CN111995499A - Methanol heat pump rectification method and device - Google Patents
Methanol heat pump rectification method and device Download PDFInfo
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- CN111995499A CN111995499A CN202010873345.3A CN202010873345A CN111995499A CN 111995499 A CN111995499 A CN 111995499A CN 202010873345 A CN202010873345 A CN 202010873345A CN 111995499 A CN111995499 A CN 111995499A
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Abstract
The invention relates to a methanol heat pump rectification method and a device, belonging to the technical field of chemical rectification. The method and the device relate to a high-pressure tower and a low-pressure tower, wherein refined methanol steam obtained from a rectifying section of the high-pressure tower and a rectifying section of the low-pressure tower respectively enters hot sides of a reboiler of the high-pressure tower and a reboiler of the low-pressure tower after being pressurized and heated by a compressor so as to be used as heat sources of the high-pressure tower and the low-pressure tower. Compared with the traditional double-effect methanol rectification, the method and the device do not use raw steam for heat supply, and the refined methanol steam obtained at the rectification section of the low-pressure tower also participates in heat supply, so that the condensation load of the refined methanol steam of the low-pressure tower is reduced, the circulating cooling water is saved, the double-tower heat pump rectification of the high-pressure tower and the low-pressure tower is realized, the traditional double-effect rectification is replaced, the low-grade heat energy of the refined methanol steam of the high-pressure tower and the low-pressure tower is converted into high-grade heat energy, the heat is reasonably utilized, and the energy-saving.
Description
Technical Field
The invention belongs to the technical field of chemical rectification, and relates to a methanol heat pump rectification method and a methanol heat pump rectification device.
Background
Methanol is an important organic chemical raw material, an industrial solvent and a novel energy fuel, and has wide application in the fields of chemical industry, light industry and clean energy. The crude methanol synthesized by the existing synthesis process contains more impurities, and needs to be refined, and rectification is the main method for refining the crude methanol at present. With the vigorous development of the coal chemical industry, the scale of methanol rectification is getting larger and larger, and the energy-saving problem in the methanol rectification process becomes the key for the survival and the improvement of the competitiveness of enterprises.
The existing methanol rectification technology mainly comprises double-tower rectification, three-tower double-effect rectification and four-tower double-effect rectification, wherein the double-tower rectification is gradually eliminated, the three-tower double-effect rectification comprises a pre-rectification tower, a pressurizing tower and an atmospheric tower, a recovery tower is added on the basis of the three-tower double-effect rectification for further recovering methanol to form the four-tower double-effect rectification, and the four-tower double-effect rectification is widely applied. In the three-tower or four-tower double-effect rectification, light components in crude methanol are removed from the tower top of a pre-rectification tower, and after materials discharged from the tower bottom are rectified by a pressurizing tower and an atmospheric tower, refined methanol is respectively obtained from materials discharged from the tower top of the pressurizing tower and the tower top of the atmospheric tower. The tower top steam of the pressurized tower is used as a heat source of the atmospheric tower reboiler to form double-effect rectification, and the double-effect rectification has a certain energy-saving effect. In recent years, the yield of the domestic methanol is excessive, the supply is more than the demand, and the demand for newly building a methanol rectifying device is small. Under the background, energy-saving modification of the existing methanol rectifying device with high energy consumption is urgently needed.
Disclosure of Invention
In view of the above, the present invention aims to provide a methanol heat pump rectification method and apparatus, which are suitable for energy saving transformation of an existing methanol three-tower or four-tower double-effect rectification apparatus, and solve the problem of energy saving and emission reduction faced by the existing methanol three-tower or four-tower double-effect rectification apparatus by using double-tower heat pump rectification instead of double-effect rectification.
In order to achieve the purpose, the invention provides the following technical scheme:
a methanol heat pump rectification method comprises the following steps:
the initial methanol aqueous solution without light components enters a high-pressure tower, refined methanol steam is obtained from a rectifying section of the high-pressure tower, the refined methanol steam and the refined methanol steam from a rectifying section of a low-pressure tower and pressurized by a primary compressor enter a secondary compressor to be pressurized, part of the refined methanol steam pressurized by the secondary compressor is used as a heat source to enter the hot side of a reboiler of the high-pressure tower, part of the refined methanol steam is used as the heat source to enter the hot side of the reboiler of the low-pressure tower, the refined methanol steam is condensed to form refined methanol liquid after heat exchange, part of the refined methanol liquid is used as reflux liquid of the rectifying section of the high-pressure tower to return to the high-pressure tower, part of the refined methanol steam is used; obtaining a methanol aqueous solution from a stripping section of the high-pressure tower, enabling a part of the methanol aqueous solution to enter a cold side of a reboiler of the high-pressure tower, forming steam after heat exchange and returning the steam to the high-pressure tower, and enabling a part of the steam to enter a low-pressure tower; obtaining refined methanol steam from the rectifying section of the low-pressure tower, feeding the refined methanol steam into a primary compressor, and feeding the pressurized refined methanol steam and the refined methanol steam from the high-pressure tower into a secondary compressor; obtaining methanol water solution from the stripping section of the low-pressure tower, enabling part of the methanol water solution to enter the cold side of a reboiler of the low-pressure tower, forming steam after heat exchange to return to the low-pressure tower, and enabling part of the steam to be extracted to enter a subsequent process.
