Preparation device and preparation method of hydroxypivalaldehyde

Abstract

The invention relates to the technical field of industrial preparation of hydroxypivalaldehyde, in particular to a hydroxypivalaldehyde preparation device and a preparation method thereof.The hydroxypivalaldehyde preparation device comprises a premixer, a tower reactor and a forced circulation pump, and a first reaction zone and a second reaction zone are arranged in the tower reactor and communicated through a plurality of downcomer distribution pipes; a discharge port at the bottom of the tower reactor is respectively connected with a discharge pipeline and a circulating pipeline I, the forced circulating pump is arranged on the circulating pipeline I, the circulating pipeline I is communicated with the plurality of nozzles, the circulating pipeline I is connected with a circulating pipeline II in parallel, and the circulating pipeline II is communicated with the circulating material inlet. According to the present invention, the mixing efficiency of the raw material and the catalyst can be substantially improved, the layering of the material is effectively avoided, the reaction time is ensured, the reaction circulation amount entering the second reaction zone and the first reaction zone is adjusted, the retention time and the reaction temperature of the circulation liquid in the reactor are controlled, the side reaction is reduced, and the HPA yield is improved.

Description

Technical Field

[0001] The invention relates to the technical field of industrial preparation of hydroxypivalaldehyde, in particular to a preparation device and a preparation method of hydroxypivalaldehyde. Background Art

[0002] 2.2-dimethyl-3-hydroxypropanal (commonly known as hydroxypivalaldehyde, referred to as HPA) is an intermediate product in the synthesis of 2.2-dimethyl-1,3-propanediol (commonly known as neopentyl glycol, referred to as NPG). In the entire NPG production process, most of the side reactions occur in the condensation reaction stage of isobutyraldehyde and formaldehyde under the action of organic base or aliphatic amine catalyst. The key to the reaction lies in whether the raw materials and catalysts involved in the reaction can be fully mixed according to the mass ratio, and there is no stratification of the raw materials, catalyst and reaction liquid. Whether the appropriate reaction temperature and reaction time can be controlled to reduce the disproportionation reaction of isobutyraldehyde and formaldehyde under alkaline conditions to generate corresponding acids and alcohols, and the acid and alcohol part generated by the disproportionation will undergo esterification reaction to obtain the corresponding esters, thereby reducing the yield of NPG products. In addition, a small amount of the main reaction product hydroxypivalaldehyde undergoes a disproportionation reaction under alkaline conditions to generate hydroxypivalic acid and neopentyl glycol. The generated neopentyl glycol is esterified with isobutyric acid and hydroxypivalic acid to generate the corresponding hydroxypivalic acid neopentyl glycol ester, referred to as HPN, which reduces the yield of NPG products and increases the difficulty of separating NPG tower products.

[0003] At present, in the overall preparation process of neopentyl glycol, the condensation section uses multiple reactors with stirring in series, or more than two containers are used for buffering, and multiple conveying equipment is used for forced circulation and mixing reaction. However, the forced circulation of multiple reaction equipment using agitators and conveying equipment has dead corners and wall flow, raw materials, catalysts and reaction liquids are not stratified, raw materials are not mixed sufficiently, and the concentrations in different areas or time periods vary greatly, resulting in reaction time and temperature being difficult to control or reaction residence time being too long, and side reactions increasing. In order to ensure a certain reaction time and mixing effect, a certain amount of kinetic energy and multiple equipment in series are required, resulting in small processing capacity, large floor space, high equipment investment, and high energy consumption. Summary of the invention

[0004] The invention aims to provide a preparation device and a preparation method of hydroxypivalaldehyde. Through the design of a premixer, a tower reactor, a forced circulation pump, a liquid level online analyzer, a circulation pipeline 1 and a circulation pipeline 2, the adequacy of mixing raw materials and catalysts is improved, the reaction time is guaranteed, the equipment investment and the floor area are reduced, and the height of the equipment is reduced. In the preparation process, the value of the hydroxypivalaldehyde of the reaction product is analyzed online by the liquid level online analyzer, the reaction circulation amount entering the second reaction zone and the first reaction zone is adjusted, and the reaction temperature of the circulating liquid is controlled by a heat exchanger to prevent excessive side reactions from being generated due to a long reaction time and a high temperature, thereby improving the yield of HPA and indirectly improving the subsequent product yield of NPG.

[0005] In order to solve the above technical problems, the present invention provides a preparation device of hydroxypivalaldehyde, comprising a premixer, a tower reactor and a forced circulation pump, wherein one end of the premixer is provided with a mixing inlet and a circulating material inlet, and the other end is provided with a mixing outlet, the mixing inlet has two and is symmetrically arranged on both sides of the circulating material inlet, the two mixing inlets are respectively connected to a mixing pipe, the mixing pipe is connected to a raw material feeding end, the mixing inlet is connected to the mixing outlet, a valve plate assembly is provided between the circulating material inlet and the mixing outlet, and the mixing outlet is connected to the top feed port of the tower reactor through a feed pipe;

[0006] The tower reactor is provided with a first reaction zone and a second reaction zone from top to bottom in sequence, the first reaction zone and the second reaction zone are connected through a plurality of downcomer distribution pipes, the first reaction zone is provided with multiple layers of mixed reaction components, each layer of the mixed reaction components is provided with a plurality of liquid outlets, and the liquid outlets of two adjacent layers are staggered, a plurality of nozzles are provided on the inner wall of the second reaction zone, a heat exchange member is provided below the second reaction zone, a plurality of medium inlets connected to the inner cavity of the second reaction zone are provided on the top of the heat exchange member, a plurality of medium outlets are provided at the bottom, and the plurality of medium outlets are connected to the bottom discharge port of the tower reactor, the bottom discharge port is respectively connected to a discharge pipe and a circulation pipe 1, the forced circulation pump is provided on the circulation pipe 1, the circulation pipe 1 is connected to a plurality of nozzles, a circulation pipe 2 is connected in parallel to the circulation pipe 1, and the circulation pipe 2 is connected to the circulation material inlet;

[0007] The circulation pipeline 1 and the circulation pipeline 2 are respectively provided with regulating valve 1 and regulating valve 2, and one side of the downcomer distribution pipe is provided with a liquid level online analyzer, and the liquid level online analyzer is connected with the regulating valve 1 and the regulating valve 2 through a control system.

