[001 ] The present invention relates to a fluidized bed reactor arrangement in accordance with the preamble of the patent claim 1 , in which a fluidized bed reactor comprises at least a bottom portion, a roof portion and at least one side wall vertically extending between the bottom portion and the roof portion, said side wall being arranged inclined at the lower portion thereof in such a manner that the cross-section of the reaction chamber of the reactor decreases towards the bottom portion, and which fluidized bed reactor arrangement comprises a heat exchange chamber at the inclined area of said side wall outside the reaction chamber, and in which said side wall, extending between the bottom portion and the roof portion and being arranged inclined at the lower portion thereof forms a partition wall between the heat exchange chamber and the reac- tion chamber, and in which the heat exchange chamber extends from the partition wall to the other side of the plane extending through the side wall.

[002] The reactor chamber of the fluidized bed reactor typically comprises an interior which is rectangular of the horizontal cross-section, defined by four side walls, a bottom and a roof, in which interior bed material containing solid material and, for example, fuel is fluidized by means of fluidizing gas, generally oxygenous, primary gas required for the exothermic chemical reactions taking place in the reaction chamber. The interior, in other words the reaction chamber, is called a combustion chamber and the reactor a fluidized bed boiler, when a combustion process is performed in a fluidized bed reactor. The side walls of the reaction chamber are typically also provided at least with conduits for fuel feed and feed of secondary air.

[003] The side walls of the reaction chamber are generally fabricated to com- prise panels formed of tubes and fins therebetween, whereby the energy released in the chemical reactions of the fuel is used for evaporating of the water flowing in the tubes. Superheater surfaces are also often provided in a fluidized bed reactor to further increase the energy content of the steam. [004] A fluidized bed reactor may be, for example, a circulating fluidized bed reactor or a bubbling bed reactor. Fluidized bed reactors are used in various combustion processes, heat exchange processes, chemical and metallurgical processes. In the combustion processes, components of the fluidized bed may include granular fuels, like coal, coke, lignite, wood, waste or peat, and also other granular substances, like sand, ash, desulphurating agents or catalysts.

[005] A characteristic feature of the fluidized bed reactor is the use of solid bed material as process material. The bed material acts as, for example, a temperature stabilizing component in the reaction chamber and binds a considerable amount of heat therein. Bed material can thus be used also for transferring heat from the reaction to the medium. In fluidized bed combustion plants, heat recovery typically takes place in a combustion chamber and in a convec- tion part by means of heat exchange surfaces, which is arranged downstream of a particle separator in the gas flow. Heat exchange surfaces, such as superheaters, are typically arranged, for example, in a free space in the upper portion of the reaction chamber and in the convection part subsequent thereto in order to superheat steam.

[006] In the fluidized bed reactors, it is known per se to use heat exchanger chambers for solids separated from the reaction chamber, i.e. fluidized bed heat exchangers, to which bed material can be supplied from the reaction chamber and cooled in the fluidized bed heat exchanger, for example, prior to recirculating the solids back to bed material of the reaction chamber.

[007] Such fluidized bed heat exchangers typically operate as a so called bubbling bed. The heat exchange chamber can be arranged either inside the reactor itself or outside thereof. Finnish patent publication No. FI1 19916 dis- closes such a heat exchange chamber arranged inside the reactor. When the heat exchange chamber is inside the reactor, it is preferably supported by means of the walls and/or the bottom portion of the reactor. [008] Publication WO 94/22571 discloses a heat exchange chamber, which is arranged outside the actual reaction chamber. The heat exchange chamber is arranged in connection with the circulating fluidized bed reactor in such a manner that it participates in a so called internal circulation for the solids. There, part of the bed material flow inside the reaction chamber is guided directly from the reaction chamber to the heat exchange chamber and from there back to the reaction chamber.

[009] Publication US 4,896,717 discloses a heat exchange chamber, which is outside the actual reactor. Here, the heat exchange chamber is connected to the external circulation for the solids in the circulating fluidized bed reactor, in other words the solids led to the heat exchange chamber are separated from the gas exiting the reaction chamber. [0010] The support and connection of the heat exchange chamber for solids separated from the reaction chamber to the actual reaction chamber is problematic especially in that the heat exchange chamber horizontally extending far from the reaction chamber, i.e. at least partially outside the plane of the side wall of the reaction chamber, requires a separate support, which takes space around the reaction chamber and, thus, diminishes the possibilities to position the auxiliary equipment. For example, the heat exchange chamber disclosed in US publication No. 4,896,717 extends far under the solids separator, so in practice it must be supported very strongly, for example, supporting it from the cyclone above, whereby only a portion of the mass thereof transfers to the wall of reaction chamber.

