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 annually have drawn increasing attention from the National 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. 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 heat transfer, mass transfer methods, and deoxygenation capacity of the spiral membrane deoxygenator differ from those of the existing spray and spray plate deoxygenators. It is a new type of thermal deoxygenator, which has won the Science and Technology Innovation Award for New Technology and New Products from the Ministry of Power and has been listed as a key promotion product by the Ministry.

II. Advantages

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

2: Stable operation with no vibration. Suitable for vacuum start 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 discharge volume less than 0.1% of the incoming water volume; no additional exhaust cooler required. The equipment is optimized, reducing the heat consumption by 1/3 compared to other types of heat exchangers 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 its accessories.

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

2. Membrane Assembly: Comprising a water chamber, membrane tube, condensate return pipe, and make-up water pipe. Both the membrane tube and the drain pipe are made of stainless steel, requiring no maintenance throughout the year. It is a major component of the rotary membrane deaerator, with 98% of the oxygen removed here.

3. Drip Grating: The water supplied after deoxygenation in the film formation section and the condensed water introduced through the drain pipe are reduced in flow and redistributed here, creating a uniform rainfall-like descent to protect the lower liquid-vapor network. The grating's open area is not less than 50% of the total cross-sectional area, constructed with stainless steel, and operates year-round without the need for maintenance.

4. Filling Liquid-Gas Network: Composed of spaced flat steel strips and a cylindrical body, it houses two layers of specially designed 0.3mm thick stainless steel O-shaped mesh. Here, water is fully contacted with secondary steam, heated to saturation temperature, and deeply deoxygenated 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 a state of even steam distribution. It rises to heat softened water under non-throttling conditions, working to achieve saturation temperature and perform deaeration.

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

7. Water Tank: Welded from a cylindrical body and stamped elliptical end caps, internally fitted with reinforcing rings. The base is fixed on a prefabricated workbench, with one end fixed and the other end for installing the expansion roller assembly. The tank is equipped with a manhole for maintenance, safety valve connection, drain outlet, reboiler pipe outlet, water seal cylinder opening, level gauge interface, pressure gauge port, temperature gauge port, water intake, etc.

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 feed water, raise the water temperature, and gradually increase 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, and the partial pressure of dissolved gases is zero, meaning water no longer has the ability to dissolve gases, including oxygen, which can then be removed. The effectiveness of deaeration depends on whether the feed water is heated to the boiling temperature at the corresponding pressure and on the speed of dissolved gas expulsion, which is greatly related to the contact surface area between water and steam.

Principle of operation for spiral membrane oxygen scavenger (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 assembly in the deaerator, and 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, a large amount of heated steam is drawn into the jet during its movement (experiments prove that the jet has an entrainment effect); a剧烈的 mixing and heating effect is produced over a very short distance and small travel, resulting in a significant increase in water temperature. The rotating water then continues to spiral down along the inner wall of the membrane tube, forming a swirling water film skirt (the critical Reynolds number of the water decreases significantly during rotation, causing turbulent eddies). 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 can only rise with the steam through the exhaust pipe and into the atmosphere. The feed water from the coarse deaeration section and the condensate introduced through the drain pipes are mixed here for a second distribution, falling uniformly like rain onto the liquid-vapor grid below, and are then deeply deaerated before flowing into the water tank. The oxygen content in the water within the tank is 0-7 μg/L at high pressure and less than 15 μg/L at low pressure, meeting the departmental operational standards.

Due to the oxygenator's operation maintaining water in a turbulent state and having a sufficiently large heat exchange surface area, the better the heat and mass transfer effects, the smaller the exhaust steam volume (meaning less steam used for heating, resulting in smaller energy losses and significant economic benefits). The excellent deoxygenation effect allows the oxygenator to operate at an overload (usually up to 50% over the rated output for a short period) or achieve operating standards under full water replenishment with low water temperatures.

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 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 incoming water and heating steam, achieving the desired deaeration effect while ensuring the deaeration temperature is maintained 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 rate based on the temperature of the deaerated water. After topping up is complete, the electric actuator automatically shuts off.

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 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 cease using it once the startup is complete with load. Additionally, a prevent-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 significantly affects pump cavitation. Without a prevent-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 and water tank are焊接 on-site, hydrostatic testing must be conducted. The pressure parameters for the test are: 0.2 Mpa for atmospheric oxygen-removing units and 0.75 Mpa for pressure oxygen-removing units. The condensed steam should first accumulate in the intermediate storage tank before being evenly delivered to the oxygen-removing unit to ensure stable load operation.

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 meeting the design technical specifications.

(2) Oxygen Scavenger Membrane should be equipped with both local and remote water level gauges, and include high and low water level alarms as well as hazardous high and low water level action devices. Water level control for the oxygen scavenger: when the water level drops, the softening water pump (condensate pump) automatically starts to replenish the oxygen scavenger; when the water level rises, the pump automatically stops.

7. Preheat the deaerator shell with auxiliary steam for 10-15 minutes before starting up in cold condition. Under a certain steam pressure, introduce the demineralized water into the deaerator head while adjusting and increasing the steam inlet valve to heat the feedwater in the film formation section to nearly the steam saturation temperature of the deaerator 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 both deaerators need to operate in parallel, to balance the pressure and water level within the deaerator, each deaerator tank must have a connecting steam and water equalizing pipe. Aim for the pressure, water temperature, and water level to be as consistent as possible.) When the water level reaches ±200mm of the normal level, the high-level drain valve (electromagnetic gate valve) should open smoothly to drain water, and it should automatically close when the water level decreases. During operation, it is essential to frequently 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 opening to about 2/3, 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, do the opposite.

12. When operating the deaerator, if water in the exhaust steam is observed, the following methods can be adopted for handling the situation:

a. Adjust the heating steam inlet valve

b. Inspect Pressure Adjustment Device

c. Manual pressure reduction 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 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 set intervals, record the readings on various monitoring instruments, to ensure the proper operation of the deaerator.

15. Important Notes

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

b. During operation, it should be noted that the pressure within the deaerator should not drop sharply, nor should a vacuum occur.

c. In case of short-term shutdown, prevent the deaerator from forming a vacuum or becoming full of air. Gently open the bypass steam valve to introduce a small amount of steam, maintaining a hot 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 failure.

e. If the deaerator is 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 Standard 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 function.

· Pressure Gauge — Installed at the top of the deaerator to monitor 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 aid of an automatic regulator to maintain the pressure within the deaerator at the rated level.

· Water-seal pipe --- When the liquid level rises, the pressure difference exceeds the water column pressure, causing the balance to be disrupted, and the liquid flows out through the water seal. It also acts 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 control system to maintain the normal water level of the tank.

·Adjustable Valve --- Installed on the replenishing pipe, it regulates the flow rate of replenishing water with the aid of an electric water level control system, to maintain the normal water level of the tank.

Electrical contact level monitoring—consisting of a sampling cylinder (primary instrument) and a high-purity ceramic electrode with a display (secondary instrument)—is installed on the water tank to monitor the water level inside, with the electrodes outputting a 4-20 mA signal to the control room for regulating the water level valve.

· Magnetic Float Level Gauges - Installed on water tanks, for on-site monitoring of water levels within the tank. Also capable of connecting to remote systems and outputting a 4-20 mA signal to the control room for regulating the water level valve.

Balanced Vessel — Used in conjunction with pressure/differential pressure transmitters and level gauges, it can reflect the descaler (weight) level of the boiler during startup, shutdown, and normal operation.

· Electric gate valve --- Installed on the water 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 the electric water level regulation system, and the excess water above the limit level is drained 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 supply water flow and controls the overflow valve (electric gate valve) at the maximum water level.

Section 6: Order Provision Data

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

2: Oxygen remover operating pressure, temperature...

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

Section 7: Renovation

Our factory not only supplies complete sets of new water film deaerators but also undertakes改造 for the电厂's spray plate and spray packing deaerators. Specifically, it includes:

Low改造cost, 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 section, remove all the spray tray or spray packing components inside the original deaerator head, retain the lower steam inlet disk, and then install a liquid-gas mesh and a water grate at a certain position above the lower steam inlet disk. Finally, seal and secure the ring plate to prevent water-gas short-circuiting during future operation.

3. Next, disconnect and weld the junction of the cap and cylinder into the film former, connect the other pipeline components according to the provided modification scheme, and the job is complete. After passing the acceptance inspection, it can be put into operation.

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