Acid making and denitration combined treatment system

Abstract

The utility model relates to the technical field of flue gas denitration environmental protection, and discloses an acid making and denitration combined treatment system. The system comprises an acid making unit, a denitration device and a third heat exchanger, the acid making unit comprises a first heat exchanger, a second heat exchanger, a conversion device and an absorption device which are sequentially connected along a process gas conveying pipeline, after the process gas containing sulfur dioxide is treated by the acid making unit, sulfuric acid is prepared in the absorption device, and acid making tail gas containing nitric oxide is discharged; the acid-making tail gas from the absorption device firstly enters the third heat exchanger to perform primary heat exchange with the denitrated tail gas from the denitration device, then enters the second heat exchanger to perform secondary heat exchange with the process gas from the first heat exchanger, and then enters the denitration device to perform denitration reaction. The system not only meets the low-concentration emission requirement of nitrogen oxides, but also does not increase the energy consumption of the device.

Description

Technical Field

[0001] This utility model relates to the field of flue gas denitrification and environmental protection technology, specifically to a combined acid production and denitrification treatment system. Background Technology

[0002] Resource recovery of sulfur-containing waste liquids and gases typically involves recycling sulfur to produce concentrated sulfuric acid. This technology usually employs high-temperature pyrolysis to decompose the sulfur in the waste liquids and gases into sulfur dioxide, thus producing a sulfuric acid production process gas containing a certain concentration of sulfur dioxide. However, this decomposition process involves the generation of thermal and fuel-type nitrogen oxides, causing the nitrogen oxide content in the final exhaust gas from the sulfuric acid production unit to fail to meet the national standard of ≤100 mg / m³. 3 Environmental requirements are in place. Even without the generation of fuel-based nitrogen oxides, thermal nitrogen oxides alone cannot consistently guarantee this level. As environmental policies become increasingly stringent, local policies are beginning to require that the nitrogen oxide concentration in the exhaust gas from acid production plants treating sulfur-containing wastewater and waste gas be ≤50 mg / m³. 3 Even ≤30mg / m 3 .

[0003] Current treatment methods include SCR denitrification technology or ozone denitrification technology.

[0004] In wet acid production, an SCR reaction bed is installed in the converter. Reducing agents such as urea and ammonia are injected to reduce nitrogen oxides in the acid production tail gas to nitrogen. The reaction temperature is typically 410-420℃, during which ammonia escapes, resulting in ammonium sulfate impurities in the product acid, causing turbidity and reduced transparency. Some literature mentions using low-temperature SCR denitrification technology for the tail gas, utilizing the surplus heat from the conversion unit to heat the acid production tail gas to 150-190℃ before it enters the denitrification reactor. Since the temperature of the tail gas after acid production is only 50-60℃, the required energy is relatively large. The conversion unit actually does not have surplus heat above 100℃; it can only meet a temperature rise of less than 80℃ at most.

[0005] Ozone denitrification technology utilizes the oxidizing properties of ozone to convert nitrogen oxides into nitrates or nitrites, thus transferring pollutants from exhaust gas to wastewater. However, it does not completely solve the problem of waste gas, wastewater, and solid waste emissions. Furthermore, ozone denitrification technology is energy-intensive and uneconomical.

[0006] Therefore, there is an urgent need for a low-energy denitrification system that utilizes internal energy to heat the acid production tail gas in order to solve the current problem of ultra-low nitrogen oxide emission concentration requirements for acid production tail gas. Utility Model Content

[0007] The purpose of this invention is to overcome the problems of existing technologies where nitrogen oxides in acid production tail gas cannot be completely eliminated or where denitrification of acid production tail gas requires a large amount of energy. This invention provides a combined acid production and denitrification treatment system that meets the requirements for low-concentration nitrogen oxide emissions, does not increase the energy consumption of the equipment, and does not reduce the quality of the finished acid.

[0008] To achieve the above objectives, this utility model provides a combined acid production and denitrification system, which includes an acid production unit, a denitrification device, and a third heat exchanger.

[0009] The acid production unit includes a first heat exchanger, a second heat exchanger, a conversion device, and an absorption device connected in sequence along the process gas delivery pipeline. After the process gas containing sulfur dioxide is processed by the acid production unit, sulfuric acid is produced in the absorption device, and acid production tail gas containing nitrogen oxides is discharged.

[0010] The acid production tail gas from the absorption device first enters the third heat exchanger to exchange heat once with the denitrified tail gas from the denitrification device, then enters the second heat exchanger to exchange heat a second time with the process gas from the first heat exchanger, and then enters the denitrification device to carry out the denitrification reaction.

