Low-temperature water waste heat recovery system in urea production

Abstract

The invention discloses a low-temperature water waste heat recovery system in urea production, and relates to the technical field of chemical energy conservation and heat energy recovery, and the low-temperature water waste heat recovery system comprises the following steps: collecting original data in a urea production process, establishing a three-dimensional model of the low-temperature water waste heat recovery system, and preliminarily setting system parameters; based on the three-dimensional model and the preliminarily set system parameters, evaluating the pipeline performance of the three-dimensional model by simulating the flow characteristics of the fluid in the pipeline through CFD; dynamically optimizing the pipeline layout and the fluid flow direction according to the evaluation result, and verifying the optimized system characteristics; by means of the optimized pipeline design scheme, an intelligent temperature control model is designed, temperature changes are predicted, and the valve opening degree and the pump speed are dynamically adjusted according to the prediction result; and evaluating the performance of the low-temperature water waste heat recovery system, and adjusting the control parameters according to an evaluation result. The pipeline layout and the fluid flow direction are optimized through CFD simulation, the opening degree of the valve and the pump speed are adjusted through the intelligent temperature control model, the energy efficiency of urea production is improved, and positive significance is achieved on environment protection.

Description

Technical Field

[0001] The invention relates to the technical field of chemical energy saving and heat recovery, in particular to a low-profile water waste heat recovery system in urea production. Background Art

[0002] The large amount of waste heat generated during the urea production process is a valuable energy resource. In the traditional urea production process, this waste heat is usually discharged directly into the environment, resulting in energy waste. In recent years, with the promotion of energy-saving and emission reduction policies and technological advances, waste heat recovery technology in the urea production process has developed rapidly. Early waste heat recovery systems mainly relied on simple heat exchangers and heat exchange technologies. Although they could achieve heat recovery and utilization to a certain extent, their efficiency was low. With the application of advanced simulation technologies such as computer-aided design (CAD) and computational fluid dynamics (CFD), waste heat recovery systems in modern urea production can not only achieve efficient heat recovery, but also improve the overall performance of the system through modeling and optimization techniques.

[0003] Although the current waste heat recovery technology for urea production has made significant progress, there are still some problems that need to be solved. First, when establishing the initial model, the existing waste heat recovery system often relies on hand-drawn two-dimensional drawings and rough estimates, which makes it difficult to accurately reflect the actual process conditions. Secondly, the optimization of traditional waste heat recovery systems is mostly based on empirical rules or simple numerical simulations, lacking a comprehensive and automated optimization process. In addition, due to the lack of intelligent temperature control methods, the system often cannot respond in a timely manner according to changes in actual operating conditions during operation, resulting in large energy losses. Finally, the evaluation of system performance is also relatively simple, and the comprehensive performance indicators of the system are not taken into account, making the optimization effect not obvious enough. Summary of the invention

[0004] In view of the above existing problems, the present invention is proposed.

[0005] Therefore, the present invention provides a low-profile water waste heat recovery system in urea production to solve the problems of inaccurate modeling, incomplete optimization, unintelligent temperature control and single performance evaluation in the prior art.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0007] The embodiment of the present invention provides a low-profile water waste heat recovery system in urea production, which includes: a fluid dynamics building module: collecting raw data in the urea production process, establishing a three-dimensional model of the low-profile water waste heat recovery system, and preliminarily setting system parameters;

[0008] Fluid dynamics optimization simulation: Based on the 3D model and the preliminary setting of system parameters, CFD is used to simulate the flow characteristics of the fluid in the pipeline and evaluate the pipeline performance of the 3D model;

[0009] Optimization and verification module: dynamically optimizes pipeline layout and fluid flow direction based on evaluation results, and verifies optimized system characteristics;

[0010] Intelligent temperature control model design module: Use the optimized pipeline design to design an intelligent temperature control model, predict temperature changes, and dynamically adjust the valve opening and pump speed based on the prediction results;

[0011] System evaluation and optimization module: Evaluate the performance of low-temperature water waste heat recovery system and adjust control parameters according to the evaluation results.

[0012] As a preferred solution of the low-cost water waste heat recovery system in urea production of the present invention, the specific steps of collecting the raw data in the urea production process are as follows:

[0013] Obtain raw data of low-profile water waste heat recovery systems from urea production sites, including pipe dimensions, materials, and fluid properties;

[0014] The collected raw data are cleaned and standardized.

