FREQUENTLY ASKED QUESTIONS (FAQ)
What steam flow range (turndown) is possible with the available steam side pressure drop? (ONLY FOR VENTURI)
Answer:
The range of steam flow that can be accommodated by the IMTECH-KIEKENS DESUPERHEATER
depends on the available steam side pressure drop. In the VENTURI style
desuperheater the cooling water spray is maintained by the dynamic energy
of the steam flow. Accordingly, if the steam flow is turned down from maximum
to zero, at some point there will be insufficient dynamic energy to atomize
the spray water. The dynamic energy of the steam flow is related to the
steam side pressure drop over the DESUPERHEATER. Research and experience
have proven the pressure drop of an IMTECH-KIEKENS DESUPERHEATER has to
be over 0.05 bar* in order to provide sufficient dynamic energy.
There is an approximate relationship between pressure drop and steam flow
of:
= maximum
steam flow/minimum steam flow
Consequently, at an available maximum pressure
drop of 0.5 bar, the steam flow range will be
or approximately
3:1
Therefore, in preparing requirements, extra attention must be paid to the steam flow range; especially in applications without pressure reduction and/or where pressure drop is limited.
Why is it not possible to obtain controlled steam at saturation temperature?
Answer:
If we have an application where on the outlet saturated steam is requested,
we always recommend a set point of the temperature controller at 5ºC
above saturation temperature, due to the occurring practical control limitations.
The temperature sensor (TT), located at several meters downstream the water
injection point, that regulates the opening of the water control valve,
has to operate in a so called “dry” environment to operate
properly. If “wet” steam reaches the TT, the system will start
to oscillate resulting in rapid opening and closing of the water valve
and no control is possible. This means that the steam must not contain
any water droplets. At saturation temperature the steam flow will start
to contain water (gets “wet”). Therefore in practice the outlet
temperature will always be controlled at several degrees above the saturation
temperature.
We can achieve and recommend a gap of 5ºC for our VENTURI unit and about 7ºC for the MNS unit