A molten sulfur residual liquid waste gas treatment system and method

Abstract

This invention discloses a system and method for treating waste gas from molten sulfur residue, comprising a residue tank, a first mixing tower, an induced draft fan, and a desulfurization tower. The residue tank is used to hold molten sulfur residue. The residue tank and the first mixing tower are connected by a pipeline to transport the molten sulfur residue to the first mixing tower. Waste gas is passed through the first mixing tower to react with the molten sulfur residue for desulfurization. The desulfurization tower contains molten sulfur residue. The induced draft fan is connected to both the first mixing tower and the desulfurization tower. The induced draft fan bubbles the waste gas discharged from the first mixing tower into the molten sulfur residue in the desulfurization tower. The induced draft fan is connected to the atmosphere through a pipeline to ensure that the waste gas entering the desulfurization tower is mixed with oxygen. A regulating valve is installed on the pipeline connected to the atmosphere to control the flow rate. This invention provides a system and method for treating waste gas from molten sulfur residue, enabling the recycling and reuse of molten sulfur residue.

Description

Technical Field

[0001] This invention relates to the field of waste gas treatment technology, and more specifically, to a system and method for treating waste gas from molten sulfur residue. Background Technology

[0002] Industries such as chemical processing and wastewater treatment generate large amounts of hydrogen sulfide-containing waste gas, which is typically treated using wet desulfurization. Wet desulfurization systems produce molten sulfur residue as a byproduct during the sulfur melting process. Its main components are sodium carbonate, thiosulfate, sulfate, and small amounts of sulfur particles and catalyst. It is widely believed in the industry that molten sulfur residue contains many impurities and high levels of byproduct salts, and can only be disposed of in a harmless manner, not directly reused in the desulfurization system. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a system and method for treating molten sulfur residue waste gas, which can recycle and reuse molten sulfur residue.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: a molten sulfur residue waste gas treatment system, comprising a residue tank, a first mixing tower, an induced draft fan, and a desulfurization tower. The residue tank is used to hold molten sulfur residue. The residue tank and the first mixing tower are connected by a pipeline to transport the molten sulfur residue to the first mixing tower. Waste gas is passed through the first mixing tower to react with the molten sulfur residue for desulfurization. The desulfurization tower contains molten sulfur residue. The induced draft fan is connected to both the first mixing tower and the desulfurization tower. The induced draft fan bubbles the waste gas discharged from the first mixing tower into the molten sulfur residue in the desulfurization tower. The induced draft fan is connected to the atmosphere through a pipeline to mix oxygen into the waste gas entering the desulfurization tower. A regulating valve is installed on the pipeline connected to the atmosphere to control the flow rate.

[0005] Furthermore, a spray assembly is installed inside the desulfurization tower. The inlet end of the spray assembly is connected to the molten sulfur residue in the desulfurization tower through a pipeline. The molten sulfur residue in the desulfurization tower is transported to the inlet end of the spray assembly through the fifth pump body.

[0006] Furthermore, the residual liquid pool is connected to a filter press via pipeline. The filter press is used to separate the solid and liquid components of the incoming molten sulfur residual liquid, and the liquid in the separated molten sulfur residual liquid is returned to the residual liquid pool.

[0007] Furthermore, the desulfurization tower and the residual liquid pool are connected by a pipeline, and a sixth pump is installed in the pipeline between the desulfurization tower and the residual liquid pool to transport the molten sulfur residual liquid in the desulfurization tower to the residual liquid pool.

[0008] Furthermore, the exhaust end of the first mixing tower is connected to the second mixing tower via a pipeline, and the second mixing tower is connected to the residual liquid pool via a pipeline. The molten sulfur residual liquid is transported from the residual liquid pool through the second mixing tower and then to the first mixing tower. The exhaust end of the second mixing tower is connected to the air inlet end of the induced draft fan via a pipeline.

[0009] Furthermore, it also includes a cooling separator, which is used to condense and collect water vapor in the exhaust gas. The exhaust gas then enters the first mixing tower after passing through the cooling separator.

[0010] The present invention also adopts the following technical solution: a method for treating waste gas from molten sulfur residue, using a waste gas treatment system for molten sulfur residue, comprising the following steps: S1: Pretreatment: the waste gas is dehydrated and then introduced into a first mixing tower; S2: Desulfurization: ① the molten sulfur residue in the residue pool is transported to the first mixing tower, where the molten sulfur residue reacts with the waste gas for the first desulfurization; ② the waste gas discharged from the first mixing tower enters a second mixing tower to react with the molten sulfur residue in the second mixing tower for the second desulfurization; ③ the waste gas discharged from the second mixing tower is mixed with oxygen and then introduced into the molten sulfur residue in the desulfurization tower, and the molten sulfur residue overflows in a bubbling manner for the third desulfurization; S3: the waste gas after three desulfurizations is discharged from the desulfurization tower.

[0011] Furthermore, after the exhaust gas is mixed with oxygen, its oxygen content is controlled at 8%–12% Vol.

[0012] Furthermore, the opening degree of the regulating valve is determined based on the value of the command Y_total, Y_total = Y_feed + Y_pid; where Y_feed = K_feed × Q_gas × C_in; K_feed is the feedforward coefficient, ranging from 0.00025 to 0.0004; Q_gas is the real-time flow rate of exhaust gas; C_in is the inlet hydrogen sulfide concentration; Y_pid = Y_lastpid + ΔY_pid; Y_lastpid is the valve opening degree of the previous cycle; ΔY_pid is the change in valve opening degree; ΔY_pid = Kp (e_k - e_k-1) + Ki × e_k + Kd (e_k-2e_k-1 + e_k-2), where e_k is the deviation between the oxygen content setpoint and the measured value, e_k-1 is the oxygen content deviation of the previous control cycle, e_k-2 The oxygen content deviation is from the previous control cycle, Kp=2.0, Ki=0.1, Kd=0.05.

[0013] In summary, the present invention has the following beneficial effects:

[0014] 1. Breaking through the industry's common misconception that "molten sulfur residue has many impurities, high by-product salt content, and can only be disposed of harmlessly but not reused," it directly uses molten sulfur residue as a desulfurization absorbent for recycling, without the need to add fresh alkali sources such as sodium carbonate. It treats waste with waste, significantly reducing the cost of desulfurizing agent procurement and hazardous waste disposal, and achieving efficient utilization of by-product resources.

[0015] 2. A multi-stage combined process is adopted, which combines cooling and dehydration pretreatment, two-stage packing absorption in the first and second mixing towers, and deep desulfurization by bubbling and spraying in the desulfurization tower. The waste gas and the molten sulfur residue are in full contact, which can remove hydrogen sulfide step by step. This overcomes the shortcomings of traditional single desulfurization towers, such as low desulfurization efficiency and insufficient gas-liquid contact. The hydrogen sulfide concentration in the treated waste gas is consistently below 50 mg / m³.

[0016] 3. The circulating sulfur melting residue is separated into solid and liquid by a filter press, and the sulfur particles and elemental sulfur precipitated from the reaction are recovered. The purified residue is returned to the system as desulfurization liquid, which has environmental, economic and resource benefits. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of an embodiment;

[0018] Figure 2 This is a process diagram of waste gas flow;

[0019] Figure 3 This is a flow chart of a process for handling residual sulfur melt.

[0020] Figure 4 This is a diagram showing another process flow for residual sulfur melt.

[0021] Reference numerals in the attached drawings: Cooling separator 1, First pump body 11, Exhaust gas 12, Residual liquid pool 2, Second pump body 21, Second mixing tower 3, Third pump body 31, Fourth pump body 32, Exhaust fan 4, Regulating valve 41, Desulfurization tower 5, Fifth pump body 51, Spray assembly 52, Exhaust port 53, Sixth pump body 54, Filter press 6, First mixing tower 7. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Example 1:

[0024] like Figures 1-4As shown, this embodiment discloses a waste gas treatment system for molten sulfur residue, including a residue tank 2, a first mixing tower 7, a second mixing tower 3, an induced draft fan 4, and a desulfurization tower 5. The residue tank 2 is used to hold molten sulfur residue, and the residue tank 2 is connected to the first mixing tower 7 via a pipeline. More precisely, the exhaust end of the first mixing tower 7 is connected to the second mixing tower 3 via a pipeline. The first mixing tower 7 is an injection tower, with an inlet for waste gas 12 at the top and a liquid outlet and a gas outlet at the bottom, which are connected to the second mixing tower 3 via pipelines.

