Panel-cooled submerged combustion melter geometry and methods of making molten glass

Abstract

A melter apparatus includes a floor, a ceiling, and a substantially vertical wall connecting the floor and ceiling at a perimeter of the floor and ceiling, a melting zone being defined by the floor, ceiling and wall, the melting zone having a feed inlet and a molten glass outlet positioned at opposing ends of the melting zone. The melting zone includes an expanding zone beginning at the inlet and extending to an intermediate location relative to the opposing ends, and a narrowing zone extending from the intermediate location to the outlet. One or more burners, at least some of which are positioned to direct combustion products into the melting zone under a level of molten glass in the zone, are also provided.

Claims

1. A melter apparatus comprising: a) a floor and a ceiling; b) a substantially vertical wall connecting the floor and ceiling at a perimeter of the floor and ceiling, the substantially vertical wall comprising two opposing substantially vertical side walls, a substantially vertical inlet end wall, and a substantially vertical outlet end wall, a melting zone being defined by the floor, ceiling and the substantially vertical wall, the melting zone having a feed inlet in the substantially vertical inlet end wall and a molten glass outlet in the substantially vertical outlet end wall, the substantially vertical inlet end wall and the substantially vertical outlet end wall positioned at opposing ends of the melting zone, the melting zone comprising an expanding zone beginning at the substantially vertical inlet end wall and extending to an intermediate location relative to the opposing ends of the melting zone, and a narrowing zone extending from the intermediate location to the substantially vertical outlet end wall, at least the substantially vertical side walls in the narrowing zone each having a free-flowing form devoid of angles; and c) a plurality of burners, at least some of which are positioned to direct combustion products into the melting zone under a level of molten glass in the melting zone.

2. The melter apparatus of claim 1 wherein the intermediate location is positioned where the melting zone has a maximum width.

3. The melter apparatus of claim 1 wherein at least some of the substantially vertical wall comprises fluid-cooled refractory panels.

4. The melter apparatus of claim 3 wherein the fluid-cooled refractory panels are liquid-cooled refractory panels comprising one or more passages for flow of a liquid into and out of the passages.

5. The melter apparatus of claim 3 wherein the fluid-cooled refractory panels are cooled by a heat transfer fluid selected from the group consisting of gaseous, liquid, or combinations of gaseous and liquid compositions that functions or is capable of being modified to function as a heat transfer fluid.

6. The melter apparatus of claim 5 wherein the gaseous heat transfer fluids are selected from the group consisting of ambient air, treated air, inert inorganic gases, inert organic gases, and mixtures of inert gases with small portions of non-inert gases, and wherein the liquid heat transfer fluids are selected from the group consisting of inert liquids which may be organic, inorganic, or some combination thereof.

7. The melter apparatus of claim 1 wherein the expanding zone has a plan view trapezoidal shape defined by a trapezoid having a base positioned at the intermediate location and substantially perpendicular to a longitudinal axis of the melter, the trapezoid having a side parallel to the base and positioned at the inlet end wall.

8. The melter apparatus of claim 1 wherein at least some of the plurality of burners are floor-mounted and positioned in one or more parallel rows substantially perpendicular to a longitudinal axis of the melter.

9. The melter apparatus of claim 8 wherein the number of the plurality of burners in each row is proportional to width of the melter.

10. The melter apparatus of claim 1 wherein depth of the melter decreases as width of the melter in the narrowing zone decreases.

11. The melter apparatus of claim 1 wherein the intermediate location comprises a constant width zone positioned between the expanding zone and the narrowing zone.

12. The melter apparatus of claim 1 wherein at least some of the plurality of burners are oxy-fuel burners.

13. The melter apparatus of claim 1 having a throughput of 2 ft.sup.2/stpd or less.

14. The melter apparatus of claim 13 having a throughput of 0.5 ft.sup.2/stpd or less.

15. The melter apparatus of claim 14 wherein the melter substantially vertical wall comprises all fluid-cooled panels, the substantially vertical wall comprising a refractory liner at least between the fluid-cooled panels and the molten glass.

16. The melter apparatus of claim 1 wherein each of the two opposing substantially vertical side walls in the expanding zone and the narrowing zone are non-linear.

17. The melter apparatus of claim 1, wherein each of the two opposing substantially vertical side walls has a free-flowing form, devoid of angles in the expanding zone.

