SUBMERGED COMBUSTION MELTERS AND METHODS

Abstract

A submerged combustion melter is arranged with a melting chamber, which may be cylindrical, and at least five submerged combustion burners.

Claims

1.-11. (canceled)

12. A method of providing a molten vitrifiable material comprising the steps of: introducing solid batch material into a melter; and melting the solid batch material in the melter by submerged combustion to provide the molten vitrifiable material within the melter; wherein during the melting step an essentially toroidal melt flow pattern is generated in the melt of vitrifiable material, comprising a major centrally inwardly convergent flows at the melt surface, the central axis of revolution of the torroidal flow being essentially vertical.

13. The method of claim 12 wherein the melt moves downwardly in the center at proximity of the axis of revolution and is recirculated in an ascending movement back to the melt surface, thus defining an essentially toroidal flow pattern.

14. (canceled)

15. The method of claim 12 wherein velocity vectors of the moving melt form a circulation pattern in which said velocity vectors fill cross-sections of an essentially horizontal toroid.

16. The method of claim 12 wherein the melt in the melter comprises a single such toroidal flow pattern.

17. The method of claim 12 wherein the melter has a substantially circular cross-section and the central axis of revolution of the toroidal flow pattern essentially corresponds with the melter axis.

18. The method of claim 12 for the manufacture of flat glass, hollow glass, glass fibers, continuous fibers for reinforcement purposes, mineral fibers for insulation purposes, mineral wool, stone wool or glass wool.

19. The method of claim 12 wherein the solid batch material comprises silicates, basalt, limestone, soda ash, zeolite catalyst, spent catalyst, spent pot liner, refractory materials, aluminum dross, aluminum melting scum, sand based fire extinguisher waste, sludge, galvanic sludge, clinker, waste materials, ash and combinations thereof.

20. The method of claim 12 wherein the composition of the melt produced comprises TABLE-US-00003 composition (% weight) SiO.sub.2 35-70 Al.sub.20.sub.3 5-30 CaO 5-20 MgO 0-10 Na.sub.2O 0-20 K.sub.2O 0-15 Fe.sub.2O.sub.3 (total iron) 0-15 B.sub.2O.sub.3 0-10 TiO.sub.2 0-5 BaO P.sub.2O.sub.5 0-3 MnO 0-3 Na.sub.2O + K.sub.2O 5-30 (alkali metal oxide) CaO + MgO 5-30 (alkaline earth metal oxide) SiO.sub.2 + Al.sub.2O.sub.3 50-85

21. The method of claim 20 wherein the composition of the melt produced comprises TABLE-US-00004 composition (% weight) SiO.sub.2 40-65 Al.sub.20.sub.3 15-25 CaO 5-12 MgO 1-7 Na.sub.2O 5-18 K.sub.2O 0-10 Fe.sub.2O.sub.3 (total iron) 0.5-10 B.sub.2O.sub.3 0-5 TiO.sub.2 0-2 BaO P.sub.2O.sub.5 0-2 MnO 0-2 Na.sub.2O + K.sub.2O 5-20 (alkali metal oxide) CaO + MgO 5-20 (alkaline earth metal oxide) SiO.sub.2 + Al.sub.2O.sub.3 60-80

22. The method of claim 12 wherein the boron content of the glass produced, expressed as B.sub.2O.sub.3, is 1 w %, 2 w %, 3 w %, 5 w % and/or 20 w %, 18 w %, 15 w % or 10 w %.

23. The method of claim 12 wherein hot fumes from the melting chamber are used to preheat raw material and/or a portion of their thermal energy is recovered.

Description

[0040] An embodiment of the invention is described in more details below, by way of example only, with reference to the accompanying drawings of which:

[0041] FIG. 1 is a horizontal cross-sectional plan view of a melter;

[0042] FIG. 2 shows a vertical section through the melter of FIG. 1;

[0043] FIG. 3 is a schematic representation of the burner layout; and

[0044] FIG. 4 is a schematic representation of a preferred toroidal flow pattern.

[0045] The glass melter 10 illustrated in FIGS. 1, 2 and 3 comprises a melting chamber 11, that is to say a portion of the melter 10 adapted to retain and melt a heated melt 17, for example of a composition for manufacturing stone wool or glass wool fiber, and an upper chamber 90.

[0046] The illustrated melting chamber 11 is cylindrical and has a vertical central melting chamber axis 7, a periphery 12 defined by its internal circumference which has a diameter of about 2 m, a base 13 forming the lower ender of the cylinder and an open end at the upper end of the cylinder which communicates with the upper chamber 90.

[0047] The upper chamber 90 is provided with: [0048] a chimney 91 for evacuation of the gasses from the melting chamber 11; [0049] baffles 92, 93 that block access to any melt projections which may be thrown up from the surface of the melt 14; and [0050] a raw material feeder 15 arranged at the level of the upper chamber 90 to load fresh raw material into the melter 10 at a batch introduction position 101 located above a surface 18 of the melt and close to the peripheral side wall 12 of the melter.

[0051] The feeder 15 comprises a screw or other horizontal feeder which transports a raw material mix to a hopper which may be opened and closed by a piston.

[0052] The melter has a double steel peripheral wall 19 having a cooling liquid, preferably water, circulating through its interior at a flow rate which is sufficient to maintain a desired temperature of the melter and of the cooling fluid and withdraw energy from the inside peripheral wall 12 such that a portion of the melt can solidify or partially solidify on the internal peripheral wall to form a boundary layer.

[0053] If desired the melter may be mounted on dampers to absorb vibrations.

[0054] Six submerged burners 21, 22, 23, 24, 25, 26 are arranged, equally spaced around a substantially circular burner line 27 which is concentric with the central vertical melting chamber axis 7 and has a diameter of approximately 1.4 m. Each submerged combustion burner has a respective central burner axis 31,32,33,34,35,36 and one or more outlet nozzles 41, 42, 43, 44, 45, 46 from which flames and/or combustion fluids are projected in to the melt 17. Each burner is positioned at a substantially identical adjacent burner spacing 512, 523, 534, 545, 556, 561 with respect to each of its two closest adjacent burner positions. The burner nozzles 41, 42, 43, 44, 45, 46 in the illustrated embodiment are arranged to project slightly above the base 13 of the melting chamber, each at the same vertical height as a burner positioning plane 14.

[0055] Each central burner axis 31,32,33,34,35,36 has a respective burner axis circle 71,72,73,74,75,76 which extends around the central burner axis and has a radius r1,r2,r3,r4,r5,r6 which is substantially equal to the distance between the central burner axis and the peripheral wall 12 of the melting chamber. These burner axis circles define a central zone 70 at the positioning plane 14 having a diameter of at least 250 mm.

[0056] The melt 17 may be withdrawn from the melting chamber through a controllable outlet opening 16 located in the melter chamber periphery side wall 12, close to the melter bottom 13, substantially opposite the raw material feeder 15.

[0057] The submerged burners 21,22,23,24,25,26 are tube in tube burners, sometimes referred to as concentric pipe burners, operated at gas flow or speed in the melt of 100 to 200 m/s, preferably 110 to 160 m/s. The burners generate combustion of fuel gas and air and/or oxygen within the melt. The combustion and combustion gases generate high mixing and high rates of heat transfer within the melt before they escape from the melt into the upper chamber 90 and are exhausted through the chimney 91. These hot gases may be used to preheat raw material and/or the fuel gas and/or oxidant (air and/or oxygen) used in the burners. The exhaust fumes are preferably cooled, for example by dilution with ambient air, and/or filtered prior to release to the environment.

[0058] It is preferable that the arrangement generates a toroidal melt flow as illustrated in FIG. 4 in which the melt follows an ascending direction close to the central burner axis of each submerged burner, flows inwardly towards the vertical central melting chamber axis 7 at the melt surface 18 and then flows downwards in an substantially cylindrical portion of the melting chamber which projects along the vertical central melting chamber axis 7 from the central melting zone 70. Such a toroidal flow generates high mixing in the melt, ensures good stirring of the melt and absorption of fresh raw material and allows for appropriate residence time of the material in the melter, thereby avoiding premature outflow if insufficiently melted or mixed raw materials.

[0059] The burners generate an ascending movement of melt in their proximity and a circulation within the melt. In one preferred embodiment, each burner axis is vertically oriented or inclined at an angle of no more than 15 from vertical, advantageously towards the center of the melter, in order to favor the generation of toroidal flow as taught above.

[0060] To further improve homogeneity of the melt, one or more burners may impart a tangential velocity component to its combustion gases, hence imparting a swirling movement to the melt flow, in addition to the toroidal flow pattern described above. For that purpose, the central burner axis of one or more burners may form a swirl angle of at least 1 with respect to a plane which is perpendicular to burner positioning plane 14 and which passes through the vertical central melting chamber axis 7 and the burner position.

[0061] The melter may be equipped with an auxiliary burner (not shown) notably for temporary use for example for preheating the melter when starting, in the case of malfunction of one of the submerged burners described above or in other cases where additional heat is temporarily required. The auxiliary burner is advantageously mounted on a rail so that it can be guided into an opening provided in the melter peripheral wall 12, the opening being closed when the auxiliary burner is not in use.

[0062] The internal melter wall 12 advantageously comprises a multitude of tabs or pastilles (not shown) projecting inside the melter chamber 11. It is believed these projections favor the formation and fixation of a solidified melt layer on the cooled wall 12, which constitutes an insulating layer. In the case of a glass melt for instance, glass solidifies on the cooled wall and forms an insulating boundary layer. Glass is thus melted in glass and the melt is not contaminated with erosion residues of any refractory material.

[0063] A melter according to the invention is particularly advantageous in a glass fiber, glass wool or stone wool production line because its efficiency provides for low energy consumption and its flexibility facilitates changes of raw material composition. Ease of maintenance and low capital costs of the melter are also of major interest in building such a production line. The same advantages also make the invention melter the melter of choice in waste and ash vitrification processes.