Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D45/00—Separating dispersed particles from gases or vapours by gravity, inertia, or centrifugal forces
  • B01D45/12—Separating dispersed particles from gases or vapours by gravity, inertia, or centrifugal forces by centrifugal forces
  • B01D45/16—Separating dispersed particles from gases or vapours by gravity, inertia, or centrifugal forces by centrifugal forces generated by the winding course of the gas stream, the centrifugal forces being generated solely or partly by mechanical means, e.g. fixed swirl vanes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B04—CENTRIFUGAL APPARATUS OR MACHINES FOR CARRYING-OUT PHYSICAL OR CHEMICAL PROCESSES
  • B04C—APPARATUS USING FREE VORTEX FLOW, e.g. CYCLONES
  • B04C3/00—Apparatus in which the axial direction of the vortex flow following a screw-thread type line remains unchanged ; Devices in which one of the two discharge ducts returns centrally through the vortex chamber, a reverse-flow vortex being prevented by bulkheads in the central discharge duct
  • B04C3/06—Construction of inlets or outlets to the vortex chamber
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B04—CENTRIFUGAL APPARATUS OR MACHINES FOR CARRYING-OUT PHYSICAL OR CHEMICAL PROCESSES
  • B04C—APPARATUS USING FREE VORTEX FLOW, e.g. CYCLONES
  • B04C3/00—Apparatus in which the axial direction of the vortex flow following a screw-thread type line remains unchanged ; Devices in which one of the two discharge ducts returns centrally through the vortex chamber, a reverse-flow vortex being prevented by bulkheads in the central discharge duct
  • B04C2003/003—Shapes or dimensions of vortex chambers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B04—CENTRIFUGAL APPARATUS OR MACHINES FOR CARRYING-OUT PHYSICAL OR CHEMICAL PROCESSES
  • B04C—APPARATUS USING FREE VORTEX FLOW, e.g. CYCLONES
  • B04C3/00—Apparatus in which the axial direction of the vortex flow following a screw-thread type line remains unchanged ; Devices in which one of the two discharge ducts returns centrally through the vortex chamber, a reverse-flow vortex being prevented by bulkheads in the central discharge duct
  • B04C2003/006—Construction of elements by which the vortex flow is generated or degenerated

Definitions

• the object of the present invention is an axial cyclonic apparatus for the abatement of particulate matter and sparks from a gaseous flow and a smoke suction system of a metallurgical furnace equipped with such cyclonic apparatus .
• axial cyclones are used to separate solid particulate matter from a gaseous flow by means of centrifugal force.
• One type of axial cyclone provides for the particulate matter to be removed from the cyclone through peripheral openings in a cylindrical portion of the cyclone's mantle. The particulate matter coming out of these openings is collected in a hopper outside the flow of passage of the cyclone.
• These cyclones may have different variants that provide the possibility of introducing convergents and/or divergent s along the flow. Examples of such cyclones are described for example in European Patent EP0210910A2 and in US Patent US7320718B2.
• the cyclone is equipped with a divergent portion D that connects to the peripheral annular chamber C. Due to the swirling motion imparted by the axial vaned body G at the entrance of the cyclone, the particulate matter tends to migrate radially outwards by entering this annular chamber C, while the gaseous flow (free of particulate matter) enters the axial outlet duct B.
• This annular chamber C is closed downstream in a longitudinal direction (i.e. in the outlet direction) with a perforated circular part that typically connects with four truncated pyramid walls forming a volume such as to collect dust.
• the chamber is equipped with at least one large radial opening E fluidically connected to a particulate matter collection hopper, which ends in a discharge or sealing member such as a rotary valve. This prevents the accumulation of particulate matter inside the cyclone.
• Hoppers are typically radial for horizontal axis cyclones. If the cyclone is installed with a vertical axis, there are one or more side hoppers obtained by extending the larger cylindrical portion. For inclined axis cyclones, single radial or lateral hoppers are usually used depending on the inclination of the axis.