It should be noted that the pressure of the higher pressure tower is higher than that of the lower pressure tower, where the "higher pressure" of the higher pressure tower and the "lower pressure" of the lower pressure tower are relative terms, and the lower pressure tower may be an atmospheric tower in a practical application scenario.
Further, the refined methanol steam obtained from the rectifying section of the low-pressure tower is divided into two parts, one part enters a first-stage compressor, the pressurized refined methanol steam and the refined methanol steam from the rectifying section of the high-pressure tower enter a second-stage compressor, and the other part is condensed to form refined methanol liquid which is used as reflux of the rectifying section and returned to the low-pressure tower.
Further, fusel oil is extracted from the side line of the stripping section of the low-pressure tower.
Further, the method also comprises a preliminary rectification step of a pre-rectification tower: preheating a crude methanol raw material by a crude methanol preheater, introducing the preheated crude methanol raw material into a pre-rectifying tower, obtaining light components from a rectifying section of the pre-rectifying tower, condensing and separating the light components, returning a solution formed after condensation to the pre-rectifying tower as a reflux liquid of the rectifying section, and separating and extracting uncondensed non-condensable gas; the methanol aqueous solution obtained from the stripping section of the pre-rectifying tower is divided into two parts, one part enters the cold side of a reboiler of the pre-rectifying tower, steam formed after heat exchange returns to the pre-rectifying tower, and the other part enters the high-pressure tower; and introducing the extraction water from the rectifying section of the pre-rectifying tower while introducing the crude methanol raw material into the pre-rectifying tower.
Further, the method also comprises a re-rectification step of a recovery tower: methanol aqueous solution extracted from the stripping section of the low-pressure tower enters a recovery tower; obtaining refined methanol steam from a rectifying section of a recovery tower, dividing refined methanol liquid formed after condensation into two streams, returning one stream to the recovery tower as reflux liquid of the rectifying section, and extracting the other stream as a refined methanol product; the methanol water solution obtained from the stripping section of the recovery tower is divided into two parts, one part enters the cold side of a reboiler of the recovery tower, steam is formed after heat exchange and returns to the recovery tower, and the other part is extracted as waste liquid; and obtaining fusel oil from the side line of the stripping section of the recovery tower.
A methanol heat pump rectifying device comprises a high-pressure tower, a high-pressure tower reboiler, a low-pressure tower and a low-pressure tower reboiler, wherein the high-pressure tower and the low-pressure tower both comprise a rectifying section and a stripping section, a feed liquid feed port is arranged between the two sections, the rectifying section is provided with a rectifying section discharge port and a reflux liquid reflux port, the stripping section is provided with a stripping section discharge port and a stripping steam feed port, and the stripping section discharge port of the high-pressure tower is communicated with the feed liquid feed port of the low-pressure tower; the stripping section discharge port and the stripping steam feed port of the high-pressure tower are communicated with the cold side of the high-pressure tower reboiler in a circulating manner, and the stripping section discharge port and the stripping steam feed port of the low-pressure tower are communicated with the cold side of the low-pressure tower reboiler in a circulating manner; the discharge port of the rectifying section of the low-pressure tower is sequentially communicated with a primary compressor and a secondary compressor, the inlet end of the secondary compressor is also communicated with the discharge port of the rectifying section of the high-pressure tower, and the outlet end of the secondary compressor is respectively communicated with the hot sides of a reboiler of the high-pressure tower and a reboiler of the low-pressure tower; and the hot sides of the high-pressure tower reboiler and the low-pressure tower reboiler are provided with reflux channels which are respectively communicated with a reflux liquid reflux port of the high-pressure tower and a reflux liquid reflux port of the low-pressure tower, and the high-pressure tower reboiler and the low-pressure tower reboiler are also provided with product acquisition channels for acquiring refined methanol products.
Furthermore, a discharge port of the rectification section of the low-pressure tower is sequentially communicated with a low-pressure tower condenser and a low-pressure tower reflux tank, and a reflux channel at the hot side of the low-pressure tower reboiler is communicated with a reflux liquid reflux port of the low-pressure tower through the low-pressure tower reflux tank.
Further, a fusel oil collecting port is arranged on the side line of the stripping section of the low-pressure tower.
The pre-rectifying tower comprises a rectifying section and a stripping section, a feed liquid feed inlet is formed between the two sections, the rectifying section is provided with a rectifying section discharge port and a reflux liquid reflux port, the stripping section is provided with a stripping section discharge port and a stripping steam feed inlet, and a stripping section discharge port of the pre-rectifying tower is communicated with the feed liquid feed inlet of the high-pressure tower; the cold side of a pre-rectifying tower reboiler is circularly communicated between a stripping section discharge port and a stripping steam feed port of the pre-rectifying tower; the feed liquid feed inlet of the pre-rectifying tower is communicated with the cold side of the crude methanol preheater; the discharge port of the rectifying section of the pre-rectifying tower is sequentially communicated with a pre-rectifying tower primary condenser, a pre-rectifying tower secondary condenser and a non-condensable gas separator, the outlet ends of the pre-rectifying tower primary condenser, the pre-rectifying tower secondary condenser and the non-condensable gas separator are communicated with a pre-rectifying tower reflux tank, and the outlet end of the pre-rectifying tower reflux tank is communicated with a reflux liquid reflux port of the pre-rectifying tower; the non-condensable gas separator is also provided with a non-condensable gas outlet; the rectifying section of the pre-rectifying tower is provided with a water inlet for introducing extraction water.
The recovery tower comprises a rectifying section and a stripping section, a feed liquid feed inlet is arranged between the rectifying section and the stripping section, the rectifying section is provided with a rectifying section discharge port and a reflux liquid reflux port, the stripping section is provided with a stripping section discharge port and a stripping steam feed inlet, and a stripping section discharge port of the low-pressure tower is communicated with the feed liquid feed inlet of the recovery tower; the cold side of a reboiler of the recovery tower is circularly communicated between a stripping section discharge port and a stripping steam feed port of the recovery tower; a discharge port of a rectifying section of the recovery tower is sequentially communicated with a recovery tower condenser and a recovery tower reflux tank, and an outlet end of the recovery tower reflux tank is communicated with a reflux liquid reflux port of the recovery tower; the outlet end of the reflux tank of the recovery tower is also provided with a product collecting channel; a fusel oil collecting port is arranged on the side line of the stripping section of the recovery tower.
The invention has the beneficial effects that:
(1) the invention discloses a methanol heat pump rectification method and a device, wherein the refined methanol steam obtained from the rectification section of a high pressure tower and the refined methanol steam obtained from the rectification section of a low pressure tower and processed by a primary compressor enter a secondary compressor for pressurizing and heating, the refined methanol steam discharged from the secondary compressor is respectively used as the heat source of a reboiler of the high pressure tower and a reboiler of the low pressure tower, raw steam is not used for heat supply, the refined methanol steam of the rectification section of the low pressure tower also participates in heat supply, the condensation load of the low pressure tower is reduced, circulating cooling water is saved, the double-tower heat pump rectification of the high pressure tower and the low pressure tower is realized, the traditional double-effect rectification is replaced, the low-grade heat energy of the refined methanol steam obtained from the rectification section of the high pressure tower and the low pressure tower is converted into high-grade heat energy, the heat is reasonably utilized, compared with the existing three-tower or four-tower double-effect rectification, the emission of carbon dioxide is reduced by more than 60%, the energy-saving and emission-reducing effects are obvious, and the green development indexes are met.
(2) The invention discloses a methanol heat pump rectification method and a device, wherein the load of each tower is similar to that of each tower of the existing double-effect rectification, and the refined methanol discharge amount of a high-pressure tower and a low-pressure tower is basically unchanged compared with that of a pressurizing tower and a normal-pressure tower of the existing double-effect rectification respectively, so that the method and the device can be directly applied to energy-saving reconstruction of the existing double-effect rectification device without replacing existing tower equipment.
(3) The invention discloses a methanol heat pump rectification method and a device, because a high-pressure tower reboiler and a low-pressure tower reboiler use pressurized refined methanol steam as a heat source, double-effect rectification is not adopted, and the heat is supplied to an atmospheric tower reboiler without the existing double-effect rectification, so that the steam obtained at the rectification section of a pressurizing tower and the tower bottom liquid of the atmospheric tower have enough heat exchange temperature difference, and the pressurizing tower keeps higher pressure. The rectification method and the rectification device can reduce the operating pressure of the high-pressure tower and improve the safety.
(4) The invention discloses a methanol heat pump rectification method and a device, wherein the refined methanol steam of the rectification section of a low-pressure tower is divided into two parts, the flow of the refined methanol steam used as the heat source of a high-pressure tower reboiler and the low-pressure tower reboiler can be controlled by the distribution of the refined methanol steam obtained by the rectification section of the low-pressure tower, so that the working condition change of the high-pressure tower and the low-pressure tower is adapted, and the flexibility of the process operation is improved.
