A vacuum evaporation multi-stage step pressure reduction stability judgment safety control method

Abstract

This application belongs to the field of industrial evaporation and concentration technology, specifically a multi-stage stepped pressure reduction and stability control method for vacuum evaporation, including the following steps: Step 1: Detect the water production rate of the vacuum evaporator using a first flow meter and the rate of liquid level drop in the vacuum evaporator using a level gauge; Step 2: Transmit the water production rate and the rate of liquid level drop to the PLC control system in real time; Step 3: If the water production rate increases and the rate of liquid level drop in the vacuum evaporator increases, the PLC control system controls the vacuum system to reduce the amount of air pumped into the vacuum evaporator to maintain a constant pressure inside the vacuum evaporator; if the water production rate decreases and the rate of liquid level drop in the vacuum evaporator decreases, the PLC control system controls the vacuum system to increase the amount of air pumped into the vacuum evaporator. This solves the problem of flash evaporation in current industrial evaporation and concentration processes and how to prevent the impact of flash evaporation on the equipment.

Description

Technical Field

[0001] This application belongs to the field of industrial evaporation and concentration technology, specifically a method for safe control of multi-stage step-down pressure reduction in vacuum evaporation. Background Technology

[0002] In the past, the environmental protection industry used MVR system evaporation, which could reduce energy consumption. However, due to atmospheric pressure evaporation, the boiling point would rise sharply as the concentration of the mother liquor increased, which could easily lead to violent flash evaporation. Currently, there is no stabilization mechanism for evaporation, so the evaporation process is prone to overpressure and impact on equipment. Summary of the Invention

[0003] The purpose of this application is to address the shortcomings of existing technologies by designing a multi-stage stepped pressure reduction and stability control method for vacuum evaporation through the use of a level gauge and a first flow meter in conjunction with a PLC control system. This method solves the problems of flash evaporation in current industrial evaporation and concentration processes and how to prevent the impact of flash evaporation on the equipment.

[0004] To achieve the above objectives, the following technical solution is adopted: A method for safe control of multi-stage stepped pressure reduction in vacuum evaporation includes the following steps: Step 1: Detect the water production rate of the vacuum evaporator using the first flow meter, and detect the rate at which the liquid level drops inside the vacuum evaporator using the level gauge; Step 2: Transmit the water production rate of the vacuum evaporator detected by the first flow meter and the data detected by the level gauge to the PLC control system in real time; Step 3: If the first flow meter detects an increase in the rate of water production and the level gauge detects an increase in the rate of liquid level drop in the vacuum evaporator, and the pressure sensor inside the vacuum evaporator is used for auxiliary judgment, then the PLC control system controls the vacuum system to reduce the amount of air pumped into the vacuum evaporator to keep the pressure inside the vacuum evaporator stable. If the first flow meter detects a decrease in the rate of water production and the level gauge detects a decrease in the rate of liquid level drop in the vacuum evaporator, and the pressure sensor shows that the pressure inside the vacuum evaporator is increasing, then the PLC control system controls the vacuum system to increase the amount of air pumped into the vacuum evaporator to bring the vacuum level inside the vacuum evaporator to the next level.

[0005] Preferably, in step one, a vacuum system and a first flow meter are installed at the output end of the vacuum evaporator, and both the vacuum system and the first flow meter are signal-connected to the PLC control system to obtain the water production rate and the speed at which the liquid level drops.

