# Mechanical Operations Questions and Answers – Thickeners

This set of Mechanical Operations Multiple Choice Questions & Answers (MCQs) focuses on “Thickeners”.

1. When washing is difficult, the cake can be ________
a) Charged
b) Discharged
c) Compressed
d) Decompressed

Explanation: When washing becomes difficult, the unwashed cake may be discharged and then mixed with the wash liquid to form a fresh slurry.

2. When cake is difficult to separate then, a ________ is employed.
a) High pressure
b) String discharge
c) Extra force
d) Compressor

Explanation: When the cake is difficult to remove or when it is desirable to deliver it intact, a string discharge is employed.

3. Careful adjustment of the doctor knife is essential.
a) True
b) False

Explanation: There is an essential need to make adjustment in the doctor’s knife, for it is set too close to the drum the cloth may get damaged.

4. What is the thickness range for a cake of rotary drum?
a) 50 to 60 mm
b) 3 to 100 mm
c) 100 to 200 mm
d) 500 to 1000 mm

Explanation: Cake of varying thickness can be built up by the altering speed of rotation of the filter, the usual range is given as 3 to 100 mm.

5. The rotary disc consists of the number of ______ filter mounted.
a) Rectangular
b) Circular
c) Triangular
d) Spherical

Explanation: The rotary disc filter consists of the number of circular leaves mounted on a heavy horizontal tubular shaft.
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6. A rotary drum filter is _______
a) Continuous vacuum filter
b) Continuous pressure filter
c) Discontinuous pressure filter
d) Discontinuous vacuum filter

Explanation: The rotary drum is a continuous type of vacuum filter, the vacuum is applied to suck the cake from the slurry feed.

7. Filter aids are added to the slurry prior to filtration in order to form _______
a) Compact cakes of low porosity
b) Cakes of increased porosity
c) Crystalline cakes
d) Baked cake

Explanation: Filter aids are the media that are used to increase the rate of cake formation and it also makes the cake porous thus increasing efficiency.

8. In a filter bed, the liquid flow ________
a) Is laminar
b) Is turbulent
c) Is between laminar and turbulent
d) Cannot be predicted

Explanation: The flow in the filter bed is generally kept laminar because as the flow becomes turbulent the formation of eddies take place and result in choking of cake.

9. In S.I. system, the unit of filter medium resistance is _______
a) kg /m2S
b) m2/S
c) kg /m3S
d) m-1

Explanation: As per the formulation and the unit basis the filter medium resistance has the unit of meter inverse i.e. m-1.

10. The moore filter, operates under _______
a) High pressure
b) Low pressure

Explanation: The filter operates under reduced pressure, so that pressure difference is limited and hot liquid cannot be filtered.

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