However, the addition of lime raw materials to a highly concentrated ammonium nitrate melt under conditions of high temperatures and a long stay in this melt has such a disadvantage as the formation of 70% hygroscopic calcium nitrate and the release of free ammonia. This leads to a deterioration in the quality of the product, significantly narrows the raw material base, since only inert limestone is used for the process. According to these methods, to prevent the formation of calcium nitrate in the finished product, ammonium sulfate or other additives are added to the ammonium nitrate solution. Solutions after wet cleaning of waste gases by these methods can be returned to the process.

Among the disadvantages of these methods can also be attributed: - large capital costs for the construction of granbashts and - installation of equipment; - the impossibility of obtaining large granules and, as a result, - problems with the sale of the finished product; - the impossibility of changing the size of the granules at the given height of the granule; - low strength of granules; - use of only inert limestone; - energy costs for the preparation of lime raw materials and the supply of VAS components to the Grand Tower;

There is also a known method of obtaining granulated lime-ammonium nitrate in a two-shaft (screw) granulator |1). The main unit is a tray where two shafts rotate in different directions. Blades are located on the shafts along the helical line. In the screw granulator, the retort is mixed with lime raw materials (ground limestone, dolomite, lime of any grade), liquid ammonium nitrate with a concentration of 98.0-99.095, and a solution after wet cleaning of waste gases at a temperature of 125 - 14090 and granulated in the process of passing along the granulator . After that, the granules are dried in a drying drum or in a fluidized bed dryer and fractionated. aw!

The disadvantages of this method include: - high mixing temperature, which can lead to the formation of hygroscopic calcium nitrate and the release of ammonia; Ge) - energy consumption due to the need for drying in a drying drum or in a fluidized bed dryer;

Zo - the return of a large amount of external return (three times the amount of the finished product); yuyu - high energy consumption due to the need to maintain the return temperature at the level of 1202С throughout the entire technological cycle, which complicates the conditions of operation of the equipment.

The closest to the claimed method is the method of obtaining granulated lime-ammonium nitrate in a spheroidizer (drums-granulators-dryers-coolers) by spraying a melt of ammonium nitrate on the curtain from the retort and limestone, which is formed due to the rotation of the drum |1) . In this method, the same raw materials are used as in the previous method. :z» The disadvantages of the method closest in essence include: - complication of the exhaust gas purification process due to the fact that a large amount of limestone dust is removed from the drum; step 15 - the impossibility of obtaining a homogeneous composition of the granules, which reduces the strength of the granules and worsens the quality of the finished product; (Ce) The invention is based on the task of developing a method of obtaining granulated lime-ammonium nitrate from reactive sedimentary limestone by granulating the product in a drum-granulator-dryer (BGS), to ensure the homogeneity of the composition of granulated VAS and to minimize the content of unwanted calcium nitrate in it by ) 50 levels, which meets the requirements of customers. o The problem is solved as follows: before granulation in the BGS, ammonium nitrate solution, with a concentration not lower than 8695, is mixed with a solution from the stage of wet purification of incoming gases and ammonium sulfate, then the resulting solution passes through a heat exchanger, where it is cooled to the required temperature, after which the solution is mixed with reactive limestone. The resulting VAS suspension is sprayed onto the curtain through a nozzle, from the return, which is formed when the drum rotates. In the claimed method, the curtain in the BGS consists only of a return,

GF) in the prototype - from return and limestone. 7 The optimal amount of ammonium sulfate in the VAS suspension is 0.4-1.590 (in terms of 10095 VAS).

The temperature of the VAS suspension in the mixer is maintained no higher than 1252C. Maintaining the required temperature in the VAS suspension is ensured by adjusting the temperature of the solution, which, after passing through the heat exchanger, is fed for mixing with limestone. The selected temperature regime, together with the presence of ammonium sulfate in the suspension, prevents the decomposition of ammonium nitrate and the formation of unwanted calcium nitrate.

Spraying the suspension of VAS on the curtain from the return leads to the receipt of homogeneous strong granules, the quality of which meets the requirements of customers.

When dosing ammonium sulfate, its presence in the ammonium nitrate solution and in the solution from stage b5 of waste gas purification is taken into account. The limitations of the temperature of the VAS suspension and the amount of ammonium sulfate are explained by the results of experiments conducted at a laboratory facility. The laboratory installation is a container with a stirrer, in which a suspension is obtained by mixing liquid ammonium nitrate, limestone and ammonium sulfate

YOU. A constant temperature is maintained in the mixer, and samples are taken at the outlet of the mixer for analysis of the amount of calcium nitrate in the VAS suspension. Ground sedimentary limestone from various deposits of Ukraine was used in laboratory studies. The averaged results of laboratory experiments are shown in the table.

VAS, 26. converted to 10095 VAS), 90 (converted to 10095 VAS), 90 7

AND

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The results of the experiments confirm that at a temperature of the VAS suspension not higher than 1259C and the presence of ammonium sulfate in the suspension in the amount of 0.4-1.590 (in terms of 10095 VAS), the amount of calcium nitrate in the finished product will not exceed the indicators that meet the requirements of customers.

The essential features of the claimed method are as follows: - a suspension of VAS is obtained by mixing the components in a certain sequence and immediately before granulation: first, ammonium nitrate solution is mixed with ammonium sulfate and a solution from the waste gas purification stage, then - by adding reactive limestone; - the temperature of the VAS suspension is maintained at no higher than 1252C and is regulated by the temperature of the solution that is fed to the mixing plant for mixing with limestone; o - the amount of ammonium sulfate in the VAS suspension is 0.4-1.595 (per 10095 VAS); - the VAS suspension is sprayed onto the curtain consisting only of the return; - granulation is carried out in BGS. at

Waste gases after BGS, containing lime-ammonium nitrate dust, are sent to a wet cleaning system for dust collection, then they are released into the atmosphere, and the solution from the waste gas cleaning stage is returned (ав) to obtain a VAS suspension. The composition of this washing solution, that is, the solution from the waste gas purification stage, is proportional to the composition of the BAS. On average, it contains: ammonium nitrate - up to 3090; limestone - up to 1095; ammonium sulfate - up to 0.595. Gee)

The claimed method allows the use of reactive limestone for the production of VAS, that is, sedimentary limestone with a loose structure that reacts with ammonium nitrate at a sufficiently high rate. It is widely distributed and cheap, which makes it possible to expand and reduce the cost of the raw material base for obtaining an effective VAS fertilizer that prevents soil acidification. At the same time, the quality of VAS meets the requirements of customers.

Since spraying of the VAS suspension in BGS is carried out on a curtain consisting only of a return, the productivity of the process can also be increased due to the introduction of a larger amount of drying agent. -at

Sources of information: p. 1. Journal of the VHO named after D. I. Mendeleev, 4, 1983, p. 82-84.

Claims (1)

;" The formula of the invention The method of obtaining granulated lime-ammonium nitrate from limestone, which includes granulation in a (Se) drum-granulator-dryer by spraying liquid ammonium nitrate on a curtain from the return, as well as drying, because it differs from that on a curtain consisting only of return, spray the suspension obtained before granulation by first mixing molten ammonium nitrate with ammonium sulfate and a solution from the purification stage (а) 50 waste gases with the subsequent addition of reactive limestone, while the amount of ammonium sulfate is 0.4-1.5 96 (in terms of per 100,956 VAS), and the temperature of the suspension is maintained no higher than 12,590 and regulated by the temperature of the solution, which is served for mixing with limestone. Official bulletin "Industrial Property". Book 1 "Inventions, useful models, topographies of integrated microcircuits", 2006, M 10, 15.10.2006. State Department of Intellectual Property of the Ministry of Education and (F) Science of Ukraine. name) 60 b5