Coal-to-urea liquid ammonia preheating and hydrolysis waste heat synergic regulation system

Abstract

The present application relates to the technical fields of heat energy engineering and waste heat recovery, and discloses a coal-to-urea liquid ammonia preheating and hydrolysis waste heat collaborative regulation system, through a data acquisition and preprocessing module, high-precision acquisition of hydrolysis clean water, liquid ammonia, synthetic tower load and environmental multi-dimensional parameters is realized, then a waste heat recovery module is taken as the core, energy output is stabilized through a buffer pressure stabilizing submodule, heat energy is transferred to a liquid ammonia temperature control module in a directional manner, then the liquid ammonia temperature control module realizes uniform heat exchange with the help of a double-jacketed tube dedicated preheater, a self-adaptive algorithm submodule combines a liquid ammonia temperature self-adaptive prediction control deviation correction formula to generate accurate instructions to drive a frequency conversion pump and an electric regulating valve, heat load is regulated in a bidirectional manner to ensure high-precision stability of the liquid ammonia temperature, finally, a collaborative regulation module is taken as the core, based on a waste heat, temperature and load dynamic matching total heat load balance formula, feedback data of all modules are integrated to analyze the quantitative relationship among waste heat supply, liquid ammonia demand and synthetic tower load.

Description

Technical Field

[0001] This invention relates to the field of thermal energy engineering and waste heat recovery technology, and in particular to a synergistic control system for preheating liquid ammonia and controlling waste heat from hydrolysis in coal-to-urea production. Background Technology

[0002] Background technology of a coal-to-urea liquid ammonia preheating and hydrolysis waste heat synergistic control system: Under the background of the deepening national "dual-carbon" strategy, it is clearly required to tap the potential for energy saving and efficiency improvement through technological upgrades to promote the green and sustainable development of the industry. As a core industry in the coal chemical industry, the energy utilization efficiency and synergistic matching degree of the core reaction of "liquid ammonia and carbon dioxide to synthesize urea" and the key by-process of "hydrolysis treatment of ammonia-containing wastewater" in the production process of coal-to-urea directly affect the overall energy efficiency, operational stability and economic benefits of the urea plant, and have become a key entry point for the industry to implement the goals of energy conservation and carbon reduction. In the production of coal-to-urea, liquid ammonia, as the core raw material, needs to be preheated to the process-suitable temperature of 65~80℃ before entering the synthesis system together with carbon dioxide at about 130℃. This temperature range is an important prerequisite for ensuring the stability of the ammonia-to-carbon ratio and improving the urea synthesis conversion rate. Therefore, the heat supply stability and energy economy of the liquid ammonia preheating stage are crucial. Meanwhile, the ammonia-containing wastewater generated during the production process needs to be treated by a hydrolysis system. After the wastewater is hydrolyzed to generate recyclable ammonia and carbon dioxide, the bottom of the stripping tower will produce hydrolyzed purified water with a stable temperature. Its initial temperature is about 143°C, and after preliminary heat exchange, it still maintains 92~98°C. This part of low-grade waste heat has significant potential for recovery and utilization. If it can be reasonably guided to the heat-requiring process links, the plant's dependence on external energy can be further reduced.

[0003] Regarding the above-mentioned and existing related technologies, the inventors believe that the following defects often exist:

[0004] 1. Existing technologies all assume that the waste heat source is a mixture of multiple sources, and use general-purpose heat exchangers and storage devices. They do not design dedicated recovery equipment for the physical properties of water purified by hydrolysis. At the same time, they have never linked waste heat utilization with the key node of liquid ammonia preheating, which directly affects the efficiency of the synthesis reaction. This results in low waste heat utilization efficiency and no direct benefit to the core process.

[0005] 2. In the existing technology, waste heat utilization and temperature control are two completely independent systems. When the flow rate and temperature of the hydrolysis purified water fluctuate or the load of the synthesis tower changes, the imbalance between waste heat supply and liquid ammonia preheating demand cannot be corrected through real-time regulation, resulting in large fluctuations in liquid ammonia temperature, which seriously affects the urea conversion rate. Summary of the Invention

[0006] The technical problem to be solved by this invention is that the default waste heat source in the prior art is a mixture of multiple sources, which leads to low waste heat utilization efficiency. To address this, we propose a synergistic control system for preheating liquid ammonia in coal-to-urea production and waste heat from hydrolysis.

[0007] To achieve the above objectives, this application adopts the following technical solution: a coal-to-urea liquid ammonia preheating and hydrolysis waste heat coordinated control system, including a data acquisition and preprocessing module, a waste heat recovery module, a liquid nitrogen temperature control module and a coordinated control module;

[0008] The data acquisition and preprocessing module is used to acquire multi-dimensional parameters of waste heat source, heat exchange process and process terminal in the coal-to-urea production process. Its output data is directly transmitted to the waste heat recovery module, liquid nitrogen temperature control module and collaborative regulation module.

[0009] The waste heat recovery module receives waste heat source parameters transmitted by the data acquisition and preprocessing module, constructs an internal energy transfer link for water hydrolysis and heat exchange medium, and outputs stable heat energy directly to the liquid ammonia temperature control module. At the same time, it feeds back waste heat recovery status data to the collaborative control module.

[0010] The liquid ammonia temperature control module receives a stable heat energy supply from the waste heat recovery module, combines the liquid ammonia parameters transmitted by the data acquisition and preprocessing module, and feeds back the output real-time liquid ammonia temperature data to the collaborative control module.

[0011] As the central hub of the system, the coordinated control module receives process terminal parameters from the data acquisition and preprocessing module, waste heat status data from the waste heat recovery module, and temperature feedback data from the liquid ammonia temperature control module, and outputs control commands to the waste heat recovery module and the liquid ammonia temperature control module.

[0012] The data acquisition and preprocessing module includes a sensor group submodule, a signal transmission submodule, and a data filtering submodule;

[0013] The sensor group submodule is based on the resistance value of platinum resistance thermometer, temperature characteristics, Faraday's law of electromagnetic induction and diffused silicon piezoresistive effect to acquire temperature, flow rate and pressure parameters respectively. The raw data acquired is directly transmitted to the signal transmission submodule.

[0014] The signal transmission submodule adopts industrial Ethernet differential signal transmission technology, combined with CRC check mechanism, to transmit the raw data of the sensor group submodule to the data filtering submodule, and at the same time receive parameter acquisition instructions from the collaborative control module to dynamically adjust the acquisition frequency.

[0015] The data filtering submodule uses the Kalman filtering algorithm to predict, update and iterate the raw data received by the signal transmission submodule. The optimized data is then synchronously transmitted to the collaborative control module, the waste heat recovery module and the liquid ammonia temperature control module.

[0016] The waste heat recovery module includes a dedicated heat exchanger submodule, a buffer and pressure stabilization submodule, and a circulation conveying submodule;

[0017] The dedicated heat exchanger submodule adopts a counter-flow spiral plate structure, receives the heat exchange medium delivered by the circulating conveying submodule, and its heat exchange status data is fed back to the buffer and pressure stabilizing submodule and the collaborative control module in real time.

[0018] The buffer and pressure stabilizing submodule uses heat transfer oil as the energy storage medium, receives the high-temperature heat exchange medium output from the dedicated heat exchanger submodule, and delivers the stabilized heat exchange medium to the circulation delivery submodule. At the same time, the medium temperature and liquid level data are fed back to the collaborative control module.

[0019] The circulating delivery submodule uses a variable frequency driven circulating pump to receive the stable heat exchange medium from the buffer and pressure stabilization submodule and the flow control command from the collaborative control module, accurately delivering the heat exchange medium to the dedicated heat exchanger submodule and the dedicated preheater submodule of the liquid ammonia temperature control module.

[0020] The liquid ammonia temperature control module includes a dedicated preheater submodule, an actuator submodule, and an adaptive algorithm submodule;

[0021] The dedicated preheater submodule adopts a double-tube structure, receiving the high-temperature heat exchange medium circulated from the waste heat recovery module and performing uniform countercurrent heat exchange with the liquid ammonia supplied by the actuator submodule. The liquid ammonia temperature data after heat exchange is fed back to the adaptive algorithm submodule in real time.

[0022] The actuator submodule includes a variable frequency liquid ammonia transfer pump and a high-precision electric regulating valve. It receives control commands from the adaptive algorithm submodule and feeds back execution status data to the adaptive algorithm submodule and the collaborative control module.

[0023] The adaptive algorithm submodule embeds a long short-term memory neural network model, receives liquid ammonia parameters from the data acquisition and preprocessing module, temperature feedback data from the dedicated preheater submodule, and status data from the actuator submodule. It generates control commands through the liquid ammonia temperature adaptive predictive control deviation correction formula and transmits them to the actuator submodule. At the same time, it feeds back the predicted data to the collaborative control module.

[0024] The formula for correcting the deviation of liquid ammonia temperature adaptive predictive control is:

[0025] ;

[0026] in, Let k be the adjustment amount of the actuator. This is the proportionality coefficient. The integral coefficient is... The differential coefficients are... The real-time temperature deviation at time k is... Calculations based on feedback data from the dedicated preheater submodule Let be the temperature deviation at time i. To control the cycle, For dynamic weighting coefficients, Predicting for LSTM models Temperature deviation after a certain time.

[0027] The coordinated control module includes a logic operation submodule, an instruction output submodule, and a feedback correction submodule;

[0028] The logic operation submodule is based on the first law of thermodynamics and the kinetics of urea synthesis reaction. It receives synthesis tower load and ambient temperature data from the data acquisition and preprocessing module, waste heat supply data from the waste heat recovery module, and temperature feedback data from the advanced liquid ammonia temperature control module. It then analyzes the quantitative relationship between waste heat supply, liquid ammonia preheating demand, and synthesis tower load.

[0029] The logic operation submodule performs heat load balance calculation and control parameter derivation by dynamically matching the total heat load balance formula with waste heat, temperature, and load, and transmits the calculation results to the instruction output submodule.

[0030] The formula for balancing total heat load by dynamically matching waste heat, temperature, and load is:

[0031] ;

[0032] in, Effective waste heat can be utilized for water purification via hydrolysis. The total efficiency of the two-stage heat exchange is given. The heat load required for preheating liquid nitrogen This is the correction factor for load fluctuations in the synthesis tower. This is the ambient temperature correction factor. The coefficient is the adaptation factor for the differences in physical properties of water purified by hydrolysis.

[0033] The instruction output submodule converts the calculation results of the logic operation submodule into industrial standard control signals and outputs them to the circulation conveying submodule of the waste heat recovery module and the actuator submodule of the liquid ammonia temperature control module. At the same time, it feeds back the instruction issuance status to the feedback correction submodule.

[0034] The feedback correction submodule receives operational feedback parameters from each module in real time.

[0035] A dedicated heat exchanger submodule is used to receive feedback on the hydrolysis purification parameters from the data acquisition and pretreatment module.

[0036] The buffer voltage regulator submodule is equipped with dual monitoring units for liquid level and temperature.

[0037] The variable frequency circulating pump of the circulating conveying submodule adopts a sealed structure.

[0038] The LSTM model in the adaptive algorithm submodule achieves coordinated correction of prediction bias and real-time bias through a bias correction formula;

[0039] Dynamic weighting coefficients Calculated based on real-time temperature deviation and smoothing coefficient;

[0040] The flow rate regulation range of the variable frequency liquid ammonia transfer pump in the actuator submodule covers the range of liquid ammonia supply required for the load fluctuations of the synthesis tower.

[0041] Calculation based on the deviation between the real-time load and the reference load of the synthesis tower;

[0042] Calculated based on the deviation between real-time ambient temperature and standard ambient temperature;

[0043] The deviation threshold of the feedback correction submodule is set according to the accuracy requirements of liquid ammonia temperature control.

[0044] The technical effects and advantages of this invention are as follows:

[0045] In this invention, a data acquisition and preprocessing module, based on platinum resistance thermometer characteristics and Faraday's law of electromagnetic induction, achieves high-precision acquisition of multi-dimensional parameters of water hydrolysis purification, liquid ammonia, synthesis tower load, and environment. After low-latency transmission via industrial Ethernet and Kalman filtering for noise reduction, clean and standardized data is output to provide precise support for the entire system. Then, a waste heat recovery module, using a counter-current spiral plate heat exchanger made of corrosion-resistant alloy material as its core, adapts to the physical properties of the water hydrolysis purification to construct a forced turbulence condition, efficiently recovering waste heat and stabilizing energy output through a buffer and pressure-stabilizing submodule. The heat energy is then directionally transferred to the liquid ammonia temperature control module, breaking down the process barriers between waste heat utilization and liquid ammonia preheating. Subsequently, the liquid ammonia temperature control module achieves uniform heat exchange with a dedicated double-tube preheater. An adaptive algorithm submodule embedding an LSTM model is then implemented. The adaptive predictive control deviation correction formula for liquid ammonia temperature generates precise commands to drive the variable frequency pump and electric regulating valve, bidirectionally regulating the heat load to ensure high-precision stability of liquid ammonia temperature. Finally, the collaborative control module acts as the central hub, based on the dynamic matching formula of waste heat, temperature, and load to achieve total heat load balance. It integrates feedback data from various modules to analyze the quantitative relationship between waste heat supply, liquid ammonia demand, and synthesis tower load. Through logical operations, command output, and feedback correction, a closed loop is formed to adjust the intensity of waste heat recovery and temperature control strategy in real time. It dynamically corrects the supply and demand imbalance caused by changes in hydrolysis water flow rate, temperature fluctuations, and synthesis tower load. Ultimately, it achieves efficient and directional recovery of waste heat from hydrolysis water and precise and stable control of liquid ammonia temperature, simultaneously solving the problems of low waste heat utilization efficiency and large liquid ammonia temperature fluctuations, providing a stable guarantee for the urea synthesis reaction. Attached Figure Description

[0046] The disclosure of this invention is illustrated with reference to the accompanying drawings. It should be understood that the drawings are for illustrative purposes only and are not intended to limit the scope of protection of this invention. In the drawings, the same reference numerals are used to refer to the same parts:

[0047] Figure 1 This is a schematic diagram of the overall process of a coal-to-urea liquid ammonia preheating and hydrolysis waste heat synergistic control system according to the present invention.

[0048] Figure 2 This is a flowchart of the lower sub-module of the liquid ammonia temperature control module in the coal-to-urea liquid ammonia preheating and hydrolysis waste heat synergistic regulation system of the present invention. Detailed Implementation

[0049] It is readily understood that, based on the technical solution of this invention, those skilled in the art can propose various interchangeable structural methods and implementations without altering the essential spirit of the invention. Therefore, the following detailed embodiments and accompanying drawings are merely illustrative examples of the technical solution of this invention and should not be considered as the entirety of the invention or as limitations or restrictions on the technical solution of this invention.

[0050] Reference Figure 1-2 As shown, the present invention provides a technical solution: a coal-to-urea liquid ammonia preheating and hydrolysis waste heat synergistic control system, including a data acquisition and preprocessing module, a waste heat recovery module, a liquid nitrogen temperature control module and a synergistic control module, each module forming a closed-loop operation system through bidirectional coupling of thermodynamic energy flow and cybernetics data flow;

[0051] The data acquisition and preprocessing module is used to acquire multi-dimensional parameters of waste heat source, heat exchange process and process terminal in coal-to-urea production process, and to perform noise reduction preprocessing to provide high-precision basic data for system control. Its output standardized data is directly transmitted to the waste heat recovery module, liquid nitrogen temperature control module and collaborative control module, forming the core data support for the operation of each module.

[0052] The waste heat recovery module is designed based on the physical properties of water hydrolysis. It receives the waste heat source parameters transmitted by the data acquisition and preprocessing module, realizes the directional and efficient recovery and stable energy output of waste heat from water hydrolysis, and constructs an internal energy transfer link between water hydrolysis and heat exchange medium. Its output stable heat energy is directly supplied to the liquid ammonia temperature control module, while feeding back the waste heat recovery status data to the collaborative control module.

[0053] The liquid ammonia temperature control module receives a stable heat energy supply from the waste heat recovery module. Combined with the liquid ammonia parameters transmitted by the data acquisition and preprocessing module, it achieves high-precision closed-loop control of the liquid ammonia preheating temperature through dedicated heat exchange equipment and adaptive predictive control algorithm, which meets the raw material preprocessing requirements of the urea synthesis reaction. Its output liquid ammonia temperature real-time data is fed back to the collaborative control module.

[0054] As the central hub of the system, the collaborative control module receives process terminal parameters from the data acquisition and preprocessing module, waste heat status data from the waste heat recovery module, and temperature feedback data from the liquid ammonia temperature control module. By constructing a multi-parameter coupling model, it dynamically balances the relationship between waste heat supply, liquid ammonia preheating demand, and synthesis tower load, and outputs control commands to the waste heat recovery module and liquid ammonia temperature control module, forming a closed-loop linkage of data acquisition, energy transfer, temperature control, and collaborative correction.

[0055] Through bidirectional coupling and time-series linkage of various modules, the synergistic effect of precise data support for energy recovery, energy-oriented temperature control, and dynamic correction of process parameters by control commands is achieved. Ultimately, the maximum recovery and utilization of waste heat from water purification through hydrolysis and the precise and stable control of liquid ammonia temperature are achieved, significantly improving the efficiency of urea synthesis reaction and the economic efficiency of system operation.

[0056] The data acquisition and preprocessing module includes a sensor group submodule, a signal transmission submodule, and a data filtering submodule;

[0057] The sensor group submodule is based on platinum resistance resistance, temperature characteristics, Faraday's law of electromagnetic induction and diffused silicon piezoresistive effect to achieve high-precision acquisition of temperature, flow rate and pressure parameters, covering key monitoring points such as waste heat source inlet and outlet, liquid ammonia inlet and outlet, synthesis tower inlet and energy storage unit. The raw data acquired is directly transmitted to the signal transmission submodule to form the initial link of data acquisition.

[0058] The signal transmission submodule adopts industrial Ethernet differential signal transmission technology, combined with CRC check mechanism, to transmit the original signal of the sensor group submodule;

[0059] Data is transmitted to the data filtering submodule without distortion, and at the same time, it receives parameter acquisition instructions from the collaborative control module, dynamically adjusts the acquisition frequency, realizes the linkage and adaptation between data acquisition and control requirements, ensures low latency and integrity of data transmission, and meets real-time control requirements.

[0060] The data filtering submodule uses the Kalman filtering algorithm to predict, update and iterate the raw data received by the signal transmission submodule, remove random noise interference in the industrial field, and synchronously transmit the optimized data to the collaborative control module, waste heat recovery module and liquid ammonia temperature control module, providing clean data input for the operation and control of each module.

[0061] Through the serial linkage of acquisition, transmission, filtering, and distribution of the three sub-modules, as well as the bidirectional feedback of instructions with the collaborative control module, a closed loop of end-to-end data processing is achieved, ensuring that the accuracy of parameters acquired by each core module is ≥99%, avoiding control deviations caused by noisy data, and significantly improving the timeliness of system response and the reliability of control decisions.

[0062] The waste heat recovery module includes a dedicated heat exchanger submodule, a buffer and pressure stabilization submodule, and a circulation conveying submodule;

[0063] The dedicated heat exchanger submodule employs a counter-flow spiral plate structure made of corrosion-resistant alloy material. It receives the heat exchange medium from the circulating conveying submodule and exchanges heat with the hydrolyzed purified water in a counter-flow manner. Its heat exchange status data is fed back in real-time to the buffer and pressure stabilization submodule and the collaborative control module, contributing to the heat load balance calculation. The quantitative analysis provides measured data, and by optimizing the flow channel parameters to construct a forced turbulence condition, the heat transfer coefficient is improved, the logarithmic mean temperature difference is maximized, and the efficient transfer of waste heat is achieved, thus solving the problem of low efficiency caused by the mismatch between general heat exchange equipment and the physical properties of water purified by hydrolysis.

[0064] The buffer and pressure stabilization submodule uses heat transfer oil as the energy storage medium. It receives the high-temperature heat exchange medium output from the dedicated heat exchanger submodule. Based on the thermodynamic energy storage principle, it buffers the temperature shock caused by the fluctuation of waste heat supply. It then delivers the stabilized heat exchange medium to the circulation delivery submodule. At the same time, the medium temperature and liquid level data are fed back to the collaborative control module to provide a basis for adjusting the heat exchange medium flow rate and maintain the stability of energy output.

[0065] The circulating delivery submodule uses a variable frequency driven circulating pump to receive the stable heat exchange medium from the buffer and pressure stabilization submodule and the flow control command from the collaborative control module. Based on the fluid dynamics pipeline resistance equation, it adjusts the operating parameters, changes the fluid delivery characteristics, and accurately delivers the heat exchange medium to the dedicated heat exchanger submodule and the dedicated preheater submodule of the liquid ammonia temperature control module, ensuring the stable flow rate of the heat exchange medium.

[0066] Through the closed-loop linkage of heat exchange, pressure stabilization, and transportation of the three sub-modules, as well as the one-way energy supply with the liquid ammonia temperature control module and the two-way data interaction with the collaborative regulation module, the waste heat recovery efficiency is ≥92% and the temperature fluctuation of the heat exchange medium is ≤±2℃. This not only ensures a stable energy supply for liquid ammonia preheating but also avoids waste heat and equipment corrosion, extending the service life of the heat exchange system by ≥5 years.

[0067] The liquid ammonia temperature control module includes a dedicated preheater submodule, an actuator submodule, and an adaptive algorithm submodule;

[0068] The dedicated preheater submodule adopts a double-tube structure made of alloy material with excellent low-temperature toughness. It receives the high-temperature heat exchange medium circulated from the waste heat recovery module and performs uniform countercurrent heat exchange with the liquid ammonia delivered by the actuator submodule. This avoids the vaporization of liquid ammonia caused by local hot spots and is suitable for the low-temperature and high-pressure working conditions of liquid ammonia. After heat exchange, the liquid ammonia temperature data is fed back to the adaptive algorithm submodule in real time as the core basis for temperature deviation calculation.

[0069] The actuator submodule includes a variable frequency liquid ammonia transfer pump and a high-precision electric regulating valve. It receives control commands from the adaptive algorithm submodule and achieves bidirectional control of the heat load by changing the flow rate of the heated medium and the flow rate of the heating medium, respectively. At the same time, it feeds back the execution status data to the adaptive algorithm submodule and the collaborative control module to provide status support for the correction of control commands.

[0070] The adaptive algorithm submodule embeds a long short-term memory neural network model, receives liquid ammonia parameters from the data acquisition and preprocessing module, temperature feedback data from the dedicated preheater submodule, and status data from the actuator submodule. Through the structural design of forget gate, input gate, and output gate, it memorizes historical operating data and disturbance patterns, predicts temperature change trends, and, combined with PID control logic, generates control commands through the liquid ammonia temperature adaptive predictive control deviation correction formula and transmits them to the actuator submodule. At the same time, the predicted data is fed back to the collaborative control module.

[0071] The formula for correcting the deviation of liquid ammonia temperature adaptive predictive control is:

[0072] ;

[0073] in, Let k be the adjustment amount of the actuator. This is the proportionality coefficient. The integral coefficient is... The differential coefficients are... The real-time temperature deviation at time k is... Calculations based on feedback data from the dedicated preheater submodule , The target outlet temperature for liquid ammonia. The measured temperature of liquid ammonia at time k. Let be the temperature deviation at time i. To control the cycle (consistent with the data acquisition cycle). The dynamic weighting coefficient is calculated based on real-time temperature deviation and smoothing coefficient. Predicting for LSTM models Temperature deviation after a given time;

[0074] Through the closed-loop linkage of heat exchange, execution, algorithm, and feedback of the three sub-modules, as well as the deep coupling with the parameter support of the data acquisition module, the energy supply of the waste heat recovery module, and the instruction correction of the collaborative control module, the liquid ammonia temperature control accuracy of ±0.5℃ and dynamic response time of ≤5s were achieved. This effectively solved the problem of temperature instability caused by waste heat fluctuations and load changes, and ensured the quality of raw material pretreatment for urea synthesis reaction.

[0075] The coordinated control module includes a logic operation submodule, an instruction output submodule, and a feedback correction submodule;

[0076] The logic operation submodule is based on the first law of thermodynamics and the kinetics of urea synthesis reaction. It receives synthesis tower load and ambient temperature data from the data acquisition and preprocessing module, waste heat supply data from the waste heat recovery module, and temperature feedback data from the liquid ammonia temperature control module. It analyzes the quantitative relationship between waste heat supply, liquid ammonia preheating demand and synthesis tower load.

[0077] The total heat load balance is calculated and control parameters are derived by dynamically matching waste heat, temperature, and load with the total heat load balance formula. The calculation results are then transmitted to the instruction output submodule.

