Process and apparatus for the production of ferrous sulfate monohydrate

Abstract

This invention provides a method and apparatus for preparing ferrous sulfate monohydrate. The preparation method includes the following steps: (1) dissolving ferrous sulfate heptahydrate solid in one or more of the secondary steam, high-temperature condensate, and crystal slurry generated during the evaporation and concentration of ferrous sulfate monohydrate filtrate to obtain a ferrous sulfate solution; (2) heating the ferrous sulfate solution to convert it into crystals, separating the solid and liquid to obtain ferrous sulfate monohydrate solid and ferrous sulfate monohydrate filtrate; (3) evaporating and concentrating the ferrous sulfate monohydrate filtrate with live steam to obtain secondary steam, high-temperature condensate, and crystal slurry, and then introducing the secondary steam and high-temperature condensate into the next cycle; (4) separating the crystal slurry to obtain ferrous sulfate monohydrate solid and crystal slurry filtrate; and then introducing the crystal slurry filtrate into the next cycle. This invention utilizes the high-temperature condensate and crystal slurry produced during the evaporation process to dissolve ferrous sulfate heptahydrate and provide a heat source, which improves resource utilization, saves energy and reduces consumption, and also reduces wastewater treatment costs.

Description

Technical Field

[0001] This invention relates to the field of chemical technology, and in particular to a method and apparatus for preparing ferrous sulfate monohydrate. Background Technology

[0002] The traditional wet process for producing ferrous sulfate monohydrate is as follows: Ferrous sulfate heptahydrate solid enters a pulping tank, where it is heated with steam to dissolve and obtain ferrous sulfate mother liquor. This mother liquor is then pumped to a wet crystallization tank for heating and crystallization. The water in the ferrous sulfate mother liquor evaporates, and it gradually dehydrates in the wet crystallization tank, transforming into grayish-white ferrous sulfate monohydrate crystals, i.e., crystal slurry. Once all the liquid in the tank has turned grayish-white, the transformed crystal slurry is separated into solid and liquid using a centrifuge. A portion of the filtrate after solid-liquid separation is returned to the pulping tank for reuse, while the remaining ferrous sulfate mother liquor is discharged for treatment.

[0003] Traditional wet production processes have the following drawbacks: the filtrate produced during the solid-liquid separation of ferrous sulfate monohydrate still contains about 29.6% dissolved ferrous sulfate. Only a portion of the filtrate is recycled, while the other portion is directly discharged, which wastes resources and increases wastewater treatment costs.

[0004] A Chinese patent document, CN113371763A, discloses a "Method and Apparatus for Producing Ferrous Sulfate Monohydrate." This invention features a crystallization tank equipped with a steam compressor, condenser, and solid-liquid separator, which is energy-saving and emission-reducing, significantly lowering the production cost of ferrous sulfate monohydrate crystals and thus has promotional value. However, this apparatus requires a steam compressor, resulting in high equipment and production costs. Summary of the Invention

[0005] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a method and apparatus for preparing ferrous sulfate monohydrate, which solves the problems of low resource utilization and high wastewater treatment costs in the traditional wet process of ferrous sulfate monohydrate production.

[0006] To achieve the above and other related objectives, the present invention provides a method for preparing ferrous sulfate monohydrate, comprising the following steps:

[0007] (1) Use one or more of the following as heat sources to dissolve ferrous sulfate heptahydrate solid: secondary steam generated during the evaporation and concentration of ferrous sulfate monohydrate filtrate, high-temperature condensate, and residual heat of crystal slurry, to obtain ferrous sulfate solution.

[0008] (2) The ferrous sulfate solution was heated to crystallize and then separated into solid and liquid to obtain ferrous sulfate monohydrate solid and ferrous sulfate monohydrate filtrate.

[0009] (3) The ferrous sulfate monohydrate filtrate obtained in step (2) is concentrated by evaporation of live steam to obtain secondary steam, high-temperature condensate and crystal slurry. The secondary steam and high-temperature condensate are then fed into step (1) for the next cycle.

[0010] (4) The solid-liquid separation step (3) yields ferrous sulfate monohydrate solid and slurry filtrate; the slurry filtrate is then fed into step (1) for the next cycle.

[0011] This application uses high-temperature and high-pressure live steam to evaporate, concentrate, and crystallize the ferrous sulfate monohydrate slurry or filtrate after crystallization. The secondary steam produced during the evaporation process is used for crystallization or dissolution of ferrous sulfate heptahydrate. At the same time, the high-temperature condensate and residual heat of the crystal slurry produced during the evaporation process are used to provide a heat source for dissolving ferrous sulfate heptahydrate. This not only improves resource utilization and saves energy and reduces consumption, but also reduces wastewater treatment costs.

[0012] Preferably, the temperature of the live steam is 120–300°C.

[0013] Preferably, step (1) further includes a low-temperature flash evaporation process of ferrous sulfate solution. In order to balance the secondary steam, high-temperature condensate and residual heat of crystal slurry obtained in step (3), the concentration of ferrous sulfate solution can be increased before crystallization by the low-temperature flash evaporation process of ferrous sulfate solution, while maximizing the utilization of the secondary steam, high-temperature condensate and residual heat of crystal slurry generated in step (3).

[0014] Preferably, step (3) further includes a flash evaporation process for the crystal slurry to obtain high-temperature flash steam and low-temperature crystal slurry. The low-temperature crystal slurry is then separated into solid and liquid components to obtain ferrous sulfate monohydrate and low-temperature crystal slurry filtrate. The high-temperature flash steam and low-temperature crystal slurry filtrate are then fed into step (1) for the next cycle. If the pulping process cannot balance the use of secondary steam, the pulping material can be subjected to low-temperature flash evaporation to evaporate a small amount of water.

[0015] This invention also provides an apparatus for preparing ferrous sulfate monohydrate, applied to the above-mentioned method for preparing ferrous sulfate monohydrate, comprising a pulping tank, a crystallization tank, a first solid-liquid separator, and an evaporator connected in sequence. The pulping tank is provided with a ferrous sulfate heptahydrate solid feed inlet, a high-temperature condensate inlet, a crystal slurry filtrate inlet, and a ferrous sulfate solution outlet. The crystallization tank includes a first ferrous sulfate solution feed inlet and a ferrous sulfate crystal slurry outlet. The pulping tank and / or the crystallization tank is provided with a secondary steam inlet. The first ferrous sulfate solution feed inlet is connected to the ferrous sulfate solution outlet. The first solid-liquid separator is used for solid-liquid separation of the ferrous sulfate crystal slurry discharged from the first ferrous sulfate crystal slurry outlet to obtain ferrous sulfate monohydrate solid and primary filtrate. The evaporator is provided with a primary filtrate inlet, a secondary steam outlet, a live steam inlet, a high-temperature condensate outlet, and a primary concentrated filtrate outlet. The secondary steam outlet is connected to the secondary steam inlet, the high-temperature condensate outlet is connected to the high-temperature condensate inlet, and the primary concentrated filtrate outlet is connected to the crystal slurry filtrate inlet.

[0016] Preferably, the pulping tank is equipped with a flash evaporator cooler.

[0017] Preferably, a flash evaporator and a second solid-liquid separator are sequentially provided between the evaporator and the pulping tank. The flash evaporator is provided with a high-temperature primary concentrated filtrate inlet, a flash steam outlet, and a low-temperature primary concentrated filtrate outlet. The second solid-liquid separator is used to separate the low-temperature primary concentrated filtrate discharged from the low-temperature primary concentrated filtrate outlet to obtain ferrous sulfate monohydrate solid and crystal slurry filtrate. The pulping tank is also provided with a flash steam inlet, which is connected to the flash steam outlet.

[0018] Preferably, the evaporator is further provided with a concentrated filtrate circulation outlet, which is connected to the primary filtrate inlet through a circulation pipeline, and a circulation pump is provided on the circulation pipeline.

[0019] This invention also provides a method for preparing ferrous sulfate hydrate, comprising the following steps:

[0020] (1) Use one or more of the following as heat sources to dissolve solid ferrous sulfate heptahydrate: secondary steam generated during the evaporation, concentration and crystallization of ferrous sulfate solution, high-temperature condensate and residual heat of crystal slurry, to obtain ferrous sulfate solution.

[0021] (2) The ferrous sulfate solution obtained in step (1) is concentrated by evaporation of live steam. The ferrous sulfate solution is converted into crystals at the same time as it is concentrated, and secondary steam, high-temperature condensate and crystal slurry are obtained. The secondary steam and high-temperature condensate are then fed into step (1) for the next cycle.

[0022] (3) The solid-liquid separation step (2) yields ferrous sulfate monohydrate solid and slurry filtrate; the slurry filtrate is then fed into step (1) for the next cycle.

[0023] Preferably, the process further includes the following steps: using the high-temperature condensate obtained in step (2) to preheat the ferrous sulfate solution obtained in step (1) to obtain low-temperature condensate and high-temperature ferrous sulfate solution, and then sending the low-temperature condensate into step (1) for the next cycle.

[0024] Preferably, step (1) further includes a low-temperature flash evaporation process of the ferrous sulfate solution. In order to balance the secondary steam, high-temperature condensate and residual heat of the crystal slurry obtained in step (2), this application increases the concentration of the ferrous sulfate solution by performing low-temperature flash evaporation on the ferrous sulfate solution obtained in step (1), while maximizing the utilization of the secondary steam, high-temperature condensate and residual heat of the crystal slurry generated in step (2).

[0025] The present invention also provides an apparatus for preparing ferrous sulfate monohydrate, applied to the above-mentioned method for preparing ferrous sulfate monohydrate, comprising a pulping tank, an evaporator, and a third solid-liquid separator. The pulping tank is provided with a ferrous sulfate heptahydrate solid feed inlet, a high-temperature condensate inlet, a crystal slurry filtrate inlet, a ferrous sulfate solution outlet, and a secondary steam inlet. The evaporator is provided with a second ferrous sulfate solution feed inlet, a secondary steam outlet, a live steam inlet, a high-temperature condensate outlet, and a crystal slurry outlet. The secondary steam outlet is connected to the secondary steam inlet, the high-temperature condensate outlet is connected to the high-temperature condensate inlet, and the ferrous sulfate solution outlet is connected to the first ferrous sulfate solution feed inlet. The third solid-liquid separator is used for solid-liquid separation of the ferrous sulfate crystal slurry discharged from the crystal slurry outlet to obtain ferrous sulfate monohydrate solid and crystal slurry filtrate.

