Method for producing titanium tetrachloride and method for producing sponge titanium

Abstract

To provide: a titanium tetrachloride production method which can use a cooling device for cooling of crude titanium tetrachloride liquid to be brought into contact with crude titanium tetrachloride gas in good condition over a relatively long period; and a sponge titanium production method.SOLUTION: A titanium tetrachloride production method of the present invention which is a method for producing titanium tetrachloride from crude titanium tetrachloride gas produced in a chlorination furnace includes: a condensation step of bringing the crude titanium tetrachloride gas produced in the chlorination furnace into contact with cooling crude titanium tetrachloride liquid so as to condense the crude titanium tetrachloride gas to obtain crude titanium tetrachloride liquid; and a cooling step of separating a portion of the crude titanium tetrachloride liquid from the crude titanium tetrachloride liquid produced in the condensation step and cooling the portion of the crude titanium tetrachloride liquid using a cooling device before using the portion of the crude titanium tetrachloride liquid as the cooling crude titanium tetrachloride liquid in the condensation step. In the cooling step, the supply amount of a coolant to the cooling device is lower and / or the temperature of the coolant to be supplied to the cooling device is higher in a period between a use start time point of the cooling device and a time point of a lapse of a period of 50% of an entire use period from the use start time point than in a period between a time point of dating back a period of 50% of the entire use period from a use end time point of the cooling device and the use end time point.SELECTED DRAWING: None

Description

Technical Field

[0001] This invention relates to a method for producing titanium tetrachloride from crude titanium tetrachloride gas generated in a chlorination furnace, and a method for producing sponge titanium using the titanium tetrachloride thus obtained.

Background Art

[0002] Sponge titanium is industrially widely produced by the Kroll process in which titanium tetrachloride is reduced with metallic magnesium. To obtain titanium tetrachloride as a raw material for sponge titanium, titanium ore is heated together with coke in a chlorination furnace while supplying chlorine gas thereto, and titanium oxide in the titanium ore is reacted with chlorine.

[0003] In the chlorination furnace, crude titanium tetrachloride gas containing a large number of impurities derived from titanium ore, coke, etc. is generated. The crude titanium tetrachloride gas discharged from the chlorination furnace may be brought into contact with the crude titanium tetrachloride liquid for cooling by spraying the crude titanium tetrachloride liquid for cooling in a condenser or the like, cooled to a temperature below the boiling point, and condensed to obtain a crude titanium tetrachloride liquid.

[0004] A part of the crude titanium tetrachloride liquid obtained by condensing the crude titanium tetrachloride gas as described above is separated for use as the above-mentioned crude titanium tetrachloride liquid for cooling, and cooled to a temperature suitable for cooling the crude titanium tetrachloride gas by a cooling device such as a heat exchanger. On the other hand, with respect to the remainder of the crude titanium tetrachloride liquid, liquid titanium tetrachloride (purified titanium tetrachloride) with a reduced impurity content is obtained by performing distillation that separates and concentrates using the difference in boiling points of titanium tetrachloride and various impurities, or rectification that repeats distillation.

[0005] Regarding cooling the crude titanium tetrachloride liquid before bringing it into contact with the crude titanium tetrachloride gas, Patent Document 1 discloses that "in a fluidized furnace, titanium oxide-containing ore and coke are reacted with chlorine gas to obtain crude TiCl 4 gas, and this gas is cooled in a crude TiCl 4 gas cooling step, and the cooled crude TiCl 4Liquefy the gas with a condenser to obtain crude TiCl 4 liquid, and purify this crude TiCl 4 liquid. In the method for producing TiCl 4 , the liquefaction of the crude TiCl 4 gas in the condenser is carried out by introducing the crude TiCl 4 liquid liquefied and extracted by the condenser into a crude TiCl 4 liquid cooler for cooling, and returning the cooled crude TiCl 4 liquid to the condenser to contact with the crude TiCl 4 gas, and the temperature of the crude TiCl 4 liquid introduced into the crude TiCl 4 liquid cooler is set to 85°C or lower. A method for producing TiCl 4 has been proposed. In this Patent Document 1, it is described that "the amounts of NbCl 4 and FeCl 5 dissolved in the TiCl 3 liquid increase rapidly in a quadratic function as the temperature of the TiCl 4 liquid rises. Therefore, if the temperature of the crude TiCl 4 liquid introduced into the heat exchanger is lowered in advance, the concentrations of NbCl 4 and FeCl 5 in the crude TiCl 3 liquid brought into the heat exchanger can be greatly reduced, and the adhesion rate of these chlorides to the heat transfer plate surface can be significantly reduced. NbCl 4 and FeCl 5 precipitated as the temperature of the crude TiCl 3 liquid decreases can be sedimentation-separated before being introduced into the heat exchanger."

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] In the method described in Patent Document 1, "since the temperature of the crude TiCl 4 solution introduced into the liquid cooler is set to 85°C or lower", it is necessary to perform prior cooling in a "storage tank" or the like before introduction into the "crude TiCl 4 solution cooler". In that case, impurities precipitate and accumulate on the cooling surface of the cooling mechanism of the "storage tank" during the prior cooling, and the cooling capacity decreases in the same way as in the "crude TiCl 4 solution cooler". Therefore, the fundamental solution to the problem that the service life of the cooling device such as the cooling mechanism installed in the "crude TiCl 4 solution cooler" and the "storage tank" is shortened has not been achieved. 4

[0008] An object of the present invention is to provide a method for producing titanium tetrachloride and a method for producing sponge titanium in which a cooling device for a crude titanium tetrachloride solution brought into contact with crude titanium tetrachloride gas can be used favorably for a relatively long period.

Means for Solving the Problems

[0009] During the operation of the titanium tetrachloride production facility, as described in Patent Document 1, the cooling capacity of the cooling device for the crude titanium tetrachloride solution may gradually decrease due to the precipitation or adhesion of impurities inside it. It has newly been found that such a decrease in cooling capacity becomes particularly prominent when the crude titanium tetrachloride is excessively cooled in the cooling device at the initial stage of the cooling after the start of use of the cooling device. This is because impurities are likely to precipitate due to the excessive cooling at the initial stage, and the cooling capacity rapidly decreases due to the adhesion of this precipitate to the inner wall of the flow path of the cooling device. As a result, the service life of the cooling device is significantly shortened. In contrast, the inventor has found that by changing the settings of the cooling device from the initial stage to the final stage of cooling in the cooling device so that the crude titanium tetrachloride solution is not excessively cooled at the initial stage, it is possible to achieve a longer service life of the cooling device.

[0010] The method for producing titanium tetrachloride according to the present invention is a method for producing titanium tetrachloride from the crude titanium tetrachloride gas generated in a chlorination furnace. The method includes a condensation step of bringing the crude titanium tetrachloride gas generated in the chlorination furnace into contact with a crude titanium tetrachloride liquid for cooling to condense and obtain a crude titanium tetrachloride liquid, and a cooling step of separating a part of the crude titanium tetrachloride liquid from the crude titanium tetrachloride liquid obtained in the condensation step and cooling the part of the crude titanium tetrachloride liquid with a cooling device prior to using it as the crude titanium tetrachloride liquid for cooling in the condensation step. In the cooling step, during the period between the start time of using the cooling device and the time when 50% of the total usage period has elapsed since the start time of using the cooling device (hereinafter also referred to as the "50% period on the start side of use"), the supply amount of the refrigerant to the cooling device is made smaller and / or the temperature of the refrigerant supplied to the cooling device is made higher than during the period between the time when 50% of the total usage period has elapsed retrogressively from the end time of using the cooling device and the end time of using the cooling device (hereinafter also referred to as the "50% period on the end side of use"). The above-mentioned "start time of use" refers to the time when the supply of a part of the crude titanium tetrachloride liquid separated from the crude titanium tetrachloride liquid obtained in the condensation step to the cooling device is started. Also, the above-mentioned "end time of use" refers to the time when the operation is stopped to perform maintenance or replacement with a new one for the cooling device. Here, the average value of the supply amount of the refrigerant to the cooling device and / or the average value of the temperature of the refrigerant supplied to the cooling device in each of the 50% period on the start side of use and the 50% period on the end side of use is calculated, and the magnitude relationship between those average values in the 50% period on the start side of use and the 50% period on the end side of use is confirmed. The measurement interval of the supply amount of the refrigerant and the temperature of the refrigerant depends on the device used for the measurement. For example, if the interval is as short as about 1 second, an average value with sufficiently high accuracy can be calculated.

[0011] During the period between the start time of using the cooling device and the time when 40% of the total usage period has elapsed since the start time of use (hereinafter, also referred to as the "40% period on the start side of use"), the period between the time retrogressed 40% of the total usage period from the end time of using the cooling device and the end time of use (hereinafter, also referred to as the "40% period on the end side of use") may be made less than the amount of refrigerant supplied to the cooling device, and / or the temperature of the refrigerant supplied to the cooling device may be increased. Also, during the period between the start time of using the cooling device and the time when 30% of the total usage period has elapsed since the start time of use (hereinafter, also referred to as the "30% period on the start side of use"), the period between the time retrogressed 30% of the total usage period from the end time of using the cooling device and the end time of use (hereinafter, also referred to as the "30% period on the end side of use") may be made less than the amount of refrigerant supplied to the cooling device, and / or the temperature of the refrigerant supplied to the cooling device may be increased.

[0012] Also, at the initial stage of cooling the titanium tetrachloride solution in the cooling device, the amount of refrigerant supplied to the cooling device can be made less than that at the final stage of cooling the titanium tetrachloride solution, and / or the temperature of the refrigerant supplied to the cooling device can be increased. Here, in the entire usage period of the cooling device during continuous operation of the titanium tetrachloride production facility, "the initial stage of cooling" means the period until 3 days have elapsed since the start time of using the cooling device, and "the final stage of cooling" means the period from 5 days before the end time of using the cooling device to the end time of use. If the amount of refrigerant supplied during the above-mentioned period of 2 days (48 hours) or more in the initial stage of cooling is less than the maximum supply amount in the final stage of cooling, and / or if the temperature of the refrigerant during the above-mentioned period of 2 days (48 hours) or more in the initial stage of cooling is higher than the lowest temperature in the final stage of cooling, it is regarded that the amount of refrigerant supplied is less and / or the temperature of the refrigerant is higher in the initial stage of cooling than in the final stage of cooling. In other words, even if the amount of refrigerant supplied does not become less than the maximum supply amount in the final stage of cooling and the temperature of the refrigerant does not become higher than the lowest temperature in the final stage of cooling during a short period (less than 1 day (24 hours)) in the initial stage of cooling, it does not matter.

[0013] In the cooling step, it is preferable to maintain the temperature of the crude titanium tetrachloride liquid after cooling by the cooling device (cooling target temperature) within the range of 60°C to 80°C.

[0014] In the cooling step, during 50% of the starting period of use, it may be acceptable to maintain the temperature of the crude titanium tetrachloride liquid after cooling by the cooling device (cooling target temperature) within the range of 60°C to 80°C.

[0015] In the cooling step, it is preferable to adjust the supply amount of the refrigerant to the cooling device within the range of 10 L / min to 5000 L / min.

[0016] In the cooling step, it is preferable to adjust the temperature of the refrigerant within the range of -10°C to 40°C.

[0017] In the above manufacturing method, it is preferable to send a part of the crude titanium tetrachloride liquid to the cooling device without cooling it, and cool it by the cooling device in the cooling step.

[0018] The temperature of the crude titanium tetrachloride liquid obtained in the condensation step is preferably 90°C or lower.

[0019] It is preferable to include a distillation step of distilling the remaining crude titanium tetrachloride liquid separated from the crude titanium tetrachloride liquid obtained in the condensation step.

[0020] The method for manufacturing sponge titanium of this invention uses titanium tetrachloride manufactured by any of the above methods for manufacturing titanium tetrachloride.

Advantages of the Invention

[0021] According to the method for manufacturing titanium tetrachloride of this invention, the cooling device for the crude titanium tetrachloride liquid brought into contact with the crude titanium tetrachloride gas can be used well over a relatively long period.

Brief Description of the Drawings

[0022]

Figure 1

Embodiments for Carrying Out the Invention

[0023] Hereinafter, embodiments of the present invention will be described in detail. The method for producing titanium tetrachloride according to an embodiment of the present invention includes a condensation step and a cooling step. In the condensation step, the crude titanium tetrachloride gas generated in the chlorination furnace is brought into contact with a crude titanium tetrachloride liquid for cooling to condense and obtain a crude titanium tetrachloride liquid. A part of the crude titanium tetrachloride liquid obtained in the condensation step is separated and supplied to the cooling step. In the cooling step, the part of the crude titanium tetrachloride liquid is cooled by a cooling device. The crude titanium tetrachloride liquid cooled through the cooling step is used as the above-mentioned crude titanium tetrachloride liquid for cooling in the condensation step to be brought into contact with the crude titanium tetrachloride gas.

[0024] And in the cooling step, during the period between the start time of using the cooling device and the time when 50% of the total usage period has elapsed since the start time of using, the supply amount of the refrigerant to the cooling device is made less than the period between the time retrogressed 50% of the total usage period from the end time of using the cooling device and the end time of using, and / or the temperature of the refrigerant supplied to the cooling device is made higher. By not over-cooling the crude titanium tetrachloride liquid during the 50% period on the start side of use in this way, precipitation of impurities in the cooling device during that period can be suppressed, so that a decrease in cooling capacity at an early stage and thus a shortening of the life can be suppressed. Further, it is preferable to change the setting of the cooling device during operation in accordance with the decrease in the cooling capacity of the cooling device as time elapses from the start of operation so that the temperature of the crude titanium tetrachloride liquid after cooling by the cooling device is maintained within the range of 60°C to 80°C. In this case, even if the cooling capacity of the cooling device decreases, particularly before the decrease in the cooling capacity, excessive cooling of the crude titanium tetrachloride liquid by the cooling device and excessive temperature drop of the crude titanium tetrachloride liquid after cooling can be further suppressed. As a result, a large amount of precipitation of impurities due to such excessive cooling can be suppressed, so that the cooling device can be used well for a longer period of time.

