MISSALLA, Michael (Kleine Schmieh 34, Oberursel, 61440, DE)
GILGEN, Rolf (Wiesbadener Strasse 141b, Königstein, 61462, DE)
ERLER, René-Arndt (Im Prüfling 33, Frankfurt, 60389, DE)
MISSALLA, Michael (Kleine Schmieh 34, Oberursel, 61440, DE)
GILGEN, Rolf (Wiesbadener Strasse 141b, Königstein, 61462, DE)
| Claims 1. An apparatus for the treatment of solids and/or gases, comprising a fluidized- bed reactor (1 ) in which the solids are fluidized by means of fluidizing gas and are thermally and/or chemically treated, and comprising a centrifugal separator (2) in which gas and solids are separated from each other, wherein the fluidized-bed reactor (1 ) is connected with the centrifugal separator (2) via a transfer duct (3), characterized in that the transfer duct (3) branches off from the fluidized-bed reactor (1 ) with a cross- section whose horizontal dimension is greater than the vertical dimension and that the cross-section of the transfer duct (3) expands downwards in vertical direction from the fluidized-bed reactor (1 ) to the centrifugal separator (2). 2. The apparatus according to claim 1 , characterized in that the lower boundary surface (4) of the transfer duct (3) is inclined downwards towards the centrifugal separator (2). 3. The apparatus according to claim 1 or 2, characterized in that the cross-section of the transfer duct (3) tapers in horizontal direction from the fluidized-bed reactor (1 ) towards the centrifugal separator (2). 4. The apparatus according to any of the preceding claims, characterized in that the cross-section of the transfer duct (3) is smaller at the inlet of the centrifugal separator (2) than at the outlet of the fluidized-bed reactor (1 ). 5. The apparatus according to claim 4, characterized in that the cross-section of the transfer duct (3) is smaller at the inlet of the centrifugal separator (2) than at the outlet of the fluidized-bed reactor (1 ) by the factor of 1.1 to 2.5. 6. The apparatus according to any of the preceding claims, characterized in that the transfer duct has a trapezoidal cross-section in vertical and/or horizontal direction. 7. The apparatus according to any of the preceding claims, characterized in that the centrifugal separator (2) is a recirculation cyclone of a circulating fluidized bed. |
The present invention relates to an apparatus for the treatment of solids and/or gases, comprising a fluidized-bed reactor in which the solids are fluidized by means of fluidiz- ing gas and are thermally and/or chemically treated, and comprising a centrifugal separator in which gas and solids are separated from each other, wherein the fluidized- bed reactor is connected with the centrifugal separator via a transfer duct.
Such apparatuses have long since been known for example for calcining solids (cf. EP 0 861 208 B1 ). In a fluidized-bed reactor the solids are treated with hot gases and calcined. The gas/solids mixture is discharged from the reactor via a transfer duct and separated in a centrifugal separator, in particular a cyclone, wherein the gases are withdrawn upwards and the solids are withdrawn downwards from the centrifugal separator. It was found out, however, that the formation of streaks at the inlet of the centrifugal separator has a negative influence on its segregation behavior.
In existing plants, the conduits merely were designed according to the requirements of the flow velocity at the inlet of the cyclone, whereas the formation of streaks was not taken into account.
US 6,322,601 for example describes an inlet conduit for a cyclone, which is defined by an extrados face and an intrados face, wherein the intrados face is curved such that tangents mentally applied thereto intersect the extrados face at certain points. With the curved shape of the intrados face solid particles should be directed onto the extrados face and into the cyclone, in order to improve the acceleration efficiency. For further optimization, the intrados face can include grooves for guiding the solids flow. The flow velocity should be optimized thereby. A formation of streaks in the upper part of the cyclone is, however, not avoided.
Measurements in existing plants with circulating fluidized bed have confirmed that the influence of the formation of streaks on the segregation behavior of the cyclone is not negligeable and chiefly depends on the formation of the inlet flow. Streaks which are formed in the upper part of the inlet conduit and therefore cover the uppermost boundary layer of the centrifugal separator must be avoided. Therefore, it is the object of the present invention to avoid the formation of a streak extremely loaded with solids in the upper region of the centrifugal separator.
In an apparatus as mentioned above, this object in particular is solved in that the transfer duct branches off from the fluidized-bed reactor with a cross-section whose horizon- tal dimension is greater than the vertical dimension and that the cross-section of the transfer duct expands downwards in vertical direction from the fluidized-bed reactor to the centrifugal separator.
As has already been mentioned, the design of the inlet duct into the centrifugal separa- tor is particularly important for its segregation behavior. Therefore, it is an essential aspect of the present invention to minimize the disadvantageous effect of the impulse directed upwards in solids systems delivering downwards. With the present invention, the effective length of the inlet duct is increased and the formation of the streak in the lower part of this duct thereby is supported. In addition, the construction height of the apparatus delivering upwards can be reduced with the present invention and in addition a reentry into the duct of the streak formed in the upper part of the cyclone can be prevented, which leads to a distinctly lower material wear.
To achieve a uniform flow, the lower boundary surface of the transfer duct is inclined downwards towards the centrifugal separator in accordance with a preferred aspect of the invention.
When, as provided in accordance with a preferred embodiment, the cross-section of the transfer duct is smaller at the inlet of the centrifugal separator than at the outlet of the fluidized-bed reactor, the velocity of the gas stream can be increased.
In accordance with a development of this invention, the cross-section of the transfer duct is smaller at the outlet of the fluidized-bed reactor than at the inlet of the centrifug- al separator by the factor of 1.1 to 2.5, in particular 1.2 to 1.8. The factor is calculated from the ratio (cross-section of the transfer duct at the outlet of the fluidized-bed reactor) / (cross-section of the transfer duct at the inlet of the centrifugal separator). Preferably, the cross-section of the transfer duct tapers in horizontal direction from the fluidized-bed reactor to the centrifugal separator.
In accordance with a development of the invention, the transfer duct has a trapezoidal cross-section in vertical and/or horizontal direction, whereby manufacture is facilitated.
The apparatus in accordance with the invention can be used for dedusting streams with a high solids load, e.g. in a calcining plant for the treatment of alumina. Preferably, the centrifugal separator is a recirculation cyclone of a circulating fluidized bed. However, a use of the apparatus in other centrifugal separators likewise is part of the invention.
Further developments, advantages and possible applications can also be taken from the following description of embodiments and the drawing. All features described and/or illustrated form the subject-matter of the invention per se or in any combination, independent of their inclusion in the claims or their back-reference.
Fig. 1 shows a schematic view of an apparatus in accordance with the invention.
Fig. 2 shows another schematic view of the apparatus in accordance with the invention.
The apparatus including the invention comprises a fluidized-bed reactor 1 and a centrifugal separator 2 configured e.g. as dedusting cyclone, which are connected with each other via a transfer duct 3. The outlet opening of the fluidized-bed reactor 1 is formed as a transverse slot, so that at its inlet the cross-section of the transfer duct 3 is greater in horizontal direction than in vertical direction. The outlet region of the fluidized-bed reactor 1 therefore is relatively flat with the same outlet area, so that the height of the fluidized-bed reactor 1 can be configured lower as compared to the conventional use of a rectangular, high transfer duct 3.
As can be taken from the Figures, the transfer duct 3 has a substantially trapezoidal cross-section both in horizontal and in vertical direction, with the width of the transfer duct 3 being reduced towards the centrifugal separator 3. In vertical direction, however, the transfer duct 3 is inclined downwards towards the centrifugal separator 2, so that its cross-section is increased. In general, the cross-section at the inlet of the centrifugal separator 2 is smaller by the factor of 1.8 to 1.2 than the cross-section at the outlet of the fluidized-bed reactor 1 , so that the gas velocity is raised.
By the design of the transfer duct 3 it is achieved that streaks are formed in the lower portion of the transfer duct 3, whereas the penetration of upwardly directed solids into the transfer duct 3 is minimized. A formation of streaks in the upper boundary layer of the centrifugal separator 2 is reliably avoided or reduced, and the separation properties of the centrifugal separator 2 are improved. In a non-illustrated manner, the solids can be recirculated from the centrifugal separator 2 into the fluidized-bed reactor 1 (circulating fluidized bed) or be supplied to another treatment stage. Via an opening 5, the gas stream is withdrawn from the top of the centrifugal separator 2. The present invention can be employed in all centrifugal separators to increase efficiency, especially in cyclones with high input loads, as they are used in fluidized-bed techology e.g. for calcining alumina, for dedusting in roasting plants, or the like. List of Reference Numerals fluidized-bed reactor centrifugal separator transfer duct lower boundary surface opening