Definitions
Biomass
Biomass means any of the following:
- products consisting of any vegetable matter from agriculture or forestry which can be used as a fuel for the purpose of recovering its energy content;
- The following waste:
- vegetable waste from agriculture and forestry;
- vegetable waste from the food processing industry, if the heat generated is recovered;
- fibrous vegetable waste from virgin pulp production and from production of paper from pulp, if it is co-incinerated at the place of production and the heat generated is recovered;
- cork waste;
- wood waste with the exception of wood waste which may contain halogenated organic compounds or heavy metals as a result of treatment with wood preservatives or coating and which includes, in particular, such wood waste originating from construction and demolition waste.
- SEPA’s Authorisation Guidance for Biomass Combustion provides guidance on when biomass is considered a fuel and when it is considered waste and therefore which permit is required.
Boiler
Large vessel containing water that is heated by a burner (gas, oil, etc.) which then can be used to provide steam, or for other industrial purposes. Furnaces would usually be considered a boiler.
Combined cycle gas turbine (CCGT)
The exhaust from a gas turbine is used to turn water into steam and run a steam turbine. A CCGT has good efficiency and can provide a rapid response. CCGT can be expensive to construct, but the lower running costs may offset the construction costs.
Combustion engine
An internal combustion engine (ICE) like in a car, with pistons which move in cycles. It is inefficient but can be easily scaled down to very small sizes.
Combustion engines are usually used as a backup in industrial settings.
Combustion engines lose efficiency due to heat loss and to the number of moving parts (in different directions).
Dual Fuel Engine
An internal combustion engine which uses compression ignition and operates according to the Diesel cycle when burning liquid fuels and according to the Otto cycle when burning gaseous fuels.
Dual Fuel combustion plant is capable of burning more than one fuel without a significant change to the setup e.g., natural gas and diesel.
There are some emission limit values categories that differ with dual fuel combustion plant.
Gas Turbine
Any rotating machine which converts thermal energy into mechanical work, consisting mainly of a compressor, a thermal device in which fuel is oxidised in order to heat the working fluid, and a turbine; this includes both open cycle and combined cycle gas turbines, and gas turbines in cogeneration mode; all with or without supplementary firing.
Gas turbines are commonly used in power plant, these are very similar in construction to jet engines, where gas is the fuel. The torque produced is used to run the generator.
Gas turbines are not as efficient as steam or combined cycle but more efficient than combustion engines. The power output can quickly meet changing demands.
Generator
An internal combustion engine with a built-in alternator. Fuel is combusted to provide momentum which the alternator then converts to electrical power. Generators are usually diesel but can be converted to other fuel types.
Heavy and liquid fuel oils (HFO/LFO)
- Any petroleum-derived liquid fuel falling within CN codes 2710 19 51 to 2710 19 68, 2710 20 31, 2710 20 35, or 2710 20 39; or
- Any petroleum-derived liquid fuel, other than gas oil as defined in point 19, which, by reason of its distillation limits, falls within the category of heavy oils intended for use as fuel and of which less than 65 % by volume (including losses) distils at 250 °C by the ASTM D86 method. If the distillation cannot be determined by the ASTM D86 method, the petroleum product is likewise categorised as a heavy fuel oil.
HFO/LFO are not gas oil and biodiesel is not gas oil.
Multiple fuels
Where a medium combustion plant simultaneously uses two or more fuels, the emission limit value for each pollutant shall be calculated by:
- taking the emission limit value relevant for each individual fuel as set out in Annex II of the MCPD;
- determining the fuel-weighted emission limit value, which is obtained by multiplying the individual emission limit value;
- by the thermal input delivered by each fuel, and dividing the product of multiplication by the sum of the thermal inputs delivered by all fuels;
- aggregating the fuel-weighted emission limit values.
See Article 6(13) of the MCPD.
Natural gas
Means naturally occurring methane with no more than 20% (by volume) of inerts and other constituents. Natural gas must contain a minimum of 80% methane. Landfill gas tends to contain 60% methane and 40% CO2 so is not natural gas.
Net rated thermal input
The rate at which fuel can be burned at the maximum continuous rating of the appliance multiplied by the net calorific value of the fuel expressed as megawatts thermal.
Steam turbine
Gas heats water in a boiler; the overheated steam runs through turbines and is then cooled. Steam turbines use the same principle as most other thermal power plants (coal, nuclear, geothermal).
Steam turbines are usually large installations and can take a long time to get up to speed (so no rapid response to demand) but are very efficient.
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