18. A melter apparatus comprising: a) a floor and a ceiling; b) a substantially vertical wall connecting the floor and ceiling at a perimeter of the floor and ceiling, the substantially vertical wall comprising two opposing substantially vertical side walls, a substantially vertical inlet end wall, and a substantially vertical outlet end wall, a melting zone being defined by the floor, ceiling and the substantially vertical wall, the melting zone having a feed inlet in the substantially vertical inlet end wall and a molten glass outlet in the substantially vertical outlet end wall, the substantially vertical inlet end wall and the substantially vertical outlet end wall positioned at opposing ends of the melting zone, the melting zone comprising an expanding zone beginning at the substantially vertical inlet end wall and extending to an intermediate location relative to the opposing ends of the melting zone, and a narrowing zone extending from the intermediate location to the substantially vertical outlet end wall, the intermediate location comprising a constant width zone positioned between the expanding zone and the narrowing zone, wherein at least some of the substantially vertical wall comprises fluid-cooled refractory panels, the two opposing substantially vertical side walls in the narrowing zone each having a free flowing form, and the two opposing substantially vertical side walls in the expanding zone each being linear and intersecting the substantially vertical wall in the constant width zone at an angle larger than 90 degrees; and c) a plurality of burners, at least some of which are positioned to direct combustion products into the melting zone under a level of molten glass in the melting zone.

19. The apparatus of claim 18 wherein at least some of the plurality of burners are floor-mounted and positioned in one or more parallel rows substantially perpendicular to a longitudinal axis of the melter.

20. The apparatus of claim 18 having a throughput of 2 ft.sup.2/stpd or less.

21. A process comprising: feeding at least one partially vitrifiable material into a feed inlet of a melting zone of a refractory melter apparatus comprising a floor, a ceiling, and a substantially vertical wall connecting the floor and ceiling at a perimeter of the floor and ceiling, the substantially vertical wall comprising two opposing substantially vertical side walls, a substantially vertical inlet end wall, and a substantially vertical outlet end wall, the melting zone comprising an expanding zone beginning at the substantially vertical inlet end wall and extending to an intermediate location relative to opposing ends of the melter, and a narrowing zone extending from the intermediate location to the substantially vertical outlet end wall, at least the substantially vertical side walls in the narrowing zone each having a free flowing form devoid of angles; heating the at least one partially vitrifiable material with at least one burner directing combustion products into the melting zone under a level of the molten glass in the melting zone; and discharging molten glass from a molten glass outlet positioned in the substantially vertical outlet end wall.

22. The process of claim 21 comprising discharging at least 0.5 short tons per day per square foot of melter floor.

23. The process of claim 21 comprising discharging at least 2 short tons per day per square foot of melter floor.

24. The process of claim 21 comprising cooling the substantially vertical wall by the substantially vertical wall comprising cooled refractory panels and directing a heat transfer fluid through the cooled refractory panels.

25. The process of claim 21 wherein the heating comprises directing combustion products into the melting zone under a level of the molten glass in the melting zone employing two or more floor-mounted burners.

26. The process of claim 25 comprising directing combustion products into the melting zone under a level of the molten glass in the melting zone employing two or more rows of floor-mounted burners arranged substantially perpendicular to a longitudinal axis of the melter.

27. The process of claim 24 comprising decreasing depth of the molten glass as it moves from the intermediate location to the molten glass outlet.

28. A process comprising: feeding at least one partially vitrifiable material into a feed inlet of a melting zone of a refractory melter apparatus comprising a floor, a ceiling, and a substantially vertical wall connecting the floor and ceiling at a perimeter of the floor and ceiling, the substantially vertical wall comprising two opposing substantially vertical side walls, a substantially vertical inlet end wall, and a substantially vertical outlet end wall, the melting zone comprising an expanding zone beginning at the substantially vertical inlet end wall and extending to an intermediate location relative to opposing ends of the melter, and a narrowing zone extending from the intermediate location to the substantially vertical outlet end wall, the intermediate location comprising a constant width zone positioned between the expanding zone and the narrowing zone, and with the two opposing substantially vertical side walls in the narrowing zone having a free flowing form, and the two opposing substantially vertical side walls in the expanding zone each being linear and intersecting the substantially vertical wall in the constant width zone at an angle larger than 90 degrees; heating the at least one partially vitrifiable material with at least one burner directing combustion products into the melting zone under a level of the molten glass in the melting zone; cooling the substantially vertical wall by the substantially vertical wall comprising cooled refractory panels and directing a heat transfer fluid through the cooled refractory panels; and discharging molten glass from a molten glass outlet positioned in the substantially vertical outlet end wall.

