US2505861A - Regenerative hot-blast system - Google Patents

Description

y 2, 1950 F. H. JOHNSON 2,505,861

REGENERATIVE nor BLAST SYSTEM Filed April 11, 1946 3 Sheets-Sheet l INVENTORI HIS ATTORNEY.

y 2, 1950 F. H. JOHNSON 2,505,861

REGENERATIVE HOT BLAST SYSTEM Filed April 11, 1946 3 Sheets-Sheet 2 2242, if FIGS- INVENTOR.

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May 2, 1950 F. H. JOHNSON 2,505,861

REGENERATIVE HOT BLAST SYSTEM Filed April 11, 1946 FIE 4;

3 Sheets-Sheet 3 INVENTORZ H15 ATTORNEY.

Patented May 2, 1950 BEGENERATIVE HOT-BLAST SYSTEM Fred H. Johnson, Chicago, 111., minor to Carnegie-Iliinois Steel Corporation, a corporation of New Jersey Application April 11, 1946, Serial No. 661,374

4 Claims.

This invention relates to an improved regenerative hot-blast system of the type including two or more single-pass stoves each devoid of a cornbustionchamber and connected to a separate structure affording a combustion chamber common to the plurality of stoves.

The objects of the invention are to provide a blast furnace stove arrangement which will be capable of delivering suflicient hot air to a mod ern blast furnace of large size without an increase in number and size of stoves; to provide a blast furnace stove arrangement suitable for installation in existing stove settings and thus increase the heating surface to a maximum for the size of the stove shell available and, therefore, permit rebuilding and modernization of existing furnaces with resultant increased production without increasing the size of the stoves; to provide a blast furnace stove arrangement which will permit continuous operation of the blast furnace without the necessity of providing any spare stoves, as is necessary under present-day blast furnace operations; and to provide a blast furnace stove arrangement which can be automatically operated, i. e., the sequence of stove reversal can be fully automatic and can be actuated or set in motion by the straight line temperature control of the hot blast to the furnace.

It is to be understood that while the description of my invention relates to improvements in blast furnace operation for pig iron production, the novel blast furnace stove arrangement described and claimed herein is applicable to other uses requiring a preheated air blast or gas to complete the operation.

The accompanying drawings illustrate the invention as embodied in a two-stove layout served by a common exterior combustion chamber.

, In the drawings:

Figure 1 is a front elevation showing a twostove arrangement with a separate combustion chamber for supplying hot air to a typical blast furnace.

Figure 2 is a plan view showing the two-stove arrangement and its relation to the blast furnace.

Figure 3 is a cross-sectional view taken on line III-III of Figure 1, illustrating piping arrangement and connections between stoves, combustion chamber and blast furnace.

Figure 4 is a sectional view taken on line IVIV of Figure 2.

Figure 5 is a sectional view taken on line VV of Figure 2, showing the combustion chamber in section.

The stove arrangement of my invention con-- sists of two or more one-pass stoves I 0 connected by suitable hot gas valves H and piping l2 to a separate combustion chamber it. The stoves III preferably consist of a welded or riveted steel shell M, a ringwall I! with suitable insulation to curtail heat losses, and checkerbrick l6, supported on a suitable supporting structure I1. Such construction is desirable since it will allow the checkerwork to move in a vertical plane under the influence of contraction and expansion of the brickwork due to temperature fluctuations as the stoves are intermittently operated on and ofl' blast. The stoves have independently mounted domes l8 which permit a difference of temperatures to exist between the top and bottom of the stoves without interference and without causing distortion to the stove shell structure.

The combustion chamber I3 may be of any suitable shape or size best suited for combustion of blast furnace gas or other suitable fuel and preferably is a tower or shaft comprising a steel shell I! lined with firebrick 20. The combustion chamber i3 is fired from the bottom by one or more burners 2|. The burners 2| may be a single con- 'ventional blast furnace gas burner or multiple burners discharging horizontally into the combustion space as shown in Figure 5, or may be fired upwardly from the bottom. if desired. There is no limitation in the design or use of burners as is now the case in the present-day conventional type of hot blast stove, due to the location of the combustion chamber within the stove itself. Fuel is supplied to the burner by a pipe 2| 0 and air under suitable pressure by a blower 2 lb.

The hot burned gases are discharged from the top of the combustion chamber through hot gas pipes l2 having valves ii therein to the dome l8 of one of the stoves ill and pass downwardly through the checkerwork l6 and finally to the stack 22 through suitable opening 34 and duct system 35, including theusual chimney valve (not shown), connecting the bottom of the stove l0 thereto. The gases remain in contact with the checkerwork l6 for a time interval long enough to heat it to a temperature ranging from 1000 F. to 1400" F. While the checkerwork of one stove is being heated, the other stove is being used to heat the cold blast to a temperature suitable for use in a blast furnace 23. Cold blast is supplied to the bottom of the other stove from a pipe 23:: through a valved connection. The resulting hot blast is discharged through pipe l2, outlet pipe Ila branching therefrom and having a hot blast valve 24 therein. The pipes l2a are connected to a hot blast main or downcomer 25 which is connected to the bustle pipe 26 surrounding the blast furnace 23. Conventional means, not shown, lead the hot blast from the bustle pipe to the usual tuyeres equally spaced around the blast furnace.

The stoves I are alternately heated and cooled preferably by automatic control equipment which will open and close the gas and blast valves l I and 24 in a predetermined cycle. It is preferred to make the operation of the stove arrangement fully automatic, but the valves and other mechanism can be manually operated if desired.

The arrangement of hot gas valves II and hot blast valves 24, as shown on the drawings, permits the use of fully automatic equipment such as a rope and sheave with a winch and driving motor actuated by suitable control switches. The switches are preferably operated by an automatic control mechanism which will periodically shift all valves necessary to maintain the required sequence of operations.

The hot gas valves ll, Figure 4, are shown in open position, thus permitting the hot burned gases'to pass into the stove ill through the ducts I2. Each valve ii is illustrated as a conventional hot gas valve comprising a, vertical cylinder having valve seat 28. The closure member consists of a diaphragm 29 attached to a stem 30. A rope or cable is attached to the stem 30 and by means of sheaves and a. motor-driven Winch may be operated from some remote control point.

Each hot blast valve 26 is similar to the valve H in construction and has a valve seat 3! and an actuating mechanism consisting of a diaphragm 32 and stem 33.

The type of valves shown and described permits fully automatic operation of the stoves without requiring any special equipment or facilities. However, it is to be noted that similar arrangements can be made using water-cooled slide or gate valves or any other type of valves capable of withstanding the high temperatures that are encountered in this type of operation.

It is desirable to provide means for controlling the temperature of the hot burned gases entering the stoves by means of tempering gases introduced to the hot gases by secondary supply pipes H8, connected to the hot gas valves l (I. The introduction of secondary air or waste gases as by a blower 22a to the hot gas pipes will insure a positive control of the heat entering the stove l0 and thus keep the temperature below the fusion point of the checker-wort. brick and assure long life of the brickwork and continuous performance during the life of the blast furnace 23.

A means for controlling the temperature of the hot blast is also provided which consists of introducing cold blast direct to the hot blast preferably at the hot blast valve 2 3. This is done by means of secondary air inlets 27 tapped from pipe 23:: and connected to hot blast valves 26.

It is to be noted that the combustion chamber, valves and piping are installed symmetrically with respect to the stoves, and the entire space required is substantially the same as the usual threestove arrangement of present-day blast furnace plants. The axes of the stoves and combustion chamber lie substantially in a common plane and each stove has a hot-gas pipe connected thereto on both sides of said plane. The construction is such that the entire installation is supported by the stoves themselves and permits expansion and contraction without distortion of the structure itself. In general, the arrangement of the combustion chamber, valves, piping, etc., is such that they are preferably supported from the top of the stoves; and the lower part of the combustion chamber, hot blast piping, etc., is suspended from a common support at a single upper level. Suitable supporting structure is provided at the lower portion of the combustion chamber l3 and can be spring-mounted to take care of the changes in shape due to expansion or can be the usual foundation provided for similar structures.

The combustion chamber [3, being readily accessible, can be provided with all known means of combustion control equipment and can be made fully automatic, and thereby reducing the use of manpower ordinaril required to operate conventional blast furnace stoves to a minimum.

After the combustion chamber I3 has been heated up from air temperatures at the start of operations, it operates continuously to furnish hot gases alternately to each of the stoves l0, thereby eliminating the alternate heating and cooling periods which is an inherent weakness of the conventional stove design heretofore in general use which has the combustion chamber located Within the stove itself. The maintaining of substantially uniform heat in the combustion chambe eliminate the repeated expansion and contraction and thereby insures a constant source of heat to the stoves for the duration of the furnace operation without necessitating the shutting down of the blast furnace in the interim period in order to make repairs to the stoves and combustion chamber, as is the ease in prior art stove construction.

The use of a separate combustion chamber l3 common to two or more stoves It also eliminates the necessity of having to disconnect and move the burners away from a stove in order to close same and permit the passage of cold blast air through the heated stove.

With conventional construction, whenever the stove is taken off gas and put on air, that is, after the checkerwork has been heated to the desired temperature by the fuel burned in the combustion chamber, and it is desired to heat the air used in the metallurgical process in the blast furnace, this air being at a pressure as high as 30 pounds per square inch, it is necessary to remove the gas burner from the combustion chamber and seal the opening with a heavy door, held in place by a powerful clamp, locked by means of a heavy wing nut that must be screwed tight enough by means of a large wrench to prevent leakage of air.

It is evident that it is not feasible to accomplish these operations by means of automatic control, whereas in the case of my invention, the combustion chamber is entirely removed from the valves controlling the gas and air, and the burner need never be removed. It is therefore a simple matter to control the valves supplying the burner, either manually or by means of automatic control.

From an engineering standpoint, it will be recognized that the installation of suificient heating surface to permit operation of the blast furnace by means of two stoves rather than three or more will give the well recognized benefit of having the maximum possible heating surface on the line to the furnace when the stove is on air. A conventional prior art two-pass stove, say 25 feet diameter by feet high, contains checkerwork having approximately 200,000 to 225,000 square feet of heating surface. The same size stove converted to a single-pass stove with exterior combustion chamber will have 300,000 to 325,000 square feet of heating surface. Therefore, two stoves of my design will have roughly, approximately the same heating surface as now contained in three stoves.

This means the elimination of one stove together with its auxiliary equipment including burners and burner system and replacing same with a single burner system having a common combustion chamber, flue system and valve system. Thus my invention will result in materially lower first cost, and an important operating advantage is made available by a more efiicient utilization of an increased amount of the heating surface, since an increased amount of checkerwork filling all the space within one stove is always performing the function of heating the blast for the furnace.

The independent exterior combustion chamber i3 is not limited by stove design and can be of sufficient volume and have a burner system 2! provided that will burn the necessary fuel and provide the necessary heat to the stove that is to be heated so that the same may be heated in any desired fraction of the time the second stove is furnishing heated air to the furnace. The use of a common exterior combustion chamber l3 permits selection of a suitable checkerbrick design that will give the maximum heating surface, heat storage, or given volume without fear that displacement of same due to combustion diiflculties will create trouble.

While I have shown and described in considerable detail an embodiment of the invention which is highly desirable, i am not limited to the use of two stoves for a furnace, since the arrangement can be readily adapted to the use of three or more stoves, if so desired, by provision of additional connections from the top of the combustion chamber I8 to each dome l8 and various other modifications may be made by those skilled the stoves, a pipe connecting the top of each stove the stove being used to preheat incoming air, a shut-off valve in each branch, a downcomer to which said branches are connected for conducting preheated air to a point of use and a pipe extending from each hot-gas pipe to a source of tempering gases for controlling the temperature of the hot gases entering the stove.

2. The apparatus defined by claim 1 characterized by anoutlet duct system for hot combustion gases connected to the bottom of both stoves, said outlet duct system being said source of tempering gases.

3. A regenerative hot-blast system comprising a pair of spaced stoves, a combustion tower between the stoves, a vertical valve cylinder between each stove and the tower. a pipe extending from the top of the tower to the side of each valve cylinder adjacent its lower end, a pipe extending from the side of each valve cylinder ad- Jacent its upper end to the top of the adjacent stove, the pipes and cylinder between the tower and each stove providing a passage for conducting hot combustion gases to the stove being heated, a second vertical valve cylinder arfiacent each stove, a branch extending from each of said second-mentioned pipes to the side of one of said second valve cylinders, a pipe connection between said second cylinders, a downcomer extending from said connection for conducting heated air to a point of use and a pipe extending from the bottom of each of said first-mentioned cylinders to a source of tempering gases for controlling the temperature of the hot gases entering the stove.

4. The apparatus defined by claim 3 characterized by an outlet duct system for hot combustion gases connected to the bottom of both stoves and means for supplying gases from said outlet duct system to said tempering-gas pipes.

FRED H. JOHNSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 358,500 Strobel Mar. 1, 1887 1,941,448 Isley Dec. 28, 1933 2,141,036 Daniels Dec. 20, 1938 2,163,149 Linder June 20, 1939 2,175,611 Linder Oct. 10, 19 39

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