CN111852614A

CN111852614A - Tail gas treatment system and treatment method

Info

Publication number: CN111852614A
Application number: CN201910360357.3A
Authority: CN
Inventors: 王大祥; 唐万福; 奚勇
Original assignee: Shanghai Bixiufu Enterprise Management Co Ltd
Current assignee: Shanghai Bixiufu Enterprise Management Co Ltd
Priority date: 2019-04-30
Filing date: 2019-04-30
Publication date: 2020-10-30

Abstract

The invention provides a tail gas treatment system and a treatment method, wherein the treatment system comprises a plurality of sections of plasma catalysis modules, and the plasma catalysis modules comprise: a plasmatizing unit for plasmatizing the stream to be treated to provide a stream subjected to the plasmatizing treatment; and the catalytic reaction unit is used for carrying out catalytic reaction on the stream subjected to the plasma reaction treatment so as to provide the stream subjected to the catalytic reaction treatment. The treatment method comprises the step of carrying out plasma catalysis on a stream to be treated in a plurality of sectionsThe plasma catalysis comprises the following steps: carrying out plasma treatment on the stream to be treated; then carrying out catalytic reaction. The tail gas treatment system and the treatment method combine a plasma unit and a catalytic reaction unit, preferably further comprise an ultraviolet light catalytic module, and achieve the purpose of continuously, stably, permanently and reliably solving NO simultaneously_xAnd PM emission problem, and can also purify hydrocarbon THC, carbon monoxide CO and other emission pollutants simultaneously, and the treatment effect is good when the engine is started at low temperature.

Description

Tail gas treatment system and treatment method

Technical Field

The invention relates to a tail gas treatment system and a treatment method, in particular to an electric composite multi-effect catalytic tail gas treatment system and a treatment method.

Background

The diesel fuel process is a diffusion combustion process, and the diesel combustion process is lean, so that a large amount of NO is generated in high-temperature oxygen-rich areas such as a combustion interface (fire front surface)_xAnd a large amount of PM is generated in a low-temperature anoxic zone such as an oil drop atomization center. Causing the diesel engine to emit NO as the main pollution_xAnd PM, and due to NO_xContradictory causes of PM production (trade-off) and makes it difficult to reduce NO simultaneously by only internal purging_xAnd PM. With the continuous tightening of emission standards, the internal purification measures cannot solve NO_xAnd PM meeting the standard. For NO, by means of after-treatment devices_xPM and THC and CO are purified.

At present, for diesel engine purification, the conventional technical route is to remove THC and CO by using oxidation catalyst DOC, and oxidize low-valence NO into high-valence NO₂(ii) a Filtering PM with a diesel particulate trap (DPF) after DOC; after DPF, urea is injected, which decomposes into ammonia NH in the exhaust gases₃，NH₃After selective catalytic SCR and NO₂Carrying out selective catalytic reduction reaction to generate nitrogen N₂And water. Excess NH is finally added to the ammonia oxidation catalyst ASC₃By oxidation to N₂And water.

The existing purification system based on thermal catalysis needs to reach a certain working temperature no matter DOC, SCR and ASC catalysts of a diesel vehicle or TWC of a gasoline vehicle, and the catalysts can be ignited to play a role of catalytic purification. This determines that under certain conditions, additional injection is required to increase exhaust gas temperature when catalyst inlet temperature does not reach light-off temperature; on the other hand, it is also determined that the engine temperature has not yet risen at the time of engine cold start, and the exhaust gas temperature does not reach the light-off temperature of the catalyst at all times, and thus the catalytic purification effect cannot be achieved. The emissions in the cold start 600s can account for substantially around 80% of the total emissions.

The existing gasoline vehicle emission standard has a cold start working condition requirement of minus 30 ℃ to check whether an engine can still be started under an extremely cold condition. However, the emission at the cold start of minus 30 ℃ is not detected at present, and only the emission at minus 7 ℃ is detected. And along with the gradual tightening of the emission regulations, the temperature of the low-temperature cold start is gradually reduced, the emission detection value of the cold start is worse, and the emission proportion is higher in the cold start stage. The challenges of existing thermocatalytic based purification systems are more acute.

Similarly, thermal regeneration is also used for regeneration of diesel DPF and gasoline GPF used for trapping particulates, i.e. when the amount of particulates trapped by the particulate trap reaches a certain amount, the inlet temperature of DPF and GPF needs to be artificially raised, and even oil is injected into the inlet of DPF and GPF and ignited, so as to raise the inlet temperature of DPF and GPF to a temperature which is enough to ignite (or ignite) the collected particulates to burn off.

The urea hydrolysis process also requires the absorption of a certain amount of heat, and the corresponding energy source, ultimately, comes from the fuel oil.

Existing purification systems based on thermocatalysis, thermal regeneration and thermal decomposition inevitably increase energy consumption, the system needs certain temperature (generally 250 ℃ or higher) and heat for operation, and the system hardly works at low temperature (within 600s of engine start).

Disclosure of Invention

In view of the above-mentioned shortcomings of the prior art, the technical problem to be solved by the present invention is to provide an exhaust gas treatment system and method, which can continuously, stably, permanently and reliably solve NO simultaneously_xAnd PM emission problem, and can also purify hydrocarbon THC, carbon monoxide CO and other emission pollutants simultaneously, and the treatment effect is good when the engine is started at low temperature.

In order to achieve the above object, one aspect of the present invention provides an exhaust gas treatment system, which includes a plurality of sections of plasma catalytic modules, wherein the plasma catalytic modules include:

a plasmatizing unit for plasmatizing the stream to be treated to provide a stream subjected to the plasmatizing treatment;

and the catalytic reaction unit is used for carrying out catalytic reaction on the stream subjected to the plasma reaction treatment so as to provide the stream subjected to the catalytic reaction treatment.

