WO2015142294A1

WO2015142294A1 - Collecting chamber and fiber formation method

Info

Publication number: WO2015142294A1
Application number: PCT/SI2014/000016
Authority: WO
Inventors: Marko PETERNELJ; Primož MIHALIČ; Brane ŠIROK
Original assignee: Izoteh D.O.O.
Priority date: 2014-03-17
Filing date: 2014-03-17
Publication date: 2015-09-24

Abstract

Collecting chamber and fiber formation method solve technical problems of formation of vortices and recirculations within collecting chamber of melt fiberization apparatus, bonding of fiber to walls of collecting chamber, presence of shot in primary layer of fiber deposited onto perimeter wall of collecting drum of collecting chamber, and non-uniform deposition of fiber into primary layer of fiber deposited onto perimeter wall of collecting drum of collecting chamber by slanting at least one wall or ceiling of a collecting chamber in order to reduce onset of vortices-and recirculation especially at high mass flow of fiber and high gradients of multi phase flow velocity. Further, by adding shot collectors amount of shot reducing heat transfer properties of fiber is reduced. In addition, adding slats for additional air inlet to further reduce vortices-and recirculation as well as adding balancing air flow induced by fan within drum assembly comprised of perforated surface is contributing to solution of technical problem at hand. Basic goals of proposed solution are: achieve high mass flow of fiber with low vortices and recirculation, and with minimum tear of primary layer of fibers collected on surface of collecting chamber drum assembly, and - separation of shot from fiber at the onset of fiber transport from a spinner.

Description

Collecting chamber and fiber formation method

Field of Technology Melt fiberization. Technical Problem

Homogene structure of primary layer of fiber deposited within melt fiberization apparatus is tantamount to high quality of final product, i.e. mineral wool panels. There may be many influencing parameters such as air flow from spinner (i.e. device comprised of spinning wheels onto which melt is falling to be expelled in form of droplets enlogating into fibers) as well as secondary air flows induced by suction fans from collecting chamber. Further, quality of finished product is decreased if shot is present within the structure - this shot formed by frozen droplets of mineral melt which do not elongate into fibers. Usually, shots are between 10 to 30 micrometers in diameter. Also, other forms or clumps can be present resulting from various interactions between melt flow and air flow next to spinning wheels.

Technical problem to be solved by this invention is formation of vortices and recirculations within collecting chamber of melt fiberization apparatus, bonding of fiber to walls of collecting chamber, presence of shot in primary layer of fiber deposited onto perimeter wall of collecting drum of collecting chamber, and non-uniform deposition of fiber into primary layer of fiber deposited onto perimeter wall of collecting drum of collecting chamber.

Mineral wool fiberization apparatus depends on flow of fiber which is created by elongation of mineral melt droplets after ejection from spinning wheels of said melt fiberization apparatus. State of the Art

A typical fiberizing apparatus in state of the art is described in EP 1409423. Typical apparatus of the sort of 3 to 4 fiberizing rotating wheels, also known as the spinning wheels, or rotating wheels (term used in this patent application for description of new invention), or rotors. In addition to that, fiberizing apparatus is customary connected to a collecting chamber for collecting mineral fiber, equipped with some sort of mechanism for continuous collecting mineral fiber, for instance conveyor belt or preferably rotating drum.

The mineral melt discharged from the melting furnace or similar device for heating up and melting raw materials used in mineral wool formation forms a nearly vertical melt stream as it is poured onto the spinning machine. The melt stream is directed towards the mantle surface of the first wheel where it partly adheres to the surface, is drawn in motion and forms a melt film. A part of the melt forms, with the aid of the centrifugal force, liquid ligaments that solidify to the mineral wool fibers while the remaining quantity of the melt is thrown out as a cascade of drops against the mantle surface of the adjacent second wheel in the series. Again, a part of the melt adheres to the second wheel surface sufficiently to be formed into fibers and the remainder is thrown onto the mantle surface of the third wheel of the spinner machine and so forth, until the last wheel where the remaining mass flow of the melt is assumed to be low enough to fiberize completely.

