CN217712731U

CN217712731U - Plasma purification device for diesel engine tail gas

Info

Publication number: CN217712731U
Application number: CN202221908063.3U
Authority: CN
Inventors: 竹涛; 张学里; 叶泽甫; 朱竹军; 张星
Original assignee: Shanxi Gemeng Sino Us Clean Energy R & D Center Co ltd; China University of Mining and Technology Beijing CUMTB
Current assignee: Shanxi Gemeng Sino Us Clean Energy R & D Center Co ltd; China University of Mining and Technology Beijing CUMTB
Priority date: 2022-07-22
Filing date: 2022-07-22
Publication date: 2022-11-01
Anticipated expiration: 2032-07-22

Abstract

The utility model discloses a plasma purification device for diesel engine tail gas, which comprises a box body; the air inlet and the air outlet are respectively positioned at two ends of the box body; and the ammonia gas spraying component, the airflow uniform distribution plate, the corona discharge component, the electrocoagulation component, the rotary cleaning component, the electrostatic adsorption component and the back corona catalysis component are sequentially arranged in the box body from the air inlet. The utility model belongs to the technical field of the atmosphere pollution control, the main control problem who solves diesel engine tail gas pollution thing.

Description

Plasma purification device for diesel engine tail gas

Technical Field

The utility model discloses a plasma purifier for diesel engine tail gas relates to air pollution control technical field, especially relates to.

Background

The diesel engine adopts a lean combustion technology, the air-fuel ratio is high, the fuel is fully combusted due to excessive oxygen, and the emission of carbon monoxide (CO) and Hydrocarbon (HC) pollutants is less. However, due to the low degree of homogeneity of the mixture, more Nitrogen Oxides (NO) are locally formed_x) And soot particulates. NO_xThere is a trap-off effect with soot particles, the concentration of which increases and decreases, the scavenging mechanism being mutually restricted, i.e. NO_xNeeds to be reduced to N₂The soot particles are oxidized to carbon dioxide (CO)₂) And water (H)₂O). However, three-way catalytic Technology (TWC) has difficulty in reducing NO under oxygen-rich conditions_x. In addition, diesel exhaust contains sulfur dioxide (SO)₂)，SO₂Is easy to react with ammonia (NH)₃) Reaction to produce ammonium sulfate ((NH)₄)₂SO₄) Ammonium hydrogen sulfate (NH)₄HSO₄) Which tend to deposit on the catalyst surface resulting in poisoning deactivation. The tail gas of the diesel engine is easy to generate a photochemical reaction to generate secondary pollutants so as to form dust haze and photochemical smog, and the pollution treatment of the tail gas of the diesel engine becomes an important link for winning a blue-sky defense war along with the comprehensive and deep development of the atmospheric pollution treatment work.

The pollution control of the tail gas of the diesel engine generally adopts an internal purification technology and an external purification technology. The internal purification technology can reduce the exhaust emission of the diesel engine to a certain degree, but the internal purification has limitation due to the uneven oil-gas mixed compression spontaneous combustion mode of the diesel engine, the diesel engine exhaust cannot be effectively controlled only by adopting the internal purification technology, and the external purification technology generally has the problems of low purification efficiency and the like.

Therefore, a plasma purification device for diesel exhaust is proposed, which is expected to control soot particles and SO in diesel exhaust₂、NO_x。

SUMMERY OF THE UTILITY MODEL

The non-equilibrium plasma technology can generate a large amount of high-energy electrons and active free radicals under the conditions of normal temperature and normal pressure, and the non-equilibrium plasma and a Selective Catalytic Reduction (SCR) catalyst can be combined to reduce NOx in the tail gas of the diesel engine to generate nitrogen (N) at normal temperature or low temperature₂)。

To foretell diesel engine tail gas pollutant control difficult problem, the utility model discloses provide a plasma purifier for diesel engine tail gas based on nonequilibrium state plasma technique. Through optimization and improvement of a plurality of key components in the plasma purification device for the diesel engine exhaust, the soot particulate matters and SO in the diesel engine exhaust can be optimized₂、NO_xMultiple pollutants are cooperatively controlled, and simultaneously, the back corona discharge part is utilized, so that charged carbon smoke particulate matters, (NH) are effectively reduced₄)₂SO₄、NH₄HSO₄The deposition on the surface of the catalyst reduces the inactivation and regeneration cost of the catalyst, and has the advantages of simple structure, modular assembly, convenient operation, high purification efficiency, low energy consumption, long service life, no secondary pollution and the like.

According to an aspect of the utility model, a plasma purifier for diesel engine tail gas is provided, include:

a box body;

the air inlet and the air outlet are respectively positioned at two ends of the box body;

the device comprises an ammonia gas spraying component, an airflow uniform distribution plate, a corona discharge component, an electric coagulation component, a rotary cleaning component, an electrostatic adsorption component and a back corona catalysis component which are sequentially arranged in the box body from an air inlet.

Other objects and advantages of the present invention will become apparent from the following description of the embodiments of the invention, which is made with reference to the accompanying drawings, and can help to provide a comprehensive understanding of the invention.

