Method for reducing chromium containing raw material

Inactive Publication Date: 2006-05-11
SUGITATSU HIROSHI +4
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0026] If the carbonaceous atmosphere-adjusting agent is charged together with the mixture onto the hearth, volatile components devolatilized from the atmosphere-adjusting agent and gases such as CO and H2 produced in the solution loss reaction of CO2 and H2O contained in the atmosphere gas keep the vicinity of the mixture in a reducing atmosphere to prevent the reoxidation of the reduced mixture. The volatile components and the gases such as CO and H2 can also be used as fuels for the radiation heating in the moving hearth furnace to reduce the fuel consumption in the moving hearth furnace. I

Problems solved by technology

Pellet prereduction is an excellent method with low power consumption; however, this method, involving the use of a rotary kiln for the pretreatment, has the following many problems unique to the rotary kiln.
Because the fundamental principle of the rotary kiln is based on the tumbling of feedstock, the rotary kiln disadvantageously produces a large amount of dust to readily cause dam rings therein.
In addition, the rotary kiln requires an excessive length due to variations in the residence time of the feedstock, thus involving a large equipment installation area and a large surface area.
Consequently, the rotary kiln disadvantageously dissipates a large amount of heat, leading to high fuel consumption.
Furthermore, a combination with externally added coke is disadvantageous in that it causes a large oxidation loss of the externally added coke in the rotary kiln.
As a result, the reduction of chromium oxide lags behind since chromium oxide is reduced less

Method used

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  • Method for reducing chromium containing raw material
  • Method for reducing chromium containing raw material
  • Method for reducing chromium containing raw material

Examples

Experimental program
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Effect test

first embodiment

[0032]FIG. 1 is a schematic diagram of a process according to an embodiment of the present invention. Reference numeral 1 indicates a storage container for a chromium-containing material containing chromium oxide and iron oxide (or the chromium-containing material); reference numeral 2 indicates a storage container for a carbonaceous reductant; reference numeral 3 indicates a granulator; reference numeral 4 indicates a charging path for a mixture (agglomerates) fed from the granulator 3; reference numeral 5 indicates a moving hearth furnace; reference numeral 6 indicates a transfer path for a reduced mixture (preferably, in the form of agglomerates); reference numeral 7 indicates a smelting furnace; reference numeral 8 indicates a path for recovered metal; and reference numeral 9 indicates a path for removed slag.

[0033] The chromium-containing material 1 used may be chromium ore or residues produced in the manufacturing process of ferrochromium, including dust and slag produced at ...

second embodiment

[0054]FIG. 2 is a flow chart including a step of reducing a chromium-containing material according to another embodiment of the present invention. In FIG. 2, reference numeral 11 indicates a storage container for a chromium-containing material containing chromium oxide and iron oxide; reference numeral 12 indicates a storage container for a carbonaceous reductant; reference numeral 13 indicates a granulator; reference numeral 14 indicates a path for a mixture (agglomerates); reference numeral 15 indicates a moving hearth furnace; reference numeral 16 indicates a path for a recovered reduced solid; reference numeral 17 indicates a screen; reference numeral 18 indicates a metal path (or metal); and reference numeral 19 indicates a slag path (or slag).

[0055] The chromium-containing material, the carbonaceous reductant, the granulator, the feedstock mixture (agglomerates), the moving hearth furnace, and the mixing step in the second embodiment are the same as those in the first embodim...

example 1

[0064] The following reduction experiment was conducted with a small heating furnace for laboratory use to grasp the reduction condition of a mixture in a moving hearth furnace according to the present invention.

[0065] A feedstock having a composition shown in Table 1, as the chromium-containing material, and coke breeze (fixed carbon content: 77.7 percent by mass), as the carbonaceous reductant, were mixed at a mass ratio of 85.7:14.3. A proper amount of water was added to the mixture, which was then granulated with a small disc pelletizer to prepare pellets having a diameter of 13 mm. These pellets were dried, were charged in batches into the small heating furnace, and were heated and reduced at a constant temperature for different retention times. The compositions of the pellets after the reduction were chemically analyzed to determine their Cr reduction degrees and Fe metallization degrees. This experiment was conducted in a nitrogen atmosphere at 1,200° C. and 1,300° C.

TABLE...

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Abstract

An object of the present invention is to provide a method for reducing a chromium-containing material at a high chromium reduction degree. In the method of the present invention, a mixture of a feedstock containing chromium oxide and a carbonaceous reductant is heated and reduced by radiation heating in a moving hearth furnace. The average rate of raising the temperature of the mixture in the reduction is preferably 13.6° C./s or higher in the period from the initiation of the radiation heating of the mixture until the mixture reaches 1,114° C.

Description

TECHNICAL FIELD [0001] The present invention belongs to the field of ferrochromium manufacturing technology and, specifically, relates to methods for reducing a chromium-containing material. BACKGROUND ART [0002] High-carbon ferrochromium (hereinafter simply referred to as “ferrochromium”) is manufactured by smelting and reducing chromium ore after pretreatment in a submerged arc electric furnace (hereinafter simply referred to as “electric furnace”). Examples of the pretreatment of the chromium ore include briquetting, sintering, pellet firing, and pellet prereduction. [0003] In pellet prereduction, chromium ore is pulverized with coke and is granulated to prepare green pellets, which are then subjected to reduction roasting in a rotary kiln at 1,300° C. or higher to provide prereduced pellets. The reduction degree of the prereduced pellets, which is 60% to 70% only with the internally added coke, reaches 80% in combination with externally added coke. This method therefore has a si...

Claims

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Application Information

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IPC IPC(8): C21B15/00C21B13/10C22B1/244C22B5/10C22B34/32
CPCC21B13/10C22B1/244C22B5/10C22B34/32Y02P10/134
Inventor SUGITATSU, HIROSHITANAKA, HIDETOSHIHARADA, TAKAOMIYAHARA, ITSUOKOBAYASHI, ISAO
Owner SUGITATSU HIROSHI
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