Paper Machine is designed to produce paper by removing water from the Pulp using appropriate amount of Gas and Electricity. Generally at the beginning around 99% water consist in the pulp but at the finish paper the water/ moisture is around 4 – 5%.
Fourdrinier paper machine can be described in 5 divisions. Headbox, Wire Section, Press Section, Dryer Section, Converting /Finishing.
1. Headbox: The goal of the Headbox is to equally distribute the suspension /pulp in the cross direction of the paper machine and to supply from the stock preparation in a uniform speed and linear way to the wire section. Headbox can be mold type /open roll [Generally for Liner / Media Paper] or Air Cushioned or Hydraulic Headbox with dilution control.
Thus headbox is a key equipment of the paper machine defining many important quality parameter such as GSM, Fiber formation of the finished paper.
2. Wire Section: From the headbox, Pulp distributes to wire part. There are several dewatering elements and vacuum pump installed under the wire part to eliminate and drainage the water. Generally Dandy roll [for low speed machine] and Top Former /Hybrid Former [For high speed machine] or gap former is installed at the end of the wire part for improving fiber formation and water drainage of the pulp. Paper formation begins in the wire part. Wire section can be made of single wire or double or multi wire as per engineer design. Generally 18 – 20% water eliminate after the wire part.
The Basic Roll of Wire Section is:
· Extensive separation of Fibers from water.
· Begin of paper web formation
· Prevention of too much fiber flocculation.
· Deliver pulp to press section
Fourdrinier Wire Section: This is a classical method of sheet formation. Normally, the Fourdrinier is equipped with a forming board, foils and / or table rolls, suction box, wet suction boxes and suction rolls. Drainage proceeds in the direction of gravity.
3.Press Section: The purpose of the press section is to increase the dry content of the paper web as much possible by squeezing the pulp through opposite direction of Roll and Press Felt. This will help the dryer section to consume less energy required for drying the finish paper.
A conventional press section usually consists of Suction Pick up roll, Center Roll, 1st press, 2nd Press, 3rd press. The water content in the paper web is 45 – 50% after the press section.
Shoe Press: Shoe Press has been started as state of art technology for Writing & Printing, Offset paper machines since 1980s. Recently show press is also used in tissue machine. The advantage of the shoe press is higher bulk and sheet dryness upto 52% after the press section.
4.Dryer Section: The purpose of the dryer section is to increase the dry content of the paper web usually 90 – 98% by evaporation. Dryer section is the longest part of the paper machine. This section is for drying the produced paper by Steam energy. There are upto 60 in graphic paper machine and upto 90 for board and packaging paper machines arranged in an upper and a lower row distributed into 3 or 4 groups.
Dryer section is enclosed in a drying hood with doors which can be opened.
Size press, Air Dryer, MG, Calender, Pope Reel are the added equipments based on the requirement. Size press can be Film Size press or Pond Size press. Calender usually 2 nips or 3 nips. In Tissue Machine, MG is referred as Yankee.
5.Converting: From the pope reel, Finish paper transferred to Rewinder, slitter or duplex sheet cutter [For A4 Paper] and then goes for packaging to sell in the market.
Paper Machine Parameter:
In perspective of Bangladesh, 100 – 150 TPD writing & Printing Paper machine deckle is 3000 – 3500 mm with average machine working speed is 400 – 550 mpm. For Offset paper / Tissue making all raw materials is 100% imported [Virgin Pulp – Hardwood + Softwood] and for Writing & Printing /Newsprint Paper, Raw material can be virgin pulp + local waste paper / recycle Fiber etc.
Tissue Machine of 50 – 60 TPD deckles is 2850 mm with average machine speed is 1200 – 1500 mpm.
For liner / Media / Board Paper:
Generally paper machine is made of 3 layers with 3 Headbox or combination of Headbox and mold. The raw material is imported NDLKC or Local Corrugated cartoon [OCC]. For liner Paper recently Size press is installed for sizing to give better water resistance and formation of the finish paper.
Paper machine shout down valid reason is to clean the machine once in every month as well as Felt, dryer or spare parts change etc.
Paper making is a perfect combination of Art and Technology. To produce quality paper, we all should consider the above equipments and parameter carefully.
Post time: Jun-16-2021