September 2007
 

Harworth Power Ltd
 CMM Flaring 
Harworth Power 

Part of UK Coal PLC -Ex Nationalised “British Coal” • UK Coal 4000 employees, 14Mt capacity, surface and deep min• VAM oxidation technology trialled on an operating coal mine • CMM utilised in boilers since the 1960s 

• CMM utilised in gas turbines and gas engines since 1991 

• CMM utilised in high efficiency gas engines since 2000 (30MWe • CMM destructed in enclosed flares since 2004 (7 flares installe• Part of the UK ETS since 2001, 2.3Mt CO2e verified (3.9Mt tota

Separate unit specialising in assisting mines maximise cap

and utilisation – engineers deployable to assist in design implementation 

• Typical capture rates 40% - 60% of coal face district gas 

• Typical gas quality 30% to 50% methane • All gas is utilised in generators, boilers or flared 
Key Issues in Flaring of CMM 

• Gas is NOT utilised – but destroyed • Safety • Capital Cost • Operating Cost • Equipment Delivery • Will the Government allow gas to be flared rath

utilised? 

• Ideal scenario in the US – distributed remote g

without realistic or economic means us using helectricity or low quality gas near the well head
Coal to CMM Flaring 
Coal Mining General Data 

Kellingley Colliery 

Thoresby Colliery 

Welbeck Colliery 

Harworth Colliery 

Depth (m) 900 750 700 850 

Tonnage (Mt) 1.455 Mt 0.829 Mt 0.868 Mt Mothballed MinSeam Thickness 2.1 1.85 1.85 2 Gas M3/tonne 5.3 5.2 5.0 6.2 Gas Typical Flow Rate (l/s) 

400 – 600 250 - 350 350 - 450 650 – 850 

Gas Typical Concentration 

40 – 50% 30 – 40% 35 – 45% 45 – 55% 

Utilization / destruction 

2x 20,000 lb/hr 

dry sat steam 

boilers 

3x 1.4MWe gas 

engine generators 

1x 2,000 Nm3/hr 

enclosed flare 

2x 1.4MWe gas 

engine generators 

1x 2,000 Nm3/hr 

enclosed flare 

2x 20,000 lb/hr 

dry sat steam 

boilers 

2x 1.4MWe gas 

engine generators 

2 x 2,000 Nm3/hr 

enclosed flare 

2x 20,000 lb/

dry sat steam 

boilers 

5x 1.4MWe ga

engine generat

1x 2,000 Nm3/

enclosed flare 

18MWe CCGT 
Overview 

Gas Flaring. Technology: Destruction of drained methane gas through combustion in a gas flare. 2000 Nm3/hr destruction capacity per flare. 

Benefits: A low capex cost technology with a short manufacture and 

installation lead time.
 Simple, low cost and reliable to operate, gas flaring offers a very high potential for significant GHG reduction.
 Low maintenance requirements.
 Installation Requirements: 80 litres/s pure methane flow at 20% purity or above,
 Methane drainage infrastructure already in place, Suitable flame arrestor technology installed to prevent flame propagation into the mine.
 Mine Suitability: A disciplined drainage approach ensuring that methane is only drained above 20% purity. 
Flare P&I Diagram 

• 2000 Nm3/hr methane destr

• >27% CH4 for reliable flare 

• Flare will operate down to 2

• Automatic control • Internet Remote Monitoring • Skid mounted for ease of in
Importance of Gas Purity 

• Gas will not burn or explode outside of the flam

range 

• Gas will not allow an existing flame to propaga

mine outside of the flammable range 

• Multiple failsafe concentration transducers auto

stop supply of gas to extraction pumps and flar

• Careful consideration of system T90 reaction pe

• Only effective means of protection against light

ignition source 
Flammability of Methane / Air at Atmosphe

and Temperature 

The flammability of mixtures of Methane and Air 

C 

Capable of forming 

flammable 

mixtures with air 

per se. 

Flammable 

Region 

‘Coward Diagram’ 

20 

15 10 

5 0 

B 

E 

F 

Not capable of 

forming 

flammable 

mixtures with air 

Oxygen 

Concentration 

5 10 15 20 25 Methane 

Concentration
 
Hierarchy of Explosion Prevention and Mitig

1. Prevent formation of flammable atmosphere – 

concentration and stop flow 

2. Prevent exposure of ignition source to flamma

atmosphere – necessary for destruction / com

3. Prevent propagation through flammable mixtu

equipment/burner design, flame arresters and 

4. Dissipate energy – bursting discs / relief valve5. Prevent of release of explosion energy – vesse

pipework design 
Flame Propagation in Pipework 

Flame Speed 

Point of Ignition 

50 x Pipe Diameters 

Direction of flame propag

Deflagration 

Detonation 

Overdriven Detonation Choked flame 

M = 1 
Specific Flare Safety Features 

•	 Safety risk assessments carried out for 

design and operation to prevent flashback 

•	 HAZOP •	 Hazardous Area Classification •	 Flame Arrester suitability assessment •	 Multiple redundancy and safety features •	 Gas quality monitoring and oxygen intertrip •	 PLC controlled with certain high integrity 

functions duplicate hard wired 

•	 Burner velocity design to prevent 

flashback 

•	 Temperature sensing to prevent flame 

arrester burn through 

•	 Purge for start-up 
September 2007 

Thank you 

Neil Butler Technical Director 44-7798-571612 nbutler@harworthpower.com 
USA Coal Mine Methane Conference 

The modern high temperature 

St Louis, 26th September 2007 

www.clarke-energy.com
 
Clarke Energy supplies, installs and maintain

HAASE flares 

www.clarke-energy.com 
Cheap and dirty versus state-of-the-art 

60% CH4 

destruction 

www.clarke-energy.com 
HAASE flare types – high temperature contin

and low temperature emergency 

0.3s retention 

•99.9% CH4 destruction 

•CH4 down to 25% or lower 

with propane assist at ignition 

•Turn down 5:1 or greater 

HT type LT type 2 

www.clarke-energy.com 
HAASE lining – 10 year guarantee 

www.clarke-energy.com 
Cold side lining fixing
 

www.clarke-energy.com 
German and UK regulations
 

TA-Luft UK 

NOX 200 mg/m3 150 m

CO 100 mg/m3 50 mgTemperature 1,200

oC (1830

oF) 1,000

o

(Reference 3% O2 by vol. in exhaust gas) 

www.clarke-energy.com 
www.clarke-energy.com 

Naturally ventilated and fan ventilated 

20MW 

27MW 

10:1 turndown 

fan assisted 
4 x 4500m3/h + 2 x 1500m3/h (1 @ 10:1 tur

10:1 

turndown 

Total – 

105MW 

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HAASE lean gas flare (pilot) – down t

methane 

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Telecontrol system – can record value

carbon credits 

On-site-control 

www.clarke-energy.com 
Hatfield Colliery
 

 4 x Roots blow

880Nm3/h (eac

-100mbarg deli

 2 x Roots blow

1660Nm3/h (ea

+200mbarg de

www.clarke-energy.com 
The HAASE state of the art high temperature 

in summary; 

	 99.9% CH4 destruction 	 Down to 25% CH4 , or lower with propane 

assistance at ignition 

	 Turn down ratio 5:1 standard, 10:1 or gre

optional 

	 10 year lining guarantee 	 Exceeds German TA Luft requirements 

www.clarke-energy.com 
Thank you!
 

Clarke Energy distributes GE Energy Jenbacher a

best in class products – supplying, installing and m

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