JPS6360103B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for improving the quality of materials containing iron oxides and chromium oxides, such as chromite. Here, "improving quality" means removing at least a portion of iron and increasing the proportion of chromium. "Substance" herein means the aforementioned substance, unless otherwise specified;
"Iron" or "chromium" means, unless otherwise specified, an iron or chromium component present as an oxide in the material or an upgraded material thereof. Chromite basically has the theoretical formula FeO・
It is a substance with a spinel structure represented by Cr ₂ O ₃ , and its properties include partially replacing Fe ²⁺ ions with Mg ²⁺ ions, or replacing Cr ³⁺ ions with Al ³⁺ or Fe ³⁺ ions. can be changed by partially replacing . Chromite usually also contains significant amounts of silicon oxides, as well as small amounts of all or some oxides of calcium, magnesium, niobium, vanadium and titanium. Chromite is the main source of chromium used industrially or metallurgically. The main chromite mines are located on the African continent (especially the Transvaal region of South Africa), the Philippines, New Caledonia, Turkey, and the Soviet Union. South Africa also has large reserves of chromite sand. The chromium content of natural chromite varies considerably depending on location. There are large reserves of lower grade chromite with a relatively high iron content, with a chromium content of less than 50% calculated as Cr ₂ O ₃ and a chromium/iron ratio of less than 2/1. It is necessary to improve the quality of chromite ore with such a high iron content.For example, in order to use it for the production of "ferrochrome", the chromite/iron ratio must be at least higher than 2/1, preferably higher than 3/1. need to be higher. High-grade chromite has a chromium content of 50-55% by weight calculated as Cr ₂ O ₃ and a chromium/iron ratio higher than 3/1. These high-grade chromite ores are suitable for the production of chromium/iron alloys with a chromium content of about 60-70%, commonly known as "ferrochromes". However, even these high-grade chromite ores need to be modified to improve their quality in order to obtain other purposes, such as those with even higher chromium content, and improvement of these grades is also included in the purpose of the present invention. . The physical form of the natural chromite ore deposits also affects the difficulty of the upgrading process. For example, the large reserves of chromite sand in South Africa consist of relatively low-grade chromite and are particularly difficult to improve due to their fine particle size. The problem of increasing the chromium/iron ratio of chromite ores has been the subject of much research, which is briefly summarized in the preamble to US Pat. No. 3,216,817. According to this patent, chlorine has an affinity for both iron and chromium at high temperatures, so the conventional technology of selectively chlorinating chromite to remove only iron is difficult to implement, and chlorine and other chlorinating agents Even if the use of carbon as a reducing agent has certain practical advantages, it is difficult to selectively chlorinate all of the components of chromite ore as it easily completely chlorinates. Therefore, until now it has not been possible to carry out selective chlorination in a practical manner using chlorine and carbon, and it has not been possible to obtain improved chromite with a good chromium/iron ratio. The purpose of US Pat. No. 3,216,817 is to alleviate the aforementioned problems. According to this patent, chromite is selectively chlorinated in the presence of carbon in a fluidized bed to convert iron oxide to ferric chloride, and this volatile ferric chloride is released from the fluidized reaction mixture. The quality has been improved by In this method, the reaction temperature is lower than 920°C, preferably 900°C
If higher temperatures are used, the loss of chromium from the chromite increases rapidly. It is also desirable to use excess chlorine, for example, 100% or more excess chlorine. A stream containing oxides of chlorine, nitrogen and carbon is continuously discharged from the reactor. In this case, the production of ferric chloride has a higher theoretical chlorine requirement for the chromite upgrading process than the production of ferrous chloride, which increases the plant capital cost and thus reduces the economic efficiency of the process. The fluidized bed technology for selective chlorination of chromite according to US Pat. Requires the use of carbon monoxide as a reducing agent in the gas. According to the operating conditions disclosed in US Pat. No. 3,473,916, the iron content in the chromite is converted to ferric chloride. The desired method is to improve the quality of materials containing chromium oxides and iron