A BYD distillation process and system

Abstract

This invention relates to a BYD (1,4-butynediol) distillation process and system, solving the problems of high energy consumption and high steam and circulating water consumption in existing BYD distillation processes. The distillation process includes a mixed solution containing 1,4-butynediol, methanol, water, and formaldehyde from an acetylation reactor, which is preheated in a feed preheater and then fed into a stripping tower for stripping. The liquid at the bottom of the stripping tower is drawn off through the liquid phase outlet and sent to the feed preheater for indirect heat exchange with the mixed solution. It is then further cooled by the stripping tower bottom outlet cooler to obtain the BYD product for external delivery. The vapor phase from the top of the stripping tower is drawn off through the vapor phase outlet, first sent to a compressor for pressurization and heating, then sent to the stripping tower reboiler for heat recovery, and then enters the stripping tower reflux tank, before being pumped to the alcohol distillation tower. This invention features a simple process, energy saving and consumption reduction, low operating costs, effective recovery of top heat energy, significant savings in cooling water, and high product concentration.

Description

[0001] This invention belongs to the field of distillation energy-saving technology, specifically a BYD distillation process and system. Background Technology

[0002] BYD (1,4-butynediol) is widely used as an intermediate feedstock in the acetylene-aldehyde process for BDO (1,4-butanediol). Currently, the most widely used BYD distillation unit is the conventional two-tower process. The feed is the effluent from the acetylene reactor, mainly consisting of a mixed solution of 1,4-butynediol, methanol, water, and formaldehyde. This solution enters a stripping tower for distillation. The bottom of the stripping tower yields the BYD product solution, while the top of the tower separates formaldehyde, methanol, and water, which then enters an alcohol tower for further distillation. The top of the alcohol tower separates methanol, and the bottom of the tower yields a dilute formaldehyde solution. This process primarily recovers some of the heat from the stripping tower's overhead steam using a waste heat boiler, producing low-pressure steam as a byproduct. However, due to the low temperature at the top of the stripping tower, the heat recovery efficiency is relatively low, resulting in very low pressure levels for the byproduct steam, limiting its use. The alcohol tower reboiler has a high load, requiring a large amount of steam, thus leading to high steam and circulating water consumption in this process. For example, publication number 103508849A discloses a device for recovering the latent heat of steam from the top of a 1,4-butynediol stripping tower. This device includes a stripping tower, a distillation condenser, a reboiler, and a top distillation trough. The distillation condenser and reboiler are connected to the stripping tower, and the top distillation trough is connected to the distillation condenser. A waste heat boiler is installed at the upper end of the distillation condenser, and the waste heat boiler is connected to a downstream distillation tower. A pressure regulating valve is installed at the front end of the reboiler, and the reboiler and distillation condenser are connected via a condensate pipe. This scheme recovers part of the heat from the top steam of the stripping tower using a waste heat boiler, producing low-pressure steam as a byproduct. The condensate absorbs the latent heat in the top vapor phase and becomes secondary steam, which is sent to the downstream distillation tower to replace the feed preheating steam. However, this method also suffers from low heat recovery efficiency and low pressure of the byproduct steam, failing to effectively recover thermal energy.

[0003] For example, publication number 116410057A discloses a two-stage reaction purification method for 1,4-butanediol. This invention proposes a two-stage reaction and purification method for the synthesis of 1,4-butanediol. Acetylene and formaldehyde react under catalytic conditions to produce 1,4-butynediol, with excess raw materials collected and recycled. 1,4-Butynediol is then hydrogenated under catalytic conditions to produce 1,4-butanediol at a temperature of 100-120°C, with the hydrogen gas recycled. The byproducts are processed and purified into 1,4-butanediol via two towers. However, this method primarily considers the recycling of hydrogen gas and does not address the recovery of heat energy from the tower top gas. Summary of the Invention

[0004] The purpose of this invention is to solve the above-mentioned technical problems and provide a BYD distillation process that is simple, energy-saving, low-cost, can effectively recover heat energy at the top of the column, saves a lot of cooling water, and produces high product concentration.

[0005] The present invention also provides a BYD distillation apparatus for the above-mentioned process, which has a simple structure, low equipment investment and operating costs, and significant energy saving and consumption reduction.

[0006] The BYD distillation system of the present invention includes a stripping column equipped with a stripping column reboiler and an alcohol column reboiler. The vapor outlet at the top of the stripping column is connected to the material inlet of the alcohol column via a compressor, a stripping column reboiler, a stripping column reflux tank, and a stripping column reflux pump. The liquid outlet at the bottom of the stripping column is connected to the bottom outlet cooler of the stripping column via a feed preheater. The feed preheater is connected to the material inlet of the stripping column.

