Low-energy-consumption mto methanol rectifying device and method using reaction heat

Abstract

The application discloses a low-energy-consumption MTO methanol rectification device and method using reaction heat. The device comprises a methanol reactor, a methanol intermediate heat exchanger, a methanol air cooler, a methanol water cooler and a methanol buffer tank which are connected in sequence. The methanol reactor and the methanol intermediate heat exchanger form a loop. The methanol intermediate heat exchanger is also provided with a synthesis gas feeding port. The methanol buffer tank is connected with a methanol expansion tank. The methanol expansion tank is connected with a stabilizing tower. The top of the stabilizing tower is connected with a cooling reflux assembly through a reflux pipeline. The bottom of the stabilizing tower is connected with a stabilizing tower bottom pump and an MTO-grade methanol water cooler in sequence. The bottom of the stabilizing tower is also connected with a stabilizing tower reboiler through a loop. A heat medium circulation system is also connected between the methanol intermediate heat exchanger and the methanol air cooler. The heat medium circulation system is also connected to a pipeline between the methanol expansion tank and the stabilizing tower, so that the consumption of the cooling medium and the energy consumption of the stabilizing tower heating can be effectively reduced.

Description

Technical Field

[0001] This invention relates to the field of methanol synthesis technology, and in particular to a low-energy-consumption MTO methanol distillation apparatus and method utilizing reaction heat. Background Technology

[0002] The synthesis of methanol from carbon monoxide (CO) / hydrogen (H2) is a crucial process in modern coal chemical industry. The earliest method involved refining crude methanol using a methanol distillation process at 30 MPa high pressure with a zinc-chromium catalyst. This process primarily involved neutralization, deetherification, pre-distillation to remove light components and other impurities, oxidation purification, main distillation dehydration, and removal of heavy components, ultimately yielding refined methanol. With the continuous development of methanol synthesis technology and the expansion of production scale, distillation technology has also made significant progress. Currently, most methanol synthesis employs low-pressure synthesis technology at around 5 MPa. Compared to crude methanol produced by high-pressure methods, this yields higher purity products, which greatly reduces energy consumption in the distillation section. Currently, there are three main methanol distillation processes: single-tower, double-tower, and triple-tower processes. Double-tower and triple-tower processes are mainly used to produce AA-grade products conforming to the national standard GB338-2004, while single-tower processes are mainly used to produce MTO-grade methanol.

[0003] In coal-to-olefins (COO) processes, single-tower distillation (called a stabilization tower) is commonly used to refine MTO-grade methanol. However, current energy-saving research on methanol distillation mainly focuses on processes such as double-tower, triple-tower, or quadruple-tower refining, reducing steam consumption in the distillation system through methods such as thermal coupling between the pressurized and atmospheric distillation towers, utilizing the heat from the pressurized tower products, and using the heat from condensate to heat the feed to the pre-tower. There is limited research on energy saving in single-tower distillation; therefore, the production of MTO-grade methanol typically requires a significant amount of energy. MTO-grade methanol production typically involves ambient temperature feed, with the crude methanol at the methanol synthesis reactor outlet exchanging heat with the feed. However, the ambient temperature feed to the methanol distillation (stabilization tower) results in a large steam consumption in the reboiler at the bottom of the tower. Furthermore, after the crude methanol exchanges heat with the feed to the methanol synthesis reactor, the initial temperature is approximately 102 / 110℃, and the final temperature is approximately 100 / 95℃, which is relatively high, resulting in a large amount of heat. The conventional process of cooling to ambient temperature using air cooling or water cooling not only fails to fully utilize the heat but also consumes electricity, circulating water, and other cooling media, leading to excessive energy consumption. Summary of the Invention

[0004] To overcome the shortcomings of the existing technology, the present invention aims to provide a low-energy MTO methanol distillation device and method that utilizes the heat of reaction. By setting up a heat medium circulation system, the heat generated by the synthesis in the methanol reactor is effectively used to raise the temperature of the crude methanol before it enters the stabilizer, thus achieving feeding after heating, while reducing the energy consumption of air cooling, water cooling, and reboiling of the stabilizer.

[0005] To achieve the above objectives, the present invention proposes a low-energy-consumption MTO methanol distillation apparatus utilizing the heat of reaction, comprising:

[0006] The system comprises a methanol reactor, a methanol intermediate heat exchanger, a methanol air cooler, a methanol water cooler, and a methanol buffer tank connected in sequence. The methanol reactor and the methanol intermediate heat exchanger form a loop. The methanol intermediate heat exchanger is also equipped with a syngas inlet. The methanol buffer tank is connected to a methanol expansion tank, which is connected to a stabilizer tower. The top of the stabilizer tower is connected to a cooling reflux assembly via a reflux pipe. The bottom of the stabilizer tower is connected in sequence to a stabilizer tower bottom pump and an MTO-stage methanol water cooler. The bottom of the stabilizer tower is also connected to a stabilizer tower reboiler via a loop. A heat medium circulation system is also connected between the methanol intermediate heat exchanger and the methanol air cooler. The heat medium circulation system is also connected to the pipeline between the methanol expansion tank and the stabilizer tower.

[0007] In one embodiment of the present invention, the methanol reactor includes a first methanol reactor and a second methanol reactor, the methanol intermediate heat exchanger includes a first methanol intermediate heat exchanger and a second methanol intermediate heat exchanger, the methanol air cooler includes a first crude methanol air cooler and a second crude methanol air cooler, the methanol water cooler includes a first methanol water cooler and a second methanol water cooler, and the methanol buffer tank includes a first methanol buffer tank and a second methanol buffer tank, both of which are connected to the methanol expansion tank.

[0008] In one embodiment of the present invention, the heat transfer medium circulation system includes: a first crude methanol heat transfer medium heat exchanger, a second crude methanol heat transfer medium heat exchanger, a stabilizer tower feed preheater, a heat transfer medium buffer tank, and a heat transfer medium booster pump. The first crude methanol heat transfer medium heat exchanger is connected to a pipeline between the first intermediate methanol heat exchanger and the first crude methanol air cooler. The second crude methanol heat transfer medium heat exchanger is connected to a pipeline between the second intermediate methanol heat exchanger and the second crude methanol air cooler. The stabilizer tower feed preheater is connected to a pipeline between the methanol expansion tank and the stabilizer tower. The outlet end of the heat transfer medium buffer tank is connected to the heat transfer medium booster pump. The heat transfer medium booster pump is connected to the inlet ends of the first crude methanol heat transfer medium heat exchanger and the second crude methanol heat transfer medium heat exchanger, respectively. The outlet ends of the first crude methanol heat transfer medium heat exchanger and the second crude methanol heat transfer medium heat exchanger are jointly connected to the inlet end of the stabilizer tower feed preheater. The outlet end of the stabilizer tower feed preheater is connected to the inlet end of the heat transfer medium buffer tank.

[0009] In one embodiment of the present invention, the heat transfer medium circulation system further includes:

[0010] The circulating temperature of the heat medium is 60-90℃, and the initial temperature of the heat medium in the heat transfer medium buffer tank is 60℃; the temperature of the heat medium after being pressurized by the heat transfer medium booster pump is 60-70℃; the temperature of the heat medium after the first heat exchange with crude methanol is 80-90℃, which lowers the temperature of the crude methanol to 90-100℃; the temperature of the heat medium after the second heat exchange with crude methanol is 60-70℃, which raises the temperature of the crude methanol to 70-76℃.

[0011] In one embodiment of the present invention, the cooling reflux assembly includes a stabilized tower top condenser, a stabilized tower reflux tank, and a stabilized tower reflux pump connected in sequence, wherein the stabilized tower condenser and the stabilized tower reflux pump are both connected to the top of the stabilized tower to form a reflux pipeline.

[0012] To achieve the above objectives, the present invention also provides a low-energy-consumption MTO methanol distillation method utilizing the heat of reaction, comprising the following steps:

[0013] The prepared crude methanol is heat-exchanged with the syngas feed, and the crude methanol after heat exchange undergoes a first heat exchange through a heat medium circulation system to reduce the temperature of the crude methanol.

[0014] After the first heat exchange, the crude methanol is successively cooled by air and water to lower its temperature, and then the cooled crude methanol is flash evaporated.

[0015] The crude methanol after flash evaporation undergoes a second heat exchange through the heat medium circulation system, causing the crude methanol to heat up.

[0016] The heated crude methanol enters a stabilizer tower, where the non-condensable gas at the top of the stabilizer tower is condensed and the methanol bottom liquid at the bottom of the stabilizer tower is vaporized to generate MTO-grade methanol. The MTO-grade methanol is pumped out, condensed, and used as raw material for the methanol-to-olefins (MTO) process.

[0017] In one embodiment of the present invention, the method further includes the following steps:

[0018] The circulating temperature of the heat medium is 60-90℃. The initial temperature of the heat medium in the heat transfer medium buffer tank is 60℃. It is pressurized to 60-70℃ using a heat transfer medium booster pump and undergoes a first heat exchange with the crude methanol after heat exchange. The temperature of the crude methanol after heat exchange decreases to 90-100℃, and the temperature of the heat medium increases to 80-90℃. The heated heat medium undergoes a second heat exchange with the flash-evaporated crude methanol, raising the temperature of the crude methanol to 70-76℃ and lowering the temperature of the heat medium to 60-70℃. The heat medium after the second heat exchange enters the heat transfer medium buffer tank for pressurization and then undergoes another first heat exchange to extract heat.

