Coal Science and Gasification Experience

The Basic Foundation for Underground Coal Gasification Development and R&D

Hein WJP Neomagus1, Frans B Waanders1 Johan C van Dyk1,2,3, Christien A Strydom2, Johan F Brand3

1School of Chemical and Minerals Engineering, Unit of Energy Systems, North West-University, Potchefstroom 2520, South Africa, Tel: +27 18 299 19942School of Chemical and Physical Sciences, Chemical Resource beneficiation, North West-University, Potchefstroom 2520, South Africa, Tel: +27 18 299 23403African Carbon Energy (Africary), South-Africa, Tel: +27 82 550 0473

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• Coal will remain an important energy provider in the world, and specifically in South Africa (RSA)

• The energy, and specifically the electricity, market in RSA is stressed

• Smarter utilization of energy sources are needed for the short future

• Underground Coal Gasification (UCG) is an attractive alternative

I Pretorius, SJ Piketh, RP Burger, HWJP Neomagus, 2014, A global perspective of South African power plant emissions, submitted to Energy Policy

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Underground coal gasification – SA’s energy future?Posted by: ESI AfricaAugust 14, 2014Leave a CommentEskom is in talks with private companies about investing in underground coal gasification (UCG), Steve Lennon, an Eskom sustainability executive leading the UCG programme, told Reuters this week.South Africa’s state utility has been developing UCG for 10 years and is investing a further ZAR1 billion ($94 million) in research over the next five years, when it hopes to give the green light for the technology to be rolled out.Mr Lennon says Eskom is committed to funding new technology and UCG research is not under threat, although many hurdles remain.“When we first started the biggest challenges were technological,” Lennon said. “We’ve overcome that.”“Now the challenges we face are regulation, legislation and the next big one will be costs. Can we make sure this is a cost-competitive technology? The indications are we can.”Lennon says he hopes UCG will produce power at around US$5-US$6 per kilojoule, less than half the cost of its obvious competitor, imported liquefied natural gas (LNG), but around double that of shale gas in the United States, reports Reuters.Environmental questionUCG, a process that involves drilling wells to previously unrecoverable coal reserves hundreds of metres underground and injecting steam and oxygen to ignite a combustion process that produces a synthetic gas that can be used as fuel, could also face resistance from environmentalists who are concerned about how UCG can be controlled and its potential dangers accurately assessed due to the depth of operations.There is also concern that the process in the long term could raise the country’s carbon output, not lower it, by sustaining the use of the fossil fuel.Reasons to be optimistic“UCG has very large potential. It will probably be the successor to conventional coal mining,” said Xavier Prévost, senior coal analyst at Pretoria-based XMP Consulting.“It fits in perfectly with South Africa’s needs because it will create energy and minimise emissions.”The gas can be used to replace coal in existing power plants, fire gas turbine facilities or for heating and cooking. The approach promises to be cheaper than coal mining too because it eliminates transportation and ash disposal costs.The technology is being developed in Australia, Canada, India and China. Read Australia’s Linc Energy signs MOU with Tanzania to develop 400MW UGC plant.

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No single entity has ownership in UCG (except perhaps China Uni. Mining Tech.), an opportunity for international leadership in collaboration with other SA entities. Strategic investment in a “new” area that is complementary and involves considerable synergy with existing entities. Journals articles per year shown.

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1940 1950 1960 1970 1980 1990 2000 2010 2020

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YearJonathan P. Mathews, Feedback on Observations of Coal Research at Potch NWU, Potchefstroom August 18 2014

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Breakdown of UCG Institutions (all years)

Jonathan P. Mathews, Feedback on Observations of Coal Research at Potch NWU, Potchefstroom August 18 2014

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World energy outlook 2012 pp 157:

There is great potential and short-term need for UCG Research and

Development in the South African context

At an early stage already, Africary and the Coal Research Group of the NWU started

collaboration on the TUCG project (more details on TUCG project in next presentation)

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The Theunissen Underground Gasification (TUCG) project

NWU (Potchefstroom

campus)

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General information of NWU Coal Research Group

Ø 40 postgraduates (20 PhD, 20 M) in 2013 (30 on campus) (1/4/2014)

