Unit vii problem set

Page | 1

Prof S S Jahagirdar, NKOCET

AIR POLLUTION

AND CONTROL

(Elective-I) Problem set for

UNIT-VII

AIR POLLUTION

(PARTICULATE)CONTROL

EQUIPMENTS

BE (CIVIL) L- ROLL NO-

Unit- VII

Air pollution (Elective -I)

Unit-VII

Control equipment collection efficiency Problems

1. A power plant has allowable SPM rate of 1.6 tonnes/day. Assume that it burns coal

at the rate of 3800 tonnes/day and coal has ash content of 4.5 %. Find overall

efficiency required for a SPM control device.

2. Calculate the overall efficiency of a particulate control system composed of

cyclone (75 % efficient) followed by a ESP (95% efficient).

3. A stream of gas from a manufacturing plant contains 50 gms/m3 of PM.

Regulations requires overall control efficiency of 98.5%. The proposed control

system consists of a cyclone (70% efficient) followed by ESP. Calculate

a) The allowable outlet concentration of PM

b) Efficiency of ESP

4. A cyclone operates removes 75% of particulate matter fed to it. The filter is then

fed to an ESP which operates with 90% efficiency. What is the overall efficiency of

this particulate system?


Unit- VII


Unit-VII

Gravity Settling Chamber Problems

1. Calculate the terminal settling velocity for a particle of 10 µ diameter in air at 250C

and having density of 1.5 gm/cc. Assume all the necessary data.

2. A gravity settling chamber is to be used to remove particulates having dia 80 µ and density

1.5 gm/cc. What is the maximum gas velocity that can be used if the chamber is 9 m long

and 3 m high and the desired collection efficiency is to be not less than 90 %?

3. A gravity settling chamber is to be used for following data

SPM dia- 100 µ

SPM density – 1500 kg/m3

Length of chamber – 10 m

Height of chamber – 2 m

Efficiency should not be less than 90 %. What is max gas velocity that can be used?

5. A settling chamber is designed to process a flow of 150 m3/sec. Chamber length -15 m,

height – 3m and width – 5 m. Determine the efficiency of the chamber for removing 1 µ, 5

µ, 10 µ, and 20 µ dia particles having density 1.5 g/cc.

6. A gravity settling chamber is to remove 50 µ dia particles having density 1.5 gm/cc. What is

max gas velocity that can be use if the chamber is 6 m long and 2 m high? The efficiency

expected is more than 90 %

7. A settling chamber is to be designed for a waste gas flow of 30 m3/sec at 700C. The particles

to be removed are 30 µ with 80 % efficiency. Design the chamber with trays and also

calculate efficiency for 15 to 25 µ dia particles

8. Estimate the value of minimum size of particles to be removed with 100 % efficiency for a

settling chamber with length 8 m, height 1.3 m and gas velocity 25 cm/sec. The temperature

is 800F. The density of particle is 2.5 g/cm3. Viscosity of gas at given temperature is 0.067

kg/m.hr.

9. A settling chamber is designed to remove particulates from an air stream having velocity of

2 m/s and temperature of 770C. The chamber has a size of 6.25 m x 2.5 m. Determine the

size of particles which are removed 100 %. Use specific gravity of particle =2 and air

viscosity = 2.1 x 10-5 kg/m.s. If the length is changed to 8.5 m, what is percentage change in

removal efficiency of above sized particles?

10. What is smallest diameter of particulates in µ having a density of 2 gm/cc which can be

collected with 80 % efficiency in gravity settling chamber which is 12 m long and 3 m high.


Unit- VII

Gas velocity is 0.78 m/sec. Mention how you can improve the efficiency?

11. Calculate the terminal settling velocity for a particle of 1 µ diameter in air at 270C

and having density of 1.85 x 10-5N.S/m2. Assume all the necessary data.

12. Determine minimum size of particulates that will be removed with 100 % efficiency from a

settling chamber, under following conditions

i. Air : Horizontal velocity= 0.3 m/sec

Temp = 770C

ii. Particles : Sp Gr = 2.0

iii. Chamber : Length = 7.5 m

Height = 1.5 m

What will be efficiency for same particles if chamber length is 6 m?

