CN115888155A - Rectification system and rectification process for separating three-component mixture - Google Patents
Rectification system and rectification process for separating three-component mixture Download PDFInfo
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- CN115888155A CN115888155A CN202211282551.2A CN202211282551A CN115888155A CN 115888155 A CN115888155 A CN 115888155A CN 202211282551 A CN202211282551 A CN 202211282551A CN 115888155 A CN115888155 A CN 115888155A
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Abstract
A rectification system and a rectification process for separating a three-component mixture. The rectification system comprises a rectification tower, a tower top gas compressor, a water cooler, a feeding heat regenerator, a side reboiler, a tower kettle reboiler, a liquid collecting tank, a flash tank, a throttling element, a reflux buffer tank and a first pipeline, a second pipeline, a third pipeline, a fourth pipeline, a sixth pipeline and a ninth pipeline. The top gas phase outlet of the rectifying tower is respectively communicated with the inlets of the first pipeline and the second pipeline, and the outlets of the first pipeline and the third pipeline are respectively communicated with the gas inlet of the top gas compressor; and an exhaust port of the tower top gas compressor is communicated with a hot side inlet of the side reboiler, and a hot side outlet of the side reboiler is communicated with an inlet of the liquid collecting tank. And a gas phase outlet of the liquid collecting tank is communicated with an inlet of the fourth pipeline, and a liquid phase outlet is communicated with a material inlet of the flash tank through a throttling element. And a cold side inlet and a cold side outlet of the side reboiler are respectively communicated with a side line extraction outlet and a side line reflux outlet of the rectifying tower. The invention can fully utilize the waste heat of the tower top gas and reduce the consumption of tower top cooling circulating water and tower bottom steam in the rectification process.
Description
Technical Field
The invention relates to a rectification technology, in particular to a rectification energy-saving technology for separating a three-component mixture.
Background
Maleic anhydride is an important organic chemical raw material and is mainly used for producing unsaturated polyester resin, paint, ink auxiliaries and the like. Because the traditional benzene oxidation method for preparing maleic anhydride is limited by high cost, the advantage of the original method for preparing maleic anhydride by using n-butane oxidation with smaller market ratio is gradually highlighted, and the method is rapidly developed in recent years. The n-butane which is a raw material required by the n-butane oxidation method is mainly obtained by rectifying and separating mixed butane, and as the boiling point difference of the key component n/isobutane is small, and the content of C5 in some mixed butane raw materials is more (more than or equal to 2 wt.%), the separation of the three-component or multi-component system is usually carried out by adopting a rectification sequence, but the required equipment investment and energy consumption cost are higher. Multicomponent separation in a dividing wall rectifying tower is also widely researched at present, but is influenced by the problems of uneven heat transfer between the dividing walls, higher operation difficulty and the like, so that domestic industrial application is less. The heat pump rectification is an energy-saving process, generally, the saturated vapor at the top of the tower is compressed by a heat pump to improve the taste and is coupled with the tower kettle for heat exchange, and a large amount of cold and hot public engineering consumption can be saved by inputting a small amount of compression work, but the product obtained from the tower kettle by the method often cannot reach the index, and the energy consumption is higher.
Fig. 1 shows a schematic diagram of a conventional rectification system, and as shown in fig. 1, the rectification system includes a rectification column T5, a column bottom reboiler E5, a column top condenser E6, a reflux buffer tank V6, a feed pump P5, a column bottom extraction pump P6, a reflux pump P7, and the like.
Disclosure of Invention
The invention aims to provide a rectification system and a rectification process for separating a three-component mixture, which can fully utilize the waste heat of the top gas of a rectification tower, reduce the consumption of cooling circulating water at the top of the tower and steam at the bottom of the tower in the rectification process, reduce the consumption of public works and achieve the effects of economy and energy conservation.
