Waste heat mixing, utilizing and recycling system in urea production

Abstract

The invention discloses a system for mixing, utilizing and recycling waste heat in urea production, and relates to the technical field of recycling, which comprises the following steps of: before urea production starts, initially setting a heat energy distribution proportion and operating parameters, and collecting urea production data by deploying various sensors; based on urea production data, a heat energy demand prediction model is constructed, and waste heat is divided into different temperature levels; according to the prediction result, the distribution proportion of waste heat of different temperature levels is dynamically adjusted; according to the dynamically-adjusted heat energy distribution proportion, waste heat of different temperature levels is utilized in a gradient mode through a multi-level heat exchanger; waste heat which cannot be utilized immediately is guided into the phase change material to be stored, released according to production requirements and distributed again; through construction of the heat energy demand prediction model and application of the phase change material, effective division and efficient gradient utilization of waste heat of different temperature levels are achieved, and continuous supply of heat energy in the production process is ensured.

Description

Technical Field

[0001] The invention relates to the technical field of recycling, in particular to a waste heat mixed utilization recycling system in urea production. Background Art

[0002] The large amount of waste heat generated during the urea production process is a valuable energy resource. At present, waste heat recovery technology has been widely used in industrial production, but in the field of urea production, waste heat recovery technology is still in the development stage. Traditional waste heat recovery systems often focus on the recovery of waste heat at a single temperature level, and lack effective cascade utilization of waste heat at different temperature levels. In addition, the existing waste heat recovery system has deficiencies in heat energy demand prediction and heat energy distribution, and it is difficult to flexibly adjust the distribution and utilization of heat energy according to production needs; in the prior art, most waste heat recovery systems in urea production only consider simple heat energy recovery, and fail to fully consider the heat energy demand prediction and heat energy distribution adjustment in the urea production process. Traditional heat energy demand prediction methods are mostly based on fixed heat energy demand patterns, and cannot be dynamically adjusted according to real-time data in the urea production process, resulting in unreasonable heat energy distribution and waste of some heat energy resources. Summary of the invention

[0003] In view of the above existing problems, the present invention is proposed.

[0004] Therefore, the present invention provides a waste heat mixed utilization recovery system in urea production to solve the problem of low waste heat utilization efficiency in urea production.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] In a first aspect, an embodiment of the present invention provides a waste heat mixed utilization recovery system in urea production, which includes a data acquisition module responsible for initializing and setting the heat energy distribution ratio and operating parameters before the start of urea production, and collecting urea production data by deploying a variety of sensors;

[0007] The heat demand prediction module is responsible for building a heat demand prediction model based on urea production data and dividing waste heat into different temperature levels;

[0008] The heat energy distribution adjustment module is responsible for dynamically adjusting the distribution ratio of waste heat at different temperature levels based on the prediction results;

[0009] The cascade heat energy utilization module is responsible for cascading waste heat of different temperature levels through multi-stage heat exchangers according to the dynamically adjusted heat energy distribution ratio;

[0010] The thermal energy storage and release module is responsible for importing the waste heat that cannot be used immediately into the phase change material for storage, releasing it according to production needs, and redistributing it.

[0011] As a preferred solution of the waste heat mixed utilization recovery system in urea production of the present invention, wherein: the multiple sensors include a temperature sensor, a flow sensor and an external environment temperature sensor;

[0012] The urea production data include the temperature of the production line, the urea output and the external environment temperature.

[0013] As a preferred solution of the waste heat mixed utilization and recovery system in urea production of the present invention, the initialization setting of the heat energy distribution ratio and the operating parameters includes the following steps:

[0014] Setting the heat energy distribution ratio including initial high temperature waste heat, initial medium temperature waste heat and initial low temperature waste heat;

[0015] The operating parameters including sensor sampling frequency, data storage period, time window for thermal energy demand prediction, thermal energy conversion efficiency and thermal energy storage threshold are set.

[0016] As a preferred solution of the waste heat mixed utilization and recovery system in urea production of the present invention, the key features are extracted based on urea production data, including the following steps:

[0017] The urea production data was cleaned to remove outliers and missing values. The Z-score-based method was used to identify and remove outliers, and the missing values ​​were filled using the forward filling method.

[0018] The processed urea production data were used to calculate the average temperature in different time periods, the rate of change of urea production over time, and the rate of change of external ambient temperature over time.

[0019] As a preferred solution of the waste heat mixed utilization and recovery system in urea production of the present invention, the average temperature in different time periods is expressed as:

[0020]

[0021] Among them, T a (t) represents the average temperature in the time period t, Δt represents the time interval, T(τ) represents the temperature at time τ, t represents the time point, τ represents the variable time point in the integration interval, and dτ represents the small increment of the time variable τ;

[0022] The rate of change of the urea production over time is expressed as,

[0023]

[0024] Among them, R p(t) represents the rate of change of production within the time period t, and P(t) represents the urea production at time t;

[0025] The rate of change of the external ambient temperature over time is expressed as,

[0026]

[0027] Among them, R e (t) represents the rate of change of external ambient temperature during time period t, T e (t) represents the external ambient temperature at time t.

[0028] As a preferred solution of the waste heat mixed utilization and recovery system in urea production of the present invention, a heat energy demand prediction model is constructed based on the extracted key features, which is expressed as:

[0029]

[0030] Where H(t) represents the predicted heat demand at time t, A represents the benchmark heat demand, δ represents the time weighted index, θ represents the influence index of average temperature, η represents the dynamic adjustment factor of the output change rate, and T year represents the length of one year, ∈ represents the amplitude of seasonal changes, ι and κ represent the nonlinear impact indexes of the yield change rate and the external ambient temperature change rate, respectively.

[0031] As a preferred solution of the waste heat mixed utilization and recovery system in urea production of the present invention, the waste heat division threshold is calculated based on the calculated average temperature in different time periods, the change rate of urea production over time and the change rate of external ambient temperature over time to divide different temperature levels, which is expressed as:

[0032] T1=T a (t)+α·R p (t)+β·R e (t);

[0033] T2=T1-γ·R p (t)-δ·R e (t);

[0034] Among them, T1 represents the first division threshold, T2 represents the second division threshold, α represents the influence coefficient of the output change rate on the boundary temperature threshold, β represents the influence coefficient of the external environment temperature change rate on the boundary temperature threshold, γ represents the influence coefficient of the output change rate on the boundary temperature threshold, and δ′ represents the influence coefficient of the external environment temperature change rate on the boundary temperature threshold;

[0035] When the residual heat temperature is greater than the first division threshold, it means it belongs to the high temperature zone;

[0036] When the waste heat temperature is less than or equal to the No. 1 classification threshold and greater than the No. 2 classification threshold, it means it belongs to the medium temperature zone;

[0037] When the waste heat temperature is less than or equal to the second division threshold, it means it belongs to the low temperature zone.

[0038] As a preferred solution of the waste heat mixed utilization and recovery system in urea production of the present invention, the allocation ratio of waste heat at different temperature levels is dynamically adjusted according to the prediction results of the thermal energy demand prediction model, including the following steps:

[0039] The predicted heat demand at different temperature levels is calculated using the heat demand prediction model. Based on the predicted heat demand, the waste heat distribution ratio at different temperature levels is calculated, which is expressed as:

[0040]

[0041] Among them, W i (t) represents the waste heat distribution ratio of the i-th temperature level in the time period t, H i (t) represents the predicted heat energy demand at the i-th temperature level during time period t, H j (t) represents the predicted heat energy demand at the jth temperature level during time period t, N represents the number of temperature levels, i represents the index of the temperature level, and j represents the index of the predicted heat energy demand at the temperature level.

[0042] As a preferred solution of the waste heat mixed utilization and recovery system in urea production of the present invention, the waste heat of different temperature levels is utilized in a cascade manner through a multi-stage heat exchanger by using high-efficiency heat exchanger materials according to the dynamically adjusted heat energy distribution ratio, including the following steps:

[0043] The waste heat from urea production is distributed to different temperature levels by dynamically adjusting the heat energy distribution ratio;

[0044] Select graphene-enhanced copper-based composite materials as high-efficiency heat exchanger materials;

[0045] The waste heat in the low temperature zone is recycled through the first stage heat exchanger, and the recycled waste heat is used for primary heating;

[0046] The waste heat in the medium temperature zone is recycled through the second stage heat exchanger, and the recycled waste heat is used to maintain a constant temperature environment during the production process;

[0047] The waste heat in the high temperature zone is recovered through the third stage heat exchanger and the recovered waste heat is used for direct heating.

[0048] As a preferred solution of the waste heat mixed utilization and recovery system in urea production of the present invention, the waste heat that cannot be used immediately is introduced into a paraffin phase change material for storage, released according to production needs, and redistributed, including the following steps:

[0049] Use paraffin phase change materials as efficient thermal energy storage materials;

[0050] Calculate the volume of the container based on the mass and density of the paraffin phase change material, and design the shape and size of the container;

[0051] Install phase change material containers near multi-stage heat exchangers to facilitate the introduction and extraction of heat energy;

[0052] When the waste heat cannot be used immediately, it is introduced into the phase change material container through a pipeline, so that the paraffin phase change material absorbs the heat and undergoes phase change, thereby realizing thermal energy storage;

[0053] When urea production is needed, the heat stored in the paraffin-based phase change material will be released and distributed for production needs.

[0054] The beneficial effects of the present invention are as follows: by initializing the heat energy distribution ratio and operating parameters, and deploying a variety of sensors to collect urea production data, a solid foundation is laid for subsequent heat energy demand prediction and heat energy distribution adjustment; by performing data cleaning and key feature extraction on urea production data, and building a heat energy demand prediction model, the accuracy of heat energy demand prediction is improved; by dynamically adjusting the distribution ratio of waste heat at different temperature levels according to the prediction results of the heat energy demand prediction model, the reasonable distribution of heat energy between different temperature levels is ensured; by cascading waste heat at different temperature levels through multi-stage heat exchangers according to the dynamically adjusted heat energy distribution ratio, the selection of heat energy conversion materials is optimized; by introducing waste heat that cannot be immediately utilized into phase change materials for storage, and releasing and redistributing heat energy according to production needs, the efficiency of heat energy storage is improved, and the continuous supply of heat energy in the production process is ensured. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] 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.

[0056] Figure 1 This is a flow chart of the waste heat mixed utilization and recovery system in urea production in Example 1.

[0057] Figure 2 This is a diagram showing the distribution ratio of thermal energy in Example 1. DETAILED DESCRIPTION

[0058] 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.

[0059] 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.

[0060] 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.

[0061] Example 1, reference Figure 1 and Figure 2 , which is the first embodiment of the present invention, provides a waste heat mixed utilization recovery system in urea production, comprising the following steps:

[0062] S1. Before urea production begins, initialize the heat energy distribution ratio and operating parameters, and collect urea production data by deploying a variety of sensors.

[0063] A variety of sensors including temperature sensors, flow sensors, and external ambient temperature sensors;

[0064] Urea production data include production line temperature, urea output and external ambient temperature;

[0065] Set the heat energy distribution ratio including initial high-temperature waste heat, initial medium-temperature waste heat and initial low-temperature waste heat, for example: high-temperature waste heat distribution ratio: the initial setting is 40%, this part of heat energy is mainly used for processes that require high-temperature heat sources, medium-temperature waste heat distribution ratio: the initial setting is 35%, this part of heat energy can be used for processes that require medium-temperature heat sources, low-temperature waste heat distribution ratio: the initial setting is 25%, this part of heat energy can be used for processes that require low-temperature heat sources;

[0066] The operating parameters set include sensor sampling frequency, data storage period, time window for thermal energy demand prediction, thermal energy conversion efficiency and thermal energy storage threshold. Sensor sampling frequency: set to once per minute to ensure the real-time and accuracy of the data. Data storage period: set to 24 hours to retain sufficient historical data for prediction model training. Time window for thermal energy demand prediction: set to the next 24 hours to predict the trend of thermal energy demand changes in the short term. Thermal energy conversion efficiency: initially set to 85%, which is estimated based on the actual conversion efficiency of existing equipment. Thermal energy storage threshold: set to start the thermal energy storage mechanism when the remaining thermal energy in the system exceeds 10% of the current demand.

