Deaerator -- technical device, which implements the process of deaeration of some liquid (usually water or liquid fuel), that is, its purification from unwanted gas impurities present in it. On many power stations also plays the role of a regeneration stage and a feed water storage tank.
The deaerator device is intended:
* To protect pumps from cavitation.
* To protect equipment and pipelines from corrosion.
* To protect the system from air entering it, which disrupts the hydraulics and normal work injectors.
Fig.2.
1 -- tank (battery), 2 -- outlet of feed water from the tank, 5 -- water indicator glass, 4 -- pressure gauge, 5, 6 and 12 -- plates, 7 -- draining water into drainage, 8 -- automatic regulator supply of chemically purified water, 9 - steam cooler, 10 - steam release to the atmosphere, 11 I 15 - pipes, 13 - deaerator column, 14 - steam distributor, 16 - water inlet into the hydraulic seal, 17 - hydraulic shutter, 18 -- release excess water from a hydraulic valve
The thermal deaerator is based on the principle of diffusion desorption, when the liquid in the system is heated to the point of boiling. During such a process in a thermal deaerator, the solubility of gases is zero. The resulting steam carries gases out of the system, and the diffusion coefficient increases.
The vortex deaerator uses hydrodynamic effects that cause forced desorption, that is, they lead to rupture of the liquid in the weakest places - under the influence of density differences. IN in this case the liquid is not heated.
Based on pressure, thermal deaerators are classified into:
* Vacuum (DV)
* Atmospheric (YES).
*High blood pressure (HP).
Atmospheric deaerator - used with the smallest wall thickness. Under the influence of excess pressure above atmospheric pressure, steam is removed from the walls by gravity. Atmospheric deaerator DSA is designed to remove aggressive gases from the system of steam boilers and boiler plants. Atmospheric type deaerators are installed as on open areas, and indoors. The numbers indicated on the atmospheric deaerator DSA 75 and deaerator DA 25 determine the performance of the device.
Vacuum deaerator - used in conditions where boiler rooms do not have steam produced. Vacuum deaerators DV - are forced to work in conjunction with devices for vapor suction. The DV feedwater deaerator has a large wall thickness and also allows the decomposition of bicarbonates at low pressure. Depending on the performance, they are indicated by numbers (Example: Vacuum deaerator DV 25).
Deaerators DP ( high pressure) - have large wall thickness, but DP deaerators allow the use of vapor as a light working medium for condenser ejectors. Also, excess high pressure deaerators make it possible to reduce the number of metal-intensive HPHs.
Deaerator design and operating principle
In the deaerator column, water is heated and treated with steam. After passing through two stages of degassing (1st stage - jet, 2nd - bubbling) water flows from the column in streams into the BDA deaerator tank.
The design of the deaerator ensures convenient internal inspection of the deaeration column. Perforated sheet material internal devices Deaerator columns are corrosion-resistant steel.
The deaeration tank contains the third degassing stage after the deaeration column in the form of a submerged bubbling device.
In the deaerator tank, tiny gas bubbles are released from the water due to sediment.
The deaerator vapor cooler serves only to recover the heat of vapor condensation. Chemically purified water passes inside the vapor cooler tubes and is directed to the deaeration column. A vapor-gas mixture (vapor) enters the annulus, where the steam from it is almost completely condensed. The remaining gases are vented to the atmosphere, the vapor condensate is drained into a deaerator or drain tank
Tube material is brass or corrosion-resistant steel.
The deaerator operates automatically. The pressure in the deaerator is constantly regulated at 0.02 MPa. The water level in the deaerator is also constantly maintained. Deaerators are started and stopped manually
Fig.3.
The deaeration unit consists of:
· Vacuum deaerator;
· EVA (evaporation cooler, shell and tube heat exchanger, designed to condense the maximum amount of steam and utilize its thermal energy);
· EV (water jet ejector, air suction device).
The DV uses a two-stage degassing system. The 1st stage is jet, the 2nd is bubbling, non-failing perforated plate.
Thermal deaerators are usually classified according to operating pressure and the method of organizing phase contact.
According to the working pressure there are following types deaerators:
Vacuum, operating at an absolute pressure in the housing from 0.075 to 0.5 atmospheres;
Atmospheric, the absolute pressure in which varies in the range from 1.1 to 1.3 atmospheres;
High pressure, operating at absolute pressure from 5 to 12 atmospheres.
The method of organizing phase contact is determined by the design of the deaerator. Since the same deaerator, as a rule, uses deaeration devices that differ from each other in operating principles, modern deaerators are usually combined. In this case, the following main types of deaeration devices (or individual elements deaerator):
Jet, in which the phase interface is formed by the surface of water jets freely falling in a steam flow;
Bubblers, in which the heating fluid in the form of steam bubbles is distributed in the water flow;
Film, where the phase interface is formed by the film flow of water in a steam flow;
Drip systems, in which water is distributed in the steam stream in the form of drops.
The interface between the phases can be conditionally fixed, as, for example, in film deaerators with an ordered packing, or non-fixed, as in deaerators with a disordered packing, jet, drip and bubbling. The scope of application of deaerators in thermal circuits of energy facilities, as a rule, is determined by the operating pressure, deaerators high blood pressure are used exclusively as feedwater deaerators of thermal power plants with high, ultra-high and supercritical initial steam pressure;
Atmospheric pressure deaerators are used as feedwater deaerators of power plants and boiler houses of low and medium initial steam pressure, additional water deaerators of the cycle of heating power plants (CHP) with a higher initial steam pressure, make-up water deaerators of heating networks closed type(less often - for heating networks open type using deaerated water coolers), feedwater deaerators of evaporation and steam conversion units of power plants;
Vacuum deaerators are used as deaerators of make-up water in heating networks, in circuits of evaporation and steam conversion plants, and less often - as deaerators of additional water in the cycle of power plants and boiler houses.
Atmospheric pressure deaerators
The most common type of atmospheric deaerator is the jet-bubble deaerator. In such deaerators it is usually used two-stage scheme deaeration, including jet and bubbling stages. It should be noted that a deaeration stage is usually understood as one or more connected in series through water deaeration elements, working on the same principle. For example, two jet compartments located one below the other belong to one jet stage.
The designs of such deaerators are somewhat different from each other for devices of different capacities from the standard range. Most of the standard designs of jet-bubbling atmospheric deaerators were developed by NPO TsKTI im. I.I. Polzunov. Currently, both outdated models of such deaerators (type DSA) and their modern analogues (types DA and DA-m) are used. Designed by standard series standard sizes of such deaerators, differing in nominal capacity for deaerated water: 1, 3, 5, 15, 25, 50, 100, 200 and 300 t/h.
Atmospheric deaerators typically consist of a deaeration column mounted on a horizontally located cylindrical deaerator tank. The deaerator tank as part of the deaerator performs two important functions. Firstly, it serves as a means of creating a supply of deaerated water for technological scheme. If, for example, the deaerator is used as a feedwater deaerator for steam boilers low pressure, then it is necessary to create a supply of water in the deaerator tank to ensure uninterruptible power supply these boilers in emergency situations. Secondly, as shown above, the deaeration tank allows you to increase the time the water is kept at a temperature close to the saturation temperature, which helps to increase the efficiency of deaeration.
In relation to devices with low productivity (1 and 3 t/h of deaerated water), the deaerator can perform the indicated functions without a deaerator tank, since the necessary supply of water can be created directly in the body of the deaeration column, the dimensions of which will not be too large. IN standard designs Such deaerators are not distinguished between a deaeration column and a deaerator tank, but rather refer to the deaerator body as a whole. Such deaerators are called columnless.
Deaerators with higher productivity are equipped with deaerator tanks of various capacities. Domestic power engineering plants produce deaerator tanks of standard sizes with a capacity of 2, 4, 8, 15, 25, 35, 50 and 75 m 3, and each deaerator tank is designed for a deaeration column of a certain capacity. However, at the customer's request, as a rule, it is possible to supply selected deaeration columns with tanks of a different capacity from the standard range.
In addition to the deaerators developed by NPO TsKTI im. I.I. Polzunov, a number of designs of atmospheric deaerators developed by other organizations are used. Among such deaerators, we note the bubbling deaerator designed by Uralenergometallurgprom.
Currently, atmospheric deaerators are produced by the following main domestic factories:
Neftekhimmash Equipment LLC, Biysk Boiler Plant OJSC, Sibenergomash OJSC, Belenergomash OJSC, Teploenergokomplek CJSC, TKZ-Krasny Kotelshchik OJSC, Sarenergomash OJSC.
Below we will consider the main constructive solutions, used in atmospheric pressure deaerators and their piping elements: vapor coolers and safety drain devices.
Let's consider the design diagram of columnless deaerators with a capacity of 1 and 3 t/h (Fig. 3.1), developed by NPO TsKTI im. I.I. Polzunov.
Rice. 3.1. Structural diagram columnless deaerators DA-1 and DA-3: 1 - source water supply fitting; 2 - perforated water distribution manifold; 3 - jet-forming plate; 4 - water intake tray; 5 - sectioning threshold of the jet-forming plate; 6 - limiting threshold of the jet-forming plate; 7 - bubbling device; 8 - bubble sheet; 9 and 10 - partitions; 11 - fitting for draining deaerated water; 12 - heating steam supply fitting; 13 - steam line; 14 - steam receiving box; 15 - vapor transfer window; 16 - steam inlet window; 17 - inlet window of the built-in vapor cooler; 18 - vapor outlet fitting; 19 - hatch; 20 and 21 - fittings for connecting the safety drain device for steam and water, respectively; 22 - drainage fitting.
energy desorption bubbling hydrodynamic
The deaerator DA-1 or DA-3 is a vertical cylindrical vessel with elliptical bottoms and deaeration devices located inside it.
The water sent for deaeration enters the deaerator through fitting 1 and the perforated water distribution manifold 2. From the holes of the water distribution manifold 2, water flows in the form of jets onto the jet-forming plate 3, perforated in the part located above the water receiving tray 4. The jet-forming plate 3 is sectioned by a threshold 5 in such a way that that with a low hydraulic load, water flows in the form of jets into tray 4 only through holes located up to threshold 5 in the direction of water movement. With an increased hydraulic load, the water level on the jet-forming plate 3 rises, the water flows over the threshold 5 and all the holes of the jet-forming plate are switched on. This sectioning of the jet-forming plate 3 is made so that, at low hydraulic loads of the deaerator, there is no misalignment (“distortions”) between the flows of water and heating steam, leading to a deterioration in the conditions of heat exchange and deaeration. The maximum hydraulic load of the deaerator is limited by the height of the limiting threshold 6: with increased hydraulic load, the water level on the jet-forming plate increases and if water overflows over threshold 6, the efficiency of water heating and deaeration sharply deteriorates.
In the jet stream inside tray 4, the main heating of water occurs when it comes into contact with heating steam and the degassing process begins. The water draining from tray 4 in the form of a stream into the water volume of the deaerator, under most operating modes of the deaerator, remains underheated to the saturation temperature corresponding to the pressure in the steam space of the deaerator, and contains gases both in dissolved and dispersed form.
After a certain exposure of water in the water volume of the deaerator, the duration of which is determined by the hydraulic load and the water level in the deaerator, the water enters the bubbling device 7. This device is made in the form of a channel rectangular section, limited at the top and sides by solid partitions and having a perforated bubble sheet 8 at the bottom. When steam is bubbled through a layer of water in the bubbler device 7, the water is heated to a saturation temperature corresponding to the pressure in the bubbler device. This pressure is greater than the pressure in the steam space of the deaerator above the water surface by the pressure of the water column of height H, therefore the water temperature in the bubbling device becomes greater than the saturation temperature at the steam pressure above the water surface in the deaerator. In the bubbling device 7, due to the water reaching the saturation temperature, most of the dissolved gases transform into a dispersed state in the form of small gas bubbles; here, partial thermal decomposition of hydrocarbonates and hydrolysis of carbonates occurs with the formation of free carbon dioxide, which, in turn, also transforms into dispersed state.
Having left the bubbling device 7, water mixed with the non-condensed part of the heating steam enters the channel formed by partitions 9 and 10 and moves upward along this channel. During this movement, the pressure of the medium continuously decreases from the pressure in the bubbling device to the steam pressure above the surface of the water in the deaerator. Accordingly, water, which turns out to be overheated relative to the saturation temperature, boils in volume, which is accompanied by the transition of most of the gases still in dissolved form into a dispersed state. In the upper part of the water volume, phase separation occurs: water flows through partition 10 and falls towards the deaerated water outlet fitting 11, and steam with gases released from the water moves towards the jet deaeration stage.
It should be noted that the leakage of the steam-water mixture from the bubbling device 7 directly into the deaerated water outlet fitting 11 is unlikely. The flow of the medium in the gap between the partitions 9 and 10, due to the presence of steam, has a lower density than the flow of water descending in the channel formed by the partition 10 and the wall of the housing, which causes only the lifting movement of the medium between the partitions 9 and 10. Meanwhile, the gap between the partition 10 and the housing in the lower part is necessary to allow some circulation of water around the partition 10. Such circulation increases the frequency of water treatment with steam and increases the available time of the deaeration process, which increases the efficiency of removing gases from water.
All the heating steam is supplied to the deaerator through fitting 12 and through the steam line 13 enters the steam receiving box 14 under the bubble sheet 8. A steam cushion is created under the bubble sheet 8, preventing water from falling through the holes of the bubble sheet. Such bubble sheets are called non-sinking sheets.
Here it is advisable to dwell in more detail on the limiting operating mode of a non-failing bubble sheet - the “flooding” mode or injection mode. If the velocity of steam in the holes of the sheet is too high, the steam coming out of the holes of the bubble sheet will capture all the liquid, crush it and carry it away in the form of spray. It is for this reason that the maximum steam pressure under the bubble sheet must be limited. In the considered deaerators DA-1 and DA-3, for this purpose, a steam bypass window 15 is made in the partition 9, which bypasses part of the steam in addition to the holes of the bubble sheet8 when the steam pressure under this sheet increases above that required for efficient work bubbling device.
After separating the water and the steam-gas mixture in the upper part of the channel formed by partitions 9 and 10, this mixture enters through the steam inlet window 16 into the jet compartment of the deaerator, where most of the steam condenses, heating the water flow. The remaining part of the steam mixed with gases washes the jet-forming plate 3 and enters the built-in contact vapor cooler. The vapor cooler is a jet stream of water flowing from the water distribution manifold 2, through which passes the vapor-gas mixture entering through window 17. Here, water vapor is additionally condensed on the jets relatively cold water. The remaining small part of the steam and non-condensable gases are removed from the deaerator through the vapor outlet fitting 18.
Deaerators DA-1 and DA-3 are equipped with hatch 19, which provides access to the inside of the housing for inspection and repair, as well as fittings 20 and 21 for connecting a safety drain device and drain fitting 22.
An atmospheric deaerator with a capacity of 5 t/h or more (Fig. 3.2) consists of a deaeration column 7 installed on a deaerator tank 10. The column includes several (in in this example two) jet compartments formed below the upper 8 and lower 9 perforated plates, and can also be supplemented with a bubble sheet. The water to be deaerated is supplied through a water distribution system to the upper jet-forming plate 8, from where it flows onto the plate 9 located below and then onto the bubble sheet (if any) or directly into the deaerator tank (as in the example under consideration). Jet trays have special thresholds that ensure the maintenance of a certain water level on them, as well as the overflow of water in addition to the jet zone when the trays are overfilled. Bubbler sheets are usually made non-sinking (the dynamic action of the steam flow does not allow water to “fall” through the holes of the sheet), since the operation of a sinking bubble sheet is effective only in a narrow range of water and steam flow rates through it.
Fig.3.2.
1 - water supply; 2 - vapor cooler; 3, 6 - vapor to the atmosphere; 4 - supply of third-party condensate (for example, condensate of steam from production extraction of turbine units); 5-level regulator; 7 - deaeration column; 8, 9 - upper and lower jet-forming plates; 10 - deaerator tank; 11 - safety drain device; 12 - supply of bubbling steam; 13 - pressure control devices; 14 - pressure regulator; 15 - main steam supply; 16 - drainage of deaerated water; 17 - level indicator; 18 - drainage; 19 - supply of hot condensate.
Steam is usually supplied to the above-water space of the deaerator tank (and in this case is called the main steam 15), ventilates it, ensuring the removal of gases released from the water in the tank, and enters the deaeration column. Here the steam interacts with the downward flow of water, providing its heating and deaeration.
The vapor containing gases and water vapor released from the water is discharged from the deaerator into the atmosphere through pipe 6 or to the vapor cooler 2, where the thermal potential of this flow is used, for example, to heat the source water in front of the deaeration column. In this case, gas blowing 3 is carried out from the steam space of the vapor cooler. It is possible to supplement the specified design with a bubbling device for the deaerator tank. The most commonly used devices are the TsKTI system (in this example) or perforated bubble collectors mounted at the bottom of the tank along its generatrices. In this case, bubble steam 12 is supplied through a special pipeline, since the pressure of this steam must be greater than the pressure of the main steam by at least the pressure of the water column in the deaerator tank. The deaerator is equipped with a safety drain device 11; level glass 17; connections for connecting the deaerator to the steam and water equalization lines; drainage pipeline 18; deaerated water outlet pipe 16.
Experience in operating atmospheric deaeration plants shows that, regardless of the reason for the deterioration in the efficiency of water deaeration, the use of steam bubbling in the water volume of the deaeration tank allows this efficiency to be increased.
Even if the deaeration column provides the required quality of deaerated water, the bubbling device of the deaerator tank acts as a barrier, reducing the likelihood of dissolved gases leaking into the deaerated water and expanding the permissible range of changes in the hydraulic and thermal loads of the deaerator while maintaining the required quality of deaerated water. In this case, steam bubbling in the deaerator tank provides some superheating of the water relative to the saturation temperature and thereby protects the water from recontamination with gases.
In addition, it must be remembered that the part of the gases remaining in the water after the deaeration column is contained in a dispersed form and represents a multitude of tiny gas bubbles, the sizes of which are so small that they do not ensure their independent ascent due to the action of the buoyancy force. In a deaerator without bubbling in the water volume of the tank, these bubbles will fall into the deaerated water. Steam bubbling, which provides intensive mixing and turbulization of the water volume in the tank, promotes the release of some of the gases in dispersed form from the water, increasing the efficiency of deaeration as a whole.
Thus, a flooded bubbling device in a deaeration tank is often necessary even when using modern two-stage deaeration columns.
Let us consider, as an example, the bubbling device of the TsKTI system (Fig. 3.2.).
Rice. 3.2. Schematic diagram bubbling device of the deaerator tank of the TsKTI system: 1 - bubbling sheet; 2 - top shelf; 3 - lifting shaft; 4 - drainage of deaerated water; 5 - deaeration column; 6 - deaerator tank; 7 - supply of bubbling steam; 8 - main steam supply; solid lines indicate the direction of water movement; dotted lines - directions of steam movement
Water flows through the canal surface formed bubble sheet 1 and top shelf 2, and during this movement it is treated with steam escaping from the holes of the bubble sheet. The steam-water mixture, leaving the channel, enters a specially organized lifting movement shaft 3, in the upper part of which the steam and gases released from the water are separated from the water and discharged into the above-water space of the deaerator tank and mixed with the flow of the main steam, and the water is lowered in the water volume of the tank to the deaerated water outlet pipe 4.
The deaerator tanks themselves (see example in Fig. 3.4) are horizontally located cylindrical vessels with elliptical, less often conical, bottoms, mounted on two supports. And for tanks usable capacity 25 m 3 or more, one of the supports is movable (roller), providing compensation for temperature expansion of the tank during starts and stops of the deaerator. Tanks with a useful capacity of 8 m 3 or more are equipped with special belts that provide the required rigidity of the body.
Rice. 3.4. General view deaerator tank with a useful capacity of 75 m 3: A - fitting for the deaeration column; B - connection fitting for the safety-drain device for steam; B - main steam supply fitting; G - drainage fitting; D - deaerated water drainage fitting; E - connection fitting for the water safety drain device; F - fittings for connecting a level indicator; C- union for discharge from the separator continuous blowing boiler; T - fitting for introducing feed water from the feed pump recirculation line; U - fitting for the input of superheated condensates; F - fitting for introducing the steam-air mixture from the steam space of the heaters; C- fitting for supplying steam to the submerged bubbling device of the deaerator tank; Ch- reserve fitting
Columns are connected to deaerator tanks, usually by welding. In the designs of modern deaerators, the column is located near one of the ends of the deaerator tank; deaerated water is removed from the tank from the opposite end. This achieves the maximum possible time of holding water in the deaerator tank at a temperature close to the saturation temperature, given the geometric characteristics, and, accordingly, the greatest deaeration efficiency.
Deaeration tanks are equipped with a hatch that provides access to the inside of the tank for inspection and repair, as well as inspection and repair of the lower devices of the deaeration column, fittings for connecting a safety drain device for steam and water (the latter is mounted inside the tank and ends in an overflow funnel, the height of the upper edge is which determines the maximum water level in the tank). Fittings are provided for connecting the deaerator to the steam and water equalizing lines required for parallel work several deaerators, a fitting for draining deaerated water, supplying main and bubbling steam, a drain fitting, as well as a number of fittings for discharging high-potential flows, the temperature of which is higher than the saturation temperature at the operating pressure in the deaerator, or for introducing flows of already deaerated water. If streams overheated relative to the saturation temperature in the deaerator are directed not into the deaerator tank, but into the deaeration column, then the steam formed during their boiling can disrupt the normal ventilation of the steam space of the deaerator, which, in turn, will lead to a deterioration in the efficiency of water deaeration.
In industrial and heating boiler houses, to protect heating surfaces washed by water, as well as pipelines, from corrosion, it is necessary to remove corrosive gases (oxygen and carbon dioxide), which is most effectively achieved by thermal deaeration of water. Deaeration is the process of removing gases dissolved in it from water.
When water is heated to saturation temperature at a given pressure, the partial pressure of the removed gas above the liquid decreases, and its solubility decreases to zero.
Removal of corrosive gases in the boiler installation circuit is carried out in special devices– thermal deaerators.
Purpose and scope
Two-stage atmospheric pressure deaerators of the DA series with a bubbling device at the bottom of the column are designed to remove corrosive gases (oxygen and free carbon dioxide) from the feed water of steam boilers and the make-up water of heat supply systems in boiler houses of all types (except for pure water heating ones). Deaerators are manufactured in accordance with the requirements of GOST 16860-77. OKP code 31 1402.
Modifications
Example of a symbol:
DA-5/2 – atmospheric pressure deaerator with a column capacity of 5 m³/hour with a tank with a capacity of 2 m³. Serial sizes – DA-5/2; DA-15/4; DA-25/8; DA-50/15; DA-100/25; YES-200/50; DA-300/75.
At the customer's request, it is possible to supply atmospheric pressure deaerators of the DSA series, with standard sizes DSA-5/4; DSA-15/10; DSA-25/15; DSA-50/15; DSA-50/25; DSA-75/25; DSA-75/35; DSA-100/35; DSA-100/50; DSA-150/50; DSA-150/75; DSA-200/75; DSA-200/100; DSA-300/75; DSA-300/100.
Deaeration columns may be combined with tanks of larger capacity.
Rice. General view of the deaerator tank with explication of the fittings.
Technical characteristics
The main technical characteristics of atmospheric pressure deaerators with bubbling in the column are given in the table.
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Deaerator |
DA-50/15 |
DA-100/25 |
DA-200/50 |
DA-300/75 |
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Nominal productivity, t/h |
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Operating excess pressure, MPa |
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Temperature of deaerated water, °C |
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Performance range, % |
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Productivity range, t/h |
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Maximum and minimum heating of water in the deaerator,°C |
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Concentration of O 2 in deaerated water at its concentration in the source water, C to O 2, μg/kg: - corresponding to the state of saturation No more than 3 mg/kg |
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Concentration of free carbon dioxide and deaerated water, C to O 2, µg/kg |
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Trial hydraulic pressure, MPa |
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Permissible pressure increase during operation protective device, MPa |
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Specific vapor consumption at rated load, kg/td.v |
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Diameter, mm Height, mm Weight, kg |
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Useful capacity of the battery tank, m 3 |
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Deaerator tank type |
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Evapor cooler size |
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Type of safety device |
* - design dimensions deaeration columns may vary depending on the manufacturer.
Description of design
The DA series atmospheric pressure thermal deaerator consists of a deaeration column mounted on an accumulator tank. The deaerator uses a two-stage degassing scheme: stage 1 - jet, stage 2 - bubbling, both stages are located in a deaeration column, the schematic diagram of which is shown in Fig. 1. Streams of water to be deaerated are fed into column 1 through pipes 2 onto the upper perforated plate 3. From the latter, water flows in streams onto the bypass plate 4 located below, from where it flows into the initial section of the non-failing bubble sheet 5 in a narrow beam of a jet of increased diameter. Then the water passes along the bubble sheet in the layer provided by the overflow threshold (the protruding part of the drain pipe), and through drain pipes 6 is discharged into the accumulator tank, after holding in which it is discharged from the deaerator through pipe 14 (see Fig. 2), all steam is supplied to the accumulator the deaerator tank through pipe 13 (see Fig. 2), ventilates the volume of the tank and falls under the bubble sheet 5. Passing through the holes of the bubble sheet, the area of which is selected in such a way as to prevent the failure of water at the minimum thermal load of the deaerator, the steam exposes the water to without intensive processing. As the thermal load increases, the pressure in the chamber under the sheet 5 increases, the water seal of the bypass device 9 is activated and excess steam is released into the bypass of the bubble sheet through the steam bypass pipe 10. Pipe 7 ensures that the water seal of the bypass device of deaerated water is filled with a decrease in the thermal load. From the bubbling device, steam is directed through hole 11 into the compartment between plates 3 and 4. The vapor-gas mixture (vapour) is removed from the deaerator through gap 12 and pipe 13. In the jets, water is heated to a temperature close to the saturation temperature; removal of the bulk of gases and condensation of most of the steam supplied to the deaerator. Partial release of gases from the water in the form of small bubbles occurs on plates 3 and 4. On the bubble sheet, the water is heated to saturation temperature with slight condensation of steam and micro quantities of gases are removed. The degassing process is completed in the battery tank, where tiny gas bubbles are released from the water due to sediment.
The deaeration column is welded directly to the battery tank, with the exception of those columns that have a flange connection to the deaeration tank. The column can be oriented arbitrarily relative to the vertical axis, depending on the specific installation scheme. The housings of the DA series deaerators are made of carbon steel, the internal elements are made of stainless steel, fastening of elements to the body and to each other is carried out by electric welding.
Included in delivery deaeration plant included (the manufacturer agrees with the customer on the scope of delivery of the deaeration unit in each individual case):
deaeration column;
a control valve on the line for supplying chemically purified water to the column to maintain the water level in the tank;
control valve on the steam supply line to maintain pressure in the deaerator;
pressure vacuum gauge;
shut-off valve;
water level indicator in the tank;
pressure gauge;
thermometer;
safety device;
vapor cooler;
coupling shut-off valve;
drainage pipe;
technical documentation.
Rice. 1 Schematic diagram of an atmospheric pressure deaeration column with a bubbling stage.
Deaeration installation circuit diagram
The scheme for switching on atmospheric deaerators is determined by the design organization depending on the conditions of purpose and the capabilities of the facility where they are installed. In Fig. Figure 2 shows the recommended diagram of the DA series deaeration unit.
Chemically purified water 1 is supplied to the deaeration column 6 through the vapor cooler 2 and the control valve 4. The flow of the main condensate 7 with a temperature below operating temperature deaerator. The deaeration column is installed at one of the ends of the deaerator tank 9. The deaerated water 14 is removed from the opposite end of the tank in order to ensure maximum holding time of water in the tank. All steam is supplied through pipe 13 through pressure control valve 12 to the end of the tank opposite the column, in order to ensure good ventilation of the steam volume from gases released from the water. Hot condensates (clean) are supplied to the deaerator tank through pipe 10. Vapor is removed from the installation through vapor cooler 2 and pipes 3 or directly into the atmosphere through pipe 5.
To protect the deaerator from an emergency increase in pressure and level, a self-priming combined safety device 8 is installed. Periodic checking of the quality of deaerated water for the content of oxygen and free carbon dioxide is carried out using a heat exchanger for cooling water samples 15.
Rice. 2 Schematic diagram for switching on an atmospheric pressure deaeration unit:
1 - supply of chemically purified water; 2 - vapor cooler; 3, 5 - exhaust into the atmosphere; 4 - level adjustment valve, 6 - column; 7 - main condensate supply; 8 - safety device; 9 - deaeration tank; 10 - supply of deaerated water; 11 - pressure gauge; 12 - pressure control valve; 13 - hot steam supply; 14 - drainage of deaerated water; 15 - water sample cooler; 16 - level indicator; 17- drainage; 18 - pressure and vacuum gauge.
Vapor cooler
To condense the vapor-gas mixture (vapor), a surface-type vapor cooler is used, consisting of a horizontal housing in which a pipe system is located (tube material - brass or corrosion-resistant steel).
The vapor cooler is a heat exchanger into which chemically purified water or cold condensate from permanent source, heading to the deaeration column. The steam-gas mixture (vapor) enters the annulus, where the steam from it is almost completely condensed. The remaining gases are vented to the atmosphere, and the vapor condensate is drained into a deaerator or drain tank.
The vapor cooler consists of the following main elements (see Fig. 3):
Nomenclature and general characteristics vapor coolers
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Vapor cooler |
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Pressure, MPa In a pipe system In the building |
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In a pipe system In the building |
steam, water |
steam, water |
steam, water |
steam, water |
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Ambient temperature, °C In a pipe system In the building |
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Weight, kg |
Safety device (hydraulic seal) for atmospheric pressure deaerators
To ensure safe operation of deaerators, they are protected from dangerous increases in pressure and water level in the tank using a combined safety device (hydraulic seal), which must be installed in each deaerator installation.
The water seal must be connected to the steam supply line between the control valve and the deaerator or to the steam space of the deaerator tank. The device consists of two water seals (see Fig. 4), one of which protects the deaerator from exceeding the permissible pressure 9 (shorter), and the other from a dangerous increase in level 1, combined into a common hydraulic system, and expansion tank. Expansion tank 3, serves to accumulate the volume of water (when the device is activated) necessary for automatic filling of the device (after eliminating the malfunction of the installation), i.e. makes the device self-priming. The diameter of the overflow water seal is determined depending on the maximum possible water flow into the deaerator in emergency situations.
The diameter of the steam hydraulic seal is determined based on the highest permissible pressure in the deaerator when the device is operating, 0.07 MPa, and the maximum possible steam flow into the deaerator in an emergency with the control valve fully open and the maximum pressure in the steam source.
To limit the steam flow into the deaerator in any situation to the maximum required (at 120% load and 40-degree heating), an additional throttle limiting diaphragm should be installed on the steam line.
In some cases (to reduce the building height, install deaerators in rooms), instead of a safety device, safety valves (to protect against overpressure) and a condensate drain are installed to the overflow fitting.
Combined safety devices are manufactured in six standard sizes: for deaerators DA - 5 - DA - 25, DA - 50 and DA - 75, DA - 100, DA - 150, DA - 200, DA - 300.
Rice. 4 Schematic diagram of a combined safety device.
1 - Overflow water seal; 2 – steam supply from the deaerator; 3 – expansion tank; 4 – water drain; 5 – exhaust into the atmosphere; 6 – pipe for flood control; 7 – supply of chemically purified water for filling; 8 - water supply from the deaerator; 9 – water seal against pressure increase; 10 – drainage.
Installation of deaeration units
To perform installation work installation sites must be equipped with basic installation equipment, devices and tools in accordance with the work project. When accepting deaerators, you should check the completeness and compliance of the nomenclature and number of places with the shipping documents, the compliance of the supplied equipment with the installation drawings, and the absence of damage or defects in the equipment. Before installation external inspection and re-preservation of the deaerator, and the detected defects are eliminated.
Installation of the deaerator on site is carried out in the following order:
install the accumulator tank on the foundation in accordance with the installation drawing design organization;
weld the drainage neck to the tank;
cut off the lower part of the deaeration column along the outer radius of the body of the deaeration tank and install it on the tank in accordance with the installation drawing of the design organization, while the plates must be positioned strictly horizontally;
weld the column to the deaerator tank;
install the vapor cooler and safety device according to the installation drawing of the design organization;
connect pipelines to the fittings of the tank, column and vapor cooler in accordance with the deaerator piping drawings made by the design organization;
install shut-off and control valves and instrumentation;
carry out hydraulic test deaerator;
install thermal insulation as directed by the design organization.
Indication of safety measures
When installing and operating thermal deaerators, safety measures determined by the requirements of Gosgortekhnadzor, relevant regulatory and technical documents must be observed. job descriptions etc.
Thermal deaerators must undergo technical examinations (internal inspections and hydraulic tests) in accordance with the rules for the design and safe operation of pressure vessels.
Operation of DA series deaerators
1. Preparing the deaerator for start-up:
make sure that all installation and repair work is completed, temporary plugs from the pipelines are removed, hatches on the deaerator are closed, bolts on flanges and fittings are tightened, all gate valves and control valves are in working order and closed;
Maintain the nominal flow rate of vapor from the deaerator in all modes of its operation and periodically monitor it using a measuring vessel or using the balance of the vapor cooler.
Basic malfunctions in the operation of deaerators and their elimination
1. An increase in the concentration of oxygen and free carbon dioxide in deaerated water above the norm can occur for the following reasons:
a) the concentration of oxygen and free carbon dioxide in the sample is determined incorrectly. In this case it is necessary:
check that chemical analyzes are performed correctly in accordance with the instructions;
check the correctness of water sampling, its temperature, flow rate, and the absence of air bubbles in it;
check density pipe system- sampling refrigerator;
b) the vapor consumption is significantly reduced.
In this case it is necessary:
check that the surface of the vapor cooler corresponds to the design value and, if necessary, install a vapor cooler with a larger heating surface;
check the temperature and flow rate of the cooling water passing through the vapor cooler and, if necessary, reduce the water temperature or increase its flow rate;
check the degree of opening and serviceability of the valve on the outlet pipeline of the steam-air mixture from the vapor cooler to the atmosphere;
c) the temperature of the deaerated water does not correspond to the pressure in the deaerator, in this case the following should be done:
check the temperature and flow rate of the flows entering the deaerator and increase average temperature initial flows or reduce their consumption;
check the operation of the pressure regulator and, if the automation malfunctions, switch to remote or manual pressure regulation;
d) supply of steam with a high content of oxygen and free carbon dioxide to the deaerator. It is necessary to identify and eliminate sources of steam contamination with gases or take steam from another source;
e) the deaerator is faulty (clogging of the holes in the plates, warping, breakage, breakage of the plates, installation of the plates on a slope, destruction of the bubbling device). It is necessary to take the deaerator out of operation and carry out repairs;
f) the steam flow into the deaerator is insufficient (the average heating of water in the deaerator is less than 10°C). It is necessary to reduce the average temperature of the initial water flows and ensure heating of the water in the deaerator by at least 10°C;
g) drainage containing a significant amount of oxygen and free carbon dioxide is sent to the deaerator tank. It is necessary to eliminate the source of infection of the drains or feed them into the column, depending on the temperature, onto the upper or overflow plate;
h) the pressure in the deaerator is reduced;
check the serviceability of the pressure regulator and, if necessary, switch to manual regulation;
check the pressure and adequacy of heat flow in the power source.
2. An increase in pressure in the deaerator and activation of the safety device can occur:
a) due to a malfunction of the pressure regulator and a sharp increase in steam flow or a decrease in the flow of source water; in this case, you should switch to remote or manual pressure control, and if it is impossible to reduce the pressure, stop the deaerator and check the control valve and automation system;
b) with sharp increases in temperature, with a decrease in the flow rate of the source water, either reduce its temperature or reduce the steam flow.
3. An increase or decrease in the water level in the deaerator tank beyond the permissible level may occur due to a malfunction of the level regulator; it is necessary to switch to remote or manual level control; if it is impossible to maintain the normal level, stop the deaerator and check the control valve and automation system.
4. Water hammer must not be allowed in the deaerator. If water hammer occurs:
a) due to a malfunction of the deaerator, it should be stopped and repaired;
b) when the deaerator is operating in the “flooding” mode, it is necessary to check the temperature and flow rate of the initial water flows entering the deaerator; the maximum heating of water in the deaerator should not exceed 40 °C at 120 °C on the load, otherwise it is necessary to increase the temperature of the initial water or reduce its consumption.
Repair
Routine repairs of deaerators are performed once a year. At current repairs Inspection, cleaning and repair work is carried out to ensure normal operation of the installation until the next repair. For this purpose, deaeration tanks are equipped with manholes, and the columns are equipped with inspection hatches.
Planned major repairs must be carried out at least once every 8 years. If it is necessary to repair the internal devices of the deaeration column and it is impossible to carry it out using hatches, the column can be cut along a horizontal plane in the place most convenient for repair.
During subsequent welding of the column, the horizontality of the plates must be ensured and the vertical dimensions must be maintained. After completion repair work a hydraulic pressure test of 0.2941 MPa (abs.) (3 kgf/cm2) must be performed.
In industrial and heating boiler houses, to protect heating surfaces washed by water, as well as pipelines, from corrosion, it is necessary to remove corrosive gases (oxygen and carbon dioxide) from feed and make-up water, which is most effectively ensured by thermal deaeration of water. Deaeration is the process of removing gases dissolved in it from water.
When water is heated to saturation temperature at a given pressure, the partial pressure of the removed gas above the liquid decreases, and its solubility decreases to zero.
Removal of corrosive gases in the boiler installation circuit is carried out in special devices - thermal deaerators.
Specifications
| Designation | DA-5/2 | DA-15/4 | DA-25/8 | DA-50/15 | DA-100/25 |
| Productivity, t/h | 5 | 15 | 25 | 50 | 100 |
| Operating excess pressure, MPa | 0,02 | ||||
| Temperature of deaerated water, °C | 104,25 | ||||
| Performance range, % | 30-120 | ||||
| Maximum and minimum heating of water in the deaerator, °C | 40-10 | ||||
| Initial content of dissolved oxygen in deaerated (source) water, mg/kg | 3 | ||||
| Residual content of dissolved oxygen in deaerated water, µg/kg | 20 | ||||
| Content of free carbon dioxide in deaerated (source) water, mg/kg | 20 | ||||
| Content of free carbon dioxide in deaerated water | traces | ||||
| Deaeration column, dimensions, mm | 518/518/2230 | 518/518/2195 | 518/518/2915 | 800/800/2358 | 1000/1000/2365 |
| Useful capacity of the battery tank, m? | 2 | 4 | 8 | 15 | 25 |
| Deaerator tank type | BDA-2 | BDA-4 | BDA-8 | BDA-15 | BDA-25 |
| Evapor cooler size | OVA-2 | ||||
| General dimensions, mm | 2680/1212/3640 | 4100/1212/3760 | 4705/1616/3690 | 5650/2016/4350 | 7505/2216/4570 |
| Weight, kg | 2020 | 2260 | 3100 | 4990 | 8300 |
Design and principle of operation
The DA series atmospheric pressure thermal deaerator consists of a deaeration column mounted on an accumulator tank. The deaerator uses a two-stage degassing scheme: stage 1 is jet, stage 2 is bubbling, both stages are located in a deaeration column, the schematic diagram of which is shown in Fig. 1. Streams of water to be deaerated are fed into column 1 through pipes 2 onto the upper perforated plate 3. From the latter, water flows in streams onto the bypass plate 4 located below, from where it flows into the initial section of the non-failing bubble sheet 5 in a narrow beam of a jet of increased diameter. Then the water passes along the bubble sheet in the layer provided by the overflow threshold (the protruding part of the drain pipe), and through drain pipes 6 is discharged into the accumulator tank, after holding in which it is discharged from the deaerator through pipe 14 (see Fig. 2), all steam is supplied to the accumulator the deaerator tank through pipe 13 (see Fig. 2), ventilates the volume of the tank and falls under the bubble sheet 5. Passing through the holes of the bubble sheet, the area of which is selected in such a way as to prevent the failure of water at the minimum thermal load of the deaerator, the steam exposes the water to without intensive processing. As the thermal load increases, the pressure in the chamber under the sheet 5 increases, the water seal of the bypass device 9 is activated and excess steam is released into the bypass of the bubble sheet through the steam bypass pipe 10. Pipe 7 ensures that the water seal of the bypass device of deaerated water is filled with a decrease in the thermal load. From the bubbling device, steam is directed through hole 11 into the compartment between plates 3 and 4. The vapor-gas mixture (vapour) is removed from the deaerator through gap 12 and pipe 13. In the jets, water is heated to a temperature close to the saturation temperature; removal of the bulk of gases and condensation of most of the steam supplied to the deaerator. Partial release of gases from the water in the form of small bubbles occurs on plates 3 and 4. On the bubble sheet, the water is heated to saturation temperature with slight condensation of steam and micro quantities of gases are removed. The degassing process is completed in the battery tank, where tiny gas bubbles are released from the water due to sediment.
The deaeration column is welded directly to the battery tank, with the exception of those columns that have a flange connection to the deaeration tank. The column can be oriented arbitrarily relative to the vertical axis, depending on the specific installation scheme. The housings of the DA series deaerators are made of carbon steel, the internal elements are made of stainless steel, the elements are fastened to the housing and to each other by electric welding.
Schematic diagram of an atmospheric pressure deaeration column with a bubbling stage.
Scope of delivery
The delivery set of the deaeration unit includes (the manufacturer agrees with the customer on the scope of delivery of the deaeration unit in each individual case):
- deaeration column;
- a control valve on the line for supplying chemically purified water to the column to maintain the water level in the tank;
- control valve on the steam supply line to maintain pressure in the deaerator;
- pressure vacuum gauge;
- shut-off valve;
- water level indicator in the tank;
- pressure gauge;
- thermometer;
- safety device;
- vapor cooler;
- coupling shut-off valve;
- drainage pipe;
- technical documentation.
Schemes
Schematic diagram of switching on an atmospheric pressure deaeration unit:
1 - supply of chemically purified water; 2 - vapor cooler; 3, 5 — exhaust into the atmosphere; 4 — level adjustment valve, 6 — column; 7 — main condensate supply; 8 - safety device; 9 — deaeration tank; 10 — supply of deaerated water; 11 — pressure gauge; 12 — pressure control valve; 13 — hot steam supply; 14 - drainage of deaerated water; 15 — water sample cooler; 16 — level indicator; 17 - drainage; 18 - pressure and vacuum gauge.
Find out prices or
buy YES
possible through price request form or equipment order form. Expert advice can be obtained by phone 8-800-555-6001 .Deaerator- a technical device that implements the process of deaeration of some liquid (usually water), that is, its purification from unwanted gas impurities present in it (oxygen and carbon dioxide). When dissolved in water, these gases cause corrosion of feed pipes and boiler heating surfaces, resulting in equipment failure. At steam turbine stations, thermal deaeration of water is used.
The operating principle of thermal deaerators is based on the fact that the absolute pressure above a liquid is the sum of the partial pressures of gases and steam.
If we increase the partial pressure of steam so that while simultaneously removing vapor (this is a mixture of gases released from water and a small amount of steam that must be evacuated from the deaerator), then as a result we obtain the total partial pressure of gases. Then, according to Henry's law (the equilibrium mass concentration of gases in a solution is proportional to the partial pressure in the gaseous medium above the solution), i.e. there are no dissolved gases. Increases partial pressure steam, in turn, can be achieved by increasing the water temperature to the saturation temperature at a given pressure at .
Classification of thermal deaerators.
Intended use: steam boiler feedwater deaerators; make-up water and return condensate external consumers; make-up water of the heating network.
By heating steam pressure: high pressure (0.6-0.8 MPa)( D); atmospheric (0.12 MPa)( YES); vacuum (7.5-50 kPa)( Far East).
According to the method of heating deaerated water: mixing type (with mixing heating steam with heated water); deaerators of superheated water with external preheating of water with selected steam.
By design (according to the principle of formation of the interphase surface): with a contact surface formed in a turbulent mode (slim-bubble, film type with a disordered nozzle, jet disc type); with a fixed phase contact surface (film type with an ordered packing).
Schematic diagram of a deaeration installation.
Rice. Atmospheric deaerator of mixing type: 1 - tank (accumulator), 2 - outlet of feed water from the tank, 3 - water indicator glass, 4 - pressure gauge, 5, 6 and 12 - plates, 7 - draining water into the drainage tank, 8 - automatic feed regulator Chemically purified water, 9 - steam cooler, 10 - steam release into the atmosphere, 11 and 15 - pipes, 13 - deaerator column, 14 - steam distributor, 16 - water inlet into the hydraulic valve, 17 - hydraulic valve, 18 - release of excess water from hydraulic valve
The deaerator consists of a tank 1 and a column 13, inside of which a number of distribution plates 5, 6 and 12 are installed. Feed water (condensate) from the pumps enters top part deaerator onto distribution plate 12; through another pipeline through regulator 8, chemically purified water is supplied to plate 12 as an additive; From the plate, feed water is distributed in separate and uniform streams over the entire circumference of the deaerator column and flows down sequentially through a series of intermediate plates 5 and 6 located one below the other with small holes. Steam for heating water is introduced into the deaerator through pipe 15 and steam distributor 14 from below water curtain, formed when water flows from plate to plate, and, diverging in all directions, rises up, towards feed water, heating it up. At this temperature, air is released from the water and, together with the remainder of the uncondensed steam, leaves through the lead pipe 11, located in the upper part of the deaeration head, directly into the atmosphere or steam cooler 9. The oxygen-free and heated water is poured into the collection tank 1, located under the deaerator column , from where it is used to power boilers. To avoid a significant increase in pressure in the deaerator, two hydraulic valves are installed on it, as well as a hydraulic valve 17 in case of vacuum formation in it. If the pressure is exceeded, the deaerator may explode, and if there is a vacuum atmospheric pressure may crush it. The deaerator is equipped with a water indicator glass 3 with three taps - steam, water and purge, a water level regulator in the tank, a pressure regulator and the necessary measuring equipment. For reliable operation For feed pumps, the deaerator is installed at a height of at least 7 m above the pump.