Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B07—SEPARATING SOLIDS FROM SOLIDS; SORTING
  • B07B—SEPARATING SOLIDS FROM SOLIDS BY SIEVING, SCREENING, SIFTING OR BY USING GAS CURRENTS; SEPARATING BY OTHER DRY METHODS APPLICABLE TO BULK MATERIAL, e.g. LOOSE ARTICLES FIT TO BE HANDLED LIKE BULK MATERIAL
  • B07B7/00—Selective separation of solid materials carried by, or dispersed in, gas currents
  • B07B7/08—Selective separation of solid materials carried by, or dispersed in, gas currents using centrifugal force
  • B07B7/083—Selective separation of solid materials carried by, or dispersed in, gas currents using centrifugal force generated by rotating vanes, discs, drums, or brushes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B07—SEPARATING SOLIDS FROM SOLIDS; SORTING
  • B07B—SEPARATING SOLIDS FROM SOLIDS BY SIEVING, SCREENING, SIFTING OR BY USING GAS CURRENTS; SEPARATING BY OTHER DRY METHODS APPLICABLE TO BULK MATERIAL, e.g. LOOSE ARTICLES FIT TO BE HANDLED LIKE BULK MATERIAL
  • B07B11/00—Arrangement of accessories in apparatus for separating solids from solids using gas currents
  • B07B11/04—Control arrangements

Definitions

• the invention relates to a method (according to the preamble of claim 1) and an air classifier (corresponding to the preamble of claim 4) for classifying comminuted feed material (visible material).
• air classifiers of the required type are known in practice in various embodiments. These air classifiers are so-called dynamic air classifiers, in which an approximately basket-shaped classifying rotor equipped on its outer circumference with sight strips or the like is rotatably mounted and driven within a classifier housing. Especially in the outer peripheral area, ie around the classifying rotor, an essentially ring-shaped classifying area is formed, which is usually still surrounded radially outwards by a guide vane ring.
• the viewing rotor which generally rotates about a horizontal or vertical axis, is adjoined on at least one rotor end face by a tubular exhaust duct for viewing air loaded with fine material.
• Visible air and feed material are introduced into the viewing area in a suitable manner. While the heavier coarse material essentially falls down and is drawn off via a corresponding coarse material collecting space, the fine material together with the classifying air is first passed through the rotor circumference into the interior of the classifying rotor and then from there through at least one end face using a corresponding negative pressure into the extraction duct and dissipated from there into a corresponding separator or filter device.
• the fineness of the fine material discharged with the visual air flow that as fine material can be deducted, can be adjusted in a correspondingly large range by the speed of the classifying rotor and / or by regulating the quantity of classifying air.
• annular sealing air sealing zones are also provided in the transition area from the corresponding end face of the classifying rotor to the fixed exhaust duct, into which sealing air is introduced in such an amount and at such a pressure that a bypass flow is created can be suppressed as far as possible and preferably completely from the viewing space into the discharge duct. In this way, it should be deliberately prevented that large grain or semolina portions with this bypass flow can get into the extraction duct for classifying air and fine material, in order to achieve a relatively high fineness.
• cements are ground with a material bed roller mill or a grinding plant or grinding process containing a roller mill, have a higher water requirement than cements which are produced, for example, in ball mill grinding plants.
• the consequence of this higher water demand is already known that cements are ground with a material bed roller mill or a grinding plant or grinding process containing a roller mill, have a higher water requirement than cements which are produced, for example, in ball mill grinding plants. The consequence of this higher water demand
• the fineness of cement, blast furnace powder or the like is usually specified as a mass-related surface in Blaine (cm / g). The higher this
• the fineness is, the greater the strength of the concrete and mortar made from it.
• the grain size and water absorption capacity of the cement and thus strength and workability can be coordinated.
• the finished product (fine goods overall) is also to be adapted to the quality standard which is produced in grinding plants with ball mills with regard to its processing behavior and strength development (cf. EP-A-0 406 591).
• EP-A-0 406 591 the quality standard which is produced in grinding plants with ball mills with regard to its processing behavior and strength development.
• the invention is therefore based on the object
• the method according to the preamble of claim 1 and a wind sifter according to the preamble of claim 4 further improve such that the grain size distribution and thus the grain range in the fine material or finished product can be set in a reliable manner and with relatively little design effort within a sufficiently large scope.
• An essential idea of the present invention is seen in the fact that the particle size distribution in the discharged fine material, which can be drawn off as a finished product, with the aid of a variable size flowing from the visible space into the extraction channel (for the mixed air and fine material mixture) and with classifier feed material or classifier grit (Bypass material) loaded bypass stream is adjusted in that the size of this bypass stream is controlled by a very targeted adjustment of the sealing air supply in its amount.
• the sealing air is blown into the ring sealing zone between the classifier rotor and the fixed exhaust duct quite deliberately only to ensure that preferably no bypass flow and thus no spray grain (ie classifier material) or sifting) into the discharge channel for the classifying air / fine material mixture, according to the present invention, with the help of the sealing air supply, it is ensured that a selectable proportion of the bypass flow loaded with the so-called bypass material in such a quantity is introduced into the classifying air / fine material mixture in the discharge duct that the grain size distribution width of the fine material or finished product can be controlled in the manner required in each case.
• This control of the grain size distribution range (grain range) in the fine material can be carried out extremely reliably and reproducibly. Since for this control only the sealing air supply has to be adjusted in its air quantity and / or in its air pressure, this classification can be carried out in a single wind sifter, ie it can be arranged in view of the known design according to EP-A-0 406 591 at least two classifying units or air classifiers connected in parallel are dispensed with, which means a considerable reduction in the technical complexity of the plant.
• This method according to the invention can be used in a particularly advantageous and very targeted manner with high product finenesses, nevertheless an optimum grain size distribution or distribution width can be set for the respective intended use of the fine material or finished product, i.e. it is also possible to achieve an optimal compromise with regard to the quality properties of the product, that is to say between the standard compressive strength and the processability of the finished product, for example cement.
• the amount of sealing air supplied can be set in a range between approximately 5 and 25%, preferably between approximately 10 and 20%, of the amount of visible air supplied to the viewing area. This is useful at relatively low Fineness of the fine material a smaller amount of sealing air and with higher fineness of the fine material (finished product) a larger amount of sealing air.
• the pressure level of the sealing air supplied is controlled in accordance with the classifier load and the static pressure in the exhaust duct (behind the classifying rotor) for the classifying air-fine material mixture. In this way, it can be ensured in a suitable and sufficient manner that the pressure loss in the discharge duct is overcome by the sealing air or sealing air quantity supplied.
• the pressure loss in the fume channel is mainly due to the fine material loading of the classifying air, the classifying air quantity, the rotor speed and the like. is dependent, whereby a high load, a large amount of visible air and a high rotor speed lead to a high pressure loss and vice versa.
• An air classifier designed according to the invention is characterized in that one with the sealing air supply cooperating control device for adjusting the grain size distribution in the discharged fine material is provided, a bypass guide connecting the visible space with the exhaust duct via the ring seal and the sealing air supply connected to the ring seal with respect to sealing air pressure and / or quantity being controllable in such a way that a bypass guide Bypass flow of controllable size, starting from the viewing area and loaded with spraying grain, can be introduced into the discharge duct for the mixture of air and fine material.
• Fig. 2 to 4b greatly simplified detailed views in vertical section (similar cut as Fig.l) for different versions in the transition area of the view rotor to the flue or in the area of a ring seal,
• the wind sifter 1 illustrated in a simplified and very schematic manner in FIG. 1 is a dynamic high-performance sifter, of which, however, essentially only the sifter parts necessary to explain the present invention are illustrated.
• This air classifier 1 is used for classifying previously comminuted goods, ie feed material or viewing material, in at least two grain fractions (coarse and fine) used.
• a classifying rotor 3 is arranged in an outer classifier housing 2, which can be driven via a drive shaft 4 by a suitable drive 5 with a preferably adjustable speed.
• This exemplary embodiment according to FIG. 1 is an air classifier 1 with a vertical axis 1 a, which coincides with the vertical axis of rotation of the rotor 3.
• the rotor 3 is rotatably mounted essentially centrally in the upper end of the classifier housing 2.
• the classifying rotor 3 is surrounded by classifying air (continuous arrows 6) and feed material or classifying material (thin dashed arrows 7), which is preferably - as known per se - delimited radially outwards by an outer vane ring 9.
• a coarse material collecting space 10 for collecting and removing the coarse material falling downwards in the viewing space (arrows 11 shown in thick lines).
• the upper end face (end face) 3a of the viewing rotor 3 is adjoined by a fixed extraction duct 12 which, as will be explained in more detail later, for extracting or suctioning off the viewing air stream laden with fine material (dashed arrows 13) (solid arrows 6a) is determined and is connected to a separating or filtering device which is not illustrated in any more detail (since the general prior art).
• a circumferential ring seal 14 is formed, which is connected to a sealing air supply or sealing air supply device 15.
• the fineness of the finished product 13 can in principle be set in a manner known per se by the speed of the classifying rotor 3 and / or by regulating the quantity of classifying air.
• measures are provided to set or control the grain size distribution in the discharged fine material (dashed arrow 13) in a targeted manner.
• a control device 16 which cooperates with the sealing air supply 15 in a suitable manner in the sense of adjusting the grain size distribution in the fine material 13 being discharged.
• the visible space 8 is connected to the exhaust duct 12 via the ring seal 14 by a bypass guide, through which a bypass flow emanating from the visible space 8 and loaded with spray particles (coarse material or semolina content) corresponds to the dash-dot-dot arrows 17 (Fig.l) can flow into the drain channel 12.
• this ring seal 14 can be designed in a relatively simple manner so that in any case a maximum permissible large bypass flow 17 and thus a sufficiently large amount of spray grain can get from the viewing space 8 into the extraction duct 12.
• the sealing air supply 15 contains a sealing air blower 18, which can be regulated 5 in its supply quantity (sealing air quantity) and / or in the pressure level (pressure of the sealing air) by the control device 16.
• the sealing air supply 15 connected to the ring seal 14 can be regulated with regard to sealing air pressure and / or sealing air quantity in such a way that the bypass flow 17 which emanates from the sighting space 8 and is loaded with spray particles is bypass flow 17
• the sealing air supply 15 has a lower end of the trigger - 5 channels 12 ring-shaped main supply line 19 and a plurality of branching-off branch air lines 19a branched from it, which extends over the circumference of the main supply line 19 and at the same time also the ring seal 14 uniformly distributed and subsequent to this ring seal 14 'are 0 closed so that they open out in a suitable manner in this ring seal fourteenth
• the sealing air is symbolized by dash-dotted arrows 20.
• the ring seal 14 can be of relatively simple design, as can also be seen in FIG. 1.
• the ring seal 14 can only be an annular, fixed sealing element 14a fastened to the inner wall of the fixed extraction duct 12 and one on the top. ' Ren face 3a of the viewing rotor 3 attached, annular rotating sealing element 14b, wherein the fixed sealing element 14a
• the ring seal 14 can also be varied in accordance with the respective requirements of the air classifier 1 with a previously essentially identical basic structure, by using a fixed and / or rotating sealing element, a more or less strong air deflection or single or multiple air deflection and if necessary, a design in the manner of a labyrinth seal, in which the various sealing elements are interlocked, can be constructed, the detailed representations in FIGS. 2, 3, 4a and 4b show. Since the representations in these fi speak for themselves, they need no further explanation.
• this wind sifter 1 is optimally suitable for carrying out the method according to the invention described above.
• the exemplary embodiment illustrated in FIG. 1 can in principle be modified in various ways, as is known per se in the case of such dynamic classifiers with a basket-shaped classifying rotor, without the invention - 25 principle. It is also conceivable, for example, that the discharge channel for the classifying mixture of fine air and fine material does not connect to the upper end face or to the upper end end of the classifying rotor 3, but rather to the lower end face.
• the classifying air and fine material mixture assign both the upper end and the lower end face of the sifting rotor per a discharge channel for a part, however, in which case to arrange a corresponding blocking air supply in each transition region, while the classifying rotor could furthermore be divided into an upper rotor part and a lower rotor part or could also be formed by two separate rotor parts which adjoin one another coaxially.
• the last-mentioned embodiment variant is suitable for particularly high throughput rates. While an example is illustrated in FIG.
• the air classifier 1 in which the air classifier 1 can be arranged directly above a roller mill or roller mill or at the upper end of a common feed channel for classifying air and feed material, the air classifier according to the invention can in principle be used as a separate one Be designed as a unit and also have separate feeds for classifying air and feed material into the classroom.
• FIG. 5 shows an RRSB diagram which shows the grain size distributions which resulted in three typical classification tests which resulted, among other things, in the tests on which the invention is based.
• the grain size distributions of these three tests are 5 illustrates in the RRSB diagram according by the curves I, II and III, wherein on the abscissa the particle size x in / in, and), the ordinate represents the residue (sieve residue) in mass
• experiment I no sealing air supply was used.
• experiment II a sealing air volume of 300 m J / h, ie a share of 10% of the visible air volume, was used, while in experiment III with a sealing air volume of 600 m 3 / h, ie 15% of the visual air volume (400 m / h) was worked.
• the amount of visible air was the same at 3,000 m 3 / h, in experiment III it was 4,000 irr / h.
• Distribution range in the withdrawn fines or finished product can be controlled in a relatively wide range. According to this, it is also easy to imagine that if the bypass flow mentioned is completely prevented (by a correspondingly large supply of sealing air), the fine material can obtain an even greater fineness as a result of sharp sighting, but that the corresponding curve or the corresponding pitch n is still corresponding would be steeper than curve III in FIG. 5. This last-mentioned state of affairs makes it even clearer that the particle size distribution width in the finished product can be adjusted within a particularly wide range by using the classification method according to the invention.

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• Combined Means For Separation Of Solids (AREA)
• Processing And Handling Of Plastics And Other Materials For Molding In General (AREA)
• Sorting Of Articles (AREA)

Applications Claiming Priority (3)

Publications (2)

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Family Applications (1)

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• 1999
  • 1999-09-23 DE DE19945646A patent/DE19945646A1/de not_active Withdrawn
• 2000
  • 2000-09-04 AU AU70012/00A patent/AU7001200A/en not_active Abandoned
  • 2000-09-04 ES ES00958521T patent/ES2194768T3/es not_active Expired - Lifetime
  • 2000-09-04 WO PCT/EP2000/008629 patent/WO2001021328A1/fr active IP Right Grant
  • 2000-09-04 AT AT00958521T patent/ATE241434T1/de not_active IP Right Cessation
  • 2000-09-04 EP EP00958521A patent/EP1214155B1/fr not_active Expired - Lifetime
  • 2000-09-04 DE DE50002386T patent/DE50002386D1/de not_active Expired - Fee Related
  • 2000-09-04 DK DK00958521T patent/DK1214155T3/da active
  • 2000-09-04 US US09/937,861 patent/US6644479B1/en not_active Expired - Fee Related

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