BYD rectification process and system

Abstract

The invention relates to a BYD (1, 4-butynediol) rectification process and system, and solves the problems of high energy consumption and high steam and circulating water consumption in the existing BYD rectification process. The rectification process comprises the following steps: preheating a mixed solution containing 1, 4-butynediol, methanol, water and formaldehyde from an ethynylation reactor through a feed preheater, feeding the preheated mixed solution into a stripping tower for stripping, and leading out tower kettle liquid of a tower kettle of the stripping tower through a liquid phase outlet, feeding into the feed preheater, carrying out indirect heat exchange with the mixed solution, and further cooling by a stripping tower kettle discharge cooler to obtain a BYD product; a gas phase at the top of the stripping tower is led out through a gas phase outlet, is firstly fed into a compressor for pressurizing and heating, then is fed into a stripping tower reboiler for heat exchange and heat energy recovery, then enters a stripping tower reflux tank, and is fed into an alcohol tower for rectification through a reflux pump. The method has the advantages of simple process, energy saving, consumption reduction, low operation cost, effective recovery of tower top heat energy, saving of a large amount of cooling water, and high product concentration.

Description

[0001] The invention belongs to the technical field of distillation energy saving, and specifically relates to a BYD distillation process and system. Background Art

[0002] BYD (1,4-butynediol) is widely used as an intermediate raw material for BDO (1,4-butanediol) in the acetylenic aldehyde process. At present, the most widely used technical solution for BYD distillation unit is the conventional double-tower process. The feed is the discharge of the acetylation reactor, mainly including 1,4-butynediol, methanol, water, formaldehyde and other mixed solutions, which enter the stripping tower for distillation, and the BYD product solution is obtained in the tower bottom. Formaldehyde, methanol, water and the like are separated from the top of the tower, and enter the alcohol tower for further distillation. Methanol is separated from the top of the alcohol tower, and a dilute formaldehyde solution is obtained from the bottom of the tower. This process mainly recovers part of the heat of the steam at the top of the stripping tower through a waste heat boiler, and produces low-pressure steam as a by-product; because the temperature at the top of the stripping tower is not high, the heat recovery efficiency is relatively low, and the pressure level of the by-product steam is very low, so its use is relatively limited; the reboiler load of the alcohol tower is high, and a large amount of steam needs to be consumed, so the steam and circulating water consumption of this process is high. For example, Publication No. 103508849A discloses a 1,4-butynediol stripping tower overhead steam latent heat utilization recovery device, including a stripping tower, a distillation condenser, a reboiler and a tower overhead distillation tank, wherein the distillation condenser and the reboiler are respectively connected to the stripping tower, the tower overhead trough is connected to the distillation condenser, the distillation condenser is provided with a waste heat boiler at the upper end, the waste heat boiler is connected to the downstream distillation tower, the front end of the reboiler is provided with a pressure regulating valve, and the reboiler is connected to the distillation condenser through a condensate pipe. This scheme is that the waste heat boiler recovers part of the heat of the stripping tower overhead steam, and the by-product is low-pressure steam. The steam condensate absorbs the latent heat in the tower overhead gas phase to become secondary steam and is sent to the downstream distillation tower, replacing its feeding preheating steam. There are also problems of low heat recovery efficiency and low pressure of by-product steam, and there is no good recovery of heat energy.

[0003] For example, Publication No. 116410057A discloses a two-stage reaction method for refining 1,4-butanediol. The present invention proposes a two-stage reaction and separation and purification method for synthesizing 1,4-butanediol. Acetylene and formaldehyde react under the condition of a catalyst to produce 1,4-butynediol, and the excess raw materials are extracted and recycled; 1,4-butynediol is hydrogenated under the condition of a catalyst to produce 1,4-butanediol, the hydrogenation temperature is 100-120°C, the hydrogen is recycled, and the by-products are processed and 1,4-butanediol is refined through two towers. It mainly considers the recycling of hydrogen, and does not consider the heat recovery of the gas at the top of the tower. Summary of the invention

[0004] The purpose of the present invention is to solve the above technical problems and provide a BYD distillation process with simple process, energy saving and consumption reduction, low operating cost, effective recovery of top heat energy, saving of a large amount of cooling water and high product concentration.

