US2497877A - Refractory element for downdraft furnaces - Google Patents

Description

J. R. FELLows 2,497,877

REERACTORY ELEMENT EoR nowNDRAFT EURNACES Feb. 2.l, 1950 Filed oct. 7, 1944 2 sheets-sheet 2( c /37 .QL' 342 :7?

Kif/M Patented Feb. 2l, 1950 REFRACTRY ELEMENTFOR DOWNDRAFT FURNACES Julian. Robert Fellows, Urbana, Ill., assignnr to The Board of Trustees of thedlniversity-of lili--l nois, UrhanaIl1.

Application October 7, 1944, vSerial No. 557,570

(Cl. 12S-770' 6 Claims. l

-This invention relates toa refractory element for fa down-draftfurnace; particularly for al furnace ofthe type shown in Patent No. 2,295,781, issued. September 15, 1942.

Down-draft furnaces of that type are designed to .burn coal and. similar 'fuels having a high volatile contentfto the: best advantage and without substantial smoke loss. In order to accom.- plish this' 'the furnace `is arranged sov that its walls deneV a: coking chamber into which ther fresh or green coal is introduced and in which it is converted into I"c'olret a coke-burning chamber through which the coke passes and in which it is burned while a fresh charge of coal is beingv coked in the coking chamber; and a combustion chamber in which the gases generatedl during coking of the coal and the burning of the coke are 'consumed'.

:1n tjheconstruction shown in saidy patent, secondaryv air is introduced through a vertical baf-` fle-wall separat-ing thecoking chamber from the combustion chamber', the air emerging from the bottom of the wall on a line in the region where the. coking chamber, the combustion' chamber, andthe coke-burning chamber come together. It been rfound desirable to construct this baiiie wall of a refractory material and particularly of a `ceramic such: as re clay.` It is also desirable from the standpoint of economy to manufacture as.. a unitaryv element the combustion chamber andthe bailie so that the back` wall` of the combastion chamber serves; as a liner.' for the furnace, a center wall also serves asa side of the' secondary air passage` and: a side wall' of the combustion chamber vmay 'alsov serve as a.y liner for a sidev of the furnace. These walls are, ofi` course, subjected toyconsiderable expansion and contraction stresses due to the heat of combos-- tion, the cooling4 effect', of the secondary air and' the cooling eiiect of the furnace body on the`y wallsactngaslliners. For thisreasonbreakage may occur and it is. desirable; that the elercem be readily replaceablc- .y The present. element. andv furnace construction are such that theentire combustion andsecondaryair element` maybe inserted or removed withoutany modication or adjustment ofi the. :turnace` structure.- 'I'hls is accomplished: by restingthe rearI wall of the'v ele ment upon. the lining of: the furnace and resting the' front Wall ot the baille section' and theA front wall or walls of the element against fixed roof flangesl in; the furnace, against which they are held, by gravity while pivoting'. on an arcV of vwhich.

the. rear. base; .of-tha element; is thecenter of curvature.. The; rear wall of thef'elementziszslopedl from top to bottom in such manner as to clear the vertical rear wall of the furnace when thev element is swung 'intop'ositiom while pivoted from theflanges.

The invention is illustrated in the drawings, in which Fig. l is a verticalv sectional view `of a furnace'embodying the invention; Fig.. 2 is a fragmentary vertical sectional view taken along the line 2-2 in Fig. 1; Fig. 3 is av plan view of a group of elements joined together to form afurnace assembly; and Fig. 4 isa perspective view illustrating vthe improved elements in slightly modified form.

As illustrated in the drawings, the furnace II includes the normal shell or casing I2 having a door I3 for the introduction of coal and' a gas outlet I5 connecting with a chimney (not shown). A furnace body I 6, including walls 'defining a Iirebcx, is mounted within the casing in any suitable manner. The furnace illustrated provides an 'air Ispace I"9 between the shell I2 and. the body I 6, A door 2I` (which may be inclined slightly inwardly and upwardly) is provided in thev lower portion of the furnace communicating with the ash pit 20 and having an` air opening 24.

Grates 22 and v23 are mounted within the body t6. above the ash pit. Grate 22 is a stationary grate and is disposed at an angle which may be ofthe order of 30-45. The grate 23 is preferably ofthe shaker type.

The forward' portion of the furnace belowv the door I3 is preferably' sloped to provide a chute portion 30 which tends to slide the coal by grav ity toward the grate 22.

The furnace has a double roof` extending rearwardly above the firebox, and terminating in front of the rear wall, to define the gas outlet opening I5. This roof" comprises an upper plate t5 'hauling-at its rear 'orA inner endva downwardly depending flange 46. The roof' also includes a lower plate 49 parallel to and slightly below plate 45. This plate terminates in a downwardly de'wir pending 'ange 52, a predetermined distance closer to the door I3 than the flange 46. The space between the platesl 45 and 49 provides an air passageway 53 which communicates atV the frontl ofthe furnace with the atmospherethrough the openings 54. The passageway connects directly at 'the inner or rear end thereof' with the4 secondary air passageway or channel 36 within the refractory element I4'.

