Preparation method of calcium hydroxide solution for wastewater treatment in iron and steel industry

Abstract

The invention discloses a calcium hydroxide solution preparation method for wastewater treatment in the iron and steel industry. A calcium hydroxide solution preparation system is adopted for solution preparation. The solution preparation system comprises an online weighing spiral feeding device connected with a calcium oxide storage tank and a calcium hydroxide solution tank; the calcium oxide storage tank is provided with a vibrator; the calcium hydroxide solution tank is provided with an ultrasonic liquid level meter and a stirrer; and the on-line weighing spiral feeding device, the vibrator and the ultrasonic liquid level meter are controlled by a PLC (Programmable Logic Controller) control cabinet connected with the HMI. When a solution is prepared, an HMI instructs a PLC control cabinet to start a stirrer and a water valve, when the liquid level reaches a set value, a vibrator and an online weighing spiral feeding device are started, and needed calcium oxide powder is put according to the set value; and adding water to a set value of HMI to complete solution preparation. The problems that the treatment effect is difficult to guarantee and the labor intensity of operation and maintenance personnel is increased due to the fact that the concentration of the calcium hydroxide solution cannot be accurately determined during manual preparation of the calcium hydroxide solution can be solved.

Description

Technical Field

[0001] The invention relates to the technical field of wastewater treatment in the steel industry, and in particular to an automatic control method and system for preparing a calcium hydroxide solution. Background Art

[0002] Calcium hydroxide solution is an important reagent solution for water treatment in the wastewater treatment station of cold-rolled strip mills. It is mainly used for the neutralization reaction of acidic wastewater. The concentration of calcium hydroxide solution is an important indicator of the quality of calcium hydroxide solution. The preparation of calcium hydroxide solution is mainly achieved by mixing water and calcium oxide in a certain proportion. At present, the preparation of calcium hydroxide solution is mainly achieved by semi-automatic and manual preparation. This method has the following problems: 1. When using semi-automatic or manual methods, the amount of calcium oxide to be added can only be determined based on experience, and the concentration of the calcium hydroxide solution cannot be accurately determined, which makes it difficult to ensure the effect of wastewater treatment.

[0003] 2. Semi-automatic or manual methods require real-time monitoring by personnel. If the concentration is too high, it is easy to clog the pipeline, increasing the labor intensity of operators and maintenance personnel. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for preparing a calcium hydroxide solution for wastewater treatment in the steel industry, which can solve the problems existing in the prior art that a semi-automatic or manual method is used, the amount of calcium oxide to be added can only be determined empirically, the concentration of the calcium hydroxide solution cannot be accurately determined, resulting in difficulty in ensuring the effect of wastewater treatment during wastewater treatment, and the need for real-time monitoring by personnel, which increases the labor intensity of operators and maintenance personnel.

[0005] In order to solve the above problems, the technical solution of the present invention is: the calcium hydroxide solution preparation method for wastewater treatment in the steel industry adopts a calcium hydroxide solution preparation system to prepare the calcium hydroxide solution; the calcium hydroxide solution preparation system includes a calcium oxide storage tank, a radar level meter, a PLC control cabinet, a vibrator, an online weighing screw feeding device, a water valve, an ultrasonic level meter, a stirrer and a calcium hydroxide solution tank.

[0006] The bottom outlet of the calcium oxide storage tank is connected to the online weighing screw feeding device, and the other end of the online weighing screw feeding device is connected to the calcium hydroxide solution tank, and the calcium oxide powder is not transferred to the calcium hydroxide solution tank through the online weighing screw feeding device; the vibrator is also arranged on the outer side of the bottom of the calcium oxide storage tank, and the radar level meter is arranged on the top of the calcium oxide storage tank.

[0007] The top of the calcium hydroxide solution tank is connected to an online weighing screw feeding device, and the top is also provided with the ultrasonic level meter high pressure and a water inlet pipe, the water inlet pipe is provided with the water valve, and the calcium hydroxide solution tank is provided with the stirrer; The radar level meter, the online weighing screw feeding device, the vibrator and the ultrasonic level meter are all controlled by the PLC control cabinet; the PLC control cabinet is connected to the HMI via TCP / IP communication.

[0008] The steps for preparing calcium hydroxide solution are as follows: 1. When preparing the solution, the HMI sends a start command to the PLC control cabinet, and the PLC control cabinet sends a command to start the mixer and the water valve, and industrial water flows into the calcium hydroxide solution tank. The ultrasonic liquid level meter detects the liquid level in real time. When the liquid level reaches a given value, the water valve is closed and the vibrator (5) and the online weighing screw feeding device are started. According to the known liquid level and concentration before the solution is prepared, the density ρ=1000+concentration C×6.8 and the mass m=liquid level h×bottom area S×density×concentration C are calculated. The mass of calcium hydroxide in the solution before preparation is calculated according to the liquid level and concentration set by the HMI and the above formula to obtain the mass of calcium hydroxide after preparation. The mass of the calcium oxide powder to be added is obtained by subtracting the mass of the calcium hydroxide from the mass of the calcium oxide weighed by the online weighing screw feeding device and the mass calculated, and when the difference between the mass of calcium oxide weighed by the online weighing screw feeding device and the mass calculated does not exceed 10 kg, the online weighing screw feeding device and the vibrator are stopped; finally, the water valve is opened until the liquid level measured by the ultrasonic liquid level meter is equal to the HMI set value, thereby completing a solution preparation cycle; 2. Addition of calcium oxide powder in the calcium oxide storage tank (1): The radar level meter detects the height of the calcium oxide powder in the calcium oxide storage tank in real time and transmits it to the PLC control cabinet in real time and displays it on the HMI. When the material level is too low, addition is performed according to the alarm prompt.

[0009] In the above technical solution, a more specific solution is: in step one, the ultrasonic liquid level meter (9) detects the liquid level in real time, and when the liquid level reaches 1.8 meters, the water valve (7) is closed and the vibrator (5) and the online weighing screw feeding device (6) are started.

[0010] Furthermore: the online weighing screw feeder device includes a flow-stabilizing motor and a metering motor, which are connected to an online weighing screw feeder control cabinet; the online weighing screw feeder control cabinet is connected to the PLC control cabinet and is controlled by the PLC control cabinet.

[0011] Furthermore: the PLC control cabinet adopts Siemens S7-1500 control cabinet.

[0012] Further: the specification model of the ultrasonic level meter is FMU30; the specification model of the radar level meter is 7ML5440-0HB00-0AA2; Furthermore: the specifications of the current-stabilizing motor and the metering motor are YVF2-90L-4 and YVF2-90L-4 respectively.

[0013] Due to the adoption of the above technical solution, the present invention has the following beneficial effects compared with the prior art: 1. The calcium hydroxide solution is prepared by the present invention, which greatly improves the control accuracy of the concentration of the calcium hydroxide solution, reduces the concentration error to ±5%, and ensures the stability of wastewater treatment.

[0014] 2. The present invention improves the degree of automation, eliminates the need for real-time monitoring by operators, reduces labor intensity, and improves efficiency.

[0015] 3. The present invention avoids the situation where the pipeline is blocked and the delivery pump is damaged due to excessive concentration caused by unstable control. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the structure of the calcium hydroxide solution configuration device used in the present invention.

[0017] The numbers in the figure represent: 1. Calcium oxide storage tank, 2. Radar level meter, 3. Online weighing screw feeder control cabinet, 4. PLC control cabinet, 5. Vibrator, 6. Online weighing screw feeder, 6-1. Flow-stabilizing motor, 6-2. Metering motor, 7. Water valve, 8. HMI, 9. Ultrasonic level meter, 10. Mixer, 11. Calcium hydroxide solution tank. DETAILED DESCRIPTION

[0018] The present invention is further described below in conjunction with the accompanying drawings and embodiments: Figure 1 The calcium hydroxide solution preparation device comprises a calcium oxide storage tank 1, a radar level meter 2, an online weighing screw feeder control cabinet 3, a PLC control cabinet 4, a vibrator 5, an online weighing screw feeder 6, a water valve 7, an ultrasonic level meter 9, a mixer 10 and a calcium hydroxide solution tank 11.

