A method for recycling tail gas of a 1,3-propanediol plant

Abstract

The application discloses a tail gas recycling method of a 1,3-propanediol device, and belongs to the technical field of chemical production. In the method, tail gas at the top of a propenal absorption tower is introduced into a tail gas humidification tower, and after countercurrent contact with hot water introduced from the top of the tower, the tail gas is humidified and then returned to the inlet of a reactor; meanwhile, process water discharged from a PDO dehydration unit is recycled in stages, part of which is used as raw material water of a propenal hydration unit after being partially cooled, and part of which is used as hot water and recycled to the tail gas humidification tower; bottom liquid of the tail gas humidification tower is pumped out and heat-exchanged, most of which is circulated back to the top of the tower as spraying water, and part of which is sent to a quenching absorption tower as part of process water. In the application, no additional water vapor needs to be injected during normal production, for example, in an industrialized PDO device, steam consumption of the device and wastewater treatment capacity can be significantly reduced, unreacted propylene is recovered, and raw material utilization is improved; the tail gas humidification tower can wash away trace heavy components in the tail gas, effectively prolonging the operation cycle of a catalyst and the continuous production time of the device.

Description

Technical Field

[0001] This invention relates to the field of chemical production technology, and in particular to a method for recycling the tail gas of the acrolein unit in the production process of 1,3-propanediol (PDO). Background Technology

[0002] 1,3-Propanediol (PDO) is a core raw material for the production of high-performance polyester polypropylene terephthalate (PTT). PTT fibers combine the softness of nylon, the stain resistance of polyester, and the bulkiness of acrylic fibers, making them promising for applications in textiles, carpets, and engineering plastics. Therefore, developing economical, efficient, and green PDO synthesis routes has always been a focus of research in the chemical industry.

[0003] Currently, industrial PDO production mainly relies on bio-fermentation and chemical synthesis. Among these, propylene oxidation chemical synthesis has become the mainstream process due to its fast reaction rate, readily available raw materials, and ease of large-scale continuous production. The core and challenge of this process lies in the propylene oxidation to acrolein step: the mixture of propylene and air poses an explosion risk. At room temperature and pressure, the explosion limit of propylene is 2%–11%, but the high-temperature environment of 300-400℃ inside the reactor negates the explosion suppression effect of nitrogen, significantly widening the explosion range. This not only limits the propylene feed concentration and reduces production efficiency but also greatly increases the risk of safety accidents, requiring a complex interlocking system and making operation extremely difficult.

[0004] Industrially, water vapor is typically added to create a quaternary gas mixture to address this issue. Water vapor, as a superior inert component, can reduce the partial pressure of reactants and suppress explosions by quenching free radical chain reactions, exhibiting better explosion suppression effects than nitrogen or carbon dioxide. Simultaneously, water vapor can improve propylene conversion, optimize heat transfer, increase product yield, and inhibit catalyst coking. However, excessive water vapor addition increases energy consumption, system pressure drop, and wastewater treatment costs, necessitating precise control of the proportions.

[0005] Currently, the mainstream raw material preparation process for acrolein production is direct steam injection, air prehumidification, and tail gas recirculation.

[0006] (1) The direct steam injection process is simple but consumes a lot of steam and does not recover unreacted propylene in the tail gas, resulting in low raw material utilization.

[0007] (2) The air prehumidification process has low energy consumption, but it also has the problem of insufficient raw material utilization. Furthermore, there is a risk of introducing new impurities when using hot process material as the humidification water source.

[0008] (3) Conventional tail gas recirculation process can recover unreacted propylene, but since the acrolein absorption tower needs to be operated at a low temperature of 5-15℃, the water content of the tail gas at the top of the tower is extremely low, and additional water vapor still needs to be injected, which leads to complicated operation and high energy consumption. Furthermore, the trace heavy components carried in the tail gas will accelerate the deactivation of the catalyst by carbon deposition.

[0009] (4) Although the process of catalytic combustion and recycling of tail gas can remove heavy components, it also removes unreacted propylene, resulting in raw material loss.

