Patent Application
20060081501
The presence of sulfur-containing substances or compounds (e.g., organic sulfur) in certain fluids, like carbonaceous fluids or solutions of hydrocarbons, may be undesirable. For example, sulfur in petroleum-based fluids may contribute to polluting air, water, soil, and the like, as the fluids are used and sulfur is potentially released into the environment. It may be desirable to reduce or remove the sulfur-containing compounds in, for example, fuels and oils before they are burned, combusted or otherwise used, and sulfur contained in the fluids is released.
Methods for removing or reducing the amount of sulfur-containing compounds in carbonaceous fluids are available. These methods may be called desulfurization methods. In one desulfurization method, called hydrotreating or hydrosulfurization, carbonaceous fluids and hydrogen may be treated at high temperature and pressure in the presence of catalysts. Sulfur may be reduced to H2S gas which then may be oxidized to elemental sulfur.
In another method, called oxidative desulfurization, sulfur-containing compounds may be oxidized and then removed from a fluid based on one or more properties of the oxidized sulfur-containing compounds. Oxidative desulfurization may use a variety of different oxidants as well as different conditions to initiate the oxidation reactions. In one example, sulfur-containing compounds in small volumes of a carbonaceous fluid may be oxidized using a peroxy oxidant in the presence of ultrasonic energy that produces cavitation bubbles in the fluid. This method of producing cavitation bubbles may be called acoustic cavitation.
Many of the methods for removing sulfur-containing compounds from carbonaceous fluids may be costly, may include harsh reaction conditions, may be unable to remove substantial amounts of sulfur-containing compounds, may be unable to remove sulfur-containing compounds having certain chemical structures, may not facilitate scale-up to large volumes of fluids, and so on.
The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate various example methods, systems, and so on, relating to various example embodiments of oxidation of sulfur-containing compounds using hydrodynamic cavitation and desulfurization of a fluid. The drawings are for the purposes of illustrating the preferred and alternate embodiments and are not to be construed as limitations. For example, it will be appreciated that the illustrated element boundaries (e.g., boxes, groups of boxes, or other shapes) in the figures represent one example of the boundaries. One of ordinary skill in the art will appreciate that one element may be designed as multiple elements or that multiple elements may be designed as one element. An element shown as an internal component of another element may be implemented as an external component and vice versa. Furthermore, elements may not be drawn to scale and distances may be exaggerated for purposes of explanation.
This application describes processes and systems related to oxidizing sulfur-containing substances in a fluid. Oxidizing the sulfur-containing substances may facilitate their removal from the fluid. The example processes and systems generally include producing hydrodynamic cavitation in a mixture of a fluid containing sulfur-containing substances and one or more oxidizing agents. Hydrodynamic cavitation may include producing cavitation bubbles in the mixture by creating low pressure areas in the mixture. Hydrodynamic cavitation may also include collapsing the cavitation bubbles, thereby producing conditions that may initiate or catalyze one or more oxidation reactions that may oxidize or partially oxidize the sulfur-containing substances. Generally, the oxidation reactions may not oxidize other substances in the fluids, like petroleum-based substances, for example. The oxidized or partially oxidized sulfur-containing substances may be removed from the fluid using a variety of methods. The methods and systems disclosed herein generally produce fluids containing a reduced amount of various sulfur-containing substances.
The fluids containing sulfur-containing compounds that may be oxidized by the methods and systems using oxidative desulfurization, and may be removed from the fluids, may be of a variety of types. In one example, the fluids may contain carbon and may be called carbonaceous fluids or organic fluids. The carbon in the carbonaceous fluids may be part of carbon-containing compounds or substances. The carbon-containing compounds or substances may be hydrocarbons of a variety of types. One type of carbonaceous fluid may contain liquid hydrocarbons like fossil fuels, crude oil or crude oil fractions, diesel fuel, gasoline, kerosene, petroleum fractions, light oil, and others. Another type of carbonaceous fluid may contain solid hydrocarbons like coal. Another type of carbonaceous fluid may contain liquefied hydrocarbons like liquefied petroleum gas. Carbonaceous fluids may contain one or more of the liquid, solid, liquefied, and other hydrocarbons. The carbonaceous fluids may be petroleum-based fluids.