[0005] The present invention also provides a BYD distillation device for the above 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 comprises a stripping tower provided with a stripping tower reboiler and an alcohol tower with an alcohol tower reboiler, wherein the gas phase 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 phase outlet of the stripping tower kettle is connected to the stripping tower kettle discharge cooler via a feed preheater, and the feed preheater is connected to the material inlet of the stripping tower.

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

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

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

[0010] The gas phase outlet of the top of the alcohol tower is connected to the reflux inlet of the alcohol tower via the alcohol tower top condenser, the alcohol tower reflux tank and the alcohol tower reflux pump; the liquid phase outlet of the alcohol tower kettle is connected to the alcohol tower kettle discharge cooler via the alcohol tower kettle 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 the present invention comprises: a mixed solution containing 1,4-butynediol, methanol, water and formaldehyde from an acetylation reactor is preheated by a feed preheater and then sent to a stripping tower for stripping; the bottom liquid of the stripping tower is drawn out through a liquid phase outlet, sent to the feed preheater for indirect heat exchange with the mixed solution, and then further cooled by a stripping tower bottom discharge cooler to obtain a BYD product for external delivery; the top gas phase of the stripping tower is drawn out through a gas phase outlet, first sent to a compressor for pressurization and temperature increase, and then sent to a stripping tower reboiler for heat exchange and heat recovery, undergoing phase change and condensing into a saturated liquid phase, and then entering a reflux tank, and then sent to an alcohol tower for distillation through a reflux pump.

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

[0014] The flash gas at the top of the flash tank is introduced into the alcohol tower reboiler for heat exchange and heat recovery, and 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 after passing through a 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] After the gas phase at the top of the alcohol tower is condensed by the alcohol tower top condenser, the condensate is sent to the alcohol tower reflux tank, and then divided into two streams by the alcohol tower reflux pump, one stream is returned to the alcohol tower as reflux liquid, and the other stream is produced as a by-product; the bottom liquid of the alcohol tower is drawn out through the liquid phase outlet, sent to the alcohol tower bottom discharge cooler by the alcohol tower bottom pump for cooling and then sent out.

[0017] The pressure at the top of the stripping tower is 150-250 kPaG, and the temperature is 120-140°C; the pressure at the top of the alcohol tower is 5-15 kPaG, and the temperature is 45-65°C.

[0018] The stripping tower has 40-45 theoretical plates and a reflux ratio of 4-6; the alcohol tower has 40-45 theoretical plates and a reflux ratio of 10-15.

[0019] The compression ratio of the compressor is 2.5-4.

[0020] Beneficial effects:

[0021] 1) The compressor is driven by clean electric energy to directly increase the temperature and pressure of the steam at the top of the tower, and provide heat energy for the tower kettle reboiler, saving a lot of steam and circulating water, reducing costs. Under the same working conditions, it can save about 44% of operating costs each year, especially for areas with abundant power resources and tight steam supply, the operating cost reduction is more significant;

[0022] 2) By setting up a flash tank, the condensate at the top of the stripping tower after heat exchange is adiabatically flashed, and the flashed steam is used as the heat source of the alcohol tower reboiler to further recover heat. At the same time, the flash cooling method can further save a large amount of cooling water;

[0023] 3) Through the combined use of the compressor and the flash tank, efficient graded utilization of heat is achieved, and the different grades of heat requirements in the distillation system are matched and applied; compared with a simple heat pump distillation system, the present invention can maximize the utilization of the energy input by the heat pump on the one hand, and reduce the cooling water of the subsequent system on the other hand.

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

[0025] 5) By adopting the process of the present invention, the concentration of BYD+water produced from the bottom of the stripping tower is ≥99.99wt%, the concentration of methanol produced from the top of the alcohol tower is ≥99.96wt%, and the product and by-product have high concentrations and good quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a process flow chart and system diagram of the present invention.

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

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

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

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

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

[0032] The BYD distillation process of the present invention comprises the following steps: a mixed solution containing 1,4-butynediol, methanol, water and formaldehyde from an acetylation reactor is preheated by a feed preheater 5 and then sent to a stripping tower 1 for stripping; the bottom liquid of the bottom of the stripping tower 1 is drawn out through a liquid phase outlet, sent to the feed preheater 5 for indirect heat exchange with the mixed solution, and then further cooled by a stripping tower bottom discharge cooler 6 to obtain a BYD product for external delivery; the top gas phase of the stripping tower 1 is drawn out through a gas phase outlet, first sent to a compressor 2 for pressurization and temperature increase, and then sent to a stripping tower reboiler 3 for heat exchange and heat recovery, undergoing a phase change and condensing 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, and the liquid phase at the bottom of the tank is cooled by a cooler 8 and then enters a stripping tower reflux tank 9. The flash gas at the top of the tank is introduced into the alcohol tower reboiler 15 for heat exchange and heat recovery, and after condensing 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 reflux tank of the stripping tower is divided into two streams after passing through the reflux pump 10, one of which is returned to the stripping tower 1 as reflux liquid, and the other is sent to the alcohol tower 11 for distillation; the gas 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, and then divided into two streams by the alcohol tower reflux pump 14, one of which is returned to the alcohol tower 11 as reflux liquid, and the other is produced 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 discharge cooler 17 through the alcohol tower bottom pump 16 for cooling and then sent out.

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

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

[0036] Example 1

[0037] The feed flow rate is 55.155 t / h, of which the water content is 49.7%, the methanol content is 0.85%, the formaldehyde content is 0.69%, the propanol content is 0.48%, the 1,4-butynediol content is 48.28%, and the temperature is 45°C.

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

[0039] The top gas enters compressor 2 with a compression ratio of 3.1, a compressor outlet pressure of 0.65 MPaG and a temperature of 258°C.

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

[0041] The flash tank 7 maintains a pressure of 0.29 MPaG, and 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 with a temperature of about 123.2°C. After mixing with the flash liquid phase, it flows by gravity into the cooler 8, and after being cooled to 104°C, it flows by gravity into the stripping tower reflux tank 9.

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

[0043] The output of the stripping tower 1 kettle is 55.54 t / h, which is cooled to 80.8°C by the preheater 5 and then cooled to 40°C by the stripping tower kettle discharge cooler 6.

[0044] The alcohol tower reboiler 15 adopts a thermosyphon type, the circulating material flows through the pipe side, and the above-mentioned flash gas phase flows through the shell side.

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

[0046] The top gas of the alcohol tower 11 enters the alcohol tower top condenser 12, is condensed into liquid with a temperature of about 55°C, and flows into the alcohol tower reflux tank 13 by gravity. After being pressurized by the alcohol tower reflux pump 14, a part of it refluxes to the top of the alcohol tower 11 with a reflux rate of about 5.3 t / h, and the other part is produced with a production rate of about 0.38 t / h.

[0047] The output from the bottom of the alcohol tower 11 is 7.32 t / h, which is cooled to 50° C. through the alcohol tower bottom discharge cooler 17 .

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

[0049] Comparative Example 1

[0050] The processing capacity and operating parameters of all distillation towers in this comparative example are the same as those in Example 1, except that no heat recovery device is provided at the top of the tower, i.e., no compressor 2 and flash tank 7; only one waste heat boiler is provided to recover part of the heat and produce low-pressure steam as a by-product. The steam consumption of the stripping tower 1 and the alcohol tower 11 are 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, and the by-product steam is 25 t / h.

[0051] Comparison of operating costs between Comparative Example 1 and Example 1: (Based on the specific conditions of the location of the device, the steam price is 150 yuan / ton, the electricity price is 0.5 yuan / kWh, the cooling water price is 0.2 yuan / ton, and the calculation is based on 8,000 hours of operation throughout the year)

[0052]

[0053] According to calculation, the present invention can save about 44% of production operation cost compared with the prior art, greatly saving production cost, especially in the areas with high steam price, low electricity price and water shortage in the west.

Claims

1. A BYD distillation system, comprising a stripping tower provided with a stripping tower reboiler and an alcohol tower provided with an alcohol tower reboiler, characterized in that: The gas phase 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 phase outlet of the stripping tower kettle is connected to the stripping tower kettle discharge cooler via a feed preheater, and the feed preheater is connected to the material inlet of the stripping tower.

2. The BYD distillation system according to claim 1, characterized in that: The stripping tower reboiler is connected to a flash tank, and the liquid phase outlet at the bottom of the flash tank is connected to a stripping tower reflux tank via a cooler.

3. The BYD distillation system according to claim 2, characterized in that: The gas phase outlet at the top of the flash tank is connected to the cooler via an alcohol tower reboiler.

4. The BYD distillation system according to any one of claims 1 to 3, characterized in that: The outlet of the stripping tower reflux pump is respectively connected to the material inlet of the alcohol tower and the reflux inlet of the stripping tower.

5. The BYD distillation system according to any one of claims 1 to 3, characterized in that: The gas phase outlet of the top of the alcohol tower is connected to the reflux inlet of the alcohol tower via the alcohol tower top condenser, the alcohol tower reflux tank and the alcohol tower reflux pump; the liquid phase outlet of the alcohol tower kettle is connected to the alcohol tower kettle discharge cooler via the alcohol tower kettle pump.

6. The BYD distillation system according to claim 1 or 2, characterized in that: The flash tank is a single-stage flash tank or a multi-stage flash tank connected in series.

7. A BYD distillation process, comprising: preheating a mixed solution containing 1,4-butynediol, methanol, water and formaldehyde from an acetylation reactor in a feed preheater and then feeding it into a stripping tower for stripping, characterized in that: The bottom liquid of the stripping tower kettle is drawn out through the liquid phase outlet, sent to the feed preheater for indirect heat exchange with the mixed solution, and then further cooled by the stripping tower kettle discharge cooler to obtain the BYD product for external delivery; the top gas phase of the stripping tower is drawn out through the gas phase outlet, first sent to the compressor for pressurization and temperature increase, and then sent to the stripping tower reboiler for heat exchange and heat recovery, undergoing phase change and condensing into a saturated liquid phase, and then entering the stripping tower reflux tank, and then sent to the alcohol tower for distillation through a reflux pump.

8. The BYD distillation process according to claim 7, characterized in that: The saturated liquid phase exiting the reboiler of the stripping tower is first sent to the flash tank for adiabatic flash evaporation, and the flash gas is drawn out from the top of the tank. The liquid phase at the bottom of the tank is cooled by the cooler and then enters the reflux tank of the stripping tower.

9. The BYD distillation process according to claim 8, characterized in that: The flash gas at the top of the flash tank is introduced into the alcohol tower reboiler for heat exchange and heat recovery, and after being condensed into a liquid phase, it is cooled by the cooler and then enters the reflux tank.

10. The BYD distillation process according to any one of claims 7 to 9, characterized in that: The liquid phase in the reflux tank is divided into two streams after passing through a 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.

11. The BYD distillation process according to any one of claims 7 to 9, characterized in that: After the gas phase at the top of the alcohol tower is condensed by the alcohol tower top condenser, the condensate is sent to the alcohol tower reflux tank, and then divided into two streams by the alcohol tower reflux pump, one stream is returned to the alcohol tower as reflux liquid, and the other stream is produced as a by-product; the bottom liquid of the alcohol tower is drawn out through the liquid phase outlet, sent to the alcohol tower bottom discharge cooler by the alcohol tower bottom pump for cooling and then sent out.

12. The BYD distillation process according to any one of claims 7 to 9, characterized in that: The pressure at the top of the stripping tower is 150-250 kPaG, and the temperature is 120-140°C; the pressure at the top of the alcohol tower is 5-15 kPaG, and the temperature is 45-65°C.

13. The BYD distillation process according to any one of claims 7 to 9, characterized in that: The stripping tower has 40-45 theoretical plates and a reflux ratio of 4-6; the alcohol tower has 40-45 theoretical plates and a reflux ratio of 10-15.

14. The BYD distillation process according to any one of claims 7 to 9, characterized in that: The compression ratio of the compressor is 2.5-4.

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