The document summarizes the key steps and components in the paper manufacturing process using a paper machine. It describes the basic components of the paper machine including the headbox, which deposits the pulp slurry onto the wire screen, and the fourdrinier wet end, where water is removed from the web through gravity, foils, and suction before entering the press and dryer sections. It provides details on key components in the wet end like the slice, forming board, table rolls, and couch roll that work to remove water and form the paper web.

1. PAPER MANUFACTURE
VANLALNGHAKA
UG116143

2. CONTENTS
 INTRODUCTION
 THE PAPER MACHINE
 THE HEADBOX
 THE FOURDRINIER WET END

3. 1.INTRODUCTION
 Paper consists of a web of pulp fibers (normally
from wood), usually formed from an aqueous
slurry on a wire or screen, and held together by
hydrogen bonding.
 The basic steps are same for either hand- or
machine-made paper .

4. INTRODUCTION
 The steps are as follows:
1. Forming - applying the pulp slurry to a screen.
2. Draining - allowing water to drain by means of
a force such as gravity or a pressure difference
developed by a water column.
3. Pressing - further dewatering by squeezing
water from the sheet.
4. Drying - air drying or drying of the sheet over a
hot surface.

5. 2.THE PAPER MACHINE
 The paper machine is a device for continuously
forming, dewatering, pressing, and drying a
web of paper fiber. Until recently, the most
common type of wet end was the fourdrinier,
where a dilute suspension of fibers (typically
0.3-0.6% consistency) is applied to an endless
wire screen or plastic fabric.

6. THE PAPER MACHINE

7. THE PAPER MACHINE
 Water is removed by gravity, or the pressure
difference developed by table rolls, foils or
suction equipment, and the drilled couch.
 The web at this point is 18-23% consistency.
 More water is squeezed out in the press section
to a consistency of 35-55%.
 Finally the sheet is dried with steam heating in
the dryer section.

8. THE PAPER MACHINE
 Machines that use two wires to form and drain water from
the dilute, pulp slurry are called twin wire formers. These
have become popular since the late 1960s for printing and
lightweight papers.
 During the 1970s, many multi-ply formers were developed
for heavyweight board.
 These formers use up to seven wires consecutively
 and are modifications of another type of paper
 machine, used for heavy-weight board, the cylinder
 machine, which has been used since the early 1800s.

9. THE PAPER MACHINE
 For every 1 lb of fiber 200 lb of water are used.
 For this 1 lb of fiber about 195 lb of water (98%) are
removed at the wet end with the web leaving at a
consistency of 20%.
 Another 2 to 3 lb of water are removed in
 the press section (1 to 1.5%) with the web leaving
 the press section at 35-50% consistency. The
 remaining 1 to 1.5 lb (0.5 to 0.75%) of water are
 removed by the dryer section.

10. 3.THE HEADBOX
 Headbox
 It is a pressurized device that delivers a uniform pulp
slurry on the wire, through the slice, at approximately
the same velocity as that of the wire.
 The main purpose of the headbox is to convert a low
consistency fibre suspension flow (stock) in a round pipe
into a uniform flat jet several meters wide that will fall
on the wire to start the dewatering process.
 Original headboxes were open, unpressurized, and used
a hydrostatic head for the necessary pressure.

11. THE HEADBOX

12. THE HEADBOX
 Almost all headboxes on paper machines operating
below speeds of 2500 ft/min have two to five perforated
rectifier rolls (holey rolls) inside the headbox that create
microturbulence to keep the fibers in suspension, giving
even formation.
 The rolls are 0.2-0.8 meters (8-32 in.) in diameter
 with holes 1.5-2.5 cm (0.6-1.0 in.) in diameter that
occupy 40-52 % of the roll area and rotate at 5-20 rpm.
 A secondary headbox may be used part of the way down
the table to give a top coat of high quality fiber relative
to the rest of the sheet.

13. THE HEADBOX
Originally, the pressure to
accelerate the stock to the speed
of the paper machine was supplied
by a hydrostatic head of liquid.
But high speed paper machines
require too much pressure for this
to be practical, so paper machines
now used closed, pressurized
headboxes to supply the necessary
pressure.

