Production method of high-purity anhydrous sodium sulfide

Abstract

The invention relates to the field of inorganic salts, and particularly discloses a production method of high-purity anhydrous sodium sulfide, which comprises the following steps: S1, dissolving industrial-grade sodium sulfate as a raw material to prepare a saturated sodium sulfate solution, and freezing and crystallizing to prepare sodium sulfate decahydrate crystals; s2, performing high-temperature rapid dehydration treatment on the sodium sulfate decahydrate crystal through rotary drying to prepare porous anhydrous sodium sulfate with the bulk density of 0.8-1.2 g / cm < 3 >; and S3, carrying out vacuum pressurization on the porous anhydrous sodium sulfate, and then carrying out a heating reduction reaction in a reducing gas atmosphere to prepare anhydrous sodium sulfide with the purity of more than or equal to 95%. The method has the characteristics that the problem that in the process of producing anhydrous sodium sulfide by reducing sodium sulfate through gas, sodium sulfate and anhydrous sodium sulfide generate a low-temperature co-melt to hinder subsequent reaction is solved, and high-purity anhydrous sodium sulfide is prepared.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of inorganic salt chemical industry, more particularly, it relates to a production method of high-purity anhydrous sodium sulfide. BACKGROUND

[0002] As an important inorganic chemical raw material, high-purity anhydrous sodium sulfide (Na2S) has a wide application prospect in the fields of synthesizing polyphenylene sulfide (PPS), manufacturing vulcanized rubber, dye industry, and drug synthesis, etc. The high-purity requirement (usually the content of sodium sulfide needs to reach more than 95%) makes the production of high-purity anhydrous sodium sulfide a key link for the development of related industries.

[0003] At present, the mainstream production process of high-purity anhydrous sodium sulfide uses Na2S·5H2O as raw material, and removes the crystal water through vacuum drying equipment in stages. This process requires a very high vacuum degree of the equipment (usually the final vacuum degree is not less than -0.096 MPa), and is a batch production with a single-pass production time of 10-15 hours, which consumes a large amount of energy. At the same time, due to the limitation of the equipment, the production capacity is low, and the purity of the final product is usually less than 95%, so there is limited space for further improving the purity.

[0004] A production method of anhydrous sodium sulfide is given in related research literature, which directly produces anhydrous sodium sulfide by one-step reduction of sodium sulfate with gas. This method seems simple in theory, but there are many difficulties in actual production. On the one hand, molten anhydrous sodium sulfide has strong alkalinity, which seriously corrodes many materials, and requires high-quality equipment containers. Secondly, in the process of producing anhydrous sodium sulfide by reducing sodium sulfate with gas, when part of the sodium sulfide generated by the reaction of sodium sulfate and unreacted sodium sulfate forms a low-temperature eutectic, it will be obviously sticky and caked, and even blocked the reaction pipeline, which makes the reaction impossible. This is the main reason why the technology of producing anhydrous sodium sulfide by reducing sodium sulfate with gas cannot be industrialized. SUMMARY

[0005] In order to solve the problem that the generation of low-temperature eutectic by sodium sulfate and anhydrous sodium sulfide hinders the subsequent reaction in the process of producing anhydrous sodium sulfide by reducing sodium sulfate with gas, the present application provides a production method of high-purity anhydrous sodium sulfide The present application provides a production method of high-purity anhydrous sodium sulfide, which adopts the following technical scheme: A production method of high-purity anhydrous sodium sulfide, comprising the following steps: S1. Dissolving industrial-grade sodium sulfate to prepare a saturated sodium sulfate solution, and then freezing and crystallizing to obtain sodium sulfate decahydrate crystals; S2. High-temperature rapid dehydration treatment of the sodium sulfate decahydrate crystals by rotary drying to obtain porous anhydrous sodium sulfate with a bulk density of 0.8-1.2 g / cm 3 ; S3, the porous anhydrous sodium sulfate is subjected to vacuum pressurization and then heated in a reducing gas atmosphere to obtain anhydrous sodium sulfide with a purity of ≥95%.

[0006] By studying the phenomenon of sticking and caking in the process of gas direct reduction of sodium sulfate, it is found that ordinary sodium sulfate is formed by evaporation and crystallization from solution, and the generated sodium sulfate is a solid particle. When the sodium sulfate is subjected to reduction reaction with gas, it is subjected to the reaction direction from the surface to the inside, resulting in that the surface sodium sulfate has been reacted to form sodium sulfide, while the inner layer sodium sulfate has not been reacted. Sodium sulfate and sodium sulfide form a low-temperature eutectic body, and obvious problems such as sticking and caking occur, which leads to the failure of the reaction. Even if measures such as crushing are taken to reduce the particle diameter of the raw material sodium sulfate, the essence of the solid sodium sulfate particles cannot be changed, and the problem of unsynchronized reaction of sodium sulfate particles cannot be fundamentally solved.

[0007] In order to solve the above problems, first of all, in this application, industrial-grade sodium sulfate is used as raw material to prepare a saturated sodium sulfate solution, then frozen crystallization is carried out. When the sodium sulfate solution reaches the supersaturated state, during the cooling process, sodium sulfate decahydrate is preferentially crystallized. In the crystal structure, sodium sulfate molecules and crystal water form a layered arrangement, and water molecules occupy the crystal lattice interstices. Needle-like sodium sulfate crystals are prepared, and then high-temperature cyclone rapid dehydration drying is carried out. The surface crystal water evaporates instantaneously, while the internal steam nucleates and escapes to form a microporous structure. A loose and porous sponge-like anhydrous sodium sulfide is prepared, which has a large number of hollow structures and is obviously sponge-like. The bulk density is only 1 / 3-1 / 2 of that of traditional sodium sulfate, and the reaction speed is greatly improved.

[0008] Then the porous anhydrous sodium sulfate is subjected to vacuum pressurization, so that the interstices of the sponge-like porous sodium sulfate are filled with reducing gas, and then the reduction reaction is carried out in a reducing gas atmosphere. The internal and external reactions of sodium sulfate are realized during the heating reaction, effectively overcoming the low-temperature eutectic body phenomenon of sodium sulfate and sodium sulfide generated in the process of gas reduction of sodium sulfate, completely solving the sticking and bonding problems in the reaction process, and realizing the large-scale application of the gas reduction sodium sulfate production anhydrous sodium sulfide technology in industrialization.

[0009] Optionally, in step S1, the industrial-grade sodium sulfate is dissolved in water at 50±5℃ to prepare a saturated sodium sulfate solution, and then cooled to-5℃-(-10)℃ at a cooling rate of 15-20℃ / h. After sodium sulfate decahydrate is precipitated, centrifugation is carried out to obtain sodium sulfate decahydrate crystals.

[0010] Optionally, in step S2, the temperature of the sodium sulfate decahydrate crystals during the spin drying is 400-500℃, and the air inlet amount is 5000-7000m 3 / h.

[0011] Optionally, the reducing gas in step S3 includes one or more of hydrogen, carbon monoxide and methane.

[0012] Optionally, the specific operation in step S3 is to first vacuumize the porous anhydrous sodium sulfate in the vacuum pressurized tank, stop when the vacuum degree is greater than or equal to -0.09 MPa, then introduce the reducing gas to pressurize, stop when the pressure is 0.08-0.15 MPa, then carry out pressure maintaining, the pressure is greater than or equal to 0.05 MPa, and then carry out the heating reduction reaction in the reducing gas atmosphere.

[0013] By adopting the above technical solution, the porous anhydrous sodium sulfate is first vacuumized and then pressurized in the application, so that the air in the pore structure of the anhydrous sodium sulfate is completely replaced by the reducing gas, and then the subsequent gas phase reduction treatment is carried out, the pressurized hydrogen gas promotes the gas diffusion, the hydrogen gas in the pores of the porous sodium sulfate is synchronously reduced, the internal and external synchronous reduction is realized, and the particle adhesion phenomenon caused by the formation of a eutectic phase is avoided.

[0014] Optionally, the specific operation of heating reduction in step S3 is to first heat the reducing gas to 800-900℃, then add the heated high-temperature reducing gas to the lower part of the container during reduction, and when the temperature in the container is stabilized at 720-800℃, the porous anhydrous sodium sulfate is added to the upper part.

[0015] By adopting the above technical solution, the upper feeding and lower gas feeding mode is adopted in the application, so that the reducing gas and the porous anhydrous sodium sulfate move countercurrently, the reaction time is prolonged, and the reaction efficiency is improved.

[0016] Optionally, in step S3, the amount of high-temperature reducing gas introduced is 20-50 times the volume of the porous anhydrous sodium sulfate, and the feeding speed of the porous anhydrous sodium sulfate is controlled to be less than or equal to 5% of the volume of the container.

[0017] By adopting the above technical solution, the feeding speed of the porous anhydrous sodium sulfate material is controlled to prevent material adhesion. Moreover, the low-density solid feeding technology is adopted in the application, which further disperses the distribution of sodium sulfate in the reaction furnace, eliminates the problem of material adhesion, reduces the requirement for the material quality of the reaction furnace body equipment, and saves the production cost.

[0018] Optionally, in the heating reduction process in step S3, the gas inlet speed of the reducing gas is 3000-8000 mL / min, and the feeding speed of the porous anhydrous sodium sulfate is 100-200 g / min.

[0019] Optionally, after the heating reduction reaction of the porous anhydrous sodium sulfate in step S3 is completed, the generated anhydrous sodium sulfide is introduced into the storage tank, nitrogen gas is introduced to cool and store, the nitrogen gas pressure in the tank is greater than or equal to 0.05 MP, and until the anhydrous sodium sulfide material is cooled to less than or equal to 40℃, the material is discharged and packaged.

[0020] By adopting the technical scheme, the anhydrous sodium sulfide after reaction is subjected to anti-oxidation treatment by nitrogen before being discharged and packaged.

[0021] Optionally, in the step S1, the solvent used for preparing the saturated sodium sulfate solution is micro-nano bubble water, and the micro-nano bubble water is obtained by using nitrogen or hydrogen as the aeration gas, the bubble particle size of the micro-nano bubble water is 300-600 nm, and the bubble concentration in the micro-nano bubble water is 1.5*10 5 5 ) mL-1.

[0022] By adopting the technical scheme, the saturated sodium sulfate solution is prepared by using the micro-nano bubble water as the solvent, compared with the ordinary water as the solvent, the micro-nano bubble water forms a large number of gas-liquid interfaces in the solution, which provides heterogeneous nucleation sites for the crystallization of sodium sulfate, promotes the rapid formation of sodium sulfate decahydrate crystal nucleus, and more importantly, compared with the needle-shaped crystals with high aspect ratio formed by the sodium sulfate dissolved in ordinary water, the needle-shaped crystals have large bulk density and low porosity, the micro-nano bubble water promotes the lateral branching of the needle-shaped crystals, and it is easier to form interconnected pores, increase and decrease the bulk gap in the subsequent dehydration process, so that, compared with the evaporation into pores in the crystallization water by using ordinary water, the micro-nano bubble water is used to form hierarchical porous structures by the synergistic effect of bubble rupture and vapor evaporation, and the pore structure is more abundant, and the bubbles in the micro-nano bubble water can partially replace the air in the pores of the crystals in the dissolution stage, improve the filling efficiency of the subsequent reducing gas, further improve the internal and external synchronous reaction during the subsequent reduction, and avoid the incomplete reaction caused by the incomplete reaction of the local reaction, so as to avoid the formation of eutectic body of the residual sodium sulfate and the generated sodium sulfide. In addition, the hydroxyl radicals are formed in the breaking process of the micro-nano bubble water, which can inhibit the adhesion caused by the formation of low-temperature eutectic body of sodium sulfate and generated sodium sulfide, further avoid the adhesion, and improve the purity.

[0023] In summary, the present application has the following beneficial effects: 1、the present application first uses industrial-grade sodium sulfate as raw material to prepare sponge-like porous anhydrous sodium sulfate, then the porous anhydrous sodium sulfate is subjected to vacuum pressurization, so that the voids of the sponge-like porous sodium sulfate are filled with reducing gas, and then the reduction reaction is carried out in the reducing gas atmosphere, so that the internal and external synchronous reaction of sodium sulfate is realized during the heating reaction, the low-temperature eutectic body phenomenon of sodium sulfate and sodium sulfide generated during the gas reduction of sodium sulfate is effectively overcome, the adhesion and bonding problems in the reaction process are completely solved, and the gas reduction of sodium sulfate for producing anhydrous sodium sulfide is realized on a large scale in industrialization. ​2、In the application, industrial-grade sodium sulfate is used as raw material to prepare a saturated sodium sulfate solution, then frozen crystallization is carried out, when the sodium sulfate solution reaches a supersaturated state, during the cooling process, sodium sulfate decahydrate is preferentially crystallized, the crystal structure of which is a layered arrangement of sodium sulfate molecules and crystal water, and water molecules occupy the interstitial space, thus needle-like sodium sulfate crystals are prepared, then high-temperature cyclone rapid dehydration drying is carried out, the obtained sodium sulfate is not only fine-grained, but also has a large number of hollow structures, and is obviously sponge-like, thus loose and porous sponge-like anhydrous sodium sulfide is prepared. DETAILED DESCRIPTION

[0024] The application will be further described in detail below in conjunction with examples, and it is particularly pointed out that: in the following examples, the specific conditions are not specified, and the conventional conditions or the conditions recommended by the manufacturer are used, and the raw materials used in the following examples can be obtained from ordinary market sales unless otherwise specified.

[0025] The present application is directed to the study of the adhesion phenomenon in the process of preparing sodium sulfide from sodium sulfate by direct gas reduction, ordinary sodium sulfate is prepared by evaporation crystallization from a solution, and the generated sodium sulfate is a solid grain, when the reduction reaction with gas is carried out, the reaction direction is from the surface to the inside, which leads to the fact that the surface sodium sulfate has been completely reacted to generate sodium sulfide, while the inner layer sodium sulfate has not been reacted, when the content of the surface sodium sulfide reaches 63.7% (mass fraction), a eutectic system is formed with the remaining sodium sulfate, and the melting point is suddenly reduced to below 500°C (much lower than the reaction temperature of 700-800°C), which leads to the melting and adhesion of the grain, and obvious problems such as adhesion and caking occur, which leads to the fact that the reaction cannot continue In order to solve the above problems, the present application provides a new idea for the production method of high-purity anhydrous sodium sulfide, which uses market common industrial-grade sodium sulfate as raw material, dissolves to prepare a saturated sodium sulfate solution, adopts frozen crystallization to prepare sodium sulfate decahydrate, and adopts cyclone drying to rapidly dehydrate the sodium sulfate decahydrate at high temperature, so that the crystal water is instantaneously evaporated into water vapor, and high-pressure steam flow is generated in the solid. When the steam escapes from the inside of the crystal, it breaks through the constraint of the needle-shaped crystal, forms uniformly distributed micropores, and obtains porous sponge-like sodium sulfate, which is different from the traditional solid sodium sulfate grain, the porous sponge-like structure enables hydrogen to penetrate into the grain interior in the subsequent reduction reaction, realizes synchronous reaction inside and outside, avoids the formation of a low-temperature eutectic system of unreacted sodium sulfate and generated sodium sulfide, and leads to adhesion, then the porous sponge-like sodium sulfate is subjected to vacuum pressurization operation, and the air in the sponge-like sodium sulfate is completely replaced by hydrogen, and finally a tubular gas reduction furnace is used for reduction reaction to prepare high-purity anhydrous sodium sulfide.

[0026] The following is described in conjunction with specific examples.

[0027] Example 1 A production method of high-purity anhydrous sodium sulfide, comprising the following steps: S1, a kind of qualified sodium sulfate on the procurement market as raw material, determine its Na2SO4 content is 99.28%, then it is dissolved in 55 ℃ water to prepare into saturated sodium sulfate solution; Then the prepared saturated sodium sulfate solution is cooled and frozen by freezer, the cooling rate is 15 ℃ / h, and the stirring speed is 20 r / min. When the solution temperature drops to-5 ℃, the obtained slurry is centrifuged in a centrifuge to separate the solid and liquid, and the moisture content of the sodium sulfate decahydrate crystal is ≤5%. The mother liquor in the slurry is recycled in the dissolving tank. S2, the prepared sodium sulfate decahydrate crystal is put into a rotary drying furnace for rapid dehydration and drying. The inlet air temperature of the rotary drying furnace is 400 ℃, the inlet air volume is 5000 m 3 / h, and the porous anhydrous sodium sulfate with a bulk density of 1.05 g / cm 3 is obtained by controlling the drying time. The porous anhydrous sodium sulfate has a loose and porous sponge-like structure. S3, the obtained porous anhydrous sodium sulfate is first transferred into a vacuum press tank. When the porous anhydrous sodium sulfate is fed to 2 / 3 of the tank, the feeding is stopped, the feeding valve is closed, and the vacuumizing is started under the stirring of 10 r / min. When the vacuum degree is-0.09 MPa, the vacuumizing is stopped, the air valve is closed, and the hydrogen inlet valve is opened to start the pressurizing operation. When the pressure is 0.1 MPa, the pressurizing is stopped, and the inlet valve is closed. Then the anhydrous sodium sulfate material after pressurizing is introduced into a pressure maintaining storage tank through a spiral discharger, and the pressure maintaining pressure is 0.05 MPa. The hydrogen gas participating in the reduction reaction is heated by a heat exchanger to ensure that the outlet temperature is 800 ℃. Then the high-temperature hydrogen gas in the heat exchanger is introduced into the furnace body of the tubular reduction furnace from the bottom to heat the furnace. When the furnace body temperature stabilizes at 750 ℃, the porous sodium sulfate in the pressure maintaining storage tank is added from the top. The feeding speed of the porous anhydrous sodium sulfate is controlled at 100 g / min, the hydrogen inlet speed is controlled at 3000 ml / min, and the amount of reducing gas is 20 times the volume of the porous anhydrous sodium sulfate. The final reaction product, anhydrous sodium sulfide, is introduced into the storage tank at the lowest part of the furnace body, and nitrogen gas is introduced into the storage tank for cooling and storage. The nitrogen pressure in the storage tank is 0.05 MP, and the material is discharged and packaged after cooling to below 40 ℃.

[0028] The gas phase reduction time in the above tubular furnace lasts for 180 min, and the detection pressure in the tubular furnace does not increase significantly. After the reaction is completed, there is no obvious adhesion and bonding in the tube.

[0029] And the prepared anhydrous sodium sulfide is detected, wherein the Na2S content is 97.88%, the Na2SO4 content is 0.33%, the Na2SO3 content is 0.59%, the Na2S2O3 content is 0.86%, and the balance is other impurities, which fully meets the index requirements of the polyphenylene sulfide industry for high-purity anhydrous sodium sulfide.

[0030] Example 2 A production method of high-purity anhydrous sodium sulfide comprises the following steps: S1, purchasing a kind of qualified sodium sulfate on the market as raw material, measuring the Na2SO4 content of 99.28%, and then dissolving it in water at 50 DEG C to prepare a saturated sodium sulfate solution; Then the prepared saturated sodium sulfate solution is cooled and frozen by a freezer, the cooling rate is 18 DEG C / h, and the stirring speed is 30 r / min, when the solution temperature is reduced to-10 DEG C, the obtained slurry is centrifuged in a centrifuge to separate the solid and liquid, and the sodium sulfate decahydrate crystal with water content ≤5% is obtained, and the mother liquor in the slurry is recycled in a dissolving tank; S2, the prepared sodium sulfate decahydrate crystal is put into a rotary drying furnace for rapid dehydration and drying, the inlet air temperature of the rotary drying furnace is 450 DEG C, the inlet air volume is 6000 m 3 / h, and the porous anhydrous sodium sulfate with a bulk density of 0.99 g / cm 3 is obtained by controlling the drying time, the porous anhydrous sodium sulfate has a loose and porous sponge-like structure; S3, the obtained porous anhydrous sodium sulfate is first transferred into a vacuum press tank, the feeding of the porous anhydrous sodium sulfate is stopped when it is 2 / 3 of the tank, the feeding valve is closed, the vacuumizing is started under the stirring of 10 r / min, and the vacuumizing is stopped when the vacuum degree is-0.09 MPa, the air inlet valve is closed, and the pressurizing is started, and the pressurizing is stopped when the pressure is 0.08 MPa, and the air inlet valve is closed; Then the anhydrous sodium sulfate after pressurizing is introduced into a pressure maintaining storage tank through a spiral discharger, and the pressure maintaining pressure is 0.05 MPa; The hydrogen gas participating in the reduction reaction is heated by a heat exchanger, so that the outlet temperature is 800 DEG C, then the high-temperature hydrogen gas in the heat exchanger is introduced into the furnace body of a tubular reduction furnace from the bottom to bake the furnace, when the furnace body temperature is stabilized at 720 DEG C, the porous sodium sulfate in the pressure maintaining storage tank is added from the upper part, the feeding speed of the porous sodium sulfate is controlled at 150 g / min, the hydrogen gas inlet speed is controlled at 5000 ml / min, and the reduction gas inlet amount is 30 times of the volume of the porous anhydrous sodium sulfate; The anhydrous sodium sulfide generated in the final reaction is introduced into a storage tank at the lowermost part of the furnace body, and nitrogen is introduced into the storage tank for cooling and storage. The nitrogen pressure in the storage tank is 0.05 MPa. After the material is cooled to below 40℃, it is discharged and packaged.

[0031] The gas phase reduction time in the above-mentioned tube furnace lasts for 180 min, and the detection pressure in the tube furnace does not increase significantly, and there is no obvious adhesion after the reaction is completed.

[0032] The prepared anhydrous sodium sulfide is detected, and the Na2S content is 98.01%, the Na2SO4 content is 0.32%, the Na2SO3 content is 0.72%, the Na2S2O3 content is 0.64%, and the balance is other impurities, which fully meets the index requirements of the polyphenylene sulfide industry for high-purity anhydrous sodium sulfide.

[0033] Example 3 A production method of high-purity anhydrous sodium sulfide, comprising the following steps: S1, purchasing a kind of qualified sodium sulfate on the market as raw material, measuring the Na2SO4 content of 99.28%, then dissolving it in water at 45℃ to prepare a saturated sodium sulfate solution; Then the prepared saturated sodium sulfate solution is cooled and frozen by a freezer, the cooling rate is 20℃ / h, and the stirring speed is 40r / min. When the solution temperature drops to-5℃, the obtained slurry is centrifuged in a centrifuge to separate the solid and liquid, and sodium sulfate dodecahydrate with water content ≤5% is obtained, and the mother liquor in the slurry is recycled in a dissolving tank; S2, the prepared sodium sulfate dodecahydrate is introduced into a rotary drying furnace for rapid dehydration and drying. The inlet air temperature of the rotary drying furnace is 500℃, and the inlet air volume is 7000m3 / h. By controlling the drying time, porous anhydrous sodium sulfate with a bulk density of 0.96g / cm 3 The porous anhydrous sodium sulfate has a loose and porous sponge-like structure; S3, the obtained porous anhydrous sodium sulfate is first introduced into a vacuum pressurized tank. When the porous anhydrous sodium sulfate is fed to 2 / 3 of the tank body, the feeding is stopped, the feeding valve is closed, the stirring speed is 10r / min, the vacuum degree is-0.09MPa, the vacuum valve is closed, the hydrogen inlet valve is opened, the pressure is increased to 0.1MPa, and then the inlet valve is closed. Then the anhydrous sodium sulfate after pressure increase is introduced into a pressure maintaining storage tank through a screw feeder, and the pressure maintaining pressure is 0.05MPa. The hydrogen participating in the reduction reaction is heated by a heat exchanger to ensure that the outlet temperature is 900℃, then the high-temperature hydrogen in the heat exchanger is introduced into the furnace body of the tubular reduction furnace from the bottom to heat the furnace, when the temperature of the furnace body is stabilized at 800℃, the porous sodium sulfate in the pressure-keeping storage tank is added from the top, the feeding speed of the porous sodium sulfate is controlled at 200g / min, the hydrogen inlet speed is controlled at 8000ml / min, and the amount of reducing gas is 50 times the volume of the porous anhydrous sodium sulfate; The anhydrous sodium sulfide generated by the final reaction is introduced into the storage tank at the lowermost part of the furnace body, nitrogen is introduced into the storage tank for cooling and storage, the nitrogen pressure in the storage tank is 0.05MP, and the material is discharged and packaged after being cooled to below 40℃.

[0034] The gas phase reduction time in the above tubular furnace lasts for 180min, and the detection pressure in the tubular furnace does not increase significantly, and there is no obvious adhesion after the reaction.

[0035] And the prepared anhydrous sodium sulfide is detected, wherein the Na2S content is 96.09%, the Na2SO4 content is 0.83%, the Na2SO3 content is 0.71%, the Na2S2O3 content is 1.32%, and the balance is other impurities, which fully meets the index requirements of the polyphenylene sulfide industry for high-purity anhydrous sodium sulfide.

[0036] Example 4 A production method of high-purity anhydrous sodium sulfide, comprising the following steps: S1, purchasing a kind of qualified sodium sulfate on the market as raw material, measuring the Na2SO4 content of 99.28%, then dissolving it in water at 50℃ to prepare a saturated sodium sulfate solution; Then the prepared saturated sodium sulfate solution is cooled by a freezer, the cooling speed is 15℃ / h, and the stirring speed is 30r / min, when the solution temperature is reduced to-10℃, the obtained slurry is centrifuged in a centrifuge to separate the solid and liquid, and the ten water sodium sulfate crystal with water content ≤5% is obtained, and the mother liquor in the slurry is recycled in a dissolving tank; S2, the prepared ten water sodium sulfate crystal is introduced into a rotary drying furnace for rapid dehydration and drying, the inlet air temperature of the rotary drying furnace is 400℃, and the inlet air volume is 6000m3 / h, by controlling the drying time, the porous anhydrous sodium sulfate with a bulk density of 1.05g / cm3 is obtained, and the porous anhydrous sodium sulfate has a loose and porous sponge-like structure; S3, the obtained porous anhydrous sodium sulfate is first transferred into a vacuum pressure tank, the porous anhydrous sodium sulfate is fed into the tank to 2 / 3 of the tank, then the feeding is stopped, the feeding valve is closed, vacuumizing is started under the stirring of 10 r / min, the vacuum degree is stopped at -0.09 MPa, the air valve is closed, the hydrogen inlet valve is opened to start the pressurizing operation, the pressurizing is stopped at 0.15 MPa, and the inlet valve is closed; Then the anhydrous sodium sulfate after the pressurizing is introduced into a pressure maintaining storage tank through a screw feeder, and the pressure maintaining pressure is 0.05 MPa. The hydrogen participating in the reduction reaction is heated by a heat exchanger to ensure that the outlet temperature is 850℃, then the high-temperature hydrogen in the heat exchanger is introduced into the furnace body of the tubular reduction furnace from the bottom to dry the furnace, when the furnace body temperature is stabilized at 730℃, the porous sodium sulfate in the pressure maintaining storage tank is added from the upper part, the feeding speed of the porous anhydrous sodium sulfate is controlled at 150 g / min, the hydrogen inlet speed is controlled at 5000 ml / min, and the amount of the reducing gas introduced is 30 times the volume of the porous anhydrous sodium sulfate. The final reaction generated anhydrous sodium sulfide enters the storage tank at the lowermost part of the furnace body, nitrogen is introduced into the storage tank for cooling and storage, the nitrogen pressure in the storage tank is 0.05 MP, and the material is discharged and packaged after being cooled to below 40℃.

[0037] The gas phase reduction time in the above tubular furnace lasts for 180 min, and the detection pressure in the tubular furnace does not increase significantly, and there is no obvious adhesion after the reaction.

[0038] And the prepared anhydrous sodium sulfide is detected, wherein the Na2S content is 98.03%, the Na2SO4 content is 0.43%, the Na2SO3 content is 0.42%, the Na2S2O3 content is 0.77%, and the balance is other impurities, which fully meets the index requirements of the polyphenylene sulfide industry for high-purity anhydrous sodium sulfide.

[0039] Example 5 A production method of high-purity anhydrous sodium sulfide, comprising the following steps: S1, purchasing a kind of qualified sodium sulfate on the market as raw material, measuring the Na2SO4 content of 99.28%, then dissolving it in water at 50℃ to prepare a saturated sodium sulfate solution; Then the prepared saturated sodium sulfate solution is cooled and frozen by a freezer, the cooling speed is 15℃ / h, and the stirring speed is 30 r / min, when the solution temperature is reduced to -10℃, the obtained slurry is centrifuged in a centrifuge to obtain ten water sodium sulfate crystals with a water content of ≤5%, and the mother liquor in the slurry is recycled in a dissolving tank; S2, the prepared sodium sulfate decahydrate crystals are put into a rotary drying furnace for rapid dehydration drying, the air inlet temperature of the rotary drying furnace is 450°C, the air inlet amount is 6000m3 / h, and the porous anhydrous sodium sulfate with a bulk density of 1.00g / cm3 is obtained by controlling the drying time, and the porous anhydrous sodium sulfate has a loose and porous sponge-like structure; S3, the obtained porous anhydrous sodium sulfate is first transferred into a vacuum press tank, the feeding of the porous anhydrous sodium sulfate into the tank is stopped after 2 / 3 of the tank is filled, the feeding valve is closed, vacuumizing is started under the stirring of 10r / min, and the vacuumizing is stopped when the vacuum degree is-0.09MPa, the air valve is closed, and the hydrogen inlet valve is opened to start the pressurizing operation, and the pressurizing is stopped when the pressure is 0.15MPa, and the inlet valve is closed. Then, the anhydrous sodium sulfate after the pressurizing is introduced into a pressure maintaining storage tank through a screw discharger, and the pressure maintaining pressure is 0.05MPa. The hydrogen gas participating in the reduction reaction is heated by a heat exchanger to ensure that the outlet temperature is 850°C, then the high-temperature hydrogen gas in the heat exchanger is introduced into the furnace body of a tubular reduction furnace from the bottom to heat the furnace, and when the furnace body temperature is stabilized at 780°C, the porous sodium sulfate in the pressure maintaining storage tank is added from the upper part, the feeding speed of the porous sodium sulfate is controlled at 150g / min, the hydrogen gas inlet speed is controlled at 3000ml / min, and the amount of the reducing gas introduced is 30 times the volume of the porous anhydrous sodium sulfate. The anhydrous sodium sulfide finally generated by the reaction is introduced into the storage tank at the lowermost part of the furnace body, nitrogen gas is introduced into the storage tank for cooling and storage, the nitrogen gas pressure in the storage tank is 0.05MP, and the material is discharged and packaged after being cooled to below 40°C.

[0040] The gas phase reduction time in the tubular furnace lasts for 180min, and the detection pressure in the tubular furnace does not obviously increase, and there is no obvious adhesion after the reaction.

[0041] The obtained anhydrous sodium sulfide is detected, and the Na2S content is 97.09%, the Na2SO4 content is 0.48%, the Na2SO3 content is 0.60%, the Na2S2O3 content is 0.99%, and the balance is other impurities, which fully meets the index requirements of the polyphenylene sulfide industry for high-purity anhydrous sodium sulfide.

[0042] Example 6 A production method of high-purity anhydrous sodium sulfide is carried out according to the method in Example 1, and the difference is that in step S1, commercially available sodium sulfate is dissolved in micro-nano bubble water to prepare a saturated sodium sulfate solution, and the micro-nano bubble water is prepared by using nitrogen or hydrogen as the aeration gas through an aeration device, the bubble particle size of the micro-nano bubble water is 300-600nm, and the bubble concentration in the micro-nano bubble water is 1.5×105 / mL.

[0043] The prepared anhydrous sodium sulfide is detected, wherein the content of Na2S is 98.43%, the content of Na2SO4 is 0.22%, the content of Na2SO3 is 0.51%, the content of Na2S2O3 is 0.56%, and the balance is other impurities, which fully meets the index requirements of the polyphenylene sulfide industry for high-purity anhydrous sodium sulfide.

[0044] Example 7 A production method of high-purity anhydrous sodium sulfide is performed according to the method in Example 1, except that in step S1, commercially available sodium sulfate is dissolved in micro-nano bubble water to prepare a saturated sodium sulfate solution, and the micro-nano bubble water is prepared by aeration equipment with nitrogen or hydrogen as the aeration gas, the bubble particle size of the micro-nano bubble water is 300-600 nm, and the bubble concentration in the micro-nano bubble water is 2.0 x 10 5 .

[0045] The prepared anhydrous sodium sulfide is detected, wherein the content of Na2S is 98.78%, the content of Na2SO4 is 0.26%, the content of Na2SO3 is 0.31%, the content of Na2S2O3 is 0.44%, and the balance is other impurities, which fully meets the index requirements of the polyphenylene sulfide industry for high-purity anhydrous sodium sulfide.

[0046] Example 8 A production method of high-purity anhydrous sodium sulfide is performed according to the method in Example 1, except that in step S1, commercially available sodium sulfate is dissolved in micro-nano bubble water to prepare a saturated sodium sulfate solution, and the micro-nano bubble water is prepared by aeration equipment with nitrogen or hydrogen as the aeration gas, the bubble particle size of the micro-nano bubble water is 300-600 nm, and the bubble concentration in the micro-nano bubble water is 2.5 x 10 5 .

[0047] The prepared anhydrous sodium sulfide is detected, wherein the content of Na2S is 98.35%, the content of Na2SO4 is 0.37%, the content of Na2SO3 is 0.58%, the content of Na2S2O3 is 0.48%, and the balance is other impurities, which fully meets the index requirements of the polyphenylene sulfide industry for high-purity anhydrous sodium sulfide.

[0048] Comparative Example 1 A production method of high-purity anhydrous sodium sulfide includes the following steps: The market purchases a qualified sodium sulfate, and the Na2SO4 content thereof is 99.28%. The heat exchange furnace is used to heat the hydrogen gas participating in the reduction reaction, so as to ensure that the outlet temperature is 800 DEG C. The high-temperature hydrogen gas enters the furnace body of the tubular reduction furnace from the bottom to dry the furnace body, and when the furnace body temperature is stabilized at 750 DEG C, the sodium sulfate is added from the upper part, the feeding speed is controlled at 100 g / min, the hydrogen gas inlet speed is controlled at 3000 ml / min, and the amount of the reducing gas is 20 times of the volume of the porous anhydrous sodium sulfate.

[0049] The anhydrous sodium sulfide generated in the final reaction enters the storage tank at the lowermost part of the furnace body, nitrogen gas is introduced into the storage tank for cooling and storage, the nitrogen gas pressure in the storage tank is 0.05 MP, and after the material is cooled to below 40 DEG C, the material is discharged and packaged.

[0050] The gas phase reduction time in the tubular furnace is 30 min, the monitored pressure in the tubular furnace rises obviously, and after the tubular furnace is disassembled and checked, the tube is obviously blocked.

[0051] The anhydrous sodium sulfide obtained in the above test is detected, and the Na2S content is 45.09%, the Na2SO4 content is 52.00%, and the balance is other impurities, which cannot meet the industrial requirements. 2 SO 4 The anhydrous sodium sulfide obtained in the above test is detected, and the Na2S content is 45.09%, the Na2SO4 content is 52.00%, and the balance is other impurities, which cannot meet the industrial requirements.

[0052] Comparative Example 2 A production method of high-purity anhydrous sodium sulfide comprises the following steps: The market purchases a qualified sodium sulfate, and the Na2SO4 content thereof is 99.28%. The heat exchange furnace is used to heat the hydrogen gas participating in the reduction reaction, so as to ensure that the outlet temperature is 800 DEG C. The high-temperature hydrogen gas enters the furnace body of the tubular reduction furnace from the bottom to dry the furnace body, and when the furnace body temperature is stabilized at 750 DEG C, the sodium sulfate is added from the upper part, the feeding speed is controlled at 100 g / min, the hydrogen gas inlet speed is controlled at 3000 ml / min, and the amount of the reducing gas is 20 times of the volume of the porous anhydrous sodium sulfate.

[0053] The heat exchange furnace is used to heat the hydrogen gas participating in the reduction reaction, so as to ensure that the outlet temperature is 800 DEG C. The high-temperature hydrogen gas enters the furnace body of the tubular reduction furnace from the bottom to dry the furnace body, and when the furnace body temperature is stabilized at 750 DEG C, the sodium sulfate is added from the upper part, the feeding speed is controlled at 100 g / min, the hydrogen gas inlet speed is controlled at 3000 ml / min, and the amount of the reducing gas is 20 times of the volume of the porous anhydrous sodium sulfate. The anhydrous sodium sulfide generated in the final reaction enters the storage tank at the lowermost part of the furnace body, nitrogen gas is introduced into the storage tank for cooling and storage, the nitrogen gas pressure in the storage tank is 0.05 MP, and after the material is cooled to below 40 DEG C, the material is discharged and packaged.

[0054] The gas phase reduction time in the tubular furnace is 30 min, the monitored pressure in the tubular furnace rises obviously, and after the tubular furnace is disassembled and checked, the tube is obviously blocked.

[0055] The anhydrous sodium sulfide obtained in the above test was detected, and the Na2S content was 62.04%, the Na2SO4 content was 33.89%, and the balance was other impurities, which could not meet the industrial requirements.

[0056] Comparative Example 3 A market-qualified sodium sulfate was purchased, and the Na2SO4 content was determined to be 99.28%. A market-premium sodium sulfide was purchased, and the Na2S content was determined to be 94.67%. The sodium sulfate and the sodium sulfide were mixed in a weight ratio of 3:7, crushed by a pulverizer, and then passed through a 100-mesh screen to obtain a powder-state mixture.

[0057] The hydrogen gas participating in the reduction reaction was heated by a heat exchanger to ensure that the outlet temperature was 800°C. Then, the high-temperature hydrogen gas in the heat exchanger was introduced into the furnace body of the tubular reduction furnace from the bottom to heat the furnace. When the furnace body temperature was stabilized at 750°C, the powder-state mixture obtained above was added from the top, the powder-state mixture feeding speed was controlled at 100 g / min, the hydrogen gas inlet speed was controlled at 3000 ml / min, and the amount of reducing gas introduced was 20 times the volume of the porous anhydrous sodium sulfate. The anhydrous sodium sulfide generated in the final reaction was introduced into the storage tank at the lowest part of the furnace body, nitrogen gas was introduced into the storage tank for cooling and storage, the nitrogen gas pressure in the storage tank was 0.05 MP, and the material was discharged and packaged after cooling to below 40°C.

[0058] The gas-phase reduction time in the above tubular furnace lasted for 60 min, and the monitoring pressure in the tubular furnace rose significantly. After disassembling and checking, obvious blockage occurred in the tube.

[0059] The anhydrous sodium sulfide obtained in the above test was detected, and the Na2S content was 62.04%, the Na2SO4 content was 33.89%, and the balance was other impurities, which could not meet the industrial requirements.

[0060] In addition, based on Example 1, the process parameters were tested and verified multiple times. After multiple rounds of verification, the anhydrous sodium sulfide product obtained had a Na2S content of 96.0% or more, a Na2SO4 content of less than 0.80%, a Na2SO3 content of less than 0.80%, and a Na2S2O3 content of less than 1.20%, completely meeting the index requirements of the polyphenylene sulfide industry for high-purity anhydrous sodium sulfide. In addition, the tube material was obviously bonded and adhered during the reduction reaction process.

[0061] Referring to the results in the above examples and comparative examples, it can be seen that the anhydrous sodium sulfide product obtained by the production method of high-purity anhydrous sodium sulfide provided in the present application has stable quality, and the product meets the requirements of subsequent production processes. Compared with the existing production process of directly using ordinary sodium sulfate in a gas tube-type reduction furnace, the phenomenon of low-temperature eutectic of sodium sulfate and sodium sulfide generated in the process of gas reduction of sodium sulfate is overcome, and the problems of sticking and bonding in the reaction process are completely solved.

[0062] The specific embodiments are merely illustrative of the present application, and are not intended to limit the present application. Those skilled in the art can make modifications to the embodiments without creative contribution after reading the specification, as long as the modifications are within the scope of the claims of the present application.

Claims

1. A method for producing high-purity anhydrous sodium sulfide, characterized in that: The following steps are involved: S1, using industrial grade sodium sulfate as raw material to dissolve and prepare a saturated sodium sulfate solution, and then freeze crystallize to obtain sodium sulfate decahydrate crystals; S2, the sodium sulfate decahydrate crystals are subjected to high temperature rapid dehydration treatment by rotary drying to obtain a bulk density of 0.8-1.2 g / cm 3 of porous anhydrous sodium sulfate; S3. The porous anhydrous sodium sulfate is vacuum-pressurized and then heated in a reducing gas atmosphere for reduction reaction to obtain anhydrous sodium sulfide with a purity of ≥95%.

2. The production method of high-purity anhydrous sodium sulfide according to claim 1, wherein: In step S1, industrial-grade sodium sulfate is dissolved in water at 50±5°C to prepare a saturated sodium sulfate solution, which is then cooled to -5°C to (-10)°C at a cooling rate of 15-20°C / h to precipitate sodium sulfate decahydrate, which is then centrifuged to obtain sodium sulfate decahydrate crystals.

3. The production method of high-purity anhydrous sodium sulfide according to claim 1, wherein: The temperature of the sodium sulfate decahydrate crystals during rotary drying in step S2 is 400-500°C, and the air inlet volume is 5000-7000m 3 / h.

4. The production method of high-purity anhydrous sodium sulfide according to claim 1, wherein: The reducing gas in step S3 includes one or more of hydrogen, carbon monoxide and methane.

5. A method for producing high-purity anhydrous sodium sulfide according to claim 1, characterized in that: The specific operation in step S3 is to add porous anhydrous sodium sulfate into a vacuum pressure tank and first evacuate the tank, stop when the vacuum degree is ≥-0.09 MPa, then introduce reducing gas for pressurization, stop when the pressure reaches 0.08-0.15 MPa, and then maintain the pressure, the pressure is ≥0.05 MPa, and then heat the reduction reaction in the reducing gas atmosphere.

6. A method for producing high-purity anhydrous sodium sulfide according to claim 5, characterized in that: The specific operation of heating reduction in step S3 is as follows: first, the reducing gas is heated to 800-900°C, and then the heated high-temperature reducing gas is added to the lower part of the container during reduction. When the temperature in the container is stabilized at 720-800°C, porous anhydrous sodium sulfate is added to the upper part.

7. A method for producing high-purity anhydrous sodium sulfide according to claim 6, characterized in that: In step S3, the amount of high-temperature reducing gas introduced is 20-50 times the volume of the porous anhydrous sodium sulfate; and the feeding rate of the porous anhydrous sodium sulfate is controlled so that the volume of the material accounts for ≤5% of the volume of the container.

8. A method for producing high-purity anhydrous sodium sulfide according to claim 6, characterized in that: During the heating reduction process in step S3, the inlet speed of the reducing gas is 3000-8000 mL / min, and the feeding speed of the porous anhydrous sodium sulfate is 100-200 g / min.

9. A method for producing high-purity anhydrous sodium sulfide according to claim 1, characterized in that: After the heating reduction reaction of the porous anhydrous sodium sulfate in step S3 is completed, the generated anhydrous sodium sulfide enters the storage tank and is then introduced with nitrogen for cooling and storage. The nitrogen pressure in the tank is ≥0.05MP, until the anhydrous sodium sulfide material is cooled to ≤40°C and then discharged and packaged.

10. The method for producing high-purity anhydrous sodium sulfide according to claim 1, wherein: When preparing the saturated sodium sulfate solution in step S1, the solvent is micro-nano bubble water, and the micro-nano bubble water is obtained by using nitrogen or hydrogen as the aeration gas. The bubble particle size of the micro-nano bubble water is 300-600nm, and the bubble concentration in the micro-nano bubble water is 1.5×10 5 -(2.5×10 5 ) pieces / mL.