Vacuum deaerator working principle. There are several types of water deaeration in boiler rooms.

Lab #4

STUDYING THE PRINCIPLE OF OPERATION AND SCHEMES OF DEAERATORS

Objectives of the work: to study the principle of operation and schemes of deaerators, laboratory equipment that allows deaeration, to study the operation of a deaerator, to perform working water purification.

1. General information

Deaeration feed water steam boilers and make-up water for heating networks is mandatory for all boiler houses. Deaerators are designed to remove non-condensable gases dissolved in water from water. The presence of oxygen and carbon dioxide in feed and make-up water leads to corrosion of feed pipes, boiler pipes, boiler drums and network pipelines, which can lead to a severe accident. The presence of even such inert gases as nitrogen is also extremely undesirable, it interferes with heat transfer and reduces the heat output of heaters.

The amount of residual content of O 2 and CO 2 in the feed water of steam boilers is strictly regulated by the rules of Gosgortekhnadzor. So for boilers with a steel economizer at a pressure of up to 1.4 MPa, the content of O 2 should be no more than 30 μg / kg. Free carbon dioxide (CO 2 ) in the feed water after the deaerators should be absent.

For deaeration of feed water in boiler houses, jet mixing thermal deaerators are used. Depending on the pressure maintained in the deaerator, there are high pressure deaerators, atmospheric and vacuum deaerators. In boiler plants with steam boilers for pressures up to 4.0 MPa, atmospheric deaerators are used.

2. Thermal deaeration of water

Thermal deaeration of water. Corrosive (O2, CO2, NH3) and other gases are dissolved in the water of thermal power plants and require removal. The removal of gases from water is carried out mainly with the help of thermal deaerators, calciners and chemically.

Thermal deaeration (degassing) of water is based on the Henry-Dalton law, which is expressed in relation to this case by the following equation, valid for equilibrium conditions:

m = kppg = kp (p - pp),

where m is the solubility of gases in water;

p is the total pressure of gas and water vapor in the space above water;

pp, pg - partial pressures of steam and gas, respectively, in the same space;

kp is the solubility coefficient of a gas in water, depending on the temperature (the higher the temperature, the lower the solubility coefficient).

If water is heated to the boiling point, then, on the one hand, the solubility coefficients of gases in water become equal to zero, and on the other hand, the partial vapor pressure above the water surface becomes equal to the total pressure of the mixture. As a result of equilibrium, the solubility of gases in water becomes equal to zero. Hence the conclusion: to remove the gases dissolved in it from water, it is enough to heat it to the boiling point. This is the essence of thermal degassing.

Equation (18.2.1) characterizes the limit state of equilibrium, to which the system will come if certain conditions are created and enough

time. Let's briefly consider these conditions.

From the above it follows that the water must be heated. Usually, deaerated water flowing down in streams, drops and a film is heated by steam flowing towards it. Then the required amount of heat Q to heat water per unit time in the amount W from the initial temperature t1 to the boiling point tb (and the corresponding values ​​of enthalpy i1, i")

where F- heat exchange surface area;

tWed- average water temperature for heat exchange conditions;

t- temperature head;

 - heat transfer coefficient.

The right side of equation (18.2.2) allows us to conclude that it is desirable to make the heat exchange surface area as large as possible. This makes it possible to speed up the process of heat transfer and reduce the dimensions of the apparatus. Solving these problems, the water flow is crushed into jets, drops or thin films. To ensure maximum temperature difference, a counterflow of steam and water is created. The splitting of the flow and, especially, its runoff with thin films provide turbulence of the flow and, accordingly, an increase in the heat transfer coefficient.

By the same means, an increase in the rate of gas desorption from water is achieved, since the amount of gas removed from it per unit time is equal to the concentration of gas in water and in space above water, and therefore, is taken into account. (18.2.1), the difference in gas pressure in accordance with the equation

m = kdF p = kdF (pr .p - pr), (18.2.3)

where pr.p is the so-called equilibrium partial pressure of gas in water, it corresponds to the concentration of gas in water under equilibrium conditions in accordance with (18.2.1.);

pr is the partial pressure of gas over water;

kd is the desorption coefficient, which depends on the turbulence of the water flow, viscosity, surface tension, the rate of diffusion of gas in water, and, consequently, on temperature.

To achieve the minimum partial gas pressure in the space above the water, gases (with an admixture of vapors) are continuously removed from the working space of the deaerator through a special fitting for removing the deaerator steam. If the deaerator is vacuum (i.e., the pressure in it is less than atmospheric pressure), then air is sucked off by steam-jet or water-jet ejectors.

Examples of constructive implementation of deaerators are shown in fig. 12.2.3, 12.2.4. In the first of these cases, the film principle of crushing the water flow is implemented, in the second, the jet principle. On fig. 12.2.4 bubbling is used as the second stage of degassing, i.e., steam bubbles are passed through a layer of water. Bubbling is used for more complete degassing of water, especially for more complete removal of carbon dioxide.

At industrial CHP plants, deaerators are most often fed with steam from industrial controlled turbine extraction, and at condensing power plants - from unregulated turbine extractions (Fig. 18.2.5). When degassing the feed water at the TPP, the deaerator simultaneously performs the function of a heater for the next heating stage in the regeneration system.

Deaerators of the type shown in fig. 12.2.4 are called "superheated" water deaerators. Deaerators do not require heating steam to be supplied to them, steam is formed in them as a result of

throttling heated water to such a pressure, the saturation temperature at which is less than the temperature of the water entering the deaerator. This water turns out to be preliminarily superheated above the temperature in the deaerator, to which it is cooled as a result of throttling and partial conversion into steam.

In the condensers of steam turbines, a fairly complete removal of gases from the main condensate occurs, i.e., the condenser simultaneously acts as a deaerator.

Rice. 18.2.5. Feed water deaerator circuit diagrams.

a-as an independent stage of regenerative water heating; b - as an upstream heater in a given heating stage; c - to controlled extraction at CHPP; /-.steam generator; 2 - turbine; 3-capacitor; 4 - condensate pump; 5 - low pressure heater; 6 - deaerator; 7 - feed pump; 8 - high pressure heater; 9 - pressure regulator.

However, due to air suction through the glands of condensate pumps and other leaks in vacuum system turbine condensate is again polluted with gases. These gases are then removed in atmospheric deaerators (slightly above atmospheric pressure) or pressurized deaerators (pressures several times atmospheric).

The atmospheric deaerator consists of a cylindrical deaeration column and a feed water tank. The flows of deaerated water enter the water distributor, from which they flow evenly over the annular section of the column onto perforated baking sheets. Passing through the holes of the baking sheets, the water breaks into small streams and falls down. AT lower part steam is supplied to the deaerator column to heat the deaerated water to the boiling point. At a water temperature equal to the boiling point, the solubility of gases in water is zero, which determines the removal of oxygen and carbon dioxide from water. The released oxygen and carbon dioxide with a small amount of steam is removed through the wind pipe at the top of the deaeration column. For the efficient operation of the deaeration column, it is necessary that the gases released from the water are quickly removed from the column, which is ensured by evaporation. The amount of vapor is taken equal to 2 kg per 1 ton of deaerated water.

Deaerator columns are not designed for heating water by more than 10-40 ° C. The optimal mode of operation of the deaerator column, i.e. best removal gases from the feed water occurs when the average temperature of all water streams entering the column is 10-15°C below the boiling point at pressure maintained in the deaerator. For complete deaeration of the feed water, it is absolutely necessary to heat it to the boiling point. Underheating of water even by a few degrees leads to a sharp increase in the residual oxygen content in it. Therefore, deaerators are necessarily equipped with automatic regulators that maintain a correspondence between the flow of steam and water into the column.

Deaerator schemes

a - atmospheric; b - bubbling; 1 - tank; 2 - release of feed water;

3 - water-indicating glass; 4 - safety valve; 5 - plates; 6 - input of chemically purified water; 7 - wind pipe; 8 – condensate inlet; 9 - deaerator column; 10 - steam inlet; 11 - hydraulic shutter; 12 - tray; 13 - lattice; 14 - partition with blinds.

The number and capacity of the installed feed water deaerators are selected based on the full coverage of the feed water consumption by the boilers, taking into account their blowdown and the feed water consumption for injection into the ROU in the maximum winter mode. At least two deaerators must be installed. Backup deaerators are not installed. The useful total capacity of the feed water tanks should ensure its supply for at least 15 minutes in the maximum winter mode. The useful capacity of the tanks is assumed to be 85% of their geometric capacity.

Make-up water must also be deaerated in all cases. The oxygen content in the make-up water should be no more than 50 µg/kg, and free carbon dioxide should be completely absent. In heat supply systems with direct water intake, the quality of make-up water, in addition, must comply with GOST 2874-82 "Drinking water".

Make-up water deaeration is carried out either in thermal mixing atmospheric deaerators or in vacuum deaerators.

Deaerators should be installed on sites with a mark higher than the mark for the installation of feed pumps. The value of this excess is determined by the sum of the required water pressure at the pump inlet, set by the pump manufacturer, and the required hydrostatic head to overcome the resistance of pipelines from the deaerator to the pump. For boilers at pressures of ~4.0 and 1.4 MPa (40 and 14 kgf/cm2), the elevation of the deaerator platform is 10 and 6 m, respectively.

In central boiler plants operating for large open-drawn heat supply systems that require deaeration of make-up water in quantities measured in hundreds of tons, the installation of vacuum make-up deaerators is preferable. A make-up plant with atmospheric deaerators at high make-up water consumption due to the limited unit capacity of atmospheric deaerators (maximum 300 t/h) and the need to install make-up water coolers (up to 70 ° C) behind them turns out to be very cumbersome and expensive. In addition, make-up plants with atmospheric deaerators have one more significant disadvantage: in order to preserve the heating steam condensate, the chemically treated water supplied to the deaerators must be preheated to 90 ° C.

It is heated in water-water heat exchangers-coolers of deaerated make-up water and in steam-water heaters. These heaters, as well as pipelines behind them, are subject to intensive corrosion destruction and do not provide the necessary duration of operation of the heating network feed unit.

Deaeration of make-up water under vacuum makes it possible to get rid of the disadvantages of the make-up installation listed above. The industry produces vacuum deaerators with a unit capacity of up to 2000 t/h, the temperature of the make-up water given out by the deaerator is 40 ° C, and installation of special coolers is not required. At a vacuum in the deaerator of ~0.0075 MPa (0.075 kgf/cm2) at a deaeration temperature of 40°C, no preheating of the chemically treated water supplied to the deaerator is required;

When used for deaeration of make-up water in small vacuum deaerators operating under vacuum - pressure ~ 0.03 MPa (0.3 kgf / cm2), created by water jet ejectors or water ring pumps, the deaeration process proceeds at a temperature of 70 ° C. At the same time, the chemically purified water supplied to the deaerators must be preheated only up to 50°C.

In steam industrial heating boilers with closed heat supply systems, where the consumption of make-up water is determined only by leakages of the heating network, it is allowed to make up the heating network with water from feed water deaerators. Technical characteristics of deaerators are given in tables 10.1 and 10.2 (see appendix).

3. Deaerator vapor coolers

The removal of released oxygen and carbon dioxide from the deaerator column is carried out through a wind pipe in the cover of the deaerator column. Together with oxygen and carbon dioxide, a certain amount of steam leaves the column and takes heat with it, which is lost when the vapor is released into the atmosphere. In order to use the heat of the flash steam, the deaerators are equipped with special surface heat exchangers-coolers of the flash steam, in which the flash steam is condensed with chemically treated water supplied to the deaerator.

4. Feed pumps

Feeding devices are critical elements of the boiler plant, ensuring the safety of its operation. The Gosgortekhnadzor rules impose a number of requirements on feeding facilities.

Feeding devices must provide the necessary flow of feed water, at a pressure corresponding to the full opening of the working safety valves installed on the steam boiler. The total performance of the main pumps must be at least 110% for all working boilers at their nominal steam capacity, taking into account the costs of continuous blowdown, desuperheaters, reduction-cooling and cooling plants. The total performance of the feed standby pumps should provide 50% of the normal performance of all operating boilers, taking into account the blowdown, water flow to the reduction-cooling and cooling units. When choosing a pump, it is necessary to strive to ensure that, under operating conditions, the pump load is close to the nominal one. When installing multiple centrifugal pumps for parallel operation it is necessary to install pumps with the same characteristics. The loading of pumps with different characteristics in the process of capacity control changes unevenly, and the pumps may not provide the required water supply in modes other than the nominal (for which they are selected), or they will work uneconomically.

The design head of the feed pump Рnas, Pa, is determined from the following expression:

Pnas = Pk (1 + R) + Rack + Rp.v.d +
,

where Pk is the overpressure in the boiler drum;

р – pressure reserve for opening safety valves, taken equal to 5%;

Рк – resistance of the water economizer of the boiler;

Рp.v.d – resistance of high-pressure regenerative heaters;

Рnag tr - resistance of feed pipelines from the pump to the boiler, taking into account the resistance of automatic boiler power regulators;

Рvsos tr - resistance of suction pipelines;

Рс.в - pressure created by a column of water, equal in height to the distance between the axis of the boiler drum and the axis of the deaerator;

Pdr - pressure in the deaerator.

When calculating resistances, the density of water is taken from its average temperature in the discharge path, including the water economizer.

Calculated pressure in the discharge pipe feed pumps should be increased by 5-10% to provide a margin for an unforeseen increase in the resistance of the feed path. A non-return valve must be installed on the discharge pipe of the feed centrifugal pump.

The operation of feed pumps with a capacity below 10-15% of the nominal flow rate is not allowed, as this leads to pump “steaming”. To protect against a decrease in feed water consumption in excess of the allowable level, the pumps are equipped with special relief valves and recirculation lines connecting them to deaerators, where water is discharged. The recirculation lines are switched on when the pumps are started and stopped. Shut-off valves on these lines have manual control. Check valves installed downstream of the pumps have branch pipes for connecting recirculation lines.

The range of feed pumps for boilers used in boiler houses is shown in Table 10.5. Both feed centrifugal pumps and steam pumps should be installed at 0.0 below the deaerators or at a small distance from them, so that the resistance of the suction pipelines is as low as possible, according to the technological design standards - no more than 10000 Pa (1000 mm w.c.) .

Deaerator- technical device, which implements the process of deaeration of a certain liquid (usually water), that is, its purification from undesirable gas impurities present in it (oxygen and carbon dioxide). Being dissolved in water, these gases cause corrosion of the feed pipes and heating surfaces of the boiler, as a result of which the equipment fails. Thermal deaeration of water is used at steam turbine stations.

The principle of operation of thermal deaerators is based on the fact that the absolute pressure above the liquid is the sum of the partial pressures of gases and steam.

If you increase the partial pressure of steam so that while removing steam (this is a mixture of gases released from water and a small amount steam to be evacuated from the deaerator), then as a consequence we obtain the total partial pressure of gases . Then, according to Henry's law (the equilibrium mass concentration of gases in the solution is proportional to the partial pressure in the gaseous medium above the solution), i.e., there are no dissolved gases. An increase in the partial pressure of steam, in turn, can be achieved by increasing the water temperature to the saturation temperature at a given pressure at .

Classification of thermal deaerators.

By appointment: deaerators for feed water of steam boilers; make-up water and return condensate from external consumers; make-up water of the heating network.

According to the pressure of the heating steam: high pressure (0.6-0.8 MPa) ( D); atmospheric (0.12 MPa)( YES); vacuum (7.5-50 kPa) ( DV).

According to the method of heating deaerated water: mixing type (with mixing of heating steam with heated water); superheated water deaerators with external preheating of water with selective steam.

By design (according to the principle of formation of an interfacial surface): with a contact surface formed in a turbulent mode (slender-bubbling, film type with a disordered nozzle, jet plate type); with a fixed phase contact surface (film type with an ordered packing).

circuit diagram deaeration plant.

Rice. Mixing type atmospheric deaerator: 1 - tank (accumulator), 2 - feed water outlet from the tank, 3 - water-indicating glass, 4 - pressure gauge, 5, 6 and 12 - plates, 7 - draining water into the drainage tank, 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 seal, 18 - excess water outlet from a hydraulic seal

The deaerator consists of tank 1 and column 13, inside which a number of distribution plates 5, 6 and 12 are installed. Feed water (condensate) from the pumps enters upper part deaerator on the distribution plate 12; through another pipeline through the regulator 8 on the plate 12 is supplied as an additive chemically purified water; from the plate, feed water is distributed in separate and uniform streams around the entire circumference of the deaerator column and flows down sequentially through a row of intermediate plates 5 and 6 arranged one below the other with small holes. Steam for heating water is introduced into the deaerator through pipe 15 and steam distributor 14 from below under water curtain, formed by the flow of water from a plate to a plate, and, diverging in all directions, rises up towards the feed water, heating it. At this temperature, air is released from the water and, together with the rest of the uncondensed steam, leaves through the wind pipe 11, located in the upper part of the deaeration head, directly into the atmosphere or steam cooler 9. The oxygen-free and heated water is poured into the collection tank 1, located under the deaerator column , from where it is consumed to power the boilers. To avoid a significant increase in pressure in the deaerator, two hydraulic seals are installed on it, as well as a hydraulic seal 17 in case of vacuum formation in it. When the pressure is exceeded, the deaerator may explode, and when rarefied, atmospheric pressure can crush it. The deaerator is supplied with a water-indicating glass 3 with three taps - steam, water and purge, a water level regulator in the tank, a pressure regulator and the necessary measuring equipment. For reliable operation For feed pumps, the deaerator is installed at a height of at least 7 m above the pump.

Heating boilers are 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 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, the design of the deaerator hydraulic system includes 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 such equipment as vacuum deaerator, is that the steam from it must be removed forcibly, while it comes out of the atmospheric in a natural way - 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 reduced pressure equipment is also included in the thermal scheme of boiler houses.

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;

hydraulic testing of equipment is carried out.

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 the technical characteristics of the heating equipment and the design of the boiler house.

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

Example symbol deaerator

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

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 is used two-stage scheme degassing: two stages are located in the deaeration column, the 1st stage is jet, the 2nd is bubbling.

Fig 1. Scheme of atmospheric pressure deaeration plant type DA

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

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

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

The main steam is supplied to the deaerator tank through a fitting(E), ventilates the vapor volume of the tank and enters the column. Passing through the holes of the bubbling tray (9), the steam subjects the water on it to intensive 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.

Design internal devices deaeration column provides the convenience of internal inspection. Perforated sheets of internal devices are made of corrosion-resistant steel.

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

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

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

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

The device consists of two hydraulic seals, one of which protects the deaerator from exceeding the permissible pressure, and the other from a dangerous increase in level, combined into a common hydraulic system, and expansion tank. Expansion tank 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 steam hydraulic seal is determined based on the highest allowable pressure in the deaerator during operation of the device 0.07 MPa and the maximum possible pressure in emergency steam flow to the deaerator with the control valve fully open and the maximum pressure in the steam source.

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

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

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

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

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

5. The scheme of the deaeration plant should provide for the possibility of conducting its hydraulic test (before putting it into operation and periodically as necessary) overpressure 0.2 MPa. The vapor cooler is tested with an excess pressure of 0.6 MPa.

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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 uses a two-stage degassing scheme: stage 1 - jet, stage 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.

The delivery set of the deaeration unit includes (the manufacturer agrees with the customer on the completeness of the 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. 1 Schematic diagram of an atmospheric pressure deaeration column with a 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 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 (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 hydraulic seals (see Fig. 4), one of which protects the deaerator from exceeding the permissible pressure 9 (shorter), and the other from a dangerous increase in level 1, combined into a common hydraulic system, and 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 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 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.

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 the installation and operation of thermal deaerators, the safety measures determined by the requirements of Gosgortekhnadzor, the relevant regulatory and technical documents, 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 the tightness of the pipe system - sampling cooler;

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.