PSE 322 MIDTERM REVIEW QUESTIONS & ANSWERS
Fibers - Answers :Papermakers use various terms to describe this term.
Pulp
Stock
Furnish
Pulp - Answers :This term means the fibers.
Three main types: mechanical, chemical, and recycled.
Stock - Answers :This term refers to slurries of pulp fibers in water.
Furnish - Answers :This term refers to mixtures that contain other things in addition to
fibers and water.
Non-integrated mill - Answers :Pulp is purchased in the form of dry bales.
These mills utilize a pulper.
Pulper - Answers :A specialized, round chest where the sheets of pulp or waste paper
are mixed with water and exposed to high levels of hydrodynamic shear.
The combo of shearing forces and the presence of water causes most of the fibers to
become detached from each other.
Consistency - Answers :Filterable solids content.
Can be measured when a slurry of fibers flows through a coarse screen, dried, and then
measured for OD weight.
% solids = (OD wt.) / (stock mass) * 100
Thickening or Washing - Answers :The final step before the paper mill.
Important to rid the stock of harsh chemicals, salts, and extracted material after pulping
and bleaching operations that may hurt the performance of additives.
Drum filters - Answers :Typical mechanism for integrated mills to remove water from the
pulp.
Sometimes called deckers.
Filtrate from these systems returns to the corresponding pulper/bleaching system, and
eventually wastewater or chemical recovery process.
Filter cake - Answers :Comes from the pulp mill and is thickened to a consistency of 10-
20% solids.
High-Density Chest - Answers :A large tank that contains pulp that came from a
washing operation, followed by screw-press thickening. Pulp from these processes is
added to the top of the chest.
,The consistency of the pulp in this chest is too high for papermaking. At the outlet of the
chest, stock is diluted with process water to obtain a consistency of 3-5%.
Thick stock - Answers :Slurries with consistency of 3-5%.
Refining - Answers :An early technology of this mechanism is the Hollander beater,
which is oval in shape.
Repeated passes through a beating operation tend to make the fibers more flexible and
comfortable. This increases the area of adhesion (RBA) between fibers.
Double-disk refiner - Answers :The more conventional refiner used in mills.
Softwood - Answers :This type of fiber yields superior tear strength and folding
endurance.
Hardwood - Answers :This type of fiber yields better smoothness.
Blend chest - Answers :The location in which papermakers combine different streams of
stock into the system. Refining of each type of fiber is done before this location.
Thick Stock - Answers :What types of stock streams are combined in a blend chest?
Machine Chest - Answers :Acts as a buffer capacity in the system. Provides a reservoir
of stock so that papermakers can make quick adjustments in the rate at which stock is
pumped towards the paper machine.
Freeness - Answers :A measure of the rate at which water drains from fiber in the
forming process.
Allows papermakers to achieve a better combo of strength properties at a given level of
freeness. - Answers :What is the purpose of separate refining?
Tickle refiners - Answers :By having one or more of these relatively late in the process,
papermakers can make quick adjustments and begin to see the results of such
adjustments a few minutes later.
The refining plates and general design of these are often selected to give a relatively
harsh, cutting action.
Increase in load and decrease in space between refining plates = decrease in freeness
and fiber length.
Stuff box - Answers :Provides a constant head so that the flow of thick-stock furnish to
the paper machine can be accurately controlled with a valve farther downstream.
Excess furnish is recirculated back into the machine chest. Often the last point where a
chemical can be added as a stream coming out of a simple hose at ambient pressure.
, Stock valve - Answers :A papermakers primary tool for adjusting the basis weight of
paper. Controls the flow of thick stock to the paper machine.
Basis weight - Answers :Moisture-equilibrated mass per unit of area.
A constant head
A steady, known value consistency
An accurate measurement of the total flow - Answers :Steady, accurate control of thick
stock flow requires 3 things:
Mag meter - Answers :Magnetic flow analyzer
Obtains an accurate measure of total flow
Fan pump - Answers :The largest pump on the paper machine.
The furnish is diluted by a large factor before entering the forming section.
Combines metered thick stock with a lot of white water.
Thin stock - Answers :Diluted furnish coming from the fan pump.
~ 0.3 - 1.2% consistency.
The Primary Circuit - Answers :The white water loop
Includes Headbox, forming section, white water collection and silo, fan pump, and
hydrocyclone cleaners.
Hydrocyclone/Cleaner - Answers :Removes materials of different densities.
They always come in groups.
Dense particles are rejected.
Fiber flocs are dispersed.
Chemicals in reject streams are deactivated.
Inlet flow enters at a tangent, at its widest part. Rate of angular rotation increases as
liquid moves towards the small end of the cone, driving grit to outer walls.
Rejects discharged at small end ~10 - 20% of total flow.
Can be stacked to form higher level banks.
Very intense levels of hydrodynamic shear.
Highest for suspended particles that have densities very different from that of water,
larger than ~ 10 um with a relatively round/chunky shape. - Answers :When is
separation efficiency highest in a hydrocyclone?
Pressure screens - Answers :Removes large material such as shives. Individual fibers,
minerals, and other solid components of paper are able to pass through the slots or
holes in the basket of this device.
Shives - Answers :Groups of fibers that failed to become properly separated from each
other during pulping.
Fibers - Answers :Papermakers use various terms to describe this term.
Pulp
Stock
Furnish
Pulp - Answers :This term means the fibers.
Three main types: mechanical, chemical, and recycled.
Stock - Answers :This term refers to slurries of pulp fibers in water.
Furnish - Answers :This term refers to mixtures that contain other things in addition to
fibers and water.
Non-integrated mill - Answers :Pulp is purchased in the form of dry bales.
These mills utilize a pulper.
Pulper - Answers :A specialized, round chest where the sheets of pulp or waste paper
are mixed with water and exposed to high levels of hydrodynamic shear.
The combo of shearing forces and the presence of water causes most of the fibers to
become detached from each other.
Consistency - Answers :Filterable solids content.
Can be measured when a slurry of fibers flows through a coarse screen, dried, and then
measured for OD weight.
% solids = (OD wt.) / (stock mass) * 100
Thickening or Washing - Answers :The final step before the paper mill.
Important to rid the stock of harsh chemicals, salts, and extracted material after pulping
and bleaching operations that may hurt the performance of additives.
Drum filters - Answers :Typical mechanism for integrated mills to remove water from the
pulp.
Sometimes called deckers.
Filtrate from these systems returns to the corresponding pulper/bleaching system, and
eventually wastewater or chemical recovery process.
Filter cake - Answers :Comes from the pulp mill and is thickened to a consistency of 10-
20% solids.
High-Density Chest - Answers :A large tank that contains pulp that came from a
washing operation, followed by screw-press thickening. Pulp from these processes is
added to the top of the chest.
,The consistency of the pulp in this chest is too high for papermaking. At the outlet of the
chest, stock is diluted with process water to obtain a consistency of 3-5%.
Thick stock - Answers :Slurries with consistency of 3-5%.
Refining - Answers :An early technology of this mechanism is the Hollander beater,
which is oval in shape.
Repeated passes through a beating operation tend to make the fibers more flexible and
comfortable. This increases the area of adhesion (RBA) between fibers.
Double-disk refiner - Answers :The more conventional refiner used in mills.
Softwood - Answers :This type of fiber yields superior tear strength and folding
endurance.
Hardwood - Answers :This type of fiber yields better smoothness.
Blend chest - Answers :The location in which papermakers combine different streams of
stock into the system. Refining of each type of fiber is done before this location.
Thick Stock - Answers :What types of stock streams are combined in a blend chest?
Machine Chest - Answers :Acts as a buffer capacity in the system. Provides a reservoir
of stock so that papermakers can make quick adjustments in the rate at which stock is
pumped towards the paper machine.
Freeness - Answers :A measure of the rate at which water drains from fiber in the
forming process.
Allows papermakers to achieve a better combo of strength properties at a given level of
freeness. - Answers :What is the purpose of separate refining?
Tickle refiners - Answers :By having one or more of these relatively late in the process,
papermakers can make quick adjustments and begin to see the results of such
adjustments a few minutes later.
The refining plates and general design of these are often selected to give a relatively
harsh, cutting action.
Increase in load and decrease in space between refining plates = decrease in freeness
and fiber length.
Stuff box - Answers :Provides a constant head so that the flow of thick-stock furnish to
the paper machine can be accurately controlled with a valve farther downstream.
Excess furnish is recirculated back into the machine chest. Often the last point where a
chemical can be added as a stream coming out of a simple hose at ambient pressure.
, Stock valve - Answers :A papermakers primary tool for adjusting the basis weight of
paper. Controls the flow of thick stock to the paper machine.
Basis weight - Answers :Moisture-equilibrated mass per unit of area.
A constant head
A steady, known value consistency
An accurate measurement of the total flow - Answers :Steady, accurate control of thick
stock flow requires 3 things:
Mag meter - Answers :Magnetic flow analyzer
Obtains an accurate measure of total flow
Fan pump - Answers :The largest pump on the paper machine.
The furnish is diluted by a large factor before entering the forming section.
Combines metered thick stock with a lot of white water.
Thin stock - Answers :Diluted furnish coming from the fan pump.
~ 0.3 - 1.2% consistency.
The Primary Circuit - Answers :The white water loop
Includes Headbox, forming section, white water collection and silo, fan pump, and
hydrocyclone cleaners.
Hydrocyclone/Cleaner - Answers :Removes materials of different densities.
They always come in groups.
Dense particles are rejected.
Fiber flocs are dispersed.
Chemicals in reject streams are deactivated.
Inlet flow enters at a tangent, at its widest part. Rate of angular rotation increases as
liquid moves towards the small end of the cone, driving grit to outer walls.
Rejects discharged at small end ~10 - 20% of total flow.
Can be stacked to form higher level banks.
Very intense levels of hydrodynamic shear.
Highest for suspended particles that have densities very different from that of water,
larger than ~ 10 um with a relatively round/chunky shape. - Answers :When is
separation efficiency highest in a hydrocyclone?
Pressure screens - Answers :Removes large material such as shives. Individual fibers,
minerals, and other solid components of paper are able to pass through the slots or
holes in the basket of this device.
Shives - Answers :Groups of fibers that failed to become properly separated from each
other during pulping.
