US1751136A - Apparatus for heating the air blast for furnaces and the like - Google Patents

Description

, March 18, 1930. I DOVEL 1,751,136

APPARATUS FOR HEATING THE AIR BLAST FOR FURNACES AND THE LIKE Filed Dec. 16. 1926 3 Sheets-Sheet l 5 A 7g 1 I 5.-

' z 22 s 1 16 '0 fi' .--1 1 :3

' rwentcl James P, Dovel Gnome March 18,1930.

J.' P. D OVEL Filed Dec. 16,1926

APPARATUS FOR HEATING THE AIR BLAST FOR FURNACES AND THE LIKE s Shets-Sheet 2 @uomu J. P. DOVEL 1,751,136

APPARATUS FOR HEATING THE AIR BLAST FOR FURNACES AND THE LIKE March 18, 1930.

Filed Dec. 16, 1926 3 Sheets-Sheet esRDozfel Gnome Patented Mar. 18; 1930 UNITED STATES PATENT OFFICE,

JAMES P. DOVEL, or BIRMINGHAM, ALABAMA Application med December 1a, 1926. Serial No. 155,277.

My invention relates to a new and improved process for the heating of the air blasts delivered to blast furnaces, cupolas, or

wherever it is desired to heat the air blast,-

5 and to an apparatus for carryingmy said a process into effect.

While it is to be understood that my invention is applicable forservice in heating any type of blast I shall hereinafter describe it more partlcularly with reference to its. application to blast furnaces, but without thereby intending to limit myself to such specific use. i

- In Letters Patent No. 1,316,086, issued to me on September 16th, 1919, I have shown and described an air heater connected in a p by-pass across the cold air main and through this heater the waste gases from the stoves are passed in their flow to the stack. By con- 26 trolling the volume of cold air delivered to the heat transfer apparatus it was possible to absorb from the waste gases all heat in excess of that required to maintain the necessary draft in the stack.

In the practical applicationof this process I'have discovered that a more efficient and a materially less expensive means for heating the blast can behad by the simple enlargement or increase in capacity'of my air heater 30 andby supplementing the heat supplied thereto by the waste gases with burning gas or a like source of heat of active combustlon controllable in amount and regulable so that the aggregate of heat '1 [nits delivered from the waste gases and the burning gases will enable the heater to preheat the cold'air blast to the desired temperature without robbing the stack of its necessary heat, unless the draft I the-rein be maintained by a blower or'fan.

Another distinctive feature of my present process is the blending of the low and high temperature gases prior to their delivery to the transfer elements in the air heater, there- 'by to reduce the temperature of the gases entering the heater sufficiently to, avoid injury to the'heat transfer elements. lthas been demonstrated that the transfer of heat dithrough the transfer elements of my present type of heater to the air blast is a 0 more efiicient means of heating same than -drawings, in which I have illustrated the preby the indirect methods of the stoves. and in practical experience I have demonstrated that" my improved air heater for the cold bl'as't,- representing an initial installation cost of less than half that of stoves and with prac- 56 tically negli ible maintenance cost, has enabled me to dispense with one stove and still to maintain a suitable temperature in the hot blast with a marked economy in consumption. The desirability of blending the high and medium temperature (gases delivered to the air heater arises from the factthat from the point of view of prime cost it is desirable to make the heater of standard cast iron pipe which can be obtained at low cost and can be assembled with the available help at the furnace and maintained with but slight expense. Such heat transfer elements would not stand the high temperaturesof direct combustion, and to this end my present invention contemplates blending the flame of the burning gases I with the waste gases from the stoves in a Dutch oven or equivalent apparatus connected withthe air heater and provided with suitable refractory elements therein to insure an equalization of the different temperatures therein of the gases delivered to the heater. The refractory elements in the Dutch ovenare of negligible cost and of easy replacement and thus do not represent, to any appreciable extent, an element of cost in the operation of the process.

The practice of my process will be better understood by reference to the accompanying ferred type of mechanism for carrying same into efiect.

Fig. 1 is a view in side elevation of a conventional arrangementof stoves for a blast furnace with the stack flue 'and airheater 7 shown in vertical cross-section.

Fig. 2 is a transverse detail sectional view of the Dutch oven and the adjacent end of the heater taken along the line l L-ell t of Fig. 3;

r Fig. 3 is a vertical longitudinal cross-section of theapparatus; and

ratua Fig, 41s a sectional plan view of the appa- Similar reference numerals refer to simi 1211' parts through out the drawings. In the apparatus illustrated, 1 is the hot main from the stoves 2 to the blast furnace V7 or other source of use (not shown), and 3 is disposed top and bottom bafiies l0 and 11 to cause a tortuous flow of the gases therev through until dischar edthrough a flue 12 to the stack or other ischarge'. Thev Dutch oven and the air heater maybe built up in 9 accordance with any standard practice and therefore need not be specifically described otherwise than'to state that the cdnstru'cti'on is such as to withstand stovetemperatures. The cold blast main 13 leads above the air heater and is provided with by- pass connections 14 and 15 totheend's of the air heater.

I interpose a by-pass valve 16 beyond the connection 14 in the cold blast main, and also a valve 17 for the by-pass'connection 14, and a similar valve 18 in the connection 15. The valve 16 is of any suitable ty e which is adapted to be opened and closed y means of a bell crank 19 pivotally mounted on a stand ard 20 on the main 13 and having its vertically disposed arm connected to a thermostatic bar 21 which rojects into. the stack and is slidable throng 'a stulfing-box 22 suit-.

, ably anchored in the stack.- The bell crank is given an adjustable connection to the valve stem, as described in my Letters "Patent aforesaid, to which reference is made for a more detailed description of the automatic thermostatic control of thevolume of cold-airbypassed through'the air heater. The cold air entering the air heater by means of the connection 14 is delivered to a header 23 having a transverse series of elbow fittings 24 connected thereto and downturned to receive pipe coils 25 which form the heat transfer 5 elements. 'These coils extend 'bontinuously the full length of the air heater and comprise vertical" legs connected topandflbottom by U-bends'26, the lower U-bends being seated on. low cradles 27 on the floor of the air heater and the U-ben'ds are provided over head with. erforated lugs 28 which receive v connectin are 29 having spacer sleeves30 interpose so that the. heat transfer elements are suitably connected and spaced overhead so as to prevent vibration. Each heating coil at its end delivers the heated air throu h an end elbow 24 to a header '31 from whic the connection 15 leads back-tothe cold main.

1 Live gas through a main-"32 and connection 33 is delivered to a header 34 under-.-

:control of the valve 35, and from the header 34 lead suitable burners 36 which deliver through the outer end wall of the Dutch oven.- I interpose suitable refractory material 37, preferably in checker-Work design in this Dutch oven and I interpose samebetween the burner nozzles 36 and the ports 8 so that the flame from the burning gases,

delivered from the burners 36, will impinge against this refractory mass and be broken 'up and diverted in all directions to'the-end that it will become properly and uniformly mixed with the waste gases entering throu h the connection 6, thus causing the gases elivered through ports 8 to enter the air heater at a safe temperature for the durable serv ice of the heat'transfer elements therein. As

illustrative of what I have in mind, when gases passing into the airheater will be about 1400 E, which is a safe temperature for the type of heat transfer elements used. Obviously if better heat resistant transfer ele-- ments were used in the "air heater higher entering gas temperatures could be used therein and thus, a greater percentage of burning gases used. i A

The air heater is provided at suitable intervals, preferably adjacent to itsbaflles, with transverse bottom openings 38 which extend to each side of the airheater and are there provided with removable gratings 39 by which access may be had for clean out pur-" poses. The cradles 27 falling opposite these openings are supported on cross beams 40 and the ends of the headers 23 and-31,.which project through the casing, are supported by cross members 41 of its metallic frama The clean out space under the gratings 39 1s norby manhole doors 42. It' is of advantage to note that heat transfer coilswhile-suitably supported and braced together, are 'all'free to expand and contract in the air heater and are readily accessible for replacement and repair at any point. 7 In order to keep these In operation, with the apparatus set up -mally shut off from the bottom openings-38 and connected substantially in the 'manner 1 above described, the thermostatic valve 16 will control the volume of cold air byassed from the cold air main through the air eater, maintaining this volume as large as will=leave the desired amount of heat in the exhaust gases in the stack or like point of discharge,

and thus recoverable heat from the waste gases of the stoves is transferred to the cold blast. In order to raise this cold blast to a sufficiently high temperature to enable a part of the stove ca acity for the furnace to be dispensed with, deliver through the burners in the Dutch oven suflicient live gas, which burning in the oven and mingling with the entering waste gases will raise the tempera-,

ture of such gases as high as may be desired within the limits contemplated for the heat transfer elements of the air heater. To illustrate, if sufiicientlive gas is burned to raise the temperature of the waste gases entering the'air heater to 1400 F., I have found it possible to raise the temperature of the air blast sufficiently to reduce the duty on the stoves enough to enable a part of'them to be discontinued and I accomplish this highly desirable end with an outlay as to cost much less than that of the discontinued stove ca pacity. Moreover,-I obtain a much more efli- I cient and more uniform and more accurately cont-rolled transfer of heat to the. air blast than where the indirect methods of transferring heat, as by stoves, is employed, and I am able to bring the heat transfer apparatus up to full service very rapidly, which is obviously impossible with stoves. The pro vision of the refractory mass in the Dutch oven is optional, as any arrangement of de sign may be provided which will effect a mingling of the gases entering the Dutch oven an an avera 'ng of their temperatures before they enter t e air heater.

The feature to which my present invention is broadly directed, consists in a combined heat recuperating means having a combus tion chamber rovided with means to produce therein igh temperatures by active gases with the, high temperature gases of active combustion andpass the commingled gases through said combustion chamber and ments in said combustion chamber interposed in the path of the waste gases and the gases of active combustion to more effectively mix the same before they ass into the. heat recuperating means, an' means to pass air combustion, means to commingle said waste 1 heat recuperating means, refractory elethrough said heat recuperating means into said cold air main.

In testimony whereof I aflix my si JAMES 1?. DO L.

ature.

live and waste heat means controllable so as I to deliver to a heat transfer for the cold blast the requisite volume of blended hot gases to preheat the cold blast to the stoves to the desired extent without at the same time interferin with the necessary draft, for conducting t e furnace gases through the stoves and heat transfer to the desired oint of utilization or discharge, and wit out subjecting,

the heat transfer to excessive temperatures. Though I have described my invention more particularly as applied to blast furnaces where such term is used, it is inclusive 1 of any type of furnace or heating unit wherein waste gases are present andthe preheating of air delivered to the furnace or heater would be desirable.

Though I have described with great particularity the details of the embodimentof the invention herein shown, it'is not to be construed that I am limited thereto, as changes in arran ement and substitution of equivalents may e made by those skilled in the art without departin from the invention as defined in the appen ed claim.

Having thus described my invention, what

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