JP6211940B2 - Titanium tetrachloride production method - Google Patents

Description

  The present invention relates to a method for producing titanium tetrachloride by a fluidized chlorination method using a fluidized chlorination furnace. More specifically, the present invention relates to a method for producing titanium tetrachloride that can effectively eliminate a flow failure problem due to accumulation of high boiling point chloride in a fluidized bed. About.

  Titanium tetrachloride, which is a raw material for producing metal Ti, is often produced industrially by a fluid chlorination method using a fluid chlorination furnace. In the production of titanium tetrachloride by fluidized chlorination using a fluidized chlorination furnace, the raw material titanium ore (natural rutile, synthetic rutile, titanium slag) is mixed with coke powder and supplied into the fluidized chlorination furnace. Then, chlorine gas is blown from the bottom of the furnace, and a raw material fluidized bed is formed in the lower part of the furnace at a high temperature. As a result, the titanium ore is chlorinated with chlorine gas, and titanium tetrachloride gas is generated and led out from the top of the furnace.

Titanium ore contains metal oxides such as CaO and MgO as impurities. These impurities are chlorinated in the furnace to produce chlorides such as CaCl ₂ and MgCl ₂ . Since these chlorides are high-boiling chlorides having a high boiling point, they do not become a gas even in the furnace temperature range (1000 to 1100 ° C.), exist as liquids, and accumulate as the operating time of the fluidized chlorination furnace increases. Advances. Since the high boiling point chloride present as a liquid in the fluidized bed has an action of aggregating the particles, accumulation of the high boiling point chloride causes a defective flow of the particles.

  And, when falling into a fluid flow trouble such as particle aggregation or sintering, the reactivity is lowered, so that chlorine gas may be discharged out of the system without being reacted. Chlorine gas discharged outside the system is neutralized in the exhaust gas treatment facility in the short term, but since it is not a situation that can be left for a long time, the supply of chlorine gas to the fluid chlorination furnace will be stopped in the long term, Instead, measures are taken to improve the reactivity by supplying dry air or oxygen gas into the furnace to burn the coke and raising the furnace temperature. Economic loss due to becoming unavoidable.

  Previously, poor flow problems due to the accumulation of high-boiling chlorides rarely led to substantial problems because of the high quality of titanium ore and low impurity concentration. However, with the recent tightening of global demand for titanium ore, the price of ore has soared and it has been unavoidable to use titanium ore with lower purity than before. Along with this, the concentration of impurities in the titanium ore has increased, and as a result, the accumulation of high-boiling chlorides has become prominent, and economic loss due to fluid flow trouble has become a problem.

  Apart from such poor flow problems due to the accumulation of high-boiling chlorides, the production of titanium tetrachloride by the fluidized chlorination method using a fluidized chlorination furnace has the problem of reduced reactivity due to the accumulation of hardly reactive substances in the fluidized bed. There is. This is because, when the fluidized chlorination furnace is operated for a long time, among the impurities contained in the titanium ore, components that are difficult to react with chlorine gas even in the furnace temperature range accumulate in the fluidized bed as hardly reactive substances. This is a phenomenon that reduces reactivity.

A typical hardly reactive substance that accumulates in the fluidized bed is SiO ₂ . SiO ₂ which is a main component of the hardly reactive substance is brought into the fluidized bed not only from the titanium ore but also from the refractory brick installed on the inner surface of the fluidized chlorination furnace by physical wear. And when the hardly reactive substance in a fluidized bed increases more than a predetermined ratio, the reactivity of the whole fluidized bed falls remarkably.

  For the latter problem, that is, the problem of a decrease in reactivity due to accumulation of hardly reactive substances in the fluidized bed, the particulate material constituting the fluidized bed is periodically extracted, and instead reactive raw material powder and coke powder. Patent Document 1 proposes the effectiveness of supplying the liquid in the fluidized bed. As will be described in detail later, this countermeasure for extracting the fluidized particulate material is not necessarily the best for the former problem, that is, the trouble of poor flow due to the accumulation of high boiling point chloride in the fluidized bed.

JP 2000-109322 A

  An object of the present invention is to provide a titanium tetrachloride production method capable of effectively solving a flow failure trouble due to accumulation of high boiling point chloride in a fluidized bed, which is a problem in production of titanium tetrachloride by a fluid chlorination method using a fluid chlorination furnace. Is to provide.

The present inventor has been engaged in the production operation of titanium tetrachloride by fluidized chlorination using a fluidized chlorination furnace for many years, and in order to eliminate the decrease in reactivity due to accumulation of hardly reactive substances in the fluidized bed, The investigation was conducted focusing on the fluidized bed particles extracted from the furnace. When the fluidized bed particles are extracted, highly reactive substances such as SiO ₂ accumulated in the fluidized bed are excluded from the inside of the furnace, so that high reactivity can be maintained. Since high boiling point chlorides such as CaCl ₂ and MgCl ₂ were found to adhere to the surface of the hardly reactive material particles, the flowability was improved by discharging the high boiling point chloride out of the furnace. It has been found that this can also be expected to improve the reactivity.

  In other words, extraction of fluidized bed particles is not only effective in eliminating the decrease in reactivity due to the accumulation of hardly reactive substances in the fluidized bed, but also effective in eliminating fluid flow troubles due to the accumulation of high boiling point chlorides. It turned out.

  However, extraction of the fluidized bed particles cannot selectively remove the hardly-reactive substance, and unreacted titanium ore particles and coke particles are also removed at the same time, so it is inevitable that raw material loss occurs. The problem of poor flow due to the accumulation of high-boiling chlorides is a problem that becomes more prominent due to the lowering of raw material quality accompanying the increase in raw material procurement costs, so raw material loss becomes a fatal problem. In addition, when the high boiling point chloride concentration in the fluidized bed is high, it is necessary to extract a large amount of fluidized bed particles in a short period of time. In this case, in addition to the increased risk of unreacted chlorine due to a decrease in the fluidized bed volume (i.e., the reaction zone decreases), it is necessary to add a large amount of raw material at room temperature to restore the original fluidized bed volume. In addition, dry air and oxygen for raising the temperature to 1000 to 1100 ° C. are required, which causes further cost deterioration.

  Under such circumstances, the present inventor has taken out a new method for removing high-boiling chlorides while keeping in mind that extraction of fluidized bed particles, particularly removal of hardly reactive substance particles is effective for removal of high-boiling chlorides. We studied earnestly. As a result, it is effective to reversely introduce the hardly reactive material particles that have been targeted for extraction outside the furnace, and more specifically, the particle size of the hardly reactive material particles is the same. The present inventor has found that it is effective to positively introduce small fine particles into the fluidized chlorination furnace.

  That is, according to the investigation by the inventor, the high-boiling-point chloride in the liquid phase gradually accumulates in the furnace. That. Although it is true that hardly reactive substance particles accumulate in the furnace as the operation of the fluid chlorination furnace continues, it is coarse particles that have a relatively large particle diameter and accumulate in the furnace. Small fine particles are discharged outside the furnace. And since the high boiling point chloride discharged | emitted out of a furnace is adhering to the surface of the fine particle discharged | emitted out of a furnace, the fine particle is an effective carrier of high boiling point chloride. The inventor has found the fact.

  Therefore, if fine particles of difficult-to-react material that are discharged to the outside of the fluidized chlorination furnace are positively introduced into the furnace, not only the fine particles will not accumulate in the furnace, but also the high boiling point of the liquid phase on the surface of the fine particles. As the chloride adheres and is discharged to the outside of the furnace together with the fine particles, the high boiling point chloride is effectively discharged to the outside of the furnace.

The titanium tetrachloride production method of the present invention has been completed on the basis of such knowledge, and in the production method of titanium tetrachloride by a fluid chlorination method using a fluid chlorination furnace, a fine process that exhibits poor reactivity in the atmosphere in the furnace. Particles are charged directly into a fluidized bed in a fluidized chlorination furnace. Here, the direct introduction of fine particles that are difficult to react in the furnace atmosphere into the fluidized bed in the fluidized chlorination furnace means that the fine particles are introduced into the fluidized bed in the fluidized chlorination furnace and the raw material introduction path. Is to use another dedicated route.

  In the titanium tetrachloride production method of the present invention, the hardly reactive fine particles put into the fluidized bed are not decomposed due to the poor reactivity, and because they are fine particles, they are discharged out of the furnace in the particle state. Liquid phase high-boiling chlorides are deposited on the surface during the discharge process. Thereby, discharge | emission of the high boiling point chloride in a fluidized bed outside a furnace is accelerated | stimulated, and the raise of the high boiling point chloride concentration is suppressed. Moreover, there is no secondary adverse effect such as loss of raw materials or accumulation of hardly reactive fine particles in the furnace, and the efficiency is high.

  The important factors in the titanium tetrachloride production method of the present invention are the reactivity of fine particles, the particle diameter, and the input form (input location, input timing, input amount, etc.). These factors are described in detail below.

[Reactivity]
The atmosphere in the furnace during the operation of the fluidized chlorination furnace, particularly the atmosphere in the fluidized bed, is a high-temperature and high-chlorine highly reactive atmosphere having a temperature of 1000 to 1100 ° C. and a chlorine concentration of 95% or more. In the present invention, it is important that the fine particles introduced into the fluidized bed do not decompose as much as possible in this atmosphere. When the fine particles thrown into the fluidized bed undergo a decomposition reaction, not only do they lose adhesion to high boiling point chlorides, making them difficult to function as carriers, but they also produce chlorides themselves, especially when they contain Ca or Mg Causes a high boiling point chloride concentration.

Specifically, the reactivity of fine particles in the fluidized bed atmosphere is preferably such that the Gibbs free energy ΔG is 60 J / mol-Cl ₂ or more in the reaction with chlorine at 1100 ° C., and 70 J / mol-Cl _Two or more are more desirable. Since this index ΔG is better as it is larger, there is no upper limit. Examples of particulate materials that satisfy this requirement include SiO ₂ and Al ₂ O ₃ . Incidentally, these ΔG is 91J / mol-Cl ₂ approximately in SiO _2, a 72J / mol-Cl ₂ approximately in _Al 2 _{O 3.}

〔Particle size〕
In order for the fine particles introduced during the operation of the fluidized chlorination furnace to function as a high boiling point chloride carrier, it is necessary to discharge as much as possible out of the furnace. From this viewpoint, the particle size of the fine particles needs to be small, and specifically, it is preferably 100 μm or less, more preferably 50 μm or less in terms of the average particle size (Dp = 50). As for the lower limit of the particle size, if the particle size is too small, the upper end of the fluidized bed is reached immediately after the addition, and the function as a carrier of high boiling point chloride cannot be sufficiently achieved. = 50) is preferably 10 μm or more, more preferably 20 μm or more.

[Input type]
During the operation of the fluidized chlorination furnace, the fluidized bed is formed in the lower part of the furnace, and the titanium tetrachloride gas generated in the fluidized bed rises in the furnace and is discharged from the top of the furnace to the outside of the furnace. When fine particles are introduced above the fluidized bed, the particles are discharged outside the furnace without coming into contact with the fluidized bed on the rising airflow in the furnace, so that they do not function sufficiently as a carrier. Therefore, the fine particles and be introduced directly into the fluidized layer, specifically, by a separate dedicated route the raw material introducing path, directly introduced into the fluidized layer with a carrier gas such as nitrogen gas or dry air to be performed.

