Method for preparing acid from high-concentration sulfur-containing flue gas

Abstract

The invention discloses a method for preparing acid from high-concentration sulfur-containing flue gas, which is characterized in that the equilibrium conversion rate of SO2 conversion reaction is reduced and the degree of SO2 conversion reaction is inhibited by controlling the oxygen concentration in the high-concentration sulfur-containing flue gas on the basis of the characteristic of low oxygen in the high-concentration sulfur-containing flue gas, so that the reaction temperature is controlled not to be over-temperature, and meanwhile, in order to improve the total conversion rate, the reaction temperature is controlled to be over-temperature. All oxygen-containing gas required by the subsequent conversion reaction can be supplemented into the conversion outlet flue gas at one time, the concentration of SO2 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 novel method for preparing the acid from the high-concentration sulfur-containing flue gas is simple in process, convenient to operate, low in investment and suitable for a device for preparing the acid from the smelting flue gas and a device for preparing the acid from the sulfur under proper flue gas conditions.

Description

Technical Field

[0001] The invention relates to the technical fields of metallurgy and chemical engineering, and in particular to a method for producing acid from high-concentration sulfur-containing flue gas. Background Art

[0002] The key step in producing sulfuric acid using the contact method is that SO2 and O2 react chemically in the vanadium and cesium-containing catalyst layer of the converter to produce SO3. Q represents heat release. This chemical reaction is reversible and catalytically driven. The maximum operating temperature of sulfuric acid catalysts is generally less than 650°C. Due to this limitation, the SO2 concentration in the flue gas entering the sulfuric acid plant converter is typically no more than 12%. The SO2 concentration in sulfur-containing flue gas from the smelting system ranges from 15% to 25%. Sulfuric acid plants typically add air to the drying tower inlet before the conversion reaction to replenish the O2 while controlling the SO2 concentration entering the converter to no more than 12%, ensuring conversion efficiency and overheating. With technological advancements, various high-concentration flue gas acidification processes have been developed. However, these processes all rely on controlling the SO2 concentration in the sulfur-containing flue gas to control the reaction temperature. These methods each present different challenges, such as high equipment investment and complex operations. These methods are particularly difficult to adapt to flue gases with even higher SO2 concentrations, such as those from sulfur oxygen-enriched roasting, where concentrations can theoretically exceed 90%. Summary of the Invention

[0003] The present invention aims to at least partially address one of the technical problems in the related art. To this end, one object of the present invention is to provide a method for producing sulfuric 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 process, convenient operation, and low-cost method for producing sulfuric acid from high-concentration sulfur-containing flue gas.

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

[0005] Control the O2 concentration in the high-concentration sulfur-containing flue gas raw material to be less than or equal to 4%, and control the O2 to SO2 concentration ratio to be less than or equal to 0.35;

[0006] After heating the high-concentration sulfur-containing flue gas raw material, a conversion step is performed to convert SO2 into SO3;

[0007] According to the conversion rate requirements, oxygen-containing gas is added to the flue gas at the first stage conversion outlet for subsequent conversion reactions, which can be carried out in the following two situations:

[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 sent to the subsequent conversion 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 first conversion outlet at one time, it is necessary to continue to control the oxygen concentration in the flue gas and add the oxygen-containing gas to the flue gas in steps, which specifically includes the following steps: introducing oxygen-containing gas into the flue gas at the first conversion outlet and controlling the concentration ratio of O2 to SO2 in the flue gas to be below 0.4, and performing the second conversion after cooling; 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 second conversion outlet at one time, repeat the above steps 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 conversion outlet at one time; at this time, the oxygen-containing gas required for the subsequent conversion reaction is added to the flue gas at the conversion outlet at one time and sent to the subsequent conversion absorption process for treatment.

