RU2224803C1 - Method of obtaining pellets from fluorite concentrate - Google Patents

Abstract

FIELD: ferrous metallurgy; obtaining fluorite pellets from fluorite concentrates added to slag for reduction of toughness and removal of toxic components in production of quality steels. SUBSTANCE: proposed method includes preparation of molding mass containing binder, molding and subsequent drying of pellets. Used as binder is aqueous colloidal solution of sodium-carboxymethyl cellulose. Drying of pellet is performed first in air or in flow of heated air before hardening of surface layer and then at temperature of 110-300 C for 1-4 h. Relationship of components in pellets thus obtained is as follows, mass-%: sodium-carboxymethyl cellulose, 1-4 and the remainder being fluorite concentrate. EFFECT: improved quality of pellet without roasting at minimum content of admixtures. 1 tbl

Description

 The invention relates to the metallurgy of ferrous metals, in particular to the production of pellets from fluorite concentrates added to slag to reduce its viscosity and remove harmful components in the production of high-quality steels.

 Fluorite concentrate is obtained predominantly finely dispersed, with a particle size of less than 1 mm. Given its high cost and scarcity, the need for its enlargement is beyond doubt, since when using finely dispersed fluorite concentrate, its efficiency is very low due to large losses.

 The most economical and effective are non-firing methods for producing pellets from fluorite concentrate, since when using them, the technology is much simpler and the cost of production is lower.

 Inorganic (cements, sodium silicate, magnesium oxide, clays, iron chlorides, etc.) and organic (wax, starch, dextrin, peat, colemanite, etc.) substances are used as binders to obtain pellets without annealing. Moreover, when using organic binders, insufficiently strong pellets are obtained, which, moreover, burn out and dissolve in water (1. Maerchak S. Production of pellets. Transl. From Slovak. - M .: Metallurgy, 1982, p.232; Briquetting in color and ferrous metallurgy. - M .: Metallurgy, 1975, p.232).

A known method of pelletizing fluorite concentrates using liquid glass as a binder (flow rate - 10 wt.%), Including granulation and drying processes at a temperature of 300 ^o C. The strength of the obtained pellets is 37-40 kg / pellet (2. Bulletin TsIIN FM , 1971, 6, p. 32 and 33).

 The disadvantage of this method is the low strength of the obtained pellets and a high silicon content in them, above 3 wt.%, Which is extremely undesirable in obtaining high-quality steels.

The closest technical solution selected for the prototype is a method for producing pellets of fluorspar, including rolling the concentrate with a binder, drying and firing the pellets, while aluminum production dust is used as a binder and firing is carried out at 950-980 ^o C (3. Auth. St. USSR 979512, class C 22 V 1/243).

The disadvantage of this method is:
- high heat treatment temperature, leading to high energy consumption during production;
- the use of aluminum plants as a binder waste containing 9.6-25.4 F in the form of cryolite (NaAlF ₄ ) reduces the sanitary and hygienic working conditions in steelmaking, since a significant amount of fluorine is released during the decomposition of cryolite in steel-making furnaces. , contributing to the rapid deterioration of equipment and poisoning of staff;
- production waste located in dumps cannot ensure their sufficient purity from silicon impurities, which is unacceptable in the preparation of highly pure steels.

 The problem solved by the claimed technical solution is to obtain strong pellets from a fluorite concentrate in a non-firing method with a minimum content of impurities.

The problem is solved due to the fact that in the inventive method, which includes preparing a mass for molding using a binder, molding and subsequent drying of the obtained pellets, an aqueous colloidal solution of sodium carboxymethyl cellulose is used as a binder, the pellets are dried first in air or in a stream of heated air to hardening of the surface layer, and then at a temperature of 110-300 ^o C for 1-4 hours with the following ratio of components in the resulting pellets, wt. %:
Sodium Carboxymethyl Cellulose - 1-4
Fluorite Concentrate - Else
The analysis of the prior art made it possible to establish that the claimed technical solution meets the criterion of "novelty" according to current legislation.

