Patent Application
20080000836
Referring to the exemplary drawings wherein like elements are numbered alike in the several Figures:
Disclosed herein are transmix refining methods. As will be discussed in greater detail, the transmix refining method comprises passing the transmix through a membrane. In one embodiment, the membrane pre-fractionates the transmix before distillation, which advantageously allows the transmix to be separated into higher valued products. Use of a membrane to pre-fractionate the transmix can increase throughput of a transmix refining facility compared to distillation alone. Further, in other embodiments, the membrane can replace distillation completely, thereby lowering energy costs of refining compared to distillation refining.
In the descriptions that follow, the term transmix is being used to refer to a by-product of refined products pipeline operations. For example, transmix can refer to the interface or buffer material between two different pipeline products in a pipeline shipment, which is created by the mixing of different specification products during pipeline transportation. Transmix refining methods disclosed herein split the transmix back into specification products, such as unleaded gasoline and diesel fuel.
Referring to
In one embodiment, the membrane 14 is an aromatic hydrocarbon selective membrane. As used herein, the term “aromatic hydrocarbon” means a hydrocarbon-based organic compound comprising at least one aromatic ring. The rings may be fused, bridged, or a combination of fused and bridged. The membrane 14 is permselective to the aromatic components. For example, when transmix is an off-grade mixture created from diesel fuel and gasoline, gasoline blending components and diesel components can be separated using the membrane 14. More particularly, the permeate stream 16 is aromatics rich, while the retentate stream is aliphatics rich. The term “rich” is being used herein to describe a concentration relative to the transmix feed 12, that is a concentration of a given component is greater in a rich stream than in the feed stream.
The membrane 14 comprises a polymer. The term polymer includes, but is not limited to, homopolymers, copolymers, terpolymers, prepolymers, polymer blends, and oligomers. For example, suitable polymers include, but are not limited to, polyesters, polyethers, polysulfones, polyimides, polyamides, polymers derived from bisphenol-A dianhydride, polyvinyl alcohols, polyacrylonitriles, polyurethanes, polyureas, polyacrylic acids, polyacrylates, elastomeric polymers such as polybutadiene, polyisoprenes, polyvinylpyridines, halogenated polymers, fluoroelastomers, polyvinyl halides, polysiloxanes, poly dimethyl siloxanes, a copolymer comprising at least one of the foregoing polymers, a blend comprising at least one of the foregoing polymers, an alloy comprising at least one of the foregoing polymers, or a combination comprising at least one of the foregoing polymers, copolymers, blends, or alloys.
In operation, the membrane 14 can generate the permeate stream 16 and the retentate stream 18 using perstractive separation techniques, pervaporation separation techniques, and the like. For example, the transmix feed 12 is passed along one side of the membrane 14 and a vacuum is applied to the membrane 14 at the opposite side so that the aromatics selectively permeate through the membrane 14 to produce the permeate stream 16. In other embodiments, the transmix feed 12 is passed along one side of the membrane 14 and a sweep gas or liquid is passed on the opposite side of the membrane 14.
An optional holding vessel 20 is in fluid communication with the permeate stream 16 such that the permeate stream 16 can be collected and stored in the holding vessel 20 for later processing or blending with gasoline. A distillation device 22 is in fluid communication with the retentate stream 18 such that the retentate stream 18 can be fed to a distillation device 22. The number of trays, reflux ratio, and the like of distillation device 22 vary depending on the composition of the retentate stream 18. The distillation device 22 separates the retentate stream 18 into a top stream 24 and a bottom stream 26. The top stream 24 comprises lighter end components that may be employed as gasoline blending components. The top stream 24 is collected and stored in a holding vessel 20 for later processing or blending with gasoline. Similarly, the bottom stream 26 is collected and stored in a holding vessel 28 for later processing or blending with diesel fuel.
Referring to
The distillation device 22 separates the retentate stream 18 and the transmix feed into a top stream 24 and a bottom stream 26. The top stream 24 comprises lighter end components that may be employed as gasoline blending components. The top stream 24 is collected and stored in a holding vessel 20 for later processing or blending with gasoline. Similarly, the bottom stream 26 is collected and stored in an optional holding vessel 28 for later processing or blending with diesel fuel.
Referring to
The distillation device 22 separates the retentate stream 18 into the top stream 24 and the bottom stream 26. The top stream 24 comprises lighter end components that may be employed as gasoline blending components with a relatively lower sulfur concentration than the sulfur concentration initially present in the transmix feed 12. The top stream 24 is collected and stored in an optional holding vessel 32 for later processing or blending with gasoline. Similarly, the bottom stream 26 is collected and stored in the holding vessel 28 for later processing or blending with diesel fuel. More particularly, the bottom stream 26 comprises diesel components having a relatively lower sulfur concentration than the sulfur concentration initially present in the transmix feed 12.
Referring to
The holding vessel 20 is in fluid communication with the permeate stream 16 such that the permeate stream 16 can be collected and stored in the holding vessel 20 for later processing or blending with gasoline. An optional holding vessel 34 is in fluid communication with the retentate stream 18 such that the retentate stream 18 can be collected and stored in the holding vessel 34 for later processing or blending with diesel. Advantageously, this embodiment separates transmix without further processing using a distillation device. In other words, a distillation device is not employed in method 70. Since distillation devices employ more energy that the membrane 14, significant cost savings related to energy consumption can be realized. Further, in various embodiments, the membrane 14 may be employed to reduce the sulfur composition of the transmix 12. For example, the permeate stream 16 comprises a sulfur concentration much greater than the feed 12 or retentate stream 18.
Advantageously, membranes employed in transmix refining are simple passive systems with no moving parts. They increase transmix refining capacity and represent a low investment option of refining compared to distillation. Additionally, the membranes are a modular plant technology that allows for quick deployment, as well as flexibility in refining operations. Moreover, the membranes allow the transmix to be separated into higher valued products, increase throughput of a transmix refining facility compared to distillation alone, and lower energy costs of refining compared to distillation refining.
While the disclosure has been described with reference to an exemplary embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the disclosure. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the disclosure without departing from the essential scope thereof. Therefore, it is intended that the disclosure not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this disclosure, but that the disclosure will include all embodiments falling within the scope of the appended claims.
