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The Theory of Producing
Steam Water and steam are typically used as heat carriers in heating systems. It is well known that water boils and evaporates at 100°C under atmospheric pressure. By higher pressure, water evaporates at higher temperature - e.g. a pressure of 10 bar equals an evaporation temperature of 184°C. During the evaporation process, pressure and temperature are constant, and a substantial amount of heat are use for bringing the water from liquid to vapour phase. When all the water is evaporated, the steam is called dry-saturated. In this condition the steam contains a huge amount of latent heat, corresponding the heat that was led to the evaporation process under constant pressure and temperature. Despite temperature and pressure is the same for the liquid and the vapour, the amount of heat is much higher in vapour compare to the liquid. This latent heat in the dry-saturated steam can efficiently be utilized to different applications i.e. processes requiring heat. The Steam Supply The steam boiler (and steam generator) is connected to the consumers through the steam and condensate piping. When the steam is provided to the consumers, it condensates. It can then be returned to the feed water tank, from where it again is pumped to the steam boiler / steam generator. When the steam condensate is returned to
the feed water tank, a pressure reduction is unavoidable and this cause
generation of flash steam - typically just after the steam trap(s).
Steam Generator
Boiler
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In the steam generator boiler, the feed water
and steam are in the principle passing through one long tube - designed as
winded-up tube coils that are serially connected.
In this long tube (tube coils) the feed water is heated up to the evaporation temperature
in the first part
and then evaporated in the second part. The intensity of the heat, the feed water flow and the size/length of
the tube are adapted, so that the water is exactly fully evaporated at the exit of the
tube. This ensures a very small water and steam volume (content of the pressure vessel).
Thus there are no buffer in a steam generator, and is it temporary overloaded i.e. beyond
its nominal steam capacity - a separate buffer tank should be provided (accessories).
The advantages using a steam generator compared to conventional steam boilers:
Steam
Generator Design
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The steam generators heaters are made with
coils made of seamless tubes, where the feed water is preheated and evaporated during the
flow through these. The heat is transferred to the water/steam mixture as radiant heat in
the combustion chamber, where the inner cylindrical tube coil and a flat tube coil forms
the chamber wall and the bottom respectively. Consequently refractory concrete is avoided.
The combustion gasses are hereafter cooled in the outer convection part, as the gasses
pass the space between the two tube coils. The thermal design ensures a modest volume of
steam relative to the size of the heater, and allows unlimited thermal expansion due to
the high temperatures. All TT BOILERS steam generators and steam boilers are
designed and equipped according to European regulation including PED code
and EN-standards.
Beside the standard execution the
steam generators can be delivered in e.g. following variations:
Exhaust Gas Steam Boilers
Utilization of the waste heat in flue gas of
the steam boiler / steam generator itself, is called an
economizer. It can be used for preheating the feed water, but also for
external purposes including preheating of make-up water, domestic water or
central heating water.
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