The Renewable Gas Ask : Part B

In the continuing inquiry and introspection into which parties are likely to be asking the large oil and gas (and coal) companies to displace crude petroleum oil and Natural Gas (and coal) with Renewable Gas and liquid Renewable Fuels, we now move on to a wider caucus.

4. Gas Turbine and Other Power Engineers

Without Renewable Gas, the future of gas has several possible routes, and each one implies an increase in required processing before the gas can be piped into the consumer grids. It also has implications for power generation through gas combustion in gas turbines.

4a. Where Natural Gas Will Come From With Time

The chemical composition of Natural Gas will change over time, as conventional resources are depleted and unconventional resources are exploited. Much Natural Gas is produced alongside oil, as part of a spectrum of hydrocarbon molecules. A significant fraction of the gaseous constituents of conventional petroleum fields is methane, and there are very small amounts of ethane, propane and butane; but in unconventional systems, the ratios of these first four hydrocarbons are changed. In the United States for example, there is a surfeit of ethane being produced from hydraulically fractured (fracked) shale wells. Where the balance is tipped, and ethane propane and butane are in excess and there is no market for them, then these hydrocarbons would be considered to supplement Natural Gas for industrial and power generation purposes. The divergent molecular recipe for Natural Gas has an implication for gas turbine operation, and therefore also gas turbine design.

4b. Synthetically-Produced Gas

As conventional petroleum oil and gas resources enter the downward depletion trend and unconventional petroleum oil and gas resources start to falter, there will be a knock-on effect on those who are currently very focussed on one version of the “Hydrogen Economy” : in their preferred configuration, hydrogen is made from Natural Gas, but if Natural Gas becomes significantly constrained and supplies are uncertain, the case for using it to produce hydrogen will fade away. Other hydrocarbon and carbohydrate feedstocks will be considered for gas-making, but making pure hydrogen will be often be inefficient, so synthesised gas will be a mixture – a little bit like the Town Gas that used to be made by gasifying coal. Syngas being used as a fuel for power generation will also have implications for gas turbine operation and design.

The gas turbines of the future will there need to be more flexible as regards the fuel that they use. Gas-fired power plants will also need to be more flexible in terms of ramp up and ramp down, in response to variability in renewable electricity supplies. Can the need to adapt, to both a chemical change in fuels and the change in functionality required, together be too difficult to navigate ?

All this change might create chaos for gas-fired power generation utilities and gas turbine engineers. It is a possibility that they will therefore make approaches to the oil and gas companies asking for more standardised gas fuels. This would therefore lead to adoption of the cleanest and most basic gas fuels : Renewable Methane and Renewable Hydrogen.

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