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Chemical Engineering Reviewer > Process Equipment and Plant Design (Set 4) > Flashcards

Process Equipment and Plant Design (Set 4) Flashcards

Concepts and heuristics necessary for design of equipment, processes, and process systems.

1
Q

Cylindrical storage tanks used for the storage of volatile liquids (e.g., naphtha) have ____ roofs.

A

floating

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2
Q

Larger depth of liquid on the trays of a distillation column

A

both (a) & (b).

(leads to high tray efficiency.) & (results in higher pressure drop per tray.)

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3
Q

Pick out the wrong statement.
a. Plate efficiency increases with increase in superficial vapour velocity till entrainment limit.
b. Increase in depth of the liquid about the slots increases the plate efficiency, particularly if the liquid depth is < 1”.
c. Too small a plate spacing can cause a low efficiency, if the vapour velocity is greater than the allowable value.
d. none of these.

A

none of these.

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4
Q

Pick out the wrong statement.

a. In practical operation, distillation towers having diameter 3-6 metres equipped with bubble cap (round) size of 15 cms are used.

b. Height of packing in a packed tower is about 3 times the column diameter for raschig rings and about 5 to 10 times the column diameter for saddle packing.

c. In a seive tray, the minimum hole diameter is equal to the tray thickness.

d. In a stainless steel seive tray, the minimum hole diameter is equal to 10 times the plate thickness.

A

In a stainless steel seive tray, the minimum hole diameter is equal to 10 times the plate thickness.

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5
Q

In the downcomer of a distillation column, the minimum recommended residence time is about ____ seconds.

A

5

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6
Q

For identical situation, condensing film coefficient in case of a horizontal condenser is almost ____ the value expected in case of vertical condenser.

A

thrice

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7
Q

Diameter of rivet hole (d, mm) and the plate thickness (t, mm) are related by Unwin’s formula as

A

d = 1.6 sqrt(t)

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8
Q

A binary liquid azeotropic mixture has boiling point lower than either of the components, when it shows ____ deviation from Raoult’s Law.

A

positive

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9
Q

In which of the following evaporators, steam is fed inside the tube while the liquor is outside the tube?

A

Horizontal tube evaporator

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10
Q

A single pass air heater is connected to a two pass unit. For the air flow rate and other conditions remaining the same, the film heat transfer co-efficient for air will vary in the ratio of

A

2^0.8

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11
Q

In a multipass shell and tube heat exchanger, the baffles on shell side is primarily provided for

A

creating turbulence.

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12
Q

For turbine agitator, the impeller diameter is about

A

0.3 to 0.5 d

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13
Q

In a shell and tube heat exchanger having triangular pitch, the shell side equivalent diameter is given by

A

https://www.indiabix.com/_files/images/chemical-engineering/process-equipment-and-plant-design/570-146-1.png

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14
Q

If a single tube pass heat exchanger is converted to two passes; for the same flow rate, the pressure drop per unit length in tube side will ____ times.

A

increase by 2^1.6

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15
Q

Pick out the wrong statement.

A

A 90° welded elbow is diagrammatically represented by https://www.indiabix.com/_files/images/chemical-engineering/process-equipment-and-plant-design/580-290-3.png

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16
Q

Pick out the wrong statement pertaining to the design of a long tube vertical evaporator.

a. Tube dia is 3-6 cms, while tube length in 3-6 metres.
b. Steam is fed to the shell, whereas the liquor is filled inside the tube.
c. Liquor level is maintained at l/3rd to 1/2 of the height of the tube.

A

none of these.

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17
Q

Which of the following is the most common type of baffle used in industrial shell and tube heat exchanger?

A

25% cut segmental baffle.

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18
Q

What is the minimum recommended ligament for square pitch arrangement in case of heat exchangers?

A

6.5 mm

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19
Q

Pick out the correct statement

a. Centre to centre distance between two consecutives rivets in a row is called the pitch.
b. A rivetted joint made in overlapping plates is called butt joint.
c. Hole size drilled in rivetted plates is less than the actual size of the rivet.

A

Centre to centre distance between two consecutives rivets in a row is called the pitch.