The tail gas treatment system can be used for treating the following tail gases: the tail gas of various engines, various vehicles and non-road moving machinery using internal combustion engine as power and the tail gas discharged from exhaust pipe of ship and locomotive.

In some embodiments of the present invention, when the stream to be treated is a stream to be treated under a low-temperature cold start condition, operation parameters of some or all of the plasmatizing units in the plurality of sections of the plasmatizing catalytic modules are adjusted, and the plasmatizing units are first electric dust removal units and are used for removing particles in the stream to be treated.

In some embodiments of the present invention, the system further comprises a plurality of sections of ultraviolet light catalysis modules, which are used for performing ultraviolet light catalysis treatment on the stream to be treated before performing plasma and catalytic reaction; the several sections of ultraviolet photocatalysis modules comprise:

A plurality of sections of ultraviolet light sources, wherein the ultraviolet light sources are used for providing ultraviolet light for the photocatalytic reaction unit;

the system comprises a plurality of sections of photocatalytic reaction units, a plurality of sections of photocatalytic reaction units and a plurality of sections of photocatalytic reaction units, wherein the photocatalytic reaction units are used for carrying out photocatalytic reaction on a stream to be treated so as to provide the stream subjected to photocatalytic reaction treatment;

the ultraviolet light source and the photocatalytic reaction unit are alternately arranged.

In some embodiments of the invention, a second electric precipitation unit is further included for removing ash and/or particulates from the stream subjected to the number of plasmatic catalytic treatments.

In some embodiments of the present invention, the plasmatizing unit includes:

the cylinder body is internally composed of a plurality of honeycomb-shaped and hollow anode tube bundle groups;

the first negative plate is connected with the cylinder in an insulating mode, and the surface of the negative plate is provided with honeycomb-shaped holes which are the same as the openings of the anode tube bundle in shape;

the plurality of cathode wires are supported by the first cathode plate and penetrate through the anode tube bundles one by one;

wherein the anode tube bundle is insulated from the plurality of cathode wires using air.

In some embodiments of the present invention, the plasmatization unit further includes a second cathode plate, which is connected to the cylinder in an insulating manner, and a plate surface of the second cathode plate is provided with honeycomb-shaped holes, which have the same shape as the openings of the anode tube bundle; and the plurality of cathode lines penetrate through the anode tube bundles one by one and then penetrate through the catalyst in the catalytic reaction unit and are supported by the second cathode plate.

The invention also provides a tail gas treatment method, which is characterized in that a stream to be treated is subjected to a plurality of sections of plasma catalysis, wherein the plasma catalysis comprises the following steps:

plasmatizing the stream to be treated to provide a stream subjected to the plasmatizing treatment;

and performing a catalytic reaction on the stream subjected to the plasma treatment to provide a stream subjected to the catalytic reaction treatment.

In some embodiments of the present invention, the plurality of sections of plasma catalysis first perform a plurality of sections of catalytic reactions mainly including at least one or more of CO, THC, and nitrogen oxides in the oxidized exhaust gas, and then perform a plurality of sections of catalytic reactions mainly including reduction of nitrogen oxides in the reduced exhaust gas.

In some embodiments of the present invention, when the stream to be treated is a stream to be treated under a low-temperature cold start condition, operation parameters of partial or all of the plasma catalysis in several sections of plasma catalysis are adjusted, and the stream to be treated is subjected to electric precipitation to remove particles in the stream to be treated.

In some embodiments of the invention, at least one of the following technical features is also included:

1) before carrying out plasma catalysis on a plurality of sections, carrying out ultraviolet light catalysis treatment on a stream to be treated, wherein the ultraviolet light catalysis treatment comprises the following steps: carrying out photocatalytic reaction on the stream to be treated under ultraviolet irradiation to provide a stream subjected to photocatalytic reaction treatment;

2) The tail gas treatment method further comprises the following steps: and (3) performing electric precipitation on the streams subjected to the plasma catalytic treatment to remove ash and/or particles in the streams.

As mentioned above, the tail gas treatment system and the tail gas treatment method combine the plasma unit and the catalytic reaction unit, preferably further comprise the ultraviolet light catalytic module, so that the aim of continuously, stably, permanently and reliably solving NO simultaneously is achieved_xAnd PM emission problem, and can also purify particulate matter PM, nitrogen oxide NOx, hydrocarbon THC, and carbon monoxide CO etc. emission pollutant simultaneously, it is effectual to handle when cold start (within 600s of engine start).

Drawings

FIG. 1 is a schematic view of a plasmatizing unit according to the present invention.

FIG. 2 is a schematic diagram of a catalytic reaction unit according to the present invention.

Fig. 3 is a schematic diagram of a three-stage uv photocatalytic module according to the present invention.

Fig. 4 is a first schematic diagram of an exhaust gas treatment system according to the present invention.

Fig. 5 is a schematic diagram of a second exhaust gas treatment system according to the present invention.

FIG. 6 is a first schematic structural diagram of a plasmatizing unit according to the present invention.

FIG. 7 is a second schematic structural view of a plasmatizing unit according to the present invention.

Reference numerals:

1-plasma catalysis module; 11-a plasmatization unit; 111-a cylinder; 112-anode tube bundle; 113-a first cathode plate; 114-cathode lines; 115-a second cathode plate; 12-a catalytic reaction unit;

2-an ultraviolet light catalysis module; 21-a source of ultraviolet light; 22-a photocatalytic reaction unit;

3-expanding the tube.

Detailed Description

Through a large number of practical researches, the invention provides a tail gas treatment system and a treatment method, wherein the treatment system combines a plasma unit and a catalytic reaction unit, preferably further comprises an ultraviolet light catalytic module, and the purpose of continuously, stably, permanently and reliably solving NO simultaneously is achieved_xAnd PM emission problem, and can also purify hydrocarbon THC, carbon monoxide CO and other emission pollutants simultaneously, and the treatment effect is good when the engine is started at low temperature.

The invention provides a tail gas treatment system in a first aspect, which comprises a plurality of sections of plasma catalytic modules, wherein each plasma catalytic module comprises:

The plasmatizing unit is used for plasmatizing the stream to be treated so as to provide the stream subjected to the plasmatizing treatment, such as: the engine exhaust gas flowing through is partially or totally plasmatized to form high-energy plasmas, free radicals and the like formed among the high-energy plasmas, the free radicals and the like, and non-ionized molecules or compounds (containing reaction products) as shown in figure 1, wherein the inlet is PM, NOx, THC, CO, N, O2, H2O and the like, the outlet is C, O, H, N plasmas, the free radicals and the like formed among the high-energy plasmas, the free radicals and the like, and the non-ionized molecules or compounds (containing the reaction products) are shown in figure 1. The plasmatizing unit may be various apparatuses capable of achieving plasmatization in the art, and for example, may be a combination including, but not limited to, one or more of a glow discharge apparatus, a hollow cathode discharge apparatus, a pulse discharge apparatus, an arc discharge apparatus, a magnetron discharge apparatus, a capacitive coupling discharge apparatus, an inductive coupling discharge apparatus, a dielectric barrier discharge apparatus, a microwave discharge apparatus, a surface wave discharge apparatus, and a radio frequency discharge apparatus. The plasmatizing unit can comprise an anode and a cathode, is externally connected with a power supply, and adjusts voltage, waveform, frequency and output power to plasmatize the stream to be processed.

As shown in fig. 6 and 7, the plasmatizing unit 11 may include:

a cylinder 111, the interior of which is composed of a plurality of honeycomb-shaped and hollow anode tube bundles 112;

the first cathode plate 113 is connected with the cylinder 111 in an insulating manner, and the surface of the cathode plate 113 is provided with honeycomb-shaped holes which are the same as the openings of the anode tube bundle 112 in shape;

a plurality of cathode lines 114 supported by the first cathode plate 113 and penetrating the anode tube bundle 112 one by one; wherein the anode tube bundle 112 and the plurality of cathode wires 114 are insulated using air.

In addition, the plasma unit 11 further includes a second cathode plate 115 connected to the cylinder 111 in an insulating manner, and the surface of the second cathode plate 115 is provided with honeycomb-shaped holes, which are the same as the openings of the anode tube bundle 112 in shape; the plurality of cathode lines 114 penetrate the anode tube bundle 112, penetrate the catalyst in the catalytic reaction unit 12, and are supported by the second cathode plate 115.

The catalytic reaction unit is used for carrying out catalytic reaction on the stream subjected to the plasma treatment to provide the stream subjected to the catalytic reaction treatment, as shown in figure 2, for example, the inlet is carbon dioxide CO ₂，H₂O，N₂，O₂And the like, and the outlet is products such as C, O, H, N plasma, free radical and the like groups formed among the products, and un-ionized molecules or compounds (including reaction). The tail gas treatment system can comprise more than two plasma catalysis modules, for example, a first plasma catalysis module and a second plasma catalysis module, wherein the first plasma catalysis module comprises a first plasma unit and a first catalytic reaction unit, the second plasma catalysis module comprises a second plasma unit and a second catalytic reaction unit, and the stream to be treated is treated by the first plasma catalysis module and the second plasma catalysis module in sequence.

The primary purpose of the first catalytic reaction unit is: will be provided withThe CO and the THC in the stream are completely or mostly oxidized into water and CO₂The carbon particles in the exhaust gas are oxidized to CO₂Or CO, to N₂O, NO to higher nitrogen oxides N₂O₅And NO₃And the like.

The second catalytic reaction unit mainly aims at: adding NO_xReduction to N₂Removal of NO from the stream_x。

According to the emission conditions and the standard-reaching requirements of different engines, plasma catalytic modules can be added continuously, such as a third plasma catalytic module and the like, wherein the third plasma catalytic module comprises a third plasma unit and a third catalytic reaction unit, and the third catalytic reaction unit mainly aims at: continuing to remove NO from the stream _x。

When the stream to be treated is a stream to be treated under the working condition of low-temperature cold start, the plasma unit is a first electric dust removal unit and is used for removing particles in the stream to be treated by adjusting the operating parameters, such as voltage amplitude and/or output power, of part or all of the plasma units in the plurality of sections of the plasma catalysis modules 1. The low-temperature cold start refers to the start of the whole automobile or engine under the condition that the whole automobile or engine is kept still for more than 12 hours and the temperature of the whole automobile or engine body is completely the same as the ambient temperature. For example: the function of the first plasma unit can be converted into the first electric dust removal unit by adjusting the operating parameters of the first plasma unit, such as the amplitude and the output power of voltage, so that a large amount of cold-state PM and the like generated in the cold start process are adsorbed and collected, a large amount of untreated PM is prevented from being deposited on a catalyst bed layer and an inlet of a catalytic reaction unit behind the first plasma unit during cold start, and the problem that a hot catalyst does not work during low-temperature cold start can be solved. And when the exhaust temperature reaches the catalyst ignition temperature (150-180 ℃) of the catalytic reaction unit, adjusting the operating parameters of the first plasmatizing unit, such as the amplitude of voltage and the output power, to form the plasmatizing unit.