[0019] In one embodiment of the present invention, the first heat exchange occurs in a first crude methanol heat exchanger and a second crude methanol heat exchanger, and the second heat exchange occurs in a stabilizer tower feed preheater.

[0020] In one embodiment of the present invention, the condensation of the non-condensable gas at the top of the stabilizer tower includes the following steps:

[0021] The non-condensable gas at the top of the stabilizer is condensed to below 45°C. Most of the methanol is condensed and then distilled again, and pumped back into the stabilizer as reflux.

[0022] Compared with the prior art, one embodiment of the present invention has the following beneficial effects:

[0023] By connecting the methanol reactor and the intermediate methanol heat exchanger in a loop, the temperature of the crude methanol at the methanol reactor outlet can be reduced while the syngas is being fed in, thus avoiding the subsequent excessive consumption of air-cooled and water-cooled cooling media.

[0024] By setting up a heat transfer medium circulation system, the heat from the crude methanol at the outlet of the methanol reactor is used as a heat source for heating the feed to the stabilizer tower. Two crude methanol heat transfer medium heat exchangers are used, and the heat source is heated through a heat transfer medium buffer tank and a heat transfer medium booster pump and then returned to the two crude methanol heat transfer medium heat exchangers for recycling. This effectively utilizes the excess heat generated after the crude methanol is produced, while reducing the steam consumption of the reboiler at the bottom of the stabilizer tower. Attached Figure Description

[0025] Figure 1 A schematic diagram of a low-energy-consumption MTO methanol distillation device utilizing the heat of reaction provided by the present invention;

[0026] Figure 2 The present invention provides a step flow diagram of a low-energy-consumption MTO methanol distillation method utilizing the heat of reaction.

[0027] In the diagram: 11-First methanol reactor; 12-Second methanol reactor; 21-First methanol intermediate heat exchanger; 22-Second methanol intermediate heat exchanger; 31-First crude methanol air cooler; 32-Second crude methanol air cooler; 41-First methanol water cooler; 42-Second methanol water cooler; 51-First methanol buffer tank; 52-Second methanol buffer tank; 6-Methanol expansion tank; 71-Stabilizer tower; 721-Stabilizer tower top condenser; 722-Stabilizer tower reflux tank; 723-Stabilizer tower reflux pump; 73-Stabilizer tower bottom pump; 74-MTO-grade methanol water cooler; 75-Stabilizer tower reboiler; 8-Heat medium circulation system; 81-First crude methanol heat medium heat exchanger; 82-Second crude methanol heat medium heat exchanger; 83-Stabilizer tower feed preheater; 84-Heat transfer medium buffer tank; 85-Heat transfer medium booster pump. Detailed Implementation

[0028] The following describes the embodiments of the present invention through specific examples and in conjunction with the accompanying drawings. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific examples, and various details in this specification can also be modified and changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0029] Figure 1 This is a schematic diagram of a low-energy-consumption MTO methanol distillation apparatus utilizing the heat of reaction, provided by the present invention. Figure 1 As shown, the present invention discloses a low-energy-consumption MTO methanol distillation apparatus utilizing the heat of reaction, comprising:

[0030] A methanol reactor, a methanol intermediate heat exchanger, a methanol air cooler, a methanol water cooler, and a methanol buffer tank are connected in sequence. The methanol reactor and the methanol intermediate heat exchanger form a loop. The methanol intermediate heat exchanger is also equipped with a synthesis gas inlet. The methanol buffer tank is connected to a methanol expansion tank 6. The methanol expansion tank 6 is connected to a stabilization tower 71. The top of the stabilization tower 71 is connected to a cooling reflux assembly via a reflux pipe. The bottom of the stabilization tower 71 is connected in sequence to a stabilization tower bottom pump 73 and an MTO-stage methanol water cooler 74. The bottom of the stabilization tower 71 is also connected to a stabilization tower reboiler 75 via a loop. A heat medium circulation system 8 is also connected between the methanol intermediate heat exchanger and the methanol air cooler. The heat medium circulation system 8 is also connected to the pipeline between the methanol expansion tank 6 and the stabilization tower 71.

[0031] Specifically, the stabilizer 71 enables interphase mass transfer through vapor-liquid two-phase contact. A cooling reflux assembly is connected to the top of the stabilizer 71, allowing partial condensation of the vapor. Part of the condensate is returned to the top of the column as reflux liquid, and the remaining distillate is the top product. In other words, above the feed plate of the stabilizer 71, the heavy components in the rising vapor phase can be condensed and separated, while the light components in the vapor phase are purified. At the bottom of the stabilizer 71, a stabilizer reboiler 75 is connected. The stabilizer reboiler 75 partially vaporizes the liquid, causing the vapor to rise, while the remaining liquid is the bottom product. In other words, below the feed plate of the stabilizer 71, the light components in the liquid phase can be vaporized and separated, while the heavy components in the liquid phase are concentrated. The crude methanol liquid in the feed and the liquid produced in the upper section descend together along the column. The vapor in the feed and the vapor produced by reboiling in the lower section rise together along the column. The vapor comes into countercurrent contact with the descending liquid produced in the upper section. During the contact between the two phases, the light components in the descending liquid continuously transfer to the vapor, and the heavy components in the vapor continuously transfer to the descending liquid. Finally, MTO-grade methanol is formed at the bottom of the column. The MTO-grade methanol is pumped into the MTO-grade methanol water cooler 74 for cooling treatment.

