A circulating fluidized bed boiler is disclosed. The circulating fluidized bed boiler comprising: a furnace defined and enclosed by water walls, a ceiling and an air distributor, the water walls comprising front and rear walls and left and right side walls (AJ, TK) formed by water cooling tubes, and the water walls are provided with secondary air ports (Y) in the lower part thereof, and furnace flue gas outlets (AB, EF, IJ, KL, OP, ST) being provided in an upper part of the furnace; at least two cyclones connected with the furnace flue gas outlets (AB, EF, IJ, KL, OP, ST); a loop-seal is connected with solid outlets of the cyclones and the lower part of the furnace, respectively; and a flue gas duct connected with flue gas outlets of the cyclones wherein the water cooling wall tubes of the water wall form at least one vertical columnar recessed segment (BCDE, FGHI, SRQP, ONML) recessed toward the inside of the furnace, and the at least one columnar recessed segment (BCDE, SRQP, ONML) extends at least 15% of the furnace height in a vertical direction.

A tubular waterwall structure in a fluidized bed reaction chamber includes horizontally adjacent first and second portions forming a corner structure and constituted by vertical tubes and fins centrally attached to the tubes and having a first width. The first wall portion has an outermost tube next to the corner, an upper portion defining an upper vertical plane in an upper level range and a lower portion defining a lower (outwards) vertical plane in a lower level range. The lower portion has a refractory lining. The second wall portion is vertical and has an outermost tube next to the corner. The outermost tube of the second wall portion is in the lower level region connected to the outermost tube of the first wall portion by a planar lower beveled corner fin having a refractory lining and a width that is larger than the first width.

A watertube panel portion for a fluidized bed reactor and a corresponding method. The watertube panel portion includes multiple parallel metal tubes having a tube length L1, an outer surface, an original outer diameter OD1, and an original wall thickness WT1, and a circumferentially extending recess formed in a central portion of each of the tubes, between first and second end portions. The recess has a constant depth D that is less than the wall thickness WT1. The recess encircles the outer surface of the central portion of the metal tube. A circumferentially extending metal coating has a constant thickness of at most the depth D of the recess to blanket the recess of each of the multiple metal tubes. A fin is continuously welded between each pair of adjacent tubes.

A watertube panel portion for a fluidized bed reactor and a corresponding method. The watertube panel portion includes multiple parallel metal tubes having a tube length L1, an outer surface, an original outer diameter OD1, and an original wall thickness WT1, and a circumferentially extending recess formed in a central portion of each of the tubes, between first and second end portions. The recess has a constant depth D that is less than the wall thickness WT1. The recess encircles the outer surface of the central portion of the metal tube. A circumferentially extending metal coating has a constant thickness of at most the depth D of the recess to blanket the recess of each of the multiple metal tubes. A fin is continuously welded between each pair of adjacent tubes.

A particle separator module and a heat exchange chamber module connectable to a circulating fluidized bed boiler. The particle separator module includes 2N vertically aligned steam tubes, N being an integer greater than one. Each of the vertically aligned steam tubes is attached to a boiler upper portion and extends downwards to a predetermined level. Each of the 2N vertically aligned steam tubes is attached to one of N first beams. Each of the N first beams is suspended to hang in a horizontal position at the predetermined level by two adjacent steam tubes of the 2N vertically aligned steam tubes. N second beams are attached in a horizontal position to the top surface of the heat exchange chamber module, which is arranged to be suspended from the particle separator module by having each of the N second beams suspended by two adjacent beams of the N first beams.

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.

Embodiments of the invention provide a water-cooled column formed by side walls connected together to define an enclosed space, each side wall is formed of a water-cooled membrane wall, a working medium is passed through a tube of the water-cooled membrane wall from bottom to top, the water-cooled column comprising: a lower part having a cross section reduced segment, which has a cross section gradually reduced in a direction from bottom to top; and an upper part, wherein the upper part connects with the cross section reduced segment at a connection position, and a cross sectional area of the cross section reduced segment at the connection position is identical to a cross sectional area of the upper part at the connection position. Embodiments of the invention also provide a furnace for defining a reaction space, which comprises a water-cooled column defined as above disposed along a vertical direction therein.

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.