GB2036270A - Soaking pits for ingots - Google Patents

Abstract

An ingot soaking pit 10 is covered by a removable lid 11 in which several self-recuperative burners 15 are mounted so that they direct their flames down into the pit 10. <IMAGE>

Description

SPECIFICATION Soaking pits for ingots This invention relates to ingot soaking pits and to lids for such pits.

A conventional ingot soaking pit comprises a cavity which is substantially rectangular in plan and in both lateral and longitudinal cross-section.

A burner has a flame discharge nozzle connected to a port, known as a flame port, which is formed in one of the end walls of the pit adjacent the top of the pit. Waste gases are exhausted from the pit through an exhaust port which is connected to a chimney.

A lid is mounted on wheels which run on tracks whereby it can be moved into or out of a position in which it covers the top of the pit. The tracks are recessed at the locations adopted by the wheels when the lid is positioned to cover the pit so that the wheels fall into the recesses and allow the lid to bed down upon the upper periphery of the side and end walls of the pit to close the pit, there being a seal formed between the lid and the upper perimeter of the side and end walls of the pit when the lid is seated thereon. A conventional lid is a massive structure but, in order to reduce the weight of such a lid by a substantial amount, say 10 times, it has been proposed that the lid be constructed of blocks of a ceramic fibre material.

Such soaking pits have been provided with an external heat recuperator in order to improve the thermal efficiency, the hot exhaust gases being passed through the recuperator en route to the chimney and air supplied to the burner to support combustion within the burner being heated by heat exchange within the recuperator with those hot exhaust gases. In such an arrangement the exhaust port is formed in the same end wall as the flame port below the flame port. It has proved difficult to satisfactorily heat ingots laid on the floor of a pit to which such a recuperator is fitted.

An object of this invention is to overcome the difficulty of satisfactorily heating ingots laid on the floor of a soaking pit when heat recuperating means are provided.

Broadly the invention comprises the use of at least one self-recuperative fluid fuel burner as the heating means of an ingot soaking pit, the self recuperative burner or burners being mounted in the removable lid of the pit so that the flame is directed downwards into the pit by the or each burner. Use of downwardly directed burners mounted in the lid results in a more satisfactory transfer of heat to the bottom of the pit than occurs when the pit is heated by a flame that is directed through a flame port that is formed in an end wall of the pit adjacent the lid.

Preferably the lid is formed of a ceramic fibrous material and conveniently is a structure which comprises blocks of such a material. Suitable blocks of ceramic fibrous material form the subject of the cognate British Patent Applications Nos.

31736/75 and 49043/75 (Serial No. 1548866) by Clinotherm Limited. Self-recuperative burners of the kind that forms the subject of British Patent Application No. 2445/77 are readily mounted in a lid having such a construction.

The or each burner may be provided with a device by which the distributiton of air fed to the combustion zone of the respective burner to support combustion is controlled, the device being adjustable to vary that air distribution and thereby to vary the shape of the flame and the velocity of the hot gaseous discharge from the respective burner. The device may comprise means adapted to change the ratio of air flow to the combustion zone via one path to air flow to the combustion zone via another path. Means may be provided for varying the air and/or fuel settings for each burner so that the rating of one or more of the burners can be altered where to or more such burners are provided.Heating of ingots laid in the pit can be controlled by adjustment of the shape of the flame, adjustment of the velocity of the hot gaseous discharge from the burner and/or by altering the rating of one or more of the bumers.

The air and fuel supply pipes for supplying air and fuel to the or each burner mounted on a lid may be disconnected from the lid and connected to the or each burner of a similar lid so that each lid can be replaced by another such lid. The air and fuel supply pipes may be flexible.

One or more self-recuperative burners may be mounted with their discharge nozzles connected to flame ports formed in the side or end walls of the pit if required.

According to another aspect of this invention a removable lid for an ingot soaking pit is provided with one or more self-recuperative burners which are mounted in it and which are orientated with respect to it so that the or each burner directs its flame downwards into the pit when the lid is seated over the top of the pit to close the pit and the or each burner is operated.

An ingot soaking pit in which this invention is embodied, as well as some modifications, will be described now by way of example with reference to the accompanying drawings, of which: Figure 1 is a plan view of a removable ingot soaking pit lid in which this invention is embodied positioned to close a simple ingot soaking pit; Figure 2 is a side elevation of the lid installation shown in Figure 1; Figure 3 is a section through the lid and the pit shown in Figures 1 and 2 with ingots located in the pit for soaking shown in phantom, the section being on the line Ill-Ill in Figure 2; Figure 4 is a partly sectioned view of a typical one of the burners that is mounted in the lid shown in Figures 1 to 3;; Figures 5 and 6 are views similar to Figure 3 illustrating modified forms of ingot soaking pit with which the lid shown in Figures 1 to 4 can be used.

