Deaerator or boiler deaeration system is a device that provides a suitable output for boiler feed by performing a series of preheating activities and removal of water-insoluble gases and carbon dioxide. Due to the effect of deaeration of water on increasing the efficiency and performance of the boiler, this device is widely used in industry and especially in refineries. “Haft” Industrial Group, as one of the teams of design and production “Deaerator”, will fully introduce this device and how this type of this deaerator works.
What is a deaerator?
Deaerator is a device and process in which insoluble gases of oxygen and carbon dioxide are removed from the water entering the boiler. Pressure vessels or hot water boilers are used in various industries such as power plants, industrial plants and food, etc. In this group of equipment, due to the deposition of water oxygen in its walls, as well as the chemical reaction they perform with carbon dioxide, it leads to corrosion of the walls and damage to the boiler. Oxygen in water reacts with carbon dioxide to eventually produce carbonic acid, which is highly corrosive to metals.
The use of a deaerator reduces the amount of insoluble oxygen in water and carbon dioxide and ultimately prevents corrosion of the boiler wall. Note that with increasing carbon dioxide in the water entering the boiler, the pH of the water is greatly reduced and eventually the environment becomes acidic and corrosion will occur over time.
The procedure of the deaerators is based on this important rule that at saturation temperature, oxygen and nitrogen gases in the water are separated from it with the least pressure and will not be able to enter the boiler when leaving the deaerator. This law is known as Harry Dalton Law.
What is the use of deaerator?
In fact, the deaerator has two very important uses in the boiler, which are:
· Deaeration of inlet water to the boiler
· Preheat the inlet water to the boiler
Dehydration and the main reason for its use were mentioned at the beginning of the text, but another very important application of the deaerator is its use in the preheating stage of water, which will have a great impact on the efficiency and performance of the boiler. Low temperature water entering the boiler causes heat shock which will cause a lot of damage to the boiler. In addition to reducing the life of the boiler, the steaming capacity of the device is greatly reduced by the entry of low temperature water into it. For this purpose, a deaerator is used to preheat the inlet water to the boiler.
What are the working steps of deaerators?
Regardless of the method of deaeration in the Deaerator, the steps to do this can be described as follows:
· Water enters the deaerator
· Deaeration with steam
· Deaeration with oxygen absorber
In short, the operation of different types of deaeration systems is such that first water enters the device and a large volume of insoluble gases and carbon dioxide are removed and transferred out of the outlet valve. In order to remove the amount of oxygen remaining in the water, oxygen absorbers are used, the most common of which include the following:
· Sodium sulfite (Na2SO3)
· Diethyl hydroxylamine (DEHA)
· Nitrilotriacetic acid (NTA)
· Ethylenediaminetetraacetic acid (EDTA)
· Hydrazine (N2H4)
Types of deaerators
According to the work procedure and method used to separate oxygen and water-insoluble gases, boiler ventilation systems can be divided into two general groups, which are:
· Tray-type deaerator
· spray-type deaerator
One of the most common types of boiler deaerator systems is tray deaerators. The general structure of this type of deaerator consists of a horizontal boiler with a ridge in the middle, which is located on top of the ridge of a kind of cap in the shape of an arched dome. Water enters from the dome of the device and is placed on trays with multiple pores and is transported down in droplets. As water enters the tray openings, the deaerator steam moves from the bottom to the top with low pressure and passes through the tray openings. In case of water collision with the deaerator steam, due to the increase of water temperature and reaching the saturation temperature, a large part of the gases in it are separated and together with the deaerator steam are transferred out of the device from the drain valve above the dome.
After this stage, water enters the horizontal source and to separate the remaining oxygen, an oxygen absorber such as sodium sulfite is used and finally the remaining oxygen reacts with it and turns into sodium sulfate. Sodium sulfate is not corrosive and will not cause problems for the boiler. Finally, water from the drain valve will be transferred to the power supply located outside the deaerator at low pressure.
A very important point in this type of deaerator is that the gas drain valve at the top of the dome should be open enough that the oxygen in the steam can easily escape from the tank. If this is not taken into account, some of the oxygen separated from the deaeration stage will enter the water.
Spray deaerator (spring nozzles)
In another type of Deaerator, the device consists of a horizontal tank that consists of several sections, each of which has specific tasks. The left side of this device is preheated to make it easier to separate the gas from the water. Water passes through spring-shaped nozzles with small holes and enters the device by spraying, and will be heated by the steam that enters this part from the bottom of the device.
After this step, water enters the second part of the device and the aerator vapor hits it from below with low pressure, and finally insoluble gases and oxygen come out of it and will be transferred out of the top valve of the device. The resulting water is transferred to the bottom tank of the machine after the addition of oxygen absorbing material and will be used for boiler use.
Advantages of using a deaerator
The main reasons and advantages that have made the use of boiler deaeration system so widespread are:
· Prevent corrosion of boiler walls and increase boiler life
· Prevent sediment on the walls of the boiler and better performance of the steam generator
· Improved boiler evaporation
· Increase blowdown in the boiler
Due to the above advantages, this deaerator can be used in refineries, food and dairy factories, hospitals, industrial agricultural sectors such as greenhouses.
Seven Industrial Group is a manufacturer of various types of deaerators and has used all the necessary standards in the design and production of this group of products with the knowledge of its engineers and technicians. In order to buy a deaerator or to receive advice and guidance before buying these products, you can use the communication channels at the bottom of the page. It should be noted that Seven Industrial Group is one of the most well-known production teams for water and wastewater treatment products