CN113350985A

CN113350985A - Plasma-based denitration device and method

Info

Publication number: CN113350985A
Application number: CN202110626052.XA
Authority: CN
Inventors: 孙宝昌; 初广文; 邹海魁; 张亮亮; 罗勇
Original assignee: Beijing University of Chemical Technology
Current assignee: Beijing University of Chemical Technology
Priority date: 2021-06-04
Filing date: 2021-06-04
Publication date: 2021-09-07

Abstract

The invention provides a plasma-based denitration device and a method, wherein a dielectric barrier discharge method is used for forming plasma, the combination of discharge homogenization and high energy efficiency is realized through electrode structure design and dielectric barrier material screening, the initial voltage and the operating voltage are both lower, and the industrial production is safer. The denitration efficiency is high and can reach 90% or more under certain operating conditions; NOx is reduced to N2 under the action of an electric field, the traditional technology of NO conversion depending on an oxidation way is broken through, the NOx conversion is directly carried out through a reduction way, secondary treatment is not needed, the process is simplified, and the material investment is saved; the whole processing technology has simple route, only needs electric energy supply, and has low energy consumption, good economical efficiency and simple operation compared with other coaxial designs; the device has small occupied area and is suitable for industrial waste gas treatment of small and medium-sized equipment, particularly specific working conditions such as nitrification and the like; the application effect of plasma denitration is improved.

Description

Plasma-based denitration device and method

Technical Field

The invention relates to the technical field of gas absorption, in particular to a plasma-based denitration device and a plasma-based denitration method.

Background

In many industrial processes such as coal-electricity and metal smelting, a large amount of industrial waste gas is generated, and nitrogen oxides as important components pollute the atmosphere and cause environmental problems such as acid rain, so that waste gas denitration is always a hot point direction concerned in the field of environmental pollution control. In recent years, the important field of nitrogen oxide treatment has gradually transited from the electric industry to the non-electric industry, such as the steel industry and the chemical industry. Before 2020, 30% of tasks need to be finished in electric power atmosphere control, about 259 billion of capacity can be produced, 60% of tasks need to be finished in non-electric atmosphere control, about 1000 billion of capacity can be produced, and the policy of the non-electric industry tends to be strict and the process is faster. In conclusion, the denitration industry still has larger market space, and the popularization and the application of the technology have great potential.

At present, the main methods for denitration of industrial waste gas are divided into a dry method and a wet method. The dry processes are mainly Selective Catalytic Reduction (SCR) and non-selective catalytic reduction (SNCR), which use a reducing agent and high temperature conditions to convert NO in the presence or absence of a catalyst₂Reduction to N₂And H₂O, the reaction temperature needs 400-. Other methods, including porous material adsorption denitration, electrochemical catalytic purification denitration, microbial denitration, microwave denitration and the like, respectively have the defects of low efficiency, high cost, difficulty in industrial application and the like. The wet method is mainly to utilize various absorbents to absorb and treat the waste gas containing nitrogen oxides, and the main components of the nitrogen oxides are NO and NO₂. Wherein NO has poor water solubility, resulting in wet denitration efficiency of generally 40-60%, and NO is converted into NO by pretreatment₂And the nitrate and nitrite solution generated while additional resources are consumed is difficult to recycle, so that a new problem of subsequent treatment is introduced. Other methods include a liquid membrane filtration method and the like, and have a disadvantage of low treatment efficiency. At present, in order to improve the removal efficiency of nitrogen oxides, the methods are commonly combined, and NO is converted into NO by ozone and other advanced oxidation means₂Then proceed the next stepThe treatment is carried out in a step mode, but the energy consumption is high, and the problems of oxidant pollution and the like exist. Through the comparison of the background art of industrial flue gas denitration, the main three troubles exist in the current mainstream flue gas treatment modes: the method has mature technology and lower economic cost, and the flue gas treatment effect can not meet the latest standard requirement of ultralow emission; the method has mature technology and can meet the ultra-low emission standard, the cost is generally higher, and the method does not have the economy of large-scale popularization; methods that meet ultra-low emission standards while being economical at low cost generally do not have sufficient market maturity. The research of applying the plasma technology to the field of denitration mainly depends on an oxidation path at present, the effect is not good, the removal rate is only 40% -60%, and the traditional NTP technology is used in high-O₂Under conditions, it is difficult to reduce NO to N₂Secondary treatment is required.

