Pulp & Paper Exam 2

Fraction of pulp that is retained on a 3/8” perforated plate

Improves the fiber properties and reduces the refining requirements later

The most removal of pulping chemicals and lignin with the least amount of wash water

compromise of brown stock washing

brown stock washing sequence

brown stock washing mechanisms

diffusion and desorption

dissolved solids and chemicals in the interior of the pulp fibers must move into the surrounding liquor to be removed

attached dissolved solids and chemicals leaved the fibre surface for the surrounding liquor

liquor in the pulp is displaced with weaker wash liquor or clean water

pulp slurry is diluted and mixed with weak was liquor or clean water. then the liquor is extracted by thickening the pulp.

type of washer used at IP

applied to siphon the water from the washer

oven dry tons of pulp per square foot of cylinder surface

as much as possible must be removed to avoid foaming problems

weight of wash water introduced into the black liquor per unit of weight of oven dry pulp being washed

measures the effectiveness of a single washing stage

=(Cv-Cs)/(Cv-Cw)

(Win-Wout)/Win

amount of washable compounds in the pulp suspension that could have been removed in washing

washable sodium content of the pulp leaving with the pulp

washable sodium and chemically bound sodium leaving with the pulp

incorporates all washing stages on a single rotary drum

resembles fourdrinier

submerged environment, long contact time between the chips and the washing water

kamyr used at IP

determined by the amount of solute is removed and the amount of wash water needed to remove that solute

measures the degree of polymerization (viscosity test)

operation of removing oversized, troublesome particles and shives

type of screen, obsolete, rotary of flat form

type of screen, mostly obsolete, good fibers hydrate well and align themselves with the direction of the flow, while coarse fibers do not hydrate well and are carried across the plate

type of screen that is most dominantly used, utilizes perforated cylindrical plates

=(Sr/Si)*Rw

removal of contaminants or unwanted particles from pulp and paper stock by centrifugal force and fluid shear

slusher, pulp is retained on the cylinder and excess water passes through wire mesh cylinder

gravity thickener, same as slusher but a couch roll is added

valveless washers are used

multidisk thickeners are used

vacuum washers are used to extract more water from the pulp slurry

screw presses are used

has constant viscosity regardless of the shear rate or applied stress

reduces variations in kappa number and improves the bleaching control

needed if transporting pulp

liquid mixture that contains dissolved organic and/or inorganic substances will boil at a higher temperature than water at the same pressure

compound that sulfur is converted to during chemical recovery

concentration of solids in black liquor leaving the washers

what is the ideal solid concentration in black liquor before burning in the recovery furnace?

how do multi-stage evaporators work?

most common type of evaporator unit, entering weak liquor boils and thickens as it travels quickly up the tubes

fluid, usually a liquid or a gas, is driven by temperature differences. It is a passive system that does not require any mechanical pump or external power source to move the fluid

indirectly heated evaporators, industry standard

type of evaporator that consists of a series of steel tubes arranged cylindrically in a rotating wheel immersed in black liquor

type of evaporator where liquor is sprayed into the gas as it enters

type of evaporator where the black \n liquor is sprayed into a turbulent flow of \n the flue gas as it passes through a \n venturi throat.

required only if direct contact evaporators are in operation

converts unstable sulfide to a stable thiosulfate

indirectly heated evaporators, most common type is falling film with recirculation

3 functions of a recovery boiler

zones of the recovery boiler furnace

convert Na2CO3 to NaOH`

removes insolubles, unburned carbon, and inorganic impurities

mixes with violent agitation of green liquor with CaO at elevated temperatures

converts lime mud back to CaO for reuse

lime kilns are used for

3 phases in calcining

mechanical action to disperse dry, compacted pulp fibers into pulp slurry

to develop and modify the structure of pulp fibers to optimize the properties of the paper product

strains fibers by the transfer of energy from the beating element to the fibers

refining at higher consistencies with a large gap between the refiner plates creates this. increases paper strength and density

refining at low consistencies with a small distance between refiner plates creates this. increases quality of formation

fibers move parallel to the bar crossing

fibers move perpendicular to the rotating bars

does refining or beating have better control, lower operating costs, and is quicker?

an objective for beating/refining

level of consistency that produces curled, kinky fibers with low bonding ability after refining

level of consistency that produces curled, microcompressions, internal fibrillation, and swelling

optimize strength development and control of stock drainability and sheet formation

important because it controls the development of fiber to fiber contact during drying

where pulp stock and additives are mixed with an agitator

contains the final furnish mixture