Method for regulating and controlling maximum heat transfer temperature difference of cold box of natural gas light hydrocarbon removal device

Abstract

The invention discloses a method for regulating and controlling the maximum heat transfer temperature difference of a cold box of a natural gas light hydrocarbon removal device. The method comprises the following steps: firstly, acquiring the maximum heat transfer temperature difference, refrigerant separator temperature, refrigerant compressor inlet and outlet pressure and other parameters in the operation of the cold box, then analyzing the maximum heat transfer temperature difference corresponding to different parameter combinations, and determining the refrigerant flow corresponding to each parameter when the maximum heat transfer temperature difference of the cold box is equal to an allowable value; and each parameter range of the cold box below the maximum heat transfer temperature difference is determined. And according to the refrigerant separator temperature-refrigerant flow-peak heat transfer temperature difference relation and the refrigerant compressor inlet and outlet pressure correlation, the refrigerant flow, the refrigerant compressor inlet and outlet pressure and the refrigerant separator temperature are gradually adjusted, so that the maximum heat transfer temperature difference of the cold box is reduced to be below an allowable value. The method is beneficial for improving the efficiency of the cold box and reducing the production energy consumption, can be popularized and used for analyzing the influence of other parameters, and can realize real-time adjustment of production operation in combination with an automatic monitoring and control system.

Description

Technical Field

[0001] The invention belongs to the technical field of natural gas light hydrocarbon removal cold box control, and relates to a method for controlling the maximum heat transfer temperature difference of a cold box of a natural gas light hydrocarbon removal device. Background Art

[0002] Currently, multi-stream cold boxes are widely used in natural gas decarbonization production systems. The heat transfer temperature difference across the entire cold box is typically constrained by an upper limit. Within the cold box, different hot and cold streams flow through separate channels, and their performance is correlated with the heat transfer temperature difference within these channels. The maximum heat transfer temperature difference within the cold box is closely related to the refrigerant flow rate, refrigerant separator temperature, refrigerant compressor inlet pressure, refrigerant compressor outlet pressure, and natural gas composition. Because the composition of produced natural gas varies significantly over time and location, the maximum heat transfer temperature difference within the cold box can increase and exceed the upper limit. This requires adjusting the refrigerant flow rate, refrigerant separator temperature, refrigerant compressor inlet pressure, and refrigerant compressor outlet pressure accordingly to ensure that the maximum heat transfer temperature difference within the cold box does not exceed the upper limit. However, in actual production, due to the complexity of the natural gas decarbonization unit and the processes within the cold box, rapid and precise optimization and control based on natural gas composition is not possible. Summary of the Invention

[0003] In order to solve the problems existing in the background technology, the present invention proposes a method for controlling the maximum heat transfer temperature difference of a cold box of a natural gas light hydrocarbon removal device.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is as follows: A method for controlling the maximum heat transfer temperature difference of a cold box of a natural gas light hydrocarbon removal device comprises: S100: obtaining a maximum heat transfer temperature difference during operation of a cold box of a natural gas light hydrocarbon removal unit, obtaining a refrigerant separator temperature during operation of the cold box, and obtaining a refrigerant compressor inlet pressure and a refrigerant compressor outlet pressure during operation of the cold box; S200: Analyzing the maximum heat transfer temperature difference during cold box operation corresponding to different temperatures of the refrigerant separator, the refrigerant compressor inlet pressure, and the refrigerant compressor outlet pressure; S300: Determine the refrigerant flow rate corresponding to the refrigerant separator temperature, the refrigerant compressor inlet pressure, and the refrigerant compressor outlet pressure when the maximum heat transfer temperature difference of the cold box is equal to the allowable value; S400: determining the range of various parameters when the cold box is operated below the maximum heat transfer temperature difference; S500: Gradually adjust the refrigerant compressor inlet pressure, refrigerant compressor outlet pressure, refrigerant flow, refrigerant compressor outlet pressure and refrigerant separator temperature until the maximum heat transfer temperature difference of the cold box drops below the maximum allowable value.

[0005] Furthermore, in steps S200, S300, and S400, the relationship between the refrigerant separator temperature, the refrigerant flow rate, and the maximum heat transfer temperature difference is expressed as: ; in is the refrigerant separator temperature in degrees Celsius, is the refrigerant flow rate, is the maximum heat transfer temperature difference in the cold box.

[0006] Furthermore, the relationship between the refrigerant compressor inlet pressure, the refrigerant compressor outlet pressure, the refrigerant flow rate, and the maximum heat transfer temperature difference is: ; in is the refrigerant compressor inlet pressure, is the refrigerant compressor outlet pressure, is the refrigerant flow rate, is the maximum heat transfer temperature difference in the cold box.

[0007] Furthermore, in step S500, the steps of gradually adjusting the refrigerant compressor inlet pressure, refrigerant flow rate, refrigerant compressor outlet pressure and refrigerant separator temperature are as follows: Substitute the refrigerant separator temperature into the relationship between refrigerant separator temperature, refrigerant flow rate and maximum heat transfer temperature difference to obtain the refrigerant flow rate under the target maximum heat transfer temperature difference; Adjust the refrigerant separator temperature and refrigerant flow rate to obtain the actual heat transfer temperature difference; The refrigerant compressor inlet pressure remains unchanged, and the refrigerant compressor outlet pressure and the corresponding refrigerant flow rate Mj under the target heat transfer temperature difference are calculated and adjusted according to the relationship between the refrigerant compressor inlet pressure-refrigerant compressor outlet pressure-refrigerant flow rate-maximum heat transfer temperature difference; Gradually adjust the refrigerant compressor outlet pressure and refrigerant flow rate to obtain actual heat transfer temperature difference data; The outlet pressure of the refrigerant compressor remains unchanged, and the relationship between the inlet pressure of the refrigerant compressor, the outlet pressure of the refrigerant compressor, the refrigerant flow rate, and the maximum heat transfer temperature difference is corrected. The inlet pressure of the refrigerant compressor and the corresponding refrigerant flow rate under the adjusted target heat transfer temperature difference are calculated; Gradually adjust the refrigerant compressor inlet pressure and refrigerant flow rate to obtain the actual heat transfer temperature difference.

[0008] Compared with the prior art, the present invention has the following beneficial effects: Based on the multi-parameter correlation law, the present invention determines the relationship between the maximum heat transfer temperature difference in the cold box and the refrigerant flow rate, refrigerant separator temperature, refrigerant compressor inlet pressure and refrigerant compressor outlet pressure when the raw natural gas composition changes. Then, the optimal refrigerant flow rate, separator temperature, refrigerant compressor inlet pressure and refrigerant compressor outlet pressure are determined according to the cold box constraints and system operation requirements. This is of great significance for improving the efficiency of the cold box and reducing production energy consumption.

[0009] The present invention can also be extended to analyze and determine the influence of other parameters on the maximum heat transfer temperature difference of the cold box. In actual production, combined with the automatic monitoring and control system, real-time adjustment of production operations can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a flow chart of the overall method of the present invention; Figure 2 It is a schematic diagram of the cold box device optimized by the present invention; Figure 3 This is a heat transfer temperature difference distribution diagram in the cold box provided by the present invention; Figure 4 is a graph showing the relationship between the refrigerant separator temperature, the refrigerant flow rate, and the refrigerant outlet temperature of the present invention; Figure 5 This is a relationship diagram of the refrigerant compressor outlet pressure, the refrigeration unit area power consumption, and the maximum heat transfer temperature difference of the cold box of the present invention.

[0011] The markings in the accompanying drawings are: 1. cold box; 2. refrigerant compressor; 3. refrigerant separator; 4. refrigerant mixer. DETAILED DESCRIPTION

[0012] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0013] like Figure 1-Figure 5 As shown, the technical solution adopted by the present invention is as follows: A method for controlling the maximum heat transfer temperature difference of the cold box of a natural gas light hydrocarbon removal device, operating at Figure 2 The cold box device shown includes: S100: Obtaining the maximum heat transfer temperature difference during operation of the cold box 1 of the natural gas light hydrocarbon removal unit, obtaining the temperature of the refrigerant separator 3 during operation of the cold box 1, and obtaining the inlet pressure and outlet pressure of the refrigerant compressor 2 during operation of the cold box 1.

