Titanium tetrachloride production method and sponge titanium production method

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 produced in a chlorination furnace, and a method for producing titanium sponge using the titanium tetrachloride. [Background technology]

[0002] Titanium sponge is widely produced industrially by the Kroll process, in which titanium tetrachloride is reduced with metallic magnesium. To obtain titanium tetrachloride, the raw material for titanium sponge, titanium ore is heated together with coke in a chlorination furnace while chlorine gas is supplied to the furnace, causing the titanium oxide in the titanium ore to react with the chlorine.

[0003] In the chlorination furnace, crude titanium tetrachloride gas containing many impurities derived from titanium ore, coke, etc. The crude titanium tetrachloride gas discharged from the chlorination furnace may be brought into contact with the crude titanium tetrachloride liquid for cooling in a condenser by spraying the crude titanium tetrachloride liquid onto the crude titanium tetrachloride gas, and cooled to a temperature below the boiling point to condense the gas, thereby forming crude titanium tetrachloride liquid.

[0004] A portion of the crude titanium tetrachloride liquid obtained by condensing the crude titanium tetrachloride gas as described above is separated for use as the crude titanium tetrachloride liquid for cooling, and is 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, the remainder of the crude titanium tetrachloride liquid is subjected to distillation for separation and concentration utilizing the difference in boiling points between titanium tetrachloride and each impurity, or rectification by repeated distillation, to obtain liquid titanium tetrachloride with a reduced content of impurities (refined titanium tetrachloride).

[0005] Regarding cooling the crude titanium tetrachloride liquid before contacting it with the crude titanium tetrachloride gas, Patent Document 1 proposes "a TiCl4 production method comprising reacting titanium oxide-containing ore and coke with chlorine gas in a fluidized furnace to obtain crude TiCl4 gas, cooling this gas in a crude TiCl4 gas cooling step, liquefying the cooled crude TiCl4 gas in a condenser to obtain crude TiCl4 liquid, and refining the crude TiCl4 liquid, characterized in that the liquefaction of the crude TiCl4 gas in the condenser is carried out by introducing the crude TiCl4 liquid liquefied and extracted in the condenser into a crude TiCl4 liquid cooler and cooling it, and returning the cooled crude TiCl4 liquid to the condenser to contact it with the crude TiCl4 gas, and the temperature of the crude TiCl4 liquid introduced into the crude TiCl4 liquid cooler is set to 85°C or lower." Patent Document 1 states that "The amounts of NbCl5 and FeCl3 dissolved in the TiCl4 liquid increase rapidly and quadratically as the temperature of the TiCl4 liquid increases. Therefore, if the temperature of the crude TiCl4 liquid introduced into the heat exchanger is lowered in advance, the concentrations of NbCl5 and FeCl3 in the crude TiCl4 liquid brought into the heat exchanger can be greatly reduced, and the rate at which these chlorides adhere to the heat transfer plate surface can be greatly reduced. The NbCl5 and FeCl3 that precipitate as the temperature of the crude TiCl4 liquid decreases can be separated by settling before being introduced into the heat exchanger." [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2009-46337 A Summary of the Invention [Problem to be solved by the invention]

[0007] In the method described in Patent Document 1, in order to "set the temperature of the crude TiCl4 liquid introduced into the crude TiCl4 liquid cooler to 85°C or lower," prior cooling in a "storage tank" or the like is required before introduction into the "crude TiCl4 liquid cooler." In this case, impurities are precipitated and accumulated on the cooling surface of the cooling mechanism of the "storage tank" during prior cooling, and the cooling capacity decreases as with the "crude TiCl4 liquid cooler," so the problem of the shortened usable life of cooling devices such as the cooling mechanism installed in the "crude TiCl4 liquid cooler" and the "storage tank" is not fundamentally solved.

