Waste heat recycling method for replacing tubular furnace for heat exchanger and flash tank

Abstract

The invention discloses a waste heat recycling method for a heat exchanger and a flash tank replacing a tubular furnace, and relates to the field of waste heat recycling in the industrial debenzolization process, the waste heat recycling method comprises the following steps: collecting steam generated during coke oven operation in real time, and dynamically adjusting the temperature and pressure of the steam through the design of a water circulation cooling device and a multi-stage pressure reducing valve; introducing the cooled and depressurized steam into a heat exchanger, evaluating the heat exchange deviation between the steam and the pressurized crude oil in the crude benzene area based on the type of the crude oil, and adjusting the flow output of a circulating pump; conveying the crude oil subjected to heat exchange to a debenzolization tower, evaluating the debenzolization efficiency based on an infrared spectrum technology, and if the debenzolization efficiency does not reach the standard, carrying out heat exchange again and conveying the crude oil to the debenzolization tower; and the condensed steam after heat exchange is input into a flash tank, and the low-pressure saturated steam after pressure reduction is merged into a low-pressure steam pipe network to realize secondary recovery of the steam.

Description

Technical Field

[0001] The invention relates to the field of waste heat recycling in an industrial debenzene process, and in particular to a waste heat recycling method for a heat exchanger and a flash tank replacing a tubular furnace. Background Art

[0002] The original oil-rich (or oil-poor) heating in the crude benzene production area was carried out by tubular furnaces. After heating and combustion in the tubular furnaces, there were a series of problems such as chimney flue gas emissions not meeting standards, large gas consumption, the use of coke oven gas as fuel, open flame operations, and potential safety hazards.

[0003] In the coking industry, a large amount of high-temperature and high-pressure steam is generated during the operation of the coke oven. These steams usually have high temperatures and pressures and can be used as a clean heating resource. If these steams can be reasonably recycled and utilized, it can not only significantly reduce energy costs, but also reduce flue gas emissions and improve the environmental friendliness of the production process. For this reason, the high-pressure steam produced by dry coke quenching is used as the gas source after being cooled and decompressed, and a heat exchanger is configured to achieve oil-rich (or oil-poor) heating, and a flash tank is used for resource recycling, realizing the reuse of waste heat from the replacement tubular furnace for heat exchangers and flash tanks, and building an efficient, stable and environmentally friendly debenzening heating system, which provides strong technical support for the realization of green production and sustainable development. Summary of the invention

[0004] In order to solve the above technical problems, a waste heat recycling method for a heat exchanger and a flash tank replacing a tubular furnace is provided. The technical solution solves the problems raised in the above background technology.

[0005] In order to achieve the above purpose, the technical solution adopted by the present invention is:

[0006] A waste heat recycling method for a heat exchanger and a flash tank replacing a tube furnace, comprising:

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

[0008] The steam after temperature and pressure reduction is connected to the heat exchanger, and the heat exchange deviation between the steam and the pressurized crude benzene area crude oil is evaluated based on the crude oil type, and the flow output of the circulation pump is adjusted;

[0009] The crude oil after heat exchange is transported to the debenzene tower, and the debenzene efficiency is evaluated based on infrared spectroscopy technology. If it does not meet the standard, heat exchange is performed again and the crude oil is transported to the debenzene tower;

[0010] The steam condensed after heat exchange is input into the flash tank, and the low-pressure saturated steam after pressure reduction is incorporated into the low-pressure steam network to realize secondary steam recovery.

