A liquid vapor injection negative pressure system and its control method

Abstract

The invention provides a liquid-gas jet type negative pressure pumping system and a control method of the liquid-gas jet type negative pressure pumping system. The liquid-gas jet type negative pressure pumping system comprises a water ejector, a drying cylinder, a flash tank, an ejection water tank and a water pump. An outlet of the drying cylinder is connected with an inlet of the flash tank, an outlet of the flash tank is connected with a gas inlet of the water ejector, a liquid outlet of the water ejector is connected with the ejection water tank, and an outlet of the ejector water tank is connected with a liquid inlet of the water ejector through the water pump. The control method of the liquid-gas jet type negative pressure pumping system comprises the steps that differential pressure signals set at the two ends of the drying cylinder are input signals, actual differential pressure signals, measured by a differential pressure transmitter, of the two ends of the drying cylinder are feedback signals, after deviation values of the input signals and the feedback signals are calculated by a sublevel PID controller, control signals are output so that the output frequency of a frequency converter can be controlled and rotation speed of the water pump can be controlled, water in the ejection water tank is pumped by the water pump at a set speed, and secondary steam is pumped through the liquid-gas jet type negative pressure pumping system. According to the liquid-gas jet type negative pressure pumping system and the control method of the liquid-gas jet type negative pressure pumping system, the secondary steam pumping efficiency of the drying cylinder is further improved.

Description

【Technical field】 [0001] The invention belongs to the technical field of papermaking, and in particular relates to a liquid vapor jetting negative pressure pumping system and a control method thereof. 【Background technique】 [0002] The steam-water mixture from the drying cylinder of the paper machine passes through the flash tank for steam-water separation, and the steam discharged is called secondary steam. In the low-temperature section, the secondary steam is traditionally sucked outward by the water ring vacuum pump to ensure that the flash tank However, due to the high temperature of the secondary steam, it is easy to cause the water ring vacuum pump to be damaged due to thermal deformation, which will bring the loss of production to the enterprise. At the same time, the power consumption of the water ring vacuum pump is relatively large, generally around 15KW, and the price is relatively expensive. In addition, the control of the water ring vacuum pump usually only in...

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Problems solved by technology

[0002] The steam-water mixture from the drying cylinder of the paper machine passes through the flash tank for steam-water separation, and the steam discharged is called secondary steam. In the low-temperature section, the secondary steam is traditionally sucked outward by the water ring vacuum pump to ensure that the flash tank However, due to the high temperature of the secondary steam, it is easy to cause the water ring vacuum pump to be deformed and damaged by heat, which will bring the loss of production stoppage to the enterprise. At the same time, the power consumption of the water ring vacuum pump is relatively large, generally around 15KW, and the price is relatively expensive.

In addition, the control of the water ring vacuum pump usually only includes two states of start and stop, which can only provide a certain suction force and cannot be changed according to the actual situation, and the water quality that needs to enter it is purified soft water, otherwise it will cause damage to its components. damage

The above shortcomings can be avoided by using a liquid vapor jet negative pressure system instead of a water ring vacuum pump to suck the secondary steam. In addition, the differential pressure at both ends of the drying cylinder required by different paper types is within a certain range rather than a definite value. , thus, the fatigue damage of the water pump due to the constant change of the pump speed and the damage caused by the constant change of the pressure difference in the water injector

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