oxides by converting the iron content into ferrous chloride rather than ferric chloride; The theoretical requirement for chlorine is reduced, resulting in savings in equipment costs. However, ferrous chloride vapor is a difficult material to handle as it tends to form solid deposits on the internal surfaces of the equipment. Nevertheless, US Pat. No. 2,752,301 discloses a method of increasing the chromium/iron ratio of chromite by selectively producing and sublimating ferrous chloride. The process described in this patent is characterized by the use of dry hydrogen chloride as a reactant, carefully avoiding free chlorine, and including the absence or substantial absence of carbon, which The maximum amount of carbon is 1 part by weight or less for every 6 parts by weight of iron oxide remaining in the mineral residue at the end of the reaction. The object of the present invention is to selectively chlorinate the iron in a substance (ore) containing chromium oxide and iron oxide, such as chromite ore, to form ferrous chloride, thereby producing chromium oxide/iron oxide. The object of the present invention is to provide a method for improving the quality of contained substances. Another object of the present invention is to provide a process in which ferrous chloride deposits can be removed as ferrous chloride in the reaction effluent gas, rather than being removed by sublimation. Other objects of the invention will become apparent from the description below. The above-mentioned objects of the invention are achieved by carefully adjusting the combination of requirements described below. The method of the present invention for upgrading materials containing chromium oxides and iron oxides consists of reacting at least a portion of the iron content with chlorine and removing the resulting iron chloride as a vapor, which, upon expansion, forming a fluidized bed with a length of at least 1 m, said fluidized bed consisting of finely divided said material and finely divided carbon, said carbon being reacted with oxygen generated in said fluidized bed or added thereto; at least 15% of the total weight of carbon and said materials
present in an amount of 900% and the reaction temperature in the fluidized bed is 900%.
20 °C of gas kept at ~1100 °C and added to the fluidized bed
A chlorine-containing gas yielding a concentration of chlorine corresponding to ~60% by volume is introduced into the fluidized bed, and the chlorine is reacted with iron in the material to form ferrous chloride, resulting in a gaseous effluent from the fluidized bed. The partial pressure of ferrous chloride in the product is maintained low enough to prevent liquefaction of the ferrous chloride, and the gaseous ferrous chloride-containing effluent is removed from the fluidized bed to improve the quality of the remaining chromium-containing material is recovered from the fluidized bed. Materials treated according to the present invention typically have an iron content of about 10-30% by weight calculated as Fe and a chromium content of about 25-50% by weight calculated as Cr ₂ O ₃ . This material is typically in the form of ores, with particle diameters ranging from 75 x 10 ^{-6 m} to 500 x 10 ^-6 m.
It is preferable to grind the particles so that they are substantially free of particles outside the range, and the average particle size is approximately 150×
10 ^-6 m ~ 250 x 10 ^-6 m, for example 150 x 10 ^-6 m ~
A suitable value is 200×10 ^-6 m. Here, "average" means weight average. Alternatively, the material may be in the form of a natural sand, such as chromite sand, from which the finest particles are removed and adjusted to a particle size distribution similar to that described above. This sand is predominantly, for example 80% by weight, or preferably entirely within a fairly narrow particle size range, the width of which diameter range is, for example, 100x10 ^-6 m or 50x10 ^-6 m. Preferably, less than 10% by weight is finer than the above range, and similarly less than 10% by weight is coarser. The carbon introduced into the fluidized bed has a particle size somewhat coarser than the aforementioned values, e.g. an average particle size of 500 to 800×10 ^-6 m in diameter, e.g. 700×10 ^-6 m, and a particle size of 75× Anything outside the range of 10 ^-6 m to 2000×10 ^-6 m is substantially not included. Preferred is crushed coke. The amount of carbon in the fluidized bed is at least 15%, preferably 15-50%, preferably at least 20%, preferably 20-50% by weight. Remaining carbon is acceptable if the upgraded product is used for metallurgical purposes. The depth of the fluidized bed during operation also affects the practice of the invention. If the depth of the fluidized bed is less than 1 m, chloride 2
It tends to produce iron and, on the other hand, deeper than 2.5 m it does not easily form a fluidized bed due to its density.