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

[0012] Set up multi-stage pressure reducing valves, and set high-precision pressure sensors and temperature sensors after each stage of the pressure reducing valve to monitor the pressure and temperature changes of steam in real time and set the target pressure and temperature of steam regulation;

[0013] The steam generated during the operation of the coke oven is connected to the multi-stage decompression channel, and the blocking position of the multi-stage decompression channel is delineated based on the initial specific enthalpy value of the steam entering the decompression channel;

[0014] The multi-stage pressure reducing valve group before the blocking section is marked as a first-layer pressure reducing section, and the multi-stage pressure reducing valve group after the blocking section is marked as a second-layer pressure reducing section, and the steam is pressure-reduced in sections based on the pressure reducing section division;

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

[0016] The pressure difference between the initial pressure of the high-pressure steam and the target pressure of the first pressure reduction section 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 pressure reduction section;

[0017] When the steam enters the second-layer pressure reduction section, the initial opening of the pressure reducing valve of the second-layer pressure reduction section is set based on the constructed exponential proportional decreasing function combined with the target pressure of steam regulation, where the exponential proportional decreasing function is:

[0018]

[0019] In the formula, ΔP i is the set pressure reduction of the i-th pressure reducing valve in the second-layer pressure reducing section, ΔP end is the total pressure reduction demand of the second-layer pressure reduction section, ΔP base is the basic pressure reduction setting of the pressure reducing valve, Δt i is the passage time of steam in the i-th pressure reducing valve, and m is the total number of pressure reducing valves in the second-layer pressure reducing section;

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

[0021] Set up a cooling water circulation device, connect the depressurized steam to the cooling water circulation system, obtain the steam temperature when entering the cooling water circulation system and the adjustment target temperature, and calculate the cooling water flow rate requirement in real time based on the actual heat exchange efficiency of the cooling water circulation system and the cross-sectional area of ​​the cooling water circulation pipeline. The specific calculation expression is:

[0022]

[0023] Where v is the cooling water flow rate requirement, m s is the mass flow rate of steam, C s , C w are the specific heat capacities of steam and water at the outlet of the pressure reducing channel, ΔT s , ΔT w are the temperature changes after steam and water exchange, ρ is the density of water, A is the cross-sectional area of ​​the cooling water circulation pipeline, and η is the actual heat exchange efficiency;

[0024] The cooling water flow rate of the cooling water circulation system is adjusted in real time according to the cooling water flow rate demand calculation results.

[0025] Preferably, the step of connecting the steam after temperature and pressure reduction to a heat exchanger, evaluating the heat exchange deviation between the steam and the crude oil in the pressurized crude benzene region based on the crude oil type, and adjusting the output of the flow rate of the circulating pump specifically includes:

[0026] The crude oil from the crude benzene area is pressurized to the set pressure by a variable frequency driven circulating pump and then connected to the heat exchanger. At the same time, the steam after temperature and pressure reduction is connected to the heat exchanger.

[0027] The lean oil heat exchange target temperature range and the rich oil heat exchange target temperature range are set, and the crude oil connected to the heat exchanger is judged to be lean oil or rich oil based on the API gravity measurement result of the crude oil in the crude benzene area;

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

[0029] The real-time outlet temperature of the heat exchanger after the heat exchange of crude oil is completed is obtained. According to 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 is terminated.

[0030] Preferably, the crude oil after heat exchange is transported to a debenzene tower, and the debenzene efficiency is evaluated based on infrared spectroscopy technology. If the efficiency does not meet the standard, heat exchange is performed again and the crude oil is transported to the debenzene tower. Specifically, the debenzene efficiency includes:

[0031] The FTIR instrument light source emits infrared radiation, which is passed through an interferometer to generate an interference signal. The detector receives the interference signal passing through the crude oil sample and converts the signal into a time domain signal.

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

[0033] The standard benzene concentration of the crude oil after debenzening is set, and the crude oil at the outlet of the debenzening tower is diverted based on the standard benzene concentration. The crude oil exceeding the standard benzene concentration is re-connected to the heat exchanger for re-heat exchange and cyclic debenzening.

[0034] Preferably, the step of inputting the condensed steam after heat exchange into a flash tank and integrating the reduced-pressure saturated steam into a low-pressure steam network to realize secondary steam recovery specifically includes:

[0035] Collect the steam condensate formed by the cooled steam after heat exchange in the heat exchanger, and test the initial temperature and initial pressure of the steam condensate after the steam condensate is processed by the steam trap;

[0036] Based on historical samples, the saturated vapor pressure curve of steam condensate is measured, and the pressure reducing valve is dynamically adjusted to reduce the pressure of steam condensate and input it into the flash tank, so that the steam condensate in the flash tank matches the low-pressure boiling point of the saturated vapor pressure curve;

[0037] The low-pressure saturated steam generated by boiling and vaporizing the steam condensate in the flash tank is incorporated into the low-pressure steam network for secondary steam recovery;

[0038] The steam condensate that has not been re-vaporized in the flash tank is connected to the desalted water tank as a desalted water reserve.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] The combination of a water circulation cooling device and a multi-stage pressure reducing valve is used to precisely adjust the steam temperature and pressure to meet the heating requirements of different types of crude oil and ensure the stability and safety of the heat exchange process. Secondly, the output of the circulating pump flow is adjusted based on the type of crude oil to achieve the best heat exchange between steam and crude oil, effectively improving the heating efficiency and reducing energy waste. At the same time, infrared spectroscopy technology is used to monitor the debenzening efficiency in real time to ensure that the product quality meets the standards. If it does not meet the standards, it will be automatically reheated to ensure strict control of the benzene content. Finally, the condensed steam after the heat exchange is processed in a flash tank to achieve secondary recycling of low-pressure steam, which not only saves energy but also improves the utilization rate of steam.

[0041] In summary, this solution uses high-pressure steam produced by dry coke quenching, and configures heat exchangers and flash tanks to replace tubular furnace heating. It solves the problems of substandard flue gas emissions, energy consumption, and open flame operation during tubular furnace combustion. At the same time, the matching flash tank realizes steam recovery and reuse, effectively reducing energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 A flow chart of a waste heat recycling method for a heat exchanger and a flash tank replacing a tubular furnace according to the present invention;

[0043] Figure 2The present invention collects steam generated during coke oven operation in real time, and dynamically adjusts the steam temperature and pressure through a water circulation cooling device and a multi-stage pressure reducing valve design;

[0044] Figure 3 The output flow chart of the present invention is to connect the steam after temperature and pressure reduction to the heat exchanger, evaluate the heat exchange deviation between the steam and the crude oil in the pressurized crude benzene area based on the crude oil type, and adjust the flow rate of the circulation pump;

[0045] Figure 4 The flow chart of the invention is that the crude oil after heat exchange is transported to a debenzene tower, the debenzene efficiency is evaluated based on infrared spectroscopy technology, and if it does not meet the standard, heat exchange is performed again and the crude oil is transported to the debenzene tower;

[0046] Figure 5 The present invention is a flow chart of inputting the steam condensed after heat exchange into a flash tank, and merging the low-pressure saturated steam after pressure reduction into a low-pressure steam pipe network to realize secondary steam recovery; DETAILED DESCRIPTION

[0047] The following description is used to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments described below are only examples, and those skilled in the art may think of other obvious variations.

[0048] Reference Figure 1 A waste heat recycling method for a heat exchanger and a flash tank replacing a tube furnace is shown, comprising:

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

[0050] The steam after temperature and pressure reduction is connected to the heat exchanger, and the heat exchange deviation between the steam and the pressurized crude benzene area crude oil is evaluated based on the crude oil type, and the flow output of the circulation pump is adjusted;

[0051] The crude oil after heat exchange is transported to the debenzene tower, and the debenzene efficiency is evaluated based on infrared spectroscopy technology. If it does not meet the standard, heat exchange is performed again and the crude oil is transported to the debenzene tower;

[0052] The steam condensed after heat exchange is input into the flash tank, and the low-pressure saturated steam after pressure reduction is incorporated into the low-pressure steam network to realize secondary steam recovery.

