Coalescer filter separators remove impurities from process fluid streams.

The process fluid can be a gas or a liquid.

You will use a liquid-liquid coalescer filter separator to remove particulate contaminants and separate two immiscible liquids with different densities.

The most common applications involve separation of water from a hydrocarbon such as oil and vice versa.

You can also use the coalesce separators for other types of liquids provided they do not mix.

Similarly, if the process fluid is a gas, then you will use a gas-liquid coalesce filter separator to remove solid and liquid impurities from the.

It subjects the mixture through a coalescing filter cartridge and a separator cartridge which removes the discontinuous phase (contaminant) from the continuous phase (process liquid).

Coalescing filter separator

The coalescer filter separator removes contaminants through a multi-stage process.

In the first stage, the fluid goes through the coalescing filter elements which filter from inside to outside.

The pressure pushes the fluid stream through the porous medium which restrains the solid particles within the cartridge

Emulsified water is broken down into extremely fine particles of water.

As the stream proceeds through the cartridge, the droplets reach the mesh intersections and stick.

They combine with more droplets to form large size drops which move to the outer sections of the cartridge.

 Coalescing filter element

The larger droplets are acted upon by the force of gravity which drains them to the sump located at the bottom of the housing.

In the second stage, the process fluid proceeds to the separator.

The separator cartridge is placed between the coalescing filter and the outlet to act like a screen which removes the tiny water droplets.

The droplets are too tiny to respond to the force of gravity within the short distance provided for within the filter unit.

Separation in the second stage occurs following an outside to inside flow through a medium constructed using a hydrophobic material.

The cartridges allow the fluid stream to pass while retaining the water or oil droplets in case of liquid-liquid separation.

They strip water off the stream through pore catchment mechanism which is aided by a combination of critical pore size and water repulsion.

The hydrophobic materials will repel the small droplets.

Some of the droplets tend to stick on the surface of the separator due to the drag force of the process fluid.

The coalescing effect of the separator cartridge or an additional mesh installed will help enlarge their sizes making them susceptible to force of gravity.

The separator provides additional backup to ensure sufficient filtration by acting as a secondary filter element, thus resulting in the highest degree of liquid removal.

A coalescer filter separator offers more benefits compared to the traditional coalescer filters.

Some of the benefits of using a coalescer filter separator include:

• Reduced cost of operations and maintenance
• The extended interval between element replacement
• Reduced downtime costs
• Faster cartridge replacement with minimal tools required
• Reduced risk of operator exposure to hazardous materials
• Guaranteed efficient filtration of submicron water particles

The coalescing filter separators are suitable for use in a wide range of sensitive process applications that need the removal of sub-micron liquid droplets.

They can be used in the following processes:

• Compression of natural gas
• Production of fertilizers
• Power generation
• Separation of air
• Petrochemicals
• Industrial steam filtration
• Production of liquefied natural gas
• Production of plastics
• Production of organic chemicals such as ethanol
• Refineries
• Oil production and spill recovery
• Water treatment plants
• Processing plants
• Compression of industrial gas

Parts of Coalescer filter separator

The coalescer filter separator consist of the following parts:

The inlet and outlet ports: Contaminated fluid stream enters the filter separator unit through the inlet port and clean process fluid exits through the outlet port.

The coalescer elements: Entraps the solid particles and droplets of liquid contaminants from the process fluid stream.

Sumps: This is the section of the housing vessel which holds the coarse solid contaminants and coalesced liquid.

Drain: The drain is located in the lower part of the housing vessel and is important for removing the coalesced water in the sump. The drains can be automatic or manual.

Mist extraction devices/separator element: They are responsible for removing the tiny droplets of coalesced water in the process gas or liquid stream through repulsion and preventing them from moving downstream.

Housing vessel: The filter housing holds all the components of the filter unit together.

Cyclone tube: This section is found in gas-liquid coalescer filter separators installed in applications with very high fluid contamination.

It will remove coarse solids and water particles at the inlet section of the filter through centrifugal force thus extending the service life of a filter.

Pressure relieve valve: It releases excess pressure inside the coalescer separator filter during filling of the filter.

Float control: It rides the interface between the two separated liquids and generates signals for automatic opening of valves to release liquids.

A good coalescer filter separator should possess the following features:

• Utilize multi-stage filtration and separation for removing the impurities in the process fluid
• Should meet all the quality standards and codes for the respective industries
• The design should support quick and easy access to filter elements for fast changeouts
• The materials should be resistant to corrosion
• Should support more fluid flow within a given house size
• The materials should support fluid filtration over a wide range of pH.
• The design should also have a wide operating temperature and pressure range
• Achieve maximum removal of solid and liquid impurities from the process fluid
• The filter elements should have a long service life
• High Beta rating
• Should leave the fluid with less than 5 mg/m³ residual liquid contaminants in the fluid stream

There are two different types of coalescing filter separator.

They include two-phase and three-phase coalescing filter separators.

Two-phase Coalescing Filter Separators

These coalescing filters separators remove contaminants from streams containing less 5% of the dispersed phase.

