US3690636A - Recuperative furnaces - Google Patents

Recuperative furnaces Download PDF

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Publication number
US3690636A
US3690636A US94735A US3690636DA US3690636A US 3690636 A US3690636 A US 3690636A US 94735 A US94735 A US 94735A US 3690636D A US3690636D A US 3690636DA US 3690636 A US3690636 A US 3690636A
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United States
Prior art keywords
passages
flue gas
air
recuperator
area
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Expired - Lifetime
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US94735A
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English (en)
Inventor
Robert A Shannon
Charles A Waters
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United States Steel Corp
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United States Steel Corp
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Assigned to USX CORPORATION, A CORP. OF DE reassignment USX CORPORATION, A CORP. OF DE MERGER (SEE DOCUMENT FOR DETAILS). Assignors: UNITED STATES STEEL CORPORATION (MERGED INTO)
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
    • F28F21/00—Constructions of heat-exchange apparatus characterised by the selection of particular materials
    • F28F21/04—Constructions of heat-exchange apparatus characterised by the selection of particular materials of ceramic; of concrete; of natural stone
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21B—MANUFACTURE OF IRON OR STEEL
    • C21B9/00—Stoves for heating the blast in blast furnaces
    • C21B9/02—Brick hot-blast stoves
    • C21B9/06—Linings

Definitions

  • ABSTRACT Recuperative fumaces such as soaking pits, have recuperators formed of sets of ceramic tiles arranged end to end with aligned holes in each set of tiles forming one series of passages for the flue gas and openings between the sets of tiles forming a second series of passages for the air to be heated.
  • the heated air from the recuperator is directed through an air tunnel to an entry or burner port where it is mixed with coke oven gas or other fuel.
  • Combustion is completed in the combustion or heating chamber which also receives the ingots to be heated.
  • the burrlt gases pass from the chamber through a flue gas port to the recuperator. It is impossible to maintain a gas tight connection between the tile.
  • the entry port area is made at least approximately 75 percent (preferably 100 percent) of the cross sec'- tional area of the air tunnel and the flue port area is made at least approximately 75 percent (preferably 100 percent) of the total cross sectional area of the flue gas passages in the recuperator.
  • recuperative furnaces and more particularly to soaking pits for heating steel ingots in which the recuperator is made of a plurality of refractory ceramic tiles laid up dry. The reason for laying them up is that provision must be made for expansion. If the tiles are cemented together to make the joints gas tight cracks, either in the tiles or joints, will result due to expansion and contraction so that. the end result is the same as if they were laid upfdry. In both cases air leakage occursinto the inside passages of the tile which carry the flue gas from the air passages formed between the tiles.
  • Recuperators of this general type are shown in Morton et al. US. Pat. No. 2,092,402 dated Sept. 7, 1937. Air is blown through the recuperators under pressure and passes into the combustion and heating chamber of the soaking pit around or in contact with. the fuel with which it mixes and burns. The products of combustion or flue gas pass from the heating chamber and through the openings in the recuperator tile; Furnaces using this type of recuperator have b'eenin use for at least 30 years and-prior to our invention problems arose due to leakage of the combustion air into the flue gas.
  • this condition can be corrected by increasing the area of the burner and fluegas ports without loss of mixing of the air and fuel.
  • the area of the burner port must be increased so that it is at least 75 percent (preferably at least 100 percent) of the area of the air tunnel and the area of the flue gas ports must be increased until they are at least 75 percent (preferably at least 100 percent) of the total area of the flue gas openings in the recuperator.
  • Another object is to provide a soaking pit which heats ingots substantially faster than similar soaking pits not utilizing our invention.
  • Still another object is to provide such soaking pits in which there is a substantial fuel saving.
  • FIG. 1 is a schematic view of a soaking pit, mostly in vertical section except for the flues and stack;
  • FIG. 2 is a view on an enlarged scale taken on the line Il--II ofFIG'.1; t
  • FIG. 3 is a vertical sectional view on an enlarged scale of a portion of the recuperator
  • FIG. 4 is a view taken on the line IV--IV of FIG. 3;
  • FIG. 5 is an enlarged view of a tion.
  • reference numeral 2 indicates a soakingpit combustion and heating chamber having a coke bottom detail of our inven- 4 with an entry or burner port 6 therein.
  • a removable cover17 isprovided' for chamber 2. Flue gasflows from the chamber 2 through ports 8 located at opposite sides of the chamber. ltis desirable that theports 8 be provided with beveled inlets 9'to decrease-pressure drop. This is also done at theentrances to other ports.
  • a pair of recuperators 10 are provided for receiving the flue gas. .Each of the recuperators 10 includes a number of horizontal baffles 11. In FIG.
  • each bafile '11 is part of a horizontal wall covering the the full cross section of the recuperator and is made up of a plurality of ceramic tiles l2 hav ing an octagonal outer surface and a circular central opening 13. The tiles are laid up side by side with spaces 14 between tiles; The tiles in each baffle 11 are arranged inthe same MANNER as the adjacent bafl'les. Arranged between adjacent bames 11 are a plurality of thin walled ceramic tiles 15 one between each pair of tiles 12.
  • the tiles 15 have an octagonal outer surface smaller than that of tiles 12 and a circular central opening 16 the same size as opening 13.
  • the tiles 15 have an octagonal outer surface smaller than that of tiles 12 and a circular central opening 16 the same size as opening 13.
  • Air is delivered by means of blowers 18 into the lower end of the recuperators.
  • tiles 20 are inserted into some of the spaces 14 of each of the horizontal baflles 11 so that the air follows the path of travel shown by arrows in FIG. 1.
  • the baffles 11 of FIG. 1 are formed by the combination of tiles 12 and 20 and the open space shown in FIG. 1 actually consists of tiles 12 without the tiles 20 inserted in the spaces 14.
  • recuperator are also closed by tiles where necessary.
  • the air passes from the top of the recuperators through air tunnels 22 to the burner port 6.
  • Fuel gas such as coke oven gas passes to the burner port 6 through a gas pipe or port 24.
  • a hood 26 is supported on the pipe 24 by means of three lugs 28 so as to provide a peripheral opening 30 for the gas.
  • a central opening 32 is provided through the top of hood 26.
  • the total area of the openings 30 and 32 is substantially equal to the area of the pipe 24 with the opening 32 providing only a small amount of the area so that most of the fuel gas is diverted into the air streams from the recuperators.
  • Hoods or divertors of this general type have been used in the past on some types of burners. It will be understood that other types of recuperators maybe used.
  • the baffles 11 could be omitted.
  • the flue gas passes downwardly through the recuperators l and generally horizontal through flues 34 to a vertical stack 36 in the usual manner.
  • the pressure drop from the outside to the inside of the tiles 12 adjacent the top of the recuperators was approximately 0.07 of an inch of water, whereas subsequent to the change in construction, this drop decreased to approximately 0.015 inch of water. For efiicient and proper operation this drop should not exceed 0.025 inch ofwater.
  • the invention may be used with other types of recuperative furnaces or soaking pits.
  • the invention is being used on side fired pits of the type generally shown in Morton et al. US. Pat. No. 2,414,888 dated Jan. 28, 1947. It has been used in this type of fumace equipped with two air ports and two flue gas ports. In some instances a gas burner hood has been used and in others it is omitted.
  • the invention is also applicable to soaking pits of the type shown in Suydarn US. Pat. No. 3,198,855 dated Apr. 24, 1962 and Mawhinney US. Pat. No. 1,915,470 dated June 27, 1933.
  • recuperator and air tunnel refer to a single recuperator or to any number of individual recuperators arranged in parallel, it being obvious that it is immaterial whether the series of passages are arranged in one unit or in a plurality of units.
  • entry or burner port as used in the claims and the term flue gas port as used in the claims refers to either single or multiple ports, it being obvious that it is the total port area which is important.
  • the heating then continues for 1% hours with the fuel continuing to be cut until it is at a minimum of approximately 6,000 cu. ft. per hour which is sufficient to hold the pit temperature at control point. There is no change in this part of the operation.
  • the soaking period of 2 hours begins and after 2 hours the ingots are removed as they are needed by the rolling mill.
  • the total time required is 230 minutes, as compared to 315 minutes prior to our modification.
  • the ingots may be held more than 3 hours before charging into the pit and in some instances the ingots may be at ambient temperature.
  • the BTU consumed per ton of ingot averaged approximately 1,122,000; 912,000; and 791,000 before conversion and 451,000; 423,000; and 398,000 after conversion.
  • the ingot tons per hour averaged 13. 19, 11.2, and 13.2 before conversion and 26.53, 18.6 and 19.5 after conversion.
  • Two pits of the side fired type were converted by increasing the diameter of the air or burner ports from 15 to 18 in. and increasing the flue gas port area from 12 to 18 sq. ft.
  • the BTU consumed per ton of ingot averaged approximately 1,226,000 and 1,878,000 before conversion and 476,000 and 476,000 after conversion.
  • the ingot tons per hour averaged 9.1 1 and 9 before conversion and 16.4 and 17.2 after conversion.
  • a recuperator formed of sets of ceramic tiles arranged end to end with aligned holes in each set of tiles forming one series of passages and openings between the sets of tiles forming a second series of passages, an entry port to said combustion chamber for receiving air from said recuperators and fuel, means for delivering air to one end of one of said series of passages, an air tunnel connecting the other end of said air passages to said entry port, and a flue gas port for receiving burnt gases from said combustion chamber and delivering it to the other of said passages; the improvement comprising an entry port area at least approximately 75 percent of the area of said air tunnel, and a flue gas port area at least approximately 75 percent of the total area of said flue gas passages.
  • a furnace according to claim 1 in which the combustion chamber is a pit for receiving steel ingots, said entry port extends downwardly from said pit, said flue gas port is in two sections one in each of two opposed side walls of said pit, said recuperator is in two sections one connected to each of said gas port sections and said air tunnel is in two sections one extending between each recuperator and said entry port,
  • a furnace according to claim 7 including a vertical pipe below and in vertical alignment with said entry port, and means on the top of said pipe for directing gas outwardly at an angle from the vertical.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Ceramic Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Air Supply (AREA)
  • Waste-Gas Treatment And Other Accessory Devices For Furnaces (AREA)
  • Vertical, Hearth, Or Arc Furnaces (AREA)
US94735A 1970-12-03 1970-12-03 Recuperative furnaces Expired - Lifetime US3690636A (en)

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US9473570A 1970-12-03 1970-12-03

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US (1) US3690636A (es)
AU (1) AU456753B2 (es)
BR (1) BR7108002D0 (es)
CA (1) CA943762A (es)
DE (1) DE2159842A1 (es)
ES (1) ES397665A1 (es)
FR (1) FR2117286A5 (es)
GB (1) GB1341316A (es)
IT (1) IT943164B (es)
NL (1) NL7116601A (es)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4029465A (en) * 1975-02-06 1977-06-14 Hague International Corporation Energy conserving process furnace system and components thereof
US5018707A (en) * 1989-03-14 1991-05-28 Gas Research Institute Heating furnace
US20120255441A1 (en) * 2009-03-09 2012-10-11 Mitsubishi Heavy Industries, Ltd. Air pollution control apparatus and air pollution control method
US20130209948A1 (en) * 2010-05-04 2013-08-15 Rudiger Eichler Method for increasing the temperature homogeneity in a pit furnace

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1824876A (en) * 1927-09-09 1931-09-29 Chapman Stein Company Recuperative soaking pit
US2079560A (en) * 1934-02-14 1937-05-04 Amco Inc Recuperative soaking pit furnace
US2092402A (en) * 1934-08-07 1937-09-07 Amco Inc Recuperator tile structure
US2124888A (en) * 1934-07-05 1938-07-26 Amco Inc Recuperative soaking pit furnace
US2126095A (en) * 1936-10-12 1938-08-09 William T Dean Soaking pit and like heating furnace
US2297696A (en) * 1940-10-29 1942-10-06 Elder Harold Griffin Furnace
US2414888A (en) * 1941-07-03 1947-01-28 Amsler Morton Company Recuperative soaking pit furnace
US2563683A (en) * 1946-02-07 1951-08-07 United States Steel Corp Gas burner for soaking pit furnaces and the like
US3198855A (en) * 1962-04-24 1965-08-03 Loftus Engineering Corp Method of operating soaking pits

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1824876A (en) * 1927-09-09 1931-09-29 Chapman Stein Company Recuperative soaking pit
US2079560A (en) * 1934-02-14 1937-05-04 Amco Inc Recuperative soaking pit furnace
US2124888A (en) * 1934-07-05 1938-07-26 Amco Inc Recuperative soaking pit furnace
US2092402A (en) * 1934-08-07 1937-09-07 Amco Inc Recuperator tile structure
US2126095A (en) * 1936-10-12 1938-08-09 William T Dean Soaking pit and like heating furnace
US2297696A (en) * 1940-10-29 1942-10-06 Elder Harold Griffin Furnace
US2414888A (en) * 1941-07-03 1947-01-28 Amsler Morton Company Recuperative soaking pit furnace
US2563683A (en) * 1946-02-07 1951-08-07 United States Steel Corp Gas burner for soaking pit furnaces and the like
US3198855A (en) * 1962-04-24 1965-08-03 Loftus Engineering Corp Method of operating soaking pits

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4029465A (en) * 1975-02-06 1977-06-14 Hague International Corporation Energy conserving process furnace system and components thereof
US5018707A (en) * 1989-03-14 1991-05-28 Gas Research Institute Heating furnace
US20120255441A1 (en) * 2009-03-09 2012-10-11 Mitsubishi Heavy Industries, Ltd. Air pollution control apparatus and air pollution control method
US8361194B2 (en) 2009-03-09 2013-01-29 Mitsubishi Heavy Industries, Ltd. Air pollution control apparatus and air pollution control method
US8382882B2 (en) * 2009-03-09 2013-02-26 Mitsubishi Heavy Industries, Ltd. Air pollution control apparatus and air pollution control method
US8425669B2 (en) 2009-03-09 2013-04-23 Mitsubishi Heavy Industries, Ltd. Air pollution control apparatus and air pollution control method
US20130209948A1 (en) * 2010-05-04 2013-08-15 Rudiger Eichler Method for increasing the temperature homogeneity in a pit furnace

Also Published As

Publication number Publication date
ES397665A1 (es) 1975-03-01
DE2159842A1 (de) 1972-06-29
IT943164B (it) 1973-04-02
BR7108002D0 (pt) 1973-04-05
AU3627771A (en) 1973-06-07
CA943762A (en) 1974-03-19
GB1341316A (en) 1973-12-19
NL7116601A (es) 1972-06-06
FR2117286A5 (es) 1972-07-21
AU456753B2 (en) 1974-12-11

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Owner name: USX CORPORATION, A CORP. OF DE, STATELESS

Free format text: MERGER;ASSIGNOR:UNITED STATES STEEL CORPORATION (MERGED INTO);REEL/FRAME:005060/0960

Effective date: 19880112