Process for the continuous synthesis of iron disulfide powder by high temperature solid phase

Abstract

The application discloses a method for continuously synthesizing iron disulfide powder in a high-temperature solid phase, and belongs to the technical field of functional material preparation. The method comprises the following steps: uniformly mixing high-purity iron powder and high-purity sulfur powder, loading the mixture into a boat, pushing the boat into a full-automatic boat pushing furnace production line, setting the interval temperature of the boat pushing furnace and the sulfuration time, and synthesizing high-purity iron disulfide through multiple sulfurations. The method for continuously synthesizing iron disulfide powder in a high-temperature solid phase has high FeS2 purity, the boat pushing furnace production line can realize full-automatic continuous production, has high efficiency, and can recycle the excessive sulfur in the production process along with the pure nitrogen in the production line, so that the cost is low, and the problem that the existing synthesis technology of iron disulfide cannot meet the demand of industrial large-scale production can be effectively solved.

Description

Technical Field

[0001] This invention belongs to the field of functional material preparation technology, and relates to a method for preparing iron disulfide, specifically a method for high-temperature solid-phase continuous synthesis of iron disulfide powder. Background Technology

[0002] The thermal battery, using lithium alloy as the negative electrode and iron disulfide as the positive electrode material, is one of the most popular lithium batteries in current battery research. Its characteristics include high specific energy, long cycle life, and the ability to operate at 400-600℃, making it important not only in cutting-edge fields but also in civilian applications. Naturally occurring high-grade pyrite contains 290% FeS, 3% Si, and 7% other impurities, which is insufficient for thermal batteries. Therefore, it is necessary to research synthetic methods to produce products with a higher purity and the structure of natural pyrite. Currently, many methods have been applied in the artificial synthesis of iron disulfide, such as electrochemical deposition, hydrothermal synthesis, solvothermal synthesis, and gas-phase synthesis. However, existing methods for synthesizing sulfur dioxide have relatively harsh synthesis conditions, low efficiency, slow speed, difficulty in synthesizing large quantities of samples, and difficulty in guaranteeing purity.

[0003] CN111908515A discloses a method for synthesizing pyrite-type iron disulfide through a high-temperature, high-pressure, two-stage reaction and its application. The method utilizes a six-sided jacking device to provide high-temperature, high-pressure synthesis conditions, using iron powder and sulfur powder as raw materials. Under these conditions, a two-stage reaction is carried out, with the product of the first reaction used as a raw material. Excess sulfur is added and thoroughly mixed to synthesize pyrite-type iron disulfide. This method employs high-temperature, high-pressure synthesis conditions, which are costly and have poor safety, and it does not address the excess sulfur in the second reaction, making it unsuitable for large-scale industrial production. Summary of the Invention

[0004] The technical problem to be solved by this invention is that existing technologies for synthesizing iron disulfide cannot meet the needs of large-scale industrial production.

[0005] The technical solution adopted by this invention to solve its technical problem is: a method for high-temperature solid-phase continuous synthesis of iron disulfide powder: high-purity iron powder and high-purity sulfur powder are mixed evenly and then loaded into a boat, which is pushed into a fully automatic boat-pushing furnace production line. By setting the temperature range and sulfidation time of the boat-pushing furnace, high-purity iron disulfide is synthesized through multiple sulfidation processes; the fully automatic boat-pushing furnace production line includes a feeding zone, a synthesis zone, a cooling zone, and a discharging zone.

[0006] The synthesis zone is divided into seven temperature zones: Zone 1 is vulcanized at 100-110℃ for 1-2 hours, Zone 2 at 190-200℃ for 1-2 hours, Zone 3 at 300-330℃ for 2-4 hours, Zones 4 to 6 at 400-440℃ for 2-4 hours, and Zone 7 at 520-560℃ for 2-4 hours.

[0007] Furthermore, in Zone 1, the vulcanization time is 1.4-1.6 hours at 100-110℃; in Zone 2, it is 1.4-1.6 hours at 190-200℃; in Zone 3, it is 2.9-3.1 hours at 320-330℃; in Zones 4-6, it is 2.9-3.1 hours at 410-430℃; and in Zone 7, it is 2.9-3.1 hours at 520-540℃.

