Transcript Critical Environment Challanges and Constraints of Foundries and

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
[email protected]
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
Research
 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
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
Conc. (mg/Nm3)
Cupola
< 3 tph
> 3 tph
Particulate
Particulate
450
150
Induction furnaces
Particulate
150
SO2 – 300 mg/Nm3
UK emission standards
Type
Pollutant
Conc. (mg/Nm3)
Particulate
20
Particulate
Particulate
No standard
100
New cupola
Existing cupola
Less than 4 tph
4 tph and more
SPM emissions from cupola without
PCS (1300-2200 mg/Nm3)
Figure 3
Common PCS types
Minimum Particle
size, μm
Collection
efficiency, %
Cyclone
> 10
< 85
Multiple cyclone
>5
< 95
Wet cap
>5
< 95
Venturi-scrubber
> 0.5
< 99
Fabric filter
> 0.2
< 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)
WATER
DEFLECTOR
WATER FILM
CANOPY
CUPOLA
DIRTY FLUE GAS
WATER AND
ENTRAINED DUST
TO SETTLING
TANK
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]
Stack
Gas Flow from
Cupola Furnace
Venturi
Unit LU
P
Cyclone
LSC
Centrifugal fan
Bleed off
Make up water
Over flow
Drain
Re-circulation
Pump
Re-circulation Tank
Figure 4
Stainless Steel Venturi Scrubber
Environment performance
Environment performance
(a) without PCS: 2000 mg/Nm3
(b) with common PCS: 500 mg/Nm3
(c) with venturi scrubber: 50 mg/Nm3
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
Thank you
for your kind attention!