The sulfur-containing compounds and/or substances in the fluids may be of a variety of types. Examples of these compounds include, mercaptans (thiols), sulfides, disulfides, thiophenes, and others. The example thiophenes may be, for example, benzothiophenes or di-benzothiophenes.
Generally, the sulfur-containing compounds may be chemically apolar or at least chemically less polar than one or more oxidized or partially oxidized forms of the sulfur-containing compounds. In one example, the differences in the chemical polarity of the sulfur-containing compounds before they are subjected to oxidation, and the sulfur-containing compounds after they are subjected to oxidation, may be a basis for removal of the oxidized or partially oxidized forms of the sulfur-containing compounds from a fluid. Generally, the oxidized or partially oxidized sulfur-containing compounds may be chemically polar or at least more polar than one or more unoxidized forms of the sulfur-containing compounds.
Oxidizing or partially oxidizing the sulfur-containing compounds generally may occur through chemical oxidation reactions. In one example, oxidizing the sulfur-containing compounds includes chemical addition of one or more oxygen atoms to a sulfur atom. In one example, the one or more oxygen atoms may form covalent double bonds with the sulfur atoms. An example sulfur-containing compound containing a sulfur atom with an oxygen atom double-bonded to it may be called a sulfoxide. An example sulfur-containing compound containing a sulfur atom with two oxygen atoms double-bonded to it may be called a sulfone.
The chemistry that produces oxidized forms of sulfur-containing compounds generally may utilize one or more oxidizing agents or oxidants in the chemical reactions. The oxidizing agents may be of a variety of types. Example oxidizing agents may include hydrogen peroxide and water. Example oxidizing agents may include ozone. Example oxidizing agents may include hydroperoxides. Hydroperoxides may include monosubstitution products of hydrogen peroxide (i.e., dioxidane), having the chemical formula, ROOH, where R may be an organic group or an inorganic group. Examples of hydroperoxides in which R is an organic group are water-soluble hydroperoxides such as methyl hydroperoxide, ethyl hydroperoxide, isopropyl hydroperoxide, n-butyl hydroperoxide, sec-butyl hydroperoxide, tert-butyl hydroperoxide, 2-methoxy-2-propyl hydroperoxide, tert-amyl hydroperoxide, cyclohexyl hydroperoxide, and others. Examples of hydroperoxides in which R is an inorganic group are peroxonitrous acid, peroxophosphoric acid, peroxosulfuric acid, and others. Tertiary-alkyl peroxides, tert-butyl peroxide for example, are also oxidizing agents that may be used. Compounds of the ROOH type in which R is an acyl group may be called “peroxy acids.” Peroxy acids may be organic peroxy acids, inorganic peroxy acids, peroxy salts, and others.
In one example, the oxidizing agents may react directly with the sulfur-containing compounds to produce oxidized forms of the sulfur-containing compounds. In one example, the oxidizing agents may be reacted with one or more other substances to produce a form that is reactive with a sulfur-containing compound (e.g., a activated oxidizing agent). In another example, the chemical reactions that produce oxidized forms of sulfur-containing compounds may include one or more reaction or reaction steps. For example, a first chemical reaction may produce a reactive form of an oxidizing agent which can react with a sulfur-containing compound in a second reaction to produce an oxidized form of the sulfur-containing compound.
Generally, the amount of oxidizing agents used to oxidize sulfur-containing compounds may be controlled, for example, to optimize efficiency of oxidation of sulfur-containing compounds, to limit the amount of oxidation to substances in the fluid that do not contain sulfur, and for other reasons. For example, in subjecting diesel fuel to oxidation by hydrodynamic cavitation, the amount of oxidizing agents used may be sufficient for oxidizing or partially oxidizing sulfur-containing compounds, but generally may not be sufficient for oxidizing hydrocarbon compounds of the diesel fuel. In one example, the amount of oxidizing agents may be between about 0.05 and about 30 weight percent of a mixture of a carbonaceous fluid and oxidizing agents. In another example, the amount of oxidizing agents may be between about 2 and about 4 weight percent of a carbonaceous fluid and oxidizing agents.
