Industrial furnace flue gas compound alkaline absorption liquid and desulfurization and dust removal synergistic treatment process thereof

Abstract

The present application relates to the technical field of industrial furnace flue gas wet purification, and discloses a two-component complex alkaline absorption liquid system and a desulfurization and dust removal synergistic treatment process thereof.The system comprises alkaline reserve liquid A and pre-sulfurous acidification buffer B which are separately arranged and supplied, and is matched with sodium gluconate to adjust the existing state of metal components in the circulating liquid.The flue gas is first subjected to primary wet scrubbing, dust removal and cooling, and then enters the secondary wet scrubbing section to contact the complex alkaline working absorption liquid for desulfurization.The addition amount of the alkaline reserve liquid A and the buffer B is respectively adjusted, the pH value, total alkalinity and sulfite content of the working absorption liquid are synergistically controlled, and the circulating liquid is partially replaced according to the proportion of sulfate.The present application is beneficial to improving the stability of desulfurization operation under the condition of flue gas load fluctuation, and takes into account dust capture, flue gas cooling and demisting treatment.

Description

Technical Field

[0001] This invention relates to the technical field of wet purification of flue gas from industrial furnaces and kilns, and in particular to a compound alkaline absorbent solution for flue gas from industrial furnaces and kilns and its synergistic desulfurization and dust removal process. Background Technology

[0002] Industrial furnaces and kilns generate flue gas containing sulfur dioxide and dust during smelting, roasting, melting, and heat treatment processes. Flue gas temperature, flow rate, dust concentration, and sulfur dioxide concentration typically fluctuate due to variations in furnace charge composition, feeding conditions, combustion conditions, and production cycle. Wet purification processes, by contacting the flue gas with a circulating liquid, can simultaneously achieve flue gas cooling, dust capture, and acid gas absorption, and are therefore widely used for flue gas purification in various industrial furnaces and kilns.

[0003] Sodium-based wet desulfurization typically uses sodium hydroxide, sodium carbonate, or alkaline liquids containing sulfites to absorb sulfur dioxide from flue gas. After sulfur dioxide enters the liquid phase, it forms sulfite and bisulfite ions depending on the acidity or alkalinity of the circulating liquid. The proportions of these sulfur-containing forms in the circulating liquid vary with flue gas load, liquid phase pH, oxidation level, and circulation time. Under oxygen-containing conditions, sulfite and bisulfite ions can further convert to sulfate ions, gradually reducing the amount of sulfur-containing components in the circulating liquid that can continue to participate in sulfur dioxide absorption and equilibrium regulation.

[0004] Chinese patent CN102049186B discloses a method for high-concentration flue gas desulfurization. Before employing the sodium sulfite method for desulfurization, the flue gas undergoes deoxygenation treatment to reduce the impact of sulfite oxidation on subsequent desulfurization and the quality of byproducts. The patent also points out that once sodium sulfate accumulates to a certain level in the circulating absorbent, even if the absorbent still has a high pH value, the sulfur dioxide absorption efficiency may significantly decrease.

[0005] Chinese patent CN109316964A discloses a method for recovering sodium sulfite from catalytic cracking flue gas desulfurization. This method reduces the oxidation level of sodium sulfite by controlling the concentration of the circulating slurry and adding an oxidation inhibitor selected from hydroquinone, p-phenylenediamine, tea polyphenols, and ascorbic acid to the circulating slurry. The technology primarily focuses on the recovery and purity control of sodium sulfite products.

[0006] Existing sodium-alkali wet desulfurization systems typically use the pH value of the circulating absorbent as the primary basis for alkali replenishment and operational adjustments. However, pH value mainly reflects the acid-base state of the liquid phase at that time and cannot independently and completely reflect the compositional changes among sulfite, bisulfite, and sulfate ions. Under conditions of continuous fluctuations in industrial furnace flue gas load and the continuous entry of dust and its carried metal components into the circulating liquid, the conversion rate of sulfur-containing components in the circulating liquid may not be consistent with the rate of alkalinity change. Therefore, it is possible that the pH value of the circulating liquid remains within the set range, while the effective sulfur-containing absorbent components have already undergone significant changes.

[0007] Therefore, the existing technology still needs to solve the problem of how to keep the alkalinity of the circulating absorbent in a controllable correspondence with the effective sulfur-containing absorbent state under the conditions of flue gas load fluctuations in industrial furnaces and kilns and continuous entry of dust components into the circulating liquid, so as to reduce the problem of the apparent acid-base state of the absorbent being normal but the actual desulfurization capacity fluctuating when only pH value is used as the main basis for adding alkali. Summary of the Invention

[0008] The purpose of this invention is to overcome the problems in existing wet desulfurization processes for industrial furnace flue gas, such as the limited adaptability of a single alkali replenishment method to fluctuations in flue gas sulfur dioxide load, the difficulty in coordinating the pH value and sulfur content of the circulating absorbent, the susceptibility of sulfites to oxidation and loss due to the influence of metal components in the flue gas and circulating liquid, and the interference of high-temperature dusty flue gas on the stability of subsequent desulfurization. This invention provides a two-component compound alkaline absorbent system for industrial furnace flue gas desulfurization and its desulfurization and dust removal synergistic treatment process. This system ensures that alkalinity replenishment, sulfite buffering, metal ion complexation, and circulating liquid composition adjustment each have controllable supply paths, improving the stability of the compound alkaline working absorbent composition and desulfurization operation under flue gas load variations, and achieving graded synergistic treatment of flue gas cooling, dust collection, and sulfur dioxide absorption.

[0009] To achieve the above objectives, the first aspect of the present invention provides a compound alkaline absorbent for industrial furnace flue gas, comprising an alkaline stock solution A and a presulfite buffer solution B, which are separately disposed and supplied to each other, as well as a sodium gluconate component.

[0010] The alkali stock solution A contains sodium hydroxide, sodium carbonate, and water. Based on sodium hydroxide equivalents, the alkalinity provided by the sodium hydroxide accounts for 10% to 30% of the initial total alkalinity of the alkali stock solution A, and the alkalinity provided by the sodium carbonate accounts for 70% to 90% of the initial total alkalinity of the alkali stock solution A. Specifically, 1 mol of sodium carbonate is equivalent to 2 mol of sodium hydroxide.

[0011] The presulfite buffer B is prepared by reacting a portion of the alkaline stock solution A with sulfur dioxide-containing gas through a gas-liquid contact reaction. The pH value of the presulfite buffer B is 7.0 to 7.6, and the molar ratio of sulfite to bisulfite in the presulfite buffer B is 0.5 to 2.5.

[0012] The sodium gluconate component is pre-contained in at least one of the alkaline stock solution A and the presulfite buffer solution B, or is provided as a separate additive.

[0013] The alkaline stock solution A, presulfite buffer solution B, and sodium gluconate component are respectively supplied to the flue gas wet desulfurization circulating liquid to form a compound alkaline working absorbent. The compound alkaline working absorbent has a pH of 7.4 to 8.2, a total alkalinity of 0.12 to 0.35 mol sodium hydroxide equivalents / L, a combined concentration of sulfite and bisulfite of 0.02 to 0.10 mol / L, and a sodium gluconate concentration of 0.08 to 0.50 g / L.

