Method for preparing sodium sulfide using industrial sodium sulfate

Abstract

This invention provides a method for preparing sodium sulfide from industrial sodium sulfate, belonging to the field of metallurgical environmental protection technology. The method involves adding sodium sulfide powder obtained in a previous step to a mixture of sodium sulfate and activated carbon powder, followed by high-temperature calcination at 700-850℃ to efficiently obtain sodium sulfide; the conversion rate of sodium sulfate can reach 92%. Furthermore, the reaction temperature is reduced from over 950℃ in traditional methods to 700-850℃, significantly reducing energy consumption and production costs. This invention treats industrial sodium sulfate, achieving large-scale conversion of solid waste sodium sulfate, and has significant utilization value. In addition, the method for preparing sodium sulfide from industrial sodium sulfate is carried out at a temperature below the melting point of the reactants, solving the problems of melt corrosion and difficult discharge after solidification in traditional methods.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical environmental protection technology, and in particular relates to a method for preparing sodium sulfide using industrial sodium sulfate. Background Technology

[0002] More than 20 million tons of sodium sulfate waste are generated globally each year. Due to the low economic value of sodium sulfate, most factories can only dispose of it as hazardous waste through stockpiling. Therefore, to eliminate the accumulation of sodium sulfate waste, it is necessary to convert sodium sulfate into widely used products, and sodium sulfate is the main raw material for the production of sodium sulfide. Sodium sulfide is an important chemical raw material widely used in industries such as alkali production, papermaking, printing and dyeing, textiles, leather, pharmaceuticals, and non-ferrous metallurgy. The preparation of sodium sulfide is an effective way to treat and utilize waste sodium sulfate.

[0003] Currently, the industrial conversion of sodium sulfate to sodium sulfide mainly uses the high-temperature coal powder reduction method. This method involves mixing sodium sulfate with coal powder and calcining the mixture at high temperature to produce crude sodium sulfide alkali. Industrial sodium sulfide is then obtained through leaching, impurity removal, and evaporation. This method is energy-intensive, heavily polluting, produces many impurities, and suffers from severe melt corrosion.

[0004] Existing technologies also employ combustible waste gas as a heat source, melting sodium sulfate at 900-1000℃ and then reducing it with high-carbon white coal at 1050-1200℃ to produce crude alkali. While this alleviates dust and sulfur pollution, it still suffers from long processes and numerous impurities. Other existing technologies also suffer from problems such as high required reaction temperatures, high energy consumption, high production costs, and low sodium sulfide conversion rates. Summary of the Invention

[0005] The main objective of this invention is to provide a method for preparing sodium sulfide using industrial sodium sulfate, aiming to solve the problems of high energy consumption and low sodium sulfide conversion rate in existing sodium sulfide preparation methods.

[0006] To achieve the above objectives, the present invention provides a method for preparing sodium sulfide using industrial sodium sulfate, comprising the following steps:

[0007] Sodium sulfate and activated carbon powder are mixed and then subjected to a first grinding process and a first drying process to obtain a pretreated mixed powder; the mass ratio of activated carbon powder to sodium sulfate is 0.2~0.5.

[0008] The pretreated mixed powder described in the first part is subjected to a first high-temperature calcination treatment in a chemically inert gas atmosphere to obtain sodium sulfide powder; the temperature of the first high-temperature calcination treatment is 750~950℃.

[0009] The sodium sulfide powder and the pretreated mixed powder in the second part are mixed and then subjected to a second grinding process and a second drying process in sequence to obtain a sodium sulfide mixed powder; in the sodium sulfide mixed powder, the mass ratio of the sodium sulfide powder to the sodium sulfate is 0.02~0.1.

[0010] The sodium sulfide mixed powder is subjected to a second high-temperature calcination treatment in a chemically inert gas atmosphere to obtain sodium sulfide product; the temperature of the second high-temperature calcination treatment is 700~850℃.

[0011] Furthermore, the duration of the first high-temperature roasting treatment is 60-180 min; the duration of the second high-temperature roasting treatment is 5-120 min.

[0012] Furthermore, the duration of the second high-temperature calcination treatment is 25~120 min.

[0013] Furthermore, the mass ratio of the activated carbon powder to the sodium sulfate is 0.3 to 0.4.

[0014] Furthermore, the average particle size of both the product after the first grinding treatment and the product after the second grinding treatment is <50µm.

[0015] Furthermore, the duration of both the first and second grinding processes is 5 to 15 minutes.

[0016] Furthermore, the temperature of both the first drying treatment and the second drying treatment is 80~120℃; the duration of both the first drying treatment and the second drying treatment is 30~60min.

[0017] Furthermore, the chemically inert gases include nitrogen and / or argon.

[0018] Furthermore, both the first high-temperature roasting treatment and the second high-temperature roasting treatment are followed by a cooling treatment.

[0019] Furthermore, in the sodium sulfide mixed powder, the mass ratio of the sodium sulfide powder to the sodium sulfate is 0.02~0.05.

[0020] Compared with the prior art, the present invention has at least the following advantages:

[0021] The method for preparing sodium sulfide from industrial sodium sulfate provided by this invention involves adding sodium sulfide powder obtained in a previous step to a mixture of sodium sulfate and activated carbon powder, followed by high-temperature calcination at 700-850℃ to efficiently obtain sodium sulfide product; the conversion rate of sodium sulfate can reach 92%. Furthermore, the reaction temperature is reduced from over 950℃ in traditional methods to 700-850℃, significantly reducing process energy consumption and production costs. Since the target material is industrial sodium sulfate, this method achieves large-scale conversion of solid waste sodium sulfate, demonstrating significant utilization value. In addition, the method for preparing sodium sulfide from industrial sodium sulfate provided by this invention operates at temperatures below the melting point of the reactants, solving the problems of melt corrosion and difficult discharge after solidification in traditional methods. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0023] Figure 1 The image shows the X-ray diffraction (XRD) pattern of sodium sulfide powder obtained in the intermediate step of Example 1 of this invention.

[0024] Figure 2 X-ray diffraction (XRD) comparison diagrams of the various final products in Example 1 of this invention;

[0025] Figure 3 The sodium sulfate-sodium sulfide binary molten salt phase diagram in Example 1 of this invention is analyzed.

[0026] The realization of the objective, functional characteristics and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0029] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the present invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this invention, as well as the prior art known to those skilled in the art and the description of this invention, may be implemented using any prior art methods, devices, and materials similar to or equivalent to those described, used, or made of materials in the embodiments of this invention.

[0030] To address the problems of high energy consumption and low conversion rate in existing sodium sulfide preparation methods, this invention provides a method for preparing sodium sulfide using industrial sodium sulfate, comprising the following steps:

[0031] Sodium sulfate and activated carbon powder are mixed and then subjected to a first grinding process and a first drying process to obtain a pretreated mixed powder; the mass ratio of activated carbon powder to sodium sulfate is 0.2~0.5. Optionally, the particle size of the activated carbon powder is 200 mesh.

[0032] The first pretreated mixed powder is subjected to a first high-temperature calcination treatment in a chemically inert gas atmosphere to obtain sodium sulfide powder; the temperature of the first high-temperature calcination treatment is 750~950℃. It should be noted that the first pretreated mixed powder refers to a portion weighed from the pretreated mixed powder obtained in the aforementioned steps for the subsequent first high-temperature calcination treatment. Optionally, the first high-temperature calcination treatment is performed by heating to 750~950℃ at a heating rate of 5~10℃ / min in a chemically inert gas atmosphere, holding at that temperature for a period of time, followed by cooling and grinding to obtain sodium sulfide powder. Optionally, the temperature of the first high-temperature calcination treatment is 800~850℃. Optionally, the temperature of the first high-temperature calcination treatment is 750~850℃. Specifically, the sodium sulfide prepared in this step can be used as a catalyst for subsequent applications, reducing the reduction temperature of subsequent steps from above 950℃ in traditional methods to 700~850℃, significantly reducing the energy consumption of sodium sulfate reduction.

[0033] Sodium sulfide powder and the second pretreated mixed powder are mixed and then subjected to a second grinding process and a second drying process to obtain sodium sulfide mixed powder. In the sodium sulfide mixed powder, the mass ratio of sodium sulfide powder to sodium sulfate is 0.02~0.1. It should be noted that the second pretreated mixed powder refers to a portion of the pretreated mixed powder obtained in the previous steps that is weighed out and subjected to the subsequent second high-temperature calcination process. The sum of the masses of the first and second pretreated mixed powders is not necessarily equal to the mass of the pretreated mixed powder obtained in the previous steps.

[0034] Sodium sulfide mixed powder is subjected to a second high-temperature calcination treatment in a chemically inert gas atmosphere to obtain sodium sulfide product; the temperature of the second high-temperature calcination treatment is 700~850℃. Optionally, the second high-temperature calcination treatment is performed by heating to 700~850℃ in a chemically inert gas atmosphere at a heating rate of 5~10℃ / min, holding at that temperature for a period of time, and then cooling to obtain sodium sulfide product. Preferably, the temperature of the second high-temperature calcination treatment is 750~850℃. Optionally, the temperature of the second high-temperature calcination treatment is 700~750℃.

[0035] The method for preparing sodium sulfide from industrial sodium sulfate provided by this invention involves adding sodium sulfide powder obtained in a previous step to a mixture of sodium sulfate and activated carbon powder, followed by high-temperature calcination at 700-850℃ to efficiently obtain sodium sulfide product; the conversion rate of sodium sulfate can reach 92%. Furthermore, the reaction temperature is reduced from over 950℃ in traditional methods to 700-850℃, significantly reducing process energy consumption and production costs. Since the target material is industrial sodium sulfate, this method achieves large-scale conversion of solid waste sodium sulfate, demonstrating significant utilization value. In addition, the method for preparing sodium sulfide from industrial sodium sulfate provided by this invention operates at temperatures below the melting point of the reactants, solving the problems of melt corrosion and difficult discharge after solidification in traditional methods.

[0036] Furthermore, the duration of the first high-temperature roasting treatment is 60-180 min; the duration of the second high-temperature roasting treatment is 5-120 min.

[0037] Furthermore, the duration of the second high-temperature calcination treatment is 25~120 min.

[0038] Furthermore, the mass ratio of activated carbon powder to sodium sulfate is 0.3 to 0.4.

[0039] Furthermore, the average particle size of both the product after the first grinding treatment and the product after the second grinding treatment is <50µm.

[0040] Furthermore, the duration of both the first and second grinding processes is 5 to 15 minutes.

[0041] Furthermore, the temperature of both the first and second drying treatments is 80~120℃; the duration of both the first and second drying treatments is 30~60min.

[0042] Furthermore, chemically inert gases include nitrogen and / or argon.

[0043] Furthermore, both the first and second high-temperature roasting processes are followed by a cooling process.

[0044] Furthermore, in the sodium sulfide mixed powder, the mass ratio of sodium sulfide powder to sodium sulfate is 0.02~0.05.

[0045] To further illustrate the present invention, the following examples are provided:

[0046] Example 1

[0047] (1) Grind and mix 200-mesh activated carbon powder and sodium sulfate at a ratio of 0.3 for 15 min (average particle size after grinding <50µm), and dry (80℃; 60 min) to obtain pretreated mixed powder.

[0048] (2) Weigh 1.3g of pretreated mixed powder and perform the first high-temperature calcination treatment. Under a nitrogen atmosphere, heat to 850℃ at a heating rate of 5℃ / min, hold for 60min and cool naturally. Grind the solid product for 15min (average particle size after grinding <50µm) to obtain sodium sulfide powder.

[0049] (3) Add a certain proportion of sodium sulfide powder to the pretreated mixed powder obtained in step (1) and grind and mix for 15 min (average particle size after grinding <50µm). Dry under a nitrogen atmosphere (80℃; 60 min) to obtain sodium sulfide mixed powder. In this sodium sulfide mixed powder, the mass ratio of sodium sulfide powder to sodium sulfate is 0.02.

[0050] (4) Weigh 1.3g of sodium sulfide mixed powder and perform a second high-temperature calcination treatment. Under a nitrogen atmosphere, heat to 700℃ at a heating rate of 5℃ / min, hold for 30min and cool naturally to obtain sodium sulfide product; the conversion rate of sodium sulfate is 90%.

[0051] The conversion rate of sodium sulfate is calculated as follows: Sodium sulfate conversion rate = (1 - mass of sodium sulfate in the product / mass of sodium sulfate in the raw material) 100%.

[0052] The method for determining sodium sulfate in the formula is as follows: Measure 400 mL of pure water, dissolve the obtained product in the water, and filter the resulting solution; weigh 1.72 times the mass of barium chloride dihydrate in the raw material and add it to the filtrate, then filter again to obtain barium sulfate precipitate; dry the obtained barium sulfate precipitate at 60℃ for 2 h, and weigh and record the mass of the precipitate after drying; the mass of sodium sulfate in the product = the mass of the precipitate. 142 / 233. The conversion rate of sodium sulfate in subsequent experimental results was calculated using the same method.

[0053] Example 2

[0054] Compared to Example 1, only the proportion of sodium sulfide powder added in step (3) is changed; that is, in the sodium sulfide mixed powder, the mass ratio of sodium sulfide powder to sodium sulfate is 0.05.

[0055] The conversion rate of sodium sulfate was 92%.

