Heating stock in a heating chamber

A method for heating stock comprises feeding stock 9 to be heated into a heating chamber 1, causing heating gas to enter the heating chamber 1 to heat the stock 9 and leave the heating chamber 1 after heating the stock 9 and then removing the stock 9 from the heating chamber 1 on completion of heating, the heating gas being allowed to enter the heating chamber 1 by way of a plenum chamber 2,3 which communicates with the heating chamber 1. The heating gas may be supplied by a regenerative burner 4,5 as fuel combustion products. Where there are two such burners 4,5 one may be firing while the other is flueing.

The present invention relates to the heating of stock in a heating chamber 
to which a heating gas is supplied to heat the stock. According to one 
aspect of the invention, a method is provided for heating stock comprising 
feeding stock to be heated into a heating chamber, causing heating gas to 
enter the heating chamber to heat the stock and leave the heating chamber 
after heating the stock and then removing the stock from the heating 
chamber on completion of heating, the heating gas being allowed to enter 
the heating chamber by way of a plenum chamber which communicates with the 
heating chamber. 
According to another aspect of the present invention apparatus is provided 
for heating stock comprising a heating chamber for receiving the stock for 
heating with a heating gas, a plenum chamber which communicates with the 
heating chamber, a fuel-fired burner for supplying heating gas to the 
plenum chamber for distribution to the heating chamber, there being means 
for exhausting waste gas from the heating chamber. 
According to a further aspect of the present invention apparatus is 
provided for heating stock comprising a heating chamber for receiving the 
stock for heating with a heating gas, a first plenum chamber adjoining a 
first side of the heating chamber and communicating with the chamber 
through the first side, a second plenum chamber adjoining a second side of 
the heating chamber and communicating with the chamber through the second 
side, a first regenerative type burner communicating with the first plenum 
chamber and a second regenerative type burner communicating with the 
second plenum chamber, each burner being adapted on its firing cycle to 
supply heating gas to its plenum chamber for subsequent distribution to 
the heating chamber for heating the stock and on its flueing cycle to 
receive from its plenum chamber waste gas discharged from the heating 
chamber, the arrangement being that, in use, while one burner is firing 
the other is flueing.

Referring to the drawings, the apparatus comprises a heating chamber 1, two 
plenum chambers 2, 3, each communicating with the heating chamber 1 and a 
pair of regenerative type burners 4, 5, one burner communicating with a 
matching plenum chamber. 
The heating chamber 1 comprises an elongate generally rectangular or 
circular cross section furnace which is designed to reheat metal stock 
such as large section round or square billets. 
The chamber 1 forms an elongate enclosure 6 to receive the stock to be 
heated such as a long billet (eg. an aluminum log) or a multiplicity of 
billets (such as those used in forging or extrusion). The enclosure 6 is 
closed at either end by doors 7 and 8 which are raisable vertically to 
permit entry and discharge of a billet (such as that shown by reference 
9). The billet 9 enters via door 7 and leaves via door 8. 
The floor 10 of the enclosure 6 is provided with a means of stock conveying 
such as driven rolls 11 along which the billet 9 can be moved into and out 
of the enclosure 6. 
Along opposite sides of the heating chamber and of the same length, are the 
plenum chambers 2, 3, each of which forms a generally cylindrical bore 14 
extending parallel to the adjoining side of the furnace and each of which 
communicate with the heating chamber 1 by way of several longitudinally 
spaced ports 15 along the length of the heating chamber 1. The plenum 
chamber 2 is displaced slightly vrtically below the plenum chamber 3 and 
the plenum chambers 2, 3 and the heating chamber 1 are refractory lined 16 
and contained in an outermost casing 17. 
Each plenum chambers 2, 3 is either closed at one end (not shown) and is 
provided at the other end with a regenerative type burner 4, 5 each of 
which is arranged adjacent opposite ends of the heating chamber 1 or 
provided with regenerative type burners on both ends. 
The regenerative burners 4, 5 are of conventional construction and comprise 
a fuel-fired burner 18 and associated regenerator chamber 19. 
In a firing mode each regenerative burner supplies its plenum chamber with 
heating gas in the form of fuel combustion products. In a flueing mode 
each burner receives waste gas from its plenum chamber for subsequent 
discharge. 
The regenerator chamber 19 communicates with the burner part 18 by way of a 
duct 20. 
During firing the regenerator chamber 19 supplies the burner part 18 with 
preheated air by way of the duct 20 for combustion with fuel, eg. natural 
gas supplied to the burner part 18 by a fuel pipe 21. The air for 
preheating in the regenerator 19 is supplied to the regenerator 19 by a 
pipe 22. 
During flueing waste gas entering the burner part 18 is discharged to the 
regenerator chamber 19 by way of the duct 20 and is discharged from the 
regenerator 19 by way of the pipe 22. 
In use, the stock heating can either be "batch" or "continuous" depending 
upon the process requirements. 
In the "batch" mode, which would be used for heating single long metal 
billets, one burner would fire into its plenum chamber for the complete 
heating cycle of the one billet within the heating chamber. The other 
plenum chamber would act as a manifold for receiving the waste combustion 
products from the heating chamber with the other burner operating in a 
flueing mode. On completion of the heating cycle the firing burner could 
be shut down whilst the heated billet was removed from the heating chamber 
which would be recharged with cold stock. On restart the burner which had 
previously been flueing would now fire while that burner which had 
previously been firing would now serve as a flue. This cycle would be 
repeated. 
In "continuous" mode which could be used for heating short billets where 
the heating chamber would contain a large number of individual billets, 
each burner firing period could be of predetermined duration, possibly to 
coincide with the discharge interval of the stock, or alternatively, the 
firing period could be controlled by the temperature of the waste gases 
leaving the regenerator of the burner which is flueing. 
The provision of the plenum chambers along the sides of the heating chamber 
enables the heating gas to be distributed to the heating chamber in a far 
more uniform manner than would be the case if as conventional the burners 
were to be firing directly into the heating chamber. Furthermore, the 
provision of plenum chambers enables the number of burners per particular 
heating chamber to be reduced together with the number and complexity of 
controls.