WO2011076888A2

WO2011076888A2 - System and method for online detection of enclosures in mineral wool, especially during production

Info

Publication number: WO2011076888A2
Application number: PCT/EP2010/070574
Authority: WO
Inventors: Peter Kesting
Original assignee: Rockwool International A/S; Deutsche Rockwool Mineralwoll Gmbh & Co. Ohg
Priority date: 2009-12-22
Filing date: 2010-12-22
Publication date: 2011-06-30
Also published as: WO2011076888A3

Abstract

The invention relates to a system for detection of hot enclosures, such as hot coke particles, in mineral wool, particularly during production of mineral wool in a production facility, comprising: at least one microwave scanner oriented on the mineral wool to supply enclosure detection signals based on a response from the mineral wool web and/or possible enclosures to generated microwaves; at least one radiometric sensor oriented on the mineral wool to supply temperature detection signals from temperature dependent radiation originating from the mineral wool and/or the enclosures; and at least one processor arranged for processing the enclosure detection signals from the microwave scanner to determine if an enclosure is present in the mineral wool, and for processing the temperature detection signals from the radiometric sensor to determine the temperature of at least an enclosure determined to be present on the basis of the enclosure detection signals.

Description

SYSTEM AND METHOD FOR ONLINE DETECTION OF ENCLOSURES IN MINERAL WOOL, ESPECIALLY DURING PRODUCTION

The present invention relates to a system and a method for online detection of enclosures in mineral wool, in particular hot enclosures such as hot coke particles, particularly during the production of stone wool. Within the context of the present invention, and common for this technical field, the expression "online" is used to indicate that the detection is arranged to be performed at some point during the succession of processing steps, prior to storage or transport of completed products.

Such hot enclosures as for instance hot coke particles are an undesired residue from production process steps prior to actually forming the mineral wool web into a layer or slab .

In particular, stone wool is made from rock material, especially diabase which is mixed with coke and lime and subsequently melted in large cupola furnaces at

approximately 1500°C. Said coke is desired as energy source within the melting process in such cupola furnace. The resulting melted mass is directed onto fast spinning wheels that whirl the melted stones mass into thin threads, which step is also called the spinning process. Small amounts of a binding agent and oil are added and a desired density of the impregnated stone wool product can be carefully adjusted in subsequent production steps.

This can then be followed by a production step where the stone wool is hardened in special furnaces, thereby curing the binding agent. A portion of said coke that is initially introduced into the cupola furnace sometimes undesirably leave hot coke particles in the mineral wool web . The presence of hot coke particles may result in smouldering of the produced mineral wool. This may locally affect the effectiveness of the end-product with respect to the insulation properties thereof or cause damage to the packaging, which would cause end-users to wonder about the integrity of the packaged products with a damaged packaging or even in the fact that the end-products will not match the quality requirements so that they may not be distributed.

It has to date not been possible to determine with sufficient certainty if such hot coke particles are present in a layer or web of freshly produced mineral wool. For instance according some solutions proposed in the prior art, use was made of near-infra-red technology and/or heat sensitive camera's to localize enclosures in the mineral wool. However, not all types of enclosures other than hot coke particles need to be removed because of any risk of smouldering or damage to packaging of the products. For instance hot binder that is used in the production process will cool quickly enough in order not to pose any risk.

Likewise, slag and pieces of iron (which may be present in the mineral wool, especially in stone wool production) are considered harmless, unless they exceed a certain

temperature. Such other enclosures should not lead to an unwarranted interruption of the process flow for removing harmless residues or in general enclosures. Moreover, with near-IR sensors or heat sensitive camera's it is only possible to ascertain whether or not zones at or near the surface of the mineral wool are warmer than the surroundings thereof, but not to any significant depth, and then it is not even certain that such warmer or hotter zones actually comprise an enclosure (and not just warmer or hotter mineral wool) . Furthermore, even if it were possible to determine the presence of coke particles in (or rather at the surface of) the mineral wool using near-IR sensors or heat sensitive camera's, then it is still uncertain that such coke

particles actually will need to be removed, because no information is then obtained about the actual core

temperature thereof, and thus no certainty about any need to remove the coke particles is obtained. As an example of a disclosure of the use of the use of a heat sensitive camera or a near-IR detector, reference is made here to DE- 19507643.

Further, it is noted that from WO-2007/128942 and/or

DE-10053112 and/or WO90/10221 methods and systems are known where detection is based on microwave radiation. However the method and system known from WO-2007/128942 are generally intended to also find wet-spots, and are thus in fact only useful in localizing enclosures. All these methods and systems only able to determine the presence of an enclosure and/or if an enclosure has a specific inherent temperature, which has the unwanted effect that all enclosures - either or not having a certain temperature - are to be removed, whereas some (if not most) of these enclosures are harmless or will at least not lead to any smouldering or any damage to any package, since these will cool down sufficiently quickly .

According to the invention, the now newly proposed inventive system comprises at least one microwave scanner oriented on the mineral wool to supply enclosure detection signals based on a response from the mineral wool to

generated microwaves, at least one radiometric sensor oriented on the mineral wool to supply temperature detection signals from temperature dependent radiation from the mineral wool, and at least one processor arranged for processing the enclosure detection signals from the

microwave scanner to determine if an enclosure is present in the mineral wool, and for processing the temperature

detection signals from the radiometric sensor to determine the temperature of at least an enclosure determined to be present on the basis of the enclosure detection signals.

The invention thus relies on a combination of two separate measurements, which are preferably obtained as independently as possible as much as possible without interference, and to be combined in order to arrive at a highly certain determination if coke particles are enclosed in mineral wool and whether these are so warm or hot that these need to be removed.

It is noted that warm or hot coke particles result in a signature pattern in some images after imaging on the basis of signals emanating from the microwave scanner. Such patterns may be such that warm or hot coke particles are distinguishable over other materials, elements or components enclosed in the mineral wool. Thus a first selection may be provided for.

Further, every body having a higher temperature than the absolute freezing point generates electromagnetic energy, often referred to as thermal noise, which can be received using for instance an antenna. The power of the radiation received from such a body is ideally proportional to the temperature of the radiation or the brightness temperature: P = k T Af. Thus, by employing appropriate antenna's and/or receiving equipment, the radiation from such a body can be received and interpreted to determine there from the inherent temperature or core temperature of the radiating body in an absolute sense or value and with far less limitation as to the depth of the radiating body then in case of the only on near-IR or heat sensitive camera based prior art. The microwave scanner and the radiometric sensor in combination allow for an extremely reliable determination of the presence of enclosures to be removed, such as in

particular hot coke particles, while these components of the invention already in isolation deliver very useful

information, going a long way to at least identify the possible presence of warm or hot coke particles as an enclosure in the mineral wool, or the presence of a body in the mineral wool having a temperature that may warrant invasive action for removal of the body. Together, these in formations provide a high degree of certainty when hot or warm coke particles are enclosed in the mineral wool, where the coke particles have such a temperature that the removal thereof through invasive action is not just warranted, but practically necessary. This is especially required if the core or radiant temperature of the enclosure exceeds a temperature of for instance 80°C.

In a preferred embodiment the system according to the invention is such, that the microwave scanner and the radiometric sensor are arranged in the system at a

sufficient intermediate distance to essentially prevent microwaves from the microwave scanner from affecting the radiometric sensor. As a consequence microwave energy or radiation from the scanner will not or essentially not interfere with the measurements performed with the

radiometric sensor. Especially in combination with some measure or degree of directionality embodied in the

microwave scanner such a distance can be kept relatively small, but even without such directionality the distance necessary to achieve the objectives of avoiding interference can be provided quite easily in view of the length of the production lines, especially the cooling section thereof in the progression direction of the mineral wool behind the production lines, for example behind the spinner and the like .

In such an embodiment the distance is preferably at least 1 meter, more preferably more than 1,5 meter and most preferably at least 2 meter. For most configurations of systems according to the invention, such distances may suffice for the posed objectives.

Additionally or alternatively in another embodiment the system according the invention is such, that at least the radiometric sensor is provided with a shield to essentially prevent at least one of environmental influences and

microwaves from affecting the radiometric sensor. As an alternative or addition such shielding can serve to improve the independence or at least decrease (if not avoid) interference by at least to microwave scanner on the

function of the radiometric sensor. Any shield may be employed within the framework of the present invention, even a conventional shield such as a faraday cage, the material from which the door of a microwave oven is made, etcetera. Moreover any type of shield may also be provided to decrease or eliminate environmental disturbance, such as the

interference that may be experienced from electric or magnetic fields emanating from sources in the vicinity of the system, such as lighting or the mains power supply, in particular but not exclusively.

