US1173999A - Process of heat regeneration. - Google Patents

Description

H. L. DOHERTY.

PROCESS OF HEAT REGENERATION.

APPLICATION FILED DEC.3I. I909'. RENEWED MAR. 21, 1913.

1,173,999. Patented Feb.29,1916.

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PROCESS OF HEAT REGENERATION. APPLICATION HLED DEC-3|, I909- RENEWED MAR. 21. 1913- ZSHEETS-SHEET 2.

o 9 I Hen r8 L. Do hert y, gvwewtoz J QTMJZZJ alto mun TTE HENRY L. DOHERTY, OF NEW YORK, N. Y.

rnoo nss or HEAT Specification of Letters Patent.

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REGENERATION.

Patented Feb. 29, 1916.

Application filed December 31, 1909, Serial No. 535,841. Renewed March 21, 1913. Serial No. 756,020.

T 0 all whom it may concern:

Be it known that I, HENRY L. DoHER'rY, a citizen of the United States, and a resident of New York city, in the county of New York and State of New York, have invented certain new. and useful Improvementsin Processes of Heat Regeneration, of which the following is .aspecification.

This invention relates to a process of heat regeneration, and, in particular, to a process for securing heat regeneration in kilns for the burning of lime, brick kilns, billet reheating furnaces, etc., with special reference to its use in connection with the inventions which are thesubject of my Letters Patent No. 938,987, dated Nov. 2nd, 1909, and of my co-pending application Ser. No. 525,390, filed Oct. 29th, 1909.

In the accompanying drawings, I have illustrated the application of this present invention to the apparatus of the above mentioned Letters Patent and application for Letters Patent, and have, hereinafter, described such application of my invention in detail. It is to be understood, however, that I do not limit this present invention to use in connection with the above mentioned inventions.

This invention is designed specially to be used in connection with the burning or heating of materials such as ordinary building brick, which possess a high thermal capacity but require in their burning a long flame of moderate temperature, and in particular in connection withthe heating of materials ac cording to the manner described in said patent. In the burning of such materials in this manner or in the ordinary manner we are confronted with two interfering requirements. In bringing the material up to the temperature of burning, even though the latter is moderate-say 1600 to 1700 F.a large quantity of sensible heat is stored in the material. In order to recuperate this heat, it must be taken 'u by the air, or air and gas, supplied to com ustion zone of the kiln. Now, in such a case as we are considering, the quantity of. air required for the combustion taking place, is much less than that which would be necessary to recuperate the sensible heat, which the bricks carry out of the combustion zone. If now we increase the quantity of air admitted to the base of the kiln to that required to take up the heat of the bricks and return it to the combustion region, we must, in the ordinary way of burning, have anexcess of air in the combustion zone. This causes the combustion to take place with a sharp, intense flame, with a moderate excess of air. The result is that the burning is very irregular. The bricks in immediate contact with the flame are over-burned, while those not in contact with the flame are under-burned. The practical effect of this is, of course, a very ununiform product, with a large proportion of rejects.

By my invention I can conduct the burning operatlon with just the proportion of air necessary to give the quality of flame that I desire and'yet am enabled to pass through the cooling chamber and preheating chamber of the kiln the requisite quantity of air to insure the substantial recuperation of the sensible heat of the bricks. I accomplish this result in a kiln of the described type by introducing into my kiln or burning chamber a by-pass consisting of a plurality of off-take ports below the gas-admission ports, corresponding inlet ports in the kiln walls well above the combustion zone, where the excess of air will have no effect on my flame, and a suitable flue or flues connecting the OE-take and inlet ports. These ports and flues are made of such size that the retardation exerted upon the air current passing through them by friction Will be practically negligible. When the apparatus is properly designed the resistance to the passage of the air current is less in the by-pass flues than in the kiln shaft itself. The result, of course, is that a portion of the air current seeks this path of least resistance and passes around the combustion zone of the kiln through the by-pass flues. The pro portion of the air, so passing, is regulated by the adjustment of the proper dampers located in the-by-pass fiues. When the conditions are such that the draft through the by-pass fines is not suflicient to overcome the draft of the stack itself I have recourse to arrangement of a positive circulating device- (a fan or some equivalent device) interposed in the by-pass conduit to overcome the stack draft and draw ofi" the desired pro-.

portion of air below the combustion zone the same being returned to the stack above the combustion zone.

In the drawings, Figure 1 shows a vertical section through a kiln for burning bricks of the general type shown in my application for Letters Patent, -Ser. No.

525,390, modified for applying my present invention on the line C D of Fig. 2. Fig. 2 is a partial horizontal section through the battery on the line A B of Fig. 1. Fig. 3 is a partial vertical section through one of "the individual kilns on the line E F of and inlet ports. Fig. 6 is a horizontal sec-Y tion through the line I J of Fig. 5; Fig. 7. is a horizontal section through the line K L of Fig. 5; and Fig. 8 is a horizontal section through the line M N of Fig. 5. Fig. 6 will also answer'for a horizontal section on the line 0 P of Fig. 5 as they would appear the same, with the exception that the producergas conduit would not be in section.

1, 1", etc., indicate the individual kilns of a battery. The method of operation is the same in all kilns, so I will restrict the following description to kilns 1' and 1,

provided with natural and positive draft, respectively, in the air diversion-Hues.

' 2 indicates the side-walls of kiln 1"; 3,

the end walls.

4 is the shaft of the kiln; 5, 5, etc., are ports for the admission of air, having dampers 6.

7 refers to the cooler or lower part of shaft 4.

8, 8, etc., are air off-take ports; 9, 9, etc.,' are gas inlet ports; 10, 10, etc., are vertical fiues built in the kiln walls, whose upper ends communicate with the shaft of the kiln through the passages 11 and Whose lower ends communicate with the ports 8.

12 are dampers regulating the draft through the flues 10 which are accessible through the hand-holes 13,-having covers 14;. '15 indicates the combustion zone of the kiln; 16 are auxiliary air ports communieating with fiues '10, access to which is had through hand-holes 17 through which the laterally-movable, dampers 18 maybe adjusted. r

19, 19,etc., are ports for drawing off aportion of the combustion gases under the action of an injector or fan. These combustion gases are then supplied to the fuel bed of the gas producer 20. In contact with the hot fuel in 20, a portion of the CO parts with one-half of its oxygen to the carbon to generate carbon monoxidan equal volume of the same gas bein at the same time formed by the reduced C This reaction,

which is a highly endothermic one, absorbsv that portion of the sensible heat which the of the fuel bed. At the same time, for agiven amount of combustible gas required, this circulation of a portion of the hot combustion gases from the combustion zone, permits of a reduction to the minimum of the atmospheric air required in the gas producer, and thus correspondingly reduces the heat drain on the system and permits ofthe heating of the bulk of the air required by the system. by heat recovered from the burned material. Only the relatively small quantity of air required to supplement the heat carried by the combustion gases in order to maintain the fuel bed of the producerat a reactive temperature is suppliedto the same. Since, as stated in the application referred to, I pass the draft current of combustion gases through the producer un-- der conditions such that only a portion of their CO is dissociated, the combustible gas producedis diluted with a comparatively considerable proportion of noncombustible gases. This modified producer gas passes to the kiln through the conduits shown and is introduced into the lower portion of the combustion zone 15 through the ports 9. In

15 the gas is burned by that portion of the air which is permitted to ascend into 15 from the cooler 7, with the production ofa dilated frame. of moderate temperature,

'which enables me to secure an active circulation of the flame around and in contact with circul'ationof application 525,390 andthe air circulation herein disclosed I have devised an improved process of heat recuperation which permits of the securing of a greater heat economy, in the operation of apparatus of the type referred to, than is possible by the methods of operation at present known to the art.

As the combustion gas circul'atio'n,in the embodiment of my invention as applied to the operation of a kiln as an improvement upon the process of my Letters Patent No; 938,987, above referred to, is substantially the sameas described above, no further detailed description of the same is necessary.

In the t pe of kiln 1", shown in Figs. 5 to 8, provi 21 refers to that portion of the kiln shaft lwhich I designate as the pre-heating cham- 22 indicates a draft-producing means, discharging into a conduit 23.

ed with forced circulation of air,

When the kiln is in normal operating conditionthe shaft 4: is filled with bricks, lime- Y connecting flues 10, in the kiln walls, and

returns to the shaft through the ports 11. The proportion of air passing through the flues 10 is regulated by adjusting the dam- I pers 12 through the hand-holes, 13, which are ordinarily closed by covers 14. Theproportion of air' by-passed around the combustion zone, 15, through the by-pass flues seldom exceeds one-half of the total volume of air entering the bottom of the kiln,

, although I do not restrict myself-to the bypassing of any specific proportion since the proportion so by-passed will, of course, depend upon the requirements of each particular case. Usually, I permit to pass up through the stack to the combustion zone just about the theoretical quantity of air for the complete combustion of the gas introduced through 9. Under some conditions, however, I'may restrict this" portion of the air to less than this quantity, introducing the balance of the air required, to make up this quantity, through auxiliaryports 16, connected with flues 10. Suitable hand-holes 17, provide access to 16, and permit of the adjustment of the laterallymovable dampers 18, to regulate the volume of air passing through 16 to the proper quantity. By this device, I produce a long, slow burning flame of moderate temperature, in which the combustion is not completed, until it has reached a level in the shaft above the auxiliary ports 16. s The quantity of air by-passed is fixed by (a) the quantity of air necessary to cool the burned bricks (or. other material) and (b) the quantity which is required in the combustion zone proper. It is the difference between the quantities (a) and (b) which I withdraw through 8 and bypass around the region 15. The ports, 11, are located, preferably, at the. height in the kiln at which the combustion gases from the region 15 will, in normal running, have substantially the same temperature. as the by-Oassed air. "W hen, however, as in the particular application of my invention, which we are considering, a portion of the combustion gases are withdrawn from the kiln for use in regulating the thermic conditions in the producer, it is desirable to locate the ports 11 above the combustion gas off-takes 19, thus avoiding the dilution of the combustion gases going to the producer 20.

The by-passed air mingles with the currentof combustion gases in what I designate as the preheating region, 21, of my kiln and yields up its heat to the descending unburned material in the region 21. The net result of my process is, therefore, to take up from the finished material that portion of the sensible heat which it carries which the normal quantity of combustion a1r cannot take up and to transfer this heat to the descending raw material in the preheating region 21. Thus, no matter What the heat capacity of the material passing through the kiln may be, I am able to eifect substantially perfect recuperation of the heat which it carries and at the same time conduct my combustion with just the proper quantity of air to secure the conditions which 1 desire in the combustion region 15. When, as may sometimes happen in the burning of limestone, where the material is in fragments of large size and comparatively large passageways are automatically formed in the charge for the passage of the combustion gases, there may not be a sufficient difference in the draft through the by-pass flues and the stack itself to divert the desired proportion of the air through the by-pass flues, I interpose a positive draft-producing device, 22, in the it up outside the kiln. The method of operation is, however, identical with that of the apparatus, just described.

Having described my invention, what I claim is 1. In connection with theoperation of a heating or calcining chamber, the process of heat regeneration which consists'in passing in contact with the heated material from the combustion zone of said chamber, a current of air, the volume of the said air being suflicient to take up,substantially, all of the sensible heat of the said heated material, whereby the said heated'material is cooled and the said air-current heated, dividing the so-heated air current into two streams, at a place in said' chamber adjacent to the combustion zone thereof, passing one of said air streams into the said combustion zone, the

volume of said air-stream being less than I that required to support the combustion taking place in the said combustion zone, conducting the other of said air-streams around the said combustion zone. subdividing the other of said air-streams into a major and a minor portion and uniting said major portion with the products of combus tion from the said combustion zone, introducing the said minor portion into an .intermediate region of said combustion zone to complete combustion therein, and passing the commingled stream of heated air and products of combustion in contact with the relatively cold unheated material approaching the combustion zone, whereby the saidunheated material is heated and the said stream of heated air and products of combustion cooled.

2. In the operation of a heating or calcining chamber, the process of heat regeneration, which consists in transferring part of the, heat of the heated material leaving the combustion zone of said chamber,'to the relatively-cool material approaching the combustion zone of said chamber, by means of a current of-air as a vehicle, and transferring another part of the sensible heat of the heated material to the combustion zone of said chamber by means of the air supplied tosaid combustion zone as a vehicle, and re passing a portion ot the combustion gases generated in said combustion zone through a comparatively deep bed of incandescent tuel and back to said zone.

3. The processof heat regeneration which comprises passing air in contact with the heated material in. a heating chamber,

whereby the said air is heated by the sensible heat of said material, the Volume of said air being in excess of that required for the combustion in said chamber, dividing said air current into two streams, passing one of said streams into the combustion zone of said chamber, by-passing' the other of cooled, dividing the so-heated air current into two main streams, passing thefirst of said streams into the said combustion zone, at that region of the same Wherethe required fuel is introduced thereinto subdividing the second'of said'main streams into a major and a minor portion, introducing the said minor portion of said second stream into a mid region of said combustion zone, conducting the said major portion of said second air stream around the said combustion zone, uniting it with the products of combustion from the said combustion zone, and passing the commingled streams of body of material passing through a zone of combustion, passing air in'heat-absorbing relationship to the hot material passing be-.

yond the zone of combustion, transmitting a portionzof the air so heated to said zone to maintain combustion therein, diverting the residue of air so heated around the zone of combustion, passing a portion of said diverted air into contact with the material advancing toward said zone, and repassing through said zone of combustion a portion 7 of the combustion gases leaving the same.

6. The process of regenerating heat which comprises providing a moving or traveling body of material passing through a zone of combustion, passing air in heat-absorbing relationship to the hot material passing beyond the zone of combustion, transmitting a portion of the air so heated to said zone to maintain combustion of combustible gas therein, diverting the residue of the air so heated around the zone of combustion, passing an admixture of said diverted air with a first portion of the products of combustion into coiitact with the material advancing toward said zone, diverting a second portion of said products of combustion, contacting said diverted portion of products of combustion with incandescent carbon to generate combustible gas, and introducing said combustible gas into said combustion zone.

7. The process of regenerating heat which comprises providing a moving 'or traveling body of material passing through a zone of combustion, passing air in heat-absorbing relationship to the hot material passing be yond thezone of combustion, transmitting a portion of the air so heated to said zone to maintain combustion therein, diverting the residue of the air so heated around the zone of combustion, passing an admixture of said diverted air with a first portion of the hot products of combustion leaving said combustion zone into contact with the material, and repassing a second portion of said products of combustion through said combustion zone to increasethe velocity of flow of gases therethrough.

8. The process of regenerating heat which comprises providing a moving or traveling body of material passing through a zone of combustion, passing air in heat-absorbing relationship to the hot material passing beyond the zone of combustion, transmitting a portion of the air so heated to said zone to maintain combustion therein, diverting the residue of the air so heated around the masses zone of combustion, passing an admixture of a portionofsaid diverted air with a first portion of the products of combustion leaving said zone of combustion into contact with the material advancing toward said zone,-the admixture being at a point where the temperature of said products is substantially the same as that of said air, introducing another portion of said diverted air into an intermediate region of said combustion zone, diverting a second portion of said products of combustion, contacting said second portion with carbon to change a portion of said products of combustion to combustible gas, and introducing the said products of combustion, after they have been contacted with carbon, into said zone of combustion.

9. The process of heating and heat regeneration which comprises advancing material to be heated to, through and beyond a zone of combustion, cooling the hot material and heating air beyond said zone by a sufiicient supply of ontacting air, transmitting a limited amount of the air thus heated into said zone to aid and maintain combustion therein, by-passing another portion of the heated zone heating the material by combustion in the presence of a limited amount of heated air, increasing the velocity of flow of the products of said combustion through said zone by maintaining a circulation of an excess of combustion gases from the discharge end to the fuel admissionend of said zone, contacting the hot material in its passage beyond said zone with a relatively large amount of air, introducing a regulated amount of the air thus heated into said combustion zone to support said combustion, and by-passing another portion of said heated air around said combustion zone to form said admixture.

11. The process of heat regeneration which comprises advancing material to be heated to, through and beyond a zone of combustion, and in its progress toward said zone heating the material by contacting with an admixture of'heated air and products of combustion, in its progress through said zone heating the material by a long comparativelycool flame of gas burning in the presence of a limited amount of heated air,

the velocity of flow of the gases from said flame being increased by the addition thereto of combustion gases previously discharged from said zone of combustion, contacting the hot material in its passage beyond said zone with a relatively large amount of air to heat said air, introducing a regulated portion of the air thus heated into said combustion zone to support said combustion, and by-passing another portion of said heated air around said combustion zone to form said admixture.

Signed at New York city inthe county of New York and State of New York this 30th day of December A. D. 1909,

HENRY L. DGHERTL Witnesses:

7. J. QUENTIN, THos. ll. CARTER,

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