CN112920031A

CN112920031A - Method for separating and recycling acrolein in process of preparing 1, 3-propylene glycol

Info

Publication number: CN112920031A
Application number: CN202110111432.XA
Authority: CN
Inventors: 柳铭轩; 张保勇; 彭华峰; 贾振宇; 冯连芳
Original assignee: Zhejiang University ZJU; Zhejiang Henglan Technology Co Ltd
Current assignee: Zhejiang University ZJU; Zhejiang Henglan Technology Co Ltd
Priority date: 2021-01-27
Filing date: 2021-01-27
Publication date: 2021-06-08
Anticipated expiration: 2041-01-27
Also published as: CN112920031B

Abstract

The invention relates to the field of chemical industry, and discloses a method for separating and recycling acrolein in a process of preparing 1, 3-propylene glycol, which comprises the following steps: adding polymerization inhibitor into the acrolein solution for hydration reaction; the reaction product is separated from the 3-hydroxypropionaldehyde by an acrolein rectifying tower; 3-hydroxy propionaldehyde solution enters a hydrogenation reaction unit; after the steam is discharged, the steam is mixed with a polymerization inhibitor solution and atomized, and then the mixture is condensed in two stages, part of condensate liquid flows back to an acrolein rectifying tower, part of condensate liquid is used for proportioning, and non-condensable gas is pumped out in vacuum, is incorporated into the polymerization inhibitor and then enters an acrolein recovery tower in a gas phase state; after stripping, the aqueous acrolein solution is continuously discharged from the tower bottom and refluxed for proportioning, and the acetaldehyde liquid is extracted from the tower top and collected after condensation. The method adopts the rectifying tower to separate the 3-hydroxypropionaldehyde, so that the requirement of the subsequent hydrogenation reaction is met, and the steam stripping method is applied to the separation of the acetaldehyde and the acrolein, so that the entrained acetaldehyde can be thoroughly separated, and the recovery and the utilization of an acrolein solution are facilitated.

Description

Method for separating and recycling acrolein in process of preparing 1, 3-propylene glycol

Technical Field

The invention relates to the field of chemical industry, in particular to a method for separating and recycling acrolein in a process of preparing 1, 3-propylene glycol.

Background

The 1, 3-propanediol (1, 3-PDO) is mainly used as a monomer and terephthalic acid to synthesize a novel polyester material, namely polytrimethylene terephthalate (PTT), can also be used as a solvent, an antifreeze agent, a plasticizer, an emulsifier, a preservative or a protective agent and the like, and can also be used for synthesizing medicines and used as an organic synthesis intermediate. The PTT fiber has the advantages of high elastic recovery capability, good colorability, internal stress resistance, low water adsorption, low static electricity, good biodegradation, cyclic utilization and the like, and shows wide application prospect. Therefore, the 1, 3-propylene glycol also has good market prospect.

At present, the production technology of 1, 3-propylene glycol mainly comprises a chemical synthesis method and a biological engineering method, and the chemical synthesis method comprises an acrolein hydration hydrogenation method, an ethylene oxide carbonylation method and a glycerol chemical method. Of these, the former two have been industrially produced in recent years. But the international market is predominantly monopolized by Degussa, germany, shell and dupont, usa. It is very important to fill the blank of domestic industrial production as soon as possible.

In the research of producing 1, 3-propylene glycol by hydration and hydrogenation of acrolein, the inventor finds that aqueous solution of acrolein, 3-hydroxypropionaldehyde and a small amount of acetaldehyde can be obtained after hydration reaction, and if the acrolein and the 3-hydroxypropionaldehyde can not be completely separated, the selectivity and the service life of a subsequent hydrogenation catalyst can be influenced; if acrolein and acetaldehyde cannot be completely separated, acetaldehyde will continuously accumulate in the hydration system along with the recycling of acrolein, thereby affecting the selectivity of the hydration reaction and the service life of the catalyst.

Therefore, how to separate and recycle unreacted acrolein with high efficiency and energy conservation is important for industrial production. If the catalyst can be reasonably utilized, not only can various investment costs and operation costs be saved, but also the service life of the hydration catalyst can be prolonged, and the conversion rate and the selectivity of the reaction can be ensured.

Disclosure of Invention

In order to solve the technical problems, the invention provides a method for separating and recycling acrolein in the process of preparing 1, 3-propylene glycol, the method adopts a rectifying tower to separate 3-hydroxypropionaldehyde so as to meet the requirement of subsequent hydrogenation reaction, applies a steam stripping method to the separation of acetaldehyde and acrolein, has simple process, convenient operation, less equipment investment and low energy consumption, can completely separate a small amount of acetaldehyde carried in a system, is convenient for recycling an acrolein solution, avoids the influence on the selectivity of hydration reaction, prolongs the service life of a hydration catalyst, and simultaneously improves the recovery rate of the acrolein.

The specific technical scheme of the invention is as follows: a method for separating and recycling acrolein in a process of preparing 1, 3-propylene glycol comprises the following steps: adding 0.1-0.15 wt% of polymerization inhibitor into the acrolein solution in a seasoning tank to obtain a raw material liquid for hydration reaction; introducing the raw material liquid into a hydration reactor for hydration reaction; discharging a reaction product containing acrolein, water, 3-hydroxypropionaldehyde and acetaldehyde from the upper end of the hydration reactor, and separating the acrolein from the 3-hydroxypropionaldehyde in an acrolein rectifying tower; discharging the separated 3-hydroxypropionaldehyde solution from the bottom of the acrolein rectifying tower and allowing the solution to enter a subsequent hydrogenation reaction unit; discharging separated steam from the tower top, mixing the steam with a polymerization inhibitor solution containing 0.03-0.07wt% of acrolein steam (to prevent self-polymerization of the tower top due to overhigh concentration of acrolein), atomizing, condensing in two stages, partially refluxing obtained condensate to an acrolein rectifying tower, partially conveying the condensate to a blending tank for blending, vacuumizing obtained non-condensable gas, incorporating 0.15-0.2 wt% of polymerization inhibitor, and then entering an acrolein recovery tower from the middle part in a gas phase state; after steam stripping in the acrolein recovery tower, continuously discharging the obtained acrolein aqueous solution from the tower kettle and refluxing to the blending tank for blending, collecting the obtained acetaldehyde liquid from the tower top, condensing and collecting.

Compared with the traditional separation process, the technical scheme of the invention adopts the rectifying tower to separate the 3-hydroxypropionaldehyde, so that the requirement of the subsequent hydrogenation reaction is met, the steam stripping method is applied to the separation of the acetaldehyde and the acrolein, the process is simple, the operation is convenient, the equipment investment is low, the energy consumption is low, a small amount of acetaldehyde carried in the system can be thoroughly separated, the recovery and the utilization of an acrolein solution are convenient, the influence on the selectivity of the hydration reaction is avoided, the service life of a hydration catalyst is prolonged, and the recovery rate of the acrolein is improved.

The acrolein recovery column is used to dilute the column acrolein solution in addition to reducing the acetaldehyde partial pressure and aiding in acetaldehyde separation. The reduction of the concentration of the acrolein in the tower kettle can slow down the self-polymerization of the acrolein, avoid the blockage of tower kettle equipment, pipelines, instruments and the like, and ensure the continuous production; meanwhile, the consumption of secondary desalted water is saved for the subsequent preparation of hydration raw material liquid. In addition, in the whole process, the polymerization inhibitor is added into the system from three different positions, so that the self-polymerization of the acrolein can be effectively prevented.

Preferably, the reaction temperature of the hydration reaction is 35-60 ℃.

Preferably, the top pressure of the acrolein rectifying tower is 18-20 kPa (A), the top temperature is 55-60 ℃, and the bottom temperature is 63-70 ℃.

Preferably, in the two-stage condensation, the temperature of a first-stage condensation outlet is controlled to be 20-25 ℃, and the temperature of a second-stage condensation outlet is controlled to be 15-18 ℃.

Preferably, the acrolein recovery tower is a plate tower, and the theoretical plate number of the acrolein recovery tower is 10-40, preferably 15-25; or the acrolein recovery tower is a packed tower and is of a two-section type, and the height of the upper section of packing is 2-10 m, preferably 4-6 m; the height of the lower section filler is 1-5 m, preferably 2-3 m.

