Process for the production of sulphuric acid from high concentration sulphur-containing flue gases

Abstract

The application discloses a method for producing acid from high-concentration sulfur-containing flue gas, which is based on the low-oxygen characteristic of the high-concentration sulfur-containing flue gas, controls the oxygen concentration in the high-concentration sulfur-containing flue gas, reduces the equilibrium conversion rate of the SO2 conversion reaction, inhibits the degree of the SO2 conversion reaction, thereby controls the reaction temperature not to be overheated, and in order to improve the total conversion rate, all oxygen-containing gas required by the subsequent conversion reaction is supplemented to the flue gas at the conversion outlet at one time, the SO2 concentration in the flue gas is ensured to be less than 12%, and the flue gas is sent to a subsequent conversion absorption process to produce sulfuric acid. The application is a new method for producing acid from high-concentration sulfur-containing flue gas, which is simple in process, convenient in operation, low in investment, and suitable for smelting flue gas acid production devices and sulfuric acid production devices with suitable flue gas conditions.

Description

Technical Field

[0001] This invention relates to the fields of metallurgy and chemical engineering, and specifically to a method for producing acid from high-concentration sulfur-containing flue gas. Background Technology

[0002] The key step in the production of sulfuric acid using the contact process is that SO2 and O2 react chemically in the vanadium- and cesium-containing catalyst layer of the converter to produce SO3. Q indicates exothermic reaction. This chemical reaction is a reversible reaction under catalytic action. The limiting operating temperature of sulfuric acid catalysts is generally less than 650℃. Due to this limitation, the SO2 concentration in the inlet flue gas of the sulfuric acid plant converter is usually no more than 12%. The SO2 concentration in the sulfur-containing flue gas sent from the smelting system is between 15% and 25%. Sulfuric acid plants usually add air at the inlet of the drying tower before the conversion reaction to supplement O2 while controlling the SO2 concentration entering the converter to no more than 12%, ensuring the conversion rate and preventing the reaction temperature from exceeding the limit. With the development of technology, various high-concentration flue gas sulfuric acid production processes have been developed. However, these processes all rely on controlling the SO2 concentration in the sulfur-containing flue gas to ensure the reaction temperature does not exceed the limit. These methods have different problems, such as high equipment investment and complex operation. In particular, these methods are difficult to adapt to flue gas with higher SO2 concentrations, such as sulfur oxygen-enriched roasting flue gas, where the concentration can theoretically reach over 90%. Summary of the Invention

[0003] This invention aims to at least partially solve one of the technical problems in related technologies. Therefore, one objective of this invention is to provide a method for producing acid from high-concentration sulfur-containing flue gas. This method controls the conversion reaction by adjusting the O2 concentration in the high-concentration sulfur-containing flue gas, thereby achieving a simple, convenient, and cost-effective process for producing acid from high-concentration sulfur-containing flue gas.

[0004] Specifically, the present invention provides a method for producing acid from high-concentration sulfur-containing flue gas, comprising the following steps:

[0005] The concentration of O2 in high-concentration sulfur-containing flue gas feedstock shall be controlled to be less than or equal to 4%, and the concentration ratio of O2 to SO2 shall be controlled to be less than or equal to 0.35.

[0006] The high-concentration sulfur-containing flue gas raw material is heated and then subjected to a conversion process to convert SO2 into SO3.

[0007] Based on the conversion rate requirements, oxygen-containing gas is added to the flue gas at the outlet of the first-stage conversion process for subsequent conversion reactions. This is carried out in the following two ways:

[0008] (1) If the SO2 concentration in the flue gas is less than 12% after the oxygen-containing gas required for the subsequent conversion reaction is added to the flue gas at the outlet of the first-stage conversion, the oxygen-containing gas required for the subsequent conversion reaction is added to the flue gas at the outlet of the first-stage conversion and then sent to the subsequent conversion and absorption process for treatment.

[0009] (2) If the SO2 concentration in the flue gas is greater than or equal to 12% after the oxygen-containing gas required for the subsequent conversion reaction is added to the flue gas at the outlet of the first-stage conversion, the oxygen concentration in the flue gas needs to be controlled further, and oxygen-containing gas is added to the flue gas in steps. Specifically, the steps are as follows: oxygen-containing gas is introduced into the flue gas at the outlet of the first-stage conversion and the O2 to SO2 concentration ratio in the flue gas is controlled to be below 0.4. After cooling, the second-stage conversion is carried out. If the SO2 concentration in the flue gas is still greater than or equal to 12% after the oxygen-containing gas required for the subsequent conversion reaction is added to the flue gas at the outlet of the second-stage conversion, the aforementioned steps are repeated until the SO2 concentration in the flue gas is less than 12% after the oxygen-containing gas required for the subsequent conversion reaction is added to the flue gas at the outlet of the conversion. At this time, the oxygen-containing gas required for the subsequent conversion reaction is added to the flue gas at the outlet of the conversion and sent to the subsequent conversion and absorption process for processing.

