JPS629531B2 - - Google Patents

Description

Claim 1 Discrete particles of porous carbon having a particle size in the range of about -6 meshes to +140 meshes and having micropores with a pore size of less than about 20 Å, and loose particles of titanium-containing material. Fluidize and
A method for producing TiCl ₄ by chlorinating a titanium-containing substance, which comprises contacting a titanium-containing substance with a chlorine-supplying substance at a temperature of 400°C to 2000°C until the titanium content of the titanium-containing substance is substantially chlorinated. Initially, about 30% to about 95% of the total surface area of carbon in the porous carbon reductant has a particle size of about 20 Å. A porous carbon reduced body of lignite-based char or lignite-based carbon, which is characterized by having pores, is used, and vanadium valuables are thus produced.
Said method, characterized in that it is previously removed from _TiCl4 . 2. The method according to claim 1, wherein the temperature is 400°C to 800°C. 3. The first claim that the temperature is 800℃ to 2000℃
The method described in section. 4 The temperature is 1000°C to 1600°C Claim 1
The method described in section. 5 The porous carbon reductant is at least about 100 m ² /g
2. The method of claim 1, having an inner surface area of . 6 At least about 10 m ² /g of the internal surface area is about 20
6. The method according to claim 5, wherein the micropores have a pore size of Å or less. Description The present invention relates to the separation of titanium values from vanadium values in mixtures of titanium and vanadium chlorides. BACKGROUND OF THE INVENTION Titanium-containing materials are often chlorinated. This is because chlorination is an efficient and economical way to obtain a source of high purity titanium for the production of titanium alloys, titanium compounds and, in particular, pigmentary titanium dioxide. Several methods for chlorinating titanium-containing materials are disclosed in the known literature. Such methods generally involve reacting a titanium-containing feedstock, such as rutile or ilmenite ore, with a chlorine-producing material and a carbon-containing reductant according to one or both of the following reaction equations. TiO ₂ +2Cl ₂ (g) + C (s) →TiCl ₄ (g) + CO ₂ (g) 〓〓〓〓
TiO ₂ +2Cl ₂ (g) + 2C (s) → TiCl ₄ (g) + 2CO (g) Iron is a regular impurity in titanium-containing raw materials. Most chlorination methods can simultaneously chlorinate the Ti and Fe valuables of these raw materials, as shown in the reaction formula below. 2FeTiO ₃ +6Cl ₂ (g) + 3C (s)
→2TiCl ₄ (g)＋3CO ₂ (g)＋2FeCl ₂ FeTiO ₃ +3Cl ₂ (g)＋3C (s)
→TiCl ₄ (g) + 3 CO (g) + FeCl ₂ Chlorination reactions are generally carried out at about 1000° C. using various carbon reductants and chlorine sources (eg, chlorine gas and chlorine-containing compounds). However, it can be carried out at any temperature within the range of about 400°C to about 2000°C. The titanium-containing raw material to be chlorinated can be preformed into a block shape. Alternatively, the chlorination process can be carried out in a fluidized bed using particulate material. When using a fluidized bed process, the chlorine feed material is generally fed to the bottom of the bed and the product titanium tetrachloride (TiCl ₄ ) is recovered from the top of the bed. Fluidization is usually controlled so that the bed remains fluidized, but fine solid particulate matter is not carried along with the product. Selective chlorination methods also exist. These methods are designed to chlorinate only Ti or Fe values in the raw material. The reductant and chlorine source used and the reaction temperature are also similar to the non-selective method. However, alternative methods use a chlorine source with more or less iron chlorides and react with the titanium-containing feedstock in a dilute phase or at particularly high temperatures; React at high temperature inside. Titanium sources such as rutile or ilmenite ores also usually contain vanadium compounds as impurities. This vanadium compound has an adverse effect on the titanium product produced. For example, _TiO2