Preferably, the stripping steam in the acrolein recovery tower is low-pressure steam of 0.2-0.4MPa, and the mass ratio of the stripping steam to the feed gas is 1: 6-2: 3, preferably 1: 5-1: 2. Or the acrolein recovery tower is an atmospheric tower, and the discharge temperature of a tower kettle of the acrolein recovery tower is 45-65 ℃, preferably 55-60 ℃; condensing the freezing water at the top of the tower, and controlling the temperature to be 10-20 ℃, preferably 14-18 ℃; the mass ratio of the extraction amount and the feeding amount at the top of the tower is 0.01-0.05, preferably 0.015-0.04.

Preferably, the polymerization inhibitor is hydroquinone.

Preferably, the method is realized by an acrolein separation and reuse device, which comprises a preparation tank, a hydration reactor, an acrolein rectifying tower, an atomizer, an acrolein rectifying tower condenser, an acrolein rectifying tower tail cooler, a vacuum pump, an acrolein recovery tower condenser and an acetaldehyde storage tank which are sequentially connected through pipelines; condensate outlets of the acrolein rectifying tower condenser and the acrolein rectifying tower tail cooler are connected with condensate storage tanks, and the condensate storage tanks are respectively communicated with the top of the preparation tank and the top of the acrolein rectifying tower; a non-condensable gas outlet of the acrolein rectifying tower tail cooler is communicated with the middle part of the acrolein recovery tower; the bottom of the acrolein recovery tower is communicated with a blending tank.

Preferably, the hydration reactor comprises:

the top surface and the bottom surface of the shell side cylinder are respectively provided with a tube plate; the tube plate is provided with tube holes; the central area and the edge area of the tube plate are respectively a central circular non-cloth tube area and an edge annular non-cloth tube area.

And the plurality of tubes are axially arranged in the shell pass cylinder body, catalysts are filled in the tubes, and two ends of each tube are respectively communicated with tube array holes of the tube plates on the top surface and the bottom surface of the shell pass cylinder body. Each row tube is internally provided with a plurality of high-rib inner fins which are axially arranged, and the inner fins are distributed on the cross section of the row tube at equal angles.

The circular guide plates and the annular guide plates are axially and alternately arranged in the shell pass cylinder to form a zigzag medium removing flow channel; the outer diameter of the circular guide plate corresponds to the inner diameter of the edge annular non-distribution pipe area, and the inner diameter of the annular guide plate corresponds to the outer diameter of the central circular non-distribution pipe area.

The media removing inlet and the media removing outlet are directly or indirectly arranged on the outer side wall of the shell pass cylinder.

And the upper end enclosure is covered on the top of the shell pass cylinder body, and a reactor feed inlet or a reactor discharge outlet is arranged on the upper end enclosure.

And the lower end enclosure is covered at the bottom of the shell pass cylinder body, and a reactor discharge port or a reactor feed port is arranged on the lower end enclosure.

And the feeding distribution plate is arranged between the top surface or the bottom surface of the shell pass cylinder and the feeding hole of the reactor.

The heat release of the hydration reaction for preparing the 3-hydroxypropionaldehyde by acrolein hydration is large, the requirement on the reaction temperature is strict, the allowable change interval of the reaction temperature is small, and the influence of the temperature on the proportion of side reaction and the selectivity of the 3-hydroxypropionaldehyde is large, so that the realization of uniform distribution and uniform heat transfer of reaction materials are key factors considered during the design of a reactor.

The working principle of the hydration reactor of the invention is as follows: filling a catalyst into the tubes, feeding a mixed solution of raw material acrolein and water from a feed inlet of the lower end enclosure or the upper end enclosure, moving the mixed solution away from the tube pass, uniformly distributing the mixed solution to inlets of the tubes through a feed distribution plate, allowing the mixed solution to flow through the catalyst in the tubes, and discharging the mixed solution from a discharge outlet of the lower end enclosure or the lower end enclosure; meanwhile, the heat removing medium enters the shell side from the medium removing inlet and is discharged from the medium removing outlet, so that heat exchange is realized.

The hydration reactor with the structure has the characteristics and the technical effects that:

firstly, a plurality of axially arranged inner fins are arranged in the tubes, and the inner fins are distributed on the cross section of the tubes at equal angles. The inner fins are in close contact with the catalyst in the tubes, so that reaction heat can be quickly transferred to the tube wall and taken away by a heat removing medium, and meanwhile, reaction materials are divided into a plurality of parts, so that the axial flow (the radial flow is limited) of the reaction materials is enhanced, the catalytic reaction is more uniform, and the temperature of each part of the catalyst is ensured to be uniform to the greatest extent; meanwhile, due to the existence of the inner fins, the heat transfer medium can be used as a heat transfer medium to multiply the comprehensive heat transfer coefficient, and is particularly suitable for chemical reactions with large reaction heat release or strict requirements on reaction temperature change intervals.

In addition, the center and the edge ring of the tube plate are respectively provided with a central circular non-tube distribution area and an edge ring non-tube distribution area; meanwhile, the outer diameter of the circular guide plate corresponds to the inner diameter of the edge circular non-fabric-area, and the inner diameter of the circular guide plate corresponds to the outer diameter of the central circular non-fabric-area. Under the flow guide of the circular guide plates and the annular guide plates which are arranged in a staggered mode at intervals in the shell pass, the heat removing medium mainly flows in the horizontal radial direction in the area corresponding to the pipe distribution area on the cross section, and quickly changes into vertical axial flow in the area corresponding to the pipe non-distribution area, so that a vortex area and a stagnant area are easily formed in the area, and the heat removing medium is a part with poor heat transfer performance. Therefore, the invention is purposefully not provided with the tubes in the non-tube distribution area, the volume utilization rate of the device is not reduced a lot, but the formation of vortex and stagnant flow can be effectively avoided, so that the reaction materials and the heat removing medium form single cross flow, the heat transfer is more uniform and efficient, the shell-side pressure drop is reduced, and the invention is beneficial to the defects.

In conclusion, the structure of the hydration reactor can realize the uniform flow and the uniform heat exchange of materials, and control the reaction temperature within a reasonable small range, thereby improving the conversion rate and the selectivity of the hydration reaction.

Preferably, the number of the inner fins is 2-16, and the fin ratio is 1.3-4.0.

Preferably, two ends of each column tube are respectively provided with a spring support, the inner end of each spring support is filled with inert ceramic balls (the height of each spring support covers the spring support), and the inert ceramic balls at the two ends are filled with catalysts.

The spring support is convenient to disassemble and assemble, plays a role of axial support and catalyst fixation together with the inert porcelain ball, and can realize uniform distribution of reaction materials on the cross section of the tube array.

Preferably, the area ratio of the edge annular non-cloth pipe area to the central circular non-cloth pipe area is 1-1.5: 1.

Preferably, one or more pairs of annular channels are arranged on the circumference of the outer side wall of the shell pass cylinder; media withdrawing through holes are uniformly distributed on the circumference of the outer side wall of the shell pass cylinder body corresponding to the annular channel. Wherein:

scheme provided with a pair of annular channels: the two annular channels are respectively arranged on the outer side wall of the shell pass cylinder body close to the top surface and the bottom surface, and the media withdrawing inlet and the media withdrawing outlet are respectively arranged on one annular channel.

Scheme with many pairs of annular passageways: the plurality of pairs of annular channels are sequentially arranged along the axial direction of the shell pass cylinder, and the media withdrawing inlet and the media withdrawing outlet are respectively arranged on one annular channel in each pair; and shell-side intermediate partitions for isolation (for dividing the interior of the shell-side cylinder into a plurality of chambers) are arranged at adjacent pairs of annular channels in the shell-side cylinder.

The medium removing through hole is used as a channel for the heat removing medium to enter the shell side. Because the flow resistance at the medium removing through hole is far larger than the resistance in the annular channel, the medium removing through holes with the same diameter are arranged, and the heat removing medium can uniformly enter the shell pass cylinder along the circumference of the shell pass cylinder.

In addition, the design of many pairs of annular channels, and every heat removal medium's import temperature is the same, how can show the increase heat transfer difference in temperature, effectively improve reaction temperature's controllability.

Preferably, a plurality of medium withdrawing inlets or medium withdrawing outlets are arranged on the outer side of the annular channel along the circumferential direction, and a feeding baffle is arranged between each medium withdrawing inlet and the shell side cylinder.

