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

Abstract

The application discloses a method and device for preparing sodium sulfide powder by reducing sodium sulfate with ammonia, and belongs to the field of inorganic chemical products. The method comprises the following steps: heating ammonia gas to obtain secondary heating ammonia gas, and gradually suspending and heating sodium sulfate raw materials; in an external heating environment, the heated sodium sulfate raw materials are carried by the secondary heating ammonia gas to complete a gas-solid reaction to generate sodium sulfide in a dilute phase flow state; the mixed gas carrying the sodium sulfide is subjected to gas-solid separation to obtain reaction tail gas and high-temperature sodium sulfide; the high-temperature sodium sulfide is gradually suspended and cooled by raw material ammonia gas, and the sodium sulfide product is output; the raw material ammonia gas is heated to obtain primary heating ammonia gas; the sodium sulfate raw materials are gradually suspended and heated by the reaction tail gas, the reaction tail gas is cooled to obtain cooling tail gas, the cooling tail gas is purified, condensed, compressed, and recycled to recover liquid ammonia for recycling, and nitrogen gas is recovered. The application has the advantages of short reduction reaction time, good quality of the obtained sodium sulfide product, high added value, and no environmental impact caused by the recycling of the reaction tail gas.

Description

Technical Field

[0001] This application relates to the field of inorganic chemical products technology, and in particular to a method and apparatus for preparing sodium sulfide powder by reducing sodium sulfate with ammonia. Background Technology

[0002] Sodium sulfide is an inorganic compound with the chemical formula Na₂S and has broad application prospects. It is a commonly used wastewater treatment agent, primarily used to remove heavy metal ions and organic matter from wastewater, thereby effectively purifying the water. It is also an important metal surface treatment agent, reacting chemically with metal surfaces to form a purplish-black sulfide layer, protecting the metal from corrosion and preventing hydrogen embrittlement. In rubber manufacturing, sodium sulfide acts as a crosslinking agent, promoting crosslinking between rubber molecules, increasing the hardness and strength of the rubber, and improving its physical properties. Sodium sulfide also has applications in agriculture, promoting crop growth and development, increasing nutrient absorption, and improving crop yield and quality, which is of great significance to rural economic development.

[0003] Currently, sodium sulfide is commonly prepared by reducing sodium sulfate. The pulverized coal reduction method accounts for 95% of this process. This involves using solids such as coal or coke as a reducing agent, mixing sodium sulfate with anthracite or coke, and calcining the mixture in a reduction furnace at high temperature. This is a solid-solid reaction, and the entire reduction process takes 1.5 to 2.0 hours. Through a series of leaching, separation, and evaporation steps, a product containing 60% sodium sulfide is obtained. This reduction method is time-consuming, complex, and yields sodium sulfide of relatively poor quality. Furthermore, the reduction of sodium sulfate with carbon generates a significant amount of carbon dioxide, resulting in a substantial environmental impact.

[0004] While using carbon-containing gases such as CO, coal gas, coke oven gas, and natural gas as reducing agents to produce sodium sulfide simplifies the process, the presence of impurities such as sodium carbonate in the product results in a sodium sulfide content of only 90-94%. Furthermore, the use of carbon-based reducing agents leads to the emission of large amounts of carbon dioxide from the product, causing significant environmental impact. Summary of the Invention

[0005] This application provides a method and apparatus for producing sodium sulfide powder by reducing sodium sulfate with ammonia, which solves the problems of existing methods for producing sodium sulfide, such as long reduction reaction time, poor quality of sodium sulfide products, and large amounts of carbon dioxide in the products having a significant environmental impact.

[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 obtaining secondary heated ammonia gas by heating primary heated ammonia gas, and obtaining heated sodium sulfate raw material by suspending powdered sodium sulfate raw material in stages and heating it.

[0008] In an external heating environment, the heated sodium sulfate raw material undergoes a gas-solid reaction to generate sodium sulfide under the carry-on of secondary heated ammonia gas through dilute phase fluidization.

[0009] The mixed gas carrying sodium sulfide is subjected to gas-solid separation to obtain reaction tail gas and high-temperature sodium sulfide;

[0010] The high-temperature sodium sulfide is subjected to staged suspension cooling using raw ammonia gas to output sodium sulfide product. The raw ammonia gas is heated to obtain primary heated ammonia gas.

[0011] The sodium sulfate raw material is gradually suspended and heated by the reaction tail gas to obtain the heated sodium sulfate raw material, and the reaction tail gas is cooled to obtain the cooled tail gas.

[0012] In conjunction with the first aspect, in one possible implementation, the method for preparing sodium sulfide powder by ammonia reduction of sodium sulfate further includes:

[0013] The cooled exhaust gas is purified by removing dust, and the solids obtained from the dust removal are gradually suspended, heated, and recycled.

[0014] In conjunction with the first aspect, in one possible implementation, the method for preparing sodium sulfide powder by ammonia reduction of sodium sulfate further includes:

[0015] The purified tail gas is heat-exchanged with the raw material liquid ammonia. After the purified tail gas is cooled down, cooled purified tail gas and condensate are obtained. The raw material liquid ammonia is heated to obtain raw material ammonia gas, which is used for the stepwise suspension and cooling of high-temperature sodium sulfide.

[0016] The cooled and purified exhaust gas is compressed to obtain liquid ammonia and nitrogen. The liquid ammonia is recycled and reused, and the nitrogen is recovered and reused.

[0017] In conjunction with the first aspect, in one possible implementation, the gas-solid reaction temperature is 400℃~900℃ and the reaction time is 1s~15s;

[0018] The temperature of the heated sodium sulfate raw material is 100℃~600℃;

[0019] The temperature of the sodium sulfide product is 30℃~100℃.

[0020] In conjunction with the first aspect, in one possible implementation, the external heating method is at least one of resistance heating, electromagnetic induction heating, microwave heating, plasma heating, or high-temperature flue gas heating.

