Online pipeline limescale monitoring method and system for heat exchange system

Abstract

An online pipeline limescale monitoring method for a heat exchange system, comprising: firstly, determining several monitoring points on a pipeline along a length direction, acquiring a flow velocity in the pipeline at each monitoring point, and acquiring a flow velocity at an inlet of the pipeline at the same time; then comparing the flow velocity in the pipeline at each monitoring point with the flow velocity at the inlet of the pipeline, and determining a monitoring point with the flow velocity exceeding a flow velocity deviation threshold as an abnormal monitoring point; and finally calculating, on the basis of the flow velocity of the abnormal monitoring point and the flow velocity at the inlet of the pipeline, a limescale thickness, and if the limescale thickness exceeds a preset limescale thickness alarm threshold, then issuing an alarm. The method is simple to implement and has a high degree of automation, and is able to monitor the limescale thickness in the pipeline in real time, quantitatively calculate the limescale thickness, and issue the alarm without delay, thereby enabling daily limescale prevention and subsequent descaling work to be guided, and ensuring safe and stable operation of power stations. Further disclosed are an online pipeline limescale monitoring system for a heat exchange system.

Description

A method and system for online monitoring of scale in heat exchange system pipes

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to the Chinese patent application filed with the China Patent Office on July 6, 2023, with application number 202310825334.1 and invention name “A method and system for online monitoring of scale in pipes of a heat exchange system”, the entire contents of which are incorporated by reference into this application. Technical Field

[0003] The present application belongs to the technical field of scale monitoring, and specifically relates to an online monitoring method and system for scale in pipelines of a heat exchange system. Background Art

[0004] Over the long-term use of pipes, particles in the water combine to form insoluble, poorly soluble, and slightly soluble substances, known as scale. Scale typically forms through a nucleation-growth process: a few scale cores initially form and attach to the pipe surface. Then, more scaling compounds gather around these cores, forming larger scale clusters. This can affect the flow rate and flow rate of the fluid within the pipe, and in severe cases, can even block the pipe.

[0005] Currently, scale monitoring in power plant heat exchange system pipes primarily relies on on-site monitoring and laboratory scale inhibition determination. The laboratory scale inhibition determination method is primarily used for theoretical research and cannot capture actual structural conditions. The on-site monitoring method primarily utilizes a monitoring heat exchanger. This involves disassembling a monitoring heat exchanger after a certain period of operation, cutting open its heat exchanger tubes, observing the sediment deposition, and measuring the thickness of the deposited sediment layer. The monitoring heat exchanger is then used to measure the thermal resistance of the scale in the cooling water system to predict or determine the extent of sediment deposition within the heat exchanger. This method cannot achieve online monitoring and is relatively complex to implement.

[0006] Summary of the Invention

[0007] In order to solve the defects existing in the above-mentioned prior art, the purpose of this application is to provide a method and system for online monitoring of scale in the pipeline of a heat exchange system, which is simple to implement and has a high degree of automation. It can monitor the scale thickness in the pipeline in real time, quantitatively calculate the scale thickness, and issue an alarm in time. It can guide daily scale prevention and subsequent scale removal work to ensure the safe and stable operation of the power station.

[0008] This application is achieved through the following technical solutions:

[0009] The present application discloses an online monitoring method for scale in heat exchange system pipelines, comprising:

[0010] S1: Determine several monitoring points along the length of the pipeline, obtain the flow velocity in the pipeline at each monitoring point, and obtain the flow velocity at the pipeline inlet at the same time;

[0011] S2: Compare the flow velocity in the pipeline at each monitoring point with the flow velocity at the pipeline inlet, and determine the monitoring point where the flow velocity exceeds the flow velocity deviation threshold as an abnormal monitoring point;

[0012] S3: The scale thickness is calculated based on the flow velocity at the abnormal monitoring point and the flow velocity at the pipeline inlet. If the scale thickness exceeds the preset scale thickness alarm threshold, an alarm is issued.

[0013] Optionally, in step S1, the number of monitoring points is ≥3.

[0014] Optionally, in step S1, a plurality of monitoring points are distributed at equal distances.

[0015] Optionally, in step S1, on the straight pipe section, the distance between the plurality of monitoring points is ≥1.5 m.

[0016] Optionally, in step S1, the distance between the plurality of monitoring points on the curved pipe section is ≥1 m.

[0017] Optionally, in step S1, the distance between the monitoring point and the pipeline inlet is ≥1 m.

[0018] Optionally, in step S1, the flow velocity at the pipeline inlet and the flow velocity at the monitoring point are obtained by an ultrasonic Doppler flow velocity detector.

[0019] Optionally, in step S2, the flow velocity deviation threshold = the flow velocity at the pipeline inlet × 120%.