Figures 1, 2 and 3 show an ingot soaking pit 10 closed by a removable lid 1 The pit 10 is substantially rectangular in plan and in both longitudinal and lateral cross-section and has plain flat side and end walls.

The lid 11 is rectangular and is an assembly of blocks of ceramic fibre material. Wheels 1 2 are journaled in parallel slots 13, which are formed in the underside of the lid 11 along an opposed pair of the edges of the lid 11. The wheels 12 run on rails 1 4 which extnd alongside the top of the pit 10, one on either side of the pit 10.

A number (conveniently six as shown) of selfrecuperative burners 1 5 are mounted in the lid 11 at equi-spaced locations along the longitudinal axis of the lid 11. Each burner 15 is mounted within a respective aperture 1 6 which extends from top to bottom of the lid 11 so that the combustion zone outlet 1 7 of that burner 1 5 and the entrance 18 to the exhaust passage 1 9 through that burner 1 5 communicate with the interior of the pit 1 0.

Each burner 1 5 is substantially as described and illustrated in the Complete Specification filed in connection with British Patent Application No.

2445/77. The combustion zone outlet 1 7 is formed by the smaller diameter end portion of a stepped through bore which is formed centrally in a block 21 of refractory material. A short metal tube 22 is a sliding fit in the other, larger diameter end portion of that stepped through bore and is fixedly mounted within the central aperture of a radial flange which is formed at the adjacent end of a metal tube 23 which separates the exhaust passage 1 9 from an annular main combustion air supply passage 24.

A burner head 25 is a sliding fit within the short tube 22. A fuel feed pipe 26 extends centrally through the burner 1 5 from the burner head 25 to which it is fixed. The burner head 1 5 is formed as a circular disc with a circumferential array of angularly spaced spacers 27 mounted on its outer cylindrical surface. The spacers.27 are the part of the head 25 that is slidably engaged with the bore of the short tube 22 and they form a circumferential array of open-ended axiallyextending passages between the outer cylindrical surface of the circular disc and the bore of the short tube 22. The disc'also has a central aperture 28 and several through bores 29 formed in it.The central aperture 28 communicates with the interior of the fuel feed pipe 26 and serves as a fuel port by which fuel is introduced into the combustion zone from the fuel feed pipe 26. The through bores 29, together with the open-ended axiall-extending passages formed between the disc, the spacers 27 and the short tube 22, are passages by which combustion air, which is fed to the burner head 25 through the main combustion air supply passage 24 enters the combustion zone.

It will be understood that the supply of combustion air will have been heated by heat exchange with exhausted products of combustion as it flowed along the main supply passage 24 to the burner head 25.

The burner head 25 carries an annular disc 31 which extends radially passed the end of the short tube 22 that projects from the central bore of the block 21. The disc 31 co-operates with the adjacent end of the short tube 22 to determine the effective cross-sectional area of the entranec to the array of open-ended axially extending passages formed by the spacers 27. The fuel feed pipe 26 is mounted in the end wall 32 of the burner casing that is remote from the block 21.

The mounting arrangement includes adjustment screws 33 so that the location of the fuel feed pipe 26 within the casing can be adjusted. Hence the location of the burner head 25, and thus the location of the annular disc 31, relative to the short tube 22 can be adjusted by manipulation of the adjustment screws 33. Such adjustment of the relative location of the disc 31 and the tube 22 changes the effective cross-sectional area of the entrance to the array of open-ended axiallyextending cylindrical passages and thus changes the ratio of the flow of combustion air through those passages to the flow of combustion air through the through bores 29. A change in that ratio is a change in the distribution of combustion air fed to the combustion zone.Hence the means by which the relative location of the annular disc 31 and the short tube 22 can be adjusted is a means for adjusting the distribution of combustion air fed to the combustion zone. The shape of the resultant flame and the velocity of the hot gaseous discharge through the outlet 1 8 can be varied by varying the distribution of combustion air fed to the combustion zone.

The end of the fuel feed pipe 26 of each burner 1 5 outside the casing of that burner 1 5 is connected via a respective fuel flow control valve 34, a respective flexible pipe 35 and a respective disconnectable coupling 36 to a main fuel supply pipe 37.