Drawings

The invention will be explained in further detail with reference to the drawings, in which:

fig. 1 is a schematic diagram of a plasma purification apparatus for diesel exhaust according to an embodiment of the present invention;

fig. 2 is a schematic view of a corona discharge part in the plasma purification apparatus for diesel exhaust shown in fig. 1;

FIG. 3 is a schematic diagram of the electrocoagulation component of the plasma purification device for diesel exhaust shown in FIG. 1;

FIG. 4 is a schematic view of an electrostatic adsorption component in the plasma purification apparatus for diesel exhaust shown in FIG. 1;

FIG. 5 is a flow diagram of a method of making a monolithic SCR catalyst for use in a back corona catalytic component, according to an exemplary embodiment of the present invention;

fig. 6 shows a scanning electron microscope image of mullite whiskers made according to a method of an exemplary embodiment of the present invention;

figure 7 shows a scanning electron microscope image of aluminum borate whiskers prepared according to a method of an exemplary embodiment of the present invention;

fig. 8 shows a scanning electron microscope image of silicon carbide whiskers prepared according to a method of an exemplary embodiment of the present invention.

Detailed Description

The technical solution of the present invention is further specifically described below by way of examples and with reference to the accompanying drawings. In the specification, the same or similar reference numerals denote the same or similar components. The following description of the embodiments of the present invention, with reference to the drawings, is intended to explain the general inventive concept and should not be taken as limiting the invention.

Furthermore, in the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the embodiments of the disclosure. It may be evident, however, that one or more embodiments may be practiced without these specific details.

The terms of orientation such as up, down, left, right, front, and rear in the present specification are established based on the positional relationship shown in the drawings. The corresponding positional relationship may also vary depending on the drawings, and therefore, should not be construed as limiting the scope of protection.

The utility model provides a plasma purifier for diesel engine tail gas reforms transform based on nonequilibrium state plasma technique to current purifier's application.

Referring to fig. 1, an embodiment of the present invention provides a plasma purification apparatus 100 for diesel exhaust, including a housing 1, an air inlet 2, and an air outlet 10. The air inlet 2 is arranged on the left end face of the outer part of the box body 1, and the air outlet 10 is correspondingly arranged on the right end face of the outer part of the box body 1.

In addition, the plasma purification device 100 further comprises an ammonia gas spraying component 3, an airflow uniform distribution plate 4, a corona discharge component 5, an electrocoagulation component 6, a rotary cleaning component 7, an electrostatic adsorption component 8 and a back corona catalysis component 9 which are sequentially arranged in the box body 1 from the air inlet 2. Additionally, in the example shown in fig. 1, the plasma purifying apparatus 100 further includes a dust collecting chamber 11, a water-proof valve 12 and a support leg 13, as needed, and it can be understood by those skilled in the art that the above components can be arranged as needed, and are not limited to the illustrated case.

Specifically, the ammonia gas injection part 3 is provided at the inner left side of the case 1; a dust collecting chamber 11 is arranged on the lower end surface outside the box body 1, and the dust collecting chamber 11 is used for collecting soot particles, (NH)₄)₂SO₄、NH₄HSO₄And sewage; the water drain valve 12 is arranged on the outer lower end surface of the dust collecting chamber 11, and the water drain valve 12 is used for discharging sewage in the dust collecting chamber 11; four support legs 13 provided on the case 1, respectivelyFour vertices of the lower end face; the corona discharge part 5, the electrocoagulation part 6, the rotary cleaning part 7 and the electrostatic adsorption part 8 are sequentially arranged in the box body 1 by adopting a slot drawer type. It will be appreciated that the number of components mounted in a slot drawer may be selected by one skilled in the art as desired and is not limited to the embodiment illustrated.

In one example, referring to fig. 2, the corona discharge part 5 includes a corona electrode 51, a conductive link 52, and a plate frame 53, which are sequentially disposed from the direction of the air inlet 2. One end of the corona electrode 51 is connected to the conductive connecting rod 52, the other end is connected to the bottom end of the plate frame 53, and the corona discharge part 5 is powered by a negative high-voltage direct-current power supply.

In one example, referring to FIG. 3, the electrocoagulation component 6 includes a circular mesh plate 61 and gimbaled conductor wires 62 disposed thereon, with the gimbaled conductor wires 62 in adjacent rows staggered. The electrocoagulation component 6 is powered by an alternating-current high-voltage power supply, and the universal garland conductor wires 62 of two adjacent rows are respectively connected to a high-voltage pole and a grounding pole of the alternating-current high-voltage power supply.

In one example, a rotary cleaning component 7 is located between the electrocoagulation component 6 and the electrostatic adsorption component 8.

In one example, referring to fig. 4, the electrostatic adsorption part 8 includes an adsorption plate 81, a conductive link 82 and a plate frame 83, one end of the adsorption plate 81 is connected to the conductive link 82, the other end is connected to the bottom end of the plate frame 83, and the electrostatic adsorption part 8 is powered by a positive high voltage direct current power supply.

In one example, back-corona catalytic component 9 includes corona electrode 91, auxiliary electrode 92, monolithic SCR catalyst 93, and ground electrode 94 arranged in sequence from the direction of gas inlet 2, corona electrode 91 and auxiliary electrode 92 being powered by two negative high voltage dc power supplies, respectively. Preferably, the power supply electrode 91 and the auxiliary electrode 92 are each made of a tungsten wire having a diameter of between 2 and 6 mm.

Specifically, the monolithic SCR catalyst 93 comprises an SCR catalyst coated on the inner and outer surfaces of a honeycomb substrate. Preferably, the SCR catalyst is uniformly supported on the inner and outer surfaces of the honeycomb substrate. The monolithic SCR catalyst honeycomb substrate is made of cordierite, alumina, foam metal (nickel) or silicon carbide.

The inner and outer surfaces of the honeycomb substrate are grown with whiskers, and the monolithic SCR catalyst is prepared by coating an SCR catalyst on the inner and outer surfaces of the honeycomb substrate and performing drying and calcination treatment, and specifically, the following example shows a preparation method of the monolithic SCR catalyst, and a description thereof will not be repeated.

