Intelligent control system for monitoring and controlling industrial refrigeration system

Abstract

The invention provides an intelligent control system for monitoring and controlling an industrial refrigeration system, which comprises a data acquisition module, a calculation module, a trend recording module and an alarm module, and is characterized in that the data acquisition module is configured to acquire refrigerant flow parameters of refrigerant users and operation parameters of a refrigeration compressor in real time; the calculation module is configured to dynamically calculate the heat load of the heat exchanger at the outlet of the compressor based on the compressor operation parameters collected in real time, and the trend recording module is configured to store the refrigerant flow parameters of the refrigerant users and the heat load parameters, generated by the calculation module, of the heat exchanger at the outlet of the compressor in a sampling period. Carrying out time sequence analysis on the parameters to form trend characteristics; and the alarm module is configured to generate an alarm signal based on the trend characteristics when the fluctuation amplitude of any parameter in the trend exceeds an alarm threshold value.

Description

Technical Field

[0001] The present invention relates to the intelligent monitoring and early warning of industrial refrigeration systems, and more particularly to an intelligent control system and method for monitoring and controlling industrial refrigeration systems. Background Art

[0002] As the core infrastructure of process industries such as petrochemical and pharmaceutical industries, industrial refrigeration systems undertake the key task of providing stable cooling capacity for multiple user process units. With the development of the large-scale and integrated industrial plants, the refrigeration system needs to serve dozens or even hundreds of cooling capacity users simultaneously, such as fractionating towers, reactors, storage tanks, etc., forming a highly coupled cooling capacity supply and demand network. As a typical example, the propylene refrigeration system plays a very important role during the operation of the entire ethylene plant. It is a closed-loop system using propylene as the refrigerant, providing cooling capacity at different temperature levels for many users. During the actual operation, the user load may change dynamically due to factors such as raw material fluctuations, environmental temperature, changes in material components, and occurrence of abnormal situations (such as false instrument indications, valve malfunction, etc.). The change in user load directly affects the operating state of the compressor, and further affects the stability of the entire refrigeration system.

[0003] Based on long-term actual production experience, during the continuous production process of chemical plants, the following situations often occur: when a certain refrigerant user suddenly makes a large adjustment, due to the time difference in communication and adjustment between different positions, or due to reasons such as false instrument indications and valve malfunctions, the entire refrigeration system fluctuates greatly. More seriously, once the refrigeration system fluctuates, the coupling effect it brings will affect the stability of all refrigerant users, resulting in fluctuations in the entire product separation system, including C2 / C3 separation, C3 / C4 separation, C1 / C2 separation, IB units, etc.

[0004] Due to the characteristics of multi-users and complexity of the refrigeration system itself, when the refrigeration compressor fluctuates, it is very difficult for operators to find the starting point of the problem in the first time. This requires different positions and different operators to check the parameter changes of their respective refrigerant users, which will lead to a waste of precious adjustment time. As time goes by, along with the coupling effect brought by the fluctuations of each user, it will cause serious production fluctuations in the device.

[0005] Traditional monitoring may rely on fixed threshold alarms or single-parameter monitoring, and cannot effectively capture abnormal situations of multi-variable coupling. Although the existing DCS systems have realized basic data collection and logic control, the built-in alarm management module usually only supports static rule configuration and cannot analyze multi-parameter trends in real time, resulting in a lag in fault early warning.

[0006] Therefore, the present invention aims to provide an intelligent control system and method for monitoring and controlling an industrial refrigeration system. Through the intelligent control system and method of the present invention, risks existing in the refrigeration system can be accurately and quickly identified, such as abnormal adjustment by a certain user or sudden change in the compressor load, and an alarm is issued to alert the operator to intervene in advance for relevant adjustments, thereby improving the efficiency of troubleshooting and avoiding excessive fluctuations in the refrigeration system and the resulting coupling effect. Summary of the Invention

[0007] On the one hand, the present invention provides an intelligent control system for monitoring and controlling an industrial refrigeration system, which includes a data acquisition module, a calculation module, a trend recording module, and an alarm module. Among them,

