WO2010075751A1

WO2010075751A1 - Method for absorbing and processing of harmful waste gas by electrochemical means

Info

Publication number: WO2010075751A1
Application number: PCT/CN2009/076066
Authority: WO
Inventors: 黄立维; 黄纪海
Original assignee: Huang Liwei; Huang Jihai
Priority date: 2008-12-31
Filing date: 2009-12-25
Publication date: 2010-07-08
Also published as: CN101474527A

Abstract

A method for absorbing and processing harmful waste gas by electrochemical means comprises: introducing the gas to be treated which contains harmful gas into an absorption tower (6), in which the harmful gas is absorbed by absorption liquid to form an absorption product; discharging the purified gas through a gas discharge port (8); introducing the absorption liquid which contains the absorption product into an electrochemical reactor (11); converting the absorption product into a chemically stable substance by chemical reaction in the electrochemical reactor (11) and thus to regenerate the absorption liquid. The absorption liquid is an aqueous solution of acid or a mixed aqueous solution of acid and salt. Since the absorbed harmful substance is subjected to electrochemical oxidation reaction in an acid environment with greatly improved reaction rate, the method is especially suitable for reactively absorbing and processing harmful waste gases such as aqueous insoluble hydrocarbon, organic substance containing halogen, sulfur or nitrogen, waste gas of sewage plant, and ammonia, etc.

Description

(1) Technical field

The present invention relates to a method of electrochemically absorbing and treating harmful exhaust gases.

(2) Background technology

Various organic gaseous pollutants such as hydrocarbons, alcohols, ethers, aldehydes, phenols, ketones, carboxylic acids, esters, nitriles, amines and heterocyclic compounds, sulphur dioxide, hydrogen sulphide, nitrogen oxides, carbon disulfide, nitrogen trifluoride, vulcanization Inorganic pollutants such as hydrogen, hydrogen cyanide and ammonia are widely produced in industrial processes such as chemical, pharmaceutical and painting. Most of these volatile organic compounds are toxic and some are malodorous gases. When discharged into the atmosphere, they will affect the ecological environment and harm the human body. health. However, due to the chemical structure stability and the difficulty of degradation, these organic substances bring great difficulties to environmental protection.

In general, the absorption method is one of the main means for treating these organic waste gases and malodorous gases. Especially for the exhaust gas generated by chemical processes, the absorption method (generally using an aqueous solution as an absorbent) is safe and widely used. However, when the absorption method absorbs harmful substances such as halogenated hydrocarbons, triphenyls, nitrogen oxides, and ammonia which are poor in water solubility, the absorption efficiency is low, and the absorption liquid is easily saturated. In addition, if the absorbed solution is not further processed, the harmful substances absorbed by the solution will volatilize, which will cause secondary pollution.

Therefore, how to improve the absorption efficiency of these poorly water-soluble harmful substances while avoiding the generation of secondary pollutants is an urgent problem to be solved in the process of exhaust gas treatment. The applicant of the present invention has proposed to treat these difficult-to-absorb harmful gases by electrochemical treatment. The basic principle is to use electrochemical reactions generated on the surface of the electrode by electrolysis to produce strong oxidizing substances such as 0, OH, CIO and H0 ₂ . , these strong oxidizing substances are absorbed and absorbed during the process Receiving the reaction, and finally turning the harmful substances into harmless substances. Prior to this application, the applicant has applied for a related patent: ZL 200510060254.3, the invention name is a method for purifying harmful exhaust gas and its special device. The invention proposes a method for purifying harmful exhaust gas, and introduces a gas to be treated with a harmful gas containing an alcohol, an ether, an aldehyde, a phenol, a ketone or an ester organic substance into an absorption tower, wherein the harmful gas is absorbed by the absorption liquid and then enters the electrocatalytic oxidation reactor. Electrolytic oxidation reaction of the absorption liquid in the electrocatalytic oxidation reactor, further oxidizing the absorption product into a chemically stable substance, regenerating the absorption liquid, recovering the absorption capacity, and purifying the treated gas; the absorption The liquid is recycled; the absorption liquid of the absorption tower adopts an alkaline solution sodium hydroxide solution or a potassium hydroxide solution, and the mass percentage concentration is 0.5-30%, and the method is for treating alcohol, ether, aldehyde, phenol, ketone or Organic substances such as ester organics have good effects, but are less effective in treating hydrocarbons (including aromatic hydrocarbons) having a more stable chemical structure, organic substances or heterocyclic organic compounds containing halogen or sulfur or nitrogen, or inorganic substances such as ammonia. Industrial applications are more valuable by improving the formulation of the absorbent to achieve high removal efficiency of these hazardous materials.

