CN110947297A - Green treatment method for chlorine-containing waste gas - Google Patents
Green treatment method for chlorine-containing waste gas Download PDFInfo
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- CN110947297A CN110947297A CN201911336307.8A CN201911336307A CN110947297A CN 110947297 A CN110947297 A CN 110947297A CN 201911336307 A CN201911336307 A CN 201911336307A CN 110947297 A CN110947297 A CN 110947297A
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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
- B01D53/34—Chemical or biological purification of waste gases
- B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
- B01D53/77—Liquid phase processes
- B01D53/78—Liquid phase processes with gas-liquid contact
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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
- B01D53/34—Chemical or biological purification of waste gases
- B01D53/46—Removing components of defined structure
- B01D53/68—Halogens or halogen compounds
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
- C01D3/00—Halides of sodium, potassium or alkali metals in general
- C01D3/04—Chlorides
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
- C01D5/00—Sulfates or sulfites of sodium, potassium or alkali metals in general
- C01D5/02—Preparation of sulfates from alkali metal salts and sulfuric acid or bisulfates; Preparation of bisulfates
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2251/00—Reactants
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- B01D2251/304—Alkali metal compounds of sodium
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2257/00—Components to be removed
- B01D2257/20—Halogens or halogen compounds
- B01D2257/202—Single element halogens
- B01D2257/2025—Chlorine
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2259/00—Type of treatment
- B01D2259/12—Methods and means for introducing reactants
- B01D2259/124—Liquid reactants
Abstract
The invention discloses a green treatment method of chlorine-containing waste gas. The green treatment method of the chlorine-containing waste gas comprises the following steps: and (2) contacting the reducing industrial waste liquid with the chlorine-containing waste gas, wherein the reducing industrial waste liquid contains sodium sulfite and/or sodium thiosulfate, and the sodium sulfite and/or sodium thiosulfate in the reducing industrial waste liquid and the chlorine gas generate oxidation-reduction reaction, so that the chlorine gas in the chlorine-containing waste gas is absorbed. The invention provides a new green treatment process for absorbing chlorine-containing waste gas by utilizing reductive industrial waste liquid, for example, chlorine waste gas is absorbed by adopting industrial waste liquid containing sodium sulfite or sodium thiosulfate, and the redox reaction between the sodium sulfite or sodium thiosulfate and chlorine is skillfully utilized to generate stable sodium sulfate and sodium chloride, so that the generation of secondary chlorine pollution is avoided, the purpose of treating waste by waste is realized, the cost of environment-friendly reagents is greatly reduced, and the discharge amount of the waste liquid is reduced.
Description
Technical Field
The invention relates to a green process for simultaneously treating industrial waste gas and waste liquid, in particular to a green treatment method for absorbing chlorine-containing waste gas by using reductive industrial waste liquid, belonging to the field of environmental protection and treatment of manufacturing industry.
Background
The metallurgical and chemical industries are the major manufacturing sectors essential to national economy and provide a vast array of basic chemicals and metal-containing feedstocks for the entire economic development. At the same time, it also produces large amounts of waste water, liquid waste and gas waste.
First, the source and toxicity of chlorine-containing waste gas
The chlorine gas is yellow green under normal temperature and normal pressure, is a toxic gas with strong pungent smell, has higher density than air, is soluble in water and easy to compress, can be liquefied into golden yellow liquid chlorine, is one of main products in the chlor-alkali industry, and can be used as a strong oxidant. When hydrogen with the volume fraction of more than 5 percent is mixed in chlorine, the chlorine can have the explosion danger when meeting strong light. Chlorine can perform substitution reaction and addition reaction with organic matters and inorganic matters to generate various chlorides. Chlorine was used as a bleaching agent in the early papermaking and textile industries. In the chlorine-involved process stages of hydrochloric acid synthesis, PVC, metallurgical metal ion chlorine leaching and the like, chlorine is a main raw material gas and is also a main polluting gas. In the chlor-alkali industry and the process of chloride metal salt electrodeposition smelting, chlorine gas appears as a byproduct, and leakage and pollution can be caused due to poor treatment during gas collection and transportation. Such as the inventors' experience: the purity of the chlorine generated after the cobalt electrodeposition process exceeds 90%, and pure liquid chlorine can be obtained by separating chlorine gas from air through liquefaction, but the chlorine gas generated becomes a large amount of waste gas which needs to be treated instead of liquid chlorine product because a large amount of air is sucked into the chlorine gas to be mixed with the chlorine gas and the chlorine gas cannot be liquefied and separated due to the fact that a fan pumping head selected during the design of the process section is too large. The exhaust gases with entrained chlorine are diffused throughout the day in the workshop and on the ground nearby, and the environment is particularly harsh.
