Abstract: A burner assembly for a boiler unit for the production of steam extends along a longitudinal axis and comprises: a plurality of fuel conduits in which, in use, at least one fuel flows in a forward direction; a plurality of fuel injection nozzles, connected to respective fuel ducts for discharging, in use, fuel into a combustion chamber of the boiler unit; a first manifold connected to a first group of fuel conduits and to a first fuel source by means of a first supply line provided with a first regulating valve; at least one second manifold connected to a second fuel line assembly and to a source of a second fuel by means of a second supply line provided with a second regulating valve; and a control device configured for adjusting the first regulating valve and the second regulating valve based on the energy demand of the boiler unit and based on at least one characteristic parameter of the first fuel and/or the second fuel.