The SUMIT range of mist eliminators are the Chevron type of mist eliminators which consist of a set of specially designed vanes with a well defined geometry, with closely spaced corrugated plates. That force mist-laden gas to follow serpentine paths
The Gas with entrained liquid droplets flows between the vanes of the Separator. The specifically designed channels form an inertial force trapping by impact all the mist and droplets. The abrupt change in airflow direction produces an inertial force that affects the entrapped droplets. The droplets are ejected from the gas stream by inertial force, impacting against the outer wall of the channel, forming a film on the channel wall. This film then drains back to the circuit or collection channel via basic gravity. and coalesce to a size where they drop down and are collected and removed.
Vane arrays can be mounted horizontally or vertically. They are preferred in applications involving high vapour velocities, low available pressure drops, viscous or foaming liquids. slugs of liquids, or violent upsets, vane units are usually round or rectangular very similar to mesh pads. They are sometimes used in combination with mesh pads for optimum performance in special situations. Sumit standard vanes are available in metal or plastics and have various blade spacings and profiles. For special requirements, Sumit also supplies curved vanes such as the non-metallic variety.
SUMIT high-performance double-pocket vanes can operate at higher capacity and higher efficiency than conventional vanes. The design features liquid pockets that prevent re-entrainment of the separated liquid droplets. This helps increase the capacity up to twice that of conventional vanes. The higher gas velocities also help in obtaining 99.9 % removal of particale more then 10-micron droplets.
SUMIT vanes are rigid in construction and suitable for several services which may include high vapor velocity, high vibration, high temperature, high corrosion, or particulate fouling. Engineered vane units commonly replace original mesh type mist eliminators when one of the following conditions occurs:
Based on your application and process conditions, SUMIT will assist you in your mist elimination equipment selection and individually engineer the performance of your replacement or upgrade vane mist elimination system. Vane units are available in various materials but specialty designs are available by special request for any non-patented replacement in kind requirement.
Fundamental Considerations
Proper Application of mist eliminators is based on understanding how they work. Vane and mesh devices both employ the same mechanism-known as inertial impaction and thus are subject to the same basic design rules. Fiber mist eliminators, however, capture submicron droplets (those smaller than one micron) by an entirely different phenomenon-known as Brownian motion-leading to very different behavior.
Vane assemblies are fabricated in sections sized to fit through vessel man ways. Generally they are supported on an annular ring welded to the vessel wall with additional mid span supports being required where the vessel diameter exceeds approx 900mm. Hold down bars should be fitted to cleats welded to the vessel wall to secure the pack. The principal applications for this style of droplet separator are the removal of coarse entrainment with high liquid load and also services of a fouling nature. For severe fouling duty e.g. containing dust, the unit could be installed together with a spray system designed to wash out collected solids.
Inertial Capture in VanesAs shown in Figure, vanes bend the path of mistladen gas into relatively tight curves. As the gas changes direction, inertia or momentum keeps mist droplets moving in straighter paths, and some strike adjacent vanes. There, they are held by surface forces and coalesce (merge) with other droplets, eventually trickling down. If the vane material is wettable, a surface film promotes coalescence and drainage. In the case of upward flow, coalesced liquid disengages from the bottom of the vanes as droplets large enough to fall through rising gas.
The liquid collected on the vanes drains downwards under gravity so long as the vapour velocity is not high enough to cause reentrainment. The relationship between vapour rate and the droplet size range which is effectively removed (typically 99% removal).
Mist Eliminator DesignThe design of vane mist eliminators depends on many factors, but a preliminary sizing can be undertaken relatively easily using proprietary K factors in the same way as for wire mesh demisters.
Face Area Although it should be treated with caution and confirmed with Sumit before actual use, the following
Vvme = K . { (ρL - ρV ) / ρV } 0.5 The disadvantage of using the more expensive, pocketed designs is that the pressure drop is higher. To estimate the pressure drop, the following method can be used:
ΔP = C . (ρL – ρV) . K* K
Removal of very small droplets can be achieved using a two stage mist eliminator by fitting a mesh pad to the upstream face of the unit to coalesce droplets as small as 4 to 5 microns into droplets in the size range which are easily removed by the vane separator.
Sumit has designed a range of mist eliminators for critical applications in the oil and gas sector, Standard Material of construction for the Sumit series are polypropylene & stainless steel and other materials can be manufactured upon request.