[0008] Furthermore, the premixer comprises a feeding section, a mixing section, a reduced diameter section, a horizontal section and an expanded diameter section connected in sequence from left to right, the feeding section is composed of a straight section and a trapezoidal section, the circulating material inlet is arranged on one side of the straight section, and the two mixing inlets are obliquely and symmetrically arranged on the trapezoidal section;

[0009] The mixing section is cylindrical and has a group of fixed brackets therein, an inner tube and an outer tube are installed between the fixed brackets, the inner tube is located inside the outer tube and a first flow channel is provided between the inner tube, the valve plate assembly is installed on the inner tube and controls the opening and closing of the circulating material inlet, a second flow channel is provided between the outer tube and the inner wall of the mixing section, and the outer walls of the inner tube and the outer tube are provided with cross-staggered left-handed fins.

[0010] Furthermore, the valve plate assembly includes a connecting rod, a valve plate and a spring, one end of the connecting rod is inserted into the inner tube, and the other end is sleeved with the valve plate. The spring is sleeved on the connecting rod and arranged between the valve plate and the inner tube, and the end of the connecting rod away from the inner tube is provided with a limiting bolt for limiting the separation of the valve plate. The valve plate abuts against the inner wall of the straight tube section to block the circulating material inlet; under the action of high-pressure circulating fluid, the valve plate is pushed to compress the spring and separate from the inner wall of the straight tube section, thereby realizing the connection between the circulating material inlet and the mixing outlet.

[0011] Furthermore, each layer of the mixing reaction component includes a plurality of dovetail-shaped components connected to each other, an air hole 1 is provided on the top of each dovetail-shaped component, and the liquid outlet is provided between two adjacent dovetail-shaped components. The air hole 1 of the lower layer is located below the liquid outlet of the upper layer, and the liquid outlet of the bottom layer is staggered with the liquid inlet at the top of the downcomer distribution pipe.

[0012] Furthermore, several of the downcomer distribution pipes are installed between the first reaction zone and the second reaction zone through a tower plate, and several air holes are opened on the tower plate. A coil is provided above the tower plate, and the coil is wound around the outside of the several downcomer distribution pipes and is lower than the top of the downcomer distribution pipes.

[0013] Furthermore, a liquid inlet is provided at the top of the downcomer distribution pipe, and the liquid inlet is composed of a plurality of circumferentially arranged V-shaped plum blossom ports. A plurality of guide fins are provided on the inner wall of the downcomer distribution pipe, and each of the guide fins is arranged below the corresponding V-shaped plum blossom port, and a plurality of the guide fins are arranged in a spiral shape, and each of the guide fins has a structure that is wide at the top and narrow at the bottom. A plurality of layers of overflow holes are opened on the outer wall of the downcomer distribution pipe, and the aperture of the overflow holes is arranged to decrease from bottom to top.

[0014] Furthermore, several of the nozzles are annularly installed on the second reaction zone, and an annular channel connected to the several nozzles is provided on the second reaction zone. The annular channel is connected to the circulation pipe 2, and the nozzle of the nozzle is a reduced diameter fish mouth shape and the angle between the nozzle and the horizontal liquid surface is 25 to 45 degrees, and a spiral tangent groove is provided in the nozzle.

[0015] Furthermore, the heat exchange element is a spiral heat exchanger, and several medium inlets and medium outlets are connected by spiral tubes. A liquid storage cavity is provided between the medium outlet and the bottom discharge port of the tower reactor, and the bottom of the liquid storage cavity is arc-shaped. A shell-side inlet and a shell-side outlet are provided on the side wall of the spiral heat exchanger.

[0016] On the other hand, the present invention also provides a method for preparing hydroxypivalaldehyde, which is prepared by using the above-mentioned hydroxypivalaldehyde preparation device, and the method comprises the following steps:

[0017] S1, the reaction raw materials of a certain ratio, isobutyraldehyde, formaldehyde and alkaline catalyst, are respectively transported through their respective raw material feed ends, mixed through a mixing pipe, transported to a premixer from two mixing inlets, and enter from the mixing outlet of the premixer through a feeding pipe and the top feed port of the tower reactor, the mixed liquid enters the multi-layer mixed reaction component in the first reaction zone for multi-layer mixed reaction, and then enters the second reaction zone from the liquid outlet of the mixing reaction component at the bottom through the liquid inlet of the downcomer distribution pipe for reaction, and a certain liquid level is formed in the second reaction zone;

[0018] S2, the liquid after the reaction in the second reaction zone is heat exchanged through the heat exchange element, and the liquid after heat exchange is divided into two paths from the bottom discharge port of the tower reactor, one path is transported to the next process through the discharge pipe, and the other path of the circulating liquid is pressurized by the forced circulation pump, and enters the second reaction zone and the premixer through the circulation pipe 1 and the circulation pipe 2 respectively, wherein the circulating liquid entering the second reaction zone is spirally injected into the liquid surface of the second reaction zone at a certain oblique angle through a plurality of nozzles until it partially passes through the liquid surface, cutting the liquid surface into two parts and mixing and reacting in an up-and-down state; in addition, the circulating liquid entering the premixer The circulating liquid uses its own pressure to push the gate assembly and open the circulating material inlet. The liquid entering from the circulating material inlet is mixed with the raw materials entering from the two mixing inlets and enters the premixer for multiple mixing. Then, it passes through the mixing outlet through the feeding pipeline and enters the first reaction zone from the top feed port of the tower reactor. It undergoes multi-layer mixing reactions through the multi-layer mixing reaction components of the first reaction zone. Then, it enters the second reaction zone from the liquid outlet of the mixing reaction component at the bottom through the liquid inlet of the downcomer distribution pipe to continue the reaction. The reacted liquid then exchanges heat through the heat exchanger and is divided into two paths from the bottom discharge port to circulate in this way.

[0019] S3. During the circulation of the circulating liquid, the value of the reaction product hydroxytivalaldehyde is analyzed online by the liquid level online analyzer on one side of the downcomer distribution pipe, so as to control the regulating valve 1 and the regulating valve 2 and adjust the reaction circulation amount entering the second reaction zone and the first reaction zone.

