Atmospheric Deaerator (most widely used, for medium and low-pressure systems)
Operating conditions: Atmospheric pressure (slightly higher than atmospheric pressure, 0.105~0.12MPa) + high temperature (104~105ºC, near the boiling point of water). Deaeration is achieved through "heating + enhanced gas-liquid contact", with the process as follows:
Step 1: Feedwater Pretreatment - Uniform Water Distribution
The water to be deaerated (e.g., boiler feedwater, circulating water) enters the "water distribution device" (mostly multi-hole nozzles or trays) at the top of the deaerator through the water inlet pipe, and is dispersed into "fine water droplets" or "water films".→ Purpose: Increase the contact area between water and heating steam/air, creating conditions for subsequent oxygen release (the larger the contact area, the higher the deaeration efficiency).
Step 2: Core Deaeration - Heating + Gas-Liquid Exchange
Heating: "Heating steam" (usually from boiler drainage or a dedicated steam source) is introduced into the bottom of the deaerator. The steam flows upward and comes into countercurrent contact with the water droplets/water films falling from the top, heating the water to 104~105ºC (under atmospheric pressure, the boiling point of water is about 100ºC; the slightly higher temperature ensures "supersaturation" to force more complete oxygen release).
Gas-Liquid Exchange: As the water temperature rises, the solubility of dissolved oxygen and non-condensable gases in the water drops sharply, and they escape from the water in the form of "tiny bubbles" and flow upward. At the same time, the steam condenses into water when cooled, which is added to the water to be deaerated, further reducing the gas concentration in the water.→ Key component: The "packing layer" inside the deaerator (e.g., corrugated packing, ceramic rings), which can further break up water droplets, extend the gas-liquid contact time, and enable more thorough oxygen release (the efficiency of ordinary atmospheric deaerators can reach over 99%).
Step 3: Gas Discharge - Removal of Non-Condensable Gases
The escaped non-condensable gases (such as oxygen and nitrogen), together with a small amount of uncondensed steam, accumulate at the top of the deaerator and are continuously discharged through an "exhaust valve" (usually an automatic control valve).→ Note: The exhaust volume must be controlled (too much will waste steam; too little will cause gas retention and incomplete deaeration). Most equipment is equipped with a "micro-exhaust valve" to achieve precise exhaust.
Step 4: Output - Storage and Conveyance of Low-Oxygen Water
The deaerated water (oxygen content ≤ 0.05mg/L) falls into the "water tank" at the bottom of the deaerator (called a "deaerator water tank"), and then is pressurized by a feedwater pump and conveyed to downstream equipment (e.g., boilers, heat exchangers).→ Function of the water tank: It not only stores water but also allows the water to stay in the tank for a short time to further release residual tiny bubbles. Meanwhile, it stabilizes the water temperature and water level to avoid fluctuations in downstream water supply.