GB2470889A - Apparatus for supplying a source of infra-red heat to a surface or substance - Google Patents

Abstract

An apparatus 2 for supplying a source of infra-red heat to a surface or substance comprises a metal fibre yarn mat 12 having approximately 50-100 unidirectionally oriented metal fibres. The fibres are prepared by combing randomly oriented metal fibres manufactured by a melt extraction method. In further aspects, apparatus for supplying a source of infra-red heat to a surface or substance is provided: where the apparatus is at least partially constructed using lightweight, insulating, non-combustible material 10; or where the apparatus comprises a pre-mix fan 4 system for mixing gas and air together prior to any ignition. Preferably, the apparatus can be used in the repair of an asphalt surface by bringing the apparatus into contact with the surface, or into sufficiently close proximity to the surface, to heat it to a required temperature. Alternatively, the apparatus may be used for burning off gases by bringing the apparatus into contact with the gases, or into sufficiently close proximity to the gases, to burn them off cleanly at a required temperature.

Description

Heater Apparatus The present invention relates to an apparatus for supplying a source of infra-red heat to a surface or substance, and more specifically to an infra-red heater which can be used in, for example, the repair of asphalt surfaces, as well as also being applicable to other uses.

The use of infra-red heaters to repair asphalt surfaces dates at least as far back as far as the early 1970's.

It works on the principle that if asphalt is heated back to its original tethperature it can be manipulated and reset with a mixture of new material and rejuvenating agents in order to repair potholes and other damage. This method obviates the need for the removal, disposal (and thus waste) of what could be :::: perfectly useful asphalt, and also of the need for large quantities of new asphalt to replace it. The infra-red heater method means that only enough new material to fill the void is required. It also speeds up repairs on damaged roads and removes the noise S...

:1.5. associated with pneumatic drills which were previously required to carry out such :...:. repairs. **S

The heaters that have been used in this method have varied over time, from heaters with exposed flames, to heaters using various heating conductors such as heat bulbs, heat bricks, and ceramic plates in order to achieve the highest temperatures.

For the heating process to be at its most efficient and effective, the heater used must give the most even distribution of the infra-red heat. If there are patches under the heater or in the middle of the area of asphalt being treated that do not reach a desired temperature, the result will be areas within the overall area that are not easily manipulated. This results in it being difficult for an operative to perform the repair.

As a result, the majority of heaters currently in the market place consist of many flames or burners close together in order to try and give a complete blanket of heat'.

Generally in such heaters, there is provided a porous metal fibre membrane located within a burner arrangement which may be composed of one or more separate panels. This arrangement is supplied with a combustible gas which is ignited and heats the porous metal fibre membrane which, in turn, provides the infra-red heat to heat the surface. However, there are problems of control and consistency of the heating of the surface associated with this approach.

The closest that anybody has come to solving this to date is the Roads Europe Ltd patent GB2392190 that uses a knitted burner deck in order to attempt to evenly distribute heat and burn at high temperatures. The knitted material used by Roads Europe in its burner deck is described in EP 0839221 to Bekaert S.A. However, as a * S *5*S result of the material's deliberately knitted method of manufacture, it consistently has ** *S *:.:: 15 small gaps in its surface that allow for cold spots' whereby the full burner deck does S..

not reach an even or required heat. This has a detrimental effect on the manipulative :,:.:: properties of the asphalt directly beneath these cold spots. These spots are not heated *.IS to the same required temperature as the rest of the asphalt surface being repaired.

Additionally, heaters which have been available to date have had operating problems due to the fact that the heat is either too hot or is too close to the surface, or that it for other reasons carbonizes the asphalt surface. A primary fault is that the systems do not allow for variable temperatures, as they are either on' or off'. With the only control element being that they are switched off and on intermittently by electrical timing systems, they do not control heater temperature and the temperature cannot be turned up or down whilst in the on' mode. Once an asphalt surface has been carbonized, it is no longer of any use as a road or footpath and must be removed, disposed of and replaced. This is a waste of what could have been perfectly usable asphalt.

Such problems with heat are attributable to a lack of control over the combustion process. These problems are especially rife with the new types of asphalt, such as mastic asphalt, which is being used by local authorities and asphalt companies.

Mastic asphalt has a higher bitumen content than conventional asphalt, about 7-10% of the whole aggregate mix, as opposed to conventional asphalt which has only around 5% added bitumen.

Once an area of mastic asphalt has been carbonized, the entire mastic asphalt * * surface of which it is a part must be dug up and disposed of. An entirely new surface * * **** must then be brought in as it is not currently possible to dispose of and replace ** ** isolated patches of mastic asphalt. The heaters currently in use do not have the a...

capability to repair isolated patches of mastic asphalt as they carbonize what is such a : * sensitive and volatile material. This is due to their lack of controlled combustion and * S S...

inability to provide lower temperatures to suit more sensitive surfaces such as mastic asphalt. Isolated patches of e.g. mastic asphalt can be fixed with the apparatus and methods of the invention.

Furthermore, to date, all asphalt heaters have been naturally aspirated, i.e. the engines used to power them depend only upon atmospheric pressure to draw in air for combustion. The efficiency of such heaters can be significantly improved upon.

There are also issues with insulation. Existing heaters inevitably lose heat as some is always conducted away from the heating zone through the body of the heater, which are usually constructed of a metallic material, often stainless steel, and escapes.

As a result of the lost heat, more gas has to be burned to reach desired temperatures and to melt the asphalt to the required level.

Another set of problems with currently used asphalt heaters is that they are large, heavy, cumbersome, and involve risks to the operative using them because of this. They are also not well suited to urban areas as, when the ancillary materials required are also included, they weigh too much to be carried on a regular 3.5 tonne van-type vehicle. This weight requires that they be carried on larger host vehicles that incur large carbon footprints and which are unsuitable for city use and use in other areas with high volumes of traffic, or where the roads are very narrow. I...

: A further limitation on existing heater apparatuses is that they cannot be used * * I...

in very cold conditions as they will simply freeze up and stop functioning. ** S.

: * 15 It is therefore desirable to provide an apparatus which can provide infra-red S... * . S...

heat for a surface or substance, such as for the repair of asphalt surfaces, which is able S* *S to provide a controlled, consistent, all-over heating of the surface, without leaving any cold spots, which can improve gas efficiency, which can be used more effectively on different types of asphalt through the use of variable temperature and high turn-down' ratios, which insulates heat by being constructed of a mainly non-metallic material, which can be used in cold conditions, and which is lighter than existing heaters. The present invention is able to address one or more of these problems.

Therefore, in accordance with a first aspect of the invention, there is provided an apparatus for supplying a source of infra-red heat to a surface or substance, the apparatus comprising a metal fibre yarn having about 5 0-100 unidirectionally oriented metal fibres, wherein the unidirectionally oriented metal fibres are prepared by combing randomly oriented metal fibres manufactured by a melt extraction method, and wherein each metal fibre yam has a length of about 0.45 to about 0.6 rn/g and a torsion ratio of 1-9 turns/rn.

According to a second aspect of the invention, there is provided an apparatus for supplying a source of infra-red heat to a surface or substance, wherein the apparatus is at least partially constructed using a lightweight, insulating, non-combustible, non-metallic, machineable material. Typically, this material may comprise calcium silicate.

According to a third aspect of the invention, there is provided an apparatus for supplying a source of infra-red heat to a surface or substance, wherein the apparatus S...

: comprises a pre-rnix fan system for mixing gas and air together prior to any ignition S... * . S...

of the gas. SS *S

: * 15 According to a fourth aspect of the invention, the apparatus may comprise any ***. * . S...

two or more of the features contained in the first to third aspects in combination. S. S*

:*:.:: According to a fifth aspect of the invention, there is provided an apparatus for * supplying a source of infra-red heat to a surface or substance, wherein i) the apparatus comprises a metal fibre yarn having about 50-100 unidirectionally oriented metal fibres, wherein the unidirectionally oriented metal fibres are prepared by combing randomly oriented metal fibres manufactured by a melt extraction method, and wherein each metal fibre yam has a length of about 0.45 to about 0.6 m/g and a torsion ratio of 1-9 turns/rn; ii) the apparatus is at least partially constructed using a material comprising calcium silicate; and iii) the apparatus comprises a pre-mix fan system for mixing gas and air together prior to any ignition of the gas.

Although the apparatus of the invention may be used for uses other than the repair of asphalt surfaces, as detailed further below, for the purposes of illustrating the invention for convenience only, it is to this use that reference shall be made.

The apparatus of the first aspect of the present invention comprises a metal woven mat' comprising a metal fibre yarn having about 50-100 unidirectionally . : oriented metal fibres as defined above, such as that developed by Fiber Tech Co. in S... * S

* Korea and detailed in EP 1681378, which disclosure is incorporated herein by * S. : * 15 reference in its entirety. *..S * S **SS

This material is manufactured differently to the woven material employed in SS *S * the BekaertlRoads Europe documents. This different method of manufacture of the S... * S *5**

Fiber Tech material enables it to provide a much more even and consistent burn surface because the material has less gaps, enabling it to burn with substantially no cold spots and to give a consistent temperature across the entire heater blanket surface. This, in turn, means that it provides for a much more effective heater and is also more economical with gas usage. As it burns more effectively, it also means that the material can be heated to an equal or increased temperature at a faster rate than that of a knitted material. The apparatus of the invention thus creates a true heater blanket'.

The differences between the Fiber Tech and Bekaert materials are in fact explained in paragraphs [0005] and [0006] of the A' specification of EP 1681378, which cites the Bekaert reference.

Bekaert describes a fabric and a membrane for a gas burner which is produced using the fabric. Metal filaments produced through a particular machining process and which have an equivalent filament diameter of 15-150 jim are used. These filaments are combined with each other in a parallel orientation and without a twisting operation using a binding agent to form bundles of filaments, and the bundles of filaments are then woven or knitted to produce the fabric.

However, this provides problems. Metal fibres which are produced through 0*** *. : such a machining process are unidirectionally oriented. The bundles of metal fibres S...

also include a predetermined number of metal fibres. This makes it difficult to * 15 produce a porous membrane for a combustion burner having shorter fibre lengths, or I... * .

having a fibre distribution which is non-parallel or non-uniform.

* The materials in accordance with the Fibre Tech reference are produced by a S... S...

melt extraction method. This permits a random orientation of fibres or a non-uniform distribution. This fibre allows for the provision of a material having a greater combustion range, and a greater porosity.

According to one embodiment of the invention, a typical metal for use in the metal yarn is an iron-chromium-aluminium-based alloy containing about 70-83 wt.% iron, about 18-27 wt.% chromium, about 3-7 wt.% aluminium, and about 0.05-0.5 wt.% zirconium. Such an alloy is also known as Fecralloy, which is an extremely durable material due to its very high resistance to oxidation at increased temperatures.

The carrier vehicle the apparatus is carried on may also carry other containers containing other materials which are essential to the asphalt repair method of the invention, together with any equipment required to supply the surface with these materials, such as a hose or lance to distribute the rejuvenating composition(s).

Examples of such other materials include, but are not limited to hot new asphalt, rejuvenating composition(s), and gas for the burner.

A further advantage of the invention is that the vehicle carrying the apparatus of the invention can also be one which is suitable for true urban use and one which has a much reduced carbon footprint. This is made possible as the apparatus of the invention may be made from a lightweight, insulating, non-combustible material in * : accordance with the second aspect of the invention. An example of such a material **** * * **.* comprises a core of a calcium silicate board. Such a material is produced by the S. *S : 15 Skamol company, and one such product is sold under the name Skamotec 225�. * S S...

Skamotec 225� is a super lightweight, insulating, non-combustible material. S. *.

:.:: Constructing at least a part of the apparatus using such a material results in a * ,.* significant weight reduction for the apparatus, allowing it to be carried on a smaller host vehicle, and also results in less physical exertion required from an operative in today's health and safety conscious environment.

Skamotec 225�, for example, can be machined and manufactured into the desired shape and then bonded with a thin skin material, such as steel, if required, rather than the vehicle being constructed completely from steel. Using such a material will reduce the overall weight of the apparatus significantly.

As well as being super lightweight, Skamotec 225� has high levels of insulation. This means that the heat generated by the burner deck can be kept under the hood of the heater system and not conducted through to the operative or escaping to atmosphere. This makes the combination of this material with the heater blanket' even more efficient in terms of heat retention and gas usage. It also aids in increasing the heat cycle to allow for super fast infra-red asphalt repairs, and it reduces health and safety risks to operators and any other person that might be able to touch the system, particular as they are operated in public areas..

Skamotec 225� is also "frost-proof', meaning that the system can be used in cold weather conditions that other heaters will not be able to as they will freeze up and suffer ignition problems.

* ::: : The apparatus of the third aspect of the invention also allows for a controlled * * heating of the asphalt surface. This is because the apparatus is not dependent upon a r *. :* naturally aspirated combustion process as are existing asphalt heaters. Rather, it uses a * 15 pre-mix fan system'. This means that the gas and air are specifically mixed in a * * desired ratio prior to any ignition. This enables huge gas savings and also means that ***.

*1 an operator has control of the key combustion elements, i.e. gas and oxygen. The operator thus has total control over any variation of the ratio of the gas:air ratio in the premix chamber, before the fan drives it through the burner deck.

This degree of control allows the temperature to be raised or lowered in real time by an operative by increasing or decreasing the flow of gas. This means that the temperature can be turned up and down as required to suit the particular surface being worked upon. The operator can turn up the temperature sufficiently to give conventional asphalt the required manipulative properties (i.e. make it molten, as it was when it was originally laid), or can reduce the temperature sufficiently to work on the newer and more widely used mastic asphalts and ultra-mince (i.e. ultra thin) asphalt so that these more sensitive surfaces are not at risk of being carbonized.

The apparatus of the invention also allows for an almost instant return to ambient temperature from temperatures of up to 1300°C, and uses true' infra-red heating with no associated thermal mass or exposed flames.

The gas which is used in accordance with any of the aspect of the invention as described herein may be any one of a number of gases but is typically Liquid Petroleum Gas (LPG). LPG is a mixture of hydrocarbon gases and is increasingly replacing chiorofluorocarbons in application for environmental considerations.

LPGs typically include propane, butane or a combination thereof in various *::: : proportions. At least one, or both, of propylene and butylene is also typically present.

* According to another aspect of the invention, there is provided a method of * :* applying infra-red heat to a surface or substance comprising bringing an apparatus as * : : ::* 15 described in any of the first to fifth aspects of the invention hereinabove into contact : * with the surface or substance or into sufficiently close proximity to the surface or **** * * substance to heat it to a required temperature.

According to another aspect of the invention, there is provided a method of repairing an asphalt surface, comprising bringing an apparatus as described in any of the first to fifth aspects of the invention hereinabove into contact with the surface or into sufficiently close proximity to the surface to heat it to a required temperature.

Typically, the method of repairing the asphalt surface comprises the steps of: i) applying an infra-red heat to an area of an asphalt surface to be repaired; ii) raking or scarifying the heated asphalt; iii) optionally adding a rejuvenating composition andlor adding fresh asphalt aggregate to the area; iv) compacting the asphalt in the area under repair.

Typically, once the asphalt has been heated to the required temperature to allow it to be manipulated, the asphalt is raked or scarified to provide an even surface to the asphalt. Typically, a section of the heated asphalt around its edges is to remain unscarified to aid bonding of the new, compacted asphalt to the remainder of the untreated surface. If desired, a rejuvenating composition may be applied to the * asphalt; examples of possible rejuvenating compositions include but are not limited to r maltenes. Alternatively, the rejuvenating liquid comprises oils having a large content S...

*... 15 of aromatics with high levels of polar compounds. More typically, the rejuvenating * :* liquid contains a heavy paraffin distillation solvent extract and a heavy naphthenic * S..

* distillate solvent extract, water, and an emulsifier.

If necessary, extra (hot) aggregate may be added to the portion of the asphalt surface under repair to ensure that it is substantially in alignment with the level of the rest of the surface. The asphalt in the repaired portion is then compacted or rolled to complete the repair. Optionally, a final layer of a sealant may be added after the compaction. Usually, the repaired asphalt is capable having traffic driven over it within about an hour.

The size of the apparatus may be varied depending upon the size and shape of the surface to be repaired. If the area to be repaired is relatively small, it makes economical sense to only use an apparatus having a smaller heating area rather than heat a larger area unnecessarily. The appropriate apparatus size for any given area of repair will be readily apparent to a skilled person.

Furthermore, the height of the apparatus from the surface to be heated and the length of time the surface is heated for can be varied according to the depth that it is desired to heat the asphalt down to. Typically, the asphalt is heated to a depth of about mm to about 100 mm from the surface, and the heating is typically carried out over a period of about 3-25 minutes, more typically 6-15 minutes, still more typically 6-10 minutes, although weather conditions (wind, temperature) on the day and the * : :: : condition and dryness or otherwise of the surface will cause variations in the heating * ::: * time required to being the surface to a required temperature. About 8 minutes is most * typical to allow enough time for the heat to penetrate to an optimum depth without * 15 causing carbonization.

** :* According to a further embodiment of the invention, the apparatus is not limited just to the heating and manipulation of asphalt surfaces. For example, the apparatus can be used to burn off and eradicate harmful waste gases, for example vinyl chlorides, without giving off secondary gases as a result. It is able to burn off potentially hazardous gases which may be found at eg. landfill sites, manufacturing plants, and oil refineries, substantially 100% cleanly. In this embodiment of the invention the apparatus is operated upside down so that the infra-red heat is directed upwards. Current flare burners work at lower temperature ranges and this means that when burning off a gas, such as vinyl chloride, they generate other harmful gases as an exhaust. The apparatus of the invention does not.

Traditional flare burners require the gas to contain at least 40% of a combustible gas such as methane in order to explode and combust the gas. They also give off secondary gases.

The apparatus of the invention can explode gas containing as little as 15% combustible gases, and burns them off cleanly because it can burn at temperatures of up to 1300°C. Additionally, in one embodiment of the invention, the apparatus could be powered by waste gases, as long as the gas has at least about 15% combustible gas content.

As mentioned above, the temperature emitted by the apparatus can be * : :: : controlled by an operator. Therefore, if the gas to be burnt off is extremely high in . combustible content then the mixture of gas/air can be diluted so that the explosions * are more controlled. The size of the combustion can be controlled depending upon the surrounding circumstances. Traditional flares do not have this ability, nor are they * portable; the apparatus of the invention is portable due to being ultra lightweight as **** discussed above.

Therefore, there is also provided within the scope of the invention a method of burning off gases, particularly potentially hazardous gases, comprising bringing an apparatus as described hereinabove into contact with the gas or into sufficiently close proximity to the gas to heat it to a required temperature.

The fact that this invention allows for such flares to be super-lightweight means that these flares can also be mounted onto a host vehicle and become mobile around the sites on which they are used. This has a massive advantage because it saves the requirement for numerous flares on a site, you can instead have flares that move around to target areas as and when required.

According to a further embodiment of the invention, there is also provided a use of an apparatus as described hereinabove in repairing an asphalt surface or in burning off gases.

The apparatus may be carried on or affixed to a carrier vehicle. According to one embodiment, the apparatus may be affixed to the rear of the carrier vehicle and able to be moved vertically and horizontally by the operative for optimum positioning in relation to the area which is to be heated.

