Q2Engineering Chemistry
Question
2 marks
Q.2 What is meant by priming and foaming?
Answer
Priming is the highly undesirable physical carry-over of actual liquid water droplets directly with the rapidly exiting steam, whereas foaming is the continuous formation of massive, stable, unbroken froth bubbles strictly on the boiling water's surface.
In high-pressure industrial boiler operations, these two phenomena significantly degrade thermodynamic efficiency and strictly compromise mechanical safety.
- Priming: A violent, chaotic physical process where large droplets of unevaporated liquid water are violently thrown up and forcefully carried out directly by the high-velocity steam flow. It is primarily caused by maintaining dangerously high boiler water levels, excessively sudden demands for massive steam, or poor boiler design. It causes severe mechanical damage to steam turbine blades.
- Foaming: A strictly chemical phenomenon characterized entirely by the continuous generation of dense, highly persistent, stable froth exactly at the steam-water physical interface. It is caused almost exclusively by the severe chemical contamination of the boiler water with dissolved organic impurities, heavy oils, or alkaline salts that drastically lower the surface tension.