阅读说明：本技术 一种结合mvr方法生产七水硫酸镁生产工艺 (Production process for producing magnesium sulfate heptahydrate by combining MVR method ) 是由 顾逸 顾根生 徐建武 沈劲松 徐康明 章龙妹 刘晖 于 2021-01-14 设计创作，主要内容包括：本发明提供一种结合MVR方法生产七水硫酸镁生产工艺,涉及七水硫酸镁生产技术领域,包括如下步骤：(1)进料；(2)预热；(3)二次蒸汽进入MVR压缩系统；(4)压缩后的蒸汽再打入蒸发室加热物料；(5)蒸馏水板式换热器与原液进行换热；(6)预热后的物料进入蒸发器(7)得到七水硫酸镁晶体；(8)干燥,得到最终的七水硫酸镁。本发明中通过蒸馏水板式换热器与原液进行换热,使得MVR蒸发结晶系统达到热平衡,振动流化床对七水硫酸镁晶体进行干燥,出去七水硫酸镁晶体中多余的水分,提高纯度,整个发明思路清晰,系统的操作都可由配套的计算机完成,蒸发终点浓度合理,蒸发效率高,成本低,工艺环保绿色。(The invention provides a production process for producing magnesium sulfate heptahydrate by combining an MVR method, which relates to the technical field of magnesium sulfate heptahydrate production and comprises the following steps: (1) feeding; (2) preheating; (3) the secondary steam enters an MVR compression system; (4) the compressed steam is pumped into an evaporation chamber to heat materials; (5) the distilled water plate type heat exchanger exchanges heat with the stock solution; (6) the preheated material enters an evaporator (7) to obtain magnesium sulfate heptahydrate crystals; (8) drying to obtain the final magnesium sulfate heptahydrate. According to the invention, the heat exchange is carried out between the distilled water plate type heat exchanger and the stock solution, so that the MVR evaporation crystallization system reaches the heat balance, the vibrating fluidized bed dries the magnesium sulfate heptahydrate crystals, excessive moisture in the magnesium sulfate heptahydrate crystals is removed, the purity is improved, the whole invention has clear thought, the operation of the system can be completed by a matched computer, the evaporation end point concentration is reasonable, the evaporation efficiency is high, the cost is low, and the process is environment-friendly and green.)

1. A production process for producing magnesium sulfate heptahydrate by combining an MVR method is characterized in that: the method comprises the following steps:

(1) feeding: the salt-containing wastewater is sequentially conveyed to a distilled water preheater and a raw steam preheater by a feed pump, preheated to about 90 ℃ together with the distilled water and the raw steam of the MVR evaporative crystallization system, and enters a forced circulation evaporator for evaporation and concentration;

(2) in the primary feeding process of the forced circulation evaporator, firstly, fresh steam is required to be introduced to preheat the wastewater stock solution to reach the designed evaporation temperature of 90 ℃;

(3) the secondary steam from the top of the steam-liquid separator enters an MVR compression system after liquid foam is separated by a cyclone plate demister;

(4) the compressed steam is pumped into an evaporation chamber to heat materials;

(5) in the process of heating materials, condensing steam into water, discharging the water by a distilled water pump, exchanging heat with the stock solution through a distilled water plate type heat exchanger, and discharging the water out of the MVR evaporative crystallization system;

(6) after entering an evaporator, the preheated material exchanges heat with compressed secondary steam, an MVR evaporation concentration system reaches heat balance, and mother liquor after cooling, crystallization and centrifugation needs more raw steam to compensate and then returns to the MVR evaporation concentration system;

(7) conveying the concentrated solution evaporated by the forced circulation evaporator to a cooling kettle through a discharge pump, cooling, crystallizing and thickening, and then, centrifugally separating crystals in a salt centrifuge to obtain magnesium sulfate heptahydrate crystals;

(8) and drying the magnesium sulfate heptahydrate crystals generated after crystallization by using a vibrated fluidized bed to obtain the final magnesium sulfate heptahydrate.

2. The production process according to claim 1, characterized in that: in the step (2), the evaporation is formed after about 1 to 3 hours of reaching the boiling point.

3. The production process according to claim 1, characterized in that: the temperature of the secondary steam in the step (3) is 84 ℃, and after the secondary steam is compressed, the temperature can be increased to 98 ℃.

4. The production process according to claim 1, characterized in that: the temperature after heat exchange in the step (5) is 35 ℃.

