Regulation and control method for evaporation and separation of electroplating wastewater

Abstract

The invention discloses a regulation and control method for evaporating and separating electroplating wastewater, which is used for effectively treating electroplating wastewater with different components or working conditions by regulating the pressure in an evaporation and separation tower so as to realize complete crystallization before the electroplating wastewater is discharged. The regulation and control method comprises the following steps: step 10, calculating physical parameters of an electroplating wastewater solution to be treated; step 20, establishing a spray evaporation separation tower model; calculating the optimal pressure value of the electroplating wastewater solution to be treated in the evaporation separation tower according to the spray evaporation separation tower model; step 30, conveying the electroplating wastewater solution to be treated into the evaporation separation tower, wherein the electroplating wastewater solution to be treated forms mist in the evaporation separation tower through a pressure nozzle; and controlling a vortex fan and an electric heater according to the optimal pressure value in the evaporation separation tower, so that the air pressure in the evaporation separation tower is the optimal pressure value, and regulating and controlling the evaporation separation electroplating wastewater.

Description

Technical Field

[0001] The invention belongs to the technical field of sewage treatment and relates to a control method for evaporating and separating electroplating wastewater. Background Art

[0002] In recent years, the contradiction between environmental pollution and development has gradually become a prominent contradiction in economic development and production and life, and is also a major problem in the field of industrial production. In the past five years, wastewater discharge, especially industrial wastewater discharge, has continued to rise. As one of the components of industrial wastewater, electroplating wastewater is particularly important to effectively treat due to its dispersed production, rapid spread of pollution and difficulty in treatment.

[0003] Evaporation separation technology is one of the common methods for treating electroplating wastewater. This technology uses the principle of evaporation to evaporate water from wastewater, concentrate and separate harmful substances in wastewater, and thus achieve wastewater treatment and resource recycling. In traditional evaporation separation systems, high-temperature separation media are required, and the energy consumption for evaporation separation treatment is high, which cannot achieve both "zero waste liquid discharge" and high efficiency and energy saving at the same time.

[0004] In the evaporation separation process, pressure is a very important parameter. It has a direct impact on the efficiency, evaporation rate and separation effect of the evaporation process. Therefore, it is urgent to find a method to calculate the optimal pressure value of the evaporation separation process, and to efficiently treat electroplating wastewater by adjusting the pressure, and to reduce the energy consumption of the evaporation separation system. Summary of the invention

[0005] In order to solve the shortcomings and deficiencies of the prior art, the present invention provides a control method for evaporating and separating electroplating wastewater, which effectively treats electroplating wastewater of different components or working conditions by adjusting the pressure in the evaporation separation tower to achieve complete crystallization of the electroplating wastewater before discharge.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] A control method for evaporating and separating electroplating wastewater comprises the following steps:

[0008] Step 10, calculating the physical parameters of the electroplating wastewater solution to be treated, wherein the physical parameters of the electroplating wastewater solution to be treated include the specific heat capacity, density and dynamic viscosity of the electroplating wastewater solution to be treated; the electroplating wastewater solution to be treated contains n kinds of metal ion solutes; n is an integer greater than or equal to 2;

[0009] Step 20, establishing a spray evaporation separation tower model; calculating the optimal pressure value of the electroplating wastewater solution to be treated in the evaporation separation tower according to the spray evaporation separation tower model;

[0010] Step 30, conveying the electroplating wastewater solution to be treated into the evaporation separation tower, and forming a mist through a pressure nozzle in the evaporation separation tower; according to the optimal pressure value in the evaporation separation tower, controlling the vortex fan and the electric heater so that the air pressure in the evaporation separation tower is the optimal pressure value, thereby realizing the regulation of the evaporation separation of the electroplating wastewater.

[0011] As a preferred example, in step 10, the specific heat capacity of the electroplating wastewater solution to be treated is calculated according to formula (1), the density of the electroplating wastewater solution to be treated is calculated according to formula (2), and the dynamic viscosity of the electroplating wastewater solution to be treated is calculated according to formula (3):

[0012]

[0013]

[0014]

[0015] In the formula, c p represents the specific heat capacity of the electroplating wastewater solution to be treated, c p,1 represents the specific heat capacity of the first solute in the electroplating wastewater solution to be treated, represents the mass percentage of the first solute in the electroplating wastewater solution to be treated, c p,2 represents the specific heat capacity of the second solute in the electroplating wastewater solution to be treated, Indicates the mass percentage of the second solute in the electroplating wastewater solution to be treated; c p,n represents the specific heat capacity of the nth solute in the electroplating wastewater solution to be treated, represents the mass percentage of the nth solute in the electroplating wastewater solution to be treated; ρ s represents the density of the electroplating wastewater solution to be treated, ρ1 represents the density of the first solute in the electroplating wastewater solution to be treated, ρ2 represents the density of the second solute in the electroplating wastewater solution to be treated, and ρ n represents the density of the nth solute in the electroplating wastewater solution to be treated; μ s represents the dynamic viscosity of the electroplating wastewater solution to be treated, μ1 represents the dynamic viscosity of the first solute in the electroplating wastewater solution to be treated, μ2 represents the dynamic viscosity of the second solute in the electroplating wastewater solution to be treated, and μ n It represents the dynamic viscosity of the nth solute in the electroplating wastewater solution to be treated; Satisfying formula (4):

[0016]

[0017] As a preferred example, in step 20, the spray evaporation separation tower model is as shown in formula (5) and formula (6):

[0018] The Sauter mean diameter is used to represent the average size of the non-uniform droplets ejected from the pressure nozzle, as shown in formula (5):

[0019]

[0020] In the formula, r d0 is the droplet radius at the tower inlet of the evaporation separation tower, in m; a is the adjustment coefficient related to the dynamic viscosity of the electroplating wastewater solution to be treated, in kg / s 2 ; θ is the spray half angle of the pressure nozzle; μ s is the dynamic viscosity of the electroplating wastewater solution to be treated, in Pa·s; ρ a is the air density in the evaporation separation tower, in kg / m 3 ;p noz is the pressure of the pressure nozzle, in Pa; O is the spray film thickness of the pressure nozzle, in m; b is the adjustment coefficient related to the density of the electroplating wastewater solution to be treated, in Pa·m; ρ s is the density of the electroplating wastewater solution to be treated, in kg / m 3 ;

[0021]

[0022] Where, O is the spray film thickness of the pressure nozzle, in m; d noz is the spray diameter of the pressure nozzle, in m; m s is the mass flow rate of electroplating wastewater solution to be treated, in kg / s; μ s is the dynamic viscosity of the electroplating wastewater solution, in Pa·s; ρ s is the density of the electroplating wastewater solution to be treated, in kg / m 3 ;p noz is the pressure of the pressure nozzle, in Pa; p a is the air pressure in the evaporation separation tower, in Pa; l sp is the length of the pressure nozzle, in m.

[0023] As a preferred example, in step 20, according to the spray evaporation separation tower model, the process of calculating the optimal pressure value of the electroplating wastewater to be treated in the evaporation separation tower is:

[0024] Step 201: Calculate the spray film thickness O of the pressure nozzle by using formula (6), where p a The initial value is equal to the external ambient air pressure; then substitute the spray film thickness O of the pressure nozzle into formula (5) to calculate the droplet radius r at the tower inlet of the evaporation separation tower d0 ;

[0025] Step 202, the electroplating wastewater solution to be treated forms droplets through a pressure nozzle in an evaporation separation tower; the three stages of a single droplet refer to the first stage of evaporation of a single droplet without a shell, the second stage of formation of a single droplet shell, and the third stage of evaporation of a single droplet with a shell in the evaporation separation tower; in the second stage, a bottom shell is first formed at the bottom of the droplet, and then the area of ​​the bottom shell gradually increases, and finally covers the entire droplet surface, and I is defined as the ratio of the surface area of ​​the droplet not covered by the shell to the total surface area of ​​the droplet, as shown in formula (7):

[0026]

[0027] In the formula, A d is the droplet area, in m 2 ; A cr is the shell area of ​​the droplet, in m 2 ;

[0028] Calculate the droplet parameters at the outlet of the evaporation separation tower, substitute them into formula (7), and calculate the I of the droplet at the outlet of the tower; if I≤0, the wastewater at the outlet is in a completely crystallized state, and replace p in formula (6) a As the optimal pressure value; if I>0, the wastewater at the outlet is unsaturated, and p a The pressure setting decreases as the value decreases, and the process returns to step 201 until I ≤ 0. Then, the p in equation (6) is a is the optimal pressure value calculated iteratively.

[0029] As a preferred example, in step 202, the pressure reduction value is set to 10 kPa.

[0030] As a preferred example, in step 202, the droplet parameters of the tower body outlet of the evaporation separation tower are calculated, specifically including: according to the droplet radius r of the tower body outlet d,out , calculate the droplet area A d ,in, In the formula, m s is the mass flow rate of electroplating wastewater solution, in kg / s; ρ s is the density of the electroplating wastewater solution to be treated; the shell area of ​​the droplet In the formula, r cr is the droplet shell radius at the tower outlet.

