System and method for preparing sulfuric acid by recycling waste ferric sulfate crude salt in acid washing of steel industry
阅读说明：本技术 钢铁行业酸洗回收废料硫酸铁粗盐制备硫酸的系统及方法 (System and method for preparing sulfuric acid by recycling waste ferric sulfate crude salt in acid washing of steel industry ) 是由 韩景文 陈文广 于 2021-05-08 设计创作，主要内容包括：本发明公开一种钢铁行业酸洗回收废料硫酸铁粗盐制备硫酸的系统及方法,该制备系统中回转窑、布袋除尘器、填料吸收塔和引风机通过连接管道依次相连接,引风机为所述系统提供抽力,使系统在负压状态运行。本发明通过将钢铁行业酸洗回收废料硫酸铁粗盐经过：(1)硫酸铁粗盐晶体干燥；(2)硫酸铁晶体粉体加热分解,得到三氧化硫、二氧化硫和三氧化二铁,三氧化二铁可用做炼钢的原料,也可以用作生产氧化铁红原料；(3)气体过滤除尘；(4)气体吸收,三氧化硫溶于水直接生成硫酸,二氧化硫溶于水生成亚硫酸,双氧水将吸收液体中的亚硫酸氧化成硫酸。本发明硫酸铁制备硫酸的系统,规模可大可小,投资少,见效快,可接受程度高,适用性强。(The invention discloses a system and a method for preparing sulfuric acid by recycling waste ferric sulfate crude salt in acid washing in the steel industry. The invention recycles waste ferric sulfate crude salt by acid cleaning in the steel industry through the following steps: (1) drying the ferric sulfate crude salt crystal; (2) ferric sulfate crystal powder is heated and decomposed to obtain sulfur trioxide, sulfur dioxide and ferric oxide, and the ferric oxide can be used as a raw material for steelmaking and also can be used as a raw material for producing iron oxide red; (3) filtering and dedusting gas; (4) and (3) gas absorption, dissolving sulfur trioxide in water to directly generate sulfuric acid, dissolving sulfur dioxide in water to generate sulfurous acid, and oxidizing the sulfurous acid in the absorption liquid into sulfuric acid by hydrogen peroxide. The system for preparing the sulfuric acid by the ferric sulfate has the advantages of changeable scale, low investment, quick response, high acceptable degree and strong applicability.)
1. The utility model provides a system for preparation of sulphuric acid of waste material ferric sulfate coarse salt is retrieved in steel industry pickling which characterized in that: including rotary kiln, sack cleaner, filler absorption tower and draught fan, the rotary kiln the sack cleaner the filler absorption tower with link pipe connects gradually between the draught fan, the kiln head of rotary kiln is equipped with spiral feeder, the kiln tail of rotary kiln is equipped with natural gas spray gun and powder export, the sack cleaner is equipped with the spiral discharger, the filler absorption tower includes first filler absorption tower, second filler absorption tower and third filler absorption tower, first filler absorption tower the second filler absorption tower with the third filler absorption tower is connected through the link pipe, the draught fan does the system provides the draft, makes the system is at the negative pressure state operation.
2. The system for preparing sulfuric acid from waste ferric sulfate crude salt recovered by pickling in the steel industry according to claim 1, characterized in that: the lower extreme of first filler absorption tower is equipped with first air inlet, and the top is equipped with first shower nozzle, and the bottom is equipped with first absorption liquid and first spray pump, the lower extreme of second filler absorption tower is equipped with the second air inlet, and the top is equipped with the second shower nozzle, and the bottom is equipped with second absorption liquid and second spray pump, the lower extreme of third filler absorption tower is equipped with the third air inlet, and the top is equipped with the third shower nozzle, and the bottom is equipped with third absorption liquid and third spray pump, first shower nozzle the second shower nozzle with the third shower nozzle is PPH spiral atomizer.
3. The system for preparing sulfuric acid from waste ferric sulfate crude salt recovered by pickling in the steel industry according to claim 2, characterized in that: the level of the first absorption liquid is controlled below the first air inlet, the level of the second absorption liquid is controlled below the second air inlet, and the level of the third absorption liquid is controlled below the third air inlet.
4. The system for preparing sulfuric acid from waste ferric sulfate crude salt recovered by pickling in the steel industry according to claim 1, characterized in that: the first filler absorption tower is provided with a first cooling system, the second filler absorption tower is provided with a second cooling system, and the third filler absorption tower is provided with a third cooling system.
5. The system for preparing sulfuric acid from waste ferric sulfate crude salt recovered by pickling in the steel industry according to claim 1, characterized in that: the first filler absorption tower is provided with a first liquid inlet and a first liquid outlet, the second filler absorption tower is provided with a second liquid inlet and a second liquid outlet, and the third filler absorption tower is provided with a third liquid inlet and a third liquid outlet.