In summary, the advantages to using the apparatus of the present invention over existing methods for infra-red heating of a surface or substance are: * 0 S. * *::: * i) The apparatus provides a true blanket of heat, substantially removing the r *:* possibility of cold spots allowing for better asphalt manipulation; *505 * ..* 15 ii) More economical gas consumption; : S** iii) The apparatus is quicker to reach the optimum operating temperature and * S.. to cool down back to ambient temperature; iv) The operative has total control over temperature variations to suit surface under repair; v) The apparatus provides a better insulation of beat; vi) The material the apparatus may be made from I is super lightweight, allowing lower carbon footprint and more urban suitable vehicles to carry it; vii) The apparatus is substantially frost-proof; Viii) The apparatus heats via true infra-red heat, with substantially no thermal mass or flames.

The invention will now be further described with reference to the following figures, which are intended to be illustrative only and in no way limiting upon the scope of the invention.

Figure 1 shows a representation of the apparatus of the invention from above.

Figure 2 shows an exploded view of the apparatus of the invention.

Figure 1 shows the apparatus 2 as viewed from above. Visible in this Figure are a pre-mix fan 4, an outer casing 6 made from steel, and an outer side casing 8 also made from steel.

In Figure 2, all of the various components of the apparatus 2 are shown.

Viewing the Figure from top to bottom, the components are the pre-mix fan 4, the r steel outer casing 6, Skamotec 225� 10, the outer side casing 8, and a metal yarn mat * 15 12 which has been made in accordance with EP 1681378.

* :* It is of course to be understood that the present invention is not intended to be * restricted to the foregoing which are described by way of example only, and that minor modifications to the above would be readily apparent to a person skilled in the art.

Claims (13)

1. Claims 1. An apparatus for supplying a source of infra-red heat to a surface or substance, the apparatus comprising a metal fibre yarn having about 50-100 unidirectionally oriented metal fibres, wherein the unidirectionally oriented metal fibres are prepared by combing randomly oriented metal fibres manufactured by a melt extraction method, and wherein each metal fibre yam has a length of about 0.45 to about 0.6 mlg and a torsion ratio of 1-9 turns/rn.
2. 2. An apparatus according to claim 1, wherein the apparatus is at least partially constructed using a lightweight, insulating, non-combustible material. S... * * . S* * *5

   * ***.
3. 3. An apparatus according to claim 1 or claim 2, wherein the apparatus further r *:* comprises a pre-mix fan system for mixing gas and air together prior to any *.* * ... 15 ignition of the gas. ** SS * * S * S S...
4. 4. An apparatus for supplying a source of infra-red heat to a surface or substance, wherein the apparatus is at least partially constructed using a lightweight, insulating, non-combustible material.
5. 5. An apparatus according to claim 2, wherein the lightweight, insulating, non-combustible material comprises calcium silicate.
6. 6. An apparatus according to claim 4 or claim 5, wherein the apparatus further comprises a pre-mix fan system for mixing gas and air together prior to any ignition.
7. 7. An apparatus for supplying a source of infra-red heat to a surface or substance, wherein the apparatus comprises a pre-mix fan system for mixing gas and air together prior to any ignition.
8. 8. A method of applying infra-red heat to a surface or substance comprising bringing an apparatus according to any of claims 1-7 into contact with the surface or into sufficiently close proximity to the surface or substance to heat * it to a required temperature. **** * S a...*
9. 9. A method of repairing an asphalt surface, comprising bringing an apparatus S...

   *...* 15 according to any of claims 1-7 into contact with a surface or into sufficiently r * close proximity to the surface to heat it to a required temperature. * * .
10. 10. A method according to claim 9, comprising the steps of: i) applying an infra-red heat to an area of the asphalt to be repaired; ii) raking or scarifying the heated asphalt; iii) optionally adding a rejuvenating composition and/or adding fresh asphalt aggregate to the area; iv) compacting the asphalt in the area under repair.
11. 11. A method for burning off gases, comprising bringing an apparatus according to any of claims 1-7 into contact with the gas or into sufficiently close proximity to the gas to heat it to a required temperature.
12. 12. Use of an apparatus according to any of claims 1-7 in repairing an asphalt surface or in burning off gases.
13. 13. An apparatus, method or use substantially as described herein in thedescription and drawings. S... * S S S* S * S *S.. *5 *S * * e * * e * . *S S. * S S * S S. *SS