[0053] Reference Figure 2 As shown, the steam generated during the coke oven operation is collected in real time, and the steam temperature and pressure are dynamically adjusted through the water circulation cooling device and the multi-stage pressure reducing valve design. The specific details include:

[0054] Set up multi-stage pressure reducing valves, and set high-precision pressure sensors and temperature sensors after each stage of the pressure reducing valve to monitor the pressure and temperature changes of steam in real time and set the target pressure and temperature of steam regulation;

[0055] The steam generated during the operation of the coke oven is connected to the multi-stage decompression channel, and the blocking position of the multi-stage decompression channel is delineated based on the initial specific enthalpy value of the steam entering the decompression channel;

[0056] The multi-stage pressure reducing valve group before the blocking section is marked as a first-layer pressure reducing section, and the multi-stage pressure reducing valve group after the blocking section is marked as a second-layer pressure reducing section, and the steam is pressure-reduced in sections based on the pressure reducing section division;

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

[0058] The pressure difference between the initial pressure of the high-pressure steam and the target pressure of the first pressure reduction section 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 pressure reduction section;

[0059] When the steam enters the second-layer pressure reduction section, the initial opening of the pressure reducing valve of the second-layer pressure reduction section is set based on the constructed exponential proportional decreasing function combined with the target pressure of steam regulation, where the exponential proportional decreasing function is:

[0060]

[0061] Where ΔP i is the set pressure reduction of the i-th pressure reducing valve in the second-layer pressure reducing section, ΔP end is the total pressure reduction demand of the second-layer pressure reduction section, ΔP base is the basic pressure reduction setting of the pressure reducing valve, Δt i is the passage time of steam in the i-th pressure reducing valve, and m is the total number of pressure reducing valves in the second-layer pressure reducing section;

[0062] The high-pressure steam from the coke oven is cooled and reduced in temperature and pressure by a temperature reduction and pressure reduction system (main components: pressure reducing valve device, cooling water circulation device) to reduce the temperature and pressure of the original 540℃, 9.8MPa high-pressure steam to 400℃, 3.8MPa medium-pressure steam. The following is an example of pressure reduction:

[0063] Assuming that the number of pressure reduction steps N in the first pressure reduction section is 6, and the high-pressure steam after the steam enters the second pressure reduction section is 6.8MPa, then the target total pressure reduction is 3MPa, and the basic pressure reduction is 0.5MPa. If the passage time of each pressure reducing valve is 2s, then the proportional reduction pressure reduction calculation process is:

[0064]

[0065]

[0066]

[0067]

[0068] And so on, until the total pressure reaches the target total pressure reduction amount or ends the decreasing process within the set error range.

[0069] After the first and second pressure reduction sections are running stably, the actual opening of each pressure reducing valve in the second pressure reduction 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 reduction system is as follows:

[0070] Based on the Ziegler-Nichols tuning method and the actual system feedback conditions, three control parameters are set respectively.

[0071] For example, when the three control parameters obtained from the experiment are K p =2, K i =0,5,K d =0.1, based on the error value between the set pressure reduction amount and the actual pressure reduction amount of the first-stage pressure reducing valve in the proportional decreasing pressure reduction calculation process (assuming -0.2), the actual detection error accumulation (assuming -0.1) and the error change rate (assuming -0.05), the proportional term, integral term and differential term are calculated respectively:

[0072] u p (t) = K p *e(t)=2*(-0.2)=-0.4,

[0073] u i (t) = K i *∫e(t)=0.5*(-0.2)+(-0.1)=-0.2,

[0074]

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

[0076] Set up a cooling water circulation device, connect the depressurized steam to the cooling water circulation system, obtain the steam temperature when entering the cooling water circulation system and the adjustment target temperature, and calculate the cooling water flow rate requirement in real time based on the actual heat exchange efficiency of the cooling water circulation system and the cross-sectional area of ​​the cooling water circulation pipeline. The specific calculation expression is:

[0077]

[0078] Where v is the cooling water flow rate requirement, m sis the mass flow rate of steam, C s , C w are the specific heat capacities of steam and water at the outlet of the pressure reducing channel, ΔT s , ΔT w are the temperature changes after steam and water exchange, ρ is the density of water, A is the cross-sectional area of ​​the cooling water circulation pipeline, and η is the actual heat exchange efficiency.

