Zhangjiagang HuaDong Boiler Co., Ltd. |
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ASME Carbon Steel Serpentine Tube Boiler Reheater Superheater Horizontal Layout
Material composition
Carbon steel, alloy steel or heat-resistant steel, collection boxes and other supporting material. Tubes are customized types of specifications.
Design pattern
Vertical or horizontal layout.
Advantages
Beautiful appearance, size, accuracy, first-class bending and welding technology, first-class detection equipment.
Manufacturing and acceptance criteria
JB/T1611 " Technical specification for manufacturing of boiler pipes."
JB/T1612 "boiler pressure test technical conditions. "
JB/T1613 "Technical specification for welding of pressure parts of boiler."
JB/T1615"Technical specification for painting and packing of boiler."
JB/T3375 "Rules for receiving acceptance of materials for boiler construction."
For power plant boiler, it is a crutial way to increase thermal
economy of thermal power station by improving parameter of
superheated steam. The increase of superheated steam parameters are
limited by metal materials. The design of superheaters must make
sure that the temperature of outer wall of heating surface pipes is
lower than allowable temperature of oxidation resistance of steel,
and meanwhile make sure its mechanical strength. with the
development of metal material used in boilers, pwoer station
boilers in our country already generally apply high pressure, high
temperature(9.8MPa, 540 degrees) and superhigh pressure
parameters(13.7 MPa, 540 and 555 degrees), and have developed
subcritical pressure parameters(16.7MPa, 540 and 555 degrees). Now
lots of boilers apply supercritical pressure parameters(24.5MPa,
540-570 degrees), and even very few units apply higher pressure and
temperture parameters.
For boilers in large power stations, superheaters and reheaters are
necessary parts, to a large extend, they have influced the safety
and economy of boilers. Superheaters are the heating surfaces which
heat the main steam from the surnatured temperature to the rated
superheated temperature, and the reheaters are the heating surfaces
which heat the exaust from the steam turbine high pressure cylinder
to a certain temperature.When running conditions like boiler loads,
coal types change, it is to adjust them to make sure the outlet
temperature at the rated level of -10-+5 degrees.
For large boilers in power stations, superheaters and reheaters
account for a big proportion in the total heating surfaces, they
are to be arranged in the areas where smoke is with higher
temperature. To improve the efficiency of thermal circulation in
power stations, it is needed to improve the original parameters f
steam gradually, the increase of steam pressure requires the
corresponding increase of temperature for superheated steam, or the
humidity of large stage exhaust of steam turbine will be too high,
which will influence its safety. Thus, the steam flowing through
superheaters and reheaters are high temperature steam, their heat
transfer performance is quite bad, which determines that tube wall
temperatures of superheaters and reheaters are high.
Functions and characteristics of superheaters and reheaters
functions of superheaters and reheaters:
Superheaters and reheaters are important parts for the heating
surfaces, used to increase steam temperature, aiming to improve
steam enthalpy and further to increase the thermal circulation
efficiency for power station.
Superheaters work to heat surnatured steam to superheated steam
with a certain tempetature. When boiler loads or other working
conditions change, it is necessary to make sure superheated steam
temperature to be normal, and within allowable range of temperature
variation.
From the thermal circulation in power station, the original
parameters of pressure and temperature is higher, the thermal
efficiency of circulation is better, or the steam humidity of the
steam turbine rear is too high, influencing its safety. While the
superheaer steam temperature is limited by metal materials, at
present, due to limitation of metal materials, superheated
temperature for most power station boilers are still within the
range of 540-555 dgrees, and to avoid the steam humidity of blade
of steam turbine rear too big, thus middle reheating system is
applied.
Functions of reheaters are to heat exhaust of steam turbine high
pressure cylinder to the reheated temperature which is close or
equal to superheated temperature, and then send them to middle
pressure cylinder and low pressure to expand and work to increase
the dryness of blace of steam turbine rear. Usually, the pressure
of reheated steam is one fifth of that of superheated steam.
Application of reheating system can increase the thermal efficiency
for power stations by 4-5%.
So far in our country, units with capacity over 125mw all apply one
time middle reheating system. Double reheating can increase again
the thermal efficiency of circulation by 2%, but the system is very
complicated, it is not applied for national units, but it is common
for large boilers overseas.
Principle
• Principle of superheater is similar to steam generating tubes of
boiler.
• The hot gases at high temperature sweep over superheater tubes
and raise the temperature of steam which magnitude depends upon
exit gas temperature leaving the superheater and gas velocity.
Application
use for heating saturated steam, steam temperature could be up to
900 degree C.
Superheater Capacity Upgrades to Increase Power Generation
Send us required technical data, such as steam capacity, presure,
required temperature etc. We will design accordingly.
Differences
Type | Advantages | Disadvantages | Supporting method |
Pendant-type | 1.Firm structural support | 1. Flow blockage by condensed steam 2. Needs slow restart to purge the water that accumulates in the bottom. | supported from above |
Inverted-type | 1.Proper drainage of the condensed steam | 1. Lack the structural rigidity, especially in high speed gas flow | Supported from below |
Horizontal -type | 1. Proper drainage 2. Good structural rigidity. | 1. They do not view the flam directly so they are mainly from the convective type | Usually supported in the vertical gas ducts parallel to the main furnace. |