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NOx in Cement Clinker Production -

Formation and Measures to minimize NOx-Emission

June 22st, 2016 | Reinhard Beilmann | tkIS Lima, Peru, Technical Symposium for Reduction of Emissions

2 | June 22st, 2016 | Formation and Abatement of NOx-Emissions | Reinhard Beilmann tkIS

NOx – Emissions by Source in EEA member countries (2009)

Emissions Cement Plants are contributing to


1986 1991 2019

1500 mg/Nm³

500 mg/m³ new plants

800 mg/Nm³ existing plants

500 mg/Nm³

2002

Nm³ = dry at 10% O2. Conversion to 10% O2 permitted in Germany only until 2012.

2016

3

17. BlmSchV

Development of NOX Limits for Cement Plants in Germany

350 mg/Nm³ NH3=30mg/Nm³ 200 mg/Nm³

NH3=30mg/Nm³


1500

mg

NO

x/m

3

800

0

200

500

Capability of NOx-Abatement Technologies in Cement Plants

Em

iss

ion

wit

ho

ut A

ba

tem

en

t SC

R

MS

C+

SN

CR

MS

C


NOx Sources in the Clinker Burning Process Sintering zone

• High temperatures • High oxygen levels at the flame

N2 + O2 → 2 NO (N2 + 2 O2 → 2 NO2)

Formation of thermal NOx unavoidable

Calciner firing

• Low oxygen levels

• Substoichiometric at the ignition zone

• Flameless oxidation

• Uniform temperature

No thermal NOX

Fuel NOX only

Partly reduction of (kiln) NOX


Sintering zone

• High temperatures • High oxygen levels at the flame

N2 + O2 → 2 NO (N2 + 2 O2 → 2 NO2)

Formation of thermal NOx unavoidable

Theory of Low NOX Burner:

Measures to influence the NOX emission – Theory of Low NOx Burner

Reduce flame temperature • Switch to low reactivity fuel, increase

particle size • Increase flame length (reduce swirl)

Reduce oxygen content • Reduce primary air • Reduce momentum of primary air

NOx CO


Temperature

clinker quality

Thermal NOx

Oxygen Level

Options for lowering the thermal NOx formation in the sintering

zone are limited, as clinker quality is always affected.

NOx emission should be adjusted in the calciner by MSC

Theory of Low NOX Burner:

Measures to influence the NOX emission – Theory of Low NOx Burner


Lack of Air

Air Excess

HCN Calciner Fuel N NHi - radicals NOx

N2

NOx Development in the Calciner


1. Air excess number below 1

2. High temperature in substoichiometric zone

3. Long retention time in substoichiometric zone

top air: ~ 0,85-0,95,lower values possible

1

meal staging for flexible temperature control

2

1

2

3

3

retention time of ~ 1 second

MSC Multi-Stage-Combustion - A Primary Measure for NOx-Abatement

Area of reduced

combustion condition

with flexible temperature

control and sufficient

retention time

MSC

Air excess

t

Retention time

T

Temperature


Latest References for MSC-Calciner Systems of TKIS

500 mg/Nm³

Coal (40%)

< 500 mg/Nm³

Natural Gas

~ 500 mg/Nm³

RDF

Coal (28 %)

~ 650 mg/Nm³

Coal (21%)/ Petcoke

~ 800 mg/Nm³

> 30 units sold


SNCR - Selective Non Catalytic Reduction – Secondary Measure for NOx-Abatement

2 NO + 2 NH3 + 0,5 O2 2 N2 + 3 H2O

2 NO + CH4N2O 2 N2 + 2 H2O + CO

Combustion,

NO formation NH3-Slip

Typical Calciner Temperature

Urea

Ammonia


Increase of CO likely


Risk of secondary

Emissions at higher

Reduction levels


TiO2

V2O5

WO3

NOX

NOX

H2O

4NO + 4NH3 + O2 4N2 + 6H2O

SCR

reactor

Controller NOx Set point

NH4OH

Storage

Raw

Gas ~300°C

SCR - Selective Catalytic Reduction – Secondary Measure for NOx-Abatement


SCR Configurations

High Dust (HD)

Semi Dust (SD)

Tail End (TE)

Lowest investment costs Suitable flue gas temperature No interference with main process Easiest option for retrofits - Frequent cleaning of catalyst

Suitable flue gas temperature Easier cleaning of catalyst - Higher cost of installation - Complex duct routings in retrofits - Additional power for ESP

No dust cleaning required Longer lifetime of catalyst - Highest cost of installation - Requires reheating of flue gas - Complex system - Higher operating costs

SCR - Selective Catalytic Reduction – Secondary Measure for NOx-Abatement


SCR References / Projects of Elex CemCat

Monselice (2006)

Mergelstetten

(2010)

Joppa (2013)

Rezatto (2014)

Start up of SCR-Systems in 2017:

Solnhofen, Phönix, Göllheim


SCR versus SNCR - Performance of NOx Abatement

0

10

20

30

40

50

60

70

80

90

100

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5

NH3/NO

NO

-Ab

ate

men

t [%

]

SNCR

SCR

Monselice


Catalysts

ESP

Industrial References

New products

Combustion/Fuels

Preheater / Calciner

SNCR

Patents Patents

CemCat a Joint Venture of Elex and TKIS (Polysius)


Conclusion - NOx in Cement Clinker Production Formation and Measures to minimize Emissions

• Primary NOx Emission can be reduced significantly with modern MSC Calciners down to

500 – 800 mg/Nm³

• SCNR is effective for NOx abatements of 50-60%, further reduction only with secondary

emissions, mainly NH3

• SCR abatement is nearly unlimited, secondary Ammonia emissions are not only avoided,

but Ammonia is effectively used for the NO reduction

• High Dust is the favorite solution:

• lowest investment

• no extra energy

• TOC oxidation

• positive effect on downstream Hg capture

Any questions?

Thank you for your attention!

NOx in Cement Clinker Production Formation and Measures to minimize Emissions

nox in cement clinker production - formation and measures ... › downloads ›...

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