The chemical reactions that produce reactive oxidants, that produce oxidized sulfur-containing compounds, and related reactions may use energy to initiate, catalyze or facilitate completing the one or more reactions. At least some of this energy may be provided by hydrodynamic cavitation. Hydrodynamic cavitation may include producing cavitation bubbles in a fluid. The cavitation bubbles may result from a localized pressure drop in the fluid. Hydrodynamic cavitation may also include collapsing the cavitation bubbles. Collapsing cavitation bubbles may create large pressure impulses (e.g., shockwaves), high temperature conditions, high-shear conditions, sonoluminescent light (e.g., ultraviolet light), and other local energy conditions. These energy conditions may catalyze or partially catalyze the chemical reactions. One or more of, generating reactive oxidizing agents, and oxidizing sulfur-containing compounds, may then occur in and surrounding the area where cavitation bubbles are collapsing, and have collapsed.
The chemical reactions that produce oxidized forms of sulfur-containing compounds may also use one or more catalysts to initiate, catalyze or facilitate completing the one or more of the reactions. In one example, the catalysts are metallic catalysts. Examples of these catalysts are Fenton catalysts (ferrous salts) and metal ion catalysts in general such as iron (II), iron (III), copper (I), copper (II), chromium (III), chromium (VI), molybdenum, tungsten, and vanadium ions. Nickel and formic acid catalysts may also be used. The metallic catalysts when present may be used in catalytically effective amounts, which means an amount that enhances the progress of the oxidation and/or related reactions. In one example, the catalytically effective amount may range from about 1 mM to about 300 mM of the catalyst or catalysts. In another example, the catalytically effective amount may range from about 10 mM to about 100 mM.
Also included in the mixture of a carbonaceous fluid, one or more oxidants and optional catalysts that lead to oxidation of sulfur-containing compounds may be one or more surface active agents that may promote the formation of an emulsion between organic and aqueous phases upon mixing fluids, but that may spontaneously separate the product mixture (e.g., after oxidation) into aqueous and organic phases suitable for separation by decantation or other simple phase separation procedures. One example of these surface active agents may be mineral oils.
Oxidizing sulfur-containing compounds in a fluid may be better appreciated by reference to the flow diagrams of
Producing cavitation bubbles in a fluid by hydrodynamic cavitation may occur in a variety of ways. In one example, a fluid is flowed through one or more locally-constricted areas. Flowing the fluid through the locally-constricted areas generally may produce a localized pressure drop in the fluid. In one example, if the local pressure of a fluid decreases below its boiling point, vapor-filled cavities and bubbles may form (e.g., cavitation bubbles). As the pressure then increases, for example when the fluid containing the cavitation bubbles is flowed through a zone or area of elevated pressure, the bubbles may collapse, thereby creating localized energy conditions that may catalyze or partially catalyze the oxidation reactions. In one example, a mixture of the carbonaceous fluid, oxidizing agents, and optional other substances, is flowed through locally-constricted areas multiple times. The fluid may also be flowed through zones of elevated pressure multiple times. For example, multiple locally-constricted areas and/or zones of elevated pressure may be in fluid communication with one another so that they are in series.
In one example, the hydrodynamic cavitation is controlled. Control of hydrodynamic cavitation may include one or more of, controlling forming cavitation bubbles, controlling collapsing of cavitation bubbles, and controlling the location in which the cavitation bubbles are either formed or collapsed. Controlling the hydrodynamic cavitation may regulate the amount of energy produced. This may regulate the amount of oxidation that may occur, for example. In one example, control of the hydrodynamic cavitation process may facilitate oxidizing sulfur-containing compounds but may not facilitate oxidizing other substances like petroleum-based substances.
In one example, the one or more oxidizing agents and the solution containing the one or more sulfur-containing compounds are mixed together before hydrodynamic cavitation is used to produce cavitation bubbles. This may be called pre-mixing of the oxidizing agents, the solution containing the sulfur-containing compounds, and optional other substances. The pre-mixing may occur, for example, in a mixing chamber or reactor. The pre-mixing may also occur, for example, as the oxidizing agents and the solution containing sulfur-containing compounds flows through a pump. In another example, the oxidizing agents may be introduced into the solution containing the sulfur-containing compounds at or near the area where cavitation bubbles are formed. For example, the oxidizing agents may be introduced into the solution containing the sulfur-containing compounds at or near a locally-constricted area of flow.