[0067] It should be noted that by initializing the heat energy distribution ratio and operating parameters and deploying a variety of sensors to collect urea production data, the real-time and accuracy of data collection are improved, sufficient historical data is provided for prediction model training, the time window for heat energy demand prediction is optimized, and the heat energy conversion efficiency and heat energy storage threshold are reasonably set, laying a solid foundation for subsequent heat energy demand prediction and heat energy distribution adjustment.

[0068] S2. Based on urea production data, a thermal energy demand prediction model is constructed, and waste heat is divided into different temperature levels.

[0069] S2.1. Extract key features based on urea production data, including the following steps:

[0070] The urea production data was cleaned to remove outliers and missing values. The Z-score-based method was used to identify and remove outliers, and the missing values ​​were filled using the forward filling method.

[0071] The processed urea production data were used to calculate the average temperature in different time periods, the rate of change of urea production over time, and the rate of change of external ambient temperature over time.

[0072] The average temperature in different time periods is expressed as,

[0073]

[0074] Among them, T a (t) represents the average temperature during the time period t, Δt represents the time interval, T a (t) represents the temperature at time τ, t represents the time point, τ represents the variable time point within the integration interval, and dτ represents the small increment of the time variable τ, which is used for integral calculation;

[0075] The rate of change of urea production over time is expressed as,

[0076]

[0077] Among them, R p (t) represents the rate of change of production within the time period t, and P(t) represents the urea production at time t;

[0078] The rate of change of external ambient temperature over time is expressed as,

[0079]

[0080] Among them, R e (t) represents the rate of change of external ambient temperature during time period t, T e (t) represents the external ambient temperature at time t.

[0081] S2.2. Based on the extracted key features, a heat demand prediction model is constructed, which is expressed as:

[0082]

[0083] Among them, H(t) represents the predicted heat demand at time t, A represents the benchmark heat demand, which refers to the basic energy consumption level without other influencing factors, δ represents the time weighted index, which is used in the exponential decay function and reflects the influence of past data on the current forecast. When δ is large, it means that the heat demand forecast model pays more attention to recent data, θ represents the influence index of average temperature, which is used to adjust the influence of average temperature on the final heat demand forecast, η represents the dynamic adjustment factor of the output change rate, and T year It represents the length of one year and is used to calculate the impact of seasonal changes. ∈ represents the amplitude of seasonal changes and is used to adjust the amplitude of the cosine function, thereby affecting the impact of seasonal changes on thermal energy demand. l and k represent the nonlinear influence indexes of the output change rate and the external ambient temperature change rate, respectively, and are used to control the nonlinear effects of the output change rate and the external ambient temperature change rate in the model.

[0084] It should be noted that the basis of the thermal energy demand prediction model formula is to combine the key characteristics of the urea production process (such as average temperature, output change rate and external ambient temperature change rate), and by introducing parameters such as time-weighted index and seasonal change impact, a prediction model is constructed that can reflect the dynamic changes in thermal energy demand in urea production.

[0085] S2.3, based on the calculated average temperature in different time periods, the rate of change of urea production over time and the rate of change of external ambient temperature over time, the residual heat division threshold is calculated to divide different temperature levels, expressed as,

[0086] T1=T a (t)+α·R p (t)+β·R e (t);

[0087] T2=T1-γ·R p (t)-δ·R e (t);

[0088] Among them, T1 represents the first division threshold, T2 represents the second division threshold, α represents the influence coefficient of the output change rate on the boundary temperature threshold, β represents the influence coefficient of the external environment temperature change rate on the boundary temperature threshold, γ represents the influence coefficient of the output change rate on the boundary temperature threshold, δ′ represents the influence coefficient of the external environment temperature change rate on the boundary temperature threshold, β, δ, γ and δ′ are used to quantify the influence of the output change rate and the external environment temperature change rate on the boundary temperature threshold. These parameters are determined by establishing a mathematical model or using simulation software to simulate the urea production process under different parameter settings, compare the thermal energy utilization efficiency and production cost under different settings, conduct sensitivity analysis, and examine the influence of parameter changes on the boundary temperature threshold and thermal energy utilization efficiency;

[0089] When the residual heat temperature is greater than the first division threshold, it means it belongs to the high temperature zone;

[0090] When the waste heat temperature is less than or equal to the No. 1 classification threshold and greater than the No. 2 classification threshold, it means it belongs to the medium temperature zone;

[0091] When the waste heat temperature is less than or equal to the second division threshold, it means it belongs to the low temperature zone.

[0092] It should be noted that by cleaning the urea production data and extracting key features, and building a thermal energy demand forecasting model, the accuracy of the thermal energy demand forecasting is improved, the utilization of waste heat at different temperature levels is optimized, the flexibility of the thermal energy demand forecasting model is enhanced, the impact of seasonal changes on thermal energy demand is considered, the effective division of waste heat at different temperature levels is achieved, and the thermal energy utilization efficiency is improved.

[0093] S3. According to the prediction results, dynamically adjust the distribution ratio of waste heat at different temperature levels.

[0094] The predicted heat demand at different temperature levels is calculated using the heat demand prediction model. Based on the predicted heat demand, the waste heat distribution ratio at different temperature levels is calculated, which is expressed as:

[0095]

[0096] Among them, W i (t) represents the waste heat distribution ratio of the i-th temperature level in the time period t, H i (t) represents the predicted heat energy demand at the i-th temperature level during time period t, H j(t) represents the predicted heat energy demand at the jth temperature level during time period t, N represents the number of temperature levels, i represents the index of the temperature level, and j represents the index of the predicted heat energy demand at the temperature level.

[0097] It should be noted that by dynamically adjusting the distribution ratio of waste heat at different temperature levels according to the prediction results of the thermal energy demand prediction model, the flexibility and efficiency of thermal energy distribution are improved, the thermal energy utilization efficiency is optimized, the reasonable distribution of thermal energy among different temperature levels is ensured, and an effective response to changes in thermal energy demand is achieved.

[0098] S4. Based on the dynamically adjusted heat energy distribution ratio, waste heat at different temperature levels is utilized in stages through multi-stage heat exchangers.

[0099] The waste heat from urea production is distributed to different temperature levels by dynamically adjusting the heat energy distribution ratio;

[0100] Graphene-enhanced copper-based composite materials are selected as high-efficiency heat exchanger materials because they have excellent thermal conductivity and mechanical strength, which can improve heat exchange efficiency and ensure stable operation of the heat exchanger;

[0101] The waste heat in the low temperature zone is recycled through the first stage heat exchanger, and the recycled waste heat is used for primary heating;

[0102] The waste heat in the medium temperature zone is recycled through the second stage heat exchanger, and the recycled waste heat is used to maintain a constant temperature environment during the production process;

[0103] The waste heat in the high temperature zone is recovered through the third stage heat exchanger and the recovered waste heat is used for direct heating.

[0104] It should be noted that by utilizing waste heat at different temperature levels in a cascade manner through a multi-stage heat exchanger based on dynamically adjusted heat energy distribution ratios, the efficiency of heat energy utilization is improved, the flexibility of heat energy utilization is enhanced, the selection of heat energy conversion materials is optimized, efficient cascade utilization of heat energy is ensured, and full utilization of waste heat at different temperature levels is achieved.

[0105] S5. For the waste heat that cannot be used immediately, it is introduced into the phase change material for storage, released according to production needs, and redistributed.

[0106] The paraffin phase change material is selected as the high-efficiency thermal energy storage material because it has good thermal energy storage capacity and stable phase change characteristics, can effectively store and release thermal energy, and improve the overall efficiency of thermal energy utilization;

[0107] Calculate the volume of the container based on the mass and density of the paraffin phase change material, and design the shape and size of the container;

[0108] Install phase change material containers near multi-stage heat exchangers to facilitate the introduction and extraction of heat energy;

[0109] When the waste heat cannot be used immediately, it is introduced into the phase change material container through a pipeline, so that the paraffin phase change material absorbs the heat and undergoes phase change, thereby realizing thermal energy storage;

[0110] When urea production is needed, the heat stored in the paraffin-based phase change material will be released and distributed for production needs.

[0111] It should be noted that by introducing the waste heat that cannot be used immediately into phase change materials for storage, and releasing and redistributing the heat energy according to production needs, the efficiency of heat energy storage is improved, the flexibility of heat energy utilization is enhanced, the waste of heat energy is reduced, the overall efficiency of heat energy utilization is improved, and the continuous supply of heat energy in the production process is ensured.

[0112] In summary, the present invention lays a solid foundation for subsequent thermal energy demand prediction and thermal energy distribution adjustment by initializing the thermal energy distribution ratio and operating parameters, and deploying multiple sensors to collect urea production data; improves the accuracy of thermal energy demand prediction by performing data cleaning and key feature extraction on urea production data, and constructing a thermal energy demand prediction model; ensures the reasonable distribution of thermal energy among different temperature levels by dynamically adjusting the distribution ratio of waste heat at different temperature levels according to the prediction results of the thermal energy demand prediction model; optimizes the selection of thermal energy conversion materials by cascading waste heat at different temperature levels through multi-stage heat exchangers according to the dynamically adjusted thermal energy distribution ratio; improves the efficiency of thermal energy storage by introducing waste heat that cannot be immediately utilized into phase change materials for storage, and releasing and redistributing thermal energy according to production needs, and ensures the continuous supply of thermal energy in the production process.

[0113] Example 2

[0114] Referring to Table 1, which is the second embodiment of the present invention, in order to further verify the advancement of the present invention, experimental simulation data of the waste heat mixed utilization recovery system in urea production are provided.

[0115] Preparation before the experiment In the simulated urea production line, various sensors (temperature sensor, flow sensor and external ambient temperature sensor) were pre-set to collect real-time data. The sensor sampling frequency was set to once per minute, the data storage period was set to 24 hours, the time window for thermal energy demand prediction was the next 24 hours, the thermal energy conversion efficiency was initially set to 85%, and the thermal energy storage threshold was set to start the thermal energy storage mechanism when the remaining thermal energy in the system exceeded 10% of the current demand.

[0116] The simulated urea production data, including the temperature of the production line, urea output and external ambient temperature, are used. First, the data is preprocessed, and the Z-score method is used to identify and remove outliers, and the missing values ​​are filled by the forward filling method. Then, key features are extracted, including the average temperature in different time periods, the rate of change of urea output over time, and the rate of change of external ambient temperature over time.

[0117] Based on the extraction of key features, a thermal energy demand forecasting model is constructed; and the average temperature in different time periods, the rate of change of urea production over time, and the rate of change of external ambient temperature over time are calculated. Based on the calculated key features, the thresholds for different temperature levels are further determined to achieve the classification of waste heat.

[0118] According to the results of the thermal energy demand prediction model, the waste heat distribution ratio at different temperature levels is dynamically adjusted. Graphene-enhanced copper-based composite materials are selected as efficient heat exchanger materials, and waste heat at different temperature levels is cascaded through multi-stage heat exchangers to ensure efficient use of heat energy in the production process.

[0119] Waste heat that cannot be used immediately is stored through phase change materials (paraffin-based phase change materials) and released and redistributed when needed.

[0120] The details are shown in Table 1:

[0121] Table 1 Experimental record table

[0122]

[0123] It can be seen from the experimental data in Table 1 that the heat energy management and distribution method proposed in the present invention can effectively improve the efficiency of heat energy utilization. Specifically, it includes:

[0124] During the test, as the temperature of the production line changed, the urea yield showed a corresponding change trend. For example, in test 1, higher temperature corresponded to higher urea yield. This shows that temperature is one of the important factors affecting urea yield.

[0125] By calculating the average temperature in different time periods, the rate of change of urea production over time, and the rate of change of external ambient temperature over time, the future heat demand can be predicted more accurately. For example, in experiments 1 to 6, the urea production gradually increased over time, and the corresponding heat demand also increased.

[0126] Dynamically adjusting the waste heat distribution ratio at different temperature levels helps improve the efficiency of thermal energy utilization. For example, from Test 1 to Test 6, as the temperature fluctuates, the proportion of high-temperature waste heat is adjusted from 40% to 43%, while the proportion of low-temperature waste heat is adjusted from 25% to 26%. This adjustment ensures the reasonable distribution of thermal energy between different temperature levels.

[0127] For waste heat that cannot be used immediately, the phase change material can be stored and then released, which can effectively avoid the waste of heat energy and ensure the continuous supply of heat energy in the production process. In this embodiment, the utilization rate of heat energy is significantly improved through the effective management of waste heat.

[0128] In summary, the present invention significantly improves the efficiency of thermal energy utilization, reduces energy waste, and enhances the flexibility and adaptability of the system through key technologies such as thermal energy demand prediction model, waste heat classification, thermal energy distribution adjustment, and phase change material thermal energy storage. Compared with traditional thermal energy management methods, the present invention can better respond to changes in production demand and realize efficient cascade utilization of thermal energy between different temperature levels, thereby improving the energy efficiency of the entire urea production process.

[0129] 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 waste heat mixed utilization recovery system in urea production, characterized by: include, The data acquisition module is responsible for initializing the heat energy distribution ratio and operating parameters before the start of urea production, and collecting urea production data by deploying a variety of sensors; The heat demand prediction module is responsible for building a heat demand prediction model based on urea production data and dividing waste heat into different temperature levels; The heat energy distribution adjustment module is responsible for dynamically adjusting the distribution ratio of waste heat at different temperature levels based on the prediction results; The cascade heat energy utilization module is responsible for cascading waste heat of different temperature levels through multi-stage heat exchangers according to the dynamically adjusted heat energy distribution ratio; The thermal energy storage and release module is responsible for importing the waste heat that cannot be used immediately into the phase change material for storage, releasing it according to production needs, and redistributing it.

2. The waste heat mixed utilization and recovery system in urea production according to claim 1, characterized in that: The multiple sensors include temperature sensors, flow sensors and external environment temperature sensors; The urea production data include the temperature of the production line, the urea output and the external environment temperature.

3. The waste heat mixed utilization and recovery system in urea production according to claim 1, characterized in that: Initialization setting of heat energy distribution ratio and operating parameters includes the following steps: Setting the heat energy distribution ratio including initial high temperature waste heat, initial medium temperature waste heat and initial low temperature waste heat; The operating parameters including sensor sampling frequency, data storage period, time window for thermal energy demand prediction, thermal energy conversion efficiency and thermal energy storage threshold are set.

4. The waste heat mixed utilization and recovery system in urea production according to claim 3, characterized in that: Based on urea production data, key features are extracted, including the following steps: The urea production data was cleaned to remove outliers and missing values. The Z-score-based method was used to identify and remove outliers, and the missing values ​​were filled using the forward filling method. The processed urea production data were used to calculate the average temperature in different time periods, the rate of change of urea production over time, and the rate of change of external ambient temperature over time.

5. The waste heat mixed utilization and recovery system in urea production according to claim 4, characterized in that: The average temperature in the different time periods is expressed as, Among them, T a (t) represents the average temperature in the time period t, Δt represents the time interval, T(τ) represents the temperature at time τ, t represents the time point, τ represents the variable time point in the integration interval, and dτ represents the small increment of the time variable τ; The rate of change of the urea production over time is expressed as, Among them, R p (t) represents the rate of change of production within the time period t, and P(t) represents the urea production at time t; The rate of change of the external ambient temperature over time is expressed as, Among them, R e (t) represents the rate of change of external ambient temperature within the time period t, T e (t) represents the external ambient temperature at time t.

