CN103768942A - A method for plasma purification of diesel engine exhaust - Google Patents

Abstract

The invention discloses a method for purifying diesel engine tail gas by plasma, belongs to the technical field of environmental science and engineering, and relates to a method for purifying diesel engine tail gas by plasma. It is characterized by that oxygen plasma O is introduced₂⁺、O⁺、O₂^－、O^－、O、O₂^－(a¹Δ_g)、O₃Injecting into the exhaust gas discharge pipeline of the diesel engine, wherein O₂⁺Reacts with water in the tail gas to generate hydroxyl radical OH which reacts with NOx and SO in the tail gas₂Reacting to generate nitric acid and sulfuric acid mist, and forming a resource substance nitric acid solution under the action of an electrostatic field; or with Ca (OH)₂Innocent treatment of nitric acid into Ca₃)₂Meanwhile, CO, HC and carbon particles in the tail gas are eliminated, and the efficiency of eliminating pollution in the tail gas of the diesel engine by using the plasma reaches 85-99.8 percent.

Description

Translated fromChinese

一种等离子体净化柴油机尾气方法A method for plasma purification of diesel engine exhaust

技术领域technical field

本发明属于环境科学与工程技术领域，涉及一种等离子体净化柴油机尾气方法。 The invention belongs to the field of environmental science and engineering technology, and relates to a method for purifying diesel engine tail gas by plasma. the

背景技术Background technique

柴油机尾气排放的污染物已经危害人们赖以生存的环境，在柴油机尾气中最难处理的两种污染物，一是气体污染物NOx、HC、CO、SO₂等；二是固体碳烟颗粒（PM）。目前主要采用选择性催化还原法（SCR）只能净化柴油机尾气中NOx，通常采用NH₃作为还原剂，NOx在以贵重金属、碱金属氧化物或沸石等催化剂作用下被NH₃还原成N₂、H₂O，反应适宜温度为285℃～400℃。柴油机尾气中NOx通过氧化催化转化器、SCR催化器、防逸氧化催化器、液NH₃及其气化反应器等组成庞大复杂的NH₃-SCR系统后，把尾气NOx还原成N₂、H₂O，NH₃-SCR法只解决了柴油机尾气脱硝的目的。 Pollutants emitted by diesel engine exhaust have endangered the environment on which people live. The two most difficult pollutants in diesel engine exhaust are gaseous pollutants such as NOx, HC, CO, SO₂ , etc.; the second is solid soot particles ( PM). At present, the selective catalytic reduction method (SCR) is mainly used to purify NOx in diesel engine exhaust. Usually, NH₃ is used as the reducing agent, and NOx is reduced to N₂ by NH₃ under the action of catalysts such as precious metals, alkali metal oxides or zeolites. , H₂ O, and the suitable reaction temperature is 285°C to 400°C. After the NOx in the diesel engine exhaust passes through the oxidation catalytic converter, SCR catalytic converter, escape oxidation catalytic converter, liquid NH₃ and its gasification reactor to form a large and complex NH₃ -SCR system, the exhaust NOx is reduced to N₂ , H₂ O, NH₃ -SCR method only solves the purpose of denitrification of diesel engine exhaust.

采用颗粒物捕集器（DPF）捕集柴油机尾气中碳粒，捕集器的压力随碳粒捕集而降低。当捕集量超过一定体积时需再生，采用燃烧燃油或电加热到550℃～600℃以上。将碳粒高温氧化成CO₂无害气体，解决了捕集器阻塞问题。 A particulate filter (DPF) is used to trap carbon particles in diesel engine exhaust, and the pressure of the trap decreases with the capture of carbon particles. When the capture volume exceeds a certain volume, it needs to be regenerated, and it is heated to 550°C to 600°C by burning fuel oil or electric heating. High-temperature oxidation of carbon particles into CO₂ harmless gas solves the problem of trap blockage.

现有NH₃-SCR法和DPF法存在问题是需要贵重金属、碱金属等制成催化剂、还原剂NH₃，运行成本高；需增添氧化催化转化器、SCR催化转化器、防逸氧化催化转化器、液NH₃贮存罐及其气体反应器等复杂庞大的系统装置。进而造成一次性投资和运行成本高，此法只解决NOx污染问题，并没有解决柴油机尾气中HC、CO、SO₂等气体污染问题；碳粒燃烧能耗高，操作繁琐等问题。 The problem with the existing NH₃ -SCR method and DPF method is that precious metals, alkali metals, etc. are required to make catalysts and reducing agent NH₃ , and the operating cost is high; it is necessary to add oxidation catalytic converters, SCR catalytic converters, and anti-oxidation catalytic conversion device, liquid NH₃ storage tank and its gas reactor and other complex and huge system devices. This leads to high one-time investment and operating costs. This method only solves the problem of NOx pollution, but does not solve the problem of HC, CO, SO₂ and other gas pollution in diesel engine exhaust; carbon particle combustion has high energy consumption, and the operation is cumbersome.

发明内容Contents of the invention

本发明克服了现有柴油机尾气净化的不足，提供了一种等离子体净化柴油 机尾气方法。该方法是把具有高活性、高能量的氧等离子体注入柴油机尾气外排管道中，等离子体中正离子O₂⁺与尾气中水分子反应生成羟基自由基OH。由于羟基自由基具有高氧化电位（2.80V）和高反应速率常数（1.0×10^-10_cm³/_s）的特点,保证了羟基自由基能在柴油机尾气外排管道中就能消除烟气中NO₂、SO₂，并生成酸雾，经电除酸雾器捕集成化工资源硝酸、硫酸溶液；或者再用Ca(OH)₂处理成Ca(NO₃)₂、CaSO₄；同时又把HC处理成CO₂、H₂O；另一种具有较高氧化能力的三原子氧组成的臭氧O₃又将柴油机尾气中NO氧化成NO₂，为消除NO提供必备条件；同时又把尾气中CO氧化成CO₂、O₂；O₃又把碳粒氧化成CO₂和O₂，解决了颗粒捕集器随碳粒捕集而压力降低及其再生等问题。本发明只采用等离子体注入柴油机尾气排放管道的净化方法，同时解决了柴油机尾气中NOx、SO₂、CO、HC和碳粒五个污染物问题。实现了不用氧化催化剂、不用还原剂、不用添置多种复杂装置、不产生任何污染的副产品、不对环境产生任何负面影响。 The invention overcomes the deficiency of existing diesel engine tail gas purification and provides a method for plasma purification of diesel engine tail gas. The method is to inject high-activity and high-energy oxygen plasma into the exhaust pipe of diesel engine, and positive ion O₂⁺ in the plasma reacts with water molecules in the exhaust gas to generate hydroxyl radical OH. Due to the characteristics of high oxidation potential (2.80V) and high reaction rate constant (1.0×10^-10_cm³ /_s ) of hydroxyl radicals, it is guaranteed that hydroxyl radicals can eliminate smoke in the exhaust pipe of diesel engines NO₂ , SO₂ , and generate acid mist, which is captured into chemical resource nitric acid and sulfuric acid solution through electrostatic acid mist removal; or treated with Ca(OH)₂ to Ca(NO₃ )₂ and CaSO₄ ; HC is processed into CO₂ and H₂ O; another kind of ozone O₃ composed of triatomic oxygen with higher oxidation ability can oxidize NO in diesel engine exhaust to NO₂ , which provides the necessary conditions for eliminating NO; at the same time, the exhaust gas CO is oxidized into CO₂ and O₂ ; O₃ oxidizes carbon particles into CO₂ and O₂ , which solves the problems of pressure reduction and regeneration of the particle filter due to the capture of carbon particles. The invention only adopts the purification method of injecting plasma into the exhaust pipe of the diesel engine, and simultaneously solves the five pollutants of NOx, SO₂ , CO, HC and carbon particles in the exhaust of the diesel engine. Realized no oxidation catalyst, no reducing agent, no need to add a variety of complex devices, no polluting by-products, no negative impact on the environment.