[0031] As a preferred example, the evaporation separation tower comprises a top, a tower body and a base which are sequentially connected from top to bottom; and the tower body of the evaporation separation tower gradually shrinks from top to bottom.

[0032] As a preferred example, the top of the evaporation separation tower includes a first expansion portion, a middle portion, a second expansion portion and a connecting portion which are sequentially connected from top to bottom; the diameter of the first expansion portion gradually increases from top to bottom, the diameter of the second expansion portion gradually increases from top to bottom, the middle portion and the connecting portion are both cylindrical, the bottom diameter of the first expansion portion, the top diameter of the second expansion portion, and the diameter of the middle portion are equal, and the bottom diameter of the second expansion portion and the diameter of the connecting portion are equal.

[0033] As a preferred example, the tower body angle of the evaporation separation tower is 5 to 15 degrees.

[0034] Compared with the shortcomings and deficiencies of the prior art, the present invention has the following beneficial effects: the control method effectively treats electroplating wastewater of different components or working conditions by adjusting the pressure in the evaporation separation tower, and achieves complete crystallization of the electroplating wastewater before discharge. The method can calculate the optimal pressure value for evaporation separation of electroplating wastewater of different components and working conditions in the evaporation separation tower, and regulate the pressure in the evaporation separation tower to the optimal pressure value during the evaporation separation process, and can effectively treat electroplating wastewater of various concentrations and various solutes. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is a method flow chart of an embodiment of the present invention;

[0036] Figure 2 Schematic diagram of the structure of the evaporation separation device used in the embodiment of the present invention;

[0037] Figure 3 Schematic diagram of the structure of the evaporation separation tower used in the embodiment of the present invention.

[0038] In the figure: vortex fan 1, electric heater 2, evaporation separation tower 3, top 31, first expansion part 311, middle part 312, second expansion part 313, connecting part 314, tower body 32, base 33; pressure nozzle 4, liquid storage tank 5, bag filter 6. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0040] like Figure 1 As shown, a control method for evaporating and separating electroplating wastewater according to an embodiment of the present invention comprises the following steps:

[0041] Step 10, calculating the physical parameters of the electroplating wastewater solution to be treated, wherein the physical parameters of the electroplating wastewater solution to be treated include the specific heat capacity, density and dynamic viscosity of the electroplating wastewater solution to be treated; the electroplating wastewater solution to be treated contains n kinds of metal ion solutes; and n is an integer greater than or equal to 2.

[0042] Step 20, establishing a spray evaporation separation tower model; and calculating the optimal pressure value of the electroplating wastewater solution to be treated in the evaporation separation tower 3 according to the spray evaporation separation tower model.

[0043] Step 30, conveying the electroplating wastewater solution to be treated into the evaporation separation tower 3, and forming a mist through a pressure nozzle in the evaporation separation tower 3; according to the optimal pressure value in the evaporation separation tower 3, controlling the vortex fan 1 and the electric heater 2, so that the air pressure in the evaporation separation tower 3 is the optimal pressure value, thereby realizing the regulation of the evaporation separation of electroplating wastewater.

[0044] The control method of the above embodiment calculates the optimal pressure value in the evaporation separation tower 3, and then controls the gas pressure in the evaporation separation tower 3 to make it equal to the optimal pressure value. When the gas pressure in the evaporation separation tower 3 is the optimal pressure value, the electroplating wastewater solution to be treated can be in a completely crystalline solid state when discharged from the outlet of the evaporation separation tower 3. This can avoid the higher air temperature required for treating the electroplating wastewater solution at a non-optimal pressure, thereby reducing energy consumption.

[0045] The control method of the above embodiment, the electroplating wastewater to be treated contains a variety of metal ion solutes. Through this control method, it can be achieved that these metal ion solutes are discharged in the form of crystals. During operation, the temperature in the evaporation separation tower 3 is 100-150°C. The device can be operated at medium and low temperatures (within 150°C), without the need for special equipment, low sealing requirements, few consumables, low material requirements, simple and convenient, and low operating costs. This method uses air as a separation carrier to treat electroplating wastewater, and the separation carrier is easy to obtain and is basically not restricted by the environment.