[0014] Sodium hydroxide in alkali stock solution A provides a relatively quick alkalinity replenishment, while sodium carbonate constitutes a higher proportion of the alkalinity reserve. By limiting the alkalinity of sodium hydroxide and sodium carbonate within the aforementioned ratio range, alkali stock solution A can provide alkalinity response when the flue gas sulfur dioxide load or the outlet sulfur dioxide concentration increases, while also maintaining continuous neutralization capacity using the carbonate system. This reduces the risk of rapid local pH increases and excessively rapid changes in circulating liquid alkalinity when relying solely on a single strong alkali replenishment.

[0015] Presulfite buffer B is not added directly to the circulating solution as unreacted alkali. Instead, a portion of the alkali stock solution A first absorbs sulfur dioxide, forming a liquid phase system in which sulfite and bisulfite coexist. When the pH is 7.0–7.6 and the molar ratio of sulfite to bisulfite is 0.5–2.5, presulfite buffer B can be continuously added to the circulating solution at a pH close to that of the compound alkaline working absorbent, replenishing the circulating solution with sulfur-containing buffer components. The alkali stock solution A and presulfite buffer B are set up and supplied separately, allowing for independent adjustment of the added alkalinity and sulfite buffer volume. This eliminates the need for coordinated adjustment of the pH, total alkalinity, and combined concentration of sulfite and bisulfite in the compound alkaline working absorbent using only a single alkali stream.

[0016] After sodium gluconate enters the compound alkaline working absorbent, the gluconate ions can form complexes with dissolved iron, copper, and manganese in the circulating liquid, reducing the extent to which these metal components participate in the sulfite oxidation process in free or readily reactive forms. Therefore, the alkalinity provided by the alkaline stock solution A, the sulfur-containing buffer component provided by the pre-sulfite buffer solution B, and the metal component complexation conditions provided by sodium gluconate work together to maintain the effective content of sulfite and bisulfite ions in the working absorbent, and to keep the working absorbent in a liquid phase composition suitable for continuous sulfur dioxide absorption.

[0017] Preferably, based on sodium hydroxide equivalent, the alkalinity provided by the sodium hydroxide accounts for 15% to 25% of the initial total alkalinity of the alkaline stock solution A, and the alkalinity provided by the sodium carbonate accounts for 75% to 85% of the initial total alkalinity of the alkaline stock solution A; the pH value of the presulfite buffer solution B is 7.1 to 7.5; the pH value of the compound alkaline working absorbent solution is 7.5 to 8.0, and the concentration of sodium gluconate is 0.12 to 0.35 g / L.

[0018] Within the aforementioned preferred range, the ratio of rapid alkalinity to reserve alkalinity in the alkaline stock solution A is further concentrated, the pH ranges between the presulfonated buffer solution B and the compound alkaline working absorbent are interconnected, and the sodium gluconate is maintained within a range suitable for participating in the complexation of metal components without excessively increasing the concentration of soluble components in the working absorbent, thereby facilitating the formation of a relatively stable coordination relationship between alkalinity replenishment, buffer component replenishment, and metal component complexation.

[0019] Preferably, the molar ratio of gluconate to dissolved iron, copper and manganese in the compound alkaline working absorbent is 1.0 to 4.0:1; the content of dissolved iron, copper and manganese is the value obtained by detecting the content of iron, copper and manganese in the filtrate after filtering the compound alkaline working absorbent through a filter membrane with a pore size of 0.45 μm.

[0020] Using the filtrate filtered through a 0.45 μm membrane as the target for detecting dissolved iron, copper, and manganese, a correlation can be established between the amount of sodium gluconate added and the content of metal components in the working absorbent that can migrate with the liquid phase and participate in the reaction. Limiting the molar ratio of gluconate to the total amount of dissolved iron, copper, and manganese to 1.0–4.0:1 ensures that the gluconate content relative to the metal components to be complexed maintains a suitable molar ratio. This improves the targeting of sodium gluconate addition and avoids situations where fixed addition based on the circulating liquid volume fails to adapt to changes in metal component content.

[0021] Preferably, the molar amount of sulfate in the presulfite buffer B is no more than 15% of the total molar amount of sulfite, bisulfite, and sulfate; the molar amount of sulfate in the compound alkaline working absorbent is no more than 45% of the total molar amount of sulfite, bisulfite, and sulfate; and the molar ratio of sulfite to bisulfite in the compound alkaline working absorbent is 1.5 to 10.0.

[0022] Sulfate ions in the presulfite buffer B and the compound alkaline working absorbent can be formed by further oxidation of sulfite or bisulfite ions, or they can be introduced with flue gas dust, makeup water, the original circulating liquid of the system, or other sulfur-containing impurities. The contribution of each source to the sulfate content can vary under different raw material conditions and operating stages. This invention does not limit sulfate ions to originate solely from sulfite oxidation. Controlling the sulfate ion proportion in the presulfite buffer B to no more than 15% is beneficial for maintaining a state where sulfite and bisulfite ions coexist in the newly prepared presulfite buffer B. Controlling the sulfate ion proportion in the compound alkaline working absorbent to no more than 45%, and maintaining a molar ratio of sulfite to bisulfite of 1.5–10.0, is beneficial for controlling the composition ratio of each sulfur-containing component in the liquid phase based on actual detection results without distinguishing the specific source of sulfate ions, thus avoiding the situation where sulfate ions accumulate continuously and changes in the sulfur-containing component composition are masked simply by increasing alkalinity.

[0023] A second aspect of this invention provides a synergistic treatment process for desulfurization and dust removal of flue gas from industrial furnaces and kilns, comprising the following steps. The steps S1 to S5 below are used to distinguish different treatment and control processes. Except for explicitly stated material flow directions or conditional dependencies, they do not imply that each step must be completed sequentially in time: S1. Primary wet scrubbing treatment: The industrial furnace flue gas to be treated is introduced into the first wet scrubbing section, so that the industrial furnace flue gas to be treated is in gas-liquid contact with the first circulating scrubbing liquid to cool the flue gas and collect dust, thereby obtaining primary scrubbed flue gas; after the gas-liquid contact is completed, the first circulating scrubbing liquid is separated by gas and liquid and collected in the first circulating liquid collection area, and then recycled back to the first wet scrubbing section.

[0024] S2. Preparation of Alkali Stock Solution: Sodium hydroxide, sodium carbonate, and water are mixed to obtain alkali stock solution A. The alkalinity provided by the sodium hydroxide (based on sodium hydroxide equivalent) accounts for 10%–30% of the initial total alkalinity of alkali stock solution A, and the alkalinity provided by the sodium carbonate (based on sodium carbonate equivalent) accounts for 70%–90% of the initial total alkalinity of alkali stock solution A. 1 mol of sodium carbonate is equivalent to 2 mol of sodium hydroxide. During initial startup, alkali stock solution A is prepared in advance before the flue gas from the industrial furnace to be treated is introduced. During continuous operation, alkali stock solution A is replenished according to its consumption and reserves.