14. THE HEADBOX

15. THE HEADBOX
 Slice
 It is a rectangular slit in the headbox where the pulp
slurry is applied to the wire.
 It consists of a lower, fixed apron and an upper,
adjustable lip controlling the slice height.
 The slice height controls how much stock is applied
to the wire (and therefore the basis weight).
 The slice height is variable across the width of the
paper machine to insure uniformity of the paper
across the width of the paper machine.

16. 4.THE FOURDRINIER WET END
 Fourdrinier
 The fourdrinier, or flat wire machine, is a paper
machine with a horizontal, moving, fine mesh,
woven wire cloth or plastic fabric upon which the
pulp slurry is deposited, forming the web.
 The front side or tending side is the side from
which the paper machine is controlled, whereas
the other side is the backside or drive side.

17. THE FOURDRINIER WET END

18. THE FOURDRINIER WET END
 Clothing
 Paper machine clothing consists of forming fabrics (wires),
press felts, and dryer felts.
 Wire, forming fabric
 It is a continuous loop or belt of finely woven screen made
from wire or plastic; the mesh size varies from 40 to 100
mesh (openings per inch).
 Before 1960, wires were made from metals such as
bronze but now they are mostly made from polyester
which is corrosion resistant and lasts much longer,
although it stretches more and cannot handle highly
abrasive furnishes.

19. THE FOURDRINIER WET END
 The forming media has three functions:
1. to transport the fiber.
2. to permit draining the sheet.
3. to transmit power.
 The power input is usually through the couch
and wire turning roll.

20. THE FOURDRINIER WET END
 Wire showers
 Wire showers (Fig. 9-9) are high pressure showers
on the underside of the wire used to remove fillers
and other material which may plug the wire.
 Usually, they move back
and forth slowly to clean
all parts of the wire and
prevent wire wearing in
one spot.

21. THE FOURDRINIER WET END
 Web
 The continuous mat of fibers that is in the process of forming
or which has already formed the final paper is known as the
web.
 Forming board
 The forming board (Fig. 9-12) consists of a large leading blade
to reach in close to the slice followed by several smaller blades,
usually with gaps between them.
 Breast roll
 The breast roll is located under the headbox and
serves to return the fabric to the forming area to receive the
stock once again. It must be rigid enough to resist deflection.

22. THE FOURDRINIER WET END
 Deckle board
 They are used to prevent the stock from flowing off
the two sides of the forming fabric when a thick
layer of stock is delivered to the fabric by a large
slice opening.
 Trim squirts, edge squirts
 The width of the sheet delivered to the press section
is controlled by trim squirts. The narrow bands of
stock left on the fabric are knocked off by edge
squirts.

23. THE FOURDRINIER WET END
 Table roll
 Table rolls are freely revolving rolls under the
fourdrinier wire that support the weight of the
wire and wet web.
 Water is removed from the bottom of the web by
a partial vacuum at the meniscus that forms at
the nip where the roll leaves the wire.

24. THE FOURDRINIER WET END
 Foils
 A foil introduced by Wrist and Burkhard (1956), is a
stationary blade 5-10 cm wide with a divergent surface so
that an angle forms between the stationary fabric and the
foil surface. The angle is usually between 0.5 to 3°.
 Lovacs
 A lovac (Hansen, 1991) develops suction using water-filled
drop legs to provide siphoning action.
 These are sometimes called wet boxes.

25. THE FOURDRINIER WET END
 Dandy roll
 The dandy roll (Fig. 9-27) is a hollow, light, wire
covered roll that rides on top of the fourdrinier wire
just ahead of the suction boxes.
 This roll has four purposes:
1. to impart a water mark to the sheet.
2. to improve the top surface for printing.
3. to improve formation by mechanical shear.
4. to increase the drainage capacity of the flat wire.

26. THE FOURDRINIER WET END
 Couch roll
 The couch roll is the guide or turning roll for the
fourdrinier wire, where the paper web leaves the
wire and the wire returns to the breast roll.
 It has two purposes: to transmit power to the fabric
and to increase the dryness of the sheet.
 Lump breaker roll
 The lump breaker roll (Fig. 9-28) is a solid roll with a
suitable soft cover that is mounted over the couch
roll to assist in drying the sheet by pressure.

27. THE FOURDRINIER WET END
 Pickup (transfer) felt
 The pickup felt is a traveling felt (blanket)
designed to pick the wet paper web off the wire
and transfer it to press section. This means that
the web is supported at all times by either the
wire or felt.

28. THE END
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