Seeking advice on deaerator issues
Thread Content
1. The thermal deaerator uses steam to heat the feedwater in order to remove oxygen and maintain the pressure within the deaerator. When the water inflow remains constant but the supply of heating steam is insufficient, which of the following situations may occur? ( ) A. The level in the deaeration tank rises B. The level in the deaeration tank drops C. The pressure in the deaerator increases D. Vaporization occurs at the inlet of the feed pump. How should this question be answered?
A. Deoxygenation is achieved by evaporating some water to carry away oxygen; if the steam pressure is not sufficient, the amount of evaporation decreases.
Due to insufficient steam supply, the oxygen content in the effluent may exceed the specified limits and become unqualified.
As long as there isn’t too little steam, the deaerator is a self-balancing system, and the operating pressure will decrease. The water level is mainly related to fluctuations in the amount of water required by the high-pressure heaters; it has nothing to do with those factors ； As the steam volume decreases, the saturation pressure drops; and since the saturation pressure is the operating pressure, the pressure will only decrease and not increase. Due to the decrease in operating pressure in the water-oxygen system, the water in the tank becomes supersaturated, causing steam to escape; this escaping steam can easily lead to cavitation in the water pump.
The answer is indeed A, but I think your solution is not accurate.
Having learned A, deoxygenation is achieved by allowing some water to evaporate, thereby removing oxygen; however, if the steam pressure is not sufficient, the amount of evaporation decreases.
It’s A – sometimes I have insufficient steam, and as a result the liquid level rises. Think about it: when there’s not enough steam, the pressure in the deaerator drops, and the water inflow volume increases in a short period of time.