A waste heat recovery device for a sulfuric acid plant low-temperature recovery section

Abstract

The present application relates to waste heat recovery technical field, specifically to a kind of sulphating chemical low-temperature recovery section waste heat recovery device, including the concentrated sulfuric acid of evaporative feedwater heater for conveying the sulfuric acid one inlet pipe, and the concentrated sulfuric acid temperature is 140 ℃-190 ℃, still including phase-change heat energy recovery device, its one side is provided with sulfuric acid import and sulfuric acid one inlet pipe intercommunication for 140 ℃-190 ℃ concentrated sulfuric acid enters, and its one side is provided with the sulfuric acid outlet for the concentrated sulfuric acid of temperature 100 ℃-150 ℃ after heat exchange and discharges;Deaerated water inlet pipe, it is used to transport temperature 90 ℃-110 ℃ deaerated water to phase-change heat energy recovery device and concentrated sulfuric acid heat exchange generates 0.1-0.2MPa steam, and phase-change heat energy recovery device top is connected with the main steam discharge port for discharging steam;Desalted water heat exchanger, it is used to carry out secondary waste heat recovery to concentrated sulfuric acid after phase-change heat energy recovery device processing, and finally concentrated sulfuric acid is cooled to 40 ℃-90 ℃.This process makes full use of the waste heat of concentrated sulfuric acid, further improves the energy recovery utilization rate.

Description

Technical Field

[0001] This invention relates to the field of waste heat recovery technology, specifically to a waste heat recovery device for a low-temperature recovery section in a sulfuric acid chemical process. Background Technology

[0002] Sulfuric acid, as a basic chemical raw material, is widely used in many fields such as fertilizers, metallurgy, petrochemicals, chemical fibers, and non-ferrous smelting. Its production scale and output are one of the important indicators for measuring a country's chemical industry level. In recent years, with the continuous growth of the global economy and the continuous advancement of industrialization, the consumption of sulfuric acid has shown a steady upward trend. In the low-temperature recovery section of the sulfuric acid industry, the concentrated sulfuric acid solution from the heat recovery tower, after passing through the evaporator and the evaporation feedwater heater, has its temperature reduced to 140-190℃ before being sent to the demineralized water heat exchanger to heat the demineralized water. The demineralized water from the demineralized water pipe gallery, at 20℃-50℃, is heated to 80-110℃ and then sent to the deaerator, while the concentrated sulfuric acid solution is reduced from 140℃-190℃ to about 100℃-130℃ before being sent to the circulating acid pump tank for subsequent processes. However, especially in the low-temperature recovery section, a large amount of waste heat resources are not being fully utilized.

[0003] For example, patent document CN117023523A discloses a low-temperature recovery system for sulfuric acid production from pyrite. After the SO3-containing primary conversion gas from the third stage of the converter is input through the inlet pipe, the SO3 flows from bottom to top through the packing and comes into countercurrent contact with concentrated sulfuric acid (concentration of 99%, temperature of 165-175℃ and 50-60℃ respectively) flowing from the first-stage spray pipe and the second-stage spray pipe through the packing. After absorbing SO3, the concentration of the concentrated sulfuric acid is 99.5%, and the temperature increases by 20℃. Then, the concentrated sulfuric acid at the bottom of the high-temperature absorption tower is pumped to the high-temperature acid circulation tank through the first circulating acid pump, and then pumped to the steam generator through the second circulating acid pump for heat exchange to generate low-pressure steam. At the same time, the temperature of the concentrated sulfuric acid after heat exchange in the steam generator decreases by 20℃, so as to realize the recovery and utilization of the low-temperature waste heat generated in the SO3 absorption step to generate steam.

[0004] In existing technologies, evaporative feedwater heaters are designed to initially cool concentrated sulfuric acid, enabling it to participate more efficiently in the demineralized water heating process and achieve cascaded heat utilization. However, in actual industrial applications, the temperature drop of concentrated sulfuric acid after flowing through the evaporative feedwater heater is extremely limited, with the actual temperature remaining significantly higher than expected. Professional thermodynamic analysis and comparison with actual operating data reveal that the excessively high temperature of the concentrated sulfuric acid, upon entering the demineralized water heat exchanger, causes a series of problems detrimental to efficient heat utilization. Firstly, the large initial temperature difference between the concentrated sulfuric acid and the demineralized water leads to an excessively rapid and difficult-to-control heat transfer rate, resulting in localized heat concentration and rapid temperature increases in the heat exchanger. This not only exacerbates internal thermal stress and shortens the equipment's lifespan but also poses potential risks such as scaling and corrosion on the heat exchanger tube walls due to localized overheating, further reducing heat exchange efficiency. Therefore, this application proposes a waste heat recovery device for a low-temperature recovery section in sulfuric acid chemical production. Summary of the Invention

[0005] The purpose of this invention is to provide a waste heat recovery device for a low-temperature recovery section in a sulfuric acid chemical process, so as to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a waste heat recovery device for a low-temperature recovery section of a sulfuric acid chemical plant, comprising a sulfuric acid inlet pipe for conveying concentrated sulfuric acid from an evaporation feedwater heater, wherein the temperature of the concentrated sulfuric acid is 140℃-190℃, and further comprising:

[0007] The phase change heat energy recovery device has a sulfuric acid inlet on one side connected to a sulfuric acid inlet pipe to supply concentrated sulfuric acid at 140℃-190℃, and a sulfuric acid outlet on the other side to discharge concentrated sulfuric acid at a temperature of 100℃-150℃ after heat exchange.

[0008] The deoxygenated water inlet pipe is used to transport deoxygenated water at a temperature of 90℃-110℃ to the phase change heat recovery device for heat exchange with concentrated sulfuric acid to generate 0.1-0.2MPa steam. The top of the phase change heat recovery device is connected to the main steam outlet for discharging steam.

[0009] The demineralized water heat exchanger is used for secondary waste heat recovery of concentrated sulfuric acid after treatment by the phase change heat energy recovery device. One end of the demineralized water heat exchanger is connected to a demineralized water inlet pipe for conveying raw demineralized water at a temperature of 20℃-50℃ into its interior, and the other end of the sulfuric acid outlet is provided with a sulfuric acid second inlet pipe for concentrated sulfuric acid to be discharged into the demineralized water heat exchanger to exchange heat with the raw demineralized water. The bottom of the demineralized water heat exchanger is connected to a sulfuric acid second outlet pipe for the concentrated sulfuric acid after secondary recovery to be discharged into the circulating acid pump tank, and finally the concentrated sulfuric acid is cooled to 40℃-90℃.

[0010] Preferably, the top of the main steam outlet is connected to a steam pipe, and the steam pipe is connected to a compressor. The compressor is used to pressurize the low-pressure steam and channel it into the main steam pipe through the steam outlet pipe. The steam outlet pipe is equipped with a venting valve for releasing gas.

[0011] Preferably, one side of the sulfuric acid inlet pipe is connected to a sulfuric acid bypass pipe that changes the flow direction of concentrated sulfuric acid, and one end of the sulfuric acid bypass pipe is connected to the sulfuric acid outlet pipe. One end of the sulfuric acid outlet is connected to a sulfuric acid outlet pipe that is connected to the sulfuric acid bypass pipe, and one end of the sulfuric acid inlet pipe is connected to the sulfuric acid bypass pipe.

[0012] Preferably, one side of the deoxygenated water inlet pipe is connected to a deoxygenated water bypass pipe, and the deoxygenated water bypass pipe supplies a portion of the deoxygenated water to be transported to the compressor outlet for regulating the compressor outlet steam temperature, and the interior of the deoxygenated water bypass pipe is connected to the main sewage pipe for controlling the discharge of water.

[0013] Preferably, one end of the compressor is connected to an air pipe for compressed air to enter.

[0014] Preferably, the bottom of the phase change heat energy recovery device is provided with a drain outlet for periodic drainage, the bottom of the phase change heat energy recovery device is provided with a sewage outlet for continuous sewage discharge, the demineralized water heat exchanger is provided with a drain pipe and a side drain pipe for drainage, the drain pipe and the side drain pipe are connected to a main sewage pipe extending into the sewage discharge tank, and the sewage outlet and the drain outlet are both connected to the main sewage pipe.

[0015] Preferably, the sulfuric acid inlet pipe is internally connected to an acid discharge bypass pipe that supplies acid to the main acid discharge pipe; the phase change heat recovery device is internally connected to an acid discharge port that is connected to the acid discharge bypass pipe; the demineralized water heat exchanger is provided with an acid discharge second pipe and an acid discharge first pipe that are respectively connected to the acid discharge bypass pipe; and the sulfuric acid inlet pipe is internally provided with a pipeline for acid discharge that is connected to the acid discharge bypass pipe.

[0016] Preferably, both sides of the phase change heat energy recovery device are provided with liquid level and gas pressure connector interfaces for detecting the internal gas pressure and water level. The top of the phase change heat energy recovery device is connected to a deoxygenated water interface for deoxygenated water to enter. The top of the phase change heat energy recovery device is provided with a bypass steam outlet, and the top of the bypass steam outlet is connected to a bypass pipe connected to a steam pipe.

[0017] Preferably, the steam pipe is internally connected to a plurality of narrowing pipes with a diameter smaller than that of the pipe, and the bottom of each narrowing pipe is fixedly connected to a conical ring, the top of each narrowing pipe is fixedly connected to a slope ring, and the inner wall of the slope ring is fixedly connected to a flow-blocking ring.

