A method for waste heat recovery of an alternative tube furnace for heat exchanger and flash tank

Abstract

The application discloses a waste heat recycling method for replacing a tubular furnace of a heat exchanger and a flash tank, relates to the field of waste heat recycling of an industrial benzene removal process, and comprises the following steps: collecting steam generated in real time during coke oven operation, dynamically adjusting the steam temperature and pressure through a water circulation cooling device and a multi-stage pressure reducing valve, connecting the adjusted steam into a heat exchanger, evaluating the heat exchange deviation of the steam and the pressurized crude benzene region crude oil based on the crude oil type, adjusting the output of the flow of a circulating pump, conveying the heat-exchanged crude oil to a benzene removal tower, evaluating the benzene removal efficiency based on infrared spectroscopy technology, re-performing heat exchange and conveying to the benzene removal tower if the benzene removal efficiency is not up to the standard, and inputting the condensed steam after heat exchange into a flash tank, and realizing secondary steam recovery by connecting the low-pressure saturated steam after pressure reduction into a low-pressure steam pipe network.

Description

Technical Field

[0001] This invention relates to the field of waste heat recovery in industrial benzene removal processes, and more specifically to a method for waste heat recovery from a waste heat source that replaces a tubular furnace for use in heat exchangers and flash tanks. Background Technology

[0002] The original heating of the crude benzene production area used tubular furnaces for rich (or lean) oil heating. After combustion, the chimney emissions were substandard, the gas consumption was high, and the use of coke oven gas as fuel and open flame operation posed a series of safety hazards.

[0003] In the coking industry, coke oven operations generate a large amount of high-temperature, high-pressure steam. This steam, typically possessing high temperature and pressure, can serve as a clean heating resource. Properly recovering and utilizing this steam can significantly reduce energy costs, decrease flue gas emissions, and improve the environmental friendliness of the production process. Therefore, this paper utilizes self-generated high-pressure steam from dry quenching, after desuperheating and depressurization, as a gas source. A heat exchanger is configured to heat oil-rich (or oil-lean) products, and a flash tank is used for resource recovery. This achieves waste heat reuse in the heat exchanger and flash tank, replacing the waste heat from the tubular furnace. This constructs a highly efficient, stable, and environmentally friendly benzene removal heating system, providing strong technical support for achieving green production and sustainable development. Summary of the Invention

[0004] To solve the above-mentioned technical problems, a method for waste heat recovery from an alternative tubular furnace for heat exchangers and flash tanks is provided. This technical solution solves the problems mentioned in the background art.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for waste heat recovery from an alternative tubular furnace used in heat exchangers and flash tanks includes:

[0007] The steam generated during coke oven operation is collected in real time, and the steam temperature and pressure are dynamically regulated through a water circulation cooling device and a multi-stage pressure reducing valve design.

[0008] The cooled and depressurized steam is fed into the heat exchanger. The heat exchange deviation between the steam and the pressurized crude benzene region crude oil is evaluated based on the crude oil type, and the output flow rate of the circulating pump is adjusted accordingly.

[0009] After heat exchange, the crude oil is transported to the benzene removal tower. The benzene removal efficiency is evaluated based on infrared spectroscopy. If the efficiency is not up to standard, the crude oil is re-heat exchanged and transported to the benzene removal tower.

[0010] The condensed steam after heat exchange is fed into a flash tank, and the depressurized low-pressure saturated steam is then incorporated into a low-pressure steam network to achieve secondary steam recovery.

[0011] Preferably, the real-time collection of steam generated during coke oven operation, and the dynamic adjustment of steam temperature and pressure through a water circulation cooling device and a multi-stage pressure reducing valve design, specifically includes:

[0012] A multi-stage pressure reducing valve is installed, with a high-precision pressure sensor and temperature sensor installed after each stage of the pressure reducing valve to monitor the pressure and temperature changes of the steam in real time, and to set the target pressure and target temperature for steam regulation.

[0013] The steam generated during coke oven operation is connected to a multi-stage pressure reducing channel, and the segmentation position of the multi-stage pressure reducing channel is determined based on the initial specific enthalpy value of the steam entering the pressure reducing channel.

[0014] The multi-stage pressure reducing valve group before the barrier position is marked as the first pressure reducing section, and the multi-stage pressure reducing valve group after the barrier position is marked as the second pressure reducing section. Based on the division of the pressure reducing sections, the steam is subjected to segmented pressure reduction.

[0015] Set a pressure requirement threshold for steam to enter the second-level depressurization section, and mark this threshold as the target pressure of the first-level depressurization section;

[0016] The pressure difference between the initial pressure of the high-pressure steam and the target pressure of the first step of pressure reduction is divided into N pressure reduction steps in the same proportion, and each pressure reduction step corresponds to each pressure reducing valve in the first step of pressure reduction.

[0017] After steam enters the second-stage pressure-reducing section, the initial opening of the pressure-reducing valve in the second-stage pressure-reducing section is set based on the constructed exponential proportional decreasing function combined with the target pressure of steam regulation. The exponential proportional decreasing function is:

[0018] ;

[0019] In the formula, It is the set pressure reduction amount of the i-th pressure reducing valve in the second-stage pressure reduction section. This is the total voltage reduction demand of the second-stage step-down section. This is the basic pressure reduction setting of the pressure reducing valve. It is the passage time of steam at the i-th pressure reducing valve. This refers to the total number of pressure-reducing valves in the two-stage pressure-reducing section;

[0020] After the first and second pressure reduction sections are running stably, the actual opening degree of each pressure reducing valve in the second pressure reduction section is adjusted in real time based on the PID control algorithm.

[0021] A cooling water circulation device is installed to introduce depressurized steam into the cooling water circulation system. The steam temperature upon entering the system and the target temperature are obtained. Based on the actual heat exchange efficiency of the cooling water circulation system and the cross-sectional area of ​​the cooling water circulation pipes, the required cooling water flow rate is calculated in real time. The specific calculation expression is as follows:

[0022] ;

[0023] In the formula, It is the cooling water flow rate requirement. It is the mass flow rate of steam. , These are the specific heat capacities of steam and water at the outlet of the pressure-reducing channel, respectively. , These are the temperature changes after the exchange of steam and water. It is the density of water. It is the cross-sectional area of ​​the cooling water circulation pipe. This represents the actual heat exchange efficiency;

[0024] The cooling water flow rate of the cooling water circulation system is adjusted in real time based on the calculation results of the cooling water flow rate requirement.

[0025] Preferably, the step of introducing the cooled and depressurized steam into the heat exchanger, assessing the heat exchange deviation between the steam and the pressurized crude benzene region crude oil based on the crude oil type, and adjusting the output flow rate of the circulating pump specifically includes:

[0026] Crude oil from the crude benzene region is pressurized to a set pressure by a variable frequency drive circulating pump and then fed into a heat exchanger. At the same time, steam that has been cooled and depressurized is fed into the heat exchanger.

[0027] Set target temperature ranges for lean oil heat exchange and rich oil heat exchange, and determine whether the crude oil connected to the heat exchanger is lean or rich based on the API degree measurement results of the crude oil in the crude benzene region.

[0028] Adjust the opening of the regulating valve on the steam inlet pipe of the heat exchanger according to the target temperature range corresponding to the type of crude oil to heat the crude oil inside the heat exchanger;

[0029] The real-time temperature of the crude oil outlet after heat exchange in the heat exchanger is obtained. Based on the deviation ratio from the lower limit of the heat exchange target temperature range, the flow output of the circulation pump is continuously adjusted according to the set scale until the crude oil temperature at the heat exchanger outlet reaches the set target temperature range and the adjustment ends.

[0030] Preferably, the step of transporting the heat-exchanged crude oil to the benzene removal tower, evaluating the benzene removal efficiency based on infrared spectroscopy, and if the efficiency is not up to standard, repeating the heat exchange and transporting the crude oil to the benzene removal tower specifically includes:

[0031] The infrared radiation emitted by the light source of the FTIR instrument is used to generate an interference signal through the interferometer. The interference signal passing through the crude oil sample is received by the detector and converted into a time domain signal.

[0032] The time-domain signal is processed by the Fourier transform algorithm to obtain the infrared absorption spectrum. Based on the infrared absorption spectrum, the intensity of the infrared absorption peak of benzene in the crude oil sample at the outlet of the benzene stripping tower is monitored in real time, and the concentration of benzene in the crude oil sample at the outlet of the benzene stripping tower is calculated.

[0033] Set the benzene standard concentration for the crude oil after benzene removal, and divert the crude oil at the outlet of the benzene removal tower based on the benzene standard concentration. Crude oil exceeding the benzene standard concentration is reconnected to the heat exchanger for reheating and circulating benzene removal.

[0034] Preferably, the step of inputting the condensed steam after heat exchange into the flash tank and merging the depressurized low-pressure saturated steam into the low-pressure steam pipeline network to achieve secondary steam recovery specifically includes:

[0035] Collect the condensate formed by the cooled steam after heat exchange in the heat exchanger, and then test the initial temperature and initial pressure of the condensate after it is treated by a steam trap.

[0036] Based on the saturated vapor pressure curve of the steam condensate determined from historical samples, the pressure reducing valve is dynamically adjusted to reduce the pressure of the steam condensate before it is fed into the flash tank, so that the low-pressure boiling point of the steam condensate in the flash tank matches the saturated vapor pressure curve.

[0037] The low-pressure saturated steam generated after the steam condensate in the flash tank boils and vaporizes is incorporated into the low-pressure steam pipeline network for secondary steam recovery.

[0038] Unvaporized steam condensate from the flash tank is connected to the demineralized water tank as a reserve of demineralized water.

[0039] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0040] By utilizing a combination of a water-circulating cooling system and multi-stage pressure-reducing valves, the steam temperature and pressure are precisely regulated to meet the heating requirements of different types of crude oil, ensuring the stability and safety of the heat exchange process. Secondly, the flow rate of the circulating pump is adjusted based on the type of crude oil to optimize the heat exchange between steam and crude oil, effectively improving heating efficiency and reducing energy waste. Simultaneously, infrared spectroscopy technology is used to monitor benzene removal efficiency in real time, ensuring product quality meets standards. If standards are not met, automatic reheating is performed to ensure strict control of benzene content. Finally, the condensed steam after heat exchange is treated in a flash tank, achieving secondary recovery and reuse of low-pressure steam, which not only saves energy but also improves steam utilization.

[0041] In summary, this solution utilizes self-generated high-pressure steam from dry quenching coke, equipped with a heat exchanger and flash tank, to replace tubular furnace heating. This solves the problems of substandard flue gas emissions, energy consumption, and open flame operation inherent in tubular furnaces. Simultaneously, the accompanying flash tank enables steam recovery and reuse, effectively reducing energy consumption. Attached Figure Description

[0042] Figure 1 This is a flowchart of a waste heat recovery method for an alternative tubular furnace used in heat exchangers and flash tanks according to the present invention.

[0043] Figure 2 The present invention provides a flowchart of the process for dynamically adjusting the temperature and pressure of steam generated during coke oven operation through a water circulation cooling device and a multi-stage pressure reducing valve.

[0044] Figure 3 The present invention provides a flowchart for adjusting the flow rate of the circulating pump by introducing cooled and depressurized steam into a heat exchanger, evaluating the heat exchange deviation between the steam and the pressurized crude benzene region crude oil based on the crude oil type;

[0045] Figure 4 The present invention describes the process of transporting the heat-exchanged crude oil to the benzene removal tower, evaluating the benzene removal efficiency based on infrared spectroscopy, and repeating the heat exchange process if the efficiency is not met.

[0046] Figure 5 The present invention provides a process flow diagram for the secondary steam recovery of steam by inputting the condensed steam after heat exchange into a flash tank and merging the depressurized low-pressure saturated steam into a low-pressure steam pipeline network. Detailed Implementation

[0047] The following description is intended to disclose the invention and enable those skilled in the art to implement it. The preferred embodiments described below are merely examples, and other obvious variations will occur to those skilled in the art.

[0048] Reference Figure 1 As shown, a method for waste heat recovery from an alternative tubular furnace used in heat exchangers and flash tanks includes:

[0049] The steam generated during coke oven operation is collected in real time, and the steam temperature and pressure are dynamically regulated through a water circulation cooling device and a multi-stage pressure reducing valve design.

[0050] The cooled and depressurized steam is fed into the heat exchanger. The heat exchange deviation between the steam and the pressurized crude benzene region crude oil is evaluated based on the crude oil type, and the output flow rate of the circulating pump is adjusted accordingly.

[0051] After heat exchange, the crude oil is transported to the benzene removal tower. The benzene removal efficiency is evaluated based on infrared spectroscopy. If the efficiency is not up to standard, the crude oil is re-heat exchanged and transported to the benzene removal tower.

[0052] The condensed steam after heat exchange is fed into a flash tank, and the depressurized low-pressure saturated steam is then incorporated into a low-pressure steam network to achieve secondary steam recovery.

[0053] Reference Figure 2As shown, the system collects steam generated during coke oven operation in real time and dynamically regulates the steam temperature and pressure through a water circulation cooling device and a multi-stage pressure reducing valve design. Specifically, this includes:

[0054] A multi-stage pressure reducing valve is installed, with a high-precision pressure sensor and temperature sensor installed after each stage of the pressure reducing valve to monitor the pressure and temperature changes of the steam in real time, and to set the target pressure and target temperature for steam regulation.

[0055] The steam generated during coke oven operation is connected to a multi-stage pressure reducing channel, and the segmentation position of the multi-stage pressure reducing channel is determined based on the initial specific enthalpy value of the steam entering the pressure reducing channel.

[0056] The multi-stage pressure reducing valve group before the barrier position is marked as the first pressure reducing section, and the multi-stage pressure reducing valve group after the barrier position is marked as the second pressure reducing section. Based on the division of the pressure reducing sections, the steam is subjected to segmented pressure reduction.

[0057] Set a pressure requirement threshold for steam to enter the second-level depressurization section, and mark this threshold as the target pressure of the first-level depressurization section;

[0058] The pressure difference between the initial pressure of the high-pressure steam and the target pressure of the first step of pressure reduction is divided into N pressure reduction steps in the same proportion, and each pressure reduction step corresponds to each pressure reducing valve in the first step of pressure reduction.

[0059] After steam enters the second-stage pressure-reducing section, the initial opening of the pressure-reducing valve in the second-stage pressure-reducing section is set based on the constructed exponential proportional decreasing function combined with the target pressure of steam regulation. The exponential proportional decreasing function is:

[0060] ;

[0061] In the formula, It is the set pressure reduction amount of the i-th pressure reducing valve in the second-stage pressure reduction section. This is the total voltage reduction demand of the second-stage step-down section. This is the basic pressure reduction setting of the pressure reducing valve. It is the passage time of steam at the i-th pressure reducing valve. This refers to the total number of pressure-reducing valves in the two-stage pressure-reducing section;

[0062] High-pressure steam from the coke oven is cooled and depressurized through a desuperheating and depressurization system (main components: pressure reducing valve device, cooling water circulation device) to become medium-pressure steam at 400℃ and 3.8MPa, instead of the original 540℃, 9.8MPa high-pressure steam. Below is an example of pressure reduction:

[0063] Assuming the pressure reduction step number N in the first-stage pressure reduction section is 6, and the high-pressure steam pressure after entering the second-stage pressure reduction section is 6.8 MPa, then the target total pressure reduction is 3 MPa, and the basic pressure reduction is 0.5 MPa. If the passage time of each pressure reducing valve is 2 seconds, then the proportional decreasing pressure reduction calculation process is as follows:

[0064] ,

[0065] ,

[0066] ,

[0067] ,

[0068] This process continues until the total pressure reaches the target total pressure drop or the decrease ends within the set error range.

[0069] After the first and second pressure-reducing sections have stabilized, the actual opening degree of each pressure-reducing valve in the second pressure-reducing section is adjusted in real time based on the PID control algorithm. The specific process of applying the PID control algorithm to the steam pressure-reducing system is as follows:

[0070] Three control parameters were set based on the Ziegler-Nichols tuning method and the actual system feedback.

[0071] For example, when the three control parameters obtained from the experiment are respectively , , Based on the error between the set pressure reduction and the actual pressure reduction of the first-stage pressure reducing valve (assumed to be -0.2), the cumulative actual detection error (assumed to be -0.1), and the error change rate (assumed to be -0.05), the proportional term, integral term, and differential term are calculated respectively:

[0072] ,

[0073] ,

[0074] ,

[0075] At this point, the PID controller output is -0.605, which means that the opening of the pressure reducing valve should be reduced by 0.605 basis points to reduce the system pressure.

[0076] A cooling water circulation device is installed to introduce depressurized steam into the cooling water circulation system. The steam temperature upon entering the system and the target temperature are obtained. Based on the actual heat exchange efficiency of the cooling water circulation system and the cross-sectional area of ​​the cooling water circulation pipes, the required cooling water flow rate is calculated in real time. The specific calculation expression is as follows:

[0077] ;

[0078] In the formula, It is the cooling water flow rate requirement. It is the mass flow rate of steam. , These are the specific heat capacities of steam and water at the outlet of the pressure-reducing channel, respectively. , These are the temperature changes after the exchange of steam and water. It is the density of water. It is the cross-sectional area of ​​the cooling water circulation pipe. This represents the actual heat exchange efficiency.

[0079] The required temperature change in this plan is 140 degrees Celsius. Based on this premise, here is an example calculation:

[0080] ;

[0081] The calculated result for the cooling water flow rate requirement is then: The cooling water flow rate of the cooling water circulation system is adjusted in real time based on the calculation results of the cooling water flow rate requirement.

[0082] Reference Figure 3 As shown, the cooled and depressurized steam is connected to the heat exchanger. Based on the crude oil type, the heat exchange deviation between the steam and the pressurized crude benzene region crude oil is evaluated. The output flow rate of the circulating pump is adjusted, specifically including:

[0083] Crude oil from the crude benzene region is pressurized to a set pressure by a variable frequency drive circulating pump and then fed into a heat exchanger. At the same time, steam that has been cooled and depressurized is fed into the heat exchanger.

[0084] Target temperature ranges for lean oil and rich oil heat exchange are set. Based on the API gravity measurement results of crude oil in the crude benzene region, the crude oil entering the heat exchanger is determined to be lean or rich. Generally, lean oil has a high API gravity, low density (usually greater than 31.1°API; when API gravity is greater than 31.1, it is called "light oil"), low specific gravity, and low viscosity. Lean oil is rich in light hydrocarbons, making it easier to refine and process. It also contains more combustible gases and light liquids, making it suitable for producing light petroleum products such as gasoline and diesel. Heavy oil (rich oil) has a low API gravity (usually less than 20°API), high density, high viscosity, and contains more heavier hydrocarbons. Heavy oil contains a large amount of high molecular weight substances, making it more difficult to refine and often requiring higher temperatures and pressures for processing.

[0085] Adjust the opening of the regulating valve on the steam inlet pipe of the heat exchanger according to the target temperature range corresponding to the type of crude oil to heat the crude oil inside the heat exchanger. The temperature of cold rich oil (or lean oil) can reach 180-300 degrees after heat exchange in the heat exchanger.

[0086] The real-time temperature of the crude oil outlet after heat exchange in the heat exchanger is obtained. Based on the deviation ratio from the lower limit of the heat exchange target temperature range, the flow output of the circulation pump is continuously adjusted according to the set scale until the crude oil temperature at the heat exchanger outlet reaches the set target temperature range and the adjustment ends.

[0087] Reference Figure 4 As shown, the crude oil after heat exchange is transported to the benzene removal tower. The benzene removal efficiency is evaluated based on infrared spectroscopy. If the efficiency is not up to standard, the crude oil is re-exchanged and transported to the benzene removal tower. Specific steps include:

[0088] Infrared spectroscopy is based on the principle that molecules absorb infrared light of different wavelengths. When infrared light shines on a sample, the chemical bonds in the molecules absorb light of specific frequencies, causing the molecules to vibrate or rotate. Different chemical bonds have different absorption peaks in the infrared region, so the composition of a substance can be identified and analyzed by measuring the position and intensity of these absorption peaks. FTIR instruments emit infrared radiation from a light source, which is then passed through an interferometer to generate an interference signal. This interference signal is received by a detector and converted into a time-domain signal.

[0089] In crude oil, benzene compounds (such as benzene, toluene, and xylene) exhibit characteristic infrared absorption peaks. These peaks primarily originate from the CH bending vibration of the benzene ring and the stretching vibration of the C=C double bond. By analyzing the absorption peaks in the infrared spectrum of crude oil samples, the time-domain signal is processed using a Fourier transform algorithm to obtain the infrared absorption spectrum. Based on the infrared absorption spectrum, the intensity of the infrared absorption peak of benzene in the crude oil sample exiting the benzene stripping tower is monitored in real time, and the benzene concentration in the crude oil sample exiting the stripping tower is calculated. The principle is that the CH stretching vibration of the benzene molecule and the C=C vibration of the aromatic ring typically occur at approximately 30-30 cm⁻¹. -1 (CH stretching vibration) and approximately 1500-1600 cm -1 A distinct absorption peak is generated near the (C=C stretching vibration).

[0090] Set the benzene standard concentration for the crude oil after benzene removal, and divert the crude oil from the benzene removal tower based on the benzene standard concentration. Crude oil exceeding the benzene standard concentration is reconnected to the heat exchanger for reheating and circulating benzene removal.

[0091] Reference Figure 5 As shown, the condensed steam after heat exchange is fed into a flash tank, and the depressurized low-pressure saturated steam is then incorporated into a low-pressure steam network to achieve secondary steam recovery. Specifically, this includes:

[0092] Collect the condensate formed by the cooled steam after heat exchange in the heat exchanger, and then test the initial temperature and initial pressure of the condensate after it is treated by a steam trap.

[0093] After heat exchange, the cooled steam condenses into steam condensate and enters the flash tank through the steam trap and pressure reducing valve. When the high-pressure, high-temperature steam condensate is depressurized and enters the flash tank, the boiling point of the steam condensate also decreases due to the sudden drop in pressure. This causes the steam condensate to boil and vaporize rapidly. The low-pressure saturated steam generated after vaporization is incorporated into the low-pressure steam pipeline network to achieve steam recovery and reuse.

[0094] Based on historical sample measurements, the corresponding relationship of saturated vapor pressure of steam condensate is obtained using experimental or database data. The corresponding boiling point pressure of steam condensate at various temperatures is obtained. The experimental data is fitted into a saturated vapor pressure curve. The pressure reducing valve is dynamically adjusted to reduce the pressure of steam condensate before it is fed into the flash tank, so that the low-pressure boiling point of steam condensate in the flash tank matches the saturated vapor pressure curve.

[0095] The low-pressure saturated steam generated after the steam condensate in the flash tank boils and vaporizes is incorporated into the low-pressure steam pipeline network for secondary steam recovery.

[0096] By connecting the unrevaporized steam condensate in the flash tank to the demineralized water tank as a demineralized water reserve, the above technical solution can effectively recover and utilize the heat energy and water resources of the steam condensate generated by the heat exchanger. This process not only achieves secondary energy recovery but also reduces waste caused by direct steam emissions, improving the system's economic efficiency and environmental performance.

[0097] The specific process flow for the waste heat recovery method used to replace tubular furnaces in heat exchangers and flash tanks is as follows:

[0098] High-pressure steam at 540℃ and 9.8MPa from the coking plant is cooled and reduced in pressure by a desuperheating and pressure-reducing system (main components: pressure-reducing valve device and cooling water circulation device), transforming it into medium-pressure steam at 400℃ and 3.8MPa. The pressure-reducing valve device mainly consists of a TG01 thermometer, a PG01 pressure gauge, and a PV01 pressure-reducing valve. The cooling water circulation device mainly consists of an FV02 regulating valve and a PG03 pressure gauge. A safety valve PSV01 is installed on the pipeline after the high-pressure steam desuperheating and pressure-reducing device to ensure system safety; temperature sensor TG02 and pressure sensor PG02 monitor the system pressure and temperature in real time.

[0099] The medium-pressure steam obtained after desuperheating and depressurization exchanges heat with rich (or lean) oil from the crude benzene zone. After heat exchange in heat exchanger E01, the heated rich (or lean) oil is sent to the benzene removal tower. A temperature transmitter TE01 and a pressure gauge TG04 are installed at the outlet of the heat exchanger for the rich (or lean) oil. A regulating valve FV01 is installed at the steam inlet of the heat exchanger. The steam flow rate is controlled by adjusting the opening of valve FV01, thereby regulating the temperature of the rich (or lean) oil. When the temperature of the rich (or lean) oil at the heat exchanger outlet is low, the valve opening is increased; when the temperature is high, the valve opening is decreased.

[0100] Steam cooled after heat exchange in the heat exchanger condenses into condensate. The condensate, containing water, air, and carbon dioxide, is first discharged through a steam trap. Then, it passes through a pressure reducing valve PV02, reducing the pressure from 3.8 MPa to 0.6 MPa, before entering the flash tank V01. When the high-pressure, high-temperature condensate is depressurized, the sudden pressure drop lowers the boiling point of the condensate, causing it to rapidly boil and vaporize. The resulting low-pressure saturated steam is then incorporated into the low-pressure steam network for steam recovery and reuse. The flash tank V01 is equipped with a safety valve PSV02, a temperature instrument TE02, and a pressure gauge PG08 to monitor the tank's status in real time, ensuring tank safety.

[0101] Furthermore, this solution also proposes a waste heat recovery method for an alternative tubular furnace used in heat exchangers and flash tanks. The storage medium on which the method stores a computer-readable program, which, when invoked, executes the aforementioned waste heat recovery method for an alternative tubular furnace used in heat exchangers and flash tanks.

[0102] It is understandable that the storage medium can be a magnetic medium, such as a floppy disk, hard disk, or magnetic tape; an optical medium, such as a DVD; or a semiconductor medium, such as a solid-state drive (SSD).

[0103] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention. The scope of protection claimed by the appended claims and their equivalents is defined.

Claims

1. A method for waste heat recovery from an alternative tubular furnace used in heat exchangers and flash tanks, characterized in that, include: The steam generated during coke oven operation is collected in real time, and the steam temperature and pressure are dynamically regulated through a water circulation cooling device and a multi-stage pressure reducing valve design. The cooled and depressurized steam is fed into the heat exchanger. The heat exchange deviation between the steam and the pressurized crude benzene region crude oil is evaluated based on the crude oil type, and the output flow rate of the circulating pump is adjusted accordingly. After heat exchange, the crude oil is transported to the benzene removal tower. The benzene removal efficiency is evaluated based on infrared spectroscopy. If the efficiency is not up to standard, the crude oil is re-heat exchanged and transported to the benzene removal tower. The condensed steam after heat exchange is fed into a flash tank, and the depressurized low-pressure saturated steam is incorporated into the low-pressure steam network to achieve secondary steam recovery. The real-time collection of steam generated during coke oven operation, and the dynamic adjustment of steam temperature and pressure through a water circulation cooling device and a multi-stage pressure reducing valve design, specifically includes: A multi-stage pressure reducing valve is installed, with a high-precision pressure sensor and temperature sensor installed after each stage of the pressure reducing valve to monitor the pressure and temperature changes of the steam in real time, and to set the target pressure and target temperature for steam regulation. The steam generated during coke oven operation is connected to a multi-stage pressure reducing channel, and the segmentation position of the multi-stage pressure reducing channel is determined based on the initial specific enthalpy value of the steam entering the pressure reducing channel. The multi-stage pressure reducing valve group before the barrier position is marked as the first pressure reducing section, and the multi-stage pressure reducing valve group after the barrier position is marked as the second pressure reducing section. Based on the division of the pressure reducing sections, the steam is subjected to segmented pressure reduction. Set a pressure requirement threshold for steam to enter the second-level depressurization section, and mark this threshold as the target pressure of the first-level depressurization section; The pressure difference between the initial pressure of the high-pressure steam and the target pressure of the first step of pressure reduction is divided into N pressure reduction steps in the same proportion, and each pressure reduction step corresponds to each pressure reducing valve in the first step of pressure reduction. After steam enters the second-stage pressure-reducing section, the initial opening of the pressure-reducing valve in the second-stage pressure-reducing section is set based on the constructed exponential proportional decreasing function combined with the target pressure of steam regulation. The exponential proportional decreasing function is: ； In the formula, It is the set pressure reduction amount of the i-th pressure reducing valve in the second-stage pressure reduction section. This is the total voltage reduction demand of the second-stage step-down section. This is the basic pressure reduction setting of the pressure reducing valve. It is the passage time of steam at the i-th pressure reducing valve. This refers to the total number of pressure-reducing valves in the two-stage pressure-reducing section; After the first and second pressure reduction sections are running stably, the actual opening degree of each pressure reducing valve in the second pressure reduction section is adjusted in real time based on the PID control algorithm. A cooling water circulation device is installed to introduce depressurized steam into the cooling water circulation system. The steam temperature upon entering the system and the target temperature are obtained. Based on the actual heat exchange efficiency of the cooling water circulation system and the cross-sectional area of ​​the cooling water circulation pipes, the required cooling water flow rate is calculated in real time. The specific calculation expression is as follows: ； In the formula, It is the cooling water flow rate requirement. It is the mass flow rate of steam. , These are the specific heat capacities of steam and water at the outlet of the pressure-reducing channel, respectively. , These are the temperature changes after the exchange of steam and water. It is the density of water. It is the cross-sectional area of ​​the cooling water circulation pipe. This represents the actual heat exchange efficiency; Adjust the cooling water flow rate of the cooling water circulation system in real time based on the calculation results of the cooling water flow rate requirement; The process of introducing the cooled and depressurized steam into the heat exchanger, assessing the heat exchange deviation between the steam and the pressurized crude benzene region crude oil based on the crude oil type, and adjusting the output flow rate of the circulating pump specifically includes: Crude oil from the crude benzene region is pressurized to a set pressure by a variable frequency drive circulating pump and then fed into a heat exchanger. At the same time, steam that has been cooled and depressurized is fed into the heat exchanger. Set target temperature ranges for lean oil heat exchange and rich oil heat exchange, and determine whether the crude oil connected to the heat exchanger is lean or rich based on the API degree measurement results of the crude oil in the crude benzene region. Adjust the opening of the regulating valve on the steam inlet pipe of the heat exchanger according to the target temperature range corresponding to the type of crude oil to heat the crude oil inside the heat exchanger; The real-time temperature of the crude oil outlet after heat exchange in the heat exchanger is obtained. Based on the deviation ratio from the lower limit of the heat exchange target temperature range, the flow output of the circulation pump is continuously adjusted according to the set scale until the crude oil temperature at the heat exchanger outlet reaches the set target temperature range and the adjustment ends.

2. The waste heat recovery method for an alternative tubular furnace to a heat exchanger and flash tank according to claim 1, characterized in that, The process of transporting the heat-exchanged crude oil to the benzene removal tower, evaluating the benzene removal efficiency based on infrared spectroscopy, and repeating the heat exchange process before transporting it to the benzene removal tower if the efficiency is not met, specifically includes: The infrared radiation emitted by the light source of the FTIR instrument is used to generate an interference signal through the interferometer. The interference signal passing through the crude oil sample is received by the detector and converted into a time domain signal. The time-domain signal is processed by the Fourier transform algorithm to obtain the infrared absorption spectrum. Based on the infrared absorption spectrum, the intensity of the infrared absorption peak of benzene in the crude oil sample at the outlet of the benzene stripping tower is monitored in real time, and the concentration of benzene in the crude oil sample at the outlet of the benzene stripping tower is calculated. Set the benzene standard concentration for the crude oil after benzene removal, and divert the crude oil at the outlet of the benzene removal tower based on the benzene standard concentration. Crude oil exceeding the benzene standard concentration is reconnected to the heat exchanger for reheating and circulating benzene removal.

3. A method for waste heat recovery from a replacement tubular furnace for heat exchangers and flash tanks according to claim 2, characterized in that, The process of inputting the condensed steam after heat exchange into the flash tank and then integrating the depressurized low-pressure saturated steam into the low-pressure steam pipeline network to achieve secondary steam recovery specifically includes: Collect the condensate formed by the cooled steam after heat exchange in the heat exchanger, and then test the initial temperature and initial pressure of the condensate after it is treated by a steam trap. Based on the saturated vapor pressure curve of the steam condensate determined from historical samples, the pressure reducing valve is dynamically adjusted to reduce the pressure of the steam condensate before it is fed into the flash tank, so that the low-pressure boiling point of the steam condensate in the flash tank matches the saturated vapor pressure curve. The low-pressure saturated steam generated after the steam condensate in the flash tank boils and vaporizes is incorporated into the low-pressure steam pipeline network for secondary steam recovery. Unvaporized steam condensate from the flash tank is connected to the demineralized water tank as a reserve of demineralized water.

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