[0046] Preferably, in step 10, the specific heat capacity of the electroplating wastewater solution to be treated is calculated according to formula (1), the density of the electroplating wastewater solution to be treated is calculated according to formula (2), and the dynamic viscosity of the electroplating wastewater solution to be treated is calculated according to formula (3):

[0047]

[0048]

[0049]

[0050] In the formula, c prepresents the specific heat capacity of the electroplating wastewater solution to be treated, c p,1 represents the specific heat capacity of the first solute in the electroplating wastewater solution to be treated, represents the mass percentage of the first solute in the electroplating wastewater solution to be treated, c p,2 represents the specific heat capacity of the second solute in the electroplating wastewater solution to be treated, Indicates the mass percentage of the second solute in the electroplating wastewater solution to be treated; c p,n represents the specific heat capacity of the nth solute in the electroplating wastewater solution to be treated, represents the mass percentage of the nth solute in the electroplating wastewater solution to be treated; ρ s represents the density of the electroplating wastewater solution to be treated, ρ1 represents the density of the first solute in the electroplating wastewater solution to be treated, ρ2 represents the density of the second solute in the electroplating wastewater solution to be treated, and ρ n represents the density of the nth solute in the electroplating wastewater solution to be treated; μ s represents the dynamic viscosity of the electroplating wastewater solution to be treated, μ1 represents the dynamic viscosity of the first solute in the electroplating wastewater solution to be treated, μ2 represents the dynamic viscosity of the second solute in the electroplating wastewater solution to be treated, and μ n It represents the dynamic viscosity of the nth solute in the electroplating wastewater solution to be treated; Satisfying formula (4):

[0051]

[0052] Preferably, in step 20, the spray evaporation separation tower model is as shown in formula (5) and formula (6):

[0053] The Sauter mean diameter is used to represent the average size of the non-uniform droplets ejected from the pressure nozzle, as shown in formula (5):

[0054]

[0055] In the formula, r d0 is the droplet radius of the tower inlet of the evaporation separation tower 3, in m; a is the adjustment coefficient related to the dynamic viscosity of the electroplating wastewater solution to be treated, in kg / s 2 ; θ is the spray half angle of the pressure nozzle; μ s is the dynamic viscosity of the electroplating wastewater solution to be treated, in Pa·s; ρ a is the air density in the evaporation separation tower 3, in kg / m 3 ;p noz is the pressure of the pressure nozzle, in Pa; O is the spray film thickness of the pressure nozzle, in m; b is the adjustment coefficient related to the density of the electroplating wastewater solution to be treated, in Pa·m; ρs is the density of the electroplating wastewater solution to be treated, in kg / m 3 Preferably, a = 2.26 kg / s 2 , b = 0.195 Pa·m.

[0056]

[0057] Where, O is the spray film thickness of the pressure nozzle, in m; d noz is the spray diameter of the pressure nozzle, in m; m s is the mass flow rate of electroplating wastewater solution to be treated, in kg / s; μ s is the dynamic viscosity of the electroplating wastewater solution, in Pa·s; ρ s is the density of the electroplating wastewater solution to be treated, in kg / m 3 ;p noz is the pressure of the pressure nozzle, in Pa; p a is the air pressure in the evaporation separation tower, in Pa; l sp is the length of the pressure nozzle, in m.

[0058] Preferably, in step 20, according to the spray evaporation separation tower model, the process of calculating the optimal pressure value of the electroplating wastewater to be treated in the evaporation separation tower is:

[0059] Step 201: Calculate the spray film thickness O of the pressure nozzle by using formula (6), where p a The initial value is equal to the external ambient air pressure; then substitute the spray film thickness O of the pressure nozzle into formula (5) to calculate the droplet radius r at the tower inlet of the evaporation separation tower d0 ;

[0060] Step 202, the electroplating wastewater solution to be treated forms droplets through a pressure nozzle in the evaporation separation tower 3; the three stages of the single droplet refer to the first stage of single droplet evaporation without shell, the second stage of single droplet shell formation and the third stage of single droplet evaporation with shell in the evaporation separation tower 3; in the second stage, a bottom shell is first formed at the bottom of the droplet, and then the area of ​​the bottom shell gradually increases, and finally covers the entire droplet surface, and I is defined as the ratio of the surface area of ​​the droplet not covered by the shell to the total surface area of ​​the droplet, as shown in formula (7):

[0061]

[0062] In the formula, A d is the droplet area, in m 2 ; A cr is the shell area of ​​the droplet, in m 2 ;

[0063] Calculate the droplet parameters at the outlet of the evaporation separation tower, substitute them into formula (7), and calculate the I of the droplet at the outlet of the tower; if I≤0, the wastewater at the outlet is in a completely crystallized state, and replace p in formula (6) a As the optimal pressure value; if I>0, the wastewater at the outlet is unsaturated, and p a The pressure setting decreases as the value decreases, and the process returns to step 201 until I ≤ 0. Then, the p in equation (6) is a It is the optimal pressure value calculated by iteration. Preferably, the pressure setting reduction value is 10 kPa.