[0015] As a preferred solution of the low-cost water waste heat recovery system in urea production of the present invention, the three-dimensional model of the low-cost water waste heat recovery system is established and the system parameters are preliminarily set. The specific steps are as follows:

[0016] Based on the pipe size and layout, ANSYS Fluent was used to build a 3D model of the low-profile water waste heat recovery system and mesh the built 3D model;

[0017] Based on the original data of the low-profile water waste heat recovery system obtained from the urea production site, the fluid properties, pipeline dimensions and fluid flow conditions of the system are preliminarily set.

[0018] As a preferred solution of the low-cost water waste heat recovery system in urea production of the present invention, the following specific steps are taken to simulate the flow characteristics of the fluid in the pipeline based on the three-dimensional model and the preliminary setting of system parameters:

[0019] The inlet boundary conditions of the 3D model were set according to the fluid properties, including velocity, pressure, and flow rate at the inlet, and the outlet boundary conditions were set to atmospheric pressure;

[0020] Run CFD simulations to simulate the flow of fluids in the low-temperature water waste heat recovery system in urea production in a 3D model, observe the fluid flow, and analyze the fluid flow path and pressure distribution;

[0021] Use ANSYS Fluent software to perform CFD simulation to obtain the flow characteristics of the fluid in the pipeline, including fluid flow efficiency, energy loss and fluid distribution uniformity;

[0022] Based on fluid flow efficiency, energy loss and fluid distribution uniformity, a comprehensive performance index P for evaluating pipeline layout and fluid flow direction is defined as the optimization target, and the expression is:

[0023]

[0024] Among them, η is the fluid flow efficiency, Q represents the effective utilization rate of the fluid passing through the channel per unit time, ΔE represents the energy loss during the fluid flow process, and D var Indicates the uneven distribution of fluid inside the pipe.

[0025] As a preferred solution of the low-cost water waste heat recovery system in urea production of the present invention, the specific steps of evaluating the pipeline performance of the three-dimensional model are as follows:

[0026] Based on the expected minimum performance standard of low-profile water waste heat recovery water system, a performance standard threshold N is defined, and the pipeline performance is evaluated by comparing the comprehensive performance index P with the standard threshold N;

[0027] When P ≥ N, it indicates that the pipeline performance exceeds the expected minimum standard and achieves a good optimization effect;

[0028] When P<N, it indicates that the pipeline performance does not meet the expected standards and needs further optimization.

[0029] As a preferred solution of the low-cost water waste heat recovery system in urea production of the present invention, the pipeline layout and fluid flow direction are dynamically optimized according to the evaluation results, and the optimized system characteristics are verified. The specific steps are as follows:

[0030] When the pipeline performance meets the standards, the pipeline design scheme in the 3D model is applied, including pipeline layout and fluid flow direction;

[0031] When the performance of the pipeline does not meet the standards, adjust the size, shape and connection method of the pipeline;

[0032] Rebuild the 3D model based on the adjusted parameters and perform CFD simulation again to calculate the optimized comprehensive performance index P′;

[0033] Compare the comprehensive performance indicators before and after optimization to determine whether the optimization is effective;

[0034] When P′>P, the optimization is considered effective, and the optimized comprehensive performance index P′ is compared with the standard threshold T to evaluate whether the pipeline performance meets the expected standard;

[0035] When P′≤P, the optimization is considered invalid and the parameters are adjusted continuously.

[0036] As a preferred solution of the low-cost water waste heat recovery system in urea production of the present invention, wherein: the optimized pipeline design scheme is used to design an intelligent temperature control model to predict the temperature change trend. The specific steps are as follows:

[0037] Based on the optimized pipeline layout and fluid flow direction, temperature sensors are installed at key locations to regularly collect temperature data and perform cleaning and standardization processing;

[0038] Correlation analysis method is used to extract features related to temperature changes from the processed data;

[0039] Arrange the extracted temperature change related features in order and integrate them into a comprehensive feature vector X;

[0040] The machine learning model is trained using the comprehensive feature vector X to build a temperature prediction model based on a neural network to predict the temperature changes at key locations of the low-temperature water heat recovery system during urea production. The expression is:

[0041] T′(t)=W2σ(W1X t-1 +b1)+b2;

[0042] Among them, X t-1 is the comprehensive feature vector input at time point t-1, T′(t) is the predicted temperature value at time point t, W1 is the weight matrix from the input layer to the hidden layer, b1 is the bias vector of the hidden layer, W2 is the weight matrix from the hidden layer to the output layer, b2 is the bias vector obtained by the input layer, and σ is the activation function.

