A CIRCULATION FLUIDIZED BED REACTOR

Abstract: A circulating fluidized bed reactor (1) having a cyclone separator (4), the horizontal vortex chamber (3) of which is provided with two return ducts (9, 11) for separated particulate material. The first return duct (9) is connected to an opening (8) on the periphery of the vortex chamber and disposed near the gas inlet channel (6) in axial direction. The second return duct (11) is connected to another opening (10) disposed at a distance from the first duct near the discharge opening (7) for the purified gas in axial direction.

Description: A circulating fluidized bed reactor The present invention relates to a circulating fluidized bed reactor in which solid particles are conveyed by gas through the reactor and separated from the gas by means of a cyclone separator or a εimilar device and returned to the reactor. Today circulating fluidized bed reactors are more and more applied in various uses such as chemical processes, combustion and gasifying. The object of the invention is to accomplish a circulating fluidized bed reactor, in which solid material can effectively be separated from . the flue gas and returned to a required place in the reactor. According to the invention this is achieved by means of a cyclone separator for separating particulate material from the flue gases from the reactor chamber, the horizontal vortex chamber of which being provided with openings on its periphery to which openings is connected a duct leading gas from the reactor chamber and a return duct leading separated solid material to the reactor chamber and from which vortex chamber gas is discharged from one or both ends, wherein one discharge opening for separated solid material is disposed by the inlet opening for gas and the other by the discharge opening for purified gas at a distance from the inlet opening in the longitudinal axial direction of the vortex chamber. FI patent application 841126 discloses ε circulating fluidized bed reactor in which solid material is separated by means of a horizontal cyclone disposed on top of the reactor. To the periphery of the separation chamber of the horizontal chamber is connected a return duct for separated material, preferably to the lowest part of the periphery, and the purified gases are discharged from one or both ends of the separation chamber. The separated solids are discharged from the separation chamber via one opening that stretches over its whole width. In the known application of the horizontal cyclone separator the discharge opening for solid material and the inlet opening for gas stretching over the whole width disturb the flow condition in the separation chamber. In the apparatus according to the invention in which the separator is provided with two discharge openings spaced a distance apart from each other, most of the dust coming into the cyclone is separated due to centrifugal force already during the first cycle and is discharged from the vortex chamber via an opening disposed by the inlet opening for the gas. The remaining dust load is relatively small and cannot essentially decelerate the gas vortex formed in the c lone, thus the effect of the vortex remains good throughout the cyclone. The rest of the dust that can be separated is dis¬ charged via an opening disposed at the other end of the cyclone. Separation of the remaining dust takes place in an undisturbed flow condition in such a part of the vortex chamber where there are no openings on the periphery. By means of the design according to the invention the separation efficiency of a horizontal cyclone is improved, which efficiency iε, as known, lower than that of a conventional vertical cyclone, but there are economic advantages compared with a circulating fluidized bed reactor having a conventional vertical cyclone. When most of the whirling mass is removed from the beginning of the horizontal cyclone, the rest of the cyclone will wear more slowly (the amount of the remaining whirling mass is smaller and an average grain size is smaller) . The invention will be described further, by way of example, with reference to the accompanying drawings in which Fig. 1. shows one embodiment according to the invention as a side view. Fig. 2. shows a section along the line A-A of Fig. 1, Fig. 3. shows a section along the line B-B in Fig. 1, Fig. 4. shows another embodiment according to the invention as a side view ard Fig. 5. shows a section along the line C-C in Fig. 4. In figures 1-3 is shown a circulating fluidized bed reactor, on top of a vertical reactor chamber 2 of which is disposed a cyclone separator 4 provided with a horizontal vortex chamber 3. Gases leaving the upper part of the reactor chamber are led to the vortex chamber by means of a tangentially connected duct 5 that is connected to a gas inlet opening 6 disposed on the periphery of the vortex chamber in the vicinity of one of its ends 12. The width 1 of the gas inlet opening 6 iε smaller than the width L of the vortex chamber, which width is as large as that of the reactor chamber. In the other end 13 of the vortex chamber there is a gas outlet opening, through which the purified gases are discharged. A first discharge opening 8 for separated solid material is disposed by the gas inlet opening in the direction of the longitudinal axis, but on the opposite side of the vortex chamber. A first return duct 9 for solid material functioning as a discharge pipe is connected to the discharge opening 8. At the other end of the vortex chamber a second discharge opening 10 for separated solid material is disposed at a distance from the first dis¬ charge opening 8 in the direction of the longitudinal axis. A second return duct 11 is connected to this second discharge opening. The lower ends of both return ducts are connected to the lower part of the reactor chamber. Fluidizing gas, for example combustion air, is led in a way known per se to the lower part of the reactor. Most of the solid material that is discharged with the flue gas from the upper part of the reactor chamber iε separated at the gas inlet end of the vortex chamber and returned to the lower part of the reactor via the return duct 9. The rest of the solid material that can be separated iε separated at the end near the gas discharge opening 7 and returned via the return duct 11. Purified gases are discharged from the vortex chamber via the opening 7 that can be connected to a heat recovery apparatus. In the embodiment according to the invention shown in figures 4 and 5, the width L of the separator of the vortex chamber 23 disposed on top of the reactor chamber 22 is larger than the width of the reactor chamber, consequently the vortex chamber stretches partly over the convection part 24 located beside the reactor chamber. Due to the large width an effective separation of solid material from the flue gas is accomp¬ lished. The width 1 of the duct 25 leading to the vortex chamber and of the inlet opening 26 is as large as the width of the reactor chamber. The solid material separated on the periphery of the vortex chamber is returned to the lower part of the reactor chamber via return ducts 29 and 31, of which one is connected to an opening 28 by the gas inlet opening and the other to an opening by the gas outlet opening. The puri¬ fied gas leaving through the gas discharge opening 27 is led via a duct 32 to -the convection part. The invention is not intended to be limited to the embodiments presented here as examples only but it can be modified and applied within the scope of the protection defined by the patent claims. For example, the vortex chamber can be conical in its longitudinal section or is can be formed by two cylind¬ rical parts of different sizes connected by a conical part. The number of return ducts can be larger than two. The puri¬ fied gas can be discharged from both ends of the vortex chamber.

Claims: Claims 1. A circulating fluidized bed reactor having a vertical reactor chamber and a cyclone separator for separating particulate material from the flue gases from the reactor chamber, the horizontal vortex chamber (3, 23) of which being provided with openings on its periphery to which openings is connected a duct (5, 25) leading gas from the reactor chamber and a return duct (9, 11; 29, 31) leading separated solid material to the reactor chamber and from which vortex chamber gas is discharged from one or both ends, c h a r a c t e ¬ r i z e d in that one discharge opening (8, 28) for separated solid material is disposed by the inlet opening (6, 26) for gas and an other (10, 30) by the discharge opening (7, 27) for purified gas at a distance from the inlet opening in the longitudinal direction of the vortex chamber (3, 23) . 2. A circulating fluid.ized bed reactor as claimed in claim 1, c h a r c t e r i z e in that one discharge opening (8) for separated material has been disposed at one end (12) of the vortex chamber and the other (10) at its other end (13) . 3. A circulating fluidized bed reactor as claimed in claim 1 or 2, c h a r a c t e r i z e d in that the vortex chamber (3, 23) is disposed on top of the reactor chamber (2, 22). 4. A circulating fluidized bed reactor as claimed in claim 3, c h r a c t e r i z e d in that the width (L) of the vertex chamber (3, 23) is greater than the width (1) of the reactor chamber (2?) . 5. A circulating fluidized bed reactor aε claimed in claim 4, c h a r a c t e r i z e d in that the vortex chamber (23) reaches at least partly over a convection part (24) disposed beside the reactor chamber (22) .

Inventors: ARPALAHTI OLLI, ARPALAHTI, OLLI
Applicants: AHLSTROEM OY, A. AHLSTROM CORPORATION
Application year: 1987
Main classification: B01J8
IPC codes: B01J8, B04C3, F23C10