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DESSCRIPTION:
Industry´s ever increasing demand for the improved usage of fossil energy carriers in thermal combustion processes, has triggered efforts to make use of available waste heat, such as waste gases from gas turbines, for downstream processing.
As a rule, however, the temperature of such gas turbine waste gases is not high enough to supply any downstream waste heat boiler with sufficient calorific energy.
In order to deal with this problem, M&S who are known as one of the leading suppliers of firing systems and look back on thirty years of marketing experience, have developed the COMB Ductburner.
The object of the COMB Ductburner is to reheat turbine waste gases or flue gases for the purpose of operating a downstream process. For this purpose, the ductburner is installed as an auxiliary firing device directly into the gas turbine waste gas duct.
Liquid and/or gaseous fuels may be used as combustibles.
If the turbine waste gases contain a sufficient amount of oxygen, it is feasable to operate exclusively with turbine waste gases.
However, if there is any intention of operating the ductburner independently of gas turbine operation or if the oxygen content of the turbine waste gas is not sufficiently high for the combustion of secondary fuels, it is possible to operate with forced draft air alone or with a combination of forced draft air/turbine waste gases.
The COMB Ductburner therefore has a number of advantages, p. ex.:
• turbine waste gas operation or forced draft air operation possible
• combined turbine waste gas / forced draft air operation possible
• liquid and/or gaseous fuels may be used
• stable temperature profile of +/-30°C after ductburner
• variable mounting possibilities
• low emission values
DISCRIPTION / FUNCTION:
The COMB Ductburner consists principally of the cylindrical duct, an interior combustion chamber and the combined gas/oil burner.
TURBINE WASTE GAS OPERATION:
On entering the duct, the turbine waste gas is divided into three streams which are fed into the following areas of the ductburner:
• the primary register of the burner which is adjustable from the outside
• the secondary register of the burner which is adjustable from the outside
• the annular gap between the combustion chamber and the outer duct sleeve at the end of which there is a mixing area.
The combined gas/oil burner completely burns the fuel in the combustion chamber with an air surplus of about 30 - 40%. The hot flue gases coming from the combustion chamber mix in the mixing area at the end of the combustion chamber with the relatively cold turbine waste gases thus attaining the desired temperature.
FORCED DRAFT OPERATION:
The feed line from the turbine to the ductburner and also the secondary register of the burner are closed. Combustion air is brought into the ductburner system by a forced draft fan and divided into two streams which are fed into the following burner areas:
• the primary register of the burner in high enough quantities for the fuel to burn with an air surplus of appoximately 30%
• the anular gap between the combustion chamber and the outer sleeve.
Both streams are fed into the ductburner system controlled by air dampers which as a result leads to a stable temperature profile.
TECHNICAL DATAS :
Range of Capacity: 5-200 MW firing capacity
Range of Control: 10:1
Pressure Loss Turbine Waste Gas Operation: 2-5 mbar
Pressure Loss Forced Draft Air Operation: 10 mbar
Temperature Profile Downstream of Ductburner: +/- 30°C
Turbine Waste Gas Temperatures: up to 600°C
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