CA2506787C

CA2506787C - Industrial equipment for environmental protection by random streamer discharge plasmas and its applications

Info

Publication number: CA2506787C
Application number: CA2506787A
Authority: CA
Inventors: Keping Yan; Ruinian Li; Hongdi Zhang
Original assignee: GUANGDONG J-TECH ENVIRONMENT SCIENCE Co Ltd
Current assignee: Guangdong J Tech Environmental Technology Co Ltd
Priority date: 2002-11-26
Filing date: 2003-03-17
Publication date: 2012-02-21
Anticipated expiration: 2023-03-17
Also published as: CN1502402A; WO2004049769A1; CA2506787A1; AU2003227161A1; CN1266988C

Abstract

The invention discloses industrial equipment for environmental protection by random streamer discharge plasmas, which is composed of a power source, reactor(s) and a chemical physical technological processing system. Said power source is comprised of a DC power source, a high frequency AC or pulse power source and an LR matching network(s). Said reactor are vertical or horizontal, dry or wet type; a wet type reactor has its thermal chemical reaction region and plasma reaction in one body (integrative type reactor) or in different bodies (separate type reactor); the plasma reaction region of a separate type reactor has its plasma gas reaction and plasma liquid reaction in one body (integrative type plasma reactor) or in different bodies (separate type plasma reactor); the reaction regions in the reactor are connected in parallel or in series and different sections of the reactor get power supply independently or in a collective and distributive way. The industrial equipment for generation of random steamer plasma has random steamers with good temporal spatial distribution, wide voltage ranges, high repetition frequency, large power output, broad application, and of low costs.

Description

FP05019CAAmendment under PCT article 41 Industrial equipment for environmental protection by random streamer discharge plasmas and its applications Field of the invention The present invention relates to the field of environmental protection techniques with plasmas, more especially, to industrial equipment for environmental protection by random type streamer discharge plasmas and its applications Description of the prior art It is well known that the electric gas discharge mode to initiate effective chemical effects is positive streamer plasmas. So far, all the publicly reported streamer plasma generation techniques belong to synchronous ones. Their characteristics are to energize reactors with narrow (or short)-pulsed high voltages.
Under these conditions, when the pulsed voltages become higher than the onset corona voltage, the pulsed streamers are formed and plasmas are generated in the reactors. The electrode configurations of said reactors have types of wire-tube, wire-plate, point-plate and wire-wire. When the pulsed high voltages transmit from one end to the other of a reactor, the streamers are successively generated at different positions. The time lag AT of the first streamers at two different positions will be generally satisfied the following inequality, namely, LT/L\L<5ns / m, where AL
is the distance between them.
In practice under the conditions of pulse energization, the effective length of the discharge wires generally ranges from one to six meters. So the streamers in the reactor almost are generated simultaneously, which is named as synchronous streamer plasmas. To the accompaniment of every pulse voltage the streamers initiate a pulse discharge current. The pulse voltage can be superimposed with a DC bias-voltage and the produced pulse discharge current , and the streamers have the same characteristics.
The narrow pulse voltage source for generation of synchronous plasmas has voltage rise time ranging from 10 to 100ns, pulse width ranging from 50 to 500ns and repetition frequency ranging from 1 Hz to 2kHz. It is very difficult to popularize applications of said narrow pulse voltage source in industries because of its high costs and high technical difficulties. Moreover the high voltage, high current, high-speed switch in it needs further research and development.
The modes of electric discharge initiated by DC positive high voltage with the elevation of the voltage may manifest onset streamer, glow, pre-breakdown streamer and spark discharge. The streamers generated with DC voltage appear within narrow voltage ranges and leave larger dead zone and unstable phenomena etc. in industrial plasma reactors.