29. The process of claim 28 comprising discharging at least 0.5 short tons per day per square foot of melter floor.

30. The process of claim 28 comprising discharging at least 2 short tons per day per square foot of melter floor.

31. The process of claim 28 wherein the heating comprises directing combustion products into the melting zone under a level of the molten glass in the melting zone employing two or more floor-mounted burners.

32. The process of claim 31 comprising directing combustion products into the melting zone under a level of the molten glass in the melting zone employing two or more rows of floor-mounted burners arranged substantially perpendicular to a longitudinal axis of the melter.

33. The process of claim 28 comprising decreasing depth of the molten glass as it moves from the intermediate location to the molten glass outlet.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The manner in which the objectives of the invention and other desirable characteristics can be obtained is explained in the following description and attached drawings in which:

(2) FIGS. 1-5, inclusive, are plan views, with parts broken away, of five melter embodiments in accordance with the present disclosure;

(3) FIG. 6 is a side sectional view of the melter of FIG. 1; and

(4) FIG. 7 is a perspective view of one cooled panel useful in melters of the present disclosure.

(5) It is to be noted, however, that the appended drawings are not to scale and illustrate only typical embodiments of this invention, and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.

DETAILED DESCRIPTION

(6) In the following description, numerous details are set forth to provide an understanding of various melter apparatus and process embodiments in accordance with the present disclosure. However, it will be understood by those skilled in the art that the melter apparatus and processes of using same may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible which are nevertheless considered within the appended claims.

(7) Referring now to the figures, FIGS. 1-5 are plan views, with parts broken away, of five melter embodiments in accordance with the present disclosure. FIG. 6 is a side cross-sectional view of the melter apparatus illustrated in FIG. 1. The same numerals are used for the same or similar features in the various figures. In the plan views illustrated in FIGS. 1-5, it will be understood in each case that the roof and exhaust chimney are not illustrated in order to illustrate more clearly the key features of each embodiment. Embodiment 100 of FIG. 1 comprises a peripheral wall 2 of melter 100, wall 2 having an inlet 4, a batch feed chute 5, and a melter discharge 6 through which molten glass exits the melter. Melter 100 also comprises a roof 7 (FIG. 6), a floor 8, a feed end 9, and a discharge end 11.

(8) An important feature of all melter apparatus described herein, and exemplified in melter 100 of FIG. 1, is that wall 2 forms an expanding melting zone 14 formed by a first trapezoidal region, and a narrowing melting zone 16 formed by a second trapezoidal region of wall 2. The first trapezoid forming expanding melting zone 14 and the second trapezoid forming narrowing melting zone 16 share a common base in this embodiment, indicated at B, at an intermediate location between the melter inlet 4 and discharge 6. Common base B defines the location of the maximum width, W.sub.M, of melter 100. The primary importance of these melting zones is that no 90 degree corners are present in the melter where there may be stagnation of molten glass flow.

(9) Another important feature of melter apparatus 100 is the provision of submerged combustion burners 10. In embodiment 100, burners 10 are floor-mounted burners, illustrated in rows substantially perpendicular to the longitudinal axis, L, of melter 100. In certain embodiments, burners 10 are positioned to emit combustion products into molten glass in the melting zones 14, 16 in a fashion so that the gases penetrate the melt generally perpendicularly to the floor. In other embodiments, one or more burners 10 may emit combustion products into the melt at an angle (see FIG. 6, angle ) to the floor; angle may be more or less than 45 degrees, but in certain embodiments may be 30 degrees, or 40 degrees, or 50 degrees, or 60 degrees, or 70 degrees, or 80 degrees.