Oxidizing agents may also be added to the solution containing sulfur-containing compounds multiple times. For example, oxidizing agents may be pre-mixed with the solution containing sulfur-containing compounds and also introduced at or near the area where cavitation bubbles are formed. In another example, the solution containing sulfur-containing compounds may be flowed through locally-constricted areas and zones of elevated pressure multiple times. In one example of this, oxidizing agents may be added to the solution one or more times before the solution flows through the individual locally-constricted areas.
In one example, the method 300 for oxidizing sulfur-containing substances in a fluid may include removing the at least partially-oxidized sulfur-containing compounds from the mixture. The oxidized or partially oxidized sulfur-containing compounds may be removed from the mixture in a variety of ways. For example, the oxidized or partially oxidized sulfur-containing compounds may be removed by methods including, for example, adsorption, decomposition, distillation, extraction, and others. These methods may be described in U.S. Pat. No. 3,647,683 to Kelly, U.S. Pat. No. 5,958,224 to Ho et al., and U.S. Pat. Nos. 6,402,940 and 6,406,616 to Rappas, the contents of all of which are herein incorporated by reference.
In one example, the oxidized or partially oxidized sulfur-containing compounds may be removed with a solvent (e.g., by selective extraction) in which the oxidized or partially oxidized compounds are soluble or at least more soluble than they are in the original carbonaceous fluid before it is subjected to hydrodynamic cavitation These solvents generally are solvents that are immiscible with the carbonaceous fluid containing the sulfur-containing compounds that have not been oxidized. These solvents generally may be polar solvents. Generally, the solvents may be sufficiently polar for the oxidized or partially-oxidized sulfur-containing compounds to be selectively soluble or more soluble in the solvent as compared to the mixture of the carbonaceous fluid and oxidizing agents. Generally, unoxidized sulfur-containing compounds are less soluble in the solvent as compared to the mixture of the carbonaceous fluid and oxidizing agents. In one example, the solvents may be one or more of, methanol, acetonitrile, dimethyl sulfoxide, furans, chlorinated hydrocarbons, trialkylphosphates, N-methylpyrrolidone, and others.
In one example, the mixture that contains the oxidized and/or partially oxidized sulfur-containing compounds may be recirculated back through all or part of the processes illustrated in
Systems configured to oxidize sulfur-containing substances in a fluid and, optionally, to remove the oxidized sulfur-containing substances from the fluid are illustrated in
An example mixing tank 510 may be configured to hold the carbonaceous fluids and oxidizing agents 530 that have flowed into the tank 510. The mixing tank or mixing reactor 510 generally may be configured to produce a mixture from the components that are added to the tank 510. In one example, the mixing tank may have blades 535 configured to rotate to produce the mixture. It will be appreciated that many different designs of a mixing tank 510 are possible.
An example pump 540 may be configured to produce a mixture from the components that flow therethrough. The pump 540 may also be configured to facilitate flow of the mixture through the system 500 and into a cavitation chamber 545. One example type of pump may be a centrifugal pump. It will be appreciated that other pump designs may be used. In the illustrated system, a third conduit 550 provides fluid communication between the mixing tank 510 and the pump 540. As will be seen from a discussion of additional example systems that follow, this configuration of a mixing tank 510 in fluid communication with a pump 540 is only one of many possible configurations and arrangements that may be used.
The illustrated system 500 also includes at least one cavitation chamber 545. Example cavitation chambers 545 may be of various designs. Generally, cavitation chambers 545 are configured to produce hydrodynamic cavitation in a fluid flowing therethrough. In one design, a cavitation chamber 545 produces one or more local areas of low pressure in a fluid flowing therethrough. The local areas of low pressure generally produce cavitation bubbles in the fluid. One example cavitation chamber 545 includes baffles and/or orifices that produce the local areas of low pressure in the fluid. An example cavitation chamber 545 may also be configured to collapse cavitation bubbles. In other examples, collapse of cavitation bubbles may not be a property of the cavitation chamber, but may be included elsewhere within the example system 500. Suitable examples of cavitation chambers 545 that ban be used include those disclosed in U.S. Pat. Nos. 5,810,052, 5,937,906, 5,969,207, 5,971,601, 6,012,492, and 6,502,979, all to Kozyuk, the contents of all of which are herein incorporated by reference. It will be appreciated that cavitation chambers of other designs may also be used.
The example system 500 is configured for continuous flow of the mixture therethrough. The system 500 includes a fifth conduit 560 providing fluid communication between the cavitation chamber 545 and the mixing tank 510. This design may provide for a mixture to circulate through the system multiple times (e.g., recirculate). This design may facilitate continuous flow of a mixture therethrough. As will be seen from discussion of additional example systems that follow, other designs may not facilitate recirculation. In these systems, a mixture may flow through the system one time. These designs may facilitate batch flow of a mixture therethrough.
Continuous and batch systems may have one or more valves that facilitate flow of the mixture out of a system. As illustrated in example system 500, a valve 565 may be included. One example valve 565 may be configured, in one arrangement, to facilitate flow of the mixture therethrough and out of the system 500. This example valve 565 may also be configured, in another arrangement, to prevent flow of the mixture therethrough and keep the mixture within the system 500. In one example, the valve may be in fluid communication with the system 500 through a sixth conduit 570. A seventh conduit 575 may be in fluid communication with the valve 565 and may permit flow of the mixture from the valve 565, out of the system 500.
In operation of the system 500, a carbonaceous fluid containing sulfur-containing substances and one or more oxidizing agents may flow into the mixing tank 510, from the first reservoir 505 and second reservoir, respectively. The system may provide means for controlling or regulating the flow of the materials out of the reservoirs and into the mixing tank 510. The mixing tank 510 may mix the fluid and oxidizing agents to produce a mixture, by rotation of the blades 535, for example. The pump 540 may provide forces that flow the mixture from the mixing tank 510, through the pump 540, and into and through the cavitation chamber 545. The system may provide means for controlling or regulating the flow of the materials from the mixing tank 510 and into the cavitation chamber 545. In one example, the pump 540 may provide this control. Flow of the mixture into and through the cavitation chamber 545 may produce, and optionally collapse, cavitation bubbles, thereby catalyzing oxidation reactions that oxidize sulfur-containing compounds in the mixture. The mixture containing oxidized sulfur-containing compounds may flow back into the mixing tank 510 where additional oxidizing agents may be added. The mixture again may flow through the continuous system 500. This cycle may occur multiple times. At some point in time, the valve 565 may permit some of the mixture to flow out of the system 500, where it may be subjected to methods for removing the oxidized or partially oxidized sulfur-containing compounds from the mixture. Flow of some of the mixture out of the system may facilitate flow of additional carbonaceous fluid and/or oxidizing agents from the first reservoir 505 and second reservoir 520, respectively, into the system 500.
The example is for the purpose of illustrating an embodiment and is not to be construed as a limitation.
The carbonaceous fluid was diesel fuel that contained 0.036 weight percent sulfur. The oxidizing agent was a 30 weight percent solution of hydrogen peroxide in water. The system used in this study was similar to the example apparatus 500 for oxidizing sulfur-containing substances illustrated in
While example systems, methods, and so on have been illustrated by describing examples, and while the examples have been described in considerable detail, it is not the intention of the applicants to restrict or in any way limit the scope of the appended claims to such detail. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the systems, methods, and so on described herein. Additional advantages and modifications will readily appear to those skilled in the art. Therefore, the invention is not limited to the specific details, the representative apparatus, and illustrative examples shown and described. Thus, this application is intended to embrace alterations, modifications, and variations that fall within the scope of the appended claims. Furthermore, the preceding description is not meant to limit the scope of the invention. Rather, the scope of the invention is to be determined by the appended claims and their equivalents.
To the extent that the term “includes” or “including” is employed in the detailed description or the claims, it is intended to be inclusive in a manner similar to the term “comprising” as that term is interpreted when employed as a transitional word in a claim. Furthermore, to the extent that the term “or” is employed in the detailed description or claims (e.g., A or B) it is intended to mean “A or B or both”. When the applicants intend to indicate “only A or B but not both” then the term “only A or B but not both” will be employed. Thus, use of the term “or” herein is the inclusive, and not the exclusive use. See, Bryan A. Garner, A Dictionary of Modern Legal Usage 624 (2d. Ed. 1995). Also, to the extent that the terms “in” or “into” are used in the specification or the claims, it is intended to additionally mean “on” or “onto.” Furthermore, to the extent the term “connect” is used in the specification or claims, it is intended to mean not only “directly connected to,” but also “indirectly connected to” such as connected through another component or components.
