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Single cylinder deaerator

key word:Heat exchange element


Product description

Single cylinder deaerator

 

1. Introduction

1.1. Purpose

The single cylinder deaerator is an important auxiliary equipment in the multistage regenerative system of steam turbine generator set. It is a hybrid heating and separating equipment. It can integrate the deaerator and the water storage tank by installing a new and efficient deaerator into the steam side space of the water supply tank.

1.2. Model meaning

SSD-**/##

SSD ------ Code of single cylinder deaerator

** --------- rated (maximum) output of deaerator (t/h)

## -------- effective water storage volume of deaerator (m3)

1.3. Structural features

1.3.1. Structure description (see figure 28-1). The condensate enters the spray valve through the jellyfish pipe, because the pressure of the condensate is higher than the working pressure in the deaerator. The pressure difference on both sides causes the spring to compress, the disc opens, the condensed water is injected into the steam space in a thin film, contacts with the heating steam, and is heated to or near the saturation temperature of the deaerator working pressure, so as to carry out preliminary deaeration. The condensate after preliminary deaeration is evenly placed on the deaerator plate through the water distribution device, and the oxygen content of boiler feed water reaches the standard value. Since the oxygen and other gases in the condensate are not discharged through the steam separator, the oxygen and other gases in the condensator are not discharged at the same time. The deoxidized water meeting the standard value is stored in the lower water storage space to meet the requirements of boiler water supply. The steam water flow of single drum deaerator is shown in figure 28-2.

1.3.2. Description of important components. The single cylinder deaerator is a typical horizontal vessel. The upper part is the deoxygenation area, and the lower part is the water storage area. It is mainly composed of shell, support, water supply device, spray valve, water distribution device, deaerator, exhaust device, heating steam device, high pressure heater drain device, re boiling installation and feed water pump recirculating tube, etc. (see figure 28-3).

1.3.2.1. The shell is welded by the cylinder body and two standard elliptical heads at both ends, and is supported by saddle support. The deaerator is equipped with one fixed support and the rest are sliding supports. According to the size of the unit, there are 2 bearings, 3 bearings, 4 bearings, etc.

The 1.3.2.2. water supply device is made up of a jellyfish pipe and a plurality of pipe joints. The condensate is distributed to each nozzle through the jellyfish pipe and then uniformly flows into the spray valves.

1.3.2.3. The start-up exhaust and continuous operation exhaust pipes of the exhaust system shall be set separately. A start-up exhaust pipe is set on the left and right parts of the equipment respectively, which can discharge oxygen and other non condensable gases in the equipment smoothly during startup. The continuous operation exhaust device is composed of exhaust branch pipe, throttle orifice and exhaust main pipe. One exhaust branch pipe and one throttle orifice are set in each deaerator unit to ensure that the oxygen and other non condensable gases precipitated during the deaerator continuous operation are discharged in time. The structure can reduce the steam heat loss to the minimum, thus improving the thermal efficiency of the unit; at the same time, the concentrated oxygen corrosion will not occur in the deaerator.

1.3.2.4. The heating steam device is composed of steam inlet pipe, casing and anti scour device. The anti impact device is composed of stainless steel steam baffle and steam baffle, which is used to prevent the steam from eroding the inner wall and internal parts of deaerator after entering the shell.

1.3.2.5. The deaerator is equipped with reboiler device (also known as preheating device). The reboiler device is composed of one steam inlet pipe (with casing pipe), one steam distribution main pipe and several branches evenly distributed. The steam is ejected through a small hole in each branch pipe, and the water is evenly heated, so as to avoid the vibration and noise of the equipment. The role of the reboiler device is: first, when the unit is started, the cold water should be heated to the saturation temperature under the working pressure of the deaerator as soon as possible, so as to speed up the deaeration speed of the feed water; Second, in normal operation, if the oxygen content of feed water is unqualified, auxiliary steam can be introduced from this pipe to make the water in deaerator boil again, so as to remove oxygen and other non condensable gas in feed water.

1.3.2.6. When the unit is in start-up or low load operation, part of the feed water will return to the deaerator through the recirculation pipe to maintain the flow of the feed water pump and avoid cavitation, vibration and noise of the feed pump. In order to avoid the vibration and noise of the deaerator, a porous nozzle structure is made at the specific position of the recirculation pipe of the feed pump and the drain pipe of the high-pressure heater which extends into the inner side of the shell.

The 1.3.2.7. deaerator is the main component of the single cylinder deaerator. Therefore, it is very important to ensure the atomization performance of the spray valve and the efficient heat and mass transfer function of the deaeration element. Deaerator components include spray valves, deaerator discs and water distribution devices, as shown in figure 28-4.

The condensate is distributed through the water supply pipe and uniformly flows to each stainless steel spray valve of the deaerator. The rated flow rate of spray valve is 100t/h, and spring adjustment is adopted. The flow rate of the spray valve increases with the increase of pressure difference, so that the condensate can be ejected uniformly in good film shape under various load conditions, so as to meet the needs of deaeration equipment under variable conditions, and can adapt to the variable load range of 10%~110%. This spray valve is also a check valve. Its characteristic is that it can effectively prevent the steam from flowing back into the condensate water, so the spray valve can prevent the water hammer phenomenon.

The condensate which is initially heated and deoxidized is evenly sprinkled on the deaerator tray through the water distribution device for deep deaeration. The deaerator tray is a kind of high-efficiency deoxidizing element. Water is broken and dissected again here, forming a membrane layer by layer downward flow. At the same time, the water also flows horizontally in the deaerator tray, which greatly increases the contact area of steam and water, the time of mass transfer and heat transfer, and ensures the full contact of condensate water and steam from bottom to top, providing sufficient time and power for the escape of dissolved oxygen And achieve the purpose of deep deoxidization.

A device for collecting and redistributing condensate water ejected by a spray valve includes a water tank device and a water bucket device.

1.3.3. Description of important characteristics:

1.3.3.1. The heating steam produces very small pressure loss, which reduces the heat consumption of the whole unit and improves the thermal economy of the unit.

1.3.3.2. Under all load conditions such as sudden load change and turbine trip, the deaerator can operate safely, stably and reliably without water hammer, excessive noise, vibration and deformation.

1.3.3.3. The performance of deoxidization is excellent. In the range of 10% ~ 110% output, the oxygen content in effluent is less than 5 ppb, and the normal operation is usually about 2 ppb.

1.3.3.4. When the low-pressure heater is out of service or cannot operate normally, and the steam extraction capacity of deaerator increases to maintain water temperature, the deaerator can adapt to the requirements of feed water temperature and flow. When one low-pressure heater is shut down, the output of deaerator shall not be less than 90% of its rated output.

1.3.3.5. When the boiler is cold started and steam from other steam sources is used, the deaerator can operate under the specified pressure and flow, and the feed water temperature can meet the requirements of boiler startup.

1.3.3.6. The reliability of the equipment is high, and the service life of the shell and main deoxidizing components is 30 years.

 

 

2. Main technical parameters and product appearance

2.1. Main technical parameters (see table 28-1 and table 28-2)

Table 28-1 main technical parameters of typical single cylinder deaerator

 

Item 300MW Unit 600MW Unit 1000MW Unit
Rated output (t/h) 1080 1995 3185
Effective volumem3) 150 235 310
Equipment and materials 16MnR 16MnR 16MnR
Internal diameter of equipment (mm) 3900 3900 4000
Total equipment length (mm) 18 000 30 000 36 000
Wall thickness of cylinder (mm) 28 28 32
Equipment weight (t) 70 126 178
Corrosion allowance (mm) 1.6 1.6 1.6
Coefficient of welded joint 1 1 1
Effluent oxygen content (ppb) 5 5 5
Exhaust loss (‰) I2 1~2 1~2
Number of spray valves (only) 9 16 22
Quantity of deaerator tray 36 144 176
Same distance between supports (m) 10 10 10
Number of supports 2 3 4

 

Table 28-2 parameters of supporting accessories

No. Model & Name Suit 300WM unit Suit 600WM unit Suit 1000WM unit
Specification Quantity Specification Quantity Specification Quantity
1 A48Y-25 spring full lift safety valve PN2.5, DN150 2 PN2.5, DN150 3 PN2.5, DN200 4
2 Pressure gauge Y-150 1 Y-150 2 Y-150 2
3 Bimetal thermometer WSS 2 WSS 2 WSS 2
4 Magnetic flap water level gauge (including primary valve) L=3400mm 2 L=3400mm 2 L=3600mm 2
5 Tee valve (for pressure gauge)  J11-32; PN32, DN4 2 J11-32; PN32, DN4 2 J11-32; PN32, DN4 2
6 Balance vessel (including primary door) Single chamber 3 Single chamber 3 Single chamber 3
7 Electric exhaust valve (for starting exhaust) PN2.5, DN80 1 PN2.5, DN100 2 PN2.5, DN100 2
8 Exhaust valve (for operation exhaust) PN2.5, DN100 1 PN2.5, DN100 1 PN2.5, DN150 2
9 Deaerator emergency water discharge electric valve PN2.5, DN200 1 PN2.5, DN250 1 PN2.5, DN250 1
10 High water level overflow electric valve PN2.5, DN150 1 PN2.5, DN200 1 PN2.5, DN200 1

 

2.2. Product appearance

 

3. Selection method

3.1. Performance parameters

The following data shall be included in the user's relevant documents:

3.1.1. Requirements for design conditions or design parameters.

Rated output.

3.1.3. Effective water storage volume.

3.1.4. Special requirements for equipment materials, shell, deaerator, etc.

3.1.5. Support spacing and number.

3.1.6. Structural requirements, such as built-in type.

3.1.7. Design standards and relevant standards, such as ASME and national standards.

3.1.8. Requirements for painting, marking, packaging and transportation.

3.1.9. Performance guarantee requirements.

3.1.10. Heat balance diagram of steam turbine under various operating conditions.

3.1.11. Requirements for accessories and local instruments.

3.2. Site conditions

If the following site conditions can be provided, it will be helpful for the selection.

3.2.1. Main original data of the project, including meteorological characteristics and environmental conditions.

3.2.2. Basic earthquake intensity.

3.2.3. Installation and operation conditions, such as indoor or outdoor.

3.2.4. System and related equipment overview, such as unit type, etc.

3.3. Supply requirements

3.3.1. Special requirements for structure and materials (such as single barrel type, shell material, support position and quantity, etc.).

3.3.2. Specific requirements for valves and accessories, such as exhaust valve (electric, manual, regulating mode, etc.) and other types, specifications, quantities and relevant requirements of valves to be provided.

3.3.3. Any additional requirements related to measuring instruments, such as level switch, level measuring cylinder, etc.

3.3.4. Whether platform stairs are included. If platform stairs are required, specific requirements for platform escalators shall be put forward.

 

4. Scope of supply

The scope of supply includes product design, procurement, manufacturing, factory testing and on-site installation and commissioning guidance (the specific scope of supply can be increased or decreased according to customer demand). Typical supplied devices and accessories are as follows:

4.1. Deaerator body.

4.2. Support (including anchor bolts and sliding parts).

4.3. Valves and accessories (including safety valve, instrument primary valve, etc.).

4.4. Instrument control elements (including pressure gauge, thermometer, local water level gauge, etc.).

4.5. Counter flange and matching connector.

4.6. Metal components for thermal insulation (excluding insulation layer and outer layer).

4.7. Spare parts (manhole gasket).