Heating – Work chamber having heating means – Combustion products heat work by contact
Reexamination Certificate
1998-11-17
2001-06-26
Gravini, Stephen (Department: 3742)
Heating
Work chamber having heating means
Combustion products heat work by contact
C432S180000, C432S181000
Reexamination Certificate
active
06250917
ABSTRACT:
FIELD OF THE INVENTION
The invention is directed to a method for heating a fuel-fired industrial furnace, particularly a metal smelting furnace, upon employment of regenerators and burners through which hot exhaust gas and cold combustion air flow in alternation. The invention is also directed to a regenerator/burner module system for the implementation of the method.
BACKGROUND OF THE INVENTION
Industrial furnaces such as, for example, aluminum melting furnaces must be heated and kept warm with burners. It is thereby known to utilize regenerators through which hot exhaust gas and cold combustion air flow in alternation. The regenerators being in the position, as heat store, to preheat cold combustion air to high temperature, energy being thereby saved. In the regenerator, the hot exhaust gas cools, for example, from 1200° C. to, for example, 400° C., whereas the cold combustion air can be preheated to, for example, 1000° C. in the regenerator in a following period.
Embodiments previously disclosed for heating industrial furnaces with employment of regenerators and burners proceed on the basis of a paired or, respectively, symmetrical arrangement of the regenerators/burners in a single unit. For example, the storing of the exhaust heat in one regenerator of one pair ensues in the exhaust gas mode (heating periods) and the unstoring of the heat of other regenerator ensues in the other regenerator/burner pair by alternately switching to the burner mode (cooling period) (for example, GB-A-2 224 563). As a result of the strictly paired, symmetrical allocation and operation of the two regenerators, however, individually different thermic conditions of the regenerators as well as time and space demands in view of the heat requirements for the operation of the smelting furnace cannot be taken into consideration, and a fast replacement of the regenerator/burner modules cannot be undertaken in case of maintenance and repair.
SUMMARY OF THE INVENTION
The invention is based on the object of creating a regenerative, energy-saving heating for an industrial furnace, particularly for a metal smelting furnace. The heating can flexibly react to all possible time and space thermic operating conditions and demands of the regenerators as well as to the furnace to be heated, particularly given large smelting furnace systems.
This object is achieved a plurality, an even-numbered or an odd-numbered plurality of regenerator/burner modules arranged distributed around the circumference of an industrial furnace in the inventive method that are switched from burner mode into the regenerator mode from the process controller of the industrial furnace, it also becomes possible to operate the individual regenerator/burner units unpaired or, respectively, asymmetrically, taking operational limits into consideration. There is also the possibility of having burners fire in an over-plurality or in an under-plurality as well. A critical feature of the invention is, thus, that the selection and/or the module ratio of the plurality of firing burners to the plurality of extracted burners (or, respectively, burners with reverse flow) can be variably controlled and, for example, dependent on the thermic condition of the individual regenerator/burner modules (units). The evaluation criteria for the thermic condition of the individual regenerator/burner modules include for example, the exhaust gas temperature and the combustion air temperature. However, a controlled utilization corresponding to the measured or actual furnace temperatures in a plurality of representative furnace sectors, for example with radiant pyrometers, also enables a designational heating of the various furnace regions. In this way, the inventive method for heating a fuel-fired industrial furnace can react flexibly to all possible time and space operating conditions and demands of the furnace to be heated.
According to a further feature of the invention, the clock times of the operation of the respectively firing burner and the respectively extracted burner can be fixed or variable, and the clock times can overlap to a greater or lesser extent. Inventively, the known paired division of the burner units has been cut up into individual burner or, respectively, individual exhaust gas operation. A very beneficial heat distribution is achieved within the furnace to be heated since the firing can be clocked according to the requirements of the smelting material.
The inventive regenerator/burner system for the implementation of the heating method is characterized in that a regenerator and a burner are respectively combined to form a respective, compact regenerator/burner (regenerator burner, regenerator and burner, or regenerative burner) module (unit), whereby at least two regenerator/burner modules are in communication with an exhaust gas conduit with two ventilators that are reversible and/or that interact with reverse valves. Each compact module can be easily separated from the smelting furnace as a unit (i.e. is detachably connected to the smelting furnace) and replaced with a different, available regenerator/burner module. The regenerator/burner module removed from the smelting furnace can then be serviced with appropriate care without interfering with furnace operations. Such a replacement, which causes only short interruptions in operation, can be facilitated when the entire regenerator/burner unit is provided with a truck with which the respective units can be moved away from the furnace. Given a vertical regenerator, a horizontal connecting flange at the regenerator conduit, which is located under the burner projecting in the upper regenerator part, makes it possible to align the burner well. A conical or an annular burner head seat in the furnace housing wall with expansion elements between burner and adapter to the regenerator promotes this.
The burner is directed onto the useful product such as, for example, a molten bath. The regenerator that is arranged immediately in front of the burner can be arranged vertically downward or upward as well. However, a regenerator attached approximately horizontally to the burner is also possible. A gas-permeable bulk fill—for example, of balls or rings—or honeycomb members placed on one another can be utilized as heat store for the vertical regenerator. Honeycomb members are clearly better-suited for horizontal regenerators in most instances. Compared to bulk fills, moreover, ceramic honeycomb members, for example, have a considerably lower flow resistance, the advantage of correspondingly lower ventilator capacities, as well as the advantage of a lower contamination hazard. The distribution of the flow resistances and, thus, the throughput distribution in the regenerator can also be influenced by the layering length of the honeycomb members.
Further, practically no heat losses occur during operation of the compact regenerator/burner since the burner is arranged immediately following the regenerator, and, thus, no lowering of the temperature of the combustion air heated in the regenerator occurs on the very short adapter to the burner. The burner can also be compactly built into the regenerator housing, in regenerator mode, the hot exhaust gas is extracted from the industrial furnace in reverse direction through combustion air channels of the burner directly into the regenerator and heats the latter. The exhaust gas thereby cools down to about 400° C. in the regenerator, so that the following units such as conduits, valves, ventilators and the like are subject to a correspondingly lower thermal load. Additionally, a recirculation conduit can be provided between the upper smelting furnace part and upper regenerator part, so that exhaust gas can additionally flow through the regenerator in regenerator mode.
Ventilator pair may be utilized for the operation of the regenerator/burner modules at a furnace: one ventilator for the combustion air and one ventilator for the exhaust gases. A pair of reverse valves that connect the regenerator to or disconnect the regenerator from the combustion air conduit or the ex
Bender Wolfgang
Engelberg Ing Franz
Villinger Gerhard
Wicker Martin
Gautschi Electro-fours S.A.
Gravini Stephen
Lu Jiping
Sonnenschein Nath & Rosenthal
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