US1872057A

US1872057A - Cupola furnace

Info

Publication number: US1872057A
Application number: US430821A
Authority: US
Inventors: Alfred L Boegehold
Original assignee: General Motors Research Corp
Current assignee: General Motors Research Corp
Priority date: 1930-02-24
Filing date: 1930-02-24
Publication date: 1932-08-16
Anticipated expiration: 1949-08-16

Description

g- 1932- A. L. BOEGEHOLD 1,872,057

CUPOLA FURNACE Filed Feb. 24; 1930 2 Sheets-Sheet l Aug. 16, 1932. A. 1.. BOEGEHOLD 1,372,057

' CUPOLA FURNACE Filed Feb. 24, 19:50 2 Sheets-Sheet 2 fl MW du Patented Aug. 16, 1932 UNITED STATES PATE T- OFFICE ALFRED L. BOEGEHOLI), or DETROIT, MICHIGAN, AssIeNOR TO CENERAIZ NIOTORS m- SEARCH CORPORATION, OF DETROIT, MICHIGAN, A CORPORATION OFDELAWARE GUIE'OLA FURNACE This invention relates to cupola furnaces designed for the economical production of cast iron; and more particularly to Cupolas adapted to be operated with a reducing atmosphere in the melting zone.

Among the objects of the invention are to operate a cupola with a reducing atmosphere in and over the charge containing portions; to utilize substantially all of the gases rising from the melting zone and charge containing portion to restore heat to the charges; to so charge the cupola that no gases may be lost during the charging operation, to heat the air to be forced through the tuyeres' by burning all the combustible gas produced in the cupola and transferring the heat produced to the air blast; to. dry the air to be forced through the tuyeres; to reactivate hydro scopic'material used to dry said air by forcing pure hot air drawn from the hot air on its way to thecupola into contact with said material andotherwise to improve methods and means for producing cast iron.

In the accompanying drawings which disclose somewhat diagrammatically an apparatus adapted to practice the invention.

Fig. 1 is a plan view of a cupola with associated blast drier and heater.

Fig.2 is a sectional elevation of the-ap numeral 10, which contains the charges of I coke and Iron or steel, is circular In section and lined with fire-resistant material as is customary. The upper charge admitting portion of the cupola 11 is preferablysquare in section as illustrated. Throughiwo vertically spaced closures is this square portion the charges of coke and metal are introduced into'the'cupola. Inasmuch as it is desired to utilize in the charge irregular steel scrap. such as fiashings and the like the closures thru which the charges are introduced are adapted to open so as to leave charging openings of the full cross-sectional area of the cupola.

-At least the lowerwclosure consists of one or two doors hinged to the wall of the cupola to -open downward so as to leave a free passageway afiording no obstructions with which irregular scrap maybecome entangled;

One closure is at the top bf the cupola, and one farther down within the sq ared portion each illustrated as composed 0 two hinged doors. The doors 12 of the upper closure may be opened for the reception of a as at 14, to assist in sustaining the charge and controlled by suitable mechanism (not shown). The upper doors 12 may then be closed and the doors .13 swung downward to drop the charge into the circular charge containing portion of the cupola. Where two doors 12 are used one of them has a lip 15 secured to it, said lip projecting under the edge of the mating door when in closed position. In case two doors 13 are used one of them has a similar lip 16 adapted toengage with the edge of the door which mates with it when in closed position as shown. Spaces are formed in the opposite inner sides of the cupola to receive the doors 13 when open.

In order to direct a blast of air for combustion purposes into the coke at the bottom of the cupola, an .annular windbox, or encircling manifold 17 surrounds the lower portion of the cupola and communicates with one above the other in zigzag form,

the interior thereof thru a plurality of tuyeres 18. A pipe 19 connects the box 17 with the heater H, which contains a heat interchanger or transfer device of the surface type comprising upper and

lower headers

20 and 21 respectively, into which a plurality of" vertical tubes 22 are connected at their ends. The upper header is spaced from the top wall 23 of the casing 24, and the lower header 21 is spaced from a perforated transverse wall'25 about midway between the header 21 and the floor 26 of a gas burner or furnace structure 27 which may have a door 63 or other controlled opening. The space below the perforated-wall 215 receives combustible gases from the cupola G, thru the stand pipe 28, which extends upward between the heater and the c'upola and is provided with two

branches

29 and 30. The branch 29 enters the square portion 01 the cupola beneath the doors 13 and above the charges and the branch 30 enters said portion of the cupola between the doors 12 and 13. At the junction of the branch 30 wit the pipe 28, there is a slight enlargement 31 which provides a shoulder 32 in line with the under side of branch 30. The shoulders .thus formed constitute a seat for a valve 33,

which, as shown, is suitably connected with one of the doors, 12, so that when said door' is opened by moving it upward the valve 33 is permitted to descend and engage the valve seat, thereby cutting off communication between the pipe 28 and the open cupola or external air thru the branch 30.

