Method and device for automatic detection and control of liquid level in precondensation reactor with stirring

Abstract

The invention discloses an automatic detection and control method and device for the liquid level in a pre-polycondensation reaction kettle with a stirring function. According to the technical scheme, a laser distance meter is arranged above the reaction kettle, a detection block is fixedly arranged on the shaft wall, exposed out of the reaction kettle, of a stirring shaft, and a detection switch is arranged on a fixed position outside the reaction kettle. When the detection switch detects a detection block signal, a stirring paddle on the stirring shaft is at the position which does not shield the laser emitted by the laser distance meter; in the state, the actual liquid level of the reaction kettle is calculated according to a distance signal measured by the laser distance meter; the actual liquid level is compared with a preset liquid level value through a PID module in a PLC controller, and the compared data is used for controlling the frequency of a discharge pump frequency converter, so that the rotation speed of a discharge pump motor is adjusted. The scheme solves the problem that the shielding of the stirring paddle in the reaction kettle interferes with laser measurement, and the measured liquid level precision of materials can be + / -3mm. The device has the advantages of being simple in structure and reliable in running and is suitable for liquid level detection and control of a variety of polymer pre-polycondensation reaction kettles.

Description

technical field [0001] The invention relates to a method for automatically detecting the liquid level in a reaction kettle, and then automatically controlling the discharge speed and stabilizing the liquid level according to the detected liquid level, and an automatic liquid level detection and control device for implementing the above method, which is suitable for polymer production lines The utility model relates to a precondensation reaction kettle with agitation on top, which belongs to the technical field of polymer production and control. Background technique [0002] In the production process of most polymers, it is necessary to go through the pre-condensation reaction from the esterification reaction to the final polycondensation reaction. It will finally complete the esterification reaction of the esterified product obtained by the esterification reaction, and carry out the polycondensation reaction under certain vacuum conditions. Generate prepolymers, so as to ens...

AI Technical Summary

Problems solved by technology

The above-mentioned laser measurement technology is also widely used in the precondensation reactor, but in the actual use process, there are still the following deficiencies in the liquid level measurement and control of the material in the precondensation reactor: ① Due to the blocking of the stirring paddle in the reactor , the use of laser measurement will be interfered by the stirring paddle, which will affect the accuracy of the measurement; ②Similarly due to the existence of the stirring paddle, it is difficult to directly detect the liquid level from the top of the reactor, and the material liquid level can be determined by human observation and the discharge pump can be manually adjusted The speed is used to control the discharge, which will easily lead to shortcomings such as insufficient accuracy, time-consuming and labor-intensive, and low efficiency; ③The materials in the pre-condensation reactor are generally viscous and easy to stick. If laser measurement is not used, flange liquid level transmitters are used To detect the liquid level of the material, the membrane head is easy to stick to the material, which will affect the reliability of the detection data

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