[0021] Secondly, another embodiment of the present invention provides an apparatus for producing sodium sulfide powder by ammonia reduction of sodium sulfate, characterized in that, based on the above-described method for producing sodium sulfide powder by ammonia reduction of sodium sulfate, it includes a reheating tank, a co-current conveying bed reaction structure, a gas-solid separator, a suspension heating structure, and a suspension cooling structure; the co-current conveying bed reaction structure includes a reaction tube and an external heating element; the output port of the reheating tank is connected to the input port of the reaction tube, and is configured to heat the primary heating ammonia gas to obtain secondary heating ammonia gas, and then convey the secondary heating ammonia gas to the reaction tube; the powdered sodium sulfate raw material is successively suspended and heated by the suspension heating structure to obtain heated sodium sulfate raw material, and the heated sodium sulfate raw material is conveyed to the bottom of the reaction tube, where it is fluidized in a dilute phase under the carry of the secondary heating ammonia gas to complete the gasification process. Sodium sulfide is produced by a solid-solid reaction. The reaction tube is heated by an external heating element during the reaction process. The gas-solid separator is connected to the output end of the reaction tube and is configured to separate the mixed gas carrying sodium sulfide flowing out of the reaction tube into reaction tail gas and high-temperature sodium sulfide. Both the suspension heating structure and the suspension cooling structure are connected to the gas-solid separator. The suspension cooling structure uses raw ammonia gas to perform staged suspension cooling of the high-temperature sodium sulfide, outputting sodium sulfide product. The raw ammonia gas is heated to obtain primary heated ammonia gas. The suspension cooling structure is connected to the reheat tank, and the primary heated ammonia gas is input to the reheat tank. The suspension heating structure uses the reaction tail gas to staged heat the sodium sulfate raw material to obtain the heated sodium sulfate raw material. The reaction tail gas is cooled to obtain cooled tail gas.

[0022] In conjunction with the second aspect, in one possible implementation, the co-current conveying bed reaction structure further includes an inclined cone, a discharge pipe, and a valve; the large opening end of the inclined cone is connected to the top of the reaction tube, and the small opening end is connected to one end of the discharge pipe; the valve is disposed on the discharge pipe; the other end of the discharge pipe is connected to the bottom of the reaction tube.

[0023] In conjunction with the second aspect, in one possible implementation, the apparatus for producing sodium sulfide powder by reducing sodium sulfate with ammonia further includes a gas dust removal structure; the input end of the gas dust removal structure is connected to the suspension heating structure.

[0024] In conjunction with the second aspect, in one possible implementation, the apparatus for producing sodium sulfide powder by reducing sodium sulfate with ammonia further includes a condenser group and a compressor; the condenser group includes one or more condensers connected in series; the gas dust removal structure is connected to the condenser group via an induced draft fan, and the condenser group is also connected to the suspension cooling structure and the compressor; the raw material liquid ammonia and the purified tail gas are input into the condenser group for heat exchange to obtain raw material ammonia gas, cooled purified tail gas and condensate, and the raw material ammonia gas is transported to the suspension cooling structure to continue to perform staged suspension cooling of the high-temperature sodium sulfide.

[0025] In conjunction with the second aspect, in one possible implementation, the apparatus for producing sodium sulfide powder by reducing sodium sulfate with ammonia further includes a gas-liquid separator and a liquid ammonia storage tank; the inlet of the compressor is connected to the outlet of the condenser assembly, and the outlet is connected to the gas-liquid separator; the gas-liquid separator includes a top gas outlet and a bottom liquid outlet, and the bottom liquid outlet of the gas-liquid separator is connected to the liquid ammonia storage tank; the top gas outlet of the gas-liquid separator outputs nitrogen for recycling; the liquid ammonia storage tank is connected to the inlet of the condenser assembly.

[0026] One or more technical solutions provided in the embodiments of the present invention have at least the following technical effects or advantages:

[0027] The method for producing sodium sulfide powder by ammonia reduction of sodium sulfate provided in this invention involves first heating primary ammonia gas to obtain secondary ammonia gas, then sequentially suspending and heating powdered sodium sulfate raw material to obtain heated sodium sulfate raw material. Subsequently, in an external heating environment, the heated sodium sulfate raw material, carried by the secondary ammonia gas, undergoes a gas-solid reaction in a dilute phase fluidized state to generate sodium sulfide. Next, the mixed gas carrying sodium sulfide undergoes gas-solid separation to obtain reaction tail gas and high-temperature sodium sulfide. Finally, the high-temperature sodium sulfide is sequentially suspended and cooled using the raw material ammonia gas to output the sodium sulfide product. The raw material ammonia gas is heated to obtain primary ammonia gas. This application discloses a method for preparing sodium sulfide powder by reducing sodium sulfate with ammonia. The method involves a gas-solid reaction in a dilute-phase fluidized bed of ammonia gas and powdered, high-temperature sodium sulfate raw material, achieved through secondary heating. This results in a large contact area between the gas and solid phases, an increased reaction surface, and turbulent flow that causes the sodium sulfide particles to tumble. This leads to a high Reynolds coefficient, a thinner boundary layer for heat and mass transfer, and a larger temperature and concentration gradient. The reaction surface is constantly renewed, significantly improving mass and heat transfer between the two phases, as well as the reaction rate. This increases the transfer driving force and overall transfer rate, thereby greatly shortening the reaction time (from 0.5-2.0 h in existing technologies to 1-15 s). The reduction reaction time is short, and the reaction efficiency is high. The method eliminates the need for leaching, separation, and evaporation processes, simplifying the entire preparation process and reducing operating costs. The chemical equation for the reaction is 3Na₂SO₄ + 8NH₃ → 3Na₂S + 4N₂ + 12H₂O; -167.99 kJ. Because the reducing agent is ammonia, the product consists only of a mixture of solid sodium sulfide, nitrogen, and high-temperature water vapor. The product is free of impurities such as sodium sulfate, resulting in high-purity sodium sulfide (≥94%). This leads to a high product value, with a market price of 40,000-45,000 RMB / ton. The production cost of sodium sulfide is low, and the added value is high. Furthermore, the ammonia and nitrogen in the reaction tail gas can be recovered and reused, and the water vapor does not harm the environment. In addition, ammonia is widely available, inexpensive, and convenient to transport, store, and use. Heating ammonia is safer than heating hydrogen and requires less sophisticated equipment and materials, resulting in lower production costs. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a flowchart of a method for preparing sodium sulfide powder by ammonia reduction of sodium sulfate provided in an embodiment of this application;

[0030] Figure 2 This is a schematic diagram of the apparatus for producing sodium sulfide powder by reducing sodium sulfate with ammonia, as provided in an embodiment of this application.

[0031] Icons: 1-Reheat tank; 2-Co-current conveying bed reaction structure; 21-Reaction tube; 22-Inclined cone; 3-Gas-solid separator; 4-Suspension heating structure; 5-Suspension cooling structure; 6-Gas dust removal structure; 7-Induced draft fan; 8-Condenser group; 9-Compressor; 10-Gas-liquid separator; 20-Liquid ammonia storage tank. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] In the description of the embodiments of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the embodiments of the present invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention. The terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of the present invention according to the specific circumstances.

[0034] Please refer to Figures 1-2 As shown in the figure, this embodiment of the invention provides a method for preparing sodium sulfide powder by ammonia reduction of sodium sulfate, comprising the following steps:

[0035] Step 101: The primary heating ammonia gas is heated to obtain secondary heating ammonia gas. Powdered sodium sulfate raw material is then subjected to staged suspension heating to obtain heated sodium sulfate raw material. Specifically, the primary heating ammonia gas is heated in reheat tank 1 to obtain secondary heating ammonia gas, which is then conveyed to reaction tube 21 of the co-current conveying bed reaction structure 2. The powdered sodium sulfate raw material is heated through suspension heating structure 4 to obtain heated sodium sulfate raw material.

[0036] Step 102: In an externally heated environment, the heated sodium sulfate feedstock undergoes a gas-solid reaction in a dilute-phase fluidized state, carried by secondary heated ammonia, to produce sodium sulfide. Specifically, the heated sodium sulfate feedstock is transported to the bottom of reaction tube 21, where it undergoes a gas-solid reaction in a dilute-phase fluidized state, carried by secondary heated ammonia, to produce sodium sulfide. The reaction in reaction tube 21 is conducted under external heating.

[0037] Dilute phase fluidization refers to a process in which the airflow velocity in equipment or pipelines is relatively high, causing particles to be transported in a suspended state. The porosity of the gas-solid mixture is ≥0.99, and the airflow velocity can typically reach 4m / s to 15m / s. Under these conditions, the solid particles are uniformly distributed in a suspended state. By using dilute phase conveying, sodium sulfate raw material is suspended in a high-temperature reducing gas stream, increasing the contact area with the high-temperature reducing gas, accelerating the reaction rate, improving the reaction effect, and shortening the overall reduction reaction time.

[0038] Step 103: The mixed gas carrying sodium sulfide is subjected to gas-solid separation to obtain reaction tail gas and high-temperature sodium sulfide. Specifically, the gas-solid separator 3 performs gas-solid separation on the mixed gas carrying sodium sulfide flowing out of the reaction tube 21 to obtain reaction tail gas and high-temperature sodium sulfide.

[0039] Step 104: High-temperature sodium sulfide is subjected to staged suspension cooling using raw ammonia gas to output sodium sulfide product. The raw ammonia gas is heated to obtain primary heated ammonia gas. Specifically, the suspension cooling structure 5 uses raw ammonia gas to perform staged suspension cooling of high-temperature sodium sulfide to output sodium sulfide product, and heats the raw ammonia gas to obtain primary heated ammonia gas, which is then input into the reheat tank 1.

[0040] Step 105: The sodium sulfate raw material is gradually suspended and heated using the reaction tail gas to obtain heated sodium sulfate raw material, and the reaction tail gas is cooled to obtain cooled tail gas. Specifically, in the suspension heating structure 4, the sodium sulfate raw material is gradually suspended and heated using the reaction tail gas to obtain heated sodium sulfate raw material, and the reaction tail gas is cooled to obtain cooled gas.

[0041] The method for producing sodium sulfide powder by ammonia reduction of sodium sulfate provided in this invention involves first heating primary ammonia gas to obtain secondary ammonia gas, then sequentially suspending and heating powdered sodium sulfate raw material to obtain heated sodium sulfate raw material. Subsequently, in an external heating environment, the heated sodium sulfate raw material, carried by the secondary ammonia gas, undergoes a gas-solid reaction in a dilute phase fluidized state to generate sodium sulfide. Next, the mixed gas carrying sodium sulfide undergoes gas-solid separation to obtain reaction tail gas and high-temperature sodium sulfide. Finally, the high-temperature sodium sulfide is sequentially suspended and cooled using the raw material ammonia gas to output the sodium sulfide product. The raw material ammonia gas is heated to obtain primary ammonia gas. This application discloses a method for preparing sodium sulfide powder by reducing sodium sulfate with ammonia. The method involves a gas-solid reaction in a dilute-phase fluidized bed of ammonia gas and powdered, high-temperature sodium sulfate raw material, achieved through secondary heating. This results in a large contact area between the gas and solid phases, an increased reaction surface, and turbulent flow that causes the sodium sulfide particles to tumble. This leads to a high Reynolds coefficient, a thinner boundary layer for heat and mass transfer, and a larger temperature and concentration gradient. The reaction surface is constantly renewed, significantly improving mass and heat transfer between the two phases, as well as the reaction rate. This increases the transfer driving force and overall transfer rate, thereby greatly shortening the reaction time (from 0.5-2.0 h in existing technologies to 1-15 s). The reduction reaction is fast, efficient, and efficient. The method eliminates the need for leaching, separation, and evaporation, simplifying the entire preparation process and reducing operating costs. The chemical equation for the reaction is 3Na₂SO₄ + 8NH₃ → 3Na₂S + 4N₂ + 12H₂O - 167.99 kJ. Because the reducing agent is gaseous ammonia, the only products are a mixture of solid sodium sulfide, nitrogen, and high-temperature water vapor. The product does not contain impurities such as sodium sulfate, resulting in high-purity sodium sulfide (≥94%). This leads to a high product value, with a market price of 40,000-45,000 RMB / ton. The production cost of sodium sulfide is low, and the added value is high. Furthermore, the ammonia and nitrogen in the reaction tail gas can be recovered and reused, and the water vapor does not harm the environment. In addition, ammonia is widely available, inexpensive, and convenient to transport, store, and use. Heating ammonia is safer than heating hydrogen and requires less sophisticated equipment and materials, resulting in lower production costs.

[0042] Furthermore, the method for preparing sodium sulfide powder by reducing sodium sulfate with ammonia also includes:

[0043] Step 106: The cooled exhaust gas is purified by removing dust, and the solid obtained from the dust removal is then recycled through a series of suspension heating processes. Specifically, the cooled exhaust gas is purified by passing it through the gas dust removal structure 6, and the solid obtained from the dust removal is fed into the suspension heating structure 4 to be mixed with sodium sulfide raw material before reuse.

[0044] Furthermore, the method for preparing sodium sulfide powder by reducing sodium sulfate with ammonia also includes:

[0045] Step 107: The purified tail gas exchanges heat with the raw material liquid ammonia. After cooling, the purified tail gas is obtained as cooled purified tail gas (containing nitrogen, ammonia, and a small amount of non-condensable gases) and condensate (containing water and ammonia). The raw material liquid ammonia is heated to obtain raw material ammonia gas, which is used for the staged suspension cooling of high-temperature sodium sulfide. Specifically, the purified tail gas and raw material liquid ammonia are fed into condenser group 8 for heat exchange. After cooling, the purified tail gas is obtained as cooled purified tail gas and condensate. The raw material liquid ammonia is heated to obtain raw material ammonia gas. The raw material ammonia gas is transported to the suspension cooling structure 5 to continue the staged suspension cooling of high-temperature sodium sulfide.

[0046] Step 108: The cooling and purified exhaust gas is compressed to obtain liquid ammonia and nitrogen. The liquid ammonia is recycled and reused, and the nitrogen is recovered and reused. Specifically, the cooling and purified exhaust gas from condenser group 8 is pressurized by compressor 9, where the gaseous ammonia is converted into liquid ammonia, and the nitrogen is retained in the gas phase. The liquid ammonia is separated by gas-liquid separator 10 and stored in liquid ammonia storage tank 20 for later use. The nitrogen is used as industrial gas.

[0047] The ammonia gas is heated at a temperature of 200℃ to 700℃ initially to facilitate subsequent reactions. The ammonia gas is then heated at a temperature of 600℃ to 1000℃ to accelerate the reduction reaction. The gas-solid reaction temperature is 400℃ to 900℃ to ensure rapid reduction, with a reaction time of 1 to 15 seconds. The temperature of the sodium sulfate feedstock is raised to 100℃ to 600℃. The temperature of the sodium sulfide product is raised to 30℃ to 100℃.

[0048] The external heating method is at least one of resistance heating, electromagnetic induction heating, microwave heating, plasma heating, or high-temperature flue gas heating. Direct heating methods such as resistance heating, electromagnetic induction heating, microwave heating, and plasma heating are convenient and efficient. Alternatively, the high-temperature flue gas from the combustion of fuel can be heated indirectly by flowing through an outer sleeve fitted onto the reaction tube 21. The fuel used for combustion is at least one of coal, natural gas, liquefied petroleum gas, fuel oil, industrial coal gas, hydrogen, or CO.

[0049] Another embodiment of the present invention provides an apparatus for producing sodium sulfide powder by reducing sodium sulfate with ammonia, and based on the above-mentioned method for producing sodium sulfide powder by reducing sodium sulfate with ammonia, including a reheat tank 1, a co-current conveying bed reaction structure 2, a gas-solid separator 3, a suspension heating structure 4, and a suspension cooling structure 5.

[0050] The co-current conveying bed reaction structure 2 includes a reaction tube 21 and an external heating element.

[0051] like Figure 1As shown, the reaction tube 21 includes multiple first straight pipe sections and second straight pipe sections. The multiple first straight pipe sections are arranged in parallel, with adjacent sections connected by second straight pipe sections, which alternately occupy the upper and lower ends of the first straight pipe sections. In practice, to ensure a more complete reduction reaction, the reaction tube 21 is often designed to be long and tall, resulting in higher installation positions for the suspension heating structure 4 and suspension cooling structure 5, as well as higher civil engineering frames. This makes operation and management inconvenient and increases construction investment and costs. However, by configuring the reaction tube 21 as multiple first and second straight pipe sections, making it bendable, the length of the reaction tube 21 can be increased while reducing the height of the reactor and installation structures, thus ensuring a more complete reaction. Simultaneously, the arrangement can reduce the installation height of the suspension heating structure 4, suspension cooling structure 5, and the entire device. Figure 2 The diagram shows the structure of the reaction tube 21, which includes two first straight pipe sections and one second straight pipe section.

[0052] The outlet of the reheat tank 1 is connected to the inlet of the reaction tube 21 and is configured to heat the primary heating ammonia gas to obtain secondary heating ammonia gas, and then deliver the secondary heating ammonia gas to the reaction tube 21.

[0053] The reheat tank 1 is heated using at least one of direct heating and indirect heating methods, including at least one of resistance heating, induction heating, microwave heating, plasma heating, and fuel combustion heating. The fuel used for fuel combustion heating is at least one of coal, natural gas, liquefied petroleum gas, fuel oil, industrial coal gas, and hydrogen.

[0054] Powdered sodium sulfate raw material is gradually suspended and heated through the suspension heating structure 4 to obtain heated sodium sulfate raw material. The heated sodium sulfate raw material is then transported to the bottom of the reaction tube 21. Under the influence of reheated ammonia gas, it is fluidized in a dilute phase within the reaction tube 21, allowing for thorough contact and rapid gas-solid reaction to produce sodium sulfide. During the reaction process, the reaction tube 21 is heated by an external heating element to meet the equilibrium heat requirements and maintain the reaction temperature.

[0055] The gas-solid separator 3 is connected to the output end of the reaction tube 21 and is configured to perform gas-solid separation on the mixed gas carrying sodium sulfide flowing out of the reaction tube 21 to obtain reaction tail gas and high-temperature sodium sulfide. This gas-solid separator 3 can be a high-temperature cyclone separator. The reaction tail gas consists of water vapor, nitrogen, ammonia, and a small amount of sodium sulfate powder and sodium sulfide powder.

[0056] Both the suspension heating structure 4 and the suspension cooling structure 5 are connected to the gas-solid separator 3. The suspension cooling structure 5 uses raw ammonia gas to perform staged suspension cooling of high-temperature sodium sulfide, outputting sodium sulfide product. Simultaneously, the raw ammonia gas is heated to obtain primary heated ammonia gas while cooling the sodium sulfide. The suspension cooling structure 5 utilizes the staged cooling of high-temperature sodium sulfide with raw ammonia gas, employing direct contact between gas and solid materials for heat transfer, resulting in high heat transfer efficiency. It also fully utilizes the process heat source, efficiently recovering the enthalpy from the high-temperature sodium sulfide while achieving efficient cooling, reducing the energy consumption for heating the raw ammonia gas. Furthermore, the raw ammonia gas can be heated to obtain primary heated ammonia gas, providing heat to the sodium sulfate reduction reaction system, thus rationally utilizing thermal energy and reducing production energy consumption.

[0057] The suspension cooling structure 5 is connected to the reheat tank 1, and primary heating ammonia gas is input into the reheat tank 1.

[0058] The suspension heating structure 4 heats the sodium sulfate raw material in stages using the reaction tail gas, resulting in heated sodium sulfate raw material. The reaction tail gas is then cooled to obtain cooled tail gas. The suspension heating structure 4 utilizes the heat from the reaction tail gas to heat the sodium sulfate raw material in stages, employing direct gas-solid contact for heat transfer, resulting in high heat transfer efficiency. This fully utilizes the process heat source, rationally utilizes thermal energy, and reduces the heating energy consumption of the sodium sulfate raw material. Furthermore, the sodium sulfate raw material can cool the reaction tail gas, reducing subsequent cooling energy consumption.

[0059] The apparatus for producing sodium sulfide powder by ammonia reduction of sodium sulfate provided in this embodiment of the invention involves heating primary heated ammonia gas in a reheat tank 1 to obtain secondary heated ammonia gas, which is then conveyed to the reaction tube 21 of the co-current conveying bed reaction structure 2. Sodium sulfate raw material is heated by a suspension heating structure 4 to obtain heated sodium sulfate raw material, which is then conveyed to the bottom of the reaction tube 21. Carried by the secondary heated ammonia gas, it undergoes a gas-solid reaction in the reaction tube 21 in a dilute phase fluidized state to generate sodium sulfide. The reaction tube 21 is externally heated during the reaction process. A gas-solid separator 3 separates the mixed gas carrying sodium sulfide exiting the reaction tube 21 to obtain reaction tail gas and high-temperature sodium sulfide. The suspension heating structure 4 heats the sodium sulfate raw material stage by stage using the reaction tail gas to obtain heated sodium sulfate raw material, and then cools the reaction tail gas to obtain cooling gas. The suspension cooling structure 5 uses ammonia to gradually cool high-temperature sodium sulfide, outputting sodium sulfide product. The ammonia is then heated to obtain primary heated ammonia, which is input into the reheat tank 1 for utilization. The apparatus for producing sodium sulfide powder by ammonia reduction of sodium sulfate in this application involves a gas-solid reaction of secondary heated ammonia with powdered high-temperature sodium sulfate raw material in a dilute-phase fluidized state within the reaction tube 21 of the co-current conveying bed reaction structure 2. The reaction tube 21 has a large contact area between the gas and solid phases, increasing the reaction surface. The sodium sulfide particles tumble with the airflow, resulting in fully developed turbulence, a high Reynolds coefficient, a thinner boundary layer for heat and mass transfer, and larger temperature and concentration gradients. The reaction surface is constantly renewed, greatly improving mass transfer, heat transfer, and reaction rate between the two phases. This increases the transfer driving force and significantly enhances the overall transfer rate, thereby greatly shortening the reaction time (from 0.5h–2.0h in the prior art to 1s–15s). The reduction reaction time is short, the reaction speed is fast, and the reaction efficiency is high. The reaction eliminates the need for leaching, separation, and evaporation, simplifying the entire preparation process and reducing production costs. Since the reducing agent is gaseous ammonia, the resulting product is a mixture of solid sodium sulfide, nitrogen, and high-temperature water vapor. The product is free of impurities such as sodium sulfate, resulting in high-purity sodium sulfide (≥94%). This leads to a high-value product with a market price of 40,000-45,000 RMB / ton. The production cost of sodium sulfide is low, and the product has high added value. Furthermore, the ammonia and nitrogen in the reaction tail gas can be recycled, and the water vapor does not harm the environment. Additionally, ammonia is widely available, inexpensive, and convenient to transport, store, and use. Heating ammonia is safer than heating hydrogen and requires less sophisticated equipment and materials, further reducing production costs.