[0043] As a preferred solution of the low-cost water waste heat recovery system in urea production of the present invention, the valve opening and pump speed are dynamically adjusted according to the prediction results. The specific steps are as follows:

[0044] Based on comprehensive considerations of system safety and economy, a target temperature threshold T is defined. ta , by the target temperature threshold T ta Compare with the temperature prediction value T′(t) to dynamically adjust the valve opening and pump speed;

[0045] When T′(t)<T ta When the temperature is decreasing, the valve opening should be increased and the pump speed should be increased.

[0046] When T′(t)>Tta It indicates that the temperature is rising and the valve opening should be reduced and the pump speed should be lowered.

[0047] As a preferred solution of the low-cost water waste heat recovery system in urea production of the present invention, the specific steps of evaluating the performance of the low-cost water waste heat recovery system are as follows:

[0048] According to the actual operation data of the low-temperature water waste heat recovery system, the waste heat recovery efficiency of the system is calculated as follows:

[0049]

[0050] Where m is the mass flow rate of the fluid, c p is the specific heat capacity of the fluid, T in is the temperature of the fluid entering the system, T ot is the temperature of the fluid leaving the system, T ab is the actual temperature, J is the waste heat recovery rate of the low-profile water waste heat recovery system;

[0051] Based on the performance target of the low-profile water waste heat recovery system, a waste heat recovery standard Z is defined, and the performance of the low-profile water waste heat recovery system is evaluated by comparing the waste heat recovery rate J of the low-profile water waste heat recovery system with the waste heat recovery standard E;

[0052] When J ≥ Z, it is considered that the waste heat recovery efficiency of the low-pressure water waste heat recovery system has reached the set standard;

[0053] When J<Z, it is considered that the waste heat recovery efficiency of the low-pressure water waste heat recovery system does not meet the set standard.

[0054] As a preferred solution of the low-cost water waste heat recovery system in urea production of the present invention, wherein: the control parameters are adjusted according to the evaluation results, and the specific steps are as follows:

[0055] When the waste heat recovery efficiency of the low-profile water waste heat recovery system reaches the set standard, the current parameter settings are maintained;

[0056] When the waste heat recovery efficiency of the low-pressure water waste heat recovery system does not meet the set standard, the valve opening should be increased, the pump speed should be increased, the fluid temperature and flow rate should be adjusted, and the pipeline layout should be adjusted.

[0057] The beneficial effects of the present invention are as follows: by collecting the original data in the urea production process and establishing a three-dimensional model, the preliminary setting of the low-pressure water waste heat recovery system and the evaluation of the fluid dynamic characteristics are realized, and then the pipeline layout and fluid flow direction are optimized through CFD simulation, thereby improving the system performance. The intelligent temperature control model is used to predict temperature changes and dynamically adjust the valve opening and pump speed according to the prediction results, thereby achieving efficient operation of the system. Finally, by evaluating the performance of the low-pressure water waste heat recovery system and adjusting the control parameters, the stable operation of the system and efficient energy recovery are ensured. The present invention not only improves the energy efficiency of urea production, but also reduces production costs, and also has positive significance for environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0059] Figure 1 This is a flow chart of the low-cost water waste heat recovery system in urea production in Example 1.

[0060] Figure 2 This is a flow chart for dynamically adjusting valve opening and pump speed in Example 1. DETAILED DESCRIPTION

[0061] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the accompanying drawings.

[0062] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0063] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0064] Example 1, reference Figure 1 and Figure 2 , which is the first embodiment of the present invention, provides a low-cost water waste heat recovery system in urea production, comprising the following steps:

[0065] S1. Collect the original data in the urea production process, establish a three-dimensional model of the low-profile water waste heat recovery system, and preliminarily set the system parameters.

