Industrial electric heating furnaces – Resistance furnace device
Reexamination Certificate
2001-11-13
2004-03-02
Hoang, Tu Ba (Department: 3742)
Industrial electric heating furnaces
Resistance furnace device
C373S115000
Reexamination Certificate
active
06700918
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an electric furnace for the production of metal oxides and, in particular, to the production of lead oxides with high standards of quality of the product and of the process, affording considerable advantages over the prior art.
SUMMARY OF THE INVENTION
The main objects of the present invention are to achieve a high quality of the final product and great flexibility with regard to the quality of the raw material, combined with easy management of the furnace, with a reliable and precise control system, and with a reduction in problems in the working environment and in the environment outside the plant. Moreover, according to the present invention, it is possible to achieve considerable advantages over currently known furnaces, such as: low investment and installation cost, low energy cost per ton of product produced, low maintenance cost, much quicker start-up, and a reduction in residues produced during start-up.
To achieve its objects, the present invention provides for a tubular furnace with a tubular treatment chamber made of stainless refractory steel (AISI-310) and provided with a plurality of heating zones with individual control probes, in particular, three heating zones, each of which comprises six resistors connected so as to achieve a balance in electrical consumption between phases, each heating zone having its optimal adjustment point in dependence on the quality of the raw material, on its physical and chemical characteristics, and on the physical and chemical characteristics of the finished product to be produced.
The electrical control panel comprises controllers of consumption per phase and of voltage between phases, and can warn of any electrical problem with the resistors.
The heating control system permits adjustment of the electrical consumption of the furnace at any moment in dependence on the state of the furnace, as well as the use of full power during start-up and, during the normal process, consumption controlled by the temperatures of the chamber.
The construction of the furnace enables great functional flexibility to be achieved therein in order to adapt to the quality of the raw material used, for which purpose energy consumption is adjusted according to the quality of the raw material.
The raw material introduced into the tubular chamber is urged by an agitator shaft towards the end of the furnace body at which the finished product is discharged by a rotary valve. The agitator shaft rotates by virtue of the driving action of a geared motor unit controlled by a frequency meter from the control panel of the furnace. The agitator shaft is of mixed construction, with the use of AISI-310 stainless steel in the portion which is in contact with the product and AISI-304 for the rest. It is constituted by a central tubular element with a square cross-section, constituted by welded plates and a set of vanes welded to the central tube on its respective faces and arranged in a manner such as together to constitute a helical screw. One of the characteristics of the agitator shaft of the furnace of the present invention is that it has, in its outer portions, percussion devices or “hammers” with balls inside them which, by virtue of the rotation of the agitator shaft, cause impacts and vibration inside the shaft, preventing the product from adhering to the shaft.
The quality of the final product is adjusted by control of the time spent by the product inside the furnace and also by the output or final production flow, for which purpose the present invention provides for a frequency variator which controls the rate of rotation of the agitator shaft and also the rate of rotation of the helical screw which feeds raw material to the furnace. According to the invention it will also be possible to install two separate speed variators, one for the agitator shaft and the other for the worm screw for feeding the raw material to the furnace itself. The furnace as a whole is thermally insulated by refractory bricks with a temperature classification of up to 1,260° C., the bricks additionally providing the necessary support for the electrical resistors. The insulation is completed by high-density ceramic fibre (128 kg/m
3
) with a temperature classification of up to 1,260° C.
To compensate for the large expansions brought about in the tubular element of the furnace, according to the present invention, movable elements are provided which allow the tube to lengthen freely. In particular, a free extension system is provided, which takes up the expansions of the tubular chamber and of the displacement screw resulting from the temperature difference produced inside the heating chamber.
The furnace is controlled by a centralized panel which comprises the elements necessary for the control of temperature in the chamber of the furnace and alarm elements for providing warnings when the values of the control parameters depart from the range of values provided for during the production process.
REFERENCES:
patent: 4352969 (1982-10-01), Wulf
patent: 4606283 (1986-08-01), DesOrmeaux et al.
patent: 4631026 (1986-12-01), McKinney
patent: 4912301 (1990-03-01), McKinney et al.
patent: 5579334 (1996-11-01), Baxter et al.
patent: 0 365 260 (1990-04-01), None
patent: 0 406 954 (1991-01-01), None
patent: 8405134 (1984-09-01), None
Coplosa, S.A.
Darby & Darby
Hoang Tu Ba
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