6. A method for preparing sulfuric acid by recycling waste ferric sulfate crude salt in pickling of steel industry, which utilizes the system for preparing sulfuric acid by recycling waste ferric sulfate crude salt in pickling of steel industry as claimed in any one of claims 1 to 5, and is characterized in that: the method comprises the following steps:
(1) drying of iron sulfate crude salt crystals
Drying ferric sulfate coarse salt crystals obtained by recycling acid pickling nitric acid waste liquor in the steel industry by a parallel-flow rotary-cutting hot air dryer to obtain ferric sulfate crystal powder, wherein the external water content of the ferric sulfate crystal powder is 1-3 wt%;
(2) iron sulfate crystal powder heating decomposition
Ferric sulfate crystal powder is added into a rotary kiln through a spiral feeder, the rotary kiln head moves towards the rotary kiln tail and is gradually heated, the temperature of the rotary kiln head is controlled to be 200 ℃ plus one temperature, the temperature of the rotary kiln body is controlled to be 500 ℃ plus one temperature, the temperature of the rotary kiln tail is controlled to be 750 ℃ plus one temperature, a natural gas spray gun is arranged at the rotary kiln tail, the excess air coefficient is controlled to be 1.2 through the natural gas spray gun, the rotary kiln is ensured to be oxidizing atmosphere, so that the volume content ratio of sulfur trioxide to sulfur dioxide in the mixed gas of sulfur trioxide and sulfur dioxide generated by heating decomposition of ferric sulfate is more than or equal to 99: 1;
(3) gas filtration dust removal
The method comprises the following steps of pumping gas and dust in a rotary kiln into a bag-type dust remover by using an induced draft fan, controlling the temperature of the gas in the bag-type dust remover to be 180-fold and 200 ℃, blocking the dust in mixed gas out of a bag by the bag-type dust remover, and discharging the dust through a spiral discharger at the lower part of the bag-type dust remover;
(4) gas absorption
Under the action of the suction force of the draught fan, gas after dust filtration enters a first air inlet through a connecting pipeline, passes through a packing layer of a first packing absorption tower, enters a second air inlet from the top of the first packing absorption tower through the connecting pipeline, passes through a packing layer of a second packing absorption tower, enters a third air inlet from the top of the second packing absorption tower through the connecting pipeline, passes through the packing layer of the third packing absorption tower, and enters an inlet of the draught fan from the top of the third packing absorption tower through the connecting pipeline;
the first spray pump pressurizes first absorption liquid and downwards sprays the first absorption liquid through a first spray head at the top of the first filler absorption tower to absorb gas upwards passing through a filler layer of the first filler absorption tower, and a first cooling system controls the temperature of the first absorption liquid to be less than 75 ℃;
a second spray pump pressurizes second absorption liquid and downwards sprays the second absorption liquid through a second spray head at the top of a second filler absorption tower to absorb gas upwards passing through a filler layer of the second filler absorption tower, and a second cooling system controls the temperature of the second absorption liquid to be lower than 60 ℃;
and a third spray pump pressurizes third absorption liquid and sprays the third absorption liquid downwards through a third spray head at the top of the third packing absorption tower to absorb gas which upwards passes through a packing layer of the third packing absorption tower, and a third cooling system controls the temperature of the third absorption liquid to be less than 45 ℃.
7. The method for preparing sulfuric acid from the crude salt of iron sulfate, which is a waste material recovered in the pickling of steel industry, according to claim 6, is characterized in that: the coarse ferric sulfate salt crystals in the step (1) are coarse ferric sulfate dodecahydrate salt crystals, and the external water content of the coarse ferric sulfate dodecahydrate salt crystals is 35-45 wt%.
8. The method for preparing sulfuric acid from the crude salt of iron sulfate, which is a waste material recovered in the pickling of steel industry, according to claim 6, is characterized in that: the drying temperature of the parallel-flow rotary-cutting hot air dryer in the step (1) is set to be 250-350 ℃.
9. The method for preparing sulfuric acid from the crude salt of iron sulfate, which is a waste material recovered in the pickling of steel industry, according to claim 6, is characterized in that: and (4) the gas in the rotary kiln in the step (3) is sulfur trioxide, sulfur dioxide and residual oxygen, nitrogen and water vapor generated by combustion, and the dust in the rotary kiln is ferric oxide powder and ferric sulfate powder.
10. The method for preparing sulfuric acid from the crude salt of iron sulfate, which is a waste material recovered in the pickling of steel industry, according to claim 6, is characterized in that: the first absorption liquid is purified water, the second absorption liquid is purified water, and the third absorption liquid is 0.5-1wt% of hydrogen peroxide solution.
Technical Field
The invention relates to the technical field of solid waste utilization, in particular to a system and a method for preparing sulfuric acid by recycling waste ferric sulfate crude salt in acid washing in the steel industry.
Background
China is a large stainless steel production country, and the production capacity of various types of stainless steel is huge. In the production of the ISI200 series and AISI300 series stainless steel strips, it is necessary to remove the scale on the surface of the stainless steel using various strong acids through annealing and pickling processes. Sulfuric acid and nitric acid are used in the stainless steel pickling process. In order to improve the utilization rate of acid, reduce the acid consumption and reduce the pollution to the environment, the acid is generally regenerated. The stainless steel is pickled by using sulfuric acid, the waste sulfuric acid containing ferrous ions in a sulfuric acid tank is generally regenerated by adopting a freezing crystallization method, and ferrous sulfate heptahydrate crystal solid waste is obtained after the waste sulfuric acid is regenerated, but the regeneration rate of the waste sulfuric acid in the sulfuric acid tank is low, and the waste water and the waste material are discharged more. The solid waste ferrous sulfate heptahydrate is calcined, sulfur dioxide generated by calcination enters a conventional sulfuric acid production system to prepare sulfuric acid, the recovery treatment process is complex, the investment cost is high, and most stainless steel pickling enterprises are not acceptable.
And the stainless steel is pickled by using nitric acid, the waste nitric acid containing ferric ions in the nitric acid tank is subjected to regeneration treatment by using a sulfuric acid displacement method, the waste nitric acid can obtain a solid waste of the dodecahydrate ferric sulfate coarse salt crystal after regeneration, the treated waste acid can be completely recycled, the regeneration rate of the waste acid is high, and only the waste dodecahydrate ferric sulfate coarse salt crystal is discharged. For the solid waste, namely, the coarse ferric sulfate dodecahydrate salt crystal generated by regenerating the waste nitric acid by adopting a sulfuric acid displacement method, a treatment system and a treatment method which are convenient in process, quick in effect, high in acceptable degree and strong in applicability are urgently needed to be provided, so that resources are effectively utilized.
Disclosure of Invention
Aiming at the technical problems, the invention provides a system and a method for preparing sulfuric acid by recycling waste ferric sulfate crude salt in acid washing in the steel industry, which are characterized in that ferric sulfate dodecahydrate crude salt crystals are heated and decomposed into sulfur trioxide, sulfur dioxide and ferric oxide, the generation of the sulfur dioxide is inhibited by controlling the excess air coefficient, the ferric oxide can be used as a raw material for steelmaking and can also be used as a raw material for producing iron oxide red, the sulfur trioxide is dissolved in water to directly generate sulfuric acid, a small amount of sulfur dioxide is dissolved in water to generate sulfurous acid, the sulfurous acid is unstable, the sulfurous acid in absorption liquid is oxidized into the sulfuric acid by utilizing hydrogen peroxide, and resources are effectively utilized. The system for preparing the sulfuric acid by utilizing the ferric sulfate has the advantages of changeable scale, low investment, quick response, high acceptable degree and strong applicability.