The design of a plurality of medium withdrawing inlets or medium withdrawing outlets and the arrangement of the feeding baffle plate at the inner side of each medium withdrawing inlet can ensure that the heat withdrawing media are uniformly distributed in the annular channel, thereby realizing the uniform feeding of the medium withdrawing at each part.

Preferably, the feeding baffle is arc-shaped or splayed.

Preferably, distribution plate through holes are uniformly distributed in the areas of the feed distribution plate, which do not correspond to the edge annular non-pipe distribution area and the central circular non-pipe distribution area.

Preferably, the upper end socket and the lower end socket are of a spherical cap end socket type.

The upper and lower seal heads of the hydration reactor are both spherical seal heads, the spherical seal heads are directly welded with the flange of the shell pass cylinder, and a pipe box straight cylinder section is not arranged, so that the retention time of reaction materials in the seal heads can be reduced, and the occurrence of self-polymerization reaction and side reaction of the materials can be reduced.

Preferably, the acrolein rectifying tower comprises a tower body, and the top, the side and the bottom of the tower body are respectively provided with a tower top gas phase outlet, a feeding hole and a tower bottom liquid phase outlet. The tower body is divided into a rectifying section positioned at the upper section and a stripping section positioned at the lower section by taking the feed inlet as a boundary; a plurality of guide three-dimensional jet tower plates and a plurality of efficient guide tower plates are arranged in the rectifying section from bottom to top; a plurality of guide composite three-dimensional jet tower plates are arranged in the stripping section; the high-efficiency guide tower plates, the guide three-dimensional spray tower plates and the guide composite three-dimensional spray tower plates are respectively arranged in a staggered mode to form a baffling channel.

The acrolein rectifying tower is divided into rectifying section and stripping section with the material inlet as boundary, the upper part of the rectifying section adopts high efficiency guide column plate, the lower part of the rectifying section adopts guide stereo jet column plate, and the stripping section adopts guide composite stereo jet column plate. The operating principle of the acrolein rectifying tower is as follows: the separated material liquid (the hydration liquid solution containing acrolein and 3-hydroxy propionaldehyde) enters the tower from the feed inlet, the mixed liquid and the gas phase rising from the tower bottom carry out mass transfer on the tower plate of the stripping section, and part of the uncondensed gas phase enters the reflux liquid on the tower plate of the rectifying section to continuously carry out gas-liquid mass transfer. The light component acrolein is obtained at the tower top and the water solution of the heavy component 3-hydroxypropionaldehyde is obtained at the tower bottom through the gas-liquid mass transfer process on the tower plates of the rectifying section and the stripping section.

The rectifying tower has high acrolein concentration and high polymerization possibility, so that the rectifying tower has high efficient guide sieve tray in the upper part and high guide stereo jet tray in the lower part. The concentration of acrolein in the stripping section is reduced, but the concentration of the hydration product 3-hydroxypropionaldehyde is increased, the operation temperature is higher, and the possibility of polymerization is higher, so that the guide composite three-dimensional injection column plate is selected, the mass transfer efficiency of the column plate is improved, and the column plate also has higher anti-blocking performance. In a word, the invention can solve the problem of polymerization of acrolein and 3-hydroxypropionaldehyde in the separation process by selecting different internal parts in the rectifying tower, thereby increasing the operation period of the rectifying tower.

Preferably, the efficient guide column plate is provided with guide holes, the edges of the guide holes are provided with guide plates protruding upwards, and the opening of a slot formed by the guide holes and the guide plates is consistent with the flowing direction of the liquid phase on the efficient guide column plate where the guide holes and the guide plates are located.

In the above structure, the guide hole and the guide plate are combined to form a slit, and the opening of the slit coincides with the flow direction of the liquid phase. During operation, the gas phase rising from the lower tray enters the liquid phase on the tray through the guide holes and the slits, and in the process, the direction of the gas phase ejected from the slits and the direction of the liquid flow are at an angle, and the gas phase can be divided into a horizontal direction and a vertical direction by a velocity decomposition method (see FIG. 4). The gas phase in the vertical direction vertically rises and passes through the liquid layer on the tower plate to form bubbling for mass transfer, and the horizontal direction is the same as the flowing direction of the liquid phase on the tower plate, so that the flowing of the liquid phase on the tower plate can be promoted, the reduction of the liquid phase gradient is promoted, the occurrence of back mixing is reduced, and the formation of a dead zone on the tower plate is prevented.

Preferably, the distribution density of the guide holes on the high-efficiency guide tower plate at the position close to the side wall of the tower body is greater than that of the center of the high-efficiency guide tower plate.

The reason for the above design is: the part close to the tower wall is a liquid phase flow slow zone on the tower plate, and a mass transfer dead zone is easily formed at the position. The arrangement number of the guide holes is increased, so that the liquid phase on the pushing plate can be pushed to flow, and mass transfer dead zones can be prevented.

Preferably, the guided solid spray tray comprises a tray and a cap; the central area of the tower plate and the position close to the side wall of the tower body are respectively provided with a large hole and a guide hole; each large hole upper cover is provided with the cap cover, the side wall of the cap cover is provided with sieve holes, and the top and the bottom of the side wall of the cap cover are circumferentially provided with an upper end slit and a lower end slit respectively; the edge of the guide hole is provided with a guide plate protruding upwards, and a hole seam opening formed by the guide hole and the guide plate is consistent with the flowing direction of the liquid phase on the tower plate where the guide hole and the guide plate are located.

In the structure, the tower plate is provided with a large hole (such as a round or rectangular hole), the hole is provided with a cap cover with a corresponding shape, the side surface of the upper end of the cap cover is provided with a sieve hole, the top and the bottom of the cap cover are provided with a slit, and the slit is arranged between the bottom of the cap cover and the tower plate. A number of guide holes are arranged close to the tower side wall. In the operation process, the gas phase of the lower tower plate enters the tower plate through the guide holes and the large holes on the plate respectively. The gas phase entering the guide holes and the slits promotes the reduction of the liquid phase gradient and reduces the occurrence of back-mixing, preventing the formation of dead zones on the tray. The gas phase entering the large holes on the plate lifts the liquid phase on the column plate from the slit at the lower end of the bottom of the cap cover, the liquid phase starts to be broken in the lifting process to form small liquid drops and is fully contacted and mixed with the gas phase, one part of the rising gas-liquid mixed phase is sprayed out of the cap cover through the sieve holes on the cap cover, and the other part of the rising gas-liquid mixed phase is sprayed out of the slit at the upper end of the top of the cap.

Preferably, the guide composite three-dimensional jet tower plate comprises a tower plate, a cap and a filler; the central area of the tower plate and the position close to the side wall of the tower body are respectively provided with a large hole and a guide hole; each large hole upper cover is provided with the cap cover, the filler is filled at the top of the cap cover, sieve holes are distributed on the side wall of the cap cover, and the top and the bottom of the side wall of the cap cover are circumferentially provided with an upper end slit and a lower end slit respectively; the edge of the guide hole is provided with a guide plate protruding upwards, and a hole seam opening formed by the guide hole and the guide plate is consistent with the flowing direction of the liquid phase on the tower plate where the guide hole and the guide plate are located.

The difference between the guiding composite stereo jet tower plate and the guiding stereo jet tower plate is that a packing layer is additionally arranged at the upper end of a cap cover, a part of liquid phase entering the cap cover from a slit at the lower end of the bottom of the cap cover is sprayed out of the cap cover from a sieve hole after being crushed into small liquid drops, and the other part of liquid phase enters the packing layer at the upper end of the cap cover to complete mass transfer of gas phase and liquid phase.

Preferably, the cross section of the guide plate is an arc shape with an inner arc surface facing the guide hole.

The arc-shaped arrangement can effectively change the ascending gas phase direction into the direction of nearly 45 degrees obliquely upwards.

Preferably, the filler is a metal open-cell plate corrugated filler or a metal open-cell wire mesh filler.

Preferably, the number of the high-efficiency guide tower plates accounts for 10-40%, preferably 15-30% of the total number of the tower plates; the number of the guide three-dimensional jet tower plates accounts for 5-35%, preferably 15-30% of the total number of the tower plates; the number of the guide composite three-dimensional jet tower plates accounts for 15-70%, preferably 30-60% of the total number of the tower plates.