Disclosure of Invention

The invention aims to provide a plasma-based denitration device and a plasma-based denitration method, so as to solve at least one of the problems in the prior art.

In order to achieve the purpose, the invention adopts the following technical scheme:

the invention provides a plasma-based denitration device, which comprises:

a housing;

the columnar electrode is positioned in the center of the shell;

the first insulating medium is arranged around the outer side of the columnar electrode;

the second insulating medium is coaxially arranged with the first insulating medium and is positioned outside the first insulating medium, and an isolation cavity is formed between the first insulating medium and the second insulating medium; and

and the grounding electrode is arranged around the outer side surface of the second insulating medium and is matched with the columnar electrode to generate plasma in the isolation cavity after being electrified.

In a preferred embodiment, further comprising:

and the power supply equipment is coupled with the columnar electrode and used for providing an excitation voltage.

In a preferred embodiment, further comprising: and the rotating motor is fixedly connected with one end of the first insulating medium.

In a preferred embodiment, further comprising:

and the voltage regulator is used for regulating the excitation voltage of the power supply equipment.

In a preferred embodiment, the first insulating medium or the second insulating medium comprises quartz.

In a preferred embodiment, further comprising:

and a cooling circulation pipeline which contains cooling liquid in a circulating flow, wherein one part of the cooling circulation pipeline is arranged inside the shell, and the other part of the cooling circulation pipeline is arranged in a low-temperature field.

In a preferred embodiment, a plurality of spoilers are arranged on the outer side wall of the first insulating medium; or a plurality of turbulence members are arranged on the inner side wall of the second insulating medium.

In a preferred embodiment, the spoiler comprises a protrusion or a deflector.

The present invention further provides a method for denitration using the denitration apparatus as described above, comprising:

inputting industrial flue gas to the denitration device;

and electrifying the columnar electrode of the pin removal device to form a plasma field in the isolation cavity so as to obtain purified gas for removing the nitrogen oxide.

In a preferred embodiment, further comprising:

and pumping the cooling liquid into the denitration device through a cooling circulation pipeline.

The invention has the advantages of

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.

Fig. 1 shows a schematic structural view of a plasma-based pinning device in an embodiment of the present invention.

FIG. 2 shows a reaction mechanism diagram of nitrogen oxide treatment performed in the example of the present invention.

Reference numbers in figure 1: 1-high voltage electrode, 2-insulating medium, 3-discharge gap (NTP reaction zone), 4-insulating medium, 5-grounding electrode, 6-rotating shaft, 7-rotating power device, 8-exhaust port, 9-air inlet, 10-coaxial rotating jiezhi barrier device reaction component, 11-excitation power supply, 12-grounding electrode interface, 13-high voltage electrode interface, 14-voltage regulator and 15-coaxial rotating medium barrier device power supply component.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.

The following disclosure provides many different embodiments, or examples, for implementing different features of the invention. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to limit the invention. For example, in the description that follows, forming a first feature over or on a second feature may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact; also, in the following description, the "coupling" of the first and second components may include an embodiment in which the first and second components are formed in direct contact, and may also include an embodiment in which an additional component may be formed between the first and second components so that the first and second components may not be in direct contact.

Moreover, for convenience of description, descriptions related to "first", "second", etc. in the present invention are provided for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicit to the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In addition, technical solutions between the various embodiments can be combined with each other, but must be realized by a person skilled in the art, and when the technical solutions are contradictory or cannot be realized, the combination of the technical solutions should be considered to be absent and not be within the protection scope of the present invention.