本发明解决其技术所采用技术方案是： The technical solution adopted by the present invention to solve its technology is:

第一步，制取等离子体 The first step is to generate plasma

采用小型化窄间隙介质阻挡强电场电离放电方法把O₂制成浓度达到80m_g/L～400m_g/L的O₂⁺、O₃、O⁺、O₂^－、O^－、O、O₂^－(a¹Δ_g)、O(¹D)等氧等离子体。在距离为0.05mm～0.2mm的放电极板与接地极之间放电间隙中建立折合电场强度为300Td～500Td的电离放电电场，电子从电场中获得平均能量达到7eV～9eV，电子具有能量是按麦克斯韦规律分布，其中大部分电子所具有的最有用能量（≥12.5eV）将沉积在O₂上，足以把O₂离解、电离成高浓度等离子体，并在电场参数调控下分别定向生成O₂⁺、O₃、O⁺、O₂^－、O^－、O、O₂^－(a¹Δ_g)、O(¹D)，其中O⁺、O^－、O、O₂^－(a¹Δ_g)、O(¹D)等也将进一步参与等离子体化学反 应，最终产物也将是O₂⁺、O₃，由于O₂^－具有能量很低，不具有参与等离子体化学反应条件，最终只有O₂⁺、O₃等分子被注入烟道中参加柴油机尾气净化的等离子体化学反应。产生等离子体反应模式如图2中1强电离放电电场产生等离子体反应模式所示，其等离子体反应式： Using miniaturized narrow-gap dielectric barrier strong electric field ionization discharge method to make O₂ into O₂⁺ , O₃ , O⁺ , O₂^- , O^- , O, O₂ with a concentration of 80_mg /L to 400_mg /L^- (a¹ Δ_g ), O(¹ D) and other oxygen plasmas. In the discharge gap between the discharge electrode plate and the ground electrode with a distance of 0.05mm ~ 0.2mm, an ionization discharge electric field with a reduced electric field strength of 300Td ~ 500Td is established, and the electrons obtain an average energy of 7eV ~ 9eV from the electric field. The electrons have energy according to Maxwell’s regular distribution, in which the most useful energy (≥12.5eV) of most electrons will be deposited on_O2 , which is enough to dissociate_O2 and ionize into high-concentration plasma, and generate_O2 directionally under the control of electric field parameters⁺ , O₃ , O⁺ , O₂^－ , O^－ , O, O₂^－ (a¹ Δ_g ), O(¹ D), where O⁺ , O^－ , O, O₂^－ (a¹ Δ_g ), O(¹ D) and so on will further participate in the plasma chemical reaction, and the final products will also be O₂⁺ , O₃ . Since O₂^- has very low energy, it does not have the conditions to participate in the plasma chemical reaction, and finally only O₂⁺ , O₃ and other molecules are injected into the flue to participate in the plasma chemical reaction of diesel engine exhaust purification. The generation of plasma reaction mode is shown in Figure 2 as shown in the plasma reaction mode of 1 strong ionization discharge electric field, and its plasma reaction formula:

e+O₂→O₂⁺+2e e+O₂ →O₂⁺ +2e

e+O₂→O⁺+O+2e e+O₂ →O⁺ +O+2e

e+O₂→O^－+O e+O₂ →O^－ +O

e+O₂→O₂(a¹Δ_g)+e e+O₂ →O₂ (a¹ Δ_g )+e

e+O₂→O+O(¹D)+e e+O₂ →O+O(¹ D)+e

e+O₂→O+O+e e+O₂ →O+O+e

e+O₂(a¹Δ_g)→O⁺+O+2e e+O₂ (a¹ Δ_g )→O⁺ +O+2e

e+O₂(a¹Δ_g)→O₂⁺+2e e+O₂ (a¹ Δ_g )→O₂⁺ +2e

O(¹D)+O₂→O+O₂(a¹Δ_g) O(¹ D)+O₂ →O+O₂ (a¹ Δ_g )

