Liquid purification or separation – Diverse distinct separators – Including a filter
Patent
1992-11-12
1995-10-03
Dawson, Robert A.
Liquid purification or separation
Diverse distinct separators
Including a filter
210338, 2104931, 2104973, 210DIG5, B01D 2958
Patent
active
054549450
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the coalescing art, and specifically to an improved coalescing filter element which may be used in virtually any coalescing filter assembly. More particularly, the invention relates to a coalescing filter element used in separating liquid droplets from gases or other liquids, and having a conical configuration. The conical configuration allows for lower velocity of the primary phase fluid in the area between the outside surface of the coalescing element or elements and the filter assembly inner wall, thereby reducing the maximum droplet diameter which may be supported by or reentrained in the primary phase fluid. This allows for more efficient separation of the coalesced droplets from the primary phase fluid. It also allows for lower pressure drop through the coalescing filter elements.
2. Description of the Prior Art
The need to separate liquid droplets from gases or other liquids is long standing in the art. Common liquids found in air and gas streams include lube oils, water, salt water, acids, caustics, hydrocarbons, completion fluids, glycol and amine. The liquid normally is present in the form of tiny droplets, or aerosols. The size distribution of the aerosols is primarily dependent on the surface tension of the liquid contaminant and the process from which they are generated. As the surface tension is reduced, the size of the aerosol is reduced accordingly. This is because the intermolecular cohesive forces (the forces which attract the surface molecules of an aerosol inward in order to minimize surface area with respect to volume) are weaker.
It has been found that greater than 50% of all oil aerosols by weight are less than 1 micrometer in diameter. Due to their similar surface tensions, the same holds true for glycols, amines and hydrocarbons. Conventional filtration/separation equipment such as settling chambers, wire mesh (impingement) separators, centrifugal or vane (mechanical) separators and coarse glass or cellulose filters are only marginally efficient at 1 micrometer, and remove virtually none of the prevalent sub-micrometer aerosols and particles. In order to remove these problem-causing contaminants, high efficiency coalescing filters must be used.
All previous coalescing filters and coalescing elements of the type with which the present invention is concerned are configured in a tubular or cylindrical arrangement, and used to flow in to out or, from out to in. While it is advantageous to flow from out to in for many filter applications, there is also a definite advantage for flowing in to out for the coalescing of liquid droplets and aerosols from gases, or the coalescing of two immiscible liquid phases.
In these applications, it is common to use coalescing elements secured within a pressure-containing vessel or housing to form a coalescing filter assembly. The continuous phase gas or liquid contains dispersed liquid aerosol droplets, sometimes referred to as the discontinuous phase. The mixture enters the assembly through an inlet connection and then flows to the inside of the coalescing element. As the fluid flows through the filter media of the coalescing element, the liquid droplets come in contact with the fibers in the media and are removed from the fluid stream. Within the media, the droplets coalesce with other droplets and grow to emerge as large droplets on the downstream surface of the element which are capable of being gravitationally separated from the continuous phase fluid. If the density of the droplets is greater than that of the fluid, such as oil droplets in air, the droplets will settle gravitationally to the bottom of the filter assembly, countercurrent to the upward flow of air. If the density of the droplets is less than that of the fluid, such as oil droplets in water, the droplets will rise to the top of the assembly countercurrent to the downward flow of the water.
The droplet size, droplet density, fluid viscosity, and fluid density will determine how rapidly the droplet
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Dawson Robert A.
Porous Media Corporation
Walker W. L.
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