Continuous DOTP (Dioctyl Terephthalate) pulp preparation and esterification system

Abstract

The utility model discloses a continuous DOTP (Dioctyl Terephthalate) pulp preparation esterification system. A feed opening of a PTA (Pure Terephthalic Acid) stock bin is connected with a pulping tank through a PTA weighing device; a fresh isooctanol pipe is connected with the pulping tank through the tube pass of the isooctanol preheater; a discharge port of the pulping tank is connected with a first esterification reaction kettle, the top of the first esterification reaction kettle is further connected with a first esterification catalyst pipe and a nitrogen pipe, and an overflow discharge port of the first esterification reaction kettle is connected with a second esterification reaction kettle; gas phase outlets of the two esterification kettles are connected with a process tower; a bottom outlet of the process tower is connected with reflux isooctanol injection ports in the tops of the esterification reaction kettles I and II; a top exhaust port of the process tower is respectively connected with the tower top condenser and a shell pass inlet of the isooctanol preheater, a shell pass outlet of the tower top condenser and a shell pass outlet of the isooctanol preheater are connected with a tube pass inlet of the tail gas condenser, a condensate outlet of each device is connected with the tower top receiving tank, and an overflow port of the tower top receiving tank is connected with a top reflux port of the process tower. The system is low in investment cost and energy consumption and can realize continuous production.

Description

Technical Field

[0001] This utility model relates to the preparation of a polymer material, and more particularly to a DOTP continuous slurry mixing and esterification system, belonging to the technical field of polyester production equipment. Background Technology

[0002] Dioctyl terephthalate (DOTP) is an organic compound, a transparent oily liquid, insoluble in water but soluble in common organic solvents. In industrial applications, DOTP is a high-performance primary plasticizer for polyvinyl chloride (PVC) plastics. Compared to the commonly used diisooctyl phthalate (DOP), it has advantages such as heat resistance, cold resistance, low volatility, pull-out resistance, flexibility, and good electrical insulation properties. In finished products, it exhibits excellent durability, soap water resistance, and low-temperature flexibility. As a benchmark for environmentally friendly plasticizers, DOTP has become the preferred choice in high-end fields such as wire and cable, food packaging, and medical devices due to its excellent low-temperature resistance, low volatility, and regulatory compliance.

[0003] Currently, DOTP is mainly produced by reacting terephthalic acid and isooctanol under titanate catalysis, a reaction that is a liquid-solid heterogeneous system. Industrially, stirred tank reactors are commonly used for DOTP production, typically in a batch operation mode. This process suffers from slow reaction rates, low production efficiency, and high energy consumption.

[0004] Chinese Patent Publication No. CN114768278A discloses an energy-efficient and high-performance continuous DOTP production device and its production process. It includes a feeding system, n-stage reactive distillation systems connected in series, and a reaction liquid post-treatment system, where n is an integer ≥3. Each stage of the reactive distillation system includes a stirred reactor with a reflux condenser system. The reflux condenser system includes a packed tower at the top of the stirred reactor, a primary condenser, a secondary condenser, an alcohol-water tank, and a reflux alcohol heater at the top of the packed tower. This device can operate in steady state. The reactive distillation system can stably produce isooctanol vapor with water, and the latent heat of vaporization of the isooctanol vapor is recovered through the primary condenser. The reflux condenser system achieves the heat reflux of most of the isooctanol through staged condensation, reducing the heat load required by the stirred reactor. It also prevents the rising vapor in the packed tower of the reactive distillation system from being cooled by the low-temperature reflux isooctanol and carrying moisture back to the stirred reactor, thus significantly reducing energy consumption.

[0005] This technical solution meets the requirements for continuous production of DOTP, but the following problems still exist:

[0006] 1. The number of reactors is relatively large, resulting in high initial investment costs;

[0007] 2. The feeding system relies on manual feeding, which does not fully meet the requirements of continuous production, and manual feeding limits the overall production capacity;

[0008] 3. The esterification steam is condensed and stored in the steam drum, and the waste heat of the esterification steam is not fully utilized;

[0009] 4. Each esterification reactor is equipped with a separate condensation reflux system, which is complex to control and not conducive to actual production operation. Utility Model Content

[0010] The purpose of this invention is to overcome the problems existing in the prior art and provide a DOTP continuous slurry preparation and esterification system with low initial investment cost, which can fully meet the requirements of continuous production, improve the production line capacity, and has low energy consumption and simple operation.

[0011] To solve the above technical problems, this utility model provides a continuous DOTP slurry preparation and esterification system, including a PTA silo. The bottom discharge port of the PTA silo is connected to the inlet of a PTA weighing device, and the outlet of the PTA weighing device is connected to the powder inlet of a pulping tank. A fresh isooctanol pipe is connected to the tube-side inlet of an isooctanol preheater, and the tube-side outlet of the isooctanol preheater is connected to the alcohol inlet of the pulping tank via an isooctanol feed pipe. The discharge port of the pulping tank is connected to the inlet of a slurry delivery pump, and the outlet of the slurry delivery pump is connected to the top inlet of an esterification reactor. The top of the esterification reactor is also connected to an esterification catalyst pipe and a nitrogen pipe. The overflow outlet of the esterification reactor is connected to the esterification discharge outlet. The pipe is connected to the feed inlet of the esterification reactor II; the gas phase outlets of the esterification reactor I and esterification reactor II are respectively connected to the lower inlet of the process tower, and the bottom outlet of the process tower is connected to the reflux isooctanol injection port at the top of the esterification reactor I and esterification reactor II; the top exhaust port of the process tower is respectively connected to the shell-side inlet of the top condenser and the isooctanol preheater, the shell-side outlet of the top condenser and the isooctanol preheater is connected to the lower tube-side inlet of the tail gas condenser, the shell-side condensate outlet of the top condenser and the isooctanol preheater and the bottom tube-side outlet of the tail gas condenser are respectively connected to the liquid seal pipe of the top receiving tank, and the upper overflow port of the top receiving tank is connected to the top reflux port of the process tower.

[0012] As an improvement of this utility model, the bottom outlet of the esterification reactor is connected to an emptying pipe, and the outlet of the emptying pipe is connected to the esterification discharge pipe through an injection valve.

[0013] As a further improvement of this utility model, the inlet of the PTA silo is connected to the upper outlet of the PTA chain conveyor via a chute, and the horizontal conveying section of the PTA silo is provided with a tank car feeding port and a manual feeding port.

[0014] As a further improvement of this utility model, the isooctanol supply pipe is equipped with an isooctanol supply regulating valve and an isooctanol flow meter, and the opening degree of the isooctanol supply regulating valve is controlled by the feeding amount of the PTA weighing device.

[0015] As a further improvement of this utility model, the lower part of the inner cavity of the esterification reactor is provided with a steam heating coil, the inlet of which is connected to a steam pipe and the outlet of which is connected to a condensate recovery pipe.

[0016] As a further improvement of this utility model, the esterification reaction vessel is a horizontal four-chamber structure, with partitions between adjacent chambers and overflow grooves at the top of each partition. The first to fourth chambers are equipped with independent steam heating coils and stirring devices. The bottom of the first chamber is provided with an esterification inlet, and the top of the first chamber is connected to the esterification catalyst tube. The reflux isooctyl alcohol injection port at the top of each chamber is connected to the bottom outlet of the process tower. The bottom outlet of the fourth chamber is connected to the downstream section through the esterification discharge pipe.

[0017] As a further improvement of this utility model, the reflux isooctanol injection pipe of the esterification reactor is equipped with a top reflux regulating valve and a top reflux flow meter of the esterification reactor, and the reflux isooctanol injection pipes of each chamber of the esterification reactor are respectively equipped with a top reflux regulating valve and a top reflux flow meter of the esterification reactor.

[0018] As a further improvement of this utility model, the upper outlet of the tube side of the exhaust gas condenser is connected to the exhaust gas treatment system through the end exhaust regulating valve.

[0019] As a further improvement of this utility model, the upper overflow port of the top receiving tank is connected to the top reflux port of the process tower through an isooctanol reflux regulating valve and an isooctanol reflux flow meter, and the bottom outlet of the top receiving tank is connected to the wastewater treatment station through a drainage regulating valve.

[0020] Compared with the existing technology, the present invention has achieved the following beneficial effects: 1. The system can make the reaction continuous, with a high degree of automation, reducing the frequency of personnel operation, fewer procedures, convenient operation, stable product quality, significant increase in production capacity, low equipment investment cost, low operating cost, low energy consumption, low raw material consumption, and significant continuous operating profit.

[0021] 2. It can precisely control the raw material molar ratio, which is more conducive to the stable progress of the reaction and improves the quality and stability of the product; the esterification reactor I adopts a fully mixed reactor, and the esterification reactor II is horizontal and divided into four chambers. The division of the four chambers makes the material flow approximately horizontally, ensuring the stability of continuous reaction and more uniform molecular weight distribution; it also reduces the number of reactors, lowers equipment investment costs, and improves land utilization.

[0022] 3. The esterification reactor I and esterification reactor II share a single process tower. The bottom of the tower is completely refluxed to the two esterification reactors. Each reactor's reflux pipe is equipped with a regulating valve and a flow meter to control the reflux ratio, making the continuous reaction more stable and reducing equipment investment.

[0023] 4. An isooctanol preheater is installed at the top of the process tower to heat fresh isooctanol using the waste heat at the top of the process tower. The heated isooctanol is then used directly for slurry preparation. This not only facilitates PTA mixing but also allows the higher-temperature slurry to enter the esterification reactor, effectively reducing the heat load on the esterification reactor and achieving high efficiency and energy saving. Attached Figure Description

[0024] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The drawings are provided for reference and illustration only and are not intended to limit the present invention.

[0025] Figure 1 This is a flowchart of the DOTP continuous slurry preparation and esterification system of this utility model;

[0026] In the diagram: 1. Powder tanker; 2. Feeding hoist; 3. PTA chain conveyor; 4. PTA silo; 5. PTA weighing device; 6. Pulping tank; 7. Pulp transfer pump; 8. Esterification reactor I; 9. Esterification reactor II; 10. Process tower; 11. Tower top condenser; 12. Isooctyl alcohol preheater; 13. Tail gas condenser; 14. Tower top receiving tank; 15. Tail gas treatment system; 16. Wastewater treatment station;

[0027] G1. Fresh isooctanol pipe; G2. Isooctanol feed pipe; G3. Esterification I catalyst pipe; G4. Nitrogen pipe; G5. Esterification I discharge pipe; G6. Esterification II catalyst pipe; G7. Esterification II discharge pipe; G8. Process tower exhaust pipe; G9. Steam pipe; G10. Condensate recovery pipe; G11. Cooling water inlet pipe; G12. Cooling water outlet pipe;

[0028] V1. Isooctanol feed regulating valve; Q1. Isooctanol flow meter;

[0029] V2. Esterification-top reflux regulating valve; Q2. Esterification-top reflux flow meter;

[0030] V3. Top reflux regulating valve for esterified bismuth sub-ester; Q3. Top reflux flow meter for esterified bismuth sub-ester;

[0031] V4. Isooctanol reflux regulating valve; Q4. Isooctanol reflux flow meter;

[0032] V5. Injection valve; V6. Process tower exhaust regulating valve; V7. End exhaust regulating valve; V8. Drainage regulating valve. Detailed Implementation

[0033] In the following description of this utility model, the terms "upper," "lower," "front," "rear," "left," "right," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this utility model and simplifying the description, and do not mean that the device must have a specific orientation. All pressures mentioned herein refer to absolute pressure.

[0034] To make the technical means, creative features, objectives and effects of this utility model easier to understand, the following description, in conjunction with specific illustrations, further elaborates on this utility model.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0036] like Figure 1 As shown, the DOTP continuous slurry esterification system of this utility model includes a PTA chain conveyor 3, a PTA silo 4, a PTA weighing device 5, a pulping tank 6, an esterification reactor 1 8, and an esterification reactor 2 9. The upper discharge port of the PTA chain conveyor 3 is connected to the inlet of the PTA silo 4 via a chute. The horizontal conveying section of the PTA chain conveyor 3 is equipped with a tank truck feeding port and a manual feeding port, which can perform both tank truck unloading and manual feeding functions, and can be applied to larger capacity units. When the powder tank truck 1 delivers material, it can be directly unloaded through the tank truck feeding port; when material is retrieved from the warehouse, it can be fed through the feeding hoist 2 to the manual feeding port, and both are conveyed into the large-capacity PTA silo 4 by the PTA chain conveyor 3.

[0037] The bottom discharge port of PTA silo 4 is connected to the inlet of PTA weighing device 5, which facilitates accurate measurement and stable discharge of PTA. The outlet of PTA weighing device 5 is connected to the powder inlet of pulping tank 6.

[0038] The outlet of the isooctanol feed pipe G2 is connected to the alcohol inlet of the pulping tank 6 through the isooctanol feed regulating valve V1 and the isooctanol flow meter Q1. The isooctanol feed rate is controlled by the isooctanol feed regulating valve V1 and the isooctanol flow meter Q1, and the isooctanol flow rate is interlocked with the PTA feed rate to achieve stable and continuous feeding. This allows for more precise control of the raw material molar ratio, which is more conducive to the smooth progress of the reaction and improves the quality and stability of the product.

[0039] A stirring shaft and stirring blades are installed along the axis of the pulping tank 6. The stirring blades mix and pulp the PTA powder and isooctanol in the pulping tank 6. The outlet of the pulping tank 6 is connected to the inlet of the slurry transfer pump 7, and the outlet of the slurry transfer pump 7 is connected to the top inlet of the esterification reactor 8. The outlet of the esterification catalyst tube G3 is also connected to the top inlet of the esterification reactor 8. The esterification reactor 8 is a vertical fully mixed reactor, equipped with controls for temperature, pressure, material level, and reflux ratio to ensure stable operation of the continuous reactor.

[0040] A stirring shaft and stirring blades are provided along the axis of the esterification reactor 8. A steam heating coil is provided in the lower part of the inner cavity of the esterification reactor 8. The inlet of the steam heating coil is connected to the steam pipe G9, and the outlet of the steam heating coil is connected to the condensate recovery pipe G10. The esterification reactor requires a large amount of heat. High-pressure steam and a regulating valve are used to control the reactor temperature to heat the slurry and provide the heat for the esterification reaction.

[0041] The overflow outlet of the esterification reactor 8 is connected to the esterification discharge pipe G5. The top of the esterification reactor 8 is also equipped with a nitrogen injection port connected to the nitrogen pipe G4, which facilitates the material to be squeezed out from the overflow outlet.

[0042] Under the indirect heating of steam and the action of titanium-based catalyst, PTA undergoes an esterification reaction with isooctanol. When the esterification rate reaches about 90%, it is discharged from the esterification discharge pipe G5.

[0043] The bottom outlet of the esterification reactor 8 is connected to the esterification discharge pipe G5 through an evacuation pipe and an injection valve V5, which facilitates the complete discharge of materials from the esterification reactor 8 under the action of nitrogen.

[0044] The discharge pipe G5 of esterification stage 1 is connected to the bottom inlet of esterification stage 2 reactor 9. Esterification stage 2 reactor 9 is horizontal and divided into four chambers, each equipped with a heating coil to ensure stable and uniform heating for each stage. The four chambers allow for a near-plug flow of the material, ensuring stable continuous reaction and a more uniform molecular weight distribution. This also reduces the number of reactors, lowers equipment investment costs, and improves land utilization. The discharge port of esterification stage 2 reactor 9 is connected to the subsequent stages via esterification stage 2 discharge pipe G7. The top of esterification stage 2 reactor 9 also has a catalyst inlet connected to esterification stage 2 catalyst pipe G6 for easy injection of titanium-based catalyst.

[0045] Each of the four chambers is equipped with a steam heating coil at its bottom. The inlet of each steam heating coil is connected to a steam pipe G9, and the outlet of each steam heating coil is connected to a condensate recovery pipe G10. The esterification reactor 9 is equipped with controls for temperature, material level, pressure, and reflux ratio to ensure stable operation of the device.

[0046] The process steam generated by the esterification reaction is pretreated through process tower 10. The gas phase outlets of esterification reactor 8 and esterification reactor 9 are connected to the lower inlet of process tower 10. The bottom outlet of process tower 10 is connected to the reflux isooctanol injection port of esterification reactor 8 through esterification reactor 1 top reflux regulating valve V2 and esterification reactor 1 top reflux flow meter Q2. The bottom outlet of process tower 10 is connected to the reflux isooctanol injection ports of each chamber in esterification reactor 9 through esterification reactor 2 top reflux regulating valve V3 and esterification reactor 2 top reflux flow meter Q3.

[0047] Esterification reactor 8 and esterification reactor 9 share a process tower 10. The process steam mainly consists of a mixture of isooctanol, water and a small amount of esterified products. The process tower 10 processes and separates the esterified products carried out by the process steam.

[0048] The isooctanol and esterified products at the bottom of the tower are then refluxed back to esterification reactor 8 and esterification reactor 9 via a differential flow. The reflux management of the esterification reactors is equipped with regulating valves and flow meters to control the reflux ratio, ensure the molar ratio in the reaction system, ensure the reaction rate, make the continuous reaction more stable, and reduce equipment investment.

[0049] The top exhaust port of the process tower 10 is connected to the process tower exhaust pipe G8. The outlet of the process tower exhaust pipe G8 is connected to the shell-side inlet of the top condenser 11. The shell-side outlet of the top condenser 11 is connected to the lower tube-side inlet of the tail gas condenser 13. The bottom tube-side outlet of the tail gas condenser 13 is connected to the inlet pipe of the top receiving tank 14. The upper tube-side outlet of the tail gas condenser 13 is connected to the tail gas treatment system 15 through the end exhaust regulating valve V7.

[0050] The condensate enters the shell side of the overhead condenser 11 for cooling, and the cooled condensate returns to the overhead receiving tank 14. Isooctol and water separate into layers within the overhead receiving tank 14; the upper isooctol is refluxed to the process column 10, and the bottom water is discharged to wastewater treatment via a regulating valve. A regulating valve is installed on the gas phase outlet line of the overhead condenser 11 to control the overhead pressure of the process column 10.

[0051] The shell-side inlets of the top condenser 11 and the tail gas condenser 13 are connected to the cooling water inlet pipe G11, and the shell-side inlets of the top condenser 11 and the tail gas condenser 13 are connected to the cooling water outlet pipe G12.

[0052] The top of the process tower 10 is also equipped with an isooctanol preheater 12. The outlet of the process tower exhaust pipe G8 is connected to the shell-side inlet of the isooctanol preheater 12 through the process tower exhaust regulating valve V6. The shell-side outlet of the isooctanol preheater 12 is also connected to the lower tube-side inlet of the tail gas condenser 13. The outlet of the fresh isooctanol pipe G1 is connected to the tube-side inlet of the isooctanol preheater 12, and the tube-side outlet of the isooctanol preheater 12 is connected to the isooctanol feed pipe G2. The fresh isooctanol exchanges heat with the process steam, which can condense the azeotrope and separate isooctanol from water, and heat the fresh isooctanol, utilizing waste heat and reducing energy consumption. The heated isooctanol is directly used for slurry preparation; this not only facilitates PTA mixing, but also allows the higher-temperature slurry to enter the esterification reactor 8, effectively reducing the heat load of the esterification reactor 8 and achieving high efficiency and energy saving.

[0053] The condensate outlets from the shell side of the top condenser 11 and isooctanol preheater 12 are connected to the inlet pipes of the top receiving tank 14. Each inlet pipe of the top receiving tank 14 extends to the lower part of the tank. The bottom outlet of the top receiving tank 14 is connected to the wastewater treatment station 16 via a drain regulating valve V8. The upper overflow port of the top receiving tank 14 is connected to the top reflux port of the process column 10 via an isooctanol reflux regulating valve V4 and an isooctanol reflux flow meter Q4.

[0054] The top receiving tank 14 is a vertical and slender type, which can effectively separate isooctanol and water in the top receiving tank 14. The upper isooctanol is refluxed to the process tower 10 to reduce the consumption of raw materials, and the bottom water is discharged to the wastewater treatment station 16 for treatment through the drain regulating valve V8.

[0055] The exhaust gas discharged from the shell side of the top condenser 11 and the isooctanol preheater 12 enters the tube side of the exhaust gas condenser 13 to further collect the isooctanol in the exhaust gas; this not only reduces the load of subsequent exhaust gas treatment, but also effectively reduces raw material loss, lowers costs, and improves the product's market competitiveness.

[0056] The above description is merely a preferred embodiment of the present utility model, showing and describing the basic principles, main features, and advantages of the present utility model. It is not intended to limit the scope of patent protection of the present utility model. Those skilled in the art should understand that the present utility model is not limited to the above embodiments. In addition to the above embodiments, the present utility model may have other implementations without departing from the spirit and scope of the present utility model. Various changes and improvements to the present utility model are also possible. All technical solutions formed by equivalent substitutions or equivalent transformations fall within the scope of protection claimed by the present utility model. The scope of protection claimed by the present utility model is defined by the appended claims and their equivalents. Technical features not described in the present utility model can be implemented by or using existing technology, and will not be elaborated here.

Claims

1. A DOTP continuous compounding esterification system comprising PTA silo (4) characterized by, The bottom discharge port of the PTA silo (4) is connected to the inlet of the PTA weighing device (5), and the outlet of the PTA weighing device (5) is connected to the powder inlet of the pulping tank (6). The fresh isooctanol tube (G1) is connected to the tube-side inlet of the isooctanol preheater (12), and the tube-side outlet of the isooctanol preheater (12) is connected to the alcohol inlet of the pulping tank (6) through the isooctanol feed tube (G2). The outlet of the pulping tank (6) is connected to the inlet of the slurry conveying pump (7), the outlet of the slurry conveying pump (7) is connected to the top inlet of the esterification reactor (8), the top of the esterification reactor (8) is also connected to the esterification catalyst tube (G3) and the nitrogen tube (G4), and the overflow outlet of the esterification reactor (8) is connected to the inlet of the esterification reactor (9) through the esterification discharge tube (G5); The gas phase outlets of the esterification reactor (8) and the esterification reactor (9) are connected to the lower inlet of the process tower (10), and the bottom outlet of the process tower (10) is connected to the reflux isooctyl alcohol injection port at the top of the esterification reactor (8) and the esterification reactor (9). The top exhaust port of the process column (10) is connected to the shell-side inlet of the top condenser (11) and the isooctanol preheater (12), respectively. The shell-side outlets of the top condenser (11) and the isooctanol preheater (12) are connected to the lower tube-side inlet of the tail gas condenser (13). The shell-side condensate outlet of the top condenser (11) and the isooctanol preheater (12) and the bottom tube-side outlet of the tail gas condenser (13) are also connected. The liquid seal pipes are respectively connected to the top receiving tank (14) of the tower, and the upper overflow port of the top receiving tank (14) is connected to the top reflux port of the process tower (10).

2. The DOTP continuous compounding esterification system of claim 1, wherein: The bottom outlet of the esterification reactor (8) is connected to an emptying pipe, and the outlet of the emptying pipe is connected to the esterification discharge pipe (G5) through an injection valve (V5).

3. The DOTP continuous compounding esterification system of claim 1, wherein: The inlet of the PTA silo (4) is connected to the upper outlet of the PTA chain conveyor (3) via a chute. The horizontal conveying section of the PTA silo (4) is equipped with a tank car feeding port and a manual feeding port.

4. The DOTP continuous compounding esterification system of claim 1, wherein: The isooctanol feed pipe (G2) is equipped with an isooctanol feed regulating valve (V1) and an isooctanol flow meter (Q1). The opening degree of the isooctanol feed regulating valve (V1) is controlled by the feed amount of the PTA weighing device (5).

5. The DOTP continuous compounding esterification system of claim 1, wherein: The lower part of the inner cavity of the esterification reactor (8) is provided with a steam heating coil. The inlet of the steam heating coil is connected to the steam pipe (G9), and the outlet of the steam heating coil is connected to the condensate recovery pipe (G10).

6. The DOTP continuous compounding esterification system of claim 1, wherein: The esterification reactor (9) is a horizontal four-chamber structure. Each adjacent chamber is separated by a partition plate, and each partition plate has an overflow trough at its top. Each of the first to fourth chambers is equipped with an independent steam heating coil and a stirring device. The bottom of the first chamber is provided with an esterification inlet, and the top of the first chamber is connected to the esterification catalyst tube (G6). The reflux isooctyl alcohol injection port at the top of each chamber is connected to the bottom outlet of the process tower (10), and the bottom outlet of the fourth chamber is connected to the downstream section through the esterification discharge pipe (G7).

7. The DOTP continuous compounding esterification system of claim 6, wherein: The reflux isooctyl alcohol injection pipe of the esterification reactor (8) is equipped with a top reflux regulating valve (V2) and a top reflux flow meter (Q2) of the esterification reactor (9). The reflux isooctyl alcohol injection pipes of each chamber of the esterification reactor (9) are respectively equipped with a top reflux regulating valve (V3) and a top reflux flow meter (Q3) of the esterification reactor (9).

8. The DOTP continuous compounding esterification system of claim 1, wherein: The upper outlet of the exhaust gas condenser (13) is connected to the exhaust gas treatment system (15) via the end exhaust regulating valve (V7).

9. The DOTP continuous compounding esterification system of any one of claims 1 to 8, wherein: The upper overflow port of the top receiving tank (14) is connected to the top reflux port of the process tower (10) through the isooctanol reflux regulating valve (V4) and the isooctanol reflux flow meter (Q4), and the bottom outlet of the top receiving tank (14) is connected to the wastewater treatment station (16) through the drain regulating valve (V8).

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