The tail gas treatment system provided by the invention also comprises a plurality of sections of ultraviolet light catalysis modules 2, which are used for carrying out ultraviolet light catalysis treatment on the streams to be treated before carrying out plasma and catalytic reaction; the several sections of ultraviolet photocatalytic modules 2 include:

a plurality of segments of ultraviolet light sources 21 for providing ultraviolet light to the photocatalytic reaction unit;

a plurality of sections of photocatalytic reaction units 22 for subjecting the stream to be treated to a photocatalytic reaction to provide a stream subjected to a photocatalytic reaction treatment;

the ultraviolet light sources 21 and the photocatalytic reaction units 22 are alternately arranged, as shown in fig. 3, 4 and 5.

The ultraviolet light catalysis module is used for catalyzing methane (CH) in tail gas₄Most stable and most oxidizable) THC and CO, thereby purifying the target gas and simultaneously purifying NO and N₂Oxidation of lower nitrogen oxides, e.g. O, to NO₂Or even N₂O₅、NO₃And nitrogen oxides with high valence states.

The exhaust gas treatment system may include more than two ultraviolet light catalysis modules, for example, a first ultraviolet light catalysis module, a second ultraviolet light catalysis module, and a third ultraviolet light catalysis module, as shown in fig. 3, the first ultraviolet light catalysis module includes a first ultraviolet light source and a first photocatalytic reaction unit, the second ultraviolet light catalysis module includes a second ultraviolet light source and a second photocatalytic reaction unit, the third ultraviolet light catalysis module includes a third ultraviolet light source and a third photocatalytic reaction unit, and the stream to be treated is successively treated by the first ultraviolet light catalysis module, the second ultraviolet light catalysis module, and the third ultraviolet light catalysis module.

The plasma catalysis module (including the plasma catalysis unit and the catalysis reaction unit) and the ultraviolet catalysis module (including the ultraviolet light source and the photocatalysis reaction unit) can be freely combined to realize different purification targets, as shown in fig. 4, the tail gas treatment system comprises a first ultraviolet catalysis module, a second ultraviolet catalysis module, a first plasma catalysis module and a second plasma catalysis module, and the first ultraviolet catalysis moduleThe catalysis module includes first ultraviolet source and first photocatalytic reaction unit, second ultraviolet catalysis module includes second ultraviolet source and second photocatalytic reaction unit, first plasma ization catalysis module includes first plasma ization unit and first catalytic reaction unit, second plasma ization catalysis module includes second plasma ization unit and second catalytic reaction unit. The first ultraviolet light catalysis module and the second ultraviolet light catalysis module are used for treating methane (CH) in tail gas₄Most stable and most oxidizable) THC and CO, thereby purifying the target gas and simultaneously purifying NO and N₂Oxidation of lower nitrogen oxides, e.g. O, to NO₂Or even N₂O₅、NO₃And nitrogen oxides with high valence states. The first catalytic reaction unit is a catalytic oxidation reaction unit which completely or mostly oxidizes CO and THC in the stream into water and CO ₂The carbon particles in the exhaust gas are oxidized to CO₂Or CO, to N₂O, NO to higher nitrogen oxides N₂O₅And NO₃And the like. The second catalytic reaction unit is a catalytic reduction reaction unit for removing NO in the stream_x。

The tail gas treatment system provided by the invention also comprises a second electric precipitation unit for removing ash and/or particulate matters in the streams subjected to the plasma catalytic treatment. The second electric precipitation unit can be a plasmatization unit, and the voltage amplitude and the output power of the plasmatization unit are adjusted, so that the function of the plasmatization unit is electric precipitation.

The second aspect of the present invention provides a tail gas treatment method, wherein a stream to be treated is subjected to several sections of plasma catalysis, and the plasma catalysis includes:

In the method for treating tail gas provided by the present invention, the tail gas may be tail gas of various engines, or tail gas discharged from exhaust pipes of various automobiles, non-road moving machines and ships, or locomotives, which are powered by internal combustion engines, the engine may be a machine capable of converting other forms of energy into mechanical energy, and may generally generate tail gas containing substances including, but not limited to, particulate matter, nitrogen oxides, organic volatile pollutants, carbon monoxide, etc., for example, chemical energy of fuel may be converted into mechanical energy, and specifically, the tail gas may include, but not limited to, diesel engines, gasoline engines, gas engines, mixed fuel engines, etc., or may include, but not limited to, compression ignition fuel engines, etc.

In the tail gas treatment method provided by the invention, the temperature of the stream to be treated can be 0-800 ℃, 0-10 ℃, 10-20 ℃, 20-30 ℃, 30-50 ℃, 50-100 ℃, 100-200 ℃, 200-300 ℃, 300-500 ℃ or 500-800 ℃.

