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Vacuum Deaeration

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Summary:

The following descriptions refer to thermal vacuum deaeration of water only, meaning deaeration at less than atmospheric pressure with continuous inflow of heat. Intermittent deaeration processes without heat inflow are not covered, while →thermal deaeration processes at higher than atmospheric pressure are described elsewhere.

Thermal deaeration is a physical process for removal of dissolved gases from water. For thermal deaeration, the water to be deaerated is brought to the boiling point by addition of heat. For vacuum deaeration, the boiling occurs at less than atmospheric pressure, resulting in a boiling temperature of less than 100 °C. This is of advantage especially for hot water or warm water systems, e.g. in district heating.

A vacuum deaerator may be designed either as a separate upright vessel, or attached to a downstream storage tank. The required heat inflow is usually achieved with either steam or hot water, either by direct contact heating and mixing or indirectly by heat transfer through a tube bundle. The vacuum is usually created by either jet pumps or liquid ring vacuum pumps, supported by condensation processes within a vent condenser.

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Design Example:

Vacuum deaeration plant: Vacuum deaerator, upright, without storage vessel, including vent condenser, liquid ring vacuum pumps, valves, and instrumentation.

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Common Applications:

District heating and other hot water systems: Deaeration of the make-up water and side stream deaeration of the circulating water.

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Technical Data:

deaerated water mass flow	available from approx. 5 000 up to 300 000 kg/h ≈ 1.5 ... 80 kg/s for each line
amount of lines	usually 1x100 %
deaerated water quality	oxygen	< 20 μg/L O₂ (standard) < 50 μg/L O₂ (option)
	free carbon dioxide	< 1 mg/L CO₂
operating pressure, absolute	< 1 bar, usually approx. 0.1 ... 0.6 bar
operating temperature	< 100 °C, usually approx. 45 ... 85 °C
storage time water seal	without separate storage vessel approx. 5 ... 15 minutes with additional downstream storage vessel usually approx. 60 ... 120 minutes
material options	deaerator	• stainless steel (e.g. 1.4541, 1.4571)
	storage vessel	• carbon steel (e.g. S235JR, P265GH) • stainless steel (e.g. 1.4541, 1.4571)
	pipelines	• polyvinyl chloride (PVC-C) • polypropylene (PP) • carbon steel (e.g. P235GH) • stainless steel (e.g. 1.4541, 1.4571)
	valves	• polyvinyl chloride (PVC-C) • polypropylene (PP) • grey cast iron (e.g. 5.1301) • spheroidal cast iron (e.g. 5.3101, 5.3106) • cast steel (e.g. 1.0619) • stainless steel (e.g. 1.4408)
	gaskets	• EPDM • PTFE • NBR composite • graphite composite
control options	closed loop pressure control	• electric, intermittent (on/off) • electric, continuous (PI, PID)
	closed loop temperature control	• mechanical, continuous (P control) • electric, continuous (PI, PID, or 3-point control)
	closed loop level control	• mechanical, continuous (P control) • electric, intermittent (open/closed) • electric, continuous (PI, PID, or 3-point control)

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Downloads:

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2018-05-05 • water treatment made in Germany • Company Information • Privacy