Influence of temperature and gasification agent on …tu-freiberg.de/sites/default/files/media/professur-fuer...Coal-to-Products Processes Current utilisation – Power generation

Energy, Fuels and Reaction Engineering Research Gro upOur Focus: Scientific R&D for Practical Solutions

Influence of temperature and gasification agent on the release of alkali, sulphur and chlorine species during high temperature

gasification of low rank coals

PhD Project Supervisors:Prof. Sankar Bhattacharya

Prof.Dr.-Ing. Klaus R.G. Hein

Joanne Tanner1, Michael Müller2

6th International Freiberg Conference on IGCC & XtL Technologies,Coal Conversion and Syngas

19-22 May 2014, Dresden/Radebeul, Germany

1 Monash University, Department of Chemical Engineering

2 Forschungszentrum Jülich ,Institute for Energy Research (IEK-2),

• High moisture low rank

• Strip ratio of 1:7 low mining cost

• Estimated > 35 billion tonnes recoverable

• Currently used for mine-mouth electricity generation, briquette production

• Potential for use in coal-to-products processes

Coal Property Range

HHV (MJ/kg) 7 - 10

Moisture (% ar) 55 - 70

Ash (% ar) 0.4 – 2.0

EDR Data Source: http://www.dpi.vic.gov.au/earth-resources/coal/fact-sheet-brown-coal-victoria

Coal Properties: Durie, R.A., The Science of Victorian Brown Coal, Butterworth Heinemann, 1991

Victorian Brown Coal (VBC)


Coal-to-Products Processes

� Current utilisation

– Power generation– Briquetting

� Potential products

– Secondary fuels– Chemicals– Feedstocks

� E.g. syncrude production for use in existing domestic refineries

� Dominant gasification technologies are entrained flow (EF) configuration

3


Entrained flow gasification of low rank coals

� Multi-project, multi-student investigation of entrained flow (EF) gasification behaviour of low rank coals

� Equipment development to emulate semi-industrial conditions

� Provide data for process design and modelling

� Victorian brown coals + German, Chinese and Thai lignites

4

Project Component Equipment / Technique

Char gasification kinetics Pressurised thermogravimetric analysis (PTGA)

Char conversion High temperature entrained flow reactor (EFR)

Syngas yield and composition High temperature entrained flow reactor (EFR)

Slag viscosity Controlled atmosphere rheometry (custom rheometer)

Ash/slag phase changes Australian Synchrotron (AS-XRD)

Release of inorganic species Molecular beam mass spectrometry (MBMS)

EF gasification modelling CFD model using Fluent software package


The release of inorganic species

� Alkali, sulphur and chlorine species are released upon high temperature gasification of low rank coals

� Known to contribute to slagging and fouling in lower temperature, downstream process equipment

� Basic release investigations are crucial to the design and development of appropriate control measures and hot gas cleaning strategies for low rank coal gasification systems

� Monash collaboration with FZ Jülich through Group of 8 / DAAD grant

5


Molecular Beam Mass Spectrometry (MBMS)

� Low vacuum analysis system generates a beam of individual molecules

� Molecules ionised and detected by quadrupole MS

� Qualitative and semi-quantitative results:

– Individual spectra for each species / fragment– Comparative data for different coals / different temperatures

� 6 coals (Victorian brown coals and German lignites)

� 100 mg samples, 6 repeats

� 20 m/z ratios measured corresponding to various species of interest

� Data averaged and normalised to feed CO2/H2O concentration

6


Pyrolysis and gasification phases – MS spectra

� 2 phases evident – pyrolysis (devolatilisation) and gasification

� Pyrolysis up to completion of volatiles evolution e.g. NaCl

� Gasification marked by a sharp initial dropoff then gradual return to baseline of the CO2 concentration

� CO formation from Boudouardreaction mirrors CO2 consumption as expected

7

�(�) + ��(�) → ��(�)min

min

Morwell coal, 1400 °C, 20% CO 2/N2


Release of Na, K, Cl species – MS spectra

� Volatile species released during pyrolysis phase up to 0.1 s

� Alkalis weakly bound to functional groups in the organic matrix or dissolved in pore water

8


min

min

��(�) + �� (�) → �� (�) + ��(�)

� m/z=39 attributed predominantly to NaO+ due to low K content of the Vic and Rhenish coals

� NaO+ is a fragment of NaOH

� NaOH / NaCl equilibrium


Release of S species – MS spectra

� Volatile pyritic S released during the pyrolysis phase as H2S

� Intermediate sulphates are also formed, capturing volatile sulphur

� Sulphate S initially re-released as COS, considered an intermediary between CO2 and H2S

� Remainder is released as SO2 from sulphate decomposition

9

��(�) +��(�) → ��(�) +��(�)

��(�) +��(�) → ��(�) + ��(�)

��(�) → ��(�) + ��(�) +�

��(�)


min

min


Release of Na, K species – semi-quantitative results

� NaO+ release increases to 1200°, then decreased at higher temp.

– Alkali aluminosilicate decomposition / formation

– NaOH / NaCl equilibrium

10

��(�) + �� (�) → �� (�) + ��(�)

� NaCl+ demonstrates equilibrium with NaO+

� Mild increase with temperature to 1200°C, then a jump at 1400°C as the equilibrium shifts to the right

58NaCl+HKN-S-HKN-S+ HKS HKT LY MOR

Ave

rag

ed

, No

rma

lise

d P

ea

k A

rea

0.0

5.0e-4

1.0e-3

1.5e-3

2.0e-31100°C1200°C1400°C


Summary of fixed bed gasification release results

� Inorganic species present in low rank coals will volatilise under gasification conditions

� Known to cause corrosion and fouling in downstream processes e.g. aluminosilicate and sulphate deposition

� Distinct pyrolysis and gasification phase observed

� Various sulphur species evolved in stages during initial pyrolysis and subsequent gasification phases

� Relative release amount of volatile species released are not always linearly dependant on temperature

� Gas-phase equilibrium determines final composition

� Operating temperature of the gasifier, gas cleaning and downstream processes are crucial

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Entrained flow release apparatus, Jülich

� HELMA: H igh temperatureEntrained flow Laboratory reactor with Mass spectrometric Analysis

� Currently running experiments

� Configuration mimics gas and particle residence time of the Monash entrained flow reactor as closely as possible

� Solid residue collected and analysed offline

� Use CO as a basis for comparison

� Final outcome will demonstrate potential gas-phase issues related to these fuels

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Entrained flow reactor at Monash, Australia

� HELENA H igh temperatureELectrically heatedENtrained flowApparatus

� Designed and commissioned as part of the PhD project

� Purpose:

– Char preparation– Char conversion– Syngas yields– Syngas composition

� Specification:

– 1600°C– Entrained flow up to 500 μm

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Ongoing work

� Intrinsic kinetics of brown coal gasification

� MBMS

– Entrained flow experiments partially complete

– Comparison between fixed bed and entrained flow release

– Comparison with HELENA results

� HELENA:

– 2 VBC and 4 Rhenish lignites

– Char preparation and gasification under CO2 and H2O conditions from 1100 °C and 1600 °C

– Char conversion, syngas yield and composition for each coal type

– Char and solid residue characterisation

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Acknowledgements

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Influence of temperature and gasification agent on …tu-freiberg.de/sites/default/files/media/professur-fuer...Coal-to-Products Processes Current utilisation – Power generation