Method for utilizing low-temperature waste heat of carbon plant

Abstract

The application discloses a method for utilizing low-temperature waste heat in a carbon factory, which comprises the following steps: recovering heat from high-temperature flue gas and material cooling sections of a tank-type calcining furnace and converging the heat to obtain first waste heat conducting oil; recovering heat from main flue gas and cooling furnace chambers of a baking furnace and converging the heat to obtain second waste heat conducting oil; recovering heat from low-temperature flue gas of the tank-type calcining furnace to obtain third waste heat conducting oil; dividing first-level heat utilization terminals, second-level heat utilization terminals and third-level heat utilization terminals according to heat utilization temperature requirements of production processes; respectively supplying the first waste heat conducting oil, the second waste heat conducting oil and the third waste heat conducting oil to the first-level heat utilization terminals, the second-level heat utilization terminals and the third-level heat utilization terminals; and distributing low-temperature oil return of each heat utilization terminal to a conducting oil inlet of each waste heat recovery link according to a preset oil return priority based on heat utilization parameters of each heat utilization terminal. The technical scheme provided by the application can improve utilization rate of low-temperature waste heat in the carbon factory.

Description

Technical Field

[0001] This application belongs to the field of energy-saving technology in the production of carbon products for aluminum, and particularly relates to a method for utilizing low-temperature waste heat in carbon plants. Background Technology

[0002] With the development of the electrolytic aluminum industry and carbon manufacturing technology, the production scale of carbon products such as prebaked anodes continues to expand. Core high-temperature processes such as calcination and roasting generate a large amount of waste heat resources. Recovering and utilizing this waste heat is an important way to reduce production energy consumption and improve production efficiency. However, existing waste heat recovery systems in carbon plants generally suffer from incomplete coverage and a lack of resource allocation mechanisms. Not only is it difficult to effectively recover the material cooling heat and low-temperature flue gas waste heat from the calcination process, as well as the decentralized cooling hot air waste heat from the roasting process, but the waste heat resources cannot be graded and precisely allocated according to the heat temperature requirements of different production stages. This easily leads to mismatches between waste heat supply and demand, and surplus waste heat cannot be reused across processes. As a result, the overall utilization rate of low-temperature waste heat in the entire plant is low, causing a waste of energy resources and increasing carbon emissions in the production process.

[0003] Therefore, how to improve the utilization rate of low-temperature waste heat in carbon plants has become an urgent technical problem to be solved. Summary of the Invention

[0004] The embodiments of this application provide a method for utilizing low-temperature waste heat in a carbon plant, which can at least improve the utilization rate of low-temperature waste heat in the carbon plant to a certain extent.

[0005] Other features and advantages of this application will become apparent from the following detailed description, or may be learned in part from practice of this application.

[0006] According to a first aspect of the embodiments of this application, a method for utilizing low-temperature waste heat in a carbon plant is provided. The method includes: recovering and converging heat from the high-temperature flue gas and material cooling section of a tank calciner to obtain a first-path waste heat transfer oil; recovering and converging heat from the main flue gas and cooling chamber of a roasting furnace to obtain a second-path waste heat transfer oil; recovering heat from the low-temperature flue gas of the tank calciner to obtain a third-path waste heat transfer oil; dividing the heat-using terminals into primary, secondary, and tertiary heat-using terminals according to the heat temperature requirements of the production process; supplying the first-path, second-path, and third-path waste heat transfer oils to the primary, secondary, and tertiary heat-using terminals respectively; and, based on the heat parameters of each heat-using terminal and according to a preset oil return priority, allocating the low-temperature return oil from each heat-using terminal to the heat transfer oil inlet of each waste heat recovery link to ensure the temperature stability of the first-path waste heat transfer oil.

[0007] In some embodiments of this application, based on the aforementioned scheme, the step of recovering heat from the high-temperature flue gas and material cooling section of the tank calciner and converging them to obtain a first waste heat transfer oil includes: setting a heat transfer oil jacket in the tank cooling section of the tank calciner; absorbing the cooling heat of the calcined material through circulating heat transfer oil; and absorbing the heat from the high-temperature flue gas of the tank calciner through a waste heat boiler; converging the heat transfer oil corresponding to the material cooling heat and the heat transfer oil corresponding to the high-temperature flue gas and adjusting the flow rate to obtain the first waste heat transfer oil with a temperature in a first temperature range.

[0008] In some embodiments of this application, based on the aforementioned scheme, the step of recovering heat from the main flue gas of the calcining furnace and the cooling furnace chamber and converging them to obtain a second waste heat transfer oil includes: setting a movable exhaust frame at the observation hole of the forced cooling furnace chamber of the calcining furnace to extract hot air with a temperature in the second temperature range; introducing the hot air into the annular flue through the exhaust frame interface to mix with the flue gas discharged from the main flue of the calcining furnace to obtain mixed flue gas with a temperature in the third temperature range; and setting a ceramic tube heat exchanger at the outlet of the annular flue of the calcining furnace to absorb the heat of the mixed flue gas through circulating heat transfer oil to obtain the second waste heat transfer oil with a temperature in the fourth temperature range.

[0009] In some embodiments of this application, based on the foregoing scheme, the step of recovering heat from the low-temperature flue gas of the tank calciner to obtain the third waste heat transfer oil includes: installing a ceramic tube heat exchanger at the outlet of the flue gas waste heat boiler of the tank calciner, and absorbing the heat of the low-temperature flue gas with a temperature in the fifth temperature range through circulating heat transfer oil to obtain the third waste heat transfer oil with a temperature in the sixth temperature range.

[0010] In some embodiments of this application, based on the foregoing scheme, the method further includes: setting up a mixing heat exchange tank, mixing and adjusting the temperature of waste heat transfer oils at different temperatures through the mixing heat exchange tank, wherein a stirrer is provided inside the mixing heat exchange tank; dividing the heat transfer oil after temperature adjustment by the mixing heat exchange tank into a first temperature level and a second temperature level, wherein the first temperature level is used to supply the primary heat-using terminal and the secondary heat-using terminal, and the second temperature level is used to supply the secondary heat-using terminal and the tertiary heat-using terminal, wherein the first temperature level is higher than the second temperature level.

[0011] In some embodiments of this application, based on the foregoing scheme, the method further includes: when the heat demand of the primary heat-using terminal is saturated and there is a surplus of the first-path waste heat transfer oil, the surplus first-path waste heat transfer oil is introduced into the mixing heat exchange tank for temperature adjustment and then distributed to the secondary heat-using terminal and the tertiary heat-using terminal; when the heat demand of the secondary heat-using terminal is saturated and there is a surplus of the second-path waste heat transfer oil, the surplus second-path waste heat transfer oil is introduced into the mixing heat exchange tank for temperature adjustment and then distributed to the tertiary heat-using terminal.

[0012] In some embodiments of this application, based on the aforementioned scheme, the mixing heat exchange tank is provided with an insulation layer on the outside, and the internal storage temperature is maintained in the seventh temperature range. The standby capacity meets the low-load heat demand of the carbon plant within a preset time period. When the heat demand of the carbon plant is saturated, the excess waste heat transfer oil is introduced into the mixing heat exchange tank for storage. When the heat demand rises, the stored heat transfer oil is released to supplement the energy supply.

[0013] In some embodiments of this application, based on the aforementioned scheme, the preset oil return priority includes: the waste heat recovery stage corresponding to the first waste heat transfer oil has a higher priority than the waste heat recovery stage corresponding to the second waste heat transfer oil; the waste heat recovery stage corresponding to the second waste heat transfer oil has a higher priority than the waste heat recovery stage corresponding to the third waste heat transfer oil.

