Method and device for preparing sodium sulfide powder by reducing sodium sulfate with gas

Abstract

The application discloses a method and device for preparing sodium sulfide powder from sodium sulfate by gas reduction, and belongs to the field of inorganic chemical products. The method comprises the following steps: mixing sodium sulfate raw material and sodium sulfide raw material according to a preset ratio to obtain a mixture; the mixture is freely settled from top to bottom, and a reduction gas flows from bottom to top and flows reversely with the mixture, so that in an external heating environment, the heated mixture and the heated reduction gas complete a gas-solid reaction in a contact form of dilute phase fluidization to generate high-temperature sodium sulfide, and reduction waste gas is obtained; the freely settled mixture exchanges heat with the reduction waste gas to obtain heated mixture; the freely settled high-temperature sodium sulfide exchanges heat with the reduction gas to obtain cooled sodium sulfide and heated reduction gas; and the cooled sodium sulfide is cooled, part of which is used as sodium sulfide product, and the other part is mixed with the sodium sulfate raw material as sodium sulfide raw material. The whole reaction process can realize continuous production, has high production efficiency, low operation cost, fast reaction speed and low overall energy consumption.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of inorganic chemical products, in particular to a method and device for preparing sodium sulfide powder by reducing sodium sulfate with gas. BACKGROUND

[0002] Sodium sulfide has various applications in industry. For example, in the alkaline etching solution for aluminum and alloys, adding an appropriate amount of sodium sulfide can improve the etching surface quality and be used for removing alkali-soluble heavy metal impurities. Sodium sulfide can also be used for the treatment of conductive layer in direct electroplating, forming a conductive layer on the non-metal surface by generating colloidal palladium sulfide. In the leather industry, it is used for hydrolysis to remove hair from rawhide, and sodium polysulfide is prepared to accelerate the softening of dry hide. In the printing and dyeing industry, it can be used as a mordant for dissolving sulfide dyes. In addition, sodium sulfide is also used as a corrosion inhibitor, and is a raw material for sodium thiosulfate, sodium polysulfide, sulfide dyes, etc. With the continuous deepening of technical research, the application field of sodium sulfide will be more extensive, and the requirement for the production process of sodium sulfide will be higher and higher.

[0003] At present, the production of sodium sulfide at home and abroad mostly adopts the pulverized coal reduction method, that is, solid substances such as coal are used as reducing agents, mirabilite is mixed with anthracite or coke in proportion, and the reduction reaction is carried out in a reduction furnace at high temperature. The whole reduction reaction needs 1.5-2h, and the chemical reaction equation is: Na2SO4+2C=Na2S+2CO2↑. And through a series of leaching, separation, evaporation and other processes, sodium sulfide products are obtained. The main shortcomings of this production process are: 1) the reduction reaction is a solid-solid reaction in semi-piled state, the reaction time is long, the reaction efficiency is low, and the thermal efficiency is low. 2) The product is affected by impurities in the solid reducing agent, forming insoluble silicates and low-melting-point salts, etc., which reduces the product quality and easily causes the reduction furnace to form a ring, affecting normal production. 3) Using carbon-based anthracite or coke as a reducing agent, the CO2 emission in the product is large. 4) A large amount of waste residue is generated in the leaching process. 5) The Na2S content in the reaction product discharged from the reduction furnace is only 60-70%, and the Na2S content in the sodium sulfide obtained after leaching and evaporation is 60-62%, the product purity is not high, the value is low, and the market price is 3000-4000 yuan / ton.

[0004] Patent CN107619025A discloses a process for preparing anhydrous sodium sulfide from sodium sulfate by gas reduction. First, industrial sodium sulfate is heated until completely melted. Then, it undergoes a gas-liquid reaction with a reducing gas (hydrogen, natural gas, coke oven gas, etc.) under heating, with a reaction time of approximately 1.0 hour. Finally, after the reaction is complete, the discharge system is activated, allowing the molten material to flow out into a mold for cooling and shaping (in blocks) or spraying it into granular sodium sulfide. This process has the following problems: 1) The gas-liquid reaction between the gaseous reducing agent and the molten liquid sodium sulfate has a low driving force and a long reaction time of approximately 1.0 hour, resulting in low reaction efficiency. 2) Solid sodium sulfate needs to be heated to 880–900℃ to reach a molten state, and the reduction reaction temperature needs to be controlled at 1100℃–1200℃. The energy consumed during cooling is not well recovered and utilized, resulting in high overall energy consumption. 3) The heating, reaction, and cooling processes are intermittent batch processes, making continuous production impossible and resulting in low production efficiency. Summary of the Invention

[0005] This application provides a method and apparatus for producing sodium sulfide powder by gas reduction of sodium sulfate, which can solve the problems of long reaction time, low reaction efficiency, high overall energy consumption and low production efficiency in the existing process for preparing sodium sulfide powder.

[0006] To achieve the above objectives, the technical solution of this invention is as follows:

[0007] In a first aspect, embodiments of the present invention provide a method for preparing sodium sulfide powder by gas reduction of sodium sulfate, comprising:

[0008] Powdered sodium sulfate raw material and powdered sodium sulfide raw material are mixed in a preset ratio to obtain a powdered mixture.

[0009] The mixture is allowed to settle freely from top to bottom, while the reducing gas flows upwards in the opposite direction to the mixture. This allows the heated mixture and the heated reducing gas to undergo a gas-solid reaction in a dilute-phase fluidized state under external heating conditions, generating high-temperature sodium sulfide and producing reducing waste gas. The free settling of the mixture and the counter-current flow of the reducing waste gas exchange heat to obtain the heated mixture. The free settling of the high-temperature sodium sulfide and the counter-current flow of the reducing gas exchange heat to obtain cooled sodium sulfide and the heated reducing gas.

