Vacuum deaeration of water in a hot water boiler. Atmospheric deaerators

Heating boilers most often made of steel. The water passing through them contains oxygen and carbon dioxide. Both of these elements have metal constructions the boiler is extremely Negative influence. Constant contact of steel with these gases inevitably leads to its rusting. In order to correct the situation and extend the life of the equipment, a special installation is switched on in boiler rooms - a deaerator. What it is? We will talk about this later in the article.

Definition

The deaerator is called special equipment designed to remove oxygen from the coolant of heating systems by heating the latter with steam. Thus, in addition to the cleaning function, devices of this type also perform thermal. The same deaeration unit can be used to heat and treat both feed and make-up water.

Design features

The relative simplicity of design is what distinguishes the deaerator. What is it, we found out. Now let's see how this equipment works. It is a boiler tank deaerator (BDA) with a vertical column (KDA) mounted on it, mounted on supports. Optional element equipment of this type is a hydraulic system that protects it from overpressure. The column is welded to the tank without a flange - directly.

On the horizontal tank deaerator, inlet and outlet pipes were installed to connect the medium supply and discharge lines. Plums are installed below. Another design element is a collection tank designed to collect degassed water. It is located under the bottom of the BDA.

Equipment such as a deaerator, the diagram of which is presented below, usually consists of two water seals. One of them protects the device from any excess allowable pressure, and the second - from the dangerous. Also in the design hydraulic system deaerator included expansion tank. The vapors from the deaerator enter a special cooler, which has the form of a horizontal cylinder.

Column design

The column is a cylindrical shell with an elliptical bottom. As on the tank, it has branch pipes for supplying and discharging the medium. Inside the column there are special plates with holes through which water passes. This design allows you to significantly increase the area of ​​contact between the medium and steam, and therefore, to produce heating at maximum speed.

Equipment types

In modern boiler rooms, a water deaerator can be installed:

vacuum;

atmospheric.

In the first type of deaerators, the removal of gases from water is carried out in a vacuum. The design of such installations additionally includes a steam or water jet ejector. The latter type of nodes is most often used in systems with medium or low power. Instead of ejectors, special pumps can be used to create a vacuum. Some disadvantage of equipment such as a vacuum deaerator is that steam must be removed from it forcibly, while it comes out of the atmosphere naturally - under pressure.

In addition to the two types of deaerators considered, high-pressure devices can be installed in boiler rooms. They work at 0.6-0.8 MPa. Sometimes in thermal scheme boiler rooms also include reduced pressure equipment.

Scope of use

Where can a deaerator be used? What is it, you now know. Since such a device is designed to degas the working environment, it is mainly used where there is heating equipment made of steel.

Most often, deaerators are used in heating and hot water systems. Boiler rooms with hot water boilers usually equipped with vacuum type. Also in such schemes atmospheric deaerators can be used. Reduced and increased pressure installations are mainly used in systems that function due to the operation of a steam boiler. The first variety (at 0.025-0.2 MPa) is mounted in not too powerful systems designed for a small number of consumers. are used in thermal circuits with boilers supplying a large number of pair.

Disc deaerator: principle of operation

The gas purification scheme in deaerators is implemented in two stages: jet (in the column) and bubbling (in the tank). In addition, a flooded bubbling device is included in the system. Water is fed into the column, where it is treated with steam. Then it flows into the tank, is kept in it and is discharged back into the system. Steam is initially supplied to the BDA. After ventilation of the internal volume, it enters the column. Passing through the holes of the bubbling tray, the steam heats the water to saturation temperature.

The jet method removes all gases from the water. At the same time, steam condenses. Its residues are mixed with the gas released from the medium and discharged into the cooler. The steam condensate drains into drainage tank. During the settling of water in the tank, residual small gas bubbles come out of it. Water is drained into a collection tank. Sometimes a horizontal tank is used only for settling. In such installations, both stages of degassing are placed in a column.

Make-up water deaeration

The coolant in the heating system circulates continuously. But its volume over time, as a result of leaks, still gradually decreases. Therefore, make-up water is supplied to the heating system. Like the main one, it must undergo a deaeration process. Initially, water enters the heater, and then passes through the filters chemical cleaning. Further, as well as nutrient, it enters the deaerator column. Released from flows to the latter directs it to the suction manifold or storage tank.

Chemical deaeration

Thus, the answer to the question of what a boiler room deaerator is is simple. This is equipment designed to boil water with hot steam in order to remove oxygen. However, sometimes gases from the coolant in such installations are not completely removed. In this case, for additional purification, boiler water can be added different kind reagents designed to bind oxygen. It can be, for example, In this case, for high-quality deaeration of water, its heating is required. Otherwise chemical reactions will be too slow. Also, various kinds of catalysts can be used to accelerate the process of oxygen binding. Sometimes water is also deaerated by passing through a layer of ordinary metal shavings. The latter in this case are rapidly oxidized.

Mounting Features

The deaerator device is not too complicated. However, its installation must be carried out with strict observance of all required technologies. When installing such equipment, they are primarily guided by the drawings attached to it by the manufacturer and the design of the boiler room. Before installation, the installation is inspected and depreserved. Found defects are eliminated. The actual installation procedure itself includes the following steps:

the tank is mounted on the foundation;

a spillway neck is welded to it;

the lower part of the column is cut to the outer diameter;

the column is installed on the tank (at the same time, the plates fixed inside it must be located strictly horizontally);

the column is welded to the tank;

a vapor cooler and a water seal are installed;

in accordance with the drawings, the lines are connected;

shut-off and control valves are installed;

are held hydraulic tests equipment.

Spray installations

The designs discussed above are called dish-shaped. There are also spray deaerators. Devices of this type are used less often and also represent a horizontal storage tank large capacity. The absence of a column is what distinguishes such a deaerator. Its working principle is also slightly different. Steam in such installations comes from below - from a comb located horizontally in the tank. The container itself is divided into a heating and deaeration zone. The feed water of the boiler enters the first compartment from the atomizer located on top. Here it is heated to the boiling point and enters the deaeration zone, where oxygen is removed from it by steam.

So, that's all that can be said about such a device as a deaerator. What is it, we hope you understand, since we have given a fairly detailed answer to this question. This is the name of the installation that provides long work hot water and steam boilers. The choice of the type and methods of installation of this equipment is carried out in accordance with technical specifications heating equipment and boiler room project.

In order to achieve durability and quality of the hydraulic system, it is necessary to use a deaerator. It is used in all boiler houses, as it establishes a stable and correct work systems. In our article, we will consider in more detail what a deaerator is in a boiler room.

What is a deaerator and why is it used in a boiler room

Deaeration is the process of purifying a liquid from various impurities. For example, from carbon dioxide and oxygen. To organize a water treatment system in a boiler room, a deaerator must be used. It helps improve the quality of your work.

The first method is chemical deaeration. In this case, reagents are added to the water, as a result of which excess gases are removed from the water. The second method is called thermal deaeration. Water is heated to a boil until it is clear of gaseous substances that are dissolved in it.

Deaerators are divided into atmospheric and vacuum. The former are used with water or steam. And vacuum only with steam.

Deaerators have a common two-stage device. Thus, water enters the tank, where it flows through the membranes, and then it is cleaned of impurities. Chemical water, which is in the tank, prevents the formation of various natural impurities in the coolant.

Deaerators are of low and high pressure. Since oxygen and carbon dioxide are corrosive gases, they contribute to the formation of corrosion in pipelines, and also wear them out. In order to prevent this from happening, it is necessary to prepare it before supplying water through pipelines. This is what air filters are used for.

Due to the gas content of water, various malfunctions occur in the system. Some of them can lead to a water or gas leak or completely disable the system. The presence of gas bubbles in the water leads to poor performance of pumps, nozzles and impairs the function of the hydraulic system. Installing a deaerator in a boiler room will be cheaper than frequently repairing the system.

Deaeration of water in a steam boiler

Water deaeration in a steam boiler is necessary to protect the entire steam generator system and pipelines. In the presence of harmful impurities, the system will wear out and begin to corrode.

Gaseous and natural impurities can cause pump cavitation. And it, in turn, can lead to hydraulic shocks and disrupt the operation of the pumping mode. AT worst case the hydraulic system may break or the pumps will stop working altogether.

The deaerator, which is used for a steam boiler, has the form of a tank with special membranes and plates. They are arranged vertically on the water tank. Under low pressure, water enters the tank from the supply line, then flows through the membranes and plates, and thus impurities are removed.

Spray deaerators are sometimes used in steam boilers. In them, water is sprayed in such a way that impurities immediately go into the evaporation.

High pressure system

The high pressure system is used for boilers with high power. They supply a lot of steam and also provide the necessary temperature regime for centralized heating system under high pressure. The operation of the system requires a pressure of more than 0.6 MPa.

Such an installation is thermal as well as a reduced pressure deaerator. This means that with an increase in the temperature regime of water and steam supply, the system is released from gaseous impurities.

Water seals are installed in the system. They lower the pressure when it rises.

Reduced pressure system

For a reduced pressure system, atmospheric and vertical type, which are equipped with a bubbling additional tank. Evaporation occurs through it.

In the main tank of the system, the chemically prepared mixture is mixed with water, then it flows through membranes and plates, and then all impurities are separated.

Boilers that provide hot water need a vacuum thermal system. Since vacuum degassing is best suited for such a boiler room. Such a system is used to purify water in water-heating boilers.

Depending on what mode of steam supply is required for steam boilers, high or low pressure deaerators are used. For less powerful boiler rooms that provide a low temperature regime, which is suitable for central heating, use the setup with reduced pressure. It can be 0.025-0.2 MPa.

Proper operation

For high-quality operation of the boiler and to prevent emergencies the deaerator and the entire system must be used correctly. To do this, it is necessary to maintain the water in the tank at a certain level with a decrease in pressure, check the conditions of the required mode, follow all the rules for use and check the operation of the devices more than 1 time per shift.

AT chemical water it is necessary to add substances correctly, as well as to control their level. Check the quality of chemical water.

Water seals must be easy to move. In the event of an increase in pressure, they must be used without any interference. All devices must be metrologically qualified and tested. They must comply with pre-established schedules. The water level can be monitored using a special water-indicating glass. Do not forget about the control of the manometer readings.

All automation devices must work properly for the correct operation of the deaerator. It is necessary to check the operation of machines and devices. To do this, regular inspections and checks are carried out.

The deaerator acts as protection for the entire boiler system. Therefore, each boiler room is equipped with such an installation.

Since cavitation leads to failure of the pump and hydraulic system, the deaerator is simply necessary in the boiler room. Such a device completely purifies water from all impurities. Thus, the system works without any damage.

N.N. Gromov, Chief Engineer AP "Teploset" of the Krasnogorsk region

AT recent times a large number of steam boilers (DKVR, DE, E, etc.) are converted into hot water mode, while the deaerators of boiler rooms remain without steam. Effective Method, developed and tested for 10 years in the AP "Teploset" of the Krasnogorsk region, allows degassing water without steam supply and without disadvantages without alterations of the deaerator vacuum deaeration.

Thermal deaeration

Water always contains dissolved aggressive gases, primarily oxygen and carbon dioxide, which cause corrosion of equipment and pipelines. Corrosive gases enter the source water as a result of contact with the atmosphere and other processes, such as ion exchange. The main corrosive effect on the metal is oxygen. Carbon dioxide accelerates the action of oxygen, and also has independent corrosion properties.

For protection against gas corrosion deaeration (degassing) of water is applied. Thermal deaeration has found the greatest distribution. When water is heated at constant pressure, the gases dissolved in it are gradually released. When the temperature rises to the saturation (boiling) temperature, the concentration of gases decreases to zero. Water is freed from gases.

Underheating of water to a saturation temperature corresponding to a given pressure increases the residual content of gases in it. The influence of this parameter is very significant. Underheating of water even by 1 °C will not allow to achieve the requirements of the "Rules ..." for feed water steam and hot water boilers.

The concentration of gases dissolved in water is very low (of the order of mg/kg), so it is not enough to separate them from the water, but it is also important to remove them from the deaerator. To do this, it is necessary to supply excess steam or evaporation to the deaerator, in excess of the amount necessary to heat the water to a boil. With a total steam consumption of 15-20 kg / t of treated water, the evaporation is 2-3 kg / t. Reducing flash steam can significantly degrade the quality of deaerated water. In addition, the deaerator tank must have a significant volume, ensuring that water stays in it for at least 20 ... 30 minutes. long time necessary not only for the removal of gases, but also for the decomposition of carbonates.

Atmospheric deaerators with steam supply

For deaeration of water in boiler rooms with steam boilers mainly thermal two-stage deaerators are used atmospheric type(DSA) operating at a pressure of 0.12 MPa and a temperature of 104 °C. Such a deaerator consists of a deaeration head with two or more perforated plates, or other special devices, due to which the source water, breaking into drops and jets, falls into the storage tank, encountering countercurrent steam on its way. In the column, water is heated and the first stage of its deaeration takes place. Such deaerators require the installation of steam boilers, which complicate the thermal scheme of a hot water boiler and the scheme of chemical water treatment.

Vacuum deaeration

In boiler rooms with hot water boilers, as a rule, vacuum deaerators are used, which operate at water temperatures from 40 to 90 ° C.

Vacuum deaerators have many significant shortcomings: large metal consumption, a large number of additional auxiliary equipment (vacuum pumps or ejectors, tanks, pumps), the need to be located at a considerable height to ensure the performance of make-up pumps. The main disadvantage is the presence of a significant amount of equipment and pipelines under vacuum. As a result, air enters the water through the seals of pump shafts and fittings, leaks in flanged joints and welded joints. In this case, the effect of deaeration completely disappears, and even an increase in the oxygen concentration in the make-up water is possible compared to the initial one.

Atmospheric deaeration without steam supply

Recently, a large number of steam boilers have been switched to hot water mode. Effective method deaeration in boiler rooms with such boilers was developed and passed a long-term test in the AP "Teploset" of the Krasnogorsk region.

The water after the sodium-cation exchange plant is heated to 106-110 °C and injected into the head of the atmospheric deaerator, where water drops boil due to pressure reduction. When boiling, corrosive gases are also removed from the water along with steam, more actively than in deaerators with steam supply. The scheme was implemented on equipment that was operated in a steam boiler house with three DKVr 10/13 boilers, when transferred to a hot water mode with coolant parameters of 115/70 °C. At the same time, the deaerator of the DSA type does not require any modifications. To heat make-up water, steam network heaters were used, modified to operate on heating water with a temperature of 110-113 ° C, and not on steam. On the technical solutions applied in the boiler houses of the Krasnogorsk region, a patent of the Russian Federation was received.

This scheme eliminates the disadvantages of vacuum deaeration and deaeration with steam supply. The advantage of the new deaeration scheme is its simplicity and reliability, which allows it to operate stably in any hot water boiler.

Besides

When transferring boilers DKVr 10/13 with heat carrier parameters of 115/70 °C to the water-heating mode according to the TsKTI scheme, we encountered a decrease in the heat output of the boiler unit (it does not decrease with a schedule of 150/70). Such a decrease was unacceptable in terms of the load on the heating network, so we developed and implemented changes to the CKTI scheme. Structurally, the changes are not significant, but they made it possible to improve the circulation in the rear screens and increase the boiler's heat output to the required one. The scheme of water movement in the boiler circuit is patented. The boilers have been in operation for 10 years without any complaints.

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 liquid 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 are 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 aggressive 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 flash steam 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 accommodates 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 treated water passes inside the tubes of the vapor cooler and is directed to 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.

Deaeration plants

AND CONDENSATE PUMPS

§ Types, designs, deaerator switching schemes.

§ Material and heat balances of the deaerator.

§ Switching schemes feed pumps, type of drive.

§ Schemes for switching on condensate pumps.

Air dissolved in condensate, feed and make-up water contains corrosive gases (oxygen, carbon dioxide) that cause corrosion of power plant equipment and pipelines. Corrosion increases with increasing water temperature and pressure.

Oxygen and free carbon dioxide enter the feed water with air suction into the condenser and equipment of the regenerative system, which is under vacuum, and with additional water.

To protect against gas corrosion, water deaeration is used, i.e. removal of air dissolved in it, or degassing of water, i.e. removal of the corrosive gas dissolved in it.

Used to remove dissolved air thermal deaeration water, which is the main method for removing dissolved gases from water. The oxygen remaining in the water after thermal deaeration is additionally neutralized by binding it chemical reagent(ammonia compounds).

Thermal deaeration of water is based on the following. According to the Henry-Dalton law, the equilibrium concentration of a gas dissolved in water, µg/kg, is proportional to the partial pressure of this gas above its surface and does not depend on the presence of other gases

where is the coefficient of proportionality, depending on the type of gas, its pressure and temperature, mg/(kgּPa). The relative composition of gases when air is dissolved in water, in accordance with this law, differs from their composition in air. For example, at 0°C and normal pressure water contains 34.9% oxygen by volume (21% in air), 2.5% carbon dioxide (0.04% in air), 62.6% nitrogen and other inactive gases (78.96% in air).

The concentration of gas dissolved in water can be expressed in terms of the equilibrium partial pressure:

When the partial pressure of the gas above the water surface is below the equilibrium< происходит десорбция (выделение) газа из раствора; если >, the gas is adsorbed (absorbed) by water, and if = is equal, a state of dynamic equilibrium occurs. Thus, in order to ensure the removal of the gas dissolved in it from the water, it is necessary to lower its partial pressure in the surrounding space. This can be achieved by filling the space with water vapor. The process of gas desorption from the solution will in this case be accompanied by water heating to saturation temperature. driving force process of gas desorption is the difference between the equilibrium partial pressure of gas in deaerated water and its partial pressure in a vapor medium.

The absolute pressure above the liquid phase is the sum of the partial pressures of gases and water vapor:

.

Therefore, it is necessary to increase the partial pressure of water vapor above the water surface, achieving , and as a result, obtain .

Feed water for steam boilers of TPPs in accordance with the Rules technical operation power plants (PTE) should contain oxygen less than 10 mcg/kg.

Compared with the removal of O, the release of CO from water is a more difficult task, since in the process of heating water, the amount of carbon dioxide increases due to the decomposition of bicarbonates and the hydrolysis of the formed carbonates.

In addition to removing dissolved aggressive gases from water, deaerators also serve for regenerative heating of the main condensate and are a place for collecting and storing feed water.

Thermal deaerators steam turbine plants of power plants are divided into:

Assigned to:

1) deaerators for feed water of steam boilers;

2) deaerators for additional water and return condensate of external

consumers;

3) make-up water deaerators for heating networks.

Heating steam pressure on the:

1) high pressure deaerators (type DP, working pressure 0.6–0.7 MPa, less often 0.8–1.2 MPa, saturation temperature 158–167 C and 170–188 C, respectively);

2) atmospheric deaerators (type DA, working pressure 0.12 MPa, saturation temperature 104 C;

3) vacuum deaerators (type DV, operating pressure 0.0075–0.05 MPa, saturation temperature 40–80 C).

According to the method of heating deaerated water on the:

1) deaerators of mixing type with mixing of heating steam and heated deaerated water. This type of deaerators is used at all TPPs and NPPs without exception;

2) superheated water deaerators with external preheating of water with selective steam.

By design (according to the principle of formation of an interfacial surface) on the:

1) deaerators with a contact surface formed during the movement of steam and water:

a) jet-sparging;

b) film type with random packing;

c) jet (dish) type;

2) deaerators with a fixed phase contact surface (film type with an ordered packing).

AT vacuum deaerators, the pressure is below atmospheric and an ejector is required to suck the gases released from the water. There is a danger of re-contamination of water with oxygen due to suction atmospheric air in the path before the pump. Vacuum deaerators are used when it is required to deaerate water at a temperature below 100 (make-up water of heating networks, water in the chemical treatment path). These also include condenser deaeration attachments.. Water deaeration is carried out not only in deaerators, but also in condensers steam turbines. However, on the way from the condenser to the condensate pump, the oxygen content may increase due to air leakage through the pump seals and other leaks.

atmospheric deaerators operate with a slight excess of internal pressure above atmospheric pressure (approximately 0.02 MPa), which is necessary for gravity evacuation of released gases into the atmosphere. The advantage of atmospheric deaerators is minimum thickness body walls (metal savings).

Currently, atmospheric deaerators are mainly used for make-up water of evaporators and make-up water of heating networks.

High pressure deaerators are used for the treatment of feed water of power boilers with an initial steam pressure of 10 MPa and above. The use of deaerators of the DP type at thermal power plants allows, at more than high temperature regenerative water heating to be limited in the thermal circuit a small amount serially connected HPH (no more than three), which contributes to an increase in reliability and reduction in the cost of the installation and favorably affects the operation due to the lower temperature drop of the feed water when the HPH is turned off.

In deaerators superheated water water first enters the upstream surface heater, where the water to be subsequently deaerated is heated to a temperature that is 5–10 °C higher than the saturation temperature at the pressure in the deaerator. To prevent the water from boiling in the heater, the water pressure must be 0.2–0.3 MPa higher than in the deaerator. When entering the deaerator, the water pressure decreases and the water boils, releasing steam, which fills the column.

The principle of preheating followed by boiling water improves the quality of deaeration. However, superheated water deaerators are complex in design, not reliable enough, difficult to regulate, and therefore are not currently used in our power industry.

Useful for thermal deaeration, the principle of preliminary overheating of water with subsequent boiling is implemented in deaerators bubbling type. In them, steam is introduced under the water level in the accumulator or in an intermediate tank located in the column. Due to the hydrostatic backwater, the steam introduced into the water layer has a slightly increased pressure compared to the pressure in the vapor space of the column. Upon contact with water in the depth of the layer, the steam heats it to a temperature exceeding the saturation temperature at the surface. When the water moves, entrained by steam bubbles up the bubbling compartment, the water boils and intensively releases dissolved gases.

In deaerators mixing type heating steam is introduced into lower part columns, filling it, and water in it upper part. The water flow is broken up into drops, jets or films to increase the surface of contact with steam and moves towards it from top to bottom. The gases escaping from the water are removed through the flash line located at the top of the column.

Together with the gases, a certain amount of steam, called evaporation, is removed from the deaerator column. Usually, evaporation is 1–2 kg, and if there is a significant amount of free or bound carbon dioxide in the source water, it is 2–3 kg per ton of deaerated water. Evaporation causes an additional loss of heat and coolant and, for these reasons, should be minimal.

Table 10.1

Free carbon dioxide in the water after the deaerator should be absent, and the pH value (at 25) of the feed water should be maintained within 9.1 0.1.