[0014] In some embodiments of this application, based on the aforementioned scheme, before allocating the low-temperature return oil of each heat-using terminal to the heat transfer oil inlet of each waste heat recovery stage according to a preset return oil priority based on the heat parameters of each heat-using terminal, the method further includes: setting a temperature sensor and a heat load acquisition device at each heat-using terminal to collect the current temperature, target temperature and real-time heat load of each heat-using terminal in real time; and transmitting the collected current temperature, target temperature and real-time heat load as the heat parameters to the control system.

[0015] In some embodiments of this application, based on the foregoing scheme, the method further includes: setting up a gas-fired waste heat boiler in the generation stage of the first waste heat transfer oil, and when the temperature of the high-temperature flue gas or the cooling heat of the material in the tank calciner flues, supplementing the heat through the gas-fired waste heat boiler to maintain the temperature of the first waste heat transfer oil within the first temperature range.

[0016] Based on the technical solution proposed in this application, the current situation of limited coverage, mismatch between supply and demand of waste heat resources, and low overall utilization rate in traditional carbon plants can be effectively improved. This application simultaneously recovers high-temperature flue gas, material cooling heat, and low-temperature flue gas from the tank calciner, as well as flue gas from the main flue of the roasting furnace and waste heat from the cooling furnace chamber. By incorporating all the dispersed low-temperature waste heat from multiple sources into a unified recovery system, the coverage of waste heat recovery can be significantly expanded, increasing the total amount of usable waste heat from the source. Furthermore, according to the heat temperature requirements of the production process, three levels of heat-using terminals are defined, and three channels of waste heat transfer oil with different temperature levels are precisely matched with the corresponding heat-using terminals, realizing the tiered utilization of waste heat resources. This avoids the energy quality waste caused by using high-quality waste heat in low-demand scenarios and improves the overall efficiency of waste heat utilization. Furthermore, by combining a dynamic oil return distribution mechanism based on heat parameters and a preset oil return priority, the temperature stability of the core high-temperature circuit can be prioritized under fluctuating waste heat conditions. This ensures that the recovered waste heat can be stably put into production for reuse, reducing waste heat idleness and emissions. Ultimately, this significantly improves the comprehensive utilization rate of low-temperature waste heat in carbon plants and reduces the consumption of purchased energy and carbon emissions in the production process. Attached Figure Description

[0017] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. It is obvious that the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort. In the drawings: Figure 1 A flowchart of a method for utilizing low-temperature waste heat in a carbon plant, as illustrated in an embodiment of this application, is shown. Figure 2 A schematic diagram of the multi-source waste heat collection and staged heat exchange process in an embodiment of this application is shown; Figure 3 The following diagram illustrates the priority control logic of the intelligent allocation unit in an embodiment of this application. Detailed Implementation

[0018] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0019] Furthermore, the described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. Numerous specific details are provided in the following description to give a thorough understanding of embodiments of this application. However, those skilled in the art will recognize that the technical solutions of this application can be practiced without one or more of the specific details, or other methods, components, apparatuses, steps, etc., can be employed. In other instances, well-known methods, apparatuses, implementations, or operations are not shown or described in detail to avoid obscuring various aspects of this application.

[0020] The block diagrams shown in the accompanying drawings are merely functional entities and do not necessarily correspond to physically independent entities. That is, these functional entities can be implemented in software, in one or more hardware modules or integrated circuits, or in different network and / or processor devices and / or microcontroller devices. It should also be noted that, for the sake of simplicity, certain components in the drawings that do not affect the interpretation of the technical solution of this application have been appropriately omitted.

[0021] The flowchart shown in the attached diagram is for illustrative purposes only and does not necessarily include all content and operations / steps, nor does it necessarily have to be performed in the described order. For example, some operations / steps can be broken down, while others can be combined or partially combined. Therefore, the actual execution order may change depending on the actual situation.

[0022] In the description of this application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "multiple" means two or more.

[0023] This application proposes a scheme for utilizing low-temperature waste heat in carbon plants, which aims to improve the utilization rate of low-temperature waste heat in carbon plants, thereby avoiding the waste of energy resources and mitigating carbon emissions during the production process.

[0024] Next, this application will elaborate on the proposed low-temperature waste heat utilization scheme for carbon plants. (Refer to...) Figure 1 The flowchart illustrates a method for utilizing low-temperature waste heat from a carbon plant, as described in an embodiment of this application. Figure 1 As shown, the method includes at least steps 110 to 140, which are described in detail below: In step 110, heat is recovered from the high-temperature flue gas and material cooling section of the calciner and collected to obtain the first waste heat transfer oil; heat is recovered from the main flue gas and cooling chamber of the roasting furnace and collected to obtain the second waste heat transfer oil; and heat is recovered from the low-temperature flue gas of the calciner to obtain the third waste heat transfer oil.

[0025] In this application, step 110 is mainly the waste heat recovery link in the entire waste heat utilization scheme. Its core is to convert the originally scattered and wasteful multi-source low-temperature waste heat in the two core processes of calcination and roasting in the carbon plant into heat transfer oil carriers of different temperature levels through heat exchange devices, providing a heat source basis for subsequent graded utilization and intelligent allocation. In the traditional carbon plant production system, waste heat recovery is mostly only for a single heat source of a single process. For example, only the high-temperature flue gas of the calcination furnace is recovered for heating the molding process. A large amount of material cooling heat, low-temperature flue gas heat, and roasting cooling hot air are directly lost to the environment, causing serious energy waste. Step 110, through the three-way parallel waste heat recovery design, can comprehensively cover the high and low temperature flue gas and material cooling heat of the calcination process, as well as the main flue gas and cooling furnace hot air of the roasting process, realizing the full recovery of the main low-temperature waste heat of the entire plant.

[0026] Next, this application will provide a detailed description of the recovery process of the three waste heat transfer oils: In such Figure 1 In step 110, the process of recovering heat from the high-temperature flue gas and material cooling section of the calciner and converging it to obtain the first waste heat transfer oil can be performed according to steps 111 to 112 as follows: Step 111: A heat transfer oil jacket is installed in the cooling section of the tank body of the tank calciner to absorb the cooling heat of the calcined material through circulating heat transfer oil, and to absorb the high-temperature flue gas heat of the tank calciner through a waste heat boiler.

[0027] Step 112: Merge the heat transfer oil corresponding to the material cooling heat with the heat transfer oil corresponding to the high temperature flue gas and adjust the flow rate to obtain the first waste heat heat transfer oil with the temperature in the first temperature range.

[0028] In this application, the heat transfer oil jacket can be a closed jacket structure surrounding the outer wall of the cooling section of a tank furnace, with circulating heat transfer oil flowing inside the jacket.

[0029] In actual production, the temperature of freshly calcined coke can typically reach 600 to 800 degrees Celsius. During the cooling section, the heat from the material is transferred through the furnace wall to the heat-conducting oil in the jacket, thus achieving simultaneous material cooling and heat recovery. In traditional processes, this cooling section usually uses a water jacket structure, where the cooling water absorbs heat and then dissipates it directly into the air through a cooling tower, resulting in complete heat loss. This application uses a heat-conducting oil jacket instead of a traditional water jacket, effectively collecting this previously wasted cooling heat without affecting the material cooling effect.

[0030] In this application, the waste heat boiler can be installed at the high-temperature flue gas outlet of a tank-type calciner. The temperature of the high-temperature flue gas discharged from the calciner can typically reach 800 to 1100 degrees Celsius. When the flue gas flows through the waste heat boiler, it transfers heat to the heat transfer oil inside the boiler, thereby realizing the recovery of waste heat from the high-temperature flue gas. This waste heat boiler can be equipped with a fully automatic gas-fired supplementary heating module, which supplements the heat by burning a small amount of gas when the waste heat is insufficient, ensuring a stable output oil temperature.