Binder may be applied on the formed mineral fibers, either during fiber formation or afterwards, in form of a droplet spray. The mineral fibers formed on the wheels of the spinning machine are transported away from the point of origin on the melt film, initially in the radial direction due to the centrifugal force. As the fibers enter the zone of the coaxial air flow generated by the spinning machine fan, i.e. the blow-in flow, they are drawn in predominantly axial motion and transported to the collecting chamber where the primary layer of the mineral wool is formed.

Existing collecting chambers are usually of a simple designes of half-closed chambers neglecting aerodynamic properties of the flow at the inlet, and further at position of formation of primary layer of mineral wool on perforated conveyer belts or drum transporters. In addition, there is no accounting for interaction between formed fiber and air flow from spinner toward conveyer belt or drum which is induced by suction fans attached to collection ducts of collecting chamber.

Mass fraction of fiber in air flow is relatively small requiring rather large air flow, and due to high velocity of blow-off on spinner nozzles also increased volumetric flow of suction from the collecting chamber in order to reduce or preempt turbulence, vortices, or recirculation. For fiber formation on the spinner one needs air velocities up to 150 m/s. The velocity of air through the pores or holes in the conveyer belt or drum transporter is much lower, between 4-10 m/s as higher velocity would cause short fibers to exit through the pores or tearing of primary layer of deposited fiber. Comparing these values results in conclusion that there are relatively high velocity gradients requing optimization of geometry of inlet part of collecting chamber.

In addition, there are no collecting chambers equipped to collect shot (i.e. droplets which were not elongated but remained essentially same size and froze, or lumped fiber and droplets in larger forms). So shot is usually thrown onto the transporter and becomes part of primary layer reducing quality of the finished product.

Description of new invention

Collecting chamber and fiber formation method solve above referenced technical problem by slanting at least one wall or ceiling of a collecting chamber in order to reduce onset of vortices and recirculation especially at high mass flow of fiber and high velocity gradients of multi phase flow in such a way that the channel so formed is essentially divergent above a plane, said plane defined by connecting axis of a drum of drum assembly and center of the first spinning wheel.Further, by adding shot collectors, amount of shots in final product is reduced and therefore the thermal and mechanical properties of a final product are better. In addition, adding regulation slats in front of collecting chamber and (or) adding balancing air flow within drum assembly further reduce vortices and recirculation of fibers within the collecting chamber. Basic goals of proposed solution are:

achieve high mass flow of fiber with low vortices and recirculation, and with minimum tear of primary layer of fibers collected on surface of collecting chamber drum assembly, and

- separation of shot from fiber at the onset of fiber transport from a spinner.

These two basic goals are achieved by proposed new solution.

Fiberizing apparatus for fiberization of mineral melt is comprised of a spinner comprising rotating wheels, and of collecting chamber. Collecting chamber collects mineral fiber which is transported from said collecting chamber using collection means such as conveyer belt, or drum, or similar. Collecting chamber in accordance with this invention is constructed to meet basic goals of proposed solution.

Collecting chamber can be roughly separated into three parts: inlet part, middle part, and exit part.

Inlet part comprises shot collectors for catching shot ejected from rotating wheels, and converging part of collecting chamber. Middle part comprises diverging walls and ceiling - this can be achieved by at least one slanted surface be it either ceiling, either side wall, or even bottom. Exit part comprises drum assembly with preferably perforated surface. Drum of drum assembly rotates and collects fiber deposited by air flow onto its mantle surface.

It should be clearly stated that any part of these three part collecting chamber has independent properties giving it an advantage, i.e., only inlet part of collecting chamber can be combined with state of the art middle and exit parts of collecting chambers (former featuring simple design comprised of essentially straight ceiling, walls, and bottom, and latter usually featuring conveyer belt rather than drum). Same is true for middle, and exit parts of collecting chamber in accordance with this invention - they can be combined with state of the art inlet part, or exit part, or middle part. However, best results were achieved by combining all features of collecting chamber into single collecting chamber assembly.

Shot collectors according to this invention are chambers positioned strategically around perimeter of the spinning wheels of said centrifuge. During spinning melt is ejected with high velocity. Melt breaks up into droplets, and these are either elongated into fibers, or cooled prematurely, and remain in form of frozen droplets, so called shots. Air flowing in direction from spinner toward collecting chamber exit entrains fibers but cannot entrain shots. Said shots therefore flies from the spinning wheels in general lateral direction. In state of the art collecting chambers said shots ricochets from the walls thus interfering with air entrained fiber flow, or disrupts formation of primary layer of fiber within exit part of collecting chamber, or gets imbedded into primary layer thus reducing its quality. It is therefore desirable to prevent shots from ricocheting from the walls, and best way is to collect them using shot collectors. As stated, shot collectors are chambers with openings arranged to face the spinning wheels. In principle they could be arranged around whole perimeter of collecting chamber, however, sufficient results were achieved by placing one shot collector on the top of collecting chamber, and two on either side of said collecting chamber. The opening of these shot collectors can be either of variable size, or constant. Shot accumulated in these shot collectors should be removed either continuously or by batch. Continuous removal can be achieved by means of a transporter. Worm transporters are convenient, and robust, so they are preferred.

During shot collecting shot impinges onto the wall of said shot collectors contributing to their excessive wear. To help alleviate this problem wear resistant protective panels may be attached to the walls, and walls themselves can be shaped in a shape most effectively reducing the momentum of shots: for example they can be curved.

Also, in the inlet portion of the collecting chamber, air inlets can be added in order to stabilize the flow field. Recirculation mark points of low pressure which can be reduced by adding more air to the field. This can be achieved by opening front wall of the collecting chamber, below the spinner by making openings. These openings can be regulated by louvers, or by slats which may be slanted at an angle thus serving as air routers giving entering air direction as well as regulating amount of air entering the collecting chamber.

Middle part of collecting chamber is crucial for developing the flow field. Flow field has direct influence on quality of fibers. Vortices, and recirculation are undesirable as they result in lower quality fiber primary layer deposited onto drum assembly surface. Fibers, as stated, are entrained by air flow. If such flow starts to swirl and recirculate this tends to clump many fibers together resulting in non uniform fiber deposition, clods forming and by this lowering product yield.. In addition, vortices and recirculation tend to deposit fiber onto the walls and ceiling (and bottom) of the collecting chamber rather than onto the drum surface. As such, middle part of the collecting chamber should be constructed to reduce vortices and recirculation. One of possibilities is to streamline the flow by means of shaping collecting chamber in general form of a nozzle, for example, Venturi. Of course, practical constraints will not allow exact Venturi pipe to be constructed, however, the walls and the ceiling can be slanted in order to first reduce cross section of said collecting chamber, and then gradually expand cross section of said collecting chamber. Reduction is achieved by reduction of cross section behind shot collectors, and enlargement by slanting at least one of the following: the ceiling, the sides, the bottom of said collecting chamber. Best results were achieved by slanting the ceiling and the sides while keeping the bottom in its usual form for other reasons of practicality. It can be said that said collecting chamber is comprised of walls, bottom, and ceiling, comprising at least one of the following: slanted side wall, slanted ceiling, slanted bottom; said collecting chamber having general divergent duct properties diverging in direction from inlet into said collecting chamber to exit from said collecting chamber.

The problems of deposition of fiber onto side walls and ceiling of the collecting chamber may be increased by fact that fibers are treated with binder to help with formation of mineral wool products. Fibers therefore tend to deposit onto the side walls, and stay bonded. This can be prevented by condensation of said walls - this can be achieved by cooling the walls and/or the ceiling to temperatures below dew point temperature.

