Product Details with Images and Text 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 garnered increasing attention from the National Electric Power Department. The department has issued the GB1576-2001 "Water Quality Standards for Industrial Boilers" and the "Safety Supervision Regulations for Pressure Deaerators in Power Plants," which set departmental standards for oxygen content in deaerators. Specifically, the oxygen content in the feed water of low-pressure deaerators should be less than 15 μg/L, and for high-pressure deaerators, it should be less than 7 μg/L.

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

II. Advantages

High deoxygenation capacity; high qualified rate of water oxygen content after deoxygenation.

2: Operation is stable with no vibration. Suitable for vacuum start-up and sliding pressure operation, it reduces the complex manual adjustments during start-up and operation.

Good adaptability, not stringent requirements for water quality and temperature, can operate at 150% capacity for short periods.

4: Steam discharge volume less than 0.1% of the inlet water volume; no additional exhaust cooler required. Optimizes the equipment, reduces heat consumption, and consumes 1/3 less energy than other types of deaerators with the same output.

Section 3: Structure and Principle

The structure of the rotary membrane oxygen removal unit 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 Assembly: Comprising a water chamber, film-forming tube, condensate inlet, and make-up water inlet. Both the film-forming tube and the drain pipe are made of stainless steel, ensuring year-round operation without maintenance. It is also a major component of the rotating film deaerator, from which 98% of the oxygen is removed.

3. Water Spray Grating: The feed water after oxygen removal in the membrane-forming section and the condensate introduced through the drain pipes are reduced in flow and redistributed here, allowing water to fall evenly in a sprinkling pattern, thereby protecting the lower liquid-vapor grid. The space area of the water grating is not less than 50% of the total cross-section, made of stainless steel, and requires no maintenance throughout the year.

4. Filling Liquid-Vapor Mesh: Composed of spaced flat steel bands and a cylindrical body, it contains two layers of specially designed 0.3mm O-type stainless steel flat wire mesh. Here, the water is fully contacted with the secondary steam, heated to saturation temperature, and deeply deoxygenated to ensure the oxygen content of the deoxygenated water.

5. Steam Distribution Plate: The main heating steam is introduced here, the regular equal division structure ensures excellent heating quality, maintaining an equal distribution of the heating steam. It rises to heat the softened water without throttling, working at saturated temperature for deaeration.

6. Air-Water Separator: Composed of stainless steel packing, the internal mesh is designed with a ventilation structure. It effectively separates and returns water from the air during exhaust, and is an indispensable component to ensure exhaust without water.

7. Water Tank: Consists of a cylinder body and a welded elliptical end cover, internally equipped with reinforcing rings. The base is fixed on a prefabricated workbench, with one end fixed and the other for installing the expansion roller assembly. The tank is equipped with manholes for maintenance, safety valve connection ports, drain outlets, reboiler pipe openings, water seal cylinder openings, level gauge interfaces, pressure gauge ports, temperature gauge ports, and water intake ports.

Deaerator Thermal Deaeration Basic Principle: 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 feedwater, increasing the water temperature. This causes the partial pressure of steam above the water surface to gradually increase while the partial pressure of dissolved gases decreases. As a result, dissolved gases continuously escape from the water. 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. This means the water no longer has the ability to dissolve gases, including oxygen, and 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 expulsion, which is greatly related to the contact surface area between water and steam.

Principle of operation for the rotating film 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 inner cavity being filled with rising heated steam, the water in the jet draws in a large amount of heated steam (experiments prove that the jet has an entrainment effect); a剧烈的mixing and heating occurs over a very short distance, resulting in a significant increase in water temperature. As the rotating water continues to spiral down along the inner wall of the membrane tube, it forms a swirling water film skirt (the critical Reynolds number of water in rotational flow decreases significantly, causing turbulent rolling). At this point, the turbulent state of the water achieves an ideal heat and mass transfer effect, reaching the saturation temperature. Oxygen is then separated out, as it cannot diffuse freely within the inner cavity and must rise with the steam, exiting through the exhaust pipe to the atmosphere. The feed water after coarse deaeration in the demister section and the condensate introduced from the drain pipes are mixed here for a secondary distribution, falling uniformly like rain onto the liquid-vapor net below. After deep deaeration, it then flows into the water tank. The oxygen content in the water in the tank is less than 7 μg/L at high pressure and less than 15 μg/L at low pressure, meeting the departmental operational standards.

Due to the vortex membrane oxygen remover keeping the water in a turbulent state during operation and having a sufficiently large heat exchange surface area, the better the heat and mass transfer effects, the smaller the exhaust gas volume (meaning less steam used for heating, leading to reduced energy loss and significant economic benefits). The excellent deoxygenation effect allows the oxygen remover to operate beyond its load capacity (usually up to 50% over its rated output for a short period) or meet operating standards under low water temperature and full water replenishment.

4. Installation, Operation, and Maintenance

1. The installation, operation, and maintenance of deaerators, water tanks, and accessories should be conducted according to the CYD (G) type deaerator system diagram and the "Technical Supervision Regulations for 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 incoming water pipe, and a water level transmitter on the deaerator. Detect signals such as incoming water temperature, flow rate, and deaerator water level, and input these signals to the calculation and processing module. This controls the hydraulic and thermal conditions of the deaerator's incoming water and heating steam to achieve the desired deaeration effect, ensuring the deaeration temperature is maintained at (104±1.5℃). Adjust the electric actuator regulating valve installed on the steam pipeline to regulate the steam flow based on the temperature of the deaeration water. After water topping up is stopped, 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 of the water within the tank. The unit should stop using it after startup 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 the anti-rotation plate, the water level must be maintained at three times the pipe diameter, while with the plate, it can be reduced to below 1.5 times.

5. After the deaerator and water tank are现场welded, a hydrostatic test must be conducted. The pressure parameters for the 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 supplied to the deaerator, ensuring 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, the quantity and specifications of which should meet the design technical specifications.

(2) Oxygen Scavenger should be equipped with local and remote water level gauges, along with high and low water level alarms and high and low water level action devices. Water level control of the oxygen scavenger: when the water level decreases, the softening 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, send the demineralized water into the deaerator head, while adjusting and increasing the steam inlet valve to heat the feed water in the film-forming section to a temperature close to the steam saturation temperature of the deaerator's operating pressure (i.e., 102-104℃).

8. Adjust the water level regulation 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 inside the deaerators, each deaerator tank must have a balance 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 water level drain valve (electromagnetic gate valve) should open freely to drain water, and it should automatically close when the water level decreases. During operation, regularly check the responsiveness of the electromagnetic water level regulation system and the responsiveness of the make-up water 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 about 2/3 open, so that the exhaust flow is around 2-3kg per ton of deoxygenated water.

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

12. When operating the deaerator, if you find a phenomenon of steam discharge with water, you may take the following methods to handle it:

Adjust the heating steam inlet valve

b. Inspect pressure adjustment device

c. Manual pressure reduction operation

d. Gradually close the secondary heating steam cut-off valve.

13. Test the oxygen content of the water in the sampling tank to ensure it meets the standard. If it does not, 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 on various monitoring instruments, to ensure the normal operation of the deaerator.

15. Cautionary Notes

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

b. During operation, it is crucial to ensure that the pressure within the deaerator does not drop sharply, and a vacuum should absolutely be avoided.

c. In case of a short-term shutdown, prevent the deaerator from creating a vacuum or filling with air. Gently open the bypass steam valve to introduce a small amount of steam, maintaining the heater head in a heated state, and releasing 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 failure.

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

Five. Oxygen Remover Standard Accessories

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

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

Thermometer — installed below the water tank, monitoring the water temperature inside the tank.

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

· 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.

· Check valve—Installed on the water补给管，it adjusts the water supply flow using the electric water level regulation system to maintain the normal water level of the tank.

·Regulating Valve --- Installed on the water补给管，it adjusts the water flow for replenishment using an electric water level control system to maintain the normal water level in the tank.

Electrical contact liquid level monitoring—consists of a sampling tube (primary instrument) and a high-purity ceramic electrode with a display (secondary instrument). Installed on the 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 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 Vessel - Used in conjunction with pressure/differential pressure transmitters and level gauges, it can reflect the water level (quality/weight) of the deaerator during boiler startup, shutdown, and normal operation.

· Electric gate valve --- Installed on the water outlet pipe 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 the electric water level regulation system, discharging the excess water above the limit into the drain 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 water supply flow and controls the limit water level discharge valve (electric gate valve).

Section 6: Order Data Provided

1: Oxygenator output (T/H) and effective volume of the water tank (m3).

2: Oxygen separator operating pressure, temperature...

3: Only replace the oxygen-depletion tower and provide the installation connection diagram for the original oxygen-depletion tower.

Section 7: Renovation

Our factory supplies complete sets of new water film deaerators and also undertakes renovations for the deaeration systems of power plants involving spray plate and spray packing deaerators. Specifically, this includes:

1. Modification costs are low, approximately half the price of replacing the deaerator head.

2. Fast progress, easy to process and on-site modification installation. Utilize the original deaerator head's shell end, remove all the spray disk or spray packing components inside the original deaerator head, 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. Finally, use the annular pressure plate for sealing and fixation to prevent water-vapor short-circuiting during future operation.

3. After separating the connection between the head and the cylinder, weld and install them into the film former. Connect the other pipeline components according to the provided modification plan, and the job is complete. Upon passing the inspection, the equipment can be put into operation.

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