[0031] After the high-temperature flue gas from the tank-type calciner and the heat transfer oil from the material cooling section have absorbed heat, they can be converged into the same main pipeline through a manifold. The flow ratio of the two heat transfer oils is adjusted separately by an electric regulating valve, and combined with real-time feedback from temperature sensors, the temperature of the converged heat transfer oil can be stably controlled within a first temperature range of 240 to 280 degrees Celsius. The heat transfer oil in this temperature range is the highest quality waste heat carrier in the entire plant, capable of meeting the high-temperature heat requirements of the core production processes.

[0032] This application can effectively expand the scope of waste heat recovery in the calcination process by synergistically recovering and converging temperature control of the two heat sources mentioned above, and incorporate the material cooling heat that was originally directly lost into the recovery system. At the same time, the output oil temperature can be stably controlled by flow regulation, providing a reliable high-temperature heat source for subsequent core production processes, thereby improving the total amount of waste heat recovered and the heating stability of the calcination process from the source.

[0033] In such Figure 1 In step 110, the process of recovering heat from the main flue gas of the calcining furnace and the cooling furnace chamber and converging it to obtain the second waste heat transfer oil can be performed according to steps 113 to 115 as follows: Step 113: Install a movable air extraction frame at the observation hole of the forced cooling furnace chamber of the roasting furnace to extract hot air with a temperature in the second temperature range.

[0034] Step 114: The hot air is introduced into the annular flue through the exhaust frame interface and mixed with the flue gas discharged from the main flue of the roasting furnace to obtain mixed flue gas with a temperature in the third temperature range.

[0035] Step 115: A ceramic tube heat exchanger is installed at the annular flue outlet of the calcining furnace to absorb the heat of the mixed flue gas through circulating heat transfer oil, thereby obtaining the second waste heat transfer oil with a temperature in the fourth temperature range.

[0036] In this application, the cooling chambers of the roasting furnace are typically evenly distributed along the annular furnace body, and different chambers are in different roasting cycles. Only the chambers in the cooling stage will discharge high-temperature hot air. Therefore, this heat source is characterized by its dispersed distribution and dynamic location that changes with the production cycle. Traditional fixed pipelines are difficult to collect effectively, and for a long time, it has been directly discharged into the workshop environment. This application uses a movable exhaust frame, which can be flexibly moved to the observation hole position of the corresponding cooling chamber according to the roasting cycle of the furnace chamber, extending into the furnace chamber to extract high-temperature hot air, thus effectively solving the problem of difficult collection of dispersed heat sources.

[0037] In this application, the extracted hot air can be connected to the exhaust frame interface via a high-temperature resistant hose, ultimately converging into the annular flue of the roasting furnace, where it mixes with the roasting flue gas discharged from the main flue. The flue gas temperature in the main flue of a traditional roasting furnace is typically between 220 and 280 degrees Celsius. After mixing with cooling hot air at 250 to 400 degrees Celsius (i.e., the second temperature range), the overall flue gas temperature can be raised to a third temperature range of 280 to 350 degrees Celsius. This increase in flue gas temperature effectively increases the heat exchange temperature difference, improving the efficiency of subsequent heat exchange processes and the output oil temperature.

[0038] In this application, the mixed flue gas enters the ceramic tube heat exchanger at the outlet of the annular flue and undergoes indirect heat exchange with the heat transfer oil flowing inside the tube, transferring heat to the heat transfer oil to obtain a second waste heat heat transfer oil at 220 to 260 degrees Celsius (i.e., the fourth temperature range).

[0039] In this application, ceramic tubes are used as heat exchange elements because the calcination flue gas contains a large amount of dust, tar, and corrosive gases. Ordinary metal heat exchangers are prone to scaling, corrosion, and rapid wear, resulting in short service life and high maintenance costs. Ceramic materials have excellent properties such as high temperature resistance, corrosion resistance, and wear resistance, making them very suitable for heat exchange scenarios involving dusty and corrosive flue gas, and can effectively improve the service life and operational stability of the equipment.

[0040] In this application, the residence time of the flue gas in the ceramic tube heat exchanger can be set to greater than or equal to 3 seconds. This ensures that the flue gas has sufficient time to exchange heat with the heat transfer oil within the heat exchanger, preventing insufficient heat exchange due to excessively high flue gas flow rate. In this application, the circulating flow rate of the heat transfer oil can be set to 3 to 5 cubic meters per hour. This matches the total heat generated at the flue gas temperature and flow rate, ensuring that the outlet temperature of the heat transfer oil remains stable within the target range, while avoiding energy waste from the circulating pump due to excessive flow rate.

[0041] In this application, when applied to high-altitude areas with an altitude of not less than 3000 meters, the heat transfer coefficient of flue gas decreases under low-pressure environments. Therefore, the thickness of the outer insulation layer of the jacket in the cooling section of the calcining furnace can be appropriately increased to reduce heat loss. Simultaneously, the flue gas residence time in the ceramic tube heat exchanger of the calcining furnace is extended to ensure heat exchange efficiency. Through this targeted parameter adjustment, this solution can be adapted to production scenarios at different altitudes, thus having a wider range of applications.

[0042] This application uses a movable exhaust frame to collect dispersed cooling hot air, which is then mixed with the flue gas in the main flue to increase the heat exchange temperature zone. Combined with a ceramic tube heat exchanger, it achieves stable medium-temperature hot oil output, which can effectively fill the technical gap in the large-scale recovery of low-temperature waste heat in the roasting process, significantly improve the amount of waste heat recovered in the roasting process, and the flexible collection method can also be well adapted to the periodic production characteristics of the roasting furnace, ensuring the waste heat recovery efficiency throughout the entire production cycle.

[0043] In such Figure 1 In step 110, the step of recovering heat from the low-temperature flue gas of the calciner to obtain the third waste heat transfer oil can be performed according to step 116 as follows: Step 116: A ceramic tube heat exchanger is installed at the outlet of the waste heat boiler of the calcining furnace. The heat from the low-temperature flue gas in the fifth temperature range is absorbed by circulating heat transfer oil to obtain the third waste heat transfer oil in the sixth temperature range.

[0044] In this application, after the high-temperature flue gas from the calcining furnace recovers its high-temperature heat in the main waste heat boiler, the flue gas temperature drops to the fifth temperature range of 200 to 250 degrees Celsius. This portion of flue gas is typical low-temperature flue gas. Due to its low temperature, traditional metal heat exchangers have low heat exchange efficiency and are prone to corrosion. Existing processes typically do not recover this heat and directly discharge it into the atmosphere through the chimney, resulting in a significant waste of low-grade waste heat. This application adds a ceramic tube heat exchanger to the outlet flue of the waste heat boiler as a deep waste heat recovery device. This device can further absorb the waste heat from this portion of low-temperature flue gas, further reducing the flue gas temperature before discharge, thus achieving cascaded recovery of waste heat.

[0045] In this application, the flue gas velocity within the heat exchanger can be controlled within the range of 1.8 to 2.2 meters per second, which is an optimized value after comprehensively considering heat exchange efficiency, equipment wear, and investment costs. If the flue gas velocity is too low, the heat transfer coefficient of the flue gas within the heat exchanger will decrease, requiring a larger heat exchange area to achieve the target heat exchange capacity, thus increasing the equipment's investment cost and floor space. If the flue gas velocity is too high, dust particles in the flue gas will cause severe erosion and wear on the inner wall of the ceramic tubes, shortening the equipment's service life. Insufficient flue gas residence time will also lead to inadequate heat exchange, making it difficult for the outlet oil temperature to meet design requirements.

[0046] In this application, the flue gas velocity in the ceramic tube heat exchanger can be controlled within a velocity range of 1.8 to 2.2 meters per second, ensuring heat exchange efficiency while taking into account the service life and operating economy of the equipment.

[0047] This application, by adding a low-temperature ceramic tube heat exchanger at the tail end of the waste heat boiler, can deeply recover the waste heat of the calcination low-temperature flue gas that was originally directly emitted, further tapping the waste heat potential of the calcination process. The resulting low-temperature heat transfer oil at 160 to 190 degrees Celsius (i.e., the sixth temperature range) can accurately match the low-grade heat demand in the plant area, avoiding the waste of energy quality from using high-temperature waste heat to supply low-temperature scenarios, realizing the cascade utilization of energy, and effectively improving the overall utilization efficiency of waste heat in the entire plant.

[0048] Continue to refer to Figure 1 In step 120, the heat-using terminals are divided into primary heat-using terminals, secondary heat-using terminals and tertiary heat-using terminals according to the heat temperature requirements of the production process.

[0049] In the production process of carbon products, the heat temperature requirements of different processes and stages vary significantly, and their impact on production also differs. If a uniform high-temperature heat source is used to supply all heat-using stages without grading, it will result in a serious problem of high energy being underutilized, with a large amount of high-quality heat being wasted in low-demand scenarios. Therefore, in step 120 above, the entire plant's heat-using terminals can be divided into three levels according to the temperature requirements and production importance of each heat-using stage. This allows for a precise matching relationship with the three different temperature-controlled waste heat transfer oils mentioned earlier, laying the foundation for graded adaptation of waste heat.

[0050] In this application, the primary heat-using terminal may include asphalt melting equipment, a dry material preheating screw, a kneader, and a vibration molding machine. Specifically, the primary heat-using terminal corresponds to the core production process of carbon product molding, has the highest temperature requirements, and directly determines the quality of the final product. The asphalt melting equipment needs to heat the solid asphalt to a completely molten state and maintain a suitable viscosity to ensure the uniformity of the subsequent kneading process. The dry material preheating screw, kneader, and vibration molding machine need to maintain a stable high temperature to ensure the paste has good plasticity and fluidity, preventing the paste from cooling and clumping, which would affect the molding quality. These stages not only have high temperature requirements but also the most stringent requirements for temperature stability.

[0051] In this application, the secondary heat terminal may include asphalt pipeline insulation equipment and raw coke drying equipment. Specifically, the temperature requirement of the secondary heat terminal is slightly lower than that of the core forming process, and it is an important auxiliary link in production. The function of the asphalt pipeline insulation equipment is to maintain the temperature of the molten asphalt in the conveying pipeline, preventing the asphalt from cooling and solidifying during long-distance transportation, which could cause pipeline blockage. The raw coke drying equipment is used to remove moisture from the raw petroleum coke, preventing excessive moisture content from affecting the stable operation of the calcining furnace and the quality of the calcined coke. The temperature requirement of this part is at a moderate level, and it can be met by using a medium-temperature waste heat carrier.

[0052] When the moisture content of raw coke is high, for example, not less than 1.0%, the heat load of the raw coke drying process can be increased to 550 to 600 kilowatts, the temperature of the waste heat transfer oil supplied to the raw coke drying process can be adjusted to 205 to 210 degrees Celsius, and the target temperature for raw coke drying can be increased to 195 to 200 degrees Celsius. This ensures that the moisture content of the dried raw coke is stably controlled within the qualified range, and avoids the adverse effects of raw material moisture fluctuations on subsequent production.

[0053] In this application, the three-stage heat-using terminals may include preheating equipment for batching silos, preheating equipment for chutes, insulation equipment for raw block warehouses, and heating equipment for factory living quarters. Specifically, the three-stage heat-using terminals have the lowest temperature requirements and are mostly used for auxiliary production and living heating scenarios. Preheating of batching silos and chutes can prevent cold materials from entering the kneading process, causing a sudden drop in paste temperature and affecting kneading quality. Winter insulation of raw block warehouses can prevent newly formed raw blocks from cracking due to excessively low ambient temperatures, thus improving the yield. Factory living heating includes scenarios such as hot water for employee showers and winter heating for workshops and office buildings. These processes do not have high temperature requirements, and low-grade waste heat can fully meet the needs.

[0054] This application classifies heat-using terminals according to temperature requirements and production importance, allowing waste heat carriers of different qualities to find the most suitable heat-using scenarios, thus avoiding energy waste from high-energy underutilization at the source. It also provides a clear classification basis for subsequent priority control and intelligent allocation, which helps to achieve optimal allocation of waste heat resources.

[0055] Continue to refer to Figure 1 In step 130, the first waste heat transfer oil, the second waste heat transfer oil, and the third waste heat transfer oil are respectively supplied to the primary heat-using terminal, the secondary heat-using terminal, and the tertiary heat-using terminal.

[0056] This application employs a tiered heat supply model, where the highest-temperature waste heat transfer oil (first stream) is prioritized for supplying the primary heat-consuming terminals with the highest temperature requirements; the second stream (medium-temperature) supplies the secondary heat-consuming terminals; and the third stream (lowest-temperature) supplies the tertiary heat-consuming terminals. This one-to-one supply method ensures precise matching between heat source quality and heat demand. The heat transfer oil is directly transported from the recovery stage to the applicable heat-consuming terminals, minimizing the heat exchange path, reducing heat loss during pipeline transportation, and maximizing the system's basic operating efficiency.

[0057] Under normal and stable production conditions, the output of waste heat from each source basically matches the heat demand of the corresponding terminal. The system can operate according to this basic mode, with simple and clear control logic and low operation and maintenance costs. When the operating conditions fluctuate and the waste heat output deviates from the heat demand, dynamic adjustments are made through subsequent allocation mechanisms.

[0058] This application enables the primary tiered configuration of waste heat resources by directly supplying three waste heat sources to three levels of heat-using terminals, minimizing energy quality loss caused by mixing heat transfer oils at different temperatures, and improving the overall efficiency of waste heat utilization. At the same time, the direct supply mode under basic operating conditions simplifies the system's control logic and reduces the complexity of operation and maintenance.

[0059] Continue to refer to Figure 1 In step 140, based on the heat usage parameters of each heat-using terminal, and according to the preset oil return priority, the low-temperature return oil of each heat-using terminal is allocated to the heat transfer oil inlet of each waste heat recovery link to ensure the temperature stability of the first waste heat heat transfer oil.

[0060] In this application, after the heat transfer oil releases heat at each heat-using terminal, its own temperature drops, becoming low-temperature return oil. This oil needs to be transported back to each waste heat recovery stage to absorb heat and reheat, completing a closed-loop cycle. The distribution method of the return oil directly affects the output temperature and circulation flow rate of each waste heat heat transfer oil, which is crucial for the stable operation of the entire circulation system.

[0061] In this application, the return oil is not evenly distributed across each recovery stage, but rather dynamically allocated based on real-time heat usage parameters collected from each heat-using terminal, combined with preset priority rules. This allows for flexible adjustment of the circulation flow rate of each path according to the actual heat load and waste heat output, ensuring temperature stability in the core loop.

[0062] In this application, steps 151 to 152 may also be performed: Step 151: Set up a mixing heat exchange tank to mix and adjust the temperature of waste heat transfer oils at different temperatures. The mixing heat exchange tank is equipped with a stirrer.

[0063] Step 152: The heat transfer oil after being conditioned by the mixing heat exchange tank is divided into a first temperature level and a second temperature level. The first temperature level is used to supply the primary heat-using terminal and the secondary heat-using terminal, and the second temperature level is used to supply the secondary heat-using terminal and the tertiary heat-using terminal. The first temperature level is higher than the second temperature level.

[0064] In this application, the operating speed of the stirrer can be set to 60 to 80 revolutions per minute; the first temperature setting can be set to 220 to 240 degrees Celsius; and the second temperature setting can be set to 190 to 220 degrees Celsius.