[0008] An object of the present invention is to provide a method for producing titanium tetrachloride and a method for producing titanium sponge, which enable good use of a cooling device for a crude titanium tetrachloride liquid which is brought into contact with a crude titanium tetrachloride gas for a relatively long period of time. [Means for solving the problem]

[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 liquid may gradually decrease due to the precipitation or adhesion of impurities to the inside of the device. It has been newly discovered that such a decrease in cooling capacity is particularly noticeable when the crude titanium tetrachloride is excessively cooled in the cooling device in the initial stage of cooling after the start of use of the cooling device. This is because the initial excessive cooling makes it easier for impurities to precipitate, and the precipitate adheres to the inner wall of the flow path of the cooling device, causing a rapid decrease in cooling capacity. As a result, the usable life of the cooling device is significantly shortened. In response to this, the inventor has found that the life of the cooling device can be extended by changing the settings of the cooling device between the initial stage and the final stage of cooling in the cooling device to prevent the crude titanium tetrachloride liquid from being cooled too much in the initial stage.

[0010] The method for producing titanium tetrachloride of the present invention is a method for producing titanium tetrachloride from crude titanium tetrachloride gas produced in a chlorination furnace, and includes a condensing step of contacting the crude titanium tetrachloride gas produced in the chlorination furnace with a crude titanium tetrachloride liquid for cooling to condense the crude titanium tetrachloride gas produced in the chlorination furnace with a crude titanium tetrachloride liquid for cooling to 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 condensing step and cooling the part of the crude titanium tetrachloride liquid in a cooling device prior to using the part of the crude titanium tetrachloride liquid as the crude titanium tetrachloride liquid for cooling in the condensing step, wherein in the cooling step, the amount of refrigerant supplied to the cooling device is made smaller and / or the temperature of the refrigerant supplied to the cooling device is made higher during the period between the start of use of the cooling device and the point at which 50% of the total usage period has elapsed from the start of use (hereinafter also referred to as the "50% period on the start of use side") than during the period between the point 50% of the total usage period prior to the end of use of the cooling device and the end of use (hereinafter also referred to as the "50% period on the end of use side"). The above "start 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 process to the cooling device is started. The above "end of use" refers to the time when the operation is stopped and the cooling device is maintained or replaced with a new one. Here, the average value of the amount of refrigerant supplied to the cooling device and / or the average value of the temperature of the refrigerant supplied to the cooling device during each of the 50% period on the start of use side and the 50% period on the end of use side are calculated, and the magnitude relationship between these average values ​​during the 50% period on the start of use side and the 50% period on the end of use side is confirmed. The measurement interval of the amount of refrigerant supplied and the temperature of the refrigerant depends on the equipment used for the measurement, but if the interval is relatively short, for example about 1 second, an average value with sufficiently high accuracy can be calculated.

[0011] In the period between the start of use of the cooling device and the time when 40% of the total usage period has elapsed since the start of use (hereinafter also referred to as the "40% period on the start of use side"), the amount of refrigerant supplied to the cooling device may be made smaller and / or the temperature of the refrigerant supplied to the cooling device may be made higher than in the period between the time when 40% of the total usage period has elapsed since the end of use of the cooling device and the time when the usage ended (hereinafter also referred to as the "40% period on the end of use side"). Also, in the period between the start of use of the cooling device and the time when 30% of the total usage period has elapsed since the start of use of the cooling device (hereinafter also referred to as the "30% period on the start of use side"), the amount of refrigerant supplied to the cooling device may be made smaller and / or the temperature of the refrigerant supplied to the cooling device may be made higher than in the period between the time when 30% of the total usage period has elapsed since the end of use of the cooling device and the time when the usage ended (hereinafter also referred to as the "30% period on the end of use side").

[0012] Also, in the initial stage of cooling the crude titanium tetrachloride liquid in the cooling device, the amount of refrigerant supplied to the cooling device can be made smaller than that in the final stage of cooling the crude titanium tetrachloride liquid. Here, in the entire period of use of the cooling device during the continuous operation of the titanium tetrachloride production facility, "initial stage of cooling" means the period from the start of use of the cooling device until 3 days have passed, and "final stage of cooling" means the period from 5 days before the end of use of the cooling device until the end of use. If the amount of refrigerant supplied during the initial period of 2 days (48 hours) or more of cooling is less than the maximum amount supplied during the final stage of cooling, and / or if the temperature of the refrigerant during the initial period of 2 days (48 hours) or more of cooling is higher than the lowest temperature during the final stage of cooling, it is considered that the amount of refrigerant supplied during the initial period of cooling is less than that during the final stage of cooling, and / or the temperature of the refrigerant during the initial period of 2 days (48 hours) or more of cooling is higher than the lowest temperature during the final stage of cooling. In other words, during a short period (less than one day (24 hours)) at the beginning of cooling, the amount of refrigerant supplied may not be less than the maximum amount supplied at the end of cooling, and the temperature of the refrigerant may not be higher than the lowest temperature at the end of cooling.