13. A settling chamber is designed for removing 80µ dia particles with 100 % efficiency. The

particulate matter density is 1500 kg/m3. Depth and width of chamber is 2 m each.

Determine:-

i. Length of chamber required without trays.

ii. Length of chamber with 10 trays.


Unit- VII


Unit-VII

Cyclone Problems

1. A cyclone is designed with an inlet of 10 cm and 5 effective turns. The inlet gas

velocity is to be 10 m/s and particulate density is 1.7 gm/cc. Estimate the particle

size that will be collected with 50 % efficiency, if the gas is air and its temperature

is 3500 K. Viscosity of air is 0.075 kg/m.hr




is 350 0K. Viscosity of air is 0.0748 kg/m.hr

3. An air stream with flow rate of 7 m3/sec is passed through a cyclone of standard

proportions. The diameter of cyclone is 2m and air temperature is 770C and

numbers of effective turns are 5. Density of particle is 1500 kg/m3

i. Determine the particle size which can be removed with 50 % efficiency.

ii. Sketch the cyclone giving all dimensions in meter.




is 3500 K. Viscosity of air is 0.075 kg/m.hr.

5. An air stream with a flow rate of 7 m3/sec is passed through a cyclone of standard

proportions. The dia of cyclone is 2 m. µ = 2.1 x 10-5 kg/m-sec.

a) Determine the removal efficiency for a particle with a density of 1500

kg/m3 and a dia of 10 µ. Take Ne = 5 turns

b) Determine the collection efficiency base on the above if bank of 64

cyclones with diameters 24 cm are used instead of single cyclone.

6. A conventional cyclone with dia. 1 m handles 3 m3/sec of standard air, carrying

particles with a density of 2000 kg/m3. For Ne = 6, determine the cut size and the

efficiency as function of particle diameter. µg = 1.81 x 10-5 kg/m-sec


Unit- VII


Unit-VII

Bag house filter Problems

1. A filter bag house is to be designed for a gas flow of 150 m3/sec. Make necessary

assumptions and determine the size of bag and no. of bags. Draw neat sketch

2. A fabric filter is to be constructed using bags having 22 cm diameter and 6 m height.

The bag house is to receive 12 m3/s of air and filtering velocity is restricted to 2

m/min. Determine the number of bags required for a continuously cleaned operation.

3. A fabric filter is to be constructed using bags having 0.2 m diameter and 6 m height.

The bag house is to receive 10 m3/s of air and air to cloth ratio is 2 m/min. Determine

the cloth area and number of bags required.

4. A fabric filter must process 15 m3/sec of waste gas. The bag house is to be divided

into 8 sections of equal cloth area, so that one section can shut down for cleaning

while other continues operations. Assume air to cloth ratio 9 m3/min/m2 and bag

diameter 0.25 m and 7 m long. Determine no of bags and physical arrangement

5. Determine no of bags necessary to treat 16 m3/sec of polluted air laden with

particulates. The air/cloth ratio = 10 m/min. The bags have 0.25 m dia and 7 m length


Unit- VII


Unit-VII

Electrostatic Precipitator (ESP) Problems

1. An ESP with overall spacing 23 cm and mean gas velocity of 1.5 m/s has collector

plate area of 6000 m2 gives 97 % efficiency in treating 200 m3/s of flue gas. To

achieve 98 % and 99 % efficiency what should be plate area required?

2. For an ESP of given geometry and operating conditions, the collection efficiency

for 2 µ particle is 99.90 %. On the basis of Deutch equation for efficiency, estimate

the collection efficiency for

i. 1 µ

ii. 0.5 µ

iii. 0.1 µ.

3. Design the ESP are for controlling 40 m3/s of dirty gas containing 60 % particles of

1 µ dia, 40 % of 0.5 µ dia. The overall efficiency required is 99 %

Technology

Unit vii problem set