Reference Manual

15−3
Figure 15-4. Disc Refiner
Drawing is from TAPPI’s Making Pulp and
Paper Series and is used with permission.
2. Jordan (or Conical) refiner: In this type, the
rotating plug (rotor) and its housing (stator) are
fitted with metal bars oriented lengthwise. The
fibers flow parallel to the bars. The position of the
plug determines the clearance of the bars and
controls the amount of work done on the fibers for
a constant stock throughout.
It has been shown that having a disc refiner is
more advantageous to a mill. They have lower
no-load energy consumption, which lowers energy
costs. They have greater versatility of their refiner
plate designs and, because of these designs, can
take on higher stock consistencies. They are more
compact than the Jordan and are a lower capital
investment.
Blend Chest
All the furnish components including hardwood
pulp, softwood pulp, and broke are mixed together
in the blend chest. All components must be well
blended before the stock is diluted down to
papermaking consistency.
Stock Screening
In some mills, this process follows the blend chest.
High consistency pulp of around 4% is run through
fine slotted screens to remove hard debris that
could cause defects in the sheet of paper (figure
15-5). Arranged in multiple stages, the screens
generally have a protection screen followed by two
stages of fine slotted screens using 6 to 10
thousandth of an inch, although this size varies
based on the furnish or grade of paper (figure
15-6). The first two stages run at a high
consistency, but the final tailing screen runs at a
Figure 15-5. Fine Slotted Screens
Drawing is from TAPPI’s Making Pulp and
Paper Series and is used with permission.
Figure 15-6. Stock Screening Process
Drawing is from TAPPI’s Making Pulp and
Paper Series and is used with permission.
somewhat lower consistency, around 1.0 to 1.5%,
in order to make a better split between good fiber
and debris.
Machine Chest
This is the last chest in the thick stock part of
stock prep. By this point, all the fibers have been
blended and the consistency controlled. It is
important that the consistency, anywhere from 3%
to 4%, is controlled when going forward in the
system as this stock controls the basis weight of
the paper. It is from here the stock will enter the
thin stock portion of stock prep.