Exit part of the collecting chamber is also very important as it comprises drum assembly, said drum assembly comprising drum with preferably perforated perimeter surface, and open to the sides, for depositing primary layer of fiber onto the perimeter surface of said drum. In one of the embodiments, the drum is simply rotating while the fibers are deposited.

Numerical simulations and measurements of the velocity field at the level of perforated surface of said drum have shown that high velocity of air flow induced by the spinning wheels may cause on the surface of said drum in a zone closest to the centrifuge local pressure increase - stagnation pressure. This results in local velocity extreme influencing formation of the primary layer. On one hand deposition of fiber in area of this velocity extreme is increased while it is decreased elsewhere, further resulting in uneven deposition of fiber into primary layer and local transport of fiber from central line of perforated drum surface.

In order to provide uniform deposition of fibers onto the perimeter side of said drum, axial fan can be used on the inside of the drum creating balancing air flow in direction toward or away from the perimeter surface of said drum. To optimize the result said fan can be mounted pivotally so optimum angle of balancing flow can be found. Instead of a fan a tube with air outlet on one side can be used to achieve the same result.

Also, instead of air fan, or in addition to it, part of perimeter surface of the drum can be blocked effectively by erecting a screen on the inside of the drum further influencing the flowfield within the drum and deposition of fiber onto the drum surface by preventing air flow through the holes or pores of perforated surface of collecting means. This screen can be curved, and it can have pointed edge with angle (28) from -45° to 45°. Also, the screen can be hinged in order to find the optimum position of this edge.

Fig. 1 shows side view longitudinal cross section of collecting chamber according to this invention, and shows entrance part of collecting chamber (I) , middle part of collecting chamber (II), exit part of collecting chamber (III), spinner assemby (1), air flow out of spinner assembly (2), spinning wheels (3), direction of shots from spinning wheels toward shot collector (4), walls of shot collector (5), top shot collector (6), top shot collector transporter (7), transition wall between top shot collector and ceiling (8), collecting chamber (9), flow of formed fibers (10), ceiling of collecting chamber (1 1), top sealing roller (12), finished primary fiber layer (13), drum assembly (14), primary fiber layer during formation (15), bottom sealing roller (16), bottom waste transporter (17).

Fig. 2 shows top view longitudinal cross section of collecting chamber according to this invention, and shows entrance part of collecting chamber (I) , middle part of collecting chamber (II), exit part of collecting chamber (III), spinner assemby (1), collecting chamber (9), primary fiber layer during formation (15), adjustable entry width of side shot collector (18), outer side shot collector wall (19), side shot collector (20), transition wall between side shot collector and collecting chamber slanted side wall (21), slanted side wall (22), exit air channel (23), air flow through exit air channel (24).

Fig. 3 shows side view longitudinal cross section of collecting chamber according to this invention, and shows axial fan (25), angle of said axial fan between its rotational axis and horizontal line(26).

Fig. 4 shows top view longitudinal cross section of collecting chamber according to this invention, and shows axial fan (25).

Fig. 5 shows top view longitudinal cross section of collecting chamber according to this invention, and shows screen (27).

Fig. 6 shows side view longitudinal cross section of collecting chamber according to this invention, and shows screen (27) with edge (A), angle of edge (28), slats (29), angle of slats (30). For purposes of this invention axial fan (25) can be replaced by a duct starting at position where said axial fan (25) is presented in figure 3, and extending outward of said collecting chamber, with an axial fan and optionally a filter installed anywhere inside of said duct.

In preferred embodiment said collecting chamber (9) is comprised of entrance part of said collecting chamber (I) close to the spinning wheels (3) , middle part of said collecting chamber (II) between said spinning wheels and a drum assembly (14) and exit part of said collecting chamber (III) comprising said drum assembly (14).