The depth of the fluidized bed is therefore preferably between 1.5 and 2.5 m, particularly preferably between 1.5 and 2.25 m. A preferred method of forming a fluidized bed is to fluidize it by flowing a stream of added oxygen, optionally chlorine, and an inert diluent gas upward through a fluidized bed reactor containing the mixture. The reaction that produces ferrous chloride is less exothermic than the reaction that produces ferric chloride. Therefore, it is necessary to add heat to the fluidized bed to maintain the desired reaction temperature. Preferably, the desired reaction temperature is maintained under the influence of an exothermic reaction between the carbon in the fluidized bed and the free, ie, chemically unbound, oxygen introduced into the fluidized bed. Particularly preferably, sufficient free oxygen is introduced into the fluidized bed to maintain the desired reaction temperature. However, the required amount of free oxygen to be added depends, at least in part, on the amount of oxygen already present chemically bound to the iron in the fluidized bed. The amount of carbon present in the fluidized bed is preferably at least sufficient to react with the oxygen previously present in the fluidized bed or added to the fluidized bed, particularly preferably in excess thereof. , the temperature of the fluidized bed is adjusted by adjusting the amount of oxygen added. The amount of oxygen introduced anywhere in the fluidized bed is preferably less than 10% by volume of the total amount of gas introduced into the fluidized bed, otherwise the temperature in some parts of the fluidized bed may become unduly high. I get used to it. If the desired reaction temperature cannot be maintained by introducing 10% by volume or less of oxygen only once, it is desirable to supplement the portion where the initial oxygen concentration is deficient with oxygen. The amount of oxygen supplementation is adjusted so as not to exceed the maximum allowable concentration of oxygen. A preferred mode of carrying out the invention is that the chlorine is introduced from the top of the fluidized bed, the fluidizing gas introduced at the bottom of the bed containing more than 10% by volume of oxygen, and that the chlorine is already present at the point of introduction of the chlorine. It is desirable that it be consumed to match the maximum permissible concentration. Preferably, the diameter of the fluidized bed reactor increases stepwise at the point of chlorine introduction so that the velocity of the fluidizing gas flowing upward through the bed remains constant. Another method of maintaining the desired reaction temperature is to introduce externally generated heat into the fluidized bed. This is accomplished by placing the fluidized bed reactor in a furnace and applying heat externally and/or by preheating the solids or gases introduced into the bed, such as chlorine-containing gas or its constituents. . If necessary, the desired reaction temperature may be maintained partly under the influence of the reaction between oxygen and carbon in the fluidized bed and partly by introducing externally generated heat into the bed. . If the reaction temperature is lowered unduly, ie below 900° C., the combustion process becomes significantly less efficient in providing the necessary heat to enable practical operation.
On the other hand, if the reaction temperature is too high, the chromium component in the ore will be unduly chlorinated. Therefore, the preferred reaction temperature in the present invention is higher than 920°C and 1050°C.
