Energy-saving and environment-friendly petroleum coke calcining system

Abstract

The present application relates to the technical field of petroleum coke calcination, and particularly discloses an energy-saving and environment-friendly petroleum coke calcination system. The system comprises a rotary kiln calcination unit, a flue gas waste heat deep recovery unit, a kiln body radiation heat recovery and heat preservation strengthening unit, and an intelligent thermal regulation and control unit. The flue gas waste heat unit recovers flue gas in multiple stages through high-temperature radiation, medium-temperature convection, and low-temperature heat pipe heat exchangers. The kiln body unit recovers kiln body heat dissipation through heat-conducting pads, heat pipe arrays, and cooling jackets, and uses an outer heat preservation layer to inhibit heat loss. The intelligent regulation and control unit dynamically optimizes system operation based on real-time data. The scheme realizes efficient use of the full spectrum of heat energy, improves system thermal efficiency, and reduces energy consumption.

Description

Technical Field

[0001] This invention belongs to the field of petroleum coke calcination technology, specifically relating to an energy-saving and environmentally friendly petroleum coke calcination system. Background Technology

[0002] Petroleum coke calcination is a key heat treatment process in carbon material production and aluminum anode preparation. Its core function is to remove volatiles from petroleum coke at high temperatures to improve its physicochemical properties. The calcination system, as the fundamental equipment for this process, directly impacts the economic benefits and environmental compliance of production due to its energy efficiency and environmental performance.

[0003] Rotary kilns are the most widely used equipment for calcining petroleum coke. Their basic working principle involves rotating the kiln body, causing the petroleum coke to move within and be heated by high-temperature flue gas from the burner, thus completing the calcination process. In existing technologies, the high-temperature flue gas discharged from the calcining kiln typically enters a subsequent waste heat boiler or quench tower for treatment. However, the large amount of sensible heat contained in the flue gas is not fully recovered, resulting in a waste of thermal energy.

[0004] The surface of the kiln, operating at high temperatures, continuously radiates heat into the environment, constituting another significant heat loss. This unused heat not only reduces the overall thermal efficiency of the system, increases fuel consumption and production costs, but also exacerbates the load and energy consumption of the cooling system. Furthermore, heat loss means that more fuel needs to be burned to maintain the process temperature inside the kiln, indirectly increasing greenhouse gas and pollutant emissions. Therefore, how to systematically recover and utilize waste heat from flue gas and suppress heat dissipation from the kiln has become a pressing technical challenge to improve the energy efficiency and environmental protection level of petroleum coke calcination systems. Summary of the Invention

[0005] The purpose of this invention is to provide an energy-saving and environmentally friendly petroleum coke calcination system to solve the technical problems in the prior art, such as insufficient waste heat recovery from flue gas during petroleum coke calcination, severe heat loss from the kiln surface, resulting in low overall system thermal efficiency, high energy consumption, and significant environmental pressure.

[0006] This invention provides an energy-saving and environmentally friendly petroleum coke calcination system, comprising:

[0007] The rotary kiln calcination unit is used to perform the high-temperature calcination process of petroleum coke. The rotary kiln calcination unit includes a kiln body, a drive unit, a feeding unit, a discharging unit, and a main burner located at the kiln head.

[0008] The deep waste heat recovery unit is connected to the flue gas outlet end of the rotary kiln calcination unit and is used to extract energy from the high-temperature flue gas generated during calcination through multi-stage fractionation. The deep waste heat recovery unit includes a high-temperature radiant heat exchanger, a medium-temperature convective heat exchanger group and a low-temperature heat pipe heat exchanger.

[0009] The kiln body radiant heat recovery and insulation enhancement unit is tightly wrapped around the outer surface of the rotary kiln calcination unit to simultaneously realize the heat dissipation recovery and insulation performance enhancement of the kiln body. The kiln body radiant heat recovery and insulation enhancement unit includes a flexible thermally conductive silicone pad layer, an embedded heat pipe array, a circulating cooling medium jacket, and a nano aerogel composite insulation layer.

[0010] The intelligent thermal control unit is used to coordinate the operation status and energy distribution of the entire heat recovery network. The intelligent thermal control unit includes a distributed temperature and pressure sensor network, a flow actuator, a data acquisition module, an industrial control computer, and a heat balance optimization algorithm module.

[0011] Preferably, in the deep waste heat recovery unit of the flue gas, the high-temperature radiant heat exchanger directly receives the high-temperature flue gas discharged from the rotary kiln with a temperature in the range of 900 degrees Celsius to 1100 degrees Celsius. It is equipped with a high-temperature resistant radiant heating surface inside and extracts the high-temperature sensible heat from the flue gas through thermal radiation to produce high-temperature air or superheated steam with a temperature of not less than 500 degrees Celsius.

[0012] The medium-temperature convection heat exchanger group is connected in series after the high-temperature radiation heat exchanger to receive medium-temperature flue gas after preliminary cooling. The flue gas temperature ranges from 400 degrees Celsius to 600 degrees Celsius. The medium-temperature convection heat exchanger group consists of at least two stages of finned tube heat exchangers. It extracts heat from the flue gas through forced convection to heat boiler feedwater or preheat combustion air.

[0013] The low-temperature heat pipe heat exchanger is located at the end of the flue gas treatment process. The flue gas inlet temperature is no more than 200 degrees Celsius. The low-temperature heat pipe heat exchanger uses the phase change heat transfer principle of the working fluid in the heat pipe to recover the low-temperature waste heat of the flue gas, and finally reduces the exhaust temperature to below 120 degrees Celsius.

[0014] Preferably, the medium-temperature convection heat exchanger group adopts a compartmentalized series structure, and the medium-temperature convection heat exchanger group is divided into two independent heat exchange compartments.

[0015] The first-stage heat exchange chamber is specifically designed for preheating combustion air, and its heat exchange tube bundle is made of corrosion-resistant ND steel.

[0016] The second-stage heat exchange chamber is specifically used for heating boiler feedwater, and the heat exchange tube bundle is made of 20G boiler steel.

[0017] The two compartments are connected by a flue gas connecting pipe, and the flue gas flows through the two compartments in sequence.

[0018] Preferably, in the kiln body radiant heat recovery and insulation enhancement unit, the flexible thermally conductive silicone pad is directly attached to the outer wall of the high-temperature section of the kiln body, and the thermal conductivity is not less than 2 watts per meter per Kelvin.

[0019] The embedded heat pipe array is arranged in a matrix and embedded in the flexible thermally conductive silicone pad layer. The evaporation section of the heat pipe is in close contact with the flexible thermally conductive silicone pad layer, while the condensation section extends into the circulating cooling medium jacket.

[0020] The circulating cooling medium jacket covers the outside of the heat pipe array and the flexible thermally conductive silicone pad, and the internal circulation contains forced-circulation thermally conductive oil or softened water as the cooling medium.

[0021] The nano-aerogel composite insulation layer, as the outermost layer, has a thermal conductivity of less than 0.02 watts per meter per Kelvin and is tightly wrapped around the outside of the circulating cooling medium jacket.

[0022] Preferably, the heat recovered in the kiln body radiant heat recovery and insulation enhancement unit is utilized through an integrated heat medium distribution station;

[0023] The heat medium distribution station is equipped with a high-temperature heat transfer oil circuit and a low-temperature hot water circuit;

[0024] The high-temperature heat transfer oil circuit is connected to the outlet of the circulating cooling medium jacket, and the recovered heat with a temperature of 180 degrees Celsius to 220 degrees Celsius is preferentially transported to the drum dryer in the petroleum coke raw material drying process.

[0025] The low-temperature hot water circuit is connected to the hot water side outlet of the low-temperature heat pipe heat exchanger, and recovers heat with a temperature of 60 degrees Celsius to 80 degrees Celsius for use in the factory bathroom hot water supply or winter heating system.

[0026] The heat medium distribution station is equipped with a plate heat exchanger and a three-way regulating valve, which are used to dynamically adjust the flow distribution ratio of the two heat media under the command of the intelligent thermal control unit.

[0027] Preferably, in the intelligent thermal control unit, a distributed sensor network monitors in real time the temperature of each section of the rotary kiln, the temperature and pressure of the flue gas before and after each heat exchange node, the inlet and outlet temperatures and flow rates of the cooling medium jacket, and the parameters of each heat exchange point.

[0028] The data acquisition module aggregates the sensor signals to the industrial control computer;

[0029] The heat balance optimization algorithm module is based on real-time collected system full-condition data. It takes the minimum total energy consumption of the system as the objective function and the safe operating range of each heat exchanger and the process temperature requirements as constraints. Through dynamic optimization calculation, it solves the optimal solution set of the main burner fuel quantity, the medium flow rate of each heat exchange loop, and the recovery heat distribution strategy in real time.

[0030] The flow actuator receives instructions from the industrial control computer to precisely adjust the opening degree of the gas valve, the frequency of the water pump, and the position of the damper.

[0031] Preferably, the heat balance optimization algorithm module adopts a model predictive control strategy;

[0032] The model predictive control strategy first establishes a simplified mechanism model that includes a rotary kiln calcination dynamics model, a heat transfer model for each heat exchanger, and a pipeline resistance model. In each control cycle, the algorithm solves the optimal control problem in the finite time domain based on the current system state and the predicted production plan disturbances in the future.

[0033] The decision variables for this optimal control problem include the fuel valve position and the setpoint of each pump frequency in multiple future sampling periods. The objective is to minimize the sum of total fuel consumption and pumping power consumption in the prediction time domain.

[0034] The first element of the optimal control sequence obtained by solving is applied to the actuator at the current time, and rolling optimization is performed again in the next cycle.

[0035] Preferably, in the heat balance optimization algorithm module, the objective function is to minimize the weighted sum of fuel consumption and total power consumption of each circulating pump in the prediction time domain;

[0036] The constraints include a main burner outlet temperature of not less than 1250 degrees Celsius, a high-temperature radiant heat exchanger outlet flue gas temperature of not more than 650 degrees Celsius, and an upper limit of 250 degrees Celsius for the temperature of the circulating cooling medium.

[0037] Preferably, the system also includes an emergency thermal bypass and protection subsystem;

[0038] The emergency heat bypass and protection subsystem consists of high-temperature flue gas bypass valves installed before and after the high-temperature radiant heat exchanger, an emergency radiator installed on the jacket of the circulating cooling medium, and interlocking control logic.

[0039] When the intelligent thermal control unit detects that the outlet flue gas temperature of the high-temperature radiant heat exchanger is greater than the safety threshold of 650 degrees Celsius, or the medium temperature in the circulating cooling medium jacket is greater than the safety threshold of 250 degrees Celsius, the interlock control logic is immediately activated, partially opening the high-temperature flue gas bypass valve and introducing the overheated cooling medium into the emergency radiator for forced air cooling.

[0040] Preferably, the embedded heat pipe array is arranged with non-uniform density according to the temperature field distribution characteristics of the outer surface of the kiln.

[0041] In the axial direction of the kiln body, the heat pipes are arranged at a higher density in the zone of intense calcination reaction than in the preheating zone and the cooling zone.

[0042] In the circumferential direction, the density of heat pipes in the lower half of the kiln body is greater than that in the upper half.

[0043] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0044] 1. This invention constructs a full-spectrum, multi-medium cascade heat energy recovery network, encompassing high-temperature flue gas at 1100°C, low-temperature heat sources at 60°C, and radiant heat from the kiln surface. Through precise matching and series arrangement of four differentiated heat exchange technologies—high-temperature radiation, medium-temperature convection, low-temperature heat pipes, and kiln heat pipe jackets—the flue gas temperature is reduced from the conventional above 200°C to below 120°C. Furthermore, the recoverable heat dissipation from the kiln surface is collected, improving the overall thermal efficiency of the system and reducing main fuel consumption and operating costs.

[0045] 2. This invention features a unique kiln radiant heat recovery and insulation enhancement unit, transforming traditional passive insulation into a synergistic model of "active recovery + enhanced insulation." Flexible thermally conductive silicone and an embedded heat pipe array solve the technical challenge of efficient heat extraction during rotary kiln rotation, ensuring heat dissipation is conducted. The outer nano-aerogel insulation layer cuts off the final path of heat loss to the environment. This design not only recovers previously wasted heat for production but also improves the working environment by reducing the kiln's surface temperature and reduces additional fuel consumption to compensate for heat dissipation, offering multiple benefits including energy saving, cost reduction, and environmental protection.

[0046] 3. This invention integrates the entire multi-loop, strongly coupled thermal energy system into an intelligent entity through an intelligent thermal control unit and advanced thermal balance optimization algorithms. The system can perceive the global thermal state in real time and dynamically optimize the distribution of fuel, air, water, and heat transfer medium, ensuring that the system always operates at or near its optimal energy efficiency point. This global collaborative optimization overcomes the shortcomings of traditional systems where each unit operates independently and is difficult to optimize as a whole, improving the system's adaptability and stability in response to raw material fluctuations and changes in production load, and achieving a leap from static design energy saving to dynamic operational energy saving.

[0047] 4. The modular design and emergency protection subsystem of this invention ensure the reliability and safety of the system. The compartmentalized heat exchanger facilitates maintenance and targeted corrosion prevention; the integrated heat medium distribution station improves the flexibility of heat utilization; and the emergency bypass and interlock logic can quickly respond to abnormal operating conditions such as over-temperature, protecting equipment from damage and ensuring the industrial needs of long-term continuous and stable production. Attached Figure Description

[0048] Figure 1 This is a schematic diagram of the overall technical solution architecture of the present invention;

[0049] Figure 2 This is a schematic diagram of the core principle framework of the kiln body radiant heat recovery and heat preservation enhancement unit in this invention;

[0050] Figure 3 This is a flowchart illustrating the multi-stage thermal energy recovery and utilization logic of the deep waste heat recovery unit in flue gas in this invention.

[0051] Figure 4 This is a schematic diagram of the heat balance collaborative optimization framework based on model predictive control for the intelligent thermal control unit in this invention;

[0052] Figure 5 This is a schematic diagram of the interlocking control logic and heat flow switching of the emergency heat bypass and protection subsystem in this invention. Detailed Implementation

[0053] Example 1: The overall structure and operating logic of the petroleum coke energy-saving and environmentally friendly calcination system of the present invention are as follows: Figure 1 As shown in the figure. This system, with the rotary kiln calcination unit as its core, constructs a full-spectrum heat energy cascade recovery and redistribution network covering the heat dissipation from high-temperature flue gas to low-temperature kiln body through the coordinated operation of a deep flue gas waste heat recovery unit, a kiln body radiant heat recovery and insulation enhancement unit, and an intelligent thermal control unit. The following will be combined with the attached... Figure 1 To be continued Figure 5 It provides a detailed and comprehensive technical description of each component, unfolding it layer by layer.

