A method for calculating the kinematic viscosity of polyacrylamide solutions and a mixing system

Abstract

This invention belongs to the field of coal slurry water treatment technology, specifically relating to a method for calculating the kinematic viscosity of a polyacrylamide solution and a mixing system. The kinematic viscosity γ of the polyacrylamide solution in this invention is obtained through the following formula: The formula for calculating the kinematic viscosity of the polyacrylamide solution in this invention enables rapid and accurate calculation of the kinematic viscosity of the polyacrylamide solution, facilitating real-time monitoring of the mixing state of the solution in the mixing tank. Based on the comparison between the current kinematic viscosity and a preset specified viscosity value, targeted addition of materials or water is made until the optimal mixture, i.e., the polyacrylamide solution, is obtained efficiently and conveniently online.

Description

Technical Field

[0001] This invention belongs to the field of coal slurry water treatment technology, specifically relating to a method for calculating the kinematic viscosity of a polyacrylamide solution and a mixing system. Background Technology

[0002] Coal slurry water treatment is a crucial step in the wet coal preparation process. From both economic and environmental perspectives, deep clarification of the coal slurry water and closed-loop circulation of the wash water are essential. Coal preparation plants typically use coagulation to treat coal slurry water. This involves adding a coagulant to the coal slurry water system, causing particles to agglomerate and settle due to gravity. Commonly used coagulants are organic polymeric flocculants, such as polyacrylamide. However, due to their large molecular weight and long side chains, organic polymeric flocculants suffer from drawbacks such as long dissolution times and incomplete dissolution. Improper preparation can lead to low concentrations and waste, and in severe cases, directly impact the treatment efficiency of the coal slurry water. Traditionally, coal preparation plants manually add powdered flocculants directly to a mixing tank and stir. However, uneven feeding and insufficient mixing often result in agglomeration and incomplete dissolution. Furthermore, a dedicated operator is required to monitor the liquid level and add powdered flocculants on time, which introduces a certain degree of lag. Although utility model patent 201721157662.5 proposes using a screw feeder to solve the problem of uneven feeding, and invention patent 201410260122.4 proposes using a chemical dispersion sieve to achieve uniform dispersion of the chemical during the feeding process, these patents cannot solve the problems of insufficient mixing, agglomeration during stirring, and arching and clumping in the storage bin. Therefore, a precise and efficient mixing system is essential. On the other hand, as the most common flocculant, the efficient dispersion and sufficient dissolution of polyacrylamide are also crucial for achieving efficient coal slurry water treatment. Therefore, there is an urgent need to implement online monitoring in a more efficient and convenient way to provide better flocculant conditions for subsequent coal slurry water treatment. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for calculating the kinematic viscosity of polyacrylamide solution. This method can efficiently and conveniently calculate the kinematic viscosity of polyacrylamide solution, ultimately ensuring the efficient online mixing effect of polyacrylamide.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A method for calculating the kinematic viscosity of polyacrylamide solutions, characterized by:

[0006] The kinematic viscosity γ of the polyacrylamide solution is obtained by the following formula:

[0007]

[0008] in:

[0009] P represents the stirring power of the stirring motor, measured in watts (W).

[0010] ρ is the density of the polyacrylamide solution, in kg / m³. 3 ;

[0011] N represents the number of revolutions per second of the impeller, expressed in r / s.

[0012] d is the diameter of the agitator impeller, in meters (m).

[0013] D is the diameter of the mixing tank, in meters (m).

[0014] u represents the blade width of the agitator impeller, in meters (m).

[0015] α is the lateral tilt angle of the impeller blades;

[0016] β is the longitudinal tilt angle of the impeller blades.