[0020] Furthermore, the ratio of isobutyraldehyde, formaldehyde and alkaline catalyst in S1 is controlled at 1:1.12-1.28:0.017-0.025, and the formaldehyde concentration is 37%; the reaction temperature in the tower reactor is controlled at 67°C-73°C, and the reaction pressure is controlled at 0.25MPa-0.4MPa; the premixers in S1 and S2 are provided with inner and outer tubes, the outer wall of the inner tube adopts X-shaped left-handed fins, and the outer wall of the outer tube adopts left-handed 180° vertical fins, and the materials of the inner and outer pipelines are combined and pressurized through the reduced diameter section of the premixer, and then begin to reduce pressure and increase speed after passing through the horizontal section and expansion section of the premixer and enter the tower reactor; the nozzle of the nozzle in S2 is a reduced diameter fish mouth type, and the angle between the nozzle and the horizontal liquid surface is 25-45°, and the circulating liquid is spirally injected into the liquid surface of the second reaction zone at an angle of 25-45°.

[0021] The beneficial effects of the present invention are:

[0022] 1. The present invention improves the adequacy of mixing raw materials and catalysts, ensures the reaction time, reduces equipment investment and floor space, and reduces the height of equipment through the design of a premixer, a tower reactor, a forced circulation pump, a liquid level online analyzer, a circulation pipeline 1, and a circulation pipeline 2. In addition, during the preparation process, the value of the reaction product hydroxypivalaldehyde is analyzed online by the liquid level online analyzer to adjust the reaction circulation volume entering the second reaction zone and the first reaction zone, and the reaction temperature of the circulating liquid is controlled by a heat exchanger to prevent excessive side reactions from being generated due to high reaction temperature, thereby increasing the yield of HPA and indirectly increasing the subsequent product yield of NPG.

[0023] 2. The present invention adopts a premixer structural design, specifically including a feed section, a mixing section, a reduced diameter section, a horizontal section and an expanded diameter section connected in sequence from left to right, so that the high-pressure reaction circulating liquid entering the premixer uses its own pressure to push the gate of the gate assembly to separate from the inner wall of the straight section, and the high-pressure circulating liquid enters from the circulating material inlet and enters the premixer together with the mixed liquid entering from the two mixing inlets to be mixed, wherein the high-speed flowing circulating liquid forms a local negative pressure in the area behind the gate, attracting the merged mixed liquid to enter the mixing area of ​​the mixing section from the two mixing inlets in a diagonal manner, reducing the flow rate, and the liquid can be mixed while flowing under the action of the cross-displaced left-handed fins on the outer walls of the inner tube and the outer tube, while heating the entering mixed liquid to control the reaction temperature, and when approaching the reduced diameter section, the materials from the first flow channel and the second flow channel are merged, and then the pressure is increased through the reduced diameter section, and then the pressure is reduced and the speed is increased, and then the materials enter the first reaction zone in the tower reactor after passing through the horizontal section to the expanded diameter section, thereby greatly improving the mixing efficiency of the materials in the premixer;

[0024] 3. The present invention adopts a design that the multi-layer mixed reaction components in the first reaction zone and each layer of the mixed reaction components includes a plurality of dovetail components connected to each other, each dovetail component is provided with an air hole 1 at the top, a liquid outlet is provided between two adjacent dovetail components, the air hole 1 of the lower layer is located below the liquid outlet of the upper layer, and the liquid outlet of the bottom layer is staggered with the liquid inlet at the top of the downcomer distribution pipe, so that the liquids at the tails of the two adjacent dovetail components of each layer intersect from top to bottom and then separate and fall down to the dovetail component of the next layer, staggered with the air hole 1 on the dovetail component of the layer, and the lower part is staggered to the bottom. A small amount of gas on the top of the tower reactor contacts and reacts with the descending liquid in reverse through the tail of the dovetail component. In addition, a small amount of gas that has not reacted or has been gradually vaporized by the reaction is discharged from the air hole at the top of the dovetail component and contacts and reacts with the descending liquid again. Some of the gas that has not been discharged from the small hole accumulates and is discharged from the tail of the dovetail component and contacts and reacts with the liquid with the outlet downward between two adjacent dovetail components in reverse, thereby reducing the accumulation of gas at the top of the tower reactor and reducing the downward flow speed of the liquid, so that the liquid and gas contact and mix multiple times, thereby increasing the reaction time and effectively reducing the height of the equipment.

[0025] 4. The present invention has a plurality of downcomer distribution pipes installed between the first reaction zone and the second reaction zone through a tower tray, which can extend the time for the material to enter the second reaction zone, thereby controlling the reaction time of the material. Specifically, the top of the downcomer distribution pipe of the present invention is provided with a liquid inlet, which is composed of a plurality of circumferentially arranged V-shaped plum blossom ports. The structural design of the V-shaped plum blossom port here can ensure the overflow rate under different generation loads;

[0026] A plurality of guide fins are arranged on the inner wall of the downcomer distribution pipe, each guide fin is arranged below the corresponding V-shaped plum blossom port, so that the liquid overflowing through the V-shaped plum blossom port can fall onto the corresponding guide fin, and the plurality of guide fins are arranged in a spiral shape, which can increase the time the liquid stays in the downcomer distribution pipe, thereby improving the reaction efficiency. Each guide fin has a structure of being wide at the top and narrow at the bottom, which can cope with the large overflow volume at the top of the V-shaped plum blossom port under high load;

[0027] A number of overflow holes are provided on the outer wall of the downcomer distribution pipe. The diameter of the overflow holes is set to decrease from bottom to top, which can meet 20% to 35% of the overall liquid level overflow, preventing the liquid that descends from the top to the bottom of the tray from staying for a long time and increasing side reactions. In addition, the liquid entering through the overflow holes can be mixed with most of the liquid that overflows through the V-shaped plum blossom mouth, greatly improving the mixing efficiency.

