Vane packs

Standard vane packs, together with wire mesh demisters, are the most widely used internals for separating liquid droplets entrained in gas streams.

Separation

Vane packs consist of a series of channels and vanes through which the gas carrying the droplets flows. As the gas changes direction, the droplets are captured by the vanes. The liquid droplets flow down along the vanes and are drained through a pipe towards the lower part of the vessel.

Flow velocity

Compared to wire mesh demisters, the flow velocity is higher, allowing a reduction in the cross-sectional area, separator size and, consequently, vessel diameter.

Performance

The minimum diameter of the liquid droplets that can be captured is greater than with a wire mesh demister. For this reason, vane packs are not recommended when high separation efficiency is required.

With mesh pad agglomerators

The wire mesh agglomerator can be installed before the plate pack when process conditions require a preliminary droplet coalescence stage, such as in the following cases:

• The droplet size is too small to be captured by the plates.
• The flow velocity is too high for a conventional wire mesh demister, resulting in droplet carryover downstream.
• The required separation efficiency is higher than the performance achievable with a plate pack.
• The vessel diameter is too small to install a wire mesh demister of adequate size.

As shown in the drawing, as the droplets pass through the agglomerator, they progressively increase in size until they reach the lamellar pack with optimal size and velocity for proper separation.

With perforated distribution plates

When the vessel diameter is too small to allow proper flow distribution, there is a risk that the gas will pass through only a fraction of the available area of the plate pack window. This poor gas flow distribution causes two problems:

• Excessive gas flow velocity through the plate pack.
• Lower process efficiency, because many droplets captured by the plates may be re-entrained due to the excessive velocity.

These issues can be resolved by installing a perforated distribution plate that allows the flow to be distributed across the entire available area of the lamellar pack window.

The so-called “W bank” is a specific type of plate pack used when reducing the vessel length is a priority.
Thanks to its distinctive V-shaped configuration, it is possible to achieve a sufficient flow area to ensure the required separation efficiency with a plate pack that is half the length, while also reducing the overall vessel dimensions.

The W bank retains all the features and qualities of a standard plate pack, allowing separators to be assembled with different types of plates or a wire mesh agglomerator to be installed to increase separation efficiency.