A cold warming method for high concentration flue gas sulphuric acid conversion catalyst

Abstract

The present application relates to a kind of cold state heating methods for high concentration flue gas acid conversion catalyst, start-up preheating furnace output high temperature flue gas, it is divided into two flue gas by shunt device, first flue gas is sent into first layer converter, flows through catalyst heat exchange and is heated, second flue gas is sent to the inlet of second layer converter by heat preservation bypass flue;First flue gas and second flue gas are converged before the inlet of second layer converter, form mixed flue gas, adjust flow ratio, mixed flue gas is passed into second layer converter, in turn flows through third to fifth layer converter, while monitoring the temperature at the inlet of each layer converter, when reaching the catalytic ignition temperature of sulfur dioxide, smelting sulfur dioxide flue gas is passed in. High temperature second flue gas and first flue gas after first converter are mixed as required, by optimizing heat source configuration and transmission path, the system heating efficiency is effectively improved, energy consumption significantly decreases, adjust flue gas ratio, so that the temperature of first section catalyst gradually increases, reduce thermal shock, increase service life.

Description

Technical Field

[0001] This invention relates to the field of sulfuric acid production technology, and in particular to a cold-state heating method for a high-concentration flue gas-to-acid conversion catalyst. Background Technology

[0002] In the copper smelting flue gas sulfuric acid production industry, to meet different conversion efficiency requirements, the "two-conversion-two-absorption" process mainly adopts a "3+1" four-stage converter layout or a "4+1" five-stage converter layout. Regardless of the configuration, the preheating of the conversion system is a crucial step to ensure smooth system startup and production targets are met. However, existing preheating technologies have several shortcomings, severely restricting production efficiency and economic viability.

[0003] When the system is started up from a cold state, all equipment and catalysts are at room temperature and must be preheated using an external heat source. Early preheating methods commonly used involved directly introducing the high-temperature hot gas generated by the preheating furnace through a single pipe to the inlet of the catalyst layer at the very front of the system (i.e., the first layer). This "single-point injection" mode has significant drawbacks: although the high-temperature hot gas flows downstream, it must pass through multiple catalyst layers and intermediate heat exchange equipment sequentially. The heat is gradually reduced during transfer, and by the time it reaches the final bed layer, the temperature has dropped significantly, making it difficult to heat the downstream catalyst, prolonging the preheating cycle, resulting in insufficient thermal energy utilization and high natural gas consumption.

[0004] Furthermore, the concentrated heat input from the first stage can easily cause the first bed to heat up too quickly while the last bed lags significantly, resulting in excessive temperature differences between the layers. This leads to substantial thermal stress on the converter shell and internal components, increasing the risk of equipment deformation and leaks at flange connections. Simultaneously, to compensate for insufficient heating at the last stage, operators are often forced to increase the hot air inlet temperature, which exacerbates the thermal shock of the first-stage catalyst, shortens its service life, and may cause localized overheating and burn out internal support components. Moreover, the single injection path lacks adjustment mechanisms, making it impossible to flexibly distribute heat according to the actual temperature of each layer. The preheating process has poor controllability, easily leading to uneven heating of the entire system and prolonging start-up preparation time.

[0005] The above problems urgently need to be addressed. Summary of the Invention

[0006] This invention discloses a cold-state heating method for a catalyst used in the conversion of high-concentration flue gas to acid, aiming to solve the technical problems existing in the prior art.

[0007] The present invention adopts the following technical solution, including: S1, flue gas diversion: during the system start-up phase, the preheating furnace produces high-temperature flue gas, which is divided into a first flue gas and a second flue gas by a diversion device, wherein the initial diversion ratio is set to the second flue gas accounting for 30% of the high-temperature flue gas; S2, branched conveying: the first flue gas is sent into the inlet of the first-layer converter, flows through the interior of the first-layer converter to exchange heat with the catalyst and raise its temperature, and the second flue gas is sent to the inlet of the second-layer converter through an insulated bypass flue; S3. Mixing and Temperature Adjustment: The first flue gas passes through the first-layer converter and reaches the second-layer converter, where it merges with the second flue gas before the inlet of the second-layer converter to form a mixed flue gas. The flow ratio is adjusted, wherein the temperature of the mixed flue gas is controlled between 400 degrees Celsius and 500 degrees Celsius, and the second flue gas accounts for 0% to 70% of the mixed flue gas. S4. Stable Temperature Rise: The mixed flue gas is introduced into the second-layer converter and flows sequentially through the third, fourth, and fifth-layer converters. The temperature at the inlet of each converter is monitored. When the catalytic ignition temperature of sulfur dioxide is reached, smelting sulfur dioxide flue gas is introduced.

[0008] Optionally, before the flue gas is diverted, the method further includes: purging the furnace and all flues of the start-up preheating furnace, wherein the purging time exceeds five minutes; and the start-up preheating furnace is started in a cold state using an ignition and heating method with low fuel supply, low heat output, and low-speed gradient heating.

[0009] Optionally, the mixing temperature control includes: real-time monitoring of the mixed flue gas temperature at the inlet of the second-layer converter, using a proportional-integral-derivative continuous stepless adjustment method to calculate the relationship between the increase in mixed flue gas temperature and the diversion ratio of the second flue gas, and continuously adjusting the flow ratio between the first flue gas and the second flue gas, wherein the change in the proportion of the second flue gas in a single adjustment does not exceed 5%.

[0010] Optionally, the stable temperature rise includes an initial temperature rise period, a first isothermal plateau period, a differentiated temperature rise period, a second isothermal plateau period, and a final temperature rise period; the initial temperature rise period passes through the first isothermal plateau period, the differentiated temperature rise period, the second isothermal plateau period, and finally the final temperature rise period, during which the temperature of the multilayer converter gradually increases.

[0011] Optionally, the initial heating period: after the furnace temperature of the preheating furnace stabilizes at 200 degrees Celsius, a high-fire heating method is used to increase the load of the preheating furnace and raise the outlet temperature of the preheating furnace to 500 degrees Celsius.

[0012] Optionally, during the first constant temperature plateau period: the temperatures of the second, third, fourth, and fifth layer converters are monitored in real time. When the temperature difference between each converter layer does not exceed 10 degrees, the opening of the insulation bypass flue is adjusted to the maximum. After the temperature difference between each converter layer exceeds 20 degrees, the opening of the insulation bypass flue is adjusted using a proportional-integral-derivative continuous stepless adjustment method. The maximum opening of the insulation bypass flue needs to be achieved at least three times.

[0013] Optionally, the differentiated heating period is as follows: after the constant temperature plateau period lasts for 4 hours, the load of the start-up preheating furnace is increased to more than 70%, and after the outlet temperature of the start-up preheating furnace rises to 650 degrees Celsius at a steady rate, the opening of the insulation bypass flue is adjusted to the maximum; the process of the outlet temperature of the start-up preheating furnace rising to 650 degrees Celsius at a steady rate is completed within four hours.

[0014] Optionally, the second constant temperature plateau period: the stable temperature rise continues until the 40th hour, the catalyst in the first layer converter reaches the ignition temperature of the sulfur dioxide oxidation reaction, and sulfur dioxide flue gas of a preset concentration is introduced at the first layer converter; the load of the start-up preheating furnace is controlled between 40% and 50%.

[0015] Optionally, the final heating period is as follows: after the catalyst in the first layer converter reaches the heating temperature due to the heat released by the combustion of sulfur dioxide flue gas, the high-temperature flue gas of the start-up preheating furnace is stopped, the conveying flue of the start-up preheating furnace and the heat-insulating bypass flue are closed, and the high-concentration sulfur dioxide flue gas is prevented from entering the preheating branch and forming an airflow short circuit.

[0016] The technical solution adopted in this invention can achieve at least one of the following beneficial effects: In this embodiment of the invention, S1, flue gas diversion: during the system start-up phase, the preheating furnace produces high-temperature flue gas, which is divided into a first flue gas and a second flue gas by a diversion device, wherein the initial diversion ratio is set to the second flue gas accounting for 30% of the high-temperature flue gas; S2, branched delivery: the first flue gas is sent into the inlet of the first-layer converter, flows through the interior of the first-layer converter to exchange heat with the catalyst and raise its temperature, and the second flue gas is sent to the inlet of the second-layer converter through an insulated bypass flue; S3. Mixing and Temperature Regulation: The first flue gas passes through the first-stage converter and reaches the second-stage converter, where it merges with the second flue gas before the inlet of the second-stage converter to form a mixed flue gas. The flow ratio is adjusted, and the temperature of the mixed flue gas is controlled between 400°C and 500°C. The second flue gas accounts for 0% to 70% of the mixed flue gas. S4. Stable Heating: The mixed flue gas is introduced into the second-stage converter and then flows sequentially through the third, fourth, and fifth-stage converters. The temperature at the inlet of each converter is monitored. Once the catalytic ignition temperature of sulfur dioxide is reached, smelting sulfur dioxide flue gas is introduced. By mixing the high-temperature second flue gas and the first flue gas after the first converter as needed, and by optimizing the heat source configuration and transfer path, the system heating efficiency is effectively improved, and energy consumption is significantly reduced. Adjusting the proportion of the first flue gas gradually increases the temperature of the first-stage catalyst, reducing the thermal shock of the first-stage catalyst and increasing its service life. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below, forming part of the present invention. The illustrative embodiments of the present invention and their descriptions explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings: Figure 1 This is a flowchart of a cold-state heating method for a high-concentration flue gas acid conversion catalyst according to the present invention; Figure 2 This is a diagram showing the apparatus connection for a cold-state heating method for a high-concentration flue gas acid conversion catalyst according to the present invention. Figure 3 This is a catalyst heating curve diagram of a cold-state heating method for a catalyst used in the conversion of high-concentration flue gas to acid production according to the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. In the description of this invention, it should be noted that the term "or" is generally used to include the meaning of "and / or," unless otherwise expressly indicated.

[0019] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or a magnetic connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. Furthermore, in the description of this application, the terms "first," "second," etc., are used only for distinguishing descriptions and should not be construed as indicating or implying relative importance. In the description of this invention, "a plurality of" means at least two, such as two, three, or more, unless otherwise explicitly specified.

[0020] Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0021] To address the problems existing in related technologies, this application provides a cold-state heating method for a high-concentration flue gas acid conversion catalyst.

[0022] This embodiment provides a cold-state heating method for a high-concentration flue gas acid conversion catalyst, such as... Figure 1 and Figure 2 As shown, Figure 1 This is a flowchart of a cold-state heating method for a high-concentration flue gas acid conversion catalyst according to the present invention. Figure 2 This is a diagram showing the apparatus connection for a cold-state heating method for a high-concentration flue gas acid conversion catalyst according to the present invention. The method includes: Step S1, Flue Gas Diversion: During the system start-up phase, the preheating furnace produces high-temperature flue gas. The high-temperature flue gas is divided into a first flue gas and a second flue gas through a diversion device. The initial diversion ratio is set so that the second flue gas accounts for 30% of the high-temperature flue gas. Optionally, the high-temperature flue gas (around 500 degrees Celsius) generated by the preheating furnace is divided into two streams at the outlet by a diversion device. The first stream of flue gas enters the "preheating path," and the second stream enters the "insulation bypass path." Here, preheating refers to preheating each layer of catalyst.

[0023] In some preferred embodiments, before the flue gas is diverted, the method further includes: purging the furnace and all flues of the start-up preheating furnace, wherein the purging time exceeds five minutes; and when the start-up preheating furnace is started in a cold state, an ignition and heating method with low fuel supply, low heat output, and low-speed gradient heating is adopted.

[0024] Optionally, before starting the system, it is necessary to confirm that the shut-off valves on the flue between the first and second converters, as well as the insulated bypass flue leading directly to the second converter, are in the open position. Confirm that all electric valves are energized, operate smoothly without jamming, and are in "automatic" control mode. Simultaneously, check and confirm that the catalyst in each layer is properly packed and not pulverized.

[0025] In addition, it is necessary to confirm that the fuel, combustion fan, dilution fan, and ignition system are functioning properly.

[0026] After the above preparations are completed, the system purging and ignition start-up combustion fans and dilution fans are activated to purge the furnace and insulation bypass flue of the start-up preheating furnace to remove any possible combustible gases. The purging time shall not be less than 5 minutes. After purging, the burner of the start-up preheating furnace is ignited. In the initial stage, low-load combustion is used to allow the furnace and refractory materials to heat up slowly and evenly, avoiding thermal shock.

[0027] Step S2, Branching and Conveying: The first stream of flue gas is sent into the inlet of the first-layer converter, flows through the interior of the first-layer converter to exchange heat with the catalyst and raise its temperature, and the second stream of flue gas is sent to the inlet of the second-layer converter through the insulated bypass flue. Optionally, the first flue gas flows into the second shell-and-tube heat exchanger as designed, or it can bypass the second heat exchanger and directly enter the first converter, where it heats the bed catalyst inside, while the temperature of the first flue gas itself drops significantly. Since the temperature of the first flue gas is insufficient to heat the second layer catalyst, the second flue gas is then delivered directly to the inlet area of ​​the second converter with almost no temperature drop through a well-insulated bypass duct, directly heating the bed catalyst inside the second converter.

[0028] The new split-flow preheating process, by precisely controlling the inlet temperature of the second catalyst bed, keeps it within the optimal reactivity range, thus significantly improving the conversion efficiency of sulfur dioxide. Actual operational data verifies that the system can be started up from a cold state in just 40 hours, reducing the system heating time by more than 8 hours, significantly reducing the natural gas consumption of the start-up furnace and saving production costs. Due to the split-flow heating, the temperature conditions of the second conversion layer are better, and the sulfur dioxide conversion rate can be increased by 10% to 15% in the initial stage of flue gas production. The improved conversion rate directly leads to a significant reduction in the total amount of sulfur dioxide in the exhaust gas, thereby greatly reducing the treatment load of the subsequent exhaust gas desulfurization section, allowing for more efficient use of hydrogen peroxide (…). The consumption of desulfurizing agent can be reduced by up to 30% year-on-year, achieving efficient, low-carbon and low-cost operation from source to end.

[0029] Step S3, Mixing and Temperature Adjustment: The first flue gas passes through the first converter and reaches the second converter, where it merges with the second flue gas before the inlet of the second converter to form a mixed flue gas. The flow rate ratio is adjusted, wherein the temperature of the mixed flue gas is controlled between 400 degrees Celsius and 500 degrees Celsius, and the second flue gas accounts for 0% to 70% of the mixed flue gas. Optionally, the first and second flue gases, with a significant temperature difference, are thoroughly mixed in a mixer before the inlet of the second-layer converter. By monitoring the temperature after mixing in real time, the opening of the diversion valve is adjusted accordingly, thereby precisely controlling the final temperature entering the second-layer catalyst. This temperature is both higher than the catalyst's ignition temperature and absolutely safer than its sintering temperature.

[0030] Optionally, the high-temperature heat source (second flue gas) and the medium-temperature heat source (first flue gas cooled by the first-stage converter) can be mixed as needed. By optimizing the heat source configuration and transfer path, the system's heating efficiency is effectively improved, allowing the preheating furnace to stop operating two hours before reaching the reaction critical point. This results in a significant reduction in the natural gas consumption of the preheating furnace. Specifically, 1063 The amount of natural gas used is sufficient to meet the heating process of the entire system, compared to the original 2000 This significantly reduces energy consumption. It achieves precise matching and maximum efficiency in energy quality utilization, avoiding unnecessary devaluation of high-quality energy, and improving energy efficiency by more than 50% compared to traditional methods.

[0031] In some preferred embodiments, the mixing temperature control includes: real-time monitoring of the mixed flue gas temperature at the inlet of the second-stage converter, using a proportional-integral-derivative continuous stepless adjustment method to calculate the relationship between the increase in mixed flue gas temperature and the diversion ratio of the second flue gas, and continuously adjusting the flow ratio between the first and second flue gas, wherein the change in the proportion of the second flue gas in a single adjustment does not exceed 5%.

[0032] Optionally, a distributed control system is used to link the dedicated temperature display and control measurement point at the inlet of the second-stage converter for automatic proportional-integral-derivative adjustment. The standard control temperature of the mixed flue gas is set at 450 degrees Celsius. When the measured temperature of the mixed flue gas at the inlet of the second-stage converter increases by one degree Celsius, the total proportion of the second flue gas is automatically reduced by two percent, with a single adjustment fluctuation not exceeding 5%. When the temperature is lower than the set range, the proportion of bypass flue gas is increased in the opposite direction. Throughout the process, the proportion of the second flue gas is constrained to maintain at 0-70%, and the overall temperature fluctuation of the mixed flue gas is controlled within ±5 degrees Celsius.

[0033] Optionally, the complete calculation principle of proportional-integral-derivative continuous stepless adjustment is as follows: First, the required numerical values ​​are defined, specifically: the standard temperature r of the mixed flue gas at the inlet of the second-stage converter is set to 450 degrees Celsius; the measured temperature y(k) at the inlet of the second-stage converter is sampled for the kth time; and the temperature deviation is e(k) = ry(k). Constraints also need to be adjusted: the total proportion of the second flue gas is permanently limited to the range of 0-70%; additionally, when e(k) < 0 (measured temperature > 450 degrees Celsius, temperature is too high), a negative increment is output to reduce the proportion of the second flue gas; when e(k) > 0 (measured temperature is too low), a positive increment is output to increase the proportion of the second flue gas.

[0034] Based on the above numerical values ​​and some constraints, an incremental formula is set up: in, For proportional gain, the setting here is 0.02, which means that for every one degree Celsius deviation in temperature, the proportion of flue gas changes by two percent in a single adjustment. The integral gain is set to 0.0015 to eliminate long-term steady-state temperature deviation. The differential gain is 0.008, used to suppress temperature overshoot and oscillation. This represents the current sampling temperature deviation. Previous cycle deviation; Deviation in the first two cycles; This represents the change in the proportion of the second flue gas stream during this period, expressed as a percentage.

[0035] Optionally, a proportional-integral-derivative continuous stepless control method is adopted. The integral stage can gradually accumulate the adjustment amount when the temperature is continuously too high or too low for a long time, eliminating the long-term steady-state temperature difference and ensuring that the steady-state temperature fluctuation is controlled within ±5 degrees Celsius. The derivative stage can predict the rapid rise or fall of the temperature and adjust in reverse in advance to avoid temperature overshoot exceeding the 400-500 degrees Celsius range. The continuous stepless control can be based on the controller sampling the temperature once per second and outputting small opening changes in real time. There is no gear switching, the flue gas ratio changes smoothly and continuously, and there is no temperature shock.

[0036] Step S4, Stabilize Heating: The mixed flue gas is introduced into the second-layer converter, and then flows through the third-layer converter, the fourth-layer converter, and the fifth-layer converter in sequence. At the same time, the temperature at the inlet of each converter is monitored. When the catalytic ignition temperature of sulfur dioxide is reached, the smelting sulfur dioxide flue gas is introduced.

[0037] Optionally, the mixed flue gas can be further heated in subsequent parts of the system according to the process flow. Overall flue gas route: In the initial stage of operation, the circulating air is heated through a preheating furnace. Once the air temperature reaches 400-500 degrees Celsius, the sulfur dioxide fan is started to provide power to the medium in the pipeline. The heated gas is divided into two paths: one part is regulated by the first valve and enters the inlet of the first-stage converter through the shell side of the second shell-and-tube heat exchanger, or directly enters the first-stage catalyst to preheat the catalyst layer; after passing through the catalyst, the flue gas temperature drops after the first-stage heat exchange, no longer meeting the heating requirements of the second-stage catalyst. The other part of the high-temperature gas is transported to the inlet of the second-stage converter with almost no temperature drop through a well-insulated bypass flue, where it is directly heated.

[0038] Subsequently, the mixed flue gas flows out from the second-stage converter, passes through the tube side of the second heat exchanger, and enters the third-stage converter. It then flows sequentially through the fourth and fifth-stage converters for preheating. Once the catalyst temperatures in each stage reach the start-up conditions, the system begins to introduce smelting sulfur dioxide flue gas. The process flue gas is transported by a sulfur dioxide blower and sequentially passes through the fourth heat exchanger, the start-up preheating furnace, the second heat exchanger, or a bypass of the second heat exchanger before entering the first-stage converter to undergo the conversion reaction. The gas after the reaction exits from the first-stage converter, passes through the tube side of the first heat exchanger, and then enters the second-stage converter.

[0039] Optionally, the flue gas then sequentially passes through the tube side of heat exchanger No. 2, the third-stage converter, the tube side of heat exchanger No. 3, the fourth-stage converter, the tube side of heat exchanger No. 4, and the waste heat boiler, finally entering the high-temperature absorption tower. The absorbed flue gas is then heated sequentially through the shell side of heat exchangers No. 5, No. 3, and No. 1 to meet the reaction temperature requirements, before entering the fifth-stage converter. After the reaction, the flue gas enters the second absorption tower for further treatment via the tube side of heat exchanger No. 5.

[0040] The acid production tail gas discharged from the second absorption tower enters the lower part of the desulfurization tower and comes into countercurrent contact with the circulating liquid. Sulfur dioxide and hydrogen peroxide react rapidly to form dilute sulfuric acid. After desulfurization, the flue gas passes through an electrostatic precipitator to remove acid mist, and finally passes through the tail gas chimney to meet emission standards.

[0041] Optionally, as the preheating furnace continuously heats the sulfur dioxide flue gas, the system gradually stabilizes and reaches thermal equilibrium, at which point the preheating furnace is shut down. At this point, the flue gas from the sulfur dioxide blower first passes through the fourth heat exchanger, where it exchanges heat with the hot flue gas exiting the fourth catalyst layer, reaching a temperature of 248 degrees Celsius. It then enters the second heat exchanger, where it exchanges heat with the hot flue gas exiting the second catalyst layer, reaching a temperature of 400 degrees Celsius before entering the first catalyst layer inside the first converter. In the first catalyst layer, some of the sulfur dioxide in the flue gas is converted to sulfur trioxide. Since the conversion of sulfur dioxide to sulfur trioxide is exothermic, the flue gas temperature rises. The flue gas exiting the first catalyst layer of the converter is then cooled sequentially through the first heat exchanger and the waste heat boiler, reaching a temperature of 430 degrees Celsius before entering the second catalyst layer of the converter, completing the self-heating supply.

[0042] In some preferred embodiments, the stable heating includes an initial heating period, a first isothermal plateau period, a differentiated heating period, a second isothermal plateau period, and a final heating period; the temperature of the multilayer converter gradually increases from the initial heating period through the first isothermal plateau period, the differentiated heating period, the second isothermal plateau period, until the final heating period.

[0043] Optionally, due to the shorter and more direct preheating path, the overall system resistance drop (pressure loss) is reduced. The operating load of the sulfur dioxide blower powered by flue gas can be reduced during the start-up preheating phase, thus saving electricity. Here, the sulfur dioxide in the flue gas is further converted into sulfur trioxide, and the flue gas temperature rises. Part of the flue gas exiting the second catalyst layer enters the second heat exchanger, and after being cooled by the heat exchanger, the temperature drops to 440 degrees Celsius before entering the third catalyst layer of the converter.

[0044] Optionally, it enables precise and targeted control of the inlet temperature of the crucial first-layer catalyst. This stabilizes the temperature within the optimal activation range, ensuring both speed and safety while maximizing preheating efficiency. It better handles the smelting flue gas generated by an initial feed rate of 120 t / h in a flash smelting furnace, ensuring the entire system remains stable and controllable. Furthermore, placing the bypass flue gas at the inlet of the second-layer converter effectively prevents a decrease in conversion rate due to valve leakage in the bypass. A small portion of the leaked flue gas enters the second-layer converter, where the catalyst absorbs and converts the sulfur dioxide gas, thus ensuring that emissions do not exceed standards and reducing environmental risks.

[0045] In some preferred embodiments, during the initial heating period: after the furnace temperature of the preheating furnace stabilizes at 200 degrees Celsius, a high-fire heating method is used to increase the load on the preheating furnace and raise the outlet temperature of the preheating furnace to 500 degrees Celsius.

[0046] Optionally, after establishing the preheating flow path and stabilizing the flame in the initial split preheating furnace, the load is slowly increased to gradually raise the outlet flue gas temperature to approximately 500 degrees Celsius. A target value is set for the second-stage converter inlet temperature controller (TIC-2) on the control system (DCS). The DCS will automatically output commands to adjust the opening of each valve based on the set target value. In the initial stage, a larger proportion of flue gas (100%) is typically allowed to enter the heating flue to quickly establish system circulation and allow the first-stage converter inlet temperature to approach the set value as soon as possible.

[0047] Once the furnace temperature of the preheating furnace stabilizes at 200 degrees Celsius, the load is gradually increased to control the furnace outlet temperature to rise steadily to 500 degrees Celsius. Simultaneously, the sulfur dioxide blower is started to establish system circulation and the circulating gas volume is controlled.

[0048] Optional, such as Figure 3 As shown, Figure 3 This is a catalyst temperature rise curve diagram of a cold-state heating method for a catalyst used in the conversion of high-concentration flue gas to acid. The temperature rise curve of the first catalyst layer steadily increases from 30 degrees Celsius at 0 hours to 65 degrees Celsius at 3 hours, 110 degrees Celsius at 6 hours, and finally reaches 150 degrees Celsius at 8 hours. During this period, the heating rate is stable at 20-25 degrees Celsius / hour, demonstrating good temperature control performance. The temperature rise of the second catalyst layer is relatively slow, gradually increasing from an initial 30 degrees Celsius to 55 degrees Celsius at 3 hours, 100 degrees Celsius at 6 hours, and reaching 140 degrees Celsius at 8 hours. This temperature change trend conforms to the phenomenon that the heating process focuses on the first catalyst layer, and after it accumulates sufficient heat, the excess heat energy is gradually transferred to the second catalyst layer, thus achieving an orderly distribution of heat energy. At the same time, the temperature rise trends of the third and fifth catalyst layers are quite similar, reflecting that the internal heat distribution of the system has gradually become more balanced, and the overall thermal stability is good.

[0049] In some preferred embodiments, during the first constant temperature plateau period: the temperatures of the second, third, fourth, and fifth layer converters are monitored in real time. When the temperature difference between each converter does not exceed 10 degrees, the opening of the insulation bypass flue is adjusted to the maximum. After the temperature difference between each converter exceeds 20 degrees, the opening of the insulation bypass flue is adjusted using a proportional-integral-derivative continuous stepless adjustment method. The state of maximum opening of the insulation bypass flue needs to be formed at least three times.

[0050] Optionally, fine-tuning and temperature control are implemented, closely monitoring the temperature changes of TIC-2. The DCS system continuously compares the measured values ​​with the set target values ​​and automatically fine-tunes the opening of the second-stage converter inlet valve through incremental proportional-integral-derivative (PID) calculations. If the TIC-2 temperature is lower than the set value, the diversion ratio of the insulated bypass flue can be increased, allowing more high-temperature flue gas to go directly to the mixing point. If the TIC-2 temperature is higher than the set value, the diversion ratio of the first flue gas can be increased, allowing more flue gas to go to the first-stage converter first. During this stage, the load and outlet temperature of the start-up preheating furnace are gradually increased, while the temperature of TIC-2 should be firmly controlled near the set value (±5 degrees Celsius). Throughout this process, the outlet temperature of the first-stage converter needs to be constantly monitored to ensure that it also rises within a reasonable range.

[0051] During the overall preheating and monitoring of the system to maintain stable control of TIC-2 and ensure continuous heat transfer to the system, it is also necessary to observe the temperature gradient changes of the subsequent third, fourth, and fifth catalyst layers and each heat exchanger. The entire system should be preheated uniformly according to the process airflow direction. Record the temperature rise curves of each layer (e.g., Figure 3 As shown in the figure, the preheating process was confirmed to be stable.

[0052] Optionally, after 8 hours, the temperatures of the catalyst layers in the system reach a relative equilibrium point, specifically: 150 degrees Celsius for the first layer, 140 degrees Celsius for the second layer, 135 degrees Celsius for the third layer, and 140 degrees Celsius for the fifth layer. At this point, the heating rate of the first layer catalyst slows down significantly, indicating a plateau. It is necessary to maintain a stable load on the preheating furnace, keeping the preheating furnace outlet temperature at 500 degrees Celsius. The bypass valve opening should be gradually increased, this adjustment process completed in three stages, increasing by a small amount each time, to ensure a smooth system transition.

[0053] The heat absorbed by the first catalyst layer reaches a dynamic equilibrium with the heat transferred to other parts of the system. By increasing the bypass opening, some of the high-temperature flue gas can be directly introduced to the second catalyst layer, which can break the original thermal equilibrium and promote the system to transition to a new equilibrium point.

[0054] During the 4-hour isothermal period, the temperature of each layer remained consistent. Specifically, the first layer stabilized at 150°C ± 2°C, the second layer slowly increased from 140°C to 150°C, the third layer increased from 135°C to 150°C, and the fifth layer increased from 140°C to 150°C. During this process, the maximum temperature difference at various points in the system decreased from the initial 20°C to less than 5°C, indicating that the system achieved excellent thermal equilibrium.

[0055] In some preferred embodiments, the differentiated heating period is as follows: after the constant temperature plateau period lasts for 4 hours, the load of the start-up preheating furnace is increased to more than 70%, and after the outlet temperature of the start-up preheating furnace rises to 650 degrees Celsius at a steady rate, the opening of the insulation bypass flue is adjusted to the maximum; the process of the outlet temperature of the start-up preheating furnace rising to 650 degrees Celsius at a steady rate is completed within four hours.

[0056] Optionally, after a 12-hour isothermal plateau, if the temperature of each catalyst layer begins to rise synchronously, it indicates that the system is ready to enter the next heating phase. The preheating furnace load is then increased to over 70%, and the furnace outlet temperature rises to 650 degrees Celsius at a steady rate. The bypass valve opening is further increased; this adjustment is completed in stages over 4 hours.

[0057] like Figure 3 As shown, the first catalyst layer exhibits the most rapid temperature response: 12 hours (150°C) → 16 hours (200°C) → 24 hours (300°C) → 32 hours (360°C) → 40 hours (400°C), with a heating rate of 8-15°C / hour. The second catalyst layer shows a slow-then-rapid temperature rise, maintaining at 150°C for 16 hours, then jumping to 200°C after 24 hours, and subsequently rising at a rate of 5-10°C / hour to 320°C. This differentiated heating curve demonstrates the intelligent control capability of the preheating system.

[0058] In this stage, the high-temperature flue gas, directly supplied to the second-stage converter via an insulated bypass pipe, plays a crucial role. Once the temperature of the second-stage catalyst exceeds 150 degrees Celsius, the catalyst begins to exhibit activity, forming a synergistic heating effect with the first-stage catalyst. Simultaneously, the temperature rise curves of the third and fifth stages are smooth and stable, indicating a significant improvement in the system's heat transfer efficiency.

[0059] In some preferred embodiments, the second isothermal plateau period: the stable temperature rise continues until the 40th hour, the catalyst in the first-layer converter reaches the ignition temperature of the sulfur dioxide oxidation reaction, and sulfur dioxide flue gas of a preset concentration is introduced at the first-layer converter; the load of the start-up preheating furnace is controlled between 40% and 50%.

[0060] Optionally, when the inlet temperature of the second-stage converter stabilizes above 390 degrees Celsius and the overall system temperature distribution is good, the sulfur dioxide process flue gas from the purification section can be slowly and gradually introduced into the first-stage converter. As the exothermic reaction begins, the system gradually generates self-heat. At this point, the load on the preheating furnace is gradually reduced. Based on the system temperature rise, the regulating valves of each pipeline are gradually closed (or the TIC-2 setpoint is lowered) to reduce the supplementation of external heat sources.

[0061] Optionally, after 40 hours of system operation, the temperatures of each catalyst layer reach a new thermal equilibrium state, specifically distributed as follows: first layer 400 degrees Celsius, second layer 320 degrees Celsius, third layer 300 degrees Celsius, and fifth layer 310 degrees Celsius. At this point, the first catalyst layer has reached the ignition temperature for the sulfur dioxide oxidation reaction, meeting the conditions for introducing process flue gas. Therefore, sulfur dioxide flue gas with a concentration of 7%-8% can be introduced at this node, while controlling the inlet gas volume within 40%-50% of the design normal load. Through the combined heating of the sulfur dioxide reaction heat of the first catalyst layer and the start-up preheating furnace, continuous heating of subsequent catalyst layers is achieved, further improving the overall system temperature level.

[0062] Optionally, at this stage, by precisely controlling the opening of the bypass valve, the heat flow distribution between the first and second catalyst layers is effectively optimized while maintaining a stable operating load on the preheating furnace. This effectively improves the overall thermal balance of the system, ensuring efficient and stable heat transfer between each catalyst layer, thereby achieving coordinated and unified system thermal management and a balanced operating state.

[0063] Optionally, after introducing sulfur dioxide flue gas with a concentration of 7%-8%, the first catalyst layer continuously and stably releases heat through its own sulfur dioxide oxidation reaction heat, maintaining its temperature within the optimal reaction range of approximately 400 degrees Celsius. Simultaneously, the start-up preheating furnace maintains low-load operation, working synergistically with the reaction heat to heat subsequent bed layers. During the subsequent 5-hour isothermal period, the temperature of each layer rises slowly and steadily: the second layer from 320 degrees Celsius to 355 degrees Celsius, the third layer from 300 degrees Celsius to 340 degrees Celsius, and the fifth layer from 310 degrees Celsius to 340 degrees Celsius. The heating rate of each layer is uniformly controlled at 5-10 degrees Celsius / hour, achieving system temperature consistency and thermal stability, facilitating the subsequent full integration of process flue gas and achieving system self-heating balance.

[0064] In some preferred embodiments, during the final heating period: after the catalyst in the first-layer converter reaches the heating temperature due to the heat released by the combustion of sulfur dioxide flue gas, the high-temperature flue gas of the start-up preheating furnace is stopped, the conveying flue and the insulation bypass flue of the start-up preheating furnace are closed, and the high-concentration sulfur dioxide flue gas is prevented from entering the preheating branch and forming an airflow short circuit.

[0065] Optionally, after the system has been running for 45 hours, it enters the final heating stage. At this point, the temperature of the first catalyst layer has been stabilized at around 400 degrees Celsius through the sulfur dioxide reaction heat. The preheating furnace is then started up, and the operating load is gradually reduced, with the furnace outlet temperature controlled at around 650 degrees Celsius. The opening of the bypass valve needs to be adjusted to ensure that the second catalyst layer receives sufficient heat without affecting the normal reaction temperature of the first layer.

[0066] Optionally, during this stage, the temperature of the second catalyst layer steadily increased from 355 degrees Celsius to 385 degrees Celsius, demonstrating good temperature rise tracking characteristics; the temperature of the third catalyst layer increased from 330 degrees Celsius to 376 degrees Celsius, and the temperature of the fifth catalyst layer increased from 340 degrees Celsius to 362 degrees Celsius. The temperature rise curves of each catalyst layer were smooth, and the overall temperature distribution tended to be uniform. By 50 hours, the temperature of each catalyst layer in the system had reached the optimal reaction temperature range, the temperature distribution uniformity met the process requirements, and the natural gas consumption was only 50% of the planned amount. The system was fully ready to switch to normal operation.

[0067] Optionally, during the final 5 hours of heating, the maximum temperature fluctuation of each layer does not exceed ±3 degrees Celsius, and the temperature gradient remains stable, indicating that the system has excellent thermal stability. After 50 hours, the temperature of each catalyst layer has stabilized within the optimal reaction temperature range, and natural gas consumption is reduced by up to 50% compared to the planned value, demonstrating outstanding energy efficiency.

[0068] Optionally, when the process flue gas volume reaches the normal load and the catalyst temperature in multiple converters is entirely maintained by the heat of reaction, the start-up preheating furnace is completely shut down, and the shut-off valves on the first preheating flue and the insulated bypass flue are closed sequentially. At this time, the normal production system enters a fully self-heating balanced normal production state, and the preheating system is completely isolated and can operate independently.

[0069] Through steps S1 to S4, the maximum temperature deviation of each catalyst layer during the entire preheating process is kept within ±5 degrees Celsius, maintaining a stable temperature rise. Furthermore, actual fuel consumption is 50% of that of traditional processes, resulting in significant energy savings. The total preheating time is 50 hours, more than 12 hours shorter than traditional processes, demonstrating a significant efficiency improvement. Moreover, the system maintains positive pressure throughout the entire process, with no leaks detected, and the fifth catalyst layer maintains 100% activity. The system also achieves fully automatic operation, requiring only the setting of the target temperature to automatically complete the entire preheating process.

[0070] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A cold-state heating method for a high-concentration flue gas acid conversion catalyst, characterized in that, include: S1, Flue Gas Diversion During the system startup phase, the preheating furnace produces high-temperature flue gas. The high-temperature flue gas is divided into a first flue gas and a second flue gas by a diversion device. The initial diversion ratio is set so that the second flue gas accounts for 30% of the high-temperature flue gas. S2, Branch Conveying The first stream of flue gas is sent into the inlet of the first-layer converter and flows through the interior of the first-layer converter to heat the catalyst. The second stream of flue gas is sent to the inlet of the second-layer converter through the heat-insulated bypass flue. S3, Hybrid Temperature Control The first flue gas passes through the first-stage converter and reaches the second-stage converter, where it merges with the second flue gas before the inlet of the second-stage converter to form a mixed flue gas. The flow ratio is adjusted, wherein the temperature of the mixed flue gas is controlled between 400 degrees Celsius and 500 degrees Celsius, and the second flue gas accounts for 0% to 70% of the mixed flue gas. S4, Stable Heating The mixed flue gas is introduced into the second-layer converter, and then flows through the third-layer converter, the fourth-layer converter, and the fifth-layer converter in sequence. At the same time, the temperature at the inlet of each converter is monitored. When the catalytic ignition temperature of sulfur dioxide is reached, smelting sulfur dioxide flue gas is introduced.

2. The cold-state heating method for a high-concentration flue gas acid conversion catalyst according to claim 1, characterized in that, Before flue gas diversion, the method also includes: The furnace chamber and all flues of the preheating furnace to be started are purged, and the purging time exceeds five minutes; When the preheating furnace is started from a cold state, it adopts an ignition and heating method with small fuel supply, low heat output, and low-speed gradient heating.

3. The cold-state heating method for a high-concentration flue gas acid conversion catalyst according to claim 1, characterized in that, The hybrid temperature control includes: The temperature of the mixed flue gas at the inlet of the second-stage converter is monitored in real time. The proportional-integral-derivative continuous stepless adjustment method is used to calculate the relationship between the increase in the temperature of the mixed flue gas and the diversion ratio of the second flue gas. The flow ratio between the first flue gas and the second flue gas is continuously adjusted, wherein the change in the proportion of the second flue gas in a single adjustment does not exceed 5%.

4. The cold-state heating method for a high-concentration flue gas acid conversion catalyst according to claim 1, characterized in that, The stable heating period includes the initial heating period, the first isothermal plateau period, the differentiated heating period, the second isothermal plateau period, and the final heating period. The initial heating period consists of a first isothermal plateau period, a differentiated heating period, a second isothermal plateau period, and finally a final heating period, during which the temperature of the multilayer converter gradually increases.

5. The cold-state heating method for a high-concentration flue gas acid conversion catalyst according to claim 4, characterized in that, The initial warming period: After the furnace temperature of the preheating furnace stabilizes at 200 degrees Celsius, a high-temperature heating method is used to increase the load of the preheating furnace and raise the outlet temperature of the preheating furnace to 500 degrees Celsius.

6. The cold-state heating method for a high-concentration flue gas acid conversion catalyst according to claim 4, characterized in that, The first isothermal plateau period: The temperatures of the second, third, fourth, and fifth converters are monitored in real time. When the temperature difference between each converter does not exceed 10 degrees, the opening of the insulation bypass flue is adjusted to the maximum. When the temperature difference between each converter exceeds 20 degrees, the opening of the insulation bypass flue is adjusted using a proportional-integral-derivative continuous stepless adjustment method. The maximum opening state of the thermal insulation bypass flue needs to be achieved at least three times.

7. The cold-state heating method for a high-concentration flue gas acid conversion catalyst according to claim 4, characterized in that, The differentiated warming period: After the constant temperature plateau period lasts for 4 hours, the load of the start-up preheating furnace is increased to more than 70%. After the outlet temperature of the start-up preheating furnace rises to 650 degrees Celsius at a steady rate, the opening of the insulation bypass flue is adjusted to the maximum. The process of raising the outlet temperature of the preheating furnace to 650 degrees Celsius at a steady rate is completed within four hours.

8. The cold-state heating method for a high-concentration flue gas acid conversion catalyst according to claim 4, characterized in that, The second isothermal plateau period: The stable heating continues until the 40th hour, when the catalyst in the first layer converter reaches the ignition temperature of the sulfur dioxide oxidation reaction, and sulfur dioxide flue gas of a preset concentration is introduced at the first layer converter. The load of the preheating furnace is controlled between 40% and 50%.

9. A cold-state heating method for a high-concentration flue gas acid conversion catalyst according to claim 4, characterized in that, The final warming period: When the catalyst in the first-layer converter reaches the heating temperature after the sulfur dioxide flue gas combustion releases heat, the high-temperature flue gas of the start-up preheating furnace is stopped, the conveying flue of the start-up preheating furnace and the heat preservation bypass flue are closed, and the high-concentration sulfur dioxide flue gas is blocked from entering the preheating branch to form an airflow short circuit.

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