AU2006317587A1 - Process and apparatus for highway marking - Google Patents

Description

WO 2007/061552 PCT/US2006/041261 PROCESS AND APPARATUS FOR HIGHWAY MARKING CROSS REFERENCE TO RELATED APPLICATIONS 5 N/A STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT N/A 10 BACKGROUND OF THE INVENTION The methods of "painting" lines on highways or road markings have changed very little in the past thirty years. Herein the word "painting" refers to any method of 15 applying a coating to a road surface to form a line or road marking. Prior to this invention, there were only three widely used methods to paint lines on highways. The most common technique is to spray a chemical paint on to the road and wait for the paint to dry. The apparatus to 20 spray this paint is typically an "air" or "airless" paint machine wherein the paint is carried by air and projected to the road surface or where the paint is forced through a small hole at very high pressure and projected onto the road surface. The "chemical spray" is the most widely used 25 system to paint lines on highways or road markings. The second technique to paint lines on highways is to apply a tape to the road surface wherein this tape is bonded to the road surface either with heat or with suitable chemicals. US Patent No. 4,162,862 illustrates a 30 "Pavement Striping Apparatus and Method" using a machine to press the tape into hot fresh asphalt. US Patent No. 4,236,950 illustrates another method of applying a multilayer road marking prefabricated tape material. -1- WO 2007/061552 PCT/US2006/041261 A third technique is to use a high velocity, oxygen fuel ("HVOF") thermal spray gun to spray a melted power or ceramic powder onto a substrate. This is shown in US Patent No. 5,285,967. 5 Of the three painting methods, the first method of spraying a chemical onto the road surface and waiting for the paint to dry is the predominant technique used today. The history of line painting indicates that there are at least three properties of "paint" which are important 10 to the highway marking industry: (1) the speed at which the paint dries, (2) the bonding strength of the paint to the road surface, and (3) the durability of the paint to withstand the action of automobiles, sand, rain, water, etc. 15 As discussed in US Patent No. 3,706,684 (Dec. 19, 1972), the first conventional traffic paints were based on drying oil alkyds to which a solvent, such as white spirits or naphtha, was added. The paint dries as the solvent is released by evaporation. However, the paint 20 "drying" (oxidation) process "continues and the film becomes progressively harder, resulting in embrittlement and reduction of abrasive resistance thereof causing the film to crack and peel off." The above patent describes "rapid-dry, one-package, epoxy traffic paint compositions 25 which require no curing agent." As described in US Patent No. 4,765,773: "The road and highways of the country must be painted frequently with markings indicating dividing lines, turn lanes, cross walks and other safety signs. While these 30 markings are usually applied in the form of fast drying paint, the paint does not dry instantly. Thus a portion of the road or highway must be blocked off for a time sufficient to allow the paint to dry. This, however, can lead to traffic congestion. If the road is not blocked for -2- WO 2007/061552 PCT/US2006/041261 sufficient time to allow the paint to dry, vehicle traffic can smear the paint making it unsightly. Also in some instances the traf fic will mar the marking to such an extent that the safety message is unclear, which could 5 lead to accidents." Low-boiling volatile organic solvents evaporate rapidly after application of the paint on the road to provide the desired fast drying characteristics of a freshly applied road marking. 10 The 4,765,773 patent illustrates the use of microwave energy to hasten the paint drying process of such solvents. While the low-boiling volatile organic solvents promote rapid drying, "this type of paint formulation 15 tends to expose the workers to the vapors of the organic solvents. Because of these shortcomings and increasingly stringent environmental mandates from governments and communities, it is highly desirable to develop more environmentally friendly coatings or paints while 20 retaining fast drying properties and/or characteristics" (US Patent No. 6,475,556). To solve this problem paints have been developed using waterborne rather than solvent based polymers or resins. US Patent No. 6,337,106 describes a method of 25 producing a fast-setting waterborne paint. However, the drying times of waterborne paints are generally longer than those exhibited by the organic solvent based coatings. In addition the waterborne paints are severely limited by the weather and atmospheric conditions at the 30 time of application. Typically the paint cannot be applied when the road surface is wet or when the temperature is below -10' centigrade. Also, the drying time strongly depends upon the relative humidity of the atmosphere in which the paint is applied. A waterborne paint may take -3- WO 2007/061552 PCT/US2006/041261 several hours or more to dry in high humidity. Lastly the waterborne paints, which are generally known as "rubber based paints", are made from aqueous dispersion polymers. These polymers are generally very "soft" and abrade easily 5 from the road surface due to vehicular traffic, sand and weather erosion. The above patents all attempt to solve the paint drying problem when using "waterborne" paints and speeding the drying process. The present invention solves the 10 drying problem by not using any solvents in the "painting process". The present invention relates closely to the work done to repair coke ovens, glass furnaces, soaking pots, reheat furnaces and the like which are lined with 15 refractory brick or castings. This process is known today as "ceramic welding". US Patent No. 3,800,983 describes a process for forming a refractory mass by projecting at least one oxidizable substance which burns by combining with oxygen 20 with accompanying evolution of heat and another non combustible substance which is melted or partially melted by the heat of combustion and projected against the refractory brick. The invention is designed to repair, in situ, the lining of a furnace while the furnace is 25 operating. Typically the temperature of the walls of the furnace is over 15000 centigrade and the projected powder(s) ignites spontaneously when projected against the hot surface. In this process it is extremely important that both the oxidizable and non-combustible particles are 30 matched chemically and thermally with the lining of the furnace. If the thermal properties are not correct, the new refractory mass will crack off from the lining of the furnace due to the differential expansion of the -4- WO 2007/061552 PCT/US2006/041261 materials. If the chemical composition is not correct, the new refractory mass will "poison" the melt in the furnace. In the 3,800,983 patent the oxidizable and non oxidizable particles are combined as one powdered mixture. 5 The powder is then aspirated from the powder hopper by using pure oxygen under pressure. The resulting powder oxygen mixture is then driven through a flexible supply line to a water-cooled lance. The lance is used to project the powder-oxygen mixture against the refractory lining of 10 the furnace to be repaired. The powder-oxygen mixture ignites spontaneously when it impinges on the hot surface of the oven. The object of the '983 invention and those that followed is to select the composition of the powders to 15 match the characteristics of the refractory lining and to prevent "flashback" up the lance and back towards the operator of the equipment. "Flashback" is the process wherein the oxygen-powder stream burns so quickly that the flame travels in the reverse direction from the oxygen 20 powder and causes damage to the equipment and serious hazards to the equipment operator. US Patent No. 4,792,468 describes a process similar to that above and specifically illustrates the chemical and physical properties of the oxidizable and refractory 25 particles needed to form a substantially crack-free refractory mass on the refractory lining. US Patent No. 4,946,806 describes a process based upon the 3,800,893 patent wherein the invention provides for the use of zinc metal powder or magnesium metal powder 30 or a mixture of the two as the heat sources in the formation of the refractory mass. US Patent No. 5,013,499 describes a method of flame spraying refractory materials (now called "ceramic welding") for in situ repair of furnace linings wherein -5- WO 2007/061552 PCT/US2006/041261 pure oxygen is used as the aspirating gas and also the accelerating gas and the highly combustible materials can be chromium, aluminum, zirconium or magnesium without flashback. The apparatus is capable of very high 5 deposition rates of material. US Patent No. 5,002,805 improves 'on the chemical composition of the oxidizable and non-oxidizable powders by adding a "fluxing agent" to the mixture. US Patent No. 5,202,090 describes an apparatus 10 similar to that shown in US Patent No. 5,013,499. In the '090 patent, there are specific details about the mechanical equipment used to mix the powdered material with oxygen and transport the oxygen-powder combination to the lance. This apparatus also permits very high 15 deposition rates of the refractory material without flashback. US Patent No. 5,401,698 describes an improved "Ceramic Welding Powder Mixture" for use in the apparatus shown in the previous patents listed. This mixture 20 requires that at least two metals are used as fuel powder and the refractory powder contains at least magnesia, alumina or chromic oxide. US Patent No. 5,686,028 describes a ceramic welding process where the refractory powder is comprised of at 25 least one silicon compound and also that the non-metallic precursor is selected from either CaO, MgO or Fe 2 0 3 . US Patent No. 5,866,049 is a further improvement on the composition of the ceramic welding powder described in No. 5,686,028. 30 US Patent No. 6,372,288 is a further improvement on the composition of the ceramic welding powder wherein the powder contains at least one substance which enhances production of a vitreous phase in the refractory mass. -6- WO 2007/061552 PCT/US2006/041261 BRIEF SUMMARY OF THE INVENTION The invention provides a method of and an apparatus for flame spraying refractory material directly onto a road surface to provide a highly reflective, very durable 5 and instant drying "paint" to said road surface. Since the paint contains no solvents and the flame spraying process operates at very high temperatures, the "paint" can be applied under widely varying conditions of temperature and humidity. 10 The present invention makes use of a ceramic welding process in which one or more non-combustible ceramic powders are mixed with a metallic fuel and an oxidizer. The mixture is transported to, a combustion chamber, ignited and projected against the surface of the road. 15 Alternately, the constituents can be mixed in the combustion chamber. The fuel is typically aluminum or silicon powder and the non-combustible ceramic powder is typically silicon dioxide, titanium dioxide or mixtures thereof or other oxides described below. The oxidizer is 20 typically a chemical powder, but can also be pure oxygen or air. The heat of combustion melts or partially melts the ceramic powder forming a refractory mass that is projected against the road surface, the temperature of the materials causing the refractory mass to adhere durably to 25 the surface. In another aspect of the invention a metallic powder of silicon or aluminum is combusted in a combustion chamber to melt a mixture of silicon dioxide (Si0 2 ), calcium oxide (CaO) and sodium carbonate (Na 2