In order to achieve the purpose of the invention, the technical scheme adopted by the invention is as follows:
the utility model provides a system for steel industry pickling is retrieved waste material ferric sulfate crude salt and is prepared sulphuric acid, includes rotary kiln, sack cleaner, filler absorption tower and draught fan, the rotary kiln the sack cleaner the filler absorption tower with link gradually through the connecting tube between the draught fan, the kiln head of rotary kiln is equipped with the spiral feeder, the kiln tail of rotary kiln is equipped with natural gas spray gun and powder export, the sack cleaner is equipped with the spiral discharger, the filler absorption tower includes first filler absorption tower, second filler absorption tower and third filler absorption tower, first filler absorption tower the second filler absorption tower with the third filler absorption tower is connected through the connecting tube, the draught fan does the system provides the suction, makes the system is in the negative pressure state operation.
Preferably, the lower end of the first filler absorption tower is provided with a first air inlet, the top of the first filler absorption tower is provided with a first spray head, the bottom of the first filler absorption tower is provided with first absorption liquid and a first spray pump, the lower end of the second filler absorption tower is provided with a second air inlet, the top of the second filler absorption tower is provided with a second spray head, the bottom of the second filler absorption tower is provided with second absorption liquid and a second spray pump, the lower end of the third filler absorption tower is provided with a third air inlet, the top of the third filler absorption tower is provided with a third spray head, the bottom of the third filler absorption tower is provided with third absorption liquid and a third spray pump, and the first spray head, the second spray head and the third spray head are PPH spiral atomization spray heads.
Preferably, the level of the first absorption liquid is controlled below the first gas inlet, the level of the second absorption liquid is controlled below the second gas inlet, and the level of the third absorption liquid is controlled below the third gas inlet.
Preferably, the first packed absorption tower is provided with a first cooling system, the second packed absorption tower is provided with a second cooling system, and the third packed absorption tower is provided with a third cooling system.
Preferably, the first filler absorption tower is provided with a first liquid inlet and a first liquid outlet, the second filler absorption tower is provided with a second liquid inlet and a second liquid outlet, and the third filler absorption tower is provided with a third liquid inlet and a third liquid outlet.
The method for preparing the sulfuric acid by adopting the system for preparing the sulfuric acid by recycling the waste ferric sulfate crude salt in the acid washing of the steel industry comprises the following steps:
(1) drying of iron sulfate crude salt crystals
Drying ferric sulfate coarse salt crystals obtained by recycling iron-containing mixed acid waste liquid in the iron and steel industry by a parallel-flow rotary-cutting hot air dryer to obtain ferric sulfate crystal powder, wherein the external water content of the ferric sulfate crystal powder is 1-3 wt%;
(2) iron sulfate crystal powder heating decomposition
Ferric sulfate crystal powder is added into a rotary kiln through a spiral feeder, the rotary kiln head moves towards the rotary kiln tail and is gradually heated, the temperature of the rotary kiln head is controlled to be 200 ℃ plus one temperature, the temperature of the rotary kiln body is controlled to be 500 ℃ plus one temperature, the temperature of the rotary kiln tail is controlled to be 750 ℃ plus one temperature, a natural gas spray gun is arranged at the rotary kiln tail, the excess air coefficient is controlled to be 1.2 through the natural gas spray gun, the rotary kiln is ensured to be oxidizing atmosphere, so that the volume content ratio of sulfur trioxide to sulfur dioxide in the mixed gas of sulfur trioxide and sulfur dioxide generated by heating decomposition of ferric sulfate is more than or equal to 99: 1;
(3) gas filtration dust removal
The method comprises the following steps of pumping gas and dust in a rotary kiln into a bag-type dust remover by using an induced draft fan, controlling the temperature of the gas in the bag-type dust remover to be 180-fold and 200 ℃, blocking the dust in mixed gas out of a bag by the bag-type dust remover, and discharging the dust through a spiral discharger at the lower part of the bag-type dust remover;
(4) gas absorption
Under the action of the suction force of the draught fan, gas after dust filtration enters a first air inlet through a connecting pipeline, passes through a packing layer of a first packing absorption tower, enters a second air inlet from the top of the first packing absorption tower through the connecting pipeline, passes through a packing layer of a second packing absorption tower, enters a third air inlet from the top of the second packing absorption tower through the connecting pipeline, passes through the packing layer of the third packing absorption tower, and enters an inlet of the draught fan from the top of the third packing absorption tower through the connecting pipeline;
the first spray pump pressurizes first absorption liquid and downwards sprays the first absorption liquid through a first spray head at the top of the first filler absorption tower to absorb gas upwards passing through a filler layer of the first filler absorption tower, and a first cooling system controls the temperature of the first absorption liquid to be less than 75 ℃;
a second spray pump pressurizes second absorption liquid and downwards sprays the second absorption liquid through a second spray head at the top of a second filler absorption tower to absorb gas upwards passing through a filler layer of the second filler absorption tower, and a second cooling system controls the temperature of the second absorption liquid to be lower than 60 ℃;
and a third spray pump pressurizes third absorption liquid and sprays the third absorption liquid downwards through a third spray head at the top of the third packing absorption tower to absorb gas which upwards passes through a packing layer of the third packing absorption tower, and a third cooling system controls the temperature of the third absorption liquid to be less than 45 ℃.
Preferably, the ferric sulfate crude salt crystals in the step (1) are ferric sulfate dodecahydrate crude salt crystals, and the external water content of the ferric sulfate dodecahydrate crude salt crystals is 35-45 wt%.
Preferably, the drying temperature of the cocurrent flow rotary-cut hot air dryer in the step (1) is set to 250-350 ℃.
Preferably, in the step (3), the gas in the rotary kiln is sulfur trioxide, sulfur dioxide, and residual oxygen, nitrogen and water vapor from combustion, and the dust in the rotary kiln is ferric oxide powder and ferric sulfate powder.
Preferably, the first absorption liquid is purified water, the second absorption liquid is purified water, and the third absorption liquid is 0.5-1wt% of hydrogen peroxide solution.
The invention has the beneficial effects that:
1. according to the invention, the ferric sulfate dodecahydrate crude salt crystal is heated and decomposed into sulfur trioxide, sulfur dioxide and ferric oxide, the generation of sulfur dioxide is inhibited by controlling the excess air coefficient, the ferric oxide can be used as a raw material for steelmaking and also can be used as a raw material for producing iron oxide red, sulfur trioxide is dissolved in water to directly generate sulfuric acid, a small amount of sulfur dioxide is dissolved in water to generate sulfurous acid, the sulfurous acid is unstable, the sulfurous acid in absorption liquid is oxidized into sulfuric acid by using hydrogen peroxide, and resources are effectively utilized.
