Liquid purification or separation – Processes – Ion exchange or selective sorption
Reexamination Certificate
2001-08-09
2002-06-04
Smith, Duane (Department: 1724)
Liquid purification or separation
Processes
Ion exchange or selective sorption
C210S662000, C210S746000, C210S804000, C210S808000, C210S924000
Reexamination Certificate
active
06398966
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed to an apparatus and method for removing oil, hydrocarbons and other organic materials from water, particularly industrial waste waters, ship bilge pump waters, produced water and rainwater collected on offshore oil drilling and production platforms, by adsorption with an oil adsorbent, while electronically monitoring the adsorbent with an embedded probe to determine when the adsorbent needs replacement. More particularly, the present invention is directed to an apparatus and method that includes relatively crude, gravity separation of oil from the water and then contacting the separated water, containing a small amount of hydrocarbons, such as oil and grease, with an organophilic clay to purify the water. During adsorption of the hydrocarbons, the adsorbent is monitored, by the probe, to determine when the absorbent is saturated and should be replaced or regenerated. Further, the present invention is directed towards an improved vessel for housing a plurality of cartridges of the organophilic clay with a removable header for directing filtered water out of the vessel.
BACKGROUND OF THE INVENTION AND PRIOR ART
Offshore drilling and production platforms used for recovering oil from subterranean formations disposed beneath ocean water includes a number of structural support legs for supporting a plurality of work deck areas at substantial heights above the water level, e.g., disposed from 40 to 100 or more feet above sea level. During the recovery of oil at one or more of these work deck areas, oil, grease and other hydrocarbons are unavoidably spilled onto the deck area(s) and it is not permissible to discard these hydrocarbons into the ocean water. Such work deck areas or platform surfaces are constructed to be fluid-impermeable in order to contain the spilled hydrocarbons on the work deck areas. These hydrocarbons, such as recovered oil, grease, surfactants and other organic contaminants, are directed from the work deck or platform areas, either by water washing or rainwater, into a sump pump container or sump tank where the water and oil separate by gravity so that the water can be removed from a lower portion of the sump tank, for conveyance back to the ocean, and the oil can be pumped from an upper portion of the sump tank into an oil recovery container so that the oil is not returned to the ocean.
These contained deck areas on offshore structures collect a significant amount of water during periods of high rainfall. The rainwater and entrained hydrocarbons, particularly recovered oil, grease and surfactants, are conveyed to the sump tank or collection tank through a gravity drain system from each of the work deck areas. These sump tanks rely on retention time as the primary oil/water separation mechanism in order to skim the lighter density hydrocarbons from a top of the sump tank so that the water can be returned to the ocean.
The sump tanks presently used on offshore platforms suffer from a number of major drawbacks which result in significant amounts of hydrocarbons, particularly oil, paraffins, grease, and refined hydrocarbons being returned to the ocean causing significant ecological contamination. One major drawback of the presently used sump tanks is that they are designed for a maximum of about three inches of rainwater per hour. It has been found that it is not uncommon to experience eight to ten inches of rainfall per hour in areas such as the Gulf of Mexico. Another major drawback of the sump tanks presently used on offshore drilling platforms is that a tank containing a layer of oil disposed above a layer of water will lose the water by evaporation over an extended dry period and the oil layer, as a result, will coat the inside surfaces of the sump tank. This phenomena is known in the art as sheening. As a result of the sump tank sheening, water generated from even a modest rain shower, after this drying period, carries the oil through a water leg or drain portion of the sump tank as the water initially washes lower inner surfaces of the sump tank, thereby carrying the oil to the ocean.
Another water treatment problem associated with offshore oil platforms is the treatment of the aqueous solutions used in acid fracturing processes. Specifically, acidic solutions are commonly pumped down under pressure to cause fractures in the oil producing regions of the formation. As these acidic solutions are returned to the surface, they are often contaminated with oil or hydrocarbons. As discussed above with respect to rainwater, the hydrocarbons must be removed from the solutions before the water is returned to the ocean.
Another problem associated with all auxiliary equipment used on oil platforms is the need for equipment to be designed in a space efficient manner. Specifically, auxiliary equipment, including water treatment equipment, must be designed in as space efficient manner as possible because horizontal square footage on an oil platform is scarce. Therefore, there is a need for water treatment equipment that can treat water at a fast rate, but which is also space efficient.
SUMMARY OF THE INVENTION
In accordance with one embodiment of the present invention, an improved apparatus is provided for separating hydrocarbons from a liquid containing water and hydrocarbons. The apparatus includes an improved vessel design. The vessel includes an inlet for conveying contaminated water into the vessel and an outlet for transporting treated water out of the vessel. A removable header is connected to the outlet and housed within the vessel. Permeable conduits are connected to the header and extend upward therefrom. Cartridges containing organophilic media for adsorbing hydrocarbons are then stacked on the permeable conduits. Each cartridge includes a permeable outer cover, a permeable inner tube with the organophilic media disposed therebetween. A pressure drop is provided between the vessel inlet and the vessel outlet, and therefore between the vessel inlet and the permeable conduits. As a result, the contaminated liquid flows radially inwardly through the outer cover of the cartridges, through the media and through the inner tube of the cartridge before flowing into the conduit. Intimate contact between the media and the contaminated liquid results in adsorption of the hydrocarbon contaminants on the media. The header is detachably connected to the treated liquid outlet thereby facilitating removal of the header for replacement or servicing. Accumulated solids, which do not pass through the cartridges, are conveniently collected at the bottom of the vessel and can be flushed out through a drain valve.
In accordance with another aspect of the present invention, an improved method of manufacturing such a vessel is provided. A bottom structure is welded to an open bottom end of a hollow cylinder. The bottom structure includes a drain outlet with a valve disposed exterior to the bottom structure for opening and closing the drain outlet. The bottom structure also includes a treated liquid outlet with an inner end disposed inside the bottom structure. The inside surfaces of the bottom structure and the cylinder are coated with a protective coating to resist corrosion in the presence of salt water and very acidic or basic solutions. A header is connected to the inner end of the liquid outlet and contained within the bottom structure of the vessel. Permeable conduits are then connected to the header and extend upward through the cylindrical section of the vessel. Cartridges, like those described above, are placed singly or are stacked one on top of another with the permeable conduits extending through the inner tubes of the cylindrical cartridges. The improved method enables the weld connecting the bottom structure to the bottom end of the cylinder to be easily coated with the protective coating. Further, because a header is employed, the bottom of the vessel may be used to accumulate solids that do not pass through the cartridges and, because the bottom of the vessel is not needed to collect treated water, a greater porti
Berger Michael A.
Darlington, Jr. Jerald W.
Johnson Michael R.
Occhipinti John
Robichaux Elmo
AMCOL International Corporation
Lawrence Frank M.
Marshall Gerstein & Borun.
Smith Duane
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