[0008] The cooling zone includes a slow cooling zone and a water cooling zone. The temperature is cooled to ≤100°C in the slow cooling zone and to near room temperature in the water cooling zone.

[0009] The above production process is carried out under a fully sealed pure nitrogen atmosphere with a purity of ≥99.99%, and the flow rate of pure nitrogen introduced into the fully automated pusher furnace production line is 15-25 Nm³. 3 / h, maintaining a slight positive pressure within the fully automated pushboat furnace production line.

[0010] Furthermore, the micro-positive pressure refers to the air pressure inside the fully automated pushboat furnace production line being 20-50 Pa higher than the external atmospheric pressure.

[0011] The purity of the aforementioned high-purity iron disulfide is ≥98%, and its thermal stability is an initial decomposition temperature ≥560℃.

[0012] A method for continuous high-temperature solid-phase synthesis of iron disulfide powder specifically includes the following steps:

[0013] a. Mix high-purity iron powder and high-purity sulfur powder at a mass ratio of 1:1-1.5 and load them into a boat. Then, the boat enters the fully automatic push-boat furnace production line for sulfidation. After discharge, the material is deagglomerated, crushed, and graded until it passes through a 160-mesh sieve to obtain semi-finished product 1.

[0014] b. Mix semi-finished product 1 and high-purity sulfur powder at a mass ratio of 1:1-1.5, load them into a boat, then perform sulfidation, and after discharge, pass them through a 100-mesh sieve to obtain semi-finished product 2;

[0015] c. Mix the semi-finished product 2 and high-purity sulfur powder at a mass ratio of 1:0.5-1, load them into a boat, and then perform sulfidation. After discharge, pass the material through an 80-mesh sieve. After passing the internal control standard test, mix the mixture, and then package and label it to obtain the high-purity iron disulfide product.

[0016] Furthermore, in the above-mentioned method for continuous synthesis of iron disulfide powder in a high-temperature solid phase, all processes are carried out in a dry environment with an ambient humidity of ≤2%.

[0017] Furthermore, during the loading of the boat, the amount of boat material in step a is controlled to be 30-35 kg, and the amount of boat material in steps b and c is controlled to be 40-50 kg.

[0018] Furthermore, during the vulcanization process in steps a, b, and c above, the rate at which the boat enters the fully automated boat-pushing furnace production line is controlled to be 1-2 hours per boat.

[0019] Furthermore, in step a above, the total iron content in the semi-finished product 1 is ≤60%.

[0020] Furthermore, in step b above, the total iron content in the semi-finished product 2 is ≤49%.

[0021] Furthermore, in step c above, the internal control standard requires that the iron disulfide content be ≥98%, the total iron content be 46.5-47.5%, the total sulfur content be 52.4-54.0%, and the elemental sulfur content be ≤0.2%.

[0022] Furthermore, the above-mentioned method for continuous high-temperature solid-phase synthesis of iron disulfide powder is equipped with a sulfur recovery device. After each sulfidation is completed, the excess sulfur powder is vaporized at high temperature for 3 hours and then carried into the sulfur recovery device for collection along with pure nitrogen.

[0023] The beneficial effects of this invention are as follows: The FeS2 synthesized using the high-temperature solid-phase continuous synthesis method of iron disulfide powder provided by this invention has high purity (≥98%) and low impurity content; the resulting battery exhibits long discharge time, good thermal stability, and good chemical stability. Compared with traditional methods for preparing iron disulfide, the pusher furnace production line of this invention can automatically and continuously produce iron disulfide, overcoming the shortcomings of traditional technologies such as unstable process control, long single-furnace production time, and low output. This invention's high-temperature solid-phase continuous synthesis of iron disulfide has high output and high efficiency. The entire production process is carried out under slight positive pressure, resulting in a higher safety factor compared to traditional high-pressure production processes. Excess sulfur during production can be recovered and reused along with pure nitrogen in the production line, resulting in low cost and meeting the needs of large-scale industrial production, thus possessing significant application value. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the zoning layout of the fully automated push-boat furnace production line of the present invention;

[0025] Figure 2 This is a physical image of the fully automated pushboat furnace production line of the present invention;

[0026] Figure 3 This is a flowchart of the production process of the present invention;

[0027] Figure 4 Thermogravimetric analysis curve of Example 1 of the present invention;

[0028] Figure 5 This is a phase analysis diagram of Example 1 of the present invention;

[0029] Figure 6 This is an electron microscope image of Embodiment 1 of the present invention. Detailed Implementation

[0030] The technical solution of the present invention can be implemented in the following manner.

[0031] A method for high-temperature solid-phase continuous synthesis of iron disulfide powder: High-purity iron powder and high-purity sulfur powder are mixed evenly in a certain proportion, loaded into a boat in a dry environment, and pushed into a fully automatic boat-pushing furnace production line. By setting different temperature zones and sulfidation times in the boat-pushing furnace, high-purity iron disulfide is synthesized through multiple sulfidation processes.

[0032] Preferably, the above-mentioned high-purity iron powder must meet the following quality requirements: (1) Appearance: grayish-black powder, free from lumps and visible impurities; (2) Chemical indicators: total iron (TFe) ≥ 98.00%, metallic iron ≥ 95.00%, hydrochloric acid insoluble matter ≤ 0.20%; (3) Physical indicators: sieve particle size -325 mesh ≥ 95.00, +100 mesh none, loose density ≥ 0.55 g / cm³. 3 .

[0033] Preferably, the above-mentioned high-purity sulfur powder must meet the following quality requirements: (1) Appearance: light yellow powder, free from lumps and visible impurities; (2) Chemical indicators: total sulfur (TS) ≥ 99.50%, moisture ≤ 2.00%, ash ≤ 0.10%, organic matter content ≤ 0.30%.

[0034] The zonal layout of the fully automated pushboat furnace production line described in this invention is as follows: Figure 1 , 2 As shown, the fully automated push-boat furnace production line includes a feeding zone, a synthesis zone, a cooling zone, and a discharging zone. The synthesis zone is divided into seven temperature zones, and the cooling zone is divided into a slow cooling zone, a water-cooled zone 1, and a water-cooled zone 2.

[0035] Preferably, the synthesis zone is controlled as follows: Zone 1 is vulcanized at 100-110℃ for 1-2 hours, Zone 2 at 190-200℃ for 1-2 hours, Zone 3 at 300-330℃ for 2-4 hours, Zones 4 to 6 at 400-440℃ for 2-4 hours respectively, and Zone 7 at 520-560℃ for 2-4 hours.

[0036] More preferably, the synthesis zone is controlled to vulcanize at 100-110℃ for 1.4-1.6h in zone one, at 190-200℃ for 1.4-1.6h in zone two, at 320-330℃ for 2.9-3.1h in zone three, at 410-430℃ for 2.9-3.1h in zones four to six, and at 520-540℃ for 2.9-3.1h in zone seven.

[0037] When the boat enters the fully automated push-boat furnace production line and reaches synthesis zone one, the surface water of the material can be removed. When the boat passes through synthesis zones two and three, the sulfur powder in the material begins to melt, and the liquid sulfur can fully coat the Fe to ensure that the subsequent sulfidation reaction proceeds fully. It enters zones four, five and six to start sulfidation to generate FeS2. Finally, it passes through zone seven for gasification. After sulfidation, the excess S is gasified at high temperature and carried into the sulfur recovery device for collection along with pure nitrogen.

[0038] Preferably, the vessel is cooled to ≤100°C in a slow cooling zone, then cooled to near room temperature in a water cooling zone, and then enters the discharge zone.

[0039] Figure 1 "Air cooling" refers to a situation where, due to the design of equipment in actual production lines, it is impossible for the boat / dish to seamlessly connect directly from the slow cooling zone to the first water cooling zone and from the first water cooling zone to the second water cooling zone. Instead, after exiting the slow cooling zone, the boat / dish passes through a short gap before entering the first water cooling zone. In this invention, this gap is considered air cooling. The same principle applies when entering the second water cooling zone from the first water cooling zone. The air cooling process in this invention does not affect the overall process control of this invention.

[0040] Preferably, the boat is loaded using a stainless steel boat. After loading, the boat is pushed into the feeding zone of the fully automated boat-pushing furnace production line. Pure nitrogen gas is introduced into the fully automated boat-pushing furnace production line from the water-cooled secondary zone and is discharged along with sulfur vapor after the feeding zone and before the synthesis zone. The production process is carried out under a fully sealed pure nitrogen atmosphere with a purity ≥99.99%. The flow rate of pure nitrogen gas introduced into the fully automated boat-pushing furnace production line is 15-25 Nm³. 3 / h, maintaining a slight positive pressure within the fully automated pushboat furnace production line.

[0041] Preferably, the micro-positive pressure refers to the gas pressure inside the fully automatic push-boat furnace production line being 20-50 Pa higher than the external atmospheric pressure. The purpose of maintaining a micro-positive pressure inside the fully automatic push-boat furnace production line is to ensure that there is pressure inside the production line, which can prevent external gases or impurities from entering, and ensure that the gas or substances inside the push-boat furnace can only be output from the inside to the outside, thereby ensuring that there are no impurities intruding during the production process and improving the purity of the product.

[0042] Preferably, the high-purity iron disulfide has a purity of ≥98% and a thermal stability of an initial decomposition temperature of ≥560℃.

[0043] The process flow of the above-mentioned high-temperature solid-phase continuous synthesis of iron disulfide powder is as follows: Figure 3 As shown, the specific steps include the following:

[0044] a. Mix high-purity iron powder and high-purity sulfur powder at a mass ratio of 1:1-1.5 and load them into a boat. Then, the boat enters the fully automatic push-boat furnace production line for sulfidation. After discharge, the material is deagglomerated, crushed, and graded until it passes through a 160-mesh sieve to obtain semi-finished product 1.

[0045] b. Mix semi-finished product 1 and high-purity sulfur powder at a mass ratio of 1:1-1.5, load them into a boat, then perform sulfidation, and after discharge, pass them through a 100-mesh sieve to obtain semi-finished product 2;

[0046] c. Mix the semi-finished product 2 and high-purity sulfur powder at a mass ratio of 1:0.5-1, load them into a boat, and then perform sulfidation. After discharge, pass the material through an 80-mesh sieve. After passing the internal control standard test, mix the mixture, and then package and label it to obtain the high-purity iron disulfide product.

[0047] Preferably, the mixing is carried out using a mixing tank. Before adding materials, the mixing tank is purged with pure nitrogen. After adding materials, pure nitrogen is introduced again for 2-3 minutes to ensure positive pressure inside the tank. The amount of materials added to the mixing tank each time is less than 2 / 3 of the volume of the mixing tank.

[0048] Preferably, in steps a and b above, the mixing time is ≥1 hour for both forward and reverse mixing in the mixing tank, until the color of the mixed material is consistent or the deviation of the total iron content from the theoretically calculated iron content is less than 0.50%; in step c, the batch mixing time is ≥2 hours for both forward and reverse mixing in the mixing tank, until the color of the mixed material is consistent.

[0049] Preferably, during the loading of the boat, the amount of boat material in step a is controlled to be 30-35 kg, and the amount of boat material in steps b and c is controlled to be 40-50 kg.

[0050] Preferably, when controlling the vulcanization process in steps a, b, and c above, the rate at which the boat enters the fully automated boat-pushing furnace production line is controlled to be 1-2 hours per boat.

[0051] Preferably, in step a above, the total iron content in the semi-finished product 1 is ≤60%.

[0052] Preferably, in step b above, the total iron content in the semi-finished product 2 is ≤49%.

[0053] Preferably, in step c above, the internal control standard requires that the iron disulfide content be ≥98%, the total iron content be 46.5-47.5%, the total sulfur content be 52.4-54.0%, and the elemental sulfur content be ≤0.2%.

[0054] Preferably, the above-mentioned method for continuous high-temperature solid-phase synthesis of iron disulfide powder is equipped with a sulfur recovery device. After each sulfidation is completed, the excess sulfur powder is vaporized at high temperature for 3 hours and then carried into the sulfur recovery device for collection along with pure nitrogen.

[0055] The high-temperature solid-phase continuous synthesis method for iron disulfide powder of the present invention is carried out entirely in a dry environment with an ambient humidity of ≤2%. After each sulfidation, if there is any material remaining on the sieve, it must be deagglomerated, crushed, and graded until all material passes through the sieve. In step c, if any unqualified products are found during testing according to internal control standards, they are returned to step c as semi-finished product 2 for further sulfidation until all products are qualified.

[0056] The technical solution and effects of the present invention will be further explained below through practical examples.

[0057] Example

[0058] This invention provides three examples (1-3) of preparing iron disulfide using the above-mentioned high-temperature solid-phase continuous synthesis method for iron disulfide powder. The specific experimental steps are as follows.

[0059] I. Raw Material Preparation

[0060] Self-made high-purity iron powder (TFe≥98.00%) and purchased high-purity sulfur powder (TS≥99.50%) were used. The sulfur powder complied with the national standard GB / T2449.1-2021. The specific monitoring indicators and results of the raw materials are shown in Table 1.

[0061] Table 1 Raw Material Testing Table

[0062]

[0063] II. Experimental Procedure

[0064] The iron disulfide powder was prepared according to the process flow of high-temperature solid-phase continuous synthesis of iron disulfide powder, and the process control parameters are as follows.

[0065] 1. Process control parameters of the fully automatic pusher furnace production line: (1) Temperature zone control (as shown in Table 2); (2) Pushing frequency: one pusher every 1-2 hours; (3) Nitrogen flow rate: 15-25 Nm 3 / h (pure nitrogen); (4) uniform mixing and smooth fabric distribution; (5) spray device frequency: 20-40Hz.

[0066] Table 2 Temperature Zone Control of Pushboat Furnace

[0067] Temperature setting ℃ 100-110 190-200 320-330 410-430 410-430 410-430 520-540 Reaction time / h 1.5 1.5 3 3 3 3 3

[0068] 2. Depolymerization and classification process control parameters: (1) Nitrogen protection: purity ≥ 99.90%; (2) Main unit frequency: 10-30Hz; (3) Feeding frequency: 30-50Hz.

[0069] 3. Screening process control parameters: (1) Semi-finished products pass through a +160 / 100 mesh sieve (pure nitrogen as protective gas, ultrasonic vibration screening); (2) Finished products pass through a +80 mesh sieve (pure nitrogen as protective gas, ultrasonic vibration screening).

[0070] 4. Mixing process control parameters: (1) Motor frequency: 25Hz; (2) Forward and reverse rotation: 2-3h each; (3) Feeding amount: ≤3 tons.

[0071] III. Finished Product Inspection

[0072] Iron disulfide products were prepared according to the above process flow and parameters, and then tested. The test results are shown in Table 3 (purity was calculated based on the theoretical Fe or S content in FeS2). The thermogravimetric analysis curves are shown in Table 3. Figure 4 As shown, the phase analysis diagram is as follows: Figure 5 As shown in Figure 6, the electron microscope morphology image shows that the main phase of the product prepared in this embodiment is FeS2, and it does not contain other impurities.

[0073] Table 3. Detection Report of Synthetic FeS2

[0074]

[0075] The production process of this invention includes four inspection points: raw material inspection, furnace charge inspection, depolymerization and screening mixing inspection, and finished product inspection. According to internal control standards, except for the finished product which undergoes initial and re-inspections, all other inspection points are implemented for every boat. Through the reasonable setup of inspection points and the appropriate number of inspections, product quality can be effectively controlled. No defective products are produced during the production process. Substandard semi-finished products will undergo a second vulcanization process to meet the required technical specifications.

[0076] In production, a fully automatic push-boat furnace production line of this invention can produce 500-700 kg of semi-finished products per day through primary vulcanization, 600-800 kg of semi-finished products per day through secondary vulcanization, and 700-900 kg of finished products per day through tertiary vulcanization, with a product yield of ≥93% and a monthly output of 6-8 tons, thus possessing high economic value.

[0077] The iron disulfide product of this invention employs a unique high-temperature solid-phase thermal synthesis production technology and process, with the entire process carried out under pure nitrogen protection, ensuring stable quality. The production line, site layout, and production environment of the iron disulfide product meet the process requirements. The incoming inspection and supply capacity of raw materials (iron powder, sulfur) can guarantee the needs of mass production. Inspection points are rationally set up during the product production process, ensuring effective control. The produced iron disulfide product has passed the company's inspection and meets the technical requirements.

Claims

1. A method for continuous high-temperature solid-phase synthesis of iron disulfide powder, characterized in that: High-purity iron powder and high-purity sulfur powder are mixed evenly and then loaded into a boat. The boat is then pushed into a fully automatic pusher furnace production line. By setting the temperature range and sulfidation time of the pusher furnace, high-purity iron disulfide is synthesized through multiple sulfidation processes. The fully automatic pusher furnace production line includes a feeding zone, a synthesis zone, a cooling zone, and a discharging zone. The synthesis zone is divided into seven temperature zones: Zone 1 is vulcanized at 100-110℃ for 1-2 hours, Zone 2 at 190-200℃ for 1-2 hours, Zone 3 at 300-330℃ for 2-4 hours, Zones 4 to 6 at 400-440℃ for 2-4 hours, and Zone 7 at 520-560℃ for 2-4 hours. Specifically, the steps include the following: a. Mix high-purity iron powder and high-purity sulfur powder at a mass ratio of 1:1-1.5 and load them into a boat. Then, the boat enters the fully automatic push-boat furnace production line for sulfidation. After discharge, the material is deagglomerated, crushed, and graded until it passes through a 160-mesh sieve to obtain semi-finished product 1. b. Mix semi-finished product 1 and high-purity sulfur powder at a mass ratio of 1:1-1.5, load them into a boat, then perform sulfidation, and after discharge, pass them through a 100-mesh sieve to obtain semi-finished product 2; c. Mix the semi-finished product 2 and high-purity sulfur powder at a mass ratio of 1:0.5-1, load them into a boat, and then carry out sulfidation. After discharge, pass through an 80-mesh sieve. After passing the test according to the internal control standard requirements, mix them evenly, and then package and label them to obtain high-purity iron disulfide products. In step c, the internal control standard requires that the iron disulfide content be ≥98%, the total iron content be 46.5-47.5%, the total sulfur content be 52.4-54.0%, and the elemental sulfur content be ≤0.2%.

2. The method for continuous high-temperature solid-phase synthesis of iron disulfide powder according to claim 1, characterized in that: Zone 1 is vulcanized at 100-110℃ for 1.4-1.6 hours, Zone 2 at 190-200℃ for 1.4-1.6 hours, Zone 3 at 320-330℃ for 2.9-3.1 hours, Zones 4-6 at 410-430℃ for 2.9-3.1 hours, and Zone 7 at 520-540℃ for 2.9-3.1 hours.

3. The method for continuous high-temperature solid-phase synthesis of iron disulfide powder according to claim 1, characterized in that: The cooling zone includes a slow cooling zone and a water cooling zone. The temperature is cooled to ≤100°C in the slow cooling zone and to near room temperature in the water cooling zone.

4. The method for continuous high-temperature solid-phase synthesis of iron disulfide powder according to claim 1, characterized in that: The production process is carried out under a fully sealed pure nitrogen atmosphere with a purity of ≥99.99%. The flow rate of pure nitrogen introduced into the fully automated pusher furnace production line is 15-25 Nm³. 3 / h, maintaining a slight positive pressure within the fully automated pushboat furnace production line.

5. The method for continuous high-temperature solid-phase synthesis of iron disulfide powder according to claim 1, characterized in that: The high-purity iron disulfide has a purity of ≥98% and a thermal stability of an initial decomposition temperature of ≥560℃.

6. The method for continuous high-temperature solid-phase synthesis of iron disulfide powder according to claim 1, characterized in that: When loading the boat, control the amount of boat material in step a to be 30-35 kg, and the amount of boat material in steps b and c to be 40-50 kg; when vulcanization is carried out in steps a, b, and c, control the rate at which the boat enters the fully automatic boat pushing furnace production line to be 1-2 h / boat.

7. The method for continuous high-temperature solid-phase synthesis of iron disulfide powder according to claim 1, characterized in that: In step a, the total iron content of the semi-finished product 1 is ≤60%; in step b, the total iron content of the semi-finished product 2 is ≤49%.

8. The method for continuous high-temperature solid-phase synthesis of iron disulfide powder according to claim 1, characterized in that: A sulfur recovery device is installed. After each sulfurization process, excess sulfur powder is vaporized at high temperature for 3 hours and then collected in the sulfur recovery device along with pure nitrogen.

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