The reason for the above allocation is: the high-efficiency guide sieve plate has good anti-blocking performance, but has poor mass transfer efficiency and high pressure drop, and is used in an area with higher acrolein concentration at the upper part of the rectification section; the anti-blocking performance of the guide three-dimensional injection tower is weaker than that of the guide three-dimensional injection tower, but the mass transfer efficiency is higher and the pressure drop is low, and the guide three-dimensional injection tower is used for the lower part of the rectifying section; the guide composite stereo jet tower plate has high mass transfer efficiency, great pressure drop and poor blocking resistance, and is used in the stripping section area.

Preferably, the aperture ratio of the high-efficiency guide column plate is 5-15%; the aperture ratio of the guide three-dimensional jet tower plate is 5-20%, and the aperture of the upper aperture of the cap cover is 3-15 mm; the aperture ratio of the guide composite three-dimensional jet column plate is 5-20%, the aperture of the upper aperture of the cap cover is 3-15 mm, and the thickness of the filler accounts for 20-40% of the height of the cap cover.

The aperture ratio is reasonable, the pressure drop of the tower plate can be increased if the aperture ratio is small, the temperature of the tower kettle is not favorably reduced, abnormal operations such as liquid leakage and the like are easily generated on the tower plate with large aperture ratio, the mass transfer efficiency of the tower plate is reduced, and the number of theoretical plates of the whole tower is reduced. Similarly, too small an aperture will increase the pressure drop of the column plate, and too large an aperture will be unfavorable for the contact of gas-liquid two-phase, reducing the mass transfer efficiency of the column plate.

Preferably, the upper side and the lower side of the notch edge of the high-efficiency guide tower plate, the guide three-dimensional spray tower plate and the guide composite three-dimensional spray tower plate are respectively provided with an overflow weir and a down-flow guide plate; wherein: the height of an overflow weir on the high-efficiency guide column plate is 5-45 mm, the height of an overflow weir on the guide three-dimensional spray column plate is 10-50 mm, and the height of an overflow weir on the guide composite three-dimensional spray column plate is 10-50 mm; the radial cross section of falling liquid deflector is the arc parallel with the tower body lateral wall, falls the liquid deflector and is cascaded downwardly extending and be close to the tower body lateral wall and arc length shortens.

Compared with the prior art, the invention has the beneficial effects that:

(1) compared with the traditional separation process, the method adopts the rectifying tower to separate the 3-hydroxypropionaldehyde, so that the requirement of the subsequent hydrogenation reaction is met, the steam stripping method is applied to the separation of the acetaldehyde and the acrolein, the process is simple, the operation is convenient, the equipment investment is low, the energy consumption is low, a small amount of acetaldehyde carried in a system can be thoroughly separated, the recovery and the utilization of an acrolein solution are convenient, the influence on the selectivity of the hydration reaction is avoided, the service life of a hydration catalyst is prolonged, and the recovery rate of the acrolein is improved.

(2) The hydration reactor can meet the hydration reaction characteristics of preparing 3-hydroxy-propionaldehyde by acrolein hydration, and has the advantages of uniform material distribution and heat transfer, high reaction efficiency, high production stability and low energy consumption. The hydration reactor of the invention is not only suitable for preparing 3-hydroxy propionaldehyde by acrolein hydration, but also suitable for other reactions with similar reaction conditions.

(3) The acrolein rectifying tower of the present invention selects different types of tower plates, the upper part of the rectifying section adopts the high-efficiency guide tower plate, the lower part of the rectifying section adopts the guide three-dimensional injection tower plate, and the stripping section adopts the guide composite three-dimensional injection tower plate. Compared with the rectifying device adopting the large-pore sieve plate in the prior art, the utility model has the advantages that the tower plate efficiency is improved by 100 percent, the operation elasticity is improved by more than 50 percent, and the processing load is improved by 100 percent. Compare with patent CN101033180A column plate compound mode, the anti stifled performance of device is better, and the guiding hole on the column plate promotes the evenly distributed of liquid layer on the board, reduces the formation in liquid phase dead zone, and the rectifying column top adopts high-efficient direction sieve mesh column plate to change the washing moreover.

Drawings

FIG. 1 is a schematic structural diagram of an acrolein separation and recycling device according to the present invention;

FIG. 2 is a front cross-sectional view of a hydration reactor of the present invention;

FIG. 3 is a cross-sectional view of a tube array in a hydration reactor in accordance with the present invention;

FIG. 4 is a longitudinal sectional view of a tube array in a hydration reactor in accordance with the present invention;

FIG. 5 is a top view of a tube sheet in a hydration reactor of the present invention;

FIG. 6 is a cross-sectional view of a shell-side cartridge and annular channel in a hydration reactor of the present invention;

FIG. 7 is a top view of a feed distribution plate in a hydration reactor of the present invention;

FIG. 8 is a schematic view of the internal structure of an acrolein rectifying column according to the present invention;

FIG. 9 is a schematic structural view of a guide three-dimensional spray tray in an acrolein rectification column according to the present invention;

FIG. 10 is a schematic structural view of a guided composite three-dimensional spray tray in an acrolein rectification column according to the present invention;

FIG. 11 is a schematic view of a guide hole and a guide plate in an acrolein rectification column according to the present invention;

FIG. 12 is a schematic view of the open area of one of the three-dimensional jet trays and the composite three-dimensional jet tray in the acrolein rectification column of the present invention.

The reference signs are:

the system comprises a preparation tank 1, a hydration reactor 2, an acrolein rectifying tower 3, an atomizer 4, an acrolein rectifying tower condenser 5, an acrolein rectifying tower tail cooler 6, a vacuum pump 7, an acrolein recovery tower 8, an acrolein recovery tower condenser 9, an acetaldehyde storage tank 10 and a condensate storage tank 11;

the device comprises a shell side cylinder 1000, a tube array 1001, a circular guide plate 1002, an annular guide plate 1003, a medium removing inlet 1004, a medium removing outlet 1005, an upper seal head 1006, a lower seal head 1007, a reactor feed inlet 1008, a reactor discharge outlet 1009, a feed distribution plate 1010, an annular channel 1011, a tube plate 1012, a tube array hole 1013, a central circular non-tube distribution area 1014, an edge annular non-tube distribution area 1015, a medium removing through hole 1016, a middle partition plate 1017, a feed baffle 1018, a spring support 1019, inert porcelain balls 1020, inner fins 1021 and distribution plate through holes 1022;

the tower body 100, a gas phase outlet 101 at the top of the tower, a feed inlet 102, a liquid phase outlet 103 at the bottom of the tower, a guide three-dimensional spray tray 104, a high-efficiency guide tray 105, a guide composite three-dimensional spray tray 106, a guide hole 107, a guide plate 108, a tray 109, a cap 110, a large hole 111, a sieve hole 112, an upper end slit 113, a lower end slit 114, a filler 115, an overflow weir 116 and a downcomer guide plate 117.

Detailed Description

The present invention will be further described with reference to the following examples.

General examples

A method for separating and recycling acrolein in a process of preparing 1, 3-propylene glycol comprises the following steps: adding 0.1-0.15 wt% of polymerization inhibitor into the acrolein solution in a seasoning tank to obtain a raw material liquid for hydration reaction; introducing the raw material liquid into a hydration reactor, and carrying out hydration reaction at 35-60 ℃; discharging a reaction product containing acrolein, water, 3-hydroxypropionaldehyde and acetaldehyde from the upper end of the hydration reactor, and separating the acrolein and the 3-hydroxypropionaldehyde in an acrolein rectifying tower, wherein the tower top pressure of the acrolein rectifying tower is 18-20 kPa (A), the tower top temperature is 55-60 ℃, and the tower kettle temperature is 63-70 ℃; discharging the separated 3-hydroxypropionaldehyde solution from the bottom of the acrolein rectifying tower and allowing the solution to enter a subsequent hydrogenation reaction unit; discharging steam obtained by separation from the tower top, mixing the steam with a polymerization inhibitor solution containing 0.03-0.07wt% of acrolein steam, atomizing, then carrying out two-stage condensation (the temperature of a first-stage condensation outlet is controlled to be 20-25 ℃, the temperature of a second-stage condensation outlet is controlled to be 15-18 ℃), partially refluxing the obtained condensate to an acrolein rectifying tower, partially conveying the condensate to a blending tank for blending, vacuum-pumping the obtained non-condensable gas, incorporating 0.15-0.2 wt% of the polymerization inhibitor, and then entering an acrolein recovery tower from the middle part in a gas phase state; after steam stripping in the acrolein recovery tower, continuously discharging the obtained acrolein aqueous solution from the tower kettle and refluxing to the blending tank for blending, collecting the obtained acetaldehyde liquid from the tower top, condensing and collecting.