[0066] "Low-temperature water" generally refers to low-temperature water used for heat exchange.

[0067] Furthermore, the original data of the low-profile water waste heat recovery system, including pipe size, material and fluid properties, was obtained from the urea production site;

[0068] Clean and standardize the collected raw data to ensure data consistency and integrity;

[0069] It should be noted that data cleaning specifically includes: Removing duplicates: Checking whether there are duplicate records in the data set and removing them, Handling missing values: Checking the missing values ​​in the data and deciding whether to fill the missing values ​​(e.g., using the average value) or delete the records with missing values, Outlier detection: Using statistical methods (e.g., Z-score) to identify and handle outliers, and deciding whether to keep, modify, or delete these values;

[0070] The standardization process is specifically: through standardization processing such as (minimum-maximum scaling), data of different dimensions are converted to the same scale for comparison and processing.

[0071] Based on the pipe size and layout, ANSYS Fluent is used to build a 3D model of the low-profile water waste heat recovery system. The built 3D model is meshed to generate a mesh structure that can be used for CFD simulation. The density of the mesh needs to be balanced based on the accuracy requirements and computing resources.

[0072] Based on the original data of the low-profile water waste heat recovery system obtained from the urea production site, the fluid properties, pipeline dimensions and fluid flow conditions of the system are preliminarily set.

[0073] It should also be noted that the specific process of building a 3D model of a pipeline system is as follows: First, relevant data of the pipeline needs to be collected, such as size, shape, and material. Then, in ANSYS Fluent, a geometric model of the pipeline is created based on this data, including using the tools provided by the software to draw various parts of the pipeline, such as straight pipe sections, elbows, valves, etc., and ensure that the model accurately reflects the design of the actual pipeline system.

[0074] Meshing is done by selecting the appropriate mesh type (such as structured or unstructured mesh). Then, the mesh density is defined based on the required simulation accuracy and computing resource constraints. For complex geometric features or areas that require higher accuracy, local refinement is used. Finally, the mesh quality is checked to ensure that there are no distortions or bad units, thereby ensuring the accuracy of the simulation results.

[0075] S2. Based on the three-dimensional model and the preliminary setting of system parameters, the flow characteristics of the fluid in the pipeline are simulated by CFD to evaluate the pipeline performance of the three-dimensional model.

[0076] Based on fluid flow efficiency, energy loss and fluid distribution uniformity, a comprehensive performance index P for evaluating pipeline layout and fluid flow direction is defined as the optimization target, and the expression is:

[0077]

[0078] Among them, η is the fluid flow efficiency, Q represents the effective utilization rate of the fluid passing through the channel per unit time (Q is calculated by calculating the ratio of the actual flow rate to the theoretical maximum flow rate), ΔE represents the energy loss during the fluid flow process, and D var Indicates the uneven distribution of fluid inside the pipe.

[0079] It should be noted that D var The expression is:

[0080]

[0081] Among them, v j is the velocity of the fluid at any point in the pipe, It represents the average velocity of the fluid in the pipe.

[0082] Based on the expected minimum performance standard of the low-profile water waste heat recovery water system, a performance standard threshold N is defined, which reflects the minimum performance requirement of the system under ideal conditions. The pipeline performance is evaluated by comparing the comprehensive performance index P with the standard threshold N.

[0083] When P ≥ N, it indicates that the pipeline performance exceeds the expected minimum standard and achieves a good optimization effect;

[0084] When P < N, it indicates that the pipeline performance does not meet the expected standards and needs further optimization.

[0085] It should also be noted that the expected minimum performance standard refers to the minimum performance requirement that the system must achieve under ideal conditions. This standard is set by the system designer or engineer based on the system's intended use, operating conditions, and industry specifications. It includes but is not limited to requirements for fluid flow efficiency, energy loss, and fluid distribution uniformity.

[0086] S3. Based on the evaluation results, dynamically optimize the pipeline layout and fluid flow direction, and verify the optimized system characteristics.

