Abstract: A nozzle assembly which comprises nozzle duct having inlet and discharge ends is provided with a tubular support. The support has a first end in fluid communication with the nozzle duct adjacent the discharge end thereof. The second end of the support extends to a location where it is accessible, to enable a source of cleaning fluid to be coupled thereto, and is normally capped.

Abstract: A procedure is disclosed for substantially decreasing the amount of nitrogen oxides (NO.sub.x) in waste furnace gases during the combustion of fossil fuel, in which as a primary measure, the fuel is subjected in the combustion space to a stepped, pyrolyzing combustion with low combustion temperatures and decreased available oxygen (substoichiometric amounts) in the reaction zone and with prolonged residence times in the combustion space and then as a secondary measure, the reactive waste gas components, which are thereby formed to an increased extent, such as carbon monoxide (CO), hydrocarbons (CH), etc. are eliminated, if necessary with the addition of more air, by catalytic oxidation at a temperature within the range of 800.degree. C. to 200.degree. C., before the waste gases reach the atmosphere.