Critical environment challenges and constraints of foundries and feasible clean technology options
Workshop on
Sustainable Environment Practices in Foundry Sector, Kolkata
Prosanto Pal
Senior Fellow,
TERI, New Delhi prosanto@teri.res.in
24 August 2012

Outline
 About TERI
 Cleaner technology demonstrations in the foundry sector and
TERI’s work
 Environment challenges and way forward

Origins of TERI
 Conceived by Late Sri Darbari Sethi of Tata Chemicals
 Registered as ‘Tata Energy Research Institute’ in 1974
 1974-82 – operated from Mumbai
 Moved to Delhi in 1982
 Own premises at India Habitat Centre in 1994

Research orientation
 Independent, non-profit, research institute
 Core competencies – research, information & communication and training & outreach
 Undertakes sponsored research projects in energy, environment and sustainable development areas
 Major sponsors include GOI, corporate, multilateral & bilateral agencies
Outreach
Research
Information and communication

Salient features of gray iron foundries
 Cupola is common melting furnace
 Conventional cupolas poorly designed and operated leading to high coke consumption
 No standardized design of pollution control system to control suspended particulate matter (SPM)
Commissioning of the demonstration plant

Present technology status
 Cupola
– Poor furnace design
– Poor operating practices
– Non-uniform size of charge material
 PCS
– Variety of PCS designs
– Short life/high corrosion
– Poor knowledge on emission standards and
PCS technology

Pollution reduction at source by
Energy Efficient Cupola
 Divided blast cupola
– Reduces coke consumption by about 25%
– Increases tapping temperature by about 50º C
– Increases melting rate
 Best operating practice
– optimization of blast rate
– bed preparation
– sizing the raw material
– charging practices

CPCB emission standards
Type Pollutant
Cupola
< 3 tph
> 3 tph
Particulate
Particulate
Induction furnaces Particulate
Conc. (mg/Nm 3 )
450
150
150
SO
2
– 300 mg/Nm 3

UK emission standards
Type
New cupola
Pollutant
Particulate
Existing cupola
Less than 4 tph
4 tph and more
Particulate
Particulate
Conc. (mg/Nm 3 )
20
No standard
100

SPM emissions from cupola without
PCS (1300-2200 mg/Nm 3 )
Figure 3

Common PCS types
Cyclone
Multiple cyclone
Wet cap
Venturi-scrubber
Fabric filter
Minimum Particle size, μm
> 10
Collection efficiency, %
< 85
> 5
> 5
< 95
< 95
> 0.5
> 0.2
< 99
< 99

Selection criteria of PCS
 Fines in cupola emissions is high (< 5 μm 16%)
 Ability to meet the 150 mg/Nm3 norm
 Life of the equipment
 Ability to control SO2 emissions

Different PCS initiatives in Howrah
 CPCB-NML ‘cyclone’ system at M/s Crawley & Ray
 NML-IFA cyclone system at M/s Shree Uma Foundries (P) Ltd, Liluah
 B.E. College-WBPCB ‘wet scrubber’ at M/s Bharat Engineering Works
 Jadavpur-HFA ‘cyclone and submerged wet-scrubber’ system
 TERI-SDC ‘venturi-scrubber’ system at M/s Bharat Engineering Works

Spark arrestor/ dry arrestor/Chinese hat type (Coimbatore)

Wet-scrubber system (PCST)
CUPOLA
WATER AND
ENTRAINED DUST
TO SETTLING
TANK
DIRTY FLUE GAS
WATER
DEFLECTOR
WATER FILM
CANOPY

Photo of wet cap

Three stage wet-scrubber system
(B.E.- WBPCB)

Cyclone & submerged wet-scrubber system
Cupola  conventional cyclone  high efficiency cyclone  submerged wet scrubber
 ID fan

Twin cyclone

TERI-SDC demonstration plant
Demonstration Plant at Bharat
Engineering Works, Howrah
Commissioned 1998
DBC – Divided Blast Cupola
Bucket charging system
PCS – Pollution Control System
(venturi-scrubber)
100 ft free standing chimney

Demonstration plant

Salient features of the TERI-SDC design
 Divided blast cupola
– matching molten metal requirement to cupola size
– increase stack height to utilize heat in flue gas
– proper selection of cupola blower
– proper distribution of blast air
– feedstock weighted & charged mechanically
 Venturi scrubber system
– fitted with variable throat
– critical surfaces made of stainless steel
– gas tight construction with explosion doors

Photos of PCS

Energy performance
Coke charge in CC 13.6%
Coke charge in DBC 8.8 %
Energy savings 35 %
[(13.6 – 8.8)/13.6]

Gas Flow from
Cupola Furnace
Venturi
Unit LU
P
Cyclone
LSC
Bleed off
Re-circulation
Pump
Make up water
Re-circulation Tank
Figure 4
Over flow
Drain
Centrifugal fan

Stainless Steel Venturi Scrubber

Environment performance

Environment performance
(a) without PCS: 2000 mg/Nm 3
(b) with common PCS: 500 mg/Nm 3
(c) with venturi scrubber: 50 mg/Nm 3

Environmental challenges
 High cost of pollution control especially for small foundry units

Pollution control cost is same for small and large foundries
 Particle size analysis is most important in selection of pollution control system
 Can be done using centrifugal dust classifier or image analyzer
(more accurate)
 Fine particles get deposited in filter paper

Environmental challenges
 Problems in isokinetic sampling : accuracy of stack velocity measurement
 At no time the gas pressure at sampling point should be negative
 Lowest pressure level which can be accurately measured in field conductions is about 3 m/s
 If ratio of highest to lowest pitot-static reading exceeds 9:1 (ratio of highest to lowest gas velocity exceeds 3:1) new sampling position needs to be sought

Repeat the readings of gas velocity and temperature
 If the sum of pitot static readings differ by more than 10% (or sum of gas velocity readings by more than 5%) the test is not accurate
 Measurement of emission level using instrument based on light extinction principle (using laser light) is better

Way-forward
 Adopt energy efficient DBC for all new cupola
 Develop clearer guidelines for selection of PCS
 Appoint independent agency to validate design, fabrication and installation
 Develop approved list of vendors/fabricators for fabricating/ installing PCS
 Provide soft loans for PCS
 Hold regular training programs on stack monitoring and PCS design/operation for PCB staff, fabricators and entrepreneurs