[0014] S200: Analyze the maximum heat transfer temperature difference during operation of the cold box 1 corresponding to different temperatures of the refrigerant separator 3, the inlet pressure of the refrigerant compressor 2, and the outlet pressure of the refrigerant compressor 2.

[0015] S300: Determine the refrigerant flow rate corresponding to the temperature of the refrigerant separator 3, the inlet pressure of the refrigerant compressor 2, and the outlet pressure of the refrigerant compressor 2 when the maximum heat transfer temperature difference of the cold box 1 is equal to the allowable value.

[0016] S400: Determine the range of various parameters when the cold box 1 is operated below the maximum heat transfer temperature difference.

[0017] S500: gradually adjusting the refrigerant compressor 2 inlet pressure, refrigerant compressor 2 outlet pressure, refrigerant flow, refrigerant compressor 2 outlet pressure and refrigerant separator 3 temperature until the maximum heat transfer temperature difference of the cold box 1 drops below the maximum allowable value.

[0018] When running the method provided by the present invention, first obtain the maximum heat transfer temperature difference during the operation of the cold box 1 of the natural gas light hydrocarbon removal unit, obtain the temperature of the refrigerant separator 3 during the operation of the cold box 1, and obtain the inlet pressure of the refrigerant compressor 2 and the outlet pressure of the refrigerant compressor 2 during the operation of the cold box 1. Collect these key operating parameters to provide a data basis for subsequent analysis and optimization of the operation of the cold box 1. The maximum heat transfer temperature difference reflects the efficiency and degree of heat transfer inside the cold box 1, the temperature of the refrigerant separator 3 affects the phase state and separation effect of the refrigerant, and the inlet pressure of the refrigerant compressor 2 and the outlet pressure of the refrigerant compressor 2 are related to the compression work and circulation power of the refrigerant. A comprehensive understanding of these parameters will help to gain a deeper understanding of the operating status of the cold box 1.

[0019] After obtaining the data to be analyzed, the maximum heat transfer temperature difference during operation of the cold box 1 corresponding to the different temperatures of the refrigerant separator 3, the inlet pressure of the refrigerant compressor 2, and the outlet pressure of the refrigerant compressor 2 is analyzed. By studying the relationship between these parameters, the influence of each factor on the maximum heat transfer temperature difference can be clearly determined. This helps to identify the key factors affecting the heat transfer efficiency of the cold box 1 and provides direction for subsequent optimization and adjustment. For example, if it is found that a small change in the temperature of the refrigerant separator 3 will cause a large fluctuation in the maximum heat transfer temperature difference, then in actual operation, this temperature can be focused on and controlled.

[0020] Determine the refrigerant flow rate corresponding to the refrigerant separator 3 temperature, the refrigerant compressor 2 inlet pressure, and the refrigerant compressor 2 outlet pressure when the maximum heat transfer temperature difference of cold box 1 is equal to the allowable value. The required refrigerant flow rate and other corresponding parameters, while meeting the maximum allowable heat transfer temperature difference, are clearly defined. This provides specific operational indicators for actual operation, ensuring that cold box 1 operates within a safe and efficient range. Precise control of these parameters ensures that cold box 1 achieves optimal heat transfer while remaining within safety limits.

[0021] Determine the ranges for various parameters when operating cold box 1 below the maximum heat transfer temperature difference. Define the range of values ​​for each operating parameter when the maximum heat transfer temperature difference is within a safe range. This provides operators with clear operational boundaries, preventing performance degradation or malfunction of cold box 1 due to improper parameter settings. When operators can control parameters within reasonable ranges, they can ensure long-term stable operation of cold box 1.

[0022] like Figure 3 、 Figure 4 As shown, the relationship between the temperature of the refrigerant separator 3, the refrigerant flow rate and the maximum heat transfer temperature difference is expressed as: ; in is the temperature in Celsius of the refrigerant separator 3, is the flow rate of refrigerant; is the maximum heat transfer temperature difference in cold box 1.

