Gas Turbine Fuel Flexibility: What Buyers Should Ask

Pipeline natural gas

Pipeline gas is the standard fuel for most new turbines. Even so, gas composition varies between networks and over time. Buyers should provide the turbine supplier with a full gas analysis and the expected range of variation, including heating value, inert content and heavier hydrocarbons.

Turbines with dry low-emission combustors can be sensitive to rapid changes in gas quality. The supplier should confirm acceptable limits and any monitoring needed.

LNG and regasified gas

Gas from LNG terminals can differ from local pipeline gas, often with higher heating value. Projects relying on LNG should confirm the composition range from the terminal and check it against the turbine fuel specification.

Where a site may switch between pipeline gas and LNG, the combustion system must handle both without retuning each time.

Liquid fuel backup

Many turbines can burn diesel or light distillate as a backup fuel. Dual-fuel capability allows the plant to keep running if gas supply is interrupted. It requires liquid fuel nozzles, a fuel forwarding system, storage tanks and often water injection for emissions control.

Buyers should confirm how long the turbine can run on liquid fuel, how emissions limits are met and how often liquid fuel systems must be exercised to stay reliable.

Fuel switching under load

Some turbines can transfer from gas to liquid fuel and back while carrying load. This is valuable for critical loads such as data centers or industrial processes. Transfer performance varies between models and combustion systems.

Ask the supplier for tested transfer capability, including the load range in which transfer is allowed and any temporary output reduction.

LPG and propane

Liquefied petroleum gas, propane and butane can fuel turbines in places without natural gas networks. They require vaporisation equipment and careful control of fuel temperature and composition. Not all combustion systems accept these fuels.

Confirm suitability and emissions performance with the supplier before planning a project around LPG.

Associated and process gases

Oilfield associated gas, refinery off-gases and other process gases can be valuable fuels, reducing flaring and fuel costs. They often contain heavy hydrocarbons, hydrogen sulphide or variable heating value, which require treatment and special combustion hardware.

Gas conditioning skids that remove liquids and contaminants are usually needed. Industrial turbines with conventional combustors often tolerate these gases better than low-emission versions.

Hydrogen blending

Interest in hydrogen blending is growing, and many suppliers offer turbines capable of burning a share of hydrogen mixed with natural gas. Our article on hydrogen-capable turbines covers the questions in detail.

For most projects today, hydrogen capability is a future option rather than an operating requirement. Buyers should understand what upgrades would be needed later.

Combustion systems and emissions

The combustion system decides which fuels a turbine can burn and at what emissions level. Dry low-emission systems achieve low nitrogen oxides on gas but may have narrower fuel limits. Conventional diffusion combustors accept a wider range of fuels but usually need water or steam injection, or after-treatment, to meet strict limits.

Our guides to turbine combustion and NOx control explain the trade-offs.

Fuel treatment and storage

Every fuel needs some treatment. Gas may need filtering, heating and pressure regulation. Liquid fuel needs filtration, water removal and storage that prevents contamination. Process gases may need extensive conditioning.

Include treatment and storage in the project budget and layout from the start, rather than treating them as add-ons.

Fuel quality limits and warranties

Turbine warranties and service agreements usually depend on fuel meeting the supplier’s specification. Fuel outside the limits can void warranties or increase maintenance costs. Buyers should understand the limits and how compliance will be monitored.

Regular fuel sampling and online analysers help prove compliance and detect problems early.

Running hours on backup fuel

Dual-fuel turbines that rarely run on liquid fuel can suffer from coked nozzles, stale fuel and seized valves when the backup is finally needed. A routine of periodic transfers to liquid fuel, with the forwarding system, nozzles and controls exercised under load, keeps the backup ready. Stored distillate should be sampled and polished on a schedule, and tank capacity should match the longest gas interruption the site is designed to ride through.

Permits sometimes cap running hours on liquid fuel. Check those limits early, because they decide how much testing is allowed and how long the plant may legally run on backup during a gas outage.

Fuel cost and future flexibility

Fuel prices and availability change over a plant’s life. A turbine ordered with wider fuel capability, or with a clear upgrade path, can adapt to new supply options without a major rebuild. Weigh the extra capital cost against the value of that option, using realistic scenarios for gas supply, liquid fuel prices and emissions rules over the expected life of the plant.

Specifying flexibility in the RFQ

State the fuels required, their composition ranges, the need for dual-fuel or switching capability, emissions limits for each fuel and the expected running hours on each. Ask suppliers to confirm capability with reference installations and test data.

Clear fuel requirements in the request for quotation avoid costly changes after order and help compare bids on equal terms.