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"INTECH GmbH"
We are interested in cooperation with the manufacturers of electrostatic precipitators, who are looking for an official and reliable distributor to deal with supply & delivery of their equipment to the industrial plants in Russia.
The company’s top management and sales team are well acquainted with the Russian market, its mentality and laws; they also understand industrial specifics of the financial and economic activities of the Russian customers. All our sales managers have a large customer database, extensive experience of successful sales and well-established connections with the potential buyers of your electrostatic precipitators. This allows our managers to promptly set out the most promising directions for promotion and to ensure a rapid entry of the products into the promising Russian market. Our employees, who are fluent in English and German, are focused on working at the international market with the supplies of foreign equipment.
Our team of experienced engineers, who can handle the most serious technical problems, constantly keeps in touch with the Russian customers, holds meetings and delivers presentations regarding the latest achievements of our manufacturing partners. They point out the engineering challenges and actively communicate with all the departments at Russian plants. That is why the specifics of doing a business in the Russian Federation are well-known to us, and we also know the equipment of the local industrial plants and their up-to-date modernization needs.
Once we become your authorized representative in Russia, our marketing staff will carry out a market research in order to check the demand for electrostatic precipitators, will submit a market overview for electrostatic precipitators that you offer and evaluate the needs for this type of equipment at local plants. Our specialists will also estimate the potential and capacity of this market at local industrial plants. Our IT-team will start developing a website for your products in Russian. Our experts will assess the conformity between your electrostatic precipitators and customer needs as well as analyze the common reaction to the new goods in general. We will look into the categories of potential customers, and pick out the largest and the most promising plants.
Upon becoming your authorized agent on the territory of Russia, ‘Intech GmbH’ LLC (ООО «Интех ГмбХ»), will obtain certificates, if required, for a batch of the goods, for various types of electrostatic precipitators in compliance with Russian standards. We can also arrange the inspection in order to obtain TR TS 010 and TR TS 012 Certificates. These certificates provides permission to operate your equipment at all industrial plants of the EAEU countries (Russia, Kazakhstan, Belarus, Armenia, Kyrgyzstan), including the hazardous industrial facilities. Our company is eager to assist in issuing Technical Passports for electrostatic precipitators as per Russian and other EAEU countries’ requirements.
Our engineering company ‘Intech GmbH’ LLC (ООО «Интех ГмбХ»), collaborates with several Russian design institutes in various industrial segments, which allows us to conduct preliminary design as well as subsequent design works according to the standards, construction rules and regulations that are applicable in Russia and other CIS countries. It also enables us to include your electrostatic precipitators into the future projects.
The Company has its own logistics department that can provide packing service, handling as well as the most efficient and cost effective mode of transportation of the goods (incl. over dimensional and overweight goods). The goods can be delivered on DAP or DDP-customer’s warehouse basis in full compliance with all the relevant regulations and requirements that are applicable on the Russian market.
Our company has its own certified specialists who will carry out installation supervision and commissioning of the delivered equipment, as well as further guarantee and post-guarantee maintenance of electrostatic precipitators. They will also provide necessary training and guidance for the customer’s personnel.
Gas cleaning by electrical precipitation. Advantages and principle of operation
Electrostatic precipitators are composed of the following key elements:
The advantages of gas cleaning by electrical precipitation method:
To understand the principle of operation of electrostatic precipitator, first, it is necessary to consider the electric circuit. It is composed of such elements as a current source and two metal plates, located parallel to each other and separated by air. This device is nothing else than the air condenser; however electric current will not flow in such a circuit because the air between the plates, like other gases, is non-conducting.
However, as soon as the required difference of potential is applied to metal plates, galvanometer connected to this circuit will record the electric current flow due to the ionization of air between the plates.
As for the ionization of gas between the two electrodes, it may occur in two cases:
For gas cleaning by electrical precipitation, only the second method of ionization is applied, i.e. self-maintained ionization.
