JPH01299647A - Multiple electric field-type electrostatic fluocculator - Google Patents

Abstract

PURPOSE:To flocculate submicron particles to particles having >=1 micron size and to increase dust collecting efficiency by impressing an AC-superposed DC high voltage between plural plate electrodes of a dust collector provided on the downstream side of the charging equipment and plural rod-shaped electrodes. CONSTITUTION:An AC-superposed DC high voltage is impressed between the plate electrode 4 and rod-shaped electrode 3 arranged in parallel with a current of a dust-contg. fluid, and a low-electric-field region 7 surrounded with a high- electric-field region 6 is formed in the flowing direction. The conductive particles of carbon, etc., are polarized in the electric field, and collected at a strong- electric-field part. Meanwhile, the nonconductive particles of fly ash, etc., previously charged tend to be collected at a weak-electric-field part, and simultaneously oscillated by the AC electric filed. Since the collision flocculation due to the high electric field and the electric field flocculation due to the nonuniform high electric field are drastically promoted, the submicron particles flowing between the electrodes 3 and 4 are flocculated and coarsened, and flocculation is further accelerated by the exerted Coulomb's force.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an electrostatic concentrator that uses electrostatic force to aggregate and coarsen fine particles in a fluid. More specifically, the present invention provides a multi-layer EI electric field type electrostatic li which condenses submicron particles to a size of microns or more that is easy to electrostatically collect.
Concerning a collection device.

(Prior technology) Large electrostatic precipitators have traditionally been used to treat the exhaust gas of coal combustion, where the gas flow rate is extremely high and the amount of dust contained therein is large. Since the main material is fly ash, the conventional flocculation equipment has high dust collection efficiency and there is little need for agglomeration and coarsening.
A simple structure in which the voltage applied to parallel plate electrodes is AC voltage or DC voltage is common.

(Problem to be solved by the invention) However, in recent years, in order to increase the energy recovery rate of resources and convert them into electrical energy as much as possible, there has been a trend toward burning coal by crushing it into even finer pieces. A situation has arisen in which a large amount of submicron fly ash and carbon, which had not been prepared before, are included.

A large amount of two types of submicron particles with very different electrical properties, non-conductive fly ash with high electrical resistance and conductive carbon particles with extremely low electrical resistance, coexist and a large gas flow rate. When it flows in with
The problem arises that the dust collection rate is significantly reduced due to the insufficient charge of the fly ash particles and the jumping movement of the carbon particles. In particular, in the case of carbon fine particles, in conventional agglomeration devices, they sometimes adhere and accumulate on the dust collecting plate at ground potential, but the electric charge is discharged through the dust collecting plate at ground potential and the electric attraction is lost.
There is a problem that it cannot be collected even on an S dust plate and that the stability of aggregated particles is poor.

This change in the properties of the exhaust gas may cause a problem of a significant decrease in blood collection efficiency of submicron aerosols contained in large amounts in the exhaust gas after pulverized coal combustion.

SUMMARY OF THE INVENTION An object of the present invention is to provide an electrostatic agglomeration device that aggregates submicron particles and coarsens them into micron or larger particles that are easily converted to 4A dust. In addition, the present invention can also be used for two types of dust-containing fluids that have large amounts of electrical properties and that are contained in a large amount in a large amount of dust-containing fluid.
The purpose of this invention is to provide an electrostatic collector capable of simultaneously coarsening more than one species of submicron particles.

(Means for Solving the Problems) In order to achieve the above object, the multipole electric field type electrostatic precipitator of the present invention has a plurality of opposing flat plate electrodes disposed downstream fl11 of the charging device and a plurality of plate electrodes disposed between them. A rod-shaped electrode is arranged parallel to the flow of the dust-containing fluid, and a high DC voltage with AC superimposition is applied between the rod-shaped electrode and the plate electrode.

(Function) Therefore, if the electrode is charged with a DC high voltage with AC superimposition, an electric field is formed in the low electric field area surrounded by the high electric field area along the flow direction of the dust-containing fluid, and conductive particles such as carbon Non-conductive particles such as fly ash, which are polarized in the electric field and have been given a charge in advance in areas where the electric field is strong, tend to gather in the area where the electric field is weak, that is, surrounded by the high electric field area and the low electric field area. . At the same time, since it is shaken by an alternating electric field, fly ash tends to collect in the low electric field area at the center of the electric field. For this reason, collision aggregation due to a high electric field and electric field aggregation due to an uneven high electric field are dramatically promoted, and while submicron particles flow between '84ii, they aggregate and become coarse. Furthermore, on the downstream side, the coarsened charged fly ash particles and carbon particles collide due to the Coulomb force between them, breaking free from the control of the electric lines of force, and aggregation is further promoted. At the same time, it also exhibits am-collecting ability due to the action of the direct current field.

