GB2319770A - Process and apparatus for production of vitreous fibre - Google Patents

Abstract

A process of producing vitreous fibres comprises forming a melt from a charge of mineral material, pouring the melt into or onto at least one fiberising rotor rotating about a substantially horizontal axis, allowing the melt to be flung from the periphery of the rotor or rotors as fibres to form a substantially annular cloud of fibres, carrying the cloud of fibres axially from the rotor or rotors towards a collector surface and spraying additive material in liquid form outwardly into the cloud of fibres and preferentially in an upward direction. Improved distribution of liquid additive throughout the mineral wool web is obtained. Apparatus is also provided constructed to produce mineral wool in this way and to spray liquid radially outwardly and preferentially in an upward direction.

Description

PROCESS AND APPARATUS FOR PRODUCTION OF MINERAL FIBRE The invention relates to a process for the production of mineral fibre products containing one or more additives, and to apparatus for carrying out this process.

It is well known to produce mineral fibre, for instance glass wool or stone wool, by applying mineral melt to a fiberising rotor rotating about a substantially horizontal axis and thereby throwing the melt from the periphery of the rotor as fibres and forming a substantially annular cloud of fibres, carrying the fibres forward from the rotor, generally within a collecting chamber, towards a collector surface and collecting the fibres on the collector surface as a web. When there are several adjacent rotors arranged in a cascade spinner, the individual annular clouds merge into a single substantially annular cloud around the cascade. This annular cloud is carried forward towards a collector and loses its annular configuration as it travels away from the rotor or rotors.

It is generally found that fibres tend to be formed from each individual rotor primarily in the outward sector rather than in the upper or lower sectors. When several adjacent rotors are arranged in a cascade it is found that the majority of the fibres are produced from the final one or two rotors and thus the majority of the fibres are formed in the lower sector of the substantially annular cloud of fibres formed around the cascade as a whole.

It is well known to apply binder materials to the fibres during this process. The binder may be sprayed into the cloud from outside the annular cloud. It is also known to spray binder radially outwardly from inside the annular cloud.

It is also known to incorporate particles of materials such as filler in the web. One way which has been proposed for achieving this is spraying a filler-containing slurry into the annular cloud radially outwardly from a position inside the annular cloud.

It is well known to aim for distribution of binder or filler within the web which is as uniform as possible.

Various disclosures have described the possibility of spraying binder and/or particulate material from a position within the annular cloud of fibres coming from the rotor rotating about a substantially horizontal axis. These disclosures include US 4,433,992, US 3,343,933, US 3,233,989 and US 4,668,267. These and other typical disclosures all require spraying of the binder and/or slurry of particulate material to be substantially equal in all radial directions. It is often suggested that this uniform spraying aids in achieving uniform distribution of binder and/or filler within the web.

In WO90/15032 a similar system is described. Nozzles are placed in a position at the front of a rotor and on the horizontal axis of rotation of the rotor and are arranged to spray material radially outwardly. This disclosure suggests that sectorised spraying may be used, and in particular suggests that the majority of the sprayed liquid should be directed towards the sectors from which the majority of fibres are formed. In the illustrated apparatus two rotors are shown in a cascade, each having sectorised spraying. Each directs liquid material outwardly and only in a direction away from the other rotor. Substantially equal amounts of liquid are sprayed upwardly as downwardly.

It would indeed be expected that concentrating sprayed liquid on the areas in which major fibre formation takes place would result in improved distribution of the sprayed material.

However, we have found surprisingly that if substantially all of the sprayed liquid is directed upwardly an excellent distribution of material throughout the web can be obtained, loss of additive can be reduced and the amount of sprayed additive which hits the walls and base of the spinning chamber can be reduced.

According to the invention we provide a process of producing man-made vitreous fibre (MMVF) containing an additive, the process comprising melting a charge of mineral material to form a melt, pouring the melt into or onto at least one fiberising rotor, each of which is rotating about a substantially horizontal axis, allowing the melt to be flung from the periphery of the rotor or rotors as fibres to form a substantially annular cloud of fibres, carrying the cloud of fibres axially from the rotor or rotors towards a collector surface and spraying additive material in liquid form outwardly into the cloud of fibres and in the process the spraying of additive is preferentially in an upward direction.

The invention also includes an apparatus for the production of man-made vitreous fibre comprising at least one fiberising rotor, each of which is mounted in a housing for rotation about a substantially horizontal axis and has a fiberising periphery and is constructed for receiving mineral melt and throwing it radially outwards from the periphery as fibres, a liquid flow duct leading to a spray position in the region forward of the rotor or rotors and defined by the periphery of the cross-sectional area of the housing, and a spray means at the spray position constructed to spray liquid radially outwardly from the spray position and in the apparatus the spray means is constructed to spray liquid preferentially in an upward direction.

The apparatus of the invention is particularly suitable for carrying out the process of the invention.

The rotor or rotors are each mounted for rotation about a substantially horizontal axis. Preferably each has a solid fiberising periphery onto which can be poured mineral melt which is then flung from the periphery as fibres. These are then carried forward of the rotor through a collecting chamber toward a collecting device, all in standard manner.

In the process and apparatus a single rotor can be used. Preferably however at least two rotors are provided so that melt flung from the first rotor hits the periphery of the second rotor and is flung from that as fibres.

Preferred apparatuses comprise three or four rotors arranged in a cascade formation.

In the invention it is essential that the liquid additive is sprayed preferentially upwardly. That is, well over half, and generally at least three quarters, of the liquid additive is directed upwardly. That is, of the possible 360" range for the spray, the majority of the liquid additive is sprayed in the upper 1800 section.

Preferably substantially all the liquid additive is directed upwardly, i.e. small amounts of additive, for instance below 10%, preferably below 5%, may be sprayed in the lower 1800 section.

Normally the majority of the liquid additive is sprayed over an angle of 1750 or less, preferably 1500 or less, for instance up to or around 1350. For some systems spray angles of from 1350 or 1500 to 1750 can be useful.

Preferably the liquid additive is sprayed in such a manner that the spray is symmetrical about a vertical plane i.e. equal amounts of additive are sprayed on each side of the rotor or the set of rotors. However, this is not essential, and non-symmetrical sprays can also be used.

The liquid additive is sprayed outwardly into the cloud of fibres. That is, it is sprayed from a position within the annular cloud of fibres. In the apparatus of the invention this is achieved by providing a spray position which is in the region forward of the rotor or rotors and defined by the periphery of the cross-sectional area of the housing, that is it is in a position which is inside the substantially annular cloud which is formed when the apparatus is in use. Spraying may be from any point within this region, provided that it is preferentially upwardly. The spray position is preferably as close as possible to the front face area of the rotor or set of rotors and is not spaced away from the rotor or rotors.

Preferably at least one of the rotors has a spray means associated with it at a spray position forward of that rotor and on or close to the substantially horizontal axis of rotation of that rotor, and preferably on this axis. In this case also the spray position is preferably directly at or on the front face of the rotor and is not spaced away from the rotor.

The liquid additive is supplied to the spray means at the spray position via a liquid flow duct. If the spray means is not associated with one particular rotor, the liquid flow duct can pass through the region between the rotors. If the spray means is associated with one particular rotor then suitably the liquid flow duct passes through that rotor. Preferably the rotor is mounted for rotation on a rotating shaft through which the liquid flow duct passes to the centre of the front of the rotor.

The liquid flow duct may rotate with the rotating shaft. Alternatively and preferably the liquid flow duct is substantially non-rotatable. This is particularly preferred if the liquid additive is such that part of the liquid, for instance solid materials, would tend to separate centrifugally whilst passing along a rotating liquid flow duct.

Each spray means may be supplied by one or more liquid flow ducts. The liquid flow ducts may all carry the same type of liquid additive or they may carry different types of liquid additives.

The liquid flow duct or ducts supply a spray means placed at the spray position. The spray means may be any construction arranged to spray liquid additive in a substantially upward direction, through one or more spray orifices. For instance it may comprise as spray orifices one or more nozzles arranged to point substantially upwardly.

