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A coalescer is a device which induces coalescence in a medium. They are primarily used to separate emulsions into their components via various processes, operating in reverse to an emulsifier.
Coalescers are of two main types: mechanical and electrostatic. Mechanical coalescers use filters or baffles to make droplets coalesce, while electrostatic coalescers use DC or AC electric fields (or combinations).
Mechanical coalescers, which are the more common type of coalescers, operate by physically altering a droplet by mechanical means. They are commonly applied in the global oil and gas industries for the removal of water or hydrocarbon condensate. While coalescers by definition function as a separation tool for liquids, they are also used, and mistakenly referred to, as filters.
In the area of compressed air purification, coalescing filters are used to separate liquid water and oil from compressed air using a coalescing effect. Coalescence (physics) shows how coalescing filters operating at lower temperatures and high pressures work better. [1] These filters additionally remove particles. The most commonly used media in this case is borosilicate micro-fiber.
In the Oil and Gas, Petrochemical and Oil Refining industries, liquid-gas coalescers are widely used to remove water and hydrocarbon liquids to less than 0.011 mW (plus particulate matter to less than 0.3 μm in size) from natural gas to ensure natural gas quality and protect downstream equipment such as compressors, gas turbines, amine or glycol absorbers, molecular sieves, PSA's, metering stations, mercury guard beds, gas fired heaters or furnaces, heat exchangers or gas-gas purification membranes.
In the natural gas industry, gas/liquid coalescers are used for recovery of lube oil downstream of a compressor. All liquids will be removed but lube oil recovery is the primary reason for installing a coalescer on the outlet of a compressor. Liquids from upstream of the compressor, which may include aerosol particles, entrained liquids or large volumes of liquids called "slugs" and which may be water and/or a combination of hydrocarbon liquids should be removed by a filter/coalescing vessel located upstream of the compressor. Efficiencies of gas/liquid coalescers are typically 0.3 μm (0.3 micron) liquid particles, with efficiencies to 99.98%.
Liquid-liquid coalescers can also be used to separate hydrocarbons from water phases such as oil removal from produced water. They have been also used in pyrolysis gasoline (benzene) removal from quench water in ethylene plants, although in this application, the constant changing of cartridges can lead to operator exposure to BTX (benzene, toluene and xylene), as well as disposal issues and high operating costs from frequent replacement.
Electrostatic coalescers use electrical fields to induce droplet coalescence in water-in-crude-oil emulsions to increase the droplet size. The squared dependence of droplet diameter in Stokes' law, increase the settling speed and destabilizes the emulsion. The effects on the water droplet arise from the very different dielectric properties of the conductive water droplets dispersed in the insulating oil. Water droplets have a permittivity that is much higher than the surrounding oil. Furthermore, water with dissolved salt is also a very good conductor. When an uncharged droplet is subjected to an AC electric field, the field will polarize the droplet, creating an electric field around the droplet to counteract the external field. As the water droplet is very conductive, the induced charges will reside on the surface. The droplet has no net charge but one positive and one negative side. Inside the droplet, the electric field is zero. When two droplets with induced dipoles get close to each other, they will experience a force pulling the droplets closer until they coalesce.
In oil production, co-produced water is mixed with the oil in choke valves and process equipment producing water-in-oil emulsions. The amount of water increases during the production life of the reservoir. The emulsions are destabilized using gravitational separators, and the settling rates are increased by applying heat, demulsifiers, and AC electric fields. The AC electric field gives rise to attractive forces between water droplets and increases the probability of coalescence at contact. According to Stokes' law, the settling rate increases proportionally with the square of the drop diameter. By promoting coalescence of small water droplets, the settling rate can be greatly increased. The water content is normally reduced to less than 0.5 vol% if this is the final treatment stage before the crude oil is exported.
Typical electrostatic coalescers are large settling tanks containing electrodes and operate under laminar-flow conditions with bare electrodes that may be vulnerable to short circuiting. An alternative to this type of coalescer is a flow through pre-coalescer that is installed upstream in a separator tank. In the Compact Electrostatic Coalescer, [2] droplet coalescence is achieved by applying AC electric fields (50–60 Hz) to water-in-oil emulsions under turbulent-flow conditions. The turbulence increases the collision frequency between the water drops. The electrodes are insulated to prevent short circuiting, and permit water contents of up to 40% as well as water slugs. The equipment is a separate flow-through electrostatic treatment section installed upstream of a gravity separator to improve the performance. By keeping the treatment and settling sections separate, a compact electrostatic coalescer can be obtained that can also be retrofitted.