[0017] Preferably, the mixing system, which applies the kinematic viscosity calculation method based on polyacrylamide solution, is characterized by: including a stirring device for agitating the flocculant, a water replenishment device for replenishing water into the stirring device, and a drug replenishment device for replenishing the stirring device with a high-concentration initial mixture; wherein:

[0018] Preferably, the liquid replenishment device includes a two-stage dissolving assembly; the two-stage dissolving assembly includes a dissolving tank with an internal partition, the partition dividing the inner cavity of the dissolving tank into a primary dissolving chamber in the upper layer and a secondary dissolving chamber in the lower layer. A return pipe is provided between the two dissolving chambers to allow liquid in the primary dissolving chamber to flow into the secondary dissolving chamber, and an inlet pipe is provided to allow liquid in the secondary dissolving chamber to be pumped into the primary dissolving chamber via a pressure pump. A heating element is arranged at the bottom of the secondary dissolving chamber and is connected to a water source through a first water pipe equipped with a first water pump. The secondary dissolving chamber is also connected to a stirring device through an outlet pipe. Switch valves are arranged on both the first water pipe and the outlet pipe. A feeding assembly is arranged at the top of the primary dissolving chamber.

[0019] Preferably, the feeding assembly includes a storage silo, within which a screw feeder is arranged to deliver the powdered flocculant into the quantitative weighing assembly. The outlet of the quantitative weighing assembly is connected to the secondary dissolution chamber. The quantitative weighing assembly includes a drum cavity and a weighing pan that rotates within the drum cavity via a rotating shaft. The cantilevered plate surface of the weighing pan forms a weighing surface for receiving the powdered flocculant. The power sources of both the quantitative weighing assembly and the screw feeder are electrically connected to a PLC control device.

[0020] Preferably, the water replenishment device includes a second water pipe with a second water pump, the outlet of the second water pipe being connected to a stirring device; the two ends of the liquid outlet pipe are respectively connected to the secondary dissolving chamber and the second water pipe; a first solenoid valve is arranged at the outlet of the first water pipe, a second solenoid valve is arranged at the inlet of the liquid outlet pipe, and a third solenoid valve is located at the outlet of the second water pipe, and each solenoid valve is electrically connected to a PLC control device.

[0021] Preferably, the stirring device includes a stirring tank and a stirring shaft arranged inside the stirring tank. A stirring motor is arranged at the top of the stirring shaft, and a stirring impeller is arranged at the bottom of the stirring shaft. A drain pipe is provided at the bottom of the stirring tank, and a fourth solenoid valve is provided on the drain pipe. The stirring motor and the fourth solenoid valve are electrically connected to a PLC control device.

[0022] Preferably, the inner wall of the mixing tank is equipped with a first float level gauge for monitoring the liquid level inside the tank, and the first ultrasonic probe of the first float level gauge is electrically connected to a PLC control device.

[0023] Preferably, the wall of the primary dissolving chamber is equipped with a second float level gauge for monitoring the liquid level in the chamber, and the second ultrasonic probe of the second float level gauge is electrically connected to a PLC control device.

[0024] Preferably, a temperature sensor is arranged on the wall of the secondary dissolution chamber, and the temperature sensor is electrically connected to the PLC control device.

[0025] The beneficial effects of this invention are as follows:

[0026] 1) Through the above scheme, the present invention can quickly and accurately calculate the kinematic viscosity of the polyacrylamide solution based on the stirring process of the stirring components in the current mixing system, so as to facilitate the monitoring of the current mixing state of the solution in the stirring tank at any time. Based on the comparison between the current kinematic viscosity and the preset specified viscosity value, materials or water are added in a targeted manner until the optimal mixture, i.e., the polyacrylamide solution, is obtained online in a highly efficient and convenient manner. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the hybrid system.

[0028] Figure 2 This is a schematic diagram of the drug replenishment device;

[0029] Figure 3 The graph shows the fitting relationship between the Reynolds number and the power number after 18 million polyacrylamide solutions are stirred and dissolved.