(10) Melter apparatus in accordance with the present disclosure may also comprise one or more wall-mounted submerged combustion burners, as indicated at 25 in FIG. 1, and/or one or more roof-mounted burners 26, as indicated at 26 in FIG. 6. Roof-mounted burners may be useful to pre-heat the melter apparatus melting zones 14, 16, and serve as ignition sources for one or more submerged combustion burners 10. Melter apparatus having only wall-mounted, submerged-combustion burners are also considered within the present disclosure. Roof-mounted burners 26 may be oxy-fuel burners, but as they are only used in certain situations, are more likely to be air/fuel burners. Most often they would be shut-off after pre-heating the melter and/or after starting one or more submerged combustion burners 10. In certain embodiments, all submerged combustion burners 10 are oxy/fuel burners (where oxy means oxygen, or oxygen-enriched air, as described earlier), but this is not necessarily so in all embodiments; some or all of the submerged combustion burners may be air/fuel burners. Furthermore, heating may be supplemented by electrical heating in certain embodiments, in certain melter zones.

(11) FIGS. 2-5 illustrate further embodiments and features of melter apparatus of this disclosure. Embodiment 200 of FIG. 2 illustrates that wall 20 may have a free-flowing form, devoid of angles. Embodiment 300 of FIG. 3 illustrates that wall 320 may be configured so that intermediate location 12 may comprise an intermediate region of melter 300 having constant width, extending from a first trapezoidal region 14 to the beginning of the narrowing melting region 160. Narrowing melting region 160 in embodiment 300 has alternating narrowing and expanding regions, formed by wall sections 321, 322, although it has a narrowing effect overall leading to discharge 6. Embodiment 400 of FIG. 4 comprises a narrowing melting zone comprising a first narrowing section formed by wall sections 420A and 420B which lead to a narrow channel formed by wall sections 421A and 421B, and then a short expanding zone formed by wall sections 422A and 422B, and finally narrowing down again to discharge 6. Embodiment 400 may provide a final melt mixing or retention zone between wall sections 422A and 422B, which may advantageous in certain embodiments, for example when colorants are added to the melt. Embodiment 500 of FIG. 5 illustrates an embodiment similar to embodiment 100 of FIG. 1, except that wall 520 forms an intermediate melting zone 120 of constant width.

(12) FIG. 6 is a side sectional view of the melter of FIG. 1, and illustrates a charge of batch material 15 being fed into melter inlet 4 through feeder 5. Three floor-mounted submerged combustion burners are indicated, 10A, 10B, and 10C. FIG. 6 also illustrates angles and , where angle is defined as an angle between floor-mounted burner 10C central axis 50 and horizontal 52, and angle is defined as the angle between horizontal and a line 54 through the floor of the decreasing depth region of the melter. Values for angle were mentioned earlier. Angle may range from about 0 degrees to about 90 degrees, or from about 0 degrees to about 60 degrees.

(13) As angle is decreased, allowable values for angle may increase, all other factors being equal. When angle is large, say for example 45 degrees or larger, if angle is too small, for example 45 degrees or less, unacceptable refractory wear may occur near or on the inclined region of floor 8, potentially accompanied by lesser quality glass melt, as the refractory material becomes part of the melt. It should also be noted that certain melter embodiments may include one or more oxy-fuel and/or air-fuel burners mounted in the inclined floor region, or wall 2 of the inclined floor region.

(14) FIG. 7 is a perspective view of a portion of a melter, illustrating two embodiments of cooled panels useful in melter apparatus of the present disclosure. Also illustrated in FIG. 7 is a portion of melter floor 8, and three floor-mounted burners 10. A first cooled-panel 130 is liquid-cooled, having one or more conduits or tubing 131 therein, supplied with liquid through conduit 132, with another conduit 133 discharging warmed liquid, routing heat transferred from inside the melter to the liquid away from the melter. Liquid-cooled panel 130 as illustrated also includes a thin refractory liner 135, which minimizes heat losses from the melter, but allows formation of a thin frozen glass shell to form on the surfaces and prevent any refractory wear and associated glass contamination. Another cooled panel 140 is illustrated, in this case an air-cooled panel, comprising a conduit 142 that has a first, small diameter section 144, and a large diameter section 146. Warmed air transverses conduit 142 in the direction of the curved arrow. Conduit section 146 is larger in diameter to accommodate expansion of the air as it warms. Air-cooled panels such as illustrated in FIG. 7 are described more fully in U.S. Pat. No. 6,244,197, which is incorporated herein by reference.

(15) In operation of melter apparatus of this disclosure illustrated schematically in FIG. 1, feed material, such as E-glass batch (melts at about 1400 C.), insulation glass batch (melts at about 1200 C.), or scrap in the form of glass fiber mat and/or insulation having high organic binder content, glass cullet, and the like, is fed to the melter through a chute 5 and melter inlet 4. One or more submerged combustion burners 10 are fired to melt the feed materials and to maintain a molten glass melt in regions 14 and 16. Molten glass moves toward discharge outlet 6, and is discharged from the melter. Combustion product gases (flue gases) exit through exit duct 60, or may be routed to heat recovery apparatus, as discussed herein. If oxy/fuel combustion is employed in some or all burners, the general principle is to operate combustion in the burners in a manner that replaces some of the air with a separate source of oxygen. The overall combustion ratio may not change. Importantly, the throughput of melter apparatus described in the present disclosure may be 2 ft.sup.2 per short ton per day (2 ft.sup.2/stpd) or less, and in some embodiments 0.5 ft.sup.2/stpd or less. This is at least twice, in certain embodiments ten times the throughput of conventional melter apparatus.

(16) Melter apparatus described in accordance with the present disclosure may be constructed using only refractory cooled panels, and a thin refractory lining, as discussed herein. The thin refractory coating may be 1 centimeter, 2 centimeters, 3 centimeters or more in thickness, however, greater thickness may entail more expense without resultant greater benefit. The refractory lining may be one or multiple layers. Alternatively, melters described herein may be constructed using cast concretes such as disclosed in U.S. Pat. No. 4,323,718. The thin refractory linings discussed herein may comprise materials described in the 718 patent, which is incorporated herein by reference. Two cast concrete layers are described in the 718 patent, the first being a hydraulically setting insulating composition (for example, that known under the trade designation CASTABLE BLOC-MIX-G, a product of Fleischmann Company, Frankfurt/Main, Federal Republic of Germany). This composition may be poured in a form of a wall section of desired thickness, for example a layer 5 cm thick, or 10 cm, or greater. This material is allowed to set, followed by a second layer of a hydraulically setting refractory casting composition (such as that known under the trade designation RAPID BLOCK RG 158, a product of Fleischmann company, Frankfurt/Main, Federal Republic of Germany) may be applied thereonto. Other suitable materials for the refractory cooled panels, melter refractory liners, and refractory block burners (if used) are fused zirconia (ZrO.sub.2), fused cast AZS (alumina-zirconia-silica), rebonded AZS, or fused cast alumina (Al.sub.2O.sub.3). The choice of a particular material is dictated among other parameters by the melter geometry and type of glass to be produced.

(17) Burners useful in the melter apparatus described herein include those described in U.S. Pat. Nos. 4,539,034; 3,170,781; 3,237,929; 3,260,587; 3,606,825; 3,627,504; 3,738,792; 3,764,287; and 7,273,583, all of which are incorporated herein by reference in their entirety. One useful burner, for example, is described in the 583 patent as comprising a method and apparatus providing heat energy to a bath of molten material and simultaneously creating a well-mixed molten material. The burner functions by firing a burning gaseous or liquid fuel-oxidant mixture into a volume of molten material. The burners described in the 583 patent provide a stable flame at the point of injection of the fuel-oxidant mixture into the melt to prevent the formation of frozen melt downstream as well as to prevent any resultant explosive combustion; constant, reliable, and rapid ignition of the fuel-oxidant mixture such that the mixture burns quickly inside the molten material and releases the heat of combustion into the melt; and completion of the combustion process in bubbles rising to the surface of the melt. In one embodiment, the burners described in the 583 patent comprises an inner fluid supply tube having a first fluid inlet end and a first fluid outlet end and an outer fluid supply tube having a second fluid inlet end and a second fluid outlet end coaxially disposed around the inner fluid supply tube and forming an annular space between the inner fluid supply tube and the outer fluid supply tube. A burner nozzle is connected to the first fluid outlet end of the inner fluid supply tube. The outer fluid supply tube is arranged such that the second fluid outlet end extends beyond the first fluid outlet end, creating, in effect, a combustion space or chamber bounded by the outlet to the burner nozzle and the extended portion of the outer fluid supply tube. The burner nozzle is sized with an outside diameter corresponding to the inside diameter of the outer fluid supply tube and forms a centralized opening in fluid communication with the inner fluid supply tube and at least one peripheral longitudinally oriented opening in fluid communication with the annular space between the inner and outer fluid supply tubes. In certain embodiments, a longitudinally adjustable rod is disposed within the inner fluid supply tube having one end proximate the first fluid outlet end. As the adjustable rod is moved within the inner fluid supply tube, the flow characteristics of fluid through the inner fluid supply tube are modified. A cylindrical flame stabilizer element is attached to the second fluid outlet end. The stable flame is achieved by supplying oxidant to the combustion chamber through one or more of the openings located on the periphery of the burner nozzle, supplying fuel through the centralized opening of the burner nozzle, and controlling the development of a self-controlled flow disturbance zone by freezing melt on the top of the cylindrical flame stabilizer element. The location of the injection point for the fuel-oxidant mixture below the surface of the melting material enhances mixing of the components being melted and increases homogeneity of the melt. Thermal NO.sub.x emissions are greatly reduced due to the lower flame temperatures resulting from the melt-quenched flame and further due to insulation of the high temperature flame from the atmosphere.