In relation to the selected prototype, the claimed technical solution has the following set of distinctive features:
- as a binder use an aqueous colloidal solution of sodium carboxymethyl cellulose;
- drying of the obtained pellets is carried out first in air or in a stream of heated air until the surface layer is hardened;
- then drying is carried out at a temperature of 110-300 ^o C for 1-4 hours;
- get pellets containing 1-4 wt.% sodium carboxymethyl cellulose.

 Information about the fame of these distinguishing features in the totality of the signs of known technical solutions was not found. Based on this, it is concluded that the claimed technical solution meets the criterion of "inventive step".

 To prove the compliance of the claimed technical solution to the criterion of "industrial applicability" we give specific examples of the method.

 Example 1

100 g of fluorite concentrate is mixed with a colloidal solution of sodium carboxymethyl cellulose (NKMTs), obtained by mixing 25 ml of water with 1 g of NKMTs powder, followed by exposure to a colloidal solution. Pellets are formed from the dough obtained by known methods. The obtained pellets are dried in a stream of air until the surface layer hardens, which allows their transportation to drying ovens. Hardening drying is carried out at a temperature of 110 ^o C for 4 hours.

 The resulting pellets have a strength of 31 kg / pellet.

 Example 2

100 g of fluorite concentrate is mixed with a NKMTs colloidal solution obtained by mixing 25 ml of water with 2 g of NKMTs powder, followed by exposure of the solution to its colloidal state. Molded pellets are dried in air until the surface layer is hardened, and then dried at a temperature of 300 ^o C for 2 hours. The strength of the pellets obtained is 45 kg / pellet.

 Example 3

The example is similar to examples 1 and 2, only when preparing a colloidal solution in 25 ml of water 3 grams of NKMTS powder are dissolved. Hardening drying is carried out at 300 ^o C for 1 hour. The strength of the obtained pellets is 74 kg / pellet.

 Example 4

The example is similar to the above examples, only when preparing a colloidal solution in 25 ml of water, 4 grams of NCCM are dissolved, and hardening drying is carried out at 300 ^o C for 3 hours.

 The strength of the obtained pellets 93 kg / pellet.

 Example 5

The example is similar to the above examples, only when preparing a colloidal solution in 25 ml of water, 4.2 grams of NKMC are dissolved, and hardening drying is carried out at 250 ^o C for 4 hours. The mechanical strength of the pellets obtained is 97 kg / pellet.

In the inventive method used fluorite concentrate containing 96 wt. % CaF ₂ , as well as a polymeric organic substance, sodium carboxymethyl cellulose (NKMTs), obtained according to TU 6-55-40-90 or according to the method developed by NIH ICTTM SB RAS using mechanochemical activation of plant materials.

 Strength tests of the obtained pellets were carried out on a 2PG-10 hydraulic press.

 All examples of a specific implementation of the method are summarized in table.

As can be seen from the table, the most durable pellets are obtained under the following conditions:
- the content of sodium carboxymethyl cellulose 1-4 wt.%;
- temperature hardening drying 110-300 ^o With;
- the duration of hardening drying 1-4 hours.

Pellets cannot contain sodium carboxymethyl cellulose above 4 wt.%, Since the content of CaF ₂ in them will be lower than allowed by GOST 24626-81.

 The claimed technical solution allows to obtain a non-firing method of durable pellets from fluorite concentrate with a minimum content of impurities that can be used in the smelting of very pure steels.

 In addition, the use of sodium carboxymethyl cellulose as a binder in the preparation of pellets provides good sanitary and hygienic working conditions for steelmaking, and also does not contribute to the rapid wear of equipment during smelting, since no aggressive gases are released during thermal decomposition of sodium carboxymethyl cellulose.

Claims (1)

A method of producing pellets from a fluorite concentrate, comprising preparing a mass for molding using a binder, molding and then drying the obtained pellets, characterized in that an aqueous colloidal solution of sodium carboxymethyl cellulose is used as a binder, the pellets are dried first in air or in a stream of heated air to hardening of the surface layer, and then at a temperature of 110-300 ° C for 1-4 hours, with the following ratio of components in the obtained pellets, wt.%: Sodium Carboxymethyl Cellulose 1-4 Fluorite Concentrate

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