A high water content crude methanol refining process

Abstract

This invention discloses a process for refining crude methanol with high water content. The crude methanol with high water content enters a pre-distillation tower, and the bottom products are then fed into a pressurized tower and a medium-pressure tower, respectively. The bottom product of the pressurized tower enters an atmospheric tower, and the bottom product of the medium-pressure tower enters a negative-pressure tower. The top products of the atmospheric tower and the bottom products of the negative-pressure tower enter a recovery tower. The top of the pre-distillation tower heats the reboiler of the negative-pressure tower, the top of the pressurized tower heats the reboiler of the medium-pressure tower, the top of the medium-pressure tower heats the reboiler of the atmospheric tower, and the top of the atmospheric tower heats the reboilers of both the pre-distillation tower and the recovery tower. The top of the recovery tower heats the reboiler of the negative-pressure tower. Simultaneously, the bottom products of the pre-distillation tower, pressurized tower, medium-pressure tower, and recovery tower are used to preheat their respective feeds. This invention employs parallel flow splitting and multi-effect thermal coupling technology, which significantly reduces the energy consumption of high-water-content crude methanol refining without relying on high-power heat pumps. Steam consumption can be reduced to below 0.56 tons / ton of refined methanol, and it has the advantages of low energy consumption, simple control, and wide applicability.

Description

Technical Field

[0001] This invention relates to the field of crude methanol refining technology, and in particular to a process for refining crude methanol with high water content. Background Technology

[0002] Methanol distillation is one of the most energy-intensive units in a methanol plant, and it is the core step in transforming crude methanol into a qualified product. On the one hand, because distillation is at the end of the production process, it provides qualified raw materials for dozens of important downstream chemical industry chains, and its technological level and product quality are directly related to the healthy development of the entire chemical ecosystem. On the other hand, distillation is the main battleground for methanol plants to save energy, reduce costs, and increase yields; the advancement of distillation technology is an important indicator of a methanol production enterprise's technological and energy-saving capabilities.

[0003] In the design of chemical distillation and separation systems, especially methanol distillation systems, achieving overall optimization of multiple objectives such as unit energy consumption, yield, and product quality is the key and challenging aspect of the design.

[0004] Processing crude methanol with high water content often involves high energy consumption. In methanol-water systems, the separation difficulty peaks when the water content is between 30% and 70%. The core reason is the combined effect of the increased intermolecular hydrogen bonding strength between methanol and water at this concentration, the degree of solution non-ideality, and the concentration difference characteristics between the gas and liquid phases, which significantly increases the energy consumption and equipment requirements of distillation separation. Secondly, the latent heat of vaporization of water is much higher than that of methanol. High water content means that a large amount of water needs to be heated and vaporized in the column, and the phase change process of this water consumes far more energy than methanol separation. Finally, during production adjustment, the lower limit of the reflux ratio for high-moisture-content feed is strictly locked by product purity requirements, resulting in energy consumption for high-moisture-content crude methanol refining being about 25% higher than that for ordinary methanol distillation. For example, using "a three-tower, three-effect crude methanol refining process system ZL201820870873.1", the energy consumption is 1.2-1.3 t of steam per ton of refined methanol. However, using "a high-moisture-content crude methanol refining device CN222534119U", which adds a dehydration tower to the traditional system and uses a high-power compressor, the energy consumption can be reduced to 0.7 t of steam per ton of refined methanol. Therefore, it is evident that the high-moisture-content crude methanol refining process cannot yet control energy consumption within a low range, and the technical route to achieve the low-energy-consumption target is highly dependent on the application of auxiliary equipment such as heat pump compressor systems. However, this technology has significant regional and production control limitations: in regions with high electricity costs or insufficient renewable energy supply, the long-term economic efficiency of high-power heat pumps is poor, and heat pump systems increase the difficulty of production control. This creates an urgent technological contradiction: on the one hand, under the dual pressure of global carbon reduction and cost control, reducing the energy consumption of the distillation process is imperative; on the other hand, existing energy-saving technologies are limited by the energy structure and electricity pricing system.

[0005] Therefore, the industry urgently needs to develop a new energy-saving technology that is less reliant on expensive electricity, more universally applicable, and easier to control. This technology needs to achieve a significant reduction in energy consumption without a substantial increase in investment or the use of heat pumps, thereby effectively reducing the carbon footprint and carbon dioxide emissions in the production process, and providing a highly operable, economically viable, and widely applicable solution for the green distillation of materials with high water content. Summary of the Invention

[0006] This invention addresses the problems of high energy consumption, low methanol quality, low yield, and heavy reliance on high-power heat pumps and other auxiliary equipment in the existing high-moisture-content crude methanol refining process. It develops a novel high-moisture-content crude methanol refining process.

