S2 Flashcards
Height equivalent to a theoretical plate (HETP) is the height of packing that will give the same separation as one theoretical plate in gas-liquid mass transfer operations like distillation, absorption/stripping and humidification/dehumidification. HETP which is experimentally determined, depends upon the
all a, b & c.
Needle valves are generally not used for
very large diameter pipes.
Pick out the wrong statement.
Safety valves are provided in heat exchangers for removal of non-conden-sables.
With increase in gas flow rate to fabric surface area ratio (Nm3/hr/m2 fabric surface area), the size & the cost of a bag filter
decreases
A head comprises of straight flange section, corner torus, section and central dished section. Crown radius and knuckle radius in a head is related respectively to the
central dished section and corner torus section.
Which of the following is used to set the diameter of the distillation column?
Allowable vapour velocity.
Ponchon Savarit method is based on the use of enthalpy concentration diagram, which contains the bubble point curve (saturated liquid curve), dew point curve (saturated vapour curve) and equilibrium tie lines. As compared to McCabe-Thiele’s method, this method
all ‘a’, ‘b’ & ‘c’.
The optimum size ratio for two mixed reactors in series depends on the kinetics of the reaction and the conversion level. For reaction orders more than one, the
smaller reactor should come first.
Which of the following is not a graphical method (but is an analytical method) for the calculation of theoretical number of stages in case of continuous binary distillation?
Sorel-Lewis method.
Saddle supports are used for supporting __________ vessels.
horizontal cylinderical
The diameter of a propeller agitator used in agitation tank ranges from __________ percent of the tank diameter and its peripherial speed is normally 300 to 500 metres/minute.
15 to 30
In packed towers provided with saddle packing, liquid redistributors are positioned at every __________ times column diameter or 6 metres whichever is less.
5-8
Optimum reflux ratio in a continuous distillation column is determined by the
total cost consideration (fixed cost of the column plus the cooling water & steam cost).
Cooling water fouling factors vary in the range of 0.001 to 0.003
(BTU/hr.ft^2 . °F)^-1
Minimum recommended baffle spacing in a shell and tube heat exchanger is about (where, D = shell diameter)
0.2 D
The maximum liquid gradient over a tray must not exceed
0.5” -1.25”.
An underdesigned steam trap will
back up condensate and cause water hammer in steam line.
The slope of the feed line in distillation opeartion is given by (where, q = fraction of the feed stream that is liquid.)
-q/(1-q)
Speed of industrial paddle agitator ranges from __________ rpm.
20 to 100
__________ strain is measured using a ‘strain rosetter’.
Linear
Thin spherical shells subjected to internal pressure, develop __________ stresses.
radial
With increase in the reflux ratio for a fixed production from a continuous binary distillation column, the __________ decreases.
fixed charges initially
The slope of operating line in the rectifying section of a distillation column is unity, if the reflux ratio is
∞
Vertical vessels are not supported by
saddles
With increase in pressure drop (for a given particle size), the dust collection efficiency of a cyclone separator will
increase
Spherical shaped pressure vessel is considered to be the most ideal, because it can
withstand higher pressure for a given metallic shell thickness.
An adequate clearance between the tray and the shell wall of a distillation column is provided to
allow for thermal expansion and facilitate installation.
Overall tray efficiency of a distillation column is the ratio of the number of
ideal trays required to the number of real trays required.
Pick out the wrong statement about the design of a sieve plate column.
Minimum recommended downcomer residence time for the disengagement of entrained vapour is the same for both foaming and non-foaming liquids, which is about 20 seconds.
Generally, no corrosion allowance in wall thickness of a part is required, if the thickness is more than __________ mm.
30
Multiple blade paddle agitator is used for mixing high viscosity liquids/paste in which the paddle diameter is commonly 0.8 times the tank diameter. However, the width of the blade is in the range of __________ times the paddle diameter.
0.1 to 0.25
In a __________ rivetted joint, the rivets in the various rows are opposite to each other.
chain
Pick out the wrong statement:
The value of crushing load is more than that of buckling load for long columns.
Generally, elliptical dished heads
all (a), (b) and (c)
Pick out the wrong statement pertaining to the comparative evaluation of performance of the packed tower and the plate tower.
The total weight of a dry plate tower is usually much more than that of a dry packed tower designed for the same duty.
The circumferential (hoop) stress in a thin walled cylinderical vessel under internal pressure is
pd/2t
LMTD correction factor is used in heat exchanger design for
multipass shell and tube heat exchanger.
Floating head heat exchangers are used for the
cases where temperature difference between the shell and the tubes is more (>50°C).
The most common standard size of bubble caps used in industrial operation is
6” dia cap with 4” dia riser.
Compensation against openings in process vessels for giving inlet and outlet connections, for providing sight glasses and manholes etc. is provided for strength and rigidity. The most efficient type of compensation is of __________ type.
nozzle or rim
In case of a continuous distillation column, increase in reflux ratio may result in the
all (a), (b) and (c).
In a distillation column, the minimum residence time for liquid in the downspout is about __________ seconds.
8
Thickness of the frame of a plate and frame filter as compared to that of plates is
more
Which of the following factors affect the pressure drop in a co-current gas-liquid absorption packed tower?
All (a), (b) and (c).
The thickness of heat transfer plates used in the plate type heat exchanger ranges from __________ mm, pressed in a single piece provided with grooves & corrugations.
1.25 to 3.125
Rivets are generally specified by the
shank diameter
Length to diameter ratio of most rotary driers is in the range of
4 to 10
