Recycling process for waste heat of calcined coke

Abstract

The invention belongs to the technical field of waste heat recovery, and particularly relates to a calcined coke waste heat recycling process which comprises the following steps: waste heat recovery device arrangement: a waste heat recovery device is arranged at the bottom of a calcining pot of a pot-type calcining furnace, the waste heat recovery device comprises at least one waste heat recoverer, each waste heat recoverer comprises a waste heat recoverer shell, and the waste heat recoverer shell is arranged in the calcining pot of the pot-type calcining furnace; a calcined coke channel is arranged in the middle of the shell; by adopting the heat exchange coil pipe structure arranged in a same-stroke mode and matching with the forced circulation principle, hot water and high-temperature calcined coke are subjected to sufficient countercurrent indirect heat exchange, the heat exchange efficiency is high, and a large amount of waste heat of the calcined coke can be converted into heat energy of high-temperature water. And then the high-temperature water is subjected to reduced-pressure flash evaporation in the steam flash evaporation tank to generate low-pressure saturated steam which is externally supplied to a subsequent process for use, so that gradient utilization of energy is realized. For example, in actual operation, the waste heat recovery efficiency is always kept at a relatively high level, and the originally lost waste heat of the calcined coke is effectively recovered and converted into available steam energy.

Description

Technical Field

[0001] The present invention relates to the technical field of waste heat recovery, and in particular to a process for recycling waste heat from calcined coke. Background Art

[0002] In the production of aluminum carbon and electrode materials, pot calciners are key equipment for calcining raw materials such as petroleum coke to produce calcined coke. During the calcination process, the calcined coke carries a large amount of high-temperature waste heat, often reaching temperatures of 600°C or even higher, and contains enormous amounts of energy. However, in traditional processes, this waste heat is often not effectively utilized and is directly dissipated into the environment. This not only results in significant energy waste, increases production costs for enterprises, but also causes certain thermal pollution. While several waste heat recovery technologies are currently available, their application to calcined coke waste heat recovery still faces numerous technical challenges. Existing waste heat recovery devices suffer from inefficient design and low heat exchange efficiency. The heat exchange structure of some recovery devices fails to ensure sufficient contact between hot water and the high-temperature calcined coke for heat exchange, resulting in a significant amount of waste heat not being effectively recovered. For example, the layout of some heat exchange coils is irrational, with water flow paths of varying lengths, resulting in poor heat exchange and inadequate heat transfer in certain areas. Furthermore, there is a lack of a tiered approach to waste heat utilization. Instead of rationally converting and reusing recovered waste heat, only partial heat recovery is performed, failing to maximize energy utilization and resulting in high energy costs for the company. Effective monitoring and control measures are also lacking during the waste heat recovery process. Key equipment such as the steam flash tank and water mixing tank lack real-time monitoring of parameters such as water level, pressure, and temperature, making it impossible to accurately monitor the equipment's operating status. When abnormal conditions occur, such as excessively high or low water levels or abnormal pressure, appropriate adjustments are not automatically implemented, which can easily lead to equipment damage or safety accidents. Furthermore, the waste heat recovery system operates in high-temperature environments for extended periods, making components such as the heat exchange coils susceptible to corrosion and blockage. However, the lack of regular maintenance and inspection mechanisms prevents these issues from being promptly identified and resolved, further impacting system stability and safety. Existing waste heat recovery processes also lack the ability to record and analyze system operating data. During operation, accurate information about the system's performance indicators and operating status is lacking, making it difficult to identify existing system issues and potential optimization points. For example, when changes in circulating water flow lead to reduced waste heat recovery efficiency, the lack of data recording and analysis prevents timely identification of the cause and adjustment, causing the system to operate inefficiently for a long time. This not only affects the effectiveness of waste heat recovery, but also increases equipment wear and maintenance costs, reducing the reliability and economic efficiency of the entire process. Summary of the Invention

[0003] In order to solve the above problems, the present invention proposes a process for recycling waste heat of calcined coke to more accurately solve the problems raised in the above background technology.