[0030] The actual correspondence between the reference numerals and component names in this invention is as follows:

[0031] 10-Stirring device; 11-Drainage pipeline; 12-First float level gauge;

[0032] 20 - Water supply device; 21 - Second water pipe; 22 - Second water pump;

[0033] 30-Medicine solution replenishment device; 31-Dissolving tank; 31a-Baffle plate; 31b-Primary dissolving chamber; 31c-Secondary dissolving chamber; 31d-Return pipe; 31e-Inlet pipe; 32-Heating element; 32a-First water pump; 32b-First water pipe; 33-Temperature sensor; 34-Discharge pipe; 35a-Storage bin; 35b-Screw feeder; 35c-Drum cavity; 35d-Weighing pan; 35e-Rotating shaft; 36-Second float level gauge;

[0034] 41-First solenoid valve; 42-Second solenoid valve; 43-Third solenoid valve; 44-Fourth solenoid valve. Detailed Implementation

[0035] For ease of understanding, this section combines... Figure 1-3 The specific structure and operation of the present invention are further described below:

[0036] like Figure 1 As shown, this invention includes a stirring device 10, a water replenishment device 20 for replenishing water and a drug replenishment device 30 for replenishing high-concentration initial mixed solution, respectively. These devices can be linked together via a PLC control device, effectively improving the level of automation. In particular, the measurable viscosity of the solution within the stirring device 10 greatly reduces the input of manpower and resources, resulting in more uniform dispersion and mixing of the drug in the aqueous solution, faster drug dissolution, and ultimately obtaining the drug with the most suitable viscosity, thereby reducing drug consumption. Simultaneously, the quantitative weighing component effectively avoids deviations in drug addition caused by human factors, further improving drug mixing efficiency.

[0037] 1. Medicine replenishment device 30

[0038] The liquid replenishment device 30 includes a two-stage dissolution assembly, a feeding assembly, and corresponding first water pump 32a, first water pipe 32b, and liquid outlet pipe 34.

[0039] The feeding assembly includes a storage bin 35a, such as Figure 1-2 As shown, the top of the storage silo 35a is designed with an openable feed inlet, facilitating the pouring of powdered flocculant and observation of the silo's contents. Once the storage silo 35a is filled, staff can participate in inspections at other work stations. The discharge from the storage silo 35a is automatically controlled. A screw conveyor 35b connects the storage silo 35a to the discharge outlet. The power source at its upper end, namely the variable frequency drive motor, is controlled by a PLC control device, ensuring uniform rotation and guaranteeing even discharge of the powdered flocculant, i.e., powdered polyacrylamide, preventing blockages and clumping during the discharge process.

[0040] A quantitative weighing assembly is installed below the storage silo 35a for quantitatively conveying and adding powdered flocculant. The quantitative weighing assembly consists of a spherical weighing chamber (drum 35c), a weighing pan 35d, and an electrically operated rotating shaft 35e. The powdered flocculant is fed onto the weighing pan 35d by the screw feeder 35b. When the pre-set mass range is reached, the PLC control device controls the variable frequency drive motor to stop rotating. Then, the PLC control device controls the rotating shaft 35e to rotate, pouring the powdered flocculant from the weighing pan 35d into the primary dissolving chamber 31b.

[0041] The drug dispersion process of this invention is mainly completed by a two-stage dissolution assembly and a stirring device 10. The two-stage dissolution assembly includes a dissolution tank 31, which is divided into a primary dissolution chamber 31b and a secondary dissolution chamber 31c by a partition 31a. After being quantitatively weighed, the powdered flocculant is directly placed in the upper layer, i.e., the primary dissolution chamber 31b, to await dissolution. The lower layer is the secondary dissolution chamber 31c, which contains a heating element 32 and a temperature sensor 33, both controlled by a PLC control device. The heating element 32 first heats the water to 25 degrees Celsius, and the temperature sensor 33 stops heating after feeding back the temperature to the PLC control device. When the water temperature reaches 25 degrees Celsius, a pressure pump between the two dissolution chambers draws the water from the lower layer to the upper layer through the inlet pipe 31e to mix with the powdered flocculant. A return pipe 31d connects the upper and lower layers. The dissolved agent in the upper layer flows into the lower layer through the return pipe 31d. This continues for a period of time until all the agent in the upper layer dissolves in the water and flows into the lower layer, forming a pre-dissolved, high-concentration initial mixture in the lower layer. A second float level gauge 36, including a corresponding ultrasonic probe and float, can be installed in the upper layer, i.e., the primary dissolution chamber 31b. The float is installed in the float channel on the outer edge of the tank and moves vertically up and down with the liquid level. The second float level gauge 36 transmits the measured liquid level data to the PLC control device. When the liquid level in the upper layer stabilizes, it indicates that the powdered flocculant has been preliminarily dissolved into a solution.

