Patent Application
20130277399
This application claims the priority of German Patent Application, Serial No. 10 2012 206 590.3, filed Apr. 20, 2012, pursuant to 35 U.S.C. 119(a)-(d), the content of which is incorporated herein by reference in its entirety as if fully set forth herein.
The invention relates to a method for operating a cellular wheel sluice. Furthermore, the invention relates to a cellular wheel sluice for carrying out the method.
Cellular wheel sluices also known as rotary feeders or rotary valves in various configurations are known from the prior art, for example from DE 40 38 237 A1, DE 298 19 748 U1, EP 0 082 947 A1, DE 34 32 316 A1, DE 198 04 431 A1 and EP 1 879 827 A2.
An object of the present invention is to develop an operating method for a cellular wheel sluice in such a way that at a given dimensioning of the cellular wheel sluice, its throughput is increased, or in that a predetermined throughput can be achieved with a cellular wheel sluice that is smaller in dimension.
This object is achieved according to the invention by an operating method having the method steps:
Tests have shown that by applying a pressure drop from top to bottom and operating the cellular wheel sluice at a higher peripheral speed, the rotational speed, at which a throughput maximum of the cellular wheel sluice is achieved at otherwise given boundary conditions, is significantly increased in comparison to an operation without a pressure drop or an operation with a reversed pressure drop. An increase in the peripheral speed in these pressure conditions therefore does not lead, and this is very surprising, to a reduction in the throughput, but to a throughput increase. A limit peripheral speed at given pressure and dimension ratios of a specific cellular wheel, depending on the pressure drop between the feed shaft and the outlet shaft, leads to greater peripheral speeds. As extensive test series of the Applicant have shown, the output, which is thus pressure-assisted, from the cellular wheel sluice leads to a displacement of a throughput maximum or an output maximum toward higher rotational speeds. The speed of the outer periphery of the cellular wheel, in other words the product of the cellular wheel outer periphery and the rotational speed, may be greater than 0.62 m/s, may be greater than 0.65 m/s, may be greater than 0.7 m/s, may be greater than 0.8 m/s, may be greater than 0.9 m/s, may be greater than 1.0 m/s, may be greater than 1.1 m/s, may be greater than 1.2 m/s, may be greater than 1.3 m/s, may be greater than 1.5 m/s or may even be greater still and. for example, be 1.8 m/s or 2.0 m/s. This speed is also called the tangential speed. The pressure difference between the feed shaft and the outlet shaft may be in the region of 1 bar and may alternatively, to apply an excess pressure to the feed shaft, also be achieved, for example, in that a negative pressure is applied to the outlet shaft. The pressure difference may be 1 bar, but may also be greater than 1 bar, which is achieved by applying an excess pressure at least at the feed shaft. The pressure drop may be 2 bar, may be greater than 2 bar, may be 3 bar, may be greater than 3 bar, may be 4 bar, may be greater than 4 bar, may be 5 bar, or may be still greater than 5 bar. Such modes of operation may be present in reactor output sluices and, for example, in typical applications, such as an output from pressure-loaded fluidized bed dryers, pressure rotary filters or pressure filters, as used, for example, in a PTA wet cake process. The advantages of a cellular wheel sluice of this type come to the fore, in particular, for example, in conjunction with a PTA wet cake process, in other words in a method for producing terephthalic acid (PTA), which is described, for example, in WO 00/71226 A1 or JP 11 179 115 A. A corresponding operating method can also be used in the output in lignite drying and in the output of beet pulp from a fluidized bed dryer or in the output of mineral substances from pressure filters. Because of the pressure drop, the advantage is also produced that in a cellular wheel sluice operated in this manner, products can also be conveyed which are poorly or scarcely free-flowing, for example slurry-like or highly viscous and sticky products.