[0007] This invention is achieved through the following technical solution: This invention provides a process for refining crude methanol with high water content, the process comprising the following steps: High-moisture-content crude methanol is fed to a pre-distillation column for rectification. The bottom product of the pre-distillation column is divided into two streams: one stream is fed to a pressurized column for rectification, and the bottom product of the pressurized column is fed to an atmospheric column for rectification; the other stream is fed to a medium-pressure column for rectification, and the bottom product of the medium-pressure column is fed to a negative-pressure column for rectification. The top products of the atmospheric column and the bottom products of the negative-pressure column are fed to a recovery column for rectification. Refined methanol is collected from the top of the pressurized column, the negative-pressure column, the medium-pressure column, and the recovery column. The material drawn from the top of the pre-column is heated by the first reboiler of the negative pressure column, the material drawn from the top of the pressurized column is heated by the reboiler of the medium pressure column, the material drawn from the top of the medium pressure column is heated by the reboiler of the atmospheric pressure column, the material drawn from the top of the atmospheric pressure column is heated by the reboilers of the pre-column and the recovery column, and the material drawn from the top of the recovery column is heated by the second reboiler of the negative pressure column. The materials collected from the bottom of the pre-tower, pressurization tower, medium-pressure tower, and recovery tower are respectively the feed preheating materials of the pre-tower, pressurization tower, medium-pressure tower, and recovery tower.

[0008] Specifically, the material collected at the bottom of the pre-tower is the preheated feed material, the material collected at the bottom of the pressurized tower is the preheated feed material, the material collected at the bottom of the medium-pressure tower is the preheated feed material, and the material collected at the bottom of the recovery tower is the preheated feed material.

[0009] This invention innovatively proposes a refining process for crude methanol with high water content. This process changes the traditional series flow of materials in methanol distillation, innovatively adopting a parallel flow. This overcomes the issue of lower methanol content and higher reflux ratio in parallel processes compared to series-connected processes when materials flow to the final column. Simultaneously, this strategy effectively reduces column diameter, avoiding excessively large single-column diameters, while also reducing construction difficulty and project investment. Furthermore, this invention fully utilizes the waste heat from the top and bottom of the columns. The bottom heat from the pre-column, pressurized, medium-pressure, and recovery columns is used to heat the feed to each column, further reducing waste heat loss from the bottom and achieving full utilization of the waste heat. At the same time, the top heat is fully utilized in stages through reasonable flow direction and distribution. Building upon the above, the high-moisture-content crude methanol refining process controls energy consumption within a low range. In particular, it achieves a technical solution that eliminates reliance on additional equipment such as high-power heat pump compressor systems while maintaining low energy consumption. This solution significantly reduces high electricity costs and alleviates the stringent requirements of heat pump compressor systems for production control, resulting in a novel energy-saving technology that is less dependent on expensive electricity, more universally applicable, and easier to control. This technology achieves a significant reduction in energy consumption, substantially lowering methanol distillation energy consumption, reducing costs, and increasing yield, thereby effectively reducing the carbon footprint and carbon dioxide emissions during production. It provides a highly operable, economically viable, and widely applicable solution for the green distillation of high-moisture-content crude methanol.

[0010] As a further embodiment, the water content in the high-moisture-content crude methanol is 30% to 70% by mass.

[0011] This invention is particularly suitable for the refining of crude methanol with high water content. It overcomes the drawback of relying on additional equipment such as heat pump compressor systems to achieve efficient methanol distillation in the refining of crude methanol with high water content. This invention can reduce the steam consumption per ton of methanol production to less than 0.65 tons per ton when the water content in crude methanol is between 30% and 70%.

[0012] As a further preferred embodiment, the water content in the high-moisture crude methanol is 35% to 70% by mass.

[0013] Even for crude methanol with a high water content of ≥35%, the high water content crude methanol refining process of this invention can reduce the steam consumption per ton of methanol production to below 0.56 tons of steam / ton without using auxiliary equipment such as high-power compressors.

[0014] As a further embodiment, the process method also includes a steam heat source, which is divided into two streams. One stream is heated by the pre-tower reboiler and then exits the boundary, while the other stream is heated by the pressurized tower reboiler, the pressurized tower feed, the medium-pressure tower feed, and the recovery tower feed and then exits the boundary.

[0015] As a further option, the high-moisture-content crude methanol is passed sequentially through a primary preheater and a secondary preheater before entering the pre-tower for distillation.

[0016] As a further embodiment, the material collected from the top of the pre-tower is heated by the reboiler of the negative pressure tower and then successively transported to the top condenser of the pre-tower, the pre-tower reflux tank, and the pre-tower reflux pump before flowing back to the top of the pre-tower.

[0017] As a further preferred embodiment, the material collected at the bottom of the pre-tower is heated by the pre-tower feed preheater and then divided into two streams. One stream is sent to the pressurized tower for distillation, and the other stream is sent to the medium-pressure tower for distillation.

[0018] As a further embodiment, the material collected at the bottom of the pre-tower is heated by the first-stage preheater of the pre-tower feed and then divided into two streams. One stream is preheated successively by the first-stage preheater of the pressurized tower feed and the second-stage preheater of the pressurized tower feed. The preheated material is then transported to the pressurized tower for distillation.

