KR20130143577A - Low energy distillation system and method - Google Patents

Abstract

The present invention provides a distillation system for separating two or more components of a multicomponent fluid feed, the system comprising a stripper section, the stripper section containing (i) a feed of fluid containing two or more components. An inlet to (i) a compressor in fluid communication with the more volatile fraction of the fluid in the stripper section to provide an effluent feed, and (iii) in fluid communication with a less volatile fraction in the stripper section. Includes reboiling. The distillation system also includes a rectifier zone aligned vertically below the stripper zone and for receiving the effluent feed from the compressor, which further comprises: (i) receiving a cooling fluid; A condenser in fluid communication with the more volatile fraction of the effluent feed from the compressor, the outlet including a outlet for removing one or more components from the more volatile fraction of the effluent feed, and (ii) less of the effluent feed from the compressor. An outlet for recycling the volatile fraction back to the stripper zone. A heat pipe is provided between the lower rectifier zone and the upper stripper zone to transfer heat energy from the rectifier zone to the stripper zone, thereby improving the effective energy efficiency of the distillation.

Description

LOW ENERGY DISTILLATION SYSTEM AND METHOD}

The present invention relates to energy efficient distillation systems and methods, including energy efficient distillation systems and methods for use in oil refinery operations and the like.

Refineries consume a lot of energy. In a typical refinery process, about 10% of the energy content of crude oil is spent to refine the crude into various end products. Large amounts of energy are used to carry out gas-liquid equilibrium separation by bringing liquid and semi-liquid feeds near their boiling points. Less energy distillation techniques will greatly improve the total energy efficiency of the refinery.

In a conventional distillation process, the waste heat of the condenser at the top of the column is not recovered. This results in very low energy efficiency (e.g., less than 10% effective efficiency). Thermal integrated distillation columns (HIDiC) have already been disclosed but have not yet been commercialized. Shell and tube type constructions, or distillation columns with two central trays, and distillation columns with rectifier sections inside the stripper section are generally described. Since the HIDiC structure presented in the academic literature generally utilizes a horizontal arrangement of rectifier and stripper zones, the need for complex parallel heat transfer arrangements and dual parallel columns for thermal integration is a barrier, which increases the working process. Such an arrangement may not be practical for retrofitting existing columns.

1 illustrates a conventional distillation operation 1000. A condenser 1010 located on top of column 1020 removes heat from vapor-rich process stream 1030 to produce a liquid product stream 1040 that is richer in more volatile ("lighter") products. do. The condenser also produces a reflux stream 1050 that is used to improve the quality of the gas-liquid stage separation process. The heat removed in the condenser is not recovered but is discharged to cooling water or air, resulting in low energy efficiency of distillation. In a distillation column, the second law thermodynamic efficiency, also referred to as energy efficieny, is generally less than 10%. Effective energy efficiency defines how efficient a system is compared to a thermodynamically complete system starting with the same inlet feed and performing the same operation to produce the same product stream.

As can be seen in FIG. 1, in a conventional distillation column, rectifier zone 1060 is positioned vertically adjacent to stripper zone 1070.

2 is described in J. of Chem. Tech. and Biotech., 78: 241-248 (2003), the entirety of which is hereby incorporated by reference. Unlike the distillation column of FIG. 1 where the rectifier zone 1060 is located above the stripper zone 1070, the rectifier zone 2060 and the stripper zone 2030 in FIG. 2 are used for heat transfer from the rectifier zone to the stripper zone. It is located in parallel with additional equipment. A compressor 2010 is used to compress the vapor from the stream 2020 exiting the stripping region 2030, which is the region defined as the region below the feed 2040. This compression causes higher temperatures in the rectifier zone 2060, which is generally the column 2080 shown on the right side of FIG. In order to control the flow of the stream 2100 exiting the bottom of the rectifying zone, a valve 2090 is provided at a location proximate to the feed. The upper portion of the second column 2080 produces a gas-rich stream 2110, which is sent to the condenser 2120 to the low volatility product 2130 and the reflux stream 2140 (rectifier zone 2060). Cycles).

When heat is transferred from the rectifier zone 2060 to the stripper zone 2030, a stream 2100 is created that provides liquid reflux between the rectifying and stripping zones. The “reflux ratio” of the stream 2100 that provides the liquid reflux function is set by a column heat balance that is estimated and controlled based on the amount exiting the rectification zone bottom by the valve 2090.

