Atmospheric pressure deaerators are designed to remove corrosive gases (oxygen and free carbon dioxide) from feed water steam boilers and make-up water for heating systems and in the boiler room.
An example of a deaerator symbol
DA-5/2
Where: YES - atmospheric deaerator;
5 - column productivity m³/h;
2 - tank capacity m³;
Specifications, completeness and types of Deaerators
| Options | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Productivity, t/h | 5 | 5 | 15 | 15 | 25 | 25 | 50 | 50 | 100 | 100 | 100 |
| Productivity range, t/h | 1,5-6 | 1,5-6 | 4,5-18 | 4,5-18 | 7,5-30 | 7,5-30 | 15-60 | 15-60 | 30-120 | 30-120 | 30-120 |
| Working pressure, MPa | 0,02 | ||||||||||
| Temperature of deaerated water, °C | 104,25 | ||||||||||
| Average water heating in the deaerator, °C | 10..50 | ||||||||||
| Column | KDA-5 | KDA-15 | KDA-25 | KDA-50 | KDA-100 | KDA-100 | |||||
| Weight, kg | 210 | 210 | 210 | 210 | 427 | 427 | 647 | 647 | 860 | 860 | 860 |
| Tank | BDA-4 | BDA-8 | BDA-15 | BDA-25 | |||||||
| Tank capacity, m³ | 2 | 4 | 4 | 8 | 8 | 15 | 15 | 25 | 25 | 35 | 50 |
| Weight, kg | 1100 | 1395 | 1395 | 2565 | 2565 | 3720 | 3720 | 5072 | 5072 | 7046 | 9727 |
| Vapor cooler | OVA-2 | OVA-2 | OVA-2 | OVA-2 | OVA-2 | OVA-2 | OVA-2 | OVA-8 | OVA-8 | ||
| Heat exchange surface area of the vapor cooler, m2 | 2 | 2 | 2 | 2 | 2 | 2 | 2 | 2 | 8 | 8 | 8 |
| Weight, kg | 232 | 232 | 232 | 232 | 232 | 232 | 232 | 232 | 472 | 472 | 472 |
| Safety device | DA-25 | DA-25 | DA-25 | DA-25 | DA-25 | DA-50 | DA-100 | DA-100 | |||
| Weight, kg | 277 | 277 | 277 | 277 | 277 | 277 | 401 | 401 | 813 | 813 | 813 |
Design and principle of operation of the deaerator
The deaerator includes:
- deaeration column;
- deaerator tank;
- vapor cooler;
- a combined safety device for protection against emergency increases in pressure and level.
The deaerator uses two-stage scheme degassing: two stages are located in the deaeration column: the 1st stage is jet, the 2nd is bubbling.
Fig 1. Diagram of an atmospheric pressure deaeration plant type DA
1 - Deaerator tank; 2 - Deaeration column; 3 - Vapor cooler; 4 - Safety device; 5 - Level regulator; 6 - Pressure regulator; 7 - Sampling refrigerator; 8 - Bubbler device; 9 - Bubbler plate; 10 - Bypass plate; 11 - Upper plate; 12 - Steam transfer device; 13 - Level indicator; 14 - Manhole.
The deaerator tank contains a third, additional stage in the form of a submerged 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 bubble plate (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 steam is transferred into the bypass of the bubbler plate. When the heat load decreases, the water seal is filled with water, stopping the steam bypass.
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 gases are removed and most of the steam condenses. The remaining vapor-gas mixture (vapor) is discharged from the upper zone of the column through fitting (B) into the vapor cooler (3) or directly into the atmosphere. The degassing process is completed in the deaerator tank (1), where tiny gas bubbles are released from the water due to sediment. Part of the steam can be supplied through a fitting into 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 deaerator loads.
Design internal devices deaeration column provides convenience of internal inspection. Perforated sheets of internal devices are made of corrosion-resistant steel.
A surface-type vapor cooler consists of a horizontal body and a pipe system located in it (the pipe material is brass or corrosion-resistant steel).
Chemically purified water passes inside the tubes and is directed to the deaeration column through fitting (A). The steam-gas mixture (vapor) enters the annulus, where the steam from it is almost completely condensed. The remaining gases are vented to the atmosphere, and the vapor condensate is drained into a deaerator or drain tank.
To provide safe operation deaerators are protected from dangerous increases in pressure and water level in the tank using a combined safety device.
The device is connected to the deaerator tank through the overflow fitting.
The device consists of two water 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 activated) necessary for automatic filling of the device (after eliminating the disturbance in the operation of the installation), i.e. makes the device self-priming.
The diameter of the steam hydraulic seal is determined based on the highest permissible pressure in the deaerator when the device is operating, 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 procedure for installing the deaerator
Before installing the deaerator it is necessary to: carry out inspection and re-preservation; Cut off the welded plugs with gas, and cut the edges of the pipes for welding.
1. It is preferable to place the deaerator indoors. Installing it on outdoors 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 installed anchor bolts), or on a metal shelf. One support is rigidly secured with bolts, the second is freely supported on the support sheet.
3. The deaeration column is installed on the tank by welding to the adapter fitting. The column can be oriented arbitrarily relative to the vertical axis, depending on the specific installation layout.
