Presentation by Josef Waltisberg on controlling Hg in cement kilns

1. The Critical Cycles of Mercury in
Cement Kiln System - Installation of
Valves
Hg
Josef Waltisberg
Eichhaldenweg 23
CH-5113 Holderbank / Switzerland
josef@waltisberg.com
Problem and Solution
Problem: Kiln with partly high Hg emission
Level (average): Direct operation: 30 to 40 [µg/m3N,dry]
Compound operation: < 10 [µg/m3N,dry]
Peaks: Direct operation: 60 to 100 [µg/m3N,dry]
Solution: Reduction of Hg emission in direct operation
by installation of “Mercury-Valve”
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Waltisberg Consulting JW / 04.2010
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2. Mercury Measurement
Volume
Stream
to Chimney All the dust from the
filter was recycled to the silo
Dust
Direct Operation
Temperature: 155 [° C]:
Emission: 36 [µg/m3N,dry] at 10 [%] oxygen
µ
Dust ~ 8 [%] related to clinker
Compound Operation
Temperature: 106 [°C]:
Emission: < 8 [µg/m3N,dry] at 10 [%] oxygen
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Waltisberg Consulting JW / 04.2010
Mercury - Balance
Ratio Direct / Compound: 40 : 60
Exhaust Gas Volume: 2 [m3N,dry/kg Cli]
Concentration Mass Flow
Raw Material 0.01 [ppm] 0.019 [mg/kg Cli]
Fuel 0.155 [ppm] 0.016 [mg/kg Cli]
Kiln without Valve
Emission
• Direct 36.4 [µg/m3]
µ 0.029 [mg/kg Cli]
• Compound 4.6 [µg/m3] *) 0.005 [mg/kg Cli]
*) Measurement < 8 [µg/m3] ; for simulation: 4.6 [µg/m3]
Reduction possibility: During direct operation the dust
is discarded from the kiln system
INSTALLATION OF A VALVE ! ! !
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Waltisberg Consulting JW / 04.2010
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3. Mercury Valve
Output Gas Volume
from Preheater Stream
Gas + Dust 4 to Chimney
Input to
Preheater
2
1: Conditioning Tower
1 2: Homogenizing Silo
3: Raw Mill
4: Filter System
3
Dust and Raw Meal
Gas Stream
Output(s) of Dust
VALVE
to Outside Kiln Process
e.g. Cement Mill 5
Waltisberg Consulting JW / 04.2010
Mercury Balance
Ratio Direct / Compound: 40 : 60
Exhaust Gas Volume: 2 [m3N,dry/kg Cli] Measurements:
Direct: 36 [µg/m3]
Concentration Mass Flow Compound:
Raw Material 0.01 [ppm] 0.019 [mg/kg Cli] < 8 [µg/m3]
Fuel 0.155 [ppm] 0.016 [mg/kg Cli]
Assumptions:
Kiln without Valve Temperature
in filter system
Emission not changed
• Direct 36.4 [µg/m3]
µ 0.029 [mg/kg Cli]
Same filter
• Compound 4.6 [µg/m3] 0.005 [mg/kg Cli]
behavior
Kiln with Valve -- Dust during direct operation discarded
Emission
• Direct 16.1 [µg/m3]
µ 0.013 [mg/kg Cli]
• Compound 2.0 [µg/m3] 0.002 [mg/kg Cli]
Valve 0.019 [mg/kg Cli]
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Waltisberg Consulting JW / 04.2010
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4. Mercury - Valve
Emission in Function of Discarded Dust
[%] of discarded direct operation dust
(e.g. to cement mill)
40
35
Emission [ug/m3]
30
25
20 Direct
15 Compound
10
5
0
0 20 40 60 80 100
Valve - Direct [%]
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Waltisberg Consulting JW / 04.2010
Final Conclusions
Reduction of high emission level in direct operation
36 [µg/m3N,dry] 16 [µg/m3N,dry]
Hg Peaks in direct operation < 50 [µg/m3N,dry] (limit)
Additionally also other cycles cut
e.g. thallium, dioxin/furans, etc
Problem: In some countries (e.g. USA, Canada)
it is not allowed to discard the dust to the cement mill.
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