TiO ₂ will change color if more than 10 ppm of vanadium is present in titanium tetrachloride, the raw material for TiO 2 production. Because the chemical and physical properties of titanium and vanadium compounds are similar, methods for removing such impurities have traditionally been complex and cumbersome. For example, _TiCl4 melts at -25°C and boils at 136.4°C. Also, VCl ₄ melts at -28°C and boils at 148.5°C. Such similarities in properties also apply to comparisons of compounds of these two types of atoms. Therefore, in conventional chlorination methods, the vanadium values in the titanium-containing raw material react in substantially the same manner as the titanium values. Additionally, each chlorinated product has nearly identical chemical and physical properties. Therefore, it is extremely difficult to separate undesired chlorinated vanadium values from desirable titanium values. For example, fractional distillation removes most impurities from _TiCl4 , but
It is ineffective in removing vanadium impurities. The method used commercially involves refluxing with copper;
Vanadium impurities are removed from TiCl ₄ by treatment with H ₂ S in the presence of heavy metal soaps, or by treatment with alkali metal soaps or oils to convert the vanadium impurities to a less volatile form. In each of these conventional methods, the treated TiCl ₄
is then further distilled. However, the organic materials used are easily decomposed and a viscous and sticky film is deposited on the heat exchanger surfaces, pipes and vessel walls. This will cause the process to shut down and
It also requires frequent maintenance of the equipment. In accordance with the present invention, a simple, efficient, and economical method for removing vanadium values from chlorinated titanium-containing materials has been discovered. The method of the present invention uses high surface area carbon to react with titanium-containing materials during chlorination. By using high surface area carbonaceous materials. The vanadium values present in the titanium-containing material can be converted to a less volatile form and thus can be easily removed as a solid from gaseous or liquid TiCl ₄ products. One of the advantages of the invention is that the process can be carried out with existing equipment for the chlorination of titanium-containing materials. Another advantage is that the method of the invention uses inexpensive raw materials. Additionally, there are other benefits. The CO value of the generated exhaust gas is sufficiently enhanced to assist in the combustion of said exhaust gas and can be combusted for complete conversion to CO ₂ . In this way, problems such as air pollution conventionally caused by exhaust gases are avoided. These and other advantages will become more apparent in the Detailed Description of the Invention. Another advantage of the present invention is the surprising economic effect of the particular type of reactive carbon used in fluidized bed reactions.
It is in. Reactive carbon, lignite or brown coal based char (CHDR), whose surface area does not change or practically increases during use, provides better combustibility of exhaust gases than previously utilized. It has the unique property of providing Also, the greater the surface area of the carbonaceous material in the bed, the more efficient the chlorination reaction will be. When treated anthracite is used for the chlorination of conventional titanium-bearing ores, the carbon surface area is reduced to a stable equilibrium value. Reactivity is directly related to surface area.
If the "as-made" surface area is large enough, the equilibrium surface area is also large enough to obtain good chlorination results, as shown in the table below. The lower the initial surface area of carbon, the lower the CO level and the higher the vanadium impurity level, as shown in the table below. Vanadium level
Organic additives in crude liquid form if higher than 10ppm
Must be added to TiCl ₄ to help reduce vanadium levels below 10ppm.