O₂+O⁺→O₂⁺+O O₂ +O⁺ →O₂⁺ +O

2O₂(a¹Δ_g)+O₂→2O₃2O₂ (a¹ Δ_g )+O₂ →2O₃

O₂(a¹Δ_g)+O^－→O₃+e O₂ (a¹ Δ_g )+O^－ →O₃ +e

O₂(a¹Δ_g)+O⁺→O₂⁺+O O₂ (a¹ Δ_g )+O⁺ →O₂⁺ +O

O+O₂→O₃O+O₂ →O₃

本发明采用介质阻挡间隙为0.05mm～0.2mm的强电离放电方法构建等离子体源7。向柴油机尾气排放管道提供等离子体的浓度达到80mg/L～400mg/L。 The present invention adopts a strong ionization discharge method with a dielectric barrier gap of 0.05 mm to 0.2 mm to construct theplasma source 7 . The concentration of the plasma provided to the exhaust pipe of the diesel engine reaches 80mg/L-400mg/L. the

第二步，在柴油机尾气排放管道中制取OH The second step is to produce OH in the exhaust pipe of diesel engine

将等离子体源产生的等离子体注入排气管道中，注入等离子体浓度80mg/L～400mg/L。在柴油机尾气排气管道中的O₂⁺与柴油机尾气中水反应生成 水合离子O₂⁺·H₂O，O₂⁺·H₂O再与柴油机尾气中水反应生成羟基自由基OH；而O₃与NOx（NO+NO₂）中的NO反应生成NO₂，O₃与尾气中CO反应生成CO₂，OH与NO₂、SO₂反应生成酸雾，OH再与CH反应生成CO₂和H₂O。其等离子体反应模式如图2中2是在柴油机外排尾气管道中的OH形成及消除污染物化学反应模式所示，其等离子体反应式： The plasma generated by the plasma source is injected into the exhaust pipe, and the injected plasma concentration is 80mg/L-400mg/L. O₂⁺ in the exhaust pipe of diesel engine reacts with water in diesel engine exhaust to generate hydrated ions O₂⁺ ·H₂ O, and O₂⁺ ·H₂ O reacts with water in diesel engine exhaust to generate hydroxyl radical OH; while O₃ reacts with NO in NOx (NO+NO₂ ) to generate NO₂ , O₃ reacts with CO in the exhaust gas to generate CO₂ , OH reacts with NO₂ and SO₂ to generate acid mist, and OH reacts with CH to generate CO₂ and H₂ O. Its plasma reaction mode is shown in Figure 2, 2 is the chemical reaction mode of OH formation and pollutant elimination in the exhaust pipe of the diesel engine, and its plasma reaction formula is:

O₃+NO→NO₂+O₂O₃ +NO→NO₂ +O₂

O₃+CO→CO₂+O₂O₃ +CO→CO₂ +O₂

O₂⁺+H₂O→O₂⁺·H₂O O₂⁺ +H₂ O→O₂⁺ ·H₂ O

O₂⁺·H₂O+H₂O→H₃O⁺+OH+O₂O₂⁺ ·H₂ O+H₂ O→H₃ O⁺ +OH+O₂

NO₂+OH→HNO₃NO₂ +OH→HNO₃

SO₂+2OH→H₂SO₄SO₂ +2OH→H₂ SO₄

羟基自由基OH浓度达到3mg/L～150mg/L，反应速率常数为10^-15cm³/s～10^-10cm³/s。 The concentration of hydroxyl radical OH reaches 3mg/L～150mg/L, and the reaction rate constant is 10^-15 cm³ /s～10^-10 cm³ /s.

第三步，在柴油机排气管道中实现柴油机尾气净化 The third step is to realize the purification of diesel exhaust gas in the exhaust pipe of diesel engine

反应温度控制在30℃～200℃，等离子体化学反应速率为10^-15cm³/s～10^-10cm³/s；反应时间为50μs～50ms，在排气管道中NOx、SO₂形成酸雾，含有酸雾尾气进入电除酸雾器中被捕集成硝酸、硫酸混合溶液，净化后柴油机尾气外排出去。电除酸雾器内的电场强度控制在0.8kV/cm～30kV/cm。其等离子体化学反应模式如图2中2柴油机外排尾气管道中OH形成及消除污染物化学反应模式所示。其反应式：NO₂+OH→HNO₃，SO₂+2OH→H₂SO₄，HC+OH+O₃→H₂O+CO₂+1/2O₂。 The reaction temperature is controlled at 30°C~200°C, the plasma chemical reaction rate is 10^-15 cm³ /s~10^-10 cm³ /s; the reaction time is 50μs~50ms, NOx and SO₂ form acid in the exhaust pipe Fog, the exhaust gas containing acid mist enters the electrostatic acid mist remover and is captured into a mixed solution of nitric acid and sulfuric acid, and the exhaust gas of the diesel engine is discharged after purification. The electric field strength in the electrostatic acid mist remover is controlled at 0.8kV/cm~30kV/cm. Its plasma chemical reaction mode is shown in Figure 2 as the chemical reaction mode of OH formation and pollutant elimination in the exhaust pipe ofdiesel engine 2. Its reaction formula: NO₂ +OH→HNO₃ , SO₂ +2OH→H₂ SO₄ , HC+OH+O₃ →H₂ O+CO₂ +1/2O₂ .