[0078] The formula for balancing total heat load by dynamically matching waste heat, temperature, and load is:

[0079] The formula for balancing the total heat load by dynamically matching waste heat, temperature, and load is as follows:

[0080] ;

[0081] ;

[0082] in, Effective waste heat can be utilized for water purification via hydrolysis. The inlet temperature for hydrolyzed purified water, The inlet temperature for hydrolyzed purified water, The outlet temperature of the purified water after hydrolysis. This is the heat loss coefficient of the heat exchanger; The total efficiency of the two-stage heat exchange is given. The heat load required for preheating liquid nitrogen is calculated using the following formula: , For liquid ammonia flow rate, The density of liquid ammonia, The specific heat capacity of liquid ammonia. The target outlet temperature for liquid ammonia. This refers to the inlet temperature of the liquid ammonia. The formula for calculating the load fluctuation correction factor for the synthesis tower is as follows:

[0083] ;

[0084] For load sensitivity coefficient, For the real-time CO2 flow rate of the synthesis tower, The CO2 flow rate is the baseline for the synthesis tower. The ambient temperature correction factor is calculated using the following formula: , Environmental sensitivity coefficient, For real-time ambient temperature, Standard ambient temperature, The adaptation coefficient for the differences in physical properties of water purified by hydrolysis is calculated using the following formula: , To determine the real-time corrosive ion content in the purified water via hydrolysis. The standard for corrosive ion content in water purified by hydrolysis;

[0085] The instruction output submodule converts the calculation results of the logic operation submodule into industrial standard control signals and outputs them to the circulation conveying submodule (flow regulation instruction) of the waste heat recovery module and the actuator submodule (valve opening and pump frequency adjustment instruction) of the liquid ammonia temperature control module, ensuring the speed and accuracy of instruction transmission. At the same time, it feeds back the instruction issuance status to the feedback correction submodule.

[0086] The feedback correction submodule receives the operating feedback parameters (waste heat recovery efficiency, liquid ammonia temperature deviation, actuator status) from each module in real time, compares the deviation with the predicted values ​​of the logic operation submodule, and when the deviation exceeds the set threshold (liquid ammonia temperature deviation ±0.3℃, waste heat supply deviation ±5%), it triggers the logic operation submodule to perform a secondary calculation based on the above heat load balance formula, generates a correction command, and sends it out through the command output submodule.

[0087] Through the coordinated operation of the three sub-modules and the full-process control of other core modules, the dynamic matching of waste heat supply, liquid ammonia demand and load changes is achieved. When the synthesis tower load fluctuates by ±20% and the hydrolysis water flow fluctuates by ±10%, the system can still maintain the balance between heat load supply and demand, ensuring the system stability under disturbance conditions and solving the problem of poor adaptability caused by the independent operation of each system in the existing technology.

[0088] The system constructs an internal energy closed loop for water purification via thermodynamic coupling, encompassing the processes of water hydrolysis, heat exchange medium, liquid ammonia, and urea synthesis.

[0089] The data acquisition and preprocessing module provides end-to-end parameter support for the energy closed loop, the waste heat recovery module provides an efficient transfer carrier for the energy closed loop, the liquid ammonia temperature control module provides a precise utilization terminal for the energy closed loop, and the collaborative regulation module provides dynamic balance assurance for the energy closed loop. There is no additional energy consumption, significantly improving energy utilization efficiency and reducing system energy consumption by ≥30%.

[0090] Through dedicated equipment and adaptive design, the dedicated heat exchanger sub-module of the waste heat recovery module is precisely matched with the characteristics of hydrolyzed purified water, and the dedicated preheater sub-module of the liquid ammonia temperature control module is deeply adapted to the liquid ammonia operating conditions.

[0091] By combining the real-time monitoring of the data acquisition module with the dynamic correction of the collaborative control module, a protective closed loop of material property adaptation, data monitoring, and dynamic control is formed, which solves the equipment wear and tear problem caused by the corrosiveness of hydrolysis water purification, extends the equipment service life by ≥5 years, and reduces maintenance costs by more than 30%.

[0092] Through high-precision temperature control and multi-parameter coordinated regulation, the adaptive algorithm submodule of the liquid ammonia temperature control module receives real-time parameters from the data acquisition module and correction instructions from the coordinated regulation module. Based on the deviation correction formula, it precisely controls the preheating temperature of liquid ammonia, ensuring that the ammonia-to-carbon ratio of the urea synthesis reaction remains stable within the optimal range (1.6-1.65). Combined with the stable supply of waste heat from hydrolysis, the reaction conversion rate is increased by 2.5-3 percentage points, and the product quality qualification rate is ≥99.8%.

[0093] Through a dynamic load adaptation mechanism, the collaborative control module coordinates data from various modules and adjusts waste heat recovery efficiency and temperature control strategies in real time based on the heat load balance formula. This broadens the system's adaptability to fluctuations in synthesis tower load (±20%) and waste heat supply (±10%), enhances the robustness of system operation, and avoids production interruptions caused by fluctuations in operating conditions.

[0094] The corrosion-resistant alloy material of the dedicated heat exchanger submodule is austenitic stainless steel with added molybdenum. By optimizing the helix angle and plate spacing parameters, the fluid Reynolds number meets the requirements of forced turbulence, and the heat transfer coefficient is improved by more than 80% compared with the general shell and tube heat exchanger. It forms a flow linkage with the circulation transport submodule (adjusting the heat transfer intensity according to the medium flow rate of the circulation transport submodule), and at the same time receives feedback from the hydrolyzed purified water parameters of the data acquisition and pretreatment module, realizing efficient heat exchange between the heat exchange medium and the hydrolyzed purified water. The waste heat recovery efficiency is improved by 32 percentage points compared with the existing technology.

[0095] The buffer and pressure stabilization submodule is equipped with dual monitoring units for liquid level and temperature. It forms a temperature linkage with the dedicated heat exchanger submodule (adjusting the storage buffer strategy according to the temperature of the medium after heat exchange) and a flow linkage with the circulation and conveying submodule (adjusting the medium output according to the conveying flow rate). Combined with the instruction feedback from the collaborative control module, it maintains the temperature fluctuation of the heat exchange medium within the preset range (≤±2℃), avoiding the impact of sudden temperature changes on the preheating of liquid ammonia.

