Gas Turbines
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Gas turbines are thermodynamic engines which use a steady flow of a gas (mostly air), compressed and fired with gaseous or liquid fuel. This high pressure mixture is expanded through a turbine to generate output power for thrust in an aircraft engine, for marine propulsion, or as shaft power for stationary energy applications. (Note: "gas turbine" is a general term regardless of fuel used.) A unique feature of these units is that there is considerable heat still available in the exhaust stream to provide energy to other applications such as cogeneration or combined heat and power (CHP).
Gas turbine plants, fuelled by natural gas, are one of the cleanest types of fossil fuelled equipment available for power production. They produce little or no sulphur dioxide (SO2) or carbon monoxide (CO). Overall efficiency increases can contribute to low carbon dioxide (CO2) emissions per unit of energy output. There are about 1000 units in Canadian stationary applications, mostly in gas pipeline compression, electric power peaking, and in cogeneration or CHP systems. They consist of 14000 MW of aero-derivative and industrial frame units in service by the end of 2005.
The availability of abundant, competitively priced natural gas will result in the increasing use of gas turbine combined cycles for electricity production. Gas turbine combined cycles with steam turbines may become an important re-powering option for older existing utility steam plants. If a nearby large industrial complex requiring steam for process or space heating is available, additional efficiencies should be realized by CHP systems with cogeneration and district energy. These types of systems, using cleaner fuel choices such as natural gas or biomass, will become important for dealing with air pollution and global climate change issues.
As part of the NOx/VOC Management Plan published in November 1990 by the Canadian Council of Ministers of the Environment (CCME), Environment Canada and a multi-stakeholder working group developed the National Emission Guideline for Stationary Combustion Turbines, published in December 1992. This Guideline for new engines is based on emission levels achievable through reliable pollution prevention and energy efficiency (to minimise CO2 emissions). The Guideline was developed to promote cogeneration applications of gas turbines, without the need on a national basis to go to ultra-low nitrogen oxide (NOx) levels requiring back-end cleanup. The Guideline is unique in that it provides for a Power Output Allowance, and a Heat Recovery Allowance, with NOx limits expressed on a mass per unit energy output basis (grams per Gigajoule, or MW output).