[0010] The cooled sodium sulfide is cooled, and a portion of it is used as a sodium sulfide product, while the other portion is used as a raw material for sodium sulfide and mixed with the raw material for sodium sulfate.

[0011] In conjunction with the first aspect, in one possible implementation, the method for producing sodium sulfide powder by gas reduction of sodium sulfate further includes:

[0012] The reduced waste gas is then subjected to dust removal to obtain dust-removed waste gas.

[0013] With reference to the first aspect, in a possible implementation manner, the method for preparing sodium sulfide powder by gas reduction of sodium sulfate further includes:

[0014] The purified waste gas is obtained after the dust removal waste gas is condensed and dehydrated.

[0015] With reference to the first aspect, in a possible implementation manner, when the mixed material is heated by reverse flow heat exchange with the reduction waste gas during the free settling of the mixed material, the method further includes:

[0016] The mixed material is sufficiently dispersed.

[0017] With reference to the first aspect, in a possible implementation manner, the reduction gas is one or a combination of two of H2, CO, coal gas, natural gas and ammonia.

[0018] With reference to the first aspect, in a possible implementation manner, the reaction temperature of the gas-solid reaction is 200-900 ℃, and the reaction time is 1-30 s.

[0019] The temperature of the cooled sodium sulfide is 0-50 ℃.

[0020] With reference to the first aspect, in a possible implementation manner, the preset ratio is 1:9-4:6.

[0021] In a second aspect, the embodiments of the present application provide a device for preparing sodium sulfide powder by gas reduction of sodium sulfate, based on the method for preparing sodium sulfide powder by gas reduction of sodium sulfate, comprising a metering bin, a mixer, a downward bed reactor, a terminal cooler and a heating structure; the output ends of two metering bins are respectively in communication with the input end of the mixer, and the two metering bins respectively weigh the powdered sodium sulfate raw material and the powdered sodium sulfide raw material according to a preset ratio, and then deliver them to the mixer for mixing to obtain a powdered mixture; the downward bed reactor comprises a reaction cylinder; the reaction cylinder comprises, from top to bottom, a raw material preheating zone, a reaction zone and a cooling zone; the upper end of the reaction cylinder is in communication with the output end of the mixer, and the lower end is in communication with the input end of the terminal cooler; the mixture is input into the reaction cylinder and freely settles from top to bottom, while the reducing gas flows from bottom to top and flows countercurrently to the mixture, so that, in the heating environment of the external heating structure, the heated mixture and the heated reducing gas complete the gas-solid reaction in the reaction zone of the reaction cylinder in the form of dilute phase fluidization to generate high-temperature sodium sulfide, and the reducing waste gas is obtained; the freely settled mixture and the reducing waste gas flow countercurrently in the raw material preheating zone of the reaction cylinder to exchange heat and obtain heated mixture; the freely settled high-temperature sodium sulfide and the reducing gas flow countercurrently in the cooling zone of the reaction cylinder to exchange heat and obtain cooled sodium sulfide and heated reducing gas; the output end of the terminal cooler is in communication with the input end of the metering bin for metering sodium sulfide raw material, and the cooled sodium sulfide is input into the terminal cooler to exchange heat and then is cooled, part of which is used as sodium sulfide product, and the other part is input into the metering bin as the sodium sulfide raw material to be mixed with the sodium sulfate raw material.

[0022] In combination with the second aspect, in a possible implementation manner, the downward bed reactor further comprises a powder dispersing structure; the powder dispersing structure is arranged in the raw material preheating zone of the reaction cylinder; the powder dispersing structure comprises a circular ring piece and a support piece; a plurality of the circular ring pieces have inconsistent diameters, the inner walls thereof form acute angles with the central axes thereof, and the circular ring pieces are arranged in a spaced sleeve manner from small to large in diameter; the support piece is arranged between the outer wall of the central circular ring piece and the inner wall of the outermost circular ring piece; and a plurality of the support pieces are arranged in a ring array around the central axis of the powder dispersing structure.

[0023] In combination with the second aspect, in a possible implementation manner, the device for preparing sodium sulfide powder by gas reduction of sodium sulfate further comprises a dust removal structure, a condenser and a fan; the input end of the dust removal structure is in communication with the output end of the upper end of the downward bed reactor, and the output end is in communication with the input end of the condenser, and is configured to remove dust from the reducing waste gas to obtain dust removal waste gas; the input end of the condenser is in communication with the output end of the dust removal structure, and is configured to condense and remove water from the dust removal waste gas to obtain purified waste gas; and the fan is in communication with the output end of the condenser, and is configured to extract the purified waste gas.

[0024] The one or more technical solutions provided in the embodiments of the present application have at least the following technical effects or advantages:

