Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
Title: ~`URN}~CE FOR BRIG~T ~N~I~RI,ING OF COP:PER
The present inventior is of irnportance
for bri.gh.t anneallng of copper or copper alloys.
To accomplish this purpose it is necessary to heat
and cooi -~he copper in an atrnosphere that preverlts
an undesired chemical reaction on the surface of the
copper. The protective atmosphere most commonly used
i~. lean exothermi.c produced by the con-trolled combusti..on
of a hydro-carbon fuel, normally natural gas,.with air.
To date there have been two basic approaches to the
ger.eration of thi.s atmosphere, either externally in
a separate cham~er or i.nternally in the furnace proper.
There have been disadvantages to both approaches.
External atmosphere generation, the presently
preferred approach, is easier to roIltrol ancl more
reliable. However, the heat generated by combusting
the hydrocarbon fuel has been to date wasted. And
in todayls energY crisis thi.s is a definite disadvantage.
The internally produced atmosphere approach
has the potential of utllizing all or a-t ~east much of
the heat released in producin~ the at.mosphere. But,
to date there have been design problems.
First, it is ext~emely difficult to rnaintain
the correct air to fuel ratio because the heat load of
the furna~e changes as the processing condition~ change,
The variation in operatin~ pressures through the colmbustic)n
sy~tem as the ternperature control zones chan~e the burner
f.irin~ rates complicates th~ .ratio control.
Seconcd, as the through-put of copper product
30 i3 reduc:ed or stopped the heat requirement of the furnace
fal.ls helow that released irl proclucLng ~ufficient atmos-
phexe. Therefore, it. has been n~cessary to incorpora-te
a separate heat loss on/in the furnace to absorb the
extr2 .heat released by the combustion for producing ,
atmosphere. This separate heat loss has normally
been in the form of a constant energy drain on the
furnace. Consequently, the eneryy savings have been
minimized.
Sun~a.ry of the Invention:
The present invention improves these two ~ '
design deficiencies by first having a separate atmos-
phere producing system that fires cons-tantly, independent
of the tem.perature control system and secondly having
a cooling system that only extracts the excess heat
produced by the combustion for atmosphere. :
The invention utili.zes a conventional burner
system of the type heretoore used or.ly exte.rnally of
the furnace but places such burner system internally
w.ithi.n the furnace. This burner system fires constantly
independently of the furnace temperature control system.
Ratio control to produce the desired inert annealing
atmosphere is accomplished in the same manner and
with the same relia~ility as the conventional ext~rnal
burner system.
Since the burner system is exothermic and is
within the furnace, the heat thereby produced raises
~S the temperature of the furnace and by proper pre-setting
of the bur.n~rs, the desired temperatures in the several
furnace zones can be maintained for normal. operation
when the work load of copper passing throucJh the fu~nace
is at an opti~um level.
If during operation the temperature o~ any
zon~ is above or below that de~,ired for the annealinq
operati,on, adjustment and recJulation i5 o~tained ~y
auxiliar~ heating and/or cc.olinc3 means, wh:ich are
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automatically operated by the temperature controlling system.
In this way the proper temperatures can be maintained in the
furnace without continually regulating the gas ratios for
the atmosphere producing burners.
In one particular aspect the present invention provides
in a controlled atmosphere heat treating furnace having a
tunnel, the combination of an at~osphere producing device
pre set to fire continuously into said tunnel at a constant
rate and ratio independently of any thermostatic control to
produce the desired atmospheric composition whereby the heat
is continuously released directly within said tunnel iDdependent
of any thermostatic regulation, auxiliary heat transfer means
within said tunnel for transferring heat as required with
respect to the atmosphere within said tunnel without affecting
the composition of said atmosphere, and thermostatic means
responsive to the temperature within said tunnel ~or regulating
the heat transfer means to regulate the heat transferred thereby
independent of the heat continuously released in said tunnel
by said atmosphere producing device to maintain the required
temperature in said tunnel.
In another particular aspect the present invention
provides in a controlled atmosphere heat treating ~urnace
having a tunnel, a series of successive heat treating æones
and a conveyor for transporting a work load through the
successive zones, the combination of a plurality of atmosphere
producing burners, each firing directly into one of said heat
treating zones and pre-set independently of any thermostatic
control to produce the desired atmospheric con~position at a
constant rate and ratio oE ~uel andair and to develop
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sufficie~t heat in said zone to raise the temperature to
approximate heat treating range when an optimum work load
is passing through said tunnel 7 the products of combustion
being permitted to travel through successive zones and freely
pass through said tunnel to be discharged at an end thereof,
a plurality of separate radiant tube systems each located
in one of said heating treating zones each radiant tube being
provided with means for selectively introducing fuel and air
thereinto in variable amounts to develop heat therein, a
plurality of thermostats one in each of said zones and
operatively connected to the radiant tube in said zone to
regulate the heat developed therein to supplement the heat
produced in said zone from said pre-set burner, whereby the
temperature of said zone is maintained at heat treating
temperature when said work load is varied from said optimum,
each of said thermostats being completely independent of the
operation of said burners.
