Method for preparing anhydrous flaky sodium sulfide from industrial waste salt containing sodium sulfate

Abstract

The invention relates to the technical field of sodium sulfide preparation, in particular to a method for preparing anhydrous flaky sodium sulfide from industrial waste salt containing sodium sulfate. Comprising the following steps: S1, crushing coke, grinding and proportioning; s2, roasting to generate a slurry-shaped sodium sulfide semi-finished product; s3, thermalization: carrying out thermalization leaching on the sodium sulfide semi-finished product obtained in S2 to obtain a sodium sulfide solution; s4, clarifying and filtering: clarifying and filtering the sodium sulfide solution in S3 to obtain sodium sulfide clear liquid; s5, evaporation and concentration: pumping the sodium sulfide clear liquid obtained in S4 into evaporation and concentration equipment to obtain sodium sulfide refined brine; s6, cooling crystallization: cooling and crystallizing the sodium sulfide refined brine solution obtained in S5 in crystallization equipment while stirring to obtain crystal grains; s7, centrifugal separation: carrying out solid-liquid separation on the crystal grains obtained in the step S6 by utilizing a centrifugal machine; and S8, drying, screening and packaging: drying the sodium sulfide crystal grains separated in the S7 by using a drying machine, screening after drying, and feeding into a packaging machine to prepare the anhydrous flaky sodium sulfide.

Description

Technical Field

[0001] The invention relates to the technical field of sodium sulfide preparation, in particular to a method for preparing anhydrous flaky sodium sulfide by using industrial waste salt containing sodium sulfate. Background Art

[0002] Sodium sulfide is an inorganic compound widely used in dyeing, printing and dyeing, papermaking, textiles, leather making, electroplating, pharmaceuticals, mineral flotation, and wastewater treatment industries. Converting industrial waste salt into sodium sulfide would transform waste into treasure, creating a crucial resource for its utilization and even higher-value utilization.

[0003] Currently, the main commercially available industrial sodium sulfide forms are red and yellow flakes. There are two main methods for preparing sodium sulfide from sodium sulfate salts: coal reduction and gas reduction. Because the gas reduction method is still in the laboratory research stage and has not yet been commercialized, the production of industrial sodium sulfide primarily relies on the coal reduction method, which accounts for approximately 95% of total production. Summary of the Invention

[0004] The technical solution of the present invention addresses the technical problem that the existing technical solutions are too single, and provides a solution that is significantly different from the existing technology. In order to overcome the above-mentioned defects of the existing technology, the present invention provides a method for preparing anhydrous flaky sodium sulfide using industrial waste salt containing sodium sulfate, aiming to solve the problems raised in the above-mentioned background technology.

[0005] To achieve the above object, the present invention provides a method for preparing anhydrous flaky sodium sulfide using industrial waste salt containing sodium sulfate, comprising the following steps:

[0006] S1: coke crushing, grinding and batching;

[0007] S2: roasting to produce a paddle-shaped sodium sulfide semi-finished product, and producing sodium sulfide by the coke reduction of sodium sulfate method;

[0008] S3: thermally leaching the sodium sulfide semi-finished product obtained in S2 to obtain a sodium sulfide solution;

[0009] S4: clarifying and filtering the sodium sulfide solution in S3 to obtain a sodium sulfide clear solution;

[0010] S5: Evaporation and concentration: the sodium sulfide clear liquid obtained in S4 is pumped into an evaporation and concentration device to obtain a sodium sulfide brine solution;

[0011] S6: Cooling and crystallizing, the sodium sulfide brine obtained in S5 is placed in a crystallization device, stirred, cooled and crystallized to obtain (Na2S.9H2O) product grains;

[0012] S7: Centrifugal separation: using a centrifuge to separate the solid and liquid of the crystals obtained in S6, and using mother liquor to wash the crystals. The separated crystals are cooled by air-cooled drums and then transported to the next process;

[0013] S8: Drying, screening, and packaging. The sodium sulfide crystals separated in S7 are dried using a dryer. After drying, they are screened and sent to a semi-automatic packaging machine for packaging to obtain anhydrous sodium sulfide (Na2S). The finished flakes are obtained by a tablet press and then packaged.

