CN114053839B - Method and system for cleaning and treating cyanide-containing SRG gas and purifying tail gas of hot blast stove - Google Patents

Method and system for cleaning and treating cyanide-containing SRG gas and purifying tail gas of hot blast stove Download PDF

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CN114053839B
CN114053839B CN202010778087.0A CN202010778087A CN114053839B CN 114053839 B CN114053839 B CN 114053839B CN 202010778087 A CN202010778087 A CN 202010778087A CN 114053839 B CN114053839 B CN 114053839B
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washing tower
wastewater
gas
sulfuric acid
stage washing
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CN114053839A (en
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杨本涛
魏进超
康建刚
李俊杰
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Zhongye Changtian International Engineering Co Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
    • B01D53/18—Absorbing units; Liquid distributors therefor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
    • B01D53/1431—Pretreatment by other processes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
    • B01D53/1456—Removing acid components
    • B01D53/1481—Removing sulfur dioxide or sulfur trioxide
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
    • B01D53/1493—Selection of liquid materials for use as absorbents
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/66—Treatment of water, waste water, or sewage by neutralisation; pH adjustment
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2252/00—Absorbents, i.e. solvents and liquid materials for gas absorption
    • B01D2252/10—Inorganic absorbents
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
    • C02F2103/18—Nature of the water, waste water, sewage or sludge to be treated from the purification of gaseous effluents

Abstract

A method for cleaning and treating cyanide-containing SRG gas and purifying tail gas of a hot blast stove comprises the following steps: 1) The cyanide-containing SRG gas sequentially passes through a first-stage washing tower, a second-stage washing tower and a third-stage washing tower, and the washed gas is discharged from the third-stage washing tower; 2) The washed gas enters an acid making system for acid making to obtain concentrated sulfuric acid; 3) The process water sequentially passes through a three-stage washing tower, a second-stage washing tower and a first-stage washing tower to wash and purify SRG gas, the wastewater in the first-stage washing tower is discharged to a primary sedimentation tank, and the wastewater at the upper part of the primary sedimentation tank enters SO 2 A desorption tower; SO (SO) 2 Desorption tower for removing SO in wastewater 2 Discharging the wastewater to a wastewater collection tank; 4) Conveying the process water and the concentrated sulfuric acid into a concentrated sulfuric acid diluter for mixing to obtain dilute sulfuric acid; and (3) introducing dilute sulfuric acid into a wastewater collection tank, introducing hot blast furnace tail gas into the wastewater collection tank, reacting the dilute sulfuric acid with wastewater, and discharging acid washing wastewater. The invention uses the tail gas of the hot blast stove as a heat source, improves the temperature of the waste water and realizes the efficient utilization of residual energy.

Description

Method and system for cleaning and treating cyanide-containing SRG gas and purifying tail gas of hot blast stove
Technical Field
The invention relates to a method for treating SRG gas, in particular to a method and a system for cleaning and treating cyanide-containing SRG gas and purifying tail gas of a hot blast stove, belonging to the field of resource environment protection.
Background
The sintering flue gas in the steel industry adopts an active carbon method to carry out desulfurization and denitrification to carry out a flue gas purification process, and sulfur dioxide gas collected by active carbon is concentrated and released and then is sent to a sulfur resource workshop to produce sulfur resources. The flue gas enriched with sulfur dioxide gas is called sulfur-rich gas (SRG flue gas) for short, and the gas can be prepared into sulfur resources meeting the national standard through the procedures of purification, drying, conversion, absorption and the like, and the resource recovery value is high. However, impurities and harmful elements in the flue gas can be simultaneously washed and enter acid washing wastewater in a purification process in the sulfur resource production process, and part of sulfur dioxide gas in the flue gas can be absorbed by water vapor and brought into the wastewater.
Generally, acidic wash wastewater tends to be acidic because the acidic species in the SRG gas are greater than the basic species. When cyanide and derivatives thereof exist in the front-end flue gas, the cyanide and derivatives thereof enter SRG gas and are finally dissolved in the acidic washing wastewater, so that the alkalinity of the wastewater (such as hydrolysis of cyanic acid to generate ammonia nitrogen) is increased, and the acidic washing wastewater is neutral. Since the acidic washing wastewater is neutral, a large amount of SO in SRG gas can be caused 2 The acid gas dissolves, causing a dramatic increase in bisulphite in the wastewater. The detection result shows that the concentration of the hydrogen sulfite of the acid washing wastewater generated by the cyanide-free SRG gas washing is 2-5 g/L, and the concentration of the hydrogen sulfite of the acid washing wastewater generated by the cyanide-containing SRG gas washing is 240-300 g/L.
The acidic washing wastewater with the high-concentration hydrogen sulfite has great treatment difficulty if entering a subsequent wastewater treatment system. On one hand, the alkali consumption is increased sharply, so that the waste of liquid alkali is caused, and the wastewater discharge amount is increased; in addition, sodium sulfite is crystallized and separated out in the alkaline adding process, so that the system is blocked and paralyzed.
In addition, in the prior art, a hot blast stove is generally used to burn blast furnace gas or coke oven gas and then produce high-temperature flue gas (500 ℃) as a heat source. And after the high-temperature flue gas enters the analysis tower, the heating and regeneration of the activated carbon are realized through indirect heat exchange of the tube array. And after the high-temperature flue gas passes through the resolving tower, the temperature can be reduced to about 280 ℃, namely the tail gas of the hot blast stove. Through detection, the tail gas of the hot blast stove mainly comprises CO 2 、H 2 O、N 2 And a small amount of dust. From the following componentsThe tail gas of the hot blast stove has a certain temperature, and the activated carbon flue gas purification system is sensitive to the temperature, so that the hot blast stove is difficult to directly return to the activated carbon adsorption tower, and most of similar projects at present adopt chimney direct discharge treatment to cause dust discharge pollution.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a method and a system for cleaning and treating cyanide-containing SRG gas and purifying tail gas of a hot blast stove. The invention dilutes part of concentrated sulfuric acid prepared in the acid preparation process, adjusts washing wastewater to be acidic and discharges the acidic wastewater, simultaneously utilizes waste heat of hot blast stove tail gas to heat the acidic wastewater, utilizes a self system to carry out waste gas treatment, prevents secondary pollution, realizes effective removal of pollutants in the hot blast stove tail gas, and finally realizes great reduction of salt content of the acidic washing wastewater and great improvement of sulfuric acid yield.
According to a first embodiment of the invention, a method for cleaning and treating cyanide-containing SRG gas and purifying tail gas of a hot blast stove is provided.
The method for cleaning and treating the cyanide-containing SRG gas and purifying the tail gas of the hot blast stove comprises the following steps:
1) The SRG gas containing cyanogen enters a first-stage washing tower from the lower part, sequentially passes through the first-stage washing tower, a second-stage washing tower and a third-stage washing tower, and is respectively in countercurrent contact with washing solution in each tower, and the washed gas is discharged from the top of the third-stage washing tower.
2) And (3) introducing the gas discharged from the top of the three-stage washing tower into an acid making system for acid making to obtain concentrated sulfuric acid.
3) The process water enters a three-stage washing tower from the bottom, the process water sequentially passes through the three-stage washing tower, a second-stage washing tower and a first-stage washing tower to wash and purify the SRG gas containing cyanide, the wastewater in the washing and purifying first-stage washing tower is discharged to a primary sedimentation tank, and the wastewater at the upper part of the primary sedimentation tank enters SO 2 And (3) a desorption tower. SO (SO) 2 Desorption tower for removing SO physically dissolved in wastewater 2 The wastewater is then discharged to a wastewater collection tank.
4) And (3) conveying the process water and the concentrated sulfuric acid prepared in the step (2) into a concentrated sulfuric acid diluter for mixing to obtain dilute sulfuric acid. And (3) introducing dilute sulfuric acid into a wastewater collection tank, introducing hot blast furnace tail gas into the wastewater collection tank, reacting the dilute sulfuric acid with wastewater, and discharging acid washing wastewater after the reaction.