[0025] S3. Preparation of presulfitization buffer solution: A portion of the alkali stock solution A is continuously fed into the presulfitization preparation zone. A portion of the primary scrubbing flue gas is separated as a sulfur dioxide-containing bypass flue gas. The sulfur dioxide-containing bypass flue gas undergoes a gas-liquid contact reaction with the alkali stock solution A entering the presulfitization preparation zone until the pH value of the liquid phase reaches 7.0-7.6 and the molar ratio of sulfite to bisulfite in the liquid phase reaches 0.5-2.5, thus obtaining presulfitization buffer solution B. The bypass flue gas after the gas-liquid contact reaction is returned to the flue gas inlet of the second wet scrubbing section and combined with the primary scrubbing flue gas for further treatment.

[0026] S4. Secondary Wet Desulfurization Treatment: The primary scrubbing flue gas is introduced into the second wet scrubbing section, allowing it to come into gas-liquid contact with the second circulating liquid. After gas-liquid contact, the second circulating liquid undergoes gas-liquid separation and is collected in the second circulating liquid collection area before being recycled back to the second wet scrubbing section. Alkali reserve solution A (not yet in the pre-sulfonation preparation area) and pre-sulfonation buffer solution B are metered and added to the second circulating liquid, and sodium gluconate is added to form a compound alkaline working absorbent. The pH of the compound alkaline working absorbent is controlled at 7.4–8.2, the total alkalinity at 0.12–0.35 mol sodium hydroxide equivalent / L, the combined concentration of sulfite and bisulfite at 0.02–0.10 mol / L, and the concentration of sodium gluconate at 0.08–0.50 g / L.

[0027] S5. Absorbent Supply Adjustment: During the continuous introduction of the industrial furnace flue gas to be treated, the pre-sulfitization buffer solution B is continuously added to the second circulating liquid; the unit time addition flow rate of the alkali reserve solution A is adjusted according to the sulfur dioxide mass flow rate in the industrial furnace flue gas to be treated, the sulfur dioxide concentration in the flue gas at the outlet of the second wet scrubbing section, and the pH value of the compound alkaline working absorbent solution; the unit time addition flow rate of the pre-sulfitization buffer solution B is adjusted according to the total concentration of sulfite and bisulfite in the compound alkaline working absorbent solution.

[0028] During the initial system startup phase, S2 is implemented before flue gas is introduced to prepare the alkali reserve solution A required for startup. Simultaneously, the operating levels and circulation states of the first and second circulating scrubbing liquids are established. Sodium gluconate and alkali reserve solution A, used to establish the initial pH and total alkalinity, are added to the second circulating liquid. After the industrial furnace flue gas to be treated begins to flow in, S1 and S4 are initiated, causing the flue gas to pass through the first wet scrubbing section in the flow direction before entering the second wet scrubbing section. Before the first batch of presulfite buffer solution B reaches the specified pH value and sulfite to bisulfite molar ratio, the initial desulfurization conditions of the second circulating liquid are maintained by the alkali reserve solution A. After the first-stage scrubbing flue gas is formed, sulfur dioxide-containing bypass flue gas is separated and S3 is implemented. After the first batch of presulfite buffer solution B reaches the specified conditions, it is continuously added to the second circulating liquid, causing the second circulating liquid to enter the composition control state of the compound alkaline working absorbent.

[0029] During the stable flue gas operation phase, S1 and S4 are performed simultaneously and continuously, with the flue gas passing through the first and second wet scrubbing sections sequentially in both equipment and material flow directions. S3 runs in parallel with S1 and S4 to continuously prepare presulfite buffer solution B online. S5, as a feedback regulation process, is executed synchronously with S3 and S4 to adjust the addition flow rates of alkali stock solution A and presulfite buffer solution B in real time or periodically. S2 can either complete the preparation of the first batch of alkali stock solution A before startup or be implemented in parallel with S1, S3, S4, and S5 during continuous operation, depending on the storage and consumption levels. Therefore, S1 to S5 are not an intermittent sequential relationship where the next step begins only after the previous one is completed.

[0030] The above process utilizes a first wet scrubbing section to cool the flue gas and collect dust in the upward flow direction, followed by a second wet scrubbing section for sulfur dioxide absorption under a compound alkaline working absorbent solution. This separates the high temperature and high dust load from the subsequent desulfurization circulating liquid phase. Pre-sulfitization buffer solution B is prepared online using a portion of the sulfur dioxide from the first-stage scrubbing flue gas. The bypass flue gas after the reaction returns to the inlet of the second wet scrubbing section, thus forming a closed flue gas treatment path with the main flue gas desulfurization process. Alkali stock solution A is adjusted based on the flue gas sulfur dioxide load, outlet sulfur dioxide concentration, and working absorbent pH value. Pre-sulfitization buffer solution B is adjusted based on the combined concentration of sulfite and bisulfite in the working absorbent solution, thereby corresponding to the alkalinity and sulfur-containing buffer component requirements, respectively.

[0031] Preferably, the unit time volumetric flow rate of the alkali stock solution A delivered to the pre-sulfation preparation zone accounts for 20% to 45% of the total unit time supply volumetric flow rate of the alkali stock solution A; a stirring device is provided in the pre-sulfation preparation zone, and the average liquid phase residence time of the alkali stock solution A in the pre-sulfation preparation zone is 15 to 60 minutes; during the stable flue gas operation phase, the unit time volumetric flow rate ratio of the alkali stock solution A that has not entered the pre-sulfation preparation zone to the pre-sulfation buffer solution B when it is added to the second circulating liquid is 55:45 to 80:20; the total average residence time of the pre-sulfation buffer solution B in the pre-sulfation preparation zone, buffer zone, and delivery pipeline does not exceed 4 hours, and no aeration step using air as a gas source is set in the preparation, buffering, and delivery process of the pre-sulfation buffer solution B.

[0032] 20%–45% of the alkali stock solution A is used to prepare presulfite buffer solution B, allowing the remaining alkali stock solution A to still be used as a direct alkalinity supplement. A liquid-phase average residence time of 15–60 min, combined with a stirring device, provides the necessary conditions for gas-liquid contact between the alkali stock solution A and the bypass flue gas to achieve the target pH value and sulfite / bisulfite ratio. Limiting the total average residence time of presulfite buffer solution B from preparation to delivery to within 4 hours and eliminating the aeration step using air as a gas source reduces the chance of further oxidation due to prolonged contact with oxygen-containing gas before the addition of the second circulating solution, thus helping to maintain its sulfite and bisulfite composition.

[0033] Preferably, the arithmetic mean of the sulfur dioxide concentration in the flue gas of the industrial furnace to be treated, measured within 10 consecutive minutes prior to the current detection time, is used as the baseline concentration.

[0034] When the sulfur dioxide concentration in the flue gas from the industrial furnace to be treated, as currently detected, increases by more than 20% relative to the baseline concentration, or when the sulfur dioxide concentration in the flue gas at the outlet of the second wet scrubbing section exceeds 40 mg / Nm³, the situation is considered as follows: 3 At that time, the flow rate of the alkaline stock solution A added per unit time is increased by 10% to 25% relative to the flow rate added per unit time before adjustment, while maintaining or increasing the flow rate of the presulfite buffer solution B added per unit time.

[0035] When the sulfur dioxide concentration in the flue gas from the industrial furnace to be treated, as currently detected, decreases by more than 20% relative to the baseline concentration, and the sulfur dioxide concentration in the flue gas at the outlet of the second wet scrubbing section is less than 20 mg / Nm³, 3At this time, the unit time addition flow rate of the alkali stock solution A is reduced by 10% to 25% relative to the unit time addition flow rate before adjustment, while the presulfonation buffer solution B is continuously added; the adjustment of the unit time addition flow rate of the alkali stock solution A continues until the sulfur dioxide concentration in the flue gas at the outlet of the second wet scrubbing section recovers to 20 to 40 mg / Nm³. 3 .

[0036] Using the average sulfur dioxide concentration over the previous 10 minutes as a dynamic baseline, the current concentration change can be compared with the recent stable load. When the inlet sulfur dioxide concentration increases significantly or the outlet concentration exceeds the upper limit, the flow rate of alkali stock solution A is increased first to replenish alkalinity; when the inlet load decreases significantly and the outlet concentration is below the lower limit, the flow rate of alkali stock solution A is reduced to minimize unnecessary alkalinity accumulation. Presulfite buffer B is continuously added under both adjustment conditions, ensuring a continuous supply of buffer components in the working absorbent while the alkalinity supply changes with the load. This reduces fluctuations in liquid phase composition caused by relying solely on the start-stop adjustment of alkali stock solution A during load switching.

[0037] Preferably, ethylene oxide-propylene oxide block polyether is added to the first circulating washing liquid as a low-foaming wetting component; the concentration of ethylene oxide-propylene oxide block polyether in the first circulating washing liquid is 5-40 mg / L, and the surface tension of the first circulating washing liquid at 25°C is 45-58 mN / m.

[0038] Ethylene oxide-propylene oxide block polyether, at the above concentration, is used to adjust the wetting properties of the first circulating washing liquid, enabling it to more fully contact the dust particles carried by the flue gas and promote particle entry into the liquid phase, while maintaining a low-foaming state suitable for circulating spraying. Limiting the surface tension of the first circulating washing liquid to 45–58 mN / m helps to achieve a balance between enhancing dust wetting and capture and avoiding excessive foam formation during circulating washing, thereby reducing the dust load entering the second wet washing section.

[0039] Preferably, the contents of sulfite, bisulfite and sulfate in the compound alkaline working absorbent are detected separately, and the molar amount of sulfate is calculated as a percentage of the total molar amount of sulfite, bisulfite and sulfate.

[0040] When the proportion of sulfate molar amount to the total molar amount is higher than 45% and the pH value of the compound alkaline working absorbent is not lower than 7.4, the second circulating liquid is partially replaced. Each time, 5% to 20% of the second circulating liquid is partially replaced, and the presulfite buffer solution B and water are added. The alkaline reserve solution A is added in the amount required to maintain the operating liquid level, pH value and total alkalinity of the second circulating liquid until the proportion of sulfate molar amount to the total molar amount is reduced to below 45%.

[0041] During the partial replacement process, increasing the unit time addition flow rate of the alkali stock solution A is not used as a control measure to reduce the proportion of sulfate molar amount.

[0042] When the pH of the working absorbent is still not lower than 7.4 but the sulfate ratio is already higher than 45%, regardless of whether the sulfate is formed by the oxidation of sulfite or introduced by flue gas dust, makeup water, the original circulating liquid of the system, or other sulfur-containing impurities, the liquid phase control target is the detected sulfate accumulation and the resulting change in the proportion of sulfur-containing components, rather than making a single judgment on the source of sulfate. At this time, draining 5% to 20% of the second circulating liquid and adding pre-sulfitization buffer B, water, and alkali reserve solution A required to maintain liquid level, pH value, and total alkalinity can reduce the proportion of sulfate in sulfur-containing components and restore the compositional relationship between sulfite, bisulfite, and sulfate. Limiting the use of simply increasing the flow rate of alkali reserve solution A as a control measure to reduce the sulfate ratio can avoid temporarily masking the imbalance of sulfur-containing components by only raising the pH value when sulfate has not been removed.

[0043] Preferably, the temperature of the industrial furnace flue gas to be treated before entering the first wet scrubbing section is 80–140°C, and the dust concentration is 500–3500 mg / Nm³. 3 The concentration of sulfur dioxide is 50–1000 mg / Nm³. 3 .

[0044] Both the first and second wet scrubbing sections employ a reverse-jet turbulent scrubbing method. The first and second circulating scrubbing liquids are injected into their respective wet scrubbing sections in directions opposite to the flow direction of the corresponding flue gas. The liquid-to-gas ratios of the first and second wet scrubbing sections are 4.0–7.0 L / Nm³, respectively. 3 The pH value of the first circulating washing liquid, which is collected in the first circulating liquid collection area and circulated back to the first wet washing section, is 6.3 to 7.1.

[0045] The flue gas after being treated by the second wet scrubbing section is cooled to 45-55°C, causing some of the water vapor in the flue gas to condense. The cooled flue gas is then demisted before being discharged.

[0046] For industrial furnace flue gas within the aforementioned temperature, dust concentration, and sulfur dioxide concentration range, a two-stage counter-current turbulent scrubbing process enhances the contact between the flue gas and the circulating liquid through reverse gas-liquid contact. The first circulating scrubbing liquid maintains a pH of 6.3–7.1, allowing the primary wet scrubbing stage to mainly handle flue gas cooling and dust collection. The second wet scrubbing stage, under the composition control of the compounded alkaline working absorbent, further desulfurizes the flue gas. After the secondary treatment, the flue gas is cooled to 45–55°C, and some water vapor is converted into condensate. Further demisting reduces the liquid droplets carried in the discharged flue gas, thus sequentially connecting wet scrubbing, cooling and condensation, and gas-liquid separation.

[0047] The present invention, by adopting the above technical solution, has the following beneficial effects: (1) In this invention, the alkaline stock solution A containing sodium hydroxide and sodium carbonate and the presulfite buffer solution B are set up separately and supplied separately, so that the alkalinity replenishment and the sulfite buffer component replenishment have independent adjustment paths. Sodium hydroxide provides a faster alkalinity response, sodium carbonate provides a higher proportion of alkalinity reserve, and the presulfite buffer solution B is continuously replenished with sulfite and bisulfite ions under conditions close to the operating pH value of the working absorbent, which is beneficial to take into account the pH value, total alkalinity and sulfur-containing buffer component concentration of the working absorbent when the sulfur dioxide load changes.