[0018] Preferably, the narrowing tube has multiple reflux grooves that penetrate the slope ring inside, the inner wall of the conical ring has multiple flow grooves, and the narrowing tube has a collection groove for collecting condensate inside, and the slope ring and flow grooves are all connected to the collection groove.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] 1. The sulfuric acid inlet pipe delivers concentrated sulfuric acid at 140℃-190℃ to the phase change heat recovery unit. Through heat exchange with deoxygenated water at 90℃-110℃, the heat of the concentrated sulfuric acid is transferred to the deoxygenated water, causing the deoxygenated water to heat up and vaporize, producing steam at 0.1-0.2MPa. This process achieves preliminary recovery of waste heat from the concentrated sulfuric acid, improving energy utilization and reducing energy waste. The generated low-pressure steam is discharged through a steam pipe to compressor 301 for pressurization, becoming superheated steam at 0.2-0.3MPa, which is then discharged into the main steam pipe through a steam exhaust pipe. The compressor further pressurizes the low-pressure steam, improving its quality and enabling it to better meet the pressure and temperature requirements of subsequent processes, further improving energy utilization efficiency. The demineralized water heat exchanger performs secondary waste heat recovery from the concentrated sulfuric acid treated by the phase change heat recovery unit. Raw demineralized water at 20℃-50℃ enters the demineralized water heat exchanger through the demineralized water inlet pipe, where it exchanges heat with concentrated sulfuric acid at 100℃-150℃, heating the demineralized water to 85-115℃. This process fully utilizes the waste heat of the concentrated sulfuric acid, further improving energy recovery and utilization efficiency and reducing energy consumption. The heated demineralized water is then sent to the deaerator, where the temperature can be increased according to the deaerator's needs, thereby reducing the deaerator's steam consumption and achieving rational energy allocation and efficient utilization. A deaerator bypass pipe supplies a portion of the deaerator water to the compressor outlet for regulating the compressor outlet steam temperature. The drain pipe and side drain pipe installed in the demineralized water heat exchanger remove impurities accumulated inside the heat exchanger, ensuring the normal operation and heat exchange effect of the demineralized water heat exchanger.

[0021] 2. By connecting the water level gauge and the pressure gauge, the pressure and water level of the deoxygenated water in the phase change heat energy recovery device can be detected in real time and accurately. In conjunction with the deoxygenated water inlet pipe, when a drop in water level is detected, deoxygenated water can be replenished in time through the deoxygenated water inlet pipe to maintain the normal water level in the device. When the steam volume increases, the bypass steam outlet is opened, and steam can flow into the steam pipe through the bypass pipe to avoid excessive pressure in the phase change heat energy recovery device, thus playing a safety protection role. The narrowing of the pipe increases the steam flow rate and prevents steam backflow. The conical ring shortens the diameter to further accelerate the steam flow rate and reduce the residence time of steam in the pipe. The flow-blocking ring and the slope ring cooperate to prevent some of the condensate from continuing to move upward. Attached Figure Description

[0022] Figure 1 This is a schematic diagram showing the connection relationship of the various components in this invention;

[0023] Figure 2 This is a schematic diagram showing the flow direction of concentrated sulfuric acid in this invention;

[0024] Figure 3 This is a schematic diagram of the sewage and acid discharge flow direction in this invention;

[0025] Figure 4 This is a schematic diagram of the compressor in this invention;

[0026] Figure 5 This is a schematic diagram of the phase change heat recovery device in this invention;

[0027] Figure 6 This is a schematic diagram of the steam pipe structure in this invention;

[0028] Figure 7 This is a schematic diagram of the narrowing tube in this invention.