The objectives of the invention and the advantageous
results obtained thereby will be more fully set forth after
describing a preferred embodiment.
Brief Description of the Drawings:
Figure 1 is A sectional elevation of a furnace shown
schematically.
Figure 2 is a schematic plan view thereof.
Figure 3 is a transverse section on line 3--3 oE
Figure 1.
Deta_led Description
F:igures 1 to 3 represent a heat-treating furnace designed
for bright annealing of copper. In general construction the
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furnace ls of conventional design for transporting the
copper to be annealed by a conveyor 10 through a tunnel ll
in which the heat ~reating is performed. There is a loading
area 12 which includes a charge table 13. The copper work
load is placed on the rollers 14 and advanced by the driving
system of the conveyor through the curtain zone 15 and the
low ceiling entrance zones 16 into the annealing furnace 17.
At the discharge end of the furnace is a low ceiling exit
zone 18, a cooling section 19 containing water cooling
curtains 20 and a curtain zone 21. The cooled copper load
travels then to an unloading area 22 which includes a discharge
table 23. The preceding description represents a conventional
annealing apparatus designed to operate automatically with
whatever copper work load requiring annealing treatmen~L.
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Wi-thin the tunnel 11 of ~hc- heat treating
por~ion of the annealing furnace there is an atmosphere
producing burner system B and four successive heat treating
zones I, II~ III and IV. Each of these zones is provided
with a radiant heating and/or cooling system R, and in
some instances supplementary electric heating devices E.
Each zone may also have a fan F for circulating the heated
atmosphere and a thermostat T for regulating the temperature
within the zone.
The atmosphere producing burners B are`each
of conventional design such as are normally located
externally of the heat treating furnace. Each is
provided with a supply of fuel and air with means
for regula-ting the ratio in order to get the desired
composition of the combustion gases produced. The
fuel may be natural gas or other hydrocarbon fuel.
The radiant system R may also be a converltlonal
radiant tube with means for regulating th~ fuel and
air introduced thereinto in such a way that the heat
produced may be varied within the necessary limits to
supplement that produced by the constantl~ firing atrnos-
phere producing burners. The contr~l of the heat produced
within the radiant tubes i5 by means of a thermostatic
operation, monitored by the thermostat T in the same
zone as the radiant tube. If -the work load in the
furnace should drop sa low that the constantly firing
atmosphere burners produce too much heat to ~intain
the desired ~one temperature, then one way of absorbing
the excess heat is to pass air only through the tubes R.
Alternative separate cooling tubes can be provided for
extracting the exGe~ss heat. Means for thermo.statically
controlling the operation of the radiant tubes R and/o~
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electrical heatirlg devices E are conventional in
annealin~ furnaces and are incorporated herein by
reference. The fundamental diference in the present
invention over the conve~tional annealing furnaces,
is that the thermostatic control does not change the
operation oE the atmosphere producing burners B, but
only the ra~iant tubes R or supplementary electrical
hea1ing devices Eo The burners B release all of the
heat within the annealing furnace so that none is
wasted whereas the variation in heat required for
varying work load conditions is provided by the auto-
matic thermost~t control of the radiant tubes R or
electrical heaters E.
From the above description i-t will be seen
that the invention provides a new concept for a bright
annealing furnace for copper with integral atrnosphere
generation which eliminates much of the heat hitherto
wasted in conventional furnaces, and has a simplified
method of ratio control when the heat load of the
furnace chanyes as processing conditions change.
As described above and illustrated in the
drawings th~ reference characters B represent ~he atmosphere
producing direct firing burners. They fire at a constant,
pre-set rate, to produce the amount of atmosphere required.
They are completely independent of the tamperature
control sys~em. Thexefore, ratio control can be
accomplished in the same basic manner and with the
same reliability as external atmosphere generation.
If desired this ratio can be automatically adjusted by .
analyzin~ the furnace atmosphere.
The additional heat re~uired to process more
than the minimum amount of copper is produaed by a
separate system consisting of gas/propanejoil radiant
tubes and/or electric heating elements. This heat
source is controlled by the furnace temperature control
system.
l~hen the production of copper falls below a
minimum amount the atmosphere producing system releases
more heat than re~uired to keep the furnace at operating
temperature. This excess heat is ex-tracted from the
furnace interior by passing air through the gas/propane/
oil radiant tubes or separate cooling tubes if all
secondary heating is electric. The air flow through
these tubes is controlled by the furnace temperature
control system. In this way heat is only extracted
when excess heat is produced, maximi2ing the utilization
of energy.
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