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Page 1: Study on Technology of KR Desulfurization for Hot Metal with Vanadium and Titanium

Study on technology of KR desulfurization for hot metal with vanadium and titanium

Wang Jian1 a, Ge Wensun1 b, Chen Lian1 c, Huang Shengquan2 d, Fan Jiarong 2 e Zhong Zhenghua2 f

1PanGang Group Research Institute Co.,Ltd. , State Key Laboratory of Vanadium and

Titanium Resources Comprehensive Utilization,Panzhihua 617000, Sichuan, china

2Pangang Group Chengdu steel & vanadium Co.,Ltd. , Chengdu, 610303, Sichuan.

[email protected], [email protected], [email protected], [email protected], [email protected]

Key words: hot metal with vanadium and titanium, KR desulphurization, slag modifier for

desulphurization, desulphurization rate.

Abstract. Through the adjustment of desulfurizer in KR desulfurization process, the efficiency of

desulfurization is increased obviously on condition of maintaining the same KR desulfurization

process. While the desulfurization rate is as high as 84.2% and this is 3.2% higher than that before

optimization. Consumption of desulfurizer is 12.3kg/t hot metal on average which is 1.4kg/t hot

metal than that before optimization. In addition, TFe content in desulfurizing slag is 10.4%, which

is reduce by 3.25% of the value before optimization. There is nearly the same content of carbon and

vanadium in hot metal. The optimized desulfurizer can be used in KR desulfurization process, and

wonderful results have been gotten. Therefore, it has a good prospect of application.

Introduction

It plays an important role for hot metal desulphurization to lighten the loads of converter

steelmaking, to heighten the cleanliness of molten steel and to heighten the product quality.

Therefore, hot metal desulphurization is applied in steelmaking plants widely. And it is beneficial to

economic benefit improvement for steelmaking plants.

There are dozens of desulphurization methods for hot metal, such as mechanical stirring, gas

stirring, dusting method, and so on. At present, usual desulphurization process contains KR

desulphurization, Mg particles injection, Co-injection with magnesium-based desulphurizer, mixed

powder injection process.

Hot metal desulphurization developed in China in the 1970s, and at that time, hot metal

desulphurization stations were established in Panzhihua steel, Bao steel, Wu steel and An steel, etc.

In recent years, Mg-based desulphurizer is applied widely at home and abroad, and wonderful

application effects have been gotten. With the Mg-based desulphurizer, sulfur content in hot metal

is in 0.020%, and even is bellow 0.005% in foreign enterprises and Bao steel.

Slag adjustment technology of hot metal desulphurization is developed combined with the

advantages of KR desulphurization dynamics [1]. Industrial tests show that the desulphurization is

84.2%, which is higher than that of before (81%). And desulphurizer consumption is reduced by

1.4kg/t hot metal. It does not affect the content of carbon and vanadium in hot metal in

desulphurization process. In addition, total Fe content in desulfurized slag is 10.4% on average,

which is 3.25% lower than that of before optimization. Furthermore, it is beneficial to cost control.

Advanced Materials Research Vols. 581-582 (2012) pp 1077-1082Online available since 2012/Oct/22 at www.scientific.net© (2012) Trans Tech Publications, Switzerlanddoi:10.4028/www.scientific.net/AMR.581-582.1077

All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP,www.ttp.net. (ID: 130.207.50.37, Georgia Tech Library, Atlanta, USA-14/11/14,14:47:31)

Page 2: Study on Technology of KR Desulfurization for Hot Metal with Vanadium and Titanium

Characteristics of hot metal with vanadium and titanium

Compared with Bao steel, An steel and Wu steel, it is difficult to desulphurize for hot metal in

Panzhihua steel. It is because of the characteristics in Panzhihua steel, and the characteristics are as

following: ① with vanadium bearing titaniferous magnetite as materials, sulfur content in hot metal

is 0.05%~0.070% higher than that of other plants (Ben steel and An steel); ② the temperature of

hot metal is 40~50℃ lower than that of other plants, and because of low Si content, low

temperature, and the exist of vanadium and titanium, it is difficult to desulphurize. ③ lots of

precipitates such as TiC,TiN, Ti(C, N) and other dystectic precipitates will be formed with the

CaO-SiO2-Al2O3-TiO2 system BF slag, which will take bad dynamic conditions for

desulphurization [2]

.

Program design of slag adjustment for desulfurization

The reaction between CaC2 and hot metal will take place, and the slag with CaS can be removed

easily [3]

. According to the characteristic, the program of slag adjustment for desulfurization is

shown in Table 1. And the physicochemical index of slag modifier for desulphurization is shown in

Table 2.

Table 1 Program of slag adjustment for desulfurization

Programs Details Ratio of

desulphurizer Remarks

Ⅰ: Slag adjustment

In order to reduce the iron loss, Al2O3

system slag adjustment in KR

desulphurization is carried out.

Desulphurizer-to-lime

ratio is 1:9 Fluotite-to-lime

ratio before

optimization is

1:9

Ⅱ: High- type slag

adjustment

Adding CaC2 to desulphurizer to

heighten the desulphurization rate.