[0008] The data acquisition module is configured to obtain the refrigerant flow parameters of each refrigerant user and the operating parameters of the refrigeration compressor in real time; the calculation module is configured to dynamically calculate the heat load of the heat exchanger at the compressor outlet based on the real-time collected compressor operating parameters; the trend recording module is configured to store the refrigerant flow parameters of each refrigerant user and the heat load parameters of the heat exchanger at the compressor outlet generated by the calculation module at a certain sampling period, and perform efficient time series analysis on these parameters to form trend characteristics; the alarm module is configured to generate an alarm signal based on the trend characteristics when the change in any of the parameters fluctuates beyond the alarm threshold in the trend.

[0009] On the other hand, the present invention provides a method for monitoring and controlling an industrial refrigeration system, and the method includes the following steps:

[0010] Collect and obtain the compressor operating parameters of the refrigeration system and the refrigerant flow parameters of each refrigerant user in real time;

[0011] Based on the real-time collected compressor operating parameters, dynamically calculate the heat load of the heat exchanger at the compressor outlet;

[0012] Store the refrigerant flow parameters of each refrigerant user and the heat load parameters of the heat exchanger at the compressor outlet at a preset sampling period, perform time series data analysis, and form the trends of each parameter;

[0013] Generate an alarm signal based on the trend characteristics.

[0014] In one embodiment, the operating parameters of the compressor include the circulating water flow rate and the circulating water outlet / inlet temperature of the heat exchanger at the compressor outlet.

[0015] In one embodiment, the refrigerant flow parameters of each refrigerant user include the opening degree of the regulating valve.

[0016] Through the intelligent control system and method of the present invention, the key influencing factors of all refrigerant users are integrated, their changes are continuously monitored, certain alarm thresholds are set, and early warnings are issued the moment they exceed the adjustment thresholds, enabling operators to identify existing risks in advance, accurately identify and locate the starting point of problems, intervene early, and make relevant adjustments to problem users, thereby avoiding excessive fluctuations in the refrigerant system and the resulting coupling effects. Detailed implementation manner

[0017] The intelligent control system for an industrial refrigeration system of the present invention includes a data acquisition module, a calculation module, a trend recording module, and an alarm module. The intelligent control system is preferably a distributed control system DCS.

[0018] In the intelligent control system of the present invention, preferably the distributed control system, the data acquisition module is configured to obtain in real time the refrigerant flow parameters of each refrigerant user and the operating parameters of the refrigeration compressor. In a specific implementation, the refrigerant flow parameters of each refrigerant user include the opening degree of the regulating valve. In another implementation, the operating parameters of the refrigeration compressor include the circulating water flow rate and the circulating water inlet / outlet temperature of the heat exchanger at the compressor outlet, etc. The heat exchanger is preferably a water cooler.

[0019] The calculation module is configured to dynamically calculate the heat load of the heat exchanger at the compressor outlet based on the real-time collected operating parameters of the compressor. The heat load is usually calculated based on the following formula: Q = m × c p ×ΔT, where m is the mass flow rate of the circulating water, c p is the specific heat capacity of water, and ΔT is the temperature difference between the circulating water outlet / inlet temperatures (T 出口 -T 入口 ).

[0020] The trend recording module is configured to store at a certain sampling period the refrigerant flow parameters of each refrigerant user and the heat load parameters of the heat exchanger at the compressor outlet generated by the calculation module, and perform time series analysis on these parameters to form trend characteristics. Specifically, on the display screen of an intelligent control system such as DCS, a trend change graph with time as the horizontal axis and the relevant parameters such as the flow rate, regulating valve opening degree, and heat load as the vertical axis is displayed in real time to achieve real-time and dynamic monitoring of these parameters. The trend characteristics can also reflect the change laws of these parameters by looking up historical data. In a specific implementation, for the refrigerant flow parameters of each refrigerant user, preferably the regulating valve opening degree, the preset value of the sampling period is 5 - 10 seconds, such as 5 seconds; for the heat load at the compressor outlet, the preset value of the sampling period is 5 - 10 seconds, such as 5 seconds. The sampling period can be optimized and adjusted according to the actual production situation.

