Excess Air COntrolled Operation Of Boilers and Furnaces by Means of Wobbe Number Measurement

摘要

For a long time combustion engineers have been aware that the air ratio of gas burners should be maintained within an advantageous ragne in all operating states to avoid increased emisisons, high thermal loads, small efficiencies, and problemstic ignition behavior as wel las a restriction of the operation field and high noise of the burner. For this reason, frequent wariations of the natural gas quality are a problem becuase higher or lower caloric gas components result sin a shift in the air ratio. In conventional burners, however, continuous adaptation of the air-fuel ratio to varying gas qualities is either impossible or requires measurements during combustion or in the exhaust. The technique of air number controlled combustion presented here allows the burner to be operated withthe optimum air ratio independently of the current gas quality, the gas quality being determined before the combustion sot aht, unlkie with measurement during or after combustion, the measurement equipment is not exposed to high temperatures The compact sensing device, which was between the viscosity of the fuel gas and the air rquirement and/or Wobbe number both technically and economically useful in a burner control unit. The precondition for feasibility was accurate determination of the gas viscosity . The procedure suitable for this is capillary viscosimetry, where the drop in gas pressure along the capillary, gas temeprature ad volume flow must be determined in addition to the capillary geometry, in order to measure the viscosity fro mwhich the Wobbe number or the air requirement can be precisely determined for all natural gases. The ue of this procedure for a burner control has not been possible sor far because no methods are available to measure small volume flows economically. For this reason, the developed swnsor is based on modern piezoelectric components, which avoids this problem. An accuracy of+-5