An air nozzle arrangement for a fluidized bed boiler, comprising an air feed pipe and an air nozzle which limit an air feed duct configured to supply air to the furnace of the fluidized bed boiler. The air nozzle arrangement comprises a surface configured to guide coarse material along said surface. At least part of said surface is thermally insulated from the air nozzle and/or the air feed pipe. Furthermore, at least part of said surface is configured to protect at least part of said air nozzle and/or air feed pipe. Thus, the temperature of said surface is configured to be high when the fluidized bed boiler is in operation, whereby the solidification of molten material of the fluidized bed in the air nozzle arrangement is reduced.

An air nozzle arrangement for a fluidized bed boiler, comprising an air feed pipe and an air nozzle which limit an air feed duct configured to supply air to the furnace of the fluidized bed boiler. The air nozzle arrangement comprises a surface configured to guide coarse material along said surface. At least part of said surface is thermally insulated from the air nozzle and/or the air feed pipe. Furthermore, at least part of said surface is configured to protect at least part of said air nozzle and/or air feed pipe. Thus, the temperature of said surface is configured to be high when the fluidized bed boiler is in operation, whereby the solidification of molten material of the fluidized bed in the air nozzle arrangement is reduced.

A grate block for a combustion grate, wherein consecutive grate blocks are arranged one over the other in a staircase manner and rearrange to convey the combustible material during combustion by means of pushing motions performed in relation to each other. The grate block includes a block body including an upper wall forming a bearing surface, along which wall the combustible material is conveyed, and a front wall forming a push surface, which has first air supply openings formed by a first air supply channel for feeding air to the combustion grate, and a lower bearing edge intended to come into contact with the bearing surface of a grate block located adjacent in the pushing direction S. Further air supply channels, which traverse and are directed obliquely with respect to the direction of the first air supply channels, are arranged in the upper and front walls for cooling the walls.

A grate block for a combustion grate, wherein consecutive grate blocks are arranged one over the other in a staircase manner and rearrange to convey the combustible material during combustion by means of pushing motions performed in relation to each other. The grate block includes a block body including an upper wall forming a bearing surface, along which wall the combustible material is conveyed, and a front wall forming a push surface, which has first air supply openings formed by a first air supply channel for feeding air to the combustion grate, and a lower bearing edge intended to come into contact with the bearing surface of a grate block located adjacent in the pushing direction S. Further air supply channels, which traverse and are directed obliquely with respect to the direction of the first air supply channels, are arranged in the upper and front walls for cooling the walls.

An improved fire grate may provide fresh oxygen rich air to a secondary combustion zone, created by the improved fire grate, of a combustion chamber where a combustion gas stream is typically oxygen starved assisting in the burning process of incompletely burned particulates and reducing other harmful emissions. A baffle plate may be introduced in the secondary combustion zone to increase a combustion chamber temperature, encourage mixing of oxygen starved air with oxygen rich air and increase a residence time of the combustion gas within the combustion chamber. These aspects of the baffle plate promote more efficient burning of the biomass/fuel. Additionally, log lighter(s) may be disposed in the secondary combustion zone to increase a temperature of the combustion chamber for the purposes of reducing harmful emissions. The improved fire grate may be horizontally and vertically adjusted to fit within different sized fireplace combustion chambers.

The plate-formed grate element (1, 2) has a top wall (12), a bottom wall (13), a front end (14) and a back end (15). The front end has a lower inwardly curved wall portion (16) adapted to maintain a predetermined clearance with a back tip edge of a corresponding grate element. An internal cooling fluid chamber (18) includes an internal front cooling fluid channel (19) extending along the front end (14) of the grate element. The grate element has an outwardly curved front wall (22) having a nominal wall thickness varying by less than 35 percent and extending from the top wall of the grate element to the lower inwardly curved wall portion of the front end, and a front tip edge (23) of the front end is formed by the outwardly curved front wall at its connection with the lower inwardly curved wall portion.

The plate-formed grate element (1, 2) has a top wall (12), a bottom wall (13), a front end (14) and a back end (15). The front end has a lower inwardly curved wall portion (16) adapted to maintain a predetermined clearance with a back tip edge of a corresponding grate element. An internal cooling fluid chamber (18) includes an internal front cooling fluid channel (19) extending along the front end (14) of the grate element. The grate element has an outwardly curved front wall (22) having a nominal wall thickness varying by less than 35 percent and extending from the top wall of the grate element to the lower inwardly curved wall portion of the front end, and a front tip edge (23) of the front end is formed by the outwardly curved front wall at its connection with the lower inwardly curved wall portion.