Furnaces – With control means responsive to a sensed condition – Feed control
Reexamination Certificate
1999-03-26
2001-06-19
Ferensic, Denise L. (Department: 3749)
Furnaces
With control means responsive to a sensed condition
Feed control
C110S186000, C431S068000
Reexamination Certificate
active
06247416
ABSTRACT:
This application claims priority under 35 U.S.C. §§119 and/or 365 to 98 04115 filed in France on Apr. 2, 1998; the entire content of which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method of operating a furnace such as, for example, a rotary oxycombustion furnace, comprising an elbowed flue pipe for discharging the smoke at the furnace outlet, means of introducing ambient air into the said flue pipe and a smoke extractor arranged in the flue pipe, downstream of the said means of introducing ambient air.
2. Description of the Related Art
Methods of running such a furnace are known, and in these methods, in a first step, a gas analyser is used to analyse the, for example, CO content of the smoke and, in a second stage, the amounts of fuel and of oxidizing agent introduced into the furnace are adjusted as a function of the measurement result obtained.
These methods of operating a furnace using a gas analyser have the drawback of being expensive and complex.
This is because gas analysers are technologically advanced measurement instruments which are therefore very expensive, especially where highly reliable and very accurate analysers are concerned.
Furthermore, because of the construction and operation of a gas analyser, the measurement results it yields drift over time, which means that the analyser requires regular calibration.
Added to this is the fact that this gas analyser requires the attention of a specially qualified operator to maintain this measurement instrument and keep it operating correctly.
The invention sets out to alleviate these various drawbacks by proposing a method of operating a furnace and a device for implementing this method which is reliable and of low cost.
SUMMARY OF THE INVENTION
To this end, the subject of the invention is a method of operating a furnace comprising a flue pipe for discharging the smoke, means of introducing ambient air into the said flue pipe and a smoke extractor arranged in the said flue pipe, downstream of the said means of introducing ambient air, characterized in that:
the temperature of the smoke is measured at two points, one of which is close to the outlet of the furnace, and the other of which is in the flue pipe, downstream of the first point,
the temperature measured at the second point is subtracted from the one measured at the first point,
the result of the subtraction is compared with a positive or zero datum value &Dgr;T, and
the ratio of the flow rate of fuel to the flow rate of oxidizing agent introduced into the furnace is decreased when the result of the subtraction is below the datum value &Dgr;T.
The method according to the invention may additionally comprise one or more of the following features:
the datum value &Dgr;T corresponds to the difference between the temperature of the smoke at the first point and that at the second point when the furnace is running optimally,
the datum value &Dgr;T is equal to zero,
after the said reduction, the temperature measured at the first point is also compared with a reference temperature and the ratio of the flow rate of fuel to the flow rate of oxidizing agent introduced into the furnace is increased when the temperature of the smoke measured at the first point is below the reference temperature.
Another subject of the invention is a device for operating a furnace comprising a flue pipe for discharging the smoke, means of introducing ambient air into the said flue pipe and a smoke extractor arranged downstream of the said means of introducing ambient air, for implementing the method as defined hereinabove, characterized in that it further comprises a first and a second sensor for measuring the smoke temperature, the first of which is placed close to the outlet of the furnace, and the second of which is placed in the flue pipe, downstream of the first sensor, means of subtracting the temperature measured by the second sensor from the one measured by the first sensor, means of comparing the result of the subtraction with a datum value &Dgr;T and, controlled by the said comparison means, means of reducing the ratio of the flow rate of fuel to the flow rate of oxidizing agent introduced into the furnace when the result of the subtraction is below a datum value.
The device according to the invention may additionally comprise the feature whereby it additionally comprises means of storing a reference temperature, means of comparing the temperature measured by the first sensor with the reference temperature and, controlled by the said means of comparing the temperature measured by the first sensor with the reference temperature, means of increasing the ratio of the flow rate of fuel to the flow rate of oxidizing agent introduced into the furnace when the smoke temperature measured by the first sensor is below the reference temperature.
REFERENCES:
patent: Re. 34298 (1993-06-01), Gitman et al.
patent: 4649834 (1987-03-01), Heran et al.
patent: 5832842 (1998-11-01), Frontini et al.
patent: 0160884 (1985-11-01), None
patent: 0 553 632 A2 (1993-08-01), None
patent: 2 128 776 (1984-05-01), None
patent: 06313542 (1994-08-01), None
patent: WO 96/06432 (1990-06-01), None
Beaudoin Philippe
Loiselet Benoit
Ferensic Denise L.
L'Air Liquide Societe Anonyme pour l'Etude et l'E
Rinehart K. B.
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