A device for heat coupling of butanol and octanol and methanol rectification

Abstract

The utility model discloses a kind of butanol and methanol rectification heat coupling's device, including methanol pre-distillation column, it is characterized in that, butyraldehyde isomer rectification column, octanol rectification column, methanol-butyraldehyde heat exchanger and methanol-octanol heat exchanger, the crude methanol of the feed of methanol pre-distillation column enters the methanol-butyraldehyde heat exchanger, after with butyraldehyde isomer rectification column overhead gas phase heat exchange, enter the methanol pre-distillation column, butyraldehyde isomer rectification column overhead gas phase heat exchange after entering butyraldehyde isomer rectification column overhead condenser;The methanol pre-distillation column tower kettle liquid phase enters the methanol-octanol heat exchanger, after with octanol rectification column overhead gas phase heat exchange, return methanol pre-distillation column tower kettle, octanol rectification column overhead gas phase heat exchange after entering octanol rectification column overhead condenser.The device can realize cross-device energy grade matching, make full use of waste heat, save steam and circulating water cooling consumption, enhance ORC power generation efficiency.

Description

Technical Field

[0001] This utility model belongs to the field of coal chemical technology, specifically relating to a device for thermal coupling of butanol and octanol distillation. Background Technology

[0002] The butanol / octanol unit uses propylene and syngas as feedstocks, and a rhodium / triphenylphosphine complex as a catalyst. Through a carbonyl synthesis reaction, mixed butyraldehyde is produced. Direct hydrogenation of the mixed butyraldehyde produces n-butanol and isobutanol. To produce octanol, n-butyraldehyde and isobutyraldehyde are first separated in a butyraldehyde isomer distillation column. The n-butyraldehyde undergoes a self-condensation reaction to produce octenal, which is then hydrogenated to produce octanol. The reaction product is purified by distillation to obtain octanol. In the coal chemical industry chain, the methanol-to-olefins (MTO) technology extends to form a "methanol-propylene-butanol / octanol" technical route.

[0003] Distillation is the most energy-intensive unit operation in the coal chemical separation process, accounting for 30%-50% of the total energy consumption of the unit (e.g., distillation energy consumption accounts for 40% in methanol-to-olefins units). Product purity determines the value chain. Methanol distillation requires the removal of water, light components (dimethyl ether), and heavy components (long-chain alcohols) from crude methanol; otherwise, it directly affects the catalyst life in the production of downstream products such as formaldehyde and acetic acid. In butanol and octanol units, the precision of distillation separation of n- and isobutyraldehyde affects the octanol hydrogenation efficiency; octanol purity needs to reach above 99.5% to meet the requirements of high-end plasticizers. At the same time, VOC emissions from the top gas of the distillation column and COD content in the bottom wastewater are strictly limited by environmental regulations, increasing distillation energy consumption and operational difficulty. Coal chemical enterprises generally adopt measures such as high-efficiency distillation and secondary utilization of waste heat and pressure to achieve the goal of reducing energy consumption.

[0004] In existing coal chemical plants, methanol pre-distillation columns, butyraldehyde isomer distillation columns, and octanol distillation columns, which are related to the separation of products such as methanol and octanol, generally adopt an independent operation mode of low-pressure steam heating in the column bottom and circulating water cooling at the top. This mode has the following problems: low energy utilization efficiency, with waste heat (70-128℃) from the material at the top of the column being directly discharged through circulating water cooling, resulting in a large waste of low-grade heat energy; high steam consumption, with the reboiler of the distillation column relying on steam (5kg or 13kg class) for heating, resulting in high operating costs; and high cooling load, with a large amount of circulating water required for condensation at the top of the methanol / butyraldehyde / octanol columns, resulting in a double waste of water and electricity resources. In addition, the power generation efficiency of the Organic Rankine Cycle (ORC) system adopted for waste heat utilization and energy consumption reduction is limited. Because the reboiler steam condensate of the methanol pre-distillation column is reused to heat the crude methanol feed, the condensate temperature is low, which means that the power generation of the Organic Rankine Cycle (ORC) system is not optimal.

[0005] The limitations of the available energy-saving distillation technologies in distillation separation are analyzed below: Summary of the Invention

[0006] The purpose of this invention is to provide a device for thermally coupling butanol and octanol distillation, which integrates the methanol unit and the butanol and octanol unit into a system. The top materials of the butyraldehyde isomer distillation column and the octanol distillation column are used as heat sources to preheat the crude methanol feed and provide heat to the bottom of the methanol pre-distillation column, thereby utilizing waste heat and saving steam and circulating water cooling consumption; at the same time, the steam condensate temperature is increased to enhance ORC power generation efficiency.