[0019] As a further embodiment, the material extracted from the bottom of the pre-tower is heated by the first-stage preheater of the pre-tower feed and then divided into two streams. One stream is preheated successively by the first-stage preheater of the medium-pressure tower feed and the second-stage preheater of the medium-pressure tower feed. The preheated material is then transported to the medium-pressure tower for distillation.

[0020] As a further embodiment, the material collected from the top of the pressurized tower is heated by the reboiler of the medium-pressure tower and then transported to the pressurized tower reflux tank. The material collected from the top of the pressurized tower is divided into two streams: one stream is returned to the top of the pressurized tower by the pressurized tower reflux pump, and the other stream is preheated by the secondary feed preheater of the pre-tower and then transported to the refined methanol tank.

[0021] As a further option, the material collected at the bottom of the pressurized tower is heated by the primary preheater of the pressurized tower feed and then transported to the atmospheric distillation tower for rectification.

[0022] As a further embodiment, the material collected from the top of the atmospheric distillation column is divided into two streams: one stream is used to heat the reboiler of the recovery column, and the other stream is used to heat the reboiler of the pre-distillation column. The two streams are respectively transported to the atmospheric distillation column reflux tank. Through the atmospheric distillation column reflux pump, part of the material is transported to the top of the atmospheric distillation column, and part of the material is transported to the recovery column for distillation. The material collected from the bottom of the atmospheric distillation column is used to collect the waste liquid through the atmospheric distillation column bottom collection pump.

[0023] As a further embodiment, the material collected from the top of the medium-pressure tower is heated by the reboiler of the atmospheric tower and then transported to the reflux tank of the medium-pressure tower. Through the reflux pump of the medium-pressure tower, one stream is transported to the top of the medium-pressure tower, and the other stream is collected as refined methanol through the condenser of the liquid collected from the top of the medium-pressure tower and sent to the refined methanol tank.

[0024] As a further option, the material collected from the bottom of the medium-pressure tower is heated by the primary preheater of the medium-pressure tower feed and then transported to the negative-pressure tower for distillation.

[0025] As a further embodiment, after the material drawn from the top of the negative pressure tower is transported to the negative pressure tower reflux tank, it is then refluxed back to the top of the negative pressure tower by the negative pressure tower reflux pump, and refined methanol is drawn out to the refined methanol tank.

[0026] As a further embodiment, the material collected from the bottom of the negative pressure tower passes through the primary preheater and the secondary preheater of the recovery tower feed, and is then transported to the recovery tower for distillation by the recovery tower feed pump.

[0027] As a further embodiment, the material collected from the top of the recovery tower is heated by the second reboiler of the negative pressure tower and then transported to the recovery tower reflux tank. Through the recovery tower reflux pump, one stream flows back to the top of the recovery tower, and the other stream passes through the condenser of the liquid collected from the top of the recovery tower to collect refined methanol into a refined methanol tank. The material collected from the bottom of the recovery tower is collected as waste liquid after being heated by the first-stage preheater of the recovery tower feed.

[0028] As a further option, the steam heat source is divided into two streams. One stream is heated by the pre-tower steam reboiler and then discharged as condensate. The other stream is heated by the pressurized tower reboiler, the pressurized tower feed secondary preheater, the medium-pressure tower feed secondary preheater, and the recovery tower feed secondary preheater in sequence and then discharged as condensate.

[0029] As a further embodiment, the top temperature of the pre-tower is 67~69℃, the top temperature of the pressurized tower is 146~148℃, the top temperature of the atmospheric tower is 100~102℃, the top temperature of the medium-pressure tower is 127~129℃, the top temperature of the negative-pressure tower is 31~34℃, and the top temperature of the recovery tower is 67~69℃.

[0030] As a further embodiment, the top pressure of the pre-column is 108~112 kPaA, the top pressure of the pressurized column is 1298~1302 kPaA, the top pressure of the atmospheric column is 198~202 kPaA, the top pressure of the medium-pressure column is 798~802 kPaA, the top pressure of the negative-pressure column is 23~27 kPaA, and the top pressure of the recovery column is 98~102 kPaA.

[0031] The features and beneficial effects of this invention are as follows: (1) This invention provides a refining process for crude methanol with high water content, which can achieve an increase in capacity of more than 30% compared to the traditional three-tower methanol distillation (co-current double-effect distillation) process, while reducing steam consumption by 45%-50%. It is highly operable and adopts energy-saving measures such as heat recovery optimization through heat exchange network, which greatly reduces steam consumption. In particular, it obtains a technical solution for refining crude methanol with high water content that controls energy consumption within a low range without relying on additional equipment such as high-power heat pump compressor systems. This solution significantly reduces the high cost of electricity and the strict requirements of heat pump compressor systems for production control, resulting in a new energy-saving technology that is less dependent on expensive electricity, more universal, and easier to control. This technology achieves a leap in energy consumption, significantly reducing methanol distillation energy consumption, lowering costs, and increasing yield, thereby effectively reducing the carbon footprint and carbon dioxide emissions in the production process. It provides a highly operable, economically applicable, and widely applicable solution for the green distillation of crude methanol with high water content.

[0032] (2) The thermal coupling method adopted in this invention realizes the full utilization of the top materials of the pre-tower, medium-pressure tower, pressurized tower, atmospheric tower, negative pressure tower and recovery tower.

[0033] (3) The present invention adopts a parallel feeding process. Compared with the traditional methanol distillation feeding process which usually adopts a series form, this process changes the material flow and adopts a parallel method. This changes the situation where the material flow to the last tower is lower than that of the parallel process when the towers are connected in series. At the same time, it can effectively reduce the tower diameter, avoid the single tower diameter being too large, and reduce the construction difficulty and project investment.

[0034] (4) This invention fully utilizes the waste heat of the bottom products from the towers, using the bottom products from the pre-tower, pressurized tower, intermediate-pressure tower, and recovery tower to preheat the feed to each tower, thus reducing the loss of waste heat from the bottom products. This invention also innovatively uses the top product of the pressurized tower or the intermediate-pressure tower to preheat the crude alcohol feed: the steam condensate transported to the pressurized tower heats the reboiler of the pressurized tower and also preheats the feed to the pressurized tower, intermediate-pressure tower, and recovery tower. The waste heat utilization of the steam condensate is versatile, allowing preheating of any stream in the process that requires preheating, further fully utilizing the waste heat of the steam. This achieves a production efficiency of less than 0.56 tons of steam per ton of methanol. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 The high-moisture-content crude methanol refining apparatus used in Example 1.

[0037] Explanation of reference numerals in the attached figures: T1: Pre-pressurized tower, T2: Pressurized tower, T3: Medium-pressure tower, T4: Atmospheric tower, T5: Negative-pressure tower, T6: Recovery tower; Q101: Primary preheater for pre-feed to the pre-tower; Q102: Secondary preheater for pre-feed to the pre-tower; Q103: Pre-tower overhead condenser; Q104: Pre-tower reflux tank; Q105: Pre-tower reflux pump; Q106: Pre-tower reboiler; Q107: Pre-tower steam reboiler; Q201: Primary preheater for pressurized column feed; Q202: Secondary preheater for pressurized column feed; Q203: Pressurized column reflux tank; Q204: Pressurized column reflux pump; Q205: Pressurized column reboiler; Q301: Primary preheater for intermediate-pressure column feed; Q302: Secondary preheater for intermediate-pressure column feed; Q303: Intermediate-pressure column reflux tank; Q304: Intermediate-pressure column reflux pump; Q305: Intermediate-pressure column overhead effluent condenser; Q306: Intermediate-pressure column reboiler. Q401: Atmospheric pressure tower reflux tank; Q402: Atmospheric pressure tower reflux pump; Q403: Atmospheric pressure tower reboiler; Q404: Atmospheric pressure tower bottom product pump; Q501: Negative pressure tower reflux tank; Q502: Negative pressure tower reflux pump; Q503: Negative pressure tower first reboiler; Q504: Negative pressure tower second reboiler; Q505: Negative pressure tower vacuum pump; Q506: Negative pressure tower top primary condenser; Q507: Negative pressure tower top secondary condenser; Q601: Recovery tower reflux tank; Q602: Recovery tower reflux pump; Q603: Recovery tower reboiler; Q604: Recovery tower feed primary preheater; Q605: Recovery tower feed secondary preheater; Q606: Recovery tower feed pump; Q607: Recovery tower top product condenser; Q701: Refined methanol tank; K1: Pre-tower feed inlet, K2: Pressurized tower feed inlet, K3: Medium-pressure tower feed inlet, K4: Atmospheric tower feed inlet, K5: Negative-pressure tower feed inlet, K6: Recovery tower feed inlet; X1: Steam heat source pipeline; X2: First branch of steam heat source pipeline; X3: Second branch of steam heat source pipeline; X4: Pre-tower feed pipeline; X5: Top material reflux pipeline of pressurized tower; X6: Refined methanol collection pipeline of pressurized tower; X7: Top material reflux pipeline of atmospheric pressure tower; X8: First feed pipeline of recovery tower; X9: Waste liquid collection pipeline of atmospheric pressure tower; X10: Top material reflux pipeline of medium pressure tower. 11: Medium-pressure tower refined methanol outflow pipeline; X12: Negative-pressure tower top material reflux pipeline; X13: Negative-pressure tower refined methanol outflow pipeline; X14: Recovery tower top material reflux pipeline; X15: Recovery tower refined methanol outflow pipeline; X16: Recovery tower waste liquid outflow pipeline; X17: Extraction water pipeline; X18: Gas phase outflow pipeline; X19: Fusel alcohol side outflow pipeline; X20: Recovery tower feed second pipeline. Detailed Implementation

[0038] To facilitate understanding of the present invention, a more comprehensive description of the present invention will be given below, and embodiments of the present invention will be provided, but this does not limit the scope of the present invention.

