JPS6121462B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of supplying a slurry of terephthalic acid and ethylene glycol, and more particularly to a method of supplying a slurry of a constant molar ratio to a batch-type esterification reactor. .

From terephthalic acid (hereinafter referred to as TPA) and ethylene glycol (hereinafter referred to as EG), bis-β-hydroxyethyl terephthalate and/or its low polymer is obtained through an esterification reaction, and then polycondensation reaction is performed to produce polyethylene. Direct polymerization methods to obtain terephthalates are well known. It is also well known that direct esterification is an economically more advantageous method than transesterification starting from dimethyl terephthalate.
Furthermore, direct esterification methods are known as continuous and batch methods, but continuous esterification methods cannot completely prevent the formation of gelled substances and foreign substances in the reactor, and furthermore, they are not suitable for the purpose of producing a wide variety of products. However, there are disadvantages such as lack of functionality. In addition, in the batch esterification method, it is difficult to always supply a slurry of TPA and EG with a constant molar ratio. It is difficult to supply a slurry with a constant molar ratio in a method of carrying out a batch esterification reaction by distributing the slurry to esterification reaction vessels.
Generally, when EG/TPA slurry is continuously fed to a batch type esterification reaction tank, the feeding time is 40% to 80% of the reaction time. Therefore, as shown in Figure 1, it has one slurry tank and slurry circulation line,
When slurry is supplied to a plurality of batch-type esterification reaction vessels from the middle of the process, the total amount of slurry supplied to each reaction vessel at each time, that is, the required amount of slurry at each time changes significantly.

For this reason, the conventional approach was to install a slurry tank with a sufficiently large capacity to accommodate changes in the required amount. However, this method not only requires a high equipment cost for the slurry tank itself, but also requires stirring a highly viscous and sedimentary slurry, which requires a slurry tank agitator, which requires a huge equipment cost. The inventors of the present invention have arrived at the present invention as a result of extensive studies aimed at solving the problem of equipment costs and stably supplying slurry with a uniform molar ratio at low cost.

That is, in the present invention, when a slurry consisting of TPA and EG is manufactured and supplied to a batch type esterification reaction tank, a liquid level gauge is provided in the slurry tank, and the signal from the level gauge is used to control the EG flow rate controller and the TPA. This is a method for supplying slurry of TPA and EG, characterized in that the production amount and molar ratio of the slurry are controlled by interlocking a weight controller and a molar ratio calculator.

The present invention will be specifically explained with reference to the drawings.

FIG. 1 shows an embodiment of the present invention in which there are four esterification tanks. The TPA stored in the hopper 1 is passed through a rotary valve 2, measured by an endless belt type, electromagnetic feeder type, or rotary feed type weighing machine 3, and then supplied to a kneading machine 4. On the other hand, EG is supplied to the kneader 4 via a flow meter 6 and a flow control valve 5. With kneading machine 4
Mix TPA and EG to produce slurry. The obtained slurry is supplied to the slurry tank 7, passes through the circulation pump 8 and the circulation line 9, and is then sent to the esterification reaction tanks 30 to 30.
33. The supply amount of this slurry is controlled by appropriately increasing or decreasing the rotation speed of the circulation pump 8 according to the required amount of each esterification tank. Therefore, the liquid level in the slurry tank 7 is measured by the slurry tank liquid level gauge LRC11, and the slurry production amount is controlled in cascade so as to maintain the set liquid level range. This cascade control method measures the liquid level in the slurry tank 7 and sends this signal.
The weight is given to the TPA weight controller WRC12, and the belt speed of the TRA weighing machine 3 and the rotational speed of the rotary valve 2 are adjusted to control the TPA weight. TPA
The weight controller WRC12 controls the TPA weight and at the same time sends the weight measurement signal to the molar ratio calculator MX1.
It is given to 4. The molar ratio calculator MX14 calculates the amount of EG commensurate with the TPA weight and the set molar ratio. Set this value to EG flow controller FRC.
13, and the EG flow rate controller FRC13 controls the EG by adjusting the opening degree of the flow rate control valve 5 so as to measure EG commensurate with this value. In the above control method, the EG amount is controlled from the TPA supply amount, but it goes without saying that the TPA supply amount may be controlled from the EG amount. The slurry produced from TPA and EG controlled in this manner is stored in a slurry tank 7 and supplied to a circulation line 9 through a circulation pump 8. The slurry extracted from the three-way extraction valves 21-24 provided in the circulation line 9 is continuously supplied to the batch-type esterification reaction tanks 30-33 via supply pumps 25-28. Circulation line 9
If necessary, an intermediate slurry tank can be installed before the esterification tank. of the present invention
A preferred setting ratio of EG/TPA molar ratio is in the range of 0.8 to 2.0. In the present invention, the range of change in the molar ratio set within this range can be set to a highly accurate constant molar ratio of ±0.02 of the set value.

By supplying slurry in the method of the invention,
The capacity of the slurry tank and the slurry tank agitator could be made very small. As a result, we were able to significantly reduce equipment costs. In addition, it is possible to control changes in the amount of slurry used due to troubles in the esterification reaction, making it unnecessary for operators to monitor the slurry production process.

[Brief explanation of the drawing]

FIG. 1 shows a preferred process schematic diagram of the present invention when there are four esterification tanks. 3...TPA measuring machine, 4...kneading machine, 5...EG
Flow rate control valve, 6...EG flow meter, 7...Slurry tank, 8...Slurry circulation pump, 9...Slurry circulation line, 11...Liquid level gauge, 12...TPA weight controller, 13...EG flow rate controller, 1
4... Molar ratio calculator, 30-33... Esterification reaction tank.

Claims (1)

[Claims] 1. When producing a slurry consisting of terephthalic acid and ethylene glycol and supplying it to a batch-type esterification reaction tank, a level gauge is installed in the slurry tank, and a signal from the level gauge is used to control the ethylene glycol flow rate controller and terephthalic acid. A method for supplying slurry of terephthalic acid and ethylene glycol, characterized in that the production amount and molar ratio of the slurry are controlled by interlocking a weight controller and a molar ratio calculator.