[001 1] Although the fluidized bed reactors known from the prior art are advantageous as such, a need has arisen recently to provide an improved fluidized bed reactor, in which a heat exchange chamber is connected to the fluidized bed reactor in an improved manner.

[0012] Objects of the invention are achieved by means of a fluidized bed reactor arrangement, in which the fluidized bed reactor comprises at least a bottom portion, a roof portion and at least one side wall vertically extending between the bottom portion and the roof portion, which side wall is arranged at the lower portion thereof inclined in such a manner that the cross-section of the reaction chamber of the reactor decreases towards the bottom portion and which flui- dized bed reactor arrangement comprises a heat exchange chamber outside the reaction chamber at an area of the side wall which is arranged inclined, , and in which said side wall, which is inclined at the lower portion thereof extending between the bottom portion and roof portion forms a partition wall between the heat exchange chamber and the reaction chamber, and in which flui- dized bed reactor arrangement, the heat exchange chamber extends from the partition wall to the other side of the plane extending via the side wall. It is characteristic of the invention that the rear wall of the heat exchange chamber is connected to the side wall of the reaction chamber from the upper portion of the rear wall at a connection area in such a manner that the direction thereof aligns with the direction of the side wall at least in the connection area.

[0013] Thus, the transfer of the mass forces of the heat exchange chamber to the reaction chamber can be arranged in an advantageous manner by supporting the heat exchange chamber substantially completely to the reaction cham- ber. Thus, substantially the major part of the mass forces thereof, preferably substantially all the mass forces, are directed to the reaction chamber. Thereby, no such separate support structures are required for the heat exchange chamber, which support it to the foundation or to the supporting framework of the fluidized bed arrangement.

[0014] According to an embodiment, said inclined side wall forms a partition between the heat exchange chamber and the reaction chamber. Thus, the supporting forces can be transferred directly to the reaction chamber and the structure is robust and simple.

[0015] According to another embodiment, the plane P extending via the side wall of the fluidized bed reactor aligns at least at the connection area with the plane extending via the rear wall. Thus, a minimal force component deviating from the vertical direction is generated at the connection and the connection is thus strong. [0016] According to yet another preferred embodiment, the heat exchange chamber comprises end walls in connection with both edges of the rear wall, extending from said connection area to the bottom portion of the heat exchange chamber and the heat exchange chamber is horizontally arranged only to a portion of the distance between the edges of the side walls of the reaction cham- ber.

[0017] According to yet another embodiment, the fluidized bed reactor arrangement comprises a number of heat exchange chambers within the distance between the edges of the side wall.

[0018] According to yet another embodiment, the rear wall of the heat exchange chamber is formed of a membrane structure and the side wall of the fluidized bed reactor is formed of a membrane structure, and the membrane structure of the rear wall is connected to the feed water system of the fluidized bed reactor and the membrane structure of the side wall is connected to the steaming system of the fluidized bed reactor system. Thereby, the fluidized bed reactor arrangement is preferably a once through boiler.

[0019] According to yet another embodiment, the rear wall of the heat ex- change chamber is formed of a membrane structure and the side wall of the fluidized bed reactor is formed of a membrane structure, and in the connection area, a first group of membrane structured tubes is arranged to extend in the inclined side wall and a second group of membrane structured tubes is arranged to extend in the rear wall of the heat exchange chamber.

[0020] According to yet another embodiment, the heat exchange chamber has a certain center of gravity especially in a situation, in which the heat exchange chamber contains a predetermined nominal amount of solids, so called bed material, therein, which is distributed in a predetermined manner, and that the heat exchange chamber is arranged in such a manner that the center of gravity joins with plane P.

[0021] Other additional features typical of the invention become clear from the accompanying claims and description of the embodiments in the drawings.

[0022] The invention and the operation thereof are described below with reference to the accompanying schematic drawings, in which

Fig. 1 illustrates an embodiment of a fluidized bed reactor arrangement in ac- cordance with the invention;

Fig. 2 illustrates an embodiment of a heat exchange chamber of the fluidized bed reactor arrangement in accordance with the invention;

Fig. 3 illustrates a preferred connection in accordance with the invention; and Fig. 4 illustrates another preferred connection in accordance with the inven- tion.

[0023] The invention is described below, when applicable, with reference to both Fig. 1 and Fig.2, in which same reference numbers are used when refer- ring to corresponding features. Fig. 1 schematically illustrates an embodiment of the fluidized bed reactor arrangement 10 in accordance with the invention. The fluidized bed reactor arrangement 10 comprises a fluidized bed reactor, having, for example, a reactor chamber 20, a solids separator 18. The fluidized bed reactor is preferably a circulating fluidized bed boiler. Fig. 2 illustrates a heat exchange chamber 30 of a fluidized bed reactor arrangement in the lower portion of the reactor.