[0025] The method for preparing sodium sulfide powder by reducing sodium sulfate with gas provided by the embodiments of the present application first mixes powdered sodium sulfate raw material and powdered sodium sulfide raw material according to a preset ratio to obtain powdered mixed material. Then, the mixed material is allowed to freely settle from top to bottom, and reducing gas is allowed to flow from bottom to top and flow reversely with the mixed material, so that in an external heating environment, the heated mixed material and the heated reducing gas complete the gas-solid reaction in a contact form of dilute phase fluidization to generate high-temperature sodium sulfide, and reducing waste gas is obtained. The mixed material is allowed to freely settle and exchange heat with the reducing waste gas reversely to obtain heated mixed material. The high-temperature sodium sulfide is allowed to freely settle and exchange heat with the reducing gas reversely to obtain cooled sodium sulfide and heated reducing gas. Finally, the cooled sodium sulfide is cooled, and part of it is used as sodium sulfide product, and the other part is mixed with sodium sulfate raw material as sodium sulfide raw material. The method of the embodiments of the present application improves the melting point of the raw material in the down-flow bed reactor by the way of sodium sulfide circulation batching, reduces the amount of liquid phase generated, and fully utilizes the coupling of the process technology equipment of heat transfer, mass transfer and reaction between the dilute phase fluidization gas-solid phases. The process flow is simple, the reduction reaction efficiency is high, the product purity is high, and is as high as 92% or more. The whole reaction process can realize continuous production, the production efficiency is high, the operation cost is low, and the added value is high. The heated reducing gas is reacted with the powdered mixed material, the temperature gradient and the concentration gradient of the gas-solid two phases in the down-flow bed reactor are large, the reaction material co-melting point is improved, the reaction temperature is increased, the transfer power is increased, the comprehensive transfer efficiency is greatly improved, the reaction speed is fast, and the reaction time is only 1-30 s. Compared with the existing rotary kiln and dense phase fluidized bed reaction process, the method of the present application has the advantages of short reduction reaction time and high decomposition rate of sodium sulfate. The heated reducing gas is obtained by heating the reducing gas with high-temperature sodium sulfide, and the heated mixed material is obtained by heating the mixed material with reducing waste gas, so that the heat energy can be fully utilized, and the overall energy consumption is low. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the description of the embodiments of the present application will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without any creative labor on the basis of these drawings.

[0027] Figure 1 The flow chart of the method for preparing sodium sulfide powder by reducing sodium sulfate with gas provided by the embodiments of the present application is shown in the figure.

[0028] Figure 2 The structural schematic diagram of the device for preparing sodium sulfide powder by reducing sodium sulfate with gas provided by the first embodiment of the present application is shown in the figure.

[0029] Figure 3 A structure schematic diagram of a device for preparing sodium sulfide powder by gas reduction of sodium sulfate is provided for Embodiment Two of the application;

[0030] Figure 4 A structure schematic diagram of a device for preparing sodium sulfide powder by gas reduction of sodium sulfate is provided for Embodiment Three of the application;

[0031] Figure 5 A structure schematic diagram of a powder dispersion structure is provided for the application.

[0032] Icon: 1 - metering bin; 2 - mixer; 3 - down-flow bed reactor; 31 - raw material preheating zone; 32 - reaction zone; 33 - cooling zone; 34 - powder dispersion structure; 341 - circular ring piece; 342 - support piece; 4 - terminal cooler; 5 - dust removal structure; 6 - condenser; 7 - fan; 8 - reduction gas storage tank; 9 - air lock discharge structure. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only a part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the application.

[0034] In the description of the embodiments of the application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", and the like indicate the orientation or positional relationship shown in the drawings, and are only for the purpose of facilitating the description of the embodiments of the application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the application. The terms "first", "second", "third" are only for the purpose of description, and cannot be understood as indicating or implying relative importance. In addition, the terms "mounting", "connecting", "connecting" should be understood broadly, for example, it can be fixedly connected, or detachably connected, or integrally connected; it can be mechanically connected, or electrically connected; it can be directly connected, or indirectly connected through an intermediate medium, or the communication between two elements inside. For those skilled in the art, the specific meaning of the above terms in the embodiments of the application can be understood according to the specific circumstances.

[0035] Please refer to Figure 1 A method for preparing sodium sulfide powder by gas reduction of sodium sulfate is shown in the drawings, which comprises the following steps:

[0036] Step 101: The powdered sodium sulfate raw material and the powdered sodium sulfide raw material are mixed in a preset ratio to obtain a powdered mixture. Specifically, two metering bins 1 weigh the powdered sodium sulfate raw material and the powdered sodium sulfide raw material in a preset ratio respectively and then deliver them to a mixer 2 for mixing to obtain the powdered mixture.

[0037] The preset ratio is 1:9-4:6. Sodium sulfate and sodium sulfide are easy to eutectic, and the reaction process is always the transformation of sodium sulfate to sodium sulfide. When the proportion of sodium sulfate is high, in the reduction reaction, sodium sulfate will be reduced to sodium sulfide, and the proportion of sodium sulfate will gradually decrease, resulting in a decrease in eutectic temperature. The eutectic phenomenon will always occur, leading to unreacted sodium sulfate wrapping, bonding, and plugging, thereby affecting the entire production process. When the preset ratio is 1:9-4:6, the eutectic temperature of sodium sulfate and sodium sulfide can be increased, which is conducive to the reduction reaction.

[0038] Step 102: The mixture is allowed to settle freely from top to bottom, while the reducing gas flows from bottom to top and flows countercurrently with the mixture, so that in the external heating environment, the heated mixture and the heated reducing gas complete the gas-solid reaction in a dilute phase fluidization contact form to generate high-temperature sodium sulfide, and obtain a reducing waste gas. The heated mixture is obtained by heat exchange between the freely settling mixture and the reducing waste gas flowing countercurrently. The freely settling mixture falls downward by its own gravity, and the reducing gas has upward force on the mixture due to buoyancy and drag force, which promotes the heat exchange and reaction of the mixture after turning over, thereby improving the heat exchange and reaction efficiency, so that the heated mixture and the heated reducing gas can complete the gas-solid reaction in a dilute phase fluidization state.