Drawings
In order to make the objects, technical solutions and advantages of the present invention more clear, the present invention is illustrated by the following drawings:
FIG. 1 is a schematic flow chart of the present invention.
Reference numerals: the system comprises a pre-rectifying tower 1, a high-pressure tower 2, a low-pressure tower 3, a recovery tower 4, a crude methanol preheater 5, a pre-rectifying tower first-stage condenser 6, a pre-rectifying tower reflux tank 7, a pre-rectifying tower second-stage condenser 8, a noncondensable gas separator 9, a pre-rectifying tower reboiler 10, a second-stage compressor 11, a high-pressure tower reboiler 12, a first-stage compressor 13, a low-pressure tower condenser 14, a low-pressure tower reflux tank 15, a low-pressure tower reboiler 16, a recovery tower condenser 17, a recovery tower reflux tank 18 and a recovery tower reboiler 19.
Detailed Description
Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.
As shown in fig. 1, the embodiment provides a methanol heat pump rectification device, specifically a methanol four-tower heat pump rectification device, which includes a pre-rectification tower 1, a high-pressure tower 2, a low-pressure tower 3, and a recovery tower 4. In other embodiments, the methanol heat pump rectifying device can also be a methanol three-tower heat pump rectifying device, including a pre-rectifying tower 1, a high-pressure tower 2 and a low-pressure tower 3.
The pre-rectifying tower 1 comprises a rectifying section and a stripping section, a feed liquid feed port is arranged between the rectifying section and the stripping section, the rectifying section is provided with a rectifying section discharge port and a reflux liquid reflux port, the stripping section is provided with a stripping section discharge port and a stripping steam feed port, and the stripping section discharge port of the pre-rectifying tower 1 is communicated with the feed liquid feed port of the high-pressure tower 2; the cold side of a pre-rectifying tower reboiler 10 is circularly communicated between a stripping section discharge port and a stripping steam feed port of the pre-rectifying tower 1; the feed liquid feed inlet of the pre-rectifying tower 1 is communicated with the cold side of a crude methanol preheater 5; the discharge port of the rectifying section of the pre-rectifying tower 1 is sequentially communicated with a pre-rectifying tower primary condenser 6, a pre-rectifying tower secondary condenser 8 and a noncondensable gas separator 9, the outlet ends of the pre-rectifying tower primary condenser 6, the pre-rectifying tower secondary condenser 8 and the noncondensable gas separator 9 are communicated with a pre-rectifying tower reflux tank 7, and the outlet end of the pre-rectifying tower reflux tank 7 is communicated with a reflux liquid reflux port of the pre-rectifying tower 1; the non-condensable gas outlet is also formed in the non-condensable gas separator 9; the rectifying section of the pre-rectifying tower 1 is provided with a water inlet for introducing extraction water.
The high-pressure tower 2 and the low-pressure tower 3 both comprise a rectifying section and a stripping section, a feed liquid feed inlet is arranged between the rectifying section and the stripping section, the rectifying section is provided with a rectifying section discharge port and a reflux liquid reflux port, the stripping section is provided with a stripping section discharge port and a stripping steam feed inlet, and the stripping section discharge port of the high-pressure tower 2 is communicated with the feed liquid feed inlet of the low-pressure tower 3; the cold side of a high-pressure tower reboiler 12 is circularly communicated between a stripping section discharge port and a stripping steam feed port of the high-pressure tower 2, and the cold side of a low-pressure tower reboiler 16 is circularly communicated between a stripping section discharge port and a stripping steam feed port of the low-pressure tower 3; a discharge port of a rectifying section of the low-pressure tower 3 is sequentially communicated with a primary compressor 13 and a secondary compressor 11, an inlet end of the secondary compressor 11 is also communicated with a discharge port of a rectifying section of the high-pressure tower 2, and an outlet end of the secondary compressor 11 is respectively communicated with hot sides of a reboiler 12 of the high-pressure tower and a reboiler 16 of the low-pressure tower; the hot sides of the high-pressure tower reboiler 12 and the low-pressure tower reboiler 16 are provided with reflux channels which are respectively communicated with a reflux liquid reflux port of the high-pressure tower 2 and a reflux liquid reflux port of the low-pressure tower 3, and are also provided with product collection channels for collecting refined methanol products. The arrangement mode of the return channel can be two types: in one embodiment, the reflux channel at the hot side of the high-pressure tower reboiler 12 is communicated with the reflux liquid reflux port of the high-pressure tower 2, the reflux channel at the hot side of the low-pressure tower reboiler 16 is communicated with the reflux liquid reflux port of the low-pressure tower 3, and the two reflux channels are independent of each other; and the other is that an refined methanol liquid mixing channel is communicated between the two reflux channels, and refined methanol liquid flowing out from the hot side of the high-pressure tower reboiler 12 and the hot side of the low-pressure tower reboiler 16 is mixed and then respectively refluxed to the high-pressure tower 2 and the low-pressure tower 3.
