Hydraulic and earth engineering – Fluid control – treatment – or containment – Fluid storage in earthen cavity
Reexamination Certificate
2003-02-24
2004-01-06
Bagnell, David (Department: 3672)
Hydraulic and earth engineering
Fluid control, treatment, or containment
Fluid storage in earthen cavity
C299S006000
Reexamination Certificate
active
06672798
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a system for the storage of sulfur and, more particularly, to a system for storing sulfur for prolonged periods of time. Specifically, the invention is concerned with novel techniques for the storage of commercially produced sulfur in subterranean cavities.
BACKGROUND OF THE INVENTION
Sulfur is the key raw material in the manufacture of sulfuric acid, the largest commodity chemical in the world in terms of tonnage, and is also used in many other industrial, analytical and medical applications throughout the world. Historically, mined natural sulfur has been the primary source of commercially produced sulfur, although this position has given way in recent years to sulfur recovered from crude oil and natural gas processing. Natural sulfur is mined primarily from underground formations by the Frasch hot water injection process, while considerable lesser amounts are obtained from volcanic rock and other types of ores by traditional mining techniques. Recovered sulfur is obtained largely as a byproduct of crude oil and natural gas production operations by the treatment of gaseous hydrogen sulfide streams in Claus Process plants and the like. Regardless of its source, all mined and recovered sulfur must be properly stored prior to its commercial use.
Conventional sulfur storage methods and facilities often involve the use of steam-heated tanks, where molten sulfur is kept at temperatures usually exceeding 260° F., or they may involve the accumulation of solid sulfur storage blocks, also known as “vats”, in contained open areas from which pieces of sulfur may be broken off by mechanical means, crushed and shipped in solid form, or remelted and transported in liquid form.
Molten sulfur storage tanks are expensive to fabricate, operate and maintain. Although often suitable for short-term storage, e.g., less than three months or so, their use is not always economically feasible. The capital cost involved in their fabrication, the expenses associated with correcting corrosion problems, and the cost of the energy required to provide a constant source of steam for keeping the stored sulfur in liquid state do not always make molten sulfur storage tanks best suited for the long-term safekeeping of commercially produced sulfur inventories.
Commercially produced sulfur storage vats (sometimes also referred to as “blocks”) are formed by pouring molten run-of-mine or recovered sulfur in contained open areas where the sulfur is allowed to cool and solidify by exposure to ambient conditions. Vats tend to pick up water from rain and atmospheric moisture and form sulfuric acid which, through seepage under the solidified blocks of sulfur and through water runoff, becomes a source of soil and water contamination. In addition, when the sulfur is broken off from the vats to be transported, particulate sulfur is often given off which becomes a source of air contamination. To avoid or minimize releases of particulate sulfur, the sulfur scheduled for transportation is often melted in situ prior to shipping it to the desired locations, and this step adds more capital, operating and maintenance costs to the storage system. Vats also tend to retain sporadic pockets of hot molten sulfur which are not always easy to detect, and which therefore constitute an industrial safety hazard. In some locations, the handling, transportation and/or storage of solid sulfur is prohibited, or so encumbered by regulatory controls as to make them commercially unattractive. Conventional sulfur storage techniques and equipment are described in U.S. Pat. Nos. 4,149,837, 4,151,234, 4,171,200, 4,190,627, 4,595,350, 4,705,432, 5,041,275 and 5,340,383.
In recent years, the inventories of recovered sulfur have increased dramatically worldwide, partly because of the implementation of stricter environmental regulations in practically every country in the world. Industrial plant gases and other sources of sulfur from crude oil and natural gas production operations must be treated to remove their sulfur constituents before releasing them to the atmosphere or otherwise disposing of them. The result is that large inventories of byproduct recovered sulfur continue to be generated which often exceed the current demand for sulfur as a commodity chemical. These inventories must be properly stored, sometimes for long periods of time, i.e., for five or ten years, or even longer, until the market demand calls for their use.
From the foregoing, it is apparent that an important need exists for commercially produced sulfur storage means that are not only capable of safekeeping large industrial tonnages of sulfur for long periods of time, but are also cost effective and environmentally sound. The present invention is directed toward providing such means.
It is an object of the present invention to provide a system for the proper and safe storage of both solid and liquid sulfur. Another object of this invention is to provide a commercially practicable technique for the long-term storage of sulfur at relatively low maintenance and operating costs. A specific object of the invention is to provide a commercially practicable system for the storage of “recovered sulfur”, that is, sulfur that has been recovered, or produced, as a byproduct of crude oil and natural gas production operations. A further object of the present invention is to provide an environmentally attractive system for storing commercially produced sulfur, which minimizes the release of sulfur compounds to the atmosphere during storage. Another object of this invention is to provide a system for the storage of commercially produced sulfur at a location close to where the sulfur is mined or recovered, thereby minimizing the costs associated with the transportation and the handling of the sulfur in special sulfur storage tanks or vats. Another object of the invention is to provide an environmentally sound system for the long-term storage of commercially produced sulfur from which the sulfur may be easily and inexpensively reclaimed, when needed, by means of pressurized hot water techniques. A further object of the present invention is to provide an improved system for the conservation of an important natural resource, i.e., sulfur, which system will help prevent, or at least minimize, future shortages of this important natural resource as its sources become gradually depleted. These and other objects of the invention will be apparent to those skilled in the art from the description that follows.
SUMMARY OF THE INVENTION
The system of this invention centers around the innovative concept of injecting commercially produced sulfur in a mined subterranean cavity. Commercial sulfur, in elemental state, is produced by mining, or as a byproduct of industrial operations such as crude oil and natural gas production operations. Commercially produced sulfur is often found in molten state as well as in solid state. At ambient pressures and temperatures, elemental sulfur is solid. At ambient pressures and elevated temperatures, that is, at atmospheric pressures and at temperatures higher than about 240° F., elemental sulfur is liquid. The system of this invention is particularly suited for the long-term storage of recovered sulfur, which is often produced in liquid form. However, the system may also be used to store mined sulfur, produced in solid form or in molten state, and recovered sulfur produced in solid form. According to the technique of this invention, a mined subterranean cavity is first located or created within a naturally occurring earth formation, and a borehole is provided on the surface of the earth and through the earth formation, which penetrates the subterranean cavity near its top, or at some other convenient location on the cavity. The sulfur to be stored is then injected through the borehole by means of pumping equipment adapted to handle the flow of sulfur, or simply by allowing the sulfur to flow by gravity into the subterranean cavity. The injection of sulfur in this manner is continued until a significant portion of the cavity is fil
Bagnell David
Crescent Technology, Inc.
Fonte Raúl V.
Stephenson Daniel P.
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