[0032] Preferably, the methanol reactor includes a first methanol reactor 11 and a second methanol reactor 12, the methanol intermediate heat exchanger includes a first methanol intermediate heat exchanger 21 and a second methanol intermediate heat exchanger 22, the methanol air cooler includes a first crude methanol air cooler 31 and a second crude methanol air cooler 32, the methanol water cooler includes a first methanol water cooler 41 and a second methanol water cooler 42, and the methanol buffer tank includes a first methanol buffer tank 51 and a second methanol buffer tank 52, both of which are connected to the methanol expansion tank 6.

[0033] Specifically, the first methanol reactor 11, the first methanol intermediate heat exchanger 21, the first crude methanol air cooler 31, the first methanol water cooler 41, the first methanol buffer tank 51 and the methanol expansion tank 6 are connected in sequence, and the second methanol reactor 12, the second methanol intermediate heat exchanger 22, the second crude methanol air cooler 32, the second methanol water cooler 42, the second methanol buffer tank 52 and the methanol expansion tank 6 are connected in sequence.

[0034] The outlet of the first methanol reactor 11 is connected to the first methanol intermediate heat exchanger 21, which is in turn connected to the first methanol reactor 11. The first methanol intermediate heat exchanger 21 has a syngas inlet, forming a loop between the methanol reactor and the intermediate heat exchanger. This allows the syngas to exchange heat with the crude methanol produced in the first methanol reactor 11 during its intake. Similarly, the second methanol reactor 12 and the second methanol intermediate heat exchanger 22 form a loop in the same manner, allowing the syngas to exchange heat with the crude methanol produced in the second methanol reactor 12 during its intake.

[0035] Preferably, the heat transfer medium circulation system 8 includes: a first crude methanol heat transfer medium heat exchanger 81, a second crude methanol heat transfer medium heat exchanger 82, a stabilizer tower feed preheater 83, a heat transfer medium buffer tank 84, and a heat transfer medium booster pump 85. The first crude methanol heat transfer medium heat exchanger 81 is connected to the pipeline between the first methanol intermediate heat exchanger 21 and the first crude methanol air cooler 31. The second crude methanol heat transfer medium heat exchanger 82 is connected to the pipeline between the second methanol intermediate heat exchanger 22 and the second crude methanol air cooler 32. The stabilizer tower feed preheater 83 is connected to the pipeline between the first methanol intermediate heat exchanger 21 and the second crude methanol air cooler 32. On the pipeline between the methanol expansion tank 6 and the stabilization tower 71, the outlet end of the heat transfer medium buffer tank 84 is connected to the heat transfer medium booster pump 85. The heat transfer medium booster pump 85 is connected to the inlet ends of the first crude methanol heat exchanger 81 and the second crude methanol heat exchanger 82, respectively. The outlet ends of the first crude methanol heat exchanger 81 and the second crude methanol heat exchanger 82 are jointly connected to the inlet end of the stabilization tower feed preheater 83. The outlet end of the stabilization tower feed preheater 83 is connected to the inlet end of the heat transfer medium buffer tank 84.

[0036] Specifically, the heat transfer medium buffer tank 84 is pressurized by nitrogen purging and isolated from air.

[0037] Preferably, the heat medium circulation system 8 further includes:

[0038] The temperature of the heat medium circulation is 60~90℃, and the initial temperature of the heat medium in the heat transfer medium buffer tank 84 is 60℃; the temperature of the heat medium after being pressurized by the heat transfer medium booster pump 85 is 60~70℃.

[0039] The temperature of the crude methanol after the first heat exchange between the heat medium and the crude methanol is 80~90℃, which lowers the temperature of the crude methanol to 90~100℃; the temperature of the crude methanol after the second heat exchange between the heat medium and the crude methanol is 60~70℃, which raises the temperature of the crude methanol to 70~76℃.

[0040] Specifically, preferably, the temperature of the heat medium circulation is 60-90℃, and can also be 65-95℃; the temperature of the heat medium after the second heat exchange with the crude methanol is preferably 60-70℃, and can also be 55-70℃, raising the temperature of the crude methanol to a preferred temperature of 70-76℃, and can also be 60-80℃. The heat medium and crude methanol undergo a first heat exchange in the first crude methanol heat medium heat exchanger 81 and the second crude methanol heat medium heat exchanger 82, and the heat medium and crude methanol undergo a second heat exchange in the stabilizer tower feed preheater. The heat medium in the heat medium circulation system 8 is methanol, demineralized water, or other organic media that are non-toxic and harmless to methanol products and MTO reaction catalyst.

[0041] Preferably, the cooling reflux assembly includes a stabilized tower top condenser 721, a stabilized tower reflux tank 722, and a stabilized tower reflux pump 723 connected in sequence. The stabilized tower top condenser 721 and the stabilized tower reflux pump 723 are both connected to the top of the stabilized tower 71 to form a reflux pipe. Example 1

[0042] Taking the initial process with a pure methanol capacity of 2.37 million tons / year as an example, and using low-temperature hot water as the heat medium (i.e., heat medium water), the following is a detailed explanation in conjunction with Table 1:

[0043] Referring to Table 1, the crude methanol produced by the first methanol reactor 11 passes through the first methanol intermediate heat exchanger 21, where it exchanges heat with the feed of the first methanol reactor 11, causing the temperature of the crude methanol to drop from 264℃ to 102℃. The crude methanol after heat exchange then enters the first crude methanol heat exchanger 81, where it undergoes a first heat exchange with a heat medium at a temperature of 60-70℃, reducing the temperature of the crude methanol to 90-100℃. After the first heat exchange, the crude methanol sequentially enters the first crude methanol air cooler 31 and the first methanol... Water cooler 41 performs air cooling and water cooling to lower the temperature of crude methanol to 45°C. The cooled crude methanol then passes through the first methanol buffer tank 51 and enters the methanol expansion tank 6, where it undergoes flash evaporation. Similarly, the crude methanol produced by the second methanol reactor 12 sequentially passes through the second methanol reactor 12, the second methanol intermediate heat exchanger 22, the second crude methanol heat medium heat exchanger 82, the second crude methanol air cooler 32, the second methanol water cooler 42, and the second methanol buffer tank 52 before entering the methanol expansion tank 6. The flash-evaporated crude methanol then enters the stabilization tower. The feed preheater 83, connected to the first crude methanol heat exchanger 81 and the second crude methanol heat exchanger 82, delivers a heat medium at a temperature of 80-90°C generated from the first and second crude methanol heat exchangers 81 and 82 to the feed preheater 83 for a second heat exchange with the crude methanol, raising its temperature from 45°C to 70-76°C. The crude methanol after this second heat exchange enters the stabilizer 71, with the feed point being the second theoretical tray. The non-condensable medium at the top of the stabilizer 71... The gas enters the stabilizer tower top condenser 721 and is cooled to below 45°C, condensing most of the methanol. It then enters the stabilizer tower reflux tank 722 and is returned to the stabilizer tower 71 by the stabilizer tower reflux pump 723. A small portion of the distillate is output as the top product. The stabilizer tower 71 bottom is connected to the stabilizer tower reboiler 75 to vaporize the bottom liquid. The vapor rises along the stabilizer tower, and the remaining liquid is MTO-grade methanol. The MTO-grade methanol at the bottom of the tower is pumped by the stabilizer tower bottom pump 73 into the MTO-grade methanol water cooler 74, cooling it from 93°C to below 40°C. The heat transfer medium temperature after exiting the stabilizer tower feed preheater 83 is 60~70°C. It then enters the heat transfer medium buffer tank 84 and is further sent to the first crude methanol heat transfer medium heat exchanger 81 and the second crude methanol heat transfer medium heat exchanger 82 for heat extraction via the heat transfer medium booster pump 85.

[0044] Table 1 Main Process Operating Conditions for Heat Transfer Water Circulation

[0045]

[0046] Example 2

[0047] The present invention also provides a preferred embodiment of the heat medium circulation process of a heat medium circulation system 8. In this preferred embodiment, the heat medium circulation process of the heat medium circulation system 8 includes:

[0048] The temperature of the entire heat medium circulation is 60~90℃. The initial temperature of the heat medium in the heat transfer medium buffer tank 84 is about 60℃. After being pressurized by the heat transfer medium booster pump 85, it is sent to the first crude methanol heat medium heat exchanger 81 and the second crude methanol heat medium heat exchanger 82. The temperature of the pressurized heat medium is 60~70℃.

[0049] In the first crude methanol heat exchanger 81, the heat medium temperature is 60~70℃, exchanging heat with crude methanol at a temperature of about 102℃. After the heat exchange, the heat medium temperature rises to 80~90℃, and the crude methanol temperature drops to 90~100℃. The same principle applies in the second crude methanol heat exchanger 82, and will not be described again. This is the first heat medium heat exchange.

[0050] The first crude methanol heat exchanger 81 and the second crude methanol heat exchanger 82 are connected to the stabilizer tower feed preheater 83. The heat medium at 80~90℃ in the first crude methanol heat exchanger 81 and the second crude methanol heat exchanger 82 is input into the stabilizer tower feed preheater 83.

[0051] In the stabilizer tower feed preheater 83, the heat medium temperature is 80~90℃, which exchanges heat with crude methanol at a temperature of 45℃. After the heat exchange, the temperature of the heat medium decreases to 60~70℃, and the temperature of the crude methanol increases to 70~76℃. This is the second heat medium heat exchange.

[0052] The heat medium output from the stabilizer tower feed preheater 83 enters the heat transfer medium buffer tank 84, and is then continuously sent to the first crude methanol heat medium heat exchanger 81 and the second crude methanol heat medium heat exchanger 82 for heat extraction via the heat transfer medium booster pump 85, forming a heat medium circulation.

[0053] In addition, the heat medium in the heat medium circulation system 8 is methanol, desalinated water, or other organic media that are non-toxic and harmless to methanol products and MTO reaction catalysts.

[0054] Figure 2 This invention provides a flowchart of a low-energy-consumption MTO methanol distillation method utilizing the heat of reaction. Figure 2 As shown, the present invention discloses a low-energy-consumption MTO methanol distillation method utilizing the heat of reaction, comprising the following steps:

[0055] Step S201: The prepared crude methanol is heat-exchanged with the syngas feed, and the crude methanol after heat exchange undergoes a first heat exchange through a heat medium circulation system to lower the temperature of the crude methanol.

[0056] Step S202: After the first heat exchange, the crude methanol is successively cooled by air and water to cool down the crude methanol, and then the cooled crude methanol is flash evaporated.

[0057] In step S203, the crude methanol after flash evaporation undergoes a second heat exchange through the heat medium circulation system to raise the temperature of the crude methanol.

[0058] In step S204, the heated crude methanol enters the stabilizer tower, where the non-condensable gas at the top of the stabilizer tower is condensed and the methanol bottom liquid at the bottom of the stabilizer tower is vaporized to generate MTO-grade methanol. The MTO-grade methanol is pumped out, condensed, and used as raw material for the methanol-to-olefins section.

[0059] Specifically, crude methanol is prepared using a methanol reactor. The crude methanol undergoes heat exchange with the feed of the methanol reactor through an intermediate methanol heat exchanger, causing its temperature to drop by more than 100°C. The crude methanol after heat exchange is then transported to a heat medium circulation system for the first heat medium heat exchange. After the first heat medium heat exchange, the crude methanol is sequentially transported to a methanol air cooler and a methanol water cooler for further cooling, reducing the temperature of the crude methanol after heat exchange, the first heat medium heat exchange, and cooling to 45°C. The cooled crude methanol is then transported through a methanol buffer tank to a methanol expansion tank for flash evaporation. After flash evaporation, the crude methanol undergoes a second heat medium heat exchange through the heat medium circulation system and is then transported to a stabilizer to remove light components. The non-condensable gas at the top of the stabilizer is cooled by a cooling reflux assembly and returned to the stabilizer, causing most of the methanol in the stabilizer to condense. The stabilizer reboiler connected to the bottom of the stabilizer vaporizes the bottom liquid. The MTO-grade methanol generated at the bottom of the stabilizer is pumped into an MTO-grade methanol water cooler for cooling to below 40°C by a stabilizer bottom pump.

[0060] Specifically, the stabilizer column enables interphase mass transfer through vapor-liquid two-phase contact. A cooling reflux assembly is connected to the top of the stabilizer column, allowing partial condensation of the vapor. Part of the condensate is returned to the top of the column as reflux liquid, and the remaining distillate is the top product. In other words, above the feed plate of the stabilizer column, the heavy components in the rising vapor phase can be condensed and separated, while the light components in the vapor phase are purified. At the bottom of the stabilizer column, a reboiler is connected. The reboiler partially vaporizes the liquid, causing the vapor to rise, and the remaining liquid is the bottom product. In other words, below the feed plate of the stabilizer column, the light components in the liquid phase can be vaporized and separated, while the heavy components in the liquid phase are concentrated. The crude methanol liquid in the feed and the liquid produced in the upper section descend together along the column. The vapor in the feed and the vapor produced by reboiling in the lower section rise together along the column. The vapor comes into countercurrent contact with the descending liquid produced in the upper section. During the contact between the two phases, the light components in the descending liquid continuously transfer to the vapor, and the heavy components in the vapor continuously transfer to the descending liquid. Finally, MTO-grade methanol is formed at the bottom of the column. The MTO-grade methanol is pumped into an MTO-grade methanol water cooler for cooling.

[0061] Preferably, the method further includes:

[0062] The circulating temperature of the heat medium is 60-90℃. The initial temperature of the heat medium in the heat transfer medium buffer tank is 60℃. It is pressurized to 60-70℃ using a heat transfer medium booster pump and undergoes a first heat exchange with the crude methanol after heat exchange. The temperature of the crude methanol after heat exchange decreases to 90-100℃, and the temperature of the heat medium increases to 80-90℃. The heated heat medium undergoes a second heat exchange with the flash-evaporated crude methanol, raising the temperature of the crude methanol to 70-76℃ and lowering the temperature of the heat medium to 60-70℃. The heat medium after the second heat exchange enters the heat transfer medium buffer tank for pressurization and then undergoes another first heat exchange to extract heat.

[0063] Preferably, the temperature of the heat medium circulation is 60~90℃, and can also be 65~95℃; the temperature of the heat medium after the second heat exchange with the crude methanol is preferably 60~70℃, and can also be 55~70℃, so that the temperature of the crude methanol is raised to a preferred temperature of 70~76℃, and can also be 60~80℃.

[0064] Preferably, the first heat exchange occurs in the first crude methanol heat exchanger and the second crude methanol heat exchanger, and the second heat exchange occurs in the stabilizer tower feed preheater.

[0065] Specifically, the heat medium, initially at 60°C in the heat transfer medium buffer tank, is pressurized by the heat transfer medium booster pump and then sent to the first and second crude methanol heat medium heat exchangers. After pressurization, the heat medium, at a temperature of 60-70°C, undergoes a first heat exchange with the crude methanol, causing the crude methanol temperature to drop to 90-100°C and the heat medium temperature to rise to 80-90°C. The heated heat medium then enters the stabilizer tower feed preheater for a second heat exchange with the crude methanol, causing the crude methanol temperature to rise to 70-76°C and the heat medium temperature to drop to 60-70°C. The heat medium after the second heat exchange enters the heat transfer medium buffer tank and is then continued to be sent to the first and second crude methanol heat medium heat exchangers for heat extraction by the heat transfer medium booster pump.

[0066] Preferably, the condensation of the non-condensable gas at the top of the stabilizer tower includes the following steps:

[0067] The non-condensable gas at the top of the stabilizer is condensed to below 45°C. Most of the methanol is condensed and then distilled again, and pumped back into the stabilizer as reflux.

[0068] Specifically, the non-condensable gas at the top of the stabilizer column enters the stabilizer column condenser and is cooled to below 45°C, condensing most of the methanol. The condensed methanol then enters the stabilizer column reflux tank and is subsequently pumped back to the stabilizer column as reflux. The stabilizer column reflux tank is used for repeated distillation to improve the recovery rate.

[0069] It should be noted that the low-energy MTO methanol distillation method utilizing the heat of reaction of the present invention corresponds to a low-energy MTO methanol distillation apparatus utilizing the heat of reaction. Other undescribed contents refer to the contents of the low-energy MTO methanol distillation apparatus utilizing the heat of reaction, and will not be repeated here.

[0070] In summary, the present invention provides a low-energy-consumption MTO methanol distillation apparatus and method utilizing reaction heat. A heat transfer medium circulation system is set up to use the heat from the crude methanol at the methanol reactor outlet as a heat source for heating the feed to the stabilizer tower. This effectively reduces the cooling load on the crude methanol at the methanol reactor outlet and transfers the heat from the syngas to the methanol distillation section via the heat transfer medium, thereby increasing the temperature of the methanol entering the distillation tower and reducing the heat load on the reboiler of the methanol distillation (stabilizer tower).

[0071] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can make modifications and changes to the above embodiments without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention should be as set forth in the claims.

Claims

1. A low-energy consumption MTO methanol rectification device utilizing reaction heat, comprising: a methanol reactor, a methanol intermediate heat exchanger, a methanol air cooler, a methanol water cooler and a methanol buffer tank connected in sequence, the methanol reactor and the methanol intermediate heat exchanger forming a loop, the methanol intermediate heat exchanger being further provided with a synthesis gas inlet, the methanol buffer tank being connected with a methanol expansion tank (6), the methanol expansion tank (6) being connected with a stabilizing tower (71), the top of the stabilizing tower (71) being connected with a cooling reflux assembly through a reflux pipeline, the bottom of the stabilizing tower (71) being connected with a stabilizing tower bottom pump (73) and an MTO grade methanol water cooler (74) in sequence, the bottom of the stabilizing tower (71) being further connected with a stabilizing tower reboiler (75) through a loop, the methanol intermediate heat exchanger and the methanol air cooler being further connected with a heat medium circulation system (8), the heat medium circulation system (8) being further connected with a pipeline between the methanol expansion tank (6) and the stabilizing tower (71); the methanol reactor comprising a first methanol reactor (11) and a second methanol reactor (12), the methanol intermediate heat exchanger comprising a first methanol intermediate heat exchanger (21) and a second methanol intermediate heat exchanger (22), the methanol air cooler comprising a first crude methanol air cooler (31) and a second crude methanol air cooler (32), the methanol water cooler comprising a first methanol water cooler (41) and a second methanol water cooler (42), the methanol buffer tank comprising a first methanol buffer tank (51) and a second methanol buffer tank (52), the first methanol buffer tank (51) and the second methanol buffer tank (52) being connected with the methanol expansion tank (6); the heat medium circulation system (8) comprising a first crude methanol heat medium heat exchanger (81), a second crude methanol heat medium heat exchanger (82) and a stabilizing tower feed preheater (83), the first crude methanol heat medium heat exchanger (81) being connected with a pipeline between the first methanol intermediate heat exchanger (21) and the first crude methanol air cooler (31), the second crude methanol heat medium heat exchanger (82) being connected with a pipeline between the second methanol intermediate heat exchanger (22) and the second crude methanol air cooler (32), the stabilizing tower feed preheater (83) being connected with a pipeline between the methanol expansion tank (6) and the stabilizing tower (71); the heat medium circulation system (8) further comprising a heat medium buffer tank (84) and a heat medium booster pump (85), the outlet end of the heat medium buffer tank (84) being connected with the heat medium booster pump (85), the heat medium booster pump (85) being connected with the inlet end of the first crude methanol heat medium heat exchanger (81) and the second crude methanol heat medium heat exchanger (82) respectively, the outlet end of the first crude methanol heat medium heat exchanger (81) and the second crude methanol heat medium heat exchanger (82) being jointly connected with the inlet end of the stabilizing tower feed preheater (83), the outlet end of the stabilizing tower feed preheater (83) being connected with the inlet end of the heat medium buffer tank (84). The heat medium circulating temperature is 60-90℃, the initial temperature of the heat medium in the heat medium buffer tank (84) is 60℃; the temperature of the heat medium after being pressurized by the heat medium medium booster pump (85) is 60-70℃; the temperature of the heat medium after the first heat medium heat exchange with the crude methanol is 80-90℃, so that the temperature of the crude methanol is reduced to 90-100℃; the temperature of the heat medium after the second heat medium heat exchange with the crude methanol is 60-70℃, so that the temperature of the crude methanol is increased to 70-76℃; The cooling reflux assembly comprises a stabilizing tower top condenser (721), a stabilizing tower reflux tank (722) and a stabilizing tower reflux pump (723) connected in sequence, and the stabilizing tower top condenser (721) and the stabilizing tower reflux pump (723) are both connected with the tower top of the stabilizing tower to form a reflux pipeline.

2. A distillation method using the low-energy-consumption MTO methanol rectification device utilizing reaction heat according to claim 1, comprising the following steps: The prepared crude methanol is heat-exchanged with the synthesis gas feed, and the heat-exchanged crude methanol is subjected to the first heat medium heat exchange by the heat medium circulating system, so that the temperature of the crude methanol is reduced; The crude methanol after the first heat medium heat exchange is subjected to air cooling and water cooling in sequence, so that the crude methanol is cooled, and the cooled crude methanol is subjected to flash evaporation; The crude methanol after the flash evaporation is subjected to the second heat medium heat exchange by the heat medium circulating system, so that the crude methanol is heated; The heated crude methanol enters the stabilizing tower, the non-condensable gas at the top of the stabilizing tower is condensed, and the methanol kettle liquid at the bottom of the stabilizing tower is vaporized to generate MTO-grade methanol, and the condensed MTO-grade methanol is pumped out as the raw material of the methanol-to-olefin section; The heat medium circulating temperature is 60-90℃, the initial temperature of the heat medium in the heat medium buffer tank is 60℃, the heat medium is pressurized to 60-70℃ by the heat medium medium booster pump, and then subjected to the first heat medium heat exchange with the heat-exchanged crude methanol, so that the temperature of the heat-exchanged crude methanol is reduced to 90-100℃, and the temperature of the heat medium is increased to 80-90℃; the heat medium with the increased temperature is subjected to the second heat medium heat exchange with the crude methanol after the flash evaporation, so that the temperature of the crude methanol is increased to 70-76℃, and the temperature of the heat medium is reduced to 60-70℃; the heat medium after the second heat medium heat exchange enters the heat medium buffer tank for the first heat medium heat exchange after being pressurized.

3. The rectification method according to claim 2, wherein The first heat medium heat exchange occurs in the first crude methanol heat medium heat exchanger and the second crude methanol heat medium heat exchanger, and the second heat medium heat exchange occurs in the stabilizing tower feed preheater.

4. The rectification method according to claim 2, wherein The condensation of the non-condensable gas at the top of the stabilizing tower comprises the following steps: The non-condensable gas at the top of the stabilizing tower is condensed to below 45℃, most of the methanol is condensed and then repeatedly distilled, and is pumped into the stabilizing tower as reflux.

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