[0026] Preferably, the pulping tank is equipped with a flash cooler, which is connected to a vacuum generator. The flash cooler has a cooling water inlet, a cooling water outlet, a low-concentration ferrous sulfate solution inlet, and a high-concentration ferrous sulfate solution outlet. The pulping tank has a low-concentration ferrous sulfate solution outlet and a high-concentration ferrous sulfate solution inlet. The low-concentration ferrous sulfate solution outlet is connected to the low-concentration ferrous sulfate solution inlet, and the high-concentration ferrous sulfate solution inlet is connected to the high-concentration ferrous sulfate solution outlet.

[0027] Preferably, a heat exchanger is provided between the pulping tank and the evaporator. The heat exchanger has a heat medium inlet, a heat medium outlet, a low-temperature ferrous sulfate solution inlet, and a high-temperature ferrous sulfate solution outlet. The heat medium inlet is connected to the high-temperature condensate drain outlet, and the heat medium outlet is connected to the high-temperature condensate inlet. The low-temperature ferrous sulfate solution inlet is connected to the ferrous sulfate solution outlet, and the high-temperature ferrous sulfate solution outlet is connected to the ferrous sulfate solution feed inlet.

[0028] Preferably, the evaporator is further provided with a crystal slurry circulation outlet, which is connected to the ferrous sulfate solution inlet through a circulation pipeline, and a circulation pump is provided on the circulation pipeline.

[0029] As described above, the present invention has the following beneficial effects: high-temperature and high-pressure live steam is used to evaporate, concentrate and crystallize the ferrous sulfate monohydrate slurry or filtrate after crystallization, and the secondary steam produced during the evaporation process is used for crystallization or dissolution of ferrous sulfate heptahydrate. At the same time, the high-temperature condensate and residual heat of the crystal slurry produced during the evaporation process are used to dissolve ferrous sulfate heptahydrate and provide a heat source, which not only improves resource utilization and saves energy and reduces consumption, but also reduces wastewater treatment costs. Attached Figure Description

[0030] Figure 1 The diagram shown is a schematic diagram of the apparatus for preparing ferrous sulfate monohydrate in Example 1.

[0031] Figure 2 The diagram shown is a schematic diagram of the apparatus for preparing ferrous sulfate monohydrate in Example 1.

[0032] Figure 3 The diagram shown is a schematic diagram of the apparatus for preparing ferrous sulfate monohydrate in Example 2.

[0033] Figure 4 The diagram shown is a schematic diagram of the apparatus for preparing ferrous sulfate monohydrate in Example 2.

[0034] Figure 5 The diagram shown is a structural schematic of the apparatus for preparing ferrous sulfate monohydrate as shown in Example 3.

[0035] Figure 6 The diagram shown is a schematic diagram of the apparatus for preparing ferrous sulfate monohydrate in Example 3.

[0036] Figure 7 The diagram shown is a structural schematic of the apparatus for preparing ferrous sulfate monohydrate as shown in Example 4.

[0037] Figure 8 The diagram shown is a schematic diagram of the apparatus for preparing ferrous sulfate monohydrate in Example 4.

[0038] Explanation of reference numerals: 1. Pulping tank; 11. Ferrous sulfate heptahydrate solid feed inlet; 12. High-temperature condensate inlet; 13. Crystal slurry filtrate inlet; 14. Ferrous sulfate solution outlet; 15. Flash steam inlet; 16. Flash cooler; 17. Vacuum generator; 161. Cooling water inlet; 162. Cooling water outlet; 163. Low-concentration ferrous sulfate solution inlet; 164. High-concentration ferrous sulfate solution outlet; 165. High-concentration ferrous sulfate solution inlet; 166. Low-concentration ferrous sulfate solution outlet; 2. Crystallization tank; 21. First ferrous sulfate solution inlet; 22. Secondary steam inlet; 23. Ferrous sulfate crystal slurry outlet; 3. First solid-liquid separator; 4. Evaporator 41. Primary filtrate inlet; 42. Secondary steam outlet; 43. Live steam inlet; 44. High-temperature condensate outlet; 45. Primary concentrated filtrate outlet; 46. Secondary ferrous sulfate solution inlet; 47. Crystal slurry outlet; 48. Concentrated filtrate circulation outlet; 49. Crystal slurry circulation outlet; 5. Flash evaporator; 51. High-temperature primary concentrated filtrate inlet; 52. Flash steam outlet; 53. Low-temperature primary concentrated filtrate outlet; 6. Second solid-liquid separator; 7. Third solid-liquid separator; 8. Heat exchanger; 81. Heat medium inlet; 82. Heat medium outlet; 83. Low-temperature ferrous sulfate solution inlet; 84. High-temperature ferrous sulfate solution outlet; 9. Circulation pump; 10. Transfer pump. Detailed Implementation