[0011] Preferably, a purification device and a drying device are also sequentially arranged between the second heat exchanger and the absorption device of the acid production unit along the process gas delivery pipeline.

[0012] Preferably, the denitrification device includes a denitrification reactor and a mixer; vaporized liquid ammonia and air are mixed in the mixer, and the resulting mixed gas is introduced into the denitrification reactor to denitrify the acid production tail gas after secondary heat exchange.

[0013] Preferably, after the vaporized liquid ammonia is mixed with air in the mixer, the volume concentration of the vaporized liquid ammonia is <5%.

[0014] Preferably, the denitrification reactor has N reaction bed layers, where N≥2, and one of the reaction bed layers is a spare reaction bed layer.

[0015] Preferably, the denitrification device further includes an online concentration analyzer for detecting and analyzing the concentration of ammonia in the mixer.

[0016] Preferably, the denitrification device further includes a liquid ammonia metering pump and a first flow meter; the vaporized liquid ammonia is metered sequentially by the liquid ammonia metering pump and the first flow meter before entering the mixer.

[0017] Preferably, the denitrification device further includes a second flow meter; air enters the mixer after being metered by the second flow meter.

[0018] Preferably, a metering valve and a third flow meter are sequentially installed on the pipeline between the mixer and the denitrification reactor along the flow direction of the mixed gas, for measuring the amount of mixed gas entering the denitrification reactor.

[0019] Preferably, the denitrification reactor is also equipped with a soot blower for purging the reaction bed.

[0020] Preferably, the system further includes a desulfurization unit; after the denitrification tail gas exchanges heat with the acid production tail gas in the third heat exchanger, it enters the desulfurization unit for desulfurization.

[0021] Preferably, the second heat exchanger and the third heat exchanger are plate-type gas-to-gas heat exchangers.

[0022] Preferably, the sulfuric acid from the absorption unit is cooled by a cooling device before entering the ammonium sulfate unit to produce ammonium sulfate.

[0023] Compared with the prior art, the present invention has at least the following beneficial effects:

[0024] The combined acid production and denitrification system of this invention exchanges heat between the acid production tail gas and the denitrified tail gas and the process gas before purification from the denitrification device in sequence. This can raise the temperature of the acid production tail gas to the denitrification temperature. The entire denitrification process does not require additional external heat; it only utilizes the heat of the flue gas before the purification unit, reducing the heat transfer load of the purification unit by 8%-15%, improving the heat utilization of the device, and without reducing the quality of the finished acid.

[0025] In a preferred embodiment, the system described in this invention converts nitrogen oxides in acid production tail gas into nitrogen gas by introducing an appropriate amount of vaporized liquid ammonia and air into the denitrification device, thereby meeting the requirements for low-concentration nitrogen oxide emissions.

[0026] In a preferred embodiment, the denitrification reactor provided by this invention is equipped with a soot blower, which can reduce catalyst blockage and corrosion and improve the denitrification effect. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the system for heating acid-producing tail gas using energy within the system, as described in this utility model.

[0028] Figure 2 This is a schematic diagram of the denitrification device described in this utility model.

[0029] Explanation of reference numerals in the attached figures

[0030] 1. Acid production unit; 2. Denitrification device; 3. Third heat exchanger; 4. Desulfurization unit; 11. First heat exchanger; 12. Second heat exchanger; 13. Purification device; 14. Drying device; 15. Conversion device; 16. Absorption device; 21. Denitrification reactor; 22. Mixer; 23. Reaction bed; 24. Online concentration analyzer; 25. Liquid ammonia metering pump; 26. First flow meter; 27. Second flow meter; 28. Metering valve; 29. ​​Third flow meter. Detailed Implementation

[0031] The specific embodiments of this utility model are described in detail below. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the scope of this utility model.

[0032] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0033] The combined acid production and denitrification system provided by this utility model, such as Figure 1 As shown, the system includes an acid production unit 1, a denitrification device 2, and a third heat exchanger 3;

[0034] The acid production unit 1 includes a first heat exchanger 11, a second heat exchanger 12, a conversion device 15, and an absorption device 16 connected in sequence along the process gas delivery pipeline. After the process gas containing sulfur dioxide is processed by the acid production unit 1, sulfuric acid is produced in the absorption device 16, and acid production tail gas containing nitrogen oxides is discharged.

[0035] The acid production tail gas from the absorption device 16 first enters the third heat exchanger 3 to exchange heat once with the denitrified tail gas from the denitrification device 2, then enters the second heat exchanger 12 to exchange heat twice with the process gas from the first heat exchanger 11, and then enters the denitrification device 2 to carry out the denitrification reaction.