[0007] The stripping tower reboiler is connected to the flash tank, and the liquid phase outlet at the bottom of the flash tank is connected to the stripping tower reflux tank via a cooler.

[0008] The vapor phase outlet at the top of the flash tank is connected to the cooler via the alcohol tower reboiler.

[0009] The outlet of the stripping tower reflux pump is connected to both the material inlet of the alcohol tower and the reflux inlet of the stripping tower.

[0010] The gas phase outlet at the top of the alcohol column is connected to the reflux inlet of the alcohol column via the alcohol column top condenser, alcohol column reflux tank, and alcohol column reflux pump; the liquid phase outlet at the bottom of the alcohol column is connected to the alcohol column bottom discharge cooler via the alcohol column bottom pump.

[0011] The flash tank is a single-stage flash tank or a multi-stage flash tank connected in series.

[0012] The BYD distillation process of this invention includes: a mixed solution containing 1,4-butynediol, methanol, water, and formaldehyde from an acetylation reactor is preheated by a feed preheater and then fed into a stripping tower for stripping; the bottom liquid of the stripping tower is drawn out through the liquid phase outlet and sent to the feed preheater for indirect heat exchange with the mixed solution, and then further cooled by the bottom liquid cooler of the stripping tower to obtain the BYD product for external delivery; the vapor phase from the top of the stripping tower is drawn out through the vapor phase outlet, first sent to a compressor for pressurization and heating, then sent to the stripping tower reboiler for heat exchange and recovery of heat energy, undergoing phase change and condensing into a saturated liquid phase, then entering a reflux tank, and then being pumped to the alcohol distillation tower.

[0013] The saturated liquid phase exiting the reboiler of the stripper is first sent to the flash tank for adiabatic flash evaporation. Flash vapor is drawn out from the top of the tank, and the liquid phase at the bottom of the tank is cooled by the cooler and then enters the stripper reflux tank.

[0014] The flash vapor from the top of the flash tank is introduced into the reboiler of the alcohol tower for heat exchange and recovery of heat energy. After being condensed into a liquid phase, it is cooled by the cooler and then enters the stripping tower reflux tank.

[0015] The liquid phase in the reflux tank is divided into two streams by the reflux pump. One stream is sent back to the stripping tower as reflux liquid, and the other stream is sent to the alcohol tower for distillation.

[0016] The vapor phase at the top of the alcohol column is condensed by the alcohol column top condenser, and the condensate is sent to the alcohol column reflux tank. Then, it is divided into two streams by the alcohol column reflux pump. One stream is sent back to the alcohol column as reflux liquid, and the other stream is collected as a by-product. The liquid at the bottom of the alcohol column is drawn out through the liquid phase outlet, and then sent to the alcohol column bottom discharge cooler by the alcohol column bottom pump for cooling before being sent out.

[0017] The stripping tower has a top pressure of 150–250 kPaG and a temperature of 120–140 °C, while the alcohol tower has a top pressure of 5–15 kPaG and a temperature of 45–65 °C.

[0018] The stripping tower has a theoretical plate number of 40-45 and a reflux ratio of 4-6, while the alcohol tower has a theoretical plate number of 40-45 and a reflux ratio of 10-15.

[0019] The compressor has a compression ratio of 2.5 to 4.

[0020] Beneficial effects:

[0021] 1) The compressor is driven by clean electricity to directly heat and pressurize the steam at the top of the tower and provide heat energy for the reboiler in the bottom of the tower, saving a lot of steam and circulating water usage and reducing costs. Under the same operating conditions, it can save about 44% of the operating costs per year. The reduction in operating costs is even more significant in areas with abundant power resources and tight steam supply.

[0022] 2) By setting up a flash tank, the condensate at the top of the stripping tower after heat exchange is subjected to adiabatic flash evaporation. The flashed steam is used as a heat source for the reboiler of the alcohol tower to further recover heat. At the same time, the flash evaporation cooling method can further save a lot of cooling water.

[0023] 3) By combining the compressor and flash tank, efficient staged utilization of heat is achieved, and the heat demand of different grades in the distillation system is matched and applied. Compared with a simple heat pump distillation system, this invention can maximize the utilization of the energy input from the heat pump on the one hand, and reduce the cooling water of the downstream system on the other hand.

[0024] 4) The flash pressure can be adjusted according to the actual heat demand of different equipment to obtain different flash steam volumes for matching, resulting in high operational flexibility. In practical applications, multi-stage flash evaporation can be set up to meet the needs of more heat grades.

[0025] 5) Using the process of this invention, the concentration of BYD+ water collected from the bottom of the stripping tower is ≥99.99wt%, and the concentration of methanol collected from the top of the alcohol tower is ≥99.96wt%, resulting in high concentration and good quality of products and by-products. Attached Figure Description

[0026] Figure 1 This is a process flow diagram or system diagram of the present invention.

[0027] Among them, 1 is the stripping tower, 2 is the compressor, 3 is the stripping tower reboiler, 4 is the stripping tower bottom pump, 5 is the feed preheater, 6 is the stripping tower bottom discharge cooler, 7 is the flash tank, 8 is the cooler, 9 is the stripping tower reflux tank, 10 is the stripping tower reflux pump, 11 is the alcohol tower, 12 is the alcohol tower top condenser, 13 is the alcohol tower reflux tank, 14 is the alcohol tower reflux pump, 15 is the alcohol tower reboiler, 16 is the alcohol tower bottom pump, and 17 is the alcohol tower bottom discharge cooler. Detailed Implementation

[0028] The present invention will be further explained below with reference to the accompanying drawings:

[0029] See Figure 1 In this embodiment, the BYD distillation system includes a stripping tower 1 equipped with a stripping tower reboiler 3 and an alcohol tower 11 equipped with an alcohol tower reboiler 15.

[0030] The vapor outlet at the top of the stripping tower 1 is connected to the flash tank 7 (single-stage or multi-stage flash tanks in series) via the compressor 2 and the stripping tower reboiler 3; the liquid outlet at the bottom of the flash tank 7 is connected to the stripping tower reflux tank 9 via the cooler 8; the vapor outlet at the top of the flash tank 7 is connected to the cooler 8 via the alcohol tower reboiler 15; the stripping tower reflux tank 9 is connected to the material inlet of the alcohol tower 11 and the reflux inlet of the stripping tower 1 via the stripping tower reflux pump 10; the liquid outlet of the stripping tower 1 bottom is connected to the stripping tower bottom outlet cooler 6 via the feed preheater 5; the feed preheater 5 is connected to the material inlet of the stripping tower 1.

[0031] The gas phase outlet at the top of the alcohol column 11 is connected to the reflux inlet of the alcohol column 11 via the alcohol column top condenser 12, the alcohol column reflux tank 13, and the alcohol column reflux pump 14; the liquid phase outlet at the bottom of the alcohol column 11 is connected to the alcohol column bottom discharge cooler 17 via the alcohol column bottom pump 16.

[0032] The BYD distillation process of this invention includes a mixed solution containing 1,4-butynediol, methanol, water, and formaldehyde from an acetylation reactor. After preheating by a feed preheater 5, the solution is fed into a stripping tower 1 for stripping. The liquid at the bottom of the stripping tower 1 is drawn out through a liquid phase outlet and sent to the feed preheater 5 for indirect heat exchange with the mixed solution. After further cooling by a stripping tower bottom outlet cooler 6, the BYD product is obtained and shipped out. The vapor phase at the top of the stripping tower 1 is drawn out through a vapor phase outlet, first sent to a compressor 2 for pressurization and heating, and then sent to a stripping tower reboiler 3 for heat exchange and recovery of heat energy. A phase change occurs, and the vapor phase condenses into a saturated liquid phase. The saturated liquid phase exiting the stripping tower reboiler 3 is first sent to a flash tank 7 for adiabatic flash evaporation. The liquid phase at the bottom of the flash tank is cooled by a cooler 8 and then enters the stripping tower reflux tank 9. The flash vapor at the top of the tank is introduced into the reboiler 15 of the alcohol tower for heat exchange and recovery of heat energy. After being condensed into a liquid phase, it is cooled by the cooler 8 and then enters the stripping tower reflux tank 9.

[0033] The liquid phase in the stripping tower reflux tank is divided into two streams by the reflux pump 10. One stream is sent back to the stripping tower 1 as reflux liquid, and the other stream is sent to the alcohol tower 11 for rectification. The vapor phase at the top of the alcohol tower 11 is condensed by the alcohol tower top condenser 12, and the condensate is sent to the alcohol tower reflux tank 13. It is then divided into two streams by the alcohol tower reflux pump 14. One stream is sent back to the alcohol tower 11 as reflux liquid, and the other stream is collected as a by-product. The bottom liquid of the alcohol tower 11 is drawn out through the liquid phase outlet, sent to the alcohol tower bottom pump 16 for cooling in the alcohol tower bottom discharge cooler 17, and then sent out.