Liquid-liquid coalescers are also widely used in the oil refining industry to remove the last traces of contaminants like amine or caustic from intermediate products in oil refineries, and also for the last stage dewatering of final products like kerosene (jet fuel), LPG, gasoline and diesel to less than 15 mW free water in the hydrocarbon phase. These coalescers are often electrostatic type, in which a DC electrical field encourages the water droplets to coalesce, thus settling by gravity.
A diving air compressor is a breathing air compressor that can provide breathing air directly to a surface-supplied diver, or fill diving cylinders with high-pressure air pure enough to be used as a hyperbaric breathing gas. A low pressure diving air compressor usually has a delivery pressure of up to 30 bar, which is regulated to suit the depth of the dive. A high pressure diving compressor has a delivery pressure which is usually over 150 bar, and is commonly between 200 and 300 bar. The pressure is limited by an overpressure valve which may be adjustable.
Natural-gas condensate, also called natural gas liquids, is a low-density mixture of hydrocarbon liquids that are present as gaseous components in the raw natural gas produced from many natural gas fields. Some gas species within the raw natural gas will condense to a liquid state if the temperature is reduced to below the hydrocarbon dew point temperature at a set pressure.
An electrostatic precipitator (ESP) is a filterless device that removes fine particles, such as dust and smoke, from a flowing gas using the force of an induced electrostatic charge minimally impeding the flow of gases through the unit.
Electrocoagulation (EC) is a technique used for wastewater treatment, wash water treatment, industrially processed water, and medical treatment. Electrocoagulation has become a rapidly growing area of wastewater treatment due to its ability to remove contaminants that are generally more difficult to remove by filtration or chemical treatment systems, such as emulsified oil, total petroleum hydrocarbons, refractory organics, suspended solids, and heavy metals. There are many brands of electrocoagulation devices available, and they can range in complexity from a simple anode and cathode to much more complex devices with control over electrode potentials, passivation, anode consumption, cell REDOX potentials as well as the introduction of ultrasonic sound, ultraviolet light and a range of gases and reactants to achieve so-called Advanced Oxidation Processes for refractory or recalcitrant organic substances.
A dust collector is a system used to enhance the quality of air released from industrial and commercial processes by collecting dust and other impurities from air or gas. Designed to handle high-volume dust loads, a dust collector system consists of a blower, dust filter, a filter-cleaning system, and a dust receptacle or dust removal system. It is distinguished from air purifiers, which use disposable filters to remove dust.
A turboexpander, also referred to as a turbo-expander or an expansion turbine, is a centrifugal or axial-flow turbine, through which a high-pressure gas is expanded to produce work that is often used to drive a compressor or generator.
A desalter is a process unit in an oil refinery that removes salt from the crude oil. The salt is dissolved in the water in the crude oil, not in the crude oil itself. The desalting is usually the first process in crude oil refining. The salt content after the desalter is usually measured in PTB – pounds of salt per thousand barrels of crude oil. Another specification is Basic sediment and water.
An oily water separator (OWS) (marine) is a piece of equipment specific to the shipping or marine industry. It is used to separate oil and water mixtures into their separate components. This page refers exclusively to oily water separators aboard marine vessels. They are found on board ships where they are used to separate oil from oily waste water such as bilge water before the waste water is discharged into the environment. These discharges of waste water must comply with the requirements laid out in Marpol 73/78.
The Schiehallion oilfield is a deepwater offshore oilfield approximately 175 kilometres (110 mi) west of the Shetland Islands in the North Atlantic Ocean. The Schiehallion and adjacent Loyal field were jointly developed by BP on behalf of the Schiehallion field partners; BP, Shell, Amerada Hess, Murphy Oil, Statoil and OMV, and the Loyal field partners; BP and Shell.
An oil production plant is a facility which processes production fluids from oil wells in order to separate out key components and prepare them for export. Typical oil well production fluids are a mixture of oil, gas and produced water. An oil production plant is distinct from an oil depot, which does not have processing facilities.
The term separator in oilfield terminology designates a pressure vessel used for separating well fluids produced from oil and gas wells into gaseous and liquid components. A separator for petroleum production is a large vessel designed to separate production fluids into their constituent components of oil, gas and water. A separating vessel may be referred to in the following ways: Oil and gas separator, Separator, Stage separator, Trap, Knockout vessel, Flash chamber, Expansion separator or expansion vessel, Scrubber, Filter. These separating vessels are normally used on a producing lease or platform near the wellhead, manifold, or tank battery to separate fluids produced from oil and gas wells into oil and gas or liquid and gas. An oil and gas separator generally includes the following essential components and features:
An API oil–water separator is a device designed to separate gross amounts of oil and suspended solids from industrial wastewater produced at oil refineries, petrochemical plants, chemical plants, natural gas processing plants and other industrial oily water sources. The API separator is a gravity separation device designed by using Stokes Law to define the rise velocity of oil droplets based on their density and size. The design is based on the specific gravity difference between the oil and the wastewater because that difference is much smaller than the specific gravity difference between the suspended solids and water. The suspended solids settles to the bottom of the separator as a sediment layer, the oil rises to top of the separator and the cleansed wastewater is the middle layer between the oil layer and the solids.
In chemical engineering, a vapor–liquid separator is a device used to separate a vapor–liquid mixture into its constituent phases. It can be a vertical or horizontal vessel, and can act as a 2-phase or 3-phase separator.
The Douglas Complex is a 54-metre (177 ft) high system of three linked platforms in the Irish Sea, 24 kilometres (15 mi) off the North Wales coast. The Douglas oil field was discovered in 1990, and production commenced in 1996. Now operated by Eni, the complex consists of the wellhead platform, which drills into the seabed, a processing platform, which separates oil, gas and water, and thirdly an accommodation platform, which is composed of living quarters for the crew. This accommodation module was formerly the Morecambe Flame jack-up drilling rig.
A centrifugal water–oil separator, centrifugal oil–water separator or centrifugal liquid–liquid separator is a device designed to separate oil and water by centrifugation. It generally contains a cylindrical container that rotates inside a larger stationary container. The denser liquid, usually water, accumulates at the periphery of the rotating container and is collected from the side of the device, whereas the less dense liquid, usually oil, accumulates at the rotation axis and is collected from the center.
A separation process is a method that converts a mixture or a solution of chemical substances into two or more distinct product mixtures, a scientific process of separating two or more substances in order to obtain purity. At least one product mixture from the separation is enriched in one or more of the source mixture's constituents. In some cases, a separation may fully divide the mixture into pure constituents. Separations exploit differences in chemical properties or physical properties between the constituents of a mixture.
A conical plate centrifuge is a type of centrifuge that has a series of conical discs which provides a parallel configuration of centrifugation spaces.
Electrohydrodynamic droplet deformation is a phenomenon that occurs when liquid droplets suspended in a second immiscible liquid are exposed to an oscillating electric field. Under these conditions, the droplet will periodically deform between prolate and oblate ellipsoidal shapes. The characteristic frequency and magnitude of the deformation is determined by a balance of electrodynamic, hydrodynamic, and capillary stresses acting on the droplet interface. This phenomenon has been studied extensively both mathematically and experimentally because of the complex fluid dynamics that occur. Characterization and modulation of electrodynamic droplet deformation is of particular interest for engineering applications because of the growing need to improve the performance of complex industrial processes(e.g. two-phase cooling, crude oil demulsification). The primary advantage of using oscillatory droplet deformation to improve these engineering processes is that the phenomenon does not require sophisticated machinery or the introduction of heat sources. This effectively means that improving performance via oscillatory droplet deformation is simple and in no way diminishes the effectiveness of the existing engineering system.
An oil water separator (OWS) is a piece of equipment used to separate oil and water mixtures into their separate components. There are many different types of oil-water separator. Each has different oil separation capability and are used in different industries. Oil water separators are designed and selected after consideration of oil separation performance parameters and life cycle cost considerations. "Oil" can be taken to mean mineral, vegetable and animal oils, and the many different hydrocarbons.
Compressed air dryers are special types of filter systems that are specifically designed to remove the water that is inherent in compressed air. The compression of air raises its temperature and concentrates atmospheric contaminants, primarily water vapor, as resulting in air with elevated temperature and 100% relative humidity. As the compressed air cools down, water vapor condenses into the tank(s), pipes, hoses and tools connected downstream from the compressor which may be damaging. Therefore water vapor is removed from compressed air to prevent condensation from occurring and to prevent moisture from interfering in sensitive industrial processes.