begg cousland

Boiler Steam Drums

Demisting / Droplet Separation

PROCESS INFORMATION

The primary function of the boiler steam drum is separate water from steam which prevents carryover of the condensate into to the steam header (the separated steam is sent to super heaters and the water is recirculated for conversion to steam with a purity in the range of 5 PPB to 1 PPM)

Steam can be purified by steam drum internals such as baffle separators, cyclone separators, Chevron vane separators, and/or demisters.

When the boiler is fitted with cyclone separators, all the water steam mixture is collected in a chamber. The mixture is made to pass through multiple cyclones. The cyclones separate the water and return to the water space of the drum. The cyclones can have a chevron separator or demister meshpad on the top. The steam leaves through the top chevron vane unit or demister meshpad below the exit nozzle.

PROBLEMS TO SOLVE

Prevent water droplet carryover (Liquid droplets entrained in the steam leaving a boiler also contain dissolved solids, which impact the condensate purity)

DESIGN SOLUTIONS

If Cyclones are used, the Becovane STV chevron vane or the Becoil demister meshpad can be supplied in 321 Stainless Steel.

  1. The steam drum exit can be fitted with a horizontal  Becovane STV chevron vane in a housing below the nozzle
  2. The steam drum exit can be fitted with a vertical  Becovane STV or DPV chevron vane in a housing before the nozzle
  3. The steam drum exit can be fitted with a horizontal  Becoil demister meshpad in 321 Stainless Steel in a housing before the nozzle

Note : In all cases (A) to (C) extreme care must be taken to prevent preferential flow in the chevron vane or demister by ensuring the flow is even over the surface area, to ensure even distribution of the air to and from the chevron vane or demister by giving sufficient distance before and after them, to allow proper drainage at the design velocity.

Steam Drum Two Views

Demister Meshpad located at top exit of Boiler Steam Drum

Typical fixing method in a Boiler Steam Drum housing

Typical fixing method in a Boiler Steam Drum housing

Vessel Views with BC Logo

Horizontal and Vertical Demister and Chevron Vane Arrangements

cyclone demister

Meshpad demisters on top of Boiler Steam Drum cyclones