[0024] A circulating fluidized bed boiler 10 comprises a bottom portion 12 and a roof portion 16 and walls 14 extending therebetween. Further, it is clear that the fluidized bed reactor comprises many parts and elements which are not shown here for the sake of clarity. The bottom portion, the roof portion and the walls 14 form said reaction chamber 20, which is called a furnace in the boiler. The bottom portion 12 also includes a grid 25, through which fluidizing gas is supplied to the reactor. The circulating fluidized bed reactor further comprises a solids separator 18, which is typically a cyclone separator. The solids separator is connected to the reaction chamber from the upper portion thereof, close to the roof portion by means of a connecting channel 22, through which reaction gas and solids can flow to the solids separator 18. In the solids separator, solid ma- terial is separated from the gas, which solid material may be recirculated, after possible treatment, such as cooling, back to the reaction chamber 20, i.e. to the furnace. For this purpose, the solids separator is connected, for example, to the lower portion of the reaction chamber 20 by means of a return duct 24. The gas, of which solid material has been separated, is led in the system for further treatment through a gas discharge connection 26 of the solids separator.

[0025] Two opposite side walls 14.1 , 14.2 of the fluidized bed reactor are arranged inclined in the lower portion of the fluidized bed reactor in such a manner that the side walls approach each other towards the bottom portion 12. Here, the reaction chamber 20 is quadrangular of the cross-section, so it is limited in addition to the side walls also by end walls, of which only one 14.3 is shown in this connection. The walls 14 comprise evaporation tubes, which are preferably arranged in such a way that the thermal stress of the reactor against all of them is substantially equal. It has to be noted that in the figure the tubes are, for simplicity, shown in lines and the fins connecting in reality the tubes are shown by the distances between the lines. In practice, the walls of the fluidized bed reactor are preferably formed of a membrane structure 31 , in which the adjacent flow tubes/channels are connected to each other by means of a plate- structured fin.

[0026] The fluidized bed arrangement 10 comprises a heat exchange chamber 30 for cooling solid particles. The heat exchange chamber 30 is arranged in connection with the fluidized bed reactor arrangement 10 in such a manner that it preferably has a common partition wall 32 with the reaction chamber 20. The partition wall 32 is an inclined wall 14.1 in the lower portion of the fluidized bed reactor. Heat exchange chamber also comprise a rear wall 34, joining from the upper portion thereof to a side wall 14.1 of the reaction chamber 20 of the fluidized bed reactor arrangement. The rear wall is horizontally parallel with the partition wall 32 and an interior space of the heat exchange chamber 30 is formed therebetween. The connection 36 is realized in such a manner that the mass forces can be transferred by means of the rear wall 34 to the side wall 14.1 of the reactor. In the connection 36 of the heat exchange chamber 30 and side wall 14.1 , the direction of the rear wall aligns with the direction of the side wall. Thereby, the direction of the force transferring to the side wall 14.1 of the reaction chamber 20 via the rear wall 34 is substantially parallel to the side wall 14.1 and the connection 36 is especially strong. The connection can also be described in such a manner that a plane P extends via the side wall 14.1 of the reactor and thereby a portion of the rear wall is arranged in such a manner that the plane P extending via the side wall 14.1 joins the plane extending via said portion of the rear wall 34. This portion thus extends to a distance from the connection, whereafter the rear wall is directed away from the partition wall 32. [0027] The heat exchange chamber 30 comprises end walls 38 in connection with both edges of the rear wall 34 thereof. The rear wall 34 is connected to the end walls 38 at least for a distance D, for which distance the rear wall 34 is parallel with the side wall 14.1 . The end walls are preferably also connected to an inclined side wall, in other words, to the partition wall 32. The end walls are pre- ferably arranged to an area between the connection 36 and bottom portion 12. Thereby, the portion of the side wall 14.1 above the connection 36 remains free of end walls, which enables easier positioning of other devices related to the reactor, such as a recycling system for solid material in particular and/or feed devices for gas/fuel.

[0028] The heat exchange chamber is provided with a fluidized bed heat exchanger, comprising at the bottom of said heat exchanger means 40 for supplying fluidizing gas, an inlet 42 and an outlet 44 for solid material and heat exchange surfaces 46, 48. The heat exchange chamber 30 extends from the par- tition wall 32 running to the other side via the plane P, whereby it at least partially extends outside the vertical projection in respect to the reaction chamber, in other words to both sides. Thereby, also the rear wall 34 of the heat exchange chamber 30 comprises at least one inclined portion. The inclination of the rear wall 34 is directed to opposite direction in relation to the inclination of the partition wall 32. The heat exchange chamber has a certain center of gravity G especially in situations, in which it contains a nominal amount of solid material, in other words bed material, therein, distributed in a predetermined manner. The heat exchange chamber is arranged according to a preferred embodiment in such a manner, that the center of gravity G joins with plane P. Thus, the stress against the side wall 14.1 of the reaction chamber 20 in the connection 36 of the rear wall is distributed in an advantageous manner and the structure is especially strong. The weight of the heat exchange chamber is arranged to dis- tribute for a long distance in the side wall 14.1 and in the rear wall 34 of the heat exchange chamber via the end walls of the heat exchange chamber. The length D of the portion of the rear wall parallel with the side wall at the connection 36 of the rear wall is determined in such a manner that the ratio of the length D to the distance 30' between the end walls 38 in connection with both edges of the rear wall 34 of the heat exchange chamber 30 is at least 0,5. The stress of the heat exchange chamber can thus be distributed in an advantageous manner to the rear wall.

[0029] The width of the end walls 38 of the heat exchange chamber in the por- tion 38' joining with plane P, substantially corresponds at least with the perpendicular distance X of the rear wall 34 from the partition wall 32 within a distance D from the connection 36. Thus, the rear wall 34 is connected to the end wall in the area within the edge thereof, whereby the force transferring between the rear wall and the end wall is distributed in an advantageous manner, more evenly than in situations, in which the rear wall were connected to the edge of the end wall.

[0030] When the reactor is used, a fluidized bed is generated in the reactor, preferably a circulating fluidized bed. In the circulating fluidized bed, a fast flui- dized bed of solid particles generates an internal circulation of particles in the reaction chamber, whereby solid particles mainly flow upwards in the central portion of the reaction chamber and downwards along the side walls thereof. Further, solid particles move horizontally causing the particles to mix efficiently. Mainly finer solid particles are entrained with the gas to the upper portions of the reaction chamber 20 thus flowing downwards along the walls or sideways within the reaction chamber, the coarser particles accumulating to the bottom portion of the reaction chamber. [0031] Particles of such an internal circulation, flowing down along the side walls, can be guided through openings of the partition wall 32, so called inlet 42 to the heat exchange chamber. A so called bubbling bed is arranged inside the heat exchange chamber. Solid material is recirculated therefrom back to the fast fluidized bed in the reaction chamber and new solid material is continuously added to the upper portion of the bubbling bed. The heat exchange chamber may also be in connection with the return duct 24' of the solids separator. In the fluidized reactor arrangement, it is also possible to have a number of heat exchange chambers, of which a portion or all can be connected to the above described internal circulation and/or return duct of the solids separator.

[0032] Fig. 3 schematically illustrates a preferred steam circuit coupling 300 of a fluidized bed reactor arrangement for the steam system in accordance with the invention, whereby the fluidized bed reactor arrangement is a once through fluidized bed boiler. Here, a feed water system 304 comprising a feed water heater and positioned downstream of a feed water pump 302 i n th e steam/water flow direction comprises membrane wall of the end walls 38 and/or rear wall 34 of the heat exchange chamber 30. An evaporator system 306 in turn comprises membrane wall of the reaction chamber 20. A superheater system 308 can comprise, for example, heat exchange surface 46 arranged in the fluidized bed of the heat exchange chamber.

[0033] Fig. 4 schematically illustrates another preferred steam circuit coupling 300 of a fluidized bed reactor arrangement for the steam system in accordance with the invention, whereby the fluidized bed reactor arrangement is a natural circulation boiler. In this embodiment, there is a feed water system 304 downstream of the feed water pump 302 in the steam/water flow. The evaporator system 306 of the boiler comprises membrane wall of both the end walls 38 and/or the rear wall 34 of the heat exchange chamber and membrane wall of the reaction chamber 20. Also, in this embodiment, the superheater system 308 can comprise, for example, heat exchange surface 46 arranged in the flui- dized bed of the heat exchange chamber. Thereby, a first group of the tubes of the membrane structure 31 of the partition wall 32 in the connection area 36 is arranged to extend in the inclined side wall and a second group of the tubes of the membrane structure is arranged to extend in the rear wall 34 of the heat exchange chamber (Fig. 1 ).

[0034] While the invention has been described herein by way of examples in connection with what are, at present, considered to be the most preferred em- bodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but is intended to cover various combinations or modifications of its features and several other applications included within the scope of the invention as defined in the appended claims. Thus the heat exchange chamber can also be in connection with the return duct 24' of the solids separa- tor. The features disclosed with the embodiments can be utilized with other embodiments within the scope of the invention and/or the disclosed features can be combined to form various entities, if such are desired and they are technically feasible.