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

[0014] In the cooling step, the temperature of the crude titanium tetrachloride liquid after cooling in the cooling device (target cooling temperature) may be maintained within the range of 60°C to 80°C during 50% of the period from the start of use.

[0015] In the cooling step, the amount of the refrigerant supplied to the cooling device is preferably adjusted within a range of 10 L / min to 5000 L / min.

[0016] In the cooling step, the temperature of the refrigerant is preferably adjusted within a range of -10°C to 40°C.

[0017] In the above production method, it is preferable that 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.

[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 in which the remaining crude titanium tetrachloride liquid separated from the crude titanium tetrachloride liquid obtained in the condensation step is distilled.

[0020] The method for producing titanium sponge of the present invention uses titanium tetrachloride produced by any one of the above-mentioned methods for producing titanium tetrachloride. Effect of the Invention

[0021] According to the process for producing titanium tetrachloride of the present invention, the cooling device for the crude titanium tetrachloride liquid which is brought into contact with the crude titanium tetrachloride gas can be used satisfactorily for a relatively long period of time. [Brief description of the drawings]

[0022] [Figure 1]FIG. 1 is a schematic diagram showing an example of equipment that can be used in a method for producing titanium tetrachloride according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Hereinafter, an embodiment of the present invention will be described in detail. A method for producing titanium tetrachloride according to one embodiment of the present invention includes a condensation step and a cooling step. In the condensation step, the crude titanium tetrachloride gas produced in the chlorination furnace is brought into contact with a crude titanium tetrachloride liquid for cooling and condensed to 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 in a cooling device. The crude titanium tetrachloride liquid cooled through the cooling step is used to come into contact with the crude titanium tetrachloride gas as the crude titanium tetrachloride liquid for cooling in the condensation step.

[0024] In the cooling step, the amount of refrigerant supplied to the cooling device is reduced and / or the temperature of the refrigerant supplied to the cooling device is increased during the period between the start of use of the cooling device and the time when 50% of the total use period has elapsed from the start of use, compared to the period between the time when 50% of the total use period has elapsed from the end of use of the cooling device and the end of use. By not cooling the crude titanium tetrachloride liquid too much during the 50% period on the start of use side, the precipitation of impurities in the cooling device during that period is suppressed, so that early deterioration of the cooling capacity and, in turn, shortening of the life of the cooling device can be suppressed. Furthermore, it is preferable to change the settings of the cooling device during operation in accordance with the deterioration of the cooling capacity of the cooling device over time from the start of operation so that the temperature of the crude titanium tetrachloride liquid after cooling in 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 is reduced, the excessive cooling of the crude titanium tetrachloride liquid in the cooling device and the excessive temperature reduction of the crude titanium tetrachloride liquid after cooling can be further suppressed, especially before the deterioration of the cooling capacity. As a result, the precipitation of a large amount of impurities caused by such excessive cooling is suppressed, and the cooling device can be used satisfactorily for an even longer period of time.

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

[0026] (Chlorination process) In the chlorination step, the titanium oxide in the titanium ore is chlorinated 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 below the raw material containing titanium ore and coke toward the upper side, forming a fluidized bed. Crude titanium tetrachloride gas is produced in the fluidized bed. At this time, carbon dioxide, sulfur-containing compounds, etc. may also be produced 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 (TiCl4), it contains the above-mentioned impurities and has a lower purity than the titanium tetrachloride finally produced (refined titanium tetrachloride). Note that the term "titanium tetrachloride" is used when there is no distinction between the above-mentioned crude titanium tetrachloride and refined titanium tetrachloride.

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

[0031] At this time, the crude titanium tetrachloride gas is cooled using crude titanium tetrachloride liquid that has undergone a cooling step described below (also referred to as "crude titanium tetrachloride liquid for cooling"). More specifically, in the condenser 2, the crude titanium tetrachloride gas can be brought into contact with the crude titanium tetrachloride liquid by, for example, spraying the crude titanium tetrachloride liquid toward the crude titanium tetrachloride gas fed thereto. The crude titanium tetrachloride gas is cooled and condensed by contact with the crude titanium tetrachloride liquid, becoming the crude titanium tetrachloride liquid.

[0032] The temperature of the crude titanium tetrachloride liquid obtained in the condensation step may be maintained at 90°C or lower, and is preferably in the range of 65°C to 90°C. If the temperature of the crude titanium tetrachloride liquid obtained in the condensation step is relatively low as described above, it is not necessary to significantly lower the temperature to a predetermined temperature in the subsequent cooling step, so that the amount of impurities precipitated in the cooling device 4 can be suppressed from increasing. On the other hand, if the temperature is too high, there is a risk of an increase in the risk of failure of the pump for circulating the crude titanium tetrachloride liquid (hereinafter also referred to as the "circulation pump"). In addition, if the temperature of the crude titanium tetrachloride liquid obtained in the condensation step is less than 65°C, the crude titanium tetrachloride liquid will be in a supercooled state, which will consume unnecessary cooling energy, so it is sufficient to maintain an appropriate temperature as necessary.

[0033] Changing the settings of the cooling device 4 during operation so that the temperature of the crude titanium tetrachloride liquid obtained in the condensation step is maintained within a predetermined range may include changing the amount of refrigerant supplied to the cooling device 4 and / or changing the temperature of the refrigerant supplied to the cooling device 4. More specifically, for example, the temperature of the crude titanium tetrachloride liquid at the inlet 2a and outlet 2b of the crude titanium tetrachloride liquid in the condenser 2, particularly at the outlet 2b, is monitored, and the aperture of the refrigerant flow rate control valve of the cooling device 4 is adjusted according to the temperature, and / or the temperature of the refrigerant supplied to the cooling device 4 is changed, either automatically or manually. Preferably, the equipment further includes a control device (not shown), which automatically performs such control of adjustments, changes, and the like.

[0034] The crude titanium tetrachloride liquid obtained in the condensation step may be stored in the storage tank 3 as necessary. However, it is preferable not to cool the crude titanium tetrachloride liquid in the storage tank 3. In addition, it is preferable not to cool the crude titanium tetrachloride liquid obtained in the condensation step, not limited to the storage tank 3, from the condenser 2 through the storage tank 3, until a part of it is separated and sent to the cooling device 4. If the crude titanium tetrachloride liquid from the condenser 2 is cooled before being sent to the cooling device 4, impurities may precipitate during the cooling, which may cause problems such as a decrease in the cooling capacity. Note that the cooling here means intentional cooling using a heat exchanger or other machine, and natural cooling is not included and is therefore permitted.

[0035] (cooling process) The crude titanium tetrachloride liquid obtained in the condensation step is stored in a storage tank 3 in some cases, and then a portion of it is separated and sent to a cooling device 4. In the cooling device 4, as a cooling step, the portion 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 the equipment 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 the precipitation. In response to such a decrease in the cooling capacity of the cooling device 4, it is preferable to change the settings of the cooling device 4 during operation so that the temperature of the crude titanium tetrachloride liquid after cooling in the cooling device 4 (i.e., the temperature of the crude titanium tetrachloride liquid at the outlet 4b of the cooling device 4) is maintained within a 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 a range of 60°C to 80°C may be the entire use period of the cooling device, but it is preferable to set it to at least 50% of the period from the start of use.

