A salt slurry washing and purification system for salt and nitrate co-production process by evaporation method and a salt and nitrate co-production system

Abstract

The invention discloses a salt slurry washing and purification system for a salt-salt co-production process by evaporation method and a salt-salt co-production system, which comprises a salt discharge buffer tank, a first salt slurry pump, a cyclone, a washing salt slurry barrel, a second salt slurry pump, an elutriation overflow thickener, a salt centrifuge and a salt drying device, which are sequentially arranged behind the salt discharge foot of a salt group tank of the evaporation method salt-salt co-production system; the system has a low transformation cost, maintains the water and brine balance in the system without interfering with the operation of the existing system, can improve the purity of the finished salt to 99.9%, does not significantly increase energy consumption, and has significant economic benefits.

Description

Technical Field

[0001] The invention relates to the technical field of salt-nitrate co-production equipment by evaporation method, in particular to a salt slurry washing and purification system for a salt-nitrate co-production process by evaporation method and a salt-nitrate co-production system. Background Art

[0002] Under the condition of higher than normal temperature, the solubility of NaCl in the NaCl-Na2SO4-H2O brine system increases with the increase of temperature, while the solubility of Na2SO4 decreases with the increase of temperature. Based on this characteristic, domestic mineral salts are basically produced by the evaporation method of salt and nitrate co-production (see Figure 1 ).

[0003] Theoretically, according to the solubility characteristics of the solutes in the NaCl-Na2SO4-H2O brine, it is possible to extract NaCl and Na2SO4 with a purity close to 100% by cold crystallization and thermal evaporation. However, when the nitrate content of the original brine exceeds 30g / l, the dissolution of sodium sulfate back into the salt nitrate slurry by washing the original brine is limited, and the purpose of further purification cannot be achieved. Therefore, the purity of the finished salt can reach 99.6%, and the purity of the mirabilite can reach 99%, which cannot be further improved. Summary of the invention

[0004] The purpose of the present invention is to solve the problem that the prior art cannot further purify the purity of finished salt, and to propose a salt slurry washing and purification system for a salt-nitrate co-production process by evaporation.

[0005] In order to achieve the above-mentioned object, the present invention adopts the following technical scheme: a salt slurry washing and purification system for evaporation salt-salt co-production process, comprising a salt discharge buffer tank, a first salt slurry pump, a cyclone, a washing salt slurry barrel, a second salt slurry pump, an elutriation overflow thickener, a salt centrifuge and a salt drying device, which are sequentially arranged behind the salt discharge foot of the salt group tank of the evaporation salt-salt co-production system;

[0006] The salt discharge buffer tank is used to buffer and store the salt slurry discharged from the salt discharge foot of the salt group tank;

[0007] The first salt slurry pump is used to pump the salt slurry in the salt discharge buffer tank to the hydrocyclone;

[0008] The hydrocyclone is used to separate the salt slurry to obtain salt crystals and salt solution with high solid content;

[0009] The washing salt slurry barrel is used to mix and wash the salt crystals separated by the hydrocyclone with the refined brine overflowing from the washing overflow thickener;

[0010] The second salt slurry pump is used to pump the salt slurry obtained by mixing and washing in the washing salt slurry barrel to the washing overflow thickener;

[0011] The elutriation overflow thickener is used to concentrate the salt slurry and separate the salt solution and high-concentration salt crystals. A refined brine flushing pipeline is provided in the elutriation overflow thickener. The refined brine flushing pipeline is used to connect the inlet of the pipeline to the refined brine pipeline of the salt and saltpeter co-production by the evaporation method. The outlet of the refined brine flushing pipeline overflows to the elutriation salt slurry barrel.

[0012] The salt centrifuge is used to separate and dehydrate the high-purity salt slurry obtained from the elutriation overflow to obtain salt crystals;

[0013] The salt drying device is used to dry the salt crystals after centrifugation.

[0014] Furthermore, the salt solution obtained by the cyclone separation is introduced into the lower circulation pipe of the group tank of the evaporation method salt and nitrate co-production system through a pipeline.

[0015] Furthermore, the salt solution obtained by separation in the elutriation overflow thickener is refluxed to the salt mother liquor piping system of the evaporation method salt and nitrate co-production system.

[0016] Furthermore, the salt slurry washing and purification system for the evaporation method salt-nitrate co-production process also includes a pipe system for collecting the ground salt and salt dust removal water of the evaporation method salt-nitrate co-production system, and the pipe system pumps the low-concentration salt liquid into the washing salt slurry barrel to wash the salt slurry.

[0017] The present invention also provides an evaporation method salt-nitrate co-production system, which adds the aforementioned salt slurry washing and purification system for the evaporation method salt-nitrate co-production process on the basis of the existing evaporation method salt-nitrate co-production system.

[0018] The beneficial effect of the present invention is that, compared with the traditional evaporation method of salt and saltpeter co-production, it is impossible to further improve the purity of the finished salt. If it is forced to increase, the water-brine balance in the system will inevitably be disrupted, causing the system operation to be unstable and the quality of the finished salt to be unstable. The present method overcomes the above-mentioned defects and has a low transformation cost. On the basis of not interfering with the existing system operation, it maintains the water-brine balance in the system and can increase the purity of the finished salt to 99.9%. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a process flow chart of the salt and nitrate co-production process by evaporation method proposed by the present invention;

[0020] Figure 2 This is a general diagram of the salt slurry washing and purification system for the evaporation salt-nitrate co-production process proposed by the present invention and the evaporation salt-nitrate co-production system.

[0021] In the figure: 1. Salt discharge foot of salt group tank; 2. Circulation pipe under group tank; 3. Salt discharge buffer tank; 4. First salt slurry pump; 5. Cyclone; 6. Elutriation salt slurry barrel; 7. Second salt slurry pump; 8. Elutriation overflow thickener; 9. Salt centrifuge; 10. Salt mother liquor barrel; 11. Salt recovery barrel; 12. Salt drying device; 13. Dust removal device; A. Evaporation method salt and nitrate co-production system; B. Salt slurry elutriation and purification system for evaporation method salt and nitrate co-production process. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0023] In the description of this patent, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", and "set" should be understood in a broad sense, for example, it can be fixedly connected or set, or it can be detachably connected or set, or connected or set in one piece. For ordinary technicians in this field, the specific meanings of the above terms in this patent can be understood according to specific circumstances.

[0024] Reference Figure 1 The evaporation method of the existing technology of the salt and saltpeter co-production system uses refined brine to be fed downstream after condensation and secondary steam preheating, and 201 to 304 are evaporated to make salt, and the refined brine is discharged in the horizontal flow, and the washed salt is dehydrated and dried to obtain the finished salt; the salt making mother liquor is preheated by secondary steam in the flash tank 302 and the saltpeter making tank 301, and then enters the 301 heat pump saltpeter making evaporation tank for evaporation, and the product saltpeter is obtained after dehydration and drying. The actual production data are shown in Table 1.

[0025] Table 1 Production data of sodium sulfate brine introduced by evaporation method for salt and nitrate co-production

[0026]

[0027] The above data are collected after the production with the verified extremely stable process parameter settings. In order to ensure the stable yield and quality, the process parameters of each process stage in the system cannot be adjusted at will, otherwise it may cause many problems such as increased energy consumption and unstable salt quality. Therefore, how to maintain the balance in the original system and adopt a low-cost transformation to further improve the purity of the salt production has always been a difficult problem in the industry.

[0028] Example

[0029] like Figure 2As shown, a salt slurry washing and purification system for salt-salt co-production process by evaporation method comprises a salt discharge buffer tank 3, a first salt slurry pump 4, a cyclone 5, a washing salt slurry barrel 6, a second salt slurry pump 7, an elutriation overflow thickener 8, a salt centrifuge 9 and a salt drying device 12; the salt discharge buffer tank 3 buffers and stores the salt slurry discharged from the salt discharge foot 1 of the salt group tank; the first salt slurry pump 4 pumps the salt slurry in the salt discharge buffer tank 3 to the cyclone 5; the cyclone 5 separates the salt slurry to obtain salt crystals and salt solution with high solid content; the salt crystals are mixed with the refined brine overflowed from the elutriation overflow thickener 8 and The salt slurry is washed in the washing salt slurry barrel 6; the second salt slurry pump 7 pumps the salt slurry obtained by the mixed washing in the washing salt slurry barrel 6 to the washing overflow thickener 8; the washing overflow thickener 8 concentrates the mixed washed salt slurry in the washing salt slurry barrel 6 and separates the salt solution and high-concentration salt crystals. The washing overflow thickener 8 is provided with a refined brine flushing pipeline, which flushes the salt slurry in the washing overflow thickener 8. The inlet of the refined brine flushing pipeline is connected to the refined brine pipeline of the evaporation method salt and nitrate co-production, and the outlet of the refined brine flushing pipeline overflows to the washing salt slurry barrel 6; the salt centrifuge 9 separates and dehydrates the high-purity salt slurry obtained from the washing overflow to obtain salt crystals; the salt crystals are then dried by the salt drying device 12 and packaged into finished salt.

[0030] In order to reduce the waste of brine and balance the salt and brine components in the system, the brine separated by the cyclone 5 is introduced into the lower circulation pipe 2 of the group tank of the evaporation method salt and nitrate co-production system A through a pipeline.

[0031] In order to fully recycle the dissolved salt in the brine, the salt solution separated by the washing overflow thickener 8 is returned to the salt mother liquor pipeline system of the evaporation salt and nitrate co-production system A and finally merged into the circulation pipe 2 under the group tank.

[0032] In order to reduce the addition of clean water or brine to the system and reduce the evaporation heat load of the evaporation salt-nitrate co-production system A, the system is further provided with a pipe system 11 for collecting the ground salt and salt dust removal water of the evaporation salt-nitrate co-production system. The pipe system 11 pumps the collected low-concentration salt solution such as the scattered salt from the salt vibrating screen and the dust removal water from the salt drying into the washing salt slurry barrel 5 for washing the salt slurry.

[0033] The working principle of the present invention is as follows: the existing evaporative salt method nitrate co-production system A is limited by the characteristics of the mineral brine itself and the solutions of sodium sulfate and sodium chloride. When the nitrate content of the original brine exceeds 30g / l, it is impossible to further purify the finished salt through the method of cold crystallization and hot evaporation cycle. The purity of the finished salt reaches 99.6%, which is the theoretical limit. On the basis of the existing system, the present system uses refined brine to wash the salt slurry twice before dehydration and drying, so as to dilute the impurity ions in the salt slurry, and finally takes away the impurity ions through the salt solution by concentration, centrifugation and the like, so as to improve the purity of the finished salt. This system does not destroy the system balance of the existing evaporative salt method nitrate co-production system A, does not increase the heat load of evaporation and crystallization in the system, always maintains the water balance in the system, and has significant economic benefits.

[0034] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A salt slurry washing and purification system for salt and nitrate co-production process by evaporation, characterized by: It comprises a salt discharge buffer tank, a first salt slurry pump, a cyclone, an elutriation salt slurry barrel, a second salt slurry pump, an elutriation overflow thickener, a salt centrifuge and a salt drying device which are sequentially arranged behind the salt discharge foot of the salt group tank in the evaporation salt-salt co-production system; The salt discharge buffer tank is used to buffer and store the salt slurry discharged from the salt discharge foot of the salt group tank; The first salt slurry pump is used to pump the salt slurry in the salt discharge buffer tank to the hydrocyclone; The hydrocyclone is used to separate the salt slurry into salt crystals with high solid content and salt solution, and the salt solution separated by the hydrocyclone is introduced into the lower circulation pipe of the group tank of the salt-salt co-production system by evaporation through a pipeline; The washing salt slurry barrel is used to mix and wash the salt crystals obtained by the hydrocyclone separation with the refined brine overflowing from the washing overflow thickener, and the salt solution obtained by the washing overflow thickener separation is refluxed to the salt mother liquor piping system of the evaporation method salt and saltpeter co-production system; The second salt slurry pump is used to pump the salt slurry obtained by mixing and washing in the washing salt slurry barrel to the washing overflow thickener; The elutriation overflow thickener is used to concentrate the salt slurry in the elutriation salt slurry barrel and separate the salt solution and high-concentration salt crystals. A refined brine flushing pipeline is provided in the elutriation overflow thickener. The refined brine flushing pipeline is used to connect the inlet of the pipeline to the refined brine pipeline of the salt and saltpeter co-production by the evaporation method. The outlet of the refined brine flushing pipeline overflows to the elutriation salt slurry barrel. The salt centrifuge is used to separate and dehydrate the high-purity salt slurry obtained from the elutriation overflow to obtain salt crystals; The salt drying device is used to dry the salt crystals after centrifugation, and the salt crystals are then dried by the salt drying device and packaged into finished salt, and the purity of the finished salt reaches 99.9%; The purification system also includes a pipe system for collecting the ground salt and salt dust removal water of the evaporation salt-nitrate co-production system, and the pipe system pumps the low-concentration salt liquid to the washing salt slurry in the washing salt slurry barrel.

2. An evaporation method salt and nitrate co-production system, characterized by: The evaporation method salt-nitrate co-production system also includes the salt slurry washing and purification system for the evaporation method salt-nitrate co-production process as described in claim 1.

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