LU83756A1 - SYSTEM FOR THE CONTINUOUS MEASUREMENT OF THE TEMPERATURE OF A LIQUID, METALLIC OR NON-METALLIC BATH - Google Patents

Description

A 681

Patent application for .......-...................................... .....

Designation of the Inventor

(1) I o eniiQQiqnô René NEYEN, ARBED Central Administration

........... Box 'Postale: ï802', 'L -' 2930 LUXEMBOURG .......................... .........................

acting as BJ & ägjSHääffl: - as agent for the depositor - (2) ARBEP S.A.

Avenue de la Liberté L - 2930 LUXEMBOURG (s) of the invention concerning:

Continuous measurement system for the temperature of a liquid bath,> metallic or non-metallic.

designated as inventor (s): 1. Name and first names ..MATHGE.M. .Georges ................................................ .................................................. ........................

Address 41 rue de Beggen ’L" 2930 LUXEMBOURG

2. Surname and first names ............................................. .................................................. .................................

RUe ^ ean Jaur®s address> L - 3 ^ 90 DUDELANGE

3. Name and first names ...?. Ç.! ®?.?.? ....? £ Uert ........................ .................................................. ..................................................

. , 30 Grand-Rue. L - 1660 LUXEMBOURG

Address ................................................. .................................................. .................................................. .......................................

He affirms the sincerity of the aforementioned indications and declares to assume full responsibility for them.

4: CLEES Roland, 66 rue Tattenberg, L - 3569 DUDELANGE Luxembourg> th November 16 19.81 ..

—- ·> Λί oj As—

René NEYEN (representative) (signature) A 68026_____ (1) Last name, first names, firm, address.

Nnm nrpnnms pt pHrpssp end ripnnsant.

A 681

Patent application »Applicant: ARBED S.A.

Avenue de la Liberté L - 2930 LUXEMBOURG

Continuous measurement system for the temperature of a liquid bath, metallic or non-metallic.

Continuous measurement system for the temperature of a liquid bath, metallic or non-metallic .___

The present invention relates to a system for continuously measuring the temperature of a liquid bath, metallic or non-metallic.

Knowing at all times the exact temperature of a liquid, metallic or non-metallic bath is important insofar as the reactions likely to take place in this bath are sensitive to changes in temperature.

Thus in the case of the fusion of non-metallic materials, in particular inorganic oxides, intended for the manufacture of mineral or ceramic fibers, refractory products or non-metallic granules, the quality of these products depends essentially on the chemical nature and consistency of the temperature of the liquid bath in the melting machine.

The mass and geometrical regularity with which the jet leaving the furnace hits the thinning equipment, the granulation drum or the casting mold, also depends on the constancy of the temperature of the casting product.

Any variation affecting the criteria listed above negatively influences the quality and / or quantity of the final product, either by degrading its physical or chemical properties, or by reducing the yield of processing equipment such as the stripper or the granulator.

The best way to predict the temperature of the poured product or a variation of it is to know at any time the temperature prevailing within the liquid bath.

- 2 - 5 For this, the temperature must be measured at a place in the bath where the temperature is representative of that of the heart of the bath.

Thus the measurement means desirable in the present context must be integrated as much as possible in the container / bath system, in order to rapidly follow its thermal evolution.

To guarantee the representativeness of the measurement, the temperature measurement system must also not disturb the thermal uniformity of the bath.

The object of the present invention is to provide a continuous temperature measurement system which meets these criteria.

This object is fully achieved by the system according to the invention which is characterized in that a graphite conduit which crosses the refractory wall of the container containing the bath has a closed nose plunging into the liquid mass and that a means of temperature measurement is arranged towards said conduit so that the contact area of the sensor itself is limited to the area of said nose.

"

A first embodiment of the system according to the invention provides that the temperature measurement means is a .thermocouple. To measure temperatures continuously on the order of 1550 ° C., an 18% Pt-PtRh thermocouple is preferably used. The Pt and PtRh 18% wires pass through a ceramic rod, each through a different hole. This rod, necessary as a support and for electrical insulation, is itself usefully placed in at least one protective sheath 35 in the form of a hollow tube closed on the side of the welding point of the thermocouple filaments. The thermocouple can, for example, be constructed in a manner similar to that prescribed by 43733. The thermocouple provided with its protective sheath touches the interior wall of the duct, in particular in the region of the nose.

In addition, it is very important to prevent any infiltration of materials liable to destroy the filament of the thermocouple, in particular any CO infiltration which may result from the reaction of oxygen with the heated graphite duct. For this it is essential that the crimping of the protective sheath of the thermocouple is gas tight, so as to prevent any re-entry of oxygen into the conduit.

10

A preferred method of protecting the thermocouple against infiltration of carbon monoxide consists in providing the protective ceramic sheath with a very thin layer of chromium stopping any diffusion through the ceramic sheath.

15

In addition, it is useful to prevent any infiltration of harmful gas by the cold end of the thermocouple by providing a seal between the tube at the flange surrounding the ceramic sheath and the latter, so as to prevent any penetration of gas, from the oven, 20 in the thermocouple head, i.e. where the filaments come out of their ceramic sheath.

A second embodiment provides that the means for measuring the temperature is an optical pyrometer.

25

The graphite block with the conduit is designed to be inserted into the refractory wall of the container, so that it fits perfectly there. It will preferably be replaceable from outside the oven. This block will be usefully placed at such a place in the oven that it will be possible to replace it even without emptying the oven; this by tilting the oven so as to bring the block in question above the liquid bath level.

The idea of using graphite as the material for the conduit brings considerable advantages; first graphite is an excellent conductor of heat and then it is not wetted by most of the materials involved; it does not undergo significant attack, even at extremely high temperatures, provided of course that there are no oxidizers.

The conductivity of graphite is such that the temperature gradient across the nose of the conduit is minimal and practically does not vary over a wide range of temperatures. The temperature measured is therefore practically that of the bath in contact with the graphite nose. , and this at any time.

The duct usefully has a conical shape, the thickness of the walls increasing from the nose, to easily replace it from the outside.

According to the invention, the duct is separated from the external wall of the furnace by at least one and preferably two insulating layers of annular section.

In the choice of materials used, care will be taken that the thermal conductivities decrease as the layers 20 move away from the nose of the conduit.

Behind the graphite nose, cellular carbon is preferably used, followed by refractory concrete.

A non-limiting illustration of a possible embodiment of the system according to the invention is provided by means of the drawings, in which FIG. 1 shows a longitudinal section through the measuring system and in particular the part of the duct itself, while FIG. 2 shows a longitudinal section through a thermocouple 30 intended to be inserted into said conduit.

In fig. 1 there is a graphite conduit (1), the nose (2) of which dips freely in the bath. In the case where the temperature measuring means is a thermocouple, it is located inside the duct (1), while in the case of using an optical pyrometer this will be mounted on the outside of the flange (3).

- 5 -

To avoid any penetration of air towards the graphite duct when using an optical pyrometer, a quartz glass, transparent to the measured light rays, will usefully close the orifice in the flange (3).

5

The hot part of the duct (1) is preferably surrounded by a layer of carbon or graphite (12), embedded in the refractory of the container. Thanks to the layer (12) the gradient between the extreme heat prevailing in the bath, towards the part of the conduit which is housed in the refractory, is attenuated, given the good conductivity of carbon and graphite.

The graphite nose (2) is followed by an insulation layer (4), preferably of cellular carbon, which has a thermal conductivity lower than that of graphite, although higher than that of the layer (5) which succeeds him, where we will preferably use an insulating concrete.

The flange (3) rests against the concrete layer (5) by means of a ring (6) made of ceramic fibers.

Fig. 2 shows the thermocouple which can be executed eg according to DIN 43733 (AKK type), ie that it is surrounded by two protective ceramic sheaths. The outer sheath (13), the only one shown, is provided with a thin layer of chromium (14). Between the protective sheath and the metal fixing tube (9) is a first seal (18) and between the mounting flange (20) and its counterpart (21) another seal (19), preferably in têflon.

30

It is understood that the measuring means can be connected to an instrument for converting the measured signal into an appropriate signal to be used in an electronic computer regulating the operation of the entire fusion installation.

Claims (13)

1. System for continuously measuring the temperature of a metallic or non-metallic bath, characterized in that a graphite duct which crosses the refractory wall of the container containing the bath, has a closed nose plunging into the liquid mass and that a means for measuring the temperature is arranged with respect to said conduit so that the contact area of the sensor itself is limited to the area of said nose. 10 2. System according to claim 1, characterized in that the measuring means is a thermocouple, provided with a protective ceramic sheath which is gas-tight by an external coating of chromium. i 3. System according to claims 1-2, characterized in that the interior of the duct is hermetically isolated from the external atmosphere by means of seals between the protective sheath and the thermocouple fixing tube on the one hand, and between mounting flange and counterflange on the other hand. 4. System according to claim 1, characterized in that the measuring means is an optical pyrometer. 5. System according to claims 1 and 4, characterized in that the conduit is hermetically isolated from the external atmosphere '25 by means of a quartz glass, by which the pyrometer targets the interior of the graphite nose. 6. System according to claims 1-5, characterized in that the duct has a conical shape, the thickness of the walls increasing from the nose. 7. System according to claims 1-6, characterized in that the duct is separated from the outer wall of the furnace by at least one insulating layer of annular section. 35 - 2 - 8. System according to claims 1-7, characterized in that the different layers have different thermal conductivities and which decrease away from the nose of the duct. 5 9. System according to claims 1-8, characterized in that the material of the layer, which surrounds the graphite duct, is graphite or carbon. 10. System according to claims 1-9, characterized in that the material of the first layer, which follows the graphite conduit is cellular carbon. 11. System according to claims 1-10, characterized in that the second layer succeeding the graphite duct is refractory concrete. 12. System according to claims 1-11, characterized in that a metal flange keeps the duct in place. 20 13. System according to claims 1-12, characterized in that the conduit is separated from the retaining flange by a ring of compressible material, preferably ceramic fibers. *