KR20200020901A - Method and apparatus for using waste heat stream in aromatic complex - Google Patents

Abstract

The present invention relates to a method and apparatus for using a waste heat stream in an aromatics complex. More specifically, the present invention relates to a method and apparatus for using waste heat to drive multiple compressor services in an aromatic complex to achieve energy savings and provide otherwise low heat.

Description

Method and apparatus for using waste heat stream in aromatic complex

Priority statement

This application claims the benefit of US Provisional Application No. 62 / 527,710, filed June 30, 2017, the contents of which are hereby incorporated by reference in their entirety.

Technical Field

The present invention relates to a method and apparatus for using a waste heat stream in an aromatics complex. More specifically, the present invention relates to a method and apparatus for using waste heat to drive multiple compressor services in an aromatic complex to achieve energy savings and otherwise use waste heat.

In Organic Rankine Cycle (ORC) systems, process waste heat that is otherwise delivered to air- and water-cooled coolers can be used to vaporize the low-boiling refrigerant working fluid at moderate temperatures and pressures, and from vapor Energy can be recovered. A typical organic Rankine cycle (ORC) uses a working fluid to drive a turboexpander connected to a generator that delivers power to an electrical grid. The application of an ORC to recover waste heat at a refinery is typically a relatively low efficiency system with high capital costs, with 50% of the capital costs associated with turboexpanders and generators.

Rankine cycles are useful for generating power from low or medium temperature heat sources. The working fluid is evaporated when exchanging heat with the heat source, for example in an evaporator or boiler, and then the evaporated fluid is used in a turboexpander that drives a generator or other load. The exhaust steam from the turboexpander condenses and the resulting fluid can be recycled for heat exchange. ORC uses organic fluid as the working fluid. Known applications of ORC systems include generating power from geothermal heat sources, as described in US Pat. No. 5,497,624 and US Pat. No. 6,539,718. The use of ORCs in combination with fuel cell products and other forms of waste heat is described in US 2006/0010872, WO 2006/104490, and WO 2006/014609. Applications of ORCs, including solar energy and biomass, can be found in Chinese patent 11055121, Japanese Patent Application Publication No. 2003227315A2, International Journal of Energy Research, 28 (11): 1003-1021 (2004), And Energy, 32 (4): 371-377 (2007). The use of ORCs for the exothermic reaction of paraxylene to terephthalic acid and especially for the recovery of energy from liquid phase oxidation is also taught in US Pat. No. 7,049,465.

There is a continuing need in the art for a method of recovering energy, such as electricity, from sources that provide otherwise low heat waste, particularly those resulting from refinery and petrochemical plant operations. This need is particularly important in view of the high amounts of low heat generated in these operations and the high energy and cost savings potentially realized by recovering even some of this heat. The net generation of electricity is of significant benefit to refiners and petrochemical producers due to the reduced emissions of combustion products CO ₂ from materials used as raw materials in power plants (eg coal).

The proposed invention will significantly improve economics by significantly reducing the capital costs associated with turboexpander and generator systems by replacing turboexpander and generator systems with direct compressor drive systems. The compressor is a relatively high consumer of power in the refinery process unit, which is typically driven by either a steam turboexpander or an electric motor. The proposed invention seeks to replace the compressor power supply with the power supplied by the organic working fluid. Compressor drivers are a low cost alternative to turboexpanders and generators. The power saved in compressor operation is equal to or greater than the power that would otherwise be supplied to the grid.

Even energy efficient aromatic complexes can have a significant amount of lower waste heat, which can be recovered to generate electricity using organic Rankine cycles. The present invention seeks to significantly improve capital costs and capital recovery. Such energy recovery systems can be applied to several different columns that produce overhead energy used to drive both recycle gas compressors.

1 illustrates a method and apparatus for using waste heat to drive multiple compressor installations in an aromatic complex.

The following detailed description is merely illustrative in nature and is not intended to limit the applications and uses of the described embodiments. Furthermore, there is no intention to be bound by any theory presented in the background above or in the detailed description below.

Further description of the method of the invention is presented with reference to FIG. 1. 1 is a simplified flow diagram of a preferred embodiment of the present invention and is not intended as an undue limitation on the generally broad scope of the description and the appended claims provided herein. Certain hardware, such as valves, pumps, compressors, heat exchangers, instrumentation and controllers, have been omitted since they are not essential to a clear understanding of the present invention. The use and application of such hardware is well within the ordinary skill in the art.

The present invention relates to a method of generating power from a source of lower heat, in particular refinery and petrochemical process streams, through the use of an organic Rankine cycle (ORC). The source of lower heat may include any process stream from which it is desired to recover at least a portion of the heat content in electrical form. These streams are often commonly cooled with air and / or water, because these streams are economically useful for heat integration applications (eg, preheating, low pressure, medium or high pressure steam generation, or distillation column reboiling). It is not high enough temperature for). The temperature of this source of lower heat is generally between 75 ° C and 180 ° C, and often between 50 ° C and 120 ° C. Representative streams as a source of lower heat include refinery and petrochemical process streams having temperatures within these ranges, and specific examples include distillation columns and other columns (e.g., absorbers, strippers, quench towers) as described above. overhead steam from vapor-liquid contact devices such as quenching towers, scrubbers, and the like, and more generally overhead products. Another preferred example is a product run-down cooler, for example a desorbent cooler in an aromatic complex, especially for preheater installations. Another example of a low temperature heat source is a reactor effluent stream after process exchange before a typical air cooled product condenser.

Distillation columns refer to those used in the separation process based on the difference in the relative volatility of the components present in the mixture that is not pure. Distillation involves purifying components with different relative volatility by achieving a number of theoretical stages of vapor-liquid equilibrium along the length of the vertical column. Rising vapor, which is rich in lower boiling constituents as compared to liquid vaporized at lower stages in the column, is contacted with descending liquid, which is rich in higher boiling constituents than vapor condensing at higher stages in the column.

Distillation columns, which also include a fractionation column that provides a plurality of product fractions each having components within a predetermined boiling range, are widely used, for example, for separating effluent from the reaction zone. The reaction zone generally comprises one or more reactors which are used to convert (eg catalytically) the feedstock into more valuable reactor effluents which contain product fractions which are subsequently separated off by fractionation. Thus, the hydrocarbon-containing feed to a vapor-liquid contacting device, such as a distillation column, may optionally contain a single stage high temperature, medium temperature, and / or low temperature for removing hydrogen and / or light hydrocarbons such as methane. After initial treatment or separation (in a separator), otherwise upgraded hydrocarbon products comprising at least a portion of the reactor effluent or reactor effluent. These hydrocarbon-containing feeds generally comprise at least 80% by weight hydrocarbons, often at least 90% by weight hydrocarbons.

The claimed invention is a method of using waste heat to drive multiple compressor installations in an aromatic complex. There are several heat sources located near power sources with complexes. There are two potential waste heat sources where the column overhead condenser and process cooler are located. Locations on toluene columns can be used, and locations on para-xylene extraction zones can be used. However, it is contemplated that other locations may also be used. The recycle gas compressor may be located at a location outside the toluene extraction zone and at a location outside the isomerization zone. However, it is contemplated that other locations may also be used.

A method of using waste heat to drive multiple compressor installations in an aromatic complex, according to an exemplary embodiment of the present invention, is illustrated in FIG. 1. As shown, fractionation column 100 fractionates hydrocarbon feed 5, which may be, for example, a hydrocarbon product upgraded from the reaction zone of a petrochemical process. As discussed above, the overhead product 10, which may be completely or substantially vapor phase, is generally removed from the fractionation column 100 at a temperature that results in a lower heat source suitable for power generation according to the methods described herein. do. In addition, overhead product 10 may be somewhat cooled to a temperature suitable for this application after exiting fractionation column 100. The overhead product 10 may be all or part of the net overhead from the fractionation column 100.

According to the embodiment shown in FIG. 1, the overhead product 10 is for indirect heat exchange with an organic fluid 18 which typically has a boiling point 5 ° C. to 14 ° C. lower than the temperature of the overhead product 10. Passed to evaporator 200. All operating pressures in the ORC system are adjustable so that the refrigerant characteristics match the heat source temperature. Suitable organic fluids include fluorocarbons and chlorofluorocarbons (CFCs) which are used commercially as refrigerants. Representative fluorocarbons include 1,1,1,3,3-pentafluoropropane (HFC-245fa), 1,1,1,2-tetrafluoroethane (HFC-134a), 1,1,2,2 Tetrafluoroethane (HFC-134), 1,1,1,3,3-pentafluorobutane (HFC-365mfc), 1,1,1,2,3,3,3-heptafluoropropane ( HFC-227ea), and mixtures thereof. Representative CFCs include CFC-113 (1,1,2-trichloro-1,2,2-trifluoroethane), CFC-11 (trichlorofluoromethane), CFC-12 (dichlorodifluoromethane) , CFC-22 (chlorodifluoromethane), and mixtures thereof. In addition, mixtures of fluorocarbons and chlorofluorocarbons may be used in the organic fluid.

Indirect heat exchange between the overhead product 10 and the organic fluid 18 in the evaporator 200 generally has a temperature of 10 ° C. to 75 ° C. lower than the temperature of the overhead product 10 immediately before heat exchange. Provide the cooled overhead product 20. In an exemplary embodiment, the cooled overhead product 20 generally has a temperature of 50 ° C. to 125 ° C., and often 65 ° C. to 100 ° C., immediately after exchanging heat. Some or all of the heat removed from overhead product 20 as a result of indirect heat exchange is at least a portion (and such) of cooled overhead product 20, in contrast to sensible heat that causes a temperature decrease of such product. Latent heat causing condensation of the overall increased liquid fraction of the product).

In addition, vapor-rich fluid 22 with increased vapor fraction relative to organic fluid 18 exits evaporator 200 as a result of indirect heat exchange. Preferably, the vapor-rich fluid 22 is completely vaporous after exiting the evaporator 200. The vapor-rich fluid 22 is then used in the turboexpander wheel (s) 300 to drive a generator or other type of load (for generating electricity). The turboexpander 300 is directly connected to the generator 320 and one or more compressors 340 and 350. The power supplied to the turboexpander by the refrigerant is transferred directly to the compressor installation (s) via internal or external gears such as bull gears with multiple pinions. The generator can be used as a motor for starting a compressor installation that initially uses the power supplied from the power grid, and then converted into a generator that powers the grid as the ORC system starts to provide power from cold heat recovery. Can be.

There is an effort to integrate aromatic complex related compression equipment into a single installed turbomachinery asset, using recycle gas stream 340 and recycle gas stream 350 from different units. In one example, recycle gas stream 340 is from toluene unit and recycle gas stream 350 is from isomerization unit. The installation of a single multi-equipment compressor and turboexpander asset may be combined with three separate dedicated assets, for example, toluene unit recycle gas compressor 340, isomerization unit recycle gas compressor 350 and ORC turboexpander 300. It should be appreciated that this provides dramatic initial capital cost and installation cost advantages when compared to the installation of generator set 320.

The application of the machine type described retains the ability to independently compress the recycle gas stream without cross contamination of the process stream (340/350 / ORC refrigerant) or without any compromise on critical process performance. As illustrated in FIG. 1, there is a process boundary 342 and a process boundary 344. It is to be appreciated that the toluene unit and isomerization unit reactor loops have optimum performance at different operating pressures and temperatures. There is an opportunity to use inlet guide vanes to maximize operating flexibility for each installation 340, 350, 300 at the lowest initial cost while minimizing compressor power requirements.

In order to establish a complete ORC, turboexpander exhaust 24 from turboexpander 300 may be condensed, for example using air-cooled exchanger 400, to regenerate organic fluid 18, which is generally completely liquid. have. The example shown in FIG. 1 uses a wet surface air cooled condenser (WSAC), which is preferred for minimizing the temperature of the refrigerant, minimizing the size of the air cooled condenser and achieving optimal ORC energy. Organic fluid 18 may then be pumped through pump 500 for indirect heat exchange within evaporator 200, as discussed above.

Often, cooling of the overhead product 10 using the evaporator 200 replaces at least a portion of the cooling using conventional air-cooled and / or water-cooled indirect heat exchangers that dissipate lower heat into the environment. The cooled overhead product 20 may, in some cases, depending on its temperature, be further cooled, such as a water-cooled exchanger or a trim condenser, before passing through the overhead receiver 700.

Exchange 600 is used to preheat the refrigerant stream 18. In the example shown in FIG. 1, preheating is performed using two exchangers 600. However, in other embodiments, it is contemplated that preheating may use additional process exchangers. The preheaters can be arranged in series or in parallel to match the available low temperature heat of the aromatic complex. In another embodiment, an exchanger may be present between the turboexpander exhaust stream 24 and the condenser 400 that exchanges heat with the refrigerant pumped before the evaporator facility 200.

Condenser 400 with the proposed advanced cooling technology is a wet surface air cooled condenser (WSAC). In this technique, water is sprayed onto the tubes of the air cooled condenser, while air is directed downwards over the tube bundle. The air is then separated from the water and the water is recycled. Water significantly improves the heat transfer coefficient, and vaporization transfers heat directly from water to air. This system design is more compact and modular than typical cooling water systems because it minimizes cooling towers, heat exchangers, pumps, and associated piping. Some key WSAC benefits include the coldest outlet temperature possible, water conservation due to higher concentrations of impurities allowed, compact footprint, lower parasitic energy compared to traditional water cooling, and competitive cost and maintenance It includes having a reward.

These preheaters can be in series or parallel to match the available low temperature heat of the aromatic complex. In the overhead receiver 700, the vapor phase is removed as net column overhead 26 and the liquid phase is returned back to fractionator 100 as reflux 28.

Overall, aspects of the present invention include lower heat sources from refinery and petrochemical processes, including overhead products such as overhead vapor from vapor-liquid contacting devices including distillation columns, absorbers, strippers, quench towers, scrubbers, and the like. A method for generating power from Instead of dumping the low temperature heat contained in these steams into cooling air and / or cooling water, this steam can be used to evaporate the organic working fluid. The vapor of the working fluid can then be sent to a turboexpander to drive a generator or other load, thereby reducing overall usability requirements and otherwise emissions such as CO ₂ generated in electricity production.

In view of the present disclosure, it will be appreciated that several advantages may be achieved and other advantageous results obtained. Those skilled in the art will appreciate the applicability of the methods disclosed herein to any of a number of refineries, petrochemicals, and other processes. Those skilled in the art having the knowledge obtained from the present disclosure will recognize that various changes can be made in the above process without departing from the scope of the invention. The mechanisms used to describe theoretical or observed phenomena or results are to be construed as illustrative only and do not in any way limit the scope of the appended claims.

While the invention has been described by what is considered to be the presently preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiment but is intended to cover various modifications and equivalent arrangements falling within the scope of the appended claims.

Specific embodiment

While the following is described in connection with specific embodiments, it will be understood that this description is intended to be illustrative, and not to limit the scope of the foregoing description and the appended claims.

A first embodiment of the present invention is a method of using waste heat, which method uses a column waste heat stream from a column, a turboexpander with one turboexpander wheel (s), one or more compressor installation (s), and a generator for a single installation machine. Passing through an expansion zone therein to produce a compressed stream; Passing the compressed stream through a condensation zone to produce a condensed stream; Passing the condensed stream through a preheating zone to produce a preheated stream; Passing the preheated stream through an evaporation zone to produce an evaporated stream; And passing the evaporated stream back to the column. One embodiment of the invention is one of any of the previous embodiments of this paragraph up to the first embodiment of this paragraph, any of which may be derived from a plurality of waste heat sources in the aromatic complex. Form, or all embodiments. One embodiment of the invention is one, any or all of the previous embodiments of this paragraph up to the first embodiment of this paragraph wherein the temperature of the waste heat stream is between 100 ° C. and 140 ° C. Form. One embodiment of the present invention is one, any, or all of the previous embodiments of this paragraph up to the first embodiment of this paragraph, wherein the column may be any column in an aromatic complex. Form. One embodiment of the invention is one, any, or all of the previous embodiments of this paragraph up to the first embodiment of this paragraph wherein the column is an extraction column. One embodiment of the present invention is one, any, or all of the previous embodiments of this paragraph up to the first embodiment of this paragraph, wherein the column is a reformate splitter. to be. One embodiment of the present invention is one, any, or all of the previous embodiments of this paragraph up to the first embodiment of this paragraph wherein the column is an A ₈ stripper. One embodiment of the present invention is one, any, or all of the previous embodiments of this paragraph up to the first embodiment of this paragraph, wherein the preheating section includes a plurality of preheaters. . An embodiment of the invention is one, any or all of the previous embodiments of this paragraph up to the first embodiment of this paragraph, wherein the evaporation zone comprises a plurality of evaporators. .

A second embodiment of the present invention is an apparatus using waste heat, which includes an inlet in direct communication with a column having an overhead line; The overhead line is in direct communication with the evaporation zone having an overhead line in direct communication with the expansion zone and an outlet line in direct communication with the overhead receiver; The expansion zone has an expansion zone outlet line in direct communication with the condensation zone having a compression zone outlet line, the expansion zone having a turboexpander wheel (s) with turboexpander wheel (s), one or more compressor installation (s), and a generator with a single installation machine. Contained within; The condensation zone outlet line is in direct communication with the preheating zone having the preheating zone outlet line; The preheat zone outlet line is in direct communication with the evaporation zone. One embodiment of the present invention is one, any or all of the previous embodiments of this paragraph up to the second embodiment of this paragraph wherein the waste heat stream is a vapor-rich fluid. One embodiment of the invention is one, any or all of the previous embodiments of this paragraph up to the second embodiment of this paragraph wherein the temperature of the waste heat stream is between 100 ° C. and 140 ° C. Form. One embodiment of the present invention is one, any, or all of the previous embodiments of this paragraph up to the second embodiment of this paragraph, wherein the column may be any column in an aromatic complex. Form. One embodiment of the invention is one, any, or all of the previous embodiments of this paragraph up to the second embodiment of this paragraph wherein the column is an extraction column. One embodiment of the invention is one, any, or all of the previous embodiments of this paragraph up to the second embodiment of this paragraph wherein the column is a reformate splitter. One embodiment of the present invention is one, any, or all of the previous embodiments of this paragraph up to the second embodiment of this paragraph wherein the column is an A ₈ stripper. One embodiment of the present invention is one, any, or all of the previous embodiments of this paragraph up to the second embodiment of this paragraph, wherein the preheating section comprises a plurality of preheaters. . An embodiment of the invention is one, any or all of the previous embodiments of this paragraph up to the second embodiment of this paragraph, wherein the evaporation zone comprises a plurality of evaporators. .

Without further elaboration, using the preceding description, one of ordinary skill in the art, without departing from the spirit and scope of the present invention, can make the best use of the present invention and easily identify the essential features of the present invention to make various changes and modifications of the present invention. It is believed that this can be achieved and adapted to various uses and conditions. Accordingly, the foregoing preferred specific embodiments are to be construed as illustrative only, without restricting the remainder of the invention in any way, and are intended to cover various modifications and equivalent arrangements falling within the scope of the appended claims.

In the above, unless otherwise indicated, all temperatures are described in degrees Celsius, and all parts and percentages are by weight.

Claims (10)

As a method of using waste heat,
Passing the column waste heat stream from the column to the expansion zone to produce a compressed stream, the expansion zone comprising a turboexpander with turboexpander wheel (s), one or more compressor service (s), And including the generator in a single installed machine;
Passing the compressed stream through a condensation zone to produce a condensed stream;
Passing the condensed stream through a preheating zone to produce a preheated stream;
Passing the preheated stream through an evaporation zone to produce an evaporated stream; And
Passing the evaporated stream back to the column
Including, the method. The method of claim 1, wherein the column waste heat stream may be derived from a plurality of waste heat sources in an aromatics complex. The method of claim 1, wherein the waste heat stream has a temperature of 100 ° C. to 140 ° C. 7. The method of claim 1, wherein the column can be any column in an aromatic complex. The method of claim 1, wherein the column is an extraction column. The method of claim 1, wherein the column is a reformate splitter. The method of claim 1, wherein the column is an A ₈ stripper. As a device using waste heat,
An inlet in direct communication with the column having an overhead line;
The overhead line is in direct communication with the evaporation zone having an overhead line in direct communication with the expansion zone and an outlet line in direct communication with the overhead receiver;
The expansion zone has an expansion zone outlet line in direct communication with a condensation zone having a compression zone outlet line, the expansion zone uniting a turret expander with turboexpander wheel (s), one or more compressor installation (s), and a generator. Contained in an installed machine;
The condensation zone outlet line is in direct communication with a preheating zone having a preheating zone outlet line;
The preheating zone outlet line is in direct communication with the evaporation zone. The apparatus of claim 8, wherein the waste heat stream is a vapor-rich fluid. The apparatus of claim 8, wherein the waste heat stream has a temperature of 100 ° C. to 140 ° C. 10.

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