The combustion air inlet 38 of each burner 15 is connected via a respective air flow control valve 39, a respective flexible pipe 41 and a respective disconnectable coupling 42 to a main air supply pipe 43.

In order to heat soak ingots, the lid 10 is first displaced to one side of the pit 11 by being rolled along the track formed by the rails 14. If the flexible pipes 35 and 41 allow, the lid 10 may be displaced without being disconnected from the main fuel and air supply pipes 37 and 43 otherwise the couplings 36 and 42 must be uncoupled before the lid 10 is moved.

The ingots are then inserted into the pit 11, as shown at 44 in Figure 3, and the lid 10 replaced to cover the pit 11. the couplings 36 and 42 are remade if they were uncoupled.

The required rating of each burner 1 5 is set by operation of the respective fuel flow control valve 34 and/or the respective air flow control 39 as necesary, and any adjustments to the relative location of the annular disc 31 and the short tube 22 of each burner 1 5 necessary to provide the required flame shape and velocity of hot gaseous discharge from that burner 1 5 are made by appropriate adjustment of the adjustment screws provided on that burner 1 5.

The burners 1 5 are then fixed so that they direct their flames and hot gaseous discharge down into the pit 11 for a sufficient time to heat soak the ingots 44 whereafter the burners 1 5 are turned off and the lid 10 displaced to uncover the pit 11 and allow removal of the ingots 44.

Provision of each burner 1 5 with flexible air and fuel supply pipes and disconnectable couplings enables one lid 11 to be replaced by another, similar lid 11 to cover the same pit 10, the flexible pipes 35 and 43 of the replacement lid 11 being connected to the main supply pipe 37 and 43 by the couplings 36 and 42 in place of those of the replaced lid 11.

Figure 5 shows that a self-recuperative burner 45, similar to the burners 1 5, may be mounted with its discharge nozzle connected to a flame port 46 formed in a side wall of the pit 47 which is covered by a lid 11. Figure 6 shows that a selfrecuperative burner 48, similar to the burners 1 5 and 45, may be mounted with its discharge nozzle connected to a flame port 49 in an end wall of a pit 51 which is covered by a lid 11.

Claims (12)

1. A removable lid for an ingot soaking pit, the lid being provided with one or more selfrecuperative fluid fuel burners which are mounted in it and which are orientated with respect to it so that the or each burner directs its flame downwards into the pit when the lid is seated over the top of the pit to close the pit and the or each burner is operated.

2. A removable lid according to Claim 1, provided with more than one such burner and means for varying the air and/or fuel settings for each burner so that the rating of one or more of the burners can be altered.

3. A removable lid according to Claim 1 or Claim 2, wherein the or each burner is provided with a device by which the distribution of air fed to the combustion zone of the respective burner to support combustion is controlled, the device being adjustable to vary that air distribution and thereby to vary the shape of the flame and the velocity of the hot gaseous discharge from the respective burner.

4. A removable lid according to Claim 3, wherein the device comprises means adapted to change the ratio of air flow to the combustion zone via one path to air flow to the combustion zone via another path.

5. A removable lid according to Claim 1, Claim 2, Claim 3 or Claim 4 and formed of a ceramic fibrous material.

6. A removable lid according to Claim 5, which is a structure which comprises blocks of ceramic fibrous material.

7. A removable lid according to any one of Claims 1 to 6 in combination with an ingot soaking pit which has its top covered by the lid when the lid is seated over it to close it.

8. A reamovable lid according to any one of Claims 1 to 6 in combination with an ingot soaking pit which has its top covered by the lid when the lid is seated over it to close it, there being air and fuel supply pipes for supplying air and fuel to the or each burner mounted in the lid and disconnectable coupling means by which the or each burner in the lid can be disconnected from the air and fuel supply pipes.

9. A removable lid in combination with an ingot soaking pit as claimed in Claim 8, wherein the air and fuel supply pipes are flexible.

10. A removable lid in combination with an ingot soaking pit as claimed in Claim 7, Claim 8 or Claim 9, mounted with their discharge nozzles connected to flame ports formed in the side or end walls of the pit.

11. A removable lid for an ingot soaking pit substantially as described hereinbefore with reference to and as illustrated in Figures 1 to 4 of the accompanying drawings.

12. An ingot soaking pit covered by a removable lid substantially as described hereinbefore with reference to and as illustrated in Figures 1 to 4 of the accompanying drawings or modified substantially as described hereinbefore with reference to and as illustrated in Figure 5 or Figure 6 of the accompanying drawings.