[0065] In this application, the mixing heat exchange tank serves as the heat distribution hub of the entire system. Its main function is to uniformly mix waste heat transfer oils at different temperatures to produce heat transfer oils that meet specific temperature requirements for cross-level heat distribution. The agitator installed inside the mixing heat exchange tank accelerates the convective mixing of the heat transfer oils within the tank through mechanical stirring, allowing the heat transfer oils at different temperatures to quickly reach a uniform temperature and preventing temperature stratification within the tank. The agitator speed is set to 60 to 80 revolutions per minute, which ensures uniform mixing while avoiding excessive speed that could cause air bubbles in the heat transfer oil or increase unnecessary stirring energy consumption.

[0066] In this application, the temperature-adjusted heat transfer oil can be divided into two standard temperature ranges. This allows it to adapt to the temperature requirements of different levels of heating terminals and simplifies the distribution and control logic. The first temperature range of 220 to 240 degrees Celsius can simultaneously meet the minimum temperature requirements of both primary and secondary heating terminals, making it suitable for supplementing heating gaps in either primary or secondary terminals. The second temperature range of 190 to 220 degrees Celsius can simultaneously meet the temperature requirements of both secondary and tertiary heating terminals, making it suitable for allocating surplus heat from secondary to tertiary levels or supplementing the heating needs of tertiary terminals.

[0067] This application enables flexible allocation of waste heat transfer oil at different temperatures by setting up a mixing heat exchange tank with stirring and dividing it into standard temperature adjustment levels. This breaks the traditional limitation that waste heat from a single process can only be used for a single purpose, allowing surplus waste heat to flow across different levels of heat-using terminals. This significantly improves the flexibility of waste heat resource allocation and further enhances the overall utilization rate of waste heat throughout the plant.

[0068] In this application, steps 161 to 162 may also be performed: Step 161: When the heat demand of the primary heat-using terminal is saturated and there is a surplus of the first-line waste heat transfer oil, the surplus first-line waste heat transfer oil is introduced into the mixing heat exchange tank for temperature adjustment and then distributed to the secondary heat-using terminal and the tertiary heat-using terminal.

[0069] Step 162: When the heat demand of the secondary heat terminal is saturated and there is a surplus of the second waste heat transfer oil, the surplus second waste heat transfer oil is introduced into the mixing heat exchange tank for temperature adjustment and then distributed to the tertiary heat terminal.

[0070] In actual production, the output of waste heat and the demand of heat-using terminals change dynamically with factors such as production pace, raw material condition, and ambient temperature, making it difficult to maintain a perfect match at all times. For example, in winter, the demand for heating in the factory area is high, resulting in a high tertiary heat load. However, in summer, the demand for heating disappears, and the tertiary heat load drops significantly, potentially leading to a surplus of low-temperature waste heat. Alternatively, if the molding process reduces production, the primary heat load decreases, resulting in a surplus of high-temperature waste heat.

[0071] This application establishes a top-down, tiered surplus heat allocation mechanism. When surplus heat occurs at higher levels, it is not directly discharged and wasted. Instead, it is introduced into a mixing heat exchange tank, adjusted to a suitable temperature, and then supplied to the next level of heat-consuming terminals. Specifically, after the first level of heat consumption is saturated, the surplus high-temperature heat transfer oil can be allocated to the second and third level terminals; after the second level of heat consumption is saturated, the surplus medium-temperature heat transfer oil can be allocated to the third level terminal. This tiered allocation logic ensures that high-quality heat is prioritized to meet the needs of higher levels, and the surplus is then gradually utilized at lower levels, resulting in no idle or wasted heat throughout the process.

[0072] In this application, the surplus heat is allocated to the downstream terminals in a step-by-step manner, which can fully utilize the surplus heat under different operating conditions, avoid the idle discharge of waste heat resources, and improve the heating capacity of the downstream heat-using terminals without the need for additional heat sources. This enhances the system's adaptability to load fluctuations, maximizes the utilization of waste heat resources, and effectively improves the overall waste heat utilization rate of the entire plant.

[0073] In this application, the mixing heat exchange tank may be provided with an insulation layer on the outside, the internal storage temperature may be maintained in the seventh temperature range, and the standby capacity may meet the low-load heat demand of the carbon plant within a preset time period.

[0074] In this application, the seventh temperature range can be set to 180 to 230 degrees Celsius; the preset duration can be set to 1 to 2 hours.

[0075] In this application, the mixing heat exchange tank, in addition to its temperature regulation function, also possesses heat storage and energy storage capabilities. The external insulation layer of the tank effectively reduces heat loss from the heat transfer oil during storage, maintaining a stable internal temperature over a long period. The standby capacity is designed to meet the plant's low-load heat demand for 1 to 2 hours, determined based on the common duration of production fluctuations in carbon plants. This design can handle most short-term operational fluctuations without resulting in wasted investment due to an excessively large tank.

[0076] In this application, the following step 171 may also be performed: Step 171: When the heat demand of the carbon plant is saturated, the excess waste heat transfer oil is introduced into the mixing heat exchange tank for storage. When the heat demand increases, the stored heat transfer oil is released to supplement the energy supply.

[0077] Specifically, the energy storage mechanism in step 1171 above can transfer waste heat over time, playing a role in peak shaving and valley filling. For example, during full-load production during the day, the waste heat output is large, and the heat demand cannot be fully absorbed. The excess heat transfer oil can be stored in a mixing heat exchange tank. During low-load production at night, or when a certain process suddenly experiences a heat demand peak, the heat transfer oil stored in the tank can be released to supplement the heat supply, thus smoothing the fluctuations between supply and demand.

[0078] This application utilizes the heat storage function of the mixed heat exchange tank to smooth out the time and magnitude difference between waste heat supply and heat demand, realize the time dimension transfer of waste heat resources, improve the heating stability of the system, reduce the consumption of supplementary heating gas, and avoid the waste of heat emission during peak waste heat, further improve the utilization efficiency of waste heat resources, and make the system more adaptable to different production rhythms.

[0079] In this application, the preset oil return priority may include: the waste heat recovery stage corresponding to the first waste heat transfer oil has a higher priority than the waste heat recovery stage corresponding to the second waste heat transfer oil; the waste heat recovery stage corresponding to the second waste heat transfer oil has a higher priority than the waste heat recovery stage corresponding to the third waste heat transfer oil.

[0080] In this application, the priority of oil return is set one-to-one with the production importance level of the heat-using terminals. Since the primary heat-using terminal is the core of production and has the highest requirement for temperature stability, its corresponding first-stage waste heat recovery stage also enjoys the highest oil return priority. When allocating low-temperature oil return, the system prioritizes meeting the flow requirements of the first-stage recovery stage, ensuring sufficient heat transfer oil for circulation and heat exchange in the high-temperature circuit, maintaining stable output temperature. After meeting the requirements of the first stage, the remaining oil return is then allocated sequentially to the second and third-stage recovery stages.

[0081] This application, through a clear oil return priority setting, can prioritize the heating capacity of the core high-temperature circuit when the total circulation volume of heat transfer oil in the whole plant is limited or the total amount of waste heat is insufficient. This ensures the stable heat use of the core production process, avoids product quality degradation due to waste heat fluctuations, and effectively improves the operational reliability of the entire waste heat system.

[0082] In this application, as Figure 1Before step 140, that is, before distributing the low-temperature return oil of each heat-using terminal to the heat transfer oil inlet of each waste heat recovery stage according to the preset return oil priority based on the heat-using parameters of each heat-using terminal, the following steps 131 to 132 can also be performed: Step 131: Install temperature sensors and heat load acquisition devices at each heat-using terminal to collect the current temperature, target temperature and real-time heat load of each heat-using terminal in real time.

[0083] Step 132: The current temperature, target temperature and real-time heat load are collected and transmitted to the control system as the heat parameters. The response time of the control system can be less than or equal to 0.5 seconds.

