What is a deaerator in a boiler room. Feed water deaeration

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.

For protection 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 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. The driving force of the gas desorption process is the difference between the equilibrium partial pressure of the gas in the deaerated water and its partial pressure in the 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 stock feed water.

Thermal deaerators of steam turbine 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. advantage atmospheric deaerators is an 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 scheme 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 preheating 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.

Vacuum deaerator used to deaerate water if its temperature is below 100 °C (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 use a 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 make-up. 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.

The word "deaeration" means the process freeing fluid from impurities- in particular from gaseous substances which include oxygen and carbon dioxide. The deaerator, in turn, is a mandatory device for water treatment systems in boiler rooms, which can significantly extend and improve their operation.

They are widely used chemical and thermal deaeration. In the first case, the removal of excess gases is carried out by adding reagents to the water, in the second - by heating the water to the boiling point until it is free from any gaseous substances dissolved in it.

Why do you need a deaerator in a boiler room?

Carbon dioxide and oxygen are so-called "aggressive" gases that stimulate rapid wear and corrosion of the pipelines of the boiler system. Before running water through the pipes, it must be prepared, and this is what deaerating filters are used for.

Malfunctions caused by gas contamination of water can eventually lead to failure of the entire system, to the occurrence of water and gas leaks. Gas bubbles in the boiler water lead to a deterioration in the operational functions of the hydraulic system, adversely affect the operation of the nozzles and provoke the failure of the pumps.

In the long run, installing a reliable deaerator in a boiler room is cheaper than emergency repairs.

What is a deaerator in a boiler room?

Deaerators can be vacuum and atmospheric: the former are used with steam, the latter with steam or water.

As a rule, all deaerators for boiler plants have a common two-stage device. Water enters a special deaeration tank, where it passes through membranes and plates, and is subsequently purified from all aggressive gases and impurities. According to the results of processing, oxygen and carbon dioxide are converted into vapor, which is removed from the system, and the presence in the tank chemical water prevents the formation of all kinds of natural impurities in the coolant.

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 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 corrosive gases from the system of steam boilers and boiler plants. Deaerators atmospheric type 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 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 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 jets into the BDA deaerator tank.

The design of the deaerator ensures the convenience of internal inspection 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.

In industrial and heating boiler houses, to protect against corrosion of heating surfaces washed by water, as well as pipelines, 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 water 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 scheme of the boiler plant is carried out in special devices - thermal deaerators.

Purpose and scope

Two-stage atmospheric pressure deaerators of the DA series with a bubbling device in the lower part of the column 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 in boiler houses of all types (except for pure hot water). Deaerators are manufactured in accordance with the requirements of GOST 16860-77. OKP code 31 1402.

Modifications

Symbol example:

DA-5/2 - atmospheric pressure deaerator with a column capacity of 5 m³ / h 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; DA-200/50; DA-300/75.

At the request of the customer, 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 larger tanks.

Rice. General form deaerator tank with an explication of fittings.

Technical specifications

Main specifications atmospheric pressure deaerators with bubbling in the column are shown in the table.

* - design dimensions of deaeration columns may vary depending on the manufacturer.

Design description

The atmospheric pressure thermal deaerator of the DA series consists of a deaeration column mounted on an accumulator tank. The deaerator is used two-stage scheme degassing stage 1 - jet, 2 - bubbling, and both stages are placed in a deaeration column, the schematic diagram of which is shown in fig. 1. Flows of water to be deaerated are fed into column 1 through pipes 2 to the upper perforated plate 3. From the latter, water flows in jets to the bypass plate 4 located below, from where it merges with a narrow jet of increased diameter to the initial section of the non-failure bubbling sheet 5. Then the water passes over the bubbling sheet in the layer provided by the overflow threshold (protruding part of the drain pipe), and through drain pipes 6 drains 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 deaerator accumulator tank through pipe 13 (see Fig. 2), ventilates the volume of the tank and enters under the bubbling sheet 5. Passing through the openings of the bubbling sheet, the area of ​​which is chosen in such a way as to exclude the failure of water at the minimum thermal load of the deaerator, the steam subjects the water to intensive treatment on it. With an increase in the heat load, the pressure in the chamber under the sheet 5 increases, the hydraulic seal of the bypass device 9 is activated, and excess steam is passed into the bypass of the bubbling sheet through the steam bypass pipe 10. Pipe 7 ensures that the hydraulic seal of the bypass device is flooded with deaerated water when the heat load is reduced. From the bubbling device, steam is directed through hole 11 to the compartment between plates 3 and 4. The vapor-gas mixture (vapour) is removed from the deaerator through gap 12 and pipe 13. Water is heated in the jets to a temperature close to the saturation temperature; removal of the main mass of gases and condensation of most of the steam supplied to the deaerator. Partial release of gases from water in the form of small bubbles occurs on plates 3 and 4. On the bubbling sheet, the water is heated to saturation temperature with slight condensation of steam and the removal of trace amounts of gases. The degassing process is completed in the accumulator tank, where the smallest gas bubbles are released from the water due to sludge.

The deaeration column is welded directly to battery tank, except for those dispensers that are flanged to the deaerator tank. Relative to the vertical axis, the column can be oriented arbitrarily, depending on the specific installation scheme. Cases of DA series deaerators are made of carbon steel, internal elements are made of of stainless steel, the fastening of the elements to the body and to each other is carried out by electric welding.

Included in delivery deaeration plant included (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;

a control valve on the steam supply line to maintain pressure in the deaerator;

pressure gauge;

shut-off valve;

water level indicator in the tank;

manometer;

thermometer;

safety device;

vapor cooler;

shut-off valve;

drain pipe;

technical documentation.

Rice. one circuit diagram atmospheric pressure deaeration column with bubbling stage.

Scheme of switching on the deaeration unit

The scheme of inclusion of atmospheric deaerators is determined by the design organization, depending on the conditions of appointment and the capabilities of the facility where they are installed. On fig. 2 shows the recommended scheme of the deaeration unit of the DA series.

Chemically purified water 1 is fed through the vapor cooler 2 and the control valve 4 to the deaeration column 6. 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. Deaerated water 14 is drained from the opposite end of the tank in order to ensure the maximum holding time of water in the tank. All steam is supplied through the pipe 13 through the pressure control valve 12 to the end of the tank, opposite the column, in order to ensure good ventilation of the steam volume from the gases released from the water. Hot condensates (clean) are fed into the deaerator tank through pipe 10. The vapor is removed from the unit through the vapor cooler 2 and pipe 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 testing 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 of the inclusion of an atmospheric pressure deaeration unit:
1 - chemically purified water supply; 2 - vapor cooler; 3, 5 - exhaust into the atmosphere; 4 - level control 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 - removal of deaerated water; 15 - water sample cooler; 16 - level indicator; 17- drainage; 18 - pressure gauge.

Vapor cooler

To condense the vapor-gas mixture (vapour), a surface-type vapor cooler is used, consisting of a horizontal body in which a pipe system is placed (pipe material is brass or corrosion-resistant steel).

The vaporizer cooler is a heat exchanger in which chemically treated water or cold condensate from a constant source heading to the deaeration column. 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.

The vapor cooler consists of the following main elements (see Fig. 3):

Nomenclature and general characteristics vapor coolers

Safety device (hydraulic seal) of atmospheric pressure deaerators

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 (hydraulic trap), which must be installed in each deaerator installation.

The water seal must be connected to the supply steam 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 allowable pressure 9 (shorter) and the other from a dangerous increase in level 1, combined into a total hydraulic system, and expansion tank. Expansion tank 3, serves to accumulate the volume of water (when the device is triggered), which is necessary for automatic filling of the device (after the malfunction in the installation has been eliminated), i.e. makes the device self-priming. The diameter of the overflow water seal is determined depending on the maximum possible expense water to the deaerator in emergency situations.

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.

In order to limit the steam flow to the deaerator in any situation to the maximum required (at 120% load and 40-degree heating), a restrictive throttle diaphragm should be additionally installed on the steam pipeline.
In some cases (to reduce the construction height, install deaerators in the premises), instead of a safety device, safety valves are installed (to protect against overpressure) and a steam trap to the overflow fitting.

Combined safety devices are manufactured in six 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 the 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 controlling the bay; 7 - supply of chemically purified water for pouring; 8 - water supply from the deaerator; 9 - hydraulic seal against pressure increase; 10 - drainage.

Installation of deaeration plants

For execution installation work mounting sites must be equipped with a basic mounting equipment, fixtures and tools in accordance with the project for the production of works. Upon acceptance of the deaerators, it is necessary to 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, the absence of damage and defects in the equipment. Before installation, visual inspection and depreservation of the deaerator, and the detected defects are eliminated.

Installation of the deaerator at the facility is carried out in the following order:

install the storage tank on the foundation in accordance with the installation drawing of the design organization;

weld a spillway to the tank;

cut off the lower part of the deaeration column along the outer radius of the deaeration tank body and install it on the tank in accordance with the installation drawing of the design organization, while the plates must be located strictly horizontally;

weld the column to the deaerator tank;

install the vapor cooler and the 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;

conduct hydraulic test deaerator;

install thermal insulation at the direction of the design organization.

Specifying Security Measures

During installation and operation thermal deaerators the safety measures determined by the requirements of Gosgortekhnadzor, the relevant regulatory and technical documents must be observed, job descriptions etc.

Thermal deaerators must be subject to 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 are removed from the pipelines, hatches on the deaerator are closed, bolts on flanges and fittings are tightened, all gate valves and control valves are in good order and closed;

Maintain the nominal flow rate of flash steam from the deaerator in all modes of its operation and periodically monitor it using a measuring vessel or according to the balance of the flash cooler.

The main 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 determination of the concentration of oxygen and free carbon dioxide in the sample is incorrect. In this case it is necessary:

check the correct execution chemical analyzes in accordance with the instructions;

check the correctness of water sampling, its temperature, flow rate, absence of air bubbles in it;

check density pipe system- refrigerator sampling;

b) the steam consumption is significantly underestimated.

In this case, it is necessary:

check that the surface of the vaporizer cooler conforms to the design value and, if necessary, install a vaporizer cooler with larger surface heating;

check the temperature and flow rate of the cooling water passing through the vapor cooler and, if necessary, reduce the temperature of the water or increase its flow rate;

check the degree of opening and serviceability of the valve on the pipeline for the removal 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 it should be:

check the temperature and flow rate of the flows entering the deaerator and increase the average temperature of the initial flows or reduce their flow rate;

check the operation of the pressure regulator and, if the automation fails, switch to remote or manual pressure control;

d) steam supply to the deaerator with high content oxygen and free carbon dioxide. It is necessary to identify and eliminate the centers of contamination of steam with gases or take steam from another source;

e) the deaerator is out of order (clogging of the holes in the trays, warpage, breakage, breakage of the trays, installation of the trays with a slope, destruction of the bubbling device). It is necessary to take the deaerator out of operation and repair;

f) insufficient steam flow to the deaerator (average water heating in the deaerator is less than 10°C). It is necessary to reduce the average temperature of the initial water flows and ensure that the water in the deaerator is heated by at least 10°C;

g) drains containing a significant amount of oxygen and free carbon dioxide are sent to the deaerator tank. It is necessary to eliminate the source of contamination of the drains or feed them into the column, depending on the temperature, on the upper or overflow plates;

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 sufficiency of heat flow in the power source.

2. An increase in pressure in the deaerator and the operation of a 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 the automation system;

b) with a sharp increase in temperature with a decrease in the flow rate of the source water, either reduce its temperature, or reduce the steam flow rate.

3. An increase and decrease in the water level in the deaerator tank above the permissible level may occur due to a malfunction of the level controller, it is necessary to switch to remote or manual level control, if it is impossible to maintain a normal level, stop the deaerator and check the control valve and automation system.

4. Water hammer must not be allowed in the deaerator. In case of water hammer:

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 source water or reduce its consumption.

Repair

Current repair of deaerators is carried out once a year. At current repair inspection, cleaning and repair work is carried out to ensure normal operation of the plant until the next repair. For this purpose, deaeration tanks are equipped with manholes, and columns with inspection hatches.

Planned overhauls 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 do it with the help of hatches, the column can be cut along a horizontal plane in the most convenient place for repair.

During the subsequent welding of the column, the horizontality of the plates and the vertical dimensions must be maintained. After finishing repair work a hydraulic pressure test of 0.2941 MPa (abs.) (3 kgf/cm2) must be performed.