(18) The term fuel, according to this invention, means a combustible composition comprising a major portion of, for example, methane, natural gas, liquefied natural gas, propane, atomized oil or the like (either in gaseous or liquid form). Fuels useful in the invention may comprise minor amounts of non-fuels therein, including oxidants, for purposes such as premixing the fuel with the oxidant, or atomizing liquid fuels.

(19) The total quantities of fuel and oxidant used by the combustion system are such that the flow of oxygen may range from about 0.9 to about 1.2 of the theoretical stoichiometric flow of oxygen necessary to obtain the complete combustion of the fuel flow. Another expression of this statement is that the combustion ratio is between 0.9 and 1.2. In certain embodiments, the equivalent fuel content of the feed material must be taken into account. For example, organic binders in glass fiber mat scrap materials will increase the oxidant requirement above that required strictly for fuel being combusted. In consideration of these embodiments, the combustion ratio may be increased above 1.2, for example to 1.5, or to 2, or 2.5, or even higher, depending on the organic content of the feed materials.

(20) The velocity of the fuel gas in the various burners depends on the burner geometry used, but generally is at least about 15 m/s. The upper limit of fuel velocity depends primarily on the desired mixing of the melt in the melter apparatus, melter geometry, and the geometry of the burner; if the fuel velocity is too low, the flame temperature may be too low, providing inadequate melting, which is not desired, and if the fuel flow is too high, flame might impinge on the melter floor, roof or wall, and/or heat will be wasted, which is also not desired.

(21) In certain embodiments of the invention it may be desired to implement heat recovery. In embodiments of the invention employing a heat transfer fluid for heat recovery, it is possible for a hot intermediate heat transfer fluid to transfer heat to the oxidant or the fuel either indirectly by transferring heat through the walls of a heat exchanger, or a portion of the hot intermediate fluid could exchange heat directly by mixing with the oxidant or the fuel. In most cases, the heat transfer will be more economical and safer if the heat transfer is indirect, in other words by use of a heat exchanger where the intermediate fluid does not mix with the oxidant or the fuel, but it is important to note that both means of exchanging heat are contemplated. Furthermore, the intermediate fluid could be heated by the hot flue gases by either of the two mechanisms just mentioned.

(22) In certain embodiments employing heat recovery, the primary means for transferring heat may comprise one or more heat exchangers selected from the group consisting of ceramic heat exchangers, known in the industry as ceramic recuperators, and metallic heat exchangers further referred to as metallic recuperators. Apparatus and methods in accordance with the present disclosure include those wherein the primary means for transferring heat are double shell radiation recuperators. Preheater means useful in apparatus and methods described herein may comprise heat exchangers selected from ceramic heat exchangers, metallic heat exchangers, regenerative means alternatively heated by the flow of hot intermediate fluid and cooled by the flow of oxidant or fuel that is heated thereby, and combinations thereof. In the case of regenerative means alternately heated by the flow of hot intermediate fluid and cooled by the flow of oxidant or fuel, there may be present two vessels containing an inert media, such as ceramic balls or pebbles. One vessel is used in a regeneration mode, wherein the ceramic balls, pebbles or other inert media are heated by hot intermediate fluid, while the other is used during an operational mode to contact the fuel or oxidant in order to transfer heat from the hot media to the fuel or oxidant, as the case might be. The flow to the vessels is then switched at an appropriate time.

(23) Although only a few exemplary embodiments of this invention have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel apparatus and processes described herein. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the following claims. In the claims, no clauses are intended to be in the means-plus-function format allowed by 35 U.S.C. 112, paragraph 6 unless means for is explicitly recited together with an associated function. Means for clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures.