Shen
(Guizhou Zunyi Titanium Industry Co., Ltd. 563004)
In the reduction production process of sponge titanium, a large number of annular climbing titanium will be produced on the upper wall of the reactor. The amount of titanium climbing produced in one furnace ranges from 500 kg to 800- 1000 kg, which not only makes it difficult to take out the products, but also increases the labor intensity of operators, resulting in poor quality and great economic losses. In this paper, the formation mechanism of titanium creeping in sponge titanium and the reasons for the increase of titanium creeping in the production process are analyzed, and the maximum feeding speed limit in the middle and late stage of reduction is put forward, which is the main way to reduce titanium creeping in the production process, so as to alleviate the fierce reaction, control the small fluctuation of reaction liquid level in the range of 1# and prevent the formation of new active centers.
Key words: titanium climbing production of sponge titanium, feeding speed, reaction liquid level height
Study on the formation of titanium in the tube wall during the production of sponge titanium by magnesium method
, Shen
(Guizhou Zunyi Titanium Industry Co., Ltd. 563004)
Abstract: In the process of reduction and distillation, a large amount of cyclic titanium will be produced on the upper wall of the reactor. The output of each batch ranges from 500kg to 800kg or 1 1,000kg. It is difficult for operators to take out the products, which also affects the quality. Therefore, hanging titanium not only increases the labor intensity, but also causes great losses. In this paper, the formation mechanism of hanging titanium and the reasons for its increase in output are analyzed. At the same time, in order to alleviate the strong reaction, make the reaction wave level not exceed1"and prevent the formation of new active centers, this paper introduces the main method to reduce the formation of titanium on the wall, that is, readjust the maximum feed rate in the middle and late stage of reduction distillation.
Keywords: feed rate of titanium production on sponge titanium wall, liquid level reaction
1 preface
In the reduction production process of sponge titanium, a large amount of annular climbing titanium will be generated on the upper wall of the reactor, as shown in figure 1. Climbing titanium will lead to the following adverse consequences: First, due to the current double-flange reactor, the heat loss in the upper part of the reactor is large (there are three water jackets in the upper part, and the height of the reactor is about 300 mm outside the heating furnace), and the magnesium chloride in the upper part of the climbing titanium is difficult to evaporate, which makes the climbing titanium contain high impurity element chlorine, and a large amount of magnesium and magnesium chloride will be attached to the mouth of the reactor (the uppermost part of the climbing titanium) when stripping products. Secondly, the reduction distillation reactor of sponge titanium is made of iron. Due to the strong adhesion of climbing titanium on the reactor wall, the heat loss in the upper part of the double-flange reactor is large. In order to ensure the temperature in the upper part of the reactor, the heating furnace 1# and 2# heating resistance wires are frequently energized for a long time during distillation, which leads to the general luminescence phenomenon of climbing titanium. The analysis results show that the impurity element iron content is high. Thirdly, the titanium climbing in the upper space of the reactor is easily polluted by leaked air, which makes the impurity elements nitrogen and oxygen content in the product higher. It can be seen from the table 1 that the quality grade of climbing titanium is basically Grade 3-5 (a few of them are above Grade 2), and a few of them become off-grade due to too high impurity elements. The output of a batch of titanium varies from about 500 kg to 800- 1000 kg, causing huge economic losses. In addition, too much titanium climbing also makes it difficult to take out the product, which increases the labor intensity of operators. In order to reduce the generation and loss of titanium climbing, we carried out experiments to control the liquid level height and adjust the feeding speed.
Table 1 Quality Statistics of Pan Ti in the Second Half of 2007
Analysis of batch number (batch) Grade 2 Product batch number (batch) Grade 3 ~ 5 Product batch number (batch) Out-of-grade batch number (batch) Grade 2 Product influencing factors Grade 3 ~ 5 Products and out-of-grade influencing factors.
75 12 5 1 12 hemoglobin, iron, chlorine, oxygen, nitrohemoglobin, iron and chlorine.
Formation mechanism of climbing titanium
The main reaction of magnesium reduction of TiCl _ 4 is: TiCl _ 4+2 mg = Ti+2 MgCl2. At the beginning of the reduction reaction, most of the added TiCl _ 4 was gasified, resulting in the reaction of gaseous TiCl _ 4-gaseous Mg or gaseous TiCl _ 4-liquid Mg. At the same time, some liquid TiCl _ 4 enters into liquid magnesium before gasification, which leads to liquid TiCl _ 4-liquid Mg reaction. The reduction begins at the angle between the iron wall of the reactor and the surface of molten magnesium. Once the titanium crystal appears, the peak or edge of the titanium crystal exposed above the surface of molten magnesium becomes the active center. The reduction of TiCl4 by [1] magnesium is mainly carried out on this active center. Liquid magnesium climbs along the pores of iron wall and titanium crystal through surface tension, adsorbs on the active center, and reacts with vapor TiCl4 _ 4 to generate initial sponge titanium particles. With the progress of the reaction, the generated titanium sponge particles gradually grow along the reactor wall and float on the surface of the melt, relying on its adhesion to the reactor wall and the support of the buoyancy of the melt. As the generated sponge titanium blocks become thicker and larger and magnesium chloride is discharged, most of the sponge titanium blocks without buoyancy support of the melt will sink to the bottom of the melt, so that the annular sponge titanium will adhere to the reactor wall. In fact, this part is also the initial titanium climbing. In addition, in the initial stage of the reduction reaction, the evaporation surface of liquid magnesium is large and the space pressure is low, so the evaporation rate of magnesium is high. In the middle of the reduction reaction, when the reaction temperature is high and the bottom of the reactor is heated, some magnesium will evaporate. Magnesium vapor condenses on the reactor wall and the bottom of the big cover after volatilization, and reacts with gaseous TiCl4 _ 4 _ 4 to generate part of wall-climbing titanium. After the sponge titanium blocks sink to the bottom of the melt, the free surface of liquid magnesium will be exposed to the surface of the melt again, and the reduction reaction will return to a higher speed. With the progress of the reaction, sponge titanium bridge will regenerate on the surface of melt. By discharging magnesium chloride, the titanium bridge is destroyed, and the sponge titanium block sinks by its own weight, creating conditions for the growth of the next layer of sponge titanium. In this process, titanium climbing will gradually form, and the reduction reaction will be repeated until the utilization rate of magnesium reaches 65%-75%.
Cause analysis of titanium output increase in Panzhihua Iron and Steel Company
3. 1 feed speed in the middle and late stage
With the progress of the reduction reaction, especially after entering the middle stage, the feeding speed is gradually increased, and the reaction is very intense. The highest temperature in the center of the reaction zone on the melt surface can be above 1200℃, while the boiling point of magnesium is only 1 105℃, at which time magnesium is in a boiling state. In addition, according to the actual calibration of glass rotor flowmeter, the feed rate of reduction operation is compared with that of automatic feed system. Because the glass rotor flowmeter is calibrated with water when it leaves the factory, when the measured medium is TiCl4, its correction coefficient should be 1. 13 after calculation. When the scale of the glass rotor shows that the maximum feed rate is 150 kg /0.5h, the actual feed rate has reached 160 ~ 170kg/0.5h, which further aggravates the seriousness of the reaction. Boiling liquid magnesium will be continuously adsorbed on a small amount of annular climbing titanium formed on the initial reactor wall, climb up through the pores of titanium crystals, and react with vapor-phase TiCl4 _ 4 to generate new climbing titanium, which makes the original annular climbing titanium increase and thicken. In addition, due to the increase of reaction intensity, the gasification of liquid magnesium is also intensified. After the liquid magnesium vapor volatilizes, it condenses and adheres to the upper part of the reactor wall and the bottom of the big cover, and reacts with the vapor TiCl4 _ 4 to generate climbing titanium, which mainly adheres to the upper part of the reactor wall and the bottom of the big cover. Therefore, the longer the maximum feed rate lasts, the more climbing titanium is produced (Table 2).
Table 2 Statistics of titanium output of some large-scale high-speed climbing walls
Maximum feed rate
(kg /0.5 hour) duration
(h) Total output of climbing titanium
Proportion (%)
Production furnace-1155 ~1653512.75
Production furnace-2145 ~155 4013.55
Production furnace-3155 ~1653615.67
Production furnace-4155 ~1654010.35
Production furnace-5155 ~1653510.75
3.2 Reaction liquid level height
When the reaction liquid level is too low and the fluctuation amplitude is too large, the amount of titanium climbing will increase. The reasons are as follows: First, when the reaction level is too low, TiCl _ 4 is relatively far away from the surface of liquid magnesium, the reaction between liquid TiCl _ 4 and liquid Mg is relatively reduced, and the reaction between gaseous TiCl _ 4 and magnesium vapor is relatively increased, thus increasing the amount of titanium climbing. Secondly, due to the untimely and inaccurate quantitative discharge of MgCl2, the reaction liquid level fluctuates greatly, and it is easy to form new active centers outside the active centers of titanium crystals. Liquid magnesium climbs along the pores of iron wall and titanium crystal through surface attraction, and is adsorbed on the active center, thus adhering to the reactor wall to form new climbing titanium. Therefore, if the liquid level is not well controlled, the MgCl2 emission will be timely and accurate, and the titanium climbing output will also increase (Table 3).
Table 3 Statistical Table of Large Fluctuation of Reaction Liquid Level Height
Total output of titanium climbing in the range of height fluctuation of reaction liquid level
Proportion (%)
Production furnace-61# ~ 211.88
Production furnace -7 1 # ~ 2 # 12.82
Production furnace -8 1 # ~ 2 # 13.67
Production furnace -9 1 # ~ 2 # 15.02
Production furnace-101# ~ 2 #14.02
Production furnace-11# ~ 2 #12.4438+0
Four measures
From the above analysis, it can be seen that climbing titanium will inevitably form in the production process of sponge titanium, but its output can be controlled. Therefore, we adjusted the feeding speed and the reaction liquid level height. Combined with the production practice, two measures were taken: First, the maximum feeding speed of the furnace with poor ventilation and heat dissipation in the middle stage of reduction was limited to 135 ~ 140 kg/0.5h to alleviate the severity of the reaction. Because the reaction temperature of special furnace is too low, it can be appropriately increased to 160 ~ 170 kg/. The maximum feed rate in the later stage is limited to105 ~110 kg/0.5h. Secondly, the reaction liquid level is controlled to fluctuate slightly in the range of 1# to prevent the formation of new active centers, so as to achieve the purpose of reducing titanium crawling (Table 4).
Table 4 Comparison Table of Experiment on Adjustment of Feed Rate and Discharge Rate of Magnesium Chloride System
The feeding speed and output of MgCl2 system, the average ratio of titanium climbing to total output (kg), the average weight of titanium blocks (kg) and the average feeding time.
(h) Average maximum feed rate in the middle period (kg /0.5h) and average maximum feed rate in the later period (kg /0.5h)
Before adjustment,11.56 5291.89160120.
After adjustment, 8.28 5483 87 138 107.
From the statistical data in Table 4, it can be seen that by controlling the maximum feed rate, the liquid level height and discharging magnesium chloride timely and accurately, the proportion of titanium crawling produced by the product in the total output has greatly decreased, with the average titanium crawling before adjustment being 1 1.56%, and after adjustment being 8.28%, with an average decrease of 3.28%. In the experiment of adjusting the feed rate, the experiment of increasing the feed rate to 155 ~ 165 kg/0.5 h was carried out again for the first batch of products from production furnace -59. Results The titanium creeping increased to 14.93% of the total output, which also proved the influence of feeding speed on the formation of titanium creeping. In addition, before adjustment, the average weight of titanium block was 529 1 kg, after adjustment, the average weight of titanium block was 5483 kg, and the average gross weight was not affected. The average feeding time before adjustment was 89 hours, and after adjustment, the average feeding time was 87 hours, and the feeding time was also slightly reduced. The experiment reduced the output of titanium climbing, shortened the reduction production cycle and reduced the reduction power consumption, and achieved good results.
5 conclusion
5. 1 The maximum feed rate of the furnace affected by poor ventilation is limited to 135 ~ 140 kg/0.5h in the middle stage of reduction and105 ~110 kg/0.5h in the later stage.
5.2 Control the reaction liquid level to fluctuate slightly within the range of 1#.
Under the condition of consolidating the output of sponge titanium block, this experiment reduced the amount of titanium crawling and achieved results, which laid the foundation for further research and exploration of titanium crawling production of sponge titanium.
reference data
[1], Deng, Luo Fangcheng. Titanium metallurgy [M]. Edition (second edition). Beijing: Metallurgical Industry Press, 1998:28 1-293.