In the method for treating exhaust gas provided by the present invention, the pollutant in the stream to be treated may be one or a combination of more than one of Particulate Matters (PM), nitrogen oxides (NOx), organic volatile pollutants (VOCs), carbon monoxide (CO), fuel oil (for example, oil leakage generated by an engine), and the like, and for example, the particulate matters may specifically be organic particulate matters and inorganic particulate matters including, but not limited to, PM2.5, PM0.1 to PM60, PM0.1 to PM0.5, PM0.5 to PM1, PM1 to PM1.5, PM1.5 to PM2.5, PM2.5 to PM5, PM5 to PM10, PM10 to PM20, PM20 to PM40, PM40 to PM60, and the like, and for example, the content of the particulate matters in the stream to be treated may be 0.05 to 20000mg/m³、0.05～0.1mg/m³、 0.1～0.5mg/m³、0.5～1mg/m³、1～5mg/m³、5～10mg/m³、10～20mg/m³、20～30mg/m³、30～50mg/m³、50～100mg/m³、100～200mg/m³、200～300mg/m³、300～500mg/m³、500～1000mg/m³、 1000～2000mg/m³、2000～3000mg/m³、3000～5000mg/m³、5000～10000mg/m³、10000～15000mg/m³Or 15000 to 20000mg/m³E.g. in the stream to be treatedThe content of the oxynitride can be 2-4000 mg/m³、 2～5mg/m³、5～10mg/m³、10～20mg/m³、20～30mg/m³、30～50mg/m³、50～100mg/m³、100～200mg/m³、 200～300mg/m³、300～500mg/m³、500～1000mg/m³、1000～2000mg/m³、2000～3000mg/m³Or 3000-4000 mg/m³For another example, the content of the organic volatile contaminants in the stream to be treated can be 0.8-1000 mg/m ³、0.8～1mg/m³、1～3mg/m³、3～5mg/m³、5～10mg/m³、10～20mg/m³、20～30mg/m³、30～50mg/m³、 50～100mg/m³、100～200mg/m³、200～300mg/m³、300～500mg/m³Or 500 to 1000mg/m³For another example, the carbon monoxide content of the stream to be treated can be 2-1000 mg/m³、2～3mg/m³、3～5mg/m³、5～10mg/m³、 10～20mg/m³、20～30mg/m³、30～50mg/m³、50～100mg/m³、100～200mg/m³、200～300mg/m³、 300～500mg/m³Or 500 to 1000mg/m³. After plasma catalytic treatment, the removal rate of Particulate Matters (PM) and organic volatile pollutants (VOCs) can reach more than 99%, the removal rate of nitrogen oxides (NOx) can reach more than 85%, and the removal rate of other pollutants can reach more than 95%.

In the tail gas treatment method provided by the invention, the stream to be treated is plasmatized to provide the stream subjected to the plasmatization treatment, namely most or all substances in the stream to be treated are ionized to become high-energy active atoms, ions or free radicals, and the reaction mechanism is as follows:

(1) electric field + electrons → energetic electrons

(3) Active group + oxygen → product + heat

(4) Active group + active group → product + heat

During low-temperature cold start, the streams to be treated can be subjected to electric precipitation by adjusting the operating parameters of plasmatization, such as voltage amplitude and/or output power, so that a large amount of cold-state PM and the like generated in the cold start process are adsorbed and collected, a large amount of untreated PM is prevented from being deposited on a catalyst bed layer and an inlet during the cold start, and the problem that a hot catalyst does not work during the low-temperature cold start can be solved. When the exhaust temperature reaches the catalyst ignition temperature (150-180 ℃), regulating the operating parameters of plasmatizing, such as voltage amplitude and output power, to carry out plasmatizing.

In the tail gas treatment method provided by the invention, the stream subjected to plasma treatment is subjected to catalytic reaction to provide the stream subjected to catalytic reaction treatment, namely, a catalyst is utilized on the surface of the catalyst to promote high-energy active ions or free radicals formed by various ionized gases and corresponding atoms or ionic groups to perform complex catalytic purification reaction, further various molecules or chemical combination references which are not in ionization or free radical formation are initiated to perform pre-catalytic reaction, and finally the target pollutant is removed. The stream subjected to the plasmatization treatment is a mixture of molecules, ions, atoms and radicals of each substance, and then catalytic reaction is carried out, complex catalytic reaction occurs on the catalyst bed, and gas phase reaction also possibly occurs above the surface of the catalyst bed. To improve the catalytic purification efficiency, the catalyst formulation may be adjusted to improve the purification efficiency according to the composition and characteristics of the inlet gas.

The elements in ionic, radical or atomic state have high activity and may react completely in the chemical thermodynamic direction to form the final species under the action of the catalyst. Even at lower temperatures, the reaction may be thermodynamically oriented. It is also possible for groups, clusters, or molecules bound to these ions, radicals, or atoms to react in full or in part in the chemical thermodynamic direction. After the reaction between the ionized elements and the related molecular groups and clusters begins, neutral molecules, molecular groups, molecular clusters and other species which are not ionized are likely to be induced and excited to perform catalytic reaction on the surface of the catalyst according to the chemical kinetic direction.

The catalyst generally comprises a catalyst substrate (substrate), catalyst active components (activities) and a catalyst coating (coating), and can selectively enhance the selectivity of a certain reaction species or a certain product species, so as to achieve the complete catalytic purification effect of the exhaust gas. The catalyst substrate may be one or more of a ceramic honeycomb support, a metal honeycomb support, ceramic balls, ceramic foam, metal foam, wire mesh, wire balls, and the like, including but not limited to. The catalyst active component may be a noble metal including, but not limited to, platinum Pt, palladium Pd, rhodium Rh, and the like, and compounds thereof in various forms, and combinations thereof; transition metals such as copper Cu, iron Fe, zinc Zn, and the like, compounds in different forms thereof, and combinations of different forms thereof; various different types of perovskite structure compounds and combinations of different forms thereof; a vanadium-based catalyst; and different combinations between the different types of active ingredients mentioned above. The catalyst coating may be a compound including but not limited to aluminum, cerium, zirconium, and the like, oxides or other forms thereof, and combinations thereof in different amounts and in different forms. For example: oxidation of CO, THC to Water and CO ₂The carbon particles in the exhaust gas are oxidized to CO₂Or CO, to N₂O, NO to higher nitrogen oxides N₂O₅And NO₃The catalyst can be Pt/Pd or single Pd active component, alumina coating or alumina and cerium zirconium composite alumina coating catalyst. Removal of NO from exhaust gases_xThe catalyst can be Pt/Pd or single Pt/Rh active component, alumina coating or alumina and cerium zirconium composite alumina coating catalyst. The catalyst can be used as a section of the plasmatizing unit or directly coated on a part of the pipe wall of the plasmatizing unit (and can also play a role of medium discharge at the same time).

In the tail gas treatment method provided by the invention, the stream to be treated can be subjected to multi-section plasma catalysis, for example: and carrying out first-stage plasma catalysis and second-stage plasma catalysis.