[0087] Furthermore, when the pipeline performance meets the standards, the pipeline design scheme in the 3D model is applied, including pipeline layout and fluid flow direction;

[0088] When the performance of the pipeline does not meet the standard, adjust the parameters such as the size, shape and connection method of the pipeline to improve the fluid distribution, reduce energy loss and improve the flow efficiency;

[0089] For example, the diameter of a pipe can be increased to reduce friction losses, or the angle of a pipe elbow can be changed to improve fluid flow;

[0090] Rebuild the 3D model based on the adjusted parameters and perform CFD simulation again to calculate the optimized comprehensive performance index P′;

[0091] Compare the comprehensive performance indicators before and after optimization to determine whether the optimization is effective;

[0092] When P′>P, the optimization is considered effective, and the optimized comprehensive performance index P′ is compared with the standard threshold T to evaluate whether the pipeline performance meets the expected standard;

[0093] When P′≤P, the optimization is considered invalid and the parameters are adjusted continuously;

[0094] It should also be noted that if P′ ≤ P or does not reach the expected standard N, it will be adjusted again until it reaches the expected standard or reaches the maximum number of iterations;

[0095] The maximum number of iterations is determined based on the optimization goal of the system, the computational resource constraints, and the time limit of the optimization process.

[0096] S4. Use the optimized pipeline design to design an intelligent temperature control model, predict temperature changes, and dynamically adjust the valve opening and pump speed based on the prediction results.

[0097] Based on the optimized pipeline layout and fluid flow direction, install temperature sensors at key locations (such as where the fluid enters and exits the pipeline, near the heat exchanger, and other key nodes that may affect system performance), and ensure that they are in good contact with the pipeline to obtain accurate temperature readings. Collect temperature data regularly and perform cleaning and standardization.

[0098] Correlation analysis method is used to extract features related to temperature changes from the processed data;

[0099] Specifically, the correlation strength between different variables and temperature changes is evaluated through correlation analysis methods, such as Pearson correlation coefficient or Spearman rank correlation coefficient and other statistical methods. On this basis, variables that are highly correlated with temperature changes are screened out as features, such as fluid flow, pipeline pressure, ambient temperature, and equipment operating status.

[0100] The extracted temperature change related features are arranged in order and integrated into a comprehensive feature vector X, which is expressed as:

[0101] Xt-1 =[T(t-1),F(t-1),A(t-1),B(t-1),S(t-1)];

[0102] Among them, T(t-1) is the temperature characteristic at the previous moment, F(t-1) is the fluid flow characteristic at the previous moment, A(t-1) is the pipeline pressure characteristic at the previous moment, B(t-1) is the ambient temperature characteristic at the previous moment, S(t-1) is the equipment operation status characteristic at the previous moment, and X t-1 is the comprehensive eigenvector of the previous moment;

[0103] Based on the comprehensive feature vector X, a machine learning model is trained to build a temperature prediction model based on a neural network to predict the temperature changes at key locations of the low-temperature water heat recovery system in the urea production process. The expression is:

[0104] T′(t)=W2σ(W1X t-1 +b1)+b2;

[0105] Among them, X t-1 is the comprehensive feature vector input at time point t-1, T′(t) is the predicted temperature value at time point t, W1 is the weight matrix from the input layer to the hidden layer, b1 is the bias vector of the hidden layer, W2 is the weight matrix from the hidden layer to the output layer, b2 is the bias vector obtained by the input layer, σ is the activation function, which can be specifically expressed as ReLU(x)=max(0,x);

[0106] Neural networks were chosen as the machine learning algorithm because the temperature variation in the low-profile waste heat recovery water system in urea production may be affected by a variety of complex factors, and neural networks are able to capture these nonlinear relationships and patterns, making them more suitable for handling such complex multivariable problems.

[0107] Based on comprehensive considerations of system safety and economy, a target temperature threshold T is defined. ta , by the target temperature threshold T ta Compare with the temperature prediction value T′(t) to dynamically adjust the valve opening and pump speed;

[0108] When T′(t)<T ta When the temperature is decreasing, the valve opening should be increased and the pump speed should be increased to increase the heat input.

[0109] When T′(t)>T ta When , it indicates that the temperature is rising, the valve opening should be reduced and the pump speed should be lowered to reduce heat input.

[0110] It should also be noted that the target temperature threshold T ta The value range is usually determined based on the following factors:

[0111] Process requirements: Determine a reasonable temperature range based on the process requirements of the low-temperature water waste heat recovery system in the urea production process.

