Flue gas acid making system

Abstract

This application belongs to the field of flue gas sulfuric acid production, specifically providing a flue gas sulfuric acid production system. This system includes: a drying unit to remove moisture from smelting flue gas, yielding a first flue gas and a first sulfuric acid; a conversion unit connected to the drying unit, used to convert sulfur dioxide in the first flue gas into sulfur trioxide, yielding a second flue gas; an HRS (High-Concentration Steam Reduction) unit, including an absorption unit, a heat recovery unit, and a diluent; and an acid concentration balancing tank connected to the heat recovery unit via a first connecting pipeline, supplying the high-concentration sulfuric acid to the heat recovery unit when the acid concentration in the heat recovery unit is below 99%. This flue gas sulfuric acid production system can maintain the normal operation of the HRS unit under low gas volume and low gas concentration conditions, and produces relatively more low-pressure steam.

Description

Technical Field

[0001] This application belongs to the field of flue gas acid production technology, specifically relating to a flue gas acid production system. Background Technology

[0002] Traditional low-temperature heat recovery systems (HRS) use alloy materials that are highly sensitive to temperature changes, requiring strict control of acid concentration within the system, typically above 99%. However, due to the cyclical nature of smelting flue gas operations, fluctuating flue gas volume and sulfur dioxide concentration can easily disrupt the acid-water balance in the dry absorption section, making it difficult to maintain acid concentration in the HRS. Therefore, there is an urgent need to design a flue gas acid production system to eliminate the impact of flue gas fluctuations, ensure stable acid concentration of sprayed acid in the HRS unit, maintain the normal operation of the low-temperature heat recovery system, and increase low-pressure steam production.

[0003] Application content

[0004] This application aims to at least partially solve one of the technical problems in the related art. To this end, this application proposes a flue gas sulfuric acid production system, which can maintain the normal operation of the HRS unit under low gas volume and low gas concentration conditions, and produce relatively more low-pressure steam.

[0005] This application proposes a flue gas sulfuric acid production system. The system includes: a drying unit for removing moisture from smelting flue gas by spraying sulfuric acid to obtain a first flue gas and a first sulfuric acid; a conversion unit connected to the drying unit for converting sulfur dioxide in the dried flue gas into sulfur trioxide to obtain a second flue gas; an HRS unit including an absorption unit, a heat recovery unit, and a diluent; the absorption unit is connected to the conversion unit and the diluent for absorbing sulfur trioxide in the second flue gas with sulfuric acid to obtain a third flue gas and a second sulfuric acid; the heat recovery unit is connected to the absorption unit for cooling the second sulfuric acid to obtain a third sulfuric acid; the diluent is connected to the drying unit, the heat recovery unit, and the absorption unit for adjusting the acid concentration of the third sulfuric acid using the first sulfuric acid to obtain a fourth sulfuric acid, which is then transported to the absorption unit to absorb sulfur trioxide in the second flue gas; and an acid concentration balancing tank connected to the heat recovery unit via a first connecting pipe, which supplies the high-concentration sulfuric acid to the heat recovery unit when the acid concentration in the heat recovery unit is below 99%.

[0006] This flue gas acid production system can eliminate the impact of flue gas fluctuations on the HRS unit, especially under low gas flow and low gas concentration conditions. By replenishing the HRS unit with high-concentration acid through an acid concentration balance tank, the concentration of the third sulfuric acid is maintained above 99%, ensuring the normal operation of the flue gas acid production system under these conditions. Furthermore, while maintaining the concentration of the third sulfuric acid in the HRS unit, it also produces at least 90% high-value finished acid, improving economic efficiency.

[0007] According to an embodiment of this application, the acid concentration balance tank is connected to the heat recovery unit via a second connecting pipeline, and the third sulfuric acid is transported to the acid concentration balance tank as the high-concentration sulfuric acid. Thus, the third sulfuric acid can be stored in the acid concentration balance tank under normal operating conditions for use under low gas flow and low gas concentration conditions.

[0008] According to an embodiment of this application, the acid concentration balance tank is connected to the drying device and stores high-concentration sulfuric acid with an acid concentration of not less than 99.4%. When the concentration of the first sulfuric acid is lower than 90%, the high-concentration sulfuric acid is supplied to the drying device. Therefore, when the system is in a low gas flow and low gas concentration condition, and the acid concentration of the first sulfuric acid is lower than 90%, the efficiency of sulfur trioxide absorption decreases. At this time, supplying the high-concentration sulfuric acid from the acid concentration balance tank to the drying device maintains the acid concentration of the drying acid above 90%, so that sulfur trioxide can be absorbed efficiently without affecting the operation of the acid production system.

[0009] According to an embodiment of this application, the flue gas acid production system further includes a desorption tower connected to the drying device, used to remove sulfur dioxide from the first sulfuric acid to obtain a fifth sulfuric acid. Thus, when most of the moisture in the first flue gas is removed in the drying device, trace amounts of sulfur dioxide will dissolve in the sprayed sulfuric acid. The desorption tower can remove this sulfur dioxide, thereby ensuring that the sulfur dioxide concentration in the finished acid product meets the standards.

[0010] According to an embodiment of this application, the flue gas acid production system further includes a secondary absorption device connected to the desorption tower. The secondary absorption device is used to absorb sulfur trioxide with added sulfuric acid to obtain a sixth sulfuric acid. The fifth sulfuric acid is transported to the secondary absorption device to adjust the acid concentration of the sixth sulfuric acid. Thus, in the secondary absorption device, under normal operating conditions, the addition of 98%-98.5% sulfuric acid to absorb sulfur trioxide from the flue gas of the conversion unit will lead to a higher concentration of the sixth sulfuric acid. Simultaneously, when the system is under low gas flow and low gas concentration conditions, although the concentration of the sixth sulfuric acid will not naturally increase, it will continue to rise due to moisture evaporation. When the acid concentration of the sixth sulfuric acid exceeds 98.5%, it will exacerbate the volatilization of sulfur trioxide, forming acid mist. At this time, a lower concentration of the fifth sulfuric acid from the desorption tower is added to the sixth sulfuric acid to actively dilute it and maintain its concentration at no higher than 98.5% and no lower than 98%, thereby ensuring the concentration of the finished acid.

[0011] According to an embodiment of this application, the secondary absorption device is also connected to the absorption unit. The sixth sulfuric acid is transported to the absorption unit to absorb sulfur trioxide in the third flue gas, yielding the seventh sulfuric acid. Thus, the sixth sulfuric acid obtained from the secondary absorption device is cooled and then transported to the absorption unit of the HRS device. It serves as spray acid in the upper packing layer of the absorption unit to absorb sulfur trioxide from the third flue gas. Its main function is to create a gentle temperature gradient in the upper packing layer, effectively controlling the formation of acid mist.

[0012] According to an embodiment of this application, the flue gas acid production system further includes a finished acid storage tank connected to the secondary suction device for storing the sixth sulfuric acid. Thus, the qualified sixth sulfuric acid is sent as finished acid to the finished acid processing section for storage.

[0013] According to an embodiment of this application, the drying device includes: a drying tower, a drying circulation pump tank, and a drying acid cooler connected in sequence. The drying circulation pump tank is connected to the acid concentration balance tank. A first discharge port and a second discharge port are provided between the drying acid cooler and the drying tower. The first discharge port is connected to the desorption tower, and the second discharge port is connected to the absorption unit. Thus, under normal operating conditions, moisture in the flue gas is absorbed in the drying tower to obtain first flue gas and first sulfuric acid. The drying circulation pump tank is used to receive and store the first sulfuric acid, providing a buffer volume. The first sulfuric acid is sent to the drying acid cooler, and after cooling, it is sent back to the top of the drying tower for spraying. When the concentration of the first sulfuric acid drops below 90%, the high-concentration sulfuric acid in the acid concentration balance tank is used to adjust the concentration of the first sulfuric acid in the drying circulation pump tank.

[0014] According to an embodiment of this application, the HRS device further includes: an HRS steam ejector and an HRS heat recovery pump tank, wherein the HRS steam ejector is connected to the absorption unit; the HRS heat recovery pump tank is disposed between the absorption unit and the heat recovery unit, and is connected to the acid concentration balance tank. Thus, sulfur trioxide in the first flue gas is converted into gaseous sulfuric acid in the HRS steam ejector, making it easier to absorb after entering the absorption unit and reducing the formation of acid mist in the absorption unit; the HRS heat recovery pump tank is used to store the third sulfuric acid from the absorption unit; when the concentration of the third sulfuric acid drops below 99%, the high concentration of sulfuric acid in the acid concentration balance tank is used to adjust the concentration of the third sulfuric acid in the HRS heat recovery pump tank.

[0015] According to an embodiment of this application, the secondary absorption device includes a secondary absorption tower, a secondary absorption circulating pump tank, and a secondary absorption acid cooler connected in sequence. The secondary absorption circulating pump tank is connected to the secondary absorption tower. The secondary absorption tower and the secondary absorption acid cooler are provided with a third discharge port and a fourth discharge port. The third discharge port is connected to the absorption unit, and the fourth discharge port is connected to the finished acid storage tank. Thus, sulfur trioxide in the flue gas from the conversion unit is absorbed in the secondary absorption tower to obtain fifth sulfuric acid; the secondary absorption circulating pump tank can receive and store the fifth sulfuric acid; after being cooled in the secondary absorption acid cooler, the fifth sulfuric acid can be divided into three parts: one part is returned to the top of the secondary absorption tower for spraying to form a closed loop circulation, one part is transported to the absorption unit for spraying, and the other part is transported to the finished acid storage tank as finished acid. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of a flue gas acid production system according to an embodiment of this application.

[0017] Figure 2 This is a schematic diagram of the structure of a flue gas acid production system according to another embodiment of this application.

[0018] Figure label:

[0019] 10: Drying device; 11: Drying tower; 12: Drying circulating pump tank; 13: Drying acid cooler; 20: Conversion device; 30: HRS device; 31: Absorption unit; 32: HRS heat recovery pump tank; 33: Heat recovery unit; 34: HRS diluent; 35: HRS steam ejector; 40: Acid concentration balance tank; 50: Desorption tower; 60: Secondary absorption device; 61: Secondary absorption tower; 62: Secondary absorption circulating pump tank; 63: Secondary absorption acid cooler; 70: Finished acid storage tank; 81: First discharge port; 82: Secondary discharge port; 83: Third discharge port; 84: Fourth discharge port. Detailed Implementation

[0020] The embodiments of this application are described in detail below, with examples of these embodiments illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0021] In flue gas sulfuric acid production systems, to maintain acid concentration balance, sulfuric acid of different concentrations is transferred and adjusted between various towers or circulating tanks through a specific process. This process is called "sulphur transfer." In this paper, the sulphur transfer process refers to the initial sulfuric acid, after absorbing moisture in the drying unit, being transferred in a certain proportion to the HRS unit and the secondary absorption unit to adjust the sulfuric acid concentration within the system. This ensures that the sulfuric acid concentration in each unit is within a suitable range, allowing the absorption reaction to proceed efficiently, improving the conversion and absorption rates of sulfur trioxide, thereby increasing the yield and quality of sulfuric acid. Furthermore, it reduces equipment corrosion, extends equipment lifespan, and also contributes to stable system operation and energy conservation. Additionally, the absorption of sulfur trioxide by concentrated sulfuric acid is an exothermic reaction, generating heat that raises the temperature of the sulfuric acid. The high-temperature sulfuric acid obtained after sulfur trioxide absorption in the heat recovery unit is sent to the heat recovery unit for heat exchange with demineralized water, generating low-pressure steam. This achieves effective recovery and reuse of waste heat, improving the system's energy efficiency.

[0022] In this article, demineralized water refers to the finished water obtained after water treatment processes have removed suspended solids, colloids, and inorganic cations and anions from the water. The fewer impurities in demineralized water, the higher its purity.

[0023] The first aspect of this application proposes a flue gas acid production system. (Refer to...) Figure 1 The system includes: a drying device 10, which removes moisture from smelting flue gas by spraying sulfuric acid to obtain a first flue gas and a first sulfuric acid; a conversion device 20, connected to the drying device 10, for converting sulfur dioxide in the dried flue gas into sulfur trioxide to obtain a second flue gas; and an HRS device 30, including an absorption unit 31, a heat recovery unit 33, and a diluent 34; the absorption unit 31 is connected to the conversion device 20 and the diluent 34, for allowing sulfuric acid to absorb sulfur trioxide in the second flue gas to obtain a third flue gas and a second sulfuric acid; the heat recovery unit 33 is connected to the absorption unit 31. The first sulfuric acid is connected to the second sulfuric acid to cool it down to obtain the third sulfuric acid. The diluent 34 is connected to the drying device 10, the heat recovery unit 33, and the absorption unit 31. It is used to adjust the acid concentration of the third sulfuric acid with the first sulfuric acid to obtain the fourth sulfuric acid. The fourth sulfuric acid is then transported to the absorption unit 31 to absorb sulfur trioxide in the second flue gas. The acid concentration balance tank 40 is connected to the heat recovery unit 33 through a first connecting pipe. When the acid concentration in the heat recovery unit is lower than 99%, the high-concentration sulfuric acid is transported to the heat recovery unit.

[0024] The first sulfuric acid, after being fed into the HRS diluent, enters the HRS diluent. By adjusting the concentration of the third sulfuric acid to 99.3%–99.5%, the fourth sulfuric acid is obtained. This concentration range offers the highest absorption efficiency for sulfur trioxide. Under normal operating conditions, the high-concentration sulfuric acid in the HRS unit is pre-stored in the acid concentration balance tank. Under low gas flow and low gas concentration conditions, the concentration of the first sulfuric acid will drop below 90%. After the acid feeding process, the concentration of the third sulfuric acid in the HRS unit will drop below 99%. By replenishing the HRS unit with acid through the acid concentration balance tank, the concentration of the third sulfuric acid can be maintained above 99%, eliminating the impact of flue gas fluctuations on the HRS unit, especially ensuring the normal operation of the flue gas sulfuric acid production system under low gas flow and low gas concentration conditions. This also produces high-value sulfuric acid, improving economic efficiency. Furthermore, while replenishing the HRS unit with acid, the first sulfuric acid is continuously fed into the HRS unit, thereby increasing the production of low-pressure steam.

[0025] In this article, sulfuric acid with an acid concentration higher than 90% is considered high-value sulfuric acid with high economic value, while sulfuric acid with an acid concentration lower than 90% is considered low-value sulfuric acid with low economic value.

[0026] The volume of the acid concentration balance tank is not infinite. It can be calculated based on the principle of dynamic material conservation. This requires considering the amount of acid replenishment needed to reduce the acid concentration in the HRS and drying units when the gas flow rate and concentration are low. It also involves calculating the decrease in acid concentration due to the reduction in sulfur dioxide content in the flue gas over a certain period, thus determining the required amount of replenishment acid to be stored in the acid concentration balance tank, i.e., the tank's volume. Accurate volume calculation ensures stable system operation, continuous production, and guarantees sufficient high-concentration sulfuric acid for timely replenishment during low gas flow and concentration periods, reducing production interruptions caused by acid concentration issues and improving production efficiency.

[0027] Specifically, the volume calculation of the acid concentration balancing tank can be referenced using the following formula:

[0028] V={X×xX×(y1-y2)×98 / 64 / r1×(1-r1)}×r1 / (1-r1) / r2 / ρ×t×K

[0029] Where X: smelting flue gas volume (m) 3 / h; x: Moisture content of smelting flue gas (kg / m³) 3 y1: Sulfur dioxide content (kg / m³) in the process flue gas from the purification section 3 y2: Sulfur dioxide content (kg / m³) in the first flue gas exiting the drying section 3; t: Storage time of high-concentration sulfuric acid (not less than 99.4%) (10-15 days); r1: Acid concentration of finished acid (98%-98.5%); r2: Acid concentration of fourth sulfuric acid (99.3%-99.5%); ρ: Acid density of fourth sulfuric acid; K: Coefficient (1.2-1.5); V: Volume of acid concentration balance tank.

[0030] According to embodiments of this application, the acid concentration balancing tank is at least one of a horizontal tank with a head and a vertical tank. In some embodiments, the horizontal tank with a head adopts a steel-lined high-temperature resistant and acid-resistant brick structure and material; in other embodiments, the vertical tank adopts a high-temperature resistant and concentrated acid-resistant high-silicon stainless steel material.

[0031] According to the embodiments of this application, referring to Figure 1 The acid concentration balance tank 40 is connected to the heat recovery unit 33 via a second connecting pipe, and the third sulfuric acid is transported to the acid concentration balance tank 40 as the high-concentration sulfuric acid. Thus, the third sulfuric acid can be stored in the acid concentration balance tank under normal operating conditions for use under low gas flow and low gas concentration conditions.

[0032] According to the embodiments of this application, referring to Figure 1 The acid concentration balance tank 40 is connected to the drying device 10 and stores high-concentration sulfuric acid with an acid concentration of not less than 99.4%. When the concentration of the first sulfuric acid is lower than 90%, the high-concentration sulfuric acid is supplied to the drying device 10. Therefore, when the system is in a low gas flow and low gas concentration condition, and the concentration of the first sulfuric acid is lower than 90%, the absorption efficiency of sulfur trioxide decreases. At this time, the high-concentration sulfuric acid in the acid concentration balance tank is supplied to the drying device to maintain the concentration of the first sulfuric acid above 90%, so that sulfur trioxide can be absorbed efficiently without affecting the operation of the acid production system.

[0033] According to the embodiments of this application, referring to Figure 1 The flue gas acid production system also includes a desorption tower 50, which is connected to the drying device 10 and is used to remove sulfur dioxide from the first sulfuric acid to obtain the fifth sulfuric acid. Thus, when most of the moisture in the first flue gas is removed in the drying device, trace amounts of sulfur dioxide will dissolve in the resulting first sulfuric acid. The desorption tower can remove the sulfur dioxide, thereby ensuring that the sulfur dioxide concentration in the finished acid product meets the standards.

[0034] According to the embodiments of this application, the structure of the desorption tower 50 is an integrated tower-tank structure. The upper absorption tower can be used to remove sulfur dioxide from the first sulfuric acid, and a portion of the first sulfuric acid can be stored in the tank at the bottom, which plays a certain buffering role.

[0035] According to an embodiment of this application, the flue gas acid production system further includes a secondary absorption device 60, which is connected to the desorption tower 50. The secondary absorption device 60 is used to absorb sulfur trioxide with added sulfuric acid to obtain a sixth sulfuric acid. The fifth sulfuric acid is transported to the secondary absorption device 60 to adjust the acid concentration of the sixth sulfuric acid. Thus, in the secondary absorption device, under normal operating conditions, the addition of 98%-98.5% sulfuric acid to absorb sulfur trioxide will lead to a higher concentration of the sixth sulfuric acid. At the same time, when the system is in a low gas flow and low gas concentration condition, although the concentration of the sixth sulfuric acid will not increase naturally, it will also cause the acid concentration to continue to increase due to water evaporation. When the acid concentration of the sixth sulfuric acid is higher than 98.5%, it will aggravate the volatilization of sulfur trioxide and the formation of acid mist. At this time, a lower concentration of the fifth sulfuric acid from the desorption tower is added to the sixth sulfuric acid to actively dilute the sixth sulfuric acid, so as to maintain the concentration of the sixth sulfuric acid not higher than 98.5% and not lower than 98%, thereby ensuring the concentration of the finished acid and maintaining a high absorption efficiency of sulfur trioxide.

[0036] According to an embodiment of this application, the second absorption device 60 is also connected to the absorption unit 31, and the sixth sulfuric acid is transported to the absorption unit 31 to absorb sulfur trioxide in the third flue gas to obtain the seventh sulfuric acid.

[0037] Therefore, the absorption unit is structured in two parts: an upper packing layer and a lower packing layer. The sprayed acid in the upper packing layer comes from the cooled, low-temperature fifth sulfuric acid from the secondary absorption device 60. Its main function is to create a gentle temperature gradient (gradually decreasing from bottom to top) within the upper packing layer by contacting the low-temperature fifth sulfuric acid with the rising, higher-temperature third flue gas. This gradient prevents the temperature of the third flue gas from suddenly dropping below the acid dew point near the top of the absorption unit 31, thus effectively suppressing fine acid mist particles and making residual sulfur trioxide more readily absorbed by the liquid-phase sulfuric acid. The spray in the lower packing layer comes from the high-temperature, high-concentration (99.3%-99.5%) fourth sulfuric acid regulated by the HRS diluter 34, which efficiently absorbs most of the sulfur trioxide in the second flue gas. This process releases a large amount of condensation heat, absorption heat, and reaction heat, causing the acid temperature to rise. The sixth sulfuric acid obtained in the second absorption device is cooled and then transported to the absorption unit 31 of the HRS device 30. As the spray acid in the upper packing layer of the absorption unit 31, it absorbs sulfur trioxide from the third flue gas. The cooled fifth sulfuric acid can form a gentle temperature gradient in the upper packing layer, effectively controlling the formation of acid mist.

[0038] In this article, flue gas acid dew point refers to the condensation temperature of sulfur trioxide in flue gas, which combines with water vapor to form sulfuric acid vapor. When the flue gas temperature is below the acid dew point, acid mist will form, which will adhere to the equipment surface and accelerate the corrosion of the equipment.

[0039] According to the embodiments of this application, referring to Figure 1The flue gas acid production system also includes a finished acid storage tank 70, connected to the secondary suction device 60, for storing the sixth sulfuric acid. Thus, the qualified sixth sulfuric acid is sent as finished acid to the finished acid processing section.

[0040] According to the embodiments of this application, referring to Figure 2 The drying apparatus includes a drying tower 11, a drying circulation pump tank 12, and a drying acid cooler 13 connected in sequence. The drying circulation pump tank 12 is connected to the acid concentration balance tank 40. A first discharge port 81 and a second discharge port 82 are provided between the drying acid cooler 13 and the drying tower 11. The first discharge port 81 is connected to the desorption tower 50, and the second discharge port 82 is connected to the absorption unit 31. Thus, under normal operating conditions, moisture in the flue gas is absorbed in the drying tower to obtain first flue gas and first sulfuric acid. The drying circulation pump tank 12 is used to receive and store the first sulfuric acid, providing a buffer volume. The first sulfuric acid is sent to the drying acid cooler 13, and after cooling, it is sent back to the top of the drying tower 11 for spraying. When the concentration of the first sulfuric acid drops below 90%, the high-concentration sulfuric acid in the acid concentration balance tank 40 is used to adjust the concentration of the first sulfuric acid in the drying circulation pump tank 12, thereby avoiding corrosion of the drying tower and the production of worthless first sulfuric acid with a concentration below 90%.

[0041] According to the embodiments of this application, referring to Figure 2 The HRS device further includes an HRS steam ejector 35 and an HRS heat recovery pump tank 32. The HRS steam ejector 35 is connected to the absorption unit 31. The HRS heat recovery pump tank 32 is disposed between the absorption unit 31 and the heat recovery unit 33, and is connected to the acid concentration balance tank 40. Thus, low-pressure steam mixes with sulfur trioxide in the second flue gas in the HRS steam ejector 35, converting the sulfur trioxide into gaseous sulfuric acid, which is more easily absorbed after entering the absorption unit 31, suppressing the formation of acid mist in the absorption unit 31. The heat recovery unit 33 is used to cool the second sulfuric acid to obtain third sulfuric acid. The concentration of the third sulfuric acid drops below 99%, and the high concentration of sulfuric acid in the acid concentration balance tank 40 is used to adjust the concentration of the third sulfuric acid in the HRS heat recovery pump tank 32.

[0042] According to the embodiments of this application, referring to Figure 2The secondary absorption device includes a secondary absorption tower 61, a secondary absorption circulating pump tank 62, and a secondary absorption acid cooler 63 connected in sequence. The secondary absorption circulating pump tank 62 is connected to the desorption tower 50. The secondary absorption tower 61 and the secondary absorption acid cooler 63 are provided with a third discharge port 83 and a fourth discharge port 84. The third discharge port is connected to the absorption unit 31, and the fourth discharge port is connected to the finished acid storage tank 60. Thus, sulfur trioxide is absorbed by added sulfuric acid in the secondary absorption tower 61 to obtain the fifth sulfuric acid; the secondary absorption circulating pump tank 62 can receive and store the fifth sulfuric acid; after being cooled by the secondary absorption acid cooler 63, the fifth sulfuric acid can be divided into three parts: one part is returned to the top of the secondary absorption tower for spraying to form a closed loop circulation, one part is transported to the absorption unit for spraying, and the other part is transported to the finished acid storage tank as finished acid.

[0043] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0044] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0045] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A flue gas acid production system, characterized in that, include: The drying device removes moisture from the smelting flue gas by spraying sulfuric acid to obtain the first flue gas and the first sulfuric acid; A conversion device, connected to the drying device, is used to convert sulfur dioxide in the first flue gas into sulfur trioxide to obtain the second flue gas. The HRS device includes an absorption unit, a heat recovery unit, and a diluent; The absorption unit is connected to the conversion device and the diluter, and is used to allow sulfuric acid to absorb sulfur trioxide in the second flue gas to obtain the third flue gas and the second sulfuric acid. The heat recovery unit is connected to the absorption unit and is used to cool the second sulfuric acid to obtain the third sulfuric acid. The diluent is connected to the drying device, the heat recovery unit and the absorption unit, and is used to adjust the acid concentration of the third sulfuric acid with the first sulfuric acid to obtain the fourth sulfuric acid, and the fourth sulfuric acid is transported to the absorption unit to absorb sulfur trioxide in the second flue gas; An acid concentration balancing tank is connected to the heat recovery unit via a first connecting pipe. When the acid concentration in the heat recovery unit is below 99%, high-concentration sulfuric acid is supplied to the heat recovery unit.

2. The flue gas acid production system according to claim 1, characterized in that, The acid concentration balance tank is connected to the heat recovery unit through a second connecting pipeline, and the third sulfuric acid is transported to the acid concentration balance tank as the high-concentration sulfuric acid.

3. The flue gas acid production system according to claim 1, characterized in that, The acid concentration balance tank is connected to the drying device and stores high-concentration sulfuric acid with an acid concentration of not less than 99.4%. When the concentration of the first sulfuric acid is less than 90%, the high-concentration sulfuric acid is supplied to the drying device.

4. The flue gas acid production system according to claim 1, characterized in that, Also includes: A desorption tower, connected to the drying device, is used to remove sulfur dioxide from the first sulfuric acid to obtain the fifth sulfuric acid.

5. The flue gas acid production system according to claim 4, characterized in that, Also includes: The secondary absorption device is connected to the desorption tower. The secondary absorption device is used to absorb sulfur trioxide with added sulfuric acid to obtain the sixth sulfuric acid. The fifth sulfuric acid is transported to the secondary absorption device to adjust the acid concentration of the sixth sulfuric acid.

6. The flue gas acid production system according to claim 5, characterized in that, The second absorption device is also connected to the absorption unit, and the sixth sulfuric acid is transported to the absorption unit to absorb sulfur trioxide in the third flue gas to obtain the seventh sulfuric acid.

7. The flue gas acid production system according to claim 5, characterized in that, Also includes: The finished acid storage tank is connected to the second suction device and is used to store the sixth sulfuric acid.

8. The flue gas acid production system according to claim 4, characterized in that, The drying device includes: a drying tower, a drying circulation pump tank, and a drying acid cooler connected in sequence. The drying circulation pump tank is connected to the acid concentration balance tank. A first discharge port and a second discharge port are provided between the drying acid cooler and the drying tower. The first discharge port is connected to the desorption tower, and the second discharge port is connected to the absorption unit.

9. The flue gas acid production system according to claim 1, characterized in that, The HRS device further includes: an HRS steam ejector and an HRS heat recovery pump tank, wherein the HRS steam ejector is connected to the absorption unit; the HRS heat recovery pump tank is disposed between the absorption unit and the heat recovery unit, and is connected to the acid concentration balance tank.

10. The flue gas acid production system according to claim 7, characterized in that, The double-absorption device includes a double-absorption tower, a double-absorption circulating pump tank, and a double-absorption acid cooler connected in sequence. The double-absorption circulating pump tank is connected to the desorption tower. The double-absorption tower and the double-absorption acid cooler are provided with a third discharge port and a fourth discharge port. The third discharge port is connected to the absorption unit, and the fourth discharge port is connected to the finished acid storage tank.

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