In another preferred embodiment the system according to the invention is such that the microwave scanner comprises a set of at least one microwave transmitter, such as an antenna, for generating the microwaves for providing an excitation, and at least one microwave receiver to detect a response from the mineral wool and provide enclosure

detection signals for supply to the processor. As a result the scanner may be made fully operational independently from the radiometric sensor. In case of failure of the radiometric sensor, the results from the microwave scanner may still provide at least an indication of the presence of warm or hot coke particles, so that appropriate action like removal of such an enclosure may still be decided on.

In some an embodiment, the system may be such that the microwave transmitter and the microwave receiver in the set are arranged on the same side in relation to a layer of the mineral wool, and detection is based on reflections from the mineral wool. This enables another set to be arranged on the opposite side of the mineral wool, allowing an improved depth insight into the presence of unwanted enclosures in the mineral wool, as an alternative or an addition to employing more than one working frequency for the scanner. Also, the effective depth to which enclosures may be

detected can be increased with opposite sets. In an

embodiment with a single set on one side, interference caused by guide means such as conveyors or transport rollers, opposite the set, may be reduced, decreased or even eliminated. It is noted that the invention is not restricted to embodiments based on reflection, but may also comprise embodiments based on transmission. These are considered to constitute similar features and for this reason most of the relevant claims are not limited to either option.

In an embodiment of a system according to the invention wherein the scanner at least comprises a set of a

transmitter and a receiver (possibly on the same side of the mineral wool) , the microwave receiver comprises a

radiometric sensor module, which is tuned to a frequency in the microwave bandwidth corresponding with the frequency of microwaves generated by the microwave transmitter. Although another frequency may be selected within the framework of the invention according to the claims, confidential testing has shown that such tuning achieves good results on

excitation by the transmitter.

In another preferred embodiment a system according to the invention is such, that the microwave scanner is arranged to function on at least one working frequency from the range of frequencies between 1 and 25 GHz, preferably between 1,1 and 20 GHZ, more preferably between 1,2 and 10 GHZ, and most preferably between or either or both of 2,45 and 5,8 GHz. At such working frequencies coke particles and other elements present in the mineral wool are through appropriate imaging or other forms of detection, appear to be quite well distinguishable, allowing for a first

selection of enclosures in the mineral wool that are

possibly required to be removed.

In such an embodiment, the system may be such, that the microwave scanner is arranged to function on at least two working frequencies to obtain enclosure detection signals for more than one wavelength dependent microwave penetration depth into the mineral wool. Consequently it is beneficially possibly to construct, as it were, a three dimensional image or at least an identifiable indication of an enclosure that may be required to be removed.

In an embodiment according to a selection of claims, the system according to the invention may be such, that the microwave scanner comprises two or more sets of at least one microwave transmitter and at least one microwave receiver, wherein each set is tuned to one of the at least two working frequencies. Thus an improved in depth insight into the interior of especially the freshly mineral wool may be provided for deciding whether an intervention to remove the enclosure is warranted.

In another preferred embodiment of the invention, the system is such, that the radiometric sensor comprises at least one radiometric sensor module which is tuned to a frequency corresponding with a predetermined temperature of an enclosure, at or above which predetermined temperature removal of the enclosure may be required, for instance 80°C or higher, and a corresponding frequency, for example 10 GHz. As a consequence the radiometric sensor having such a radiometric sensor module is capable of determining the core or radiant temperature of an enclosure, whether or not such an enclosure has prior thereto already been identified as for instance a coke, so that even other enclosures can still be identified as possibly posing a risk. Also in some embodiments, the system may be such, that the measurements with the radiometric sensor having the radiometric sensor module may provide result that are only used, if and when results from the microwave scanner indicate the presence of warm or hot coke particles, based on their signature

presence in the results obtainable with the microwave scanner .

In yet another preferred embodiment a system according to the present invention may be such, that radiometric sensors and/or radiometric sensor modules and/or microwave transmitters and/or microwave receivers are arranged in a diagonal staggering pattern with respect to a layer of mineral wool and a direction of movement thereof. Thus it has been made possible to fully cover the width of mineral wool, for instance a layer having a width of 2 meters or any other width, regardless of the individual dimensions of the components of the microwave scanner and/or the radiometric sensor. Even if such components are wider than the working area of the mineral wool that these components are intended to "cover", the diagonal staggering pattern allows for a sufficient resolution to detect even small enclosures and to determine the inherent heat or core temperature or assess the possible risk thereof.

In yet another preferred embodiment, an embodiment of the system according to the invention may be such, that radiometric sensors and/or radiometric sensor modules and/or microwave transmitters and/or microwave receivers, such as antennas, are provided with funnelling means for directing temperature dependent radiation from the mineral wool onto a sensor or microwaves from a transmitter in the microwave scanner into the mineral wool. In such an embodiment, the directivity of the radiation inbound or outbound into or out of the mineral wool may be improved and as a consequence also interference between the microwave scanner and the radiometric sensor may be reduced or eliminated. Moreover, an improved insight into the area of mineral wool that is actually at some point in time under investigation can thus be provided without interference or disturbance from other areas of the mineral wool.

The system according to any one of the preceding claims, wherein radiometric sensors and/or radiometric sensor modules and/or microwave transmitters and/or

microwave receivers comprise means for setting the

directivity or orientation. Thus an optimum for the area of the mineral wool at one particular time under investigation may instantaneously be determined and set, to improve the efficiency and accuracy of the system.

In a further embodiment of the invention, the system exhibits the feature that at least two microwave scanners are provided, which are arranged on opposite sides of a layer of mineral wool. Consequently the depth to which the scanners can in combination inspect the mineral wool is increased at least twofold. The present invention will be further elucidated herein below through description of non-limiting embodiments as shown in the accompanying drawings, in which identical and at least functionally corresponding or similar embodiments may be identified with the same reference numbers and in which :

Fig. 1 shows a perspective view of an embodiment of a microwave scanner to be employed in a system according to the present invention;

Fig. 2 shows a radiometric scanner arranged over a layer of mineral wool in an embodiment of a system according to the present invention, for instance in combination with a configuration of figure 1 ;

Fig. 3 shows a perspective view of a radiometric sensor module according to an embodiment of the present invention;

Fig. 4 shows a diagonal staggering configuration of a plurality of radiometric sensor modules like the one, shown in fig. 3 ;

Fig. 5 shows a combination of microwave transmitter antennas in a microwave scanner according to the present invention ;

Fig. 6 shows a front view of a frame incorporating a microwave scanner according to the invention;

Fig. 7 shows a side view;

Fig. 8 shows an image that can be formed by

constructing or imaging measurements and interconnecting Fl- values obtained by the microwave scanner, wherein the obtained image is a signature representation for the

presence of coke particles;

Fig. 9 is a similar view as fig. 8, wherein not coke particles but warm binder in mineral wool material is detectable on the basis of the signature representation thereof; and Fig. 10 shows how the microwave scanner can be embodied with multiple working frequencies to achieve determination of the presence of an enclosure at different depths.

In fig. 1 a microwave scanner 1 has an essential component of a system according to the present invention as shown. In fig. 2 a radiometric sensor 2 is depicted.

The microwave scanner 1 in fig. 1 comprises a frame 3 and on the frame 3 two sets of microwave transmitter

antennas and microwave receiver antennas are arranged above and below a passing layer for a mineral wool. Each set of microwave transmitter antennas 5 and microwave receiver antennas 6 is arranged in a housing 7, where one housing 7 with the microwave receiver antennas 6 and the microwave transmitter antennas 5 is arranged below the layer 4 of mineral wool and another housing 7 is arranged above the layer 4 of mineral wool. The microwave transmitter antennas 5 and the microwave receiver antennas 6 are connected to a central processing system, for instance comprising a

computer 8.

The radiometric sensor 2 comprises an arm 10, from which a housing 9 is suspended, in which a number of

radiometric sensor modules are accommodated.

The radiometric sensor 2 and the microwave scanner 1 are arranged at a distance from one another. As a

consequence, microwave radiation emanating from the

microwave transmitter antennas 5 cannot interfere with the measurements that are taken with the radiometric sensor modules 11, like the one shown in fig. 3. It is noted, that in itself the microwave scanner 1 comprises also a number of radiometric sensor modules 11, like the one shown in fig. 3, but then tuned to a different frequency, corresponding the frequency that emanates from the microwave transmitter antennas 5. Consequently, the microwave receiver antennas 6 could be embodied as a radiometric sensor module 11 like the one shown in fig. 3.