You can use them to clean process fluid in coming to or going to the storage tanks or streaming g from a primary separator, cooler or condenser.

The mean droplet size filtered by this type of a coalescer range from 100 to 300 microns.

In the first stage, the coalescing filter removes solid particles and larger liquid droplets.

In the second stage, also known as the settling stage, it goes through a separating media which ‘polishes’ the fluid stream before it leaves through the outlet.

Three-phase Coalescing Filter Separator

The device filters the incoming fluid stream into three phases including gas phase, light-phase liquid and heavy phase liquid.

These coalescence separators are common in oil and gas production applications or other process systems involving gas filtration.

The impurities in this device ingress the filter at a higher velocity due to the presence of a gas.

The high speed can result in the creation of small droplets as a result of turbulence in the inlet lines.

To reduce excessive turbulence and droplet formation, you can use a vane inlet to reduce momentum and remove the heavy solids and droplets in gas-liquid filtration.

Alternatively, you can force the fluid flow towards the upstream vessel head.

Installing turbulence separation place between separation side and inlet side will help reduce turbulence effects on the downstream separation media.

You can also use a cyclone separator on the inlet especially where the process fluid stream is highly contaminated with solid contaminants.

In the case of gas-liquid filtration, you can use a vane mist removers and a wire mesh to help coalesce the droplets faster.

In liquid-liquid separation, use a separator cartridge.

The lower end of the cartridge should be open to avoid plugging in case solid particles are present.

The gas-liquid interface Is maintained by a level control instruments.

An overflow baffle will set the liquid level on the interface between the light phase and heavy phase liquid on the settling region of the vessel.

The gas escapes through a vent line on top of the vessel while the heavy liquid leaves through a port located in the vessel bottom.

The lighter liquid exits the vessel through an overflow nozzle, all under interface control.

Coalescer filter separator mainly removes water and oil contaminants present in the process gas or liquid.

Coalescer filter

Water

Three types of water can be present in the process fluid.

They include:

Free water: This is the surplus water that remains after the process gas or liquid has dissolved water to full capacity. You will see free water inform of a haze when it surpasses 30 to 40 ppm.

Entrained/Emulsified water: This is discrete water that floats in the fluid stream. It comes as a result of condensation or other uses of water in the system.

Dissolved water: This type of water is mixed with the process fluid and is not visible. The quantity of dissolved water is proportional to water temperature and warmer fluids hold more dissolved water.

Oil

Oil can find its way into the water through different methods.

The viscosity of the oil should be low for efficient removal using coalescing filter separators.

There are different forms of oil found contaminating the process fluid.

They include free, solubilized, dispersed, molecularly dissolved, chemically emulsified, and suspended solids coated with oil.

 Coalescer filter separator system

A coalescing filter separator housing is one of the most critical components of a filter.

You can select the material of construction from a wide range of options available.

Some of the most widely used materials include:

• Stainless steel
• Carbon steel
• Aluminium
• Copper-nickel
• Monel
• Cast iron
• Nickel
• Chrome etc.

When selecting material for constructing the housing, ensure that you consider the following factors:

Chemical Properties of Process Fluid and Contaminants

The material of construction should be compatible with the process fluid and contaminants you are filtering out.

You can use stainless steel SS 316 for highly corrosive fluids since it has molybdenum which makes it highly resistant to corrosion.

Alternatively, you can coat a material which is readily corroded with a layer that is inert to the process fluid.

Working Conditions for the Application

You will need a strong material for the construction of filter housing where the process application is very harsh like in the natural gas mining industries.

Under such conditions, you should select a durable material with strong tensile strength.

High tensile carbon steel and stainless steel will offer viable options under such conditions.

Special Requirement of the Application

Some applications which require sanitary conditions have special cleanliness standards that the material has to adhere to.

Stainless steel is the best material choice when cleanliness is of primary concern.

In situations where the application requires lightweight filters, you can use aluminum.

However, this material can easily crack under unfavorable conditions and is also prone to corrosion.

Cost

The ownership cost of construction material is very important but should be a secondary consideration compared to efficiency.

Stainless steel always costs more compared to other materials but provides satisfying results.

When your process application is not very sensitive, then you select a less costly material that can meet all the filtration needs.

The service life of coalescing and separating cartridges in a coalescing filter separator depends on a lot of things.

However, the cartridges should not last more than a year under operation even when the changeout pressure differential has not reached.

Since the filter unit has two types of cartridges, that is, the coalescing cartridge and separator cartridge, you can use different materials for construction.

 Coalescing filtration system

Coalescing Filter Media

The coalescing filter media can be synthetic or natural.

The media of a coalescing filter uses hydrophilic (water-loving) in case of removing water droplets and oleophilic (oil-loving) in case of coalescing oil droplets.

Some of the common examples of hydrophilic materials are fiberglass and stainless steel while oleophilic materials include polypropylene and fluoropolymers.

You can also use cellulose which Is a natural material.

You can use nylon to make a coalescing filter for removing water, amine and caustic from hydrocarbons and removing water from strong solvents.

For gas-liquid coalescing filter separators, you can use fiberglass, nylon, polyester and stainless steel.

Separator Filter Media

The material for making the separator media will vary depending on the type of contaminant you want to

The materials should be repellant to the impurities being removed.

Separation of water will require the use of a hydrophobic material while that of oil should be oleophobic.

Some of the hydrophobic materials which you can use to construct a separator for repelling water droplets include:

Teflon Coated Fine Mesh

This is the most common type of and highly preferred in most applications.

It is more suitable for jet fuel filtration because it generates less static charges compared to other types of the filter medium.

The main advantage of using Teflon coated cartridges is the ability to reuse them with constant inspection and cleaning.

Pleated Paper Cartridges

You will use these filter cartridges once and then dispose of.

Consequently, they are suitable for use in fluids which possess materials that stick to the elements and cannot be removed.

Synthetic Media

You can use a uniquely woven synthetic material as the filter medium.

Usually, you can clean them for several cycles before they outlive their usefulness.

You can also consider a siliconized paper cartridge.

You can either select a vertical or horizontal coalesce filter separator.

The choice of the design will depend on the preference for ground space or volume of filtration.

When deciding on the right size, you should be able to answer the basic questions such as:

Coalescing filtration system

The Efficiency of Filtration targeted

The efficiency of filtration depends on the condition of incoming processes fluid and the output fluid.

Usually, an oversized filtration unit gives better results in cases where the incoming fluid stream is highly contaminated.

Frequency of Element Replacement

When using smaller filters, you will need to conduct frequent filter element change out compared to larges size filters.

Even though the initial unit cost of a smaller filter cartridge may be low, cumulative costs associated with purchase and replacement are much higher.

This is compared to that of larger filters in the long run.

Similarly, your application process may also not support frequent opening and filter change-outs without incurring considerable downtime losses.

The Operating Flow Rate

The size of a filter is directly proportional to the process application flow rate.

An application that has a higher fluid flow rate requires bigger filters that can withstand the process requirements.

Cost

You should take an insightful consideration into the operational cost of a filter when the cost is of primary concern. ­­­­

Include the costs associated with purchase, installation, change out, labor and other miscellaneous costs associated with the use of the filter.

The performance of a coalescence filter separator depends on the following factors:

• The type of solid and liquid contaminants
• The size of particles and droplets
• The dirt levels in the incoming process fluid
• The size of the filter and dirt holding capacity of the filter elements
• The operating conditions, that is, operating temperature, pressure and flow rates
• Physical properties and chemical compatibility of the filtration media
• The rating of the coalescing and separation cartridges

The coalescer filter separators are rated using an absolute rating or Beta rating.

The absolute rating indicates the ability of the coalescing filter separator to filter out particles of a given size.

On the other hand, the Beta ratio rating gives the ability of the filter to remove a given percentage of a particular size of contaminant from the fluid stream.

The coalescing filter separator is produced under ISO standards 9001: 2015 which encompasses quality management systems.

However, different industries have different ISO standards that specify the cleanliness levels expected from the final process fluid after filtration.

Other than ISO, the manufacture and use of coalescer filter separator should adhere to the following industry standards:

• ASME Code Section VIII, Div.1
• API 12J
• NACE MR0175
• PED
• CE
• UL, Exp
• ANSI B31.3 Class M (H2S)
• API 6A, API 6D

Yes, you can clean and reuse coalescer and separator cartridges which are cleanable.

However, ensure that you check the instructions provided on the cartridges to confirm if they are cleanable.

Usually, pleated paper elements are not cleanable while synthetic media cartridges can be cleaned.

Ensure that drains are manually emptied daily to avoid any system shutdown.

Though automatic drains can be less laborious to use, they can also fail and lead to stoppage of the process application.

Conduct regular monitoring of the pressure differential gauge and monitor the readings daily.

Change the coalescer elements as soon as pressure drop signals.

Clean the housing using the recommended solutions every time you are conducting element replacement and also clean the separator cartridges during the process.

When using a Teflon coated screen separator filters, ensure that you maintain them as follows:

• Inspect for damage, test and clean the separator cartridges according to the manufactures recommendation at each coalescence filter change out
• Hold the cartridge at an angle and pour water onto the surface at no more than three inches from the separator surface.

Confirm, that it forms a bead and rolls off the surface for a proper functioning filter.

However, in case of wetting of the separator cartridge, then it has failed the water test and not fit for installation. Clean the separator and try again.

• Avoid touching the surface of the separator cartridge with your bare and after cleaning it. You can clean and dry poly-bag to hold it and reinstall after it is dry.

 Coalescer filter separator system

You should replace the coalesce filter cartridges when they reach the pressure differentials recommended by the filter manufacture.

However, you should not use an element for more than one year even if it has not reached its full-service life.

You should also replace or clean the separator cartridge when changing the coalescing elements.

Similar to coalescing filter elements, ensure that you replace the separator cartridges at least once per year.

In short, once you consider everything mentioned in this guide, you will get high quality and reliable Coalescer filter separator.

At FilSon Filters, we can help you get the best Coalescer filter separator at affordable prices.