RU2532735C2 - Method of producing calcium granules - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to metallurgy. Calcium chips in depth not exceeding mean particle size of the calcium granule main fraction are ground successively at two grinders with spinning rotor to remove grinding products from grinding zone via meshes of screen arranged around the rotor. Second grinder represents one with smaller screen meshes. Fire extinguishing additives are added to grinding zone. After grinding particles are rolled to calcium granules to be fed into cyclone for separation of said fire extinguishing powders therefrom. Said fire extinguishing powders can be those of calcium fluoride or potassium fluoride.

EFFECT: decreased sticking effect, lower risks of inflammability.

2 cl, 1 dwg, 1 tbl, 1 ex

Description

The invention relates to the field of non-ferrous metallurgy, in particular calcium, and can be used to obtain coarse powders or granules of metals, including plastic and chemically active.

Existing methods for producing powders and granules are divided into mechanical and physico-chemical (“Technology of metals and materials science.” Edited by LF Usova, M .: Metallurgy, 1987). Of the physicochemical methods for producing calcium powders, electrolysis of molten salts is most suitable. However, the separation of the obtained metal particles from the electrolyte, for example, by washing with water or salt solutions, is not suitable for calcium because of its chemical activity.

Of the mechanical methods currently used, such as spraying a jet of molten metal (RF patent No. 2199734, bull. No. 15, 05/27/2000) and metal processing by cutting to produce particles, rather than drain chips.

The disadvantage of the melt spraying method is the high energy consumption for heating and melting the metal, as well as the need to create a protective atmosphere for the calcium melt.

For the production of powders, various methods of grinding metals by cutting are also carried out using mills and crushers (Gert Schubert. "Aufbereitung metallischer Sekundarrohstoffe", VEB Deutscher Verlag fur Grundstoffindustrie, Leipzig, 1984).

Closest to the claimed method is a known method for producing calcium powder (patent RU 2203774 C2, B22F 9/04, publ. 05/10/2003), including grinding calcium chips on a rotating rotor, removing powder from the crushing zone through openings covering the rotor of the sieve.

The known method does not provide protection against fire and explosion hazard, its disadvantage is the low productivity of the process of obtaining metal powders.

The high fire and explosion hazard of the method is due to the fact that when cutting the chip elements, the resulting powder has a significant polydispersity. A small part of particles with linear dimensions determined by the diameter of the lattice holes is removed from the working zone. The bulk of the metal is in the gap between the rotor shaft and the grill. In this case, the resulting powder is in conditions of intense friction. When the material is abraded, a dust-air mixture is formed and the working zone is heated, which increases the fire and explosion hazard of the process, especially when obtaining powders of flammable metals in air.

As a result of heating above 300 ° C, calcium begins to interact with oxygen and nitrogen in the air (Doronin N.A. “Calcium metallurgy.” M .: Atomizdat, 1958). These reactions have an exothermic effect, due to which the working area of the crusher receives an additional amount of heat.

It should also be noted that in the field of cutting, the metal goes through all stages of deformation and collapses. Under such conditions, calcium undergoes polymorphic transformations (ME Drits. "Alloys of alkaline and alkaline earth metals", reference book. M: "Metallurgy", 1989). In this case, the ductility sharply increases and the strength of the metal decreases (A. V. Bobylev. "Mechanical and technological properties of metals", reference book. M: "Metallurgy", 1987). In practice, this leads to intense metal sticking to the cutting edge of the tool and, accordingly, to a sharp increase in cutting forces and a decrease in productivity, as well as to additional heating of the working area.

The invention solves the problem of increasing the productivity of the process of producing calcium granules and reducing the fire and explosion hazard of the operation.

To do this, in the inventive method, including grinding calcium chips, use calcium chips with a thickness of not more than the average particle size of the main fraction of the obtained calcium granules, grinding calcium chips are carried out sequentially in two crushers with a rotating rotor and the removal of crushing products from the crushing zone through the holes covering the rotor of the sieve moreover, as the second crusher, a crusher with a smaller size of the sieve openings than the first crusher is used, fire extinguishing powders are added to the crushing zone , after grinding, the particles are rolled up to obtain calcium granules, the obtained calcium granules are sent to a cyclone to separate them from fire extinguishing powders.

As extinguishing powders, it is preferable to use powders of calcium fluoride or potassium chloride.

