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CN-121994033-A - Low-temperature waste heat recovery system and recovery method for zinc smelting flue gas acid production

CN121994033ACN 121994033 ACN121994033 ACN 121994033ACN-121994033-A

Abstract

The invention relates to the technical field of nonferrous metal smelting flue gas treatment, in particular to a zinc smelting flue gas acid making low-temperature waste heat recovery system and a recovery method. The recovery system comprises a cooling and dedusting assembly, a purifying and heat exchanging assembly, a drying and circulating assembly, a conversion assembly and a dry absorption acid making low-temperature waste heat recovery assembly which are sequentially arranged along the flow direction of zinc smelting flue gas. In the zinc smelting process, the recovery system not only can convert the high-humidity flue gas with low SO 2 concentration into sulfuric acid with the mass concentration of 98wt% and low-pressure saturated steam, but also can realize that the total conversion rate of SO 2 gas in the zinc smelting flue gas is more than 99.9% and the total absorption rate of the converted SO 3 gas is more than 99.99%, wherein the yield of the low-pressure saturated steam is more than 0.3 times of the ton of sulfuric acid.

Inventors

  • LI WEIDA
  • CHEN YANMEI
  • WEI TAO
  • CHEN YUPING
  • MO YONGMING
  • DU YIJING
  • XU PING
  • YUAN AIWU

Assignees

  • 长沙有色冶金设计研究院有限公司
  • 南丹县南方有色金属有限责任公司

Dates

Publication Date
20260508
Application Date
20260409

Claims (10)