[0007] To achieve the above-mentioned objectives, this utility model provides a device for thermal coupling of butanol and octanol distillation, comprising a methanol pre-distillation column, characterized in that it further comprises a butyraldehyde isomer distillation column, an octanol distillation column, a methanol-butyraldehyde heat exchanger, and a methanol-octanol heat exchanger. The crude methanol feed to the methanol pre-distillation column enters the methanol-butyraldehyde heat exchanger, exchanges heat with the overhead vapor phase of the butyraldehyde isomer distillation column, and then enters the methanol pre-distillation column. The overhead vapor phase of the butyraldehyde isomer distillation column exchanges heat with the feed crude methanol in the methanol-butyraldehyde heat exchanger and then enters the overhead condenser of the butyraldehyde isomer distillation column. The liquid phase from the bottom of the methanol pre-distillation column enters the methanol-octanol heat exchanger, exchanges heat with the overhead vapor phase of the octanol distillation column, and then returns to the bottom of the methanol pre-distillation column. The overhead vapor phase of the octanol distillation column exchanges heat with the liquid phase from the bottom of the methanol pre-distillation column in the methanol-octanol heat exchanger and then enters the overhead condenser of the octanol distillation column.

[0008] Furthermore, the vapor phase at the top of the octanol distillation column is connected to the condenser at the top of the octanol distillation column via an automatic regulating valve of the methanol-octanol heat exchanger.

[0009] The device described is a thermal integration system for a methanol-butanol / octanol combined unit. It thermally integrates the methanol pre-distillation column, butyraldehyde isomer distillation column, and octanol distillation column, which were originally operating independently in the methanol unit and the butanol / octanol unit, to achieve cross-process energy integration optimization. None of the distillation columns, their overhead condensers, or their reboilers require modification or replacement.

[0010] Furthermore, the apparatus also includes a condensate ORC unit, wherein the reboiler vapor condensate from the methanol pre-distillation column, the butyraldehyde isomer distillation column, and the octanol distillation column is sent to the condensate ORC unit.

[0011] Beneficial Effects: This utility model's device for thermally coupling butanol and octanol with methanol distillation achieves thermal coupling between methanol distillation and butyraldehyde and octanol distillation within the butanol / octanol unit. Octanol vapor is used as one of the heat sources for the methanol pre-distillation column's reboiler. After heat exchange, it returns to the original top condenser. The crude methanol feed to the methanol pre-distillation column no longer exchanges heat twice with the reboiler condensate; instead, it exchanges heat with butyraldehyde vapor. The waste heat of the butyraldehyde vapor is utilized and returned to the original top condenser, effectively realizing waste heat resource utilization and simultaneously reducing steam and circulating water consumption. Furthermore, the increased temperature of the reboiler condensate boosts the ORC system's power generation. The comprehensive benefits of this device include: Overall energy consumption reduction: The overall energy consumption of the entire unit decreased by 0.5%, realizing the utilization of low-grade waste heat resources and reducing thermal pollution from cooling towers and CO2 emissions from steam boilers; Investment savings: Compared to heat pump systems, it eliminates the need for compressors (approximately 10 million yuan per unit) and additional multi-effect distillation towers (approximately 20 million yuan). Attached Figure Description

[0012] Figure 1 is a schematic diagram of the device for thermal coupling of butanol and methanol distillation according to this invention. Among them, 1. Steam, 2. Condensate, 3. Pre-reboiler, 4. Methanol pre-distillation column, 5. Methanol top condenser, 6. Methanol reflux tank, 7. Methanol-octanol heat exchanger, 8. Butyraldehyde reboiler, 9. Butyraldehyde isomer distillation column, 10. Methanol-butyraldehyde heat exchanger, 11. Butyraldehyde top condenser, 12. Butyraldehyde reflux tank, 13. Crude methanol feed, 14. Octanol distillation column, 15. Octanol top condenser, 16. Automatic regulating valve of methanol-octanol heat exchanger, 17. Octanol reflux tank, 18. Octanol reboiler, 19. Condensate ORC unit. Detailed Implementation

[0013] The technical solution of this utility model will be further described in detail below through specific embodiments. However, it should be noted that the following embodiments are only used to describe the content of the invention and do not constitute a limitation on the protection scope of this utility model.

[0014] In the methanol and butanol / octanol units, to achieve the separation of products such as methanol and octanol, there are independently operating methanol pre-distillation column 4, butyraldehyde isomer distillation column 9, and octanol distillation column 14, which employ low-pressure steam heating at the bottom and circulating water cooling at the top. The methanol pre-distillation column 4 includes a pre-reboiler 3 and a methanol top condenser 5. Steam 1 exchanges heat with the liquid at the bottom of the column in the pre-reboiler 3, providing a heat source for the methanol pre-distillation column 4. The methanol vapor phase at the top of the column is condensed by the circulating water-cooled methanol top condenser 5 and then enters the methanol reflux tank 6. The butyraldehyde isomer distillation column 9 and the octanol distillation column 14 operate under the same conditions.

[0015] like Figure 1A device for thermally coupling butanol and octanol distillation is a thermally integrated system of a methanol-butanol-octanol combined unit. It includes a methanol pre-distillation column 4, a butyraldehyde isomer distillation column 9, and an octanol distillation column 14, all thermally coupled together, as well as a methanol-octanol heat exchanger 7 and a methanol-butyraldehyde heat exchanger 10. Butyraldehyde vapor (86℃, 50kPa) at the top of the butyraldehyde isomer distillation column 9 exchanges heat with the crude methanol feed from the methanol pre-distillation column 4 through the methanol-butyraldehyde heat exchanger 10, preheating the methanol. The crude methanol feed utilizes the waste heat at the top of the column and reduces the amount of circulating water used for cooling. Octanol vapor (128℃, 47kPa) from the top of octanol distillation column 14 serves as a heat source, supplying heat to methanol pre-distillation column 4 (boiler temperature 74-79℃) via methanol-octanol heat exchanger 7. This can completely replace the original reboiler vapor (5kg), or partially replace it when the octanol unit load is low, thus utilizing the waste heat at the top and reducing the amount of circulating water used for cooling. The waste heat from the octanol vapor is returned to the original octanol column top condenser 15, and the waste heat from the butyraldehyde vapor is returned to the original butyraldehyde column top condenser 11. The crude methanol feed to methanol pre-distillation column 4 no longer exchanges heat with the condensate 2 of the pre-coiler 3. This setup creates staged cooling, significantly saving circulating water and simultaneously increasing the condensate temperature. The reboiler vapor condensate from the methanol pre-distillation column 4, the butyraldehyde isomer distillation column 9, and the octanol distillation column 14 is sent to the condensate ORC unit, which significantly enhances the ORC power generation efficiency.

[0016] The thermal coupling of the device includes the following key technical features: 1. Cross-unit energy cascade matching: Utilizing the sensible and latent heat of the butyraldehyde / octanol top vapor, precisely matching the medium and low temperature heat demand of the methanol distillation system; 2. Dynamic pressure-temperature control: Maintain stable heat source quality of octanol vapor through pressure control to ensure that the reboiler heat transfer temperature difference is ≥15℃; 3. Waste heat-ORC synergy: High-temperature condensate (heated by 20-30°C after thermal coupling) is directly input into the ORC system, improving power generation efficiency by 10%.

[0017] Using the aforementioned thermal coupling device, after the methanol pre-distillation column 4, butyraldehyde isomer distillation column 9, and octanol distillation column 14 are started up and circulation is established according to the original distillation process, a small amount of crude methanol feed 13 is introduced into the methanol-butyraldehyde heat exchanger 10. After the pipeline is full, all of the crude methanol feed 13 is introduced, and the steam flow rate 1 of the pre-distillation column reboiler 3 is appropriately reduced according to the temperature. Then, the top steam of the octanol distillation column 14 is slowly introduced into the methanol-octanol heat exchanger 7. After the pipeline is warmed up and full, the flow rate of octanol vapor into the methanol-octanol heat exchanger 7 is increased, and the steam flow rate 1 of the original pre-distillation column reboiler 3 is reduced simultaneously to ensure that the top temperature and reflux flow rate of the methanol pre-distillation column 4 are as stable as possible until the steam flow rate 1 of the pre-distillation column reboiler 3 is completely shut off. The excess octanol vapor at the top of the octanol distillation column 14 enters the original octanol column top condenser 15 directly through the automatic regulating valve 16 of the methanol-octanol heat exchanger. When the octanol unit is shut down for maintenance, the methanol distillation process is switched back to the original process to avoid fluctuations. The condensate from reboilers 3, 8, and 18 of each tower is all fed into the condensate ORC unit 19 for power generation.

