SU1502640A1 - Method of producing fluxed pellets - Google Patents

Abstract

The invention is intended for the production of fluxed pellets from iron ore concentrates. The purpose of the invention is to increase the strength and decrease the temperature of desulfurization of the pellets. The method includes the introduction of mineral additives into the mixture, mixing, pelletization and heat treatment of the pellets in an oxidizing atmosphere, and boron oxide is used in the amount of 0.1-2.2% by weight of the mixture as a mineral additive. For each 1% content of silicon oxide in the charge, 0.10-0.15% boron oxide is introduced. 1 hp ff, 3 tab.

Description

The invention relates to ferrous metallurgy and can be used in the production of oxidized iron ore fluxed okrastein for the domain processing.

The purpose of the invention is to increase the strength and decrease the temperature of the pellet desulfurization.

Input of boron oxide allows to obtain high-strength pellets in the drying zone as a result of hydration of boron oxide in a humid environment and the appearance of a strengthening pellet of phase B, Oj 3H20 in its place, to achieve low-temperature liquid-phase strengthening in the heating zone due to dissociation of the hydrate phase and melting boron oxide at 450-470 s and lower the sulfur content in the final product due to a decrease in the temperature of silicate formation.

In the process of forming fluxed pellets without intensifying additives, the initial strength is ensured by the presence of tight mechanical contacts between the grains of ore and silicate components of the concentrate, flux and bentonite. At the same time, their strength is 0.8-1.0 kg / kg. During oxidative roasting, prior to the occurrence of the primary melt, hardening of the pellets occurs as a result of solid-phase processes, where oxidation, sintering and recrystallization of the fine ore fraction and ferrite formation at the contact of hematite grains and flux are key. Liquid phase hardening process

starts with either melting syiks of the enclosing rocks, if there are synerals with a low melting point (up to 1200 C) among them, or melting of ferritic phases (1230-1250 C) if the enclosing silicates have a high melting point (more than 1250 C). In both cases, in the range of 1250-1350 C, an iron silicate melt is formed which, upon cooling, solidifies as a silicate binder, which is (it is the carrier of the strength of the pellet during reduction-heat treatment. The beginning of the burnout of sulfate sulfur from the fluxed pellets is determined by the temperature of the primary melt. In pellets of skarn-type concentrates, where silicates are represented by low-temperature thermal minerals, the onset of sulphate sulfur burnout is confined to the temperature range of 1000–113 ° C. As a result, ferrous quartzite concentrates of the melt appear due to the melting of solid ferrites and therefore the onset of sulfur burnout occurs at a higher temperature of 1200–1250 ° C.

The introduction of fluxed boron oxide pellets into the charge mixture changes the mechanism of pellet hardening at all stages of their production at the stage of pelletizing charge oxide. boron is hydrated due to the moisture of the concentrate and turns into the hydrate phase (). The hydrate needle-like crystals form the first hardening - the youngest skeleton of the pellets. The strength of an eye as a result of hydration of boron oxide increases by 5-10 ra,. During roasting, the hydrate phase loses water, y, boric oxide melts at 470 ° C, forming the primary melt. With an increase in the firing temperature, the primary boron-containing melt assimilates the silicates of the host rocks and the flux, enriched with silica and calcium. The iron silicate melt intensifies the processes of sintering and recrystallization and forms the very composition and microstructure of the pellets. The emergence of a melt in the early stages of firing displaces the processes of sulfur burnout and hardening of the pellets in the region of more low temperatures, Formulation

the end product in this case ends up at a temperature level of 1100-1150 C. Therefore,

upon receipt of boron-containing pellets B of industrial conditions of the H1 core layer and the layer – bed interface, where the burning temperature does not exceed 1150 ° C, high strength cBoi iCTBa and low sulfur content are observed;

PRI me R. Using iron ore 11 concentrate with different content of silica. E mixer osu5 sh, osgvll n gemesmeshin PIE flux and. Then mixed flux and boron oxide with: iron: opyne K {5nc trato1. {And bentonite, taken in amounts from the calculation of the basicity of CaO / Si02 1.2.

0 Content; bentonite accounted for 055-0.7% of the weight of the charge. The resulting mixture was moistened and pelletized. The firing was carried out at a heating rate of 70 C / min, with an exposure at a given

 temperature for 20 minutes and subsequent cooling at a rate of 00 C / min.

In tab. Figures 1 and 3 present data on the strength and content of residual sulfur calcined 1) when 0.1-2.2% fijO are introduced into their composition when using iron ore concentrate with a grade — keeping SiO. ; 1 uzneschrnii dsbanki above 2.2% strength (1XLL neck falls due to excessive development of the melt, which, when cooled, solidifies in the form of a silicate bond, the strength of which in a cold state is inferior to the strength of the ores} 1st link.

Table 2 gives the results of a study of the strength and degree of reduction of pellets with different contents after the reduction-thermal process.

The effect is manifested in the character of the destruction of Slides during recovery-heat treatment. With an increase in pellets of cht 0.3 to 2.0%, 7, and a noticeable increase in the products of their recovery is the fraction of the fraction (+10 mm and reduced fractions (5-0.5) IC-O.mm (Table .2) With a content of 2.0--2.2%, the hiccups are not destroyed during recovery, but the evolution of the strength of the pellets during the recovery of linkage with a change in the quantity and properties of crystalline (linkage).

five

0

five

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which during reduction heat treatment is a carrier of pellet strength, the same explains the decrease in the degree of reduction of pellets with an increase in their content (table 2). In spite of the increase in the strength of the pellets during recovery and the positive effect on the character of sulfur removal, the addition of boron oxide more than 2.2% is not economically feasible.

Thus, as a result of the implementation of the method of producing fluxed pellets with the addition of boron oxide, iron ore pellets with high strength, properties and desulphurization degree at lower temperatures are possible.

The advantage of the method is that as a result of the redistribution of boron-containing oxides, a doped metal is obtained, which possesses improved, as compared to usual properties.

Boron does not adversely affect the environment or aggressively affect structures.

aggregates, as is the case with the use of calcium fluoride additives in the charge for crumpling. The use of fluxed boron-containing pellets in blast furnaces saves 2-3 kg of coke per each smelted ton of pig iron.

Claims (2)

1. A process for the production of iron ore concentrates from iron ore concentrates, including input into a mixture containing silicon oxide, mineral additives, mixing, pelletizing and heat treatment of the pellets in an oxidizing atmosphere, characterized in that, in order to reduce the strength and decrease the temperature of desulfurization of the pellets , as a mineral additive, boron oxide is used in an amount of 0.1-2.2 percent by weight of the mixture. 2. The method according to claim 1, which differs from the fact that for each percent of the silicon oxide content in the charge, 0.10-0.15% boron oxide is introduced. Table 1 table 2