[0112] Heat recovery efficiency: Based on the system's heat recovery efficiency target, set a temperature threshold that can ensure heat recovery efficiency without causing overheating.

[0113] Safety and economy: Consider the safety and economy of system operation, ensure that the temperature threshold does not exceed the tolerance range of the equipment, and avoid unnecessary energy consumption.

[0114] S5. Evaluate the performance of the low-temperature water waste heat recovery system and adjust the control parameters based on the evaluation results.

[0115] Furthermore, the waste heat recovery efficiency of the system is calculated based on the actual operation data of the low-temperature water waste heat recovery system, and the expression is:

[0116]

[0117] Where m is the mass flow rate of the fluid, c p is the specific heat capacity of the fluid, T in is the temperature of the fluid entering the system, T ot is the temperature of the fluid leaving the system, T ab is the actual temperature, J is the waste heat recovery rate of the low-profile water waste heat recovery system;

[0118] Based on the performance target of the low-profile water waste heat recovery system, a waste heat recovery standard Z is defined, and the performance of the low-profile water waste heat recovery system is evaluated by comparing the waste heat recovery rate J of the low-profile water waste heat recovery system with the waste heat recovery standard E;

[0119] When J ≥ Z, it is considered that the waste heat recovery efficiency of the low-pressure water waste heat recovery system has reached the set standard;

[0120] When J<Z, it is considered that the waste heat recovery efficiency of the low-pressure water waste heat recovery system does not meet the set standard.

[0121] When the waste heat recovery efficiency of the low-profile water waste heat recovery system reaches the set standard, the current parameter settings are maintained;

[0122] When the waste heat recovery efficiency of the low-profile water waste heat recovery system does not meet the set standard, the valve opening should be increased to allow more fluid to pass through, the pump speed should be increased to increase the fluid flow, the fluid temperature and flow should be adjusted to improve the heat recovery efficiency of the system, and the pipeline layout should be adjusted to improve fluid distribution and reduce energy loss.

[0123] It should also be noted that the performance target of the low-profile water waste heat recovery system refers to the heat recovery efficiency level and other key performance indicators that the system is expected to achieve during operation. These targets usually include but are not limited to improving thermal energy utilization efficiency, reducing energy consumption, reducing production costs, ensuring long-term stable operation of the system, and meeting environmental protection requirements. Specifically, the performance target can be to achieve a certain percentage of heat recovery efficiency, ensure that the system operates efficiently within a specific temperature range, and maintain stable heat recovery performance under different operating conditions.

[0124] In summary, the present invention achieves the preliminary setting of the low-profile water waste heat recovery system and the evaluation of the fluid dynamic characteristics by: collecting the original data in the urea production process and establishing a three-dimensional model, and then optimizing the pipeline layout and fluid flow direction through CFD simulation to improve the system performance. The intelligent temperature control model is used to predict temperature changes and dynamically adjust the valve opening and pump speed according to the prediction results to achieve efficient operation of the system. Finally, by evaluating the performance of the low-profile water waste heat recovery system and adjusting the control parameters, the stable operation of the system and efficient energy recovery are ensured. The present invention not only improves the energy efficiency of urea production, but also reduces production costs, and also has positive significance for environmental protection.

[0125] Example 2, referring to Table 1, is the second example of the present invention. To further verify the advancement of the present invention, experimental simulation data of a low-cost water waste heat recovery system in urea production are provided.

[0126] In the preparation stage before the experiment, the research team conducted careful preparation to ensure the scientific design of the experiment and the accuracy of the experimental results. This included collecting field data of the low-temperature water waste heat recovery system in the urea production process and strictly screening and processing the data.

[0127] Firstly, the raw data of low-profile water waste heat recovery system were obtained from the urea production site, and the data were cleaned and standardized.

[0128] Secondly, a three-dimensional model of the system was constructed based on these data, and the system parameters were preliminarily set.

[0129] Next, the pipeline performance was evaluated through CFD simulation, and optimization measures were taken for performance that did not meet the standards, including increasing the pipe diameter, adjusting the elbow angle and pump speed.

[0130] Finally, by comparing the comprehensive performance indicators before and after optimization, the effectiveness of the optimization measures was verified and the performance of the system was improved.

