Image and Text Details Product details

I. Overview

The deaerator is one of the key equipment in boilers and heating systems. The severe losses caused by oxygen corrosion to the boiler feed water pipes, economizers, and other auxiliary equipment annually have drawn increasing attention from the National Electric Power Department. The Department has issued the GB1576-2001 "Water Quality Standard for Industrial Boilers" and the "Safety Supervision Regulations for Pressure Deaerators in Power Stations," which set departmental standards for the oxygen content of deaerators, namely, the oxygen content of feed water for low-pressure deaerators should be less than 15 μg/L, and for high-pressure deaerators, less than 7 μg/L.

The rotating film deaerator differs from the existing spray and spray plate deaerators in its heat and mass transfer methods, as well as deaeration capacity. It is a new type of thermal deaerator, having won the Ministry of Power's New Technology and New Product Science and Technology Innovation Award and been listed as a key promotion product by the Ministry of Power.

II. Advantages

High deoxygenation capability, with a high rate of qualified oxygen content in the water after deoxygenation.

2: Stable operation with no vibration. Suitable for vacuum start-up and sliding pressure operation, reducing the need for complex manual adjustments during start-up and operation.

3: High adaptability, not stringent requirements for water quality and temperature; can operate at 150% capacity for short periods.

4: Steam volume less than 0.1% of the inlet water volume; no additional exhaust cooler required. Optimized equipment, reduced heat consumption, and consumes one-third less energy than other types of heat exchangers with the same output.

Section 3: Structure and Principle

The structure of the rotary membrane deaerator consists of the deaerator head and the water tank. The deaerator head is composed of the outer shell, rotary membrane assembly, water grating, liquid-gas mesh, steam distribution plate, and steam-water separator, which are the six main parts. The water tank is made up of the main body and accessories.

The shell is made by welding the cylindrical body and the pressed elliptical end caps.

2. Membrane Assembly: Composed of the water chamber, membrane tube, condensate water inlet, and make-up water inlet. Both the membrane tube and the drain pipe are made of stainless steel, requiring no maintenance throughout the year. It is also a major component of the rotating membrane deaerator, from which 98% of the oxygen is removed.

3. Drip Grating: The water for the oxygen-removing membrane section and the condensate introduced from the drain pipes are here reduced in flow and redistributed, creating a uniform drizzle-like descent to protect the lower liquid-vapor grid. The grating's open area is not less than 50% of the total cross-section. Made of stainless steel, it operates year-round without maintenance.

4. Filling Liquid-Vapor Network: Consists of alternating flat steel strips and a cylindrical body, internally fitted with two layers of specially designed 0.3mm thick stainless steel O-shaped wire mesh. Here, water comes into full contact with secondary steam, heating to saturation temperature and undergoing deep deoxygenation to ensure the oxygen content in the deoxygenated water.

5. Steam Distribution Plate: The main heating steam is connected here, and the uniform distribution structure ensures excellent heating quality, making the heating steam uniformly distributed. It rises to heat the softened water under no throttling condition, working to achieve saturation temperature for deoxygenation.

6. Air-Water Separator: Composed of stainless steel packing, the inner mesh is designed with a ventilation structure, which effectively separates and recirculates water from the exhaust air, making it an indispensable component for ensuring steam exhaust without water.

7. Water Tank: Welded from a cylindrical body and a stamped elliptical end cap, internally equipped with reinforcing rings. The base is mounted on a prefabricated workbench, with one end fixed and the other for installing the expansion roller assembly. The tank is equipped with inspection manholes, safety valve connection ports, drain outlets, boil-over pipe openings, water seal tube openings, level gauge interfaces, pressure gauge ports, temperature gauge ports, and water intake ports.

The basic principle of deaerator thermal deaeration: In the container, the amount of gas dissolved in water is proportional to the partial pressure of the gas above the water surface. The main method of thermal deaeration is to use steam to heat the feedwater, raising its temperature, which gradually increases the partial pressure of steam above the water surface while decreasing the partial pressure of dissolved gases. This causes the dissolved gases to continuously escape. When the water is heated to the boiling temperature at the corresponding pressure, the surface is entirely steam, with the partial pressure of dissolved gases at zero, meaning the water no longer has the ability to dissolve gases, including oxygen, thus they can be removed. The effectiveness of deaeration depends on whether the feedwater is heated to the boiling temperature at the corresponding pressure and on the rate of dissolved gas exclusion, which is greatly related to the contact surface area between water and steam.

Principle of the Rotating Disc Oxygen Remover (jet, entrainment, turbulence, heat transfer, mass transfer, water film skirt, rain-like, saturated)

Condensate and make-up water first enter the water chamber of the internal spiral membrane unit in the deaerator, and under a certain pressure difference, they are obliquely jetted into the inner cavity from the small holes of the membrane tubes, forming a jet. Due to the inner cavity being filled with rising heated steam, the water in the jet motion draws in a large amount of heated steam (tests have proven that jet motion has an entrainment effect); a violent mixing and heating effect is produced over a very short distance and small travel, causing the water temperature to rise significantly. The rotating water continues to spiral down along the inner wall of the membrane tube, forming a swirling water film skirt (the critical Reynolds number of water in rotational flow decreases significantly, causing turbulent swirling). At this point, the turbulent state of the water has an ideal heat transfer and mass transfer effect, and the water temperature reaches the saturation temperature. Oxygen is then separated out, as it cannot diffuse freely within the inner cavity and must rise with the steam through the exhaust pipe to the atmosphere. The feed water from the coarse deaeration section and the condensate introduced through the drain pipes are mixed here for a secondary distribution, falling in a uniform rain-like pattern onto the liquid-vapor mesh below, and then undergo deep deaeration before flowing into the storage tank. The oxygen content in the water within the tank is 0-7 mg/L at high pressure and less than 15 mg/L at low pressure, meeting the departmental operational standards.

Due to the vortex deaerator's continuous maintenance of water in turbulent flow and its ample heat exchange surface area, the better the heat transfer and mass transfer effect, the smaller the steam exhaust volume (meaning less steam used for heating, resulting in minimal energy loss and considerable economic benefits). The excellent deoxygenation effect generates surplus capacity that allows the deaerator to operate at an overload (usually up to 50% over the rated output for a short period) or achieve operating standards under full补水 with low water temperatures.

4. Installation, Operation, and Maintenance

1. Installation, operation, and maintenance of deaerators, water tanks, and accessories should be conducted according to the CYD(G) type deaerator system diagram and <<Technical Supervision Regulations for the Safety of Power Plant Deaerators>>.

2. The deaerator should be placed above the feed pump, with the height difference between the low water level of the deaerator tank and the centerline of the feed pump not less than 6 to 7 meters. The bottom plate of the tank support should be in firm contact with the concrete.

3. Install temperature transmitters and flow sensors on the deaerator's inlet water pipe, a water level transmitter on the deaerator, to monitor signals such as incoming water temperature, flow rate, and deaerator water level. These signals are then input to the calculation and processing module to control the hydraulic and thermal conditions of the deaerator's water intake and heating steam, ensuring the deaeration effect is achieved. This includes maintaining the deaeration temperature at (104±1.5℃). Adjust the electric actuator regulating valve installed on the steam pipe to control the steam flow, which automatically adjusts based on the temperature of the deaerated water. After topping up is complete, the electric actuator automatically closes.

4. The lower part of the water tank is equipped with a reboiling tube, which is used for heating and deoxygenation during the boiler's water filling and unit startup. When the water level in the tank exceeds half, slowly open the reboiling heating tube valve at the bottom of the tank to heat the water inside, maintaining a boiling state. The unit should stop using it once it starts up with load. Additionally, a anti-rotation plate is installed at the outlet tank opening to prevent water whirl at low water levels, thereby increasing the effective volume of the tank. Tests have proven that water whirl has a significant impact on pump cavitation. Without an anti-rotation plate, the water level must be maintained at three times the pipe diameter. With the plate, it can be reduced to below 1.5 times.

5. After the oxygen-removing reactor and water tank are现场welded, a hydrostatic test should be conducted. The pressure parameters for the hydrostatic test are: 0.2 Mpa for atmospheric oxygen-removing reactors and 0.75 Mpa for pressure oxygen-removing reactors. The condensate steam is first accumulated in an intermediate storage tank before being sent to the oxygen-removing reactor, ensuring a uniform distribution to maintain stable reactor load.

6. Protection and Alarm of the Rotating Membrane Oxygen Remover

(1) Sufficient full-open safety valves are installed on the water tank and deaerator, with the number and specifications meeting the design technical specifications.

(2) The oxygen-scavenging membrane should be equipped with both local and remote water level gauges, along with high and low water level alarms and high and low water level action devices. The water level control of the oxygen-scavenger: when the water level decreases, the软化water pump (condensate pump) automatically starts to replenish the oxygen-scavenger; when the water level rises, the pump automatically stops.

7. For the cold start of the deaerator, it is recommended to preheat the shell with auxiliary steam for 10-15 minutes. Under a certain steam pressure, feed the demineralized water into the deaerator head while adjusting and increasing the steam inlet valve to heat the feedwater in the film-forming section to a temperature close to the steam saturation temperature for deaerator operation (i.e., 102-104°C).

8. Adjust the water level control system to maintain the water level in the tank within ±100mm of the normal level. (When two deaerators need to run in parallel, to balance the pressure and water level within the deaerators, each deaerator tank must have a connecting pipe for steam and water to achieve balance. Aim for consistency in pressure, water temperature, and water level as much as possible.) When the water level reaches ±200mm of the normal level, the high water level drain valve (electromagnetic gate valve) should open freely to drain water, and should automatically close when the water level decreases. During operation, it is essential to frequently check the responsiveness of the electric water level control system and the responsiveness of the water supply regulating valve.

9. Gently open the top exhaust valve, open the valves on the steam pipe, supply steam for heating, and record the steam pressure and temperature. Adjust the exhaust valve to be generally open to 2/3, so that the exhaust flow is around 2-3kg per ton of deaerated water.