6. The waste heat mixed utilization and recovery system in urea production according to claim 5, characterized in that: Based on the extracted key features, a heat energy demand prediction model is constructed, which is expressed as: Where H(t) represents the predicted heat demand at time t, A represents the benchmark heat demand, δ represents the time weighted index, θ represents the influence index of average temperature, η represents the dynamic adjustment factor of the output change rate, and T year represents the length of one year, ∈ represents the amplitude of seasonal changes, l and κ represent the nonlinear impact indexes of the yield change rate and the external ambient temperature change rate, respectively.

7. The waste heat mixed utilization and recovery system in urea production according to claim 6, characterized in that: Based on the calculated average temperature in different time periods, the rate of change of urea production over time, and the rate of change of external ambient temperature over time, the residual heat division threshold is calculated to divide different temperature levels, which is expressed as: T1=T a (t)+α·R p (t)+β·R e (t); T2=T1-γ·R p (t)-δ′·R e (t); Among them, T1 represents the first division threshold, T2 represents the second division threshold, α represents the influence coefficient of the output change rate on the boundary temperature threshold, β represents the influence coefficient of the external environment temperature change rate on the boundary temperature threshold, γ represents the influence coefficient of the output change rate on the boundary temperature threshold, and δ′ represents the influence coefficient of the external environment temperature change rate on the boundary temperature threshold; When the residual heat temperature is greater than the first division threshold, it means it belongs to the high temperature zone; When the waste heat temperature is less than or equal to the No. 1 classification threshold and greater than the No. 2 classification threshold, it means it belongs to the medium temperature zone; When the waste heat temperature is less than or equal to the second division threshold, it means it belongs to the low temperature zone.

8. The waste heat mixed utilization and recovery system in urea production according to claim 7, characterized in that: According to the prediction results of the thermal energy demand prediction model, the distribution ratio of waste heat at different temperature levels is dynamically adjusted, including the following steps: The predicted heat demand at different temperature levels is calculated using the heat demand prediction model. Based on the predicted heat demand, the waste heat distribution ratio at different temperature levels is calculated, which is expressed as: Among them, W i (t) represents the waste heat distribution ratio of the i-th temperature level in the time period t, H i (t) represents the predicted heat energy demand at the i-th temperature level during time period t, H j (t) represents the predicted heat energy demand at the jth temperature level during time period t, N represents the number of temperature levels, i represents the index of the temperature level, and j represents the index of the predicted heat energy demand at the temperature level.

9. The waste heat mixed utilization and recovery system in urea production according to claim 8, characterized in that: According to the dynamically adjusted heat energy distribution ratio, high-efficiency heat exchanger materials are used to cascade the waste heat at different temperature levels through multi-stage heat exchangers, including the following steps: The waste heat from urea production is distributed to different temperature levels by dynamically adjusting the heat energy distribution ratio; Select graphene-enhanced copper-based composite materials as high-efficiency heat exchanger materials; The waste heat in the low temperature zone is recycled through the first stage heat exchanger, and the recycled waste heat is used for primary heating; The waste heat in the medium temperature zone is recycled through the second stage heat exchanger, and the recycled waste heat is used to maintain a constant temperature environment during the production process; The waste heat in the high temperature zone is recovered through the third stage heat exchanger and the recovered waste heat is used for direct heating.

10. The waste heat mixed utilization and recovery system in urea production according to claim 9, characterized in that: For waste heat that cannot be used immediately, it is introduced into paraffin phase change materials for storage, released according to production needs, and redistributed, including the following steps: Use paraffin phase change materials as efficient thermal energy storage materials; Calculate the volume of the container based on the mass and density of the paraffin phase change material, and design the shape and size of the container; Install phase change material containers near multi-stage heat exchangers to facilitate the introduction and extraction of heat energy; When the waste heat cannot be used immediately, it is introduced into the phase change material container through a pipeline, so that the paraffin phase change material absorbs the heat and undergoes phase change, thereby realizing thermal energy storage; When urea production is needed, the heat stored in the paraffin-based phase change material will be released and distributed for production needs.

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