[0037] In this way, excessive cooling and a large drop in temperature at the outlet 4b, particularly in the early stages of operation, can be avoided when a predetermined excessive setting is always maintained in anticipation of a drop in cooling capacity over time, so that an increase in the amount of impurities precipitated and a large drop in cooling capacity can be suppressed. From this perspective, it is preferable that the temperature of the crude titanium tetrachloride liquid after cooling in the cooling device 4 be maintained at 60°C to 70°C.

[0038] Changing the settings of the cooling device 4 during operation so as to maintain the temperature of the titanium tetrachloride liquid after cooling within a predetermined range may include changing the amount of coolant supplied to the cooling device 4 and / or changing the temperature of the coolant supplied to the cooling device 4. More specifically, for example, the temperature of the crude titanium tetrachloride liquid at the outlet 4b of the cooling device 4 may be monitored, and depending on the temperature, the aperture of the coolant flow rate control valve of the cooling device 4 may be adjusted and / or the temperature of the coolant supplied to the cooling device 4 may be changed, either automatically or manually. Preferably, the facility further includes a control device (not shown), which automatically performs such control of adjustments, changes, and the like.

[0039] In this embodiment, the amount of refrigerant supplied to the cooling device is made smaller and / or the temperature of the refrigerant supplied to the cooling device is made higher in the 50% period leading up to the start of use of the cooling device 4 than in the 50% period leading up to the end of use of the cooling device 4. Also preferably, the amount of refrigerant supplied to the cooling device 4 is made smaller and / or the temperature of the refrigerant supplied to the cooling device 4 is made higher in the early stage of cooling of the crude titanium tetrachloride liquid than in the final stage of cooling of the crude titanium tetrachloride liquid. In this case, since excessive cooling in the early stage is suppressed, it is possible to suppress a shortening of the usage period due to a large amount of precipitation of impurities in the early stage of the cooling device, and it is possible to realize a longer life of the cooling device.

[0040] The amount of the coolant supplied to the cooling device is preferably 5% to 10% of the value at the end of cooling in the early stage of cooling, that is, the amount of the coolant supplied during the initial period of 2 days (48 hours) or more is 5% to 10% of the maximum amount supplied during the final period of cooling. In addition, the temperature of the coolant is preferably ±0°C to 50°C of the value at the final period of cooling in the early stage of cooling, that is, the temperature of the coolant is preferably ±0°C to 50°C of the maximum temperature at the final period of cooling during the initial period of 2 days (48 hours) or more. Note that, during the period between the early stage and the final stage, the amount of the coolant supplied to the cooling device may be temporarily increased and / or the temperature of the coolant supplied to the cooling device may be lowered compared to the final period of cooling of the crude titanium tetrachloride liquid. However, it is preferable to gradually increase the amount of the coolant supplied and / or gradually increase the temperature of the coolant from the early stage of cooling to the final period of cooling.

[0041] When changing the amount of coolant supplied to the cooling device 4, the amount of coolant supplied is preferably adjusted within a range of 10 L / min to 5000 L / min. By not increasing the amount of coolant supplied too much, excessive cooling of the crude titanium tetrachloride liquid is easily suppressed. On the other hand, by not decreasing the amount of coolant supplied too little, the temperature of the crude titanium tetrachloride liquid at the outlet 2b of the condenser 2 is prevented from becoming too high, which suppresses the cooling required in the subsequent stages and reduces the risk of failure of the circulation pump.

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

[0043] In the cooling step, it is preferable that the temperature drop of the crude titanium tetrachloride liquid inside the cooling device 4 is relatively narrow from the viewpoint of suppressing the precipitation of impurities. If the temperature drop is wide, impurities will precipitate in an amount corresponding to the temperature drop due to the relationship between the solubility of the impurities in titanium tetrachloride and the temperature. Specifically, the liquid temperature drop ΔT, 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 thus cooled in the cooling device 4 is sent to the condenser 2, where it is brought into contact with the crude titanium tetrachloride gas flowing from the chlorination furnace 1 into the condenser 2, and is used to cool the crude titanium tetrachloride gas.

[0045] (Distillation process) The remaining crude titanium tetrachloride liquid separated from the portion of the crude titanium tetrachloride liquid sent to the cooling device 4 is heated and evaporated in the evaporation pot 5, and is distilled to become crude titanium tetrachloride gas. The crude titanium tetrachloride gas is then supplied to the rectification tower 6. Note that in the distillation step, the remaining crude titanium tetrachloride liquid separated from the portion of the crude titanium tetrachloride liquid sent to the cooling device 4 may be configured to be supplied directly to the rectification tower 6 without passing through the evaporation pot 5.

[0046] The inside of the distillation tower 6 is divided by multiple shelves arranged at different heights in the vertical direction, and at each stage, the high-boiling point components and low-boiling point components of the crude titanium tetrachloride are separated based on the difference in boiling point through gas-liquid contact. As a result, the titanium tetrachloride (refined titanium tetrachloride) obtained through the distillation tower 6 has many of the impurities contained in the crude titanium tetrachloride gas sufficiently removed. Note that the term "distillation" is used to include not only distillation that separates and concentrates titanium tetrachloride and each impurity by utilizing the difference in boiling point, but also rectification in which such distillation is repeated.

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

[0048] The production of titanium sponge involves, for example, contacting molten magnesium metal with titanium tetrachloride by dropping it into the metal in a reduction vessel, and reducing the titanium tetrachloride with the magnesium metal according to the reaction: TiCl4+2Mg→Ti+2MgCl2. This reduction causes the titanium metal to grow as a titanium sponge mass, and a titanium sponge mass is obtained.

[0049] The titanium sponge mass is then removed from the reduction vessel and crushed to produce a titanium sponge of a predetermined size. EXAMPLES

[0050] Next, the method for producing titanium tetrachloride according to the present invention was experimentally carried out, and its effects were confirmed, which will be described below. However, the description here is merely for illustrative purposes and is not intended to be limiting.

[0051] A titanium tetrachloride production facility as shown in FIG. 1 was operated to produce titanium tetrachloride. More specifically, the crude titanium tetrachloride gas produced in the chlorination furnace was sent to a condenser, and was cooled and condensed in the condenser by spraying a crude titanium tetrachloride liquid for cooling, and the crude titanium tetrachloride liquid obtained was stored in a storage tank. The crude titanium tetrachloride liquid was not intentionally cooled in the storage tank. Then, after a part of the crude titanium tetrachloride liquid in the storage tank was cooled in a cooling device (heat exchanger), this was 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 evaporator and a rectification column, and was used for the production of titanium tetrachloride. Here, the temperature of the crude titanium tetrachloride after cooling in the cooling device (cooling target temperature) was set to 70°C.

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

[0053] In Table 1, "initial stage" and "end stage" are as described above. "Life" in Table 1 refers to the point in time when the temperature of the crude titanium tetrachloride liquid after cooling no longer drops below the target temperature (target cooling temperature) even if the temperature and supply amount of the coolant during supply are changed to the upper limit of the settable range, and is shown here as an index value based on Comparative Example 1. Tables 2 and 3 show the average values ​​of each temperature and supply amount for the 50% period and 30% period on the start and end of use sides, respectively.

[0054] In Comparative Example 1, the temperature of the cooled crude titanium tetrachloride liquid (the outlet temperature of the cooling device) initially dropped to 40° C., which caused the amount of impurities adhering to the inside to increase, causing an early drop in the cooling capacity, and within a short period of time, the temperature of the cooled crude titanium tetrachloride liquid could no longer be maintained at the cooling target temperature of 70° C. In Comparative Example 1, this state was deemed to be 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 when it was supplied to the cooling device was lowered to 20°C.

[0056] In Comparative Example 2, by lowering the temperature of the coolant, the temperature of the crude titanium tetrachloride liquid after the initial cooling dropped to 30°C. This caused the adhesion and growth of impurities inside the cooling device to progress rapidly, shortening the life of the cooling device. However, although the life of Comparative Example 2 was shorter than that of Comparative Example 1, the crude titanium tetrachloride liquid was easily cooled due to the low temperature of the coolant, and therefore the life of the device was not shortened extremely.

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

[0058] In Example 1, the amount of coolant supplied was initially reduced to prevent the crude titanium tetrachloride liquid from being cooled too much, and then the amount of coolant supplied was increased in accordance with the decrease in cooling capacity, so that the temperature of the cooled crude titanium tetrachloride liquid during operation was maintained at about 70° C. As a result, the adhesion and growth of impurities inside the cooling device was suppressed, and the life was dramatically 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 when it was supplied to the cooling device was 20°C.

[0060] In Example 2, as in Example 1, the temperature of the crude titanium tetrachloride liquid after cooling during operation was maintained at approximately 70°C by initially suppressing the amount of coolant supplied, and a significant improvement in life was confirmed. In Example 2, the temperature of the coolant was lower than in Example 1, making it easier to cool the crude titanium tetrachloride liquid, and therefore the life was 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 supplied to the cooling device was lowered in accordance with the decrease in cooling capacity, and the temperature of the refrigerant supplied at the final stage was set to 20°C.

[0062] As a result, compared to Example 2, the initial cooling was further suppressed, and the adhesion and growth of impurities was suppressed, so the life was slightly longer.

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

[0064] As a result, compared to Example 3, the lifespan was extended by further lowering the refrigerant temperature at the end.

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

[0066] As a result, the adhesion and growth of impurities inside the cooling device was suppressed, and the life was extended compared to Comparative Example 1. However, the cooling capacity was reduced compared to Example 1 due to excessive cooling caused by increasing the amount of refrigerant supplied on the first day, and the amount of refrigerant supplied necessary to maintain the temperature of the cooled crude titanium tetrachloride liquid at 70°C on the second day increased slightly, and the life was slightly shorter than in Example 1.

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

[0068] As a result, adhesion and growth of impurities inside the cooling device was suppressed, and the life was extended compared to Comparative Example 1. However, the cooling capacity was reduced compared to Example 1 due to excessive cooling caused by increasing the amount of refrigerant supplied on the second day, and therefore the life 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 initial liquid temperature drop ΔT was large, which led to greater precipitation of impurities, which is believed to have led to a shorter lifespan. On the other hand, in Examples 5 and 6, although there were times when the liquid temperature drop ΔT temporarily increased, in Examples 1 to 6, the liquid temperature drop ΔT was small overall, which is presumably why precipitation of impurities was suppressed and the lifespan was extended.

[0072] From the above, it has been suggested that the present invention may enable the cooling device to be used satisfactorily for a relatively long period of time. [Explanation of symbols]

[0073] 1 Chlorination furnace 2 Condenser 2a Inlet for crude titanium tetrachloride liquid 2b Outlet for crude titanium tetrachloride liquid 3. Storage tank 4 Cooling device 4a Inlet for crude titanium tetrachloride liquid 4b Outlet for crude titanium tetrachloride liquid 5. Evaporation pot 6 Rectification tower

Claims

1. A method for producing titanium tetrachloride from crude titanium tetrachloride gas produced in a chlorination furnace, comprising the steps of: a condensation step of contacting the crude titanium tetrachloride gas produced in the chlorination furnace with a crude titanium tetrachloride liquid for cooling to condense the gas, thereby obtaining 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 in a cooling device prior to use as the crude titanium tetrachloride liquid for cooling in the condensation step; Including, a cooling step in which an amount of refrigerant supplied to the cooling device is less and / or a temperature of the refrigerant supplied to the cooling device is higher during a period between a time point when use of the cooling device is started and a time point when 50% of a total usage period has elapsed since the time point when use of the cooling device is started than during a period between a time point that is 50% of a total usage period going back from a time point when use of the cooling device is ended and the time point when use is ended.

2. 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 in the cooling device is maintained within a range of 60° C. to 80° C.

3. 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 in the cooling device is maintained within a range of 60° C. to 80° C. during a period between the start of use of the cooling device and the point at which 50% of a total period of use has elapsed since the start of use.

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

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

6. 2. 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. 3. 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. 2. The method for producing titanium tetrachloride according to claim 1, further 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. 1. A method for producing titanium sponge, comprising the steps of: A method for producing titanium sponge, comprising using titanium tetrachloride produced by the method for producing titanium tetrachloride according to any one of claims 1 to 8.

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