US2845343A - Method for controlling the bath temperature in a blast furnace - Google Patents

Description

July 29,'1958 KURO KANAMORI' METHOD FOR CONITROLLINC; THE BATH TEMPERATUREJN A BLAST FURNACE Filed Jan.

roEcuzamarz' Unit d METHOD FOR CUNTRGLLING THE BATH TEMPERATURE IN A BLAST FURNACE Kuro Kanamori, Suginami-kn, Tokyo-to, Japan, assignor of one-half to Yawata Seitetsu K. K. (Stock Company),

Chiyoda-ku, Tokyo-to, Japan This invention relates to a method for adjusting the bath temperature in a blast furnace.

It is well-known that bath temperature in a blast furnace is an important factor for the reaction in said furnace and the operation thereof. Therefore, if it is possible to adjust at will said temperature, it brings a remarkable improvement of the efiiciency in the furnace operation. The bath temperature, however, has a relation to various conditions in the furnace, so that it has been regarded that for the adjustment of said temperature' there are no methods except an indirect method such as adjustment of the amount of charge or the temperature of the air fed into the furnace because of dif-' ficulty in direct and simple adjustment of said temperature.

Therefore, a principal object of this invention is to provide a method capable of adjusting simply and effectively the bath temperature in a blast furnace.

According to this invention, said object and other objects of this invention have been accomplished by directly adjusting the temperature of the molten pig iron in the blast furance by means of feeding under pressure any one or mixture of the substances such as oxygen, nitrogen, carbon dioxide, water vapour and water through a pipe which is inserted intothe molten pig iron in the bath of the blast furnace through the inclined tuyere arranged at the slagging hole or the furnace wall. Said feeding under pressure can be done so that water may be fed together. with said gas or gases and the other substances maybe fedindividually or under mixed condition.

The oxygen fed as above acts to increase the bath temperature by subjecting the silicon, manganese, carbon etc. contained in the molten pig iron to a combustion and the other substances fed as above act to derive said pig iron of a heat through a physical and chemical reaction such as conductivity, evaporation, dissociation etc., so that it is possible to adjust at will the temperature of the molten pig iron by varying the mixing ratio of said substances.

The objects and advantages of this invention will be apparent from the following description taken in connection with the drawings, wherein:

Fig. 1 is a vertically sectioned elevation of a blast furnace for embodying the principle of this invention.

Fig. 2 is a vertically sectioned elevation of the attached apparatus for measuring the temperature of the bath, which can be employed whenever necessary to this operation.

As shown in Fig. 1, when water is applied to the operation, a blow pipe 3 is inserted into the bath through the inclined tuyere 2 of the blast furnace 1. Said pipe 3 is employed so that oxygen and inert gas may be blown into the molten pig iron 4 through said pipe and water may be emitted into said pipe through a connecting pipe 6 from a water tank 5.

The apparatus for measuring the bath temperature, as shown in Fig. 2, comprises a carbon pipe 7 inserted into the molten pig iron 4 through the wall hole 8 made in atent O the furnace 1, and end temperature of said pipe 7 can be measured through the upper opening 9 thereof by a proper pyrometer, whereby the temperature of the molten pig iron can be easily measured.

According to the present invention, the following merits .will be obtained.

(a) The such impurities contained in the pig iron as silicon, manganese, carbon etc. can be readily oxidized by feeding oxygen or the mixture of oxygen and nitrogen under pressure into the bath of the blast furnace, resulting in temperature rise of the bath due to the heat produced by oxidation, so that the bad condition due to temperature decrease in the furnace can be easily recovered.

On the other hand, if a strong basic slag and a reduc-' ing atmosphere are established effectively in the furnace,

the desulphurization and reduction of manganese will be promoted, whereby it becomes possible to produce an excellent pig iron of low silicon, low sulphur, high manganese and high temperature.

Example.0peration was held on a 3-ton test furnace during the period from November 10, 1951, to November 14, 1951. Operation conditions were as follows:

The operation result of said period was as follows: The diiference between the tapping temperature at the tapping hole and the hearth temperature at the furnace base (temperature at the carbon pipe) was over 200 C.

Moreover, the number of times for tapping out the pig iron increased and the composition of the ,pig iron was so deteriorated as of lower silicon and manganese, and higher sulphur content.

Another operation was held during the period from November 15, 1951, to November 19, 1951.

During said period, the amount of limestone was increased up to 44 kg. to produce a strong basic slag, while the mixture of oxygen and nitrogen was fed at a high pressure into the molten pig iron through a pipe 3 as shown in Fig. 1.

