US2922386A - Furnace closure - Google Patents

Description

Jan. 26, 1960 F. ENDTER 2,922,386

FURNACE CLOSURE Filed Nov. 15, 1956 2 Sheets-Sheet 1 I N VENTOR FK/EDF/Ch' E/VD 757?,

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ATTORNEY Jan. 26, 1960 F. ENDTER 2,922,336

FURNACE CLOSURE Filed Nov. 15, 1956 Y 2 Sheets-Sheet 2 INVENTOR v 17 FF/EO/F/CH EVDZEX;

ATTORNEYS United States Patent FURNACE CLOSURE Friedrich Endter, Konstanz, Germany, assignor to Deutsche Goldand Silber-Scheideanstalt vormals Roessler, Frankfurt am Main, Germany Application November 15, 1956, Serial No. 622,423

Claims priority, application Germany November 19, 1955 7 Claims. (Cl. 110-98) The present invention relates to improvements in closure means for furnaces and more particularly furnaces which are provided with vertically suspended tubes, the free ends of which project through the closure end of the furnace.

In chemical reactions which are carried out on catalytically active surfaces at relatively high temperatures, it is often necessary to employ furnaces in which the reaction space is subdivided into a number of separate tubes. In such instances where the reaction is carried out at temperatures at which metal tubes cannot be used, whether it be for thermal or chemical reasons, such furnaces are equipped with ceramic tubes, for example, tubes of sintered alumina, sillimanite and the like, which, if necessary, are associated to form bundles of tubes. Special precautions are necessary in the use of such ceramic tubes in reaction units in view of their comparatively high sensitivity to mechanical shock and impact and in view of their low resistance to temperature shock. Therefore it has been usual to support the tubes only at the upper end of the furnace and to permit the lower free ends to extend freely from the bottom of the furnace so as to prevent high stresses or even destruction of the tubes upon occurrence of temperature strains.

As a consequence, certain requirements must be met in the closure provided at the end of the furnace from which the free end of the tubes extend, as such closure must on one hand be such as to seal off the furnace heating chamber as tightly as possible tov prevent untenable heat losses and, on the other hand, must not hinder the mobility of the tubes to such an extent that changes in volume and changes in temperature cannot be compensated for. It has been found that temperature changes not only cause a movement in the direction of the longitudinal axis of such tubes but also transverse to such axis. When the lower furnace closure in any way prevents such lateral movement of the free lower tube end it can easily result in stresses on the tubes or their destruction.

The closures normally employed have not satisfactorily fulfilled the requirement of providing a good heat seal with simultaneous provision for the required lateral freedom of movement of the tubes. For example, if the lower end of the furnace is closed with a refractory plate rigidly connected to the furnace and provided with openings permitting passage of the free ends of the tubes therethrough, it was found that the lateral play provided for the tubes is still too small even though the closure plate is subdivided a number of times to provide better thermal stability. If, on the other hand, the openings in the closure plate are selected to be large enough to provide suflicient space between the inner wall of the openings and the outer surface of the tubes, considerable radiation losses occur through the space thus left free and such radiation losses are extremely disadvantageous for the thermal efficiency of the furnace.

According to the invention it was found that these difiiculties can be overcome in a simple manner by pro ice j sutficiently large to provide the desired lateral play for' the tubes. The insulating bodies which rest loosely upon the supporting element are larger than the openings pro,- vided in the supporting element and of thesarne crosssectional shape. Each insulating body is provided with an opening permitting passage of a single tube, the opening however does not have to be substantially larger than the: external diameter of the tube. It is of particular importance accordingto the invention thatthe insulating bodies are so dimensioned that a space is left between them on all sides so that they do not touch one another. The

dimension of the space between the insulating bodies;

should be sufficiently large so as not to prevent deflection of any insulating body when a tube associated therewith may become distorted and thereby cause the body to move laterally. It has been found in practical use of the closure means according to the invention that horizontal spacings of about 2-8 mm. between the lateral surfaces of the individual insulating bodies are satis-l factory. The multipart closure means according to the invention have proved very satisfactory for'the purposes indicated as they provide a good thermalseal even at high furnace temperatures and, on the other hand, they are also, able to yield to every movement of the tubes caused by volume changes of such tubes so as to avoid danger of destruction of the tubes.

Furthermore, the closure means according to the in vention can be employed to close furnace chambers of any desired size without producing the mechanical or" thermal sensitivity as exists with unitary shaped closure elements such as insulating plates and the like conforming in size and shape to the furnace chamber to be closed off.

As already indicated, it is essential that the shaped bodies which form an important element of the closure means according to the invention are of the same crosssectional form as in this way, depending upon the arrangement of the tubes in the furnace, it is best possible to provide an adequate seal against heat losses. Shaped bodies whose horizontal cross-section is in the form of V a regular hexagon have been found particularly suitable for the purposes of the invention, as despite the gap which must be provided between the vertical boundary surfaces of such hexagonally shaped bodies, they can be as'so-,

ciated together to form an optimal tight packing. The"v supporting element is preferably also adapted to this form of the shaped bodies in that it is in the shape of a lattice I grid in which the grid bars are connected to each other in honeycomb fashion.

element preferably have trapezoidal cross section, the

tapered side of which is on the side facing away from the furnace.

In order that the heat loss which might still occur through the spaces provided between the shaped in sulating bodies be kept as low as possible, it has proved expedient to provide projections and corresponding recesses in the adjacent vertical surfaces of the shaped bodies to provide -a telescoping tongue and groove 'joint therebetween. It is also possible to offset the boundary surfaces of the adjacent shaped bodies so that the slots or spaces between the bricks appear discontinuous or staggered laterally in relation to one another. Furthermore, it is also possible to provide complementary re.

The grid bars of the supporting.

cusses at anysuitable 'height in the sides of the adjacent spaced insulating bodies in which horizontal closure plates can be loosely placed in such a way as still to permit the desired relative movement between the individual shaped insulating bodies.

Furthermore, it has been found expedient to shape the bores in the insulating bodies intended for passage of the furnace tubes conically so that they flare outwardly on the side of the shaped bodies facing the interior of the furnace. This construction has been found particularly favorable for the provision of a temperature distribution at the furnace outlet which takes the sensitivity of the ceramic tubes to temperature variations into account.

It is obvious of course that the size of the openings in the supporting element facing the insulating bodies is smaller than the horizontal cross-section of the insulating bodies associated therewith and conversely that the size of the opening at the botom of the insulating body must be smaller than the opening in the supporting element with which it is associated.

The accompanying drawings serve to illustrate the closure means according to the invention.

In such drawings:

Fig. 1 is a top View of a closure means according to the invention with some of the individual insulating bodies removed for sake of simplicity;

Fig. 2 is a vertical cross-section through a portion of the closure means according to the invention illustrating the relationship of a furnace tube therewith;

,Fig. 3 is a vertical cross-sectional view through a portion, of a closure means according to the invention illustrating the modification of the individual insulating bodies which are provided with complementary recesses and projections; and

Fig. 4 is a sectional view of a furnace with the closure means according to the invention mounted therein.

,In Fig. 1, 11 designates the grid bars of the supporting element 18 which are connected to one another to form a honeycomb shaped lattice defining hexagonal openings 12 to permit passage of the furnace tubes. The openings 12 are as large as possible and the bars 11 are as narrow as possible in order to provide for small contact surfaces for transfer of heat between the insulating shaped bodies 13 and the supporting element. The insulating shaped bodies which are of hexagonal crosssection rest on grid bars 11 in such a way to leave gaps 14 between the vertical surfaces of the adjacent insulating bodies to permit lateral movement of such shaped bodies relative to each other. Each insulating body is also provided with an opening 15 to permit passage of a furnace tube therethrough and through the opening 12 in the supporting member associated therewith.

Fig. 2 which shows a vertical sectional view of a portion of the closure means according to the invention shown in Fig. 1, shows the trapezoidal form of grid bars 11 as well as the outwardly flaring top portion of opening. 15 in insulating bodies 13 which rest upon the sup-. porting member covering openings 12 therein. This figure also shows a furnace tube 10 associated with the closure means passing through openings 12 and 15. Asindicated in broken lines, insulating bodies 13 can be provided on their facing surfaces with pocket-like recesses 16, into which a loose fitting sealing plate 17 is inserted so as not to hinder lateral movement of the insulating bodies while at the same time bridging gap 14.

In Fig. 3 the insulating bodies 13' have been provided with complementary projections 17' and recesses 16' to provide a telescoping tongue and groove joint therebetween.

Fig. 4" shows how the supporting element 18 is loosely aszaese carried on an angle member 19 which is rigidly connected with furnace body 20. Such figure furthermore illustrates how the furnace tubes 10 are supported in the furnace by a common head 21.

I claim: s

1. In combination with a furnace of the type described having vertically suspended tubes projecting freely from the furnace at its lower end, a closure means for such lower furnace end comprising a horizontal supporting element having spaced openings resting on holding means fixed to the furnace, -each of said openings permitting passage of one of the furnace tubes therethrough and each of said openings in the support member being large relative to the diameter of the furnace tube passing therethrough to allow for substantial lateral displacement of the tube, and a plurality of insulating bodies of the same horizontal cross-sectional form as said openings but larger than said openings loosely resting upon the horizontal surface of the supporting element, each provided with an opening smaller than the openings in said supporting element permitting passage of one of the furnace tubes therethrough, each resting over an opening in the supporting element in contact with the periphery is in the form of a lattice work grid with grid bars conof such opening and having its opening in alignment with such opening in the supporting element, the lateral surfaces of such insulating bodies being spaced in the horizontal direction from the lateral surfaces of the insulating bodies adjacent thereto to permit individual lateral relative movement of each individual body upon lateral movement of the furnace tube passing through the opening therein.

2. A device as claimed in claim 1 in which the spacing between the lateral surfaces of the adjacent insulating bodies is 2 to 8 mm.

.3. A device as claimed in claim 1 in which the horizontal cross-sectional form of said insulating bodies conforms to a regular hexagon and the supporting element nected in honeycomb fashion.

4-. A device as claimed in claim 3 in which said grid bars are tapered toward the bottom.-

5. A device as claimed in claim 1 in which the lateral surfaces of adjacent insulating bodies are provided with complementary recesses and projections which overlap each other but are so dimensioned as to permit the individual lateral relative movement of the insulating bodies.

-6. A device as claimed in claim 1 in which the lateral surfaces of adjacent insulating bodies are provided with aligned horizontal slot like recesses and the adjacent insulatin'g bodies are bridged by a plate member telescoping into'the aligned recesses in the adjacent lateral surfaces of such insulating bodies, said recesses and plate members being so dimensioned as to permit the individual lateral relative movement of the insulating bodies.

7. A device as claimed in claim 1 in whichthe opening in the insulating bodies flares outwardly in the direction away from the supporting element.

References Cited in the file of this patent UNITED STATES PATENTS

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