(3) Invention content

The technical problem to be solved by the present invention is to provide an electrochemical method for absorbing harmful exhaust gas for removing hydrocarbons (including aromatic hydrocarbons), alcohols, ethers, aldehydes, phenols, ketones, carboxylic acids, esters, nitriles, from a gas stream. Amines and heterocyclic compounds, inorganic pollutants such as sulfur dioxide, hydrogen sulfide, nitrogen oxides, carbon disulfide, nitrogen trifluoride, hydrogen sulfide, hydrogen cyanide and ammonia, so that these harmful substances contained in the gas stream are quickly absorbed in the device. And oxidation to achieve the purpose of gas purification.

In order to solve the above technical problems, the technical solution adopted by the present invention is as follows:

An electrochemical method for absorbing and treating harmful exhaust gas, the method is as follows: The gas containing the harmful gas is introduced into the absorption tower, wherein the harmful gas is absorbed by the absorption liquid into an absorption product, and the purified gas is discharged from the gas discharge port; the absorption liquid containing the absorption product enters the electrochemical reactor, and the absorption product is in the electrochemical reactor The chemical reaction is converted into a chemically stable substance, the absorption liquid is regenerated, the absorption capacity is restored, and the absorption tower is re-entered into the absorption tower for recycling; the absorption liquid is an aqueous acid solution or a mixed aqueous solution of an acid and a salt.

The apparatus used in the present invention is the same as the patent of the application number 200510060254.3.

The harmful gas according to the present invention is one or more of the following: hydrocarbon, alcohol, ether, aldehyde, phenol, ketone, carboxylic acid, ester, nitrile, amine and heterocyclic compound, sulfur dioxide, hydrogen sulfide, nitrogen oxide Inorganic pollutants such as carbon disulfide, nitrogen trifluoride, hydrogen sulfide, hydrogen cyanide and ammonia. Among them, the hydrocarbons are anthracene hydrocarbons (excluding formazan), cyclic hydrocarbons, unsaturated hydrocarbons, aromatic hydrocarbons and halogenated hydrocarbons. In the method of the present invention, when a direct current or a pulsed electric current is applied to the electrode of the electrochemical reactor, an electrochemical redox reaction occurs in the electrochemical reactor, and a strong oxidizing substance such as 0, HO is generated in the electrolysis process. ^PC10 _2, etc. These strong oxidizing substances are chemically reacted with harmful substances in an absorption process in an absorption tower and an electrochemical reactor under acidic conditions to convert them into chemically stable substances. Generally, the oxidation products of organic hydrocarbons (which are effective as unsaturated hydrocarbons and aromatic hydrocarbons), amines and furans are mainly organic acids, and further oxidation of organic acids can be converted into carbon dioxide and water. For example, the main product of oxidation of toluene and styrene is benzoic acid. The sulfur and nitrogen contained in the organic matter are mainly converted into sulfate ion and nitrate ion, sulfur dioxide is oxidized to sulfate ion, sulfuric acid is oxidized to elemental sulfur and sulfate ion, and nitrogen oxide is oxidized. The main products of oxidation of the substance are nitrate ions, inorganic ammonia converted to nitrogen and nitrate ions. In the case where the absorption liquid is acidic, especially for harmful substances containing 3⁄4 or sulfur or nitrogen elements which are difficult to be oxidized, such as halogenated hydrocarbons, oxazinone, tetrahydrofuran, organic amines, inorganic ammonia, carbon disulfide and nitrogen trifluoride, etc. Very good removal effect.

The absorption liquid of the present invention may be an aqueous solution of an acid, and the acid is preferably hydrochloric acid or sulfur. One or a mixture of two acids. When the absorbing liquid is a hydrochloric acid solution, the mass percentage of hydrogen chloride in the absorbing liquid is preferably 0.01 to 5%, preferably 0.1 to 1%; and when the absorbing liquid is a sulfuric acid solution, the The mass percentage concentration of sulfuric acid in the absorption liquid is preferably 0.02 to 10%; when the absorption liquid is a mixed solution of hydrochloric acid and sulfuric acid, the mass percentage concentration of hydrogen chloride in the absorption liquid is preferably 0.01 to 5%, and the quality of sulfuric acid The percentage concentration is preferably 0.02 to 10%.

Further, in order to increase the conductivity of the absorbing liquid and further improve the absorption effect, the present invention may form a mixed aqueous solution of an acid and a salt as an absorbing liquid by adding a certain amount of a salt to the aqueous solution of the above-mentioned acid, and the salt is preferably selected from the following ones. Or a combination of two or more of any ratio: sodium chloride, potassium chloride, sodium sulfate, potassium sulfate, and the mass percentage of the salt in the absorption liquid is preferably 0.1 to 20%.

The invention finds that when the absorption liquid is in an acidic environment, the removal efficiency of the harmful gas is greatly improved compared with the use of the sodium chloride solution, the alkaline solution or the pure water as the absorption liquid, and the removal effect increases with the acid concentration. improve. When the acid solution is hydrochloric acid, the absorption effect is better than that of the sulfuric acid solution.

The invention has the beneficial effects that the invention adopts a hydrogen chloride solution or a sulfuric acid solution or a mixed solution of an acid and a salt as an absorption liquid, so that the absorbed harmful substances are electrochemically oxidized in an acidic environment, and the reaction speed is greatly improved, the harmful gas The removal efficiency is greatly improved when using sodium chloride solution, alkaline solution or pure water as the absorption liquid, and is especially suitable for hydrocarbons with poor water solubility, organic substances containing 3⁄4 or sulfur or nitrogen, sewage station waste gas. It is absorbed and treated by harmful exhaust gas such as ammonia.

(4) Description of the drawings

Figure 1 is a schematic view showing the structure of a special device used in the method of the present invention; Circulating pump; 2 circulating tank; 3 liquid level gauge; 4 filling port; 5 air inlet; 6 absorption tower; 7 absorption tower inlet; 8 purge gas outlet; 9 bypass pipe; 10 liquid return pipe; Electrocatalytic oxidation reactor; 12 communicating tubes; 13 drain ports.

2A is a schematic structural view of a mesh electrode electrochemical reactor used in Embodiment 1; the components are: Γ liquid outlet tube; 2' mesh electrode plate; 3' electrode terminal; 4' inlet tube; ' Bypass; 6' drain. Figure 3 shows the structure of a plate-shaped electrochemical reactor consisting of multiple sets of plate electrode units.

2B is a cross-sectional view of the grid electrode electrochemical reactor of Embodiment 1 taken along line A-A; FIG. 3A is a schematic structural view of the plate electrode electrochemical reactor used in Example 2; Outlet tube; 2" electrode terminal; 3" inlet tube; 4" bypass tube; 5", 7" electrode plate; 6" water flow distribution plate; 8" drain port.

Fig. 3B is a cross-sectional view showing the A-A of the plate electrode electrochemical reactor used in Example 2.

(5) Specific implementation methods

The present invention will be further described in detail below with reference to the accompanying drawings and embodiments, but the scope of the invention is not limited thereto.

A schematic diagram of the structure of the absorption-electrocatalytic oxidation system of the present invention is shown in Fig. 1 (the same as the patent of Application No. 200510060254.3).

The special device structure is that the lower part of the absorption tower 6 is provided with an air inlet 5, the top of the absorption tower is provided with an air outlet 8, and the bottom of the absorption tower 6 is provided with a circulation tank 2, and the lower liquid outlet of the circulation tank 2 passes through the circulation pump 1. The pipe and the valve are connected to the liquid inlet 7 in the top of the absorption tower 6, and the lower portion of the absorption tower 6 is also communicated with the top of the electrochemical reactor 11 through the liquid return pipe 10, and the communication pipe 12 at the lower portion of the electrochemical reactor 11 is connected. The circulation tank 2 at the bottom of the absorption tower is further provided with a liquid discharge port 13 and a valve at the lower portion of the electrochemical reactor 11. The lower part of the absorption tower 6 is also passed by The through tube 9 and the valve are in communication with the top of the electrochemical reactor 11.

The treatment process is that the exhaust gas to be treated enters the absorption tower 6 from the inlet port 5 and contacts the spray liquid, and absorbs the reaction, and the treated exhaust gas is discharged from the top gas outlet port 8. The absorbing liquid enters the electrochemical reactor 11 through the liquid return pipe 10 at the bottom of the column to carry out an electrochemical reaction, and then enters the circulation tank 2 through the communication pipe 12, and is returned to the absorption tower through the circulation pump 1. The gas generated by the electrochemical reaction is communicated with the inlet chamber of the lower portion of the absorption tower through the bypass pipe 9 and the valve.

The schematic diagram of the structure of the electrochemical reactor of the present invention is shown in Figures 2 and 3, wherein Figure 2 is a mesh electrode electrochemical reactor composed of a plurality of sets of electrode units.

Example 1: Experimental system system flow is shown in Figure 1, and the electrochemical reactor is shown in Figure 2. The structure of the reactor is 400mm X 400mm X 1200mm, which is composed of 6 sets of mesh electrode units, and the distance between the plates is 50mm. The mesh anode material is Ru0 ₂ /Ti, and the mesh cathode material is stainless steel. The electrode mesh size is 380mm X 380mm, thickness 3mm, and the electrode mesh is 5mm X 5mm. The absorption tower is a packed tower, the tower diameter is Φ 500mm, and the height of the packing layer is 2500mm. The simulated exhaust gas is an air + gaseous harmful pollutant, which is introduced into the air inlet at the bottom of the absorption tower, and is discharged from the upper portion after passing through the absorption reaction zone.

The experimental conditions are: Power parameters: Current 60A

Gas flow: 500m ³ /h, gas temperature: 25°C

Absorption circulating fluid flow: 10m ³ /h

Absorbent: 0.1% hydrogen chloride solution or 0.1% hydrogen chloride solution mixed with 1% sodium chloride solution or 0.2% sulfuric acid solution.

The experimental results are shown in Table 1.

Table 1 Hazard removal effect

1-2 petroleum ether 260 36 25 50

1-3 trichloroethylene 310 43 32 64

1-4 Ethylene oxide 230 10 5 12

1-5 carbon disulfide 65 6 4 6

1-6 Formaldehyde 340 10 5 12

1-7 methyl sulfide 98 9 6 17

1-8 Acrylonitrile 140 15 10 25

1-9 Toluene 379 38 29 47-10 Azinone 110 22 15 36- 11 Vinyl acetate 195 20 11 25-12 Diethylamine 55 0 0 0-13 Hydrogen sulfide 85 6 5 6-14 Sulfur dioxide 670 45 33 50 -15 Nitric Oxide 720 53 37 61-16 Hydrogen cyanide 60 0 0 1-17 Ammonia 210 0 0 0-18 Nitrogen trifluoride 170 45 30 55-19 Tetrahydrofuran 76 5 3 5-20 Pyridine 77 7 5 7- 21 Hydrogen sulfide 110 5 0 5-22 Acrylic 160 10 5 10-23 Wastewater station waste gas 130 10 5 15 Example 2: The electrochemical reactor is shown in Figure 3. The reactor structure size is 400mmx400mmx 1200mm, consisting of 2 sets of plate electrodes, each set consisting of 6 pairs of cells, separated by a fluid distributor between the two groups. The plate anode material is Ru0 ₂ /Ti, and the plate cathode material is stainless steel. The electrode size is 190mm x 380mm and the plate thickness is 3mm. The distance between the electrode plates is 50 mm. Other conditions are the same as in the first embodiment

The experimental conditions are: Power parameters: Pulse frequency is 100Hz, current 100A

Gas flow: 500m ³ /h, gas temperature: 25°C

Circulating pump flow: 10m ³ /h.

Absorbent: 0.3% hydrochloric acid solution or a mixed solution of 0.5% sulfuric acid and 4% sodium sulfate or a mixed solution of 0.5% sulfuric acid and 0.1% hydrochloric acid.

The experimental results are shown in Table 2.

Table 2 Hazard removal effect

-12 Diethylamine 65 0 0 0-13 Hydrogen Sulfide 125 5 7 6-14 Sulfur Dioxide 710 31 46 40-15 Nitric Oxide 802 43 61 55-16 Hydrogen cyanide 45 0 0 1-17 Ammonia 235 0 0 0- 18 Nitrogen trifluoride 195 40 30 45-19 Tetrahydrofuran 66 3 5 4-20 Pyridine 77 4 7 5-21 Hydrogen sulfide 120 3 6 3-22 Acrylic acid 180 6 15 8-23 Wastewater station waste gas 145 5 10 5

Claims

Claim

A method for absorbing and absorbing harmful exhaust gas by an electrochemical method, characterized in that the method is as follows: a gas containing a harmful gas to be treated is introduced into an absorption tower, wherein the harmful gas is absorbed by the absorption liquid into an absorption product, and the purified gas is from The gas discharge port is discharged; the absorption liquid containing the absorption product enters the electrochemical reactor, and the absorption product is chemically converted into a chemically stable substance in the electrochemical reactor, so that the absorption liquid is regenerated, the absorption capacity is restored, and the absorption tower cycle is re-entered. The absorption liquid is an aqueous solution of an acid or a mixed aqueous solution of an acid and a salt; the harmful gas is selected from one or a mixture of two or more of the following: hydrocarbon, alcohol, ether, aldehyde, phenol, ketone, carboxylic acid, ester , nitrile, amine, heterocyclic compound, sulfur dioxide, hydrogen sulfide, nitrogen oxides, carbon disulfide, nitrogen trifluoride, hydrogen sulfide, hydrogen cyanide, ammonia.

The method of electrochemically absorbing a harmful exhaust gas according to claim 1, wherein the acid is hydrochloric acid, and the mass percentage of hydrogen chloride in the absorbent is 0.01 to 5%.

The method of electrochemically absorbing a harmful exhaust gas according to claim 1, wherein the acid is sulfuric acid, and the mass percentage of sulfuric acid in the absorbent is 0.02 to 10%.

The method for electrochemically absorbing harmful exhaust gas according to claim 1, wherein the acid is a mixture of hydrochloric acid and sulfuric acid, and the mass percentage of hydrogen chloride in the absorption liquid is 0.01 to 5%. The mass percentage of sulfuric acid in the absorption liquid is 0.02 to 10%.

A method of electrochemically absorbing a harmful exhaust gas according to any one of claims 2 to 4, wherein said absorbing liquid is an aqueous acid solution.

The method for electrochemically absorbing harmful exhaust gas according to any one of claims 1 to 4, wherein the absorption liquid is a mixed aqueous solution of an acid and a salt, and the salt is selected from the following one or two Any combination of the above ratios: sodium chloride, potassium chloride, sodium sulfate, potassium sulfate, the mass percentage concentration of the salt in the absorption liquid is 0.1 to 20%.

7. The method of electrochemically absorbing a harmful exhaust gas according to claim 1, wherein said harmful gas is selected from the group consisting of one or a mixture of two or more of the following: toluene, styrene, petroleum ether, trichloroethylene, Epoxy acetamidine, carbon disulfide, formaldehyde, methyl sulfide, acrylonitrile, oxazinone, vinyl acetate, diethylamine, hydrogen sulfide, sulfur dioxide, nitrogen monoxide, hydrogen sulfide, hydrogen cyanide, ammonia, nitrogen trifluoride , tetrahydrofuran, pyridine, acrylic acid, sewage station malodorous gas.