[0039] The high-temperature sodium sulfide freely settles and exchanges heat with the reducing gas flowing countercurrently to obtain cooled sodium sulfide and heated reducing gas. The powdered mixture completes preheating, reduction reaction, and primary cooling in the downflow bed reactor 3. Specifically, the mixture is input into the reaction cylinder and freely settles from top to bottom, while the reducing gas flows from bottom to top and flows countercurrently with the mixture, so that in the external heating environment, the heated mixture and the heated reducing gas complete the gas-solid reaction in a dilute phase fluidization contact form in the reaction zone 32 of the reaction cylinder to generate high-temperature sodium sulfide, and obtain a reducing waste gas. The heated mixture is obtained by heat exchange between the freely settling mixture and the reducing waste gas flowing countercurrently in the raw material preheating zone 31 of the reaction cylinder, so that the heat energy of the reducing waste gas can be used to heat the mixture, and the heat energy is fully utilized. The high-temperature sodium sulfide freely settles and exchanges heat with the reducing gas flowing countercurrently in the cooling zone 33 of the reaction cylinder to obtain cooled sodium sulfide and heated reducing gas, so that the heat energy of the high-temperature sodium sulfide can be fully utilized to heat the reducing gas to obtain heated reducing gas, which is used for subsequent reduction reaction.

[0040] The external heating method is a direct heating method of one or more combinations of resistance heating, electromagnetic induction heating, microwave heating, and plasma heating, or an indirect heating method of high-temperature flue gas.

[0041] The free settling refers to a process that the gas flow velocity in the equipment or pipeline is relatively low, so that the particles are in free settling in the gas flow, the porosity of the gas-solid mixed system is greater than or equal to 0.99, and the gas flow velocity can generally be below 1 m / s, so that the solid particles are in a uniform distribution of suspended state. The sodium sulfate raw material is in a suspended state in the high-temperature reducing gas flow by free settling, the contact area with the high-temperature reducing gas is increased, the reaction speed is accelerated, the reaction effect is good, and the whole reduction reaction time is shortened.

[0042] Step 103: cooling the cooled sodium sulfide, part of which is used as a sodium sulfide product, and the other part is mixed with the sodium sulfate raw material as a sodium sulfide raw material. Specifically, the cooled sodium sulfide is input into the terminal cooler 4 for heat exchange and then cooled to below 45 DEG C, part of which is used as a sodium sulfide product, and the other part is input into the metering bin 1 as a sodium sulfide raw material and mixed with the sodium sulfate raw material. The sodium sulfate and sodium sulfide mixed system is prone to melting, and the eutectic temperature is low. Generally, an iron-based catalyst is added to reduce the reaction temperature to below 660 DEG C, and the reaction time needs dozens of minutes. The sodium sulfide product and the iron-based catalyst are difficult to separate completely, and there are defects of low production efficiency and poor product quality. The embodiment of the present application can improve the eutectic temperature of the sodium sulfate and sodium sulfide mixed system by recycling the sodium sulfide and mixing with the sodium sulfate, reduce the liquid phase amount in the reaction process, and can increase the reaction temperature, which is beneficial to the smooth flow of the material and the improvement of the reaction rate.

[0043] The method for preparing sodium sulfide powder by reducing sodium sulfate with gas provided by the embodiment of the present application first mixes powdered sodium sulfate raw material and powdered sodium sulfide raw material according to a preset ratio to obtain powdered mixed material. Then the mixed material is allowed to freely settle from top to bottom, while the reducing gas flows from bottom to top and flows reversely with the mixed material, so that in an external heating environment, the heated mixed material and the heated reducing gas complete the gas-solid reaction to generate high-temperature sodium sulfide in a contact form of dilute phase fluidization, and obtain reducing waste gas. The heated mixed material is obtained by allowing the mixed material to freely settle and exchange heat with the reducing waste gas. The cooled sodium sulfide is obtained by allowing the high-temperature sodium sulfide to freely settle and exchange heat with the reducing gas. Finally, the cooled sodium sulfide is cooled, part of which is used as sodium sulfide product, and the other part is mixed with the sodium sulfide raw material and the sodium sulfate raw material. The method of the embodiment of the present application improves the melting point of the raw material in the down-flow bed reactor 3 by means of sodium sulfide recycling, reduces the amount of liquid phase generated, and fully utilizes the coupling of the process technology equipment of heat transfer, mass transfer and reaction between the gas-solid phases of dilute phase fluidization. The process flow is simple, the reduction reaction efficiency is high, the product purity is high, which is as high as 92% or more, the whole reaction process can realize continuous production, the production efficiency is high, the operation cost is low, and the added value is high. The heated reducing gas is used for reaction with the powdered mixed material, the temperature gradient and the concentration gradient of the gas-solid two phases in the down-flow bed reactor 3 are large, the co-melting point of the reactants is improved, the reaction temperature is increased, the transfer power is increased, the comprehensive transfer efficiency is greatly improved, the reaction speed is fast, and the reaction time is only 1-30s. Compared with the existing rotary kiln and dense phase fluidized bed reaction process, the method of the present application has the advantages of short reduction reaction time and high decomposition rate of sodium sulfate. The heated reducing gas is obtained by heating the reducing gas with the high-temperature sodium sulfide, and the heated mixed material is obtained by heating the mixed material with the reducing waste gas, so that the heat energy can be fully utilized, and the overall energy consumption is low.

[0044] Further, the method for preparing sodium sulfide powder by reducing sodium sulfate with gas further comprises:

[0045] Step 104: The reducing waste gas is subjected to dust removal to obtain dust removal waste gas. The reducing waste gas contains reducing gas, water vapor, a small amount of sodium sulfide and sodium sulfate. After dust removal, the sodium sulfide and the sodium sulfate can be removed, and the dust removal waste gas contains reducing gas and water vapor.

[0046] Further, the method for preparing sodium sulfide powder by reducing sodium sulfate with gas further comprises:

[0047] Step 105: The dust removal waste gas is condensed to remove water to obtain purified waste gas. According to the concentration of the reducing gas in the purified waste gas, the purified waste gas is all or partially flowed into the reducing gas storage tank 8, so that the reducing gas in the purified waste gas can be recycled.

[0048] As Figures 2 to 4As shown, when the mixture undergoes free settling and counter-current flow heat exchange with the reducing waste gas to obtain a heated mixture, the process further includes: fully dispersing the mixture. Specifically, the mixture is fully dispersed in the powder dispersion structure 34. Fully dispersing the mixture allows it to be in powder form, which facilitates subsequent dilute-phase sulfidation reaction with the heated reducing gas.

[0049] The reducing gas is one or a combination of two of H2, CO, coal gas, natural gas, and ammonia. Using H2, CO, coal gas, natural gas, or ammonia as reducing agents, with widely available sources and reduction products being water or a small amount of CO2, this technology belongs to the field of clean production technology.

[0050] like Figure 2 As shown, when the reducing gas is hydrogen, the reaction equation is: Na₂SO₄(s) + 4H₂(g) → Na₂S(s) + 4H₂O(g). The reduction waste gas contains hydrogen, sodium sulfate, water vapor, and sodium sulfide. The reduction waste gas passes through dust removal structure 5 to remove sodium sulfate and sodium sulfide, resulting in dust-removed waste gas containing hydrogen and water vapor. The dust-removed waste gas enters condenser 6, where the hydrogen and water vapor are condensed and dehydrated to obtain purified waste gas, which is mainly composed of hydrogen.

[0051] At this time, the method for producing sodium sulfide powder by gas reduction of sodium sulfate also includes:

[0052] The reducing gas from the purified waste gas is stored in the reducing gas storage tank 8. The hydrogen contained in this reducing gas is used as a reducing gas to exchange heat with high-temperature sodium sulfide in a counter-current flow to obtain heated reducing gas, which is then recycled. Specifically, the hydrogen in the reducing gas storage tank 8 is used as a reducing gas to exchange heat with high-temperature sodium sulfide in a counter-current flow in the cooling zone 33 of the downward-flowing bed reactor 3 to obtain heated reducing gas, thereby making full use of the high-temperature sodium sulfide to heat the hydrogen.

[0053] like Figure 3 As shown, when the reducing gas is ammonia, the reaction equation is: 3Na₂SO₄(s) + 8NH₃(g) → 3Na₂S(s) + 4N₂(g) + 12H₂O(g). The reduction waste gas contains ammonia, water vapor, nitrogen, sodium sulfate, and sodium sulfide. The reduction waste gas passes through dust removal structure 5 to remove sodium sulfate and sodium sulfide, resulting in dust-removed waste gas containing ammonia, water vapor, and nitrogen. The dust-removed waste gas enters condenser 6, where it is condensed and dehydrated to obtain purified waste gas. This purified waste gas is then discharged and further separated to separate liquid ammonia and nitrogen for industrial use.

[0054] In the method for producing sodium sulfide powder by gas reduction of sodium sulfate, cooling the sodium sulfide includes:

[0055] The cooled sodium sulfide is heat-exchanged by liquid ammonia to obtain ammonia. Specifically, the cooled sodium sulfide and the liquid ammonia are both input into the terminal cooler 4, the cooled sodium sulfide is heat-exchanged by the liquid ammonia to obtain ammonia. The ammonia is output from the terminal cooler 4 and heat-exchanged with the high-temperature sodium sulfide in the cooling zone 33 of the down-flow bed reactor 3 in a reverse flow to obtain the cooled sodium sulfide and the heated reducing gas, so that the cooled sodium sulfide can be fully utilized to heat the ammonia.

[0056] As shown in Figure 4 When the reducing gas is the producer gas, the reducing waste gas contains carbon dioxide, gaseous water, sodium sulfate and sodium sulfide, etc. The reducing waste gas passes through the dust removal structure 5 to remove the sodium sulfate and the sodium sulfide to obtain the dust removal waste gas, which contains carbon dioxide, etc. The dust removal waste gas enters the condenser 6, and after condensing water, the purified waste gas is obtained, and then the purified waste gas is discharged.

[0057] At this time, the method for preparing sodium sulfide powder by gas reducing sodium sulfate comprises the following steps:

[0058] The producer gas in the reducing gas tank 8 is used as the reducing gas to heat-exchange with the high-temperature sodium sulfide in the cooling zone 33 of the down-flow bed reactor 3 to obtain the heated reducing gas, so that the high-temperature sodium sulfide can be fully utilized to heat the producer gas.

[0059] The reaction temperature of the gas-solid reaction is 200-900℃, so that a better reaction effect can be achieved, the energy consumption is low, and the reaction time is 1-30s, the reaction time is short, and the efficiency is high. The temperature of the cooled sodium sulfide after cooling is 0-50℃.

[0060] Please refer to Figures 2 to 4 Another embodiment of the present application provides a device for preparing sodium sulfide powder by gas reducing sodium sulfate, which is based on the above-mentioned method for preparing sodium sulfide powder by gas reducing sodium sulfate, and comprises a metering bin 1, a mixer 2, a down-flow bed reactor 3, a terminal cooler 4 and a heating structure.

[0061] The output ends of the two metering bins 1 are respectively communicated with the input ends of the mixer 2, and the two metering bins 1 respectively weigh the powder-shaped sodium sulfate raw material and the powder-shaped sodium sulfide raw material according to a preset ratio, and then convey the raw materials to the mixer 2 to mix to obtain the powder-shaped mixed material.

[0062] The down-flow bed reactor 3 comprises a reaction cylinder. The reaction cylinder comprises, from top to bottom, a raw material preheating zone 31, a reaction zone 32 and a cooling zone 33. The upper end of the reaction cylinder is communicated with the output end of the mixer 2, and the lower end is communicated with the input end of the terminal cooler 4.