  In addition, although the efficiency is lowered, it is also possible to mix the hardly reactive fine particles with the raw material powder (titanium ore powder and coke powder) and put it into the fluidized bed through the raw material charging path.

  With respect to the charging time, the high boiling point chloride concentration in the fluidized bed may be used as an index, and the charging may be performed whenever it is detected. This charging period is, for example, several hours to several days.

  If the input amount during the input period (strictly, the input amount per unit time at the input speed) is too small, the effect of lowering the high boiling point chloride concentration is small, and if it is too large, the chlorination reaction of titanium ore may be inhibited. Therefore, it is preferably 5 to 20% in terms of the ratio (weight ratio) to the raw material input amount (total input amount of titanium ore powder and coke powder). The feed of the raw material is usually continuous, but the feed of the hardly reactive fine particles may be continuous or intermittent. The total input amount is obtained by multiplying the input amount by the input time per day and further by the input period (number of days). The total amount of input generally corresponds to the concentration of high-boiling chloride to be reduced.

In the titanium tetrachloride production method of the present invention, in the production operation of titanium tetrachloride by the fluid chlorination method using a fluid chlorination furnace, in the fluidized bed in the form of fine particles such that the hardly reactive substance particles are discharged out of the furnace. By directly charging into the fluidized bed, the high boiling point chloride in the fluidized bed can be efficiently discharged out of the furnace without accumulating the hardly-reactive substance particles in the furnace and without causing loss of raw materials. Therefore, it is possible to efficiently avoid trouble of flow failure due to high boiling point chloride in the fluidized bed, and it is effective for improving operational efficiency and economy.

It is a vertical section elevation with a schematic structure figure of a fluid chlorination furnace used for one embodiment of the present invention.

  Embodiments of the present invention will be described below with reference to the drawings.

  As shown in FIG. 1, the fluidized chlorination furnace used in the titanium tetrachloride production method of the present embodiment continuously feeds titanium ore powder as raw material powder together with coke powder into the lower part of a cylindrical furnace body 1. In addition, the fluidized bed 2 is formed in the lower part of the furnace body 1 by continuously blowing chlorine gas into the furnace from the furnace bottom. In the fluidized bed 2, the titanium ore is chlorinated at a high temperature of 1000 to 1100 ° C., thereby generating titanium tetrachloride gas. The produced titanium tetrachloride gas is sequentially discharged from the furnace top to the outside of the furnace.

Titanium ore contains metal oxides such as CaO and MgO as impurities. Since these impurities are reactive substances, they are chlorinated in the furnace to produce high-boiling chlorides such as CaCl ₂ and MgCl ₂ , which accumulate in the fluidized bed 2 in the liquid phase and cause troubles in flow failure. As described above, it is the cause. Apart from this, hardly reactive substance particles such as SiO ₂ and Al ₂ O ₃ brought in from titanium ore or refractories in the furnace also accumulate in the fluidized bed 2 as impurities.

The titanium tetrachloride production method of this embodiment, during the operation of the fluidized chlorination furnace to monitor the high-boiling chloride concentration in the fluidized bed 2, here is represented by the concentration of CaCl _2. As described above, the upper limit of the CaCl ₂ concentration is 5% by mass, and if it exceeds this, a flow failure trouble occurs due to aggregation or sintering of particles. Therefore, when the monitor value of the CaCl ₂ concentration approaches this upper limit, from the fine particle supply pipe 3 directly connected to the fluidized bed 2 in the furnace body 1, hardly reactive fine particles such as SiO ₂ are used as nitrogen gas or dry air as the carrier gas. Directly into the fluidized bed 2.

  The hardly reactive fine particles introduced into the fluidized bed 2 rise in the furnace body 1 without being decomposed and are discharged from the furnace top to the outside of the furnace body 1 together with the titanium tetrachloride gas. At this time, the hardly reactive fine particles cause the high boiling point chloride in the fluidized bed 2 to adhere to the surface and are discharged to the outside of the furnace body 1, thereby contributing to the reduction of the high boiling point chloride concentration in the fluidized bed 2.