[0084] In this application, the temperature sensors can be installed at the inlet and outlet of the heat transfer oil and the material outlet of each heat-using terminal to monitor the actual temperature of the heat exchange medium and the material in real time. The heat load acquisition device can calculate the real-time heat load of the terminal by collecting the inlet and outlet temperature difference and real-time flow rate of the heat transfer oil, combined with the specific heat capacity of the heat transfer oil. These parameters are the core data basis for the system's dynamic allocation, and the accuracy and frequency of parameter acquisition directly determine the accuracy and timeliness of the allocation.

[0085] In this application, the collected heat parameters can be transmitted to the central control system in real time via an industrial bus. The response time of the control system is set to be less than or equal to 0.5 seconds, which can ensure that when the production conditions fluctuate rapidly, the system can complete data calculation and valve adjustment in a very short time, avoiding large deviations in the temperature of the heat-using terminals.

[0086] In this application, the temperature control accuracy of the primary heating terminal can be controlled to ±3 degrees Celsius, the asphalt melting temperature can be controlled to 220 to 230 degrees Celsius, and the kneader temperature can be controlled to 180 to 190 degrees Celsius. The high-precision temperature control of the primary heating terminal ensures that the asphalt remains within a suitable melt viscosity range, maintaining the plasticity of the paste during kneading, thereby improving kneading uniformity and molding quality, and reducing waste caused by temperature fluctuations.

[0087] In this application, the temperature of the raw coke drying in the secondary heat terminal can be controlled at 180 to 200 degrees Celsius, and the moisture content of the dried material can be controlled to be less than or equal to 0.5%. Stable raw coke drying temperature and moisture content can ensure the stability of the raw coke properties entering the calcining furnace, avoid fluctuations in moisture content that cause fluctuations in the calcining furnace operating conditions, improve the quality stability of the calcined coke, and also reduce additional energy consumption during the calcination process.

[0088] In this application, the temperature for preheating the dry material in the three-stage heating terminal can be controlled to be between 120 and 140 degrees Celsius. A suitable preheating temperature for the dry material can reduce the temperature drop when the dry material enters the kneader, ensure the stability of the kneading temperature, and also prevent condensation on the surface of the material, thereby improving the uniformity of the batching.

[0089] This application utilizes a high-precision, real-time acquisition and rapid-response control system for heat-consuming parameters to achieve precise closed-loop temperature control at each heat-consuming terminal, ensuring long-term stability of process parameters in core production processes. This improves the quality consistency of carbon products and reduces the scrap rate. Simultaneously, precise load monitoring provides reliable data support for the dynamic allocation of waste heat, making oil return distribution and heat scheduling more accurate and timely, further enhancing system operating efficiency.

[0090] In this application, the following step 181 may also be performed: Step 181: A gas-fired waste heat boiler is set up in the generation stage of the first waste heat transfer oil. When the temperature of the high-temperature flue gas or the cooling heat of the material in the tank calciner flues, the gas-fired waste heat boiler is used to supplement the heat so as to maintain the temperature of the first waste heat transfer oil within the first temperature range.

[0091] In this application, when the temperature of the high-temperature flue gas or the cooling heat of the material in the tank calciner flues, the temperature of the first waste heat transfer oil will be lower than the preset range.

[0092] In this application, the gas-fired waste heat boiler is an integrated device that combines waste heat recovery and supplementary heating functions. Under normal operating conditions, it functions as a waste heat boiler, relying on the heat from the high-temperature flue gas to heat the thermal oil. The gas-fired supplementary heating function is only activated when the waste heat is insufficient. Supplementary heating is only applied to the highest priority first waste heat thermal oil circuit, which is the heat source corresponding to the core production process, ensuring the stability of the core process.

[0093] When the calcining furnace experiences fluctuations in feed rate, changes in raw material calorific value, or temporary production reductions, the temperature of the high-temperature flue gas or the total cooling heat of the material may decrease, causing the temperature of the first-stage waste heat transfer oil to fall below the preset range of 240 degrees Celsius. In this situation, the control system automatically activates the combustion module of the gas-fired waste heat boiler, supplementing the heat by burning a small amount of natural gas to bring the temperature of the transfer oil back to the first temperature range of 240 to 280 degrees Celsius, ensuring stable heating for the primary heat-consuming terminals. This precise heat supplementation mechanism, which only provides a small amount of supplementary heat to the core loop when waste heat is insufficient, solves the industry pain point of unstable heating in core processes caused by fluctuations in waste heat resources, ensuring the continuous and stable operation of core production processes, while avoiding energy waste from system-wide heat supplementation, thus balancing system stability and energy-saving benefits.

[0094] Reference Figure 2This diagram illustrates a multi-source waste heat collection and staged heat exchange process in an embodiment of this application. (Refer to...) Figure 3 The diagram shows the priority control logic of the intelligent allocation unit in the embodiments of this application.

[0095] To enable those skilled in the art to better understand this application, the following will be combined with Figure 2 and Figure 3 This paper provides several specific embodiments of the present application to further illustrate the feasibility and adaptability of the technical solution. All embodiments are based on a carbon plant with an annual production capacity of 200,000 tons of prebaked anodes, which is equipped with 8 pot furnaces and 2 roasting furnaces.

[0096] Example 1: Process parameters for waste heat recovery: High-temperature flue gas temperature in the tank calciner is 850°C; low-temperature flue gas temperature is 230°C; corresponding flue gas velocity in the ceramic tube heat exchanger is 2.0 m / s. High-temperature material temperature in the tank calciner is 620°C. Main flue gas temperature in the roasting furnace is 270°C; corresponding flue gas residence time in the ceramic tube heat exchanger is 3.5 seconds. Hot air recovery temperature in the cooling chamber of the roasting furnace is 350°C; corresponding heat transfer oil circulation flow rate in the ceramic tube heat exchanger is 4 cubic meters per hour.

[0097] Parameters for staged heating and temperature regulation: The initial temperature of the low-temperature heat transfer oil at the inlet of the ceramic tube heat exchanger is 130 degrees Celsius, which rises to 190 degrees Celsius after heat exchange. The temperature of the heat transfer oil mixed in the mixing heat exchange tank is adjusted to 230 degrees Celsius, the circulation flow rate is 6 cubic meters per hour, and the agitator speed is 70 revolutions per minute.

[0098] Intelligent allocation and heat terminal parameters: In the primary heat terminal, the heat load of the asphalt melting equipment and kneader is 800 kW, the heat transfer oil supply temperature is 220 to 230 degrees Celsius, and the temperature fluctuation is ±2 degrees Celsius. In the secondary heat terminal, the heat load of the raw coke drying equipment is 500 kW, the heat transfer oil supply temperature is 190 to 200 degrees Celsius, and the moisture content of the dried material is 0.4%. In the tertiary heat terminal, the heat load for dry material preheating is 300 kW, and the heat transfer oil supply temperature is 170 to 175 degrees Celsius.

[0099] Heat replenishment and energy storage: The heat replenishment function of the gas-fired waste heat boiler and the energy storage function of the mixing heat exchange tank were not activated.

[0100] Implementation results: The overall waste heat utilization rate of the plant reached 88%, which can save 4,800 tons of standard coal and reduce carbon dioxide emissions by 12,000 tons per year.

[0101] Example 2: This embodiment is applied to high-altitude areas with an altitude of not less than 3000 meters.

[0102] Waste heat recovery process parameters: The high-temperature flue gas temperature in the tank calciner is 800 degrees Celsius, and the flue gas velocity in the ceramic tube heat exchanger corresponding to the low-temperature flue gas in the tank calciner is adjusted to 2.2 meters per second. The high-temperature material temperature in the tank calciner is 600 degrees Celsius. The flue gas temperature in the main flue of the roasting furnace drops to 260 degrees Celsius, corresponding to a flue gas residence time of 4 seconds in the ceramic tube heat exchanger. The recovered hot air temperature in the cooling chamber of the roasting furnace is 300 degrees Celsius, corresponding to a heat transfer oil circulation flow rate of 5 cubic meters per hour in the ceramic tube heat exchanger.

