DE2121520A1 - Standardisation of pore sizes - in ore agglomerates - Google Patents

Abstract

Combustible or volatile material is added to the ore to be agglomerated and is then partly or completely removed during subsequent hot processing, (sintering or reduction). The ratio of fines : volatile can be 2,3 or 4 : 1. The volatilisation or combustion of this material gives rise to uniform porosity and also improves the subsequent heat balance, aids further reduction (e.g. by depositing C in iron ore pellets) and favourably improving the smeltability of the pellets.

Description

Method for adjusting the pore size in ore agglomerates The invention relates to porous ore agglomerates with at least one cnemically bound, in one metallurgical Process to be reduced metal, which is made from finely divided ore concentrates getting produced.

Especially in the field of iron ore reduction, it has been shown that that iron ore pellets in addition to the blast furnace also in various other processes can be used for partial (pre-) or complete reduction. the Requirements for the quality figures are based on the reduction process to be used and reducing agents. While in processes with high mechanical requirements the material used (shaft furnaces, rotary kilns) does not fall below a minimum strength can be and only secondarily the reducibility are taken into account can, is sufficient for processes with lower mechanical requirements (moving beds) a much lower strength, so that a high porosity - i.e. a large Reaction surface is preferable. In addition to the type of procedure, the type of used reducing agents play a major role. Especially when using gaseous Reducing agents, especially in the field of direct reduction technology come more into the foreground (OS 1 914 400), has a high porosity of the ore agglomerates a considerable acceleration of the reduction process result.

In one proposed procedure, the reduction of iron ore pellets with gaseous reducing agent on a low-coated traveling grate (DBP 1 173 497), the strength of green pellets is sufficient, so that here at Compliance with a minimum strength pellets with the greatest possible porosity are used can be.

It is recognized to produce a different strength of a Basic fraction of the finely divided ore or ore concentrate present has a different Mix in fine fraction (Gudenau, H.W., Dr.-Ing.-Diss., Techn. Hochsch. Aachen 1967, p. 4y). It is also known to improve the strength of binders (e.g. bentonite), the smelting properties (e.g.

CaCO3) and the heat balance (e.g. coal dust AS 1.242.653) others To mix aggregates with the fine ore, which may also have cavities when burning leave behind. These additives have definitely been used so far because of the improvement of the properties mentioned, but not used to control the pore sizes. Finally, it is known to use raw materials for the production of coarse-pored insulating blocks Include burnout materials (Harders, F. and S. Kienow: Feuerfestkunde. Berlin / Göttingen / Heidelberg 1960, p. 907); However, this process only aims at certain material properties, especially the thermal conductivity.

Because of the reasons stated at the beginning (higher strength requirements, partial use of solid reducing agents) was the question of a targeted, den Reduction conditions (reduction process, reducing agent) adapted, optimal Porosity has not yet been so much in the foreground. The way in which the admixture different fines for strength control at the same time a different one Preserving pore space is useful for targeted porosity control, among other things.

because of the relatively high manual and sieving costs. Especially ins What matters, however, is that the empty spaces between the ore particles remain unused.

The invention is based on the object of economically producing ore agglomerates to produce the greatest possible porosity with sufficient strength, i.e. inner reaction surface, and in addition to this, when generating ung this pore space at the same time the entire manufacturing and subsequent use process can be favorably influenced.

This object is achieved in that the fine ore in the production of the green agglomerates in targeted Maj.e in finely comminuted Form volatilizers (e.g. naphthalene, styrofoam) or burnout substances (e.g. Wood sawdust, Kohlens @ aub) to ¢, which will be mixed with subsequent Exposure to heat (e.g.

Burning process) can be completely or partially removed. In the case of suitable On the one hand, the burning process is supported on the one hand and thereby the heat balance improves; on the other hand, there are residues in coked form is an additional reducing agent for direct reduction. There are basically also additives for increasing the strength and / or the improvement of the smelting properties conceivable, which - in finely crushed Form added - itself in the course of the process, leaving behind cavities decompose, so that also in this way the combination of setting a particular Porosity with simultaneous improvement of the quality property is possible.

The subject of the invention is a method for targeted adjustment the pore size in ore agglomerates, and the invention is characterized in that the fine ore to be agglomerated is admixed with burnout and / or volatilizing substances will be wholly or partially restored in the event of a subsequent exposure to heat removed.

Such burnout materials are preferably added to the fine ore to be agglomerated mixed in, in addition to the creation of a certain pore space in a subsequent The effects of heat support the heat balance, e.g. coking burn-out substances iron ore pelleting.