[0131] The details are shown in Table 1:

[0132] Table 1 Comparison of optimized performance of low-profile water waste heat recovery system

[0133]

[0134] By comparing the systems before and after optimization, we can clearly see the significant improvement brought about by the optimization measures. The comprehensive performance index P of the original system was 0.85, which was lower than the standard threshold N = 1.0, indicating that its performance did not meet the expected minimum standard. After optimization, the comprehensive performance index P′P′ increased to 0.92, 1.05 and 1.10 respectively, which not only exceeded the standard threshold, but also significantly higher than the performance level before optimization.

[0135] The low-profile waste heat recovery system for water in the urea process of the present invention not only solves the problems of large energy loss and uneven fluid distribution in the original system, but also significantly improves the comprehensive performance index of the system, reaches the preset standard threshold, and achieves the expected goal. This proves that the present invention has obvious creativity and novelty in improving the performance of the low-profile waste heat recovery system for water in the urea production process.

[0136] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A low-profile water waste heat recovery system in urea production, characterized in that: include, Fluid dynamics building module: collects raw data from the urea production process, builds a three-dimensional model of the low-profile water waste heat recovery system, and preliminarily sets system parameters; Fluid dynamics simulation module: Based on the 3D model and the preliminary setting of system parameters, the flow characteristics of the fluid in the pipeline are simulated by CFD to evaluate the pipeline performance of the 3D model; Optimization and verification module: dynamically optimizes pipeline layout and fluid flow direction based on evaluation results, and verifies optimized system characteristics; Intelligent temperature control model design module: Use the optimized pipeline design to design an intelligent temperature control model, predict temperature changes, and dynamically adjust the valve opening and pump speed based on the prediction results; System evaluation and optimization module: Evaluate the performance of low-temperature water waste heat recovery system and adjust control parameters according to the evaluation results.

2. The low-cost water waste heat recovery system in urea production according to claim 1, characterized in that: The specific steps of collecting the raw data in the urea production process are as follows: Obtain raw data of low-profile water waste heat recovery systems from urea production sites, including pipe dimensions, materials, and fluid properties; The collected raw data are cleaned and standardized.

3. The low-cost water waste heat recovery system in urea production according to claim 2, characterized in that: The three-dimensional model of the low-profile water waste heat recovery system is established and the system parameters are preliminarily set. The specific steps are as follows: Based on the pipe size and layout, ANSYS Fluent was used to build a 3D model of the low-profile water waste heat recovery system and mesh the built 3D model; Based on the original data of the low-profile water waste heat recovery system obtained from the urea production site, the fluid properties, pipeline dimensions and fluid flow conditions of the system are preliminarily set.

4. The low-cost water waste heat recovery system in urea production according to claim 3, characterized in that: Based on the three-dimensional model and the preliminary setting of system parameters, the flow characteristics of the fluid in the pipeline are simulated by CFD. The specific steps are as follows: The inlet boundary conditions of the 3D model were set according to the fluid properties, including velocity, pressure, and flow rate at the inlet, and the outlet boundary conditions were set to atmospheric pressure; Run CFD simulations to simulate the flow of fluids in the low-temperature water waste heat recovery system in urea production in a 3D model, observe the fluid flow, and analyze the fluid flow path and pressure distribution; Use ANSYS Fluent software to perform CFD simulation to obtain the flow characteristics of the fluid in the pipeline, including fluid flow efficiency, energy loss and fluid distribution uniformity; Based on fluid flow efficiency, energy loss and fluid distribution uniformity, a comprehensive performance index P for evaluating pipeline layout and fluid flow direction is defined as the optimization target, and the expression is: Among them, η is the fluid flow efficiency, Q represents the effective utilization rate of the fluid passing through the channel per unit time, ΔE represents the energy loss during the fluid flow process, and D var Indicates the uneven distribution of fluid inside the pipe.

5. The low-cost water waste heat recovery system in urea production according to claim 4, characterized in that: The specific steps of evaluating the pipeline performance of the three-dimensional model are as follows: Based on the expected minimum performance standard of the low-profile water waste heat recovery water system, a performance standard threshold N is defined, and the pipeline performance is evaluated by comparing the comprehensive performance index P with the standard threshold N; When P ≥ N, it indicates that the pipeline performance exceeds the expected minimum standard and achieves a good optimization effect; When P<N, it indicates that the pipeline performance does not meet the expected standards and needs further optimization.