[0029] In the diagram: 100, Sulfuric acid inlet pipe 1; 101, Sulfuric acid outlet pipe 1; 102, Sulfuric acid inlet pipe 2; 103, Sulfuric acid outlet pipe 2; 104, Sulfuric acid bypass pipe; 105, Acid discharge bypass pipe; 200, Phase change heat recovery device; 201, Sulfuric acid inlet; 202, Sulfuric acid outlet; 203, Support; 204, Sewage outlet; 205, Drain outlet; 206, Acid discharge outlet; 207, Liquid level and gas pressure connector interface; 208, Deoxygenated water interface; 209, Main steam outlet; 210, Bypass steam outlet; 211, Steam pipe; 212, Narrowing pipe; 213, Restriction pipe. Flow ring; 214. Conical ring; 215. Flow channel; 216. Return channel; 217. Collection channel; 218. Slope ring; 219. Bypass pipe; 300. Deoxygenated water inlet pipe; 301. Compressor; 302. Deoxygenated water bypass pipe; 303. Main sewage pipe; 304. Air pipe; 305. Steam exhaust pipe; 306. Vent valve; 400. Demineralized water heat exchanger; 401. Demineralized water inlet pipe; 402. Demineralized water exhaust pipe; 403. Acid discharge pipe 1; 404. Acid discharge pipe 2; 405. Drain pipe; 406. Side drain pipe; 407. Main sewage pipe. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Example 1: Please refer to Figure 1 , Figure 2 as well as Figure 4The present invention provides a technical solution: a waste heat recovery device for a low-temperature recovery section of a sulfuric acid chemical plant, comprising a sulfuric acid inlet pipe 100 for conveying concentrated sulfuric acid from an evaporation feedwater heater, wherein the temperature of the concentrated sulfuric acid is 140℃-190℃, and a phase change heat energy recovery device 200, wherein a sulfuric acid inlet 201 is provided on one side and connected to the sulfuric acid inlet pipe 100 to allow concentrated sulfuric acid at 140℃-190℃ to enter, and a sulfuric acid outlet 202 is provided on one side to discharge concentrated sulfuric acid at a temperature of 100℃-150℃ after heat exchange. By setting up the phase change heat energy recovery device 200, preliminary waste heat recovery can be performed on the concentrated sulfuric acid at 140℃-190℃.

[0032] It also includes a deoxygenated water inlet pipe 300, which is used to transport deoxygenated water at a temperature of 90℃-110℃ to the phase change heat recovery device 200 for heat exchange with concentrated sulfuric acid to generate 0.1-0.2MPa steam. The top of the phase change heat recovery device 200 is connected to a main steam outlet 209 for discharging steam. The top of the main steam outlet 209 is connected to a steam pipe 211, and the steam pipe 211 is connected to a compressor 301. The compressor 301 is used to pressurize the low-pressure steam and pass it through... Steam pipe 305 connects to the main steam pipe. Steam pipe 305 is equipped with a venting valve 306 for venting. Deoxygenated water at 90℃-110℃ is introduced into the phase change heat recovery device 200 to exchange heat with concentrated sulfuric acid at 140℃-190℃, causing the deoxygenated water to heat up and vaporize. This steam is discharged for later use. The steam generated in the phase change heat recovery device 200 is low-pressure steam, which is discharged to the compressor 301 through steam pipe 211 for pressurization to improve steam quality.

[0033] The deoxygenated water inlet pipe 300 is connected to a deoxygenated water bypass pipe 302 on one side. The deoxygenated water bypass pipe 302 allows some deoxygenated water to pass through and be transported to the outlet of the compressor 301 to regulate the steam temperature at the compressor outlet. The deoxygenated water bypass pipe 302 is internally connected to a main sewage pipe 303 to control the discharge of water. One end of the compressor 301 is connected to an air pipe 304 for compressed air to enter. The deoxygenated water bypass pipe 302 allows a small amount of deaerator water to be sprayed into the outlet of the compressor 301 to precisely regulate the steam temperature and prevent overheating and damage to the equipment.

[0034] It also includes a demineralized water heat exchanger 400, which is used for secondary waste heat recovery of concentrated sulfuric acid after treatment by the phase change heat recovery device 200. One end of the demineralized water heat exchanger 400 is connected to a demineralized water inlet pipe 401 for conveying raw demineralized water at a temperature of 20℃-50℃ into its interior. One end of the sulfuric acid outlet 202 is provided with a sulfuric acid second inlet pipe 102 for concentrated sulfuric acid to be discharged into the demineralized water heat exchanger 400 for heat exchange with the raw demineralized water. The bottom of the demineralized water heat exchanger 400 is connected to a sulfuric acid second outlet pipe 103 for the concentrated sulfuric acid after secondary recovery to be discharged into the circulating acid pump tank. Finally, the concentrated sulfuric acid is cooled to 40℃-90℃. One side of the sulfuric acid first inlet pipe 100 is connected to a device for changing the temperature of the concentrated sulfuric acid. The sulfuric acid flows through a bypass pipe 104, with one end of the bypass pipe 104 connected to a second sulfuric acid outlet pipe 103. One end of the sulfuric acid outlet 202 is connected to a first sulfuric acid outlet pipe 101 connected to the bypass pipe 104, and one end of the second sulfuric acid inlet pipe 102 is connected to the bypass pipe 104. By setting up a demineralized water heat exchanger 400, the concentrated sulfuric acid can be recycled for secondary waste heat recovery. After heat exchange with deoxygenated water, the concentrated sulfuric acid is further recycled by heat exchange with the original demineralized water at a lower temperature. The waste heat of the concentrated sulfuric acid is further utilized. When the phase change heat recovery device 200 is damaged or under maintenance, the flow direction of the concentrated sulfuric acid can be changed and it can be directly introduced into the demineralized water heat exchanger 400 for heat recovery, so as not to affect production.

