Introduction:
The electric tar catcher adopts three types of structures: concentric circle, tube and honeycomb. Regardless of the structure, its working principle is to apply high-voltage direct current between the metal wire and the metal tube wall (or plate) to maintain an electric field sufficient to ionize the gas and form a corona zone between the anode and cathode.
Theoretical basis:
According to the electric field theory, positive ions are adsorbed on the negatively charged corona pole, and negative ions are adsorbed on the positively charged precipitation pole; all ionized positive and negative ions fill the entire space between the corona pole and the precipitation pole. When the gas containing impurities such as tar mist droplets passes through the electric field, the impurities adsorbed negative ions and electrons move to the precipitation pole under the action of the electric field Coulomb force, and release the charged, and adsorbed on the precipitation pole, thereby achieving purification The purpose of the gas is usually called the charging phenomenon. When the amount of impurities adsorbed on the precipitation electrode increases to be greater than its adhesion, it will automatically flow down and discharge from the bottom of the electric tar catcher. The net gas will leave the upper part of the electric tar catcher and enter the next process.
Working mechanism:
Gas discharge process: Under normal circumstances, the gas is not conductive, but under the action of a high-voltage electric field, the electrons inside the gas will obtain enough energy to become free electrons and conduct electricity, which is called spontaneous ionization. Spontaneous ionization of gas is established in a non-uniform electric field. In a uniform electric field, as the voltage increases, as long as ionization occurs at any point in between, the two poles will be immediately filled with charged ions, and the gas in the entire space is broken down. At this time, the current increases sharply to form a spark discharge. In a non-uniform electric field, the strength of the electric field decreases rapidly as the distance between the two poles increases.
Choices in industry:
Depending on the polarity of the power supply, corona is divided into negative corona and positive corona. In industrial production, negative corona is mostly used, because under the same conditions, negative corona can obtain a higher current than positive corona, and its flashover voltage is also much higher than positive corona discharge.
The main factors affecting the electric catching performance:
Since there are many factors that affect the operation performance of the electric tar catcher, please inform the density, viscosity, specific resistance, gas temperature, pressure, humidity, flow velocity and impurity concentration of the dust and mist droplets when selecting the model.
Structural analysis
The three types of electric tar traps are composed of shell, precipitation electrode, corona electrode, upper and lower hangers, gas redistribution plate, steam purge tube, insulation box and feed box. The main difference is the precipitation electrode Form, arrangement of corona pole, insulation box and feed box
Structure comparison of three electric tar catchers
(1) Concentric electric tar catcher. It consists of several steel plate cylinders of different diameters, with the same vertical axis as the center of the circle, and sleeved together at the same spacing to form the precipitation pole. Due to the homogeneity between the corona poles. The electric field will appear small holes, that is, field strength caves. It is easy to cause the gas to be short-circuited in the cave and reduce the trapping effect. At the same time, the manufacturing accuracy of the concentric circular electric tar trap is high, and the installation and debugging are extremely strict. It is easier to make the concentricity, horizontality and verticality in manufacturing, installation and transportation. Changes in the temperature will cause discharge between the cathode and anode or other components. It is difficult to achieve the required voltage, which directly affects the tar collection efficiency, and it is also easy to break the electric porcelain bottle. Because the voltage change value of the field strength is 400V/mm, even if there is a deviation of 1mm between the cathode and anode, the change value of the field strength voltage can be as high as 400V. The concentric electric tar catcher has the advantages of large flow area, low gas flow rate and low steel consumption.
(2) Tubular electric tar catcher. Since the steel pipe and the corona wire form an electric field separately, the field strength voltage depends on the radius of the steel pipe, and its value is 400R. Since the tube-type electric tar trap forms an electric field with equal pole spacing in each tube section, and there is a vacancy between the tubes, the holes are blocked by the tube sheet blind area, which reduces the use of the effective space in the cylinder Rate, reducing the cross-sectional area of the purification channel. This type of electric tar catcher consumes a large amount of steel, but it is widely used in large and medium-sized gas purification plants due to its advantages of easy manufacturing, equipolar spacing electric fields, easy availability of materials, and convenient installation and debugging.
(3) Honeycomb electric tar catcher. The structure of the honeycomb type and the tube type is the same, which is to change the cross section of the channel from a circle to a regular hexagon. Two adjacent regular hexagons share one side, that is, the six sides of the regular hexagon in the middle are shared by the six regular hexagons surrounding it. Honeycomb panels made of 2~3mm steel plates can meet the requirements of process and mechanical strength. Because the honeycomb electric tar catcher has the advantages of compact and reasonable structure, no electric field cavitation, high effective space utilization, light weight, low steel consumption and good trapping characteristics, but it is difficult to manufacture. It is easy to produce shortcomings such as errors during transportation and installation. With the improvement of equipment manufacturing process level, the advantages of honeycomb electric tar catcher will be more and more valued by people, and it will gradually replace concentric and tube electric tar catchers.
structure type
The electric tar catcher is the main equipment for gas purification. Its function is to remove the tar and dust from the washed and cooled gas and send it to the next process.
Brief structure
The electric tar catcher is composed of the main body of the electric tar catcher and the rectifying equipment supplying high-voltage direct current. The electric tar catcher is composed of four parts: cylinder, precipitation electrode, corona electrode and electrical insulation box.
Barrel
The barrel is cylindrical (the inner diameter is determined by the gas flow), and has a head. The upper part of the barrel is equipped with an air outlet pipe, the lower part is equipped with an air inlet pipe, and two manholes and an explosion-proof valve.
Precipitation tube bundle
The precipitation pole tube bundle is composed of the tube bundle, and communicates with the upper and lower parts of the barrel.
Corona electrode
The corona electrode device is suspended in an insulating box at the top by a suspender, which is composed of an upper suspender and a tie rod, upper and lower frames, a corona electrode wire, and a weight.
Electrical insulation box
The insulation box is set on the top of the cylinder, which is a circular box suspending the corona electrode device. The interior is equipped with suspension bracket, high-pressure porcelain bottle and heating jacket.
Technical parameters of electric tar catcher
Name | C-9 | C12 | C-21 | C-25 | C-37 | C-49 | C-61 | C-72 | C-76 | C-97 | C-140 |
Be applicable | Bituminous coal, anthracite, coke | ||||||||||
Outer diameter（mm) | 1280 | 1620 | 1820 | 2020 | 2420 | 2820 | 2860 | 3120 | 3300 | 3820 | 4200 |
Barrel height（mm) | 6800 | 7400 | 8940 | 9000 | 9000 | 9000 | 9000 | 9000 | 9000 | 9000 | 9000 |
Corona pole number | 9 | 12 | 21 | 25 | 37 | 49 | 61 | 72 | 76 | 97 | 140 |
Precipitation pole number | 9 | 12 | 21 | 25 | 37 | 49 | 61 | 72 | 76 | 97 | 140 |
Precipitation pole inner diameter（mm) | 250 | 250 | 250 | 250 | 250 | 250 | 250 | 250 | 250 | 250 | 250 |
Effective cross-sectional area（m2) | 0.48 | 0.6 | 1.03 | 1.2 | 1.8 | 2.1 | 2.99 | 3.53 | 3.73 | 4.76 | 6.89 |
Processing power(nm/h) | 1050-1750 | 1375-2290 | 2100-3800 | 3000-5000 | 4300-7050 | 5100-9040 | 6440-12700 | 7600-15000 | 8020- 15830 | 10200-17200 | 14800 -24700 |
Operating temperature℃ | 80-110 | ||||||||||
Operating Voltage（kV) | 45-60 | ||||||||||
Maintenance specifications
1. When repairing the electric catch, the high-voltage power supply must be turned off, the electric gate must be pulled down, and the warning sign should be hung. Use a ground rod to discharge the output end of the high-voltage power supply; after discharging, connect the ground rod to the output end of the high-voltage power transformer to form a ground short-circuit protection.
2. For three months of operation, the electric catcher should be stopped and cleaned with steam once, and the insulated porcelain bottles and wall bushings in the insulation box and feeder box should be scrubbed once, and brushed with gauze soaked in benzene or alcohol and dried during cleaning.
3. When entering the electric trap for inspection and maintenance, in addition to the first operation, steam purge and replacement should be performed to block the blind plate. The steps are as follows:
1. Power outage, grounding, and hanging warning signs are the same as the first.
2. Close the inlet and outlet valves of the electric catcher.
3. Open the valve of the bleeder first, and then open the upper purge steam valve. After the bleeder discharges the steam, open the lower purge steam valve. After 15 minutes of purge, turn off the purge first, then close the purge valve.
4. After the cylinder of the electric catch is cooled and cooled down, insert an iron blind plate at the connection between the inlet and outlet valves of the electric catch and the electric catch body.
5. After the blind plate is installed, perform a second steam purge, the purge time is 30 minutes (the operation sequence is the same as Article 3 above).
6. Turn off the steam purge, the cylinder of the electric catcher cools, and after cooling down, open the upper and lower manhole covers of the electric catcher.
Note:
(1) For this operation, pay attention to the valve leakage and the steam cooling water of the discharge pipe to prevent burns.
(2) Open the steam valve when the temperature of the body of the electric catcher is relatively low, it should be opened a little at the beginning, so that the temperature of the body can be evenly raised to prevent rapid cooling and rapid heating, causing deformation and cracking of the weld of the cylinder.
7. Perform a blast test 24 hours after the upper and lower manhole covers are opened. Use a blasting sampler to sample in the electric trap at the upper manhole of the electric trap and carry out a sampling test. Only after passing the test, can you enter the electric trap for internal inspection and maintenance.
4. Inspection items in the electric trap:
1. The coking condition inside the porcelain bottle is cleaned and kept clean immediately.
2. The tar adhesion of the corona pole line and the precipitation pole tube. If too much tar on the corona line will reduce the decoking efficiency of the electric catch, the corona line should be handled or replaced in time.
3. Check whether the surface of the precipitation electrode tube is protruding or easily cause breakdown discharge, and deal with it immediately.
4. Check whether the lower air distribution plate is blocked by tar, and clean it with steam.
5. Check whether the corona wire is broken or not, and whether the weight falls off, and deal with it in time.
6. Whether the corona polar line is located in the center of the precipitation tube, the eccentric corona polar line and bending deformation should be dealt with immediately.
5. After the inspection and maintenance work of the electric catch is completed, an empty field test shall be carried out.
Empty field test: The operation of the high voltage is the same as that of the operation, and the voltage is gradually increased gradually. If the flashover discharge is captured in the electric trap, the discharge point should be checked, and the power failure should be dealt with. After the treatment, continue the test until the voltage is raised to 40-55KV (no Flashover discharge phenomenon).
6. Maintenance personnel must ensure that they have good ventilation facilities when entering the electric trap for inspection and maintenance. If necessary, they must wear gas masks or oxygen masks; and they must have full-time safety guardians to carry out safety supervision.
7. During the operation and maintenance period of the electric catcher, the fire protection work should be done well so that the fire protection facilities are in place and intact to prevent accidents.
Trapping mechanism
1. When replacing the fuse, the fusing current should match the current of the loop;
2. Disconnect the power, check whether the rack of the control cabinet has reliable grounding, and make the grounding resistance not greater than 4Ω;
3. There are voltages of different natures on the control cabinet (DC 110V; AC single-phase 220V; three-phase AC), and the circuit must be distinguished during maintenance to prevent short-circuit accidents;
4. All electrical switches on the control cabinet should be flexible and reliable, without significant noise, and there should be no loosening of the connecting wire knots and terminals, and there should be no breakage of the steel wire at the moving contact connecting wire knots;
5. Use a soft brush or blower to clear the dust accumulation of the panel plug-in and all the electromagnetic switch parts, and check the status of the electrical switch contacts in the control cabinet, the contact status, the insulation of the coil surface and the reliability of the movement of the mechanical components.