[0020] Optionally, in step S3, the scale thickness d at the abnormal monitoring point is calculated by the following formula:

[0021] Where r1 is the radius of the pipe inlet, V1 is the flow velocity at the pipe inlet, and V2 is the flow velocity at the abnormal monitoring point.

[0022] The system disclosed in the present application for realizing the above-mentioned method for online monitoring of scale in the heat exchange system pipeline includes a pipeline outlet flow velocity acquisition unit, a flow velocity comparison unit, a scale thickness calculation unit, an alarm unit, a scale thickness comparison unit and a plurality of monitoring point flow velocity acquisition units;

[0023] A pipe inlet flow velocity acquisition unit, which acquires the flow velocity at the pipe inlet and sends it to the flow velocity comparison unit;

[0024] Flow velocity acquisition units at several monitoring points acquire the flow velocity in the pipeline and send it to the flow velocity comparison unit

[0025] A flow rate comparison unit compares the flow rate in the pipeline at each monitoring point with the flow rate at the pipeline inlet, and determines the monitoring point where the flow rate exceeds the flow rate deviation threshold as an abnormal monitoring point;

[0026] a scale thickness calculation unit, which calculates the scale thickness according to the flow velocity at the abnormal monitoring point and the flow velocity at the pipeline inlet, and sends the scale thickness calculation result to the scale thickness comparison unit;

[0027] The scale thickness comparison unit compares the calculated scale thickness with a preset scale thickness alarm threshold, and sends an alarm instruction to the alarm unit if the scale thickness exceeds the preset scale thickness alarm threshold;

[0028] The alarm unit receives the alarm instruction from the scale thickness comparison unit and sends an alarm.

[0029] Compared with the existing technology, this application has the following beneficial technical effects:

[0030] The present application discloses an online monitoring method for scale in a heat exchange system pipeline. By setting a number of monitoring points on the pipeline, the flow velocity in the pipeline is monitored online in real time, and the flow velocity at the pipeline inlet at the same time is used as a benchmark for comparison. Generally, scale is not easy to form at the pipeline inlet. When scale exists on the inner wall of the pipeline, the flow area at that point will decrease, and the corresponding flow velocity will increase. If the flow velocity at the monitoring point exceeds the set flow velocity deviation threshold, the monitoring point will be used as an abnormal monitoring point. The scale in the pipeline can usually be approximated as a ring that clings to the inner wall of the pipeline. Therefore, the scale thickness can be further quantitatively calculated. If the scale thickness exceeds the preset scale thickness alarm threshold, an alarm will be issued to prompt the operation and maintenance personnel to carry out the next step of descaling. The present application is simple to implement and has a high degree of automation. It can monitor the scale thickness in the pipeline in real time, quantitatively calculate the scale thickness, and issue an alarm in time. It can guide daily anti-scaling and subsequent descaling work to ensure the safe and stable operation of the power station.

[0031] Optionally, the number of monitoring points is ≥3, which enables multi-point segmented monitoring of the pipeline to improve the accuracy of the monitoring results and positions.

[0032] Optionally, several monitoring points are distributed at equal distances to improve the comparability of flow velocity data between the monitoring points and improve the accuracy of the monitoring results.

[0033] Optionally, on a straight pipe section, the distance between several monitoring points should be ≥1.5m. If the distance is too small, the flow velocity remains approximately unchanged, and setting too many monitoring points will increase costs. At the same time, since the length of the curved pipe section is relatively short, the distance between several monitoring points on the curved pipe section should be ≥1m.

[0034] Optionally, the distance between the monitoring point and the pipeline inlet is ≥1m. If the distance is too small, the monitored value will not change much.

[0035] The system disclosed in the present application for realizing the above-mentioned method for online monitoring of scale in heat exchange system pipes is simple to construct, is well compatible with existing heat exchange systems, and can be applied to new power plants and renovation of existing power plants. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] FIG1 is a schematic diagram of the method flow of the present application;

[0037] FIG2 is a schematic diagram of the monitoring point setting of this application. DETAILED DESCRIPTION

[0038] The present application will be further described in detail below with reference to the accompanying drawings and specific embodiments, which are intended to explain the present application rather than to limit it.

[0039] As shown in FIG1 , the online monitoring method for scale in the heat exchange system pipe of the present application includes:

[0040] S1: Determine several monitoring points along the length of the pipeline, obtain the flow velocity in the pipeline at each monitoring point, and obtain the flow velocity at the pipeline inlet at the same time;

[0041] S2: Compare the flow velocity in the pipeline at each monitoring point with the flow velocity at the pipeline inlet, and determine the monitoring point where the flow velocity exceeds the flow velocity deviation threshold as an abnormal monitoring point;

[0042] S3: The scale thickness is calculated based on the flow velocity at the abnormal monitoring point and the flow velocity at the pipeline inlet. If the scale thickness exceeds the preset scale thickness alarm threshold, an alarm is issued.

[0043] The scale thickness alarm threshold is usually set based on a comprehensive consideration of equipment type, pipe material, and pipe diameter.

[0044] In a preferred embodiment of the present application, in step S1, the number of monitoring points is ≥3.

[0045] In a preferred embodiment of the present application, in step S1, a plurality of monitoring points are distributed at equal distances.

[0046] In a preferred embodiment of the present application, in step S1, the distance between the plurality of monitoring points on the straight pipe section is ≥1.5 m.

[0047] In a preferred embodiment of the present application, in step S1, the distance between the plurality of monitoring points on the curved pipe section is ≥ 1 m.

[0048] In a preferred embodiment of the present application, the distance between the monitoring point and the pipeline inlet is ≥1 m.

[0049] In a preferred embodiment of the present application, in step S1, several monitoring points are set on the same type of pipeline, where the pipeline type refers to a straight pipe or a curved pipe.

[0050] In a preferred embodiment of the present application, in step S1, the flow velocity at the pipeline inlet and the flow velocity at the monitoring point are obtained by an ultrasonic Doppler flow velocity detector.

[0051] In a preferred embodiment of the present application, in step S2, the flow rate deviation threshold = the flow rate at the pipeline inlet × 120%.

[0052] In a preferred embodiment of the present application, in step S3, the scale thickness d at the abnormal monitoring point is calculated by the following formula:

[0053] Where r1 is the radius of the pipe inlet, V1 is the flow velocity at the pipe inlet, and V2 is the flow velocity at the abnormal monitoring point.

[0054] The present invention provides a system for realizing the above-mentioned heat exchange system pipeline scale online monitoring method.

[0055] It includes a pipe port flow velocity acquisition unit, a flow velocity comparison unit, a scale thickness calculation unit, an alarm unit, a scale thickness comparison unit and several monitoring point flow velocity acquisition units;

[0056] A pipe inlet flow velocity acquisition unit, which acquires the flow velocity at the pipe inlet and sends it to the flow velocity comparison unit;

[0057] Flow velocity acquisition units at several monitoring points acquire the flow velocity in the pipeline and send it to the flow velocity comparison unit

[0058] A flow rate comparison unit compares the flow rate in the pipeline at each monitoring point with the flow rate at the pipeline inlet, and determines the monitoring point where the flow rate exceeds the flow rate deviation threshold as an abnormal monitoring point;

[0059] a scale thickness calculation unit, which calculates the scale thickness according to the flow velocity at the abnormal monitoring point and the flow velocity at the pipeline inlet, and sends the scale thickness calculation result to the scale thickness comparison unit;

[0060] The scale thickness comparison unit compares the calculated scale thickness with a preset scale thickness alarm threshold, and sends an alarm instruction to the alarm unit if the scale thickness exceeds the preset scale thickness alarm threshold;

[0061] The alarm unit receives the alarm instruction from the scale thickness comparison unit and sends an alarm.

[0062] Among them, the pipeline mouth flow velocity acquisition unit and several monitoring point flow velocity acquisition units can be implemented using an ultrasonic Doppler flow velocity detector and its accessories. The detection end of the ultrasonic Doppler flow velocity detector penetrates into the pipeline, and the connection part with the pipeline is fixed with a matching tooling seat. The tooling seat and the pipeline are welded to ensure that there is no water leakage.

[0063] The flow rate comparison unit, the scale thickness calculation unit, the scale thickness comparison unit and the alarm unit can be integrated into the central control system of the power station, and the alarm unit can be connected to sound, light and electric alarms to issue an alarm.

[0064] The present application is further explained below with a specific embodiment:

[0065] Scale monitoring was performed on the pipes of a power plant's cooling water system. For example, the pipe at the outlet of the heat exchanger, as shown in Figure 2, consists of a straight pipe and a curved pipe. Both are DN80 pipes with a diameter of 80.0 mm. The straight pipe is 8 meters long, and the curved pipe is 2.5 meters long. Monitoring point C0 was set at the pipe inlet, where the heat exchanger and the straight pipe meet. Monitoring points C1, C2, C3, and C4 were set on the straight pipe, and monitoring points C5 and C6 were set on the curved pipe. Each monitoring point was equipped with an ultrasonic Doppler flowmeter. The distance between C0 and C1 was 1.5 meters, the distance between C1, C2, C3, and C4 was 2 meters, and the distance between C5 and C6 was 1.5 meters.