Ø Inflow 2014: 11 M, 4 PhD Ø Outflow 2014: 8 M, 2 PhD (expected)

Ø ~ 20 undergraduate 4th year projects 2014Ø 12 NWU staff members involved (~ 8 FTE): Ø Trans-disciplinary between natural sciences and engineering Ø (International) external visiting membersØ 12 journal publications in 2013 Ø ~ 30 conference proceedings in 2013; Ø ~ MR 6.5 funding for 2014Ø Strong national and international collaboration

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Resources: Networksq Wits University (Petrographic characterisation)q Stellenbosch University (SS-NMR)q University of Cape Town (HR-TEM)q University of Pretoria (XRD, XRF)q Penn State University (Coal properties / molecular modelling)q University of Freiberg (Reactor modelling, student exchange)q Imperial college (tar, molecular modelling)q University of Twente (Biomass)q Eskom (QEMSCAN)q Petrographics SA (Contract petrography)q CSIR (pilot-plant operation / modelling)q CSIRO – Australia (SANS, SAXS, etc.)q NECSA (Tomography)

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Gasification (18)•Catalytic gasification (2)

•Biomass co-feeding (2)

•Tar formation (3)

•Kinetics (5)

•Breakage (3)

•Reactor modelling (2)

•Pyrolysis (1)

Coal Research Group(40 post graduate students)

Beneficiation (9)•Dry beneficiation (2)

•Reflux classifier (1)

•Valuable products (1)

•Fine coal (3)

•Ash usage (1)

•Drying (1)

Combustion (13)•ESP (3)

•de-SOx(6)

•Water (1)

•de-CO2 (2)

•de-NOX (1)

Current Portfolio

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FROM MICRO SCALE TO COAL FACE (UCG) POSSIBILITIES

Molecular structure of coal

(nm scale)

Intrinsic properties of coal

(µm scale)

Particle modelling of coal

(mm scale)

Reactor modelling of coal processes

(m scale)

Van Niekerk and Mathews (2010) Fuel, 89:73.

Waterberg coal before (left) and after (right) pyrolysis (MT Beukman 2010)

X 1000 X 1000 X 1000

Coal Chemistry Coal EngineeringTrans-disciplinary between natural sciences and engineering

UCG

(km scale)

X 1000

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Funding

Sasol: Hub and Spoke Initiative2nd cycle 2011 – 2015; (1st cycle 2006 – 2010)

Eskom: Eskom Power Plant Engineering Initiative (EPPEI) Emission control chair: 1st cycle 2012 – 2016

CoalTech: Collaborative research programme with coal producers (project based)

DST: South African Minerals and Metals Research Initiative (SAMMRI)

SACPS: South African Coal Processing Society

NRF: 1) South African Research Chair Initiative (SARChI); 1st cycle 2013 – 2017

2) Technology and Human Resources for Industry Programme (THRIP)

NWU: Strategic funding, student bursaries etc.

EVRAZ: Contract research (iron pre-reduction)Africary: Contract research (UCG)DoH-NW Contract research (Coal quality)

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R&D FOCUS AREAS AND NEEDS FOR UNDERGROUND COAL GASIFICATION TECHNOLOGY DEVELOPMENT AND IMPROVEMENT

WHERE NWU HAS ALREADY SCIENTIFIC EXPERTISE TO EXPAND ON THESE TOPICS

1. Understanding cavity growth versus agent flow rates / kinetics / composition of agent (in combination with Computational Fluid Dynamics (CFD))

2. Coal ignition technologies tested on laboratory scale.

3. Recycle and capture of waste streams into an UCG cavity, i.e. H2S, CO2.

4. Is it possible to enhance surface kinetics during gasification – catalytic gasification?

5. Effect of mineral composition and distribution (homogeneous versus fragmented or layered) on the carbon efficiency and gasification reactivity (melting, agglomeration, catalytic / inhibition effects)

6. Oxygen capture in mineral structure due to high concentrations of Si/Al and high acid/base ratios

7. Can the surface reaction kinetics be enhanced by changing the pore structure with upfront pyrolysis followed by gasification?