[0063] The mixture is fed into the reaction chamber and, under gravity, freely settles from top to bottom through the descending bed reactor 3. Simultaneously, the reducing gas flows from bottom to top, counter-currently to the mixture. This allows the heated mixture and the heated reducing gas to undergo a gas-solid reaction in the reaction zone 32 of the reaction chamber, in a dilute-phase fluidized state, generating high-temperature sodium sulfide and producing reducing waste gas. The freely settling mixture and the counter-current flow of the reducing waste gas then exchange heat in the raw material preheating zone 31 of the reaction chamber, resulting in a heated mixture. Finally, the high-temperature sodium sulfide freely settles and exchanges heat in the cooling zone 33 of the reaction chamber, resulting in cooled sodium sulfide and heated reducing gas.

[0064] like Figures 2 to 4 As shown, an airlock feeding structure 9 is provided between the output end of the descending bed reactor 3 and the input end of the terminal cooler 4. This airlock feeding structure 9 is at least one of a gravity airlock valve, a rotary valve, a gravity valve, and a locking hopper. When two or more are used, they are arranged in series.

[0065] The output end of the terminal cooler 4 is connected to the input end of the metering chamber 1 for metering sodium sulfide raw material. The cooled sodium sulfide is input into the terminal cooler 4 for heat exchange and cooling. Part of it is used as sodium sulfide product, and the other part is used as sodium sulfide raw material and input into the metering chamber 1 to mix with sodium sulfate raw material.

[0066] Furthermore, such as Figures 2 to 4 As shown, the descending bed reactor 3 also includes a powder dispersion structure 34. When the mixture enters the descending bed reactor 3, it tends to clump together. This powder dispersion structure 34 can fully disperse the mixture, increasing the contact area between the gas and solid during the gas-solid reaction, which is beneficial for subsequent heat exchange and gas-solid reduction reactions. The powder dispersion structure 34 is located in the raw material preheating zone 31 of the reaction cylinder of the descending bed reactor 3.

[0067] like Figure 5 As shown, the powder dispersion structure 34 includes annular plates 341 and support plates 342. The annular plates 341 have different diameters, their inner walls form an acute angle with their own central axis, and they are arranged in an alternating pattern with increasing diameter.

[0068] A support plate 342 is inserted between the outer wall of the innermost annular plate 341 and the inner wall of the outermost annular plate 341. Multiple support plates 342 are arranged in a ring array around the central axis of the powder dispersion structure 34. During installation, the outermost annular plate 341 is engaged in the preheating zone of the descending bed reactor 3. The number of annular plates 341 is determined based on the inner diameter of the preheating zone and the agglomeration characteristics of the mixture. When the inner diameter of the preheating zone is large, more annular plates 341 are used; when the inner diameter of the preheating zone is small, fewer annular plates 341 are used; when the mixture is prone to agglomeration, more and denser annular plates 341 are used.

[0069] The powder dispersion structure 34 provided by the embodiment of the present application is a static device, and does not need external energy supply to realize the dispersion of the mixture. The inner wall of the plurality of annular plates 341 is at an acute angle with the central axis thereof, so that the entire powder dispersion structure 34 is in an inverted conical shape. The mixture falls vertically from top to bottom on the inclined surface of the annular plate 341 by gravity, and then the inclined surface gives the mixture an ejection force, so that the mixture can be dispersed. At the same time, the upper surface of the annular plate 341 and the support plate 342 can cut the lumpy mixture, and also can disperse the mixture. The support plate 342 can also support the entire structure, so that the plurality of annular plates 341 are arranged in a sleeved manner with the diameters gradually increasing.

[0070] With reference to the above Figures 2 to 4 As shown in the figure, the device for preparing sodium sulfide powder by gas reduction of sodium sulfate further comprises a dust removal structure 5, a condenser 6 and a fan 7. The input end of the dust removal structure 5 is in communication with the output end of the upper end of the down-flow bed reactor 3, and the output end is in communication with the input end of the condenser 6, which is configured to obtain dust removal waste gas after dust removal of the reduction waste gas.

[0071] The input end of the condenser 6 is in communication with the output end of the dust removal structure 5, which is configured to obtain purified waste gas after condensation and water removal of the dust removal waste gas.

[0072] The fan 7 is in communication with the output end of the condenser 6, which is configured to extract the purified waste gas.

[0073] The device for preparing sodium sulfide powder by gas reduction of sodium sulfate provided by the embodiment of the present application has the following material flow route: the sodium sulfate raw material and the sodium sulfide raw material are mixed in the mixer 2 according to a predetermined ratio (sodium sulfate raw material:sodium sulfide raw material = 1:9-4:6) to obtain a mixture. The mixture is input into the feeding port of the upper end of the down-flow bed reactor 3. In the down-flow bed reactor 3, the mixture is in a free settling state from top to bottom through the down-flow bed reactor 3, and sequentially completes preheating, reduction reaction and primary cooling. Then, the high-temperature sodium sulfide is input into the terminal heat exchanger to be secondarily cooled to a temperature below 50°C. Part of the sodium sulfide is recycled into the mixer 2 to be mixed with the sodium sulfate raw material, and the remaining sodium sulfide is input into the product storage and packaging process.

[0074] The gas flow route is as follows: the reduction gas is input into the down-flow bed reactor 3 from the reduction gas storage tank 8, passes through the reactor from bottom to top, and reacts with the sodium sulfate in the mixture in the reaction zone 32 of the reactor to obtain reduction waste gas. After heat exchange with the mixture in the preheating zone, the reduction waste gas is input into the dust removal structure 5 for dust removal.

[0075] The following provides a specific implementation of the method for preparing sodium sulfide powder by gas reduction of sodium sulfate provided by the embodiment of the present application.

[0076] Embodiment one

[0077] The process flow is as follows Figure 2The raw material is industrial sodium sulfate, Na2SO4 content 98.5%, powder particle, average particle size 64 μm. High purity sodium sulfide, powder particle, Na2S content 96.3%. The reducing gas is hydrogen. The above-mentioned powder sodium sulfate raw material and powder sodium sulfide raw material are homogenized in two metering bins 1 respectively, and are mixed uniformly in a mixer 2 according to the mass ratio of Na2SO4:Na2S=4:6, and then are sent into the top inlet of a down-flow bed reactor 3 through a screw feeder. The mixture falls into the down-flow bed reactor 3 in a free settling state, is dispersed in the powder dispersion structure 34 of the raw material preheating zone 31 of the down-flow bed reactor 3, and exchanges heat with the reducing waste gas from the reaction zone 32 in the raw material preheating zone 31. High temperature sodium sulfide is obtained by the reduction reaction of the reaction zone 32 with hydrogen from the cooling zone 33, and the high temperature sodium sulfide exchanges heat with hydrogen to reduce the temperature to 165°C in the cooling zone 33, and then enters a terminal cooler 4 through a gravity air lock valve to reduce the temperature to 38°C. The apparent residence time of the mixture in the reaction zone 32 of the down-flow bed reactor 3 is about 3 seconds, the top temperature of the reaction zone 32 is 695°C, the bottom temperature is 715°C, and the pressure is 300 Pa. The Na2S content of the high purity sodium sulfide product is 96.3%. 73% of the high purity sodium sulfide product is sent into the metering bin 1 for recycling reaction.

[0078] Hydrogen enters the down-flow bed reactor 3 from a reducing gas storage tank 8, and the reducing waste gas out of the down-flow bed reactor 3 is dusted by a dust removal structure 5 (bag filter), dehydrated by a condenser 6, and then enters the reducing gas storage tank 8 under the action of a fan 7. The heating mode of the reaction zone 32 of the down-flow bed reactor 3 is resistance heating. The cooling medium of the terminal cooler 4 is water.

[0079] Example Two

[0080] The process flow is as follows Figure 3The raw material is industrial sodium sulfate, Na2SO4 content 99.9%, powder particle, average particle size 52 μm. High purity sodium sulfide, powder particle, Na2S content 97.5%. The reducing gas is ammonia. The above-mentioned powder sodium sulfate raw material and powder sodium sulfide raw material are homogenized in two metering bins 1 respectively, and are mixed uniformly in a mixer 2 according to the ingredient mass ratio of Na2SO4:Na2S=1:9, and then are sent into the top feed inlet of a down-flow bed reactor 3 through a screw feeder. The mixture falls into the down-flow bed reactor 3 in a free settling state, is dispersed in the powder dispersion structure 34 of the raw material preheating zone 31 of the down-flow bed reactor 3, and exchanges heat with the reducing waste gas from the reaction zone 32 in the raw material preheating zone 31. High temperature sodium sulfide is obtained by the reduction reaction of the reaction zone 32 with ammonia gas from the cooling zone 33, and the high temperature sodium sulfide exchanges heat with ammonia gas in the cooling zone 33 to be cooled to 186°C, and then is sent into a terminal cooler 4 through a rotary valve to be cooled to 33°C. The apparent residence time of the mixture in the reaction zone 32 of the down-flow bed reactor 3 is about 1 second, the top temperature of the reaction zone 32 is 720°C, the bottom temperature is 780°C, and the pressure is 200 Pa. The Na2S content of the high purity sodium sulfide product is 97.5%. 94% of the high purity sodium sulfide product is sent into the metering bin 1 for recycling reaction.

[0081] Liquid ammonia enters the terminal cooler 4 from a liquid ammonia storage tank, is gasified after being warmed, and then enters the bottom of the down-flow bed reactor 3. The reducing waste gas from the down-flow bed reactor 3 is dedusted by a dust removal structure 5 (bag filter), is dehydrated by a condenser 6, and then enters the tail gas purification process under the action of a fan 7. The heating mode of the reaction zone 32 of the down-flow bed reactor 3 is high temperature gas heating. The cooling medium of the terminal cooler 4 is liquid ammonia.

[0082] Example Three

[0083] The process flow is as follows Figure 4The raw material is industrial sodium sulfate, Na2SO4 content 98.5%, powder particle, average particle size 36 μm. High purity sodium sulfide, powder particle, Na2S content 92.5%. The reducing gas is producer gas. The powder sodium sulfate raw material and the powder sodium sulfide raw material are homogenized in two metering bins 1 respectively, and are mixed uniformly in a mixer 2 according to the metering mass ratio of Na2SO4:Na2S=2:8, and then are sent into the top inlet of a down-flow bed reactor 3 through a screw feeder. The mixture falls into the down-flow bed reactor 3 in a free settling state, is dispersed in the powder dispersion structure 34 of the raw material preheating zone 31 of the down-flow bed reactor 3, and exchanges heat with the reducing waste gas from the reaction zone 32 in the raw material preheating zone 31. High temperature sodium sulfide is obtained by the reduction reaction of the reaction zone 32 with the coal gas from the cooling zone 33, and the high temperature sodium sulfide exchanges heat with the coal gas in the cooling zone 33 to be cooled to 173℃, and then is sent into a terminal cooler 4 through a lock hopper to be cooled to 45℃. The apparent residence time of the mixed powder in the reaction zone 32 of the down-flow bed reactor 3 is about 15 seconds, the temperature at the top of the reaction zone 32 is 714℃, the temperature at the bottom is 752℃, and the pressure is 1000 Pa. The Na2S content of the high purity sodium sulfide product is 92.5%. 88% of the high purity sodium sulfide product is sent into the metering bin 1 for recycling reaction.