[0048] (2) In this invention, an alkaline reserve solution A is prepared in advance before the first start-up, and a portion of the sulfur dioxide-containing bypass flue gas in the primary scrubbing flue gas is used to prepare a pre-sulfitization buffer solution B online after flue gas is introduced. During the stable flue gas operation phase, the online preparation of the primary wet scrubbing, secondary wet desulfurization, and pre-sulfitization buffer solution B, as well as the regulation of the absorbent supply, are carried out in parallel. Thus, the problem of no primary scrubbing flue gas available for pre-sulfitization during the first start-up is solved, and the buffer solution preparation process is seamlessly integrated with the continuous treatment process of the main flue gas.

[0049] (3) In this invention, the addition flow rate of the alkali reserve solution A is adjusted based on the inlet flue gas sulfur dioxide mass flow rate, the outlet flue gas sulfur dioxide concentration, and the working absorbent pH value, and the addition flow rate of the presulfite buffer solution B is adjusted based on the total concentration of sulfite and bisulfite. By separately adjusting the alkalinity requirement and the sulfur-containing buffer component requirement, the situation of excessive addition of alkali solution or insufficient replenishment of buffer components during flue gas load increases or decreases can be reduced, thereby improving the controllability of the working absorbent composition during continuous operation.

[0050] (4) This invention establishes the metal complexation conditions by adjusting the molar ratio between sodium gluconate and dissolved iron, copper, and manganese elements. It also reduces the chance of further oxidation of sulfite and bisulfite ions during preparation, transportation, and recycling by limiting the residence time of the pre-sulfite buffer B and eliminating air aeration. Simultaneously, it monitors the sulfate ratio in the liquid phase to comprehensively control sulfate ions formed by sulfite oxidation and those introduced from outside the system or from the existing liquid phase. This helps maintain the compositional relationship between sulfite, bisulfite, and sulfate ions in the working absorbent.

[0051] (5) In this invention, when the sulfate ratio is higher than 45% and the pH of the working absorbent is not lower than 7.4, the second circulating liquid is partially replaced, and it is explicitly stated that increasing the flow rate of the alkali reserve liquid A alone is not a measure to reduce the sulfate ratio. This control method does not rely on determining the specific source of sulfate, but rather updates the liquid phase based on the actual detected sulfate accumulation, avoiding the confusion between abnormal sulfur-containing component composition and simple alkalinity deficiency, thereby improving the correspondence between circulating liquid maintenance measures and the actual liquid phase state.

[0052] (6) This invention employs a first wet scrubbing section and a second wet scrubbing section for graded treatment. The first circulating scrubbing liquid first cools the high-temperature dust-laden flue gas and collects the dust, and then the compounded alkaline working absorbent liquid desulfurizes the first-stage scrubbing flue gas. The low-foaming wetting component in the first circulating scrubbing liquid can improve the contact between dust and scrubbing liquid, reduce the dust load entering the second wet scrubbing section, and thus reduce the interference of dust on the composition control of the second circulating liquid and the gas-liquid mass transfer process.

[0053] (7) The present invention cools the flue gas after secondary wet scrubbing to 45-55°C, so that some water vapor is condensed and then demisting is performed. The flue gas after desulfurization passes through cooling and condensation and droplet separation in sequence, which helps to reduce the water vapor load and droplet entrainment in the discharged flue gas, and makes the flue gas desulfurization, dust removal, cooling and demisting form a continuous synergistic treatment process. Detailed Implementation

[0054] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0055] Unless otherwise defined, the scientific and technical terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. "Continuous addition" as used in this invention refers to maintaining a continuous supply with a non-zero flow rate during the corresponding stable operation phase, allowing the metering pump to make small-amplitude frequency adjustments within the control cycle; "separate supply" refers to the alkaline stock solution A and the pre-sulfation buffer solution B entering the second circulating solution through independent storage units, metering units, or control loops, rather than being replaced by a method of pre-mixing the two completely and then supplying them with the same controlled quantity.

[0056] The sodium hydroxide, sodium carbonate, sodium gluconate, and ethylene oxide-propylene oxide block polyether used in the following examples are all commercially available; the process water is softened water or demineralized water. Unless otherwise specified, all liquid phase samples were immediately sealed, protected from light, and cooled to 4°C after sampling, and the sulfur-containing components were detected within 2 hours to reduce deviations caused by continued oxidation after sampling.

[0057] The present invention will now be described in conjunction with embodiments and comparative examples.

[0058] I. Detection Methods 1. Alkalinity Equivalent. Sodium hydroxide is calculated as 1 mol sodium hydroxide providing 1 mol sodium hydroxide equivalent, and sodium carbonate is calculated as 1 mol sodium carbonate providing 2 mol sodium hydroxide equivalent. The initial total alkalinity of alkali stock solution A is the ratio of the sum of the sodium hydroxide equivalents provided by both to the volume of alkali stock solution A. The total alkalinity of the compound alkaline working absorbent solution is determined by the endpoint method of titration to pH 4.5 with standard hydrochloric acid and is expressed as mol sodium hydroxide equivalents / L.

[0059] 2. Sulfur-containing components. Liquid samples were filtered through a 0.45 μm filter membrane. The total concentrations of sulfite and bisulfite were determined using iodometric titration calibrated with sulfite standard solution. The sulfate concentration was determined by ion chromatography. The molar ratio of sulfite to bisulfite was calculated based on the simultaneously measured pH value, test temperature, and the second-order dissociation equilibrium constant of sulfite at that temperature. The sulfate ratio was calculated as n(SO4) 2- ) / [n(SO3 2- )+n(HSO3 - )+n(SO4 2- )]×100% calculation.

[0060] 3. Metal elements and gluconate. After filtering the liquid sample through a 0.45 μm filter membrane, the concentrations of iron, copper, and manganese were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES) and converted to the total amount of the three elements. The concentration of gluconate was determined by ion chromatography or high-performance liquid chromatography (HPLC). The molar ratio of gluconate to dissolved iron, copper, and manganese was the ratio of the amount of gluconate to the total amount of the three elements.

[0061] 4. Flue gas indicators. Sulfur dioxide concentration was continuously measured using a non-dispersive infrared analyzer calibrated with zero gas and standard gas; dust concentration was measured using the isokinetic sampling-gravimetric method. Sulfur dioxide removal rate was calculated according to (C... in -C out ) / C in Calculated as ×100%, dust removal rate is based on (D) in -D out ) / D in Calculate by multiplying by 100%, where C in C out These represent the sulfur dioxide concentrations at the inlet and outlet of the second wet scrubbing section, respectively. in D out These are the dust concentrations at the inlet and outlet of the first wet scrubbing section, respectively.

[0062] 5. Liquid phase stability. Using a 2-hour evaluation window after stable flue gas flow, the pH value of the compound alkaline working absorbent was recorded every 1 minute, and the average value and standard deviation were calculated. The evaluation period was from the start of the load step until the outlet sulfur dioxide concentration returned to 20–40 mg / Nm³. 3 The recovery time is defined as 10 minutes. The sulfite retention rate is calculated as the ratio of the total S(IV) concentration at the end of the evaluation window to the total S(IV) concentration at the beginning of the window.

[0063] 6. Surface tension and foam. The surface tension of the first cycle of washing liquid was determined using the platinum plate method at 25°C. 500 mL of the circulating liquid was aerated at a fixed gas rate for 5 min, and the foam height was recorded. The residual foam height was recorded 1 min after aeration was stopped. These measurements were used to evaluate low-foaming wetting conditions.

[0064] II. Implementation Examples and Comparative Examples Example 1 This embodiment has a processing capacity of 1000 Nm. 3 The system was implemented on a pilot-scale system with a capacity of [number] h. The system comprises a first wet scrubbing section, a second wet scrubbing section, a flue gas cooling section, and a demisting section, connected sequentially. The first wet scrubbing section and the first circulating liquid collection area constitute the first cycle, and the second wet scrubbing section and the second circulating liquid collection area constitute the second cycle. The system also includes an alkali storage tank, a pre-sulfurization preparation tank, a buffer tank, three independent metering pumps, an online pH meter, a flue gas sulfur dioxide analyzer, a liquid phase sampling port, and a flow controller.

[0065] The specific steps are as follows: S1, Level 1 wet washing Ethylene oxide-propylene oxide block polyether was added to the first circulating liquid to a concentration of 20 mg / L, and the surface tension at 25°C was adjusted to 51 mN / m. The temperature was then set to 110°C, and the dust concentration was 2000 mg / Nm.3 The sulfur dioxide concentration was 500 mg / Nm³. 3 The flue gas to be treated is introduced into the first wet scrubbing section; a reverse jet turbulent scrubbing method is adopted, with a liquid-to-gas ratio of 5.5 L / Nm³. 3 The pH of the first-cycle scrubbing liquid is controlled at 6.7. After gas-liquid contact is completed, the first-cycle scrubbing liquid is collected and recycled after gas-liquid separation, and the primary scrubbing flue gas enters the second wet scrubbing section.

[0066] S2, Preparation of Alkali Stock Solution A Approximately 800 L of water was added to an alkali storage tank equipped with a stirrer. Under stirring, 16.00 kg of sodium hydroxide and 84.80 kg of anhydrous sodium carbonate were added sequentially. After dissolution and cooling to 25–30 °C, water was added to bring the total volume to 1000 L, yielding alkali stock solution A with an initial total alkalinity of 2.00 mol sodium hydroxide equivalents / L. Sodium hydroxide provided 0.40 mol / L alkalinity, accounting for 20% of the initial total alkalinity; sodium carbonate provided 1.60 mol sodium hydroxide equivalents / L alkalinity, accounting for 80% of the initial total alkalinity.

[0067] Online preparation of S3 and presulfite buffer B 32% of the total supply flow of alkali stock solution A is continuously fed into the pre-sulfitization mixing tank. A paddle agitator is installed in the mixing tank, and the average residence time of the liquid phase is 35 minutes. Sulfur dioxide-containing bypass flue gas is separated from the primary scrubbing flue gas and introduced through a microporous gas distributor at the bottom of the mixing tank, where it comes into counter-current contact with alkali stock solution A; the tail gas is returned to the inlet of the second wet scrubbing section. Through cascade adjustment of the bypass flue gas flow rate and the liquid phase flow rate, the pH of the liquid phase is controlled to 7.3, and the molar ratio of sulfite to bisulfite is controlled to 1.5, yielding pre-sulfitization buffer solution B. The total average residence time of buffer solution B from the mixing tank, buffer tank, to the second circulating liquid inlet is controlled to 2 hours; no air is introduced during preparation, buffering, and transportation.

[0068] S4, secondary wet desulfurization and absorption liquid composition establishment The second wet scrubbing section employs a reverse jet turbulent washing method with a liquid-to-gas ratio of 5.5 L / Nm³. 3 Before starting the system, establish the operating level and circulation flow rate of the second circulating solution. Add alkali stock solution A, pre-sulfite buffer solution B, and sodium gluconate independent additive solution sequentially to prepare the compound alkaline working absorbent with the following composition: pH 7.8, total alkalinity 0.22 mol sodium hydroxide equivalent / L, total sulfite and bisulfite concentration 0.06 mol / L, sodium gluconate concentration 0.25 g / L, and sulfite to bisulfite molar ratio 4.0. Based on the total amount of iron, copper, and manganese measured after filtration through a 0.45 μm filter membrane, adjust the amount of sodium gluconate to achieve a molar ratio of gluconate to the aforementioned metal elements of 2.5:1.

[0069] S5, Absorbent Liquid Supply Adjustment During stable operation, the volumetric flow rate ratio of alkali stock solution A (not entering the pre-sulfitization mixing tank) to pre-sulfitization buffer solution B entering the second circulation liquid is controlled at 68:32. Pre-sulfitization buffer solution B is continuously added; alkali stock solution A is adjusted according to the inlet flue gas sulfur dioxide mass flow rate, outlet sulfur dioxide concentration, and working absorbent pH; buffer solution B is adjusted according to the combined concentration of sulfite and bisulfite. The flue gas after the second wet scrubbing is cooled to 50°C, causing some water vapor to condense, and then discharged after removing entrained droplets through a demister.

[0070] Table 1. Benchmark Operation Settings and Test Records for Example 1

[0071] Example 1 was designed to run continuously for 24 hours after all set conditions reached stability. During operation, the cumulative usage of alkali stock solution A, buffer solution B, and sodium gluconate, flue gas inlet and outlet data, liquid phase composition, surface tension of the first cycle washing liquid, foam height, pressure drop, and condensate volume should be recorded.

[0072] Examples 2-32 Examples 2 through 32 are based on Example 1. Except for the differences listed in the table below, the raw materials, equipment, preparation steps, flue gas conditions, sampling methods, and detection methods are all the same as in Example 1. When a certain liquid phase parameter is changed, it is achieved by adjusting the corresponding material addition amount or the degree of contact of the bypass flue gas, while other controlled variables are kept near the set values ​​of Example 1.

[0073] Table 2 Specific settings of Examples 2-32

[0074] In Examples 2-5, the initial total alkalinity of the alkali stock solution A was maintained at 2.00 mol sodium hydroxide equivalent / L. For each example, 1000 L of alkali stock solution A was prepared first, and after cooling, the total alkalinity was measured and the equivalent ratio of the two alkali sources was verified. In Examples 6-11, the pH and sulfur-containing forms of buffer solution B were adjusted by bypass flue gas flow rate, gas-liquid contact degree, and liquid phase residence time. Since the molar ratio of sulfite to bisulfite is constrained by pH, temperature, and ionic strength, these two are not treated as completely independent control variables. Instead, the simultaneously measured pH and the calculated molar ratio are used to determine whether the conditions of the corresponding example are met. Air aeration is not used during the preparation process.

[0075] In Examples 20-23, before each addition of sodium gluconate, the second circulating solution sample was filtered through a 0.45 μm filter membrane and the contents of Fe, Cu, and Mn were measured; the amount of sodium gluconate to be added was calculated according to the target molar ratio. If the target concentration and the target molar ratio could not be met simultaneously, the corresponding metal levels were established by changing the batch of circulating solution containing different metal backgrounds or by adding a mixed standard working solution of iron, copper, and manganese of known concentration.

[0076] In Example 31, sodium gluconate was added and dissolved after the alkaline stock solution A was cooled to below 30°C; in Example 32, sodium gluconate was added after the buffer solution B left the gas-liquid contact zone and before entering the sealed buffer tank. Both methods ensured that the concentration of sodium gluconate in the working absorbent reached 0.25 g / L, and that the molar ratio of gluconate to dissolved metal elements was 2.5:1.

[0077] Example 33 This embodiment uses the system and process of Example 1. After stable operation for 30 minutes, the arithmetic mean of the inlet sulfur dioxide concentration over the previous 10 minutes is used as the baseline concentration C0. The inlet sulfur dioxide concentration is first reduced from 500 mg / Nm³. 3 Increased to 650 mg / Nm 3 The increase was 30%; the control system increased the flow rate of alkali stock solution A by 20% per unit time and maintained the continuous addition of buffer solution B. When the outlet sulfur dioxide concentration returned to 20–40 mg / Nm³... 3 The concentration was then stabilized for another 30 minutes. Subsequently, the inlet sulfur dioxide concentration was reduced to 350 mg / Nm³. 3 The decrease was 30%; when the sulfur dioxide concentration at exports was below 20 mg / Nm³. 3 At this time, reduce the flow rate of alkali stock solution A by 20% per unit time, and continue adding buffer B until the outlet concentration recovers to 20-40 mg / Nm³. 3 .

[0078] The inlet / outlet sulfur dioxide concentration, working absorbent pH, total alkalinity, total S(IV) concentration, instantaneous flow rates of A and B, and recovery time were recorded during the load increase and decrease phases, respectively. The recovery time for load increase was 14.7 min, the recovery time for load decrease was 11.2 min, the maximum pH deviation was 0.27, and the maximum deviation for total S(IV) concentration was 0.0068 mol / L.

[0079] Examples 34-35 Using the compound alkaline working absorbent solution of Example 1, the sulfate molar ratio of SO3 is adjusted by continuous operation or by adding a known amount of sodium sulfate. 2- HSO3 - and SO4 2-The total molar ratio reached 48%, while maintaining the pH at 7.8. In Example 34, 5% of the second circulating solution was discharged, and in Example 35, 20% was discharged; subsequently, buffer B and water were added, and alkali stock solution A was added according to the operating level, pH, and total alkalinity. Increasing the flow rate of A alone was not used as a measure to reduce the sulfate ratio during the replacement process. Monitoring continued until the sulfate ratio dropped below 45%.

[0080] Table 3 Replacement records of Examples 34-35

[0081] Comparative Example The following comparative examples are all based on Example 1, with only the difference conditions changed; the raw materials, equipment, flue gas conditions, circulating liquid volume, sampling methods and detection methods are the same as in Example 1 unless otherwise specified.

[0082] Table 4 Specific settings for Comparative Examples 1-10

[0083] III. Performance Index Test Results Examples 1-35 and Comparative Examples 1-10 were evaluated according to the aforementioned detection method. The test results are shown in the table below.

[0084] Table 5 Desulfurization and Dynamic Stability

[0085] Table 6 Dust removal, foaming, and operating resistance

[0086] Table 7 Sulfur-containing components and oxidation stability

[0087] Table 8. Chemical Consumption and Condensation Demisting

[0088] 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 compound alkaline absorbent solution for industrial furnace flue gas, characterized in that, It includes a separate alkaline stock solution A and a presulfite buffer solution B, which are set up and supplied separately, as well as a sodium gluconate component; The alkaline stock solution A contains sodium hydroxide, sodium carbonate and water. The alkalinity provided by the sodium hydroxide accounts for 10% to 30% of the initial total alkalinity of the alkaline stock solution A, based on the sodium hydroxide equivalent. The presulfite buffer B is prepared by reacting a portion of the alkaline stock solution A with sulfur dioxide-containing gas through a gas-liquid contact reaction. The pH value of the presulfite buffer B is 7.0 to 7.6, and the molar ratio of sulfite to bisulfite in the presulfite buffer B is 0.5 to 2.

5. The sodium gluconate component is pre-contained in at least one of the alkaline stock solution A and the presulfite buffer solution B, or is provided as a separate addition solution; The alkaline stock solution A, presulfite buffer solution B, and sodium gluconate component are respectively supplied to the flue gas wet desulfurization circulating liquid to form a compound alkaline working absorbent. The compound alkaline working absorbent has a pH of 7.4 to 8.2, a total alkalinity of 0.12 to 0.35 mol sodium hydroxide equivalents / L, a total concentration of sulfite and bisulfite of 0.02 to 0.10 mol / L, and a sodium gluconate concentration of 0.08 to 0.50 g / L. 1 mol of sodium carbonate is equivalent to 2 mol of sodium hydroxide.

2. The compound alkaline absorbent liquid for industrial furnace flue gas according to claim 1, characterized in that, Based on sodium hydroxide equivalent, the alkalinity provided by the sodium hydroxide accounts for 15% to 25% of the initial total alkalinity of the alkali stock solution A, and the alkalinity provided by the sodium carbonate accounts for 75% to 85% of the initial total alkalinity of the alkali stock solution A. The pH value of the presulfite buffer B is 7.1–7.5; The pH value of the compound alkaline working absorbent is 7.5-8.0, and the concentration of sodium gluconate is 0.12-0.35 g / L.

3. The compound alkaline absorbent liquid for industrial furnace flue gas according to claim 1, characterized in that, The total molar ratio of gluconate to dissolved iron, copper and manganese in the compound alkaline working absorbent solution is 1.0 to 4.0:

1. The content of dissolved iron, copper and manganese elements is the value obtained by detecting the content of iron, copper and manganese elements in the filtrate after filtering the compound alkaline working absorption solution through a filter membrane with a pore size of 0.45 μm.

4. The compound alkaline absorbent liquid for industrial furnace flue gas according to claim 1, characterized in that, The proportion of sulfate molar in the presulfite buffer B to the total molar amount of sulfite, bisulfite and sulfate is no more than 15%. The proportion of sulfate molar in the compound alkaline working absorbent solution to the total molar amount of sulfite, bisulfite and sulfate is not higher than 45%, and the molar ratio of sulfite to bisulfite in the compound alkaline working absorbent solution is 1.5 to 10.

5. A process for the synergistic treatment of industrial furnace flue gas desulfurization and dust removal using a compound alkaline absorbent solution as described in any one of claims 1 to 4, characterized in that, Includes the following steps: S1. Primary wet scrubbing treatment: The industrial furnace flue gas to be treated is introduced into the first wet scrubbing section, so that the industrial furnace flue gas to be treated is in gas-liquid contact with the first circulating scrubbing liquid to cool the flue gas and collect dust, thus obtaining primary scrubbed flue gas; after the gas-liquid contact is completed, the first circulating scrubbing liquid is separated by gas and liquid and collected in the first circulating liquid collection area, and then recycled back to the first wet scrubbing section. S2. Preparation of alkaline stock solution: Sodium hydroxide, sodium carbonate and water are mixed to obtain alkaline stock solution A; S3. Preparation of presulfitization buffer solution: A portion of the alkali stock solution A is continuously fed into the presulfitization preparation zone. A portion of the primary scrubbing flue gas is separated as a sulfur dioxide-containing bypass flue gas. The sulfur dioxide-containing bypass flue gas undergoes a gas-liquid contact reaction with the alkali stock solution A entering the presulfitization preparation zone until the pH value of the liquid phase reaches 7.0-7.6 and the molar ratio of sulfite to bisulfite in the liquid phase reaches 0.5-2.5, resulting in presulfitization buffer solution B. The bypass flue gas after the gas-liquid contact reaction is returned to the flue gas inlet of the second wet scrubbing section and combined with the primary scrubbing flue gas for further treatment. S4. Secondary wet desulfurization treatment: The primary scrubbing flue gas is introduced into the second wet scrubbing section, so that the primary scrubbing flue gas and the second circulating liquid can make gas-liquid contact; after the gas-liquid contact is completed, the second circulating liquid is separated by gas and liquid and collected in the second circulating liquid collection area, and then recycled back to the second wet scrubbing section. The alkaline stock solution A, which has not entered the presulfonation preparation zone, and the presulfonation buffer solution B are metered and added to the second circulating solution, and sodium gluconate is added to the second circulating solution to form a compound alkaline working absorbent solution. S5. Absorbent supply adjustment: During the continuous introduction of the flue gas from the industrial furnace to be treated, the presulfite buffer solution B is continuously added to the second circulating liquid; The flow rate of the alkali reserve solution A is adjusted according to the mass flow rate of sulfur dioxide in the flue gas of the industrial furnace to be treated, the concentration of sulfur dioxide in the flue gas at the outlet of the second wet scrubbing section, and the pH value of the compound alkaline working absorbent. The flow rate of the presulfite buffer B added per unit time is adjusted according to the total concentration of sulfite and bisulfite in the compound alkaline working absorbent solution.

6. The industrial furnace flue gas desulfurization and dust removal co-treatment process according to claim 5, characterized in that, The volumetric flow rate of alkali stock solution A delivered to the pre-sulfatation preparation zone accounts for 20% to 45% of the total supply volumetric flow rate of alkali stock solution A per unit time. A stirring device is provided in the pre-sulfation preparation zone, and the average residence time of the alkali stock solution A in the pre-sulfation preparation zone is 15 to 60 minutes. During the stable flue gas operation phase, the ratio of the volumetric flow rate per unit time of the alkali reserve solution A (which has not entered the pre-sulfonation preparation zone) to the pre-sulfonation buffer solution B when added to the second circulating liquid is 55:45 to 80:

20. The total average residence time of the presulfonation buffer solution B in the presulfonation preparation area, buffer zone and delivery pipeline does not exceed 4 hours, and no aeration step using air as a gas source is set in the preparation, buffering and delivery process of the presulfonation buffer solution B.

7. The industrial furnace flue gas desulfurization and dust removal co-treatment process according to claim 5, characterized in that, The arithmetic mean of the sulfur dioxide concentration in the flue gas of the industrial furnace to be treated, measured within 10 consecutive minutes prior to the current detection time, is used as the baseline concentration. When the sulfur dioxide concentration in the flue gas from the industrial furnace to be treated, as currently detected, increases by more than 20% relative to the baseline concentration, or when the sulfur dioxide concentration in the flue gas at the outlet of the second wet scrubbing section exceeds 40 mg / Nm³, the situation is considered to be inappropriate. 3 At that time, the flow rate of the alkaline stock solution A added per unit time is increased by 10% to 25% relative to the flow rate added per unit time before adjustment, and the flow rate of the presulfite buffer solution B added per unit time is maintained or increased. When the sulfur dioxide concentration in the flue gas from the industrial furnace to be treated, as currently detected, decreases by more than 20% relative to the baseline concentration, and the sulfur dioxide concentration in the flue gas at the outlet of the second wet scrubbing section is less than 20 mg / Nm³, 3 At that time, the flow rate of the alkaline stock solution A added per unit time is reduced by 10% to 25% relative to the flow rate added per unit time before adjustment, while the presulfite buffer solution B is continuously added; The rate of addition of the alkaline stock solution A per unit time is adjusted until the sulfur dioxide concentration in the flue gas at the outlet of the second wet scrubbing section recovers to 20–40 mg / Nm³. 3 .

8. The industrial furnace flue gas desulfurization and dust removal co-treatment process according to claim 5, characterized in that, Ethylene oxide-propylene oxide block polyether is added to the first circulating washing liquid as a low-foaming wetting component; The concentration of ethylene oxide-propylene oxide block polyether in the first circulating washing solution is 5-40 mg / L, and the surface tension of the first circulating washing solution at 25°C is 45-58 mN / m.

9. The industrial furnace flue gas desulfurization and dust removal co-treatment process according to claim 5, characterized in that, The contents of sulfite, bisulfite and sulfate in the compound alkaline working absorbent were detected respectively, and the molar amount of sulfate was calculated as a percentage of the total molar amount of sulfite, bisulfite and sulfate. When the proportion of sulfate molar amount to the total molar amount is higher than 45% and the pH value of the compound alkaline working absorbent is not lower than 7.4, the second circulating liquid is partially replaced. Each time, 5% to 20% of the second circulating liquid is partially replaced and the presulfite buffer solution B and water are added. The amount of alkaline reserve solution A is added according to the amount required to maintain the operating liquid level, pH value and total alkalinity of the second circulating liquid until the proportion of sulfate molar amount to the total molar amount is reduced to below 45%. During the partial replacement process, increasing the unit time addition flow rate of the alkali stock solution A is not used as a control measure to reduce the proportion of sulfate molar amount.

10. The industrial furnace flue gas desulfurization and dust removal co-treatment process according to claim 5, characterized in that, The temperature of the industrial furnace flue gas to be treated before entering the first wet scrubbing section is 80-140℃, and the dust concentration is 500-3500 mg / Nm³. 3 The concentration of sulfur dioxide is 50–1000 mg / Nm³. 3 ; Both the first and second wet scrubbing sections employ a reverse-jet turbulent scrubbing method. The first and second circulating scrubbing liquids are injected into their respective wet scrubbing sections in directions opposite to the flow direction of the corresponding flue gas. The liquid-to-gas ratios of the first and second wet scrubbing sections are 4.0–7.0 L / Nm³, respectively. 3 ; The pH value of the first circulating washing liquid, which is collected in the first circulating liquid collection area and circulated back to the first wet washing section, is 6.3 to 7.

1. The flue gas after being treated by the second wet scrubbing section is cooled to 45-55°C, causing some of the water vapor in the flue gas to condense. The cooled flue gas is then demisted before being discharged.

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