【table】

[Table] Conventional fluidized bed chlorination was carried out using various carbons. Typically, low surface area carbons, such as petroleum coke or bituminous char, undergo little change in surface area during chlorination. U.S. Patent No. 4310495 (issued January 12, 1982)
and No. 4,329,322 (published May 11, 1982), in accordance with the method of the present invention, instead of using "high grade" coal-based char, such as anthracite, lignite-based char is used. The results obtained from its use were completely unexpected. This char is a low grade lignite based ANSI/ASTM Class
Derived from coal. The surface area of this carbon increased during chlorination as shown in the table. Although this char had a surface area only 30% of the "as-made" surface area of the treated anthracite in the table, it gave better chlorination results.

[Table] Lignite-based char is available in large quantities within the size range suitable for fluidized bed chlorination, and at surprisingly low prices. The relationship between carbonaceous sources and surface area changes during chlorination was further investigated. Another ANSI/ASTM Class
Experiments were conducted on lignite carbon. As shown in the table, the surface area of this carbon also increased during chlorination. Very high CO levels and very low vanadium impurity levels were observed, as would be expected from a bed carbon with high equilibrium surface area.

Table: The chemical and physical properties of reactive carbons are summarized in the table below. 〓〓〓〓

TABLE The only change from conventional methods contemplated by the present invention is in the carbonaceous material used. The disclosures of the above-mentioned US patents are representative of the methods in which the discoveries of the present invention can be used. The lignite or brown coal type char considered best for use in the process of the present invention is Australian Char Pty.
, Ltd. and sold under the trade name "Auschar". This preferred char has the following typical characteristics. Physical properties Average size = 0.5 to 2.3 mm Specific gravity = 1.2 Porosity = 33% Bulk density = 640 Kg/m ³ Approximate analysis of dry char Ash content = 2-3% Volatile content = 2-5% Fixed carbon 91-95% (Note: Other sizes are available to suit specific method applications) Surface area measurement (by CO ₂ absorption at 0°C) approximately 750 m ² /g Ash melting temperature: in oxidizing atmosphere = 1460°C Reducing Atmosphere = 1400℃ Total dry calorific value = 7900kcal/Kg The tear is dry when it leaves the retort, but
Cheer traps moisture in the air. After some time, the char may contain about 10% moisture. This number suggests that the produced char has low volatility. It should be noted that the analysis can be modified to the extent that highly volatile substances are produced if necessary. Approximate analysis of dried char (typical example) Carbon = 94.5% Calcium = 0.08% Hydrogen = 1.1% Magnesium = 0.24% Titanium = 0.6% Aluminum = 0.06% Sulfur = 0.27% Silicon = 0.05% Iron = 0.33% Sodium =0.11% and trace amounts of chlorine, sodium, potassium,
For more information on the lignite or brown color of phosphorous, titanium, and copper sources, see Kirk and Othmer, "Encyclopedia of Chemical Technology," 3rd edition, Volume 14, pages 313-343. The chlorination process of the present invention differs from the post-chlorinated vanadium removal process disclosed in US Pat. No. 4,279,871, which uses activated carbon prepared from lignite. In the process of this US patent, high surface area activated carbon prepared from lignite leaves a hot fluidized bed.
entrained in the chlorinated gaseous product stream.
This treatment significantly reduces vanadium impurity levels. In the process of the invention, chlorination is carried out in a fluidized bed consisting of lignite or brown coal char and ore. SUMMARY OF THE INVENTION Briefly described, the process of the present invention consists of using low-grade lignite or lignite char in place of conventional high-grade or anthracite-based char. This is an improvement on the conventional method for chlorinating brookite or ilmenite. Using lignite or lignite char in a fluidized bed and treating the metallized ore in the presence of a chlorinating agent, e.g. chlorine (which can also be diluted with an inert gas such as nitrogen) , especially with titanium-containing ores. For such fluidized bed operations, the lignite-based or lignite-based char as used in such operating methods has a particle size within the range of about -6 mesh (U.S. standard sieve size) to about +140 mesh. . Also, in this char, 30% to 90% of the surface area of carbon is 20% at the beginning.
It is characterized by having a microporous structure consisting of micropores with a diameter of less than Å. Chlorination is carried out in the range of 400℃ to 2000℃ until the metal-containing substance is substantially chlorinated〓〓〓〓
more particularly at a temperature within the range from 800°C to 2000°C, in particular at a temperature within the range from 1000°C to 1600°C. Vanadium impurities present in titanium-containing ores have different degrees of chlorination and, as a result, different boiling points, making it easy to separate vanadium impurities from TiCl ₄ by fractional condensation (see U.S. Pat. No. 4,329,322). Therefore, it can be almost completely removed.

[Detailed description of the invention]