Chlorine is a fatal toxic gas, 1m3The air may contain chlorine gas at most 1mg, and the amount exceeding this amount causes poisoning of human body. The dose lethal to humans with chlorine is 500ppm/5M for human inhaled LCLo. Chlorine mainly invades the human body through the respiratory tract and dissolves in the water contained in the mucous membrane to generate hypochlorous acid and hydrochloric acid, and the upper respiratory tract mucous membrane is damaged, wherein the hypochlorous acid causes the tissues to be strongly oxidized; hydrochloric acid stimulates mucous membranes to generate inflammatory swelling, so that the mucous membranes of respiratory tracts are swollen, and a large amount of mucus is secreted to cause dyspnea, so that the obvious symptom of chlorine poisoning is severe cough. When the symptoms are severe, pulmonary edema can occur, making circulation difficult and leading to death. Chlorine gas entering the body from the esophagus can cause nausea, vomiting, chest pain and diarrhea. Therefore, the treatment of chlorine-containing waste gas and tail gas is very necessary.
Second, the chlorine leakage absorption process progress and the deficiency thereof
The chlorine absorption device is also called a chlorine leakage absorption device, a chlorine leakage absorption device and a chlorine leakage neutralization device, is a safety emergency device when a chlorine leakage accident occurs, and can absorb and treat leaked chlorine. The chlorine concentration is high, and the chlorine is not used except for emergency use, and once the chlorine is used, the safety of staff and pedestrians nearby the relevant process section is involved. In recent years, chlorine leakage accidents happen occasionally, so that huge losses and threats are caused to national property and lives of people, and how to select and install a chlorine leakage absorption device which is advanced in technology, reasonable in design and reliable in operation becomes the most important factor for production safety work of chlorine units. The first generation originated in the early part of the twentieth century where liquid chlorine was absorbed using sodium hydroxide. The absorption mechanism of the chlorine leakage absorption device sold in the market at present is that alkaline solution is used for absorbing chlorine, and the chlorine leakage absorption device belongs to neutrality, and the reaction formula is as shown in formula (1):
Cl2+2NaOH＝NaClO+NaCl+H2O (1)
from the above equation, it can be seen that: as the alkali liquor generated after chlorine absorption can not regenerate salt crystals, the spray nozzles and the fillers of the spray pipes of the absorption tower are blocked, the concentration of sodium hydroxide in the absorption liquid is gradually reduced along with the extension of the absorption time, the absorption capacity is gradually reduced, and the amount of chlorine absorbed at one time is limited. However, the absorption liquid after absorbing chlorine gas cannot be regenerated, the subsequent maintenance amount is large, the operation cost is high, the service life is short, and the like, so the absorption liquid is gradually replaced by the redox type chlorine leakage absorption device.
The second generation generated in the early 90 s, chlorine gas was absorbed by a ferrous salt solution. The absorption liquid can be continuously recycled without replacement. However, the tower body structure adopts the first generation of double-tower series structure (the first tower is used for absorption, and the second tower is used for steam-water separation), the problem that more elbows and larger wind resistance are caused, and the absorption efficiency is reduced; the box body is of a square structure, and the absorption liquid has a circulating dead angle. The reaction principle is that a ferrous salt solution is used for absorbing chlorine, belongs to the oxidation-reduction property, and has a reaction formula of a formula (2):
absorption (oxidation) reaction: 2Fe2++Cl2＝2Fe3++2Cl-(2)
Regeneration (reduction) reaction: 2Fe3++Fe＝3Fe2+(3)
From the above equation, it can be seen that: the absorption and regeneration of ferrous salt are carried out synchronously, a large amount of chlorine can be absorbed at one time, the absorption capacity is far greater than the rated absorption capacity (the reason is shown in the reaction formula), the absorption liquid does not need to be replaced, the crystallization cannot be generated, the chlorine absorption amount at one time cannot be unlimited, and the absorbed chlorine generates ferric salt (Fe) according to the law of constant substances3+) Then through reduction reaction to generate ferrous salt (Fe)2+) The chlorine gas is stored in a regeneration box, the space and the regenerant of the regeneration box are limited, when the device absorbs a large amount of chlorine gas, only part of absorption liquid needs to be recycled, and the regenerant is added to react according to the formula (3). But the continuous addition of iron powder results in an increase in the amount of iron-containing waste liquid to be treated in the future.
Third, the current situation and the deficiency of the absorption process of the low-concentration chlorine-containing waste gas
In general, a chlorine gas-containing exhaust gas or tail gas does not leak, and has a high concentration, and for example, more than 8% of the chlorine gas generated by air purification in a chlorine plant, electrolysis or electrodeposition using a metal salt of hydrochloric acid is generated, and the chlorine gas cannot be separated from air by liquefaction and used as a product because the generated chlorine gas contains more than 8% of air due to improper treatment measures such as excessive power of a compressor. The tail gas after the leaching reaction of the chlorine gas is metallurgically used must also ensure that the chlorine gas is completely absorbed before being discharged. The air separated after the chlorine product is compressed and liquefied also contains chlorine, and before being discharged, the air can be emptied after the chlorine is absorbed and fixed. These require a long period of time for the continuous absorption of low concentrations of chlorine.
At present, most of chlorine-containing tail gas or waste gas is absorbed by using sodium hydroxide or calcium hydroxide solution. However, the treatment process has the following defects during treatment:
1. the alkali liquor can generate a large amount of heat when absorbing the tail gas, thereby causing the temperature to rise. The chemical reaction principle of this absorption treatment is simple, following formula (4):
2NaOH+Cl2＝NaCl+NaClO+H2o (Cold water) (4)
6NaOH+3Cl2＝5NaCl+NaClO3+3H2O (greater than 70 deg.C) (5)
From the reaction formula (5), it seems that the chlorine absorption efficiency does not decrease after the temperature is high. However, according to the practical experience of the inventor, if the concentration of the chlorine is large, the temperature of the absorption liquid is increased too fast in a short time, so that the subsequent chlorine absorption rate is greatly reduced. In the practice of the actual absorption process, the inventor has found in the production practice that when the temperature of the absorption liquid is higher than 70 ℃, the alkali liquid is quickly boiled in the high-altitude zone of more than 1000 meters, and strong yellow green is released in the absorption tail gas.
2. The product of the alkali liquor after absorbing the chlorine is sodium hypochlorite or calcium hypochlorite. The two compounds are unstable, and are easy to decompose again when the solution contains heavy metals and meets acid solution or after the solution is exposed to light, and chlorine gas is released again to generate secondary pollution. Because a large metallurgical enterprise often encounters secondary pollution of chlorine, in order to solve the problem of unstable sodium hypochlorite solution after absorption, a transnational enterprise is required to make an expensive sodium hypochlorite decomposition device, and a catalyst is adopted to decompose sodium hypochlorite, so that the decomposition efficiency is not high, and besides the equipment of the process is tens of millions, the consumption of the decomposition catalyst per year is up to hundreds of thousands yuan. And the secondary pollution of chlorine is not stopped from the source.
3. The reagent cost of the lye is high and again becomes an unstable waste stream that needs to be disposed of.
All of these determine that the current chlorine-related tail gas is costly to treat, and generates unstable waste liquid which needs to be disposed of again, or secondary chlorine pollution.
Production of reductive industrial waste liquid
In fact, other waste liquids or waste residues with reducing activity are generally generated in or near the unit related to the chlorine-containing tail gas. The large-scale metallurgical enterprises are generally matched with a plurality of chemical industries for providing large-scale raw materials for the metallurgical industry, such as the chlor-alkali industry for providing caustic soda and chlorine for chlorine leaching. At present, the most economic and environment-friendly treatment mode of sulfur dioxide-containing flue gas generated in the pyrometallurgical process section of metallurgical enterprises is generally used for producing sulfuric acid and sodium sulfite. Tail gas from sulfuric acid production is generally absorbed by caustic soda solution, which produces a large amount of alkaline waste liquor containing sodium sulfite. The mother liquor separated by crystallization in the sodium sulfite production process is also a waste liquor containing saturated sodium sulfite, and the mother liquor is recycled all the time, which can cause the enrichment of a large amount of impurities to reduce the product quality, so that the mother liquor also needs to be discharged as the waste liquor regularly. These effluents are generally discharged into an effluent collecting tank, which generally contains a large amount of acid, and therefore the reaction according to formula (6) often occurs, with secondary pollution of sulfur dioxide.
Na2SO3+2H+＝Na++H2O+SO2↑ (6)
In conclusion, the treatment of industrial waste gases and liquid wastes is a process segment which needs to pay a large amount of treatment cost in addition to the production of main products, and the economical efficiency is not good. Chlorine is a fatal poisonous gas, for the treatment of chlorine-containing waste gas, sodium hydroxide solution is generally adopted in industry to absorb chlorine-containing waste gas, the cost of reagent is high, and the generated sodium hypochlorite is unstable, is rapidly decomposed by acid or visible light, and is easy to release secondary chlorine pollution again; there is also a drawback that the exothermic absorption reaction is severe, which causes the temperature of the reaction solution to rise too fast, affecting the absorption effect. Therefore, the development of a new low-cost and stable green treatment process for chlorine-containing waste gas is urgently needed.
Disclosure of Invention
The invention aims to provide a green treatment method of chlorine-containing waste gas, thereby overcoming the defects of the prior art.
In order to achieve the purpose, the technical scheme adopted by the invention comprises the following steps:
the embodiment of the invention provides a green treatment method of chlorine-containing waste gas, which comprises the following steps:
contacting a reducing industrial waste liquor with a chlorine-containing waste gas, the reducing industrial waste liquor comprising sodium sulfite and/or sodium thiosulfate;
and (3) carrying out redox reaction on the sodium sulfite and/or sodium thiosulfate in the reducing industrial waste liquid and chlorine gas, so that the chlorine gas in the chlorine-containing waste gas is absorbed.
In some preferred embodiments, the preparation method specifically comprises:
conveying the reducing industrial waste liquid to a liquid distributor at the top of the absorption tower, and spraying the reducing industrial waste liquid from the top of the absorption tower to the bottom of the absorption tower;
and inputting the chlorine-containing waste gas from a gas inlet at the bottom of the absorption tower and conveying the chlorine-containing waste gas to the top of the absorption tower, so that the reducing industrial waste liquid and the chlorine-containing waste gas are in countercurrent contact.
Compared with the prior art, the invention has the beneficial effects that:
the invention provides a new green treatment process for absorbing chlorine-containing waste gas by utilizing reductive industrial waste liquid, for example, chlorine waste gas is absorbed by adopting industrial waste liquid containing sodium sulfite or sodium thiosulfate, and stable sodium sulfate and sodium chloride are generated by skillfully utilizing the redox reaction between the sodium sulfite or sodium thiosulfate and chlorine, so that the generation of secondary chlorine pollution is avoided, the purpose of treating waste by waste is realized, the cost of environment-friendly reagents is greatly reduced, and the discharge amount of the waste liquid is reduced; also, the present invention is advantageous for the recovery of heavy metals.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments described in the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a diagram of an experimental bench for absorbing chlorine-containing tail gas by using three solutions of caustic soda solution, sodium sulfite solution and caustic soda + sodium sulfite solution in an exemplary embodiment of the present invention.
FIG. 2 is a schematic structural diagram of a general glass fiber reinforced plastic absorption tower which can be industrially used for absorbing chlorine-containing waste gas from alkaline reducing industrial waste liquid in an exemplary embodiment of the present invention.
Detailed Description
In view of the defects of the prior art, the inventor of the present invention provides the technical scheme of the present invention through long-term research and a great deal of practice, and the novel low-cost green treatment process of the present invention theoretically utilizes the oxidizing property of chlorine gas to perform oxidation-reduction reaction with reducing waste liquid generated by other surrounding processes, so that the treated absorption liquid becomes stable and has no chemical activity, the reversibility of the reaction is reduced, the secondary pollution of the chlorine gas is reduced and eliminated, the waste treatment by waste is realized, and the cost consumption of process equipment cost and reagent medicines is greatly reduced. The technical solution, its implementation and principles, etc. will be further explained as follows.
In one aspect, the present invention relates to a green treatment method for chlorine-containing waste gas, comprising:
contacting a reducing industrial waste liquor with a chlorine-containing waste gas, the reducing industrial waste liquor comprising sodium sulfite and/or sodium thiosulfate;
and (3) carrying out redox reaction on the sodium sulfite and/or sodium thiosulfate in the reducing industrial waste liquid and chlorine gas, so that the chlorine gas in the chlorine-containing waste gas is absorbed.
In the invention, the chlorine in the chlorine-containing waste gas is absorbed by redox reaction by using the reducing industrial waste liquid to generate stable sodium sulfate and sodium chloride, so that the irreversibility of treatment reaction and the stability of products can be greatly improved.