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R&D FOCUS AREAS AND NEEDS FOR UNDERGROUND COAL GASIFICATION TECHNOLOGY DEVELOPMENT AND IMPROVEMENT

8. UCG kinetic model and kinetic burn profiles.

9. Physical properties and coal seam thickness / roof structure on the impact of surface changes.

10.Fundamental understanding of gas liquor and liquid hydrocarbon formation (quality and quantity). Pyrolysis modelling of a UCG cavity. Effect of operating conditions on water, gas liquor and liquid hydrocarbon formation:

i. Coal type – the coal rank may determine the type and relative amounts of chemicals produced during a UCG process, for example, liquid hydrocarbons, phenols, etc.

ii. Amount of coal gasified – this quantity may be related to the amount of chemicals generated.

iii. Injection agent – the chemical composition of the atmosphere in which the coal is pyrolysed may influence the type of chemicals formed.

iv. System pressure – this factor influences the distances which volatile chemicals can move from the burn cavity during UCG.

v. Burn cavity temperature – the temperature affects the mineralogy of the coal ash in the burn cavity and the leach-ability of constituents within the ash.

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Resources: Capacity (In House)

q BET (N2/CO2)q Hg-intrusionq Bomb calorimeter (CV)q SEM EDSq TEMq He-pycnometerq Malvern Mastersizer (PSD)q XRDq Proximate/Ultimate analysisq FT-IR and Raman probeq NMR-Liquid Stateq GC-MSq TG/DTA and TMA (also Strength testing equipment)q CFD modelling capacities

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Reactivity measurementsq TGA’s

Ø Large Particle.Ø High Pressure.Ø High Temperature.

q Horizontal pipe reactor

Large Particle TGA. High Temperature TGA.

High Pressure, High Temperature TGA.

Horizontal pipe Reactor with gas analysis.

TG-MS

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CO2 adsorption measured Micromeritics ASAP 2020

Accelerated Surface Area and Porosimetry System

(NWU, 2014)

HWJP Neomagus, G Okolo and GH Coetzee (2014), Internal Africary Report: Part 1- Surface Area and Porosity Measurement by CO2 Adsorption on TUCG 02 and TUCG 09 coal samples and derived chars at 600 and 920 °C

wt% adb TUCG-02 TUCG-09% Moisture 2.3 5.2% Ash 43.6 23.5% Volatile 10.1 22.2% Fixed Carbon 44.0 49.1

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Large particle TGA (reactivity measurements for large particles)

Vertical tube

furnace

Nitrogen gas cylinder

Water source

Peristaltic pump

Heating mantle

Mass balance

Regulator

Brooks 0254 mass flow controller and control unit

Coal sample

Sample holder

Courtesy: Sansha Coetzee

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1. Movable oven2. Stand3. Mass balance4. Winch system5. Steam feed system6. Gas feed system7. Sample bucket8. Coal particles

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Large particle TGA

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Sample Bucket TGA

Gas flowCoal particlesQuartz woolSandstone sieveProduct flowStand

Sample Holder

0% conversion 50% conversion complete conversion

CFD modeling of large particle TGA

(Courtesy: Hennie Coetzee)

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Steam Gasification of large coal gasification

Before After

Before After

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Specs:

Temperature: Ambient - 1200 oC (continuous) (Thermal stable heated zone: 12 cm)

Heating rate: 0 - 20 oC/min Particle size: 75 µm - 45 mm (after swelling)

Sample mass: 1 – 100 gPressure: atmosphericSteam%: 0 – 100%Gas flow rate: 1 – 10 NL/min

Continuous logging of m, T and t (2 s – 1 min intervals)

Specs large particle TGA

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Char reactivity measurements

Table 1: Specific reactivity (kg/kg h) of the 2 samples and comparison with other South African

coals

Rs (kg/kg hr) TUCG-02 TUCG-09 Witbank Seam 4 Highveld Seam 4

Particle size

Powder 1.6±0.1 2.1±0.2 1.4

10 mm 0.44±0.04 0.50±0.06

Other 0.25 (2 mm)

0.07 (20 mm)

1.6 (2 mm)

*extrapolated value from T = 900 oC.