[0039] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0040] Example 1

[0041] like Figure 1As shown in the figure, this application provides an apparatus for preparing ferrous sulfate monohydrate, including a pulping tank 1, a wet crystallization tank 2, a first solid-liquid separator 3, and an evaporator 4 connected in sequence. The pulping tank is provided with a ferrous sulfate heptahydrate solid feed inlet 11, a high-temperature condensate inlet 12, a crystal slurry filtrate inlet 13, and a ferrous sulfate solution outlet 14. The wet crystallization tank includes a first ferrous sulfate solution inlet 21, a secondary steam inlet 22, and a ferrous sulfate crystal slurry outlet 23. The first ferrous sulfate solution inlet is connected to the ferrous sulfate solution outlet. The first solid-liquid separator is used for solid-liquid separation of the first ferrous sulfate solution... The ferrous sulfate slurry discharged from the ferrous slurry outlet yields ferrous sulfate monohydrate solid and primary filtrate. The evaporator is equipped with a primary filtrate inlet 41, a secondary steam outlet 42, a live steam inlet 43, a high-temperature condensate outlet 44, a primary concentrated filtrate outlet 45, and a concentrated filtrate circulation outlet 48. The concentrated filtrate circulation outlet is connected to the primary filtrate inlet via a circulation pipeline, on which a circulation pump 9 is installed. The secondary steam outlet is connected to the secondary steam inlet, the high-temperature condensate outlet is connected to the high-temperature condensate inlet, and the primary concentrated filtrate outlet is connected to the slurry filtrate inlet. A second solid-liquid separator 6 is installed between the evaporator 4 and the pulping tank 1. This separator separates the primary concentrated filtrate discharged from the primary concentrated filtrate outlet 45 of the evaporator 4 to obtain ferrous sulfate monohydrate solid and slurry filtrate. Transfer pumps 10 are installed between the pulping tank 1 and the wet crystallization tank 2, and between the wet crystallization tank 2 and the first solid-liquid separator 3. Both the first solid-liquid separator 3 and the second solid-liquid separator 6 use centrifuges.

[0042] This application also provides a method for preparing ferrous sulfate monohydrate based on the above-mentioned apparatus for preparing ferrous sulfate monohydrate, comprising the following steps:

[0043] Combination Figure 1 and Figure 2 Ferrous sulfate heptahydrate solid is fed into pulping tank 1 through ferrous sulfate heptahydrate solid feed port 11. The liquid used for pulping is 100°C crystal slurry filtrate produced by the second solid-liquid separator 6. The heat required for pulping tank is provided by 120°C high-temperature condensate, 100°C secondary steam and 100°C crystal slurry filtrate produced by evaporator 4. A 60°C ferrous sulfate solution is obtained. The 60°C ferrous sulfate solution is discharged from ferrous sulfate solution outlet 14 of pulping tank 1 and then pumped into wet crystallization tank 2 through first ferrous sulfate solution inlet 21 by transfer pump 10. The heat used for crystallization is 100°C secondary steam produced by evaporator 4. The ferrous sulfate solution is heated in crystallization tank and completely converted into 110°C ferrous sulfate monohydrate crystal slurry.

[0044] The 110℃ ferrous sulfate monohydrate crystal slurry was separated into solid and liquid by the first solid-liquid separator 3. The solid obtained was ferrous sulfate monohydrate, and the liquid was the 100℃ primary filtrate.

[0045] The 100°C primary filtrate is pumped into the evaporator 4 through the primary filtrate inlet 41 by the circulation pump 9. 120°C live steam is introduced through the live steam inlet 43 to evaporate and concentrate the primary filtrate, resulting in 100°C secondary steam and 105°C primary concentrated filtrate. Part of the 100°C secondary steam discharged from the secondary steam outlet 42 enters the crystallization tank 2 to provide heat for wet crystallization in the next cycle, and the other part enters the pulping tank 1 to dissolve the solid ferrous sulfate heptahydrate in the next cycle. Part of the 105°C primary concentrated filtrate is pumped back into the evaporator 4 through the primary filtrate inlet 41 by the circulation pump 9 for secondary evaporation and concentration. The other part of the 105°C primary concentrated filtrate is separated by the second solid-liquid separator 6 to obtain ferrous sulfate monohydrate and 100°C crystal slurry filtrate. The 100°C crystal slurry filtrate enters the pulping tank 1 through the crystal slurry filtrate inlet 13 to dissolve the solid ferrous sulfate heptahydrate in the next cycle.

[0046] Example 2

[0047] like Figure 3 As shown in the figure, this application provides an apparatus for preparing ferrous sulfate monohydrate, including a pulping tank 1, an evaporator 4, and a third solid-liquid separator 7. The pulping tank is equipped with a flash evaporator 16, which is connected to a vacuum generator 17. The flash evaporator has a cooling water inlet 161, a cooling water outlet 162, a low-concentration ferrous sulfate solution inlet 163, and a high-concentration ferrous sulfate solution outlet 164. The pulping tank has a high-concentration ferrous sulfate solution inlet 165 and a low-concentration ferrous sulfate solution outlet 166. The low-concentration ferrous sulfate solution outlet is connected to the low-concentration ferrous sulfate solution inlet, and the high-concentration ferrous sulfate solution inlet is connected to the high-concentration ferrous sulfate solution outlet. The pulping tank is also equipped with a ferrous sulfate heptahydrate solid feed inlet 11, a high-temperature condensate inlet 12, a crystal slurry filtrate inlet 13, a ferrous sulfate solution outlet 14, and a secondary steam inlet 22. The evaporator is equipped with a second ferrous sulfate solution inlet 46, a secondary steam outlet 42, a live steam inlet 43, a high-temperature condensate outlet 44, a crystal slurry outlet 47, and a crystal slurry circulation outlet 49. The crystal slurry circulation outlet is connected to the ferrous sulfate solution inlet through a circulation pipeline. A circulation pump 9 is installed on the circulation pipeline. The secondary steam outlet is connected to the secondary steam inlet. The high-temperature condensate outlet is connected to the high-temperature condensate inlet. The ferrous sulfate solution outlet is connected to the first ferrous sulfate solution inlet. The third solid-liquid separator is used for solid-liquid separation of the ferrous sulfate crystal slurry discharged from the crystal slurry outlet to obtain ferrous sulfate monohydrate solid and crystal slurry filtrate.

[0048] This application also provides a method for preparing ferrous sulfate monohydrate based on the above-mentioned apparatus for preparing ferrous sulfate monohydrate, comprising the following steps:

[0049] Combination Figure 3 and Figure 4 Ferrous sulfate heptahydrate solid is fed into pulping tank 1 through ferrous sulfate heptahydrate solid feed port 11. The liquid used for pulping is 100°C crystal pulp filtrate produced by the third solid-liquid separator 7. The heat required for pulping tank is provided by 100°C secondary steam produced by evaporator 4 and 100°C low-temperature condensate obtained after preheating ferrous sulfate solution by heat exchanger; 80°C low-concentration ferrous sulfate solution is obtained.

[0050] An 80°C low-concentration ferrous sulfate solution is flash-cooled by a flash evaporator 16 to produce high-temperature steam. This high-temperature steam is condensed by cooling water and discharged as condensate, simultaneously yielding a 70°C high-concentration ferrous sulfate solution. This condensate is returned to the pulping tank 1 from the high-concentration ferrous sulfate solution inlet 165 and pumped into the evaporator 4 from the ferrous sulfate solution outlet 14 via a transfer pump 10. 130°C live steam is introduced through the live steam inlet 43 to evaporate and concentrate the 70°C high-concentration ferrous sulfate solution, yielding 100°C secondary steam, 105°C ferrous sulfate slurry, and 130°C high-temperature condensate. The secondary steam... After being discharged from steam outlet 42, the steam enters the pulping tank 1 through secondary steam inlet 22 to dissolve the solid ferrous sulfate heptahydrate in the next cycle. A portion of the 105°C primary concentrated filtrate is pumped again from the second ferrous sulfate solution inlet 46 by circulation pump 9 into evaporator 4 for secondary evaporation and concentration. Another portion of the 105°C primary concentrated filtrate is separated by the third solid-liquid separator 7 to produce 100°C crystal slurry filtrate. The 100°C crystal slurry filtrate enters the pulping tank 1 through crystal slurry filtrate inlet 13 to dissolve the solid ferrous sulfate heptahydrate in the next cycle.

[0051] Example 3

[0052] like Figure 5As shown in the figure, this application provides an apparatus for preparing ferrous sulfate monohydrate, including a pulping tank 1, a wet crystallization tank 2, a first solid-liquid separator 3, and an evaporator 4 connected in sequence. The pulping tank is provided with a ferrous sulfate heptahydrate solid feed inlet 11, a high-temperature condensate inlet 12, a crystal slurry filtrate inlet 13, and a ferrous sulfate solution outlet 14. The wet crystallization tank includes a first ferrous sulfate solution inlet 21, a secondary steam inlet 22, and a ferrous sulfate crystal slurry outlet 23. The first ferrous sulfate solution inlet is connected to the ferrous sulfate solution outlet. The first solid-liquid separator is used for solid-liquid separation of the first ferrous sulfate solution... The ferrous sulfate slurry discharged from the ferrous slurry outlet yields ferrous sulfate monohydrate solid and primary filtrate. The evaporator is equipped with a primary filtrate inlet 41, a secondary steam outlet 42, a live steam inlet 43, a high-temperature condensate outlet 44, a primary concentrated filtrate outlet 45, and a concentrated filtrate circulation outlet 48. The concentrated filtrate circulation outlet is connected to the primary filtrate inlet via a circulation pipeline, on which a circulation pump 9 is installed. The secondary steam outlet is connected to the secondary steam inlet, the high-temperature condensate outlet is connected to the high-temperature condensate inlet, and the primary concentrated filtrate outlet is connected to the slurry filtrate inlet. A flash evaporator 5 and a second solid-liquid separator 6 are sequentially arranged between the evaporator and the pulping tank. The flash evaporator is equipped with a high-temperature primary concentrated filtrate inlet 51, a flash steam outlet 52, and a low-temperature primary concentrated filtrate outlet 53. The second solid-liquid separator is used to separate the low-temperature primary concentrated filtrate discharged from the low-temperature primary concentrated filtrate outlet to obtain ferrous sulfate monohydrate solid and slurry filtrate. A transfer pump 10 is provided between the pulping tank 1 and the wet crystallization tank 2, and between the wet crystallization tank 2 and the first solid-liquid separator 3. Both the first solid-liquid separator 3 and the second solid-liquid separator 6 are centrifuges.

[0053] This application also provides a method for preparing ferrous sulfate monohydrate based on the above-mentioned apparatus for preparing ferrous sulfate monohydrate, comprising the following steps:

[0054] Combination Figure 5 and Figure 6 Ferrous sulfate heptahydrate solid is fed into pulping tank 1 through ferrous sulfate heptahydrate solid feed port 11. The liquid used for pulping is the 80°C crystal pulp filtrate produced by the second solid-liquid separator 6. The heat required for pulping tank is provided by the 150°C high-temperature condensate produced by evaporator 4 and the 75°C flash steam produced by the flash evaporation of the 130°C primary concentrated filtrate; a 60°C ferrous sulfate solution is obtained.

[0055] After being discharged from the ferrous sulfate solution outlet 14 of the pulping tank 1, the 60℃ ferrous sulfate solution is pumped into the wet crystallization tank 2 through the first ferrous sulfate solution inlet 21 by the transfer pump 10. The heat used for crystallization is the 120℃ secondary steam produced by the evaporator 4. The ferrous sulfate solution is heated in the crystallization tank and completely converted into 110℃ ferrous sulfate monohydrate crystal slurry.

[0056] The 110℃ ferrous sulfate monohydrate crystal slurry was separated into solid and liquid by the first solid-liquid separator 3. The solid obtained was ferrous sulfate monohydrate, and the liquid was the 100℃ primary filtrate.

[0057] The 100℃ primary filtrate is pumped into the evaporator 4 through the primary filtrate inlet 41 by the circulation pump 9. 150℃ live steam is introduced through the live steam inlet 43 to evaporate and concentrate the primary filtrate, yielding 120℃ secondary steam and 130℃ primary concentrated filtrate. The secondary steam, after exiting through the outlet 42, enters the wet crystallization tank 2 through the secondary steam inlet 22 to provide heat for the wet crystallization process in the next cycle. A portion of the 130℃ primary concentrated filtrate is re-entered by the circulation pump 9 and pumped back into the evaporator 4 through the primary filtrate inlet 41 for secondary evaporation and concentration. Another portion enters the flash evaporator 5 from the high-temperature primary concentrated filtrate inlet 51 for flash evaporation, yielding 75°C flash steam and 85°C low-temperature concentrated filtrate. The 75°C flash steam exits from the flash steam outlet 52 and then enters the pulping tank 1 from the flash steam inlet 15, where it is used to dissolve the solid ferrous sulfate heptahydrate in the next cycle. The 85°C low-temperature concentrated filtrate undergoes solid-liquid separation in the second solid-liquid separator 6 to obtain ferrous sulfate monohydrate and 80°C crystal slurry filtrate. The 80°C crystal slurry filtrate enters the pulping tank 1 from the crystal slurry inlet 13, where it is used to dissolve the solid ferrous sulfate heptahydrate in the next cycle.

[0058] Example 4

[0059] like Figure 7As shown in the figure, this application provides an apparatus for preparing ferrous sulfate monohydrate, including a pulping tank 1, an evaporator 4, and a third solid-liquid separator 7. The pulping tank is provided with a ferrous sulfate heptahydrate solid feed port 11, a high-temperature condensate inlet 12, a crystal slurry filtrate inlet 13, a ferrous sulfate solution outlet 14, and a secondary steam inlet 22. The evaporator is provided with a second ferrous sulfate solution inlet 46, a secondary steam outlet 42, a live steam inlet 43, a high-temperature condensate outlet 44, a crystal slurry outlet 47, and a crystal slurry circulation outlet 49. The crystal slurry circulation outlet is connected to the ferrous sulfate solution inlet through a circulation pipeline, and a circulation pump 9 is provided on the circulation pipeline. The secondary steam outlet is connected to the secondary steam inlet, the high-temperature condensate outlet is connected to the high-temperature condensate inlet, and the ferrous sulfate solution outlet is connected to the first ferrous sulfate solution inlet. The third solid-liquid separator is used to separate the ferrous sulfate crystal slurry discharged from the crystal slurry outlet to obtain ferrous sulfate monohydrate solid and crystal slurry filtrate. A heat exchanger 8 is provided between the pulping tank and the evaporator. The heat exchanger has a heat medium inlet 81, a heat medium outlet 82, a low-temperature ferrous sulfate solution inlet 83, and a high-temperature ferrous sulfate solution outlet 84. The heat medium inlet is connected to the high-temperature condensate drain outlet, and the heat medium outlet is connected to the high-temperature condensate inlet. The low-temperature ferrous sulfate solution inlet is connected to the ferrous sulfate solution outlet, and the high-temperature ferrous sulfate solution outlet is connected to the ferrous sulfate solution feed inlet. A transfer pump 10 is provided between the pulping tank 1 and the heat exchanger 4.

[0060] This application also provides a method for preparing ferrous sulfate monohydrate based on the above-mentioned apparatus for preparing ferrous sulfate monohydrate, comprising the following steps:

[0061] Combination Figure 7 and Figure 8 Ferrous sulfate heptahydrate solid is fed into pulping tank 1 through ferrous sulfate heptahydrate solid feed port 11. The liquid used for pulping is 100°C crystal pulp filtrate produced by the third solid-liquid separator 7. The heat required for pulping tank is provided by 100°C secondary steam produced by evaporator 4 and 100°C low-temperature condensate obtained after preheating ferrous sulfate solution by heat exchanger; 80°C ferrous sulfate solution is obtained.

[0062] The 80℃ ferrous sulfate solution is preheated by heat exchanger 8 to obtain a 100℃ ferrous sulfate solution. The heat medium of heat exchanger 8 is the 150℃ high-temperature condensate generated by evaporator 4. The 100℃ low-temperature condensate generated enters the pulping tank 1 from the high-temperature condensate inlet 12 to dissolve the solid ferrous sulfate heptahydrate in the next cycle.

[0063] A 100°C ferrous sulfate solution is pumped into the evaporator 4 through the second ferrous sulfate solution inlet 46 by the circulation pump 9. 150°C live steam is introduced through the live steam inlet 43 to evaporate and concentrate the 100°C ferrous sulfate solution, yielding 100°C secondary steam, 105°C ferrous sulfate slurry, and 150°C high-temperature condensate. The secondary steam, after exiting through the secondary steam outlet 42, enters the pulping tank 1 through the secondary steam inlet 22 to dissolve the heptahydrate solid ferrous sulfate in the next cycle. A portion of the 130°C primary concentrated filtrate is then... The circulating pump 9 pumps the second ferrous sulfate solution into the evaporator 4 again for secondary evaporation and concentration; another part of the 130°C concentrated filtrate is separated into 100°C crystal slurry filtrate by the third solid-liquid separator 7. The 100°C crystal slurry filtrate enters the pulping tank 1 from the crystal slurry filtrate inlet 13 to dissolve the heptahydrate ferrous sulfate solid in the next cycle; the 150°C high-temperature condensate enters the heat exchanger 8 from the heat medium inlet 81 to preheat the ferrous sulfate solution to be concentrated and crystallized in the next cycle.

[0064] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for preparing ferrous sulfate monohydrate, characterized in that, Includes the following steps: (1) Use one or more of the following as heat sources to dissolve ferrous sulfate heptahydrate solid during the evaporation and concentration of ferrous sulfate monohydrate filtrate: secondary steam, high-temperature condensate, and residual heat of crystal slurry, to obtain ferrous sulfate solution. (2) The ferrous sulfate solution was heated to crystallize and the solid and liquid were separated to obtain ferrous sulfate monohydrate solid and ferrous sulfate monohydrate filtrate. (3) The ferrous sulfate monohydrate filtrate obtained in step (2) is concentrated by evaporation with live steam to obtain secondary steam, high-temperature condensate and crystal slurry. The secondary steam and high-temperature condensate are then fed into step (1) for the next cycle. (4) The solid-liquid separation step (3) yields ferrous sulfate monohydrate solid and slurry filtrate; the slurry filtrate is then fed into step (1) for the next cycle.

2. The preparation method according to claim 1, characterized in that, Step (1) also includes a low-temperature flash evaporation process of ferrous sulfate solution; Step (3) also includes a flash evaporation process of crystal slurry to obtain high-temperature flash steam and low-temperature crystal slurry, and solid-liquid separation of low-temperature crystal slurry to obtain ferrous sulfate monohydrate and low-temperature crystal slurry filtrate; the high-temperature flash steam and low-temperature crystal slurry filtrate are then fed into step (1) for the next cycle.

3. A method for preparing ferrous sulfate monohydrate, characterized in that, Includes the following steps: (1) Use one or more of the following as heat sources to dissolve solid ferrous sulfate heptahydrate: secondary steam generated during the evaporation, concentration and crystallization of ferrous sulfate solution, high-temperature condensate and residual heat of crystal slurry, to obtain ferrous sulfate solution. (2) The ferrous sulfate solution obtained in step (1) is concentrated by evaporating live steam. The ferrous sulfate solution is converted into crystals at the same time as it is concentrated, resulting in secondary steam, high-temperature condensate and crystal slurry. The secondary steam and high-temperature condensate are then fed into step (1) for the next cycle. (3) The solid-liquid separation step (2) yields ferrous sulfate monohydrate solid and slurry filtrate; the slurry filtrate is then fed into step (1) for the next cycle.

4. The method for preparing ferrous sulfate monohydrate according to claim 3, characterized in that: It also includes the following processes: The high-temperature condensate obtained in step (2) is used to preheat the ferrous sulfate solution obtained in step (1) to obtain low-temperature condensate and high-temperature ferrous sulfate solution. The low-temperature condensate is then fed into step (1) for the next cycle. Step (1) also includes a low-temperature flash evaporation process of the ferrous sulfate solution.

5. An apparatus for preparing ferrous sulfate monohydrate, characterized in that: The method for preparing ferrous sulfate heptahydrate as described in claim 1 or 2 includes a pulping tank (1), a crystallization tank (2), a first solid-liquid separator (3), and an evaporator (4) connected in sequence. The pulping tank is provided with a ferrous sulfate heptahydrate solid feed inlet (11), a high-temperature condensate inlet (12), a crystal slurry filtrate inlet (13), and a ferrous sulfate solution outlet (14). The crystallization tank includes a first ferrous sulfate solution inlet (21) and a ferrous sulfate crystal slurry outlet (23). The pulping tank and / or the crystallization tank are provided with a secondary steam inlet (22). The feed inlet is connected to the ferrous sulfate solution outlet. The first solid-liquid separator is used to separate the ferrous sulfate crystal slurry discharged from the first ferrous sulfate crystal slurry outlet to obtain ferrous sulfate monohydrate solid and primary filtrate. The evaporator is provided with a primary filtrate inlet (41), a secondary steam outlet (42), a live steam inlet (43), a high-temperature condensate outlet (44), and a primary concentrated filtrate outlet (45). The secondary steam outlet is connected to the secondary steam inlet, the high-temperature condensate outlet is connected to the high-temperature condensate inlet, and the primary concentrated filtrate outlet is connected to the crystal slurry filtrate inlet.

6. The preparation apparatus according to claim 5, characterized in that: The pulping tank is equipped with a flash evaporator cooler; between the evaporator and the pulping tank, there is a flash evaporator (5) and a second solid-liquid separator (6) in sequence. The flash evaporator is equipped with a high-temperature primary concentrated filtrate inlet (51), a flash steam outlet (52) and a low-temperature primary concentrated filtrate outlet (53). The second solid-liquid separator is used to separate the low-temperature primary concentrated filtrate discharged from the low-temperature primary concentrated filtrate outlet to obtain ferrous sulfate monohydrate solid and crystal slurry filtrate. The pulping tank is also equipped with a flash steam inlet (15), which is connected to the flash steam outlet. The evaporator is also equipped with a concentrated filtrate circulation outlet (48), which is connected to the primary filtrate inlet through a circulation pipeline. A circulation pump (9) is provided on the circulation pipeline.

7. An apparatus for preparing ferrous sulfate monohydrate, characterized in that: The method for preparing ferrous sulfate heptahydrate as described in claim 3 or 4 includes a pulping tank (1), an evaporator (4), and a third solid-liquid separator (7). The pulping tank is provided with a ferrous sulfate heptahydrate solid feed port (11), a high-temperature condensate inlet (12), a crystal slurry filtrate inlet (13), a ferrous sulfate solution outlet (14), and a secondary steam inlet (22). The evaporator is provided with a second ferrous sulfate solution feed port (46), a secondary steam outlet (42), a live steam inlet (43), a high-temperature condensate outlet (44), and a crystal slurry outlet (47). The secondary steam outlet is connected to the secondary steam inlet, the high-temperature condensate outlet is connected to the high-temperature condensate inlet, and the ferrous sulfate solution outlet is connected to the second ferrous sulfate solution feed port. The third solid-liquid separator is used for solid-liquid separation of ferrous sulfate crystal slurry discharged from the crystal slurry outlet to obtain ferrous sulfate monohydrate solid and crystal slurry filtrate.

8. The preparation apparatus according to claim 7, characterized in that: The pulping tank is equipped with a flash cooler (16), which is connected to a vacuum generator (17). The flash cooler is equipped with a cooling water inlet (161), a cooling water outlet (162), a low-concentration ferrous sulfate solution inlet (163), and a high-concentration ferrous sulfate solution outlet (164). The pulping tank is equipped with a high-concentration ferrous sulfate solution inlet (165) and a low-concentration ferrous sulfate solution outlet (166). The low-concentration ferrous sulfate solution outlet is connected to the low-concentration ferrous sulfate solution inlet, and the high-concentration ferrous sulfate solution inlet is connected to the high-concentration ferrous sulfate solution outlet.

9. The preparation apparatus according to claim 7, characterized in that: A heat exchanger (8) is provided between the pulping tank and the evaporator. The heat exchanger is provided with a heat medium inlet (81), a heat medium outlet (82), a low-temperature ferrous sulfate solution inlet (83), and a high-temperature ferrous sulfate solution outlet (84). The heat medium inlet is connected to the high-temperature condensate drain outlet, and the heat medium outlet is connected to the high-temperature condensate inlet. The low-temperature ferrous sulfate solution inlet is connected to the ferrous sulfate solution outlet, and the high-temperature ferrous sulfate solution outlet is connected to the second ferrous sulfate solution inlet.

10. The preparation apparatus according to claim 7, characterized in that: The evaporator is also provided with a crystal slurry circulation outlet (49), which is connected to the second ferrous sulfate solution inlet through a circulation pipeline, and a circulation pump (9) is provided on the circulation pipeline.

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