WITH RADIOACTIVE MATERIALS

INVENTOR: LEN WALL

TECHNICAL FIELD

[0001] The present invention relates to a process for remediating articles contaminated with radioactive materials. The present invention particularly relates to such a process for remediating articles used in producing and refining oil and gas. Such articles may include piping, vessels, and other equipment.

BACKGROUND

[0002] Naturally occurring radioactive materials (hereinafter NORMs) in oil and gas formations may be deposited in equipment during production, transportation, and refining. During production of oil and gas, when produced fluids from reservoirs carry sulfates up hole, Barium, Calcium and Strontium cations may be coproduced with the sulfates.

[0003] Sulfates are larger compounds, and smaller atoms, such as Radium 226 and Radium 228 can also fit into the empty spaces of such the compound and be carried through the produced fluids. As the fluids approach the surface, changes in the temperature and pressure cause the Barium, Strontium and Radium sulfates to precipitate out of solution and form scales on the inside, or on occasion, the outside of completion strings and/or casings.

[0004] During the refining of crude oil, cracking and distillation of large volumes of crude oil occurs between clean outs. NORMs may accumulate and be concentrated at various points in these refining processes.

[0005] Radon gas is also one of the NORMs. It has a short half-life and decays to produce radioactive isotopes of Polonium, Bismuth, and Lead. It can be concentrated in the natural gas streams.

[0006] Radioactive tracers may be used in the exploration for and production of oil and gas. Some of these materials, such as radioactive forms of Calcium, may also contribute to contamination of oil and gas production and refining equipment. [0007] Once at the surface of the Earth, these radioactive materials, sometimes referred to as Technologically Enhanced Naturally Occurring Radioactive Material (TENORM), can cause injury and must be handled appropriately. Some of these NORMs and tracers, at dangerous concentrations, may become affixed to the interiors of the production and refining equipment to which they are contacted in such a way that they resist removal by conventional methods.

[0008] It would be desirable in the art of oil and gas production and refining to be able to safely and economically treat equipment that has become contaminated with NORMs.

SUMMARY

[0009] In one aspect, the invention is a process for remediating articles which have surfaces contaminated with radioactive materials, the method including a step of contacting the surfaces of the contaminated articles with a Pyrolysis Oil for a time sufficient to mitigate or eliminate radioactive emissions from the articles.

[0010] In another aspect, the invention is a cleaning composition comprising Pyrolysis Oil.

DETAILED DESCRIPTION

[0011] In one aspect, the invention of the application is a process for remediating articles which have surfaces contaminated with radioactive materials, the method including a step of contacting the surfaces of the contaminated articles with a Pyrolysis Oil for a time sufficient to mitigate or eliminate radioactive emissions from the articles. [0012] The method of the application is particularly useful for situations where conventional decontamination is either not possible or would itself increase the danger for the NORMs. For example, if the NORMs are incorporated into the equipment to be treated in the form of scale or other surface deposits, it could be undesirable to remove the scale via sandblasting or use of conventional descaling compositions as it would result in an even larger volume of radioactive materials to remove. For example, WIPO Publication WO 2010115240 to Wills discloses a process for treating radioactive scale b grinding it to a size suitable for disposal offshore. The is an expensive process that can also result in the release of radioactive dust.

[0013] Alternatively, US Patent Number 7,360,967 to Matthews, discloses a process for treating solid oil or gas production waste including providing an oil or gas product obtained from a subterranean geological formation; separating solid production waste from the oil or gas product; introducing the solid waste to a carbon material; heating the solid waste and carbon material to about 1000° C. or higher to reduce at least a portion of the solid waste to a reduced barium sulfide waste product; dissolving the reduced waste product; and disposing of the dissolved reduced waste product. The reference teaches reinjecting the resultant materials. Again, an expensive process that is, in itself, subject to hazards.

[0014] In marked contrast, the present process is performed at ambient to moderate temperatures and does not require reducing the radioactive materials to a dry state.

[0015] In one embodiment, where the equipment is a drill stem or other form of piping or equipment which can support pumping a fluid through it, introducing a cleaning composition comprising at least 0.1 volume percent Pyrolysis Oil into the piping or equipment and circulating it through the piping or equipment. This offers the advantage of leaving the piping or equipment in place while decontamination occurs, which also limits the amount to time that human operators would need to be exposed to radiation. [0016] In some embodiments, the piping or equipment is filled to a level sufficient that contaminated surfaces are in contact with the cleaning composition and held for a time sufficient to mitigate or remove radioactive materials.

[0017] In still another embodiment, the piping or equipment can be decontaminated employing a process such as the one disclosed to US9,770,741 to Snow, where the cleaning composition is introduced into the piping or equipment using a perforated lance or other spraying system.

[0018] Any method known to those of ordinary skill in the art of cleaning piping or equipment to be useful for contacting a surface with a cleaning composition of the application may be used with the invention. This includes, but is not limited to filling and holding, recirculation, use of a bath, and the like.

[0019] One advantage of the cleaning compositions of the application is that it is very effective at removing NORMs and other radioactive materials from the surface of metal. While not wishing to be bound by any theory, it is nevertheless believed that the Pyrolysis Oil component of the cleaning compositions somehow interferes with ligands that bind radioactive materials to a metal’s surfaces.

[0020] The cleaning compositions of the application include from about 0.1 to 100 volume percent Pyrolysis Oil. In some embodiments the concentration of Pyrolysis Oil is from about 5 to about 75 volume percent. In other embodiments the concentration is about 50 volume percent.

[0021] Pyrolysis Oil is a necessary component of the cleaning compositions of the application. Pyrolysis Oil is a material produced by subjecting a material that includes one or more polymers and/or copolymer to heat under conditions sufficient to reduce the materials to a liquid mixture of hydrocarbons and other chemicals that present as an oil at ambient conditions. For example, one type of Pyrolysis Oil may be produced by heating dried biomass in an oxygen free environment at about 500°C.

[0022] In one embodiment, the Pyrolysis Oil used with the method of the invention is a composition comprising the hydrocarbons derived from pyrolysis of tires (Tire Pyrolysis Oil). The global economy generates approximately 2 billion end-of-life tires annually. Often these tires are sent to landfills, incinerators, or abandoned at illegal dump sites where they create pollution and vectors for disease.

[0023] End-of-life tires are valuable chemical resources. Tire pyrolysis can produce recovered carbon black to make new tires or rubber products as well as valuable liquid co-products for specialty chemical and fuel uses. Processing end-of- life tires in this way is an important aspect of the circular economy that advances the principles of reduce, reuse, and recycle.

[0024] Recycling end-of-life also tires has a much smaller environmental footprint than producing these materials in conventional ways. Greenhouse gas emissions associated with the production of recovered carbon black are substantially lower than virgin carbon black. For this reason, materials produced from tire pyrolysis commonly are referred to as “green” products.

[0025] In one embodiment, the Tire Pyrolysis Oil used with the method of the application is prepared by subjecting rubber and carbon black based tires to a process that includes depolymerizing the rubber to produce a hydrocarbon stream. Optionally, the process may include steps such as removing metal from the tires prior to processing and recovering other products.

[0026] The Tire Pyrolysis Oil may be prepared by any process known to be useful to those of ordinary skill in the art. The Tire Pyrolysis Oil may be prepared employing a low energy method of pyrolysis of rubber, especially rubber recovered during tire recycling. In this process the rubber is heated in the presence of a clay or clay and elemental metal catalysts. High quality carbon black and Tire Pyrolysis Oil are produced with a substantial reduction in the amount of energy expended and carbon dioxide produced. This method is disclosed, in part, in U.S. Patent Application No. 6,835,861 which is incorporated herein by reference in its entirety.

[0027] In the ‘861 process, a low energy method of pyrolysis of rubber is provided wherein the rubber is heated while maintaining a vacuum, using a clay catalyst. In an additional embodiment, this reference discloses that the temperature of the reaction chamber and corresponding fuel input is varied either over time or spatially within the reaction chamber.

[0028] Another process for preparing the tire pyrolysis can be found in United States Patent Publication No. 2008/0096787 which is incorporated herein by reference in its entirety.

[0029] In this process, a method of manufacturing a solvent from rubber tires is disclosed that involves conveying tire particles into a rotary drum heated to 730-800°F under vacuum to generate hydrocarbon vapors and carbon black solids. The vapors pass through a condensing column to collect liquid hydrocarbons. The resulting solvent contains a high percentage by volume of both Limonene and naphthalene.

[0030] Generally, Tire Pyrolysis Oil is a very complex mixture of hydrocarbons including alkanes, alkenes, amines, amides, esters, and thio-compounds. For example, in one embodiment, the Tire Pyrolysis Oil can have a composition of: