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Filtration processes

Hydro-mechanical processes

1. Coalescers

Are designed for treatment of liquid and gaseous medias and separation of solid and liquid contaminants from the process stream. Separation of liquid contaminants in coalescers is effected due to the ability of filter-element to coalesce (accumulate) liquid aerosol particles of fine diameter (starting from 0,3 micron) into larger droplets and to drain these droplets into the sump system. Models VGC – gas and SW and V – liquid coalescers separate various liquid contaminants from hydrocarbon flow, simultaneously catching solid particles of micron size.

Coalescing cartridges are worked out for liquid and gaseous media processing, where fine treatment is required. In general, filtration process is realized due to the following mechanisms of particles capture: contacting, sieving, acceleration capture, gravitation and diffusion sedimentation, electrostatic interaction.

Captured inside the filtration material and accumulated on filtration material surface particles serve for newly coming particles as complex element of filtration media and improve filtration efficiency. As particles quantity increase, gas permeability of filtration media goes down, thus filter cartridges have to be replaced. In case only liquid contaminants are captured, filter operates with a permanent resistance in self-regeneration mode.

Superfine mist of lubes or moisture, contained in gas, is captured due to movement of the stream around the structural obstacles of pore layer. As filtered flow goes thru several layers of filtration material with further increase of pore diameter, mist particles reach droplet size and move inside the layer from inside down under gravitation force. Depending upon separation efficiency required, Omni Technologies equips its filters-coalescers with filter cartridges of necessary configuration and efficiency parameters.

2. Centrifugal filtration

Separation systems with multicyclone elements are designed for separation both of liquid and solid contaminants from gas, air or vapor flows and have the following advantages: absence of moving parts, reliable operation under the temperature up to 500 °С, high efficiency, stable pressure drop value, simple maintenance and wide range of application.

Major property of design – installation of cyclone tubes section, fixed between two tube sheets. Gas enters the cyclone section and then enters each tube, where fast spinning and gravity force move contaminants (both solid and liquid) from inside the tube to its outer wall. Further on the contaminants under gravity influence move to the bottom sump and then are forced out by the operator or automatically. Clear gas passes through gas nozzles, located at the upper tube sheet and then leaves the vessel.

3. Inertial-centrifugal filtration

LCK® side-stream separation system

This gas purification system incorporates two methods of filtration: inertial filtration in the stage side-stream separator and centrifugal filtration in vortex tube of the liquid collection section.

 

Description and operation principle

First stage of filtration – side-stream separator

Key feature of the separator is a stage separation device inside the body, integrated in the concentrator (2).

The gas flow comes into the separator and through the venturi pipe (1) gets to the concentrator. Inside the concentrator the incoming contaminated gas flow divides into two flows: the cleaned main flow and the secondary flow. The secondary flow with solids is separated from the main flow and funneled to sedimentation tank.

Going between the lamellas inside the separation unit, the main flow changes its direction several times. With that solid and liquid particles (aerosols) with low surface tension (<50-60 mN/m – glycols, corrosion inhibitor, hydrocarbons and oils) collide with the lamellas and jump off into the secondary gas flow. On the contrary, liquid particles and aerosols with high surface tension (>50-60 mN/m – water, oils, condensate, tars) coalesce when hitting the lamellas and go adrift until the edge of lamellas as the main flow passes through the separator. After that the main flow with the coalesced particles goes to the liquid collection section.

The secondary flow in which solids and liquids are concentrated adds up to 10% of the main flow. As going through the concentrator, the secondary flow is gradually separated from the main flow, and then it goes to the sedimentation tank through the drain pipe (3). Due to the low gas velocity, solid particles and liquid droplets with low surface tension get separated from the flow and sediment in the first section of the sedimentation tank.

Passing through the second section of the sedimentation tank the secondary flow hits the lamellas (4) that deflect the stream, providing a better sedimentation of particles inside the vessel.

The cleaned secondary flow that might carry leftover particles goes through the outlet nozzle of the sedimentation tank (5) and comes back to the side-stream separator via pipe (6). Recycling of the secondary flow into the main flow happens due to the venturi pipe’s diffusor, which causes pressure loss at the inlet and consequently provides velocity and flow rate increase. After that the combined gas flow passes through the concentrator once again.

Second stage of filtration – Liquid collection section

After the first stage the main gas flow with coalesced liquid particles comes into the liquid separator where it accelerates tangentially due to the vortex (7) fixed inside the separator body. With that the coalesced aerosol particles start circulating near the vortex lamellas and by centrifugal force get thrown off to the separator body internal surface. The separated aerosol particles pass through chuting system set inside the perforated pipe (8) and are removed to the sump via the drain pipe (9).

After that the cleaned gas flow passes through the vortex’s outlet blade system where a gas current free from swirls/rips takes shape. The gas flow completely cleaned from liquid droplets and solid particles goes inside the outlet nozzle of the liquid collection section.

LCK® side-stream separation system advantages:

  1. A compact design provides a relatively easy installation within the existing pipeline.
  2. Sedimentation vessels can be cleaned without the system shutdown.
  3. High fineness of filtration of fractions over a wide operational range.
  4. Filtration efficiency comparable with that of a quality cartridge filters.
  5. Due to automated self-cleaning feature, the system does not require maintenance over a long period of time.
  6. Relatively low pressure loss inside the system depends solely on media density and flow rate.

The advanced side-stream separator system design is especially effective for filtration of self-ignite media.

 

Mass exchanging processes

1. Separators with punched pleated elements.

For fine treatment of natural and process gas downstream standard dust filters of casual type, for the second stage of filtration genuine filters –separators with pleated punched elements and standard filter elements have been designed.

Such filter-separator consists of:

  • “inertia-based” pre-separation unit to separate both liquids and solids from gas flow;
  • contaminants filtration and liquid contaminants coalescing unit;
  • fine separation of colloid solvent.

Most significant difference between such vessels and other filter-separators is in the vector of the gas flow, leaving filter elements. In filter separator with a casual flow vector, dust and coalesced droplets may be partially splintered and taken back to the collector tube by accelerated gas flow. Then these contaminants reach the second stage, where wire mesh of vanes are usually installed, drops and particles sized less than 8-10 microns are not fully caught, therefore some contaminants leave separator together with gas.

We offer the unit where gas first goes through separation section (pre-separation unit), than through the sections with filter elements, and then through the section with punched pleated elements, designed for low velocity flow. Such filter separates almost all dust and mist, as well as free liquid and coalesced particles.

Function of the second section is based on absorption mechanism, where two phases-liquid and solid are in one and the same process.

When absorbent is moved into the inlet nozzle, separation and interaction (mass-exchanging process) of absorbent and gas flow occur. Gas/liquid mass exchange proceeds on the surface of a punch element in “film mode”.

Punch elements are structurally oriented. Plates corrugation, riffling and application of bended elements assist turbulization of liquid film and increase the contact surface.

Such structural design allows to separate fully solid and liquid contaminants from gas flow and to drain free water and coalesced particles. Gas treatment process efficiency is reached due to increase of capturing ability of the punch element and improvement of captured liquid drain conditions.

Punch elements are also used for dehydration of natural and oil gas by liquid sorbents, as well as for water glycol solutes regeneration.