Process for co-processing of lead smelting off-gas, acid and desulfurization

Abstract

This invention discloses a co-process for acid production and desulfurization of lead smelting flue gas, belonging to the field of non-ferrous metallurgical flue gas purification and resource utilization. The process includes: purifying and deeply removing mercury from high-concentration sulfur-containing flue gas from an Osmet oxygen-enriched top-blown furnace to obtain purified flue gas; desorbing low-concentration sulfur-containing flue gas from a reduction furnace and a fuming furnace using an ion-liquid desulfurization system to obtain high-concentration SO2 regenerated flue gas; mixing the two flue gas, drying them, and then performing a two-stage conversion and two-stage absorption process to produce acid, with the flue gas being diverted before the intermediate absorption tower and washed with nicotine acid to produce analytical-grade sulfuric acid; the tail gas is absorbed by a circulating liquid spray, and the circulating liquid is cooled and reused to control the plume. This invention eliminates white plumes without sacrificing desulfurization efficiency by upgrading the existing ion-liquid desulfurization system at low cost, performing co-processing of flue gas based on different gas types, performing low-temperature deep mercury removal, and coupling hydrogen peroxide tail absorption with circulating liquid cooling. The total SO2 conversion rate can reach over 99.97%, and the SO2 tail gas emission does not exceed 400 mg / Nm³. 3 It is characterized by high efficiency, cleanliness, high resource utilization, and high economic benefits.

Description

Technical Field

[0001] This invention belongs to the field of non-ferrous metallurgical flue gas purification and resource utilization technology, specifically involving a synergistic treatment process for acid production and desulfurization of lead smelting flue gas. Background Technology

[0002] During lead smelting, the Osmet oxygen-enriched top-blown furnace, reduction furnace, and fuming furnace generate large amounts of SO2-containing flue gas. In traditional treatment methods, high-concentration SO2 flue gas is fed into the acid production system to produce industrial sulfuric acid. Low-concentration SO2 flue gas (such as that from the reduction furnace and fuming furnace) is not economically viable for direct acid production, and traditional processes only perform desulfurization treatment before emission, resulting in a waste of sulfur resources. Furthermore, with the technological upgrading and transformation of the smelting system, the composition, flow rate, and SO2 concentration of the flue gas have changed significantly. The original ion-liquid desulfurization system is unable to match the new operating conditions, revealing problems such as low conversion rate, high acid mist, excessive mercury, and significant plume. A complete replacement of the absorption tower, regeneration tower, and other main equipment is required to meet the new requirements.

[0003] Existing mercury removal technologies typically utilize condensation to capture liquid mercury. However, the residual mercury content in the flue gas remains high after removal, failing to provide sufficiently clean flue gas feedstock for the production of chemical reagent-grade sulfuric acid. Further deep mercury removal often requires additional processes such as chemical spraying, resulting in high operating costs and the potential introduction of new impurities. In the tail gas desulfurization stage, some processes employ hydrogen peroxide absorption for deep removal of residual SO2. However, in winter or at low ambient temperatures, saturated wet flue gas easily condenses into a white plume upon entering the atmosphere. To eliminate the plume, the exhaust temperature needs to be lowered to reduce water vapor content. However, excessive cooling inhibits the reaction rate of hydrogen peroxide oxidation of SO2, leading to decreased desulfurization efficiency or increased energy consumption, making it difficult to balance desulfurization efficiency with plume control.

[0004] Therefore, developing an acid production and desulfurization process that can adapt to multiple flue gas sources, co-produce high-purity sulfuric acid, and balance desulfurization efficiency with plume control, and adapt to new operating conditions, has significant practical importance and application value. Summary of the Invention