[0066] The flow rate in the pipeline measured at C0 is 3m / s, and the flow rate deviation threshold is set to 3.6m / s. The flow rate values ​​at each measuring point are as follows: C1 is 3.08m / s, C2 is 3.12m / s, C3 is 3.45m / s, C4 is 3.72m / s, C5 is 3.86m / s, and C6 is 3.87m / s. Among them, C4, C5 and C6 are abnormal detection points. After calculation, the scale thickness at C4 is 1.29mm, the scale thickness at C5 is 2.69mm, and the scale thickness at C6 is 2.79mm. In this embodiment, the scale thickness alarm threshold is set to 5% of the pipeline radius. Therefore, the C5 and C6 monitoring points trigger an alarm to remind the operation and maintenance personnel to perform descaling; at the same time, anti-scaling operations are performed on the C4 monitoring point.

[0067] It should be noted that the above is only part of the implementation method of this application. Equivalent changes made based on the system described in this application are all included in the scope of protection of this application. Those skilled in the art of the technology to which this application belongs can make similar substitutions for the specific examples described. As long as they do not deviate from the structure of this application or exceed the scope defined by the claims, they are all within the scope of protection of this application.

Claims

1. A method for online monitoring of scale in pipelines of a heat exchange system, characterized in that: include: S1: Determine several monitoring points along the length direction of the pipeline, obtain the flow velocity in the pipeline at each monitoring point, and obtain the flow velocity at the pipeline inlet at the same time; S2: Compare the flow velocity in the pipeline at each monitoring point with the flow velocity at the pipeline inlet, and determine the monitoring point whose flow velocity exceeds the flow velocity deviation threshold as an abnormal monitoring point; S3: The scale thickness is calculated based on the flow velocity at the abnormal monitoring point and the flow velocity at the pipeline inlet. If the scale thickness exceeds a preset scale thickness alarm threshold, an alarm is issued.

2. The method for online monitoring of scale in pipelines of a heat exchange system according to claim 1, characterized in that: In step S1, the number of monitoring points is ≥3.

3. The on-line monitoring method for scale in heat exchange system pipes according to claim 1, characterized in that: In step S1, a number of monitoring points are distributed at equal distances.

4. The method for online monitoring of scale in pipelines of a heat exchange system according to claim 1, characterized in that: In step S1, on the straight pipe section, the distance between several monitoring points is ≥1.5m.

5. The on-line monitoring method for scale in pipelines of a heat exchange system according to claim 1, characterized in that: In step S1, on the curved pipe section, the distance between several monitoring points is ≥ 1 m.

6. The method for online monitoring of scale in pipelines of a heat exchange system according to claim 1, characterized in that: In step S1, the distance between the monitoring point and the pipeline inlet is ≥1m.

7. The on-line monitoring method for scale in heat exchange system pipes according to claim 1, characterized in that: In step S1, the flow velocity at the pipeline inlet and the flow velocity at the monitoring point are obtained by an ultrasonic Doppler flow velocity detector.

8. The on-line monitoring method for scale in pipelines of a heat exchange system according to claim 1, characterized in that: In step S2, the flow velocity deviation threshold = the flow velocity at the pipeline inlet × 120%.

9. The on-line monitoring method for scale in pipelines of a heat exchange system according to claim 1, characterized in that: In step S3, the scale thickness d at the abnormal monitoring point is calculated by the following formula: Where r1 is the radius of the pipeline inlet, V1 is the flow velocity at the pipeline inlet, and V2 is the flow velocity at the abnormal monitoring point.

10. A system for realizing the on-line monitoring method for scale in pipelines of a heat exchange system according to any one of claims 1 to 9, characterized in that: It includes a pipeline outlet flow velocity acquisition unit, a flow velocity comparison unit, a scale thickness calculation unit, an alarm unit, a scale thickness comparison unit and a plurality of monitoring point flow velocity acquisition units; A pipeline inlet flow velocity acquisition unit, which acquires the flow velocity at the pipeline inlet and sends it to the flow velocity comparison unit; Several monitoring point flow rate acquisition units obtain the flow rate in the pipeline and send it to the flow rate comparison unit A flow rate comparison unit compares the flow rate in the pipeline at each monitoring point with the flow rate at the pipeline inlet, and determines the monitoring point whose flow rate exceeds the flow rate deviation threshold as an abnormal monitoring point; A scale thickness calculation unit calculates the scale thickness according to the flow velocity at the abnormal monitoring point and the flow velocity at the pipeline inlet, and sends the scale thickness calculation result to the scale thickness comparison unit; The scale thickness comparison unit compares the scale thickness calculation result with the preset scale thickness alarm threshold, and sends an alarm instruction to the alarm unit if the scale thickness exceeds the preset scale thickness alarm threshold; The alarm unit receives the alarm instruction from the scale thickness comparison unit and sends an alarm.

Images