[0036] In a preferred embodiment, a purification device 13 and a drying device 14 are sequentially arranged along the process gas delivery pipeline between the second heat exchanger 12 and the absorption device 16 of the acid production unit 1. In the system described in this invention, the process in the acid production unit 1 includes: high-temperature decomposition of sulfur-containing waste liquid and / or sulfur-containing waste gas into process gas containing sulfur dioxide and nitrogen oxides; sequential cooling of the process gas in the first heat exchanger 11, further cooling in the second heat exchanger 12, purification treatment in the purification device 13 to remove metal and / or non-metal micro / nano-level dust from the process gas, drying in the drying device 14, conversion of sulfur dioxide to sulfur trioxide in the conversion device 15, conversion of sulfur trioxide to sulfuric acid in the absorption device 16, and discharge of the acid production tail gas containing nitrogen oxides. In this invention, the temperature of the process gas containing sulfur dioxide and nitrogen oxides obtained from the high-temperature decomposition of sulfur-containing waste liquid and / or sulfur-containing waste gas can be 1000-1200℃. In this invention, the first heat exchanger 11 can be a waste heat recovery unit. After the process gas is cooled in the first heat exchanger 11, the temperature drops to 300-350°C. This process gas recovers heat and produces steam byproducts through the waste heat recovery unit.

[0037] In the system described in this utility model, the process carried out in the denitrification device 2 includes: acid production tail gas containing nitrogen oxides enters the denitrification device 2 to carry out a denitrification reaction, which can convert nitrogen oxides into nitrogen gas.

[0038] The inventors of this invention discovered through research that the acid-producing tail gas from the absorption device 16 is first exchanged with the denitrified tail gas from the denitrification device 2 in the third heat exchanger 3. Then, the acid-producing tail gas is exchanged with the process gas cooled in the first heat exchanger 11 in the second heat exchanger 12. Through this two-stage heating of the denitrified tail gas and the unpurified process gas, the temperature of the acid-producing tail gas is raised to the denitrification temperature. The heated acid-producing tail gas is then fed into the denitrification device 2 for the denitrification reaction. The resulting denitrified tail gas is discharged from the denitrification device 2, while the heat-exchanged process gas continues to be processed sequentially into the purification device 13, drying device 14, conversion device 15, and absorption device 16. The system described in this invention can raise the temperature of the acid-producing tail gas to the denitrification temperature through two-stage heating, enabling the entire denitrification process to achieve the purpose of denitrification without the need for additional external heat.

[0039] In this invention, before the acid-producing tail gas and the denitrified tail gas undergo a heat exchange in the third heat exchanger 3, the temperature of the denitrified tail gas discharged from the denitrification device 2 is 170-190°C, and the temperature of the acid-producing tail gas discharged from the absorption device 16 is 40-60°C before the heat exchange. After the heat exchange, the temperature of the denitrified tail gas drops to 100-120°C, and the temperature of the acid-producing tail gas rises to 90-130°C.

[0040] In this invention, before the acid production tail gas and the process gas undergo secondary heat exchange in the second heat exchanger 12, the temperature of the process gas from the first heat exchanger 11 is 300-350°C, and the temperature of the acid production tail gas from the third heat exchanger 3 is 90-130°C before secondary heat exchange. After the acid production tail gas and the process gas undergo secondary heat exchange, the temperature of the process gas drops to 250-280°C and then enters the purification device 13 for treatment, while the temperature of the acid production tail gas rises to above 150°C, preferably 170-190°C, and then enters the denitrification device 2 for denitrification reaction.

[0041] In the method described in this utility model, such as Figure 2 As shown, the denitrification device 2 includes a denitrification reactor 21 and a mixer 22; vaporized liquid ammonia and air are mixed in the mixer 22, and the resulting mixed gas enters the denitrification reactor 21 to denitrify the acid production tail gas after secondary heat exchange. In this invention, vaporized liquid ammonia refers to the product obtained by vaporizing liquid ammonia.

[0042] In a preferred embodiment, to control ammonia escape and ensure proper metering, the volume concentration of the vaporized liquid ammonia is <5% after mixing with air in the mixer 22. The vaporized liquid ammonia acts as a reducing agent to reduce nitrogen oxides to nitrogen gas, while the air lowers the lower explosive limit of the mixed gas, preventing an explosion.

[0043] like Figure 2 As shown, the denitrification device 2 also includes an online concentration analyzer 24, which is used to detect and analyze the concentration of ammonia in the mixer 22 to ensure that the concentration of vaporized liquid ammonia in the mixer 22 is within a suitable range.

[0044] In this utility model, such as Figure 2 As shown, the denitrification device 2 also includes a liquid ammonia metering pump 25 and a first flow meter 26; the vaporized liquid ammonia is metered sequentially by the liquid ammonia metering pump 25 and the first flow meter 26 and then enters the mixer 22, thereby accurately controlling the amount of vaporized liquid ammonia entering the mixer 22 and ensuring that the concentration of vaporized liquid ammonia in the mixer 22 is within a suitable range.

[0045] In this utility model, such as Figure 2 As shown, the denitrification device 2 also includes a second flow meter 27; air enters the mixer 22 after being measured by the second flow meter 27, thereby accurately controlling the amount of air entering the mixer 22 and ensuring that the concentration of vaporized liquid ammonia in the mixer 22 is within a suitable range.

[0046] In the system described in this utility model, a metering valve 28 and a third flow meter 29 are sequentially installed on the pipeline between the mixer 22 and the denitrification reactor 21 along the direction of the mixed gas flow. These are used to measure the amount of mixed gas entering the denitrification reactor 21, thereby achieving precise control and preventing excessive gasified liquid ammonia from entering the denitrification reactor 21.

[0047] In the system described in this utility model, such as Figure 2 As shown, the denitrification reactor 21 has N reaction bed layers 23, where N≥2, and one of the reaction bed layers 23 is a spare reaction bed layer to achieve online catalyst replacement. In a preferred embodiment, each reaction bed layer 23 is connected to a third flow meter 29 and a metering valve 28, thereby improving the denitrification effect.

[0048] In a preferred embodiment, the denitrification reactor 21 provided by this invention is equipped with a soot blower for blowing away the reaction bed 23, which can reduce catalyst blockage and corrosion and improve the denitrification effect.

[0049] In this utility model, such as Figure 1 As shown, the system also includes a desulfurization unit 4; after the denitrification tail gas exchanges heat with the acid production tail gas in the third heat exchanger 3, it enters the desulfurization unit 4 for desulfurization. The denitrification tail gas meets emission standards after desulfurization, with SO2 ≤ 9.8 mg / m³ in the discharged tail gas. 3 Acid mist ≤4.9mg / m³ 3 NOx ≤ 28 mg / m³ 3 Particulate matter ≤9.5mg / m³ 3 .

[0050] In this invention, the second heat exchanger can be any heat exchanger known in the art. Preferably, the second heat exchanger 12 is a plate gas-to-gas heat exchanger.

[0051] In this invention, the third heat exchanger 3 can be a waste heat recovery device for denitrification exhaust gas. In the system described in this invention, the third heat exchanger 3 can be any type of heat exchanger commonly used in the art; preferably, the third heat exchanger 3 is a plate gas-to-gas heat exchanger.

[0052] In this invention, the sulfuric acid obtained from the absorption device 16 is cooled by a cooling device and then enters the ammonium sulfate unit to produce ammonium sulfate. The cooling device can be a cooler commonly used in the art, and the ammonium sulfate unit can be an apparatus commonly used in the art to produce ammonium sulfate.

[0053] The system described in this invention exchanges heat sequentially with the denitrified tail gas and the pre-purification process gas from the denitrification device, thereby raising the temperature of the acid production tail gas to the denitrification temperature. The entire denitrification process does not require additional external heat, improving the heat utilization of the device and not reducing the quality of the finished acid.

[0054] This utility model also provides a method for combined acid production and denitrification, which is carried out in the system described above, and the method includes:

[0055] The process gas containing sulfur dioxide is processed by the acid production unit 1 and then sulfuric acid is produced in the absorption device 16. The acid production tail gas containing nitrogen oxides is discharged.

[0056] The acid production tail gas from the absorption device 16 first enters the third heat exchanger 3 to exchange heat with the denitrified tail gas from the denitrification device 2, raising the temperature of the acid production tail gas to 90-130°C. Then, it enters the second heat exchanger 12 to exchange heat with the process gas from the first heat exchanger 11, raising the temperature of the acid production tail gas to above 150°C. Finally, it enters the denitrification device 2 to carry out the denitrification reaction.

[0057] In the method described in this invention, the process of treating the sulfur dioxide-containing process gas through the acid production unit 1 includes: decomposing the sulfur-containing waste liquid and / or sulfur-containing waste gas at high temperature into process gas containing sulfur dioxide and nitrogen oxides; then cooling the process gas sequentially in the first heat exchanger 11, further cooling it in the second heat exchanger 12, purifying it in the purification device 13 to remove metal and / or non-metallic micro-nano-level dust from the process gas, drying it in the drying device 14, converting sulfur dioxide into sulfur trioxide in the conversion device 15, converting sulfur trioxide into sulfuric acid in the absorption device 16, and discharging the acid production tail gas containing nitrogen oxides. In the method described in this invention, the denitrification process includes: passing the acid production tail gas containing nitrogen oxides into the denitrification device 2 for a denitrification reaction, converting the nitrogen oxides into nitrogen gas.

[0058] In this invention, the temperature of the process gas containing sulfur dioxide and nitrogen oxides obtained from the high-temperature decomposition of sulfur-containing waste liquid and / or sulfur-containing waste gas can be 1000-1200℃. In this invention, the first heat exchanger 11 can be a waste heat recovery unit. After the process gas is cooled in the first heat exchanger 11 to 300-350℃, the waste heat recovery unit recovers heat and produces byproduct steam.

[0059] The inventors of this invention discovered through research that the acid-producing tail gas from the absorption device 16 is first exchanged with the denitrified tail gas from the denitrification device 2 in the third heat exchanger 3. Then, the acid-producing tail gas is exchanged with the process gas cooled in the first heat exchanger 11 in the second heat exchanger 12. Through this two-stage heating of the denitrified tail gas and the unpurified process gas, the temperature of the acid-producing tail gas is raised to the denitrification temperature. The heated acid-producing tail gas is then fed into the denitrification device 2 for the denitrification reaction. The resulting denitrified tail gas is discharged from the denitrification device 2, while the heat-exchanged process gas continues to be processed sequentially into the purification device 13, drying device 14, conversion device 15, and absorption device 16. The system described in this invention can raise the temperature of the acid-producing tail gas to the denitrification temperature through two-stage heating, enabling the entire denitrification process to achieve the purpose of denitrification without the need for additional external heat.

[0060] In this invention, before the acid-producing tail gas and the denitrified tail gas undergo a heat exchange in the third heat exchanger 3, the temperature of the denitrified tail gas discharged from the denitrification device 2 is 170-190°C, and the temperature of the acid-producing tail gas discharged from the absorption device 16 is 40-60°C before the heat exchange. After the heat exchange, the temperature of the denitrified tail gas drops to 100-120°C, and the temperature of the acid-producing tail gas rises to 90-130°C.

[0061] In this invention, before the acid production tail gas and the process gas undergo secondary heat exchange in the second heat exchanger 12, the temperature of the process gas from the first heat exchanger 11 is 300-350°C, and the temperature of the acid production tail gas from the third heat exchanger 3 is 90-130°C before secondary heat exchange. After the acid production tail gas and the process gas undergo secondary heat exchange, the temperature of the process gas drops to 250-280°C and then enters the purification device 13 for treatment, while the temperature of the acid production tail gas rises to above 150°C, preferably 170-190°C, and then enters the denitrification device 2 for denitrification reaction.

[0062] In the method described in this utility model, such as Figure 2 As shown, the denitrification device 2 includes a denitrification reactor 21 and a mixer 22; vaporized liquid ammonia and air are mixed in the mixer 22, and the resulting mixed gas enters the denitrification reactor 21 to denitrify the acid production tail gas after secondary heat exchange.

[0063] In a preferred embodiment, to control ammonia escape, the vaporized liquid ammonia is mixed with air in the mixer 22, and the volume concentration of the vaporized liquid ammonia is <5%. The vaporized liquid ammonia acts as a reducing agent to reduce nitrogen oxides to nitrogen gas, while the air lowers the lower explosive limit of the mixed gas.

[0064] The method described in this invention involves exchanging heat sequentially between the acid production tail gas and the denitrified tail gas and the pre-purification process gas from the denitrification device. This process can raise the temperature of the acid production tail gas to the denitrification temperature. The entire denitrification process does not require additional external heat, thus improving the heat utilization of the device and not reducing the quality of the finished acid.

[0065] The following examples further illustrate the combined acid production and denitrification system and method of this utility model. These examples are implemented based on the technical solution of this utility model, providing detailed implementation methods and specific operating procedures; however, the scope of protection of this utility model is not limited to the following examples.

[0066] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods in the art. Unless otherwise specified, the experimental materials used in the following embodiments are commercially available.

[0067] The following examples are implemented in a combined acid production and denitrification system, such as... Figure 1 As shown, the system includes an acid production unit 1, a denitrification device 2, a third heat exchanger 3, and a desulfurization unit 4;

[0068] The acid production unit 1 includes a first heat exchanger 11, a second heat exchanger 12, a purification device 13, a drying device 14, a conversion device 15, and an absorption device 16 connected in sequence along the process gas conveying pipeline. The process gas containing sulfur dioxide is processed by the acid production unit 1 and then sulfuric acid is produced in the absorption device 16. After being cooled by the cooling device, the sulfuric acid enters the ammonium sulfate unit to produce ammonium sulfate and discharges acid production tail gas containing nitrogen oxides.

[0069] The acid production tail gas from the absorption device 16 first enters the third heat exchanger 3 to exchange heat once with the denitrified tail gas from the denitrification device 2, then enters the second heat exchanger 12 to exchange heat twice with the process gas from the first heat exchanger 11, and then enters the denitrification device 2 for denitrification reaction. After the denitrified tail gas exchanges heat with the acid production tail gas in the third heat exchanger 3, it enters the desulfurization unit 4 for desulfurization. The second heat exchanger 12 and the third heat exchanger 3 are plate gas-to-gas heat exchangers.

[0070] like Figure 2 As shown, the denitrification device 2 includes a denitrification reactor 21, a mixer 22, an online concentration analyzer 24, a liquid ammonia metering pump 25, a first flow meter 26, and a second flow meter 27. A metering valve 28 and a third flow meter 29 are sequentially installed on the pipeline between the mixer 22 and the denitrification reactor 21 along the direction of the mixed flow. A soot blower is also installed in the denitrification reactor 21 for blowing the reaction bed 23.

[0071] Vaporized liquid ammonia is metered sequentially by the liquid ammonia metering pump 25 and the first flow meter 26 before entering the mixer 22. Air is metered sequentially by the second flow meter 27 before entering the mixer 22. The vaporized liquid ammonia and air are mixed in the mixer 22 to detect and analyze the concentration of ammonia in the mixer 22. The volume concentration of vaporized liquid ammonia is <5%. The resulting mixed gas is metered sequentially by the metering valve 28 and the third flow meter 29 before entering the denitrification reactor 21 to denitrify the acid tail gas after secondary heat exchange. The denitrification reactor 21 has three reaction bed layers 23, one of which is a spare reaction bed layer.

[0072] Example 1

[0073] like Figure 1 Waste sulfuric acid with a concentration of 90% by volume and a processing capacity of 3.57 tons per hour is decomposed at high temperature using natural gas as fuel to produce process gas containing sulfur dioxide at a temperature of 1050°C. The sulfur dioxide concentration in the process gas entering the conversion unit 15 is 8.35% by volume. After passing through the first heat exchanger 11, the temperature of the process gas drops to 315°C. Then, it enters the second heat exchanger 12 to exchange heat with the acid production tail gas. The process gas continues to cool down to 268°C and then enters the purification unit 13, drying unit 14, conversion unit 15, and absorption unit 16 for treatment in sequence. Sulfuric acid is produced in the absorption unit 16, and acid production tail gas containing nitrogen oxides is discharged.

[0074] The acid production tail gas from the absorption device 16 first enters the third heat exchanger 3 and exchanges heat once with the denitrified tail gas from the denitrification device 2. After the denitrification tail gas cools from 185°C to 110°C, it enters the subsequent desulfurization unit for desulfurization and is discharged after meeting the standards. The SO2 content in the discharged tail gas is ≤9.8 mg / m³. 3 Acid mist ≤4.9mg / m³ 3 NOx ≤ 28 mg / m³ 3 Particulate matter ≤9.5mg / m³ 3 The acid production tail gas is heated from 55°C to 120°C and then enters the second heat exchanger 12 to exchange heat with the process gas from the first heat exchanger 11. The acid production tail gas is heated from 120°C to 185°C and then enters the denitrification device 2 to carry out the denitrification reaction. The process gas is cooled to 268°C.

[0075] In the denitrification device 2, the acid production tail gas at 185°C enters the denitrification reactor 21 from top to bottom, and each bed is equipped with an ammonia injection system. After the liquid ammonia is vaporized, it is mixed evenly with air in the mixer 22, with an ammonia volume concentration of <5%. Then, it is accurately metered by the metering valve 28 and the third flow meter 29 before entering each bed.

[0076] The workflow of this embodiment utilizes the 350kW flue gas heat within the system, saving the 437kWh of electricity required for heating with an electric furnace.

[0077] Example 2

[0078] like Figure 1 Waste sulfuric acid with a concentration of 70% by volume and a processing capacity of 3.57 tons per hour is decomposed at high temperature using natural gas as fuel to produce process gas containing sulfur dioxide at a temperature of 1050°C. The sulfur dioxide concentration in the process gas entering the conversion unit 15 is 6.5% by volume. After passing through the first heat exchanger 11, the temperature of the process gas drops to 305°C. Then, it enters the second heat exchanger 12 to exchange heat with the acid production tail gas. The process gas continues to cool down to 262°C and then enters the purification unit 13, drying unit 14, conversion unit 15, and absorption unit 16 for treatment in sequence. Sulfuric acid is produced in the absorption unit 16, and acid production tail gas containing nitrogen oxides is discharged.