. Drier D comprises a casing are disposed a number of pans 41 arranged as shown. These pans 41 are designed to receive a hygroscopic material such as calcium chloride or silica-gel, preferably the latter. There are a plurality of driers D preferablynot less than three, as shown in Fig. 1, for a purpose to be made known presently. Each drier D is connected by'severa'l passages 42 with an air inlet condnit 43. The passages 42 are shown as flaring or gradually enlarging in section from their connection with the pipe 43 toward the drier; and in the ori fices at the points 43 are arranged a number of baffles 44 :for the purpose of well distributing the air flowing thru the pipe 43 to theseveral passages 42. The pipe air header pipe 45 extending crosswise of the several driers, bymeans of upright short contween pipes tion as shown in duits 46. A lower normal atmospheric air header pipe 47, which may be fed with air by ablower64', is also connected with each of said pipes 43. Each of the openings besaid pipes and header--47, are adapted to be closed, alternately, by a valve 48. When the valve 48 of any drier D 1s m the upper posiwhile the passa e in which.

of connection a with pipe 43 communicates with a moist 43 and header 45, and between- Fig. 2 thepassage from ravens? pipe 43 through pipe 46 to header is closed from pipe 43 to header 47 is opened. en the valve 48 is lowered over the communication between the pipe 43 and the header 47, the latter is closed oil from communication with said pipe 43, and the passage to header pipe 45 is opened.

The outlet forair from a drier on its way to the heater is indicated at 49. There is an outlet 49 for each drier and each of said outlets communicates by means of a short section of piping 50 with a header pipe 51 disposed above the outlet, and by means of a pipe 'section 52 with a header pipe 53 disposed below said outlet 49. In the outlet 49 there is a valve 54, which, when it is'in lowered position, as illustrated in Fig. 2, closes the communication between said pipe 49 and the pipe 52 and header,53, but when in its upper position closes the communication between'pipe 49, pipe 50 and header 51 leaving the lower communication open.

The valve 48 at the inlet side of each drier h and the valve 54 at the outletside of the same drier are suitably connected, as by the flexible connector 55, in such relation that when the valve 48 is on its upper seat, as illustrated, the valve 54 is on its lower seat. I

The header pipe 51 is connected by a single conduit 56 with the blast heater H, as shown in Fi 2, while the lower header 53 is connecte by the single pipe 57 with the pipe 19 which leads directly from the blast heater to the wind box 17.

Within. the posed in between the tubes 22, so that dry air entering the heater thru the pipe 56 will have to take a somewhat tortuous passage around the baffles before passing from the heater into the pipe 19 on its way to the cu-pola.

Rising from the moist air header pipe 45, before referred to, atone end, is a stack 59 adapted to discharge moist air from an exhaust blower 60. V, v

Rising from the heater H is a stack 61 in which is disposed an exhaust blower 62 adapted to discharge waste gases of combustion from the heater H.

In operation, successive charges of coke and metal are introduced into the cupola as needed. To introduce acharge of coke and metal the doors 12 are opened and the valve 33 closed upon its lower seat thus shutting off communication between stand pipe 28 and the outer atmosphere. The charge is deposited upon the doors 13. When" a sufiicient quantity has been deposited on doors 13, the

doors 12 are closed thus lifting valve 33, thereby establishing;communication between stand pipe 28 and the space between the two. closures in the cupola thru pipe 30. The doors 13 are then opened and the charge dropped into the cupola. 7 Successive charges are introduced into the cupola in this manner.

Assuming the lower layer of coke to have been ignited:

With the apparatus adjusted as shown in Fig. 2, air enters the lower .header pipe 47 from a blower 64 (shown in Fig. 1) as indicated by the arrow at the left. It passes up into the pipe 43 and thence thru the drier D. From the drier Dit passes thru the pipe 49 and into the header 51 and thence into the heater H. From the heaterH it passes thru the pipe 19 into the manifold or wind box 17 and thru the tuyeres into the cupola where it enters into the lower coke bed. The heater H, when the cokeis burning, receives the unburned gases which rise thru the charges to the top of the cupola thru stand pipe 28 into the furnace27 where it is ignited. The gas and products of combustion from the gas burning in the furnace 27 pass up thru the holes in the floor 25 and thru the tubes 22 and,

after having given up a proportion oftheir heat to the air surrounding tubes 22 in the heater, the resulting burned gases are drawn thru the stack 61 by the exhaust blower 62 and are driven out of the top of the stack.

A plurality of driers is used so that when the hygroscopic drying material in one of them has become saturated with moisture this material may be reactivated by absorbing the moisture in a current of hot air. When it has been decided-to reactivate one of the driers the valves 54 and 48 appertaining to that particular drier are reversed in position with respect to that shown in Fig. 2. With the valves inthis new position some of the pure dry hot air flowing from the heater toward the cupola is shunted off thru the pipe 57, conducted to the header 53 and thence to the drier thru the open port pertaining to that particular drier. This pure dry hot air passes over the pans containing the hygroscopic material and now laden with moisture picked up from the hygroscopic material flows into the pipe 46 and then upward into the header pipe 45, which is subject'to the draught produced by the exhaust blower 60,

and thence it is driven out thru the stack 59. Whenthe material in this particular drier has been reactivated it is again put into serv-- ice to dry incoming air as previously described. Each of the several-driers may be reversed for reactivating the hygroscopic materials in the same manner and again put into service without interfering with the operation of the others.

In theapparatusdisclosed all of the gases generated in the cupola are drawn oli and used to heat the. air blast. Even when charges are being introduced no gases escape;

when the lower doors 13 are closed they es-. cape thru the cross pipe 29, and when av charge is being dropped thru thedoors 13 they escape also thru the pipe 30, into the furnace 27 where the combustibile ingredi cuts are burned. If there is insuflicient air in the gases proceeding from the cupola to support combustion additional air may be 1 cupola because of the large heat losses resulting from' losses of carbon monoxide. But in the melting of iron it is desirable to have a reducing atmosphere, both on account of the improved quality of the metal produced and because it is possible to obtain a greater carburizing action permitting the use of large quantities of steel scrap ill l consequently lowering the cost of the cast iron produced.

With the apparatus disclosed herein it is possible to obtain a satisfactory reducing atmosphere without substantial losses of carbon monoxide because the heat available from its combustion is transferred to the air blast and so restored to the cupola. I In the ordinary cupola the gases in the melting zone and charge containing portion carbon collected by the iron' being absorbed when the iron is molted from the incandescent coke incontact with it. By burning the fuel so that the gases in the melting zone are composed of about 25% of carbon monoxide and 12% of carbon dioxide, the carbon'monoxide becomes a powerful carburizer, and inv creases the amount of carbon that'can be introduced into the iron metal during the melting. As a result the iron drawn from the cupola will contain the quantity of carbon to make good cast iron even though a large proportion of steel scrap be used in the charge.

I claim:

1. In apparatus for producin cast iron, 3. cupola having a charge containing portion, a charge admission portion of rectangular section above the charge containing portion, vertically spaced upper and lower closures within the rectangular charge admission portion, the lower closure comprising at least' one door hinged at one side and opening downward so as to provide 'an opening of substantially the full cross sectional area of the cupola for admitting the charges, and

the upper closure comprising at least one door hinged above and outside of the charge admission portion so as to swing upward and outward entirely clear of the entrance for the charge.

2. The combination of a cupola'having a charge containing portion, a charge admittlng portion above the charge containing portion, spaced upper and lower closures in the charge admitting portion and tuyeres adjacent ,the bottom of the charge containing portion; a heat interchanger provided with an inlet for air to be heated, and an outlet for heated air in communication with-the tuyeres; a gas burner associated with the heat charge containing portion, a heat interchanger provided with aninlet for air to be heated, and an outlet for hot air in communication with the tuyeres; a- 'gas' burner associated with the heat interchanger, and a gas conductor leading to-the gas burner said conductor having branches one of which oommunicates with the cupola at a point between the closures and the other at a point above the'charge forming portion and below the lower closure.

' tending across 4:. The combination defined in claim 3 with a vlave for closing ofl' communication between the gas conductor and the space in the cupola between the closures.

5. The combination defined in claim 3 with a valveclosing ofi' communication be-- tween the gas conductor and the space in the cupola between the closures, and operating means connecting the valve to the upper closure..

6.. The combination of a'cupola provided with tuyeres, a charge admitting closure exthe cupola above the charge containing portion, a heat interchanger, a hot air pipe communicating with the heat interchanger and the tuyeres, a gas burner as- 8. The combination defined in claim 6 in which the conduit connecting the hot air pipe to the drier, and the cool dry air conduit leading from drier to heater terminate at the drier end in opposite valve seats, a valve adapted to close said seats alternately; opposite valve seats and a single valve controlling the inlet for fresh air to and the outlet for moist air from the drier, and means 0011-. necting said two valves and compelling then] to operate in unison. I

In testimonly whereof I afix my signature.

A FRED L. BOEGEHOLD.

sociated with the heat interohanger, a gas conduit communicating with the cupola at a point above the charge containing portion and below the closure for conducting gas from the cupola to the gas burner, a drier adapted to contain hygroscopic material,

'said drier having an inlet for fresh air and an outlet for moist air; a conduit for conducting cool dry air from the drier to the heat interchanger, a conduit connecting the drier with said hot air pipe that communicates with the heat interchanger and the tuyeres, and control means for providing an open passage for air through the drier and heater to the tuyeres, or alternately from the heater through the drier to the external air at W'lll.

7'. The combination defined in claim 6 with valve mechanismfor controlling the course of air through the drier in order to conduct dry hot air to the cupola or reactivate the hygroscopic material in the drier at will.