In the present invention, the method comprises: 5) The concentrated sulfuric acid obtained in step 2) was used for the sale.
Preferably, in step 4), the amount of hot blast stove off-gas (Nm) fed to the waste water collection tank 3 And/h) is the amount of wastewater (m) in the wastewater collection tank 3 /h)) 200-300 times. Preferably, the temperature of the hot blast stove tail gas is 220-350 ℃, preferably 250-320 ℃, more preferably 270-290 ℃.
Preferably, in step 3), the wastewater in the lower part of the primary settling tank is passed to a wastewater collection tank. Preferably, the wastewater at the lower part of the primary settling tank is also led to a sludge storage tank.
In the invention, one part of the wastewater at the lower part (or bottom) of the primary sedimentation tank is introduced into a wastewater collection tank, and the other part is introduced into a sludge storage tank for further treatment. The wastewater amount introduced into the wastewater collection tank is 1/20-1/30 of the total wastewater amount of the primary sedimentation tank.
Preferably, in step 1), the SRG gas is passed through a primary scrubber prior to being combined with SO 2 And merging sulfur-containing gas generated by the desorption tower, and then entering a secondary washing tower for washing and purifying. Preferably, in step 4), the waste gas after the reaction of dilute sulfuric acid with the waste water is introduced into SO 2 And (3) a desorption tower.
In step 3) of the present invention, a part of the wastewater in the upper part of the preliminary sedimentation tank enters (overflows to) SO 2 The other part of the desorption tower is led into (overflowed to) the first-stage washing tower.
In the invention, the wastewater at the upper part of the primary sedimentation tank enters SO 2 The ratio of the waste water amount of the desorption tower to the waste water amount (volume) of the waste water introduced into the first-stage washing tower is 1:5-10.
Preferably, in the step 3), a part of the process water entering the three-stage washing tower is recycled in the three-stage washing tower, and the other part enters the second-stage washing tower. One part of the wastewater entering the second-stage washing tower from the third-stage washing tower is recycled in the second-stage washing tower, and the other part enters the first-stage washing tower.
In the invention, the first-stage washing tower, the second-stage washing tower and the third-stage washing tower aim at removing impurities in SRG gas by adopting wet washing, and the gas and the solution in the washing tower are in reverse contact, namely the gas flows from bottom to top and the solution flows from top to bottom. Wherein, the volume ratio of the solution amount used for the circulation in the three-stage washing tower to the solution amount introduced into the two-stage washing tower is 5-12:1. The ratio of the solution amount circularly used in the second-stage washing tower to the solution amount introduced into the first-stage washing tower is 5-12:1.
In step 4) of the present invention, the pH of the acidic washing wastewater after the reaction is 0 to 3, preferably 0.5 to 2.5, more preferably 1 to 2.
Preferably, in step 4), the amount of dilute sulfuric acid fed to the wastewater collection tank is such that the ratio of the molar amount of hydrogen ions in the dilute sulfuric acid to the molar amount of sulfite ions in the wastewater is from 1:0.1 to 1, preferably from 1:0.2 to 0.6, more preferably from 1:0.3 to 0.5.
That is, in the present invention, only a part (as needed) of the concentrated sulfuric acid produced in step 2) is fed to the primary scrubber, while the remaining part of the concentrated sulfuric acid is still available for sale.
Preferably, the concentration of sulfuric acid in the dilute sulfuric acid is 30 to 80%, preferably 40 to 70%, more preferably 50 to 60%.
In step 3) of the present invention, the pH of the liquid entering the three-stage scrubber is 5 to 7, preferably 5.5 to 6.
Preferably, in step 3), the pH of the liquid entering the secondary scrubber is between 3 and 5, preferably between 3.5 and 4.5.
Preferably, in step 3), the liquid entering the primary scrubber has a pH of 2 to 4, preferably 2.5 to 3.5.
Preferably, in step 3), the liquid discharged from the primary scrubber has a pH of 4 to 6, preferably 4.5 to 5.5.
In step 1) of the present invention, the temperature of the SRG gas entering the primary scrubber is from 250 to 480 ℃, preferably from 300 to 450 ℃, more preferably from 380 to 430 ℃.
Preferably, in step 1), the temperature of the gas entering the secondary scrubber is 50 to 150 ℃, preferably 70 to 100 ℃.
Preferably, in step 1), the gas temperature entering the three-stage scrubber is from 10 to 80 ℃, preferably from 30 to 60 ℃.
Preferably, in step 1), the temperature of the gas discharged from the three-stage scrubber is from 10 to 60 ℃, preferably from 20 to 40 ℃.
In step 3) of the present invention, the temperature of the liquid entering the three-stage scrubber is 10 to 60 ℃, preferably 20 to 40 ℃.
Preferably, in step 3), the temperature of the liquid entering the secondary scrubber is between 10 and 80 ℃, preferably between 30 and 60 ℃.
Preferably, in step 3), the temperature of the liquid entering the primary scrubber is from 30 to 100 ℃, preferably from 50 to 80 ℃.
Preferably, in step 3), the temperature of the liquid discharged from the primary scrubber is 50 to 120 ℃, preferably 70 to 90 ℃.
In the present invention, the concentration of suspended matter in the wastewater collection tank is 600 to 2500mg/L, preferably 800 to 2300mg/L.
In the invention, a part of wastewater at the bottom of the primary sedimentation tank is introduced into the wastewater collection tank to control the suspended matter content of the wastewater collection tank so as to realize the adsorption of colloidal sulfur.
In step 3) of the present invention, the concentration of suspended matter in the wastewater at the upper part of the preliminary tank is 0 to 100mg/L, preferably 1 to 80mg/L, more preferably 2 to 50mg/L.
The primary settling tank removes suspended matters through the sedimentation effect of the gravity of the suspended matters.
According to a second embodiment of the invention, a system for cleaning and treating cyanide-containing SRG gas and purifying tail gas of a hot blast stove is provided.
A system for cleaning and treating cyanide-containing SRG gas and purifying hot blast stove tail gas using the above method, the system comprising: primary washing tower, secondary washing tower, tertiary washing tower, acid making system, primary settling tank and SO 2 A desorption tower, a waste water collecting tank and a concentrated sulfuric acid diluter. The SRG gas conveying pipeline is connected to the gas inlet of the first-stage washing tower, and the first-stage washing tower is provided with a gas inlet The gas outlet of the scrubbing tower is connected to the gas inlet of the second-stage scrubbing tower via a first pipeline, the gas outlet of the second-stage scrubbing tower is connected to the gas inlet of the third-stage scrubbing tower via a second pipeline, and the gas outlet of the third-stage scrubbing tower is connected to the acid making system via a third pipeline.
The first conveying pipeline of the process water is connected to the bottom liquid inlet of the three-stage washing tower, the liquid outlet of the three-stage washing tower is connected to the lower liquid inlet of the second-stage washing tower through a fourth pipeline, the liquid outlet of the second-stage washing tower is connected to the lower liquid inlet of the first-stage washing tower through a fifth pipeline, the liquid outlet of the first-stage washing tower is connected to the primary settling tank through a sixth pipeline, and the upper liquid outlet of the primary settling tank is connected to SO through a seventh pipeline 2 A liquid inlet of the desorption column. SO (SO) 2 The liquid outlet of the desorption column is connected to the wastewater collection tank via an eighth conduit. The liquid outlet of the acid making system is connected to the concentrated sulfuric acid diluter through a concentrated sulfuric acid conveying pipeline, and the process water second conveying pipeline is connected to the concentrated sulfuric acid diluter. The liquid outlet of the concentrated sulfuric acid diluter is connected via a ninth pipe to the liquid inlet of the wastewater collection tank. The hot blast stove tail gas conveying pipeline is connected to the gas inlet of the waste water collecting tank.
Preferably, the bottom liquid outlet of the primary settling tank is connected to the liquid inlet of the wastewater collection tank via a tenth conduit. Preferably, an eleventh pipeline is branched from the tenth pipeline, and the eleventh pipeline is connected to the sludge storage tank.
Preferably, a twelfth pipe leading from the waste gas outlet of the waste water collecting tank is connected to the SO 2 A gas inlet of the desorption column. SO (SO) 2 The gas outlet of the desorption column is connected to the first conduit via a thirteenth conduit.
Preferably, a fourteenth pipe is branched from the seventh pipe, and the fourteenth pipe is connected to the upper liquid inlet of the first-stage scrubber.
Preferably, a fifteenth pipe is branched from the fifth pipe, and the fifteenth pipe is connected to the upper liquid inlet of the secondary scrubber. A sixteenth pipeline is separated from the fourth pipeline and is connected to the upper liquid inlet of the three-stage washing tower.
In the invention, the gas inlet of the first-stage washing tower, the second-stage washing tower or the third-stage washing tower is arranged at the lower part of the corresponding device, and the gas outlet is arranged at the top of the corresponding device. The bottom liquid inlet is typically located at the bottom of the device. While the upper liquid inlet and the lower liquid inlet are a relative concept, generally the upper liquid inlet is arranged in the upper part of the device and the lower liquid inlet is arranged in the lower part of the device, the upper liquid inlet being located above the lower liquid inlet. The upper liquid outlet and the lower liquid outlet are also a relative concept, and generally the upper liquid outlet is located above the lower liquid outlet.
In the prior art, after the SRG gas is washed and purified by process water, sulfur dioxide gas with higher purity is obtained and is used for preparing acid by two-rotation and two-absorption, and the waste water generated after washing is finally discharged from a system after passing through a stripping tower, so that acid washing waste water is formed. Generally, the acidic materials in SRG gases are greater than the basic materials, and thus, acidic wash wastewater tends to be acidic. However, when cyanide and its derivatives are present in the front-end flue gas, the cyanide and its derivatives may enter the SRG gas and eventually dissolve in the wash wastewater, and as the cyanic acid hydrolyzes to form ammonia nitrogen, the dissolution of cyanide and its derivatives may increase the alkalinity of the wash wastewater, rendering the wash wastewater neutral. When the washing wastewater is neutral, a large amount of SO in SRG gas can be caused 2 The acid gas dissolves, causing a sharp increase in sulfite in the wastewater. The washing wastewater with high concentration of sulfite has great treatment difficulty.
In consideration of the condition that cyanide and derivatives thereof exist in front-end flue gas, the self-produced sulfuric acid is diluted, washing wastewater is regulated to be acidic and then discharged, and a self-system is utilized for waste gas treatment. By this improvement, there are the following advantages:
(1) The cyanide and the derivative thereof are hydrolyzed into ammonium ions, so that the washing liquid is weak acid or neutral. According to SO 3 2- The ion fraction curve of (2) shows that SO when the solution is weakly acidic or neutral 2 Can be dissolved and become bisulphite. Thus, the solution for washing the SRG is mainly prepared by ammonium bisulfate (NH) 4 HSO 3 ) Is present, a cyanide is available according to reactions (1) and (2)And derivatives thereof, can be reacted with a sulfur dioxide. Because of the low pH required for forming the bisulfate, the invention adds dilute sulfuric acid into the wastewater, and can decompose ammonium bisulfate into SO through reasonable control 2 The solution is mainly ammonium sulfate. According to reaction (3) two cyanides and derivatives thereof are required to react with one sulfate.
Cyanide and derivative hydrolysis: HOCN+H 2 O→NH 3 +CO 2 (1)
The reaction when the solution is weakly acidic or neutral: NH (NH) 3 +SO 2 +H 2 O→NH 4 HSO 3 (2)
After the acid is regulated by the solution: 2NH 4 HSO 3 +H 2 SO 4 →(NH 4 ) 2 SO 4 +2H 2 O+2SO 2 (3)
According to the reaction process, the salt content of the acid washing wastewater can be greatly reduced, and the sulfuric acid yield can be greatly improved. Before the process of the invention is adopted, the wastewater amount is 4m according to the detection result 3 And/h, wherein the chloride ion content is 40g/L, the total concentration of sulfate radicals and hydrogen sulfite radicals is 238g/L, and the concentration of the hydrogen sulfite radicals is 160g/L.
Figure SMS_1
Reduced salt mass concentration = ammonium bisulfide mass concentration-ammonium sulphate mass concentration,
thus, the first and second substrates are bonded together,
Figure SMS_2
the salt mass concentration reduction percentage is the ratio of the salt mass concentration reduced after the process of the invention to the salt mass concentration before the process of the invention:
percentage reduction in salt concentration = reduced salt mass concentration +.f (original ammonium sulfate mass concentration + ammonium bisulfide mass concentration + ammonium chloride mass concentration);
the preparation method comprises the following steps:
Figure SMS_3
the reaction may not take place completely due to the fact that the reaction is not complete. However, since heating is advantageous in carrying out the above reaction (3), the reaction efficiency thereof increases. In conclusion, according to the actual improvement result, the salt mass concentration in the acid washing wastewater can be reduced by about 16.5% after the process is adopted.
In addition, from reaction (3), it was found that the modified process produced 1mol of sulfur dioxide corresponding to 1mol of the reaction system, but consumed 0.5mol of sulfuric acid at the same time, i.e., increased 0.5mol of sulfuric acid. According to the detection result, the acid yield before process modification is 32t/d. The reaction process for preparing sulfuric acid from sulfur dioxide comprises the following steps:
sulfur dioxide conversion process: 2SO 2 +O 2 →2SO 3 (4)
Absorption process: SO (SO) 3 +H 2 O→H 2 SO 4 (5)
Thus, 98% sulfuric acid yield = increased sulfuric acid amount per cubic water x water amount x 24 h/sulfuric acid mass fraction;
namely: increase 98% sulfuric acid yield = 160/81 x 98 x 4 x 24/1000/98% = 18.96t/d;
reaction consumption 98% sulfuric acid amount=160/81×98×4×24/1000/98%/2=9.48 t/d;
total increase sulfuric acid amount= (increase 98% sulfuric acid yield-reaction consumption 98% sulfuric acid amount) ×actual reaction efficiency, i.e.:
total increase sulfuric acid = 9.48 x 16.5/17.95 = 8.71t/d;
the acid yield after transformation reaches 40.71t/d.
Thus, with the process of the present invention, the sulfuric acid yield is increased by 27.22%.
(2) After the wastewater collection Chi Suanxing washing wastewater reacts with dilute sulfuric acid, ammonium bisulfate can be decomposed into SO 2 After the compressed air is introduced, the reaction is intensified and a large amount of acid gas is discharged. If the acid gas is discharged at will, the acid gas can lead to the atmosphereAnd (5) pollution. Due to SO 2 The desorption tower adopts negative pressure air intake to introduce acid gas generated by the reaction into SO 2 The desorption tower further enters a secondary washing tower, so that the atmospheric pollution can be avoided and the recovery of sulfur resources can be realized.
(3) The invention directly adds the sulfuric acid self-produced in the two-rotation two-suction process into the system, realizes the internal recycling of sulfur resources, avoids additional substances, and has simple operation and convenient improvement.
(4) The waste hot blast stove tail gas is utilized to intensify the acidolysis waste water process, the waste heat of the hot blast stove can be utilized to heat the acid waste water, and meanwhile, the dust in the hot blast stove tail gas is effectively removed. The temperature of the acidic wastewater is increased, so that the acidification decomposition rate of ammonium bisulfate is improved, and the speed of activated carbon adsorption of colloidal sulfur generated after acidolysis of the acidic wastewater can be accelerated.