[0035] Please see Figure 1 , Figure 2 as well as Figure 3 Furthermore, the bottom of the phase change heat energy recovery device 200 is provided with a drain outlet 205 for periodic drainage, and the bottom of the phase change heat energy recovery device 200 is provided with a drain outlet 204 for continuous sewage discharge. The demineralized water heat exchanger 400 is provided with a drain pipe 405 and a side drain pipe 406 for drainage. The drain pipe 405 and the side drain pipe 406 are connected to a main sewage pipe 407 extending into the sewage trough. The drain outlet 204 and the drain outlet 205 are both connected to the main sewage pipe 407. The drain outlet 205 and the drain outlet 204 can discharge the impurities accumulated in the phase change heat energy recovery device 200 to prevent scaling and blockage, while the drain pipe 405 and the side drain pipe 406 can discharge the impurities accumulated in the demineralized water heat exchanger 400. All of them flow into the main sewage pipe 407 for discharge.

[0036] Furthermore, the sulfuric acid inlet pipe 100 is internally connected to an acid discharge bypass pipe 105 that supplies acid to the main acid discharge pipe. The phase change heat recovery device 200 is internally connected to an acid discharge port 206 that is connected to the acid discharge bypass pipe 105. The demineralized water heat exchanger 400 is equipped with an acid discharge second pipe 404 and an acid discharge first pipe 403 that are respectively connected to the acid discharge bypass pipe 105. The sulfuric acid inlet pipe 102 is internally connected to a pipeline for acid discharge that is connected to the acid discharge bypass pipe 105. The acid discharge port 206, the acid discharge first pipe 403, and the acid discharge second pipe 404 allow the acid to be discharged to the acid treatment system or recycled.

[0037] Specifically, concentrated sulfuric acid at 140-190℃ from the evaporation feedwater heater is transported to the phase change heat recovery device 200 via sulfuric acid inlet pipe 100 connected to sulfuric acid inlet 201. Simultaneously, deaerator water at 90℃-110℃ enters the phase change heat recovery device 200 via deaerated water inlet pipe 300, exchanging heat with the concentrated sulfuric acid to form low-pressure steam of 0.1-0.2MPa. This steam is then discharged through steam pipe 211 to the compressor 301, where it is pressurized to 0.2-0.3MPa. Superheated steam is discharged into the main steam pipe through steam pipe 305. Simultaneously, deoxygenated water inlet pipe 300 is connected to deoxygenated water bypass pipe 302, allowing some deaerator water to be pumped to the compressor 301 outlet for spraying, thus regulating the steam temperature at the compressor 301 outlet. Concentrated sulfuric acid undergoes heat exchange through phase change heat recovery device 200, reducing its temperature to 100℃-150℃. This concentrated sulfuric acid then flows into demineralized water heat exchanger 400, while the original demineralized water inlet pipe is pumped to the demineralized water heat exchanger 400 through demineralized water inlet pipe 401. The concentrated sulfuric acid in the heater 400 exchanges heat with the concentrated sulfuric acid and is discharged to the original demineralized water return pipe through the demineralized water drain pipe 402. During this process, the demineralized water is heated to 85-115℃. The heated demineralized water is then sent to the deaerator. The temperature of the demineralized water can be increased according to the needs of the deaerator, reducing the steam consumption of the deaerator. The concentrated sulfuric acid is finally cooled to 40℃-90℃ and then sent to the lower acid pipe of the secondary absorption tower of the sulfuric acid unit, entering the circulating acid pump tank. This reduces the overall temperature of the circulating acid pump tank, thereby reducing the temperature of the acid cooler in the drying tower and the finished acid cooler. The circulating water consumption is controlled. The acid discharge port 206 is connected to the acid discharge bypass pipe 105 to discharge acid for the phase change heat energy recovery device 200. At the same time, the acid discharge pipe 403 and the acid discharge pipe 404 are respectively connected to the acid discharge bypass pipe 105 to discharge acid for the demineralized water heat exchanger 400. The sewage discharge port 204 and the drain port 205 can periodically discharge sewage and water for the phase change heat energy recovery device 200. The drain pipe 405 drains water for the demineralized water heat exchanger 400. The drain port 205, the drain pipe 405 and the sewage discharge port 204 are all connected to the sewage discharge main pipe 407 to collect sewage and water.

