Field of Technology

Melt fiberization, fiber air transport. Technical Problem

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.

Homogenous 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.

Underlying problems in melt fiberization are 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 mesh of collecting drum or conveyer belt or some other collecting means of collecting chamber, and non-uniform deposition of fiber into primary layer of fiber deposited onto perimeter wall or collecting means (such as conveyer belt or rotating drum) of collecting chamber.

Technical problem to be solved by this invention is clumping of fiber as a direct result of vortices and/or recirculation cells (i.e. areas of absolutely or relatively stagnating flows) formed within the collecting chamber as well as presence of shot in final product. These vortices and/or recirculation cells may be either stationary, or traveling about the chamber. Ideally, air should flow smoothly from spinner (or plurality thereof) on one side of the chamber toward the depositing surface (rotating drum, or conveyer belt) on the other side of the chamber, carrying fiber with it. The mineral fiber thrown off said spinner is entrained by the air and follows air flow. There should be no vortices and/or recirculation cells formed. If there are vortices and/or recirculation cells formed, the fiber following air flow would not be deposited but rather would follow these air patterns, and clump together in the process. Such clumps have increased inertia as well as mass as compared to single fiber, and they do not follow air flow as well as single fiber. As a result they are falling toward the bottom of the chamber where they are deposited on collection means and they form lower quality product which is usually discarded, or reused, or sold at lower value. Also, shot which is formed, is deposited in final product changing its properties, and thus reducing the quality.

But it should be clear, from the onset, that there may be beneficial recirculation, and this is one of possible embodiments described herein, aimed at technical problem of increasing production of primary layer.

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 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.

The mechanism of forming fiber is not completely understood. Nevertheless, the results of melt fiberization are both fibers, and shot. As far as it is understood, the expelled melt forms ligaments which are elongated, in leading droplet, and trailing fiber. While travelling through air, said ligament is increased in length until such time that the temperature of ligament decreases sufficiently so melt solidifies into shot (frozen leading droplet), and fiber. At approximately such time connection between shot and fiber is broken. Fiber, having small diameter, and being long, and being light is entrained by air flow so it basically follows air while shot having larger diameter has higher inertia and it follows its own path. Of course trajectory of shot is influenced by air flow, but not as much as fiber. At the end, there is flow of mineral formed, in general shape of tapered cone, expanding in its cross section from spinner toward collecting means. At the outer perimeter of this cone ratio of shot to fiber is the highest, and toward the center of this cone ratio of shot to fiber is the lowest.

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. Blow-off centerline is an imaginary line from center of gravity of spinner(s) plane and extending essentially normal to said plane toward primary layer depositing means (e.g. perforated conveyer belts or drums or other similar devices).

Existing collecting chambers are usually of simple designs 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 prevent 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 requiring optimization of geometry of inlet part of collecting chamber, and also middle part of said collecting chamber in order to solve above referenced technical problems.

Fort the purpose of this application quality of primary layer is described in terms of ratio of shot to fiber in deposited fiber onto said collecting means. Higher quality means lower shot to fiber ratio in the final product. Increasing the quality, therefore, for purposes of this application, means decreasing ratio of shot to fiber, i.e. less shot and more fiber in finished product. Description of new invention

Collecting chamber comprising at least one adjustable wall and process for collecting of mineral wool solves above referenced technical problems by manipulating cross section and shape of entry zone (comprised of shot separation section /inlet part/ (I) and/or adjustable section /middle part/ (II)). Such manipulation may serve three purposes: to reduce vortices and/or recirculation cells within collecting chamber, to separate shot from fiber, and to induce backflow where beneficial. There are many ways to achieve such manipulation. There can be apertures, moving walls, objects, membranes and other means for achieving said goal. In preferred embodiment this manipulation is performed by means of at least one adjustable wall, said adjustable wall adjusted by moving, preferably in rotatable manner about an axis, preferably in lateral direction relative to air flow within said collecting chamber. In so doing, the cross section of flow comprised at least of air, and fiber, is changed.

This means that during operation of fiberizing apparatus said adjustable wall is adjusting to flow and other parameters as described herein. Further, said collecting chamber may comprise at least one shot collector, preferably two, more preferably three shot collectors.

Said adjustment may be a result of visual inspection of primary layer of fiber as deposited on collecting means, or some other inspection means, but it can also be a result of predetermined action of an operator based on experience.

In preferred embodiment said adjustable wall is comprised of a leading edge, preferably in form of a shot roller, either rotating (in either rotation direction), or not, positioned laterally to incoming air flow from a spinner or plurality thereof. The effects of this leading edge may be augmented by means of an apron in close proximity of said leading edge, or attached to it, either permanently or detachable, and in such case both of them (i.e. leading edge, and apron) form said adjustable wall. Apron for purposes of this application refers to a wall, or part of the wall, being adjustable, or not, being adjacent to, or essentially parallel to, or attached to, or in close proximity to any wall of said collecting chamber. Apron may also refer to a membrane, or sheet metal, porous or non- porous, perforated or non-perforated attachment to said leading edge, whether attachment is flexible, or fixed. Apron can be resilient or rigid, it can be movable (rotatable or otherwise movable) or immobile. Apron can be made of a single part, or plurality of parts. In more preferred embodiment this manipulation of flow field is performed by means of two said leading edges preferably shot rollers, to each side of air flow, with associated aprons, as presented in Figure 3 accompanying this application. The details of said preferred embodiment comprising leading edge and associated apron are shown, in particularly, in Figures 4, 5 and 6.

Figure 4 shows neutral position of said leading edge which is shot roller (15) in this preferred embodiment, with accompanying apron (12), both of them forming adjustable wall. As seen in the Figure 4, said adjustable wall is rotatable about an axis. It may rotate toward blow-off centerline (Figure 5), for preset angle (32), or rotate away from said blow-off centerline (Figure 6), for another preset angle (33), or it may rotate to any desired position within these two limits. This rotation of adjustable wall is an example of adjustable wall adjustment as described herein.

Near the spinner, two main flows of solidified particles appear. First is the flow of fibers which is toward the center of coaxial primary air flow (closer to blow-off centerline). Second is flow of shots formed from non-fiberized melt (further away from blow-off centerline as compared to fiber flow). These shots may be almost spherical in shape and further, their mass causes their trajectories not to depend on intense primary coaxial air flow as much as on inertial trajectories of fibers. As a result, shot to fiber ratio is usually higher toward the outskirt of air flow and lower toward its center. Said adjustable wall, preferably side adjustable wall can be used for at least partial separation of flow predominantly composed of shot from flow predominantly composed of fiber by simply presenting an obstacle around which the flow separates - flow with higher shot to fiber ratio remains on the outside of said adjustable wall, preferably side adjustable wall, and flow with higher fiber to . shot ratio remains on the inside of said adjustable wall, preferably side adjustable wall continuing toward said collecting means. Fibers should (in ideal case) also be equally collected by collecting means of collecting chamber as a thin homogenous layer (usually on perforated mesh). Boundary between fiber flow and shot flow is not fixed, rather it is transient, which means that there are always some shots present in the fiber flow but their amount generally decreases with distance away from blow-off centerline. Shots are not wanted in the primary layer, so they should be separated from the fiber flow as much as possible. It is therefore aim of this invention to help in this process, i.e. in decrease of shot amount in fiber flow and consequently increase in fiber layer quality.

Shot concentration in fiber flow is difficult or even impossible to predict in design phase of collecting chamber and is also dependent on other parameters such as air flow conditions and spinner or spineers rotation speed. It is therefore desirable to design such chamber which could adapt to flow conditions and consequently as much shot would be extracted from fiber flow as possible. This basic idea is embodied in providing at least one adjustable wall of said collecting chamber. Said adjustable wall would change its position relative to other walls in such a way to improve characteristics of the flow and reduce concentration of shot in final product.

In embodiment of this invention at least one adjustable wall, preferably side adjustable wall is used to adjust collecting chamber inlet cross section so the best product (primary layer) is achieved. Self-cleaning function is realized by means of a scraper, said scraper scraping off accumulated material from shot roller which has deposited on it during operation of melt fiberization apparatus.

In addition, adjustable lower shot roller is also provided in one of the embodiments to prevent shots accumulation on collecting means.

As previously mentioned, shots are always present in fiber flow so they cannot be totally separated from the flow. When low quality product is manufactured, there can be more shots in final product; this means that separation boundary can be set further form blow-off centerline causing higher production capacity because more fibers are collected. When high product quality is needed, adjustable wall, preferably side adjustable wall or plurality thereof comprising leading edge, preferably shot roller or plurality thereof can be moved toward centerline of blow-off air flow and more shots are separated from fiber flow, but on the other hand there is less fiber collected which means lower production capacity of production line.

The shape of adjustable wall, preferably side adjustable wall comprised of leading edge (15) and apron (12), said leading edge preferably shot roller in one of embodiments may be such that backflow coming from collecting means is directed back to main fiber flow located essentially around blow-off centerline flow. Namely, for hydrodynamic reasons it can happen that backflow is induced next to collecting chamber walls (41). This backflow (41) reduces amount of fiber collected and increases loss. It is beneficial to have this backflow (41) redirected again toward collecting means in order to cause said fiber to be deposited. This is achieved by changing position of adjustable wall so backflow (41) is redirected into main fiber flow going from spinner to collecting means, said fiber flow flowing essentially around blow-off centerline. This change in adjustable wall position causes fibers to return and accumulate on collecting means and are not lost as waste on shot conveyor. This backflow-mainflow can be also seen as a recirculation cell, but in this case such recirculation cell is intended result as opposed to uncontrolled recirculation cells actually causing fiber to clump. This recirculation cell is controlled by movement of said adjustable wall.

In preferred embodiment, said side walls comprising shot rollers and/or associated aprons are water cooled to prevent fiber sticking and binder solidification. Shot rollers are equipped with scrapers that clean thin layer of accumulated fiber from its surface. If there is no immediate cleanup of the surface that is closest to the spinner rotors accumulation speed of fibers becomes progressive this means fibers are accumulated faster and faster. When enough fibers is collected a curtain shaped feature is formed and when mass of it is large enough it fall off dawn to waste conveyor or air flow sucks it on collecting means. Both events are negative, first presents fiber loses and second pure homogeneity of primary layer. Above referenced technical problem is also solved by a process comprised of following steps:

- pouring mineral melt onto at least one spinner to discharge said mineral melt;

- blowing said mineral melt, said mineral melt separating into shot, and fiber, said fiber entrained by an air flow flowing predominantly from said spinner toward collecting means;

- separating said fiber from shot by means of an adjustable wall (15, 12) in accordance with description above.

This process may further comprise step of adjusting an angle (32, 33) of said adjustable wall (15, 12) to either obtain better quality and less quantity of primary layer if said adjustable wall (15, 12) is moved toward blow-off centerline, or worse quality and larger quantity of primary layer if said adjustable wall is moved away from blow-off centerline, said quality relating to ratio of shot to fiber, higher ratio of fiber to shot meaning higher quality.

The process as disclosed in this application also comprises step of directing backflow (41) of said fiber flow coming from collecting means (1) toward main fiber flow around blow-off centerline in order for said fiber flow coming from perforated means to be re- entrained by main fiber flow and deposited on said collecting means to reduce loss of fiber.

Below, invention is further explains by means of figures accompanying this application, said figures forming part of this application and showing embodiment of this invention, this embodiment not limiting the scope of this invention but rather explaining it in better detail to one skilled in the art.

Fig 1. shows preferred embodiment as longitudinal cross section of collection chamber in time of operation. There are shown inlet part or shots separation chamber (I), middle part or adjustable section (II) of collection chamber and third part or non-adjustable section (III) of collection chamber. This separation of sections is not exclusive, there may be chambers in accordance with this invention only comprised of the inlet part and of the middle part. Shot separation chamber starts at the inlet side of collecting chamber so the whole mantle surface of the spinner wheel (34) is in the first zone (I). Zones (I) and (II) are separated by the axes of leading edge (15), in this embodiment vertical shot roller (15). Zone (II) reaches to the end of sealing wedge (13) between stationary and adjustable wall, preferably side adjustable wall. From sealing wedge (13) starts the non- adjustable section of collecting chamber. On the inlet part (I) of collecting chamber the spinner wheels (34) and fiber blow off air flow (35) are shown. In order to regulate inlet air flow (45) under the spinner (61) the air duct dampers (40) are installed.

In inlet part (I) of collecting chamber mineral fibers (38) are formed and are transported, preferably by means of air flow, to the collecting means (1) that in zone (III) travels in one direction, preferably upward (20). Transport by air flow entraining said fiber and fiber deposition is in this embodiment achieved by secondary suction air flow (47). On collecting means (1) primary layer (59) of fibers (38) is formed and exits under the sealing roller (48) as finished primary layer (60).

Besides fibers (38) shots (36) are also formed from the mental surface of spinner wheels and have their own trajectories (37) with inertia higher than that of fiber.

Top of collecting chamber is in this embodiment sealed by water cooled ceiling (46). On the beginning of collecting means (1) horizontal shot roller (19) is installed. In order to continues removal of shots (36) that travels in vertical direction shot separator screw conveyor (42) is installed. Shots in screw conveyor are transported left and right in vertical shot channels (18) and fall through openings (43) into shot collecting shaft (44).

Fig. 2 shows top view cross section of collecting chamber at the time of operation. Inside of collecting chamber of this particular embodiment there are four zones as opposed to previously described three zones. As stated previously, at least one zone (inlet or middle) is necessary to carry out this invention. These zones are:

• I - inlet part or shots separation chamber. This zone starts from plane defined by edges of inlet part (I) and ends at plane defined by left and right axes of left and right leading edge (15), in this embodiment vertical shot rollers. On the left and right side of zone (I) there are zones (IV-L) and (IV-D);

• II - middle part or adjustable section. Zone (II) and (III) are separated by plane defined by left and right edge of left and right sealing wedge (13). On the left and right side of zone (II) there are aprons (12) and mantle surface of leading edge (15), in this embodiment vertical shot rollers;

• III - third part or non-adjustable section. This is space between zone (II), collecting means (1), sealing roller (48) and non-adjustable walls (2) of said collecting chamber;

• IV-L and IV-D are side shot collectors. Zone lies next to zone (I) and side wall (22). Side shot collectors are used as leading edges (15) of respective adjustable wall, preferably side adjustable wall.

In inlet part (I) at least one spinner (61) is installed. From spinner wheels (34) melt is thrown to form fibers (38), which are blown off by spinner blow off air flow (35). In general, fibers travel in direction (39) towards collecting means (1). Shots (36) are also formed from droplets of melt thrown off mantle of spinner wheels (34) and in this embodiment travel mainly in left and right side shot collectors (IV-L) and (IV-D), respectively. Under the spinner (61) air dust dampers (40) are mounted. Top view cross section shows shot channels (18).

Along the side walls (2), backflow (41) is formed caused by intensive spinner blow off flow (35) toward collecting means (1) and partially formed primary layer (59) and is redirected on the sides and further along walls (2). Guiding surface (58) of said apron (12) redirects this backflow (41) back to collecting means (1) by directing it toward main flow which then entrains said backflow and directs it again toward collecting means (1).

Fig. 3 show top view cross section in isometric projection in neutral position (no fiber flow separation). On left side collecting means (1) moving in direction (20) is visible. On the edge of collecting means (1) stationary side water cooled wall (2) is mounted. The connection between collecting means (1) and stationary water cooled wall (2) is sealed by sealing (3). In side wall (2) cleaning doors (4) are installed. On the edge of side wall (2) water cooled column (5) is installed which is connected to the collecting chamber support column (8) by hinge support (6). Hinges (1 1) of apron (12) are mounted on support (6). Apron (12) is ended by curved backflow (41) guiding surface (58) that ends essentially tangentially at leading edge (15), in this embodiment vertical shot roller. Fig. 4 also shows leading edge (15) and apron (12) in neutral position.

Sealing between column (5) and apron (12) is carried out by sealing wedge (13). Side wall adjustment direction (25) is possible around axis (24). Shot roller support column (14) is attached to the apron (12) by connecting angle beams (29) and (30). Through the shot roller support column (14) cooling water pipe (27) is inserted and connected to the side wall (12) by fitting (62). Thinner tube (28) is also placed inside column (14) in order to re-lubricated lower radial bearing of leading edge (15), in this embodiment vertical shot roller rotating in direction (31).

Continuous leading edge (15), in this embodiment vertical shot roller cleaning is achieved by means of a scraper (16). In case the adjustable wall, preferably side adjustable wall is made of multiple pieces water cooling tube bridge (26) is connecting two neighboring pieces.

Primary sealing of zones (IV-L) and (IV-D) is carried out by radial sealing sheet metal (10) that can along with shot roller support column (14) rotate along axes (24). Sealing sheet metal (10) touches the stationary sealing sheet metal (9) mounted on collecting chamber support column (8) by clamps (21). Secondary sealing or zones (IV-L) and (IV-D) is carried out by sheet metal (7) mounted on columns (5) and (8). Zones (IV-L) and (IV-D) are closed by wall (22) in which cleaning doors are mounted (17).

On outer side of wall (22) vertical shot channel (18) is mounted. Due to optimal shot trajectory redirection and consequently separation the side wall (22) is curved and anti- wear plates (23) are mounted. Fig. 5 Shows maximum negative angle (33) between stationary surface of wall (2) and adjustable wall comprised of leading edge (15) and apron (12).

Fig. 6 Shows maximum positive angle (32) between stationary surface of wall (2) and adjustable wall comprised of leading edge (15) and apron (12).

Fig. 7 shows transition of vertical shot roller support column (14) and shaft (63) through collecting chamber ceiling (46). On top of column (14) there is cooling water inlet (50) and outlet (51) fitting. In ceiling (46) a partial circular openings with center in axis (24) are made. Openings are sealed with sealing plates (52) and (53), according to location of apron (12). Weight of vertical shot roller is supported via axial bearing in support (56) mounted on column (14). Adjustment of vertical wall (12) is done by lever (49). Inlet (54) and outlet (55) cooling water of vertical shot roller is achieved through rotary joint (57).

Fig. 8 shows vertical cross section of shot separation system. Screw conveyor (42) in installed on top of separation section (I) of collecting chamber. In order to transport collected shots as fast as possible half of screw has left sided helix and the other half right sided helix. By two sided helix screw design shots are transported from center of the screw to closest vertical channel and fall through opening (43) in shot collecting shaft (44).

Channels (18) are used to achieve that shots collected in screw (42) cannot come back in fiber flow and further in primary layer. This event was possible in state of the art apparatus where shots fall at the end of screw conveyor inside of collecting chamber, where air turbulences could transport them in fiber flow and further deposit them on primary layer.