A supporting beam arrangement (14) for supporting a flue gas duct (10) to a support frame (16) of the flue gas duct. The supporting beam arrangement comprises two horizontal first supporting beams (18) that are parallel and on two opposite sides of the flue gas duct (10) and separated by a distance from the flue gas duct, and further are connected to the support frame (16). The supporting beam arrangement (14) comprises a horizontal second supporting beam (20) defining two opposite ends (22) that are supported to the first supporting beams (18), the second supporting beam extending through the flue gas duct (10) that is supported to the second supporting beam. At least one or each one of the first supporting beams comprises an opening (24), in which opening one of the two opposite ends (22) of the second supporting beam is placed to rest on the first supporting beam (18). A power boiler (50) comprises the supporting beam arrangement (14), the flue gas duct (10) and the support frame (16).

A waste heat boiler system for cooling a process gas, including a first shell-and-tube heat exchanger for cooling relatively hot gas down to relatively warm gas, an intermediate chamber for receiving gas, cooled down to relatively warm gas, coming out of tubes of the first heat exchanger, and a second shell-and-tube heat exchanger for cooling relatively warm gas further down to relatively cool gas. The intermediate chamber is provided with an outlet fluidly connected to a bypass channel for allowing a part of the relatively warm gas to bypass tubes of the second heat exchanger. The bypass channel and tubes of the second heat exchanger are both fluidly connected with a mixing chamber for mixing together relatively warm gas flowed from the intermediate chamber into the mixing chamber via the bypass channel and relatively cool gas come out of the tubes of the second heat exchanger.

A waste heat boiler system for cooling a process gas, including a first shell-and-tube heat exchanger for cooling relatively hot gas down to relatively warm gas, an intermediate chamber for receiving gas, cooled down to relatively warm gas, coming out of tubes of the first heat exchanger, and a second shell-and-tube heat exchanger for cooling relatively warm gas further down to relatively cool gas. The intermediate chamber is provided with an outlet fluidly connected to a bypass channel for allowing a part of the relatively warm gas to bypass tubes of the second heat exchanger. The bypass channel and tubes of the second heat exchanger are both fluidly connected with a mixing chamber for mixing together relatively warm gas flowed from the intermediate chamber into the mixing chamber via the bypass channel and relatively cool gas come out of the tubes of the second heat exchanger.

A flame tube having a tubular body with an inner side surface, extending around an axis (A), an inlet section and an outlet section, a plurality of fins leaning out, substantially in the radial direction (R), from the inner side surface towards the axis (A) is provided. The fins have an extended surface whose tangent (T), in a point (C) normal to the radial direction (R), is skew with respect to the axis (A), a first and a second fin forming an interspace between the respective extended surfaces facing one another and whose ideal extension (P) in the direction of the tangent (T) encounters a third fin.

A flame tube having a tubular body with an inner side surface, extending around an axis (A), an inlet section and an outlet section, a plurality of fins leaning out, substantially in the radial direction (R), from the inner side surface towards the axis (A) is provided. The fins have an extended surface whose tangent (T), in a point (C) normal to the radial direction (R), is skew with respect to the axis (A), a first and a second fin forming an interspace between the respective extended surfaces facing one another and whose ideal extension (P) in the direction of the tangent (T) encounters a third fin.

An evaporator with integrated heat recovery incorporates a vapor tube in a combustion chamber surrounded by a water jacket. The water jacket is in fluid communication with an exhaust gas heat exchanger. Coolant circulates through the exhaust gas heat exchanger to recover heat from exhaust gasses leaving the combustion chamber and then circulates through the water jacket surrounding the combustion chamber to recover heat not delivered to the operating fluid. The evaporator may incorporate a condenser within the housing and in fluid communication with the exhaust gas heat exchanger and water jacket. Coolant may enter the evaporator housing at the condenser before circulating through the exhaust gas heat exchanger and water jacket.

A gas-fired atmospheric pressure steam humidifier having high efficiency and ultra-low NOx(3) emissions is disclosed. In some examples, the gas-fired humidifier can have an efficiency of greater than 90 percent and a NOx(3) output of less than 20 parts per million (ppm). In one aspect, the humidifier includes a secondary heat exchanger having a first heat exchange section for pre-heating combustion air and a separate second heat exchange section for pre-heating make-up water, wherein the first and second heat exchange sections are in heat transfer communication with exhaust gases generated by the gas-fired burner and combustion blower assembly. In some examples, the first heat exchange section includes orifices for enabling flue gas recirculation.

A gas-fired atmospheric pressure steam humidifier having high efficiency and ultra-low NOx(3) emissions is disclosed. In some examples, the gas-fired humidifier can have an efficiency of greater than 90 percent and a NOx(3) output of less than 20 parts per million (ppm). In one aspect, the humidifier includes a secondary heat exchanger having a first heat exchange section for pre-heating combustion air and a separate second heat exchange section for pre-heating make-up water, wherein the first and second heat exchange sections are in heat transfer communication with exhaust gases generated by the gas-fired burner and combustion blower assembly. In some examples, the first heat exchange section includes orifices for enabling flue gas recirculation.

A fire tube with three hollow tube sections, two of which are parallel to each other and one of which is perpendicular to and connects the ends of the first two tube sections. The bottom-most tube section, which contains the burner, has an inner ceramic liner that is made up of one or more separate ceramic tubular sections. An upper set of cooling funs surrounds the top part of the bottom-most tube section, and a lower set of cooling fins surrounds the bottom part of the bottom-most tube section.

A fire tube with three hollow tube sections, two of which are parallel to each other and one of which is perpendicular to and connects the ends of the first two tube sections. The bottom-most tube section, which contains the burner, has an inner ceramic liner that is made up of one or more separate ceramic tubular sections. An upper set of cooling funs surrounds the top part of the bottom-most tube section, and a lower set of cooling fins surrounds the bottom part of the bottom-most tube section.