The role of the demisting device is to remove small liquid droplets from the gas stream (ie. to “de-mist”), in order to protect any downstream equipment such as compressors and other processing equipment, to reduce carry-over and loss of any valuable chemicals and to prevent pollution.

Demisting devices come in many different forms such as filters, wire mesh mist eliminators (mesh pads), vane packs and cyclonic devices. For all these devices, the basic working principal of operation is velocity based, as such the gas velocity in the separator will be determined by the correct choice of demisting device regards efficiency, size etc. In summary, the correct selection of demisting device can allow a reduction in the vessel
diameter and overall weight, leading to a reduction in Capital Expenditure (CAPEX) as well as increasing the performance of the separator.

Dependent on the operating conditions (i.e. pressure, wax, solids loading, foaming etc) and physical properties (i.e. liquid density, viscosity, surface tension etc) a different type of demisting device can be used. The general attributes of commonly supplied demisting devices are summarised below.

Type of Demisting Device	Attributes of the Demisting Devices
Mesh Type Demisting Device	V. Poor	5 µm	V. Good	Low	Low	Yes	Yes	<5 mbar
ZP-090 Type (“Chevron” Vanes)	V. Good	20 µm (note 1)	V. Poor	Low	Low	Yes	Yes	<5 mbar
ZP-110 Single Pocket (Hooked) Vanes	Good	12 µm (note 1)	Poor	Medium	Medium	Yes	No	<5 mbar
ZP-210 Double Pocket (Trough) Vanes	Poor	8 µm (note 1)	Av.	High	High	Yes	No	<10mbar
ZP-310 Double Pocket (Trough) Vanes	Poor	8 µm (note 1)	Av.	High	High	No	Yes	<10mbar
4G-FD Demisting Cyclones	Good	5 µm	V. Good	V. High	V. High	Yes	Yes	<100mbar

Note 1: At atmospheric pressure.