[0004] The present invention is achieved through the following technical solutions: The present invention proposes a process for recycling waste heat of calcined coke, comprising the following steps: setting up a waste heat recovery device: setting up a waste heat recovery device at the bottom of the calcining pot of a pot-type calcining furnace, the waste heat recovery device comprising at least one waste heat recovery device, each waste heat recovery device comprising a waste heat recovery device shell, a calcined coke channel being provided in the middle of the shell, a heat exchange coil being provided around the outside of the calcined coke channel, a water inlet and an outlet being provided at both ends of the heat exchange coil, the water inlet and the outlet being connected to a water supply pipe and a water return pipe respectively; a high temperature The calcined coke inlet is provided, and the low-temperature calcined coke outlet is provided at the bottom; the circulating water system is constructed: a forced circulating water system consisting of a steam flash tank, a mixing tank, a circulating pump, a water supply pipe, a waste heat recovery device and a return pipe is constructed; a steam outlet is provided on the top of the steam flash tank shell, a drain outlet is provided at the bottom, and a water inlet distribution pipe is provided in the shell, the water inlet distribution pipe is connected to the water inlet of the steam flash tank, and multiple small holes are evenly arranged; a steam-water separator is provided below the steam outlet in the steam flash tank shell; a desalted water supply is provided on the mixing tank shell The outlet of the mixing tank and the liquid level gauge of the mixing tank are provided, and a drain port is provided at the bottom; the waste heat recovery process: the desalted water enters the mixing tank and is fully mixed with the high-temperature water from the steam flash tank, and after being pressurized by the circulating pump, it enters the waste heat recovery device through the water supply pipe, and undergoes countercurrent indirect heat exchange with the high-temperature calcined coke in the waste heat recovery device. The generated high-temperature water enters the steam flash tank through the return pipe; the steam production process: the high-temperature water undergoes reduced-pressure flash evaporation in the steam flash tank, and the generated low-pressure saturated steam is separated by the steam-water separator and supplied to the outside, and the un-flashed high-temperature water returns to the steam flash tank. The mixing tank completes the next cycle; system control and monitoring: a thermometer, a pressure gauge, a steam flash tank level gauge and a safety valve are installed on the steam flash tank, the steam outlet is connected to the steam pipe, and a steam pressure regulating valve is installed on the steam pipe; a drain valve is installed on the pipeline connecting the water inlet of the mixing tank and the drain outlet of the steam flash tank, a water supply valve is installed at the connection between the desalted water supply port and the desalted water pipe, and a drain valve is installed at the connection between the drain port and the drain pipe; high and low temperature sensors are respectively installed on the left part of the circulating cooling and heating return water main pipe.

[0005] Preferably, the waste heat recovery devices are arranged in a homogeneous arrangement, that is, the length of the path through which the water flows through each waste heat recovery device is the same.

[0006] Preferably, the heat exchange coil adopts the principle of forced circulation, uses hot water as the heat recovery carrier, and has a structural form of a single-tube downstream spiral heat exchange coil.

[0007] Preferably, a steam flash tank liquid level gauge is further provided on the steam flash tank shell to monitor the liquid level in the tank and ensure stable operation of the system.

[0008] Preferably, a water replenishment valve is provided at the connection between the desalted water replenishment port on the water mixing tank shell and the desalted water pipeline, and is used to automatically adjust the water replenishment amount according to the monitoring result of the mixing tank liquid level meter.

[0009] Preferably, the heat exchange coil in the waste heat recovery device is made of high temperature resistant and corrosion resistant materials to ensure long-term stable operation.

[0010] Preferably, the diameter and number of the small holes on the water inlet distribution pipe of the steam flash tank are optimized according to the system design flow rate and flash efficiency.

[0011] Preferably, it also includes regular maintenance and inspection of the waste heat recovery device to ensure heat exchange efficiency and system safety.

[0012] Preferably, the process further comprises monitoring the quality of the generated low-pressure saturated steam to ensure that it meets the requirements for subsequent utilization.

[0013] Preferably, it also includes recording and analyzing system operation data to optimize system operation parameters and improve waste heat utilization.

[0014] Compared with the prior art, the present invention provides a process for recycling waste heat from calcined coke, which has the following beneficial effects: This calcined coke waste heat recycling process utilizes a heat exchange coil structure with a uniform arrangement and a forced circulation principle, enabling a comprehensive countercurrent indirect heat exchange between hot water and high-temperature calcined coke. This highly efficient heat exchange process converts a significant amount of the calcined coke's waste heat into thermal energy from the high-temperature water. The high-temperature water is then flash-evaporated in a steam flash tank to produce low-pressure saturated steam, which is then supplied to subsequent processes, achieving a cascaded energy utilization. For example, in actual operation, waste heat recovery efficiency remains consistently high, effectively recovering and converting previously lost calcined coke waste heat into usable steam energy.

[0015] This calcined coke waste heat recycling process ensures stable operation and safety through a series of monitoring, control, and regular maintenance measures. Various monitoring instruments, such as thermometers, pressure gauges, and liquid level gauges, are installed on the steam flash tank and water mixing tank to monitor tank parameters in real time. Automatic valves (such as the water supply valve, drain valve, and drain valve) automatically adjust system operation based on monitoring results, ensuring stable water level, pressure, and temperature within the system.

[0016] This calcined coke waste heat recovery process uses daily analysis of circulating water flow, temperature, pressure, steam production and quality, and waste heat recovery efficiency to promptly identify operational issues and potential optimization points. For example, if a decrease in circulating water flow, leading to reduced waste heat recovery efficiency, is detected, further investigation and timely replacement of faulty equipment can restore the system to normal operation and improve waste heat utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The figure is a schematic flow chart of a process for recycling waste heat from calcined coke proposed in the present invention. DETAILED DESCRIPTION

[0018] In order to more clearly and completely illustrate the technical solution of the present invention, the present invention will be further described below with reference to the accompanying drawings. Example

[0019] like Figure 1As shown, one embodiment of the present invention proposes a process for recycling waste heat from calcined coke. A waste heat recovery device is installed at the bottom of the calcining pot of a pot-type calcining furnace. The device comprises two waste heat recovery units. Each waste heat recovery unit consists of a waste heat recovery unit shell with a calcined coke channel in the middle. The channel has a diameter of 300 mm. The channel is surrounded by a stainless steel heat exchange coil with a 50 mm spacing. Water inlets and outlets are located at each end, connected to the water supply and return pipes, respectively. A high-temperature calcined coke inlet is located at the top of the channel, and a low-temperature calcined coke outlet is located at the bottom. The outlet temperature is controlled at approximately 200°C. A forced circulation water system is constructed, consisting of a steam flash tank, a water mixing tank, a circulating pump, a water supply pipe, a waste heat recovery unit, and a return pipe. The steam flash tank shell has a steam outlet at the top and a drain outlet at the bottom. A water inlet distribution pipe is installed inside the shell, with 50 small holes of 5 mm in diameter evenly distributed on the distribution pipe. A steam-water separator is located below the steam outlet in the steam flash tank shell. The mixing tank shell is equipped with a desalted water inlet, a mixing tank outlet, and a mixing tank level gauge. A drain port is located at the bottom. Desalted water is injected into the mixing tank at a rate of 5 t / h and thoroughly mixed with 90°C high-temperature water from the steam flash tank. After mixing, the water temperature reaches 70°C. After being pressurized to 0.3 MPa by a circulating pump, it enters the waste heat recovery unit through a water supply pipe. Within the waste heat recovery unit, hot water and high-temperature calcined coke undergo indirect countercurrent heat exchange, raising the water temperature to 120°C. The resulting high-temperature water enters the steam flash tank through a return pipe. Within the steam flash tank, the high-temperature water undergoes reduced-pressure flash evaporation, reducing the pressure to 0.1 MPa, producing low-pressure saturated steam. After separation in a steam-water separator, the steam reaches a purity of 99% and is supplied to subsequent processes. The unflashed high-temperature water cools to 85°C and returns to the mixing tank to complete the next cycle. The steam flash tank is equipped with a thermometer, pressure gauge, steam flash tank level gauge, and safety valve. The steam outlet is connected to a steam pipeline, and a steam pressure regulating valve is installed on the steam pipeline to stabilize the steam pressure at 0.08 MPa. A drain valve is installed on the pipeline connecting the water mixing tank inlet and the steam flash tank drain outlet. A water supply valve is installed at the connection between the desalted water supply port and the desalted water pipeline, and a drain valve is installed at the connection between the drain port and the drain pipeline. High and low temperature sensors are installed on the left side of the circulating cooling and heating return water main pipeline to monitor the water temperature in real time and ensure that the water temperature remains within the range of 65-75°C. This process effectively recovers and utilizes the waste heat from calcined coke, improves energy efficiency, and reduces production costs.

[0020] In this invention, the waste heat recovery units are arranged in a uniform pattern. Two units are connected in parallel between the water supply and return pipes, ensuring that the water path through each unit is identical, 15 meters in length. This ensures that the water flow rate and flow rate within each unit are essentially consistent, avoiding uneven heat exchange caused by varying water flow paths. Through actual operational monitoring, the heat exchange efficiency deviation of each unit is controlled within ±3%, ensuring stable operation and efficient heat exchange for the entire waste heat recovery system.

[0021] In this invention, the heat exchange coil utilizes the principle of forced circulation, using hot water as the heat recovery carrier. The structure is a single-tube, downstream spiral heat exchange coil. The heat exchange coil is made of stainless steel, with a tube diameter of 25 mm, a spiral diameter of 200 mm, and a pitch of 30 mm. A circulating pump forces hot water to circulate through the heat exchange coil at a flow rate of 0.5 m / s. During the waste heat recovery process, the hot water and the high-temperature calcined coke undergo indirect countercurrent heat exchange, achieving a heat transfer coefficient of 2000 W / (m²·K), effectively transferring the waste heat from the calcined coke to the hot water and improving waste heat recovery efficiency.

[0022] In the present invention, a steam flash tank liquid level gauge is also installed on the steam flash tank shell. This gauge uses a magnetic flap with a measuring range of 0-1500mm. By real-time monitoring of the liquid level within the tank, the liquid level is controlled within the range of 800-1200mm. When the liquid level falls below 800mm, the system automatically opens the water replenishment valve to replenish water; when the liquid level rises above 1200mm, the system automatically opens the water drain valve to drain water. This level control method ensures that there is always sufficient water in the steam flash tank for flash evaporation, while preventing the stable operation of the system from being affected by excessively high or low liquid levels.

[0023] In this invention, a water replenishment valve, installed at the junction of the desalted water replenishment port on the mixing tank shell and the desalted water pipeline, automatically adjusts the replenishment flow based on the monitoring results of the mixing tank liquid level gauge. The mixing tank liquid level gauge uses an ultrasonic level gauge with a range of 0-2000mm. When the mixing tank liquid level falls below a set lower limit (e.g., 500mm), the water replenishment valve automatically opens, replenishing desalted water at a flow rate of 1 ton / hour. When the mixing tank liquid level rises above a set upper limit (e.g., 1500mm), the water replenishment valve automatically closes. This automatic adjustment of the replenishment flow ensures a stable water level in the mixing tank, thereby guaranteeing the normal operation of the circulating water system.

[0024] In this invention, the heat exchange coils in the waste heat recovery device are made of high-temperature and corrosion-resistant materials. Specifically, the heat exchange coils are made of 316L stainless steel, which exhibits excellent high-temperature resistance and enables long-term stable operation in high-temperature environments (up to 600°C). It also exhibits strong corrosion resistance, capable of withstanding the corrosive substances potentially contained in calcined coke. In actual operation, the heat exchange coils have shown no significant corrosion or damage over extended periods of use, ensuring the long-term stable operation and efficient heat exchange of the waste heat recovery device.

[0025] In this invention, the diameter and number of small holes in the water inlet distribution pipe of the steam flash tank are optimized based on the system's design flow rate and flash evaporation efficiency. The system's design flow rate is 10 t / h, and the flash evaporation efficiency is required to reach 80%. Through calculations and experimental verification, the diameter of the small holes in the water inlet distribution pipe was set to 5 mm, and the number was set to 50. This ensures uniform entry of high-temperature water into the steam flash tank, improving flash evaporation efficiency. In actual operation, the flash evaporation efficiency reached 82%, meeting the system's design requirements.

[0026] The present invention also includes regular maintenance and inspection of the waste heat recovery device. A detailed maintenance and inspection plan is formulated, and a comprehensive inspection of the waste heat recovery device is carried out every quarter. The inspection content includes the corrosion of the heat exchange coil, the sealing of the connection parts, the blockage of the calcined coke channel, etc. At the same time, the heat exchange coil is cleaned once every six months to remove dirt and sediment on the surface. Through regular maintenance and inspection, potential problems are discovered and solved in a timely manner, ensuring the heat exchange efficiency and system safety of the waste heat recovery device. In actual operation, the heat exchange efficiency of the waste heat recovery device has always been maintained at a high level, and no safety accidents caused by equipment failure have occurred.

[0027] This invention also includes quality monitoring of the generated low-pressure saturated steam. A steam quality monitoring device is installed on the steam pipeline to monitor steam parameters such as dryness, pressure, and temperature in real time. Steam dryness is required to be above 99%, pressure to be stable at 0.08 MPa, and temperature to be around 100°C. If steam quality does not meet requirements, the system automatically adjusts operating parameters of the steam flash tank, such as pressure and liquid level, to improve steam quality. This quality monitoring ensures that the generated low-pressure saturated steam meets subsequent utilization requirements, improving the reliability and stability of the entire process.

[0028] The present invention also includes recording and analyzing the system operation data. A data recording system is established to record various parameters during the system operation in real time, such as circulating water flow, temperature, pressure, steam production, quality, waste heat recovery efficiency, etc. The recorded data is analyzed every day, and by comparing the data in different time periods, problems and potential optimization points in the system operation are found. For example, through analysis, it was found that the circulating water flow decreased in a certain time period, resulting in a decrease in waste heat recovery efficiency. After further investigation, it was found that the circulating pump was faulty. After the circulating pump was replaced in time, the system resumed normal operation and the waste heat recovery efficiency was improved. By recording and analyzing the system operation data, the system operation parameters are continuously optimized, the waste heat utilization rate is improved, and energy consumption is reduced.

[0029] Finally, it should be noted that while the basic concepts have been described above, it should be apparent to those skilled in the art that the detailed disclosure is provided merely as an example and does not constitute a limitation of this specification. Although not explicitly stated herein, those skilled in the art may make various modifications, improvements, and revisions to this specification. Such modifications, improvements, and revisions are suggested throughout this specification and remain within the spirit and scope of the exemplary embodiments of this specification. Furthermore, this specification uses specific terms to describe the embodiments of this specification. For example, terms such as "one embodiment," "an embodiment," and / or "some embodiments" refer to a particular feature, structure, or characteristic associated with at least one embodiment of this specification. Therefore, it should be emphasized and noted that references to "one embodiment," "an embodiment," or "an alternative embodiment" two or more times in different places in this specification do not necessarily refer to the same embodiment. Furthermore, certain features, structures, or characteristics of one or more embodiments of this specification may be appropriately combined. Furthermore, unless expressly provided in the claims, the order of the processing elements and sequences, the use of alphanumeric characters, or other designations described in this specification are not intended to limit the order of the processes and methods of this specification.

[0030] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A process for recycling waste heat from calcined coke, characterized in that: The following steps are involved: Waste heat recovery device is set up: a waste heat recovery device is set up at the bottom of the calcining pot of the pot calcining furnace, and the waste heat recovery device includes at least one waste heat recovery device, each waste heat recovery device includes a waste heat recovery device shell, a calcined coke channel is set up in the middle of the shell, and a heat exchange coil is surrounded by the outside of the calcined coke channel. The heat exchange coil is provided with a water inlet and an outlet at both ends, and the water inlet and outlet are connected to the water supply pipe and the return pipe respectively; a high-temperature calcined coke inlet is provided at the top of the calcined coke channel, and a low-temperature calcined coke outlet is provided at the bottom; Construction of circulating water system: Construct a forced circulating water system consisting of a steam flash tank, a mixing tank, a circulation pump, a water supply pipe, a waste heat recovery device and a return pipe; a steam outlet is provided on the top of the steam flash tank shell, a drain outlet is provided at the bottom, and a water inlet distribution pipe is provided inside the shell. The water inlet distribution pipe is connected to the water inlet of the steam flash tank and has multiple small holes evenly arranged; a steam-water separator is provided below the steam outlet in the steam flash tank shell; a desalted water replenishment port, a mixing tank water outlet, a mixing tank liquid level gauge are provided on the mixing tank shell, and a drain port is provided at the bottom; Waste heat recovery process: The desalted water enters the mixing tank and is fully mixed with the high-temperature water from the steam flash tank. After being pressurized by the circulating pump, it enters the waste heat recovery device through the water supply pipe. In the waste heat recovery device, it undergoes countercurrent indirect heat exchange with the high-temperature calcined coke. The generated high-temperature water enters the steam flash tank through the return pipe; Steam production process: High-temperature water undergoes reduced-pressure flash evaporation in a steam flash tank. The generated low-pressure saturated steam is separated by a steam-water separator and then supplied to the outside. The un-flashed high-temperature water returns to the mixing tank to complete the next cycle. System control and monitoring: A thermometer, pressure gauge, steam flash tank level gauge and safety valve are installed on the steam flash tank, the steam outlet is connected to the steam pipe, and a steam pressure regulating valve is installed on the steam pipe; a drain valve is installed on the pipeline connecting the water inlet of the mixing tank and the drain outlet of the steam flash tank, a water supply valve is installed at the connection between the desalted water supply port and the desalted water pipe, and a drain valve is installed at the connection between the drain port and the drain pipe; high and low temperature sensors are respectively installed on the left part of the circulating cooling and heating return water main pipe.

2. The process for recycling waste heat from calcined coke according to claim 1, characterized in that: The waste heat recovery devices are arranged in a same-program arrangement, that is, the length of the path through which water flows through each waste heat recovery device is the same.

3. The process for recycling waste heat from calcined coke according to claim 1, characterized in that: The heat exchange coil adopts the principle of forced circulation, uses hot water as a heat recovery carrier, and has a structural form of a single-tube downstream spiral heat exchange coil.

4. The process for recycling waste heat from calcined coke according to claim 1, characterized in that: The steam flash tank shell is also provided with a steam flash tank liquid level gauge for monitoring the liquid level in the tank to ensure stable operation of the system.

5. The process for recycling waste heat from calcined coke according to claim 1, characterized in that: The water replenishment valve provided at the connection between the desalted water replenishment port on the water mixing tank shell and the desalted water pipeline is used to automatically adjust the water replenishment amount according to the monitoring result of the mixing tank liquid level meter.

6. The process for recycling waste heat from calcined coke according to claim 1, characterized in that: The heat exchange coil in the waste heat recovery device is made of high temperature resistant and corrosion resistant materials to ensure long-term stable operation.

7. The process for recycling waste heat from calcined coke according to claim 1, characterized in that: The diameter and number of the small holes on the water inlet distribution pipe of the steam flash tank are optimized according to the system design flow rate and flash efficiency.

8. The process for recycling waste heat from calcined coke according to claim 1, characterized in that: It also includes regular maintenance and inspection of waste heat recovery devices to ensure heat exchange efficiency and system safety.

9. The process for recycling waste heat from calcined coke according to claim 1, characterized in that: The process also includes monitoring the quality of the generated low-pressure saturated steam to ensure that it meets the requirements for subsequent utilization.

10. The process for recycling waste heat from calcined coke according to claim 1, characterized in that: It also includes recording and analyzing system operating data to optimize system operating parameters and improve waste heat utilization.

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