[0010] This invention leverages the low oxygen content of high-concentration sulfur-containing flue gas. By controlling the oxygen concentration in this gas, the equilibrium conversion rate of the SO2 conversion reaction is reduced, inhibiting its extent and thus preventing the reaction temperature from exceeding the limit. Simultaneously, to improve the overall conversion rate, all the oxygen-containing gas required for subsequent conversion reactions can be added to the flue gas at the conversion outlet in one go, ensuring the SO2 concentration in the flue gas is less than 12%, before it is sent to the subsequent conversion and absorption process to produce sulfuric acid. This invention provides a novel method for producing sulfuric acid from high-concentration sulfur-containing flue gas. It features a simple process, convenient operation, low investment, and is suitable for sulfuric acid production units using smelting flue gas and sulfur-based sulfuric acid production facilities with suitable flue gas conditions.

[0011] According to some embodiments of the present invention, the SO2 concentration in the high-concentration sulfur-containing flue gas feedstock is 12% or more, preferably 20%-30%.

[0012] According to some embodiments of the present invention, the O2 concentration in the high-concentration sulfur-containing flue gas feedstock is controlled to be 1%-4%, and the O2 to SO2 concentration ratio is controlled to be 0.05-0.35.

[0013] According to some embodiments of the present invention, oxygen-containing gas is introduced into the flue gas at the outlet of the first-stage conversion and the concentration ratio of O2 to SO2 in the flue gas is controlled to be 0.05-0.4. After cooling, the second-stage conversion is carried out.

[0014] According to some embodiments of the present invention, the oxygen-containing gas required for subsequent conversion reactions is replenished in one go according to an O2 to SO2 concentration ratio of 0.5-1.2.

[0015] According to some embodiments of the present invention, the oxygen-containing gas includes one or more of air, oxygen, and oxygen-enriched air; the oxygen-containing gas is a purified and dried oxygen-containing gas.

[0016] According to some embodiments of the present invention, controlling the O2 concentration in high-concentration sulfur-containing flue gas feedstock to be less than or equal to 4% includes: reducing the O2 concentration by reducing air leakage and / or increasing fuel combustion; or increasing the O2 concentration by supplementing oxygen-containing gas.

[0017] According to some embodiments of the present invention, the fuel includes at least one of sulfur and diesel.

[0018] According to some embodiments of the present invention, the high-concentration sulfur-containing flue gas raw material is purified and dried before being heated.

[0019] According to some embodiments of the present invention, the subsequent conversion and absorption process includes a two-conversion-two-absorption acid production process or a three-conversion-three-absorption acid production process.

[0020] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0021] Figure 1 This is a process flow diagram of Embodiment 3 of the present invention. Detailed Implementation

[0022] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0023] In the description of this invention, unless otherwise stated, "a plurality of" means two or more. "Multiple" means two or more. Throughout this document, the terms "comprising" or "including" are open-ended expressions, meaning they include the contents specified in this invention but do not exclude other aspects.

[0024] 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.

[0025] In the description of the embodiments of the present invention, the term "and / or" is merely a description of the relationship between associated objects, indicating that there can be three relationships. For example, A and / or B can represent three situations: A exists, A and B exist simultaneously, and B exists.

[0026] The key step in the production of sulfuric acid using the contact process is that SO2 and O2 react chemically in the vanadium- and cesium-containing catalyst layer of the converter to produce SO3. Q indicates exothermic reaction. This chemical reaction is a reversible reaction under catalytic action. The limiting operating temperature of sulfuric acid catalysts is generally less than 650℃. Due to this limitation, the SO2 concentration in the inlet flue gas of the sulfuric acid plant converter is usually no more than 12%. The SO2 concentration in the sulfur-containing flue gas sent from the smelting system is between 15% and 25%. Sulfuric acid plants usually add air at the inlet of the drying tower before the conversion reaction to supplement O2 while controlling the SO2 concentration entering the converter to no more than 12%, ensuring the conversion rate and preventing the reaction temperature from exceeding the limit. With the development of technology, various high-concentration flue gas sulfuric acid production processes have been developed. However, these sulfuric acid production processes all rely on controlling the SO2 concentration in the sulfur-containing flue gas to ensure that the reaction temperature does not exceed the limit, resulting in high equipment investment and complex operation.

[0027] Studies have found that the equilibrium constant K for the sulfuric acid production conversion reaction is K = [SO3] / ([SO2]*[O2]). 1 / 2 K is determined by temperature; the higher the temperature, the smaller K becomes. The equilibrium conversion rate is related to conditions such as temperature and pressure, and is also limited by the concentrations of SO2 and O2.

[0028] Existing high-concentration sulfur-containing flue gas conversion processes only consider adjusting the SO2 concentration. In many cases, the O2 concentration in high-concentration sulfur-containing flue gas is low. When the O2 concentration is low, even if the SO2 concentration in the flue gas is high, the equilibrium conversion rate will be low. When the O2 concentration in high-concentration sulfur-containing flue gas meets certain conditions, the degree of conversion reaction is limited by chemical equilibrium, and the reaction temperature will not exceed the limit. For sulfuric acid production, this condition can be utilized to adjust the O2 concentration in the flue gas to a suitable range, and then supplement O2 before subsequent conversion reactions, thereby improving the overall conversion rate and meeting the requirements for sulfuric acid production.

[0029] For example, the O2 concentration in the flue gas exiting a copper smelting furnace is about 2%. Even with a 15% air leakage rate in subsequent dust removal, purification, and drying processes, the O2 concentration remains very low. Directly carrying out the conversion reaction will not cause the reaction temperature to exceed the limit, and may even require additional O2. However, for high-concentration sulfur-containing flue gas with a slightly higher O2 concentration, the O2 concentration can be reduced by decreasing air leakage and burning fuel, depending on the production situation, to ensure the equilibrium reaction temperature does not exceed the limit.

[0030] Based on the above findings, this invention proposes a novel method for producing sulfuric acid from high-concentration sulfur-containing flue gas. This method leverages the low oxygen content of high-concentration sulfur-containing flue gas by controlling the oxygen concentration to reduce the equilibrium conversion rate of the SO2 conversion reaction and inhibit its extent, thereby controlling the reaction temperature to prevent overheating. Simultaneously, to improve the overall conversion rate, all the oxygen-containing gas required for subsequent conversion reactions can be added to the flue gas at the conversion outlet in one go, ensuring the SO2 concentration in the flue gas is less than 12%, before being sent to the subsequent conversion and absorption process to produce sulfuric acid. This invention is a novel method for producing sulfuric acid from high-concentration sulfur-containing flue gas, with a simple process, convenient operation, and low investment. It is suitable for sulfuric acid production units using smelting flue gas and sulfur-based sulfuric acid production units with suitable flue gas conditions.

[0031] Specifically, the present invention provides a method for producing acid from high-concentration sulfur-containing flue gas, comprising the following steps:

[0032] The concentration of O2 in high-concentration sulfur-containing flue gas feedstock shall be controlled to be less than or equal to 4%, and the concentration ratio of O2 to SO2 shall be controlled to be less than or equal to 0.35.

[0033] The high-concentration sulfur-containing flue gas raw material is heated and then subjected to a conversion process to convert SO2 into SO3.

[0034] Based on the conversion rate requirements, oxygen-containing gas is added to the flue gas at the outlet of the first-stage conversion process for subsequent conversion reactions. This is carried out in the following two ways:

[0035] (1) If the SO2 concentration in the flue gas is less than 12% after the oxygen-containing gas required for the subsequent conversion reaction is added to the flue gas at the outlet of the first-stage conversion, the oxygen-containing gas required for the subsequent conversion reaction is added to the flue gas at the outlet of the first-stage conversion and then sent to the subsequent conversion and absorption process for treatment.

[0036] (2) If the SO2 concentration in the flue gas is greater than or equal to 12% after the oxygen-containing gas required for the subsequent conversion reaction is added to the flue gas at the outlet of the first-stage conversion, the oxygen concentration in the flue gas needs to be controlled further, and oxygen-containing gas is added to the flue gas in steps. Specifically, the steps are as follows: oxygen-containing gas is introduced into the flue gas at the outlet of the first-stage conversion and the O2 to SO2 concentration ratio in the flue gas is controlled to be below 0.4. After cooling, the second-stage conversion is carried out. If the SO2 concentration in the flue gas is still greater than or equal to 12% after the oxygen-containing gas required for the subsequent conversion reaction is added to the flue gas at the outlet of the second-stage conversion, the aforementioned steps are repeated until the SO2 concentration in the flue gas is less than 12% after the oxygen-containing gas required for the subsequent conversion reaction is added to the flue gas at the outlet of the conversion. At this time, the oxygen-containing gas required for the subsequent conversion reaction is added to the flue gas at the outlet of the conversion and sent to the subsequent conversion and absorption process for processing.

[0037] In this invention, "concentration" refers to volume concentration. SO2 concentration refers to the volume concentration of SO2 in flue gas. O2 concentration refers to the volume concentration of O2 in flue gas. "Concentration ratio" refers to the volume concentration ratio. "O2 to SO2 concentration ratio" refers to the ratio of the volume concentration of O2 to the volume concentration of SO2 in flue gas, hereinafter referred to as the oxygen-sulfur ratio. The concentration in this invention refers to the dry basis concentration without considering the moisture content in the flue gas.

[0038] In this invention, "first-stage conversion outlet flue gas" refers to the flue gas discharged at the outlet of the first-stage converter after first-stage conversion; "second-stage conversion outlet flue gas" refers to the flue gas discharged at the outlet of the second-stage converter after second-stage conversion; and so on.

[0039] In this invention, "one-time replenishment of oxygen-containing gas required for subsequent conversion reactions" means that all the oxygen-containing gas required for subsequent conversion reactions is introduced into the flue gas at the outlet of the first-stage conversion process in one go. In this statement, "oxygen-containing gas required for subsequent conversion reactions" refers to the total amount of oxygen-containing gas required for all conversion processes after the previous stage of conversion to further convert SO2 into SO3. Typically, the total amount of oxygen-containing gas theoretically required for subsequent conversion reactions (denoted as N, a calculation method known to those skilled in the art) can be calculated based on the SO2 concentration in the flue gas at the outlet of the previous stage and the oxygen-sulfur ratio. In actual production, to improve the conversion rate, more oxygen-containing gas is usually introduced than the theoretical amount; that is, in this invention, the amount of "oxygen-containing gas required for subsequent conversion reactions" replenished in one go is greater than or equal to N. However, considering economic costs, the amount of oxygen-containing gas replenished should not be excessive. Typically, the oxygen-containing gas required for subsequent conversion reactions is replenished in one go according to an oxygen-sulfur ratio of 0.5-1.2, where an oxygen-sulfur ratio of 0.5 corresponds to the total amount of oxygen-containing gas theoretically required for subsequent conversion reactions.

[0040] In this invention, "previous stage conversion" and "subsequent stage conversion" or "follow-end conversion" are relative terms. After the "previous stage conversion" is completed, the flue gas from the outlet of the previous stage conversion enters the "subsequent stage conversion" or "follow-end conversion".

[0041] In some embodiments, the SO2 concentration in the high-concentration sulfur-containing flue gas feedstock is 12% or higher, preferably 15%-100%, for example 15%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 100%. The method of the present invention is suitable for acid production processes using high-concentration sulfur-containing flue gas.

[0042] In some specific embodiments, the SO2 concentration in the high-concentration sulfur-containing flue gas can be 12%-50%.

[0043] In some embodiments, the O2 concentration in the high-concentration sulfur-containing flue gas feedstock can be controlled at 1%-4%, and the O2 to SO2 concentration ratio can be controlled at 0.05-0.35. When the SO2 concentration in the sulfur-containing flue gas feedstock is above 12%, a lower O2 concentration and a lower oxygen-sulfur ratio can be controlled to make the reaction system an oxygen-deficient state, thereby ensuring that the flue gas temperature after the reaction does not exceed the catalyst operating temperature.

[0044] In some specific embodiments, the O2 concentration in the high-concentration sulfur-containing flue gas feedstock can be controlled to be 1%, 2%, 3%, or 4%. Furthermore, the O2 to SO2 concentration ratio can be controlled to be 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, or 0.35.

[0045] In some specific embodiments, the high-concentration sulfur-containing flue gas feedstock can come from a metallurgical plant. If the O2 concentration in the feedstock is suitable, it can ensure that the final reaction temperature does not exceed the catalyst operating temperature (approximately 650°C). In this case, the purified and dried feedstock flue gas can be directly sent to the converter. When the O2 concentration in the feedstock is too low, oxygen-containing gas can be added. When the O2 concentration in the feedstock is too high, it will cause the final reaction temperature to exceed the catalyst operating temperature. In this case, the O2 concentration in the feedstock can be reduced in the upstream process by reducing air leakage and increasing fuel combustion, so that the O2 concentration in the flue gas meets the requirements.

[0046] In some specific embodiments, the high-concentration sulfur-containing flue gas feedstock can be heated to above the catalytic ignition temperature (e.g., 380℃-460℃, such as 380℃, 400℃, 420℃, 440℃, or 460℃) before being introduced into a first-stage converter for primary conversion. The temperature of the flue gas exiting the first-stage converter can be 625℃-635℃, such as 625℃, 630℃, or 635℃. After oxygen-containing gas is introduced into the flue gas exiting the first-stage converter and before it enters the subsequent converter, it needs to be cooled to 380℃-460℃ (e.g., 380℃, 400℃, 420℃, 440℃, or 460℃) before entering the subsequent converter for conversion, and so on. In short, the flue gas exiting the first-stage converter needs to be cooled to 380℃-460℃ (e.g., 380℃, 400℃, 420℃, 440℃, or 460℃) before entering the next stage converter. Each converter section includes a catalyst layer where sulfur-containing flue gas undergoes balanced conversion.

[0047] In this invention, "heating" and "cooling" can be performed in a heat exchange device. The heat exchange device can be a heat exchanger, or it can be a boiler, economizer, superheater, or other similar equipment.

[0048] In some embodiments, oxygen-containing gas is introduced into the flue gas exiting the first-stage conversion, and the O2 to SO2 concentration ratio in the flue gas is controlled at 0.05-0.4. After cooling, the second-stage conversion is carried out. After the first-stage conversion, the SO2 concentration in the flue gas will decrease, but there will still be a situation where the SO2 concentration is greater than or equal to 12%. In this case, it is still necessary to control the oxygen concentration in the flue gas. The O2 to SO2 concentration ratio can be appropriately higher than the O2 to SO2 concentration ratio in the high-concentration sulfur-containing flue gas feedstock to improve the conversion rate, provided that the flue gas temperature after the reaction does not exceed the catalyst operating temperature.

[0049] In some specific embodiments, oxygen-containing gas is introduced into the flue gas exiting the first-stage conversion, and the O2 to SO2 concentration ratio is controlled at 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, or 0.4. The gas is then cooled before undergoing second-stage conversion.

[0050] When the SO2 concentration in the flue gas is less than 12%, the O2 concentration no longer affects the flue gas temperature after the reaction. Therefore, if the SO2 concentration in the flue gas is less than 12% after the oxygen-containing gas required for the subsequent conversion reaction is added to the flue gas at the outlet of the previous conversion stage, the oxygen-containing gas required for the subsequent conversion reaction can be added to the flue gas at the outlet of the previous conversion stage and sent to the subsequent conversion and absorption process for treatment. It is not necessary to introduce oxygen-containing gas for each conversion, which simplifies the operation and saves investment.

[0051] In some embodiments, if the SO2 concentration in the flue gas is still greater than or equal to 12% after a one-time replenishment of the oxygen-containing gas required for the subsequent conversion reaction into the flue gas at the outlet of the second-stage conversion, the steps of "introducing oxygen-containing gas into the flue gas at the outlet of the conversion and controlling the O2 to SO2 concentration ratio in the flue gas to be below 0.4, and then carrying out conversion after cooling" are repeated until the SO2 concentration in the flue gas is less than 12% after a one-time replenishment of the oxygen-containing gas required for the subsequent conversion reaction into the flue gas at the outlet of the conversion. Afterwards, the flue gas at the outlet of the conversion can be replenished with the oxygen-containing gas required for the subsequent conversion reaction in one go and sent to the subsequent conversion and absorption process for further treatment.

[0052] In some embodiments, the oxygen-containing gas includes one or more of air, oxygen, and oxygen-enriched air. The oxygen-containing gas is purified and dried. Purifying and drying the oxygen-containing gas helps reduce introduced impurities and moisture, prevents catalyst damage, and contributes to improved product quality.

[0053] In some embodiments, controlling the O2 concentration in high-concentration sulfur-containing flue gas feedstock to be less than or equal to 4% includes: reducing the O2 concentration by reducing air leakage and / or increasing fuel combustion; or increasing the O2 concentration by supplementing with oxygen-containing gas. The above methods for adjusting the O2 concentration are merely examples; other suitable methods may be used in this invention.

[0054] In some embodiments, the fuel includes at least one of sulfur and diesel.

[0055] In some embodiments, oxygen-containing gas can be supplied via a makeup air system. The makeup air system may include main equipment such as gas filters, a drying tower circulation system, and fans. The makeup air location can be set in the flue or equipment between the outlet of the first-stage converter and the inlet of the second-stage converter, simultaneously meeting heat exchange and mixing requirements; the makeup air location can also be set in the flue or equipment between the outlet of the second-stage converter and the inlet of the third-stage converter, simultaneously meeting heat exchange and mixing requirements; and so on.

[0056] In some embodiments, the high-concentration sulfur-containing flue gas feedstock is purified and dried before being heated. Purifying and drying the feedstock helps reduce side reactions and improves product purity.

[0057] In some embodiments, the step of adding oxygen-containing gas required for subsequent conversion reactions to the flue gas at the conversion outlet in one go and sending it to the subsequent conversion and absorption process for processing includes: adding oxygen-containing gas required for subsequent conversion reactions to the flue gas at the conversion outlet in one go, cooling it down, and then sending it to the subsequent conversion and absorption process for processing.

[0058] In some embodiments, the subsequent conversion and absorption process includes a two-conversion-two-absorption sulfuric acid production process or a three-conversion-three-absorption sulfuric acid production process. The two-conversion-two-absorption process is a classic sulfuric acid production process, including a first conversion, a first absorption, a second conversion, and a second absorption. When the SO3 concentration in the flue gas is too high, a three-conversion-three-absorption process can also be used. The three-conversion-three-absorption sulfuric acid production process includes a first conversion, a first absorption, a second conversion, a second absorption, a third conversion, and a third absorption. Using a two-conversion-two-absorption or three-conversion-three-absorption sulfuric acid production process is beneficial for improving the SO2 conversion rate and sulfuric acid production efficiency, while reducing pollutant emissions.

[0059] The present invention will be explained below with reference to embodiments. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0060] Example 1

[0061] (1) Adjust the SO2 concentration in the high-concentration sulfur-containing flue gas feedstock to 25% (dry basis) and O2 concentration to 4% (dry basis) by supplementing air (oxygen-sulfur ratio is 0.16).

[0062] (2) After purification and drying, the high-concentration sulfur-containing flue gas feedstock is heated to about 420°C through heat exchange and then sent to a first-stage converter for first-stage conversion. The equilibrium conversion rate of the conversion reaction is about 30%. After the reaction, the temperature of the flue gas at the outlet of the first-stage converter is about 627°C. The SO2 concentration in the flue gas at the outlet of the first-stage converter is 18.18%, the O2 concentration is 0.26%, and the SO3 concentration is 7.79%.

[0063] (3) The oxygen-sulfur ratio used in the conversion reaction is generally 0.5-1.2. If the purified and dried air is replenished once at an oxygen-sulfur ratio of 0.9, the SO2 concentration in the flue gas after gas mixing will be 10.29%, the O2 concentration will be 9.26%, and the SO3 concentration will be 4.41%. By cooling through heat exchange, the flue gas temperature is controlled at about 420℃ and then sent to subsequent conversion and absorption equipment for acid production in a two-conversion and two-absorption process.

[0064] Example 2

[0065] (1) Adjust the SO2 concentration in the high-concentration sulfur-containing flue gas feedstock to 35% (dry basis) and O2 concentration to 3.85% (dry basis) (oxygen-sulfur ratio of 0.11) by supplementing air.

[0066] (2) After purification and drying, the high-concentration sulfur-containing flue gas feedstock is heated to about 420°C through heat exchange and then sent to a first-stage converter for first-stage conversion. The equilibrium conversion rate of the conversion reaction is about 21%. After the reaction, the temperature of the flue gas at the outlet of the first-stage converter is about 627°C. The SO2 concentration in the flue gas at the outlet of the first-stage converter is 28.57%, the O2 concentration is 0.10%, and the SO3 concentration is 7.79%.

[0067] (3) The oxygen-sulfur ratio used in the conversion reaction is generally 0.5-1.2. If purified and dried air (oxygen concentration 21%) is added once at an oxygen-sulfur ratio of 0.9, the SO2 concentration in the flue gas after gas mixing will be 12.87%, the O2 concentration will be 11.58%, and the SO3 concentration will be 3.5%. During the second-stage conversion, the outlet temperature of the second-stage conversion will be approximately 660℃, exceeding the limit. Therefore, a step-by-step air supply is adopted. The flue gas at the outlet of the first-stage conversion is supplemented with purified and dried air at an oxygen-sulfur ratio of 0.18. The SO2 concentration in the flue gas after gas mixing will be 23.04%, the O2 concentration will be 4.15%, and the SO3 concentration will be 6.28%. By cooling through heat exchange, the flue gas temperature is controlled to approximately 420℃ for the second-stage conversion. The equilibrium conversion rate of the conversion reaction is approximately 28%. After the reaction, the outlet temperature of the second-stage conversion flue gas is approximately 627℃, and the SO2 concentration in the second-stage conversion flue gas is 17.17%, the O2 concentration is 0.97%, and the SO3 concentration is 13.13%.

[0068] (4) The flue gas from the second-stage conversion outlet is supplemented with purified and dried air at an oxygen-to-sulfur ratio of 1. The SO2 concentration, O2 concentration, and SO3 concentration in the flue gas after gas mixing are 9.69%, 9.69%, and 7.41%, respectively. The flue gas temperature is controlled at approximately 420°C by heat exchange cooling and then sent to subsequent conversion and absorption equipment for a two-stage conversion and two-stage absorption acid production process.

[0069] Example 3

[0070] according to Figure 1 The flowchart shown illustrates the acid production process, with the specific steps as follows:

[0071] (1) Adjust the SO2 concentration in the high-concentration sulfur-containing flue gas feedstock to 35% (dry basis) and O2 concentration to 3.85% (dry basis) (oxygen-sulfur ratio of 0.11) by supplementing air.

[0072] (2) After purification and drying, the high-concentration sulfur-containing flue gas feedstock is heated to about 420°C through heat exchange and then sent to a first-stage converter for first-stage conversion. The equilibrium conversion rate of the conversion reaction is about 21%. After the reaction, the temperature of the flue gas at the outlet of the first-stage converter is about 627°C. The SO2 concentration in the flue gas at the outlet of the first-stage converter is 28.57%, the O2 concentration is 0.10%, and the SO3 concentration is 7.79%.

[0073] (3) The oxygen-sulfur ratio used in the conversion reaction is generally 0.5-1.2. If purified and dried oxygen-enriched air (O2 concentration 90%) is added once at an oxygen-sulfur ratio of 0.9, the SO2 concentration in the flue gas after gas mixing will be 22.24%, the O2 concentration will be 20.00%, and the SO3 concentration will be 6.06%. At this time, the outlet temperature of the second-stage conversion will be about 750℃, which will exceed the temperature limit. Therefore, oxygen-enriched air is added in stages. If purified and dried oxygen-enriched air (O2 concentration 90%) is added to the flue gas at the outlet of the first-stage conversion at an oxygen-sulfur ratio of 0.2, the SO2 concentration in the flue gas after gas mixing will be 26.89%, the O2 concentration will be 5.38%, and the SO3 concentration will be 7.33%. By cooling through heat exchange, the flue gas temperature is controlled at approximately 420℃ before entering the second-stage conversion. The equilibrium conversion rate of the conversion reaction is approximately 28%. After the reaction, the temperature of the flue gas at the outlet of the second-stage conversion is approximately 627℃. The SO2 concentration in the flue gas at the outlet of the second-stage conversion is 20.15%, the O2 concentration is 1.69%, and the SO3 concentration is 15.41%.

[0074] (4) The oxygen-sulfur ratio used in the conversion reaction is generally 0.5-1.2. If purified and dried oxygen-enriched air (O2 concentration 90%) is added once at an oxygen-sulfur ratio of 0.9, the SO2 concentration in the flue gas after gas mixing will be 17.04%, the O2 concentration will be 15.33%, and the SO3 concentration will be 13.03%. At this time, the outlet temperature of the third-stage conversion will be about 720℃, which will exceed the temperature limit. Therefore, the oxygen-enriched air is added in stages. The outlet flue gas of the second-stage conversion is supplemented with purified and dried oxygen-enriched air (O2 concentration 90%) at an oxygen-sulfur ratio of 0.68. The SO2 concentration in the flue gas after gas mixing will be 17.78%, the O2 concentration will be 12.09%, and the SO3 concentration will be 13.60%. By cooling through heat exchange, the flue gas temperature is controlled at approximately 420℃ before entering the three-stage conversion process. The equilibrium conversion rate of the conversion reaction is approximately 42%. After the reaction, the temperature of the flue gas at the outlet of the three-stage conversion is approximately 627℃. The SO2 concentration in the flue gas at the outlet of the three-stage conversion is 10.68%, the O2 concentration is 8.66%, and the SO3 concentration is 21.92%.

[0075] (5) According to the conversion rate requirements, the flue gas from the three-stage conversion outlet is supplemented with purified and dried air at an oxygen-to-sulfur ratio of 1. The flue gas after gas mixing has an SO2 concentration of 10.44%, an O2 concentration of 10.44%, and an SO3 concentration of 21.44%. The mixed flue gas is cooled down to about 200°C by heat exchange and then sent to the absorption tower of the subsequent conversion and absorption equipment for acid production. After absorbing SO3 in the flue gas, it is heated up by heat exchange again to carry out two-stage conversion and two-stage absorption for acid production.

[0076] Comparative Example 1

[0077] The acid was prepared according to the method described in Example 1, except that in step 1, the SO2 concentration in the high-concentration sulfur-containing flue gas feedstock was adjusted to 25% (dry basis) and the O2 concentration to 5% (dry basis) (oxygen-sulfur ratio of 0.2) by supplementing air. After the first-stage conversion reaction, the temperature of the flue gas at the outlet of the first-stage conversion was approximately 660°C, which was above the acceptable temperature.

[0078] Comparative Example 2

[0079] The acid was prepared according to the method described in Example 1, except that in step 1, the SO2 concentration in the high-concentration sulfur-containing flue gas feedstock was adjusted to 25% (dry basis) and the O2 concentration to 10% (dry basis) (oxygen-sulfur ratio of 0.4) by supplementing air. After the first-stage conversion reaction, the temperature of the flue gas at the outlet of the first-stage conversion was approximately 750°C, which was considered an overtemperature.

[0080] Comparative Example 3

[0081] The acid production method described in Example 2 differs in that, in step 3, the flue gas from the first-stage conversion outlet is supplemented with purified and dried air at an oxygen-to-sulfur ratio of 0.5. The flue gas after gas mixing has an SO2 concentration of 17.10%, an O2 concentration of 8.55%, and an SO3 concentration of 4.66%. After the second-stage conversion reaction, the temperature of the flue gas from the second-stage conversion outlet is approximately 710°C, which is above the acceptable temperature.

[0082] By comparing the above embodiments and comparative examples, it can be seen that this invention, based on the low oxygen content in high-concentration sulfur-containing flue gas, reduces the equilibrium conversion rate of the SO2 conversion reaction and inhibits the degree of SO2 conversion reaction by controlling the oxygen concentration in the high-concentration sulfur-containing flue gas, thereby controlling the reaction temperature. After some SO2 reaction reduces the SO2 concentration to approximately 12%, oxygen-containing gas is added to the flue gas to increase the oxygen-sulfur ratio before sending it to the subsequent conversion stage to ensure the overall conversion rate. This invention is a novel method for producing sulfuric acid from high-concentration sulfur-containing flue gas. It has a simple process, is easy to operate, requires less investment, and is suitable for sulfuric acid production units from smelting flue gas and sulfur-based sulfuric acid production units with suitable flue gas conditions.

[0083] The terms "first" and "second" used in this document are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature marked "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0084] 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 the present invention. 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.

[0085] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A process for the production of acid from a high-sulphur content sulphur-containing flue gas, characterised in that, Includes the following steps: The volume concentration of O2 in high-concentration sulfur-containing flue gas feedstock shall be controlled to be less than or equal to 4%, and the volume concentration ratio of O2 to SO2 shall be controlled to be less than or equal to 0.

35. The high-concentration sulfur-containing flue gas raw material is heated and then subjected to a conversion process to convert SO2 into SO3. Based on the conversion rate requirements, oxygen-containing gas is added to the flue gas at the outlet of the first-stage conversion process for subsequent conversion reactions. This is carried out in the following two ways: (1) If the SO2 volume concentration in the flue gas is less than 12% after the oxygen-containing gas required for the subsequent conversion reaction is added to the flue gas at the outlet of the first-stage conversion, the oxygen-containing gas required for the subsequent conversion reaction is added to the flue gas at the outlet of the first-stage conversion and then sent to the subsequent conversion and absorption process for treatment. (2) If the SO2 volume concentration in the flue gas is greater than or equal to 12% after the oxygen-containing gas required for the subsequent conversion reaction is added to the flue gas at the outlet of the first-stage conversion, the oxygen volume concentration in the flue gas needs to be controlled and oxygen-containing gas is added to the flue gas in steps. Specifically, the steps are as follows: oxygen-containing gas is introduced into the flue gas at the outlet of the first-stage conversion and the volume concentration ratio of O2 to SO2 in the flue gas is controlled to be below 0.

4. After cooling, the second-stage conversion is carried out. If the SO2 volume concentration in the flue gas is still greater than or equal to 12% after the oxygen-containing gas required for the subsequent conversion reaction is added to the flue gas at the outlet of the second-stage conversion, the aforementioned steps are repeated until the SO2 volume concentration in the flue gas is less than 12% after the oxygen-containing gas required for the subsequent conversion reaction is added to the flue gas at the outlet of the conversion. At this time, the oxygen-containing gas required for the subsequent conversion reaction is added to the flue gas at the outlet of the conversion and sent to the subsequent conversion and absorption process for processing.

2. The method of claim 1, wherein, The SO2 volume concentration in the high-concentration sulfur-containing flue gas feedstock is above 12%.

3. The method of claim 1, wherein, The SO2 volume concentration in the high-concentration sulfur-containing flue gas feedstock is 20%-50%.

4. The method of claim 1, wherein, The volume concentration of O2 in the high-concentration sulfur-containing flue gas feedstock is controlled at 1%-4%, and the volume concentration ratio of O2 to SO2 is controlled at 0.05-0.

35.

5. The method of claim 1, wherein, Oxygen-containing gas is introduced into the flue gas at the outlet of the first-stage conversion, and the volume concentration ratio of O2 to SO2 in the flue gas is controlled at 0.05-0.

4. After cooling, the second-stage conversion is carried out.

6. The method of claim 1, wherein, The oxygen-containing gas required for the subsequent conversion reaction is replenished in one go, with the O2 to SO2 volume concentration ratio being 0.5-1.

2.

7. The method of claim 1, wherein, The oxygen-containing gas includes one or more of air, oxygen, and oxygen-enriched air; the oxygen-containing gas is purified and dried.

8. The method of claim 1, wherein, Controlling the O2 volume concentration in high-concentration sulfur-containing flue gas feedstock to be less than or equal to 4% includes: reducing the O2 volume concentration by reducing air leakage and / or increasing fuel combustion; or increasing the O2 volume concentration by supplementing oxygen-containing gas.

9. The method of claim 8, wherein, The fuel includes at least one of sulfur and diesel.

10. The method of claim 1, wherein, Before heating the high-concentration sulfur-containing flue gas raw material, the high-concentration sulfur-containing flue gas raw material is purified and dried.

11. The method of claim 1, wherein, The subsequent conversion and absorption process includes a two-conversion, two-absorption acid production process or a three-conversion, three-absorption acid production process.

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