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Production TiCl4 Using Combined Fluidized Bed by Titanium Slag Containing High-Level CaO and MgO
Studies in Surface Science and Catalysis, volume 159 Hyun-Ku Rhee, In-Sik Nam and Jong Moon Park (Editors) 9 2006 Elsevier B.V. All rights reserved
493
Production TiCi4 Using Combined Fluidized Bed by Titanium Slag Containing High-Level CaO and MgO Cong Xu, Zhangfu Yuan*, Xiaoqiang Wang, Jianfeng Fan, Jing Li and Zhi Wang Institute of Process Engineering, Chinese Academy of Sciences, P. O. Box 353, Beijing 100080, P.R China ([email protected]) 1. INTRODUCTION Titanium tetrachloride has been widely utilized as intermediate materials for producing titanium white and titanium sponge, two major products in titania industry. For present commercial production, TiCI4 has mainly been obtained by chloridizing high-grade titania feed-stock (HGTF) such as rutile and high titanium slag in bubble bed. The total content of CaO and MgO in HGTF is required to be lower than 0.5--1.0 wt% in order to reduce the particle agglomeration Ii31. The storage capacity of worldwide futile suitable to bubble bed, however, composes only 7.0wt% of gross reserves of titanium resource. In China, at least 90.5wt% of the titanium resources are located in PANZHIHUA, which all belong to magnetite with high-level of CaO and MgO I4J. Some researchers have studied on the problem I5-91, but these studies have mainly focused on the improvement of the reaction conditions in bubble bed and little research about a new reactor has been done. In this paper, our work is devoted to develop a new reactor which can be used in the chloridization of materials with high-level CaO and MgO and examine its anti-agglomeration effect and reaction yield.
2. EXPERIMENTAL PROCEDURE A new reactor, combined fluidized bed, which can chloridize materials with high-level CaO and MgO, is shown in Fig. l-a. The reactor may be composed of one or more parts, each of which consists of a riser tube and a semi-circulating fluidized bed (SCFB), and a structure such as riser-SCFB-riser. The method of anti-agglomeration for this reactor is to break up the liquid bridge between the particles by the shear force generated from the turbulence before the bridge is strengthened. In the riser tube, the gas velocity of chlorine, is greater than both of the terminal velocities of the slag particle and the petrocoke particle, makes the particles to be at a pneumatic transport state. No agglomeration occurs in the riser tube. At the top of the riser tube, a
494 R., ,um
Gas arm Sc<(l
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45O 100
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d,
0.0
u =-
A: lot ,lae particle~
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0.5
B: for pelr ..... ke panicle,1.0
Re' mm
c~
a) combined fluidized bed b) operation range Fig. 1 Diagram of the combined fluidized bed and operation range distributor is set up to distribute the gases and particles. In the semi-circulating fluidized bed, the gas velocity is controlled to be lower than the transport velocity (utr.c) ofpetrocoke particle and higher than the transition velocity (Ucc) as shown in Fig. l-b. As for the high titanium slag particles, the case is different from the petrocoke particles in that only a part of the particles (large particles) are at turbulent fluidization (Ucrtgtr.r). That is, all of the petrocoke particles and a part of the slag particles (large) form a turbulent bed, at meanwhile, a circulating fluidized bed formed by the other part of the slag particles (fine) is superposed on the turbulent bed. Such combination may be called semi-circulating fluidized bed, in which the turbulent fluidization brings on higher shear force than the conventional bubble fluidization. On the other hand, because the residence time of the slag particles in the semi-circulating fluidized bed is shorter than in the bubble bed, the source of the liquid CaC12 and MgC12 can quickly leave the reaction area and get isolated to reduce the danger of the agglomeration. Moreover, the mass transfer rate as well as heat transfer rate is superior to semi-circulating bed than in the bubble bed. A quartz reactor is employed in the experiment, in which the first riser tube is 710mm (height)x22mm (i. d.), the semi-circulating fluidized bed is 636mm (height)x59mm (i. d.), and the second riser tube is 320mm (height)• (i. d.).The distributor has a hole of 10mm diameter in the centre and the opening fraction is 0.03. Two kinds of high titanium slag, in which the total content of CaO and MgO is 2.03 wt% and 9.09wt%, are utilized in this work, and the corresponding chemical constitution is shown in Table 1. The material 2 is obtained from PANZHIHUA. In the experiment, 75-165gm of high titanium slag particles and 0.5-0.85mm ofpetrocoke particles are used, as shown in Figure l-b). Table I Chemical constitution of high titanium slag(%) No T i O 2 S i O 2 A1203 Z Fe V 1 2
91.55 76.76
1.20 4.70
1.23 2.15
2.53 5.02
0.18 0.083
. CaO
. . MgO
. Cr
. . MnO
Others
0.29 1.72
1.74 7.37
0.032 -
1.12 0.832
0.128 1.365
495
3. EXPERIMENTAL RESULTS AND DISCUSSIONS 3.1. Examinations on anti-agglomeration No agglomeration occurs in the combined fluidized bed, much of the CaCI2 and MgC12 can be found in the solids collected by the cyclone. An experiment is designed to obtain mass balance data of Mg before and after reaction. As suggested in Fig. 2, although the content of MgO in the slag is as high as 7.37wt%, the mass amount discharged from reactor approximately equals to the that fed into the reactor even after 1.5h. This means Mg is not accumulated in the reactor. 3.2. Chloridizing efficiency From Table 2 it can be seen that at 923K and 973K the conversion (XTio2) of TiO2 lies between 20%--45%, the conversion (Xcl2) of chlorine is less than 36% and the production capacity(Rvicn4) of TiC14 achieve about 26.0 t-TiC14 9 m -2 ~ d ~ at most. In conventional bubble bed, 95% of conversion for TiO2, 1% (by volume) of the residual chlorine in off-gas and the production capacity of 25-40 t-TiC14 9 m -2 9 d- ~ are generally required tT~~ . In contrast to the bubble bed, it is no doubt that the conversion of TiO2 and chlorization is comparatively low. The value of RTiCI4 under some cases, e.g. L-3 and L-6-8, can achieve the lower-limit of production capacity of TIC14 for the bubble bed. This suggests that the low-temperature chloridization can be adopted to obtain TIC14 using materials with high-level of CaO and MgO, meanwhile avoid the agglomeration. The conversion of TiO2 and chlorine at higher temperature (at 1023K and 1073K) increased, but the conversions of 50---85% for TiO2 and less than 80% for chlorine are still not comparable to that in the bubble bed. It can be seen that the RTicl4 at the higher temperature is 40-75 t 9 m -2 9 d l , which is 1---3 times the RTiCI4 in the bubble bed. That is, the production capacity of the combined fluidized bed is superior to that of the bubble bed.
o.o6o - - " - - F,o ~g, Feeding rate of Mg -- 9
',"
Foo~Mg' Discharging rate of Mg
0.045
O) ,,.-2
9
9
/
m
9
-
-
9
0.030 u. =0.015
.... /o
.......8 0 9 ' 0
t, min
T=1023K.Ug=0.9m.s~. Gs=4.rkg.h~. SlagCoke=100kg:40kg Fig.2 Mass balance of Mg before and after chlorination
496 Table 2 Effect of temperature on reaction efficiency. No. L- 1 L-2 L-3 L-4 L-5 L-6 L-7 L-8 H- 1 H-2 H-3 H-4 H-5
T K 923 973 973 973 973 973 973 973 1023 1023 1023 1023 1073
Ug m/s 0.9 0.7 0.9 1.1 0.7 0.9 1.2 0.9 0.7 0.9 1.1 0.9 0.9
Gs kg . h -~ 4.6 4.6 4.6 4.6 5.8 5.8 5.8 7.0 4.6 4.6 4.6 5.8 5.8
Slag/Petrocoke kg/kg 100:30 100:30 100:30 100:30 100:30 100:30 100:30 100:30 100:30 100:30 100:30 100:30 100:30
Xci2 % 20.62 23.51 35.45 25.40 32.91 32.17 29.88 33.75 71.02 63.53 33.61 58.04 78.36
X l i 0 2 Xpetrocoke % 23.54 21.31 45.04 30.87 23.80 30.55 34.90 25.65 71.09 82.86 54.04 60.04 81.06
% 12.96 11.06 24.23 15.87 12.49 15.92 18.36 13.76 39.78 44.02 28.98 32.85 43.93
RTiCI4 t . m -2 9 d-i 13.99 12.67 26.77 18.35 18.09 23.21 26.51 23.72 52.47 61.16 39.89 55.88 75.44
4. C O N C L U S I O N S In this paper, a method for producing TIC14 from high titanium slag with high-level of CaO and MgO has been proposed using a new reactor, the combined fluidized bed. The agglomeration caused by the molten MgCI2 and CaC12 can be effectively prevented by the enhancement of the shear forces in the new reactor. The low-temperature chlorination (less than 973K) in the combined fluidized bed can be utilized in the production of TiCI4 in comparison to the low limit of production capacity of TiCI4 in the bubble bed. The production capacity of TIC14 for the new reactor in the high-temperature chloridization (more than 973K) is 1-3 times the production capacity for the conventional bubble bed. ACKNOWLEDGEMENTS This work was supported by National Natural Science Foundation (No. 20306030) of China. REFERENCES
[1 ] [2]
B. Li, Z. Yuan, W. Li and C. Xu. China Particuology, No.2 (2004) 84. Z. Yuan, C. Xu, S. Zheng and J. Zhou. Modern Chemical Industry, No. 23 (2003) I.
[3] [4] [5] [6] [7] [8] [9] [ 10]
J. Wang. Complex Utilization of Mineral, No.1 (1997) 23 G. Den. Vanadium and Titanium, No. 1 (1994) 36. F.L.Yang and V. Hlavacek. AIChE J., No.46 (2000) 355. G. Tardos, D Mazzone and R Pfeffer. Can. J. Chem. Eng, No.63 (1985) 377. A.J. Morris and R.F. Jensen. Metall. Trans. B, No.7 (1975) 1976. C. Lin and T. Lee. J. Chin. I. Ch.E., No.17 (1986) 2. I. Barin and W. Schuler. Metall. Trans. B, No. I I (1980) 199. W. Wen. Journal of Guangdong Nonferrous Metals, No.9 (1999) 18.
493
Production TiCi4 Using Combined Fluidized Bed by Titanium Slag Containing High-Level CaO and MgO Cong Xu, Zhangfu Yuan*, Xiaoqiang Wang, Jianfeng Fan, Jing Li and Zhi Wang Institute of Process Engineering, Chinese Academy of Sciences, P. O. Box 353, Beijing 100080, P.R China ([email protected]) 1. INTRODUCTION Titanium tetrachloride has been widely utilized as intermediate materials for producing titanium white and titanium sponge, two major products in titania industry. For present commercial production, TiCI4 has mainly been obtained by chloridizing high-grade titania feed-stock (HGTF) such as rutile and high titanium slag in bubble bed. The total content of CaO and MgO in HGTF is required to be lower than 0.5--1.0 wt% in order to reduce the particle agglomeration Ii31. The storage capacity of worldwide futile suitable to bubble bed, however, composes only 7.0wt% of gross reserves of titanium resource. In China, at least 90.5wt% of the titanium resources are located in PANZHIHUA, which all belong to magnetite with high-level of CaO and MgO I4J. Some researchers have studied on the problem I5-91, but these studies have mainly focused on the improvement of the reaction conditions in bubble bed and little research about a new reactor has been done. In this paper, our work is devoted to develop a new reactor which can be used in the chloridization of materials with high-level CaO and MgO and examine its anti-agglomeration effect and reaction yield.
2. EXPERIMENTAL PROCEDURE A new reactor, combined fluidized bed, which can chloridize materials with high-level CaO and MgO, is shown in Fig. l-a. The reactor may be composed of one or more parts, each of which consists of a riser tube and a semi-circulating fluidized bed (SCFB), and a structure such as riser-SCFB-riser. The method of anti-agglomeration for this reactor is to break up the liquid bridge between the particles by the shear force generated from the turbulence before the bridge is strengthened. In the riser tube, the gas velocity of chlorine, is greater than both of the terminal velocities of the slag particle and the petrocoke particle, makes the particles to be at a pneumatic transport state. No agglomeration occurs in the riser tube. At the top of the riser tube, a
494 R., ,um
Gas arm Sc<(l
-150
" ........
2
L
0
15O
uiu,:,s,
3O0
45O 100
U. (U). m . s " | size d/stributior~...
80
. .-"
m
.-"" T=I02.
K
~:" 1 Oistnbutor~
o~
60
E
:--
40
n e u r r ~ c tianspor~ "/
..
^Sokd materials
d,
0.0
u =-
A: lot ,lae particle~
B- - - ' ~
0.5
B: for pelr ..... ke panicle,1.0
Re' mm
c~
a) combined fluidized bed b) operation range Fig. 1 Diagram of the combined fluidized bed and operation range distributor is set up to distribute the gases and particles. In the semi-circulating fluidized bed, the gas velocity is controlled to be lower than the transport velocity (utr.c) ofpetrocoke particle and higher than the transition velocity (Ucc) as shown in Fig. l-b. As for the high titanium slag particles, the case is different from the petrocoke particles in that only a part of the particles (large particles) are at turbulent fluidization (Ucr
91.55 76.76
1.20 4.70
1.23 2.15
2.53 5.02
0.18 0.083
. CaO
. . MgO
. Cr
. . MnO
Others
0.29 1.72
1.74 7.37
0.032 -
1.12 0.832
0.128 1.365
495
3. EXPERIMENTAL RESULTS AND DISCUSSIONS 3.1. Examinations on anti-agglomeration No agglomeration occurs in the combined fluidized bed, much of the CaCI2 and MgC12 can be found in the solids collected by the cyclone. An experiment is designed to obtain mass balance data of Mg before and after reaction. As suggested in Fig. 2, although the content of MgO in the slag is as high as 7.37wt%, the mass amount discharged from reactor approximately equals to the that fed into the reactor even after 1.5h. This means Mg is not accumulated in the reactor. 3.2. Chloridizing efficiency From Table 2 it can be seen that at 923K and 973K the conversion (XTio2) of TiO2 lies between 20%--45%, the conversion (Xcl2) of chlorine is less than 36% and the production capacity(Rvicn4) of TiC14 achieve about 26.0 t-TiC14 9 m -2 ~ d ~ at most. In conventional bubble bed, 95% of conversion for TiO2, 1% (by volume) of the residual chlorine in off-gas and the production capacity of 25-40 t-TiC14 9 m -2 9 d- ~ are generally required tT~~ . In contrast to the bubble bed, it is no doubt that the conversion of TiO2 and chlorization is comparatively low. The value of RTiCI4 under some cases, e.g. L-3 and L-6-8, can achieve the lower-limit of production capacity of TIC14 for the bubble bed. This suggests that the low-temperature chloridization can be adopted to obtain TIC14 using materials with high-level of CaO and MgO, meanwhile avoid the agglomeration. The conversion of TiO2 and chlorine at higher temperature (at 1023K and 1073K) increased, but the conversions of 50---85% for TiO2 and less than 80% for chlorine are still not comparable to that in the bubble bed. It can be seen that the RTicl4 at the higher temperature is 40-75 t 9 m -2 9 d l , which is 1---3 times the RTiCI4 in the bubble bed. That is, the production capacity of the combined fluidized bed is superior to that of the bubble bed.
o.o6o - - " - - F,o ~g, Feeding rate of Mg -- 9
',"
Foo~Mg' Discharging rate of Mg
0.045
O) ,,.-2
9
9
/
m
9
-
-
9
0.030 u. =0.015
.... /o
.......8 0 9 ' 0
t, min
T=1023K.Ug=0.9m.s~. Gs=4.rkg.h~. SlagCoke=100kg:40kg Fig.2 Mass balance of Mg before and after chlorination
496 Table 2 Effect of temperature on reaction efficiency. No. L- 1 L-2 L-3 L-4 L-5 L-6 L-7 L-8 H- 1 H-2 H-3 H-4 H-5
T K 923 973 973 973 973 973 973 973 1023 1023 1023 1023 1073
Ug m/s 0.9 0.7 0.9 1.1 0.7 0.9 1.2 0.9 0.7 0.9 1.1 0.9 0.9
Gs kg . h -~ 4.6 4.6 4.6 4.6 5.8 5.8 5.8 7.0 4.6 4.6 4.6 5.8 5.8
Slag/Petrocoke kg/kg 100:30 100:30 100:30 100:30 100:30 100:30 100:30 100:30 100:30 100:30 100:30 100:30 100:30
Xci2 % 20.62 23.51 35.45 25.40 32.91 32.17 29.88 33.75 71.02 63.53 33.61 58.04 78.36
X l i 0 2 Xpetrocoke % 23.54 21.31 45.04 30.87 23.80 30.55 34.90 25.65 71.09 82.86 54.04 60.04 81.06
% 12.96 11.06 24.23 15.87 12.49 15.92 18.36 13.76 39.78 44.02 28.98 32.85 43.93
RTiCI4 t . m -2 9 d-i 13.99 12.67 26.77 18.35 18.09 23.21 26.51 23.72 52.47 61.16 39.89 55.88 75.44
4. C O N C L U S I O N S In this paper, a method for producing TIC14 from high titanium slag with high-level of CaO and MgO has been proposed using a new reactor, the combined fluidized bed. The agglomeration caused by the molten MgCI2 and CaC12 can be effectively prevented by the enhancement of the shear forces in the new reactor. The low-temperature chlorination (less than 973K) in the combined fluidized bed can be utilized in the production of TiCI4 in comparison to the low limit of production capacity of TiCI4 in the bubble bed. The production capacity of TIC14 for the new reactor in the high-temperature chloridization (more than 973K) is 1-3 times the production capacity for the conventional bubble bed. ACKNOWLEDGEMENTS This work was supported by National Natural Science Foundation (No. 20306030) of China. REFERENCES
[1 ] [2]
B. Li, Z. Yuan, W. Li and C. Xu. China Particuology, No.2 (2004) 84. Z. Yuan, C. Xu, S. Zheng and J. Zhou. Modern Chemical Industry, No. 23 (2003) I.
[3] [4] [5] [6] [7] [8] [9] [ 10]
J. Wang. Complex Utilization of Mineral, No.1 (1997) 23 G. Den. Vanadium and Titanium, No. 1 (1994) 36. F.L.Yang and V. Hlavacek. AIChE J., No.46 (2000) 355. G. Tardos, D Mazzone and R Pfeffer. Can. J. Chem. Eng, No.63 (1985) 377. A.J. Morris and R.F. Jensen. Metall. Trans. B, No.7 (1975) 1976. C. Lin and T. Lee. J. Chin. I. Ch.E., No.17 (1986) 2. I. Barin and W. Schuler. Metall. Trans. B, No. I I (1980) 199. W. Wen. Journal of Guangdong Nonferrous Metals, No.9 (1999) 18.