Said feeding was adjusted so that the temperature at the furnace base may be maintained at about l400 C.-

v Theresult of said operation was-as follows:

The difference between the temperature at the tapping hole and the temperature at the bottom of the hearth was reduced, number of tapping times decreased, sulphur c'ontent of the pig iron decreased, and manganese content increased. I

Total results of the operations were figured as follows:

Tapping Hearth Contents of pig-iron Number temperatempera- Basicity Date of times ture ture of slag (N o v.) (on (mean. (mean (mean) Si, Mn, S, blowing 'C'.) 0.) perperpercent cent cent 1, 315 1,110 1. 30 0. 91 0. 70 O. 200 0 1, 320 1, 100 1.23 0. 73, 0. 76 0.210 0 l, 320 1, 105 l. 28, 0. 29 O. 40. 0. 327 0' 1,330 1,105 1. 30 0. 35 0. 43 0, 279 Q 1, 340 1,165 1. 29 0. 27 0. 37 0. 344 6- 1, 360 1, 285 1. 38 O. 23 0. 39 0. 183 1, 390 1, 395 1. 51 0. 09 0. 87 O. 098 4 1, 385 1, 425 1. 48. 0. 42 1. 57 0. 040 4 1, 425 1, 435' 1. 47 0. 24 1. 02 0. 044 1 1, 405 1, 415 1. 50. 0.59 1. 44. 0.038

Basicity of the. slag is a ratio CaO/Si0 on the basis of percent by Weight of each compound in the slag.

(b), In theoperation of a blast furnace, when the silicon content in the pig iron is too high due to excessively high temperature of the bath, it is possible to decrease said silicon content by feeding water or other gas besides oxygen and nitrogen under suppressing the temperature rise at the bath.

(c) It is possible. to maintain continuously the bath temperature at an optional constant value resulting in very stability of the furnace operation. Furthermore, it is possible to protect rapid corrosion due to oxidation of the feeding pipe and tuyere.

under pressure into the molten pig iron through said pipe to decrease the temperature of the molten pig iron. On the other hand, oxygen, air or their mixture was fed under pressure to remove the contained chrome by oxidation thereof. Out of these substances to be fed, water may be fed together with a gas such as N CO 0 air, or their mixture, While the others may be fed individually or in their combination.

The mixing ratio and feeding rate were adjusted. so that the temperature of the molten pig iron may become fastly up to the value suitable for oxidation of chrome and said suitable temperature may be maintained continuously.

(A) Dechromation at an acidic operation.--The-composition of the charge was as follows:

COk Omonhon Honalrnn Lime.

kg. ore, kg. ore, kg. stone, kg.

The feeding rate of air was 18 m. /min. and. the torn perature thereof was 400 C.

(1) The case, wherein CO was employed: After tho. I

as shown, in the following table, whereby. the temperature at the pig iron was adjusted between 1255 C.-1380. C.

('d), It becomes possible to remove remarkably the 30 The dechromation factor in said react1on.was.87%.

Amount Blowing Temperature Blowing gas (111. time variation, Baslcity Gr Percent'in ptgdtun (min) C.

Sample from inside furnace, 0.99; 001 15.1...- s. 1, 325-1, 315

20 1, 295-1, 260 13. 1. 255-1, 340 151 1, 340-1, 380 (12) Sample from Mr furnace, 0.43. CO: 35. 7 15 1, 350-1, 270 Ston (11) 0z+air (01-50%) 22.9 (01)-- 12 1, 270-1,35o

Pig iron out, 0.54--- Pig iron out, 0.18.

Consequently, smelting of the ore, r

containing chrome or nickel-chrome, which has been regarded as most diflicult to treat in the blast furnace (2) The case, wherein CO and N were employed? After the lapse of six hours from production of pig iron,- such operation as shown in the following table was carried out. By controlling the temperature of the bath at! value between 1270 C.-1380 C., the dechromatioir factor of 79.5% was obtained.

Amount Blowing time Temperature Blowngas (mfl) (min) variation, Basicity Cr percent-in C. pig iron 36.0""--- 18 min. 15 sec--. 1, 330-1, 295

(11 sec) 7 22.4 11 sec 1, 290-1, 275 (7 sec.)

20.2 (O 13 min., 25 sec. 1, 270-1, 370 Slag out, 0.49..

(21 sec) 0.67. 39.9 15 sec 1, 350-1, 255 m 0r-air (Oz-50%) 26.5 (01)-- 14 sec 1,265-1380.

Pig iron out, Plg'ironont; 0.84. 0.29.

operation, becomes possible by the very method of this invention.