2. The system for preparing the sulfuric acid from the iron sulfate can be configured according to the actual conditions of enterprises, and has the advantages of large or small scale, low investment, quick response, high acceptable degree and strong applicability.
Drawings
FIG. 1 is a schematic diagram of the system of the present invention;
in the figure: 1-rotary kiln, 2-bag-type dust collector, 3-filler absorption tower, 4-induced draft fan, 5-connecting pipeline, 11-kiln head, 12-spiral feeder, 13-kiln tail, 14-natural gas spray gun 14, 16-powder outlet, 21-spiral discharger 21, 31-first filler absorption tower, 32-second filler absorption tower, 33-third filler absorption tower, 311-first air inlet, 312-first spray nozzle, 313-first absorption liquid, 314-first spray pump, 315-first cooling system, 316-first liquid inlet, 317-first liquid outlet, 321-second air inlet, 322-second spray nozzle, 323-second absorption liquid, 324-second spray pump, 325-second cooling system, 326-second liquid inlet, 327-second liquid outlet, 331-third gas inlet, 332-third spray head, 333-third absorption liquid, 334-third spray pump, 335-third cooling system, 336-third liquid inlet, 337-third liquid outlet.
Detailed Description
For a further understanding of the invention, reference will now be made to the preferred embodiments of the invention by way of example, and it is to be understood that the description is intended to further illustrate features and advantages of the invention, and not to limit the scope of the claims.
As shown in fig. 1:
the utility model provides a system for steel industry pickling recovery waste material ferric sulfate crude salt preparation sulphuric acid, includes rotary kiln 1, sack cleaner 2, filler absorption tower 3 and draught fan 4, connects gradually through connecting tube 5 between rotary kiln 1, sack cleaner 2, filler absorption tower 3 and the draught fan 4, and draught fan 4 provides the draft for the system, makes the system move at negative pressure state.
The kiln head 11 of the rotary kiln 1 is provided with a spiral feeder 12, and the kiln tail 13 of the rotary kiln 1 is provided with a natural gas spray gun 14 and a powder outlet 16. The bag-type dust collector 2 is provided with a spiral discharger 21. The packed absorption tower 3 includes a first packed absorption tower 31, a second packed absorption tower 32, and a third packed absorption tower 33, and the first packed absorption tower 31, the second packed absorption tower 32, and the third packed absorption tower 33 are connected by a connecting pipe 5. The material of filler absorption tower 3 is acidproof PPH material, and the packing layer of filler absorption tower 3 is acidproof PPH material pall ring.
The lower end of the first packed absorption tower 31 is provided with a first gas inlet 311, the top is provided with a first spray head 312, and the bottom is provided with a first absorption liquid 313 and a first spray pump 314. The second packed absorption tower 32 has a second gas inlet 321 at the lower end, a second spray head 322 at the top, and a second absorption liquid 323 and a second spray pump 324 at the bottom. The third packing absorption tower 33 has a third air inlet 331 at its lower end, a third spray head 332 at its top, and a third absorption liquid 333 and a third spray pump 334 at its bottom. The first spray head 312, the second spray head 322 and the third spray head 332 are PPH spiral atomizer spray heads.
The level of the first absorption liquid 313 is controlled below the first gas inlet 311, the level of the second absorption liquid 323 is controlled below the second gas inlet 321, and the level of the third absorption liquid 333 is controlled below the third gas inlet 331.
The first packed absorption tower 31 is provided with a first cooling system 315, the second packed absorption tower 32 is provided with a second cooling system 325, and the third packed absorption tower 33 is provided with a third cooling system 335.
First packed absorption tower 31 is provided with first liquid inlet 316 and first liquid outlet 317, second packed absorption tower 32 is provided with second liquid inlet 326 and second liquid outlet 327, and third packed absorption tower 33 is provided with third liquid inlet 336 and third liquid outlet 337.
Comparative example 1
The method for preparing the sulfuric acid by adopting the system for preparing the sulfuric acid by recycling the waste ferric sulfate crude salt in the acid washing of the steel industry comprises the following steps:
(1) drying of iron sulfate crude salt crystals
The ferric sulfate crude salt crystal obtained by the recovery treatment of the iron-containing mixed acid waste liquid in the steel industry is a dodecahydrate ferric sulfate crude salt crystal, and the external water content of the dodecahydrate ferric sulfate crude salt crystal is 40 wt%. And (3) drying the ferric sulfate coarse salt crystal obtained by recycling the iron-containing mixed acid waste liquid in the iron and steel industry at 300 ℃ by using a parallel-flow rotary-cutting hot air dryer to obtain ferric sulfate crystal powder, wherein the external water content of the ferric sulfate crystal powder is 2%.
(2) Iron sulfate crystal powder heating decomposition
Ferric sulfate crystal powder is added into the rotary kiln 1 through a spiral feeder 12, moves from the kiln head 11 of the rotary kiln to the kiln tail 13 of the rotary kiln and is gradually heated. And in the temperature rise process, the external water is gradually discharged, and the crystal water is gradually discharged. When the iron sulphate crystals are heated above 480 ℃, decomposition starts. Theoretically, ferric sulfate crystals can only generate ferric oxide and sulfur trioxide through thermal decomposition, but in practice, sulfur trioxide gas can be decomposed into sulfur dioxide and oxygen in a small amount under the action of high temperature.
The temperature of a kiln head 11 of the rotary kiln is controlled to be 200 ℃, the temperature of a kiln body 15 of the rotary kiln is controlled to be 400 ℃, the temperature of a kiln tail 13 of the rotary kiln is controlled to be 800 ℃, a natural gas spray gun 14 is arranged at the kiln tail 13 of the rotary kiln, the air excess coefficient is controlled to be 1.0 through an air-natural proportional valve of the natural gas spray gun 14, the rotary kiln 1 is ensured to be an oxidizing atmosphere, the volume content ratio of sulfur trioxide to sulfur dioxide in the mixed gas of sulfur trioxide and sulfur dioxide generated by heating decomposition of ferric sulfate is 90: 10;
(3) gas filtration dust removal
The method comprises the steps of utilizing an induced draft fan 4 to suck gas sulfur trioxide and sulfur dioxide in a rotary kiln 1, and residual oxygen, nitrogen and water vapor generated by combustion, dust ferric oxide powder and ferric sulfate powder into a bag-type dust collector 2, controlling the gas temperature in the bag-type dust collector to be 200 ℃, blocking dust in mixed gas out of a bag by the bag-type dust collector 2, and discharging the dust through a spiral discharger 21 at the lower part of the bag-type dust collector 2.