[0042] II. Water supply device 20

[0043] like Figure 1 As shown, the water replenishment device 20 consists of a second water pipe 21 and a second water pump 22. At this time, there is an intersection between the second water pipe 21 and the liquid outlet pipe 34, so that the second water pipe 21 and the liquid outlet pipe 34 together form a single outlet, and the outlet is effectively controlled by the third solenoid valve 43.

[0044] Correspondingly, the first solenoid valve 41 is located at the outlet of the first water pipe 32b, the second solenoid valve 42 is located at the inlet of the liquid outlet pipe 34, and the fourth solenoid valve 44 is located as follows: Figure 1 All solenoid valves on the drain pipe 11 located at the bottom of the mixing tank are electrically connected to the PLC control device.

[0045] III. Stirring Device 10

[0046] Stirring device 10 Figure 1 As shown, the system includes a mixing tank, a mixing shaft, a mixing motor, and a mixing impeller. A liquid level measuring device, namely the first float level gauge 12, is also installed inside the mixing tank. The mixing motor can also be controlled by a PLC control device, allowing for adjustments to different speeds to achieve precise mixing. Of course, as with the aforementioned PLC control device, the signal transmission and control operations of the control module for the solenoid valves and various motors are standard procedures and will not be elaborated upon here.

[0047] In actual operation, a force sensor can be installed at the lower end of the stirring shaft to record the torque, speed, and time of the stirring shaft rotation, and feed the data back to the PLC control device in real time. At the same time, the stirring power P of the stirring device 10 can be calculated as follows:

[0048]

[0049] In the formula:

[0050] P represents power, measured in W; T represents torque; and n represents rotational speed, measured in r / min.

[0051] Based on the above structure, to further facilitate understanding of the present invention, the derivation process of the formula of the present invention is given here as follows:

[0052] Using a glass constant temperature water bath as a stirring tank, 10L of test water was added, and the liquid level was 20cm.

[0053] The mixing tank has a diameter of 30cm and the mixing shaft rotates at a speed of 200-1600r / s.

[0054] The impeller blades are 2cm in diameter, 0.1cm wide, and 3.3cm high, with a lateral tilt angle of 30° and a longitudinal tilt angle of 10°.

[0055] The stirring shaft is 19.4cm long and 0.6cm in diameter. The blades of the stirring impeller are 8cm from the bottom of the mixing tank.

[0056] The experiment was conducted in accordance with GB / T 17514-2017 "Anionic and Nonionic Polyacrylamide for Water Treatment". Specifically, a cantilevered stirring device was used in a glass constant-temperature water bath with the stirring speed set. Polyacrylamide was then stirred to prepare a 0.5‰ polyacrylamide solution. The experiment was stopped when the conductivity value of the conductivity meter showed no significant change within 2 minutes. The time from the addition of polyacrylamide to the point where the conductivity value remained constant was defined as the dissolution time.

[0057] The absence of significant change in conductivity over 2 minutes was used as the indicator for evaluating the complete dissolution of the flocculant.

[0058] At this point, 10L of water was weighed using a graduated cylinder and poured into a glass constant-temperature water bath. The stirring speed of the stirring device was set to 200–1600 r / s, increasing by 200 r / s in each group, for a total of 8 groups, corresponding to a blade linear velocity of 0.21–1.68 m / s. The constant temperature was set to 25℃. Once the temperature reached the set value, the cantilevered stirring device was turned on for stirring. 5g of anionic polyacrylamide, weighed by an electronic balance, was slowly and evenly poured in along the edge of the vortex generated by stirring. Stirring continued until the conductivity value of the conductivity meter showed no significant change within 2 minutes, at which point the experiment was stopped. The viscometer was set to rotor number zero and the rotation speed was 60 r / s. The dynamic viscosity of the polyacrylamide solution after dissolution was measured and recorded. The density of the solution after dissolution was measured and calculated using a weighing method. The stirring power, kinematic viscosity, Reynolds number, and power coefficient of the solution after dissolution were calculated using formulas.