  1. 1. The low-temperature waste heat recovery system for preparing acid from zinc smelting flue gas is characterized by comprising a cooling and dust removing assembly, a purifying and heat exchanging assembly, a drying and circulating assembly, a converting assembly and a dry absorption acid preparation low-temperature waste heat recovery assembly which are sequentially arranged along the flowing direction of the zinc smelting flue gas; The purification heat exchange assembly comprises front purification equipment, a gas cooling tower (2), a nitrogen cooling device (3) and rear purification equipment, wherein a first packing layer, a first air inlet and a first air outlet are arranged in the gas cooling tower (2), the first air inlet and the first air outlet are respectively arranged below the first packing layer, the cooling and dust removing assembly at the front end is connected with the first air inlet through the front purification equipment, the first air outlet is connected with the drying and circulating assembly at the rear end through the rear purification equipment, a first spray head is further arranged in the gas cooling tower (2), the first spray head is arranged above the first packing layer, and a liquid return channel is further arranged below the first packing layer in the gas cooling tower (2); The nitrogen cooling device (3) is internally provided with an interlayer transfusion cavity and a heat exchange pipeline (3.1), the heat exchange pipeline (3.1) is arranged in the interlayer transfusion cavity, an inlet (3.2) of the interlayer transfusion cavity is lower than an outlet (3.3) of the interlayer transfusion cavity, the outlet is connected with the first spray head, the inlet is communicated with the liquid return channel, and the heat exchange pipeline (3.1) comprises a second air inlet communicated with a nitrogen outlet of nitrogen supply equipment and a second air outlet communicated with a nitrogen inlet of the nitrogen supply equipment.
  2. 2. The zinc smelting flue gas acid making low-temperature waste heat recovery system according to claim 1, wherein the drying cycle assembly comprises a drying tower (7) and a first circulation tank (8); The drying tower (7) comprises a third air inlet arranged below the second packing layer and a third air outlet arranged above the second packing layer, the rear purifying equipment is communicated with the third air inlet, the third air outlet is communicated with the conversion assembly through an SO 2 main fan, a first liquid outlet is arranged at the bottom of the drying tower (7), and a first liquid inlet is arranged at the top of the drying tower; The first circulating tank (8) is arranged below the drying tower (7) and is communicated with the first liquid outlet, a first conveying pump is arranged in the first circulating tank (8) and is communicated with the first liquid inlet through a liquid conveying pipeline, and a second liquid outlet communicated with the dry absorption acid-making low-temperature waste heat recovery assembly is arranged on the liquid conveying pipeline.
  3. 3. The zinc smelting flue gas acid making low-temperature waste heat recovery system according to claim 2 is characterized in that the drying circulation assembly further comprises a degassing tower (9), a third packing layer, a fourth air inlet, a fourth air outlet and a second liquid inlet are arranged below the third packing layer, above the third packing layer and above the third packing layer respectively, the fourth air inlet is connected with air, the second liquid inlet is communicated with a branch pipeline of the liquid feeding pipeline, the fourth air outlet is communicated with the third air inlet, and a third liquid outlet communicated with the dry acid making low-temperature waste heat recovery assembly is arranged at the bottom of the degassing tower (9); The drying cycle assembly further comprises a first heat exchanger (10) arranged on the liquid conveying pipeline, and the first heat exchanger (10) is arranged between the second liquid outlet of the liquid conveying pipeline and a branch pipeline of the liquid conveying pipeline.
  4. 4. A zinc smelting flue gas acid making low-temperature waste heat recovery system according to claim 3, wherein the dry absorption acid making low-temperature waste heat recovery component comprises a secondary absorption tower (11), a second circulation tank (12), a high-temperature absorption tower (14), a third circulation tank (15), an acid-acid heat exchanger (16), a diluter (17) and a waste heat recovery steam generating component; An upper packing layer and a lower packing layer which are arranged up and down are arranged in the high-temperature absorption tower (14); the high-temperature absorption tower (14) further comprises a fifth air inlet, a fifth air outlet, a third liquid inlet and a fourth liquid inlet, wherein the fifth air inlet is arranged below the lower packing layer, the fifth air outlet and the third liquid inlet are arranged above the upper packing layer, the fourth liquid inlet is arranged between the upper packing layer and the lower packing layer, the fifth air inlet is communicated with SO 3 gas generated by primary conversion of the conversion assembly, the fifth air outlet is communicated with the air inlet end of the conversion assembly and is used for conveying residual SO 2 gas in the gas into the conversion assembly for secondary conversion, a third spray head communicated with the third liquid inlet and a fourth spray head communicated with the fourth liquid inlet are arranged in the high-temperature absorption tower (14), the third spray head is arranged above the upper packing layer, and the fourth spray head is arranged between the upper packing layer and the lower packing layer; A fourth liquid outlet is arranged at the bottom of the high-temperature absorption tower (14) and is communicated with the third circulating tank (15) through a pipeline, the liquid inlet end of the third circulating tank (15) is higher than the liquid outlet end, a second conveying pump is arranged at the liquid outlet end in the third circulating tank (15) and is communicated with the inlet of the acid-acid heat exchanger (16) through a first main pipeline, a first branch pipeline is arranged on the first main pipeline and is communicated with the fourth liquid inlet through the diluter (17), and the second liquid outlet is communicated with the diluter (17) through the acid-acid heat exchanger (16); The outlet of the acid-acid heat exchanger (16) is sequentially communicated with the inlet of the second circulation tank (12) after heat exchange of the deoxygenated water preheater (21) and the desalted water preheater (18) is performed through a pipeline, a third conveying pump is arranged in the second circulation tank (12) and is communicated with a fifth liquid inlet arranged at the top of the second absorption tower (11) through a second main pipeline, a second branch pipeline used for being communicated with the third liquid inlet and a third branch pipeline used for being communicated with the inlet of the first circulation tank (8) are arranged on the second main pipeline; The device comprises a second suction tower (11), a fourth packing layer arranged in the second suction tower (11), a fifth spray head arranged above the fourth packing layer and communicated with the fifth liquid inlet, a fifth liquid outlet arranged at the bottom of the second suction tower (11) and communicated with a second circulation groove (12) arranged below the second suction tower (11), SO 3 gas secondarily converted by the conversion assembly, tail gas discharged from the sixth gas outlet, which is processed by desulfurization equipment and is discharged after reaching standards, and a process water inlet of the second circulation groove (12) and communicated with the third liquid outlet at the bottom of the degassing tower (9); The waste heat recovery steam generating assembly comprises a desalted water preheater (18), a deaerator (19), a first circulating water pump (20), a deaerated water preheater (21), a steam drum (22) and a second circulating water pump (23) which are sequentially arranged along the flowing direction of desalted water, wherein a liquid outlet, a first liquid inlet, a second liquid inlet and a steam generating port are arranged on the steam drum (22), the liquid outlet is communicated with an inlet of the second circulating water pump (23), an outlet of the second circulating water pump (23) is communicated with the first liquid inlet through a first pipeline and the second liquid inlet through a second pipeline respectively, and the first pipeline and the second pipeline are arranged in a penetrating manner from a liquid outlet end to a liquid inlet end of the third circulating groove (15).
  5. 5. The zinc smelting flue gas acid making low-temperature waste heat recovery system according to claim 4, wherein the dry absorption acid making low-temperature waste heat recovery assembly further comprises flow regulating valves arranged on the first pipeline and the second pipeline; The heat exchanger also comprises a second heat exchanger (13) arranged on the second main pipeline, and the second heat exchanger (13) is arranged at the front ends of the second branch pipeline and the third branch pipeline.
  6. 6. The zinc smelting flue gas acid making low temperature waste heat recovery system according to claim 5, wherein the dry absorption acid making low temperature waste heat recovery assembly further comprises a steam injector (24), and the steam injector (24) is arranged at the fifth air inlet of the high temperature absorption tower (14) and is communicated with the fifth air inlet.
  7. 7. The zinc smelting flue gas acid making low-temperature waste heat recovery system according to claim 6, wherein the pre-purification equipment comprises a primary high-efficiency scrubber (1); the post-purification equipment comprises a second-stage efficient scrubber (4), a first electric defogging device (5) and a second electric defogging device (6) which are sequentially communicated.
  8. 8. The zinc smelting flue gas acid making low-temperature waste heat recovery system according to claim 7, wherein the cooling and dust removing assembly comprises a waste heat boiler and a dust collecting system which are sequentially arranged along the flow direction of the zinc smelting flue gas; The conversion assembly comprises a first conversion layer, a second conversion layer, a third conversion layer and a fourth conversion layer which are sequentially arranged from top to bottom; the first conversion layer, the second conversion layer, the third conversion layer and the fourth conversion layer have the same structure and comprise a catalytic layer, a heat-resistant porcelain ball, a stainless steel wire mesh, a grate plate, an upright post and a supporting beam which are sequentially arranged from top to bottom, the catalytic layer is a catalyst filling layer, a primary conversion unit is formed by combining the first conversion layer, the second conversion layer and the third conversion layer and used for completing primary conversion of gas conveyed into the conversion assembly by the SO 2 main fan, an inlet communicated with the SO 2 main fan is arranged on the first conversion layer, an outlet communicated with a fifth air inlet of a high-temperature absorption tower (14) is arranged on the third conversion layer, circulating heat exchange pipelines communicated with external heat exchange equipment are arranged on the first conversion layer, the second conversion layer and the third conversion layer, an outlet on the third conversion layer is arranged on a circulating heat exchange pipeline 53road, a secondary conversion unit is formed by the fourth conversion layer and used for completing primary conversion of gas conveyed into the conversion assembly, an outlet communicated with a fifth air inlet of the high-temperature absorption tower (14) is arranged on the fourth conversion layer, a residual high-temperature gas (14) is not communicated with the fifth air inlet of the high-temperature absorption tower) is arranged on the fourth conversion layer (14), the circulating heat exchange pipeline is arranged on the fourth conversion layer and is communicated with external heat exchange equipment, and the outlet on the fourth conversion layer is arranged on a return pipeline of the circulating heat exchange pipeline on the fourth conversion layer.