Preferred embodiment according to this invention comprises middle part (II) of collecting chamber (9) comprising collection section formed in general form of diverging duct comprising at least one slanted side wall (22), in preferred embodiment two slanted side walls (22) forming an angle with each other, said angle between 5° and 45°, preferably between 10° and 30°, more preferably around 20°. Further, said collection section may instead or in addition to slanted wall or plurality thereof further comprise a ceiling (1 1), preferably slanted, also forming general form of diverging duct above imaginary plane connecting axis of said drum of said drum assembly (14) and center of the first spinning wheel, said ceiling forming an angle with axis essentially parallel to the first spinning wheel axis between 5° and 50°. According to this invention said collecting chamber is narrowed close to the rotating wheels, and widened further on thus giving rise to effect similar to that of a Venturi tube meaning that the velocity of exiting air entraining forming fiber is increased close to the rotating wheels, and then gradually decreased with low gradient toward collecting surface. This results in prevention of creation of coherent- vortex structure and reverse flow of fibers formed in the process.

Preferred embodiment may also comprise a shot collector (6, 20) providing for catching of shots (4) formed during fiberization process. There may be a single shot collector (6, 20) or plurality therof. Said shot collector (6, 20) can be positioned either at the top (6), or at side (20) of a collecting chamber. Actual form of said shot collector (6, 20) depends on its position. Top shot collector (6) comprises a channel used for directing said shots (4) onto a transporter means, preferably a worm (7) for transporting said shot (4) out of a collecting chamber. Side shot collector (20) comprises walls slowing down said shot (4) on impact and directing said shots (4) onto the bottom of said collecting chamber, said bottom further comprising at least one transporter means, preferably a worm (17) for transporting said shots (4) out of a collecting chamber. Said walls are preferably in curved shape to more efficiently reduce momentum of said shot (4), to reduce wear as a result of said shots (4) impinging onto said walls, and/or to reduce noise as a result of said shots (4) impinging onto said walls. Further, to protect said walls there are wear resistant protective panels connected to said walls. Same can be applied to top shot collector (6) as well. Said shot collector can have either fixed or variable entrance size, however, best results were achived with entrance width size between 100 and 1000 mm. The diameter of said worms are between 50 and 500 mm.

Preferred embodiment may also comprise axial fan (25) inside said drum assembly (14) within exit part (III) of said collecting chamber (9). Said axial fan (25) can blow air toward or away from the inlet of the chamber and balance air flow helping with formation of primary layer (15) on surface of said drum assembly (14). In order to achieve this said surface of said drum assembly (14) is made of perforated or porous material able to let air through. In addition, axial fan (25) can have adjustable air flow in order to achieve optimum balancing air flow velocity. Said adjustable air flow of said axial fan is preferably achived by frequency regulation. Said axial fan (25) can be pivotaly mounted in order to be tilted to achieve best results.

Preferred embodiment may also comprise a screen (27) comprising an edge (A) for preventing air flow through holes or pores of said perforated walls of said drum of said drum assembly (14) . This screen may be movable about an axis for an angle (28).

Preferred embodiment may also comprise at least one slat (29) for routing air flow entering said collecting chamber (9) further alleviating problem of coherent-vortex structure. Each of said slats (29) can be individually adjusted for appropriate angle (30) serving to optimize (reduce) said vortices within said collecting chamber (9). Preferred embodiment further comprises forced cooling of at least part of walls of said collecting chamber by coolant, preferably with water, said water having temperature between 1°C and 20°C, preferably between 5°C and 15°C. Cooled inside wall surface reduces temperature of air close to said wall surface resulting in formation of condensation. Said condensation on said walls (22) and ceiling (11) in turn prevents bonding of binder treated fibers to the inside of said walls (22) of said collecting chamber.

Claims

PATENT CLAIMS

1. Collecting chamber for collecting of mineral wool fiber comprised in melt fiberization apparatus further comprising a spinner comprising at least one rotating wheel, and at least one collecting means, preferably drum or conveyer belt, said collecting chamber comprised of walls, bottom, and ceiling, comprising at least one of the following: slanted side wall, slanted ceiling, slanted bottom; said collecting chamber having general divergent duct properties above a plane defined by connecting axis of a drum of drum assembly (14) and center of the first spinning wheel of said one spinning wheel or plurality thereof, diverging in direction from inlet into said collecting chamber to exit from said collecting chamber.

2. Collecting chamber according to claim 1 , comprising middle part (II) of collecting chamber (9) comprising collection section formed in general form of diverging duct comprising at least one slanted side wall (22), in preferred embodiment two slanted side walls (22) forming an angle with each other, said angle between 5° and 45°, preferably between 10° and 30°, more preferably around 20°.

3. Collecting chamber according to claim 1 , comprising middle part (II) of collecting chamber (9) comprising collection section formed in general form of diverging duct comprising a ceiling (1 1), preferably slanted, also forming general form of diverging duct, forming an angle with axis essentially parallel to the first spinning wheel axis between 5° and 50°.

4. Collecting chamber according to claim 1 , further comprising shot collectors for collecting shot ejected from said rotating wheel and essentially preventing said shot from being entrained into primary layer of deposited fiber on said collecting means.

5. Collecting chamber according to claim 4, said shot collector (6) positioned on the top of said collecting chamber (9), said shot collector (6) comprising a channel used for directing said shot (4) onto a transporter means, preferably a worm (7) for transporting said shot (4) out of a collecting chamber.

6. Collecting chamber according to claim 4, said shot collector (20) positioned to the side of said collecting chamber (9), said shot collector (20) comprises walls slowing down said shot (4) on impact and directing said shot (4) onto the bottom of said collecting chamber, said bottom of said collecting chamber further comprising at least one transporter means, preferably a worm (17) for transporting said shot (4) out of a collecting chamber.

7. Collecting chamber according to claim 5 or claim 6 whereby walls of said shot collector (6, 20) are curved to better direct said shot and minimize effect of said shot (4) impinging onto said walls of said shot collector (20).

8. Collecting chamber according to claim 5 or claim 6 whereby walls of said shot collector (6, 20) are equipped with wear resistant protective panels to protect said walls against said shot (4).

9. Collecting chamber according to claim 1 , comprising exit part (HI) of said collecting chamber (9), said exit part (III) comprising drum assembly (14) comprising drum with perforated perimeter walls, said drum assembly (14) further comprising an axial fan (25), said axial fan (25) blowing air toward or away from the inlet of said collecting chamber (9), said axial fan (25) optionally installed in an air duct extending outside of said collecting chamber.

10. Collecting chamber according to claim 1, comprising exit part (III) of said collecting chamber (9), said exit part (III) comprising drum assembly (14) comprising drum with perforated perimeter walls, said drum assembly (14) further comprising pivotable screen (27) with optional pointed edge (A) with angle (28) from -45° to 45°.

1 1. Collecting chamber according to claim 1, comprising inlet part (I) of said collecting chamber (9), said inlet part (I) comprising a wall below said spinner, said wall having at least one opening, said opening equipped with at least one slat (29) for routing air flow entering said collecting chamber (9), said slat (29) optionally pivotable.

12. Fiber formation method using fiberizing apparatus comprising at least two rotating wheels for forming mineral melt into fibers comprising the following steps: a. pouring melt onto spinning wheels of said fiberizing apparatus;

b. directing portion of said melt which is transformed into fibers through diverging collecting chamber;

c. depositing said portion of said melt which is transformed into fibers into primary layer on collecting means, preferably conveyer belt or drum with perforated perimeter walls.

13. Fiber formation method according to claim 12, further comprising step of catching most of portion of said melt which is transformed into shots by into shot collectors and transporing said shot outside of said collecting chamber.

14. Fiber formation method according to claim 12, further comprising step of creating balancing flow within a drum assembly (14) by means of an axial fan (25) or a tube.

15. Fiber formation method according to claim 12, further comprising step of creating screen preventing part of air flow carrying fiber from flowing through openings in perforated perimeter walls of said drum of said drum assembly (14).