[0103] Parameters for staged heating and temperature regulation: The initial temperature of the low-temperature heat transfer oil at the inlet of the ceramic tube heat exchanger is 120 degrees Celsius, which rises to 180 degrees Celsius after heat exchange. The temperature of the heat transfer oil mixed in the mixing heat exchange tank is adjusted to 220 degrees Celsius, the circulation flow rate is 7 cubic meters per hour, and the agitator speed is 75 revolutions per minute.

[0104] Intelligent allocation and heat terminal parameters: In the primary heat terminal, the heat load of the asphalt melting equipment and kneader is 750 kW, and the heat transfer oil supply temperature is 220 to 225 degrees Celsius. In the secondary heat terminal, the heat load of the raw coke drying equipment is 450 kW, the heat transfer oil supply temperature is 190 to 195 degrees Celsius, and the moisture content of the dried material is 0.45%. In the tertiary heat terminal, the heat load for dry material preheating is 280 kW, and the heat transfer oil supply temperature is 165 to 170 degrees Celsius. The mixing heat exchange tank storage temperature is 190 degrees Celsius, and the standby capacity accounts for 30% of the total capacity.

[0105] Heating and energy storage stage: The heating function of the gas waste heat boiler is activated, with a gas consumption of 5 cubic meters per hour. At the same time, the heat transfer oil at a temperature of 190 degrees Celsius in the mixing heat exchange tank is transported to the heat transfer oil inlet of the gas waste heat boiler. After mixing with the original return heat transfer oil, it is reheated to improve the stability of the heat transfer oil supply temperature of the primary heat-using terminal.

[0106] Implementation results: The overall waste heat utilization rate of the plant reached 82%, which can be well adapted to the high-altitude and low-pressure environment, and can save 4,200 tons of standard coal per year.

[0107] Example 3: This embodiment corresponds to summer production conditions.

[0108] Process parameters for waste heat recovery: The high-temperature flue gas temperature in the tank calciner is 1000 degrees Celsius; the low-temperature flue gas temperature in the tank calciner rises to 250 degrees Celsius, corresponding to a flue gas velocity of 1.8 m / s in the ceramic tube heat exchanger. The high-temperature material temperature in the tank calciner is 700 degrees Celsius. The flue gas temperature in the main flue of the roasting furnace is 290 degrees Celsius, corresponding to a flue gas residence time of 3 seconds in the ceramic tube heat exchanger. The recovered hot air temperature in the cooling chamber of the roasting furnace is 390 degrees Celsius, corresponding to a heat transfer oil circulation flow rate of 3.5 cubic meters per hour in the ceramic tube heat exchanger.

[0109] Parameters for the staged heating and temperature regulation process: The initial temperature of the low-temperature heat transfer oil at the inlet of the ceramic tube heat exchanger is 140 degrees Celsius, which rises to 200 degrees Celsius after heat exchange. The temperature of the heat transfer oil mixed in the mixing heat exchange tank is regulated to 240 degrees Celsius, and the circulation flow rate is 7 cubic meters per hour.

[0110] Intelligent heat allocation and terminal parameters: In the primary heat terminal, the heat load of the asphalt melting equipment and kneader is 850 kW, and the heat transfer oil supply temperature is 235 to 240 degrees Celsius. In the secondary heat terminal, the heat load of the raw coke drying equipment is 550 kW, and the heat transfer oil supply temperature is 200 to 205 degrees Celsius. In the tertiary heat terminal, the heat load of dry material preheating is 350 kW, and the heat transfer oil supply temperature is 175 to 180 degrees Celsius. Excess waste heat is introduced into a mixing heat exchange tank for storage at a storage temperature of 200 degrees Celsius. The stored heat released at night can meet 30% of the production heat demand.

[0111] Heat replenishment and energy storage: The gas-fired waste heat boiler's heat replenishment function was not activated.

[0112] Implementation results: The overall waste heat utilization rate of the plant reached 90%, saving 5,000 tons of standard coal annually.

[0113] Example 4: This embodiment corresponds to a production condition where the moisture content of the raw coke is not less than 1.0%.

[0114] Waste heat recovery process parameters: High-temperature flue gas temperature in the tank calciner is 880°C; low-temperature flue gas temperature is 240°C; correspondingly, the flue gas velocity in the ceramic tube heat exchanger is adjusted to 2.1 m / s. High-temperature material temperature in the tank calciner is 620°C. Main flue gas temperature in the roasting furnace is 280°C; correspondingly, the heat transfer oil circulation flow rate in the ceramic tube heat exchanger is increased to 4.5 cubic meters per hour. Hot air recovery temperature in the roasting furnace cooling chamber is 360°C; correspondingly, the heat transfer oil circulation flow rate in the ceramic tube heat exchanger is 4 cubic meters per hour.

[0115] Parameters for the staged heating and temperature regulation process: The initial temperature of the low-temperature heat transfer oil at the inlet of the ceramic tube heat exchanger is 135 degrees Celsius, which rises to 195 degrees Celsius after heat exchange. The temperature of the heat transfer oil mixed in the mixing heat exchange tank is adjusted to 210 degrees Celsius, and the circulation flow rate is 6.5 cubic meters per hour.

[0116] Intelligent allocation and heat terminal parameters: In the primary heat terminal, the heat load of the asphalt melting equipment and kneader is 800 kW, and the heat transfer oil supply temperature is 225 to 230 degrees Celsius. In the secondary heat terminal, the heat load of the raw coke drying equipment is increased to 600 kW, the heat transfer oil supply temperature is 205 to 210 degrees Celsius, the target drying temperature of the raw coke is 200 degrees Celsius, and the moisture content of the material after drying is reduced to 0.3%. In the tertiary heat terminal, the heat load for dry material preheating is 250 kW, and the heat transfer oil supply temperature is 165 to 170 degrees Celsius.

[0117] Heat replenishment and energy storage: The gas-fired waste heat boiler's heat replenishment function was not activated.

[0118] Implementation results: The overall waste heat utilization rate of the plant reached 86%, saving 4,600 tons of standard coal annually.

[0119] Example 5: This embodiment corresponds to the working condition of reduced production output and reduced total waste heat.

[0120] Process parameters for waste heat recovery: High-temperature flue gas temperature in the tank calciner is 810°C; low-temperature flue gas temperature is 205°C; correspondingly, the flue gas velocity in the ceramic tube heat exchanger is adjusted to 1.9 m / s. High-temperature material temperature in the tank calciner is 600°C. Main flue gas temperature in the roasting furnace is 230°C; correspondingly, the flue gas residence time in the ceramic tube heat exchanger is 3.2 seconds. Hot air temperature recovered in the cooling chamber of the roasting furnace is 360°C; correspondingly, the heat transfer oil circulation flow rate in the ceramic tube heat exchanger is 3 cubic meters per hour.

[0121] Parameters for the staged heating and temperature regulation process: The initial temperature of the low-temperature heat transfer oil at the inlet of the ceramic tube heat exchanger is 125 degrees Celsius, which rises to 185 degrees Celsius after heat exchange. The temperature of the heat transfer oil mixed in the mixing heat exchange tank is regulated to 225 degrees Celsius, and the circulation flow rate is 4.5 cubic meters per hour.

[0122] Intelligent allocation and heat terminal parameters: In the primary heat terminal, the heat load of the asphalt melting equipment and kneader is 500 kW, and the heat transfer oil supply temperature is 225 to 230 degrees Celsius. In the secondary heat terminal, the heat load of the raw coke drying equipment is 300 kW, and the heat transfer oil supply temperature is 190 to 195 degrees Celsius. In the tertiary heat terminal, the heat load of the dry material preheating is 180 kW, and the heat transfer oil supply temperature is 160 to 165 degrees Celsius. The storage temperature of the mixing heat exchange tank is 185 degrees Celsius.

[0123] Reheating and energy storage stage: The reheating function of the gas waste heat boiler is activated, with a gas consumption of 6 cubic meters per hour. At the same time, the heat transfer oil at a temperature of 185 degrees Celsius in the mixing heat exchange tank is transported to the inlet of the heat transfer oil jacket of the cooling section of the tank calciner. After mixing with the original return heat transfer oil, it absorbs heat again and increases the temperature, thereby improving the stability of the heat transfer oil supply temperature of the primary heat-using terminal.

[0124] Implementation results: The overall waste heat utilization rate of the plant reached 84%, the temperature fluctuation of each heat terminal was controlled within ±3 degrees Celsius, the energy consumption during the commissioning period was reduced by 35% compared with the traditional process, and 3,800 tons of standard coal can be saved annually.

[0125] Based on the above embodiments, it can be seen that in practical industrial applications, for a carbon plant with an annual production capacity of 200,000 tons of prebaked anodes, the low-temperature waste heat utilization method proposed in this application can increase the overall waste heat utilization rate of the entire plant from less than 40% in the traditional process to over 85%. Calculations under normal operating conditions show that this can save over 4,500 tons of standard coal and reduce carbon dioxide emissions by over 11,000 tons annually, demonstrating significant energy-saving and carbon-reduction benefits. Simultaneously, due to the improved stability of process temperatures in each stage, the density compliance rate of carbon products can be increased to over 99%, significantly improving product quality consistency. Under conditions of sufficient waste heat in summer, the overall waste heat utilization rate can even reach 90%, saving up to 5,000 tons of standard coal annually. Under low-load conditions with reduced output, with the addition of gas-fired heating and energy storage regulation, the overall waste heat utilization rate can still be maintained above 84%, with temperature fluctuations at each heat-using terminal controlled within ±3 degrees Celsius. During commissioning, energy consumption is reduced by 35% compared to the traditional process. Furthermore, this solution is based on the modification of existing production equipment, without the need to build new core equipment. The investment in new equipment is about one-quarter of that of building a new waste heat recovery production line. The modification cost is controllable, the compatibility is strong, and it has high industrialization promotion value.

[0126] The above description is merely an embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A method for utilizing low-temperature waste heat in a carbon plant, characterized in that, The method includes: Heat is recovered from the high-temperature flue gas and material cooling section of the calciner and collected to obtain the first waste heat transfer oil; heat is recovered from the main flue gas and cooling chamber of the roasting furnace and collected to obtain the second waste heat transfer oil; heat is recovered from the low-temperature flue gas of the calciner to obtain the third waste heat transfer oil. According to the heat temperature requirements of the production process, heat terminals are divided into primary heat terminals, secondary heat terminals and tertiary heat terminals. The first waste heat transfer oil, the second waste heat transfer oil, and the third waste heat transfer oil are respectively supplied to the primary heat-using terminal, the secondary heat-using terminal, and the tertiary heat-using terminal. Based on the heat usage parameters of each heat-using terminal, and according to the preset oil return priority, the low-temperature return oil of each heat-using terminal is distributed to the heat transfer oil inlet of each waste heat recovery link to ensure the temperature stability of the first waste heat heat transfer oil.

2. The method according to claim 1, characterized in that, The process of recovering and converging heat from the high-temperature flue gas and material cooling section of the tank calciner to obtain the first waste heat transfer oil includes: A heat transfer oil jacket is installed in the cooling section of the tank body of the tank calciner to absorb the cooling heat of the calcined material through circulating heat transfer oil, and to absorb the heat of the high-temperature flue gas of the tank calciner through a waste heat boiler. The heat transfer oil corresponding to the material cooling heat and the heat transfer oil corresponding to the high temperature flue gas are merged and the flow rate is adjusted to obtain the first waste heat heat transfer oil with the temperature in the first temperature range.

3. The method according to claim 1, characterized in that, The process of recovering heat from the main flue gas of the roasting furnace and the cooling furnace chamber and converging them to obtain the second waste heat transfer oil includes: A movable exhaust frame is installed at the observation hole of the forced cooling chamber of the roasting furnace to extract hot air with a temperature in the second temperature range. The hot air is introduced into the annular flue through the exhaust frame interface and mixed with the flue gas discharged from the main flue of the roasting furnace to obtain mixed flue gas with a temperature in the third temperature range. A ceramic tube heat exchanger is installed at the outlet of the annular flue of the calcining furnace. The heat of the mixed flue gas is absorbed by circulating heat transfer oil to obtain the second waste heat transfer oil with a temperature in the fourth temperature range.

4. The method according to claim 1, characterized in that, The process of recovering heat from the low-temperature flue gas of the calciner to obtain the third waste heat transfer oil includes: A ceramic tube heat exchanger is installed at the outlet of the waste heat boiler of the calcining furnace. The heat from the low-temperature flue gas in the fifth temperature range is absorbed by circulating heat transfer oil to obtain the third waste heat transfer oil in the sixth temperature range.

5. The method according to claim 1, characterized in that, The method further includes: A mixing heat exchange tank is provided to mix and regulate the temperature of waste heat transfer oils at different temperatures. The mixing heat exchange tank is equipped with a stirrer. The heat transfer oil, after being conditioned by the mixing heat exchange tank, is divided into a first temperature level and a second temperature level. The first temperature level is used to supply the primary heat-using terminal and the secondary heat-using terminal, and the second temperature level is used to supply the secondary heat-using terminal and the tertiary heat-using terminal. The first temperature level is higher than the second temperature level.

6. The method according to claim 5, characterized in that, The method further includes: When the heat demand of the primary heat-using terminal is saturated and there is a surplus of the first-line waste heat transfer oil, the surplus first-line waste heat transfer oil is introduced into the mixing heat exchange tank for temperature adjustment and then distributed to the secondary heat-using terminal and the tertiary heat-using terminal. When the heat demand of the secondary heat-using terminal is saturated and there is a surplus of the second waste heat transfer oil, the surplus second waste heat transfer oil is introduced into the mixing heat exchange tank for temperature adjustment and then distributed to the tertiary heat-using terminal.

7. The method according to claim 5, characterized in that: The mixing heat exchange tank is equipped with an external insulation layer, and the internal storage temperature is maintained in the seventh temperature range. The standby capacity meets the low-load heat demand of the carbon plant within a preset time period. When the heat demand of the carbon plant is saturated, the excess waste heat transfer oil is introduced into the mixing heat exchange tank for storage. When the heat demand increases, the stored heat transfer oil is released to supplement the energy supply.

8. The method according to claim 1, characterized in that, The preset oil return priority includes: The waste heat recovery process corresponding to the first waste heat transfer oil has a higher priority than the waste heat recovery process corresponding to the second waste heat transfer oil. The waste heat recovery process corresponding to the second waste heat transfer oil has a higher priority than the waste heat recovery process corresponding to the third waste heat transfer oil.

9. The method according to claim 1, characterized in that, Before allocating the low-temperature return oil from each heat-using terminal to the heat transfer oil inlet of each waste heat recovery stage based on the heat-using parameters of each heat-using terminal and according to a preset return oil priority, the method further includes: Temperature sensors and heat load acquisition devices are installed at each heat-consuming terminal to collect the current temperature, target temperature and real-time heat load of each heat-consuming terminal in real time. The collected current temperature, target temperature, and real-time heat load are transmitted to the control system as heat parameters.

10. The method according to claim 1, characterized in that, The method further includes: A gas-fired waste heat boiler is installed in the generation stage of the first waste heat transfer oil. When the temperature of the high-temperature flue gas or the cooling heat of the material in the tank calciner flues, the gas-fired waste heat boiler is used to supplement the heat so as to maintain the temperature of the first waste heat transfer oil within the first temperature range.

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