The first stage catalytic reaction mainly adopts selective oxidation to completely or mostly oxidize CO and THC in the exhaust gas into water and CO₂The carbon particles in the exhaust gas are oxidized to CO₂Or CO, to N₂O, NO to higher nitrogen oxides N₂O₅And NO₃And the like.

And (3) carrying out second-stage plasmatization (ionization and plasma reaction) on the stream obtained by the first-stage catalytic reaction, and removing a part of waste gas. The second stage catalytic reaction is mainly selective reduction with the aim of removing NO from the exhaust gas _xAll are removed.

According to the emission conditions and the standard reaching requirements of different engines, the third stage of plasma reaction and the third stage of catalytic reaction can be continuously added.

The complex reactions that occur with plasmatation catalysis can be simply as follows (the element symbols represent the energetic ions, radicals or atoms after activation, the equation is not balanced):

nO→O₃

C(soot)+nO→CO/CO₂

THC+nO/₃→CO/CO₂+H₂O

_xNO+O₃→NO₂/N₂O₅/NO₃

NO₂/N₂O₅/NO₃+CO/CO₂/THC→N₂+H₂O+CO₂

CO+O₂/O₃/ _xNO→CO₂N₂

in the tail gas treatment method provided by the invention, before carrying out a plurality of sections of plasma catalysis, a stream to be treated is subjected to a plurality of sections of ultraviolet light catalysis treatments, wherein the ultraviolet light catalysis treatments comprise the following steps: subjecting the stream to be treated to a photocatalytic reaction under ultraviolet irradiation to provide a stream subjected to the photocatalytic reaction, and enhancing methane (CH) by adjusting light energy, light wavelength and active components of the photocatalyst₄Most stable and oxidizable) and the like, and thereby CO, and the like, to thereby obtainThe purification of the target gas is achieved, and NO and N are simultaneously removed₂Oxidation of lower nitrogen oxides, e.g. O, to NO₂Or even N₂O₅、NO₃And nitrogen oxides with high valence states. The photocatalyst comprises a photocatalyst substrate, a photocatalyst active component and a photocatalyst coating, wherein the photocatalyst substrate can be one or more of honeycomb ceramic carrier, honeycomb metal carrier, ceramic ball, ceramic foam, metal wire mesh, metal wire ball and the like, and the photocatalyst active component can be TiO, but is not limited to ₂。

The ultraviolet light catalysis treatment has the greatest advantages of being realized at normal temperature and solving the defect that the hot catalyst cannot work when being started at low temperature, so that the problems that a catalyst pore channel or a catalytic interface is blocked and the like caused by repeated low-temperature starting in the using process of the catalyst are solved.

The stream to be treated is subjected to a photocatalytic reaction under ultraviolet irradiation, which is complex and mainly comprises the following possible reaction processes (equation of reaction is not balanced):

after the ultraviolet light catalysis treatment, the removal efficiency of Particulate Matters (PM) can reach more than 60 percent, wherein the purification efficiency of organic components such as SOF soluble organic matters and the like in the particulate matters can reach more than 85 percent; the purification efficiency of the catalyst on organic volatile pollutants (VOCs) and CO can reach more than 70 percent, and the catalyst can be used for purifying Nitrogen Oxides (NO)_x) The oxidation efficiency of the catalyst can reach more than 85 percent.

The tail gas treatment method provided by the invention further comprises the following steps: and (3) performing electric precipitation on the streams subjected to the plasma catalytic treatment to remove ash and/or particles in the streams. For metal salts and the like (Ash) which do not participate in the reaction, electric precipitation may be performed at the end to remove Ash, as well as unreacted soot.

Example 1

An exhaust gas treatment system, as shown in fig. 5, comprising:

the three-section ultraviolet light catalysis module 2 is used for carrying out ultraviolet light catalysis treatment on the stream to be treated before carrying out plasma and catalysis reaction; the three-section ultraviolet light catalysis module 2 comprises:

two segments of ultraviolet light sources 21 for providing ultraviolet light to the photocatalytic reaction unit;

three sections of photocatalytic reaction units 22 for subjecting the stream to be treated to a photocatalytic reaction to provide a stream subjected to a photocatalytic reaction treatment;

the photocatalytic reaction units 22 and the ultraviolet light sources 21 are alternately arranged, as shown in fig. 5, one section of ultraviolet light source 21 is arranged between each two sections of photocatalytic reaction units 22;

three sections of plasmatizing catalytic modules 1, wherein each section of plasmatizing catalytic module 1 comprises a plasmatizing unit 11 and a catalytic reaction unit 12, the plasmatizing unit 11 is used for plasmatizing a stream to be treated, to provide a stream subjected to a plasmatizing treatment, the catalytic reaction unit 12 for catalytically reacting the stream subjected to the plasmatizing treatment, to provide a stream subjected to catalytic reaction, the three sections of plasmatized catalytic modules are a first plasmatized catalytic module, a second plasmatized catalytic module and a third plasmatized catalytic module, the first plasma catalytic module comprises a first plasma unit and a first catalytic reaction unit, the second plasmatizing catalysis module comprises a second plasmatizing unit and a second catalysis reaction unit, the third plasmatization catalysis module comprises a third plasmatization unit and a third catalytic reaction unit. And when the stream to be treated is the stream to be treated under the working condition of low-temperature cold start, adjusting the operating parameters of a first plasmatizing unit, wherein the first plasmatizing unit is a first electric dust removal unit and is used for removing particles in the stream to be treated.

Each section of ultraviolet light source in the three sections of ultraviolet light catalysis modules is the same as each section of photocatalytic reaction unit, and the method comprises the following steps:

ultraviolet light source 21: a quartz ultraviolet tube (5 vertical rows) with the inner diameter of 30mm, the wall thickness of 4mm and the length of 90mm is used as an ultraviolet irradiation light source. The square flange is fixed by an outer square cylinder (with a square flange) with an air cooling jacket, and the side length of the square flange is 200 mm.

