US2378387A - Coking retort oven - Google Patents

Description

vPatented June 19, 1945 UNITED STATES PATENT OFFICE Joseph Becker, Pittsburgh, Pa., assignor, by 'mesne assignments, to Koppers Company, Inc.,

a corporation of Delaware Application May 16 1942, Serial No. 443,191

6 Claims.

The present invention relates in general to coke-oven heating systems and more specifically comprehends improvements in the heating systerns of those coke ovens having their rich heatinsas conduits formed in and of silica masonry and arranged during thecoke-ovens heating re: currently to receive the cooler combustion-mediumand to convey it to the heating flues.

Most modern coke ovens are constructed substantially throughout of silica masonry which, as is well known, possesses the advantages of: high resistance to deformation at the elevated temperatures of fast coking rates; low coefficient of expansion at such temperatures; high conductivity for heat; and high resistance to abrasion. All 7 these characteristics make silica an especially suitable material, to meet the exacting demands of modern coke-oven practice, i

Uniform temperatures do not obtain throughout all parts of the masonry structure of coke ,ovens during their operation nor are the prevail- 'ing' temperatures at all points thereof within .that higher range of temperatures wheresilica exhibits its advantageously low coefficient of expansion, but, to the contrary, certain of their-- structural features in consequence of their funct'ions within coke-oven structures fluctuate between temperatures within a lower range at which the coefiicient of expansion of silica masonry is relatively high, the result being that. the crystalline'bonding between its silica moieties is con tinuously subjected to stressing and straining ing-gas conduits are continuously and diversely and rapidly altering; this constitutes a severe thermal shock especially to the conduit inner walls and more particularly at their outer ends where not only is the range of temperature change the greater but also where the prevailing temperature range is within that range whereat silica has its higher coefilcient of expansion. This'coolthat can bring about in such parts sooner or later fracture and deterioration that eventually leads to local flaking and spalling necessitating tedious patching or expensive substitution of parts, and can develop conditions whereby rich fuel-gas can short-circuit into the regenerators or to the face of the coke oven.

To this category of structural features belong those conduits for receiving and convfiy to the individual heating flues the unpreheated rich heating-gas supplied to the coke-oven structure,

and the above-described phenomenon of relatively rapid masonry impairment is more especially observable to extend a considerable distance inside the coke ovens along said rich-gas conduits from a point close to their inlet-end portions.

.From the above-mentioned, the existence of such condition is not surprising when it is considered that duringan on period of an oven-heating .mass of the; silica of the conduit walls at or adjacent their inner surfaces and continuesso to do for a considerable distance therealong and during the entire on period of the heating cycle. Thereafter, during the oiif period oithe ing effect of inflowing rich-gas on the gun-bricks of horizontal coke ovens is well known to cokeoven operators who have noted that for some distance from their inlet ends the gun-bricks are at a temperature below that at which the silica masonry approaches even a dull red color, even though the lower ends of the heating fiues immediately thereabove are at temperatures of incandescence.

An object of the present invention is therefore the provision of simple and effective means whereby the conduits for conveying of unpreheated rich fuel-gas within the silica masonry of coke ovens can also be formed of silica and the manifest structural advantages of having the walls of said conduits and their adjacent masonry all formed'of material having the same thermal properties can continue to be enjoyed without the above-described disadvantages and inconveniences of oven operation and maintenance.

A furtherobject of invention is to provide practical means for protecting more especially the inlet-end portions of silica-walled-conduits, that are arranged for conveying unpreheated rich fuel gas to the heating flues of coke ovens, against the recurrent thermal shock incident to intermittently admitting said gas thereinto at a lower temperature.

The invention has for further objects. such other improvements and such other operative advantages or results as may be found to obtain in the processes or apparatus hereinafter described or claimed.

According to the present invention, in a silicamasonry horizontal coke-oven, a silica-walled conduit for distributing an unpreheated rich fuel- ,gas to the heating fiues of aheating-wall is provided from its inlet end and extending'inwardly 'therealong to preferably at least a region thereof where its temperatures are normally above those temperatures at which silica-masonry shows an abrupt reduction in its rate of thermal expansion, with an inner protective covering or lining of a non-metallic refractory. This protective covering can be a cannulated member, or members, of fireclay that exhibits a lower rate of thermal expansion and, consequently, a greater resistance to thermal shock than does silica, said member having a perforation, or perforations, that is disposed preferably to register with those ducts communicably connecting said silica-walled,

rich-gas conduit with its ports into the heating fiues thereabove. The protective covering of ,invention can also be constituted of a member, or members, that is formed from preformed asbestos shapes which are either fired or unfired.

In its preferred form, a refractory cannulated member of invention is shaped similar to a holl'ow drain-tile having a lateral perforation, or perforations, and an external diameter such that it is slideably insertable into the said heating-gas conduit when either is hot or cold; the said member can be efiectively used when allowed to rest loosely on the inner surface of the heating-gas conduit, or the annular interspace therebetween can be stopped with a cement or with yieldable sealing material such as a fibrous refractory, or those inner-wall surfaces of said conduit that are adjacent to the cannulated member can be recessed in such manner that the latter rests in the former in bushing-like fashion-this latter arrangement offers the advantage that the benefits of the invention can be enjoyed without any reduction in available cross-section of the heating-gas conduit along its entire length.

Those metallic fittings that are located at the battery-face and are employed for controlling flow of rich-gas into the rich-gas conduit are carefully insulated from contact with the cannulated member by preferably yieldable insulating material, so that they will not in consequence of the relatively high conductive and radiating capacity of their metal aggravate those fluctuations of temperature that normally take place in the rich-gas conduits during an oven-heating cycle and can be so destructive of silica masonry. If a metallic body is directly in contact with hot masonry at its one end and at the other end is exposed to the atmosphere, the range of temperature fluctuations that could normally take place in such masonry is greater than would otherwise obtain and this effect is amongst the contributory causes why such metallic tubular liners as those shown for gas-guns of horizontal coke ovens in U. S. No. 1,528,808 only aggravated that deterioration of their adjacent oven masonry which they purported to obviate.

In the accompanying drawings forming a part of this specification and showing for purposes of exemplification a preferred apparatus and method in which theinvention may be embodied and practiced but without limiting the claimed invention specifically to such illustrative instance or instances:

Fig. 1 is a vertical section take crosswise of a battery of horizontal coke ovens provided with the present improvement in conduits for conveying unpreheated rich heating-gas into coke-oven heating fiues, the sections A-A and B--B being taken respectively along the lines A-A and B- B of Fig. 2;

Fig. 2 is a vertical section taken along the line 11-11 of Fig. 1;

Fig. 3 is an enlarged'view of a fragment of Fig. 2 and showing in greater detail the improvement provided by the present invention for protecting those coke-oven conduit walls of silica masonry for conveying unpreheated rich heating-gas to the heating fiues;

Fig. 4 is an enlarged view of a fragment of Fig. 1 showing a vertical section taken through the gas-gun conduit of the therein illustrated battery embodying the present improvement; and

Fig. 5 is a chart showing curves contrasting the change with increasing temperature of the per cent of linear expansion of a characteristic well-fired silica brick and of a typical fireclaybrick material such as is suitable to form the heating-gas conduit liner of the present improvement.

In the drawings, the present improvement is shown embodied for purposes of exemplification in that type of the well-known Becker coke-oven wherein non-regeneratively-preheated heating- .gas is introduced into silica-walled gun-brick conduits, formed in the silica masonry of the capitals of regenerator walls, for conveying said gas to the heating fiues, but it will be understood that the advantages of the instant improvement can be realized in coke-ovens of other types and designs having silica conduits that recurrently receive colder rich heating-gas and consequently fluctuate in temperature within a relatively wide range thereof that is substantially below those temperatures obtaining in adjacent portions of the coke-oven heating-flue system.

Referring to the drawings, coking chamber ID that receives the coal to be coked is sealed at each end by a door H and is heated at either side by heating walls l2 that are each formed with a plurality of vertically-disposed heating fiues 13 that are, with the exception of the single fiues at each end of a heating wall, arranged in groups of four fiues that are communicably connected with a corresponding group of four fiues in an opposite heating wall by means of a, cross-over duct (4 that conveys combustion-products from all the fiues of a group into'all the fiues of said opposite corresponding group, the heating of the heating walls being effected by the combustion in the individual heating fiues of currents of rich fuel-gas and air individually delivered thereinto.

The air required for the combustion-reaction in each heating wall fiows from the outside atmosphere into a pair of sole-channels l5, l5, whence it is distributed by means of ports l6 along the tops thereof through the associated checker-brick-filled regenerator spaces ll, for purpose of preheating, and thereafter fiows from each of a pair of up-flowing regenerators through a duct [8 into the lower part of each heating fiue of a heating-wall in quantities individually regulated by the free-space between the walls of the air-port l9 and the outer surface of replaceable port-core 20.

In the illustrated battery, the Whole regenerative space beneath the coking chambers is so divided, by'means of the silica-masonry of chambers is so'divided, by means of the silica-masonry of capital walls 2|, supporting the masOnry of the fiued heating walls, and also by the masonry of regenerator division-walls 22 located beneath the coking chambers, that the fiues of each heating wall each communicate with a pair of regenerators and in consequence the battery-structure can be heated with non-regeneratively-preheated rich gas or with regeneratively-preheated lean gas; i. e., it is a battery of so-called combination coke ovens.

-most of the time. -Although during thebfi -In the illustrated battery, rich heating-gas that does not'require preheating for its efiective combustion is delivered into the battery structure through suitable valved piping-connections 23 at each side thereof and enters, at their outer ends, silica-walled conduits 24 that are formed in the silica masonry of the capitals of regenerator walls 2| and extend crosswise of the battery beneath the heating flues of the heating walls to which they are individual. The delivered rich-heatin gas is conveyed along said conduits 24 and is apportioned to the individual heating fiues thereabove through ducts 25 in accordance with the chosen size of aperture 25 in replaceable gasnozzle 21, the rich gas entering a heating flue I3 through the latter and being burned, as it flows upwardlyin said flue, by preheated air that also enters the same through air-port IS, the combustion-'products'thereof being carried by means of a cross-over duct l4 into heating flues of an adjacent'heating wall whence they pass to the stack after traversing regenerators I! located beneath said adjacent heating wall.

When theillustrated coke ovens are in operation the silica-masonry surrounding the silicawalled rich-gas conduits 24 is at incandescent heat as well as is also said conduititself along the major part of its length within the interior of the battery. During the cycles of regenerative heating, unpreheated rich heating-gas is at periodic, predetermined intervals flowed into the outerends of said conduits 24 in amounts regulated by the valves of'metallic pipe-connections 23 for delivering said rich heating-gas thereto; that'is, cooler heating-gas is delivered to a conduit 24during that interval of the regenerative heating cycle when the associated heating-fines thereabove are flame-fiues, the delivery of such heating-gas being cut-off during the immediately following interval of said heating cycle when the fiame-flues become combustion-products flues. Thus, during the respective intervals of each regenerative heating cycle, the silica walls of a conduit 24 are respectively giving up heat to inflowing rich heating-gas and are thereafterabsorbi'ng heat from the surrounding silica-masom-y. This condition obtains throughout'the life-cycle of'a coke oven, and causes the Walls of conduits 24 to be substantially continuously changing in their temperatures. The extent of temperature fluctuation is'manifestly the greatest adjacent inlet-end portions of conduits 24 by reason of the fact that in these zones the inflowing rich gas is at its lowest temperature and the quantity thereof thatis extracting heat from the conduit walls, is the largest; as the median of the coke oven is approacheol, the quantity of heating-gas conveyed by said conduits continuously decreases by reason of its delivery to successive heating flues, and in result the said conduit walls fluctuate in temperature least at the operation,the heat that accumulates in the silica at the; inner surfaces of the inlet-end portions 'ovenmedian they are substantially at the operating temperature of their surrounding masonry period of the heating cycl ithere is a tendency to correct thisinequality of temperature, long before such condition has been established the on period of gas-flow in the heating cycle is commenced, and the cooling of the conduit Walls is again started. y