If one starts to increase the potential difference between metal plates, it will reach a critical point at some time (breakdown voltage for air layer), air will be "broken" and electric current intensity will increase dramatically in the electric circuit, and the spark will appear between the metal plates. This spark is called a self-maintaining gas discharge.
Voltage-carrying air molecules begin to split into positively and negatively charged ions and electrons. Ions move to the oppositely charged electrodes under the influence of the electrical field. With the increase in strength of the electric field, velocity and kinetic energy of ions and electrons begins to gradually increase. When their velocity reaches a critical value and slightly exceeds it, they split all the neutral molecules they meet. That is how the ionization of all gas occurs in between the two electrodes.
When a significant number of ions is formed simultaneously between the plates located parallel to each other, the strength of the electric current begins to increase and a spark discharge occurs.
Due to the fact that air molecules get pulses produced by ions moving in a certain direction, so-called "collision" ionization is accompanied by a rather intense air movement.
A self-maintained gas ionization in the procedure of gas cleaning by electrical precipitation is carried out by application of high voltage to electrodes. When using this method of ionization, it is necessary to achieve break-down of gas layer only at a certain interval between the two electrodes. It is necessary that some gas shall remain not broken-down and serve as a kind of insulation protecting parallel electrodes from short-circuit, spark or arc (preventing a dielectric breakdown).
Such "isolation" is created by adjusting the shape of electrodes and the distance between them in accordance with voltage. It should be noted that the electrodes in the form of two parallel planes are not suitable in this case, since the same voltage will always be between them at any point in the field, i.e. the field will always be uniform. When difference of potentials between one plate electrode and the other plate electrode reaches the breakdown voltage, all the air will be broken-down and a spark discharge will occur; however, no air ionization will occur as the field is uniform.
The non-uniform field can only occur between the electrodes having the form of concentric cylinders (of pipe and wire) or a plane and cylinder (plate and wire). Field intensity is so high directly near the wire that ions and electrons are capable of ionization of neutral molecules. However, with distance from the wire, the field intensity and the velocity of the ions are reduced so that the collision ionization simply becomes unreal.
The ratio between the radius of the pipe (R) and the radius of the wire (r) must be determined to avoid a spark between two cylindrical electrodes. Calculations showed that gas ionization without short-circuit is possible when R/r is 2.72 or over.
A weak glow around the wire or a so called "corona" is the main visible sign of ion discharge. This phenomenon is called a corona discharge. Faint glow is constantly accompanied by a distinctive sound: it may be crackling or hissing.
The wire (electrode) around which a glow discharge occurs is called a corona electrode. "Corona" can be either positive or negative depending on the pole to which the wire is connected. For gas cleaning by electrical precipitation, only the second variant is used, i.e. negative "corona". Although it is less uniform than the positive one, it is able to provide a higher critical difference of potential.
The process of dust precipitation in an electrostatic precipitator is rather complicated. Only a very small portion of dust (mist) that falls in the area of "corona" is deposited on the corona wire. Most of gas-suspended dust particles, having received a negative electric charge, start to move towards the collecting electrodes and give them their charge. Conductivity of dust particles is a very important indicator.
When highly conductive dust particles are collected, their layer deposited on the electrode receives a charge of the same sign and is pushed into the gas flow. At the same time, some part of dust can be simply taken out of the electrostatic precipitator.
If dust particles are non-conductive, they are pressed against the electrode by the electric field to form a quite dense layer thereon.
A dust layer charged negatively and deposited on the electrodes simply starts to push off particles with the same sign, approaching it, i.e. it seems to react against the main electric field.
Potential difference created in dust pores can reach a critical level and exceed it, causing corona effect of the air in these pores. As a result, positive ions are formed to neutralize the negative dust particles. This phenomenon is called back "corona". It sharply and greatly reduces the efficiency of dust collection.
To eliminate the adverse effect of dust deposited on the electrodes, these electrodes are thoroughly shaken or conductivity of this dust is increased by moistening it with water by liquid spraying into hot gas before it enters the electrostatic precipitator.
- by the purpose
All electrostatic precipitators are divided into two main groups according their purpose:
1. dry electrostatic precipitators;
2. wet electrostatic precipitators.