[0038] In summary, the sulfuric acid inlet pipe 100 transports concentrated sulfuric acid at 140℃-190℃ to the phase change heat recovery device 200. Through heat exchange with deoxygenated water at 90℃-110℃, the heat of the concentrated sulfuric acid is transferred to the deoxygenated water, causing the deoxygenated water to heat up and vaporize, generating steam at 0.1-0.2MPa. This process achieves preliminary recovery of waste heat from the concentrated sulfuric acid, improving energy utilization and reducing energy waste. The generated low-pressure steam is discharged through steam pipe 211 to compressor 301 for pressurization, becoming superheated steam at 0.2-0.3MPa, which is then discharged through steam outlet pipe 305 into the steam main. The compressor 301 pressurizes the low-pressure steam, improving its quality and enabling it to better meet the steam pressure and temperature requirements of subsequent processes, further improving energy utilization efficiency. The demineralized water heat exchanger 400 performs secondary waste heat recovery on the concentrated sulfuric acid treated by the phase change heat recovery device 200. Raw demineralized water at 20℃-50℃ enters the demineralized water heat exchanger 400 through the demineralized water inlet pipe 401, where it exchanges heat with concentrated sulfuric acid at 100℃-150℃, heating the demineralized water to 85-115℃. This process fully utilizes the waste heat of the concentrated sulfuric acid, further improving energy recovery and utilization efficiency and reducing energy consumption. The heated demineralized water is then sent to the deaerator, where the temperature can be increased according to the deaerator's requirements, thereby reducing the deaerator's steam consumption and achieving rational energy allocation and efficient utilization. The deaerator bypass pipe 302 supplies a portion of the deaerator water to the outlet of the compressor 301 for regulating the compressor outlet steam temperature. The drain pipe 405 and the side drain pipe 406 in the demineralized water heat exchanger 400 can remove impurities accumulated in the heat exchanger, ensuring the normal operation and heat exchange effect of the demineralized water heat exchanger 400.

[0039] Example 2: Please refer to Figure 1 , Figure 2 as well as Figure 5 The present invention also provides a technical solution, which differs from the technical solution of Embodiment 1 as follows: a waste heat recovery device for a low-temperature recovery section of a sulfuric acid chemical plant, wherein both sides of the phase change heat energy recovery device 200 are provided with liquid level and pressure connector interfaces 207 for detecting the internal gas pressure and water level, the top of the phase change heat energy recovery device 200 is connected to a deoxygenated water interface 208 for deoxygenated water to enter, the top of the phase change heat energy recovery device 200 is provided with a bypass steam outlet 210, and the top of the bypass steam outlet 210 is connected to a bypass pipe 219 connected to a steam pipe 211. By setting the liquid level and pressure connector interface 207, a water level detector and a pressure detector can be connected to detect the gas pressure and water level of the deoxygenated water in the phase change heat energy recovery device 200. When the water level in the phase change heat energy recovery device 200 decreases, more deoxygenated water can be supplied through the deoxygenated water inlet pipe 300, and the bypass steam outlet 210 can be opened when the steam volume increases, allowing steam to flow into the steam pipe 211 through the bypass pipe 219.

[0040] Please see Figure 5 , Figure 6 as well as Figure 7 Furthermore, the steam pipe 211 is internally connected to multiple narrowing pipes 212 with diameters smaller than its own. Each narrowing pipe 212 has a conical ring 214 fixedly connected to its bottom and a slope ring 218 fixedly connected to its top. The inner wall of the slope ring 218 is fixedly connected to a flow-blocking ring 213. Multiple return grooves 216 penetrating the slope ring 218 are formed inside the narrowing pipe 212. Multiple flow grooves 215 are formed on the inner wall of the conical ring 214. A collection trough 217 for collecting condensate is formed inside the narrowing pipe 212. Furthermore, the slope ring 218 and the flow channel 215 are both connected to the collection tank 217. By setting the narrowing pipe 212, the flow rate of steam can be increased, thereby preventing steam backflow. When the steam passes through the narrowing pipe 212, it will further come into contact with the inner wall of the narrowing pipe 212 to generate condensate, which will then adhere to the inner wall of the flow channel 215. As the steam continues to flow, some of the condensate will continue to move upward and pass through the flow-blocking ring 213 and flow back into the collection tank 217 through the return channel 216. Meanwhile, some of the condensate will move downward in the flow channel 215 and approach the collection tank 217 for collection.

[0041] Specifically, the gas generated by the heat exchange between deoxygenated water and concentrated sulfuric acid is discharged through steam pipe 211 and passes through multiple narrowing pipes 212. The conical rings 214 installed in the multiple narrowing pipes 212 shorten the diameter and accelerate the flow speed of steam. At the same time, the gaps between the multiple steam pipes 211 can form turbulent steam and reduce condensate retention. During production, the condensate will adhere to multiple flow channels 215. The condensate will enter the collection tank 217 for storage through the return channel 216 and the flow channels 215 respectively.