' From the above recited, it is now obvious that the silica material at and adjacent the inner surfaces of rich heating-gas conduits. 24 is throughout a regenerative heating cycle at temperatures ranging from relatively cool, at the inlet end or ends, to the, or about the, coke-oven operating temperature, at or adjacent the median of a cokeoven battery. I

Throughout a substantial portion of the length of these rich-gas conduits the continuously changing temperatures have little, if any, deleterious effect on the integrity of their silica walls. primarily because the range of temperatures to which these fluctuations of temperature is limited, is restricted to that range wherein silica exhibits relatively minor changes in expansion with changing temperature, and there is in consequence in suchzones littleinternal strain developed within the crystals of silica themselves or their mutual bonding medium. However, from their inlet ends inwardly for a considerable distance, the relatively greater changes in temperature through which the conduit walls are continuously passing are within that range of termperatures wherein the expansion of silica with change of temperature is relativelyhigh and the ovens said vmedian point. In fact, during ovenmaterial of the conduit walls is subjected to such shock and strain as rather quickly eifects disintegration of the bonding andof the silica moieties of the material comprising the conduit-wall structure. There isthus occasioned that cracking, flaking and spalling commonly observed in the latter said conduit-wall portions. These differences of expansion of silica'with temperature changes in the low and in the high temperature ranges, and also the difierences-in effects,- that fluctuations of temperature of the conduit walls within these ranges produce, will be more quickly apparent by reference to Fig. 5 wherein there is shown a graph representing the percentage changes in linear expansion of well-fired silica bricks with changes in temperature. The therein illustrated curve shows that from about to 4 600 F. silica bricks will expand about one per cent of a linear dimension, and from 600 F. to about 1200 F. this expansion is reduced to about 0.25 per cent, and-from the latter said temperature to the average flue temperature (about 2400" F.) of an operating coke oven there is relatively insignificant expansion exhibited by silica bricks. Thus, the structurally disruptive forces continuously operating at the inlet ends of silica-walled conduits whereinto cooler heating-gas is recurrentlyflowed become manifest and the more so when it'is observed that: adjacent the conduit inlet-ends, temperatures of about 300 F. commonly obtain; the temperatures at any one point in these cooler conduit-portions can vary as much as 50 F. in a coke-oven heating cycle; and those temperatures at which silica shows little expansion or contraction with change of temperature are normally not encountered for several feet downstream of said conduit inlets.

In contrast to silica bricks, which are structurally crystalline and bonded predominantly by virtue of interlocking silica crystals, thus making them structurally peculiarlysensitive to the'high j dominantly glassy bond and arev much less sensitive to thermal shock. This contrast is clearly visible by comparison of the two curves in Fig. 5. During the heating of well-fired silica bricks from about 200 to 600 F; their linear expansion is about 5-6 times as fast as fire-clay bricks heated through the same temperature range; in heating them from about 200 to 1100 F., the silica bricks show overall linear expansion at about three times the rate exhibited by fire-clay bricks.

- Above about 1100 F., silica bricks expand or conmaterial; in its preferred form, but not necessarily limited thereto, said means are formed of non-metallic material that, with thermal changes, expands and'contracts at a lower rate than does silica in the same temperature range. The. said protective means. are arranged to extend from the inlet ends of said conduits inwardly of 'the ovens preferably to at least a region where the conduit temperatures throughout the regenerative-heating cycle of the ovens are normally above about 1100-1200 F. A practical material for forming the conduit bufier-coverings ofv in- 'vention has been found to be fire-clay that is molded and fired in a shape similar to that of the heating-gas conduits themselves and, in their embodiment shown in the drawings, they are provided with a cross-section sufficiently less than that of the silica-walled conduits 24 that they are slidably insertable thereinto when either is hot or cold, Preformed shapes of an asbestos composition are also practical, or the buffer-coverings can be fashioned of shapes formed of silica itself if they are supplementary to the main conduit-walls and, function to preserve them and maintain them gas-tight. As is clearly visible in Figs. 1, 3, and 4, these. conduit buffer-coverings 28-of invention are formed similar to hollow drain-tile and have lateral openings 29 arranged for registry with those vertical heating-gas ducts 25 whereby vrich gas is delivered directly into the heating iiues. The members 28 can be supported loosely on the bottom of conduits 24, as shown in the drawings, or they can be supported by spacers. out of. direct contact with the conduit walls and with the space therebetween either free or sealed with, for example, a friable cement or yieldable sealing material without departing from the spirit of the invention. In all instances, however, the inlet ends of the buffercovering members of invention are disposed in such fashion as directly to receive rich heatinggas discharged from the gas-flow control means 23 therefor, and to prevent its immediately thereafter coming into direct, contact with the silica. walls of said conduits 24.

In the embodiment shown in the drawings, the walls of conduits 24 are formed, adjacent the battery-face, by metallic butt-blocks 30 whereto are bolted piping-connections 23 for delivering heating-gas into said conduits. To the end of preventing that rapid conduction of heat, from silica, fire-clay bricks, for example, have a prethe hot interior masonry of the battery and into the atmosphere, which could .be otherwise occasioned by the exposed metal of said butt-blocks, the adjacent inlet ends of the present novel buffer-covering members 28 are heat insulated therefrom by means of coils 31 of heat-resistant insulating and packing material that are supported on the outer surface of bushing-like member 32 that is itself retained out'of contact with the metal of the adjacent butt-block, The coils 3| of yieldable heat-resistant material serve to seal, to gas-flow, the space between members 28 and the walls of conduits 24 and also to insulate the former from contact with metal of the buttblocks.

As is well known to those experienced in the art, the transfer of heat to gases by bringing them into contact with regeneratively heated solids of refractory material causes, in the interior of the mass of the refractory solids, but little temperature fluctuation during a cycle of operation. Most of the extreme temperature change extends only a relatively short distance beneath the skin of the employed refractory material. Thus, when the buffer-coverings are of adequate thickness, the present improvement makes it possible to restrict those extremes of temperature fluctuation, that take place along the walls of the inlet portions of coke-oven conduits recurrently receiving colder rich gas for conveyance to the heating fiues, to said coverings and to such resistant refractory material as firebrick, or its equivalent, that is by nature better able to withstand the said temperature fluctuations than is the silica masonry from which the walls of said conduits are formed; and, in consequence, it becomes possible to maintain said conduit walls, if not at substantially coke-oven oper-- ating temperatures throughout their entire extent, atleast within those ranges of temperatures wherein silica shows little expansion or contraction with changing temperatures, thereby promoting the permanency of their structure and that of the coke even as a whole, and also obviating detrimental fracturing and disintegration of the silica that can lead to leakage and shortcircuiting of heating-gas within the gas-flow system. Practical operation has demonstrated that the said temperature fluctuations are substantially restricted to said members 23 when they are formed of fire-brick material with a wall thickness of three-fourths inch.

As hereinbefore mentioned, the heat-buffer fire-clay members 28 can be employed within the scope of the invention by loosely inserting them in the channel of heating-gas conduits 24, or they can be mortared in place therein, or they can be in bushing-like manner let into the silica masonry of said conduit walls in such fashion as not to reduce the available cross-section of the conduit channel; it is, however, preferred that any contact between said members 28 and the adjacent conduit walls be a yieldable one, so that the differences in expansion of their two unlike materials can be accommodated without rupture of either during especially the heating-up period for the oven. This difference in thermal expansions of silica and of fire-clay is that which makes it impractical in a silica coke oven to incorporate in its masonry rich-gasv conduit walls formed entirely of fire-clay material; if such were done, the divers expansions and contractions of silica and fire-clay at the various temperatures through which the masonry of coke ovens passes,-

during the heating-up and at the different cok ing times of subsequent operation, would open up fissures and joints and give rise to cross-leakage.

The invention as hereinabove set forth is embodied in particular form and manner but may be variously embodied within the scope of the claims hereinafter made.

I claim:

1. In a regeneratively heated coke oven formed of silica masonry comprising, a horizontal coking chamber with heating walls on opposite sides thereof and each constituted of vertical flues each of said flues being operatively disposed for upflow combustion and downfiow of combustion products in alternation, regenerators disposed at a level below the levels of the bottoms of the coking chamber and heating walls, and horizontal rich fuel-gas distribution channels extending inwardly from ends of the heating walls lengthwise thereof under the heating fines and formed as hollow passages in the silica masonry betweenthe bottoms of the fiues and the upper portions of the regenerators, said channels each communicating with a multiplicity of the vertical fines of a heating wall through masonry ports distributed longitudinally of said channels and being adapted to communicate with a fuel gas supply outside the oven at an outer end of its heating wall, for

inflow distribution of cold rich fuel-gas from said supply to said flues only when said fiues are operable for upflow combustion, so that, during the ovens regenerative heating, outer ends of channels would be alternately cooled by the entering cold rich fuel-gas to be distributed to the vertical fiues during upflow combustion therein and interniittently reheated by the heat of the downflow stream, and said conduits having their nonmetallic refractory walls of a thickness to avoid cooling of the inner surfaces of the outer ends of said silica walled channels by conduction of heat therefrom through the walls of said conduits to the entering gas to be intermittently conveyed to the multiplicity of vertical flues by said respective silica Walled channels.

2. Coke oven apparatus as claimed in claim 1,

') and in which each of said thermal-shock shield conduits comprises an elongate heat buffer-conduit of fireclay having a wall thickness as aforesaid.

' 3. Coke oven apparatus as claimed in claim 1, and in which the replaceable thermal-shock shield conduits extend into so much of the outer ends of said silica-walled channels as would be, in the absence of such thermal-shock shield conduits, alternately cooled and reheated, by respectively the entering rich fuel-gas and heat derived from oven masonry contiguous said silica walled conduits, within a range of temperatures below about 1100 F. below which silica exhibits a marked increase in its rate of thermal expansion, and in which the thermal-shock shield conduits are non-integral with the silica-Walled channels to accommodate differences in expansion between the two without rupturing the channels.

'masonry contiguous said silica-walled conduits,

within .a, range of temperatures below about 1100 F. below which silica exhibits a marked increase in its rate of thermal expansion, and in which each of the thermal-shock shield conduits comprises a conduit of material that has a lesser thermal expansion and contraction than silica at temperatures below 1100 F.

5. Coke oven apparatus as claimed in claim 1, and in which the non-metallic thermal-shock shield conduits are composed of a material that has a lesser thermal expansion and contraction than has silicawith corresponding changes. of temperature below 1100 F., and in which said thermal-shock shield conduits are mounted in said silica-walled channels for yielding contact therewith to accommodate differences in expansion between said conduits and said channels without rupturing the latter.

6. A regeneratively heated coke oven formed of silica masonry between the bottoms of the flues and'the upper portions of the regenerators, said channels each communicating with a multiplicity of the vertical fiues of a heating wall through masonry ports distributed longitudinally of said channels and being adapted to communicate with a fuel gas supply outside the oven at an outer end at an end of its heating wall, for inflow distribution of fuel gas from said supply to said fiues only when said fines are operable for upflow combustion, so that, during the ovens regenerative heating, outer ends of said channels would be alternately cooled by the entering gas to be distributed to the vertical lines during upflow combustion therein and intermittently reheated by the heat of the downflow of combustion products to the regenerators, the improvement comprising, means for decreasing the extent of thermal change in the silica of said outer ends of said channels, said means comprising a thermal-shock shield of non-metallic refractory material disposed within the outer end portions of said silicawalled channels and forming therein a passage for the initial conveying of the main bulk of the heating-gas stream to be intermittently conveyed to the multiplicity of vertical fiues by said respective channels, and o'f'metal piping extending a short distance from the surface of the battery into the masonry for introducing the entering rich gas to the channels, and heat-insulation interposed between said non-metallic refractory thermalshock shield member and said metal piping.

JOSEPH BECKER.

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