CO

3 ) to 30 produce a soda-lime glass (Na 2 Si 2 0 5 ) . The material resulting from the combustion is a slurry of liquid soda lime and crystalline silicon dioxide and CaSiO 3 or Ca 2 SiO 4 in crystalline form. This glass-like composition melts at a temperature of about 12800 Kelvin (1007 0 C or 1845 0 F) -7- WO 2007/061552 PCT/US2006/041261 which is much lower than the temperature needed to melt silicon dioxide. Iron powder can be employed as the metallic fuel and during the combustion process forms Fe 2 0 3 which is yellow 5 in color and which can serve as the yellow pigment for road marking. The combustion chamber can be embodied as a reverse vortex flow chamber in which a reverse vortex provides a thermal insulating layer of gas along the walls of the 10 chamber to prevent the high temperatures of combustion from melting or otherwise damaging the chamber walls. The object of the present invention is to present a method of "painting" lines on roads, wherein the "paint" dries instantly, adheres durably to the road, has extreme 15 resistance to abrasion and erosion, wind, sand and rain, and is inherently safe from "flashback". This "paint" can be applied at any temperature and under wet and rainy conditions. The operating temperature of the combustion chamber is typically on the order of 20000 Kelvin (3632'F) 20 or above. BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS The invention will be more fully described in the following detailed description taken in conjunction with 25 the drawings in which: Fig. 1 is a diagrammatic representation of apparatus in accordance with the invention; Fig. 2 is a diagrammatic representation of an alternative embodiment of the apparatus according to the 30 invention; Fig. 3 is a diagrammatic representation of a further embodiment of the apparatus according to the invention; -8- WO 2007/061552 PCT/US2006/041261 Fig. 4 is a diagrammatic representation of one embodiment of a combustion chamber employed in the invention; Fig. 5 is a diagrammatic representation of a frustum 5 shaped reverse vortex combustion chamber employed in the invention; Fig. 6 is a cross-sectional view of one embodiment of a multiple nozzle arrangement used in the combustion chamber of Fig. 5; 10 Fig. 7 is a diagrammatic representation of a cylindrical-shaped combustion chamber employed in the invention. Fig. 8 is a diagrammatic view of an alternative version of the combustion chamber; 15 Fig. 9 shows a variation in the combustion chamber of Fig. 8; Fig. 10 shows a further embodiment of a combustion chamber having a double vessel construction; Fig. 11 is a cross-sectional view of the embodiment 20 of Fig. 10; and Fig. 12 shows a screw feeder employed in the invention. DETAILED DESCRIPTION OF THE INVENTION 25 Fig. 1 illustrates a typical embodiment of apparatus employed in this invention. A first hopper (1) contains the metallic fuel powder (2) typically aluminum powder or silicon powder. Other suitable combustible powders include zinc, magnesium, zirconium, iron and chromium. Mixtures 30 of two or more combustible powders can also be used. A second hopper (6) contains the powdered oxidizer (7), typically ammonium nitrate, potassium nitrate or sodium nitrate. The non-combustible ceramic material, typically silicon dioxide, titanium dioxide or powdered or ground -9- WO 2007/061552 PCT/US2006/041261 glass, can be combined with the fuel powder, the chemical oxidizer or both. Each hopper feeds the powder by gravity into a venturi (3 and 8) fed by a first air/oxygen source (4) and a second air/oxygen source (9) . The gas flowing 5 through the venturi is controlled by a first valve (13) or a second valve (14) and aspirates the powder into the air stream. The air streams from the first and second hoppers travel in a first supply line (5) and a second supply line (10) and combine in the combustion chamber (11) where the 10 airstreams are mixed and ignited, typically by an electric arc (12) or gas fed pilot light or plasma arc. The resulting combustion melts at least the surface of the non-combustible materials and the air streams project the melted material onto the road surface. The materials form 15 a coherent ceramic or refractory mass that adheres durably to the surface of the road. The first and second supply lines (5, 10) go directly to the top portion (23) of the combustion chamber (11). The combustion chamber (11) has three areas of interest: a 20 top portion (23) is where the metallic fuel and oxidizer mix; a middle portion (24) is where the fuel is ignited and high temperature burning takes place; and a lower portion (25) is the lowest temperature portion of the combustion chamber (11) where secondary combustion effects 25 take place. In Fig. 1, the oxidizer may be pure oxygen supplied from the air/oxygen source (9) and controlled by the second valve (14). The oxygen goes via the second supply line (10) directly to the combustion chamber (11) . In 30 this case no powdered oxidizer (7) is required and the second hopper (6) is not required. It is important that only air be used to aspirate the metallic fuel powder (2) from the first hopper (1) to the combustion chamber (11). The use of air to aspirate the metallic fuel powder (2) -10- WO 2007/061552 PCT/US2006/041261 eliminates the possibility of "flashback" to the metallic fuel powder (2). Fig. 2 illustrates another method of injecting pure oxygen into the combustion chamber (11). In this 5 illustration, the metallic fuel powder (2) is aspirated into the first supply line (5) and driven towards the combustion chamber (11). At a point in the first supply line (5) that is close to the combustion chamber (11) , a supply of oxygen is injected into the first supply line 10 (5) at a point (16) from an oxygen source (17) . The oxygen from the oxygen source (17) accelerates the fuel air mixture and supplies the oxygen necessary for combustion. The injection of oxygen close to the combustion chamber (11) prevents "flashback" since the 15 fuel is aspirated with air up to the point (16) . Air is insufficient to maintain combustion of the metallic fuel powder (2) . Therefore, the powdered fuel-air mixture cannot burn in the reverse direction towards the first hopper (1). By injecting the oxygen into the first supply 20 line (5), the oxygen aids in the acceleration of the fuel and ceramic powder mixture towards the road surface and also promotes better mixing of the metallic fuel powder (2) with the oxygen. This process is inherently safe from "flashback" 25 because the typical aluminum-powdered or silicon-powdered fuel is transported by air and is separated from the powdered oxidizer (7) until the chemicals are combined in the combustion chamber (11) . It is almost impossible to cause aluminum or silicon powder to flashback when 30 transported by plain air. In addition, the powdered oxidizer (7) does not burn (or burns very slowly) in air thus preventing any flashback in the second supply line (10) transporting the powdered oxidizer (7). -11- WO 2007/061552 PCT/US2006/041261 Another safety feature is that aluminum or silicon powder is very difficult to ignite in air. While there are many cautions regarding the use of aluminum powder, the aluminum powder cannot ignite in air unless the flame 5 temperature (from a match, etc.) exceeds the melting temperature of aluminum oxide (23130 K). This inventor has run experiments with several particle sizes of aluminum powder; i.e., from 1 micron up to 100 microns and has been unable to ignite any of the powders using a propane torch. 10 In addition, the non-combustible ceramic powder may be mixed with the metallic fuel powder (2) or the powdered oxidizer (7). If the non-combustible powder is mixed with the metallic powdered fuel (2), it will dilute the concentration of the powdered fuel and minimize the 15 possibility of flashback or accidental ignition of the metallic fuel powder (2). According to the various ceramic welding patent disclosures, the quantity of the metallic powdered fuel (2) will typically be less than 15% by weight of the non-combustible ceramic powder. 20 In other cases, air alone, without supplemental pure oxygen, is sufficient to supply the oxygen needed for combustion. In this case, air can be injected at the point (16) of Fig. 2 to accelerate the mixture toward the surface and promote better mixing of the metallic powdered 25 fuel (2) with the air. Fig. 3 illustrates in greater detail the apparatus used in this invention. The first hopper (1) contains either the metallic powdered fuel (2) or the powdered oxidizer (7). The metallic fuel powder (2) and powdered 30 oxidizer (7) are fed by a screw conveyer (18) which is driven by a variable speed motor (19) . The screw conveyor (18) feeds into a funnel (20) which is in fluid communication with the venturi (3) into which a stream of air from the first air/oxygen source (4) is directed. The -12- WO 2007/061552 PCT/US2006/041261 rate of flow of the air stream is controlled by the first valve (13) in series with the first air/oxygen source (4) . The venturi (3) aspirates the metallic powdered fuel (2) from the funnel (20) into the first supply line (5) 5 wherein the entrained particles are delivered to the combustion chamber (11). The rate of deposition of the refractory mass onto the surface can be controlled by the rate of movement between the surface and the exit of the combustion chamber (11) . The variable speed motor along 10 with the screw conveyor (18) and the first valve (13) provide an accurate means of dispensing the metallic powdered fuel (2) and powdered oxidizer (7) to the combustion chamber (11) and varying the rate of combustion and deposition of the refractory mass onto the surface of 15 the road. The variable speed motor (19) and first valve (13) are controlled by a device which measures the speed of the "line painting machine" relative to the surface of the road. In this manner the thickness of the deposition on the road surface can be controlled independently of the 20 speed of the line painting machine relative to the surface of the road. The surface may be preheated prior to projecting the refractory mass thereon. The choice of powdered oxidizer (7) is very important to the safety and economics of the line painting process. 25 The powdered oxidizer (7) must be low cost, readily available, non-toxic, and burn with a flame temperature sufficiently high to soften or melt the ceramic materials used in this process. The following chemicals were considered: 30 Ammonium Perchlorate (NH 4 C10 4 ) Ammonium Nitrate (NH 4

NO

3 ) Potassium Nitrate (KNO 3 ) Sodium Nitrate (NaNO 3 ) Potassium Perchlorate (KC10 4 ) -13- WO 2007/061552 PCT/US2006/041261 Sodium Perchlorate (NaClO 4 ) Potassium Chlorate (KC10 3 ) Sodium Chlorate (NaClO 3 ) Air 5 Pure oxygen Ammonium perchlorate is a well known and well characterized oxidizer used in solid state rocket fuels. It is the oxidizer for the solid rocket boosters for the space shuttle. It is relatively expensive and made by only 10 one company in the United States. The combustion products are primarily NO and a small amount of NO 2 , chlorine and hydrogen chloride (HCL), all of which are toxic. Therefore, ammonium perchlorate was ruled out for use as the oxidizer in this application. 15 Ammonium nitrate (NH 4

NO

3 ) is one of the better oxidizers because it contains no chlorine and therefore produces no HCL. It may generate toxic amounts of NO, although the concentration of the NO when combined with air is likely to be very low. Ammonium nitrate is also 20 known as a fertilizer and widely used in explosives. It is widely available and inexpensive. However, it takes 4.45 pounds of ammonium nitrate to burn one pound of aluminum and therefore ammonium nitrate will require larger volumes and weight than other potential oxidizers. 25 Potassium nitrate (KNO 3 ) and sodium nitrate (NaNO 3 ) are widely available, very inexpensive and will also generate a toxic amount of NO. Again, it is expected that the NO will be very much diluted with free air in the operation of this invention. Both potassium nitrate and 30 sodium nitrate will generate byproducts which will react with air to create hydroxides. These hydroxides are soluble in water and may (or may not) cause problems with the deposition and adherence of the refractory mass on the road surface. Only 2.25 pounds of KNO 3 are required to -14- WO 2007/061552 PCT/US2006/041261 burn one pound of aluminum. Therefore, KNO 3 is a very good candidate for the powered oxidizer (7). Sodium nitrate (NaNO 3 ) has very similar properties to

KNO

3 . It is readily available, low cost and only requires 5 1.89 pounds of KNO 3 to burn one pound of aluminum. The other perchlorates and chlorates are similar in performance and combustion properties to sodium and potassium nitrate and will also generate byproducts that are water soluble. They are more expensive and less 10 available than sodium and potassium nitrate. Air is a very good candidate for use as the oxidizer. Obviously it is readily available and only requires a compressor. The question is: Can sufficient air be injected into the apparatus to supply sufficient- oxygen 15 for the combustion and also not drain too much of the heat away? Pure oxygen is an excellent candidate for the oxidizer. Using pure oxygen would create a process very similar to ceramic welding. There are no toxic byproducts 20 and the valves and controls are inexpensive. Pure oxygen is very inexpensive and readily available. If compressed oxygen (as a gas) is used, the containers are very large and heavy relative to the amount of oxygen stored. Also, the problem of "flashback" must be addressed. 25 Liquid oxygen (LOX) is a very good candidate for large volume highway painting applications. It is very inexpensive and widely available. The only problem is the storage and handling of the LOX. The following non-combustible ceramic materials were 30 considered for use as the "paint pigment" in this apparatus: Silicon Dioxide Titanium Dioxide Aluminum Oxide -15- WO 2007/061552 PCT/US2006/041261 Chromium Oxide produced from refused grain brick. Magnesium Oxide Iron Oxide Crushed colored glass 5 Magnesite regenerate Corhart-Zac A1 2 0 3 - /Bauxite-Regenerate The prime criteria for the selection of the "paint pigment" are cost and availability. Titanium dioxide is 10 the prime pigment used in white paints, is readily available, and is very low in cost. Aluminum oxide is also readily available, but is much more costly than titanium dioxide. Silicon dioxide is normally known as "sand" and may be the least expensive of all of the "paint pigments". 15 Chromium oxide, if produced from refused grain brick, is also a low cost ceramic material, but may not be consistent in its mixture. Refused grain brick is available commercially as, for example, Cohart RFG or Cohart 104 Grades. Magnesium oxide may be used in small 20 amount to enhance the thermal properties of the final paint product. Magnesite regenerate, corhart-zac and bauxite-regenerate are recycled refractory products that were previously used in high temperature furnaces. A mixture of two or more non-combustible ceramic materials 25 can be used. In one embodiment, at least two non-combustible materials are mixed with at last one metallic fuel powder (2) and an oxidizer. One of the non-combustible materials has a melting point in excess of the flame temperature of 30 the burning metallic fuel powder (2) and powdered oxidizer (7), and the second non-combustible material has a melting point that is lower than the flame temperature of the burning metallic fuel powder (2) and the powdered oxidizer (7). The mixture is ignited so that the combustible -16- WO 2007/061552 PCT/US2006/041261 particles react in an exothermic manner with the powdered oxidizer (7) and release sufficient heat to melt the lower melting point non-combustible material but not sufficient to melt the higher melting point non-combustible material. 5 The materials are then projected onto the surface, and the lower melting point non-combustible material acts as a glue for the higher melting point non-combustible material and the products of combustion, and the resulting refractory mass adhere durably to the surface. Preferably, 10 the higher melting point non-combustible material includes titanium dioxide, aluminum oxide, magnesium oxide, chromium oxide, iron oxide, zirconium oxide, tungsten oxide or a mixture of two or more of these. The lower temperature non-combustible material is silicon dioxide or 15 crushed glass (glass frit) and the metallic combustible powder is silicon or aluminum. Some line painting compositions that are suitable for coating a road surface include a composition comprising titanium dioxide and silicon; a composition comprising 20 titanium dioxide, silicon dioxide, and silicon; a composition comprising aluminum oxide and silicon; a composition comprising aluminum oxide, silicon dioxide, and silicon; a composition comprising iron oxide and silicon; a composition comprising iron oxide, silicon 25 dioxide, and silicon; a composition comprising magnesium oxide and silicon; and a composition comprising magnesium oxide, silicon dioxide, and silicon. In some instances a small amount of aluminum can be employed to facilitate the ignition of the mixture in the combustion chamber (11). 30 A glass-like line painting composition can alternatively be employed. A presently preferred composition comprises silicon oxide (SiQ 2 ) calcium oxide (CaO) and sodium carbonate (Na 2

CO

3 ). The metallic fuel powder (2) can typically be silicon or aluminum powder. -17- WO 2007/061552 PCT/US2006/041261 Titanium oxide (TiO 2 ) can be utilized as a pigment to form a white marking composition. Air is employed as the preferred oxidizer. The heat of combustion forms a soda lime glass as a liquid and a slurry of silicon dioxide and 5 titanium oxide in crystalline form. The combustion temperature is about 1000*C which is substantially less than the combustion temperature needed for melting silicon dioxide in the above described line painting compositions comprising one or more ceramic materials. 10 The ceramic compositions described above are primarily composed of silicon dioxide (sand) mixed with a pigment such as titanium dioxide for white lines or crushed yellow glass for yellow lines. The pigment normally is about 10% of the silicon dioxide content in 15 the mixture. Sufficient heat must be supplied to melt the silicon dioxide and form a slurry with the pigment. The resulting slurry is projected from the combustion chamber (11) onto the surface of the road for adherence durably thereon. Silicon dioxide melts at approximately 1900-2000* 20 Kelvin (1727 0 C or 3141 0 F) . This very high temperature can cause difficulty in the design of the combustion chamber (11) and the selection of pigments to generate the intended color. For example, yellow iron oxide decomposes at a temperature several hundred degrees less than the 25 melting temperature of silicon dioxide. Therefore, yellow iron oxide cannot be used as a pigment to generate the yellow color if the prime product of the combustion process is liquid silicon dioxide. Glass-like materials can be employed in accordance 30 with the invention which can be melted at much lower temperatures. As an example, silicon dioxide (SiO 2 ), calcium oxide (CaO) and sodium carbonate (Na 2 CO3) can be combined and heated by burning a metallic fuel powder (2) -18- WO 2007/061552 PCT/US2006/041261 such as silicon or aluminum to create a soda-lime glass (Na 2 Si 2 O) as a liquid which melts at a temperature about 12800 Kelvin (1007cC or 1845*F) . The resultant composition is a slurry of liquid soda-lime glass with crystalline 5 silicon dioxide and either CaSi 3 or Ca 2 SiO 4 in crystalline form. A glass slurry can be created at about one-half of the temperature required to melt silicon dioxide. The glass slurry acts as a "glue" to hold the silicon dioxide and other solid particles to the highway surface and 10 improves the adherence of the paint on the highway surface. Titanium oxide can be utilized as a pigment to form a white marking composition. Iron can be employed as the metallic fuel powder (2) which when burned forms yellow 15 iron oxide (Fe 2 0 3 ) which serves as the yellow pigment for yellow highway marking lines. Other pigments can be employed as described below. The glass type compositions work well on highways covered with asphalt. The lower temperature glass 20 compositions may not adhere well to concrete which melts at about the same temperature as silicon dioxide. In addition to the selection of low cost ceramic or other materials for use as "paint pigment", there is a requirement for coloring materials to produce the colors 25 of yellow, blue and red on road surfaces. These coloring materials may be pre-mixed with the ceramic powder or powdered fuel, or may be added to the combustion chamber (11) via a separate supply line. The coloring material can be, for example, tungsten, zirconium, crushed yellow or 30 another color glass, or ferric oxide (Fe 2 0 3 ) . Similarly, retro-reflective beads can be added. Since the powdered oxidizer (7) tend to be hygroscopic, it is necessary to add "anti-caking" agents to the powdered oxidizer (7) to prevent the formation of -19- WO 2007/061552 PCT/US2006/041261 clumps, which inhibits the powder from flowing smoothly. The "anti-caking" agent is also known as a "flow" agent. The typical flow agent is TCP (tri-calcium phosphate), although others are well known in the art. 5 Fig. 4 illustrates one aspect of the combustion chamber (11) . Since the apparatus operates at extremely high temperature, typically at or above 20000 Kelvin, it is important that the combustion chamber (11) be designed to be low cost and have a very long life at elevated 10 temperature. The combustion chamber (11) may be made of a suitable ceramic material, metal or a metal that is coated on the inside with a high temperature ceramic coating. Fig. 4 illustrates the use of small lateral venturies (21) built into the sides of the combustion chamber (11) . As 15 the combustion products are projected from the combustion chamber (11), the velocity of the combustion gases create a partial vacuum on the inside surface of the combustion chamber (11). Cooler air is sucked into the lateral venturi (21) and flows along the inside surface (22) of 20 the combustion chamber (11). This air both cools the inside surface (22) of the -combustion chamber (11) and also reduces the build up of residual products on the inside of the combustion chamber (11). Because of the very high temperatures involved in the 25 flame spray operation, typically 2000 0 C and higher, it is very important to insulate the walls of the combustion chamber (11) from the combustion process inside of the combustion chamber (11). One very effective method of doing this is to create a "reverse vortex" air flow inside 30 of the combustion chamber (11). Fig. 5 illustrates one form of a reverse vortex combustion chamber (311). The reverse vortex combustion chamber (311) is shaped as a frustum (27) of a cone, which -20- WO 2007/061552 PCT/US2006/041261 is a cone cut off at the narrow end. The narrow portion of the frustum (27) is the entrance or closed end of the reverse vortex combustion chamber (311) and the wider portion (28) is the exit or open end of the reverse 5 vortex combustion chamber (311). An exit aperture is typically provided at the open end and from which the flame spray is emitted. The powdered fuel/ceramic mixture is injected at (26) into the closed end of the reverse vortex combustion chamber (311) as shown, and along the 10 axis (29) of the reverse vortex combustion chamber (311). The igniter (29) can be positioned on the side of the reverse vortex combustion chamber (311) or along the axis (29) as the fuel injection point. The gas carrier (typically air) of the powdered fuel/ceramic mixture 15 causes an axial flow from the closed end to the open end of the reverse vortex combustion chamber (311). As an alternative, a portion of the powdered fuel/ceramic mixture can be introduced into the reverse vortex combustion chamber (311) along with air injected for the 20 reverse vortex, such as at second vortex points (30). Air is injected tangentially at one or more points second vortex (30) near the open end of the reverse vortex combustion chamber (311). This produces a first tangential gas flow (31) tangential to the walls of the 25 frustum (27). The air flows relatively slowly from the open end to the closed end of the reverse vortex combustion chamber (311). Since the tangential air flow travels from the open end to the closed end of the reverse vortex combustion chamber (311), it is called a "reverse" 30 vortex. It has been shown that a reverse vortex acts as an extremely good thermal insulator preventing the high temperature combustion along the axis of the reverse vortex combustion chamber (311) from melting the walls of the reverse vortex combustion chamber (311), (See "Thermal -21- WO 2007/061552 PCT/US2006/041261 Insulation of Plasma in Reverse Vortex Flow" by Dr. A. Gutsol, Institute of Chemistry and Technology, Kola Science Centre of the Russian Academy of Sciences) (Also see published application WO 2005/004556). Optionally, a 5 second tangential gas flow (33) may be introduced at one or more first vortex points (32) near the closed end of the reverse vortex combustion chamber (311) . The second tangential gas flow (33) is directed so that the direction of rotation about the axis of the reverse vortex 10 combustion chamber (311) is in the same direction as that produced by the air injected at second vortex points (30). This second tangential gas flow (33) promotes a faster reverse vortex and promotes better mixing of the fuel/air mixture. 15 Fig. 6 depicts a cross-sectional view of a multiple nozzle arrangement, wherein gas enters the combustion chamber (11) tangentially at (34) through four nozzles (35) coupled to a plenum (36), thereby creating a gas flow tangential to the wall of the exit of the combustion 20 chamber (11). This creates a vortex gas flow which gradually moves from the open end to the closed end of the combustion chamber (11) with a strong circumferential velocity component. Fig. 7 illustrates another form of the combustion 25 chamber (11) in the shape of a cylindrical combustion chamber (411). As before, the powdered fuel/air mixture (26) is injected into the combustion chamber (11) at the closed end (31) along the axis (29A) of the cylinder. Air is injected tangentially at the second vortex point (30) 30 and/or the first vortex point (32) to create a reverse vortex flow from the open end (28) to the closed end (31) of the cylindrical combustion chamber (511). The exit from the cylindrical combustion chamber (411) may have a restricted aperture or a specially shaped nozzle. -22- WO 2007/061552 PCT/US2006/041261 The frustum (27) shown in Fig. 5 can be configured to improve the operation of the reverse vortex combustion chamber (311) . For example, the powdered fuel/ceramic mixture can be injected directly into the second vortex 5 points (30) in the reverse vortex combustion chamber (311), thereby causing improved mixing of the air with the powdered fuel/ceramic mixture. In addition, the powdered fuel/ceramic mixture will absorb radiant heat from the center of the combustion chamber (311) thereby preheating 10 the powdered fuel/ceramic mixture while at the same time insulating the reverse vortex combustion chamber (311) walls from the heat of combustion. If the selected fuel is silicon powder, there is an added benefit. Silicon powder is black as coal dust and 15 acts as a perfect "black body" absorber. This will significantly improve the preheating of the fuel/air mixture and cool the walls of the combustion chamber (11, 311, 411). If the powdered fuel/ceramic mixture is injected into 20 the first vortex point (32), then the igniter(29) can be centered on the axis (29A) of the reverse vortex combustion chamber (311) at the closed end. Likewise, the same approach can be taken with the -cylindrical combustion chamber (411) shown 25 in Fig. 7. In this case the powdered fuel/ceramic mixture is injected into the second vortex points (30) along with the air flow to support combustion and cool the walls of the cylindrical combustion chamber (411) . In this case the igniter (29) can be placed at the center of the closed 30 end of the cylindrical combustion chamber (411). Fig. 8 illustrates another important aspect of the invention, illustrated with a cylindrical combustion chamber (62) having a curved end (64) and, optionally, an inwardly extending conical portion (66). The reverse -23- WO 2007/061552 PCT/US2006/041261 vortex air stream is illustrated as (60) and is produced by air or oxygen injected at second vortex points (30) as described. This air steam flows along the inside walls of the combustion chamber (62) with an initial rotational 5 angular velocity. When the air stream approaches the curved end (64) of the cylindrical combustion chamber (62), the diameter of the cylindrical combustion chamber (62) is reduced according to the specific shape of the curved end (64) . The velocity of the reverse vortex air 10 stream (60) remains basically constant and therefore the angular velocity of the air stream increases as the diameter of the cylindrical combustion chamber (62) decreases. The shape of the curved end (64) also causes the 15 reverse vortex air stream (60) to reverse direction and travel to the open end of the cylindrical combustion chamber (62) and in the axial center of the cylindrical combustion chamber (62). The higher angular velocity caused by the shape of the curved end (64) of the 20 cylindrical combustion chamber (62) improves the mixing of the fuel/air/ceramic thereby improving combustion and heat transfer to the non-combustible powder. In addition, the angular rotation of the air stream increases the effective length of the cylindrical combustion chamber (62) and thus 25 increases the dwell or residence time of the cylindrical combustion chamber (62). The shape of the curved end (64) of the cylindrical combustion chamber (62) can be designed to "focus" the reverse vortex air stream as it travels from the curved end to the open end of the cylindrical 30 combustion chamber (62). The fuel/powder mixture can be introduced at second vortex points (30) and/or at other ports into the cylindrical combustion chamber (62), as described above. -24- WO 2007/061552 PCT/US2006/041261 Another embodiment of the combustion chamber (11) in accordance with the invention is shown in Fig. 9. The combustion chamber (70) is of cylindrical shape having a conical section (72) end and a curved transitional section 5 (74) which joins an optional inwardly extending conical portion (76) . A pair of concentric pipes, i.e., inner pipe (78) and outer pipe (80), are positioned at the closed end of the annular area of conical portion (76). The inner pipe (80) is part of the plasma igniter. The 10 outer pipe (78) serves to inject air and the powdered fuel/ceramic mixture into the combustion chamber (70). A small amount of powdered fuel/ceramic mixture may be introduced with a larger volume of air into the combustion chamber (70) at second vortex points (30), as in the above 15 embodiment. The open end of the combustion chamber (70) has an aperture (82) which is in communication with a nozzle (84) for providing the plasma spray to a work surface. The nozzle (84) may not be necessary for all applications. For applications not requiring a nozzle 20 (84), the plasma spray emanates from the aperture (82) of the chamber. A further embodiment of the combustion chamber (11) is shown in Fig. 10 as a double-walled combustion chamber (711). The double-walled combustion chamber (711) has a 25 cylindrically shaped ceramic inner lining (90) that has a closed end of curved configuration which terminates in an optional inwardly extending conical portion similar to that shown in Fig. 9. This closed end is shaped to change the direction of the reverse vortex. Alternatively, the 30 closed end of the double-walled combustion chamber (711) may be flat. The double-walled combustion chamber (711) has an outer housing (92) which is typically made of steel or titanium. The space (94) between the ceramic inner chamber lining (90) and outer housing (92) is in fluid -25- WO 2007/061552 PCT/US2006/041261 communication with the inside of the double-walled combustion chamber (711) by means of holes or openings (96) provided through the wall of the double-walled combustion chamber (711) near the open or exit end 5 thereof. The openings (96) are preferably oriented tangentially to the inside surface of the double-walled combustion chamber (711) and directed toward the closed end of the double-walled combustion chamber (711). The openings (96)are oriented at a tangential angle of 10 approximately 200. In one version of a combustion chamber shown in Fig. 10 two concentric pipes, i.e., inner pipe (78) and outer pipe (80), are located at the closed end of the double walled combustion chamber (711) . As discussed in Fig. 9, 15 the inner pipe (80) is normally configured as a high temperature plasma igniter and the outer pipe (78) serves as the entry port for the powdered fuel/ceramic mixture and air/oxygen mixture. As discussed below, the igniter and entry ports can be otherwise located. 20 In one form of the double-walled combustion chamber (711) the powdered fuel/air mixture is injected at one or more points (98) into the space (94) between the ceramic inner lining (90) and outer housing (92). The air is injected tangentially to the inside wall of the outer 25 housing (92) and results in a forward vortex of air/fuel which spirals in space (94) toward the open end of the double-walled combustion chamber (711). The forward vortex cools the surface of the inner ceramic shell [NOTE DESCRIBED] and thermally insulates the outer housing (92) 30 from the inner ceramic shell and preheats the air/fuel mixture prior to the mixture being injected into the double-walled combustion chamber (711) at openings (96). Since the space (94) is sealed, pressure builds up in this space and forces the air/fuel mixture through the openings -26- WO 2007/061552 PCT/US2006/041261 (96) and into the double-walled combustion chamber (711). The orientation of the openings (96) causes a reverse vortex to be formed on the inside of the double-walled combustion chamber (711) which flows in a spiral manner 5 from the open end towards the closed end of the chamber. A plasma igniter (100) extends through the outer housing (92) and wall of the inner ceramic shell into the exit portion of the double-walled combustion chamber (711), as illustrated. The plasma igniter (100) directs 10 its ignition plasma tangentially to the wall of the double-walled combustion chamber (711) and pointed slightly toward the closed end of the double-walled combustion chamber (711). The plasma igniter (100) causes the fuel/air mixture to ignite approximately at point 15 (110) and the flame to propagate in a reverse vortex manner toward the closed end of the double-walled combustion chamber (711). As described above, the closed end of the double-walled combustion chamber (711) is preferably shaped to reverse the direction of the burning 20 reverse vortex and increase the tangential velocity of the resulting vortex which propagates forwardly toward the open end of the double-walled combustion chamber (711). The result of the fuel/air mixture burning during the traversal of the reverse vortex in the double-walled 25 combustion chamber (711) and the continued burning of the mixture in the forward propagation of the vortex increases the time that burning occurs inside the double-walled combustion chamber (711). This residence time is an important factor in causing the fuel to burn completely 30 and to transfer the maximum amount of heat energy to the non-combustible ceramic powders mixed with the combustible metallic powders. The exit aperture (112) of the double walled combustion chamber (711) may be significantly smaller than the inside diameter of the double-walled -27- WO 2007/061552 PCT/US2006/041261 combustion chamber (711). This choked double-walled combustion chamber (711) serves to increase the residence time of the burning mixture in the double-walled combustion chamber (711), to increase the pressure in the 5 double-walled combustion chamber (711) and to increase the velocity of the exhaust from the double-walled combustion chamber (711) . The exhaust speed of the molten ceramic particles is very important in achieving the intended adhesion of the particles on the surface to be coated. 10 Optionally, an exhaust nozzle (114) may be attached to the output of the double-walled combustion chamber (711). Fig. 11 illustrates a cross-sectional view of the embodiment of Fig. 10. Arrows (120) illustrate the rotational and spiral flow of the air/fuel mixture in the 15 space (94) toward the open end of the double-walled combustion chamber (711). As the only exit from the space (94) is through openings (96) in the double-walled combustion chamber (711) wall, the fuel/air mixture is forced through these openings (96) in a tangential manner 20 and onto the inner surface of the double-walled combustion chamber (711) . The reverse vortex formed inside the double-walled combustion chamber (711) is ignited by the plasma igniter (100) as described above and results in a burning reverse vortex flame propagation pattern 25 illustrated by arrows (122). In another form of the double-walled combustion chamber (711), only a portion of the powdered fuel/air mixture is injected at one or more points (98) into the space (94) between the inner ceramic lining (90) and outer 30 housing (92). The powdered fuel-air mixture is configured to be a lean mixture which is not sufficient to maintain combustion. This mixture is injected tangentially to the inside wall of the outer housing (92) and results in a forward vortex of air/fuel which spirals in space (94) -28- WO 2007/061552 PCT/US2006/041261 toward the open end of the double-walled combustion chamber (711) . The forward vortex cools the surface of the inner ceramic shell and thermally insulates the outer shell from the inner ceramic shell and preheats the 5 air/fuel mixture prior to the mixture being injected into the double-walled combustion chamber (711) at openings (96) . Since the space (94) is sealed, pressure builds up in this space (94) and forces the air/fuel mixture through the openings (96) and into the double-walled combustion 10 chamber (711). The orientation of the openings (96) causes a reverse vortex to be formed on the inside of the double-walled combustion chamber (711) which flows in a spiral manner from the open end towards the closed end of the double-walled combustion chamber (711). 15 In this case the plasma igniter (100) is typically placed on the central axis of the double-walled combustion chamber (711) and at the closed end as indicated by the inner pipe (80). The majority of the powdered fuel/ceramic mixture air/oxygen mixture is projected into 20 the double-walled combustion chamber (711) via outer pipe (78) located at the closed end of the double-walled combustion chamber (711). When mixed with the lean mixture from the reverse vortex the resulting fuel/air mixture now sustains combustion. 25 Typically, the combustion chamber is formed as a molded or machined ceramic vessel, which can be a single replaceable unit. A typical ceramic material is aluminum oxide which has a melting point of 3762 0 F. Since the typical combustible metallic fuel is silicon and the 30 typical non-combustible material is silicon dioxide, the combustion chamber is designed to operate at a temperature of about 3110OF which is the melting temperature of silicon dioxide. -29- WO 2007/061552 PCT/US2006/041261 The outer housing (92) is typically made from steel or titanium and this outer housing (92) is isolated from the extreme temperatures on the inside of the ceramic combustion chamber by the forward vortex of air and 5 powdered fuel which is caused to flow between the inner and outer shells. In the embodiments of the combustion chamber described herein, it will be appreciated that air or oxygen can be introduced into the combustion chamber at 10 one or more different positions, and that fuel and/or powder can also be introduced into the combustion chamber at one or more positions, separate from or together with the air/oxygen. The igniter can also be variously located to ignite the mixture in the chamber. 15 Fig. 12 shows a powder feeder. The powder feeder includes a screw conveyer (130) having a trough (131) and screw feeder (132) which conveys the combustible and non combustible powders contained in a hopper (133) or other container through a feeder tube (134) to a pipe or hose 20 (136) which serves as a supply line to the combustion chamber. The pipe or hose (136) may be flexible or rigid depending on the particular installation. Air or oxygen is injected into tube (138) for mixing with the powdered fuel/ceramic mixture provided by the screw conveyer (130). 25 Tube (138) may be in fluid communication with the hopper (133) via tube (145) . In this case the hopper (133) will have be sealed from the normal atmospheric pressure by a cover. The tube (145) serves to equalize the pressure at both ends of the screw feeder (132) and prevent the powder 30 from being driven backward through the feeder tube (134) to the hopper (133) . The ratio of air/oxygen to the powdered fuel/ceramic mixture can be independently controlled to provide precise mixing of an intended amount of air/oxygen and powdered fuel/ceramic mixture. An -30- WO 2007/061552 PCT/US2006/041261 electric motor (140) drives the screw conveyer (130) via a pulley and belt assembly (142) and speed reducer (144) . Other motive means can be utilized in alternative implementations. 5 The invention is not to be limited by what has been particularly shown and described and is to embrace the full spirit and scope of the appended claims. -31-

Claims (50)

1. An apparatus for forming a coherent refractory mass 5 on a surface of a road, the apparatus comprising: a combustion chamber adapted to be disposed on the surface; a container for holding one or more metallic fuel powders and one or more non-combustible ceramic materials; 10 a first supply line for transporting the one or more metallic fuel powders, the one or more non-combustible ceramic materials and an oxidizer to the combustion chamber; a second supply line for supplying at least one gas 15 carrier to the combustion chamber to supply an oxygen, to assist in projecting the refractory mass from the combustion chamber and for cooling the combustion chamber; and an igniter to ignite the one or more metallic fuel 20 powders, the one or more non-combustible ceramic materials and the oxidizer in the combustion chamber to cause the one or more metallic fuel powders to react with the oxygen and release heat to form the refractory mass adhering to the surface. 25

2. The apparatus of claim 1 wherein the rate of deposition of the refractory mass onto the surface is controlled by the rate of movement between the surface and the exit of the combustion chamber. 30

3. The apparatus of claim 1 wherein the combustion chamber contains a plurality of openings into which a gas is injected to prevent a combustion product from contacting the inside surface of the combustion chamber. -32- WO 2007/061552 PCT/US2006/041261

4. The apparatus of claim 1 wherein the second supply line causes a reverse vortex to form inside the combustion chamber. 5

5. The apparatus of claim 4 wherein the chamber is substantially a frustum of a cone.

6. The apparatus of claim 4 wherein the chamber is 10 substantially a cylinder.

7. The apparatus of claim 5 wherein the combustion chamber has a closed end and an open end, and wherein the first supply line injects the one or more metallic fuel 15 powders, the one or more non-combustible ceramic materials and the oxidizer into the closed end of the combustion chamber and substantially along the axis of the frustum of the cone. 20

8. The apparatus of claim 7 wherein the combustion chamber has a closed end and an open end, and wherein the first supply line injects the one or more metallic fuel powders, the one or more non-combustible ceramic materials and the oxidizer into the closed end of the 25 cylinder and substantially along the axis of the cylinder.

9. The apparatus of claim 4 wherein the apparatus comprises a flow of the at least one gas carrier which flows substantially circumferentially along the inside 30 surface of the combustion chamber and travels from an open end to a closed end of the combustion chamber.

10. The apparatus of claim 9 wherein the apparatus comprises one or more inlet nozzles oriented substantially -33- WO 2007/061552 PCT/US2006/041261 tangentially relative to the inside wall of the combustion chamber.

11. The apparatus of claim 1 wherein the igniter is 5 located with respect to an axis of the combustion chamber.

12. The apparatus of claim 5 wherein the combustion chamber has a closed end which is shaped so as to increase the velocity of the at least one gas carrier as the at 10 least one gas carrier changes direction from a reverse vortex to a forward vortex.

13. The apparatus of claim 6 wherein the combustion chamber has a closed end which is shaped so as to increase 15 the velocity of the at least one gas carrier as the at least one gas carrier changes direction from a reverse vortex to a forward vortex.

14. The apparatus of claim 1 wherein the container is a 20 screw conveyer.

15. The apparatus of claim 1 wherein the rate of delivery of the one or more metallic fuel powders and the one or more non-combustible ceramic materials is controlled by a 25 speed of a screw conveyer.

16. The apparatus of claim 14 wherein the output of the screw conveyer is in fluid communication with the container. 30

17. The apparatus of claim 14 wherein the container is sealed from an atmosphere. -34- WO 2007/061552 PCT/US2006/041261

18. The apparatus of claim 1 wherein the combustion chamber is substantially cylindrical, is formed from at least two concentric shells with the space between the at least two concentric shells in fluid communication with 5 the combustion chamber.

19. The apparatus of claim 18 wherein a first end of the combustion chamber is closed to prohibit a combustion product and a second end is open to permit the combustion 10 product.

20. The apparatus of claim 19 wherein the second supply line injects the one or more metallic fuel powders, the one or more non-combustible ceramic materials and the 15 oxidizer into the space between the at least two concentric shells to cause a forward vortex to form in the space between the at least two concentric shells wherein the forward vortex travels in the direction from the first end to the second end. 20

21. The apparatus of claim 20 wherein the forward vortex is in a fluid communication with a central portion of the combustion chamber and causes a reverse vortex to flow substantially circumferentially along the inside surface 25 of the central portion of the combustion chamber and to travel in the direction from the second end to the first end.

22. The apparatus of claim 19 wherein the second supply 30 line injects the at least one gas carrier into the space between the at least two concentric shells of the combustion chamber to cause a forward vortex to form in the space between the at least two concentric shells of -35- WO 2007/061552 PCT/US2006/041261 the combustion chamber wherein the forward vortex travels in the direction from the first end to the second end.

23. The apparatus of claim 22 wherein the forward vortex 5 is in fluid communication with a central portion of the combustion chamber and causes a reverse vortex to flow substantially circumferentially along the inside surface of the central portion of the combustion chamber and to travel in the direction from the second end to the first. 10

24. The apparatus of claim 19 wherein the first supply line injects the one or more metallic fuel powders, the one or more non-combustible ceramic materials and the oxidizer into the first end. 15

25. The apparatus of claim 19 wherein the igniter is located on one of the axis of the combustion chamber and the first end. 20

26. An apparatus for forming a coherent refractory mass on a surface of a road, the apparatus comprising: a combustion chamber adapted to be disposed on the surface; a container for holding one or more metallic fuel 25 powders and one or more non-combustible ceramic materials; a supply line for transporting the one or more metallic fuel powders, the one or more non-combustible ceramic materials and an oxidizer to the combustion chamber; and 30 an igniter to ignite the one or more metallic fuel powders, the one or more non-combustible ceramic materials and the oxidizer in the combustion chamber to cause the one or more metallic fuel powders to react with the -36- WO 2007/061552 PCT/US2006/041261 oxidizer and release heat to form the refractory mass adhering to the surface.

27. The apparatus of claim 26 wherein a first end of the 5 combustion chamber is closed to prohibit a combustion product and a second end is open to exhaust the combustion product.

28. The apparatus of claim 26 wherein the rate of 10 delivery of the one or more metallic fuel powders and the one or more non-combustible ceramic materials is controlled by a screw conveyer.

29. The apparatus of claim 26 wherein the supply line 15 causes a reverse vortex to form inside the combustion chamber.

30. The apparatus of claim 26 wherein the chamber is substantially a cylinder. 20

31. The apparatus of claim 27 wherein the supply line injects the one or more metallic fuel powders, the one or more non-combustible ceramic materials and the oxidizer into a closed end of the combustion chamber and 25 substantially along the axis of the combustion chamber.

32. The apparatus of claim 29 wherein the apparatus comprises a flow of at least one gas carrier which flows substantially circumferentially along the inside surface 30 of the combustion chamber and travels from an open end to a closed end of the combustion chamber.

33. The apparatus of claim 29 wherein the apparatus comprises one or more inlet nozzles oriented substantially -37- WO 2007/061552 PCT/US2006/041261 tangentially relative to the inside wall of the combustion chamber.

34. The apparatus of claim 26 wherein the igniter is 5 located with respect to the axis of the combustion chamber.

35. The apparatus of claim 27 where the supply line injects the one or more metallic fuel powders, the one or 10 more non-combustible ceramic materials and the oxidizer at a point at the open end of the combustion chamber and causes a reverse vortex to form inside the combustion chamber. 15

36. The apparatus of claim 27 wherein the closed end of the combustion chamber is shaped so as to increase the velocity of at least one gas carrier as the at least one gas carrier changes direction from a reverse vortex to a forward vortex. 20

37. The apparatus of claim 26 wherein the container is a screw conveyer.

38. The apparatus of claim 37 wherein the rate of 25 delivery of the one or more metallic fuel powders and the one or more non-combustible ceramic materials is controlled by a speed of the screw conveyer.

39. The apparatus of claim 37 wherein the output of the 30 screw conveyer is in fluid communication with the container.

40. The apparatus of claim 37 wherein the container is sealed from an atmosphere. -38- WO 2007/061552 PCT/US2006/041261

41. The apparatus of claim 26 wherein the combustion chamber is substantially cylindrical, is formed from at least two concentric shells with the space between the at 5 least two concentric shells in fluid communication with the combustion chamber.

42. The apparatus of claim 41 wherein a first end of the combustion chamber is closed to prohibit a combustion 10 product and a second end is open to permit the combustion product.

43. The apparatus of claim 42 wherein the supply line injects the one or more metallic fuel powders, the one or 15 more non-combustible ceramic materials and the oxidizer into the space between the at least two concentric shells to cause a forward vortex to form in the space between the at least two concentric shells wherein the forward vortex travels in the direction from the first end to the second 20 end.

44. The apparatus of claim 43 wherein the forward vortex is in a fluid communication with a central portion of the combustion chamber and causes a reverse vortex to flow 25 substantially circumferentially along the inside surface of the central portion of the combustion chamber and to travel in the direction from the second end to the first end. 30

45. The apparatus of claim 42 wherein the supply line injects a first portion the one or more metallic fuel powders, the one or more non-combustible ceramic materials and the oxidizer into the first end of the combustion chamber and a second portion of the one or more metallic -39- WO 2007/061552 PCT/US2006/041261 combustible powders, the one or more non-combustible ceramic materials and the oxidizer into the space between the at least two concentric shells. 5

46. The apparatus of claim 45 wherein the second portion causes a forward vortex flowing substantially circumferentially from the first end towards the second end. 10

47. A method for forming a coherent refractory mass on a surface of a road, the method comprising the steps of: providing a composition comprising one or more metallic fuel powders and one or more powdered oxidizers; transporting the composition to a combustion chamber; 15 igniting the composition in the combustion chamber so that the one or more metallic fuel powders react with the one or more powdered oxidizers and release heat to form a refractory mass; and projecting said refractory mass onto the surface so 20 that the mass adheres to the surface.

48. The method of claim 1 wherein the one or more powdered oxidizers is substituted by at least a gas. 25

49. The method of claim 1 wherein a combustion temperature is sufficient to melt soda-lime glass but is insufficient to melt silicon dioxide.

50. The method of claim 1 wherein the step of providing 30 further includes a step of including aluminum. -40-