WorksheetsM4-6 ParTech
Total questions: 58
Worksheet time: 45mins
PERIOD OF SETTLING
After a short period of acceleration, the maximum attainable velocity is reached
and is maintained constant. The velocity attained here is called the (1) velocity
or the (2) velocity
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(a)
SETTLING REGIME
In the ___ ______ regime, the particles settle at a constant rate and are assumed to be moving at terminal velocity.
(a)
The movement of particles is not affected by the presence of other particles.
FREE SETTLING
HINDERED SETTLING
TERMINAL VELOCITY
NONE OF THE CHOICES
The rate of settling is not constant since the movement of a particle is impeded by other particles.
FREE SETTLING
HINDERED SETTLING
TERMINAL VELOCITY
NONE OF THE CHOICES
__D__E__AT__N is the partial separation or concentration of suspended solids from a liquid based on the motion of particles through fluids.
(a)
The rate of sedimentation of a suspension of fine particles is difficult to predict because of different factors such as:
Height of vessel
Diameter of Vessel
Shape of Vessel
All of the above
SEDIMENTATION is the separation of (1) slurry into a
clear fluid and a (2) slurry, with higher solid content, by settling.
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(a)
Sedimentation can either be by (a) sedimentation and (b) sedimentation.
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(a)
This affects the degree of flocculation and hence the mean size and density of
the flocs.
Flocculation
presence of ionized solute and nature of surface of particles
degree of agitation of suspension
Concentration of suspension
Gentle stirring may produce accelerated settling if the suspension behaves as a
non-Newtonian fluid. It can also prevent “bridge formation”
degree of agitation of suspension
Concentration of suspension
presence of ionized solute and nature of surface of particles
NONE OF THE CHOICES
The behavior of suspensions of fine particles is influenced by whether the
particles flocculate.
Flocculation
degree of agitation of suspension
Concentration of suspension
NONE OF THE CHOICES
The higher the concentration, the ____ the rate of sedimentation
SAME
LOWER
HIGHER
CANNOT BE DETERMINED
If the ratio of diameter of vessel to diameter of particle is greater than about ___,
the walls of the container will have no significant effect on the rate of
sedimentation.
2100
200
100
10
For smaller values of the ratio of vessel diameter to particle diameter, the sedimentation rate may be reduced because of the (a) influence of the walls.
Shape of vessel
Provided that the walls of the vessel are vertical with depth and that the cross-sectional area does not vary with depth, it has ___ effect on sedimentation rate.
NO
LITTLE
GREAT
我不知道
For an inclined vessel, the rate of sedimentation will be affected since a
part of the cross section is obstructed.
FALSE
TRUE
我不知道
TRALSE
The overall effect of flocculation is to create
(1) of particles which in turn leads to (2) sedimentation.
(1) large conglomerations
(2) accelerated
(2) deaccelerated
(1) large agglomerations
The mixing of solids, whether free flowing or cohesive, resembles to some extent the mixing of ___–_________ liquids.
(a)
more power is normally required in mixing pastes and dry
solids than in blending liquids.
FALSE
TRUE
TRALSE
A ____–_____ product is one that does what is
required and has the necessary properties such as visual uniformity, high strength, uniform burning rate or other desire characteristic.
(a)
A good (1) is one that produces this well
mixed product at the (2) overall cost.
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(a)
In mixing pastes and powders, the product often consists of two or more identifiable phases which may contain individual particles of considerable size. This means, that “well-mixed” solids will differ markedly in composition.
TRUE
FALSE
WELL-MIXED PRODUCT
none of the choices
uniform
burning rate
visual uniformity
high strength
In the mixing of solid particles, the following mechanisms may be involved:
____ ______, where slipping planes are formed
(a)
In the mixing of solid particles, the following mechanisms may be involved:
______ ______, in which groups of particles are moved from one position to
another
(a)
In the mixing of solid particles, the following mechanisms may be involved:
______ ______, where the particles are distributed over a freshly developed
interface
(a)
When dealing with solid particles, the (1) variation in composition among sample withdrawn at a time from a mix is commonly used as a measure of (2).
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(a)
the mixing of materials in a simple drum mixer depends
on:
total volume of the material
volume of the drum
speed of rotation of the drum
particle size and density of each component
relative volume of each component
Mixing can be done by (1) – speed agitation of the mass with an (2).
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(a)
Mixing can be done by slow – speed agitation of the mass with an impeller, by
centrifugal smearing
tumbling
impact
none
With (1) solids, the mixing elements cannot generate flow currents; instead they (2), fold, stretch, and (3) the material to be mixed
(a)
Examples of cohesive solids
NONE
rubber
plastic materials
pastes
___-_____ _______
Used to blend viscous liquids or light pastes
(a)
Used to mix deformable or plastic solids. It involves squashing the mass flat,
folding it over on itself, and squashing it once more.
Kneaders
Dispersers
Masticators
ALL
handles suspensions, pastes, and light plastic masses
Two arm kneader
Continuous Kneaders
Masticators or Intensive mixers
Disperser
compounding of lacquer bases from pigments; shredding cotton linters
Two arm kneader
Continuous Kneaders
Masticators or Intensive mixers
Disperser
it works additives and colouring agents into stiff materials
Two arm kneader
Continuous Kneaders
Masticators or Intensive mixers
Disperser
it can disintegrate scrap rubber and compound the
toughest plastic masses
Two arm kneader
Continuous Kneaders
Masticators or Intensive mixers
Disperser
can handle light to fairly heavy materials
Two arm kneader
Continuous Kneaders
Masticators or Intensive mixers
Disperser
The mix is cut and folded while in the mixing chamber and subjected to
additional shear as it flows through the die.
(a)
Subjects pastes and deformable solids to intense shear by passing them between
smooth metal rolls turning at different speeds.
(a)
a smearing or rubbing action similar to that in a mortar and pestle
(a)
Mixing is done by blades and knives set in a helical pattern on a horizontal shaft
turning in an open through or closed cylinder.
(a)
Consists of a horizontal trough containing a central shaft and a helical ribbon
agitator.
Ribbon Blenders
Internal Screw Mixers
Tumbling Mixers
Impact Wheels
Mixing results from the turbulence induced by the counteracting
agitators
Ribbon Blenders
Internal Screw Mixers
Tumbling Mixers
Impact Wheels
Used to mix free – flowing grains and other light solids
Ribbon Blenders
Internal Screw Mixers
Tumbling Mixers
Impact Wheels
Consists of a container rotating about a horizontal axis
Ribbon Blenders
Internal Screw Mixers
Tumbling Mixers
Impact Wheels
The material is blended continuously be spreading them out in a thin layer under
centrifugal action
Ribbon Blenders
Internal Screw Mixers
Tumbling Mixers
Impact Wheels
Used to blend fine, light powders such as insecticides
Ribbon Blenders
Internal Screw Mixers
Tumbling Mixers
Impact Wheels
There are several stages in the settling of a flocculated suspension, and different zones are formed as sedimentation proceeds.
Laboratory Sedimentation
Batch Sedimentation
Continuous Sedimentation
Sedimentation
increase concentration of suspended solids
(select 2 that apply)
Thickening
Clarification
Continuous Sedimentation
Batch Sedimentation
to remove a relatively small quantity of suspended particles and
produce a clarified effluent
(select 2 that apply)
Thickening
Clarification
Continuous Sedimentation
Batch Sedimentation
height at which free settling stops and hindered settling begins.
(a)
This approach makes use of the (a) Method of using a setline curve which is preferable for flocculent solids in the slurry
Area Requirement for Thickening
(a)
MATERIALS HANDLING
involves movement of materials over short distances, usually
not exceeding 10 ft, and only when the quantity does not exceed 4 to 5 tons
(a)
recommended when the radius of work is increases to 100 to
200 ft to lift loads weighing more than 100 to 150 lbs.
(a)
PERIOD OF SETTLING
In (1) , the velocity increases from (2) to its terminal velocity. It is very short, usually in the order of tenths of a second or less
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(a)