(Example) Hereinafter, the configuration of the present invention will be described in detail based on an example shown in the drawings.

The multipole electric field type "11 collector 10 of the present invention has a charging device 1 (which can also be used as an existing upstream electrostatic precipitator) that charges submicron fine particles in advance, and a charging device 1 that precharges submicron fine particles. A plurality of rod-shaped poles 3A, 3B,...
- and a plurality of flat plate types i4 facing each other so as to sandwich them are arranged parallel to the flow of the dust-containing fluid, and the electrode rods 3A, 3B,
... and the flat plate electrode 4 are charged with a DC high voltage with AC superimposition, and a dust-containing fluid is caused to flow between the electrodes.

For example, as shown in FIG. 1, two flat plate electrodes 4 at ground potential are placed parallel to the flow of the dust-containing fluid, and two wooden rod-shaped electrodes 3A, 3B are arranged one above the other between them. A negative high DC voltage superimposed on an AC voltage is applied. Electrode 3A.

3B is for controlling only the electric field, and a rod-like object having a thickness that does not cause corona discharge, for example, in this embodiment, a cylindrical shape is adopted. Further, the flat plate electrode 4 is installed in a duct 5 in which a dust-containing fluid such as pulverized coal combustion exhaust gas flows, facing in parallel to the flow.Normally, this flat plate electrode 4 is constructed separately from the duct 5. However, depending on the case, it is also possible to use the duct 5 itself as a flat electrode.

The embodiment shown in FIG. 1 includes two rod-shaped electrodes 3 and two flat electrodes 4.
This is an example of a four-electrode electric field type electrostatic condensation device configured with a low electric field region surrounded by a high electric field region 6 due to the repulsion of electric lines of force coming out from the flat plate electrode 4 toward the central rod-shaped electrodes 3A and 3B. Since 7 is widely present in the center, it is suitable for agglomeration when a large proportion of charged fly ash particles, ie, nonconductor particles, are contained in the dust-containing fluid. When the flow rate or amount of dust contained in the dust-containing fluid is large, it is preferable to install several sets of this aI collection device in the vertical and horizontal directions of the flow path. Normally, several layers are provided continuously in the vertical and horizontal directions of 1. In FIG. 1, the flow direction of the dust-containing fluid is perpendicular to the plane of the paper.

Further, FIG. 2 shows a five-principal electric field type electrostatic concentrator 11 consisting of three rod-shaped poles 3A, 3B, and 3C and two flat electrodes 4. This device consists of two devices installed parallel to the gas flow and facing each other.
Three rod-shaped electrodes 3A, 3L3, 3C are arranged at regular intervals between the flat plate electrodes 4 in parallel to the gas flow direction,
The central cylindrical electrode 3C and the flat plate 11i4 are at ground potential,
The rod-shaped electrodes 3A and 3B at both ends are charged with a negative DC high voltage superimposed with an AC voltage. Therefore, the electric field extends from the central electrode 3C to the electrodes 3A at both ends.

Electric lines of force toward 3B and electric current IJi at both ends from the flat plate electrode 4
High electric field region 1! The distribution is such that the low electric field region 7 surrounded by A6 is divided into left and right and narrowly formed.

In this case, since the high-intensity region 6 is wider than in the above-mentioned four-principal type, it is suitable for agglomeration from a fluid containing a large proportion of conductive particles, such as a conductive carphone. In the case of this 5-main electrode type, three rod-shaped electrodes 3A, 38.3C and two flat plate type [4
A set of 11 concentrators is formed, and like the four electrodes in FIG. 1, it is possible to set many layers continuously in the vertical and horizontal directions as shown by the imaginary lines. In this case, it is also possible to share a flat plate electrode or a rod-shaped electrode.

These coagulation devices 10 may be incorporated as an intermediate stage of a known large-scale electrostatic precipitator in which several stages of dust collection units are connected, or they may be configured as a coagulation dust collector that is independently equipped with a charging device and a dust collection means. For example, as shown in Figure 3, in a case where a dust collection unit containing a discharge electrode and a collection electrode as one set is connected in several stages depending on the processing gas area, the main stage is installed in the middle stage. The agglomerating device 10 of the present invention is installed, and after large-diameter dust is collected in advance in the electrostatic precipitator l as a charging device in the preceding stage, the submicron dust is collected and coarsened in the aggregating device 10 of the present invention. The particles are collected in an electric precipitator 2 as a subsequent dust collecting means. In this case, since the submicron particles of nonconductor such as fly ash are charged in the pre-stage electrostatic precipitator 1, the electric field in the aggregation device 10 causes the particles to collide and become coarse. Further, conductor particles such as carbon are polarized in the electric field, aS in the strong electric field 6, increasing the chance of collision, and becoming coarse. Furthermore, Ij! l! Fly ash and carbon, which are separated into the electric field region 6 and the low electric field region 7 and have different electrical properties, become coarser as they flow downstream, increasing the Coulomb force, and the Coulomb force of each other allows them to escape from the control of the electric lines of force. They collide and grow into stable IS-like coarse particles. Then, the dust is collected by the electric precipitator 2 in the latter stage.

We also have our own charging device and dust collection means! 'i, 01il
It is also possible to construct a single electrostatic coagulation dust collecting unit. In this case, a small-scale charging device/discharge electrode is placed on the upstream side of the flat plate electrode and the rod-shaped electrode, and a dust collection electrode is provided on the downstream side to collect coarse submicron particles. Such embodiments are effective when applied to purification of fluids mainly composed of submicron particles, such as air purifiers and clean room air purification devices. In addition, since a negative DC high voltage is applied to the rod-shaped electrode, it has a dust collection effect.

In this example, the exhaust gas from pulverized coal combustion is mainly used as the dust-containing fluid, but other gases as well as liquids containing submicron particle dust, especially low-viscosity liquids, may be used. is also applicable.

(Effects of the Invention) As is clear from the above description, the electrostatic condensation device of the present invention continuously forms a strong electric field region and a low electric field region surrounded by the strong electric field region in the flow direction of the aluminium-containing fluid, An alternating current electric field is applied to nonconductor particles that have been charged in advance and conductor particles that are polarized in an electric field, and are separated into a strong electric field region and a low electric field region by the influence of electric lines of force, and are brought together to collide with each other and coagulate. On the other hand, as these become coarser, the Coulomb force possessed by each other causes them to escape from the control of the electric lines of force and cohere, so 2s! with different electrical properties! The above submicron particles can be collected efficiently at the same time. Of course, even when only nonconducting particles such as fly ash are collected, the flocculation effect is not inferior, so the dust collection efficiency is improved. An example is shown in FIG. 4. From this figure, it can be seen that the dust collection effect for particles of 1 or less is significantly different when the aggregation device is activated and when it is not activated. That is, it can be seen from this figure that when the agglomeration device operates, the proportion of particles with a particle size of 11JI11 or less decreases, and there is an aggregation effect. Looking at the weight percentage of particles with a particle size of IIJ11 or less, when the agglomeration device was not in operation, it reached 10% of the total, but when the device was in operation, it decreased to 2%. It should be noted that the fJ axis represents the weight distribution integrated from particles with a large particle size with respect to the particle size on the horizontal axis.

4. Explanation of drawings Figures 1 and 2 show an example of a multi-pole electric field type electrostatic condensation device of the present invention, and Figure 1 shows an example of a 4-plane electric field type electrostatic condensation device. Schematic Principle Diagram: FIG. 2 is a schematic principle diagram showing an example of a five-electrode electric field type electrostatic 11 concentrator. FIG. 3 shows the multi-71Ltf! of the present invention! A schematic diagram of the case where an electric field type static @ agglomeration device is incorporated into a large precipitator. Figure 4 shows the electric field collector a with and without the 4-electrode electric field type electrostatic concentrator in Figure 1 activated. 2 is a graph showing the particle size distribution of aerosol particles at the exit of 2iS.

DESCRIPTION OF SYMBOLS 1... Charging device, 2... Dust collector, 3... Rod-shaped electrode, 4... Flat electrode, 5... Duct, 6... Strong electric field region, 7... Low electric field region .

Patent employee: Central Research Institute of Electric Power Industry, Figure 4 Particle diameter (-)

Claims (1)

[Claims] On the downstream side of the charging device, a plurality of opposing flat plate electrodes and a plurality of rod-shaped electrodes arranged between them are arranged parallel to the flow of the dust-containing fluid, and a superimposed alternating current is generated between the rod-shaped electrodes and the flat plate electrode. A multipole electric field type electrostatic condensation device that applies a high DC voltage.