Joanne Tanner 1, Michael Müller 2. 6 th International Freiberg Conference on IGCC & XtL Technologies, Coal Conversion and Syngas

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1 Influence of temperature and gasification agent on the release of alkali, sulphur and chlorine species during high temperature gasification of low rank coals Joanne Tanner 1, Michael Müller 2 6 th International Freiberg Conference on IGCC & XtL Technologies, Coal Conversion and Syngas May 2014, Dresden/Radebeul, Germany 1 Monash University, Department of Chemical Engineering 2 Forschungszentrum Jülich, Institute for Energy Research (IEK-2), PhD Project Supervisors: Prof. Sankar Bhattacharya Prof.Dr.-Ing. Klaus R.G. Hein

2 Victorian Brown Coal (VBC) High moisture low rank Strip ratio of 1:7 low mining cost Estimated > 35 billion tonnes recoverable Coal Property Range HHV (MJ/kg) 7-10 Moisture (% ar) Ash (% ar) Currently used for mine-mouth electricity generation, briquette production Potential for use in coal-to-products processes EDR Data Source: Coal Properties: Durie, R.A., The Science of Victorian Brown Coal, Butterworth Heinemann, 1991

3 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

4 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 Project Component Char gasification kinetics Char conversion Syngas yield and composition Slag viscosity Ash/slag phase changes Release of inorganic species EF gasification modelling Equipment / Technique Pressurised thermogravimetric analysis (PTGA) High temperature entrained flow reactor (EFR) High temperature entrained flow reactor (EFR) Controlled atmosphere rheometry (custom rheometer) Australian Synchrotron (AS-XRD) Molecular beam mass spectrometry (MBMS) CFD model using Fluent software package 4

5 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

6 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 CO 2 /H 2 O concentration 6

7 Pyrolysis and gasification phases MS spectra Morwell coal, 1400 C, 20% CO 2 /N 2 2 phases evident pyrolysis (devolatilisation) and gasification min Pyrolysis up to completion of volatiles evolution e.g. NaCl Gasification marked by a sharp initial dropoff then gradual return to baseline of the CO 2 concentration CO formation from Boudouard reaction mirrors CO 2 consumption as expected min () + () () 7

8 Release of Na, K, Cl species MS spectra Morwell coal, 1400 C, 20% CO 2 /N 2 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 m/z=39 attributed predominantly to NaO + due to low K content of the Vic and Rhenish coals NaO + is a fragment of NaOH min NaOH / NaCl equilibrium () + () () + () min 8

9 Release of S species MS spectra Morwell coal, 1400 C, 20% CO 2 /N 2 Volatile pyritic S released during the pyrolysis phase as H 2 S () + () () + () Intermediate sulphates are also formed, capturing volatile sulphur Sulphate S initially re-released as COS, considered an intermediary between CO 2 and H 2 S () + () () + () min min Remainder is released as SO 2 from sulphate decomposition () () + () + () 9

10 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 () + () () + () 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 Averaged, Normalised Peak Area 2.0e-3 1.5e-3 1.0e-3 5.0e C 1200 C 1400 C HKN-S-HKN-S+ HKS HKT LY MOR 58 NaCl + 10

11 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 11

12 Entrained flow release apparatus, Jülich HELMA: High temperature Entrained 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 12

13 Entrained flow reactor at Monash, Australia HELENA High temperature ELectrically heated ENtrained flow Apparatus 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 13

14 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 CO 2 and H 2 O conditions from 1100 C and 1600 C Char conversion, syngas yield and composition for each coal type Char and solid residue characterisation 14

15 Acknowledgements 15