[0010] This invention leverages the low oxygen content of high-concentration sulfur-containing flue gas. By controlling the oxygen concentration in this flue gas, the equilibrium conversion rate of the SO2 conversion reaction is reduced, suppressing the extent of the SO2 conversion reaction and thus controlling the reaction temperature from overheating. Furthermore, to improve the overall conversion rate, the flue gas at the conversion outlet is replenished with all the oxygen-containing gas required for subsequent conversion reactions, ensuring the SO2 concentration in the flue gas is less than 12%, before being fed to the subsequent conversion and absorption process to produce sulfuric acid. This novel method for producing sulfuric acid from high-concentration sulfur-containing flue gas features a simple process, easy operation, and low investment. It is suitable for use in smelting flue gas acid production plants and sulfuric acid production plants 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 raw material is above 12%, preferably 20%-30%.

[0012] According to some embodiments of the present invention, the O2 concentration in the high-concentration sulfur-containing flue gas raw material is controlled to be 1%-4%, and the concentration ratio of O2 to SO2 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, and the second-stage conversion is performed after cooling.

[0014] According to some embodiments of the present invention, the oxygen-containing gas required for the subsequent conversion reaction is replenished at one time according to a concentration ratio of O 2 to SO 2 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; and the oxygen-containing gas is purified and dried oxygen-containing gas.

[0016] According to some embodiments of the present invention, controlling the O2 concentration in the high-concentration sulfur-containing flue gas raw material 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, before the high-concentration sulfur-containing flue gas raw material is heated, the high-concentration sulfur-containing flue gas raw material is purified and dried.

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

[0020] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 1 is a process flow chart of Example 3 of the present invention. DETAILED DESCRIPTION

[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 understood as limiting the present invention.

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

[0024] The endpoints of the ranges and any values ​​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 endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0025] In the description of the embodiments of the present invention, the term "and / or" is merely a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B may represent three situations: A exists, A and B exist at the same time, and B exists.

[0026] The key step in producing sulfuric acid using the contact method is that SO2 and O2 react chemically in the vanadium and cesium-containing catalyst layer of the converter to produce SO3. Q represents heat release. This chemical reaction is reversible and catalytically driven. The maximum operating temperature of sulfuric acid catalysts is generally less than 650°C. Due to this limitation, the SO2 concentration in the flue gas entering the sulfuric acid plant converter is typically no more than 12%. The SO2 concentration in sulfur-laden flue gas from the smelting system ranges from 15% to 25%. Sulfuric acid plants typically add air to the drying tower inlet before the conversion reaction to replenish the O2 while controlling the SO2 concentration entering the converter to no more than 12%, ensuring conversion efficiency and overheating. With technological advancements, various high-concentration flue gas acidification processes have been developed. However, these processes all rely on controlling the SO2 concentration in the sulfur-laden flue gas to control the reaction temperature, resulting in high equipment investment and complex operation.

[0027] The study found that the equilibrium constant of sulfuric acid production conversion reaction K = [SO3] / ([SO2]*[O2] 1 / 2 ), K is determined by temperature; the higher the temperature, the smaller K. The equilibrium conversion rate is not only related to conditions such as temperature and pressure, but is also limited by the concentrations of SO2 and O2.

[0028] Existing conversion processes for high-concentration sulfur-laden flue gas only consider adjusting the SO2 concentration. In many cases, the O2 concentration in high-concentration sulfur-laden 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-laden flue gas meets certain conditions, the conversion reaction is limited by chemical equilibrium, and the reaction temperature does not exceed the specified range. For sulfuric acid production, this condition is exploited to adjust the O2 concentration in the flue gas to an appropriate range, and then supplement O2 before the subsequent conversion reaction, thereby improving the overall conversion rate and meeting the requirements for sulfuric acid production.

[0029] For example, the O2 concentration in the flue gas from a copper smelting furnace is approximately 2%. With a 15% air leakage rate for subsequent dust removal, purification, and drying processes, the O2 concentration remains very low, allowing the conversion reaction to proceed directly without exceeding the reaction temperature, and even requiring a certain amount of O2 supplementation. For sulfur-containing flue gas with slightly elevated O2 concentrations, the O2 concentration can be lowered, depending on production conditions, by reducing air leakage and burning fuel, to keep the equilibrium reaction temperature within the specified range.

[0030] Based on the above findings, the present invention proposes a novel method for producing sulfuric acid from high-concentration sulfur-containing flue gas. This method, taking advantage of the low oxygen content of high-concentration sulfur-containing flue gas, controls the oxygen concentration in the high-concentration sulfur-containing flue gas to reduce the equilibrium conversion rate of the SO2 conversion reaction, inhibiting the extent of the SO2 conversion reaction and thereby controlling the reaction temperature from overheating. Furthermore, to improve the overall conversion rate, the flue gas at the conversion outlet is replenished with all the oxygen-containing gas required for subsequent conversion reactions, ensuring that 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. The present invention is a novel method for producing sulfuric acid from high-concentration sulfur-containing flue gas, featuring a simple process, easy operation, and low investment. It is suitable for smelting flue gas acid production plants and sulfuric acid production plants with suitable flue gas conditions.

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

[0032] Control the O2 concentration in the high-concentration sulfur-containing flue gas raw material to be less than or equal to 4%, and control the O2 to SO2 concentration ratio to be less than or equal to 0.35;

[0033] After heating the high-concentration sulfur-containing flue gas raw material, a conversion step is performed to convert SO2 into SO3;

[0034] According to the conversion rate requirements, oxygen-containing gas is added to the flue gas at the first stage conversion outlet for subsequent conversion reactions, which can be carried out in the following two situations:

[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 sent to the subsequent conversion 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 first conversion outlet at one time, it is necessary to continue to control the oxygen concentration in the flue gas and add the oxygen-containing gas to the flue gas in steps, which specifically includes the following steps: introducing oxygen-containing gas into the flue gas at the first conversion outlet and controlling the concentration ratio of O2 to SO2 in the flue gas to be below 0.4, and performing the second conversion after cooling; 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 second conversion outlet at one time, repeat the above steps 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 conversion outlet at one time; at this time, the oxygen-containing gas required for the subsequent conversion reaction is added to the flue gas at the conversion outlet at one time and sent to the subsequent conversion absorption process for treatment.

[0037] In the present invention, "concentration" refers to volume concentration. SO2 concentration refers to the volume concentration of SO2 in the flue gas. O2 concentration refers to the volume concentration of O2 in the 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 the flue gas, hereinafter referred to as the oxygen-sulfur ratio. Concentrations in the present invention refer to dry basis concentrations, ignoring the moisture content of the flue gas.

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

[0039] In the present invention, "one-time supplementation of the oxygen-containing gas required for the subsequent conversion reaction" means that all the oxygen-containing gas required for the subsequent conversion reaction is introduced into the flue gas at the outlet of the first stage of conversion at one time. In this statement, "the oxygen-containing gas required for the subsequent conversion reaction" refers to the total amount of oxygen-containing gas required for all conversion steps for continuing to convert SO2 into SO3 after the previous stage of conversion. Usually, the total amount of oxygen-containing gas required for the subsequent conversion reaction in theory can be calculated based on the SO2 concentration in the flue gas at the outlet of the previous stage and combined with the oxygen-sulfur ratio (denoted as N, the calculation method is well known to those skilled in the art). In actual production, in order to improve the conversion rate, more oxygen-containing gas is usually introduced than the theoretical amount; that is, in the present invention, the amount of "oxygen-containing gas required for the subsequent conversion reaction" supplemented at one time is greater than or equal to N. However, considering the economic cost, the amount of oxygen-containing gas supplemented should not be too much. Usually, the oxygen-containing gas required for the subsequent conversion reaction is supplemented at one time according to an oxygen-sulfur ratio of 0.5-1.2. The oxygen-sulfur ratio of 0.5 corresponds to the total amount of oxygen-containing gas required for the subsequent conversion reaction in theory.