In addition, a discharge port of the rectification section of the low-pressure tower 3 is also sequentially communicated with a low-pressure tower condenser 14 and a low-pressure tower reflux tank 15. In the case where the low-pressure column condenser 14 and the low-pressure column reflux tank 15 are not provided, the reflux passage on the hot side of the low-pressure column reboiler 16 is directly communicated with the reflux liquid reflux port of the low-pressure column 3, and in this embodiment, the reflux passage on the hot side of the low-pressure column reboiler 16 is communicated with the reflux liquid reflux port of the low-pressure column 3 through the low-pressure column reflux tank 15.
The recovery tower 4 comprises a rectifying section and a stripping section, a feed liquid feed port is arranged between the rectifying section and the stripping section, the rectifying section is provided with a rectifying section discharge port and a reflux liquid reflux port, the stripping section is provided with a stripping section discharge port and a stripping steam feed port, and the stripping section discharge port of the low-pressure tower 3 is communicated with the feed liquid feed port of the recovery tower 4; the cold side of a reboiler 19 of the recovery tower is circularly communicated between a stripping section discharge port and a stripping steam feed port of the recovery tower 4; a discharge port of a rectifying section of the recovery tower 4 is sequentially communicated with a recovery tower condenser 17 and a recovery tower reflux tank 18, and an outlet end of the recovery tower reflux tank 18 is communicated with a reflux liquid reflux port of the recovery tower 4; the outlet end of the recovery tower reflux tank 18 is also provided with a product collecting channel; a fusel oil collecting port is arranged on the side line of the stripping section of the recovery tower 4. In the methanol three-tower heat pump rectifying device, a recovery tower 4 is not arranged, and a fusel oil collecting port is arranged on the side line of the stripping section of a low-pressure tower 3.
The embodiment also provides a methanol heat pump rectification method, which comprises the following steps:
preliminary rectification in a pre-rectifying tower 1: preheating a crude methanol raw material by a crude methanol preheater 5, introducing the preheated crude methanol raw material into a pre-rectifying tower 1, obtaining light components from a rectifying section of the pre-rectifying tower 1, condensing and separating the light components, returning a solution formed after condensation to the pre-rectifying tower 1 as a reflux liquid of the rectifying section, and separating and extracting uncondensed non-condensable gas; the methanol water solution obtained from the stripping section of the pre-rectifying tower 1 is divided into two parts, one part enters the cold side of a pre-rectifying tower reboiler 10, steam formed after heat exchange returns to the pre-rectifying tower 1, and the other part enters the high-pressure tower 2; introducing extraction water from a rectifying section of the pre-rectifying tower 1 while introducing a crude methanol raw material into the pre-rectifying tower 1;
and (3) heat pump rectification of the high-pressure tower 2 and the low-pressure tower 3: the initial methanol aqueous solution without light components enters a high pressure tower 2, refined methanol steam is obtained from a rectifying section of the high pressure tower 2, the refined methanol steam and the refined methanol steam which comes from a rectifying section of a low pressure tower 3 and is pressurized by a primary compressor 13 enter a secondary compressor 11 for pressurization, part of the refined methanol steam pressurized by the secondary compressor 11 is used as a heat source to enter a hot side of a reboiler 12 of the high pressure tower, part of the refined methanol steam is used as the heat source to enter a hot side of a reboiler 16 of the low pressure tower, the refined methanol steam is condensed after heat exchange to form refined methanol liquid, part of the refined methanol liquid is used as reflux liquid of the rectifying section of the high pressure tower 2 to return to the high pressure tower 2, part of the refined methanol liquid is used as reflux liquid of the rectifying; obtaining a methanol aqueous solution from the stripping section of the high-pressure tower 2, enabling a part of the methanol aqueous solution to enter the cold side of a reboiler 12 of the high-pressure tower, forming steam after heat exchange and returning the steam to the high-pressure tower 2, and enabling a part of the steam to enter a low-pressure tower 3; refined methanol steam is obtained from the rectifying section of the low-pressure tower 3 and is divided into two parts, one part enters a primary compressor 13, the pressurized refined methanol steam and the refined methanol steam from the rectifying section of the high-pressure tower 2 enter a secondary compressor 11, and the other part is condensed to form refined methanol liquid which is used as reflux of the rectifying section and returns to the low-pressure tower 3; obtaining a methanol aqueous solution from the stripping section of the low-pressure tower 3, wherein the methanol concentration of the methanol aqueous solution is lower than that of the methanol aqueous solution obtained from the stripping section of the high-pressure tower 2, allowing a part of the methanol aqueous solution to enter the cold side of a reboiler 16 of the low-pressure tower, forming steam after heat exchange to return to the low-pressure tower 3, and allowing a part of the steam to be extracted to enter a subsequent process;