[0054] The rotary kiln calcination unit is the fundamental process unit of the entire system, used to complete the conversion of petroleum coke into precursors for volatile matter removal, densification, and graphitization under high-temperature conditions. This fundamental process unit includes the kiln body, drive unit, feeding device, discharging device, and main burner. The kiln body is a cylindrical steel structure lined with high-alumina or corundum refractory material, and its axis is installed at an angle of 2 to 5 degrees to the horizontal plane to ensure that the material moves slowly from the feeding end to the discharging end under gravity. The drive unit consists of a variable frequency speed-regulating motor, a reducer, and a large gear ring, which drives the kiln body to rotate at an adjustable speed of 0.5 to 3 revolutions per minute through gear meshing, thereby achieving uniform tumbling and full heating of the material in the kiln. The feeding device uses a sealed screw feeder to continuously and stably feed the pretreated petroleum coke raw material into the kiln tail; the discharging device is a water-cooled chain conveyor used to receive and cool the high-temperature calcined coke discharged from the kiln head. The main burner is installed inside the kiln head hood and adopts a multi-channel swirl structure. It can simultaneously inject fuels such as natural gas, liquefied petroleum gas or pulverized coal. By adjusting the ratio of primary air and secondary air, it controls the flame shape and temperature distribution to ensure that the highest temperature inside the kiln is maintained between 1250 degrees Celsius and 1350 degrees Celsius, which meets the thermodynamic requirements of petroleum coke calcination.

[0055] The deep waste heat recovery unit is connected to the flue gas outlet end of the rotary kiln, and its structure and heat flow path are as follows: Figure 3As shown, this deep waste heat recovery unit for flue gas adopts a three-stage series, fractional recovery architecture, consisting of a high-temperature radiant heat exchanger, a medium-temperature convection heat exchanger group, and a low-temperature heat pipe heat exchanger. The high-temperature radiant heat exchanger directly receives the raw flue gas discharged from the rotary kiln at a temperature between 900°C and 1100°C. Its shell is a vertical cylindrical structure, with multiple rows of radiant heating surface tubes made of heat-resistant alloys (such as Inconel 601) arranged vertically inside, through which compressed air or saturated steam flows. Since the high-temperature flue gas mainly transfers energy through thermal radiation, the high-temperature radiant heat exchanger can heat the working medium to a high temperature of not less than 500°C in a very short process, while simultaneously rapidly reducing the flue gas temperature to around 600°C. The high-temperature heat medium recovered in this stage can be directly used to drive a small back-pressure steam turbine for power generation, or used as a high-grade heat source to supply other high-temperature process stages.

[0056] The medium-temperature convection heat exchanger unit follows the high-temperature radiant heat exchanger, receiving medium-temperature flue gas with a temperature range of 400°C to 600°C. This unit employs a compartmentalized series structure, divided into two independent heat exchange chambers by physical partitions. The first-stage heat exchange chamber is dedicated to preheating combustion air. Its internal heat exchange tube bundles are made of ND steel (09CrCuSb) resistant to sulfuric acid dew point corrosion, with high-frequency welded spiral fins added to the outside to enhance heat transfer efficiency. Ambient air is supplied to this chamber by a blower and heated to 200°C to 250°C under forced convection before being directly returned to the main burner as combustion air, reducing fuel consumption and improving combustion efficiency. The second-stage heat exchange chamber is used to heat boiler feedwater. Its heat exchange tube bundles are made of 20G boiler steel and also feature a finned structure. Softened water from the deaerator is heated to 150-180 degrees Celsius here, and then sent to the waste heat boiler or used as process hot water. A flue gas connecting pipe between the two compartments ensures unidirectional flow of flue gas, guaranteeing that heat energy is released step-by-step according to temperature grade, avoiding heat loss caused by the absorption of high-grade heat by low-grade media.

[0057] The low-temperature heat pipe heat exchanger is located at the end of the flue gas treatment process, handling low-temperature flue gas with an inlet temperature not exceeding 200 degrees Celsius. This heat pipe heat exchanger consists of hundreds of densely arranged gravity-fed heat pipes. Each heat pipe is filled with a specific working fluid (such as a water-copper system or an ammonia-carbon steel system). After absorbing heat from the flue gas in the evaporation section, a phase change occurs, and the steam rises along the pipe to the condensation section, releasing latent heat. The condensate flows back by gravity, forming a pump-free self-circulation. The heat pipe condensation section is immersed in a softened water circulation loop, using the recovered heat for preheating system makeup water or providing heating for the factory's office areas. Through this process, the final exhaust temperature of the flue gas is controlled below 120 degrees Celsius, far lower than the above 200 degrees Celsius of conventional systems, significantly reducing exhaust heat loss.

[0058] The kiln body radiant heat recovery and insulation enhancement unit is tightly wrapped around the outer surface of the rotary kiln. Its core structural principle is as follows: Figure 2 As shown. The kiln radiant heat recovery and insulation enhancement unit consists of a flexible thermally conductive silicone pad, an embedded heat pipe array, a circulating cooling medium jacket, and a nano-aerogel composite insulation layer, from the inside out. The flexible thermally conductive silicone pad is directly attached to the outer wall of the high-temperature section of the kiln (usually the front 70% of the kiln's length), with a thickness of 5 mm to 10 mm, a thermal conductivity of not less than 2 watts per Kelvin per meter, and good elasticity and temperature resistance (long-term operating temperature can reach 300 degrees Celsius), ensuring close contact with the metal shell during kiln rotation and efficiently dissipating radiant and convective heat emitted from the kiln surface. The embedded heat pipe array is arranged in a 50 mm × 50 mm matrix and is completely embedded inside the silicone pad. The evaporation section of each heat pipe is in full contact with the silicone pad, while the condensation section extends vertically into the external circulating cooling medium jacket. Heat pipes use copper-water or stainless steel-ammonia working fluid pairs, utilizing a phase change heat transfer mechanism to rapidly transfer heat from the high-temperature evaporation end to the low-temperature condensation end, with a heat transfer efficiency far greater than that of pure heat-conducting materials.

[0059] The circulating cooling medium jacket is a ring-shaped closed cavity that surrounds the heat pipe array and silicone pad. It is filled with forced-circulation heat transfer oil (such as L-QB300 type) or softened demineralized water. A circulating pump drives the cooling medium to flow through the jacket at a velocity of 0.5 to 1.5 meters per second, continuously absorbing the heat released from the heat pipe condensation section. The recovered heat medium temperature is typically maintained between 180 and 220 degrees Celsius, making it highly valuable. The outermost nano-aerogel composite insulation layer is made of silica aerogel particles and glass fiber felt, with a thickness of 30 to 50 millimeters. It has a thermal conductivity of less than 0.02 watts per Kelvin per meter and possesses excellent compressive strength and hydrophobic properties. The nano-aerogel composite insulation tightly wraps the entire outer surface of the jacket, forming a near-insulating barrier that minimizes secondary heat loss to the environment. This design not only enables the active recovery of heat dissipation from the kiln body, but also improves the operating environment by reducing the surface temperature of the kiln body and reduces the additional fuel consumption due to heat dissipation compensation.

[0060] The recovered heat is utilized through an integrated heat transfer medium distribution station. This station has two independent channels: a high-temperature heat transfer oil circuit and a low-temperature hot water circuit. The high-temperature heat transfer oil circuit connects to the outlet of the circulating cooling medium jacket, prioritizing the delivery of heat transfer medium at 180°C to 220°C to the drum dryer in the petroleum coke raw material drying process, serving as its primary heat source and replacing some of the heat originally required for combustion. The low-temperature hot water circuit connects to the hot water outlet of the low-temperature heat pipe heat exchanger, outputting hot water at 60°C to 80°C for domestic hot water supply in the plant's bathrooms or for the winter heating system. The heat transfer medium distribution station is internally equipped with a plate heat exchanger and an electric three-way regulating valve. When the downstream heat demand changes (such as a reduction in the drying process load), the intelligent thermal control unit issues a command to adjust the opening ratio of the three-way valve, directing excess heat to another circuit or allowing it to return via a bypass, ensuring stable pressure and temperature in the heat transfer medium system and preventing energy waste.

[0061] The intelligent thermal control unit acts as the central nervous system of the system, and its collaborative optimization framework is as follows: Figure 4 As shown in the diagram, the intelligent thermal control unit consists of a distributed temperature and pressure sensor network, a flow actuator, a data acquisition module, an industrial control computer, and a thermal balance optimization algorithm module. The distributed sensor network covers all key nodes of the system: at least 10 infrared temperature measurement points are arranged axially on the rotary kiln shell to monitor the material temperature in each section in real time; thermocouples and differential pressure transmitters are installed at the inlet and outlet of each stage of the waste heat recovery unit to collect flue gas temperature, pressure, and pressure drop; PT100 platinum resistance thermometers and electromagnetic flowmeters are installed at the inlet and outlet of the circulating cooling medium jacket to monitor the temperature and flow rate of the heat medium; and feedback sensors are installed at each hot spot. All signals are transmitted to the data acquisition module via shielded twisted-pair cable or industrial Ethernet, which then aggregates the data to the industrial control computer at a frequency of once per second.