[0006] Preferably, step three further includes: Step S1: Evacuate the vacuum evaporator to -55 kPa using the vacuum system and maintain this pressure for a period of time. At this point, the evaporation temperature is 80°C. If the rate of liquid level drop and water production in the vacuum evaporator increase, the vacuum level will decrease. The PLC control system will then reduce the pumping speed to maintain a constant pressure within the vacuum evaporator, allowing the liquid to continue evaporating. If the rate of liquid level drop and water production decrease, the vacuum level will increase, indicating that the liquid temperature in the vacuum evaporator has dropped to 80°C. At this point, the PLC control system will then increase the pumping speed to proceed to step S2. Step S2: The vacuum evaporator is evacuated to -70 kPa using the vacuum system and maintained for a period of time. At this point, the evaporation temperature is 80°C. If the rate at which the liquid level drops in the vacuum evaporator increases and the water production increases, the vacuum level will decrease. In this case, the PLC control system will control the vacuum system to reduce the pumping speed to maintain the pressure inside the vacuum evaporator and allow the liquid inside to continue to evaporate. If the rate at which the liquid level drops in the vacuum evaporator decreases and the water production decreases, the vacuum level will increase, indicating that the liquid inside the vacuum evaporator has dropped to the evaporation temperature of 72°C. At this point, the PLC control system will control the vacuum system to increase the pumping speed to proceed to step S3. Step S3: The vacuum evaporator is evacuated to -85 kPa using the vacuum system and maintained for a period of time. At this point, the evaporation temperature is 58°C. If the rate at which the liquid level drops in the vacuum evaporator increases and the water production increases, the vacuum level will decrease. In this case, the PLC control system will control the vacuum system to reduce the pumping speed to maintain the pressure inside the vacuum evaporator and allow the liquid inside the vacuum evaporator to continue to evaporate on its own. If the rate at which the liquid level drops in the vacuum evaporator decreases and the water production decreases, the vacuum level will increase, indicating that the liquid inside the vacuum evaporator has now dropped to the evaporation temperature of 58°C. At this point, the PLC control system will control the vacuum system to increase the pumping speed to proceed to step S4. Step S4: The vacuum evaporator is evacuated to -95 kPa using the vacuum system and maintained for a period of time. At this point, the evaporation temperature is 40°C. If the rate at which the liquid level drops in the vacuum evaporator increases and the water production increases, the vacuum level will decrease. In this case, the PLC control system will control the vacuum system to reduce the pumping speed to maintain a constant pressure inside the vacuum evaporator, allowing the liquid inside to continue to evaporate. If the rate at which the liquid level drops in the vacuum evaporator decreases and the water production decreases, the vacuum level will increase, indicating that the liquid inside the vacuum evaporator has now dropped to the evaporation temperature of 40°C. Then, the PLC control system will control the pumping speed of the vacuum system to maintain a constant pressure inside the vacuum evaporator.

[0007] Preferably, step one further includes installing a temperature sensor inside the vacuum evaporator, and connecting the temperature sensor signal to the PLC control system to detect the internal temperature of the vacuum evaporator.

[0008] Preferably, step one further includes installing a centrifugal pump at the input end of the vacuum evaporator, and connecting the centrifugal pump signal to the PLC control system, so that after step S4, the PLC control system controls the centrifugal pump to deliver liquid into the vacuum evaporator.

[0009] Preferably, step one further includes installing a second flow meter at the input end of the vacuum evaporator, and connecting the PLC control system through the signal of the second flow meter, so that after step S4, the PLC control system controls the speed of liquid delivery into the vacuum evaporator, thereby ensuring that the temperature inside the vacuum evaporator is between 40℃ and 58℃.

[0010] Compared with the prior art, the beneficial effects of the technical solution of this application are: This application proposes a multi-stage stepped pressure reduction and stability control method for vacuum evaporation by setting up a level gauge and a first flow meter in conjunction with a PLC control system. This method solves the problems of flash evaporation in current industrial evaporation and concentration processes and how to prevent the impact of flash evaporation on the equipment. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the structure of this application.

[0012] Among them, 1. First flow meter; 2. Vacuum evaporator; 3. Liquid level gauge; 4. Vacuum system; 5. Temperature sensor; 6. Centrifugal pump; 7. Second flow meter. Detailed Implementation

[0013] Reference Figure 1 A method for safe control of multi-stage stepped pressure reduction in vacuum evaporation includes the following steps: Step 1: Detect the water production rate of vacuum evaporator 2 using the first flow meter 1, and detect the rate of liquid level drop inside vacuum evaporator using the level gauge 3. Step 2: Transmit the water production rate of the vacuum evaporator 2 detected by the first flow meter 1 and the data detected by the liquid level meter 3 to the PLC control system in real time. Step 3: If the first flow meter 1 detects an increase in the rate of water production and the level gauge 3 detects an increase in the rate of liquid level drop in the vacuum evaporator, and the pressure sensor inside the vacuum evaporator is used for auxiliary judgment, then the PLC control system controls the vacuum system 4 to reduce the amount of air pumped into the vacuum evaporator to keep the pressure inside the vacuum evaporator stable. If the first flow meter 1 detects a decrease in the rate of water production and the level gauge 3 detects a decrease in the rate of liquid level drop in the vacuum evaporator, and the pressure sensor shows that the pressure inside the vacuum evaporator is increasing, then the PLC control system controls the vacuum system 4 to increase the amount of air pumped into the vacuum evaporator to bring the vacuum level inside the vacuum evaporator to the next level.

[0014] With this design, the intensity of evaporation can be judged by the degree of liquid level drop in the evaporation container 2. At the same time, the water flowing out of the first flow meter 1 (water production) can be used to assist in judging the intensity of evaporation, which is more accurate. Then, the PLC control system controls the vacuum system 4 to adjust the pressure in the evaporation container 2, thus solving the problem of pressure stabilization control.

[0015] As a preferred method, in step one, a vacuum system 4 and a first flow meter 1 are installed at the output end of the vacuum evaporator 1, and both the vacuum system 4 and the first flow meter 1 are signal-connected to the PLC control system to obtain the water production rate and the speed at which the liquid level drops.

[0016] As a preferred embodiment, step three further includes: Step S1: The vacuum evaporator is evacuated to -55 kPa using the vacuum system 4 and maintained for a period of time. At this time, the evaporation temperature is 80℃. If the rate of liquid level drop and water production in the vacuum evaporator increase, the vacuum level will decrease. The PLC control system will control the vacuum system 4 to reduce the pumping speed to maintain the pressure inside the vacuum evaporator and allow the liquid inside the vacuum evaporator to continue to evaporate on its own. If the rate of liquid level drop and water production in the vacuum evaporator decrease, the vacuum level will increase, indicating that the liquid inside the vacuum evaporator has dropped to the evaporation temperature of 80℃. At this time, the PLC control system will control the vacuum system 4 to increase the pumping speed to proceed to step S2. Step S2: The vacuum evaporator is evacuated to -70 kPa using the vacuum system 4 and maintained for a period of time. At this point, the evaporation temperature is 80°C. If the rate at which the liquid level drops in the vacuum evaporator increases and the water production increases, the vacuum level will decrease. In this case, the PLC control system will control the vacuum system 4 to reduce the pumping speed to maintain the pressure inside the vacuum evaporator and allow the liquid inside the vacuum evaporator to continue to evaporate on its own. If the rate at which the liquid level drops in the vacuum evaporator decreases and the water production decreases, the vacuum level will increase, indicating that the liquid inside the vacuum evaporator has dropped to the evaporation temperature of 72°C. At this point, the PLC control system will control the vacuum system 4 to increase the pumping speed to proceed to step S3. Step S3: The vacuum evaporator is evacuated to -85 kPa using the vacuum system 4 and maintained for a period of time. At this point, the evaporation temperature is 58°C. If the rate at which the liquid level drops in the vacuum evaporator increases and the water production increases, the vacuum level will decrease. In this case, the PLC control system will control the vacuum system 4 to reduce the pumping speed to maintain the pressure inside the vacuum evaporator and allow the liquid inside the vacuum evaporator to continue to evaporate on its own. If the rate at which the liquid level drops in the vacuum evaporator decreases and the water production decreases, the vacuum level will increase, indicating that the liquid inside the vacuum evaporator has dropped to the evaporation temperature of 58°C. At this point, the PLC control system will control the vacuum system 4 to increase the pumping speed to proceed to step S4. Step S4: The vacuum evaporator is evacuated to -95 kPa using the vacuum system 4 and maintained for a period of time. At this time, the evaporation temperature is 40℃. If the rate at which the liquid level drops in the vacuum evaporator increases and the water production increases, the vacuum level will decrease. In this case, the PLC control system will control the vacuum system 4 to reduce the pumping speed to maintain the pressure inside the vacuum evaporator and allow the liquid inside the vacuum evaporator to continue to evaporate on its own. If the rate at which the liquid level drops in the vacuum evaporator decreases and the water production decreases, the vacuum level will increase, indicating that the liquid inside the vacuum evaporator has dropped to the evaporation temperature of 40℃. Then, the PLC control system will control the pumping speed of the vacuum system to maintain the pressure inside the vacuum evaporator. By depressurizing the evaporator 2 four times, the mixture formed by the original liquid (90°C) and the unevaporated liquid in the evaporator 2 can continue to evaporate within the evaporator 2. Because the evaporator 2 undergoes four stages of depressurization (four stages of vacuuming), the evaporation temperature in the evaporator 2 only needs to be 40°C, and the temperature of the mixed liquid is basically above 40°C. Therefore, there is no need to heat the evaporator 2 additionally to ensure that the temperature of the mixed liquid is between 40°C and 58°C.

