Method for measuring limit concentration multiple of circulating cooling water

Abstract

A method for measuring the limit concentration multiple of circulating cooling water relates to the technical field of circulating water simulation experiments, and adopts the technical scheme that the method comprises the following steps: S1, establishing a dynamic simulation device; s2, measuring the water inlet conductivity, starting a simulation device, and calculating the heat resistance value of a cleaning pipe of the heat exchanger after the circulating water flow, the heat exchanger water inlet temperature, the heat exchanger water outlet temperature and the heat exchanger temperature are stable; s3, the simulation device is controlled to stably operate under different circulating water conductivity, the corrosion rate change condition is monitored, and the instantaneous fouling thermal resistance value of the heat exchanger is calculated till the corrosion rate or the instantaneous fouling thermal resistance value is close to the respective limiting value; and calculating the concentration multiple when the corrosion rate is close to the limit value or the instantaneous fouling thermal resistance value is close to the limit value, and taking the smaller concentration multiple as the limit concentration multiple of the circulating water. The method is suitable for the circulating water dynamic simulation device, the deviation between the measurement result and the traditional measurement method is within 5%, the repeated sampling detection work in the traditional measurement method is avoided, and the manual workload is reduced.

Description

Technical Field

[0001] This invention relates to the field of circulating water simulation experiment technology, and in particular to a method for determining the limiting concentration factor of circulating cooling water. Background Technology

[0002] The implementation of environmental quality standards and pollution emission standards has become a primary objective for power plant operations, and the efficient and compliant operation of circulating cooling water systems has also become a major consideration. Circulating water dynamic simulation devices, as the main equipment for verifying water treatment effectiveness, primarily use high-precision water quality sensors, data acquisition modules, and automatic control modules to simulate real-world operating conditions in a laboratory setting. They can accurately measure experimental parameters such as inlet and outlet temperatures, steam temperature, inlet water flow rate, and conductivity, achieving efficient monitoring of the heat exchange efficiency of heat exchange equipment, thereby inferring the actual application effect of water treatment technologies or methods.

[0003] However, the determination of the limiting concentration factor currently mostly still relies on the experimental method provided in HG / T 4541-2013 "Determination of Scale Inhibition Performance of Water Treatment Agents - Limiting Carbonate Method," which requires multiple sampling and testing of circulating water for analysis of the limiting concentration factor, resulting in a significant workload. Therefore, it is necessary to design a method for determining the limiting concentration factor suitable for dynamic simulation devices of circulating water. Summary of the Invention

[0004] To address the issues of existing methods for determining the ultimate concentration factor requiring multiple sampling and testing, this invention provides a method for determining the ultimate concentration factor of circulating cooling water.

[0005] This invention provides the following technical solution: a method for determining the limiting concentration factor of circulating cooling water, comprising the following steps: S1. Establish a dynamic simulation device, which includes a water tank, a circulating pump, a simulated heat exchanger, and a cooling tower connected in sequence via circulating water pipes. The outlet of the cooling tower is connected to the water tank. The circulating water pipes are equipped with a flow meter, a heat exchanger inlet water temperature sensor, a heat exchanger outlet water temperature sensor, a circulating water conductivity sensor, and a corrosion rate sensor. The simulated heat exchanger is equipped with a heat exchanger temperature sensor. The water tank is equipped with an inlet valve, and the circulating water pipes are equipped with a drain valve. S2, open the inlet valve to add circulating water, measure the conductivity of the inlet water, and start the simulation device. After the circulating water flow rate, heat exchanger inlet water temperature, heat exchanger outlet water temperature, and heat exchanger temperature stabilize, calculate the thermal resistance value of the cleaning tube of the simulated heat exchanger. S3 controls the simulation device to operate stably under different circulating water conductivity, monitors the changes in corrosion rate, and calculates the instantaneous fouling thermal resistance value of the simulated heat exchanger until the corrosion rate or instantaneous fouling thermal resistance value approaches their respective limits; calculates the concentration factor when the corrosion rate or instantaneous fouling thermal resistance value approaches the limit value, and takes the smaller one as the limit concentration factor of the circulating water.

[0006] Preferably, in S1, the simulated heat exchanger includes a heat exchanger cavity and a heat exchange tube penetrating the heat exchanger cavity, the heat exchange tube being connected in series with the circulating water pipe, and the heat exchanger cavity being connected to a steam source.

[0007] Preferably, the heat exchange tube is detachably connected to the heat exchanger cavity.

[0008] Preferably, the steam source includes a housing and a heater disposed within the housing.

[0009] Preferably, the calculation formulas for the thermal resistance value of the cleaning pipe and the instantaneous dirt thermal resistance value are as follows:

[0010] In the formula, This is the thermal resistance value of the cleaning tube. This is the instantaneous thermal resistance of the dirt. The inner diameter of the heat exchange tube. G represents the effective length of the heat exchange tube, and G represents the circulating water flow rate. For heat exchanger temperature, and These are the heat exchanger inlet water temperature and heat exchanger outlet water temperature determined in S2, respectively. and These are the real-time inlet water temperature and outlet water temperature of the heat exchanger in S3, respectively.

[0011] Preferably, the specific steps of S3 include: S31, stabilize the conductivity of the circulating water in the dynamic simulation device at a preset value and run it continuously for a period of time, and monitor the instantaneous fouling thermal resistance value. S32, if the instantaneous fouling thermal resistance is less than the limit during the operation of S31, the conductivity of the circulating water is increased and the operation is stable for the same period of time. If the instantaneous fouling thermal resistance is still less than the limit, the conductivity of the circulating water is further increased until the instantaneous fouling thermal resistance exceeds the limit. The current concentration factor is then calculated. S33. If the instantaneous fouling thermal resistance value is greater than the limit during the operation of S31, replace the simulated heat exchanger of the same specification and reduce the preset value in S31 to re-execute S31. If the instantaneous fouling thermal resistance value is still greater than the limit, replace the simulated heat exchanger again and further reduce the preset value in S31 to re-execute S31 until the instantaneous fouling thermal resistance value is less than the limit. Then further increase the conductivity of the circulating water and run it stably for the same time. If the instantaneous fouling thermal resistance value is still less than the limit, further increase the conductivity of the circulating water until the instantaneous fouling thermal resistance value exceeds the limit. Calculate the current concentration ratio.

[0012] Preferably, the corrosion rate is monitored synchronously in S3. If the corrosion rate exceeds the limit, the experiment is stopped and the current concentration factor is calculated.

[0013] Preferably, the instantaneous fouling thermal resistance is limited to 3.44 × 10⁻⁶. -4 m 2 ·K / W.

[0014] Preferably, the corrosion rate limit for heat exchangers made of carbon steel is 0.075 mm / a.

[0015] Preferably, the corrosion rate limit for heat exchangers made of copper alloy or stainless steel is 0.005 mm / a.

[0016] The beneficial effects of this invention are: it designs a method for determining the ultimate concentration factor suitable for a dynamic simulation device of circulating water, and the deviation of the determination result from the traditional determination method is within 5%, which avoids the work of multiple sampling and testing in the traditional determination method and reduces the amount of manual work. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a dynamic simulation device.

[0018] Figure 2 This is a graph showing the change of instantaneous fouling thermal resistance over time in Example 1.

[0019] Figure 3 The graph shows the corrosion rate over time in Example 1.

[0020] Figure 4 This is a graph showing the change of instantaneous fouling thermal resistance over time in Example 2.

[0021] Figure 5 This is a graph showing the corrosion rate over time in Example 2.

[0022] Reference numerals: 11-Water tank, 12-Circulating pump, 131-Heat exchanger cavity, 132-Heat exchanger tube, 133-Steam source, 14-Cooling tower, 151-Flow meter, 152-Heat exchanger inlet water temperature sensor, 153-Heat exchanger outlet water temperature sensor, 154-Heat exchanger temperature sensor, 155-Circulating water conductivity sensor, 156-Corrosion rate sensor. Detailed Implementation

[0023] The embodiments of the present invention will be described in more detail below with reference to the accompanying drawings and reference numerals, so that those skilled in the art can implement them after reading this specification. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention.

[0024] This invention provides a method for determining the limiting concentration factor of circulating cooling water, which is applicable to determining the limiting concentration factor of circulating cooling water using a circulating water dynamic simulation device.