[0096] The variable frequency circulating pump of the circulating conveying submodule adopts a high-temperature resistant sealing structure, which is suitable for the working temperature range of the heat exchange medium (80-185℃). Through the linkage with the medium supply of the buffer and pressure stabilizing submodule (adjusting the conveying pressure according to the buffered medium inventory) and the linkage with the command of the collaborative control module (adjusting the conveying flow rate according to the heat load calculation results), the flow rate can be continuously adjusted (80-120m³ / h) to meet the heat exchange requirements under different working conditions and ensure that the dedicated preheater submodule of the liquid ammonia temperature control module obtains a stable energy supply.

[0097] The LSTM model in the adaptive algorithm submodule is trained using historical working condition data, achieving a prediction accuracy of no less than 98%, with a prediction step size of [missing information]. It can be dynamically adjusted according to the system response characteristics. It is linked with the parameter feedback of the data acquisition and preprocessing module (real-time acquisition of liquid ammonia inlet temperature and flow fluctuation data) and the status feedback of the actuator sub-module (real-time acquisition of valve opening and pump frequency execution data). Through the deviation correction formula, it realizes the coordinated correction of predicted deviation and real-time deviation, avoiding control overshoot or lag caused by single deviation feedback.

[0098] Dynamic weighting coefficients Based on real-time temperature deviation and smoothing coefficient calculation, and through linkage with temperature feedback data of dedicated preheater submodule (dynamically adjusting weight allocation ratio according to measured temperature deviation), the temperature control response speed is improved by 50%, ensuring that deviation can still be quickly compensated when waste heat fluctuates by ±10%.

[0099] The electric regulating valve of the actuator submodule has an adjustment accuracy of no less than ±1% of the opening degree. The flow regulation range of the variable frequency liquid ammonia transfer pump (80-96m³ / h) covers the liquid ammonia supply range required for the load fluctuation of the synthesis tower. Its linkage with the instructions of the adaptive algorithm submodule (precisely executing the adjustment amount output by the deviation correction formula) and the linkage with the correction instructions of the collaborative control module (secondary calibration of execution parameters) realizes bidirectional precise control of the heat load, ensuring that the liquid ammonia temperature is stable within the target range (80-95℃).

[0100] Based on the deviation calculation between the real-time load and the reference load of the synthesis tower, and through linkage with the synthesis tower load data of the data acquisition and preprocessing module, a load sensitivity coefficient is introduced to quantify the impact of load changes on heat load demand, so as to ensure that the heat load calculation is accurately matched with the process requirements.

[0101] Based on the deviation between real-time ambient temperature and standard ambient temperature, and through linkage with the ambient temperature data of the data acquisition and preprocessing module (to acquire ambient temperature fluctuation data in real time), the impact of ambient temperature changes on heat exchanger heat dissipation loss is compensated, ensuring that the accuracy error of heat load calculation is ≤±2%.

[0102] The deviation threshold of the feedback correction submodule is set according to the accuracy requirements of liquid ammonia temperature control (±0.3℃). By linking with the temperature feedback data of the liquid ammonia temperature control module (real-time monitoring of liquid ammonia outlet temperature deviation) and with the waste heat status data of the waste heat recovery module (real-time monitoring of waste heat supply deviation), the correction cycle is consistent with the data acquisition cycle (≤1s), achieving rapid deviation correction and ensuring that the final deviation of liquid ammonia temperature is ≤±0.5℃.

[0103] The system is applicable to coal-to-urea production plants of all sizes. Each module is modularly connected through standardized interfaces. The data acquisition and preprocessing module provides a unified data interface for all modules. The waste heat recovery module and the liquid ammonia temperature control module achieve energy docking through standardized pipelines. The collaborative control module achieves command interoperability with other modules through a common industrial protocol. The modular design can realize energy-saving retrofitting of existing plants and integrated deployment of new plants.

[0104] Through unified data support from the data acquisition and preprocessing module, directional energy supply from the waste heat recovery module, precise temperature control from the liquid ammonia temperature control module, and closed-loop dynamic correction from the collaborative control module, the modules form a deep linkage of data, energy, and control. The transformation process does not require large-scale reconstruction of the production process. At the same time, it achieves multiple benefits, including a 32 percentage point increase in waste heat utilization efficiency, a 10-fold increase in liquid ammonia temperature control accuracy, and a 2.5-3 percentage point increase in urea conversion rate. The investment payback period is short (≤2 years), and it has significant economic benefits, environmental benefits, and industry promotion value.

[0105] The system's operation process is executed sequentially through the steps of initialization preparation, end-to-end data processing, targeted waste heat recovery, precise temperature control, collaborative closed-loop correction, and dynamic operating condition adaptation. Each step is deeply integrated with its corresponding module, and the entire process is controllable through data exchange, energy transfer, and command verification between modules. The specific operation steps are as follows:

[0106] Step 1: System Initialization: Utilizing the data acquisition and preprocessing module, waste heat recovery module, liquid ammonia temperature control module, and collaborative regulation module;

[0107] After the system starts up, the coordinated control module issues an initialization command, the sensor group submodule of the data acquisition and preprocessing module is powered on, preheated and calibrated, the signal transmission submodule establishes an industrial Ethernet communication link, the data filtering submodule initializes the Kalman filter parameters, the circulation conveying submodule of the waste heat recovery module starts the variable frequency pump, injects the heat exchange medium into the dedicated heat exchanger submodule and the buffer pressure stabilization submodule, and completes the pipeline filling; the actuator submodule of the liquid ammonia temperature control module is reset to the initial state, and the adaptive algorithm submodule loads the trained LSTM model parameters.

[0108] Each module completes startup calibration synchronously, eliminating initial deviations, ensuring sensor acquisition accuracy ≥99%, no media leakage in pipelines, and algorithm model readiness, laying a stable foundation for subsequent operation.

[0109] Step 2: The data acquisition and preprocessing module, in conjunction with the collaborative control module, waste heat recovery module, and liquid ammonia temperature control module, collects multi-dimensional raw data such as hydrolysis purification parameters, liquid ammonia parameters, synthesis tower load parameters, and environmental parameters through the sensor group submodule. The data is then transmitted to the data filtering submodule with a delay of ≤10ms via the signal transmission submodule. Noise is removed using the Kalman filter algorithm, and the processed standardized data is synchronously distributed to the other three core modules. At the same time, the collaborative control module sends acquisition frequency commands to the signal transmission submodule to dynamically adapt to the operating conditions.