It may also comprise as spray orifice a simple opening directed upwardly, preferably of diameter small enough to result in some atomisation of the liquid as it leaves the opening.

A further possibility is that the spray means comprises as spray orifice a slot extending over the required angle of spray, for instance up to 1750, preferably up to 1500, and pointing in an upward direction.

A further possibility is that the spray means also comprises a liquid distribution means mounted for rotation on the front of the rotor. Such a liquid distribution means can comprise for instance slinger plates of the type described in US 2,944,284. It can also have a surface which is an open, substantially frustoconical distribution surface as described in our British Application No.

9524607.0, priority application for International Application Number ... filed today, reference 60/3487/03.

When the spray means includes a liquid distribution means the liquid additive is passed from the spray orifice onto the distribution surface, which is rotating rapidly.

The rapid rotation induces the liquid to pass rapidly to the edge of the distribution surface and to be flung from it in the form of droplets. It will be seen that the direction of movement of the liquid may change as it crosses the distribution surface. In the invention however the liquid additive flung from the edge of the distribution surface still travels substantially upwardly.

The liquid additive can be any material which is required to be added to the web, provided in liquid form.

For instance it may be aqueous binder. It may also be a slurry of solid particulate material such as filler in a carrier liquid, for instance water. The liquid additive may be a dispersion (thermodynamically unstable suspension of liquid droplets in carrier liquid) or an emulsion (thermodynamically stable dispersion of liquid droplets in carrier liquid). When the liquid additive is a slurry, dispersion or emulsion, the carrier liquid may be aqueous binder. The additive may be surfactant material provided in aqueous solution, dispersion or emulsion, for instance if the final MMVF product is to be used as a horticultural medium. The liquid additive may comprise an oil.

Processes of the invention may be used to spray coarse slurries of filler particles having high density of at 3 least 1.1 g/cm , preferably at least 1.2 or at least 1.3 and often at least 1.4 g/cm3. Slurries may be used which contain at least 2%, often at least 5%, by weight of the slurry, of coarse particulate filler, and often the amount of this particulate filler is at least 10% and usually above 20%. It can be as much as 60 or even 75, up to 98%.

Suitable amounts are 10 to 90% by weight, for instance 40 to 90 or 10 to 50% by weight. Preferably the filler which is present in these amounts has a mean particle size of at least 5Zm, often at least 10,us, more preferably at least 20cm, most preferably at least 30,um or 40m. It can be up to 50pm or greater. Often at least 90% by weight of the coarse filler has a size above 5,um, e.g., above 10 or 20cm.

The invention is particularly useful within processes as described in our British Application Number 9524608.8, priority application for International Application Number ... filed today, reference PRL03608WO. Liquids of density below 1.1 g/cm3 or below 1.0 g/cm3 may also be used.

In the invention it is possible to combine a spray means constructed to spray liquid additive preferentially or substantially only in an upward direction with a diffusing means constructed to spray liquid additive radially and equally in all directions. In this system liquid additive is sprayed preferentially upwardly in that the majority of the total liquid additive is sprayed upwardly.

Such systems can be used to spray a single type of liquid additive equally in all radial directions using the diffusing means and preferentially or substantially upwardly using the spray means. However, such a system is particularly useful for the spraying of two different types of additive in liquid form. For instance in the invention it is possible to use a spray means to spray a slurry of solid particulate filler substantially only upwardly and at the same time to use a diffusing means to spray aqueous binder radially equally in all directions. These systems are particularly appropriate when associated with one or more particular rotors, so that the diffusing means and spray means are both arranged to spray liquid additive from a position close to or on the substantially horizontal axis of a rotor.

Normally if both a spray means and a diffusing means are used each is supplied by its own liquid flow duct.

Other materials, such as aqueous binder, may be sprayed from outside the annular cloud of fibres in standard manner.

In the invention it is preferred to use an apparatus comprising three or four rotors arranged in a cascade formation. Preferably at least one rotor has associated with it a spray means at a spray position forward of that rotor and on or close to its substantially horizontal axis.

It is particularly preferred that the final rotor is constructed in this way. Preferably also the penultimate rotor is constructed in this way. It is especially desirable in a 4-rotor cascade spinner that the final two rotors are constructed in this way.

The fibres formed as the melt is flung from the periphery of the rotor or rotors are carried forward of the set of rotors along the direction of the substantially horizontal axis or axes of rotation of the rotors (i.e axially). Normally they are collected on a collecting device as a web.

To aid in carrying the fibres axially forward of the rotor or rotors in the form of an annular cloud, blasts of air may be provided in known manner. Primary air may be provided adjacent to the rotor or rotors, for instance through slots adjacent to the rotors. Transportation air may be provided more distant from the rotors.

The process and apparatus of the invention may be used for the production of any type of mineral fibre. They are particularly useful for the production of fibres normally known as stone wool, slag wool and rock wool.

The web which is produced in the invention may be used as such, often after compression and heating to cure it.

Often, however, the uncured web is laid upon itself to form a thicker batt, which is then impressed and cured in conventional manner. The batt can be in the form of a flat slab or it can be of any desired shape, for instance a pipe section. If desired, the web can be comminuted to form a tufted or granulated product which can be used as a pourable insulation material.

The MMVF materials produced by the process according to the invention may be used for any purpose known for MMVF products, eg fire insulation and protection, thermal insulation, noise reduction and regulation, construction, horticultural media, reinforcement of other products such as plastics and as a filler. The materials may be in the formed of bonded batts (which may be flat or curved) or the materials may be comminuted into the granulate.

The invention will now be illustrated with reference to the accompanying drawings.

Figure 1 shows a cross-section through a rotor for use in the invention.

Figure 2 shows a front view of the rotor of Figure 1.

Figure 3 shows a perspective view of a spinner configured according to the invention.

Figure 4 shows a perspective view of a further spinner configured according to the invention.

Figure 1 shows a solid rotor 1 of the type used in a cascade spinner mounted on a rotatable shaft 3. Fixed to the rotor is a liquid distribution means 16 having a distribution surface 11. The substantially frustoconical surface 11 is a concave surface containing a plurality of grooves 18, of which six are illustrated. The distribution surface has a short edge 12 and a long edge 14, the long edge 14 being forward of the short edge 12. The long edge 14 is at a radius 0.6 R, where R is the radius of the rotor. The rotor 1 is supported, on the rotating shaft 3, by roller bearings 32. The non-rotatable liquid flow duct 5 is supported on bearings 30, usually roller bearings, between the rotating shaft 3 and the non-rotatable liquid flow duct 5. The non-rotatable liquid flow duct 5 leads into and is fixed to the spray means 7, which is also nonrotatable. This has a spray orifice 9 configured in the form of a slot extending over an angle of about 1350 and facing upwardly. The slot may be inclined rearwardly at an angle of 10-450 so as to ensure sprayed liquid additive meets the distribution surface at the smallest possible radius.

In use a suspension of particulate solids in aqueous binder is supplied (supply means not shown) to the liquid flow duct 5 which extends through the rotatable shaft 3, and into the spray means 7. The suspension then passes through the slot 9.

The partially atomised suspension passes across an air gap in the direction of the arrows and onto the distribution surface 11. The rapid spinning of the liquid distribution means 16 induces radial outward movement of the suspension, guided by the grooves 18, to the end points 20 of the grooves at the edge 14. From these end points the suspension is flung in atomised form from the distribution surface radially outwards, substantially upwardly and forward of the rotor.

If any suspension fails to travel radially outwards along the grooves 18, but tends to leak back into the apparatus, it passes along the inlet channel 28 into the rotating annular chamber 24. Rotation of the chamber induces the suspension to move to the outer wall of the chamber, from where it flows along outlet channel 26 onto the distribution surface at its short edge. A seal 34 is positioned between the chamber 24 and the roller bearings 30. Leakage into other regions of the apparatus is thus avoided.

Concurrently, melt is applied to the periphery 22 of the rotor 1 which is spinning rapidly and flinging the melt from the periphery as fibres. The fibres are blown forward by conventional air supply means (not shown) in an annular cloud. As the fibres are blown forward they are met by the atomised suspension from the liquid distribution means.

The suspension and additives it contains penetrate the annular cloud and coat the fibres.

The fibres are then collected as a web containing uniformly distributed additive on a collector in conventional manner. The web may be subjected to crosslapping to form a batt, and the product may be compressed and heat cured in conventional manner.

Figure 2 shows a front view of the spray means 7.

Liquid additive exits the liquid flow duct 5 through the slot 9 and is passed to the liquid distribution surface 11.

The liquid additive flows over the region 38. The "spiral" type path of the liquid arises as a result of the rapid rotation of the distribution surface in a clockwise direction. In other embodiments the surface may rotate in an anticlockwise direction. The liquid additive is thus flung from the long edge 14 of the distribution surface in a substantially upward direction over around 1350 of the circumference of the distribution surface.

Figure 3 shows an alternative spinner. This is a 4rotor cascade spinner. Melt 40 is applied to the periphery of the top rotor 42. Some of this melt is flung from the periphery as fibres. The majority is thrown on to the second rotor 44, and then on to the third rotor 46 and fourth rotor 48. Liquid flow ducts 5 (non-rotatable) each supply the spray means 7 positioned in the centre of each of the third (46) and fourth (48) rotors. Each spray means 7 has a spray orifice configured in the form of a nozzle 50 which sprays liquid additive in an upward direction.

Figure 4 shows a similar cascade spinner having four rotors 42, 44, 46 and 48. Liquid additive is supplied to a spray position at the centre of each of the third and fourth rotors. The spray means 7 each comprise as spray orifices three nozzles 52, arranged so that the liquid exiting the nozzles is sprayed in a substantially upward direction.

In each of the illustrated forms of apparatus additional aqueous binder may be sprayed into the fibre cloud from outside the annular cloud.

Claims (11)

1. A process of producing man-made vitreous fibre containing an additive, the process comprising melting a charge of mineral material to form a melt, pouring the melt into or onto at least one fiberising rotor, each of which is rotating about a substantially horizontal axis, allowing the melt to be flung from the periphery of the rotor or rotors as fibres to form a substantially annular cloud of fibres, carrying the cloud of fibres axially from the rotor or rotors towards a collector surface and spraying additive material in liquid form outwardly into the cloud of fibres characterised in that the spraying of additive material is preferentially in an upward direction.

2. A process according to claim 1 comprising providing a first fiberising rotor and one or more subsequent fiberising rotors each mounted for rotation about a substantially horizontal axis and pouring melt on to the first fiberising rotor and allowing it to be thrown on to the or each fiberising rotor in turn and allowing it to be flung from the periphery of the rotors as fibres to form a substantially annular cloud of fibres.

3. A process according to any preceding claim in which additive material in liquid form is sprayed from a position forward of the rotor or rotors and close to or on the substantially horizontal axis of rotation of a rotor.

4. A process according to any preceding claim in which the spraying of additive material is substantially only in an upward direction.

5. A process according to any preceding claim in which the additive is sprayed over a region covering an angle of up to 1500, preferably about 1350.

6. A process according to any preceding claim in which the spraying of additive is over a region symmetrical about a vertical plane.

7. A process according to any preceding claim in which the additive in liquid form is aqueous binder, a slurry of filler material in aqueous binder, aqueous surfactant or an oil-containing liquid.

8. An apparatus for the production of man-made vitreous fibre comprising at least one fiberising rotor, each rotor being mounted in a housing for rotation about a substantially horizontal axis and having a fiberising periphery and constructed for receiving mineral melt and throwing it radially outwardly from the periphery as fibres, a liquid flow duct leading to a spray position in the region forward of the rotor or rotors and defined by the periphery of the cross-sectional area of the housing and a spray means at the spray position constructed to spray liquid radially outwardly from the spray position, characterised in that the spray means is constructed to spray liquid preferentially in an upward direction.

9. An apparatus according to claim 8 in which the spray means comprises one or more nozzles arranged to spray liquid in an upward direction only.

10. An apparatus according to claim 8 in which the spray means comprises a slot arranged to direct liquid in an upward direction only.

11. An apparatus according to any of claims 8 to 10 in which the liquid flow duct is non-rotatable.