rotating-film deaerator

1、 Overview:
The installation type of the new water film deaerator is: horizontal water tank, vertical deaerator head, and welded to each other. The new rotary film deaerator is the latest type of thermal deaerator developed by our company (patent number: ZL 2010 2 0265898.2). It has won the first New Technology, New Product, and Science and Technology Innovation Award from the Ministry of Electric Power and has been listed as a key promoted and applied product by the Ministry of Electric Power. This product is essentially different from the spray packing type and water film type deaerator. Especially after the re improvement in 2004, the product performance has become more perfect, and the qualified rate of dissolved oxygen in effluent has reached 100%. When operating under the design state, the high-pressure deaerator can be controlled below 5 μ g/L, and the low-pressure can be controlled below 10 μ g/L The heat and mass transfer method of the new rotary film deaerator is different from the existing drip tray, atomization, and rotary film methods. It combines the above three forms of heat and mass transfer methods into one. It has high heat transfer efficiency and deoxygenation ability.  

2、 Technical Status:
At present, there are three types of deaerator commonly used in the market, namely, water spray tray deaerator, spray type deaerator and spray packing type deaerator. The water spray tray deaerator has been gradually eliminated due to its easy vibration in operation and low deaerating efficiency. The spray type and spray packing type deaerator are still used by some users because of their advantages, so their disadvantages are gradually emerging in operation. Especially, the defects of both types of deaerators being unable to operate beyond their output under special circumstances and prone to vibration of the deaerator head during low water temperature operation have attracted increasing attention from the technical community.
The principle of the atomizing nozzle of the spray type deaerator is basically the same as that of the spray packing deaerator. The water supply of the spray packing deaerator is sprayed down the nozzle after film rising through the film hole, and the heating steam rising from the lower part of the deaerator intersects with it to form a heat exchange area. The atomized water that stays momentarily falls on the omega packing for heating, and finally falls to the lower water tank to complete the heat exchange process. Since the heat exchange of the spray deaerator is mainly at 300mm from the outlet at the lower end of the nozzle, the deaerated water in this section is atomized, so the deaeration efficiency of the upper section is basically close to that of the spray deaerator. The Ω ring packing layer serves as a deep deoxygenation zone for deoxygenated water. The dispersion and easy deformation characteristics of "Ω" packing often cause it to fall off from the drain hole to the water tank after running for a period of time, or deform and press tightly into blocks, affecting the flow of water and greatly reducing the output of the deaerator. These shortcomings of the spray packed deaerator enable it to meet the deoxygenation requirements issued by the national ministry at the initial stage of operation, but after the problems occur in the packing layer, the deoxygenated water is unqualified, some even exceed the standard by more than three times, and the dissolved oxygen in the outlet water of the low-pressure deaerator reaches 50 μ g/L. And it requires frequent replacement of fillers, long maintenance downtime, and high maintenance costs.  

The disadvantages of the above three types of deaerators are as follows:

1. Due to the imbalance of the exchange process, it is prone to vibration during operation.  

2. When the load changes, it cannot be adjusted according to the load, and the dissolved oxygen is not qualified.  

3. High failure rate, short maintenance cycle, and high maintenance costs.  

4. The exhaust volume is large, consumes a lot of new steam, and is not energy-saving.  

5. The nozzle is prone to detachment.  

6. The filler is prone to detachment or deformation, resulting in a small exchange area when compressed into blocks, which affects the output.  

3、 Technical characteristics of new water film deaerator

The new rotating film deaerator is a new generation product of spray type and water film type. It combines the advantages of various deaerator and carries out deep optimization design.  

The steam exhaust volume is small, which can meet the requirements of energy conservation (the steam exhaust volume data of all types of deaerator: 5% for spray tray, 3% for spray packing type, and 1% for rotary membrane type). The energy-saving economy is quite considerable.
（1） Technical performance:

The main indicators pursued and researched by various countries for thermal deaerators are water spray density (also known as heavy flow rate) and the difference in temperature and dissolved oxygen concentration. The efficiency of water film deaerator is much higher than other types of deaerators. The efficiency of various types of deaerators is summarized in Table 1-1:

Table 1-1 Efficiency Ratio of Various Deaerators

             Note: 1. * represents the measured value; **For practical value. 2. Others are compiled from literature and drawings.

（2） The advanced five stage deoxygenation principle is adopted in the mechanism of action, as follows:

1. Primary deoxygenation

The high-efficiency membrane generator is a modification of the original membrane deaerator by replacing the simple membrane tube with a feedwater preheater, with the upper layer being the water chamber and the lower layer being the steam chamber. The water in the water chamber is injected into the pipe wall through tangential membrane holes. During the high-speed downward rotation along the pipe wall, the water flow intersects and exchanges heat with the upstream steam flow in the steam chamber. This heat exchange section is the first stage of the new water film deaerator, namely the preheating section, where 80% of the heat exchange occurs.  

2. Secondary deoxygenation

The special design of circulating deoxygenated water to the outlet of the membrane tube after preheating the pipe wall uses deoxygenated water to continue membrane skirt spraying and mixing with secondary heating steam. This section is the second stage heating section, which is the deoxygenated water saturation section. At this stage, the water is approaching or reaching saturation, and oxygen and other gases dissolved in the water overflow from the boiling water. The oxygen content in this stage is usually close to 15 μ g/L.  

3. Third level deoxygenation

The lower part of the membrane opener is also designed with a water spray grate layer, through which the water is redistributed, fully mixed and exchanged with steam water, and the water flow is evenly distributed to reduce the surface tension of the water film and further remove oxygen.  

4. Fourth level deoxygenation

This form of deaerator adopts high-efficiency regular wire mesh packing, which not only has extremely high heat transfer efficiency, but also has the advantages of long service life, high temperature resistance, no deformation, and no detachment. It is made of stainless steel material. The water supply undergoes deep deoxygenation in this section, and when it falls into the water tank, the oxygen content has reached 10 μ g/L.  

5. Five level deoxygenation

The reboiler device at the bottom of the new water film deaerator can not only serve as a preheating device for the water tank during unit start-up, but also achieve uniform heating and continuous operation without vibration due to its reasonable design, playing an auxiliary role in deaeration.  

The five stage deoxygenation principle of the new water film deaerator ensures the deoxygenation efficiency during normal operation of the equipment Its characteristics are as follows:

1. The dissolved oxygen content can reach below 10 μ g/L, far below the national standard of 15 μ g/L,

2. The surplus of deoxygenation space enables the deaerator to operate significantly at overload (usually exceeding 50% of the rated output)

3. Due to its very high heat transfer efficiency, it can operate at low temperatures with full water replenishment.

4、 Technical characteristic parameters of rotary film deaerator:

  CYG series new pressure type deaerator

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