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

[0080]

[0081] At this time, the cooling water flow rate demand calculation result is 8.23m / s, and the cooling water flow rate of the cooling water circulation system is adjusted in real time according to the cooling water flow rate demand calculation result.

[0082] Reference Figure 3 As shown, the steam after temperature and pressure reduction is connected to the heat exchanger, and the heat exchange deviation between the steam and the pressurized crude benzene area crude oil is evaluated based on the crude oil type. The output of the flow rate of the circulating pump is adjusted specifically including:

[0083] The crude oil from the crude benzene area is pressurized to the set pressure by a variable frequency driven circulating pump and then connected to the heat exchanger. At the same time, the steam after temperature and pressure reduction is connected to the heat exchanger.

[0084] The target temperature range for heat exchange of lean oil and the target temperature range for heat exchange of rich oil are set. Based on the API gravity measurement results of crude oil in the crude benzene area, it is determined whether the crude oil connected to the heat exchanger is lean oil or rich oil. Generally speaking, lean oil has a high API gravity and a low density, usually greater than 31.1°API (when the API gravity is greater than 31.1, it is called "light oil"), a small specific gravity, and a low viscosity. Lean oil is rich in light hydrocarbon components, usually easier to refine and process, and contains more combustible gases and light liquids. It is suitable for the production of light petroleum products such as gasoline and diesel. Heavy oil (rich oil) has a low API gravity, usually less than 20°API, with a high density, high viscosity, and contains more heavier hydrocarbons. Heavy oil contains a large amount of high molecular weight substances, which are more difficult to refine and often require higher temperatures and pressures for processing.

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

[0086] The real-time outlet temperature of the heat exchanger after the heat exchange of crude oil is completed is obtained. According to 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 is terminated.

[0087] Reference Figure 4 As shown, the crude oil after heat exchange is transported to the debenzene tower, and the debenzene efficiency is evaluated based on infrared spectroscopy technology. If it does not meet the standard, heat exchange is performed again and the crude oil is transported to the debenzene tower. The specific steps include:

[0088] Infrared spectroscopy is based on the principle that molecules absorb infrared light of different wavelengths. When infrared light is irradiated to the sample, the chemical bonds in the molecules absorb light of a specific frequency, causing the molecules to vibrate or rotate. Different chemical bonds have different absorption peaks in the infrared region, so the composition of the substance can be identified and analyzed by measuring the position and intensity of these absorption peaks. The FTIR instrument light source emits infrared radiation, which is then passed through an interferometer to generate an interference signal. The detector receives the interference signal passing through the crude oil sample and converts the signal into a time domain signal.

[0089] In crude oil, benzene compounds (such as benzene, toluene, xylene, etc.) will have characteristic infrared absorption peaks, which are mainly derived from the CH bending vibration of the benzene ring and the stretching vibration of the C=C double bond. By analyzing the absorption peaks of crude oil samples in infrared spectra, the time domain signals are processed by Fourier transform algorithm to obtain infrared absorption spectra. Based on the infrared absorption spectra, the infrared absorption peak intensity of benzene in the crude oil samples at the outlet of the debenzene tower is monitored in real time, and the benzene concentration in the crude oil samples at the outlet of the debenzene tower is calculated. The principle is that the CH stretching vibration in the benzene molecule and the C=C vibration of the aromatic ring usually produce obvious absorption peaks around about 3030cm-1 (CH stretching vibration) and about 1500-1600cm-1 (C=C stretching vibration).