The use of shavings with a given thickness of not more than the average particle size of the main fraction of the obtained granules allows to reduce the degree of polydispersity of the crushing products, due to which the formed metal particles are easily removed from the crushing zone through the sieve openings.

Sequential crushing of chips in two crushers, the first of which has a larger size of the sieve openings compared to the second, allows to reduce the heating of the crushed metal and, accordingly, its tendency to stick to the edges of the knives.

This allows you to reduce the heating of the metal in order to reduce its ductility. However, in practice, it does not exclude the occurrence of the sticking effect when cutting high-purity metals, for example, such as calcium. The addition of extinguishing powders to the crushing zone eliminates the sticking effect due to a change in the mechanical properties of the metal. The use of fire extinguishing powders of calcium fluoride or potassium chloride is due to the fact that they do not interact with calcium, as well as the high stability of their properties when stored in air.

The proposed method is illustrated in figure 1, which shows a diagram of the production of calcium granules.

An example of the method

According to the scheme shown in figure 1, from the ingots of calcium 1 received chips by cutting with a mill 2. The resulting chips were cooled on a vibration cooler 3.

The chip thickness was set by the feed rate of the ingot onto the cutter and was about 2.0 mm. The resulting chips after passing through a vibrating cooler was fed through a conveyor belt 4 first to the first crusher 5, which has a larger size of the sieve holes, and then to the second crusher 6 with a smaller size of the sieve holes.

Signs of the occurrence of the sticking effect were a sharp increase in temperature in the crushing zone and an increase in the current load on the rotor rotor drive motor of the crusher. To eliminate sticking to the conveyor belt before the crusher, calcium fluoride or potassium chloride powders recommended for quenching were added. The change in the parameters of the process of crushing calcium when adding powders is shown in table 1 for the example of the second crusher, in which the sticking effect was noted.

Table 1 The results of using fire extinguishing powder additives in the process of producing calcium granules Type of powder Powder consumption per 1 ton of granules, kg Temperature in the second crusher, ° C Current load on the crusher engine, A before adding after the supplement before adding after the supplement CaF ₂ 6.0 ÷ 10.5 55 37 ÷ 40 60 ÷ 65 45 ÷ 50 Kcl 0.5 ÷ 1.0 55 29 ÷ 32 60 ÷ 65 35 ÷ 40

The resulting crushing products were sent to the pelletizer 7, where the particles were given a shape close to spherical. The granules thus obtained were sent to cyclone 8, where the previously added powders were separated and carried away to the gas cleaning system. A slight increase in the impurity of the added powders in the finished product was within the error of the chemical analysis. Thus prepared finished granules were supplied to a vibrating screen 9 for separating a commodity fraction of less than 2 mm and then to packaging 10. Granules with sizes greater than 2 mm were returned to the beginning of the process.

The resulting commodity granules of calcium had the following particle size distribution:

- particle size 1.0-1.4 mm - 10.3%;

- particle size 1.4-1.6 mm - 14.8%;

- the particle size of 1.6-2.0 mm - amounted to ~ 67.7% of the total amount (the main fraction corresponding to the chip thickness).

The remaining fraction of the granules had a particle size of 0.4-1.0 mm and was part of the conditioned granules as an impurity.

In the analyzed sources of patent and scientific and technical information, the set of essential features of the claimed invention was not identified. At the same time, it helps to increase the fire safety of the process and the yield of suitable granules.

The proposed method is shown in the example of obtaining calcium granules. However, this does not limit its scope. The method can be used to obtain granules or powders of other ductile and chemically active metals, such as magnesium, aluminum, as well as their alloys.

Claims (2)

1. A method of producing calcium granules, including grinding calcium chips, characterized in that using calcium chips with a thickness of not more than the average particle size of the main fraction of the obtained calcium granules, grinding calcium chips are carried out sequentially in two crushers with a rotating rotor and removing crushing products from the crushing zone through the openings of the enclosing rotor of the sieve, moreover, a second crusher uses a crusher with a smaller size of the sieve openings than the first crusher, and into the crushing Adds fire extinguishing powders, and after grinding is carried out to obtain particles sloshing calcium granules which are fed to a cyclone for separation of fire-extinguishing powders. 2. The method according to claim 1, characterized in that the powders of calcium fluoride or potassium chloride are used as fire extinguishing powders.

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