A high-efficiency and energy-saving sulfuric acid evaporation and concentration system and process

Abstract

The present invention discloses a highly efficient and energy-saving sulfuric acid evaporation and concentration system and process. The system includes a falling-film heat exchange absorption tower, a concentrating evaporator, a raw acid storage tank, a concentrated acid storage tank, a tower top gas phase condenser, a vacuum system, and a wastewater tank. The falling-film heat exchange absorption tower comprises an upper tower and a lower tower, which are separated by a tube sheet. A raw acid inlet is provided on the side of the lower end of the upper tower. Several falling-film heat exchange absorption tubes are longitudinally arranged in the upper tower. A falling film device is provided on the top of each falling-film heat exchange absorption tube. The lower ends of the falling-film heat exchange absorption tubes pass through tube sheet one and extend into the lower tower, where they are connected to tube sheet two located at the bottom of the lower tower. The bottom end of the lower tower is a sulfuric acid outlet. A concentrated acid inlet and outlet are provided on the side of the lower tower between tube sheets one and two. The present invention is characterized by high efficiency, energy saving, a compact system, low equipment investment cost, high sulfuric acid concentration, and high exhaust gas purity.

Description

Technical Field

[0001] The present invention relates to a sulfuric acid evaporation and concentration system and process, in particular to a high-efficiency and energy-saving sulfuric acid evaporation and concentration system and process. Background Art

[0002] Traditional waste acid treatment primarily involves discharge or lime neutralization, resulting in significant resource waste and environmental pollution if improperly handled. With increased national regulation of hazardous chemicals and strengthened management of hazardous waste, many companies are opting to outsource their waste sulfuric acid for disposal. However, this approach carries significant safety risks, and any problems with the treatment process can negatively impact normal production. Therefore, concentrating, purifying, and regenerating waste sulfuric acid is the best way to fundamentally address this issue.

[0003] Existing waste sulfuric acid concentration processes primarily rely on evaporation, a process that consists of an evaporator, a preheating unit, and a steam treatment unit. After preheating, the waste sulfuric acid is heated and evaporated in the evaporator, removing most of the water, thereby converting the dilute waste sulfuric acid into concentrated sulfuric acid. The secondary steam generated by evaporation is then processed in a steam treatment unit and discharged. However, both the concentrated sulfuric acid and the secondary steam generated by evaporation contain a significant amount of heat. Directly discharging the steam from the concentration system would result in significant energy waste. Furthermore, since the raw acid is typically heated to temperatures exceeding 160°C, the secondary steam contains acid mist in addition to water vapor. If this mist is not recycled, it can also lead to sulfuric acid loss. Furthermore, handling the secondary steam containing acid mist is also complex. In order to absorb the acid mist in the secondary steam and recover the heat of the secondary steam and concentrated sulfuric acid, existing reports have shown that some systems have added waste heat recovery and acid mist recovery systems, but these systems have the disadvantages of being large and having complex equipment. In addition, it is difficult to prepare concentrated sulfuric acid above 98% with a single-effect evaporator. In order to increase the concentration of concentrated sulfuric acid, multi-effect evaporators are currently used for evaporation and concentration, which undoubtedly further expands the system, making it more complex and requiring greater equipment investment. Summary of the Invention

[0004] The purpose of the present invention is to provide a highly efficient and energy-saving sulfuric acid evaporation concentration system and process. The present invention has the characteristics of high efficiency, energy saving, compact system, low equipment investment cost, high sulfuric acid concentration, and high purity of discharged waste gas.

[0005] The technical solution of the present invention is: a high-efficiency and energy-saving sulfuric acid evaporation and concentration system, comprising a falling film heat exchange absorption tower, a concentration evaporator, a raw acid storage tank, a concentrated acid storage tank, a tower top gas phase condenser, a vacuum system and a wastewater tank;

[0006] The falling film heat exchange absorption tower consists of an upper tower and a lower tower, which are separated by a tube sheet. A raw acid inlet is provided on the side of the lower end of the upper tower, and the raw acid inlet is connected to the raw acid storage tank; a secondary steam outlet is provided on the top of the upper tower, and the secondary steam outlet is connected to the tower top gas phase condenser; a plurality of falling film heat exchange absorption tubes are provided in the longitudinal direction of the upper tower, and a falling film device is provided on the top of the falling film heat exchange absorption tube. The lower end of the falling film heat exchange absorption tube passes through the tube sheet 1 and extends into the lower tower, and is connected to the tube sheet 2 provided at the bottom of the lower tower; the bottom end of the lower tower is a sulfuric acid outlet, and is connected to the secondary steam outlet of the evaporator provided on the concentrating evaporator. A concentrated acid inlet and a concentrated acid outlet are provided on the side of the lower tower between the tube sheets 1 and 2, the concentrated acid outlet is connected to the concentrated acid storage tank, and the concentrated acid inlet is connected to the concentrated acid outlet of the evaporator provided on the concentrating evaporator.

[0007] This solution integrates and connects the falling film heat exchange absorption tower with the concentrating evaporator, and sets the falling film heat exchange absorption tower into two parts, the upper tower and the lower tower, and sets a falling film heat exchange absorption tube through the upper tower and the lower tower, and sets a falling film device at the top of the falling film heat exchange absorption tube. After coming out of the concentrating evaporator, the high-temperature secondary steam directly enters the falling film heat exchange absorption tube and contacts with the raw acid liquid film in the falling film heat exchange absorption tube. While completing the contact heat exchange, the low-temperature raw acid is used to absorb the acid mist in the secondary steam, thereby improving the purity of the exhaust gas. In the upper tower section, the secondary steam not only contacts with the raw acid, but also absorbs the acid mist in the secondary steam. In addition to contact heat exchange, the liquid film also performs inter-wall heat exchange with the raw acid outside the falling film heat exchange absorption tube, further absorbing the preheat in the secondary steam, improving the waste heat recovery rate and saving energy consumption; and the high-temperature concentrated sulfuric acid discharged from the concentrating evaporator, after passing through the lower tower, performs heat exchange with the raw acid in the falling film heat exchange absorption tube in the lower tower, further absorbing the preheat in the concentrated sulfuric acid, saving energy consumption; in addition, because the falling film heat exchange absorption tower of this scheme completes the processes of waste heat recovery, acid mist absorption and primary evaporation, while having a high heat recovery rate, it also greatly simplifies the system and reduces the cost investment of equipment.

[0008] A preferred solution, the aforementioned high-efficiency and energy-saving sulfuric acid evaporation and concentration system, wherein the concentrating evaporator is horizontal, comprising an evaporator shell, wherein the outer sides of both ends of the evaporator shell are respectively provided with a steam inlet and a steam condensate outlet, and the inner sides are respectively provided with tube sheets three and four, and a number of heat exchange tubes are provided between tube sheets three and four; an evaporator secondary steam outlet and an evaporator concentrated acid outlet are provided on the evaporator shell between tube sheets three and four, the evaporator secondary steam outlet is close to one end of the steam inlet, and the evaporator concentrated acid outlet is close to one end of the steam condensate outlet; a plurality of groups of partitions are distributed in the evaporator shell between the evaporator secondary steam outlet and the evaporator concentrated acid outlet, the upper end of the partition is a fluid channel, the height of all partitions is set to be the same, an overflow plate is provided between adjacent partitions, the height of the upper end face of the overflow plate is lower than the height of the upper end face of the partition, the upper end of the overflow plate is a fluid channel, and the height of the upper end of the overflow plate decreases step by step with the flow direction of the fluid.

[0009] This solution optimizes the structure of the concentrating evaporator to achieve multi-stage continuous evaporation and concentration within a single concentrating evaporator, significantly increasing the concentration of sulfuric acid and enabling the production of over 98% concentrated sulfuric acid. This also further simplifies the system and reduces equipment costs. By setting the overflow plate height to a certain gradient, which gradually decreases, this not only prevents backflow but also further ensures that the concentration of the concentrated sulfuric acid in the latter stage exceeds the required concentration.

[0010] A preferred embodiment of the aforementioned efficient and energy-saving sulfuric acid evaporation and concentration system is characterized in that the concentrating evaporator is further connected to an overflow tank, the bottom of the overflow tank being connected to the concentrated acid outlet of the evaporator via an inverted U-shaped overflow pipe, the drainage level of the inverted U-shaped overflow pipe being consistent with the height of the upper end surface of the last overflow plate; the top of the overflow tank being connected to a pressure balance port provided on the evaporator shell; and the side of the overflow tank being connected to the concentrated acid inlet.

[0011] This solution can ensure that the liquid level in the concentration evaporator is always at a fixed height by further providing an overflow tank and an inverted U-shaped overflow pipe, and the sulfuric acid concentration can be further guaranteed.

[0012] A preferred embodiment of the aforementioned high-efficiency, energy-saving sulfuric acid evaporation and concentration system comprises a first baffle plate disposed within the upper tower. This embodiment, by disposing the first baffle plate within the upper tower, can extend the flow path of the raw acid, thereby enabling more complete heat exchange between the raw acid and the secondary steam within the falling-film heat exchange absorption tubes, and achieving a higher waste heat recovery rate.

[0013] A preferred embodiment of the aforementioned efficient and energy-saving sulfuric acid evaporation and concentration system is characterized by a second baffle being provided in the lower tower. This embodiment, by providing the second baffle in the lower tower, can extend the flow path of the high-temperature concentrated sulfuric acid, thereby enabling more complete heat exchange between the concentrated sulfuric acid and the raw acid in the falling-film heat exchange absorption tubes and achieving a higher waste heat recovery rate.

[0014] A preferred embodiment of the aforementioned efficient and energy-saving sulfuric acid evaporation and concentration system comprises a steam jet pump as the vacuum system, the steam jet pump being connected to the tower top vapor phase condenser and having a steam injection inlet. The steam jet pump is preferably a vacuum system in this embodiment, which has a stronger evacuation capacity, lower positive voids in the falling film heat exchange absorption tower and the concentrating evaporator, and higher evaporation efficiency.

[0015] In a preferred embodiment of the aforementioned energy-efficient sulfuric acid evaporation and concentration system, a steam condenser is connected to the steam outlet of the vacuum system. This condenser is connected in parallel with the overhead vapor phase condenser and then to the wastewater tank. This embodiment further improves vacuuming capacity by connecting the steam condenser to the vacuum system, utilizing the principle that the volume of the ejected steam decreases dramatically upon condensation.

[0016] A highly efficient and energy-saving sulfuric acid evaporation and concentration process comprises the following steps:

[0017] (1) The raw acid at room temperature is fed into the upper tower through the raw acid inlet, flows upward along the inner cavity of the upper tower, and after the liquid level reaches the top of the falling film heat exchange absorption tube, it forms a film through the falling film device and flows downward along the inner wall of the falling film heat exchange absorption tube into the shell side of the concentrating evaporator below;

[0018] (2) When the raw acid flows into the concentrating evaporator, high-temperature steam is charged into the heat exchange tube of the concentrating evaporator. The high-temperature steam in the heat exchange tube exchanges heat with the raw acid in the shell side, heating the raw acid to above the boiling point, thereby evaporating the water and part of the sulfuric acid therein, forming secondary steam containing acid mist;

[0019] (3) The secondary steam containing acid mist flows upward through the falling film heat exchange absorption tube of the step, and contacts with the raw acid during the counterflow process. While absorbing the acid mist in the steam, it also performs contact preheating with the raw acid in the falling film heat exchange absorption tube, and performs inter-wall heat exchange with the raw acid flowing upward in the upper tower, fully recovering the heat in the secondary steam. The secondary steam discharged from the top of the falling film heat exchange absorption tube enters the tower top gas phase condenser for condensation and separation under the action of the vacuum system. While the vacuum system is pumping out the secondary steam, it also forms a negative pressure in the concentration evaporator;

[0020] (4) The concentrated sulfuric acid formed after evaporation and concentration in step (2) is discharged through the concentrated acid outlet of the evaporator and sent to the shell side of the lower tower to further exchange heat with the raw acid in the falling film heat exchange absorption tube in the lower tower, thereby recycling the preheated concentrated sulfuric acid. The concentrated sulfuric acid after the heat exchange is sent to the concentrated acid storage tank for storage.

[0021] In a preferred embodiment, the aforementioned efficient and energy-saving sulfuric acid evaporation and concentration process is characterized in that after the raw acid flows into the concentration evaporator, it flows in an S-shaped route under the action of multiple groups of alternately arranged partitions and overflow plates, and is evaporated and concentrated step by step.

[0022] The process of the present invention relies on the aforementioned evaporation and concentration system for implementation. The process is different from the traditional process steps and has the advantages of high efficiency, energy saving, and high sulfuric acid concentration.

[0023] 1. The present invention integrates and connects the falling film heat exchange absorption tower with the concentrating evaporator, and sets the falling film heat exchange absorption tower into two parts, the upper tower and the lower tower, and sets a falling film heat exchange absorption tube through the upper tower and the lower tower, and sets a falling film device at the top of the falling film heat exchange absorption tube. After coming out of the concentrating evaporator, the high-temperature secondary steam directly enters the falling film heat exchange absorption tube and contacts with the raw acid liquid film in the falling film heat exchange absorption tube. While completing the contact heat exchange, the low-temperature raw acid is used to absorb the acid mist in the secondary steam, thereby improving the purity of the exhaust gas. In the upper tower section, the secondary steam not only contacts with the raw acid, but also absorbs the acid mist in the secondary steam. In addition to contact heat exchange, the acid liquid film also performs inter-wall heat exchange with the raw acid outside the falling film heat exchange absorption tube, further absorbing the preheat in the secondary steam, improving the waste heat recovery rate and saving energy consumption; and the high-temperature concentrated sulfuric acid discharged from the concentrating evaporator, after passing through the lower tower, performs heat exchange with the raw acid in the falling film heat exchange absorption tube in the lower tower, further absorbing the preheat in the concentrated sulfuric acid, saving energy consumption; in addition, because the falling film heat exchange absorption tower of the present invention completes the processes of waste heat recovery, acid mist absorption and primary evaporation, while having a high heat recovery rate, it also greatly simplifies the system and reduces the cost investment of equipment.

[0024] 2. By optimizing the structure of the concentrating evaporator, the present invention achieves multi-stage continuous evaporation and concentration within a single concentrating evaporator, significantly increasing the concentration of sulfuric acid and enabling the production of over 98% concentrated sulfuric acid. Furthermore, the system is further simplified, reducing equipment costs. By setting the height of the overflow plate to a certain gradient, which gradually decreases, this not only prevents backflow but also extends the sulfuric acid flow path, improving heat exchange efficiency. Furthermore, it ensures the maximum average temperature difference between the acid solution and the service-side medium, resulting in a higher sulfuric acid concentration.

[0025] 3. The present invention further provides an overflow tank and an inverted U-shaped overflow pipe, so that the liquid level in the concentration evaporator is always at a fixed height, and the sulfuric acid concentration can be further guaranteed.

[0026] 4. The present invention provides a first baffle in the upper tower to extend the flow path of the raw acid, allowing for more complete heat exchange between the raw acid and the secondary steam in the falling-film heat exchange absorption tubes, resulting in a higher waste heat recovery rate. The provision of a second baffle in the lower tower also extends the flow path of the high-temperature concentrated sulfuric acid, allowing for more complete heat exchange between the concentrated sulfuric acid and the raw acid in the falling-film heat exchange absorption tubes, resulting in a higher waste heat recovery rate.

[0027] 5. The vacuum system of the present invention preferably utilizes a steam jet pump, which offers enhanced evacuation capabilities, lower positive voids within the falling-film heat exchange absorber and concentrating evaporator, higher evaporation efficiency, lower operating temperatures, and greater energy efficiency. By connecting a steam condenser to the vacuum system, the system utilizes the principle of a sudden decrease in volume upon condensation of ejected steam, further enhancing evacuation capabilities, lowering the system operating temperature, and achieving greater energy efficiency.

[0028] 6. The process of the present invention relies on the aforementioned evaporation and concentration system. The process is different from the traditional process steps and has the advantages of high efficiency, energy saving, and high sulfuric acid concentration. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Attachment Figure 1 Schematic diagram of the structure of the system of the present invention;

[0030] Attachment Figure 2 This is a schematic structural diagram of a falling film heat exchange absorption tower of the system of the present invention;

[0031] Attachment Figure 3 Schematic diagram of the structure of the concentrating evaporator of the system of the present invention;

[0032] Description of the accompanying symbols: 1-falling film heat exchange absorption tower, 101-upper tower, 102-lower tower, 103 tube sheet 1, 104-raw acid inlet, 105-secondary steam outlet, 106-falling film heat exchange absorption tube, 107-falling film device, 108-tube sheet 2, 109-concentrated acid inlet, 110-concentrated acid outlet, 111-sulphuric acid outlet, 112-baffle 1, 113-baffle 2, 2-concentration evaporator, 201 evaporator shell, 202- Steam inlet, 203-steam condensate outlet, 204-evaporator secondary steam outlet, 205-evaporator concentrated acid outlet, 206-tube sheet three, 207-tube sheet four, 208-heat exchange tube, 209-partition, 210-overflow plate, 211-pressure balance port, 3-raw acid storage tank, 4-concentrated acid storage tank, 5-tower top gas phase condenser, 6-vacuum system, 7-wastewater tank, 8-overflow tank, 9-steam condenser, 10-jet steam inlet. DETAILED DESCRIPTION

[0033] The present invention will be further described below with reference to the examples, but they are not intended to limit the present invention.

[0034] Embodiments of the Invention Example 1

[0035] The “connections” described in this embodiment are all pipeline connections.

[0036] A highly efficient and energy-saving sulfuric acid evaporation and concentration system, as shown in the attached Figure 1-3As shown, it includes a falling film heat exchange absorption tower 1, a concentration evaporator 2, a raw acid storage tank 3, a concentrated acid storage tank 4, a tower top gas phase condenser 5, a vacuum system 6 and a waste water tank 7; the falling film heat exchange absorption tower 1 is composed of an upper tower 101 and a lower tower 102, the upper tower 101 and the lower tower 102 are separated by a tube plate 103, a raw acid inlet 104 is provided on the side of the lower end of the upper tower 101, and the raw acid inlet 104 is connected to the raw acid storage tank 3; a secondary steam outlet 105 is provided on the top of the upper tower 101, and the secondary steam outlet 105 is connected to the tower top gas phase condenser 5; a plurality of falling film heat exchange absorption tubes 106 are provided in the longitudinal direction of the upper tower 101, and the falling film A falling film device 107 is provided at the top of the heat exchange absorption tube 106. The lower end of the falling film heat exchange absorption tube 106 passes through the tube sheet 103 and extends into the lower tower 102, and is connected to the tube sheet 2 108 provided at the bottom of the lower tower 102; the bottom end of the lower tower 102 is a sulfuric acid outlet 111, which is connected to the evaporator secondary steam outlet 204 provided on the concentrating evaporator 2. A concentrated acid inlet 109 and a concentrated acid outlet 110 are provided on the side of the lower tower 102 between the tube sheet 103 and the tube sheet 2 108. The concentrated acid outlet 110 is connected to the concentrated acid storage tank 4, and the concentrated acid inlet 109 is connected to the evaporator concentrated acid outlet 205 provided on the concentrating evaporator 2.

[0037] The working principle of this embodiment is as follows: the raw dilute acid at room temperature of 25°C is fed into the raw acid storage tank 3 for storage. When evaporation and concentration are required, it is fed into the raw acid inlet 104 via the feed pump and feed pipe, and flows into the shell side of the upper tower 101, flows upward, and when the liquid level is higher than the falling film device 107, the raw dilute acid forms a film along the inner wall of the falling film heat exchange absorption tube 106 and flows downward, and flows into the concentration evaporator 2 below. After high-temperature heat exchange in the concentration evaporator 2, most of the water and a small amount of sulfuric acid in the raw dilute acid evaporate to form two The secondary steam is discharged through the secondary steam outlet 204 of the evaporator, and flows upward in the falling film heat exchange absorption tube 106 in the countercurrent process. During the countercurrent process, it performs contact heat exchange with the raw material dilute acid, and preheats the raw material dilute acid while also utilizing the raw material dilute acid to absorb the acid mist in the secondary steam. The secondary steam after cooling and removing the acid mist is discharged through the secondary steam outlet 105, and enters the tower top gas phase condenser 5 for condensation under the action of the vacuum system 6. The condensed wastewater enters the wastewater tank 7, and the non-condensable gas is directly discharged.

[0038] When the secondary steam enters the upper tower 101, it not only exchanges heat with the sulfuric acid liquid film in the falling film heat exchange absorption tube 106, but also exchanges heat with the raw dilute acid outside the falling film heat exchange absorption tube 106, thereby increasing the preheating temperature of the raw dilute acid.

[0039] The temperature of the concentrated sulfuric acid discharged from the concentrating evaporator 2 is also around 160°C. The concentrated sulfuric acid is introduced into the shell side of the lower tower 102 and undergoes heat exchange with the raw dilute acid in the falling film heat exchange absorption tube 106 of the lower tower 102. The raw dilute acid in the falling film heat exchange absorption tube 106 of this section has initially reached its boiling point under the combined heating action of the high-temperature secondary steam and the high-temperature concentrated sulfuric acid. Part of the water evaporates in this section, flows upward with the secondary steam and is discharged, while the remaining raw dilute acid enters the concentrating evaporator 2 below.

[0040] Further embodiments, such as the attached Figure 1-3 As shown, the concentrating evaporator 2 is horizontal and includes an evaporator shell 201. The outer sides of the two ends of the evaporator shell 201 are respectively provided with a steam inlet 202 and a steam condensate outlet 203, and the inner sides are respectively provided with a tube sheet 3 206 and a tube sheet 4 207. A plurality of heat exchange tubes 208 are provided between the tube sheet 3 206 and the tube sheet 4 207. The evaporator shell 201 between the tube sheet 3 206 and the tube sheet 4 207 is provided with an evaporator secondary steam outlet 204 and an evaporator concentrated acid outlet 205. The evaporator secondary steam outlet 204 is close to one end of the steam inlet 202, and the steam The concentrated acid outlet 205 of the evaporator is close to one end of the steam condensate outlet 203; a plurality of groups of partitions 209 are distributed in the evaporator shell 201 between the secondary steam outlet 204 of the evaporator and the concentrated acid outlet 205 of the evaporator, and the upper end of the partition 209 is a fluid channel. The height of all partitions 209 is set to be the same, and an overflow plate 210 is provided between adjacent partitions 209. The height of the upper end surface of the overflow plate 210 is lower than the height of the upper end surface of the partition 209. The upper end of the overflow plate 210 is a fluid channel, and the height of the upper end of the overflow plate 210 decreases step by step with the direction of fluid flow.

[0041] The working principle of this embodiment is consistent with the previous embodiment, with the difference that after the raw dilute acid enters the concentrating evaporator 2, it flows around the lower end of the partition 209 and the upper end of the overflow plate 210 in sequence. The entire flow channel is S-shaped, and the overflow height of the next stage is always lower than the overflow height of the previous stage.

[0042] Further embodiments, such as the attached Figure 1-3 As shown, the concentrating evaporator 2 is also connected to an overflow tank 8, and the bottom of the overflow tank 8 is connected to the concentrated acid outlet 205 of the evaporator via an inverted U-shaped overflow pipe 11. The drainage level of the inverted U-shaped overflow pipe 11 is consistent with the height of the upper end surface of the last overflow plate 210; the top of the overflow tank 8 is connected to the pressure balance port 211 provided on the evaporator shell 201; and the side of the overflow tank 8 is connected to the concentrated acid inlet 109.

[0043] The working principle of this embodiment is consistent with the above embodiment, except that: under the action of the inverted U-shaped overflow pipe 11 and the pressure balance port 211, the liquid level at the last overflow pipe 11 in the concentrating evaporator 2 is always maintained at an appropriate position.

[0044] Further embodiments, such as the attached Figure 1-3 As shown, a baffle 112 is provided in the upper tower 101. The working principle of this embodiment is consistent with the previous embodiment, except that the raw material dilute acid in the shell side of the upper tower 101 flows around the baffle 112 along the S-shaped flow channel.

[0045] Further embodiments, such as the attached Figure 1-3 As shown, a second baffle 113 is provided in the lower tower 102. The working principle of this embodiment is consistent with the previous embodiment, except that the concentrated sulfuric acid in the shell side of the lower tower 102 flows around the second baffle 113 along an S-shaped flow channel.

[0046] Further embodiments, such as the attached Figure 1-3 As shown, the vacuum system 6 is a steam jet pump, which is connected to the tower top gas phase condenser 5 and is provided with a jet steam inlet 10. The working principle of the steam jet pump of this embodiment is consistent with that of the existing steam jet pump.

[0047] Further embodiments, such as the attached Figure 1-3 As shown, the steam ejection end of the vacuum system 6 is connected to a steam condenser 9, which is connected in parallel with the tower top gas phase condenser 5 and then connected to the wastewater tank 7. The working principle of this embodiment is that the high-temperature steam ejected by the steam jet pump suddenly decreases in volume after entering the steam condenser 9, generating a large negative pressure and improving the vacuuming capacity. Example 2

[0048] A highly efficient and energy-saving sulfuric acid evaporation and concentration process, which relies on the system of Example 1, comprises the following steps:

[0049] 1. The raw acid at room temperature is fed into the upper tower 101 through the raw acid inlet 104. The acid flows upward along the inner cavity of the upper tower 101. After the liquid level reaches the top of the falling film heat exchange absorption tube 106, it passes through the falling film device 107 to form a film. The acid then flows downward along the inner wall of the falling film heat exchange absorption tube 106 into the shell side of the concentrating evaporator 2 below.

[0050] 2. As the raw acid flows into the concentrating evaporator 2, high-temperature steam is charged into the heat exchange tube 208 of the concentrating evaporator 2. The high-temperature steam in the heat exchange tube 208 exchanges heat with the raw acid in the shell side, heating the raw acid to above its boiling point, thereby evaporating the water and part of the sulfuric acid therein, forming secondary steam containing acid mist;

[0051] 3. The acid mist-containing secondary steam flows upward countercurrently through the falling film heat exchange absorption tube 106 of step 1. During the countercurrent process, the secondary steam contacts the raw acid, absorbs the acid mist in the steam, and simultaneously performs contact preheating with the raw acid in the falling film heat exchange absorption tube 106 and performs partitioning heat exchange with the raw acid flowing upward in the upper tower 101, thereby fully recovering the heat in the secondary steam. The secondary steam discharged from the top of the falling film heat exchange absorption tube 106 enters the tower top vapor phase condenser 5 for condensation and separation under the action of the vacuum system 6. The vacuum system 6 also forms a negative pressure in the concentrating evaporator 2 while pumping the secondary steam.

[0052] 4. The concentrated sulfuric acid formed after evaporation and concentration in step 2 is discharged through the concentrated acid outlet 205 of the evaporator and fed into the shell side of the lower tower 102, where it undergoes further heat exchange with the raw acid in the falling film heat exchange absorption tube 106 in the lower tower 102, thereby recycling the preheated concentrated sulfuric acid. After the heat exchange, the concentrated sulfuric acid is fed into the concentrated acid storage tank 4 for storage.

[0053] In a preferred embodiment, after the raw acid flows into the concentrating evaporator 2, it flows in an S-shaped route under the action of multiple groups of partitions 209 and overflow plates 210 that are alternately arranged, and is evaporated and concentrated step by step.

[0054] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, can make equivalent replacements or changes based on the technical solutions and inventive concepts of the present invention, which should be covered by the scope of protection of the present invention.

Claims

1. A highly efficient and energy-saving sulfuric acid evaporation and concentration system, characterized by: It includes a falling film heat exchange absorption tower (1), a concentration evaporator (2), a raw acid storage tank (3), a concentrated acid storage tank (4), a tower top gas phase condenser (5), a vacuum system (6) and a wastewater tank (7); The falling film heat exchange absorption tower (1) is composed of an upper tower (101) and a lower tower (102). The upper tower (101) and the lower tower (102) are separated by a tube plate (103). A raw acid inlet (104) is provided on the side of the lower end of the upper tower (101). The raw acid inlet (104) is connected to the raw acid storage tank (3). A secondary steam outlet (105) is provided on the top of the upper tower (101). The secondary steam outlet (105) is connected to the tower top gas phase condenser (5). A plurality of falling film heat exchange absorption tubes (106) are provided in the longitudinal direction of the upper tower (101). A falling film device (107) is provided on the top of the falling film heat exchange absorption tube (106). The lower end of the lower tower (106) passes through the tube sheet one (103) and extends into the lower tower (102), and is connected to the tube sheet two (108) provided at the bottom of the lower tower (102); the bottom end of the lower tower (102) is a sulfuric acid outlet (111), which is connected to the evaporator secondary steam outlet (204) provided on the concentrating evaporator (2); a concentrated acid inlet (109) and a concentrated acid outlet (110) are provided on the side of the lower tower (102) between the tube sheet one (103) and the tube sheet two (108); the concentrated acid outlet (110) is connected to the concentrated acid storage tank (4), and the concentrated acid inlet (109) is connected to the evaporator concentrated acid outlet (205) provided on the concentrating evaporator (2); The concentrating evaporator (2) is horizontal and includes an evaporator shell (201). The outer sides of both ends of the evaporator shell (201) are respectively provided with a steam inlet (202) and a steam condensate outlet (203). The inner sides are respectively provided with a tube sheet three (206) and a tube sheet four (207). A plurality of heat exchange tubes (208) are provided between the tube sheet three (206) and the tube sheet four (207). An evaporator secondary steam outlet (204) and an evaporator concentrated acid outlet (205) are provided on the evaporator shell (201) between the tube sheet three (206) and the tube sheet four (207). The evaporator secondary steam outlet (204) is located near one end of the steam inlet (202). , the concentrated acid outlet (205) of the evaporator is close to one end of the steam condensate outlet (203); a plurality of groups of partitions (209) are distributed in the evaporator shell (201) between the secondary steam outlet (204) of the evaporator and the concentrated acid outlet (205) of the evaporator, the upper ends of the partitions (209) are fluid channels, the heights of all the partitions (209) are set to be the same, an overflow plate (210) is provided between adjacent partitions (209), the height of the upper end surface of the overflow plate (210) is lower than the height of the upper end surface of the partition (209), the upper end of the overflow plate (210) is a fluid channel, and the height of the upper end of the overflow plate (210) decreases step by step along the direction of fluid flow; The vacuum system (6) is a steam jet pump, which is connected to the tower top gas phase condenser (5), and is provided with a jet steam inlet (10); The steam ejection end of the vacuum system (6) is connected to a steam condenser (9), and the steam condenser (9) is connected in parallel with the tower top gas phase condenser (5) and then connected to the waste water tank (7).

2. The efficient and energy-saving sulfuric acid evaporation and concentration system according to claim 1, characterized in that: The concentrating evaporator (2) is further connected to an overflow tank (8), the bottom of the overflow tank (8) being connected to the concentrated acid outlet (205) of the evaporator via an inverted U-shaped overflow pipe (11), the drainage level of the inverted U-shaped overflow pipe (11) being consistent with the height of the upper end surface of the last overflow plate (210); the top of the overflow tank (8) being connected to a pressure balance port (211) provided on the evaporator shell (201); and the side of the overflow tank (8) being connected to the concentrated acid inlet (109).

3. The efficient and energy-saving sulfuric acid evaporation and concentration system according to claim 1 is characterized in that: A baffle plate 1 (112) is provided in the upper tower (101).

4. The efficient and energy-saving sulfuric acid evaporation and concentration system according to claim 1 is characterized in that: A second baffle (113) is provided in the lower tower (102).

5. A process for efficient and energy-saving sulfuric acid evaporation and concentration using the system according to any one of claims 1 to 4, characterized in that: The steps include: (1) The raw acid at room temperature is fed into the upper tower (101) through the raw acid inlet (104), flows upward along the inner cavity of the upper tower (101), and after the liquid level reaches the top of the falling film heat exchange absorption tube (106), forms a film through the falling film device (107), and flows downward along the inner wall of the falling film heat exchange absorption tube (106) into the shell side of the concentrating evaporator (2) below; (2) When the raw acid flows into the concentrating evaporator (2), high-temperature steam is charged into the heat exchange tube (208) of the concentrating evaporator (2). The high-temperature steam in the heat exchange tube (208) exchanges heat with the raw acid in the shell side, and the temperature of the raw acid is heated to above the boiling point, thereby evaporating the water and part of the sulfuric acid therein, forming secondary steam containing acid mist; (3) The secondary steam containing acid mist flows upward countercurrently through the falling film heat exchange absorption tube (106) of step (1), contacts with the raw acid during the countercurrent process, absorbs the acid mist in the steam, and simultaneously performs contact preheating with the raw acid in the falling film heat exchange absorption tube (106), and performs inter-wall heat exchange with the raw acid flowing upward in the upper tower (101), fully recovering the heat in the secondary steam. The secondary steam discharged from the top of the falling film heat exchange absorption tube (106) enters the tower top gas phase condenser (5) for condensation and separation under the action of the vacuum system (6). The vacuum system (6) forms a negative pressure in the concentration evaporator (2) while pumping out the secondary steam; (4) The concentrated sulfuric acid formed after evaporation and concentration in step (2) is discharged through the concentrated acid outlet (205) of the evaporator and fed into the shell side of the lower tower (102) to further undergo heat exchange with the raw acid in the falling film heat exchange absorption tube (106) in the lower tower (102), thereby recycling the waste heat in the concentrated sulfuric acid. After the heat exchange, the concentrated sulfuric acid is fed into the concentrated acid storage tank (4) for storage.

6. The efficient and energy-saving sulfuric acid evaporation and concentration process according to claim 5, characterized in that: After the raw acid flows into the concentration evaporator (2), it flows in an S-shaped route under the action of multiple groups of partitions (209) and overflow plates (210) arranged alternately, and is evaporated and concentrated step by step.

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