Heating boilers are most often made of steel. The water passing through them has oxygen and carbon dioxide in its composition. Both of these elements have an extremely negative effect on the metal structures of the boiler. The constant contact of steel with these gases inevitably leads to its rusting. In order to rectify the situation and extend the life of the equipment, a special installation, a deaerator, is included in the boiler house thermal circuit . What it is? We will talk about this later in the article.
Definition
Deaerator is a special equipment designed to remove oxygen from a heating medium 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 purify both feed and make-up water.
Design features
The relative simplicity of the design is what distinguishes the deaerator. What is it, we have found out. Now let's see how this equipment works. It is a boiler tank deaerator (BDA) with a vertical column mounted on it (KDA), mounted on supports. An additional element of this type of equipment is a hydraulic system that protects it from excess pressure. The column is welded to the tank without a flange - directly.
On the horizontal tank of the deaerator mounted inlet and outlet pipes for connecting the supply and exhaust lines. Bottom installed plums. Another design element is a collection tank for collecting 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 locks. One of them protects the device from any excess of permissible pressure, and the second from dangerous. Also, an expansion tank is included in the design of the hydraulic system of the deaerator. Vapor from the deaerator enters a special cooler, which has the form of a horizontal cylinder.
Column design
The column is a cylindrical shell with an elliptical bottom. Like the tank, it has nozzles 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 contact area of the medium and steam, and therefore, produce heating at maximum speed.
Types of equipment
In modern boiler rooms, a water deaerator can be installed:
In the first type of deaerators, gas is removed from the water in a vacuum. The design of such installations additionally includes a steam or water jet ejector. The latter kind of nodes is most often used in systems with boilers of medium or low power. Instead of ejectors, special pumps can be used to create a vacuum. A certain drawback of such equipment as a vacuum deaerator is that the steam must be removed from it by force, while it leaves the atmosphere by natural means - under pressure.
In addition to the two considered types of deaerators, 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 boiler house thermal circuit.
Scope of use
Where can a deaerator be used? What is it, you now know. Since such a device is intended for the degassing of the working environment, it is mainly used where there is heating equipment made of steel.
Most often, deaerators are used in heating and domestic hot water. Boiler houses with boilers are usually equipped with vacuum-type installations. Also, atmospheric deaerators can be used in such schemes. Low and high pressure units are used to a large extent in systems that operate 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. High pressure units are used in thermal circuits with boilers that supply a large amount of steam.
Poppet deaerator: principle of operation
The gas purification scheme in deaerators is implemented in two stages: jet (in the column) and bubble (in the tank). In addition, a flooded bubbler device is included in the system. Water is supplied to the column, where it is treated with steam. Then it flows into the tank, kept in it and 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 bubbler plate, steam heats the water to saturation temperature.
By jet method, all gases are removed from the water. At the same time, steam condensation occurs. Its residues are mixed with the gas released from the medium and discharged to a cooler. The condensate from the vapor is drained into a drainage tank. During the settling of water in the tank, residual small gas bubbles come out of it. Water is discharged into a collection tank. Sometimes a horizontal tank is used only for sedimentation. In such installations, both stages of degassing are placed in the column.
Make-up water deaeration
The coolant in the heating system circulates continuously. 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, water enters the heater, and then passes through the chemical cleaning filters. Further, like nutrient, it enters the deaerator column. Water freed from oxygen flows to the make-up pump. The latter directs it to the intake manifold or to the storage tank.
Chemical deaeration
Thus, the answer to the question of what a boiler deaerator is is simple. This equipment is 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 in the boiler water, various reagents designed to bind oxygen can be added. It can be, for example, sodium sulfite. In this case, high-quality deaeration of water requires its heating. Otherwise, chemical reactions will occur too slowly. Also, various kinds of catalysts can be used to accelerate the process of oxygen binding. Sometimes water is also deaerated by passing ordinary metal chips through a layer. 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 the exact observance of all the required technologies. When installing such equipment, they are guided primarily by the drawings and the design of the boiler room attached to it by the manufacturer. Before starting the installation, the installation is inspected and re-mothballed. Detected defects are eliminated. Actually, the installation procedure itself includes the following steps:
the tank is mounted on the foundation;
a spillway neck is welded to it;
the bottom of the column is trimmed to the outer diameter;
the column is mounted on the tank (while the plates fixed inside it must be placed strictly horizontally);
the column is welded to the tank;
a vapor cooler and a water seal are mounted;
in accordance with the drawings, the lines are connected;
shut-off and control valves are installed;
hydraulic testing of equipment
Spraying units
The constructions 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 of large capacity. The absence of a column is what distinguishes such a deaerator. Its principle of operation is also slightly different. Steam in such installations comes from below - from a horizontal comb located in the tank. The tank itself is divided into a heating and deaeration zone. Boiler feed water 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. We hope that you understand what this is, since we gave a fairly detailed answer to this question. This is the name of the installation, providing long-term operation of hot water and steam boilers. The selection of the variety 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 room.