Installation of a deaerator in a boiler room. Deaerators

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. Same way vacuum deaerators 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 battery tank located at zero. 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 version of the 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.

Because 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 mass 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.

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 oxygen) from feed and make-up water. carbon dioxide), which is most effectively provided 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 at the bottom of the column are designed to remove corrosive gases (oxygen and free carbon dioxide) from feed water steam boilers and make-up water of heat supply systems in boiler houses of all types (with the exception of purely water heating ones). Deaerators are manufactured in accordance with the requirements of GOST 16860-77. OKP code 31 1402.

Modifications

Example symbol:

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 deaeration column installed on the battery 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 holes of the bubbling sheet, the area of ​​which is chosen in such a way as to prevent water from sinking 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 the storage tank, except for those columns that have a flange connection 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

Switching scheme atmospheric deaerators is determined by the design organization depending on the conditions of appointment and the capabilities of the facility on which 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. The deaerated water 14 is drained from the opposite end of the tank in order to ensure maximum water holding time 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 from the unit is removed 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 gas-vapor 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 the dangerous rise in level 1, combined into a common hydraulic system, and an 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 violation 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 lower part 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 a hydraulic test of the 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. Repair if needed internal devices deaeration column and the impossibility of its implementation using hatches, the column can be cut horizontally 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.

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.

An example of a deaerator symbol

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

Technical characteristics, 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.

The deaerator tank contains the 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 processing (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 placed in it (the material of the pipes is 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 ensure the safe operation of 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 the permissible pressure, and the other from a dangerous increase in level, combined into a common hydraulic system, and an 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 maximum allowable pressure in the deaerator during operation of the device 0.07 MPa and the maximum possible steam flow into the deaerator in an emergency with the control valve fully open and the maximum pressure in the steam source.

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. The scheme of the deaeration plant should provide for the possibility of carrying it 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.

Buy a deaerator
To purchase a deaerator, please contact the contacts listed at the top of the page.

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 the failure of the entire system, to the occurrence of water and gas leaks. Gas bubbles in boiler water lead to poor performance 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.

final stage technological process preparation of feed water for steam boilers is the removal of aggressive gases dissolved in it, primarily oxygen, as well as carbon dioxide, which causes corrosion of the metal of thermal power plants. Oxygen corrosion is the most dangerous, as it manifests itself on separate sections surface of the metal in the form of small pits and develops into the depth of the metal up to the formation of through fistulas. For modern steam boilers with large steam capacity, even the smallest concentration of oxygen dissolved in the feed water can cause a violation normal operation and failure individual elements of which the economizer is usually the first to corrode.

Thus, to ensure the reliable operation of modern steam boilers, it is necessary to strive for the almost complete absence of dissolved oxygen in the feed water.

The process of removing dissolved gases from water is called degassing or deaeration. Currently, several methods of deaeration are known - thermal and chemical.

The most widespread thermal method water deaeration. This method is based on the fact that the solubility of gases in water decreases with an increase in its temperature, and at a temperature equal to the boiling point, gases are almost completely removed from water. In this way, gases are removed from the water in special devices, which are commonly called thermal deaerators.

Deaerators are mainly used for water degassing. atmospheric type operating at an absolute pressure of 0.1 MPa (1 kgf/cm2), and vacuum deaerators operating at an absolute pressure of 0.0007 to 0.05 MPa (0.075 to 0.5 kgf/cm2), i.e. at temperatures of deaerated water from 40 to 80 °C. Water deaeration is based on Henry's law, according to which the amount of gas dissolved in a unit volume of water is proportional to the partial pressure of this gas in a gas or vapor-gas mixture above the water surface. To completely remove gases from water, it is necessary to create conditions under which the partial pressures of these gases above the water surface will be equal to zero, which is possible at the boiling point of water, i.e., when it is brought to saturation temperature at a pressure in the deaerator and gases are removed from the vapor space deaerator.

In steam boilers, atmospheric deaerators - DSA (Fig. 3.1) are most widely used. A two-stage bubbling deaerator consists of a small-sized deaeration column and an accumulator tank with a built-in bubbling device and baffles forming special compartments. The deaeration column has two plates with holes through which water flows into the storage tank. A device for better mixing of the condensate and chemically treated water flows entering the deaerator is mounted on the first plate along the water course. These flows enter the outer ring of the mixing device, after which water enters the perforated part of the first plate through two weirs.

After the column, the deaerated water enters the tank-accumulator, in the lower part of which, at the opposite end, a flooded bubbling device is placed. The heating steam is fed through the pipe into the steam box and bubbles through the holes of the perforated sheet through a layer of water slowly moving over the sheet in a hundred

Ronu branch pipe for draining water from the deaerator. The water leaving the bubbling device enters the lifting shaft. Boiling is explained by the presence of a slight overheating of water relative to the saturation temperature, which corresponds to the pressure in the vapor space of the storage tank. Superheating is determined by the height of the liquid column above the bubbling sheet.

The steam passing through the bubbling device and the water column, getting into the steam space, moves above the water surface towards the column. Placing the column on the opposite side of the bubbling device ensures a clearly defined countercurrent movement of water and steam flows and good ventilation of the vapor space of the tank.

The steam required for deaeration is supplied to the bubbling device from the pressure regulator: steam pressure before the regulator is 0.6-0.7 MPa (6-7 kgf / cm2), after the regulator - 0.05-0.07 MPa (0.5 -0.7 kgf/cm2). On deaerators with a capacity of more than 50 t / h, a branch pipe is provided for supplying low-temperature steam with a pressure of 0.02-0.03 MPa (0.2-0.3 kgf / cm2) (from continuous blowdown expanders, from piston steam pumps, turbopumps) directly to the steam space of the deaerator for better ventilation of the steam volume of the deaerator and to the first stage of deaeration in the deaeration column.

The vapor from the deaeration column is discharged to the vapor cooler and from it to the sewer, and the gases are discharged through the air vent to the atmosphere. Deaerators are equipped with hydraulic seals for protection against overpressure.

Atmospheric deaerators are designed to operate at a pressure of 0.01-0.02 MPa (0.1-0.2 kgf/cm2) and a water temperature of 102-104 °C. According to GOST 16860-71 "Thermal deaerators", the change in water heating in deaerators should be no more than 10-40 °C.

NPO CKTI developed new design two-stage bubbling deaerators (DA type) of atmospheric type. These deaerators are distinguished by the fact that the bar-boat device in them is located in the lower part of the deaeration column. The column is installed on the deaeration tank old design. The supply of chemically treated water and condensate is carried out in upper part columns, steam is supplied to the steam space of the deaerator tank from the side opposite to the column. Such a supply of steam ensures reliable ventilation of the steam volume of the tank. Water is drained from the deaerator from the side opposite to the column.

The advantages of the new deaerators compared to DSA deaerators are: increased factory readiness, reduced metal consumption, simplified installation, increased operational reliability, reduced corrosion of deaerator tanks. The overall height compared to the DSA increased by 600-700 mm.

Vacuum deaerators are mainly used in hot water boilers.

Vacuum deaeration unit is a vacuum column (deaerator) and an accumulator tank under atmospheric pressure.

The vacuum column has two stages of degassing: jet and bubbling.

Heated water enters the upper plate, which is sectioned in such a way that only a part of the holes in the inner sector work at minimum loads. When the load increases, additional rows of holes are included in the work, this makes it possible to avoid hydraulic distortions in water and steam during load fluctuations. Steam or superheated water (120-140°C) is supplied under the bubbling sheet, when it boils, a steam cushion is formed and the process of steam bubbling takes place.

Vacuum deaerators are equipped with steam coolers, water-to-water ejectors, automatic regulation and control system and corresponding control valves.

Water degassing by chemical means carried out by sulfing, i.e., introducing a solution of sodium sulfite Na2S0.5 into heated (up to 80 ° C) feed water. This method is more expensive than thermal degassing and is therefore not widely used.

The method of water treatment for a particular boiler plant should be determined by a specialized (design, commissioning) organization. According to the requirements of the Boiler Regulations, all boilers with a steam capacity of 0.7 t/h or more must be equipped with pre-boiler water treatment plants.

In boiler houses with boilers with a steam output of less than 0.7 t/h, the installation of water treatment devices is not necessary, but the frequency of boiler cleaning should be such that by the time the boiler is stopped for cleaning, the thickness of deposits on the most heat-intensive areas of its heating surface does not exceed 0.5 mm.

For each boiler house with boilers with a steam capacity of 0.7 t / h and above, an instruction (mode maps) for water treatment should be developed and approved by the administration of the enterprise by a design, commissioning or other specialized organization. The instructions must specify the quality standards for feed and boiler water for a given boiler plant, the mode of continuous and periodic blowdown, the procedure for performing analyzes of boiler and feed water and servicing water treatment equipment, the timing of stopping the boiler for cleaning and flushing, and the procedure for inspecting stopped boilers. IN necessary cases The instructions should also include checking the aggressiveness of the boiler water.

To exclude cases of power supply to the boiler raw water, on the reserve raw water lines connected to the feed water lines, two shut-off bodies and a control valve between them must be installed. The shut-off organs should be sealed in the closed position (the control valve is open), and each case of feeding with raw water should be recorded in the water treatment log, indicating the reasons.