[0025] The manufacturing method of this embodiment may be implemented using equipment as shown in FIG. 1, for example. The equipment shown in FIG. 1 includes a chlorination furnace 1 for performing a chlorination process, a condensation device 2 for performing a condensation process on the crude titanium tetrachloride gas generated in the chlorination furnace 1, a storage tank 3 for storing the crude titanium tetrachloride liquid obtained by the condensation device 2, a cooling device 4 for performing a cooling process on a part of the separated crude titanium tetrachloride liquid sent from the storage tank 3, an evaporation kettle 5 for evaporating the remaining crude titanium tetrachloride liquid separated and sent from the storage tank 3 as a distillation process, and a rectification column 6 for performing rectification on the crude titanium tetrachloride gas generated in the evaporation kettle 5. Details of each process will be described below, but as long as it includes a predetermined condensation process and a cooling process, it is included in the present invention.

[0026] (Chlorination Process) In the chlorination process, a chlorination reaction of titanium oxide in the titanium ore is caused in the chlorination furnace 1 to generate crude titanium tetrachloride gas.

[0027] More specifically, for example, at a high temperature of about 1000 ° C. in the chlorination furnace 1, chlorine gas is supplied from the lower side to the upper side of the raw material containing titanium ore and coke to form a fluidized bed therein. Crude titanium tetrachloride gas is generated in the fluidized bed. At this time, carbon dioxide, sulfur-containing compounds, etc. may also be generated as by-products.

[0028] The crude titanium tetrachloride gas thus obtained may contain many impurities derived from titanium ore, coke, etc., specifically, for example, carbon, oxygen, sulfur, phosphorus, chlorine, iron, aluminum, niobium, vanadium, etc.

[0029] Here, "crude titanium tetrachloride" such as crude titanium tetrachloride gas and crude titanium tetrachloride liquid means that in addition to titanium tetrachloride (TiCl 4 ), impurities as described above are contained, and the purity is lower than that of the finally manufactured titanium tetrachloride (purified titanium tetrachloride). The term "titanium tetrachloride" is used when not distinguishing between the above-mentioned crude titanium tetrachloride and purified titanium tetrachloride.

[0030] (Condensation process) The crude titanium tetrachloride gas generated in the chlorination furnace 1 is sent to a condensation device 2 such as a condenser connected to the chlorination furnace 1, and is cooled to a temperature below the boiling point in the condensation device 2 to become a crude titanium tetrachloride liquid.

[0031] At this time, for cooling the crude titanium tetrachloride gas, a crude titanium tetrachloride liquid (also referred to as "crude titanium tetrachloride liquid for cooling") after going through a cooling process described later is used. More specifically, in the condensation device 2, the crude titanium tetrachloride gas can be brought into contact with the crude titanium tetrachloride liquid by spraying the crude titanium tetrachloride liquid toward the crude titanium tetrachloride gas fed therein. The crude titanium tetrachloride gas is cooled and condensed by contact with the crude titanium tetrachloride liquid to become a crude titanium tetrachloride liquid.

[0032] The temperature of the crude titanium tetrachloride liquid obtained in the condensation process may be maintained at 90°C or lower, and particularly preferably within the range of 65°C to 90°C. When the temperature of the crude titanium tetrachloride liquid obtained in the condensation process is low to a certain extent as described above, it is not necessary to significantly lower the temperature until it reaches a predetermined temperature in the subsequent cooling process, so an increase in the precipitation amount of impurities in the cooling device 4 can be suppressed. On the other hand, if the above temperature is too high, there is a risk of an increase in the failure risk of a pump (hereinafter also referred to as a "circulation pump") for circulating the crude titanium tetrachloride liquid. Also, when the temperature of the crude titanium tetrachloride liquid obtained in the condensation process is less than 65°C, the crude titanium tetrachloride liquid is in a supercooled state and consumes unnecessary cooling energy, so the appropriate temperature may be maintained as necessary.

[0033] In order to maintain the temperature of the crude titanium tetrachloride liquid obtained in the condensation step within a predetermined range, changing the settings of the cooling device 4 during operation may include changing the supply amount of the refrigerant to the cooling device 4 and / or changing the temperature of the refrigerant supplied to the cooling device 4. More specifically, for example, among the inlet 2a and the outlet 2b of the crude titanium tetrachloride liquid of the condensation device 2, particularly the temperature of the crude titanium tetrachloride liquid at the outlet 2b is monitored, and according to the temperature, the opening degree of the flow rate adjustment valve of the refrigerant of the cooling device 4 is adjusted, and / or the temperature of the refrigerant supplied to the cooling device 4 is changed, which can be performed automatically or manually. Preferably, a control device (not shown) is further included in the equipment, and such control as adjustment and change is automatically performed by the control device.

