US1735605A - Heating furnace - Google Patents

Description

Nov. 12, 1929.-

,W. H. FITCH HEATING FURNACE Filed Dec. 18, 1926 4 Sheets-Sheet l $1 I. r\. x r. c...

T I Z M A. PL g ATTORNEYS Nov. 12, 1929.

Filed Dec. 18, 1926 v w. H. FITCH HEATING FURNACE I JIM.

4 Sheets-Sheet 2 l I l l I l l INVENTOR ATTORNEYS Nov-12,1929: w. H, FITCH 1,735,605

HEATING FURNACE Filed Dec'. 18. 1926 4 Sheets-Sheet a mv r ngz I Z I ATToRuEYs Nov. 12, 1929. w. H. FITCH I HEATING FURNACE 4 Sheets-Sheet 4 Filed Dec. 18, 1926 INVENTO ATTORNEY5 Patented Nov. 12, 1929 UNITED ST TES PATEN OFFICE HEATING- FURNACE Application filed December 18, 1926. Serial No. 155,592.

This invention relates to continuous heating furnace installations of the type in which the articles to be heated are transported through the furnace chamber on suitable 5 conveyances, such as cars, and is concerned particularly with. an installation which includes a furnace of this type and a recuperative device by which the heat in the waste gases from the furnace is recovered and used for preheating the air for combustion. The invention not only includes the complete in stallation presently to be descibed, but also a recuperative device of novel form, which is highly eflicient in action and so arranged'that the heat transfer elements may be periodically cleaned, inspected, and replaced with great facility.

An installation embodying this invention through which the articles to be fired are moved on cars. This chamber has a combustion zone mid-way of its length and at this point the fuel, together with air for combustion, is introduced upwardly along one side of the chamber by suitable means. posite side of the chamber and beyondthe cars are ducts or passages for the exhaust gases which are led downwardly from the combustion chamber so that the path of the flames is upwardly along one side of the chamber,-across the latter, and then down at the opposite side. Dis osed outside the chamber at one side thereo is the recuperative device which includes passages through which the air for combustion and the hot burned gases flow in heat exchange relationship, so that the heat carried by the gases is transferred to the air, thus preheating the'lat ter before it enters the combustion zone. y

In recuperative devices ofthis type it is desirable that the air and gases should be led through passages in such relation to' each other that an eflicient and uniform heating effect is brought about and it is particularly desirable that the flow of the gases and air should be controlled and limited to definite paths, so that the desired result can be attained. Also, the'means by which these passages are defined should be arranged'so that may include an elongated furnace chamber At the op-- v is subjected to successive heating operations,

and between these operations enters a chamher where it may expand and become mixed,

thus insuring uniformity. of the heating effect. By limiting the heat transfer action substantially to the points where the air is confined inthe tubes, the direction of flow of them, and the use of the chambers between which the tubes are placed in banks affords a ready means for inspection and repair of the tubes. Preferably the chambers are successi ve'ly wide and narrow, with the wide chambers of a width greater than the length of the tubes. Thus, when the furnace isshut down, workmen may enter the chambers, inspect the tubes, and any tubes which require replacement may be moved into the wide chambers and new ones readily inserted in position.

The invention includes various other important features in addition to those above mentioned, which will best be understood by reference to the accompanying drawings and the detailed description to follow. In these drawings Fig. 1 is a view in vertical longitudinal section of the recuperative device constructed in accordance with the present invention,

v Fig. 2 is a transverse longitudinal section I of the device illustrated in Fig. 1,

Fig. 3 is a transverse vertical section through the furnace chamber and recuperator J "associated with it, taken on the line 33 of of which is provided with a track 12. These chambers may be of-any standard construction, but ordlnarily are built as illustrated in Fig. 3, including a lining of suitable refractory brick 13, encased within a layer 14 of heat insulating material, such, for instance, as the commercial product known as silocel, the outerwalls 15 being formed of standard red brick. The furnaces include the usual side walls 16 and arch 17 which rest on a foundation 18, such as concrete. The walls are supported by the outside buck stays 19 with the .transverse rods 20. The construction thus described is in accordance with standard practice. Within the chambers the tracks 12 are suitably mounted on the foundation 18 a so andon these tracks run cars, such as that conventionally illustrated at 21 in Fig. 3.

y In each furnace chamber there is a'central combustion zone mid-way of its ends, and

V generally designated 22 (Fig. 6). At: this point a suitable manifold or duct 23 (Fig. 3) is built beneath the floor of the furnace chamber and provides an intake for air for combustion, the air flowing up through vertical passageways 24 dis osed along one wall of the chamber into t e latter. Near the upper ends ofthese passages fuel for combustion may be introduced. The fuel employed may be natural or artificial gas, or any other suitable fuel for the purpose. In the installation illustrated, the fuel in the form of gas is introduced into the combustion chamber through pipes 25 connected to 8 main 26 eXten-ding'along the combustionzone, these pipes leading through the wall of the chamber and having discharge nozzles 27, which introduce the gas into the streams of air issuing from the vertical ducts. The fuel is then consumed Within the furnacechamber and flows across it as indicated by the arrows in Fig. 3. At the opposite side of thefurnace chamber are vertical passages 28, leading.

down to a flue 29.which in the installation illustrated=is connected by a duct or flue 30 with therecuperative device 31. Into this device air for combustion is introduced by meansof a motor-driven blower 32, and the air passes by means of a duct 33 to the manifold 23. The hot gases of combustion passin out through the flues 29 and 30 enter the en of the'recuperative device opposite to that through in heat transfer relation ,yvith the air, then pass out through a flue-34nd may be led to a stack or, inasmuch as these gases still retain a considerable quantity of heat, the gases may be passed through a dryer 35 be- I fore flowing to the stack 36.

I In the installation shown in Fig. 6, there are two heating chambers placed si e-by-side,

each provided with its own heating means and itsindividual recu-perative device. The cars on'which the material is to be heated pass through the chambers in opposite directions, as indicated by the arrow, and the dividing wall between the chambers in an installationof this sort is preferably arranged for heat transfer so that heat given off by the articles carried by the cars-which have passed through the heating zone will be transferred through this wall to the articles which have just entered the adjacent heating'chamber. Asidefrom the direction of movement of the cars, the heating'eha'mbers and their associated devices are substantial duplicates.

The recuperative devic'e'usedwith this installation is shown more clearly in Figs. 1 to 5 inclusive, and'this device includes anelongated chamber with suitable side walls 37 and an arch 38, these walls being illustrated as of the same general construction as is used in connection with the heatin chamber. The chamber is likewise provided with the usual buck stays 39, At one end the'chamber includes an air inlet chamber 40, with which is connected the delivery end of the motordriven blower 32. The air entering this chamber flows upwardly and across it, as indicated by the arrows Fig. 1), and then enters tubes 41 which lea from this chamber to a smaller chamber 42. The air flows across the chamber 42, entering another grou of tubes, generally designated 43, and through these tubes into a chamber 44 similar tothe chamber40 size. Flowing across the chamber 44, the air enters another group'of tubes 45 leading to a small chamber 46, similar to the chamber 42, then flows across this chamber, entering the last group of tubes 47 which lead to an outlet chamber .48. This outlet chamber, as shown in Fi s. 2 and 3, has. an opening 49 in the floor t ereof with which communicates -'a flue 50 leading to the duct 33 connected to the manifold 23, the flue 50 and the ductand manifold all bein suitably heat insulated, as illustrated, an also leading through the foundation of the installation so as to prevent loss of heat from the air. I 9 1 The flue 29, as shown in Fig. 3, extends along the combustion chamber in the foun- OWS brings about the precipitation of ash or other solid residues carried along with these'gases.

into which the air is introduced, flow there- The flue 29 is connected-by the duct 30, which extends beneath the foundation of the furnace chamber, to the passage 51 which extends beneath the air outlet chamber 48 and leads to an upwardly extending passage 52 through which the gases flow in a direction transverse to the flow of air through the tubes 47. The tubes 47 extend across the passage 52 in the path of flow of the gases flowing through the passage 52 to the connecting. chamber 53 at the top of the recuperator. In this chamber the gases flow around the top of the inspection chamber 46 to a downwardly extent-ling passage 54 which leads the gases past the next bank of tubes 45. In this flow the gases are again directed transverse to the flow of air through the tubes and with this arrangement it will be seen that the gases at their highest tempera ture come into contact with the lowest tubes in the bank 47. Then the gases, after the reduction in' temperature, due to their flow through this bank, are led immediately to the bank of tubes '45, coming into contact with the uppermost tubes of this bank and flowing downwardly past the bank to the longitudinal passageway-'55. It will be further noted that the air, after its passage through the bank of tubes enters the chamber 46 where the air has a chance to flow so as to equalize temperatures in the different parts of the air screen. With this arrangement, all parts of each tube in a bank are subjected to heat carried by thel gases and by reason of the break in the air flow through the chamber 46, temperature con ditions in the air are equalized.

After their downward passage past the bank of tubes 45, the gases enter the passage 55 which leads beneath the replacement chamber 44 to an upwardly extending passagev 56 in which the gases are directed past the bank of tubes 43 into the chamber 57 which'leads aroundthe top of the inspection chamber 42 to the downwardly extending passage '58 leading past the bank of tubes 41. which directs the gases to the dryer 35, if this dryer is used, or otherwise to the stack 36. If desired, the stack draft may be increased by a fan, should the necessity arise.

The heat transfer tube construction'is illustrated more clearly in Figs. 4 and5. These tubes are made of material suitable for the purpose, but preferably the tubes which come into contact with the hottest gases are matle of silicon carbide, although the tubes in the bank 41, for example. may be-of cast iron or other suitable material.

-bank 47, for example, are mounted at one The tubes of the end in the wall 59 separating the passage 52 from the chamber 48, and these tubes are mounted at their other ends in the wall 60 separating the passage 52 from the chamber 46. The chamber 48 is provided'with a door generally designated at 61, and this chamber The passage 58 leads/to the flue 34- has a width slightly greater'than the length of the tubes in the bank 47. In the installation of the tubes a workman enters the chamber 48 and another workman enters the chamber 46 which is likewise provided with a door or other means of access. The tubes are then introduced through suitable openings through the wall 59 with their remote ends entering openings in the wall 60. These walls may be made of refractory material, as, for example, they may be built up of tile, and the end of each tube is caulked by means of asbestos wicking, for example, wrapped about the tube as indicated at 62; then at the end the tube may be secured in place as at 63 by cement, such as that commonly known as silicon carbide cement.

Each tube contains a rod 64 known as a i corebuster. This rod is of fire clay and'is provided withlegs 65 which hold the rod at tion rounded at its end, as indicated at 65', while the intermediate sections 66 are of cylindrical shape. Therounding of the end section permits proper distribution of the air and the presence of the rod at the center of the tube causes the air to flow in a thin film over the walls of the tube, thus'improving the heat transfer action. The number of tubes in a bank, and the size of these tubes, will of course, depend on the amount of air that is' to be sup lied for combustion "poses in the cham er.

It will be observed that the chambers 40, 44, and 48 are of a width greater than the length of the tubes which lead to these cham.- bers, while the intermediate chambers 42 and 46 are relatively narrow. All of these chambers are provided'with doors or other means of access, and with this arrangement, when the furnaceis shut down for inspection or repairs, a pair of workmen can examine the tubes and replace them or makesuch repairs as are necessary. When replacement is necessary, the tubes are withdrawn into the large chambers and the small intermediate chambers provide space for examining the interiors of the tubes and also securing their ends in the intermediate walls.

made in separate sections, with each end secpur-- With the new recu-perator it will be seen that the air and gases. flow in heat tranfer relationship ina number of passes, the device illustrated providing for four passes. Between each pair of passes=th'e air enters a chamber in which temperature conditions in the air can be equalized, and likewise the gas flows into-a chamber where the same result can be effected. In each pass the gases and air How in directions transverse to each other and the flow is so directed that there can be no short circuiting and all parts of the heat transfer tubes operate at substantially the same efficiency.

- In a continuous heating furnace. installa tion of this type a high degree of efliciency weather.

is attained, since the material to beheated. is

gradually raised in temperature at the en trance end of the heating chamber, due to the overflow of the gases into this end, then subjected to a hi h temperature in the combustion-hone, an finally allowed to give up much of its heat before leaving the chamber.

At the same time the hot waste gases of combustion are used in a highly efficient-manner in preheating the air for combusion, and the recuperative device employed is constructed so that the maximum heat transfer will take place within it. This device is arranged for ready inspection and repair; should occasion arise, and such examination can be made whenever the furnace is shut down at its regular intervals. By reason bf the manner of constructing the lines which lead from the heating chamber to the recuperator, much of the solid material carried along by the gases is deposited before en-terin the recu erator, and the precipitation is so lirought a out by the frequent change in direction of flow of the hot gases. Suitable ports or other means of access to the hot gas ducts in the recuperator maybe provided so that this deposited material may readily be removed and the tubes themselves may be readily cleaned by means of the ordinary soot blowers usually employed for such purposes.

The novel recuperator operates at a high efficiency, due to the rapidity of heat transfer through the tubes provided for the purpose and in addition, by shutting off the recuperator, heat can be storedin it in the event that the furnace is shutdown, so that when firing is again commenced only a short period of time is required to bring the recuperator to the most efiicient operating temperature.

While the recuperator has been shown connected for preheating air usedfor' combusposes of the plant buildings during cold I claim:

1. A recu erator for use in connection with a furnace or transferring heat from the burned gases therefrom to the. air usedfor combustion therein which comprises a structure including a plurality-of wide and narrow chambers arranged alternately in a row, the first chamber in the row having an inlet for air and the last chamber anair outlet, tubes for the flow of air connecting adjacent chambers, and passages for leading the hot gases past these tubes in a direction transverse to the direction ofair-fiow therethrou-gh.

2. ,A recuperator for use in connection with a furnace for; transferring heat from the burned gases therefrom to the air used for combustion therein which comprises a structure containing a series of wide and narrow chambers arranged alternately, each of these chambers having means of access thereto, anvair inlet connected to the first chamber in the series and an air outlet from the last chamber, tubes for conducting air between adjacent chambers, the chambers being so placed that the tubes have a length less than the width of a wide chamber, and means for passing hot gases past these tubes in a direction transverse theretox 3. A recuperator for use in connection with a furnace for transferring heat from the burned gases therefrom to the air used for combustion therein which comprises a structure which includes -a series of separated. chambers, each pair of adjacent chambers being connected by a bank of tubes, an inlet for air leading to the first chamber of the series, and an outlet for air from the last chamber, and means for conducting hot gases past the tubes.

4.. A recuperator for use in connection with 'a furnace for transferring heat from the burned gases therefrom to the airused for combustion therein which comprisesa structure containing a series of separated chambers, adjacent chambers being connected by a" bank' of tubes, an'inlet for air to the first chamber in the series and an outlet for air from the last chamber, and means for conducting hot gases past the tubes in a direction transverse to the axes of the tubes, the gases being conducted past the banks successively and in opposite directions past alternate banks.

5. A recuperator for use in connection with a furnace for transferring heat from the burned ases therefrom to the air used for combustion therein which comprises a structure containing a series of separated cham bers, adjacent chambers being'connected by a bank of tubes with the tubes of the successive banks lying with their axes parallel, means for introducing air into the first chamber in the series for passage through the chambers and tubes successively to the last chamber,- j

an outlet for air from the last chamber, and

' means for leading hot gases past the tubes,

the gases being introduced into the struc: ture at the end opposite to that at which the air is admitted to the first chamber.

6. A recuperator for use in connection with a furnace for transferring heat from the burned gases therefrom to the air used for combustion therein which comprises a series of separated chambers, adjacent chambers being connected by a. bank of tubes, means for admitting air to the first chamber of the series, an outlet for air from the last cham her, and means forpassing the hot. gases in heat transfer relationship with the air, the gases being led in the direction transverse to the direction of flow of the air through the tubes and past alternate banks of tubes in opposite directions, the air flowing around the end of a chamber between each bank of tubes. I

7. In a recuperator for use in transferring heat from hot burnedgases to air for combustion, the combination of a plurality of separated chambers arranged in a series, tubes extending between adjacent chambers, each end of each tube being mounted in a Wall of each chamber, alternate chambers havin a width greater than the length of the tu es connected thereto, and means by which. ac-. cess can be had to each chamber in the series.

8. A recuperator for use in connection with a furnace for transferring heat from the burned gases therefrom to the air used for combustion therein which comprises a structure including a series of separated cham= bers, tubes connectin adjacent chambers, each tube communicating with the chambers through the walls thereof, means for admitting air into the first chamber .for passage through the chambers and tubes successively,

an outlet from the last chamber in the series, means in each tube for causing the air to flow therethrough in a relatively thin film along the wall of the tube, and means for I leading hot gases past the tubes to give up heat to the air through thetube walls.

9.'A duct for use in a recuperator which comprises a tube of silicon carbide and a rod of refractory material supported within the tube at the center thereof, this rod exte ing from end to end of the tube and being made up of sections with the outer ends of the 'end sections rounded.

10. A recuperator for use in connection with a furnace for transferring heat from the burned gases therefrom to the air used for combustion therein, which comprises a structure including a plurality of groups of tubes arranged substantially end-to-end, temperature-equalizing spaces between the end ,of the tubes of ad acent groups, an inlet for leading air through the tubes of the successive groups, and means for conducting gases successively past each group of tubes.

11 A recuperator for use in connection with a furnace for transferring heat from the burned ases therefrom to the air used for combustion therein, which comprises a struc ture including a plurality of spaced banks of tubes, means fordelivering air to the tubes of "the first bank, means for confinin' the air flowing from the tubes of one ban to the .tubes of "the bank next following itin se- "ries, the said means permitting access to the I. ends of the tubes in adjacent banks, and

means for conducting gases past the tubes of the banks successively, the cooler gases engaging'the tubes containing the cool air first.

'12. A recuperator for use in connection ,with a furnace for transferring heat from the burned gasestherefrom to the air used for combustion therein, which comprises a plu- In testimony whereof I aflix my signature. I

WHJLIAM- H. FITCH.

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