[0025] The determination method includes the following steps: S1, Establish a dynamic simulation device. The circulating water dynamic simulation device can refer to existing technology. In this invention, please refer to... Figure 1 The dynamic simulation device includes a water tank 11, a circulating pump 12, a simulated heat exchanger, and a cooling tower 14, which are connected in sequence via circulating water pipes. The outlet of the cooling tower 14 is connected to the water tank 11. The circulating water is stored in the water tank 11, pumped by the circulating pump 12 to the simulated heat exchanger for heat exchange and temperature increase, and then pumped to the cooling tower 14 for cooling before returning to the cooling tower water pool 11, in a continuous cycle.

[0026] The simulated heat exchanger includes a heat exchanger cavity 131 and heat exchange tubes 132 penetrating the cavity. The heat exchange tubes 132 are connected in series with the circulating water pipe. The heat exchanger cavity 131 is also connected to a steam source 133, which introduces high-temperature steam into the cavity to heat the circulating water flowing through the heat exchange tubes 132. Excess steam returns to the steam source 133 through a return pipe. The steam source 133 can be a box and a heater installed inside the box. The heater heats the water in the box to form high-temperature steam. The heat exchange tubes 132 are made of the same material as the heat exchange equipment to be simulated, typically carbon steel, copper alloy, or stainless steel, to ensure the validity and accuracy of the results from the dynamic simulation experiment. The heat exchange tubes 132 are detachably connected to the heat exchanger cavity 131; any contaminated heat exchange tubes must be replaced when repeating the experiment.

[0027] The circulating water pipe is equipped with a flow meter 151, a heat exchanger inlet water temperature sensor 152, a heat exchanger outlet water temperature sensor 153, a circulating water conductivity sensor 155, and a corrosion rate sensor 156. The simulated heat exchanger is also equipped with a heat exchanger temperature sensor 154, which are used to provide feedback on data such as circulating water flow rate, heat exchanger inlet water temperature, heat exchanger outlet water temperature, circulating water conductivity, corrosion rate, and heat exchanger temperature, providing a basis for determining the concentration ratio. The heat exchanger temperature can be the steam temperature in the heat exchanger cavity 131. The water tank 11 is also equipped with an inlet valve, through which the experimental circulating water enters the dynamic simulation device. The circulating water pipe is also equipped with a drain valve, which can be used to control the conductivity of the circulating water system by opening and closing the drain valve.

[0028] S2, open the inlet valve to add circulating water to the water tank 11 and measure the conductivity of the inlet water; start the simulation device, and the circulating pump 12, simulated heat exchanger, cooling tower 14 and various sensors begin to work. After the circulating water flow rate, heat exchanger inlet water temperature, heat exchanger outlet water temperature and heat exchanger temperature stabilize, calculate the thermal resistance value of the clean tube of the heat exchanger, that is, the thermal resistance value of its heat exchanger tube when no dirt adheres to it. The calculation formula is as follows:

[0029] In the formula, The inner diameter of the heat exchange tube. G represents the effective length of the heat exchange tube, and G represents the circulating water flow rate. For heat exchanger temperature, and These are the heat exchanger inlet water temperature and heat exchanger outlet water temperature when the experimental cycle initially stabilizes.

[0030] S3 controls the simulation device to operate stably under different circulating water conductivity levels, monitors changes in corrosion rate, and calculates the instantaneous fouling thermal resistance of the heat exchanger until either the corrosion rate or the instantaneous fouling thermal resistance approaches its respective limit. The concentration factor at which either the corrosion rate or the instantaneous fouling thermal resistance approaches its limit is calculated, and the smaller of these is taken as the ultimate concentration factor for the circulating water. The concentration factor is the ratio of the current circulating water conductivity to the influent conductivity.

[0031] The specific steps include the following.

[0032] S31, stabilize the conductivity of the circulating water in the dynamic simulation device at a preset value and run it continuously for a period of time to conduct the first stage experiment and calculate the instantaneous fouling thermal resistance value; the formula for calculating the instantaneous fouling thermal resistance value can be referred to the following formula.