[0064] The optimal pressure value of the electroplating wastewater to be treated in the evaporation separation tower is obtained through iterative calculation of step 201 and step 202. The iterative calculation determines whether the air pressure in the tower is at the optimal value at this time through parameter I. After the optimal value of the air pressure in the tower is iteratively calculated, the electroplating wastewater solution can be effectively treated to a crystalline state and energy consumption can be reduced.

[0065] Preferably, in step 202, calculating the droplet parameters at the tower outlet of the evaporation separation tower specifically includes:

[0066] According to the droplet radius r at the tower outlet d,out , calculate the droplet area A d ,in, In the formula, m s is the mass flow rate of electroplating wastewater solution, in kg / s; ρ s is the density of the electroplating wastewater solution to be treated; the shell area of ​​the droplet In the formula, r cr is the radius of the droplet shell at the tower outlet. cr =0.02r d0 .

[0067] The surface heat transfer coefficient and the surface mass transfer coefficient of the single droplet in the three stages of the electroplating wastewater solution to be treated in the evaporation separation tower 3 are calculated; the electroplating wastewater solution to be treated forms droplets through a pressure nozzle in the evaporation separation tower 3; the three stages of the single droplet refer to the first stage of single droplet evaporation without shell, the second stage of single droplet shell formation and the third stage of single droplet evaporation with shell in the evaporation separation tower 3.

[0068] The single droplet surface heat transfer coefficient α1 in the first stage is calculated according to formula (8):

[0069]

[0070] In the formula, λ a is the thermal conductivity of the air in the evaporation separation tower 3, in W·m -1 ℃ -1 ; Nu sis the Nusselt number of the electroplating wastewater solution to be treated, dimensionless; r d is the droplet radius, in m.

[0071] The single droplet surface heat transfer coefficient α3 in the third stage is calculated according to formula (9):

[0072]

[0073] In the formula, λ a is the thermal conductivity of the air in the evaporation separation tower 3, in W·m -1 ℃ -1 ; Nu s is the Nusselt number of the electroplating wastewater solution to be treated, dimensionless; r d is the droplet radius, in m; λ cr is the shell thermal conductivity of the droplet, in W·m -1 ℃ -1 ; δ cr is the shell thickness of the droplet, in m.

[0074] The single droplet surface mass transfer coefficient β1 in the first stage is calculated according to formula (10):

[0075]

[0076] In the formula, C M,a,1 is the air mass transfer diffusion coefficient in the first stage, in m 2 / s; Sh s is the Sherwood number of the electroplating wastewater solution to be treated, dimensionless; r d is the droplet radius, in m.

[0077] The single droplet surface mass transfer coefficient β3 in the third stage is calculated according to formula (11):

[0078]

[0079] In the formula, C M,a,1 is the air mass transfer diffusion coefficient in the first stage, in m 2 / s; Sh s is the Sherwood number of the electroplating wastewater solution, dimensionless; r d is the droplet radius, in m; C M,a,3 is the air mass transfer diffusion coefficient in the third stage, in m 2 / s; δ cr is the shell thickness of the droplet, in m.

[0080] In the second stage, a bottom shell is first formed at the bottom of the droplet, and then the bottom shell area gradually increases, eventually covering the entire droplet surface. I is defined as the ratio of the surface area of ​​the droplet not covered by the shell to the total surface area of ​​the droplet, as shown in formula (7):

[0081]

[0082] In the formula, A d is the droplet area, in m 2 ; A cr is the shell area of ​​the droplet, in m 2 .

[0083] The single droplet surface heat transfer coefficient α2 in the second stage is calculated according to formula (12):

[0084] α2=Iα1+(1-I)α3Formula (12).

[0085] The single droplet surface mass transfer coefficient β2 in the second stage is calculated according to formula (13):

[0086] β2=Iβ1+(1-I)β3 Formula (13).

[0087] Preferably, Figure 2 As shown, the evaporation separation device used in the control method of this embodiment includes a vortex fan 1, an electric heater 2, an evaporation separation tower 3, a pressure nozzle 4, a liquid storage tank 5, and a bag filter 6. The evaporation separation tower 3 includes a top 31, a tower body 32 and a base 33 connected in sequence from top to bottom. From top to bottom, the tower body 32 of the evaporation separation tower gradually shrinks. Preferably, the tower body 32 of the evaporation separation tower has a retraction angle of 5 to 15°. The vortex fan 1 is connected to the top 31 of the evaporation separation tower through a first pipeline, and the electric heater 2 is connected in the first pipeline. The vortex fan 1 is used to extract external ambient air. The electric heater 2 is used to heat the external ambient air to a desired temperature. The external ambient air is heated to a desired temperature by the vortex fan 1 and the electric heater 2 to form hot air, which is then transported to the inner cavity of the top 31 of the evaporation separation tower. The temperature of the hot air is 110 to 150°C. The external ambient air is air at room temperature, such as air at 18 to 22°C. The outlet of the liquid storage tank 5 is connected to the pressure nozzle 4 through a valve, and the pressure nozzle 4 is located at the upper part of the inner cavity of the evaporation separation tower 3. An exhaust pipe is provided at the bottom of the evaporation separation tower 3, and a bag dust collector 6 is provided in the exhaust pipe.

[0088] The liquid storage tank 5 is used to store the electroplating wastewater to be treated. The pressure nozzle 4 is used to atomize the electroplating wastewater into a spray. During operation, the valve is opened, and the electroplating wastewater in the liquid storage tank 5 is pressurized by the pump and flows to the pressure nozzle 4. The electroplating wastewater is atomized into a spray in the inner cavity of the top 31 of the evaporation separation tower through the pressure nozzle 4. Atomizing the electroplating wastewater into a spray through the pressure nozzle 4 is more conducive to the heat exchange between the electroplating wastewater and the hot air transported from the hot air component, so that the water in the mist electroplating wastewater is easier to evaporate. The mist electroplating wastewater and the hot air converge at the top 31 of the evaporation separation tower and flow from top to bottom. During the flow process, the mist electroplating wastewater and the hot air further exchange heat.

[0089] The electric heater 2 can adjust the air temperature. According to different electroplating wastewater components or working conditions, the heat and mass transfer process in the evaporation separation tower 3 is enhanced by adjusting the flow rate and pressure of the electroplating wastewater and the air temperature.

[0090] The electroplating wastewater and hot air fall from top to bottom in the evaporation separation tower 3, and heat exchange is achieved during the falling process, and the water in the electroplating wastewater evaporates. At the bottom of the evaporation separation tower 3, the exhaust gas is discharged from the exhaust pipe, and the water in the electroplating wastewater evaporates to form solid recovery. The electroplating wastewater flows from top to bottom in the tower body 32 of the evaporation separation tower, and the concentration is getting higher and higher. Compared with the electroplating wastewater located at the upper part of the tower body 32, the electroplating wastewater located in the middle and lower part of the tower body 32 is high-concentration electroplating wastewater. The high-concentration electroplating wastewater in the middle and lower part of the evaporation separation tower 3 has a large thermal resistance to heat and mass transfer with hot air, resulting in poor heat and mass transfer effect. In this embodiment, the tower body 32 of the evaporation separation tower gradually shrinks, rather than being a cylinder with equal diameter. The tower body of the evaporation separation tower 3 gradually shrinks, and the heat and mass transfer driving force can be increased after reducing the pressure of the high-concentration electroplating wastewater, which plays a role in strengthening the heat and mass transfer between the high-concentration electroplating wastewater and the hot air.

[0091] Preferably, Figure 3 As shown, the top portion 31 of the evaporation separation tower includes a first expansion portion 311, a middle portion 312, a second expansion portion 313 and a connecting portion 314 which are sequentially connected from top to bottom; the diameter of the first expansion portion 311 gradually increases from top to bottom, the diameter of the second expansion portion 313 gradually increases from top to bottom, the middle portion 312 and the connecting portion 314 are both cylindrical, the bottom diameter of the first expansion portion 311, the top diameter of the second expansion portion 313, and the diameter of the middle portion 312 are equal, and the bottom diameter of the second expansion portion 313 and the diameter of the connecting portion 314 are equal. The cylindrical connecting portion 314 is provided to connect the top portion 31 of the evaporation separation tower to the tower body 32. Figure 3As described, the top 31 of the evaporation separation tower can be connected to the tower body 32 by a connecting flange. The first expansion portion 311 and the second expansion portion 313 are both in the shape of a trumpet with a small top and a large bottom, in order to reduce the speed of the airflow, so that the hot air can be more fully mixed with the mist electroplating wastewater, so that the water in the mist electroplating wastewater evaporates faster. The airflow flowing through the vortex fan 1 and the electric heater 2 has a faster speed after entering the top 31 of the evaporation separation tower. The airflow velocity is reduced by the first expansion portion 311 and the second expansion portion 313.