本发明把等离子体注入柴油机尾气排放管道中，O₂⁺与柴油机尾气中水反应生成OH；O₃又分别把柴油机尾气中NO、CO分别氧化成NO₂、CO₂，OH与 NO₂、SO₂反应生成硝酸、硫酸雾，OH、O₃又把HC氧化成H₂O、CO₂，这些反应属于高级氧化技术首次应用在净化柴油机尾气的新领域。由于其化学反应速率快，比目前现有柴油机尾气净化方法高出3个数量级以上，所以净化柴油机尾气的化学反应时间仅为50μs～50ms，因而可以实现在柴油机尾气排放管道中完成柴油机尾气净化全过程，其流程大幅度缩短。 In the present invention, plasma is injected into the exhaust pipe of the diesel engine, and O₂⁺ reacts with water in the exhaust of the diesel engine to generate OH; O₃ oxidizes NO and CO in the exhaust of the diesel engine to NO₂ and CO₂ respectively, and OH and NO₂ , SO₂ react to generate nitric acid and sulfuric acid mist, and OH and O₃ oxidize HC to H₂ O and CO₂ . These reactions belong to the new field where advanced oxidation technology is first applied to purify diesel engine exhaust. Due to its fast chemical reaction rate, which is more than 3 orders of magnitude higher than the existing diesel exhaust purification methods, the chemical reaction time for purifying diesel exhaust is only 50 μs to 50 ms, so it can be realized in the diesel exhaust pipeline to complete the complete diesel exhaust purification. process, its flow is greatly shortened.

本发明装置数量少，大幅度降低设备投资和运行成本，降低能耗；实现了不用外加氧化催化剂，不用NH₃作为还原剂净化柴油机尾气；也相应降低了运行成本。本发明不产生其它污染物，解决了目前柴油机尾气净化存在环境污染问题，实现了环境零污染，并达到了高级氧化技术原则的要求。 The invention has a small number of devices, greatly reduces equipment investment and operating costs, and reduces energy consumption; realizes that no external oxidation catalyst is used, and_NH3 is not used as a reducing agent to purify diesel engine exhaust; and correspondingly reduces operating costs. The invention does not produce other pollutants, solves the problem of environmental pollution existing in the exhaust gas purification of diesel engines at present, realizes zero environmental pollution, and meets the requirements of advanced oxidation technology principles.

附图说明Description of drawings

下面结合附图和实施例对本发明作进一步说明。 The present invention will be further described below in conjunction with drawings and embodiments. the

图1是本发明工艺结构示意图。 Fig. 1 is a schematic diagram of the process structure of the present invention. the

图2是等离子体产生及消除柴油机尾气污染物的化学反应模型图。 Fig. 2 is a chemical reaction model diagram of plasma generation and elimination of diesel engine exhaust pollutants. the

图3是等离子体与NOx、SO₂、HC、碳粒摩尔比n对消除率影响曲线图。 Fig. 3 is a graph showing the effect of the molar ratio n of plasma to NOx, SO₂ , HC, and carbon particles on the elimination rate.