6. The low-cost water waste heat recovery system in urea production according to claim 5, characterized in that: According to the evaluation results, the pipeline layout and fluid flow direction are dynamically optimized, and the optimized system characteristics are verified. The specific steps are as follows: When the pipeline performance meets the standards, the pipeline design scheme in the 3D model is applied, including pipeline layout and fluid flow direction; When the performance of the pipeline does not meet the standards, adjust the size, shape and connection method of the pipeline; Rebuild the 3D model based on the adjusted parameters and perform CFD simulation again to calculate the optimized comprehensive performance index P′; Compare the comprehensive performance indicators before and after optimization to determine whether the optimization is effective; When P′>P, the optimization is considered effective, and the optimized comprehensive performance index P′ is compared with the standard threshold T to evaluate whether the pipeline performance meets the expected standard; When P′≤P, the optimization is considered invalid and the parameters are adjusted continuously.

7. The low-cost water waste heat recovery system in urea production according to claim 6, characterized in that: The optimized pipeline design scheme is used to design an intelligent temperature control model to predict the temperature change trend. The specific steps are as follows: Based on the optimized pipeline layout and fluid flow direction, temperature sensors are installed at key locations to regularly collect temperature data and perform cleaning and standardization processing; Correlation analysis method is used to extract features related to temperature changes from the processed data; Arrange the extracted temperature change related features in order and integrate them into a comprehensive feature vector X; The machine learning model is trained using the comprehensive feature vector X to build a temperature prediction model based on a neural network to predict the temperature changes at key locations of the low-temperature water heat recovery system during urea production. The expression is: T′(t)=W2σ(W1X t-1 +b1)+b2; Among them, X t-1 is the comprehensive feature vector input at time point t-1, T′(t) is the predicted temperature value at time point t, W1 is the weight matrix from the input layer to the hidden layer, b1 is the bias vector of the hidden layer, W2 is the weight matrix from the hidden layer to the output layer, b2 is the bias vector obtained by the input layer, and σ is the activation function.

8. The low-cost water waste heat recovery system in urea production according to claim 7, characterized in that: The specific steps of dynamically adjusting the valve opening and pump speed according to the prediction results are as follows: Based on comprehensive considerations of system safety and economy, a target temperature threshold T is defined. ta , by the target temperature threshold T ta Compare with the temperature prediction value T′(t) to dynamically adjust the valve opening and pump speed; When T′(t)<T ta When the temperature is decreasing, the valve opening should be increased and the pump speed should be increased. When T′(t)>T ta It indicates that the temperature is rising and the valve opening should be reduced and the pump speed should be lowered.

9. The low-cost water waste heat recovery system in urea production according to claim 8, characterized in that: The specific steps for evaluating the performance of the low-profile water waste heat recovery system are as follows: According to the actual operation data of the low-temperature water waste heat recovery system, the waste heat recovery efficiency of the system is calculated as follows: Where m is the mass flow rate of the fluid, c p is the specific heat capacity of the fluid, T in is the temperature of the fluid entering the system, T ot is the temperature of the fluid leaving the system, T ab is the actual temperature, J is the waste heat recovery rate of the low-profile water waste heat recovery system; Based on the performance target of the low-profile water waste heat recovery system, a waste heat recovery standard Z is defined, and the performance of the low-profile water waste heat recovery system is evaluated by comparing the waste heat recovery rate J of the low-profile water waste heat recovery system with the waste heat recovery standard E; When J ≥ Z, it is considered that the waste heat recovery efficiency of the low-pressure water waste heat recovery system has reached the set standard; When J<Z, it is considered that the waste heat recovery efficiency of the low-pressure water waste heat recovery system does not meet the set standard.

10. The low-cost water waste heat recovery system in urea production according to claim 9, characterized in that: The specific steps of adjusting the control parameters according to the evaluation results are as follows: When the waste heat recovery efficiency of the low-profile water waste heat recovery system reaches the set standard, the current parameter settings are maintained; When the waste heat recovery efficiency of the low-pressure water waste heat recovery system does not meet the set standard, the valve opening should be increased, the pump speed should be increased, the fluid temperature and flow rate should be adjusted, and the pipeline layout should be adjusted.

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