CN101045220A - Electrical charging coagulation method for dust in flue gas transfering pipeline - Google Patents

Abstract

A method for electrically charging and coagulating powder dust in the fume delivering pipeline features that the charging and coagulating reaction of powder dust is performed at the entrance of an electric duster to make the dust particles be electrically saturated and to increase their diameter by 4-400 times, so increasing the dusting efficiency.

Description

In the ducted dust charge electrocoagulation of supplied flue gases method

Technical field

The invention belongs to technical fields such as gas ionization discharge, plasma physics, aerodynamics and environmental project, relate in the ducted dust charge electrocoagulation of supplied flue gases method.

Background technology

China enters 21 century with higher economic growth rate, thereby will consume the more energy, and the building materials iron and steel, chemical industry of adding China be with industrial high speed developments such as non-ferrous metals, and then causes the smoke contamination thing to increase significantly.Environmental ecology safety and residents ' health have been caused harm.Meanwhile, electric cleaner (ESP) can be obtained high speed development in the application of aspects such as thermal power plant and steel plant, cement plant.The quantity of electric cleaner accounts for 75% of domestic market total amount at present, and China has become electric cleaner production in the world, used big country.China implemented new " country of thermal power plant allows discharge standard " and " cement industry atmosphere pollutants emission standards " in 2004, and flue dust, dust emission standard all are lower than 30～50mg/m ³, most flue dust that are difficult to reach new allow discharge standard in existing new, the old electric cleaner with making, and this also is to having a kind of challenge of electric cleaner theory and technology now.Make electric cleaner reach new standard, just need on the electric cleaner theory and technology, strengthen the research dynamics,, the popularization of electric cleaner technology is developed on higher level so that make a breakthrough.

Because electric precipitation (purification) utensil has the big exhaust gas volumn that can handle high temperature (350 ℃) high humidity [40% (v/v)] degree; Low (the 100Pa～300Pa) of the pressure loss; Can capture small dust; Characteristics such as operating cost is low.Thereby, by universally acknowledged be high-effective dust-removing equipment.Make ion attached on the grit, charged grit is attached on the dust collecting electrode by being driven under the electric field force effect, and in addition rapping is collected, and has realized flue gas ash removal.(～0.1MPa) non-equilibrium (non-heat, cold) plasma physics viewpoint, electric cleaner is the assembly of a huge plasma source and reative cell from hyperbar.Yet China plasma physics section development strategy group research report was pointed out " mechanism that produces the atmospheric pressure non-equilibrium plasma at present it be unclear that " in 2004." under hyperbar the transport property of plasma research also at the early-stage, but forming new research focus." because the hysteresis of atmospheric pressure (plasma physics is called hyperbar) plasma physics research has restricted the mechanism research of electrostatic precipitation technology.Up to the present, the theory of countries in the world electrostatic precipitation technology is still incomplete, goes no further, and also is on the level sixties basically, the subject that belongs to the experience engineering is so the quality of electric cleaner depends on hit rate, the accuracy of manufacture, installation quality, supplied character and the maintenance management etc. of design.Owing to the shortcoming of the fundamental research of electric precipitation causes the once investment height of electric cleaner, bulky, rolled steel dosage too much and capture problems such as fine flue dust efficient is low.

50～sixties, China introduces for sleeping in, vertical electric cleaner from the former Soviet Union and Eastern Europe, since the eighties again respectively from German Ruthmuble and Lurgi, Sweden Flakt, the GE of the U.S. and Lodge-Cottrell, companies such as SUMITOMO CHEMICAL heavy-duty machine, Nippon Steel and Mitsubishi introduce electric cleaner equipment and manufacturing technology, and part domesticizes.In a word, China is in Technical Follow-Up to grind imitative is the main stage.

Summary of the invention

It is low and bulky to the objective of the invention is to solve present electric cleaner capture fine dust efficient, and problems such as energy consumption height are provided at the ducted dust charge electrocoagulation of supplied flue gases method.This method makes dust in ducted charged device, and is charged with the anion or the cation collision of high number density; Saturated charged dust again in the alternating electric field in coacervation device cohesion increase thick.Can make the dust that enters electric cleaner saturated in advance charged, tens of again, hundreds of times of ground increases of particle diameter simultaneously, this will improve the capture fine dust efficient of electric cleaner widely, reduce the electric cleaner volume simultaneously again significantly, reduce rolled steel dosage, reduced cost of investment one time; Reduce energy consumption, reduced operating cost.

Technical scheme of the present invention is: the dust cohesion device of placing the dust charge electric installation lotus high voltage alternating electric field of 1-4 cover direct current, burst pulse high-voltage discharge in the inlet supplied flue gases pipeline of electric cleaner, make the dust that enters electric cleaner saturated in advance charged, and dust size is increased 4 times～400 times.This fine dust arresting efficiency that will solve present electric cleaner is low, bulky, problems such as energy consumption height.

One. solve the technology path of the existing problem of electric cleaner

Electric cleaner mainly is to finish under electric field action by charged soot dust granule to smoke catching.Usually characterize the efficiency of dust collection of electric cleaner with many according to strange dedusting (meter is heavy) efficiency equation, formula is

$\mathrm{\η}=1-e(-\frac{A}{Q}\·\mathrm{\ω})---\left(1\right)$

A is the total control of dust area of electric cleaner in the formula; Q is pretreated exhaust gas volumn, and ω is that charged grit drives the migration velocity to dust collecting electrode.Ignoring under the inertia force condition of grit, the migration velocity of charged grit is

$\mathrm{\ω}=\frac{q{E}_0}{6\mathrm{\π}{d}_s\mathrm{\μ}}---\left(2\right)$

From formula as can be known, under the certain situation of the physical condition of flue gas, the carrying capacity q of the migration velocity ω of charged grit and grit, the electric field strength E in dedusting zone ₀Be directly proportional, with the Stokes particle diameter d of grit _sBe inversely proportional to, μ is the aerodynamic force viscosity in the formula.Account for flue dust weight below 1% less than 0.4 μ m particle in the flue dust for coal-fired (powder) boiler; If the granule number with grit calculates, this part fine flue dust accounts for more than 40% of soot dust granule sum.For example, the meta particle diameter of 1,2,3 electric fields of certain coal power plant electric cleaner collection grit is respectively 27.1 μ m, 23.1 μ m, 14.9 μ m.The efficiency of dust collection of 3 electric fields reaches 99%, and the outlet dust concentration is 412mg/Nm ³, surpass country and allow discharge standard (50mg/Nm ³) more than 6 times.The meta particle diameter position of remaining flue dust is 4.7 μ m, and porosity only accounts for below 1% of flue dust total amount greater than 81%; And calculate about more than 40% with the grit number.For solving the big fine flue dust of this part porosity, need increase by one the 4th electric field again.The heavy efficiency of dust collection of its meter only brings up to 99.88% from 99%, has only increased by 0.8%, and the side makes and effluxes dust concentration and allow discharge standard a little less than country.From these data as can be known, how big capture fine flue dust difficulty, and this also will be a present electrostatic precipitation technology research topic anxious to be solved.

Two. dust charge electrocoagulation method

Grit is charged by realizing that with the charged particle collision grit collides the charged two kinds of mechanism that mainly contain: a kind of is that charged particle is charged with the regular collision of grit under the electric field force effect in the gas, is called electric-field charge; Another kind is that charged particle is charged with gas random motion and grit collision, is called diffusional charging.In the electric precipitation process, these two kinds of mechanism are simultaneous.The flue dust particle diameter is non-homogeneous one, and flue dust (greater than 1 μ m) is based on the electric field electric charge in the anterior electric field of electric cleaner usually; Grit in its rear portion electric field (about 0.4 μ m) is based on diffusional charging; In the electric field of electric cleaner middle part, there are two kinds of charged mechanism of while.The flue dust carrying capacity is

$q=q_d+q_k$

$=\frac{3{\mathrm{\ϵ\ϵ}}_0{\mathrm{\πd}}^2{E}_0}{\mathrm{\ϵ}+2}\·\frac{1}{1+\frac{{4\mathrm{\ϵ}}_0}{\mathrm{Nekt}}}+\frac{{2\mathrm{\π\ϵ}}_0\mathrm{dkT}}{e}\ln (1+\frac{d\stackrel{\‾}{u}{\mathrm{Ne}}^{2}t}{{8\mathrm{\ϵ}}_0\mathrm{kT}})---\left(3\right)$

Q in the formula _dElectric-field charge amount for grit; q _kDiffusional charging amount for grit; ε ₀Be permittivity of vacuum; ε is the relative dielectric constant of grit; D is the grit diameter; N is the charged particle number; K is a Boltzmann's constant; T is that grit enters the electric field time; T is the aerothermodynami temperature; The arithmetic average speed u=(8kT/m π) of ion ^0.5From formula (3) as can be known, the carrying capacity of flue dust is being restricted by N, d, because electro-coagulation, the flue dust particle diameter restricted by the charged particle concentration of gas also will.Along with carrying capacity increases, then particle diameter also increases in coacervation process slightly.As seen, the charged particle concentration of dedusting electric field is the principal element that influences the flue dust carrying capacity.

Three. the Mathematical Modeling of charged particle electrocoagulation

From efficiency of dust collection equation and grit migration velocity formula as can be known, the carrying capacity of flue dust, particle size have determined to be characterized by main electric precipitation performance with efficiency of dust collection.If can adopt the electrocoagulation method that grit is condensed into big size particles, and will obtain more electric weight, not only it can improve the efficiency of dust collection of electric cleaner, can solve simultaneously behind the electric cleaner the low problem of fine flue dust efficiency of dust collection in the level electric field again, is beneficial to again and captures fine flue dust.Recent research shows that the heat-coagulation speed of the electrocoagulation speed ratio neutral particle of submicron particle has improved 10 ²To 10 ⁴Electrocoagulation COEFFICIENT K for the grit of 1 μ m can reach 10 ^-13～10 ^-14m ³/ s, this result of study causes the extensive concern of being engaged in clarifying smoke scientific circles, also provides an effective alternative solution for researching and solving the existing problem of electric cleaner.

The key of determining the cohesion rate approximate solution is to ask the electrocoagulation coefficient.Can obtain by the diffusion equation of ion under the effect of Coulomb force.

$K=\frac{q_1{q}_2}{\mathrm{kT}{\mathrm{\ϵ}}_0}(D_1+D_2){[\exp \frac{q_1{q}_2}{4\mathrm{\πkT}{\mathrm{\ϵ}}_0(a_1+a_2)}-1]}^{-1}---\left(4\right)$

Q in the formula ₁q ₂Be respectively radius a ₁, a ₂The carried charge of grit; D ₁, D ₂Be respectively radius a ₁, a ₂The grit diffusion coefficient.Cohesion formula according to the conservation of mass and monodispersity dust before and after the cohesion comes the number concentration of approximate calculation polydispersity flue dust when t $n\left(t\right)=n_0{(1+\frac{1}{2}K{n}_{0}t)}^{-1},$ N in the formula ₀Number concentration for flue dust in the gas before condensing; T is a pool time.The meso-position radius d (t) that can try to achieve cohesion back dust according to quality before and after the cohesion is

$d\left(t\right){=[1+\frac{1}{2}K{n}_{0}t]}^{1/3}{d}_0---\left(5\right)$

D in the formula ₀Be grit meso-position radius before condensing; n ₀Be initial grit calculating concentration.From (4) formula as seen, the carrying capacity of flue dust is the main parameters of electrocoagulation coefficient, and electrocoagulation speed, cohesion back grit particle diameter all are functions of electrocoagulation coefficient.If adopt new results such as strong ionization discharge, hyperbar nonequilibrium plasma physics, can increase considerably plasma density, grit carrying capacity, and then improved electrocoagulation speed, the grit particle diameter of flue dust, impel again conversely to have increased thick grit carrying capacity and significantly increase.As seen, electrocoagulation plays stack multiplication effect to dust removal performance in dust removal process.

The carrying capacity of flue dust is the main parameters of electrocoagulation coefficient, and electrocoagulation speed, cohesion back grit particle diameter all are functions of electrocoagulation coefficient.By increasing charged particle concentration, grit carrying capacity, can improve electrocoagulation speed, the grit particle diameter of flue dust, impel again conversely and increased the charged significantly increase of thick grit.As seen, electrocoagulation plays stack multiplication effect to dust removal performance in dust removal process.

Effect of the present invention and benefit are: dust has been finished the saturated charged and particle diameter of dust and has been increased thick tens of times～hundreds of times in smoke conveying duct.This will improve the efficient of electric cleaner capture fine dust widely; Simultaneously can reduce the electric cleaner volume significantly again, reduce the consumption of steel, and then reduced a cost of investment of electric cleaner; Can reduce energy consumption again, reduce the operating cost of electric cleaner.The present invention can also be applied to become saturated charged big particle diameter dust after the charged in advance cohesion of dust of dedusters such as cloth bag, whirlpool, sedimentation, and this will increase substantially the purification efficiency of cloth bag, whirlpool, sedimentation deduster.

Description of drawings

Fig. 1 is the electric cleaner schematic diagram that the charged coacervation device of pipeline is housed.

Among Fig. 1: 1 cathode rapping transmission, 2 rain-proof cover, 3 protection tubes; 4 negative electrode big frames, 5 anode vibration bodies, 6 ash buckets; 7 steel brackets, 8 anodes, 9 negative electrodes; 10 anode vibration bodies, 11 vibrating rods, 12 electricity remove device import flue gas; 13 electricity remove device outlet flue gas, 14 smoke conveying ducts, 15 dust charge electric installations; 16 dust cohesion devices, 17 wind scoops.

Fig. 2 is charged, the coacervation device structural representation of dust in the pipeline.

Among Fig. 2: 18 earthing poles, 19 discharge electrodes, 20 high-field electrodes, the outlet flue gas of 21 flue gas input channels, 22 insulators, 23 direct currents or pulsed high voltage generator, 24 ac high voltage sources.

The specific embodiment

Be described in detail specific embodiments of the invention below in conjunction with technical scheme and accompanying drawing.

Step 1.

In the smoke conveying duct 14 of the import flue gas 12 in Fig. 1, dust charge electric installation 15 and dust cohesion device 16 are set, the dust cohesion device should be placed on the front end near electric cleaner inlet wind scoop 17, and the dust cohesion device should be placed on the front end of dust cohesion device.The treating apparatus that 1～4 cover dust is charged, condense can be set in the smoke conveying duct of electric cleaner import as required.

Step 2.

Electrode such as the discharge electrode 19 of pre-charged device 15, star linear by the circle of metal, zigzag or fishbone is formed in Fig. 2; Electrodes such as earthing pole 18 is the narrow boards types by metal, and cylindrical, oval or circle is linear are formed.The corresponding setting of discharge electrode with earthing pole, earthing pole is received on the metallic conduit wall, and the direct current of discharge electrode, pulse high-voltage by high voltage source 23 through insulators 22 power supplies.The corona streamer-discahrge takes place near discharge electrode, has formed the flue gas of the ion that contains high concentration in discharge channel.The ion of sufficient high concentration is provided for dust is charged.

Step 3.

Dust cohesion device 16 at Fig. 2 is made up of high-field electrode 20, earthing pole 18, ac high voltage source 24.High-field electrode, earthing pole are to be processed into linear, the narrow boards shape, cylindrical or oval of circle by metal.The alternation high voltage of ac high voltage source is to add on the high-field electrode by insulator 22, and earthing pole is by receiving on the metallic conduit and ground connection.Alternating electric field at high pressure electroplax and earthing pole formation 5Hz-40Hz impels charged dust to make the back and forth movement vertical with airflow direction in electric field, has increased substantially the dust cohesion probability.

Claims (6)

1. one kind in the ducted dust charge electrocoagulation of supplied flue gases method, it is characterized in that the charged of dust and aggregation process are to carry out in the gas approach of electric cleaner, make the dust that enters electric cleaner reach capacity charged and particle diameter increases to 4 times～400 times.

2. a kind of dust charge electrocoagulation method in the supplied flue gases flue according to claim 1, the dust cohesion device that it is characterized in that changed electric field is arranged in the flue of electric cleaner arrival end, the alternating electric field frequency is the alternating electric field of 5Hz-40Hz, and electric-field intensity is 5kV/cm～40kV/cm.

3. the dust charge electrocoagulation method in a kind of supplied flue gases flue according to claim 1, the dust charge electric installation that it is characterized in that direct current or pulse high-voltage corona streamer-discahrge is arranged on electricity except that in the device gas approach, and being placed on the front end of dust cohesion device, discharge electric field intensity is 5kV/cm～40kV/cm.

4. according to claim 1 and 2 a kind of in the ducted dust charge electrocoagulation of supplied flue gases method, it is characterized in that the high-field electrode of alternating electric field dust cohesion device, the shape of earthing pole are linear, the narrow boards shapes, cylindrical or oval of circle.

5. according to claim 1 or 3 described a kind of in the ducted dust charge electrocoagulation of supplied flue gases method, the discharge polar form shape that it is characterized in that the dust charge electric installation makes that circle is linear, star, zigzag or fishbone; The ground connection shape is a narrow boards shape, cylindrical, oval or round linear.

6. according to claim 2 or 3 described a kind of in the ducted dust charge electrocoagulation of supplied flue gases method, the dust charge electric installation, the coacervation device that it is characterized in that placing in the flue are 1～4 cover.

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