[0042] In summary, by connecting the water level gauge and the pressure gauge, the pressure and water level of the deoxygenated water in the phase change heat recovery device 200 can be detected in real time and accurately. In conjunction with the deoxygenated water inlet pipe 300, when a drop in water level is detected, deoxygenated water can be replenished in time through the deoxygenated water inlet pipe 300 to maintain the normal water level in the device. When the steam volume increases, the bypass steam outlet 210 is opened, and steam can flow into the steam pipe 211 through the bypass pipe 219 to avoid excessive pressure in the phase change heat recovery device 200 and play a safety protection role. The narrowing pipe 212 increases the steam flow rate and prevents steam backflow. The conical ring 214 shortens the diameter to further accelerate the steam flow rate and reduce the residence time of steam in the pipe. The flow-blocking ring 213 cooperates with the slope ring 218 to prevent some of the condensate from continuing to move upward.

[0043] Working principle: Concentrated sulfuric acid at 140-190℃ from the evaporative feedwater heater is transported to the phase change heat recovery device 200 through sulfuric acid inlet pipe 100 connected to sulfuric acid inlet 201. At the same time, deaerator water at 90℃-110℃ enters the phase change heat recovery device 200 through deaerator water inlet pipe 300 and exchanges heat with concentrated sulfuric acid to form low-pressure steam of 0.1-0.2MPa. It is discharged to the compressor 301 through steam pipe 211. After being pressurized by the compressor 301, it becomes superheated steam of 0.2-0.3MPa and is discharged to the steam main pipe through steam outlet pipe 305. At the same time, deaerator water inlet pipe 300 is connected to deaerator water bypass pipe 302, so that part of the deaerator water is transported to the outlet of compressor 301 through deaerator water bypass pipe 302 for spraying water, thereby regulating the steam temperature at the outlet of compressor 301.

[0044] After the concentrated sulfuric acid undergoes heat exchange in the phase change heat recovery device 200, its temperature drops to 100℃-150℃. Subsequently, the concentrated sulfuric acid flows into the demineralized water heat exchanger 400. Meanwhile, the water from the original demineralized water inlet pipe is transported to the demineralized water heat exchanger 400 through the demineralized water inlet pipe 401 to exchange heat with the concentrated sulfuric acid and then discharged into the original demineralized water return pipe through the demineralized water outlet pipe 402. During this process, the demineralized water is heated to 85-115℃. The heated demineralized water is then sent to the deaerator. The temperature of the demineralized water can be increased according to the needs of the deaerator, thereby reducing the steam consumption of the deaerator. The concentrated sulfuric acid is finally cooled to 40℃-90℃ and then sent to the lower acid pipe of the second absorption tower of the sulfuric acid unit, entering the circulating acid pump tank. This reduces the overall temperature of the circulating acid pump tank, thereby reducing the circulating water consumption of the drying tower acid cooler and the finished acid cooler.

[0045] The acid discharge port 206 is connected to the acid discharge bypass pipe 105 to discharge acid for the phase change heat energy recovery device 200. At the same time, the acid discharge pipe 403 and the acid discharge pipe 404 are respectively connected to the acid discharge bypass pipe 105 to discharge acid for the demineralized water heat exchanger 400. The sewage discharge port 204 and the drain port 205 can periodically discharge sewage and water for the phase change heat energy recovery device 200. The drain pipe 405 drains water for the demineralized water heat exchanger 400. The drain port 205, the drain pipe 405 and the sewage discharge port 204 are all connected to the sewage main pipe 407 to collect sewage and water.

[0046] The gas generated by the heat exchange between deoxygenated water and concentrated sulfuric acid is discharged through steam pipe 211 and passes through multiple narrowing pipes 212. The conical rings 214 installed in the multiple narrowing pipes 212 shorten the diameter and accelerate the flow speed of steam. At the same time, the gaps between the multiple steam pipes 211 can form turbulent steam and reduce condensate retention. During production, the condensate will adhere to multiple flow channels 215. The condensate will enter the collection tank 217 for storage through the return channel 216 and the flow channels 215 respectively.

[0047] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0048] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A waste heat recovery device for a low-temperature recovery section of a sulfuric acid chemical plant, comprising a sulfuric acid inlet pipe (100) for conveying concentrated sulfuric acid from an evaporation feedwater heater, wherein the temperature of the concentrated sulfuric acid is 140℃-190℃, characterized in that, Also includes: The phase change heat recovery device (200) has a sulfuric acid inlet (201) on one side connected to a sulfuric acid inlet pipe (100) for the intake of concentrated sulfuric acid at 140℃-190℃, and a sulfuric acid outlet (202) on one side for the discharge of concentrated sulfuric acid at 100℃-150℃ after heat exchange. The deoxygenated water inlet pipe (300) is used to transport deoxygenated water at a temperature of 90℃-110℃ to the phase change heat recovery device (200) for heat exchange with concentrated sulfuric acid to generate 0.1-0.2 MPa steam. The top of the phase change heat recovery device (200) is connected to a main steam outlet (209) for discharging steam. A demineralized water heat exchanger (400) is used to perform secondary waste heat recovery on concentrated sulfuric acid after treatment by the phase change heat recovery device (200). One end of the demineralized water heat exchanger (400) is connected to a demineralized water inlet pipe (401) for conveying raw demineralized water at a temperature of 20℃-50℃ into its interior. One end of the sulfuric acid outlet (202) is provided with a sulfuric acid second inlet pipe (102) for discharging concentrated sulfuric acid into the demineralized water heat exchanger (400) to exchange heat with the raw demineralized water. The bottom of the demineralized water heat exchanger (400) is connected to a sulfuric acid second outlet pipe (103) for discharging the concentrated sulfuric acid after secondary recovery to the circulating acid pump tank. Finally, the concentrated sulfuric acid is cooled to 40℃-90℃. The top of the main steam outlet (209) is connected to a steam pipe (211), and the steam pipe (211) is connected to a compressor (301). The compressor (301) is used to pressurize the low-pressure steam and then feed it into the main steam pipe through the steam outlet pipe (305). The steam outlet pipe (305) is provided with a venting valve (306) for venting. The deoxygenated water inlet pipe (300) is connected to a deoxygenated water bypass pipe (302) on one side. The deoxygenated water bypass pipe (302) allows some deoxygenated water to pass through and be transported to the outlet of the compressor (301) to regulate the outlet steam temperature of the compressor. The deoxygenated water bypass pipe (302) is internally connected to the main sewage pipe (303) for controlling the discharge of water. Both sides of the phase change heat recovery device (200) are provided with liquid level and pressure connector interfaces (207) for detecting the internal air pressure and water level. The top of the phase change heat recovery device (200) is connected to a deoxygenated water interface (208) for deoxygenated water to enter. The top of the phase change heat recovery device (200) is provided with a bypass steam outlet (210), and the top of the bypass steam outlet (210) is connected to a bypass pipe (219) connected to a steam pipe (211). The steam pipe (211) is internally connected to a plurality of narrowing pipes (212) with a diameter smaller than that of the pipe, and the bottom of each narrowing pipe (212) is fixedly connected to a conical ring (214), the top of each narrowing pipe (212) is fixedly connected to a slope ring (218), and the inner wall of the slope ring (218) is fixedly connected to a flow-blocking ring (213). The narrowing tube (212) has multiple return grooves (216) that penetrate the slope ring (218) inside, the inner wall of the cone ring (214) has multiple flow grooves (215), the narrowing tube (212) has a collection groove (217) for collecting condensate inside, and the slope ring (218) and flow grooves (215) are all connected to the collection groove (217).

2. The waste heat recovery device for a low-temperature recovery section of a sulfuric acid chemical plant according to claim 1, characterized in that: One side of the sulfuric acid inlet pipe (100) is connected to a sulfuric acid bypass pipe (104) that changes the flow direction of concentrated sulfuric acid, and one end of the sulfuric acid bypass pipe (104) is connected to the sulfuric acid outlet pipe (103). One end of the sulfuric acid outlet (202) is connected to a sulfuric acid outlet pipe (101) that is connected to the sulfuric acid bypass pipe (104), and one end of the sulfuric acid inlet pipe (102) is connected to the sulfuric acid bypass pipe (104).

3. The waste heat recovery device for a low-temperature recovery section of a sulfuric acid chemical plant according to claim 1, characterized in that: One end of the compressor (301) is connected to an air pipe (304) for compressed air to enter.

4. The waste heat recovery device for a low-temperature recovery section of a sulfuric acid chemical plant according to claim 1, characterized in that: The bottom of the phase change heat energy recovery device (200) is provided with a drain outlet (205) for periodic drainage, and the bottom of the phase change heat energy recovery device (200) is provided with a sewage outlet (204) for continuous sewage discharge. The demineralized water heat exchanger (400) is provided with a drain pipe (405) and a side drain pipe (406) for drainage. The drain pipe (405) and the side drain pipe (406) are connected to a main sewage pipe (407) extending into the sewage trough. The sewage outlet (204) and the drain outlet (205) are both connected to the main sewage pipe (407).

5. The waste heat recovery device for a low-temperature recovery section of a sulfuric acid chemical plant according to claim 1, characterized in that: The sulfuric acid inlet pipe (100) is internally connected to an acid discharge bypass pipe (105) that supplies acid to the main acid discharge pipe. The phase change heat recovery device (200) is internally connected to an acid discharge port (206) that is connected to the acid discharge bypass pipe (105). The demineralized water heat exchanger (400) is provided with an acid discharge second pipe (404) and an acid discharge first pipe (403) that are respectively connected to the acid discharge bypass pipe (105). The sulfuric acid inlet pipe (102) is internally provided with a pipeline for acid discharge that is connected to the acid discharge bypass pipe (105).

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