(4) Gas absorption
Under the effect of draught fan 4 suction, the gas after filtering the dust gets into first air inlet 311 through connecting tube 5, passes first filler absorption tower 31 packing layer, gets into second air inlet 321 through connecting tube 5 from first filler absorption tower 31 top, passes second filler absorption tower 32 packing layer, gets into third air inlet 331 through connecting tube 5 from second filler absorption tower 32 top, passes third filler absorption tower 33 packing layer, gets into the entry of draught fan 4 through connecting tube 5 from third filler absorption tower 33 top.
The first spray pump 314 pressurizes and sprays out the first absorption liquid 313 downward through the first spray head 312 at the top of the first packed absorption tower 31, absorbing the gas passing upward through the packing layer of the first packed absorption tower 31, and the first cooling system 315 controls the temperature of the first absorption liquid 313 to 70 ℃.
The second spray pump 324 pressurizes the second absorption liquid 323 and sprays it downward through the second spray head 322 at the top of the second packed absorption tower 32, absorbing the gas passing upward through the packing layer of the second packed absorption tower 32, and the second cooling system 325 controls the temperature of the second absorption liquid 323 to 55 ℃.
The third spray pump 334 pressurizes the third absorption liquid 333 and sprays it downward through the third spray head 332 at the top of the third packed absorption tower 33, absorbing the gas passing upward through the packing layer of the third packed absorption tower 33, and the third cooling system 335 controls the temperature of the third absorption liquid 333 to 40 ℃.
The first absorption liquid 313 is purified water, the second absorption liquid 323 is purified water, and the third absorption liquid 333 is hydrogen peroxide with a mass concentration of 1 wt%.
The data indexes of the embodiment are the hydrogen peroxide reaction amount and the sulfuric acid generation amount in the third absorption liquid:
the time required for the decomposition rate of ferric sulfate crystals (dry basis, calculated without external water) to reach 99.5% (firing period, i.e. the time from the feeding of the material from the screw feeder to the discharge of ferric oxide from the tail of the rotary kiln) is 4 hours.
63.38 kg of industrial hydrogen peroxide with the concentration of 27.5 percent is consumed by each ton of dry-based ferric sulfate dodecahydrate crystals, the effective utilization rate of the hydrogen peroxide is 95 percent, and 5 percent of hydrogen peroxide is decomposed. Namely, 132.8 kilograms of industrial hydrogen peroxide with the concentration of 27.5 percent is consumed for generating 1 ton of sulfuric acid
Example 1
The method for preparing the sulfuric acid by adopting the system for preparing the sulfuric acid by recycling the waste ferric sulfate crude salt in the acid washing of the steel industry comprises the following steps:
(1) drying of iron sulfate crude salt crystals
The ferric sulfate crude salt crystal obtained by recycling the iron-containing mixed acid waste liquid in the steel industry is a dodecahydrate ferric sulfate crude salt crystal, and the external water content of the dodecahydrate ferric sulfate crude salt crystal is 35 wt%. And (3) drying the ferric sulfate coarse salt crystal obtained by recycling the iron-containing mixed acid waste liquid in the iron and steel industry at 250 ℃ by using a parallel-flow rotary-cutting hot air dryer to obtain ferric sulfate crystal powder, wherein the external water content of the ferric sulfate crystal powder is 3%.
(2) Iron sulfate crystal powder heating decomposition
Ferric sulfate crystal powder is added into the rotary kiln 1 through a spiral feeder 12, moves from the kiln head 11 of the rotary kiln to the kiln tail 13 of the rotary kiln and is gradually heated. And in the temperature rise process, the external water is gradually discharged, and the crystal water is gradually discharged. When the iron sulphate crystals are heated above 480 ℃, decomposition starts. Theoretically, ferric sulfate crystals can only generate ferric oxide and sulfur trioxide through thermal decomposition, but in practice, sulfur trioxide gas can be decomposed into sulfur dioxide and oxygen in a small amount under the action of high temperature.
The temperature of the kiln head 11 of the rotary kiln is controlled to be 180 ℃, the temperature of the kiln body 15 of the rotary kiln is controlled to be 300 ℃, the temperature of the kiln tail 13 of the rotary kiln is controlled to be 500 ℃, the natural gas spray gun 14 is arranged at the kiln tail 13 of the rotary kiln, the air excess coefficient is controlled to be 1.2 through the air natural proportional valve of the natural gas spray gun 14, the rotary kiln 1 is ensured to be an oxidizing atmosphere, the volume content ratio of sulfur trioxide to sulfur dioxide in the mixed gas of sulfur trioxide and sulfur dioxide generated by heating decomposition of ferric sulfate is more than or equal to 99: 1.
(3) Gas filtration dust removal
The method comprises the steps of utilizing an induced draft fan 4 to suck gas sulfur trioxide and sulfur dioxide in a rotary kiln 1, and residual oxygen, nitrogen and water vapor generated by combustion, dust ferric oxide powder and ferric sulfate powder into a bag-type dust collector 2, controlling the gas temperature in the bag-type dust collector to be 180 ℃, blocking dust in mixed gas out of a bag by the bag-type dust collector 2, and discharging the dust through a spiral discharger 21 at the lower part of the bag-type dust collector 2.
(4) Gas absorption
Under the effect of draught fan 4 suction, the gas after filtering the dust gets into first air inlet 311 through connecting tube 5, passes first filler absorption tower 31 packing layer, gets into second air inlet 321 through connecting tube 5 from first filler absorption tower 31 top, passes second filler absorption tower 32 packing layer, gets into third air inlet 331 through connecting tube 5 from second filler absorption tower 32 top, passes third filler absorption tower 33 packing layer, gets into the entry of draught fan 4 through connecting tube 5 from third filler absorption tower 33 top.