Three types of dry electrostatic precipitators are available: devices for conductive dust collecting, devices for non-conductive dust collecting, and dry electrostatic precipitators for hot gas cleaning. Wet electrostatic precipitators are divided into two categories: the first one includes devices for acid mists precipitation, the second one includes devices for wet precipitation of resins.
- by the form of collecting electrodes
All electrostatic precipitators are divided into two main groups depending on the form of collecting electrodes:
Pipe electrostatic precipitators. Description and design
Circular or hexagonal metal pipes are used as collecting electrodes in electrostatic precipitators of the first group (pipe electrostatic precipitators), while wires tightened along the pipe axis are used as corona electrodes.
Pipes usually have a length of 3000 to 4000 mm, and their diameter is within the range of 150 to 300 millimeters. Neutral gas is usually cleaned in electrostatic precipitators having steel pipes. Acidic gases are cleaned in electrostatic precipitators with lead pipes.
The pipe electrostatic precipitator consists of the following elements: inlet and outlet gas flues, pipe collecting and corona electrodes, a frame, insulators, a lateral box, rapping mechanism and cone bottom.
This is the principle of operation of this device. Gas subject to cleaning first enters the chamber of electrostatic precipitator from below through the gas flue. Then, it goes up, passes through an electric field between collecting electrodes and exits through the outlet gas flue located on the top. Corona electrodes made of 1.5 to 2 mm wire and located along the pipe axis are suspended from a common frame which rests on insulators. The insulators are installed in lateral boxes to avoid pollution. Dust particles deposited on the inside of pipes are shaken off by a rapping mechanism located above the pipes and fall into a cone bottom.
It seemed to be better to enter gas through pipes from the bottom upwards for the best deposition of particles, but in practice it is entered from below; in this case, gas gets to insulators, being already purified. This prevents contamination of insulators. Gas moves alternately in multi-chamber electrostatic precipitators: from the bottom upwards, from the top downwards and thus passes successively through all chambers.
Plate-type electrostatic precipitators. Description and design
Several surfaces located in parallel with a series of corona wires suspended between them, serve as collecting electrodes in plate-type electrostatic precipitators. Collecting electrodes are usually made of smooth metal sheets. However, in some cases they may be made of corrugated sheets or rods or grids, which are put on the frames and suspended in close proximity to each other.
Plate-type electrostatic precipitators are made in two variants: they can be either horizontal or vertical. The height of collecting electrodes in horizontal electrostatic precipitators is between 3 and 18 meters, and in vertical ones, it is up to 15 meters.
The vertical plate-type electrostatic precipitator consists of the following elements: inlet and outlet gas flues, a chamber, and plate-type collecting and corona electrodes.
Here is the principle of operation of such electrostatic precipitator. Gas enters the chamber of the electrostatic precipitator through the inlet gas flue, passes around its baffle, passes between the plate-type collecting electrodes from the bottom upwards and appears in the field of corona electrodes, and then it is discharged out of the device through the outlet gas flue. Electrodes in the electrostatic precipitator are freely suspended from the upper part of the chamber. Dust is deposited on the plates of collecting electrodes. When they are shaken, it falls into the lower part of the chamber, and then it is removed from the device.
Such factors as all properties of cleaned gas (chemical composition, temperature, pressure and humidity), required quality of its cleaning, as well as properties of dispersed phase contained in a gas (concentration, dispersivity and electrical conductivity), etc. are decisive when choosing the design of electrostatic precipitator.
Pipe electrostatic precipitators have some advantages over plate-type electrostatic precipitators. Gas is distributed better and creates a more effective electric field for improved gas cleaning or increased rate of gas flow, i.e. it allows to increase the performance of the device.
However pipe electrostatic precipitators, besides their advantages, have some drawbacks. They are pretty difficult to install, and corona electrodes shaking causes difficulties; moreover, these electrodes often swing. The energy consumption per unit of the wires length in the pipe electrostatic precipitator somewhat exceeds that one of any of the plate-type electrostatic precipitators.