5. The production process according to claim 1, characterized in that: and (4) after the MVR evaporation concentration system reaches the heat balance in the step (6), heating is not needed by external fresh steam, and the heat balance of the MVR evaporation concentration system is maintained only by a compressor.

6. The production process according to claim 1, characterized in that: the centrifugal mother liquor treated by the centrifuge is pumped to the front end by a mother liquor pump, mixed with the stock solution, preheated and returned to the MVR evaporation concentration system, the preheated material enters an evaporator, and then is subjected to heat exchange evaporation with the steam with the temperature raised after compression, and the whole system reaches heat balance.

7. The production process according to claim 1, characterized in that: the shell pass pressure of the evaporator is maintained by non-condensable gas through a vacuum pump and an opening degree of a self-control regulating valve.

8. The production process according to claim 1, characterized in that: the MVR evaporative crystallization system is controlled by a PLC, and all output and input signals and the operation of the system can be completed by a matched computer.

9. The production process according to claim 1, characterized in that: and (4) after the step (8), the water content of the magnesium sulfate heptahydrate is lower than 0.5%.

Technical Field

The invention relates to the technical field of magnesium sulfate heptahydrate production, in particular to a production process for producing magnesium sulfate heptahydrate by combining an MVR method.

Background

Magnesium sulfate heptahydrate is an important inorganic chemical raw material, and has wide application in the fields of agriculture, industry, food, medicine, textile and the like. As 85% of domestic magnesite reserves are distributed in the Haicheng and Yingkou area of Liaoning, other provinces are less distributed, and the main production areas of magnesium sulfate products are also distributed in the areas with raw materials. The magnesium sulfate products in northeast and eastern areas of China are transported to western areas, the transport distance is long, the transport cost is high, and the transport cost is higher than the value of the products.

At present, the method for producing magnesium sulfate heptahydrate mainly comprises the following steps:

firstly, a sulfuric acid method, wherein the ore containing magnesium oxide (dolomite, magnesite and serpentine) is crushed or the calcined powder (magnesium hydroxide or magnesium carbonate can also be used) and sulfuric acid are respectively metered according to the proportion. The product produced by the method has good quality but high cost, and the product is applied to industries such as industry, feed, food and the like, and if the product is used as a fertilizer, the economic benefit is basically not generated.

The salt lake bitter bittern method adopts natural crystallization of natural resources and artificial purification, so that the product quality is good and the cost is low; however, the method has low yield and long cycle.

And thirdly, the bittern re-sun method has high content of miscellaneous salt (NaCI) and poor quality of the product, and magnesium sulfate heptahydrate can be prepared by adopting a water washing method or a recrystallization method for purification, so that the method has high cost and is not beneficial to industrial mass production.

And fourthly, the high-temperature salt leaching method is less in use at present, mainly because the method is higher in cost.

Disclosure of Invention

The invention aims to provide a production process for producing magnesium sulfate heptahydrate by combining an MVR method so as to solve the technical problem.

In order to solve the technical problems, the invention adopts the following technical scheme:

a production process for producing magnesium sulfate heptahydrate by combining an MVR method comprises the following steps:

(1) feeding: the salt-containing wastewater is sequentially conveyed to a distilled water preheater and a raw steam preheater by a feed pump, preheated to about 90 ℃ together with the distilled water and the raw steam of the MVR evaporative crystallization system, and enters a forced circulation evaporator for evaporation and concentration;

(2) in the primary feeding process of the forced circulation evaporator, firstly, fresh steam is required to be introduced to preheat the wastewater stock solution to reach the designed evaporation temperature of 90 ℃;

(3) the secondary steam from the top of the steam-liquid separator enters an MVR compression system after liquid foam is separated by a cyclone plate demister;

(4) the compressed steam is pumped into an evaporation chamber to heat materials;

(5) in the process of heating materials, condensing steam into water, discharging the water by a distilled water pump, exchanging heat with the stock solution through a distilled water plate type heat exchanger, and discharging the water out of the MVR evaporative crystallization system;

(6) after entering an evaporator, the preheated material exchanges heat with compressed secondary steam, an MVR evaporation concentration system reaches heat balance, and mother liquor after cooling, crystallization and centrifugation needs more raw steam to compensate and then returns to the MVR evaporation concentration system;

(7) conveying the concentrated solution evaporated by the forced circulation evaporator to a cooling kettle through a discharge pump, cooling, crystallizing and thickening, and then, centrifugally separating crystals in a salt centrifuge to obtain magnesium sulfate heptahydrate crystals;

(8) and drying the magnesium sulfate heptahydrate crystals generated after crystallization by using a vibrated fluidized bed to obtain the final magnesium sulfate heptahydrate.

Preferably, the boiling point of the product obtained in step (2) is about 1 to 3 hours to form evaporation.

Preferably, the temperature of the secondary steam in the step (3) is 84 ℃, and the temperature can be increased to 98 ℃ after the secondary steam is compressed.

Preferably, the temperature after the heat exchange in the step (5) is 35 ℃.

Preferably, after the MVR evaporation and concentration system reaches the thermal equilibrium in the step (6), external fresh steam is not required for heating, and only a compressor is required for maintaining the thermal equilibrium of the MVR evaporation and concentration system.

Preferably, the centrifugal mother liquor treated by the centrifuge is pumped to the front end by a mother liquor pump, mixed with the stock solution, preheated and returned to the MVR evaporation and concentration system, the preheated material enters an evaporator and then exchanges heat with steam with increased temperature after being compressed for evaporation, and the whole system reaches thermal balance.

Preferably, the shell side pressure of the evaporator is maintained by the non-condensable gas through a vacuum pump and an opening degree of a self-control regulating valve.

Preferably, the MVR evaporative crystallization system is controlled by a PLC, and all output and input signals and the operation of the system can be completed by a matched computer.

Preferably, the water content of the magnesium sulfate heptahydrate obtained after the step (8) is less than 0.5%.

The invention has the beneficial effects that:

according to the invention, through the arrangement of the distilled water preheater and the raw steam preheater, the salt-containing wastewater, the distilled water of the evaporative crystallization system and the raw steam can be directly driven into an MVR forced circulation part after being heated to a set temperature, the liquid foam separator can be used for carrying out liquid foam separation on the mixed liquid, the purity of magnesium sulfate heptahydrate is improved, heat exchange is carried out between the distilled water plate type heat exchanger and the stock solution, the MVR evaporative crystallization system achieves thermal balance, cooling crystallization thickening treatment can concentrate solid particles in suspension liquid, the preheated material enters the evaporator and then carries out heat exchange evaporation with the steam with the temperature raised after compression, the whole system achieves thermal balance, the vibrating fluidized bed dries the magnesium sulfate heptahydrate crystals, excess water in the magnesium sulfate heptahydrate crystals is removed, the purity is improved, the whole invention has clear thought, and the operation of the system can be completed by a matched computer, strong raw material adaptability, difficult scaling of equipment, reasonable concentration of evaporation end point, high evaporation efficiency, low cost, environment-friendly and green process and the like.

Detailed Description

The present invention will be further described with reference to specific embodiments for the purpose of facilitating an understanding of technical means, characteristics of creation, objectives and functions realized by the present invention, but the following embodiments are only preferred embodiments of the present invention, and are not intended to be exhaustive. Based on the embodiments in the implementation, other embodiments obtained by those skilled in the art without any creative efforts belong to the protection scope of the present invention. The experimental methods in the following examples are conventional methods unless otherwise specified, and materials, reagents and the like used in the following examples are commercially available unless otherwise specified.

Example 1

A production process for producing magnesium sulfate heptahydrate by combining an MVR method comprises the following steps:

(1) feeding: the salt-containing wastewater is sequentially conveyed to a distilled water preheater and a raw steam preheater by a feed pump, preheated to about 90 ℃ together with the distilled water and the raw steam of the MVR evaporative crystallization system, and enters a forced circulation evaporator for evaporation and concentration;

(2) in the primary feeding process of the forced circulation evaporator, firstly, fresh steam is required to be introduced to preheat the wastewater stock solution to reach the designed evaporation temperature of 90 ℃;

(3) the secondary steam from the top of the steam-liquid separator enters an MVR compression system after liquid foam is separated by a cyclone plate demister;

(4) the compressed steam is pumped into an evaporation chamber to heat materials;

(5) in the process of heating materials, condensing steam into water and discharging the water by a distilled water pump, exchanging heat with the stock solution by a distilled water plate type heat exchanger, wherein the temperature after heat exchange is 35 ℃, and then discharging the water out of the MVR evaporative crystallization system;

(6) after entering an evaporator, the preheated material exchanges heat with compressed secondary steam, an MVR evaporation concentration system reaches heat balance, and mother liquor after cooling, crystallization and centrifugation needs more raw steam to compensate and then returns to the MVR evaporation concentration system;

(7) conveying the concentrated solution evaporated by the forced circulation evaporator to a cooling kettle through a discharge pump, cooling, crystallizing and thickening, and then, centrifugally separating crystals in a salt centrifuge to obtain magnesium sulfate heptahydrate crystals;

(8) and drying the magnesium sulfate heptahydrate crystals generated after crystallization by using a vibrated fluidized bed to obtain the final magnesium sulfate heptahydrate.

Example 2

A production process for producing magnesium sulfate heptahydrate by combining an MVR method comprises the following steps:

(1) feeding: the salt-containing wastewater is conveyed to a forced circulation evaporator by a feed pump for evaporation and concentration;

(2) in the primary feeding process of the forced circulation evaporator, firstly, fresh steam is required to be introduced to preheat the wastewater stock solution to reach the designed evaporation temperature of 90 ℃;

(3) the secondary steam from the top of the steam-liquid separator enters an MVR compression system after liquid foam is separated by a cyclone plate demister;

(4) the compressed steam is pumped into an evaporation chamber to heat materials;

(5) in the process of heating materials, condensing steam into water and discharging the water by a distilled water pump, exchanging heat with the stock solution by a distilled water plate type heat exchanger, wherein the temperature after heat exchange is 35 ℃, and then discharging the water out of the MVR evaporative crystallization system;

(6) after entering an evaporator, the preheated material exchanges heat with compressed secondary steam, an MVR evaporation concentration system reaches heat balance, and mother liquor after cooling, crystallization and centrifugation needs more raw steam to compensate and then returns to the MVR evaporation concentration system;

(7) conveying the concentrated solution evaporated by the forced circulation evaporator to a cooling kettle through a discharge pump, cooling, crystallizing and thickening, and then, centrifugally separating crystals in a salt centrifuge to obtain magnesium sulfate heptahydrate crystals;

(8) and drying the magnesium sulfate heptahydrate crystals generated after crystallization by using a vibrated fluidized bed to obtain the final magnesium sulfate heptahydrate.

Example 3

A production process for producing magnesium sulfate heptahydrate by combining an MVR method comprises the following steps:

(1) feeding: the salt-containing wastewater is sequentially conveyed to a distilled water preheater and a raw steam preheater by a feed pump, preheated to about 90 ℃ together with the distilled water and the raw steam of the MVR evaporative crystallization system, and enters a forced circulation evaporator for evaporation and concentration;

(2) in the primary feeding process of the forced circulation evaporator, firstly, fresh steam is required to be introduced to preheat the wastewater stock solution to reach the designed evaporation temperature of 90 ℃;

(3) the secondary steam from the top of the vapor-liquid separator enters an MVR compression system;

(4) the compressed steam is pumped into an evaporation chamber to heat materials;

(5) in the process of heating materials, condensing steam into water and discharging the water by a distilled water pump, exchanging heat with the stock solution by a distilled water plate type heat exchanger, wherein the temperature after heat exchange is 35 ℃, and then discharging the water out of the MVR evaporative crystallization system;

(6) after entering an evaporator, the preheated material exchanges heat with compressed secondary steam, an MVR evaporation concentration system reaches heat balance, and mother liquor after cooling, crystallization and centrifugation needs more raw steam to compensate and then returns to the MVR evaporation concentration system;

(7) conveying the concentrated solution evaporated by the forced circulation evaporator to a cooling kettle through a discharge pump, cooling, crystallizing and thickening, and then, centrifugally separating crystals in a salt centrifuge to obtain magnesium sulfate heptahydrate crystals;

(8) and drying the magnesium sulfate heptahydrate crystals generated after crystallization by using a vibrated fluidized bed to obtain the final magnesium sulfate heptahydrate.

Example 4

A production process for producing magnesium sulfate heptahydrate by combining an MVR method comprises the following steps:

(1) feeding: the salt-containing wastewater is sequentially conveyed to a distilled water preheater and a raw steam preheater by a feed pump, preheated to about 90 ℃ together with the distilled water and the raw steam of the MVR evaporative crystallization system, and enters a forced circulation evaporator for evaporation and concentration;

(2) in the primary feeding process of the forced circulation evaporator, firstly, fresh steam is required to be introduced to preheat the wastewater stock solution to reach the designed evaporation temperature of 90 ℃;

(3) the secondary steam from the top of the steam-liquid separator enters an MVR compression system after liquid foam is separated by a cyclone plate demister;

(4) the compressed steam is pumped into an evaporation chamber to heat materials;

(5) in the process of heating materials, condensing steam into water and discharging the water by a distilled water pump, exchanging heat with the stock solution by a distilled water plate type heat exchanger, wherein the temperature after heat exchange is 25 ℃, and then discharging the water out of the MVR evaporative crystallization system;

(6) after entering an evaporator, the preheated material exchanges heat with compressed secondary steam, an MVR evaporation concentration system reaches heat balance, and mother liquor after cooling, crystallization and centrifugation needs more raw steam to compensate and then returns to the MVR evaporation concentration system;

(7) conveying the concentrated solution evaporated by the forced circulation evaporator to a cooling kettle through a discharge pump, cooling, crystallizing and thickening, and then, centrifugally separating crystals in a salt centrifuge to obtain magnesium sulfate heptahydrate crystals;

(8) and drying the magnesium sulfate heptahydrate crystals generated after crystallization by using a vibrated fluidized bed to obtain the final magnesium sulfate heptahydrate.

Example 5

A production process for producing magnesium sulfate heptahydrate by combining an MVR method comprises the following steps:

(1) feeding: the salt-containing wastewater is sequentially conveyed to a distilled water preheater and a raw steam preheater by a feed pump, preheated to about 90 ℃ together with the distilled water and the raw steam of the MVR evaporative crystallization system, and enters a forced circulation evaporator for evaporation and concentration;

(2) in the primary feeding process of the forced circulation evaporator, firstly, fresh steam is required to be introduced to preheat the wastewater stock solution to reach the designed evaporation temperature of 90 ℃;

(3) the secondary steam from the top of the steam-liquid separator enters an MVR compression system after liquid foam is separated by a cyclone plate demister;

(4) the compressed steam is pumped into an evaporation chamber to heat materials;

(5) in the process of heating materials, condensing steam into water and discharging the water by a distilled water pump, exchanging heat with the stock solution by a distilled water plate type heat exchanger, wherein the temperature after heat exchange is 45 ℃, and then discharging the water out of the MVR evaporative crystallization system;

(6) after entering an evaporator, the preheated material exchanges heat with compressed secondary steam, an MVR evaporation concentration system reaches heat balance, and mother liquor after cooling, crystallization and centrifugation needs more raw steam to compensate and then returns to the MVR evaporation concentration system;

(7) conveying the concentrated solution evaporated by the forced circulation evaporator to a cooling kettle through a discharge pump, cooling, crystallizing and thickening, and then, centrifugally separating crystals in a salt centrifuge to obtain magnesium sulfate heptahydrate crystals;

(8) and drying the magnesium sulfate heptahydrate crystals generated after crystallization by using a vibrated fluidized bed to obtain the final magnesium sulfate heptahydrate.

Example analysis:

in the embodiment 1 and the embodiment 2, the salt-containing wastewater in the embodiment 1 is preheated by a distilled water preheater and a raw steam preheater, while the salt-containing wastewater in the embodiment 2 is directly subjected to evaporation concentration by a forced circulation evaporator;

in the embodiments 1 and 3, the secondary steam in the embodiment 1 passes through the cyclone plate demister to separate liquid foam, while the secondary steam in the embodiment 3 directly enters the MVR compression system without a liquid foam separation process;

in examples 4 and 5, the temperatures after heat exchange in step (5) in examples 4 and 5 were 25 ℃ and 45 ℃ respectively, compared to example 1, whereas example 1 was 35 ℃.

Experimental analysis:

the method comprises the steps of uniformly dividing 20L of salt-containing wastewater into 5 parts, namely A, B, C, D groups and E groups, producing five groups of magnesium sulfate heptahydrate by using the methods in examples 1-5, and detecting the quality and purity of the five groups of magnesium sulfate heptahydrate to obtain the best example group.

The foregoing shows and describes the general principles, essential features, and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, and the preferred embodiments of the present invention are described in the above embodiments and the description, and are not intended to limit the present invention. The scope of the invention is defined by the appended claims and equivalents thereof.