[0092] In the method of this embodiment, the evaporation separation tower is operated to maintain an optimal pressure value so that the inlet air temperature required for complete evaporation separation is minimized. Therefore, reducing the pressure in the evaporation separation tower can achieve complete evaporation separation of the electroplating wastewater at a low inlet air temperature. Preferably, the temperature of the hot air entering the evaporation separation tower is 110-150°C. According to the different components or working conditions of the electroplating wastewater, the pressure in the evaporation separation tower is adjusted to optimize and control the evaporation separation treatment of the electroplating wastewater.

[0093] The method of this embodiment determines the optimal pressure for treating electroplating wastewater of different components or working conditions by establishing an evaporation separation tower model with adjustable pressure, and performs regulation. The tower body of the evaporation separation tower is a tapered structure from top to bottom. The pressure of the electroplating wastewater in the tower is gradually reduced by using the principle of tapered nozzles, and the electroplating wastewater with higher concentration in the middle and lower parts of the tower body can be effectively treated.

[0094] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A control method for evaporating and separating electroplating wastewater, characterized in that: The control method comprises the following steps: Step 10, calculating the physical parameters of the electroplating wastewater solution to be treated, wherein the physical parameters of the electroplating wastewater solution to be treated include the specific heat capacity, density and dynamic viscosity of the electroplating wastewater solution to be treated; the electroplating wastewater solution to be treated contains n kinds of metal ion solutes; n is an integer greater than or equal to 2; Step 20, establishing a spray evaporation separation tower model; calculating the optimal pressure value of the electroplating wastewater solution to be treated in the evaporation separation tower (3) according to the spray evaporation separation tower model; Step 30, conveying the electroplating wastewater solution to be treated into the evaporation separation tower (3), wherein the electroplating wastewater solution to be treated is formed into a mist through a pressure nozzle in the evaporation separation tower (3); and controlling the vortex fan (1) and the electric heater (2) according to the optimal pressure value in the evaporation separation tower (3), so that the air pressure in the evaporation separation tower (3) is the optimal pressure value, thereby realizing the regulation and control of the evaporation separation of the electroplating wastewater.

2. The control method for evaporating and separating electroplating wastewater according to claim 1, characterized in that: In step 10, the specific heat capacity of the electroplating wastewater solution to be treated is calculated according to formula (1), the density of the electroplating wastewater solution to be treated is calculated according to formula (2), and the dynamic viscosity of the electroplating wastewater solution to be treated is calculated according to formula (3): In the formula, c p represents the specific heat capacity of the electroplating wastewater solution to be treated, c p,1 represents the specific heat capacity of the first solute in the electroplating wastewater solution to be treated, represents the mass percentage of the first solute in the electroplating wastewater solution to be treated, c p,2 represents the specific heat capacity of the second solute in the electroplating wastewater solution to be treated, Indicates the mass percentage of the second solute in the electroplating wastewater solution to be treated; c p,n represents the specific heat capacity of the nth solute in the electroplating wastewater solution to be treated, represents the mass percentage of the nth solute in the electroplating wastewater solution to be treated; ρ s represents the density of the electroplating wastewater solution to be treated, ρ1 represents the density of the first solute in the electroplating wastewater solution to be treated, ρ2 represents the density of the second solute in the electroplating wastewater solution to be treated, and ρ n represents the density of the nth solute in the electroplating wastewater solution to be treated; μ s represents the dynamic viscosity of the electroplating wastewater solution to be treated, μ1 represents the dynamic viscosity of the first solute in the electroplating wastewater solution to be treated, μ2 represents the dynamic viscosity of the second solute in the electroplating wastewater solution to be treated, and μ n It represents the dynamic viscosity of the nth solute in the electroplating wastewater solution to be treated; Satisfying formula (4):