[0014] The system of the present invention has a short process, a simple structure, a small footprint, simple operation, high production efficiency, a high degree of automation, and has broad market prospects and significant economic benefits.

[0015] Preferably, S1 is specifically as follows: the coke is crushed into a particle size of less than 3 mm by a hammer crusher and sent into the coke silo; the coke in the coke silo and the waste thenardite in the waste thenardite silo are respectively sent into the metering silo by a belt conveyor; after being mixed in proportion, they are sent to the converter.

[0016] Most of the waste thenardite as raw material comes from the evaporation and crystallization process of sodium chromium sulfate production, and its main components are sodium sulfate and trace amounts of hexavalent chromium.

[0017] Preferably, S2 is specifically as follows: natural gas and excess air are introduced into the furnace for complete combustion; the temperature in the converter is controlled at 850-1250°C. After the furnace temperature reaches 900°C, the coke and the waste thenard react chemically to generate a paddle-shaped sodium sulfide semi-finished product, and sodium sulfide is produced by the coke reduction thenard method.

[0018] The main reactions during the roasting process are as follows:

[0019] Na2SO4+2C→Na2S+2CO2

[0020] Na2SO4+4CO→Na2S+4CO2

[0021] While generating Na2S, a side reaction also occurs, so a certain amount of impurities such as Na2CO3 and Cr appear in the crude alkali. 6+ Will be reduced to Cr by C 3+ ; The reaction equation is as follows:

[0022] 2Na2Cr2O7+3C=2Cr2O3+2Na2O+3CO2

[0023] Na2Cr2O7+Na2S=Cr2O3+2Na2O+SO2

[0024] Cr 6+ Will be reduced to Cr by C 3+ Enter the subsequent mud.

[0025] Preferably, the content of sodium sulfide solution in S3 is 28%.

[0026] This concentration of solution has good fluidity at room temperature, making it easy to transport and mix on site. At the same time, its moderate concentration reduces composition fluctuations caused by volatilization or moisture absorption, facilitating long-term storage and precise dosing.

[0027] Preferably, S4 is specifically as follows: a sodium sulfide solution with a content of 28% is sent to one or more clarification tanks for standing to allow the suspended matter in the sodium sulfide solution to settle, the upper clear liquid in the clarification tank is pumped to the next-level supernatant clarification tank, and the lower clear liquid in the clarification tank is discharged from the lower part of the tank through a pipe, the pipe port is equipped with a metal filter screen, and the filtered lower clear liquid enters the next-level lower liquid clarification tank. The clarification and filtration of the next-level clarification tank are exactly the same as the above process. After multiple clarifications and filtrations, a sodium sulfide clear liquid is obtained, and the sodium sulfide clear liquid is sent to the next process.

[0028] This design greatly reduces the insoluble impurity content in the sodium sulfide solution through multiple clarifications and filtrations. After the impurity content meets the standards after analysis, it is sent to the next process.

[0029] Preferably, S5 specifically comprises: pumping the sodium sulfide clear liquid to a tubular evaporator, evaporating and concentrating it until the sodium sulfide content is greater than 32% to form sodium sulfide semen, and then pumping it to a crystallization device.

[0030] The shell-and-tube evaporator and crystallization equipment both utilize commercially available structures. This approach is common knowledge and will not be elaborated upon. The steam condensate generated during the evaporation and concentration process is recycled and reused in production, rather than discharged, demonstrating the environmental friendliness of this system.

[0031] Preferably, S6 specifically comprises: stirring the sodium sulfide semen in a crystallization device and cooling and crystallizing the solution, wherein the temperature during crystallization is less than 50° C., to obtain product crystals.

[0032] The crystallization equipment is pre-equipped with a stirring mechanism and a cooling mechanism, and the exhaust gas generated in the crystallization process equipment is mainly water vapor, which is extracted by the induced draft fan and discharged outside the factory.

[0033] Preferably, the mother liquor in S7 is recovered to a mother liquor collection tank for temporary storage and then sent to the evaporation and concentration process in batches for utilization.

[0034] This design forms a recycling function for the mother liquor, further reflecting the environmental friendliness of this system.

[0035] Preferably, S8 is specifically as follows: sodium sulfide crystals are placed in a vacuum rake dryer, the dryer is sealed, the vacuum pump is turned on, the Roots blower is turned on, and after the vacuum table stabilizes, the circulating oil pump is turned on, and the circulating oil is heated to control the temperature of the circulating oil. The rake dryer is stirred at a uniform speed. After the equipment runs for a specified time, stirring is stopped, the upper valve of the dryer is closed, nitrogen is introduced into the dryer, the feeding port is opened, the material is quickly taken, and the residual water content is measured using a thermogravimetric analyzer. After the dehydration reaction is completed, the vacuum pump and the Roots blower are turned off, stirring is stopped, and the temperature is lowered and the material is discharged; wherein the vacuum degree must be ≥0.095MPa, and two-stage temperature is used for drying, one low temperature 80°C is heated for 1h; the second high temperature 108°C is heated for 0.5h; the material is cooled to below 40°C for discharge, and then screened and sent to a semi-automatic packaging machine for packaging to obtain anhydrous sodium sulfide (Na2S), and the anhydrous flaky sodium sulfide product is obtained by tabletting and packaging.

[0036] During the screening process, the unqualified materials screened out are dissolved and returned to the evaporation and concentration process.

[0037] The beneficial effects of the present invention are:

[0038] When used, the present invention has the characteristics of high efficiency in preparing sodium sulfide by reducing industrial waste salt containing sodium sulfate and high product purity, and realizes continuous, rapid and stable conversion of industrial waste salt containing sodium sulfate into sodium sulfide. The amount of dust in the reaction process is small, and environmental pollution is small. In addition, the system of the present invention has a short process, a simple structure, a small footprint, simple operation, high production efficiency, a high degree of automation, and has broad market prospects and significant economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0040] Figure 1 It is a process flow chart of a specific embodiment of the present invention. DETAILED DESCRIPTION

[0041] The following describes embodiments of the present invention in detail. Examples of the embodiments are shown in the accompanying drawings. Preferably, the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to explain the present invention, but are not to be construed as limiting the present invention.

[0042] In the description of the present invention, it should be understood that the terms "length," "width," "up," "down," "front," "back," "left," "right," "vertical," "horizontal," "top," "bottom," "inside," "outside," and the like, indicating positions or location relationships, are based on the positions or location relationships shown in the accompanying drawings and are intended only to facilitate the description of the present invention and simplify the description. They do not indicate or imply that the devices or elements referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limiting the present invention. Furthermore, in the description of the present invention, "plurality" means two or more, unless otherwise expressly and specifically defined.

[0043] See also Figure 1 The present invention provides a method for preparing anhydrous flaky sodium sulfide using industrial waste salt containing sodium sulfate, comprising the following steps:

[0044] S1: coke crushing, grinding and batching;

[0045] S2: roasting to produce a paddle-shaped sodium sulfide semi-finished product, and producing sodium sulfide by the coke reduction of sodium sulfate method;

[0046] S3: thermally leaching the sodium sulfide semi-finished product obtained in S2 to obtain a sodium sulfide solution;

[0047] S4: clarifying and filtering the sodium sulfide solution in S3 to obtain a sodium sulfide clear solution;

[0048] S5: Evaporation and concentration: the sodium sulfide clear liquid obtained in S4 is pumped into an evaporation and concentration device to obtain a sodium sulfide brine solution;

[0049] S6: Cooling and crystallizing, the sodium sulfide brine obtained in S5 is placed in a crystallization device, stirred, cooled and crystallized to obtain (Na2S.9H2O) product grains;

[0050] S7: Centrifugal separation: using a centrifuge to separate the solid and liquid of the crystals obtained in S6, and using mother liquor to wash the crystals. The separated crystals are cooled by air-cooled drums and then transported to the next process;

[0051] S8: Drying, screening, and packaging. The sodium sulfide crystals separated in S7 are dried using a dryer. After drying, they are screened and sent to a semi-automatic packaging machine for packaging to obtain anhydrous sodium sulfide (Na2S). The finished flakes are obtained by a tablet press and then packaged.

[0052] S1 is specifically as follows: the coke is crushed into particles less than 3mm in size by a hammer crusher and sent to the coke silo; the coke in the coke silo and the waste thenardite in the waste thenardite silo are respectively sent to the metering silo by a belt conveyor, mixed in proportion, and then sent to the converter.

[0053] S2 is specifically as follows: natural gas and excess air are introduced into the furnace for complete combustion; the temperature in the converter is controlled at 850-1250°C. After the furnace temperature reaches 900°C, the coke and waste thenardite react chemically to produce a paddle-shaped sodium sulfide semi-finished product. Sodium sulfide is produced by the coke reduction thenardite method.

[0054] The content of sodium sulfide solution in S3 is 28%.

[0055] S4 is specifically as follows: a sodium sulfide solution with a content of 28% is sent to one or more clarification tanks for standing to allow the suspended matter in the sodium sulfide solution to settle, the upper clear liquid in the clarification tank is pumped to the next-level supernatant liquid clarification tank, and the lower clear liquid in the clarification tank is discharged from the lower part of the tank through a pipe installed with a metal filter screen. The filtered lower clear liquid enters the next-level lower liquid clarification tank. The clarification and filtration of the next-level clarification tank are exactly the same as the above process. After multiple clarifications and filtrations, a sodium sulfide clear liquid is obtained, and the sodium sulfide clear liquid is sent to the next process.

[0056] S5 is specifically as follows: the sodium sulfide clear liquid is pumped to a tubular evaporator, evaporated and concentrated until the sodium sulfide content is greater than 32% to form sodium sulfide semen, and then pumped to a crystallization device.

[0057] S6 specifically comprises stirring the sodium sulfide semen in a crystallization device and cooling and crystallizing the solution. The temperature during crystallization is less than 50° C. to obtain product crystals.

[0058] The mother liquor in S7 is recovered to the mother liquor collection tank for temporary storage and then sent to the evaporation and concentration process in batches for utilization.

[0059] S8 is specifically as follows: sodium sulfide crystals are placed in a vacuum rake dryer, the dryer is sealed, the vacuum pump is turned on, the Roots blower is turned on, and after the vacuum gauge is stabilized, the circulating oil pump is turned on and the circulating oil is started to heat, the temperature of the circulating oil is controlled, and the rake dryer stirs at a uniform speed. After the equipment has run for a specified time, stirring is stopped, the upper valve of the dryer is closed, nitrogen is introduced into the dryer, the feeding port is opened, the material is quickly taken out, and the residual water content is measured using a thermogravimetric analyzer. After the dehydration reaction is completed, the vacuum pump and the Roots blower are turned off, stirring is stopped, and the material is cooled and discharged; the vacuum degree must be ≥0.095MPa, and two-stage temperature drying is adopted: a low temperature of 80°C for heating for 1h; a high temperature of 108°C for heating for 0.5h; the material is cooled to below 40°C and discharged, and then sent to a semi-automatic packaging machine for packaging after screening to obtain anhydrous sodium sulfide (Na2S), which is tableted by a tablet press to obtain anhydrous flaky sodium sulfide finished product and packaged. Specific embodiment one:

[0061] In this embodiment:

[0062] First, the coke is crushed into particles less than 3mm in size by a hammer crusher and sent to the coke silo. The coke in the coke silo and the waste thenardite in the waste thenardite silo are respectively sent to the metering silo by a belt conveyor. After being mixed in proportion, they are sent to the converter.

[0063] Secondly, natural gas and excess air are introduced into the above-mentioned furnace to achieve sufficient combustion; the temperature in the converter is controlled at 850-1250°C. After the furnace temperature reaches 900°C, the coke and the waste saltpeter react chemically to produce a paddle-shaped sodium sulfide semi-finished product. The coke reduction saltpeter method produces sodium sulfide;

[0064] Next, the sodium sulfide semi-finished product obtained above is subjected to thermal leaching to obtain a sodium sulfide solution with a content of 28%;

[0065] Next, the sodium sulfide solution with a content of 28% is sent to one or more clarification tanks and allowed to stand to allow the suspended matter in the sodium sulfide solution to settle. The upper clear liquid in the clarification tank is pumped to the next-level supernatant liquid clarification tank, and the lower clear liquid in the clarification tank is discharged from a pipe at the bottom of the tank. The pipe port is equipped with a metal filter. The filtered lower clear liquid enters the next-level lower liquid clarification tank. The clarification and filtration of the next-level clarification tank are exactly the same as the above process. After multiple clarification and filtration, a sodium sulfide clear liquid is obtained, and the sodium sulfide clear liquid is sent to the next process.