In order to facilitate understanding of the technical solutions provided in the present application, the following briefly describes the research background of the technical solutions in the present application.

By the end of 2019, the installed capacity of thermal power in China reaches 11.9 hundred million kilowatts, meanwhile, the ultra-low emission transformation process in China is gradually changed from the thermal power industry to the non-electric industry, the current main transformation industry is the steel industry, and the restricted industry race track is widened along with the further tightening of the ultra-low emission policy in the future. It is expected that various traditional non-electric industries (steel, coking, cement, electrolytic aluminum, glass, ceramic, carbon and the like) and various high-pollution-emission industrial industries (printing, waste incineration and the like) are brought into the control range of the ultra-low emission standard, so that a suitable process for gravity center transfer in the denitration industry is urgently needed to be invented. Aiming at the defects of low removal efficiency, large energy consumption, difficult treatment of byproducts and the like of the conventional denitration method, the mature technology is more suitable for treating large-scale equipment such as thermal power plants, steel refining and the like. The process scheme has the advantages of better economy, easy construction of the device, high removal efficiency and no secondary pollution aiming at the industrial flue gas denitration treatment of small and medium-sized devices.

The invention innovatively provides a coaxial rotating dielectric barrier discharge device and a coaxial rotating dielectric barrier discharge method based on plasma reduction denitration, and solves the key technical problems that nitrogen oxides can be converted into green harmless substances after being treated in a plasma state in the device, secondary treatment is not needed, and secondary pollution is avoided; the method is more suitable for the matched treatment of industrial waste gas of devices such as medium and small boilers and the like; the operation process is simplified, and the industrial application value is high; on the basis of ensuring higher nitrogen oxide removal rate (the denitration efficiency reaches more than 90% under certain conditions), the device realizes the homogenization of discharge, improves the energy efficiency of the treatment process and improves the economic benefit.

Referring to fig. 1, an embodiment of the present invention provides a plasma-based pinning device, as shown in fig. 1, including: a housing 10; a columnar electrode 1 located at the center of the housing 10; the first insulating medium 2 is arranged around the outer side of the columnar electrode 1; a second insulating medium 4, which is arranged coaxially with the first insulating medium 2 and is located outside the first insulating medium 2, wherein an isolation cavity 3 is formed between the first insulating medium 2 and the second insulating medium 4; and the grounding electrode 5 is arranged around the outer side surface of the second insulating medium 4 and is matched with the columnar electrode 1 to generate plasma in the isolation cavity 3 after being electrified.

The invention forms plasma by using a dielectric barrier discharge method, realizes the combination of discharge homogenization and high energy efficiency by electrode structure design and dielectric barrier material screening, and has lower initial voltage and operating voltage and safer industrial production. The denitration efficiency is high and can reach 90% or more under certain operating conditions; NOx is reduced to N2 under the action of an electric field, the traditional technology of NO conversion depending on an oxidation way is broken through, the NOx conversion is directly carried out through a reduction way, secondary treatment is not needed, the process is simplified, and the material investment is saved; the whole processing technology has simple route, only needs electric energy supply, and has low energy consumption, good economical efficiency and simple operation compared with other coaxial designs; the device has small occupied area and is suitable for industrial waste gas treatment of small and medium-sized equipment, particularly specific working conditions such as nitrification and the like; the application effect of plasma denitration is improved.

In a preferred embodiment, further comprising: and the power supply equipment is coupled with the columnar electrode and used for providing an excitation voltage.

In a preferred embodiment, further comprising: and the voltage regulator is used for regulating the excitation voltage of the power supply equipment.

In a preferred embodiment, further comprising: and a cooling circulation pipeline which contains cooling liquid in a circulating flow, wherein one part of the cooling circulation pipeline is arranged inside the shell, and the other part of the cooling circulation pipeline is arranged in a low-temperature field.

In a preferred embodiment, the spoiler comprises a protrusion or a deflector.

