Image and Description 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 each year have drawn increasing attention from the National Electricity Department. The department has issued GB1576-2001 "Industrial Boiler Water Quality Standard" and "Technical Supervision Regulation for Safety of Power Station Pressure-type Deaerators," setting departmental standards for the oxygen content of deaerators, i.e., the oxygen content in the feed water of low-pressure deaerators should be less than 15 μg/L, and that of high-pressure deaerators should be less than 7 μg/L.

The spiral membrane oxygen removal unit differs from the existing spray and spray plate types in its heat transfer, mass transfer methods, and oxygen removal capacity. It is a new type of thermal oxygen removal unit, which has won the Science and Technology Innovation Award for New Technology and New Products from the Power Ministry and is listed as a key promotion product by the Power Ministry.

II. Advantages

High deoxygenation capability, with a high qualified rate of water oxygen content 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: Excellent adaptability; not stringent requirements for water quality and temperature; can operate at 150% capacity for short periods.

4: Steam exhaust 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 thermal deaerators with the same output.

Section 3: Structure and Principle

The structure of the rotary membrane oxygen remover consists of the oxygen removal head and the water tank. The oxygen removal head is composed of six main parts: the outer shell, the rotary membrane assembly, the water grate, the liquid-gas mesh, the steam distribution plate, and the steam-water separator. The water tank is made up of the main body and accessories.

1. Shell: Welded from the cylinder body and stamped elliptical end caps.

2. Membrane Unit: Composed of water chamber, membrane tube, condensate outlet pipe, and make-up water inlet pipe. 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, where 98% of the oxygen is removed.

3. Drip Grating: The water for deoxygenation in the membrane formation section and the condensate introduced from the drain pipes are reduced in flow and redistributed here, forming a uniform drizzle-like descent to protect the lower liquid-vapor network. The space area of the grating is not less than 50% of the total cross-section, constructed of stainless steel, and operates year-round without the need for maintenance.

4. Filling Liquid-Vapor Network: Composed of spaced flat steel strips and a cylindrical body, it houses two layers of specially designed 0.3mm O-shaped stainless steel flat wire mesh. Here, the water is fully contacted with the secondary steam, heated to saturation temperature, and undergoes deep deoxygenation to ensure the oxygen content in the deoxygenated water.

5. Steam Distribution Plate: The main heating steam is introduced here, and the uniform distribution structure ensures excellent heating quality, maintaining an even distribution of the heating steam. It rises to heat softened water under non-restrictive conditions, working at saturation temperature for deoxygenation.

6. Air-Water Separator: Composed of stainless steel packing, the internal network is designed with a ventilation structure, effectively separating and recycling water from the exhaust gas, an indispensable component to ensure exhaust gas is water-free.

7. Water Tank: Welded from a cylindrical body and a stamped elliptical end cap, the tank internally features reinforcing rings. The base is mounted on a prefabricated worktable, with one end fixed and the other for installing the expansion roller assembly. The tank is equipped with a manhole for maintenance, a safety valve connection, drain outlet, boil-over pipe opening, water seal cylinder opening, level gauge interface, pressure gauge port, thermometer port, and water intake.

The basic principle of deaerator thermal deaeration: In a 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 feed water, raising the water temperature and gradually increasing the partial pressure of steam above the water surface while decreasing the partial pressure of dissolved gases. As a result, the dissolved gases continuously escape. When the water is heated to its boiling point 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. The effectiveness of deaeration depends on whether the feed water is heated to the boiling temperature at the corresponding pressure and on the rate of dissolved gas expulsion, which is greatly related to the size of the contact surface area between water and steam.

Principle of operation for the spiral membrane oxygen removal unit (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 separator in the deaerator, where, under a certain pressure difference, they are sprayed diagonally into the inner cavity through small holes in the membrane tubes, forming a jet. Due to the presence of rising heated steam in the inner cavity, the water in the jet draws in a large amount of heated steam (experiments have proven the jet's entrainment effect); this results in a rapid and intense mixing and heating process over a very short distance, significantly increasing the water temperature. As the rotating water continues to spiral down the inner wall of the membrane tubes, it forms a swirling water film skirt (the critical Reynolds number of the water in the rotating flow decreases significantly, causing turbulent swirling). At this point, the turbulent state of the water has ideal heat and mass transfer effects, reaching the saturation temperature. Oxygen is then separated, as it cannot freely diffuse within the inner cavity and is instead carried up with the steam through the exhaust pipe and released into the atmosphere. The feed water from the deaerator's membrane section and the condensate introduced from the drain pipes are mixed here for a secondary distribution, falling in a uniform drizzle-like pattern onto the liquid-vapor grid below. After deep deaeration, the water is then flowed into the water tank. The oxygen content in the water within the tank is 0-7 цɡ/L at high pressure and less than 15 цɡ/L at low pressure, meeting the departmental operational standards.

Due to the vortex membrane deaerator keeping the water in a turbulent state during operation and having a sufficiently large heat exchange surface area, the better the heat transfer and mass transfer effect, the smaller the exhaust gas volume (meaning less steam used for heating, resulting in lower energy loss and significant economic benefits). The effective deoxygenation produces a surplus that allows the deaerator to operate at overload (typically up to 50% over the rated output for a short period) or achieve operating standards under low water temperatures with full make-up.

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 the "Safety Supervision Regulations for Deaerators in Power Stations."

2. The deaerator should be placed above the feed pump, and the height difference between the low water level of the deaerator tank and the centerline of the feed pump should be no 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 by 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 the steam flow size based on the temperature of the deaerated water. After补水 stops, the electric actuator automatically closes.

4. The bottom 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 start-up. 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 and is loaded. Additionally, a prevent-rotation plate is installed at the outlet tank mouth 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 a prevent-rotation plate, the water level in the tank must be maintained at three times the pipe diameter. With a prevent-rotation plate, it can be reduced to below 1.5 times.

5. After the deaerator and water tank are field-welded, they should undergo hydrostatic testing. The pressure parameters for the hydrostatic test are: 0.2 Mpa for atmospheric deaerators and 0.75 Mpa for pressure deaerators. The condensate from steam is first accumulated in an intermediate storage tank before being evenly fed into the deaerator to ensure stable deaerator load.

6. Protection and Alarm of the Rotating Membrane Oxygen Remover

(1) The water tank and deaerator are equipped with an adequate number of full-open safety valves, with the quantity and specifications of the safety valves meeting the design technical specifications.

(2) Oxygen Remover should be equipped with both local and remote water level gauges, and include high and low water level alarms, as well as safety high and low water level operation devices. The oxygen remover's water level change control: when the water level drops, the softening pump (condensate pump) is automatically started to replenish the oxygen remover; 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, send 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 the deaerator operating pressure (i.e., 102-104°C).

8. Adjust the water level regulation system to maintain the water level in the water tank within ±100mm of the normal level. (When both deaerators need to run in parallel, in order to balance the pressure and water level inside the deaerators, each deaerator water tank must have a balanced pipe for connecting steam and water. Aim to make the pressure, water temperature, and water level as consistent as possible.) When the water level reaches ±200mm of the normal level, the high-level drain valve (electric gate valve) should open freely to drain water, and it should automatically close when the water level drops. During operation, it is essential to frequently check the responsiveness of the electric water level regulation system and the responsiveness of the makeup water regulating valve.

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

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

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

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

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

15. Cautionary Notes

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

b. During operation, attention should be paid to ensure that the pressure within the deaerator does not drop sharply, and a vacuum should be avoided at all costs.

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 are required to prevent nozzle clogging, packing corrosion or compaction, and instrument failure.

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

Five. Oxygen Scavenger 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 protection.

· 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 on the heating steam pipeline, it adjusts the flow of heating steam with the help of an automatic regulator to maintain the pressure inside the deaerator within the rated range.

· Water-seal pipe - When the liquid level rises, the pressure difference exceeds the pressure of the water column, causing the balance to be disrupted, and the liquid flows 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 topping-up pipe, it adjusts the flow of supply water with the help of an electric water level regulation system to maintain the normal water level of the tank.

·Adjustable Valve --- Installed on the topping-up pipe, it regulates the flow of topping-up water using an electric water level control system to maintain the normal water level of the tank.

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

· Magnetic Flip Level Gauge --- Installed on the water tank, it monitors 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 Container - Used in conjunction with pressure/differential pressure transmitters and level gauges, it can reflect the deaerator's (weight) water level during the boiler startup, shutdown process, and normal operation.

Electric gate valve —— Installed on the drain pipeline of the water tank, when the water level in the tank exceeds a certain limit, the electric gate valve automatically opens with the help of an electric water level regulating system, draining the excess water above the limit into the overflow tank.

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

· Electric Water Level Regulation System --- Automatically adjusts the flow of supply water and controls the overflow valve (electric gate valve) at the maximum water level.

Section 6: Order Provision Data

1: Oxygen Scavenger Output (T/H) and Effective Tank Volume (m³) equipped.

2: Oxygen remover operating pressure, temperature...

3: Only replace the deaerator tower and provide the installation connection drawing for the original deaerator tower.

Section 7: Renovation

Our factory not only provides complete sets of new-type water film deaerators, but also undertakes the renovation of deaerators with spray tray and spray packing for power plants. Specifically, this includes:

1. Retrofitting costs are low, 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 plate, then install a liquid-gas mesh and a water grate at a certain position above the lower steam inlet plate, and finally seal and secure it with a circular pressure plate to prevent water-vapor short-circuit during future operation.

3. After separating the interface between the head and the cylinder, weld and install them into the film former. Connect the other components of the pipeline opening according to the provided modification scheme diagram. The project is then complete. Upon passing the inspection, it can be put into operation.

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