  During operation of the fluidized chlorinating furnace, the concentration of chlorine gas in the titanium tetrachloride gas is monitored in the titanium tetrachloride take-out pipe extending from the top of the furnace body 1, and the reactivity of the fluidized bed 2 is determined by the monitored value of the chlorine gas concentration. Monitor. When the chlorine gas concentration in the titanium tetrachloride gas is increased and the reactivity of the fluidized bed 2 is deteriorated, the oxidation promoting gas such as dry air or oxygen gas is directly fed into the fluidized bed 2 through the gas supply path at the bottom of the furnace. By blowing, the coke in the fluidized bed 2 is combusted and the reactivity of the fluidized bed 2 is improved. Moreover, the reactivity of the fluidized bed 2 is improved by extracting the particulate material constituting the fluidized bed 2 to the outside of the furnace body 1 as necessary.

  The deterioration of the reactivity of the fluidized bed 2 here is mainly due to accumulation of the titanium ore powder and hardly reactive coarse particles having a large particle diameter brought in from the refractory constituting the inner wall of the furnace body 1 in the fluidized bed 2. On the other hand, the flow failure trouble due to the increase in the high-boiling chloride concentration in the fluidized bed 2 and the decrease in the reactivity of the fluidized bed 2 due to this are effective by direct injection of the hardly reactive fine particles into the fluidized bed 2. To be avoided.

  Next, the effectiveness of the above-described titanium tetrachloride production method, that is, the results of an actual investigation on the effect of directly introducing the hardly reactive fine particles into the fluidized bed will be described.

In the actual operation of titanium tetrachloride production by the fluid chlorination method using a fluid chlorination furnace, the CaCl ₂ concentration was monitored as the high boiling point chloride concentration in the fluidized bed. As the operating period of the fluidized chlorination furnace became longer, the CaCl ₂ concentration increased. When the monitored value of the CaCl ₂ concentration reached a preset countermeasure starting concentration, SiO ₂ particles having an average particle diameter (Dp = 50) of 50 μm were introduced into the fluidized bed as difficult-to-react fine particles.

The carrier gas used for charging is nitrogen gas. The input amount was 10% as a ratio (weight ratio) to the raw material input amount (total input amount of titanium ore powder and coke powder). The charging time was 5 hours per day. The charging period was 3 days, and the transition of CaCl ₂ concentration in the fluidized bed was investigated. The concentration at which the countermeasure was started was set with reference to a concentration that reached the upper limit when left for several days to 10 days (here, one week).

The same investigation was conducted on SiO ₂ particles having an average particle diameter (Dp = 50) of 100 μm and Al ₂ O ₃ particles having an average particle diameter (Dp = 50) of 50 μm. The transition of the CaCl ₂ concentration in the fluidized bed is shown in Table 1, including the case where no countermeasure (uncharged) has been taken. The CaCl ₂ concentration in the table is expressed as a ratio with the concentration before the start of particle introduction, that is, the countermeasure starting concentration being 100.

In the case of no countermeasure (uninjected), it is predicted that the CaCl ₂ concentration in the fluidized bed increases every day, increases by 40% after 3 days, and reaches the upper limit after 1 week. When SiO ₂ particles having an average particle diameter (Dp = 50) of 50 μm were added, the CaCl ₂ concentration in the fluidized bed decreased, and after 30 days, the concentration decreased by nearly 30% and after 3 days, it decreased by 50% or more. Even when SiO ₂ particles having an average particle diameter (Dp = 50) of 100 μm were added, the CaCl ₂ concentration was lowered, but the extent thereof was compared with that when SiO ₂ particles having an average particle diameter (Dp = 50) of 50 μm were added. And small. When Al ₂ O ₃ particles having an average particle diameter (Dp = 50) of 50 μm were added, although the CaCl ₂ concentration decreased, SiO ₂ particles having an average particle diameter (Dp = 50) of 100 μm were added. Even smaller than the case.