According to another embodiment of the present invention, there is also provided a plasma purification method for diesel exhaust, which uses the plasma purification apparatus 100 for diesel exhaust for purification treatment. The plasma purification method includes: the collected diesel exhaust enters the purification apparatus 100 through the air inlet 2 and then passes through the ammonia gas injection part 3, wherein NH is injected when passing through the ammonia gas injection part 3₃With SO in diesel exhaust₂Reacting to generate ammonium sulfate; under the action of guiding and distributing air by the air flow uniform distribution plate 4, the tail gas of the diesel engine is uniformly distributed in the purification device 100; the diesel engine tail gas passing through the gas flow uniform distribution plate 4 sequentially passes through a corona discharge component 5, an electrocoagulation component 6, a rotary cleaning component 7, an electrostatic adsorption component 8 and a back corona catalysis component 9.

In one example, diesel engine tail gas collected by a pipeline enters the plasma purification device 100 through the air inlet 2, and after passing through the ammonia gas injection part 3, the diesel engine tail gas is uniformly distributed in the plasma purification device 100 under the action of guiding and distributing air by the air flow uniform distribution plate 4 and sequentially passes through the corona discharge part 5, the electrocoagulation part 6, the rotary cleaning part 7, the electrostatic adsorption part 8 and the back corona catalysis part 9; while passing through the ammonia gas injection part 3, NH₃With SO in diesel engine exhaust₂Reaction to form (NH)₄)₂SO₄、NH₄HSO₄(ii) a When passing through the corona discharge part 5, the negative high voltage direct current power supply supplies power to the corona electrode 51, so that the gas near the electrode is ionized to generate a large amount of negative charges, and carbon smoke particulate matters, (NH), with the particle size of 2-50 micrometers, in the tail gas of the diesel engine₄)₂SO₄、NH₄HSO₄Carbon smoke particulate matter (NH) with negative charge and particle size of 0.01-2 microns under the action of negative direct current corona₄)₂SO₄、NH₄HSO₄Are difficult to be charged.

When passing through the electrocoagulation part 6, because an AC high-voltage power supply supplies power to the universal garland conductor wires 62 and the universal garland conductor wires 62 in two adjacent rows are respectively connected on a high-voltage pole and a grounding pole of the AC high-voltage power supply, gas near the universal garland conductor wires 62 is ionized to generate a large amount of charges, carbon smoke particulate matters (NH) with the grain diameter of 0.01-2 microns₄)₂SO₄、NH₄HSO₄And the condensed and aggregated particles are charged and finally trapped by the electrostatic adsorption member 8.

The rotary cleaning part 7 can perform rotary flushing cleaning on the electrocoagulation part 6 and the electrostatic adsorption part 8 for example at regular time to remove soot particulate matters, (NH) deposited on the surfaces of the electrocoagulation part 6 and the electrostatic adsorption part 8₄)₂SO₄、NH₄HSO₄。

When the catalyst passes through the back corona catalytic component 9, the corona electrode 91 and the auxiliary electrode 92 in the back corona catalytic component 9 are respectively powered by two negative high-voltage direct-current power supplies, wherein the corona electrode 91 ionizes gas near the corona electrode 91 in the discharging process to generate a large amount of negative charges and accumulate the negative charges on the inner surface and the outer surface of the integral SCR catalyst 93, the accumulated charges generate an overlapped electric field in the inner pores of the honeycomb matrix, and when the field intensity of the overlapped electric field exceeds the breakdown field intensity of whiskers on the surface of the inner pores of the honeycomb matrix, punctiform discharge occurs to generate a back corona phenomenon. The dust is charged by different charges due to back corona and is sputtered and transferred to the negative high-voltage electrode under the action of electric field force, and charged carbon smoke particles, (NH)₄)₂SO₄、NH₄HSO₄The reverse sputtering is trapped by the electrostatic adsorption component 8 to avoid carbon smoke particulate matter, (NH)₄)₂SO₄、NH₄HSO₄The deposition on the surface of the SCR catalyst prevents the SCR catalyst from being poisoned and deactivated, and prolongs the service life of the SCR catalyst. At the same time, back corona plasma is generated in the inner pores of the honeycomb substrate, thereby formingA plasma reaction channel, free electrons, energetic ions, active particles and NH generated in the plasma reaction channel₃、NO_xInteraction to form NH₂An active group of "NH", "N", "H", "NH₂Active groups of NH, N and H are tightly combined with active components of the SCR catalyst on the inner surface and the outer surface of the integral SCR catalyst 93, so that the advantages of high reaction activity of plasma and high reaction selectivity of SCR are fully exerted, the reaction activity of the SCR catalyst is activated, the reaction selectivity of back corona plasma is improved, the SCR reaction is promoted to be generated at normal temperature or low temperature, and finally NO in the tail gas of the diesel engine is generated_xIs reduced to N₂. The auxiliary electrode 92 suppresses the development of the discharge of the corona electrode 91 to the spark discharge; the purified diesel exhaust exits the plasma purification apparatus 100 through the outlet 10.

Three specific examples are provided below to illustrate the monolithic SCR catalyst on monolithic SCR catalyst 93 and the method of preparation and the corresponding exhaust treatment process in detail.

The preparation method of the integral SCR catalyst comprises the following steps: providing whisker raw material, anhydrous aluminum sulfate and anhydrous sodium sulfate and a honeycomb matrix in a predetermined ratio and embedding the honeycomb matrix with the whisker raw material, the anhydrous aluminum sulfate and the anhydrous sodium sulfate to obtain a mixed material; roasting the mixed material at 900-1200 ℃ for 2-12 hours, cooling, and growing whiskers on the surface of the honeycomb matrix; providing SCR catalyst powder and mixing the SCR catalyst powder with sodium carboxymethyl cellulose, silica sol and water in a preset ratio to obtain SCR catalyst slurry; and coating the SCR catalyst slurry on the inner surface and the outer surface of the honeycomb substrate, drying, and roasting to obtain the integral SCR catalyst.

Because whiskers grow on the inner surface and the outer surface of the honeycomb matrix, the honeycomb matrix has a large specific surface area and can provide larger attachment sites for SCR catalyst coating. A large amount of negative charges are generated in the discharging process and accumulated on the inner and outer surfaces of the integral SCR catalyst, the accumulated charges generate an overlapped electric field in the inner pores of the honeycomb matrix, and when the field intensity of the overlapped electric field exceeds the breakdown field intensity of whiskers on the surface of the inner pores of the honeycomb matrix, the overlapped electric field generatesBack corona plasma can effectively avoid carbon smoke particulate matter, (NH)₄)₂SO₄、NH₄HSO₄In addition, the Fe-Mn bimetal single-site catalyst with high dispersibility can effectively increase the sulfur resistance of the catalyst and prolong the service time of the SCR catalyst.

Fig. 5 illustrates a method of making a monolithic SCR catalyst for use in a back corona catalytic component according to an exemplary embodiment of the invention. As shown, the method comprises:

obtaining a mixed material: providing whisker raw material, anhydrous aluminum sulfate and anhydrous sodium sulfate in a predetermined ratio with a honeycomb substrate (including cordierite, alumina, a foamed metal (e.g., nickel) or silicon carbide) and embedding the honeycomb substrate with the whisker raw material, the anhydrous aluminum sulfate and the anhydrous sodium sulfate to obtain a mixed material;

growing whiskers: calcining the mixture at 900-1200 ℃, preferably 1000-1100 ℃ for 2-12 hours (preferably 4-10 hours, more preferably 6 hours), cooling (preferably to room temperature), and growing whiskers on the surface of the honeycomb substrate;

obtaining SCR catalyst slurry: providing SCR catalyst powder and mixing the SCR catalyst powder with sodium carboxymethyl cellulose, silica sol and water in a preset ratio to obtain SCR catalyst slurry;

obtaining the monolithic SCR catalyst: and coating the SCR catalyst slurry on the inner surface and the outer surface of the honeycomb matrix for growing the whiskers, drying, and roasting to obtain the integral SCR catalyst.

In an embodiment, the step of obtaining an SCR catalyst slurry comprises: uniformly mixing the SCR catalyst powder with sodium carboxymethylcellulose, silica sol and water according to the mass ratio of (20-40) to (10-30) to (10-20) to (20-40) to obtain SCR catalyst slurry. For example, the mass ratio of the SCR catalyst powder to the sodium carboxymethyl cellulose, the silica sol, and the water may be 40:15:13:32.

in an embodiment, the step of obtaining the monolithic SCR catalyst comprises: coating the SCR catalyst slurry on the inner and outer surfaces of the honeycomb substrate with the grown whiskers on a vacuum coating machine, drying the coated material, and roasting at 300-600 ℃ for 2-10 hours to obtain the integral SCR catalyst. In an embodiment, drying may be carried out in a drying oven at 80-120 ℃ (preferably 100 ℃) for 1-4 hours (preferably 2 hours). In an embodiment, the calcination can be carried out in a muffle furnace at 400-500 deg.C (preferably 450 deg.C) for 4-8 hours (preferably 6 hours).

In the embodiment, the method of the utility model can grow mullite whisker, aluminum borate whisker or silicon carbide whisker.

In the embodiment, when mullite whiskers are grown, the whisker raw material is obtained by the following steps: dissolving an organic silicon source in an organic solvent and forming a silica sol, treating the silica sol in a water bath at 40-80 ℃ (preferably 60 ℃) for 0.5-5 hours (preferably 1-4 hours, more preferably 2 hours); dissolving an inorganic aluminum salt in an inorganic solvent to form an inorganic aluminum salt solution; adding an inorganic aluminum salt solution into the silica sol treated by the water bath to form silicon-aluminum mixed sol; treating the silicon-aluminum mixed sol in a water bath at 40-80 ℃ (preferably 60 ℃) for 6-18 hours (preferably 10-15 hours, more preferably 12 hours), and grinding after drying in an oven (preferably 80-100 ℃, more preferably 90 ℃) to obtain silicon-aluminum gel powder which is the raw material of the whisker.

In an embodiment, the organic silicon source is at least one of ethyl orthosilicate, methyl orthosilicate and propyl orthosilicate. In an embodiment, the inorganic aluminum salt is at least one of aluminum nitrate, aluminum nitrate nonahydrate, aluminum chloride, aluminum chlorohydrate, and aluminum sulfate. In an embodiment, the inorganic solvent is deionized water. In an embodiment, the organic solvent is absolute ethanol. In an embodiment, the molar ratio of aluminium to silicon in the silica-alumina hybrid sol is between 2 and 6. In an embodiment, the honeycomb matrix: silicon-aluminum gel powder: anhydrous aluminum sulfate: the mass ratio of the anhydrous sodium sulfate is (40-50): (15-25): (10-20), for example, 40:25:20:15.

in the examples, the hydrolysis of the source of organic silicon to form the silica sol is promoted, for example, by the addition of an additive under stirring, which is 2 to 4mL of aqueous ammonia.