[0021] The alarm module is configured to generate an alarm signal based on the trend feature when the fluctuation amplitude of any of the above parameters exceeds the alarm threshold in the trend. The preset value of the alarm threshold is a change amplitude of 5%-10%, for example 5%, relative to the parameter of the most recent sampling. Based on historical trends and production reality, those skilled in the art can dynamically adjust the alarm threshold. The alarm signal prompts the operator which user's regulating valve opening has an abnormal fluctuation or which compressor outlet heat load has an abnormal fluctuation.

[0022] Based on the alarm signal, the operator can accurately identify the problem source and intervene in a timely manner for adjustment. If there is an obvious change in the valve position of a certain user, the root cause of the problem can be quickly located. If there is an abnormal fluctuation in the heat load while the valve positions of each user remain unchanged, the problem may lie in the abnormal anti-surge system of the compressor itself, such as an unplanned opening, or a significant change in the ambient temperature, such as a sudden weather anomaly like heavy rain. As an example, the anti-surge system of the compressor is used to provide a circulation loop from the compressor outlet to the inlet when the total amount of refrigerant used by each user is small, so that part of the compressed refrigerant returns to the compressor inlet to ensure the minimum design flow rate of the compressor, thereby avoiding compressor surge. In one embodiment, if the compressor heat load changes by more than the alarm threshold compared to the previous sampling period, but the valve positions of each user do not change (indicating that the total amount of refrigerant used by each user has not decreased significantly and the anti-surge system circulation loop should not be activated), this may indicate an abnormal anti-surge system. Accordingly, the alarm module can generate an anti-surge system fault prompt to remind the operator to check the surge system. In a preferred embodiment, the alarm module is further configured that when the fluctuation amplitude of the regulating valve opening exceeds the alarm threshold in the trend, it instructs the data acquisition module to read the change in the liquid level of the corresponding refrigerant user within a specified time period, and generates a liquid level false indication prompt related to the corresponding refrigerant user when there is a non-smooth change in the liquid level of the corresponding refrigerant user within the specified time period. For example, the specified time period can generally be within 1-5 minutes before the alarm occurs. When the liquid level related to the refrigerant user changes by more than the alarm threshold compared to the value of the previous sampling period, it is considered a non-smooth change. This configuration can quickly locate the liquid level false indication fault of the refrigerant user, enabling the operator to promptly switch the liquid level gauge of the corresponding refrigerant user and eliminate the root cause of the problem. At the same time, under normal circumstances, there is no need to continuously track or display the liquid levels of each refrigerant user during parameter tracking to reduce the amount of data that the operator needs to pay attention to.

[0023] In another preferred embodiment, the data acquisition module is further configured to obtain weather parameters in real time, and the trend recording module is further configured to, when the weather parameters indicate a sudden weather warning, adjust the sampling period to one m-th of the original preset value of the sampling period, and instruct the alarm module to adjust the alarm threshold to one n-th of the original preset value of the alarm threshold; and when the weather parameters indicate the lifting of the sudden weather warning, adjust the sampling period back to the preset value of the original sampling period, and instruct the alarm module to adjust the alarm threshold back to the preset value of the original alarm threshold, where m and n can be positive integers from 2 to 10, preferably from 2 to 5, and m is less than or equal to n. The values of m and n can be determined and adjusted according to the actual situation. Taking the preset value of the sampling period as 10 seconds and the preset value of the alarm threshold being a 10% change amplitude relative to the parameters of the most recent sampling as an example, when m = 2 and n = 2, the sampling period is shortened to 5 seconds and the preset value of the alarm threshold is reduced to a 5% change amplitude relative to the parameters of the most recent sampling, that is, the sensitivity to the relative speed of parameter change remains unchanged, but each parameter is tracked more frequently. As another example, in the case of the same preset values as above, when m = 4 and n = 5, the sampling period is shortened to 2.5 seconds and the preset value of the alarm threshold is reduced to a 2% change amplitude relative to the parameters of the most recent sampling. In this case, not only are the parameters tracked more frequently, but the sensitivity to the relative speed of parameter change is also increased simultaneously. This configuration can trigger the shortening of the monitoring time interval and / or the reduction of the alarm threshold before the sudden weather occurs, so that the monitoring can respond more sensitively to weather changes, and the refrigeration system can also operate more stably during sudden weather anomalies.

