০১। 200 mesh seive size corresponds to __________ microns.
ক) 24
খ) 74
গ) 154
ঘ) 200
০২। A 30% (by volume) suspension of spherical sand particles in a viscous oil has a hindered settling velocity of 4.44 μm/s. If the Richardson Zaki hindered settling index is 4.5, then the terminal velocity of a sand grain is
ক) 0.90 μm/s
খ) 1 μm/s
গ) 22.1 μm/s
ঘ) 0.02 μm/s
০৩। A belt conveyor used for the transportation of materials can
ক) run upto 1 km.
খ) travel at a speed upto 300 metres/minute.
গ) handle materials upto 5000 tons/hr.
ঘ) all (a), (b) and (c).
০৪। A centrifugal filtration unit operating at a rotational speed of w has inner surface of the liquid (density ρL) located at a radial distance R from the axis of rotation. The thickness of the liquid film is δ and no cake is formed. The initial pressure drop during filtration is
ক) w2 . R2 . ρL
খ) w2 . δ2 . ρL
গ) w2 . δρL (2R + δ)
ঘ) w2 . R . ρL(R + 2δ)
০৫। A compressible cake has the
ক) maximum porosity at the upstream side.
খ) maximum porosity at the filter medium.
গ) same porosity throughout the cake thickness.
ঘ) none of these.
০৬। A cottrel precipitator makes use of the __________ for dusty air cleaning.
ক) electric spark
খ) corrona discharge
গ) alternating current
ঘ) none of these.
০৭। A filter press is
ক) a batch filter.
খ) not suitable, if the liquid is the main product.
গ) having prohibitively high maintenance cost.
ঘ) not suitable for wide range of materials under varying operating conditions of cake thickness and pressure.
০৮। A fluid energy mill is used for
ক) cutting
খ) grinding
গ) ultra grinding
ঘ) crushing
০৯। A gravity decanter is meant for the separation of two __________ density.
ক) immiscible liquids of different
খ) miscible liquids of different
গ) immiscible liquids of same
ঘ) miscible liquids of same
১০। A pebble mill
ক) is a ball mill.
খ) employs flints or ceramic pebbles as the grinding medium.
গ) is a tube mill lined with ceramic or other non-metallic liner.
ঘ) both (b) and (c).
১১। A propeller agitator
ক) produces mainly axial flow.
খ) is used for mixing high viscosity pastes.
গ) runs at very slow speed (2 rpm).
ঘ) all (a), (b) and (c)
১২। A sand mixture was screened through a standard 10-mesh screen. The mass fraction of the oversize material in feed, overflow and underflow were found to be 0.38, 0.79 and 0.22 respectively. The screen effectiveness based on the oversize is
ক) 0.50
খ) 0.58
গ) 0.68
ঘ) 0.62
১৩। A screen is said to be blinded, when the
ক) oversizes are present in undersize fraction.
খ) undersizes are retained in oversize fraction.
গ) screen is plugged with solid particles.
ঘ) screen capacity is abruptly increased.
১৪। A straight line is obtained on plotting reciprocal of filtration rate vs. the volume of filtrate for __________ flow of filtrate.
ক) compressible cakes and laminar
খ) incompressible cake and laminar
গ) compressible cake and turbulent
ঘ) incompressible cake and turbulent
১৫। A suspension of glass beads in ethylene glycol has a hindered settling velocity of 1.7 mm/s, while the terminal settling velocity of a single glass bead in ethylene glycol is 17 mm/s. If the Richardson-Zaki hindered settling index is 4.5, the volume fraction of solids in the suspension is
ক) 0.1
খ) 0.4
গ) 0.6
ঘ) none of these
১৬। A tube mill as compared to a ball mill
ক) employs smaller balls.
খ) gives finer size reduction but consumes more power.
গ) has larger length/diameter ratio (>2 as compared to 1 for ball mill).
ঘ) all (a), (b) and (c).
১৭। A tube mill compared to a ball mill
ক) has a higher length/diameter ratio.
খ) produces a coarser product.
গ) has a higher diameter/length ratio.
ঘ) uses much larger balls.
১৮। A widely used size reduction equipment for __________ is Bradford breaker.
ক) talc
খ) coal
গ) iron core
ঘ) wheat
১৯। A __________ employs a set of screen across a flow channel for the separation of dirt/rust from a flowing liquid stream.