℃ or less, particularly preferably higher than 920℃
The temperature is below 1000℃. In the present invention, the selective attack of iron over chromium, the production of ferrous chloride over ferric chloride, and the economics of actual operation depend on the concentration of chlorine in the chlorine-containing gas used and the depth of the fluidized bed. It's related. By using at least the aforementioned minimum amount of carbon required by the present invention, the amount of carbon does not act as a limiting factor that disrupts the effectiveness of controlling chlorine concentration. According to the present invention, chlorine reacts with iron in the fluidized bed to produce ferrous chloride in preference to chromium chloride and ferric chloride, and the produced ferrous chloride is transported as vapor. Ferrous chloride tends to adhere and accumulate on the inside of equipment, such as the inner walls of pipes, at temperatures below 1000°C, causing problems with operation. However, in the present invention, the partial pressure of ferrous chloride vapor is adjusted in relation to the temperature of the ferrous chloride, so that the above-mentioned deposits of ferrous chloride are avoided or reduced. Reaction temperature is 1000℃
The partial pressure of ferrous chloride in the effluent from the fluidized bed is preferably 0.006 (T-900) + 0.2×
It is kept below 10 ⁵ N/m ² (T=reaction temperature), particularly preferably below 0.005 (T-900) + 0.2×10 ⁵ N/m ² . The partial pressure of ferrous chloride is a function of the chlorine concentration of the gas introduced into the fluidized bed, up to an upper limit at which ferric chloride and/or chromium chloride begin to form. The amount of chlorine increases with the chlorine concentration of the gas introduced into the fluidized bed. Above said limit value, ferric chloride is produced instead of ferrous chloride, and the production of a limited amount of ferric chloride can be used as a means of controlling the process. The partial pressure of ferrous chloride in the effluent from the fluidized bed is preferably regulated by controlling the concentration of chlorine introduced into the fluidized bed. Desirably, the production of ferric chloride is less than 1 mole per mole of ferrous chloride, preferably less than 1 mole per 3 moles of ferrous chloride, particularly preferably less than 1 mole per 5 moles of ferrous chloride. It is maintained. The concentration of chlorine in the gas introduced into the fluidized bed is preferably between 25 and 55% by volume, particularly preferably 30% by volume.
~50% by volume, the balance preferably being a suitable inert gas diluent such as oxygen and nitrogen. One of the features of the present invention is that the production of ferrous chloride does not involve the production of ferric chloride in an amount exceeding the above-mentioned limit.
It is one. When ferric oxide is formed, chromium chloride tends to form as well, resulting in an overall loss of chromium from the product, increased chlorine requirements, and the disadvantage of chromium chloride deposits in the fluidized bed. be. The method of the present invention substantially completely removes iron from a portion of the raw material and mixes the resulting substantially iron-free modified raw material with the untreated raw material to reduce the iron content on average. It is used to economically obtain mixed products. Such a mixed product is acceptable as a raw material for the production of "ferrochrome". or substantially iron-free materials,
Alternatively, materials from which some of the iron content has been removed are desirable products of the present invention. Chromite sand is a particularly suitable raw material for the last mentioned embodiment of the process according to the invention, since its large particle size can be directly fluidized as is and can be homogeneously mixed without further special processing. Can be done. Chromite contains several minor components incorporated as spinel structures or as separate phases. Aluminum is present in an amount of about 10% by weight calculated as Al ₂ O ₃ , and magnesium is present in an amount of 20% by weight or less calculated as MgO. Most of the aluminum and up to 60% of the magnesium in the ore remains unchlorinated. This is not a disadvantage if the product is used for metallurgical processing. Chromite also contains silica as a separate phase, and in the case of chromite sand, the silica is present in the form of independent particles. These particles of silica are finely divided and only the large particle size of the chromite is treated according to the invention, leaving the majority of the silica in the unchlorinated fine particle size fraction, making it difficult to operate according to the invention. has no effect on There are various starting procedures for the method of the invention. According to one suitable embodiment, the mixture of upgrading substance and carbon is formed into a fluidized bed using an inert fluidizing gas preheated with externally generated heat, after which the desired temperature is reached. The chlorine-containing gas is then reacted with chlorine in the chlorine-containing gas, which is also a fluidizing gas and contains oxygen if necessary to generate the desired temperature at least partially in the fluidized bed. It's okay. According to a further suitable procedure of the invention, the substance to be upgraded is formed into a fluidized bed using air, this fluidized bed is preheated by externally generated heat and then carbon is added, If necessary, a chlorine-containing gas is introduced as a fluidizing gas with the addition of oxygen as a substitute for air. According to a preferred and particularly efficient procedure, the mixture of the substance to be modified and the carbon forms a fluidized bed using air as the fluidizing gas, and the preheating is performed in the fluidized bed by combining the carbon with the oxygen contained in the air. at least in part by the reaction between. When the desired reaction temperature is reached, chlorine-containing gas is introduced as part of the fluidizing gas. Within the scope of the present invention, adaptations of the above-described procedure can easily be made, such as by using a mixture of oxygen and diluent gas in place of air. The process of the invention can be operated batchwise or continuously. The former is preferable when substantially all of the iron content is removed from the raw material, and the latter is preferable in other cases. The upgraded material removed from the fluidized bed is optionally treated to separate it from residual carbon. The effect of the present invention is that the theoretical chlorine demand can be reduced compared to that of U.S. Pat. No. 3,216,817, and unlike the method of U.S. Pat.
Rather than subliming the iron deposits, it is now possible to incorporate them into the gaseous reaction effluent and remove them. The gaseous effluent from the fluidized bed containing ferrous chloride may be treated to regenerate the chlorine content.
The gaseous effluent from the fluidized bed containing ferrous chloride is preferably contacted with oxygen in excess of the amount stoichiometrically necessary to convert the ferrous chloride to ferric oxide and chlorine; The partial pressure of ferrous chloride in the gaseous effluent remains below ferrous chloride for at least 2 seconds after the contact.
kept low enough to prevent liquefaction of the iron,
The effluent has sufficient velocity to transport the ferric oxide particles that form, and the ferric oxide particles are separated from the remaining chlorine-containing effluent. The regenerated chlorine can be used to further modify materials after the necessary treatments to increase purity. Such a cyclic procedure is a particularly advantageous embodiment of the invention. The invention will be explained in more detail by the following examples. The reaction vessel used in both examples was a vertical fused silica cylinder with an internal diameter of 150 mm and a length of approximately 2 m, with a conical base and an inlet for the solid reactant at the top of the reaction vessel. , a gas inlet at the bottom of the conical section, means for removing solids from the bottom, an outlet for removing the volatile products of the reaction from the top of the reaction vessel to a cyclone; At the top and bottom of the vessel are thermocouples surrounded by fused silica. The reaction vessel is located in a heated enclosure to provide temperature control. The material to be upgraded in both examples is a chromite ore having the following composition in weight percent: 30.2% Cr (Cr ₂ O ₃ 15.8% Al ₂ O ₃ 1.6% SiO ₂ 44.1%) 22.6% FeO 8.7% MgO 0.21% MnO 3.6% Fe ₂ O ₃ 0.12% CaO The coke used in this example is All particles have particle sizes ranging from 90 to 1800 x 10 ^-6 m. The particle size distribution of the coke used in this example is as follows. Particle size (micron) Cumulative % Over 1200 16.5 710 〃 48.8 500 〃 66.5 300 〃 84.2 210 〃 90.9 150 〃 95.2 125 〃 97.6 Including those under 125 100.0 Ore used in both examples is substantially All particles have a particle size in the range 106 to 250×10 ⁻⁶ m. The particle size distribution of this ore is as follows. Particle size (micron) Cumulative % Over 250 0 212 〃 6.3 180 〃 32.7 150 〃 57.7 125 〃 82.6 106 〃 92.4 Including those under 106 100.0 Nitrogen and chlorine gases used in these examples are stored in liquid form. obtained from things. Example 1 A reaction vessel was preheated by passing a flow of nitrogen through the gas inlet at a rate of about 36 min. A mixture of 24.0 Kg of chromite ore and 6.0 Kg of petroleum coke was placed in a reaction vessel and a stream of nitrogen fluidized these solids to form a fluidized bed. The bed was preheated to a temperature in the range 950-1000°C and the temperature was kept within this range during the subsequent reaction. To carry out the reaction, the nitrogen flow was replaced with a mixture of nitrogen and 33% by volume chlorine flowing at a rate of 36.0/min. This condition was maintained for 180 minutes, during which time a small sample of the floor was taken for testing. At the end of this period, the fluidizing gas is returned to nitrogen at approximately 36/min, the bed and vessel are cooled, and the color of the bed changes from the black of chromite ore to a dark green resembling chromic oxide (Cr ⁺³ ). Ivy. This rapid change indicated that the first attack occurred on the surface of the particle, and subsequent attacks moved to the center in a stepwise manner, following the known topochemical behavior of chromite toward reagents. The formation of a green color indicates that although the chromium oxide is exposed to chlorine on the surface of the particles, the chromium itself is attacked only slowly or not at all. The solids recovered by cooling the product gas consist mostly of iron chloride and ferric chloride.
The iron/ferrous chloride molar ratio was 1/18. The remaining gaseous products of the reaction are analyzed to be nitrogen,
It was carbon monoxide and carbon dioxide. In this example the CO ₂ /CO molar ratio was 1.66, but this value will vary depending on the reaction conditions used. The recovered bed was found to be a mixture of 4.1 Kg residual coke and 15.2 Kg green product. When the chromium and iron contents of the separated product are converted into metals and compared with those of the initial ore, the results are as follows.

[Table] The remaining components of the treated ore were as follows. 19.2% _Al2O3 ; 0.10%CaO; 1.5% _{SiO2 ;} 0.04
%MnO; and 10.7%MgO.The recovery rate of chromium in the treated ore was 94%, excluding the material removed as a sample during the reaction.
It was hot. Example 2 Ore is introduced into a reaction vessel similar to Example 1, and 36
Preheated in fluidized state for 30 minutes in the presence of an air flow of /min. Coke was added and fluidization was then started as in Example 1 using a gas mixture containing 33% by volume chlorine in nitrogen. Similar behavior as above was observed. The composition of the final product was also similar to that described above and was as follows. 40.5% Cr; and
1.6% Fe (both present as oxides); 19.7%
Al ₂ O ₃ ; 9.1% MgO; 1.8% SiO ₂ ; 0.12% CaO; It can be seen that a product rich in chromium and low in iron is obtained. Other elements in the ore are also removed to a greater or lesser extent, but their removal has no effect on the subsequent processing of the ore. The various elements removed from the ore in the above example are summarized as follows.

【table】

【table】

Claims (1)

[Scope of Claims] 1. The above-mentioned chromium can be produced by reacting at least a part of the iron content of a substance containing chromium oxide and iron oxide with chlorine and removing the obtained iron chloride as steam. A method for upgrading a material containing oxides of iron and iron oxides, comprising forming a fluidized bed containing finely ground said material and finely ground carbon, having an expanded depth of at least 1 meter, said carbon shall be present in an amount at least sufficient to react with oxygen added to or generated in said fluidized bed and in an amount of at least 15% of the total weight of carbon and said material; The reaction temperature in the bed is maintained at 900°C to 1100°C, and a chlorine-containing gas is introduced into the fluidized bed in an amount such that the concentration is 20 to 60% by volume of the gas added to the fluidized bed, and the chlorine is added to the substance. the partial pressure of ferrous chloride in the gaseous effluent from the fluidized bed is maintained low enough to prevent liquefaction of the ferrous chloride. chromium oxide and iron oxide, characterized in that the gaseous ferrous chloride-containing effluent is removed from the fluidized bed and the remaining enhanced chromium-containing material is recovered from the fluidized bed. A method for improving the quality of containing products. 2. The upgrading method according to claim 1, wherein a reaction temperature of 900°C to 1100°C is maintained under the influence of an exothermic reaction between free oxygen and carbon introduced into the fluidized bed. 3. The method of claim 2, wherein free oxygen is introduced into the fluidized bed in an amount sufficient to maintain the reaction temperature by reaction with carbon in the fluidized bed. 4. The method according to any one of claims 1 to 3, wherein the reaction temperature is maintained higher than 920°C. 5. The method according to any one of claims 1 to 4, wherein the reaction temperature is maintained at 1050°C or lower. 6. The amount of oxygen introduced into any part of the fluidized bed is 10% by volume of the total amount of gas introduced into the fluidized bed.