[0024] The intelligent control system of the present invention is applicable to single-stage and multi-stage compression cycle systems, and is particularly applicable to the propylene refrigeration system in an ethylene plant.

[0025] The method for monitoring and controlling an industrial refrigeration system of the present invention can be implemented by the intelligent control system described in the present invention. The intelligent control system and method of the present invention will be described in detail below by taking the propylene refrigeration system as an example.

[0026] Each refrigerant user of the propylene refrigeration system usually includes an ethylene rectification column, a deethanizer column, a top condenser of a depropanizer column, etc. In the propylene refrigeration system, the compressor is usually divided into a first stage, a second stage, and a third stage (or more stages) for compression. Each stage undertakes different pressure and temperature ranges and provides different temperature grades for different refrigerant users. For example, according to different temperature requirements, propylene refrigerant is divided into low-pressure propylene refrigerant (-38°C), medium-pressure propylene refrigerant (-21°C), and high-pressure propylene refrigerant (+10°C), and their suction pressures respectively correspond to the inlet of the first stage, the inlet of the second stage, and the inlet of the third stage of the propylene refrigeration compressor. In the method of the present invention, first, the data acquisition module of the intelligent control system is used to obtain in real time the refrigerant flow parameters of each refrigerant user, including all high, medium, and low-pressure propylene refrigerant users, preferably the opening degree of the regulating valve, and the compressor operation parameters, preferably the circulating water flow rate and the circulating water outlet / inlet temperature of the compressor outlet water cooler.

[0027] Then, the calculation module is used to dynamically calculate the heat load of the heat exchanger at the compressor outlet based on the above-mentioned compressor operation parameters collected in real time through the formula Q = m × c p ×ΔT.

[0028] Through the trend recording module of the intelligent control system, for example, the refrigerant flow parameter changes of each refrigerant user are automatically read every 5 seconds, preferably the opening degree change of the regulating valve and the heat load change of the heat exchanger at the compressor outlet, and a trend is formed. Monitor the changes of the above parameters in the trend. When the change range of any of the above parameters in the trend exceeds the alarm threshold of 5%-10%, for example, 5%, compared with the most recent sampling, the alarm module generates an alarm signal. This alarm signal prompts the operator to intervene and adjust in advance to alleviate the negative impact brought by the load fluctuation and avoid large fluctuations in the entire refrigeration system. In some embodiments, the early warning of the parameter trend is only based on the change range of the parameter compared with the most recent sampling, without considering the earlier change trend of the corresponding parameter. The change of parameters (such as the opening degree of the refrigerant user regulating valve, the heat load of the heat exchanger at the compressor outlet, etc.) has a strong instantaneous impact on the operating state of the compressor. Therefore, only focusing on the change range compared with the most recent sampling and selectively ignoring the earlier change trend can assist the operator to improve the prediction of the instantaneous impact through the alarm and reduce the impact of the earlier change trend on the instantaneous sensitivity of the early warning.

[0029] In an existing propylene refrigeration system, for example, when the level gauge of a certain propylene refrigerant user in the first stage of the compressor shows a false indication, such as the indicated value being lower than the actual value, the regulating valve of this refrigerant user will automatically open wider, increasing the amount of gaseous propylene entering the inlet of the first stage of the compressor, which will cause the inlet pressure of the compressor to rise. According to the control logic of the existing design, when it is detected that the suction pressure of the first stage of the compressor rises, the system will automatically increase the compressor speed. The increase in the compressor speed will affect the reduction of the suction pressures of the second and third stages of the compressor, and the outlet pressure of the third stage will rise. After observing the abnormal rise in the outlet pressure of the third stage of the compressor, the operator will only then consider whether the device load has changed and whether the ambient temperature has changed. If there is no change, it is necessary to notify each post to check their respective refrigerant users to identify which user's load has changed significantly and what caused this change. This process often takes a certain amount of time, and it is very difficult for the operator to identify the false indication of this level in the first place. As time goes by, each level of user is affected by the pressure fluctuation change and needs to adjust the opening of its refrigerant valve, resulting in changes in the operating loads of each stage of the compressor, and ultimately causing large fluctuations in the entire system.