[0090] The standard benzene concentration of the crude oil after debenzening is set, and the crude oil at the outlet of the debenzening tower is diverted based on the standard benzene concentration. The crude oil exceeding the standard benzene concentration is re-connected to the heat exchanger for re-heat exchange and cyclic debenzening.

[0091] Reference Figure 5 As shown, the steam condensed after heat exchange is input into the flash tank, and the low-pressure saturated steam after pressure reduction is merged into the low-pressure steam network to realize the secondary recovery of steam. Specifically, it includes:

[0092] Collect the steam condensate formed by the cooled steam after heat exchange in the heat exchanger, and test the initial temperature and initial pressure of the steam condensate after the steam condensate is processed by the steam trap;

[0093] The steam cooled down after heat exchange condenses into steam condensate and enters the flash tank through the steam trap and pressure reducing valve. When the high-pressure and 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, which 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 to realize steam recovery and reuse.

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

[0095] The low-pressure saturated steam generated by boiling and vaporizing the steam condensate in the flash tank is incorporated into the low-pressure steam network for secondary steam recovery;

[0096] The steam condensate that has not been re-vaporized in the flash tank is connected to the desalted water tank as a desalted water reserve. Through the above technical solution, the heat energy and water resources of the steam condensate generated by the heat exchanger can be effectively recovered and utilized. This process not only realizes the secondary recovery of energy, but also reduces the waste caused by direct steam discharge, and improves the economic benefits and environmental performance of the system.

[0097] The process flow of the waste heat recycling method for heat exchangers and flash tanks replacing tubular furnaces is as follows:

[0098] The high-pressure steam of 540℃ and 9.8MPa from the coking plant is reduced in temperature and pressure by the temperature reduction and pressure reduction system (main components: pressure reducing valve device, cooling water circulation device), and the original 540℃ and 9.8MPa high-pressure steam is reduced in temperature and pressure to become 400℃ and 3.8MPa medium-pressure steam. The pressure reducing valve device is mainly composed of: TG01 temperature gauge, PG01 pressure gauge, and pressure reducing valve PV01. The cooling water circulation device is mainly composed of FV02 regulating valve and PG03 pressure gauge. The pipeline after the high-pressure steam temperature reduction and pressure reduction device is equipped with a safety valve PSV01 to ensure system safety; the temperature detection TG02 and the pressure detection PG02 monitor the system pressure and temperature in real time.

[0099] The medium-pressure steam obtained after temperature reduction and pressure reduction is heat exchanged with the rich oil (or lean oil) from the crude benzene zone. After heat exchange in the heat exchanger E01, the heated hot rich oil (or lean oil) is sent to the debenzene tower. The outlet of the hot rich oil (lean oil) of the heat exchanger is equipped with a temperature transmitter TE01 and a pressure gauge TG04. The steam inlet of the heat exchanger is equipped with a regulating valve FV01. The steam volume is controlled by adjusting the opening of the valve FV01 to adjust the rich oil (or lean oil) temperature. The valve opening is adjusted to a large degree when the temperature of the rich oil (or lean oil) at the outlet of the heat exchanger is low, and the valve opening is adjusted to a small degree when the temperature is high.

[0100] The steam cooled down after heat exchange in the heat exchanger condenses into steam condensate, and the condensate, air and carbon dioxide in the steam are discharged through the steam trap first; then the pressure is reduced from 3.8MPa to 0.6MPa through the pressure reducing valve PV02, and enters the flash tank V01. When the high-pressure and high-temperature steam condensate is decompressed, the boiling point of the steam condensate is also reduced due to the sudden drop in pressure, which causes the condensate to boil and vaporize rapidly. The low-pressure saturated steam generated after vaporization is incorporated into the low-pressure steam pipeline to realize steam recovery and reuse. Safety valve PSV02, temperature instrument TE02 and pressure gauge PG08 are set on the flash tank V01 to detect the status of the storage tank in real time to ensure the safety of the storage tank.