Pipe electrostatic precipitators are typically used when complete cleaning of gas is required or the deposition conditions are more difficult due to specific features or properties of gas or dust. They are also when electrode shaking is not required (for example, during deposition of liquid from mist).
Plate-type electrostatic precipitators have the following advantages: easy installation, easy electrodes shaking, the chamber performance can be increased (of course, to a certain degree) without its initial size increase.
Vertical plate-type electrostatic precipitator
The design of a vertical plate-type two-chamber electrostatic precipitator is composed of the following elements: inlet and outlet gas flues, a vertical chamber, collecting and corona electrodes, chambers, a frame, dust collector, valve and distribution grid.
Chambers of this electrostatic precipitator are made of bricks and dust collectors are made of a durable material such as reinforced concrete, which is lined with acid-resistant bricks from the inside.
Thin plates made of steel wire only 3 mm thick are used as collecting electrodes in this vertical plate-type two-chamber electrostatic precipitator. These plates are suspended at the distance of 250 millimeters from each other. Corona electrodes are usually made of thin nickel-chromium wire (2 mm) or of fechral wire of the same diameter, tensioned between the upper and the lower frame at the distance of 200 mm from each other. Both frames connected with rods are suspended by rod and traverse from the outer porcelain insulators. Electrodes are shaken manually using a special impact device. It should be noted that corona electrodes in this device are shaken by hitting the frame every two hours, only after electric current is switched off.
Cleaned sulfur dioxide gas first enters the chamber through the inlet gas flue; then, having passed through the distribution grids, it goes in two chambers connected in parallel.
Grids are made rotating in order to clean them from dust. They are used for gas distribution all over the cross section of electrostatic precipitator.
After passing through electric field and gates similar to those installed at the device’s inlet, gas enters the chamber, and then it is discharged through the outlet gas flue of the electrostatic precipitator.
The so-called butterfly valves, which shut off gas entry for the time of electrodes shaking, are located under the input gate.
Dust collected on the electrodes is shaken off and falls into dust collectors from which it is periodically discharged.
Vertical plate-type two-chamber electrostatic precipitators used to clean furnace gases in sulfuric production can lower dust content down to 0.2 g per cubic meter at gas velocity of 0.7 meters per second.
Horizontal plate-type electrostatic precipitator
The design of the horizontal plate-type electrostatic precipitator serving to collect dust particles from high temperature gases (400 to 450 degrees) consists of the following elements: inlet and outlet gas flues, chambers, collecting and corona electrodes, a beam, starting fan, and insulator box.
The electrodes suspended close together to prevent their vibrations are usually produced from quite thick (8 mm in diameter) steel bars.
With the gas flow moving in the horizontal direction and passing sequentially three electric fields (in three chambers of the device), horizontal plate-type electrostatic precipitators offer the highest quality of gas cleaning.
Wet electrostatic precipitators, which are able to perform a complete cleaning of gases from fine dust and mist, are applied in the modern production of sulfuric acid by contact method.
Typically, two devices located one after the other are installed at the production facility. Gas, after passing the first electrostatic precipitator, is moistened in a so-called intermediate tower which is cooled by a weak solution of sulfuric acid. Complete precipitation of dust particles occurs in the second device due to moisture condensation on dust particles.
Design of wet electrostatic precipitators consists of a rectangular chamber made of natural beschtaunite or acid-resistant andesite, having two identical sections separated by a partition. Each of these chamber sections has its own gas inlet and high-voltage power supply.
Collecting electrodes suspended from chambers arches, made of two halves of ferrosilid or graphite-carbon pipes, are used in this electrostatic precipitator. Ferrosilid pipes have several advantages over graphite-carbon pipes, as they are more stable, their height is 3500-4000 mm and their diameter is in the range from 250 to 300 millimeters.
In this device, corona electrodes are suspended from the beam. The beam itself is suspended from strings of insulators which are separated from the chamber by oil seals. These seals are able to operate without oil if natural air suction is created through the openings in the insulator box. An arch-shaped cover of the device is usually made of bricks or of such a material as ferrosilid.
Air is continuously blown by fan into the insulator box during start-up of the wet electrostatic precipitator to eliminate acid mist condensation on the insulators when passing through the device.
Multistage electrostatic precipitators consist of several sections of collecting electrodes, which are connected in series. Thus, several electric fields function in multistage electrostatic precipitators, providing a better cleaning.
Efficiency of electrical precipitation depends largely on how properly current intensity and voltage applied to the electrodes are preset. Only direct current is used for electrostatic precipitators. This is done to ensure movement of gas-suspended particles only in one direction. If the electrostatic precipitator will be powered by alternating current, the direction of the field will vary at each change, and as a consequence, the direction of force influencing a charged particle will vary too. As a result, the charged particle experiencing a series of pulses moving it to one electrode and then to another, simply will be taken out by gas flow from the device before it has time to reach the surface of one of the electrodes. Therefore, the corona electrode is connected only to a direct current source.
It is important to power the corona electrodes by direct current with a negative sign and not with a positive sing, as negatively charged ions are more mobile than positive ions. The velocity of such ions is almost 50 per cent higher than that of the positive ions. In addition, according to the rules, dust particles must be collected precisely on the collecting electrode in electrostatic precipitators, and if the corona electrode has a positive charge, dust would be precipitated only on it in the case of higher velocity of negative ions.
The speed of dust particles moving to the collecting electrode begins to increase with the increase of the electric current intensity to improve dust collection. As a rule, the required current intensity is expressed in milliamps (mA) in relation to the running meters (rm) of the corona electrode. For pipe electrodes, electric current intensity (I) is applied ranging from 0.3 to 0.5 mA/rm; for plate-type electrodes, it is applied from 0.1 to 0.35 mA/rm.
The electric current intensity directly depends on the distance between one electrode and the other. The more this distance is, the higher current can be received. The electric current intensity also depends on the diameter of the corona electrode. The smaller the diameter of the latter, the higher the current. That is why the corona electrodes are made quite thin today: their diameter generally ranges from 2 to 4 millimeters. Among other things, electric current intensity is directly proportional to the applied potential difference; therefore, catchability of dust particles is better in the case of potential difference increase in electrostatic precipitators.
Voltage in the electrostatic precipitator should not be below that one at which the spark discharge occurs, i.e. it should be no less than Vo. It should be noted that this value is influenced by several factors: gas composition, its temperature, pressure and humidity, as well as the form and the number of corona electrodes (in the plate-type electrostatic precipitator). During electrical precipitation of gases with normal temperature, the value of voltage drop per unit of a distance between one electrode and the other one (which is called a voltage gradient) is typically accepted as no more than 4.8 kilovolt per centimeter (kV/cm); for hot gases it is even less: it is up to 4 kV/cm.
If the gas contains moisture and sulfur dioxide, the breakdown voltage somewhat increases in it allowing for increase of the voltage gradient. The voltage value of the accepted voltage gradient can be somewhat reduced. For this purpose, it is necessary to reduce the distance between the oppositely charged electrodes. However, it will make the electrostatic precipitator more sophisticated and increase the price. The optimal voltage is usually determined by calculating the feasibility and it is typically chosen in the range from 35 to 70 kilowatts. In most cases, the distance between one electrode and the other one is between 100 and 200 millimeters.
In electrostatic precipitators, the precipitation rate of gas-suspended particles depends mainly on the charge which they have received. In its turn, this charge may vary from e0 (elementary electric charge) to ε (dielectric constant of particles).
Influence of electric wind, value of the particles charge, which was obtained by the particles before getting into the field, as well as particles charging by ions of both signs in the area of "corona", and the non-uniformity of the ion field are simply neglected when maximum particle charge is determined. The maximum particle charge is determined as per the following formula:
n·e0 = Ex·[1 + 2·(ε-1)/(ε+2)]·[d²/4]
where n is the number of elementary electric charges;
e0 is an elementary electric charge (4.8x10-10 ESU);
Ex is an electric field intensity (it is measured in absolute units: 300 V/cm);
ε is a dielectric constant;
d is a diameter of particle (measured in cm);
For gases, the dielectric constant (ε) equals to 1’ for metals, it equals to ∞; for metal oxides, it equals from 12 to 18.
Each gas-suspended particle is exposed to electric field and wind, to induction and to the gravity force in the electrostatic precipitator.
The following requirements are made on the collecting electrodes: they shall be heavy-duty, rigid, have a smooth surface so that the collected dust can be easily removed, as well as relatively high aerodynamic performance.
Collecting electrodes are conventionally divided into three large groups according to their form and design: 1) plate-type electrodes; 2) box-shaped electrodes; 3) grooved electrodes (see Figure).
Corona electrodes must meet the following requirements: a precise shape to provide intense and fairly uniform corona discharge; sufficient mechanical strength and rigidity to ensure reliable, trouble-free and long-lasting operation under conditions of shaking and vibration; easy manufacture and low cost since the corona electrodes’ length (overall) can reach 10 kilometers; resistance to aggressive media.
Corona electrodes are divided into two large groups (see Figure.): electrodes without fixed discharge points and electrodes with fixed discharge points over the entire length of the electrode. Spurs or nib points serve as discharge sources for electrodes of the second group, and it is possible to control the electrode operation. To do this, it is necessary to change the distance between spurs.
The system of collecting and corona electrodes is usually located inside a welded metal casing or (rarely) inside a reinforced concrete casing which is made as an inverted U-frames. Equipment is charged inside the casing either from the top or from the side. The casing should always be insulated from outside to avoid thermal deformation and moisture condensation.
The assembly of supply and uniform distribution of dusty air usually consists of a system of gas distribution grids mounted upstream the main chamber where the system of collecting and corona electrodes is located. It is made of perforated sheets mounted in two tiers, with their open area of 35 to 50 percent.
Special systems of electrodes rapping are used to remove collected dust from electrostatic precipitators. Some of such systems (spring-cam, impact-hammer, vibration or magnetic pulse system) are typically used in dry electrostatic precipitators. In addition, collected particles can be simply washed from electrodes with water.
In the space between collecting and corona electrodes, the particles are exposed to the following forces displacing them relative to the gas flow:
Electrostatic dust removal is based on attraction of oppositely charged dust particles to each other due to electrostatic charge.
During electrostatic dust removal, gas flow with dust particles is passed between the corona electrode with a b negative charge and the positively charged collecting electrode.
The corona electrode has a high voltage. It gives gas molecules locating near it to a negatively charged electron. Gas molecules are attracted by the positively charged collecting electrode; and then they are moved towards the collecting electrode by the corona electrode and the collecting electrode in the high voltage field. In their way towards the collecting electrode, charged gas molecules collide with dust particles flowing past them. Molecules give them their charge, charging them negatively. Thereafter, the negatively charged particles are attracted to the collecting electrodes and move towards it. Then, they are discharged and connected with other particles to form flocs. By vibrations and pushing out, such flocs come off the collecting electrode and fall down.
Filters
Upon becoming the official distributer of fabric filters, our company ‘Intech GmbH’ LLC (ООО «Интех ГмбХ»), carries out the following: finds the buyers of your products on the market, conducts technical and commercial negotiations with the customers regarding the supplies of your equipment, concludes contracts. Should a bidding take place, we will collect and prepare all the documents required for the participation, conclude all the necessary contracts for the supply of your equipment, as well as register the goods (fabric filters) and conduct customs clearance procedures. We will also register a certificate of transaction (Passport of Deal) required for all foreign trade contracts in the foreign currency control department of the authorized Russian bank so that currency transaction could be effected. If required, our company will implement an equipment spacing project in order to integrate your equipment into the existing or newly built production plant.
We are convinced that our company ‘Intech GmbH’ LLC (ООО «Интех ГмбХ»), will become your reliable, qualified and efficient partner & distributor in Russia.
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