High-sulfur bauxite oxidation and microwave synergistic desulfurization method

Abstract

The invention belongs to the field of hydrometallurgy, and particularly relates to a high-sulfur bauxite oxidation and microwave synergistic desulfurization method. The oxidation and microwave synergistic desulfurization method for the high-sulfur bauxite is characterized by comprising the following steps: (1) crushing the high-sulfur bauxite into particles through a crusher; (2) uniformly mixing the granular high-sulfur bauxite in the step (1) with ferric sulfate powder; and (3) heating and roasting the high-sulfur bauxite and ferric sulfate powder which are uniformly mixed in the step (2) in microwaves. Ferric sulfate is uniformly mixed into high-sulfur bauxite and heated in microwaves, and the ferric sulfate and the microwaves generate a synergistic desulfurization effect. The method has the technical advantages of high desulfurization rate, short reaction time and high production efficiency.

Description

Technical Field

[0001] The present invention belongs to the field of hydrometallurgy, and particularly relates to a method for synergistic desulfurization of high-sulfur bauxite by oxidation and microwave. Background Art

[0002] At present, the reserves of diaspore-type high-sulfur bauxite in China are 800 million tons, and the prospective reserves are about 2 billion tons, which are mainly distributed in Henan, Guizhou, Guangxi, Chongqing and other places. Among them, high-sulfur bauxite with an aluminum-silicon ratio (A / S) of 4-7 accounts for more than half. When the mass fraction of total sulfur in bauxite is greater than 0.7%, it is high-sulfur bauxite. When the sulfur content in bauxite reaches 0.30%, it will seriously affect the production of alumina. Sulfur will increase the alkali consumption, accelerate the process of equipment corrosion, make it difficult to evaporate and discharge salts, reduce the product quality, etc., seriously affecting the normal operation of the alumina production process.

[0003] At present, the advantage of the ore pretreatment desulfurization technology is that it can treat high-sulfur bauxite with a higher sulfur content, and the production operation is basically not affected by the alumina production process. The ore pretreatment desulfurization technology can be divided into wet pretreatment desulfurization technology and pyrometallurgical pretreatment desulfurization technology; the wet pretreatment desulfurization technologies include flotation desulfurization, microbial desulfurization and electrochemical desulfurization, etc. Among them, the flotation desulfurization technology has been industrialized in many enterprises such as Cayman Aluminum and Orient Hope (Sanmenxia) Aluminum. However, the sulfur in bauxite cannot be completely removed by flotation, and certain desulfurization measures still need to be taken during the alumina production process to ensure the stable operation of production. Among the pyrometallurgical pretreatment desulfurization technologies, the most studied is the ore roasting desulfurization technology, which has unique advantages such as a simple process, the concentrate not containing adsorbed water, and the simultaneous removal of organic matter.

[0004] In the prior art, there are also related studies on microwave desulfurization technology. However, in practical applications, due to the encapsulation between minerals, under the action of a strong microwave energy field, the desulfurization reaction cannot transfer a large amount of oxygen in a short time, resulting in the inability to apply microwave desulfurization in industrial production.

[0005] In summary, the development and utilization of high-sulfur bauxite is an important way to reduce China's high dependence on foreign bauxite resources and ensure the sustainable development of China's alumina industry.

[0006] Therefore, there is an urgent need to provide a technical solution to address the deficiencies of the above-mentioned prior art. Summary of the Invention

[0007] In order to overcome the deficiencies of the prior art, the present invention provides a method for synergistic desulfurization of high-sulfur bauxite by oxidation and microwave, which has a high desulfurization rate, a short reaction time and a high production efficiency.

[0008] In order to achieve the above object, a method for synergistic desulfurization of high-sulfur bauxite by oxidation and microwave provided by the present application adopts the following technical solution: A synergistic desulfurization method for high-sulfur bauxite by oxidation and microwave, comprising the following steps: (1) Crushing the high-sulfur bauxite into particulate state by a crusher; (2) Uniformly mixing the particulate high-sulfur bauxite in step (1) with ferric sulfate powder; (3) Heating and roasting the uniformly mixed high-sulfur bauxite and ferric sulfate powder in step (2) in a microwave.

[0009] Preferably, in step (1), the high-sulfur bauxite is crushed into particles with a diameter less than 80 μm.

[0010] Further preferably, the sulfur content in the high-sulfur bauxite is 0.01 - 10.00%.

[0011] Further preferably, the high-sulfur bauxite contains pyrite.

[0012] Even more preferably, the pyrite contains sulfur in the -1 valence state, and under the action of microwave, the sulfur in the -1 valence state of sulfur undergoes a disproportionation reaction to generate elemental sulfur and sulfur in the -2 valence state of the compound.

[0013] Preferably, in step (2), the mixing amount of ferric sulfate powder accounts for 2 - 8% of the mass of the high-sulfur bauxite.

[0014] Preferably, in step (3), the frequency of the microwave is 300 MHz to 300 GHz, the roasting temperature is 300 - 500 °C, and the roasting time is 2 - 10 min.

[0015] Beneficial effects: (1) During the heating process of the microwave, the microwave composed of an electric field and a magnetic field agitates the dipoles, free electrons, and magnetic domains, changes their movement directions and positions, and the rotation direction of the electrons. When placed in the microwave field, the molecules therein will be polarized to generate dipoles, thereby quickly absorbing the microwave and being uniformly heated in a loss form. The high-sulfur bauxite usually contains different components. Due to the difference in the dielectric properties of each component, the heating rate in the microwave field is different, resulting in a large temperature gradient, thereby generating thermal stress at the mineral phase interface, and even bursting and dissociation, so as to efficiently solve the problems of insufficient reaction and low reaction rate caused by the mutual wrapping and embedding of multiple components in the high-sulfur bauxite.

[0016] (2) Bauxite contains pyrite. During the microwave heating of high-sulfur bauxite, the pyrite particles in the minerals absorb microwaves. While accumulating heat inside and causing the Fe-S bonds to break, the surface temperature of the pyrite particles rises, forming a large temperature gradient with the surfaces of other mineral particles with weak wave absorption, accelerating the heat transfer between mineral particles, thereby increasing the overall heating rate of the material, which is beneficial to the removal of sulfur by ferric iron ions in ferric sulfate, and effectively solving the problems of insufficient reaction and low reaction rate caused by the mutual wrapping and embedding of multiple components in high-sulfur bauxite.

[0017] (3) The reaction mechanism during the microwave heating of high-sulfur bauxite is as follows: The sulfur in pyrite in bauxite is sulfur in the -1 valence state. Under the action of microwaves, the sulfur in the -1 valence state may undergo disproportionation reactions to transform into elemental sulfur and sulfur in the -2 valence state; and the microwave heating effect is related to the dielectric properties of substances. Ferric ions (Fe 3+ ) are ions with three positive charges, having strong oxidizing properties and relatively high dielectric properties. Sulfide ions (S 2- ) are ions with two negative charges, having certain reducing properties. Ions in the microwave field will move, which is beneficial for the occurrence of redox reactions between ferric ions (Fe 3+ ) and sulfide ions (S 2- ). Under the action of microwaves, it will produce a synergistic effect on the desulfurization of ferric sulfate, which is beneficial for advantages such as shortening the reaction time, reducing the reaction temperature, improving the reaction selectivity, and improving the production efficiency. Specific implementation manners

[0018] The following will describe the present application in detail with reference to embodiments. Each example is provided by way of explanation of the present application rather than limiting the present application. In fact, those skilled in the art will clearly understand that modifications and variations can be made to the present application without departing from the scope or spirit of the present application. For example, features shown or described as part of one embodiment can be used in another embodiment to produce yet another embodiment. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention shall fall within the scope of protection of the embodiments of the present invention.

[0019] Example 1 A method for synergistic desulfurization of high-sulfur bauxite by oxidation and microwave includes the following steps: (1) Take 200 g of high-sulfur bauxite particles with a diameter less than 80 μm and a sulfur content of 3.25% (the total sulfur mass fraction is measured by the combustion iodometric method of GB3257.18 - 1999) (2) Take 10 g of ferric sulfate powder and mix it evenly with the above-mentioned high-sulfur bauxite particles; (3) Place the mixture in a microwave for roasting. Set the roasting temperature at 400 °C and the roasting time at 5 min. After analyzing the sulfur content, calculate the desulfurization rate to be 94%.

[0020] Example 2 A synergistic desulfurization method for high-sulfur bauxite by oxidation and microwave, comprising the following steps: (1) Take 200 g of high-sulfur bauxite particles with a diameter less than 80 μm and a sulfur content of 4.65% (the total sulfur mass fraction is determined by the combustion iodometric method in GB3257.18 - 1999); (2) Take 15 g of ferric sulfate powder and mix it evenly with the above high-sulfur bauxite particles; (3) Place the mixture in a microwave for roasting. Set the roasting temperature at 500 °C and the roasting time at 8 min. After analyzing the sulfur content, calculate the desulfurization rate to be 93%.

[0021] Example 3 A synergistic desulfurization method for high-sulfur bauxite by oxidation and microwave, comprising the following steps: (1) Take 200 g of high-sulfur bauxite particles with a diameter less than 80 μm and a sulfur content of 2.32% (the total sulfur mass fraction is determined by the combustion iodometric method in GB3257.18 - 1999); (2) Take 6 g of ferric sulfate powder and mix it evenly with the above high-sulfur bauxite; (3) Place the mixture in a microwave for roasting. Set the roasting temperature at 350 °C and the roasting time at 4 min. After analyzing the sulfur content, calculate the desulfurization rate to be 93%.

[0022] Comparative Example 1 Take 200 g of high-sulfur bauxite particles with a diameter less than 80 μm and a sulfur content of 3.25% (the total sulfur mass fraction is determined by the combustion iodometric method in GB3257.18 - 1999), place them in a microwave for roasting. Set the roasting temperature at 400 °C and the roasting time at 5 min. After analyzing the sulfur content, calculate the desulfurization rate to be 85%.

[0023] Comparative Example 2 Take 200 g of high-sulfur bauxite particles with a diameter less than 80 μm and a sulfur content of 4.65% (the total sulfur mass fraction is determined by the combustion iodometric method in GB3257.18 - 1999), place them in a microwave for roasting. Set the roasting temperature at 500 °C and the roasting time at 8 min. After analyzing the sulfur content, calculate the desulfurization rate to be 86%.

[0024] Comparative Example 3 Take 200 g of high-sulfur bauxite particles with a diameter less than 80 μm and a sulfur content of 2.32% (the total sulfur mass fraction is determined by the combustion iodometric method in GB3257.18-1999), place them in a microwave for roasting, set the roasting temperature at 350 °C, and the roasting time at 4 min. After analyzing the sulfur content, the desulfurization rate is calculated to be 84%.

[0025] Pyrite is contained in bauxite. During the process of microwave heating high-sulfur bauxite, the pyrite particles in the mineral absorb microwaves. While accumulating heat inside to promote the breakage of Fe-S bonds, the surface temperature of the pyrite particles rises, forming a large temperature gradient with the surfaces of other mineral particles with weak wave absorption, accelerating the heat transfer between mineral particles, thus accelerating the overall heating rate of the material, which is beneficial to the removal of sulfur by ferric iron ions in ferric sulfate, and efficiently solving problems such as insufficient reaction and low reaction rate caused by the mutual wrapping and embedding of multiple components in high-sulfur bauxite.

[0026] The reaction mechanism during the process of microwave heating high-sulfur bauxite is as follows: The sulfur in pyrite in bauxite is sulfur in the -1 valence state. Under the action of microwaves, the sulfur in the -1 valence state may undergo disproportionation reactions to transform into elemental sulfur and sulfur in the -2 valence state; and the microwave heating effect is related to the dielectric properties of substances. Ferric ions (Fe3+) are ions with three positive charges, having strong oxidizing properties and relatively high dielectric properties. Sulfide ions (S2-) are ions with two negative charges, having certain reducing properties. Ions in the microwave field will move, which is beneficial to the occurrence of redox reactions between ferric ions (Fe3+) and sulfide ions (S2-). Under the action of microwaves, it will produce a synergistic effect on the desulfurization of ferric sulfate, which is beneficial to advantages such as shortening the reaction time, reducing the reaction temperature, improving the reaction selectivity, and improving production efficiency.

[0027] From the analysis of the examples and comparative examples, compared with the desulfurization analysis of bauxite ferric sulfate oxidation and microwave alone, the synergistic desulfurization of bauxite ferric sulfate oxidation and microwave is higher.

[0028] In the present invention, the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0029] The above are only the preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the protection scope of the present application.

Claims

1. A synergistic desulfurization method for high-sulfur bauxite by oxidation and microwave, characterized in that, It includes the following steps: (1) Crushing high-sulfur bauxite into particulate state by a crusher; (2) Uniformly mixing the particulate high-sulfur bauxite in step (1) with ferric sulfate powder; (3) Heating and roasting the uniformly mixed high-sulfur bauxite and ferric sulfate powder in step (2) in a microwave.

2. The co - desulfurization method of high - sulfur bauxite by oxidation and microwave according to claim 1, wherein, In step (1), the high-sulfur bauxite is crushed into particles with a diameter less than 80 μm.

3. The co - desulfurization method of high - sulfur bauxite oxidation and microwave according to claim 2, characterized in that The sulfur content in the high-sulfur bauxite is 0.01 - 10.00%.

4. The co - desulfurization method of high - sulfur bauxite by oxidation and microwave according to claim 2, characterized in that The high-sulfur bauxite contains pyrite.

5. The co - desulfurization method of high - sulfur bauxite by oxidation and microwave according to claim 4, characterized in that, The pyrite contains sulfur in the -1 valence state, and under the action of microwave, the sulfur in the -1 valence state of sulfur generates elemental sulfur and sulfur in the -2 valence state of the compound through disproportionation reaction.

6. The synergistic desulfurization method of high-sulfur bauxite oxidation and microwave according to claim 1, characterized in that, In step (2), the mixing amount of ferric sulfate powder accounts for 2 - 8% of the mass of the high-sulfur bauxite.

7. The co - desulfurization method of high - sulfur bauxite by oxidation and microwave according to claim 1, characterized in that, In step (3), the frequency of the microwave is 300 MHz to 300 GHz, the roasting temperature is 300 - 500 °C, and the roasting time is 2 - 10 min.