Wherein the acrolein recovery tower is a plate tower, and the theoretical plate number of the acrolein recovery tower is 10-40, preferably 15-25; or the acrolein recovery tower is a packed tower and is in a two-section type, and the height of the upper section of packing is 2-10 m, preferably 4-6 m; the height of the lower section filler is 1-5 m, preferably 2-3 m.

The stripping steam in the acrolein recovery tower is low-pressure steam of 0.2-0.4MPa, and the mass ratio of the stripping steam to the feed gas is 1: 6-2: 3, preferably 1: 5-1: 2; or the acrolein recovery tower is an atmospheric tower; the discharge temperature of the tower kettle of the acrolein recovery tower is 45-65 ℃, and the preferable temperature is 55-60 ℃; condensing the freezing water at the top of the tower, and controlling the temperature to be 10-20 ℃, preferably 14-18 ℃; the mass ratio of the extraction amount and the feeding amount at the top of the tower is 0.01-0.05, preferably 0.015-0.04.

Preferably, the polymerization inhibitor is hydroquinone.

As shown in fig. 1, an acrolein separation and recycling device comprises a preparation tank 1, a hydration reactor 2, an acrolein rectifying tower 3, an atomizer 4, an acrolein rectifying tower condenser 5, an acrolein rectifying tower tail cooler 6, a vacuum pump 7, an acrolein recovering tower 8, an acrolein recovering tower condenser 9 and an acetaldehyde storage tank 10 which are connected in sequence through pipelines. Condensate outlets of the acrolein rectifying tower condenser and the acrolein rectifying tower tail cooler are connected with a condensate storage tank 11, and the condensate storage tank is respectively communicated with the top of the preparation tank and the top of the acrolein rectifying tower; a non-condensable gas outlet of the acrolein rectifying tower tail cooler is communicated with the middle part of the acrolein recovery tower; the bottom of the acrolein recovery tower is communicated with a blending tank.

As shown in fig. 2, the hydration reactor includes:

the shell-side cylinder 1000 has tube sheets 1012 on the top and bottom; tube arraying holes 1013 are distributed on the tube plate; the central region and the edge region of the tube sheet are a central circular non-tube distribution region 1014 and an edge annular non-tube distribution region 1015 (shown in fig. 5), respectively, and the areas of the central circular non-tube distribution region and the edge annular non-tube distribution region are equal.

And the plurality of tubes 1001 are axially arranged in the shell pass cylinder, and two ends of each tube are respectively communicated with tube array holes of tube plates on the top surface and the bottom surface of the shell pass cylinder. Spring supports 1019 (the inner end is in a conical shape) are respectively arranged at two ends of each row tube, inert ceramic balls 1020 are filled at the inner ends of the spring supports, and a catalyst is filled between the inert ceramic balls at the two ends (as shown in fig. 4). In addition, each row of tubes is provided with 6 inner fins 1021 arranged axially, and the fin ratio is 2.1. The inner fins are distributed at equal angles on the cross section of the tube array (as shown in figure 3). Three groups of multi-point armored thermocouples are arranged in the tube nest to measure the temperature of the catalyst bed layer, two groups of thermocouples are arranged on the shell pass along the axial height, and three thermocouples in each group are uniformly distributed along the circumferential direction of the outer diameter of the cylinder body and are used for measuring the temperature of a heat removing medium (not shown in the thermocouple figure). And the shell side intermediate partition 1017 is arranged in the shell side cylinder body and separates the shell side into two chambers. A pair of annular channels 1011 (two annular channels in each pair) is respectively arranged on the circumference of the outer side wall of each chamber, and 2 media withdrawing inlets 1004 and media withdrawing outlets 1005 (the media withdrawing inlets are positioned on one side far away from the feed inlet) are respectively arranged on the two annular channels in each pair; and an arc-shaped feeding baffle 1018 is arranged between each medium withdrawing inlet and the shell pass cylinder. And 24 medium withdrawing through holes 1016 (shown in fig. 6) with the same diameter are uniformly distributed on the circumference of the outer side wall of the shell-side cylinder body corresponding to the annular channel.

Each cavity in the shell pass cylinder is respectively provided with 2

circular guide plates

1002 and 3 annular guide plates 1003 which are axially and alternately arranged in the shell pass cylinder to form a zigzag medium removing flow channel; the outer diameter of the circular guide plate is the same as the inner diameter of the edge annular non-pipe distribution area, and the inner diameter of the annular guide plate is the same as the outer diameter of the central circular non-pipe distribution area.

An upper seal head 1006 (of a spherical cap seal head type) covers the top of the shell pass cylinder, and a reactor discharge hole 1009 is arranged on the upper seal head.

And a lower end enclosure 1007 (of a spherical cap type) is covered at the bottom of the shell pass cylinder, and a reactor feed port 1008 is arranged on the lower end enclosure.

And the feeding distribution plate 1010 is arranged between the top surface or the bottom surface of the shell pass cylinder and the feeding hole of the reactor. Distribution plate through holes 1022 (shown in fig. 7) are uniformly distributed in the feed distribution plate in the areas not corresponding to the edge annular non-pipe distribution area and the central circular non-pipe distribution area.

As shown in fig. 8, the acrolein rectifying column comprises a column body 100, wherein a top gas phase outlet 101, a feed inlet 102 and a bottom liquid phase outlet 103 are respectively arranged at the top, the side and the bottom of the column body. The tower body is divided into a rectifying section positioned at the upper section and a stripping section positioned at the lower section by taking the feed inlet as a boundary; a plurality of guide three-dimensional jet tower plates 104 and a plurality of efficient guide tower plates 105 are arranged in the rectifying section from bottom to top; a plurality of guide composite three-dimensional jet tower plates 106 are arranged in the stripping section; the high-efficiency guide tower plates, the guide three-dimensional spray tower plates and the guide composite three-dimensional spray tower plates are respectively arranged in a staggered mode to form a baffling channel.

Wherein:

the efficient guide tower plate is provided with guide holes 107 (the opening rate is 5-15%), as shown in fig. 11, the edges of the guide holes are provided with guide plates 108 protruding upwards, and the opening of a hole seam formed by the guide holes and the guide plates is consistent with the flowing direction of a liquid phase on the efficient guide tower plate where the guide holes and the guide plates are located. The distribution density of the guide holes on the efficient guide tower plate close to the side wall of the tower body is greater than that of the center of the efficient guide tower plate.

As shown in FIG. 9, the guided solid jet tray comprises a tray 109 and a cap 110; as shown in fig. 12, the central area of the tower plate and the position close to the side wall of the tower body are respectively provided with a large hole 111 and a guide hole, and the opening rate is 5-20%; each large-hole upper cover is provided with the cap cover, the side wall of each cap cover is provided with a sieve pore 112 (the pore diameter is 3-15 mm), and the top and the bottom of the side wall of each cap cover are circumferentially provided with an upper end slit 113 and a lower end slit 114 respectively; the edge of the guide hole is provided with a guide plate protruding upwards, and a hole seam opening formed by the guide hole and the guide plate is consistent with the flowing direction of the liquid phase on the tower plate where the guide hole and the guide plate are located.

As shown in FIG. 10, the guided composite three-dimensional spray tray comprises a tray, a cap and packing 115 (metal open-plate corrugated packing or metal open-wire mesh packing); the central area of the tower plate and the position close to the side wall of the tower body are respectively provided with a large hole and a guide hole, and the opening rate is 5-20%; each large hole upper cover is provided with the cap cover, the top of the cap cover is filled with the filler (the thickness accounts for 20-40% of the height of the cap cover), the side wall of the cap cover is provided with sieve pores (the pore diameter is 3-15 mm), and the top and the bottom of the side wall of the cap cover are circumferentially provided with an upper end slit and a lower end slit respectively; the edge of the guide hole is provided with a guide plate protruding upwards, and a hole seam opening formed by the guide hole and the guide plate is consistent with the flowing direction of the liquid phase on the tower plate where the guide hole and the guide plate are located.

In the above structure, the cross section of the guide plate is an arc shape in which the intrados faces the guide hole. The number of the efficient guide tower plates accounts for 10-40%, preferably 15-30% of the total number of the tower plates; the number of the guide three-dimensional jet tower plates accounts for 5-35%, preferably 15-30% of the total tower plates; the number of the guide composite three-dimensional jet tower plates accounts for 15-70%, preferably 30-60% of the total number of the tower plates.

The upper side and the lower side of the notch edge of the high-efficiency guide tower plate, the guide three-dimensional spray tower plate and the guide composite three-dimensional spray tower plate are respectively provided with an overflow weir 116 and a down-flow guide plate 117; wherein: the height of an overflow weir on the high-efficiency guide column plate is 5-45 mm, the height of an overflow weir on the guide three-dimensional spray column plate is 10-50 mm, and the height of an overflow weir on the guide composite three-dimensional spray column plate is 10-50 mm; the radial cross section of falling liquid deflector is the arc parallel with the tower body lateral wall, falls the liquid deflector and is cascaded downwardly extending and be close to the tower body lateral wall and arc length shortens.

Example 1

The flow shown in fig. 1 is adopted: in a seasoning tank, adding 0.1wt% of polymerization inhibitor hydroquinone into 15wt% of acrolein solution to obtain raw material liquid for hydration reaction; introducing the raw material liquid into a hydration reactor, and carrying out hydration reaction at the temperature of 45-55 ℃; discharging a reaction product containing acrolein, water, 3-hydroxypropionaldehyde and acetaldehyde from the upper end of the hydration reactor, and separating the acrolein and the 3-hydroxypropionaldehyde in an acrolein rectifying tower, wherein the tower top pressure of the acrolein rectifying tower is 18-20 kPa (A), the tower top temperature is 55-60 ℃, and the tower kettle temperature is 63-70 ℃; discharging the separated 3-hydroxypropionaldehyde solution (the content of acrolein is 37 ppm) from the bottom of an acrolein rectifying tower into a subsequent hydrogenation reaction unit; discharging steam obtained by separation from the tower top, mixing the steam with a polymerization inhibitor solution containing 0.05wt% of acrolein steam, atomizing, then carrying out two-stage condensation (the temperature of a first-stage condensation outlet is controlled to be 20-25 ℃, the temperature of a second-stage condensation outlet is controlled to be 15-18 ℃), converting 77% of the steam into condensate, partially refluxing to an acrolein rectifying tower, partially conveying to a blending tank for blending, vacuum-pumping 23% of non-condensable gas (containing 1% of acetaldehyde), merging 0.2wt% of polymerization inhibitor, and then entering an acrolein recovery tower from the middle part in a gas phase state (the flow is 240 kg/h); after steam stripping in the acrolein recovery tower, continuously discharging the obtained acrolein aqueous solution from the tower kettle and refluxing to the blending tank for blending, collecting the obtained acetaldehyde liquid from the tower top, condensing and collecting.

Wherein the acrolein recovery column has a theoretical plate number of 15, is fed from the 11 th plate, has an overhead pressure of normal pressure, and is fed with low-pressure steam of 0.3MPa from the bottom at a flow rate of 48 kg/h. The tower bottom discharge is directly injected into an acrolein solution preparation tank for recycling, the tower top steam is condensed by an acrolein recovery tower condenser, and part of the tower top steam is extracted to an acetaldehyde storage tank. When the ratio of the liquid phase extraction amount and the feeding amount of the tower top is 0.015, the content of acetaldehyde in the acrolein solution at the tower bottom is reduced to 730ppm, the recovery rate of the acrolein is 99.3 percent, and the energy consumption required by separation is 34.12 kw.

As shown in fig. 2, the hydration reactor includes:

the top surface and the bottom surface of the shell side cylinder body 1 are respectively provided with a tube plate 101; the tube plate is provided with tube array holes 102; the central area and the edge area of the tube plate are respectively a central circular non-tube distribution area 103 and an edge annular non-tube distribution area 104 (as shown in fig. 5), and the areas of the central circular non-tube distribution area and the edge annular non-tube distribution area are equal.

And the plurality of tubes 2 are axially arranged in the shell pass cylinder, and two ends of each tube are respectively communicated with tube array holes of the tube plates on the top surface and the bottom surface of the shell pass cylinder. Spring supports 201 (the inner end is in a conical shape) are respectively arranged at two ends of each row tube, the inner ends of the spring supports are filled with inert ceramic balls 202, and catalysts are filled between the inert ceramic balls at the two ends (as shown in fig. 4). In addition, each row of tubes is provided with 6 axially arranged inner fins 203, and the fin ratio is 2.1. The inner fins are distributed at equal angles on the cross section of the tube array (as shown in figure 3). Three groups of multi-point armored thermocouples are arranged in the tube nest to measure the temperature of the catalyst bed layer, two groups of thermocouples are arranged on the shell pass along the axial height, and three thermocouples in each group are uniformly distributed along the circumferential direction of the outer diameter of the cylinder body and are used for measuring the temperature of a heat removing medium (not shown in the thermocouple figure).

And the shell side intermediate partition plate 106 is arranged in the shell side cylinder body and separates the shell side into two chambers. A pair of annular channels 12 (each pair of two annular channels) is respectively arranged on the circumference of the outer side wall of each chamber, and 2 media withdrawing inlets and media withdrawing outlets (the media withdrawing inlets are positioned on one side far away from the feed inlet) are respectively arranged on the two annular channels in each pair; and an arc-shaped feeding baffle 107 is arranged between each media withdrawing inlet and the shell pass cylinder. 24 medium withdrawing through holes 105 (as shown in fig. 6) with the same diameter are uniformly distributed on the circumference of the outer side wall of the shell-side cylinder body corresponding to the annular channel.

Each cavity in the shell pass cylinder is respectively provided with 2

circular guide plates

3 and 3 annular guide plates 4 which are axially and alternately arranged in the shell pass cylinder to form a zigzag medium removing flow channel; the outer diameter of the circular guide plate is the same as the inner diameter of the edge annular non-pipe distribution area, and the inner diameter of the annular guide plate is the same as the outer diameter of the central circular non-pipe distribution area.

And the upper end enclosure 7 (in a spherical cap end enclosure type) covers the top of the shell pass cylinder, and a reactor discharge port 10 is arranged on the upper end enclosure.

And the lower end enclosure 8 (in a spherical cap type) is covered at the bottom of the shell pass cylinder body, and a reactor feed port 9 is arranged on the lower end enclosure.

And the feeding distribution plate 11 is arranged between the top surface or the bottom surface of the shell pass cylinder and the feeding hole of the reactor. The feed distribution plate is uniformly distributed with distribution plate through holes 1101 (shown in fig. 7) in the areas of the feed distribution plate not corresponding to the edge annular non-pipe distribution area and the central circular non-pipe distribution area.

As shown in fig. 8, the acrolein rectification column comprises a column body 100 (column height 8000 mm, column diameter 500 mm), wherein the top, side and bottom of the column body are respectively provided with a top gas phase outlet 101, a feed inlet 102 and a bottom liquid phase outlet 103. The tower body is divided into a rectifying section positioned at the upper section and a stripping section positioned at the lower section by taking the feed inlet as a boundary; 8 guide three-

dimensional jet trays

104 and 2 high-efficiency guide trays 105 are arranged in the rectifying section from bottom to top; the stripping section is internally provided with 4 guide composite three-dimensional jet trays 106; the high-efficiency guide tower plates, the guide three-dimensional spray tower plates and the guide composite three-dimensional spray tower plates are respectively arranged in a staggered mode to form a baffling channel.

Wherein:

the efficient guide column plate is provided with guide holes 107 (the aperture is 10 × 20mm rectangular open holes, the aperture ratio of the guide holes is 2%), as shown in fig. 11, the edge of each guide hole is provided with a guide plate 108 protruding upwards, the height of each protrusion is 3mm, and the opening of a hole seam formed by the guide holes and the guide plates is consistent with the flow direction of the liquid phase on the efficient guide column plate where the guide holes and the guide plates are located. The distribution density of the guide holes on the efficient guide tower plate close to the side wall of the tower body is greater than that of the center of the efficient guide tower plate.

As shown in FIG. 9, the guided solid jet tray comprises a tray 109 and a cap 110; as shown in fig. 12, the central region of the tray and the position close to the tower side wall are respectively provided with large holes 111 (rectangular holes with a pore size of 60 × 180 mm) and guiding holes 1 (rectangular holes with a pore size of 10 × 20 mm), and the total opening rate is 15%; each large hole upper cover is provided with the cap cover, the side wall of the cap cover is provided with sieve holes 112 (the aperture is 6 mm), and the top and the bottom of the side wall of the cap cover are circumferentially provided with an upper end slit 113 and a lower end slit 114 respectively; the edge of the guide hole is provided with a guide plate protruding upwards, and a hole seam opening formed by the guide hole and the guide plate is consistent with the flowing direction of the liquid phase on the tower plate where the guide hole and the guide plate are located.

As shown in FIG. 10, the guided composite three-dimensional jet tray comprises a tray, a cap and packing 115 (metal apertured plate corrugated packing); the central area of the tower plate and the position close to the side wall of the tower body are respectively provided with a large hole and a guide hole, and the opening rate is 15%; each large hole upper cover is provided with the cap cover, the top of the cap cover is filled with the filler (the thickness accounts for 30% of the total height of the cap cover), the side wall of the cap cover is provided with sieve pores (the pore diameter is 6 mm), and the top and the bottom of the side wall of the cap cover are circumferentially provided with an upper end slit and a lower end slit respectively; the edge of the guide hole is provided with a guide plate protruding upwards, and a hole seam opening formed by the guide hole and the guide plate is consistent with the flowing direction of the liquid phase on the tower plate where the guide hole and the guide plate are located.

The upper side and the lower side of the notch edge of the high-efficiency guide tower plate, the guide three-dimensional spray tower plate and the guide composite three-dimensional spray tower plate are respectively provided with an overflow weir 116 and a down-flow guide plate 117; wherein: the height of an overflow weir on the high-efficiency guide tower plate is 15mm, the height of an overflow weir on the guide three-dimensional jet tower plate is 15mm, and the height of an overflow weir on the guide composite three-dimensional jet tower plate is 15 mm; the radial cross section of the down-flow guide plate is an arc parallel to the side wall of the tower body, and the down-flow guide plate extends downwards in a stepped mode and has an increasing arc diameter.

Comparative example 1

Similar to the scheme shown in FIG. 1, acrolein containing 1% by mass of acetaldehyde is separated by a conventional rectification method for recovering acrolein.

The material is fed from the middle part of the acrolein recovery tower, the flow is 240kg/h, the number of theoretical plates of the tower is 15, the material is fed from the 11 th plate, the pressure of the tower top is normal pressure, the reflux ratio is 50, and the ratio of the liquid phase extraction amount and the feeding amount of the tower top is 0.018. The content of acetaldehyde in the acrolein solution discharged from the column bottom was 720ppm, the recovery rate of acrolein was 99.3%, and the energy consumption required for separation was 67.74 kw.

Under the condition of equivalent separation purity, the energy consumption required by the stripping tower is 50.4 percent of that of the common rectifying tower.

Example 2

As in the flow shown in fig. 1: acrolein raw material, water and 0.1% polymerization inhibitor solution are mixed in a mixing tank to form 15% acrolein solution, which is pumped into the lower end of a hydration reactor, discharged from the upper end after reaction and enters an acrolein rectifying tower from the middle upper part of the tower. Controlling the pressure at the top of the tower to be 18-20 kPa (A), the temperature at the top of the tower to be 55-60 ℃ and the temperature at the bottom of the tower to be 63-70 ℃. The bottom discharge was a 3-hydroxypropanal solution with an acrolein content of 37 ppm. 77% of the overhead vapor was condensed, part was refluxed into the column, part was pumped into a blending tank for blending, and 23% of the gas was directly fed from the middle of the acrolein recovery column by a vacuum pump, wherein the acetaldehyde content was 5% (by mass) at a flow rate of 240kg/h, the number of theoretical plates was 15, the feed was from the 11 th plate, the overhead pressure was atmospheric pressure, and low-pressure steam of 0.3MPa was fed from the bottom at a flow rate of 115 kg/h. The tower bottom discharge is directly injected into an acrolein solution preparation tank for recycling, the tower top steam is condensed by an acrolein recovery tower condenser, and part of the tower top steam is extracted to an acetaldehyde storage tank. When the ratio of the liquid phase output quantity of the tower top to the feed quantity is 0.035, the content of acetaldehyde in the acrolein solution discharged from the tower bottom is 608ppm, the recovery rate of the acrolein is 99.6 percent, and the energy consumption required by separation is 80.21 kw.

Comparative example 2

Similar to the scheme shown in FIG. 1, acrolein containing 5% by mass of acetaldehyde is separated by a conventional rectification method for recovering acrolein.

The material is fed from the middle part of the acrolein recovery tower, the flow is 240kg/h, the number of theoretical plates of the tower is 15, the material is fed from the 11 th plate, the pressure of the tower top is normal pressure, the reflux ratio is 35, and the ratio of the liquid phase extraction amount of the tower top to the feeding amount is 0.054. The content of acetaldehyde in the acrolein solution discharged from the tower bottom is 627ppm, the recovery rate of acrolein is 99.6 percent, and the energy consumption required by separation is 152.6kw at the moment.

Under the condition of equivalent separation purity, the energy consumption required by the stripping tower is 52.6 percent of that of the common rectifying tower.

The raw materials and equipment used in the invention are common raw materials and equipment in the field if not specified; the methods used in the present invention are conventional in the art unless otherwise specified.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and all simple modifications, alterations and equivalents of the above embodiments according to the technical spirit of the present invention are still within the protection scope of the technical solution of the present invention.

Claims

1. A method for separating and recycling acrolein in a process of preparing 1, 3-propylene glycol is characterized by comprising the following steps: adding 0.1-0.15 wt% of polymerization inhibitor into the acrolein solution in a seasoning tank to obtain a raw material liquid for hydration reaction; introducing the raw material liquid into a hydration reactor for hydration reaction; discharging a reaction product containing acrolein, water, 3-hydroxypropionaldehyde and acetaldehyde from the upper end of the hydration reactor, and separating the acrolein from the 3-hydroxypropionaldehyde in an acrolein rectifying tower; discharging the separated 3-hydroxypropionaldehyde solution from the bottom of the acrolein rectifying tower and allowing the solution to enter a subsequent hydrogenation reaction unit; discharging steam obtained by separation from the tower top, mixing the steam with a polymerization inhibitor solution containing 0.03-0.07wt% of acrolein steam, atomizing, condensing in two stages, refluxing part of the obtained condensate to an acrolein rectifying tower, conveying part of the condensate to a blending tank for blending, vacuumizing the obtained non-condensable gas, merging 0.15-0.2 wt% of polymerization inhibitor, and then feeding the non-condensable gas into an acrolein recovery tower from the middle part in a gas phase state; after steam stripping in the acrolein recovery tower, continuously discharging the obtained acrolein aqueous solution from the tower kettle and refluxing to the blending tank for blending, collecting the obtained acetaldehyde liquid from the tower top, condensing and collecting.

2. The method of claim 1, wherein:

the reaction temperature of the hydration reaction is 35-60 ℃;

the overhead pressure of the acrolein rectifying tower is 18-20 kPa (A), the overhead temperature is 55-60 ℃, and the tower kettle temperature is 63-70 ℃;

in the two-stage condensation, the temperature of a first-stage condensation outlet is controlled to be 20-25 ℃, and the temperature of a second-stage condensation outlet is controlled to be 15-18 ℃.

3. The method of claim 1, wherein:

the acrolein recovery tower is a plate tower, and the theoretical plate number of the acrolein recovery tower is 10-40; or

The acrolein recovery tower is a packed tower and is of a two-section type, and the height of the upper section of packing is 2-10 m; the height of the lower section filler is 1-5 m.

4. The method of claim 1, wherein:

steam stripping steam in the acrolein recovery tower is low-pressure steam of 0.2-0.4MPa, and the mass ratio of the steam stripping steam to the feed gas is 1: 6-2: 3; or

The acrolein recovery tower is an atmospheric tower;

the discharge temperature of the tower kettle of the acrolein recovery tower is 45-65 ℃; condensing the tower top by using chilled water, and controlling the temperature to be 10-20 ℃; the mass ratio of the extraction amount and the feeding amount at the top of the tower is 0.01-0.05.

5. The method of claim 1, wherein: the device is realized by an acrolein separation and recycling device, and comprises a preparation tank (1), a hydration reactor (2), an acrolein rectifying tower (3), an atomizer (4), an acrolein rectifying tower condenser (5), an acrolein rectifying tower tail cooler (6), a vacuum pump (7), an acrolein recovery tower (8), an acrolein recovery tower condenser (9) and an acetaldehyde storage tank (10) which are sequentially connected through pipelines; condensate outlets of the acrolein rectifying tower condenser and the acrolein rectifying tower tail cooler are connected with a condensate storage tank (11), and the condensate storage tank is respectively communicated with the top of the preparation tank and the top of the acrolein rectifying tower; a non-condensable gas outlet of the acrolein rectifying tower tail cooler is communicated with the middle part of the acrolein recovery tower; the bottom of the acrolein recovery tower is communicated with a blending tank.

6. The method of claim 5, wherein: the hydration reactor comprises:

the top surface and the bottom surface of the shell pass cylinder (1000) are respectively provided with a tube plate (1012); the tube plate is provided with tube array holes (1013); the central area and the edge area of the tube plate are respectively a central circular non-cloth area (1014) and an edge annular non-cloth area (1015);

the shell side tube body is provided with a plurality of tube arrays (1001) axially arranged in the shell side tube body, catalysts are filled in the tube arrays, and two ends of the tube arrays are respectively communicated with tube array holes of tube plates on the top surface and the bottom surface of the shell side tube body; a plurality of axially arranged inner fins (1021) are arranged in each row tube, and the inner fins are distributed on the cross section of the row tube at equal angles;

the circular guide plates (1002) and the annular guide plates (1003) are axially and alternately arranged in the shell pass cylinder to form a zigzag medium removing flow channel; the outer diameter of the circular guide plate corresponds to the inner diameter of the edge annular non-distribution pipe area, and the inner diameter of the annular guide plate corresponds to the outer diameter of the central circular non-distribution pipe area;

the media removing inlet (1004) and the media removing outlet (1005) are directly or indirectly arranged on the outer side wall of the shell side cylinder;

the upper sealing head (1006) is covered on the top of the shell pass cylinder body, and a reactor feeding hole (1008) or a reactor discharging hole (1009) is formed in the upper sealing head;

the lower end enclosure (1007) is covered at the bottom of the shell pass cylinder body, and a reactor discharge port or a reactor feed port is arranged on the lower end enclosure;

and the feeding distribution plate (1010) is arranged between the top surface or the bottom surface of the shell side cylinder body and the feeding hole of the reactor.

7. The method of claim 6, wherein:

spring supports (1019) are respectively arranged at two ends of each row tube, inert ceramic balls (1020) are filled at the inner ends of the spring supports, and catalysts are filled between the inert ceramic balls at the two ends;

the number of the inner fins is 2-16, and the fin ratio is 1.3-4.0;

the area ratio of the edge annular non-pipe distribution area to the central circular non-pipe distribution area is 1-1.5: 1.

8. The method of claim 6, wherein: one or more pairs of annular channels (1011) are arranged on the circumference of the outer side wall of the shell pass cylinder; media withdrawing through holes (1016) are uniformly distributed on the circumference of the outer side wall of the shell pass cylinder body corresponding to the annular channel; wherein:

scheme provided with a pair of annular channels: the two annular channels are respectively arranged on the outer side wall of the shell pass cylinder body close to the top surface and the bottom surface, and the media withdrawing inlet and the media withdrawing outlet are respectively arranged on one annular channel;

scheme with many pairs of annular passageways: the plurality of pairs of annular channels are sequentially arranged along the axial direction of the shell pass cylinder, and the media withdrawing inlet and the media withdrawing outlet are respectively arranged on one annular channel in each pair; and shell side intermediate clapboards (1017) are arranged at the adjacent and opposite annular passages in the shell side cylinder body for isolation.

9. The method of claim 8, wherein:

a plurality of media withdrawing inlets or media withdrawing outlets are arranged on the outer side of the annular channel along the circumferential direction, and a feeding baffle (1018) is arranged between each media withdrawing inlet and the shell side cylinder; the feeding baffle is arc-shaped or splayed;

distribution plate through holes (1022) are uniformly distributed in the areas of the feed distribution plate, which do not correspond to the edge annular non-pipe distribution area and the central circular non-pipe distribution area;

the upper end enclosure and the lower end enclosure are of a spherical cap type.

10. The method of claim 5, wherein: the acrolein rectifying tower comprises a tower body (100), wherein a tower top gas phase outlet (101), a feed inlet (102) and a tower bottom liquid phase outlet (103) are respectively arranged at the top, the side and the bottom of the tower body, and the tower body is divided into a rectifying section positioned at the upper section and a stripping section positioned at the lower section by taking the feed inlet as a boundary; a plurality of guide three-dimensional jet tower plates (104) and a plurality of efficient guide tower plates (105) are arranged in the rectifying section from bottom to top; a plurality of guide composite three-dimensional jet tower plates (106) are arranged in the stripping section; the efficient guide tower plates, the guide three-dimensional spray tower plates and the guide composite three-dimensional spray tower plates are respectively arranged in a staggered manner to form a baffling channel;

guide holes (107) are distributed on the high-efficiency guide column plate, guide plates (108) protruding upwards are arranged at the edges of the guide holes, and a hole seam opening formed by the guide holes and the guide plates is consistent with the flowing direction of a liquid phase on the high-efficiency guide column plate where the guide holes and the guide plates are located;

the guide three-dimensional spray tray comprises a tray (109) and a cap (110); the central area of the tower plate and the position close to the side wall of the tower body are respectively provided with a large hole (111) and a guide hole; each large hole upper cover is provided with the cap cover, the side wall of the cap cover is provided with a sieve mesh (112), and the top and the bottom of the side wall of the cap cover are circumferentially provided with an upper end slit (113) and a lower end slit (114) respectively; the edge of the guide hole is provided with a guide plate protruding upwards, and a slot opening formed by the guide hole and the guide plate is consistent with the flowing direction of the liquid phase on the tower plate where the guide hole and the guide plate are positioned;

the guide composite three-dimensional jet tower plate comprises a tower plate, a cap and a filler (115); the central area of the tower plate and the position close to the side wall of the tower body are respectively provided with a large hole and a guide hole; each large hole upper cover is provided with the cap cover, the filler is filled at the top of the cap cover, sieve holes are distributed on the side wall of the cap cover, and the top and the bottom of the side wall of the cap cover are circumferentially provided with an upper end slit and a lower end slit respectively; the edge of the guide hole is provided with a guide plate protruding upwards, and a hole seam opening formed by the guide hole and the guide plate is consistent with the flowing direction of the liquid phase on the tower plate where the guide hole and the guide plate are located.

11. The method of claim 10, wherein:

the section of the guide plate is arc-shaped with an inner arc surface facing the guide hole;

the distribution density of the guide holes on the efficient guide tower plate close to the side wall of the tower body is greater than that of the center of the efficient guide tower plate;

the filler is metal perforated plate corrugated filler or metal perforated wire mesh filler.

12. The method of claim 10, wherein:

the number of the efficient guide tower plates accounts for 10-40% of the total number of the tower plates;

the number of the guide three-dimensional jet tower plates accounts for 5-35% of the total tower plates;

the number of the guide composite three-dimensional jet tower plates accounts for 15-70% of the total tower plates;

the aperture ratio of the efficient guide column plate is 5-15%;

the aperture ratio of the guide three-dimensional jet tower plate is 5-20%, and the aperture of the upper aperture of the cap cover is 3-15 mm;

the aperture ratio of the guide composite three-dimensional jet column plate is 5-20%, the aperture of the upper aperture of the cap cover is 3-15 mm, and the thickness of the filler accounts for 20-40% of the height of the cap cover.

13. The method of claim 10, wherein: the upper side and the lower side of the notch edge of the high-efficiency guide tower plate, the guide three-dimensional spray tower plate and the guide composite three-dimensional spray tower plate are respectively provided with an overflow weir (116) and a down-flow guide plate (117); wherein: the height of an overflow weir on the high-efficiency guide column plate is 5-45 mm, the height of an overflow weir on the guide three-dimensional spray column plate is 10-50 mm, and the height of an overflow weir on the guide composite three-dimensional spray column plate is 10-50 mm; the radial cross section of falling liquid deflector is the arc parallel with the tower body lateral wall, falls the liquid deflector and is cascaded downwardly extending and be close to the tower body lateral wall and arc length shortens.