[0034] The crude titanium tetrachloride liquid obtained in the condensation step may be stored in the storage tank 3 as needed. However, it is desirable not to cool the crude titanium tetrachloride liquid in the storage tank 3. Also, not limited to the storage tank 3, it is preferable that the crude titanium tetrachloride liquid obtained in the condensation step is not cooled until a part of it is separated and sent to the cooling device 4 after passing through the storage tank 3 from the condensation device 2. This is because if it is cooled between the condensation device 2 and when a part of the crude titanium tetrachloride liquid is sent to the cooling device 4, impurities may precipitate during the cooling, which may cause problems such as a decrease in the cooling capacity during the cooling. Here, the cooling mentioned means intentional cooling using a heat exchanger or other machinery, and natural cooling does not fall under this and is thus allowed.

[0035] (Cooling step) The crude titanium tetrachloride liquid obtained in the condensation step may, in some cases, be stored in the storage tank 3 and then a part of it is separated and sent to the cooling device 4. In the cooling device 4, as a cooling step, a part of the crude titanium tetrachloride liquid is cooled to a temperature appropriate for use as the crude titanium tetrachloride liquid for cooling in the condensation step.

[0036] When titanium tetrachloride is produced by operating equipment as shown in Fig. 1, it is difficult to completely prevent the precipitation of impurities in the cooling device 4 as time passes from the start of operation, and the cooling capacity of the cooling device 4 decreases due to such precipitation. In response to this, in accordance with the decrease in the cooling capacity of such a cooling device 4, by changing the settings of the cooling device 4 during operation, the temperature of the crude titanium tetrachloride liquid after cooling in the cooling device 4 (that is, the temperature of the crude titanium tetrachloride liquid at the outlet 4b of the cooling device 4) is preferably maintained within the range of 60°C to 80°C. The period during which the temperature of the crude titanium tetrachloride liquid after cooling in the cooling device 4 is maintained within the range of 60°C to 80°C may be the entire usage period of the cooling device, but it is preferably at least 50% of the period on the start-up side.

[0037] By doing so, in the case of always maintaining a predetermined excessive setting in anticipation of the aging reduction of the cooling capacity, excessive cooling particularly at the initial stage of operation and a significant temperature drop at the outlet 4b are avoided, so an increase in the precipitation amount of impurities and thus a large reduction in the cooling capacity can be suppressed. From this perspective, the temperature of the crude titanium tetrachloride liquid after cooling in the cooling device 4 is preferably maintained at 60°C to 70°C.

[0038] To change the settings of the cooling device 4 during operation so that the temperature of the titanium tetrachloride liquid after cooling is maintained within a predetermined range, it may include changing the supply amount of the refrigerant to the cooling device 4 and / or changing the temperature of the refrigerant supplied to the cooling device 4. More specifically, for example, monitoring the temperature of the crude titanium tetrachloride liquid at the outlet 4b of the cooling device 4, and adjusting the opening degree of the flow rate adjustment valve of the refrigerant in the cooling device 4 according to the temperature, and / or changing the temperature of the refrigerant supplied to the cooling device 4 can be performed automatically or manually. Preferably, a control device (not shown) is further included in the equipment, and such control such as adjustment and change is automatically performed by the control device.

[0039] In this embodiment, during the 50% period on the start side of the cooling device 4 rather than the 50% period on the end side of its use, the supply amount of the refrigerant to the cooling device is reduced, and / or the temperature of the refrigerant supplied to the cooling device is increased. Preferably, at the initial stage of cooling the titanium tetrachloride solution in the cooling device 4, rather than at the final stage of cooling the titanium tetrachloride solution, the supply amount of the refrigerant to the cooling device 4 is reduced, and / or the temperature of the refrigerant supplied to the cooling device 4 is increased. In this case, excessive initial cooling can be suppressed, so that shortening of the service life due to massive precipitation of impurities at the initial stage of the cooling device can be suppressed, and long life of the cooling device can be realized.

[0040] The supply amount of the refrigerant to the cooling device should be 5% - 10% of the value at the final stage of cooling at the initial stage of cooling, that is, during a period of 2 days (48 hours) or more at the initial stage of cooling, the supply amount of the refrigerant is 5% - 10% of the maximum supply amount at the final stage of cooling, which is preferable. Also, the temperature of the refrigerant should be ±0°C - 50°C of the value at the final stage of cooling at the initial stage of cooling, that is, during a period of 2 days (48 hours) or more at the initial stage of cooling, the temperature of the refrigerant is ±0°C - 50°C of the highest temperature at the final stage of cooling, which is preferable. Note that during the period between the initial stage and the final stage, temporarily, the supply amount of the refrigerant to the cooling device may be increased more than that at the final stage of cooling the titanium tetrachloride solution, and / or the temperature of the refrigerant supplied to the cooling device may be decreased. However, it is preferable to gradually increase the supply amount of the refrigerant and / or gradually increase the temperature of the refrigerant from the initial stage to the final stage of cooling.