[0030] By using the intelligent control system and method of the present invention, it can be detected at the initial stage when the refrigerant regulating valve of the faulty user opens abnormally wide, that is, an alarm signal is sent at the initial stage of the load change. The operator can locate the abnormal user in the first time, quickly intervene, change the refrigerant regulating valve of this user to manual control, and adjust it to the normal valve opening, thus avoiding subsequent system fluctuations.

[0031] Through the intelligent control system for monitoring and controlling industrial refrigeration systems of the present invention, it enables the staff to quickly locate which system's refrigerant user load has changed significantly according to the system prompt. While communicating well with relevant personnel, adjustments can be made in advance, thus avoiding greater fluctuations and coupling effects, and improving the operating stability and anti-fluctuation ability of the entire propylene refrigeration system.

Claims

1. An intelligent control system for monitoring and controlling an industrial refrigeration system, comprising a data acquisition module, a calculation module, a trend recording module and an alarm module, wherein: The data acquisition module is configured to obtain the refrigerant flow parameters of each refrigerant user and the operating parameters of the refrigeration compressor in real time. The calculation module is configured to dynamically calculate the heat load of the heat exchanger at the compressor outlet based on the compressor operating parameters collected in real time. The trend recording module is configured to store the refrigerant flow parameters of each refrigerant user and the heat load parameters of the heat exchanger at the compressor outlet generated by the calculation module at a sampling period, and perform time series analysis on these parameters to form trend characteristics; The alarm module is configured to generate an alarm signal based on the trend feature when the fluctuation amplitude of any parameter in the trend exceeds an alarm threshold.

2. The intelligent control system according to claim 1 is a distributed control system DCS.

3. The intelligent control system according to claim 1 or 2, wherein the compressor operating parameters include the circulating water flow rate and the circulating water outlet / inlet temperature of the heat exchanger at the compressor outlet.

4. The intelligent control system according to claim 1 or 2, wherein the refrigerant flow parameter of each refrigerant user includes a regulating valve opening.

5. The intelligent control system according to claim 4, wherein the alarm module is further configured to instruct the data acquisition module to read the change of the liquid level of the corresponding refrigerant user within a specified time period when the fluctuation amplitude of the regulating valve opening in the trend exceeds the alarm threshold, and to generate a false liquid level indication prompt related to the corresponding refrigerant user when there is a non-smooth change in the change of the liquid level of the corresponding refrigerant user within the specified time period.

6. The intelligent control system according to claim 1 or 2, wherein the heat load of the heat exchanger at the compressor outlet is calculated by the following formula: Q = m × c p ×ΔT, where m is the mass flow rate of circulating water, c p is the specific heat capacity of water, and ΔT is the temperature difference between the inlet and outlet of the circulating water.

7. The intelligent control system according to claim 1 or 2, wherein the preset value of the sampling period is 5-10s.

8. The intelligent control system according to claim 7, wherein the preset value of the alarm threshold is a change range of 5%-10% relative to the most recently sampled parameter.

9. The intelligent control system according to claim 8, wherein the data acquisition module is also configured to acquire weather parameters in real time, and the trend recording module is also configured to adjust the sampling period to one m of the preset value of the sampling period and instruct the alarm module to adjust the alarm threshold to one n of the preset value of the alarm threshold when the weather parameters indicate a sudden weather warning; and when the weather parameters indicate that the sudden weather warning is lifted, adjust the sampling period back to the preset value of the sampling period and instruct the alarm module to adjust the alarm threshold back to the preset value of the alarm threshold, wherein m and n are positive integers of 2-10, and m is less than or equal to n.

10. The intelligent control system according to claim 1 or 2, wherein the industrial refrigeration system is a propylene refrigeration system of an ethylene plant.