Example-..A 3-ton test furnace was employed and Omonhon sintered ore was used as the starting ore, which contains nickel and chrome. The mixture of said; one and Hongkong me being equal amount witsflihfitfi'id: so that the pig iron produced in the bath may contain, chrome of about 1 A blow pipe is inserted-into the moltenpig iron. in the bath through theinclined tuyere and water, water vapour, air, or carbon dioxide is. 7.5

(B) Dechromation at a basic 0perati0n..The composition of the charge was as follows:

Cok Omonhon Hong- Limekg. ore, kg. kong ore; stone,

conditions at the experimental furnace andby few nurrl:

ber of times of experimental treatment. 1

Therefore, it will be right that if the temperature con-. dition are same, dechromation factor over 90% will be? obtained in the same furnace conditions. i

Since it is obvious that many changes and modifications can be made inthe' above-described details without departing from the nature and spirit of invention; it" is not limited within said examples and illustrations.

Blowing gas Amount Blowing time Temperature Basicity Or percent in (1.11. (min) variation, C. pig iron 1,335l,390- Slag Out, 0.93..

6 m 1,3401, (3 min., see.)

11 5 7min 1370-1 295 0.32. (2 min., 30 sec.) 32 16 min Stop (3 min s 02 air (02-50%) 16. 2 9 min. Stop (6 min 0. 22. 0: air (Or-%) 11.9 7 min 1, 355-1, 395.- O 35 Pig iron out, 1 1g iron out,

(2) The case, wherein water was employed: I claim:

After the lapse of seven hours from tapping, bath was cooled by feeding water under pressure together with air into the molten pig iron by means of the apparatus as shown in Fig. 1. Then the pig iron was oxidized by blowing oxygen enriched air into pig iron. Said operations were repeated two times and the following table shows the results obtained.

In said operation, blow pipe 3 was inserted into the bath through the inclined tuyere 2 of the furnace 1 and through it gas was fed into the molten pig iron 4, while water in the tank 5 was emitted into said pipe 3 through connecting pipe 6.

l. A method for controlling the bath temperature in a 35 blast furnace which contains molten pig iron in the hearth thereof, which comprises forcing water under pressure and in the form of finely divided liquid particles directly into the said molten pig iron, whereby a temperature change in the bath temperature is achieved incidental 0 to the heating of the water and the change thereof from Blowing gas Amount (mfi) Blowing time Temperature Basicity Cr Percent in (min) variation, 0. P iron 0. 92. 7 min., 25 see 1, 430-1, 425.--. (4 min)..." 6 min 1,415-constant.

(3 min.).. 3 min., 35 sec.

m 7 min, 25 sec Lass-1,345...

According to the examples as above, it seems that dechromation factor is different in various cases.

How-

pressure and in the form of finely divided liquid particles and also a member selected from the group consisting of ever, said difierence is caused by difference of the internal oxygen, nitrogen, carbon dioxide and mixtures thereof 7 under pressure 'directly into the said molten pig iron, whereby the heating of the water and the change thereof from the liquid phase into the gaseous phase in situ in the moltenpig iron results in a change in the temperature characteristics of the latter.

3. A method for controlling the bath temperature in a blast furnace which contains molten pig iron in the hearth thereof, which comprises forcing water under pressure and in the form of finely divided liquid particles and, as sole gaseous constituent, carbon dioxide under pressure directly into the said molten pig iron, whereby a temperature change in the bath temperature is achieved incidental to the heating of the water and the change thereof from the liquid phase into the gaseous phase in situ in.the molten pig iron and incidental to the thermal decomposition of the carbon dioxide. 7

4. A method for controlling the bath temperature-in a blast furnace which contains molten pig iron including at least one undesired oxidizable impurity in the hearth thereof, which comprises forcing water under pressure and in the form of finely divided liquid particles and a mixture of oxygen and nitrogen under pressure directly into the said molten pig iron, whereby the heating of the water and the change thereof from the liquid phase into the gaseous phase in situ in the molten pig iron may be used to maintain the temperature of the bath at a sub hearth thereof, which conprises forcing a heat controlling agent consisting of carbon dioxide directly into the said molten pig iron, whereby the decomposition of the said carbon dioxide alters the temperature characteristics of the latter.

References .Cited in the file of this patent UNITED STATES PATENTS 24,060 Shunk May 17, 1859 1,420,127 Moxham June 20, 1922 FOREIGN PATENTS 915 Great Britain of '1859 2,090 Great Britain of 1856

Claims (1)

1. A METHOD FOR CONTROLLING THE BATH TEMPERATURE IN A BLAST FURNACE WHICH CONTAINS MOLTEN PIG IRON IN THE HEARTH THEREOF, WHICH COMPRISES FORCING WATER UNDER PRESSURE AND IN THE FORM OF FINELY DIVIDED LIQUID PARTICLES DIRECTLY INTO THE SAID MOLTEN PIG IRON, WHEREBY A TEMPERATURE CHANGE IN THE BATH TEMPERATURE IS ACHIEVED INCIDENTAL TO THE HEATING OF THE WATER AND THE CHANGE THEREOF FROM THE LIQUID PHASE INTO THE GASEOUS PHASE IN SITU IN THE MOLTEN PIG IRON.

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