AU620344B2

AU620344B2 - Production of iron or high carbon fecr in a converter-type smelter

Info

Publication number: AU620344B2
Application number: AU23055/88A
Authority: AU
Inventors: Shigeru Inoue; Katsuhiro Iwasaki; Masahiro Kawakami; Hitoshi Kawata; Kenji Takahashi; Haruyoshi Tanabe
Original assignee: Nippon Kokan Ltd
Current assignee: JFE Engineering Corp
Priority date: 1987-09-10
Filing date: 1988-09-09
Publication date: 1992-02-20
Anticipated expiration: 2008-09-09
Also published as: EP0436718A1; EP0436718A4; EP0436718B1; AU2305588A

Description

i ii--i i P/00/011 Form PATENTS ACT 1990 COMPLETE SPECIFICATION

(ORIGINAL)

FOR OFFICE USE Class: Int. Cl: Application Number: Lodged: Complete Specification Lodged: Accepted: Published: Priority: Related Art: I- TO BE COMPLETED BY APPLICANT Name of Applicant: Address of Applicant: Actual Inventor/s: Address for Service: NKK CORPORATION 1-2 Marunouchi, 1-chome, Chiyoda-ku, Tokyo, 100, Japan Haruyoshi TANABE Masahiro KAWAKAMI Kenji TAKAHASHI Katsuhiro IWASAKI Shigeru INOUE Hitoshi KAWATA CARTER SMITH BEADLE Patent Trademark Attorneys Qantas House 2 Railway Parade CAMBERWELL VIC 3124 Australia Complete Specification for the invention entitled: A METHOD OF CHARGING CHROMIUM ORES IN A SMELTING REDUCTION The following statement is a full description of this invention, including the t -st method of performing it known to me:j i r i 8 j h J2:.-

I

BACKGROUND OF MHE INVENTION High Cr steel as stainless steel has been i TECHNICAL FIELD The present invention relates to a method of charging powder Cr ore raw materials, iron ores and coal in a smelting reduction thereof.

BACKGROUND OF THE INVENTION High Cr steel as stainless steel has been conventionally produced from ferrochromium as raw o "material. In view of saving energy and securing low production cost, a so-called smelting reduction method has been recently remarked, which directly obtains high Cr molten metal from Cr ores. In this method, Cr ores, coal and so on are charged into a reduction furnace of a converter type for reducing Cr so as to directly produce high Cr molten metal therefrom.

15 Cr raw ores are very fine in grain diameters, and ordinarily around 90% have grain diameters of not more than 1 mm. Therefore, when powder Cr raw ores are charged into the reduction furnace from its top part onto the Dath, they lose up to 30% by upflowing gas.

To avoid flying losses, an injection charging may be used, but special facilities are required independently therefor, and transporting pipes are easily damaged by hard Cr ores. Thus, such measures could not be adopted in practice.

25 In view of these circumstances, Cr raw ores are formed into pellets or briquettes, resulting in high S bc/10/7749nkk.spe 91 824 )TI ii -3production costs. If the ores are agglomerated, the specific surface areas of the ores reduce so that a preheating time is increased and the reduction rate is lowered to increase the treatment time.

On the other hand, as an iron making method in place of the furnace production, the smelting reduction method of iron ores has been remarked as stated above in view of saving the energy and securing the low o production cost.

10 In this smelting reduction method of iron ores, the flying loss of ores is not a big problem because the ores are coarse, but a considerable amount of coal combustion fuel is lost.

According to the inventors' studies, the reason why yield of the coal is inferior in the top charge method is because the coal is broken by the rapid increase in temperature. Since the coal has volatility and the interior of the smelting furnace is at very high temperature (more than 1400°C), the coal charged by top charge method abruptly increases in temperature, cracks Sand fine powders are exhausted out of the furnace together with the exhausted gas. The flying of the coal makes unit consumption of carbonaceous materials deteriorate in the smelting reduction of the iron ores.

The present invention is to provide a method of charging ores, carbonaceous material as checking their flying losses in the smelting reduction method of Cr i~~b .c/10/7749nkk. sp. 91 824; j 4 ores, iron ores and so on.

SUMMARY OF THE INVENTION To accomplishing this object in the invention, powder Cr raw ores, or iron ores and coal are charged into the furnace through a charging chute extending nearly a furnace mouth of the smelting furnace of the converter type or connected to the furnace body thereof, i so that the flying losses of the ores and coal are checked.

