AU596253B2

AU596253B2 - A blast furnace

Info

Publication number: AU596253B2
Application number: AU82946/87A
Authority: AU
Inventors: Hirohisa Hotta; Hitoshi Kawada; Yotaro Oono; Kazuhiko Tsujimoto; Kazumasa Wakimoto
Original assignee: Nippon Kokan Ltd
Current assignee: JFE Engineering Corp
Priority date: 1986-12-27
Filing date: 1987-12-22
Publication date: 1990-04-26
Anticipated expiration: 2007-12-22
Also published as: KR880007746A; CN1007161B; DE3787518T2; KR930004473B1; DE3787518D1; CN87105991A; EP0273420A2; EP0273420A3; EP0273420B1; AU8294687A

Description

FORTY Ul-L'-n j M IL OFICER.. I .4

AUSTRALIA

PATENTS ACT 1952 COMPLETE SPECIFICATION Form

(ORIGINAL)

FOR OFFICE USE Short Title: Int. Cl: Application Number: Lodged: 3* 3 t re 33 33 Complete Specification-Lodged: Accepted: Lapsed: Published: Priority: Related Art: This document contains the amendments made under Section 49 and is correct for printing.

TO BE COMPLETED BY APPLICANT Name of Applicant: Address of Applicant: I I I I '41 NIPPON KOKAN KABUSHIKI KAISHA 1-2, 1-CHOME, MARUNOUCHI,

CHIYODA-KU

TOKYO

JAPAN

CLEMENT HACK CO., 601 St. Kilda Road, Melbourne, Victoria 3004, Australia.

Actual Inventor: Address for Service: Complete Specification for the invention entitled: A BLAST FURNACE The following statement is a full description of this invention including the best method of performing it known to me:-

SPECIFICATION

Title of the Invention A Blast Furnace Background of the Invention Field of the Invention The present invention relates to a blast furnace for iron-making, and more particularly, to blow-in of preheating gas to preheat burdens introduced into a r Ir ii' blast furnace.

Description of the Prior Arts 4' rI 4 10 In the conventional blast furnace operation for producing pig iron from iron ores, hot air blast has been dependent mainly blow-in through tuyeres almost without exception. Nitrogen, occupying 79% of blast air content, takes no part in reduction, but contributes to 15 giving enormous calories to burdens piling between a level of and the stock line of the blast furnace to Saccelate the gas reduction. In other words, nitrogen has work of heat supplementary aid to cokes which work as reduction agent and as heat source. Therefore, it is particularly effective in preheating burdens existing in the upper portion of furnace shaft, and so there has been no need of heat supply for preheating the burdens.

Recently, in order to raise productivity in blast furnace operation, or make use of furnace top gas material for synthetic chemical products, various 0'

I

2 methods for blast furnace operation wherein blast gas blown in through the tuyeres is mainly composed of oxygen have been proposed. For example, a method is disclosed in a Japanese Patent Application Laid Open (KOKAI) No. 159104/85 wherein: Through a furnace top, burdens composed mainly of iron ores and cokes are charged into a blast furnace; Through furnace tuyeres, pure oxygen, pulverized coal and temperature control gas which prevents flame temperature at the tuyere nose from rising are blown in; Through an intermediate level of the blast furnace, preheating gas which is free substantially from nitrogen is blown in to preheat the burdens; and 0.4. 15 By means of the pure oxygen blown in, the cokes o" included in the burdens are burned to melt and reduce the 0 iron ores charged as well as to generate a blast gas which is substantially free from nitrogen from the furnace top.

With this method, however, it is difficult to maintain a stable blast furnace operation with a low fuel I ratio throughout a long period of time.

Summary of the Invention *t.0 According to the present invention there is provided a blast furnace comprising: S.*25" a blast furnace body; 0 00 0 0 00 82946/87 r i 3 tuyeres set in a lower part of the blast furnace body, at a given distance from a stock line, through which gas of at least 40 vol. oxygen is blown into the blast furnace body; means for producing a high-temperature preheating gas; and blow-in inlets coupled to the preheating gas producing means and placed in a position downward from said stock line within the range between 0.15 and 0.60 of said given distance.

The other features of the present invention will become more apparent from the detailed description to follow, taken in conjunction with the appended drawings.

Brief Description of the Drawings 15 Fig. 1 is a sectional vertical view of a blast furnace of the present invention; Fig. 2 is a horizontal end view of the blast furnace, taken on line II-II in Fig. 1, according to the present invention; Fig. 3 is a graphic representation showing relation of relative position of blow-in inlets to fuel ratio of the blast furnace according to the present invention; Fig. 4 is a graphic representation showing relation of relative position of blow-in inlets to Si content in .25 molten iron; and Fig. 5 is a schematic sectional view of a burner of the present invention.

00001 9 0 90 f 6 0 *0I 06 06 01 4 r 82946/87 i. Cl- 4 Description of the Preferred Embodiment With specific reference to Fig. 1 of the drawing, an embodiment of a blast furnace according to the present invention will now be described.

