US3212763A

US3212763A - Reheating furnace

Info

Publication number: US3212763A
Application number: US349608A
Authority: US
Inventors: Justin E Foldessy
Original assignee: United States Steel Corp
Current assignee: United States Steel Corp
Priority date: 1964-03-05
Filing date: 1964-03-05
Publication date: 1965-10-19
Anticipated expiration: 1982-10-19

Description

Oct. 19, 1965 J. E. FOLDESSY 3,212,763

REHEATING FURNACE Filed March 5, 1964 4 Sheets-Sheet 1 INVENTOR. JUST/IV E FOLDESS) Oct. 19, 1965 J. E. FOLDESSY REHEATING FURNACE 4 Sheets-Sheet 2 Filed March 5, 1964 JUS T/N E. FOL 0555 Y B A! farney Oct. 19, 1965 Filed March 5, 1964 J. E. FOLDESSY REHEATING FURNACE 4 Sheets-Sheet 3 INVENTOR. JUS T/N E. FOLDESS Y Attorney Oct. 19, 1965 J. E. FOLDESSY 3,212,763

REHEATING FURNACE Filed March 5, 1964 4 Sheets-Sheet 4 INVENTOR. JUST/N E. FOLDESSY Attorney United States Patent Filed Mar. 5, 1964, Ser. No. 349,608 4 Claims. (Cl. 2636) This invention relates to an improved furnace for reheating semifinished metal shapes, such as steel slabs, blooms, billets or the like.

A conventional continuous reheating furnace includes an elongated enclosure and a set of water-cooled skids which support the work as it travels through the enclosure. Such furnaces are equipped with one or more recuperators which utilize sensible heat in the products of combustion to preheat incoming combustion air. The recuperators usually are located above or alongside the furnace enclosure and are a costly adjunct to install and maintain. Water-cooling the skids takes heat from the furnace, and any leakage is destructive to the furnace refractory. The work usually has cool spots, known as skid marks, in areas which contact the water-cooled skids.

An object of my invention is to provide an improved reheating furnace which largely overcomes the foregoing disadvantages, that is, in which the skids are air-cooled, and in which air heated by contact with the skids is used as combustion air in the furnace, thus diminishing the size of recuperators needed.

A more specific object is to provide an improved reheating furnace in which the skids and their supports are air-cooled in sections, and in which air heated in the skids is used as combustion air in the furnace, either passing through recuperators for further heating or blending with heated air from the recuperators before reaching the furnace.

In the drawings:

FIGURE 1 is a top plan view of a furnace constructed in accordance with my invention;

FIGURE 2 is a longitudinal vertical section on line IIII of FIGURE 1;

FIGURE 3 is a horizontal section on line IIIIII of FIGURE 2;

FIGURE 4 is a vertical cross section on line IV-IV of FIGURE 2; and

FIGURE 5 is a vertical cross section on line VV of FIGURE 2.

The drawings show a continuous reheating furnace 10, which can be of conventional construction apart from the skids and the air distribution system, hereinafter described. The furnace enclosure includes the usual bottom wall 12, roof 13 and side walls 14. The ends of the enclosure have

doors

15 and 16 through which work W enters and leaves the furnace. Work-supporting skids 17, constructed in accordance with my invention, extend from the entry door 15 to .a short hearth section 18 in front of the exit door 16. The furnace illustrated has a first heating zone 19 above the skids, second and

third heating zones

20 and 21 below the skids, and a soaking zone 22 above the hearth section 18, but the number and arrangement of zones can vary. The furnace illustrated is counterfired, and each zone has burners 23. Products of combustion discharge through an olftake 24 in the roof 13 near the entry end and pass through a recuperator 25 above the furnace enclosure and thence out a stack, not shown. The recuperator also can be of conventional construction, although preferably smaller than normally included with a furnace of any given size. A cold air main 26, equipped with a blower 27, extends along one side of the recuperator for introducing cold air thereto. A hot air main 28 extends along the other side of the recuper- 3,212,763 Patented Oct. 19, 1965 :ator for receiving the heated air therefrom and carrying it to the burners 23. The burners also are connected to a suitable fuel supply, not shown.

In accordance with my invention, I construct skids 17 in a plurality of sections 17a, 17b and 17c placed end-toend. Each section includes a plurality of longitudinal pipes 29, a plurality of transverse pipes 30, and a plurality of supports 31. The work rests on the longitudinal pipes 29, which overlie the transverse pipes 30. As FIG- URE 5 shows, each support 31 is formed of a pipe of inverted U-shape, and the supports are arranged in opposed pairs under the transverse pipes 30.

A cooling air main 32, equipped with a blower 33, extends horizontally alongside the lower portion of the furnace enclosure and has

transverse branches

32a, 32b and 320 corresponding in number with the skid sections 17a,

' 17b and 170. I connect the longitudinal pipes 29 at the entry end of the skid sections 17a, 17b and 17c to the

branches

32a, 32b and 320 respectively via vertical pipes 34 which extend upwardly from the branches. I connect the other ends of pipes 29 to tranverse pipes 35 via vertical pipes 36, which extend downwardly from pipes 29. Pipes 35 are located immediately beneath the bottom wall 12 of the furnace enclosure, but lead upwardly at one side thereof to a collector main 37, which extends lengthwise of the enclosure near the cold air main 26. I connect one end of each transverse pipe 30 of the skid sections to the cooling air main 32 via respective vertical pipes 38 which extend upwardly from the main. I connect the other end of each pipe 30 to the collector main 37 via vertical pipes 39 which extend both upwardly and downwardly from pipes 30. I connect opposite ends of the supporting pipes 31 to the cooling air main 32 and to the vertical pipes 39 via

horizontal pipes

40 and 41 respectively, arranged as shown in FIGURE 5.

I connect the collector main 37 to the cold air main 26 via a connecting main 42. I also connect the collector main to the hot air main 28 via another connecting main 43. The connecting

mains

42 and 43 are equipped with air control valves 44 and 45 respectively. The collecting main 37 has an air bleeder 46.

In operation, I fire the furnace and push work W therethrough in the usual manner to heat the work for rolling. I also use the recuperator 25 to preheat incoming combustion air. I blow cold air from the cooling air main 32 through

pipes

29, 30 and 31 which form the skid sections. This air of course is heated as it passes through the pipes. The air then goes to the collector main 37, from which I can direct it either to the cold air main 26 or the hot air main 28 by proper adjustment of valves 44 or 45. In either event it ultimately reaches the burners, where it is utilized as preheated combustion air in con junction with air preheated in the recuperator. As a further alternative, I can bleed air from the collector main via the bleeder 46 in the event there is an excess.

From the foregoing description it is seen that my invention affords a simple effective arrangement for cooling the skids of a continuous reheating furnace and overcoming disadvantages of previous arrangements. By forming the skids in sections, I overcome any likelihood of portions of the skids becoming overheated. Each section receives air while the air is relatively cool. The capacity of recuperator needed is dimnished substantially with a resulting cos-t saving.

While I have shown and described only a single embodiment of my invention, it is apparent that modifications may arise. Therefore, I do not wish to be limited to the disclosure set forth but only by the scope of the appended claims.

I claim:

1. In a continuous reheating furnace which includes an enclosure adapted to have work travel therethrough, burners mounted Within said enclosure for heating the work therein, a'recuperator, an olftake connecting said enclosure and said recuperator for carrying products of combustion to the recuperator, a cold air main connected to said recuperator, and a hot air main connected to said recuperator and to said burners for supplying preheated combustion air to the burners, the combination therewith of a skid construction within said enclosure for supporting the work, said skid construct-ion comprising a plurality of aligned sections placed end-to-end, each formed of a plurality of pipes extending longitudinally of the enclosure, transverse pipes underneath said first-named pipes, and supporting pipes underneath said transverse pipes, each of said longitudinally extending pipes having a continuous fixed upper surface, means connected to said pipes for supplying cooling air directly to each of said sections, and means connecting said pipes with one of said mains for carrying air heated in the pipes to said burners to be used as preheated combustion air in conjunction with air preheated in said recuperator.