[0066] Next, the sodium sulfide clear liquid is pumped to a tubular evaporator, evaporated and concentrated to a sodium sulfide content greater than 32% to form a sodium sulfide semen, and then pumped to a crystallization device;

[0067] Next, the sodium sulfide semen is stirred in a crystallization device and cooled to crystallize. The temperature during crystallization is less than 50°C to obtain product crystals.

[0068] Then, the crystals obtained above are separated into solid and liquid by a centrifuge, and the mother liquor is used to wash the crystals. The separated crystals are cooled by an air-cooled drum and then transported to the next process. During the separation process, the mother liquor is recovered and temporarily stored in a mother liquor collection tank, and then sent to the evaporation and concentration process in batches for use;

[0069] Finally, the sodium sulfide crystals are placed in a vacuum rake dryer, the dryer is sealed, the vacuum pump is turned on, the Roots blower is turned on, and after the vacuum gauge is stable, the circulating oil pump is turned on and the circulating oil is started to heat. The temperature of the circulating oil is controlled, and the rake dryer is stirred at a uniform speed. After the equipment runs for a specified time, the stirring is stopped, the upper valve of the dryer is closed, nitrogen is introduced into the dryer, the feeding port is opened, the material is quickly taken out, and the residual water content is measured using a thermogravimetric analyzer. After the dehydration reaction is completed, the vacuum pump and the Roots blower are turned off, the stirring is stopped, and the temperature is lowered and the material is discharged; the vacuum degree must be ≥0.095MPa, and two-stage temperature drying is adopted: a low temperature of 80°C for heating for 1h; a high temperature of 108°C for heating for 0.5h; the material is cooled to below 40°C and discharged, and then sent to a semi-automatic packaging machine for packaging after screening to obtain anhydrous sodium sulfide (Na2S), which is tableted by a tablet press to obtain anhydrous flaky sodium sulfide finished product and packaged.

[0070] The above disclosure is only a preferred embodiment of the present invention, and certainly cannot be used to limit the scope of the rights of the present invention. Ordinary technicians in this field can understand that all or part of the processes of the above embodiment and equivalent changes made in accordance with the claims of the present invention are still within the scope of the invention.

Claims

1. A method for preparing anhydrous flaky sodium sulfide using industrial waste salt containing sodium sulfate, characterized in that: The following steps are involved: S1: coke crushing, grinding and batching; S2: roasting to produce a paddle-shaped sodium sulfide semi-finished product, and producing sodium sulfide by the coke reduction of sodium sulfate method; S3: thermally leaching the sodium sulfide semi-finished product obtained in S2 to obtain a sodium sulfide solution; S4: clarifying and filtering the sodium sulfide solution in S3 to obtain a sodium sulfide clear solution; S5: Evaporation and concentration: the sodium sulfide clear liquid obtained in S4 is pumped into an evaporation and concentration device to obtain a sodium sulfide brine solution; S6: Cooling and crystallizing, the sodium sulfide brine obtained in S5 is placed in a crystallization device, stirred, cooled and crystallized to obtain (Na2S.9H2O) product grains; S7: Centrifugal separation: Use a centrifuge to separate the solid and liquid of the crystals obtained in S6, and use the mother liquor to wash the crystals. The separated crystals are cooled by air-cooled drums and then transported to the next process; S8: Drying, screening, and packaging. The sodium sulfide crystals separated in S7 are dried using a dryer. After drying, they are screened and sent to a semi-automatic packaging machine for packaging to obtain anhydrous sodium sulfide (Na2S). The finished flakes are obtained by a tablet press and then packaged.

2. The method for preparing anhydrous flaky sodium sulfide using industrial waste salt containing sodium sulfate as claimed in claim 1, wherein: S1 is specifically as follows: the coke is crushed into particles less than 3mm in size by a hammer crusher and sent to the coke silo; the coke in the coke silo and the waste thenardite in the waste thenardite silo are respectively sent to the metering silo by a belt conveyor, mixed in proportion, and then sent to the converter.

3. The method for preparing anhydrous flaky sodium sulfide using industrial waste salt containing sodium sulfate as claimed in claim 1, wherein: S2 is specifically as follows: natural gas and excess air are introduced into the furnace for complete combustion; the temperature in the converter is controlled at 850-1250°C. After the furnace temperature reaches 900°C, the coke and waste thenardite react chemically to produce a paddle-shaped sodium sulfide semi-finished product. Sodium sulfide is produced by the coke reduction thenardite method.

4. The method for preparing anhydrous flaky sodium sulfide using industrial waste salt containing sodium sulfate as claimed in claim 1, wherein: The content of sodium sulfide solution in S3 is 28%.

5. The method for preparing anhydrous flaky sodium sulfide using industrial waste salt containing sodium sulfate as claimed in claim 1, wherein: S4 is specifically as follows: a sodium sulfide solution with a content of 28% is sent to one or more clarification tanks for standing to allow the suspended matter in the sodium sulfide solution to settle, the upper clear liquid in the clarification tank is pumped to the next-level supernatant liquid clarification tank, and the lower clear liquid in the clarification tank is discharged from the lower part of the tank through a pipe installed with a metal filter screen. The filtered lower clear liquid enters the next-level lower liquid clarification tank. The clarification and filtration of the next-level clarification tank are exactly the same as the above process. After multiple clarifications and filtrations, a sodium sulfide clear liquid is obtained, and the sodium sulfide clear liquid is sent to the next process.

6. The method for preparing anhydrous flaky sodium sulfide using industrial waste salt containing sodium sulfate as claimed in claim 1, wherein: S5 is specifically as follows: the sodium sulfide clear liquid is pumped to a tubular evaporator, evaporated and concentrated until the sodium sulfide content is greater than 32% to form sodium sulfide semen, and then pumped to a crystallization device.

7. The method for preparing anhydrous flaky sodium sulfide using industrial waste salt containing sodium sulfate as claimed in claim 1, wherein: S6 specifically comprises stirring the sodium sulfide semen in a crystallization device and cooling and crystallizing the solution. The temperature during crystallization is less than 50° C. to obtain product crystals.

8. The method for preparing anhydrous flaky sodium sulfide using industrial waste salt containing sodium sulfate as claimed in claim 1, characterized in that: The mother liquor in S7 is recovered to the mother liquor collection tank for temporary storage and then sent to the evaporation and concentration process in batches for utilization.

9. The method for preparing anhydrous flaky sodium sulfide using industrial waste salt containing sodium sulfate as claimed in claim 1, wherein: S8 is specifically as follows: sodium sulfide crystals are placed in a vacuum rake dryer, the dryer is sealed, the vacuum pump is turned on, the Roots blower is turned on, and after the vacuum gauge is stabilized, the circulating oil pump is turned on and the circulating oil is started to heat, the temperature of the circulating oil is controlled, and the rake dryer stirs at a uniform speed. After the equipment has run for a specified time, stirring is stopped, the upper valve of the dryer is closed, nitrogen is introduced into the dryer, the feeding port is opened, the material is quickly taken out, and the residual water content is measured using a thermogravimetric analyzer. After the dehydration reaction is completed, the vacuum pump and the Roots blower are turned off, stirring is stopped, and the material is cooled and discharged; the vacuum degree must be ≥0.095MPa, and two-stage temperature drying is adopted: a low temperature of 80°C for heating for 1h; a high temperature of 108°C for heating for 0.5h; the material is cooled to below 40°C and discharged, and then sent to a semi-automatic packaging machine for packaging after screening to obtain anhydrous sodium sulfide (Na2S), which is tableted by a tablet press to obtain anhydrous flaky sodium sulfide finished product and packaged.

Images