US2399609A - Furnace - Google Patents

Description

April 30, 1946. I E. WAINER FURNACE Filed Oct. 11, 1941 5 Sheets-Sheet l INVENTOR age/7e wa/oer' BY aw, wa g gm.

April 1946i E. WAINER 2,399,609

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ATT NEY5 April 1946- E. WAVINER 2,399,609

' FURNACE v Filed 001;. 11, 1941 5 Sheets-Sheet 3 INVENTOR April 1946- E. WAINER 2,399,609

FURNACE Filed Oct. 11, 1941 5 Sheets-Sheet 4 f/GJ'.

INVENTOR 64/76/76 00m April 30, 1946. E. WAINER 2,399,609

FURNACE Filed Oct. 11, 1941. 5 Sheets-Sheet 5 INVENTOR cf'uq'e/ze (Va/her Patented Apr. 30, 1946 FURNACE Eugene Wainer, Niagara Falls, N. Y., assignor to The Titanium Alloy Manufacturing Company, New York, N. Y., a corporation of Maine Application October 11, 1941, Serial No. 414,654

Claims.

This invention relates to high temperature recuperator furnaces, and more particularly to such furnaces in which the products of combustion do not come into direct contact with the material being heated.

In recent years, electric furnaces of all kinds have come into extensive use for the treatment of materials at high temperatures. These furnaces are of the arc type, the resistance type and the induction type. One outstanding advantag of such furnaces over those which employ solid, liquid or gaseous fuel has been that they can be used for the treatment of materials of all kinds without subjecting such treated materials to the action of gaseous products of combustion passing over the materials. On the other hand, electric furnaces are subject to the disadvantage that the cost of current to produce a given heating effect far xceeds the cost of the usual gaseous, liquid and solid fuels required to produce the same heating effect. .A need has therefore long been felt for a practical type of furnace or heating unit which will secure the advantages of electric furnaces for high temperature work, but which will use solid, liquid or gaseous fuels, with the consequent great saving in operating costs. It has been known, of course, i to secure these advantages in relatively low temperature work or medium temperature work. Thus, coal, oil or gas heated boilers of one type or another, for heating water, etc., have been known for hundreds of years. Similarly, at medium temperatures retorts and other containers of various kinds have been employed for holding materials to be heated. At very high temperatures, however, such as in excess of 1800 C.,

9 these expedients fail, both because of the difficulty of securing such high temperatures, and becaus the materials used to separate the substances being heated from the gaseous products of combustion melt or otherwise decompose or 5 break down under the influence of high temperatures.

It is therefore an object of this invention to provide a commercially practical type of furnace or heating apparatus suitable for high temperature work, employing fluid fuel. It is another object to provide such a furnace in which the a supply conduit 24 for air or other oxygengaseous products of combustion do not come into contact with the material being treated. It is a further object to provide such a furnac or heating apparatus which is compact and which can be easily combined with any desired type of chamber containing the material being heated. Other objects will appear hereinafter.

In the drawings:

Figure 1 is a front elevation, with parts in cross section, of a preferred form of furnace according to the invention. Figur 2 is a cross section, on a larger scale and in more detail than in Figure 1, of the cooling apparatus for the exit gases employed in the furnace of Figure 1. Figure 3 is a view taken along the line 3-3 of Figure 2. Figures 4, 5 and 6 are front elevations, partly in cross section, of modified forms of furnace, corresponding to Figure 1.

Referring to Figure 1, the present novel type of furnace or heating apparatus is composed of two stoves or burning units indicated generally at 20 and 40, respectively, which may conveniently be of substantially similar size and shape. The'burning unit 20 is composed of a central chamber 2|, which is partly cylindrical and partly conical in shape. A pipe 22 serves as a means both for introducing air or other oxygencontaining gas (such as pure oxygen), which may beunder forced draft, to support combustion within the chamber 2|, and also for withdrawing spent products of combustion from the burning unit 40, as hereinafter pointed out. When pipe 22 is used for introducing air or other oxygencontaining gas, a valve 23 communicating with containing gas is kept open, while a valve 25 communicating with a water-cooled chimney 26 is kept closed. When pipe 22 is used for withdrawingspent products of combustion, valve 25 is open while valve 23 is closed. At its opposite end, the chamber 2i forms a cylindrical passageway 21, which turns at right angles and then in turn communicates with a passageway which forms a continuation of the passageway 21.

Also communicating with. the portion 21 of chamber 2i is a nozzle 28, preferably made of zircon, serving to direct gas or other fluid fuel under pressure from the supply pipe 29 into the chamber 2|, the supply of gas being controlled by the valve 30. A sighting glass 3! of Pyrex" or similar high temperature resistant glass may be provided for observing the combustion within the chamber 2!, which occurs when gas from the nozzle 28 comes in contact with air from the supply line 2t. Combustion thus occurs in the end of chamber 2| adjacent to passageway 21, and the hot products of combustion pass thence successively through passageways 21 and 60.

Most of the remaining space in the chamber 2i between the nozzle 28 and the pipe 22 is filled with irregular refractory particles or lumps 32 and 33. which conveniently may average 95 to 1 inch in size. These lumps advantageously fill about half the space or more between the beginning of the passageway 21 and the end of the chamber 2| adjacent the pipe 22. The lumps 32 adJacent the pipe 22 are composed of the highly refractory material zircon -(zirconlum silicate). while the lumps 33 furthermost from pipe 22 are composed of the even more refractory material zirconium dioxide (zirconia), for reasons hereinafter pointed out. Because of the way 21, are provided with a lining 36 of zirconium dioxide such as of the semi-vitreous tile-link type. Finally, the entire structure may, if desired, be backed up with insulating firebrick of the flreclay type (not shown), although normally this is not necessary. To hold the structure together, a cast iron shell 36 may be provided. To secure access to the interior of the chamber 2|, there is provided a removable plug 31 of zircon in one wall of the chamber, adjacent the pass eway 21, and a removable cast iron plug 36 in the eI-id of the chamber adjacent the pipe 22. Spent and dirty lumps 32 and 33 may thus be removed by removing plug 36, and fresh lumps 32 and 33 inserted by removing plug 31. Similarly, the chamber 2| may be cleaned at periodic intervals, as desired, after removing plugs 31 and 36. The plug 36 may if desired be provided with a valved passageway (not shown) for removing water condensing within the chamber 2|.

At the end of chamber 2| adjacent pipe 22 is a cooling unit indicated generally at 39. This can be understood more easily by reference to Figures 2 and 3 of the drawings. separate units, that is, an external cooling ring 16, a spiral loop of pipe 13, and a squirrel cage grate 14. The cooling ring 16 has its own-water supply line II and water outlet 12. Spiral loop 13 and squirrel cage grate 16, however, are connected in series. Cooling water comes in through supply line 15, passes through the successive spirals of spiral loop 13, and then into the circular pipe 16 of squirrel cage grate I6. From pipe 16 the water passes through straight pipes 11 connecting circular pipe 16 with a second circular pipe 18. Thence the cooling water finally passes out through outlet pipe 13. The interior of the squirrel cage grate 16 is filled with lumps 32, not shown in Figure 2.

The cooling unit 33 may be dispensed with entirely, if desired. Ordinarily this will require a chamber 2| of great length, in order that the exit gases may be cooled to the proper degree. Since this sacrifices the desirable feature of compactness to some extent, it is generally preferred to include the cooling unit. the unit 39 may also be and preferably is employed as a source of hot water or steam for other uses; and this constitutes one 01 the advantages of the use of this cooling unit.

The stove or burning unit 46 is constructed in a. fashion very similar to that of unit 26. Cen- It consists of three In actual operation,

asaaeoe same manner and for the same purposes as the similar elements 26, 26, "and 26, respectively, in unit 26. Similarly nozzle 66, supply line 63, valve 66, and sighting glass 6| serve the same purp ses as similar elements 26, 26, 36 and 3|, respectively, of unit 26. The dividing line between lumps of zircon 62 and lumps of zirconium dioxide 63, and also the free surface of lumps 63, are in this case level or horizontal, since chamber 4| is oriented vertically. The zircon walls 66, zirconium dioxide lining 66, iron shell 66, plugs 51 and 66 and cooling unit 66 are constructed similarly to the corresponding elements 36, 36, 36, 37,36 and 39 of unit 26.

Both units 26 and 66 are preferably of generally cylindrical or circular shape, since the problem of placing and welding into place sheet iron shells 36 and 66 is thereby simplified. Furthermore, the interiors of the units preferably should be free from corners or cut backs, or should be otherwise streamlined to prevent erosion by whirlpools or eddies of flames at very high temperatures.

The tube or wall 6| of the passageway 66 is constructed of zirconium dioxideof relatively thin cross section. It may be built up of individual sections of tile suitably cemented together with zirconium dioxide cement, or cast in a single piece. It should be of relatively dense structure, so that it is as impervious as possible to the gaseous products' of combustion going through the passageway 66, and also so that heat may be conducted as efilciently as possible to the exterior surface of the tube 6|. For strengthening purposes, the tube 6| may if desired rest in suitable recesses (not shown) in the refractory linings 35 and 66. The tube 6| may be of any desired cross section, such as circular, elliptical,

square, rectangular, etc., and may be straight or ure 1, it is indicated as a chamber about 3 feet high and 3 feet wide, but wide variations from this are of course permissible. The chamber 62 is also preferably completely surrounded with suitable refractory insulating walls (not shown) of any required thickness, to, prevent or minimize heat losses. Chamber 62 may also be provided with doors or other openings, thermometers, sight glasses, etc., also not shown. 1 v

In addition to or in place of the means shown, other expedients may be employed to increase the efilciency of heat transfer, to insure safety of operation, 'etc. Thus, the tube 6| may be filled with checkerwork or suitably supported lumps of zirconium dioxide to slow down the velocity v 2,809,609 of travel of the products of combustion passing through the tube. Suitable cooling means may be combined with any excessively hot regions that develop. Instead of a single nozzle 23 or 42, a plurality of nozzles radially disposed about place in chamber 32 by suitably balancing the pressure in passageway 30. This can be done, for example, by suitably increasing the pressure of the entrant air and gases and the exiting products of combustion. In addition, the use of combinations of zirconium dioxide joined to refractory insulatingzircon ware enables the relative cheapness, high temperature resistant qualities and heat insulation properties of the latlter to be combined with the characteristic of on the opposite side of the partition by means of a similar pipe entering the chamber 2I in .a diametrically opposite position. Thus, both air and gaseous fuel would be preheated by passing through the mass of lumps and burn in the space beyond such lumps.

The furnace is operated as follows: Valves 43, 50 and are opened, while valves 45, 23 and are closed. Air and gas are thus caused to simultaneously enter chamber 4I. Combustion is then initiated in the upper part of chamber 4| such as by means of an electric or cerium spark. The hot products of combustion pass through the passageway 60, causing heat to be radiated from the exterior surface of tube 6i. Thence thehot products of combustion pass into chamber 2I and successively through lumps 33 and 32 and out through pipe 22 and chimney 26, being cooled by means of cooling unit 39. In this fashion, the temperature of lumps 33 and 32 is raised to a high point, lumps.33 being hotter than lumps 32 because the hot products of combustion pass through the former first.

When the temperatures'of lumps 32 and 33 are raised to the required degree, valves 43,

and 25 are shut while valves 45, 23 and 30 are opened, these operations being effected by suitable thermostatio-controls, if desired. when this is done, air passing from pipe 22 through lumps 32 and 33 are heated thereby to a high degree, so that when the air mixes with gas from nozzle 23 in passageway 21 combustion takes place instantly without any externally applied heat. Also as a result thereof, the hot products of combustion reach a much higher temperature, and the heat radiation from the exterior surface of tube BI is greatly increased. The hot prodnets of combustion, pass successively down through lumps 53 and 52 and out through pipe 42 and 46, being cooled by means of cooling unit 50. The temperature of lumps 53 and 52 is thus raised to a high point. When the required temperature of lumps 53 and 52 is reached, the cycle is again reversed, and this is repeated as often as is desired, to secure the required temperature in chamber 62. Each time the cycle is reversed, the temperature of chamber '2 increases until equilibrium is reached.

It will be seen that, by the practice of the present invention, the heat resisting qualities and other high temperature characteristics of zircon and zirconium dioxide are utilized to the highest degree. In particular, construction of the tube 5| out of zirconium dioxide enables chemical reactions of all.sorts to high temperatures in the chamber 82 without appreciably affecting the zirconium dioxide. Reactions under high pressure can be made to take the former of being able to resist still higher temperatures.

The form of furnace illustrated in Figure 1 is particularly advantageous because it enables gases to be conducted most directly from the combustion chamber to the passageway 60. Also, the furnace may be used either with a horizontal or a vertical tube 60, merely by turning the entire apparatus over on its side-so that unit 20 becomes vertical and unit '40 horizontal.

Other forms of furnaces may also be used, which secure additional advantages at the expense of certain disadvantages. Thus the form shown in Figure 4 has the advantage that the chamber I00 (corresponding to the chamber 82) in. which the material to be heated is placed, may

be built up and taken down with the greatest ease. Also the U-shaped tube IOI (corresponding to the tube BI) offers a somewhat larger surface area, thus increasing the radiation surface.

In this form of-furnace, the lower parts of the burning units or stoves I02 and H2 are constructed exactly the same as in unit 40. Gas is supplied through the nozzles I03 and H3, respectively, and air through the pipes I04 and III, re-

spectively, these pipes (as with pipes 22 and 42-) also serving to withdraw spent products of combustion. Thus, in one cycle air from pipe I04 and gas from nozzle I03 both pass into central chamher I01, the air passing successively through zirconlumps I05 and zirconium dioxide lumps I08. After the air and gas are burned, the spent products of combustion pass through passageway I08 andpassageway I09 defined by tube IOI. Thence the products of combustion pass out through passageway II8 into chamber I I1, and then down successively through zirconium dioxide lumps IIB and zircon lumps H5 and out through pipe H4.

The cycle is reversed exactly as with the apparatus of Figure 1. As with the apparatus of Figure 1, the walls IIO of the furnace are composed of zircon, the hottest portions III being provided take place at portions I39 being provided with a lining of zirwith a lining of zirconium dioxide.

In the form of furnace shown in Figure 5, both burning units or stoves I20 and I30 lie in a horizontal position. Otherwise, the operation is exactly the same as in the forms shown in Figures 1 and 4. In one cycle, air from pipe I2l and gas from nozzle I22 both pass into passageway I24 forming a continuation of central chamber I23, the air passing successively through zircon lumps I25 and zirconium dioxide lumps I26. After the air and gas are burned, the spent products of combustion pass into passageway heat to be radiated from the exterior surface of the tube I28. Thence the products of combustion pass out through passageway I 34 into chamber I33, and. then down successively through zirconium dioxide lumps I36 and zircon lumps I35 and out through pipe I3I. The cycle is reversed exactly as with the apparatus of Fi ure 1. As with the apparatus of Figure 1, the walls I29 of the furnace are composed of zircon, the hottest conium dioxide. The plugs I40 and I are pro- I2I, so as to cause I23 and I" re- I burning units or stoves Ill and m lie in a vertical position. Otherwise, the operation is exactly the same as in the forms shown in Figures 1, 4

and 5. In one cycle, air from pipe, iii and gas from nozzle I52 both pass into passageway I54 forming a continuation of central chamber I 53, the air passing successively through zircon lumps I and'zirconium dioxide lumps I 56. After the air and gas are burned, the spent productsof combustion pass into passageway I51, so as to cause heat to be radiated from the exterior sur-' face of tube I58. Thence the products of combustion pass directly into chamber I63, and then down successively through zirconium dioxide lumps I66 and zircon lumps I 65 and out through pipe I. The cycle. is reversed exactly as with the apparatus of Figure 1. As with the apparatus of Figure l, the walls I59 of the furnace are composed of zircon, the hottest portions I69 being provided with a lining of zirconium dioxide.

From the above description, it will be seen that I the present type of furnace is admirablysuited aseacoo tion of term alloys, fused alumina, fused quartz,

fused slags, calcium carbide, carbon bisulflde, car- 1. A high temperature recuperating furnace,

capable of generating temperatures in excess of 1800 C., comprising a pair of burning units and a closed passageway connecting said burning units; at least a part of said passageway being enclosed only by a tube essentially of zirconium dioxide, the exterior surface of said tube constituting a heat radiating surface for the heating of substances placed in proximity therewith; each of said burning units comprising a central chamber containing lumps of zirconium dioxide, a

- conduit for oxygen containing gas, a conduit for fluid fuel, each of said conduits communicating by separate means with the portion of said central chamber between said tube and the free surface of said lumps, at least one of said conduits communicating with said first named portion through a portion of said central chamber occupied by said lumps, and a conduit for waste gases communicating with said first named portion through said second named portion of said central chamber; one of said burning units acting as a unit for supplying hot gaseous products of combustion to the interior of said closed passageway while at the same time the other of said burning units acts as a unit for withdrawing said hot gaseous products of combustion from the interior of said closed passageway, each of said units being adapted to interchangeably act as a supplying unit and as a withdrawing unit.

2. A high temperature recuperating furnace,

a closed passageway connecting said burning units; at least a part of said passageway being enclosed only by a tube essentially of zirconium dioxide, the. exterior surface of said tube constituting a heat radiating surface for the heating of substances placed in proximity therewith; each of said burning units comprising a central chamber containing lumps of zirconium dioxide, a conduit for orwgen containing gas, a conduit for fluid fuel, each of said conduits communicating by separate means with the portion of said central chamber between said tube and the free surface of said lumps, at least one of said conduits communicating with said first named portion through a portion of said central chamber occupied by said lumps,- a conduit for waste gases communicating with said first named portion through said second named portion of said central chamber, and the interior surface of said first named portion being essentially of zirconium dioxide; one of said burning units acting as a unit for supplying hot gaseous products of combustion to the interior of said closed passageway while at the same time the other'of said burning units acts as a unit for withdrawing said hot gaseous products of combustion from the interior unit and as a withdrawing unit.

3. A high temperature recuperating furnace, capable of generating temperatures in excess of 1800 C., comprising a pair of burning units and a closed passageway connecting said burning units; at least a part of said passageway being enclosed only by a tube essentially of zirconium dioxide, the exterior surface of said tube constituting a heat radiating surface for the heating of substances placed in proximity therewith; each of said burning units comprising a central chamber containing a plurality of layers of lumps, the layer nearest said tube being composed essentially of zirconium dioxide and another of said layers being composed essentially of zircon, a conduit for oxygen containing gas, a conduit for fluid fuel, each of said conduits communicating by separate means with the portion of said central chamber between said tube and the free surface of said lumps, at least one of said conduits communicating with said first named portion through aportion of said central chamber occupied by said lumps, a conduit for waste gases communicating with said first named portion through said second named portion of said central chamber, the walls of said central chamber being composed principally of zircon but being provided at said first named portion with a lining essentially of zirconium dioxide; one of said burning units acting as a unit for supplying hot gaseous products of combustion to the interior of said closed passageway while at the same time the other of said burning units acts as a unit for withdrawing said hot gaseous products of combustion from the interior of said closed passageway, each of said units being adapted to interchangeably act as a supplying unit and as a withdrawing unit.

4. A high temperature recuperating furnace, capable of generating temperatures in excess of 1800' C., comprising a pair of burning units and a closed passageway connecting said burning units; said passageway being enclosed only by a thin-walled tube essentially of zirconium dioxide, the exterior surface of said tube constituting a heat radiating surface for the heating of substances, placed in proximity therewith; each of said burning units comprising walls composed principally of zircon, a central chamber enclosed by said walls, a quantity of zirconium dioxide lumps within said chamber and having a free surface exposed in the direction towards said tube, a quantity of zircon lumps Within said chamber and being covered by said zirconiuming waste gases from a portion of said chamber K filled with said zircon lumps, a lining of zirconium dioxide in said first named portion of said chamber, and a cooling unit adjacent said second named portion of said chamber and also adjacent said second named conduit; one of said burning units acting as a unit for supplying hot gaseous products of combustion to the interior of said closed passageway, while at the same time the other of said burning units acts as a unit for withdrawing said hot gaseous products of combustion from the interior of said closed passageway, each of said units being adapted to interchangeably act as a supplying unit and as a withdrawing unit.

5. A high temperature recuperating furnace, capable of generating temperatures in excess of 1B00 0., comprising a horizontally disposed burning unit, a vertically disposed burning unit, and a closed passageway connecting said burning units; said passageway being enclosed only by a thin- -walled tube essentially of zirconium dioxide, the exterior surface of said tube constituting a heat radiating surface for the heating of substances placed in proximity therewith; each of said burning units comprising walls composed principally of zircon, a central chamber enclosed by said walls, a quantity of zirconium dioxide lumps within said chamber and having a free surface exposed in the direction towards said tube, a quantity of zircon lumps within said chamber and being covered by said zirconium dioxide lumps, a conduit and nozzle for introducing fluid fuel into a, portion of said chamber between said tube and said free surface of the zirconium dioxide lumps, a conduit for introducing oxygen-containing gas into and for withdrawing waste gases from a portion of said chamber filled with said zircon lumps, a lining of zirconium dioxide in said first named portion of said chamber, and a cooling unit adjacent said second named portion of said chamber and also adjacent said second named conduit, one of said burning units acting as a unit for supplying hot gaseous products of combustion to the interior of said closed passageway while at the same time the other of said burning units acts as a unit for withdrawing said hot gaseous products of combustion from the interiorsof said closed passageway, each of said units being adapted to interchangeably act as a supplying unit and as a withdrawing unit.

EUGENE WAINER.

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