the recovery tower 4 is rectified again: methanol aqueous solution extracted from the stripping section of the low-pressure tower 3 enters a recovery tower 4; refined methanol steam is obtained from the rectifying section of the recovery tower 4, the refined methanol liquid formed after condensation is divided into two streams, one stream is used as reflux liquid of the rectifying section and returns to the recovery tower 4, and the other stream is used as a refined methanol product and is extracted; the methanol aqueous solution obtained from the stripping section of the recovery tower 4 is divided into two parts, one part enters the cold side of a reboiler 19 of the recovery tower, steam is formed after heat exchange and returns to the recovery tower 4, and the other part is extracted as waste liquid; and obtaining fusel oil from the side line of the stripping section of the recovery tower 4. Under the condition that the recovery tower 4 is not arranged and the methanol heat pump rectifying device is a methanol three-tower heat pump rectifying device, fusel oil is obtained from the side line of the stripping section of the low-pressure tower 3 and is extracted.
In this embodiment, the extracted refined methanol product is used as a heat source of the crude methanol preheater 5. The low-shift gas generated by the hydrogen production device in the crude methanol synthesis process is used as a heat source of the pre-rectifying tower reboiler 10 and the recovery tower reboiler 19. When the refined methanol vapor pressurized by the secondary compressor 11 is rich in the load of the high-pressure column reboiler 12 and the low-pressure column reboiler 16, a part of the refined methanol vapor can be taken out as a heat source of the pre-rectifying column reboiler 10.
In this example, the crude methanol feed was 9000kg/h and comprised 85.65% w methanol, 12.54% w water, 0.05% w ethanol, 0.04% w n-butanol, 0.03% w isobutanol, 1.38% w carbon dioxide, and 0.31% w dimethyl ether. After rectification treatment, 7632.2kg/h of refined methanol product is obtained, wherein the methanol content is 99.99% w, the water content is 0.01% w, and the methanol recovery rate is 99.0%.
In this embodiment, the pre-rectifying tower 1 is operated at 65 to 90 ℃ under 130 to 180kpa (absolute) at a reflux ratio of 1.0 to 2.8. The operating temperature of the high-pressure tower 2 is 75-95 ℃, the operating pressure is 180-240 kpa (absolute pressure), and the reflux ratio is 2.0-3.5. The operating temperature of the low-pressure tower 3 is 60-90 ℃, the operating pressure is 110-140 kpa (absolute pressure), and the reflux ratio is 1.5-2.5. The operation temperature of the recovery tower 4 is 60-120 ℃, the operation pressure is 110-160 kpa (absolute pressure), and the reflux ratio is 6.5-8.5.
In this embodiment, the refined methanol vapor discharged from the secondary compressor 11 is used as a heat source for the high-pressure column reboiler 12 and the low-pressure column reboiler 16, raw steam is not used for heat supply, the refined methanol vapor in the rectifying section of the low-pressure column 3 also participates in heat supply, the condensing load of the low-pressure column 3 is reduced, circulating cooling water is saved, double-column heat pump rectification of the high-pressure column 2 and the low-pressure column 3 is realized, the traditional double-effect rectification is replaced, the low-grade heat energy of the refined methanol vapor obtained in the rectifying section of the high-pressure column 2 and the rectifying section of the low-pressure column 3 is converted into high-grade heat energy, heat is reasonably utilized, compared with the existing three-column or four-column double-effect rectification, the comprehensive energy consumption of unit methanol rectification is reduced by more than 60%, the.
The load of each tower is similar to that of the existing double-effect rectification tower, the discharge amount of the refined methanol of the high-pressure tower 2 and the low-pressure tower 3 is basically unchanged compared with the pressurized tower and the normal-pressure tower of the existing double-effect rectification tower, and the refined methanol rectification method can be directly applied to energy-saving transformation of the existing double-effect rectification device without replacing existing tower equipment.
The existing double-effect rectification is to use steam of a pressurized tower to supply heat to a reboiler of the atmospheric tower, and the pressurized tower needs to keep higher pressure to ensure that the steam obtained at the rectification section of the pressurized tower and the tower bottom liquid of the atmospheric tower have enough heat exchange temperature difference; the invention adopts heat pump rectification instead of double-effect rectification, can reduce the pressure of the high-pressure tower 2 and improve the safety.
The refined methanol steam obtained from the rectifying section of the low-pressure tower 3 is divided into two parts, 30% -90% of the refined methanol steam enters the primary compressor 13 and is used as a heat source for the high-pressure tower reboiler 12 and the low-pressure tower reboiler 16, the flow distribution can be flexibly adjusted according to the actual working conditions of the high-pressure tower 2 and the low-pressure tower 3, and when the loads of the high-pressure tower reboiler 12 and the low-pressure tower reboiler 16 are increased, the refined methanol steam leading to the primary compressor 13 can be improved to obtain more secondary refined methanol steam for heat supply.
Finally, the above embodiments are only intended to illustrate the technical solutions of the present invention and not to limit the present invention, and although the present invention has been described in detail with reference to the preferred embodiments, it will be understood by those skilled in the art that modifications or equivalent substitutions may be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions, and all of them should be covered by the claims of the present invention.
Claims (10)
1. A methanol heat pump rectification method is characterized by comprising the following steps:
the initial methanol aqueous solution without light components enters a high-pressure tower, refined methanol steam is obtained from a rectifying section of the high-pressure tower, the refined methanol steam and the refined methanol steam from a rectifying section of a low-pressure tower and pressurized by a primary compressor enter a secondary compressor to be pressurized, part of the refined methanol steam pressurized by the secondary compressor is used as a heat source to enter the hot side of a reboiler of the high-pressure tower, part of the refined methanol steam is used as the heat source to enter the hot side of the reboiler of the low-pressure tower, the refined methanol steam is condensed to form refined methanol liquid after heat exchange, part of the refined methanol liquid is used as reflux liquid of the rectifying section of the high-pressure tower to return to the high-pressure tower, part of the refined methanol steam is used; obtaining a methanol aqueous solution from a stripping section of the high-pressure tower, enabling a part of the methanol aqueous solution to enter a cold side of a reboiler of the high-pressure tower, forming steam after heat exchange and returning the steam to the high-pressure tower, and enabling a part of the steam to enter a low-pressure tower; obtaining refined methanol steam from the rectifying section of the low-pressure tower, feeding the refined methanol steam into a primary compressor, and feeding the pressurized refined methanol steam and the refined methanol steam from the high-pressure tower into a secondary compressor; obtaining methanol water solution from the stripping section of the low-pressure tower, enabling part of the methanol water solution to enter the cold side of a reboiler of the low-pressure tower, forming steam after heat exchange to return to the low-pressure tower, and enabling part of the steam to be extracted to enter a subsequent process.
2. The heat pump methanol rectification method as claimed in claim 1, wherein the refined methanol vapor obtained from the rectification section of the low pressure column is divided into two parts, one part is introduced into the first stage compressor, the pressurized refined methanol vapor enters the second stage compressor together with the refined methanol vapor from the rectification section of the high pressure column, and the other part is condensed to form refined methanol liquid which is returned to the low pressure column as the reflux of the rectification section.
3. The heat pump distillation method of methanol as claimed in claim 1 or 2, wherein fusel oil is extracted from the side line of the stripping section of the low-pressure tower.
4. The heat pump distillation method of methanol as claimed in claim 1 or 2, further comprising a preliminary distillation step of the pre-rectifying tower: preheating a crude methanol raw material by a crude methanol preheater, introducing the preheated crude methanol raw material into a pre-rectifying tower, obtaining light components from a rectifying section of the pre-rectifying tower, condensing and separating the light components, returning a solution formed after condensation to the pre-rectifying tower as a reflux liquid of the rectifying section, and separating and extracting uncondensed non-condensable gas; the methanol aqueous solution obtained from the stripping section of the pre-rectifying tower is divided into two parts, one part enters the cold side of a reboiler of the pre-rectifying tower, steam formed after heat exchange returns to the pre-rectifying tower, and the other part enters the high-pressure tower; and introducing the extraction water from the rectifying section of the pre-rectifying tower while introducing the crude methanol raw material into the pre-rectifying tower.
5. The heat pump distillation method of methanol as claimed in claim 1 or 2, further comprising the step of re-rectifying in a recovery column: methanol aqueous solution extracted from the stripping section of the low-pressure tower enters a recovery tower; obtaining refined methanol steam from a rectifying section of a recovery tower, dividing refined methanol liquid formed after condensation into two streams, returning one stream to the recovery tower as reflux liquid of the rectifying section, and extracting the other stream as a refined methanol product; the methanol water solution obtained from the stripping section of the recovery tower is divided into two parts, one part enters the cold side of a reboiler of the recovery tower, steam is formed after heat exchange and returns to the recovery tower, and the other part is extracted as waste liquid; and obtaining fusel oil from the side line of the stripping section of the recovery tower.