The first spray pump 314 pressurizes and sprays out the first absorption liquid 313 downward through the first spray head 312 at the top of the first packed absorption tower 31, absorbing the gas passing upward through the packing layer of the first packed absorption tower 31, and the first cooling system 315 controls the temperature of the first absorption liquid 313 to 70 ℃.
The second spray pump 324 pressurizes the second absorption liquid 323 and sprays it downward through the second spray head 322 at the top of the second packed absorption tower 32, absorbing the gas passing upward through the packing layer of the second packed absorption tower 32, and the second cooling system 325 controls the temperature of the second absorption liquid 323 to 55 ℃.
The third spray pump 334 pressurizes the third absorption liquid 333 and sprays it downward through the third spray head 332 at the top of the third packed absorption tower 33, absorbing the gas passing upward through the packing layer of the third packed absorption tower 33, and the third cooling system 335 controls the temperature of the third absorption liquid 333 to 40 ℃.
The first absorbing liquid 313 is purified water, the second absorbing liquid 323 is purified water, and the third absorbing liquid 333 is a hydrogen peroxide solution having a mass concentration of 0.5 wt%.
The data indexes of the embodiment are the hydrogen peroxide reaction amount and the sulfuric acid generation amount in the third absorption liquid:
the time required for the decomposition rate of ferric sulfate crystals (dry basis, calculated without external water) to reach 99.5% (firing period, i.e. the time from the feeding of the material from the screw feeder to the discharge of ferric oxide from the tail of the rotary kiln) is 8 hours.
6.338 kg of industrial hydrogen peroxide with the concentration of 27.5 percent is consumed by each ton of dry-based ferric sulfate dodecahydrate crystals, the effective utilization rate of the hydrogen peroxide is 95 percent, and 5 percent of hydrogen peroxide is decomposed. Namely, 13.28 kilograms of industrial hydrogen peroxide with the concentration of 27.5 percent is consumed for generating 1 ton of sulfuric acid.
Example 2
The method for preparing the sulfuric acid by adopting the system for preparing the sulfuric acid by recycling the waste ferric sulfate crude salt in the acid washing of the steel industry comprises the following steps:
(1) drying of iron sulfate crude salt crystals
The ferric sulfate crude salt crystal obtained by the recovery treatment of the iron-containing mixed acid waste liquid in the steel industry is a dodecahydrate ferric sulfate crude salt crystal, and the external water content of the dodecahydrate ferric sulfate crude salt crystal is 40 wt%. And (3) drying the ferric sulfate coarse salt crystal obtained by recycling the iron-containing mixed acid waste liquid in the iron and steel industry at 300 ℃ by using a parallel-flow rotary-cutting hot air dryer to obtain ferric sulfate crystal powder, wherein the external water content of the ferric sulfate crystal powder is 2%.
(2) Iron sulfate crystal powder heating decomposition
Ferric sulfate crystal powder is added into the rotary kiln 1 through a spiral feeder 12, moves from the kiln head 11 of the rotary kiln to the kiln tail 13 of the rotary kiln and is gradually heated. And in the temperature rise process, the external water is gradually discharged, and the crystal water is gradually discharged. When the iron sulphate crystals are heated above 480 ℃, decomposition starts. Theoretically, ferric sulfate crystals can only generate ferric oxide and sulfur trioxide through thermal decomposition, but in practice, sulfur trioxide gas can be decomposed into sulfur dioxide and oxygen in a small amount under the action of high temperature.
The temperature of the kiln head 11 of the rotary kiln is controlled to be 200 ℃, the temperature of the kiln body 15 of the rotary kiln is controlled to be 400 ℃, the temperature of the kiln tail 13 of the rotary kiln is controlled to be 600 ℃, the natural gas spray gun 14 is arranged at the kiln tail 13 of the rotary kiln, the air excess coefficient is controlled to be 1.2 through the air natural proportional valve of the natural gas spray gun 14, the rotary kiln 1 is ensured to be an oxidizing atmosphere, the volume content ratio of sulfur trioxide to sulfur dioxide in the mixed gas of sulfur trioxide and sulfur dioxide generated by heating decomposition of ferric sulfate is more than or equal to 99: 1.
(3) Gas filtration dust removal
The method comprises the steps of utilizing an induced draft fan 4 to suck gas sulfur trioxide and sulfur dioxide in a rotary kiln 1, and residual oxygen, nitrogen and water vapor generated by combustion, dust ferric oxide powder and ferric sulfate powder into a bag-type dust collector 2, controlling the gas temperature in the bag-type dust collector to be 200 ℃, blocking dust in mixed gas out of a bag by the bag-type dust collector 2, and discharging the dust through a spiral discharger 21 at the lower part of the bag-type dust collector 2.
(4) Gas absorption
Under the effect of draught fan 4 suction, the gas after filtering the dust gets into first air inlet 311 through connecting tube 5, passes first filler absorption tower 31 packing layer, gets into second air inlet 321 through connecting tube 5 from first filler absorption tower 31 top, passes second filler absorption tower 32 packing layer, gets into third air inlet 331 through connecting tube 5 from second filler absorption tower 32 top, passes third filler absorption tower 33 packing layer, gets into the entry of draught fan 4 through connecting tube 5 from third filler absorption tower 33 top.
The first spray pump 314 pressurizes and sprays out the first absorption liquid 313 downward through the first spray head 312 at the top of the first packed absorption tower 31, absorbing the gas passing upward through the packing layer of the first packed absorption tower 31, and the first cooling system 315 controls the temperature of the first absorption liquid 313 to 70 ℃.
The second spray pump 324 pressurizes the second absorption liquid 323 and sprays it downward through the second spray head 322 at the top of the second packed absorption tower 32, absorbing the gas passing upward through the packing layer of the second packed absorption tower 32, and the second cooling system 325 controls the temperature of the second absorption liquid 323 to 55 ℃.
The third spray pump 334 pressurizes the third absorption liquid 333 and sprays it downward through the third spray head 332 at the top of the third packed absorption tower 33, absorbing the gas passing upward through the packing layer of the third packed absorption tower 33, and the third cooling system 335 controls the temperature of the third absorption liquid 333 to 40 ℃.
In this embodiment, the first absorbing liquid 313 is purified water, the second absorbing liquid 323 is purified water, and the third absorbing liquid 333 is a hydrogen peroxide solution with a mass concentration of 1 wt%.
