Outline

( Fuel-flexibility - \Nhat benefit?

c The driving factors influencing the need

" Fuels issues

'- Environmental factors

r Technical challenges

' O&M

Project decisions

Conclusions and recommendations 0 National Power

C National Power PLC, 1999

Driving Factors

,. Povver purchase agreement often based on availability payments

'~· Fuel purchase agreement interruptible fuel agreements

,. Merchant plant energy sales

0 National Power PLC. 1999

'pool' price is often volatile for gas and electricity

may want to trade gas increased plant value with 'black' start 0

National Power

Other Important 1 Fuel' Flexibility Issues

t Over-firing for grid compliance additional capacity

*- Power augmentation for additional capacity

( Operation use when the pool purchase price is high hot summer's day to maintain output

'Black' start 0 National Power

C National Power PLC. 1999

Fuel Factors

f Changing fuel is not a trivial matter changing from one natural gas to another

• requires care

- CV, dew-point and Wobbe index may all be within specification but the gas turbine may encounter emissions or pulsation problems

( Cost implications of fuel s\Nitching must be assessed in terms of:

capital; operational; fuel; plant output and availability 0

National Power I!:> National Power PLC. 1999

Fuel Quality and Variability

- Natural gas is not 100% methane

{ Gas composition will change as the well 'matures'

( Gas may be from two different sources gas A has a CH4 content of 82 % , CV of 9,260kCal m-3 ± 8%

gas B has a CH4 content of 84%, CV of 9,SSOkCal m-3 ± 9%

but the station cannot control the source 0 National Power

C National Power PLC, 1999

Fuel Quality and Variability

{ Delivery pressure pressure can vary over the day and has been seen to cause combustion problems

( Relative fuel density - again this can vary on a daily basis has been

seen to cause combustion problems

Level of longer-chain hydrocarbons

C National Power PLC. 1999

increased levels of CG+ in the gas stream has

0 been seen to cause combustion problems

National Power

Environmental Issues

f Liquid fuels storage

- spills

- contaminated water from washing of heavy fuel oil fire hazard drain oil from failed starts

0 National Power

IO National Power PLC. 1999

Environmental Issues

( It may be possible to get exceptions from the strictest emissions limits vvhile burning 'alternative' fuels, vvhere it can be shovvn that: - the fuel is being burnt in the most

environmental way

all efforts are being made to keep emissions to best achievable levels

where local air quality is not an issue

0 National Power

<O National Power PLC. 1999

Maintenance

c Need to ensure that fuel {and vvater) distribution is optimal for~ fuels

c Control system must be 'intelligent' to be able to handle the range of fuels

-~ adaptive?

'· Regular maintenance is required on all fuel systems but especially liquid fuel systems

0 National Power

~National Power PLC, 1999

Operations

( l It is important to regularly exercise all of the fuel systems

but risk of tripping machine

reduced availability

( J Fuel svvitching on gas fuel in DLN machines is not seamless

emissions limits may be exceeded

combustion pulsations may occur

load swings 0 the Change-over needs tO be SeamleSS NationalPower

C National Power PLC. 1999

NG only - may need to renegotiate PPA

NG + DFO ~t option

Conclusions

.. _ Fuel flexibility can offer improved profitability

~· Fuel flexibility must include the ability to handle natural gases of differing properties

The technical challenges to improve secondary fuel availability exist

Flexibility should also include options for povver augmentation

at10nal Power PLC , 1999

0 National Power

Recommendations

( Take care when specifying secondary fuel handling systems if you need high availability

' Develop a methodology to identify the value and costs of a back-up fuel system to see if you really do need it

Ensure that sufficient interest from both operations and maintenance is focused O on the secondary fuel system

National Power ional Power PLC , 1999