Fig. 1 shows a vertical sectional view illustrating a blast furnace of the present invention. Burdens composed of iron ores, cokes and fluxes are charged into the blast furnace until they pile up to a predetermined level of stock line 14. Tuyeres 12 are set in blast furnace body 11. The level of the nose of each tuyere is indicated by the line 15. Through tuyeres 12, gas of 40 vol.% or more oxygen, pulverized coal and flame temperature control agent are blown in into the blast furnace. Blow-in inlets 13 for f •introducing preheat gas are set in a level at 0.50 apart from the stock line where a distance from the stock line 15 t through the level of the tuyeres equals to 1.0. The blow-in inlets constitute a set consisting of sixteen inlets set in a single level, and have a downward sloping of an angle of 250 with respect to the horizontal level.

Through these blow-in inlets 13, preheating gas is introduced into the blast furnace to preheat the burdens.

coc Thus the gas of 40 vol.% or more oxygen blown in allows cokes and pulverized coal to perfectly combust, and thanks to the generated reduction gas of high temperature, iron o 25 ores are melted and reduced to pig iron and slag. Fig. 2 is a horizontal end view taken on line II-II in Fig. 1.

82946/87 i I- -i 5 16 blow-in inlets 13 are set, in an equal interval, one another on the peripheral circle.

Position of Blown-in Inlets In the embodiment, the position of blow-in inlets is set at the level of 0.50 downward from a stock line where a distance between the stock line and a level of the tuyere nose equals to 1.0. The position, however, can be set at any point of a range of 0.15 to 0.60 downward from the stock line. The position ranges more t I 10 preferably 0.30 to 0.55 from the stock line.

f* The reason for limiting the range of the position I I will now be described.

Fig. 3 graphically representsrelation of a relative position'of blow-in inlets 13, to a fuel ratio in blast furnace operation. In the abscissa, a ratio of a distance from a stock line to a position of the blowin inlets is shown where a distance between the stock 'line and the level of the tuyere nose eauals to S, Fig. 4 graphically shows4relation of a relative position of blow-in inlets 13 for introducing preheating gas to Si content in molten pig iron. In the abscissa, similarly to Fig. 3, a ratio of a distance between a stock line and a position of the blow-in inlets is shown where a distance from the stock line and the level of the blow-in inlets equals to As seen from Fig. 3, in the range of 0.15 to 0.60 downward from the stock line where a distance between

V@B~

~-I

-6 the stock line and the level of the tuyere nose equals to 1, fuel ratio is low enough to range 500 to 600 kg/ton., molten pig iron, and, in addition, trouble occurrence is also infrequent. If the blow-in inlets are set in a position of less than 0.15 downward from the stock line, decrease of molten iron temperature or damage of wearing plates occurs in the case that a blast furnace is operated at a fuel ratio of 650 kg/ton., molten pig iron or less. If the blow-in inlets are set ttt.

in a position of over 0.60 from the stock line, decrease of molten iron temperature or hanging occurs. When the blow-in inlets are set in a position of less than 0.15 or more than 0.60 from the stock line, it is impossible to maintain a stable blast furnace operation throughout a long period unless the blast furnace is operated at a ,i fuel ratio of more than 700 kg/ton., molten pig iron.

lt As recognized from Fig. 4, when the position of the blow-in inlets is set at 0.15 to 0.60 downward from t it i the stock line, Si content in molten iron is reduced to almost 0.30 wt.% or less. This is quite advantageous to the blast furnace operation, since desiliconization after tapping of molten iron becomes needless.

The position of the blow-in inlets for preheating gas ranges more preferably 0.30 to 0.55 downward from the stock line. This range reduces further not only the fuel ratio but also the Si content in molten iron.

Thanks to limiting the position range of blowing i -7in preheating gas as described in the foregoing, reduction of the fuel ratio, prevention of operation trouble and production of low Si molten iron can be attained.

Levels of Blow-in Inlets and. Number thereof in Each Level Preheating gas is blown-in, based on the results of measuring burden temperature or gas temperature by means of probes provided with in the intermediate ii., o 10 portion of the furnace shaft. The blow-in of the 4.

S",0 preheating gas is blown in through a single or multiple t #4° ,,levels of the blown-in inlets. In the case of the blowing through the multiple levels of the blow-in inlets, blow-in inlets of each level set in peripheral r circle of the furnace wall are divided into some zone t groups, and then, if gas amount and gas temperature is I 4 varied simultaneously between an upper group and a lower zone group which are vertically positioned in the same zone, the effect in preheating comes out by far quicker than in the case of the blowing control through the single-level of the blow-in inlets. In the case of the multiple levels of the blow-in inlets, it is preferable to design the arrangement of the blow-in inlets so as to at allow gas amount or gas temperature to be changed4everlevel, or between blown-in inlets adjacent to each other on the same level. In this arrangement, various optional controls can be carried out. In addition, in i iI-- 8 the case of blowing in through the multiple levels of the blow-in inlets, it is preferable that each of the blow-in inlets is positioned so as to form a staggered parallel one another in relation to up and down levels in. view of allowing gas to flow up uniformly along the periphery of the furnace wall.

When the same amount gas is blown in without change of temperature, it is desirable to blow in preheating gas of high temperature through branch pipes deriving from a ring-shaped pipe. These blow-in inlets of every level are not specifically limited in number.

8 to 18 of blow-in inlets are preferable so as to allow gas constituent and temperature prevailing near the furnace wall to become almost homogeneous at the vicinity of the stock line level. Furthermore, different levels of the blow-in inlets range preferably 1 to 4 levels in number.

X Angle of Blow-in Inlets V% t It is preferable that an angle of downward slope of the blow-in inlets to be set in the blast furnace body is larger than a repose angle of burdens. This is because powdery particles of burdens block openings of the blow-in inlets. The downward slope of the blow-in inlets into the in-furnace with regard to the horizontal level ranges preferably 20 to 500. If the downward slope is less than 200, the powdery particles of burdens block the openings of the blow-in inlets. On the other i -i 9 hand, it is useless to let the downward slope be more than 50°, considering that the repose angle of the burdens is 45 to 500 at the most. In addition, more than 50° downward slope is undesirable in view of protecting a furnace body, since, due to this obtuse angle, blow-in holes become large.

Preparation of Preheating Gas There are two methods of preparing preheating gas to be considered.

One is a method wherein preheating gas is generated, by means of furnace top gas generated from a blast furnace and oxygen, in a combustion furnace built in the neighbourhood of the blast furnace. In carrying out this method, it is recommendable that in order to blow-in preheating gas uniformly into a blast furnace, I t hot blast leading pipe is let to go upto the furnace shaft level and still to connect to fireproofed heavy l ring-shaped pipe, which are further connected, by means of lots of branches, to every blow-in inlet.

In another method, gas burners having a fuel gas supply pipe, an oxygen supply pipe and a gas temperature control gas supply pipe are set at the blow-in inlets to introduce preheating gas into the blast furnace. Every or A tle burner independently controlsjtemperature and 4 amount of preheating gas by controlling fuel gas amount and oxygen gas amount. Those transfer pipes leading to the burners are not required to be fireproofed. In this method

A'

L111 10 different from the first method wherein hot blast is transferred from a large-scaled combustion furnace, a burner is set at every blow-in inlet and gas temperature, and the amount can be freely and simply controlled at every one of the blow-in inlets. Furthermore, there is no need for laying a heavy ring-shaped hot blast pipe on the furnace shaft. In operation, quick response to movement of furnace conditions can be practised.

Fig. 5 schematically illustrates a sectional view of a burner to be used for the present invention. Either of fuel gas supply pipe 21 and oxygen supply pipe 22 is connected to burner body 28 in such a manner that the gas flow amount can be freely controlled. Pilot burner 29 is set at a portion where oxygen jets out. The outer side of 15 the burner body is covered with a sheet iron shell 27. Gas *o supply pipe 25 is also jointed to burner body 28 for controlling freely temperature of gas generated in the o burner. The sheet iron shell 27 is lined with refractory 26. Pipes for cooling water are composed of water feed pipe 23 and water drain pipe 24.

9 0 9 0i 9.

4 9 82946/87

Claims

1. A blast furnace comprising: a blast furnace body; tuyeres set in a lower part of the blast furnace body, at a given distance from a stock line, through which gas of at least 40 vol. oxygen is blown into the blast furnace body; means for producing a high-temperature preheating gas; and blow-in inlets coupled to the preheating gas producing means and placed in a position downward from said stock line within the range between 0.15 and 0.60 of said given distance.

2. A blast furnace according to Claim 1, wherein said range is from 0.30 to 0.55 of said given distance.

3. A blast furnace according to Claim 1, wherein the blow-in inlets are arranged in a single level of Che blast furnace-body.

4. A blast furnace according to Claim 1, wherein the blow-in inlets are arranged in at least two different levels of the blast furnace body. A blast furnace according to Claim 1, wherein the blow-in inlets have a downward sloping angle into the blast furnace body of 20 to 50 with regard to a horizontally t level line. 8294 6/87 2 NT ~PIIIC~ICI) IIIILII~mY ~rPL 12

6. A blast furnace according to Claim 1, wherein the preheating gas producing means include having gas burners equipped with fuel gas supply pipes, oxygen supply pipes and gas conveying pipes for controlling gas temperature of the preheating gas.

7. A blast furnace according to Claim 1, wherein said preheating gas producing means includes a combustion furnace wherein a furnace-top gas generated therein is combusted to produce a high temperature preheat gas, a hot blast conveying pipe in communication with a ring-shaped pipe, wherein the preheat gas is transferred, through branch pipes, from the hot blast conveying pipe to the blown-in inlets.

44.4 4111 Cott 8. A blast furnace substantially as described herein with reference to and as illustrated in the accompanying t t drawings. DATED this 23rd day of January, 1990. NIPPON KOKAN KABUSHIXI KAISHA By Its Patent Attorneys #Ott r414 Sr GRIFFITH HACK CO. Fellows Institute of Patent Attorneys of Australia. 4 t 82946/87 eo~ 82946/'87