[0101] Furthermore, the present invention also proposes a storage medium for a method for recycling waste heat of a heat exchanger and a flash tank instead of a tubular furnace, on which a computer-readable program is stored. When the computer-readable program is called, the above-mentioned method for recycling waste heat of a heat exchanger and a flash tank instead of a tubular furnace is executed.

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

[0103] The above shows and describes 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 above embodiments and descriptions only describe the principles of the present invention. The present invention may be subject to various changes and improvements without departing from the spirit and scope of the present invention. These changes and improvements fall within the scope of the present invention. The scope of protection claimed by the present invention is defined by the attached claims and their equivalents.

Claims

1. A waste heat recycling method for heat exchangers and flash tanks replacing tubular furnaces, characterized in that: include: The steam generated during the coke oven operation is collected in real time, and the steam temperature and pressure are dynamically adjusted through the water circulation cooling device and multi-stage pressure reducing valve design; The steam after temperature and pressure reduction is connected to the heat exchanger, and the heat exchange deviation between the steam and the pressurized crude benzene area crude oil is evaluated based on the crude oil type, and the flow output of the circulation pump is adjusted; The crude oil after heat exchange is transported to the debenzene tower, and the debenzene efficiency is evaluated based on infrared spectroscopy technology. If it does not meet the standard, heat exchange is performed again and the crude oil is transported to the debenzene tower; The steam condensed after heat exchange is input into the flash tank, and the low-pressure saturated steam after pressure reduction is incorporated into the low-pressure steam network to realize secondary steam recovery.

2. A waste heat recycling method for heat exchangers and flash tanks replacing tubular furnaces according to claim 1, characterized in that: The real-time collection of steam generated during the operation of the coke oven and the dynamic adjustment of the steam temperature and pressure through the water circulation cooling device and the multi-stage pressure reducing valve design specifically include: Set up multi-stage pressure reducing valves, and set high-precision pressure sensors and temperature sensors after each stage of the pressure reducing valve to monitor the pressure and temperature changes of steam in real time and set the target pressure and temperature of steam regulation; The steam generated during the operation of the coke oven is connected to the multi-stage decompression channel, and the blocking position of the multi-stage decompression channel is delineated based on the initial specific enthalpy value of the steam entering the decompression channel; The multi-stage pressure reducing valve group before the blocking section is marked as a first-layer pressure reducing section, and the multi-stage pressure reducing valve group after the blocking section is marked as a second-layer pressure reducing section, and the steam is pressure-reduced in sections based on the pressure reducing section division; Set the pressure requirement threshold for steam to enter the second-layer depressurization section, and mark the threshold as the target pressure of the first-layer depressurization section; The pressure difference between the initial pressure of the high-pressure steam and the target pressure of the first pressure reduction section 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 pressure reduction section; When the steam enters the second-layer pressure reduction section, the initial opening of the pressure reducing valve of the second-layer pressure reduction section is set based on the constructed exponential proportional decreasing function combined with the target pressure of steam regulation, where the exponential proportional decreasing function is: In the formula, ΔP i is the set pressure reduction of the i-th pressure reducing valve in the second-layer pressure reducing section, ΔP end is the total pressure reduction demand of the second-layer pressure reduction section, ΔP base is the basic pressure reduction setting of the pressure reducing valve, Δt i is the passage time of steam in the i-th pressure reducing valve, and m is the total number of pressure reducing valves in the second-layer pressure reducing section; After the first and second pressure reduction sections are running stably, the actual opening of each pressure reducing valve in the second pressure reduction section is adjusted in real time based on the PID control algorithm; Set up a cooling water circulation device, connect the depressurized steam to the cooling water circulation system, obtain the steam temperature when entering the cooling water circulation system and the adjustment target temperature, and calculate the cooling water flow rate requirement in real time based on the actual heat exchange efficiency of the cooling water circulation system and the cross-sectional area of ​​the cooling water circulation pipeline. The specific calculation expression is: Where v is the cooling water flow rate requirement, m s is the mass flow rate of steam, C s , C w are the specific heat capacities of steam and water at the outlet of the pressure reducing channel, ΔT s , ΔT w are the temperature changes after steam and water exchange, ρ is the density of water, A is the cross-sectional area of ​​the cooling water circulation pipeline, and η is the actual heat exchange efficiency; The cooling water flow rate of the cooling water circulation system is adjusted in real time according to the cooling water flow rate demand calculation results.

3. A waste heat recycling method for heat exchangers and flash tanks replacing tubular furnaces according to claim 2, characterized in that: The step of connecting the steam after temperature and pressure reduction to the heat exchanger, evaluating the heat exchange deviation between the steam and the crude oil in the pressurized crude benzene region based on the crude oil type, and adjusting the output of the flow rate of the circulating pump specifically includes: The crude oil from the crude benzene area is pressurized to the set pressure by a variable frequency driven circulating pump and then connected to the heat exchanger. At the same time, the steam after temperature and pressure reduction is connected to the heat exchanger. The lean oil heat exchange target temperature range and the rich oil heat exchange target temperature range are set, and the crude oil connected to the heat exchanger is judged to be lean oil or rich oil based on the API gravity measurement result of the crude oil in the crude benzene area; According to the target temperature range corresponding to the crude oil type, the opening of the regulating valve on the steam inlet pipe of the heat exchanger is adjusted to heat the crude oil inside the heat exchanger; The real-time outlet temperature of the heat exchanger after the heat exchange of crude oil is completed is obtained. According to 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 is terminated.

4. A waste heat recycling method for heat exchangers and flash tanks replacing tubular furnaces according to claim 3, characterized in that: The heat exchanged crude oil is transported to the debenzene tower, and the debenzene efficiency is evaluated based on infrared spectroscopy technology. If the efficiency does not meet the standard, the heat exchange is performed again and the crude oil is transported to the debenzene tower, which specifically includes: The FTIR instrument light source emits infrared radiation, which is passed through an interferometer to generate an interference signal. The detector receives the interference signal passing through the crude oil sample and converts the signal into a time domain signal. The time domain signal is processed by Fourier transform algorithm to obtain infrared absorption spectrum, and the infrared absorption peak intensity of benzene in the crude oil sample at the outlet of the debenzene tower is monitored in real time based on the infrared absorption spectrum to deduce the benzene concentration in the crude oil sample at the outlet of the debenzene tower; The standard benzene concentration of the crude oil after debenzening is set, and the crude oil at the outlet of the debenzening tower is diverted based on the standard benzene concentration. The crude oil exceeding the standard benzene concentration is re-connected to the heat exchanger for re-heat exchange and cyclic debenzening.

5. A waste heat recycling method for heat exchangers and flash tanks replacing tubular furnaces according to claim 4, characterized in that: The method of inputting the condensed steam after heat exchange into a flash tank and merging the low-pressure saturated steam after pressure reduction into the low-pressure steam network to realize secondary steam recovery specifically includes: Collect the steam condensate formed by the cooled steam after heat exchange in the heat exchanger, and test the initial temperature and initial pressure of the steam condensate after the steam condensate is processed by the steam trap; Based on historical samples, the saturated vapor pressure curve of steam condensate is measured, and the pressure reducing valve is dynamically adjusted to reduce the pressure of steam condensate and input it into the flash tank, so that the steam condensate in the flash tank matches the low-pressure boiling point of the saturated vapor pressure curve; The low-pressure saturated steam generated by boiling and vaporizing the steam condensate in the flash tank is incorporated into the low-pressure steam network for secondary steam recovery; The steam condensate that has not been re-vaporized in the flash tank is connected to the desalted water tank as a desalted water reserve.

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