[0110] It realizes closed-loop processing of multi-source heterogeneous data acquisition, transmission, filtering, and distribution, providing measured data of waste heat sources for waste heat recovery, basic parameters of liquid ammonia for temperature control, and process terminal data for coordinated regulation, avoiding regulation deviations caused by noise data.

[0111] Step 3: The waste heat recovery module, in coordination with the data acquisition and pretreatment module, the liquid ammonia temperature control module, and the collaborative regulation module, receives the hydrolysis purification parameters transmitted by the data acquisition and pretreatment module through a dedicated heat exchanger submodule. It then performs countercurrent heat exchange with the heat exchange medium transported by the circulation conveying submodule. The heat exchange status data is fed back to the buffer and pressure stabilization submodule and the collaborative regulation module in real time. The buffer and pressure stabilization submodule buffers waste heat fluctuations based on thermodynamic principles, maintaining the temperature fluctuation of the heat exchange medium at ≤±2℃, and then transports the stabilized medium to the circulation conveying submodule. The circulation conveying submodule, according to the flow instructions of the collaborative regulation module, accurately transports the high-temperature heat exchange medium to the dedicated preheater submodule of the liquid ammonia temperature control module.

[0112] A directional energy transfer link is constructed between the hydrolysis water purification and heat exchange medium, with a waste heat recovery efficiency of ≥92%, which is 32 percentage points higher than the existing technology. This provides a stable and high-grade energy source for liquid ammonia preheating, while avoiding equipment damage caused by the corrosiveness of hydrolysis water purification.

[0113] Step 4: The liquid ammonia temperature control module works in conjunction with the waste heat recovery module, data acquisition and preprocessing module, and collaborative regulation module;

[0114] The dedicated preheater submodule receives the high-temperature heat exchange medium and the liquid ammonia delivered by the actuator submodule, completes uniform countercurrent heat exchange, and provides real-time feedback of the liquid ammonia outlet temperature data. The adaptive algorithm submodule receives this temperature data, the liquid ammonia inlet parameters from the data acquisition and preprocessing module, and the status data from the actuator submodule. It calculates the adjustment amount through the liquid ammonia temperature adaptive predictive control deviation correction formula and sends commands to the variable frequency liquid ammonia delivery pump and electric regulating valve. The actuator submodule precisely adjusts the liquid ammonia flow rate and the heat exchange medium flow rate, and at the same time feeds back the execution status to the algorithm submodule and the collaborative control module.

[0115] It achieves high-precision control of liquid ammonia temperature within ±0.5℃, with a dynamic response time ≤5s, solving the problem of temperature instability caused by waste heat fluctuations and load changes, and meeting the stringent requirements of urea synthesis reaction for raw material temperature.

[0116] Step 5: The coordinated control module coordinates with the other three core modules. It receives feedback data from each module through the logic operation submodule, and completes the heat load balance calculation and control parameter derivation by dynamically matching the total heat load balance formula. The instruction output submodule converts the calculation results into industrial standard signals and sends them to the circulation conveying submodule of the waste heat recovery module and the actuator submodule of the liquid ammonia temperature control module. The feedback correction submodule compares the operating parameters of each module with the predicted values ​​in real time. When the deviation exceeds the threshold, it triggers the logic operation submodule to perform a second operation and generate a correction instruction to be sent in a closed loop.

[0117] The system achieves dynamic matching of waste heat supply, liquid ammonia demand, and load changes. Even if the synthesis tower load fluctuates by ±20% and the hydrolysis water flow rate fluctuates by ±10%, the system can still maintain a balance between heat load supply and demand, ensuring stable operation under disturbance conditions.

[0118] Step Six: The system continues to repeat steps two through five. The data acquisition and preprocessing module updates the operating data in real time, the waste heat recovery module adjusts the heat exchange intensity according to the collaborative instructions, the liquid ammonia temperature control module optimizes the temperature control strategy through algorithm iteration, and the collaborative regulation module coordinates all parameters and dynamically adjusts and corrects the threshold and control logic.

[0119] The system is highly robust and can adapt to various operating conditions in coal-to-urea production, maintaining the ammonia-to-carbon ratio of the urea synthesis reaction within the optimal range, increasing the reaction conversion rate by 2.5-3 percentage points, and extending the continuous operation time of the equipment by ≥5 years.

[0120] The technical scope of this invention is not limited to the content described above. Those skilled in the art can make various modifications and variations to the above embodiments without departing from the technical concept of this invention, and all such modifications and variations should fall within the protection scope of this invention.

Claims

1. A system for coordinated control of preheating of liquid ammonia and waste heat from hydrolysis in coal-to-urea production, characterized in that, It includes a data acquisition and preprocessing module, a waste heat recovery module, a liquid nitrogen temperature control module, and a collaborative regulation module; The data acquisition and preprocessing module is used to acquire multi-dimensional parameters of waste heat source, heat exchange process and process terminal in the coal-to-urea production process. Its output data is directly transmitted to the waste heat recovery module, liquid nitrogen temperature control module and collaborative regulation module. The waste heat recovery module receives waste heat source parameters transmitted by the data acquisition and preprocessing module, constructs an internal energy transfer link for water hydrolysis and heat exchange medium, and outputs stable heat energy directly to the liquid ammonia temperature control module. At the same time, it feeds back waste heat recovery status data to the collaborative control module. The liquid ammonia temperature control module receives a stable heat energy supply from the waste heat recovery module, combines the liquid ammonia parameters transmitted by the data acquisition and preprocessing module, and feeds back the output real-time liquid ammonia temperature data to the collaborative control module. The coordinated control module, as the central hub of the system, receives process terminal parameters from the data acquisition and preprocessing module, waste heat status data from the waste heat recovery module, and temperature feedback data from the liquid ammonia temperature control module, and outputs control commands to the waste heat recovery module and the liquid ammonia temperature control module. The coordinated control module includes a logic operation submodule, an instruction output submodule, and a feedback correction submodule; The logic operation submodule is based on the first law of thermodynamics and the kinetics of urea synthesis reaction. It receives synthesis tower load and ambient temperature data from the data acquisition and preprocessing module, waste heat supply data from the waste heat recovery module, and temperature feedback data from the advanced liquid ammonia temperature control module. It analyzes the quantitative relationship between waste heat supply, liquid ammonia preheating demand and synthesis tower load, and completes heat load balance calculation and control parameter derivation. The logic operation submodule completes the heat load balance calculation and control parameter derivation by dynamically matching the total heat load balance formula with waste heat, temperature, and load, and transmits the calculation results to the instruction output submodule. The formula for balancing the total heat load by dynamically matching waste heat, temperature, and load is as follows: ； in, Waste heat can be effectively utilized for water purification through hydrolysis. The total efficiency of the two-stage heat exchange is given. The heat load required for preheating liquid nitrogen This is the correction factor for load fluctuations in the synthesis tower. This is the ambient temperature correction factor. The coefficient is the adaptation factor for the differences in physical properties of water purified by hydrolysis.