[0023] like Figure 5 As shown, the relationship between the inlet pressure of refrigerant compressor 2, the outlet pressure of refrigerant compressor 2, the refrigerant flow rate and the maximum heat transfer temperature difference is: ; in is the inlet pressure of refrigerant compressor 2, is the outlet pressure of refrigerant compressor 2, is the refrigerant flow rate, is the maximum heat transfer temperature difference in cold box 1.

[0024] After calculating the relationship between the refrigerant separator 3 temperature-refrigerant flow-maximum heat transfer temperature difference and the relationship between the refrigerant compressor 2 inlet pressure-refrigerant compressor 2 outlet pressure-refrigerant flow-maximum heat transfer temperature difference, gradually adjust the refrigerant compressor 2 inlet pressure, refrigerant flow, refrigerant compressor 2 outlet pressure and refrigerant separator 3 temperature until the maximum heat transfer temperature difference of the cold box 1 drops below the maximum allowable value.

[0025] Substituting the refrigerant separator 3 temperature into the relationship between refrigerant separator 3 temperature, refrigerant flow rate, and maximum heat transfer temperature difference yields the refrigerant flow rate at the target maximum heat transfer temperature difference. Using the established mathematical relationship and the known refrigerant separator 3 temperature, the refrigerant flow rate required to meet the target maximum heat transfer temperature difference can be accurately calculated, providing a precise reference value for subsequent adjustments.

[0026] Adjust the temperature of the refrigerant separator 3 and the refrigerant flow rate to obtain the actual heat transfer temperature difference. By changing these two parameters, observe the changes in the actual heat transfer temperature difference to determine whether the adjustment direction is correct, and then further optimize the parameter combination to make the heat transfer temperature difference closer to the target value.

[0027] The inlet pressure of refrigerant compressor 2 remains unchanged. The outlet pressure and corresponding refrigerant flow rate Mj under the target heat transfer temperature difference are calculated based on the relationship between the inlet pressure of refrigerant compressor 2, the outlet pressure of refrigerant compressor 2, the refrigerant flow rate, and the maximum heat transfer temperature difference. When the inlet pressure of refrigerant compressor 2 is fixed, the outlet pressure of refrigerant compressor 2 and the refrigerant flow rate are determined based on the parameter relationship. This allows for targeted adjustment of the outlet pressure of refrigerant compressor 2, while also combining changes in the refrigerant flow rate to achieve effective control of the heat transfer temperature difference.

[0028] Gradually adjust the outlet pressure and refrigerant flow rate of refrigerant compressor 2 to obtain actual heat transfer temperature difference data. By gradually changing the outlet pressure and refrigerant flow rate of refrigerant compressor 2, a series of actual heat transfer temperature difference data is obtained. Analyzing this data can find the optimal parameter match to achieve the goal of reducing the heat transfer temperature difference to below the allowable value.

[0029] The outlet pressure of Refrigerant Compressor 2 remains unchanged. The relationship between Refrigerant Compressor 2 inlet pressure, Refrigerant Compressor 2 outlet pressure, Refrigerant flow rate, and Maximum heat transfer temperature difference is corrected. The Refrigerant Compressor 2 inlet pressure and the corresponding refrigerant flow rate are calculated for the adjusted target heat transfer temperature difference. While the outlet pressure of Refrigerant Compressor 2 is fixed, the inlet pressure of Refrigerant Compressor 2 and the corresponding refrigerant flow rate are adjusted to further explore the potential of parameter adjustment and ensure that the optimal parameter combination can be found under different operating conditions to meet the requirements of the Maximum heat transfer temperature difference.

[0030] Gradually adjust the inlet pressure and refrigerant flow rate of refrigerant compressor 2 to obtain the actual heat transfer temperature difference. Continuously adjust the inlet pressure and refrigerant flow rate of refrigerant compressor 2. Based on the feedback of the actual heat transfer temperature difference, continuously optimize the parameters to achieve the best operation of cold box 1. Effectively control the maximum heat transfer temperature difference below the maximum allowable value to ensure the efficient and stable operation of cold box 1.

[0031] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for controlling the maximum heat transfer temperature difference of a cold box of a natural gas light hydrocarbon removal unit, characterized in that: Includes: S100: obtaining a maximum heat transfer temperature difference of a cold box (1) of a natural gas light hydrocarbon removal unit during operation, obtaining a temperature of a refrigerant separator (3) during operation of the cold box (1), and obtaining an inlet pressure of a refrigerant compressor (2) and an outlet pressure of the refrigerant compressor (2) during operation of the cold box (1); S200: Analyze the maximum heat transfer temperature difference during operation of the cold box (1) corresponding to different temperatures of the refrigerant separator (3), the inlet pressure of the refrigerant compressor (2), and the outlet pressure of the refrigerant compressor (2); S300: determining the refrigerant flow rate corresponding to the temperature of the refrigerant separator (3), the inlet pressure of the refrigerant compressor (2), and the outlet pressure of the refrigerant compressor (2) when the maximum heat transfer temperature difference of the cold box (1) is equal to the allowable value; S400: determining the range of various parameters when operating the cold box (1) below the maximum heat transfer temperature difference; S500: gradually adjusting the refrigerant compressor (2) inlet pressure, the refrigerant compressor (2) outlet pressure, the refrigerant flow rate and the refrigerant separator (3) temperature until the maximum heat transfer temperature difference of the cold box (1) is reduced to below the maximum allowable value.

2. The method for controlling the maximum heat transfer temperature difference of a cold box of a natural gas light hydrocarbon removal device according to claim 1, characterized in that: The steps of step S500 are as follows: The temperature of the refrigerant separator (3) is substituted into the relationship between the temperature of the refrigerant separator (3) - the refrigerant flow rate - the maximum heat transfer temperature difference to obtain the refrigerant flow rate under the target maximum heat transfer temperature difference; Adjust the temperature of the refrigerant separator (3) and the refrigerant flow rate to obtain the actual heat transfer temperature difference; The inlet pressure of the refrigerant compressor (2) remains unchanged, and the outlet pressure of the refrigerant compressor (2) and the corresponding refrigerant flow rate Mj under the target heat transfer temperature difference are calculated and adjusted according to the relationship of the inlet pressure of the refrigerant compressor (2) - the outlet pressure of the refrigerant compressor (2) - the refrigerant flow rate - the maximum heat transfer temperature difference; Gradually adjust the outlet pressure and refrigerant flow rate of the refrigerant compressor (2) to obtain actual heat transfer temperature difference data; The outlet pressure of the refrigerant compressor (2) remains unchanged, the relationship between the inlet pressure of the refrigerant compressor (2) - the outlet pressure of the refrigerant compressor (2) - the refrigerant flow rate - the maximum heat transfer temperature difference is corrected, and the inlet pressure of the refrigerant compressor (2) and the corresponding refrigerant flow rate under the adjusted target heat transfer temperature difference are calculated; The inlet pressure of the refrigerant compressor (2) and the refrigerant flow rate are gradually adjusted to obtain the actual heat transfer temperature difference.

3. The method for controlling the maximum heat transfer temperature difference of a cold box of a natural gas light hydrocarbon removal device according to claim 2, characterized in that: The relationship between the refrigerant separator (3) temperature, refrigerant flow rate, and maximum heat transfer temperature difference is expressed as: ； in is the temperature of the refrigerant separator (3) in degrees Celsius, is the refrigerant flow rate, is the maximum heat transfer temperature difference in the cold box (1).

4. The method for controlling the maximum heat transfer temperature difference of a cold box of a natural gas light hydrocarbon removal device according to claim 2, characterized in that: The relationship between the refrigerant compressor (2) inlet pressure, the refrigerant compressor (2) outlet pressure, the refrigerant flow rate, and the maximum heat transfer temperature difference is: ； in is the inlet pressure of the refrigerant compressor (2), is the outlet pressure of the refrigerant compressor (2), is the refrigerant flow rate, is the maximum heat transfer temperature difference in the cold box (1).

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