Gravity separator

A gravity separator is an apparatus for separating particles or dusts due to gravity . The gravity separators, which are part of the mass force separators, are often used for coarse dedusting during exhaust gas cleaning.

Working principle and designs

The operating principle of gravity separators is based on the fact that the particles suspended in the gas can no longer follow the flow movement due to gravity and are separated on built-in components or walls. The most commonly used designs are shown in

Gravity countercurrent separator and
Gravity cross-flow separator

distinguished.

Both types of apparatus have in common that the dust-laden gas flow generally slows down when it enters the apparatus and thus increases the residence time in the system. A relative movement of the particles transversely to the direction of flow (cross-flow separator) or against the direction of flow (counter-flow separator) causes them to be partially separated. The sedimentation speed of the particles can be described as follows: ${\ displaystyle v_ {s}}$

{\ displaystyle v_ {s} = d ^ {2} \ cdot {\ frac {\ Delta \ rho \ cdot g} {18 \ cdot \ eta}}}

with: d particle diameter , density difference particle-gas, g acceleration due to gravity, viscosity of the gas.

{\ displaystyle \ Delta \ rho}

{\ displaystyle \ eta}

Gravity separators are preferably used for coarse dedusting , since a sedimentation speed that is acceptable for separation is only achieved with particle diameters of a few hundred micrometers (µm). In order to slow the flow, they require large construction volumes. Due to their simple design and the low pressure loss, gravity separators cause low investment and operating costs. As a result of turbulence and uneven speed profiles, the separation curves of gravity separators are usually blurred.

With the countercurrent separator, the gas to be cleaned flows through the apparatus perpendicularly against the direction of gravity. The particles experience a relative movement against the direction of flow. Particles are deposited when the relative speed of the particles is greater than the flow speed.

In the cross-flow separator, the gas to be cleaned flows through the apparatus horizontally. The particles it contains sediment perpendicular to the direction of flow. Particles are separated out when they are so sedimented that they can no longer be discharged.

literature

VDI 3676: 1999-09 Inertial Separators. Beuth Verlag, Berlin. ( Summary online , table of contents )

Individual evidence

^ Günter Baumbach: Air pollution control. Formation, spread and effects of air pollution. Measurement technology, emission reduction and regulations. 2nd Edition. Springer, Berlin et al. 1992, ISBN 3-540-55078-X , p. 314.
↑ Matthias Stieß: Mechanical process engineering. Volume 2. Springer, Berlin et al. 1994, ISBN 3-540-55852-7 , p. 6.
^ Franz Joseph Dreyhaupt (ed.): VDI-Lexikon Umwelttechnik. VDI-Verlag, Düsseldorf 1994, ISBN 3-18-400891-6 , p. 1060.

[1] Günter Baumbach: Air pollution control. Formation, spread and effects of air pollution. Measurement technology, emission reduction and regulations. 2nd Edition. Springer, Berlin et al. 1992, ISBN 3-540-55078-X , p. 314.

[2] Matthias Stieß: Mechanical process engineering. Volume 2. Springer, Berlin et al. 1994, ISBN 3-540-55852-7 , p. 6.

[3] Franz Joseph Dreyhaupt (ed.): VDI-Lexikon Umwelttechnik. VDI-Verlag, Düsseldorf 1994, ISBN 3-18-400891-6 , p. 1060.