CN109675332B - Toluene column fractionation device and method driven by heat pump - Google Patents
Toluene column fractionation device and method driven by heat pump Download PDFInfo
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- CN109675332B CN109675332B CN201710979714.5A CN201710979714A CN109675332B CN 109675332 B CN109675332 B CN 109675332B CN 201710979714 A CN201710979714 A CN 201710979714A CN 109675332 B CN109675332 B CN 109675332B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
- B01D3/007—Energy recuperation; Heat pumps
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
- B01D3/14—Fractional distillation or use of a fractionation or rectification column
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
- B01D3/14—Fractional distillation or use of a fractionation or rectification column
- B01D3/32—Other features of fractionating columns ; Constructional details of fractionating columns not provided for in groups B01D3/16 - B01D3/30
- B01D3/322—Reboiler specifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
- B01D3/42—Regulation; Control
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C7/00—Purification; Separation; Use of additives
- C07C7/005—Processes comprising at least two steps in series
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C7/00—Purification; Separation; Use of additives
- C07C7/04—Purification; Separation; Use of additives by distillation
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/10—Process efficiency
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/50—Improvements relating to the production of bulk chemicals
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/10—Greenhouse gas [GHG] capture, material saving, heat recovery or other energy efficient measures, e.g. motor control, characterised by manufacturing processes, e.g. for rolling metal or metal working
Abstract
The invention provides a toluene tower fractionating device driven by a heat pump and a method thereof. The device comprises: a toluene column; the compression preheater is communicated with the top of the toluene tower through a first stop valve; the compressor is communicated with the compression preheater; the heat pump reboiler is communicated with the compressor and the compression preheater and is communicated with the bottom of the toluene tower; the pressure relief valve is communicated with the compression preheater; the tower top heat output heat exchanger is communicated with the pressure release valve through a second stop valve and communicated with the top of the toluene tower through a third stop valve; the tower top waste heat recovery heat exchanger is communicated with the tower top heat output heat exchanger; the tower top reflux tank is communicated with the tower top waste heat recovery heat exchanger; the tower top reflux pump is communicated with the tower top reflux tank and the top of the toluene tower; and the tower bottom reboiler is communicated with the bottom of the toluene tower. The toluene tower is used for separating toluene from C8-C9 aromatic hydrocarbon, and the toluene tower is driven by the heat pump, so that the energy consumption of a single-tower system is reduced by 50-70%, and the advantages of energy conservation and consumption reduction are obvious.
Description
Technical Field
The invention relates to the technical field of aromatic hydrocarbon separation, in particular to a toluene tower fractionating device and method driven by a heat pump.
Background
The extraction of aromatic hydrocarbon is an important component device for separating aromatic hydrocarbon from reformate in petrochemical enterprises, and is widely applied to the industrial production by a liquid-liquid solvent extraction method and a solvent extraction distillation method. Wherein, domestic petrochemical enterprises mostly adopt an extractive distillation technology to recover aromatic hydrocarbons, and the working principle is to change the relative volatility of feeding components by using a high-selectivity solvent. In a mixture in which aromatic hydrocarbons and non-aromatic hydrocarbons coexist, the relative volatility of the non-aromatic components is increased by the action of the solvent, and this increase allows the non-aromatic components to be distilled to the top of the column in a conventional distillation column while the aromatic hydrocarbons are enriched at the bottom of the column.
The aromatics rectification section typically includes a clay column, a benzene column, and a toluene column. The extract mixed aromatic hydrocarbon of the extractive distillation part may contain trace amount of olefin and other impurities, and can significantly influence the acid-washing colorimetric index of the benzene and toluene products. To remove these trace impurities, the extract is treated with clay prior to fractionation. The mixed aromatic hydrocarbon from the clay tower bottom exchanges heat with the tower feeding material and then enters the middle part of the benzene tower. The benzene tower is rectified under normal pressure, and the benzene product is extracted from the upper part of the tower. The benzene bottom product is sent to a toluene column for separation. The toluene tower overhead product is toluene, and the toluene tower bottom C8-C9 aromatic hydrocarbon product is sent to a reformate fractionating tower of a continuous reforming device. The toluene column reboiler typically used xylene column side stream or 3.5MPa steam as the heat source. The reboiling energy consumption of the toluene tower accounts for 50-70% of the energy consumption of the aromatic hydrocarbon rectification part, and the energy-saving research is carried out on the reboiling energy consumption of the toluene tower, so that the reboiling energy consumption of the toluene tower has important significance for the energy saving and consumption reduction of the aromatic hydrocarbon extraction device and the aromatic hydrocarbon rectification part.
The heat pump is similar to a water pump, absorbs heat from a low-temperature heat source, and then releases heat to a high-temperature heat sink, which is equivalent to transferring heat from low temperature to high temperature, so the heat pump is called as a heat pump in an image manner. The history of heat pumps can be traced back to 1824 published carnot cycle, which lays the theoretical foundation of heat pumps. The heat pump mainly comprises four parts, namely a compressor, a condenser, an expansion valve and an evaporator. The heat transfer is completed by a certain working medium, the working medium is evaporated at a lower temperature in the evaporator to absorb heat, the working medium is changed into a gas state from a liquid state, the temperature of the cooled material is reduced, then the gas-phase working medium enters the compressor to be compressed to a higher pressure, the temperature of the compressed working medium is increased, and then the gas-phase working medium enters the condenser to emit heat in the condenser and is changed into liquid. The liquid working medium is expanded to low pressure by the expansion valve, then the temperature is reduced, and the liquid working medium enters the evaporator again, so that a thermodynamic cycle is completed.
The condenser and evaporator of the heat pump cycle are relative to the working fluid. The working medium is condensed in the condenser, so that heat is released, the condenser is actually equivalent to a heater for materials, the working medium is evaporated in the evaporator, and the evaporator is actually equivalent to a cooler for materials. The heat pump is applied to a rectifying tower, and the tower top condenser is an evaporator for the heat pump; the kettle reboiler is a condenser for the heat pump. Along with the gradual deepening of energy saving and consumption reduction work of refining enterprises, the heat pump technology gradually becomes one of the technical means for energy saving of the rectifying tower.
Disclosure of Invention
The invention aims to provide a toluene tower fractionating device and method driven by a heat pump, which can reasonably reduce energy consumption.
In order to achieve the above object, the present invention provides a heat pump driven toluene column fractionation apparatus comprising: a toluene column; the compression preheater is communicated with the top of the toluene tower through a first stop valve; the compressor is communicated with the compression preheater; the heat pump reboiler is communicated with the compressor and the compression preheater and is communicated with the bottom of the toluene tower; the pressure relief valve is communicated with the compression preheater; the tower top heat output heat exchanger is communicated with the pressure release valve through a second stop valve and communicated with the top of the toluene tower through a third stop valve; the tower top waste heat recovery heat exchanger is communicated with the tower top heat output heat exchanger; the tower top reflux tank is communicated with the tower top waste heat recovery heat exchanger; the tower top reflux pump is communicated with the tower top reflux tank and the top of the toluene tower; and the tower bottom reboiler is communicated with the bottom of the toluene tower.
Further, the heat pump driven toluene column fractionator further comprises a bottoms cooler.
In order to achieve the above object, the present invention provides a heat pump driven toluene column fractionation method performed in the heat pump driven toluene column fractionation apparatus as described above, the method comprising: feeding a feed containing toluene and C8-C9 aromatic hydrocarbon into a toluene tower for distillation, and extracting overhead gas; the tower top gas enters the compression preheater through a first stop valve, and absorbs heat to raise the temperature; the heated tower top gas enters a compressor to be compressed, and the tower top gas is further heated; the tower top gas after further temperature rise enters a heat pump reboiler for heat exchange, the tower top gas releases heat and is cooled, and the heat released by the tower top gas is used as a reboiling heat source of a part of reboiling material flow of the toluene tower; returning the cooled tower top gas to the compression preheater, and further cooling the tower top gas by heat release; the tower top gas after further cooling is decompressed through a decompression valve; the decompressed tower top gas sequentially enters a tower top heat output heat exchanger and a tower top waste heat recovery heat exchanger through a second stop valve, exchanges heat with a heat exchange medium, and then enters a tower top reflux tank; part of the fluid in the tower top reflux tank returns to the toluene tower through a tower top reflux pump, and the rest part is taken as a toluene product; and part of the bottom stream of the toluene tower is reboiled as a reboiled stream by a reboiler at the bottom and then returned to the toluene tower, part of the bottom stream is reboiled as a reboiled stream by a reboiler at a heat pump and then returned to the toluene tower, and the rest of the bottom stream is extracted as a C8-C9 aromatic hydrocarbon product.
Further, the toluene column has a feed temperature of 140-.
Further, the toluene column is operated to increase the pressure, the pressure at the top of the toluene column is 0.1 to 0.3MPa, and the pressure at the bottom of the toluene column is 0.4 to 0.6 MPa.
Further, the temperature of the top gas is 190-.
Further, the extraction pressure of the tower top gas is 0.2-0.5MPa, the pressure of the preheated gas entering a compressor is 0.2-0.5MPa, the pressure of the preheated gas is 1.4-1.6MPa after the gas is compressed by the compressor, the pressure of the preheated gas after the gas is subjected to heat exchange by a heat pump reboiler and a compression preheater is 1.35-1.45MPa, the pressure of the preheated gas is 0.2-0.5MPa after the gas is decompressed by a decompression valve, and the pressure of the preheated gas after the gas is subjected to heat exchange by a tower top heat output heat exchanger and a tower top waste heat recovery heat exchanger is 0.15-0.45 MPa.
Further, the temperature of the reboiling material flow is 210-220 ℃, and the heat source of the bottom reboiler is 3.5MPa steam.
Further, the load of the heat pump reboiler accounts for 60-80% of the total reboiling load, and the load of the tower bottom reboiler accounts for 20-40% of the total reboiling load.
Further, the heat exchange medium of the tower top waste heat recovery heat exchanger is hot medium water with the temperature of 70-120 ℃.
The invention has the following beneficial effects:
the toluene tower is used for separating toluene from C8-C9 aromatic hydrocarbon, and the heat pump is arranged to drive the toluene tower, so that the heat pump reboiler shares 60-80% of the total reboiling load, the reboiling energy consumption of the toluene tower is reasonably reduced, the large consumption of 3.5MPa steam or the consumption of fuel gas by arranging a reboiling furnace is avoided, the energy consumption of a single-tower system is reduced by 50-70%, and the advantages of obvious energy conservation and consumption reduction are achieved.
Additional features and advantages of the invention will be set forth in the detailed description which follows.
Drawings
The above and other objects, features and advantages of the present invention will become more apparent by describing in more detail exemplary embodiments thereof with reference to the attached drawings, in which like reference numerals generally represent like parts throughout.
Fig. 1 shows a schematic of a heat pump driven toluene column fractionator according to one embodiment of the present invention.
Fig. 2 shows a schematic diagram of a conventional toluene column fractionation plant.
Description of the reference numerals
1 toluene column, 2 overhead heat output heat exchanger, 3 overhead waste heat recovery heat exchanger, 4 overhead reflux tank, 5 overhead reflux pump, 6 bottom reboiler, 7 bottom product cooler, 8 first stop valve, 9 compression preheater, 10 compressor, 11 heat pump reboiler, 12 pressure release valve, 13 second stop valve, 14 third stop valve, 15 feed, 16 overhead gas, 17 overhead gas after heat output, 18 overhead gas after waste heat recovery, 19 overhead reflux, 20 toluene product, 21 extracted bottom reboiler reboiling material flow, 22 bottom reboiler reboiling material flow, 23C 8-C9 aromatic hydrocarbon product before cooling, 24C 8-C9 aromatic hydrocarbon product after cooling, 25 preheated overhead gas after preheating, 26 compressed overhead gas after compression, 27 overhead gas after heat pump heat exchange, 28 preheated overhead gas after heat exchange, 29 pressure released overhead gas, 30 extracted heat pump reboiler material flow, 31, returning a heat pump reboiler reboiling material flow of the tower, 32 heat medium water before heat exchange, 33 heat medium water after heat exchange, 34 heat output heat exchange material flow before heat exchange and 35 heat output heat exchange material flow after heat exchange.
Detailed Description
Preferred embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. While the preferred embodiments of the present invention are shown in the drawings, it should be understood that the present invention may be embodied in various forms and should not be limited to the embodiments set forth herein.
Referring to fig. 1, the heat pump driven toluene column fractionation apparatus according to the present invention includes: it includes: a toluene column 1; a compression preheater 9 communicated with the top of the toluene column through a first stop valve 8; the compressor 10 is communicated with the compression preheater 9; a heat pump reboiler 11 communicating with the compressor 10 and the compression preheater 9 and communicating with the bottom of the toluene column; the pressure release valve 12 is communicated with the compression preheater 9; the tower top heat output heat exchanger 2 is communicated with the pressure release valve 12 through a second stop valve 13 and communicated with the top of the toluene tower through a third stop valve 14; the tower top waste heat recovery heat exchanger 3 is communicated with the tower top heat output heat exchanger 2; the tower top reflux tank 4 is communicated with the tower top waste heat recovery heat exchanger 3; the tower top reflux pump 5 is communicated with the tower top reflux tank 4 and the top of the toluene tower; and the tower bottom reboiler 6 is communicated with the bottom of the toluene tower. Under normal working conditions, the first stop valve 8 and the second stop valve 13 are opened, and the third stop valve 14 is closed; under the abnormal working condition, the first stop valve 8 and the second stop valve 13 are closed, and the third stop valve 14 is opened.
In an embodiment of the heat pump driven toluene column fractionator according to the present invention, referring to fig. 1, the heat pump driven toluene column fractionator further comprises a bottom product cooler 7 which is connected to the bottom of the toluene column and cools a bottom product flowing out from the bottom of the toluene column.
Referring to fig. 1, the toluene column fractionation method according to the present invention includes: feeding a feed 15 containing toluene and C8-C9 aromatic hydrocarbon into a toluene tower 1 for distillation, and extracting overhead gas; the tower top gas enters a compression preheater 9 through a first stop valve 8, and the tower top gas absorbs heat and is heated; the heated gas at the top of the tower enters a compressor 10 to be compressed, and the gas at the top of the tower is further heated; the tower top gas after further temperature rise enters a heat pump reboiler 11 for heat exchange, the tower top gas releases heat and is cooled, and the heat released by the tower top gas is used as a reboiling heat source of a part of reboiling material flow of the toluene tower 1; returning the cooled tower top gas to the compression preheater 9, and further cooling the tower top gas by heat release; the tower top gas after further cooling is decompressed through a decompression valve 12; the decompressed tower top gas sequentially enters the tower top heat output heat exchanger 2 and the tower top waste heat recovery heat exchanger 3 through the second stop valve 13, exchanges heat with a heat exchange medium, and then enters the tower top reflux tank 4; part of the fluid in the tower top reflux tank 4 returns to the toluene tower 1 through a tower top reflux pump 5, and the rest is extracted as a toluene product 20; part of the bottom stream of the toluene column 1 is reboiled as a reboiled stream by the bottom reboiler 6 and returned to the toluene column 1, part of the bottom stream is reboiled as a reboiled stream by the heat pump reboiler 11 and returned to the toluene column 1, and the remaining part is recovered as a C8-C9 aromatic hydrocarbon product.
In the toluene column fractionation process according to the present invention, the toluene column 1 may be a conventional choice in the aromatics rectification section of a petrochemical enterprise aromatics extraction plant. The feed 15 refers to the toluene column bottoms of the aromatics rectification section of the aromatics extraction plant and consists primarily of toluene and C8-C9 aromatics. The corresponding pipelines are adopted for communication between the devices.
In the toluene column fractionation process according to the present invention, the C8-C9 aromatic hydrocarbon product withdrawn at the bottom of the column is cooled in the bottom product cooler 7.
In the toluene column fractionation process according to the present invention the temperature of the feed 15 to the toluene column 1 is 140-.
In the toluene column fractionation method according to the present invention, the toluene column 1 is operated at elevated pressure, and the pressure at the top of the toluene column 1 is 0.1 to 0.3MPa, preferably 0.2 to 0.25 MPa. The pressure at the bottom of the column is 0.4-0.6MPa, preferably 0.4-0.45 MPa.
In the toluene column fractionation process according to the present invention, the overhead gas withdrawal temperature is 160-. The temperature of the preheated gas entering the compressor 10 is 200-230 ℃, and preferably 210-220 ℃. The temperature after compression by the compressor 10 is 250-270 ℃, preferably 255-265 ℃. The temperature after heat exchange by the heat pump reboiler 11 is 230-240 ℃. The temperature after heat exchange by the compression preheater 9 is 190 ℃ and 210 ℃. The temperature after the pressure is released by the pressure release valve 12 is 170-180 ℃, and preferably 170-175 ℃. The temperature after heat exchange by the tower top heat output heat exchanger 2 is 150-170 ℃, and preferably 150-160 ℃. The temperature after heat exchange by the tower top waste heat recovery heat exchanger 3 is 140-160 ℃, and preferably 140-155 ℃.
In the toluene column fractionation process according to the present invention, the overhead gas take-off pressure is 0.2 to 0.5MPa, preferably 0.35 to 0.4 MPa. After preheating, the pressure in the compressor 10 is 0.2-0.5MPa, preferably 0.35-0.4 MPa. The pressure after compression by the compressor 10 is 1.4-1.6MPa, preferably 1.5-1.6 MPa. The pressure is 1.35-1.45MPa after heat exchange by the heat pump reboiler 11 and the compression preheater 9. The pressure after being decompressed by the decompression valve 12 is 0.2 to 0.5MPa, preferably 0.3 to 0.4 MPa. The pressure is 0.15-0.45MPa after heat exchange by the tower top heat output heat exchanger 2 and the tower top waste heat recovery heat exchanger 3.
In the toluene column fractionation process according to the present invention, the temperature of the reboiled stream in the bottom reboiler 6 and the heat pump reboiler 11 is 210-.
The duty of the heat pump reboiler 11 is 60 to 80%, preferably 70 to 75%, of the total reboiling duty, and the duty of the bottom reboiler 6 is 20 to 40%, preferably 25 to 30%, of the total reboiling duty.
In the toluene column fractionation method according to the present invention, the heat exchange medium of the overhead waste heat recovery heat exchanger 3 is water. The toluene tower 1 is provided with a tower top heat output heat exchanger 2 and a tower top waste heat recovery heat exchanger 3 to recover the waste heat of the tower top gas, the tower top heat output heat exchanger 2 provides a heat source for a reboiler of a certain fractionating tower, the tower top waste heat recovery heat exchanger 3 utilizes heat medium water to recover residual heat, the heat medium water enters the heat exchanger at 70 ℃, and the temperature after heat exchange is 120 ℃.
In the toluene column fractionation method according to the present invention, referring to fig. 1, in the heat pump driving operation, the first and second cut-off valves 8 and 13 are opened, and the third cut-off valve 14 is closed; under the abnormal working condition driven by the heat pump, the first stop valve 8 and the second stop valve 13 are closed, the third stop valve 14 is opened, and the tower top gas enters the tower top reflux tank 4 after heat exchange through the tower top heat output heat exchanger 2 and the tower top waste heat recovery heat exchanger 3.
The toluene tower is used for separating toluene from C8-C9 aromatic hydrocarbon, and the heat pump is arranged to drive the toluene tower, so that the heat pump reboiler shares 60-80% of the total reboiling load, the reboiling energy consumption of the toluene tower is reasonably reduced, the large consumption of 3.5MPa steam or the consumption of fuel gas by arranging a reboiling furnace is avoided, the energy consumption of a single-tower system is reduced by 50-70%, and the advantages of obvious energy conservation and consumption reduction are achieved.
The present invention will be described in detail with reference to examples, but the present invention is not limited to these examples.
In the invention, the reference working condition refers to the working condition of the existing toluene column process of the aromatic hydrocarbon rectifying part of the aromatic hydrocarbon extraction device. Fig. 2 shows a schematic diagram of a conventional toluene column fractionation plant. The current toluene column fractionation method is as follows:
feeding a feed 15 containing methylbenzene and C8-C9 aromatic hydrocarbon into a toluene tower 1 to be distilled to produce a tower top gas 16, sequentially feeding the tower top gas 16 into a tower top heat output heat exchanger 2 and a tower top waste heat recovery heat exchanger 3 to exchange heat with a heat exchange medium to form a fluid, feeding the fluid into a tower top reflux tank 4 at the top of the tower, feeding a heat output heat exchange material flow 34 before heat exchange into the tower top heat output heat exchanger 2 to exchange heat to form a heat output heat exchange material flow 35 after heat exchange, leading out the heat output heat exchange material flow, and feeding a heat medium water 32 before heat exchange into the tower top waste heat recovery heat exchanger 3 to exchange heat to form a heat medium water 33 after heat exchange and leading out the heat medium water; the overhead reflux pump 5 pumps an overhead reflux 19 back to the overhead reflux pump 5 in the toluene column 1 and the remainder of the reflux is withdrawn as a toluene product 20. The bottom material flow is divided into two parts, one part is taken out and becomes the bottom reboiler reboiling material flow 22 which returns to the toluene tower 1 after reboiling by the bottom reboiler 6, the other part is C8-C9 aromatic hydrocarbon product 23 before cooling after cooling by the bottom product cooler 7, and becomes the cooled C8-C9 aromatic hydrocarbon product 24 for extraction.
Fig. 1 shows a schematic of a heat pump driven toluene column fractionator according to one embodiment of the present invention. The toluene column fractionation method of this example is as follows:
feeding a feed 15 containing toluene and C8-C9 aromatic hydrocarbon into a toluene tower 1 for distillation to produce overhead gas 16; the tower top gas 16 enters a compression preheater 9 through a first stop valve 8 for preheating, and the preheated tower top gas 25 is obtained after heat absorption and temperature rise; compressing the preheated tower top gas 25 by a compressor 10, and further heating to obtain compressed tower top gas 26; the compressed tower top gas 26 enters a heat pump reboiler 11 to heat the extracted reboiled material flow 30 of the heat pump reboiler, and the heat is released and cooled to obtain the tower top gas 27 after heat exchange of the heat pump; the overhead gas 27 after heat exchange of the heat pump returns to the preheater 9, exchanges heat with the overhead gas 16 entering the compression preheater 9 through the first stop valve 8, releases heat and further lowers the temperature to obtain the overhead gas 28 after preheating and heat exchange; the preheated and heat exchanged tower top gas 28 is decompressed through a decompression valve 12 to obtain decompressed tower top gas 29; the decompressed tower top gas 29 sequentially enters the tower top heat output heat exchanger 2 and the tower top waste heat recovery heat exchanger 3 through the second stop valve 13, is cooled by the heat output heat exchange material flow 34 before heat exchange in the tower top heat output heat exchanger 2 to become the tower top gas 17 after heat output, and is converted into the heat output heat exchange material flow 35 after heat exchange by the heat output heat exchange material flow 34 before heat exchange and is led out; in the tower top waste heat recovery heat exchanger 3, the tower top gas 18 after waste heat recovery is obtained by cooling the heat medium water 32 before heat exchange, and the heat medium water 32 before heat exchange becomes the heat medium water 33 after heat exchange and is led out; the overhead gas 18 after waste heat recovery enters an overhead reflux tank 4, wherein an overhead reflux 19 returns to the toluene column 1 through an overhead reflux pump 5; the remaining part is taken out as a toluene product 20; the bottom material flow of the toluene column 1 is divided into three parts, one part is extracted, the bottom reboiler reboiling material flow 21 is reboiled by a bottom reboiler 6 to become a bottom reboiler reboiling material flow 22 returned to the column, and then the bottom reboiler reboiling material flow is returned to the toluene column 1; a part of the heat pump reboiler reboiling material flow 30 extracted from the heat pump reboiler is heated and reboiled by the heat pump reboiler 11 to become a heat pump reboiler reboiling material flow 31 returning to the tower, and then returns to the toluene tower 1; the third part of the C8-C9 aromatic hydrocarbon product 23 before cooling is extracted after being cooled by a tower bottom product cooler 7 to become a cooled C8-C9 aromatic hydrocarbon product 24.
The following examples are presented to illustrate the heat pump driven toluene column fractionation process of the present invention. In the following examples, a toluene column with a nominal design capacity of 150 ten thousand tons/year in the aromatic hydrocarbon rectification part of an aromatic hydrocarbon extraction device of a petrochemical enterprise is used for accounting, the raw materials are benzene column bottom products, the components mainly comprise toluene and other C8-C9 aromatic hydrocarbons, the flow rate is 172.0t/h, and the components are shown in Table 1. The theoretical plate number of the toluene column was 42.
The process quality control indexes are as follows: the toluene content in the toluene product is more than or equal to 99.5mol percent, and the C8-C9 aromatic hydrocarbon in the C8-C9 aromatic hydrocarbon product at the bottom of the tower is more than or equal to 90.0mol percent.
In order to illustrate the effects of the embodiments, the specific working conditions (working conditions one) are shown in table 2 by comparing the existing toluene column process flow (schematic diagram is shown in fig. 2) of the aromatics rectification part of the aromatics extraction device of the petrochemical enterprise. The specific operating conditions (operating conditions two) of the example are shown in table 2.
TABLE 1 feed composition
TABLE 2 working conditions of the process of the present invention and the prior art process
| Parameter(s) | Unit of | Working condition one | Working condition two |
| Temperature of feed | ℃ | 150 | 150 |
| Pressure of feed | MPa | 0.4 | 0.4 |
| Temperature of gas extraction at the top of the column | ℃ | 175 | 175 |
| Pressure of gas extraction at the top of the column | MPa | 0.38 | 0.38 |
| Preheating temperature of top gas | ℃ | / | 215 |
| Post-compression temperature of overhead gasDegree of rotation | ℃ | / | 259 |
| Post-compression pressure of overhead gas | MPa | / | 1.5 |
| Reboil stream temperature | ℃ | 214-218 | 214-218 |
| Pressure at the bottom of the column | MPa | 0.45 | 0.45 |
| Temperature of tower top gas after pressure relief | ℃ | / | 175 |
| Pressure after pressure relief of tower top gas | MPa | / | 0.38 |
| Reboiler duty at the bottom of the column | M kCal | 27.0 | 7.0 |
| Heat pump reboiler duty | M kCal | / | 20.0 |
| Heat output heat quantity | M kCal | 13.0 | 13.0 |
| Low temperature waste heat | M kCal | 10.55 | 1.0 |
| Compression preheater load | M kCal | / | 4.5 |
| Steam consumption of 3.5MPa | t/h | 50 | 13 |
| Consumption of electricity | kWh | 60 | 5060 |
| Single tower energy consumption of toluene tower | kgEO/t | 15.0 | 5.8 |
| Energy saving ratio | ％ | 0 | 61.0 |
Compared with the first working condition of the toluene column process in the aromatic hydrocarbon rectification part of the aromatic hydrocarbon extraction device of the petrochemical enterprise, the engineering change content of the second working condition of the embodiment comprises the following steps: and a first stop valve 8, a compression preheater 9, a compressor 10, a heat pump reboiler 11, a pressure relief valve 12, a second stop valve 13, a third stop valve 14 and corresponding pipelines are additionally arranged.
The results show that the heat pump driven toluene tower is arranged, the total reboiling load is shared by the heat pump reboiler by 60-80%, and the energy consumption of the single-tower system is reduced by 50-70%, so that the process system has the advantages of obvious energy conservation and consumption reduction.
Having described embodiments of the present invention, the foregoing description is intended to be exemplary, not exhaustive, and not limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments.
Claims (7)
1. A heat pump driven toluene column fractionation method characterized in that the heat pump driven toluene column fractionation method is carried out in a heat pump driven toluene column fractionation apparatus,
the heat pump driven toluene column fractionation apparatus includes:
a toluene column;
the compression preheater is communicated with the top of the toluene tower through a first stop valve;
the compressor is communicated with the compression preheater;
the heat pump reboiler is communicated with the compressor and the compression preheater and is communicated with the bottom of the toluene tower;
the pressure relief valve is communicated with the compression preheater;
the tower top heat output heat exchanger is communicated with the pressure release valve through a second stop valve and communicated with the top of the toluene tower through a third stop valve;
the tower top waste heat recovery heat exchanger is communicated with the tower top heat output heat exchanger;
the tower top reflux tank is communicated with the tower top waste heat recovery heat exchanger;
the tower top reflux pump is communicated with the tower top reflux tank and the top of the toluene tower;
the tower bottom reboiler is communicated with the bottom of the toluene tower;
the heat pump driven toluene column fractionation plant further comprises a bottoms cooler;
the method comprises the following steps:
feeding a feed containing toluene and C8-C9 aromatic hydrocarbon into a toluene tower for distillation, and extracting overhead gas;
the tower top gas enters the compression preheater through a first stop valve, and absorbs heat to raise the temperature;
the heated tower top gas enters a compressor to be compressed, and the tower top gas is further heated;
the tower top gas after further temperature rise enters a heat pump reboiler for heat exchange, the tower top gas releases heat and is cooled, and the heat released by the tower top gas is used as a reboiling heat source of a part of reboiling material flow of the toluene tower;
returning the cooled tower top gas to the compression preheater, and further cooling the tower top gas by heat release;
the tower top gas after further cooling is decompressed through a decompression valve;
the decompressed tower top gas sequentially enters a tower top heat output heat exchanger and a tower top waste heat recovery heat exchanger through a second stop valve, exchanges heat with a heat exchange medium, and then enters a tower top reflux tank;
part of the fluid in the tower top reflux tank returns to the toluene tower through a tower top reflux pump, and the rest part is taken as a toluene product;
part of the bottom material flow of the toluene tower is reboiled as reboiled material flow by a reboiler at the bottom of the toluene tower and then returned to the toluene tower, part of the bottom material flow is reboiled as reboiled material flow by a reboiler at a heat pump and then returned to the toluene tower, and the rest part is extracted as C8-C9 aromatic hydrocarbon products;
the toluene tower is operated to increase the pressure, the pressure at the top of the toluene tower is 0.1-0.3MPa, and the pressure at the bottom of the toluene tower is 0.4-0.6 MPa;
the load of the heat pump reboiler accounts for 60-80% of the total reboiling load, and the load of the reboiler at the bottom of the tower accounts for 20-40% of the total reboiling load.
2. The heat pump driven toluene column fractionation method as claimed in claim 1, wherein the toluene column feed temperature is 140-160 ℃.
3. The heat pump driven toluene column fractionation method as claimed in claim 1, wherein the toluene column feed temperature is 145-155 ℃.
4. The heat pump driven toluene column fractionation method as claimed in claim 1, wherein the temperature of the top gas is 160-.
5. The heat pump-driven toluene column fractionation method according to claim 1, wherein the overhead gas extraction pressure is 0.2 to 0.5MPa, the preheated pressure is 0.2 to 0.5MPa in the compressor, the pressure after compression by the compressor is 1.4 to 1.6MPa, the pressure after heat exchange by the heat pump reboiler and the compression preheater is 1.35 to 1.45MPa, the pressure after pressure relief by the pressure relief valve is 0.2 to 0.5MPa, and the pressure after heat exchange by the overhead heat output heat exchanger and the overhead waste heat recovery heat exchanger is 0.15 to 0.45 MPa.
6. The heat pump driven toluene column fractionation process of claim 1, wherein the reboiled stream temperature is 210 ℃ and 220 ℃, and the heat source for the bottom reboiler is 3.5MPa steam.
7. The heat pump driven toluene column fractionation method according to claim 1, wherein a heat exchange medium of the overhead heat recovery heat exchanger is hot water of 70 to 120 ℃.
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| US4395310A (en) * | 1981-07-14 | 1983-07-26 | Exxon Research And Engineering Co. | Fractionation system |
| CN1006786B (en) * | 1984-04-26 | 1990-02-14 | 新日铁化学株式会社 | Process for distillation of styrenes |
| BR9912289A (en) * | 1998-07-20 | 2001-04-17 | Shell Int Research | Process for the joint preparation of styrene and propylene oxide. |
| CN101602640B (en) * | 2008-06-12 | 2012-10-10 | 中国石油化工股份有限公司 | Energy-saving separation method of ethylbenzene/styrene |
| US8182654B2 (en) * | 2008-10-27 | 2012-05-22 | Uop Llc | Heat pump for high purity bottom product |
| FR2998301B1 (en) * | 2012-11-22 | 2016-01-01 | Axens | LOW TEMPERATURE HEAT RECOVERY METHOD AND APPLICATION OF THE METHOD TO THE AROMATIC COMPLEX |
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