10. When the deaerator is in operation, the inlet valve should be opened first, followed by the steam inlet valve. When stopping, the sequence is reversed.

12. When operating the deaerator, if water in the exhaust steam is observed, the following methods can be employed to address the issue:

Adjust heating steam inlet valve

b. Inspect Pressure Adjustment Device

c. Manual降压operation

d. Gradually close the secondary heating steam cutoff valve.

13. Test the dissolved oxygen content of the water in the sampling tank to ensure it meets the standard. If it doesn't, adjust the water, air, and exhaust flow rates to achieve compliance. Once qualified, you can supply water to the boiler.

14. Regularly test the oxygen content of incoming and outgoing water at set intervals, record the readings of various monitoring instruments, to ensure the normal operation of the deoxygenator.

15. Important Notes

a. When the deaerator experiences severe vibration and water ejection, water hammer has occurred. Reduce the water inflow accordingly.

b. During operation, attention should be paid to ensure that the pressure inside the deaerator does not drop sharply, and a vacuum should not be formed.

c. In case of short-term shutdown, prevent the deaerator from forming a vacuum or becoming air-filled. Gently open the bypass steam valve to introduce a small amount of steam, maintaining a heated state within the deaerator head, and expel a trace of steam from the air exhaust.

d. Regular inspections of the deaerator should be conducted to prevent nozzle clogging, packing corrosion or compaction, and instrument malfunction.

e. If the deaerator is to be out of service for an extended period, the water in the tank should be drained completely to prevent corrosion of the vessel.

Five, Oxygen Remover General Accessories

·Safety Valve --- Installed on the water tank, it automatically opens to relieve pressure when the internal pressure of the equipment exceeds the allowable limit, serving as a safety protective function.

· Pressure Gauge --- Installed at the top of the deaerator, monitoring the pressure inside the equipment.

Thermometer — Located at the bottom of the water tank, monitoring the water temperature inside.

· Butterfly valve --- Installed in the heating steam pipeline, it adjusts the flow of heating steam with the aid of an automatic regulator to maintain the pressure inside the deaerator within the rated range.

· Water Seal Tube --- When the liquid level rises, the pressure difference exceeds the water column pressure, causing the balance to be disrupted, and the liquid to flow out through the water seal. It also serves as a pressure relief function when the operating equipment's air pressure exceeds the safe limit.

· Stop Valve - Installed on the water supply pipe, it adjusts the water supply flow with the help of an electric water level control system to maintain the normal water level in the tank.

·Adjustable valve---mounted on the water replenishment pipe, it adjusts the flow rate of water replenishment with the help of an electric water level control system to maintain the normal water level of the water tank.

Electrical contact liquid level monitoring is composed of a sampling tube (primary instrument) and a super-pure ceramic electrode and display unit (secondary instrument). Installed on a water tank, it monitors the water level inside and outputs a 4-20mA signal to the control room to regulate the water level valve.

· Magnetic Flip Level Gauges — Installed on water tanks, they monitor the water level in situ and can also be connected remotely to output a 4-20mA signal to the control room for adjusting the water level valve.

·Balanced Tank - Used in conjunction with pressure/differential pressure transmitters and level gauges, it can reflect the quality (weight) level of the deaerator during boiler start-up, shutdown, and normal operation.

·Electric gate valve—mounted on the water drain pipeline of the water tank, automatically opens with the electric water level control system when the water level in the tank exceeds a certain limit, and discharges the excess water to the overflow tank.

Pressure Automatic Regulator - Automatically adjusts the opening of the steam inlet valve, regulating the steam flow while maintaining stable pressure within the deaerator.

· Electric Water Level Regulation System - Automatically adjusts the supply water flow and controls the limit water level drain valve (electric gate valve).

Section 6: Order Provision Data

1: Oxygen remover output (T/H) and equipped water tank effective volume (m³).

2: Oxygen separator operating pressure, temperature...

3: Only provide the installation connection diagram for the original deaerator tower, replacing the deaerator tower.

Section 7: Renovation

Our factory not only supplies the complete set of new water film deaerator but also undertakes the renovation of deaerators for power plants, including those with sprinkling tray and spray packing designs. Specifically:

1. Low modification costs, approximately half the price of replacing the deaerator head.

2. Fast progress, easy to process and on-site modification installation. Specifically, utilize the head part of the original deaerator's shell, remove all the spray tray or spray packing components inside the original deaerator, retain the lower steam inlet dish, and then install a liquid-gas mesh and a water grate at a certain position above the lower steam inlet dish. Finally, use a circular pressure plate for sealing and fixing to prevent water and steam short-circuiting during future operation.

3. After separating and welding the joint between the head and cylinder into the film former, connect the remaining pipeline components according to the provided modification scheme diagram. The job is then complete. Upon passing inspection, the equipment can be put into operation.

4. During the modification process, the diameter of the deaerator head is generally not increased; instead, its height is appropriately adjusted based on the specific circumstances, usually only raised or installed and welded at the original height.