In addition, in the prior art, the SRG gas is washed by the washing solution in the first-stage washing tower, the wastewater at the lower part of the first-stage washing tower after washing and purifying is introduced into the conical settling tank, and the wastewater at the upper part of the conical settling tank overflows to the supernatant storage tank. According to practical research, the carbon powder in the washing wastewater is finer, and when a conical sedimentation tank and a supernatant liquid storage tank are adopted, the carbon powder is not settled enough due to larger disturbance in water in the operation process, so that the solution circulated to the primary washing tower also contains more carbon powder. After several times of circulation, the carbon powder amount in the solution can be increased sharply, and the discharge of the acid-making wastewater is increased to avoid the blockage of the washing nozzle. In the present invention, a primary settling tank is used instead of a conical settling tank and a supernatant storage tank. Because the primary settling tank adopts a mode of entering from the middle and exiting from the two sides, the hydraulic disturbance is less, and the sedimentation of carbon powder is facilitated, so that the discharge amount of the acid-making wastewater is less.
Before the process of the invention is adopted, the suspended matters in the wastewater are higher, so that the chloride ion concentration in the water is generally 50000mg/L. After improvement, the suspended matters are low and are no longer used as control indexes. The control index can be adjusted to detect the concentration of chloride ions in the primary precipitation tank to be 70000mg/L. I.e. the wastewater can be concentrated by 1.4 times, and the water quantity can be reduced by 28.6 percent. According to the actual improvement results, the amount of water entering the wastewater collection tank can be reduced by about 25%.
The invention provides an external circulation cleaning and treating method and system for cyanide-containing SRG gas, wherein the technical process and the technical principle are briefly described as follows:
(1) three-stage washing: according to the nature of the SRG gas components, three stages of scrubbing are adopted, wherein the first stage is used for removing dust, cyanide and derivatives thereof and a small amount of fluorine and chlorine in the SRG gas, and simultaneously reducing the temperature of flue gas. The second stage is mainly used for removing fluorine and chlorine, deeply removing impurities and further reducing the temperature of SRG gas. The third stage is a deep removing section of the pollutant, and the pollutant which cannot be removed due to the fluctuation of the previous two stages is removed.
(2) And (3) separating carbon powder: the principle that the carbon powder is easy to settle by self gravity is utilized to realize the removal of the carbon powder. In the invention, the primary sedimentation tank is adopted to replace the conical sedimentation tank and the supernatant liquid storage tank, and because the primary sedimentation tank adopts a mode of entering from the middle and exiting from the two sides, water inlet and water outlet and mud discharge are independent, disturbance is basically avoided, and secondary suspension of settled fine carbon powder can be avoided.
(3) Acidifying and blowing off: the pH value of the wastewater solution generated by the primary washing tower is 4-6, and the wastewater solution contains a large amount of ammonium bisulfide. After adding dilute sulfuric acid to the solution, the bisulfate in the ammonium bisulfate is converted into sulfurous acid. The sulfurous acid is decomposed to release sulfur dioxide under the condition of acidity and air disturbance. One sulfate radical is used to replace two bisulfites, so that the salt concentration is reduced. The research shows that the acidification stripping is an endothermic reaction, and the risk of aeration does not exist. However, the concentration of the dilute sulfuric acid added is not too high, which can lead to corrosion of equipment, and the reaction is severe, so that local high temperature is generated. However, the concentration of the added dilute sulfuric acid is not too low, and the reaction speed is slow, the average acid consumption is increased, and a large amount of wastewater is generated. Therefore, the concentration of the dilute sulfuric acid is preferably selected to be medium to high (for example, the concentration of sulfuric acid in the dilute sulfuric acid is 30 to 80%, preferably 40 to 70%, more preferably 50 to 60%).
④SO 2 Blowing off and recycling: the acidic washing wastewater contains a certain amount of sulfurous acid in SO 2 Air is introduced into the desorption tower, so that the decomposition of sulfurous acid can be accelerated, and sulfur dioxide is blown out. In addition, sulfur dioxide blown off by acidification enters SO 2 Desorption towerThe negative pressure pipeline of the sulfur dioxide recovery device can prevent sulfur dioxide from escaping, and can recover sulfur resources and improve sulfuric acid yield.
(5) Colloid sulfur adsorption: studies have shown that SRG gas containing sulfur vapor is scrubbed into solution in a primary column and further reacts with bisulphite to form thiosulfate. Thiosulfate enters a wastewater collection tank along with wastewater and is decomposed under acidic conditions to generate colloidal sulfur. Based on the property of activated carbon for adsorbing the colloidal sulfur, the wastewater (namely the carbon powder part) at the bottom of the primary sedimentation tank is transferred into the wastewater collection tank, so that the deep removal of the colloidal sulfur is realized, and the blocking caused by the sticking of the colloidal sulfur to equipment is prevented.
(6) Heating and purifying the hot blast stove: because the hot blast stove contains a certain amount of heat, the temperature of the wastewater can be increased after the hot blast stove is introduced into the wastewater collection tank. As the acidification decomposition reaction is an endothermic reaction, after the temperature is increased, the decomposition rate and efficiency can be improved. In addition, research shows that the temperature increase is beneficial to accelerating the adsorption of the activated carbon to the colloidal sulfur, and therefore, the wastewater temperature increase is beneficial to the removal of the colloidal sulfur. After the hot blast stove is introduced into the waste water, the purpose of wet washing is achieved, and small dust particles in tail gas of the hot blast stove can be effectively removed.
The invention provides a method and a system for cleaning and treating cyanide-containing SRG gas and purifying tail gas of a hot blast stove, which can be used for treating desorption gas of an adsorbent by an adsorption method, wherein the cyanide-containing SRG gas is only one of the cyanide-containing SRG gas. Wherein the adsorbent comprises a solid or liquid, e.g., the adsorbent is one or more of activated carbon, molecular sieves, MOFs, ionic liquids, organic amines.
Compared with the prior art, the invention has the following beneficial technical effects:
1. the invention can realize the cleaning treatment of the SRG gas by reasonably designing the SRG gas washing process and utilizing the SRG product and reasonably designing the washing and purifying process on the basis of not adding other substances.
2. According to the invention, through acidification and stripping, waste gas is circulated into the system based on the characteristics of the system, so that secondary pollution is prevented, and acid yield is improved.
3. The salt content of the acid washing wastewater discharged by the method is greatly reduced, the treatment cost of the acid washing wastewater is correspondingly reduced, and the subsequent treatment cost can be reduced.
4. The invention adopts neutral washing to convert elemental sulfur into a dissolved state, avoids blocking washing equipment, combines waste carbon powder adsorption, controls the source of decomposed colloidal sulfur, and avoids blocking the equipment.
5. The waste hot blast stove tail gas is used as a heat source, the waste water temperature is improved, the residual energy is effectively utilized, small dust particles in the hot blast stove tail gas can be removed, and environmental pollution is avoided.
Drawings
FIG. 1 is a process flow diagram of a method for cleaning and treating cyanide-containing SRG gas and purifying tail gas of a hot blast stove;
FIG. 2 is a schematic structural diagram of a cyanide-containing SRG gas cleaning and treating and hot blast stove tail gas purifying system according to the present invention;
FIG. 3 is SO 3 2- Ion fraction graph of (2).
Reference numerals: 1: a first-stage washing tower; 2: a second-stage scrubber; 3: three-stage washing towers; 4: an acid making system; 5: a primary sedimentation tank; 6: SO (SO) 2 A desorption tower; 7: a wastewater collection tank; 8: a concentrated sulfuric acid diluter; 9: a sludge storage tank;
la: an SRG gas delivery conduit; lb: a first process water delivery pipe; lc: concentrated sulfuric acid conveying pipeline; ld: a second conveying pipeline for process water; le: tail gas conveying pipeline of hot blast stove;
l1: a first pipe; l2: a second pipe; l3: a third conduit; l4: a fourth conduit; l5: a fifth pipe; l6: a sixth conduit; l7: a seventh pipe; l8: an eighth conduit; l9: a ninth conduit; l10: a tenth pipe; l11: an eleventh conduit; l12: a twelfth duct; l13: a thirteenth conduit; l14: a fourteenth conduit; l15: a fifteenth conduit; l16: sixteenth pipe.
