A ground supported power boiler is described combining a refractory lined and insulated conical floor; an insulated cylindrical combustion chamber; a cylindrical furnace with water tube wall; a rectangular convective section; a single vertical steam drum; tangential injection of the fuel and combustion air; means for fluidizing the fuel bed; means for selectively stripping particulates from the flue gases; multi-stage particulate stripping and filtering from flue gases, means for using the walls of steam drum as steam/water droplet separator, means for recirculating and capturing heat from the flue gases; means for pressurizing the interior of the boiler above atmospheric pressure; means for heating and drying fuel prior to feeding the fuel to the boiler; means for creating hydrogen shift reaction; means for eliminating any need for sootblowing; and designed to not require the use of an induced draft fan.

The purpose of the present invention is to provide a furnace wall in which a throat section with a smaller channel diameter than other regions can be formed using all peripheral wall tubes. Provided is a furnace wall comprising: a plurality of peripheral wall tubes (142), which are disposed so as to form a cylindrical shape when aligned in one direction and through the interior of which cooling water flows; and fins (140) that connect neighboring peripheral wall tubes (142) in an airtight manner. In a throat section in which the diameter of a horizontal cross-section of the cylindrical shape is reduced in comparison to other regions, the peripheral wall tubes (142) are disposed so as to be in mutual contact and the fins (140) are disposed on the inner circumferential sides of the cylindrical shapes.

An expansion joint for a solids return system includes a female joint portion, a male joint portion received by the female joint portion, the male joint portion and the female joint portion forming a lateral breach therebetween, a double rope seal positioned within the lateral breach, the double rope seal being configured to accommodate relative lateral movement between the female joint portion and the male joint portion, and an insulating pillow received about the male joint portion and abutting a distal end surface of the female joint portion, the insulating pillow being configured to accommodate relative axial movement between the female joint portion and the male joint portion.

Various aspects provide for a multistage fluidized bed reactor, particularly comprising a volatilization stage and a combustion stage. The gas phases above the bed solids in the respective stages are separated by a wall. An opening (e.g., in the wall) provides for transport of the bed solids from the volatilization stage to the combustion stage. Active control of the gas pressure in the two stages may be used to control residence time. Various aspects provide for a fuel stream processing system having a pretreatment reactor, a combustion reactor, and optionally a condensation reactor. The condensation reactor receives a volatiles stream volatilized by the volatilization reactor. The combustion reactor receives a char stream resulting from the removal of the volatiles by the volatilization reactor.

A circulating fluidized bed boiler is described, comprising a furnace, a loopseal, and a loopseal heat exchanger arranged in the loopseal. The loopseal heat exchanger comprises walls limiting an interior of the loopseal heat exchanger, a first particle outlet for letting out particulate material from the loopseal heat exchanger, an inlet for receiving bed material, heat exchanger tubes arranged in the interior of the loopseal heat exchanger, and a first ash removal channel configured to let out ash from the loopseal heat exchanger. An ash cooler is configured to receive ash from the first ash removal channel. In the loopseal heat exchanger the first ash removal channel is arranged at a lower level than the first particle outlet.

A circulating fluidized bed boiler is described, comprising a furnace, a loopseal, and a loopseal heat exchanger arranged in the loopseal. The loopseal heat exchanger comprises walls limiting an interior of the loopseal heat exchanger, a first particle outlet for letting out particulate material from the loopseal heat exchanger, an inlet for receiving bed material, heat exchanger tubes arranged in the interior of the loopseal heat exchanger, and a first ash removal channel configured to let out ash from the loopseal heat exchanger. An ash cooler is configured to receive ash from the first ash removal channel. In the loopseal heat exchanger the first ash removal channel is arranged at a lower level than the first particle outlet.

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).

The solution comprises a method of and a system for maintaining steam temperature and therefore electricity production efficiency with decreased loads of a steam turbine power plant comprising a fluidized bed boiler (12) and a fluidized bed superheater (2) adapted to superheat steam supplied to a steam turbine (3). According to the solution, the steam temperature may be maintained by providing, outside a furnace (10), additional heating to the fluidized bed material in its outer circulation, thereby increasing the amount of thermal energy available in the fluidized bed material to be transferred in the fluidized bed superheater (2) to the steam supplied to the steam turbine (3). Such additional heating may be performed by selectably supplying combustible gas with nozzles (111) into and/or burned with a burner in or in the vicinity of the fluidized bed material outside the furnace (10). As an additional aspect of the disclosed solution, the combustible gas may be produced with a gasifier (4).

A method of operating a furnace having a firing system is disclosed. The method includes providing a solid fuel to a sieve; separating the fuel into a portion and a second portion; providing a first portion of a flue gas to a first fuel dryer comprising a first duct; providing the first portion of fuel to the first duct, and drying the first portion of fuel therein; conveying the first portion of fuel through the first duct to the furnace; burning the first portion of fuel with firing system; conveying the second portion of fuel and a second portion of the flue gas to a second fuel dryer in a lower portion of the furnace, providing the second portion of fuel to a mill; pulverizing the second portion of fuel with the mill; conveying the second portion of fuel to the furnace; and burning the second portion of fuel.

The invention relates to a method for operating a fluidized bed boiler (6), comprising the steps of: a) providing fresh ilmenite particles having a shape factor of 0.8 or lower as bed material to the fluidized bed boiler (6); b) carrying out a fluidized bed combustion process; c) removing at least one ash stream comprising ilmenite particles from the fluidized bed boiler; d) separating ilmenite particles from the at least one ash stream, wherein the separation includes a step of using a magnetic separator (12) comprising a field strength of 2,000 Gauss or more; e) recirculating separated ilmenite particles into the bed of the fluidized bed boiler; wherein the average residence time of ilmenite particles in the fluidized bed is 100 h or more.