Sulfuric acid chemical low-temperature recovery section waste heat recovery device

Abstract

The invention relates to the technical field of waste heat recovery, in particular to a waste heat recovery device for a sulfuric acid chemical low-temperature recovery section, which comprises a sulfuric acid inlet pipe for conveying concentrated sulfuric acid from an evaporation feed water heater, and further comprises a phase change heat energy recovery device, a sulfuric acid inlet communicated with a sulfuric acid inlet pipe is formed in one side of the sulfuric acid tank, so that concentrated sulfuric acid at 140-190 DEG C enters the sulfuric acid tank, and a sulfuric acid outlet for discharging concentrated sulfuric acid at the temperature of 100-150 DEG C after heat exchange is formed in the other side of the sulfuric acid tank; the deoxygenated water inlet pipe is used for conveying deoxygenated water with the temperature ranging from 90 DEG C to 110 DEG C into the phase change heat energy recovery device to be subjected to heat exchange with concentrated sulfuric acid to generate steam with the pressure ranging from 0.1 MPa to 0.2 MPa, and the top of the phase change heat energy recovery device is communicated with a main steam exhaust port used for exhausting steam. And the desalted water heat exchanger is used for carrying out secondary waste heat recovery on the concentrated sulfuric acid treated by the phase change heat energy recovery device and finally cooling the concentrated sulfuric acid to 40-90 DEG C. The waste heat of concentrated sulfuric acid is fully utilized in the process, and the recycling rate of energy is further increased.

Description

Technical Field

[0001] The present invention relates to the technical field of waste heat recovery, and in particular to a waste heat recovery device for a low-temperature recovery section of a sulfuric acid chemical industry. Background Art

[0002] As a basic chemical raw material, sulfuric acid is widely used in numerous fields, including fertilizers, metallurgy, petrochemicals, chemical fibers, and nonferrous metallurgy. Its production scale and output are key indicators of a country's chemical industry capabilities. In recent years, with the continued growth of the global economy and the advancement of industrialization, sulfuric acid consumption has shown a steady upward trend. In the low-temperature recovery section of the sulfuric acid industry, concentrated sulfuric acid in the heat recovery tower passes through the evaporator's concentrated sulfuric acid solution. After passing through the evaporation feedwater heater, the temperature is lowered to 140-190°C before being fed into the desalted water heat exchanger to heat the desalted water. The 20-50°C desalted water from the desalted water pipeline corridor is heated to 80-110°C before being fed to the deaerator. The concentrated sulfuric acid solution is cooled from 140-190°C to approximately 100-130°C before being fed to the circulating acid pump tank for subsequent processes. However, significant waste heat resources, particularly in the low-temperature recovery section, remain underutilized.

[0003] For example, the patent document with the prior art publication number CN117023523A discloses a low-temperature recovery system for pyrite acid production. After the primary conversion gas containing SO3 from the third stage of the converter is input from the air inlet pipe, the SO3 passes through the filler from bottom to top and is countercurrently contacted with concentrated sulfuric acid (the concentration of concentrated sulfuric acid is 99%, and the temperature of the concentrated sulfuric acid is 165-175°C and 50-60°C, respectively) passing through the filler from the first spray pipe and the second spray pipe from top to bottom. The concentration of the concentrated sulfuric acid after absorbing SO3 is 99.5%, and the temperature is increased by 20°C; the concentrated sulfuric acid at the bottom of the high-temperature absorption tower is then pumped into the high-temperature acid circulation tank through the first circulating acid pump, and the concentrated sulfuric acid is pumped to the steam generator for heat exchange through the second circulating acid pump to generate low-pressure steam. At the same time, the temperature of the concentrated sulfuric acid after heat exchange in the steam generator is reduced by 20°C to achieve recycling and utilization of the low-temperature waste heat generated in the SO3 absorption step to generate steam.

[0004] In the existing technical system, the evaporative feedwater heater was originally designed to perform a preliminary cooling treatment on concentrated sulfuric acid so that it can participate in the desalted water heating link more efficiently in the subsequent process and realize the cascade utilization of heat. However, in actual industrial production application scenarios, after the concentrated sulfuric acid flows through the evaporative feedwater heater, its temperature drop is extremely limited, and the actual temperature remains at a high state far higher than expected. After professional thermodynamic analysis and comparison with actual operation data, the excessively high concentrated sulfuric acid temperature causes a series of problems that are not conducive to the effective utilization of heat after entering the desalted water heat exchanger. On the one hand, due to the large initial temperature difference between the concentrated sulfuric acid and the desalted water, the heat transfer rate is too fast and difficult to control accurately, resulting in heat concentration and sudden temperature rise in local areas of the heat exchanger. This not only aggravates the thermal stress inside the heat exchanger and shortens the service life of the equipment, but also causes potential risks such as scaling and corrosion on the heat exchange tube wall due to local overheating, further reducing the heat exchange efficiency. To this end, the present application proposes a waste heat recovery device for the low-temperature recovery section of sulfuric acid chemical industry. Summary of the Invention

[0005] The object of the present invention is to provide a waste heat recovery device for a low-temperature recovery section of a sulfuric acid chemical industry to solve the problems raised in the above-mentioned background technology.

[0006] To achieve the above object, the present invention provides the following technical solution: a waste heat recovery device for a low-temperature recovery section of a sulfuric acid chemical industry, comprising a sulfuric acid inlet pipe for conveying concentrated sulfuric acid from an evaporation feedwater heater, wherein the concentrated sulfuric acid has a temperature of 140°C to 190°C, 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 for entry of concentrated sulfuric acid at 140°C-190°C, and a sulfuric acid outlet on the other side for discharge of concentrated sulfuric acid at a temperature of 100°C-150°C after heat exchange;

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

[0009] The desalted water heat exchanger is used to recover the secondary waste heat of the concentrated sulfuric acid after being treated by the phase change heat energy recovery device. One end of the desalted water heat exchanger is connected to a desalted water inlet pipe for conveying the original desalted water with a temperature of 20°C-50°C into the interior thereof, and one end of the sulfuric acid outlet is provided with a second sulfuric acid inlet pipe for discharging the concentrated sulfuric acid into the desalted water heat exchanger for heat exchange with the original desalted water. The bottom of the desalted water heat exchanger is connected to a second sulfuric acid outlet pipe for discharging the concentrated sulfuric acid after secondary recovery into the circulating acid pump tank, and finally the concentrated sulfuric acid is cooled to 40°C-90°C.

[0010] Preferably, the top of the main steam outlet is connected to a steam pipe, and the steam pipe is connected to a compressor, and the compressor is used to increase the pressure of low-pressure steam and flow into the steam main pipe through the steam exhaust pipe. A vent valve for venting is provided in the steam exhaust pipe.

[0011] Preferably, one side of the sulfuric acid inlet pipe is connected to a sulfuric acid bypass pipe for changing the flow direction of concentrated sulfuric acid, and one end of the sulfuric acid bypass pipe is connected to the second sulfuric acid outlet pipe, one end of the sulfuric acid outlet is connected to the sulfuric acid outlet pipe connected to the sulfuric acid bypass pipe, and one end of the second 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 allows part of the deoxygenated water to pass through and be transported to the outlet of the compressor 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 water discharge.

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

[0014] Preferably, a drain outlet for periodic drainage is provided at the bottom of the phase change heat energy recovery device, a drain outlet for continuous sewage discharge is provided at the bottom of the phase change heat energy recovery device, and the desalted 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 commonly connected to a main sewage pipe extending into the sewage trough, and the sewage outlet and the drain outlet are both connected to the main sewage pipe.

[0015] Preferably, the first sulfuric acid inlet pipe is internally connected to an acid discharge bypass pipe for discharging acid to the acid discharge main pipe, the phase change heat energy recovery device is internally connected to an acid discharge port connected to the acid discharge bypass pipe, the desalted water heat exchanger is provided with two acid discharge pipes and one acid discharge pipe respectively connected to the acid discharge bypass pipe, and the second sulfuric acid inlet pipe is provided with a pipeline for acid discharge 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 air pressure connector interfaces for detecting the internal air pressure and water level thereof, the top of the phase change heat energy recovery device is connected with a deoxygenated water interface for the entry of deoxygenated water, the top of the phase change heat energy recovery device is provided with a side steam outlet, and the top of the side steam outlet is connected with a bypass pipe connected to the steam pipe.

[0017] Preferably, the interior of the steam pipe is fixedly connected with a plurality of narrowing tubes with a smaller diameter than the steam pipe, and the bottoms of the plurality of narrowing tubes are fixedly connected with cone rings, the tops of the narrowing tubes are fixedly connected with slope rings, and the inner walls of the slope rings are fixedly connected with flow-blocking rings.

[0018] Preferably, the interior of the narrowing tube is provided with a plurality of reflux grooves penetrating the slope ring, the inner wall of the cone ring is provided with a plurality of flow grooves, the interior of the narrowing tube is provided with a collection groove for collecting condensed water, and the slope ring and the flow groove are both connected to the collection groove.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. The sulfuric acid inlet pipe transports concentrated sulfuric acid at 140°C-190°C to the phase-change heat recovery unit. Through heat exchange with deoxygenated water at 90°C-110°C, the concentrated sulfuric acid transfers its heat to the deoxygenated water, causing it to heat up and vaporize, producing 0.1-0.2 MPa steam. This process achieves initial recovery of the concentrated sulfuric acid's waste heat, improving energy utilization and reducing energy waste. The generated low-pressure steam is discharged through a steam pipe to compressor 301 for pressure boosting, becoming superheated steam at 0.2-0.3 MPa, which is then discharged through a steam exhaust pipe to the steam main. The compressor boosts 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 efficiency. The desalted water heat exchanger performs secondary waste heat recovery on the concentrated sulfuric acid after treatment in the phase-change heat recovery unit. Raw desalted water at 20°C-50°C enters the desalted water heat exchanger through the desalted water inlet pipe, where it undergoes heat exchange with concentrated sulfuric acid at 100°C-150°C, heating the desalted water to 85-115°C. This process fully utilizes the waste heat of the concentrated sulfuric acid, further improving energy recovery and reducing energy consumption. The heated desalted water is then fed to the deaerator, where its 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 deoxygenated water bypass pipe allows some of the deoxygenated water to pass through and be transported to the compressor outlet, where it is used to control the compressor outlet steam temperature. The desalted water heat exchanger's drain pipe and side drain pipe remove impurities accumulated within the heat exchanger, ensuring its normal operation and heat exchange efficiency.

[0021] 2. By connecting the water level detector and the air pressure detector, the air 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 it is detected that the water level is lowered, the 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 the steam can be collected into the steam pipe through the bypass pipe to avoid excessive pressure in the phase change heat energy recovery device, playing a safety protection role. The narrowing tube increases the steam flow rate and prevents steam backflow. The cone ring shortens the diameter to further accelerate the flow rate of steam and reduce the residence time of steam in the pipeline. The baffle ring cooperates with the slope ring to prevent part of the condensate from continuing to move upward. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the connection relationship of various components in the present invention;

[0023] Figure 2 Schematic diagram of the flow direction of concentrated sulfuric acid in the present invention;

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

[0025] Figure 4 Schematic diagram of the compressor in the present invention;

[0026] Figure 5 Schematic diagram of the structure of the phase change heat energy recovery device in the present invention;

[0027] Figure 6 Schematic diagram of the structure of the steam pipe in the present invention;

[0028] Figure 7 Schematic diagram of the structure of the narrowing tube in the present invention.

[0029] In the figure: 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, drainage outlet; 206, acid discharge outlet; 207, liquid level and air pressure connector interface; 208, deaerated water interface; 209, main steam outlet; 210, bypass steam outlet; 211, steam pipe; 212, narrowing pipe; 213, resistance Flow ring; 214, cone ring; 215, flow trough; 216, reflux trough; 217, collecting trough; 218, slope ring; 219, bypass pipe; 300, deaerated water inlet pipe; 301, compressor; 302, deaerated water bypass pipe; 303, water pipe connected to the main sewage pipe; 304, air pipe; 305, steam exhaust pipe; 306, air release valve; 400, desalted water heat exchanger; 401, desalted water inlet pipe; 402, desalted water exhaust pipe; 403, acid exhaust pipe 1; 404, acid exhaust pipe 2; 405, drain pipe; 406, side drain pipe; 407, main sewage pipe. DETAILED DESCRIPTION

[0030] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts 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 industry, comprising a sulfuric acid inlet pipe 100 for conveying concentrated sulfuric acid from an evaporation water heater, wherein the concentrated sulfuric acid has a temperature of 140°C-190°C, and a phase change heat energy recovery device 200, wherein a sulfuric acid inlet 201 is provided on one side thereof and is connected to the sulfuric acid inlet pipe 100 for supplying concentrated sulfuric acid at a temperature of 140°C-190°C, and a sulfuric acid outlet 202 is provided on one side thereof for discharging concentrated sulfuric acid at a temperature of 100°C-150°C after heat exchange. By providing the phase change heat energy recovery device 200, preliminary waste heat recovery can be performed on the concentrated sulfuric acid at a temperature of 140°C-190°C.

[0032] The deoxygenated water inlet pipe 300 is further included, which is used to transport deoxygenated water with a temperature of 90°C-110°C to the phase change heat recovery device 200 for heat exchange with concentrated sulfuric acid to generate 0.1-0.2MPa steam, and the top of the phase change heat recovery device 200 is connected to a main steam outlet 209 for discharging steam, and 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, and the compressor 301 is used to increase the pressure of low-pressure steam and pass through The steam exhaust pipe 305 merges into the steam main pipe. A vent valve 306 for venting is provided in the steam exhaust pipe 305. Deoxygenated water at 90°C-110°C is introduced into the phase change heat energy recovery device 200 for heat exchange with concentrated sulfuric acid at 140°C-190°C, so that the deoxygenated water is heated and vaporized. The steam is discharged for later use. The steam generated in the phase change heat energy recovery device 200 is low-pressure steam, which is discharged to the compressor 301 through the steam pipe 211 for pressure increase to improve the steam quality.

[0033] Among them, one side of the deoxygenated water inlet pipe 300 is connected to a deoxygenated water bypass pipe 302, and the deoxygenated water bypass pipe 302 allows part of the deoxygenated water to pass through and be transported to the outlet of the compressor 301 for regulating the compressor outlet steam temperature, and the interior of the deoxygenated water bypass pipe 302 is connected to a main sewage pipe 303 for controlling water discharge. One end of the compressor 301 is connected to an air pipe 304 for compressed air to enter. The setting of the deoxygenated water bypass pipe 302 can spray a small amount of deaerator water at the outlet of the compressor 301, accurately regulate the steam temperature, and avoid overheating and damage to the equipment.

[0034] It also includes a desalted water heat exchanger 400, which is used to recover the secondary waste heat of the concentrated sulfuric acid after being treated by the phase change heat energy recovery device 200. One end of the desalted water heat exchanger 400 is connected to a desalted water inlet pipe 401 for conveying the original desalted water with a temperature of 20°C-50°C into the desalted water heat exchanger, and 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 desalted water heat exchanger 400 for heat exchange with the original desalted water. The bottom of the desalted 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°C-90°C. One side of the sulfuric acid first inlet pipe 100 is connected to a sulfuric acid second outlet pipe 103 for changing the concentrated sulfuric acid. A sulfuric acid bypass pipe 104 is provided in the direction of acid flow, and one end of the sulfuric acid bypass pipe 104 is connected to the second sulfuric acid outlet pipe 103. One end of the sulfuric acid outlet 202 is connected to the first sulfuric acid outlet pipe 101 connected to the sulfuric acid bypass pipe 104, and one end of the second sulfuric acid inlet pipe 102 is connected to the sulfuric acid bypass pipe 104. By setting up a desalted water heat exchanger 400, the concentrated sulfuric acid can be subjected to secondary waste heat recovery. The concentrated sulfuric acid after heat exchange with deoxygenated water is heat exchanged with the original desalted water with a lower temperature to further utilize the waste heat of the concentrated sulfuric acid. The sulfuric acid bypass pipe 104 can change the flow direction of the concentrated sulfuric acid when the phase change heat energy recovery device 200 is damaged for maintenance and directly introduce the desalted water heat exchanger 400 for heat recovery, thereby not affecting production.

[0035] See also Figure 1 、 Figure 2 as well as Figure 3 Furthermore, a drain port 205 for periodic drainage is provided at the bottom of the phase change heat energy recovery device 200, a drain port 204 for continuous sewage discharge is provided at the bottom of the phase change heat energy recovery device 200, and a drain pipe 405 and a side drain pipe 406 for drainage are provided in the desalted water heat exchanger 400. The drain pipe 405 and the side drain pipe 406 are commonly connected to a sewage main pipe 407 extending into the sewage tank. The sewage port 204 and the drain port 205 are both connected to the sewage main pipe 407. The drainage port 205 and the sewage port 204 can discharge impurities accumulated in the phase change heat energy recovery device 200 to prevent scaling and clogging, and the drain pipe 405 and the side drain pipe 406 can remove impurities accumulated in the desalted water heat exchanger 400, and all of them are discharged into the sewage main pipe 407.

[0036] Furthermore, the interior of the sulfuric acid inlet pipe 100 is connected to an acid discharge bypass pipe 105 for discharging acid to the acid discharge main pipe, the interior of the phase change heat energy recovery device 200 is connected to an acid discharge port 206 connected to the acid discharge bypass pipe 105, the desalted water heat exchanger 400 is provided with an acid discharge second pipe 404 and an acid discharge first pipe 403 respectively connected to the acid discharge bypass pipe 105, and the interior of the sulfuric acid inlet pipe 102 is provided with a pipeline for acid discharge connected to the acid discharge bypass pipe 105, wherein the setting of the acid discharge port 206, the acid discharge first pipe 403 and the acid discharge second pipe 404 enables the acid liquid to be discharged to the acid treatment system or recycled.

[0037] Specifically, concentrated sulfuric acid at 140-190°C from the evaporative feedwater heater is connected to the sulfuric acid inlet 201 through the sulfuric acid inlet pipe 100 and transported to the interior of the phase change heat energy recovery device 200. At the same time, water from the deaerator at 90-110°C enters the interior of the phase change heat energy recovery device 200 through the deoxygenated water inlet pipe 300 and heat exchanges with the concentrated sulfuric acid to form 0.1-0.2 MPa low-pressure steam, which is discharged to the interior of the compressor 301 through the steam pipe 211 and then pressurized by the compressor 301 to become 0.2-0.3 MPa. The superheated steam is discharged into the steam main through the steam exhaust pipe 305. At the same time, the deoxygenated water inlet pipe 300 is connected with the deoxygenated water bypass pipe 302, so that part of the water from the deaerator is transported to the outlet of the compressor 301 through the deoxygenated water bypass pipe 302 for water spraying, and the steam temperature at the outlet of the compressor 301 is regulated. The concentrated sulfuric acid is subjected to heat exchange through the phase change heat energy recovery device 200, and its temperature is reduced to 100°C-150°C. Then the concentrated sulfuric acid is merged into the desalted water heat exchanger 400, and the water from the original desalted water inlet pipe is transported to the desalted water heat exchanger 400 through the desalted water inlet pipe 401. The concentrated sulfuric acid is heat exchanged with the concentrated sulfuric acid in the heat exchanger 400 and discharged into the original desalted water return pipe through the desalted water discharge pipe 402. In this process, the desalted water is heated to 85-115°C and sent to the deaerator after heating. The desalted water temperature can be increased according to the needs of the deaerator to reduce the steam consumption of the deaerator, and the concentrated sulfuric acid is finally cooled to 40-90°C. The cooled concentrated sulfuric acid is finally sent to the acid pipe of the lower tower of the second absorption tower of the sulfuric acid unit and enters the circulating acid pump tank, thereby reducing the overall temperature of the circulating acid pump tank, thereby reducing the drying tower acid cooler and the finished acid cooler. The circulating water consumption is calculated, and 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 103 and the acid discharge pipe 204 are respectively connected to the acid discharge bypass pipe 105 to discharge acid for the desalted water heat exchanger 400, and the sewage discharge port 204 and the drain port 205 can be used for regular sewage and drainage of the phase change heat energy recovery device 200, and the drain pipe 405 is used to drain the desalted water heat exchanger 400. The drain port 205, the drain pipe 405 and the sewage discharge port 204 are simultaneously connected to the sewage main pipe 407 to summarize the sewage and drainage.

[0038] In summary, the sulfuric acid inlet pipe 100 delivers concentrated sulfuric acid at 140-190°C to the phase-change heat recovery device 200. Through heat exchange with deoxygenated water at 90-110°C, the concentrated sulfuric acid transfers its heat to the deoxygenated water, causing it to heat up and vaporize, producing 0.1-0.2 MPa steam. This process achieves initial recovery of the concentrated sulfuric acid's waste heat, improving energy utilization and reducing energy waste. The resulting low-pressure steam is discharged through steam pipe 211 to compressor 301 for pressure boosting, becoming superheated steam at 0.2-0.3 MPa, which is then discharged through steam exhaust pipe 305 to the steam main. The boosting of the low-pressure steam by compressor 301 improves its quality, enabling it to better meet the steam pressure and temperature requirements of subsequent processes, further enhancing energy efficiency. The desalted water heat exchanger 400 performs secondary waste heat recovery on the concentrated sulfuric acid after treatment by the phase-change heat recovery device 200. Raw desalted water at 20°C-50°C enters the desalted water heat exchanger 400 through the desalted water inlet pipe 401, where it undergoes heat exchange with concentrated sulfuric acid at 100°C-150°C, heating the desalted water to 85°C-115°C. This process fully utilizes the waste heat of the concentrated sulfuric acid, further improving energy recovery and reducing energy consumption. The heated desalted water is then fed to the deaerator, where its 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 portion of the deoxygenated water is transported through the deoxygenated water bypass pipe 302 to the outlet of the compressor 301, where it is used to control the compressor outlet steam temperature. The desalted water heat exchanger 400 is equipped with a drain pipe 405 and a side drain pipe 406 to remove impurities accumulated within the heat exchanger, ensuring its normal operation and heat exchange efficiency.

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

[0040] See also Figure 5 、 Figure 6 as well as Figure 7 Furthermore, the interior of the steam pipe 211 is fixedly connected to a plurality of narrowing tubes 212 having a smaller diameter than the steam pipe 211, and the bottoms of the plurality of narrowing tubes 212 are fixedly connected to a cone ring 214, the tops of the narrowing tubes 212 are 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 interior of the narrowing tube 212 is provided with a plurality of reflux grooves 216 penetrating the slope ring 218, the inner wall of the cone ring 214 is provided with a plurality of flow grooves 215, and the interior of the narrowing tube 212 is provided with a collection groove 217 for collecting condensed water. The slope ring 218 and the flow groove 215 are both connected to the collection groove 217. By setting the narrowing tube 212, the flow rate of the steam can be increased, thereby preventing the steam from flowing back. When the steam passes through the narrowing tube 212, it will further collide with the inner wall of the narrowing tube 212 to produce condensed water, which will adhere to the inner wall of the flow groove 215. As the steam continues to flow, part of the condensed water will continue to move upward and pass over the blocking ring 213 and flow back to the collection groove 217 through the reflux groove 216, while part of the condensed water will move down in the flow groove 215 and approach the collection groove 217 for collection.

[0041] Specifically, the gas generated by the heat exchange between deoxygenated water and concentrated sulfuric acid is discharged through the steam pipe 211 and will pass through multiple narrowing tubes 212. The tapered rings 214 arranged in the multiple narrowing tubes 212 shorten the diameter to accelerate the flow rate of steam. At the same time, the gaps between the multiple steam pipes 211 can form turbulent steam and reduce the retention of condensed water. The condensed water will adhere to the multiple flow grooves 215 during production, and the condensed water will enter the collection groove 217 through the reflux groove 216 and the flow groove 215 for storage.

[0042] In summary, by connecting the water level detector and the air pressure detector, the air pressure and water level of the deoxygenated water in the phase change heat energy recovery device 200 can be detected in real time and accurately. In cooperation with the deoxygenated water inlet pipe 300, when it is detected that the water level is lowered, the 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 the steam can be collected into the steam pipe 211 through the bypass pipe 219 to avoid excessive pressure in the phase change heat energy recovery device 200, thereby playing a safety protection role. The narrowing tube 212 increases the flow rate of the steam to prevent steam backflow. The cone ring 214 shortens the diameter to further accelerate the flow rate of the steam and reduce the residence time of the steam in the pipeline. The blocking ring 213 cooperates with the slope ring 218 to prevent part of the condensed water from continuing to move upward.

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

[0044] After the concentrated sulfuric acid undergoes heat exchange through the phase change heat energy recovery device 200, its temperature drops to 100°C-150°C. The concentrated sulfuric acid is then introduced into the desalted water heat exchanger 400, and the water from the original desalted water inlet pipe is transported to the desalted water heat exchanger 400 through the desalted water inlet pipe 401 to undergo heat exchange with the concentrated sulfuric acid and then discharged into the original desalted water return pipe through the desalted water discharge pipe 402. During this process, the desalted water is heated to 85-115°C and sent to the deaerator. The heated desalted water temperature can be increased according to the needs of the deaerator to reduce the steam consumption of the deaerator, and the concentrated sulfuric acid is finally cooled to 40°C-90°C. The cooled concentrated sulfuric acid is finally sent to the acid pipe of the lower tower of the second absorption tower of the sulfuric acid unit and enters the circulating acid pump tank, thereby reducing the overall temperature of the circulating acid pump tank and further reducing the circulating water consumption of the drying tower acid cooler and the finished product 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 103 and the acid discharge pipe 204 are respectively connected to the acid discharge bypass pipe 105 to discharge acid for the desalted water heat exchanger 400. The sewage discharge port 204 and the drain port 205 can be used to regularly discharge sewage and water for the phase change heat energy recovery device 200. The drain pipe 405 is used to drain water for the desalted water heat exchanger 400. The drain port 205, the drain pipe 405 and the sewage discharge port 204 are simultaneously 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 the steam pipe 211 and will pass through multiple narrowing tubes 212. The tapered rings 214 arranged in the multiple narrowing tubes 212 have shortened diameters to accelerate the flow rate of steam. At the same time, the gaps between the multiple steam pipes 211 can form turbulent steam and reduce the retention of condensed water. The condensed water will adhere to the multiple flow grooves 215 during production, and the condensed water will enter the collection groove 217 through the reflux groove 216 and the flow groove 215 for storage.

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

[0048] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention 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 industry, comprising a sulfuric acid inlet pipe (100) for conveying concentrated sulfuric acid from an evaporation feedwater heater, wherein the concentrated sulfuric acid has a temperature of 140°C to 190°C, and is characterized in that: Also includes: A phase-change heat energy recovery device (200) is provided with a sulfuric acid inlet (201) on one side thereof, which is connected to a sulfuric acid inlet pipe (100) for admitting concentrated sulfuric acid at a temperature of 140° C. to 190° C., and a sulfuric acid outlet (202) on one side thereof for discharging concentrated sulfuric acid at a temperature of 100° C. to 150° C. after heat exchange; A deoxygenated water inlet pipe (300) is used to transport deoxygenated water with a temperature of 90° C.-110° C. to the phase-change heat energy recovery device (200) for heat exchange with concentrated sulfuric acid to generate 0.1-0.2 MPa steam, and the top of the phase-change heat energy recovery device (200) is connected to a main steam outlet (209) for discharging steam; The desalted water heat exchanger (400) is used for secondary waste heat recovery of concentrated sulfuric acid treated by the phase change heat energy recovery device (200). One end of the desalted water heat exchanger (400) is connected to a desalted water inlet pipe (401) for conveying original desalted water at a temperature of 20°C-50°C into the desalted water heat exchanger, and one end of the sulfuric acid outlet (202) is provided with a second sulfuric acid inlet pipe (102) for discharging concentrated sulfuric acid into the desalted water heat exchanger (400) for heat exchange with the original desalted water. The bottom of the desalted water heat exchanger (400) is connected to a second sulfuric acid outlet pipe (103) for discharging the concentrated sulfuric acid after secondary recovery into a circulating acid pump tank. Finally, the concentrated sulfuric acid is cooled to 40°C-90°C.

2. A waste heat recovery device for a low-temperature recovery section of a sulfuric acid chemical industry according to claim 1, characterized in that: 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 increase the pressure of low-pressure steam and flow it into the steam main pipe through a steam exhaust pipe (305). A degassing valve (306) for degassing is provided in the steam exhaust pipe (305).

3. The waste heat recovery device for the low-temperature recovery section of sulfuric acid chemical industry 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) for changing the flow direction of concentrated sulfuric acid, and one end of the sulfuric acid bypass pipe (104) is connected to the second sulfuric acid outlet pipe (103). One end of the sulfuric acid outlet (202) is connected to a sulfuric acid outlet pipe (101) connected to the sulfuric acid bypass pipe (104), and one end of the second sulfuric acid inlet pipe (102) is connected to the sulfuric acid bypass pipe (104).

4. The waste heat recovery device for the low-temperature recovery section of a sulfuric acid chemical industry according to claim 2, characterized in that: One side of the deoxygenated water inlet pipe (300) is connected to a deoxygenated water bypass pipe (302), and the deoxygenated water bypass pipe (302) allows part of the deoxygenated water to pass through and be transported to the outlet of the compressor (301) for regulating the compressor outlet steam temperature, and the interior of the deoxygenated water bypass pipe (302) is connected to a main sewage pipe (303) for controlling water discharge.

5. The waste heat recovery device for the low-temperature recovery section of the sulfuric acid chemical industry according to claim 2, characterized in that: One end of the compressor (301) is connected to an air pipe (304) for compressed air to enter.

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

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

8. The waste heat recovery device for the low-temperature recovery section of sulfuric acid chemical industry according to claim 1, characterized in that: Liquid level and air pressure connector interfaces (207) for detecting the internal air pressure and water level are provided on both sides of the phase-change heat recovery device (200); the top of the phase-change heat recovery device (200) is connected to a deoxygenated water interface (208) for allowing deoxygenated water to enter; a side steam outlet (210) is provided on the top of the phase-change heat recovery device (200); and the top of the side steam outlet (210) is connected to a bypass pipe (219) connected to a steam pipe (211).

9. The waste heat recovery device for the low-temperature recovery section of sulfuric acid chemical industry according to claim 2, characterized in that: The steam pipe (211) is fixedly connected to a plurality of narrowing pipes (212) having a smaller diameter than the steam pipe (211), and the bottoms of the plurality of narrowing pipes (212) are fixedly connected to a cone ring (214), the tops of the narrowing pipes (212) are 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).

10. A waste heat recovery device for a low-temperature recovery section of a sulfuric acid chemical industry according to claim 9, characterized in that: The narrowing tube (212) is provided with a plurality of reflux grooves (216) penetrating the slope ring (218), the inner wall of the cone ring (214) is provided with a plurality of flow grooves (215), the narrowing tube (212) is provided with a collection groove (217) for collecting condensed water, and the slope ring (218) and the flow grooves (215) are both connected to the collection groove (217).

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