US248483A - Regenerative hot-blast apparatus - Google Patents

Description

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iTan STATES PATENT OFFICE.

JOHN 0. LONG, OF MEGHANIOSBURG, PENNSYLVANIA.

REGENERATIVE HOT-BLAST APPARATUS.

SPECIFICATION forming part of Letters Patent No. 248,483, dated October 18, 1881.

Application filed April 27, 1881. (No model.)

. Apparatus for Metallurgical Furnaces, ot'which the following is a specification.

My invention relates to certain improvements in regenerative hot-blast apparatus for metallurgical furnaces; and the improvements consist in certain combinations and arrangements of parts, which will be first fully described, and then specifically pointed out in the claims.

Referring to the accompanying drawings, making part of this speoification,and in which like letters of reference indicate corresponding parts, Figure 1 is a horizontal section through the perforated air cylinders and blocks on line. 2 c, Fig. 5. Fig. 2 is a horizontal section through the gas and air connections on line y 3 Fig. 5. Fig. 3 is a horizontal section through the air cylinders and blocks on line z 2, Fig. (5, showing a modification of the dividing pipe, distributing main, connections, and combustion-chainber. Fig. 4 is a horizontal section of the same on line y y, Fig. b. Fig. 5 is a vertical longitudinal section on line 00 00, Figs. 1 and 2, showing the hot and cold gas and hot and cold air and chimney connections. Fig. 6 is a longitudinal section on line mw, Figs. 3 and 4, showing the hot and cold gas and hot and cold air and chimney connections, the same being a modification of the parts shown in Fig.5. Fig.7 is a vertical section through the combustion-chamber on line a to, Figs. 1 and 2. Fig. 8 is a vertical section through the combustion-chamber on line a a, Figs. 3 and 4, showing a modification of the dividingpipes, connections, mains, and combustion-chamber shown in Fig. 7. Fig. 9 is a vertical transverse section of the oven on line 'v Figs. 1,2,3, and 4. Figs. 10, 11, and 12 are perspective views of portions of the walls, showing their construction, so as to provide against the effects of expansion and contraction. Fig.13 is a longitudinal vertical section on line 3/ 31 of Fig. 14 of an oven whose regenerator-tlues are arranged in groups or sets, showingthe modified method of forming the horizontal distributing-fines. Fig. 14 is a horizontal section of the same on line :0 .20 of Fig. 13. Fig. 15 is a top or plan view of four combined ovens and gas-heaters arranged in couples directly connected, having two gas-supply mains at hot or combustion chamber sides. Fig. 16 is a top or plan view of four combined ovens and gas-heaters arranged in couples and having a common gas-supply main connected to their several combustion-chambers. Fig. 17 is a top or plan view of three combined ovens and gas-heaters arranged above a common gas-supply main. Fig. 18 is a top or plan view of three ordinary regenerative hot-blast ovens altered to my improved system Without adding a fourth ordinary oven or a combined oven and'gas-heater.

The object of this invention is to provide a regenerative hot-blast oven which can be used either for heating the blast or for heating the combustible gas burned in the apparatus, so thatitmay be substituted for either a special blast-oven or a special gas-heater, or both, in order to heat the combustible gas prior to its being burned in the apparatus, whereby a more intense heat may be developed therein than, when the. apparatus is heated by the combustion of gas which has not been heated after leaving its source, and which is so arranged with suitable connections that it can be used either for heating the blast orforheating the combustible gas by being heated for each obj ectspecially; or itcan be used asa gasheater without being specially heated therefor by making available the large quantity of heat yet in the oven when used to heat the blast after it has lost that portion of its heat which is effective in'heating the blast to the required temperature, and which combined blast-oven and gas-heater may be substituted for either the special gas-heaters or blast-ovens, or for both, as aforesaid, so that when used as agasheater it can, in case of failure or repair of the blast-ovens, be used for heating the blast, thus furnishing a duplicate set of blast-ovens without increasing th cost of the plant, and at the same time avoid g the danger incident to a failureof the hot blast by the giving out of the special blast-ovens; and in addition thereto the object is to furnish a means of altering the regenerative hot-blast apparatus now in use to my improved system, either by adding thereto one or more combined blast-ovens and gas-heaters directly connected thereto, so as to form couples, each consisting of anloven used as a gas-heater and an oven used as a blastoven, as hereinafter described, or all may be connected to a common hot-gas main, as in Fig. 16, and in both cases adding to the other ovens the necessary hot and cold gas and air connections, so that any or all may be used as blast-ovens or gas-heaters, as desired; or a plant consisting of four blast-ovens may be altered to my system where the ovens are arranged along a common coldgas-supply main having no other branches by putting in the main a valve between the ovens and blast-turnace or other source of gas supply, and then using the portion thus cut ed as a hot-gas main or, in case each pair of ovens has a common gas-supply main without other branches, then by cutting it oil as above described a hot-gas main is formed leading from one oven to the other, and the pair is worked as a couple. In both cases the necessary additional hot and cold gasand air connections are made so that any oven may be used as a gas heater or blast-oven, as desired.

In the case of a plant consisting of three ovens it may, owing to the fact that the combustible gas necessary to heat the apparatus has am uch smaller volume and less velocity and greater heatabsorbing power than the blast, while the specific heat is about the same in both cases, be altered to my improved system without increasing the number of ovens, by altering them into combined blast'ovens and gasheaters by adding to the ovens the necessary cold-gas main and connect ions at the cool end, in order to supply the gas to be heated, and at the hot end a hot-gas main connecting all of the ovens; or,in case the ovens have a common gas-supply main, then, by cutting it oft by a valve between the ovens and blastfurnace or other source of gas-supply, a hot-gas main is formed, using the ordinary gas-connections with the ovens for the passage of the heated gas. with hot air, then the necessary connections must be made as hereinafter described; but it cold air is used for combustion, then the ordinary air-connections can be used.

A plant of three blast-ovens may also be altered by adding one of the combined ovens and gas'heaters and the necessary blast and gas and air connections to the other ovens and cutting off the gassupply main, as above described.

The object is also to provide a means of heating a mixed blast of air and vapor, and at the same time furnish pure highly-heated atmospheric air for combustion in the ovens and gasheaters; also, to provid for expansion and contraction and for the alual heating of the oven and equal distribution of the gas or blast to be heated.

In this specification when speakin gof cold or cool gas, I mean gas at the temperature it has after leaving the blast-furnace or. other source of supply less the temperature lostin transmission to the apparatus in which it is burned-that is, combustible gas which has not been heated after leaving the apparatus in- If it is desired to burn the heated gas which it was produced and prior to its introductioninto the apparatus in which itis burned.

The tendency of modern blast-furnace engineering is to reduce the temperature of the waste gases from the blast-furnace as low as possible, and is a result of the widening of the blast-furnace throat, as now done in the more modern blast-furnaces, in order to save fuel and improve the working of the furnace. In fact, one very high authority says the temperature ot' the waste gases ot a blastfurnace should not exceed 212 Fahrenheit; hence the necessity of having a means of heating the gas so as to be able to command an intenselyheated blast.

The invention consists in the regenerative hot-blast oven having cold blast or air and cold-gas and chimney connections at the cool or chimney end, and having at the hot or combustionehamber end hot-blast and hot-gas delivery connections, as well as the hot and cold gas and hot and cold air connections for sup plying the necessary hot or cold gas to heat the oven by being burned therein by hot or cold air or bya mixture of hot or cold air, and whose walls are so constructed as to provide for expansion and contraction of the several walls, and whose root is constructed as shown.

It also consists in the horizontal tines and the several connecting pipes and flues or distrilniting-mains at the cool end, whereby the gas or blast to be heated is equally distributed, and of the fines and pipes and mains at the hot end, whereby the combustible gas to be burned therein is equally distributed.

It also consists in the combustionchamber divided into single or double compartments by longitudinal walls extending from the root'and to or near thebottom,andhavingtheair blocks or cylinders extending through the casing and into the wall separating the comlmstion-chamber and regenerator.

It also consists in the combination of the pipes and valves by which hot air is supplied for combustion in the ovens or gas heatersindependent of the hot-blast main.

It further consists in the combination ofone or more of the above described ovens, used either as blast-ovens or gas-heaters, with one or more ordinary regenerative or above-described ovens used as blast'ovens.

It further consists in the combination of two or more combined ovens and gas-heaters, which are used successively for heating the blast and for heating the combustible gas.

It further consists in the combination, with two or more ordinary regenerative hot-blast ovens, of the necessary hound 001d gas mains, and connections by which they may be used as blast-ovens and gas-heatem,oithar successively or in couples, allessentiml lym hereinafter more particularly described.

The combined oven and gas heater is constructed of ordinary fire-brick or of similarlyshaped blocks of fire-brick or other refractory materials, and whose dimensionavary with the temperature of the blast desire-(1,150 that allof Ils crease s the material in the bricks orblocks may be useful in storing up and giving out heat, for with different temperatures the depth to which the effective heat penetrates and is given off varies. Itisrectangularin form and is supported by curved segmental walls A of common or red brick, sand, slag, &c., and incased in sheetiron; or it may be made without the supporting-walls A, with a rectangular casing of sheetiron properly supported by outside girders or bracing; or the sheets may be put on horizontally in strips whose length is equal to the width of the several sides of the oven, and with their edges upturned flange-like and fastened, thus providing for lateral pressure. It is divided into two partsB, the regenerator and O, the combustion-chamber-by the wall I), which extends from the bottom to near the top, but allowing space for the horizontal tines S and from side to side. Itis also divided into severalindependentcompartments, either double or single, by means of the roof-supporting walls E, which extend from front to rear and from the roof to the bottom, except the regenerator part of those in the middle of the double compartments, which rest on arches tormiiig the horizontal flues G, and in the combustion-chamber in which those forming the double compartments extend, either as in Fig. 7 to below the connection I,or, as in Fig. 8,they extend to thetop of thehorizontal fine 0. They may extend, as in Fig. 7, to the bottom, in which case each compartment would have a passage, as at I, for removing the dust.

The walls E in the middle of the double compartments may extend to between the airblocks or cylinders H, and the connection I for passage of blast and gas, as in Fig. 7, or they may be cut off above the air cylinders or blocks, as in Fig. 7; but in this case the air cylinders or blocks are supported by the walls J, to prevent sagging from the effects of heat.

The combustion-chamber maybe constructed as in Fig.8, in which the walls E in the middle of the compartments may be cut otf above the air blocks or cylinders. WVhen so modified the compartments may be made single by extending all of the walls E to the top of the flue O, and each compartment is provided with a connection, I. In order th at there may more certainly be an equal distribution of the combustible gas and the heated products ot'combustion, the mouths of the connections I are placed in the middle of each of the compartments, either double or single.

The air for combustion is introduced through the perforated blocks or cylinders H, placed either in the middle walls, E, of the compartments, as in Fig. 7, or in the walls which form the sides of the single or double compartments, as in Fig. 8. The air cylinders or blocks H extend through and even with the casing and into the wall D, so that in case of repair they may readily be replaced from the outside of the oven by removing the connecting-pipe J and connections K.

The air blocks or cylinders may be made of fire clay or brick, metal, or other refractory material, and, if necessary. may be cooled by causinga current of air or water to tlow through a pipe, K, which may be embedded therein. The air cylinders or blocks H are connected by pipes J, having regulating-valves M, to the pipe K, having valve L. The pipe K connects with the pipe N, communicating with the combustion-chamber G and having valve 0, Figs. 1, 3, and 7, which may be made in the form of a check-valve by having a suitable-sized seat-valve so balanced as to be automatic, so as to prevent any back flow of air when the oven is being heated or is heating gas; but when the oven is heating the blast opens automatically to allow the air necessary for combustion in the other ovens to flow into the pipe N, and thence by the pipe A, which connects it to the similar pipes, N, of the other ovens. When the ovens are in the same line, as in Fig. 17, the pipe N extends only be yond pipe K, to meet pipe A, which joins all pipes N; but when the ovens are opposite each other, as in Figs. 15 and 16, then the extension of the pipes N, after connecting by pipes A to meet the corresponding pipes N of the opposite ovens, is necessary to complete the circuit of the air-passages for the air for combustion independent of the hotblast main.

If in allof thecompartmentsexceptthatnext the cold-blast entrance a blast of steam or vapor be introduced in the connections F, together with the cold air introduced by the cold-blast connection H,thenin allof the compartments there will be a mixed blast, excepting the first, in which it will be of pure atmospheric air, and this will, by the connection N, be fuinished for combustion,.while a mixed hot blast will be supplied to the furnace. The pipe N is also connected to the cold-air main 0 by the pipe Q having valve P, by which means cold air may be supplied for combustion.

The dust may be removed from the combustion-chamber through the openings 1, which may also be used for tiring the gas. The dust in the regenerator is removed through the openings A The several compartments of the combustion-chamber are also provided with the connections I to the distributingmain 0, connected to the dividingpipes P, which enter the main 0 midway between the connections I, so as to equally distribute the combustible gas burned in the oven.

The main 0 may be formed like main G, outside of the oven, as in Figs. 1, 2, and 5, when the connections I will be horizontal; or the main 0 may be formed in the bottom of the combustion-chan'iber by arching it over, as in Figs. 3, 4, 8, and 14, and making the vertical connections I to the several compartments.

The outside connections will be by the dividing-pipe P entering the oven and main 0, thus formed midway between the connections I. The pipes P are connected to the opposite oven by the pipe Q, having valve 0, either directly or by means of similar dividing pipes and distributing main, as illustrated in Figs. 1:: and 16. The pipeQ is connected to the hot blast main B, Figs. 5 and 6, by means of the vertical pipe 1t, valve S, and branches T. The opposite oven is connected similarly to the hot-blastmain B by the connection F.

In the case of a plant of four ovens connected directly with opposite ones, thus forming two couples, as in Fi s. 15 and 16, in each of which one oven is used as a gas-heater, while the other is, used as a blast-oven, the pipeQconnectingeachcoupleisconnected with the corresponding pipe Q of the other couple by the pipe P, in free communication therewith, having valves Q, by means of which hot gas may be supplied from one oven used as a gas-heater to the other used as a gas-heater by opening the valves to pass the proper quantity of gas. and then leaving them open. The pipe Q is also connected to the source of cold-gas supply by the valve \V and main W, by means of which cold gas may be supplied to the ovens or gas-heaters for combustion.

The main may he used as a hot-gas main by placing a valve,\ ,in it between the ovens and the sonice ot' cold-gas supply, and may be common to the opposite ovens or gas-heaters, as in Fig. 16, and conn cted to each by connections having valves\\. This construction will admit of three ovens in a plant ot t'our ovens being used, or will give the advantages of having gasheaters in a plant of three combined ovens and gas-heaters. In case of the three regenerative hot-blast ovens in the apparatus now generally used, they may he altered to my improved system, as in Fi 17, by adding the necessary llOt-tlll connections for supplying the air necessary for (.Ollll)LtSL-()ll it it is desired to burn-the gas by means of a blast of hot air, or the ordinary air-connections may be used, as in Fig. 18, by placing a valve, \W, in the cold-gas-supply main \V, thus cutting off communication with the furnace or other source of cold gas supply and, forming a hot-gas main of the portion thus cut otf. The present gassnpply connection thus serves for the passage of the heated gas into and out of the oven, and then add a cold-gas mainflv and connections L and valve 11 at the cool ends in order to supply the gas to be heated in the apparatus, as in Fig. 18.

The above construction of the main W will allow ot' the apparatus being extended, as in case of four ovens and gas-heaters, with a minimum cost, by additional ovens to the common main.

The regenerator B is composed of the walls E and I), t'orn'iin'g the vertical tlues T. The walls I) extend from the horizontal flues G as high as the wall D, so as to allow sufficient space for the horizontal tlue S. The fines T are arrangid in one set, as in Figs. 5 and 6,

so that the products of combustion and gas or blast to be heated passthrough theregenerator in but one direction-that is, the former pass down while the latter pass upthus decreasing the friction. The roof-supporting walls E extend from thelbottom to the roof, except in the double compartments, in which they commence at the top of the arches supporting them.

The flues G are either single or double. In the latter case they are formed by the arches carrying the walls D and middle walls, E, of the double compartments. In either case they have the connections F placed in the middle of the compartments for the passage of the blast or gas to be heated, as well as the products of combustion. The connections F connect with thedistributing-mainG,havingcoldblast connection and valve H, and chimneyconnections M, and communicating with the cold-gas-supply main 7 by the dividing-pipes L, having valve R. The pipes L are so placed as to be midway between the connections F, which open into the middleot'thecompartments, so as to equally distribute the gas to be heated. The distributing-main G and connections F also serve. to equally distribute the blast to be heated. It" the tluesare arranged as in Fig. 13 then the distributing-main G may be formed in the lower part of the last set of flues by arching it over and making themain G thus formed continuous, asin the combustion-chamber, Fig. 8, by removing parts of the walls E and making vertical openings corresponding: to the connections F and opening into the middle of the compartments. The connection of the coldgas main will then he by the dividing pipes L, having valve R and entering the oven and main G thus formed midway between the openings F, which may be made into each compartment separately or may open into two jointly. The chimney and cold-blast communications may then be made directly to the oven and opening into the main G thus formed, as shown in Fig. 14. The vapor-pipe J, having valve 10, has branches L" extending into all of the connections F, excepting the one next the cold blast connection, Figs. 1, 2, and 5, and into which they discharge the steam or vapor. In case of forming main G in oven, as in Figs. 13 and 14, then the branches L open into the compartments above the main G if it is desired to heat a mixed blast.

The roof is formed of a number of rectangular blocks N and wedge-shaped blocks R of fire-brick or other refractory material, and whose length equals the distance between the centers of the roof-supporting walls E, upon which they rest. The wedge-shaped blocks are placed in those parts which are removed when access is desired, as shown in Figs. 5 and 6.

The root" blocks are covered with strips of sheet-iron E, whose width equals the length of the blocks, and having upturned flange -like edges 0 which are bolted together and held in place by the girders 1P, placed transversely upon the flanges and fastened to the outside casing, as shown in Figs. 7,8, and 9. The strips E extend only over each portion, either that over the wedge-shaped blocks, and which is removed when access is desired, as in clean- IIO ing, or over that formed by the rectangular blocks. The strips E covering the wedgeshaped blocks may slightly overlap the strips E" covering the rectangular blocks, and to which they are bolted, and may, if necessary, be held down by girders; or the strips E covering the wedge-shaped blocks may meet the strips E over the rectangular blocks with upturned flange-edges 0 as in Figs. 5 and 6, and bolted together. In case access is desired for cleaningthe girders, if used, the sheetiron strips E and wedge-shaped blocks under them only need be removed.

The several walls of the oven and gas heater are constructed of ordinary fire-brick or similar rectangular-shaped blocks of fire-brick or other refractory materials, whose dimensions vary with the temperature of the blast desired and the temperature to which they are exposed, so that in case of the hotter blast they may be made larger as the depth to which the effective heat is absorbed and subsequently given out increases with the temperature. The bricksor blocks are laid diagonally in reverse directions in the adjacent walls or courses in the same horizontal planes and in the adjacent courses in the same vertical planes, as shown in Figs. 10, 11, and 12, and they are laid on edge or flat, as above described. The walls may also be made by having the bricks or blocks placed on end and overlapping diagonally to different distances.

The bond is formed by having a horizontal bonding-brick, 13-, extending from one wall to the other, and which is itself held in place and bonded by the vertical bonding-bricks D placed at each side and alternate ends of the ho izontal bonding-bricks B The bondingbricks D extend from the middle of one horizontal bonding-brick, B across the next and to the middle of the third, and, in addition, the boiuling-bricks D break joints, as in Fig. 10. The bonding-bricks D may also be placed horizontally, as shown in Fig. 11. The walls may also be bonded horizontally by a bond-brick, E extending from the middle of one wall to the middle of the bond-brick B as in Fig. 10.

The walls maybe made bylaying the bricks flat and diagonally and in reverse directions,

as shown in Fig. 12, and bonded by a single bond-brick, F and by a part of a brick, l and a whole brick, G extending into the side wall, as shown. The next bond formed in this manner-by a whole brick, G and part I is so arranged that the whole brick Gr shall extend into the other wall, as shown in Fig. 12. This construction of the walls E and D is continued until they reach the top of the fines T, when the walls E are constructed by laying the bricks diagonally and in reverse courses, as the wallsD were constructed, as shown in Fig. 11, until they reach their proper height.

By having the bricks laid diagonally and in reverse courses and bonded in manner shown, the effects of expansion and contraction are efiectually provided against, which is a matter of the greatest importance in regenerative hotbla'st ovens. In some cases this'is provided for by saving a space between the brick-work of the oven and the casing; in others by having walls with loose sliding bricks both between the walls and the casing. In all these cases the expansion sought to be provided for is due to the summation of the expansions of all the abutting bricks in the several walls as ordinarily constructed, and which resultantis transferred to thecasing to there be met; whereas in my arrangement each brick is free to expand harmlessly into-the flues and not to add its linear expansion to that of the others in the same course, as when they abut as in ordinary wall, and so transfer the whole expansion to the outside casing. The lateral expansion of the bricks is harmless and only has a tendency to turn the bricks to a greater angle with the wall. Those forming the bond, as B expand by pressing diagonally the ones against which they abut, or if the walls are laid as shown in lower part of Fig. 11, in which two bordingbricks, B are used, then the expansion is perfeetl y free. By constructing the walls thus the expansion is provided for as it is produced in each separate brick, while in the old or ordinary method of constructing the walls, in which the bricks abut, the resultant of all the expansions is transferred to the outside casing, which must be very heavy in order to counteract it. In addition to providing for expansion and contraction, the strength of the walls is very greatly increased, so that they can be made much thinner without fear of buckling, and at the same time the efficiency of the material is greatly increased, owing to the fact that the bricks composing the walls extend through the walls from flue to flue and are not shut off by a coating of mortar, which in practice is found to be a much poorer conductor of heat than the fire-brick. Even a thin coating like a wash prevents to a marked degree the passage of heat.

A wall constructed as shown has a greater power of conducting heat into or out of the wall than when the wall is made of several courses of brick each parallel to the direction of the wall, for in the case of a fourteen-inch wall those bricks that are surrounded by mortar are practically of but little, if any, benefit either in storing up or giving out heat. This defectis avoided by theconstruction as shown in Figs. 10, 11, and 12.

The various valves used in the apparatus may be of any suitable construction.

Methods of working: When using the oombined blast-oven and gasheater as a gas-heater, supposingallvalvesclosed,proeeed as followsin order to heat it: Open the chimney-valve M"; then admit air for combustion by opening the valve L and the regulating-valves M, which remain open after having been properly set; then open valve W to admit cold gas, when the main W is used as a cold-gas main, or hot gas when the main W is used as a hot gas main by closing the valve TV when the apparatus is arranged in couples, as before described; then IIC the hot combustible gas maybe admitted to one gas-heater from the other through the pipe P by opening the valves Q to the proper extent and leaving them open. Now, after the apparatus has become sufficiently heated, in order to heat the combustible gas proceed as follows: Close the air-supply valve L; then close the gas'supply valve it cold combustible gas is admitted, but if the main is used as a hot-gas main then valve W remains open or is opened more fully to allow the heated gas to passinto the mainWused as a hot-gas main; then close the chimney-valve M and open the cold-gas'supply valve It to admit cold gas from themain W then, if the hot gas passes directly to the opposite blast-oven, open the bot-gas valve G. The valves Q remain open so as to pass the hot gas from one even used as a gas-heater to the other used for the same purpose, thus furnishing a supply of highlyheated combustible gas. Then, after the gasheater has parted with its eii'ective heat it is reversed and again heated when used in couples as follows: Close the hot-gas valve and the cold-gas valve R and open the chimney-valve M and air-supply valve L. The hot gas to be burned is admitted through the valves Q,which remain open. If cold gas is burned then it is admitted from the main W by the valve 7'. I11 case the main is used as allot-gas main, then the valve \V remains open or is only partially closed.

When the combined oven and gas-heater is used as a blast-oven, in order to heat the oven, all valves being closed, proceed as follows: Open the chimnevvalve M; then open the hotgas valve G, if the gas is supplied that way, or if the gas is supplied by the main \V, used either as a hot or cold gas-main, then open the valve 1V instead of C then open the air-valve L and the regulating-valves M, which, when properly set, remain open, by which means the oven becomes highly heated by burning therein a highly-heated or cold gas with a blast of highly-heated air. After the apparatus has become sufficiently heated it is reversed and a highly-heated blast produced, as follows: Close the gas-supply valve 0 or \V, as the case may be; then close the chimney-valve M and open the cold-air-hlast valve H, and the steam or vapor valve K if a mixed blast is heated; then open the hot-blast valve S, by which means a blast of highly-heated air or a mixed blast of air and vapor is supplied. The valve L always remains open when the apparatus is used as a blast-oven. Then, after it has parted with its effective heat it is reversed and again heated by closing the hot blast valve S, then closing the cold-air valve H, and the valve K if used, and opening the chimney-valve M. It may be necessary, owing to the pressure on the valve M, to open a supplementary valve or a dust-door, opening outwardly to relieve the pressure by allowing the air to escape, or a slide-valve may be substituted for the seat-valve. Then open the gassupply valve (1 or W, as the case may be.

When one or more above-described combined ovens and gas-heaters are used in c0m bination and directly connected with one or more blast-ovens, thus forming couples, each consisting of a gas-heater and blast-oven, in the reversal ofthe couples the blast-ovens must be reversed first in the following manner: Supposing that in one couple, A and 13*, Figs. 15 and 16, the gas-heater A is, as above described, heating the combustible gas which is burned in its blast-oven B as above described, and that in the other couple, 0 and D Figs. 15 and 16, the gas-heater C is being heated while its blast-oven I) is heating the blast, as above described, then, after the blast-oven D and gas-heater A or either of them, has parted with its effective heat, or the other oven B and gas-heater C or either of them, has be.- come sufficiently heated, the reversal is as follows: Always comniencingwith the blast-oven B which is being heated, in which close hotgas valve and the chimney-valve M and open the cold-blast valve H and the hot-blast valve S, so that there may always be a hotblast going to thefurnace and a pressure maintained in the pipes N, pipes A, and pipes K and connections, then reverse the gas-heater (J in the other couple, which has been heated, by closing the air-valve L and the chimneyvalve M and open the cold-gas valve B, so that there may always be a suflicient supply of heated gas; then reverse the other blastoven D which has been heating the blast, by closing the hot-blast valve S and the cold-blast valve H, and opening the chimney-valve M and hot-gassupply valve G and the air-supply valve L, which then remains open while the oven is used as a blast-oven then reverse the other gas-heater A by closing the coldgas valve R and opening the chimney-valve M and the air-valve L, gas for combustion being admitted by valve W or Q, as the case may be, as above described. Then, after a suitable interval, the apparatus is ItWGI'St'd in the same way.

In thecase of altering, asin Fig. 18, a plantof the three regenerative hot-blast ovens generally used to my improved system without adding a fourth oven or gas-heater, and working them or three of the above-described combined blastoveus and gas-heaters, asin Fig. 16,in both cases as blast-ovens and gas-heaters successively, and in both of which cases theheated gas is conveyed from the oven in which it is heated to the oven in which it is burned by means of a common hot-gas main or aportion of the usual cold-gas main, W, cut off for the purpose of being used as a hot-gas main by means of the valve W, as before described, so that at any time cold gas may be used in the usual way, the heated gas is burned by a blast of heated air, as in Fig. .17, or by ordinary methods in other ovens, as in Fig. 18.

This method of working with three ovensis somewhat different from the above-described methods, and is based on the fact that the oven which has heated the blast still contains a large amount of heat which is not of a sufficiently-high temperatureorintensity toheatthe blast to the desired degree,butwhich can heat the combustible gas. sufficiently high, owing to the gas having a much less volume and velocity and greater heat-absorbing power than the blast, and is as follows: Supposing all valves closed; then, in the first oven, 11, open the cold-blast valve H; then the hot-blast valve S; then in the second oven, 1 open the coldgas-supply valve R at chimney side of the oven; then open the gas-valve \N at the combustion-chamber; then in the third oven, K open the chimney-valve M" and the gas-valve W at the combustion-chamber to admit the gas to be burned; then open the air-valve L, Fig. 17, or the ordinary air-valve L, Fig. 18, to supply air for combustion, by which means this oven K becomes heated; then after a suitable interval the apparatus is reversed as follows: Always commencing with the oven K, which is being heated, in which close the gassupply valve W at the combustionchainber, and the air-valves L supplying air for combustion, then close the chimney-valve M and open the cold-air-blast valve H, and then the hot-blast valve S; then in the other oven, H through which the blast is passing, close the hot-blast valve S and the cold-blast valve H, and open the chimney-valve M, to allow the air in the oven H to pass out through the chimney; then open the gas-valve W at the combustion-chamber, and after a suitable interval, so as to allow the air in the oven to be drawn into the chimney and the oven to be filled with gas, in order to avoid the danger of an explosion from a mixture of air and gas in the oven and hotgas main, then close the chimney-valve M and open the cold-gas valve R at the chimney side of the oven, thus having gas pass through the oven and into the hot-gas main; thenintheother oven,I through which gas is passing, close the cold-gas valve R at chimney side of the oven and open the chimney-valve M and the valves L, to supply the air necessary for combustion, by which means this oven 1 becomes heated. Then, after the oven K which isheating the blast, has part ed with its effective heat, or the one, 1 which is being heated, has become sufficiently heated, the apparatus is reversed in the same manner, always commencing with the oven 1 which is being heated, and then the oven K, which is heating the blast, and lastly reverse the oven H which is heating the gas. Now, after the first reversal,the apparatus is heated with cold gas burned with hot or cold air, dependingon the system used while a heated blast'is being furnished. After the second reversal the apparatus is heated by the hot gas burned with hot or cold air, depending on the system used, in addition to furnishing a highly-heated blast to the furnace, and so on. After each reversal hotter gasis used with hotter air, and thus after each reversal a hotter temgerature is developed.

In changing the oven which is heating the blast so as toheatthe gas, it may be necessaryto open a supplementary valve or dust-door openingoutward to take the prcssurcotl'oi'thechimney-valve if it is a scat-valve, or a slide-valve may be substituted. It may be found in practice that the opening of the chimney-valve in the reversal of the oven which has been heatingthe blast is unnecessary. Then the reversal can be made by closing the hot-blast valve and cold-blast valve, opening the gas-valve at the combustion -chamber, and then the coldgas valve at the chimney side of the oven.

The following method of working may be used instead of those before described: Supposing one oven, H is heating the blast, the other, 1*", is being heated, while the third, K is heating the gas; then, in order to reverse the apparatus, always commence with the oven 1 which is being heated, in order to always have blast going to the furnace, and reverse it as follows: Close the gas-supply valve W connecting with the hot-gas main W, and close the valves supplying the air for combustion and the chimney-valve M; then open the cold-blast valve H and the hot-blast valve S, thus causing a current of air to flow through it and furnishing a highly-heated blast; then in the other oven, H through which airis passing, close the hot-blast valve S, and then the cold-blast valve H,and open the chimney-val ve M, to allow the air in the oven to pass out through the chimney; then open the gas-valve W at the combustion-chamber, and after a suitable interval, so as to allow the air in the oven to be drawn into the chimney and the oven to be filled with gas, in order to avoid the danger of an explosion from the mixture of air and gas in the oven and hot-gas main, then close the chimney-valve M and open the coldgas valve R at the chimney side of the oven, thus having gas pass through the oven and become highly heated and passed into the hot-gas main; then in the other oven, K on gas close the cold-gas supply valve It at the chimney side of the oven and open the chimney-valve M, and then open the valves supplying the air necessary for combustion, by which means this oven K becomes highly heated. Then, after the oven 1 which is heating the blast, has parted with its effective heat, or the one,'K which is being heated, has become sufficiently heated, theapparatus is reversed in the same manner, always commencing with the oven K which is being heated, then the one, 1 which is heatingthe blast, and lastly reversethe one, H heating the combustible gas, thus producinga more intensely heated blast after each reversal.

In changing the oven which is on blast to heating gas the same precautions should be taken as in the other methods.

In the case of arranging four or more com bined blast-ovens and gas-heaters or four or more ordinary regenerative hot-blast ovens changed into combined blast-ovens and gas-

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