study on technology of kr desulfurization for hot metal with vanadium and titanium
Post on 17-Mar-2017
216 Views
Preview:
TRANSCRIPT
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.
apgwj66@126.com, bgewensun@sina.com, cpyychenlian@163.com, dhsquan002008@sina.com, fpcgzzh1206@126.com
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)
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
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
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
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
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
Frontiers of Materials, Chemical and Metallurgical Technologies 10.4028/www.scientific.net/AMR.581-582 Study on Technology of KR Desulfurization for Hot Metal with Vanadium and Titanium 10.4028/www.scientific.net/AMR.581-582.1077
top related