[0034] The stripping tower 1 has a top pressure of 150–250 kPaG and a temperature of 120–140 °C, while the alcohol tower 11 has a top pressure of 5–15 kPaG and a temperature of 45–65 °C.

[0035] The stripping tower 1 has 40-45 theoretical plates and a reflux ratio of 4-6; the alcohol tower 11 has 40-45 theoretical plates and a reflux ratio of 10-15; and the compressor has a compression ratio of 2.5-4.

[0036] Example 1

[0037] The feed flow rate is 55.155 t / h, containing 49.7% water, 0.85% methanol, 0.69% formaldehyde, 0.48% propanol, and 48.28% 1,4-butynediol, at a temperature of 45℃.

[0038] The 55.155 t / h feed is heated to 110°C in the feed preheater 5 and then fed into the upper part of the stripping tower 1. The operating pressure at the top of the tower is controlled at 0.21 MPaG, the top temperature is 133°C, and the bottom temperature is 145°C. 8.1 t / h of 1.2 MPaG saturated steam is introduced into the bottom of the tower.

[0039] The gas from the top of the tower enters compressor 2 with a compression ratio of 3.1. The compressor outlet pressure is 0.65 MPaG and the temperature is 258℃.

[0040] The stripping tower reboiler 3 adopts a thermosiphon type, with the circulating material going through the tube side and the compressed high-temperature and high-pressure gas going through the shell side. After continuous heat exchange, the shell side gas is condensed into liquid at a temperature of about 163°C and flows into the flash tank 7 by gravity.

[0041] Flash tank 7 maintains a pressure of 0.29 MPaG. After flash evaporation, a gas phase and a liquid phase at 138.7°C are obtained. The high-temperature gas phase enters the shell side of the alcohol tower reboiler 15 as a heat source and is condensed into a liquid at a temperature of approximately 123.2°C. After mixing with the flash liquid phase, it flows by gravity into cooler 8 and is cooled to 104°C before flowing by gravity into stripping tower reflux tank 9.

[0042] The stripper reflux tank 9 maintains a pressure of 0.2 MPaG. After the liquid phase in the reflux tank is pressurized by the stripper reflux pump 10, part of it is refluxed and part of it is used as feed for the alcohol tower 11. The reflux flow rate is about 37 t / h, and the feed for the alcohol tower 11 is about 7.7 t / h.

[0043] The bottom output of stripping tower 1 is 55.54 t / h. After being cooled to 80.8℃ by preheater 5, it is further cooled to 40℃ by stripping tower bottom outlet cooler 6.

[0044] The alcohol reboiler 15 adopts a thermosiphon type, with the circulating material flowing through the tube side and the aforementioned flash vapor phase flowing through the shell side.

[0045] The material from the stripping tower reflux tank 9 is fed into the middle of the alcohol tower 11. The operating pressure at the top of the tower is controlled at 7 kPaG, the temperature at the top of the tower is 66℃, and the temperature at the bottom of the tower is 102.9℃.

[0046] The gas from the top of methanol tower 11 enters the top condenser 12 of methanol tower, where it is condensed into liquid at a temperature of about 55°C. It then flows by gravity into the methanol tower reflux tank 13. After being pressurized by the methanol tower reflux pump 14, a portion of the gas is refluxed back to the top of methanol tower 11 at a flow rate of about 5.3 t / h, while the other portion is collected at a rate of about 0.38 t / h.

[0047] The bottom output of alcohol column 11 is 7.32 t / h, which is cooled to 50°C by alcohol column bottom cooler 17.

[0048] The concentration of BYD+water in the bottom of stripping tower 1 is ≥99.99wt%, and the concentration of methanol in the top of alcohol tower 11 is ≥99.96wt%.

[0049] Comparative Example 1

[0050] In this comparative example, the throughput and operating parameters of all distillation columns are the same as in Example 1. The difference is that no top heat recovery device is installed, i.e., there is no compressor 2 and flash tank 7; only a waste heat boiler is installed to recover part of the heat and produce low-pressure steam as a byproduct. The steam consumption of stripping column 1 and alcohol column 11 is 53.1 t / h and 3 t / h, respectively. The circulating water consumption of the top condenser is 862 t / h and 156 t / h, respectively. The circulating water consumption of the discharge cooler is 521 t / h and 40.4 t / h, respectively. The byproduct steam is 25 t / h.

[0051] Comparison of operating costs between Comparative Example 1 and Example 1: (Calculated based on the specific conditions of the location of the equipment, with a steam price of 150 yuan / ton, an electricity price of 0.5 yuan / kWh, a cooling water price of 0.2 yuan / ton, and an annual operating time of 8000 hours)

[0052]

[0053] Calculations show that this invention can save approximately 44% of production and operating costs compared to existing technologies, significantly reducing production costs. It is particularly competitive in regions with high steam prices, low electricity prices, and water shortages in the west.

Claims

1. A BYD distillation system, comprising a stripping column equipped with a stripping column reboiler and an alcohol column reboiler, characterized in that, The vapor outlet at the top of the stripping tower is connected to the material inlet of the alcohol tower via a compressor, a stripping tower reboiler, a stripping tower reflux tank, and a stripping tower reflux pump; the liquid outlet at the bottom of the stripping tower is connected to the bottom outlet cooler of the stripping tower via a feed preheater, and the feed preheater is connected to the material inlet of the stripping tower. The stripping tower reboiler is connected to the flash tank, and the liquid phase outlet at the bottom of the flash tank is connected to the stripping tower reflux tank via a cooler; the gas phase outlet at the top of the flash tank is connected to the cooler via the alcohol tower reboiler; the outlet of the stripping tower reflux pump is connected to the material inlet of the alcohol tower and the reflux inlet of the stripping tower, respectively.

2. The BYD distillation system as described in claim 1, characterized in that, The gas phase outlet at the top of the alcohol column is connected to the reflux inlet of the alcohol column via the alcohol column top condenser, alcohol column reflux tank, and alcohol column reflux pump; the liquid phase outlet at the bottom of the alcohol column is connected to the alcohol column bottom discharge cooler via the alcohol column bottom pump.

3. The BYD distillation system as described in claim 1, characterized in that, The flash tank is a single-stage flash tank or a multi-stage flash tank connected in series.

4. A BYD distillation process, employing the BYD distillation system according to any one of claims 1-3, comprising: a mixed solution containing 1,4-butynediol, methanol, water, and formaldehyde from an acetylation reactor, preheated by a feed preheater, and then fed into a stripping tower for stripping; characterized in that... The liquid in the bottom of the stripping tower is drawn out through the liquid phase outlet and sent to the feed preheater for indirect heat exchange with the mixed solution. After further cooling by the stripping tower bottom outlet cooler, the BYD product is obtained and shipped out. The vapor phase at the top of the stripping tower is drawn out through the vapor phase outlet, first sent to the compressor for pressurization and heating, and then sent to the stripping tower reboiler for heat exchange and recovery of heat energy. It undergoes a phase change and condenses into a saturated liquid phase, then enters the stripping tower reflux tank, and is then pumped to the alcohol tower for distillation by the reflux pump.

5. The BYD distillation process as described in claim 4, characterized in that, The saturated liquid phase exiting the stripper reboiler is first sent to the flash tank for adiabatic flash evaporation. Flash vapor is drawn from the top of the tank, and the liquid phase at the bottom of the tank is cooled by a cooler before entering the stripper reflux tank.

6. The BYD distillation process as described in claim 5, characterized in that, The flash vapor from the top of the flash tank is introduced into the reboiler of the alcohol tower for heat exchange and recovery of heat energy. After being condensed into a liquid phase, it is cooled by the cooler and then enters the reflux tank.

7. The BYD distillation process as described in any one of claims 4-6, characterized in that, The liquid phase in the reflux tank is divided into two streams by the reflux pump. One stream is sent back to the stripping tower as reflux liquid, and the other stream is sent to the alcohol tower for distillation.

8. The BYD distillation process as described in any one of claims 4-6, characterized in that, The vapor phase at the top of the alcohol column is condensed by the alcohol column top condenser, and the condensate is sent to the alcohol column reflux tank. Then, it is divided into two streams by the alcohol column reflux pump. One stream is sent back to the alcohol column as reflux liquid, and the other stream is collected as a by-product. The liquid at the bottom of the alcohol column is drawn out through the liquid phase outlet, and then sent to the alcohol column bottom discharge cooler by the alcohol column bottom pump for cooling before being sent out.

9. The BYD distillation process as described in any one of claims 4-6, characterized in that, The stripping tower has a top pressure of 150–250 kPaG and a temperature of 120–140 °C, while the alcohol tower has a top pressure of 5–15 kPaG and a temperature of 45–65 °C.

10. The BYD distillation process according to any one of claims 4-6, characterized in that, The stripping tower has a theoretical plate number of 40-45 and a reflux ratio of 4-6, while the alcohol tower has a theoretical plate number of 40-45 and a reflux ratio of 10-15.

11. The BYD distillation process according to any one of claims 4-6, characterized in that, The compressor has a compression ratio of 2.5 to 4.

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