[0059] Based on the data obtained from the above experiments, the following table shows the derivation process of the formula for the data verification of the stirring and dissolving test of 18 million molecular weight polyacrylamide:

[0060] Table 1. Stirring and Dissolution Test Results of 18 Million Molecular Weight Polyacrylamide

[0061]

[0062] 1) The impeller linear velocity is calculated based on the impeller diameter and impeller speed:

[0063] v=πdN

[0064] In the formula:

[0065] v is the linear velocity of the impeller, in m / s; d is the diameter of the impeller, in m; N is the number of revolutions per second of the impeller, in r / s.

[0066] 2) Kinematic viscosity is the ratio of the solution's dynamic viscosity to its density, and it is also an evaluation index for selecting the optimal stirring speed. Therefore:

[0067]

[0068]

[0069] In the formula:

[0070] γ is the kinematic viscosity of the solution after dissolution, in m. 2 / s; μ is the dynamic viscosity of the solution after dissolution, in Pa·s; ρ is the density of the solution after dissolution, in kg / m³. 3 Re is the Reynolds number.

[0071] 3) Given the geometric parameters of the stirred vessel, the power number K can be calculated using the power number of Susumu Nagata, as follows:

[0072]

[0073] In the formula:

[0074] K is the power number; H is the liquid level height in meters; D is the diameter of the mixing tank in meters; u is the blade width of the impeller in meters; α is the blade tilt angle; d is the diameter of the impeller in meters; A, B, and C are intermediate variables.

[0075] 4) For the existing stirring power formula P=KρN 3 d 5 The improvement involves changing the single-factor impeller diameter d to a three-factor product: the ratio of impeller diameter to mixing tank diameter d / D, the mixing tank diameter D, and the product of the impeller blade width u and the impeller tilt angle sinα. The indices for these three factors are obtained through data fitting as follows:

[0076] P = f(ρ, d, D, u, α, N) = Kρ a d b D c (usinα) e N f

[0077]

[0078] In the formula:

[0079] P is the stirring power, in W; K is the power number; d is the diameter of the stirring impeller, in m; D is the diameter of the stirring tank, in m; N is the number of revolutions per second of the stirring impeller, in r / s; u is the blade width of the stirring impeller, in m; α is the blade tilt angle; M is the dimension of mass; L is the dimension of length; T is the dimension of time.

[0080] 5) Based on the aforementioned experimental data, the mathematical relationship between the stirring power P and the power coefficient K suitable for dissolving polyacrylamide is fitted as follows:

[0081]

[0082] Figure 3 The figure shows the fitting relationship between the Reynolds number and the power number after 18 million polyacrylamide solutions are stirred and dissolved. That is, under the condition that other conditions are constant, the Reynolds number and the power number are power-law related in the stirring speed range of 200 to 1600 r / s.

[0083] At this point, the general formula relating the Reynolds number Re to K for various molecular weights of polyacrylamide is obtained as follows:

[0084] K = 10.048Re -0.532

[0085] Subsequently, the original formulas for calculating impeller linear velocity and Reynolds number were improved by adding the longitudinal tilt angle β of the impeller blades as an influencing factor.

[0086] v=πNdcosβ

[0087]

[0088] 6) Based on the above mathematical relationships, the kinematic viscosity γ of the solution is finally obtained as:

[0089]

[0090] During operation, if the viscosity of the solution in the stirring device is greater than the required viscosity value, the PLC control device controls the water replenishment device 20 to add water; if the viscosity of the solution is less than the required viscosity, the PLC control device controls the corresponding solenoid valve to obtain a high-concentration initial mixture from the dissolving tank 31 to replenish the stirring tank.

[0091] The actual workflow of this invention is as follows:

[0092] The storage silo 35a can be manually opened, and powdered flocculant can be added to fill it. After closing the silo cover, no manual control is required.

