Method of introducing a metalliferous feed in an ironmaking process

Abstract

A method of introducing a metalliferous feed in an ironmaking process, the method including the steps of, pre-drying an iron containing sludge by drying means to an amount of 15 to 30% (w/w) moisture, mixing the pre-dried iron containing sludge with a binder material to obtain a granulate, having a particle size of less than 4 millimeter and drying the granulate to a maximum of 3% (w/w) moisture, thereby forming the metalliferous feed, wherein the metalliferous feed is subsequently injected into a cyclone part of a metallurgical vessel.

Claims

1. A method of introducing a metalliferous feed in an ironmaking process, the method comprising the steps of, pre-drying an iron containing sludge comprising reduced iron in a pre-dryer to an amount of 15 to 30% (w/w) moisture, mixing the pre-dried iron containing sludge comprising reduced iron with an organic binder material to form a mixture and to obtain a granulate, the granulate having a particle size of less than 4 millimeter, and drying the granulate to a maximum of 3% (w/w) moisture, thereby forming the metalliferous feed, subsequently injecting a stream of the metalliferous feed into a cyclone part of a metallurgical vessel for iron-making by a pneumatic transport system, wherein the mixture consists of the pre-dried iron containing sludge with the 15 to 30% (w/w) moisture and the organic binder material, and wherein the granulate consists of the pre-dried iron containing sludge and the organic binder material and moisture.

2. The method according to claim 1, wherein the metalliferous feed consists of the pre-dried iron containing sludge with a maximum of 3% (w/w) moisture and the organic binder material.

3. The method according to claim 1, wherein the binder material consists of a cellulose derivative.

Description

(1) In the drawing:

(2) FIG. 1 shows a metallurgical vessel with a cyclone part;

(3) Whenever in the FIGURES the same reference numerals are applied, these numerals refer to the same parts.

(4) FIG. 1 depicts the basic elements required for manufacturing iron according to the process disclosed in patent application EP-A-0 726 326, wherein a vessel 1 is applied with on top of the vessel 1 a cyclone 10. As FIG. 1 shows metalliferous feed 4 is injected in the smelt cyclone 10 at the top of the vessel 1. The metalliferous feed 4 melts and partly pre-reduces at this point, after which it drips into the vessel 1 and forms molten iron 2. Further FIG. 1 shows the bath of molten iron 2, a layer of slag 3, the introduction points for carbon containing material 5 and oxygen containing gas 7, iron outlet 8, slag outlet 9 and reaction gases outlet 11. For this invention only the introduction point of the metalliferous feed 4 is of importance.

(5) Experiments were conducted to study the size distribution and compressive strength of several granules. Granules were produced with a 5 L Eirich mixer with a two steps mixing procedure. First, BOS-sludge and binder (Peridur 300D) were loaded together and mixed at 2000 rpm for 45 sec to ensure good homogenisation. Secondly, the materials were mixed at 500 rpm for 45 sec to reach a stable granulation. The amount of moisture in the BOS sludge and binder content was varied. The Table shows the particle size distribution indicators with respect to the parameters of the tests.

(6) TABLE-US-00001 binder Moisture <0.25 mm drop sample (wt %) (wt %) D10 D50 D90 (wt %) test 1 0.2 17 0.11 0.62 2.26 23.7 + 2 0.4 17 0.09 0.63 2.53 27.6 + 3 0.6 17 0.08 0.56 2.62 29.4 + 4 0.2 21.7 0.62 1.39 2.50 1.5 + 5 0.4 21.7 0.57 1.45 3.02 2.1 + 6 0.6 21.7 1.07 2.60 4.78 1.4 +
Flowability studies with a Hosokawa powder tester on granulates filtered at different particle sizes (3 mm, 1 mm, 0.4 mm) indicated that the maximum particle size should be less than 4 mm, preferably less than 3 mm in order to enable smooth pneumatic injections. Therefore, the granules should preferably have a D90 below 4 mm, more preferably below 3 mm. Granules with a larger particle size can optionally be removed by a filter. The D10 should preferably be above 0.5 to avoid carry over. The mechanical resistance of the granules was tested by a drop test to establish the optimal binder content. 500 g of each sample was selected from the matured granules (dried from original moisture in the air) and dropped 2 times from a height of 2 m, the particle size distribution of the granules before and after were similar for all granules, indicating a good mechanical resistance, even at a binder content of 0.2%. In general, a lower binder content is desired, as this will reduce the overall costs of the granules.
Sample 4 was further subjected to a plate compression test, both for green and dried granules. The average diameters of the green and dried granules are 2.4 and 2.7 mm, respectively. The average breaking forces of the green (15 to 30% moisture) and dried (at most 3% moisture) granules are 4.65 and 18.05 N, respectively. Hence, the dried granules are much stronger and better suitable for pneumatic transport and storage.

(7) Although the invention has been discussed in the foregoing with reference to exemplary embodiments of the invention, the invention is not restricted to these particular embodiments which can be varied in many ways without departing from the invention. The discussed exemplary embodiments shall therefore not be used to construe the appended claims strictly in accordance therewith. On the contrary, the embodiments are merely intended to explain the wording of the appended claims, without intent to limit the claims to these exemplary embodiments. The scope of protection of the invention shall therefore be construed in accordance with the appended claims only, wherein a possible ambiguity in the wording of the claims shall be resolved using these exemplary embodiments.