[0028] 5. The present invention adopts the design of the nozzle and the fish-mouth nozzle with a reduced diameter, and the angle between the nozzle and the horizontal liquid surface is 25-45 degrees. The nozzle is provided with a spiral tangent groove, which can make the liquid enter the liquid surface in a spiral state when passing through the nozzle until part of it passes through the liquid surface for mixing reaction, and cut the liquid surface into two parts and mix and react in an up and down state, thereby greatly improving the mixing efficiency;

[0029] 6. The present invention can control the reaction temperature entering the second reaction zone and the temperature of the circulating liquid through the design of the coil below the first reaction zone and the heat exchanger below the second reaction zone, thereby ensuring the mixed reaction and preventing the generation of excessive side reactions due to high reaction temperature, thereby greatly increasing the production of HPA. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solution of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0031] Figure 1 It is a structural schematic diagram of a device for preparing hydroxypivalaldehyde of the present invention;

[0032] Figure 2 yes Figure 1 A magnified image of area A;

[0033] Figure 3 It is a structural schematic diagram of a premixer of the present invention;

[0034] Figure 4 It is a structural schematic diagram of the downcomer distribution pipe of the present invention;

[0035] Figure 5 yes Figure 4 A top view of

[0036] Figure 6 It is a schematic diagram of the structure of the nozzle of the present invention;

[0037] In the figure: 1-premixer, 2-tower reactor, 3-forced circulation pump, 4-mixing pipeline, 5-feeding pipeline, 6-discharging pipeline, 7-circulation pipeline 1, 8-circulation pipeline 2, 9-regulating valve 1, 10-regulating valve 2, 101-liquid level online analyzer, 11-mixing inlet, 12-circulation material inlet, 13-mixing outlet, 14-valve plate assembly, 15-fixed bracket, 16-inner pipe, 17-outer pipe, 111-feeding section, 112-mixing section, 113-reducing section, 114-horizontal section, 115-expanding section, 21-first reaction zone , 22-second reaction zone, 23-downcomer distribution pipe, 24-heat exchange element, 25-tower plate, 26-coil, 27-bottom discharge port, 28-liquid storage chamber, 100-first flow channel, 200-second flow channel, 141-connecting rod, 142-valve plate, 143-spring, 144-limiting bolt, 211-mixing reaction component, 2111-liquid outlet, 2112-air hole 1, 221-nozzle, 2211-nozzle, 231-liquid inlet, 232-V-shaped plum blossom mouth, 233-overflow hole, 241-medium inlet, 242-medium outlet. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the specification of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] In a specific embodiment of the present invention, Figure 1-6 As shown, a preparation device of hydroxypivalaldehyde comprises a premixer 1, a tower reactor 2 and a forced circulation pump 3, a mixing inlet 11 and a circulating material inlet 12 are provided at one end of the premixer 1, and a mixing outlet 13 is provided at the other end, the mixing inlet 11 has two and is symmetrically arranged on both sides of the circulating material inlet 12, the two mixing inlets 11 are respectively connected to a mixing pipe 4, the mixing pipe 4 is connected to a raw material feed end, the mixing inlet 11 is connected to the mixing outlet 13, a valve plate assembly 14 is provided between the circulating material inlet 12 and the mixing outlet 13, and the mixing outlet 13 is connected to the top feed port of the tower reactor 2 through a feed pipe 5;

[0040] A first reaction zone 21 and a second reaction zone 22 are sequentially arranged in the tower reactor 2 from top to bottom. The first reaction zone 21 and the second reaction zone 22 are connected through a plurality of downcomer distribution pipes 23. A plurality of mixed reaction components 211 are arranged in the first reaction zone 21. A plurality of liquid outlets 2111 are arranged on the mixed reaction components 211 of each layer. The liquid outlets 2111 of two adjacent layers are staggered. A plurality of nozzles 221 are arranged on the inner wall of the second reaction zone 22. A heat exchanger 24 is arranged below the second reaction zone 22. A plurality of medium inlets communicating with the inner cavity of the second reaction zone 22 are arranged on the top of the heat exchanger 24. A plurality of medium outlets are arranged at the bottom. The plurality of medium outlets are communicated with a bottom discharge port 27 of the tower reactor 2. The bottom discharge port 27 is respectively connected with a discharge pipe 6 and a circulation pipe 1 7. A forced circulation pump 3 is arranged on the circulation pipe 1 7. The circulation pipe 1 7 is communicated with a plurality of nozzles 221. A circulation pipe 2 8 is connected in parallel to the circulation pipe 1 7. The circulation pipe 2 8 is communicated with a circulation material inlet 12.

[0041] A regulating valve 1 9 and a regulating valve 2 10 are respectively provided on the circulation pipeline 1 7 and the circulation pipeline 2 8, and a liquid level online analyzer 101 is provided on one side of the downcomer distribution pipe 23. The liquid level online analyzer 101 is connected to the regulating valve 1 9 and the regulating valve 2 10 through a control system.

[0042] like Figure 3 As shown, the premixer 1 comprises a feed section 111, a mixing section 112, a diameter reduction section 113, a horizontal section 114 and a diameter expansion section 115 connected in sequence from left to right, the feed section 111 is composed of a straight section and a trapezoidal section, the circulating material inlet 12 is arranged on one side of the straight section, and the two mixing material inlets 11 are obliquely and symmetrically arranged on the trapezoidal section;

[0043] The mixing section 112 is cylindrical and has a group of fixed brackets 15 disposed therein, an inner tube 16 and an outer tube 17 are mounted between the group of fixed brackets 15, the inner tube 16 is located inside the outer tube 17 and a first flow channel 100 is disposed therebetween, the valve plate assembly 14 is mounted on the inner tube 16 and controls the opening and closing of the circulating material inlet 12, a second flow channel 200 is disposed between the outer tube 17 and the inner wall of the mixing section 112, and cross-displaced left-handed fins are disposed on the outer walls of the inner tube 16 and the outer tube 17, so that the liquid can be mixed while flowing, and the incoming mixed liquid can be heated at the same time to control the reaction temperature;

[0044] In the present invention, the inner tube 16 adopts a left-handed X-fin component, and the outer tube 17 adopts a left-handed 180° vertical fin. The materials in the first flow channel 100 and the second flow channel 200 are combined and pressurized in the reduced diameter section 113, and then the pressure is reduced and the speed is increased. After passing through the horizontal section 114 and the expanded diameter section 115, they enter the first reaction zone 21 in the tower reactor 2.

[0045] The valve plate assembly 14 includes a connecting rod 141, a valve plate 142 and a spring 143. One end of the connecting rod 141 is inserted into the inner tube 16, and the other end is sleeved with the valve plate 142. The spring 143 is sleeved on the connecting rod 141 and arranged between the valve plate 142 and the inner tube 16. The end of the connecting rod 141 away from the inner tube 16 is provided with a limiting bolt 144 for limiting the disengagement of the valve plate 142. The valve plate 142 abuts against the inner wall of the straight tube section to block the circulating material inlet 12; under the action of the high-pressure circulating fluid, the valve plate 142 is pushed to compress the spring 143 and separate from the inner wall of the straight tube section, thereby realizing the connection between the circulating material inlet 12 and the mixing outlet 13.

[0046] like Figure 2 As shown, each layer of the mixing reaction component 211 includes a plurality of dovetail-shaped components connected to each other, each dovetail-shaped component is provided with an air hole 1 2112 at the top, and a liquid outlet 2111 is provided between two adjacent dovetail-shaped components, the air hole 1 2112 of the lower layer is located below the liquid outlet 2111 of the upper layer, and the liquid outlet 2111 of the bottom layer is staggered with the liquid inlet at the top of the downcomer distribution pipe 23; a plurality of downcomer distribution pipes 23 are installed between the first reaction zone 21 and the second reaction zone 22 through a tower tray 25, a plurality of air holes 251 are opened on the tower tray 25, and a coil 26 is provided above the tower tray 25, and the coil 26 is wound around the outside of the plurality of downcomer distribution pipes 23 and is lower than the top of the downcomer distribution pipes 23;

[0047] In the present invention, the height-to-diameter ratio of the first reaction zone 21 is 4.5-7, and the mixed reaction member 211 can be provided with 5-7 layers, each layer being spaced 350 mm-500 mm apart. The material from the premixer 1 is sprayed on the multilayer mixed reaction member 211 in the first reaction zone 21. Specifically, Figure 2The flow direction indicated by the middle arrow is as follows: the liquids from the tails of two adjacent dovetail components in each layer intersect from top to bottom and then separate again and fall downward to the dovetail component of the next layer, staggered with the air holes 2112 on the dovetail component of this layer, and circulate downward in sequence; a small amount of gas from the bottom upward passes through the tail of the dovetail component and reacts in reverse contact with the descending liquid. In addition, the unreacted or gradually reacted gas is discharged from the air hole 2112 at the top of the dovetail component and reacts with the descending liquid again. Some of the gas that has not been discharged from the small hole accumulates and is discharged from the tail of the dovetail component and meets the liquid outlet 2111 between the two adjacent dovetail components. The downward liquid reverse contact reaction reduces the gas accumulation at the top of the tower reactor 2, reduces the downward flow rate of the liquid, makes the liquid and gas contact and mix multiple times, increases the reaction time, and can effectively reduce the height of the equipment. The first reaction liquid and the unreacted liquid enter the tower plate 25. Through the design of the coil 26 on the tower plate 25, not only the reaction temperature entering the second reaction zone 22 can be controlled, but also excessive side reactions caused by high reaction temperature can be prevented. The reaction liquid after temperature control overflows to the second reaction zone 22 through the downcomer distribution pipe 23, and the air hole 251 on the tower plate is responsible for gas phase discharge and shutdown liquid discharge.

[0048] Specifically, Figure 4-5 As shown, a liquid inlet is provided at the top of the downcomer distribution pipe 23, and the liquid inlet is composed of a plurality of circumferentially arranged V-shaped plum blossom ports 232. A plurality of guide fins 231 are provided on the inner wall of the downcomer distribution pipe 23, and each guide fin 231 is arranged below the corresponding V-shaped plum blossom port 232, and the plurality of guide fins 231 are arranged in a spiral shape, and each guide fin 231 has a structure of being wide at the top and narrow at the bottom. A plurality of layers of overflow holes 233 are provided on the outer wall of the downcomer distribution pipe 23, and the overflow holes 233 are arranged at the center of two adjacent V-shaped plum blossom ports 232, and the aperture of the overflow holes 233 is arranged to decrease from bottom to top. The overflow hole 233 can meet 20% to 35% of the overall liquid level overflow, preventing the liquid that drops from the top to the bottom of the tower plate from staying for a long time and increasing side reactions. In addition, the liquid entering through the overflow hole 233 can be mixed with most of the liquid overflowing through the V-shaped plum blossom mouth 232. The structural design of the V-shaped plum blossom mouth here can ensure the overflow under different generation loads. The liquid overflowing through the V-shaped plum blossom mouth 232 falls on the corresponding guide fin 231. The structure of the guide fin 231 with a wide upper part and a narrow lower part can cope with the large upper overflow of the V-shaped plum blossom mouth 232 under high load, such as Figure 5 As shown, 30% to 45% of the overflow liquid from one V-shaped plum blossom port is directed to an adjacent V-shaped plum blossom port by the guide fins, and so on, and the liquid is in a rotating shape when flowing out. When the present invention is used, the fixed liquid level height on the tower plate can be designed to be 800 to 1000 mm.

[0049] Specifically, the heat exchanger 24 is a spiral heat exchanger, and a plurality of medium inlets 241 and medium outlets 242 are connected by spiral tubes, where the spiral tubes can be right-handed 180° spiral tubes, and a liquid storage chamber 28 is provided between the medium outlet 242 and the bottom discharge port 27 of the tower reactor 2, and the bottom of the liquid storage chamber 28 is in an arc shape. The side wall of the spiral heat exchanger is provided with a shell side inlet and a shell side outlet, and the heat exchange medium is introduced into the shell side inlet to exchange heat with the liquid entering the spiral heat exchanger;

[0050] Specifically, a plurality of nozzles 221 are circumferentially installed on the second reaction zone 22. The second reaction zone 22 is provided with an annular channel connected to the plurality of nozzles 221. The annular channel is connected to the circulation pipe 28. Figure 6 As shown, the nozzle 2211 of the nozzle 221 is a fish-mouth type with a reduced diameter and the angle between the nozzle 2211 and the horizontal liquid surface is 25-45°. A spiral tangent groove is provided in the nozzle 2211, and the dynamic pressure is used to mix with the material in the second reaction zone 22. The height-to-diameter ratio of the second reaction zone is 2.5 to 4. The liquid after heat exchange by the spiral heat exchanger is divided into two paths from the bottom discharge port 27, one path enters the next process through the discharge pipe; the other path circulates into the first reaction zone 21 and the second reaction zone 22 through the forced circulation pump 3, and 55% to 70% of the total circulation volume enters the second reaction zone 22. The nozzle 221 is set at a position of 5% to 15% of the liquid level in the second reaction zone. The nozzle 2211 is a fish-mouth type with a reduced diameter and an inner spiral tangent groove at the outlet of the nozzle. The groove is injected at a certain angle of the oblique line, so that the liquid is injected into the liquid surface in a spiral state when passing through the nozzle until it partially passes through the liquid surface for mixing reaction. The tangent angle is 25° to 45° when the liquid surface is 100%. This injection utilizes the centrifugal force and Bernoulli's theorem in fluid mechanics. The pipe necking mouth and the inward rotating tangent groove of the nozzle increase the speed of the fluid. The small tangent at the edge of the outlet causes the liquid to rotate to a certain extent when it is ejected due to the pressure drop and centrifugal force. The static pressure is converted into kinetic energy to prompt the liquid to further gradually pass through the liquid surface upward, cutting the liquid surface into two parts and tumbling up and down for mixing reaction, and then passing through the spiral heat exchanger below the second reaction zone for heat exchange. The design of the spiral heat exchanger increases the residence time of the reaction liquid.

[0051] On the other hand, the present invention also provides a method for preparing hydroxypivalaldehyde, which is prepared by using a preparation device for hydroxypivalaldehyde, and the method comprises the following steps:

[0052] S1, the reaction raw materials isobutyraldehyde, 37% formaldehyde and alkaline catalyst in a ratio of 1:1.12-1.28:0.017-0.025 are respectively transported through their respective raw material feeding ends, the reaction temperature in the tower reactor is controlled at 67°C-73°C, and the reaction pressure is controlled at 0.25MPa-0.4MPa; the reaction temperature in the tower reactor 2 is mainly controlled by the coil below the first reaction zone 21 and the spiral heat exchanger below the second reaction zone 22, and the heat exchange medium is hot water;

[0053] The reaction raw materials of isobutylaldehyde, 37% formaldehyde and alkaline catalyst are mixed through the mixing pipe 4, transported to the premixer 1 from the two mixing inlets 11, and enter the top feed port of the tower reactor 2 from the mixing outlet 13 of the premixer 1 through the feeding pipe 5. The mixed liquid enters the multi-layer mixing reaction component 211 in the first reaction zone 21 for multi-layer mixing reaction, and then enters the second reaction zone 22 from the liquid outlet of the mixing reaction component 211 at the bottom through the liquid inlet of the downcomer distribution pipe 23 for reaction, and a certain liquid level is formed in the second reaction zone 22;

[0054] S2, the liquid after the reaction in the second reaction zone 22 is heat exchanged through the heat exchange element, and the liquid after heat exchange is divided into two paths from the bottom discharge port 27 of the tower reactor 2, one path is transported to the next process through the discharge pipe 6, and the circulating liquid of the other path is pressurized by the forced circulation pump 3, and enters the second reaction zone 22 and the premixer 1 respectively through the circulation pipe 1 7 and the circulation pipe 2 8, wherein the circulating liquid entering the second reaction zone 22 is spirally injected into the liquid surface of the second reaction zone 22 at a certain oblique angle through a plurality of nozzles 221 until it partially passes through the liquid surface, cutting the liquid surface into two parts and performing a mixing reaction in an up and down tumbling state;

[0055] In addition, the high-pressure reaction circulating liquid (temperature is 67°C to 73°C) entering the premixer 1 uses its own pressure to push the gate 142 of the gate assembly 14 to separate from the inner wall of the straight tube section, and the high-pressure circulating liquid enters from the circulating material inlet 12, and enters the premixer 1 together with the mixed liquid (raw materials isobutylaldehyde, formaldehyde and catalyst are mixed through the mixing pipe) entering from the two mixing inlets 11 to be mixed. Specifically, the high-speed flowing circulating liquid forms a local negative pressure in the area behind the gate 142, attracting the merged mixed liquid to enter the mixing area of ​​the mixing section 112 from the two mixing inlets 11 in a diagonal manner, reducing the flow rate. Under the action of the left-handed fins on the outer walls of the inner tube and the outer tube, the liquid is mixed while flowing, and the mixed liquid is heated at the same time to increase the reaction temperature of the mixed liquid. When approaching the reduced diameter section, the liquid in the first flow channel and the second flow channel is mixed and passes through the reduced diameter section 113 to the horizontal section 114 and then enters the expanded diameter section 115;

[0056] Then, the liquid passes through the mixing outlet 13 and the feeding pipe 5 from the top feeding port of the tower reactor 2 to enter the first reaction zone 21, and undergoes a multi-layer mixing reaction through the multi-layer mixing reaction components 211 of the first reaction zone 21. Then, the liquid passes through the liquid outlet 2111 of the bottom mixing reaction component 211 and the liquid inlet of the downcomer distribution pipe 23 to enter the second reaction zone 22 to continue the reaction. The liquid after the reaction then exchanges heat through the heat exchange element 24 and is divided into two paths from the bottom discharge port 27, thereby circulating.

[0057] S3. During the circulation of the circulating liquid, the value of the reaction product hydroxytivalaldehyde is analyzed online by the liquid level online analyzer 101 on one side of the downcomer distribution pipe 23, and the reaction circulation volume entering the second reaction zone 22 and the first reaction zone 21 is adjusted. The total circulation volume accounts for 10 to 16 times the feed volume, and the circulation volume can ensure the reaction time of the material. Among them, the lower circulation volume entering the second reaction zone 22 accounts for 55% to 70% of the total circulation material volume, and the upper circulation volume entering the first reaction zone 21 accounts for 35% to 55% of the total circulation material volume. The different upper and lower circulation volumes are used to control the mixed reaction and reaction time in the first reaction zone 21 and the second reaction zone 22.

[0058] Specifically, an inner tube and an outer tube are arranged in the premixer, an X-shaped left-handed fin is adopted on the outer wall of the inner tube, and a left-handed 180° vertical fin is adopted on the outer wall of the outer tube. The materials in the inner and outer pipelines are combined and pressurized after passing through the reducing section of the premixer, and then the pressure is reduced and the speed is increased, and then the materials enter the tower reactor after passing through the horizontal section and the expanding section of the premixer; the nozzle of the nozzle in S2 is a reducing fish mouth type, and the angle between the nozzle and the horizontal liquid surface is 25 to 45 degrees, and the circulating liquid is spirally injected into the liquid surface of the second reaction zone at an angle of 25 to 45 degrees.

[0059] The present invention adopts raw materials: isobutyraldehyde, 37% formaldehyde; catalyst: trimethylamine, the ratio of raw materials to catalyst is controlled at 1:1.12-1.28:0.017-0.025; the reaction temperature is controlled at 67°C-73°C, the reaction pressure is controlled at 0.25MPa-0.4MPa, and the high-pressure reaction circulating liquid with a temperature of 67°C-73°C adjusts the circulation volume in the first reaction zone (upper part) 21 and the second reaction zone (lower part) 22 according to the different liquid level depths of the second reaction zone, and the mixing time and reaction time of the first reaction zone 21 and the second reaction zone 22 are controlled by using different upper and lower circulation volumes. The reaction temperature is controlled by the coil 26 and the hot water temperature introduced into the shell side of the spiral heat exchanger. The results of multiple sets of example data are as follows (the ratios of the materials isobutyraldehyde, 37% formaldehyde, and trimethylamine in this embodiment are all mass ratios, and the ingredients are prepared with isobutyraldehyde as the reference material):

[0060]

[0061] It can be seen from the table that during the preparation process, the reaction circulation volume is adjusted by the online analysis value of the liquid level in the first reactor, specifically controlling the circulation volume in the second reaction zone to account for 60% of the total circulation material volume and the circulation volume in the first reaction zone to account for 40% of the total circulation material volume, which can ensure the reaction time of the materials, increase the output of HPA, and more than 89% of HPA can be obtained in the second reaction zone.

[0062] The preparation device of the present invention can replace multiple reactors in series in the prior art, reduce the installation of stirring or mechanical equipment, and reduce material stratification, equipment, and equipment height while meeting the space required for the reaction. It adopts a premixer and a multilayer mixing reaction component in the first reaction zone in the tower reactor, a downcomer distribution pipe with a V-shaped plum blossom mouth, and a nozzle in the second reaction zone. By controlling the reaction circulation volume in the first reaction zone and the second reaction zone, the mixing efficiency is improved, the reaction time is guaranteed, and the HPA yield is increased.

[0063] The above disclosures are only several preferred embodiments of the present invention, which certainly cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the claims of the present invention are still within the scope of the present invention.

Claims

1. A preparation device for hydroxypivalaldehyde, characterized in that: The invention comprises a premixer (1), a tower reactor (2) and a forced circulation pump (3), wherein one end of the premixer (1) is provided with a mixing inlet (11) and a circulating material inlet (12), and the other end is provided with a mixing outlet (13), wherein the mixing inlet (11) has two and is symmetrically arranged on both sides of the circulating material inlet (12), and the two mixing inlets (11) are respectively connected to a mixing pipe (4), and the mixing pipe (4) is connected to a raw material feed end, the mixing inlet (11) is connected to the mixing outlet (13), a valve plate assembly (14) is provided between the circulating material inlet (12) and the mixing outlet (13), and the mixing outlet (13) is connected to the top feed port of the tower reactor (2) through a feed pipe (5); The tower reactor (2) is provided with a first reaction zone (21) and a second reaction zone (22) in order from top to bottom. The first reaction zone (21) and the second reaction zone (22) are connected via a plurality of downcomer distribution pipes (23). The first reaction zone (21) is provided with a plurality of mixed reaction components (211). Each layer of the mixed reaction components (211) is provided with a plurality of liquid outlets (2111). The liquid outlets (2111) of two adjacent layers are staggered. The inner wall of the second reaction zone (22) is provided with a plurality of nozzles (221). A heat exchange component (24) is provided below the second reaction zone (22). The top of the heat exchange element (24) is provided with a plurality of medium inlets connected to the inner cavity of the second reaction zone (22), and the bottom is provided with a plurality of medium outlets, and the plurality of medium outlets are connected to the bottom discharge port (27) of the tower reactor (2), and the bottom discharge port (27) is respectively connected to a discharge pipe (6) and a circulation pipe 1 (7), and the forced circulation pump (3) is arranged on the circulation pipe 1 (7), and the circulation pipe 1 (7) is connected to a plurality of the nozzles (221), and the circulation pipe 2 (8) is connected in parallel to the circulation pipe 1 (7), and the circulation pipe 2 (8) is connected to the circulation material inlet (12); The circulation pipeline one (7) and the circulation pipeline two (8) are respectively provided with a regulating valve one (9) and a regulating valve two (10); a liquid level online analyzer (101) is provided on one side of the downcomer distribution pipe (23); the liquid level online analyzer (101) is connected to the regulating valve one (9) and the regulating valve two (10) through a control system.

2. A preparation device for hydroxypivalaldehyde according to claim 1, characterized in that: The premixer (1) comprises a feeding section (111), a mixing section (112), a diameter-reducing section (113), a horizontal section (114) and a diameter-expanding section (115) which are sequentially connected from left to right, the feeding section (111) being composed of a straight section and a trapezoidal section, the circulating material inlet (12) being arranged on one side of the straight section, and the two mixing material inlets (11) being obliquely and symmetrically arranged on the trapezoidal section; The mixing section (112) is cylindrical and has a group of fixed brackets (15) arranged therein, an inner tube (16) and an outer tube (17) being installed between the group of fixed brackets (15), the inner tube (16) being located inside the outer tube (17) and having a first flow channel (100) arranged therebetween, the valve plate assembly (14) being installed on the inner tube (16) and controlling the opening and closing of the circulating material inlet (12), a second flow channel (200) being arranged between the outer tube (17) and the inner wall of the mixing section (112), and the outer walls of the inner tube (16) and the outer tube (17) being provided with cross-staggered left-handed fins.

3. A preparation device for hydroxypivalaldehyde according to claim 2, characterized in that, The valve plate assembly (14) comprises a connecting rod (141), a valve plate (142) and a spring (143). One end of the connecting rod (141) is inserted into the inner tube (16), and the other end is sleeved with the valve plate (142). The spring (143) is sleeved on the connecting rod (141) and arranged between the valve plate (142) and the inner tube (16). The end of the connecting rod (141) away from the inner tube (16) is provided with a limiting bolt (144) for limiting the separation of the valve plate (142). The valve plate (142) abuts against the inner wall of the straight tube section to block the circulating material inlet (12); under the action of the high-pressure circulating fluid, the valve plate (142) is pushed to compress the spring (143) and separate from the inner wall of the straight tube section, thereby realizing the communication between the circulating material inlet (12) and the mixing outlet (13).

4. A preparation device for hydroxypivalaldehyde according to claim 1, characterized in that: The mixing reaction component (211) of each layer comprises a plurality of dovetail-shaped components connected to each other, an air hole (2112) is provided at the top of each dovetail-shaped component, a liquid outlet (2111) is provided between two adjacent dovetail-shaped components, the air hole (2112) of the lower layer is located below the liquid outlet (2111) of the upper layer, and the liquid outlet (2111) of the bottom layer is staggered with the liquid inlet at the top of the downcomer distribution pipe (23).

5. A preparation device for hydroxypivalaldehyde according to claim 1, characterized in that: A plurality of the downcomer distribution pipes (23) are installed between the first reaction zone (21) and the second reaction zone (22) via a tower plate (25), a plurality of air holes (251) are provided on the tower plate (25), a coil (26) is provided above the tower plate (25), and the coil (26) is wound around the outside of the plurality of the downcomer distribution pipes (23) and is lower than the top of the downcomer distribution pipes (23).

6. A preparation device for hydroxypivalaldehyde according to claim 1, characterized in that: A liquid inlet is provided at the top of the downcomer distribution pipe (23), and the liquid inlet is composed of a plurality of circumferentially arranged V-shaped plum blossom ports (232). A plurality of guide fins (231) are provided on the inner wall of the downcomer distribution pipe (23), and each of the guide fins (231) is arranged below the corresponding V-shaped plum blossom port (232). The plurality of guide fins (231) are arranged in a spiral shape, and each of the guide fins (231) has a structure that is wide at the top and narrow at the bottom. A plurality of layers of overflow holes (233) are provided on the outer wall of the downcomer distribution pipe (23), and the apertures of the overflow holes (233) are arranged to decrease from bottom to top.

7. A preparation device for hydroxypivalaldehyde according to claim 1, characterized in that: A plurality of the nozzles (221) are annularly mounted on the second reaction zone (22); an annular channel connected to the plurality of the nozzles (221) is provided on the second reaction zone (22); the annular channel is connected to the second circulation pipe (8); the nozzle (2211) of the nozzle (221) is of a reduced diameter fish mouth shape and the angle between the nozzle (2211) and the horizontal liquid surface is 25 to 45 degrees; a spiral tangent groove is provided inside the nozzle (2211).

8. A preparation device for hydroxypivalaldehyde according to claim 1, characterized in that: The heat exchange element (24) is a spiral heat exchanger, wherein a plurality of medium inlets (241) and medium outlets (242) are connected via spiral tubes, a liquid storage chamber (28) is provided between the medium outlet (242) and the bottom discharge port (27) of the tower reactor (2), the bottom of the liquid storage chamber (28) is in an arc shape, and a shell side inlet and a shell side outlet are provided on the side wall of the spiral heat exchanger.

9. A method for preparing hydroxypivalaldehyde, using the hydroxypivalaldehyde preparation device according to any one of claims 1 to 8, characterized in that: The method comprises the following steps: S1, the reaction raw materials of a certain ratio, isobutyraldehyde, formaldehyde and alkaline catalyst, are respectively transported through their respective raw material feed ends, mixed through a mixing pipe, transported to a premixer from two mixing inlets, and enter from the mixing outlet of the premixer through a feeding pipe and the top feed port of the tower reactor, the mixed liquid enters the multi-layer mixed reaction component in the first reaction zone for multi-layer mixed reaction, and then enters the second reaction zone from the liquid outlet of the mixing reaction component at the bottom through the liquid inlet of the downcomer distribution pipe for reaction, and a certain liquid level is formed in the second reaction zone; S2, the liquid after the reaction in the second reaction zone is heat exchanged through the heat exchange element, and the liquid after heat exchange is divided into two paths from the bottom discharge port of the tower reactor, one path is transported to the next process through the discharge pipe, and the other path of the circulating liquid is pressurized by the forced circulation pump, and enters the second reaction zone and the premixer through the circulation pipe 1 and the circulation pipe 2 respectively, wherein the circulating liquid entering the second reaction zone is spirally injected into the liquid surface of the second reaction zone at a certain oblique angle through a plurality of nozzles until it partially passes through the liquid surface, cutting the liquid surface into two parts and mixing and reacting in an up-and-down state; in addition, the circulating liquid entering the premixer The circulating liquid uses its own pressure to push the gate assembly and open the circulating material inlet. The liquid entering from the circulating material inlet is mixed with the raw materials entering from the two mixing inlets and enters the premixer for multiple mixing. Then, it passes through the mixing outlet through the feeding pipeline and enters the first reaction zone from the top feed port of the tower reactor. It undergoes multi-layer mixing reactions through the multi-layer mixing reaction components of the first reaction zone. Then, it enters the second reaction zone from the liquid outlet of the mixing reaction component at the bottom through the liquid inlet of the downcomer distribution pipe to continue the reaction. The reacted liquid then exchanges heat through the heat exchanger and is divided into two paths from the bottom discharge port to circulate in this way. S3. During the circulation of the circulating liquid, the value of the reaction product hydroxypivalaldehyde is analyzed online by an online liquid level analyzer on one side of the downcomer distribution pipe to adjust the reaction circulation volume entering the second reaction zone and the first reaction zone.

10. The method for preparing hydroxypivalaldehyde according to claim 9, characterized in that: The mass ratio of isobutyraldehyde, formaldehyde and alkaline catalyst in S1 is controlled at 1:1.12-1.28:0.017-0.025, and the formaldehyde concentration is 37%; the reaction temperature in the tower reactor is controlled at 67°C-73°C, and the reaction pressure is controlled at 0.25MPa-0.4MPa; the premixers in S1 and S2 are provided with inner tube and outer tube, the outer wall of the inner tube adopts X-shaped left-handed fins, and the outer wall of the outer tube adopts left-handed 180° vertical fins, the materials of the inner and outer pipelines are combined, and after the pressure is increased through the reduced diameter section of the premixer, the pressure is reduced and the speed is increased, and then the materials enter the tower reactor after passing through the horizontal section and the expanded section of the premixer; the nozzle of the nozzle in S2 is a reduced diameter fish mouth type, and the angle between the nozzle and the horizontal liquid surface is 25-45°, and the circulating liquid is spirally injected into the liquid surface of the second reaction zone at an angle of 25-45°.

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