Atmospheric type deaerator purpose device. Deaerator - what is it? Types, device, principle of operation

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Deaerator -- technical device, which implements the process of deaeration of a certain liquid (usually water or liquid fuel), that is, its purification from undesirable gas impurities present in it. In many power plants, it 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 nozzles.

Fig.2.

1 - tank (accumulator), 2 - outlet of feed water from the tank, 5 - water-indicating glass, 4 - pressure gauge, 5, 6 and 12 - plates, 7 - draining water into the drain, 8 - automatic regulator supply of chemically purified water, 9 - steam cooler, 10 - steam outlet to the atmosphere, 11 and 15 - pipes, 13 - deaerator column, 14 - steam distributor, 16 - water inlet to the hydraulic seal, 17 - hydraulic shutter, 18 -- release of excess water from the hydraulic seal

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 vapor carries gases out of the system, and the diffusion coefficient increases.

The vortex deaerator uses hydrodynamic effects that cause forced desorption, that is, lead to fluid rupture in the most weak points- under the influence of the density difference. In this case, there is no heating of the liquid.

By pressure thermal deaerators classified into:

* Vacuum (DV)

* Atmospheric (YES).

* Increased pressure (DP).

Atmospheric deaerator - used in the smallest wall thickness. Under the action of excess pressure above atmospheric - steam is removed from the walls by gravity. Atmospheric deaerator DSA is designed to remove corrosive gases from the system of steam boilers and boiler plants. Atmospheric deaerators are installed both outdoors and indoors. The numbers marked on the atmospheric deaerator DSA 75 and deaerator DA 25 - determine the performance of the device.

Vacuum deaerator - are used in conditions when boiler rooms do not have released steam. Vacuum deaerators DV - are forced to work in conjunction with devices for suction of vapor. The DV feed water 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 a large wall thickness, but the DP deaerators allow the use of vapor as a light working medium for condenser ejectors. Also, excess high pressure deaerators can reduce the amount of metal-intensive HPH.

Deaerator device and principle of operation

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 the convenience of the internal inspection of the deaeration column. Material of perforated sheets internal devices deaerator columns - corrosion-resistant steel.

The deaeration tank houses the third stage of degassing after the deaeration column in the form of a flooded bubbling device.

In the deaerator tank, tiny gas bubbles are released from the water due to sludge.

The deaerator vapor cooler serves only to recover the vapor condensation heat. Chemically purified water passes inside the tubes of the vapor cooler and is directed to the deaeration column. A vapor-gas mixture (evaporator) enters the annular space, where the steam from it is almost completely condensed. The remaining gases are discharged into the atmosphere, the vapor condensate is drained into a deaerator or drainage tank

Tube material - brass or corrosion-resistant steel.

The operation of the deaerator is carried out automatically. The pressure in the deaerator is constantly regulated at the level of 0.02 MPa. The water level in the deaerator is also constantly maintained. Deaerators are started and stopped manually

Fig.3.

The deaeration plant consists of:

· Vacuum deaerator;

· HVV (vapour 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. 1st stage jet, 2nd - bubbling, non-failing perforated plate.

A vacuum deaerator is used to deaerate water if its temperature is below 100 °C (the boiling point of water at atmospheric pressure).

The area for the design, installation and operation of a vacuum deaerator are hot water boilers (especially in a block version) and heat points. Vacuum deaerators are also actively used in Food Industry for deaeration of water necessary in the technology of preparing a wide range of beverages.

Vacuum deaeration is applied to the water flows going to make up the heating network, the boiler circuit, the hot water supply network.

Features of the vacuum deaerator.

Since the process of vacuum deaeration occurs at relatively low water temperatures (on average from 40 to 80 °C, depending on the type of deaerator), the operation of a vacuum deaerator does not require the use of a coolant with a temperature above 90 °C. The heat carrier is necessary for water heating in front of the vacuum deaerator. The coolant temperature up to 90 °C is provided at most facilities where it is potentially possible to apply vacuum deaerator.

The main difference between a vacuum deaerator and an atmospheric deaerator is in the system for removing vapor from the deaerator.

In a vacuum deaerator, vapor (vapor-gas mixture formed during the release of saturated vapors and dissolved gases from water) is removed using vacuum pump.

As a vacuum pump can be used: vacuum liquid ring pump, water jet ejector, steam jet ejector. They are different in design, but are based on the same principle - reducing static pressure(creation of rarefaction - vacuum) in the fluid flow with increasing flow rate.

The fluid flow rate increases either when moving through a converging nozzle (water jet ejector) or when the fluid swirls as the impeller rotates.

When steam is removed from the vacuum deaerator, the pressure in the deaerator drops to the saturation pressure corresponding to the temperature of the water entering the deaerator. The water in the deaerator is at the boiling point. At the water-gas interface, a difference in concentrations arises for the gases dissolved in water (oxygen, carbon dioxide) and, accordingly, appears driving force deaeration process.

The quality of the deaerated water after the vacuum deaerator depends on the efficiency of the vacuum pump.

Features of the installation of a vacuum deaerator.

Because the water temperature in the vacuum deaerator is below 100 °C and, accordingly, the pressure in the vacuum deaerator is below atmospheric - vacuum, the main question arises in the design and operation of a vacuum deaerator - how to supply the deaerated water after the vacuum deaerator further to the heat supply system. This is the main problem of using a vacuum deaerator for water deaeration at boiler houses and heating stations.

Basically, this was solved by installing a vacuum deaerator at a height of at least 16 m, which provided the necessary pressure difference between the vacuum in the deaerator and atmospheric pressure. Water flowed by gravity into the storage tank located at the zero mark. The installation height of the vacuum deaerator was chosen based on the maximum possible vacuum (-10 m.a.c.), the height of the water column in the accumulator tank, the resistance of the drain pipeline and the pressure drop necessary to ensure the movement of deaerated water. But this entailed a number significant shortcomings: an increase in the initial construction costs (a 16 m high stack with a service platform), the possibility of water freezing in the drain pipeline when the water supply to the deaerator is stopped, water hammer in the drain pipeline, difficulties in inspecting and maintaining the deaerator in winter.

For block boilers that are actively designed and installed, this solution is not applicable.

The second solution to the issue of supplying deaerated water after a vacuum deaerator is to use an intermediate deaerated water storage tank - a deaerator tank and pumps for supplying deaerated water. The deaerator tank is under the same vacuum as the vacuum deaerator itself. In fact, the vacuum deaerator and the deaerator tank are one vessel. The main load falls on the deaerated water supply pumps, which take the deaerated water from under vacuum and feed it further into the system. To prevent the occurrence of cavitation in the pump for supplying deaerated water, it is necessary to ensure that the height of the water column (the distance between the water surface in the deaerator tank and the pump suction axis) at the pump suction is not less than the value indicated in the pump passport as NPFS or NPFS. The cavitation reserve, depending on the brand and performance of the pump, ranges from 1 to 5 m.

The advantage of the second layout of the vacuum deaerator is the ability to install the vacuum deaerator at a low height, indoors. Deaerated water supply pumps will ensure that deaerated water is pumped further into storage tanks or for a drink. To ensure a stable process of pumping deaerated water from the deaerator tank, it is important to choose the right pumps for supplying deaerated water.

Improving the efficiency of the vacuum deaerator.

As vacuum deaeration water is carried out at a water temperature below 100 ° C, the requirements for the technology of the deaeration process increase. The lower the water temperature, the higher the coefficient of solubility of gases in water, the harder process deaeration. It is necessary to increase the intensity of the deaeration process, respectively apply Constructive decisions based on new scientific developments and experiments in the field of hydrodynamics and mass transfer.

The use of high-speed flows with turbulent mass transfer when creating conditions in the liquid flow to further reduce the static pressure relative to saturation pressure and obtain a superheated state of water can significantly increase the efficiency of the deaeration process and reduce dimensions and the weight of the vacuum deaerator.

For complete solution the issue of installing a vacuum deaerator in the boiler room at zero with a minimum overall height, a block vacuum deaerator BVD was developed, tested, and successfully put into serial production. With a deaerator height slightly less than 4 m, the block vacuum deaerator BVD allows efficient deaeration of water in the performance range from 2 to 40 m3/h for deaerated water. The block vacuum deaerator occupies no more than 3x3 m space in the boiler room (at the base) in its most productive design.

Thermal deaerators are usually classified by operating pressure and by the method of organizing phase contact.

According to the working pressure, the following types of deaerators are distinguished:

Vacuum, operating at an absolute pressure in the housing from 0.075 to 0.5 atmospheres;

Atmospheric, the absolute pressure in which varies from 1.1 to 1.3 atmospheres;

High pressure, operating at an absolute pressure of 5 to 12 atmospheres.

The method of organizing phase contact is determined by the design of the deaerator. Since in the same deaerator, as a rule, several different from each other according to the principle of operation are used deaeration devices, modern deaerators are usually combined. In this case, the following main types of deaeration devices (or individual elements deaerators):

Jet, in which the phase interface is formed by the surface of freely falling water jets in the steam flow;

Bubbling, in which the heating coolant in the form of steam bubbles is distributed in the water flow;

Film, where the phase interface is formed during the film flow of water in a vapor stream;

Drip, in which water is distributed in the vapor stream in the form of drops.

The phase interface 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 area of ​​application of deaerators in the thermal circuits of power facilities, as a rule, is determined by the operating pressure, high-pressure deaerators are used exclusively as feed water deaerators for thermal power plants of high, ultra-high and supercritical initial steam pressure;

Atmospheric pressure deaerators are used as feed water deaerators for power plants and boiler houses with low and medium initial steam pressure, make-up water deaerators for the cycle of combined heat and power plants (CHP) with a higher initial steam pressure, make-up water deaerators for heating networks closed type(less often - for a heating network open type using deaerated water coolers), feed water deaerators for evaporative and steam-converting plants of power plants;

Vacuum deaerators are used as make-up water deaerators for heating networks, in the schemes of evaporative and steam-converting plants, less often - as make-up water deaerators for the cycle of power plants and boiler houses.

Atmospheric pressure deaerators

The most common type of atmospheric deaerator is jet-bubble deaerators. In such deaerators, as a rule, two-stage scheme deaeration, including jet and bubbling stages. It should be noted that under the stage of deaeration it is customary to understand one or more deaeration elements connected in series with water, operating according to 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-bubble atmospheric deaerators were developed by NPO TsKTI im. I.I. Polzunov. Currently, both outdated models of such deaerators (DSA type) and their modern counterparts (DA and DA-m types) are used. A standard range of standard sizes of such deaerators has been developed, which differ in the nominal capacity for deaerated water: 1, 3, 5, 15, 25, 50, 100, 200 and 300 t/h.

Atmospheric deaerators usually 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. First, it serves as a means of creating a supply of deaerated water for technological scheme. If, for example, the deaerator is used as a deaerator for steam boiler feed water low pressure, then it is necessary to create a supply of water in the deaerator tank to ensure uninterrupted power supply to these boilers in emergency situations. Secondly, as shown above, the deaerator tank allows you to increase the holding time of water at a temperature close to the saturation temperature, which helps to improve the efficiency of deaeration.

With regard to devices of low productivity (1 and 3 t / h for deaerated water), the deaerator can perform the indicated functions without a deaerator tank, since the necessary water supply can be created directly in the body of the deaeration column, the dimensions of which will not be too large. AT standard designs such deaerators do not distinguish between a deaeration column and a deaerator tank, but speak of the deaerator body as a whole. Such deaerators are called columnless.

Deaerators of higher capacity 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 request of the customer, 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 produced by the following main domestic factories:

Neftekhimmash oborudovanie LLC, Biysk Boiler Plant OJSC, Sibenergomash OJSC, Belenergomash OJSC, Teploenergokomplek CJSC, TKZ-Krasny Kotelshchik OJSC, Sarenergomash OJSC.

Below we consider the main design solutions used in atmospheric pressure deaerators and their piping elements: vapor coolers and safety drain devices.

Consider the design scheme 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 scheme columnless deaerators DA-1 and DA-3: 1 - source water inlet fitting; 2 - perforated water distribution manifold; 3 - jet-forming plate; 4 - water intake tray; 5 - sectioning threshold of the jet-forming plate; 6 - restrictive threshold of the jet-forming plate; 7 - bubbling device; 8 - bubbling sheet; 9 and 10 - partitions; 11 - outlet of deaerated water; 12 - fitting for supplying heating steam; 13 - steam pipeline; 14 - steam intake box; 15 - steam bypass window; 16 - steam inlet window; 17 - inlet window of the built-in vaporizer cooler; 18 - fitting for the removal of steam; 19 - hatch; 20 and 21 - fittings for connecting a safety drain device, respectively, for steam and water; 22 - drainage fitting.

energy desorption bubbling hydrodynamic

Deaerator DA-1 or DA-3 is a vertical cylindrical vessel with elliptical bottoms and deaeration devices placed inside it.

The water directed for deaeration enters the deaerator through a fitting 1 and a perforated water distribution manifold 2. From the holes of the water distribution manifold 2, water flows in the form of jets onto a jet-forming plate 3, perforated in the part located above the water intake tray 4. The jet-forming plate 3 is sectioned by a threshold 5 in such a way that that with a small hydraulic load, water flows in the form of jets into the tray 4 only through the holes located up to the 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 overflows through the threshold 5, and all holes of the jet-forming plate are put into operation. Such sectioning of the jet-forming plate 3 is made so that at low hydraulic loads of the deaerator there is no sweep (“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 an increased hydraulic load, the water level on the jet-forming plate increases and if water overflows through the threshold 6, the efficiency of water heating and deaeration deteriorates sharply.

In the jet stream inside the tray 4, the main heating of the water occurs when it comes into contact with the heating steam, and the degassing process begins. Water draining from tray 4 in the form of a flow into the water volume of the deaerator, under most modes of operation of the deaerator, remains subcooled to a saturation temperature corresponding to the pressure in the vapor space of the deaerator, and contains gases both in dissolved and dispersed form.

After a certain soaking 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 of rectangular cross section, limited from above and on the sides by solid partitions and having a perforated bubbling device in the lower part. sheet 8. When bubbling steam through a layer of water in the bubbling device 7, the water is heated to a saturation temperature corresponding to the pressure in the bubbling device. This pressure is greater than the pressure in the vapor space of the deaerator above the water surface by the pressure of the water column height H, therefore, the water temperature in the bubbling device becomes higher than the saturation temperature at the vapor pressure above the water surface in the deaerator. In the bubbling device 7, due to the water reaching the saturation temperature most of dissolved gases passes into a dispersed state in the form of small gas bubbles, here there is a partial thermal decomposition of bicarbonates and hydrolysis of carbonates with the formation of free carbon dioxide, which, in turn, also passes into a dispersed state.

After leaving 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 vapor pressure above the water surface in the deaerator. Accordingly, water, which turns out to be superheated relative to the saturation temperature, boils in volume, which is accompanied by the transition of most of the gases that are still in dissolved form into a dispersed state. In the upper part of the water volume, phase separation occurs: water overflows through the partition 10 and descends towards the deaerated water outlet 11, and the steam with the gases released from the water moves towards the jet deaeration stage.

It should be noted that the breakthrough of the steam-water mixture from the bubbling device 7 directly into the deaerated water outlet 11 is unlikely. The flow of the medium in the gap between the baffles 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 baffle 10 and the wall of the housing, which causes only the upward movement of the medium between the baffles 9 and 10. Meanwhile, the gap between baffle 10 and the housing in the lower part is necessary to allow some circulation of water around the baffle 10. Such circulation increases the frequency of water treatment with steam and increases the available time for the deaeration process, which increases the efficiency of removing gases from the water.

All the heating steam is supplied to the deaerator through the fitting 12 and through the steam line 13 enters the steam intake box 14 under the bubbling sheet 8. In this case, a steam cushion is created under the bubbling sheet 8, which prevents water from falling through the holes of the bubbling sheet. Such bubbling sheets are called non-failure.

Here it is advisable to dwell in more detail on the limiting mode of operation of a non-failing bubbling sheet - the “flooding” mode or the injection mode. If the steam velocity in the holes in the sheet is too high, the steam coming out of the holes in the bubbling sheet captures all the liquid, crushes it and carries it away in the form of splashes. It is for this reason that the maximum vapor pressure under the bubbling 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 bubbling sheet 8 when the steam pressure under this sheet increases in excess of what is necessary for effective work bubbling device.

After the separation of water and the vapor-gas mixture in the upper part of the channel formed by partitions 9 and 10, this mixture enters through the steam inlet 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 out of the water distribution manifold 2, through which the vapor-gas mixture passes, entering through the window 17. Here, the water vapor is additionally condensed on the jets relatively cold water. The remaining small part of the steam and non-condensable gases are discharged from the deaerator through the vapor outlet fitting 18.

Deaerators DA-1 and DA-3 are equipped with a hatch 19, which provides access to the inside of the housing for its inspection and repair, as well as fittings 20 and 21 for connecting a safety drain device and a 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 this example two) jet compartments formed below the top 8 and bottom 9 perforated trays, and can also be supplemented with a bubbling sheet. The water to be deaerated is supplied through the water distribution system to the upper jet-forming plate 8, from where it flows to the plate 9 located below and then to the bubbling sheet (if any) or directly to the deaerator tank (as in the example under consideration). Jet plates have special thresholds that maintain a certain level of water on them, as well as water overflow in addition to the jet zone when the plates overflow. Bubbling sheets are usually made non-failure (the dynamic effect of the steam flow does not allow water to “fall through” through the holes of the sheet), since the operation of a failed bubbling 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 - evaporation to the atmosphere; 4 - supply of third-party condensate (for example, steam condensate from production extractions 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 - bubbling steam supply; 13 - pressure control devices; 14 - pressure regulator; 15 - main steam supply; 16 - removal of deaerated water; 17 - level indicator; 18 - drainage; 19 - hot condensate supply.

Steam is usually supplied to the surface space of the deaerator tank (and is called in this case 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.

Evaporation 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 before the deaeration column. In this case, gas purge 3 is carried out from the steam space of the vapor cooler. It is possible to supplement this design with a bubbling device of the deaerator tank. The most commonly used devices of the CKTI system (in this example) or perforated bubbling collectors mounted on the bottom of the tank along its generatrices. The bubbling steam 12 is supplied in this case 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 glasses 17; branch pipes for connecting the deaerator to steam and water equalizing lines; drainage pipeline 18; outlet pipe for deaerated water 16.

The operating experience of 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 deaerator tank makes it possible to increase this efficiency.

Even if the deaeration column provides the required quality of deaerated water, the bubbling device of the deaerator tank works as a barrier device, which reduces the likelihood of a breakthrough of dissolved gases into the deaerated water and expands the allowable range of changes in the hydraulic and thermal loads of the deaerator while maintaining the required quality of the 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 re-contamination of 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 is a set of tiny gas bubbles, the dimensions of which are so small that they do not provide 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 enter the deaerated water. Steam bubbling, which provides intensive mixing and turbulence of the volume of water in the tank, promotes the release of part of the gases in dispersed form from the water, increasing the deaeration efficiency as a whole.

Thus, a flooded deaerator tank bubbling device is often necessary even when using modern two-stage deaerator columns.

Consider, as an example, the bubbling device of the CKTI system (Fig. 3.2.).

Rice. 3.2. circuit diagram bubbling device of the deaerator tank of the CKTI system: 1 - bubbling sheet; 2 - top shelf; 3 - mine lifting movement; 4 - removal of deaerated water; 5 - deaeration column; 6 - deaerator tank; 7 - bubbling steam supply; 8 - main steam supply; solid lines - the direction of water movement; dotted lines - steam movement directions

The water passes through the channel formed by the surface of the bubbling sheet 1 and the upper shelf 2, and in this movement is treated with steam coming out of the holes of the bubbling sheet. The steam-water mixture, leaving the channel, enters a specially organized lift 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 surface space of the deaerator tank and mixed with the flow of the main steam, and the water descends into the water tank volume to the deaerated water outlet 4.

Actually deaerator tanks (see example in Fig. 3.4) are horizontally located cylindrical vessels with elliptical, less often conical, bottoms, mounted on two supports. Moreover, for tanks with a useful capacity of 25 m 3 or more, one of the supports is movable (roller), which provides compensation for thermal 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 hull.

Rice. 3.4. General form deaerator tank with a useful capacity of 75 m 3: A - fitting for a deaeration column; B - fitting for connecting a safety-draining device for steam; В - fitting for supplying the main steam; D - drainage fitting; D - outlet of deaerated water; E - fitting for connecting the safety-draining device for water; Zh - fittings for connecting a level indicator; С - fitting for discharge from the continuous blowdown separator of the boiler; T - fitting for introducing feed water from the recirculation line feed pumps; Y - fitting for input of overheated condensates; Ф - fitting for introducing a steam-air mixture from the steam space of the heaters; C - fitting for supplying steam to the flooded bubbling device of the deaerator tank; H - reserve fitting

Columns are articulated with deaerator tanks, as a rule, by means of welding. In the designs of modern deaerators, the column is located near one of the ends of the deaerator tank, the removal of deaerated water from the tank is carried out from the opposite end. This achieves the maximum possible water holding time in the deaerator tank at a temperature close to the saturation temperature for given geometric characteristics, and, accordingly, the highest deaeration efficiency.

Deaerator 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 with an overflow funnel, the height of the upper edge is which determines the maximum level of water in the tank). Fittings are provided for connecting the deaerator to steam and water equalizing lines, necessary for the parallel operation of several deaerators, a fitting for deaerating 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 operating pressure in the deaerator, or the introduction of flows of already deaerated water. If the flows overheated relative to the saturation temperature in the deaerator are directed not to the deaerator tank, but to the deaeration column, then the steam formed during their boiling can disrupt the normal ventilation of the deaerator steam space, which, in turn, will lead to a deterioration in the efficiency of water deaeration.

Atmospheric pressure deaerators are designed to remove corrosive gases (oxygen and free carbon dioxide) from the feed water of steam boilers and make-up water of heat supply systems and in the boiler room.

Example symbol deaerator

DA-5/2
Where: YES - atmospheric deaerator;
5 - column capacity m³/h;
2 - tank capacity m³;

Specifications, completeness and types of deaerators

The device and principle of operation of the deaerator
The deaerator includes:
- deaeration column;
- deaerator tank;
- vapor cooler;
- combined safety device for protection against emergency increase in pressure and level.

The deaerator uses a two-stage degassing scheme: two stages are placed in the deaeration column: the 1st stage is jet, the 2nd is bubbling.

Fig 1. Scheme of atmospheric pressure deaeration plant type DA

1 - Deaerator tank; 2 - Deaeration column; 3 - Steam cooler; 4 - Safety device; 5 - Level regulator; 6 - Pressure regulator; 7 - Sampling refrigerator; 8 - Bubbling device; 9 - Sparging plate; 10 - Bypass plate; 11 - Top plate; 12 - Steam bypass device; 13 - Level indicator; 14 - Manhole hatch.

In the deaerator tank there is a third, additional stage, in the form of a flooded bubbling device.

Water to be deaerated is supplied to the column(2) through fittings (A, 3, I, D). Here it successively passes through the jet and bubbling stages, where it is heated and treated with steam. From the column, water flows in streams into the tank, after holding in which it is discharged from the deaerator through the fitting (G).

The main steam is supplied to the deaerator tank through a fitting(E), ventilates the vapor volume of the tank and enters the column. Passing through the holes of the bubbling tray (9), the steam subjects the water on it to intensive treatment (the water is heated to saturation temperature and micro-quantities of gases are removed). When the heat load increases, the water seal of the steam bypass device (12) is activated, through which the steam is bypassed into the bypass of the bubbling tray. When the heat load decreases, the water seal is filled with water, stopping the bypass of steam.

From the bubbling compartment, steam is directed to the jet compartment. In the jets, water is heated to a temperature close to the saturation temperature, the bulk of the gases are removed, and most of the steam is condensed. The remaining gas-vapor mixture (flash) is discharged from the upper zone of the column through the fitting (B) to the vapor cooler (3) or directly to the atmosphere. The degassing process is completed in the deaerator tank (1), where the smallest gas bubbles are released from the water due to sludge. Part of the steam can be supplied through a fitting to a bubbling device (8) located in the water volume of the tank, designed to ensure reliable deaeration (especially in the case of using water with low bicarbonate alkalinity (0.2 ... 0.4 meq / kg) and high content of free carbon dioxide (more than 5 mg/kg) and with sharply variable loads of the deaerator.

The design of the internal devices of the deaeration column ensures the convenience of internal inspection. Perforated sheets of internal devices are made of corrosion-resistant steel.

The surface vapor cooler consists of a horizontal body and a pipe system(pipe material - brass or corrosion-resistant steel).

The chemically treated water passes inside the tubes and is sent to the deaeration column through the fitting (A). The steam-gas mixture (vapour) enters the annular space, where the steam from it is almost completely condensed. The remaining gases are discharged into the atmosphere, the vapor condensate is drained into a deaerator or a drainage tank.

To provide safe operation deaerators, they are protected from a dangerous increase in pressure and water level in the tank using a combined safety device.

The device is connected to the deaerator tank through an overflow fitting.

The device consists of two hydraulic seals, one of which protects the deaerator from exceeding allowable pressure, and the other from a dangerous increase in the level, combined into a common hydraulic system, and expansion tank. The expansion tank is used to accumulate the volume of water (when the device is triggered), which is necessary for automatic filling of the device (after the elimination of a malfunction in the installation), i.e. makes the device self-priming.

The diameter of the steam hydraulic seal is determined based on the highest allowable pressure in the deaerator during operation of the device 0.07 MPa and the maximum possible pressure in emergency steam flow to the deaerator with the control valve fully open and the maximum pressure in the steam source.

Installation and installation procedure of the deaerator
Before installation of the deaerator it is necessary to: inspect and depreserve; cut off the welded plugs with gas, and cut the edges of the pipes for welding.

1. The deaerator is preferably located indoors. Its installation in the open air is allowed in justified cases (by decision of the design organization).

2. The deaerator tank is installed strictly horizontally on a pre-prepared concrete foundation (with anchor bolts installed), or on a metal shelf. One support is rigidly fixed with bolts, the second rests freely on the base sheet.

3. The deaeration column is installed on the tank by welding to the adapter. Relative to the vertical axis, the column can be oriented arbitrarily, depending on the specific installation layout.

4. Scheme of installation of the deaerator, accessory equipment and their piping, as well as the scheme and control devices and automatic regulation is determined by the design organization depending on the conditions, purpose and capabilities of the facility on which they are installed.

5. Scheme deaeration plant it should be possible to carry out hydraulic test(before commissioning and periodically as needed) overpressure 0.2 MPa. The vapor cooler is tested with an excess pressure of 0.6 MPa.

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