The data indexes of the embodiment are the hydrogen peroxide reaction amount and the sulfuric acid generation amount in the third absorption liquid:
the time required for the decomposition rate of ferric sulfate crystals (dry basis, calculated without external water) to reach 99.5% (firing period, i.e. the time from the feeding of the material from the screw feeder to the discharge of ferric oxide from the tail of the rotary kiln) is 6 hours.
6.338 kg of industrial hydrogen peroxide with the concentration of 27.5 percent is consumed by each ton of dry-based ferric sulfate dodecahydrate crystals, the effective utilization rate of the hydrogen peroxide is 95 percent, and 5 percent of hydrogen peroxide is decomposed. Namely, 13.28 kilograms of industrial hydrogen peroxide with the concentration of 27.5 percent is consumed for generating 1 ton of sulfuric acid.
Example 3
The method for preparing the sulfuric acid by adopting the system for preparing the sulfuric acid by recycling the waste ferric sulfate crude salt in the acid washing of the steel industry comprises the following steps:
(1) drying of iron sulfate crude salt crystals
The ferric sulfate crude salt crystal obtained by the recovery treatment of the iron-containing mixed acid waste liquid in the steel industry is a dodecahydrate ferric sulfate crude salt crystal, and the external water content of the dodecahydrate ferric sulfate crude salt crystal is 45 wt%. And (3) drying the ferric sulfate coarse salt crystal obtained by recycling the iron-containing mixed acid waste liquid in the iron and steel industry at 350 ℃ by using a parallel-flow rotary-cutting hot air dryer to obtain ferric sulfate crystal powder, wherein the external water content of the ferric sulfate crystal powder is 3%.
(2) Iron sulfate crystal powder heating decomposition
Ferric sulfate crystal powder is added into the rotary kiln 1 through a spiral feeder 12, moves from the kiln head 11 of the rotary kiln to the kiln tail 13 of the rotary kiln and is gradually heated. And in the temperature rise process, the external water is gradually discharged, and the crystal water is gradually discharged. When the iron sulphate crystals are heated above 480 ℃, decomposition starts. Theoretically, ferric sulfate crystals can only generate ferric oxide and sulfur trioxide through thermal decomposition, but in practice, sulfur trioxide gas can be decomposed into sulfur dioxide and oxygen in a small amount under the action of high temperature.
The temperature of the kiln head 11 of the rotary kiln is controlled to be 200 ℃, the temperature of the kiln body 15 of the rotary kiln is controlled to be 500 ℃, the temperature of the kiln tail 13 of the rotary kiln is controlled to be 750 ℃, the natural gas spray gun 14 is arranged at the kiln tail 13 of the rotary kiln, the air excess coefficient is controlled to be 1.2 through the air natural proportional valve of the natural gas spray gun 14, the rotary kiln 1 is ensured to be an oxidizing atmosphere, and the volume content ratio of sulfur trioxide to sulfur dioxide in the mixed gas of sulfur trioxide and sulfur dioxide generated by heating decomposition of ferric sulfate is more than or equal to 100%.
(3) Gas filtration dust removal
The method comprises the steps of utilizing an induced draft fan 4 to suck gas sulfur trioxide and sulfur dioxide in a rotary kiln 1, and residual oxygen, nitrogen and water vapor generated by combustion, dust ferric oxide powder and ferric sulfate powder into a bag-type dust collector 2, controlling the gas temperature in the bag-type dust collector to be 200 ℃, blocking dust in mixed gas out of a bag by the bag-type dust collector 2, and discharging the dust through a spiral discharger 21 at the lower part of the bag-type dust collector 2.
(4) Gas absorption
Under the effect of draught fan 4 suction, the gas after filtering the dust gets into first air inlet 311 through connecting tube 5, passes first filler absorption tower 31 packing layer, gets into second air inlet 321 through connecting tube 5 from first filler absorption tower 31 top, passes second filler absorption tower 32 packing layer, gets into third air inlet 331 through connecting tube 5 from second filler absorption tower 32 top, passes third filler absorption tower 33 packing layer, gets into the entry of draught fan 4 through connecting tube 5 from third filler absorption tower 33 top.
The first spray pump 314 pressurizes and sprays out the first absorption liquid 313 downward through the first spray head 312 at the top of the first packed absorption tower 31, absorbing the gas passing upward through the packing layer of the first packed absorption tower 31, and the first cooling system 315 controls the temperature of the first absorption liquid 313 to 65 ℃.
The second spray pump 324 pressurizes the second absorption liquid 323 and sprays it downward through the second spray head 322 at the top of the second packed absorption tower 32, absorbing the gas passing upward through the packing layer of the second packed absorption tower 32, and the second cooling system 325 controls the temperature of the second absorption liquid 323 to 55 ℃.
The third spray pump 334 pressurizes the third absorption liquid 333 and sprays it downward through the third spray head 332 at the top of the third packed absorption tower 33, absorbing the gas passing upward through the packing layer of the third packed absorption tower 33, and the third cooling system 335 controls the temperature of the third absorption liquid 333 to 35 ℃.
The first absorbing liquid 313 is purified water, the second absorbing liquid 323 is purified water, and the third absorbing liquid 333 is a hydrogen peroxide solution having a mass concentration of 1 wt%.
The data indexes of the embodiment are the hydrogen peroxide reaction amount and the sulfuric acid generation amount in the third absorption liquid:
the time required for the decomposition rate of ferric sulfate crystals (dry basis, calculated without external water) to reach 99.5% (firing period, i.e. the time from the feeding of the material from the screw feeder to the discharge of ferric oxide from the tail of the rotary kiln) is 5 hours.
6.272 kg of industrial hydrogen peroxide with the concentration of 27.5 percent is consumed by each ton of dry-based ferric sulfate dodecahydrate crystals, the effective utilization rate of the hydrogen peroxide is 96 percent, and 4 percent of hydrogen peroxide is decomposed. Namely, 13.14 kilograms of industrial hydrogen peroxide with the concentration of 27.5 percent is consumed for generating 1 ton of sulfuric acid.