[0010] Therefore, there is an urgent need to develop a PDO unit tail gas recycling technology that can effectively recover unreacted propylene, save water vapor consumption, reduce catalyst carbonization rate, and extend unit operation cycle. Summary of the Invention

[0011] Purpose of the invention: The purpose of this invention is to overcome the above-mentioned deficiencies in the prior art and provide a method for recycling tail gas from a 1,3-propanediol plant, so as to reduce the steam consumption of the plant, improve the utilization rate of raw materials, reduce the rate of catalyst carbonization, and extend the operating cycle of the plant.

[0012] Technical solution:

[0013] To achieve the above objectives, the present invention adopts the following technical solution:

[0014] A method for recycling tail gas from a 1,3-propanediol plant, wherein the plant comprises, in sequence along the material flow direction, an acrolein synthesis unit, an acrolein hydration unit, a 3-hydroxypropane hydrogenation unit, a 1,3-propanediol dehydration unit, and a 1,3-propanediol purification unit. The acrolein synthesis unit includes an oxidation reactor, a reaction product cooler, a quench absorption tower, and an acrolein absorption tower. The method includes the following steps:

[0015] (a) Propylene, air and recycle tail gas are mixed in a propylene / air mixer to form a raw material mixture gas, which enters an oxidation reactor and undergoes an oxidation reaction under the action of a catalyst to generate reaction products containing acrolein.

[0016] (b) The reaction products are cooled by the reaction product cooler and then enter the quench absorption tower, where they come into countercurrent contact with the process water to absorb the acrylic acid in the reaction gas to form an acrylic acid solution. The reaction gas after absorbing the acrylic acid enters the acrolein absorption tower, where it comes into countercurrent contact with the process water to absorb the acrolein in the reaction gas to form an acrolein solution. The acrolein solution discharged from the bottom of the acrolein absorption tower is sent to the acrolein refining unit.

[0017] (c) The reaction tail gas after acrolein absorption is extracted from the top of the acrolein absorption tower and divided into two streams. The first stream is sent to the tail gas humidification tower as a circulating tail gas. After being humidified by countercurrent contact with hot water entering from the top of the tower, it is pressurized by the tail gas compressor and returned to the propylene / air mixer. The second stream is sent to the waste gas treatment unit.

[0018] (d) The acrolein refined by the acrolein refining unit is mixed with demineralized water to form an acrolein solution, which is then converted into a 3-hydroxypropionaldehyde solution by a hydration reaction in the acrolein hydration unit.

[0019] (e) The 3-hydroxypropionaldehyde solution is converted into a 1,3-propanediol solution by hydrogenation reaction with hydrogen in the hydrogenation unit;

[0020] (f) The 1,3-propanediol solution enters the dehydration unit for dehydration. Part of the dehydrated process water is cooled and used as raw material preparation water for the acrolein hydration unit, and part of it is recycled as hot water to the tail gas humidification tower in step (c).

[0021] (g) The crude 1,3-propanediol solution after dehydration enters the refining unit to remove light components, heavy components and trace aldehydes, and then produces 1,3-propanediol product.

[0022] In step (c), most of the exhaust gas humidification tower bottom circulation pump outlet stream is circulated back to the top of the tower after heat exchange, and part of the stream is sent to the process water inlet of the quench absorption tower as part of the process water of the quench absorption tower.

[0023] Further, the hot water in step (c) includes process water and fresh demineralized water from the dehydration unit in step (f).

[0024] Further, in step (c), the first stream accounts for 10% to 50% of the total tail gas volume at the top of the acrolein absorber.

[0025] Further, in step (c), the temperature at the top of the exhaust gas humidification tower is controlled at 50℃~75℃, and the pressure at the top of the tower is 0.09~0.098 MPa (a).

[0026] Furthermore, during normal production, no additional water vapor is injected into the propylene / air mixer described in step (a), and all the water vapor in the raw material mixture comes from the humidified circulating exhaust gas described in step (c); the air described in step (a) is air that has been pressurized by an air compressor, and the air is only mixed with the added water vapor through the air / water vapor mixer during the start-up phase.

