FI65218B - FOERFARANDE FOER ATT TILLVARATAGA CR203 UR EN KROMHALTIG LOESNING - Google Patents

Description

r] ANNOUNCEMENT

1®J (Ί1> UTLÄGGNINGSSKRIFT 6521 O

• C (45) Vats :. Hi r.; Yonr.: Tt / 10 04 1934

Patent issued v * / (51) K ».ik.3 / Im.a3 C 01 G 37/027, C 22 B 3V32 SUOM I — FI N LAN D (21) FMmmMming 7837 ^ 0 (22) Hakaflibpllva — AmBicnincadig 05.12 .78 (23) AlkupUvi — Giitlghectdif 05.12.78 (41) Tanut {nlktMksI - Wlvft affantNg 06.06. 79

National Board of Patents and Registration (44) Date of issue. - Rci

Patent- and Register-Testing AnaBkan uthfd och. »Krtft» n puMkarad x ^ · 0: 5 (32) (33) (31) requested «toiksu» —8agird priority 05.12.77 30.11.78 (71) Union Carbide Corporation, 270 Park Avenue, New York, New York 10017, USA (72) Tadashi Jack Kagetsu, Lewiston, New York, William Brantner de Atley,

Grand Island, New York, Joseph Solomon Fox, Altamonte Springs,

Florida, Oreste Joseph Malacarne, Grand Junction, Colorado, USA (7I *) Qy Borenius & Co Ab (5U) Method for recovering Cr ^ O ^ rn from a chromium-containing solution -Förfarande for att tillvarataga Cr ^ O ^ ur en kramhaltig losning

The invention relates to a process for treating NaCl 2 O 7 or Na 2 Cr O 4 so as to obtain very pure Cr 2 O 3. A particular embodiment of the invention relates to the treatment of chromium ores to produce high purity Cr 2 O 2.

Chromium compounds are important in the oil and gas industry for anti-corrosion and catalyst production, in cooling and brine solutions and cleaning compounds in the food and beverage industry, in diesel locomotives and automobiles in the transportation industry, in stainless steel plates and chromium and copper separation, mercury arc rectifiers and dry batteries for the electrical industry, matches and rockets for the pyrotechnic industry, lithographic and engraving methods for the photographic industry. However, the main product is chromium oxide, or Cr 2 Og, which is used in metallurgy and as a pigment.

When preparing chromium metal from chromium oxide, relatively pure CrgOg is desired. In the event that the (h 2 O 2 material contains a significant amount of sodium as an impurity, this sodium will evaporate under reduced pressure in a carbon reduction process to produce pure chromium. This Sodium poses a fire hazard when it settles on the walls of the equipment and is then exposed the effects of the surrounding airspace.

In many applications, it is also important that the Cr 2 O 3 product is substantially free of aluminum and sulfur impurities.

It is therefore an object of the invention to provide a process for the preparation of high-purity C

It is also an object of the invention to provide a process for the preparation of high purity Cr 2 O 3 from chromium ores.

Other objects of the invention will become apparent from the following description and claims, which are set forth on the basis of a flow chart illustrating the method of the invention.

The process according to the invention is characterized in that 1) an aqueous solution of Na 2 Cr 7 O 7 or Na 2 CrO 2 or mixtures thereof is formed, 2) acid is added to the solution obtained in step 1) to adjust the pH to about 1 to 2, 3) in step 2 ) contacting the acidified solution with an organic extractant to recover chromium from this acidic solution to the chromium-containing organic liquid phase, 4) mixing the chromium-containing organic phase with an aqueous solution of NH 4 OH 2 to give an aqueous solution of (NH 4) 2 CrO 2, 5) evaporating to obtain a chromium-containing material, 6) annealing this solid chromium-containing material to obtain Cr 2 O 3.

A particular embodiment of the process according to the invention, which is applied to chromium ores, is characterized in that 1) a mixture of chromium ore and Na 2 CO 3 and CaO is roasted in an oxidizing gas atmosphere at about 600-1100 ° C for about 0.5-6 hours, wherein the amount of Na 2 CO 3 is such that about 1.4 to 4.2 kg of Na 2 CO 3 per kg of ore in the ore is obtained, and the amount of CaO is 3 65218 such that about 0.6 ... 1 kg CaO / kg C 2 O 2 in the broth, 2) extracting the roasted material obtained in step 1) with water at a temperature in the range of about 5 ° C ... boiling point of water, about 5 minutes ... 5 hours, 3) adding an inorganic acid, e.g. hydrochloric acid, nitric acid, sulfuric acid, to the extraction solution obtained in step 2) to adjust the pH to about 3 to 9.5 to precipitate aluminum impurities, 4) separating the precipitate from the extraction solution and then adding inorganic acid to this solution. To adjust the pH to about 1 ... 2, 5) the acidified extraction solution obtained in step 4) is contacted with an organic extractant to recover chromium from this acidic extraction solution to a chromium-containing organic liquid phase, 6) mixing the chromium-containing organic phase with an aqueous solution of NH 4 OH to give an aqueous solution of NH 4 OH, 7) evaporating the (NH 4 ClO 8) annealing the solid chromium-containing material to obtain Cr 2 O 3.

When applying this particular embodiment of the invention, natural chromium ore, e.g. transvaal ore (with 30 ... 50% Cr 2 O 3; 15 ... 25% Fe; 2 ... 10% SiO 2) is comminuted as shown in the accompanying drawing. ; 10 ... 15% Al; less than 1% Na; 6 ... 15% MgO; 0.2 ... 0.6% Ca: a) to a suitable size, e.g. 200 mesh Tyler sieve set and finer, as shown in step 10, and mixing with Na 2 CO 3 and CaO (CaO may initially be present as CaCO 3), and roasting the mixture as shown in step 20.

The amount of Na 2 CO 3 and CaO can be varied in the roasting step by using 1.4 to 4.2 kg of Na 2 CO 3 and 0.6 to 1.0 kg of CaO per kg of Cr 2 O 3 in the ore. for.

The roasting temperature can vary between 600 and 1100 ° C, and the roasting time can vary between 0.5 and 6.0 hours. Suitably the amounts of Na 2 CO 3 and CaO are 1.9 and 0.6 kg, respectively, and the suitable temperature and roasting time are 950 ° C, respectively. 2 hours. Roasting is carried out in an oxygen-containing gas space which is made to contain excess oxygen by passing air, oxygen or a combustion gas with a sufficient excess of oxygen over the roasting bed.

* 65218

The following equation describes the roasting reaction using Na 2 CO 3 to dissolve chromium 4 (Cr 2 O 3 Fe 2 O + 8 Na 2 CO 3 + 702 -► 2 Fe 2 O 3 + 8 Na 2 CrO 4 + 8CO 2 t

The burnt products obtained as a result of roasting are suitably extracted with water, as shown in point 30, so that the water-soluble chromium salts are substantially soluble and can be removed from the burnt products. The extraction can take place at a temperature in the range of 5 ° C ... the boiling point of water, and the extraction takes 5 minutes ...

5 hours, depending on the chromium concentration in the extraction step as well as the temperature. The amount of chromium extracted from the burned products can be increased by bubbling air through the extraction broth.

In addition to chromium, the extraction broth contains aluminum and sodium as harmful impurities, e.g. NaA102. The aluminum impurities are removed as shown in 40 and 50 by adding acid to the extraction broth until its pH is reduced to between 3 and 9.5, suitably 8.0. The amount of chromium precipitated together with Al (OH 3) at pH = 8 is typically about 0.6% of the total chromium content of the broth.

However, the precipitation of chromium with Al (OH3) increases in the case where the pH is lowered. If a low-sulfur product is desired, acids other than sulfuric acid, suitably hydrochloric acid, must be used.

The amount of aluminum remaining in the solution after filtering off the AMOHg) is typically less than 0.7% Al 2 O 3, based on the weight of Cr 2 O 3 in the solution.

To remove residual impurities, eg Na impurities in the extraction broth obtained after the Al (OH) 3 precipitation step, the solution extraction method indicated in 60 is applied. According to this method, a dilute solution of the extraction broth is treated with an acid (other than sulfuric acid to obtain products with a low sulfur content) so that the final pH is in the range 1 to 2, suitably 1.6, and the chromium concentration as Cr 2 O 3 is suitably 1 g / l ... 25 g / l, with a very preferred concentration of 8.2 g / l. As the organic solvent, it is possible to use either benzene, xylene or toluene alone or in admixture with an isoparaffinic hydrocarbon such as "Isopar H" (manufactured by Exxon), and a tertiary amine, e.g.

5 65218 "Alamine 336" (manufactured by General Mills) A 0.1 M solution of extractant has been used, but lower or higher concentrations ranging from 0.02 to 0.3 M can be used. that with only 2 extraction steps, 10 g / l of Cr 2 O 3 can be taken up in the organic phase and the amount remaining in the aqueous phase (raffinate) can be reduced to only 0.04 g / l, ie 40 ppm. the ratio of phase to aqueous phase can be varied between 0.33 and 1.0.

The chromium-containing organic phase is washed with water to remove residues of aqueous extraction broth containing sodium and other impurities. The number of washing steps depends on the type and efficiency of the washing step, but normally no more than 1 or 2 washing steps are required.

The chromium in the organic phase is removed as shown in 70 by stirring in about 1.5 MNH4OH solution. As a result, the phases separate rapidly (within about a minute). The aqueous phase contains (NH 4 OH) and the removed organic phase contains about 0.04 g / l Cr 2 Og. The volume ratio of the NH 4 OH-containing aqueous phase to the organic phase can be 0.5 to 10. Thus, a relatively concentrated (NH 4 OH) CrO 2 solution The chromium-purified organic phase can be recycled as shown in 65.

The (NH 1 +) 2 CrO + + solution is evaporated to dryness as shown at 80 and the resulting solid material is dried after drying to Cr 2 O 3 in an oxygen-containing gaseous state, e.g. air or oxygen, and at about 500 ° C as shown at 90. The solid material contains mainly a mixture of (NH 4) CrO 2 and (NH 2) 2 Cr 2 O 2, i.e. ammonium chromate compounds.

The above description, starting with the description of the solution extraction method, is applicable to the process according to the invention when used in connection with chromium-containing aqueous solutions prepared e.g. by dissolving commercial grade Na 2 Cr 2 O 3 or Na 2 Cr O 4 in water instead of preparing a chromium-containing aqueous solution of Na 2 Cr 2 O 4. by ore extraction. As shown in point 10 of the drawing, commercial grade Na 2 Cr 2 O 2 or Na 2 CrO 2 or a mixture thereof is dissolved in water to give an aqueous solution having a Cr 2 O 3 concentration suitably in the range of 1 g / l ...

25 g / l, preferably 5 g / l ... 25 g / l. If necessary, this solution can be filtered to remove insoluble solids. In the same manner as described above, the solution extraction method described in step 60 can be applied to an aqueous solution in the remaining steps of the method of the present invention, as described above.

An example of a process according to the invention applied to an aqueous solution of Na 2 Cl 2 O 2 is the following:

Example I

A liter of aqueous solution was prepared by dissolving 11.5 g of commercial grade Na 2 Cr 2 O 7 in water and adding 12 M HCl to the solution so that the chromium concentration of the solution (calculated as pH = 1) was 5.8 g / l at pH = 1. , 6. ^ 20 ^ 0 ^. 21 ^ 0 ^ analysis was as follows:

Na 15.38% (according to chemical analysis)

Cr: 34.63% ("" ") S: 0.029% (" "") Al 0.008-0.08% (according to spectral analysis)

Ca: 0.001-0.01% ("" ")

Mg: 0.001-0.01% ("" ") V: 0.002-0.02% (" "")

No other metal elements were detected in the analysis.

A 0.1 M organic amine solution was prepared by dissolving 49 ml of Alamine 336 (tertiary amine) and 50 ml of isodecanol in benzene to give a total of 1 liter of organic solution. Upon shaking, 50 ml of the aqueous solution described above and 50 ml of the organic solution were found to form an emulsion.

In contrast, no emulsion was formed when a tertiary amine was used with benzene or xylene or Aromatic 100 or 150 (manufactured by Exxon), or mixtures thereof with an isoparaffinic hydrocarbon such as "Isopar H" (manufactured by Exxon), but without isodecanol.

As an example, mixing and shaking 50 ml of the aqueous solution described above and 50 ml of 0.1 M organic solvent containing 49 ml of "Alamine 336" (tertiary amine) dissolved in benzene to give 1 L of solution did not form an emulsion and the phases separated rapidly, i.e. in about 1 minute.

7 65218

The organic phase was washed twice with water to remove residual impurity residues.

The aqueous phase and washings were water white and contained negligible amounts of chromium. Less than 0.1% of the chromium in the organic phase was lost in the washes.

The organic phase (50 ml) was 5.79 g / l (Cr 2 O 2) and the aqueous phase (50 ml) was 0.02 g / l (C 2 O 2). Using a ratio of 1.0 of the organic phase to the aqueous phase, 99% of chromium extracted in a single extraction step.

50 ml of an organic solution of tertiary amine and benzene were washed with 50 ml of 1.5 M aqueous NH 4 OH using a ratio of 5.0 of the organic phase to the aqueous phase to give about 10 ml of a washing solution. The washed organic phase was colorless and contained 0.04 g / l of CH 2 Cl 2. No emulsion was observed.

The washings were evaporated in a stainless steel dish and the remaining solids were annealed at 600 ° C to give (H ^ O ^ ra with a typical analysis of C ^ O ^ ra> 99% (calculated from the difference) Al 0.0004-0 .04% (according to spectrum analysis)

Ca 0.008-0.08% (according to spectral analysis)

Mg: 0.002-0.02% ("")

Na: 0.08-0.8% ("")

Si: 0.008-0.08% ("") V: 0.001-0.01% ("")

By applying the invention, compounds of ^ 2 ^ 2 () 7 or Na2CrO1 + can be obtained in a very pure C ^ O ^ product with less than 0.08-0.8%

These

The process according to the invention can be applied to solutions of commercially available compounds NagCrgCl 2 or mixtures thereof, the chromium concentration of the solution being preferably 1 to 25 g / l. In the event that the solution contains insoluble solids, the solution may first be filtered to remove these solids.

8 65218

The following example illustrates the application of the method according to the invention to chromium ore.

Example II

2.27 kg of Transvaal-type chromium ore, the analysis of which is shown below, was ground to a fine of 200 mesh.

Analysis of chromium ore (as oxides) (chemical analysis)

Ch ^ O ^ ia 44.6%

Total FejO ^ ia 27.5%

Siesta 3.5%

CaO: 0.4%

Al 2 O 3 26.9% Na 2 O * 8 0.1%

MgO: 10.1%

100 g of ground ore and 25 g of commercial grade CaO and 82.8 g of powdered reagent grade Na 2 CO 3 were mixed. The mixture was placed in an "Inconel X" type dish and roasted for 2 hours at 950 ° C by blowing air over the mixture. After roasting, the roasted mixture was extracted using 2 ml of water per gram of roasted product, and then washed using 2 ml of water per gram to obtain an extraction broth and wash water, which were analyzed as follows:

Cr203 22.3 g / l (according to chemical analysis) Al 0.1-1 g / l (according to spectral analysis)

Ga 0.004 - 0.04 g / l ("")

Mg 0.0004 -0.004 g / l ("")

Na> 20 g / l ("")

Si 0.004 - 0.04g / l (, "T")

12 M hydrochloric acid was added to the extraction broth to lower the pH from 2.8 to 8.0, resulting in the precipitation of aluminum as Al (OH) 3. After the precipitate was removed by filtration, the composition of the acidified extraction broth was analyzed as follows:

Cr 2 O 3 22.3 g / l Al 0.13 g / l

Na> 20 g / 1965218

For solvent extraction, a feed solution having a concentration of 5.8 g / l was prepared by mixing 520 ml of concentrated extraction broth (pH = 12.8) and 265 ml of 12 M hydrochloric acid and H 2 O to give 200 ml of a solution having a pH of = 1.6.

The organic solution was prepared by mixing isodecanol (5% v / v) "Isopar H" and "Alamine 336" (0.1 M) to give 2000 ml of an organic solution as proposed by the General Mills Chemical Division Chromium-Liquid Ion. Exchange, Bulletin CSDI-61. Upon shaking, 150 mL of the aqueous solution described above and 150 mL of the organic solution formed an emulsion, and the organic solution turned brown.

When isodecanol was omitted, an emulsion still formed, but the organic phase was not brown but orange, suggesting that the earlier discoloration was due to the decomposition of the alcohol.

When a tertiary amine and benzene or xylene or various aromatic diluents of the trade name Exxon were used, but without isodecanol, no emulsion formed. An example of this is: When 100 ml of the aqueous solution described above and 100 ml of a tertiary amine organic solvent in either benzene or xylene or "Aromatic 100" or -150 "were mixed, no emulsions formed and the phases separated rapidly, i.e. within about a minute. The washings were water-white and contained only negligible amounts of chromium.The amine did not decompose.

The organic phase contained 5.79 g / l Cr 2 O 3 and the aqueous phase contained 0.019 g / l Cr 2 O 3.

100 ml of chromium-containing organic phase with tertiary amine and benzene were purified with 20 ml of 1.5 M aqueous NH 4 OH solution and about 20 ml of washing broth was obtained, which was evaporated, after which the solids obtained were annealed at 600 ° C. their composition by analysis was as follows:

Cr 2 O 3> 99% (calculated from the difference) AI 0.08-0.8% (according to spectral analysis) 10 6521 8

Ca 0.008-0.08% (according to spectral analysis)

Mg: 0.0004-0.004% ("")

Na: 0.04-0.4% ("")

Si: 0.004-0.04% ("") V: 0.004-0.04% ("")

If emulsions are formed in a large-scale extraction plant, the method cannot be applied, so the selection of the right diluent or diluent combinations for the amine is very important.

More than 99% of the chromium was recovered in the extraction step.

Applying the process of the invention and using a roasting temperature of 950 ° C, 94% of the chromium was removed from the roasted products when air was bubbled through the extraction broth during the extraction step.

Unless air was bubbled during the extraction under otherwise similar conditions, only 88% of the chromium was extracted. The amounts of Na 2 CO 3 and CaO are also important for economic reasons. A 94% extraction result was obtained using 25 g of CaO and 82.8 g of NagCO2 per 100 g of chromium ore with 44.6% Cr 2 O 3. Using larger amounts, i.e. 50 g CaO and 82.8 g Na 2 CO 3, the extraction rate decreased from 88% to 83%, unless air was used in the extraction step. CaO can be added as quicklime or limestone.

In the extraction step of the roasting products, a pH value of about 12 is suitable. In the aluminum precipitation step, the pH range of 3 to 9.5 is important, and the optimum value is 8.0. At higher pH values, more chromium is lost in the Al (OH) 2 precipitate, while more chromium is lost at lower pH values in the form of dissolved chromium hydrate.

Applying the process of the invention, a high purity CO 2 Og product with less than about 0.2% aluminum and less than about 0.04-0.4% sodium can be obtained from natural chromium ores such as Transvaal ore and other chromium oxides. materials containing.

In the application of the invention, the choice of the right diluents or diluent combinations for the amine is very important, as the process could not be applied in practice if emulsions are formed in a large-scale extraction plant.

The special organic solvents used in accordance with this invention are essential for preventing emulsions. Benzene, xylene, Aromatic 100 or 150 produced by the trade name Exxon, or mixtures thereof, or mixtures of one of the above substances and an isoparaffinic hydrocarbon, such as the product "Isopar H" of the trade name Exxon, were found to be satisfactory.

It has been found that the use of isodecanol as a solvent extraction reaction modifier is detrimental because isodecanol reacts with chromium in solution, and the alcohol decomposes as a result of this reaction and contributes to the formation of an emulsion.

In addition, the process according to the invention makes it possible to obtain a substantially sulfur-free product by using other inorganic acids instead of sulfuric acid, and it has further been found that the solvent extraction reaction purification step essentially removes or as an impurity in materials. When applying the invention, hydrochloric acid is preferably used in the case where it is desired to prepare a sulfur-free product.

Claims (7)

12 6521 8 A process for recovering high purity Cr 2 O 3 from chromium ore, wherein the chromium in the form of Na 2 Cr 2 O 7 or Na 2 CrO 4 is extracted from an acidic aqueous solution with an organic substance, removed from the organic phase with NK 2 OH, and annealed, characterized in that the aqueous chromate solution is formed by a) in the gas state, a mixture of chromium ore and Na 2 CO 3 and CaO at about 600 to 1100 ° C for about 0.5 to 6 hours, the amount of Na 2 CO 3 being such that about 1.4 is obtained. ..4,2 kg Na 2 CO 3 per kg of Cr 2 O 3 in the ore and the amount of CaO is such that about 0,6 to 1 kg of CaO / kg of Cr2Ο3 in the ore are obtained, b) extracted the roasted material obtained in step a) with water at a temperature in the range of about 5 ° C to the boiling point of water for about 5 minutes to 5 hours, c) acid is added to the extraction solution obtained in step b) to adjust the pH to about 3 ... 9.5 to precipitate aluminum impurities, and these impurities are separated from the extraction solution. Process according to claim 1, characterized in that the roasting temperature of step a) is about 950 ° C and the roasting time is about 2 hours. Process according to Claim 1, characterized in that an aggregate with about 1.9 kg of Na 2 CO 3 and 0.6 kg of CaO per kg of Cr 2 O 3 in the ore is used. Process according to Claim 1, characterized in that a pH of about 8 is used in step c). Process according to Claim 1, characterized in that the acid used in step c) is an inorganic acid which does not contain sulfur in the case where it is desired to prepare a low-sulfur product. Process according to Claim 1, characterized in that the acid used in step c) is hydrochloric acid. 13 6521 8 A method according to claim 1, characterized in that in step b) air is bubbled through the water extraction liquid during the extraction step to increase the chromium recovery.