[0062] The heat balance optimization algorithm module is built into the industrial control computer and employs a model predictive control strategy. This strategy first establishes a simplified mechanistic model including a rotary kiln calcination kinetic model, heat transfer models for each heat exchanger, and a pipeline resistance model. The rotary kiln model, based on material and energy balance, describes the relationship between fuel input, material flow rate, and the kiln's temperature field. The heat exchanger models use the ε-NTU method or the logarithmic mean temperature difference method to correlate flue gas flow rate, working fluid flow rate, and heat exchange. The pipeline model calculates fluid resistance based on the Darcy-Weisbach formula. In each control cycle (typically 30 seconds), the algorithm continuously solves the optimal control problem within a finite time domain based on the current system state and predicted production plan disturbances within the next 15 minutes. The objective function of the optimization problem is:

[0063] ;

[0064] For the first Fuel consumption per predicted step size This represents the total power consumption of all circulating pumps. and Energy consumption weighting coefficient To predict the length of the time domain, The total number of predicted steps is determined by constraints including: the main burner outlet temperature must not be less than 1250 degrees Celsius, the high-temperature radiant heat exchanger outlet flue gas temperature must not exceed 650 degrees Celsius, the upper limit of the circulating cooling medium temperature is 250 degrees Celsius, and the pressure drop of each heat exchanger must not exceed limits. In the optimal control sequence obtained (including fuel valve position, water pump frequency, and damper opening for multiple future cycles), only the first element is actually applied to the actuator at the current moment; the rest are used as predictive references. In the next cycle, the system re-acquires data and performs rolling optimization, achieving adaptive control combining feedforward and feedback.

[0065] The flow actuators include a gas regulating valve, a variable frequency water pump, and an electric damper. The gas regulating valve uses an equal percentage flow characteristic with a response time of less than 2 seconds, enabling precise control of the fuel supply to the main burner. The variable frequency water pump automatically adjusts its speed according to the cooling medium circuit requirements to maintain the set flow rate. The electric damper is installed in the combustion air duct and controls the preheating air flow rate by adjusting its opening. All actuators are equipped with position feedback and fault diagnosis functions to ensure accurate execution of control commands.

[0066] The system is also equipped with an emergency thermal bypass and protection subsystem, whose interlocking logic is as follows: Figure 5 As shown, the emergency heat bypass and protection subsystem consists of a high-temperature flue gas bypass valve, an emergency radiator, and interlocking control logic. The high-temperature flue gas bypass valve is a pneumatic quick-opening butterfly valve, installed on the bypass pipe between the inlet and outlet of the high-temperature radiant heat exchanger. The emergency radiator is a set of forced air-cooled finned tube heat exchangers, connected in parallel with the circulating cooling medium jacket via a switching valve. The interlocking control logic is built into the safety module of the intelligent thermal control unit. When the system detects that the flue gas temperature at the outlet of the high-temperature radiant heat exchanger is greater than 650 degrees Celsius, or the medium temperature in the circulating cooling medium jacket is greater than 250 degrees Celsius, the interlocking logic is immediately triggered: the high-temperature flue gas bypass valve opens to 30% to 50% of its opening, allowing some of the high-temperature flue gas to bypass the radiant heat exchanger and directly enter the medium-temperature convection heat exchanger group, reducing the front-end heat load; simultaneously, the switching valve actuates, introducing the overheated cooling medium into the emergency radiator, where it is forcibly cooled by a high-power axial flow fan. Once the relevant parameters return to within the safe threshold (e.g., flue gas temperature less than 600 degrees Celsius, medium temperature less than 230 degrees Celsius) and remain so for 5 minutes, the system automatically closes the bypass valve and switching valve, returning to normal operation mode, thus preventing safety accidents such as equipment deformation, pipe bursting, or working fluid decomposition caused by overheating.

[0067] In summary, this embodiment, through the deep integration of multi-stage flue gas waste heat recovery, active kiln heat capture, intelligent global optimization, and multiple safety protections, constructs a high-efficiency, low-emission, and robust petroleum coke calcination system. The system's overall thermal efficiency is improved compared to traditional designs, saving thousands of tons of standard coal annually while reducing carbon dioxide and nitrogen oxide emissions, thus achieving both economic benefits and environmental value.

[0068] Example 2: Based on the previous examples, this example optimizes and adjusts the heat pipe array arrangement and cooling medium type of the kiln body radiant heat recovery and insulation enhancement unit to adapt to rotary kiln applications with higher rotation speeds or larger diameters. Please refer to the appendix. Figure 2 In this embodiment, the embedded heat pipe array no longer adopts a regular orthogonal matrix arrangement, but instead uses a non-uniform density arrangement based on the temperature field distribution characteristics of the outer surface of the kiln. Specifically, in the axial direction of the kiln, the heat pipe density is increased to 30 mm × 30 mm in the zone of intense calcination reaction, typically located in the 40% to 70% range along the length of the kiln, while it is sparser at 80 mm × 80 mm in the preheating and cooling zones. In the circumferential direction, the density of heat pipes in the lower half of the kiln is greater than that in the upper half, with a ratio of 3:2, to match the temperature difference between the upper and lower surfaces caused by material coverage. This non-uniform arrangement strategy ensures that heat pipe resources are concentrated in areas of high heat flux density, improving the overall heat extraction efficiency.

[0069] The medium circulating in the cooling medium jacket has been replaced by a molten salt mixture instead of heat transfer oil. The molten salt remains liquid within a temperature range of 220°C to 565°C, exhibiting higher heat capacity and thermal stability, making it suitable for conditions with higher kiln surface temperatures. An electric heating tape and a temperature zone control system are added inside the jacket to ensure the molten salt does not solidify during system start-up and shutdown. The recovered high-temperature molten salt heat transfer medium is pumped to a heat storage tank in the plant area via a dedicated pump, serving as a backup heat source during peak grid periods, further enhancing the flexibility and economy of energy utilization.

[0070] The thermal balance optimization algorithm module of the intelligent thermal control unit introduces a machine learning-assisted online model correction mechanism. Historical data accumulated during long-term system operation is used to train a lightweight neural network model. This lightweight neural network model can correct key parameters in the mechanistic model in real time, thereby improving prediction accuracy. Before each rolling optimization, the algorithm first calls the neural network model to calibrate the model parameters under the current operating conditions, and then performs optimal control solution, making the control strategy closer to the actual physical process and further reducing energy consumption.

[0071] Through the above improvements, this embodiment maintains the original energy-saving advantages, enhances the system's adaptability to extreme operating conditions, and expands the high-value utilization path of recovered heat energy, making it suitable for large-scale, intelligent modern petroleum coke calcination plants.

[0072] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0073] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A petroleum coke energy-saving and environmentally friendly calcination system, characterized in that, include: The rotary kiln calcination unit is used to perform the high-temperature calcination process of petroleum coke. The rotary kiln calcination unit includes a kiln body, a drive unit, a feeding unit, a discharging unit, and a main burner located at the kiln head. The deep waste heat recovery unit is connected to the flue gas outlet end of the rotary kiln calcination unit and is used to extract energy from the high-temperature flue gas generated during calcination through multi-stage fractionation. The deep waste heat recovery unit includes a high-temperature radiant heat exchanger, a medium-temperature convective heat exchanger group and a low-temperature heat pipe heat exchanger. The kiln body radiant heat recovery and insulation enhancement unit is tightly wrapped around the outer surface of the rotary kiln calcination unit to simultaneously realize the heat dissipation recovery and insulation performance enhancement of the kiln body. The kiln body radiant heat recovery and insulation enhancement unit includes a flexible thermally conductive silicone pad layer, an embedded heat pipe array, a circulating cooling medium jacket, and a nano aerogel composite insulation layer. The intelligent thermal control unit is used to coordinate the control of the operation status and energy distribution of the entire heat recovery network. The intelligent thermal control unit includes a distributed temperature and pressure sensor network, a flow actuator, a data acquisition module, an industrial control computer, and a heat balance optimization algorithm module. In the deep waste heat recovery unit of the flue gas, the high temperature radiation heat exchanger directly receives the high temperature flue gas discharged from the rotary kiln with a temperature range of 900 degrees Celsius to 1100 degrees Celsius. It is equipped with a high temperature resistant radiation heating surface and extracts the high temperature sensible heat in the flue gas through thermal radiation to produce high temperature air or superheated steam with a temperature of not less than 500 degrees Celsius. The medium-temperature convection heat exchanger group is connected in series after the high-temperature radiation heat exchanger to receive medium-temperature flue gas after preliminary cooling. The flue gas temperature ranges from 400 degrees Celsius to 600 degrees Celsius. The medium-temperature convection heat exchanger group consists of at least two stages of finned tube heat exchangers. It extracts heat from the flue gas through forced convection to heat boiler feedwater or preheat combustion air. The low-temperature heat pipe heat exchanger is arranged at the end of the flue gas treatment process. The flue gas inlet temperature is no more than 200 degrees Celsius. The low-temperature heat pipe heat exchanger uses the phase change heat transfer principle of the working fluid in the heat pipe to recover the low-temperature waste heat of the flue gas, and finally reduces the exhaust temperature to below 120 degrees Celsius. The medium-temperature convection heat exchanger group adopts a compartmentalized series structure, which is divided into two independent heat exchange compartments. The first-stage heat exchange chamber is specifically designed for preheating combustion air, and its heat exchange tube bundle is made of corrosion-resistant ND steel. The second-stage heat exchange chamber is specifically used for heating boiler feedwater, and the heat exchange tube bundle is made of 20G boiler steel. The two compartments are connected in series by a flue gas connecting pipe, and the flue gas flows through the two compartments in sequence; In the kiln body radiant heat recovery and insulation enhancement unit, the flexible thermally conductive silicone pad is directly attached to the outer wall of the high-temperature section of the kiln body, and the thermal conductivity is not less than 2 watts per meter per Kelvin. The embedded heat pipe array is arranged in a matrix and embedded in the flexible thermally conductive silicone pad layer. The evaporation section of the heat pipe is in close contact with the flexible thermally conductive silicone pad layer, while the condensation section extends into the circulating cooling medium jacket. The circulating cooling medium jacket covers the outside of the heat pipe array and the flexible thermally conductive silicone pad, and the internal circulation contains forced-circulation thermally conductive oil or softened water as the cooling medium. The nano-aerogel composite insulation layer, as the outermost layer, has a thermal conductivity of less than 0.02 watts per meter per Kelvin and is tightly wrapped around the outside of the circulating cooling medium jacket. The heat recovered in the kiln body radiant heat recovery and insulation enhancement unit is utilized through an integrated heat medium distribution station. The heat medium distribution station is equipped with a high-temperature heat transfer oil circuit and a low-temperature hot water circuit; The high-temperature heat transfer oil circuit is connected to the outlet of the circulating cooling medium jacket, and the recovered heat with a temperature of 180 degrees Celsius to 220 degrees Celsius is preferentially transported to the drum dryer in the petroleum coke raw material drying process. The low-temperature hot water circuit is connected to the hot water side outlet of the low-temperature heat pipe heat exchanger, and recovers heat with a temperature of 60 degrees Celsius to 80 degrees Celsius for use in the factory bathroom hot water supply or winter heating system. The heat medium distribution station is equipped with a plate heat exchanger and a three-way regulating valve, which are used to dynamically adjust the flow distribution ratio of the two heat media under the command of the intelligent thermal control unit.