Detailed Description
According to a first embodiment of the invention, a method for cleaning and treating cyanide-containing SRG gas and purifying tail gas of a hot blast stove is provided.
The method for cleaning and treating the cyanide-containing SRG gas and purifying the tail gas of the hot blast stove comprises the following steps:
1) The SRG gas containing cyanogen enters a first-stage washing tower 1 from the lower part, sequentially passes through the first-stage washing tower 1, a second-stage washing tower 2 and a third-stage washing tower 3, and is respectively in countercurrent contact with washing solutions in the towers, and the washed gas is discharged from the top of the third-stage washing tower 3.
2) And (3) introducing the gas discharged from the top of the three-stage washing tower 3 into an acid making system 4 for acid making to obtain concentrated sulfuric acid.
3) The process water enters a three-stage washing tower 3 from the bottom, the process water sequentially passes through the three-stage washing tower 3, a second-stage washing tower 2 and a first-stage washing tower 1 to wash and purify the SRG gas containing cyanide, the wastewater in the first-stage washing tower 1 after washing and purification is discharged to a primary sedimentation tank 5, and the wastewater at the upper part of the primary sedimentation tank 5 enters SO 2 And a desorption column 6.SO (SO) 2 Desorption tower 6 removes SO physically dissolved in wastewater 2 The wastewater is then discharged to a wastewater collection tank 7.
4) And (3) conveying the process water and the concentrated sulfuric acid prepared in the step (2) into a concentrated sulfuric acid diluter (8) for mixing to obtain dilute sulfuric acid. And (3) introducing dilute sulfuric acid into a wastewater collection tank 7, introducing hot blast furnace tail gas into the wastewater collection tank 7, reacting the dilute sulfuric acid with wastewater, and discharging acidic washing wastewater after the reaction.
In the present invention, the method comprises: 5) The concentrated sulfuric acid obtained in step 2) was used for the sale.
Preferably, in the step 4), the amount of the hot blast stove tail gas which is introduced into the waste water collecting tank 7 is 200-300 times of the amount of the waste water in the waste water collecting tank. Preferably, the temperature of the hot blast stove tail gas is 220-350 ℃, preferably 250-320 ℃, more preferably 270-290 ℃.
Preferably, in step 3), the wastewater in the lower part of the preliminary sedimentation tank 5 is passed into a wastewater collection tank 7. Preferably, the wastewater in the lower part of the primary settling tank 5 is also led to a sludge storage tank 9.
Preferably, in step 1), the SRG gas is passed through the primary scrubber 1 prior to being combined with SO 2 The sulfur-containing gas generated by the desorption tower 6 is converged and then enters the secondary washing tower 2 for washing and purifying. Preferably, in step 4), the sulfur is dilutedIntroducing the waste gas after the acid reacts with the waste water into SO 2 And a desorption column 6.
In step 3) of the present invention, a part of the wastewater in the upper part of the preliminary sedimentation tank 5 is introduced into SO 2 The other part of the desorption tower 6 is led into the first-stage washing tower 1.
Preferably, in the step 3), a part of the process water entering the tertiary washing tower 3 is recycled in the tertiary washing tower 3, and the other part enters the secondary washing tower 2. One part of the wastewater entering the secondary washing tower 2 from the tertiary washing tower 3 is recycled in the secondary washing tower 2, and the other part enters the primary washing tower 1.
In step 4) of the present invention, the pH of the acidic washing wastewater after the reaction is 0 to 3, preferably 0.5 to 2.5, more preferably 1 to 2.
Preferably, in step 4), the amount of dilute sulfuric acid fed to the wastewater collection tank 7 is such that the ratio of the molar amount of hydrogen ions in the dilute sulfuric acid to the molar amount of sulfite ions in the wastewater is 1:0.1-1, preferably 1:0.2-0.6, more preferably 1:0.3-0.5.
Preferably, the concentration of sulfuric acid in the dilute sulfuric acid is 30 to 80%, preferably 40 to 70%, more preferably 50 to 60%.
In step 3) of the present invention, the pH of the liquid entering the three-stage scrubber 3 is 5 to 7, preferably 5.5 to 6.
Preferably, in step 3), the pH of the liquid entering the secondary scrubber 2 is between 3 and 5, preferably between 3.5 and 4.5.
Preferably, in step 3), the pH of the liquid entering the primary scrubber 1 is between 2 and 4, preferably between 2.5 and 3.5.
Preferably, in step 3), the pH of the liquid discharged from the primary scrubber 1 is from 4 to 6, preferably from 4.5 to 5.5.
In step 1) of the present invention, the temperature of the SRG gas entering the primary scrubber 1 is 250 to 480 ℃, preferably 300 to 450 ℃, more preferably 380 to 430 ℃.
Preferably, in step 1), the temperature of the gas entering the secondary scrubber 2 is 50 to 150 ℃, preferably 70 to 100 ℃.
Preferably, in step 1), the temperature of the gas entering the three-stage scrubber 3 is between 10 and 80 ℃, preferably between 30 and 60 ℃.
Preferably, in step 1), the temperature of the gas discharged from the three-stage scrubber 3 is 10 to 60 ℃, preferably 20 to 40 ℃.
In step 3) of the present invention, the temperature of the liquid entering the three-stage scrubber 3 is 10 to 60 ℃, preferably 20 to 40 ℃.
Preferably, in step 3), the temperature of the liquid entering the secondary scrubber 2 is between 10 and 80 ℃, preferably between 30 and 60 ℃.
Preferably, in step 3), the temperature of the liquid entering the primary scrubber 1 is between 30 and 100 ℃, preferably between 50 and 80 ℃.
Preferably, in step 3), the temperature of the liquid discharged from the primary scrubber 1 is 50 to 120 ℃, preferably 70 to 90 ℃.
In the present invention, the concentration of suspended matter in the wastewater collection tank 7 is 600 to 2500mg/L, preferably 800 to 2300mg/L.
In step 3) of the present invention, the concentration of suspended matter in the wastewater at the upper part of the preliminary tank 5 is 0 to 100mg/L, preferably 1 to 80mg/L, more preferably 2 to 50mg/L.
According to a second embodiment of the invention, a system for cleaning and treating cyanide-containing SRG gas and purifying tail gas of a hot blast stove is provided.
A system for cleaning and treating cyanide-containing SRG gas and purifying hot blast stove tail gas using the above method, the system comprising: a first-stage washing tower 1, a second-stage washing tower 2, a third-stage washing tower 3, an acid making system 4, a primary settling tank 5 and SO 2 A desorption tower 6, a waste water collecting tank 7 and a concentrated sulfuric acid diluter 8.SRG gas delivery line L a Is connected to the gas inlet of the primary scrubber 1, the gas outlet of the primary scrubber 1 is connected to the gas inlet of the secondary scrubber 2 via a first pipe L1, the gas outlet of the secondary scrubber 2 is connected to the gas inlet of the tertiary scrubber 3 via a second pipe L2, and the gas outlet of the tertiary scrubber 3 is connected to the acid making system 4 via a third pipe L3.
First conveying pipeline L of process water b Is connected to the bottom liquid inlet of the tertiary scrubber 3, the liquid outlet of the tertiary scrubber 3 being viaThe fourth pipeline L4 is connected to the lower liquid inlet of the secondary washing tower 2, the liquid outlet of the secondary washing tower 2 is connected to the lower liquid inlet of the primary washing tower 1 through a fifth pipeline L5, the liquid outlet of the primary washing tower 1 is connected to the primary settling tank 5 through a sixth pipeline L6, and the upper liquid outlet of the primary settling tank 5 is connected to SO through a seventh pipeline L7 2 The liquid inlet of the desorption column 6. SO (SO) 2 The liquid outlet of the desorption column 6 is connected to a waste water collection tank 7 via an eighth conduit L8. The liquid outlet of the acid making system 4 is connected to a concentrated sulfuric acid diluter 8 via a concentrated sulfuric acid delivery pipe Lc, a process water second delivery pipe L d Is connected to a concentrated sulfuric acid diluter 8. The liquid outlet of the concentrated sulfuric acid diluter 8 is connected to the liquid inlet of the wastewater collection tank 7 via a ninth pipe L9. The stove tail gas delivery line Le is connected to the gas inlet of the waste water collection tank 7.
Preferably, the bottom liquid outlet of the primary settling tank 5 is connected via a tenth conduit L10 to the liquid inlet of the wastewater collection tank 7. Preferably, an eleventh pipeline L11 is branched from the tenth pipeline L10, and the eleventh pipeline L11 is connected to the sludge storage tank 9.
Preferably, a twelfth pipe L12 led from the exhaust gas outlet of the wastewater collection tank 7 is connected to the SO 2 The gas inlet of the desorption column 6. SO (SO) 2 The gas outlet of the desorption column 6 is connected to the first conduit L1 via a thirteenth conduit L13.
Preferably, the seventh line L7 is branched off from a fourteenth line L14, and the fourteenth line L14 is connected to the upper liquid inlet of the first-stage scrubber 1.
Preferably, the fifth line L5 is branched off from a fifteenth line L15, and the fifteenth line L15 is connected to the upper liquid inlet of the secondary scrubber 2. The fourth line L4 is branched off from a sixteenth line L16, and the sixteenth line L16 is connected to the upper liquid inlet of the three-stage scrubber 3.
Example 1
As shown in fig. 2, a system for cleaning and treating cyanide-containing SRG gas and purifying tail gas of a hot blast stove comprises: a first-stage washing tower 1, a second-stage washing tower 2, a third-stage washing tower 3, an acid making system 4, a primary settling tank 5 and SO 2 A desorption tower 6, a waste water collecting tank 7 and a concentrated sulfuric acid diluter 8.SRG gas delivery line L a Is connected to aThe gas inlet of the stage scrubber 1, the gas outlet of the stage scrubber 1 is connected to the gas inlet of the second stage scrubber 2 via a first pipe L1, the gas outlet of the second stage scrubber 2 is connected to the gas inlet of the third stage scrubber 3 via a second pipe L2, and the gas outlet of the third stage scrubber 3 is connected to the acid making system 4 via a third pipe L3.
First conveying pipeline L of process water b Is connected to the bottom liquid inlet of the three-stage scrubber 3, the liquid outlet of the three-stage scrubber 3 is connected to the lower liquid inlet of the second-stage scrubber 2 via a fourth pipe L4, the liquid outlet of the second-stage scrubber 2 is connected to the lower liquid inlet of the first-stage scrubber 1 via a fifth pipe L5, the liquid outlet of the first-stage scrubber 1 is connected to the primary settling tank 5 via a sixth pipe L6, and the upper liquid outlet of the primary settling tank 5 is connected to SO via a seventh pipe L7 2 The liquid inlet of the desorption column 6. SO (SO) 2 The liquid outlet of the desorption column 6 is connected to a waste water collection tank 7 via an eighth conduit L8. The liquid outlet of the acid making system 4 is connected to a concentrated sulfuric acid diluter 8 via a concentrated sulfuric acid delivery pipe Lc, a process water second delivery pipe L d Is connected to a concentrated sulfuric acid diluter 8. The liquid outlet of the concentrated sulfuric acid diluter 8 is connected to the liquid inlet of the wastewater collection tank 7 via a ninth pipe L9. The tail gas conveying pipeline (Le) of the hot blast stove is connected to a gas inlet of the waste water collecting tank (7).
Example 2
Example 1 was repeated except that the bottom liquid outlet of the primary settling tank 5 was connected to the liquid inlet of the wastewater collection tank 7 via a tenth pipe L10. An eleventh pipe L11 is branched from the tenth pipe L10, and the eleventh pipe L11 is connected to the sludge tank 9.
Example 3
Example 2 was repeated except that the twelfth pipe L12 led from the exhaust gas outlet of the wastewater collection tank 7 was connected to SO 2 The gas inlet of the desorption column 6. SO (SO) 2 The gas outlet of the desorption column 6 is connected to the first conduit L1 via a thirteenth conduit L13.
Example 4
Example 3 was repeated except that a fourteenth pipe L14 was branched from the seventh pipe L7, and the fourteenth pipe L14 was connected to the upper liquid inlet of the primary scrubber 1. The fifth line L5 branches off from a fifteenth line L15, the fifteenth line L15 being connected to the upper liquid inlet of the secondary scrubber 2. The fourth line L4 is branched off from a sixteenth line L16, and the sixteenth line L16 is connected to the upper liquid inlet of the three-stage scrubber 3.
Example 5
As shown in fig. 1, a method for cleaning and treating cyanide-containing SRG gas and purifying exhaust gas of a hot blast stove using the system of example 4 comprises the steps of:
1) The SRG gas containing cyanogen enters a first-stage washing tower 1 from the lower part, sequentially passes through the first-stage washing tower 1, a second-stage washing tower 2 and a third-stage washing tower 3, and is respectively in countercurrent contact with washing solutions in the towers, and the washed gas is discharged from the top of the third-stage washing tower 3.
Wherein the temperature of the SRG gas entering the primary scrubber 1 is 400 ℃. The temperature of the gas entering the secondary scrubber 2 was 80 ℃. The temperature of the gas entering the three-stage scrubber 3 was 50 ℃. The temperature of the gas discharged from the three-stage scrubber 3 was 30 ℃.
2) And (3) introducing the gas discharged from the top of the three-stage washing tower 3 into an acid making system 4 for acid making to obtain concentrated sulfuric acid.
3) The process water enters a three-stage washing tower 3 from the bottom, the process water sequentially passes through the three-stage washing tower 3, a second-stage washing tower 2 and a first-stage washing tower 1 to wash and purify the SRG gas containing cyanide, the wastewater in the first-stage washing tower 1 after washing and purification is discharged to a primary sedimentation tank 5, and the wastewater at the upper part of the primary sedimentation tank 5 enters SO 2 And a desorption column 6.SO (SO) 2 Desorption tower 6 removes SO physically dissolved in wastewater 2 The wastewater is then discharged to a wastewater collection tank 7.
Wherein the pH value of the liquid entering the three-stage washing tower 3 is 6.5, and the temperature is 30 ℃. The liquid entering the secondary scrubber 2 had a pH of 4 and a temperature of 50 ℃. The liquid entering the primary scrubber 1 had a pH of 3 and a temperature of 70 ℃. The liquid discharged from the primary scrubber 1 had a pH of 5 and a temperature of 80 ℃. The concentration of suspended matters in the wastewater at the upper part of the primary sedimentation tank 5 is 5mg/L.
4) And (3) conveying the process water and the concentrated sulfuric acid prepared in the step (2) into a concentrated sulfuric acid diluter (8) for mixing to obtain dilute sulfuric acid. And (3) introducing dilute sulfuric acid into a wastewater collection tank 7, introducing hot blast furnace tail gas into the wastewater collection tank 7, reacting the dilute sulfuric acid with wastewater, and discharging acidic washing wastewater after the reaction.
Wherein the amount of the dilute sulfuric acid fed into the wastewater collection tank 7 is the ratio of the molar amount of hydrogen ions in the dilute sulfuric acid to the molar amount of sulfite ions in the wastewater is 1:0.4. The concentration of sulfuric acid in the dilute sulfuric acid is 60%. The pH value of the acidic washing wastewater after the reaction of dilute sulfuric acid and wastewater is 2. The concentration of suspended matter in the wastewater collection tank 7 was 1700mg/L.
Example 6
Example 5 was repeated, except that in step 4), the amount of hot blast stove tail gas fed into the waste water collection tank 7 was 1000Nm 3 And/h. The temperature of the tail gas of the hot blast stove is 280 ℃.
Example 7
Example 6 was repeated except that the method included: 5) The concentrated sulfuric acid obtained in step 2) was used for the sale.
Example 8
Example 7 was repeated except that in step 3), the wastewater in the lower part of the preliminary sedimentation tank 5 was introduced into the wastewater collection tank 7. The wastewater in the lower part of the primary settling tank 5 is also led to a sludge storage tank 9.
