Patent ID: 6699029
Filing Date: 2004-03-02
Classification: A61B,F23C,F23D,F23L,F23N,Y02E

Abstract:
A method for modifying operation of a furnace, comprisingto a furnace that comprises a combustion chamber, burner means for combusting hydrocarbonaceous fuel containing bound nitrogen and having a given minimum calorific value in said combustion chamber to generate heat of combustion and gaseous combustion products, feed means for feeding said fuel and combustion air to said burner means, flue means for enabling said combustion products to leave said combustion chamber, and heating means for using said heat of combustion to produce steam, wherein said furnace is being operated to combust a first fuel containing bound nitrogen and having said minimum calorific value to produce steam at a defined minimum rate of energy content per unit of time, providing replacement fuel by replacing some or all of said first fuel with a second hydrocarbonaceous fuel whose calorific value is below that of the first fuel, at a replacement ratio such that the feed rate of said second fuel to said furnace divided by the feed rate of said first fuel to said furnace in units of energy per unit time is between 1.0 to 1.3, and feeding said replacement fuel to said burner means, feeding gaseous oxygen into said replacement fuel as the replacement fuel emerges from said burner into said combustion chamber or by adding it to air that is fed through said burner, in an amount which is less than 25% of the stoichiometric amount required for complete combustion of said replacement fuel while reducing the amount of air fed through said burner by an amount containing sufficient oxygen that the overall stoichiometric ratio in said furnace varies by not more than 10% compared to the stoichiometric ratio without said addition of oxygen, and combusting said replacement fuel with said combustion air and said oxygen.