Summary of the invention The object of this invention is to provide industrial equipment for environmental protection by random streamer discharge plasmas and its applications. The streamer plasma generator used therein has low cost, wide voltage range of streamer, high FP05019CA Amendment under PCT article 41 power and repetition rate and random generation of streamers, and can initiate stable and well space-distributed streamer discharges and realize various chemical treatment effects.
To achieve the above object, the technical scheme adopted in the present invention is to provide industrial equipment for environmental protection by random streamer discharge plasmas including electrode system comprised of discharge and grounding electrodes, power source(s), chemical physical treatment system in which there are absorbent, neutralizer, oxidant and catalyst inside and reactor(s).
Said power source is composed of a single-phased, triple-phased or high frequency rectifier DC high voltage source, high frequency AC or pulse source and an LR matching web for coupling the DC and AC or pulse sources. The power source is abbreviated as AC/DC source; said discharge and grounding electrodes are set inside the reactor, said discharge electrodes are connected with the outside power source; said chemical physical treatment system is composed of atomizers, chemical tanks, tanks and storage troughs (pool) for the generated matter. The atomizers are arranged at the inlet, the roof and (or) the lateral sides within the main reaction regions and connected with pumps, chemical tanks, tanks and storage troughs (pool) for the generated matter, respectively, through pipelines. Said tanks for the generated matter are connected with reactors and storage troughs (pool), respectively. When solid matter is treated a granulator takes the place of the atomizers.
When coupled through a capacitor, said LR matching web can be composed of 1-3 LR buffer circuits and a coupling capacitor. When coupled directly, said LR
matching web can be composed of 1-2 LR buffer circuits and an isolation transformer. The inductance L in said LR matching web is fixed, adjustable or their combination. In said matching web, accessories for coupling of AC (or pulse) and DC
can be installed. The accessories can be diodes, capacitors, transformer(s) or solid component(s) etc.
Said power source is a positive high voltage source with peak voltage less than 200kV, in which the DC voltage is less than 100kV and the periodic voltage has its half of peak-to-peak voltage in AC or pulse peak in pulse power source less than 100kV and its frequency between 1kHz and 100kHz. AC is superimposed on DC at DC onset streamer or around DC onset streamer to glow threshold.

Said voltage exerted to the discharge electrodes is a DC voltage superimposed with a high frequency AC voltage of sinusoid, triangle, square or pulse.
The reactors in the industrial equipment for environmental protection by random streamer plasmas can be vertical or horizontal; dry or wet type. The wet reactor can be differentiated as partitioned type and non-partitioned type. In a partitioned type wet reactor, its thermal chemical reaction region and plasma reaction region are successively set in series in one body or in different bodies in parallel to treat gas and liquid separately. The polluted gas passes through the thermal chemical reaction region firstly in which the pollutants in gas are absorbed by liquid chemical absorbent and concentrated in the liquid and then the gas and liquid are transferred to one plasma reaction region in the same body, or the gas and liquid are separately

2 FP05019CAAmendment under PCT article 41 transferred to different plasma reaction regions in different bodies to experience streamer plasma treatment, and further removing the gas pollutants from the gas and oxidizing or decomposing the solutes in the liquid phase are performed. In a non-partitioned wet type reactor, thermal and plasma chemical reaction regions are successively set in one body.
The electrode configurations of said plasma regions can be the types of wire-tube, wire-plate, point-plate or wire-wire. The discharge electrodes can be saw-tooth wire or knife-edge wire. The inner surfaces of grounding electrode can be porous or smooth. A reactor system can made up of one unit or several units in parallel and every unit can be made up of one stage or several stages in series. The plasma reaction regions in the reactors are connected in parallel or in series, and different units of the reactors get power supply independently or jointly in a collective and distributive way.
The industrial equipment for environmental protection by random streamer discharge plasmas provided by this invention can be applied to clean air, flue gas, water and soil.
In comparison to the equipment of synchronous plasmas, the industrial equipment for environmental protection by random streamer discharge plasmas provided by this invention has following advantageous effects:
1. A DC voltage superimposed with an AC or pulse voltage has a wide voltage range for generation of streamer discharge and can generate stable streamer discharges with good temporal and spatial distribution. Applying positive voltage of a DC
voltage superimposed with an appropriate AC or pulse voltage, the electric discharge from the discharge electrodes to the grounding electrodes only manifests two modes, i.
e.
streamer and spark, with the increased voltage.
2. The waveforms of voltage generated from DC voltage superimposed with an AC voltage such as sinusoid, triangle, square or wider pulse are wider pulses.
In comparison to streamer plasmas generated from narrow pulse voltage, the discharge from AC / DC source has no essential differences in V-A characteristics. When a streamer appears, the voltage across the reactor decreases owing to the streamer generation. Besides the duration of the voltage pulse exerted on the electrodes is long compared to that of narrow pulse but the peak voltage from an AC/DC source is relatively low. Therefore the streamers generated by AC / DC source will be distributed within a relatively long time lag of tens to hundreds microsecond ( s) so that they are random. However because of the relatively high streamer repetition rate between 1kHz and 100kHz, the streamer power appears high. The cost of manufacturing an AC/DC source used in this invention is only one tenth of a narrow pulse high power supply. So random streamer technique initiates a new development space for its industrial applications

3. In a partitioned wet type reactor, the gas pollutants are absorbed by liquid absorbent firstly in its thermal reaction region and concentrated in the liquid, and then the gas and liquid are transferred to a plasma reaction region in one body, or the gas and liquid are separately transferred to different plasma reaction regions in different bodies to experience streamer plasma treatment and further removing the gas FP05019CA Amendment under PCT article 41 pollutants from the gas and oxidizing or decomposing the solutes in the liquid phase are performed. Because the pollutants are concentrated in the liquid, the reaction speed is increased, and they can be oxidized or decomposed at a relatively low energy cost. In comparison to non-partitioned wet reactors, the partitioned wet reactors with similar volumes for thermal and plasma reactions allows 30%-50% electricity cost reduction.

4. Oxidizing or decomposing the solutes in the liquid can be carried out in either treated flue gas or external gas.

5. The surfaces of the grounding electrodes can be smooth or porous so as to increase the mass transfer rate and reaction speed initiated by the streamers Brief description of the drawings Figure 1 is schematic drawings of electrode configurations of(a)wire-tube , (b) wire-plate, (c) point-plate and (d) wire-wire;
Figure 2 is a view of capacitor coupling type LR matching web;
Figure 3 is a view of direct coupling type LR matching web;
Figure 4 (a) -4(d) are views showing different modes of electric discharges within a point-plate electrode configuration with the increase of AC/DC
voltage, in which figure 4(a) shows onset streamers, 4(b) streamers, 4(c) pre-breakdown streamers, and (d) sparks;
Figure 5 shows the charts of voltage pulses generated by positive DC
superimposed with a sinusoidal voltage;
Figure 6 shows the charts of voltage pulses generated by positive DC
superimposed with a triangle wave voltage;
Figure 7 shows the charts of voltage pulses generated by positive DC
superimposed with a squared wave voltage;
Figure 8 shows the charts of voltage pulses generated by positive DC
superimposed with a wider pulse voltage;
Figure 9 is a schematic diagram of technological process for air cleaning of highway tunnels;
Figure 10 is a schematic diagram of technological process for VOCs removal from air;
Figure 11 is a schematic diagram of technological process for hazardous air pollutants cleaning and air sterilization;
Figure 12 is a schematic diagram of technological process for semi-wet method of streamer discharge flue gas desulfurization;
Figure 13 is a schematic diagram of technological process for swimming pool water cleaning;
Figure 14 is a schematic diagram of technological process for treatment of mud and soil.

Detailed description of the preferred embodiments Example 1. Highway tunnel air cleaning Air in highway tunnels is polluted by the end gas from motor vehicles. The FP05019CA Amendment under PCT article 41 pollutants have NOx at about IOppm , hydrocarbons to some amount, sulfur-compounds and black smoke, which can not only reduce visibility, but also initiate a good many diseases. By use of this invention various hazardous gases and particles in tunnel air can be treated or collected in the example 1.
Table 1: Technical parameters for plasma cleaning of highway tunnel air Flow rate of the air treated l 0000m3 / h The reactor One stage horizontal wet reactor with a wire-plate electrode configuration Energy density of the streamer plasmas <0.3Wh / m3 Power of streamer discharge plasmas -3kW
DC high voltage source 20-30kV, 1kW
High frequency AC power source 30kV, 2kW, 50kHz, square wave(Fig.7) LR matching web Capacitor coupling, three LR buffer circuits and one coupling capacitor (Fig.2) Gas-to-liquid ratio in the reactor 2500 Volumetric rate of Cyclic water <4m3 / h Treatment time 1 s Gas flow speed 2m/s NOx emission <_ 0.5ppm Hydrocarbon and sulfur compound < lppm emission Dust emission < 5mg / m3 To prevent 03 slip, an additional ozone decomposer is installed at the end of the reactor. Wastewater is treated in some other way In the tunnels, under the action of the active radicals such as OH, 0 and HO2 generated from the streamer plasmas NOx and SO2 are oxidized to HNO3 and H2SO4, which are dissolved in water while hydrocarbons are oxidized to aerosols related. The smoke and the aerosol particles formed are forced to charge and collected under the action of Coulomb force.
Figure 9 shows the schematic diagram of the technological process. The polluted gas passes through the air-flow-distributor to the inlet of a non-partitioned horizontal reactor 6 and enters its main reaction region. The electric field of a wire-plate wet type six-unit reactor has an effective length of 2.0m, width of 1.2m and height of 1.2m. The distance between the wire and the plate is 200mm. The wires 1 are cross-saw-tooth type and connected to an AC/DC source 8. In a collective and distributive way of jointly energizing below the sparking voltage, the streamers are generated in a fairly wide range of voltage (Fig. 4c). The grounding electrodes 2 are smooth patterned plates. When the polluted gas enters the non-partitioned horizontal reactor 6, it is humidified firstly with lateral atomizers 9a and experiences thermal chemical reactions with the liquid pumped from a generated liquid tank 11 at the bottom of the non-partitioned horizontal reactor 6. Roof spraying is realized with the atomizer 9b at the top of the non-partitioned horizontal reactor 6. The chemicals for thermal chemical reactions are injected into the cyclic system through the chemical FP05019CA Amendment under PCT article 41 tank 10. When the concentration of the liquid byproduct reaches its emission limit, the liquid is let out through liquid tank 11 and enters storage troughs (pool) 12.
The treated gas is discharged through the non-partitioned horizontal reactor 6 into or out of the tunnels.

Example 2. VOC cleaning in air For controlling pollution of air due to low concentration volatile organic compounds, traditional techniques are activated carbon absorption, catalytic oxidation, combustion, ozone oxidation, ultraviolet (UV) ray decomposition and advanced oxidation techniques (UV+03+H202) and so on. The main problems of these techniques are high costs and short lifetime of the systems. In the implementation this invention is used to efficiently oxidize VOCs to transform them to aerosols and to be removed in a wet plasma reactor.
Table 2: The parameters of the system for plasma cleaning VOC in air Air flow rate 10000m3 / h The reactor Two stage wire- tube vertical wet reactor Plasma energy density <2Wh / m3 Plasma power <20kW
DC high voltage source 20-30kV, 8kW
High frequency AC power source 30kV, 12kW, 50kHz, sinusoid (Fig.5) LR matching web Direct coupling, 2 LR buffer circuits and one isolation transformer (Fig. 3) Gas to liquid ratio in the reactor 2500 Volumetric rate of Cyclic water < 4m3 / h Treatment time 2 s Gas flow speed 2m/s VOC removal rate >_ 90% (take 25ppm C8H8 Yj as an example) A wet vertical plasma reactor with two stages in series is shown as Fig. 10.
Every stage of the reactor has 46 units in parallel with wire-tube electrode configuration (seeing Fig. I a).
Every tube has its inner diameter of 200mm and length of 2000mm. Air polluted by VOC enters the first stage 6a through its top entrance and contacts the atomized absorbent, which is from the chemical tank 10 and sprayed by an atomizer 9b, and flows to the plasma reaction region. In the plasma reaction region the discharge electrodes are saw-tooth wires 1 and the grounding electrodes 2 are smooth.
The wires 1 are connected through a wall-through insulator with an AC/DC power source 8a.
The gas is transferred to the bottoms of the second stage 6b of the reactor through a channel connecting the two stages from the bottoms of the first stage 6a.
Firstly the gas contacts the generated liquid from the generated liquid tank 11 b through pipeline and sprayed by the atomizer 9b. Then the gas enters the plasma reaction region of the second stage 6b, whose configuration is same as the former. But

6 FP05019CA Amendment under PCT article 41 the discharge electrodes 1 in the second stage 6b are connected to the AC/DC
power source 8b. The two stages get power supply independently in a collective and distributive way. Before the gas is discharged from the second stage 6b, it is eluted once again with the generated liquid sprayed from the atomizer 9b at the top of the second stage 6b. The end liquid is discharged from the tank 11.
This example can also be used for other hazardous gas cleaning such as H2S, NH3. phenol, HF, NF3, C2F6, CC14, SiF4. CFC-112, CFC-113 etc.

Example 3: Removal of hazardous air pollutants and air sterilization At present there is an urgent need of equipment for removal of hazardous air pollutants and air sterilization in the industries of food processing, medicines and livestock farming. However because of complex composition of the polluted gas and its low concentrations but large amount the activated carbon absorption method used nowadays has problems such as short lifetime of the activated carbon and high operational costs. It is difficult to popularize it.
In the implementation this invention is used to very efficiently remove hazardous air pollutants and sterilize polluted air. Using plasma the gas pollutants can be oxidized and then dissolved in water. Under the action of plasma, bacteria will be oxidized and killed to realize sterilization. According to difference of sites plasma energy density for sterilization may ranged from 0.2 to 1.0 Wh / m3 . In a food processing workshop, 0.2 Wh / m3 is appropriate and 1.OWh / m3 is fit for the inlet of a chimney. Detailed parameters are shown in Table 3.
Table 3: Parameters for plasma cleaning of hazardous air pollutants and bacterium Air flow rate 5000m3 / h (chicken farm etc.) The reactor Vertical single stage wet reactor with wire-tube configuration Plasma energy density <0.5Wh / m3 Plasma power _2.5kW
DC power source 20-30kV, 1.0kW
High frequency AC power source 30kV, 1.5kW, 30kHz, triangle wave (Fig.
6) LR matching web Diode coupling, one LR buffer circuit with a diode Treatment time 1 s Gas to liquid ratio in the reactor 2500 Gas flow speed 2m/s Volumetric rate of Cyclic water <4m3 / h A vertical one-stage reactor is comprised of twenty three wire-tube units in parallel, with 200mm in diameter and 2m in length each. As shown in Figll, the polluted gas enters the wire-tube wet reactor 6 through its bottom entrance and experiences thermal chemical reactions with the liquid chemicals firstly. The chemicals from a chemical tank 10 are sprayed with an atomizer 9b. The polluted gas flows from above to below into a plasma reaction region, whose electric discharge system is made up of cross-saw-tooth discharge wires 1 and smooth tubular grounding

7 FP05019CA Amendment under PCT article 41 electrodes 2. The wires 1 are connected with an external AC/DC power source by the aid of a wall-through insulator. The polluted gas is washed by the eluting liquid and then discharged. The eluting liquid is from a tank 11 through a channel and a valve and sprayed into the plasma region and then let out from the tank 11.
Example 4: Cleaning of end gas from rubbish incinerators A 150T/Day incinerator for urban rubbish may discharge 40000Nm3 / h waste gas to be treated. At present incinerators in operation discharge large amount of gas with pollutants such as NOx, SO2, H2S, HCl, dioxin, heavy metals (Hg for example) etc.
By use of the invention this example may help realize comprehensive treatment of cleaning for the end gas from the incinerators. The main parameters are listed in Table 4.
Table 4: The operational parameters for plasma cleaning of the end gas from incinerators Air flow rate 40000Nm3 / h Composition of the gas C02: 8%; 02: 12%; H2O: 20%; N2: balance Temperature of the gas 160-190 C
HC1 300-500ppm NOx 100-200ppm SO2 100-250ppm Dioxin >5ng-TEG/ Nm3 Mercury 0.07-0. l mg/ Nm3 Dust 10-50mg/ Nm3 Hydrocarbons 1000ppm Plasma discharge power <200Kw DC+ pulse (Fig 8) Energy density of the Streamer plasma - 5 Wh / Nm3 Treatment time 2 s Linear flow speed of gas 2m/s Example 5: flue gas desulfurization and denitrification The example discloses an overall technical scheme as follows: a wet method of flue gas desulfurization by streamer discharges. By use of a partitioned wet reaction system, the solute of the end liquid byproduct is sulfates. The liquid is vaporized with the heat in the gas to be treated and after that turned into dry sulfate powder. Heat in the gas to be treated can also be used to elevate the temperature of the end gas from the wet reaction system. In this way, a stable technological process is optimized and industrialized. In the example the high voltage power source is a DC bias superimposed with a periodical voltage i.e. AC/DC power source, with which streamer plasma is generated. In order to improve efficiency of the technological process, an optimized electrode configuration is adopted so as to obtain an excellent both temporal and spatial distribution of streamer plasma within a large volume of an industrial reactor. In the example partitioned wet reactor system is adopted.
In the system there is thermal reaction region, in which SO2 is absorbed from the flue gas with liquid absorbent and the generated tetravalent sulfur compounds are concentrated

8 FP05019CA Amendment under PCT article 41 in the liquid, then this liquid and the treated gas are transferred to a plasma reaction region (in series with the former thermal reaction region) and treated with streamer discharges. In this way the sulfites in the liquid can be oxidized with a lower energy cost at a higher concentration of the solution. Meanwhile SO2 and NOx in the gas are further removed. Oxidation treatment of sulfite solutes can also be carried out in a plasma reaction region in a separate body. The gas in the separately set plasma reaction region can be external. The electricity cost of the partitioned wet reactor can be reduced by 30%-50% than the non-partitioned one. The advantages of this streamer discharge flue gas desulfurization wet technological process lie in simplicity, continuation, stability and integration; dry powder of ammonium sulfate and nitrate of recovered byproduct and smaller space occupied, lower overall energy cost and both lower fix investment and operational costs.
The example is shown in Fig. 12. The hot flue gas 17 passes through a duster and then enters a heat exchanger 18 to elevate the temperature of the end gas 20 from the wet reaction system. After that the flue gas enters a dryer 19 to vaporize water of the sulfate solution pumped from the partitioned wet reactor 6 through pipeline and turn the solution into dry powder, which then falls into a storage trough 21, being drawn and packed. The temperature of flue gas at the entrance of the dryer is selected appropriately so as to allow a temperature higher than 70 C at the exit of the dryer and ensure a good dewatering effect. The treated gas gets its temperature reduced and humidity increased in the dryer 19 and then enters the thermal reaction region 27 of the partitioned wet reactor 6 and furthers its humidification, temperature reduction and gets SO2 absorption by elution with water and solution from water tank 22 and chemical tank 10. The liquid absorbent is pumped from the tank 11 a to the sprayers through pipeline and cyclically sprayed into the thermal reaction region to absorb SO2.
When the concentration of the solution becomes appropriately high, the generated liquid is drawn at an appropriate rate and conveyed to the plasma reaction region 28 from the tank llb through pipeline and a pump. Power source 8 is connected with discharge electrode 1. The grounding electrode is porous electrode. The streamers generated from the discharge electrodes oxidize the tetravalent sulfur compounds in the solution to sulfate, increasing the concentration of sulfate and meanwhile further removing SO2 and NOx from the gas. The liquid from the plasma reaction region is transferred the tank 11 c under a demister 23. By keeping balance of the stored liquid, the liquid is continuously transferred to the dryer 19 for dewatering.
In the liquid transfer pipeline a pH detector 24 is installed. According to the data of the pH
detector 24 adjustment of neutralization for the generated liquid is carried out. The treated gas is transferred to the heat exchanger 18 through the demister 23 and the exit of the partitioned wet reactor 6 and discharged as the end gas through a chimney 25 after its temperature being elevated in the heat exchanger 18. Before the inlet of chimney 25 an ammonia detector 26 is installed to control the quantity of ammonia used and to prevent ammonia slip.
In this example the technique used to treat flue gas is the invention of the semi-wet method of desulfurization and denitrification. The temperature of the partitioned wet reactor system is T;:t60 C. The flue gas has its initial concentrations of

9 FP05019CA Amendment under PCT article 41 SO2 z~1000ppm and NOx Q00ppm. and volumetric flow rate F,&100000m3 / h. The rated power of the electric source is P=200kW, in which DC is 15kV and 100kW
and AC is 30-40kV, 100kW with a frequency f=20kHz. The energy density is E=2 Wh / m3. A capacitor coupling type LR matching web is used, which is composed of three LR buffer circuits and a coupling capacitor. The flue gas has its linear flow speed 2m/s and residence time 2s. The results are desulfurization rate r1so2 >,95 %, denitrification rate r1NOX % 50 % and ammonia injection rate is controlled with ammonia slip less than 5ppm. In addition, the removal rates of chlorides, mercury, dioxin and hydrocarbons from the flue gas are all greater than 95%. If three stages typed reaction system is used, the thermal chemical reaction stage is the first and the other two stages will be plasma regions in parallel, one for treating gas, another for treating the generated liquid. Other basic solutions can also be used as the absorbent.
Example 6: Cleaning of waste and drinking-water Waste water generally contains both organic and inorganic pollutants. Using oxidation techniques may turn the pollutants into harmless matter. At present the most popularized oxidizers are ozone, hydrogen peroxide, chlorine dioxide and potassium permanganate etc. To realize advanced oxidation treatment, (AOT) oxidizers may be combined with other effects of catalysts such as Ti02 or ultraviolet rays.
In this example, this invention is used for advanced oxidation treatment of various waste water, drinking water etc. The installation is simple and the operational cost is low.

Table 5: Parameters for plasma cleaning of waste water and drinking water Rate of treated water 50 T/h Streamer plasma power 2.5kW
DC voltage source 20kV, 1.0kW
High frequency AC source 30kV, 1.5kW, 30kHz, squared wave(Fig.
7) The Reactor Vertical wire-tube type As shown in Fig. 13, the reactor 6 is composed of three wire-tube units in parallel with the length 1000mm and diameter 120mm thereof. The water to be treated is sprayed by an atomizers 9b at the top of the reactor 6 and discharged at its bottom. Fig.
13 shows a technological process for plasma cleaning of swimming pool water. A
plasma reactor can not only remove hazardous air pollutants but also kill bacterium (take colon bacillus for example efficiency >95 %). An AC/DC power source with capacitor coupling LR matching web 5a is used. A capacitor type LR matching web 5a constructed with three LR buffer circuits 13a with constant inductors and a coupling capacitor 14 are used to couple a single-phased DC source 4 with a high frequency AC source 3. Water pool is numbered 12.
Instead of cleaning of wastewater and drinking water by random streamer discharge plasmas ozone can be generated firstly and then treat wastewater or drinking water with the generated ozone FP05019CA Amendment under PCT article 41 In the process of making ozone with air, it is necessary to drop temperature and moisture of the air. The main parameters are shown in Table 6 Table 6: Parameters for generation of ozone by streamer plasmas Volumetric flow rate of dry air 1000m3 / h Concentration of ozone 1000ppm Energy yield of ozone 71g / kWh Streamer plasma power 30kW
DC power source 20kV, 15kW
High frequency AC power source 20-30kV, 15kW, 30kHz, sinusoidal wave (Fig.5) The reactor wire-tube, vertical, dry The vertical reactor with fifteen wire-tube units in parallel is used. Each has a diameter of 100mm and height of 2000mm. The discharge electrodes are knife-edge type. The energy yield of ozone may reach 71g / kWh.
This example can also be applied for oxidation treatment of liquid, for example oxidation of solutes of sulfite to sulfate.

Example 7: Mud and soil cleaning There are various kinds of mud, which may contain both organic and inorganic pollutants, microbes, germs and virus etc. In the example, this invention is used for oxidization treatment of not only various organic and inorganic pollutants but also microbes, germs and virus. The main parameters are specified in Table 7.
Table 7: Parameters for plasma cleaning of mud and soil Treatment quantity of mud and soil 40T/day (with 20% water content) Streamer plasma power 5kW
DC power source 20kV, 2.5kW
High frequency AC power source 20-30kV, 2.5kW, 30kHz, pulse (Fig. 8) The reactor wire-tube type, vertical As shown in Fig.14, the reactor 6 is composed of ten vertical wire-tube units with a height of 2000mm and diameter of 120mm thereof. The mud to be treated spouts from a granulator 7 and passes the top of the reactor 6. The granules of the mud or soil appear fluidized in the reactor 6. Plasma can not only be generated in gas but also on the surfaces of the granules. One cycle of treatment allows a cleaning efficiency 95% for colon bacillus and other germs. An AC/DC power source with direct coupling LR matching webs 5b is used. That is two LR buffer circuits 13b are used, in which adjustable inductors and one isolation transformer 15 are used to build a direct coupling LR matching web 5b, which couples a three-phased rectification power source 4 with a high frequency AC power source 3.

Claims

1. Industrial equipment for environmental protection by random streamer discharge plasmas including:
an electrode system comprised of discharge electrodes (1) and grounding electrodes (2), chemical physical technological equipment comprised of absorbents, neutralizer, oxidants and catalysts, and a wet reactor (6) and AC/DC
superimposed power supply (8); wherein said AC/DC superimposed power supply (8) is comprised of a high frequency rectification DC high voltage source (3), a high frequency AC or pulse source (4) and an LR matching web (5) used to couple the high frequency rectification DC high voltage source (3) and the high frequency AC or pulse source (4);
said discharge electrodes (1) and grounding electrodes (2) are installed in the wet reactor (6), said discharge electrodes (1) are connected to the AC/DC
superimposed power supply (8) provided outside the wet reactor (6);
said chemical physical technological equipment is comprised of atomizers (9), a chemical tank (10), a byproduct tank (11) and a storage trough (12), wherein the atomizers (9) are installed in the wet reactor (6) and connected with the chemical tank (10) and the byproduct tank (11); said byproduct tank (11) is connected with the wet reactor (6) and the storage trough (12), polluted gas enters the wet reactor (6) and is humidified by the atomizers (9) having thermal chemical reactions with chemicals from the byproduct tank (11) or chemical tank (10), and then enters the plasma reaction region formed by the electrode system to have a streamer plasma treatment.

2. The industrial equipment for environmental protection by random streamer discharge plasmas according to claim 1 characterized in that the high frequency rectification DC high voltage source (3) of said AC/DC superimposed power supply (8) is triple-phased.

3. The industrial equipment for environmental protection by random streamer discharge plasmas according to claim 1 characterized in that the high frequency rectification DC high voltage source (3) of said AC/DC superimposed power supply (8) is single-phased.

4. The industrial equipment for environmental protection by random streamer discharge plasmas according to claim 1 characterized in that said LR

matching web (5) is comprised of 1~3 LR buffer circuits (13) and a coupling capacitor (14).

5. The industrial equipment for environmental protection by random streamer discharge plasmas according to claim 1 characterized in that said LR
matching web (5) is comprised of 1~2 LR buffer circuits (13) and an isolation transformer (15).

6. The industrial equipment for environmental protection by random streamer discharge plasmas according to claim 1 characterized in that an inductor L in said matching web (5) is constant, adjustable or combinations thereof, and said matching web (5) is provided with accessories including diodes, capacitors and transformers or components to realize AC and DC coupling.

7. The industrial equipment for environmental protection by random streamer discharge plasmas according to claim 1 characterized in that the voltage of said high frequency rectification DC power source (3) is less than 100kV and a half of peak-to-peak voltage of the AC source or peak voltage of the pulse source is less than 100kV.

8. The industrial equipment for environmental protection by random streamer discharge plasmas according to claim 1 characterized in that said high frequency AC or pulse source (4) has a frequency within the range of 1KHz to 100KHz.

9. The industrial equipment for environmental protection by random streamer discharge plasmas according to claim 1 characterized in that in the AC/DC
power supply (8), AC is superimposed on DC at DC onset streamer or around DC
onset streamer to glow threshold.

10. The industrial equipment for environmental protection by random streamer discharge plasmas according to claim 1 characterized in the waveform of the voltage exerted to the discharge electrodes (1) is a superimposition of a positive DC
bias and high frequency AC power voltage having sinusoidal, triangle, squared or pulse waveforms.

11. The industrial equipment for environmental protection by random streamer discharge plasmas according to claim 1 characterized in that said wet reactor (6) is a partitioned type wet reactor and has a thermal reaction region (27) in series with a plasma reaction region (28); gas reactions and liquid reactions in the plasma reaction region (28) are carried out in one body, and external gas is used for oxidizing the solutes in liquid phase in the plasma reaction region (28).

12. The industrial equipment for environmental protection by random streamer discharge plasmas according to claim 1 characterized in that said wet reactor (6) is a partitioned type wet reactor and has a thermal reaction region (27) in series with a plasma reaction region (28); gas reactions and liquid reactions in the plasma reaction region (28) are carried out in separate bodies and external gas is used for oxidizing the solutes in liquid phase in the plasma reaction region (28).

13. The industrial equipment for environmental protection by random streamer discharge plasmas according to claim 1 characterized in that the electrode configuration of the wet reactor (6) is wire-tube, wire-plate, point-plate or wire-wire type; the discharge electrodes are saw-tooth wire or knife-edge wire; the surfaces of the grounding electrodes are smooth or porous; said reactor (6) has one unit or several units in parallel and every unit is comprised of one stage or several stages in series.

14. The industrial equipment for environmental protection by random streamer discharge plasmas according to any one of claims 1-13 characterized in that the industrial equipment for environmental protection by random discharge plasmas is applied to the cleaning of air, flue gas, water and soil.