RU2553912C1 - Melts granulation method - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: under the suggested method of the melts granulation including product melt supply to the liquid inert medium in form of jets flowing from the calibrated holes, with installed needles, the inert medium is melt. Melting temperature of the inert medium is below melting temperature of the granulated material. The obtained product granules are cooled in the inert liquid to temperature (20-30)°C. The inert liquid density is higher than the inert medium density and below the product granules density. The product melting temperature is (1.5-1.25) of melting temperature of the granulated material, and inert medium temperature is (1.05-1.15) of its melting temperature.

EFFECT: increased quality of produced granulated product, and capacity of the process of melt granulation due to contact of the product melt droplets with inert medium in form of the melt heated to temperature below the melting temperature of the granulated material.

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Description

The technical solution relates to the field of methods for producing granular materials from melts and solutions and can find application in chemical and other industries.

A known method of producing granular materials [1] by dispersing a liquid into a free volume or a neutral medium by the formation and crystallization of liquid droplets while cooling them in air, oil, etc. The disadvantage of this method of granulation is the low productivity of the process, filling shrinkage cavities in the granules with liquid, which then requires a long and laborious operation to remove moisture or liquid from the granular material.

The closest technical solution to the proposed is a method for producing granulated TNT [2], which consists in pouring the molten product through capillary tubes into cold water. The capillary tubes are heated to a temperature slightly higher than the melting point of TNT. The jets of molten TNT are let between two jets of water into a vessel of cold water. The granules formed are squeezed out on a vacuum filter and dried in tunnel dryers. The disadvantages of this method include the following: the formation of shrinkage shells in granules that are filled with water, which requires significant energy costs and prolonged drying of the resulting product; high humidity of the finished granular material.

In the proposed technical solution, the task is to create a method of granulation of the melts, which would be free from the above disadvantages, the implementation of which would improve the quality of the obtained granular product and the productivity of the process of granulation of the melt. The problem is solved by contacting the droplets of the product melt with a heated inert medium and further cooling the product granules in an inert liquid.

This is achieved by the fact that in the proposed method of granulation of melts, including the supply of the melt of the product into a liquid inert medium in the form of jets flowing from calibrated holes with needles installed in them. The inert medium is a melt, with the melting temperature of the inert medium below the melting temperature of the granular material. Further cooling of the obtained product granules occurs in an inert liquid to a temperature of (20-30) ° C. The density of the inert liquid is higher than the density of the inert medium and less than the density of the granules of the resulting product. The melt temperature of the product is from 1.05 to 1.25 the melting temperature of the granular material, and the temperature of the inert medium is from 1.05 to 1.15 of its melting temperature.

The use of an intermediate inert medium located between the inert liquid and the jets of the molten product makes it possible to fill the shrink shells formed in the granules with an inert medium that hardens in the shells and prevents moisture from entering them.

The essence of the proposed technical solution is as follows. In an inert medium heated above its melting point, a molten product, for example trinitrotoluene in the form of jets flowing from the holes, is fed. The jets of the melt in contact with an inert medium are destroyed into droplets. Drops in an inert medium are cooled and harden, turning into granules, while the shrink shells formed in the granules are filled with a melt of an inert medium. Then, the obtained granules are immersed in an inert liquid, in which they are cooled to the required temperature and then transferred to drying. The melt temperature is from 1.05 to 1.25 the melting temperature of the granular material, the temperature of the inert medium is from 1.05 to 1.15 its melting temperature, the temperature of the inert liquid decreases from the temperature of the inert medium to (10-20) ° C as falling granules in it.

An example of a method for granulating melts. The method is as follows. An inert liquid is poured into the apparatus - water, the upper layer of water is heated to a temperature slightly higher than the melting point of the inert medium. Paraffin with a melting point of 66 ° C is used as an inert medium. An inert medium is located above the surface of heated water and its temperature is from 70 to 75 ° C. The lower layer of water is cooled to a temperature of (10-20) ° C. Then, through calibrated holes in which the needles are installed, a melt of trinitrotoluene is fed into an inert medium, the temperature of which is (90-95) ° C. The trinitrotoluene melt jets flowing down the needles break up into droplets and enter an inert medium in which the droplets crystallize and turn into granules. Then the granules enter an inert liquid - water, are cooled to a temperature of (20-30) ° C and sent for drying.

Table 1 shows comparative data on the implementation of the proposed method and the closest analogue (prototype) when using granulated material as a melt — a trinitrotoluene melt with a melting point of 79 ° C, and an inert (neutral) medium — paraffin melt with a melting point of 66 ° C. As an inert (neutral) liquid, water was used with different temperatures in the upper part and in the lower part of the layer into which the granules of the obtained product enter after passing through an inert medium.

Comparing the data presented in table 1, it is seen that when using the proposed granulation method, the quality of the obtained product improves, the moisture content of the trinitrotoluene granules decreases from 5.4% to 2.3%, and the process productivity increases by more than 2 times.

To explain the effect of the temperature parameters of the melt granulation process on the quality of the obtained product, Table 2 presents the data on the dosage of the trinitrotoluene melt with different temperatures, sequentially, into layers of an inert medium and an inert liquid. The remaining process parameters, such as the temperature of the inert medium and the temperature of the inert liquid, are unchanged. The temperature of the inert medium (paraffin melt) is 75 ° C, the temperature of the inert liquid (water) in the upper part of the layer is 75 ° C, in the lower part of the layer 20 ° C.

From the results presented in table 2, it is seen that the optimal temperature range of the dosed trinitrotoluene melt, in which the best quality of the obtained product is achieved (moisture content of granules 2.2-2.7%, temperature of granules 22-30 ° C), is from 83 ° C to 98 ° C, which corresponds to a melt temperature range of 1.05 to 1.25, the melting temperature of the granular material. At a higher temperature of the trinitrotoluene melt, the humidity of the granules and their temperature increase, undesirable accompanying phenomena appear: the cooling time of the granules increases, the droplets stick together, the melt can overheat, and its color and properties may change. With a decrease in the temperature of the trinitrotoluene melt below 83 ° C, a poor dosage of the product melt, its partial crystallization on the surface of the needles, is observed.

Table 3 shows the data on the dosing of a melt of trinitrotoluene with a constant temperature, sequentially, into layers of an inert medium and an inert liquid, while the temperature of the inert medium varies from its melting temperature to a temperature equal to 1.3 of its melting temperature. The temperature of the dosed trinitrotoluene melt is 90 ° C, the temperature of the inert liquid varies from the temperature of the inert medium to 20 ° C.

From the results presented in table 3, it can be seen that the optimal temperature range of an inert medium (paraffin), in which the best quality of the obtained product is achieved (moisture content of granules 2.1-2.3%, temperature of granules 21-25 ° C), is from 70 ° C to 75 ° C, which corresponds to a melt temperature range of 1.05 to 1.15 inert melting points. At a higher temperature of the melt of the inert medium, the humidity of the granules and their temperature increase, undesirable accompanying phenomena appear: the droplets do not solidify in an inert medium and fall into an inert liquid, which increases their humidity after crystallization. The use of other inert media, for example melts of stearin or wax, leads to similar results. The density of these substances is lower than the density of an inert liquid (water or glycerol), which allows them to be used as an inert medium.

Using the proposed method for granulating crystalline melts provides, in comparison with existing methods for producing granular materials, improving the quality of the resulting product.

Information sources

1. Klassen P.V., Grishaev I.G. Basics of granulation technology. - M: Chemistry, 1982. - S. 41.

2. England patent No. 755695, C02B 27, 1956

Claims (1)

A method of granulating melts, comprising feeding the product melt into a liquid inert medium in the form of jets flowing from calibrated holes with needles installed in them, characterized in that the cooling and crystallization of droplets of the product melt occurs in an inert medium, the melting temperature of which is lower than the melting temperature of the granular material , further cooling of the product granules to a temperature of (20-30) ° C is carried out in an inert liquid, while the density of the inert liquid is higher than the density of the inert medium and less densely the granulated material, the melt temperature of the product is from 1.05 to 1.25 the melting temperature of the granular material, and the temperature of the inert medium is from 1.05 to 1.15 of its melting temperature.