As mentioned above, the present invention is an improvement over conventional ore fluidized bed chlorination processes that consists of replacing high-grade char with low-grade char. Advantages of the method of the invention that can be recognized are: (1) It is a low-temperature chlorination process at 400℃-800℃, in which a fluidized bed of porous carbon and ore with an internal surface area of less than 20 Å pores is reacted with chlorine-containing gas. This method is disclosed in detail in US Pat. No. 4,310,495. At extremely low temperatures (<600℃),
NOCl is used alone or with gaseous chlorine (see US Pat. No. 2,761,760). (2) A high temperature chlorination process between 800°C and 2000°C, with an internal surface area of at least about 100 m ² /g, of which at least about 10 m ² /g is in micropores with a pore size of less than 20 Å. A fluidized bed of porous carbon reductant and ore is reacted with a chlorine-containing gas. This method is disclosed in US Pat. No. 4,329,322. Chlorination was carried out in a 3 inch outside diameter fused silica fluidized bed reactor. The reactor had a porous quartz plate as a gas distributor. This reactor is kept at a constant temperature by an electric furnace surrounding the reaction zone.
It was maintained at 1000℃. The hot exhaust gas from the fluidized bed is
The mill is placed in a cyclone separator maintained at 175℃.
At this point, most of the entrained solids were removed. The exhaust gas is further cooled with a water-cooled condenser or frozen condenser,
Substantially all remaining condensable vapors (mainly _TiCl4 ) were removed from the _CO2 , CO and _N2 , and the _CO2 , CO and _N2 were vented to the atmosphere. A mixture of carbon and -40 mesh of rutile ore was initially charged into the reactor resulting in a 1 foot long stationary bed containing 32 wt% carbon. As the bed mass decreased due to the chlorination reaction, fresh carbon and ore were continuously fed to keep the bed mass fairly constant. Bed mass was controlled by adjusting the feed rate to keep the metering pressure drop within the fluidized bed constant. The carbon/ore ratio in the bed was kept constant by matching the carbon/ore ratio in the feed to the carbon/ore ratio consumed by chlorination. The consumed carbon/ore ratio was calculated from CO ₂ and CO analysis of the chlorinator exhaust gas. A gas mixture consisting of 75 vol% _Cl2 and 25 vol% _N2 was metered into the titanium reactor at a rate to provide an apparent fluidization rate of 0.4 ft/sec corrected for temperature and pressure. CO ₂ , CO and N ₂ in the exhaust gas were measured every 20 minutes by gas chromatography. shutting down the reactor at regular intervals, and
It was left to cool. The surface area was then measured using a sample of the +40 mesh bed material (carbon portion). Coarse
The solids in TiCl ₄ (which caused the cyclone to be bypassed due to its inefficiency) were allowed to settle. clear supernatant liquid
A sample of _TiCl4 was used for vanadium analysis. Surface area was measured using two commercially available instruments.
Perkin-Elmer Shell Sorptometer Model212B
was used for rapid surface area measurements (Method A).
Digigorb 2500 Automated Multi-Gas Surface Area and Pore Volume Analyzer, Norcross, Georgia
A Micromeritics Instrument (manufactured by ORP) was used for precision surface area tissue measurements (Method B). Although reactive carbon derived from Class coal loses surface area and reactivity during chlorination,
It is unclear why carbon obtained from Class coal (lignite or brown coal) does not show such a reduction. Neither the chemical composition nor the fine surface texture analysis by Method B and the X-ray diffraction indicate any difference in properties that could explain the difference in surface area stability. Structural differences in the carbon atomic network are visible in the microscopic field and in the boundaries and interfaces between rock components (vegetable residues in coal). Class and coal petrographic analysis clearly show this difference. It is therefore reasonable to imagine that the carbon derived from these two grades of coal would also differ in this regard. 〓〓〓〓
Lignite-based char has a surface texture very similar to treated anthracite. Most of the surface area of treated anthracite carbon has micropores with a diameter of 20 Å or less. The maximum pore size in these carbons is in the range of 20-60 Å. Carbon derived from lignite has a different surface texture from other carbons. Most of this surface is in pores larger than 20 Å in diameter, with a maximum pore size of 450 Å. Analysis of treated anthracite samples taken from the equilibrium chlorinator bed showed that the surface area was reduced by 70-85% and the microporosity almost disappeared. In lignite carbons, microporosity remains relatively stable as carbon is consumed during chlorination, and pores larger than 20 Å in diameter increase relatively significantly. Summary data regarding surface texture is shown in the table. When compared to anthracite carbon, lignite carbon is
have similar or different surface textures,
Significantly different from anthracite carbon, the surface texture of lignite carbon changes during chlorination.

[Table] 〓〓〓〓