Within the realm of possibility of the present

invention, the microwave scanner 1 and the radiometric sensor 2 could be arranged quite close to one another, provided that sufficient precautions are taken to avoid interference of measurements taken by the radiometric sensor 2 resulting from radiation originating from the microwave transmitter antennas 5 of the microwave scanner 1 in fig. 1. For instance, a shield could be employed like a faraday cage or any other sufficient means to prevent or minimize such interference as much as possible.

However, when mineral wool is produced by a spinner and subsequent regular conventional components and elements, there is usually a cool down zone downstream relative to these high temperature components. In the course of such a cool down zone it is an elegant and simple solution to arrange the microwave scanner and the radiometric sensor 2 at a distance from one another, in order to avoid as much as possible interference from occurring. It is further noted, that other environmental influences could also hamper the proper functioning of either of the microwave scanner 1 and/or the radiometric sensor 2. Such disturbing influences could originate from lighting in a production facility, especially if such lighting is in the shape or form of discharge lamps or the like. Also motors to advance the layer full of mineral wool could cause interference, as well as other production facility related circumstances. Even rollers, over which the layer full of mineral wool is advanced, could through rotation thereof generate

interfering fields or radiation. It is well within the realm of the person skilled in the art to limit or minimize or eliminate such interfering influences, so that no further attention thereon is spent here. Particularly compensating measures can be taken on the basis of measurement of such interfering influences, rather than just simply shielding the system according to the present invention from such influences. Either possibility is however within the scope of protection of the present invention, where shielding or compensation or any other measure is included in as far as environmental influences are minimized, decreased or even eliminated .

In either of the microwave scanner 1 and the

radiometric sensor 2 radiometric sensor modules 11 as the one of fig. 3 can be employed to embody the microwave receiver antennas and/or the essential components of the radiometric sensor 2. It is noted, that such modules 11 as in fig. 3 have a measurement window 12 extending from a house 13, in which hardware, firmware or even software can be accommodated. The dimensions of the houses 13 in a row of radiometric sensor modules 11 prevent the measurement windows 12 thereof to be closely spaced. In contrast, it is quite necessary to have measurements taking at short

intermediate distances in the width direction (arrow A in fig. 4) above or below the layer of mineral wool 4 to achieve a sufficient measurement density. With radiometric sensor modules 11 like the one shown in fig. 3 a solution to this contradiction is provided by arranging modules 11 in a diagonally staggering fashion, as shown in fig. 4. This is equally the case for the microwave receiver antennas of the microwave scanner 1 in fig. 1 and the radiometric sensor modules of the radiometric sensor 2 in fig. 2. Likewise, microwave transmitter antennas 5 could be embodied in a similar fashion along diagonally staggering lines in

relation to the direction of progress or advance of the layer 4 of mineral wool as indicated with arrow B in fig. 4. In fig. 5 it is shown, that microwave transmitter antennas 5 and microwave receiver antennas 6 can be arranged along a guide 14, so that the intermediate distance there between can be altered based on necessity. Likewise, the distance between the scanner 1 and the sensor 2 could be adjusted or set by interconnecting the microwave scanner 1 and the radiometric sensor 2 by a guide 14, as a consequence of which a separate frame or arm 10 in fig. 2 for the suspension of the housing 9 accommodating radiometric sensor modules 11 could be omitted.

Further, in fig. 5, enclosures 15 are represented by dots within the layer 4 of mineral wool, which is advanced in direction of arrow B over rollers 16 forming a means for transporting the layer 4 of mineral wool.

Fig. 6 shows a front view of the microwave scanner 1 of fig. 1, clearly identifying therein the frame 3 with the housings 7 for the transmitting antennas and the receiving antennas. The antennas themselves are not visible in fig. 6.

Fig. 7 shows an alternative embodiment with housings 7 of the microwave scanner 1, for instance like the one in fig. 1, whereas the radiometric sensor 2 is provided with housings 9 above and below the advancing layer of mineral wool 4. Consequently, relative to the radiometric sensor 2 in the fig. 2, an additional housing 9 accommodating

radiometric sensor modules 11 is provided below the

advancing layer 4 of mineral wool. It is important to note, that hereto mainly distance is relied on between the

microwave scanner 1 and the radiometric sensor 2 where it concerns shielding of influences from the one of these two components on the other. A distance may be for instance at least one meter, but could preferably be more, for instance 1.5 meter and most preferably at least two meter. Such distance is indicated in fig. 7 with arrow C and can be set or adjusted, depending on necessity.