3. The control method for evaporating and separating electroplating wastewater according to claim 1, characterized in that: In step 20, the spray evaporation separation tower model is shown in formula (5) and formula (6): The Sauter mean diameter is used to represent the average size of the non-uniform droplets ejected from the pressure nozzle, as shown in formula (5): In the formula, r d0 is the droplet radius at the tower inlet of the evaporation separation tower (3), in m; a is the adjustment coefficient related to the dynamic viscosity of the electroplating wastewater solution to be treated, in kg / s 2 ; θ is the spray half angle of the pressure nozzle; μ s is the dynamic viscosity of the electroplating wastewater solution to be treated, in Pa·s; ρ a is the air density in the evaporation separation tower (3), in kg / m 3 ;p noz is the pressure of the pressure nozzle, in Pa; O is the spray film thickness of the pressure nozzle, in m; b is the adjustment coefficient related to the density of the electroplating wastewater solution to be treated, in Pa·m; ρ s is the density of the electroplating wastewater solution to be treated, in kg / m 3 ; Where, O is the spray film thickness of the pressure nozzle, in m; d noz is the spray diameter of the pressure nozzle, in m; m s is the mass flow rate of electroplating wastewater solution to be treated, in kg / s; μ s is the dynamic viscosity of the electroplating wastewater solution, in Pa·s; ρ s is the density of the electroplating wastewater solution to be treated, in kg / m 3 ; p noz is the pressure of the pressure nozzle, in Pa; p a is the air pressure in the evaporation separation tower, in Pa; l sp is the length of the pressure nozzle, in m.

4. The control method for evaporating and separating electroplating wastewater according to claim 3, characterized in that: In step 20, according to the spray evaporation separation tower model, the process of calculating the optimal pressure value of the electroplating wastewater to be treated in the evaporation separation tower is: Step 201: Calculate the spray film thickness O of the pressure nozzle by using formula (6), where p a The initial value is equal to the external ambient air pressure; then substitute the spray film thickness O of the pressure nozzle into formula (5) to calculate the droplet radius r at the tower inlet of the evaporation separation tower d0 ; Step 202: the electroplating wastewater solution to be treated is formed into droplets through a pressure nozzle in an evaporation separation tower (3); the three stages of a single droplet refer to a first stage of evaporation of a single droplet without a shell, a second stage of formation of a single droplet shell, and a third stage of evaporation of a single droplet with a shell in the evaporation separation tower (3); in the second stage, a bottom shell is first formed at the bottom of the droplet, and then the area of ​​the bottom shell gradually increases, and finally covers the entire droplet surface, and I is defined as the ratio of the surface area of ​​the droplet not covered by the shell to the total surface area of ​​the droplet, as shown in formula (7): In the formula, A d is the droplet area, in m 2 ; A cr is the shell area of ​​the droplet, in m 2 ; Calculate the droplet parameters at the outlet of the evaporation separation tower, substitute them into formula (7), and calculate the I of the droplet at the outlet of the tower; if I≤0, the wastewater at the outlet is in a completely crystallized state, and replace p in formula (6) a As the optimal pressure value; if I>0, the wastewater at the outlet is unsaturated, and p a The pressure setting decreases as the value decreases, and the process returns to step 201 until I ≤ 0. Then, the p in equation (6) is a is the optimal pressure value calculated iteratively.

5. The control method for evaporating and separating electroplating wastewater according to claim 4, characterized in that: In step 202, the pressure reduction value is set to 10 kPa.

6. The control method for evaporating and separating electroplating wastewater according to claim 4, characterized in that: In step 202, the droplet parameters at the tower outlet of the evaporation separation tower are calculated, specifically including: according to the droplet radius r at the tower outlet d,out , calculate the droplet area A d ,in, In the formula, m s is the mass flow rate of electroplating wastewater solution, in kg / s; ρ s is the density of the electroplating wastewater solution to be treated; Shell area of ​​the droplet In the formula, r cr is the radius of the droplet shell at the tower outlet.

7. The control method for evaporating and separating electroplating wastewater according to claim 6, characterized in that: The r cr =0.02r d0 .

8. The control method for evaporating and separating electroplating wastewater according to claim 1, characterized in that: The evaporation separation tower (3) comprises a top (31), a tower body (32) and a base (33) which are connected in sequence from top to bottom; the tower body (32) of the evaporation separation tower gradually shrinks from top to bottom.

9. The control method for evaporating and separating electroplating wastewater according to claim 8, characterized in that: The top (31) of the evaporation separation tower comprises a first expansion portion (311), a middle portion (312), a second expansion portion (313) and a connecting portion (314) which are sequentially connected from top to bottom; the diameter of the first expansion portion (311) gradually increases from top to bottom, the diameter of the second expansion portion (313) gradually increases from top to bottom, the middle portion (312) and the connecting portion (314) are both cylindrical, the bottom diameter of the first expansion portion (311), the top diameter of the second expansion portion (313) and the diameter of the middle portion (312) are equal, and the bottom diameter of the second expansion portion (313) and the diameter of the connecting portion (314) are equal.

10. The control method for evaporating and separating electroplating wastewater according to claim 8, characterized in that: The tower body (32) of the evaporation separation tower has a contraction angle of 5 to 15 degrees.

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