The temperature of the high-temperature zone at the tail part of the rotary kiln determines the time required by the dodecahydrate ferric sulfate crystal to reach the decomposition rate of more than 99.5 percent, namely, the temperature is high, the firing period is short, and the relative yield is high. Low temperature, long sintering period and low relative output. However, the content of sulfur dioxide gas in the mixed gas is increased rapidly after the temperature exceeds 750 ℃, so that the consumption of industrial hydrogen peroxide required for completely generating sulfuric acid from the sulfur dioxide gas and enabling tail gas to reach the standard to be discharged is increased rapidly, and therefore, the maximum firing temperature at the tail part of the rotary kiln is limited to be 500-750 ℃.
The third cooling system 335 controls the temperature of the third absorption liquid 333 to be 35 c. The effective utilization rate of hydrogen peroxide is 96%, and 4% of hydrogen peroxide is decomposed. The third cooling system 335 controls the temperature of the third absorption liquid 333 to be 40 ℃. The effective utilization rate of hydrogen peroxide is 95%, and 5% of hydrogen peroxide is decomposed. The higher the temperature of the third absorbing liquid 333 is, the more easily the hydrogen peroxide is decomposed. However, it is preferable to control the temperature of the third absorption liquid 333 at 40 ℃ from the viewpoint of the overall economy. When the temperature of the third absorption liquid 333 is controlled to be 40 ℃, the third cooling system 335 may be a cold water tower.
When the third absorption liquid 333 is a hydrogen peroxide solution with a mass concentration of 0.5-1wt%, the effective utilization rate of hydrogen peroxide can reach 95% and the decomposition rate of hydrogen peroxide can be less than 5% when a trace stabilizer is added into the hydrogen peroxide solution and the temperature is controlled below 40 ℃. When the mass concentration exceeds 1%, the effective utilization rate of hydrogen peroxide is reduced along with the increase of the concentration, and the decomposition rate of hydrogen peroxide is increased.
The external water content in the present invention is a water content excluding crystal water.
The gas absorption principle of the invention is as follows: the lower part of the filler absorption tower is filled with absorption liquid, the liquid level is controlled at the lower part of the air inlet, and the lower part of each filler absorption tower is provided with an inlet and the absorption liquidThe spraying pump is connected with the absorption liquid, the absorption liquid is pressurized by the spraying pump and is sprayed out downwards through a spray head at the top of the packing absorption tower, the spraying pump is in full contact with mixed gas which upwards passes through the packing layer, and sulfur trioxide gas is dissolved in water to generate sulfuric acid. In order to enhance the absorption effect, the absorption liquid of each filler absorption tower is provided with a set of cooling system, and the cooling system is mainly used for cooling the absorption liquid, enhancing the absorption effect and reducing the generation of acid vapor. The dissolution of sulfur trioxide gas in water produces sulfuric acid and releases heat. Each set of cooling system comprises 1 cooling circulating pump, 1 shell and tube indirect heat exchanger and 1 pipeline. The cooling circulating pump pumps absorption liquid (dilute sulfuric acid) at the lower part of the filler absorption tower, and the absorption liquid returns to the lower part of the filler absorption tower after being cooled by the tubular indirect heat exchanger. The gas generated by the rotary kiln comprises sulfur trioxide, sulfur dioxide, water vapor, and residual oxygen and nitrogen generated by combustion, and the nitrogen sequentially passes through the first filler absorption tower, the second filler absorption tower and the third filler absorption tower, the sulfur trioxide, the sulfur dioxide and part of the water vapor are absorbed, and the residual gas contains the water vapor, the residual oxygen and the nitrogen generated by combustion. And adding a small amount of industrial hydrogen peroxide into the absorption liquid at the lower part of the third filler absorption tower, wherein the concentration is controlled to be 0.5-1%, and the industrial hydrogen peroxide is mainly used for absorbing sulfur dioxide in residual gas, so that the sulfur dioxide content in the discharged gas is within the national environmental protection control standard and reaches the standard for discharge. The reaction equation is as follows: h2O2+SO2=H2SO4。
When the absorption liquid level in the lower part of the third packed absorption tower 33 rises to the high level line due to the absorption gas, the absorption liquid in the lower part of the third packed absorption tower 33 can be transferred to the second packed absorption tower 32 through the third liquid outlet 337 until the absorption liquid level in the lower part of the third packed absorption tower 33 falls to the low level line.
When the liquid level of the absorption liquid in the lower portion of the second packed absorption tower 32 rises to the high level line due to the absorption gas, the absorption liquid in the lower portion of the second packed absorption tower 32 can be transferred to the first packed absorption tower 31 through the second liquid outlet 327 until the liquid level of the absorption liquid in the lower portion of the second packed absorption tower 32 falls to the low level line.
When the liquid level of the absorption liquid in the lower portion of the first packed absorption tower 31 rises to the high level line due to the absorption gas, the absorption liquid in the lower portion of the first packed absorption tower 31 is transferred to the storage tank through the first liquid outlet 317, and then the storage tank is used in addition to the pickling line.
The method mainly comprises the step-by-step enrichment of the absorption liquid dilute sulfuric acid, wherein the concentration of the absorption liquid dilute sulfuric acid at the lower part of the third filler absorption tower 33 is generally controlled to be 10%, the concentration of the absorption liquid dilute sulfuric acid at the lower part of the second filler absorption tower 32 is controlled to be 20%, and the concentration of the absorption liquid dilute sulfuric acid at the lower part of the first filler absorption tower 31 is controlled to be 40%.
According to the invention, the ferric sulfate dodecahydrate crude salt crystal is heated and decomposed into sulfur dioxide, sulfur trioxide and ferric oxide, the generation of sulfur dioxide is inhibited by controlling the excess air coefficient, the ferric oxide can be used as a raw material for steelmaking and also can be used as a raw material for producing iron oxide red, sulfur trioxide is dissolved in water to directly generate sulfuric acid, a small amount of sulfur dioxide is dissolved in water to generate sulfurous acid, the sulfurous acid is unstable, the sulfurous acid in absorption liquid is oxidized into sulfuric acid by using hydrogen peroxide, and resources are effectively utilized.
The system for preparing the sulfuric acid by utilizing the ferric sulfate has the advantages of changeable scale, low investment, quick response and acceptance by most stainless steel pickling enterprises.
Those skilled in the art to which the present invention pertains can also make appropriate alterations and modifications to the above-described embodiments, in light of the above disclosure. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and variations of the present invention should fall within the scope of the claims of the present invention. Furthermore, although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.