Ventilation of Paper Machine Dryer Section

Ventilation system composition of the drying section

1. Steam hood

2. Steam hood exhaust fan

3. Steam hood air supply device: the hot air must be introduced into the drying section to neutralize the air volume discharged from the steam hood, if not introduced, there will produce condensation and dry paper copy problem. The air supply equipment generally includes heating coils, fans, ducts and nozzles.

4. Bag ventilation: blow box and blow roll.

5. Facilities for stabilizing webs: Used to control the flow of interfacial layers brought by the movement of the dry net and guide rollers, including ventilation devices of delivering blown boxes, Unorun blow boxes and stabilized paper sheets.

6. Heat recovery equipment: there are three forms of commonly used equipment, one is for direct spray of water, the second is the steam – gas heat exchanger, and the third is the steam – liquid heat exchanger. In the sixth phase, steam – gas heat exchanger is used, the warm steam discharged from the steam hood is used to preheat ventilation air, so that the temperature can be heated from 26 degrees to 60 degrees or more.

The function of ventilation system in the drying section

1. Capture and remove the water vapor from the drying section: the moisture into the drying part is about 7%, that is, per ton of paper in the drying section need to evaporate about 1 ton of water vapor, if simply arranged in the room, it will be very bad, which may lead to serious drip of the causing that normal production cannot be done.

Capturing and removing water vapor from the drying section is the most basic task of the dryer section. The hood and the suction system concentrate the water vapor of the dryer section and expel it from the plant.

2. Increase drying capacity and the maximum yield of the paper machine: the use of the dry network will increase the evaporation efficiency, if not timely and effectively make it discharged from the bag area, there will be high humidity, which will reduce mass transfer pressure difference of evaporation, so that the amount of evaporation capacity of dryer section will be reduced, thereby reducing the paper drying capacity and production, so for each new paper machine, the bag ventilation is very important, which has 15% impact to the drying efficiency.

3. Provide a controlled dry environment: Just as the high humidity bag area which can affect the drying capacity of the paper machine, the uneven bag humidity can cause change of the lateral drying capacity of the paper machine, which will lead to nonuniformity of moisture distribution of banners in the paper roll; besides, wrinkles, bad edges and curl may also be affected by the uniform humidity of the bag area.

4. Stabilize the paper web and improve the efficiency of the paper machine: with the continuous increase of paper machine speed, maintaining the stability of the paper web in drying section of the paper has become the main task of the ventilation system, dry paper instability may cause that speed is limited, or lots of paper machines fail to work. In order to make the paper machine have a good copy performance, a series of equipment must be used to properly handle the air of the dry section.

5. Protect paper machine equipment: If the air flow design and balance of air draft and air supply is not good, there should be condensation phenomenon, causing corrosion of the paper machine.