2. The coal-to-urea liquid ammonia preheating and hydrolysis waste heat synergistic control system according to claim 1, characterized in that: The data acquisition and preprocessing module includes a sensor group submodule, a signal transmission submodule, and a data filtering submodule; The sensor group submodule is based on the resistance value of platinum resistance thermometer, temperature characteristics, Faraday's law of electromagnetic induction and diffused silicon piezoresistive effect to collect temperature, flow rate and pressure parameters respectively, and the collected raw data is directly transmitted to the signal transmission submodule. The signal transmission submodule adopts industrial Ethernet differential signal transmission technology, combined with CRC check mechanism, to transmit the raw data of the sensor group submodule to the data filtering submodule, and at the same time receive parameter acquisition instructions from the collaborative control module to dynamically adjust the acquisition frequency. The data filtering submodule uses the Kalman filtering algorithm to predict, update and iterate the raw data received by the signal transmission submodule, and the optimized data is synchronously transmitted to the collaborative control module, the waste heat recovery module and the liquid ammonia temperature control module.

3. The coal-to-urea liquid ammonia preheating and hydrolysis waste heat synergistic control system according to claim 2, characterized in that: The waste heat recovery module includes a dedicated heat exchanger submodule, a buffer and pressure stabilization submodule, and a circulation conveying submodule. The dedicated heat exchanger submodule adopts a counter-flow spiral plate structure, receives the heat exchange medium delivered by the circulating conveying submodule, and its heat exchange status data is fed back to the buffer and pressure stabilizing submodule and the collaborative control module in real time. The buffer and pressure stabilizing submodule uses heat transfer oil as the energy storage medium, receives the high-temperature heat exchange medium output from the dedicated heat exchanger submodule, and transports the stabilized heat exchange medium to the circulation transport submodule. At the same time, the medium temperature and liquid level data are fed back to the collaborative control module. The circulating delivery submodule uses a frequency-driven circulating pump to receive the stable heat exchange medium from the buffer and pressure stabilization submodule and the flow control command from the collaborative control module, accurately delivering the heat exchange medium to the dedicated heat exchanger submodule and the dedicated preheater submodule of the liquid ammonia temperature control module.

4. The coal-to-urea liquid ammonia preheating and hydrolysis waste heat synergistic control system according to claim 1, characterized in that: The liquid ammonia temperature control module includes a dedicated preheater submodule, an actuator submodule, and an adaptive algorithm submodule. The dedicated preheater submodule adopts a double-tube structure, receiving the high-temperature heat exchange medium circulated from the waste heat recovery module and performing uniform countercurrent heat exchange with the liquid ammonia supplied by the actuator submodule. After heat exchange, the liquid ammonia temperature data is fed back to the adaptive algorithm submodule in real time. The actuator submodule includes a variable frequency liquid ammonia transfer pump and a high-precision electric regulating valve, receives control commands from the adaptive algorithm submodule, and feeds back execution status data to the adaptive algorithm submodule and the collaborative control module. The adaptive algorithm submodule embeds a long short-term memory neural network model, receives liquid ammonia parameters from the data acquisition and preprocessing module, temperature feedback data from the dedicated preheater submodule, and status data from the actuator submodule. It generates control commands through the liquid ammonia temperature adaptive predictive control deviation correction formula and transmits them to the actuator submodule. At the same time, it feeds back the predicted data to the collaborative control module. The formula for correcting the deviation of the adaptive predictive control of liquid ammonia temperature is as follows: ； in, Let k be the adjustment amount of the actuator. This is the proportionality coefficient. The integral coefficient is... The differential coefficients are... The real-time temperature deviation at time k is... Calculations based on feedback data from the dedicated preheater submodule Let be the temperature deviation at time i. To control the cycle, For dynamic weighting coefficients, Predicting for LSTM models Temperature deviation after a certain time.

5. The coal-to-urea liquid ammonia preheating and hydrolysis waste heat synergistic control system according to claim 3, characterized in that: The instruction output submodule converts the calculation results of the logic operation submodule into industrial standard control signals and outputs them to the circulation conveying submodule of the waste heat recovery module and the actuator submodule of the liquid ammonia temperature control module. At the same time, it feeds back the instruction issuance status to the feedback correction submodule. The feedback correction submodule receives operational feedback parameters from each module in real time.

6. The coal-to-urea liquid ammonia preheating and hydrolysis waste heat synergistic control system according to claim 5, characterized in that: The dedicated heat exchanger submodule is used to receive feedback on the hydrolysis water purification parameters from the data acquisition and pretreatment module. The buffer voltage stabilizing submodule is equipped with dual monitoring units for liquid level and temperature. The variable frequency circulating pump of the circulating conveying submodule adopts a sealed structure.

7. The coal-to-urea liquid ammonia preheating and hydrolysis waste heat synergistic control system according to claim 4, characterized in that: The LSTM model of the adaptive algorithm submodule achieves coordinated correction of prediction bias and real-time bias through a bias correction formula. The dynamic weighting coefficient Calculated based on real-time temperature deviation and smoothing coefficient; The flow rate adjustment range of the variable frequency liquid ammonia delivery pump in the actuator submodule covers the range of liquid ammonia supply required for the load fluctuations of the synthesis tower.

8. The coal-to-urea liquid ammonia preheating and hydrolysis waste heat synergistic control system according to claim 1, characterized in that: The Calculation based on the deviation between the real-time load and the reference load of the synthesis tower; The Calculated based on the deviation between real-time ambient temperature and standard ambient temperature; The deviation threshold of the feedback correction submodule is set according to the accuracy requirements of liquid ammonia temperature control.

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