24The influence of particle size on the conversion rate of carbon dioxide gasification of a South African inertinite rich charG. Hennie Coetzee, Hein W.J.P. Neomagus, John R. Bunt, and Raymond C. Everson (Submitted to Fuel, JFUE-D-14-00888)

Reaction kinetics are strongly particle size dependent and extrapolation of gasification rates from powder to lump size may overestimate the reaction rate significantly

25The influence of particle size from powder to lump size on the conversion rate of steam gasification of a South African Inertinite-rich coal char, G. Hennie Coetzee, Hein W.J.P. Neomagus, John R. Bunt, Raymond C. Everson, to be submitted to Fuel

8 8.2 8.4 8.6 8.8 9 9.2 9.4

x 10-4

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1/T (1/K)

ln(k

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75um212ummm20mmFit

800 oC

850 oC

900 oC

Particle sizeInitial reaction rate (g/g.hr)

950 ̊C 900 ̊C 850 ̊C 800 ̊C

75 µm 1.04 0.49 0.18 0.053

212 µm 0.82 0.34 0.15 0.039

2 mm 0.39 0.20 0.071 0.019

20 mm 0.18 0.087 0.018 0.011

950 oC

Steam Gasification of SA Highveld coal

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Large particles of coals with an FSI = 0 may show swelling behaviour

Twistdraai coal

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Twistdraai coal

28Sansha Coetzee, Hein W Neomagus, John R Bunt, Christien A Strydom, Harold H Schobert, 2014, The transient swelling

behaviour of large (-20+16 mm) South African coal particles during low-temperature devolatilisation, Fuel 136, 79-88

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Combined projects between Africary and Coal Research Group of NWU

Surface Area, Porosity and Reactivity Measurement by CO2 Adsorption on TUCG 02 and TUCG 09 coal samples and derived chars at 600 and 920 °C

Completed (2014)

Ongoing

Effect of roof and floor on coal slag sintering during underground coal gasification for TUCG-02 and TUCG-09 samples (4th year projects)

• PhD 2015 – JF Brand (Study leaders: Waanders, Van Dyk and Neomagus)• 2 x M.Sc – 2015 (Groundwater en leaching of ash) – (Dennis and Strydom)• 2 x M.Sc - 2-15 (UCG general studies) (Waanders, Neomagus and Strydom)

Planned

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LEACHABILITY OF MINERAL MATTER AND SLAG INSIDE CAVITY• Detail scientific understanding of coal composition and mineral matter

behaviour needed to complete a mass balance (Also: Melting, fusing, agglomeration)

• Trace element speciation and mineral matter transformations are operating conditions and temperature specific

• Equilibrium simulation approach supplies one piece of the puzzle – it must also be investigated empirically

• Physical / kinetic properties of trace elements and mineral matter remaining in cavity IS operating conditions specific

• Gasifier operating conditions can be optimize to minimize or eliminate leaching, BUT a detail understanding of gasification, coal properties and mineral matter behaviour are required to achieve best results

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• Ash will be prepared at various gasifier operating conditions (1000-1500oC) and UCG specific atmosphere

• ASTM-3987 – Leachability of ash• IMPORTANT – What is not in the gas cannot be assumed as

leachable towards groundwater (impact may be minimal ornegligible when gasifier operating conditions are optimized)

• AFRICARY is in discussions with other UCG pilot operating plants to obtain cavity ash and core samples for joint / collaborative R&D

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Injection and Production well material selection• Material will be exposed for years (>10) to

oxygen, steam and syngas atmospheres

• R&D on material selection now will save millions in future

• R&D test program will be UCG “operating-conditions” specific

• Joint study between NWU and Africary, with a M.Sc to continue in 2015

• Experimental and simulated approach will be followed:

• Wagner’s Theory (1950)*• FACTSAGETM

• 3-5 months initial study

"Modelling and experiment of selective oxidation and nitridation of binary model alloys at 700 °C – The systems Fe, 1 wt.%{Al, Cr, Mn, Si}"M. Auinger, Corros. Sci. (2014), http://dx.doi.org/10.1016/j.corsci.2014.06.049

Thank you

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In Summary• Focused UCG research in collaboration with industry was initiated with

more planned in the short tem

• Underground Coal Gasification is an attractive alternative for a sustained energy provision in South Africa

• Focused UCG Research is required in the short term

• It is imperative to have an integrated South African research approach towards UCG (chair(s), center)

NWU CRG 2013