A method according to any one of claims 2 to 5 below. 7. The method according to any one of claims 1 to 6, wherein the substance containing chromium oxide and iron oxide is chromite. 8. Claim 1 in which the substance containing chromium oxide and iron oxide does not substantially contain particles with a diameter outside the range of 75 x 10 ^-6 m to 500 x 10 ^-6 m.
The method described in any one of paragraphs to paragraphs 7 to 7. 9. The method according to claim 6, wherein the chromite has an average particle size of 150 x 10 ^{-6 m} to 250 x 10 ^-6 m. 10. The method according to any one of claims 1 to 7, wherein the material containing oxides of chromium and oxides of iron is natural sand. 11. Any one of claims 1 to 10, wherein carbon is present in the fluidized bed in an amount of at least 20% of the total weight of the substance containing chromium oxide and iron oxide and carbon. The method described in Section 1. 12 The total weight of carbon and a substance containing chromium oxide and iron oxide in a fluidized bed.
12. A method according to claim 11, wherein the compound is present in an amount of 20-50%. 13. According to any one of claims 1 to 12, the carbon does not substantially contain particles having a diameter outside the range of 75 × 10 ^-6 m to 2000 × 10 ^-6 m. Method described. 14 Claim 1 in which the average particle size of carbon is larger than the substance containing chromium oxide and iron oxide
The method according to any one of paragraphs 1 to 13. 15 The average particle size of carbon is 500×10 ^-6 m to 800 in diameter
×10 ^-6 m. 16. The method according to any one of claims 1 to 15, wherein the depth of the fluidized bed during operation is 1 to 2.5 m. 17 Let the partial pressure of ferrous chloride in the gaseous effluent from the fluidized bed be 0.006 (T-900) + 0.2 × 10 ⁵ N/m ² (T =
reaction temperature) while keeping the temperature in the fluidized bed lower than
The method according to any one of claims 1 to 16, wherein the method is maintained at a temperature lower than 1000°C. 18 The fluidized bed is fed such that the partial pressure of ferrous chloride in the gaseous effluent from the fluidized bed produces less than 1 mole of ferric chloride for every 3 moles of ferrous chloride produced. 18. The method according to claim 17, wherein the method is adjusted by controlling the concentration of chlorine introduced. 19. The method according to any one of claims 1 to 18, wherein the concentration of chlorine introduced into the fluidized bed is 25 to 55% by volume. 20. The method according to claim 19, wherein the concentration of chlorine introduced into the fluidized bed is 30 to 50% by volume. 21. A method according to any one of claims 1 to 20, in which the operations are carried out continuously. 22 Reacting at least a part of the iron content of the substance containing the chromium oxide and iron oxide with chlorine,
In a method for upgrading a material containing chromium oxide and iron oxide by removing the obtained iron chloride as steam, forming a fluidized bed containing the substance and finely ground carbon;
said carbon is present in an amount at least sufficient to react with oxygen added to or generated in said fluidized bed and in an amount of at least 15% of the total weight of carbon and said material; The reaction temperature in the fluidized bed is maintained at 900°C to 1100°C, and a chlorine-containing gas is introduced into the fluidized bed in an amount such that the concentration is 20 to 60% by volume of the gas added to the fluidized bed. First chloride is produced by reacting with the iron in the substance.
producing iron and keeping the partial pressure of ferrous chloride in the gaseous effluent from said fluidized bed low enough to prevent liquefaction of the ferrous chloride; 1. An article containing chromium oxides and iron oxides, characterized in that an iron-containing effluent is treated to recover at least chlorine and a residual enhanced chromium-containing material is recovered from the fluidized bed. How to improve quality. 23. The upgrading method according to claim 22, wherein the reaction temperature of 900°C to 1100°C is maintained under the influence of an exothermic reaction between free oxygen and carbon introduced into the fluidized bed. 24. The method of claim 23, wherein free oxygen is introduced into the fluidized bed in an amount sufficient to maintain the reaction temperature by reaction with carbon in the fluidized bed. 25. The method according to any one of claims 22 to 24, wherein the reaction temperature is maintained higher than 920°C. 26. The method according to any one of claims 22 to 25, wherein the reaction temperature is maintained at 1050°C or lower. 27 Claims 23 to 26, wherein the amount of oxygen introduced into any part of the fluidized bed is 10% by volume or less of the total amount of gas introduced into the fluidized bed.
The method described in any one of the preceding paragraphs. 28. The method according to any one of claims 22 to 27, wherein the substance containing an oxide of chromium and an oxide of iron is chromite. 29. Claim 22: The substance containing chromium oxide and iron oxide does not substantially contain particles having a diameter outside the range of 75 x 10 ^{-6 m} to 500 x 10 ^-6 m. The method according to any one of paragraphs to paragraph 28. 30. The method of claim 27, wherein the chromite has an average particle size of 150 x 10 ^{-6 m} to 250 x 10 ^-6 m. 31. A method according to any one of claims 22 to 28, wherein the material containing oxides of chromium and oxides of iron is natural sand. 32. Any of claims 22 to 31, wherein carbon is present in the fluidized bed in an amount of at least 20% of the total weight of carbon and the substance containing chromium oxides and iron oxides. The method described in Section 1. 33 The total weight of carbon and a substance containing chromium oxide and iron oxide in a fluidized bed.
33. A method as claimed in claim 32, wherein the compound is present in an amount of 20-50%. 34. According to any one of claims 22 to 33, the carbon does not substantially contain particles having a diameter outside the range of 75 x 10 ^-6 m to 2000 x 10 ^-6 m. Method described. 35 Claim 2 in which the average particle size of carbon is larger than the substance containing chromium oxide and iron oxide
The method according to any one of Items 2 to 34. 36 The average particle size of carbon is 500×10 ^-6 m to 800 in diameter
36. The method according to claim 35, wherein: x10 ^-6 m. 37. A process according to any one of claims 22 to 36, wherein the depth of the fluidized bed during operation is between 1 and 2.5 m. 38 Let the partial pressure of ferrous chloride in the gaseous effluent from the fluidized bed be 0.006 (T-900) + 0.2 × 10 ⁵ N/m ² (T =
reaction temperature) while keeping the temperature in the fluidized bed lower than
A method according to any one of claims 22 to 37, wherein the temperature is maintained below 1000°C. 39 The flow to the fluidized bed is such that the partial pressure of ferrous chloride in the gaseous effluent from the fluidized bed is such that less than 1 mole of ferric chloride is produced for every 3 moles of ferrous chloride produced. 39. The method according to paragraph 38, wherein the method is regulated by controlling the concentration of chlorine introduced. 40. The method according to any one of claims 22 to 39, wherein the concentration of chlorine introduced into the fluidized bed is between 25 and 55% by volume. 41. The method according to claim 40, wherein the concentration of chlorine introduced into the fluidized bed is 30 to 50% by volume. 42. A method according to any one of claims 22 to 41, wherein the operations are carried out continuously. 43 The gaseous effluent from a fluidized bed containing ferrous chloride vapor is treated with oxygen in excess of the amount stoichiometrically required to convert the ferrous chloride to ferric oxide and chlorine. contacting to form ferric oxide and chlorine, and reducing the partial pressure of ferrous chloride in the gaseous effluent to ferrous chloride for at least the first 2 seconds after said contact.
The effluent is kept low enough to prevent liquefaction of the iron, and the effluent has a velocity sufficient to transport the ferric oxide particles generating velocity, removing the ferric oxide particles from the chlorine-containing effluent. 23. The method of claim 22 for separating.