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Patent 2080380 Summary

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(12) Patent Application: (11) CA 2080380
(54) English Title: MELTING FURNACE
(54) French Title: FOURNEAU DE FUSION
Status: Dead
Bibliographic Data
(51) International Patent Classification (IPC):
  • C03B 5/425 (2006.01)
  • C03B 5/43 (2006.01)
  • F27B 3/14 (2006.01)
(72) Inventors :
  • SOLIN, PETER A. H. (Finland)
  • HJERPPE, PERTTI K. (Finland)
  • NYGARDAS, CARL-GUSTAV (Finland)
(73) Owners :
  • SOLIN, PETER A. H. (Not Available)
  • HJERPPE, PERTTI K. (Not Available)
  • NYGARDAS, CARL-GUSTAV (Not Available)
  • PAROC OY AB (Finland)
(71) Applicants :
(74) Agent: MCCARTHY TETRAULT LLP
(74) Associate agent:
(45) Issued:
(86) PCT Filing Date: 1991-04-10
(87) Open to Public Inspection: 1991-10-12
Availability of licence: N/A
(25) Language of filing: English

Patent Cooperation Treaty (PCT): Yes
(86) PCT Filing Number: PCT/FI1991/000105
(87) International Publication Number: WO1991/015433
(85) National Entry: 1992-10-09

(30) Application Priority Data:
Application No. Country/Territory Date
901842 Finland 1990-04-11

Abstracts

English Abstract

2080380 9115433 PCTABS00007
The invention describes a melting furnace for melting of raw
materials for mineral fibre production. The furnace carries on its
side walls a refractory, optionally multi-layered lining containing
materials of different thermal conductivity, whereby the lining
comprises at least one layer (14) including a zone (14') with a
restricted dimension in the direction of the height of the side
wall and arranged at a level corresponding to the melt surface (7)
and/or the interface between melt (6) and bottom iron (8) and
made of a material of a thermal conductivity which is higher than
that of the rest of the material (14'') otherwise in this layer.


Claims

Note: Claims are shown in the official language in which they were submitted.


WO 91/15433 PCT/FI91/00105


Claims

1. Melting furnace for melting of raw material for mineral
fibre production, which furnace on its side walls carries
an optionally multilayered refractory lining comprising
materials of different thermal conductivity, characterized
in that the lining comprises at least one layer (14)
including a zone (14') with a restricted dimension in the
direction of the height of the side wall, and arranged at
a level corresponding to the melt surface (7) and/or the
interface between melt (6) and bottom iron (8) and made of
a material of a thermal conductivity which is higher than
that of the material (14") otherwise in this layer.

2. Melting furnace according to the Claim 1, characterized
in that the thermal conductivity in the zone (14') is 2 to
5 times higher than in the layer otherwise.

3. Melting furnace according to the Claim 1 or 2, characte-
rized in that the material with the higher thermal conduc-
tivity and the material with the lower thermal conductivity
in the layer are of similar type, such as a ceramic
material.

4. Melting furnace according to any one of the preceeding
Claims, characterized in that the zone (14') is comprised
of a graphite, SiC- or a C-SiC-mortar or -bricks.

5. Melting furnace according to the Claim 4, characterized
in that the layer (14) otherwise is a mortar or bricks of
a Al2O3-, MgO-, MgO/Cr2O3- or Al2O3/Cr2O3-based material.

6. Melting furnace according to any one of the Claims 1 to
5, characterized in that the said layer forms an interme-
diate layer which against the melt carries a layer of the
actual furnace lining (15).

WO 91/15433 PCT/FI91/00105


7. Melting furnace according to the Claim 6, characterized
in that the furnace lining (15) consists of a Al2O3/Cr2O3-
based material.

Description

Note: Descriptions are shown in the official language in which they were submitted.


W~ 1/15~33 PC'r/~191/O~lS)S
'I
Melting furnace ~08~8~

The present invention concerns a melting furnace for
melting of raw material for mine!ral fibre production, which
furnace on its side walls carries an optionally multi~
layered refractory lining comprising materials of different
thermal conductivity.

Mineral fibres are produced e.g. by melting the raw
material, possibly rock mineral or slag from metal produc-
tion, in an electrical melting furnace, withdrawing con-
tinuously the melt from the furnace and converting it to
fibres, e.g. by transferring the melt to a spinniny unit,
which can consist of a number of rotating wheels, wherefrom
the mineral melt is centrifuged for the formation of
fibres. The thus formed fibres are collected onto a
conveyor in the form of a fibre felt. The fibre felt is
thereafter subjected to additional processing steps, it is
e.g. impregnatad with a suitable binder, such as a resin,
which is activated e.g. in a curing oven, whereby the
fibres are fixed to each other into a form stable felt of
desired density and thickness.

The melting furnace which is used for melting of the raw
material consists of a casing of steel which on its inner
side wall carries a refractory lining, the type and
thickness of which is chosen according to the material to
be melted. Onto the bottom of the furnace a sump of iron,
so called bottom iron, is formed during the operation as a
result of iron o~ides included in the raw material being
reduced to elementary iron. The lining in the whole furnace
is subject to strong chemical and thermal stresses as a
conseyuence of which the lining wears down and gradually
disappears and has to be renewed at regular intervals. It
has been observed that the attacks are especially severe at
boundary surfaces between phases, i.P. at the free melt
surface and the boundary surface between the melt and




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WO~ 5433 PCr/FI~l/00l05

2 ~ 8~ 2
bottom iron.

As the stressec on the lining are proportlonal to the
temperature in the furnace, att~mpts have been made at
reducing the wear on the lining e.g. by cooling the side
walls in different ways. Thus it has been suggested to cool
the furnace wall with water, either by cooling the outer
wall (e.g. SE 731453g), or by using cooling elements built
into the wall, e.g. cooling coils, through which water is
led (DE 2626211). However, the use of water is associated
with a risk for explosion in case water, e.g. as a result
of structural cracks, comes into contact with the melt in
the furnace. It has also been suggested to cool the outside
of the furnace wall by using a cooling system in the form
of outer cooling panels containing a non-explosive liquid
coolig agent, e.g. oil (SE 8~00514).

As an alternative to the above mentioned solutions it has
also been suggested to use copper plates built into the
furnace wall and the furnace roof, for the genaral withdra-
wal of surplus heat in an electric arc furnace
(DE 2443662).

Excess withdrawal of heat from the furnace is, however, not
desirable for the reason that this means an increase of the
energy requirement of ths furnace and consequently poor
heating economics in the furnace. It would thus be of
importance to be able to optimize ~he heat withdrawal from
the furnace by providing for * local increased withdrawal
of heat at those locations in the furnace where the lining
is especially exposed to attack from the melt, thus
preserving the lining at these exposed locations. This
object ls achieved by means of the furnace according to ~he
invention which is characteri~ed in that the lining
comprises at least one layer including a zo~e with a
restricted dimension in the direction of the height of the
side wall, and arranyed at a level corresponding to the
;




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W091/15433 Pcr/ Fl91/oolos
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melt surface and/or the lnterface between melt and bottom
iron and made of a material of a thermal conductivity which
is higher than that of the material otherwise in this
layer.

Thus the furnace lining comprises in at least one layer an
annular zone extending around the furnace and having a
restricted dime~nsion in the vertical direction, which is
made of a refractory material having a thermal conductivity
higher than that of the material otherwise in the same
layer. The term "layer" means in this connection not only
physically separate layers, but refers also to any such
layer of the lining which has a certain thickness dimension
and which is situated at the same distance from the side
wall of the furnace when viewed in the vertical direction
of the furn~ce. The material with the higher thermal
conductivity and the material with the lower thermal
conductivity in the said layer are preferably of similar
type, such as a ceramic material, in order to form as
uniform and well integrated lining as possible with as
small as possible heat strains in the boundar~ surfaces
between the materials.

The material with the higher thermal conductivity thus
forms a thermal bridge in the lining in the form of an
annular zone, which is situated at such a distance from the
furnace bottom that it in its vertical direction coincides
with the free melt surface in the furnace, and/or with the
liquid boundary line between the melt and the bottom iron.
By incorporating a thermal bridge of the said kind in the
lining it is possible to leave out further cooling systems,
if desired. It is possible to obtain a sufficiently high
heat withdrawal through the thermal bridge in order for
frozen melt to form on the inside of the lining towards the
melt, which in turn promotes thP further protection of the
lining against the stresses in the furnace.




. :

WO91/15433 PCT/F191/0010s

2(~ 3~3~ 4

According to a preferred embodiment, the thermal bridge is
comprised of a mortar or bricks of graphite, C-SiC, or SiC,
especially SiC. The material irl the said layer can otherwi-
se suitably be a mortar or bricks of a Al2O3-, MgO-,
MgO/Cr2O3- or Al2O3/Cr2O3-based material, especially if this
layer comes into contact with the melt. If the layer *orms
an intermediate layer, the material otherwise in the layer
may be chosen more freely provided its thermal conductivity
characteristics are adapted according to the material of
the thermal bridge. In the above mentioned embodiment, the
thermal conductivity of the thermal bridge is many times
greater than in the layer otherwise. In order to achieve
good results it is advantageous that the thermal conducti-
vity of the tharmal bridge is more than twice as high, and
advantageously 2 to 5 times as high as the material
otherwise in the layer.

The layer in question can be the only lining layer in the
furnace or it can be a so-called base lining, which
suitably is coated with a layer forming the actual lining
towards the melt and which may be an aluminium oxide/chro-
mium oxide lining with a high chromium content.

The invention is described in the following with reference
to the appended drawing, wherein

Fig. l shows schematically a furnace in cross-section, and

Fig. 2 shows a section of an embodiment of the urnace
wall.

The furnace as a whole is denoted with the reference
numeral l, and it comprises a bottom part 2, side walls 3
and a furnace cover 4, through which a plurality of
electrodes 5 extend into the melt 6 in the furnace. The
supply inlet openi~gs for the raw material are not shown



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Wo9l/1543~ Pcr/ Fl91/oOIoS

2C~81338
nor the outlet opening for the melt. On the surface of the
melt there is a layer of unmelted raw material, and on the
bottom of the furnace a sump 8 of iron is collected. On the
outer side of the furnace cooling panels 9 for forced
cooling are schematically shown and in which oil is used as
a cooling medium. These cool:ing elements may be of any
design, and they may extend over the whole height of the
wall, or only over parts thereof.

Figure 1 shows schematically two areas in the side wall,
which are exposed to a greater degree of stress than the
remaining parts of the side walls, that is the contact
surface between the side wall and the melt surface, and the
boundary surface between the iron sump and the melt,
respectively. These areas have been marked with the
numerals 10 and 11 in the Figure 1. According to the
in~ention these areas in the side wall lining are made of
a material which has a higher thermal conductivity than the
remaining areas of the lining in the side wall 3.

One embodiment of the invention is shown in the Figure 2.
The side wall is generally denoted with the reference
numeral 3. It comprises outermost the actual furnace
casing 12 of steel. Next ts the steel casing there is an
elastic contact layer 13 of a carbon mass, the purpose of
which is to improve the contact between the casing 12 and
the base lining (14). As is evident from the Figure 2, the
base lining comprises zones of two different kinds, that is
a conventional lining 14" of aluminium oxide bricks and
separate xones 14' of SiC-bricks. The zones 14' are
arranged in the furnace wall at a height level which
- corresponds to the free melt surface and the boundary
surface between the iron sump and melt, respectively.
According to the embodiment of the Figure 2, the base
lining 14 carries an additional layer, l.e. is the lining
15 which faces the melt itself and which sui~ably is an
aluminium oxide-chromium oxide mortar of a high chromium



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: .,

WO91/15433 PCI/F191/00105

2 ~ S~ ~8~ ~
content, preerably wlth a chromium oxide conten-t of more
than appro~imately 5~. Due to the intensified heat removal
at the level of the melt surface and the iron sump,
respectively, the temperature of the lining will at these
locations be lower than the corresponding lining without
intensified heat removal, whe!reby a crust of frozen melt
can form on the inside of the side wall, which in turn
promotes the durability of the linings at these areas.

In the embodiment according to the Figure 2, the oil
cooling panels can be divided into suitable segments, e.g.
so that the areas where the heat transfer through the wall
is intensified, i.e. at the level of the melt surface and
the iron sump, are provided with separate segments. These
elements or panels can be provided with suitable temperatu-
re and flow meters which respond to an increased heat
transfer through the furnace wall and can therefore
suitably be used for monitoring the state of wear of the
linings.




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.

Representative Drawing
A single figure which represents the drawing illustrating the invention.
Administrative Status

For a clearer understanding of the status of the application/patent presented on this page, the site Disclaimer , as well as the definitions for Patent , Administrative Status , Maintenance Fee  and Payment History  should be consulted.

Administrative Status

Title Date
Forecasted Issue Date Unavailable
(86) PCT Filing Date 1991-04-10
(87) PCT Publication Date 1991-10-12
(85) National Entry 1992-10-09
Dead Application 1995-10-10

Abandonment History

There is no abandonment history.

Payment History

Fee Type Anniversary Year Due Date Amount Paid Paid Date
Application Fee $0.00 1992-10-09
Maintenance Fee - Application - New Act 2 1993-04-12 $100.00 1992-10-09
Registration of a document - section 124 $0.00 1993-10-01
Maintenance Fee - Application - New Act 3 1994-04-11 $100.00 1994-03-31
Owners on Record

Note: Records showing the ownership history in alphabetical order.

Current Owners on Record
SOLIN, PETER A. H.
HJERPPE, PERTTI K.
NYGARDAS, CARL-GUSTAV
PAROC OY AB
Past Owners on Record
None
Past Owners that do not appear in the "Owners on Record" listing will appear in other documentation within the application.
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Document
Description 
Date
(yyyy-mm-dd) 
Number of pages   Size of Image (KB) 
Office Letter 1993-04-28 1 33
International Preliminary Examination Report 1992-10-09 8 149
Representative Drawing 1999-01-18 1 8
Drawings 1991-10-12 1 29
Claims 1991-10-12 2 57
Abstract 1991-10-12 1 61
Cover Page 1991-10-12 1 21
Abstract 1991-10-12 1 49
Description 1991-10-12 6 285
Fees 1994-03-31 1 34
Fees 1992-10-09 1 34