[0005] To address the shortcomings of existing lead smelting flue gas treatment processes after technological upgrades, the present invention aims to provide a synergistic treatment process for lead smelting flue gas acid production and desulfurization, comprising the following steps: (1) The high-concentration SO2 flue gas generated by the Osmet oxygen-enriched top-blown furnace is sent into the acid production system and successively passes through a first-stage high-efficiency scrubbing tower, a gas cooling tower, a second-stage high-efficiency scrubbing tower, a cooling mercury removal tower, and a two-stage electrostatic precipitator for purification and cooling to obtain purified flue gas; (2) The low-concentration SO2 flue gas after dust collection in the oxygen-enriched side-blown reduction furnace and the fuming furnace is sent to the ion liquid desulfurization system, mixed in the mixing tower, and then regenerated to obtain regenerated flue gas; (3) The regenerated flue gas obtained in step (2) is sent to the acid production system and mixed with the purified flue gas obtained in step (1). After being pressurized by the SO2 blower, it is sent to the "3+2" two-conversion two-absorption conversion system for a first conversion. Part of the flue gas is diverted from the first conversion gas and sent to the analytical pure sulfuric acid absorption tower to produce analytical pure sulfuric acid. The remaining flue gas absorbs SO3 in the intermediate absorption tower and then undergoes a second conversion. Finally, the remaining SO3 is absorbed in the final absorption tower. (4) The tail gas from the outlet of the final absorption tower is sent to the tail absorption desulfurization tower and absorbed by circulating liquid spraying. The circulating liquid is cooled by the cooler and then returned to the top of the tail absorption desulfurization tower for spraying.

[0006] Preferably, in step (1) of the present invention, the first-stage high-efficiency scrubbing tower, the gas cooling tower, the second-stage high-efficiency scrubbing tower, and the cooling mercury removal tower use sulfuric acid with a concentration of 5wt%~10wt% as the absorbent; the two-stage electrostatic precipitator uses a high-voltage DC electric field with a voltage of 55~65kV and a current of 100~200mA.

[0007] Preferably, in step (1) of the present invention, the SO2 flue gas temperature at the outlet of the primary high-efficiency scrubbing tower is 55~65℃; the SO2 flue gas temperature at the outlet of the gas cooling tower is 30~35℃; and the SO2 flue gas temperature at the outlet of the mercury removal cooling tower is 5~7℃. Before spraying, chilled water is used to cool the absorbent in the mercury removal cooling tower to 3~5℃ in order to condense and remove mercury from the flue gas, thereby effectively controlling the mercury content in the product and tail gas.

[0008] As a preferred embodiment, in step (2) of the present invention, the regeneration method is as follows: after being purified and cooled by a water washing tower and a primary electrostatic precipitator, the liquid enters the desulfurization absorption tower and absorbs SO2 by countercurrent contact with the ionic liquid to obtain rich liquid, and the rich liquid is desorbed by the regeneration tower to obtain regenerated flue gas.

[0009] As a further preferred embodiment, the water washing tower uses sulfuric acid with a concentration of 5wt%~10wt% as the washing agent; the primary electrostatic precipitator uses a high-voltage DC electric field with a voltage of 50~60kV and a current of 80~150mA; the regeneration tower uses a steam heating desorption process, the desorption medium is low-pressure steam with a steam pressure of 0.3~0.5MPa, a desorption temperature of 110~120℃, and a top pressure of 0.02~0.05MPa.

[0010] As a further preferred embodiment, the liquid distributor of the desulfurization absorption tower is a tray-type distributor, the packing of the desulfurization absorption tower is a Φ50mm high-flow-rate stepped ring, and the ionic liquid of the desulfurization absorption tower is a compound solution of 30wt% methyldiethanolamine aqueous solution and 5wt% 2-amino-2-methyl-1-propanol; through the above configuration, the SO2 concentration in the flue gas at the inlet of the desulfurization absorption tower is at most 5.2 g / Nm³. 3 The maximum flue gas volume that can be treated is 95932.27 Nm³.3 / h.

[0011] As a preferred embodiment, in step (3) of the present invention, the "3+2" two-conversion two-absorption conversion system adopts the III-I-V-IV-II heat exchange process, the SO2 concentration at the system inlet is 9.3%~9.36%, and the final conversion rate reaches more than 99.97%.

[0012] Preferably, in step (3) of the present invention, the intermediate absorption tower and the final absorption tower use sulfuric acid with a concentration of 98.3 wt% as the absorption liquid.