• Circular inlet A and outlet ducts B of cyclones generally have the same diameter.
• the diameters are selected to have an input speed greater than the minimum pick-up velocity of the coarsest particles. This avoids frequent cleaning and limits the velocity to avoid excessive pressure drop.
• the aforesaid input speed values to the cyclone are typically between 18 and 25 m/sec. Assuming that the smokes have a density similar to air and therefore typically around 1 kg/m3, the dynamic pressure at the cyclone inlet is between 160 and 320 Pascal. Considering that a medium- size system treats 1,000,000 m3/h, if the pressure drop is reduced by at least 0.5 dynamic pressures, in-line blowers could continuously save at least 25-50 kWh for every hour of operation. This pressure drop reduction is not, however, achievable in known axial cyclonic apparatuses .
• the separation efficiency is not affected by the selection of the velocity.
• the inlet vanes impart a very high turbulence so as to cause pressure drops in the cyclone even higher than 1000 Pascal .
• the ratio between the outer diameter of the annular end chamber C and the diameter of the inlet duct A is between 1.3 and 1.7, so as to have a sufficient volume to contain any obstruction .
• the vaned body G at the inlet has a number of vanes between 6 and 16.
• the vanes have an angle of attack of smokes parallel to the cyclone axis, i.e. equal to 0°, and an angle of detachment between 40° and 60°.
• the inlet vanes rarely consist of flat surfaces, but rather in most cases of surfaces partly or totally calendared in order to better impart the rotational motion to the fluid in the cyclone.
• double-curved vanes are not used for economic reasons .
• the support drum of the vaned body G may assume dimensions up to 0.4-0.45 diameters relative to the diameter of the inlet pipe A.
• the vane bodies lack a drum, as represented in US 7320718 B2.
• the elimination of the central drum complicates the construction of the vaned body, increasing the weight thereof, without bringing significant benefits.
• vanes of any rectifier F at the outlet are radial, i.e. they have an angle of attack and angle of detachment equal to 0°.
• This rectifier F in turn may have a drum, with a diameter of up to 0.3 times the inlet diameter .
• the main purpose of the present invention is to eliminate all or part of the drawbacks of the aforementioned technique, providing an axial cyclonic apparatus for the abatement of particulate matter and sparks from a gaseous flow that, with the same operating conditions and separation efficiency, allows one to significantly reduce pressure drops.
• a further aim of the present invention is to provide an axial cyclonic apparatus for the abatement of particulate matter and sparks from a gaseous flow that, with respect to traditional axial cyclones, has comparable system costs.
• Figure 1 shows a longitudinal cross-sectional view of an example of a traditional axial cyclone
• FIG. 2 shows a perspective view of an axial cyclonic apparatus according to a preferred embodiment of the present invention, with some parts removed to better highlight others;
• Figure 3 shows a perspective view of a cross- section of the cyclonic apparatus shown in Figure 2, conducted in a longitudinal centerline plane;
• Figure 4 shows an orthogonal view of the same section as shown in Figure 3.
• FIG. 5 shows a simplified diagram of a smoke suction plant of a metallurgical furnace equipped with an axial cyclonic apparatus according to the present invention .
• the axial cyclonic apparatus 1 comprises:
• first vaned body 4 which is equipped with a plurality of first vanes 41 and is arranged near the aforesaid inlet opening 2 coaxially thereto.
• the first vanes 41 of the aforesaid first vaned body 4 are adapted to impart a centrifugal radial component to the incoming axial gaseous flow. To the incoming gaseous flow is thus imparted a radial swirling motion to the gaseous flow, so that by centrifugal action, the particulate matter tends to abandon the gaseous flow.
• the aforesaid outlet duct 2 extends coaxially at least partially within the aforesaid mantle 10 and delimits with an end portion 12 of such mantle a peripheral annular chamber 20 for the interception of the particulate matter which separates itself from the gaseous flow.
• This peripheral annular chamber 20 is closed downstream in a longitudinal direction and is radially communicating with a particulate matter collection chamber 21.
• the peripheral annular chamber is equipped with at least one large radial opening 23 fluidically connected to a particulate matter collection hopper, which ends in a discharge or sealing member such as, for example, a rotary valve. This prevents the accumulation of particulate matter within the cyclonic apparatus .
• the aforesaid containment mantle 10 comprises a truncated- cone portion 11 axially divergent relative to the direction of the gaseous flow, which connects the inlet opening 2 to the aforesaid end portion 12 of the mantle that externally defines the peripheral annular chamber 20.
• the end portion 12 of the mantle has a cylindrical section .
• the aforesaid divergent truncated-cone portion 11 forms, with the axial direction X, an angle of divergence d between 5° and 15°.
• the aforesaid first vaned body 4 is arranged at the divergent truncated-cone portion 11.
• the aforesaid first vanes 41 each form an angle of detachment between 40° and 50° with respect to the aforesaid axial direction X.
• the axial cyclonic apparatus 1 therefore has significantly lower pressure drops relative to an analogous axial cyclonic apparatus of the traditional type, being the operating conditions (in particular, velocity of the incoming gaseous flow) and separation efficiency equal.
• the axial cyclonic apparatus allows pressure drops to be reduced by at least 0.5 dynamic pressures relative to the apparatuses previously used.
• a possible physical explanation for this significant reduction in pressure drops is that, due to the invention, the turbulence of the gaseous flow at the first vaned body is reduced (in a surprising way) . This may be attributed to a lesser vane detachment of the incoming gas flow from the divergent portion 11 of the mantle 10, which consequently makes possible a lesser turbulent centrifugation of the gas flow induced by the first vanes 41.
• the aforesaid first vaned body 4 comprises a support drum 42 for the first vanes 41.
• the aforesaid support drum 42 is cylindrical, axially aligned with the axial direction X.
• the aforesaid support drum 42 is a truncated cone, divergent from the gas flow direction along the axial direction X. It has in effect been observed that this contributes to a further reduction of pressure losses in the area of the first vaned body.
• the aforesaid drum 42 forms an angle of divergence e not exceeding 10° with the axial direction X.
• the angle of divergence d of the divergent portion 11 is increased, it is preferable that the angle of divergence e is also increased.
• the ratio of the minimum diameter D4 of the support drum 42 of the first vaned body 4 and the diameter D2 of the inlet opening 2 is between 0.2 and 0.45.
• the minimum diameter D4 means the diameter of the drum in its upstream section. If the support drum 42 is cylindrical, the minimum diameter D4 means the (constant) diameter of the support drum.
• the aforesaid support drum 42 may be equipped in front with an ogive portion 43. This may help to guide the gas flow, avoiding vorticity at the entrance.
• the aforesaid ogive portion is a truncated cone and forms an angle w between 15° and 30° with the axial direction X.
• the aforesaid portion 43 may be kept entirely within the divergent truncated-cone portion 11 of the mantle 10, as illustrated in the accompanying Figures.
• this ogive portion 43 may also extend axially at least partially outside this divergent truncated-cone portion 11.
• the aforesaid first vanes 41 each form an angle of attack f of between 0° and 15° relative to said axial direction X.
• the aforesaid first vanes 41 of the first vaned body 4 are between 6 and 16 in number.
• the first vanes 41 may be calendared cylindrically or twisted by pressing.
• the first vanes 41 extend from the support drum 42 thereof to the divergent portion 11 of the mantle 10.
• the axial cyclonic apparatus 1 comprises a second vaned body 5, which is equipped with a plurality of second vanes 51, preferably curved, and is arranged coaxially within the aforesaid outlet duct 3.
• Such second vanes 51 are adapted to facilitate an axial rectification of the outgoing swirling gaseous flow.
• the aforesaid second vaned body 5 defines, therefore, a flow rectifier.
• the aforesaid second vaned body 5 comprises a support drum 52 for the second vanes 51.
• this support drum 52 is cylindrical, axially aligned with the axial direction X.
• the ratio between the diameter D5 of the (cylindrical) support drum 52 of the second vaned body 5 and the diameter D2 of the inlet apparatus 2 is between 0.2 and 0.3.
• the aforesaid second vanes 51 each form an angle of attack b between 30° and 50° relative to said axial direction X and preferably between 30° and 37.5°.
• the ratio between the angle of detachment of the first vanes 41 and the angle of attack b of the second vanes 51 is equal to 4:3.
• the aforesaid second vanes 51 each form an angle of detachment g of between 0° and 15° relative to the axial direction X.
• the aforesaid second vanes 51 of the second vaned body 5 are between 4 and 12 in number.
• the second vanes 51 extend from the relative support drum 52 to the inner wall of the outlet duct 3.
• the aforesaid outlet duct 3 is cylindrical, and is preferably fitted at the inlet with a guiding entryway 31.
• the ratio between the inner diameter D3 of the outlet duct 3 and the diameter D2 of the inlet opening 2 is between 0.9 and 1.1.
• the ratio between the outer diameter of the peripheral annular chamber 20 C and the diameter of the inlet opening 2 is between 1.3 and 1.7, so as to have a sufficient volume to contain any obstruction.
• the separation efficiency of the 500-micron particles was not less than 99%.
• the axial cyclonic apparatus 1 Compared to cyclone apparatuses with lower pressure drops (2 dynamic pressures), the axial cyclonic apparatus 1 according to the invention thus allows a reduction in pressure drops of 0.5 dynamic pressures.
• a reduction in pressure drops of at least 0.5 dynamic pressures leads to a savings in terms of power consumed by the blowers of at least 25-50 kWh per hour of operation. This is because the unspent pressure of 80-160 Pa relative to the best existing cyclones, reduces the total pressure imparted by the in-line blowers.
• the object of the present invention is also a smoke suction system of a metallurgical furnace, which comprises at least one axial cyclonic apparatus 1 according to the invention.
• a "metallurgical furnace” is generally understood to include any furnace capable of melting waste metals of the metal to be produced and/or from raw materials suitable for the purpose.
• FIG. 5 An example of a smoke suction system 100 of a metallurgical furnace according to the invention is shown in figure 5, where a metallurgical furnace (in particular an electric arc furnace) is indicated at 101, a sleeve filter at 102 and a chimney for introducing smokes into the atmosphere at 103.
• the primary smoke capture duct of the furnace 101 is indicated at 104, whereas the secondary smoke capture duct of the furnace 101 is indicated at 105.
• each of the smoke capture ducts 104 and 105 is equipped with an axial cyclonic apparatus for the abatement of particulate matter and sparks from the gaseous flow.
• the axial cyclonic apparatus arranged along the primary smoke capture duct 104 of the furnace 101 is an axial cyclonic apparatus 1 according to the invention.
• the axial cyclonic apparatus 106 arranged along the secondary smoke capture duct 105 of the furnace 101 may also be an axial cyclonic apparatus 1 according to the invention.
• the axial cyclonic apparatus for the abatement of particulate matter and sparks from a gaseous flow according to the invention allows to significantly reduce the pressure losses with respect to traditional cyclonic apparatuses, being the operating conditions and separation efficiency equal.
• the axial cyclonic apparatus further requires system costs substantially comparable to traditional axial cyclones.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Cyclones (AREA)

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• 2018
  • 2018-04-10 IT IT102018000004356A patent/IT201800004356A1/it unknown
• 2019
  • 2019-04-09 WO PCT/IB2019/052895 patent/WO2019197978A1/en not_active Ceased
  • 2019-04-09 EP EP19721391.1A patent/EP3773982A1/de not_active Withdrawn

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