[0084] The coal gas enters the down-flow bed reactor 3 from a reducing gas storage tank 8, and the reducing waste gas out of the down-flow bed reactor 3 is de-dusted by a de-dusting structure 5 (bag filter), is de-watered by a condenser 6, and then enters a tail gas purification process under the action of a fan 7. The heating mode of the reaction zone 32 of the down-flow bed reactor 3 is medium frequency induction heating. The cooling medium of the terminal cooler 4 is water.

[0085] The various embodiments in the specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on the difference from other embodiments.

[0086] The above examples are only used to illustrate the technical solutions of the present application, and are not limited to the present application. Although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part or all of the technical features. The modification or replacement does not make the essence of the corresponding technical solution deviate from the scope of the technical solutions of the present application.

Claims

1. A method for producing sodium sulfide powder by gas reduction of sodium sulfate, characterized by, Comprise: The powder-like sodium sulfate raw material and the powder-like sodium sulfide raw material are mixed according to a preset ratio to obtain a powder-like mixture, and the preset ratio is 1:9~4:6; The mixture is freely settled from top to bottom, and the reducing gas flows from bottom to top and flows reversely with the mixture, so that in the external heating environment, the heated mixture and the heated reducing gas complete the gas-solid reaction in the form of contact of dilute phase fluidization to generate high-temperature sodium sulfide, and the reducing waste gas is obtained; the mixture is freely settled and exchanges heat with the reducing waste gas reversely to obtain the heated mixture; the high-temperature sodium sulfide is freely settled and exchanges heat with the reducing gas reversely to obtain the cooled sodium sulfide and the heated reducing gas; The cooled sodium sulfide is cooled, part of which is used as sodium sulfide product, and the other part is mixed with the sodium sulfate raw material.

2. The method of claim 1, wherein the sodium sulfate is reduced by the gas. Also include: The reducing waste gas is dedusted to obtain dedusted waste gas.

3. The method of claim 2, wherein the sodium sulfate is reduced by the gas. Also include: The dedusted waste gas is condensed and dehydrated to obtain purified waste gas.

4. The method of claim 1, wherein the sodium sulfate is reduced by the gas. When the mixture is freely settled and exchanges heat with the reducing waste gas reversely to obtain the heated mixture, it also includes: The mixture is fully dispersed.

5. The method of claim 1, wherein the sodium sulfate is reduced by the gas. The reducing gas is H2, CO, coal gas, natural gas, ammonia or a combination of one or two.

6. The method of claim 1, wherein the sodium sulfate is reduced by the gas. The reaction temperature of the gas-solid reaction is 200~900℃, and the reaction time is 1~30s; The temperature of the cooled sodium sulfide after cooling is 0~50℃.

7. An apparatus for producing sodium sulfide powder by gas reduction of sodium sulfate, characterized in that, The method for preparing sodium sulfide powder by reducing sodium sulfate based on any one of claims 1~6, comprising a metering bin, a mixer, a downward bed reactor, a terminal cooler and a heating structure; The output ends of the two metering bins are respectively communicated with the input ends of the mixer, and the two metering bins respectively weigh the powder-like sodium sulfate raw material and the powder-like sodium sulfide raw material according to a preset ratio, and then convey them to the mixer for mixing to obtain a powder-like mixture; The downward bed reactor comprises a reaction cylinder; the reaction cylinder comprises a raw material preheating zone, a reaction zone and a cooling zone from top to bottom; the upper end of the reaction cylinder is communicated with the output end of the mixer, and the lower end is communicated with the input end of the terminal cooler; The mixture is input into the reaction cylinder and freely settled from top to bottom, while the reducing gas flows from bottom to top and flows reversely with the mixture, so that in the heating environment of the external heating structure, the heated mixture and the heated reducing gas complete the gas-solid reaction in the form of contact of dilute phase fluidization in the reaction zone of the reaction cylinder to generate high-temperature sodium sulfide, and the reducing waste gas is obtained; the mixture is freely settled and exchanges heat with the reducing waste gas reversely in the raw material preheating zone of the reaction cylinder to obtain the heated mixture; the high-temperature sodium sulfide is freely settled and exchanges heat with the reducing gas reversely in the cooling zone of the reaction cylinder to obtain the cooled sodium sulfide and the heated reducing gas; The output end of the terminal cooler is communicated with the input end of the metering bin of the sodium sulfide raw material, and the cooled sodium sulfide is input into the terminal cooler for heat exchange and cooling, part of which is used as sodium sulfide product, and the other part is mixed with the sodium sulfate raw material and input into the metering bin.

8. The device for producing sodium sulfide powder by gas reduction of sodium sulfate according to claim 7, characterized in that, The downward bed reactor also comprises a powder dispersing structure; The powder dispersion structure is arranged in a raw material preheating zone of the reaction cylinder; The powder dispersion structure comprises circular ring pieces and support pieces; The diameters of the circular ring pieces are inconsistent, the inner walls of the circular ring pieces form acute angles with the central axes of the circular ring pieces, and the circular ring pieces are arranged in a manner of being sleeved in sequence from small to large in diameter; The support pieces are arranged between the outer wall of the most central circular ring piece and the inner wall of the outermost circular ring piece; The support pieces are arranged in a ring shape around the central axis of the powder dispersion structure.

9. The device for producing sodium sulfide powder by gas reduction of sodium sulfate according to claim 7, characterized in that, A dust removal structure, a condenser and a fan are further included; The input end of the dust removal structure is in communication with the output end of the upper end of the down-flow bed reactor, the output end is in communication with the input end of the condenser, and the dust removal structure is configured to obtain dust removal waste gas by dust removal of the reduction waste gas; The input end of the condenser is in communication with the output end of the dust removal structure, and the condenser is configured to obtain purified waste gas by condensation and water removal of the dust removal waste gas; The fan is in communication with the output end of the condenser, and the fan is configured to extract the purified waste gas.

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