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20
Q

Safety valves are provided in chemical equipments to guard against excessive

A

pressure/pressure fluctuation

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21
Q

The equivalent diameter for pressure drop is ____ that for heat transfer.

A

smaller than

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22
Q

Most of the storage vessels/tanks are made cylindrical, because of the fact that a cylinder

A

both (a) and (b).

has greater structural strength and is easy to fabricate.

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23
Q

The distance between the top of the slots and the liquid surface when the static liquid is just ready to flow over the overflow weir is called

A

static submergence

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24
Q

Liquid gradient over the tray results due to the

A

resistance offered to flow of liquids by caps & risers and the flow of gas.

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25
Q

The centre to centre distance between two consecutive baffles in a shell and tube heat exchanger is called the baffle pitch or baffle spacing, which is more than 1/5th the I.D. of the shell. Which of the following is not a function of the baffles?

A

To increase the tube side heat transfer co-efficient by inducing turbulence.

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26
Q

A high vapour velocity is required for high plate efficiency in a seive plate coloumn. The satisfactory value of operating vapor velocity for design purpose in seive plate column is about ____ percent of the flooding velocity.

A

80

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27
Q

The approximate liquid depth in an agitation tank is equal to (where, d = tank diameter)

A

d

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28
Q

Baffle width is normally taken as ____ times the tank diameter.

A

0.1-0.12

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29
Q

A cylinderical pressure vessel of volume 6 ?m3 has to be designed to withstand a maximum internal pressure of 10 atm. The allowable design stress of the material is 125N/mm2 and corrosion allowance is 2 mm. The thickness of the vessel for a length/diameter ratio of 3 will be close to

A

10 mm

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30
Q

Which of the following packing materials provides for maximum mass transfer?

A

Cross-partition rings.

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31
Q

____ of water makes it a widely used coolant in heat exchangers.

A

High specific heat

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32
Q

The equivalent diameter for fluid flow through a channel of constant non-circular cross section of area ‘A’ is given by (where, P = perimeter of the channel in contact with the fluid)

A

4 A/P

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33
Q

Fouling factor must be included in the calculation of over all design heat transfer coefficient, when the liquid

A

containing suspended solids flows at low velocity.

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34
Q

Lug support is meant for supporting ____ vessels.

A

small

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35
Q

Overall mass transfer co-efficient in case of absorption of ____ in water is based on the gas film co-efficient only, as the mass transfer process is gas film (phase) controlling.

A

NH3

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36
Q

Which tube arrangement in a heat exchanger would facilitate highest heat transfer rate?

A

Triangular pitch.

37
Q

In case of 1.5” heat exchanger tubes, the inside flow area ____ with decrease in BWG.

A

decreases

38
Q

Cylindrical pressure vessels in horizontal condition is generally supported on a ____ support.

A

saddle

39
Q

Pressure drop per tray in the atmospheric distillation column is about ____ psi.

A

0.07 - 0.12

40
Q

Welded joint efficiency in the design of chemical process equipment is taken as

A

0.85

41
Q

The thickness of segmental baffles (25 -35% cut truncated plates usually) is generally ____ the tube wall thickness.

A

twice

42
Q

The safe height (h) to diameter (d) ratio (i.e., h/d) for liquid/petro fuel storage tank of capacity more than 45 kilolitres is less than

A

1

43
Q

For given number of passes, pitch & tube diameter, the maximum number of tubes that can be accommodated in a shell of tripled inside diameter will be ____ times.

A

considerably more than 9

44
Q

The ratio of linear stress to linear strain is termed as the

A

modulus of elasticity

45
Q

____ head is the most economical for cylindrical vessels designed for operating at high pressure (> 15 atm.).

A

Ellipsoidal

46
Q

Bubble cap plate column is

A

a finite stage contactor.

47
Q

In seive plate column, holes are drilled or punched in sizes ranging from 2.5 to 12 mm (5 mm being widely used). The hole pitch is normally ____ times the hole diameter to give the required hole area.