Desulphurizer-to-lime

ratio is 2:8

Ⅲ: Low-CaC2 type

slag adjustment

Reducing the ratio of CaC2 in

desulphurizer

Desulphurizer-to-lime

ratio is 2:8

Table 2 Physicochemical index of slag modifier for desulphurization

Programs CaO/% S/% P/% H2O/% Al2O3/% Gas evolution

/L.kg-1

Particle size demand

Ⅰ ≥30 ≤0.20 ≤0.15 ≤0.5 ≥50 0 ≤1.5mm. Ratio of

bellow 0.5mm not less

than 60%

Ⅱ ≥60 ≤0.20 ≤0.15 ≤0.5 ≥20 ≥20

Ⅲ ≥55 ≤0.20 ≤0.15 ≤0.5 ≥25 ≥10

Industrial tests

Preparation of desulphurizer. Before the industrial tests, slag modifier for desulphurization

should be prepared and sent to the steelmaking plant. According to the program of slag adjustment

for desulphurization, suitable desulphurizer should be prepared.

1078 Frontiers of Materials, Chemical and Metallurgical Technologies

Page 3: Study on Technology of KR Desulfurization for Hot Metal with Vanadium and Titanium

Main parameters of desulphurization. Main parameters of KR desulphurization process are

shown in Table 3.

Table 3 Main parameters of KR desulphurization process

Hot metal

/t

Front slag

removal time

/min

Back slag removal

time /min

Temperature before

desulphurization/℃

Stirring time

/min

Rotation speed

/r/min

60~80 3~8 7~10 1200~1300 6~9 100~140

Test method. Hot metal is sent to KR position after the front slag removal. And then the agitator

begins to work. At the same time, the slag modifier for desulfurization is added to hot metal. After

back slag removal, hot metal will be sent to vanadium extraction in converter.

Results and analysis

Effect of desulphurization. Industrial tests with the three programs have been carried out. The

results show that desulphurization rate is reduced and desulfurizer consumption is increased with

program Ⅰ. On the contrary, desulphurization rates are improved when desulfurizer consumption

is reduced with programⅡ and program Ⅲ.

Comparisons of desulphurization effects for programⅡ and program Ⅲ are shown in Table 4

and Table 5, respectively. It is shown in Table 4 that good desulphurization effect has been gotten

compared with the process before optimization. ① Desulphurization rate is 85.2% with programⅡ,

which is 4.2% higher than that before optimization. ② Desulphurizer consumption is 12.6kg/t,

which is 1.1kg/t lower than that before optimization. ③ Sulfur content is 0.016% in hot metal after

desulphurization, which can meet the needs of requirement. ④ Temperature drop of hot metal is

27℃, which is 1℃ lower than that before optimization. However, the producing cost is increased. It

is shown in Table 5 that good desulphurization effect is achieved. ① Desulphurization rate is

84.2% with programⅢ, which is 3.2% higher than that before optimization. ② Desulphurizer

consumption is 12.3kg/t, which is 1.4kg/t lower than that before optimization. ③ Sulfur content is

0.016% in hot metal after desulphurization, which can meet the needs of requirement. ④

Temperature drop of hot metal is 25℃, which is 3℃ lower than that before optimization. However,

the producing cost is increased. Through the analysis, program Ⅲ is proposed to be the best

program using in hot metal desulphurization process.

Table 4 Comparison of desulphurization effect with programⅡ

Hot metal

/t

Slag removal

time/min

[S] before

desulphurization

/%

[S] after

desulphurization

/%

desulphurization

rate/%

Before optimization 76.1 9.2 0.105 0.020 81.0

Program Ⅱ 75.0 9.2 0.108 0.016 85.2

Difference -1.1 0 +0.003 -0.004 +4.2

Temperature drop in

desulphurization process/℃

Stirring time

/min

Quantity of

desulphurizer

/kg

Desulphurizer

consumption

/kg.t-1

hot metal

Before optimization 28 8.3 1041 13.7

Program Ⅱ 27 8.6 944 12.6

Difference -1 +0.3 -97 -1.1

Advanced Materials Research Vols. 581-582 1079

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Table 5 Comparison of desulphurization effect with program Ⅲ

Relationship between desulfurizer consumption and desulphurization rate is shown in Fig.1. It is

shown in Fig.1 that desulphurization rate is increased with the increase of desulphurizer

consumption. Furthermore, it follows the formula of Y=42.609Ln(x)-29.284. desulphurizer

consumption is 12.3kg.t-1

, and desulphurization rate is 84.2%.

Fig.1 Relationship between desulfurizer consumption and desulphurization rate

There is intimate relationship between stirring speed and desulphurization rate in the

desulphurization process. With the increase of stirring speed, desulphurization rate is increasing [4]

.

With the ongoing increase of stirring speed, desulphurization rate is sustained. The relationship

between stirring speed and desulphurization rate is shown in Fig.2.