[0027] Furthermore, in step (c), a portion of the stream sent from the outlet of the bottom circulation pump of the tail gas humidification tower to the quench absorption tower is discharged continuously or intermittently to avoid the accumulation of heavy components in the bottom liquid of the tail gas humidification tower.

[0028] Furthermore, the circulating exhaust gas pipeline described in step (c) is equipped with flow measurement and control facilities, and / or the raw material mixed gas pipeline after the propylene / air mixer described in step (a) is equipped with an automatic oxygen content analyzer.

[0029] Furthermore, in step (b), part of the acrylic acid solution discharged from the bottom of the quench absorption tower is cooled by the quench absorption tower cooler and returned to the upper inlet of the quench absorption tower, while part is sent to the acrylic acid solution treatment unit.

[0030] Further, the mass concentration of the acrolein solution in step (d) is 3% to 10%.

[0031] Furthermore, in step (c), the liquid at the bottom of the tail gas humidification tower is drawn out by the bottom circulation pump, heated to 60-80°C by a heat exchanger, and then injected from the top of the tail gas humidification tower as spray water.

[0032] Beneficial effects:

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1. Significantly reduced steam consumption: During normal production, the water vapor content in the tail gas after humidification by the tail gas humidification tower is sufficient to meet the raw material gas ratio, eliminating the need for additional water vapor injection. Taking an 80,000-ton-per-year propylene-to-PDO plant as an example, it can save 2.67 tons of water vapor per hour, and 21,360 tons of water vapor per year, significantly reducing the plant's energy consumption.

[0035] 2. Achieve tiered reuse of process water: The process water removed from the PDO dehydration unit is used in stages. Part of it is cooled and used as raw material preparation water for the acrolein hydration unit, and part of it is reused as hot water in the tail gas humidification tower. This reduces the consumption of fresh water and recovers some heat energy, further reducing the energy consumption of the unit.

[0036] 3. Reduce the cost of treating waste gas, wastewater, and solid waste: The increase in inert components carried by the circulating exhaust gas reduces the demand for water vapor in the raw material gas distribution, and the amount of wastewater in subsequent units is reduced accordingly; at the same time, some exhaust gas is recycled, which reduces the amount of waste gas emissions and saves the cost of wastewater and waste gas treatment.

[0037] 4. Improve raw material utilization: The incompletely converted propylene in the reactor is recycled to the reactor inlet with the tail gas, realizing the recycling of unreacted raw materials and reducing the consumption of propylene per unit.

[0038] 5. Extended catalyst life and unit operating cycle: The hot water in the tail gas humidification tower comes into full countercurrent contact with the tail gas, absorbing some of the heavy components (such as acrylic acid, acrolein, acetaldehyde, etc.) in the tail gas and sending them to the quench absorption tower. This reduces the proportion of heavy components in the circulating tail gas, thereby significantly reducing the coking rate of the catalyst in the reactor. The catalyst coking and regeneration cycle is extended from the original 6 months to 12 months, reducing the number of shutdowns and improving production efficiency and catalyst life. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the overall process of the present invention.

[0040] Figure Descriptions: 1. Air compressor; 2. Air / steam mixer; 3. Propylene / air mixer; 4. Tail gas humidification tower; 5. Tail gas humidification tower bottom circulation pump; 6. Tail gas compressor; 7. Oxidation reactor; 8. Reaction product cooler; 9. Quenching absorption tower; 10. Quenching absorption tower bottom pump; 11. Quenching absorption tower cooler; 12. Acrolein absorption tower; 13. Acrolein absorption tower bottom pump; 14. Acrolein absorption tower cooler; 15. Acrolein refining unit; 16. Acrolein hydration unit; 17. 3-HPA hydrogenation unit; 18. PDO dehydration unit; 19. PDO refining unit; 20. Spray water heat exchanger Detailed Implementation

[0041] The present invention will be further described in detail below with reference to specific embodiments and comparative examples.