4. Installation diagram of the deaerator, component equipment and their piping, as well as diagram and control devices and automatic regulation determined by the design organization depending on the conditions, purpose and capabilities of the facility on which they are installed.
5. The design of the deaeration installation must provide for the possibility of carrying out its hydraulic test (before putting it into operation and periodically as necessary) with an excess pressure of 0.2 MPa. The vapor cooler is tested at an overpressure of 0.6 MPa.
Buy a deaerator
To purchase a deaerator, please contact the contacts listed at the top of the page.
In industrial and heating boiler houses, to protect heating surfaces washed by water, as well as pipelines, from corrosion, it is necessary to remove corrosive gases (oxygen and carbon dioxide), which is most effectively achieved by thermal deaeration of water. Deaeration is the process of removing gases dissolved in it 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 boiler installation circuit 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 the feed water of steam boilers and the make-up water of heating systems in boiler houses of all types (with the exception of pure water heating ones). Deaerators are manufactured in accordance with the requirements of GOST 16860-77. OKP code 31 1402.
Modifications
Example of a symbol:
DA-5/2 – atmospheric pressure deaerator with a column capacity of 5 m³/hour 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; YES-200/50; DA-300/75.
At the customer's request, 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 tanks of larger capacity.
Rice. General form deaerator tank with explication of fittings.
Technical specifications
The main technical characteristics of atmospheric pressure deaerators with bubbling in the column are given in the table.
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Deaerator |
DA-50/15 |
DA-100/25 |
DA-200/50 |
DA-300/75 |
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Nominal productivity, t/h |
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Operating excess pressure, MPa |
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Temperature of deaerated water, °C |
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Performance range, % |
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Productivity range, t/h |
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Maximum and minimum heating of water in the deaerator,°C |
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Concentration of O 2 in deaerated water at its concentration in the source water, C to O 2, μg/kg: - corresponding to the state of saturation No more than 3 mg/kg |
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Concentration of free carbon dioxide and deaerated water, C to O 2, µg/kg |
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Trial hydraulic pressure, MPa |
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Permissible pressure increase during operation protective device, MPa |
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Specific vapor consumption at rated load, kg/td.v |
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Diameter, mm Height, mm Weight, kg |
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Useful capacity of the battery tank, m 3 |
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Deaerator tank type |
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Evapor cooler size |
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Type of safety device |
* - design dimensions deaeration columns may vary depending on the manufacturer.
Description of design
The DA series atmospheric pressure thermal deaerator consists of a deaeration column mounted on an accumulator tank. The deaerator uses a two-stage degassing scheme: stage 1 - jet, stage 2 - bubbling, both stages are located in a deaeration column, the schematic diagram of which is shown in Fig. 1. Streams of water to be deaerated are fed into column 1 through pipes 2 onto the upper perforated plate 3. From the latter, water flows in streams onto the bypass plate 4 located below, from where it flows in a narrow beam of a jet of increased diameter onto the initial section of the non-failing bubble sheet 5. Then the water passes along the bubble sheet in the layer provided by the overflow threshold (the protruding part of the drain pipe), and through drain pipes 6 is drained 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 falls under the bubble sheet 5. Passing through the holes of the bubble sheet, the area of which is selected in such a way as to prevent the failure of water at a minimum thermal load of the deaerator, the steam subjects the water on it to intensive processing. As the thermal load increases, the pressure in the chamber under the sheet 5 increases, the water seal of the bypass device 9 is activated and excess steam is released into the bypass of the bubble sheet through the steam bypass pipe 10. Pipe 7 ensures that the water seal of the bypass device of deaerated water is filled with a decrease in the thermal load. From the bubbling device, steam is directed through hole 11 into the compartment between plates 3 and 4. The vapor-gas mixture (vapour) is removed from the deaerator through gap 12 and pipe 13. In the jets, water is heated to a temperature close to the saturation temperature; removal of the bulk of gases and condensation of most of the steam supplied to the deaerator. Partial release of gases from the water in the form of small bubbles occurs on plates 3 and 4. On the bubble sheet, the water is heated to saturation temperature with slight condensation of steam and micro quantities of gases are removed. The degassing process is completed in the battery tank, where tiny gas bubbles are released from the water due to sediment.
The deaeration column is welded directly to the battery tank, with the exception of those columns that have a flange connection to the deaeration tank. The column can be oriented arbitrarily relative to the vertical axis, depending on the specific installation scheme. The housings of the DA series deaerators are made of carbon steel, the internal elements are made of of stainless steel, fastening of 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 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;
control valve on the steam supply line to maintain pressure in the deaerator;
pressure vacuum gauge;
shut-off valve;
water level indicator in the tank;
pressure gauge;
thermometer;
safety device;
vapor cooler;
coupling shut-off valve;
drain pipe;
technical documentation.
Rice. 1 Schematic diagram atmospheric pressure deaeration column with a bubbling stage.
Deaeration installation circuit diagram
The scheme for switching on atmospheric deaerators is determined by the design organization depending on the conditions of purpose and the capabilities of the facility where they are installed. In Fig. Figure 2 shows the recommended diagram of the DA series deaeration unit.
Chemically purified water 1 is supplied to the deaeration column 6 through the vapor cooler 2 and the control valve 4. 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 removed from the opposite end of the tank in order to ensure maximum holding time of water in the tank. All steam is supplied through pipe 13 through pressure control valve 12 to the end of the tank opposite the column, in order to ensure good ventilation of the steam volume from gases released from the water. Hot condensates (clean) are supplied to the deaerator tank through pipe 10. Vapor is removed from the installation through vapor cooler 2 and pipes 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 checking 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 for switching on an atmospheric pressure deaeration unit:
1 - supply of chemically purified water; 2 - vapor cooler; 3, 5 - exhaust into the atmosphere; 4 - level adjustment 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 - drainage of deaerated water; 15 - water sample cooler; 16 - level indicator; 17- drainage; 18 - pressure and vacuum gauge.
Vapor cooler
To condense the vapor-gas mixture (vapor), a surface-type vapor cooler is used, consisting of a horizontal housing in which a pipe system is located (tube material - brass or corrosion-resistant steel).
The vapor cooler is a heat exchanger into which chemically purified water or cold condensate from permanent source, heading to the deaeration column. The steam-gas mixture (vapor) enters the annulus, where the steam from it is almost completely condensed. The remaining gases are vented to the atmosphere, and the vapor condensate is drained into a deaerator or drain tank.
The vapor cooler consists of the following main elements (see Fig. 3):
Nomenclature and general characteristics vapor coolers
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Vapor cooler |
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Pressure, MPa In a pipe system In the building |
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In a pipe system In the building |
steam, water |
steam, water |
steam, water |
steam, water |
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Ambient temperature, °C In a pipe system In the building |
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Weight, kg |
Safety device (hydraulic seal) for atmospheric pressure deaerators
To ensure safe operation of deaerators, they are protected from dangerous increases in pressure and water level in the tank using a combined safety device (hydraulic seal), which must be installed in each deaerator installation.
The water seal must be connected to the steam supply 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 activated) necessary for automatic filling of the device (after eliminating the malfunction of the installation), i.e. makes the device self-priming. The diameter of the overflow water seal is determined depending on the maximum possible water flow into the deaerator in emergency situations.
The diameter of the steam hydraulic seal is determined based on the highest permissible pressure in the deaerator when the device is operating, 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.
To limit the steam flow into the deaerator in any situation to the maximum required (at 120% load and 40-degree heating), an additional throttle limiting diaphragm should be installed on the steam line.
In some cases (to reduce the building height, install deaerators in rooms), instead of a safety device, safety valves (to protect against overpressure) and a condensate drain are installed to the overflow fitting.
Combined safety devices are manufactured in six standard 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 a 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 flood control; 7 – supply of chemically purified water for filling; 8 - water supply from the deaerator; 9 – water seal against pressure increase; 10 – drainage.
Installation of deaeration units
For execution installation work installation sites must be equipped with basic installation equipment, devices and tools in accordance with the work project. When accepting deaerators, you should 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, and the absence of damage or defects in the equipment. Before installation visual inspection and re-preservation of the deaerator, and the detected defects are eliminated.
Installation of the deaerator on site is carried out in the following order:
install the accumulator tank on the foundation in accordance with the installation drawing design organization;
weld the drainage neck to the tank;
cut off the lower part of the deaeration column along the outer radius of the body of the deaeration tank and install it on the tank in accordance with the installation drawing of the design organization, while the plates must be positioned strictly horizontally;
weld the column to the deaerator tank;
install the vapor cooler and 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 as directed by the design organization.
Indication of safety measures
During installation and operation thermal deaerators safety measures determined by the requirements of Gosgortekhnadzor, relevant regulatory and technical documents must be observed, job descriptions etc.
Thermal deaerators must undergo technical inspections ( 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 from the pipelines are removed, hatches on the deaerator are closed, bolts on flanges and fittings are tightened, all gate valves and control valves are in working order and closed;
Maintain the nominal vapor flow from the deaerator in all modes of its operation and periodically monitor it using a measuring vessel or using the balance of the vapor cooler.
Basic 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 concentration of oxygen and free carbon dioxide in the sample is determined incorrectly. In this case it is necessary:
check that chemical analyzes are performed correctly in accordance with the instructions;
check the correctness of water sampling, its temperature, flow rate, and the absence of air bubbles in it;
check the density of the pipe system - sampling refrigerator;
b) the vapor consumption is significantly reduced.
In this case it is necessary:
check that the surface of the vapor cooler corresponds to the design value and, if necessary, install a vapor cooler with a larger heating surface;
check the temperature and flow rate of the cooling water passing through the vapor cooler and, if necessary, reduce the water temperature or increase its flow rate;
check the degree of opening and serviceability of the valve on the outlet pipeline 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 the following should be done:
check the temperature and flow rate of the flows entering the deaerator and increase average temperature initial flows or reduce their consumption;
check the operation of the pressure regulator and if the automation malfunctions, switch to remote or manual pressure regulation;
d) supply of steam with a high content of oxygen and free carbon dioxide to the deaerator. It is necessary to identify and eliminate sources of steam contamination with gases or take steam from another source;
e) the deaerator is faulty (clogging of the holes in the plates, warping, breakage, breakage of the plates, installation of the plates on a slope, destruction of the bubbling device). It is necessary to take the deaerator out of operation and carry out repairs;
f) the steam flow into the deaerator is insufficient (the average heating of water in the deaerator is less than 10°C). It is necessary to reduce the average temperature of the initial water flows and ensure heating of the water in the deaerator by at least 10°C;
g) drainage containing a significant amount of oxygen and free carbon dioxide is sent to the deaerator tank. It is necessary to eliminate the source of infection of the drains or feed them into the column, depending on the temperature, onto the upper or overflow plate;
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 adequacy of heat flow in the power source.
2. An increase in pressure in the deaerator and activation of the 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 automation system;
b) with sharp increases in temperature, with a decrease in the flow rate of the source water, either reduce its temperature or reduce the steam flow.
3. An increase or decrease in the water level in the deaerator tank beyond the permissible level may occur due to a malfunction of the level regulator; it is necessary to switch to remote or manual level control; if it is impossible to maintain the normal level, stop the deaerator and check the control valve and automation system.
4. Water hammer must not be allowed in the deaerator. If water hammer occurs:
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 initial water or reduce its consumption.
Repair
Routine repairs of deaerators are performed once a year. At current repairs Inspection, cleaning and repair work is carried out to ensure normal operation of the installation until the next repair. For this purpose, deaeration tanks are equipped with manholes, and the columns are equipped with inspection hatches.
Planned major repairs 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 carry it out using hatches, the column can be cut along a horizontal plane in the place most convenient for repair.
During subsequent welding of the column, the horizontality of the plates must be ensured 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.
Thermal deaerators are usually classified according to operating pressure and the method of organizing phase contact.
According to the working pressure there are following types deaerators:
Vacuum, operating at an absolute pressure in the housing from 0.075 to 0.5 atmospheres;
Atmospheric, the absolute pressure in which varies in the range from 1.1 to 1.3 atmospheres;
High pressure, operating at absolute pressure from 5 to 12 atmospheres.
The method of organizing phase contact is determined by the design of the deaerator. Since the same deaerator, as a rule, uses deaeration devices that differ from each other in operating principles, modern deaerators are usually combined. In this case, the following main types of deaeration devices (or individual elements deaerator):
Jet, in which the phase interface is formed by the surface of water jets freely falling in a steam flow;
Bubblers, in which the heating fluid in the form of steam bubbles is distributed in the water flow;
Film, where the phase interface is formed by the film flow of water in a steam flow;
Drip systems, in which water is distributed in the steam stream in the form of drops.
The interface between the phases can be conditionally fixed, as, for example, in film deaerators with an ordered packing, or unfixed, as in deaerators with a disordered packing, jet, drip and bubbling. The scope of application of deaerators in thermal circuits of energy facilities, as a rule, is determined by the operating pressure, deaerators high blood pressure are used exclusively as feedwater deaerators of thermal power plants with high, ultra-high and supercritical initial steam pressure;
Atmospheric pressure deaerators are used as feedwater deaerators of power plants and boiler houses of low and medium initial steam pressure, additional water deaerators of the cycle of heating power plants (CHP) with a higher initial steam pressure, make-up water deaerators of heating networks closed type(less often - for heating networks open type using deaerated water coolers), feedwater deaerators of evaporation and steam conversion units of power plants;
Vacuum deaerators are used as deaerators of make-up water in heating networks, in circuits of evaporation and steam conversion plants, and less often - as deaerators of additional water in power plants and boiler houses.
Atmospheric pressure deaerators
The most common type of atmospheric deaerator is the jet-bubble deaerator. In such deaerators, as a rule, a two-stage deaeration scheme is used, including a jet and bubbling stages. It should be noted that the deaeration stage is usually understood as one or more connected in series through water deaeration elements, working on the same principle. For example, two jet compartments located one below the other belong to one jet stage.
The designs of such deaerators are somewhat different from each other for devices of different capacities from the standard range. Most of the standard designs of jet-bubbling atmospheric deaerators were developed by NPO TsKTI im. I.I. Polzunov. Currently, both outdated models of such deaerators (type DSA) and their modern analogues (types DA and DA-m) are used. Designed by standard series standard sizes of such deaerators, differing in nominal capacity for deaerated water: 1, 3, 5, 15, 25, 50, 100, 200 and 300 t/h.
Atmospheric deaerators typically consist of a deaeration column mounted on a horizontally located cylindrical deaerator tank. The deaerator tank as part of the deaerator performs two important functions. Firstly, it serves as a means of creating a supply of deaerated water for technological scheme. If, for example, the deaerator is used as a feedwater deaerator for steam boilers low pressure, then it is necessary to create a supply of water in the deaerator tank to ensure uninterruptible power supply these boilers in emergency situations. Secondly, as shown above, the deaeration tank allows you to increase the time the water is kept at a temperature close to the saturation temperature, which helps to increase the efficiency of deaeration.
In relation to devices with low productivity (1 and 3 t/h of deaerated water), the deaerator can perform the indicated functions without a deaerator tank, since the necessary supply of water can be created directly in the body of the deaeration column, the dimensions of which will not be too large. IN standard designs Such deaerators are not distinguished between a deaeration column and a deaerator tank, but rather refer to the deaerator body as a whole. Such deaerators are called columnless.
Deaerators with higher productivity are equipped with deaerator tanks of various capacities. Domestic power engineering plants produce deaerator tanks of standard sizes with a capacity of 2, 4, 8, 15, 25, 35, 50 and 75 m 3, and each deaerator tank is designed for a deaeration column of a certain capacity. However, at the customer's request, as a rule, it is possible to supply selected deaeration columns with tanks of a different capacity from the standard range.
In addition to the deaerators developed by NPO TsKTI im. I.I. Polzunov, a number of designs of atmospheric deaerators developed by other organizations are used. Among such deaerators, we note the bubbling deaerator designed by Uralenergometallurgprom.
Currently, atmospheric deaerators are produced by the following main domestic factories:
Neftekhimmash Equipment LLC, Biysk Boiler Plant OJSC, Sibenergomash OJSC, Belenergomash OJSC, Teploenergokomplek CJSC, TKZ-Krasny Kotelshchik OJSC, Sarenergomash OJSC.
Below we will consider the main Constructive decisions, used in atmospheric pressure deaerators and their piping elements: vapor coolers and safety drain devices.
Let's consider the design diagram of columnless deaerators with a capacity of 1 and 3 t/h (Fig. 3.1), developed by NPO TsKTI im. I.I. Polzunov.
Rice. 3.1. Structural diagram columnless deaerators DA-1 and DA-3: 1 - source water supply fitting; 2 - perforated water distribution manifold; 3 - jet-forming plate; 4 - water intake tray; 5 - sectioning threshold of the jet-forming plate; 6 - limiting threshold of the jet-forming plate; 7 - bubbling device; 8 - bubble sheet; 9 and 10 - partitions; 11 - fitting for draining deaerated water; 12 - heating steam supply fitting; 13 - steam line; 14 - steam receiving box; 15 - vapor transfer window; 16 - steam inlet window; 17 - inlet window of the built-in vapor cooler; 18 - vapor outlet fitting; 19 - hatch; 20 and 21 - fittings for connecting the safety-drain device for steam and water, respectively; 22 - drainage fitting.
energy desorption bubbling hydrodynamic
The deaerator DA-1 or DA-3 is a vertical cylindrical vessel with elliptical bottoms and deaeration devices located inside it.
The water sent for deaeration enters the deaerator through fitting 1 and the perforated water distribution manifold 2. From the holes of the water distribution manifold 2, water flows in the form of jets onto the jet-forming plate 3, perforated in the part located above the water receiving tray 4. The jet-forming plate 3 is sectioned by a threshold 5 in such a way that that with a low hydraulic load, water flows in the form of jets into tray 4 only through holes located up to threshold 5 in the direction of water movement. With an increased hydraulic load, the water level on the jet-forming plate 3 rises, the water flows over the threshold 5 and all the holes of the jet-forming plate are put into operation. This sectioning of the jet-forming plate 3 is made so that, at low hydraulic loads of the deaerator, there is no misalignment (“distortions”) between the flows of water and heating steam, leading to a deterioration in the conditions of heat exchange and deaeration. The maximum hydraulic load of the deaerator is limited by the height of the limiting threshold 6: with increased hydraulic load, the water level on the jet-forming plate increases and if water overflows over threshold 6, the efficiency of water heating and deaeration sharply deteriorates.
In the jet stream inside tray 4, the main heating of water occurs when it comes into contact with heating steam and the degassing process begins. The water draining from tray 4 in the form of a stream into the water volume of the deaerator, under most operating modes of the deaerator, remains underheated to the saturation temperature corresponding to the pressure in the steam space of the deaerator, and contains gases both in dissolved and dispersed form.
After a certain exposure of water in the water volume of the deaerator, the duration of which is determined by the hydraulic load and the water level in the deaerator, the water enters the bubbling device 7. This device is made in the form of a channel rectangular section, limited at the top and sides by solid partitions and having a perforated bubble sheet 8 at the bottom. When steam is bubbled through a layer of water in the bubbler device 7, the water is heated to a saturation temperature corresponding to the pressure in the bubbler device. This pressure is greater than the pressure in the steam space of the deaerator above the water surface by the pressure of the water column of height H, therefore the water temperature in the bubbling device becomes greater than the saturation temperature at the steam pressure above the water surface in the deaerator. In the bubbling device 7, due to the water reaching the saturation temperature, most of the dissolved gases transform into a dispersed state in the form of small gas bubbles; here, partial thermal decomposition of hydrocarbonates and hydrolysis of carbonates occurs with the formation of free carbon dioxide, which, in turn, also transforms into dispersed state.
Having left the bubbling device 7, water mixed with the non-condensed part of the heating steam enters the channel formed by partitions 9 and 10 and moves upward along this channel. During this movement, the pressure of the medium continuously decreases from the pressure in the bubbling device to the steam pressure above the surface of the water in the deaerator. Accordingly, water, which turns out to be overheated relative to the saturation temperature, boils in volume, which is accompanied by the transition of most of the gases still in dissolved form into a dispersed state. In the upper part of the water volume, phase separation occurs: water flows through partition 10 and falls towards the deaerated water outlet fitting 11, and steam with gases released from the water moves towards the jet deaeration stage.
It should be noted that the leakage of the steam-water mixture from the bubbling device 7 directly into the deaerated water outlet fitting 11 is unlikely. The flow of the medium in the gap between the partitions 9 and 10, due to the presence of steam, has a lower density than the flow of water descending in the channel formed by the partition 10 and the wall of the housing, which causes only the lifting movement of the medium between the partitions 9 and 10. Meanwhile, the gap between the partition 10 and the housing in the lower part is necessary to allow some circulation of water around the partition 10. Such circulation increases the frequency of water treatment with steam and increases the available time of the deaeration process, which increases the efficiency of removing gases from water.
All the heating steam is supplied to the deaerator through fitting 12 and through the steam line 13 enters the steam receiving box 14 under the bubble sheet 8. A steam cushion is created under the bubble sheet 8, preventing water from falling through the holes of the bubble sheet. Such bubble sheets are called non-sinking sheets.
Here it is advisable to dwell in more detail on the limiting operating mode of a non-failing bubble sheet - the “flooding” mode or injection mode. If the velocity of steam in the holes of the sheet is too high, the steam coming out of the holes of the bubble sheet will capture all the liquid, crush it and carry it away in the form of spray. It is for this reason that the maximum steam pressure under the bubble sheet must be limited. In the considered deaerators DA-1 and DA-3, for this purpose, a steam bypass window 15 is made in the partition 9, which bypasses part of the steam in addition to the holes of the bubble sheet8 when the steam pressure under this sheet increases above that required for efficient work bubbling device.
After separating the water and the steam-gas mixture in the upper part of the channel formed by partitions 9 and 10, this mixture enters through the steam inlet window 16 into the jet compartment of the deaerator, where most of the steam condenses, heating the water flow. The remaining part of the steam mixed with gases washes the jet-forming plate 3 and enters the built-in contact vapor cooler. The vapor cooler is a jet stream of water flowing from the water distribution manifold 2, through which passes the vapor-gas mixture entering through window 17. Here, water vapor is additionally condensed on the jets relatively cold water. The remaining small part of the steam and non-condensable gases are removed from the deaerator through the vapor outlet fitting 18.
Deaerators DA-1 and DA-3 are equipped with hatch 19, which provides access to the inside of the housing for inspection and repair, as well as fittings 20 and 21 for connecting a safety drain device and drain fitting 22.
An atmospheric deaerator with a capacity of 5 t/h or more (Fig. 3.2) consists of a deaeration column 7 installed on a deaerator tank 10. The column includes several (in in this example two) jet compartments formed below the upper 8 and lower 9 perforated plates, and can also be supplemented with a bubble sheet. The water to be deaerated is supplied through a water distribution system to the upper jet-forming plate 8, from where it flows onto the plate 9 located below and then onto the bubble sheet (if present) or directly into the deaerator tank (as in the example under consideration). Jet trays have special thresholds that ensure the maintenance of a certain water level on them, as well as the overflow of water in addition to the jet zone when the trays are overfilled. Bubbler sheets are usually made non-sinking (the dynamic action of the steam flow does not allow water to “fall” through the holes of the sheet), since the operation of a sinking bubble sheet is effective only in a narrow range of water and steam flow rates through it.
Fig.3.2.
1 - water supply; 2 - vapor cooler; 3, 6 - vapor to the atmosphere; 4 - supply of third-party condensate (for example, condensate of steam from production extraction of turbine units); 5-level regulator; 7 - deaeration column; 8, 9 - upper and lower jet-forming plates; 10 - deaerator tank; 11 - safety drain device; 12 - supply of bubbling steam; 13 - pressure control devices; 14 - pressure regulator; 15 - main steam supply; 16 - drainage of deaerated water; 17 - level indicator; 18 - drainage; 19 - supply of hot condensate.
Steam is usually supplied to the above-water space of the deaerator tank (and in this case is called the main steam 15), ventilates it, ensuring the removal of gases released from the water in the tank, and enters the deaeration column. Here the steam interacts with the downward flow of water, providing its heating and deaeration.
The vapor containing gases and water vapor released from the water is discharged from the deaerator into the atmosphere through pipe 6 or to the vapor cooler 2, where the thermal potential of this flow is used, for example, to heat the source water in front of the deaeration column. In this case, gas blowing 3 is carried out from the steam space of the vapor cooler. It is possible to supplement the specified design with a bubbling device for the deaerator tank. The most commonly used devices are the TsKTI system (in this example) or perforated bubble collectors mounted at the bottom of the tank along its generatrices. In this case, bubble steam 12 is supplied through a special pipeline, since the pressure of this steam must be greater than the pressure of the main steam by at least the pressure of the water column in the deaerator tank. The deaerator is equipped with a safety drain device 11; level glass 17; connections for connecting the deaerator to the steam and water equalization lines; drainage pipeline 18; deaerated water outlet pipe 16.
Experience in operating atmospheric deaeration plants shows that, regardless of the reason for the deterioration in the efficiency of water deaeration, the use of steam bubbling in the water volume of the deaeration tank allows this efficiency to be increased.
Even if the deaeration column provides the required quality of deaerated water, the bubbling device of the deaerator tank acts as a barrier, reducing the likelihood of dissolved gases leaking into the deaerated water and expanding the permissible range of changes in the hydraulic and thermal loads of the deaerator while maintaining the required quality of deaerated water. In this case, steam bubbling in the deaerator tank provides some superheating of the water relative to the saturation temperature and thereby protects the water from re-contamination with gases.
In addition, it is necessary to remember that the part of the gases remaining in the water after the deaeration column is contained in dispersed form and represents a multitude of tiny gas bubbles, the sizes of which are so small that they do not ensure their independent ascent due to the action of the buoyant force. In a deaerator without bubbling in the water volume of the tank, these bubbles will fall into the deaerated water. Steam bubbling, which provides intensive mixing and turbulization of the water volume in the tank, promotes the release of part of the gases in dispersed form from the water, increasing the efficiency of deaeration as a whole.
Thus, a flooded bubbling device in a deaeration tank is often necessary even when using modern two-stage deaeration columns.
Let us consider, as an example, the bubbling device of the TsKTI system (Fig. 3.2.).
Rice. 3.2. Schematic diagram of the bubbling device of the deaerator tank of the TsKTI system: 1 - bubbling sheet; 2 - top shelf; 3 - lifting shaft; 4 - drainage of deaerated water; 5 - deaeration column; 6 - deaerator tank; 7 - supply of bubbling steam; 8 - main steam supply; solid lines indicate the direction of water movement; dotted lines - directions of steam movement
Water flows through the canal surface formed bubble sheet 1 and top shelf 2, and during this movement it is treated with steam coming out of the holes of the bubble sheet. The steam-water mixture, leaving the channel, enters a specially organized lifting movement shaft 3, in the upper part of which the steam and gases released from the water are separated from the water and discharged into the above-water space of the deaerator tank and mixed with the flow of the main steam, and the water is lowered in the water volume of the tank to the deaerated water outlet pipe 4.
The deaerator tanks themselves (see example in Fig. 3.4) are horizontally located cylindrical vessels with elliptical, less often conical, bottoms, mounted on two supports. And for tanks usable capacity 25 m 3 or more, one of the supports is movable (roller), providing compensation for temperature expansion of the tank during starts and stops of the deaerator. Tanks with a useful capacity of 8 m 3 or more are equipped with special belts that provide the required rigidity of the body.
Rice. 3.4. General view of the deaeration tank with a useful capacity of 75 m3: A - fitting for the deaeration column; B - connection fitting for the safety-drain device for steam; B - main steam supply fitting; G - drainage fitting; D - fitting for draining deaerated water; E - connection fitting for the water safety drain device; F - fittings for connecting a level indicator; C- union for discharge from the separator continuous blowing boiler; T - fitting for introducing feed water from the feed pump recirculation line; U - fitting for the input of superheated condensates; F - fitting for introducing the steam-air mixture from the steam space of the heaters; C- fitting for supplying steam to the submerged bubbling device of the deaerator tank; Ch- reserve fitting
Columns are connected to deaerator tanks, usually by welding. In the designs of modern deaerators, the column is located near one of the ends of the deaerator tank; deaerated water is removed from the tank from the opposite end. This achieves the maximum possible time for the given geometric characteristics to hold water in the deaeration tank at a temperature close to the saturation temperature, and, accordingly, the greatest deaeration efficiency.
Deaeration tanks are equipped with a hatch that provides access to the inside of the tank for inspection and repair, as well as inspection and repair of the lower devices of the deaeration column, fittings for connecting a safety drain device for steam and water (the latter is mounted inside the tank and ends in an overflow funnel, the height of the upper edge is which determines the maximum water level in the tank). Fittings are provided for connecting the deaerator to the steam and water equalizing lines required for parallel work several deaerators, a fitting for draining deaerated water, supplying main and bubbling steam, a drain fitting, as well as a number of fittings for discharging high-potential flows, the temperature of which is higher than the saturation temperature at the operating pressure in the deaerator, or for introducing flows of already deaerated water. If streams overheated relative to the saturation temperature in the deaerator are directed not into the deaerator tank, but into the deaeration column, then the steam formed during their boiling can disrupt the normal ventilation of the steam space of the deaerator, which, in turn, will lead to a deterioration in the efficiency of water deaeration.
Heading:Hello dear customers of the MetalExportProm enterprise and those who are interested in our products. Today I want to tell you in detail what are deaerators dp - high blood pressure, which are rare, but still used and represent technically complex and critical containers. Everyone who works with such equipment is familiar with an atmospheric or vacuum deaerator, but not many people know the devices I’m talking about now. And so on in order.
The name itself suggests that the device, unlike conventional devices, operates at elevated pressure. In the DA series, a pressure of 0.12 MPa is used, and in the DP series, which we are talking about now, from 0.23 to 1.08 MPa DP1000/120, this is nine times more than aspirated. Accordingly, the walls of blood vessels are much thicker. If you are interested in immediately looking at the technical characteristics, then go to nuclear power plants, or read further.
The device itself belongs to capacitive equipment, you can see more about the containers, but since heat exchange processes also take place inside it, it can also be classified as heat exchangers, about which everything is written in this section. Let's look at what it consists of.
And it consists of a deaeration column, symbol KDP, starting from KDP-80 to KDP-6000, stands for KDP - high-pressure deaerator column, and the numbers next to it are the nominal productivity measured in tons per hour or t/h, i.e. There are from 80 to 6000 tons per hour. The performance of a deaerator is the amount of prepared water leaving it, i.e. how much water it can process and produce in tons per hour. And so there can be from one to four or more such columns, in contrast to a simple atmospheric deaerator with one column, and they can be either vertical or horizontal, depending on the design of the device. Now let’s look at what function the column performs. To do this, let's start from the very beginning, why is the dp deaerator itself needed at all and where and where it is installed.
And they are installed at thermal power plants and nuclear power plants that have energy boilers with an initial steam pressure of 10 MPa, in contrast to atmospheric ones operating at low atmospheric pressure and with small hot water boilers at a pressure of 0.07 MPa. The difference is obvious, the steam pressure of energy boilers is more than a hundred times higher, just like them themselves. Let's look further to make the water treatment process itself clearer, since the entire capacitive and heat exchanger That's what it's designed for.
Water treatment
Since we are considering thermal and nuclear power plants, we will consider the processes occurring in them. Any power station is needed to generate electricity, which then goes to homes or businesses. Where does it come from? It is produced by a generator, which drives a turbine, which requires steam to operate, and the steam is produced by a steam generator or the steam boiler itself, depending on the design of the station. But steam must be generated from somewhere, and it is obtained by evaporation of feed water.
The water entering the reactor or boiler must be purified both from mechanical impurities and from gases that may be present in it. These impurities can be deposited on the walls of pipelines and the boilers themselves, thereby reducing the flow of liquids and heat exchange, and the gases present in the water cause corrosion of the pipes of the boiler walls. All this not only leads to a deterioration in operating efficiency, but can also cause an emergency. To prevent this, we need water treatment and water purification, which in our case is directly involved in, which removes corrosive gases from the feed water of reactors and steam boilers.
Only nuclear power plants have two circuits. In the first, water is prepared and poured. And this circuit works for many months, but the second circuit works a little differently, read on. There are also single-circuit ones, then the coolant water passes through full cycle from the boiler through the steam generator to the turbine, then to the condenser and again to the reactor. Such stations are cheaper, but the equipment operates under radiation conditions. Therefore, double-circuit ones are safer, since radioactive water moves only in a closed primary circuit, which is located behind the casing and concrete, this is the reactor itself, the interaction occurs in the steam generator, but this is not so strong.
Processes occurring in nuclear power plants
Let's consider all the processes from start to finish using the example of a nuclear power plant, but only those related to our topic. So. There is the heart of the station - this is the reactor block, inside of which there are rods in which the nuclear reaction. At the same time, it stands out great amount heat. This container is located inside another container, between which there is water. Those. the two tanks represent a nuclear boiler, inside which a nuclear reaction takes place and heats the water in between.
The heated water enters a heat exchanger called a steam generator, passes through it giving off heat, and leaves it and is then pumped circulation pump back into the boiler. This is the first circuit. And he is closed, i.e. water is poured in there and circulates big time, of course sometimes replenished.
But there is also a second circuit. Almost boiling water is pumped into the heat exchanger-steam generator by a pump and it already boils in it turning into steam, which is part of the generator. The steam comes out and hits the turbine blades, causing it to move, and the rotor rotates, which is connected to the generator rotor. And the generator produces electrical energy. So the steam passing through the turbine does not dissipate, why waste it, but leaves the turbine and enters the condenser, which serves to condense the steam and turn it into liquid.
You can familiarize yourself with capacitors in more detail.
Water treatment
The condensate leaving the condenser enters the deaeration column from above. The other part of the steam at the turbine outlet from the second extraction is also supplied to the column only from below. Condensate moves downwards, and steam moves towards it. As a result of this process, corrosive gases and their mixture, called vapor, oxygen, nitrogen and others rise to the top and exit into the vapor cooler, which is a shell and tube heat exchanger with a set of brass or stainless steel heat exchange pipes. The steam condenses and enters the tank, and the gases are discharged into the atmosphere. This is what the water purification process looks like, which is closely related to deaeration.
You can familiarize yourself with columns for atmospheric deaerators. The principle of its operation and purpose are also discussed in detail there.
Deaeration
Deaeration is the process of preparing feed water for boilers, associated with the removal of gases. And so in the column the water is purified from gases and drained into the deaerator tank, accumulating in it. Next, the pump pumps it into the heat exchanger and steam generator. The water inside rises and is heated by the primary circuit water and enters the evaporator.
Technical characteristics of deaerators for nuclear power plants
| Name | Nominal productivity, t/h | Absolute operating pressure, MPa (kgf/cm2) | Column | Number of columns | Column diameter, mm | Tank capacity, m 3 | Tank useful capacity mm 3 | Tank diameter, mm | Deaerator length, mm | Deaerator height, mm | Weight, kg | Weight of deaerator with water, mm |
| dp-2000-2x1000/120-A | 2000 | 0.7(7.0) | KDP-10A vertical | 2 | 2400 | 150 | 120 | 3400 | 17000 | 8300 | 43200 | 227200 |
| dp-3200-2x1600/185-A | 3200 | 0.69(0.7) | KDP-1600-A vertical | 2 | 3400 | 210 | 185 | 3400 | 23415 | 11160 | 93000 | 361000 |
| dp-3200/220-A | 3200 | 1.35(13.8) sliding | KDP-3200-A horizontal | 1 | 3000 | 350 | 220 | 3800 | 32180 | 7900 | 230000 | 710000 |
| dp-6000/250-A | 6000 | 0.82(8.4) | KDP-6000-A horizontal | 1 | 3000 | 400 | 250 | 3800 | 32180 | 7900 | 190000 | 74000 |
| dp-6000/250-A-1 tables above.
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