This refractory element which forms a com- .bined baiile, secondary airv passageway, combustion chamber'and: furnace liner, comprises as an elemrmtr,A a slightlyl sloping back wa11533,. a

center wall 34, a front or baille wall 35 and side walls 31. The distance between the front of wall 35 and of wall 34 is the same as the horizontal distance between the backs of flanges 46 and 52. These walls together with the remaining structure of the furnace dei-lne the combustion chamber 38, the secondary air passageway 36, a coking chamber 39 and a coke-burning chamber 48. The coking chamber, the coke-burning chamber and the combustion chamber, as well as the air inlet 36, come together in the region of the line 4l representing the front bottom edge of the refractory -assembly I4.

The lower portion of the furnace around the coking, coke-burning and combustion chambers is lined with a refractory such as re brick 32. In constructing the furnace this lining is inserted and it will be observed that on the rear wall it stops at the shoulder 3| upon which the rear walls 33 of the elements I4 rest. The sides of the furnace may be likewise constructed and the side walls 31 of the outside refractory elements I4 will rest thereon, the portion of the coking chamber above and forward of the bottom of the refractory elements I4 being preferably also lined with refractory.

The rear wall 33 of the elements is curved from the vertical. Preferably the thickness of the wall is maintained substantially constant. The front wall 35 terminates at its top substantially below the walls 34 and 33. The vertical distance between the top of the wall 35 and the top of the wall 34 is preferably about the same as the vertical height of the air passageway 53. Likewise, it is about the same as the vertical distance between the bottom edges of the flanges 52 and 4B.

In inserting the refractory element I4 into the furnace the top edge of the wall 35 is placed back of the flange 52. This, of course, places the top edge of the wall 34 in a corresponding position with relationship to flange 46. The cutout portion 68 of the rear wall 33 provides clearance space so that this may be accomplished readily. The element is then lifted slightly so that the lower edge of the wall 33 will clear the lining 32, and the element is swung about a point of revolution which is substantially along the flange 46, until the bottom edge 6I of the rear wall 33 is in position above the shoulder 3 I. The element is then dropped into position. When this is done the front top edge 62 of the wall 34 rests against the flange 46 and the top front edge 63 of the wall 35 correspondingly rests against the flange 52. The whole structure, therefore, is supported by the shoulder 3|, upon which the edge 6Iy rests bygravity, and by the flanges 46 and 52 against which it is swung by gravity. Of course, the side walls of the composite refractory element are also supported by the side lining of the furnace. It will be observed that the cutout portion 60 of the rear walls is sufficiently great so that the wall will not be blocked by the furnace wall I6 or the flange 46 while being swung into position. The flanges also form a tight connection for the secondary air passageway.

' The description up to this point has been made in general as if the element were made in one piece. In practice the element will generally be made in at least two pieces and may be made in three or more. Certain methods of subdividing the element are described in my copending application Serial No. 486,940, led May 14, 1943, and now Patent No. 2,433,036. These are indicated illustratively in the drawings here,

v relationship. The elements are made in individual pieces to facilitate manufacture thereof and it is obvious that the forms may be modified in many ways to produce the complete assembly I4. In all cases, however, the complete element or assembly will comprise one or more combustion chambers; one or more secondary air inlets; and a baffle wall.

The elements 88 may, however, be omitted and only forms 10 and 15 employed.

The element or assembly would preferably in all cases be supported only by resting at the rear or the rear end sides of the furnace walls, and

by forward pressing upon the stop means in the roof. The individual pieces of the element may be hung upon each other in any desired manner.

The partial elements are inserted individually by tilting the upper portion forwardly and lnserting them until the edge 68 contacts the wallv I6, and this edge is then slid upwardly until the lower edge has cleared the shoulder 3|, after' which the element is dropped into place with itsi base resting on the shoulder 3l and its walls 34' and 35 resting against anges 52 and 46.

In the form shown in Fig. 4 the refractory elements are made up in three pieces, comprising' the C-shaped section and the mirror imagethereof 86, and the shorter C-shaped element 81 which denes the secondary air passageway and the baille. The section 81 is carried by gravity on the sections 85 and 86 in any suitable manner as.' for example, a shoulder 88 fitting into a recess 89 in the front wall of the elements 85 and 86.

The foregoing detailed description has been given for clearness of understanding only, and

no unnecessary limitations should be understood' therefrom.

What I claim as new and desire to secure by Letters Patent is:

1. A refractory element for a down-draft furnace comprising a plurality of vertical walls of substantial thickness defining a pair of openended parallel channels, one of s aid channels being substantially narrower than the other land terminating at its top a predetermined distance." below the other, the wall of said element most remote from the narrower channel being inclined inwardly from substantially the bottom to thetop, and being rounded on the outside at the top thereof.

2. A down-draft furnace having interior walls including a bottom grate dening a iirebox, a roof at the top of the rebox, an air inlet through the bottom of the firebox, a secondary air inlet in the roof of the firebox communicating with the atmosphere, a removable ceramic element disposed in the upper rear portion of the rebox and' element, a coke-burning zone in the rebox below the element. and a combustion chamber and a secondary air passageway within the element,

said interior walls ofthe firebox including a rearV wall, a stop member contiguous to said rear wall, said element including a rear wall portion resting upon said stop member by gravity, andxed means in the roof of the rebox adjacent the secondary air inlet supporting said element against forward rotational movement.

3. A down-draft furnace having interior walls including a bottom grate deilning a ilrebox, a roof at the top of the ilrebox, an air inlet through the bottom of the firebox, the rear wall of the ilrebox being substantially vertical and the roof thereof including a secondary air inlet communicating with the atmosphere and terminating mcdially in the roof, a pair of transverse spaced downwardly depending ilanges in the roof defining the outlet of the secondary air inlet, the more forward of the two flanges extending a predetermined distance below the other, a removable refractory element in the upper rear portion of the ilrebox having a passageway at the front of the element open at the bottom and communicating at the top with the secondary air inlet to dene a secondary air passageway and having a second passageway behind the secondary air passageway open at top and bottom to denne a combustion 1 chamber, said ceramic element thereby providing a coking zone in the rebox in front of said element, a coke-burning zone in the ilrebox below the element and a secondary air passageway and combustion chamber within the element, a gas outlet at the top of the furnace, said combustion chamber communicating with the cokeburning zone at its lower end and with said gas outlet at its upper end, the secondary air passageway within the element being substantially parallel to the combustion chamber with the bottom of the secondary air passageway terminating at substantially the junction of the coking zone, the coke-burning zone and the combustion chamber, the front wall of said element defining one side of the secondary air passageway and terminating below the adjacent wall of said element by a predetermined distance which is substantially the same as the predetermined vertical distance between said flanges, a stop member contiguous to the rear wall of the rebox, said element resting by gravity at its rear lower edge' upon said stop member and being supported at its front top edge by said flanges, and the back,

wall of said element being sloped inward from bottom to top to permit insertion and removal.

of the element.

4. A down-draftlfurnace having interior walls including a vertical rear wall and a bottom grate dening a rebox, a roof at the top of the ilrebox terminating in front of the said vertical lrear wall to define a gas outlet, an air inlet through the bottom of the ilrebox, a secondary air inlet in the roof communicating with the atmosphere and having an opening to the flrebox adjacent and in front of said gas outlet, fixed stop means carried by said roof and defining said secondary air inlet opening, a removable ceramic element disposed in the firebox above the bottom thereof and beneath said gas outlet, and resting against said stop means, said element having a substantially vertical combustion chamber and secondary air passageway Within the element, said secondary air passageway communicating with the secondary air opening in the roof and with the rebox and the combustion chamber communicating with the gas outlet and with the firebox, with said ceramic element thereby providing a coke-burning zone below the element, a coking zone beside the element, and a secondary air passageway and a combustion chamber within the element, a support member on the vertical rear wall of the furnace, said ceramic element including a rear wall resting on said support member and said element being removable by lifting the element from the support member and swinging the bottom of the element forwardly.

5. A furnace as set forth in claim 4, in which the stop means include a pair of vertically and horizontally spaced downwardly depending flanges, and the element has walls spaced from each other to define said secondary air passageway, said walls of the secondary air passageway engaging each of said stop means to seal the connection of said secondary air inlet and secondary air passageway.

6. A down-draft furnace having interior walls including a rear wall dening a firebox, a roof at the top of the rebox, an air inlet through the bottom of the ilrebox, the rear wall of the rebox being substantially vertical and the roof thereof including a secondary air inlet communicating with the atmosphere and terminating medially in the roof, a pair of transverse spaced downwardly depending flanges in the roof defining the outlet of the secondary air inlet, the more forward of the two flanges extending a predetermined distance below the other, a gas outlet between the more rearward flange and said rear wall of the ilrebox, a removable refractory element in the rebox beneath the gas outlet, said element being above the bottom of the firebox and thereby providing a coking Zone beside the element and a coke-burning zone below the element, a secondary air passageway and combustion chamber within said element, said combustion chamber communicating with the coke-burning zone at its lower end and with said gas outlet at its upper end, the secondary air passageway being substantially parallel to the combustion chamber and communicating at its top adjacent said flanges with the secondary air inlet and at its bottom terminating at substantially the junction of the coking zone, the coke -burning zone and the bottom of the combustion chamber, the front wall of said element dening one side of the secondary air passageway and terminating at the top below another wall of said element defining the opposite side of the secondary air passageway andl REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,295,781 Fellows et al. Sept. 15, 1942 2,370,644 Esson Mar. 6, 1945

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