[0025] The second mixing tower 3 is connected to the residual liquid tank 2 via a pipeline. A fourth pump body 32 is installed in the pipeline connecting the second mixing tower 3 and the first mixing tower 7 to directly transport the liquid storage chamber at the bottom of the second mixing tower 3 to the first mixing tower 7, so as to carry out a desulfurization reaction with the exhaust gas 12 introduced into the first mixing tower 7.

[0026] In another pipeline of the second mixing tower 3, a spray pipe is connected from the residual liquid pool 2 to the upper part of the second mixing tower 3. A second pump body 21 is installed in this pipeline. The second pump body 21 transports the molten sulfur residual liquid from the residual liquid pool 2 to the second mixing tower 3. The air inlet of the second mixing tower 3 is located at the bottom, so that the waste gas 12 in the second mixing tower 3 reacts with the sprayed molten sulfur residual liquid to carry out a desulfurization reaction.

[0027] The chemical equation for the desulfurization reaction is: Na2CO3 + H2S → NaHS + NaHCO3. The main gas absorbed is hydrogen sulfide. To increase the reaction efficiency, a catalyst can be added.

[0028] The inlet of the first mixing tower 7 is connected to the outlet of the cooling separator 1. Waste gas 12 is introduced into the inlet of the cooling separator 1. The cooling separator 1 is used to condense and collect the water vapor in the waste gas 12 to prevent the increase of residual liquid in the system. The condensate is extracted through the first pump body 11. Simply put, the cooling separator 1 is a heat exchange device. The waste gas 12 flows in the internal heat exchange tubes. After the low-temperature air is introduced, it exchanges heat with the outer wall of the heat exchange tubes to form a high-temperature gas and is discharged. The temperature of the waste gas 12 in the heat exchange tubes decreases and the water vapor condenses.

[0029] The first mixing tower 7 is equipped with a packing layer (not shown in the figure). The packing layer is a Pall ring packing layer in the tower, which increases the contact area between the molten sulfur residue and the waste gas 12, so that the waste gas 12 and the molten sulfur residue can react fully to complete the first desulfurization. The second mixing tower 3 is also equipped with a packing layer. After the waste gas 12 enters the second mixing tower 3, it reacts with the molten sulfur residue again to complete the second desulfurization.

[0030] The exhaust end of the second mixing tower 3 is connected to the inlet end of the induced draft fan 4 via a pipeline, and the outlet end of the induced draft fan 4 is connected to the desulfurization tower 5. The induced draft fan 4 bubbles the exhaust gas 12 discharged from the second mixing tower 3 into the molten sulfur residue in the desulfurization tower 5. The bubbling method allows the exhaust gas 12 to fully contact the molten sulfur residue, completing the third desulfurization. The induced draft fan 4 is also connected to the atmosphere via a pipeline equipped with a regulating valve 41. By adjusting the opening of the regulating valve 41, the amount of oxygen introduced is controlled. After the oxygen enters the exhaust gas 12 and mixes, it is bubbled into the molten sulfur residue in the desulfurization tower 5. Two chemical reactions occur during this process: oxidation sulfur precipitation reaction: NaHS + ½O2 → S↓ + NaOH, alkaline regeneration: NaOH + NaHCO3 → Na2CO3 + H2O. Na2CO3 can be returned to the residue pool 2 as a desulfurizing agent for reuse. The liquid phase after the reaction between the first mixing tower 7 and the second mixing tower 3 can be pumped back to the residue pool 2 by the third pump 31.

[0031] The desulfurization tower 5 contains molten sulfur residue. A spray assembly 52 is installed inside the desulfurization tower 5. The inlet end of the spray assembly 52 is connected to the bottom of the desulfurization tower 5 through a pipeline. A fifth pump body 51 is installed in the pipeline. The fifth pump body 51 transports the molten sulfur residue at the bottom of the desulfurization tower 5 to the spray assembly 52. ​​The spray assembly 52 sprays the molten sulfur residue evenly into the desulfurization tower 5, further increasing the contact area with the exhaust gas 12 and improving the effect of the third desulfurization. An exhaust port 53 is provided at the top of the desulfurization tower 5. The exhaust gas 12 after the third desulfurization is discharged from the exhaust port.

[0032] The precipitated elemental sulfur and solid impurities need to be recovered. Specifically, a filter press 6 is connected to the residual liquid tank 2 via a pipeline. The inlet of the filter press 6 is connected to the residual liquid tank 2, and a pump is installed between them to pump the liquid phase into the filter press. The outlet of the filter press 6 is connected to the desulfurization tower 5 via a pipeline to replenish the molten sulfur residue in the desulfurization tower 5. At the same time, the liquid phase products after the reaction between the first mixing tower 7 and the second mixing tower 3 also enter the desulfurization tower 5 from the residual liquid tank 2 through the filter press 6.

[0033] The filter press 6 performs solid-liquid separation on the molten sulfur residue in the residual liquid tank 2. After removing solid impurities (elemental sulfur) from the residue, the liquid phase is fed into the desulfurization tower 5 and participates in the oxidation and sulfur precipitation reaction and alkaline regeneration. This regenerates the sodium carbonate alkaline solution used to remove hydrogen sulfide waste gas for reuse. The desulfurization tower 5 and the residual liquid tank 2 are connected by a pipeline. The sixth pump 54 in the pipeline controls the return of the liquid phase to the residual liquid tank 2. The sodium carbonate content in the returned liquid phase is increased for use in desulfurization.

[0034] Example 2:

[0035] like Figures 1-4 As shown, a method for treating residual sulfur molten liquid waste gas, using the residual sulfur molten liquid waste gas treatment system in Example 1, includes the following steps:

[0036] S1: Preprocessing

[0037] Sulfur-containing waste gas 12 is introduced into cooling separator 1. Cooling separator 1 adopts indirect cooling method to lower the temperature of waste gas 12, so that the water vapor in waste gas 12 condenses into liquid water and is collected. After dehydration treatment, waste gas 12 is introduced into first mixing tower 7.

[0038] S2: Desulfurization

[0039] ① Start the pump between the residual liquid tank 2 and the first mixing tower 7 to transport the molten sulfur residue (sulfide content of 10-15 g / L) from the residual liquid tank 2 to the first mixing tower 7. The molten sulfur residue fully contacts and reacts with the waste gas 12. The reaction temperature is controlled at 30-40℃ to carry out the first desulfurization, removing 60-70% of the sulfur-containing components from the waste gas 12. The specific flow path of the molten sulfur residue is: residual liquid tank 2 - second mixing tower 3 - first mixing tower 7.

[0040] ② The exhaust gas 12 (with sulfur content reduced to 500-800 mg / m³) discharged from the first mixing tower 7 enters the second mixing tower 3. Simultaneously, the molten sulfur residue in the residual liquid pool 2 is transported to the spray device at the top of the second mixing tower 3. The molten sulfur residue and exhaust gas 12 react fully again in the packing layer of the second mixing tower 3 for a second desulfurization, reducing the sulfur content in the exhaust gas 12 to 100-200 mg / m³. Because a self-circulation of the molten sulfur residue is formed between the first mixing tower 7 and the second mixing tower 3, the reaction utilization rate of the molten sulfur residue is improved. By detecting the concentration of sodium carbonate in the molten sulfur residue in the second mixing tower 3, if the concentration is lower than the process requirements, the third pump 31 is activated to return the molten sulfur residue in the second mixing tower 3 to the residual liquid pool 2 for subsequent sodium carbonate regeneration.

[0041] ③ Start the induced draft fan 4 to introduce the exhaust gas 12 discharged from the second mixing tower 3 into the desulfurization tower 5. At the same time, adjust the regulating valve 41 to control the oxygen flow rate to mix with the exhaust gas 12. The mixed exhaust gas 12 is introduced into the molten sulfur residue in the desulfurization tower 5 in a bubbling manner. At the same time, start the fifth pump body 51 to transport the molten sulfur residue at the bottom of the desulfurization tower 5 to the spray assembly 52. ​​The spray assembly 52 sprays the molten sulfur residue evenly. The exhaust gas 12 is in full contact with the sprayed molten sulfur residue and the molten sulfur residue in the pool, thereby completing the third desulfurization and reducing the sulfur content in the exhaust gas 12 to below 50 mg / m³.

[0042] S3: Emissions

[0043] The exhaust gas 12 after three desulfurization processes is discharged from the top exhaust port 53 of the desulfurization tower 5.

[0044] Meanwhile, the filter press 6 is started periodically, or the filter press 6 is started according to the sodium carbonate concentration and solid impurities in the residual liquid tank 2. When the sodium carbonate concentration is low or there are many solid impurities, the molten sulfur residue in the residual liquid tank 2 is separated into solid and liquid. The separated solid impurities are collected and treated harmlessly. The separated liquid phase is passed into the desulfurization tower 5 to regenerate the sodium carbonate alkali solution and is returned to the residual liquid tank 2 for recycling in the desulfurization process.

[0045] Because the H2S content in exhaust gas 12 fluctuates, the suitable oxygen content volume ratio after mixing with oxygen in exhaust gas 12 is within a very narrow range (8%–12% Vol). Excessive oxygen will exacerbate side reactions, generating sodium sulfate and thiosulfate, leading to tower blockage, corrosion, and foam deterioration; insufficient oxygen will result in incomplete catalyst regeneration and decreased desulfurization efficiency. Therefore, it is necessary to control the input of oxygen content. Specifically, this involves controlling the opening of regulating valve 41, with the control command denoted as Y_total, which ranges from 0 to 100%. The opening of regulating valve 41 is adjusted according to the value of Y_total. In actual operation, the command Y_total is converted into an electrical signal and then used to control the opening of the actuator controller of regulating valve 41.

[0046] Y_total = Y_feed + Y_pid;

[0047] Wherein, Y_feed is the feedforward compensation opening calculated based on the exhaust gas load 12, which is used to quickly track changes in operating conditions;

[0048] Y_feed = K_feed × Q_gas × C_in;

[0049] K_feed is the feedforward coefficient, ranging from 0.00025 to 0.0004. It is obtained through experimental calibration based on the system's mass transfer characteristics, tower diameter, and absorbent alkalinity. It is a fixed coefficient reflecting the oxygen consumption characteristics of this system. The numerical basis is specifically based on the fundamental values ​​calculated using the gas-liquid reaction kinetics theory of wet desulfurization: According to the stoichiometric ratio of H2S to O2 (2:1) in the overall desulfurization reaction equation, combined with the exhaust gas flow rate and H2S concentration, the theoretical oxygen consumption required for H2S oxidation per unit time is calculated. Then, considering the negative pressure of the induced draft fan, the diameter of the make-up air pipe, and the valve flow capacity, the theoretical value of K_feed is initially calculated. Subsequently, experimental calibration and correction are performed: Under stable system operation conditions, with the exhaust gas flow rate and H2S concentration fixed, the K_feed value is gradually adjusted, and the oxygen content stability is recorded to select a coefficient range that allows oxygen content fluctuations to be ≤±0.5%. Finally, on-site debugging and optimization are conducted: For different exhaust gas loads (flow rate and concentration fluctuations), the coefficient value is fine-tuned, and the final K_feed value is determined to be 0.00025~0.0004, ensuring that the feedforward compensation accurately matches the real-time oxygen demand and avoids lag.

[0050] Q_gas represents the real-time flow rate of the exhaust gas, measured in m³ / h. A higher exhaust gas flow rate indicates a greater demand for oxygen in the reaction. The data collection device is a pipe-type vortex flow meter / orifice plate flow meter, installed on the exhaust gas inlet main.

[0051] C_in represents the inlet H2S concentration, expressed in mg / m³. Higher H2S concentrations result in greater oxygen consumption during the oxidation reaction. An online hydrogen sulfide gas analyzer is used for data acquisition and is installed at the inlet of the first mixing tower 7.

[0052] Y_pid is a feedback adjustment amount based on the oxygen content deviation, used to eliminate steady-state error.

[0053] Y_pid = Y_lastpid + ΔY_pid, where Y_lastpid is the valve opening amount in the previous cycle and ΔY_pid is the change in valve opening amount.

[0054] ΔY_pid=K_p(e_k-e_k-1)+K_i×e_k+Kd(e_k-2e_k-1+e_k-2), where e_k is the deviation between the set value and the measured value of oxygen content, i.e., e_k=SP_O2-C_O2, SP_O2A=10% (set value of oxygen content), and C_O2 is the measured value of oxygen content;

[0055] The C_O2 oxygen content measurement equipment uses an online flue gas oxygen content analyzer (electrochemical / zirconia type), which is installed in the upper gas phase space of desulfurization tower 5.

[0056] e_k-1 is the oxygen content deviation of the previous control cycle, and e_k-2 is the oxygen content deviation of the control cycle before that.

[0057] Kp=2.0 (proportional coefficient) is used to quickly reduce oxygen content deviation and improve control response speed.

[0058] The value of Kp is determined using the "critical proportionality method": First, Ki and Kd are set to 0, and the value of Kp is gradually increased until the system exhibits constant amplitude oscillation. The critical proportionality coefficient Kp0 at this point is recorded. Then, based on the characteristics of the desulfurization system with large lag and strong interference, 0.45 times the critical proportionality coefficient is taken as the final value of Kp (i.e., Kp = 0.45 × Kp0). Experimental verification shows that when Kp = 2.0, the system responds fastest to oxygen content deviations without significant overshoot. This allows for rapid correction while avoiding system oscillations caused by overly sensitive adjustment.

[0059] Ki=0.1 (integral coefficient) is used to eliminate steady-state error and ensure that the oxygen content eventually returns to the 10% set value accurately, avoiding long-term deviation.

[0060] Ki is used to eliminate steady-state error in oxygen content. Its value is positively correlated with the proportional coefficient Kp and the system lag time. It is determined by "empirical formula + experimental optimization": First, the range of Ki (1.0 to 2.0) is initially calculated according to the empirical formula Ki = Kp / (0.5 to 1.0). Then, when the system is running stably, the value of Ki is gradually reduced and the change in steady-state deviation of oxygen content is observed. When Ki = 0.1, the system can eliminate steady-state deviation within 30 seconds without integral saturation. At the same time, it avoids oxygen content overshoot and increased fluctuation due to excessive integral action. Finally, Ki = 0.1 is determined.

[0061] Kd=0.05 (differential coefficient) is used to suppress oxygen content fluctuations, prevent overshoot, avoid sudden changes in oxygen content, and ensure control stability.

[0062] The differential coefficient Kd is used to suppress system oscillations and prevent overshoot. Its value is negatively correlated with the system response speed and is determined in combination with the characteristics of the desulfurization system: First, Kd = Kp × 0.025 (empirical ratio) is taken to obtain an initial value of 0.05; then, on-site commissioning is used for verification: under the conditions of fluctuating exhaust load and sudden changes in oxygen content, the system adjustment effect is observed. If overshoot occurs, Kd is increased; if response lag occurs, Kd is decreased. Finally, Kd = 0.05 is determined. At this time, the system can effectively suppress oxygen content fluctuations, with an overshoot of ≤5%, and the adjustment process is stable, which is suitable for the fluctuation characteristics of the system's operating conditions.

[0063] The final total valve opening Y_total is determined by the sum of the feedforward compensation opening Y_feed and the feedback adjustment Y_pid, in order to control the oxygen concentration.

[0064] The value of Y_total ranges from 0% to 100%, corresponding to the opening degree of the control valve 41.

[0065] The control valve 41 has a built-in valve position transmitter that provides real-time feedback on the actual valve opening. The data acquisition period is selected to be 2-5 seconds.

[0066] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A waste gas treatment system for molten sulfur residue, characterized in that, The system includes a residual liquid tank (2), a first mixing tower (7), an induced draft fan (4), and a desulfurization tower (5). The residual liquid tank (2) is used to hold molten sulfur residue. The residual liquid tank (2) and the first mixing tower (7) are connected by a pipeline to transport the molten sulfur residue to the first mixing tower (7). The first mixing tower (7) is supplied with waste gas (12) so that the waste gas (12) reacts with the molten sulfur residue to perform desulfurization. The desulfurization tower (5) contains molten sulfur residue. The induced draft fan (4) is connected to the first mixing tower (7) and the desulfurization tower (5) respectively. The induced draft fan (4) bubbles the waste gas (12) discharged from the first mixing tower (7) into the molten sulfur residue in the desulfurization tower (5). The induced draft fan (4) is connected to the atmosphere through a pipeline so that the waste gas (12) introduced into the desulfurization tower (5) is mixed with oxygen. The pipeline connected to the atmosphere is equipped with a regulating valve (41) to control the flow rate.

2. The sulfur molten residue waste gas treatment system according to claim 1, characterized in that, The desulfurization tower (5) is equipped with a spray assembly (52). The inlet end of the spray assembly (52) is connected to the molten sulfur residue of the desulfurization tower (5) through a pipeline. The molten sulfur residue of the desulfurization tower (5) is transported to the inlet end of the spray assembly (52) through the fifth pump body (51).

3. The sulfur molten residue waste gas treatment system according to claim 1, characterized in that, The residual liquid pool (2) is connected to a filter press (6) via a pipeline. The filter press (6) is used to perform solid-liquid separation on the incoming molten sulfur residual liquid. The liquid in the separated molten sulfur residual liquid flows back to the residual liquid pool (2).

4. The sulfur molten residue waste gas treatment system according to claim 3, characterized in that, The desulfurization tower (5) and the residual liquid pool (2) are connected by a pipeline. A sixth pump body (54) is installed in the pipeline between the desulfurization tower (5) and the residual liquid pool (2) to transport the molten sulfur residual liquid in the desulfurization tower (5) to the residual liquid pool (2).

5. The sulfur molten residue waste gas treatment system according to claim 1, characterized in that, The exhaust end of the first mixing tower (7) is connected to the second mixing tower (3) through a pipeline. The second mixing tower (3) is connected to the residual liquid pool (2) through a pipeline. The molten sulfur residual liquid is transported from the residual liquid pool (2) through the second mixing tower (3) and then to the first mixing tower (7). The exhaust end of the second mixing tower (3) is connected to the air inlet end of the induced draft fan (4) through a pipeline.

6. The sulfur molten residue waste gas treatment system according to claim 1, characterized in that, It also includes a cooling separator (1), which is used to condense and collect water vapor in the waste gas (12), and the waste gas (12) enters the first mixing tower (7) after passing through the cooling separator (1).

7. A method for treating residual sulfur molten liquid waste gas, using the residual sulfur molten liquid waste gas treatment system as described in claim 5, characterized in that, Includes the following steps: S1: Preprocessing: The waste gas (12) is dehydrated and then introduced into the first mixing tower (7); S2: Desulfurization ① The molten sulfur residue in the residual liquid pool (2) is transported to the first mixing tower (7), where the molten sulfur residue reacts with the waste gas (12) for the first desulfurization. ② The exhaust gas (12) discharged from the first mixing tower (7) enters the second mixing tower (3) to react with the molten sulfur residue in the second mixing tower (3) for a second desulfurization; ③ The exhaust gas (12) discharged from the second mixing tower (3) is mixed with oxygen and then passed into the molten sulfur residue of the desulfurization tower (5), and the molten sulfur residue overflows in a bubbling manner to carry out the third desulfurization; S3: The exhaust gas (12) after three desulfurization processes is discharged from the desulfurization tower (5).

8. The method for treating residual sulfur liquid waste gas according to claim 7, characterized in that, After the waste gas (12) is mixed with oxygen, its oxygen content is controlled at (8%–12% Vol).

9. The method for treating residual sulfur liquid waste gas according to claim 7, characterized in that, The opening degree of the regulating valve (41) is determined according to the value of the instruction Y_total, where Y_total = Y_feed + Y_pid; Where Y_feed = K_feed × Q_gas × C_in; K_feed is the feedforward coefficient, with a value ranging from 0.00025 to 0.0004; Q_gas is the real-time flow rate of exhaust gas; C_in represents the inlet H2S concentration; Y_pid = Y_lastpid + ΔY_pid; Y_lastpid represents the valve adjustment opening amount in the previous cycle; ΔY_pid represents the change in valve opening. ΔY_pid=K_p(e_k-e_k-1)+K_i×e_k+Kd(e_k-2e_k-1+e_k-2), where e_k is the deviation between the setpoint and the measured value of oxygen content, e_k-1 is the oxygen content deviation of the previous control cycle, e_k-2 is the oxygen content deviation of the control cycle before that, Kp=2.0, Ki=0.1, Kd=0.05.

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