In addition, the powder Cr raw ores, the iron ores 'and the coal are charged into the furnace while the gas is jetted toward the outside of the charging chute, thereby enabling charge to the raw materials as checking effectively the flying losses.

15 Accordingly, the invention provides a method of S: charging raw materials in a smelting reduction of ores using a smelting reduction converter furnace comprising a vessel for holding molten metal and slag, means for supplying a first gas into said slag, a mouth, and a hollow chute located at the mouth of said furnace for supplying raw ore therethrough into said vessel; said method comprising the steps of charging raw ore into said vessel of said furnace through said hollow chute; and concurrently with the charging of raw ore supplying 1a second gas inside said hollow chute and substantially bc/10/7749nkk.spo 918 24 T -i i ;i-i i i i ili..i 5 about the inner circumferential periphery thereof and in the same direction of travel as the charging raw ore, so as to substantially surround the raw ore while travelling through the hollow chute and while travelling into said vessel of furnace, thereby to prevent flying of said charging raw ore.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURES 1 to 5 concern the smelting reduction of Cr ores, and FIGURE 1 explains one embodiment of the 10 invention; e FIGURE 2 explains another embodiment of the invention; FIGURE 3 explains a gas jetting from an end of the charging chute; *o a 15 FIGURE 4 investigates the flying losses of grain Cr raw ores of the invention method and the comparative method; FIGURE 5 investigates Cr increasing rate in the molten metal when powder Cr raw ores are charged and pelletized Cr raw ores are charged; FIGURES 6 to 8 concern the smelting reduction of iron ores; FIGURE 6 explains a further embodiment of the .3 invention; b' /10/7749nkk.spe 91 8 24 Ilmm__ l k j i- ~6 6 FIGURE 7 explains a still further embodiment of the invention; and FIGURE 8 investigates the flying losses of grain Cr raw ores of the invention method and the comparative method.

In the drawings, 1 is a furnace body, 6, 6' are chutes.

DETAILED DESCRIPTION OF THE INVENTION The invention will now be explained in detail.

S 10 FIGURE 1 shows one embodiment of the invention in the smelting reduction of Cr ore, where the reference numeral 1 is the furnace body, and 2 is an exhausting hood provided at a top part of the furnace body. In the smelting reduction method by the converter type, there 15 have been various proposals or studies which have a a different gas blowing practices. For example, as shown in FIGURE 1, the gases are blown from a top blowing lance 3, a side blowing tuyere 4 and a bottom blowing tuyere 5 for carrying out the smelting reduction.

During the treatment, Cr ores are supplied together with carbonaceous materials, and in the invention, the powder Cr raw ores are supplied by the chute 6 extending through the exhaust hood 2 to near the furnace mouth.

The charging chute 6 is determined so that the 2A 5 height of its lower end does not contact the furnace bc/10/7749nkk.spe 91 824 7 body when the furnace is tilted.

FIGURE 2 shows that the powder Cr and raw ores are charged via a chute 6' connected to the upper part of the furnace body 1, and also in this case the same effect could be obtained.

The charging chute 6' may be separated at a part 61 on the way, and when the furnace body is tilted, this part 61 is separated.

When charging Cr ores through the chute 6 or 6', the gas (air or N 2 is jetted toward the outside of the chute from the nozzle 7 provided in a circumferential direction around the inner part of the chute as shown in 1. FIGURE 3, so that powder Cr raw ores may be charged into the furnace and the flying losses of the raw materials are thereby avoided.

If the gas is jetted from the nozzle provided in the circumferential direction within the chute toward the outside of the chute, the powder Cr ores are guided in the gas jetting direction and the ore flying is avoided. Besides, the jet gas also serves as a purge gas for preventing invasion of CO and CO, from the furnace into the chute.

FIGURE 6 shows a further embodiment of the invention in the smelting reduction of the iron ores, t where the iron ores and the coal are charged into the *furnace from the chute 6. Other structures are the same *b c/10/7749nkk.sp 91 24 Li. ;-li I I- I 8 as illustrated in FIGURE 1.

FIGURE 7 shows that the iron ores and the coal are charged via the chute 6' connected to the top part of the furnace body 1, and the structure is the same as illustrated in FIGURE 2.

In the abovementioned chargings of the iron ores and the coal by the chute 6 or while the gas (the air or N 2 is jetted toward the outside of the chute from the nozzle 7 provided in a circumferential direction of S 10 the inner part in the vicinity of the chute as shown in :FIGURE 3, the iron ores and the coal may be charged into the furnace to thereby check the flying losses of the raw materials.

EXAMPLE 1 S 15 The smelting reduction was carried out as charging the powder Cr raw ores into the smelting reduction furnace (capacity: 5 ton) of the converter type by the method as shown in FIGURE 1. The dispersion in grain diameters of the charged Cr raw ores are as follows.

s 0 S+mm +0.5mm +0.25mm +0.149mm -0.149mm 1.7% 3.8% 20.1% 42.9% 31.5% bc/10/7749nkk.se 91 8 24 9 FIGURE 4 shows the flying losses of Cr raw ores at the above charging in comparison with the case (comparative method) not using the charging chute, from which it is seen that the flying losses of Cr raw ores were considerably decreased by the present invention method.

FIGURE 5 investigates Cr reducing rate (Cr increasing rate in the molten metal) when grain Cr raw ores were charged as they were, and the pelletized Cr .10 raw ores were charged, from which it is seen that the former is shorter to pre-heat the ores, and is faster to .reduce Cr than the latter.

•EXAMPLE 2 The smelting reduction was carried out as charging the Cr iron ores and the coal into the smelting reduction furnace (capacity: 5 ton) of the converter e type by the method as shown in FIGURE 6. The comparative method did not use the charging chute as shown in FIGURE 6, and practised the smelting reduction while charging the raw materials. The producing conditions are as follows.

*P

0* 91 824 g bc/10/7749nkk.ste 918 24

I

10 r r r r r r r r TABLE 1 Comparative Invention Method Method 02 for decarburization (Nm 3 /Hr) 1300 1300 0. for post combustion (Nm 3 /Hr) 1300 1300 Gas flow rate (m/sec) 7.7 7.7 Unit consumption of carbonaceous material (including the flying loss) (kg/molten metal ton) 950 665 Unit consumption of the flying loss of carbonaceous material (kg/molten metal) 285 0 FIGURE 8 shows the flying losses of the coal in comparison with the case not using the chute (the comparative method), from which it is seen that the flying losses of the coal was decreased considerably by the present invention method.

INDUSTRIAL APPLICATION The present invention is useful for charging of raw materials or the coal as the carbonaceous materials in the smelting reduction of the Cr ores or the iron ores.

A/tY~ bc/10/7749nkkspe 91 824

Claims

1. A method of charging raw materials in a smelting reduction of ores using a smelting reduction converter furnace comprising a vessel for holding molten metal and slag, means for supplying a first gas into said slag, a mouth, and a hollow chute located at the mouth of said furnace for supplying raw ore therethrough into said vessel; said method comprising the steps of charging raw ore into said vessel of said furnace 10 through said hollow chute; and o concurrently with the charging of raw ore supplying a second gas inside said hollow chute and substantially about the inner circumferential periphery thereof and in the same direction of travel as the charging raw ore, so as to substantially surround the raw ore while travelling through the hollow chute and while travelling into said vessel of furnace, thereby to prevent flying of said charging raw ore.

2. The method of claim 1, wherein the charging raw ore is chromium ore.

3. The method of claim 1, wherein the charging raw ore is iron ore and coal.

4. The method of claim 1, wherein the second gas is supplied at least at the end of the hollow chute 25 closest to the furnace mouth. bc/10/7749nkk. spe 91824 I T 0- Cr ore B slag molten metal 12 method of claim 1, wherein the second gas is air., E~ *5 o S a S S S. S S *5 *5

5 S 9 U. .9

6. The method of claim 1, wherein the second gas is nitrogen.

7. The method of claim 1, wherein the hollow chute comprises a first part fitted to the furnace, and a second part movably attached to the first part.

8. A method of charging raw materials in a smelting reduction of ores substantially as hereinbefore described with reference to the accompanying drawings. DATED this 24 August 1991 CARTER SMITH BEADLE Fellows Institute of Patent Attorneys of Australia Patent Attorneys for the Applicant: NMKK CORPORATION bc/1O/7749lk. op.91B2 91 824