The technical field generally relates to processes and apparatuses for reforming a naphtha feed stream, and more particularly relates to processes and apparatuses for reforming naphtha feed streams to produce aromatic compounds with minimal energy expenditure.
The reforming of naphtha feed streams is an important process for producing useful products, especially for the production of gasoline. In particular, reforming naphtha feed streams is useful to produce aromatic compounds and, thus, to increase the octane value of the naphtha feed streams. To reform the naphtha feed streams, the naphtha feed streams are generally passed to a plurality of reformers that are arranged in series, with conventional systems operated at a substantially isothermal temperature profile based upon inlet temperature at each reformer.
More recently, development of reforming schemes have focused upon maximizing production of aromatics compounds and minimizing production of lower value non-aromatic by-products through manipulation of the reaction rates within the reformers in a manner that favors selectivity to desirable aromatic compounds. However, such reforming schemes are energy-intensive and often require inter-reformer heating.
Accordingly, it is desirable to provide processes and apparatuses for producing aromatic compounds from a naphtha feed stream that maximizes production of aromatics compounds while minimizing energy requirements for effectively reforming the naphtha feed stream. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.
Processes and apparatuses for producing aromatic compounds from a naphtha feed stream are provided herein. In an embodiment, a process for producing aromatic compounds includes heating the naphtha feed stream to produce a heated naphtha feed stream. The heated naphtha feed stream is reformed within a plurality of reforming stages that are arranged in series to produce a downstream product stream. The plurality of reforming stages is operated at ascending reaction temperatures. The naphtha feed stream is heated by transferring heat from the downstream product stream to the naphtha feed stream to produce the heated naphtha feed stream and a cooled downstream product stream.
In another embodiment, a process for producing aromatic compounds from a naphtha feed stream includes providing a plurality of reformers including a first reformer and a second reformer. The reformers are arranged in series. The naphtha feed stream is heated to a first reaction temperature to produce a heated naphtha feed stream. The heated naphtha feed stream is passed to the first reformer, which is operated at the first reaction temperature, to produce a first intermediate stream. The first intermediate stream is passed to the second reformer, which is operated at a second reaction temperature that is higher than the first reaction temperature, to produce a second intermediate stream. A downstream product stream is produced from the second intermediate stream using a terminal reformer of the plurality of reformers. The naphtha feed stream is heated by transferring heat from the downstream product stream to the naphtha feed stream to produce the heated naphtha feed stream and a cooled downstream product stream, and the naphtha feed stream is heated to the first reaction temperature exclusively through transferring heat from the downstream product stream to the naphtha feed stream.
In another embodiment, an apparatus for producing aromatic compounds from a naphtha feed stream includes a plurality of reformers including a first reformer and a second reformer. The reformers are arranged in series, and the plurality of reformers is adapted to produce a downstream product stream from a terminal reformer of the plurality of reformers. A first heat exchanger is disposed upstream of the first reformer and is adapted to transfer heat from the downstream product stream to the naphtha feed stream. A first heater is disposed between the first reformer and the second reformer for heating a first intermediate stream that is produced by the first reformer. The apparatus is free from a heater disposed between the first heat exchanger and the first reformer.
The various embodiments will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and wherein:
The following detailed description is merely exemplary in nature and is not intended to limit the various embodiments or the application and uses thereof. Furthermore, there is no intention to be bound by any theory presented in the preceding background or the following detailed description.
Processes and apparatuses for producing aromatic compounds from a naphtha feed stream are provided herein. The processes and apparatuses maximize production of aromatics compounds through the use of a plurality of reforming stages that are arranged in series and that are operated at ascending reaction temperatures to produce a downstream product stream while minimizing energy requirements for effectively reforming the naphtha feed stream. In particular, energy requirements are minimized by transferring heat from the downstream product stream to a naphtha feed stream. Due to operation of the plurality of reforming stages at ascending reaction temperatures, the downstream product stream is produced having a significantly higher temperature than the naphtha feed stream and a first reforming stage is operated at a lower temperature than subsequent reforming stages. As such, efficient transfer of heat from the downstream product stream to the naphtha feed stream is possible. Further, it is possible (although not required) to heat the naphtha feed stream to a first reaction temperature at which the first reforming stage is operated by transferring heat from the downstream product stream to the naphtha feed stream, thereby eliminating a need for a heater that requires energy from external to the process (such as a combustion or electric heater) to heat the naphtha feed stream prior to passing the naphtha feed stream to the first reforming stage.
An embodiment of a process for producing aromatic compounds will now be addressed with reference to an exemplary apparatus 10 for producing aromatic compounds as shown in
In accordance with the processes described herein, the naphtha feed stream 12 is reformed within a plurality of reforming stages that are arranged in series to produce a downstream product stream 42. The reforming process is a common process in the refining of petroleum, and is usually used for increasing the amount of gasoline. The reforming process comprises mixing a stream of hydrogen and a hydrocarbon mixture, such as the naphtha feed stream 12, and contacting the resulting stream with a reforming catalyst. The reforming reaction converts paraffins and naphthenes through dehydrogenation and cyclization to aromatics. The dehydrogenation of paraffins can yield olefins, and the dehydrocyclization of paraffins and olefins can yield aromatics.
Suitable reforming catalysts generally include a metal on a support. The support can include a porous material, such as an inorganic oxide or a molecular sieve, and a binder with a weight ratio from 1:99 to 99:1. The weight ratio may be from about 1:9 to about 9:1. Inorganic oxides used for support include, but are not limited to, alumina, magnesia, titania, zirconia, chromia, zinc oxide, thoria, boria, ceramic, porcelain, bauxite, silica, silica-alumina, silicon carbide, clays, crystalline zeolitic aluminasilicates, and mixtures thereof. Conventional porous materials and binders may be used. Suitable metals may include one or more Group VIII noble metals, and include platinum, iridium, rhodium, and palladium. In an embodiment, the reforming catalyst contains an amount of the metal from about 0.01% to about 2% by weight, based on the total weight of the reforming catalyst. The reforming catalyst can also include a promoter element from Group IIIA or Group WA. These metals include gallium, germanium, indium, tin, thallium and lead.
In an embodiment, the plurality of reforming stages includes a first reforming stage, a second reforming stage, and one or more additional reforming stages. For example and as shown in
Reforming is a substantially endothermic reaction and results in a significant temperature decrease in the reforming stages, although different hydrocarbon compounds within the naphtha feed stream exhibit different endothermicity during reforming In accordance with the processes described herein, the reforming stages are operated with a non-isothermal temperature profile, with temperatures of streams into the reforming stages being higher than temperatures of streams produced from the reforming stages. To facilitate reforming, the naphtha feed stream 12 is heated to produce a heated naphtha feed stream 28 (which is compositionally similar to the naphtha feed stream 12 but has a higher temperature). In particular, the naphtha feed stream 12 is heated to the first reaction temperature at which the first reforming stage is operated. In an embodiment, the first reaction temperature is from about 350° C. to about 480° C., such as from about 425° C. to about 475° C. The heated naphtha feed stream 28 is then reformed in the first reforming stage that is operated at the first reaction temperature to produce a first intermediate stream 30. For example and as shown in
Due to the endothermic nature of the reactions in the respective reforming stages, heat is further added to each intermediate stream that is produced from upstream reforming stages prior to passing into each subsequent reforming stage to maintain the temperature of reaction or to increase temperatures to desired reaction temperatures for the particular reforming stages. In an embodiment, the first intermediate stream 30 is heated to produce a heated first intermediate stream 32, followed by reforming the heated first intermediate stream 32 in the second reforming stage. For example, the heated first intermediate stream 32 may be passed to the second reformer 18 after heating, with the second reformer 18 operated at a second reaction temperature that is greater than the first reaction temperature, as described above, and with the first intermediate stream 30 heated to the second reaction temperature. In an embodiment, the second reaction temperature is at least 50° C. higher than the first reaction temperature, such as at least 80° C. higher than the first reaction temperature.
Reforming the heated first intermediate stream 32 produces a second intermediate stream 34. The second intermediate stream 34 and any subsequent intermediate streams 36, 38, 40 (e.g., those produced from the various reformers 20, 22, 24 that are downstream of the first reformer 16 and the second reformer 18 and that are not a terminal reformer 26) are heated to form respective heated intermediate streams 44, 46, 48, 50 that are reformed in the one or more additional reforming stages (e.g., in the various reformers 20, 22, 24, 26). The downstream product stream 42 is produced from the second intermediate stream 34 within a terminal reforming stage of the plurality of reforming stages. For example, in an embodiment and as shown in
The naphtha feed stream 12 is heated by transferring heat from the downstream product stream 42 to the naphtha feed stream 12 to produce the heated naphtha feed stream 28 and to further produce a cooled downstream product stream 52 (which is compositionally similar to the downstream product stream 42). For example, in an embodiment and as shown in
In embodiments as alluded to above, and as shown in
Another embodiment of a process for producing aromatic compounds from a naphtha feed stream 12 will now be addressed with reference to another exemplary apparatus 210 for producing aromatic compounds as shown in
Another embodiment of a process for producing aromatic compounds from a naphtha feed stream 12 will now be addressed with reference to another exemplary apparatus 310 for producing aromatic compounds as shown in
While at least one exemplary embodiment has been presented in the foregoing detailed description of the invention, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment of the invention. It being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set forth in the appended claims.
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