阅读说明：本技术 一种利用制盐废液生产精制盐的工艺及系统 (Process and system for producing refined salt by using salt production waste liquid ) 是由 张刚 贾启 庞学雷 王立宽 纪培良 于 2020-12-21 设计创作，主要内容包括：本发明涉及制盐技术领域,具体涉及一种利用制盐废液生产精制盐的工艺,包括如下步骤：(1)过滤预热：利用半透膜对制盐废液进行过滤,然后进入预热器进行预热,得到初级废液；(2)蒸发增稠：将初级废液进行加热蒸发,生成浓度为32-35°Be’的次级废液；(3)降温析晶：将次级废液进行降温冷却,过滤除去次生废液得结晶盐浆；(4)洗涤脱水：结晶盐浆进入洗盐器进行饱和卤水洗涤,洗涤后的结晶盐浆进入储盐仓,随后经旋流器进入离心机脱水形成湿盐,离心机脱除的卤水母液回流至洗盐器；(5)干燥。本发明经过优化工艺,避免了制盐过程中发生堵塞和精制盐结块现象的发生,进而保证了制盐生产的连续和稳定。(The invention relates to the technical field of salt production, in particular to a process for producing refined salt by using salt production waste liquid, which comprises the following steps: (1) filtering and preheating: filtering the salt production waste liquid by using a semipermeable membrane, and then preheating the salt production waste liquid by using a preheater to obtain primary waste liquid; (2) and (3) evaporation thickening: heating and evaporating the primary waste liquid to generate secondary waste liquid with the concentration of 32-35 degrees Be'; (3) cooling and crystallizing: cooling the secondary waste liquid, and filtering to remove the secondary waste liquid to obtain crystallized salt slurry; (4) washing and dewatering: the crystallized salt slurry enters a salt washer to be washed by saturated brine, the washed crystallized salt slurry enters a salt storage bin, then enters a centrifuge through a swirler to be dehydrated to form wet salt, and brine mother liquor removed by the centrifuge flows back to the salt washer; (5) and (5) drying. The invention avoids the phenomena of blockage and refined salt agglomeration in the salt production process by optimizing the process, thereby ensuring the continuity and stability of the salt production.)

1. A process for producing refined salt by using salt production waste liquid is characterized by comprising the following steps:

(1) filtering and preheating: filtering the salt making waste liquid by utilizing a semipermeable membrane, increasing the concentration of the salt making waste liquid, and then preheating the salt making waste liquid in a preheater to obtain primary waste liquid;

(2) and (3) evaporation thickening: heating and evaporating the primary waste liquid to generate secondary waste liquid with the concentration of 32-35 degrees Be';

(3) cooling and crystallizing: cooling the secondary waste liquid to generate crystallized salt slurry and secondary waste liquid, and filtering to remove the secondary waste liquid to obtain crystallized salt slurry;

(4) washing and dewatering: the crystallized salt slurry enters a salt washer to be washed by saturated brine, the washed crystallized salt slurry enters a salt storage bin, then enters a centrifuge through a swirler to be dehydrated to form wet salt, and brine mother liquor removed by the centrifuge flows back to the salt washer;

(5) and (3) drying: and (4) drying the wet salt obtained in the step (4) to obtain refined salt.

2. The process for producing refined salt by using the waste liquid from salt production as claimed in claim 1, wherein the preheating temperature in the step (1) is 70-80 ℃ and the preheating time is 15-30 min.

3. The process for producing refined salt by using the waste liquid from salt production as claimed in claim 1, wherein the heating temperature in the step (2) is 110-115 ℃, and the evaporation time is 30-60 min.

4. The process for producing refined salt by using the waste liquid of salt production as claimed in claim 1, wherein the temperature in the step (3) is reduced to 25-30 ℃ for 60-90 min.

5. The process for producing refined salt by using the waste liquid of salt production as claimed in claim 1, wherein the rotational speed of the cyclone in the step (4) is 1500-.

6. The process for producing refined salt by using the waste liquid from salt production as claimed in claim 1, wherein the reflux ratio in the step (4) is 1: 7-11.

7. The process for producing refined salt using the waste liquid from salt production as claimed in claim 1, wherein the drying device in the step (5) is a vibrating fluidized bed dryer.

8. A system for producing refined salt by using salt manufacturing waste liquid as claimed in any one of claims 1-7, characterized by comprising a semipermeable membrane (1), a preheater (2), an evaporator (3), a cooling device (4), a salt washer (5), a salt storage bin (6), a cyclone (7), a centrifuge (8) and a drying device (10) which are connected in sequence, wherein the outlet of the centrifuge (8) is connected with the salt washer (10) through a return pipeline (9).

Technical Field

The invention relates to the technical field of salt production, in particular to a process and a system for producing refined salt by using salt production waste liquid.

Background

Salts are parent to the chemical industry and have a wide range of uses. In the production process of salt, a large amount of salt-making waste liquid is generated, the concentration of the salt-making waste liquid is about 27 degrees Be', the salt-making waste liquid contains a large amount of salt, and the direct discharge can cause environmental pollution, so that the salt-making waste liquid needs to Be comprehensively utilized, and the resource utilization rate is improved. Based on this, patent ZL200710057195.3 discloses a preparation process for producing refined salt by using salt-making waste liquid as raw material, which comprises the following steps: evaporating and concentrating, thickening mother liquor, recovering bitter salt, washing and dehydrating, drying and packaging; the advanced vacuum salt making technology and salt washing technology are adopted to produce high-quality industrial salt, so that the yield and the quality of the industrial salt are improved; however, the process has high labor intensity and low preparation rate of the crystallized salt slurry, so the patent application with the application number of 201810462404.0 is improved on the basis, and provides a preparation process for producing refined salt by taking the salt-making waste liquid as a raw material, which comprises the following steps: semi-permeable filtering, evaporating for thickening, cooling for crystallization, collecting crystals, washing for dehydration, drying and packaging; the invention utilizes the semipermeable membrane to prepare the primary liquid, reduces the labor intensity of workers, and carries out cooling crystallization after evaporation and thickening, thereby quickening the speed of generating the crystallized salt slurry and improving the preparation efficiency of the crystallized salt slurry. However, the process has the following problems after practical popularization and application: firstly, the centrifugal drying process is easy to block, so that salt discharge cannot be continuous, and energy consumption is increased; secondly, the drying is not thorough, and the produced salt is easy to agglomerate.

Disclosure of Invention

Aiming at the problems of easy blockage and easy caking of the obtained salt in the conventional process for producing the refined salt by using the salt production waste liquid, the invention provides the process and the system for producing the refined salt by using the salt production waste liquid, and through the optimization process, the blockage and the caking of the refined salt in the salt production process are avoided, so that the continuity and the stability of the salt production are ensured, and the preparation efficiency is improved.

The invention provides a process for producing refined salt by using salt production waste liquid, which comprises the following steps:

(1) filtering and preheating: filtering the salt making waste liquid by utilizing a semipermeable membrane, increasing the concentration of the salt making waste liquid, and then preheating the salt making waste liquid in a preheater to obtain primary waste liquid;

(2) and (3) evaporation thickening: heating and evaporating the primary waste liquid to generate secondary waste liquid with the concentration of 32-35 degrees Be';

(3) cooling and crystallizing: cooling the secondary waste liquid to generate crystallized salt slurry and secondary waste liquid, and filtering to remove the secondary waste liquid to obtain crystallized salt slurry;

(4) washing and dewatering: the crystallized salt slurry enters a salt washer to be washed by saturated brine, the washed crystallized salt slurry enters a salt storage bin, then enters a centrifuge through a swirler to be dehydrated to form wet salt, and brine mother liquor removed by the centrifuge flows back to the salt washer;

(5) and (3) drying: and (4) drying the wet salt obtained in the step (4) to obtain refined salt.

Wherein the content of the first and second substances,

the concentration of the salt production waste liquid filtered in the step (1) is not less than 28 degrees Be', which is beneficial to subsequent evaporation and thickening.

In the step (1), the preheating temperature is 70-80 ℃, and the preheating time is 15-30 min. Preheating is carried out before evaporation thickening, so that energy consumption can be reduced, and the evaporation thickening effect can be improved.

The heating temperature in the step (2) is 110-115 ℃, and the evaporation time is 30-60 min. Under the heating evaporation condition, the content of precipitated NaCl is the largest.

And (4) cooling to 25-30 ℃ in the step (3), wherein the cooling time is 60-90 min. The cooling crystallization is carried out, the speed of generating the crystallized salt slurry can be accelerated, and the preparation efficiency of the crystallized salt slurry is improved.

The rotating speed of the cyclone in the step (4) is 1500-. The solid-liquid ratio is controlled, and the thickening and uniform feeding of the salt slurry are realized.

The reflux ratio in the step (4) is 1: 7-11. A flow of brine mother liquor is introduced into the downstream of the centrifugal machine and is merged into the salt washer, so that the flow rate in a slurry pipeline is kept reasonable, and crystal deposition and blockage are avoided.

And (5) the drying equipment is a vibrating fluidized bed dryer. The hot air passes through the wet salt for drying, so that the caking phenomenon in the drying process can be prevented, and the drying efficiency is improved.

The invention also aims to provide a system for producing refined salt by using the salt production waste liquid, which comprises a semipermeable membrane, a preheater, an evaporator, a cooling device, a salt washer, a salt storage bin, a cyclone, a centrifuge and a drying device which are sequentially connected, wherein an outlet of the centrifuge is connected with the salt washer through a return pipeline.

The beneficial effect of the invention is that,

(1) the salt production waste liquid is preheated by the preheater and then evaporated and thickened, so that the energy consumption can be reduced, and the evaporation and thickening effects can be improved; the concentration of the secondary waste liquid is maintained to Be 32-35 DEG Be', the preparation efficiency of the crystallized salt slurry is low if the concentration is too low, and the system is easy to Be unstable if the concentration is too high; the washed crystallized salt slurry is not guided into a settler for thickening, but enters a salt storage bin, and can be temporarily stored if the later centrifugation and other processes have faults such as blockage, so that the continuous and stable production process is ensured; brine mother liquor removed by the centrifuge is refluxed to the salt washer to maintain the reasonable flow velocity in the slurry pipeline, so that the deposition and blockage of crystals are avoided;

(2) according to the process and the system for producing the refined salt by using the salt production waste liquid, provided by the invention, through an optimized process, the phenomena of blockage and refined salt agglomeration in the salt production process are avoided, the continuity and stability of the salt production are further ensured, and the preparation efficiency is indirectly improved.

Drawings

FIG. 1 is a schematic diagram of a system for producing refined salt by using a salt production waste liquid provided by the invention;

in the figure, 1, a semipermeable membrane; 2. a preheater; 3. an evaporator; 4. a cooling device; 5. a salt washer; 6. a salt storage bin; 7. a swirler; 8. a centrifuge; 9. a return line; 10. and (7) a drying device.

Detailed Description

In order to make those skilled in the art better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The system provided by the invention is adopted in the following embodiment for producing refined salt, the system comprises a semipermeable membrane 1, a preheater 2, an evaporator 3, a cooling device 4, a salt washer 5, a salt storage bin 6, a cyclone 7, a centrifuge 8 and a drying device 10 which are connected in sequence, and an outlet of the centrifuge 8 is connected with the salt washer 10 through a return pipeline 9; wherein the drying device 10 is a vibrating fluidized bed dryer, and the rest devices are conventional, for example, the salt washer can be a multi-stage horizontal salt washer.

Example 1

Salt-making waste liquid is collected from a salt-making area I of a salt-making field of the company, and the sampling analysis results are shown in the table 1:

TABLE 1 chemical composition of the salt waste liquid collected from the salt production zone of this company

A process for producing refined salt by using salt-making waste liquid comprises the following steps:

(1) filtering and preheating: filtering the salt making waste liquid by using a semipermeable membrane, increasing the concentration of the salt making waste liquid to Be not less than 28-degree Be', and then preheating the salt making waste liquid in a preheater, wherein the preheating temperature is 80 ℃, and the preheating time is 15min, so as to obtain primary waste liquid;

(2) and (3) evaporation thickening: heating the primary waste liquid to 110 ℃ and evaporating for 60min to generate secondary waste liquid with the concentration of 35 DEG Be';

(3) cooling and crystallizing: cooling the secondary waste liquid to 30 ℃ for 75 min; generating crystallized salt slurry and secondary waste liquid, and filtering to remove the secondary waste liquid to obtain crystallized salt slurry;

(4) washing and dewatering: the crystallized salt slurry enters a salt washer to be washed by saturated brine, the washed crystallized salt slurry enters a salt storage bin, then enters a centrifuge through a swirler (the rotating speed of the swirler is 2000r/min) to be dehydrated to form wet salt, and brine mother liquor removed by the centrifuge flows back to the salt washer; wherein the reflux ratio is 1:7, and a strand of brine mother liquor is introduced into the downstream of the centrifuge and is merged into the salt washer, so that the flow rate in the slurry pipeline is kept reasonable, and the deposition and blockage of crystals are avoided.

(5) And (3) drying: and (4) drying the wet salt obtained in the step (4) in a vibrating fluidized bed dryer to obtain refined salt.

By the process provided by the embodiment 1, after the system runs for a period of time in summer, the system has no blocking phenomenon, the salt production process is continuous and stable, and the preparation efficiency is indirectly improved; the obtained refined salt has no caking and high quality, and can reach the standard value in the industrial salt standard, and the data is shown in Table 2:

table 2 quality standards of the refined salt

Index name	Quality standard
		Sodium chloride	≥99.1％
Calcium magnesium ion	＜0.5％
		Sulfate ion	＜0.5％
Moisture content	＜0.5％

Example 2

Salt-making waste liquid is collected from a salt-making four-zone of a salt-making field of the company, and the sampling analysis results are shown in a table 3:

TABLE 3 chemical composition of salt waste liquid collected from four regions of salt production of this company

A process for producing refined salt by using salt-making waste liquid comprises the following steps:

(1) filtering and preheating: filtering the salt making waste liquid by using a semipermeable membrane, increasing the concentration of the salt making waste liquid to Be not less than 28-degree Be', and then preheating the salt making waste liquid in a preheater, wherein the preheating temperature is 70 ℃, and the preheating time is 30min, so as to obtain primary waste liquid;

(2) and (3) evaporation thickening: heating the primary waste liquid to 113 ℃ and evaporating for 45min to generate secondary waste liquid with the concentration of 32-degree Be';

(3) cooling and crystallizing: cooling the secondary waste liquid to 25 ℃ for 60 min; generating crystallized salt slurry and secondary waste liquid, and filtering to remove the secondary waste liquid to obtain crystallized salt slurry;

(4) washing and dewatering: the crystallized salt slurry enters a salt washer to be washed by saturated brine, the washed crystallized salt slurry enters a salt storage bin, then enters a centrifuge through a swirler (the rotating speed of the swirler is 1500r/min) to be dehydrated to form wet salt, and brine mother liquor removed by the centrifuge flows back to the salt washer; wherein the reflux ratio is 1:11, and a strand of brine mother liquor is introduced into the downstream of the centrifuge and is merged into the salt washer, so that the flow rate in the slurry pipeline is kept reasonable, and the deposition and blockage of crystals are avoided.

(5) And (3) drying: and (4) drying the wet salt obtained in the step (4) in a vibrating fluidized bed dryer to obtain refined salt.

By utilizing the process provided by the embodiment 2, after the system runs for a period of time in winter, the system has no blocking phenomenon, the salt production process is continuous and stable, and the preparation efficiency is indirectly improved; the obtained refined salt has no caking and high quality, and can reach the standard value in the industrial salt standard, and the data is shown in Table 4:

table 4 quality standards of the refined salt

Index name	Quality standard
		Sodium chloride	≥99.1％
Calcium magnesium ion	＜0.5％
		Sulfate ion	＜0.5％
Moisture content	＜0.5％

Comparative example 1

The difference from the embodiment 1 is that brine mother liquor which is not removed by a centrifuge flows back to a salt scrubber process, and after a period of operation, an upstream pipeline of the centrifuge is blocked.

Comparative example 2

The difference from example 1 is that the concentration of the secondary waste liquid in step (2) is 43 Be', the rotating speed of the cyclone is 800r/min, the system has no blockage phenomenon, but the obtained refined salt has a little agglomeration.

Although the present invention has been described in detail by way of preferred embodiments, the present invention is not limited thereto. Various equivalent modifications or substitutions can be made on the embodiments of the present invention by those skilled in the art without departing from the spirit and scope of the present invention, and these modifications or substitutions are within the scope of the present invention/any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.