A supporting beam arrangement suitable for supporting a flue gas duct, wherein the supporting beam arrangement comprises: - two substantially horizontal first supporting beams that are substantially parallel and situated on two opposite sides of the flue gas duct, the first supporting beams being separated by a distance from the flue gas duct, and the first supporting beams including two opposite ends that are connected to a support frame of the flue gas duct; and - a substantially horizontal second supporting beam defining two opposite ends that are supported by the first supporting beams, the second supporting beam extending through the flue gas duct in such a way that the second supporting beam is exposed to flue gases that the flue gas duct is adapted to convey, wherein the second supporting beam supports the flue gas duct; - wherein at least one or each one of the first supporting beams comprises an opening, in which opening one of the two opposite ends of the second supporting beam rests on the first supporting beam in such a way that loads incurred by the weight of the flue gas duct are transmitted to the first supporting beam; characterized in that: - the first supporting beam defines a substantially horizontal top surface at a first height; and - the second supporting beam includes two end sections, each end section horizontally extending outside the flue gas duct between the flue gas duct and one of the first supporting beams, at least one or each one of the end sections defining a substantially horizontal top surface located at a second height, wherein the second height is less than the first height; wherein the supporting beam arrangement further comprises: - a substantially horizontal intermediate supporting beam that is substantially parallel with the first supporting beams and substantially perpendicular to the second supporting beam, the intermediate supporting beam being supported by the support frame, wherein the intermediate supporting beam is in a vertical direction located above the top surface of one of the end sections; and - substantially horizontal reinforcing bars each having a first end connected to one of the first supporting beams and an opposing second end connected to the intermediate supporting beam, wherein (i) the reinforcing bars are substantially perpendicular to the first supporting beams or (ii) the reinforcing bars extend at an oblique angle in relation to the first supporting beams, and wherein the reinforcing bars are in a vertical direction located above the top surface of one of the end sections. - two substantially horizontal first supporting beams that are substantially parallel and situated on two opposite sides of the flue gas duct, the first supporting beams being separated by a distance from the flue gas duct, and the first supporting beams including two opposite ends that are connected to a support frame of the flue gas duct; and - a substantially horizontal second supporting beam defining two opposite ends that are supported by the first supporting beams, the second supporting beam extending through the flue gas duct in such a way that the second supporting beam is exposed to flue gases that the flue gas duct is adapted to convey, wherein the second supporting beam supports the flue gas duct; - wherein at least one or each one of the first supporting beams comprises an opening, in which opening one of the two opposite ends of the second supporting beam rests on the first supporting beam in such a way that loads incurred by the weight of the flue gas duct are transmitted to the first supporting beam; - the first supporting beam defines a substantially horizontal top surface at a first height; and - the second supporting beam includes two end sections, each end section horizontally extending outside the flue gas duct between the flue gas duct and one of the first supporting beams, at least one or each one of the end sections defining a substantially horizontal top surface located at a second height, wherein the second height is less than the first height; - a substantially horizontal intermediate supporting beam that is substantially parallel with the first supporting beams and substantially perpendicular to the second supporting beam, the intermediate supporting beam being supported by the support frame, wherein the intermediate supporting beam is in a vertical direction located above the top surface of one of the end sections; and - substantially horizontal reinforcing bars each having a first end connected to one of the first supporting beams and an opposing second end connected to the intermediate supporting beam, wherein (i) the reinforcing bars are substantially perpendicular to the first supporting beams or (ii) the reinforcing bars extend at an oblique angle in relation to the first supporting beams, and wherein the reinforcing bars are in a vertical direction located above the top surface of one of the end sections.