[0041] When changing the supply amount of the refrigerant to the cooling device 4, the supply amount of the refrigerant is preferably adjusted within the range of 10 L / min - 5000 L / min. By not increasing the supply amount of the refrigerant too much, excessive cooling of the titanium tetrachloride solution is likely to be suppressed. On the other hand, by not reducing the supply amount of the refrigerant too much, the temperature of the titanium tetrachloride solution at the outlet 2b of the condenser 2 is prevented from becoming too high, necessary cooling in the subsequent stage is suppressed, and the risk of failure of the circulation pump can be reduced.

[0042] When changing the temperature of the refrigerant supplied to the cooling device 4, the temperature of the refrigerant is preferably adjusted within the range of -10°C to 40°C. By not lowering the temperature of the refrigerant too much, excessive cooling of the crude titanium tetrachloride liquid is likely to be suppressed. On the other hand, by not raising the temperature of the refrigerant too much, the temperature of the crude titanium tetrachloride liquid at the outlet 2b of the condenser 2 is prevented from becoming too high, suppressing the necessary cooling in the subsequent stage and reducing the risk of failure of the circulation pump.

[0043] Also, in the cooling process, it is preferable from the viewpoint of suppressing the precipitation of impurities that the temperature drop width of the crude titanium tetrachloride liquid inside the cooling device 4 is somewhat narrow. This is because when the temperature drop width is wide, an amount of impurities corresponding to the amount of temperature drop will precipitate according to the relationship between the solubility of impurities in titanium tetrachloride and temperature. Specifically, the temperature drop width ΔT of the liquid temperature, which is the difference (T2 - T1) between the temperature T1 of the crude titanium tetrachloride liquid at the inlet 4a of the cooling device 4 and the temperature T2 of the crude titanium tetrachloride liquid at the outlet 4b of the cooling device 4, may be 15°C or less, and is preferably 1°C to 15°C.

[0044] The crude titanium tetrachloride liquid cooled by the cooling device 4 in this way is sent to the condenser 2 and used for contact with the crude titanium tetrachloride gas flowing into the condenser 2 from the chlorination furnace 1 and for cooling the crude titanium tetrachloride gas thereby.

[0045] (Distillation process) The remaining crude titanium tetrachloride liquid separated from a part of the crude titanium tetrachloride liquid sent to the cooling device 4 is heated and evaporated in the evaporation kettle 5 and becomes crude titanium tetrachloride gas while being distilled. Then, the crude titanium tetrachloride gas is supplied to the rectification column 6. In addition, in the distillation process, a configuration may be adopted in which the remaining crude titanium tetrachloride liquid separated from a part of the crude titanium tetrachloride liquid sent to the cooling device 4 is directly supplied to the rectification column 6 without passing through the evaporation kettle 5.

[0046] The rectification column 6 is partitioned by a plurality of shelf plates arranged at different heights in the vertical direction. At each stage, through the contact of gas and liquid, the high-boiling components and low-boiling components of crude titanium tetrachloride are separated based on the difference in boiling points. As a result, the titanium tetrachloride (purified titanium tetrachloride) obtained by passing through the rectification column 6 has most of the impurities contained in the crude titanium tetrachloride gas sufficiently removed. Note that the term "distillation" is used to mean not only distillation that separates and concentrates by utilizing the difference in boiling points of titanium tetrachloride and each impurity, but also rectification that repeats such distillation.

[0047] (Method for producing sponge titanium) The titanium tetrachloride obtained as described above can be used for the production of sponge titanium.

[0048] To produce sponge titanium, for example, in a reduction container, titanium tetrachloride is brought into contact with molten metallic magnesium by dropping it, etc., and based on the reaction of the formula: TiCl 4 + 2Mg → Ti + 2MgCl 2 titanium tetrachloride is reduced with metallic magnesium. By this reduction, metallic titanium grows as a sponge titanium mass, and a sponge titanium mass is obtained.

[0049] Thereafter, the sponge titanium mass is taken out of the reduction container and crushed, whereby sponge titanium of a predetermined size can be produced.

Example

[0050] Next, the method for producing titanium tetrachloride of the present invention was experimentally implemented and its effects were confirmed, and the description thereof will be given below. However, the description here is for the purpose of mere exemplification and is not intended to be limited thereto.

[0051] The production equipment for titanium tetrachloride as illustrated in FIG. 1 was operated to produce titanium tetrachloride. More specifically, the crude titanium tetrachloride gas generated in the chlorination furnace was sent to a condenser, cooled and condensed by spraying a crude titanium tetrachloride liquid for cooling in the condenser, and the obtained crude titanium tetrachloride liquid was stored in a storage tank. Intentional cooling of the crude titanium tetrachloride liquid was not performed in the storage tank. Then, a part of the crude titanium tetrachloride liquid in the storage tank was cooled by a cooling device (heat exchanger) and then used as the crude titanium tetrachloride liquid for cooling in the condenser. The remaining part of the crude titanium tetrachloride liquid was rectified using an evaporation kettle and a rectification column and used for the production of titanium tetrachloride. Here, the temperature of the crude titanium tetrachloride after cooling (cooling target temperature) in the cooling device was set to 70°C.

[0052] (Comparative Example 1) During the operation, the settings of the cooling device were not changed, and the temperature and supply amount of the refrigerant at the time of supply shown in Table 1 were maintained.

[0053] In Table 1, "initial" and "end" are as described above. The "life" in Table 1 means the time point when the temperature of the crude titanium tetrachloride liquid after cooling does not decrease below the target temperature (cooling target temperature) even when the temperature and supply amount of the refrigerant at the time of supply are changed to the upper limit values within the settable range, and here it is shown as an index value based on Comparative Example 1. Tables 2 and 3 show the average values of the respective temperatures and supply amounts in the 50% period and 30% period on the start side and end side of use.

[0054] In Comparative Example 1, at the initial stage, due to the temperature of the crude titanium tetrachloride liquid after cooling (the outlet temperature of the cooling device) dropping to 40°C, the adhesion amount of internal impurities increased, the cooling capacity decreased early, and the temperature of the crude titanium tetrachloride liquid after cooling could not be maintained at the cooling target temperature of 70°C within a short period. In Comparative Example 1, this state was regarded as the end of the life of the cooling device.

[0055] (Comparative Example 2) The operation was carried out in the same manner as in Comparative Example 1 except that the temperature of the refrigerant at the time of supply to the cooling device was lowered to 20°C.

[0056] In Comparative Example 2, by reducing the temperature of the refrigerant, the temperature of the crude titanium tetrachloride liquid after the initial cooling decreased to 30°C. As a result, the adhesion and growth of impurities inside the cooling device advanced rapidly, and the life of the cooling device became shorter. However, although Comparative Example 2 had a shorter life than Comparative Example 1, since the temperature of the refrigerant was low, the crude titanium tetrachloride liquid was easily cooled, and thus the device life did not become extremely short.

[0057] (Example 1) The operation was carried out in the same manner as in Comparative Example 1, except that the supply amount of the refrigerant to the initial cooling device was set to 50 L / min, and the supply amount of the refrigerant was increased in accordance with the decrease in the cooling capacity. At the initial stage of cooling, a constant refrigerant temperature and supply amount were set.

[0058] In Example 1, at the initial stage, the supply amount of the refrigerant was suppressed so as not to overcool the crude titanium tetrachloride liquid, and then the supply amount of the refrigerant was increased in accordance with the decrease in the cooling capacity, and the temperature of the crude titanium tetrachloride liquid after cooling during the operation was maintained at about 70°C. As a result, the adhesion and growth of impurities inside the cooling device were suppressed, and the life was significantly extended compared to Comparative Examples 1 and 2.

[0059] (Example 2) The operation was carried out in the same manner as in Example 1, except that the temperature of the refrigerant at the time of supply to the cooling device was set to 20°C.

[0060] Also in Example 2, since the supply amount of the refrigerant was suppressed at the initial stage as in Example 1, the temperature of the crude titanium tetrachloride liquid after cooling during the operation was maintained at approximately 70°C, and a significant improvement in life was confirmed. In Example 2, compared to Example 1, since the temperature of the refrigerant was low and the crude titanium tetrachloride liquid was easily cooled, the life became slightly longer.

[0061] (Example 3) The operation was carried out in the same manner as in Example 1, except that the temperature of the refrigerant at the time of supply to the cooling device was decreased in accordance with the decrease in the cooling capacity, and the temperature of the refrigerant at the time of supply at the end stage was set to 20°C.

[0062] As a result, compared with Example 2, the initial cooling was further suppressed, the adhesion and growth of impurities were inhibited, and thus the life was slightly extended.

[0063] (Example 4) The operation was carried out in the same manner as in Example 3, except that an antifreeze (ethylene glycol-based) was used as the refrigerant and the temperature at the time of supplying the refrigerant to the final cooling device was set to -10°C. The antifreeze was cooled by a refrigerator (not shown).

[0064] As a result, compared with Example 3, the life was extended by further lowering the temperature of the refrigerant at the end stage.

[0065] (Example 5) The operation was carried out in the same manner as in Example 1, except that the supply amount of the refrigerant was set to 1000 L / min only on the first day of the start of use of the cooling device at the initial stage of cooling. In Example 5, since the target cooling temperature of the crude titanium tetrachloride solution after cooling was set to 70°C, even if the refrigerant supply amount was increased on the first day for excessive cooling, the refrigerant supply amount was adjusted so as to reach the target cooling temperature thereafter. For example, the refrigerant supply amount on the second day of start was 100 L / min as shown in Table 1.