Fig.2 Relationship of stirring speed and desulphurization rate

Hot metal

/t

Slag removal

time/min

[S] before

desulphurization

/%

[S] after

desulphurization

/%

desulphurization

rate/%

Before optimization 76.1 9.2 0.105 0.020 81.0

Program Ⅱ 75.8 9.6 0.101 0.016 84.2

Difference -1.1 +0.4 -0.004 -0.004 +3.2

Temperature drop in

desulphurization process/℃

Stirring time

/min

Quantity of

desulphurizer

/kg

Desulphurizer

consumption

/kg.t-1

hot metal

Before optimization 28 8.3 1041 13.7

Program Ⅱ 25 7.9 935 12.3

Difference -3 -0.4 -97 -1.4

1080 Frontiers of Materials, Chemical and Metallurgical Technologies

Page 5: Study on Technology of KR Desulfurization for Hot Metal with Vanadium and Titanium

In the process of desulphurization, extending stirring time and increasing stirring speed are

beneficial to desulphurization reaction. If the stirring time is extended, the reaction time can be

extended, accordingly, sulfur content in hot metal can be reduced. If the stirring speed is increased,

the desulphurization speed can be accelerated. But it will increase the cost and temperature drop of

hot metal if extending stirring time and increasing stirring speed. Thereby, stirring time is controlled

in the range of 6~8min, and stirring speed is controlled in the range of 90~120r/min. If sulfur

content is not less than 0.080%, stirring time can be extended to 10min and stirring speed can be

increased to above 130r/min. On this basis, sulfur content in hot metal after desulphurization is not

more than 0.003% [5]

.

Change of carbon and vanadium content before and after desulphurization. Content of

carbon and vanadium in hot metal before and after desulphurization is shown Table 6. It is shown in

Table 6 that there is nearly no change for carbon and vanadium change before and after

desulphurization.

Table 6 Content of carbon and vanadium in hot metal before and after desulphurization

[C]before

desulphurization/%

[C]after

desulphurization/%

[V]before

desulphurization/%

after desulphurization

[V]/%

Average 3.80 3.79 0.232 0.232

Min 3.64 3.62 0.189 0.193

Max 4.12 4.08 0.265 0.257

Desulfurized slag. Main components of desulfurized slag with program Ⅲ are shown in Table

7. It is shown in Table 7 that sulfur content in slag is as high as 6.29% with Ti in it, and it indicates

that wonderful desulphurization effect has been gotten. In addition, fCaO content in desulfurized

slag is 15.28%, and it indicate that the desulfurized slag also possess the ability of desulphurization.

Wonderful desulphurization effect has been gotten. ① MFe content in desulfurized slag is 4.2%,

which is 4.74% lower than that before optimization. ② TFe content in desulfurized slag is 10.4%

on average, which is 3.25% lower than that before optimization.

Table 7 Main components of desulfurized slag

CaO SiO2 P S fCaO F- V2O5 TiO2 TFe MFe FeO

Average 56.01 14.15 0.041 6.29 15.28 2.80 0.47 6.60 10.4 4.2 7.69

Min 52.26 12.66 0.027 4.73 13.46 2.50 0.32 4.76 5.4 0.5 5.27

Max 60.69 15.24 0.074 7.91 17.61 3.00 0.80 9.23 15.0 16.2 11.06

Conclusions

Good application effect is gotten in KR desulphurization process with the studied slag modifier for

desulphurization, and there is nearly no change of carbon and vanadium content in hot metal before

and after desulphurization. Desulphurization rate is 84.2%, which is 3.2% higher than that before

optimization. Desulfurizer consumption is 12.3kg/t hot metal, which are 1.4 kg/t hot metal lower

than that before optimization. TFe content is 10.4%, which is 3.25% lower than that before

optimization.

The KR desulphurization process can be carried out successfully with the studied slag modifier

for desulphurization, and it is worth to application and dissemination.

Advanced Materials Research Vols. 581-582 1081

Page 6: Study on Technology of KR Desulfurization for Hot Metal with Vanadium and Titanium

References:

[1] Xu Feng,Xu Anjun,Li Liansheng. Composition Optimization of KR Desulphurizer of Hot

Metal[C]. Proceedings of CSM 2007 Annual Meeting,2007: 25-29.

[2] Yang Hehui, Ge Wensun, Chen Wen. Application of high performance low magnesium

desulfurization compound[J]. Steelmaking,2010, (10):1-4.

[3] Zhang Xinzhao. Powder Injection Metallurgical Principle[M].Beijing: China Metallurgical

Industry Press, 1988.

[4] OUYang Degang,Liu Shoutang, Luo Wei. Optinization of structare parameters of KR stirrer by

hydraulic simulating experiment [J]. Research on Iron and Steel,2010,(05) :8-10.

[5] Wang Wei. Effect of KR Pretreatment Process Parameters on Hot Metal Desulphurization

Results[J]. Special Steel, 2006,(04):50-52.

1082 Frontiers of Materials, Chemical and Metallurgical Technologies

Page 7: Study on Technology of KR Desulfurization for Hot Metal with Vanadium and Titanium

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