The invention relates to a coaxial rotating dielectric barrier discharge device and a method based on plasma reduction denitration, which are characterized in that an electric field is utilized to excite a plasma state, and a large amount of active particles such as free radicals and electrons and NO are generated through electric energy supply_XThe molecules collide, dissociate and join each other of the particles in the plasmaChemical reaction, reduction to form N₂And the effect of harmless degradation treatment is achieved. Aiming at the smoke gas under the specific working conditions of nitration and the like, the components of the smoke gas mainly comprise NOx and water vapor, and no O is contained₂The oxidizing gas is suitable for green removal of nitrogen oxides by utilizing the reduction effect of plasma.

Compared with a flat plate structure, the coaxial electrode has slightly lower initial discharge voltage and operating voltage and higher periodic transmission charge quantity and discharge power. In order to utilize the advantage, the device and the method provided by the invention have the advantages that the main body is based on the common type of a coaxial dielectric barrier discharge reactor, a current path is formed by utilizing a gas gap between two shafts, and an inlet, an outlet and a reaction site are provided for flue gas. The grounding electrode is constructed by taking a conductive wire mesh as a structure and coating the conductive wire mesh on the outer surface of a circular tube made of an insulating material (quartz and the like) to form a grounding electrode-medium composite circular tube structure, the high-voltage electrode is a cylinder of which the surface is covered with a needle electrode array, and the outer surface of the high-voltage electrode is coated with the insulating medium material to form a high-voltage electrode-medium composite cylindrical structure, and the whole grounding electrode-medium composite cylindrical structure is positioned in the grounding electrode-medium composite circular tube structure. In order to improve the nonuniformity of radial electric field distribution, a rotating structure is specifically added to drive a high-voltage electrode-medium composite circular tube structure to rotate around a shaft in the circumferential direction, so that the rapid quenching and regeneration of a micro-current channel are promoted, the micro-current channel is prevented from being converted into other discharge forms, gas disturbance is increased, the homogenization of plasma atmosphere is promoted, the collision probability of reductive free radical reaction is increased, the removal efficiency is improved and can reach 90%, the energy consumption is reduced under the same condition, and the economic benefit is achieved.

NO according to the mechanism of plasma treatment of nitrogen oxides_XAnd the background gas generates a large amount of active particles under the excitation of high-energy electrons and generates hundreds of chemical reactions, the reactions can generate different conversion results, and competition effects exist among the reactions, and the competition can be different due to the change of the components of the background gas. Plasma reaction in the absence of oxygen will result in NO_XConversion to N₂And O₂I.e. degradation by reductive pathways. The plasma reaction device can controllably generate low-temperature plasma, high-voltage electrode-medium by an exciting power supply and a voltage regulator through externally supplied 220V alternating currentThe composite circular tube structure continuously runs circumferentially at a stable angular velocity. Under the condition of continuous power supply, the gas inlet is introduced with the smoke under the target working condition, and the reaction of active components such as free radicals is carried out in the gas gap of the device to convert NOx into N₂And then discharged through the gas outlet. The cooling water keeps circulating to keep reasonable temperature reduction. The product is harmless, no secondary reaction and by-product are generated, the denitration efficiency can reach more than 90 percent, and the flow rate of the smoke is 0.6m³H, background gas is N₂。

The method utilizes the capability of reducing and treating nitrogen oxides by plasma, combines the characteristics of low maintaining voltage of coaxial dielectric barrier discharge and the like, newly designs a rotating component to improve the uniformity and stability of discharge, reduces energy consumption on the premise of ensuring higher reduction rate of the nitrogen oxides, and forms a coaxial rotating dielectric barrier discharge method based on plasma reduction denitration

The technology can be used for treating nitrogen oxides including NO and NO contained in industrial flue gas₂And the like. The method for treating the nitrogen oxides in the industrial flue gas by applying the technology comprises a plasma reduction method denitration method and a coaxial rotating dielectric barrier discharge method. The invention can meet the processing requirements of small and medium-sized industrial devices, simplify the process flow, reduce the occupied area, save the power consumption and improve the economic benefit.

The present invention will be described in detail with reference to specific examples.

Example 1

Mixing a certain amount of N₂、NO、O₂、NH₃Forming simulated smoke with the flow rate of 0.75m³H, wherein N₂As background gas, the NOx concentration was 800ppmv, NH₃At a concentration of 5%, respectively in O₂The concentration was 8%, 6%, 4%, 2%. The test is carried out in time, and the composition of the material of the common industrial flue gas is met. The simulated flue gas temperature is normal temperature, and accords with the temperature range of low-temperature plasma denitration. The simulated flue gas enters from the gas inlet, the plasma reactor treats the simulated flue gas under the condition of continuous flowing supply of cooling water, the coaxial rotating structure is not started to keep the reaction device static, and the purified gas is discharged from the gas outlet. With O₂Reduced concentration of NO_XThe reduction conversion rate of the catalyst is gradually increased from 14% to 45.1%, and NO is converted into NO₂The conversion of (A) gradually decreased from 20% to 10%, and also demonstrated that NO was present in the presence of oxygen_XThe oxidation and reduction approaches of the method have a competitive relationship, and the reduction method has higher application advantages aiming at the smoke under the specific working conditions of nitration and the like.

Example 2

Mixing a certain amount of N₂、NO、H₂O forms simulated flue gas with the flow rate of 0.75m³H, wherein N₂As background gas, the NOx concentration was 800ppmv, O₂The concentration is 0%, and H of the water passing gas is controlled by adjusting the temperature₂The O concentration ranges from 3% to 10%, and meets the material composition of general industrial flue gas. The test was performed when the electric field power was stabilized at 85 w. The simulated flue gas temperature is normal temperature, and accords with the temperature range of low-temperature plasma denitration. The simulated flue gas enters from the gas inlet, the plasma reactor treats the simulated flue gas under the condition of continuous flowing supply of cooling water, the coaxial rotating structure is not started to keep the reaction device static, and the purified gas is discharged from the gas outlet. With increasing water content, NO_XThe reduction conversion of (a) gradually increased by 44% from 28%, which demonstrates that water in the absence of oxygen has a positive effect on the reductive removal of nitrogen oxides in a plasma atmosphere.

Example 3

Mixing a certain amount of N₂、NO、NO₂Forming simulated smoke with the flow rate of 1.5m³H, wherein N₂As background gas, the concentration of NOx is 1000ppmv, the material composition of industrial flue gas according with the working conditions of nitrification and the like is tested when the voltage is adjusted to display 15-85V and 5V equidifference is increased. The simulated flue gas temperature is normal temperature, and accords with the temperature range of low-temperature plasma denitration. The simulated flue gas enters from the gas inlet, the plasma reactor processes the cooling water under the condition of continuous flowing supply of the cooling water, and the coaxial rotating component is started to enable the high-voltage motor of the dielectric barrier discharge device to continuously make circumferential motion at a constant speed. The device has the advantages that the voltage changes to drive the power of the electric field to change, the removal efficiency is better when the visible gas flow is 55V, and NO is generated_XThe reduction conversion of (A) was gradually increased by 78% from 23%. And meanwhile, when the voltage regulation voltage shows 55V, the energy consumption and the removal efficiency of the device are well balanced.

Example 4

Mixing a certain amount of N₂、NO、NO₂Forming simulated flue gas with the flow rate of 0.2-1.6m³H, wherein N₂As background gas, the concentration of NOx is 1000ppmv, the material composition of industrial flue gas according with the working conditions of nitration and the like is tested when the voltage is respectively adjusted to 45V, 55V and 65V. The simulated flue gas temperature is normal temperature, and accords with the temperature range of low-temperature plasma denitration. The simulated flue gas enters from the gas inlet, the plasma reactor processes the cooling water under the condition of continuous flowing supply of the cooling water, and the coaxial rotating component is started to enable the high-voltage motor of the dielectric barrier discharge device to continuously make circumferential motion at a constant speed. The voltage changes to drive the power of the electric field to change, and the flow of the visible gas is 0.6m³The removal efficiency of the device is better in the hour of the reaction, NO_XThe reduction conversion of (A) was gradually increased from 30% to 91%. And meanwhile, when the voltage regulation voltage shows 55V, the energy consumption and the removal efficiency of the device are well balanced.

It can be seen that the innovation points of the invention are as follows: plasma is formed by using a dielectric barrier discharge method, combination of discharge homogenization and high energy efficiency is realized through electrode structure design and dielectric barrier material screening, the initial voltage and the operating voltage are both lower, and the industrial production is safer. The denitration efficiency is high and can reach 90% or more under certain operating conditions; NOx is reduced to N2 under the action of an electric field, the traditional technology of NO conversion depending on an oxidation way is broken through, the NOx conversion is directly carried out through a reduction way, secondary treatment is not needed, the process is simplified, and the material investment is saved; the whole processing technology has simple route, only needs electric energy supply, and has low energy consumption, good economical efficiency and simple operation compared with other coaxial designs; the device has small occupied area and is suitable for industrial waste gas treatment of small and medium-sized equipment, particularly specific working conditions such as nitrification and the like; the application effect of plasma denitration is improved.

The invention can treat nitrogen oxides including NO and NO contained in industrial flue gas₂And the like.

s1, inputting the industrial flue gas into the denitration device;

and S2, electrifying the columnar electrode of the pin removal device to form a plasma field in the isolation cavity so as to obtain a purified gas for removing the nitrogen oxide.

The combination of the discharge homogenization and the high energy efficiency is realized by using the dielectric barrier discharge method to form the plasma, and the electrode structure design and the dielectric barrier material screening are adopted, so that the starting voltage and the operating voltage are lower, and the industrial production is safer. The denitration efficiency is high and can reach 90% or more under certain operating conditions; NOx is reduced to N2 under the action of an electric field, the traditional technology of NO conversion depending on an oxidation way is broken through, the NOx conversion is directly carried out through a reduction way, secondary treatment is not needed, the process is simplified, and the material investment is saved; the whole processing technology has simple route, only needs electric energy supply, and has low energy consumption, good economical efficiency and simple operation compared with other coaxial designs; the device has small occupied area and is suitable for industrial waste gas treatment of small and medium-sized equipment, particularly specific working conditions such as nitrification and the like; the application effect of plasma denitration is improved.

Further, the invention may be carried out in a low temperature plasma system, i.e. further comprising:

s3: and pumping the cooling liquid into the denitration device through a cooling circulation pipeline.

In the description of the present specification, reference to the description of the terms "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the embodiments of the present specification. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example.

Furthermore, the various embodiments or examples and features of the various embodiments or examples described in this specification can be combined and combined by those skilled in the art without contradiction. The above description is only an embodiment of the present disclosure, and is not intended to limit the present disclosure. Various modifications and changes may occur to those skilled in the art to which the embodiments of the present disclosure pertain. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the embodiments of the present specification should be included in the scope of the claims of the embodiments of the present specification.

Claims

1. A plasma-based pinning device, comprising:

a housing;

the columnar electrode is positioned in the center of the shell;

2. The release mechanism of claim 1, further comprising:

3. The release mechanism of claim 1, further comprising: and the rotating motor is fixedly connected with one end of the first insulating medium.

4. The release mechanism of claim 2, further comprising:

5. The depilling device according to claim 1, wherein said first insulating medium or said second insulating medium comprises quartz.

6. The release mechanism of claim 1, further comprising:

7. The pin removal device of claim 1, wherein a plurality of spoilers are disposed on the outer sidewall of the first insulating medium; or a plurality of turbulence members are arranged on the inner side wall of the second insulating medium.

8. The release mechanism of claim 7, wherein the spoiler comprises a protrusion or deflector.

9. A method of denitration by the denitration apparatus according to claim 1, comprising:

inputting industrial flue gas to the denitration device;

10. The denitration method according to claim 9, further comprising: