Iron chrome black pigment and preparation method thereof

Abstract

The preparation method comprises the following steps: (1) smelting calcium-free chromium slag to obtain an iron-chromium alloy, and then spraying powder on the iron-chromium alloy molten at high temperature to prepare iron-chromium powder; (2) performing acid dissolution on the prepared iron-chromium powder, separating and filtering a dissolution solution to obtain an acid dissolution clear solution, and performing oxygen explosion to completely convert divalent chromium and divalent iron in the acid dissolution clear solution into trivalent chromium and trivalent iron; then continuously stirring and adding ammonia water for neutralization and precipitation to obtain a precipitate; and (3) filtering, washing and separating the precipitate to obtain chromic hydroxide and ferric hydroxide precipitate, drying by flash evaporation, feeding into a mixer, adding a regulator, mixing, and finally feeding into a rotary kiln for roasting to obtain the iron-chromium black pigment. According to the method, the beneficial components chromium and iron in the calcium-free chromium slag are comprehensively utilized, the byproduct ferrochrome obtained after waste slag treatment is subjected to powder spraying, then acid dissolution washing, neutralization precipitation and calcination are performed to produce the iron-chromium black pigment, a new way of waste utilization is provided, and the production cost of the iron-chromium black pigment is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of inorganic pigment preparation, and in particular to an iron chrome black pigment and a preparation method thereof. Background Art

[0002] Black pigment is a widely used color system. In addition to being used directly in the production of black paint, it is also used to adjust the brightness of other pigments (by adding different proportions of black pigment to the existing colors, you can get various colors of different brightness). Currently, the commonly used black inorganic pigments include carbon black, iron oxide black, copper chrome black and iron chrome black.

[0003] Iron chrome black is a mixed oxide formed by solid solution of Fe2O3 and Cr2O3 in a certain proportion, still maintaining the hematite structure, and its color is black with a reddish phase. Its composition can be expressed as Cr x Fe 2-x O3. Iron chrome black is the type of black pigment with the highest total solar reflectance (TSR value is close to 30%, while carbon black and copper chrome black TSR is about 5%). It has excellent weather resistance, high temperature resistance, acid and alkali resistance, environmental protection and non-toxicity, no migration, no color bleeding, and is insoluble in water and organic solvents. Its color spectrum ranges from reddish brown to brownish black. It is widely used in thermal insulation and cooling coatings, coil coatings, powder coatings, transportation coatings, outdoor architectural coatings, camouflage coatings, painting coatings, road sign coatings, engineering plastics, toy plastics, food packaging plastics, printing inks, masterbatches, high-performance industrial coatings, roofing materials and other building materials and ceramics.

[0004] The existing methods for producing iron chrome black mainly include the following: (1) using ferrous sulfate to reduce sodium dichromate aqueous solution, then adding alkali to form a coprecipitate, washing and drying, and then calcining at high temperature to prepare Fe-Cr pigments. However, this method has high production costs and is not conducive to industrial production; (2) using Cr(NO3)3·9H2O and Fe(NO3)3·9H2O to mix and concentrate, then self-propagating reaction, and calcining at high temperature to prepare iron chrome black pigments. The iron chrome black pigments prepared by this method have high infrared reflectivity, complete grains and concentrated distribution in the submicron range, and are suitable for coatings, plastics, inks and other industries. However, this method requires Cr(NO3)3·9H2O to be used for the preparation of iron chrome black pigments. )3·9H2O and Fe(NO3)3·9H2O are used to prepare Cr / Fe aqueous solution. The raw materials need to be specially prepared, and the production cost is relatively high. (3) The chromic anhydride byproduct sodium bisulfate and scrap iron are used as raw materials. The hexavalent chromium in the sodium bisulfate is reduced with the iron filings, and then a co-precipitate is formed with alkali. The high-temperature calcination obtains chromium black. This method uses the chromic anhydride byproduct sodium bisulfate and scrap iron filings as raw materials to prepare chromium black pigment, making good use of the chromic anhydride byproduct. However, the co-precipitation process of this method consumes a large amount of alkali and produces salt-containing wastewater. The co-precipitate obtained will also increase energy consumption during drying or calcination, resulting in a significant increase in cost.

[0005] Calcium-free chromium slag is an industrial waste residue discharged from the production of chromium salts using a calcium-free roasting process. 6+ ), is a serious source of pollution and is a hazardous waste residue, so the chromium residue needs to be detoxified. However, the traditional wet detoxification and dry pure independent detoxification methods have the disadvantages of high cost and small processing volume, which cannot fundamentally solve the pollution problem of chromium residue, let alone comprehensive resource utilization and turning waste into treasure. However, my country is a country with poor chromium resources, and 90% of chromium resources need to be imported from abroad. If they are not recycled, it will inevitably cause a waste of scarce resources. Therefore, how to use calcium-free chromium residue as a raw material for comprehensive utilization to produce useful industrial products and fundamentally achieve the purpose of thorough detoxification is an important issue that needs to be studied and solved urgently. Summary of the invention

[0006] The invention provides an iron chrome black pigment and a preparation method thereof, aiming at comprehensively utilizing the calcium-free chrome slag produced in the production process of chromium salts, smelting an iron chrome alloy and then producing the iron chrome black pigment, so as to achieve the purpose of waste utilization and reduce production costs.

[0007] To achieve its purpose, the present invention adopts the following technical solution: A method for preparing iron chrome black pigment comprises the following steps: (1) The calcium-free chromium slag produced in the process of chromium salt production is smelted to obtain ferrochromium alloy, and then the high-temperature molten ferrochromium alloy is sprayed to obtain ferrochromium powder; (2) acid-dissolving the ferrochromium powder obtained in step (1), separating and filtering the solution to obtain an acid-dissolved clear solution, and subjecting the solution to oxygen explosion to completely convert the divalent chromium and divalent iron in the acid-dissolved clear solution into trivalent chromium and trivalent iron; then continuously stirring and adding ammonia water for neutralization and precipitation to obtain a precipitate; (3) The precipitate obtained in step (2) is filtered and washed to separate chromium hydroxide and iron hydroxide precipitates, which are then flash dried and sent to a mixer and mixed with a color regulator, and finally sent to a rotary kiln for calcination to obtain iron chrome black pigment.

[0008] Furthermore, the main components of the calcium-free chromium slag in step (1) include CaO: 0-2%, MgO: 9-12%, Fe2O3: 36-40%, Al2O3: 14-16%, SiO2: 1-4%, total chromium Cr2O3: 8-10%, water-soluble Cr 6+ : 0-1.2%. Furthermore, in step (1), the calcium-free chromium slag is smelted in a special refining furnace at a smelting temperature of 1650-1700°C.

[0009] Furthermore, the ferrochromium alloy smelted in step (1) contains 15-18% chromium.

[0010] Furthermore, in step (2), the molar ratio of the acid used for acid dissolution to the ferrochromium powder is 1.5-2:0.5-1, and the temperature of the acid dissolution is 25°C±5°C.

[0011] Furthermore, in step (2), the oxygen explosion temperature is 70-80°C, and the oxygen explosion time is ≥8h.

[0012] Furthermore, when the pH value of the neutralization reaction in step (2) reaches 6.5-7.5, stirring is continued for 2-3 hours.

[0013] Furthermore, in step (3), the flash drying temperature is 120-150°C; the roasting temperature is 1000-1200°C, and the roasting time is 3-5h.

[0014] Furthermore, in step (3), the regulator is cupric chloride or cuprous chloride.

[0015] The iron chrome black pigment of the present invention can be prepared by the above-mentioned preparation method of the iron chrome black pigment.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention utilizes the calcium-free chromium slag produced in the process of chromium salt production to smelt chromium-containing iron-chromium alloy, sprays the high-temperature molten iron-chromium alloy to make iron-chromium powder, then acid dissolves, filters and separates to obtain an acid-soluble clear liquid for oxygen explosion, adds ammonia water to the acid-soluble clear liquid for neutralization, reacts until precipitation is completely completed, and finally filters and washes to separate chromium hydroxide and iron hydroxide precipitation, which enter a mixer after flash drying and are mixed with a regulator, and finally roasted to obtain iron-chromium black pigment. The beneficial components chromium and iron in the calcium-free chromium slag are comprehensively utilized, the byproduct chromium iron after waste residue treatment is sprayed with powder, then acid-dissolved and washed, neutralized and precipitated, and calcined to produce iron-chromium black pigment, a new way of waste utilization is proposed, and the purpose of harmless treatment of waste residue is achieved. Compared with the traditional preparation method, the iron-chromium black pigment is prepared by adopting the method of waste residue recycling, the production cost is greatly reduced, and the solid, liquid and gas generated in the production process are all recycled, without external discharge, energy saving and environmental protection. DETAILED DESCRIPTION

[0017] The present invention will be further described below in conjunction with embodiments: Example 1 A method for preparing iron chrome black pigment comprises the following steps: (1) The calcium-free chromium slag produced in the process of chromium salt production is smelted in a special refining furnace at 1650℃ to obtain a ferrochromium alloy containing 16% chromium, and then the high-temperature molten ferrochromium alloy is sprayed to make ferrochromium powder with a mesh size of ≤100 mesh; the main components of the calcium-free chromium slag include CaO: 2%, MgO: 9%, Fe2O3: 40%, Al2O3: 15%, SiO2: 4%, total chromium Cr2O3: 9%, water-soluble Cr6+ :0.9%; (2) A 20% hydrochloric acid solution and the ferrochromium powder obtained in step (1) are acid-dissolved in a molar ratio of 1.5:0.5, and the acid-dissolving temperature is 20°C. The dissolved solution is separated and filtered by a filter to obtain an acid-dissolved clear liquid, which is subjected to oxygen explosion at 70°C for 8.5 hours to completely convert the divalent chromium and divalent iron in the acid-dissolved clear liquid into trivalent chromium and trivalent iron; then, the solution is continuously stirred and ammonia water is added for neutralization. When the pH value is 6.5, stirring is continued for 2 hours until precipitation is completed to obtain a precipitate; (3) The precipitate obtained in step (2) is filtered and washed to separate chromium hydroxide and ferric hydroxide precipitates, which are flash dried at 120° C. and then fed into a mixer and mixed with cuprous chloride, and finally fed into a rotary kiln at 1050° C. for calcination for 4 h to obtain iron chrome black pigment.

[0018] The obtained iron chrome black pigment components were tested, and the results are shown in Table 1: Table 1 Iron chrome black pigment composition Example 2 A method for preparing iron chrome black pigment comprises the following steps: (1) The calcium-free chromium slag produced in the process of chromium salt production is smelted in a special refining furnace at 1700℃ to obtain a ferrochromium alloy containing 18% chromium, and then the high-temperature molten ferrochromium alloy is sprayed to make ferrochromium powder with a mesh size of ≤110 mesh; the main components of the calcium-free chromium slag include CaO: 1.8%, MgO: 11%, Fe2O3: 39%, Al2O3: 16%, SiO2: 3.2%, total chromium Cr2O3: 10%, water-soluble Cr 6+ :1.1%; (2) A 20% nitric acid solution and the ferrochromium powder obtained in step (1) are acid-dissolved in a molar ratio of 1.8:0.8 at a temperature of 25°C. The solution is separated and filtered through a filter to obtain an acid-dissolved clear solution, which is subjected to oxygen explosion at 75°C for 9 hours to completely convert the divalent chromium and divalent iron in the acid-dissolved clear solution into trivalent chromium and trivalent iron; then, the solution is continuously stirred and ammonia water is added for neutralization. When the pH value is 7, stirring is continued for 2.5 hours until precipitation is completed to obtain a precipitate; (3) The precipitate obtained in step (2) is filtered and washed to separate chromium hydroxide and iron hydroxide precipitates, which are flash dried at 135° C. and then fed into a mixer and mixed with cupric chloride, and finally fed into a rotary kiln at 1100° C. for calcination for 3 h to obtain iron chrome black pigment.

[0019] The obtained iron chrome black pigment components were tested, and the results are shown in Table 2: Table 2 Iron chrome black pigment composition Example 3 A method for preparing iron chrome black pigment comprises the following steps: (1) The calcium-free chromium slag produced in the process of chromium salt production is smelted in a special refining furnace at 1690℃ to obtain a ferrochromium alloy containing 15% chromium, and then the high-temperature molten ferrochromium alloy is sprayed to make ferrochromium powder with a mesh size of ≤120 mesh; the main components of the calcium-free chromium slag include CaO: 1.5%, MgO: 9%, Fe2O3: 36%, Al2O3: 16%, SiO2: 1.2%, total chromium Cr2O3: 8.2%, water-soluble Cr 6+ :0.4%; (2) A 15% hydrochloric acid solution and the ferrochromium powder obtained in step (1) are acid-dissolved in a molar ratio of 2:1 at a temperature of 30°C. The solution is separated and filtered through a filter to obtain an acid-dissolved clear solution, which is subjected to oxygen explosion at 80°C for 9 hours to completely convert the divalent chromium and divalent iron in the acid-dissolved clear solution into trivalent chromium and trivalent iron. Then, stirring is continued and ammonia water is added for neutralization. When the pH value is 7.5, stirring is continued for 3 hours until precipitation is completed to obtain a precipitate. (3) The precipitate obtained in step (2) is filtered and washed to separate chromium hydroxide and ferric hydroxide precipitates, which are flash dried at 150° C. and then fed into a mixer and mixed with cuprous chloride, and finally fed into a rotary kiln at 1200° C. for calcination for 5 h to obtain iron chrome black pigment.

[0020] The obtained iron chrome black pigment components were tested, and the results are shown in Table 3: Table 3 Iron chrome black pigment composition By testing the iron chrome black pigment in Examples 1-3, its CIE L * a * b * The color space parameters are shown in Table 4: Table 4 CIE L * a * b * Color space parameters Among them, in Table 4, L * Indicates brightness, ranging from 0-100, indicating that the color ranges from dark (black) to light (white); a * Indicates red and green. The value changes from positive to negative, indicating that the color changes from red (positive) to green (negative). The larger the a value, the redder the color, and the smaller the a value, the greener the color; b * The value changes from positive to negative, indicating that the color changes from yellow (positive) to blue (negative). The larger the b value, the yellower the color, and the smaller the b value, the bluer the color. The results in Table 4 show that the L of the obtained iron chrome black pigment *(brightness) is less than 30, and a * (red and green) and b * The values ​​of (yellow and blue) are relatively small, so the iron chrome black pigment prepared by this method is close to pure black.

[0021] By testing the iron chrome black pigment in Examples 1-3, the pigment performance parameters are shown in Table 5: Table 5 Pigment performance parameters The results in Table 5 show that the average particle size of the obtained iron chrome black pigment is about 0.7 pm, which is a general-purpose iron chrome black pigment with balanced performance; the oil absorption is ≤25, indicating that the pigment has good wettability, and has good acid and alkali resistance, heat resistance, light resistance and weather resistance; the water-soluble salt content is <0.1, and the low water-soluble salt content means that the chemical composition in the pigment is more stable, and it is not easy to cause the decomposition or deterioration of the pigment due to the penetration of water, thereby extending the service life of the pigment and the shelf life of the artwork, and having better durability and stability.

[0022] In summary, compared with the traditional iron chrome black pigment production process, the method of the present invention proposes a new way of waste utilization, comprehensively utilizes the beneficial components chromium and iron in the calcium-free chromium slag, achieves the purpose of harmless treatment of waste slag, and the various performance parameters of the prepared iron chrome black pigment meet the national standard requirements. In addition, the solid, liquid and gas generated in the production process are all recycled and utilized without external discharge, and the roasting temperature is low, thereby achieving the purpose of energy saving and efficiency improvement.

Claims

1. A method for preparing iron chrome black pigment, characterized in that: The following steps are involved: (1) The calcium-free chromium slag produced in the process of chromium salt production is smelted to obtain ferrochromium alloy, and then the high-temperature molten ferrochromium alloy is sprayed to obtain ferrochromium powder; (2) acid-dissolving the ferrochromium powder obtained in step (1), separating and filtering the solution to obtain an acid-dissolved clear solution, and subjecting the solution to oxygen explosion to completely convert the divalent chromium and divalent iron in the acid-dissolved clear solution into trivalent chromium and trivalent iron; then continuously stirring and adding ammonia water for neutralization and precipitation to obtain a precipitate; (3) The precipitate obtained in step (2) is filtered and washed to separate chromium hydroxide and iron hydroxide precipitates, which are then flash dried and sent to a mixer and mixed with a color regulator, and finally sent to a rotary kiln for calcination to obtain iron chrome black pigment.

2. The method for preparing a ferrochrome black pigment as claimed in claim 1, wherein The main components of the calcium-free chromium slag in step (1) include CaO: 0-2%, MgO: 9-12%, Fe2O3: 36-40%, Al2O3: 14-16%, SiO2: 1-4%, total chromium Cr2O3: 8-10%, water-soluble Cr 6+ : 0-1.2%.

3. The method for preparing a ferrochrome black pigment as claimed in claim 2, wherein: In step (1), the calcium-free chromium slag is smelted in a special refining furnace at a smelting temperature of 1650-1700°C.

4. The method for preparing a ferrochrome black pigment as claimed in claim 3, wherein: The iron-chromium alloy smelted in step (1) contains 15-18% chromium.

5. A method for preparing a ferrochrome black pigment as claimed in claim 4, characterized in that: In step (2), the molar ratio of the acid used for acid dissolution to the ferrochromium powder is 1.5-2:0.5-1, and the temperature of the acid dissolution is 25°C±5°C.

6. A method for preparing a ferrochrome black pigment as claimed in claim 5, characterized in that: In step (2), the oxygen explosion temperature is 70-80°C, and the oxygen explosion time is ≥8h.

7. A method for preparing a ferrochrome black pigment as claimed in claim 6, characterized in that: In step (2), the neutralization reaction is carried out until the pH value reaches 6.5-7.5, and stirring is continued for 2-3 hours.

8. A method for preparing a ferrochrome black pigment as claimed in claim 7, characterized in that: In step (3), the flash drying temperature is 120-150°C; the roasting temperature is 1000-1200°C, and the roasting time is 3-5h.

9. A method for preparing an iron chrome black pigment as claimed in claim 8, characterized in that: In step (3), the regulator is cupric chloride or cuprous chloride.

10. An iron chrome black pigment prepared by the preparation method according to any one of claims 1 to 9.

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