Deaerator - what is it? Types, device, principle of operation

Heating boilers are most often made of steel. The water passing through them in its composition has oxygen and carbon dioxide. Both these elements have an extremely negative effect on the metal structure of the boiler. The constant contact of steel with these gases inevitably leads to its rusting. In order to remedy the situation and extend the service life of the equipment, a special installation - deaerator is included in the boiler's thermal scheme. What it is? About this and talk later in the article.

Definition

Deaerator is a special equipment designed to remove oxygen from the heating medium of heating systems by heating the latter with steam. Thus, in addition to the cleaning function, devices of this type also perform thermal. The same deaeration unit can be used for heating and cleaning both nutrient and make-up water.

Design Features

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

On the horizontal tank of the deaerator are mounted the inlet and outlet branch pipes for connecting the supply and discharge lines of the medium. Plums are installed below. Another element of the design is a collecting tank intended for the collection of degassed water. It is located under the bottom of the BDA.

The hydraulic system of equipment such as a deaerator, the scheme of which is presented below, usually consists of two hydraulic seals. One of them protects the device from any excess of permissible pressure, and the second - from the dangerous. Also in the design of the deaerator hydraulic system is the expansion tank. The vapors from the deaerator come into a special cooler, which looks like a horizontal cylinder.

Column construction

The column is a cylindrical shell with an elliptical bottom. Like the tank, it has nozzles for supply and removal of the medium. Inside the column there are special plates with holes through which water flows. This design allows to significantly increase the area of contact between the medium and the vapor, and consequently, to produce heating at maximum speed.

Types of equipment

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

• vacuum;

• atmospheric.

In the first type of deaerators, gases are removed from the water in a vacuum. In the design of such installations, a steam or water jet ejector is additionally included. The last version of the nodes is most often used in systems with boilers of medium or low power. Instead of ejectors for creating vacuum, special pumps can be used. Some of the disadvantages of such equipment as a vacuum deaerator is that steam from it must be removed forcibly, while from the atmospheric it leaves naturally - under pressure.

In addition to the two types of deaerators considered, pressurized devices can be installed in the boiler houses. They work at 0.6-0.8 MPa. Sometimes low-pressure equipment is also included in the boiler room thermal scheme.

Scope of use

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

Most often deaerators are used in heating systems and hot water. Boilers with hot water boilers are usually equipped with vacuum-type units. Also in such schemes, air deaerators can be used. Installations of reduced and high pressure are used mostly in systems operating due to the operation of the steam boiler. The first version (at 0.025-0.2 MPa) is installed in not too powerful systems, designed for a small number of consumers. Installations of increased pressure are used in thermal schemes with boilers supplying a large amount of steam.

Belleville deaerator: principle of operation

The scheme of gas purification in deaerators is realized two-stage: jet (in a column) and bubbling (in a tank). In addition, the system includes a flooded bubble device. Water is fed to the column, where it is processed by steam. Then it flows into the tank, is kept in it and is taken back to the system. Steam is initially fed to the BDA. After ventilation of the internal volume, it enters the column. Passing through the holes of the bubble plate, steam warms the water to the saturation temperature.

The jet method removes all gases from the water. At the same time, condensation of steam occurs. Its residues are mixed with the gas released from the medium and diverted to the cooler. The condensate from the vapor is drained into a drainage tank. During the settling of water in the tank, residual small gas bubbles leave it. The water is taken to the collecting tank. Sometimes the horizontal container is used only for settling. In such installations, both stages of degassing are placed in the column.

Deaeration of make-up water

The heating medium circulates continuously in the heating system. But its volume eventually decreases as a result of leaks. Therefore, make-up water is supplied to the heating system. Like the main one, it must undergo a deaeration process. Initially, the water enters the preheater, and then passes through chemical cleaning filters. Further, like the nutrient, it enters the deaerator column. The water released from oxygen flows to the make-up pump. The latter directs it to the suction manifold or to the storage tank.

Chemical deaeration

Thus, the answer to the question of what a boiler plant deaerator is, is simple. This equipment is designed for boiling water with hot steam to remove oxygen. However, sometimes the gases from the coolant in such installations are not completely removed. In this case, for the further purification of the boiler room water, various kinds of reagents can be added to bind the oxygen. It can be, for example, sodium sulphite. In this case, for proper deaeration of water, its heating is required. Otherwise, chemical reactions will occur too slowly. To accelerate the process of oxygen binding, various catalysts can be used. Sometimes water is deaerated and by passing through the layer of ordinary metal chips. The latter in this case are rapidly oxidized.

Mounting Features

The deaerator device is not too complicated. However, its installation should be carried out with the exact observance of all put technologies. When installing such equipment, they are guided primarily by the drawings attached to the manufacturer and the boiler house project. Before starting the installation, the unit is inspected and its re-opening. The detected defects are eliminated. Actually the installation procedure itself includes the following steps:

• The tank is mounted on the foundation;

• The spillway is welded to it;

• The lower part of the column is cut to the outside diameter;

• The column is installed on the tank (the plates fixed inside it must be placed horizontally);

• The column is welded to the tank;

• The evaporator cooler and the water trap are mounted;

• In accordance with the drawings, the connection of the mains is made;

• A shut-off and control valve is installed;

• Hydraulic testing of equipment is carried out.

Spraying plants

The constructions considered above are called plate-like. There are also spraying deaerators. Devices of this type are used less often and also represent a horizontal storage tank of high capacity. The absence of a column is what distinguishes such a deaerator. The principle of its operation is also slightly different. Steam in such installations comes from below - from a horizontal comb in the tank. The tank itself is divided into a heating and deaeration zone. The boiler feed water enters the first compartment from the top of the sprayer. Here it is heated to the boiling point and enters the deaeration zone, where the oxygen is removed from it by the steam.

So, that's all that can be said about such a device as a deaerator. What is it, we hope, you understood, since we gave a sufficiently detailed answer to this question. This is the name of the installation, which provides long-term operation of hot water and steam boilers. The choice of the variety and ways of mounting this equipment is carried out in accordance with the technical characteristics of the heating equipment and the boiler plant design.