[0013] Preferably, in step (3) of the present invention, a nicotinic acid scrubbing tower and a fiber demister are installed before the analytical pure sulfuric acid absorption tower to purify part of the flue gas diverted from the primary conversion gas before it enters the analytical pure sulfuric acid absorption tower to produce analytical pure sulfuric acid that meets the GB / T625-2007 standard.

[0014] As a further preferred option, the nicotinic acid scrubbing tower uses concentrated sulfuric acid with a concentration of 98wt% as the scrubbing agent, and the scrubbing temperature is 40~50℃; the operating parameters of the fiber demister are: filtration velocity 0.5~1.0m / s, resistance drop ≤500Pa, and demister efficiency ≥99%.

[0015] Preferably, in step (4) of the present invention, the circulating liquid of the tail absorption desulfurization tower is composed of 1wt% hydrogen peroxide and 99wt% sulfuric acid solution, wherein the mass fraction of sulfuric acid in the sulfuric acid solution is 20%~25% and the mass fraction of hydrogen peroxide in the hydrogen peroxide solution is 27.5%.

[0016] Preferably, in step (4) of the present invention, the circulating liquid of the tail absorption desulfurization tower is cooled to 7°C by a cooler. After absorbing SO2, the circulating liquid generates 20wt%~40wt% dilute sulfuric acid, part of which is sent to the dry absorption section circulation tank for reuse.

[0017] Preferably, in step (4) of this invention, the desulfurized tail gas produced by the tail absorption desulfurization tower is treated by an electrostatic precipitator and then combined with the acid production tail gas produced by the analytical grade sulfuric acid absorption tower before being discharged, with a maximum total flue gas volume of 154849 Nm³. 3 / h, SO2 emission concentration ≤400mg / Nm 3 Acid mist ≤20mg / Nm 3 Particulate matter ≤80mg / Nm 3 .

[0018] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention adopts a synergistic treatment process of "flue gas fractional co-processing, low-temperature cooling for deep mercury removal, circulating liquid cooling and hydrogen peroxide tail absorption" to achieve the effect of improving desulfurization, acid production efficiency and acid production economic benefits while effectively controlling plume problems. The specific process is as follows: On the one hand, this invention sends the high-concentration SO2 flue gas generated by the Osmet oxygen-enriched top-blown furnace into the acid production system for treatment to obtain clean flue gas: This process adds a cooling mercury removal tower between the two-stage high-efficiency scrubber and the electrostatic precipitator, and uses chilled water to cool the circulating dilute acid to 3°C. Under low-temperature conditions, the gaseous mercury in the flue gas condenses into liquid mercury and is captured by dilute acid, thus achieving deep removal of mercury from the flue gas; On the other hand, the low-concentration SO2 flue gas generated by the oxygen-enriched side-blown reduction furnace and the fuming furnace is sent into the ion liquid desulfurization system for regeneration to obtain high-concentration SO2 regenerated flue gas, which is returned to the drying tower of the acid production system and mixed with clean flue gas to produce acid. This multi-source flue gas fractional co-processing architecture enables the recovery and utilization of SO2 in the low-concentration flue gas that is originally difficult to directly produce acid, thereby improving the utilization rate of sulfur resources.

[0019] (2) By setting up a nicotine scrubbing tower and a fiber demister before the analytical sulfuric acid absorption tower of the acid production system, the present invention eliminates the need for an additional independent acid production device. The clean flue gas of the acid production system and the regenerated flue gas of the ion liquid desulfurization system can produce analytical sulfuric acid that meets the GB / T625-2007 standard. On the basis of improving the desulfurization and acid production conversion efficiency, the overall economic benefits of the process are simultaneously improved.

[0020] (3) The present invention uses sulfuric acid circulating liquid containing hydrogen peroxide to spray and absorb the SO2 tail gas produced after completion, and generates dilute sulfuric acid with a mass fraction of 20%~40% through oxidation reaction, which deeply removes the residual SO2 in the tail gas; at the same time, the circulating liquid at the bottom of the tower is cooled by the cooler and then returned to the top of the tower for circulating spraying; the design of the circulating liquid tail absorption and cooling process can balance the temperature of SO2 oxidation and acid production reaction with the flue gas dew point, and effectively suppress the generation of white smoke plume while ensuring the efficiency of desulfurization reaction.

[0021] (4) This invention upgrades and modifies the desulfurization absorption tower by simply replacing the liquid distributor and packing, and adjusting the ionic liquid formula. After the upgrade, the ionic liquid desulfurization system can handle a maximum flue gas volume of 95932.27 Nm³. 3 / h, the highest inlet SO2 concentration reached 5.17 g / Nm³. 3 It can stably handle low-concentration flue gas from reduction furnaces and fuming furnaces, avoiding the high investment and long-term shutdown of the main equipment. It has the advantages of low investment, short construction period and strong adaptability. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the process flow of the present invention. Detailed Implementation

[0023] 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.

[0024] The "3+2" two-conversion two-absorption conversion system and the III-I-V-IV-II heat exchange process used in this invention are existing technologies. Specifically, the heat exchange process is as follows: the cold flue gas from the SO2 blower is preheated by heat exchanger (III) and then enters the first-stage converter; the hot gas from the first-stage outlet is cooled by heat exchanger (I) and then enters the second stage; the gas from the second-stage outlet is cooled by heat exchanger (V) and then enters the third stage; the gas from the third stage outlet is cooled by waste heat recovery (such as waste heat boiler) and then enters the intermediate absorption tower; the gas after the intermediate absorption tower is heated by heat exchangers (I and V) and then enters the fourth stage; the gas from the fourth stage outlet is heated by heat exchanger (II) and then enters the fifth stage; the precise control of the inlet temperature of each stage is achieved through this heat exchange network.

[0025] The desulfurization absorption tower used in this invention has an inner diameter of 3400 mm, the drying tower has an inner diameter of 3900 mm, and the intermediate absorption tower, the final absorption tower, and the tail absorption desulfurization tower all have an inner diameter of 4200 mm.

[0026] The ionic liquid desulfurization system used in this invention has undergone the following modifications: the original liquid distributor of the desulfurization absorption tower was a tubular distributor, which was replaced with a tray distributor after the modification, increasing the number of distribution points by 30%; the original packing of the desulfurization absorption tower was Φ38mm Pall rings, which was replaced with Φ50mm high-flow-rate stepped rings after the modification, increasing the porosity to 95%; the original ionic liquid of the desulfurization absorption tower was a 30wt% aqueous solution of methyl diethanolamine (MDEA); the improved ionic liquid of the desulfurization absorption tower is a compound solution of 30wt% aqueous solution of methyl diethanolamine and 5wt% 2-amino-2-methyl-1-propanol (AMP), increasing the absorption capacity by 20%.

[0027] Example 1 In this embodiment, the flue gas produced by the Osmet oxygen-enriched top-blown furnace has a flow rate of 40075.82 Nm³ / h, a temperature of 300±25℃, an SO₂ concentration of 10.088%, and a dust content of 401.52 mg / Nm³. 3 The As content is 576.66 mg / Nm³. 3 The Hg content is 4.53 mg / Nm³. 3 The flue gas volume produced by the Osmet oxygen-enriched side-blown reduction furnace is 22337.82 Nm³. 3 / h, SO2 concentration is 0.5927%; flue gas output from the fuming furnace is 57605.74 Nm³.3 / h, SO2 concentration is 0.0212%.

[0028] In this embodiment, the upper limit of SO2 concentration at the inlet of the modified desulfurization absorption tower is adjusted from 3.2 g / Nm³. 3 Increased to 5.17 g / Nm 3 After the upgrade, the flue gas handling capacity of the desulfurization absorption tower increased from 70,000 Nm³ / h to 95,932.27 Nm³ / h. 3 / h, the desulfurization rate is stable at over 98%.

[0029] The specific steps in this embodiment are as follows: (1) All the high-concentration SO2 flue gas generated by the Osmet oxygen-enriched top-blown furnace is sent to the acid production system. First, it enters the first-stage high-efficiency scrubbing tower and comes into countercurrent contact with circulating dilute sulfuric acid (concentration of about 8wt%), and the temperature drops from 300℃ to 63.9℃. Then it enters the gas cooling tower and is further cooled to 33℃. Then it enters the second-stage high-efficiency scrubbing tower (dilute sulfuric acid scrubbing, concentration of about 10wt%) for deep dust removal. Then it enters the cooling mercury removal tower. The circulating dilute sulfuric acid in the cooling mercury removal tower is cooled to 3℃ by chilled water and then sprayed to cool the flue gas to 5℃, condensing and removing most of the mercury. Finally, it passes through a two-stage electrostatic precipitator (voltage 60kV, current 150mA) to reduce the acid mist content of the flue gas to 5mg / m³. 3 The flue gas is then purified.

[0030] (2) The two low-concentration SO2 flue gas streams after dust collection in the oxygen-enriched side-blown reduction furnace and the fuming furnace are sent to the ion liquid desulfurization system. They are first mixed in the mixing tower and then pressurized to 7700Pa by the booster fan. After that, they enter the water washing tower (water washing temperature 40℃) and the primary electrostatic precipitator (voltage 55kV, current 100mA) for cooling and purification. Then they enter the desulfurization absorption tower and come into countercurrent contact with the ion liquid to absorb SO2 to obtain rich liquid. The rich liquid is heated by the lean-rich liquid heat exchanger and then enters the regeneration tower (using 0.4MPa low-pressure steam for indirect heating, desorption temperature 115℃, and regeneration tower top pressure 0.03MPa) to desorb and obtain regenerated flue gas (SO2 concentration of about 15%).

[0031] (3) After mixing the purified flue gas (approximately 52,000 kg / h) obtained in step (1) with the regenerated flue gas (401.1 kg / h) obtained in step (2), the mixture is dried in a drying tower using 93 wt% sulfuric acid to reduce the moisture content of the outlet flue gas to 0.1 g / Nm³. 3The following gas is then pressurized by an SO2 blower (inlet pressure -12400Pa, outlet pressure 44300Pa) and sent to a "3+2" two-stage two-absorption conversion system. This system employs a "3+2" five-stage, two-stage conversion process, with a heat exchange flow of III-I-V-IV-II. The inlet flue gas in the first stage is heated to 420℃, and the outlet flue gas temperature is 596℃. The inlet flue gas temperature in the second stage is 452℃, and the outlet flue gas temperature is 502℃. The inlet flue gas temperature in the third stage is 447℃, and the outlet flue gas temperature is 456℃. At this point, the cumulative conversion rate of the first stage is 96.4%. The outlet flue gas in the third stage is cooled to 180℃ by a heat exchanger and waste heat boiler, and then diverted. Part of the flue gas enters a nicotine scrubbing tower (scrubbing temperature 45℃). After passing through a fiber demister (filtration velocity 0.8 m / s, resistance drop 400 Pa), the flue gas is fed into an analytical grade sulfuric acid absorption tower to produce analytical grade sulfuric acid conforming to GB / T625-2007 standards. The remaining flue gas enters an intermediate absorption tower where SO3 is absorbed by 98.3 wt% sulfuric acid. The unabsorbed gas is heated to 429°C by heat exchange and enters the fourth stage for secondary conversion. The inlet flue gas temperature of the fourth stage is 429°C, and the outlet flue gas temperature is 436°C. The inlet flue gas temperature of the fifth stage is 380°C, and the outlet flue gas temperature is 380.4°C, with a total conversion rate of 99.97%. The outlet flue gas of the fifth stage is cooled to 154.5°C by heat exchange and then enters the final absorption tower to absorb the remaining SO3, with an absorption rate >99.995%.

[0032] (4) The tail gas (temperature of 65℃) at the outlet of the final absorption tower is sent to the tail absorption desulfurization tower and absorbed by circulating liquid spraying. The circulating liquid at the bottom of the tail absorption desulfurization tower is cooled to 7℃ by the cooler and then returned to the top of the tail absorption desulfurization tower for spraying, which cools the tail gas to 10℃ and reduces the plume. At the same time, the circulating liquid absorbs part of the SO2 in the tail gas at the outlet of the final absorption tower to generate 20wt%~40wt% sulfuric acid solution, which is sent to the dry absorption circulation tank for reuse. The remaining tail gas at the outlet of the final absorption tower is treated by the electrostatic precipitator and then combined with the acid production tail gas at the outlet of the analytical grade sulfuric acid absorption tower for discharge.

[0033] The total flue gas emission volume in this embodiment is approximately 154,849 Nm³. 3 The flue gas is emitted at a rate of / h through a 60m chimney; tests show that the SO2 concentration in the emitted flue gas is ≤400mg / Nm³. 3 Acid mist ≤20mg / Nm 3 Particulate matter ≤80mg / Nm 3 Mercury was not detected, and the exhaust plume was effectively controlled, meeting environmental protection requirements.

[0034] In this embodiment, the annual production of sulfuric acid is 131,328 tons (calculated as 100% H2SO4), of which 60,000 tons are analytical grade sulfuric acid and 71,328 tons are industrial grade sulfuric acid. After one production cycle (310 days), the mercury content in the analytical grade sulfuric acid increased from 0.005 ppm to 0.008 ppm, which is far below the trace limit not explicitly specified in GB / T625-2007 and meets the product requirements.

[0035] Example 2 In this embodiment, the modification method of the ionic liquid desulfurization system is the same as that in Example 1. After modification, the upper limit of SO2 concentration at the inlet of the absorption tower is 5.2 g / Nm³. 3 After the upgrade, the flue gas handling capacity of the desulfurization absorption tower increased from 70,000 Nm³ / h to 950,000 Nm³ / h. 3 / h, the desulfurization rate is stable at over 98%.

[0036] In this embodiment, the flue gas output of the Osmite oxygen-enriched top-blown furnace is 52000 Nm³. 3 / h, temperature 310±20℃, SO2 concentration 9.2%, dust content 380mg / Nm 3 The As content is 520 mg / Nm³. 3 The Hg content is 4.1 mg / Nm³. 3 The flue gas output of the Osmet oxygen-enriched side-blown reduction furnace is 25,000 Nm³. 3 / h, SO2 concentration is 0.68%; flue gas output from the fuming furnace is 62000 Nm³. 3 / h, SO2 concentration is 0.025%.

[0037] The specific steps in this embodiment are as follows: (1) All the high-temperature, high-concentration SO2 flue gas generated by the Osmet oxygen-enriched top-blown furnace is sent to the acid production system. First, it enters the first-stage high-efficiency scrubbing tower and comes into countercurrent contact with circulating dilute sulfuric acid (concentration of about 7wt%), and the temperature drops from 310℃ to 61℃. Then it enters the gas cooling tower and is further cooled to 31℃. Then it enters the second-stage high-efficiency scrubbing tower (dilute sulfuric acid scrubbing, concentration of about 9wt%) for deep dust removal. Then it enters the cooling mercury removal tower. The circulating dilute sulfuric acid in the cooling mercury removal tower is cooled to 5℃ by chilled water and then sprayed to cool the flue gas to 7℃, condensing and removing most of the mercury. Finally, it passes through a two-stage electrostatic precipitator (voltage 58kV, current 120mA) to reduce the acid mist content of the flue gas to 5mg / m³. 3 The flue gas is then purified.

[0038] (2) The two low-concentration SO2 flue gas streams after dust collection in the oxygen-enriched side-blown reduction furnace and the fuming furnace are sent into the modified ion liquid desulfurization system and mixed in the mixing tower. The pressure is increased to 8000Pa by the booster fan, and then enters the water washing tower (water washing temperature 42℃) and the primary electrostatic precipitator (voltage 53kV, current 90mA) for cooling and purification. After cooling, the flue gas enters the desulfurization absorption tower and is in countercurrent contact with the ion liquid to absorb SO2 to obtain rich liquid. The rich liquid is heated by the lean-rich liquid heat exchanger and then enters the regeneration tower (using 0.4MPa low-pressure steam for indirect heating, desorption temperature 112℃, and regeneration tower top pressure 0.03MPa) to desorb and obtain regenerated flue gas (SO2 concentration of about 14.5%).

[0039] (3) The purified flue gas (67600 kg / h) obtained in step (1) is mixed with the regenerated flue gas (520 kg / h) obtained in step (2), and then dried in a drying tower using 93 wt% sulfuric acid to reduce the moisture content of the outlet flue gas to 0.1 g / Nm³. 3 The following gas is then pressurized by an SO2 blower (inlet pressure -13000Pa, outlet pressure 45000Pa) and sent to a "3+2" two-stage two-absorption conversion system. The system employs a "3+2" five-stage, two-stage conversion process, with a heat exchange flow of III-I-V-IV-II. In the first stage, the inlet flue gas is heated to 415℃, and the outlet flue gas temperature is 590℃. In the second stage, the inlet flue gas temperature is 448℃, and the outlet flue gas temperature is 498℃. In the third stage, the inlet flue gas temperature is 443℃, and the outlet flue gas temperature is 452℃. At this point, the cumulative conversion rate of the first stage is 96.2%. The outlet flue gas from the third stage is cooled to 175℃ by a heat exchanger and waste heat boiler, and then diverted. Part of the flue gas enters a nicotine scrubbing tower (scrubbing temperature 43℃). After passing through a filtration system (0.7 m / s) and a fiber demister (450 Pa pressure drop), the flue gas is fed into an analytical grade sulfuric acid absorption tower to produce analytical grade sulfuric acid conforming to GB / T625-2007 standards. The remaining flue gas enters an intermediate absorption tower where 98.3 wt% sulfuric acid is used to absorb SO3. The unabsorbed gas is heated to 425°C by heat exchange and enters the fourth stage for secondary conversion. The inlet flue gas temperature of the fourth stage is 425°C, and the outlet flue gas temperature is 432°C. The inlet flue gas temperature of the fifth stage is 378°C, and the outlet flue gas temperature is 378.5°C, with a total conversion rate of 99.96%. The outlet flue gas of the fifth stage is cooled to 152°C by heat exchange and then enters the final absorption tower to absorb the remaining SO3, with an absorption rate >99.995%.

[0040] (4) The tail gas (temperature of 62°C) at the outlet of the final absorption tower is sent to the tail absorption desulfurization tower and absorbed by circulating liquid spraying. The circulating liquid at the bottom of the tail absorption desulfurization tower is cooled to 7°C by the cooler and then returned to the top of the tail absorption desulfurization tower for spraying, which cools the tail gas to 10°C and reduces the plume. At the same time, the circulating liquid absorbs part of the SO2 in the tail gas at the outlet of the final absorption tower to generate 20wt%~40wt% sulfuric acid solution, which is sent to the dry absorption circulation tank for reuse. The remaining tail gas at the outlet of the final absorption tower is treated by the electrostatic precipitator and then combined with the acid production tail gas at the outlet of the analytical grade sulfuric acid absorption tower for emission.

[0041] The total exhaust gas volume in this embodiment is approximately 165,000 Nm³. 3 The flue gas is emitted at a rate of / h through a 60m chimney; tests show that the SO2 concentration in the emitted flue gas is ≤400mg / Nm³. 3 Acid mist ≤20mg / Nm 3 Particulate matter ≤80mg / Nm 3 Mercury was not detected, and the exhaust plume was effectively controlled, meeting environmental protection requirements.

[0042] In this embodiment, the annual production of sulfuric acid is 142,500 tons (calculated as 100% H2SO4), of which 65,000 tons are analytical grade sulfuric acid and 77,500 tons are industrial grade sulfuric acid. After one production cycle (310 days), the mercury content in the analytical grade sulfuric acid increased from 0.008 ppm to 0.012 ppm, which is far below the trace limit not explicitly specified in GB / T625-2007 and meets the product requirements.

[0043] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A process for the synergistic treatment of lead smelting flue gas for acid production and desulfurization, characterized in that, Includes the following steps: (1) The high-concentration SO2 flue gas generated by the Osmet oxygen-enriched top-blown furnace is sent into the acid production system and successively passes through a first-stage high-efficiency scrubbing tower, a gas cooling tower, a second-stage high-efficiency scrubbing tower, a cooling mercury removal tower, and a two-stage electrostatic precipitator for purification and cooling to obtain purified flue gas; (2) The low-concentration SO2 flue gas after dust collection in the oxygen-enriched side-blown reduction furnace and the fuming furnace is sent to the ion liquid desulfurization system, mixed in the mixing tower, and then regenerated to obtain regenerated flue gas; (3) The regenerated flue gas obtained in step (2) is sent to the acid production system and mixed with the purified flue gas obtained in step (1). Then it is sent to the "3+2" two-conversion two-absorption conversion system for a first conversion. A portion of the flue gas is diverted from the first conversion gas to produce analytical grade sulfuric acid. The remaining flue gas absorbs SO3 in the intermediate absorption tower and then undergoes a second conversion. Finally, it is absorbed in the final absorption tower. (4) The tail gas from the outlet of the final absorption tower is sent to the tail absorption desulfurization tower and absorbed by circulating liquid spraying. The circulating liquid is cooled by the cooler and then returned to the top of the tail absorption desulfurization tower for spraying.

2. The co-treatment process for acid production and desulfurization of lead smelting flue gas according to claim 1, characterized in that, The primary high-efficiency scrubbing tower, gas cooling tower, secondary high-efficiency scrubbing tower, and cooling mercury removal tower use sulfuric acid with a concentration of 5wt%~10wt% as the absorbent; the two-stage electrostatic precipitator uses a high-voltage DC electric field with a voltage of 55~65kV and a current of 100~200mA.

3. The co-treatment process for acid production and desulfurization of lead smelting flue gas according to claim 1, characterized in that, The SO2 flue gas temperature at the outlet of the first-stage high-efficiency scrubbing tower is 55~65℃; the SO2 flue gas temperature at the outlet of the gas cooling tower is 30~35℃; and the SO2 flue gas temperature at the outlet of the cooling mercury removal tower is 5~7℃.

4. The co-treatment process for acid production and desulfurization of lead smelting flue gas according to claim 1, characterized in that, In step (2), the regeneration method is as follows: after being purified and cooled by a water washing tower and a primary electrostatic precipitator, the liquid enters the desulfurization absorption tower and is in countercurrent contact with the ionic liquid to absorb SO2 to obtain rich liquid. The rich liquid is then desorbed by the regeneration tower to obtain regenerated flue gas.

5. The co-treatment process for acid production and desulfurization of lead smelting flue gas according to claim 4, characterized in that, The washing tower uses sulfuric acid with a concentration of 5wt%~10wt% as the detergent; the primary electrostatic precipitator uses a high-voltage DC electric field with a voltage of 50~60kV and a current of 80~150mA; the regeneration tower uses a low-pressure steam heating desorption process with a low-pressure steam pressure of 0.3~0.5MPa, a desorption temperature of 110~120℃, and a top pressure of 0.02~0.05MPa.

6. The co-treatment process for acid production and desulfurization of lead smelting flue gas according to claim 4, characterized in that, The liquid distributor of the desulfurization absorption tower is a tray-type distributor, the packing of the desulfurization absorption tower is a Φ50mm high-flow-rate stepped ring, and the ionic liquid of the desulfurization absorption tower is a compound solution of 30wt% methyldiethanolamine aqueous solution and 5wt% 2-amino-2-methyl-1-propanol.

7. The co-treatment process for acid production and desulfurization of lead smelting flue gas according to claim 1, characterized in that, In step (3), the "3+2" two-conversion two-absorption conversion system adopts the III-I-V-IV-II heat exchange process; the intermediate absorption tower and the final absorption tower use sulfuric acid with a concentration of 98.3wt% as the absorbent.

8. The co-treatment process for acid production and desulfurization of lead smelting flue gas according to claim 1, characterized in that, In step (3), a nicotine scrubbing tower and a fiber demister are installed before the analytical grade sulfuric acid absorption tower.

9. The co-treatment process for acid production and desulfurization of lead smelting flue gas according to claim 1, characterized in that, In step (4), the circulating liquid of the tail absorption desulfurization tower is composed of 1wt% hydrogen peroxide and 99wt% sulfuric acid solution, wherein the mass fraction of sulfuric acid in the sulfuric acid solution is 20%~25%, and the mass fraction of hydrogen peroxide in the hydrogen peroxide solution is 27.5%.

10. The co-treatment process for acid production and desulfurization of lead smelting flue gas according to claim 1, characterized in that, In step (4), the circulating liquid in the tail absorption desulfurization tower is cooled to 7°C by a cooler.

Images