In the examples, when growing aluminum borate whiskers, the whisker starting materials include boron trioxide and aluminum nitrate. In an embodiment, the honeycomb matrix: diboron trioxide: aluminum nitrate: anhydrous aluminum sulfate: the mass ratio of the anhydrous sodium sulfate is (20-40): (10-20): (20-30), for example, 30:15:20:15:20.

in the embodiment, when growing the silicon carbide whisker, the whisker raw material is obtained by the following steps: and (2) mixing the silicon powder and a carbon source according to the Si: C molar ratio of 1. In an embodiment, during microwave heating, the microwave frequency is set to 2-3GHz (preferably 2.5 GHz) and the microwave source power is set to 3-5kW (preferably 4 kW). In an embodiment, the carbon source is at least one of carbon black, petroleum coke, graphite powder, and activated carbon. In an embodiment, the honeycomb matrix: silicon carbide powder: anhydrous aluminum sulfate: the mass ratio of the anhydrous sodium sulfate is (30-40): (20-30): (15-25): (10-30), for example, 30:20:22:28.

the following detailed description is provided for a better understanding of the present invention, and it will be understood by those skilled in the art that the following detailed description is merely a part of all embodiments of the present invention, and not all embodiments are presented for the sake of brevity.

Example 1:

(1) Preparation of monolithic SCR catalyst by honeycomb substrate for growing mullite whisker

The silica-alumina gel powder is prepared by adopting a sol-gel method. Weighing a certain amount of aluminum nitrate to be dissolved in deionized water, weighing a certain amount of tetraethoxysilane to be dissolved in absolute ethyl alcohol, and enabling the molar ratio of Al/Si to be between 3; adding 2-4mL of ammonia water into the absolute ethyl alcohol solution under the stirring condition to catalyze tetraethoxysilane to hydrolyze so as to form silica sol, and treating the silica sol in a water bath at the temperature of 60 ℃ for 2 hours; then adding the aluminum nitrate solution into the silica sol under the stirring condition, treating the mixture in a water bath at 60 ℃ for 12 hours, drying the mixed sol of silicon and aluminum in a drying oven at 90 ℃, and grinding the dried sol of silicon and aluminum to obtain the silicon and aluminum gel powder.

Weighing a certain amount of aluminum sulfate hexahydrate or aluminum sulfate octadecahydrate, heating to 400 ℃ to remove crystal water to obtain anhydrous aluminum sulfate, and then weighing a certain amount of anhydrous aluminum sulfate and anhydrous sodium sulfate to be used as a composite molten salt system.

Adding silicon-aluminum gel powder, anhydrous aluminum sulfate and anhydrous sodium sulfate into cordierite, alumina, foamed metal (nickel) or silicon carbide honeycomb matrix to ensure that the cordierite, alumina, foamed metal (nickel) or silicon carbide honeycomb matrix is prepared by the following steps: silicon-aluminum gel powder: anhydrous aluminum sulfate: the mass ratio of the anhydrous sodium sulfate is 45. And (3) roasting the mixture in a muffle furnace at 1000 ℃ for 6 hours, naturally cooling to room temperature, and growing on the surface of a cordierite, alumina, foam metal (nickel) or silicon carbide honeycomb substrate to form compact mullite whiskers. Fig. 6 shows a scanning electron microscope image of mullite whiskers.

Weighing a certain amount of cerous nitrate hexahydrate, ferric nitrate nonahydrate, manganese acetate and titanium dioxide, dissolving the cerous nitrate hexahydrate, the ferric nitrate nonahydrate, the manganese acetate and the titanium dioxide in deionized water according to the mass ratio of 10.

Uniformly mixing the SCR catalyst powder with sodium carboxymethylcellulose, silica sol and water according to a mass ratio of 30.

(2) Purifying tail gas

The diesel engine tail gas collected by the pipeline enters the plasma purification device 100 through the air inlet 2, and after passing through the ammonia gas injection part 3, the diesel engine tail gas is uniformly distributed in the plasma purification device 100 under the action of flow guiding and air distributing of the airflow uniform distribution plate 4 and sequentially passes through the corona discharge part 5, the electric coagulation part 6, the rotary cleaning part 7, the electrostatic adsorption part 8 and the back corona catalysis part 9.

While passing through the ammonia gas injection part 3, NH₃With SO in diesel exhaust₂Reaction to form (NH)₄)₂SO₄、NH₄HSO₄。

When the diesel engine tail gas passes through the corona discharge part 5, the negative high-voltage direct current power supply supplies power to the corona electrode 91, so that the gas near the corona electrode is ionized to generate a large amount of negative charges, and carbon smoke particulate matters, (NH) with the particle size of 2-50 micrometers in the diesel engine tail gas₄)₂SO₄、NH₄HSO₄Carbon smoke particulate matter (NH) with negative charge and particle size of 0.01-2 microns under the action of negative direct current corona₄)₂SO₄、NH₄HSO₄Are difficult to be charged.

When the carbon black particles (NH) pass through the electrocoagulation component 6, the universal garland conductor wires 62 are powered by the alternating-current high-voltage power supply, and the universal garland conductor wires 62 in two adjacent rows are respectively connected to the high-voltage pole and the grounding pole of the alternating-current high-voltage power supply, so that the gas near the universal garland wires is ionized to generate a large amount of charges, the particle size of the carbon black particles (soot particles) is 0.01-2 microns₄)₂SO₄、NH₄HSO₄The particles are agglomerated and charged, and are finally captured by the electrostatic adsorbing member 8.