[0060] Reference Figure 2As shown, the co-current conveying bed reaction structure 2 also includes an inclined cone 22, a discharge pipe, and a valve. The large opening end of the inclined cone 22 is connected to the top of the reaction tube 21, and the small opening end is connected to one end of the discharge pipe. The valve is installed on the discharge pipe. The other end of the discharge pipe is connected to the bottom of the reaction tube 21. Solids not carried out by the gas can be fed into the inclined cone 22, and then the valve is opened, allowing them to be transported to the bottom of the reaction tube 21 through the discharge pipe. The reactants are circulated once or multiple times in the reactor, without wasting raw materials. The connection between the large opening end of the inclined cone 22 and the reaction tube 21, and the connection between the small opening end and the discharge pipe, facilitates the accumulation of solids in the inclined cone 22. This structure allows for the partial recycling of reactants to the reactor inlet, with the amount of recycled material accounting for 0-95% of the total reactants.

[0061] Continue to refer to Figure 1 As shown, the apparatus for producing sodium sulfide powder by ammonia reduction of sodium sulfate also includes a gas dust removal structure 6. The input end of the gas dust removal structure 6 is connected to the suspension heating structure 4. The cooled exhaust gas (composed of water vapor, nitrogen, ammonia, and a small amount of sodium sulfate and sodium sulfide powder) after heat exchange from the suspension heating structure 4 is output to the gas dust removal structure 6 for dust removal, which removes solids from the cooled exhaust gas to obtain purified exhaust gas (composed of water vapor, nitrogen, and ammonia) for subsequent processes. The solid output end of the gas dust removal structure 6 is connected to the suspension heating structure 4, and the recovered solids are input into the suspension heating structure 4 and mixed with the sodium sulfide raw material for recycling.

[0062] like Figure 1 As shown, the apparatus for producing sodium sulfide powder by reducing sodium sulfate with ammonia also includes an induced draft fan 7, which is connected to the output end of the gas dust removal structure 6. This induced draft fan 7 facilitates the extraction of the reaction tail gas separated in the gas-solid separator 3 after staged heat exchange and dust removal via the suspension heating structure 4. Simultaneously, by controlling the power of the induced draft fan 7, the flow rate of the reducing gas ammonia in the reaction tube 21 of the co-current conveying bed reaction structure 2, as well as the system airflow and pressure, can be controlled, thereby controlling the reaction time and state.

[0063] Furthermore, such as Figure 1 As shown, the apparatus for producing sodium sulfide powder by reducing sodium sulfate with ammonia also includes a condenser group 8 and a compressor 9. The gas dust removal structure 6 is connected to the condenser group 8 via an induced draft fan 7. The condenser group 8 is also connected to the suspension cooling structure 5 and the compressor 9. Raw material liquid ammonia and purified tail gas are input into the condenser group 8 for heat exchange to obtain raw material ammonia gas, cooled purified tail gas, and condensate. The raw material ammonia gas is then transported to the suspension cooling structure 5 for further staged suspension cooling of the high-temperature sodium sulfide.

[0064] The purified exhaust gas is cooled by liquid ammonia, where water vapor and a small amount of ammonia are condensed into condensate, thus cooling the purified exhaust gas. The condenser group 8 can fully utilize the heat of the purified exhaust gas to preheat the liquid ammonia, making rational use of thermal energy.

[0065] Optionally, the apparatus for producing sodium sulfide powder by reducing sodium sulfate with ammonia further includes a gas-liquid separator 10 and a liquid ammonia storage tank 20. The inlet of compressor 9 is connected to the outlet of condenser assembly 8, and the outlet is connected to gas-liquid separator 10. Gas-liquid separator 10 includes a top gas outlet and a bottom liquid outlet; the bottom liquid outlet of gas-liquid separator 10 is connected to liquid ammonia storage tank 20. Nitrogen gas is discharged from the top gas outlet of gas-liquid separator 10 for recycling. Liquid ammonia storage tank 20 is connected to the inlet of condenser assembly 8.

[0066] The cooled and purified exhaust gas mainly consists of ammonia and nitrogen. Compressor 9 compresses the ammonia into recoverable liquid ammonia, which is then transported to liquid ammonia storage tank 20 for later use. Water vapor in the purified exhaust gas is indirectly condensed into condensate by the liquid ammonia, and a small amount of gaseous ammonia dissolves in the condensate to form ammonia-containing condensate. This ammonia-containing condensate can be used as an industrial ammonia product, and nitrogen is an industrial gas product. This process technology generates no waste gas or wastewater and achieves highly efficient resource utilization.

[0067] Optionally, the suspension heating structure 4 includes at least one set of heating components. Each set of heating components includes one to four stages of heaters, which can achieve the heating temperature required for the sodium sulfate raw material, and at least one set of heating components is arranged in parallel.

[0068] Preferably, the suspension heating structure 4 includes one or two sets of heating components, which can achieve a good preheating effect and has a reasonable investment cost. When two sets of heating components are set, the reaction gas from the gas-solid separator 3 is divided into two streams and enters the two sets of parallel heating components, heating the sodium sulfate raw material from bottom to top. The sodium sulfate raw material runs in series in the two sets of heating components and is directly heated and heat-exchanged with the reaction gas in a macroscopic up-down and counter-current manner, which improves the heating efficiency.

[0069] The heater structure is similar to a cyclone separator, but its dimensionless dimensions differ significantly from typical cyclone separators due to the required separation, heat exchange efficiency, and fluid resistance under specific operating conditions. The reaction tail gas contains water vapor. Above the dew point temperature, the water in the reaction gas is gaseous and does not react with the sodium sulfate feedstock. If the heating assembly has too many stages, the temperature of the reaction tail gas entering the top-level heater P1 will be relatively low because the reaction tail gas flows from bottom to top for heat exchange. When the temperature of the reaction tail gas reaches or falls below the dew point temperature, the water vapor in it easily condenses into liquid water. Since the sodium sulfate feedstock enters from top to bottom for heat exchange, the liquid water in the first-stage heater P1 will react with the sodium sulfate, causing the sodium sulfate material to easily agglomerate and prevent it from suspending and flowing. Therefore, the heating assembly is set to one to four stages of cyclone heaters, ensuring that the temperature of the reaction gas entering the first-stage heater P1 is higher than the dew point temperature to prevent the gaseous water from liquefying, ensuring the powdered sodium sulfate material remains suspended and flowing, and guaranteeing that the sodium sulfate feedstock reaches the required temperature upon output.