[0093] Subsequently, the invention begins fully automated operation. The PLC control device controls the screw feeder 35b to start working, feeding the powdered flocculant into the drum 35c. The powdered flocculant falls onto the weighing pan 35d for weighing, and the mass data is fed back to the PLC control device and recorded. When the mass reaches a preset range, the PLC control device controls the variable frequency drive motor to stop rotating, i.e., stop adding flocculant. Then, the rotating shaft 35e in the middle of the weighing pan 35d is controlled by the PLC control device to rotate the weighing pan 35d 90 degrees, pouring the powdered flocculant into the primary dissolving chamber 31b for dissolution. If the mass is insufficient after one weighing, the process can be repeated until the required mass is achieved. When adjusting the flocculant viscosity, if the high-concentration initial mixture in the dissolving tank 31 is insufficient, the feeding assembly, the first water pump 32a, and the first water pipe 32b will also work together to add a second batch of flocculant and water to achieve quantitative control of the amount of powdered flocculant added and quantitative dissolution.

[0094] The PLC control unit controls the first solenoid valve 41, causing the first water pump 32a to add a set amount of water through the first water pipe 32b into the secondary dissolving chamber 31c below the primary dissolving chamber 31b. Simultaneously, it controls the heating element 32 in the secondary dissolving chamber 31c to operate, heating the water to 25 degrees Celsius. The secondary dissolving chamber 31c is equipped with a temperature sensor 33, which feeds back temperature data to the PLC control unit. When the temperature reaches 25 degrees Celsius, the heating element 32 stops operating. Afterwards, the PLC control unit controls the pressure pump to pump water from the lower layer to the upper layer through the inlet pipe 31e. A return pipe 31d connects the upper and lower layers, allowing the liquid from the upper layer to flow back to the lower layer. After this process continues for a specific period, the powdered flocculant in the upper layer will completely dissolve into the water in the lower layer.

[0095] The PLC control unit opens the second solenoid valve 42 and the third solenoid valve 43, and simultaneously the second water pump 22 at the top of the mixing tank is also turned on, adding clean water and high-concentration initial mixture into the mixing tank. The second solenoid valve 42 and the third solenoid valve 43 can control the flow rate, and the amount of clean water and high-concentration initial mixture can be preset and quantitatively added by controlling the corresponding solenoid valves.

[0096] After adding a certain amount of clean water and a high-concentration initial mixture, the PLC control device controls the stirring motor to rotate, mixing the clean water and the high-concentration initial mixture for dissolution and stirring. During stirring, the stirring device 10 feeds data back to the PLC control device in real time, allowing the stirring power to be calculated. The relationship between the stirring power P, power number K, and Reynolds number Re obtained through experiments can be used to calculate the solution viscosity. After thorough stirring, if the solution viscosity is greater than the required viscosity value, the PLC control device controls the first water pump 32a and the third solenoid valve 43 to add water; if the solution viscosity is less than the required viscosity, the PLC control device controls the second solenoid valve 42 to obtain the high-concentration initial mixture from the secondary dissolution chamber 31c, ultimately preparing the flocculant with the optimal viscosity.

[0097] Finally, the PLC control device controls the fourth solenoid valve 44 to open, which can quantitatively deliver the required flocculant in the mixing tank to the required location, thus completing the entire automated process.

[0098] Of course, those skilled in the art will recognize that the present invention is not limited to the details of the exemplary embodiments described above, but also includes the same or similar structures that can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0099] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0100] The technologies, shapes, and structures not described in detail in this invention are all known technologies.

Claims

1. A method for calculating the kinematic viscosity of polyacrylamide solutions, characterized in that: The system includes a mixing system based on a kinematic viscosity calculation method for a polyacrylamide solution. The mixing system includes a stirring device (10) for stirring the polyacrylamide, a water replenishment device (20) for replenishing water into the stirring device (10), and a drug replenishment device (30) for replenishing a high-concentration initial mixture into the stirring device (10). The stirring device (10) includes a stirring tank and a stirring shaft arranged in the stirring tank. A stirring motor is arranged at the top of the stirring shaft and a stirring impeller is arranged at the bottom of the stirring shaft. A drain pipe (11) is provided at the bottom of the stirring tank. A fourth solenoid valve (44) is provided on the drain pipe (11). The stirring motor and the fourth solenoid valve (44) are electrically connected to a PLC control device. The kinematic viscosity γ of the polyacrylamide solution is obtained by the following formula: in: P represents the stirring power of the stirring motor, measured in watts (W). ρ is the density of the polyacrylamide solution, in kg / m³. 3 ; N represents the number of revolutions per second of the impeller, expressed in r / s. d is the diameter of the agitator impeller, in meters (m). D is the diameter of the mixing tank, in meters (m). u represents the blade width of the agitator impeller, in meters (m). α is the lateral tilt angle of the impeller blades; β is the longitudinal tilt angle of the impeller blades.