[0040] In the present invention, "the first stage conversion" and "the second stage conversion" or "subsequent conversion" are relative. After the "first stage conversion" is completed, the flue gas at the first stage conversion outlet enters the "second stage conversion" or "subsequent conversion".

[0041] In some embodiments, the SO2 concentration in the high-concentration sulfur-containing flue gas feedstock is greater than 12%, 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 a high-concentration sulfur-containing flue gas acid production process.

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

[0043] In some embodiments, the O2 concentration in the high-concentration sulfur-containing flue gas feedstock can be controlled to be between 1% and 4%, and the O2 to SO2 concentration ratio can be controlled to be between 0.05 and 0.35. When the SO2 concentration in the sulfur-containing flue gas feedstock is above 12%, the O2 concentration and oxygen-sulfur ratio can be controlled to be lower, thereby maintaining an oxygen-deficient state in the reaction system and 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%, and 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 raw material of high-concentration sulfur-containing flue gas can be sourced from a metallurgical plant. If the O2 concentration in the raw material is appropriate, it can ensure that the final reaction temperature does not exceed the catalyst operating temperature (approximately 650°C). In this case, the raw flue gas can be directly sent to the converter after purification and drying. When the O2 concentration in the raw material is too low, oxygen-containing gas can be added. When the O2 concentration in the raw material is too high, the final reaction temperature will exceed the catalyst operating temperature. In this case, the O2 concentration in the raw material can be reduced in the upstream process by reducing air leakage, increasing fuel combustion, etc., so that the O2 concentration in the flue gas meets the requirements.

[0046] In some specific embodiments, the high-concentration sulfur-containing flue gas raw material can be heated to above the catalyst ignition temperature (e.g., 380°C-460°C, such as 380°C, 400°C, 420°C, 440°C or 460°C) and then passed into a first-stage converter for a first-stage conversion. The temperature of the flue gas at the outlet of the first-stage converter can be 625°C-635°C, such as 625°C, 630°C or 635°C. After the oxygen-containing gas is passed into the flue gas at the outlet of the first-stage converter and before entering the subsequent converter, it needs to be cooled to 380°C-460°C (e.g., 380°C, 400°C, 420°C, 440°C or 460°C), and then enter the subsequent converter for conversion, and so on. In short, the flue gas at the outlet of the conversion needs to be cooled to 380°C-460°C (e.g., 380°C, 400°C, 420°C, 440°C or 460°C) before entering the next-stage converter. Each converter includes a catalyst layer, and the sulfur-containing flue gas undergoes equilibrium conversion in the catalyst layer.

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

[0048] In some embodiments, oxygen-containing gas is introduced into the flue gas at the outlet of the first-stage conversion reaction, and the O2:SO2 concentration ratio in the flue gas is controlled to be between 0.05 and 0.4. After cooling, the second-stage conversion is performed. After the first-stage conversion, the SO2 concentration in the flue gas will decrease, but if the SO2 concentration still exceeds 12%, it is still necessary to control the oxygen concentration in the flue gas. The O2:SO2 concentration ratio can be appropriately greater than the O2:SO2 concentration ratio in the high-sulfur 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 at the outlet of the first-stage reforming reaction, and the concentration ratio of O2 to SO2 is controlled to be 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35 or 0.4. After cooling, the second-stage reforming reaction is carried out.

[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 previous conversion outlet at one time, the oxygen-containing gas required for the subsequent conversion reaction can be added to the flue gas at the previous conversion outlet at one time and sent to the subsequent conversion absorption process for treatment. There is no need 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 at the secondary conversion outlet is still greater than or equal to 12% after a single addition of oxygen-containing gas required for subsequent conversion reactions, the steps of "introducing oxygen-containing gas into the flue gas at the conversion outlet, controlling the O2 to SO2 concentration ratio in the flue gas to below 0.4, and then cooling the flue gas for conversion" are repeated until the SO2 concentration in the flue gas is reduced to less than 12% after a single addition of oxygen-containing gas required for subsequent conversion reactions. Thereafter, the flue gas at the conversion outlet may be supplemented with oxygen-containing gas required for subsequent conversion reactions and sent to the subsequent conversion and absorption process for treatment.

[0052] In some embodiments, the oxygen-containing gas comprises 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 impurities and moisture, prevents catalyst damage, and improves product quality.

[0053] In some embodiments, controlling the O2 concentration in the 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. The above methods for adjusting the O2 concentration are merely examples, and other suitable methods may be used in the present invention.

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

[0055] In some embodiments, oxygen-containing gas can be supplemented through a make-up air system. This system can include key equipment such as a gas filter, a drying tower circulation system, and a fan. The make-up air location can be located in the flue or on equipment between the outlet of the first-stage converter and the inlet of the second-stage converter, meeting both heat exchange and mixing requirements. The make-up air location can also be located in the flue or on equipment between the outlet of the second-stage converter and the inlet of the third-stage converter, meeting both heat exchange and mixing requirements. And so on.

[0056] In some embodiments, the high-concentration sulfur-containing flue gas raw material is purified and dried before being heated. Purifying and drying the raw material is beneficial to reducing the occurrence of side reactions and improving product purity.

[0057] In some embodiments, the one-time supplementation of oxygen-containing gas required for subsequent conversion reactions into the conversion outlet flue gas and sending it to the subsequent conversion absorption process for treatment includes: one-time supplementation of oxygen-containing gas required for subsequent conversion reactions into the conversion outlet flue gas, cooling it and sending it to the subsequent conversion absorption process for treatment.

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

[0059] Below, the scheme of the present invention will be explained in conjunction with embodiment.It will be understood by those skilled in the art that the following examples are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention.In the embodiment, if specific technology or conditions are not indicated, the technology or conditions described in the literature in this area or the product instructions are used.The reagents or instruments used are not indicated by the manufacturer, and are all conventional products that can be obtained by commercial purchase.

[0060] Example 1

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

[0062] (2) After the high-concentration sulfur-containing flue gas raw material is purified and dried, it is heated to about 420°C through heat exchange and then sent to a first-stage converter for a 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 first-stage converter outlet is about 627°C, and the SO2 concentration in the flue gas at the first-stage converter outlet 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 supplemented at an oxygen-sulfur ratio of 0.9, the SO2 concentration in the flue gas after the air distribution will be 10.29%, the O2 concentration will be 9.26%, and the SO3 concentration will be 4.41%. Through heat exchange and cooling, the flue gas temperature is controlled at about 420℃, and then it is sent to the subsequent conversion and absorption acid-making equipment for the two-conversion and two-absorption acid-making process.

[0064] Example 2

[0065] (1) The SO2 concentration in the high-concentration sulfur-containing flue gas raw material was adjusted to 35% (dry basis) and the O2 concentration was 3.85% (dry basis) (oxygen-sulfur ratio was 0.11) by adding air.

[0066] (2) After the high-concentration sulfur-containing flue gas raw material is purified and dried, it is heated to about 420°C through heat exchange and then sent to a first-stage converter for a 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 first-stage converter outlet is about 627°C, and the SO2 concentration in the flue gas at the first-stage converter outlet 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 at this time at an oxygen-sulfur ratio of 0.9, the SO2 concentration in the flue gas after the air distribution is 12.87%, the O2 concentration is 11.58%, and the SO3 concentration is 3.5%. The second-stage conversion is carried out. At this time, the temperature at the second-stage conversion outlet is about 660°C, which is overtemperature. Therefore, step-by-step air addition 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 the air distribution is 23.04%, the O2 concentration is 4.15%, and the SO3 concentration is 6.28%. Through heat exchange cooling, the flue gas temperature is controlled at about 420°C before the second-stage conversion. The equilibrium conversion rate of the conversion reaction is about 28%. After the reaction, the temperature of the flue gas at the outlet of the second-stage conversion is about 627°C, and the SO2 concentration in the flue gas at the outlet of the second-stage conversion is 17.17%, the O2 concentration is 0.97%, and the SO3 concentration is 13.13%.

[0068] (4) The flue gas at the secondary conversion outlet is supplemented with purified and dried air at an oxygen-sulfur ratio of 1. The flue gas after air distribution has a SO2 concentration of 9.69%, an O2 concentration of 9.69%, and a SO3 concentration of 7.41%. Through heat exchange and cooling, the flue gas temperature is controlled at approximately 420°C and sent to subsequent conversion and absorption acid-making equipment for a two-conversion, two-absorption acid-making process.

[0069] Example 3

[0070] according to Figure 1 The specific steps for acid production are as follows:

[0071] (1) The SO2 concentration in the high-concentration sulfur-containing flue gas raw material was adjusted to 35% (dry basis) and the O2 concentration was 3.85% (dry basis) (oxygen-sulfur ratio was 0.11) by adding air.

[0072] (2) After the high-concentration sulfur-containing flue gas raw material is purified and dried, it is heated to about 420°C through heat exchange and then sent to a first-stage converter for a 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 first-stage converter outlet is about 627°C, and the SO2 concentration in the flue gas at the first-stage converter outlet 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 the purified, dried, oxygen-enriched air (O2 concentration of 90%) is supplemented at a ratio of 0.9, the SO2 concentration in the flue gas after gas distribution 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°C, which will exceed the temperature. Therefore, the oxygen-enriched air is supplemented in steps. The flue gas at the outlet of the first-stage conversion is supplemented with purified, dried, oxygen-enriched air (O2 concentration of 90%) at an oxygen-sulfur ratio of 0.2. The SO2 concentration in the flue gas after gas distribution will be 26.89%, the O2 concentration will be 5.38%, and the SO3 concentration will be 7.33%. Through heat exchange cooling, the flue gas temperature is controlled at about 420℃ before entering the second stage conversion. The equilibrium conversion rate of the conversion reaction is about 28%. After the reaction, the temperature of the flue gas at the outlet of the second stage conversion is about 627℃, and 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 the purified, dried, oxygen-enriched air (O2 concentration of 90%) is supplemented at this time with an oxygen-sulfur ratio of 0.9, the SO2 concentration in the flue gas after gas distribution 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°C, which will exceed the temperature. Therefore, the oxygen-enriched air will be supplemented in steps. The flue gas at the outlet of the second-stage conversion is supplemented with purified, dried, oxygen-enriched air (O2 concentration of 90%) at an oxygen-sulfur ratio of 0.68. The SO2 concentration in the flue gas after gas distribution will be 17.78%, the O2 concentration will be 12.09%, and the SO3 concentration will be 13.60%. Through heat exchange cooling, the flue gas temperature is controlled at about 420℃ for three-stage conversion. The equilibrium conversion rate of the conversion reaction is about 42%. After the reaction, the temperature of the flue gas at the outlet of the three-stage conversion is about 627℃, and 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 at the outlet of the three-stage conversion is supplemented with purified and dried air at an oxygen-sulfur ratio of 1. The SO2 concentration in the flue gas after gas distribution is 10.44%, the O2 concentration is 10.44%, and the SO3 concentration is 21.44%. The mixed flue gas is cooled to about 200°C through heat exchange and sent to the absorption tower of the subsequent conversion and absorption acid-making equipment. After absorbing the SO3 in the flue gas, it is heated and heated again to perform two-conversion and two-absorption acid-making.

[0076] Comparative Example 1

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

[0078] Comparative Example 2

[0079] Acid was produced according to the method described in Example 1, except that, in step 1, the SO₂ concentration in the high-sulfur flue gas feedstock was adjusted to 25% (dry basis) and the O₂ concentration to 10% (dry basis) by supplemental air (oxygen-sulfur ratio of 0.4). After the primary conversion reaction, the temperature of the flue gas at the primary conversion outlet was approximately 750°C, exceeding the temperature.

[0080] Comparative Example 3

[0081] Acid was produced according to the method described in Example 2, except that in step 3, the flue gas from the first-stage conversion outlet was supplemented with purified, dried air at an oxygen-sulfur ratio of 0.5. The resulting flue gas contained 17.10% SO₂, 8.55% O₂, and 4.66% SO₃. After the second-stage conversion reaction, the flue gas temperature at the second-stage conversion outlet was approximately 710°C, exceeding the upper temperature limit.

[0082] By comparing the above embodiments and comparative examples, it can be seen that the present invention, based on the low oxygen content of high-concentration sulfur-containing flue gas, controls the oxygen concentration in the high-concentration sulfur-containing flue gas to reduce the equilibrium conversion rate of the SO2 conversion reaction, inhibit the extent of the SO2 conversion reaction, and thus control the reaction temperature. After the SO2 concentration is reduced to approximately 12% by partial SO2 reaction, oxygen-containing gas is added to the flue gas to increase the oxygen-sulfur ratio and send it to the subsequent stage for conversion to ensure the overall conversion rate. The present invention is a new method for producing acid from high-concentration sulfur-containing flue gas, which has a simple process, convenient operation, and low investment. It is suitable for smelting flue gas acid production plants and sulfur acid production plants with suitable flue gas conditions.

[0083] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature specified as "first" or "second" may explicitly or implicitly include one or more of the features. Throughout the description of this application, "plurality" means two or more, unless otherwise specifically defined.

[0084] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0085] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A method for producing acid from high-concentration sulfur-containing flue gas, characterized in that: The following steps are involved: Control the O2 concentration in the high-concentration sulfur-containing flue gas raw material to be less than or equal to 4%, and control the O2 to SO2 concentration ratio to be less than or equal to 0.35; After heating the high-concentration sulfur-containing flue gas raw material, a conversion step is performed to convert SO2 into SO3; According to the conversion rate requirements, oxygen-containing gas is added to the flue gas at the first stage conversion outlet for subsequent conversion reactions, which can be carried out in the following two situations: (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 sent to the subsequent conversion absorption process for treatment; (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 first conversion outlet at one time, it is necessary to continue to control the oxygen concentration in the flue gas and add the oxygen-containing gas to the flue gas in steps, which specifically includes the following steps: introducing oxygen-containing gas into the flue gas at the first conversion outlet and controlling the concentration ratio of O2 to SO2 in the flue gas to be below 0.4, and performing the second conversion after cooling; 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 second conversion outlet at one time, repeat the above steps 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 conversion outlet at one time; at this time, the oxygen-containing gas required for the subsequent conversion reaction is added to the flue gas at the conversion outlet at one time and sent to the subsequent conversion absorption process for treatment.

2. The method according to claim 1, characterized in that The SO2 concentration in the high-concentration sulfur-containing flue gas raw material is above 12%, preferably 20%-50%.

3. The method according to claim 1, characterized in that The O2 concentration in the high-concentration sulfur-containing flue gas raw material is controlled to be 1%-4%, and the concentration ratio of O2 to SO2 is controlled to be 0.05-0.

35.

4. The method according to claim 1, wherein 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.

5. The method according to claim 1, characterized in that The oxygen-containing gas required for the subsequent conversion reaction is replenished at one time according to the concentration ratio of O2 to SO2 of 0.5-1.

2.

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

7. The method according to claim 1, characterized in that The controlling of the O2 concentration in the high-concentration sulfur-containing flue gas raw material 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.

8. The method according to claim 7, characterized in that The fuel includes at least one of sulfur and diesel.

9. The method according to claim 1, characterized in that Before heating the high-concentration sulfur-containing flue gas raw material, the high-concentration sulfur-containing flue gas raw material is purified and dried.

10. The method according to claim 1, characterized in that The subsequent conversion and absorption process includes a two-conversion and two-absorption acid-making process or a three-conversion and three-absorption acid-making process.

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