The rotary cleaning part 7 can perform rotary flushing cleaning on the electrocoagulation part 6 and the electrostatic adsorption part 8 at regular time to remove soot particulate matters, (NH) deposited on the surfaces of the electrocoagulation part 6 and the electrostatic adsorption part 8₄)₂SO₄、NH₄HSO₄。

When the catalyst passes through the back corona catalysis component 9, the corona electrode 91 and the auxiliary electrode 92 in the back corona catalysis component 9 are respectively powered by two negative high-voltage direct-current power supplies, wherein the corona electrode 91 ionizes gas near the corona electrode 91 in the discharge process to generate a large amount of negative charges and accumulate the negative charges on the inner surface and the outer surface of the integral SCR catalyst 93, the accumulated charges generate a superposed electric field in the inner pores of the honeycomb matrix, and back corona plasma is generated when the field intensity of the superposed electric field exceeds the breakdown field intensity of whiskers on the surface of the inner pores of the honeycomb matrix. Charged carbon smoke particulate matters, (NH) under the action of back corona plasma₄)₂SO₄、NH₄HSO₄The reverse sputtering is trapped by the electrostatic adsorption component 8 to avoid carbon smoke particles, (NH)₄)₂SO₄、NH₄HSO₄The deposition on the surface of the SCR catalyst prevents the SCR catalyst from being poisoned and deactivated, and prolongs the service life of the SCR catalyst. Simultaneously, back corona plasma is generated in the inner pores of the honeycomb matrix, thereby forming plasma reaction channels, and free electrons, high-energy ions, active particles and NH are generated in the plasma reaction channels₃、NO_xInteraction to form NH₂An active group of "NH", "N", "H", "NH₂NH, N and H active groups are tightly combined with active components of the SCR catalyst on the inner surface and the outer surface of the integral SCR catalyst 93, so that the advantages of high reaction activity of plasma and high reaction selectivity of SCR are fully exerted, the reaction activity of the SCR catalyst is activated, the reaction selectivity of back corona plasma is improved, the SCR reaction is promoted to occur at normal temperature or low temperature, and finally NO in the tail gas of the diesel engine is generated_xIs reduced to N₂. The auxiliary electrode 92 suppresses the development of discharge from the corona electrode 91 to spark discharge; the purified diesel exhaust exits the plasma purification apparatus 100 through the outlet 10.

Example 2:

(1) Preparation of integral SCR catalyst by honeycomb matrix for growing aluminum borate whisker

Adding diboron trioxide, aluminum nitrate, anhydrous aluminum sulfate and anhydrous sodium sulfate to a cordierite, alumina, metal foam (nickel) or silicon carbide honeycomb substrate to form a cordierite, alumina, metal foam (nickel) or silicon carbide honeycomb substrate: diboron trioxide: aluminum nitrate: anhydrous aluminum sulfate: anhydrous sodium sulfate mass ratio of 30. And (3) roasting the mixed material in a muffle furnace at 1000 ℃ for 6 hours, naturally cooling to room temperature, and growing on the surface of a cordierite, alumina, foam metal (nickel) or silicon carbide honeycomb matrix to form compact aluminum borate whiskers. Figure 7 shows a scanning electron microscope image of aluminum borate whiskers.

Weighing a certain amount of cerium nitrate hexahydrate, ferric nitrate nonahydrate, manganese acetate and titanium dioxide, dissolving in deionized water according to the mass ratio of 10.

(2) Purifying tail gas

While passing through the ammonia gas injection part 3, NH₃With SO in diesel engine exhaust₂Reaction to form (NH)₄)₂SO₄、NH₄HSO₄。

When passing through the corona discharge part 5, the negative high-voltage direct current power supply supplies power to the corona electrode 91, so that the gas near the electrode is ionized to generate a large amount of negative charges, and the particle size of the carbon smoke particulate matters (NH) in the tail gas of the diesel engine is 2-50 microns₄)₂SO₄、NH₄HSO₄Negative charge under the action of negative DC corona and particle sizeSoot particles (NH) between 0.01 and 2 microns₄)₂SO₄、NH₄HSO₄Are difficult to be charged.

The rotary cleaning part 7 can perform rotary washing cleaning on the electrocoagulation part 6 and the electrostatic adsorption part 8 at regular time to remove soot particulate matters, (NH) deposited on the surfaces of the electrocoagulation part 6 and the electrostatic adsorption part 8₄)₂SO₄、NH₄HSO₄。

When the catalyst passes through the back corona catalytic component 9, the corona electrode 91 and the auxiliary electrode 92 in the back corona catalytic component 9 are respectively powered by two negative high-voltage direct-current power supplies, wherein the corona electrode 91 ionizes gas near the corona electrode 91 in the discharging process to generate a large amount of negative charges and accumulate on the inner surface and the outer surface of the monolithic SCR catalyst 93, the accumulated charges generate a superposed electric field in the inner pores of the honeycomb matrix, and back corona plasma is generated when the field intensity of the superposed electric field exceeds the breakdown field intensity of whiskers on the surfaces of the inner pores of the honeycomb matrix. Charged carbon smoke particulate matters, (NH) under the action of back corona plasma₄)₂SO₄、NH₄HSO₄The reverse sputtering is trapped by the electrostatic adsorption component 8 to avoid carbon smoke particles, (NH)₄)₂SO₄、NH₄HSO₄The deposition on the surface of the SCR catalyst prevents the SCR catalyst from being poisoned and deactivated, and prolongs the service life of the SCR catalyst. Simultaneously, back corona plasma is generated in the inner pores of the honeycomb matrix, so that a plasma reaction channel is formed, and free electrons, high-energy ions, active particles and NH are generated in the plasma reaction channel₃、NO_xInteraction to form NH₂NH, N, H reactive groups, NH₂Active groups of NH, N and H are tightly combined with active components of the SCR catalyst on the inner surface and the outer surface of the integral SCR catalyst 93, so that the advantages of high reaction activity of plasma and high reaction selectivity of SCR are fully exerted, the reaction activity of the SCR catalyst is activated, the reaction selectivity of back corona plasma is improved, the SCR reaction is promoted to be generated at normal temperature or low temperature, and finally NO in the tail gas of the diesel engine is generated_xIs reduced to N₂. The auxiliary electrode 92 suppresses the development of the discharge of the corona electrode 91 to the spark discharge; the purified diesel exhaust exits the plasma purification apparatus 100 through the outlet 10.

Example 3:

(1) Preparation of integral SCR catalyst by honeycomb matrix for growing silicon carbide whiskers

Weighing a certain amount of carbon black and silicon powder, wherein the molar ratio of Si to C is 1.

Adding silicon carbide powder, anhydrous aluminum sulfate and anhydrous sodium sulfate into cordierite, alumina, foamed metal (nickel) or silicon carbide honeycomb matrix to ensure that the cordierite, alumina, foamed metal (nickel) or silicon carbide honeycomb matrix is prepared by the following steps: silicon carbide powder: anhydrous aluminum sulfate: the mass ratio of the anhydrous sodium sulfate is 35. And (3) roasting the mixed material in a muffle furnace at 1000 ℃ for 6 hours, naturally cooling to room temperature, and growing on the surface of a cordierite, alumina, foam metal (nickel) or silicon carbide honeycomb matrix to form compact silicon carbide whiskers.

(2) Purifying tail gas

When the diesel engine tail gas passes through the corona discharge part 5, the negative high-voltage direct current power supply supplies power to the corona electrode 91, so that the gas near the electrode is ionized to generate a large amount of negative charges, and carbon smoke particulate matters, (NH) with the particle size of 2-50 micrometers in the diesel engine tail gas₄)₂SO₄、NH₄HSO₄Carbon smoke particulate matter (NH) with negative charge and particle size of 0.01-2 microns under the action of negative direct current corona₄)₂SO₄、NH₄HSO₄Are difficult to be charged.

When passing through the electrocoagulation part 6, because an AC high-voltage power supply supplies power to the universal garland conductor wires 62 and the universal garland conductor wires 62 in two adjacent rows are respectively connected on a high-voltage pole and a grounding pole of the AC high-voltage power supply, gas near the universal garland conductor wires 62 is ionized to generate a large amount of charges, carbon smoke particulate matters (NH) with the grain diameter of 0.01-2 microns₄)₂SO₄、NH₄HSO₄The particles are agglomerated and charged, and are finally captured by the electrostatic adsorbing member 8.

When the catalyst passes through the back corona catalytic component 9, the corona electrode 91 and the auxiliary electrode 92 in the back corona catalytic component 9 are respectively powered by two negative high-voltage direct-current power supplies, wherein the corona electrode 91 ionizes gas near the corona electrode 91 in the discharging process to generate a large amount of negative charges and accumulate on the inner surface and the outer surface of the monolithic SCR catalyst 93, the accumulated charges generate a superposed electric field in the inner pores of the honeycomb matrix, and back corona plasma is generated when the field intensity of the superposed electric field exceeds the breakdown field intensity of whiskers on the surfaces of the inner pores of the honeycomb matrix. Charged carbon smoke particulate matter, (NH) under the action of back corona plasma₄)₂SO₄、NH₄HSO₄The reverse sputtering is trapped by the electrostatic adsorption component 8 to avoid carbon smoke particles, (NH)₄)₂SO₄、NH₄HSO₄The deposition on the surface of the SCR catalyst prevents the SCR catalyst from being poisoned and deactivated, and prolongs the service life of the SCR catalyst. Simultaneously, back corona plasma is generated in the inner pores of the honeycomb matrix, so that a plasma reaction channel is formed, and free electrons, high-energy ions, active particles and NH are generated in the plasma reaction channel₃、NO_xInteraction to form NH₂An active group of "NH", "N", "H", "NH₂Active groups of NH, N and H are tightly combined with active components of the SCR catalyst on the inner surface and the outer surface of the integral SCR catalyst 93, so that the advantages of high reaction activity of plasma and high reaction selectivity of SCR are fully exerted, the reaction activity of the SCR catalyst is activated, the reaction selectivity of back corona plasma is improved, the SCR reaction is promoted to be generated at normal temperature or low temperature, and finally NO in the tail gas of the diesel engine is generated_xIs reduced to N₂. The auxiliary electrode 92 suppresses the development of the discharge of the corona electrode 91 to the spark discharge; purificationThe diesel exhaust gas is discharged from the plasma purification apparatus 100 through the gas outlet 10.

When the catalyst passes through the back corona catalytic component 9, the corona electrode 91 and the auxiliary electrode 92 in the back corona catalytic component 9 are respectively powered by two negative high-voltage direct-current power supplies, wherein the corona electrode 91 ionizes gas near the corona electrode 91 in the discharge process to generate a large amount of negative charges and accumulate the negative charges on the inner surface and the outer surface of the monolithic SCR catalyst 93, the accumulated charges generate a superposed electric field in the inner pores of the honeycomb matrix, and back corona plasma is generated when the field intensity of the superposed electric field exceeds the breakdown field intensity of whiskers on the surface of the inner pores of the honeycomb matrix. Charged carbon smoke particulate matter, (NH) under the action of back corona plasma₄)₂SO₄、NH₄HSO₄The reverse sputtering is trapped by the electrostatic adsorption component 8 to avoid carbon smoke particles, (NH)₄)₂SO₄、NH₄HSO₄The deposition on the surface of the SCR catalyst prevents the SCR catalyst from being poisoned and deactivated, and prolongs the service life of the SCR catalyst. Simultaneously, back corona plasma is generated in the inner pores of the honeycomb matrix, so that a plasma reaction channel is formed, and free electrons, high-energy ions, active particles and NH are generated in the plasma reaction channel₃Interaction of NOx to form NH₂An active group of "NH", "N", "H", "NH₂Active groups of NH, N and H are tightly combined with active components of the SCR catalyst on the inner surface and the outer surface of the integral SCR catalyst 93, so that the advantages of high reaction activity of plasma and high reaction selectivity of SCR are fully exerted, the reaction activity of the SCR catalyst is activated, the reaction selectivity of back corona plasma is improved, the SCR reaction is promoted to be generated at normal temperature or low temperature, and finally NO in the tail gas of the diesel engine is generated_xIs reduced to N₂. The auxiliary electrode 92 suppresses the development of the discharge of the corona electrode 91 to the spark discharge; the purified diesel exhaust exits the plasma purification apparatus 100 through the outlet 10.