It is further noted, that in fig. 10 a special

embodiment is shown, where the microwave scanner 1 is provided with transmitting antennas 5, which are operating at different working frequencies. The higher frequencies exhibit a lesser penetration of the material of the layer 4 of mineral wool, whilst the shorter frequencies (having a longer wavelength) exhibit a higher degree of penetration into the layer 4 of mineral wool. By combining simultaneous or shortly intermittent measurements, it is possible to determine for different depths, whether or not an enclosure 15 is present at some of these depths or none thereof within the height h in the Z-direction of the layer 4 of mineral wool. By arranging transmitting and receiving antennas 5, 6 also opposite each other (above and below the advancing layer of mineral wool) , a total review or measurement along the height or depths of the layer 4 of mineral wool can be achieved. It is well within the realm of knowledge of the normally skilled person to provide values for frequencies to be used for inspecting a layer 4 of mineral wool at

different depths, but as a mere example it is noted here, that the working frequencies of the microwave scanner could be between 1 and 25 GHz, preferably between 1.5 and 20 GHz and more preferably between 1.2 and 10 GHz. However, most preferably it is been shown in confidential testing, that the working frequencies of the microwave scanner could be either between or on the limits of 2.45 and 5.8 GHz. If working frequencies of 2.45 and 5.8 GHz are used from above and from below the layer 4 of mineral wool, a complete investigation of a layer 4 of mineral wool can be achieved having a thickness of up to at least 80 mm. The present invention in neither intended nor envisaged to be limited to any such values. Fig. 8 and 9 show images, which van be constructed from measurement signals, obtained with the microwave scanner 1. By interconnecting equal Fl-values, isometric lines can be drawn in a surface representing the top surface, a cross section or the bottom surface of a layer 4 of mineral wool. In doing so, an image can be constructed, like the ones shown in fig. 8 and 9. The inventors of the present invention have noted that when using a microwave scanner 1, such images already made result quite valuable information. For instance, the image

constructed in fig. 8 corresponds with coke particles, while the image constructed in fig. 9 corresponds with mineral wool, in which a previously unknown amount of binder has clotted. The binder is hot, or maybe even just warm, and the same is true for the coke particles 17 in fig. 8. The binder clot 18 in fig. 9 will usually not result in any risk of smouldering or even fire or any other risk, whereas a coke 17 like the one shown in fig. 8 may indeed smoulder and pose a risk in the near future of a fire starting in the mineral wool. For this reason, hot coke particles 17 need to be removed. Nevertheless, it is quite clear from fig. 8 in comparison with fig. 9 that the signature image of a coke is well distinguishable relative to the signature image of for instance a clot of binder 18. The closely spaced isometric lines in fig. 8 indicating three or more usually four different and independent minima or maxima betray the presence of a coke. Binder like shown in fig. 9 is less articulated and the minima and maxima are at far greater distances. Consequently, using the microwave scanner 1 is already possible to identify from the signature image whether or not a coke is present in the mineral wool.

However, then still needs to be determined, what the

temperature of the coke is in order to determine, whether or not such a coke should actually be removed. When coke particles are not very hot, they may not even pose a problem and removal thereof may be prudent but superfluous when it comes to the objective of avoiding risks of for instance a fire starting later. Therefore, using the radiometric sensor to the inherent or core temperature of the coke 17 as shown in fig. 8 needs to be determined in order to ascertain, whether or not a coke 17 is so hot, that it needs to be removed. If the temperature of the coke 17 is not very high, then it can be left in the layer 4 of mineral wool and expenses for removal can be avoided.

After the foregoing description of the present

invention in general terms and in more specific, but non- limiting terms referring to the drawings, accompanying the present application, it should be very clear to the skilled person what the scope of protection actually is, even though such scope is not in particular restricted to the

specifically shown and described embodiments, but only through the definitions of the accompanying claims. For instance, the microwave scanner could be such, that only a set of transmitters and receivers is arranged in a single housing above or below the advancing layer of mineral wool. It has already been indicated, that a housing 9

accommodating radiometric sensor modules 11 could be either or both of above and below the advancing layer of mineral wool. Apart of the inventive insight according to the present invention is naturally, that only coke particles need to be removed, and only then, if the temperature thereof is so high, that risk exists. It is further known, that in particular in the cool down zone of the regular production process strong ventilation is employed to cool the mineral wool. The supply of air and oxygen therein is responsible for a significant flair-up of hot coke particles, so that these become even more distinguishable. For this reason it is particularly advantageous to arrange a system according to the present invention in the cool down zone .

Claims

1. A system for detection of hot enclosures, such as hot coke particles, in mineral wool, particularly during production of mineral wool in a production facility, comprising :

- at least one microwave scanner oriented on the mineral wool to supply enclosure detection signals based on a response from the mineral wool web and/or possible

enclosures to generated microwaves;

- at least one radiometric sensor oriented on the mineral wool to supply temperature detection signals from

temperature dependent radiation originating from the mineral wool and/or the enclosures; and

- at least one processor arranged for processing the

enclosure detection signals from the microwave scanner to determine if an enclosure is present in the mineral wool, and for processing the temperature detection signals from the radiometric sensor to determine the temperature of at least an enclosure determined to be present on the basis of the enclosure detection signals.

2. The system according to claim 1, wherein the

microwave scanner and the radiometric sensor are arranged in the system at a sufficient intermediate distance to

essentially prevent microwaves from the microwave scanner from affecting the radiometric sensor.

3. The system according to claim 2, wherein the

distance is at least 1 meter, more preferably more than 1,5 meter and most preferably at least 2 meter.

4. The system according to claim 1, 2 or 3, wherein at least the radiometric sensor is provided with a shield to essentially prevent at least one of environmental influences and microwaves from affecting the radiometric sensor.

5. The system according to any one of the preceding claims, wherein the microwave scanner comprises a set of at least one microwave transmitter, such as an antenna, for generating the microwaves for providing an excitation, and at least one microwave receiver to detect a response from the mineral wool and provide enclosure detection signals for supply to the processor.

6. The system according to claim 5, wherein the

microwave transmitter and the microwave receiver in the set are arranged on the same side in relation to a layer of the mineral wool, and detection is based on reflections from the mineral wool.

7. The system according to claim 5 or 6, wherein the microwave receiver comprises a radiometric sensor module, which is tuned to a frequency in the microwave bandwidth corresponding with the frequency of microwaves generated by the microwave transmitter.

8. The system according to at least one of the

preceding claims, wherein the microwave scanner is arranged to function on at least one working frequency from the range of frequencies between 1 and 25 GHz, preferably between 1,1 and 20 GHZ, more preferably between 1,2 and 10 GHZ, and most preferably between or either or both of 2,45 and 5,8 GHz.

9. The system according to claim 8, wherein the

microwave scanner is arranged to function on at least two working frequencies to obtain enclosure detection signals for more than one wavelength dependent microwave penetration depth into the mineral wool.

10. The system according to any one of the claims 5-8 and claim 9, wherein the microwave scanner comprises two or more sets of at least one microwave transmitter and at least one microwave receiver, wherein each set is tuned to one of the at least two working frequencies.

11. The system according to any one of the preceding claims, wherein the radiometric sensor comprises at least one radiometric sensor module which is tuned to a frequency corresponding with a predetermined temperature of an

enclosure, at or above which predetermined temperature removal of the enclosure may be required, for instance 80°C and a corresponding frequency, for example 10 GHz.

12. The system according to any one of the preceding claims, wherein radiometric sensors and/or radiometric sensor modules and/or microwave transmitters and/or

microwave receivers are arranged in a diagonal staggering pattern with respect to a layer of mineral wool and a direction of movement thereof.

13. The system according to any one of the preceding claims, wherein radiometric sensors and/or radiometric sensor modules and/or microwave transmitters and/or

microwave receivers, such as antennas, are provided with funnelling means for directing temperature dependent

radiation from the mineral wool onto a sensor or microwaves from a transmitter in the microwave scanner into the mineral wool .

14. The system according to any one of the preceding claims, wherein radiometric sensors and/or radiometric sensor modules and/or microwave transmitters and/or

microwave receivers comprise means for setting the

directivity or orientation.

15. The system according to any one of the preceding claims, wherein at least two microwave scanners are

provided, which are arranged on opposite sides of a layer of mineral wool.