Another presented HIDiC manipulation 3000 (see Z. Olujic et al., Energy 31: 3083-3096 (2006), incorporated herein by reference in its entirety) is shown in FIG. 3.

3 illustrates a concentric tray design with a stripping zone located outside of the rectifier zone, with the heat transfer panel 3030 disposed between the trays. Lateral heat transfer occurs between two equilibrium or concentric columns, which may be provided, for example, by the inner rectification zone 3010 surrounded by the outer stripping zone 3020.

4, disclosed in US Pat. No. 4,234,391, which is incorporated herein by reference in its entirety, illustrates a conceptual design 4000 in which heat pipe 4010 transfers heat from rectifier zone 4040 to stripping zone 4030. In the rectifier zone 4040 and the stripping zone 4030 is separated by a partition 4020. As shown in FIG. 4, the heat pipes are arranged in a transverse position. Such HIDiC designs have not been commercialized to this day.

Thus, there remains a need and desire to improve the energy efficiency of distillation operations, especially in refineries. There is also a need for a HIDiC design that can be easily retrofitted to existing distillation column internals.

One aspect of the invention provides a distillation system for separating two or more components in a multicomponent fluid feed. The system includes a stripper zone, which stripper zone is in fluid communication with (i) an inlet for receiving a supply of fluid containing two or more components, and (ii) a more volatile fraction of the fluid in the stripper zone. A compressor providing the effluent feed, and (iii) a reboiler that receives the heating fluid and is in fluid communication with the less volatile fraction in the stripper zone. The distillation system also includes a rectifier zone aligned vertically below the stripper zone and for receiving the effluent feed from the compressor, which further comprises: (i) receiving a cooling fluid; A condenser in fluid communication with the more volatile fraction of the effluent feed from the compressor, the outlet including a outlet for removing one or more components from the more volatile fraction of the effluent feed, and (ii) less of the effluent feed from the compressor. An outlet for recycling the volatile fraction back to the stripper zone.

Another aspect of the invention provides a distillation method for separating two or more components in a multicomponent fluid feed. The method includes introducing a feed of a fluid containing two or more components into a stripper zone, wherein the stripper zone is (i) an inlet for receiving a feed of the fluid, and (ii) in the stripper zone. A compressor in fluid communication with the more volatile fraction of the fluid to provide an effluent feed, and (iii) a reboiler containing the heating fluid and in fluid communication with the less volatile fraction in the stripper zone. The distillation method also includes directing the effluent feed from the compressor to a rectifier zone aligned vertically below the stripper zone, the rectifier zone containing (i) a cooling fluid, A condenser in fluid communication with the more volatile fraction of the effluent feed from the compressor and including an outlet for removing one or more components from the more volatile fraction of the effluent feed, and (ii) the effluent feed from the compressor An outlet for recycling the less volatile fraction to the stripper zone.

Hereinafter, the present invention will be described with reference to the accompanying drawings.
1 is a schematic illustration of a conventional distillation column having a rectifying zone located above the stripping zone and no energy removed is recovered in the condenser.
2 is a schematic of a conventional HIDiC concept.
3 is a schematic of a concentric HIDiC design in which heat is transferred from the inner rectifier to the outer stripper zone.
4 is a schematic diagram of a HIDiC design with heat pipes transferring heat from the rectifier zone to the stripper zone disposed in the transverse position.
5 is a schematic representation of an exemplary embodiment of the distillation system of the present invention.
6 is a schematic of another exemplary embodiment of the distillation system of the present invention.

The following definitions are provided without limitation for illustrative purposes.

"Effective energy efficiency" defines how efficient separation is compared to a thermodynamically complete system. The effective energy of each stream is the theoretical maximum work that can be produced, measured through a series of reversible steps in equilibrium with the surrounding environment. The increase in the amount of effective energy of the product relative to the input feed represents the minimum amount of work required. Effective energy is defined as the ratio of the minimum amount of work divided by the total energy consumed to actually perform the separation.

The term “produced on an industrial scale” as defined herein refers to continuous operation over a long period of time (eg, over at least one week or month, or one year) in anticipation of revenue generated from the sale or distribution of the final product. By reference (with the exception of interruptions required to maintain the plant), it indicates the type of production in which the final product is produced. Industrial scale production is typically distinguished from laboratory or pilot plant settings, which are maintained only for a limited period of time for experimentation or investigation and are performed for research purposes and do not expect to generate revenue from the sale or distribution of the final product.

According to the present invention, a distillation system is provided for separating two or more components in a multicomponent fluid feed. The system includes a stripper zone, the stripper zone being in fluid communication with (i) an inlet for receiving a supply of fluid containing two or more components, and (ii) a more volatile fraction of the fluid in the stripper zone. A compressor providing the effluent feed, and (iii) a reboiler that receives the heating fluid and is in fluid communication with the less volatile fraction in the stripper zone. The distillation system also includes a rectifier zone aligned vertically below the stripper zone and for receiving effluent feed from the compressor, the rectifier zone further comprising: (i) receiving cooling fluid; And an outlet for fluid communication with the more volatile fraction of the effluent feed from the compressor, the outlet for removing one or more components from the more volatile fraction of the effluent feed, and (ii) the effluent from the compressor An outlet for recycling the less volatile fraction of the feed back to the stripper zone.

According to another aspect of the invention, a distillation process is provided for separating two or more components in a multicomponent fluid feed. The method includes introducing a feed of a fluid containing two or more components into a stripper zone, wherein the stripper zone is (i) an inlet for receiving a feed of the fluid, and (ii) in the stripper zone. A compressor in fluid communication with the more volatile fraction of the fluid to provide an effluent feed, and (iii) a reboiler containing the heating fluid and in fluid communication with the less volatile fraction in the stripper zone. The distillation method also includes directing the effluent feed from the compressor to a rectifier zone aligned vertically below the stripper zone, the rectifier zone containing (i) a cooling fluid, A condenser in fluid communication with the more volatile fraction of the effluent feed from the compressor and including an outlet for removing one or more components from the more volatile fraction of the effluent feed, and (ii) the effluent feed from the compressor An outlet for recycling the less volatile fraction to the stripper zone.

The methods and systems disclosed herein are described in combination with one another for understanding and practice.

For illustrative purposes, without limitation, referring to the embodiment of FIG. 5, the stripper region 5250 and the rectifier region 5500 are contained in a single structure 5010 that is at least partially sealed. The multicomponent liquid feed 5100 is introduced at a temperature near the boiling point of the feed composition over the feed tray or stage 5120 of the distillation column 5010. In a preferred embodiment, the feed introduced into the distillation system is primarily hydrocarbon, but any multicomponent feed can be separated using the methods and systems disclosed herein.

Once the feed is introduced into the column, a less volatile component-rich liquid fraction flows down the column and a more volatile component-rich gas fraction in the feed flows up towards the gas compressor 5150. A partition 5200 is provided to prevent the heavier component-rich liquid fraction in the feed from entering the rectifier zone 5500 under the column. The zone between the feed and the partition constitutes a stripping or stripper zone 5250 of the distillation column.

Reboiler 5300, supplied with a source of steam or other heating fluid, introduces heat into the column and returns to base product 5350 and stripping zone 5250 rich in less volatile (“heavy”) product. Create a thin stream 5400.

Compressed steam 5450 exiting compressor 5150 is directed to the bottom of rectifier zone 5500. The compression of the gas results in a higher temperature in the rectifier zone 5500 than in the stripper zone 5250, which consists of a column section below the partition 5200. Thus, in one embodiment, rectifier zone 5500 is operated at a higher average temperature than stripper zone 5250.

In this particular embodiment, the liquid component 5600 is withdrawn from the bottom of the column and introduced into the feeder 5100 into the stripper zone 5250 or, for example, by means of a throttle valve or pump 5650. Is introduced into the feed tray 5120. A condenser 5700 is provided at the top of the rectifying zone to receive a supply of cooling water and to produce a reflux stream 5800 that is light product-rich product 5750 and sent back into the rectifying zone as a column. The composition exiting the condenser may comprise or consist essentially of the light low boiling component of the feed 5100.

In one embodiment, the final product derived from the methods and systems disclosed herein is produced on an industrial scale.

As described above, the rectifier zone 5500 is operated at a higher temperature than the stripper zone 5250. The stripper zone 5250 located vertically close above the rectifier zone 5500 transfers heat from the rectifier zone 5500 to the stripper zone 5250 using one or more heat pipes 5850 and the heat burden on the reboiler. It can be reduced. Thus, in one embodiment of the invention, the system includes one or more heat pipes intersecting between at least a portion of the rectifier zone and at least a portion of the stripper zone to transfer heat from the rectifier zone to the stripper zone. .

The heat burden of condenser 5700 as well as reboiler 5300 is significantly reduced and significantly higher energy efficiency is achieved. In essence, liquid reflux in the rectifier is generated by heat transfer from the rectifier zone to the stripper zone as well as any heat removal in the condenser.

As shown in FIG. 5, heat pipe 5850 can be oriented substantially perpendicular to the base of the rectifier zone, thereby directing condensate inside the heat pipe 5850 to the rectifier zone by gravity. The system 5000 may further be equipped with one or more hollow distillation trays 5900, 5950 located at one or more end portions of the heat pipes. Alternatively, as shown in FIG. 5, the system may include, for example, two hollow distillation trays 5900, 5950 located at both ends of the heat pipe. The hollow distillation trays 5900 and 5950 may further be provided with fins (not shown) to improve heat transfer area to and from the heat pipes.

The condensate inside the heat pipe is recycled at the bottom by gravity to the hotter rectifier zone 5500. Gravity-driven heat pipes have greater carrying capacity compared to wick-driven heat pipes such as the heat pipe shown in FIG. 4.

It should be noted that the features summarized in FIG. 5 are in accordance with only one non-limiting embodiment. For example, only one heat pipe is shown in FIG. 5 for clarity. In other embodiments, a plurality of heat pipes are provided from the stages (eg trays) of the distillation operation, in particular from some or all of the stages of the rectifier section to the corresponding trays of the stripper section.

The compression provided by the compressor 5150 causes higher temperatures in the rectifier zone 5500. Heat is transferred from the rectifier zone 5500 to the stripping zone 5250 via one or more heat pipes. This heat transfer reduces and / or reduces the heat released from the condenser. In addition, the thermal burden of the reboiler 5300 at the bottom of the stripping zone 5250 is reduced, providing an improvement in overall effective energy efficiency (eg, below 50% and above).

The heat pipe in the rectifying zone 5950 acts as an inner-condenser, and the heat pipe in the stripping zone 5900 acts as an inner-reboiler. The working fluid inside heat pipe 5850 condenses in stripping zone 5900 and vaporizes in rectifying zone 5950, transferring heat from the rectifier zone to the stripper zone. When this heat transfer occurs, the process liquid in the stripping zone is vaporized and the process gas in the rectifying zone is condensed. Based on the design of the exemplary embodiment shown in FIG. 5 or FIG. 6, the heat pipe working fluid is condensed as it moves from the hotter rectifier zone to the colder stripper zone and the work fluid is gravity again back to the rectifier zone. As it flows in, a stream is formed that provides liquid reflux function. The amount of heat pipe heat transfer is set by the design of the heat pipe, including the physical layout and gravity drive force, including the choice of working fluid, temperature difference, working fluid pressure level, surface area of the two heat transfer zones. The heat pipe design determines the amount of reflux generated by the inner-condenser and the amount of vaporization generated by the inner-reboiler.

Although the present invention has been described in terms of tray type distillation columns for convenience, it may be equally applied to packed towers. For example, packed towers may be desirable because of pressure differential considerations in situations involving debottlenecking of the distillation apparatus. In addition, the packed tower can provide the ability to compensate more of the lost area when a heat pipe is installed inside the column. A filled rectification zone with a lower pressure differential will also allow a lower compression ratio of the compression of the stripper zone overhead to feed into the rectification zone. For example, a heat pipe can be used to transfer heat from other zones of the rectifier to the corresponding zones of the stripper. The corresponding zone will be a zone that maintains the same delta temperature between the rectifying zone in-condenser and the stripping zone in-reboiler. This means that the upper inner-condenser transfers heat to the upper inner-reboiler and the lower inner-condenser transfers heat to the lower inner-reboiler, as shown in system 6000 in FIG. 6. This heat pipe may, according to one non-limiting embodiment, have a heat exchanger with fins extending radially on both ends of the heat pipe.

As with the embodiment shown in FIG. 5 or FIG. 6, the invention disclosed herein provides a more practical column structure wherein, unlike conventional distillation, the rectifier zone is located below in the vertical direction of the stripper zone. Heat transport from the rectifier zone 6500 to the stripper zone 6250 can be accomplished using one or more heat pipes, with heat being transferred primarily in the axial direction. This vertical structure causes gravity to return the condensate in the heat pipe from the stripper zone to the lower rectifier zone. Thermal integration is achieved in a single column, which facilitates retrofitting of existing columns and reduces the plot area required for the second column. FIG. 6 illustrates the use of an external heat pipe that is heat siphon oriented as a vapor riser 6851 and liquid circulation 6852 (which causes the heat pipe working fluid to agglomerate and avoid overflow). Embodiment is illustrated. Elevator 6851 and circulator 6852 are operatively coupled to internal heat transfer surface 6853. The internal heat transfer surface 6853 may be a hollow distillation tray, structural packing of a plate or frame type structure, or any other suitable heat transfer device that promotes heat transfer without limiting column performance. The same concept may also be achieved with an external heat pipe that is single-connected with countercurrent vapor and liquid flows, provided that the heat pipe is sized to avoid overflow.

Operating conditions for the systems and methods of the invention disclosed herein can be determined by one of ordinary skill in the art. See also, for example, Internal heat integration-the key to an energy-conserving distillation column, Z. Olujic, F. Fakhri, A de Rijke, F de Graauw and PJ Jansens, J of Chemical Technology and Biotechnology, 78, page 241-248 (online 2003); Internal versus External Heat Integration. Operational and Economic Analysis, J. P. Schmal, H. J. Van Der Kooi, A. De. Rijke, Z. Olujic and P. J. Jansens, Trans IChem E, Part A, Chemical Engineering Research and Design, 2006, 84, page 374-380; A new approach to the design of internally heat integrated tray distillation columns, M. Gadalla, Z. Olujic, A. de Rijke and J. P. Jansens, European Symposium on Computer Aided Process Engineering, 15: 805-810; A thermo-hydraulic approach to conceptual design of an internally heat-integrated distillation column (i-HIDiC), M. Gadalla, L. Jimenez, Z. Olujic and PJ Jansens, Computers and Chemical Engineering (2006), doi: 10.1016 / j.compchemeng. 2006.11.006]; And Conceptual design of an internally heat integrated propylene-propane splitter, Z. Olujic, L. Sun, A. de Rijke, P. J. Jansens, Energy 31 (2006) 3083-3096.

The present invention is not to be limited in scope by the specific embodiments described herein. Indeed, from the foregoing specification and the accompanying drawings, various modifications of the invention in addition to those described herein will be apparent to those skilled in the art. Such modifications are intended to fall within the scope of the appended claims.

It should also be understood that all values are approximate and provided for illustration.

Patents, patent applications, publications, product descriptions, and protocols have been cited throughout this application, each disclosure of which is incorporated herein by reference for all purposes in its entirety.

Claims (9)

A distillation system for separating two or more components in a multicomponent fluid feed,
(a) stripper zones and
(b) a rectifier zone aligned vertically below the stripper zone and for receiving an effluent feed from the compressor
Including, wherein,
The stripper zone (a)
(i) an inlet for receiving a feed of a fluid containing two or more components,
(ii) a compressor in fluid communication with the more volatile portion of the fluid in the stripper zone to provide an effluent feed, and
(iii) a reboiler containing a heating fluid and in fluid communication with a less volatile fraction in the stripper zone.
Lt; / RTI >
The rectifier zone (b) is further
(i) a condenser containing an outlet for receiving a cooling fluid and in fluid communication with a more volatile fraction of the effluent feed from the compressor and for removing one or more components from the more volatile fraction of the effluent feed, and
(ii) an outlet for recycling the less volatile fraction of the effluent feed from the compressor back to the stripper zone
Comprising a distillation system. The method of claim 1,
And the stripper zone and the rectifier zone are contained in a single structure that is at least partially sealed. 3. The method according to claim 1 or 2,
And the rectifier zone is operated at a higher average pressure and temperature than the stripper zone. The method of claim 3, wherein
And at least one heat pipe for transferring heat from said rectifier zone to said stripper zone across at least a portion of said rectifier zone and at least a portion of said stripper zone. 5. The method of claim 4,
And the heat pipe is oriented substantially perpendicular to the base of the rectifier zone. 5. The method of claim 4,
And the heat pipe directs condensate inside the heat pipe to the rectifier zone by gravity. 5. The method of claim 4,
At least one hollow distillation tray is located at at least one end of the heat pipe to increase the transfer surface area for heat transfer. The method according to any one of claims 1 to 7,
The distillation system, wherein the feed is mainly hydrocarbon. A distillation process for separating two or more components in a multicomponent fluid feed using the distillation system according to any one of claims 1 to 8.
(a) introducing a feed containing two or more components into the stripper zone,
(b) directing the effluent feed from the compressor to a rectifier zone aligned below and vertically aligned with the stripper zone;
Method comprising the same.

Images