To sum up, the utility model provides a plasma purifier for diesel engine tail gas possesses at least one in following advantage at least:

in the discharging process of the corona electrode, gas near the corona electrode is ionized to generate a large amount of negative charges and the negative charges are accumulated on the inner surface and the outer surface of the integral SCR catalyst, the accumulated charges generate a superposed electric field in the inner pores of the honeycomb matrix, and when the field intensity of the superposed electric field exceeds the breakdown field intensity of whiskers on the surfaces of the inner pores of the honeycomb matrix, punctiform discharge occurs to generate a back corona phenomenon.

The dust is charged by different charges due to back corona and is sputtered and transferred to the negative high-voltage electrode under the action of electric field force, and charged carbon smoke particles, (NH)₄)₂SO₄、NH₄HSO₄The reverse sputtering is trapped by the electrostatic adsorption component 8 to avoid carbon smoke particulate matter, (NH)₄)₂SO₄、NH₄HSO₄The deposition on the surface of the SCR catalyst prevents the SCR catalyst from being poisoned and deactivated, and prolongs the service life of the SCR catalyst.

Back corona plasma is generated in the inner pores of the honeycomb matrix, so that a plasma reaction channel is formed, and free electrons, high-energy ions, active particles and NH are generated in the plasma reaction channel₃、NO_xInteraction to form NH₂An active group of "NH", "N", "H", "NH₂Active groups of NH, N and H are tightly combined with active components of the SCR catalyst, so that the advantages of high reaction activity of plasma and high reaction selectivity of SCR are fully exerted, the reaction activity of the SCR catalyst is activated, the reaction selectivity of the back corona plasma is improved, and the SCR reaction is promoted to occur at normal temperature or low temperature.

In addition, the dense whiskers on the inner surface and the outer surface of the honeycomb matrix can improve the effect on soot particles, (NH)₄)₂SO₄、NH₄HSO₄Intercepting, trapping and purifying efficiency.

The purification device has the advantages of simple structure, modular assembly, small occupied area, convenient operation, high purification efficiency, low energy consumption, no secondary pollution and the like, and can be used immediately after being stopped.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A plasma purification apparatus for diesel exhaust, characterized in that it comprises:

a box body;

an air inlet and an air outlet which are respectively positioned at two ends of the box body;

2. The plasma purification apparatus of claim 1, wherein the back-corona catalytic component comprises a corona electrode, an auxiliary electrode, an integral SCR catalyst and a grounding electrode, which are arranged in sequence from the direction of the air inlet, wherein the corona electrode and the auxiliary electrode are respectively powered by two negative high-voltage direct-current power supplies.

3. The plasma purification apparatus according to claim 2, wherein the monolithic SCR catalyst comprises a honeycomb substrate and SCR catalysts coated on the inner and outer surfaces of the honeycomb substrate, and dense whiskers are grown on the inner and outer surfaces of the honeycomb substrate.

4. A plasma purification apparatus as recited in claim 3, wherein the whiskers on the inner and outer surfaces of the honeycomb substrate comprise mullite whiskers, aluminum borate whiskers, or silicon carbide whiskers.

5. The plasma purification apparatus of claim 1, wherein the electrostatic adsorption component comprises an adsorption polar plate, a conductive connecting rod and a plate frame, one end of the adsorption polar plate is connected to the conductive connecting rod, the other end of the adsorption polar plate is connected to the bottom end of the plate frame, and the electrostatic adsorption component is powered by a positive high-voltage direct current power supply.

6. The plasma purification apparatus of claim 1, wherein the corona discharge component comprises a corona electrode, a conductive connecting rod and a plate frame, wherein one end of the corona electrode is connected to the conductive connecting rod, the other end of the corona electrode is connected to the bottom end of the plate frame, and the corona discharge component is powered by a negative high voltage direct current power supply.

7. The plasma purification device according to claim 1, wherein the electrocoagulation part comprises a round hole screen plate and universal garland conductor wires arranged on the round hole screen plate, the universal garland conductor wires in two adjacent rows are staggered, the electrocoagulation part is powered by an alternating current high-voltage power supply, and the universal garland conductor wires in two adjacent rows are respectively connected to a high-voltage electrode and a ground electrode of the alternating current high-voltage power supply.

8. The plasma purification apparatus of any one of claims 1 to 7, wherein at least one of the corona discharge component, the electrocoagulation component and the electrostatic adsorption component is sequentially installed inside the box body in a slot-drawer type.

9. The plasma purification apparatus of claim 8, further comprising a dust collection chamber provided outside the case on a lower end surface of the case.

10. The plasma purification apparatus according to claim 9, further comprising a water drain valve provided outside the dust collecting chamber on a lower end surface of the dust collecting chamber, and four support legs located at four apexes of the lower end surface of the case.