According to a further preferred feature of the invention are to be agglomerating fine ore added such burnout materials, in addition to the production a certain pore space and / or in addition to improving the heat balance with subsequent exposure to heat, additional residues formed in the Pores support the metal extraction process, e.g. in coking burn-out substances iron ore pelleting.

It can also be expedient to add to the fine ore to be agglomerated Additions to the burn-out materials which additionally have the properties of refining have a positive influence, e.g. CaCO3 in iron ore pelleting. Also can that to agglomerating fine ore in addition to burn-out materials or such additives which, through decomposition when exposed to heat, contribute to increasing the porosity.

In order to further improve the smelting properties, there is a combination of the listed additives possible. So can by adding sawdust and coal dust at the same time have a high porosity due to burned-out sawdust and due to burnt coal dust particles a good heat balance and support of the Reduction can be achieved. On the other hand, in addition to burnout materials, you can still Additives to improve smelting, preferably lime for iron ore pellets, are mixed in.

Practical examples should be the creation of the pore spaces and their Show the importance especially for iron ore pellets.

Figure 1 shows the influence of different proportions admixtures on the Porosity and strength after the ~ firing process.

The regulation of the pore space via admixture is determined here Proportions of fine ore, volatilizer and burnout material shown. Figure 2 shows the close relationship between porosity and compressive strength. After that it is possible the greatest possible for a given reduction process with a known minimum strength Porosity and thus best:. Determine the reducibility after the in this Invention shown manner can be adjusted.

The advantages achieved with the invention are, in particular, that a porosity in ore agglomerates optimally adapted to the process and the reducing agent erzeMutgt and this can be set very precisely due to the process. As Figure 3 shows, the reduction process using gaseous reducing agents significantly accelerated with larger porosity of the agglomerates, which in the Ironmaking processed large quantities of a great economic benefit can mean. On the other hand, the addition of substances such as which besides the production of a certain porosity the process of the production of the Agglomerates and the extraction of the metal from the ore influence positively, This is an additional advantage. This is preferably the case when using coking Burnout in iron ore agglomerates is the case, as in addition to improving the Heat balance is still supported by direct reduction.

P a t e n t a n s p r ü c h e 1. Procedure for targeted child position the pore size in ore agglomerates, characterized in that the to be agglomerated Fine ore burnout and / or volatilizing substances are added, which at a subsequent exposure to heat (Bre @@ -.

Reduction process) can be completely or partially removed again.

2. The method according to claim 1, characterized in that the to be agglomerated Fine ore burn-out and / or volatilizing substances that result from subsequent exposure to heat (Burning reduction process) gan or partially removed again, in defined Volume proportions are added, preferably 1 part by volume burn-out (volatilized) substance: 2 parts by volume fine.

1 part by volume burn-out (volatilization) substance: 3 parts by volume fine.

1 part by volume burn-out (flammable) substance: 4 parts by volume fine.

Claims (7)

9. The method according to claim 2, characterized in that your to agglomerating fine ore one or more soleh burnout and / or volatilizing substances, which in a subsequent heat exposure (burning, reduction process) gana or are partially removed, are added in defined proportions by volume, the both aim to generate a certain pore volume and a) improve the heat balance (e.g. coking burnout materials in iron ore pelleting) and / or b) the metal extraction (reduction) process support through residues formed in the pores (e.g. coking burn-out substances in iron ore pelleting) and / or c) have a beneficial effect on the smelting properties (e.g. Lime in iron ore pelleting) 4, method according to claims 2 and 3, characterized in that the fur to be agglomerated such Burn-out and / or volatilizing substance that occurs when exposed to heat (Burning, reduction process) is completely or partially removed again, in defined Volume fractions is added, which both the generation of a certain pore space The aim is to also improve the heat balance 5. Procedure according to Claims 2 and 3, characterized in that the fine ore to be agglomerated such a burn-out and / or volatilizing substance that occurs when exposed to heat (Burning, reduction process) is completely or partially removed again, in defined Volume fractions are added, which both generate a certain pore volume as well as supporting the metal extraction (reduction) process. 6 * Method according to claims 2 and 3, characterized in that such a burnout and / or volatilizing substance is added to the fine ore to be agglomerated, that during the subsequent exposure to heat (combustion, reduction process) in whole or in part is removed again, is admixed in defined proportions by volume, both the production of a certain pore volume has the goal, as well as additionally the The smelting properties are favorably influenced. 7. The method according to claim 2, characterized in that the to be agglomerated Fine ore burn-out and / or volatilizing substances that result from subsequent exposure to heat (Burning, reduction process) can be completely or partially removed again, in defined Volume fractions are added, which both generate a certain pore space aim and at the same time a) improve the heat balance, b) the metal extraction (reduction) Support the process c) have a favorable effect on the smelting properties.