2. A combination as defined in claim 1 in which said last-named means includes a collector main to which said pipes are connected, a main connecting said collector main and said cold air main, a main connecting said collector main and said hot air main, valves in each of said connecting mains, and a bleeder valve in said collecting main.

3. In a continuous reheating furnace which includes an enclosure adapted to have work travel therethrough, and burners mounted within said enclosure for heating the work, the combination therewith of a skid construction within said enclosure for supporting the work, said skid construction comprising a plurality of aligned sections placed end-to-end, each section being formed of a plurality of pipes extending longitudinally of the enclosure and support means for said pipes, each of said pipes hav-- ing a continuous fixed upper surface, a cooling air main, means connecting the pipes of each section directly to said main to supply relatively cool air to each section to prevent any portion of the skid construction from becoming overheated, and means connecting the pipes of 4 each section with said burners for carrying air heated in the pipes to the burners to be used as preheated combustion air.

4. In a continuous reheating furnace which includes an enclosure adapted to have work travel therethrough, burners mounted within said enclosure for heating the work, a recuperator, an offtake connecting said enclosure and said recuperator for carrying products of combustion to the recuperator, a cold air main connected to said recuper-ator, and a hot air main connected to said recuperator and to said burners for supplying preheated combus tion air to the burners, the combination therewith of a skid construction within said enclosure for supporting the work, said skid construction comprising a plurality of aligned sections placed end-to-end, each section being formed of a plurality of pipes extending longitudinally of the enclosure and additional pipes supporting said firstnam d pipes, each of said first-named pipes having a continuous fixed upper surface, a cooling .air main, means connecting the first-named pipes and the additional pipes of each section directly to said cooling air main to supply relatively cool air to the .pipes of each section to prevent any portion of the skid construction from becoming overheated, and means connecting the pipes of each section to one of said cold air and hot air mains for carrying air heated in the pipes to said burners to be used as preheated combustion air in conjunction with air preheated in said recuperator.

References Cited by the Examiner UNITED STATES PATENTS 1,193,245 8/ 16 Dressler 263-6 X 1,515,852 11/24 Ferm 263--6 1,551,945 9/25 Fitch 263-6 X 1,634,858 7/27 Stoop 263-6 3,148,868 9/64 Sidwell 263-6 X FOREIGN PATENTS 1,146,514 4/63 Germany.

CHARLES SUKALO, Primary Examiner.

Claims

3. IN A CONTINUOUS REHEATING FURANCE WHICH INCLUDES AN ENCLOSURE ADAPTED TO HAVE WORK TRAVEL THERETHROUGH, AND BURNERS MOUNTED WITHIN SAID ENCLOSURE FOR HEATING THE WORK, THE COMBINATION THEREWITH OF A SKID CONSTRUCTION WITHIN SAID ENCLOSURE FOR SUPPORTING THE WORK, SAID SKID CONSTRUCTION COMPRISING A PLURALITY OF ALIGNED SECTIONS PLACED END-TOEND, EACH SECTION BEING FORMED OF A PLURALITY OF PIPES EXTENDING LONGITUDINALLY OF THE ENCLOSURE AND SUPPORT MEASN FOR SAID PIPES, EACH OF SAID PIPES HAVING A CONTINUOUS FIXED UPPER SURFACE, A COOLING AIR MAIN, MEANS CONNECTING THE PIPES OF EACH SECTION DIRECTLY TO SAID MAIN TO SUPPLY RELATIVELY COOL AIR TO EACH SECTION TO PREVENT ANY PORTION OF THE SKID CONSTRUCTION FROM BECOMING OVERHEATED, AND MEANS CONNECTING THE PIPES OF EACH SECTION WITH SAID BURNERS FOR CARRYING AIR HEATED IN THE PIPES TO THE BURNERS TO BE USED AS PREHEATED COMBUSTION AIR.