Gas separation: processes – Filtering – With cleaning of filter
Reexamination Certificate
1999-05-20
2001-05-29
Smith, Duane (Department: 1724)
Gas separation: processes
Filtering
With cleaning of filter
C095S286000, C055S304000, C055S484000, C055S523000, C055SDIG001, C055SDIG007
Reexamination Certificate
active
06238464
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of separators and more specifically to means intended to separate droplets or particles from a gaseous flow, whose size is less than or of the order of one micrometer.
BACKGROUND OF THE INVENTION
Many methods and devices have already been disclosed to that end.
U.S. Pat. No. 5,626,651 describes a process and a system of that type according to which the turbulent gas stream flows above a series of plates defining non turbulent zones where the particles are collected. More precisely, the plates are parallel to each other and vertical. A filtering means made of fibers can also be provided between said plates in order to improve filtration notably of the finer particles.
International patent application WO-95/28,217 describes a device based on the same principle, but according to which the plates are provided with slots or replaced by grates. Frames covered with wire mesh containing a fibrous mat are also used in this prior art.
Furthermore, patent application WO-97/00,102 relates to a separator placed at the exhaust of diesel engines in order to collect the particles contained in the exhaust gas. A honeycomb structure pierced with channels perpendicular to the opening of the honeycomb cells is preferably provided. The porosity of such a structure is of the order of 70%. However, this device cannot be used for fogs because the droplets trapped in the cells cannot be removed by drainage.
International patent application PCT/FR-97/00,164 relating to a separator with one or more vertical drains laterally delimited by fibrous corrugated elements is also known. An agglomerator is also necessarily placed upstream from the separator in order to have larger particles that can be separated at the level of the separator. This is therefore relatively expensive and implies quite significant pressure drops.
However, these well-known means do not allow effective collection and removal of particles and/or droplets smaller than about one micrometer. In U.S. Pat. No. 5,626,651, the particles captured accumulate on the walls, then fall onto the bottom of the device under the effect of gravity. Means intended to shake the walls are often necessary to cause the particles accumulated on the walls to fall. This device poses problems when very fine particles smaller than one micrometer are to be separated. In fact, in this case, the height of the drain must be very limited and the plates must therefore be very high so that the equipment is very bulky for a very small section of flow. The same problem exists in the device according to document WO-95/128,217.
In patent application WO-97/00,102, the particles collected are oxidized.
SUMMARY OF THE INVENTION
The present invention proposes to solve the particle and/or droplet removal problem in an original and unexpected way as explained hereafter.
The present invention advantageously prevents any pressure drop due to the fouling of a zone of the device; the pressure drop remains constant throughout the life of the separator according to the invention.
Furthermore, the present invention allows to obtain a very high separation rate by means of a small equipment with a low pressure loss and continuous running.
The present invention thus relates to a spongy type separator intended to process gas streams containing liquid or solid particles substantially smaller than one micrometer or of the order of one micrometer.
According to the invention, the separator is made of a reticulated foam pierced with channels intended for turbulent flow of the gas streams, said channels being such that the gas streams flow through said foam from one end of the channels to the other.
The porosity of said foam specifically ranges between 90% and 98%, preferably around 97%.
Besides, the size of the cells forming said foam ranges between about 0.5 mm and about 5 mm.
In particular, the diameter of the threads forming said foam ranges between 50 &mgr;m and 1000 &mgr;m.
According to the invention, the diameter of the channels running through said foam ranges between 3 and 100 mm.
According to an aspect of the invention, said foam is made of reticulated polyurethane.
According to another embodiment of the invention, said reticulated foam is made of a vitreous carbon; said foam can also be made from a metal such as aluminium, nickel or lead.
The device can further comprise a means for shaking said foam so as to cause the particles retained in the foam to fall.
According to a preferred use of the invention, the separator can be used to remove liquid droplets such as the oil droplets initially contained in fogs. Said foam then provides regular drainage of the captured droplets.
According to another embodiment of the invention, the device can be used to separate solid particles suspended in a gas.
In other words, the present invention relates to a device intended to separate particles contained in a gas stream, comprising a casing with an inlet and an outlet, at least one straight passageway, totally free, unsealed, open at both ends, intended to allow passage of said gas stream in turbulent state from the inlet to the outlet, a reticulated foam material which defines the walls of said passageways and fills all the space between said passageways, said foam material being made up of threads forming interconnected pores or cells which communicate freely with said passageways so as to create non-turbulent stagnant zones extending away from said passageways.
According to the invention, said particles are collected and deposited on the surfaces of threads forming the reticulated foam material, said threads being spaced apart so that the cells defined thereby allow passage of the turbulent stream over a distance of some cells (from said passageways) and prevent a direct gaseous flow from the inlet to the outlet, the cells forcing the turbulences to decrease in the non-turbulent zones occupying substantially all of the space between the passageways.
According to a characteristic, said passageways all have the same dimensions.
More specifically, the length of the passageways ranges between about 10 cm and about 200 cm.
The adjacent threads are advantageously spaced apart by a distance of about 0.5 mm to about 5 mm in each direction of the space, the peripheral threads and the spaces between said threads defining the walls of said passageways. The particles are deposited on the thread surfaces by inertial impact and by Brownian scattering phenomena.
Furthermore, the diameter of said threads ranges between about 50 &mgr;m and about 1000 &mgr;m, and the reticulated foam has a porosity ranging between about 90% and about 98%, preferably about 97%.
Besides, said reticulated foam is made of a polyurethane or PVC-coated polyurethane.
According to another possibility, said reticulated foam is made of a vitreous carbon.
According to the invention, said reticulated foam is made of a metal such as aluminium, nickel or lead.
According to another embodiment of the invention, said reticulated foam is made of a ceramic material.
According to yet another embodiment of the invention, said passageways are made by assembly of reticulated foam sheets which form channels of square or rectangular section.
In particular, said passageways are positioned horizontally, and the device allows to remove liquid droplets such as the droplets contained in an oil or water fog, the liquid formed after deposition of the droplets being drained by said foam and continuously discharged from the casing into suitable means placed at the bottom of said casing.
The passageways provided for the gas stream can be positioned horizontally or vertically, and the particles are separated from the gas stream.
The invention also relates to a process for separating particles from a gas stream in which they are contained, comprising the following stages:
passing said gas streams through at least one straight passageway, totally free, unsealed, open at both ends, in a given direction in a casing, above an area where the effluent is non-turbulent and stagnant, consisting of a plurality o
Antonelli Terry Stout & Kraus LLP
Dullien Francis A.L.
Prince Fred
Smith Duane
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