[0033]

[0034] In the formula, This is the instantaneous thermal resistance of the dirt. The thermal resistance value of the cleaning tube obtained in S2 is... The inner diameter of the heat exchange tube. G represents the effective length of the heat exchange tube, and G represents the circulating water flow rate. For heat exchanger temperature, and These are the real-time inlet water temperature and outlet water temperature of the heat exchanger, respectively.

[0035] S32, if the instantaneous fouling thermal resistance is less than the limit in the first stage, the circulating water conductivity is increased to 1.05~1.1 times the preset value and stabilized. The second stage experiment is then conducted, with the stabilization time being the same as the first stage. If the instantaneous fouling thermal resistance is still less than the limit in the second stage, the circulating water conductivity is further increased for the third, fourth, ..., Nth stage. The increase in circulating water conductivity and the stabilization time are the same in each stage, until the instantaneous fouling thermal resistance exceeds the limit. The current concentration factor is then calculated and used as the maximum concentration factor. During this process, the corrosion rate is monitored simultaneously. If the corrosion rate exceeds its limit, circulation is immediately stopped, and the current concentration factor is calculated and used as the maximum concentration factor.

[0036] S33. If the instantaneous fouling thermal resistance value is greater than the limit in the first stage, replace the simulated heat exchanger with one of the same specifications. More specifically, replace the heat exchange tube with one of the same specifications in the simulated heat exchanger, reduce the conductivity of the circulating water to 0.7 to 0.8 times the preset value in step S31, and repeat the first stage experiment. If the instantaneous fouling thermal resistance value is still greater than the limit, replace the heat exchange tube again, further reduce the conductivity of the circulating water, and repeat the first stage experiment until the instantaneous fouling thermal resistance value is less than the limit, and use the conductivity of the circulating water at this time as the second preset value.

[0037] Then, the conductivity of the circulating water is increased to 1.05~1.1 times the second preset value and stabilized for the second stage of the experiment. The stabilization time is the same as in the first stage. If the instantaneous fouling thermal resistance value is still less than the limit in the second stage, the conductivity of the circulating water is further increased for the third stage, fourth stage, and so on up to the Nth stage. The increase in conductivity and the stabilization time are the same in each stage as before, until the instantaneous fouling thermal resistance value exceeds the limit. The current concentration ratio is then calculated and used as the limit concentration ratio. During this process, the corrosion rate is monitored simultaneously. If the corrosion rate exceeds its limit, circulation is immediately stopped, and the current concentration ratio is calculated and used as the limit concentration ratio.

[0038] In this invention, the limit value of the fouling thermal resistance can be 3.44 × 10⁻⁶. -4 m 2 • K / W; The corrosion rate limit for heat exchangers made of carbon steel is 0.075 mm / a, and the corrosion rate limit for heat exchangers made of copper alloy or stainless steel is 0.005 mm / a.

[0039] Example 1

[0040] A method for determining the limiting concentration factor of circulating cooling water, using seawater from the Xiaoqing River with a conductivity of 3.83 ms / cm, includes the following steps: S1. The above-mentioned dynamic simulation device is established. The heat exchange tube is made of duplex steel. The heat exchange tube 132 has a length of 1200 mm, an effective heat exchange length of 1150 mm, and an inner diameter of 25 mm.

[0041] S2, open the inlet valve to add circulating water to water tank 11, start the simulation device to begin the experiment, and control the heat exchanger temperature, i.e., the steam temperature, at 100±0.5 ℃, and the heat exchanger inlet water temperature at 25±0.5 ℃; its circulating water flow rate reaches 1000 L / h. After stable operation for 60 min, the heat exchanger outlet water temperature stabilizes at 35±0.5 ℃, and the thermal resistance of the cleaning pipe is calculated to be 1.205 m according to the formula. 2 ·K / W.

[0042] S3, close the drain valve, raise the conductivity of the circulating water to the preset value of 4.60 ms / cm, then open the drain valve again to stabilize the conductivity at the preset value and run continuously for 48 hours. Calculate the instantaneous fouling thermal resistance using real-time temperature data to complete the first stage of the experiment. The change in instantaneous fouling thermal resistance over time is shown below. Figure 2 As shown, the thermal resistance of the fouling in the first stage is all below 3.44 × 10⁻⁶. -4 m 2 The K / W limit was further increased to 5.06 ms / cm and 5.52 ms / cm to complete multiple stages of experiments, until the instantaneous fouling thermal resistance exceeded 3.44 × 10⁻⁶. -4 m 2 • Limits for K / W. (By...) Figure 2 It can be seen that after three stages of experiments, when the conductivity of the circulating water was increased to 1.2 times the preset value, its instantaneous fouling thermal resistance value exceeded the limit, and the concentration ratio was 1.44 times.

[0043] During the experiment, the corrosion rate changed over time as follows: Figure 3 As shown, the corrosion rate did not exceed the limit of 0.005 mm / a until the end of the experiment, so the maximum concentration factor of this experiment was 1.44 times.

[0044] Example 2

[0045] A method for determining the limiting concentration factor of circulating cooling water, using circulating cooling water from a thermal power plant in Anhui Province with a conductivity of 586 μs / cm, includes the following steps: S1. The above-mentioned dynamic simulation device is established. The heat exchange tube used is made of carbon steel. The length of heat exchange tube 132 is 1200 mm, its effective heat exchange length is 1150 mm, and the inner diameter of the tube is 25 mm.

[0046] S2, open the inlet valve to add circulating water to water tank 11, start the simulation device to begin the experiment, and control the heat exchanger temperature, i.e., the steam temperature, at 100±0.5 ℃, and the heat exchanger inlet water temperature at 25±0.5 ℃; its circulating water flow rate reaches 800 L / h. After stable operation for 60 min, the heat exchanger outlet water temperature stabilizes at 35±0.5 ℃, and the thermal resistance of the cleaning pipe is calculated to be 1.209 m according to the formula. 2 ·K / W.

[0047] S3, close the drain valve, increase the conductivity of the circulating water to the preset value of 3000 μs / cm, then open the drain valve again to stabilize the conductivity at the preset value and run continuously for 48 hours. Calculate the instantaneous fouling thermal resistance using real-time temperature data to complete the first stage of the experiment. The change in instantaneous fouling thermal resistance over time is shown below. Figure 4 As shown.

[0048] Because the thermal resistance of the fouling in the first stage is already higher than 3.44 × 10⁻⁶. -4 m 2 • K / W, then successively reduce the circulating water conductivity to 2400 μs / cm and 2100 μs / cm, and replace the heat exchanger tubes to conduct two first-stage experiments, until the instantaneous fouling thermal resistance is less than 3.44 × 10 K / W when the circulating water conductivity is reduced to 2100 μs / cm. -4 m 2 ·K / W.

[0049] Then, using 2100 μs / cm as the second preset value, the conductivity of the circulating water was further increased sequentially to 2180 μs / cm, 2300 μs / cm, and 2380 μs / cm to complete multiple stages of experiments, each lasting 48 hours. Finally, after the circulating water conductivity was increased to 2380 μs / cm, the instantaneous fouling thermal resistance exceeded 3.44 × 10⁻⁶. -4 m 2 ·K / W, at this point the concentration factor is 4.06 times.

[0050] During the experiment, the corrosion rate changed over time as follows: Figure 5 As shown, the corrosion rate did not exceed the limit of 0.075 mm / a until the end of the experiment, so the maximum concentration factor of this experiment was 4.06 times.

[0051] The limiting concentration factor was determined using conventional methods with circulating water from the same source as in Examples 1 and 2. The results were 1.41 times and 4.02 times, respectively. Compared with Examples 1 and 2, the deviations of each were within 5%.

[0052] The above describes one or more embodiments of the present invention in a relatively specific and detailed manner, but it should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. A method for determining the limiting concentration factor of circulating cooling water, characterized in that, Includes the following steps: S1. Establish a dynamic simulation device, which includes a water tank, a circulating pump, a simulated heat exchanger, and a cooling tower connected in sequence via circulating water pipes. The outlet of the cooling tower is connected to the water tank. The circulating water pipes are equipped with a flow meter, a heat exchanger inlet water temperature sensor, a heat exchanger outlet water temperature sensor, a circulating water conductivity sensor, and a corrosion rate sensor. The simulated heat exchanger is equipped with a heat exchanger temperature sensor. The water tank is equipped with an inlet valve, and the circulating water pipes are equipped with a drain valve. S2, open the inlet valve to add circulating water, measure the conductivity of the inlet water, and start the simulation device. After the circulating water flow rate, heat exchanger inlet water temperature, heat exchanger outlet water temperature, and heat exchanger temperature stabilize, calculate the thermal resistance value of the cleaning tube of the simulated heat exchanger. S3 controls the simulation device to operate stably under different circulating water conductivity, monitors the changes in corrosion rate, and calculates the instantaneous fouling thermal resistance value of the simulated heat exchanger until the corrosion rate or instantaneous fouling thermal resistance value approaches their respective limits; calculates the concentration factor when the corrosion rate or instantaneous fouling thermal resistance value approaches the limit value, and takes the smaller one as the limit concentration factor of the circulating water.

2. The method for determining the limiting concentration factor of circulating cooling water according to claim 1, characterized in that, In S1, the simulated heat exchanger includes a heat exchanger cavity and a heat exchange tube that passes through the heat exchanger cavity. The heat exchange tube is connected in series with the circulating water pipe, and the heat exchanger cavity is also connected to a steam source.

3. The method for determining the limiting concentration factor of circulating cooling water according to claim 2, characterized in that, The heat exchange tube is detachably connected to the heat exchanger cavity.

4. The method for determining the limiting concentration factor of circulating cooling water according to claim 2, characterized in that, The steam source includes a housing and a heater installed inside the housing.

5. The method for determining the limiting concentration factor of circulating cooling water according to claim 2, characterized in that, The calculation formulas for the thermal resistance of the cleaning tube and the instantaneous thermal resistance of the dirt are as follows: ； In the formula, This is the thermal resistance value of the cleaning tube. This is the instantaneous thermal resistance of the dirt. The inner diameter of the heat exchange tube. G represents the effective length of the heat exchange tube, and G represents the circulating water flow rate. For heat exchanger temperature, and These are the heat exchanger inlet water temperature and heat exchanger outlet water temperature determined in S2, respectively. and These are the real-time inlet water temperature and outlet water temperature of the heat exchanger in S3, respectively.

6. The method for determining the limiting concentration factor of circulating cooling water according to claim 1, characterized in that, The specific steps of S3 include: S31, stabilize the conductivity of the circulating water in the dynamic simulation device at a preset value and run it continuously for a period of time, and monitor the instantaneous fouling thermal resistance value. S32, if the instantaneous fouling thermal resistance is less than the limit during the operation of S31, the conductivity of the circulating water is increased and the operation is stable for the same period of time. If the instantaneous fouling thermal resistance is still less than the limit, the conductivity of the circulating water is further increased until the instantaneous fouling thermal resistance exceeds the limit. The current concentration factor is then calculated. S33. If the instantaneous fouling thermal resistance value is greater than the limit during the operation of S31, replace the simulated heat exchanger of the same specification and reduce the preset value in S31 to re-execute S31. If the instantaneous fouling thermal resistance value is still greater than the limit, replace the simulated heat exchanger again and further reduce the preset value in S31 to re-execute S31 until the instantaneous fouling thermal resistance value is less than the limit. Then further increase the conductivity of the circulating water and run it stably for the same time. If the instantaneous fouling thermal resistance value is still less than the limit, further increase the conductivity of the circulating water until the instantaneous fouling thermal resistance value exceeds the limit. Calculate the current concentration ratio.

7. The method for determining the limiting concentration factor of circulating cooling water according to claim 6, characterized in that, In S3, the corrosion rate is monitored synchronously. If the corrosion rate exceeds the limit, the experiment is stopped and the current concentration factor is calculated.

8. The method for determining the limiting concentration factor of circulating cooling water according to claim 6, characterized in that, The limit for the instantaneous fouling thermal resistance is 3.44 × 10⁻⁶. -4 m 2 ·K / W.

9. The method for determining the limiting concentration factor of circulating cooling water according to claim 7, characterized in that, The corrosion rate limit for heat exchangers made of carbon steel is 0.075 mm / a.

10. The method for determining the limiting concentration factor of circulating cooling water according to claim 7, characterized in that, The corrosion rate limit for heat exchangers made of copper alloy or stainless steel is 0.005 mm / a.

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