[0019] An online weighing screw feeding device 6 is connected to the bottom outlet of the calcium oxide storage tank 1, and the other end of the online weighing screw feeding device 6 is connected to the calcium hydroxide solution tank 11, and the calcium oxide is transferred to the calcium hydroxide solution tank 11 through the online weighing screw feeding device 6; a vibrator 5 is also arranged on the outer side of the bottom of the calcium oxide storage tank 1, and a radar level meter 2 is arranged on the top of the calcium oxide storage tank 1.

[0020] The top of the calcium hydroxide solution tank 11 is connected to the online weighing screw feeding device 6 , and an ultrasonic level meter 9 and a water inlet pipe are also provided on the top, and a water valve 7 is installed on the water inlet pipe; the calcium hydroxide solution tank 11 is also provided with a stirrer 10 .

[0021] The online weighing screw feeder device 6 includes a flow-stabilizing motor 6-1 and a metering motor 6-2, which are connected to the online weighing screw feeder control cabinet 3. The online weighing screw feeder control cabinet 3 is connected to the PLC control cabinet 4 of the upper-level PLC control system. The PLC control cabinet 4 of the upper-level PLC control system cooperates with the HMI (Human Machine Interface) 8 through TCP / IP communication.

[0022] In this embodiment, the specification model of the radar level meter 2 is 7ML5440-0HB00-0AA2; The specification model of ultrasonic level meter 9 is FMU30; The specification model of the steady-current motor 6-1 is YVF2-90L-4; The specification model of the metering motor 6-2 is YVF2-90L-4; In this embodiment, the PLC control cabinet 4 of the upper-level PLC control system adopts the control cabinet of the upper-level Siemens S7-1500 control system.

[0023] The radar level meter 2, the online weighing screw feeder control cabinet 3, the vibrator 5 and the ultrasonic level meter 9 are all controlled by the superior Siemens S7-1500 control system. The superior Siemens S7-1500 control system and HMI are both existing technologies.

[0024] The steps of the calcium hydroxide solution preparation method using the calcium hydroxide solution preparation device for wastewater treatment in the steel industry are as follows: When preparing the solution, the HMI sends a start command to the S7-1500 control system, and the S7-1500 control system sends a command to start the mixer 10 and the water valve 7. The industrial water flows into the calcium hydroxide solution tank 11, and the ultrasonic liquid level meter 9 detects the liquid level in real time. When the liquid level reaches a given value, in this embodiment, when the liquid level reaches 1.8 meters, the water valve 7 is closed and the vibrator 5 and the online weighing screw feeding device 6 are started. According to the known liquid level and concentration before the solution is prepared, the mass of calcium hydroxide in the solution before preparation is calculated according to the formula density ρ=1000+concentration C×6.8, mass m=liquid level h×bottom area S×honeyness×concentration C. According to the liquid level and concentration set by the HMI, the mass of calcium hydroxide after preparation is calculated according to the above formula, and the mass of the two masses is subtracted to obtain the mass of the calcium oxide powder that needs to be added. When the mass of calcium oxide weighed by the online weighing screw feeding device differs from the calculated mass by no more than 10kg, the online weighing screw feeding device and the vibrator are stopped. Finally, the water valve 7 is opened until the liquid level measured by the ultrasonic level meter 9 is equal to the HMI setting value, thus completing a solution preparation cycle. In order to improve the degree of automatic control, a radar level meter 2 is installed on the top of the calcium oxide storage tank 1. The radar level meter 2 detects the height of the calcium oxide powder in the tank in real time and displays it on the HMI in real time. When the material level is too low, an alarm is issued to prompt the user to add material.

Claims

1. A method for preparing a calcium hydroxide solution for wastewater treatment in the steel industry, characterized in that: A calcium hydroxide solution preparation system is used to prepare the calcium hydroxide solution; the calcium hydroxide solution preparation system comprises a calcium oxide storage tank (1), a radar level meter (2), a PLC control cabinet (4), a vibrator (5), an online weighing screw feeder (6), a water valve (7), an ultrasonic level meter (9), a stirrer (10) and a calcium hydroxide solution tank (11); The two ends of the online weighing screw feeding device (6) are respectively connected to the calcium oxide storage tank (1) and the calcium hydroxide solution tank (11); the vibrator (5) is arranged at the bottom of the calcium oxide storage tank (1), and the radar level meter (2) is arranged at the top of the calcium oxide storage tank (1); The top of the calcium hydroxide solution tank (11) is provided with the ultrasonic level meter (9) and a water inlet pipe, the water inlet pipe is provided with the water valve (7), and the calcium hydroxide solution tank (11) is also provided with the stirrer (10); The radar level meter (2), the online weighing screw feeder (6), the vibrator (5) and the ultrasonic level meter (9) are all controlled by the PLC control cabinet (4); the PLC control cabinet (4) is connected to the HMI (8); The steps for preparing calcium hydroxide solution are as follows:

1. When preparing the solution, the HMI sends a start command to the PLC control cabinet (4), and the PLC control cabinet (4) sends a command to start the mixer (10) and the water valve (7), and the industrial water flows into the calcium hydroxide solution tank (11). The ultrasonic level meter (9) detects the liquid level in real time. When the liquid level reaches a given value, the water valve (7) is closed and the vibrator (5) and the online weighing screw feeding device (6) are started. According to the known liquid level and concentration before the solution is prepared, the mass of calcium hydroxide in the solution before preparation is calculated according to the formula density ρ=1000+concentration C×6.8, mass m=liquid level h×bottom area S×honeyness×concentration C, and the mass of calcium hydroxide in the solution before preparation is calculated according to the HMI setting. The liquid level, concentration, and mass of the calcium hydroxide after preparation are calculated according to the above formula, and the mass of the two is subtracted to obtain the mass of the calcium oxide powder that needs to be added. When the mass of calcium oxide weighed by the online weighing screw feeding device (6) differs from the mass calculated by no more than 10 kg, the operation of the online weighing screw feeding device (6) and the vibrator (5) is stopped; finally, the water valve (7) is opened until the liquid level measured by the ultrasonic liquid level meter (9) is equal to the HMI set value, thereby completing a solution preparation cycle; 2. Addition of calcium oxide powder in the calcium oxide storage tank (1): The radar level meter (2) detects the height of the calcium oxide powder in the calcium oxide storage tank (1) in real time and transmits it to the PLC control cabinet (4) in real time and displays it on the HMI. When the material level is too low, addition is performed according to the alarm prompt.

2. The method for preparing a calcium hydroxide solution for treating wastewater in the steel industry according to claim 1, wherein: In step one, the ultrasonic liquid level meter (9) detects the liquid level in real time. When the liquid level reaches 1.8 meters, the water valve (7) is closed and the vibrator (5) and the online weighing screw feeding device (6) are started.

3. The method for preparing a calcium hydroxide solution for treating wastewater in the steel industry according to claim 1 or 2, wherein: The PLC control cabinet (4) adopts a Siemens S7-1500 control cabinet.

4. The method for preparing a calcium hydroxide solution for treating wastewater in the steel industry according to claim 3, wherein: The online weighing screw feeder device (6) comprises a flow-stabilizing motor (6-1) and a metering motor (6-2), which are connected to an online weighing screw feeder control cabinet (3); the online weighing screw feeder control cabinet (3) is connected to the PLC control cabinet (4) and is controlled by the PLC control cabinet (4).

5. The method for preparing a calcium hydroxide solution for treating wastewater in the steel industry according to claim 4, wherein: The specification model of the ultrasonic level meter (9) is FMU30; the specification model of the radar level meter (2) is 7ML5440-0HB00-0AA2.

6. The method for preparing a calcium hydroxide solution for wastewater treatment in the steel industry according to claim 4, wherein: The specifications and models of the current-stabilizing motor (6-1) and the metering motor (6-2) are YVF2-90L-4 and YVF2-90L-4 respectively.

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