In a preferred embodiment, the industrial reducing waste liquid is a waste liquid generated by absorbing waste gas containing sulfur dioxide by using a caustic soda solution in a sulfuric acid production process, the waste liquid containing the waste gas containing sulfur dioxide is absorbed and treated by using the caustic soda solution in the sulfuric acid production process, and chlorine is reduced by using sulfurous acid in the waste liquid, so that the aim of reducing the toxicity and pollution of the chlorine is fulfilled.
In another preferred embodiment, the industrial reducing waste liquid is derived from a filtering mother liquid in the production of sodium sulfite, the chlorine-containing waste gas is absorbed by the filtering mother liquid in the production of sodium sulfite, and chlorine is absorbed and reduced by the sodium sulfite, so that the aim of reducing the toxicity and pollution of chlorine is fulfilled.
In another preferred embodiment, the industrial reducing waste liquid is derived from a filtering mother liquid in sodium thiosulfate production, chlorine-containing waste gas is absorbed by the filtering mother liquid in the sodium thiosulfate production process, and chlorine is absorbed and reduced by the sodium thiosulfate in the waste gas, so that the aim of reducing the toxicity and pollution of the chlorine is fulfilled.
In some preferred embodiments, the green processing method includes: and (3) the reducing industrial waste liquid and the chlorine-containing waste gas are in countercurrent contact, so that chlorine is fully absorbed.
In some more specific preferred embodiments, the green treatment method of chlorine-containing waste gas specifically comprises:
conveying the reducing industrial waste liquid to a liquid distributor at the top of the absorption tower, and spraying the reducing industrial waste liquid from the top of the absorption tower to the bottom of the absorption tower;
and inputting the chlorine-containing waste gas from a gas inlet at the bottom of the absorption tower and conveying the chlorine-containing waste gas to the top of the absorption tower, so that the reducing industrial waste liquid and the chlorine-containing waste gas are in countercurrent contact.
Further, the green treatment method of the chlorine-containing waste gas further comprises the following steps: and monitoring the absorbed waste gas by adopting a chlorine alarm.
Further, the industrial reducing waste liquid is placed in a liquid storage tank at the bottom of the absorption tower and is conveyed to a liquid distributor at the top of the absorption tower through an absorption liquid pump.
Further, a defogging layer, a spraying layer and a filler layer are sequentially arranged in the absorption tower from the top to the bottom.
Furthermore, the absorption tower is also provided with an observation hole.
In some more preferred embodiments, the detailed steps of the green treatment process of the chlorine-containing waste gas are as follows:
(1) the waste liquid containing sulfur dioxide tail gas is absorbed by using caustic soda solution in the sulfuric acid production process to absorb and treat the chlorine-containing tail gas by using the reaction of chlorine and alkaline sodium sulfite solution
The waste liquid to be treated after sodium hydroxide in the nearby sulfuric acid production process absorbs sulfur dioxide tail gas is directly pumped into a common glass fiber reinforced plastic absorption tower by a pipeline, the waste liquid is sprayed down from an upper liquid distributor, chlorine-containing tail gas is blown from the bottom of a tank, sulfur dioxide absorption liquid and the chlorine-containing tail gas are absorbed in a countercurrent mode, and a chlorine alarm monitors whether the chlorine in the absorbed tail gas exceeds the standard or not.
(2) Absorbing and treating chlorine-containing tail gas by using filtered mother liquor in sodium sulfite production process
The filtered mother liquor in the sodium sulfite production procedure is directly pumped into a common glass fiber reinforced plastic gas absorption tower, sprayed down from an upper liquid distributor, chlorine-containing tail gas is blown from the bottom of a tank, the sodium sulfite mother liquor and the chlorine-containing tail gas are in countercurrent contact absorption, and a chlorine alarm is used for monitoring whether the absorbed tail gas exceeds the standard or not.
(3) Absorbing chlorine-containing tail gas by adopting filtered mother liquor of sodium thiosulfate production process
Pumping the filtered mother liquor in the process of producing sodium thiosulfate by a sodium sulfite method into a liquid distributor above a common glass fiber reinforced plastic absorption tower by using a pump and a pipeline, spraying the filtered mother liquor to the lower part of the liquid distributor, blowing chlorine-containing tail gas from the bottom of a tank, carrying out countercurrent contact absorption on the sodium thiosulfate mother liquor and the chlorine-containing tail gas, and monitoring whether the chlorine content of the absorbed tail gas exceeds the standard by using a chlorine alarm.
The reaction principle for absorbing chlorine-containing tail gas or waste gas through the process route is carried out according to the formula (7):
Na2SO3+Cl2+2NaOH＝Na2SO4+2NaCl+H2O (7)
in the process, the products of sodium sulfate, sodium chloride and water have no oxidation, reducibility, volatility and secondary gas pollution, but are pure high-salinity wastewater. The sodium chloride and the sodium sulfate can be separated by a salt drying method. Therefore, the method belongs to an ideal tail gas pollution treatment reaction. If heavy metal ions appear in the reaction, most of the heavy metal ions react with a great amount of hydroxide ions to form precipitates under the alkaline condition, and the heavy metal ions such as nickel, cobalt, copper, manganese and the like carried out by the tail gas can be recovered by filtering. Therefore, from this point of view, this reaction not only eliminates the secondary pollution of chlorine, but is also advantageous for the recovery of heavy metals.
Mn++nOH-＝M(OH)n↓ (8)
The hypochlorite in the absorption liquid is not detected, which shows that the absorbed components are stable and no secondary pollution of chlorine gas occurs. Whereas 4.91 g/l hypochlorite ion appeared in the solution after the absorption was completed compared to the case of using pure sodium hydroxide solution for absorbing the same chlorine-containing tail gas. The absorption effect of the reducing sodium sulfite waste liquid on chlorine-containing waste gas is good.
The reaction principle of adopting sodium thiosulfate to absorb chlorine-containing tail gas is as shown in formula (9):
Na2S2O3+4Cl2+5H2O＝2NaCl+2H2SO4+6HCl (9)
the sodium chloride produced is a very stable compound compared to sodium hypochlorite with sulfuric acid and hydrochloric acid. The most preferred such absorption liquid is therefore an alkaline solution containing sodium thiosulfate. Similarly, the waste liquid absorbs the tail gas containing 30 percent of chlorine, and after half an hour, the sample is taken to test that no hypochlorite or chlorate ions are detected in the absorbed solution, and no chlorine alarm phenomenon occurs even if the absorption temperature exceeds 70 ℃. Whereas the control solution of pure sodium hydroxide showed hypochlorite ions at 7.46 g/l after absorption under the same conditions. The effect of absorbing chlorine-containing tail gas by the saturated mother liquor of sodium thiosulfate is better than that of a pure caustic soda solution.
By the preparation process, the invention provides a new green treatment process for absorbing chlorine-containing waste gas by using reductive industrial waste liquid, for example, chlorine waste gas is absorbed by using industrial waste liquid containing sodium sulfite or sodium thiosulfate, and stable sodium sulfate and sodium chloride are generated by skillfully utilizing the redox reaction between the sodium sulfite or sodium thiosulfate and chlorine, so that the generation of secondary chlorine pollution is avoided, the purpose of treating waste by waste is realized, the cost of environment-friendly reagents is greatly reduced, and the discharge amount of the waste liquid is reduced; also, the present invention is advantageous for the recovery of heavy metals.
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention are described in further detail below with reference to the accompanying drawings and several preferred embodiments, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention. The test methods in the following examples are carried out under conventional conditions without specifying the specific conditions. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
Example 1
As shown in figure 1, a hose is connected with a chlorine steel cylinder 1, then connected with a rotor flowmeter 2, and then connected with a three-way pipe, and the other two pipes are respectively connected with two absorption bottles filled with absorption liquid3, a control valve 4 is arranged in front of the absorption bottle, then the air outlet pipe of the absorption bottle 3 is connected with a hose, and a small chlorine alarm 5 (the chlorine alarm concentration is 1 mg/M) is arranged at the air outlet of the hose in the test3)。
Mixing prepared NaOH and Na with different concentrations2SO3NaOH and Na2SO3The mixed solution is taken as chlorine agent, 250ml of absorbent is respectively and uniformly taken, and the absorbent is sequentially filled into an absorption bottle and is subjected to absorption test under the uniform chlorine flow; when the absorption liquid is saturated, the chlorine alarm instrument at the tail gas absorption pipe automatically gives an alarm to prompt and displays a reading, and the concentration of the chlorine in the tail gas is 1mg/M3Setting values, namely finishing a group of absorption tests, and recording the saturation time of absorption liquid and the temperature of the absorption liquid; opening the absorption bottle cap, taking down the cap and the gas distribution pipe part, detecting the gas overflow condition at the bottle mouth by a chlorine alarm instrument, and taking an absorption liquid sample for inspection; when one group of absorption liquid is saturated and gives an alarm, opening a valve at the inlet of the other group of absorption bottles, closing the control valve 4 of the air inlet of the saturated absorption bottle, and performing a second group of absorption tests; the tests were conducted in alternation in the above manner to ensure uniformity of chlorine flow in each set of tests.
According to Na2SO3The saturated concentration of the solution was 180g/L, i.e., 1.42 mol/L. Selecting Na according to the convention2SO3The mole number of the absorbent is 1.2Mol, so that the absorption tower spray device and facilities in practical use are prevented from being blocked by absorbent crystallization. The results of the field tests on the absorption of the parallel tests with different absorbents are shown in Table 1, and the detection conditions of the liquid products are shown in Table 2.
TABLE 1 chlorine absorption site data sheet for different absorbents
TABLE 2 summary of the data of the component detection of the saturated chlorine absorption liquid with different absorbents
| Sampling number | Sulfite in g/L | Sodium sulfate g/L | Chloride ion g/L | pH of the absorption liquid | Hypochlorite radical |
| YA--1 | Not detected out | Not detected out | 64.38 | 4.21 | 4.91 |
| YB--1 | 44.50 | 81.92 | 114.59 | 1.43 | Not detected out |
| YC--1 | Not detected out | 112.40 | 123.09 | 3.38 | Not detected out |
The theoretical uptake of chlorine by 250ml of 8.8% sodium hydroxide solution was 0.6 mol. 250ml of 13% sodium sulfite solution has a theoretical chlorine absorption of 0.3 mol. If the rate of absorption and conversion of chlorine by the sodium hydroxide and sodium sulfite solutions are identical, the time for the sodium sulfite to reach saturation should be approximately half the time required for the sodium hydroxide solution to reach saturation. From the data in table 2 it can be seen that the sodium sulfite conversion corresponds to only 54% and that the time to saturation corresponds to 2/3 for 8.8% sodium hydroxide solution. Therefore, under the same conditions, the absorption rate of sodium sulfite is slower than that of sodium hydroxide. But the solution does not contain hypochlorite, a source of secondary pollution of chlorine gas. However, the addition of sodium sulfite does not significantly increase the total amount of chlorine absorbed by the absorption liquid. After the sodium sulfite solution is adopted for absorption, the bottle cap of the absorption bottle is opened, and obvious hydrogen chloride gas overflows, which indicates that a large amount of hydrogen chloride is generated in the reaction. The use of sodium sulfite alone is significantly less effective than the use of an alkaline sodium sulfite solution.
Example 2
Absorbing SO by using caustic soda solution of a certain plant2In the production process of anhydrous sodium sulfite, mother liquor obtained after crystallization and filtration of sodium sulfite contains 182 g/L of sodium sulfite, has a pH value of 12 and 30 g/L of sulfate radical, and is pumped into a liquid storage tank of a glass fiber reinforced plastic absorption tower shown in figure 2, and chlorine-containing tail gas is introduced from an air inlet of the absorption tower. The alkaline sodium sulfite mother liquor is pumped from a liquid storage tank at the bottom to a spraying layer at the top of the tower by a pump, is distributed by a liquid distributor to flow downwards uniformly, and is in countercurrent contact with chlorine-containing tail gas through a packing layer to generate oxidation-reduction absorption. And after water mist of the absorbed tail gas is removed through a demister, the tail gas is emptied after the chlorine content is monitored through an air outlet at the upper part.
Example 3
In the production process for producing sodium thiosulfate by reacting an alkaline sodium sulfite solution in a certain plant with sulfur, mother liquor obtained after crystallization and filtration of sodium thiosulfate contains 280 g/L of sodium sulfite and has a pH value of 10, and is pumped into a liquid storage tank of a glass fiber reinforced plastic absorption tower shown in figure 2 by a pump, wherein chlorine-containing tail gas is introduced from an air inlet of the absorption tower. The alkaline sodium sulfite mother liquor is pumped from a liquid storage tank at the bottom to a spraying layer at the top of the tower by a pump, is distributed by a liquid distributor to flow downwards uniformly, and is in countercurrent contact with chlorine-containing tail gas through a packing layer to generate oxidation-reduction absorption. And after water mist of the absorbed tail gas is removed through a demister, the tail gas is emptied after the chlorine content is monitored through an air outlet at the upper part.
In conclusion, the green treatment process for absorbing chlorine-containing waste gas by using the reductive industrial waste liquid adopts the industrial waste liquid containing sodium sulfite or sodium thiosulfate to absorb the chlorine waste gas, and skillfully utilizes the redox reaction between the sodium sulfite or sodium thiosulfate and the chlorine to generate stable sodium sulfate and sodium chloride, thereby avoiding the generation of secondary chlorine pollution, realizing the purpose of treating waste by waste, greatly reducing the cost of the environment-friendly reagent and reducing the discharge amount of the waste liquid.
The aspects, embodiments, features and examples of the present invention should be considered as illustrative in all respects and not intended to be limiting of the invention, the scope of which is defined only by the claims. Other embodiments, modifications, and uses will be apparent to those skilled in the art without departing from the spirit and scope of the claimed invention.
The use of headings and chapters in this disclosure is not meant to limit the disclosure; each section may apply to any aspect, embodiment, or feature of the disclosure.
Throughout this specification, where a composition is described as having, containing, or comprising specific components or where a process is described as having, containing, or comprising specific process steps, it is contemplated that the composition of the present teachings also consist essentially of, or consist of, the recited components, and the process of the present teachings also consist essentially of, or consist of, the recited process steps.
It should be understood that the order of steps or the order in which particular actions are performed is not critical, so long as the teachings of the invention remain operable. Further, two or more steps or actions may be performed simultaneously.
In addition, the inventors of the present invention have also made experiments with other materials, process operations, and process conditions described in the present specification with reference to the above examples, and have obtained preferable results.
While the invention has been described with reference to illustrative embodiments, it will be understood by those skilled in the art that various other changes, omissions and/or additions may be made and substantial equivalents may be substituted for elements thereof without departing from the spirit and scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from its scope. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.
Claims (10)
1. A green treatment method of chlorine-containing waste gas is characterized by comprising the following steps:
contacting a reducing industrial waste liquor with a chlorine-containing waste gas, the reducing industrial waste liquor comprising sodium sulfite and/or sodium thiosulfate; and (3) carrying out redox reaction on the sodium sulfite and/or sodium thiosulfate in the reducing industrial waste liquid and chlorine gas, so that the chlorine gas in the chlorine-containing waste gas is absorbed.
2. The green treatment method for chlorine-containing waste gas according to claim 1, characterized in that: the reducing industrial waste liquid is derived from waste liquid generated by absorbing waste gas containing sulfur dioxide by using caustic soda solution in a sulfuric acid production process.
3. The green treatment method for chlorine-containing waste gas according to claim 1, characterized in that: the reducing industrial waste liquid is derived from a filtering mother liquid in the production of sodium sulfite.
4. The green treatment method for chlorine-containing waste gas according to claim 1, characterized in that: the reducing industrial waste liquid is derived from a filtering mother liquid in the production of sodium thiosulfate.
5. A green treatment method for chlorine-containing off-gas according to any of claims 1 to 4, characterized by comprising: and (3) the reducing industrial waste liquid and the chlorine-containing waste gas are in countercurrent contact, so that chlorine is fully absorbed.
6. The green treatment method of chlorine-containing waste gas according to claim 5, characterized by comprising:
conveying the reducing industrial waste liquid to a liquid distributor at the top of the absorption tower, and spraying the reducing industrial waste liquid from the top of the absorption tower to the bottom of the absorption tower;
and inputting the chlorine-containing waste gas from a gas inlet at the bottom of the absorption tower and conveying the chlorine-containing waste gas to the top of the absorption tower, so that the reducing industrial waste liquid and the chlorine-containing waste gas are in countercurrent contact.
7. The green treatment method for chlorine-containing waste gas according to claim 6, further comprising: and monitoring the absorbed waste gas by adopting a chlorine alarm.
8. The green treatment method for chlorine-containing waste gas as claimed in claim 6, wherein: and the reductive industrial waste liquid is placed in a liquid storage tank at the bottom of the absorption tower and is conveyed to a liquid distributor at the top of the absorption tower through an absorption liquid pump.
9. The green treatment method for chlorine-containing waste gas as claimed in claim 6, wherein: and a defogging layer, a spraying layer and a filler layer are sequentially arranged from the top to the bottom in the absorption tower.
10. The green treatment method for chlorine-containing waste gas as claimed in claim 9, wherein: the absorption tower is also provided with an observation hole.
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| CN117448887A (en) * | 2023-10-13 | 2024-01-26 | 安道麦安邦(江苏)有限公司 | Control method for chlorine-in-chlorine hydrogen in chlorine alkali production |
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