From this first comparative test, it was found that the introduction of hardly reactive fine particles is effective in reducing the CaCl ₂ concentration in the fluidized bed, and that the particle size of the hardly reactive fine particles is preferably 50 μm rather than 100 μm, It can be seen that SiO ₂ is more effective as a material than Al ₂ O ₃ . The reason why SiO ₂ is more effective than Al ₂ O ₃ is that Al ₂ O ₃ is more reactive to chlorine than SiO _2, and therefore some Al ₂ O ₃ fine particles react with chlorine. This is considered to be because AlCl ₃ was volatilized due to the above.

As a second comparative test, when introducing SiO ₂ particles having an average particle diameter (Dp = 50) of 50 μm, the input amount (weight ratio with respect to the raw material input amount) was variously changed from 5% to 20%. The conditions other than the input amount (weight ratio with respect to the raw material input amount) are the same as in the first comparative test. The test results are shown in Table 2.

When the amount of SiO ₂ particles input (weight ratio to the amount of raw material input) is in the range of 5% to 20%, an effect of decreasing the CaCl ₂ concentration in the fluidized bed is observed. The effect shows a remarkable tendency as the input amount increases, but when it exceeds 20%, there is a sign that the chlorination reaction of titanium ore is inhibited.

As a third comparative test, the input amount of SiO ₂ particles (weight ratio with respect to the input amount of raw material) was 10%, and the input time per day was variously changed from 1 hour to 7 hours. Other conditions are the same as those in the first comparative test and the second comparative test. The results are shown in Table 3. It can be seen that since the total amount of input increases as the input time of the SiO ₂ particles becomes longer, the CaCl ₂ concentration in the fluidized bed tends to decrease, but it is saturated in about 5 hours. For this reason, the input time per day is preferably 5 hours or more, but it does not need to be extremely long.

1 furnace body 2 fluidized bed 3 fine particle supply pipe

Claims (6)

  Titanium ore powder and coke powder are charged into the fluidized chlorination furnace, and by injecting chlorine gas into the furnace from the furnace bottom, a fluidized bed is formed in the lower part of the furnace, and the titanium tetrachloride gas is taken out from the top of the furnace. In a method for producing titanium tetrachloride by a fluidized chlorination method using a fluidized chlorination furnace, fine particles exhibiting poor reactivity in the atmosphere in the furnace are added to the titanium ore powder and coke powder in the fluidized bed in the fluidized chlorination furnace. Titanium tetrachloride production method in which it is introduced directly through a dedicated route different from the input route.   The method for producing titanium tetrachloride according to claim 1, wherein fine particles are introduced into the fluidized bed in a timely manner when the high boiling point chloride concentration in the fluidized bed approaches a dangerous level that hinders stable operation. By this, the titanium tetrachloride manufacturing method which maintains the high boiling-point chloride density | concentration in a fluidized bed within the stable operation level. 3. The titanium tetrachloride production method according to claim 1, wherein the reactivity of the fine particles is such that the Gibbs free energy ΔG in the reaction with chlorine at 1100 ° C. is 60 J / mol-Cl ₂ or more. Production method. Four in titanium tetrachloride production process, fine particles are SiO ₂ particles or Al ₂ O ₃ of titanium tetrachloride production process is a particle according to claim 3.   The titanium tetrachloride manufacturing method according to any one of claims 1 to 4, wherein the fine particles have a mean particle size (Dp = 50) of 10 to 100 µm. In the titanium tetrachloride manufacturing method according to any one of claims 1 to 5, the input amount of fine particles is expressed as a ratio (weight ratio) to a raw material input amount (total input amount of titanium ore powder and coke powder), and 5 to 5. The titanium tetrachloride manufacturing method which is 20%.

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