[0056] Example 3

[0057] (1) Grind and mix 200-mesh activated carbon powder and sodium sulfate at a ratio of 0.3 for 15 min (average particle size after grinding <50µm), and dry (80℃; 60 min) to obtain pretreated mixed powder.

[0058] (2) Weigh 1.3g of pretreated mixed powder and perform the first high-temperature calcination treatment. Under a nitrogen atmosphere, heat to 850℃ at a heating rate of 5℃ / min, hold for 60min and cool naturally. Grind the solid product for 15min (average particle size after grinding <50µm) to obtain sodium sulfide powder.

[0059] (3) Add a certain proportion of sodium sulfide powder to the pretreated mixed powder obtained in step (1) and grind and mix for 15 min (average particle size after grinding <50µm). Dry under a nitrogen atmosphere (80℃; 60 min) to obtain sodium sulfide mixed powder. In this sodium sulfide mixed powder, the mass ratio of sodium sulfide powder to sodium sulfate is 0.1.

[0060] (4) Weigh 1.4g of sodium sulfide mixed powder and perform a second high-temperature calcination treatment. Under a nitrogen atmosphere, heat to 700℃ at a heating rate of 5℃ / min, hold for 45min and cool naturally to obtain sodium sulfide product; the conversion rate of sodium sulfate is 75%.

[0061] Example 4

[0062] (1) Grind and mix 200-mesh activated carbon powder and sodium sulfate at a ratio of 0.3 for 15 min (average particle size after grinding <50µm), and dry (80℃; 60 min) to obtain pretreated mixed powder.

[0063] (2) Weigh 1.3g of pretreated mixed powder and perform the first high-temperature calcination treatment. Under a nitrogen atmosphere, heat to 850℃ at a heating rate of 5℃ / min, hold for 60min and cool naturally. Grind the solid product for 15min (average particle size after grinding <50µm) to obtain sodium sulfide powder.

[0064] (3) Add a certain proportion of sodium sulfide powder to the pretreated mixed powder obtained in step (1) and grind and mix for 15 min (average particle size after grinding <50µm). Dry under a nitrogen atmosphere (80℃; 60 min) to obtain sodium sulfide mixed powder. In this sodium sulfide mixed powder, the mass ratio of sodium sulfide powder to sodium sulfate is 0.1.

[0065] (4) Weigh 1.4g of sodium sulfide mixed powder and perform a second high-temperature calcination treatment. Under a nitrogen atmosphere, heat to 850℃ at a heating rate of 5℃ / min, hold for 10min and cool naturally to obtain sodium sulfide product; the conversion rate of sodium sulfate is 89%.

[0066] Comparative Example 1

[0067] Compared to Example 1, sodium sulfide powder was not incorporated; that is, steps (2) and (3) were not performed. 1.3g of the pretreated mixed powder obtained in step (1) of Example 1 was directly weighed and heated to 700°C at a heating rate of 5°C / min under a nitrogen atmosphere, kept at the temperature for 60min and then naturally cooled to obtain the sodium sulfide comparative product; the sodium sulfate conversion rate was 73%.

[0068] When the temperature was maintained for 30 minutes, sodium sulfide could not be obtained as a control product.

[0069] Comparative Example 2

[0070] The temperature provided for the second high-temperature roasting treatment does not meet the requirements of the 700~850℃ comparative example. Comparative examples and conversion rate results are provided for temperatures of 680℃ and 900℃.

[0071] Compared to Example 1, only the temperature of the second high-temperature calcination treatment in step (4) is changed; that is, the temperature is raised to 600°C at a heating rate of 5°C / min under a nitrogen atmosphere, and then held for 30 minutes before natural cooling.

[0072] The conversion rate of sodium sulfate was 0%, and no reduction reaction occurred.

[0073] Comparative Example 3

[0074] Compared to Comparative Example 1, only the mass ratio of activated carbon powder to sodium sulfate was changed to 0.2, while other conditions remained unchanged; a sodium sulfide comparative product was obtained, with a sodium sulfate conversion rate of 13%. After extending the holding time to 90 min and allowing it to cool naturally, the solid product was ground for 15 min (average particle size after grinding <50µm) to obtain the sodium sulfide comparative product; the sodium sulfate conversion rate was 47%.

[0075] Analysis example 1

[0076] (1) The sodium sulfide powder prepared in Example 1 was characterized, and its X-ray diffraction (XRD) pattern is shown below. Figure 1 As shown.

[0077] from Figure 1 As can be seen from the XRD, the strong characteristic peaks are all characteristic peaks of sodium sulfide, indicating that sodium sulfate is basically reduced to sodium sulfide by carbon, and the obtained sodium sulfide has a high purity.

[0078] (2) The final products of Examples 1-3 and Comparative Example 1 were compared and characterized, and their XRD comparison diagrams are shown below. Figure 2 As shown.

[0079] from Figure 2 As can be seen, the reaction rates of the groups with different proportions of sodium sulfide powder (Examples 1-3) are much faster than those of the group without sodium sulfide powder (Comparative Example 1). The XRD patterns of the products with 0.02% sodium sulfide powder (Example 1) and 0.05% sodium sulfide powder (Example 2) show that the characteristic peaks are primarily sodium sulfide peaks, with no other characteristic peaks appearing. The XRD pattern of the product with 0.1% sodium sulfide powder (Example 3) still shows a small amount of sodium sulfate and sodium carbonate characteristic peaks, proving that the purity of the products with 0.02% sodium sulfide powder (Example 1) and 0.05% sodium sulfide powder (Example 2) is higher than that of the product with 0.1% sodium sulfide powder (Example 3).

[0080] (3) Draw a phase diagram of sodium sulfate-sodium sulfide binary molten salt based on sodium sulfide powder and sodium sulfate; the phase diagram is as follows: Figure 3 As shown. According to Figure 3 Observations show that sodium sulfide powder and sodium sulfate have the lowest eutectic point (744℃) when the molar mass ratio is 0.38:0.62. The second high-temperature roasting treatment temperature of 700℃ used in Examples 1 to 3 is lower than 744℃, indicating that the sample will not eutecticly melt during the reaction process, and the melt will not solidify during the cooling process, so the material can be discharged smoothly.

[0081] The above technical solutions of the present invention are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made using the contents of the present invention under the technical concept of the present invention, or direct / indirect applications in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A method for preparing sodium sulfide using industrial sodium sulfate, characterized in that, Including the following steps: Sodium sulfate and activated carbon powder are mixed and then subjected to a first grinding process and a first drying process to obtain a pretreated mixed powder; the mass ratio of activated carbon powder to sodium sulfate is 0.3~0.

5. The pretreated mixed powder described in the first part is subjected to a first high-temperature calcination treatment in a chemically inert gas atmosphere to obtain sodium sulfide powder; the temperature of the first high-temperature calcination treatment is 750~950℃. The sodium sulfide powder and the pretreated mixed powder in the second part are mixed and then subjected to a second grinding process and a second drying process in sequence to obtain a sodium sulfide mixed powder; in the sodium sulfide mixed powder, the mass ratio of sodium sulfide powder to sodium sulfate is 0.02~0.1; The sodium sulfide mixed powder is subjected to a second high-temperature calcination treatment in a chemically inert gas atmosphere to obtain sodium sulfide product; the temperature of the second high-temperature calcination treatment is 700~850℃.

2. The method for preparing sodium sulfide using industrial sodium sulfate according to claim 1, characterized in that, The duration of the first high-temperature roasting treatment is 60~180min; the duration of the second high-temperature roasting treatment is 5~120min.

3. The method for preparing sodium sulfide using industrial sodium sulfate according to claim 2, characterized in that, The duration of the second high-temperature roasting treatment is 25~120 min.

4. The method for preparing sodium sulfide using industrial sodium sulfate according to claim 1, characterized in that, The mass ratio of the activated carbon powder to the sodium sulfate is 0.3 to 0.

4.

5. The method for preparing sodium sulfide using industrial sodium sulfate according to claim 1, characterized in that, The average particle size of both the product after the first grinding treatment and the product after the second grinding treatment is <50µm.

6. The method for preparing sodium sulfide using industrial sodium sulfate according to claim 1, characterized in that, The duration of both the first and second grinding processes is 5 to 15 minutes.

7. The method for preparing sodium sulfide using industrial sodium sulfate according to claim 1, characterized in that, The temperature of both the first drying treatment and the second drying treatment is 80~120℃; the duration of both the first drying treatment and the second drying treatment is 30~60min.

8. The method for preparing sodium sulfide using industrial sodium sulfate according to claim 1, characterized in that, The chemically inert gases include nitrogen and / or argon.

9. The method for preparing sodium sulfide using industrial sodium sulfate according to claim 1, characterized in that, Both the first high-temperature roasting treatment and the second high-temperature roasting treatment are followed by a cooling treatment.

10. The method for preparing sodium sulfide using industrial sodium sulfate according to claim 1, characterized in that, In the sodium sulfide mixed powder, the mass ratio of the sodium sulfide powder to the sodium sulfate is 0.02~0.05.

Images