图4是反应时间对柴油机尾气消除率影响曲线图。 Figure 4 is a graph showing the influence of reaction time on the removal rate of diesel engine exhaust. the

图中：1空气；2柴油；3柴油机；4柴油机尾气；5排气管道；6等离子体；7等离子体源；8高频高压电源；9含有酸雾尾气；10电除酸雾器；11放电极；12绝缘子；13高压电缆；14直流高压电源；15净化后柴油机尾气；16硝酸硫酸混合溶液；17阀体；18槽；19Ca(OH)₂；20Ca(NO₃)₂和CaSO₄。 In the figure: 1 air; 2 diesel; 3 diesel engine; 4 diesel engine exhaust; 5 exhaust pipe; 6 plasma; 7 plasma source; 8 high-frequency high-voltage power supply; Discharge electrode; 12 insulator; 13 high-voltage cable; 14 DC high-voltage power supply; 15 purified diesel engine exhaust; 16_mixed solution of nitric acid and sulfuric acid; 17_valve body; 18 tank; 19Ca(_OH )₂ ;

具体实施方式Detailed ways

本发明采用窄间隙介质阻挡强电离放电方法构建等离子体源7，由高频高压电源8向等离子体源提供高频高压，等离子体源中的放电间隙中形成折合电场强度达到300Td～500Td的强电离电场，O₂经强电离放电电场离解、电离后形 成浓度达到80mg/L～400mg/L的等离子体6（O₂⁺、O₂^－、O₂(a¹Δ_g)、O₃等）。本发明总体实施方案如图1所示。首先把等离子体6注入柴油机3排气管道5中，等离子体6将碳烟颗粒氧化成CO₂和H₂O；同时在排气管道5中把含NOx、SO₂、HC和碳粒的柴油机尾气4中NO氧化成NO₂，O₃又把CO氧化CO₂、O₂；等离子体6中O₂⁺与柴油机尾气4中的水反应生成OH，它与尾气中NO₂、SO₂反应生成硫酸、硝酸雾；含有酸雾气体9进入电除酸雾器10，由直流高压电源14输出高电压经高压电缆13、绝缘子12施加到电除酸雾器10中放电极11上，放电极11与电除酸雾器10外壳形成高压静电场；硝酸、硫酸雾在静电场中经荷电凝并增粗后，在库仑力作用下被捕集到电除酸雾器10壁上，液体硝酸、硫酸颗粒顺着电除酸雾器10壁流下形成硝酸、硫酸混合溶液16，再经阀体17排放到槽18中作为化工资源硝酸、硫酸回收，或与Ca(OH)₂19反应生成无害的Ca(NO₃)₂和CaSO₄20。 The present invention adopts a narrow-gap dielectric barrier strong ionization discharge method to construct theplasma source 7, and the high-frequency high-voltage power supply 8 provides high-frequency high-voltage to the plasma source, and a strong electric field with a reduced electric field strength of 300Td to 500Td is formed in the discharge gap in the plasma source. Ionizing electric field, O₂ is dissociated by a strong ionizing discharge electric field, and after ionization, a plasma with a concentration of 80mg/L-400mg/L is formed6 (O₂⁺ , O₂^- , O₂ (a¹ Δ_g ), O_{3 ,} etc.) . A general embodiment of the present invention is shown in FIG. 1 . First inject the plasma 6 into the exhaust pipe 5 of the diesel engine₃ , and the plasma 6 oxidizes the soot particles into CO₂ and H₂ O; NO in the exhaust gas 4 is oxidized to NO₂ , and O₃ oxidizes CO to CO₂ and O₂ ; O₂⁺ in the plasma 6 reacts with water in the diesel engine exhaust 4 to form OH, which reacts with NO₂ and SO₂ in the exhaust gas to form Sulfuric acid and nitric acid mist; the acid mist-containing gas 9 enters the electroacid mist removal device 10, and the high voltage output by the DC high-voltage power supply 14 is applied to the discharge electrode 11 in the electroacid mist removal device 10 through the high-voltage cable 13 and the insulator 12, and the discharge electrode 11 Form a high-voltage electrostatic field with the shell of the electrostatic acid mist remover 10; after the nitric acid and sulfuric acid mist are charged and coagulated in the electrostatic field and thickened, they are trapped on the wall of the electrostatic acid mist remover 10 under the action of Coulomb force, and the liquid nitric acid Sulfuric acid particles flow down along the wall of the electrostatic acid mist remover 10 to form a mixed solution of nitric acid and sulfuric acid 16, which is then discharged into the tank 18 through the valve body 17 as a chemical resource for nitric acid and sulfuric acid recovery, or react with Ca(OH)₂ 19 to form nitric acid Harmful Ca(NO₃ )₂ and CaSO₄ 20.

本发明实施结果如图3、4所示。从图4的等离子体与NOx、SO₂、HC和碳粒摩尔比n对消除率影响曲线可知，当等离子体与NOx、SO₂、HC和碳粒摩尔比n分别为1.6、4、1.6、4时，NOx、SO₂、HC及碳粒消除率分别达到97%、85%、96%、98%。从图4的反应时间对柴油机尾气污染物消除率影响曲线可知，当柴油机尾气中NOx、SO₂、HC及碳粒脱除反应时间≥0.5ms时，NOx、SO₂、HC及碳粒消除率分别达到96%、85%、97%、98%。 The implementation results of the present invention are shown in Figures 3 and 4. From the influence curve of the molar ratio n_of plasma to NOx, SO₂ , HC and carbon particles on the elimination rate in Fig. At 4 o'clock, the elimination rates of NOx, SO₂ , HC and carbon particles reached 97%, 85%, 96% and 98% respectively. From the influence curve of reaction time on the elimination rate of diesel engine exhaust pollutants in Figure 4, it can be seen that when the reaction time of NOx, SO₂ , HC and carbon particle removal in diesel engine exhaust is ≥ 0.5 ms, the elimination rate of NOx, SO₂ , HC and carbon particle Respectively reached 96%, 85%, 97%, 98%.

Claims (4)

1. a plasma for purification diesel engine vent gas method, its feature comprises the following steps:

The first step is that 80mg/L～400mg/L contains O by concentration₂⁺, O₃plasma inject exhaust emissions of diesel engine pipeline, in pipeline, eliminate NOx in diesel engine vent gas, SO₂, CO, HC and carbon granules;

Second step, the O in diesel engine vent gas discharge duct 5₂⁺close ion O with water water generation reaction in diesel engine vent gas₂⁺h₂o, O₂⁺h₂o reacts with water in diesel engine vent gas and generates hydroxyl radical free radical OH; And O₃with NOx(NO+NO₂) in NO reaction generate NO₂, O₃react with CO in tail gas and generate CO₂, OH and NO₂, SO₂reaction generates acid mist, and OH reacts with CH and generates CO₂and H₂o; Hydroxyl radical free radical OH concentration reaches 3mg/L～150mg/L, and reaction rate constant is 10^-15cm³/ s～10^-10cm³/ s;

The 3rd step, in exhaust duct of diesel engine, reaction temperature is controlled at 30 ℃～200 ℃, and plasma chemical reaction speed is 10^-15cm³/ s～10^-10cm³/ s; Reaction time is 50 μ s～50ms, NOx, SO in discharge duct₂form acid mist, contain acid mist tail gas and enter and in electricity deacidification day with fog, be caught integrated nitric acid-sulfuric acid mixed solution, after purifying, diesel engine vent gas is arranged outward; Electric-field intensity in electricity deacidification day with fog is controlled at 0.8kV/cm～30kV/cm.

2. a kind of plasma for purification diesel engine vent gas method according to claim 1, the ionic discharge electric field reduced electric field intensity that it is characterized in that preparing plasma source is 300Td～500Td, electronics has average energy and reaches 7eV～9eV.

3. for a kind of plasma for purification diesel engine vent gas method described in claim 1 or 2, it is characterized in that, the plasma source of preparation high concentration plasma is to adopt narrow gap dielectric blocking-discharge method, and discharging gap is 0.05mm～0.2mm.

4. for the device of elimination diesel engine (3) exhaust pollutant of plasma for purification diesel engine vent gas method described in claim 3, it is characterized in that, the device of eliminating diesel engine (3) exhaust pollutant comprises discharge duct (5), high-frequency and high-voltage power supply (8), plasma source (7), electricity deacidification day with fog (10), in electricity deacidification day with fog, comprises again discharge electrode (11), DC high-voltage power supply (14), high-tension cable (13), insulator (12).

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