[0017] As a preferred embodiment, step one further includes installing a temperature sensor 5 inside the vacuum evaporator. The temperature sensor 5 is connected to the PLC control system to detect the internal temperature of the vacuum evaporator 2. After the temperature inside the vacuum evaporator 2 is measured by the temperature sensor 5, the PLC control system can control the amount of raw liquid entering the vacuum evaporator 2 to ensure... As a preferred embodiment, step one further includes installing a centrifugal pump 6 at the input end of the vacuum evaporator 2, and connecting the centrifugal pump 6 to the PLC control system via a signal, so that after step S4, the PLC control system controls the temperature of the liquid delivered by the centrifugal pump 6 into the vacuum evaporator 2 to be between 40°C and 58°C.

[0018] As a preferred embodiment, step one further includes installing a second flow meter 7 at the input end of the vacuum evaporator 2, and connecting the PLC control system via the signal of the second flow meter 7, so that after step S4, the PLC control system controls the speed at which liquid is delivered into the vacuum evaporator 2, thereby ensuring that the temperature inside the vacuum evaporator 2 is between 40℃ and 58℃.

Claims

1. A vacuum evaporation multi-stage step pressure reduction stability determination safety control method, characterized by, Includes the following steps: Step 1: Detect the water production rate of the vacuum evaporator (2) using the first flow meter (1), and detect the rate at which the liquid level in the vacuum evaporator drops using the level gauge (3); Step 2: The water production rate of the vacuum evaporator (2) detected by the first flow meter (1) and the data detected by the liquid level gauge (3) are transmitted to the PLC control system in real time. Step 3: If the first flow meter (1) detects an increase in the rate of water production and the level gauge (3) detects an increase in the rate of liquid level drop in the vacuum evaporator, and at the same time, the pressure sensor in the vacuum evaporator is observed for auxiliary judgment, then the PLC control system controls the vacuum system (4) to reduce the amount of air pumped into the vacuum evaporator to keep the pressure in the vacuum evaporator tending to be stable; if the first flow meter (1) detects a decrease in the rate of water production and the level gauge (3) detects a decrease in the rate of liquid level drop in the vacuum evaporator, and the pressure sensor shows that the pressure in the vacuum evaporator is increasing, then the PLC control system controls the vacuum system (4) to increase the amount of air pumped into the vacuum evaporator so that the vacuum degree in the vacuum evaporator enters the next level.

2. The vacuum evaporation multi-stage stepped pressure reduction stability control method according to claim 1, characterized in that, In step one, a vacuum system (4) and a first flow meter (1) are installed at the output end of the vacuum evaporator (2), and the vacuum system (4) and the first flow meter (1) are both connected to the PLC control system to obtain the water production rate and the speed at which the liquid level drops.

3. The vacuum evaporation multi-stage stepped pressure reduction stability control method according to claim 2, characterized in that, Step three also includes: Step S1: The vacuum evaporator is evacuated to -55 kPa by the vacuum system (4) and maintained for a period of time. The evaporation temperature is 80°C at this time. If the rate of liquid level drop in the vacuum evaporator increases and the water production increases, the vacuum level will decrease. The vacuum system (4) is controlled by the PLC control system to reduce the pumping volume to keep the pressure in the vacuum evaporator constant and allow the liquid in the vacuum evaporator to continue to evaporate on its own. If the rate of liquid level drop in the vacuum evaporator decreases and the water production decreases, the vacuum level will increase, indicating that the liquid in the vacuum evaporator has dropped to the evaporation temperature of 80°C. At this time, the vacuum system (4) is controlled by the PLC control system to increase the pumping volume to proceed to step S2. Step S2: The vacuum evaporator is evacuated to -70 kPa by the vacuum system (4) and maintained for a period of time. At this time, the evaporation temperature is 80°C. If the rate of liquid level drop in the vacuum evaporator increases and the water production increases, the vacuum level will decrease. Then, the vacuum system (4) is controlled by the PLC control system to reduce the pumping volume to keep the pressure in the vacuum evaporator constant and allow the liquid in the vacuum evaporator to continue to evaporate on its own. If the rate of liquid level drop in the vacuum evaporator decreases and the water production decreases, the vacuum level will increase, indicating that the liquid in the vacuum evaporator has dropped to the evaporation temperature of 72°C. At this time, the vacuum system (4) is controlled by the PLC control system to increase the pumping volume to proceed to step S3. Step S3: The vacuum evaporator is evacuated to -85 kPa by the vacuum system (4) and maintained for a period of time. The evaporation temperature is 58°C. If the rate of liquid level drop in the vacuum evaporator increases and the water production increases, the vacuum level will decrease. The PLC control system will then control the vacuum system (4) to reduce the pumping volume to keep the pressure in the vacuum evaporator constant and allow the liquid in the vacuum evaporator to continue to evaporate on its own. If the rate of liquid level drop in the vacuum evaporator decreases and the water production decreases, the vacuum level will increase, indicating that the liquid in the vacuum evaporator has dropped to the evaporation temperature of 58°C. The PLC control system will then control the vacuum system (4) to increase the pumping volume to proceed to step S4. Step S4: The vacuum evaporator is evacuated to -95 kPa by the vacuum system (4) and maintained for a period of time. The evaporation temperature is 40°C at this time. If the rate of liquid level drop in the vacuum evaporator increases and the water production increases, the vacuum level will decrease. Then, the vacuum system (4) is controlled by the PLC control system to reduce the pumping volume to keep the pressure in the vacuum evaporator constant and allow the liquid in the vacuum evaporator to continue to evaporate on its own. If the rate of liquid level drop in the vacuum evaporator decreases and the water production decreases, the vacuum level will increase, indicating that the liquid in the vacuum evaporator has dropped to the evaporation temperature of 40°C. Then, the pumping volume of the vacuum system is controlled by the PLC control system to keep the pressure in the vacuum evaporator constant.

4. The vacuum evaporation multi-stage stepped pressure reduction stability control method according to claim 3, characterized in that, Step one also includes setting a temperature sensor (5) inside the vacuum evaporator, and connecting the PLC control system through the temperature sensor (5) signal to detect the internal temperature of the vacuum evaporator (2).

5. The vacuum evaporation multi-stage stepped pressure reduction stability control method according to claim 3, characterized in that, Step one also includes setting a centrifugal pump (6) at the input end of the vacuum evaporator (2), and connecting the PLC control system through the centrifugal pump (6) so that after step S4, the PLC control system controls the centrifugal pump (6) to deliver liquid into the vacuum evaporator (2).

6. The vacuum evaporation multi-stage stepped pressure reduction stability control method according to claim 5, characterized in that, The first step also includes setting a second flow meter (7) at the input end of the vacuum evaporator (2), and connecting the PLC control system through the signal of the second flow meter (7), so that after step S4, the PLC control system controls the speed of liquid delivery into the vacuum evaporator (2), thereby ensuring that the temperature inside the vacuum evaporator (2) is between 40℃ and 58℃.

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