[0066] As a result, the adhesion and growth of impurities inside the cooling device were suppressed, and the life was extended compared with Comparative Example 1. However, since the refrigerant supply amount was increased on the first day for excessive cooling, the cooling capacity decreased compared with Example 1, and the refrigerant supply amount required to maintain the temperature of the crude titanium tetrachloride solution after cooling at 70°C on the second day increased slightly, and the life was slightly shorter than that of Example 1.

[0067] (Example 6) The operation was carried out in the same manner as in Example 1, except that the supply amount of the refrigerant was set to 1000 L / min only on the second day from the start of use of the cooling device at the initial stage of cooling.

[0068] As a result, the adhesion and growth of impurities inside the cooling device were suppressed, and the lifespan was extended compared to Comparative Example 1. However, since the cooling capacity decreased compared to Example 1 due to an increase in the refrigerant supply amount on the second day and excessive cooling, the lifespan was slightly shorter than that of Example 1.

[0069]

Table 1

[0070]

Table 2

Table 3

[0071] Also, as shown in Table 1, in Comparative Examples 1 and 2, the precipitation of impurities increased due to a large initial decrease in the liquid temperature ΔT, which is considered to have led to a shortening of the lifespan. On the other hand, in Examples 5 and 6, although the decrease in the liquid temperature ΔT sometimes temporarily increased, in Examples 1 to 6, since the overall decrease in the liquid temperature ΔT was small, it is presumed that the precipitation of impurities was suppressed and the lifespan was extended.

[0072] From the above, according to this invention, it was suggested that the cooling device could be used well over a relatively long period.

Explanation of Reference Signs

[0073] 1 Chlorination Furnace 2 Condensation Device 2a Inlet of Crude Titanium Tetrachloride Liquid 2b Outlet of Crude Titanium Tetrachloride Liquid 3 Storage Tank 4 Cooling Device 4a Inlet of Crude Titanium Tetrachloride Liquid 4b Outlet of Crude Titanium Tetrachloride Liquid 5 Evaporation Kettle 6 Rectification Tower

Claims

1. A method for producing titanium tetrachloride from the crude titanium tetrachloride gas generated in a chlorination furnace, comprising: a condensation step of bringing the crude titanium tetrachloride gas generated in the chlorination furnace into contact with a crude titanium tetrachloride liquid for cooling to condense it and obtain a crude titanium tetrachloride liquid; a cooling step of separating a part of the crude titanium tetrachloride liquid from the crude titanium tetrachloride liquid obtained in the condensation step and cooling the part of the crude titanium tetrachloride liquid with a cooling device prior to using it as the crude titanium tetrachloride liquid for cooling in the condensation step; and in the cooling step, during the period between the start point of using the cooling device and the point in time when 50% of the total usage period has elapsed since the start point of use, reducing the supply amount of the refrigerant to the cooling device and / or increasing the temperature of the refrigerant supplied to the cooling device compared to the period between the point in time retrogressing 50% of the total usage period from the end point of use of the cooling device and the end point of use; a method for producing titanium tetrachloride.

2. The method for producing titanium tetrachloride according to claim 1, wherein in the cooling step, the temperature of the crude titanium tetrachloride liquid after cooling with the cooling device is maintained within the range of 60°C to 80°C.

3. The method for producing titanium tetrachloride according to claim 1, wherein in the cooling step, during the period between the start point of using the cooling device and the point in time when 50% of the total usage period has elapsed since the start point of use, the temperature of the crude titanium tetrachloride liquid after cooling with the cooling device is maintained within the range of 60°C to 80°C.

4. The method for producing titanium tetrachloride according to claim 1, wherein in the cooling step, the supply amount of the refrigerant to the cooling device is adjusted within the range of 10 L / min to 5000 L / min.

5. The method for producing titanium tetrachloride according to claim 1, wherein in the cooling step, the temperature of the refrigerant is adjusted within the range of -10°C to 40°C.

6. The method for producing titanium tetrachloride according to claim 1, wherein the part of the crude titanium tetrachloride liquid is sent to the cooling device without being cooled and is cooled by the cooling device in the cooling step.

7. The method for producing titanium tetrachloride according to claim 2, wherein the temperature of the crude titanium tetrachloride liquid obtained in the condensation step is 90°C or lower.

8. The method for producing titanium tetrachloride according to claim 1, comprising a distillation step of distilling the remaining crude titanium tetrachloride liquid separated from the crude titanium tetrachloride liquid obtained in the condensation step.

9. A method for producing sponge titanium, comprising: A method for producing sponge titanium, which uses titanium tetrachloride produced by the method for producing titanium tetrachloride according to any one of claims 1 to 8.

Images