Superheated steam
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Why must superheated steam be desuperheated before it is fed into the heat exchanger?
To prevent excessive temperature differences, as well as the high demands that high temperatures place on the materials used in heat exchangers
When it overheats and reaches saturation, it can generate little heat, thus wasting the heat exchange area; of course, it is desirable that the latent heat be released as soon as saturation is reached.
1 The condensation heat transfer coefficient is greater than that of the superheated gas, which allows for reduced heat exchange area. 2 The process medium undergoes retrodecomposition and deterioration at high temperatures.
In our system, the heating medium tends to degrade when the temperature is too high; therefore, it is necessary to reduce the pressure and temperature first (by using deoxygenated water), before feeding the material into the reboiler.
Superheated steam enters directly as hot gas; generally, steam flows through the tube side. The pipe will be filled with steam; think about it – between a pipe of steam and a pipe of condensed water, it is the latter that has a higher enthalpy value.
There is no liquid film in the superheating section, resulting in a low heat transfer coefficient; this wastes the heat transfer area, and the overall heat transfer amount does not increase
The utilization rate of superheated steam is low; cool it down first before using it
Superheated steam has a poor heat transfer efficiency, requiring a larger heating surface area on the equipment, which is not economical
I finally understand the reason. The steam produced by our company’s boilers is superheated steam; before it enters the reboiler, it needs to be converted into saturated steam using a temperature and pressure reducer. Another advantage of this is that there is a one-to-one relationship between the pressure and temperature of saturated steam, allowing the temperature to be controlled by regulating the pressure of the saturated steam.