The photocatalytic reaction unit 22 is characterized in that a carrier adopts cordierite honeycomb ceramic with the side length of 180mm, the thickness of 30mm, the pore density of 200 and the pore wall thickness of 0.2 mm; gamma-alumina is adopted as a coating, the loading thickness of the coating is 0.2mm, and the weight of the coating is increased by 20 percent relative to the carrier; the active component is TiO₂In an amount of 2g TiO per liter of catalyst support₂. The catalyst was packed with 8mm vermiculite mat and 2mm thick 304 steel.

The three sections of ultraviolet light catalysis modules are connected into a whole by flanges, and the two ends of the ultraviolet light catalysis modules are connected with square-to-round expansion pipes. The length of the expanding end of the expanding pipe is 200mm, the diameter of the circular pipe at the contraction end is 89mm, the length of the expanding pipe is 300mm, and the expanding pipe is made of 304 steel with the wall thickness of 1.2 mm. The ultraviolet lamp is externally connected with 220V alternating current. A 400-mesh 304 wire mesh is placed at the outlet of the inlet expansion pipe and 10mm away from the outlet. The ultraviolet light wavelength is 185 nm.

Each section of plasmatization unit in the three sections of plasmatization catalysis modules is the same, and the three sections of catalysis reaction units are different, and the three sections of the catalysis reaction units are as follows:

Plasmatizing unit 11: the method comprises the following steps:

a plurality of cathode lines 114 supported by the first cathode plate 113 and penetrating the anode tube bundle 112 one by one;

wherein the anode tube bundle 112 is insulated from the plurality of cathode wires 114 using air;

the second cathode plate 115 is connected with the cylinder 111 in an insulating manner, and the surface of the second cathode plate 115 is provided with honeycomb-shaped holes which are the same as the openings of the anode tube bundle 112 in shape; the plurality of cathode lines 114 penetrate the anode tube bundle 112, penetrate the catalyst in the catalytic reaction unit 12, and are supported by the second cathode plate 115.

The external dimension is phi 350 (flange plate) 200mm, 304 hexagonal tubes with the external tangent circle diameter of 56mm and the wall thickness of 1.2mm are arranged in the external tangent circle as anodes, and titanium alloy wires with the diameter of 1.5mm are adopted as cathode wires. The external connection maximum voltage is 25kV, the maximum output power is 500W.

A first catalytic reaction unit: the carrier size phi 320 x 350mm, the pore density 400 meshes, the pore wall thickness 0.15mm, and cordierite materials are packaged by 8mm vermiculite cushion layers and 0.15mm thick 304 steel; the coating adopts gamma-alumina Al₂O₃And cerium zirconium oxide eutectic CZ, Al₂O₃The mass ratio of the CZ to the CZ is 8: 2, Ce in CZ₂O₃And ZrO₂In a molar ratio of 7: 3, the thickness of the coating is 0.2mm, and the relative weight of the carrier is increased by 20 percent; the active component is single palladium Pd, and the loading amount is 5 g/L of the carrier. Oxidizing CO and THC in the stream into water and CO completely or mostly₂The carbon particles in the exhaust gas are oxidized to CO₂Or CO, to N₂O, NO to higher nitrogen oxides N₂O₅And NO₃And the like.

A second catalytic reaction unit: the carrier size phi 320 x 350mm, the pore density 400 meshes, the pore wall thickness 0.15mm, and cordierite materials are packaged by 8mm vermiculite cushion layers and 0.15mm thick 304 steel; the coating adopts gamma-alumina Al₂O₃And cerium zirconium oxide eutectic CZ, Al₂O₃The mass ratio of the CZ to the CZ is 8: 2, Ce in CZ₂O₃And ZrO₂The mass ratio of (2) is 7: 3, the thickness of the coating is 0.2mm, and the relative weight of the carrier is increased by 20 percent; the platinum, palladium and rhodium are used as active components, wherein the molar ratio of Pt to Pd to Rh is 2: 7: 1, and the loading amount is 3.5 g/L of carrier. Adding NO_xReduction to N ₂Removal of NO from the stream_x。

A third catalytic reaction unit: the carrier size phi 320 x 350mm, the pore density 400 meshes, the pore wall thickness 0.15mm, and cordierite materials are packaged by 8mm vermiculite cushion layers and 0.15mm thick 304 steel; the coating and the active component are combined into a whole and comprise Al₂O₃CZ and ABO₃In which Al is₂O₃:CZ:ABO₃The mass ratio of (perovskite active component, high temperature type) is 4: 2: 4, Ce in CZ₂O₃And ZrO₂In a molar ratio of 7: and 3, the thickness of the coating is 0.2mm, and the relative weight of the carrier is increased by 20 percent. Adding NO_xReduction to N₂Removal of NO from the stream_x。

The first plasma catalysis module and the second plasma catalysis module are separated by 50mm and are connected by a cavity (metal cylinder) with equal diameter so as to be convenient for placing a cathode plate, in order to ensure that the plasma catalysis unit is tightly connected with the catalytic reaction unit, a cathode wire passes through a pore channel of the catalytic reaction unit and is connected with the cathode plate at the position of about 10mm of the outlet end of the catalytic reaction unit, and the cathode plate of the first plasma catalysis module is separated from the cathode plate of the second plasma catalysis module by about 30 mm; the second plasma catalysis module and the third plasma catalysis module are separated by about 15 mm. The first plasma catalysis module adopts an independent direct-current power supply, the maximum voltage is 25kV, and the maximum output power is about 500 w; the second plasma catalysis module and the third plasma catalysis module share a power supply, the maximum voltage is 25kV, and the maximum output power is 800W.