Example 9
Example 8 was repeated except that in step 1), the gas discharged from the primary scrubber 1 was reacted with SO 2 And the sulfur-containing gas generated by the desorption tower 6 is converged and then enters the secondary washing tower 2 for washing and purifying. In the step 4), the waste gas after the reaction of the dilute sulfuric acid and the waste water is introduced into SO 2 And a desorption column 6.
Example 10
Example 9 was repeated except that in step 3), a part of the wastewater in the upper part of the preliminary sedimentation tank 5 overflowed to SO 2 The other part of the desorption tower 6 overflows to the first-stage washing tower 1. In the step 3), one part of the process water entering the three-stage washing tower 3 is recycled in the three-stage washing tower 3, and the other part enters the second-stage washing tower 2. One part of the process water entering the second-stage washing tower 2 from the third-stage washing tower 3 is recycled in the second-stage washing tower 2, and the other part enters the first-stage washing tower 1.
Experiments were carried out according to the method for cleaning and treating the cyanide-containing SRG gas and purifying the tail gas of the hot blast stove provided in the embodiment. The amount of wastewater, the temperature of wastewater, the concentration of suspended matters in wastewater, (sulfuric acid, sulfurous acid) salt concentration, the concentration of chloride ions and the yield of sulfuric acid before the process of the embodiment is adopted are measured. Then, the amount of wastewater, the temperature of wastewater, the concentration of suspended matters in wastewater, (sulfuric acid, sulfurous acid) salt concentration, the concentration of chloride ions, and the yield of sulfuric acid after the process described in this example was measured.
Detection index Before the process of the embodiment After the process of the embodiment is adopted
Waste water amount, m 3 /h 4 5
Temperature, DEG C 70 75
Suspension concentration, g/L 3.2 0.1
(sulfuric acid, sulfurous acid) salt concentration, g/L 238 172
Concentration of chloride ion, g/L 40 42
Sulfuric acid yield, t/d 32 40.71

Claims (38)

1. The method for cleaning and treating the cyanide-containing SRG gas and purifying the tail gas of the hot blast stove comprises the following steps:
1) introducing the SRG gas containing cyanogen into a first-stage washing tower (1) from the lower part, sequentially passing through the first-stage washing tower (1), a second-stage washing tower (2) and a third-stage washing tower (3), enabling the SRG gas to be respectively in countercurrent contact with washing solutions in the towers, and discharging the washed gas from the top of the third-stage washing tower (3);
2) The gas discharged from the top of the three-stage washing tower (3) enters an acid making system (4) for acid making to obtain concentrated sulfuric acid;
3) The process water enters a three-stage washing tower (3) from the bottom, the process water sequentially passes through the three-stage washing tower (3), a second-stage washing tower (2) and a first-stage washing tower (1) to wash and purify the SRG gas containing cyanide, the wastewater in the first-stage washing tower (1) after washing and purification is discharged to a primary sedimentation tank (5), and the wastewater at the upper part of the primary sedimentation tank (5) enters SO 2 A desorption column (6); SO (SO) 2 The desorption tower (6) removes the SO physically dissolved in the wastewater 2 Then discharging the wastewater to a wastewater collection tank (7);
4) Conveying the process water and the concentrated sulfuric acid prepared in the step 2) into a concentrated sulfuric acid diluter (8) for mixing to obtain dilute sulfuric acid; and (3) introducing dilute sulfuric acid into a wastewater collection tank (7), introducing hot blast furnace tail gas into the wastewater collection tank (7), reacting the dilute sulfuric acid with wastewater, and discharging acid washing wastewater after the reaction.
2. The method according to claim 1, characterized in that: the method comprises the following steps: 5) The concentrated sulfuric acid obtained in step 2) was used for the sale.
3. The method according to claim 1, characterized in that: in the step 4), the amount of the tail gas of the hot blast stove which is introduced into the waste water collecting tank (7) is 200-300 times of the amount of the waste water in the waste water collecting tank (7).
4. A method according to claim 3, characterized in that: the temperature of the tail gas of the hot blast stove is 220-350 ℃.
5. The method according to claim 4, wherein: the temperature of the tail gas of the hot blast stove is 250-320 ℃.
6. The method according to claim 5, wherein: the temperature of the tail gas of the hot blast stove is 270-290 ℃.
7. The method according to any one of claims 1-6, wherein: in the step 3), the wastewater at the lower part of the primary sedimentation tank (5) is introduced into a wastewater collection tank (7); and/or
In step 1), SRG gas is firstly reacted with SO after passing through a first-stage washing tower (1) 2 The sulfur-containing gas generated by the desorption tower (6) is converged and then enters the secondary washing tower (2) for washing and purifying.
8. The method according to claim 7, wherein: the wastewater at the lower part of the primary sedimentation tank (5) is also led into a sludge storage tank (9); in the step 4), the waste gas after the reaction of the dilute sulfuric acid and the waste water is introduced into SO 2 A desorption tower (6).
9. The method according to any one of claims 1-6, 8, characterized in that: in the step 3), part of wastewater at the upper part of the primary sedimentation tank (5) enters SO 2 A desorption tower (6), and the other part is led into a first-stage washing tower (1); and/or
In the step 3), one part of the process water entering the three-stage washing tower (3) is recycled in the three-stage washing tower (3), and the other part enters the second-stage washing tower (2); part of the wastewater entering the secondary washing tower (2) from the tertiary washing tower (3) is recycled in the secondary washing tower (2), and the other part enters the primary washing tower (1).
10. The method according to claim 7, wherein: in the step 3), part of wastewater at the upper part of the primary sedimentation tank (5) enters SO 2 A desorption tower (6), and the other part is led into a first-stage washing tower (1); and/or
In the step 3), one part of the process water entering the three-stage washing tower (3) is recycled in the three-stage washing tower (3), and the other part enters the second-stage washing tower (2); part of the wastewater entering the secondary washing tower (2) from the tertiary washing tower (3) is recycled in the secondary washing tower (2), and the other part enters the primary washing tower (1).
11. The method according to any one of claims 1-6, 8, 10, wherein: in the step 4), the pH value of the acid washing wastewater after the reaction is 0-3.
12. The method according to claim 7, wherein: in the step 4), the pH value of the acid washing wastewater after the reaction is 0-3.
13. The method according to claim 9, wherein: in the step 4), the pH value of the acid washing wastewater after the reaction is 0-3.
14. The method according to claim 11, wherein: in the step 4), the pH value of the acid washing wastewater after the reaction is 0.5-2.5.
15. The method according to claim 12, wherein: in the step 4), the pH value of the acid washing wastewater after the reaction is 0.5-2.5.
16. The method according to claim 13, wherein: in the step 4), the pH value of the acid washing wastewater after the reaction is 0.5-2.5.
17. The method according to any one of claims 14-16, wherein: in the step 4), the pH value of the acid washing wastewater after the reaction is 1-2.
18. The method according to claim 11, wherein: in the step 4), the amount of the dilute sulfuric acid fed into the wastewater collection tank (7) is that the ratio of the molar amount of hydrogen ions in the dilute sulfuric acid to the molar amount of sulfite ions in the wastewater is 1:0.1-1.
19. The method according to claim 12, wherein: in the step 4), the amount of the dilute sulfuric acid fed into the wastewater collection tank (7) is that the ratio of the molar amount of hydrogen ions in the dilute sulfuric acid to the molar amount of sulfite ions in the wastewater is 1:0.1-1.
20. The method according to claim 13, wherein: in the step 4), the amount of the dilute sulfuric acid fed into the wastewater collection tank (7) is that the ratio of the molar amount of hydrogen ions in the dilute sulfuric acid to the molar amount of sulfite ions in the wastewater is 1:0.1-1.
21. The method according to any one of claims 18-20, wherein: in the step 4), the amount of the dilute sulfuric acid fed into the wastewater collection tank (7) is that the ratio of the molar amount of hydrogen ions in the dilute sulfuric acid to the molar amount of sulfite ions in the wastewater is 1:0.2-0.6.
22. The method according to claim 21, wherein: in the step 4), the amount of the dilute sulfuric acid fed into the wastewater collection tank (7) is that the ratio of the molar amount of hydrogen ions in the dilute sulfuric acid to the molar amount of sulfite ions in the wastewater is 1:0.3-0.5.
23. The method according to any one of claims 18-20, wherein: the concentration of sulfuric acid in the dilute sulfuric acid is 30-80%.
24. The method according to claim 23, wherein: the concentration of sulfuric acid in the dilute sulfuric acid is 40-70%.
25. The method according to claim 23, wherein: the concentration of sulfuric acid in the dilute sulfuric acid is 50-60%.
26. The method of any one of claims 1-6, 8, 10, 12-16, 18-20, 22, 24-25, wherein: in the step 3), the pH value of the liquid entering the three-stage washing tower (3) is 5-7; and/or
In the step 3), the pH value of the liquid entering the secondary washing tower (2) is 3-5; and/or
In the step 3), the pH value of the liquid entering the primary washing tower (1) is 2-4; and/or
In step 3), the pH value of the liquid discharged from the primary washing tower (1) is 4-6.
27. The method according to claim 26, wherein: in the step 3), the pH value of the liquid entering the three-stage washing tower (3) is 5.5-6.5; and/or
In the step 3), the pH value of the liquid entering the secondary washing tower (2) is 3.5-4.5; and/or
In the step 3), the pH value of the liquid entering the primary washing tower (1) is 2.5-3.5; and/or
In step 3), the pH value of the liquid discharged from the primary washing tower (1) is 4.5-5.5.
28. The method of any one of claims 1-6, 8, 10, 12-16, 18-20, 22, 24-25, 27, wherein: in the step 1), the temperature of SRG gas entering the first-stage washing tower (1) is 250-480 ℃; and/or
In the step 1), the temperature of the gas entering the secondary washing tower (2) is 50-150 ℃; and/or
In the step 1), the temperature of the gas entering the three-stage washing tower (3) is 10-80 ℃; and/or
In step 1), the temperature of the gas discharged from the three-stage scrubber (3) is 10 to 60 ℃.
29. The method according to claim 28, wherein: in the step 1), the temperature of SRG gas entering the first-stage washing tower (1) is 300-450 ℃; and/or
In the step 1), the temperature of the gas entering the secondary washing tower (2) is 70-100 ℃; and/or
In the step 1), the temperature of the gas entering the three-stage washing tower (3) is 30-60 ℃; and/or
In step 1), the temperature of the gas discharged from the three-stage scrubber (3) is 20 to 40 ℃.
30. The method of any one of claims 1-6, 8, 10, 12-16, 18-20, 22, 24-25, 27, 29, wherein: in the step 3), the temperature of the liquid entering the three-stage washing tower (3) is 10-60 ℃; and/or
In the step 3), the temperature of the liquid entering the secondary washing tower (2) is 10-80 ℃; and/or
In the step 3), the temperature of the liquid entering the primary washing tower (1) is 30-100 ℃; and/or
In step 3), the temperature of the liquid discharged from the primary scrubber (1) is 50 to 120 ℃.
31. The method according to claim 30, wherein: in the step 3), the temperature of the liquid entering the three-stage washing tower (3) is 20-40 ℃; and/or
In the step 3), the temperature of the liquid entering the secondary washing tower (2) is 30-60 ℃; and/or
In the step 3), the temperature of the liquid entering the primary washing tower (1) is 50-80 ℃; and/or
In step 3), the temperature of the liquid discharged from the primary scrubber (1) is 70 to 90 ℃.
32. The method of any one of claims 1-6, 8, 10, 12-16, 18-20, 22, 24-25, 27, 29, 31, wherein: the concentration of suspended matters in the wastewater collection tank (7) is 600-2500 mg/L; and/or
In the step 3), the concentration of suspended matters in the wastewater at the upper part of the primary sedimentation tank (5) is 0-100 mg/L.
33. The method as claimed in claim 32, wherein: the concentration of suspended matters in the wastewater collection tank (7) is 800-2300 mg/L; and/or
In the step 3), the concentration of suspended matters in the wastewater at the upper part of the primary sedimentation tank (5) is 1-80 mg/L.
34. The method according to claim 33, wherein: the concentration of suspended matters in the wastewater at the upper part of the primary sedimentation tank (5) is 2-50 mg/L.
35. A system for cleaning and treating cyanide-containing SRG gas and purifying hot blast stove exhaust gas using the method of any of claims 1-34, the system comprising: a first-stage washing tower (1), a second-stage washing tower (2), a third-stage washing tower (3), an acid making system (4), a primary settling tank (5) and SO 2 A desorption tower (6), a waste water collecting tank (7) and a concentrated sulfuric acid diluter (8); SRG gas transfer pipe (L) a ) The device comprises a gas inlet connected to a first-stage washing tower (1), wherein a gas outlet of the first-stage washing tower (1) is connected to a gas inlet of a second-stage washing tower (2) through a first pipeline (L1), a gas outlet of the second-stage washing tower (2) is connected to a gas inlet of a third-stage washing tower (3) through a second pipeline (L2), and a gas outlet of the third-stage washing tower (3) is connected to an acid production system (4) through a third pipeline (L3); and
First conveying pipeline of process water (L) b ) Is connected to the bottom liquid inlet of the three-stage washing tower (3), the liquid outlet of the three-stage washing tower (3) is connected to the lower liquid inlet of the second-stage washing tower (2) through a fourth pipeline (L4), the liquid outlet of the second-stage washing tower (2) is connected to the lower liquid inlet of the first-stage washing tower (1) through a fifth pipeline (L5), the liquid outlet of the first-stage washing tower (1) is connected to the primary sedimentation tank (5) through a sixth pipeline (L6), and the upper liquid outlet of the primary sedimentation tank (5) is connected to SO through a seventh pipeline (L7) 2 A liquid inlet of the desorption column (6); SO (SO) 2 The liquid outlet of the desorption tower (6) is connected to a wastewater collection tank (7) via an eighth pipeline (L8); the liquid outlet of the acid making system (4) is connected to a concentrated sulfuric acid diluter (8) via a concentrated sulfuric acid delivery pipe (Lc), a process water second delivery pipe (L d ) Is connected to a concentrated sulfuric acid diluter (8); the liquid outlet of the concentrated sulfuric acid diluter (8) is connected to the liquid inlet of the wastewater collection tank (7) via a ninth pipeline (L9); exhaust gas of hot-blast stoveThe delivery pipe (Le) is connected to the gas inlet of the wastewater collection tank (7).
36. The system according to claim 35, wherein: the bottom liquid outlet of the primary settling tank (5) is connected to the liquid inlet of the wastewater collection tank (7) via a tenth pipe (L10); and/or
A twelfth pipe (L12) led out from the waste gas outlet of the waste water collecting tank (7) is connected to SO 2 A gas inlet of the desorption column (6); SO (SO) 2 The gas outlet of the desorption column (6) is connected to the first conduit (L1) via a thirteenth conduit (L13).
37. The system according to claim 36, wherein: an eleventh pipeline (L11) is separated from the tenth pipeline (L10), and the eleventh pipeline (L11) is connected to the sludge storage tank (9).
38. The system according to any one of claims 35-37, wherein: a fourteenth pipeline (L14) is separated from the seventh pipeline (L7), and the fourteenth pipeline (L14) is connected to an upper liquid inlet of the first-stage washing tower (1); and/or
A fifteenth pipeline (L15) is separated from the fifth pipeline (L5), and the fifteenth pipeline (L15) is connected to an upper liquid inlet of the secondary washing tower (2); a sixteenth pipeline (L16) is separated from the fourth pipeline (L4), and the sixteenth pipeline (L16) is connected to the upper liquid inlet of the three-stage washing tower (3).
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