2. The energy-saving and environmentally friendly petroleum coke calcination system according to claim 1, characterized in that, In the intelligent thermal control unit, a distributed sensor network monitors in real time the temperature of each section of the rotary kiln, the temperature and pressure of the flue gas before and after each heat exchange node, the inlet and outlet temperatures and flow rates of the cooling medium jacket, and the parameters of each hot spot. The data acquisition module aggregates the sensor signals to the industrial control computer; The heat balance optimization algorithm module is based on real-time collected system full-condition data. It takes the minimum total energy consumption of the system as the objective function and the safe operating range of each heat exchanger and the process temperature requirements as constraints. Through dynamic optimization calculation, it solves the optimal solution set of the main burner fuel quantity, the medium flow rate of each heat exchange loop, and the recovery heat distribution strategy in real time. The flow actuator receives instructions from the industrial control computer to precisely adjust the opening degree of the gas valve, the frequency of the water pump, and the position of the damper.

3. The petroleum coke energy-saving and environmentally friendly calcination system according to claim 2, characterized in that, The thermal balance optimization algorithm module adopts a model predictive control strategy. The model predictive control strategy first establishes a simplified mechanism model that includes a rotary kiln calcination dynamics model, a heat transfer model for each heat exchanger, and a pipeline resistance model. In each control cycle, the algorithm solves the optimal control problem in the finite time domain based on the current system state and the predicted production plan disturbances in the future. The decision variables for this optimal control problem include the fuel valve position and the setpoint of each pump frequency in multiple future sampling periods. The objective is to minimize the sum of total fuel consumption and pumping power consumption in the prediction time domain. The first element of the optimal control sequence obtained by solving is applied to the actuator at the current time, and rolling optimization is performed again in the next cycle.

4. The energy-saving and environmentally friendly petroleum coke calcination system according to claim 3, characterized in that, In the heat balance optimization algorithm module, the objective function is to minimize the weighted sum of fuel consumption and total power consumption of each circulating pump in the prediction time domain; The constraints include a main burner outlet temperature of not less than 1250 degrees Celsius, a high-temperature radiant heat exchanger outlet flue gas temperature of not more than 650 degrees Celsius, and an upper limit of 250 degrees Celsius for the temperature of the circulating cooling medium.

5. The energy-saving and environmentally friendly petroleum coke calcination system according to claim 4, characterized in that, The system also includes an emergency thermal bypass and protection subsystem; The emergency heat bypass and protection subsystem consists of high-temperature flue gas bypass valves installed before and after the high-temperature radiant heat exchanger, an emergency radiator installed on the jacket of the circulating cooling medium, and interlocking control logic. When the intelligent thermal control unit detects that the outlet flue gas temperature of the high-temperature radiant heat exchanger is greater than the safety threshold of 650 degrees Celsius, or the medium temperature in the circulating cooling medium jacket is greater than the safety threshold of 250 degrees Celsius, the interlock control logic is immediately activated, partially opening the high-temperature flue gas bypass valve and introducing the overheated cooling medium into the emergency radiator for forced air cooling.

6. The energy-saving and environmentally friendly petroleum coke calcination system according to claim 5, characterized in that, The embedded heat pipe array is arranged in a non-uniform density according to the temperature field distribution characteristics of the outer surface of the kiln. In the axial direction of the kiln body, the heat pipes are arranged at a higher density in the zone of intense calcination reaction than in the preheating zone and the cooling zone. In the circumferential direction, the density of heat pipes in the lower half of the kiln body is greater than that in the upper half.

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