And after the three sections of plasma catalytic modules are packaged into a whole, two ends of the plasma catalytic modules are respectively connected with an expansion pipe 3 with phi 320-phi 89, and the length of the expansion pipe is 350 mm. The material is 304 steel with the thickness of 1.2 mm.

And (3) carrying out tail gas treatment on the streams to be treated by the tail gas treatment system:

and (3) low-temperature cold start:

and (3) subjecting the fluid to be treated to three-section ultraviolet catalysis treatment by the three-section ultraviolet catalysis module, wherein the three-section ultraviolet catalysis treatment comprises the following steps: carrying out photocatalytic reaction on the stream to be treated under ultraviolet irradiation to provide a stream subjected to photocatalytic reaction treatment;

and then adjusting the operating parameters of the first plasmatizing unit, wherein the first plasmatizing unit is a first electric dust removal unit, removing particulate matters, and then sequentially entering a first catalytic reaction unit, a second plasmatizing unit, a second catalytic reaction unit, a third plasmatizing unit and a third catalytic reaction unit to perform first catalysis, second plasmatizing, second catalysis, third plasmatizing and third catalysis.

Non-low temperature cold start:

Then three stages of plasma catalysis are carried out, namely, the three stages of plasma catalysis sequentially enter a first plasma reaction unit, a first catalytic reaction unit, a second plasma reaction unit, a second catalytic reaction unit, a third plasma reaction unit and a third catalytic reaction unit to carry out first plasma, first catalysis, second plasma, second catalysis, third plasma and third catalysis.

The effect after the treatment by the treatment system and the treatment method is as follows:

and (3) low-temperature cold start:

non-low temperature cold start:

	before treatment	After treatment	Efficiency of removal
				PM(mg/m³)	2500	2	99％
NO_x(mg/m³)	1500	20	98％
				THC(mg/m³)	1800	15	99％
CO(mg/m³)	2200	20	99％

The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.

Claims

1. An exhaust gas treatment system, comprising a plurality of sections of plasma ionization catalytic modules (1), the plasma ionization catalytic modules (1) comprising:

A plasmatizing unit (11) for plasmatizing the stream to be treated to provide a stream subjected to the plasmatizing treatment;

and the catalytic reaction unit (12) is used for carrying out catalytic reaction on the stream subjected to the plasma reaction treatment so as to provide the stream subjected to the catalytic reaction treatment.

2. The tail gas treatment system according to claim 1, wherein when the stream to be treated is a stream to be treated under a low-temperature cold start condition, the operation parameters of part or all of the plasmatizing units in the plurality of sections of the plasmatizing catalytic modules (1) are adjusted, and the plasmatizing units are first electric dust removing units and are used for removing particles in the stream to be treated.

3. The exhaust gas treatment system according to claim 1 or 2, further comprising a plurality of sections of ultraviolet photocatalysis modules (2) for performing ultraviolet photocatalysis treatment on the stream to be treated before performing plasma and catalytic reaction; the plurality of sections of ultraviolet photocatalytic modules (2) comprise:

a plurality of segments of ultraviolet light sources (21) for providing ultraviolet light to the photocatalytic reaction unit;

a plurality of sections of photocatalytic reaction units (22) for subjecting the stream to be treated to a photocatalytic reaction to provide a stream subjected to a photocatalytic reaction treatment;

The ultraviolet light sources (21) and the photocatalytic reaction units (22) are alternately arranged.

4. The tail gas treatment system of claim 1 or 2, further comprising a second electric precipitation unit for removing ash and/or particulates from the stream subjected to the plurality of plasma catalytic treatments.

5. The exhaust gas treatment system according to claim 1 or 2, wherein the plasmatization unit (11) comprises:

the device comprises a cylinder body (111), a plurality of anode tube bundles (112) and a plurality of anode tubes, wherein the cylinder body is internally composed of a plurality of honeycomb-shaped hollow anode tube bundles (112);

the first cathode plate (113) is connected with the cylinder (111) in an insulating mode, and the surface of the cathode plate (113) is provided with honeycomb-shaped holes which are the same as the openings of the anode tube bundle (112) in shape;

a plurality of cathode wires (114) supported by the first cathode plate (113) and penetrating the anode tube bundle (112) one by one;

wherein the anode tube bundle (112) is insulated from the plurality of cathode wires (114) using air.

6. The exhaust gas treatment system according to claim 5, wherein the plasmatization unit (11) further comprises a second cathode plate (115) connected to the cylinder (111) in an insulating manner, and the second cathode plate (115) has a honeycomb-shaped hole on the plate surface, and the hole has the same shape as the opening of the anode tube bundle (112); the plurality of cathode lines (114) penetrate through the anode tube bundle (112) one by one, penetrate through the catalyst in the catalytic reaction unit (12), and are supported by the second cathode plate (115).

7. The tail gas treatment method is characterized in that a stream to be treated is subjected to a plurality of sections of plasma catalysis, and the plasma catalysis comprises the following steps:

8. The method according to claim 7, wherein the plurality of stages of plasma catalysis are performed by a plurality of stages of catalytic reactions mainly comprising oxidation of at least one or more of CO, THC and nitrogen oxides in the exhaust gas, and then a plurality of stages of catalytic reactions mainly comprising reduction of nitrogen oxides in the exhaust gas.

9. The tail gas treatment method of claim 7, wherein when the stream to be treated is a stream to be treated under a low-temperature cold start working condition, the operation parameters of partial or all plasmatization in the plurality of sections of plasmatization catalysis are adjusted, and the stream to be treated is subjected to electric precipitation to remove particles in the stream to be treated.

10. The exhaust gas treatment method according to any one of claims 7 to 9, further comprising at least one of the following technical features: