JP7717508B2 - Titanium tetrachloride manufacturing method - Google Patents

Description

The present invention relates to a method for producing titanium tetrachloride.

Titanium tetrachloride is not only used as a raw material for producing sponge-like solid titanium metal (hereinafter referred to as "titanium sponge"), but is also widely used in the fields of catalysts and medicine. Titanium tetrachloride is produced by reacting coke, a carbon source, titanium oxide contained in titanium ore, and chlorine gas at high temperatures.

Titanium tetrachloride is produced in a fluidized bed formed inside a chlorination furnace with a refractory structure, where ore and coke are fluidized with chlorine gas. When producing titanium tetrachloride using a chlorination furnace, unreacted titanium ore and coke from the fluidized bed may be transferred together with chlorine gas from the fluidized bed through a titanium tetrachloride recovery pipe located above the chlorination furnace to a titanium tetrachloride recovery facility downstream in the production process. In such cases, the production yield of titanium tetrachloride decreases. To prevent this decrease in production yield, technology such as that described in Patent Document 1 has been reported.

Patent Document 1, cited above, describes a "method for producing titanium tetrachloride using a fluidized chlorination furnace, characterized in that after a first reducing agent is introduced into the fluidized chlorination furnace to form a fluidized bed, a second reducing agent having a calcium concentration higher than that of the first reducing agent is introduced into the fluidized chlorination furnace in order to control the temperature within the fluidized bed within a predetermined temperature range."

JP 2019-081673 A

Incidentally, when producing the required amount of titanium tetrachloride in a chlorination furnace, it is important to accurately determine the height of the fluidized bed in order to appropriately control the titanium tetrachloride production reaction in the fluidized bed formation region (hereinafter also referred to as the "fluidized bed"). It is known that the height of the fluidized bed is typically determined by the bulk density of the raw materials charged into the chlorination furnace, the amount of raw materials charged, etc.

However, because the side walls of the chlorination furnace are equipped with inner walls made of firebricks or other materials that can withstand the high heat generated during the production of titanium tetrachloride, workers cannot visually observe the height of the fluidized bed from outside the chlorination furnace, making it extremely difficult to determine the height of the fluidized bed. If the height of the fluidized bed cannot be determined and a sufficient height cannot be ensured for the amount of chlorine gas supplied per unit time, there is a risk that the reaction between titanium oxide and chlorine gas in the fluidized bed will be insufficient. In such cases, it will also lead to a decrease in the production yield of titanium tetrachloride.

Therefore, one embodiment of the present invention aims to provide a method for producing titanium tetrachloride that can improve the production yield of titanium tetrachloride.

As mentioned above, the height of the fluidized bed in a chlorination furnace cannot be visually observed from outside the furnace. Therefore, the inventors have diligently investigated a method for determining the height of the fluidized bed.

Measuring the internal pressure of the chlorination furnace is one way to determine the height of the fluidized bed. However, the area above the height of the fluidized bed in the chlorination furnace (freeboard section) is not only far from the fluidized bed, but also has a very large internal pressure difference with the fluidized bed, so it is not appropriate to use this internal pressure to determine the height of the fluidized bed. In order to determine the height of the fluidized bed, it is considered more appropriate to measure the internal pressure in the area where the fluidized bed is formed, rather than the internal pressure in the freeboard section.

On the other hand, if the internal pressure of the fluidized bed formation region in a chlorination furnace is measured in only one location, it is necessary to convert the internal pressure measurement result of one fluidized bed formation region into the height of the fluidized bed using some kind of coefficient. In this case, the fluidized bed height is calculated using a coefficient that depends on the bulk density of the titanium ore. However, because the state of the fluidized bed fluctuates depending on factors such as the timing of raw material input into the fluidized bed and fluctuations in the bulk density of the raw materials themselves, calculations using the above coefficients cannot be said to produce highly accurate results.

After careful consideration of these points, the inventors have discovered that the production yield of titanium tetrachloride can be improved by measuring the internal pressure in the fluidized bed formation region at two or more different height positions and then estimating the height of the fluidized bed based on the fluidized bed information obtained.

In other words, in one aspect, the present invention is a method for producing titanium tetrachloride by using a chlorination furnace equipped with a distributor and forming a fluidized bed containing titanium oxide-containing titanium ore, coke, and chlorine gas on the distributor, and the method further includes an estimation step of estimating the height of the fluidized bed, in which the height of the fluidized bed is estimated based on fluidized bed information obtained by measuring the internal pressure in the fluidized bed formation region at two or more different positions in the vertical direction.

In one embodiment of the titanium tetrachloride production method according to the present invention, the fluidized bed information includes a differential pressure in the height direction between the internal pressures of the two or more fluidized bed formation regions.

In one embodiment of the titanium tetrachloride production method according to the present invention, the fluidized bed information further includes the distance between measurement points of the internal pressure in the two or more fluidized bed formation regions in the height direction.

In one embodiment of the titanium tetrachloride production method according to the present invention, the side wall of the chlorination furnace surrounding the fluidized bed is provided with two or more openings at different height positions, and in the estimation step, the internal pressure of the two or more fluidized bed formation regions is measured through the openings.

In one embodiment of the method for producing titanium tetrachloride according to the present invention, the estimation step includes supplying gas from the opening toward the fluidized bed.

One embodiment of the present invention provides a method for producing titanium tetrachloride that can improve the yield in the production of titanium tetrachloride.

1 is a schematic diagram showing the internal structure of a chlorination furnace used in one embodiment of a method for producing titanium tetrachloride according to the present invention. FIG. 1B is a partially enlarged cross-sectional view showing a distributor and a fluidized bed in the chlorination furnace of FIG. 1A. 1B is a schematic end view taken along the section line XX of FIG. 1A. 1B is a schematic end view showing another example of the arrangement of the opening of the chlorination furnace shown in FIG. 1A. FIG. FIG. 2 is a schematic view showing the internal structure of a chlorination furnace used in another embodiment of the method for producing titanium tetrachloride according to the present invention. 2B is a partially enlarged cross-sectional view showing a distributor and a fluidized bed in the chlorination furnace of FIG. 2A. FIG. 1 is a schematic diagram showing the internal structure of an opening device used in one embodiment of a method for producing titanium tetrachloride according to the present invention. FIG.

The present invention is not limited to the embodiments described below, and the components can be modified and embodied without departing from the spirit of the invention. Furthermore, various inventions can be created by appropriately combining multiple components disclosed in each embodiment. For example, an invention may be created by deleting some components from all the components shown in the embodiments. Note that the drawings show some components schematically to facilitate understanding of the embodiments included in the invention, and the illustrated sizes, positional relationships, etc. may not necessarily be accurate.
In addition, in this specification, the "height direction" means a direction parallel to the vertical direction of the chlorination furnace (in the illustrated cases, the vertical direction of the chlorination furnaces 100 and 200 shown in Figures 1A and 2A). In addition, in this specification, the "height position of the openings" means the height position of the center points of the openings (in the illustrated cases, the center points C1 to C5 of the openings 112, 114, 212, 214, and 216) when viewed from the front in the height direction, as shown in Figures 1B and 2B. In addition, in this specification, the "internal pressure" means pressure (gauge pressure) expressed relative to atmospheric pressure.

[Method of producing titanium tetrachloride]
One embodiment of the method for producing titanium tetrachloride according to the present invention is a method for producing titanium tetrachloride using a chlorination furnace 100 equipped with a distributor 120 shown in FIG. 1A , and includes a step of estimating the height of the fluidized bed 140 above the distributor 120 based on fluidized bed information. The fluidized bed information is obtained by measuring the internal pressure in the formation region of the fluidized bed 140 at two or more locations at different height positions in the chlorination furnace 100. The fluidized bed information includes at least the internal pressures at the two or more locations and may also include other information. In the chlorination furnace 100, the internal pressure is typically different between the upper and lower sides of the fluidized bed 140. From the viewpoint of accurately determining the height of the fluidized bed 140, the fluidized bed information preferably includes the differential pressure in the height direction of the internal pressures measured at the two or more locations. From the viewpoint of even more accurately determining the height of the fluidized bed 140, the fluidized bed information more preferably includes the measurement point distance L (see FIG. 1B ), which is the distance along the height direction between the measurement points of the internal pressures in the formation region of the fluidized bed 140 at two or more locations. At this time, from the viewpoint of constantly maintaining the height of the fluidized bed 140 at a desired height, it is more preferable to continuously measure the internal pressure of the fluidized bed 140. If the internal pressure of the fluidized bed 140 is continuously measured, changes in the pressure can be quickly grasped, and it can be quickly determined whether or not measures to maintain the height of the fluidized bed 140, such as the addition of titanium ore or coke, are necessary. Note that a sudden drop in the measured pressure may lead to the determination that "a fluidized bed has not been formed," but the information that a fluidized bed does not exist alone may not be enough to determine the amount of chlorine gas to be supplied to the chlorination furnace, and therefore it is important to determine the "height of the fluidized bed" in the present invention.
A preferred embodiment of the estimation step will be described below while explaining the chlorination furnace 100.

(Chlorination furnace)
The chlorination furnace 100 comprises a chlorination furnace main body 110, a distributor 120, a wind box 130, a chlorine-containing gas pipe 150, a raw material supply pipe 160, and a titanium tetrachloride recovery pipe 170. Known shapes and materials can be appropriately adopted for the chlorination furnace main body 110, the distributor 120, the wind box 130, the chlorine-containing gas pipe 150, the raw material supply pipe 160, and the titanium tetrachloride recovery pipe 170. The fluidized bed 140 is formed on the distributor 120 within the chlorination furnace main body 110 after the production of titanium tetrachloride has started. The fluidized bed 140 is a component of the chlorination furnace 100 that is formed during operation.

(Opening)
The openings 112 and 114 are provided in the sidewall 111 surrounding the fluidized bed 140 from the viewpoint of facilitating measurement of the internal pressure in the formation region of the fluidized bed 140. The openings 112 and 114 are provided at different positions in the height direction on the sidewall 111 in the formation region of the fluidized bed 140, in order to measure the internal pressure in the formation region of the fluidized bed 140 at two or more different positions in the height direction. The cross-sectional shape of the openings 112 and 114 is not particularly limited, and examples include a circular shape and a polygonal shape. When the cross-sectional shape of the openings 112 and 114 is circular, the diameter of the openings 112 and 114 is, for example, 50 to 100 mm. In this case, it is preferable that the diameters of the openings 112 and 114 are approximately the same, taking into account the influence on the internal pressure that can be measured.
Deposits containing impurities derived from titanium ore and/or coke may form at the lower end of the fluidized bed 140, i.e., on the upper surface of the distributor 120. The lower end of the fluidized bed 140 may be unsuitable for measuring the internal pressure due to the influence of the deposits. For this reason, it may not be preferable to provide the opening 112 at the lower end of the fluidized bed 140. The ratio (H1/H) of the distance (H1) from the center point C2 of the lower opening 112 to the upper surface of the distributor 120 to the distance (H) from the expected upper surface of the fluidized bed 140 to the upper surface of the distributor 120 in the height direction is, for example, 0.1 to 0.4. More specifically, when the distance (H) is within the range of 1500 to 2500 mm, the distance H1 is, for example, 300 mm or more, or, for example, 500 mm or more. This allows the internal pressure of the fluidized bed 140 to be stably measured at the opening 112 for a long period of time, with little influence from the deposits.
Furthermore, for the position of the opening 114 that is higher in the height direction, the ratio (L) of the distance between the measurement points from the center point C2 of the opening 112 at a lower height to the center point C1 of the opening 114 at a higher height and the distance (H1) from the center point C2 of the opening 112 at a lower height to the upper surface of the distributor 120 in the height direction to the distance (H) from the assumed upper surface of the fluidized bed 140 to the upper surface of the distributor 120 is, for example, 0.2 to 0.7, from the viewpoint of clarifying the difference with the internal pressure of the opening 112 at a lower height. More specifically, when the distance (H) is within the range of 1500 to 2500 mm, the distance L between the measurement points is, for example, 300 mm or more, 500 mm or more. This allows the height of the fluidized bed 140 to be more accurately determined.
When measuring the internal pressure at the openings 112 and 114, gas may be supplied from the openings 112 and 114 toward the fluidized bed 140 in order to suppress deposition of titanium ore and/or coke near the openings 112 and 114. For example, as shown in FIG. 1B , one end of each of anti-clogging air pipes 113 and 115 is connected to the openings 112 and 114, respectively, and an air supply source (not shown) is connected to the other end of each of the anti-clogging air pipes 113 and 115. Furthermore, each of the anti-clogging air pipes 113 and 115 is provided with a pressure measurement pipe (not shown) for measuring the internal pressure of the fluidized bed 140. By measuring the internal pressure in the pressure measurement pipe with a pressure detection means, the internal pressure in the formation region of the fluidized bed 140 can be determined, and fluidized bed information can be obtained. An example of a specific configuration of the anti-clogging air pipes 113 and 115 will be described later.

(Example of a method for determining the height of the fluidized bed)
An example of a method for determining the height of the fluidized bed 140 will be described below.
1A and 1B, when there are two openings 112, 114 (a lower opening 112 and an upper opening 114) at different positions in the height direction, the fluidized bed height H can be calculated based on the following formula (1). It is assumed that air is supplied from the openings 112, 114 at the same flow rate.
H={P _L1 / (P _L1 - _{P L2} )}×L...Formula (1)
H: Fluidized bed height (mm)
P _L1 : Internal pressure (kPa) of the fluidized bed formation region measured by the pressure detection means of the pressure measurement pipe of the clogging prevention air pipe 113 connected to the lower opening 112
P _L2 : Internal pressure (kPa) in the fluidized bed formation region measured by the pressure detection means of the pressure measurement pipe of the clogging prevention air pipe 115 connected to the upper opening 114
L: Distance between measurement points (mm), which is the distance from the center point C2 of the lower opening 112 to the center point C1 of the upper opening 114
During operation of the chlorination furnace 100, the measured internal pressure tends to increase as the height position of the measurement point in the fluidized bed 140 decreases. Furthermore, the above-mentioned P _L1 /(P _L1 - P _L2 ) makes it possible to know the tendency of the internal pressure in the formation region of the fluidized bed 140 at a certain distance between the measurement points. The theoretical fluidized bed height H can be obtained by multiplying the above-mentioned P _L1 /(P _L1 - _{P L2} ) by the distance L between the measurement points.

Alternatively, as shown in FIG. 1D , multiple openings 114a-114d may be provided at the same height. Specifically, measurements are obtained from openings 114a-114d, and the differential pressure from opening 112 and the distance between the measurement points are substituted into equation (1) above to determine the height of each fluidized bed 140. The average of the obtained heights of fluidized bed 140 may be the height of fluidized bed 140. In the embodiment shown in FIG. 1D , if any clear abnormality is found in the internal pressure values obtained from the pressure measurement tubes of the clog prevention air pipes connected to openings 114a-114d at the same height, the abnormal internal pressure value may not be used, and the height of fluidized bed 140 may be determined based on equation (1) above. Note that clog prevention air pipes 115a-d are connected to each opening.
1D, multiple openings 114a-d are provided on the upper side of the fluidized bed 140, but multiple openings may also be provided on the lower side of the fluidized bed 140. For example, if the number of openings 114a-d on the upper side of the fluidized bed 140 is the same as the number of openings on the lower side of the fluidized bed 140, and the upper openings 114a-d and the lower openings of the fluidized bed 140 are located at the same positions in the circumferential direction, the differential pressure between each opening 114a-d on the upper side of the fluidized bed 140 and each opening on the lower side of the fluidized bed 140 located at the same position in the circumferential direction as the opening 114a-d and the distance between the measurement points are substituted into the above equation (1) to determine the height of each fluidized bed 140. The average value of the obtained heights of the fluidized bed 140 can be the height of the fluidized bed 140.

Next, another embodiment will be described below using Figures 2A and 2B. Note that the configurations of the previously described embodiment can be applied as appropriate, and redundant description will be omitted.

2A and 2B, three openings 212, 214, and 216 are provided in the side wall 111 at different heights. One ends of anti-clogging air pipes 213, 215, and 217 are connected to the openings 212, 214, and 216, and the other ends are connected to an air supply source (not shown). As described above, the anti-clogging air pipes 213, 215, and 217 may be provided with pressure measurement pipes (not shown), and the pressure measurement pipes may be provided with pressure detection means.
The differential pressure between the internal pressures of the formation region of the fluidized bed 140 and the opening 214 adjacent to the opening 212 in the height direction and the distance L1 between the measurement points (the distance from the center point C3 of the opening 212 to the center point C4 of the opening 214) are substituted into the above formula (1), and the differential pressure between the internal pressures of the formation region of the fluidized bed 140 and the opening 216 adjacent to the opening 214 and the distance L2 between the measurement points (the distance from the center point C4 of the opening 214 to the center point C5 of the opening 216) are substituted into the above formula (1) to determine the height of each fluidized bed 140. The average value of the obtained heights of the fluidized bed 140 can be the height of the fluidized bed 140.
In addition, the height of the flowing bed 140 may be calculated by substituting the differential pressure between the internal pressures of the formation region of the flowing bed 140 from the opening 212 and the opening 216 and the distance L3 between the measurement points (the distance from the center point C3 of the opening 212 to the center point C5 of the opening 216) into the above formula (1).

(Dispersion board)
The distributor 120 disperses the chlorine-containing gas supplied from the chlorine-containing gas pipe 150 and causes it to flow into the fluidized bed 140. As shown in FIG. 1B , the distributor 120 may include a bottom plate 122, a heat insulating layer 124 formed of a packing on the bottom plate 122, and a plurality of gas flow paths 125. The chlorine concentration of the chlorine-containing gas may be determined appropriately in consideration of the operating state of the chlorination furnace 100, and other gases such as oxygen and nitrogen may be contained in addition to chlorine as appropriate. The shape or material of the chlorine-containing gas pipe 150 may be any known shape or material as appropriate.

(bottom plate)
The bottom plate 122 is located above the wind box 130 in the chlorination furnace body 110, and is formed with a plurality of gas flow paths 125 through which the chlorine-containing gas passes. The distributor 120 is usually provided with a nozzle (not shown), and the chlorine-containing gas may be supplied to the fluidized bed 140 from the tip of this nozzle.
Furthermore, from the viewpoint of heat resistance, the material of the bottom plate 122 may be, for example, one or more selected from the group consisting of carbon steel, stainless steel, and Ni. The thickness of the bottom plate 122 can be designed as appropriate, but is, for example, 40 to 100 mm. Carbon steel is steel with a carbon content of 2 mass% or less, including so-called ultra-low carbon steel, low carbon steel, medium carbon steel, high carbon steel, etc. Specific examples of carbon steel include SS400. Stainless steel is steel to which chromium (Cr), nickel (Ni), etc. are added from the viewpoint of heat resistance and strength. Specific examples of stainless steel include ferritic stainless steel, austenitic stainless steel, martensitic stainless steel, duplex stainless steel, etc.

(Thermal insulation layer)
The heat insulating layer 124 is usually formed on the upper surface of the bottom plate 122. The heat insulating layer 124 may have a single-layer structure or a multi-layer structure. The heat insulating layer 124 may be, for example, a layer filled with heat-resistant ceramics. The thickness of the heat insulating layer 124 can be designed as appropriate, but is, for example, 300 to 600 mm.

(Wind Box)
The wind box 130 is provided below the chlorination furnace body 110. A distributor 120 is disposed in the wind box 130 so as to close the upper opening thereof. The shape of the wind box 130 or the material of the surrounding walls that define the wind box 130 may be any known shape or material, as appropriate.

(Fluidized bed)
The fluidized bed 140 is formed on the distributor 120 during operation of the chlorination furnace 100. The fluidized bed 140 contains titanium ore containing titanium oxide, coke as a carbon source, and a chlorine-containing gas, and maintains a fluidized state. The titanium ore, coke, and chlorine-containing gas come into contact with each other under high-temperature conditions and react with each other to produce titanium tetrachloride gas.

(raw material supply pipe)
The raw material supply pipe 160 is connected to the side wall 111 of the chlorination furnace body 110 at a position higher than the fluidized bed 140 in order to supply titanium ore and coke to the fluidized bed 140. The shape or material of the raw material supply pipe 160 may be any known shape or material as appropriate.

(Titanium tetrachloride recovery tube)
The titanium tetrachloride recovery pipe 170 is provided near the top of the chlorination furnace body 110 in order to recover the titanium tetrachloride gas produced in the chlorination furnace body 110. At this time, the recovered titanium tetrachloride gas is sent from the titanium tetrachloride recovery pipe 170 to a condenser (not shown) of the titanium tetrachloride recovery facility, where the titanium tetrachloride gas is cooled to below 136°C, the boiling point of titanium tetrachloride, and recovered as liquid titanium tetrachloride. Furthermore, any known shape or material can be appropriately adopted for the titanium tetrachloride recovery pipe 170.

(Opening device)
The configuration of the aforementioned anti-clogging air pipe can be selected as appropriate. For example, a three-way pipe may be used as the anti-clogging air pipe. That is, the opening 114 may be connected to an anti-clogging air pipe 515 included in the opening device 500 shown in FIG. 3 . The opening device 500 not only functions as the anti-clogging air pipe described above, i.e., prevents the formation of deposits derived from titanium ore and/or coke at the opening 114, but also removes deposits formed at the opening 114. The opening device 500 shown in FIG. 3 includes a crushing mechanism 510, an anti-clogging air pipe 515, a valve 520, and a storage chamber 530. Note that openings other than the opening 114 may also be equipped with opening devices.

(Crushing mechanism)
The crushing mechanism 510 has a rotating shaft 512, a small motor (not shown) is provided at the base end of the rotating shaft 512, and a bit 514 is provided at the tip of the rotating shaft 512. The bit 514 is stored in a storage room 530 during normal operation of the chlorination furnace 100.
The material of the bit 514 is preferably steel from the viewpoint of heat resistance and wear resistance.

(anti-clogging air piping)
The clogging prevention air pipe 515 is a so-called three-way pipe, one end of which is connected to the opening 114 of the chlorination furnace 100. The other end of the clogging prevention air pipe 515 is connected to a valve 520. An air supply source (not shown) is connected to yet another end of the clogging prevention air pipe 515. As described above, the clogging prevention air pipe 515 may be provided with a pressure measurement pipe (not shown), and the pressure measurement pipe may be provided with a pressure detection means.
Although the clogging prevention air pipe 515 shown in FIG. 3 is connected to the opening 114 of the chlorination furnace, it may also be connected to the opening 112 shown in FIGS. 1A and 1B.

(valve)
In operation of the chlorination furnace 100, when air is supplied from the anti-clogging air pipe 515, the valve 520 is normally closed in order to prevent the formation of deposits derived from titanium ore and/or coke at the opening 114. On the other hand, in operation of the chlorination furnace 100, the valve 520 is first opened in order to ensure good ventilation of the opening 114 and to deal with the case where deposits derived from impurities in the titanium ore and/or coke have formed at the opening 114, i.e., the case where the pressure measured by the pressure measurement tube is abnormally high. After opening the valve 520, the rotary shaft 512 is moved horizontally by a small motor, and the bit 514 at the tip of the rotary shaft 512 passes through the valve 520. The rotary shaft 512 is then rotated circumferentially by the small motor, causing the bit 514 to pulverize the deposits at the opening 114 of the chlorination furnace 100. Thereafter, the rotary shaft 512 is moved by a small motor to return the bit 514 to the storage chamber 530, and the valve 520 is closed.

(Storage room)
The storage chamber 530 is connected to the valve 520. A cooling air pipe 535 is also connected to the storage chamber 530. When the bit 514 pulverizes the deposits at the opening 114 of the chlorination furnace 100, the fluidized bed 140 is at a high temperature of 1000 to 1100°C, and the bit 514 is exposed to the fluidized bed 140 and heated, which may soften it. After the bit 514 pulverizes the deposits at the opening 114 of the chlorination furnace 100, the bit 514 is returned to the storage chamber 530 and cooled by cooling air. The storage chamber 530 may be provided with a cooling air exhaust pipe (not shown).

(Change in fluidized bed height)
In one embodiment, when the height of the fluidized bed obtained in the estimation step is different from the height of the fluidized bed being managed, the amount of titanium ore or coke charged, the amount of chlorine-containing gas, etc. may be appropriately changed to achieve a desired height of the fluidized bed.

The present invention will be specifically explained based on examples and comparative examples. The following examples and comparative examples are merely experimental examples intended to facilitate understanding of the technical content of the present invention, and the technical scope of the present invention is not limited by these examples.

[Example 1]
First, a chlorination furnace 100 having the configuration shown in FIG. 1A was used. Furthermore, two sets of opening devices 500 having the configuration shown in FIG. 3 were used. The openings 112 of the chlorination furnace 100 were arranged on the side wall 111 of the chlorination furnace 100 so that the distance (H1) from the center point C2 of the lower opening 112 to the top surface of the distributor 120 was 500 mm. The openings 114 were arranged on the side wall 111 of the chlorination furnace 100 so that the measurement point distance (L) from the center point C2 of the lower opening 112 to the center point C1 of the higher opening 114 was 500 mm. The diameter of each opening 112, 114 was 50 mm. The clog prevention air pipe 515 of the opening device 500 was connected to each opening 112, 114. A known titanium tetrachloride recovery facility was connected to the titanium tetrachloride recovery pipe 170 of the chlorination furnace 100.

An operational test of the chlorination furnace 100 was initiated by charging titanium ore and coke through the raw material supply pipe 160 of the chlorination furnace 100, supplying chlorine gas through the chlorine-containing gas pipe 150, and supplying air at the same flow rate through the openings 112 and 114. The target height of the fluidized bed 140 was set to 2000 mm, and the amounts of titanium ore and coke charged were adjusted. During the operational test of the chlorination furnace 100, in order to control the target height of the fluidized bed 140, the internal pressure difference in the formation region of the fluidized bed 140 was continuously measured via the openings 112 and 114, which were located at different height positions, and the height of the fluidized bed 140 was calculated based on the above formula (1). During the operational test of the chlorination furnace 100, if the height of the fluidized bed 140 obtained by the above formula (1) was lower than the target height of the fluidized bed 140, the amounts of titanium ore and coke charged were increased. Conversely, if the obtained height of the fluidized bed 140 was higher than the target height of the fluidized bed 140, the amounts of titanium ore and coke charged were decreased. In other words, during the operational test of the chlorination furnace 100, the amounts of titanium ore and coke charged were appropriately adjusted so that the target height of the fluidized bed 140 was reached. Furthermore, to prevent the formation of deposits, such as those derived from impurities in the titanium ore and/or coke, on the openings 112 and 114, the openings were treated with the bit 514 of the crushing mechanism 510 of the opening device 500 every four hours from the start of the operational test of the chlorination furnace 100.

In an operational test of the chlorination furnace 100, the average value of P _L1 (the internal pressure in the formation region of the fluidized bed 140 measured by the pressure detection means of the pressure measurement tube of the clogging prevention air pipe 515 connected to the lower opening 112) in the above formula (1) obtained from the start of the operational test until 24 hours had elapsed was 26.5 kPa, and the average value of P _L2 (the internal pressure in the formation region of the fluidized bed 140 measured by the pressure detection means of the pressure measurement tube of the clogging prevention air pipe 515 connected to the upper opening 114) was 19.9 kPa. In other words, the pressure difference between the internal pressure in the formation region of the fluidized bed 140 measured from the lower opening 112 and the internal pressure in the formation region of the fluidized bed 140 measured from the upper opening 114 was 6.6 kPa. Considering that L in the above formula (1) (the distance between the measurement points, which is the distance from the center point C2 of the lower opening 112 to the center point C1 of the upper opening 114) is 500 mm, it was confirmed that the average height of the fluidized bed 140 from the start of the operational test until 24 hours had elapsed was 2010 mm.
The P _L1 in the above formula (1) obtained from the start of the operational test until 24 hours had elapsed was within the range of 26.5±1.0 kPa, and the P _L2 in the above formula (1) obtained from the start of the operational test until 24 hours had elapsed was within the range of 19.9±1.0 kPa.
During the operational test of the chlorination furnace 100, the chlorine concentration in the titanium tetrachloride recovered in the titanium tetrachloride recovery facility was measured, but no increase in the chlorine concentration beyond the allowable range was confirmed.
This resulted in a good yield in the production of titanium tetrachloride.

Next, 26 hours after the start of the operational test of the chlorination furnace 100, titanium ore having a higher bulk density than the titanium ore that had been charged from the start of the operational test was charged from the raw material supply pipe 160, thereby intentionally changing the height of the fluidized bed 140. As a result of continuously calculating the height of the fluidized bed 140 based on the above formula (1), it was confirmed that the height of the fluidized bed 140 calculated from the above formula (1) after the start of charging the titanium ore with a higher bulk density became lower than the height of the fluidized bed 140 calculated from the above formula (1) before the titanium ore with a higher bulk density was charged.
Therefore, by adding additional titanium ore, the height of the fluidized bed 140 was restored to the target height of the fluidized bed 140. 30 hours had passed since the start of the operational test of the chlorination furnace 100, but no increase in the chlorine concentration in the titanium tetrachloride recovered in the titanium tetrachloride recovery facility beyond the allowable range was confirmed. This is presumably because the amounts of titanium ore, coke, and chlorine gas were appropriately controlled by maintaining the height of the fluidized bed 140 at an appropriate level, and therefore almost no unreacted chlorine was recovered.
This resulted in a good yield in the production of titanium tetrachloride.

[Comparative Example 1]
In Comparative Example 1, an operational test of the chlorination furnace 100 was started in the same manner as in Example 1, except that the opening 114 and the opening device 500 connected to the opening 114 were not used, i.e., the pressure was obtained only from the opening 112. Because pressure measurement in the formation region of the fluidized bed 140 was performed only at the opening 112, estimation using the above-mentioned formula (1) was not possible. Therefore, the internal pressure in the formation region of the fluidized bed 140 was continuously measured via the opening 112 for 24 hours from the start of the operational test of the chlorination furnace 100, and the height of the fluidized bed 140 was calculated based on the following formula (2).
H=P1×α...Formula (2)
H: Height of fluidized bed 140 (cm)
P1: Internal pressure (kPa) of the fluidized bed 140 measured by the pressure detection means of the pressure measurement pipe connected to the opening 112
α: Coefficient set based on the bulk density of the ore (cm/kPa)

26 hours after the start of the operational test of the chlorination furnace 100, the height of the fluidized bed 140 was changed by intentionally adding titanium ore with a higher bulk density than the titanium ore that had been added since the start of the operational test through the raw material supply pipe 160. The height of the fluidized bed 140 was continuously calculated based on the above formula (2). As a result, H in the above formula (2) remained the same as the desired fluidized bed height, even when titanium ore with a higher bulk density was added. However, 28 hours after the start of the operational test, more unreacted chlorine gas than usual was recovered from the titanium tetrachloride recovery facility downstream of the chlorination furnace 100. In other words, the unreacted chlorine gas passed through the fluidized bed 140 and could not be used to produce titanium tetrachloride, resulting in a decrease in the production yield of titanium tetrachloride.

[Considerations based on examples]
Although the height of the fluidized bed cannot be directly measured, in Example 1, during the operational test of the chlorination furnace, the estimation step estimated the height of the fluidized bed based on fluidized bed information obtained by measuring the internal pressure of the fluidized bed formation region at two different vertical positions. This enabled the height of the fluidized bed to be determined accurately, and as a result, it was confirmed that the yield of titanium tetrachloride production was good. Even if the height of the fluidized bed changes depending on the raw material composition ( _TiO2 , C, _SiO2 ), ore type, raw material bulk density, etc. in the chlorination furnace, the height of the fluidized bed can be calculated at any time using the above formula (1). Therefore, it is presumed that the yield of titanium tetrachloride production can be improved. Furthermore, changes in the raw materials used can be quickly and accurately accommodated, and the desired fluidized bed height can be achieved. From this perspective, it is presumed that the yield of titanium tetrachloride production can be improved.
On the other hand, in Comparative Example 1, the height of the fluidized bed was lower than expected due to a change in the bulk density of the ore. The reason for this is thought to be that the internal pressure in the fluidized bed formation region was measured at only one location, making it impossible to properly determine the height of the fluidized bed. Furthermore, although Equation (2) takes the bulk density of the ore into account, the measurement accuracy of the fluidized bed height was lower than that of Equation (1).
The life of a chlorination furnace often extends to several years. For example, as in Example 1, if the height of the fluidized bed is estimated based on fluidized bed information obtained by measuring the internal pressure in the fluidized bed formation region at two or more different positions in the vertical direction, this is thought to be highly accurate and has a significant effect in improving the yield of titanium tetrachloride production.

100, 200 Chlorination furnace 110 Chlorination furnace body 111 Side wall 112, 114, 114a to 114d, 212, 214, 216 Openings 113, 115, 115a to 115d, 213, 215, 217, 515 Anti-clogging air pipe 120 Distributor 122 Bottom plate 124 Heat insulating layer 125 Gas flow path 130 Wind box 140 Fluidized bed 150 Chlorine-containing gas pipe 160 Raw material supply pipe 170 Titanium tetrachloride recovery pipe 500 Opening device 510 Crushing mechanism 512 Rotating shaft 514 Bit 520 Valve 530 Storage chamber 535 Cooling air pipes C1 to C5 Center point

Claims (8)

A method for producing titanium tetrachloride by using a chlorination furnace equipped with a distributor and forming a fluidized bed containing titanium oxide-containing titanium ore, coke, and chlorine gas on the distributor, comprising:
a step of estimating the height of the fluidized bed,
In the estimation step, the height of the fluidized bed is estimated based on fluidized bed information obtained by measuring internal pressures in two or more fluidized bed formation regions at different positions in the height direction ;
a side wall of the chlorination furnace surrounding the fluidized bed is provided with two or more openings at different height positions;
A method for producing titanium tetrachloride , wherein the estimation step includes supplying a gas from the opening toward the fluidized bed, and measuring the internal pressure of the two or more fluidized bed formation regions through the opening . 2. The method for producing titanium tetrachloride according to claim 1 , wherein the estimation step estimates the height of the fluidized bed based on the fluidized bed information without using the internal pressure of a freeboard section above the height position of the fluidized bed. A method for producing titanium tetrachloride by using a chlorination furnace equipped with a distributor and forming a fluidized bed containing titanium oxide-containing titanium ore, coke, and chlorine gas on the distributor, comprising:
a step of estimating the height of the fluidized bed,
In the estimation step, the height of the fluidized bed is estimated based on fluidized bed information obtained by measuring the internal pressures of the fluidized bed formation regions at two or more different positions in the height direction, without using the internal pressure of a freeboard section that is above the height position of the fluidized bed. a side wall of the chlorination furnace surrounding the fluidized bed is provided with two or more openings at different height positions;
4. The method for producing titanium tetrachloride according to claim 3 , wherein in the estimation step, the internal pressures of the two or more fluidized bed formation regions are measured through the openings. The method for producing titanium tetrachloride according to any one of claims 1 to 4 , wherein the opening is provided with an opening device equipped with a crushing mechanism and an anti-clogging air pipe. The method for producing titanium tetrachloride according to claim 5 , wherein the opening device further comprises a valve and a storage chamber. The method for producing titanium tetrachloride according to any one of claims 1 to 6 , wherein the fluidized bed information includes a differential pressure in the height direction of internal pressures in the two or more fluidized bed formation regions. 8. The method for producing titanium tetrachloride according to claim 7 , wherein the fluidized bed information further includes a distance between measurement points of the internal pressure of the two or more fluidized bed formation regions in the height direction.