[0018] Taking a methanol and octanol unit with an annual production capacity of 400,000 tons and 250,000 tons per year as an example, the temperature of crude methanol 13 fed into the methanol pre-distillation column 4 is typically 35-40 degrees Celsius, the methanol vapor at the top of the column is 72 degrees Celsius, and the temperature at the bottom of the column varies from 74-79 degrees Celsius depending on the water content. The steam pressure of the pre-distillation column reboiler 3 is 5 kg / m³. The feed temperature of the butyraldehyde isomer distillation column 9 is 85-90 degrees Celsius, the butyraldehyde vapor at the top of the column is 86 degrees Celsius, and the reboiler steam pressure is 5 kg / m³. The feed temperature of the octanol distillation column 14 is 160 degrees Celsius, the octanol vapor at the top of the column is 128 degrees Celsius, and the reboiler steam pressure is 5 kg / m³. By utilizing the waste heat at the top of the butyraldehyde and octanol units in a cascade manner to replace the external energy input of the methanol distillation system, the crude methanol (liquid) from the methanol distillation unit is first sent to the top of the butyraldehyde isomer distillation column 9 to exchange heat with the butyraldehyde vapor; the octanol vapor at the top of the octanol distillation column 14 is sent to the methanol-octanol heat exchanger 7 as a heat source, replacing the water vapor consumption of the original pre-distillation column reboiler 3, thus achieving energy integration and optimization throughout the entire process.

[0019] The temperature difference matching data in the table below shows that the cross-device heat transfer temperature difference is significantly better than the applicable threshold (ΔT<30℃) for heat pump distillation.

[0020]

[0021] * Comparison based on the average temperature of crude methanol (50 degrees Celsius) and butyraldehyde vapor.

[0022] The apparatus for thermal coupling of butanol and octanol distillation of this invention is compared with other energy-saving distillation technologies in the table below.

[0023]

[0024] For enterprises with a methanol plant capacity of 400,000 tons and an octanol plant capacity of 250,000 tons, the direct economic benefits of using the aforementioned butanol-octanol distillation thermal coupling device include the following aspects: 1. Reduced steam consumption: Steam consumption of the methanol pre-distillation tower is reduced by 100%, saving approximately 80,000 tons of steam annually; 2. Reduce circulating water consumption: The cooling load at the top of the butyraldehyde isomer distillation column and octanol distillation column is reduced by 70%-80%, and the circulating water volume is reduced by 500 standard cubic meters / hour, which can save 80 kilowatts of electricity per hour; 3. ORC power generation gain: When the condensate temperature is increased to above 100℃, the annual power generation of the ORC system increases by 10%.

Claims

1. An apparatus for thermally coupling butanol and octanol distillation with methanol, comprising a methanol pre-distillation column, characterized in that, It also includes a butyraldehyde isomer distillation column, an octanol distillation column, a methanol-butyraldehyde heat exchanger, and a methanol-octanol heat exchanger. The crude methanol feed to the methanol pre-distillation column enters the methanol-butyraldehyde heat exchanger, exchanges heat with the overhead vapor phase of the butyraldehyde isomer distillation column, and then enters the methanol pre-distillation column. The overhead vapor phase of the butyraldehyde isomer distillation column exchanges heat with the feed crude methanol in the methanol-butyraldehyde heat exchanger and then enters the overhead condenser of the butyraldehyde isomer distillation column. The liquid phase from the bottom of the methanol pre-distillation column enters the methanol-octanol heat exchanger, exchanges heat with the overhead vapor phase of the octanol distillation column, and then returns to the bottom of the methanol pre-distillation column. The overhead vapor phase of the octanol distillation column exchanges heat with the liquid phase from the bottom of the methanol pre-distillation column in the methanol-octanol heat exchanger and then enters the overhead condenser of the octanol distillation column.

2. The apparatus for thermal coupling of butanol and octanol distillation according to claim 1, characterized in that, The vapor phase at the top of the octanol distillation column is connected to the condenser at the top of the octanol distillation column via an automatic regulating valve of the methanol-octanol heat exchanger.

3. The apparatus for thermal coupling of butanol and octanol distillation according to claim 1, characterized in that, The apparatus also includes a condensate ORC unit, wherein the reboiler vapor condensate from the methanol pre-distillation column, the butyraldehyde isomer distillation column, and the octanol distillation column is sent to the condensate ORC unit.

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