6. A methanol heat pump rectifying device is characterized by comprising a high-pressure tower, a high-pressure tower reboiler, a low-pressure tower and a low-pressure tower reboiler, wherein the high-pressure tower and the low-pressure tower both comprise a rectifying section and a stripping section, a feed liquid feed port is arranged between the two sections, the rectifying section is provided with a rectifying section discharge port and a reflux liquid reflux port, the stripping section is provided with a stripping section discharge port and a stripping steam feed port, and the stripping section discharge port of the high-pressure tower is communicated with the feed liquid feed port of the low-pressure tower; the stripping section discharge port and the stripping steam feed port of the high-pressure tower are communicated with the cold side of the high-pressure tower reboiler in a circulating manner, and the stripping section discharge port and the stripping steam feed port of the low-pressure tower are communicated with the cold side of the low-pressure tower reboiler in a circulating manner; the discharge port of the rectifying section of the low-pressure tower is sequentially communicated with a primary compressor and a secondary compressor, the inlet end of the secondary compressor is also communicated with the discharge port of the rectifying section of the high-pressure tower, and the outlet end of the secondary compressor is respectively communicated with the hot sides of a reboiler of the high-pressure tower and a reboiler of the low-pressure tower; and the hot sides of the high-pressure tower reboiler and the low-pressure tower reboiler are provided with reflux channels which are respectively communicated with a reflux liquid reflux port of the high-pressure tower and a reflux liquid reflux port of the low-pressure tower, and the high-pressure tower reboiler and the low-pressure tower reboiler are also provided with product acquisition channels for acquiring refined methanol products.
7. The methanol heat pump rectifying device according to claim 6, wherein a discharge port of the rectifying section of the low-pressure tower is sequentially communicated with a low-pressure tower condenser and a low-pressure tower reflux tank, and a reflux channel at a hot side of a low-pressure tower reboiler is communicated with a reflux liquid reflux port of the low-pressure tower through the low-pressure tower reflux tank.
8. The methanol heat pump rectifying device as claimed in claim 6 or 7, wherein a fusel oil collecting port is arranged on the side line of the stripping section of the low-pressure tower.
9. The methanol heat pump rectifying device according to claim 6 or 7, further comprising a pre-rectifying tower, a pre-rectifying tower reboiler and a crude methanol preheater, wherein the pre-rectifying tower comprises a rectifying section and a stripping section, a feed liquid feeding port is arranged between the rectifying section and the stripping section, the rectifying section is provided with a rectifying section discharging port and a reflux liquid reflux port, the stripping section is provided with a stripping section discharging port and a stripping steam feeding port, and the stripping section discharging port of the pre-rectifying tower is communicated with the feed liquid feeding port of the high-pressure tower; the cold side of a pre-rectifying tower reboiler is circularly communicated between a stripping section discharge port and a stripping steam feed port of the pre-rectifying tower; the feed liquid feed inlet of the pre-rectifying tower is communicated with the cold side of the crude methanol preheater; the discharge port of the rectifying section of the pre-rectifying tower is sequentially communicated with a pre-rectifying tower primary condenser, a pre-rectifying tower secondary condenser and a non-condensable gas separator, the outlet ends of the pre-rectifying tower primary condenser, the pre-rectifying tower secondary condenser and the non-condensable gas separator are communicated with a pre-rectifying tower reflux tank, and the outlet end of the pre-rectifying tower reflux tank is communicated with a reflux liquid reflux port of the pre-rectifying tower; the non-condensable gas separator is also provided with a non-condensable gas outlet; the rectifying section of the pre-rectifying tower is provided with a water inlet for introducing extraction water.
10. The methanol heat pump rectifying device according to claim 6 or 7, further comprising a recovery tower and a recovery tower reboiler, wherein the recovery tower comprises a rectifying section and a stripping section, a feed liquid feed port is arranged between the rectifying section and the stripping section, the rectifying section is provided with a rectifying section discharge port and a reflux liquid reflux port, the stripping section is provided with a stripping section discharge port and a stripping steam feed port, and a stripping section discharge port of the low-pressure tower is communicated with the feed liquid feed port of the recovery tower; the cold side of a reboiler of the recovery tower is circularly communicated between a stripping section discharge port and a stripping steam feed port of the recovery tower; a discharge port of a rectifying section of the recovery tower is sequentially communicated with a recovery tower condenser and a recovery tower reflux tank, and an outlet end of the recovery tower reflux tank is communicated with a reflux liquid reflux port of the recovery tower; the outlet end of the reflux tank of the recovery tower is also provided with a product collecting channel; a fusel oil collecting port is arranged on the side line of the stripping section of the recovery tower.
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