Method for combusting a fuel, and combustion device

A method for combusting a fuel, the method comprising:

• providing a first oxidizer mass flow;
• providing a second oxidizer mass flow;
• discharging a fuel mass flow into the first oxidizer mass flow thereby providing a fuel/oxidizer mass flow;
• apportioning the fuel mass flow such as to achieve an overstoichiometric ratio of the fuel mass flow related to the first oxidizer mass flow;
• initiating a combustion of the fuel mass flow with the first oxidizer mass flow, thereby generating a flow of combustion products, wherein the flow of combustion products includes residual combustible components;
• providing the flow of combustion products to at least one first duct of a heat exchange appliance;
• providing the second oxidizer mass flow to at least one second duct of the heat exchange appliance, whereby the flow of combustion products is provided in a heat exchange relationship with the second oxidizer mass flow through the heat exchange appliance;
• exchanging heat between the flow of combustion products and the second oxidizer mass flow, thereby heating the second oxidizer mass flow and cooling the flow of combustion products;
• discharging the flow of combustion products from the at least one first duct of the heat exchange appliance at a downstream end of the heat exchange appliance;
• discharging the second oxidizer mass flow from the second duct of the heat exchange appliance at a downstream end of the heat exchange appliance;
• combusting the residual combustible components provided in the flow of combustion products in a presence of the second oxidizer mass flow;
• and
• wherein the second oxidizer mass flow exceeds the first oxidizer mass flow.

A combustion device for combusting a fuel, the combustion device comprising:

• means for providing a first fluid flow;
• fuel discharge means for discharging a fuel flow into the first fluid flow;
• a first combustion zone adapted and configured to stabilize a flame and being disposed downstream the fuel discharge means and being in fluid communication with the means for providing the first fluid flow at an upstream end of the first combustion zone;
• a heat exchange appliance, said heat exchange compliance having at least one first duct and at least one second duct and the heat exchange appliance being configured to enable an exchange of heat between a fluid provided in the at least one first duct that comprises combustion products having residual combustible components and a fluid provided in the at least one second duct, the at least one first duct of the heat exchange appliance, at an upstream end thereof being in fluid communication with the first combustion zone at a downstream end of the combustion zone;
• a means for providing a second fluid flow to an upstream end of the at least one second duct of the heat exchange appliance;
• and
• a second combustion zone being provided downstream the heat exchange appliance, wherein the at least one first duct and the at least one second duct are provided in fluid communication with the second combustion zone at a downstream end of the respective duct;
• the second combustion zone configured so that a flow of the combustion products and the second fluid flow are discharged so as to avoid intermixing of the flow of combustion products and the second fluid flow to provide an interface between the second fluid flow and the flow of combustion products downstream of the heat exchange appliance to combust the residual combustible components at the interface between the second fluid flow and the flow of combustion products.