A

2.5 to 4.0

48
Q

Pick out the wrong statement.
a. Rivetting provides a permanent fastening method.
b. The joint made by overlapping of one plate over the other, and then rivetting the two plates together with two rows of rivets is called ‘double rivetted butt joint’.
c. Shank diameter of the rivets should be less than the size of the hole drilled in the plate for rivetting.
d. The efficiency of a rivetted joint is the ratio of the strength of the rivetted joint to the strength of the solid plate.

A

The joint made by overlapping of one plate over the other, and then rivetting the two plates together with two rows of rivets is called ‘double rivetted butt joint’.

49
Q

The force due to wind load acting on a tall vessel depends upon its

a. shape
b. outside diameter.
c. height.

A

all (a), (b) & (c).

50
Q

Bubble cap diameter used for the distillation column having diameter ranging from 1.5 to 4.5 metres is about ____ mm.

A

100

51
Q

Power required for agitation depends upon the

a. height & properties of the liquid.
b. agitator type & speed of agitation.
c. size of agitator & the tank.

A

all (a), (b) and (c).

52
Q

Tube height in a calendria type evaporator is normally less than ____ metres.

A

2

53
Q

Pick out the wrong statement.

a. Lug supports are less expensive than other type of supports.

b. A pipe is differentiated from a tube by the fact that a pipe has a greater wall thickness compared to the tube.
c. A reducer is used to change the direction of a pipe in a straight run.
d. The method of fixing tubes to a tube sheet by expanding is called ‘tube rolling’.

A

A reducer is used to change the direction of a pipe in a straight run.

54
Q

For a 25 mm hole drilled in plates to be rivetted, the shank diameter of the rivet should be ____ mm.

A

23

55
Q

In a shell and tube heat exchanger having square pitch, the shell side equivalent diameter is given by (where, P = pitch, d = outside diameter of the tube)

A

https://www.indiabix.com/_files/images/chemical-engineering/process-equipment-and-plant-design/570-145-1.png

56
Q

Optimum economic pipe diameter for fluid flow is determined by the

A

total cost considerations (pumping cost plus fixed cost of the pipe).

57
Q

Pressure differential maintained across a continuous rotary vacuum filter is in the range of ____ mm Hg column.

A

250 to 500

58
Q

Vertical storage vessels are never supported by ____ support.

A

saddle

59
Q

In a double pipe (concentric) heat exchanger, the hydraulic radius for heat transfer (for a fluid flowing through the annulus) would be

A

more than that for fluid flow.

60
Q

Elastic failure of a material occurs, when the tensile stress equals yield strength, yield point or the elastic limit. Also, the elastic failure occurs according to maximum strain theory, when the maximum tensile strain equals (where, σ = yield strength and E = modulus of elasticity)

A

σ/E

61
Q

In a pressure vessel containing multiple openings of various dimensions at different parts, stress concentration at the edges of the opening is maximum which becomes negligibly small beyond the area covered by ____ times the hole diameter.

A

two

62
Q

What is the slope of the feed line, if the feed to a distillation column is a saturated liquid?

A

∞

63
Q

Filtration rate is affected by the

a. pressure drop across the cake & filter medium.
b. cake & filter medium resistance.
c. area of filtering surface & the viscosity of filtrate.

A

all (a), (b) and (c).

64
Q

Liquid gradient over a tray can be minimised by

a. providing a higher skirt clearance or a higher weir.
b. decreasing the number of rows of caps through which the liquid flows or by decreasing the velocity of liquid flow past the caps or by reducing the distance along the tray through which the liquid must flow.
c. using split flow, radial flow or cascade flow for column diameter large than 4 ft.

A

all (a), (b) and (c).

65
Q

In a shell and tube heat exchanger for a given heat transfer surface area, smaller diameter tubes are favoured as compared to larger diameter ones ; because the smaller diameter tubes

A

can be fitted into a smaller shell diameter hence the cost of the heat exchanger would be less.

66
Q

Le/D for 90° elbow (medium radius) and 90°square elbow would be respectively around

A

25 and 60

67
Q

____ heat exchanger is also known as ‘hair pin type’ exchanger,

A

Double pipe

68
Q

What is the value of ‘q’ for saturated vapor feed to a distillation column ?(where q = fraction of the feed stream that is liquid.)

A

0

69
Q

In hydrostatic testing of welded pipe (for leakage, strength etc.) the ratio of minimum hydrostatic test pressure to internal design pressure is around

A

1.5

70
Q

Frame thickness in the plate and frame filter press is normally in the range of ____ inches.

A

0.25 to 8

71
Q

Cylinderical shell thickness of rotary drier is generally ____ mm.

A

6-8

72
Q

The ratio of lateral strain to linear strain is termed as the

A

Poisson’s ratio

73
Q

The distance between the centre of a rivet hole to the nearest edge of the plate is called

A

margin

74
Q

Mc Cable Thiele method used for finding theoretical stages in a distillation column assumes that the

a.sensible heat differences are small, because the temperature changes from tray to tray is small.
b. Trouton’s rule is applicable.
c. liquid/vapor loading across the column remains constant.

A

all (a), (b) and (c).

75
Q

A minimum clearance of about ____ mm is maintained between the distillation column wall and the bubble cap.

A

38

76
Q

Pick out the wrong statement.

a. If sufficient residence time (around 8 seconds) is not proivided to the downcoming liquid in the downcomer, it may entrain some vapour.

b. The liquid head in the downcomer should not be greater than one half the plate spacing to avoid flooding.

c. The dischare end of the downcomer must project far enough into the tray liquid so that no gas bubbles can enter the open end and by pass the bubble caps.

A

none of these.

77
Q

Pick out the wrong statement pertaining to shell and tube heat exchanger.

a. Clearance between shell & baffles and between tube & baffles should be minimum to avoid by-passing of the fluid, but it should be enough to permit the removal of tube bundle.

b. Baffles are supported independently of the tubes by tie rods and positioned by spacers.

c. Tie rods are fixed at one end in the tube sheet by making blind holes and the minimum number of tie rods is 4 with at least 10 mm diameter.

d. Bracket supports are used for horizontal shell, while saddle support is used for vertical shell.

A

Bracket supports are used for horizontal shell, while saddle support is used for vertical shell.

78
Q

Wind load consideration in the design of a support can be neglected, when the vessel is

A

short (< 2 m) and housed indoor.

79
Q

Souders Brown equation given by, https://www.indiabix.com/_files/images/chemical-engineering/process-equipment-and-plant-design/590-379-1.png , is used for the calculation of the ____ in a continuous distillation column.

A

diameter of the bubble cap column

80
Q

The ratio of volumes of the mixed reactor to the plug flow reactor (for identical feed composition, flow rate, conversion, and for all positive reaction orders) is always

A

> 1

81
Q

Steam economy is defined as the amount of evaporation per unit amount of steam used, while the capacity is the total evaporation obtained per hour. Use of multiple effect in evaporation

a. increases capacity.
b. increases economy.
c. does not affect the capacity.

A

both ‘b’ & ‘c’.

82
Q

Le/D for a Tee (used as elbow, entering run) would be around

A

60

83
Q

Log mean temperature difference in case of multi-pass shell and tube heat exchanger is always

A

less than arithmetic mean value.

84
Q

Practical dividing line between a ductile and brittle materials is suggested, when the ultimate elongation is about 5%. Generally, larger the knuckle radius, stronger is the corner torus section of a head. The knuckle radius provided should be less than ____ of the head.

a. 6% of I.D.
b. 3 times the thickness

A

either (a) or (b), whichever is larger

85
Q

Tubes are fixed to the tube sheet (a thick circular metallic plate) by the method of tube rolling and brazing (non-removable) or ferrule connection (removable). Thickness of the tube, sheet is normally ____ the outside diameter of the tube but in no case it should be less than 22 mm (7/8”).

A

equal to

86
Q

A shell may by termed as thin if its thickness to diameter ratio is less than 0.1. The factor which can be neglected in the calculation of membrane stresses is

A

bending

87
Q

Scale up problem in design based on the similarity concept takes into account ____ similarity.

a. geometrical
b. kinematic
c. dynamic

A

all (a), (b) and (c)

88
Q

____ closure is the weakest enclosure for cylindrical vessels.

A

Conical or flat plate

89
Q

Which of the following efficiencies can be greater than 100%?

A

Murphree plate efficiency.

Chemical Engineering Reviewer (42 decks)

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