U.S. patent application number 13/381704 was filed with the patent office on 2012-05-24 for method for heating lightweight metal ingots.
This patent application is currently assigned to EBNER INDUSTRIEOFENBAU GESELLSCHAFT M.B.H.. Invention is credited to Robert Ebner, Eduard Morbitzer.
Application Number | 20120125569 13/381704 |
Document ID | / |
Family ID | 42313262 |
Filed Date | 2012-05-24 |
United States Patent
Application |
20120125569 |
Kind Code |
A1 |
Morbitzer; Eduard ; et
al. |
May 24, 2012 |
METHOD FOR HEATING LIGHTWEIGHT METAL INGOTS
Abstract
A method is described for heating lightweight metal ingots (1),
with the lightweight metal ingots (1) being heated in a furnace (2)
by hot burner exhaust gases. In order to provide advantageous
heating conditions it is proposed that the lightweight metal ingots
(1), prior to their heating in the furnace (2), are preheated via
at least one preheating apparatus (9) which rests in a planar
manner thereon and is supplied by a fluid heat carrier which is
heated in heat exchange by the hot exhaust gases from the furnace
(2) and is guided in a circuit (7).
Inventors: |
Morbitzer; Eduard; (Linz,
AT) ; Ebner; Robert; (Leonding, AT) |
Assignee: |
EBNER INDUSTRIEOFENBAU GESELLSCHAFT
M.B.H.
Leonding
AT
|
Family ID: |
42313262 |
Appl. No.: |
13/381704 |
Filed: |
June 14, 2010 |
PCT Filed: |
June 14, 2010 |
PCT NO: |
PCT/AT2010/000209 |
371 Date: |
January 31, 2012 |
Current U.S.
Class: |
165/104.19 |
Current CPC
Class: |
C21D 1/34 20130101; C22F
1/002 20130101; C21D 9/0081 20130101; F27B 17/0016 20130101; C21D
1/52 20130101; C21D 9/46 20130101; F27D 17/004 20130101; C21D
9/0025 20130101 |
Class at
Publication: |
165/104.19 |
International
Class: |
F28D 15/00 20060101
F28D015/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 3, 2009 |
AT |
A 1040/2009 |
Claims
1. A method for heating lightweight metal ingots, with the
lightweight metal ingots being heated in a furnace by hot burner
exhaust gases, wherein the lightweight metal ingots (1), prior to
their heating in the furnace (2), are preheated via at least one
preheating apparatus (9) which rests in a planar manner thereon and
is supplied by a fluid heat carrier which is heated in heat
exchange by the hot exhaust gases from the furnace (2) and is
guided in a circuit (7).
2. An apparatus for heating lightweight metal ingots, comprising a
furnace heated via burners and a heat exchanger which is supplied
with the hot exhaust gases of the furnace, wherein the heat
exchanger (6) and a preheating device (9) which accommodates the
lightweight metal ingots (1) in planar contact are disposed in a
heat carrier circuit (7) for a fluid heat carrier.
3. An apparatus according to claim 2, wherein the preheating device
(9) comprises a frame (11) with a contact surface (13) for the
lightweight metal ingots (1) and a heat transfer plate (10) which
extends transversally to the contact surface (13), which forms a
contact area (15) for the lightweight metal ingots (1) and through
which the heat carrier flows.
4. An apparatus according to claim 3, wherein the heat transfer
plate (10) is composed of two layers (16, 17) which form at least
one flow conduit (18) for the heat carrier between themselves.
5. An apparatus according to claim 4, wherein the layer (16) of the
heat transfer plate (10) forming the contact area (15) is
subdivided into individual fields by grooves (22) forming bending
points.
6. An apparatus according to claim 3, wherein the heat transfer
plate (10) is resiliently supported on the side facing away from
the contact area (15).
7. An apparatus according to claim 3, wherein the contact surface
(13) of the frame (11) for the lightweight metal ingots (1) slopes
towards the contact area (15).
8. An apparatus according to claim 7, wherein the contact surface
(13) comprises rollers (12) with axes which are parallel to the
contact surface (13) and the contact area (15).
Description
FIELD OF THE INVENTION
[0001] The invention relates to a method for heating lightweight
metal ingots, with the lightweight metal ingots being heated in a
furnace by hot burner exhaust gases.
DESCRIPTION OF THE PRIOR ART
[0002] Lightweight metal ingots are heated in a furnace, usually a
pusher-type furnace, for hot rolling lightweight metal ingots. For
this purpose it is known to incinerate fluid or gaseous fuels in
burners and to subject the lightweight metal ingots to hot exhaust
gases from the burners which are circulated by means of a fan. In
order to enable the utilization of the tangible exhaust heat from
the exhaust gases of the furnace, the combustion air required for
the burner is preheated with the hot exhaust gases by means of heat
exchange, by means of which it is possible to save fuel. Higher
flame temperatures support the formation of nitrogen oxides however
which are hazardous to the environment.
[0003] For the heat treatment of sheets it is also known (EP 2 014
777 A1) to arrange the sheet between two heat-transfer plates and
to supply thermal energy to said heat-transfer plates, so that the
heat is transferred to the sheet by the heat-transfer plates which
lie in a planar manner on the sheet. Such devices for the thermal
treatment of sheets cannot make any contribution to heating
lightweight metal ingots rapidly to the required hot rolling
temperature.
SUMMARY OF THE INVENTION
[0004] The invention is thus based on the object of providing a
method for heating lightweight metal ingots of the kind mentioned
above in such a way that a preheating of the lightweight metal
ingots with reduction of the environmental pollution by nitrogen
oxides is enabled by utilizing the waste heat of the exhaust gases
of the furnace.
[0005] This object is achieved by the invention in such a way that
the lightweight metal ingots, prior to their heating in the
furnace, are preheated via at least one preheating apparatus which
rests in a planar manner thereon and is supplied by a fluid heat
carrier which is heated in heat exchange with the hot exhaust gases
from the furnace and is guided in a circuit.
[0006] By preheating the lightweight metal ingots with the help of
the tangible waste heat of the exhaust gases of the furnace,
preheating of the combustion air can be omitted, so that the flame
temperature can be lower and the likelihood of forming nitrogen
oxides is reduced considerably. Due to the preheating of the
lightweight metal ingots, the lower temperature of the exhaust
gases of the burner hardly has an influence on the processing time
of the lightweight metal ingots in the furnace, so that comparably
short heating times can be ensured. The direct preheating of the
lightweight metal ingots with the help of the hot exhaust gases
from the furnace would require complex devices which are comparable
to a furnace. In order to avoid such complexity, a fluid heat
carrier which is circulated is heated by heat exchange with the
help of the tangible waste heat of the hot exhaust gases from the
furnace, with the help of which the preheating device is supplied,
on which the lightweight metal ingots are placed in a planar
manner, so that the lightweight metal ingots resting on the
preheating device are transferred the heat of the heat carrier
supplying the preheating device. As a result of the heat carrier
circuit, the preheating device can also be placed remotely from the
furnace because the heat carrier can also be pumped over larger
distances in insulated pipelines without any special measures. The
preheating of the lightweight metal ingots can consequently be
inserted at an advantageous point in the processing line of the
lightweight metal ingots.
[0007] A conventional apparatus can be assumed for the purpose of
heating lightweight metal ingots with a furnace heated via a
burner, in which a heat exchanger can be provided which is supplied
with hot exhaust gases of the furnace. In contrast to conventional
apparatuses of this kind, the heat exchanger is arranged together
with one of the lightweight metal ingots in a preheating device in
a heat carrier circuit which accommodates the ingots in planar
contact, so that it is not the combustion air for the furnace
burners that is heated via the heat exchangers but a fluid heat
carrier which then emits its heat to the preheating device which
accommodates the lightweight metal ingots.
[0008] The relevant aspect for the heat transfer is the flush
contact of the ingots on the preheating device over the largest
possible area. For this purpose, the preheating device can comprise
a frame with a contact surface for the lightweight metal ingots and
a heat transfer plate which extends transversally to the contact
surface, which forms a contact area for the lightweight metal
ingots and through which the heat carrier flows. The heat transfer
plate is preferably composed of two layers which form at least one
flow conduit for the heat carrier between themselves and of which
the layer forming the contact area shall have advantageous
properties for heat transfer. The opposite layer shall be arranged
in such a way that heat losses are avoided to the highest possible
extent, which requires either a layer of a heat-insulating material
or a layer provided with heat insulation. In order to ensure the
contact of the one layer on the lightweight metal ingots over a
large area for the purpose of possible loss-free heat transfer, the
layer of the heat transfer plate forming the contact area can be
subdivided into fields by grooves resulting in bending points. When
the heat carrier is conveyed with sufficient conveying pressure
between the two layers in order to supply the layer of the heat
transfer plate forming the contact area with a respective hydraulic
pressure, it is possible to ensure a flush contact of this layer
forming the contact area with lightweight metal ingots in
cooperation with the groove-like bending points, even when the
lightweight metal ingots show uneven sections. The layer of the
heat exchanger plate facing away from the lightweight metal ingots
forms an abutment, so that this layer facing away from the
lightweight metal ingots must be arranged in a sufficiently rigid
manner itself or must be supported accordingly.
[0009] A further measure to support a planar contact of the
preheating device on the lightweight metal ingots is to support the
heat transfer plate in a resilient manner on the side facing away
from the contact area. This resilient support allows automatic
compensation when the contact surface does not extend parallel to
the contacting surface of the lightweight metal ingots.
[0010] Especially advantageous constructional conditions are
obtained when the contact surface of the frame for the lightweight
metal ingots slopes towards the contact area of the heat transfer
plate. In such an arrangement, the lightweight metal ingot to be
heated slides along the contact surface against the contact area in
order to lie flush against this contact area. In order to avoid
sliding friction, the contact surface can have rollers with axes
disposed parallel to the contact surface and to the contact area of
the heat transfer plate, so that a lightweight metal ingot which is
placed on the rollers of the contact surface with the help of a
hoist for example is moved via the rollers against the contact area
of the heat transfer plate and is pressed against this contact area
with the help of a weight-induced force component.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The method for heating lightweight metal ingots in
accordance with the invention will be explained below in closer
detail, wherein:
[0012] FIG. 1 shows an apparatus in accordance with the invention
for the heating of lightweight metal ingots in a schematic ingot
diagram;
[0013] FIG. 2 shows a preheating device for the lightweight metal
ingots in a vertical cross-sectional view, and
[0014] FIG. 3 shows a sectional view along line III-III of FIG. 2
on a smaller scale.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0015] In accordance with FIG. 1, a furnace 2, which is usually a
pusher-type furnace, is provided for heating the lightweight metal
ingots 1, which furnace is heated with the help of burners 3. At
least one fan 4 is provided for distributing the hot burner gases
in the furnace 2. The hot exhaust gases from the furnace 2 are
removed via an exhaust gas line 5 and supplied to a heat exchanger
6 which is part of a heat carrier circuit 7. Said heat carrier
circuit comprises a circulation pump 8 and a preheating device 9 in
addition to the heat exchanger 6 for heating the fluid heat
carrier, which preheating device comprises a heat exchanger in the
form of a heat transfer plate 10, through the fluid heat carrier
flows. The lightweight metal ingots 1 accommodated by the
preheating device 9 in a planar manner are thus preheated via the
closely sitting heat exchanger plate 10 with the help of the heat
carrier pumped in the circuit in order to be heated to the required
hot rolling temperature after their preheating in the furnace 2,
which occurs with the help of the hot exhaust gases of the burner,
the tangible waste heat of which is used for heating the fluid heat
carrier in the heat exchanger 6 after the heating of the
lightweight metal ingots 1. The utilization of the tangible waste
heat of the exhaust gases from the furnace 2 not only improves the
energy balance, but also allows operating the furnace 2 with a
lower flame temperature of burners 3, so that the likelihood of the
increased formation of nitrogen oxides can be prevented to a
substantial extent.
[0016] The preheating device 9 per se is shown in closer detail in
FIGS. 2 and 3. In accordance with the illustrated embodiment, the
preheating device 9 comprises a frame 11 which determines a contact
surface 13 which is defined by rollers 12. The heat transfer plate
10 through which the heat carrier flows extends transversally to
said contact surface 13, preferably perpendicularly thereto, with
the heat transfer plate resting on the support legs 14 of the
frame, as shown in FIG. 2. Since the frame 11 is arranged in such a
way that the contact surface 13 slopes towards the heat transfer
plate 10 and axes of the rollers 12 of the contact area 13 extend
parallel to the contact area 13 and parallel to the heat exchanger
plate 10, the lightweight metal ingots 1 which are placed on the
rollers 12 are rolled towards the heat exchanger plate 10 as a
result of their weight, which forms a contact area 15 for the
lightweight metal ingots 1. The heat exchanger plate 10 which sits
close via the contact area 15 to the respective lightweight metal
ingot 1 thus transfers the heat of the heat carrier flowing through
the heat exchanger plate 10 onto the respective lightweight metal
ingot 1 as a result of the given temperature differences.
[0017] In order to provide simple constructional conditions, the
heat exchanger plate 10 comprises two layers 16 and 17 between
which at least one flow conduit 18 is obtained for the fluid heat
carrier which is connected to a flow line 19 and a return line 20
of the heat carrier circuit 7. The flow conduit 18 which extends in
a meandering manner in the embodiment according to FIG. 3 is formed
by milled portions in one of the two layers 16 and 17, preferably
in the layer 17 facing away from the contact area 15. Since a
mutual sealed delimitation of the individual sections of the flow
conduit 18 is irrelevant, it is sufficient to seal the two layers
16 and 17 against one another by a seal 21 provided
circumferentially around the edge.
[0018] In order to support the planar contact of the contact area
15 formed by the layer 16 on the respective lightweight metal ingot
1, this layer 16 can be subdivided by grooves 22 in mutually
delimited fields, with the grooves forming bending points which
allow an adjustment of the contact area 15 to the opposite area of
the respective lightweight metal ingot 1 by respective deformation
of the layer 16 when the layer 16 is subjected to the fluid heat
carrier. The opposite layer 17 must represent a respective abutment
and must either have a sufficient rigidity against bending or must
be supported in a rigid manner against bending. In order to prevent
heat losses, the layer 17 of the heat exchanger plate 10 which
faces away from the lightweight metal ingot 1 is provided with a
thermal insulation. Layer 17 could also be produced itself from a
thermally insulation material.
[0019] A further possibility to support the flush contact of the
lightweight metal ingot 1 on the contact area 15 of the heat
exchanger plate 10 is to support the heat exchanger plate 10 via
spring elements 24 in relation to the support legs 14 of the frame
11, thus enabling an automatic overall alignment of the heat
exchanger plate 10 in relation to the stop area of the respective
lightweight metal ingot 1. The embodiment shows spring elements 24
in the form of coil springs, which is not mandatory however.
* * * * *