Process for making inorganic fibers

Description of the invention

Background of the invention

1. Field of the Invention

The present invention relates generally to the field of producing inorganic fibers, and more particularly to heat transfer and control strategies useful in methods of producing inorganic microfibers and other fibers by flame attenuation fiberization.

2. State of the art

One method of producing small diameter mineral fibers, e.g., discontinuous glass fibers with diameters generally in the range from about 0.2 microns to about 7.0 microns, is the flame attenuation process. . In this process, an electrically or gas-fired fusing kettle or melting kettle containing molten material to be converted to fiber, such as batch materials or pre-fabricated spheres, is melted and drawn from a plurality of sleeve exit holes to form continuous primary fibers. The virgin filaments are drawn from the heated vat or melting pot using pull rollers, also used to feed the filaments into a high-temperature, high-energy gas flame, which further draws the filamentous filaments to form short-length and short-length virgin filaments. diameter. These draw torches have extremely high gas flow rates to draw the filaments as they are heated to reduce their diameter. As the stretched filaments are cooled below the melting point of the glass, the filaments are ruptured by the action of the pulling force of the filaments on the filaments within a predetermined range of length, this range being a function of the operating parameters and the draw zone configuration. A filament guide, having a plurality of grooves, guides and supports the filaments into the flame so that the filaments can be inserted into the flame at a specific location without accidentally blowing around the flame. The discontinuous, small diameter fibers thus formed are collected to form a generally fibrous mat with the fibers randomly oriented within the mat.

[0003] A general method involving obtaining molten glass, forming vertical primary fibers from molten glass and drawing them using the flame of commercially available gas-oxygen burners, e.g. SELAS burners, is known from US Pat. No. 5,588,976.

[0004] Another method of producing glass fibers, comprising introducing molten glass through sleeves, forming primary vertical glass fibers, and drawing these fibers between a pair of high velocity converging flames produced by gas-air mixtures, and

ΕΡ 1,801,082 Β1 also of other fuels with air or oxygen, is known from US Patent No. 2,925,620.

[0005] Energy costs continue to rise, prompting efforts to find ways to reduce fuel while producing mineral fibers. The high speed pull blast draws cooler air out of its surroundings. This low energy, low velocity air mixes with the drag jet, thereby diluting it and reducing both its temperature and velocity. The ability of the drawing equipment to reduce the fiber diameter (i.e. to improve the filtration or insulating properties of the material) is inhibited by this unlimited dilution of the stream. To compensate for the adverse effects of dilution, it is necessary to burn more gas in order to obtain higher temperatures. Operators of the fiber manufacturing process have resorted to limiting dilution by providing a cover around the drawing area that reduces entrainment of the dilution air by restricting access to the area from the surroundings. The sheath also traps heat which increases the temperature in the drawing zone. The casing is provided with several openings to allow the advantageous entrainment of a limited amount of dilution air by the drag stream. The dilution air from at least one of the openings may be equipped with a heater using the waste heat from the pull torch to heat the air. The position of the gaseous jets can also be adjusted within the enclosure by adjusting the amount of suction air above and below the centerline of the blast or jet. The sucked air stream can be directed to create turbulence in the combined stream which causes the primary fibers to follow a tortuous path within the drawing zone which extends the time each primary fiber is exposed to the heat from the drawing zone, thus improving drawing fibers (i.e., reduces the fiber diameter).

[0006] Despite these advances in the art, there is still a need to further improve the energy efficiency in mineral fiber manufacturing processes. Due to the enormous amount of energy used in glass bath furnaces, blast furnaces in the steel industry and rotary kilns, combined with regulations limiting NO emissions_X and SO_Xl To reduce energy consumption and emissions, operators in these industries use oxygen enriched air. These are generally very high temperature processes (at least 820 ° C, 1500 ° F). In the case of very high temperature processes in blast furnaces, the formation of NO_X the long residence times of oxygen and nitrogen molecules in the hot regions of the flame and furnace favor. It has been shown that the use of substantially pure oxygen (about 90% O₂ or more), rather than air, is very effective in reducing NO emissions_X by up to 90% as all nitrogen is eliminated. However, replacing air with essentially pure oxygen increases the flame temperature and thus results in areas in larger furnaces where nitrogen-oxygen reactivity is high and NO formation_X it can increase proportionally, even though it is reduced globally compared to combustion with air. The industries mentioned above use regenerative and recuperative furnaces to recover some heat from the high temperature exhaust gases. Regenerative glass bath furnaces use hot combustion gases that would otherwise be left behind

ΕΡ 1 801 082 Β1 discharged to atmosphere to heat intermediate heat transfer material such as ceramic balls contained in towers. Typically two towers are used such that one tower is heated with combustion gases while air flows through the other tower to preheat the combustion air prior to entering the burners. The towers switch cyclically. In recuperative glass bath furnaces, the combustion air is preheated by heat exchange between the cool air and the combustion gases. In addition to preheating the air, oxygen and commercial grade oxygen enriched air may be preheated using direct or indirect heat exchange (by one or more heat transfer fluids such as inert gas) using specially designed heat exchangers. The different nature of the melt and the type of equipment (fibers versus large tanks of melt, use of fiber drawing torches versus melting torches) lead to very different problems that need to be addressed, despite the fact that reducing energy consumption is a common goal for a wide range of industries, including both float and mineral fiber industries. Since the end use of mineral fibers depends on the physical properties of the fibers, such as their ability to disperse in liquids and suspensions, or their ability to act as a filtering or insulating medium, manufacturers are wary of modifying the process by which acceptable fibers are produced. for a slight reduction in energy consumption.

[0007] For this reason, in the field of fiber fabrication, it would be advantageous to significantly reduce the energy requirements of mineral fiber manufacturing processes to make their implementation attractive, especially in situations where the physical properties of the fibers are acceptable, or even better than acceptable, in terms of fibers. higher quality and products that use these fibers, such as filtration and insulation products.

Summary of the invention

[0008] In accordance with the present invention, methods are described which surprisingly produce better quality fibers than the previously known fiber making methods. By controlling the torch flame temperature and / or other operating parameters of oxy-fuel fiber burners, the methods of the invention allow the production of inorganic fibers having greater average strength and length while reducing or eliminating the shot compared to traditional air-fuel fiber burners. which do not use an oxygen-enriched oxidant. In the case where oxygen is not available or is available but too expensive, methods and systems using air and / or fuel preheating with auxiliary heat sources such as electric resistance elements, coal fired diesel steam, and the like are described. One object of the methods of the invention is to raise the temperature of the exhaust gas leaving the burner or to raise the temperature of the flame. Energy economics may dictate the use of these alternatives instead of oxygen. In case an oxygen enriched oxidant is used,

ΕΡ 1 801 082 Β1 heat recovery techniques can also be used as oxy-fuel flame temperatures are higher than air-fuel flame temperatures.

[0009] A first aspect of the invention is a method as defined in claim 1.

If no oxygen or an oxygen-enriched oxidant is available, then the air and / or fuel entering the burner is preheated using heat recovery techniques (capturing some heat that would otherwise be lost in the process) or by the use of auxiliary heating means, thereby increasing the flame temperature. The methods of the invention include processes in which an oxy-fuel burner produces a hot flue gas stream or a flame to draw primary glass fibers. The exhaust gas 10 combines with the suction air and, in the drawn glass, with the fibers to form the composition, and substantially all of the drawn glass fibers separate from the composition to form an exhaust gas stream containing exhaust gas and sucked excess air. The methods of the invention are those in which either the fuel and / or one or more oxidants are preheated by heat exchange with at least a portion of the exhaust gas stream.

[0011] The method of the invention includes those processes in which a primary oxidant (e.g. air) and fuel are premixed prior to combustion in the burner and an oxygen-enriched secondary oxidant is used in a tobacco background burner. Other methods of the invention include those processes in which the primary oxidant and fuel are mixed together on site in the burner. The primary oxidant can be selected from air, oxygen-enriched air and technical oxygen. The base oxidizer may be compressed prior to combustion with the fuel in the burner.

For example, the primary oxidant may be air and the preheating may include heat exchange with at least a portion of the composition prior to compressing the air. The secondary oxidant is injected into the primary oxidant either before or after compression of the primary oxidant. Alternatively, the primary oxidant may be air and the preheating may include heat exchange with at least a portion of the exhaust gas stream prior to compressing the air. Other methods of the invention are those in which the secondary oxidant may be injected into the primary oxidant before or after the primary oxidant has been compressed. Still other methods of the invention are those in which the secondary oxidant is combined with the primary oxidant to form a tertiary oxidant prior to combustion of the fuel in the burner. The tertiary oxidizer may be preheated, as well as possibly the fuel may be heated, prior to combustion of the fuel with the tertiary oxidant.

[0012] All the embodiments of the inventive method may be controlled by one or more controllers. For example, the flame temperature of a fiberizing burner can be controlled by monitoring one or more parameters selected from fuel flow rate, flow rate of one or more oxidants, fuel mass flow rate, one or more oxidant mass flow rate, fuel energy content , fuel temperature at the entrance to the burner, temperature of the oxidizer at the entrance to the burner, temperature of the exhaust gas, the pressure of the oxidant at the entrance to the burner, the humidity of the oxidizer, the geometry of the burner, the proportion in which combustion occurs, and combinations thereof. In other methods of the invention, a heat transfer fluid, such as inorganic4, may be used

ΕΡ 1 801 082 Β1 A neutral, essentially inert gas, such as nitrogen, argon, helium, non-flammable hydrogen and helium mixtures, and the like. The heat transfer fluid may first receive heat from the exhaust gas stream or composition containing exhaust gas, sucked air, and fibers, and transfer its heat in one or more heat exchangers to one or more of fuel, primary oxidant, secondary oxidant, or tertiary oxidant.

[0013] Another aspect is systems, one of the systems comprising:

(a) an assembly comprising a container for an inorganic melt to be converted into a fiber and a die for forming substantially vertical primary fibers from the melt; and in (b) an oxy-fuel burner for drawing primary filaments.

[0014] If an oxygen-enriched oxidant is not available, certain systems may include heat recovery means or auxiliary heating means for preheating the air and / or fuel. The systems include those that include a compressor to compress the primary oxidant, systems comprising means for injecting an oxygen-enriched secondary oxidant into the burner or into the primary oxidant, typically a tube or split tube containing a coolant in the inter-tube ring. Other systems include those employing a heat exchanger that may be a gas-gas heat exchanger adapted to heat exchange between the effluent stream and streams selected from fuel, primary oxidant, secondary oxidant, and a mixture of primary and secondary oxidants. Some systems include a gas-gas heat exchanger adapted to exchange heat between the exhaust stream and streams selected from fuel, primary oxidant, and fuel along with the primary oxidant. Exemplary systems include a combustion controller that receives one or more input parameters selected from fuel flow rate, flow rate of one or more oxidants, fuel mass flow rate, mass flow rate of one or more oxidants, fuel energy, and fuel input temperature. burner, temperature of oxidizers at the entrance to the burner, pressures of oxidants at the entrance to the burner, humidity of the oxidants, burner geometry, oxidation ratio, exhaust gas temperatures, and combinations thereof, and uses a control algorithm to control the combustion temperature based on one or more of these input parameters.

[0015] The methods of the invention will become more apparent on reading the brief description of the drawings, the detailed description of the invention, and the claims that follow.

Brief description of the figures of the drawing

[0016] The manner in which the objects of the invention can be achieved and other desirable characteristics will be explained in the following description and in the accompanying drawings, in which:

Figure 1 is a flowchart of a prior art fiber manufacturing method that can benefit from the improvements presented in the present invention;

Figures 2-5 are flowcharts of four non-limiting methods of

ΕΡ 1 801 082 Β1 of the invention;

Figure 6 is a perspective view of a prior art fiber-making torch;

Figure 7 is a perspective view of the fiber resisting torch of Figure 6 modified to include an uncooled secondary oxidant injector;

Figure 8 is a cross sectional view of the burner of Figure 7 taken along line 8-8;

Figure 9 is a perspective view of the fiber burner of Figure 6 modified to include a gas cooled injector which may be used to inject a secondary oxidant or, after modification, fuel;

Figure 10 is a cross sectional view of the gas cooled injector of Figure 9 taken along line 10-10;

Figure 11 is a perspective view of the filament burner of Figure 6 modified to include a liquid cooled injector which may be used to inject a secondary oxidant or, after modification, fuel;

Figure 12 is a cross sectional view of the gas cooled injector of Figure 11 taken along line 12-12;

Figure 13 is a top view of a fuel / oxidant mixture nozzle burner useful in the present invention;

Figure 14 is a front view of the burner of Figure 13 and Figure 15 is a schematic illustration of some dimensions of the burner of Figure 13; and Fig. 16 is a schematic block diagram of a combustion process control according to the invention.

[0017] It should be noted, however, that the accompanying drawings are of a different scale and only illustrate typical embodiments of the present invention, and therefore cannot be considered as limiting the scope thereof, as the invention may include other equally effective embodiments.

Detailed description of the invention

[0018] The invention describes methods of making fibers from a glass material. Although the invention is not limited to a method of producing so-called "microfibers, it is helpful to define this term as a starting point. As used herein, the term "microfibers is defined as fibers having an average diameter ranging from about 0.05 to about 3.5 microns, more typically from about 0.1 to about 1.0 microns. The microfibers produced by the methods of the present invention may have a length to diameter ratio of at least about 5: 1, and more usually from about 3000: 1 to about 10: 1. The ratio of microfiber length to diameter is the most common

ΕΡ 1,801,082 Β1 averages from about 10: 1 to about 2000: 1. The average length and diameter of the microfibers can be controlled by controlling the combustion process and secondly, the composition and flow rate of the inorganic melt converted into fibers. In general, the microfibers produced using the process of the invention have an average length of less than about 0.13 cm (0.05 inch). Microfibers normally have an average length in the range of from about 1 to about 500 micrometers, more typically in the range of about 10 to about 300 micrometers, and most typically the fiber length is on average from about 25 to about 50 micrometers. Procedures for determining the average diameter and length of specific lots of microfiber are well known to those skilled in the art and need not be repeated.

[0019] The term "making fiber", unless otherwise indicated, is used as a verb function, and means the formation of short fibers, which may or may not be microfiber, from virgin or continuous filament using a hot-blown process as modified herein. an invention in which hot exhaust gases pull the primary fiber, and the suction air is used to cool the drawn fibers and cause the drawn virgin fibers to be short staple fibers.

[0020] Considering that safety, energy reduction, productivity, and physical properties of the fibers are the most important considerations, and that considerable investment has been made in existing equipment, it would be advantageous in the field of the invention if existing fiber-making systems and methods could be modified in terms of increasing safety, energy efficiency, production capacity and product quality, or if new systems were designed for these purposes, which would quickly recoup their capital expenditure as a result of increased energy efficiency and product sales. The present invention offers methods for these purposes.

[0021] Referring now to the figures, Figure 1 is an air-fuel flow diagram of a prior art fiber manufacturing method that may benefit from the systems and methods of the invention. The glass spheres are transported to the separating hopper 102 and then to the heated vat 104 where the spheres then melt into molten glass. The balls may be transported to the feed hopper 102 via a manifold to a plurality of heated vats 104, the feed rate of the heated vats 104 being a function of the vat temperature and the RPM of the cylinder 110. A heated vat 104, sometimes referred to as a ball vat, may typically include a metallic cylinder heated by a mantle heating using premixed natural gas burners on its side walls. The bottom of the ball ladle 104 may be fabricated from a metal alloy having a plurality of holes ranging in diameter from about 1.27 cm (0.05 inch) to 12.7 cm (0.5 inch), depending on the product being made. glass fiber through which the molten glass is drawn to the primary fibers 106 (only one primary fiber is shown). The primary filament 106 may be pulled and guided through rollers 112 and 114 and through filament guides 113 and 114 through the heat retaining sheath 108. Enclosure 108 may extend from the bottom of the ball ladle 104 to the top surface of the first set of rollers 110, and serves to control the cooling rate of the primary fiber. The aim is to keep the primary fiber temperature as high as possible without damaging the cushioning material in the rollers. In addition to the cover

Heat sources, such as infrared sources, may be placed in the spaces in front of the rollers 110 and 112 or behind the rollers.

[0022] The fiberizing torch 116 serves to generate a hot flame with controlled temperature, speed, and oxidation state in the methods of the invention. The glass fiber product to be manufactured is a function of the mass flow rate of the glass, the diameter of the primary glass fiber, the temperature of the flame produced by the burner 116, the gap size and pressure inside the burner 116, and the product fiber code diameter. The benefits of using oxygen or oxygen-enriched air as the oxidant in fiberizing burners include the production of fibers at a higher flame temperature, leading to increased fiber tensile strength, longer fibers, and reduced shot production or elimination, or more convenient process control in order to avoid pellet production. The fluctuations in humidity are reduced and the variability of the fiber quality is reduced.

[0023] In both the prior art methods shown in Figure 1 and the methods of the invention, a receiving chamber 118 including a generally cylindrical chute collects short fibers and entrains air into chamber 118 to rapidly cool the molten fibers. The fibers are then directed to the larger section of the chamber 118 where, at the very end, a fiber collecting drum 120 collects the fibers, with a secondary fiber collecting device 122 such as a vacuum tube or roller removing the fibers. The collection drum 120 is typically a rotating perforated steel cylinder with a filter material suitable for collecting fibers deposited on the outer surface of the cylinder by means of a vacuum on the inner side of drum 120. Exhaust gas, any particulate matter, and excess air (in the prior art method and in addition excess oxygen in the systems and methods of the invention) pass through drum 120 through conduit 124 and pass through particulate removal device 126 by exhaust fan 128. A heat exchanger 130 may be used to cool the exhaust gas escaping to atmosphere at 136. In the prior art system and methods employing air-fuel combustion, cool air 132 is used to cool the exhaust gas, resulting in low heat heated air 134 which is largely useless for heat recovery. However, at the higher temperatures achieved during oxy-fuel combustion according to the invention, this heat can be recovered and used in various ways, as will be explained hereinafter.

[0024] In light of the higher fiber burner flame temperatures experienced with oxy-fuel burners for fiber making (from about 1204.44 ° C (2200 ° F) to about 1760 ° C (3200 ° F) as opposed to 1037 (78 ° C (1900 ° F) for the flame temperature of an air-fuel burner for fiber production), there are also options for heat recovery and energy savings. Fig. 2-5 are flowcharts of four non-limiting methods of the invention. Fig. 2 shows an embodiment of process 100 in which a hot outlet stream may be used to preheat fuel, a primary oxidant (e.g., air), and / or a secondary oxidant (e.g., oxygen or oxygen-enriched air). Embodiment 100 includes one or more burners for

ΕΡ 1 801 082 Β1 fiber manufacturing 2, collecting unit 4, fiber separator 6 and heat exchanger 8. Fiber burner 2 burns fuel F, which can reach burner 2 via line 10, 12 and / or 14 using primary oxidizer PO which can enter through line 16 and / or 18 and may receive a secondary oxidant SO through line 20 and / or 22. The exhaust gas 5 exits the burner 2 as indicated via conduit 24, but the invention is not limited to this as there may be a significant space shortage between the burner 2 and the collector unit 4. Air 26 is drawn into the collector unit 4 to cool the drawn fibers exiting the burner 2. Air 26 may be ambient air or air other than ambient air, such as chilled or heated air. The composition comprising flue gas, sucked air and fibers exits the collection unit 4 as indicated through line 28 going into fiber separating unit 6. Again, although it is illustrated that the composition passes into fiber separating unit 6 through line 28, the invention is not limited to this, and it is for illustrative purpose only to indicate the overall direction of movement of the composition through the system. The fiber separator unit splits stream 28 by known means into fiber stream 30 and hot exhaust stream 32. The hot exhaust stream 32 transfers some of its heat to one or more of the fuel streams, primary oxidant and secondary oxidant in heat exchanger 8, and then escapes as a cooled exhaust gas stream 34. In certain embodiments of the invention, the hot exhaust stream 32 may be split into a plurality of streams entering heat exchanger 8. Likewise, the cool exhaust stream 34 may be composed of a plurality of cool exhaust streams exiting the heat exchanger 8. The details depend on the specific values ​​of heat transfer. and the design of the heat exchanger 8 as selected by the engineer. A suitable valve arrangement, a part of which is shown in Fig. 2, can be used to direct all, part or any of a specific flow through the heat exchanger 8. If more than two media of the fuel, primary oxidant and secondary oxidant are to obtain heat from the hot exhaust stream, then it will be desirable for the heat exchanger design to include either separate units or one unit including appropriate compartments, seals and the like to prevent premature mixing of oxidant and fuel, or primary oxidant and secondary oxidant, depending on the solution used.

Deviating from the invention, other units such as a particle recovery unit in stream 32 may be included in this process. Further, the solid material flow is not illustrated, and would include fiber precursor storage tanks such as hopper feed hoppers, ball pans, heat retention equipment, virgin fiber guides and rollers, and the like, descriptions of which are well known to those skilled in the art. of average skill in the field of glass fiber fabrication that requires no further explanation.

[0025] Fig. 3 shows an embodiment 200 in which heat from a composition comprising fibers, exhaust gas and aspirated air is used to preheat the fuel, primary oxidant, and / or secondary oxidant. The same reference numbers are used for identical components in different embodiments. Embodiment 200 also includes one or more fiberizing burners 2, a collecting unit 4, and a fiber separating unit 6, however, in embodiment 200, the heat exchanger 8 of the embodiment

ΕΡ 1 801 082 Β1

100 in Fig. 2 is replaced by one or more heat exchangers 9A and 9B shown in Fig. 3, including heat exchanger shells. Fuel F can be routed through line 36 to heat exchanger 9A, and recycled as preheated fuel through line 38, and then directed to burner 2. Likewise or alternatively, a primary oxidant may be routed through line 40 to heat exchanger 9A and returned as preheated primary oxidant through line 42 to burner 2, and a secondary oxidant may be routed through line 44 to heat exchanger 9B and returned as preheated secondary oxidant through line 46 and direct to the burner 2.

[0026] In certain other embodiments of the invention, not shown in the figures, combinations of the embodiments 100 and 200 of Figs. 2 and 3, respectively, may be used. For example, the primary oxidant may be preheated by heat exchange with hot exhaust gases as shown. generally in Fig. 2, while the fuel may be preheated by heat exchange with the equipment illustrated in Fig. 3. All these various methods are considered to be within the scope of the present invention.

[0027] Figs. 4 and 5 show two non-limiting embodiments in which an intermediate heat transfer fluid may be used that takes heat from a hot stream and then transfers some of that heat to the fuel and / or oxidant stream. Fig. 4 shows an embodiment 300 which is somewhat similar to the embodiment 100 of Fig. 2, however, the hot exhaust stream 33 passes through the heat exchanger 50 transferring some of its heat to the cool heat transfer fluid entering the heat exchanger 50, for example through conduit 13. The warm heat transfer fluid leaves heat exchanger 50, for example via conduit 11 which continues to another heat exchanger 52 by exchanging heat with fuel entering line 54, primary oxidant entering line 58, and / or secondary oxidant 62. For clarity, the various valves are not shown, but one skilled in the art will appreciate that some or all or no portion of each stream (fuel, primary oxidant, and secondary oxidant) should be preheated in any given operation. Unheated fuel, primary oxidant, and secondary oxidant may be directed directly to burner 2, such as through lines 56, 60, and 64. Moreover, the heat exchangers 50 and 52 may be a single unit or multiple units and may be placed in series or in parallel as required by any particular case. The conduits can be added or removed according to the specific embodiment in question, amount of heat transferred, production limits, and the like. Safety valves are not shown, but will be included in many of the streams, for example in conduit 13 carrying the heated heat transfer fluid.

[0028] Fig. 5 shows an embodiment 400 which is somewhat similar to the embodiment 200 of Fig. 2, but a warm stream of heat transfer fluid 15 which has absorbed heat from exhaust gas, sucked air and fibers in heat exchangers 9A. and 9B, is routed through heat exchanger 53 to preheat a cool fuel stream 66, a cool primary oxidant stream 70, and / or a cool secondary oxidant stream 74. The cooled heat transfer fluid leaves heat exchanger 53 through conduit 17 and returns to heat exchangers 9A and 9B to complete the cycle. Again, for clarity, the variety is not shown

ΕΡ 1 801 082 Β1 valves, but those skilled in the art will recognize that some, all, or no part of each stream (fuel, primary oxidant, and secondary oxidant) should be preheated in any given operation. Unheated fuel, primary oxidant, and secondary oxidant can be directed directly to burner 2 through, for example, lines 68, 72 and 76. Moreover, the heat exchangers 53,9A and 9B may be single units or multiple units and may be placed in series or in parallel as required in any particular case. Safety valves are not shown, but will be included in many of the streams, for example in conduit 17 carrying the heated heat transfer fluid.

[0029] The heat transfer fluid used may be any gaseous, liquid, or some combination of gaseous and liquid compositions which functions or may be modified to function as a heat transfer fluid. The gaseous heat transfer fluids can be selected from inert inorganic gases such as nitrogen, argon and helium, inert organic gases such as fluoro-, chloro- and chlorofluorocarbons, including perfluorinated versions such as tetrafluoromethane and hexafluoroethane, and tetrafluoroethylene and the like , and mixtures of inert gases with a small proportion of inert gases such as hydrogen, and inert liquids which may be organic liquids, inorganic or some combination thereof, for example, salt solutions, glycol solutions and the like. Other possible heat transfer fluids include water vapor, carbon dioxide, or mixtures thereof with nitrogen.

[0030] Any combination of the processes of Figs. 4 and 5, and in practice any combination of the processes of Figs. 2-5, as may be desired may be imagined. More heat transport equipment will entail increased capital expenditure, which will however be offset by reduced energy consumption. Detailed, albeit routine, calculations can be performed to determine the most cost-effective process and layout.

[0031] Fig. 16 shows a block diagram of one non-limiting control scheme for a combustion method according to the invention. Master controller 78 is shown, but the invention is not limited thereto as any combination of drivers may be used. The controller may be selected from P1 controllers, PID controllers (including any known or reasonably foreseeable variations thereof), and it calculates an error equal to the difference between a measured value and a fixed point by generating an output signal to one or more of the controls. The controller can calculate the error continuously or discontinuously. Other possible implementations of the present invention are those in which the controller includes more specialized control strategies such as strategies selected from feedforward, cascade control, internal feedback loops, predictive control, neural networks, and Kalman filtering techniques. In Fig. 16, lines and fields numbered 80-87 may represent sensors, for example sensors of the following parameters, which are only examples:

- 80 = Vfuei, speed of the fuel entering the burner;

- 81 = V._P01 primary oxidant speed entering the burner;

- 82 = V._so, speed of the secondary oxidant entering the burner;

- 83 = Mfuei, the mass flow rate of fuel entering the burner;

- 84 = Mp_Ol the mass flow rate of the primary oxidant entering the burner;

EP 1 801 082 Β1

- 85 = Tfueii temperature of the fuel entering the burner;

- 87 = Tpo, the temperature of the primary oxidant entering the burner;

- 88 = Pp₀₎ primary oxidant pressure entering the burner;

- 89 = H._P0; primary oxidant moisture

[0032] Lines and fields numbered 88-95 may represent control signals and actuators for the outputs, respectively, for the following parameters, which are only examples:

- 88 = V._fuei, speed of the fuel entering the burner;

- 89 = Vp₀the speed of the primary oxidizer entering the burner;

- 90 = Mfuei, the mass flow rate of fuel entering the burner;

- 91 = M_S.o, the mass flow rate of the secondary oxidant entering the burner;

- 92 = Tfuei, temperature of the fuel entering the burner;

- 93 - Tpo, the temperature of the primary oxidizer entering the burner;

- 94 = P_S.o, pressure of the secondary oxidant entering the burner;

- 95 = 5 M._EFF (or the mass flow rate of the hot outlet stream (or heat transfer fluid).

[0033] Other parameters, such as the desired diameter and / or length of the filament 96, the geometry of the burner 97, and the combustion ratio 98, may be taken as input values.

[0034] The term "control", when used as a transitive verb, means verification or adjustment by comparison with a standard or desired value. Control can be closed loop, feedback, feedforward, cascade, prediction, adaptation, heuristics, and combinations thereof. The term "controller" means a device at least capable of receiving real or near real time inputs from sensors and meters and sending commands directly to the burner controls and / or to local devices associated with the burner controls capable of accepting commands. . The controller may also be capable of accepting outputs from operators (human); accessing databases such as relational databases; sending data and accessing data in databases, data warehouses or data marts; and transmitting information and receiving output signals from the human readable display device. The controller may also cooperate with or be integrated with one or more computer application modules, and may oversee the interaction between the databases and one or more computer application modules.

[0035] The term "PID controller" means a proportional integral and differential controller controller. In some cases, the differential mode may not be used or its influence may be significantly limited, so that the driver may be considered a Pl driver. Those skilled in the control will also appreciate that variations of the Pl and PID controllers exist depending on how the discretization is performed. Known and predictable variations of P1, PID, and others are contemplated to be within the scope of the invention.

[0036] The drivers useful in the methods of the invention may vary in details. One of the PID controllers useful in the present invention can be mathematically described by Equation 1:

ΕΡ 1 801 082 Β1 u (t) = Κρ [e (t) + 1 / Ti -fe (t) dt + Td «ó (t)] (1) where:

f is the integral;

(t) is a derivative over time;

u (t) is the controller output which can be, for example, the flame temperature of a burner;

e (t) is the difference between the desired and measured value (real time);

Td is the constant that describes the differential part of the algorithm (the differential part can be filtered to avoid high frequency differentiation);

Ti is the constant describing the integral part of the algorithm; and

Kp is the proportional gain constant.

[0037] In the S (Laplace) plane, the PID controller can be expressed as (equation 2):

Hr (s) = Kp [1 + 1 / Ti s + Td s / (1 + Tf s)] (2) where:

s is a variable in the S plane; and

Tf is the constant describing the filtering part of the differential part of the algorithm.

[0038] Various types of transforms may be used for the discretization, and some constants may or may not be useful. For example, the constant Tf may not be necessary in some cases, but may be particularly useful in other scenarios. As one example of discretization, the z-transform can be used, which means that the integral part of the algorithm can be approximated using a trapezoidal model of the form (equation 3):

s = (1 -z-1) / T (3) while the differential part can be approximated using the Euler model (equation 4):

s = 2 / Τ · (1 - z-1) / (1 + Z-1) (4) where T is the sampling time.

[0039] The obtained discrete model can then be used directly in the combustion or burner control algorithm. Other discrete modes derived using other transforms are useful in the present invention, and will be apparent to a technician or control engineer of average skill.

[0040] The controller may employ Model Predictive Control (MPC).

MPC provides an advanced multidimensional control method for use in MIMO (multiple input / multiple output) circuits. An overview of industrial predictive control can be found at: www.che.utexas.edu/~qin/ cpcv / cpcv 14.htmi. The MPC computes a sequence of manipulated variable adjustments to optimize the future behavior of a given process. At each test time k, MPC resolves

ΕΡ 1 801 082 Β1 the problem of dynamic optimization, using the model of the controlled system so as to optimize the future behavior (at k + 1, k + 2 ... k + n) in the prediction horizon n. This is done again at k + 1 , k + 2 .... The MPC can use any derived objective function such as a Quadratic Performance Objective and the like, including functions that weigh the manipulated variables and measurements. The dynamics of the controlled process and / or system are described in an explicit process and / or system model, which can be obtained, for example, by mathematical modeling or estimated from the test data of the actual process and / or system. Some techniques for determining certain dynamic characteristics of a controlled system and / or process include step-response models, impulse-response models, and other linear or non-linear models. Often an exact model is not necessary. Entry and exit constraints may be part of the problem formulation in such a way that future violations of the constraints such as hard constraints, soft constraints, fixed point constraints, funnel constraints, return on capital constraints and the like are anticipated and prevented. It may be difficult to explicitly determine the stability of the MPC control scheme, and in some embodiments of the present invention, it may be necessary to use non-linear MPC control. In so-called advanced multi-system control, PID control can be applied to strong one-dimensional loops with few or no problematic interactions, while for strongly coupled loops one or more MPC networks or other multi-dimensional control structures can be used. In addition, computational time considerations may be a limiting factor. Some embodiments may employ nonlinear MPC control.

[0041] The feed-forward algorithm, if used, will in the most general sense be task specific, meaning that it will be specifically designed for the task for which it has been assigned. This specific design could be difficult to develop, but much is achieved by using a more general algorithm such as a first or second order filter with a given gain and time constants. Fig. 6 is a perspective view of a prior art fiber-making burner 150 including a stainless steel or other metal mantle 152, a refractory burner block 154 defining a burner aperture 156 and a combustion chamber 158. A manifold 160 and 162 direct air and fuel into the air-fuel mixture. , typically natural gas, to combustion chamber 158. Manifold 160 and 162 are secured to burner block 154 by mounting holes 164 (typically four) through the orifice 166.

[0042] Fig. 7 is a perspective view and Fig. 8 is a cross-sectional view through section 8-8 of the fiber-making burner of Fig. 6 modified to include injection of an uncooled secondary oxidant in accordance with one of the burners useful in the present invention. The burner 170 includes two secondary oxidant manifolds 172 and 174, which may be a stainless steel tube or a non-alloy tube, each containing a plurality of openings to receive the appropriate number of ceramic tubes 176 through which the secondary oxidant enters the combustion chamber. 158.

[0043] In the operation of the fiberizing burners useful in the present invention, the thin glass primary fibers are directed by guides and rollers into the flame generated by the fiberizing burner. The mass flow rate of the glass material is

EP 1 801 082 Β1 is a function of the primary filament diameter, burner flame temperature, burner geometry such as burner aperture size, burner pressure, and product filament code diameter. The operational conditions of the process are generally not independent values, but interact to some extent. The manufacture of fibers using an oxygen-enriched oxidant / fuel is significantly different to that of the traditional air-fuel fiber-making process. The general rule is to burn the burner in such a way as to replace some of the air with a separate oxygen source. The overall combustion ratio may not change. The process of combining the fuel and oxygen-enriched oxidant will take place in the burner combustion chamber after the gases have passed through the safety device to cut the flame of the burner. The flame temperature of the exhaust gas can be controlled by changing the air / oxygen ratio in the oxidizer. According to the systems and methods of the invention, with a standard burner that burns 45.31 m³/ h (1600 scfh (normal cubic feet per hour)) of natural gas, can be safely injected into the burner from 0 to approximately 11.33 m³/ h (400 scfh) oxygen, in combination with adequate air flow.

[0044] Fig. 9 is a perspective view of the fiberizing torch of Fig. 6 modified to include a gas cooled injector which may be used to inject a secondary oxidant or, after modification, fuel. Fig. 10 shows a cross-sectional view of an injector 1000 usable in a burner 900 taken along section 10-10 of Fig. 9. The burner 900 includes a metallic jacket 152, a burner refractory block 154 and 156, and an air-fuel manifold 160 and 162 of the prior art burner embodiment 150 of FIG. 6, and further includes an injector 1000 including a metallic rectangular outer tube 180 and a similar but smaller rectangular tube 184 positioned within the outer rectangular tube 180 as shown in Fig. 10. An inner rectangular tube 180 and an inner rectangular tube 184 define the volume through which cooling gas can enter through the inlets 188 and 189 and exit through the outlets 190 and 191. Fuel or secondary oxidant may be injected through manifolds 181 and 182, which may be pipes with stainless steel or other alloy metal. More orifices 186 may be uniformly disposed proximate the bottom of tube 181 and top of tube 182 for fuel or secondary oxidant injection. Since the pipes 181 and 182 are exposed to the hot flue gas, cooling is provided. Bolts or other fasteners 192 can be used to secure the injector 1200 to the burner 1100. In other embodiments, more or less than two coolant gas inlets and outlets may be provided as needed, and it is contemplated that these alternative embodiments are within the scope of the invention.

[0045] Figure 11 is a perspective view of the fiberizing burner of Figure 6 modified to include a liquid cooled injector which may be used to inject a secondary oxidant or, after modification, fuel. Fig. 12 is a cross-sectional view of a liquid cooled injector 1200 used in burner 1110 taken along section 12-12 of Fig. 11. Burner 1100 and injector 1200 are similar to burner 900 and gas cooled injector 1000 of Figures 9 and 10, except that only one inlet and one outlet need to be provided for the entry and exit of the liquid. Embodiments are contemplated employing more than one liquid coolant inlet and more than one liquid coolant outlet

ΕΡ 1 801 082 Β1 coolants are within the scope of the invention, but this may not be necessary in all cases due to better cooling of the liquid.

Fig. 13 is a top view of a fuel / oxidizer nozzle burner 1300 useful in the present invention, and Fig. 14 is a front view of the burner of Fig. 13. In burner 1300, oxygen-enriched oxidant and fuel are directed to the burner. flow through a separate plurality of tubes 206 and 207, respectively, reaching separate nozzles 214. An inlet of oxygen-enriched oxidant 202 feeds a chamber or manifold 204 which then feeds tubes 206. Likewise, fuel inlet 210 feeds a fuel chamber or manifold 212 that directs fuel through tubes 207. The fuel is then burned in nozzles 214. Combustion gases are directed through a chute defined by refractory spacer 208 and then onto inorganic virgin fibers for production. fibers. The number of oxidant tubes 206 and fuel tubes 207 can vary widely, but generally the number of oxidant tubes ranges from about 50 to about 150, and the number of fuel tubes 207 can range from about 25 to about 75 Length of each tube, L._ox and L._f) may range from about 7.62 cm (3) to about 25.4 cm (10 inches) and the diameter may range from about 0.79 mm (1/32 inch) to 12.7 mm ( 0.5 inch). The spacing between the tubes may be uniform and equal to about one tube diameter; alternatively the tubes may be placed side by side. The fuel and oxidizer inlets may be stainless steel or other alloy tubing. As can be seen in Fig. 15, this particular configuration of the burner provides a similar wide, flat filament flame production effect to the premix slot type burner. The width W of the slots 156 may range from about 7.62 cm (3) to about 91.44 cm (36 inches) and the height of the slot H may range from about 0.13 cm (0.05 inches) to about 2.54 cm (1 inch). The depth D may range from about 1.27 cm (0.5) to about 12.7 cm (5 inches), depending on the required support strength.

[0047] Filament burners and injectors are an important aspect of the invented processes, and are claimed in co-pending US Patent Application No. US 2007/0141522.

[0048] In accordance with the present invention, the fuel and oxidant are introduced into the burner either through separate tubes in the burner assembly, or they are pre-mixed. The term "fuel" as used herein means a combustible composition containing as a major part, for example, methane, natural gas, liquefied natural gas, propane, oil mist and the like (in gaseous or liquid form). The fuels useful in the present invention may contain minor amounts of non-fuel components, including oxidants, for purposes such as premixing the fuel with the oxidant, or atomizing the liquid fuels. Oxidizers include oxygen-enriched air containing at least 50 vol. oxygen, such as "industrially pure oxygen (99.5%) produced by a cryogenic air separation plant or oxygen that is not pure, such as produced by by vacuum pressure swing adsorption or membrane permeation (about 90 vol.% O₂ or more).

[0049] The total amounts of fuel and oxidant used by the combustion system are such that the oxygen flow may range from about 0.9 to about 1.2 theoretical stoichial flow.

ΕΡ 1 801 082 Β1 tric oxygen necessary for complete combustion of the flowing fuel. This statement can be expressed in another way, namely that the proportion in which combustion occurs is between 0.9 and 1.2.

[0050] The flow rate of gaseous fuel in the various burners depends on the geometry of the burner used, but is generally at least about 15 m / s. The upper limit of the fuel flow rate depends mainly on the desired geometry of the drawn filament and the geometry of the torch; if the fuel flow rate is too low then the flame temperature may be too low leading to inadequate fiber formation which is undesirable, and if the fuel flow is too high the flame may affect the downstream equipment or may be wasted. which is also undesirable.

[0051] Additionally, the invention also provides flame stabilization through the auxiliary injection of fuel and / or oxidizing gases. The injection of the oxidizing fluid may be performed by premixing the fuel and the primary oxidant, typically air, and additionally injecting a secondary oxidant using either an uncooled injector, a gas cooled injector, or a liquid cooled injector as explained with reference to the figures. When injecting a secondary oxidant, such as industrial oxygen, in a gas-cooled or liquid-cooled painik, the diameter of the bore 186 (Fig. 10) or the diameter of the tube 176 in an uncooled injector (Fig. 8) may be such that the speed of the secondary oxidant does not exceed about 60 , 96 m / s (200 ft / s) at a flow velocity of 11.39 m³/ h (400 scfh). The torch internal pressure should not exceed approximately 68.95 nPa (10 psig).

[0052] The methods of the present invention are intended to be used, for example, to replace air-fuel combustion systems in existing fiber-making burners and / or to be used as the primary energy source in new burners.

[0053] Materials suitable for the refractory block in the burners are fused zirconium oxide (ZrO₂), fused cast AZS (alumina-zirconia-silica), rebonded AZS, or fused cast alumina (A!₂ABOUT₃). The choice of a specific material is dictated by, among other things, chemical parameters and the type of inorganic fibers produced.

[0054] In embodiments of the invention employing a heat transfer fluid, it is possible with a hot brine to transfer heat to the oxidant or fuel either indirectly by transporting heat through the walls of the heat exchanger, or some portion of the hot brine can exchange heat directly by mixing with the oxidant or fuel. In most cases, heat transport will be more economical and safer if the heat transport is indirect, in other words using a heat exchanger in which the intermediate fluid is not mixed with oxidant or fuel, but it is important to note that the present invention contemplates both ways of heat transfer. Moreover, the brine may be heated by the hot exhaust gas by one of the two mechanisms just mentioned.

[0055] In some embodiments, the primary heat transfer means comprises one or more heat exchangers selected from the group consisting of ceramic heat exchangers, known in the art as ceramic recuperators, and metallic heat exchangers referred to as

ΕΡ 1 801 082 Β1 hereinafter as metallic recuperators. The systems include those in which the primary means of heat transfer are double jacketed radiant recuperators. Preheating means useful in the present invention include heat exchangers selected from ceramic heat exchangers, metal heat exchangers, regenerators alternately heated by a stream of hot intermediate fluid and cooled by a stream of oxidant or fuel that heats as a result, and combinations thereof. For regenerative agents alternately heated by a stream of hot intermediate fluid and cooled by a stream of oxidant or fuel, there may be two vessels containing an inert medium such as ceramic spheres or pebbles. Depending on the case, one vessel is used in the regeneration mode, where ceramic spheres, pebbles or another inert medium are heated by a hot intermediate fluid, while the other vessel is used during the operating mode to come into contact with the fuel or oxidant for heat transfer. from hot refrigerant to fuel or oxidizer. The flow to these vessels is then switched at the appropriate time.

[0056] In certain methods of the invention, the hot intermediate fluid exchanges heat with the fuel and oxidant in parallel preheating means, in other words, the hot intermediate fluid is split into two streams, one heat exchange stream with the fuel in the first preheating means. in the burner, a second heat exchange stream with the oxidant in the second of the preheating means in the burner. Alternatively, for safety reasons, the intermediate fluid exchanges heat first with the oxidant in one or more oxidant preheaters and then with fuel in one or more fuel pre-heaters in the plurality of exchangers.

[0057] In other exemplary embodiments, the fuel path, oxidant path, and hot brine path may be defined through holes bored in the burner block as is known in the burner manufacturing art.

[0058] In the case where the intermediate fluid is air and the combustion oxidant is oxygen, hot air may advantageously be used as a combustion oxidant by diverting hot air to the burners when the oxygen supply is interrupted.

[0059] From the description set forth herein, it is to be understood that the invented methods are not strictly limited to the embodiments in which the fuel and oxidant are heat exchanged with the intermediate fluid at the same intermediate fluid temperature. In some embodiments, it is preferable to contact the hot intermediate fluid first with the oxidant to produce an intermediate fluid having a lower temperature, and then to heat the lower temperature intermediate fluid with the fuel. Moreover, as mentioned above, it is contemplated in some embodiments that the hot intermediate fluid may be mixed with the oxidant, fuel, or both.

ΕΡ 1 801 082 Β1