The advantages of a cellular wheel sluice for carrying out the method according to the invention, wherein when applying the pressure drop in the feed shaft, a pressure is applied, which is higher than normal pressure, correspond to those which have already been described above with reference to the operating method. The cellular wheel sluice is rotatable about a horizontal axis and thus, in the assembled state, has a drive shaft, which runs horizontally.
Parameter conditions comprising a ratio of:
Cellular wheel variants comprising laterally open intermediate spaces between the cellular wheel vanes, and cellular wheel side discs, which cover at least a portion of a cellular wheel cross section and are non-rotatably connected to the cellular wheel vanes, are particularly suitable depending on the area of use and the environmental requirements. Side disc-free cellular wheels, which are also called open cellular wheels, can be used, in particular, for powder conveyance. Cellular wheels with side discs, which can laterally cover a part or the entire diameter of the cellular wheel, can be used, in particular, when conveying wear-intensive products.
An eccentricity, in which a longitudinal axis of the cellular wheel drive shaft does not coincide with a cylinder axis of the cellular wheel housing portion, allows a compensation of forces weighing on the cellular wheel during operation. This applies, in particular, to an eccentricity, in which the longitudinal axis is displaced toward the feed shaft relative to the cylinder axis. The eccentricity may be in the range between 10 μm and 500 μm and may, for example, be 20 μm, 50 μm, 100 μm, or 200 μm.
A ratio Deff/C of a diameter of an inner cell limitation on the drive shaft side and a cellular wheel diameter in a range between 0.3 and 0.8 has proven to be particularly suitable for conveying specific conveyed media. The ratio Deff/C may be in the range between 0.4 and 0.7 and may be in the range between 0.5 and 0.6. Cellular wheels of this type, which are also called compartmentalized cellular wheels, can be used, in particular, in the case of moist, slurry-like, highly viscous or sticky products. In the case of such products, it is also advisable to configure the cells with faces that are as large as possible and free of hindrances. The chambers may then be smooth-walled and without projecting assembly components toward the shaft axis, in other words optionally in the direction of the compartmentalized area, and in the region of the cellular wheel vanes.
An embodiment of the invention will be shown in more detail below with the aid of the drawings
A cellular wheel sluice 1 has a housing 2, which is upwardly limited in
The cellular wheel housing bore 4 has the form of a hollow cylinder lying transversely in
The cellular wheel 10 is side disc-free. The sector-shaped cellular wheel chambers separated from one another by cellular wheel webs or cellular wheel vanes 11 in the peripheral direction about the longitudinal axis 9, in other words the cells, are laterally limited by the housing side covers 6, 7 and the cellular wheel 10 has laterally open cellular wheel chambers between the cellular wheel webs 11. The housing side covers 6, 7 are therefore end face limitations of the cellular wheel housing bore 4.
In an alternative configuration, not shown, of the cellular wheel sluice 1, which is indicated in
The cellular wheel housing bore 4 forms an interior of the cellular wheel sluice 1, through which conveyed product is conveyed from the feed shaft 3 to the outlet shaft 5 by means of rotation of the cellular wheel 10.
The cellular wheel 10 is non-rotatably or torque proof connected to a cellular wheel drive shaft 12, which is driven by a drive motor 12a. A shaft stub 13, which axially continues the cellular wheel drive shaft 12 and is therefore part of the drive shaft, of the cellular wheel 10 is mounted in a shaft receiver or a shaft bearing 14 by means of an axial/radial bearing. The shaft can also be repeatedly stepped in terms of its diameter, between the drive shaft 12 at the axial height of the cellular wheel vanes 11 and the shaft stubs 13 on both sides. Between the axial/radial bearing and the cellular wheel housing bore 4, the cellular wheel drive shaft 12, 13 is sealed against the housing side cover 7 by means of a seal assembly, which comprises a seal and a flushing gas line, which is not shown in more detail in the schematic
At the transition of the feed shaft 3 to the housing bore 4, in other words to the cellular wheel housing portion, the housing 2 has cellular wheel feed cross section 20, which is rectangular, projected onto a plane and, parallel to the cylinder axis 9, has a cross sectional dimension A and a cross sectional dimension B perpendicular to this cross sectional dimension A (cf.
A diameter of the cellular wheel 10 has the value C. The ratio of the minimum feed diameter and the cellular wheel diameter, DÄ/C, is in the range between 0.7 and 1.3.
The ratio between the diameter D (cf.
The diameter of the shaft in a central cellular wheel body portion, where the shaft 12 passes through the housing 2, may differ from the diameter in the region of shaft end portions or shaft stubs. This diameter of the shaft 12 between the end portions may, in particular step-wise, be greater than a diameter D at the transition to the cellular wheel body shaft portion. The shaft diameter D, where maximum torques act on the shaft 12, is to be used there for the above parameter ratio D/C. This is generally the case at the transition of the shaft 12 into the cellular wheel body.
The longitudinal axis 9a of the cellular wheel drive shaft 12, in other words the rotational axis, about which the cellular wheel 10 rotates, does not coincide with the cylinder axis 9 of the cellular wheel housing portion 4. The detailed enlargement according to
The eccentricity E is thus such that the rotational axis is displaced toward the feed shaft 3 relative to the cylinder axis 9.
During operation of the cellular wheel sluice 1, a pressure drop is firstly applied, a higher pressure being present in the feed shaft 3 than in the outlet shaft 5. The pressure difference may be in the region of 1 bar, may be greater than 1 bar, may be greater than 2 bar, may be greater than 3 bar, may be greater than 4 bar, may be 5 bar, may be greater than 5 bar, may be greater than 6 bar or may even be still greater. For example, the feed shaft 3 may be placed under a pressure of 5 bar, while the outlet shaft 5 is operated at normal pressure, so a pressure difference of 4 bar is present between the feed shaft 3 and the outlet shaft 5. The outlet shaft 5 may also be placed under negative pressure, the feed shaft 3 then being able to be operated under normal pressure conditions, so a pressure difference of less than 1 bar is present.
The product is then conveyed by the cellular wheel sluice 1, in particular bulk goods in the form of a granulate or a powder or another free-flowing product. Even poorly free-flowing products, in particular moist, slurry-like, highly viscous or sticky products, can be conveyed by the cellular wheel sluice 1 operated in this manner. During the product conveyance between the feed shaft 3 and the outlet shaft 5, the cellular wheel 10 is operated at a rotational speed in such a way that an outer periphery of the cellular wheel, in other words radial outer edges 21 of the cellular wheel webs 11, reaches a speed, which is greater than 0.6 m/s. This speed may be greater than 0.8 m/s, may be greater than 1.0 m/s, may be greater than 1.5 m/s or may even be still greater.
The pressure difference between the feed shaft 3 and the outlet shaft 5, together with the gravitational force, assists the conveyance of the product by the cellular wheel 10. The output of the product from the respective opening cellular wheel chamber into the outlet shaft 5, assuming a corresponding seal of the cellular wheel webs 11 against the housing 2, takes place at a substantially abrupt pressure relief, the product present in this chamber being ejected into the outlet shaft 5. The entry of the product from the feed shaft 3 into the opening cellular wheel chamber is also assisted by the pressure difference, as the product is pressed into the opening cellular wheel chamber.
In a view similar to
The housing 2 of the cellular wheel sluice 22, in housing walls, which limit the housing bore 4, has channels 23, which can be used to guide a heat transfer medium to control the temperature of the housing 2.
In the cellular wheel sluice 22, an effective diameter Deff of the cellular wheel drive shaft 12 is enlarged by additional cell walls 24 on the shaft side, which are partition wall limitations of the cells. Sector-like cavities 25, which do not contribute to the product conveyance, remain between the cell walls 24 and the actual cellular wheel drive shaft 12. The ratio Deff/C may be in the range between 0.3 and 0.8, between 0.4 and 0.7 and between 0.5 and 0.6.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2012 206 590.3 | Apr 2012 | DE | national |
