Controlling boiler emissions in an industrial cluster-A case study

Prof. H S SyedAsst. Prof. of Env. Engg

L. D. College of Engg, Ahmedabad

November , 2011

Chimney, the stack attached to the boiler house.

• A symbol of progress and development in the past

• Now, a symbol of pollution and hence a concern

Heat requirements in the industry are satisfied by

steam generated at boiler house.

Boiler House - an important source of air pollution.

Different types of boilers, of different capacities using

different types of fuel with different operating conditions

are in use.

Case Study:

• Narol Industrial cluster of textile process houses

was identified as a major source of pollution by

Supreme Court appointed Environmental Pollution Control

Authority(EPCA) – Bhurelal Committee.

• Also identified by GPCB as major air polluter with reference to

CEPI (Comprehensive Environmental Pollution Index ) score

of MOEF .

Environmental Engg Department , L D College of

Enginering , Ahmedabad was approached by

Ahmedabad Textile Process Association (ATPA) to

study the problem and provide a solution to

pollution.

Case Study:

• Narol Industrial cluster of textile process houses

122 Process Houses

91 having Steam Boilers and Thermic Fluid Heaters

87 have been surveyed and data collected

Broad Classification Of Boilers Based On

Steam Generation Capacity

≤ 2 Ton/hr 35

5 – 7.5 Ton/hr 35

10 Ton/hr 14

≥ 10 Ton/hr 3

The Different Fuels Used In The BoilerSr No. Steam Generation Capacity Type of fuel No. of units

1 ≤ 2 T/hr Saw dust 2

Wood 33

Lignite 7

2 5 T/hr Saw dust 5

Lignite 19

Wood 8

Coal 3

3 10 T/hr Agro waste 1

Lignite 10

Coal 3

4 > 10 T/hr Agro waste 1

Lignite 2

The common fuels used are wood for ≤ 2 Ton/hr and lignite for ≥ 5

Ton/hr capacity boilers.

Proximate Analysis of Fuel

Proximate

AnalysisWood Indian Coal

Lignite

(MatanoMadh)Saw Dust

Moisture -- 5.98 11.71 37.98

Ash 0.10 38.63 20.05 1.63

Volatile Matter 76.40 34.69 41.70 81.22

Fix Carbon 23.50 20.70 26.20 17.15

The Proximate Analysis Of The Fuel

The common air pollutants encountered: PM,

SO2 & NOx

The air pollutants namely particulate matter (PM),

SO2 and NOx primarily depend on the fuel used

as well as on the operating conditions and

procedures adopted.

Based on the proximate analysis stoichometry calculation for

pollutants (50% Excess Air)

Parameters Lignite Saw Dust

PM, mg/m3 10,200 3950

SO2, ppm 500 --

Out of 87 - 30 selected units were monitored for air pollution

parameters.

Sr. No.

Steam Generation Capacity

PM mg/Nm3 SO2 ppm NOx

Range Average Range Average Range Average

1 2 Ton/hr 225 – 698 450 9 – 308 120 0.5 – 8.0 4

2 5 Ton/hr 61 – 840 435 6 – 400 175 0.5 – 9.0 7

3 10 Ton/hr 500 – 2500 1500 12 -700 350 5-14 10

The Measured Concentration Of Pollutants

The present scenario: About pollutant control equipments/

systems;

Practically all boilers are equipped with multi cyclones

Not designed appropriately

Offers only 30- 35 % removal of PM

≤ 2 Ton/hr: No economizer or pre-heaters are installed to

control temperature

≥ 5 Ton/hr: Economizer or pre – heaters are installed for heat

recovery and hence temperature control

Bag filters are installed at practically all the units.

Under compulsion and directions of Bhurelal committee and

GPCB

The boilers with steam generation capacity ≥ 5 Ton/hr,

mostly use lignite as fuel.

Lignite generates PM and SO2.

Wood generates PM

However, no system is installed to control SO2 in

the flue gas.

The multi cyclones and bag filters installed are not

appropriately designed and hence are neither

adequate nor efficient

Result is gross non - compliance of the emission

standards.

Environmental Engineering Department of L.D. College,

Ahmedabad has proposed/ developed the scheme

Design Approach:

For ≤ 2 Ton/hr capacity wood/saw dust as fuel

Multi cyclone – Venturi Scrubber– Cyclone separator-Demistifer

For ≥ 5 Ton/hr capacity lignite as fuel

Multi cyclone – Bag Filter – Packed bed Alkali wet Scrubber

1 Venturi Scrubber 7. Filter Cloth

2 Cyclonic Separator 8. Mesh Pad Type Demister

3 ID fan 9. Alkali storage tank (powder / lye)

4Stack 10. Feeder

5Filter neutsch 11. Mixing tank

6Alkali Recirculatin Pump 12. Pump (Alkali Solution)

: The Proposed Air Pollution Control System for ≤ 2 TPH Lignite based Boiler

125

10

11

1

2

7

5

6

3 4

8

The Proposed Air Pollution Control System

≥ 5 Ton/hr capacity: Lignite as Fuel

Furnace

Pre Air Heater

Multi Cyclo

ne

Bag House

Cyclone

ID FanAlkaline Wet Scrubb

er

Stack

Bypass

The Expected Results: When installed as per the

design and operated as directed the emissions

norms will be satisfied.

GOD BLESS YOU