  9. 9. A method for recovering the low-temperature waste heat of the acid making of the zinc smelting flue gas according to claim 8, which is characterized by comprising the following steps: Step S1, treating zinc smelting flue gas by the cooling and dedusting assembly to obtain cooling and dedusting flue gas, wherein the temperature is less than or equal to 320 ℃, the dust concentration is less than or equal to 500 mg/Nm 3 , the water content of the flue gas is 6% -7%, and the SO 2 content of the flue gas is 7.5% -8%; S2, delivering cooled and dedusted flue gas into the purification heat exchange assembly, wherein the flue gas flows in through the first air inlet below the gas cooling tower (2) after being purified by the front purification equipment, and continuously provides a cold source for spray acid in the interlayer transfusion cavity through a heat exchange pipeline (3.1) after heat exchange of spray acid sprayed by the first packing layer and the first spray head in the gas cooling tower (2), SO that the temperature of the flue gas is reduced to below 30 ℃, the water content of the flue gas is less than 4.8%, and the SO 2 content of the flue gas is 8.5% -8.7%, and then the flue gas flows into the rear purification equipment for purification by the first air outlet above the gas cooling tower (2), and is used for cooling the spray acid heated after heat exchange with the flue gas; S3, enabling the flue gas purified by the post-purification equipment to flow in through the third air inlet below the drying tower (7), enabling the flue gas to be dried to be below 0.1g/Nm 3 after being sprayed and dried through the second packing layer in the drying tower (7) and sulfuric acid sprayed by the second spray head, and enabling the dried flue gas to be discharged through the third air outlet and conveyed into the conversion assembly through the SO 2 main fan to complete primary conversion, enabling sulfuric acid sprayed by the second spray head to be provided by the first circulating tank (8) and the first conveying pump, enabling sulfuric acid discharged by the first liquid outlet of the drying tower (7) to flow back into the first circulating tank (8), enabling the returned sulfuric acid to flow into the degassing tower (9) through the first conveying pump, the liquid conveying pipeline and the second liquid inlet, and heat exchange through the first heat exchanger (10), enabling the sulfuric acid sprayed by the second spray head to flow into the degassing tower (9) through the third air inlet and the fourth circulating tank ( 2 ), and enabling the back flow into the degassing tower (12) through the third packing layer and the air outlet to be discharged through the fourth circulating tank (8); S4, spraying SO 3 gas generated by primary conversion of the conversion component into the high-temperature absorption tower (14) through the steam ejector (24) and the fifth air inlet, and after the SO 3 gas is sprayed and absorbed through the lower packing layer in the high-temperature absorption tower (14) and sulfuric acid sprayed by the fourth spray nozzle, wherein the mass concentration of the sulfuric acid is 99% and the temperature is 190 ℃, then, after the SO 3 gas is sprayed and absorbed through the upper packing layer in the high-temperature absorption tower (14) and sulfuric acid sprayed and absorbed through the third spray nozzle, the residual SO 2 gas in the unabsorbed gas of the high-temperature absorption tower (14) is sent into the conversion component through the fifth air outlet, the sulfuric acid sprayed by the fourth spray nozzle is returned to the sulfuric acid after being diluted by the third circulation tank (15) and the second conveying pump, and is returned to the main heat exchanger (17) through the second liquid outlet, and the sulfuric acid after the sulfuric acid sprayed and absorbed by the third spray nozzle is returned to the main heat exchanger (17), and the sulfuric acid sprayed and absorbed by the third spray pump is provided by the third conveying pump (15) through the third circulation tank (15) and the third conveying pump (13), and the sulfuric acid sprayed and the third conveying pump (6) is provided by the third conveying pump (15) and the third conveying pipeline (13%); SO 3 gas generated by secondary conversion of the conversion assembly flows into the secondary absorption tower (11) through the sixth air inlet, and after being sprayed and absorbed by sulfuric acid with the mass concentration of 98% and the temperature of 55 ℃ through the fourth packing layer and the fifth spray nozzle, the generated tail gas is discharged through the sixth air outlet and is discharged after reaching standards through desulfurization equipment, the sulfuric acid sprayed by the fifth spray nozzle is provided by the second circulation tank (12), the third conveying pump and the second main pipeline and is subjected to heat exchange through the second heat exchanger (13), and the sulfuric acid sprayed by the fifth spray nozzle flows back into the second circulation tank (12) through the fifth liquid outlet; Supplementing process water in the second circulation tank (12) for regulating and controlling the mass concentration of sulfuric acid in the second circulation tank (12) to 98%; The desalted water flows back to the steam drum (22) through the desalted water preheater (18), the deaerator (19), the first circulating water pump, the deaerated water preheater (21), the steam drum (22), the second circulating water pump and the first pipeline and the second pipeline in sequence to generate low-pressure saturated steam, wherein the third circulating tank (15), the acid heat exchanger (16), the deaerated water preheater (21) and the desalted water preheater (18) provide heat for the desalted water to convert into the low-pressure saturated steam, the yield of the low-pressure saturated steam is more than 0.3 times of the ton of sulfuric acid with the mass concentration of 98% in the second circulating tank (12), and the steam pressure is 0.4-0.8 MPa.
  10. 10. The recovery method of the zinc smelting flue gas acid making low-temperature waste heat recovery system according to claim 9, wherein the spray acid is sulfuric acid with a mass concentration of 8% -10%.

Description

Low-temperature waste heat recovery system and recovery method for zinc smelting flue gas acid production Technical Field The invention relates to the technical field of nonferrous metal smelting flue gas treatment, in particular to a zinc smelting flue gas acid making low-temperature waste heat recovery system and a recovery method. Background The main technological process of preparing acid from zinc smelting fume includes the first purifying smelting fume, turning out in a drying tower, introducing SO 2 into a conversion step to obtain SO 3 -rich fume, and desulfurizing exhausted tail gas after dry sucking the SO 3 -rich fume. The heat energy contained in the smelting flue gas is high-temperature heat energy (> 500 ℃) accounting for 51.45% of the total heat release amount, the heat energy can be used for generating medium-pressure saturated steam by a waste heat boiler and is easy to recycle, the reaction heat generated in the conversion process belongs to the medium-temperature heat energy (250-500 ℃) accounting for 17.27% of the total heat release amount, the heat energy can be used for generating steam or assisting the high-temperature heat energy to heat the water supply of the waste heat boiler or overheat the medium-pressure saturated steam generated by the waste heat boiler, when SO 3 is absorbed by sulfuric acid, a large amount of heat is released, the increased acid temperature is lower than the low-temperature heat energy (< 250 ℃), the increased acid temperature accounts for 31.28% of the total heat release amount, and the waste heat carrier is concentrated sulfuric acid with strong oxidizing property and corrosiveness, SO that the low-temperature waste heat generated in the dry absorption process is removed by using circulating cooling water and finally discharged into the atmosphere through a cooling tower, waste of waste heat resources and environmental heat pollution are further increased. In addition, oxygen produced by a cryogenic oxygen production station which is built in a matched manner in the zinc smelting process is used for zinc sulfide leaching and side-blown furnace smelting, and most of byproduct low-temperature nitrogen is directly emptied, so that obvious energy loss is caused. At present, regarding a low-temperature waste heat recovery system for preparing acid from smelting flue gas, not only can the preparation of concentrated sulfuric acid be completed, but also the low-temperature waste heat recovery (such as the generation of low-pressure steam) can be realized. However, the system has the following problems that 1) the system is suitable for smelting flue gas containing higher concentration SO 2 (such as volume fraction is 10% -12%), however, the moisture content in zinc smelting flue gas is higher, the concentration of SO 2 is lower (generally volume fraction is 7.5% -8%), after the zinc smelting flue gas is treated by a purification system, the flue gas temperature is high, the saturated water content in the flue gas is high, SO that the concentration of SO 2 is lower, the amount of SO 3 gas which can be absorbed and converted into sulfuric acid during dry absorption and conversion in a high-temperature absorption tower is less, the absorption water amount is more, the circulating acid (namely sulfuric acid) in the high-temperature absorption tower cannot be stably maintained in the acid making system, namely sulfuric acid mass concentration is higher than 98.5% (namely sulfuric acid production system 'swelling' water) to cause that the high-temperature absorption tower is easily corroded, the service life is shortened, even stopped), and 2) a waste heat carrier is concentrated sulfuric acid with strong oxidizing property and corrosivity, the temperature of the concentrated sulfuric acid is higher, the existing waste heat recovery mode adopts a pump to directly pump to pump the high-temperature concentrated sulfuric acid into an evaporator for waste heat recovery, the mode is not easy to corrode the pump, and the high-temperature concentrated sulfuric acid is directly corroded by 34 when the temperature is excessively low, and the high temperature is directly corroded by the high temperature absorption tower. Therefore, the low-temperature waste heat recovery system and the recovery method for the acid production of the zinc smelting flue gas are necessary to provide for solving the problems that 1) the water content in the zinc smelting flue gas is high, the concentration of SO 2 is low, the acid production system is expanded, a high-temperature absorption tower is easy to corrode, the service life is shortened, and even the production is stopped, and 2) the high-temperature concentrated sulfuric acid is directly pumped into an evaporator by a pump for waste heat recovery, SO that the temperature of the concentrated sulfuric acid is too low, and serious corrosion is caused to the high-temperature absorption tower in the prior art. Disclosure of Invention The inventi