What is the function of the ventilation system of the drying section?

The ventilation system of the drying section is one of the essential links in the drying process of the paper machine. The hot air hood of the drying cylinder controls the ventilation system of the whole drying section of the paper machine by controlling the exhaust air volume and supply air volume. The size of the supply air volume and exhaust air volume depends on the temperature, humidity and pressure of the air in the hood.

Process of the ventilation system of the drying section: the hot and humid air generated in the drying process of the paper web enters the waste heat recovery device through the air inlet on the closed hood, and the waste heat is recovered. The hot and humid air after the waste heat recovery is sent to the outdoor air by the exhaust fan; if the temperature of the hot air after the preheating of the heat recovery device still fails to reach the required air temperature, the hot air needs to be sent to the air again. After further heating in the heat exchanger, it is fed into the hot air hood again.

Working principle of ventilation system in drying section of paper machine

The function of the drying section of the paper machine of the ventilation equipment is to send the hot and dry air into the workshop and the hot and humid air out of the workshop, so that the paper can be dried. The press dryness of wet web is about 45%, and the paper dryness is about 95%. Therefore, the drying section of paper machine must discharge a lot of hot and humid air from the closed hood in time.

Working principle of closed hood ventilation system: the hot and humid air generated in the drying process of paper web enters the primary air-air heat recovery device through the air manifold for waste heat recovery, and then it is sent to the secondary air-water heat recovery device for waste heat recovery. In general, the paper-making enterprises carry out two-stage waste heat recovery, without three-stage waste heat recovery, the recovery value is not great. The air supply system in the pocket area uses primary air-air recovery waste heat to preheat the fresh air. After the preheated fresh air is heated to about 100 ℃ by the steam heater, it is sent to the bag area blow box and the paper web inlet and outlet blow box through pipes;

After the outdoor fresh air is preheated by the secondary stage waste heat recovery, it will be heated by the steam heater, either sent to the ceiling of the workshop, heating the ceiling of the workshop, to prevent the roof from condensation and dripping in winter and spring; or sent to the air box at the inlet and outlet of the paper web, to prevent the air inside and outside the hood from flowing against each other; the hot and humid steam after the waste heat recovery will be discharged outside the workshop by the closed hood exhaust system. The hood ventilation system is equipped with a complete control system to automatically control the hood air supply temperature, exhaust humidity, hood zero position and other parameters.

In the past, the paper drying section ventilation equipment was not equipped with a hot air hood. The hot and humid air flowed into the workshop. The heat released by the hot and humid air caused the temperature and humidity of the workshop to rise, the working environment of the workshop was bad, the heat was wasted, and the energy consumption was increased.

Main functions of the ventilation system of the drying section of the paper machine

1) remove the water evaporated from the wet web and improve the drying rate of the web;

2) recover hot and humid air, reduce steam consumption, reduce energy consumption and improve energy utilization;

3) reduce the workshop noise, prevent the diffusion of hot and humid air in the workshop, and create a comfortable working environment;

4) protect the service life of other equipment in the workshop;