[0070] Sodium sulfate raw material is fed into the heat exchange tubes of the next stage heater step by step from the first stage, while the reaction tail gas is fed into the next stage heater step by step from the last stage. Sodium sulfate raw material and reaction tail gas are directly mixed and heat exchanged, and gas-solid separation is completed in the heater. After the sodium sulfate raw material is heated by passing through each stage heater, heated sodium sulfate raw material is obtained.

[0071] Specifically, such as Figure 2 A schematic diagram of a heating assembly including a four-stage heater is shown. Sodium sulfate feedstock is metered into the heat exchange tube of the first-stage heater P1, where gas-solid separation occurs. The discharge pipe of the first-stage heater P1 is connected to the heat exchange tube of the second-stage heater P2. The sodium sulfate feedstock then enters the heat exchange tube of the second-stage heater P2 via the discharge pipe. The exhaust pipe of the second-stage heater P2 is connected to the heat exchange tube of the first-stage heater P1, thus enabling the sodium sulfate feedstock to be suspended and heated during the flow of the reaction tail gas. The discharge pipe of the second-stage heater P2 is connected to the heat exchange tube of the third-stage heater P3, and the exhaust pipe of the third-stage heater P3 is connected to the heat exchange tube of the second-stage heater P2, and so on. The discharge pipe of the final stage heater Pn-1 is connected to the heat exchange tube of the final stage heater Pn, and the exhaust pipe of the final stage heater Pn is connected to the heat exchange tube of the second-final stage heater Pn-1. After gas-solid separation in the final stage heater Pn, the sodium sulfate feedstock enters the reaction tube 21 via the discharge pipe.

[0072] The reaction tail gas exiting reaction tube 21 enters the heat exchange tube of the final stage heater Pn of the suspension heating structure 4, carrying the sodium sulfate raw material discharged from the secondary final stage heater Pn-1 into the final stage heater Pn for gas-solid separation. It then enters the heat exchange tube of the secondary final stage heater Pn-1, and so on. The reaction tail gas and the sodium sulfate raw material flow macroscopically in opposite directions, heating the sodium sulfate raw material from top to bottom. In this embodiment, the heating component uses the reaction tail gas to perform staged suspension heating of the sodium sulfide raw material. The material flow direction is opposite to the gas flow direction, resulting in good heating effect and high efficiency. When the device includes a gas dust removal structure 6, the gas dust removal structure 6 is connected to the first stage heater P1.

[0073] Furthermore, the suspended cooling structure 5 includes at least one set of cooling components. Preferably, the suspended cooling structure 5 includes one or two sets of cooling components, which achieves good cooling effect and reasonable investment cost. When two sets of cooling components are provided, the cooling efficiency can be further improved.

[0074] Each cooling assembly consists of two to five stages of cooling units, which can achieve the required cooling temperature for sodium sulfide. The cost is reasonable, and it does not increase energy consumption. At least one cooling assembly should be installed in parallel. The structure of this cooling unit is similar to a cyclone separator, but considering heat exchange and separation efficiency, its dimensionless dimensions differ significantly from those of a typical cyclone separator.

[0075] High-temperature sodium sulfide is fed into the heat exchange tubes of the first-stage cooling unit step by step to the next-stage cooling unit, while raw material ammonia is fed into the last-stage cooling unit step by step to the next-stage cooling unit. The high-temperature sodium sulfide and raw material ammonia exchange heat. After passing through each stage of cooling unit, the high-temperature sodium sulfide is cooled and the sodium sulfide product is output. The raw material ammonia is then heated to obtain primary heated ammonia.

[0076] Specifically, such as Figure 2 The diagram illustrates a suspended cooling structure 5 comprising a set of cooling components, including a schematic diagram of three coolers. High-temperature sodium sulfide enters through the heat exchange tube of the first-stage cooler CL1, where gas-solid separation occurs. The discharge pipe of the first-stage cooler CL1 is connected to the heat exchange tube of the second-stage cooler CL2, allowing the high-temperature sodium sulfide to enter the heat exchange tube of the second-stage cooler CL2. The air outlet pipe of the second-stage cooler CL2 is connected to the heat exchange tube of the first-stage cooler CL1, and so on. The discharge pipe of the second-stage cooler CLn-1 is connected to the heat exchange tube of the final-stage cooler CLn, and the air outlet pipe of the final-stage cooler CLn is connected to the heat exchange tube of the second-stage cooler CLn-1. After gas-solid separation in the final-stage cooler CLn, the sodium sulfide powder is discharged through the discharge pipe into the product transportation, storage, and packaging unit. Low-temperature raw material ammonia flows macroscopically in opposite directions to the sodium sulfide, cooling the high-temperature sodium sulfide from bottom to top. Moreover, the low-temperature raw material ammonia is first input from the last stage cooler, and then gradually suspends and cools the high-temperature sodium sulfide upwards, resulting in a better cooling effect.

[0077] The discharge pipe of the cooler is a one-way solid material flow pipe, and the one-way flow is achieved by a valve, which is at least one of a flap valve and a rotary valve.

[0078] The various embodiments in this specification are described in a progressive manner. For the same or similar parts between the various embodiments, please refer to each other. Each embodiment focuses on describing the differences from other embodiments.

[0079] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit this application. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of this application.

Claims

1. A method for preparing sodium sulfide powder by ammonia reduction of sodium sulfate, characterized in that, include: Ammonia gas is heated once to obtain ammonia gas that is heated twice, and powdered sodium sulfate raw material is suspended and heated in stages to obtain heated sodium sulfate raw material. In an external heating environment, the heated sodium sulfate raw material undergoes a gas-solid reaction to generate sodium sulfide under the carry-on of secondary heated ammonia gas through dilute phase fluidization. The mixed gas carrying sodium sulfide is subjected to gas-solid separation to obtain reaction tail gas and high-temperature sodium sulfide; The high-temperature sodium sulfide is subjected to staged suspension cooling using raw ammonia gas to output sodium sulfide product. The raw ammonia gas is heated to obtain primary heated ammonia gas. The sodium sulfate raw material is gradually suspended and heated by the reaction tail gas to obtain the heated sodium sulfate raw material, and the reaction tail gas is cooled to obtain the cooled tail gas.

2. The method for preparing sodium sulfide powder by ammonia reduction of sodium sulfate according to claim 1, characterized in that, Also includes: The cooled exhaust gas is purified by removing dust, and the solids obtained from the dust removal are gradually suspended, heated, and recycled.

3. The method for preparing sodium sulfide powder by ammonia reduction of sodium sulfate according to claim 2, characterized in that, Also includes: The purified tail gas is heat-exchanged with the raw material liquid ammonia. After the purified tail gas is cooled down, cooled purified tail gas and condensate are obtained. The raw material liquid ammonia is heated to obtain raw material ammonia gas, which is used for the stepwise suspension and cooling of high-temperature sodium sulfide. The cooled and purified exhaust gas is compressed to obtain liquid ammonia and nitrogen. The liquid ammonia is recycled and reused, and the nitrogen is recovered and reused.

4. The method for preparing sodium sulfide powder by ammonia reduction of sodium sulfate according to claim 3, characterized in that, The gas-solid reaction temperature is 400℃~900℃, and the reaction time is 1s~15s; The temperature of the heated sodium sulfate raw material is 100℃~600℃; The temperature of the sodium sulfide product is 30℃~100℃.

5. The method for preparing sodium sulfide powder by ammonia reduction of sodium sulfate according to claim 1, characterized in that, The external heating method is at least one of resistance heating, electromagnetic induction heating, microwave heating, plasma heating or high-temperature flue gas heating.

6. An apparatus for producing sodium sulfide powder by reducing sodium sulfate with ammonia, characterized in that, The method for preparing sodium sulfide powder by ammonia reduction of sodium sulfate according to any one of claims 1 to 5 includes a reheat tank, a co-current conveying bed reaction structure, a gas-solid separator, a suspension heating structure, and a suspension cooling structure. The co-current conveying bed reaction structure includes a reaction tube and an external heating element; The outlet of the reheat tank is connected to the inlet of the reaction tube and is configured to heat the primary heating ammonia gas to obtain secondary heating ammonia gas, and then deliver the secondary heating ammonia gas to the reaction tube. Powdered sodium sulfate raw material is gradually suspended and heated through the suspension heating structure to obtain heated sodium sulfate raw material. The heated sodium sulfate raw material is transported to the bottom of the reaction tube and, carried by secondary heated ammonia gas, is fluidized in a dilute phase in the reaction tube to complete the gas-solid reaction and generate sodium sulfide. The reaction tube is heated by the external heating element during the reaction process. The gas-solid separator is connected to the output end of the reaction tube and is configured to perform gas-solid separation on the mixed gas carrying sodium sulfide flowing out of the reaction tube to obtain reaction tail gas and high-temperature sodium sulfide. Both the suspended heating structure and the suspended cooling structure are connected to the gas-solid separator. The suspension cooling structure uses raw ammonia gas to perform stepwise suspension cooling on the high-temperature sodium sulfide, and outputs sodium sulfide product. The raw ammonia gas is heated to obtain primary heated ammonia gas. The suspension cooling structure is connected to the reheat tank, and the primary heating ammonia gas is input into the reheat tank; The suspended heating structure heats the sodium sulfate raw material in stages through the reaction tail gas to obtain the heated sodium sulfate raw material, and the reaction tail gas is cooled to obtain cooled tail gas.

7. The apparatus for producing sodium sulfide powder by ammonia reduction of sodium sulfate according to claim 6, characterized in that, The co-current conveying bed reaction structure also includes an inclined cone, a discharge pipe, and valves; The large opening end of the inclined cone is connected to the top of the reaction tube, and the small opening end is connected to one end of the discharge tube; The valve is installed on the discharge pipe; The other end of the discharge pipe is connected to the bottom of the reaction tube.

8. The apparatus for producing sodium sulfide powder by ammonia reduction of sodium sulfate according to claim 6, characterized in that, It also includes gas dust removal structures; The input end of the gas dust removal structure is connected to the suspension heating structure.

9. The apparatus for producing sodium sulfide powder by ammonia reduction of sodium sulfate according to claim 8, characterized in that, It also includes condenser units and compressors; The condenser group includes one or more condensers connected in series; The gas dust removal structure is connected to the condenser group via an induced draft fan, and the condenser group is also connected to the suspension cooling structure and the compressor. Raw material liquid ammonia and purified tail gas are input into the condenser group for heat exchange to obtain raw material ammonia gas, cooled purified tail gas and condensate. The raw material ammonia gas is then transported to the suspension cooling structure to continue to perform staged suspension cooling of the high-temperature sodium sulfide.

10. The apparatus for producing sodium sulfide powder by ammonia reduction of sodium sulfate according to claim 9, characterized in that, It also includes gas-liquid separators and liquid ammonia storage tanks; The compressor's input port is connected to the condenser assembly's output port, and the output port is connected to the gas-liquid separator. The gas-liquid separator includes a top gas outlet and a bottom liquid outlet, and the bottom liquid outlet of the gas-liquid separator is connected to the liquid ammonia storage tank; the top gas outlet of the gas-liquid separator outputs nitrogen for recycling. The liquid ammonia storage tank is connected to the inlet of the condenser assembly.

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