Regarding deaerators

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I. Structural features of the new type of rotary film deaerator:
Deaeration equipment mainly consists of two main components: the deaeration tower head and the deaeration water tank, along with connecting pipes and other accessories. The main component, namely the deaerator (deaeration tower head), is made up of an outer shell, a new type of rotary film device (film-forming tube), a water spraying grid, and a heat storage packing liquid-vapor network. Below, we will focus on explaining the structural principle of the deaeration tower head.

1. Outer shell: It is formed by welding a cylinder body with an elliptical head that has been stamped. Medium and low-pressure deaerators are equipped with a pair of flanges to connect the upper and lower parts, facilitating assembly and maintenance; high-pressure deaerators have manholes for maintenance purposes.

2. Rotary film device set: It consists of a water chamber, a vapor chamber, a rotary film tube, condensate water connection pipes, make-up water connection pipes, and primary steam inlet pipes. Condensate water and chemical make-up water are sprayed in a spiral pattern at a certain angle through the rotary film tube, forming a water film skirt. This water film skirt exchanges heat with the heating steam introduced through the primary steam inlet pipes, thereby achieving initial deaeration. The feed water then comes into contact with the rising secondary heating steam via the water spraying grid, getting heated to a temperature close to the saturation temperature under the deaerator’s operating pressure – usually 2–3°C below saturation temperature – thus allowing for rough deaeration. Generally, around 90–95% of the oxygen content in the feed water can be removed through this rotary film section.

3. Water spraying grid: It is composed of several layers of angular steel elements arranged in an interlaced manner. Here, the feed water that has undergone rough deaeration through the rotary film section is distributed evenly, falling like rain onto the liquid-vapor network located beneath it.

4. Heat storage packing liquid-vapor network: It consists of spaced flat steel strips and a cylindrical body filled with a special stainless steel wire mesh of a certain height. Here, the feed water comes into full contact with the secondary steam, being heated to the saturation temperature and undergoing further deaeration. In low-pressure atmospheric deaerators, the oxygen content is reduced to less than 10 ug/L, while in high-pressure deaerators it is reduced to less than 5 ug/L (the national standards are 15 ug/L for high-pressure and 7 ug/L for low-pressure deaerators).

5. Water tank: The deoxygenated feed water collects in the lower container of the deaerator, namely the water tank. The deaeration water tank is equipped with a scientifically designed high-efficiency heat exchange and reboiling device. This device enables efficient heat exchange, rapid increase in water temperature, deeper deaeration, reduction in tank vibration, and lower noise levels. All these advantages enhance the equipment’s service life and ensure its safe and reliable operation.

II. Working principle of the rotary film deaerator:
The rotary film deaerator differs fundamentally from other types of thermal deaerators such as those using spray packing or water spraying trays in terms of performance. The key difference lies in the way heat and mass are transferred between steam and water, which is determined by its spraying structure.

Condensate water and make-up water enter the water chamber of the rotary film device set inside the deaeration tower head. Under a certain pressure difference, they are sprayed diagonally from the small holes in the film tube toward the inner hole, forming a jet. Since the inner hole is filled with rising heating steam, the water, as it moves in the form of a jet, draws in a large amount of heating steam (experiments have shown that jets have a sucking effect). This results in intense mixing and heating over a short distance, causing the water temperature to rise significantly. The rotating water continues to move downward along the inner wall of the film tube, forming a swirling water film skirt (the critical Reynolds number for turbulent flow decreases significantly during rotation, resulting in turbulent motion). In this turbulent state, heat and mass transfer are most efficient, and the water temperature reaches the saturation temperature. Oxygen is thus separated from the water. Since the rotating water flows closely along the pipe walls, a gas-gas channel is formed in the middle of the film tube, eliminating dead zones for gas flow. As a result, oxygen cannot spread freely inside the inner hole, and any non-condensable gases are quickly expelled and carried away with the rising steam through the exhaust pipe into the atmosphere. (In older deaerators, although the water is heated and oxygen is separated, oxygen has a higher density than the heating steam, so some oxygen is carried back into the water tank by the flowing water, which is another reason for poor deaeration efficiency.)

The feed water that has undergone rough deaeration through the rotary film section and the drain water introduced through the drain pipes mix here and are distributed evenly, falling like rain onto the liquid-vapor network beneath it. Only after further deep deaeration does the water flow into the water tank. The oxygen content in the water tank is 5 ug/L for high-pressure deaerators and less than 10 ug/L for atmospheric deaerators – far below the national standards (7 ug/L for high-pressure and 15 ug/L for low-pressure deaerators).

Since the rotary film deaerator keeps the water in a turbulent state during operation and has a sufficiently large heat exchange surface area, it achieves excellent heat and mass transfer efficiency. This results in low exhaust steam volume (which means less energy loss and significant economic benefits). The deaeration effect is also very good, allowing the deaerator to operate at an overload capacity (usually 50% above its rated capacity) or even at lower water temperatures with full make-up water supply. III. Deaerator renovation: In addition to supplying complete sets of new rotary-diaphragm high-efficiency deaerators, Dongbang Power Equipment also undertakes the renovation of existing deaeration equipment such as spray-plate type deaerators and spray-filler type deaerators, with significant results. The advantages are as follows: 1. Low renovation costs, approximately half of those required for replacing the deaeration head. 2. Fast turnaround time – easy to process and install; deaerators with a capacity of 200 T/H or less can generally be completed within half a month. 3. Stable operation, without vibration. 4. Good adaptability – does not require strict specifications regarding water quality, temperature, or pressure. Operating temperature: 104°C; operating pressure: 0.02 Mpa gauge pressure; inlet water temperature: 40°C; design temperature: 250°C. This post was last edited by zg19870901 on 2009-3-30 at 18:25