2. The method for calculating the kinematic viscosity of polyacrylamide solution according to claim 1, characterized in that: The drug solution replenishment device (30) includes a two-stage dissolution assembly; the two-stage dissolution assembly includes a dissolution tank (31) with an internal partition (31a), the partition (31a) dividing the inner cavity of the dissolution tank (31) into a primary dissolution chamber (31b) located in the upper layer and a secondary dissolution chamber (31c) located in the lower layer. A return pipe (31d) is also provided between the two dissolution chambers to allow the liquid in the primary dissolution chamber (31b) to flow into the secondary dissolution chamber (31c), and to allow the liquid in the secondary dissolution chamber (31c) to flow into the secondary dissolution chamber (31c). The liquid inside is pumped into the inlet pipe (31e) of the first-stage dissolving chamber (31b) by a pressure pump; a heating plate (32) is arranged at the bottom of the second-stage dissolving chamber (31c) and connected to a water source through a first water pipe (33b) with a first water pump (33a); the second-stage dissolving chamber (31c) is also connected to a stirring device (10) through an outlet pipe (34); a switch valve is arranged on both the first water pipe (33b) and the outlet pipe (34); a feeding assembly is arranged at the top of the first-stage dissolving chamber (31b).

3. The method for calculating the kinematic viscosity of a polyacrylamide solution according to claim 2, characterized in that: The feeding assembly includes a storage bin (35a), inside which is arranged a screw feeder (35b) for feeding powdered polyacrylamide into the quantitative weighing assembly. The outlet of the quantitative weighing assembly is connected to the secondary dissolution chamber (31c). The quantitative weighing assembly includes a drum (35c) and a weighing pan (35d) that rotates within the drum (35c) via a rotating shaft (35e). The cantilevered plate surface of the weighing pan (35d) forms a weighing surface for receiving the powdered polyacrylamide. The power sources of the quantitative weighing assembly and the screw feeder (35b) are both electrically connected to a PLC control device.

4. The method for calculating the kinematic viscosity of a polyacrylamide solution according to claim 2 or 3, characterized in that: The water replenishment device (20) includes a second water pipe (21) with a second water pump (22), the outlet of the second water pipe (21) is connected to a stirring device (10); the two ends of the liquid outlet pipe (34) are respectively connected to the secondary dissolving chamber (31c) and the second water pipe (21); the first solenoid valve (41) is arranged at the outlet of the first water pipe (33b), the second solenoid valve (42) is arranged at the inlet of the liquid outlet pipe (34), and the third solenoid valve (43) is located at the outlet of the second water pipe (21). Each solenoid valve is electrically connected to a PLC control device.

5. The method for calculating the kinematic viscosity of a polyacrylamide solution according to claim 1, characterized in that: The inner wall of the mixing tank is equipped with a first float level gauge (12) for monitoring the liquid level inside the tank, and the first ultrasonic probe of the first float level gauge (12) is electrically connected to a PLC control device.

6. The method for calculating the kinematic viscosity of a polyacrylamide solution according to claim 2 or 3, characterized in that: The wall of the primary dissolving chamber (31b) is equipped with a second float level gauge (36) for monitoring the liquid level in the chamber. The second ultrasonic probe of the second float level gauge (36) is electrically connected to a PLC control device.

7. The method for calculating the kinematic viscosity of a polyacrylamide solution according to claim 2 or 3, characterized in that: A temperature sensor (33) is arranged on the wall of the secondary dissolution chamber (31c), and the temperature sensor (33) is electrically connected to the PLC control device.

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