[0039] The schematic diagram of this embodiment 1 is as follows: Figure 1 As shown.

[0040] The specific application data for this embodiment is as follows: The high-moisture-content crude methanol refining unit includes a pre-tower T1, a pressurized tower T2, a medium-pressure tower T3, an atmospheric tower T4, a negative-pressure tower T5, and a recovery tower T6.

[0041] The high-moisture-content crude methanol consists of 60%~65% methanol by volume, 35%~40% water by volume, and 1000ppm ethanol. The high-moisture-content crude methanol is fed at a temperature of 40℃, a feed pressure of 500kPaA, and a feed flow rate of 19800kg / h.

[0042] The steam heat source splits into two streams after passing through steam heat source pipeline X1. One stream passes through the first branch pipeline X2 of the steam heat source to preheat the feed to pre-tower T1 and then exits as condensate. The other stream passes through the second branch pipeline X3 of the steam heat source to preheat the feed to the reboiler Q205 of the pressurized tower, the feed to the pressurized tower T2, the feed to the medium-pressure tower T3, and the feed to the recovery tower T6, and then exits as condensate.

[0043] Specifically, the steam heat source splits into two streams after passing through steam heat source pipeline X1. One stream passes through the first branch pipeline X2 of the steam heat source and preheats the feed to pre-tower T1 via pre-tower reboiler Q107 before exiting as condensate. The other stream passes through the second branch pipeline X3 of the steam heat source and preheats the feed to pressurized tower reboiler Q205, pressurized tower feed secondary preheater Q202, medium-pressure tower feed secondary preheater Q302, and recovery tower feed secondary preheater Q605 before exiting as condensate.

[0044] The high-moisture-content crude methanol undergoes secondary preheating via the primary preheater Q101 and secondary preheater Q102 on the pre-tower feed pipeline X4, and then enters the pre-tower T1 for distillation through the pre-tower feed inlet K1.

[0045] The material collected from the top of the pre-tower T1 is heated by the first reboiler Q503 of the negative pressure tower, and then successively transported to the top condenser Q103, the reflux tank Q104, and the reflux pump Q105 before flowing back to the top of the pre-tower T1.

[0046] The pre-tower reflux tank Q104 is equipped with an extraction water pipeline X17 for the entry of extraction water, and a gas phase production pipeline X18 for the production of release gas is also equipped on the pre-tower reflux tank Q104.

[0047] The feed temperature of pre-tower T1 is 70℃, the top temperature of pre-tower T1 is 68.3℃, the bottom temperature of pre-tower T1 is 78.2℃, the top pressure and bottom pressure of pre-tower T1 are 110 kPaA and 120 kPaA respectively, the bottom output of pre-tower T1 is 20141 kg / h, the extraction water flow rate of pre-tower T1 is 1000 kg / h, the temperature of the extraction water of pre-tower T1 is 40℃, the pressure of the extraction water of pre-tower T1 is 400 kPaA, and the purge gas flow rate of pre-tower T1 is 660 kg / h.

[0048] The material collected at the bottom of the pre-tower T1 is heated by the first-stage preheater Q101 and then divided into two feed routes. One route is heated by the first-stage preheater Q201 and the second-stage preheater Q202 of the pressurized tower feed and then enters the pressurized tower T2 through the pressurized tower feed inlet K2 for distillation.

[0049] The material collected from the top of pressurized column T2 is fed to the reboiler Q306 of the intermediate-pressure column for heating, thus providing the heat required for distillation in the intermediate-pressure column T3. After condensation, the material collected from the top of pressurized column T2 is fed to the pressurized column reflux tank Q203. One stream flows back to the top of pressurized column T2 via the pressurized column reflux pump Q204 on the pressurized column top material reflux pipeline X5, while the other stream flows through the pressurized column refined methanol collection pipeline X6, is preheated by the preheater Q102 of the pre-column secondary feed, and then fed to the refined methanol tank Q701. The flow rate of the material collected from the top of pressurized column T2 to the refined methanol tank Q701 is 3580 kg / h.

[0050] The feed temperature of the pressurized tower T2 is 157℃, the feed pressure of the pressurized tower T2 is 1500 kPaA, the top temperature of the pressurized tower T2 is 147℃, the bottom temperature of the pressurized tower T2 is 171℃, and the top pressure and bottom pressure of the pressurized tower T2 are 1300 kPaA and 1306 kPaA, respectively.

[0051] The material collected from the bottom of the pressurized tower T2 is heated by the primary preheater Q201 and then transported to the atmospheric tower T4 for distillation through the atmospheric tower inlet K4. The feed temperature of the atmospheric tower T4 is 120℃, the top temperature of the atmospheric tower T4 is 101℃, the bottom temperature of the atmospheric tower T4 is 123℃, the top pressure of the atmospheric tower T4 is 200 kPaA, and the bottom pressure of the atmospheric tower T4 is 220 kPaA.

[0052] The material collected from the top of atmospheric distillation column T4 is divided into two streams. One stream heats the reboiler Q603 in the recovery column, providing heat for recovery column T6, with the condensate returning to the atmospheric distillation column reflux tank Q401. The other stream heats the pre-distillation column reboiler Q106, providing heat for pre-distillation column T1, with the condensate returning to the atmospheric distillation column reflux tank Q401. Part of the material returning to the atmospheric distillation column reflux tank Q401 is pumped back to the top of atmospheric distillation column T4 via atmospheric distillation column reflux pump Q402 on atmospheric distillation column top material reflux pipeline X7, and the other part is pumped to recovery column T6 for rectification via recovery column feed line X8. The material collected from the bottom of atmospheric distillation column T4 is discharged as waste liquid via atmospheric distillation column waste liquid discharge pump Q404 on atmospheric distillation column waste liquid discharge pipeline X9. The waste liquid discharge rate of atmospheric distillation column bottom discharge pump Q404 is 930.5 kg / h.

[0053] The material collected from the bottom of pre-column T1 is heated by the first-stage preheater Q101 and then divided into two feed routes. One of the feeds enters the pressurized column T2 for distillation, while the other feeds are preheated successively by the first-stage preheater Q301 and the second-stage preheater Q302 of the medium-pressure column. The preheated material is then transported to the medium-pressure column T3 for distillation through the feed inlet K3. The feed temperature of the medium-pressure column T3 is 134℃, the top temperature of the medium-pressure column T3 is 128℃, the bottom temperature of the medium-pressure column T3 is 143℃, and the top pressure and bottom pressure of the medium-pressure column T3 are 800 kPaA and 805 kPaA, respectively.

[0054] The material collected from the top of the medium-pressure tower T3 heats the reboiler Q403 of the atmospheric tower and provides heat to the atmospheric tower T4. The condensate is transported to the medium-pressure tower reflux tank Q303, and through the medium-pressure tower reflux pump Q304, part of it is refluxed and part is collected. One stream is transported to the top of the medium-pressure tower T3 through the medium-pressure tower top material reflux pipeline X10, and the other stream is collected into the refined methanol tank Q701 through the medium-pressure tower refined methanol collection pipeline X11 via the medium-pressure tower top product condenser Q305. The refined methanol collection rate of the medium-pressure tower T3 is 3830 kg / h.

[0055] The material collected from the bottom of the medium-pressure tower T3 is heated by the first-stage preheater Q301 of the medium-pressure tower feed and then transported to the negative-pressure tower T5 for distillation through the negative-pressure tower feed inlet K5.

[0056] The feed temperature of the negative pressure tower T5 is 62℃, the top temperature is 32.7℃, and the bottom temperature is 63℃. The top and bottom pressures are 25 kPaA and 30 kPaA, respectively. The material collected from the top of the negative pressure tower T5 is transported to the negative pressure tower reflux tank Q501. Then, via the negative pressure tower reflux pump Q502, one stream flows back to the top of the negative pressure tower T5 through the top material reflux pipeline X12, and the other stream flows through the negative pressure tower refined methanol collection pipeline X13 to the refined methanol tank Q701. The refined methanol collection rate of the negative pressure tower T5 is 3700 kg / h.

[0057] On the pipeline from the top of the negative pressure tower T5 to the negative pressure tower reflux tank Q501, a first-stage condenser Q506 and a second-stage condenser Q507 at the top of the negative pressure tower are sequentially connected. The first-stage condenser Q506 and the second-stage condenser Q507 at the top of the negative pressure tower are connected to the negative pressure tower reflux tank Q501 in parallel. Q507 is connected to the negative pressure tower vacuum pump Q505.

[0058] The material collected from the bottom of the negative pressure tower T5 passes through the primary preheater Q604 and the secondary preheater Q605 of the recovery tower feed, and is then transported to the recovery tower T6 for distillation via the recovery tower feed pump Q606, the second feed pipeline X20, and the recovery tower inlet K6.

[0059] In the feed stream of recovery tower T6, the feed temperature of the material collected from the top of atmospheric tower T4 is 101℃, the feed temperature of the material collected from the bottom of negative pressure tower T5 is 67℃, the top temperature of recovery tower T6 is 68℃, the bottom temperature of recovery tower T6 is 107℃, the top pressure and bottom pressure of recovery tower T6 are 100kPaA and 110kPaA respectively. The material collected from the top of recovery tower T6 is condensed after being heated by the second reboiler Q504 of the negative pressure tower. The condensate returns to the recovery tower reflux tank Q601. Through the recovery tower reflux pump Q602, one stream flows back to the top of recovery tower T6 through the recovery tower top material reflux pipeline X14, and the other stream is collected as refined methanol in the refined methanol tank Q701 through the recovery tower refined methanol collection pipeline X15 top liquid condenser Q607. The methanol recovery rate of recovery tower T6 is 570 kg / h. Recovery tower T6 also receives fusel oil via fusel oil side-collection pipeline X19 at a rate of 2800 kg / h, with a side-collection temperature of 87℃ and a side-collection pressure of 108 kPaA. The bottom product of recovery tower T6 is heated by the recovery tower waste liquid collection pipeline X16 to supply heat to the primary feed preheater Q604 before being discharged as waste liquid. The wastewater volume from the bottom product of recovery tower T6 is 4731 kg / h.

[0060] The present invention achieves a reduction in the distillation consumption of 0.56 tons of steam per ton of refined methanol by means of the above-mentioned refining process for crude methanol with high water content, without the use of additional equipment such as high-power heat pump compressor systems.

[0061] In summary, this invention innovatively provides a refining process for high-moisture-content crude methanol, achieving an increase in capacity of over 30% compared to the traditional three-tower methanol distillation (co-current double-effect distillation) process, while simultaneously reducing steam consumption by 45%-50%. It is highly operable, employing energy-saving measures such as optimized heat recovery via heat exchange networks to significantly reduce steam consumption. In particular, it provides a technical solution for refining high-moisture-content crude methanol that controls energy consumption within a low range without relying on additional equipment such as high-power heat pump compressor systems. This solution significantly reduces high electricity costs and alleviates the stringent requirements of heat pump compressor systems for production control, resulting in a novel energy-saving technology that is less dependent on expensive electricity, more universally applicable, and easier to control. This technology achieves a significant reduction in energy consumption, substantially lowering methanol distillation energy consumption, reducing costs, and increasing yield, thereby effectively reducing the carbon footprint and carbon dioxide emissions during the production process. It provides a highly operable, economically viable, and commercially viable solution for the green distillation of high-moisture-content crude methanol.

[0062] The technical features of the embodiments described above can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make modifications, alterations, substitutions, and variations to the above embodiments within the scope of the present invention. Furthermore, without contradiction, those skilled in the art can combine and integrate different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

Claims

1. A process for refining crude methanol with high water content, characterized in that, The process includes the following steps: High-moisture-content crude methanol is fed to the pre-distillation tower (T1) for rectification. The bottom product of the pre-distillation tower (T1) is divided into two streams: one stream is fed to the pressurized tower (T2) for rectification, and the bottom product of the pressurized tower (T2) is fed to the atmospheric tower (T4) for rectification; the other stream is fed to the medium-pressure tower (T3) for rectification, and the bottom product of the medium-pressure tower (T3) is fed to the negative-pressure tower (T5) for rectification. The top products of the atmospheric tower (T4) and the bottom products of the negative-pressure tower (T5) are fed to the recovery tower (T6) for rectification. Refined methanol is collected from the top of the pressurized tower (T2), the negative-pressure tower (T5), the medium-pressure tower (T3), and the recovery tower (T6). The material collected at the top of the pre-column (T1) is heated by the first reboiler (Q503) of the negative pressure column; the material collected at the top of the pressurized column (T2) is heated by the reboiler (Q306) of the medium pressure column; the material collected at the top of the medium pressure column (T3) is heated by the reboiler (Q403) of the atmospheric pressure column; the material collected at the top of the atmospheric pressure column (T4) is heated by the reboiler (Q106) of the pre-column and the reboiler (Q603) of the recovery column; and the material collected at the top of the recovery column (T6) is heated by the second reboiler (Q504) of the negative pressure column. The materials collected from the bottom of the pre-tower (T1), pressurization tower (T2), medium-pressure tower (T3), and recovery tower (T6) are the feed preheating materials of the pre-tower (T1), pressurization tower (T2), medium-pressure tower (T3), and recovery tower (T6), respectively.

2. The process method according to claim 1, characterized in that, The mass percentage of water in the high-moisture-content crude methanol is 30% to 70%. Preferably, the water content in the high-moisture crude methanol is 35% to 70% by mass.

3. The process method according to claim 1, characterized in that, The process method also includes a steam heat source, which is divided into two streams. One stream is heated by the pre-tower reboiler (Q107) and then exits the boundary. The other stream is heated by the feed of the pressurized tower reboiler (Q205), the pressurized tower (T2), the medium-pressure tower (T3), and the recovery tower (T6) and then exits the boundary.

4. The process method according to claim 1, characterized in that, The high-moisture-content crude methanol passes through the first-stage preheater (Q101) and the second-stage preheater (Q102) of the pre-tower feed in sequence before entering the pre-tower (T1) for distillation; Preferably, the material collected from the top of the pre-tower (T1) is heated by the reboiler of the negative pressure tower and then successively transported to the top condenser (Q103), the reflux tank (Q104), and the reflux pump (Q105) of the pre-tower before flowing back to the top of the pre-tower (T1). Preferably, the material collected from the bottom of the pre-tower (T1) is heated by the pre-tower feed preheater (Q101) and then divided into two streams. One stream is sent to the pressurized tower (T2) for distillation, and the other stream is sent to the medium-pressure tower (T3) for distillation.

5. The process method according to claim 1, characterized in that, The material collected at the bottom of the pre-tower (T1) is heated by the first-stage preheater (Q101) of the pre-tower feed and then split into two streams. One stream is preheated by passing through the first-stage preheater (Q201) of the pressurized tower feed and the second-stage preheater (Q202) of the pressurized tower feed. The preheated material is then transported to the pressurized tower (T2) for distillation. The material collected from the bottom of the pre-tower (T1) is heated by the first-stage preheater (Q101) of the pre-tower feed and then split into two streams. One stream is preheated by passing through the first-stage preheater (Q301) of the medium-pressure tower feed and the second-stage preheater (Q302) of the medium-pressure tower feed. The preheated material is then transported to the medium-pressure tower (T3) for distillation.

6. The process method according to claim 1, characterized in that, The material collected from the top of the pressurized tower (T2) is heated by the medium-pressure tower reboiler (Q306) and then transported to the pressurized tower reflux tank (Q203). The material collected from the top of the pressurized tower (T2) is then divided into two streams. One stream is returned to the top of the pressurized tower (T2) by the pressurized tower reflux pump (Q204), and the other stream is preheated by the pre-tower feed secondary preheater (Q102) and then transported to the refined methanol tank (Q701). Preferably, the material collected at the bottom of the pressurized tower (T2) is heated by the primary preheater (Q201) of the pressurized tower feed and then transported to the atmospheric tower (T4) for distillation; Preferably, the material collected from the top of the atmospheric distillation column (T4) is divided into two streams: one stream is used to heat the reboiler of the recovery column (Q603), and the other stream is used to heat the pre-reboiler (Q106). The two streams are respectively transported to the atmospheric distillation column reflux tank (Q401). Through the atmospheric distillation column reflux pump (Q402), part of the material is transported to the top of the atmospheric distillation column (T4), and part of the material is transported to the recovery column (T6) for distillation. The material collected from the bottom of the atmospheric distillation column (T4) is discharged as waste liquid through the atmospheric distillation column (T4) bottom collection pump.

7. The process method according to claim 1, characterized in that, The material collected from the top of the medium-pressure tower (T3) is heated by the reboiler (Q403) of the atmospheric tower and then transported to the reflux tank (Q303) of the medium-pressure tower. Through the reflux pump (Q304), one stream is transported to the top of the medium-pressure tower (T3), and the other stream is collected as refined methanol through the condenser (Q305) of the liquid collected from the top of the medium-pressure tower and sent to the refined methanol tank (Q701). Preferably, the material collected from the bottom of the medium-pressure tower (T3) is heated by the primary preheater (Q301) of the medium-pressure tower feed and then transported to the negative-pressure tower (T5) for distillation; Preferably, after the material collected from the top of the negative pressure tower (T5) is transported to the negative pressure tower reflux tank (Q501), it is returned to the top of the negative pressure tower (T5) by the negative pressure tower reflux pump (Q502), and refined methanol is collected to the refined methanol tank (Q701). Preferably, the material collected from the bottom of the negative pressure tower (T5) passes through the primary preheater (Q604) and the secondary preheater (Q605) of the recovery tower feed, and is then transported to the recovery tower (T6) for distillation by the recovery tower feed pump (Q606).

8. The process method according to claim 1, characterized in that, The material collected from the top of the recovery tower (T6) is heated by the second reboiler (Q504) of the negative pressure tower and then transported to the recovery tower reflux tank (Q601). Through the recovery tower reflux pump (Q602), one stream flows back to the top of the recovery tower (T6), and the other stream passes through the recovery tower top liquid condenser (Q607) and is then collected as refined methanol to the refined methanol tank (Q701). The material collected from the bottom of the recovery tower (T6) is collected as waste liquid after being heated by the first-stage preheater (Q604) of the recovery tower feed.

9. The process method according to claim 1, characterized in that, The steam heat source is divided into two streams. One stream is heated by the pre-tower steam reboiler (Q107) and then discharged as condensate. The other stream is heated by the pressurized tower reboiler (Q205), the pressurized tower feed secondary preheater (Q202), the medium-pressure tower feed secondary preheater (Q302), and the recovery tower feed secondary preheater (Q605) and then discharged as condensate.

10. The process method according to claim 1, characterized in that, The top temperature of the pre-tower (T1) is 67~69℃, the top temperature of the pressurized tower (T2) is 146~148℃, the top temperature of the atmospheric tower (T4) is 100~102℃, the top temperature of the medium-pressure tower (T3) is 127~129℃, the top temperature of the negative pressure tower (T5) is 31~34℃, and the top temperature of the recovery tower (T6) is 67~69℃. Preferably, the pressure at the top of the pre-tower (T1) is 108~112 kPaA, the pressure at the top of the pressurized tower (T2) is 1298~1302 kPaA, the pressure at the top of the atmospheric tower (T4) is 198~202 kPaA, the pressure at the top of the medium-pressure tower (T3) is 798~802 kPaA, the pressure at the top of the negative-pressure tower (T5) is 23~27 kPaA, and the pressure at the top of the recovery tower (T6) is 98~102 kPaA.

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