Drying and gas or vapor contact with solids – Apparatus – With means to treat gas or vapor
Reexamination Certificate
2001-10-25
2003-12-09
Lazarus, Ira S. (Department: 3749)
Drying and gas or vapor contact with solids
Apparatus
With means to treat gas or vapor
C034S073000, C034S075000, C034S237000, C110S237000, C110S229000
Reexamination Certificate
active
06658757
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates generally to a method and apparatus for the removal of hydrocarbons from solids. More particularly, the invention relates to the low-temperature thermal desorption of petroleum hydrocarbons from contaminated soil.
2. Background Art
When drilling or completing wells in earth formations, various fluids typically are used in the well for a variety of reasons. For purposes of description of the background of the invention and of the invention itself, such fluids will be referred to as “well fluids.” Common uses for well fluids include: lubrication and cooling of drill bit cutting surfaces while drilling generally or drilling-in (i.e., drilling in a targeted petroleum bearing formation), transportation of “cuttings” (pieces of formation dislodged by the cutting action of the teeth on a drill bit) to the surface, controlling formation fluid pressure to prevent blowouts, maintaining well stability, suspending solids in the well, minimizing fluid loss into and stabilizing the formation through which the well is being drilled, fracturing the formation in the vicinity of the well, displacing the fluid within the well with another fluid, cleaning the well, testing the well, implacing a packer fluid, abandoning the well or preparing the well for abandonment, and otherwise treating the well or the formation.
As stated above, one use of well fluids is the removal of rock particles (“cuttings”) from the formation being drilled. A problem in disposing these cuttings, particularly when the drilling fluid is oil-based or hydrocarbon-based. That is, the oil from the drilling fluid (as well as any oil from the formation) becomes associated with or adsorbed to the surfaces of the cuttings. The cuttings are then an environmentally hazardous material, making disposal a problem.
A variety of methods have been proposed to remove adsorbed hydrocarbons from the cuttings. U.S. Pat. No. 5,968,370 discloses one such method which includes applying a treatment fluid to the contaminated cuttings. The treatment fluid includes water, a silicate, a nonionic surfactant, an anionic surfactant, a phosphate builder and a caustic compound. The treatment fluid is then contacted with, and preferably mixed thoroughly with, the contaminated cuttings for a time sufficient to remove the hydrocarbons from at least some of the solid particles. The treatment fluid causes the hydrocarbons to be desorbed and otherwise disassociated from the solid particles.
Furthermore, the hydrocarbons then form a separate homogenous layer from the treatment fluid and any aqueous component. The hydrocarbons are then separated from the treatment fluid and from the solid particles in a separation step, e.g., by skimming. The hydrocarbons are then recovered, and the treatment fluid is recycled by applying the treatment fluid to additional contaminated sludge. The solvent must be processed separately.
Some prior art systems use low-temperature thermal desorption as a means for removing hydrocarbons from extracted soils. Generally speaking, low-temperature thermal desorption (LTTD) is an ex-situ remedial technology that uses heat to physically separate hydrocarbons from excavated soils. Thermal desorbers are designed to heat soils to temperatures sufficient to cause hydrocarbons to volatilize and desorb (physically separate) from the soil. Typically, in prior art systems, some pre- and post-processing of the excavated soil is required when using LTTD. In particular, excavated soils are first screened to remove large cuttings (e.g., cuttings that are greater than 2 inches in diameter). These cuttings may be sized (i.e., crushed or shredded) and then introduced back into a feed material. After leaving the desorber, soils are cooled, re-moistened, and stabilized (as necessary) to prepare them for disposal/reuse.
U.S. Pat. No. 5,127,343 (the '343 patent) discloses one prior art apparatus for the low-temperature thermal desorption of hydrocarbons.
FIG. 1
from the '343 patent reveals that the apparatus consists of three main parts: a soil treating vessel
10
, a bank of heaters
12
, and a vacuum and gas discharge system
14
. The soil treating vessel
10
is a rectangularly shaped receptacle. The bottom wall of the soil treating vessel
10
has a plurality of vacuum chambers, and each vacuum chamber has an elongated vacuum tube positioned inside. The vacuum tube is surrounded by pea gravel, which traps dirt particles and prevents them from entering a vacuum pump attached to the vacuum tube.
The bank of heaters
12
has a plurality of downwardly directed infrared heaters, which are closely spaced to thoroughly heat the entire surface of soil when the heaters are on. The apparatus functions by heating the soil both radiantly and convectionly, and a vacuum is then pulled through tubes at a point furthest away from the heaters
12
. This vacuum both draws the convection heat (formed by the excitation of the molecules from the infrared radiation) throughout the soil and reduces the vapor pressure within the treatment chamber. Lowering the vapor pressure decreases the boiling point of the hydrocarbons, causing the hydrocarbons to volatize at much lower temperatures than normal. The vacuum then removes the vapors and exhausts them through an exhaust stack, which may include a condenser or a catalytic converter. As the hydrocarbon removal process continues, however, the surface soil (i.e., those nearest the heaters) become dried out and hard, and effectively preventing the flow of air through the soil.
What is needed, therefore, is an improved LTTD process, which quickly and easily removes adsorbed hydrocarbons from cuttings.
SUMMARY OF THE INVENTION
In one aspect, the present invention relates to an apparatus for separating hydrocarbons from a material which comprises a process chamber, a process pan operatively connected to the process chamber and removable therefrom, a blower operatively connected to the process chamber and to a heat source. The blower is adapted to force heated air into the process chamber through the material disposed on the process pan. The forced heated air is adapted to vaporize hydrocarbons and other contaminants disposed on the material. The system includes at least one condenser operatively connected to the process chamber and adapted to condense the vaporized hydrocarbons and other contaminants.
In another aspect, the present invention relates to a method for separating hydrocarbons from a material which includes passing a stream of heated air over the material to volatilize the hydrocarbons, passing the stream of heated air containing the hydrocarbons through at least one condenser to form liquid hydrocarbons, collecting the liquid hydrocarbons, and recirculating the heated air.
In another aspect, the present invention relates to a process chamber having an inlet and an outlet, a process pan adapted to be removably inserted into the process chamber, a heat source adapted to provide heated air, the inlet and outlet of the process chamber having a sufficient pressure difference to force air heated by the heat source into the process chamber through the material disposed on the process pan, the forced heated air adapted to vaporize hydrocarbons and other contaminants disposed on the material, and a first condenser operatively connected to an outlet of the process chamber and adapted to condense the vaporized hydrocarbons and other contaminants.
Other aspects and advantages of the invention will be apparent from the following description and the appended claims.
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patent: 5076727 (1991-12-01), Johnson et al.
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patent: 5300
Connaughton Jerry T.
Fout Gary E.
Lazarus Ira S.
M-I L.L.C.
O'Malley Kathryn S.
Rosenthal & Osha L.L.P.
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