GB1559117A

GB1559117A - Method and apparatus for manufacture of mineral wool

Info

Publication number: GB1559117A
Application number: GB35463/76A
Authority: GB
Original assignee: Rockwool International AS
Current assignee: Rockwool AS
Priority date: 1975-09-01
Filing date: 1976-08-26
Publication date: 1980-01-16
Also published as: FI60189B; CH610871A5; FI762414A; YU39178B; DE2638412C2; SE7604304L; SE416295C; SE416295B; NO762839L; CA1079069A; YU212276A; NO140419C; CS209487B2; DK146297C; ATA645776A; DK146297B; JPS5231174A; AU1737776A; FI60189C; DE2638412A1

Abstract

Mineral wool is manufactured by a flow of a liquid melt being guided onto the circumferential surface of at least one rapidly rotating rotor. The melt first adheres to the surface of the rotor and is then thrown away from the surface in the form of threads. In this case, these threads are cooled by means of an air flow. The air flow is supplied in the circumferential region of the rotor in such a manner that it has both an axial as well as a tangential flow component in relation to the rotor. Provided close to the rotor (1) and along at least a part of its circumference is a slot (11) which runs concentrically with the rotor (1). Situated in this slot (11) are blades (8). Mineral wool which is manufactured in this manner has a considerably improved tensile strength. <IMAGE>

Description

(54) METHOD AND APPARATUS FOR MANUFACTURE OF MINERVAL WOOL (71) We, ROCKWOOL INTERNATIONAL A j S, a Danish Company of 501, Hovedgaden, 2640 Hedehusene, Denmark, hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement :- The present invention relates to a method for the manufacture of mineral wool, in which method a flow of liquid melt is directe lo the external peripheral surface of at least one fast rotating rotor in such a way that the melt adheres to the surface and is thrown therefrom in form of fibres which are cooled and transported to a collecting means by a flow of air that is supplie through air supply means positioned around and behind each rotor. The invention further relates to an apparats for performing the method.

In the manufacture of mineral wool a now of liquid meut, at a temperature which normally is in the area of 1000-1400 C, produced by melting rock, slag, glassforming raw-materials and other inorganic materials in an oven, normally a Cupola oven, is ied to the peripheral surface of a number of fast rotating rotors (normally 4).

The rotors in pairs rotate in opposite directions thereby throwing the main flow of melt from upper rotor to the next and so forth, untel all melt is slung away from the rotors in form of fibres of melt. This process normally is designated as a cascade spinning process.

In order to cool the fibres as well as transport the fibres to a conveyor on which they are collecte and transported to further processing into mats, slabs etc. for thermal and acoustic insulation, a flow of air is introduced along the periphery of the rotors frcm air distributing means. In order to avoid excessive cooling of the flow of melt netween the rotors, no air is introduced l. nto the inferspaee between the rotors. The air is introdueed approximately parallel with the axis of the rotors.

Products manufactured from the mineral wool derived from the above process some cimes'rave a non-satisfactory tensile strength, which may be a drawback for the finisl-. ed products, being damaged during transport and mounting, but this lack of ensile strength may also be inconvenient in somme of the finishing processes by which the wool is collecte as a eomparatively thin layer on a first conveyor from which it is made up into a thicker web by means of an overlapping process. The low tensile strengíh is mostly found in products having a low specific weight, and has the consequence that a mineraI wool product with a density of 20 kg/m3, being otherwise economically favourable, cannot be pro duced with a tensile strength which is sufi culent for its handling during transport and installation.

The object of the present invention is to provide a method for the manufacture of a mineral wool from which products having an improved tensile strength may be produced.

It is believed that the eomparatively low tensile strength of mineral wool from cascade spinning is due to the fact that the finished wool is built up from tufts of minerval fibre and not from uniformly distributed fibres. The tufts may have a size of a few centimeters, and often the tufts have a greater density than the average density of the mineral wool. The number of fibres in the portions between the tufts, therefore, are too small to establish a sufficient and satisfactory coherence between the fibres in these portions to prevent the mineral wool from being pulled apart during the normal handling.

According to studies of what happens in the area around a rotor in the cascade spinning process, the formation of tufts is due to the fact that fibres formed by the splnning form a coherent veil which to some extent is dragged by the rotation of the rotor owing to its mechanical coherence with the melt adhering to the rotors. At the same time the veil to some degree is drawn out in the axial direction of the rotor until the veil is torn apart by the air How into tufts comprising coherent, tangled tufts.

According to the invention a method is provided for the manufacture of mineral wool, in which method a flow of liquid melt is directe to the external peripheral surface of at least one fast rotating rotor in such a way that the melt adheres to the surface and is thrown therefrom in the form of fibres, which fibres are cooled and transported to a collecting means by a flow of air that is supplie through air supply means positioned around and behind each rotor and in which the flow as it emerges from the air supply means has a forward component of velocity parallel with the axis of the rotor and a tangential component of velocity in the direction of rotation of the rotor.

Owing to the tangential velocity component in the air flow around each rotor, the vieil of fibres will open before it is toron apart into tufts. This reduces the den- sity of the tufts to such a level that substantially uniform mineral wool may be produced.

It has been proved that products from mineral wool achieve a tensile {strength which is nearly double the tensile strength of products made according to the known process. The improved tensile strength is believed to be due to a more uniform fibre distribution in the mineral wool caused by the reduced density of the mineral fibre tufts.

The invention also relates to an apparats for performing the method according to the invention, the apparats comprising at least one rotor arrange for fast rotation about its axis, an air supply means positioned around and behind each rotor and in which the slow, as it emerges from the air supply means, has a forward component of velocity parallel with the axis of the rotor and a tangential component of velocity in the direction of rotation of the rotor.

Preferably the air supply means comprise an annular slot in which are dispose blades which may be substantially parallel to the axis of the rotor.

The blades may according to one embodiment be arrange on a flange at the periphery of each rotor, té lange forming one limitation of the slot, the other limitation being the walls of an air distri brution chamber. This arrangement provides a good agreement between the tangential velocity and the rotational speed of the rotor. It is, however, also possible to mount the blades on the edge of the distributing chamber, forming an angle with respect to the axis of the rotor. With this arrangement it is possible to vary the flow of air and its direction along the periphery of the rotor and, e. g., reduce the flow of air in the interspace between the rotors in order to reduce the cooling effet on the flow of melt.

It is preferre (l to place a screen in the area into which the flow of melt is introduced in order to prevent excessive cooling of the melt before it is spun into fibres.

The invention is described in detail in the following description with reference to the drawings in which Fig. I is a perspective view of a spinning rotor showing the principle of the method according to the invention, Fig. 2 is an axial section through a rotor and a distribution chamber in an arrangement in which the brades are mounted on the rotor, Fig. 3 is a detail of a rotor and a distribution chamber in section with fixed blades in the air introduction slot, and Figs. 4 and 5 show sections along vines AA and BB in Figs. 2 and 3 respectively.

Fig. I shows a rotor I rotating in the direction of the arrow O. A flow of liquid melt falls on the peripheral surface 10 of the rotor, whereby the melt adheres to the surface, and the melt is drawn with the rotor for some distance before it is thrown away from the rotor in form of fibres of melt. Along thc external peripheral surface of the rotor an annular slot 11 is arrange around and behind the rotor and through which a flow of air is introduced for transport and cooling of the fibres. In the slot 11 blades are arrange, and the flow of air as it emerges from the slot has a forward velocity component V2 and a tangential component of velocity Vt in the rotational direction of the rotor.

By introducing the cooling air in this way, the vieil of fibres surrounding the rotor will open up before the fibres, in the form of tufs. are transported to collecting means in the form of a perforated band, from the lower face of which the air is sucked away in order to deposit the fibres or tufts of fibres as a mat of mineral wool.

Fig. 2 shows an axial section through a rotor 1 which is mounted on a shaft 5, rotating in a bearing 6. The rotor comprises a rim with an external peripheral surface 10 and flanges 2 and 3. The flanPes and the rim are mounted by means of a nut 4 against an abutment 5a on the shaft.

Along the external periphery of the rim an annular slot I I is prov : ded between a collar on the inner flange and a wall 7 of an air distributing chamber, surrounding the bearing 6. In the slot blades 8 are arrange on the edge of the collar. The blades 8 are substantially parallel with the axis of the rotor and provide the flow of air with tangential velocity Vt owing to the rotation of the blades with the rotor.

Fig. 3 shows another embodiment of the means for introducing the cooling and the transport air. The annular slot 11 is arrange between flanges on the wall 7 of the air distribution chamber, and in the slot I I are the blades 9 mounted so as to form an angle with the axis of the rotor.

Fig. 4 shows a section along AA in Fig.

2. Il. s seen that the blades 8 are substantially parallel with the axis of the rotor, while Fig. 5, showing a section along BB in Fig. 3, shows the blades 9 form an angle with respect to the axis of the rotor.

With the embodient according to Fig. 2 the tangential velocity of the air will correspond exactly to the velocity of the outer surface of the rotor. Furthermore, the housing for the bearing can be used as air distribution chamber, making this part of the apparats easier to clean and maintain. The drawback of this embodiment is that the unavoidable clearance between the tips of the blades may result in formation of an unintended turbulence in the air flow. The embodiment according to Fig. 3 has not this drawback, and further makes a variation in the flow of air along the slot possible, e. g. it is possible to reduce the flow of air at the point of introduction of the flow of melt in order to reduce the cooling effect at this point A heat insulating material containing a bonding agent and which is manufactured according to the new method has a density or specific weight of 29 kg ! ml. Insulating material normally contains a bonding agent connecting the fibres at intersection points. The bonding agent in the insulat- ing material is a phenolic resin making up 1. 45% of thé. total weight of the material.

The tensile strength of this insulating material is 11. 0 kN/m-. For comparison an insulating material made according to a known cascade spinning process and having identical density and contents of bonding agent has a tensile strength of 6, 3 kN jm'.

Claims

WHAT V4 E CLAIM 1S :- 1. A method for the manufacture of mineral wool, in which method a flow of liquid melt is directe to the external peripheral surface of at least one fast rotating rotor in such a way that the melt adheres to the surface and is thrown therefrom in the form of fibres, which fibres are cooled and transported to a collecting means by a flow of air that is supplie through air supply means positioned around and behind each rotor and in which the flow as it emerges from the air supply means has a forward component of velocity parallel with the axis of the rotor and a tangential component of velocity in the direction of rota tien of the rotor.
2. An apparats for carrying out the method according to claim 1, the apparats comprising at least one rotor arrange for fast rotation about its axis, an air supply means positioned around and behind each rotor and in which the flow, as it emerges from the air supply means, has a forward component of velocity parallel with the axis of the rotor and a tangential component of velocity in the direction of rotation of the rotor.
3. An apparats according to claim 2 in which the air supply means comprise an annular slot in which are dispose blades.
4. An apparats according to claim 3 in which a flange at the external periphery of each rotor forms one limitation of the slot, the walls of an air distribution chamber forming the other limitation, and in which the blades are mounted on the flange of the rotor and are substantially parallel with the axis of he rotor.
5. An apparats according to claim 3 or claim 4 in which the blades are mounted on the air distribution chamber so as to form an angle with respect to the axis of the rotor.
6. An apparats according to claim 2 in which a screen is provided in the area in which the flow of melt is introduced, pure- venting excessive cooling of the flow of melt.
7. A methoi according to claim 1 substantially as liereinbefore described with reference to the accompanying drawings.
8. MineraI wool macre by a method according to claim 1 or claim 6.
9. Apparats according to claim 2 substantially as hercinbefore described with reference to the accompanying drawings.