[0042] Example 1

[0043] This embodiment describes the tail gas recycling process for a 10,000-ton-per-year propylene-to-PDO plant (8,000 hours of annual operation). The specific steps are as follows:

[0044] S1. Raw material preparation and propylene oxidation: Air (4t / h, dry air) is pressurized by an air compressor (1) and mixed with a small amount of water vapor in an air / water vapor mixer (2) during the start-up phase to form a first mixture stream. Then, it is mixed with gaseous propylene (0.78t / h) and pressurized oxidation tail gas (1.8t / h) in a propylene / air mixer (3) to form a second mixture stream. The second mixture stream enters an oxidation reactor (7) filled with a molybdenum-bismuth catalyst. Under the conditions of 320-380℃ and 0.1-0.2MPa, propylene undergoes an oxidation reaction to produce acrolein.

[0045] S2. Quenching and Absorption of Acrolein: The reaction products are cooled to 150-180°C by the reaction product cooler (8) and then enter the quench absorption tower (9), where they come into countercurrent contact with process water to absorb acrylic acid from the reaction gas and form an acrylic acid solution. After being pressurized by the bottom pump (10) of the quench absorption tower, part of the acrylic acid solution is cooled to 40-50°C by the quench absorption tower cooler (11) and then returned to the upper inlet of the quench absorption tower (9), while the other part is sent to the acrylic acid solution treatment unit. The reaction gas after absorbing acrylic acid is extracted from the top of the quench absorption tower (9) and enters the acrolein absorption tower (12), where it comes into countercurrent contact with process water at 5-10°C to further absorb acrolein from the reaction gas and form an acrolein solution. After being pressurized by the bottom pump (13) of the acrolein solution, part of the acrolein solution is cooled to 5-10°C by the acrolein absorption tower cooler (14) and then returned to the upper inlet of the acrolein absorption tower (12), while the other part is sent to the acrolein refining unit (15).

[0046] S3. Tail Gas Circulation and Humidification: The reaction tail gas after acrolein absorption is divided into two streams. The first stream (1.8 t / h, accounting for 30% of the total tail gas volume) is sent as circulating tail gas to the lower inlet of the tail gas humidification tower (4). The tail gas humidification tower (4) adopts a packed tower structure, and a spray water distributor is installed at the top of the tower. After the bottom liquid of the tail gas humidification tower (4) is drawn out by the bottom circulation pump (5), it is first heated to 68-75℃ by the spray water heat exchanger (20), and then injected from the top of the tail gas humidification tower (4) as spray water. The circulating tail gas and the spray hot water are in full countercurrent contact in the tower, and humidification and washing are carried out at the same time. The temperature at the top of the tail gas humidification tower (4) is controlled at 63.5℃, the pressure at the top of the tower is controlled at 0.09~0.098MPa(a), and the spray water circulation rate is controlled at 30-35t / h. The humidified exhaust gas has a moisture content of approximately 0.33 t / h. After being pressurized to 0.15-0.2 MPa by the exhaust gas compressor (6), it is sent to the propylene / air mixer (3). The second stream is sent to the waste gas treatment unit. At the same time, a small amount of fresh demineralized water is continuously added to the exhaust gas humidification tower (4), and 0.5-1 t / h of the bottom liquid is discharged to the process water inlet of the quench absorption tower (9) to avoid the accumulation of heavy components.

[0047] S4. Acrolein Refining, Hydration, and Hydrogenation: Acrolein refined in the acrolein refining unit (15) is mixed with demineralized water to form a 5% mass concentration acrolein solution. This solution undergoes a hydration reaction under the catalysis of the cation exchange resin in the acrolein hydration unit (16), transforming into a 3-HPA solution. The 3-HPA solution then undergoes a hydrogenation reaction with hydrogen in the 3-HPA hydrogenation unit (17) under the catalysis of a Raney nickel catalyst, transforming into a PDO solution.

[0048] S5. PDO Dehydration, Refining and Process Water Reuse: The PDO solution enters the PDO dehydration unit (18) for dehydration. Part of the dehydrated process water is cooled to 25-30℃ and used as raw material preparation water in the acrolein hydration unit (16), and part of it is reused as hot water in the tail gas humidification tower (4). The crude PDO solution generated after dehydration enters the PDO refining unit (19). After removing light components, heavy components and trace aldehydes by distillation, PDO products with a purity ≥99.5% are obtained and sent out of the device.

[0049] In this embodiment, no additional water vapor is required during normal production, and the catalyst in the reactor is burned every 12 months.

[0050] Comparative Example 1

[0051] The same 10,000-ton-per-year propylene-to-PDO unit as in Example 1 was used, except that during normal production, an additional 0.33t / h of steam was injected into the air / steam mixer (2), and the tail gas at the top of the acrolein absorption tower (12) was directly partially circulated without being humidified by the tail gas humidification tower (4).

[0052] In this comparative example, the catalyst carbonization regeneration cycle is 6 months, and the annual consumption of steam is approximately 2640 tons. Compared with the traditional tail gas recirculation process, Example 1 saves 0.33 tons of steam per hour, 2640 tons of steam per year, and doubles the catalyst operating cycle.

[0053] Example 2

[0054] This embodiment describes the tail gas recycling process for an 80,000-ton-per-year propylene-to-PDO plant (8,000 hours of annual operation). The specific steps are as follows:

[0055] S1. Raw material preparation and propylene oxidation: Air (32t / h, dry air) is pressurized by an air compressor (1) and mixed with a small amount of water vapor in an air / water vapor mixer (2) during the start-up phase to form a first mixture stream. Then, it is mixed with gaseous propylene (6.2t / h) and pressurized oxidation tail gas (14.3t / h) in a propylene / air mixer (3) to form a second mixture stream. The second mixture stream enters an oxidation reactor (7) filled with a molybdenum-bismuth catalyst. Under the conditions of 320-380℃ and 0.1-0.2MPa, propylene undergoes an oxidation reaction to produce acrolein.

[0056] S2. Quenching and Absorption of Acrolein: The reaction products are cooled to 150-180°C by the reaction product cooler (8) and then enter the quench absorption tower (9), where they come into countercurrent contact with process water to absorb acrylic acid from the reaction gas and form an acrylic acid solution. After being pressurized by the bottom pump (10) of the quench absorption tower, part of the acrylic acid solution is cooled to 40-50°C by the quench absorption tower cooler (11) and then returned to the upper inlet of the quench absorption tower (9), while the other part is sent to the acrylic acid solution treatment unit. The reaction gas after absorbing acrylic acid is extracted from the top of the quench absorption tower (9) and enters the acrolein absorption tower (12), where it comes into countercurrent contact with process water at 5-10°C to further absorb acrolein from the reaction gas and form an acrolein solution. After being pressurized by the bottom pump (13) of the acrolein solution, part of the acrolein solution is cooled to 5-10°C by the acrolein absorption tower cooler (14) and then returned to the upper inlet of the acrolein absorption tower (12), while the other part is sent to the acrolein refining unit (15).

[0057] S3. Tail Gas Circulation and Humidification: The reaction tail gas after acrolein absorption is divided into two streams. The first stream (14.3 t / h, accounting for 30% of the total tail gas volume) is sent as circulating tail gas to the lower inlet of the tail gas humidification tower (4). The tail gas humidification tower (4) adopts a packed tower structure, and a spray water distributor is installed at the top of the tower. After the bottom liquid of the tail gas humidification tower (4) is drawn out by the bottom circulation pump (5), it is first heated to 70-75℃ by the spray water heat exchanger (20), and then injected from the top of the tail gas humidification tower (4) as spray water. The circulating tail gas and the spray hot water are in full countercurrent contact in the tower, and humidification and washing are carried out at the same time. The temperature at the top of the tail gas humidification tower (4) is controlled at 63.5℃, the pressure at the top of the tower is controlled at 0.09~0.098MPa(a), and the spray water circulation rate is controlled at 200-230t / h. The humidified exhaust gas has a moisture content of approximately 2.67 t / h. After being pressurized to 0.15-0.2 MPa by the exhaust gas compressor (6), it is sent to the propylene / air mixer (3). The second stream is sent to the waste gas treatment unit. At the same time, a small amount of fresh demineralized water is continuously added to the exhaust gas humidification tower (4), and 1-5 t / h of the bottom liquid is discharged to the process water inlet of the quench absorption tower (9) to avoid the accumulation of heavy components.

[0058] S4. Acrolein Refining, Hydration, and Hydrogenation: Acrolein refined in the acrolein refining unit (15) is mixed with demineralized water to form a 5% mass concentration acrolein solution. This solution undergoes a hydration reaction under the catalysis of the cation exchange resin in the acrolein hydration unit (16), transforming into a 3-HPA solution. The 3-HPA solution then undergoes a hydrogenation reaction with hydrogen in the 3-HPA hydrogenation unit (17) under the catalysis of a Raney nickel catalyst, transforming into a PDO solution.

[0059] S5. PDO Dehydration, Refining and Process Water Reuse: The PDO solution enters the PDO dehydration unit (18) for dehydration. Part of the dehydrated process water is cooled to 25-30℃ and used as raw material preparation water in the acrolein hydration unit (16), and part of it is reused as hot water in the tail gas humidification tower (4). The crude PDO solution generated after dehydration enters the PDO refining unit (19). After removing light components, heavy components and trace aldehydes by distillation, PDO products with a purity ≥99.5% are obtained and sent out of the device.

[0060] In this embodiment, no additional water vapor is required during normal production, and the catalyst in the reactor is burned every 12 months.

[0061] Comparative Example 2

[0062] The same 80,000-ton-per-year propylene-to-PDO unit as in Example 2 was used, except that during normal production, an additional 2.67 t / h of steam was injected into the air / steam mixer (2), and the tail gas at the top of the acrolein absorption tower (12) was directly partially circulated without being humidified by the tail gas humidification tower (4).

[0063] In this comparative example, the catalyst carbonization regeneration cycle is 6 months, and the annual steam consumption is approximately 21,360 tons. Compared with the traditional process, Example 2 saves 2.67 tons of steam per hour and 21,360 tons of steam per year, and doubles the catalyst operating cycle.

[0064] Process Safety Instructions

[0065] From a process safety perspective, the reaction temperature in the propylene oxidation to acrolein reactor (7) is as high as 300℃~400℃. Under these high temperature conditions, the suppressive effect of nitrogen on the explosion limit of the mixed gas will be offset by the high temperature factor, resulting in an expansion of the explosion limit range. As an inert component, water vapor can not only reduce the partial pressure of propylene and oxygen in the reaction mixture, making the mixture composition far away from the explosion limit range, but more importantly, water molecules can act as a highly efficient "third body" to collide with active free radicals (such as H·, O·, OH·) in free radical chain reactions, absorb their energy and deactivate them, thereby interrupting the propagation of the chain reaction and effectively suppressing the explosion. Therefore, by humidifying the circulating tail gas to a sufficient water content through the tail gas humidification tower (4), the reaction safety is ensured, and the energy consumption and wastewater treatment burden caused by the additional injection of water vapor are avoided.

[0066] It should be noted that during the start-up phase, since there is no circulating tail gas in the system, external water vapor must be used to supplement the system to meet the water content requirements of the reaction raw material gas. After the system is running stably, the water vapor brought in by the humidification of the circulating tail gas is sufficient to meet the process requirements, and the external water vapor can be cut off to achieve zero steam injection operation.

[0067] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for recycling tail gas from a 1,3-propanediol apparatus, wherein the apparatus comprises, in sequence along the material flow direction, an acrolein synthesis unit, an acrolein hydration unit, a 3-hydroxypropane hydrogenation unit, a 1,3-propanediol dehydration unit, and a 1,3-propanediol purification unit, characterized in that, The acrolein synthesis unit includes an oxidation reactor, a reaction product cooler, a quench absorption tower, and an acrolein absorption tower. The method includes the following steps: (a) Propylene, air and recycle tail gas are mixed in a propylene / air mixer to form a raw material mixture gas, which enters an oxidation reactor and undergoes an oxidation reaction under the action of a catalyst to generate reaction products containing acrolein. (b) The reaction products are cooled by the reaction product cooler and then enter the quench absorption tower, where they come into countercurrent contact with the process water to absorb the acrylic acid in the reaction gas to form an acrylic acid solution. The reaction gas after absorbing the acrylic acid enters the acrolein absorption tower, where it comes into countercurrent contact with the process water to absorb the acrolein in the reaction gas to form an acrolein solution. The acrolein solution discharged from the bottom of the acrolein absorption tower is sent to the acrolein refining unit. (c) The reaction tail gas after acrolein absorption is extracted from the top of the acrolein absorption tower and divided into two streams. The first stream is sent to the tail gas humidification tower as a circulating tail gas. After being humidified by countercurrent contact with hot water entering from the top of the tower, it is pressurized by the tail gas compressor and returned to the propylene / air mixer. The second stream is sent to the waste gas treatment unit. (d) The acrolein refined by the acrolein refining unit is mixed with demineralized water to form an acrolein solution, which is then converted into a 3-hydroxypropionaldehyde solution by a hydration reaction in the acrolein hydration unit. (e) The 3-hydroxypropionaldehyde solution is converted into a 1,3-propanediol solution by hydrogenation reaction with hydrogen in the hydrogenation unit; (f) The 1,3-propanediol solution enters the dehydration unit for dehydration. Part of the dehydrated process water is cooled and used as raw material preparation water for the acrolein hydration unit, and part of it is recycled as hot water to the tail gas humidification tower in step (c). (g) The crude 1,3-propanediol solution after dehydration enters the refining unit to remove light components, heavy components and trace aldehydes, and then produces 1,3-propanediol product. In step (c), most of the exhaust gas humidification tower bottom circulation pump outlet stream is circulated back to the top of the tower after heat exchange, and part of the stream is sent to the process water inlet of the quench absorption tower as part of the process water of the quench absorption tower.

2. The method for recycling tail gas from a 1,3-propanediol plant according to claim 1, characterized in that, The hot water in step (c) includes process water and fresh demineralized water from the dehydration unit in step (f).

3. The method for recycling tail gas from a 1,3-propanediol plant according to claim 2, characterized in that, In step (c), the first stream accounts for 10% to 50% of the total tail gas volume at the top of the acrolein absorption tower.

4. A method for recycling tail gas from a 1,3-propanediol plant according to any one of claims 1-3, characterized in that, The temperature at the top of the exhaust gas humidification tower in step (c) is controlled at 50℃~75℃, and the pressure at the top of the tower is 0.09~0.098 MPa (a).

5. A method for recycling tail gas from a 1,3-propanediol plant according to any one of claims 1-4, characterized in that, During normal production, no additional water vapor is injected into the propylene / air mixer described in step (a), and all the water vapor in the raw material mixture comes from the humidified circulating exhaust gas described in step (c); the air described in step (a) is air that has been pressurized by an air compressor, and the air is only mixed with the added water vapor through the air / water vapor mixer during the start-up phase.

6. A method for recycling tail gas from a 1,3-propanediol plant according to any one of claims 1-5, characterized in that, In step (c), the portion of the stream sent from the bottom circulation pump outlet of the tail gas humidification tower to the quench absorption tower is discharged continuously or intermittently to avoid the accumulation of heavy components in the bottom liquid of the tail gas humidification tower.

7. A method for recycling tail gas from a 1,3-propanediol plant according to any one of claims 1-6, characterized in that, The circulating exhaust gas pipeline in step (c) is equipped with flow measurement and control facilities, and / or the raw material mixed gas pipeline after the propylene / air mixer in step (a) is equipped with an automatic oxygen content analyzer.

8. A method for recycling tail gas from a 1,3-propanediol plant according to any one of claims 1-7, characterized in that, In step (b), part of the acrylic acid solution discharged from the bottom of the quench absorption tower is cooled by the quench absorption tower cooler and returned to the upper inlet of the quench absorption tower, while part is sent to the acrylic acid solution treatment unit.

9. A method for recycling tail gas from a 1,3-propanediol plant according to any one of claims 1-8, characterized in that, The mass concentration of the acrolein solution in step (d) is 3% to 10%.

10. A method for recycling tail gas from a 1,3-propanediol plant according to any one of claims 1-9, characterized in that, In step (c), the liquid at the bottom of the tail gas humidification tower is drawn out by the bottom circulation pump, heated to 60-80°C by a heat exchanger, and then injected from the top of the tail gas humidification tower as spray water.

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