Gas Coalescers


KASRAVAND gas coalescers are designed for liquid mist and aerosol removal. Typical coalescer applications include desiccant bed protection, compressor lube oil discharge removal, feed gas filtration, process liquid reclaiming, and general low surface tension mist removal. Standard design includes filter elements, KASRAVAND full diameter quick opening closure, stilling screen and outlet baffle. Units are designed and constructed in accordance with all major design codes.

 The coalescer cartridge is usually made from glass fiber media that is supported by a metal core and contains a much finer pore size and larger surface area as compared to mesh pads or vane separators. The fine pore size allows for a different mechanism of separation for the coalescers. The coalescers are able to intercept the aerosol droplets by direct interception (sieving) as well as by the method of diffusional interception. Separation by the diffusion mechanism is caused by the random (Brownian) motion of the fine aerosol droplets that increase the probability of collision with coalescer fibers. The diffusional interception and direct interception differ from inertial impaction in that as the gas flow rate is decreased, the removal efficiency increases and, therefore, provides for a high turn down ratio. Properly designed high efficiency liquid-gas coalescers can provide separation of aerosols as low as 0.1 μm

Gas coalescers is a unique two-stage filtering concept for use on air and gas streams requiring both solids and liquids removal. By combining the principals of impingement baffling with the most efficient filtration and coalescing cartridge designs, they will remove virtually all entrained water and hydrocarbons in free, fog or mist form. Any solids larger than one micrometer will be removed from the stream at the same time. The flow enters the inlet where the impingement baffle removes solids and some entrained liquids, they collect in the quiescent sump. Mist and minute solids flow up to the coalescer cartridges where the oil and water are coalesced and the solids removed. The flow through the coalescer cartridge is inside to outside. Solids remain in the coalescer cartridges and coalesced water and oil fall by gravity to the cartridge mounting plate. The stream then flows through the centre pipe to the outlet of the vessel. Result: a clean and dry gas! 

Gas-liquid filter separators 

Gas-liquid filter separators are designed for the removal of liquids and solids from pressurised gas. 

The GC series filter separators are provided with a two-stage filtration and separation system: 

  1. A baffle system for the removal of slugs, large droplets and large solids particles.
  2. A filter/coalescer system for the removal of fine solids particles and droplets. 

Baffle plate separation 

Removal of large droplets. Slugs of liquid and course solids particles is accomplished by providing obstacles in the form of baffle plates in the gas stream entering the filter separator. The density of liquid droplets and solids particles is more than 25 times higher than the density of compressed gas. Baffle plates create sudden turns in the gas flow direction. Due to their momentum droplets and particles are propelled from the gas stream and collide with the baffle plates. The droplets coalesce on the baffle plates to form a liquid film and the liquid film on the baffle plates captures solids particles. The film flows downwards and the liquid falls into the flow-free collecting area, carrying the separated solids particles.

Filter/coalescer system 

After passing through the baffle system the gas flows through the coalescers from inside to outside. Due to the increasing diameter the flow velocity is reduced while the gas moves through the coalescing layers. This enhances the growth of the droplets and provides the possibility of droplet settling under gravity.
The coalescer element is provided with a pleated filtration section for the efficient removal of solids particles. The filtration layer also prevents fouling of the coalescing layers which cases reduced separating efficiency. The pleated filtration stage offers an extended surface area for a good solids holding capability. 

The coalescing layer of the coalescer element provides two functions: 

  1. Structural strength of the element to withstand the differential pressure occurring over the filtration layer as a result of the solids removal. Since the strength is an integrated function of the coalescing layer the coalescing media have 100% free flow area available for efficient coalescence, compared to less than 50% in coalescing elements provided with perforated metal support tubes.
  2. Coalescence by means of ultra fine treated fibreglass. Tiny liquid droplets attach temporarily to the fibres allowing the droplets to meet and coalesce into larger droplets. On the outside of the coalescing element the droplets drain to the liquid collecting area along the drain sock fitted on the outside of the element. 

After the coalescer the gas is clean and dry. The gas proceeds to the top of the vessel. The lid of the vessel is provided with a curved head to guide the gas to the internal outlet piping. This piping extends to the outlet connection located inline with the inlet connection in the lower part of the vessel. 

Level control systems 

The separated liquid is collected in the flow-free collecting area in the bottom of the vessel and the flow-free collecting area on top of the filter plate (below the coalescing elements). Both areas are provided with a level control system consisting off: 

  • Magnetic level gauge equipped with magnetic local indicator and two potential free contacts (SPDT) for high level and low level alarm.
  • Vibrating type level controllers for high level and low level signal (to be used for automatic draining purposes). 

Differential pressure transmitter 

To measure the differential pressure over the filter separator a differential pressure transmitter is mounted, provided with a manifold for isolation and testing of the instrument.