According to an aspect of an embodiment of the present invention, there is provided a rectification system for separation of a three-component mixture, including a rectification column, a top gas compressor, a water cooler, a feed heat regenerator, a side reboiler, a kettle reboiler, a liquid-collecting tank, a flash tank, a throttling element, a reflux buffer tank, and first to ninth pipelines; the top gas phase outlet of the rectifying tower is respectively communicated with the inlet of the first pipeline and the inlet of the second pipeline, and the outlet of the first pipeline and the outlet of the third pipeline are respectively communicated with the gas inlet of the top gas compressor; an exhaust port of the tower top gas compressor is communicated with a hot side inlet of the lateral line reboiler, a hot side outlet of the lateral line reboiler is communicated with an inlet of the liquid collecting tank, a gas phase outlet of the liquid collecting tank is communicated with an inlet of a fourth pipeline, and a liquid phase outlet of the liquid collecting tank is communicated with a material inlet of the flash tank through a throttling element; a cold side inlet and a cold side outlet of the side reboiler are respectively communicated with a side line extraction port and a side line return port of the rectifying tower; the liquid phase outlet of the tower kettle of the rectifying tower is divided into two paths: one path is communicated with a cold side inlet of a reboiler of the tower kettle, and the other path is used for discharging materials from the tower kettle; a cold side outlet of the tower kettle reboiler is communicated with a tower kettle steam inlet of the rectifying tower; a gas phase outlet of the flash tank is communicated with an inlet of a fifth pipeline, an outlet of the fifth pipeline is respectively communicated with an inlet of a third pipeline and an inlet of a sixth pipeline, an outlet of the sixth pipeline is respectively communicated with a hot side inlet of the water cooler and one end of a seventh pipeline, an outlet of the second pipeline is respectively communicated with the other end of the seventh pipeline and an inlet of an eighth pipeline, an outlet of the eighth pipeline is communicated with a hot side inlet of the feeding heat regenerator, a hot side outlet of the feeding heat regenerator is communicated with an inlet of a ninth pipeline, a cold side inlet of the feeding heat regenerator is used for feeding, and a cold side outlet of the feeding heat regenerator is communicated with a feeding hole of the rectifying tower; a first inlet of the reflux buffer tank is communicated with a liquid phase outlet of the flash tank, a second inlet of the reflux buffer tank is respectively communicated with a hot side outlet of the water cooler and an outlet of the ninth pipeline, the liquid phase outlet of the reflux buffer tank is divided into two paths, one path is returned to the top of the tower, and the other path is used for discharging; and a first switch valve is arranged on the third pipeline, a second switch valve is arranged on the eighth pipeline, a third switch valve is arranged at the inlet of the hot side of the water cooler, and a fourth switch valve is arranged on the sixth pipeline.
According to another aspect of embodiments of the present invention, there is provided a rectification process for the separation of a three-component mixture, comprising the steps of:
introducing the three-component mixture into a rectifying tower for rectification, discharging light component saturated steam from the top of the tower, extracting intermediate components from a side line of the tower, and discharging heavy components from a tower kettle after reboiling and concentrating;
introducing light component saturated vapor extracted from the tower top into a tower top gas compressor;
introducing gas compressed by a tower top gas compressor into a side reboiler, performing heat exchange with saturated liquid extracted from a side line of a rectifying tower as a heat source, and returning the saturated liquid into the rectifying tower from the side line of the rectifying tower after reboiling;
introducing saturated condensate at the outlet of the side reboiler into a liquid collecting tank, discharging non-condensable gas from the top of the liquid collecting tank, throttling liquid phase obtained from the liquid collecting tank, introducing the liquid phase into a flash tank, performing gas-liquid separation, and introducing the liquid phase obtained from the flash tank and liquid phase generated after condensation of a water cooler into a reflux buffer tank;
one part of condensate obtained from the reflux buffer tank flows back to the top of the tower, and the other part of condensate is taken as a product at the top of the tower;
if it is predetermined that the condensation load of the obtained compressed gas cannot meet the heat exchange load of the side reboiler after all the overhead gas and all the gas generated by the flash tank are compressed by the overhead gas compressor, introducing all the overhead gas and all the gas generated by the flash tank into the overhead gas compressor; if it is predetermined that after all the top gas is compressed by the top gas compressor, the condensation load of the obtained compressed gas is smaller than the heat exchange load of the side reboiler, but after all the top gas and all the gas generated by the flash tank are compressed by the top gas compressor, the condensation load of the obtained compressed gas is larger than the heat exchange load of the side reboiler, introducing a part of the top gas and all the gas generated by the flash tank into the top gas compressor together so that the condensation load of the compressed gas is matched with the heat exchange load of the side reboiler, introducing the other part of the top gas into the feeding heat regenerator, and if the condensation load of the part of the top gas is larger than the preheating load of the feeding heat regenerator, introducing the rest of the top gas into the water cooler for condensation under the condition of meeting the preheating load of the feeding heat regenerator; if it is predetermined that after all the overhead gas is compressed by the overhead gas compressor, the condensation load of the obtained compressed gas is greater than the heat exchange load of the side reboiler, only a part of the overhead gas is introduced into the overhead gas compressor, the other part of the overhead gas and all the gas generated by the flash tank are merged and then introduced into the feed heat regenerator, if the condensation load of the merged gas of the other part of the overhead gas and all the gas generated by the flash tank is greater than the preheating load of the feed heat regenerator, only a part of the merged gas is introduced into the feed heat regenerator, so that the condensation load of the part of the merged gas is matched with the preheating load, and the rest part of the merged gas is introduced into the water cooler for condensation.
The invention has at least the following advantages and characteristics:
1. the embodiment of the invention can fully utilize the residual heat of the surplus tower top steam to preheat the feeding material of the rectifying tower under the condition of meeting the heat exchange load of the side reboiler, thereby saving the consumption of circulating water required by partial condensing tower top gas;
2. in the embodiment of the invention, the top gas of the compression tower is directly used as a heat source of the side reboiler, and the intermediate reboiling is realized by using a small amount of compression work, so that the consumption of tower top cooling circulating water and tower bottom steam is saved, the consumption of tower bottom hot public works and tower top cold public works is greatly reduced, compared with the prior art, the energy-saving design of the rectification process is carried out by adopting a heat pump technology, and the energy-saving effect of the whole process is obvious;
3. the embodiment of the invention integrates the side line extraction and the side line heat pump in one tower, realizes the separation of three-component mixture, not only saves the equipment investment, but also reduces the separation energy consumption, and provides reference for the separation of the multi-component mixture.
Drawings
Fig. 1 shows a schematic flow diagram of a side draw process of a conventional rectification column.
FIG. 2 shows a schematic diagram of a rectification system for the separation of a three-component mixture in accordance with an embodiment of the present invention.
FIG. 3 schematically illustrates a rectification process flow diagram when the heat exchange duty of the side reboiler is not met by the compressed gas condensation duty of all overhead gas and all gas produced by the flash drum after compression.
FIG. 4 schematically illustrates a rectification process flow diagram when the condensation load of the compressed gas for all overhead gas and all gas produced by the flash drum after compression is sufficient to meet the heat exchange load of the side reboiler.
FIG. 5 schematically illustrates a rectification process flow diagram when the total overhead gas compressed gas condensation duty is sufficient to meet the heat exchange duty of the side reboiler.
Detailed Description
The invention is described in detail below with reference to the figures and specific embodiments.
Please refer to fig. 2. The rectification system for separating the three-component mixture according to the embodiment of the invention comprises a rectification tower T1, a top gas compressor C1, a feeding heat regenerator E1, a side reboiler E2, a tower kettle reboiler E3, a water cooler E4, a liquid collecting tank V1, a flash tank V2, a reflux buffer tank V3, a throttling element V4, a tower kettle extraction pump P1, a reflux pump P2, a first pipeline 11, a second pipeline 12, a third pipeline 13, a fourth pipeline 14, a fifth pipeline 15, a sixth pipeline 16, a seventh pipeline 17, an eighth pipeline 18, a ninth pipeline 19 and a tenth pipeline 20.
The top gas phase outlet of the rectifying tower T1 is respectively communicated with the inlet of a first pipeline 11 and the inlet of a second pipeline 12, the outlet of the first pipeline 11 and the outlet of a third pipeline 13 are respectively communicated with the gas inlet of a top gas compressor C1, the gas outlet of the top gas compressor C1 is communicated with the hot side inlet of a side reboiler E2, the hot side outlet of the side reboiler E2 is communicated with the inlet of a liquid collecting tank V1, the gas phase outlet of the liquid collecting tank V1 is communicated with the inlet of a fourth pipeline 14, the liquid phase outlet of the liquid collecting tank V1 is communicated with the material inlet of a flash tank V2 through a throttling element V4, and the cold side inlet and the cold side outlet of the side reboiler E2 are respectively communicated with a side line collecting outlet and a side line backflow port which are arranged on the rectifying tower T1.
In the present embodiment, the throttling element V4 is a throttle valve. The rectifying tower T1 is a plate-type rectifying tower, the side line extraction port and the side line reflux port are arranged on the same tower plate of the plate-type rectifying tower, and the tower plate is selected from a position where the temperature difference between the middle part of the tower and the top of the tower is small (the temperature difference is 10-20 ℃). The side draw outlet and the side return outlet are positioned below the position of drawing the middle component of the rectifying tower T1.
The liquid phase outlet of the tower kettle of the rectifying tower T1 is divided into two paths: one path is communicated with a cold side inlet of a tower kettle reboiler E3, and the other path is used for discharging materials from the tower kettle through a tower kettle extraction pump P1; and a cold side outlet of the tower kettle reboiler E3 is communicated with a tower kettle steam inlet of the rectifying tower T1. The hot side inlet of the column reboiler E3 is for receiving steam.
The gas phase outlet of the flash tank V2 is communicated with the inlet of a fifth pipeline 15, the outlet of the fifth pipeline 15 is respectively communicated with the inlet of a third pipeline 13 and the inlet of a sixth pipeline 16, the outlet of the sixth pipeline 16 is respectively communicated with the hot side inlet of a water cooler E4 and one end of a seventh pipeline 17, the outlet of the second pipeline 12 is respectively communicated with the other end of the seventh pipeline 17 and the inlet of an eighth pipeline 18, the outlet of the eighth pipeline 18 is communicated with the hot side inlet of a feeding regenerator E1, the hot side outlet of the feeding regenerator E1 is communicated with the inlet of a ninth pipeline 19, the cold side inlet of the feeding regenerator E1 is used for feeding, and the cold side outlet of the feeding regenerator E1 is communicated with the feeding hole of a rectifying tower T1.
The first inlet of the backflow buffer tank V3 is communicated with the liquid phase outlet of the flash tank V2, the second inlet of the backflow buffer tank V3 is communicated with the hot side outlet of the water cooler E4 and the outlet of the ninth pipeline 19 respectively, the outlet of the backflow buffer tank V3 is divided into two paths, one path of the outlet is communicated with the top of the reflux rectifying tower T1 through the reflux pump P2, and the other path of the outlet is used for discharging. The non-condensable gas outlet of the reflux buffer tank V3 and the outlet of the fourth pipeline 14 are respectively communicated with the inlet of a tenth pipeline 20, and the outlet of the tenth pipeline 20 is communicated with a non-condensable gas discharge torch.
A first switch valve S1 is arranged on the third pipeline 13, a second switch valve S2 is arranged on the eighth pipeline 18, a third switch valve S3 is arranged at the inlet of the hot side of the water cooler E4, a fourth switch valve S4 is arranged on the sixth pipeline 16, a fifth switch valve S5 is arranged on the fourth pipeline 14, and a sixth switch valve S6 is arranged at the non-condensable gas outlet of the backflow buffer tank V3.
A rectification process for the separation of a three-component mixture according to another embodiment of the invention comprises the steps of:
feeding a ternary mixture with a certain composition from a proper position of a rectifying tower T1 at a certain flow rate, discharging light component saturated steam from the top of the tower, collecting intermediate key components meeting the separation requirement at the lateral line of a constant concentration zone in the tower, and discharging heavy components from a tower kettle after reboiling and concentrating through the tower kettle;
introducing the light component saturated vapor extracted from the tower top into a tower top gas compressor;
introducing the gas compressed by the overhead gas compressor C1 into a side reboiler E2, performing heat exchange with saturated liquid extracted from a side line of the rectifying tower as a heat source, and returning the saturated liquid into the rectifying tower from the side line of the rectifying tower after reboiling; in a specific embodiment, the heat exchange temperature difference between the gas after being boosted and heated by the overhead gas compressor C1 and the saturated liquid extracted from the side line of the rectifying tower T1 is about 10-20 ℃, the partially saturated liquid extracted from the side line at a proper position below the intermediate component extraction position of the rectifying tower T1 according to the gasification rate of 20 percent is subjected to heat exchange and reboiling with the compressed gas after being boosted and heated, and then the partially saturated liquid is returned to the tower from the same position;
liquid obtained after heat exchange of compressed gas through a side reboiler E2 is discharged into a liquid collecting tank V1 through bubble point discharging, non-condensable gas is discharged from the top of the liquid collecting tank V1, liquid phase flowing out of the bottom of the liquid collecting tank V1 is decompressed to the pressure of the top of the tower through a throttling element V4, gas and liquid are separated in a flash tank V2 after partial vaporization, the liquid phase separated in the flash tank V2 and liquid phase generated after condensation of a water cooler E4 are converged into a reflux buffer tank V3, one part of condensed liquid flows back to the top of a rectifying tower T1 through a reflux pump P2 according to a certain reflux ratio, and the other part of condensed liquid is taken as a product at the top of the tower;
wherein:
if it is predetermined that after all of the overhead gas and all of the gas generated by the flash tank V2 are compressed by the overhead gas compressor C1, the condensation load of the obtained compressed gas cannot meet the heat exchange load of the side reboiler E2, introducing all of the overhead gas and all of the gas generated by the flash tank V2 into the overhead gas compressor C1, at this time, opening the first switching valve S1, turning off the second switching valve S2, the third switching valve S3 and the fourth switching valve S4, and allowing no gas to pass through the pipelines where the second switching valve S2, the third switching valve S3 and the fourth switching valve S4 are located, which are indicated by dotted lines in fig. 3;
if it is predetermined that after all of the overhead gas is compressed by the overhead gas compressor C1, the condensation load of the obtained compressed gas is smaller than the heat exchange load of the side reboiler E2, but after all of the overhead gas and all of the gas generated by the flash tank V2 are compressed by the overhead gas compressor C1, the condensation load of the obtained compressed gas is larger than the heat exchange load of the side reboiler E2, introducing a part of the overhead gas and all of the gas generated by the flash tank into the overhead gas compressor C1 together so that the condensation load of the compressed gas is adapted to the heat exchange load of the side reboiler E2, introducing the other part of the overhead gas into the feed heat regenerator E1, and if the condensation load of the part of the overhead gas is smaller than or equal to the preheating load of the feed heat regenerator E1, introducing the remaining part of the overhead gas into the feed heat regenerator E1 (at this time, the first switching valve S1 and the second switching valve S2 are opened, the third switching valve S3 and the fourth switching valve S4 are in a disconnected state, and no gas passes through the sixth pipeline 16, which is represented by a dotted line in fig. 4); if the condensation load of the other part of the top gas is greater than the preheating load of the feeding heat regenerator E1, introducing the rest of the top gas into a water cooler E4 for condensation under the condition of meeting the preheating load of the feeding heat regenerator E1 (at the moment, a first switch valve S1, a second switch valve S2 and a third switch valve S3 are opened, a fourth switch valve S4 is closed, no gas passes through a sixth pipeline 16, and gas passes through a seventh pipeline 17);
if it is predetermined that after all the overhead gas is compressed by the overhead gas compressor C1, the condensation load of the obtained compressed gas is greater than the heat exchange load of the side reboiler E2, only introducing one part of the overhead gas into the overhead gas compressor C1, merging the other part of the overhead gas with all the gas generated by the flash tank V2, and introducing the merged gas into the feed heat regenerator E1, and if the condensation load of the merged gas of the other part of the overhead gas and all the gas generated by the flash tank V2 is less than or equal to the preheating load of the feed heat regenerator E1, introducing all the merged gas into the feed heat regenerator E1, wherein at the moment, the second switch valve S2 and the fourth switch valve S4 are opened, and the first switch valve S1 and the third switch valve S3 are in an off state; if the condensation load of the another part of the combined gas of the overhead gas and all the gases generated by the flash tank V2 is greater than the preheating load of the feed heat regenerator E1, only a part of the combined gas is introduced into the feed heat regenerator E1 to make the condensation load of the part of the combined gas match the preheating load, and the rest part of the combined gas is introduced into the water cooler E4 to be condensed (at this time, the first switch valve S1 is turned off, the second switch valve S2, the third switch valve S3 and the fourth switch valve S4 are all opened, and no gas passes through the third pipeline 13, which is indicated by a dotted line in fig. 5).
The heat exchange duty of the aforementioned side reboiler E2 can be determined by calculation at a given vaporization rate based on the liquid hold-up on the corresponding tray. The aforementioned preheating load of the feed regenerator E1 refers to the heat load required to heat the feedstock to a specified temperature. On the premise of meeting the same separation task, the load required by the tower reboiler E3 is correspondingly reduced along with the increase of the preheating load. The condensation load of the compressed gas needs to determine the pressure (at the saturation temperature) at the outlet of the compressor according to the temperature of the cold side of the side reboiler E2 and a certain heat exchange temperature difference, and then a certain amount of compressed saturated steam is condensed into heat released by saturated condensate.
Aiming at the problems of high cost and energy consumption in the existing multi-component rectification separation process and the technical difficulty in energy-saving design, the three-component separation rectification process provided by the embodiment of the invention extracts key intermediate components meeting the separation requirement from a constant concentration area in a tower, selects a plate at a position with a small temperature difference (about 10 to 20 ℃) with the tower top below the side line intermediate component extraction position, extracts a part of saturated liquid at the side line to exchange heat with compressed gas, can be used for intermediate reboiling by using less compressor shaft work, and fully utilizes the residual heat of surplus tower top steam to preheat a feeding reboiler of the rectification tower, thereby greatly reducing the heat load of a tower kettle, saving the consumption of tower top cooling circulating water and tower kettle steam, achieving the purpose of energy saving and providing an energy-saving design idea for the separation of a large-temperature difference mixed system.
Application example
The technical scheme of the invention is further explained by taking the separation process of mixed butane as an example, and the superiority of the side-line heat pump rectification process of the embodiment of the invention is illustrated by comparing the energy consumption and the operation cost of the traditional direct rectification process.
The present application is described by taking the calculation simulation result of the side heat pump distillation process flow for treating 25 ten thousand ton/year mixed butane separation as an example, and the specific conditions are shown in table 1.
TABLE 1 separation of Mixed butanes Process conditions
| Item | Numerical value |
| Feed flow/(kg/h) | 31500 |
| Feed temperature/. Degree.C | 2 |
| Feed pressure/kPa | 720 |
| Feed composition/wt. -%) | C2:0.3; propane: 1.8; different from each otherButane: 32.4 of the total weight of the mixture; n-butane: 63.03; n-butene: 0.11; isobutene: 0.3; n-pentane: 1.1; isopentane: 0.95 |
| Outlet index/wt. -%) | Isobutane: not less than 90, n-butane: not less than 98 |
| Annual operating time/h | 8000 |
The process flow is described as follows:
(1) As shown in fig. 2, a mixed butane raw material is heated to 20 ℃ by a feed heat regenerator E1 at a feed rate of 31500kg/h and then sent to a rectifying tower T01, isobutane and a small amount of lighter C2 and C3 mixed hydrocarbons are taken out from the top of the tower as light components (41.6 ℃,11204.5kg/h, isobutane concentration 90 wt.%), n-butane as an intermediate component, and a product side stream is taken out in a constant concentration zone in the middle of the tower (63.2 ℃,19633kg/h, n-butane concentration 98 wt.%), and C5 and a small amount of n-butane are taken out from the bottom of the tower as heavy components (80.7 ℃,663kg/h, C5 concentration 61wt.%, n-butane concentration 39 wt.%);
(2) The tower top saturated vapor is compressed to 1540kPa by a tower top gas compressor C1 and then used as hot flow, the hot flow and saturated liquid (with the temperature difference of 20 ℃ with the tower top) collected from the middle lateral line of a rectifying tower T1 exchange heat in a lateral line reboiler E2, the cold flow is discharged at 20% of gasification rate and returns to the tower from a collecting tower plate, the hot flow after heat exchange is discharged at bubble point and enters a liquid collecting tank V1, then the pressure is reduced to 650kPa by a throttle valve V4, the gas and liquid are separated in a flash tank V2 after partial vaporization, the vapor returns to the inlet of the tower top gas compressor C1, and sufficient heat is provided for lateral line reboiling after the vapor is compressed again;
(3) And introducing part of the residual overhead gas into a feeding heat regenerator E1 to heat the raw material from 2 ℃ to 20 ℃ and then feeding the raw material into the tower, condensing the other part of the overhead gas by a water cooler E4 and then merging the condensed part of the overhead gas and the liquid phase separated from the flash tank V2 into a reflux buffer tank V3, and carrying out tower top reflux and extraction according to the reflux ratio of 9.2.
In order to compare the design energy consumption of the heat pump rectification process of the traditional direct rectification (as shown in figure 1) and the application example of the invention, the feeding and separation indexes adopted in the calculation of the two process flows are completely the same, process simulation is carried out by adopting process simulation software, the efficiency of the overhead gas compressor is calculated according to 80 percent, the public engineering specification is shown in table 2, and the calculation result of the energy consumption of each process is shown in table 3.
TABLE 2 Utility Specifications
| Item | Condition | Price |
| Circulating cooling |
20~30℃ | 0.2 yuan/t |
| Low pressure steam | 143~133℃，0.4~0.3MPaA | 150 yuan/t |
| Electric power | 10kV | 0.6 yuan/kW.h |
TABLE 3 comparison of Process energy consumption and Utility consumption (hourly unit time)
| Categories | Direct rectification | Side heat pump rectification |
| Cold loss/MW | -10.24 | -1.42 |
| Heat loss/MW | 11.05 | 0.81 |
| Power consumption/MW | 0 | 2 |
| Circulating water/t | 885.4 | 123 |
| Steam/t | 18.3 | 1.3 |
| electric/(kW. H) | 0 | 2003 |
And (4) comparing the results: the annual operating cost of each process is calculated by combining the tables 2 and 3, the same separation requirement is achieved under the same feeding condition, and the energy-saving process (1137 ten thousand yuan per year) of the side-line heat pump rectification saves the operating cost by 51.4 percent every year compared with the traditional direct rectification (2338 ten thousand yuan per year).
Compared with the traditional rectification process, the energy-saving process for the side-stream heat pump rectification of the n-butane separation of the maleic anhydride device has a remarkable energy-saving effect, and provides an idea for the energy-saving design of the multi-component rectification separation. It will be appreciated by persons skilled in the art from the foregoing description that it is not intended to limit the invention. Any modification, equivalent replacement, recombination, improvement and the like, which are made within the principle of the present invention, should be included in the protection scope of the present invention.
Claims (8)
1. A rectification system for separating a three-component mixture is characterized by comprising a rectification tower, a tower overhead gas compressor, a water cooler, a feeding heat regenerator, a side line reboiler, a tower kettle reboiler, a liquid collecting tank, a flash tank, a throttling element, a reflux buffer tank and first to ninth pipelines;
the top gas phase outlet of the rectifying tower is respectively communicated with the inlet of the first pipeline and the inlet of the second pipeline, and the outlet of the first pipeline and the outlet of the third pipeline are respectively communicated with the gas inlet of the top gas compressor; an exhaust port of the tower top gas compressor is communicated with a hot side inlet of the side reboiler, a hot side outlet of the side reboiler is communicated with an inlet of the liquid collecting tank, a gas phase outlet of the liquid collecting tank is communicated with an inlet of the fourth pipeline, and a liquid phase outlet of the liquid collecting tank is communicated with a material inlet of the flash tank through the throttling element; a cold side inlet and a cold side outlet of the side reboiler are respectively communicated with a side line extraction port and a side line return port of the rectifying tower;
the liquid phase outlet of the tower kettle of the rectifying tower is divided into two paths: one path is communicated with a cold side inlet of the tower kettle reboiler, and the other path is used for discharging materials from the tower kettle; a cold side outlet of the tower kettle reboiler is communicated with a tower kettle steam inlet of the rectifying tower;
the gas phase outlet of the flash tank is communicated with the inlet of a fifth pipeline, the outlet of the fifth pipeline is respectively communicated with the inlet of a third pipeline and the inlet of a sixth pipeline, the outlet of the sixth pipeline is respectively communicated with the hot side inlet of the water cooler and one end of a seventh pipeline, the outlet of the second pipeline is respectively communicated with the other end of the seventh pipeline and the inlet of an eighth pipeline, the outlet of the eighth pipeline is communicated with the hot side inlet of the feeding heat regenerator, the hot side outlet of the feeding heat regenerator is communicated with the inlet of a ninth pipeline, the cold side inlet of the feeding heat regenerator is used for feeding, and the cold side outlet of the feeding heat regenerator is communicated with the feeding hole of the rectifying tower;
a first inlet of the reflux buffer tank is communicated with a liquid phase outlet of the flash tank, a second inlet of the reflux buffer tank is respectively communicated with a hot side outlet of the water cooler and an outlet of the ninth pipeline, the liquid phase outlet of the reflux buffer tank is divided into two paths, one path of liquid phase outlet is at the top of the reflux tower, and the other path of liquid phase outlet is used for discharging;
the water cooler is characterized in that a first switch valve is arranged on the third pipeline, a second switch valve is arranged on the eighth pipeline, a third switch valve is arranged at the inlet of the hot side of the water cooler, and a fourth switch valve is arranged on the sixth pipeline.
2. The rectification system according to claim 1, wherein the noncondensable gas outlet of the reflux buffer tank and the outlet of the fourth pipeline are respectively communicated with an inlet of a tenth pipeline;
and a fifth switch valve is arranged on the fourth pipeline, and a sixth switch valve is arranged at a non-condensable gas outlet of the backflow buffer tank.
3. The rectification system of claim 2 wherein an outlet of the tenth conduit communicates with a non-condensable gas flare.
4. The rectification system of claim 1, wherein the rectification column is a plate rectification column, and the side draw outlet and the side reflux outlet are disposed on the same plate of the plate rectification column.
5. The rectification system as claimed in claim 1 or 4, wherein the side offtake and the side reflux opening are located below the position of withdrawal of the middle component of the rectification column T1.
6. The rectification system as claimed in claim 1, wherein said throttling element is a throttle valve.
7. A rectification process for the separation of a three component mixture comprising the steps of:
introducing the three-component mixture into a rectifying tower for rectification, discharging light component saturated steam from the top of the tower, extracting intermediate components from a side line of the tower, and discharging heavy components from a tower kettle after reboiling and concentrating;
introducing the light component saturated vapor extracted from the top of the tower into a top gas compressor;
introducing gas compressed by a tower top gas compressor into a side reboiler, performing heat exchange with saturated liquid extracted from a side line of a rectifying tower as a heat source, and returning the saturated liquid into the rectifying tower from the side line of the rectifying tower after reboiling;
introducing saturated condensate at the outlet of the side reboiler into a liquid collecting tank, discharging non-condensable gas from the top of the liquid collecting tank, throttling liquid phase obtained from the liquid collecting tank, introducing the liquid phase into a flash tank, performing gas-liquid separation, and introducing the liquid phase obtained from the flash tank and liquid phase generated after condensation of a water cooler into a reflux buffer tank;
one part of condensate obtained from the reflux buffer tank is refluxed to the top of the tower, and the other part of condensate is taken as a product at the top of the tower;
if it is predetermined that the condensation load of the obtained compressed gas cannot meet the heat exchange load of the side reboiler after all the overhead gas and all the gas generated by the flash tank are compressed by the overhead gas compressor, introducing all the overhead gas and all the gas generated by the flash tank into the overhead gas compressor; if it is predetermined that after all the top gas is compressed by the top gas compressor, the condensation load of the obtained compressed gas is smaller than the heat exchange load of the side reboiler, but after all the top gas and all the gas generated by the flash tank are compressed by the top gas compressor, the condensation load of the obtained compressed gas is larger than the heat exchange load of the side reboiler, introducing a part of the top gas and all the gas generated by the flash tank into the top gas compressor together so that the condensation load of the compressed gas is matched with the heat exchange load of the side reboiler, introducing the other part of the top gas into the feed regenerator, and if the condensation load of the part of the top gas is larger than the preheating load of the feed regenerator, introducing the rest of the top gas into the water cooler for condensation under the condition of meeting the preheating load of the feed regenerator; if it is predetermined that after all the overhead gas is compressed by the overhead gas compressor, the condensation load of the obtained compressed gas is greater than the heat exchange load of the side reboiler, only a part of the overhead gas is introduced into the overhead gas compressor, the other part of the overhead gas and all the gas generated by the flash tank are merged and then introduced into the feed heat regenerator, if the condensation load of the merged gas of the other part of the overhead gas and all the gas generated by the flash tank is greater than the preheating load of the feed heat regenerator, only a part of the merged gas is introduced into the feed heat regenerator, so that the condensation load of the part of the merged gas is matched with the preheating load, and the rest part of the merged gas is introduced into the water cooler for condensation.
8. The rectification process according to claim 7, wherein the temperature difference between the gas after being boosted and heated by the overhead gas compressor and the saturated liquid extracted from the side line of the rectification column is 10-20 ℃.
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