Cleaning and liquid contact with solids – Processes – Oils – grease – tar – or wax removal – by dissolving
Reexamination Certificate
1998-02-27
2001-11-06
Markoff, Alexander (Department: 1746)
Cleaning and liquid contact with solids
Processes
Oils, grease, tar, or wax removal, by dissolving
C134S011000, C134S010000, C134S012000, C134S031000
Reexamination Certificate
active
06312528
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an approach for removing contaminants from sorbent materials, commonly used to absorb oils, solvents and other lubricating products which have been leaked or spilled. The invention utilizes liquefied gas(es), and/or supercritical fluids, and optionally, traditional cosolvents and/or traditional or nontraditional surfactants to clean the sorbent materials such that they may be reused or disposed of in an economical and environmentally friendly fashion. The invention relates to removal of liquids from solids generally using dimethyl ether. Also, the invention relates to solvent recovery approaches.
BACKGROUND OF THE INVENTION
Granular absorbent materials include, for example, clay, fullers, and diatomaceous earth in compositions which have been processed, i.e., dried or sintered and crushed to the proper size. These granular absorbents are commonly used in garages, industrial facilities and other areas to absorb products such as oil, gasoline and other contaminants that have leaked or spilled. In a typical application of granular sorbent material, after the spill of a product occurs, the granular sorbent material is sprinkled over the spill and the user waits for a short period of time to allow the granular sorbent material to absorb the contaminating product. After the granular sorbent material has been allowed to absorb the contaminant, the granular sorbent material with the contaminant is swept into a pile and put into a barrel or other receptacle for storage. Thereafter, the facility, which uses the granular sorbent material, would have prior arrangements with a used granular sorbent material disposal service. This disposal service picks up the used granular sorbent material and treats it or disposes of it in a number of ways.
Two primary methods have been used for disposing of used granular sorbent material. The first disposal method is incineration. This method presents environmental problems such as potentially harmful air emissions and the necessity to landfill processed residuals (ash).
Another common practice for disposing of soiled granular sorbent material is to bury the used material in landfills. This is obviously an undesirable method because there is the potential for the contamination of groundwater, soil, etc. when burying petroleum-based or other products.
An alternative method of cleaning granular sorbent material involves exposing the granular sorbent material to genetically altered microbes that consume a contaminant. The purchasing, storage and use of microbes generally are not economically feasible for small shops. In addition, there is the problem of disposing of the used microbes, and individual equipment used to store the microbes can often be expensive.
Sorbent mats and pads also are used to absorb contaminants in commercial or industrial sites. The sorbent mats and pads can be cotton, polypropylene, polyethylene, or other fabrics. These sorbent mats and pads are used similarly to granular sorbent materials. After the sorbent mat or pad has absorbed the spilled products, it can be placed in a barrel for storage. The used sorbent disposal service treats the sorbent mats and pads at a laundry service, or by incineration, or by landfilling the material. The problem associated with the laundry service is that many of the contaminants are flushed into the sewer system and end up at waste water treatment plants.
SUMMARY OF THE INVENTION
The present invention generally involves a method and apparatus for cleaning granular sorbent material and absorbent mats and pads. In particular, liquefied gas(es), and/or supercritical fluids are used to remove contaminating products and other waste materials from used granular sorbent materials and sorbent mats, pads, booms, and the like.
The present invention utilizes a system wherein used granular sorbent material or sorbent mats or pads, which have absorbed synthetic oils, silicon oils and/or petroleum based products, are exposed to a liquefied gas such as dimethyl ether, propane, isobutane, butane, or a supercritical fluid such as supercritical carbon dioxide. This process removes contaminants such as petroleum oils, machining oils, hydraulic fluids, placticizers, fats, waxes, silicone oils, flux residues, soil and/or other lubricants.
The preferred apparatus envisioned for the present invention is a batch system, wherein the granular sorbent material or sorbent mats and pads are placed in a pressure vessel. The vessel generally is capable of holding a pressure between 25 and 5000 PSIG (pounds per square inch gauge) such that a selected solvent or solvents can exist in a liquefied, supercritical, or near critical state. The vessel temperature depending on the solvent used, preferably ranges from about 70°-140° F. For dimethyl ether, the preferred temperatures are about room temperature, and the preferred pressures are about 100 PSIG. For propane, the preferred temperatures are about room temperature or above, and the preferred pressures are about 150 PSIG or above. For supercritical carbon dioxide, the preferred temperatures are about 30°-40° C., and the preferred pressures are about 2000-4000 PSIG. The used granular sorbent material or sorbent mats or pads are exposed to the liquefied gases and/or supercritical fluids. A flow of solvent preferably is applied to the extraction vessel. After exposure for approximately 30 minutes or more, the used sorbent material preferably has 80% or more of its contaminants removed.
A general method according to the invention involves the following steps:
(a) Used granular sorbent material or sorbent mats or pads are placed in an extraction vessel, which can be pressurized.
(b) The vessel is closed and a solvent such as dimethyl ether, propane, butane or carbon dioxide is pumped into the vessel, at a prescribed temperature and pressure such that the solvent can exist in a state which allows the solvent to interact with and cleanse the soiled material. The solvent is as a liquefied gas or supercritical fluid.
(c) A flow of purified solvent and/or re-circulated solvent is circulated through the extraction vessel and allowed to penetrate the granular sorbent material or sorbent mats or pads for a period of time. During this time the solvent dissolves the contaminants (oils, etc.) and removes them from the absorbent material and from the extraction vessel.
(d) The solvent is drained out of the vessel. Preferably, the majority of the solvent then is recovered. Then, solvent vapor is recovered through a compressor. Any residual solvent vapor remaining in the vessel can be purged using an inert gas and/or by venting the vessel to the atmosphere or to a flare.
(e) The granular sorbent material or sorbent mats or pads are then removed from the extraction vessel.
(f) A new batch of used granular sorbent material or sorbent mats or pads are then placed in the extraction vessel.
(g) The process is repeated.
Preferably, the contaminated solvent is distilled to recover the solvent and contaminants (especially oils). The recovered solvent can be reused as purified solvent in the cleaning process. The recovered oils and the like preferably are also reused, for example, as a low grade lube stock oil.
In particular, in a first aspect, the invention features a method of removing contaminants from highly porous material, the highly porous material in virgin form having an absorbency of at least about 25 percent by weight of the virgin porous material, the method comprising:
contacting the highly porous material in a pressure chamber with a pressurized solvent to form a solvent/contaminant mixture; and
recovering the highly porous material substantially free of the contaminants, wherein the recovered highly porous material has at least about 70 percent by weight of the contaminants removed.
Some highly porous materials in virgin form have an absorbency greater than about 45 percent by weight of the virgin porous material. The highly porous material can comprise a granular material. Preferred granular materials have an average diameter from about 0.
Barcus Randall L.
Markiewicz John P.
Moses John M.
Summerfield John W.
CRI Recycling Service, Inc.
Dardi Peter S.
Markoff Alexander
Patterson Thuente Skaar & Christensen P.A.
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