[0079] The acid production tail gas from the absorption device 16 first enters the third heat exchanger 3 and exchanges heat once with the denitrified tail gas from the denitrification device 2. After the denitrification tail gas cools from 185°C to 110°C, it enters the subsequent desulfurization unit for desulfurization and is discharged after meeting the standards. The SO2 content in the discharged tail gas is ≤9.8 mg / m³. 3 Acid mist ≤4.9mg / m³ 3 NOx ≤ 28 mg / m³ 3 Particulate matter ≤9.5mg / m³ 3 The acid production tail gas is heated from 50°C to 120°C and then enters the second heat exchanger 12 to exchange heat with the process gas from the first heat exchanger 11. The acid production tail gas is heated from 120°C to 180°C and then enters the denitrification device 2 to carry out the denitrification reaction. The process gas is cooled to 262°C.

[0080] In the denitrification device 2, the acid production tail gas at 180°C enters the denitrification reactor 21 from top to bottom, and each bed is equipped with an ammonia injection system. After the liquid ammonia is vaporized, it is mixed evenly with air in the mixer 22, with an ammonia volume concentration of <5%. Then, it passes through the metering valve 28 and the third flow meter 29 for precise metering before entering each bed.

[0081] The workflow of this embodiment utilizes 378 kW of flue gas heat within the system, saving the 437 kWh of electricity required for heating with an electric furnace.

[0082] Example 3

[0083] like Figure 1Waste sulfuric acid with a concentration of 50% by volume and a processing capacity of 3.57 tons per hour is decomposed at high temperature using natural gas as fuel to produce process gas containing sulfur dioxide at a temperature of 1050°C. The sulfur dioxide concentration in the process gas entering the conversion unit 15 is 7.2% by volume. After passing through the first heat exchanger 11, the temperature of the process gas drops to 310°C. Then, it enters the second heat exchanger 12 to exchange heat with the acid production tail gas. The process gas continues to cool down to 263°C and then enters the purification unit 13, drying unit 14, conversion unit 15, and absorption unit 16 for treatment in sequence. Sulfuric acid is produced in the absorption unit 16, and acid production tail gas containing nitrogen oxides is discharged.

[0084] The acid production tail gas from the absorption device 16 first enters the third heat exchanger 3 and exchanges heat once with the denitrified tail gas from the denitrification device 2. After the denitrification tail gas cools from 175°C to 105°C, it enters the subsequent desulfurization unit for desulfurization and is discharged after meeting the standards. The SO2 content in the discharged tail gas is ≤9.8 mg / m³. 3 Acid mist ≤4.9mg / m³ 3 NOx ≤ 28 mg / m³ 3 Particulate matter ≤9.5mg / m³ 3 The acid production tail gas is heated from 55°C to 120°C and then enters the second heat exchanger 12 to exchange heat with the process gas from the first heat exchanger 11. The acid production tail gas is heated from 120°C to 175°C and then enters the denitrification device 2 to carry out the denitrification reaction. The process gas is cooled to 263°C.

[0085] In the denitrification device 2, the acid production tail gas at 175°C enters the denitrification reactor 21 from top to bottom, and each bed is equipped with an ammonia injection system. After the liquid ammonia is vaporized, it is mixed evenly with air in the mixer 22, with an ammonia volume concentration of <5%. Then, it is accurately metered by the metering valve 28 and the third flow meter 29 before entering each bed.

[0086] The workflow of this embodiment utilizes 521 kW of flue gas heat within the system, saving the 437 kWh of electricity required for heating with an electric furnace.

[0087] Comparative Example 1

[0088] The method is implemented according to Example 1, except that the acid production tail gas does not exchange heat with the denitrified tail gas from the denitrification device 2, nor does it exchange heat with the process gas from the first heat exchanger 11.

[0089] The specific operations include:

[0090] Waste sulfuric acid with a concentration of 90% by volume and a processing capacity of 3.57 tons per hour is decomposed at high temperature using natural gas as fuel to produce process gas containing sulfur dioxide at a temperature of 1050°C. The sulfur dioxide concentration in the process gas entering conversion unit 15 is 8.35% by volume. After passing through the first heat exchanger 11, the process gas temperature drops to 315°C, and then enters the second heat exchanger 12, where it continues to cool to 268°C. It then sequentially enters purification unit 13, drying unit 14, conversion unit 15, and absorption unit 16 for further treatment. Sulfuric acid is produced in the absorption unit 16, and sulfuric acid tail gas containing nitrogen oxides is discharged. This tail gas is heated to 185°C using an electric furnace and then enters the denitrification unit 2 for denitrification. After denitrification, the tail gas temperature drops from 175°C to 105°C before entering the subsequent desulfurization unit. After desulfurization, the tail gas meets emission standards and is discharged with SO2 ≤ 9.8 mg / m³. 3 Acid mist ≤4.9mg / m³ 3 NOx ≤ 28 mg / m³ 3 Particulate matter ≤9.5mg / m³ 3 .

[0091] In the denitrification device 2, the acid production tail gas enters the denitrification reactor 21 from top to bottom, and each bed is equipped with an ammonia injection system. After the liquid ammonia is vaporized, it is mixed evenly with air in the mixer 22, with an ammonia volume concentration of <5%. Then, it passes through the metering valve 28 and the third flow meter 29 for precise metering before entering each bed.

[0092] The comparative example uses an electric heating furnace to heat the acid production tail gas during the denitrification process, which requires 437 kWh of electricity.

[0093] The preferred embodiments of this utility model have been described in detail above; however, this utility model is not limited thereto. Within the scope of the technical concept of this utility model, various simple modifications can be made to the technical solution of this utility model, including combining the various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed by this utility model and are all within the protection scope of this utility model.

Claims

1. A combined acid production and denitrification system, characterized in that, The system includes an acid production unit (1), a denitrification device (2), and a third heat exchanger (3); The acid production unit (1) includes a first heat exchanger (11), a second heat exchanger (12), a conversion device (15), and an absorption device (16) connected in sequence along the process gas delivery pipeline. The process gas containing sulfur dioxide is processed by the acid production unit (1) and then sulfuric acid is produced in the absorption device (16), and acid production tail gas containing nitrogen oxides is discharged. The acid production tail gas from the absorption device (16) first enters the third heat exchanger (3) to exchange heat once with the denitrified tail gas from the denitrification device (2), then enters the second heat exchanger (12) to exchange heat twice with the process gas from the first heat exchanger (11), and then enters the denitrification device (2) for denitrification reaction.

2. The system according to claim 1, characterized in that, A purification device (13) and a drying device (14) are also sequentially installed between the second heat exchanger (12) and the absorption device (16) of the acid production unit (1) along the process gas delivery pipeline.

3. The system according to claim 1 or 2, characterized in that, The denitrification device (2) includes a denitrification reactor (21) and a mixer (22); The vaporized liquid ammonia and air are mixed in the mixer (22), and the resulting mixed gas is then introduced into the denitrification reactor (21) to denitrify the acid production tail gas after secondary heat exchange.

4. The system according to claim 3, characterized in that, After the vaporized liquid ammonia is mixed with air in the mixer (22), the volume concentration of the vaporized liquid ammonia is <5%.

5. The system according to claim 3, characterized in that, The denitrification reactor (21) has N reaction bed layers (23), where N≥2, and one of the reaction bed layers (23) is a spare reaction bed layer.

6. The system according to claim 3, characterized in that, The denitrification device (2) also includes an online concentration analyzer (24) for detecting and analyzing the concentration of ammonia in the mixer (22).

7. The system according to claim 3, characterized in that, The denitrification device (2) also includes a liquid ammonia metering pump (25) and a first flow meter (26); The vaporized liquid ammonia is metered sequentially by the liquid ammonia metering pump (25) and the first flow meter (26) before entering the mixer (22).

8. The system according to claim 3, characterized in that, The denitrification device (2) also includes a second flow meter (27); Air enters the mixer (22) after being metered by the second flow meter (27).

9. The system according to claim 3, characterized in that, A metering valve (28) and a third flow meter (29) are sequentially installed along the flow direction of the mixed gas on the pipeline between the mixer (22) and the denitrification reactor (21) to measure the amount of mixed gas entering the denitrification reactor (21).

10. The system according to claim 5, characterized in that, The denitrification reactor (21) is also equipped with a soot blower for blowing the reaction bed (23).

11. The system according to claim 1 or 2, characterized in that, The system also includes a desulfurization unit (4); After the denitrification tail gas exchanges heat with the acid production tail gas in the third heat exchanger (3), it enters the desulfurization unit (4) for desulfurization.

12. The system according to claim 1 or 2, characterized in that, The second heat exchanger (12) and the third heat exchanger (3) are plate-type gas-to-gas heat exchangers.

13. The system according to claim 1 or 2, characterized in that, Sulfuric acid from the absorption device (16) is cooled by a cooling device and then enters the ammonium sulfate unit to produce ammonium sulfate.

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